第一篇:中英文翻譯
Fundamentals This chapter describes the fundamentals of today’s wireless communications.First a detailed description of the radio channel and its modeling are presented, followed by the introduction of the principle of OFDM multi-carrier transmission.In addition, a general overview of the spread spectrum technique, especially DS-CDMA, is given and examples of potential applications for OFDM and DS-CDMA are analyzed.This introduction is essential for a better understanding of the idea behind the combination of OFDM with the spread spectrum technique, which is briefly introduced in the last part of this chapter.1.1 Radio Channel Characteristics Understanding the characteristics of the communications medium is crucial for the appropriate selection of transmission system architecture, dimensioning of its components, and optimizing system parameters, especially since mobile radio channels are considered to be the most difficult channels, since they suffer from many imperfections like multipath fading, interference, Doppler shift, and shadowing.The choice of system components is totally different if, for instance, multipath propagation with long echoes dominates the radio propagation.Therefore, an accurate channel model describing the behavior of radio wave propagation in different environments such as mobile/fixed and indoor/outdoor is needed.This may allow one, through simulations, to estimate and validate the performance of a given transmission scheme in its several design phases.1.1.1 Understanding Radio Channels In mobile radio channels(see Figure 1-1), the transmitted signal suffers from different effects, which are characterized as follows: Multipath propagation occurs as a consequence of reflections, scattering, and diffraction of the transmitted electromagnetic wave at natural and man-made objects.Thus, at the receiver antenna, a multitude of waves arrives from many different directions with different delays, attenuations, and phases.The superposition of these waves results in amplitude and phase variations of the composite received signal.Doppler spread is caused by moving objects in the mobile radio channel.Changes in the phases and amplitudes of the arriving waves occur which lead to time-variant multipath propagation.Even small movements on the order of the wavelength may result in a totally different wave superposition.The varying signal strength due to time-variant multipath propagation is referred to as fast fading.Shadowing is caused by obstruction of the transmitted waves by, e.g., hills, buildings, walls, and trees, which results in more or less strong attenuation of the signal strength.Compared to fast fading, longer distances have to be covered to significantly change the shadowing constellation.The varying signal strength due to shadowing is called slow fading and can be described by a log-normal distribution [36].Path loss indicates how the mean signal power decays with distance between transmitter and receiver.In free space, the mean signal power decreases with the square of the distance between base station(BS)and terminal station(TS).In a mobile radio channel, where often no line of sight(LOS)path exists, signal power decreases with a power higher than two and is typically in the order of three to five.Variations of the received power due to shadowing and path loss can be efficiently counteracted by power control.In the following, the mobile radio channel is described with respect to its fast fading characteristic.1.1.2 Channel Modeling The mobile radio channel can be characterized by the time-variant channel impulse response h(τ , t)or by the time-variant channel transfer function H(f, t), which is the Fourier transform of h(τ , t).The channel impulse response represents the response of the channel at time t due to an impulse applied at time t ? τ.The mobile radio channel is assumed to be a wide-sense stationary random process, i.e., the channel has a fading statistic that remains constant over short periods of time or small spatial distances.In environments with multipath propagation, the channel impulse response is composed of a large number of scattered impulses received over Np different paths,Where
and ap, fD,p, ?p, and τp are the amplitude, the Doppler frequency, the phase, and the propagation delay, respectively, associated with path p, p = 0,..., Np ? 1.The assigned channel transfer function is
The delays are measured relative to the first detectable path at the receiver.The Doppler Frequency
depends on the velocity v of the terminal station, the speed of light c, the carrier frequency fc, and the angle of incidence αp of a wave assigned to path p.A channel impulse response with corresponding channel transfer function is illustrated in Figure 1-2.The delay power density spectrum ρ(τ)that characterizes the frequency selectivity of the mobile radio channel gives the average power of the channel output as a function of the delay τ.The mean delay τ , the root mean square(RMS)delay spread τRMS and the maximum delay τmax are characteristic parameters of the delay power density spectrum.The mean delay is
Where
Figure 1-2 Time-variant channel impulse response and channel transfer function with frequency-selective fading is the power of path p.The RMS delay spread is defined as Similarly, the Doppler power density spectrum S(fD)can be defined that characterizes the time variance of the mobile radio channel and gives the average power of the channel output as a function of the Doppler frequency fD.The frequency dispersive properties of multipath channels are most commonly quantified by the maximum occurring Doppler frequency fDmax and the Doppler spread fDspread.The Doppler spread is the bandwidth of the Doppler power density spectrum and can take on values up to two times |fDmax|, i.e.,1.1.3Channel Fade Statistics The statistics of the fading process characterize the channel and are of importance for channel model parameter specifications.A simple and often used approach is obtained from the assumption that there is a large number of scatterers in the channel that contribute to the signal at the receiver side.The application of the central limit theorem leads to a complex-valued Gaussian process for the channel impulse response.In the absence of line of sight(LOS)or a dominant component, the process is zero-mean.The magnitude of the corresponding channel transfer function
is a random variable, for brevity denoted by a, with a Rayleigh distribution given by
Where
is the average power.The phase is uniformly distributed in the interval [0, 2π].In the case that the multipath channel contains a LOS or dominant component in addition to the randomly moving scatterers, the channel impulse response can no longer be modeled as zero-mean.Under the assumption of a complex-valued Gaussian process for the channel impulse response, the magnitude a of the channel transfer function has a Rice distribution given by
The Rice factor KRice is determined by the ratio of the power of the dominant path to thepower of the scattered paths.I0 is the zero-order modified Bessel function of first kind.The phase is uniformly distributed in the interval [0, 2π].1.1.4Inter-Symbol(ISI)and Inter-Channel Interference(ICI)The delay spread can cause inter-symbol interference(ISI)when adjacent data symbols overlap and interfere with each other due to different delays on different propagation paths.The number of interfering symbols in a single-carrier modulated system is given by
For high data rate applications with very short symbol duration Td < τmax, the effect of ISI and, with that, the receiver complexity can increase significantly.The effect of ISI can be counteracted by different measures such as time or frequency domain equalization.In spread spectrum systems, rake receivers with several arms are used to reduce the effect of ISI by exploiting the multipath diversity such that individual arms are adapted to different propagation paths.If the duration of the transmitted symbol is significantly larger than the maximum delay Td τmax, the channel produces a negligible amount of ISI.This effect is exploited with multi-carrier transmission where the duration per transmitted symbol increases with the number of sub-carriers Nc and, hence, the amount of ISI decreases.The number of interfering symbols in a multi-carrier modulated system is given by
Residual ISI can be eliminated by the use of a guard interval(see Section 1.2).The maximum Doppler spread in mobile radio applications using single-carrier modulation is typically much less than the distance between adjacent channels, such that the effect of interference on adjacent channels due to Doppler spread is not a problem for single-carrier modulated systems.For multi-carrier modulated systems, the sub-channel spacing Fs can become quite small, such that Doppler effects can cause significant ICI.As long as all sub-carriers are affected by a common Doppler shift fD, this Doppler shift can be compensated for in the receiver and ICI can be avoided.However, if Doppler spread in the order of several percent of the sub-carrier spacing occurs, ICI may degrade the system performance significantly.To avoid performance degradations due to ICI or more complex receivers with ICI equalization, the sub-carrier spacing Fs should be chosen as
such that the effects due to Doppler spread can be neglected(see Chapter 4).This approach corresponds with the philosophy of OFDM described in Section 1.2 and is followed in current OFDM-based wireless standards.Nevertheless, if a multi-carrier system design is chosen such that the Doppler spread is in the order of the sub-carrier spacing or higher, a rake receiver in the frequency domain can be used [22].With the frequency domain rake receiver each branch of the rake resolves a different Doppler frequency.1.1.5Examples of Discrete Multipath Channel Models Various discrete multipath channel models for indoor and outdoor cellular systems with different cell sizes have been specified.These channel models define the statistics of the 5 discrete propagation paths.An overview of widely used discrete multipath channel models is given in the following.COST 207 [8]: The COST 207 channel models specify four outdoor macro cell propagation scenarios by continuous, exponentially decreasing delay power density spectra.Implementations of these power density spectra by discrete taps are given by using up to 12 taps.Examples for settings with 6 taps are listed in Table 1-1.In this table for several propagation environments the corresponding path delay and power profiles are given.Hilly terrain causes the longest echoes.The classical Doppler spectrum with uniformly distributed angles of arrival of the paths can be used for all taps for simplicity.Optionally, different Doppler spectra are defined for the individual taps in [8].The COST 207 channel models are based on channel measurements with a bandwidth of 8–10 MHz in the 900-MHz band used for 2G systems such as GSM.COST 231 [9] and COST 259 [10]: These COST actions which are the continuation of COST 207 extend the channel characterization to DCS 1800, DECT, HIPERLAN and UMTS channels, taking into account macro, micro, and pico cell scenarios.Channel models with spatial resolution have been defined in COST 259.The spatial component is introduced by the definition of several clusters with local scatterers, which are located in a circle around the base station.Three types of channel models are defined.The macro cell type has cell sizes from 500 m up to 5000 m and a carrier frequency of 900 MHz or 1.8 GHz.The micro cell type is defined for cell sizes of about 300 m and a carrier frequency of 1.2 GHz or 5 GHz.The pico cell type represents an indoor channel model with cell sizes smaller than 100 m in industrial buildings and in the order of 10 m in an office.The carrier frequency is 2.5 GHz or 24 GHz.COST 273: The COST 273 action additionally takes multi-antenna channel models into account, which are not covered by the previous COST actions.CODIT [7]: These channel models define typical outdoor and indoor propagation scenarios for macro, micro, and pico cells.The fading characteristics of the various propagation environments are specified by the parameters of the Nakagami-m distribution.Every environment is defined in terms of a number of scatterers which can take on values up to 20.Some channel models consider also the angular distribution of the scatterers.They have been developed for the investigation of 3G system proposals.Macro cell channel type models have been developed for carrier frequencies around 900 MHz with 7 MHz bandwidth.The micro and pico cell channel type models have been developed for carrier frequencies between 1.8 GHz and 2 GHz.The bandwidths of the measurements are in the range of 10–100 MHz for macro cells and around 100 MHz for pico cells.JTC [28]: The JTC channel models define indoor and outdoor scenarios by specifying 3 to 10 discrete taps per scenario.The channel models are designed to be applicable for wideband digital mobile radio systems anticipated as candidates for the PCS(Personal Communications Systems)common air interface at carrier frequencies of about 2 GHz.UMTS/UTRA [18][44]: Test propagation scenarios have been defined for UMTS and UTRA system proposals which are developed for frequencies around 2 GHz.The modeling of the multipath propagation corresponds to that used by the COST 207 channel models.HIPERLAN/2 [33]: Five typical indoor propagation scenarios for wireless LANs in the 5 GHz frequency band have been defined.Each scenario is described by 18discrete taps of the delay power density spectrum.The time variance of the channel(Doppler spread)is modeled by a classical Jake’s spectrum with a maximum terminal speed of 3 m/h.Further channel models exist which are, for instance, given in [16].1.1.6Multi-Carrier Channel Modeling Multi-carrier systems can either be simulated in the time domain or, more computationally efficient, in the frequency domain.Preconditions for the frequency domain implementation are the absence of ISI and ICI, the frequency nonselective fading per sub-carrier, and the time-invariance during one OFDM symbol.A proper system design approximately fulfills these preconditions.The discrete channel transfer function adapted to multi-carrier signals results in
where the continuous channel transfer function H(f, t)is sampled in time at OFDM symbol rate s and in frequency at sub-carrier spacing Fs.The duration
s is the total OFDM symbol duration including the guard interval.Finally, a symbol transmitted onsub-channel n of the OFDM symbol i is multiplied by the resulting fading amplitude an,i and rotated by a random phase ?n,i.The advantage of the frequency domain channel model is that the IFFT and FFT operation for OFDM and inverse OFDM can be avoided and the fading operation results in one complex-valued multiplication per sub-carrier.The discrete multipath channel models introduced in Section 1.1.5 can directly be applied to(1.16).A further simplification of the channel modeling for multi-carrier systems is given by using the so-called uncorrelated fading channel models.1.1.6.1Uncorrelated Fading Channel Models for Multi-Carrier Systems These channel models are based on the assumption that the fading on adjacent data symbols after inverse OFDM and de-interleaving can be considered as uncorrelated [29].This assumption holds when, e.g., a frequency and time interleaver with sufficient interleaving depth is applied.The fading amplitude an,i is chosen from a distribution p(a)according to the considered cell type and the random phase ?n,I is uniformly distributed in the interval [0,2π].The resulting complex-valued channel fading coefficient is thus generated independently for each sub-carrier and OFDM symbol.For a propagation scenario in a macro cell without LOS, the fading amplitude an,i is generated by a Rayleigh distribution and the channel model is referred to as an uncorrelated Rayleigh fading channel.For smaller cells where often a dominant propagation component occurs, the fading amplitude is chosen from a Rice distribution.The advantages of the uncorrelated fading channel models for multi-carrier systems are their simple implementation in the frequency domain and the simple reproducibility of the simulation results.1.1.7Diversity The coherence bandwidth of a mobile radio channel is the bandwidth over which the signal propagation characteristics are correlated and it can be approximated by
The channel is frequency-selective if the signal bandwidth B is larger than the coherence bandwidth.On the other hand, if B is smaller than , the channel is frequency nonselective or flat.The coherence bandwidth of the channel is of importance for evaluating the performance of spreading and frequency interleaving techniques that try to exploit the inherent frequency diversity Df of the mobile radio channel.In the case of multi-carrier transmission, frequency diversity is exploited if the separation of sub-carriers transmitting the same information exceeds the coherence bandwidth.The maximum achievable frequency diversity Df is given by the ratio between the signal bandwidth B and the coherence bandwidth,The coherence time of the channel is the duration over which the channel characteristics can be considered as time-invariant and can be approximated by
If the duration of the transmitted symbol is larger than the coherence time, the channel is time-selective.On the other hand, if the symbol duration is smaller than , the channel is time nonselective during one symbol duration.The coherence time of the channel is of importance for evaluating the performance of coding and interleaving techniques that try to exploit the inherent time diversity DO of the mobile radio channel.Time diversity can be exploited if the separation between time slots carrying the same information exceeds the coherence time.A number of Ns successive time slots create a time frame of duration Tfr.The maximum time diversity Dt achievable in one time frame is given by the ratio between the duration of a time frame and the coherence time, A system exploiting frequency and time diversity can achieve the overall diversity
The system design should allow one to optimally exploit the available diversity DO.For instance, in systems with multi-carrier transmission the same information should be transmitted on different sub-carriers and in different time slots, achieving uncorrelated faded replicas of the information in both dimensions.Uncoded multi-carrier systems with flat fading per sub-channel and time-invariance during one symbol cannot exploit diversity and have a poor performance in time and frequency selective fading channels.Additional methods have to be applied to exploit diversity.One approach is the use of data spreading where each data symbol is spread by a spreading code of length L.This, in combination with interleaving, can achieve performance results which are given for
by the closed-form solution for the BER for diversity reception in Rayleigh fading channels according to [40]
Whererepresents the combinatory function,and σ2 is the variance of the noise.As soon as the interleaving is not perfect or the diversity offered by the channel is smaller than the spreading code length L, or MCCDMA with multiple access interference is applied,(1.22)is a lower bound.For L = 1, the performance of an OFDM system without forward error correction(FEC)is obtained, 9
which cannot exploit any diversity.The BER according to(1.22)of an OFDM(OFDMA, MC-TDMA)system and a multi-carrier spread spectrum(MC-SS)system with different spreading code lengths L is shown in Figure 1-3.No other diversity techniques are applied.QPSK modulation is used for symbol mapping.The mobile radio channel is modeled as uncorrelated Rayleigh fading channel(see Section 1.1.6).As these curves show, for large values of L, the performance of MC-SS systems approaches that of an AWGN channel.Another form of achieving diversity in OFDM systems is channel coding by FEC, where the information of each data bit is spread over several code bits.Additional to the diversity gain in fading channels, a coding gain can be obtained due to the selection of appropriate coding and decoding algorithms.中文翻譯 1基本原理
這章描述今日的基本面的無(wú)線通信。第一一個(gè)的詳細(xì)說(shuō)明無(wú)線電頻道,它的模型被介紹,跟隨附近的的介紹的原則的參考正交頻分復(fù)用多載波傳輸。此外,一個(gè)一般概觀的擴(kuò)頻技術(shù),尤其ds-cdma,被給,潛力的例子申請(qǐng)參考正交頻分復(fù)用,DS對(duì)1。分配的通道傳輸功能是
有關(guān)的延誤測(cè)量相對(duì)于第一個(gè)在接收器檢測(cè)到的路徑。多普勒頻率
取決于終端站,光速c,載波頻率fc的速度和發(fā)病路徑分配給速度v波αp角度頁(yè)具有相應(yīng)通道傳輸信道沖激響應(yīng)函數(shù)圖1-2所示。
延遲功率密度譜ρ(τ)為特征的頻率選擇性移動(dòng)無(wú)線電頻道給出了作為通道的輸出功能延遲τ平均功率。平均延遲τ,均方根(RMS)的時(shí)延擴(kuò)展τRMS和最大延遲τmax都是延遲功率密度譜特征參數(shù)。平均時(shí)延特性參數(shù)為
有
圖1-2時(shí)變信道沖激響應(yīng)和通道傳遞函數(shù)頻率選擇性衰落是權(quán)力頁(yè)的路徑均方根時(shí)延擴(kuò)展的定義為 同樣,多普勒頻譜的功率密度(FD)的特點(diǎn)可以定義
在移動(dòng)時(shí)變無(wú)線信道,并給出了作為一種金融衍生工具功能的多普勒頻率通道輸出的平均功率。多徑信道頻率分散性能是最常見(jiàn)的量化發(fā)生的多普勒頻率和多普勒f(shuō)Dmax蔓延fDspread最大。多普勒擴(kuò)散是功率密度的多普勒頻譜帶寬,可價(jià)值觀需要兩年時(shí)間| fDmax|,即
1.1.3頻道淡出統(tǒng)計(jì)
在衰落過(guò)程中的統(tǒng)計(jì)特征和重要的渠道是信道模型參數(shù)規(guī)格。一個(gè)簡(jiǎn)單而經(jīng)常使用的方法是從假設(shè)有一個(gè)通道中的散射,有助于在大量接收端的信號(hào)。該中心極限定理的應(yīng)用導(dǎo)致了復(fù)雜的值的高斯信道沖激響應(yīng)過(guò)程。在對(duì)視線(LOS)或線的主要組成部分的情況下,這個(gè)過(guò)程是零的意思。相應(yīng)的通道傳遞函數(shù)幅度
是一個(gè)隨機(jī)變量,通過(guò)給定一個(gè)簡(jiǎn)短表示由瑞利分布,有
是的平均功率。相均勻分布在區(qū)間[0,2π]。
在案件的多通道包含洛杉磯的或主要組件除了隨機(jī)移動(dòng)散射,通道脈沖響應(yīng)可以不再被建模為均值為零。根據(jù)信道脈沖響應(yīng)的假設(shè)一個(gè)復(fù)雜的值高斯過(guò)程,其大小通道的傳遞函數(shù)A的水稻分布給出
賴(lài)斯因素KRice是由占主導(dǎo)地位的路徑權(quán)力的威力比分散的路徑。I0是零階貝塞爾函數(shù)的第一階段是一致kind.The在區(qū)間[0,2π]分發(fā)。
1.1.4符號(hào)間(ISI)和通道間干擾(ICI)
延遲的蔓延引起的符號(hào)間干擾(ISI)當(dāng)相鄰的數(shù)據(jù)符號(hào)上的重疊與互相不同的傳播路徑,由于不同的延遲干涉。符號(hào)的干擾在單載波調(diào)制系統(tǒng)的號(hào)碼是給予
對(duì)于高數(shù)據(jù)符號(hào)持續(xù)時(shí)間很短運(yùn)輸署<蟿MAX時(shí),ISI的影響,這樣一來(lái),速率應(yīng)用,接收機(jī)的復(fù)雜性大大增加。對(duì)干擾影響,可以抵消,如時(shí)間或頻域均衡不同的措施。在擴(kuò)頻系統(tǒng),與幾個(gè)臂Rake接收機(jī)用于減少通過(guò)利用多徑分集等,個(gè)別武器適應(yīng)不同的傳播路徑的干擾影響。
如果發(fā)送符號(hào)的持續(xù)時(shí)間明顯高于大的最大延遲運(yùn)輸署蟿最大,渠道產(chǎn)生ISI的微不足道。這種效果是利用多載波傳輸?shù)牡胤?,每發(fā)送符號(hào)的增加與子載波數(shù)控?cái)?shù)目,因此,ISI的金額減少的持續(xù)時(shí)間。符號(hào)的干擾多載波調(diào)制系統(tǒng)的號(hào)碼是給予
可以消除符號(hào)間干擾由一個(gè)保護(hù)間隔(見(jiàn)1.2節(jié))的使用。
最大多普勒在移動(dòng)無(wú)線應(yīng)用傳播使用單載波調(diào)制通常比相鄰?fù)ǖ溃@樣,干擾對(duì)由于多普勒傳播相鄰?fù)ǖ赖淖饔貌皇且粋€(gè)單載波調(diào)制系統(tǒng)的問(wèn)題距離。對(duì)于多載波調(diào)制系統(tǒng),子通道間距FS可以變得非常小,這樣可以造成嚴(yán)重的多普勒效應(yīng)ICI的。只要所有子載波只要是一個(gè)共同的多普勒頻移金融衍生工具的影響,這可以補(bǔ)償多普勒頻移在接收器和ICI是可以避免的。但是,如果在對(duì)多普勒子載波間隔為幾個(gè)百分點(diǎn)的蔓延情況,卜內(nèi)門(mén)可能會(huì)降低系統(tǒng)的性能顯著。為了避免性能降級(jí)或因與ICI卜內(nèi)門(mén)更復(fù)雜的接收機(jī)均衡,子載波間隔財(cái)政司司長(zhǎng)應(yīng)定為
這樣說(shuō),由于多普勒效應(yīng)可以忽略不擴(kuò)散(見(jiàn)第4章)。這種方法對(duì)應(yīng)于OFDM的1.2節(jié)中所述,是目前基于OFDM的無(wú)線標(biāo)準(zhǔn)遵循的理念。
不過(guò),如果多載波系統(tǒng)的設(shè)計(jì)選擇了這樣的多普勒展寬在子載波間隔或更高,秩序是在頻率RAKE接收機(jī)域名可以使用[22]。隨著頻域RAKE接收機(jī)每個(gè)支部耙解決了不同的多普勒頻率。
1.1.5多徑信道模型的離散的例子
各類(lèi)離散多與不同的細(xì)胞大小的室內(nèi)和室外蜂窩系統(tǒng)的信道模型已經(jīng)被指定。這些通道模型定義的離散傳播路徑的統(tǒng)計(jì)信息。一種廣泛使用的離散多徑信道模型概述于下。造價(jià)207[8]:成本207信道模型指定連續(xù)四個(gè)室外宏蜂窩傳播方案,指數(shù)下降延遲功率密度譜。這些頻道功率密度的離散譜的實(shí)現(xiàn)都是通過(guò)使用多達(dá)12個(gè)頻道。與6頻道設(shè)置的示例列于表1-1。在這種傳播環(huán)境的幾個(gè)表中的相應(yīng)路徑延遲和電源配置給出。丘陵地形導(dǎo)致最長(zhǎng)相呼應(yīng)。
經(jīng)典的多普勒頻譜與均勻分布的到達(dá)角路徑可以用于簡(jiǎn)化所有的頻道?;蛘?,不同的多普勒譜定義在[8]個(gè)人頻道。207信道的成本模型是基于一個(gè)8-10兆赫的2G,如GSM系統(tǒng)中使用的900兆赫頻段信道帶寬的測(cè)量。造價(jià)231[9]和造價(jià)259[10]:這些費(fèi)用是行動(dòng)的延續(xù)成本207擴(kuò)展通道特性到DCS1800的DECT,HIPERLAN和UMTS的渠道,同時(shí)考慮到宏觀,微觀和微微小區(qū)的情況為例??臻g分辨率與已定義的通道模型在造價(jià)259??臻g部分是介紹了與當(dāng)?shù)厣⑸洌@是在基站周?chē)O(shè)幾組圓的定義。三種類(lèi)型的通道模型定義。宏細(xì)胞類(lèi)型具有高達(dá)500?5000米,載波頻率為900兆赫或1.8 GHz的單元尺寸。微細(xì)胞類(lèi)型被定義為細(xì)胞體積約300米,1.2 GHz或5 GHz載波頻率。細(xì)胞類(lèi)型代表的Pico與細(xì)胞體積小于100工業(yè)建筑物和辦公室中的10 m階米室內(nèi)信道模型。載波頻率為2.5 GHz或24千兆赫。造價(jià)273:成本273行動(dòng)另外考慮到多天線信道模型,這是不是由先前的費(fèi)用的行為包括在內(nèi)。
CODIT [7]:這些通道模型定義的宏,微,微微蜂窩和室外和室內(nèi)傳播的典型案例。各種傳播環(huán)境的衰落特性是指定的在NakagamiSS)的不同擴(kuò)頻碼L是長(zhǎng)度,如圖1-3所示的系統(tǒng)。沒(méi)有其他的分集技術(shù)被應(yīng)用。QPSK調(diào)制用于符號(hào)映射。移動(dòng)無(wú)線信道建模為不相關(guān)瑞利衰落信道(見(jiàn)1.1.6)。由于這些曲線顯示,辦法,AWGN信道的一對(duì)L時(shí),對(duì)MC-SS系統(tǒng)性能有很大價(jià)值。
另一種實(shí)現(xiàn)形式的OFDM系統(tǒng)的多樣性是由前向糾錯(cuò)信道編碼,在這里,每個(gè)數(shù)據(jù)位的信息分散在幾個(gè)代碼位。附加在衰落信道分集增益,編碼增益一個(gè)可因適當(dāng)?shù)木幋a和解碼算法的選擇。
第二篇:中英文翻譯
蓄電池 battery 充電 converter 轉(zhuǎn)換器 charger
開(kāi)關(guān)電器 Switch electric 按鈕開(kāi)關(guān) Button to switch 電源電器 Power electric 插頭插座 Plug sockets
第三篇:中英文翻譯
特種加工工藝
介紹
傳統(tǒng)加工如車(chē)削、銑削和磨削等,是利用機(jī)械能將金屬?gòu)墓ぜ霞羟械?,以加工成孔或去除余料。特種加工是指這樣一組加工工藝,它們通過(guò)各種涉及機(jī)械能、熱能、電能、化學(xué)能或及其組合形式的技術(shù),而不使用傳統(tǒng)加工所必需的尖銳刀具來(lái)去除工件表面的多余材料。
傳統(tǒng)加工如車(chē)削、鉆削、刨削、銑削和磨削,都難以加工特別硬的或脆性材料。采用傳統(tǒng)方法加工這類(lèi)材料就意味著對(duì)時(shí)間和能量要求有所增加,從而導(dǎo)致成本增加。在某些情況下,傳統(tǒng)加工可能行不通。由于在加工過(guò)程中會(huì)產(chǎn)生殘余應(yīng)力,傳統(tǒng)加工方法還會(huì)造成刀具磨損,損壞產(chǎn)品質(zhì)量?;谝韵赂鞣N特殊理由,特種加工工藝或稱(chēng)為先進(jìn)制造工藝,可以應(yīng)用于采用傳統(tǒng)加工方法不可行,不令人滿(mǎn)意或者不經(jīng)濟(jì)的場(chǎng)合:
1.對(duì)于傳統(tǒng)加工難以?shī)A緊的非常硬的脆性材料; 2.當(dāng)工件柔性很大或很薄時(shí); 3.當(dāng)零件的形狀過(guò)于復(fù)雜時(shí);
4.要求加工出的零件沒(méi)有毛刺或殘余應(yīng)力。
傳統(tǒng)加工可以定義為利用機(jī)械(運(yùn)動(dòng))能的加工方法,而特種加工利用其他形式的能量,主要有如下三種形式: 1.熱能; 2.化學(xué)能; 3.電能。
為了滿(mǎn)足額外的加工條件的要求,已經(jīng)開(kāi)發(fā)出了幾類(lèi)特種加工工藝。恰當(dāng)?shù)厥褂眠@些加工工藝可以獲得很多優(yōu)于傳統(tǒng)加工工藝的好處。常見(jiàn)的特種加工工藝描述如下。
電火花加工
電火花加工是使用最為廣泛的特種加工工藝之一。相比于利用不同刀具進(jìn)行金屬切削和磨削的常規(guī)加工,電火花加工更為吸引人之處在于它利用工件和電極間的一系列重復(fù)產(chǎn)生的(脈沖)離散電火花所產(chǎn)生的熱電作用,從工件表面通過(guò)電腐蝕去除掉多余的材料。
傳統(tǒng)加工工藝依靠硬質(zhì)刀具或磨料去除較軟的材料,而特種加工工藝如電火花加工,則是利用電火花或熱能來(lái)電蝕除余料,以獲得所需的零件形狀。因此,材料的硬度不再是電火花加工中的關(guān)鍵因素。
電火花加工是利用存儲(chǔ)在電容器組中的電能(一般為50V/10A量級(jí))在工具電極(陰極)和工件電極(陽(yáng)極)之間的微小間隙間進(jìn)行放電來(lái)去除材料的。如圖6.1所示,在EDM操作初始,在工具電極和工件電極間施以高電壓。這個(gè)高電壓可以在工具電極和工件電極窄縫間的絕緣電介質(zhì)中產(chǎn)生電場(chǎng)。這就會(huì)使懸浮在電介質(zhì)中的導(dǎo)電粒子聚集在電場(chǎng)最強(qiáng)處。當(dāng)工具電極和工件電極之間的勢(shì)能差足夠大時(shí),電介質(zhì)被擊穿,從而在電介質(zhì)流體中會(huì)產(chǎn)生瞬時(shí)電火花,將少量材料從工件表面蝕除掉。每次電火花所蝕除掉的材料量通常在10-5~10-6mm3范圍內(nèi)。電極之間的間隙只有千分之幾英寸,通過(guò)伺服機(jī)構(gòu)驅(qū)動(dòng)和控制工具電極的進(jìn)給使該值保持常量?;瘜W(xué)加工
化學(xué)加工是眾所周知的特種加工工藝之一,它將工件浸入化學(xué)溶液通過(guò)腐蝕溶解作用將多余材料從工件上去除掉。該工藝是最古老的特種加工工藝,主要用于凹腔和輪廓加工,以及從具有高的比剛度的零件表面去除余料?;瘜W(xué)加工廣泛用于為多種工業(yè)應(yīng)用(如微機(jī)電系統(tǒng)和半導(dǎo)體行業(yè))制造微型零件。
化學(xué)加工將工件浸入到化學(xué)試劑或蝕刻劑中,位于工件選區(qū)的材料通過(guò)發(fā)生在金屬溶蝕或化學(xué)溶解過(guò)程中的電化學(xué)微電池作用被去除掉。而被稱(chēng)為保護(hù)層的特殊涂層所保護(hù)下的區(qū)域中的材料則不會(huì)被去除。不過(guò),這種受控的化學(xué)溶解過(guò)程同時(shí)也會(huì)蝕除掉所以暴露在表面的材料,盡管去除的滲透率只有0.0025~0.1 mm/min。該工藝采用如下幾種形式:凹坑加工、輪廓加工和整體金屬去除的化學(xué)銑,在薄板上進(jìn)行蝕刻的化學(xué)造型,在微電子領(lǐng)域中利用光敏抗蝕劑完成蝕刻的光化學(xué)加工(PCM),采用弱化學(xué)試劑進(jìn)行拋光或去毛刺的電化學(xué)拋光,以及利用單一化學(xué)活性噴射的化學(xué)噴射加工等。如圖6.2a所示的化學(xué)加工示意圖,由于蝕刻劑沿垂直和水平方向開(kāi)始蝕除材料,鉆蝕(又稱(chēng)為淘蝕)量進(jìn)一步加大,如圖6.2b所示的保護(hù)體邊緣下面的區(qū)域。在化學(xué)造型中最典型的公差范圍可保持在材料厚度的±10%左右。為了提高生產(chǎn)率,在化學(xué)加工前,毛坯件材料應(yīng)采用其他工藝方法(如機(jī)械加工)進(jìn)行預(yù)成形加工。濕度和溫度也會(huì)導(dǎo)致工件尺寸發(fā)生改變。通過(guò)改變蝕刻劑和控制工件加工環(huán)境,這種尺寸改變可以減小到最小。
電化學(xué)加工
電化學(xué)金屬去除方法是一種最有用的特種加工方法。盡管利用電解作用作為金屬加工手段是近代的事,但其基本原理是法拉第定律。利用陽(yáng)極溶解,電化學(xué)加工可以去除具有導(dǎo)電性質(zhì)工件的材料,而無(wú)須機(jī)械能和熱能。這個(gè)加工過(guò)程一般用于在高強(qiáng)度材料上加工復(fù)雜形腔和形狀,特別是在航空工業(yè)中如渦輪機(jī)葉片、噴氣發(fā)動(dòng)機(jī)零件和噴嘴,以及在汽車(chē)業(yè)(發(fā)動(dòng)機(jī)鑄件和齒輪)和醫(yī)療衛(wèi)生業(yè)中。最近,還將電化學(xué)加工應(yīng)用于電子工業(yè)的微加工中。
圖6.3所示的是一個(gè)去除金屬的電化學(xué)加工過(guò)程,其基本原理與電鍍?cè)碚孟喾?。在電化學(xué)加工過(guò)程中,從陽(yáng)極(工件)上蝕除下的粒子移向陰極(加工工具)。金屬的去除由一個(gè)合適形狀的工具電極來(lái)完成,最終加工出來(lái)的零件具有給定的形狀、尺寸和表面光潔度。在電化學(xué)加工過(guò)程中,工具電極的形狀逐漸被轉(zhuǎn)移或復(fù)制到工件上。型腔的形狀正好是與工具相匹配的陰模的形狀。為了獲得電化學(xué)過(guò)程形狀復(fù)制的高精度和高的材料去除率,需要采用高的電流密度(范圍為10~100 A/cm2)和低電壓(范圍為8~30V)。通過(guò)將工具電極向去除工件表面材料的方向進(jìn)給,加工間隙要維持在0.1 mm范圍內(nèi),而進(jìn)給率一般為0.1~20 mm/min左右。泵壓后的電解液以高達(dá)5~50 m/s的速度通過(guò)間隙,將溶解后的材料、氣體和熱量帶走。因此,當(dāng)被蝕除的材料還沒(méi)來(lái)得及附著到工具電極上時(shí),就被電解液帶走了。
作為一種非機(jī)械式金屬去除加工方法,ECM可以以高切削量加工任何導(dǎo)電材料,而無(wú)須考慮材料的機(jī)械性能。特別是在電化學(xué)加工中,材料去除率與被加工件的硬度、韌性及其他特性無(wú)關(guān)。對(duì)于利用機(jī)械方法難于加工的材料,電化學(xué)加工可以保證將該材料加工出復(fù)雜形狀的零件,這就不需要制造出硬度高于工件的刀具,而且也不會(huì)造成刀具磨損。由于工具和工件間沒(méi)有接觸,電化學(xué)加工是加工薄壁、易變形零件及表面容易破裂的脆性材料的首選。激光束加工
LASER是英文Light Amplification by Stimulated Emission of Radiation 各單詞頭一個(gè)字母所組成的縮寫(xiě)詞。雖然激光在某些場(chǎng)合可用來(lái)作為放大器,但它的主要用途是光激射振蕩器,或者是作為將電能轉(zhuǎn)換為具有高度準(zhǔn)直性光束的換能器。由激光發(fā)射出的光能具有不同于其他光源的特點(diǎn):光譜純度好、方向性好及具有高的聚焦功率密度。
激光加工就是利用激光和和靶材間的相互作用去除材料。簡(jiǎn)而言之,這些加工工藝包括激光打孔、激光切割、激光焊接、激光刻槽和激光刻劃等。
激光加工(圖6.4)可以實(shí)現(xiàn)局部的非接觸加工,而且對(duì)加工件幾乎沒(méi)有作用力。這種加工工藝去除材料的量很小,可以說(shuō)是“逐個(gè)原子”地去除材料。由于這個(gè)原因,激光切削所產(chǎn)生的切口非常窄。激光打孔深度可以控制到每個(gè)激光脈沖不超過(guò)一微米,且可以根據(jù)加工要求很靈活地留下非常淺的永久性標(biāo)記。采用這種方法可以節(jié)省材料,這對(duì)于貴重材料或微加工中的精密結(jié)構(gòu)而言非常重要??梢跃_控制材料去除率使得激光加工成為微制造和微電子技術(shù)中非常重要的加工方法。厚度小于20 mm的板材的激光切割加工速度快、柔性好、質(zhì)量高。另外,通過(guò)套孔加工還可有效實(shí)現(xiàn)大孔及復(fù)雜輪廓的加工。
激光加工中的熱影響區(qū)相對(duì)較窄,其重鑄層只有幾微米?;诖?,激光加工的變形可以不予考慮。激光加工適用于任何可以很好地吸收激光輻射的材料,而傳統(tǒng)加工工藝必須針對(duì)不同硬度和耐磨性的材料選擇合適的刀具。采用傳統(tǒng)加工方法,非常難以加工硬脆材料如陶瓷等,而激光加工是解決此類(lèi)問(wèn)題的最好選擇。
激光切割的邊緣光滑且潔凈,無(wú)須進(jìn)一步處理。激光打孔可以加工用其他方法難以加工的高深徑比的孔。激光加工可以加工出高質(zhì)量的小盲孔、槽、表面微造型和表面印痕。激光技術(shù)正處于高速發(fā)展期,激光加工也如此。激光加工不會(huì)掛渣,沒(méi)有毛邊,可以精確控制幾何精度。隨著激光技術(shù)的快速發(fā)展,激光加工的質(zhì)量正在穩(wěn)步提高。
超聲加工
超聲加工為日益增長(zhǎng)的對(duì)脆性材料如單晶體、玻璃、多晶陶瓷材料的加工需求及不斷提高的工件復(fù)雜形狀和輪廓加工提供了解決手段。這種加工過(guò)程不產(chǎn)生熱量、無(wú)化學(xué)反應(yīng),加工出的零件在微結(jié)構(gòu)、化學(xué)和物理特性方面都不發(fā)生變化,可以獲得無(wú)應(yīng)力加工表面。因此,超聲加工被廣泛應(yīng)用于傳統(tǒng)加工難以切削的硬脆材料。在超聲加工中,實(shí)際切削由液體中的懸浮磨粒或者旋轉(zhuǎn)的電鍍金剛石工具來(lái)完成。超聲加工的變型有靜止(傳統(tǒng))超聲加工和旋轉(zhuǎn)超聲加工。
傳統(tǒng)的超聲加工是利用作為小振幅振動(dòng)的工具與工件之間不斷循環(huán)的含有磨粒的漿料的磨蝕作用去除材料的。成形工具本身并不磨蝕工件,是受激振動(dòng)的工具通過(guò)激勵(lì)漿料液流中的磨料不斷緩和而均勻地磨損工件,從而在工件表面留下與工具相對(duì)應(yīng)的精確形狀。音極工具振動(dòng)的均勻性使超聲加工只能完成小型零件的加工,特別是直徑小于100 mm 的零件。
超聲加工系統(tǒng)包括音極組件、超聲發(fā)生器、磨料供給系統(tǒng)及操作人員的控制。音極是暴露在超聲波振動(dòng)中的一小塊金屬或工具,它將振動(dòng)能傳給某個(gè)元件,從而激勵(lì)漿料中的磨粒。超聲加工系統(tǒng)的示意圖如圖6.5所示。音極/工具組件由換能器、變幅桿和音極組成。換能器將電脈沖轉(zhuǎn)換成垂直沖程,垂直沖程再傳給變幅桿進(jìn)行放大或壓抑。調(diào)節(jié)后的沖程再傳給音極/工具組件。此時(shí),工具表面的振動(dòng)幅值為20~50μm。工具的振幅通常與所使用的磨粒直徑大致相等。
磨料供給系統(tǒng)將由水和磨粒組成的漿料送至切削區(qū),磨粒通常為碳化硅或碳化硼。另外,除了提供磨粒進(jìn)行切削外,漿料還可對(duì)音極進(jìn)行冷卻,并將切削區(qū)的磨粒和切屑帶走。
Nontraditional Machining Processes Introduction
Traditional or conventional machining, such as turning, milling, and grinding etc., uses mechanical energy to shear metal against another substance to create holes or remove material.Nontraditional machining processes are defined as a group of processes that remove excess material by various techniques involving mechanical, thermal, electrical or chemical energy or combinations of these energies but do not use a sharp cutting tool as it is used in traditional manufacturing processes.Extremely hard and brittle materials are difficult to be machined by traditional machining processes.Using traditional methods to machine such materials means increased demand for time and energy and therefore increases in costs;in some cases traditional machining may not be feasible.Traditional machining also results in tool wear and loss of quality in the product owing to induced residual stresses during machining.Nontraditional machining processes, also called unconventional machining process or advanced manufacturing processes, are employed where traditional machining processes are not feasible, satisfactory or economical due to special reasons as outlined below: 1.Very hard fragile materials difficult to clamp for traditional machining;2.When the workpiece is too flexible or slender;3.When the shape of the part is too complex;4.Parts without producing burrs or inducing residual stresses.Traditional machining can be defined as a process using mechanical(motion)energy.Non-traditional machining utilizes other forms of energy;the three main forms of energy used in non-traditional machining processes are as follows: 1.Thermal energy;2.Chemical energy;3.Electrical energy.Several types of nontraditional machining processes have been developed to meet extra required machining conditions.When these processes are employed properly, they offer many advantages over traditional machining processes.The common nontraditional machining processes are described in the following section.Electrical Discharge Machining(EDM)
Electrical discharge machining(EDM)sometimes is colloquially referred to as spark machining, spark eroding, burning, die sinking or wire erosion.It is one of the most widely used non-traditional machining processes.The main attraction of EDM over traditional machining processes such as metal cutting using different tools and grinding is that this technique utilizes thermoelectric process to erode undesired materials from the workpiece by a series of rapidly recurring discrete electrical sparks between workpiece and electrode.The traditional machining processes rely on harder tool or abrasive material to remove softer material whereas nontraditional machining processes such as EDM uses electrical spark or thermal energy to erode unwanted material in order to create desired shapes.So, the hardness of the material is no longer a dominating factor for EDM process.EDM removes material by discharging an electrical current, normally stored in a capacitor bank, across a small gap between the tool(cathode)and the workpiece(anode)typically in the order of 50 volts/10amps.As shown in Fig.6.1, at the beginning of EDM operation, a high voltage is applied across the narrow gap between the electrode and the workpiece.This high voltage induces an electric field in the insulating dielectric that is present in narrow gap between electrode and workpiece.This causes conducting particles suspended in the dielectric to concentrate at the points of strongest electrical field.When the potential difference between the electrode and the workpiece is sufficiently high, the dielectric breaks down and a transient spark discharges through the dielectric fluid, removing small amount of material from the workpiece surface.The volume of the material removed per spark discharge is typically in the range of 10-5 to 10-6 mm3.The gap is only a few thousandths of an inch, which is maintained at a constant value by the servomechanism that actuates and controls the tool feed.Chemical Machining(CM)
Chemical machining(CM)is a well known non-traditional machining process in which metal is removed from a workpiece by immersing it into a chemical solution.The process is the oldest of the nontraditional processes and has been used to produce pockets and contours and to remove materials from parts having a high strength-to-weight ratio.Moreover, the chemical machining method is widely used to produce micro-components for various industrial applications such as microelectromechanical systems(MEMS)and semiconductor industries.In CM material is removed from selected areas of workpiece by immersing it in a chemical reagents or etchants, such as acids and alkaline solutions.Material is removed by microscopic electrochemical cell action which occurs in corrosion or chemical dissolution of a metal.Special coatings called maskants protect areas from which the metal is not to be removed.This controlled chemical dissolution will simultaneously etch all exposed surfaces even though the penetration rates of the material removed may be only 0.0025-0.1mm/min.The basic process takes many forms: chemical milling of pockets, contours, overall metal removal, chemical blanking for etching through thin sheets;photochemical machining(pcm)for etching by using of photosensitive resists in microelectronics;chemical or electrochemical polishing where weak chemical reagents are used(sometimes with remote electric assist)for polishing or deburring and chemical jet machining where a single chemically active jet is used.A schematic of chemical machining process is shown in Fig.6.2a.Because the etchant attacks the material in both vertical and horizontal directions, undercuts may develop(as shown by the areas under the edges of the maskant in Fig.6.2b).Typically, tolerances of ±10% of the material thickness can be maintained in chemical blanking.In order to improve the production rate, the bulk of the workpiece should be shaped by other processes(such as by machining)prior to chemical machining.Dimensional variations can occur because of size changes in workpiece due to humidity and temperature.This variation can be minimized by properly selecting etchants and controlling the environment in the part generation and the production area in the plant.Electrochemical Machining(ECM)
Electrochemical metal removal is one of the more useful nontraditional machining processes.Although the application of electrolytic machining as a metal-working tool is relatively new, the basic principles are based on Faraday laws.Thus, electrochemical machining can be used to remove electrically conductive workpiece material through anodic dissolution.No mechanical or thermal energy is involved.This process is generally used to machine complex cavities and shapes in high-strength materials, particularly in the aerospace industry for the mass production of turbine blades, jet-engine parts, and nozzles, as well as in the automotive(engines castings and gears)and medical industries.More recent applications of ECM include micromachining for the electronics industry.Electrochemical machining(ECM), shown in Fig.6.3, is a metal-removal process based on the principle of reverse electroplating.In this process, particles travel from the anodic material(workpiece)toward the cathodic material(machining tool).Metal removal is effected by a suitably shaped tool electrode, and the parts thus produced have the specified shape, dimensions, and surface finish.ECM forming is carried out so that the shape of the tool electrode is transferred onto, or duplicated in, the workpiece.The cavity produced is the female mating image of the tool shape.For high accuracy in shape duplication and high rates of metal removal, the process is operated at very high current densities of the order 10-100 A/cm2,at relative low voltage usually from 8 to 30 V, while maintaining a very narrow machining gap(of the order of 0.1 mm)by feeding the tool electrode with a feed rate from 0.1 to 20 mm/min.Dissolved material, gas, and heat are removed from the narrow machining gap by the flow of electrolyte pumped through the gap at a high velocity(5-50 m/s), so the current of electrolyte fluid carries away the deplated material before it has a chance to reach the machining tool.Being a non-mechanical metal removal process, ECM is capable of machining any electrically conductive material with high stock removal rates regardless of their mechanical properties.In particular, removal rate in ECM is independent of the hardness, toughness and other properties of the material being machined.The use of ECM is most warranted in the manufacturing of complex-shaped parts from materials that lend themselves poorly to machining by other, above all mechanical methods.There is no need to use a tool made of a harder material than the workpiece, and there is practically no tool wear.Since there is no contact between the tool and the work, ECM is the machining method of choice in the case of thin-walled, easily deformable components and also brittle materials likely to develop cracks in the surface layer.Laser Beam Machining(LBM)
LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.Although the laser is used as a light amplifier in some applications, its principal use is as an optical oscillator or transducer for converting electrical energy into a highly collimated beam of optical radiation.The light energy emitted by the laser has several characteristics which distinguish it from other light sources: spectral purity, directivity and high focused power density.Laser machining is the material removal process accomplished through laser and target material interactions.Generally speaking, these processes include laser drilling, laser cutting, laser welding, and laser grooving, marking or scribing.Laser machining(Fig.6.4)is localized, non-contact machining and is almost reacting-force free.This process can remove material in very small amount and is said to remove material “atom by atom”.For this reason, the kerf in laser cutting is usually very narrow , the depth of laser drilling can be controlled to less than one micron per laser pulse and shallow permanent marks can be made with great flexibility.In this way material can be saved, which may be important for precious materials or for delicate structures in micro-fabrications.The ability of accurate control of material removal makes laser machining an important process in micro-fabrication and micro-electronics.Also laser cutting of sheet material with thickness less than 20mm can be fast, flexible and of high quality, and large holes or any complex contours can be efficiently made through trepanning.Heat Affected Zone(HAZ)in laser machining is relatively narrow and the re-solidified layer is of micron dimensions.For this reason, the distortion in laser machining is negligible.LBM can be applied to any material that can properly absorb the laser irradiation.It is difficult to machine hard materials or brittle materials such as ceramics using traditional methods, laser is a good choice for solving such difficulties.Laser cutting edges can be made smooth and clean, no further treatment is necessary.High aspect ratio holes with diameters impossible for other methods can be drilled using lasers.Small blind holes, grooves, surface texturing and marking can be achieved with high quality using LBM.Laser technology is in rapid progressing, so do laser machining processes.Dross adhesion and edge burr can be avoided, geometry precision can be accurately controlled.The machining quality is in constant progress with the rapid progress in laser technology.Ultrasonic Machining(USM)
Ultrasonic machining offers a solution to the expanding need for machining brittle materials such as single crystals, glasses and polycrystalline ceramics, and for increasing complex operations to provide intricate shapes and workpiece profiles.This machining process is non-thermal, non-chemical, creates no change in the microstructure, chemical or physical properties of the workpiece and offers virtually stress-free machined surfaces.It is therefore used extensively in machining hard and brittle materials that are difficult to cut by other traditional methods.The actual cutting is performed either by abrasive particles suspended in a fluid, or by a rotating diamond-plate tool.These variants are known respectively as stationary(conventional)ultrasonic machining and rotary ultrasonic machining(RUM).Conventional ultrasonic machining(USM)accomplishes the removal of material by the abrading action of a grit-loaded slurry, circulating between the workpiece and a tool that is vibrated with small amplitude.The form tool itself does not abrade the workpiece;the vibrating tool excites the abrasive grains in the flushing fluid, causing them to gently and uniformly wear away the material, leaving a precise reverse from of the tool shape.The uniformity of the sonotrode-tool vibration limits the process to forming small shapes typically under 100 mm in diameter.The USM system includes the Sonotrode-tool assembly, the generator, the grit system and the operator controls.The sonotrode is a piece of metal or tool that is exposed to ultrasonic vibration, and then gives this vibratory energy in an element to excite the abrasive grains in the slurry.A schematic representation of the USM set-up is shown in Fig.6.5.The sonotrode-tool assembly consists of a transducer, a booster and a sonotrode.The transducer converts the electrical pulses into vertical stroke.This vertical stroke is transferred to the booster, which may amplify or suppress the stroke amount.The modified stroke is then relayed to the sonotrode-tool assembly.The amplitude along the face of the tool typically falls in a 20 to 50 μm range.The vibration amplitude is usually equal to the diameter of the abrasive grit used.The grit system supplies a slurry of water and abrasive grit, usually silicon or boron carbide, to the cutting area.In addition to providing abrasive particles to the cut, the slurry also cools the sonotrode and removes particles and debris from the cutting area.
第四篇:中英文翻譯機(jī)器人
中英文翻譯機(jī)器人
機(jī)器人 工業(yè)機(jī)器人是在生產(chǎn)環(huán)境中用以提高生產(chǎn)效率的工具,它能做常規(guī)的裝配線工作,或能做那些對(duì)于工人來(lái)說(shuō)是危險(xiǎn)的工作,例如,第一代工業(yè)機(jī)器人是用來(lái)在核電站中更換核燃料棒,如果人去做這項(xiàng)工作,將會(huì)遭受有害放射線的輻射。工業(yè)機(jī)器人亦能工作在裝配線上將小元件裝配到一起,如將電子元件安裝在電路印刷板,這樣,工人就能從這項(xiàng)乏味的常規(guī)工作中解放出來(lái)。機(jī)器人也能按程序要求用來(lái)拆除炸彈,輔助殘疾人,在社會(huì)的很多應(yīng)用場(chǎng)合履行職能。機(jī)器人可以認(rèn)為是將手臂末端的工具、傳感器和(或)手爪移到程序指定位置的一種機(jī)器。當(dāng)機(jī)器人到達(dá)位置后,他將執(zhí)行某種任務(wù)。這些任務(wù)可以是焊接、密封、機(jī)器裝料、拆卸以及裝配工作。除了編程以及系統(tǒng)的開(kāi)停之外,這些工作可以在無(wú)人干預(yù)下完成。如下敘述的是機(jī)器人系統(tǒng)基本術(shù)語(yǔ): 機(jī)器人是一個(gè)可編程、多功能的機(jī)器手,通過(guò)給要完成的不同任務(wù)編制各種動(dòng)作,它可以移動(dòng)零件、材料、工具以及特殊裝置。這個(gè)基本定義引導(dǎo)出后續(xù)段落的其他定義,從而描繪出一個(gè)完整的機(jī)器人系統(tǒng)。預(yù)編程位置點(diǎn)是機(jī)器人為完成工作而必須跟蹤的軌跡。在某些位置點(diǎn)上機(jī)器人將停下來(lái)做某寫(xiě)操作,如裝配零件、噴涂油漆或焊接。這些預(yù)編程點(diǎn)貯存在機(jī)器人的貯存器中,并為后續(xù)的連續(xù)操作所調(diào)用,而且這些預(yù)編程點(diǎn)像其他程序數(shù)據(jù)一樣,可在日后隨工作需要而變化。因而,正是這種可編程的特征,一個(gè)工業(yè)機(jī)器人很像一臺(tái)計(jì)算機(jī),數(shù)據(jù)可在這里儲(chǔ)存、后續(xù)調(diào)用與編輯。機(jī)械手上機(jī)器人的手臂,它使機(jī)器人能彎曲、延伸、和旋轉(zhuǎn),提供這些運(yùn)動(dòng)的是機(jī)器手的軸,亦是所謂的機(jī)器人的自由度。一個(gè)機(jī)器人能有 3—16 軸,自由度一詞總是與機(jī)器人軸數(shù)相關(guān)。工具和手爪不是機(jī)器人自身組成部分,但它們安裝在機(jī)器人手臂末端的附件。這些連在機(jī)器人手臂末端的附件可使機(jī)器人抬起工件、點(diǎn)焊、刷漆、電弧焊、鉆孔、打毛刺以及根據(jù)機(jī)器人的要求去做各種各樣的工作。機(jī)器人系統(tǒng)還可以控制機(jī)器人的工作單元,工作單元是機(jī)器人執(zhí)行任務(wù)所處的整體環(huán)境,包括控制器、機(jī)械手、工作平臺(tái)、安全保護(hù)裝置或者傳輸裝置。所有這些為保證機(jī)器人完成自己任務(wù)而必需的裝置都包括在這一工作單元中。另外,來(lái)自外設(shè)的信號(hào)與機(jī)器人通訊,通知機(jī)器人何時(shí)裝配工件、取工件或放工件到傳輸裝置上。機(jī)器人系統(tǒng)有三個(gè)基本部件:機(jī)械手、控制器和動(dòng)力源。A.機(jī)械手 機(jī)械手做機(jī)器人系統(tǒng)中粗重工作,它包括兩個(gè)部分:機(jī)構(gòu)和附件,機(jī)械手也有聯(lián)接附件基座,圖 1 表示了一機(jī)器人基座與附件之間的聯(lián)接情況。圖 1 機(jī)械手基座通常在工作區(qū)域的地基上,有時(shí)基座也可以移動(dòng),在這種情況下基座安裝在導(dǎo)軌或軌道上,允許機(jī)械手從一個(gè)位置移動(dòng)到另外一個(gè)位置。正如前面所提到的那樣,附件從機(jī)器人基座上延伸出來(lái),附件就是機(jī)器人的手臂,它可以是直接型,也可以是軸節(jié)型手臂,軸節(jié)型手臂也是大家所知的關(guān)節(jié)型手臂。機(jī)械臂使機(jī)械手產(chǎn)生各軸的運(yùn)動(dòng)。這些軸連在一個(gè)安裝基座上,然后再連到托架上,托架確保機(jī)械手停留在某一位置。在手臂的末端上,連接著手腕(圖 1),手腕由輔助軸和手腕凸緣組成,手腕是讓機(jī)器人用戶(hù)在手腕凸緣上安裝不同工具來(lái)做不同種工作。機(jī)械手的軸使機(jī)械手在某一區(qū)域內(nèi)執(zhí)行任務(wù),我們將這個(gè)區(qū)域?yàn)闄C(jī)器人的工作單元,該區(qū)域的大小與機(jī)器手的尺寸相對(duì)應(yīng),(圖 2)列舉了一個(gè)典型裝配機(jī)器人的工作單元。隨著機(jī)器人機(jī)械結(jié)構(gòu)尺寸的增加。工作單元的范圍也必須相應(yīng)增加。圖 2 機(jī)械手的運(yùn)動(dòng)由執(zhí)行元件或驅(qū)動(dòng)系統(tǒng)來(lái)控制。執(zhí)行元件或驅(qū)動(dòng)系統(tǒng)允許個(gè)軸在工作單元內(nèi)運(yùn)動(dòng)。驅(qū)動(dòng)系統(tǒng)可用電氣、液壓和氣壓動(dòng)力,驅(qū)動(dòng)系統(tǒng)所產(chǎn)生的動(dòng)力經(jīng)機(jī)構(gòu)轉(zhuǎn)變?yōu)闄C(jī)械能,驅(qū)動(dòng)系統(tǒng)與機(jī)械傳動(dòng)鏈相匹配。有鏈、齒輪和滾珠絲杠組成的機(jī)械傳動(dòng)鏈驅(qū)動(dòng)著機(jī)器人的各軸。B.控制器 機(jī)器人控制器是工作單元的核心??刂破鲀?chǔ)存著預(yù)編程序供調(diào)用、控制外設(shè),及與廠內(nèi)計(jì)算進(jìn)行通訊以滿(mǎn)足產(chǎn)品經(jīng)常更新的需要??刂破饔糜诳刂茩C(jī)器手運(yùn)動(dòng)和在工作單元內(nèi)控制機(jī)器人外設(shè)。用戶(hù)可通過(guò)手持的示教盒將機(jī)械手運(yùn)動(dòng)的程序編入控制器。這些信息儲(chǔ)存在控制器的存儲(chǔ)器中以備后續(xù)調(diào)用,控制器儲(chǔ)存了機(jī)器人系統(tǒng)的所有編程數(shù)據(jù),它能儲(chǔ)存幾個(gè)不同的程序,并且所有這些程序均能編輯??刂破饕竽軌蛟诠ぷ鲉卧獌?nèi)外設(shè)進(jìn)行通信。例如控制器有一個(gè)輸入端,它能標(biāo)識(shí)某個(gè)機(jī)加工操作何時(shí)完成。當(dāng)該加工循環(huán)完成后,輸入端接通,告訴控制器定位機(jī)械手以便能抓取已加工工件,隨后,機(jī)械手抓取一未加工件,將其放置在機(jī)床上。接著,控制器給機(jī)床發(fā)出開(kāi)始加工的信號(hào)??刂破骺梢杂筛鶕?jù)事件順序而步進(jìn)的機(jī)械式輪鼓組成,這種類(lèi)型的控制器可用在非常簡(jiǎn)單的機(jī)械系統(tǒng)中。用于大多數(shù)人系統(tǒng)中的控制器代表現(xiàn)代電子學(xué)的水平,是更復(fù)雜的裝置,即它們是由微處理器操縱的。這些微處理器可以是 8 位,16 位或 32 位處理器。它們可以使得控制器在操縱工程中顯非常柔性??刂破髂芡ㄟ^(guò)通信線發(fā)送信號(hào),使它能與機(jī)械手各軸交流信息,在機(jī)器人的機(jī)械手和控制器之間的雙向交流信息可以保持操作和位置經(jīng)常更新,控制器亦能控制安裝在機(jī)器人手腕上的任何工具。控制器也有與廠內(nèi)各計(jì)算機(jī)進(jìn)行通信的任務(wù),這種通信聯(lián)系使機(jī)器人成為計(jì)算機(jī)輔助制造(CAM)系統(tǒng)的一個(gè)組成部分。存儲(chǔ)器。基于微處理器的系統(tǒng)運(yùn)行時(shí)要與固態(tài)的存儲(chǔ)裝置相連,這些存儲(chǔ)裝置可以是磁泡,隨機(jī)存儲(chǔ)器、軟盤(pán)、磁帶等。每種記憶存儲(chǔ)裝置均能貯存、編輯信息以備后續(xù)調(diào)用和編輯。C.動(dòng)力源 動(dòng)力源是給機(jī)器人和機(jī)器手提供動(dòng)力的單元。傳給機(jī)器人系統(tǒng)的動(dòng)力源有兩種,一種是用于控制器的交流電,另一種是用于驅(qū)動(dòng)機(jī)械手各軸的動(dòng)力源,例如,如果機(jī)器人的機(jī)械手是有液壓和氣動(dòng)驅(qū)動(dòng)的,控制信號(hào)便傳送到這些裝置中,驅(qū)動(dòng)機(jī)器人運(yùn)動(dòng)。對(duì)于每一個(gè)機(jī)器人系統(tǒng),動(dòng)力是用來(lái)操縱機(jī)械手的。這些動(dòng)力可來(lái)源與液壓動(dòng)力源、氣壓動(dòng)力源或電源,這些能源是機(jī)器人工作單元整體的一部分。
robot The industr ial robot is a tool t hat is used in t he manufact ur ing environment to increase product ivit y.It can be used to do rout ine and tedious assembly line jobs, or it can per form jobs t hat might be hazardous to t he human worker.For example ,one of t he first indust r ial robot was used to replace t he nuclear fuel rods in nuclear power plant s.A human doing t his job might be exposed to har mful amount s of radiat ion.The indust r ial robot can also operat e on t he assembly line, putt ing toget her small component s, such as placing electronic component s on a pr int ed circuit board.Thus, t he human worker can be relieved of t he rout ine operat ion of t his t edious t ask.Robot s can also be programmed to defuse bombs, to serve t he handicapped, and to per for m funct ions in numerous applicat ions in our societ y.The robot can be t hought of as a machine t hat will move an endoperat ed.t hese microprocessors are eit her 8-bit , 16-bit ,or 32-bit processors.t his power allows t he controller to be ver y flexible in it s operat ion.The cont roller can send elect ric signals over communicat ion lines t hat allow it to t alk wit h t he var ious axes of t he manipulator.This t wo-way communicat ion bet ween t he robot manipulator and t he cont roller maint ains a const ant updat e of t he end t he operat ion of t he syst em.The cont roller also controls any tooling placed on t he end of t he robot ’s wr ist.The cont roller also has t he job of communicat ing wit h t he different plant comput ers.The communicat ion link est ablishes t he robot as part a comput er-assist ed manufact ur ing(CAM)syst em.As t he basic definit ion st at ed, t he robot is a reprogrammable, mult ifunct ional manipulator.Therefore, t he controller must contain some of memor y stot age.The microprocessor-based syst ems operates in conjunct ion wit h solid-st at e divices.These memor y devices may be magnet ic bubbles, random-access memony, floppy disks,or magnet ic tape.Each memor y storage device stores program infor mat ion fir or for edit ing.C.power suppy The power supply is t he unit t hat supplies power to t he controller and t he manipulator.The t ype of power are delivered to t he robot ic syst em.One t ype of power is t he AC power for operat ion of t he cont roller.The ot her t ype of power is used for dr iving t he var ious axes of t he manipulator.For example, if t he robot manipulator is cont rolled by hydraulic or pneumat ic drives, cont rol singals are sent to t hese devices causing mot ion of t he robot.For each robot ic syst em, power is required to operat e t he manipulator.This power can be developed from eit her a hydraulic power source, a pneumat ic power source,or an elect ric power source.There power sources are part of t he total component s of t he robot ic work cell.
第五篇:建筑結(jié)構(gòu)中英文翻譯
A acceptable quality:合格質(zhì)量 acceptance lot:驗(yàn)收批量 aciera:鋼材
admixture:外加劑
against slip coefficient between friction surface of high-strength bolted connection:高強(qiáng)度螺栓摩擦面抗滑移系數(shù) aggregate:骨料 air content:含氣量
air-dried timber allowable ratio of height to sectional thickness of masonry wall or column allowable slenderness ratio of steel member allowable slenderness ratio of timber compression member容許長(zhǎng)細(xì)比 allowable stress range of fatigue allowable ultimate tensile strain of reinforcement allowable value of crack width allowable value of deflection of structural member allowable value of deflection of timber bending member度容許值
allowable value of deformation of steel member allowable value of deformation of structural member allowable value of drift angle of earthquake resistant structure amplified coefficient of eccentricity anchorage anchorage length of steel bar approval analysis during construction stage arch arch with tie rod arch area of shear plane area of transformed section aseismic design assembled monolithic concrete structure automatic welding auxiliary steel bar
B backfilling plate:氣干材
:砌體墻、柱容許高厚比
:鋼構(gòu)件容許長(zhǎng)細(xì)比
:受壓木構(gòu)件:疲勞容許應(yīng)力幅
:鋼筋拉應(yīng)變限值 :裂縫寬度容許值
:構(gòu)件撓度容許值 :受彎木構(gòu)件撓:鋼構(gòu)件變形容許值 :構(gòu)件變形容許值 :抗震結(jié)構(gòu)層間位移角限值
:偏心距增大系數(shù) :錨具
:鋼筋錨固長(zhǎng)度
:施工階段驗(yàn)算 :拱
:拉捍拱
—shaped roof truss:拱形屋架 :剪面面積
:換算截面面積 :建筑抗震設(shè)計(jì)
:裝配整體式混凝土結(jié)構(gòu) :自動(dòng)焊接 :架立鋼筋 :墊板 balanced depth of compression zone:界限受壓區(qū)高度 balanced eccentricity:界限偏心距 bar splice:鋼筋接頭 bark pocket:夾皮 batten plate:綴板 beam:次梁
bearing plane of notch:齒承壓面(67)bearing plate:支承板(52)bearing stiffener:支承加勁肋(52)bent-up steel bar:彎起鋼筋(35)block:砌塊(43)block masonry:砌塊砌體(44)block masonry structure:砌塊砌體結(jié)構(gòu)(41)blow hole:氣孔(62)board:板材(65)bolt:螺栓(54)bolted connection:(鋼結(jié)構(gòu))螺栓連接(59)bolted joint:(木結(jié)構(gòu))螺栓連接(69)bolted steel structure:螺栓連接鋼結(jié)構(gòu)(50)bonded prestressed concrete structure:有粘結(jié)預(yù)應(yīng)力混凝土結(jié)構(gòu)(24)bow:順彎(71)brake member:制動(dòng)構(gòu)件(7)breadth of wall between windows:窗間墻寬度(46)brick masonry:磚砌體(44)brick masonry column:磚砌體柱(42)brick masonry structure:磚砌體結(jié)構(gòu)(41)brick masonry wall:磚砌體墻(42)broad—leaved wood:闊葉樹(shù)材(65)building structural materials:建筑結(jié)構(gòu)材料(17)building structural unit:建筑結(jié)構(gòu)單元(building structure:建筑結(jié)構(gòu)(2 built—up steel column:格構(gòu)式鋼柱(51 bundled tube structure:成束筒結(jié)構(gòu)(3 burn—through:燒穿(62 butt connection:對(duì)接(59 butt joint:對(duì)接(70)butt weld:對(duì)接焊縫(60)
C calculating area of compression member:受壓構(gòu)件計(jì)算面積(67)calculating overturning point:計(jì)算傾覆點(diǎn)(46)calculation of load-carrying capacity of member:構(gòu)件承載能力計(jì)算(10)camber of structural member:結(jié)構(gòu)構(gòu)件起拱(22)cantilever beam :挑梁(42)cap of reinforced concrete column:鋼筋混凝土柱帽(27)carbonation of concrete:混凝土碳化(30)cast-in—situ concrete slab column structure :現(xiàn)澆板柱結(jié)構(gòu) cast-in—situ concrete structure:現(xiàn)澆混凝土結(jié)構(gòu)(25)cavitation:孔洞(39)cavity wall:空斗墻(42)cement:水泥(27)cement content:水泥含量(38)cement mortar:水泥砂漿(43)characteriseic value of live load on floor or roof:樓面、屋面活荷載標(biāo)準(zhǔn)值(14)characteristi cvalue o fwindload:風(fēng)荷載標(biāo)準(zhǔn)值(16)characteristic value of concrete compressive strength:混凝土軸心抗壓強(qiáng)度標(biāo)準(zhǔn)值(30)characteristic value of concrete tensile strength:混凝土軸心抗拉標(biāo)準(zhǔn)值(30)characteristic value of cubic concrete compressive strength:混凝土立方體抗壓強(qiáng)度標(biāo)準(zhǔn)值(29)characteristic value of earthquake action:地震作用標(biāo)準(zhǔn)值(16)characteristic value of horizontal crane load:吊車(chē)水平荷載標(biāo)準(zhǔn)值(15)characteristic value of masonry strength:砌體強(qiáng)度標(biāo)準(zhǔn)值(44)characteristic value of permanent action·:永久作用標(biāo)準(zhǔn)值(14)characteristic value of snowload:雪荷載標(biāo)準(zhǔn)值(15)characteristic value of strength of steel:鋼材強(qiáng)度標(biāo)準(zhǔn)值(55)characteristic value of strength of steel bar:鋼筋強(qiáng)度標(biāo)準(zhǔn)值(31)characteristic value of uniformly distributed live load:均布活標(biāo)載標(biāo)準(zhǔn)值(14)
characteristic value of variable action:可變作用標(biāo)準(zhǔn)值(14)characteristic value of vertical crane load:吊車(chē)豎向荷載標(biāo)準(zhǔn)值(15)charaeteristic value of material strength:材料強(qiáng)度標(biāo)準(zhǔn)值(18)checking section of log structural member·,:原木構(gòu)件計(jì)算截面(67)chimney:煙囪(3)circular double—layer suspended cable:圓形雙層懸索(6)circular single—layer suspended cable:圓形單層懸索(6)circumferential weld:環(huán)形焊縫(60)classfication for earthquake—resistance of buildings·:建筑結(jié)構(gòu)抗震設(shè)防類(lèi)別(9)clear height:凈高(21)clincher:扒釘(?0)coefficient of equivalent bending moment of eccentrically loaded steel memher(beam-column):鋼壓彎構(gòu)件等效彎矩系數(shù)(58)cold bend inspection of steelbar:冷彎試驗(yàn)(39)cold drawn bar:冷拉鋼筋(28)cold drawn wire:冷拉鋼絲(29)cold—formed thin—walled sectionsteel:冷彎薄壁型鋼(53)cold-formed thin-walled steel structure·‘:冷彎薄壁型鋼結(jié)構(gòu)(50)cold—rolled deformed bar:冷軋帶肋鋼筋(28)column bracing:柱間支撐(7)combination value of live load on floor or roof:樓面、屋面活荷載組合值(15)compaction:密實(shí)度(37)compliance control:合格控制(23)composite brick masonry member:組合磚砌體構(gòu)件(42)composite floor system:組合樓蓋(8)composite floor with profiled steel sheet:壓型鋼板樓板(8)composite mortar:混合砂漿(43)composite roof truss:組合屋架(8)compostle member:組合構(gòu)件(8)compound stirrup:復(fù)合箍筋(36)compression member with large eccentricity·:大偏心受壓構(gòu)件(32)compression member with small eccentricity·:小偏心受壓構(gòu)件(32)compressive strength at an angle with slope of grain:斜紋承壓強(qiáng)度(66)compressive strength perpendicular to grain:橫紋承壓強(qiáng)度(66)concentration of plastic deformation:塑性變形集中(9)conceptual earthquake—resistant design:建筑抗震概念設(shè)計(jì)(9)concrete:混凝土(17)concrete column:混凝土柱(26)concrete consistence:混凝土稠度(37)concrete floded—plate structure:混凝土折板結(jié)構(gòu)(26)concrete foundation:混凝土基礎(chǔ)(27)concrete mix ratio:混凝土配合比(38)concrete wall:混凝土墻(27)concrete-filled steel tubular member:鋼管混凝土構(gòu)件(8)conifer:針葉樹(shù)材(65)coniferous wood:針葉樹(shù)材(65)connecting plate:連接板(52)connection:連接(21)connections of steel structure:鋼結(jié)構(gòu)連接(59)connections of timber structure:木結(jié)構(gòu)連接(68)consistency of mortar:砂漿稠度(48)constant cross—section column:等截面柱(7)construction and examination concentrated load:施工和檢修集中荷載(15)continuous weld:連續(xù)焊縫(60)core area of section:截面核芯面積(33)core tube supported structure:核心筒懸掛結(jié)構(gòu)(3)corrosion of steel bar:鋼筋銹蝕(39)coupled wall:連肢墻(12)coupler:連接器(37)coupling wall—beam :連梁(12)coupling wall—column...:墻肢(12)coursing degree of mortar:砂漿分層度(48)cover plate:蓋板(52)covered electrode:焊條(54)crack:裂縫(?0)crack resistance:抗裂度(31)crack width:裂縫寬度(31)crane girder:吊車(chē)梁(?)crane load:吊車(chē)荷載(15)creep of concrete:混凝土徐變(30)crook:橫彎(71)cross beam:井字梁(6)cup:翹彎
curved support:弧形支座(51)cylindrical brick arch:磚筒拱(43)
D decay:腐朽(71)decay prevention of timber structure:木結(jié)構(gòu)防腐(70)defect in timber:木材缺陷(70)deformation analysis:變形驗(yàn)算(10)degree of gravity vertical for structure or structural member·:結(jié)構(gòu)構(gòu)件垂直度(40)degree of gravity vertical forwall surface:墻面垂直度(49)degree of plainness for structural memer:構(gòu)件平整度(40)degree of plainness for wall surface:墻面平整度(49)depth of compression zone:受壓區(qū)高度(32)depth of neutral axis:中和軸高度(32)depth of notch:齒深(67)design of building structures:建筑結(jié)構(gòu)設(shè)計(jì)(8)design value of earthquake-resistant strength of materials:材料抗震強(qiáng)度設(shè)計(jì)值(1 design value of load—carrying capacity of members·:構(gòu)件承載能力設(shè)計(jì)值(1 designations 0f steel:鋼材牌號(hào)(53 designvalue of material strength:材料強(qiáng)度設(shè)計(jì)值(1 destructive test:破損試驗(yàn)(40 detailing reintorcement:構(gòu)造配筋(35 detailing requirements:構(gòu)造要求(22 diamonding:菱形變形(71)diaphragm:橫隔板(52 dimensional errors:尺寸偏差(39)distribution factor of snow pressure:屋面積雪分布系數(shù) dogspike:扒釘(70)double component concrete column:雙肢柱(26)dowelled joint:銷(xiāo)連接(69)down-stayed composite beam:下?lián)问浇M合粱(8)ductile frame:延性框架(2)dynamic design:動(dòng)態(tài)設(shè)計(jì)(8)E earthquake-resistant design:抗震設(shè)計(jì)(9:
earthquake-resistant detailing requirements:抗震構(gòu)造要求(22)effective area of fillet weld:角焊縫有效面積(57)effective depth of section:截面有效高度(33)effective diameter of bolt or high-strength bolt·:螺栓(或高強(qiáng)度螺栓)有效直徑(57)
effective height:計(jì)算高度(21)effective length:計(jì)算長(zhǎng)度(21)effective length of fillet weld:角焊縫有效計(jì)算長(zhǎng)度(48)effective length of nail:釘有效長(zhǎng)度(56)effective span:計(jì)算跨度(21)effective supporting length at end of beam:梁端有效支承長(zhǎng)度(46)effective thickness of fillet weld:角焊縫有效厚度(48)elastic analysis scheme:彈性方案(46)elastic foundation beam:彈性地基梁(11)elastic foundation plate:彈性地基板(12)elastically supported continuous girder·:彈性支座連續(xù)梁(u)elasticity modulus of materials:材料彈性模量(18)elongation rate:伸長(zhǎng)率(15)embeded parts:預(yù)埋件(30)enhanced coefficient of local bearing strength of materials·:局部抗壓強(qiáng)度提高系數(shù)(14)entrapped air:含氣量(38)equilibrium moisture content:平衡含水率(66)equivalent slenderness ratio:換算長(zhǎng)細(xì)比(57)equivalent uniformly distributed live load·:等效均布活荷載(14)etlectlve cross—section area of high-strength bolt·:高強(qiáng)度螺栓的有效截面積(58)ettectlve cross—section area of bolt:螺栓有效截面面積(57)euler’s critical load:歐拉臨界力(56)euler’s critical stress:歐拉臨界應(yīng)力(56)excessive penetration:塌陷(62)
F fiber concrete:纖維混凝仁(28)filler plate:填板門(mén)2)fillet weld:角焊縫(61)final setting time:終凝時(shí)間()finger joint:指接(69)fired common brick:燒結(jié)普通磚(43)fish eye:白點(diǎn)(62)fish—belly beam:角腹式梁(7)fissure:裂縫(?0)flexible connection:柔性連接(22)flexural rigidity of section:截面彎曲剛度(19)flexural stiffness of member:構(gòu)件抗彎剛度(20)floor plate:樓板(6)floor system:樓蓋(6)four sides(edges)supported plate:四邊支承板(12)frame structure:框架結(jié)構(gòu)(2)frame tube structure:?jiǎn)慰蛲步Y(jié)構(gòu)(3)frame tube structure:框架—簡(jiǎn)體結(jié)構(gòu)(2)frame with sidesway:有側(cè)移框架(12)frame without sidesway:無(wú)側(cè)移框架(12)frange plate:翼緣板(52)friction coefficient of masonry:砌體摩擦系數(shù)(44)full degree of mortar at bed joint:砂漿飽滿(mǎn)度(48)function of acceptance:驗(yàn)收函數(shù)(23)G gang nail plate joint:釘板連接()glue used for structural timberg:木結(jié)構(gòu)用膠 glued joint:膠合接頭
glued laminated timber:層板膠合木(¨)glued laminated timber structure:層板膠合結(jié)構(gòu)‘61)grider:主梁((㈠ grip:夾具
grith weld:環(huán)形焊縫(6÷))groove:坡口
gusset plate:節(jié)點(diǎn)板(52)
H hanger:吊環(huán)
hanging steel bar:吊筋 heartwood :心材 heat tempering bar:熱處理鋼筋(28)height variation factor of wind pressure:風(fēng)壓高度變化系數(shù)(16)heliral weld:螺旋形僻縫
high—strength bolt:高強(qiáng)度螺栓
high—strength bolt with large hexagon bea:大六角頭高強(qiáng)度螺栓 high—strength bolted bearing type join:承壓型高強(qiáng)度螺栓連接,high—strength bolted connection:高強(qiáng)度螺栓連接
high—strength bolted friction—type joint:摩擦型高強(qiáng)度螺栓連接 high—strength holted steel slsteel structure:高強(qiáng)螺栓連接鋼結(jié)構(gòu) hinge support:鉸軸支座(51)hinged connection:鉸接(21)hlngeless arch:無(wú)鉸拱(12)hollow brick:空心磚(43)hollow ratio of masonry unit:塊體空心率(46)honeycomb:蜂窩(39)hook:彎鉤(37)hoop:箍筋(36)hot—rolled deformed bar:熱軋帶肋鋼筋(28)hot—rolled plain bar:熱軋光圓鋼筋(28)hot-rolled section steel:熱軋型鋼(53)hunched beam:加腋梁(?)I impact toughness:沖擊韌性(18)impermeability:抗?jié)B性(38)inclined section:斜截面(33)inclined stirrup:斜向箍筋(36)incomplete penetration:未焊透(61)incomplete tusion:未溶合(61)incompletely filled groove:未焊滿(mǎn)(61)indented wire:刻痕鋼絲(29)influence coefficient for load—bearing capacity of compression member:受壓構(gòu)件承載能力影響系數(shù)(46)influence coefficient for spacial action :空間性能影響系數(shù)(46)initial control:初步控制(22)insect prevention of timber structure:木結(jié)構(gòu)防蟲(chóng)(?o)inspection for properties of glue used in structural member:結(jié)構(gòu)用膠性能檢驗(yàn)(71)inspection for properties of masnory units:塊體性能檢驗(yàn)(48)inspection for properties of mortar:砂漿性能檢驗(yàn)(48)inspection for properties of steelbar:鋼筋性能檢驗(yàn)(39)integral prefabricated prestressed concrete slab—column structure:整體預(yù)應(yīng)力板柱結(jié)構(gòu)(25)intermediate stiffener:中間加勁肋(53)intermittent weld:斷續(xù)焊縫(60)
J joint of reinforcement:鋼筋接頭(35)K key joint:鍵連接(69)kinetic design:動(dòng)態(tài)設(shè)計(jì)(8)knot:節(jié)子(木節(jié))(70)L laced of battened compression member lacing and batten elements lacing bar lamellar tearing lap connectlon lapped length of steel bar large pannel concrete structure large-form cocrete structure lateral bending lateral displacement stiffness of storey lateral displacement stiffness of structure lateral force resistant wallstructure leg size of fillet weld length of shear plane lift light weight aggregate concrete limit of acceptance limitimg value for local dimension of masonry structure limiting value for sectional dimension limiting value for supporting length limiting value for total height of masonry structure限值(47)linear expansion coeffcient lintel load bearing wall load-carrying capacity per bolt load(56)load log log timberstructure long term rigidity of member longitude horizontal bracing longitudinal steel bar:格構(gòu)式鋼柱(51):綴材(綴件)(51):綴條(51)
:層狀撕裂(62):疊接(搭接)(59)
:鋼筋搭接長(zhǎng)度(36)
:混凝土大板結(jié)構(gòu)(25):大模板結(jié)構(gòu)(26):側(cè)向彎曲(40)
:樓層側(cè)移剛度(20)·:結(jié)構(gòu)側(cè)移剛度(20):抗側(cè)力墻體結(jié)構(gòu)(12):角焊縫焊腳尺寸(57):剪面長(zhǎng)度(67)—slab structure:升板結(jié)構(gòu)(25)
:輕骨料混凝土(28):驗(yàn)收界限(23)·:砌體結(jié)構(gòu)局部尺寸限值(47)
:截面尺寸限值(47):支承長(zhǎng)度限值(47)·:砌體結(jié)構(gòu)總高度:線膨脹系數(shù)(18):過(guò)梁(7)
:承重墻(7)
:?jiǎn)蝹€(gè)普通螺栓承載能力(56)—carrying capacity per high—strength holt:?jiǎn)蝹€(gè)高強(qiáng)螺桂承載能力—carrying capacity per rivet:?jiǎn)蝹€(gè)鉚釘承載能力(55):原木(65)
:原木結(jié)構(gòu)(64)
:構(gòu)件長(zhǎng)期剛度(32):縱向水平支撐(5):縱向鋼筋(35)longitudinal stiffener:縱向加勁肋(53)longitudinal weld:縱向焊縫(60)losses of prestress:‘預(yù)應(yīng)力損失(33)lump material:塊體(42)
M main axis:強(qiáng)軸(56)main beam·:主梁(6)major axis:強(qiáng)軸(56)manual welding:手工焊接(59)manufacture control:生產(chǎn)控制(22)map cracking:龜裂(39)masonry:砌體(17)masonry lintel:磚過(guò)梁(43)masonry member:無(wú)筋砌體構(gòu)件(41)masonry units:塊體(43)masonry—concrete structure:磚混結(jié)構(gòu)(¨)masonry—timber structure:磚木結(jié)構(gòu)(11)mechanical properties of materials·:材料力學(xué)性能(17)melt—thru:燒穿(62)method of sampling:抽樣方法(23)minimum strength class of masonry:砌體材料最低強(qiáng)度等級(jí)(47)minor axls·:弱軸(56)mix ratio of mortar:砂漿配合比(48)mixing water:拌合水(27)modified coefficient for allowable ratio of height to sectionalthickness of masonry wall :砌體墻容許高厚比修正系數(shù)(47)modified coefficient of flexural strength for timber curved mem—:弧形木構(gòu)件抗彎強(qiáng)度修正系數(shù)(68)modulus of elasticity of concrete:混凝土彈性模量(30)modulus of elasticity parellel to grain:順紋彈性模量(66)moisture content:含水率(66)moment modified factor:彎矩調(diào)幅系數(shù) monitor frame:天窗架 mortar:砂漿
multi—defence system of earthquake—resistant building·:多道設(shè)防抗震建筑
multi—tube supported suspended structure:多筒懸掛結(jié)構(gòu)
N nailed joint:釘連接,net height:凈高l net span:凈跨度
net water/cementratio:凈水灰比
non-destructive inspection of weld:焊縫無(wú)損檢驗(yàn) non-destructive test:非破損檢驗(yàn) non-load—bearingwall:非承重墻
non—uniform cross—section beam:變截面粱
non—uniformly distributed strain coefficient of longitudinal tensile reinforcement:縱向受拉鋼筋應(yīng)變不均勻系數(shù) normal concrete:普通混凝土 normal section notch and tooth joint number of sampling O obligue section oblique one open web roof truss ordinary concrete ordinary steel bar orthogonal fillet weld outstanding width of flange outstanding width of stiffener over-all stability reduction coefficient of steel beam系數(shù)(58)
overlap overturning or slip resistance analysis
P padding plate partial penetrated butt weld partition penetrated butt weld percentage of reinforcement perforated brick pilastered wall pit pith plain concrete structure plane hypothesis plane structure plane trussed lattice grids:正截面
:齒連接 :抽樣數(shù)量 :斜截面
—angle fillet weld:斜角角焊縫
—way reinforced(or prestressed)concrete slab‘‘:?jiǎn)蜗虬?:空腹屋架,:普通混凝土(28):普通鋼筋(29)
:直角角焊縫(61)
:翼緣板外伸寬度(57):加勁肋外伸寬度(57)·:鋼梁整體穩(wěn)定:焊瘤(62)
:抗傾覆、滑移驗(yàn)算(10):墊板(52)
:不焊透對(duì)接焊縫(61):非承重墻(7)
:透焊對(duì)接焊縫(60):配筋率(34):多孔磚(43):帶壁柱墻(42)·:凹坑(62):髓心(?o)
:素混凝土結(jié)構(gòu)(24):平截面假定(32):平面結(jié)構(gòu)(11)
:平面桁架系網(wǎng)架(5)plank:板材(65)plastic adaption coefficient of cross—section:截面塑性發(fā)展系數(shù)(58)plastic design of steel structure:鋼結(jié)構(gòu)塑性設(shè)計(jì)(56)plastic hinge·:塑性鉸(13)plastlcity coefficient of reinforced concrete member in tensile zone:受拉區(qū)混凝土塑性影響系數(shù)(34)plate—like space frame:干板型網(wǎng)架(5)plate—like space truss:平板型網(wǎng)架(5)plug weld:塞焊縫(60)plywood:膠合板(65)plywood structure:膠合板結(jié)構(gòu)(64)pockmark:麻面(39)polygonal top-chord roof truss:多邊形屋架(4)post—tensioned prestressed concrete structure:后張法預(yù)應(yīng)力混凝土結(jié)構(gòu)(24)precast reinforced concrete member:預(yù)制混凝土構(gòu)件(26)prefabricated concrete structure:裝配式混凝土結(jié)構(gòu)(25)presetting time:初凝時(shí)間(38)prestressed concrete structure:預(yù)應(yīng)力混凝土結(jié)構(gòu)(24)prestressed steel structure:預(yù)應(yīng)力鋼結(jié)構(gòu)(50)prestressed tendon:預(yù)應(yīng)力筋<29)pre—tensioned prestressed concrete structure·:先張法預(yù)應(yīng)力混凝土結(jié)構(gòu)(24)primary control:初步控制(22)production control:生產(chǎn)控制(22)properties of fresh concrete:可塑混凝土性能(37)properties of hardened concrete:硬化混凝土性能(38)property of building structural materials:建筑結(jié)構(gòu)材料性能(17)purlin“—””—:檁條(4)
Q qlue timber structurer:膠合木結(jié)構(gòu)(㈠)quality grade of structural timber:木材質(zhì)量等級(jí)(?0)quality grade of weld:焊縫質(zhì)量級(jí)別(61)quality inspection of bolted connection:螺栓連接質(zhì)量檢驗(yàn)(63)quality inspection of masonry:砌體質(zhì)量檢驗(yàn)(48)quality inspection of riveted connection:鉚釘連接質(zhì)量檢驗(yàn)(63)quasi—permanent value of live load on floor or roof,:樓面、屋面活荷載準(zhǔn)永久值(15)R radial check:輻裂(70)ratio of axial compressive force to axial compressive ultimate capacity of section:軸壓比(35)ratio of height to sectional thickness of wall or column:砌體墻柱高、厚比(48)ratio of reinforcement:配筋率(34)ratio of shear span to effective depth of section:剪跨比(35)redistribution of internal force:內(nèi)力重分布(13)reducing coefficient of compressive strength in sloping grain for bolted connection:螺栓連接斜紋承壓強(qiáng)度降低系數(shù)(68)reducing coefficient of liveload:活荷載折減系數(shù)(14)reducing coefficient of shearing strength for notch and tooth connection:齒連接抗剪強(qiáng)度降低系數(shù)(68)regular earthquake—resistant building:規(guī)則抗震建筑(9)reinforced concrete deep beam:混凝土深梁(26)reinforced concrete slender beam:混凝土淺梁(26)reinforced concrete structure:鋼筋混凝土結(jié)構(gòu)(24)reinforced masonry structure:配筋砌體結(jié)構(gòu)(41)reinforcement ratio:配筋率(34)reinforcement ratio per unit volume:體積配筋率(35)relaxation of prestressed tendon:預(yù)應(yīng)筋松弛(31)representative value of gravity load:重力荷載代表值(17)resistance to abrasion:耐磨性(38)resistance to freezing and thawing:抗凍融性(39)resistance to water penetration·:抗?jié)B性(38)reveal of reinforcement:露筋(39)right—angle filletweld:直角角焊縫(61)rigid analysis scheme:剛性方案(45)rigid connection:剛接(21)rigid transverse wall:剛性橫墻(42)rigid zone:剛域(13)rigid-elastic analysis scheme:剛彈性方案(45)rigidity of section:截面剛度(19)rigidly supported continous girder:剛性支座連續(xù)梁(11)ring beam:圈梁(42)rivet:鉚釘(55)riveted connecction:鉚釘連接(60)riveted steel beam:鉚接鋼梁(52)riveted steel girder:鉚接鋼梁(52)riveted steel structure:鉚接鋼結(jié)構(gòu)(50)rolle rsupport:滾軸支座(51)rolled steel beam:軋制型鋼梁(51)roof board:屋面板(3)roof bracing system:屋架支撐系統(tǒng)(4)roof girder:屋面梁(4)roof plate:屋面板(3)roof slab:屋面板(3)roof system:屋蓋(3)roof truss:屋架(4)rot:腐朽(71)round wire:光圓鋼絲(29)
S safety classes of building structures:建筑結(jié)構(gòu)安全等級(jí)(9)safetybolt:保險(xiǎn)螺栓(69)sapwood:邊材(65)sawn lumber+A610:方木(65)sawn timber structure:方木結(jié)構(gòu)(64)saw-tooth joint failure:齒縫破壞(45)scarf joint:斜搭接(70)seamless steel pipe:無(wú)縫鋼管(54)seamless steel tube:無(wú)縫鋼管(54)second moment of area of tranformed section:換算截面慣性矩(34)second order effect due to displacement:撓曲二階效應(yīng)(13)secondary axis:弱軸(56)secondary beam:次粱(6)section modulus of transformed section:換算截面模量(34)section steel:型鋼(53)semi-automatic welding:半自動(dòng)焊接(59)separated steel column:分離式鋼柱(51)setting time:凝結(jié)時(shí)間(38)shake:環(huán)裂(70)shaped steel:型鋼(53)shapefactorofwindload:風(fēng)荷載體型系數(shù)(16)shear plane:剪面(67)shearing rigidity of section:截面剪變剛度(19)shearing stiffness of member:構(gòu)件抗剪剛度(20)short stiffener:短加勁肋(53)short term rigidity of member:構(gòu)件短期剛度(31)shrinkage:干縮(71)shrinkage of concrete:混凝干收縮(30)silos:貯倉(cāng)(3)skylight truss:天窗架(4)slab:樓板(6)slab—column structure:板柱結(jié)構(gòu)(2)slag inclusion:夾渣(61)sloping grain:‘斜紋(70)slump:坍落度(37)snow reference pressure:基本雪壓(16)solid—web steel column:實(shí)腹式鋼柱(space structure:空間結(jié)構(gòu)(11)space suspended cable:懸索(5)spacing of bars:鋼筋間距(33)spacing of rigid transverse wall:剛性橫墻間距(46)spacing of stirrup legs:箍筋肢距(33)spacing of stirrups:箍筋間距(33)specified concrete:特種混凝上(28)spiral stirrup:螺旋箍筋(36)spiral weld:螺旋形焊縫(60)split ringjoint:裂環(huán)連接(69)square pyramid space grids:四角錐體網(wǎng)架(5)stability calculation:穩(wěn)定計(jì)算(10)stability reduction coefficient of axially loaded compression:軸心受壓構(gòu)件穩(wěn)定系數(shù)<13)stair:樓梯(8)static analysis scheme of building:房屋靜力汁算方案(45)static design:房屋靜力汁算方案(45)statically determinate structure:靜定結(jié)構(gòu)(11)statically indeterminate structure:超靜定結(jié)構(gòu)(11)sted:鋼材(17)steel bar:鋼筋(28)steel column component:鋼柱分肢(51)steel columnbase:鋼柱腳(51)steel fiber reinforced concrete structure·:鋼纖維混凝土結(jié)構(gòu)(26)steel hanger:吊筋(37)steel mesh reinforced brick masonry member:方格網(wǎng)配筋磚砌體構(gòu)件(41)steel pipe:鋼管(54)steel plate:鋼板(53)steel plateelement:鋼板件(52)steel strip:鋼帶(53)steel support:鋼支座(51)steel tie:拉結(jié)鋼筋(36)steel tie bar for masonry:砌體拉結(jié)鋼筋(47)steel tube:鋼管(54)steel tubular structure:鋼管結(jié)構(gòu)(50)steel wire:鋼絲(28)stepped column:階形柱(7)stiffener:加勁肋(52)stiffness of structural member:構(gòu)件剛度(19)stiffness of transverse wall:橫墻剛度(45)stirrup:箍筋(36)stone:石材(44)stone masonry:石砌體(44)stone masonry structure:石砌體結(jié)構(gòu)(41)storev height:層高(21)straight—line joint failure:通縫破壞(45)straightness of structural member:構(gòu)件乎直度(71)strand:鋼絞線(2,)strength classes of masonry units:塊體強(qiáng)度等級(jí)(44)strength classes of mortar:砂漿強(qiáng)度等級(jí)(44)strength classes of structural steel:鋼材強(qiáng)度等級(jí)(55)strength classes of structural timber:木材強(qiáng)度等級(jí)(66)strength classes(grades)of concrete:混凝土強(qiáng)度等級(jí)(29)strength classes(grades)of prestressed tendon:預(yù)應(yīng)力筋強(qiáng)度等級(jí)(30)strength classes(grades)of steel bar :普通鋼筋強(qiáng)度等級(jí)(30)strength of structural timber parallel to grain:木材順紋強(qiáng)度(66)strongaxis:強(qiáng)軸(56)structural system composed of bar:”桿系結(jié)構(gòu)(11)structural system composed of plate:板系結(jié)構(gòu)(12)structural wall:結(jié)構(gòu)墻(7)superposed reinforced concrete flexural member:疊合式混凝土受彎構(gòu)件(26)suspended crossed cable net:雙向正交索網(wǎng)結(jié)構(gòu)(6)suspended structure:懸掛結(jié)構(gòu)(3)swirl grain:渦紋(?1)
T tensile(compressive)rigidity of section:截面拉伸(壓縮)剛度(19)tensile(compressive)stiffness of member:構(gòu)件抗拉(抗壓)剛度(20)tensile(ultimate)strength of steel:鋼材(鋼筋)抗拉(極限)強(qiáng)度(18)test for properties of concrete structural members:構(gòu)件性能檢驗(yàn)(40): thickness of concrete cover:混凝土保護(hù)層厚度(33)thickness of mortarat bed joint:水平灰縫厚度(49)thin shell:薄殼(6)three hinged arch:三鉸拱(n)tie bar:拉結(jié)鋼筋(36)tie beam,‘:系梁(22)tie tod:系桿(5)tied framework:綁扎骨架(35)timber:木材(17)timber roof truss:木屋架(64)tor-shear type high-strength bolt:扭剪型高強(qiáng)度螺栓(54)torsional rigidity of section:截面扭轉(zhuǎn)剛度(19)torsional stiffness of member:構(gòu)件抗扭剛度(20)total breadth of structure:結(jié)構(gòu)總寬度(21)total height of structure:結(jié)構(gòu)總高度(21)total length of structure:結(jié)構(gòu)總長(zhǎng)度(21)transmission length of prestress:預(yù)應(yīng)力傳遞長(zhǎng)度(36)transverse horizontal bracing:橫向水平支撐(4)transverse stiffener·:橫向加勁肋(53)transverse weld:橫向焊縫(60)transversely distributed steelbar:橫向分布鋼筋(36)trapezoid roof truss:梯形屋架(4)triangular pyramid space grids:三角錐體網(wǎng)架(5)triangular roof truss:三角形屋架(4)trussed arch:椽架(64)trussed rafter:桁架拱(5)tube in tube structure:筒中筒結(jié)構(gòu)(3)tube structure:簡(jiǎn)體結(jié)構(gòu)(2)twist:扭彎(71)two hinged arch:雙鉸拱(11)two sides(edges)supported plate:兩邊支承板(12)two—way reinforced(or prestressed)concrete slab:混凝土雙向板(27)
U ultimate compressive strain of concrete’”:混凝土極限壓應(yīng)變(31)unbonded prestressed concrete structure:無(wú)粘結(jié)預(yù)應(yīng)力混凝土結(jié)構(gòu)(25)undercut:咬邊(62)uniform cross—section beam:等截面粱(6)unseasoned timber:濕材(65)upper flexible and lower rigid complex multistorey building·:上柔下剛多層房屋(45)upper rigid lower flexible complex multistorey building·:上剛下柔多層房屋(45)Vvalue of decompression prestress :預(yù)應(yīng)力筋消壓預(yù)應(yīng)力值(33)value of effective prestress:預(yù)應(yīng)筋有效預(yù)應(yīng)力值(33)verification of serviceability limit states· ”:正常使用極限狀態(tài)驗(yàn)證(10)verification of ultimate limit states :承載能極限狀態(tài)驗(yàn)證(10)vertical bracing:豎向支撐(5)vierendal roof truss:空腹屋架(4)visual examination of structural member:構(gòu)件外觀檢查(39)visual examination of structural steel member:鋼構(gòu)件外觀檢查(63)visual examination of weld:焊縫外觀檢查(62)W wall beam:墻梁(42)wall frame:壁式框架(門(mén))wall—slab structure:墻板結(jié)構(gòu)(2)warping:翹曲(40),(71)warping rigidity of section:截面翹曲剛度(19)water retentivity of mortar:砂漿保水性(48)water tower:水塔(3)water/cement ratio·:水灰比(3g)weak axis·:弱軸(56)weak region of earthquake—resistant building:抗震建筑薄弱部位(9)web plate:腹板(52)weld:焊縫(6[))weld crack:焊接裂紋(62)weld defects:焊接缺陷(61)weld roof:焊根(61)weld toe:焊趾(61)weldability of steel bar:鋼筋可焊性(39)welded framework:焊接骨架()welded steel beam:焊接鋼梁(welded steel girder:焊接鋼梁(52)welded steel pipe:焊接鋼管(54)welded steel strueture:焊接鋼結(jié)構(gòu)(50)welding connection·:焊縫連接(59)welding flux:焊劑(54)welding rod:焊條(54)welding wire:焊絲(54)wind fluttering factor:風(fēng)振系數(shù)(16)wind reference pressure:基本風(fēng)壓(16)wind—resistant column:抗風(fēng)柱(?)wood roof decking:屋面木基層(64)Y yield strength(yield point)of steel:鋼材(鋼筋)屈服強(qiáng)度(屈服點(diǎn))