二极管泵浦被动调Q Nd:GdVO4/KTP绿光激光器

报道了一种二极管泵浦的被动调QNd：GdVO4／KTP腔内倍频绿光激光器，在注入泵浦功率为7W时，得到了平均功率为109mW、脉冲宽度为30ns、重复频率为40kHz，峰值功率为91W的被动调Q脉冲绿光输出。     

全固态被动调Q单频绿光激光器的研究

报道了一种LD近贴泵浦、KTp晶体腔内倍频的NdYVO4/CrYAG/KTP结构高重复频率被动调Q绿光激光器.当腔内加入布氏片时,获得了单频运转.在注入泵浦功率为800mW时,得到平均功率43 mW、脉冲宽度26.4 ns、重复频率39.3 kHz、峰值功率41.4 W的被动调Q单频脉冲绿激光输出.     

LD抽运被动调Q Nd:YAG/LBO绿光激光器

报道了一种LD抽运Nd:YAG,LBO腔内倍频,Cr:YAG被动调Q结构的绿光激光器.在注入抽运功率为600 mW时,得到平均功率27 mW,脉冲宽度15.2 ns,重复频率16.4 kHz,峰值功率108.1 W的被动调Q脉冲绿光输出.     

LD泵浦Nd∶YVO_4/Cr∶YAG被动调Q绿光激光器

报道了一种 LD近贴泵浦、KTP晶体腔内倍频的 Nd∶ YVO4/Cr∶ YAG结构高重复频率被动调 Q绿光激光器。在注入泵浦功率为 75 0 m W时 ,得到平均功率 86m W、脉冲宽度2 6.6ns、重复频率 79.2 k Hz、峰值功率 41 .1 W的被动调 Q脉冲绿光输出     

被动调Q绿光激光器稳定输出方法的研究

对一台LD泵浦的Cr∶YAG被动调Q绿光激光器 ,采取Cr∶YAG晶片按布氏角放置的方法控制用以引发Q脉冲形成的“噪声” ,实现了绿激光脉冲的稳定输出。在泵浦功率 80 0mW时 ,获得平均功率 4 8mW、脉冲宽度 2 6 .7ns、重复频率 4 2 .1kHz、峰值功率 4 2 .7W的绿激光脉冲输出 ,4h工作脉冲能量、峰值和周期稳定性均优于± 0 .5 %。     

LD抽运被动调Q Nd∶YAG/LBO绿光激光器

报道了一种LD抽运Nd∶YAG ,LBO腔内倍频 ,Cr∶YAG被动调Q结构的绿光激光器。在注入抽运功率为6 0 0mW时 ,得到平均功率 2 7mW ,脉冲宽度 15 2ns,重复频率 16 4kHz ,峰值功率 10 8 1W的被动调Q脉冲绿光输出。     

LD泵浦Nd:Gd0.42Y0.58VO4/Cr4 :YAG被动调Q锁模激光器

报道了一种激光二极管（LD）泵浦Nd：Gd0.42Y0.58VO4/Cr^4＋：YAG/KTP结构的被动调Q锁模绿光激光器,采用简单、结构紧凑的平凹腔设计.在注入泵浦功率7.8 W时,调Q锁模绿光平均输出功率为200 mW,调制深度约为40%,脉冲包络重复频率200 kHz,半高宽度100 ns.     

基于SESAM的被动调Q光纤光栅掺铒光纤激光器

提出并研究了一种线性腔结构的基于 SESAM(半导体可饱和吸收镜)的被动调 Q光纤光栅掺铒光纤激光器,该激光器无需采用偏振控制器控制激光偏振态,简化了调 Q 激光器的结构。该激光器的中心波长为1549.975 nm,阈值功率为143 mW,斜效率为1.2%。当泵浦功率从149 mW增加到180 mW时,脉冲重复频率从5.431 kHz增加到9.778 kHz。当泵浦功率为155 mW时,激光脉冲的能量为5.6 nJ,重复频率为6.538 kHz,脉冲宽度为40μs。     

Cr4+:YAG被动调Q4倍频全固态紫外激光器的研究

设计了LD泵浦Cr4+:YAG被动调Q的全固态Nd:YAG脉冲红外激光器。腔外首先经过焦距为100mm的聚焦透镜,将 1064nm的红外激光耦合到长为9mm的KTP2倍频晶体中,得到平均功率为29mW的脉冲绿光。然后将532nm的脉冲绿光经过焦距为30mm的聚焦透镜,耦合到长为4mm的BBO4倍频晶体上,获得了峰值功率为7.3W,平均功率为1.1mW,重复频率为12.5kHz,脉冲宽度为 12ns的266nm紫外激光,其绿光 紫外光的转换效率为3.8%,红外光紫外光的转换效率为0.7%。     

Cr:YAG被动调Q全固态473 nm蓝光激光器

报道了LD抽运，Cr:YAG被动调Q，Nd:YAG/LBO结构的473 nm全固态蓝光激光器。在注入抽运功率为1600 mW时，得到平均功率9.1mW，脉冲宽度14.5 ns，重复频率4.19 kHz，峰值功率近150 W的被动调Q蓝光脉冲输出。     

Consecutive-k, r-out-of-n:DFM systems

A dual failure mode (DFM) system is a system whose components are subject to two different kinds of failure (three-state units). In this paper, a new system (the consecutive-k, r-out-of-n:DFM system) is introduced by considering an extension of the well-known and much studied consecutive-k-out-of-n:F system to a dual failure mode environment. Recursive formulae are provided for the evaluation of the reliability of a consecutive-k, r-out-of-n:DFM system with unequal component failure probabilities. Finally, some simple upper and lower reliability bounds are established which provide quite adequate approximations, at least for highly reliable systems.     

Electrical,photovoltaic and photosensitivity characteristics of p-ZnTe:N/CdTe:Mg/n-CdTe:I/GaAs for photodiode applications

In this work, heterojunctions of p-ZnTe:N/CdTe:Mg/n-CdTe:I/GaAs for photovoltaic and photodiode application were grown epitaxially by using molecular beam system. Current-voltage profile of the heterojunction device was studied in dark and under various illumination intensities. The obtained photocurrent is found to depend on the light intensity. The main heterojunction parameters, such as shunt and series resistances, the barrier height and the ideality factor were extracted from the current-voltage profile using diverse methods at ambient temperature. Values of the barrier height and the series resistance were obtained from Cheung's functions. A large value of the series resistance causes the non-ideal characteristics of current–voltage measurements. The study of the current-voltage characteristics of high voltage region suggests a predominant space charge limited mechanism. Moderate values of short circuit current and open circuit voltage were obtained through a light intensity of 140 mW/cm², a current and voltages of 0.336 mA and 370 mV, respectively. The high photosensitivity and responsivity for the current under illumination condition suggests that the prepared heterojunction device could be employed as a photodiode sensor.     

Analytical solution of the state-dependent Erlangian queue: M/Ej/1/N with balking

The objective of this paper is to derive the analytical solution of the truncated single-channel Erlangian queue M/E_j/1/N with balking and state-dependent service rate. The researcher deduces p_ns the probability of n units in the system (n = 1, 2, 3,…, N) and the customer in service being in phase backwards, i.e. j is the first phase of service and 1 is the last (a customer leaving phase 1 actually leaves the system). p₀ is the probability of an empty system by using the iterative method. At the end of this paper some special cases are obtained.     

Second generation I/SUP 2/L/MTL: a 20 ns process/structure

A high performance, second generation I/SUP 2/L/MTL gate for digital LSI applications with TTL compatibility has successfully been designed, characterized, and demonstrated fully functional over a wide current range and the military temperature range of -55 to 125/spl deg/C. Performance is measured using an in-line five-collector gate having one end injector. The gate performed with the following characteristics at 100 /spl mu/A injector current: /spl beta//SUB U//SUP eff//spl ges/4 for all collectors at 25/spl deg/C and /spl ges/2.5 at -55/spl deg/C, /spl alpha//SUB rec///spl alpha//SUB F//spl cong/0.58 and /spl tau/~/SUB d/=18-20 ns from -55 to 125/spl deg/C, and a speed-power product of 1.4 pJ at 25/spl deg/C. At low injector currents, a constant speed-power product of 0.36 pJ at 25/spl deg/ was obtained.     

Image/video communications: joint source/channel coding

Transmission of image/video messages over communication networks is becoming a standard way of communication due to very efficient compression algorithms that reduce required channel capacity to an acceptable level. However, all compression standard techniques are strongly sensitivitive to channel disturbances and their application is suitable only for practically noiseless channels. In standard noisy channels, the effect of errors on a compressed data bit stream can be divided into two categories: systematic errors defined by the structure of data blocks, and random errors caused by amplitude changes of transmitted components. A systematic error can be detected at the receiver through control of the data stream structure and corrected by error concealment methods or by automatic repeat request (ARQ) procedures. Random errors, noise and burst‐like errors, as well as impulse noise, should be controlled through channel coding. It is reasonable that an integrated source and channel coding methods should be preferred and should give better coding performance. In this paper, a new framework for an image/video coding approach has been presented in which the source and channel coding is integrated in a unique procedure. Image compression is performed in a standard way of the JPEG algorithm based on discrete cosine transform (DCT) and error control coding is based on the real/complex‐number (N,M) BCH code using discrete Fourier transform (DFT) specified with zeros in the time domain, i.e. with roots in the frequency domain. Efficiency of the proposed method is tested on two examples, an one‐dimensional real‐valued time sequence coded by real‐number (20,16) BCH code using DFT, and an example of an image coded by complex (10,8) BCH code using DFT with the correction ability of up to 8 impulses per transmitted 8×8 block. In addition, two decoding methods based on Berlekamp–Massey algorithm (BMA) and the minimum‐norm algorithm (MNA) have also compared. Copyright © 1999 John Wiley & Sons, Ltd.     

The symmetrical /spl eta/-/spl kappa/ distribution: a general fading distribution

This paper specializes and parameterizes the general result presented elsewhere in the literature in order to introduce, fully characterize, and investigate the Symmetrical /spl eta/-/spl kappa/ Distribution, a general distribution used to describe the statistical variation of the envelope in a fast fading environment. It proposes estimators for the involved parameters and uses field measurements to validate the distribution. In spite of its specialization, the Symmetrical /spl eta/-/spl kappa/ Distribution still includes, as special cases, important distributions such as Rayleigh, Rice, Hoyt, Nakagami-q, and One-Sided Gaussian. The fact that the Symmetrical /spl eta/-/spl kappa/ Distribution has one more parameter than the well-known distributions renders it more flexible. Of course, in situations in which those distributions included in it give good results a better fitting is given by the Symmetrical /spl eta/-/spl kappa/ Distribution. In addition, in many other situations in which these distributions give poor results a good fitting may be found through the Symmetrical /spl eta/-/spl kappa/ Distribution. More specifically, its nonmonomodal feature finds applications in several circumstances, examples of which are given in this paper.     

网络协议体系结构-OSI/RM和TCP/IP及其比较

详细介绍了构建网络体系的2种标准OSI RM和TCP IP协议,指出了它们的应用范围和工作特点,并对它们的相同点和不同点作了比较深入的探讨,对于学习网络协议具有很强的参考意义和指导价值。     

Electrical analysis of Al/ZnO/p-Si,Al/PMMA/p-Si and Al/PMMA/ZnO/p-Si structures: Comparison study

Al/ZnO/p-Si, Al/PMMA/p-Si and Al/PMMA/ZnO/p-Si structures were fabricated. Based on the measured current–voltage (C–V) and capacitance–voltage curves, the electrical characteristics of these heterostructures such as ideality factor, barrier height and series resistance of each structure were analyzed and then compared with those of Al/PMMA/ZnO/p-Si. According to C–V measurement, it was found that the Al/PMMA/ZnO/p-Si structure indicates the better electronic performance rather than other structures. The obtained results represent low series resistance (19.3 Ω) after coating with polymethyl methacrylate (PMMA) over ZnO/p-Si heterojunction structure for Al/PMMA/ZnO/p-Si heterostructure.