A different approach to the analysis of data in life-tests of laser diodes

A different reading of the available I–V curves is proposed for laser diodes whose characteristics display some degradation. In particular, the usual monitoring of the optical power P and of the threshold current I_th is complemented by the inspection of two more parameters, which separately or jointly contribute to the general variation of I_th. These two parameters are related to the simplest laser model, made of an ideal diode that is voltage-clamped under operating conditions, and are completely defined by those same standard measurements that lead to evaluate I_th. A different definition of the failure modes, and a deeper insight in the possible failure mechanisms are derived. Combined voltage and optical power monitoring during constant-current life-tests is also proposed as a more discriminating measurement than usually considered.     

Functional specifications and evaluation of commercially available laser diodes for optical space links

Commercially available GaAlAs laser diodes have been tested to predict their behaviour in intersatellite communications. Three types of device with various structures have been investigated: Sharp lasers, Hitachi lasers (single longitudinal mode emission in c.w. operation) and Ortel lasers (multi-longitudinal modes). Two modulation schemes were applied to devices (NRZ and 4-PPM), corresponding to the two possible modulation formats selected for ISL experiments. Each laser had an average power output of 30 mW, whatever the modulation mode. The output signal, emission spectrum and beam divergence were measured. A reduction in peak power was found with some devices. Multimode spectra were detected under 4-PPM modulation.     

A model for the prediction of EDFA gain in a space radiation environment

Erbium-doped fiber amplifiers (EDFAs) were irradiated with /sup 60/Co /spl gamma/-rays up to a total dose of 3 kGy. Gain measurements and 1310-nm absorption were achieved during the irradiation to characterize the radiation-induced damage on the fiber. A model based on classical equations was developed to perform accurate predictions of the effects of radiation on EDFAs. This model was shown to be consistent with the experiment at various dose rates and temperatures, therefore allowing the extrapolation to a space environment simulation.     

A software tool for the design of high power PiN diodes based on the numerical study of the reverse characteristics

A physically based model of power PiN diodes was developed to simulate the reverse voltage behavior with purpose of design optimization for specific application. The model includes process simulation and 2D drift-diffusion simulation of the defined geometrical diode structure. The process simulation was adjusted to obtain the same doping profile measured on a known sample. Since bulk silicon and dopants used in high power device production are different from those used in VLSI, various analytical models of impurity diffusion phenomena were considered and parameters calibration was carried out within the range found in the literature to obtain the best fit with measurements. Impact ionization coefficients of the reverse biased diode model were tuned by comparison with measurements on a reference device and exploited to study the dependence of breakdown voltage vs. various technological parameters.A simulation campaign for many different diode structures was conducted.An ad hoc interpolation algorithm was developed and applied for using measurement and simulation results in quick design of diode structures for specific application.     

基于马氏链的网络节点重要性评价方法

针对网络攻击与防御中资源分配时需对网络节点进行重要性评估的问题,提出了基于网络拓扑图的马氏链模型。并指出若网络中存在经过奇数次跳转能够回到自己的节点时,此网络图的马氏链就是遍历的,且其极限概率为该节点的度比上所有节点度之和。然后根据上述模型,提出把其它节点以最短路径到达该节点概率之和作为节点重要性评判指标。最后进行了实验分析,实验证实了所建模型的正确性,以及节点重要性评价算法的准确性。     

线阵非成像式激光辐射源定向方法

探测报知激光威胁源的方向是激光告警必不可少的一项技术指标.从激光告警技术发展的角度,提出了一种采用线阵探测器利用非成像方式测定激光辐射源方向的方法.通过将多个线阵探测器在接收系统中进行布局,首先获得激光源在多个不同一维坐标方向上的角度信息;然后利用坐标转换将这些一维角度信息合成相对于接收系统的二维角度信息,最后根据激光...     

空间环境模拟系统光学窗口组件设计

光学窗口组件作为空间环境模拟系统与外界的接口,是不可或缺的重要组成部件。空间环境模拟系统共有两类光学窗口组件,针对两类光窗组件分别进行了结构方案设计。通过强度理论公式对光窗组件进行了强度校核,采用有限元分析软件计算了压力对光学玻璃表面变形的影响,并分析了光学玻璃表面变形对光窗组件光学性能的影响。计算结果表明:工作过程中,通光口径为Φ150 mm的光窗组件光学玻璃产生的应力为0.82 MPa;通光口径为Φ350 mm的光窗组件光学玻璃产生的应力为3.28 MPa,均满足强度要求。利用Zemax软件分析得到,通光口径为Φ150 mm的光窗组件波像差PV值为λ/8;通过计算得到通光口径为Φ350 mm的光窗组件在Φ170 mm~Φ190 mm环带区域内光程差为0.8 nm,均满足光学性能要求。因此,光学窗口组件结构方案设计既满足强度和可靠性要求,又满足光学性能要求,整个光学窗口组件安全可靠。     

Thermal buffer materials for enhancement of device performance of organic light emitting diodes fabricated by laser imaging process

Laser Induced Thermal Imaging (LITI) is a laser addressed thermal patterning technology with unique advantages such as an excellent uniformity of transfer film thickness, a capability of multilayer stack transfer and a possibility to fabricate high resolution as well as large-area display. Nevertheless, it has been an obstacle to use such a laser imaging process as a commercial technology so far because of serious deterioration of the device performances plausibly due to a re-orientation of the molecular stacking especially in the emitting layer during thermal transfer process. To improve device performances, we devised a new concept to suppress the thermal degradation during such kind of thermal imaging process by using a high molecular weight small molecular species with large steric hindrance as well as high thermostability as a thermal buffer layer to realize highly efficient LITI devices. As a result, we obtained very high relative efficiency (by EQE) up to 91.5% at 1000 cd/m² from the LITI devices when we utilize 10-(naphthalene-2-yl)-3-(phenanthren-9-yl)spiro[benzo[ij]tetraphene-7,9′-fluorene] as a thermal buffer material.     

The nonhomogeneous Poisson process — A model for the reliability of complex repairable systems

Generally the reliability of complex repairable systems is characterized by time dependent rate of occurence of failures. The corresponding mathematical model is the nonhomogeneous Poisson process. This paper comprises mathematical properties of the nonhomogeneous Poisson process, some frequently used types of failure intensity functions, and some results and aspects of statistical inference. The given models are applicable to the reliability of complex repairable systems, software systems, and to the reliability growth problemacy.     

FUCEM: futuristic cooperation evaluation model using Markov process for evaluating node reliability and link stability in mobile ad hoc network

The cooperation between the nodes is one of the potential factor for successful routing in mobile ad hoc networks. The non-cooperative behaviour of the node disturbs the routing as well as degrades network performances. The non-cooperativeness is due to the resource constraint characteristics of a mobile node. The battery energy is an important constraint of a node because it exhausts after some period. On the other side, the mobility of nodes also affects routing performances. Hence, this work concentrates on evaluating cooperation of a node by probing future node energy and mobility. This paper proposes a futuristic cooperation evaluation model (FUCEM) for evaluating node reliability and link stability to establish effective routing. The FUCEM model examines influencing factors of cooperation and state transition of nodes using Markov process. Node reliability and link stability manipulated through the Markov process. The Markov process helps in fixing the upper and lower bounds of the cooperation and calculates the cooperation factor. The NS2 simulator simulates the proposed work and evaluates performance results with different scenarios. The result indicates that the proposed FUCEM has 13–21% higher packet delivery ratio than other algorithms. The remaining energy of the nodes increases to 6–7% as compared with the existing algorithms in a higher mobility scenario. Further, it significantly improves the results of routing overhead and average end-to-end delay than the existing models.

     

A protocol for piggy-backing on Markov based wavelength reservation in WDM optical networks

During lightpath establishment in WDM optical networks, two important steps, other than routing, are: wavelength selection and wavelength reservation. If two or more lightpaths select the same wavelength, wavelength collision occurs. The basic reason for collision is the non-availability of the updated wavelength usage information. Markov based wavelength selection guesses a unique wavelength in advance, where each node periodically broadcasts its adjoining link usage information at a regular interval T. But, at any intermediate time t (0<t<T), all nodes use the old update which is already outdated by time t. If T is large, the problem becomes severe. To get around this problem without introducing any extra overhead, we propose a novel technique where the normal control packets, passing through the relevant nodes during [0,T], can be leveraged to carry the desired link state information. This may allow us even to increase the value of T (thereby reducing broadcast overhead), when control packets are frequent in the network. We apply the proposed modification to our previous work on Markov selection Split Reservation Protocol (MSRP) and call the modified protocol Fast updated MSRP (FMSRP). In fast update, we “piggy-back” normal control packets with link usage information, in addition to the usual periodic broadcasting of the same at every T. It obviously increases the chance for the nodes to get the latest information of link usage. We have simulated FMSRP and compared it with MSRP and also with another current best protocol (i.e., Markov based Backward Reservation Protocol) to show that the blocking probability for FMSRP improves considerably over them in some regions of offered load.     

基于灰色层次分析法的雷达对抗训练电磁环境复杂度评估方法研究

针对复杂电磁环境对雷达对抗训练的影响,提出了基于灰色层次分析法的电磁环境复杂度评估方法,实现了客观与主观的统一。实践证明,该方法具有一定的参考价值。     

低功率He-Ne激光血管内照射治疗下肢静脉栓塞临床观察

目的通过采用低功率氦氖激光血管内照射,治疗下肢静脉栓塞。方法按常规进行静脉穿刺,将氦氖激光纤针留置在血管内,即激光光斑在血管内血液中照射,探讨其疗效。结果患者通过氦氖激光血管内照射后有效率为10 0 % ,治愈率为5 4.5 5 % ,显效率为3 6.45 % ,好转为9%。结论患者经过治疗后,可使临床症状减轻或消失,均取得满意效果。     

激光扫平仪光电自动检测系统中扫描激光线的图像处理

对激光扫平仪光电自动检测系统中扫描激光线图像处理的实际情况，先采用隔行中值滤波来对图像进行预处理。然后，结合图像采集卡动态采集图像的特点，在分析扫描线区域的灰度值的基础上，提出根据图像采集卡奇、偶场采集结果的不同来对图像进行二值化处理的方法，实现了对扫描激光线图像的自动处理，获得了满意的效果。     

The ultrasonic wedge/wedge bonding process investigated using in situ real-time amplitudes from laser vibrometer and integrated force sensor

The ultrasonic transversal force transmitted to a chip during ultrasonic bonding is derived from measurements of the vibration amplitude at the tool tip and the die edge. To proof the derivation, the transversal force is measured as well by means of a microsensor, which is sensitive to the stress field in the silicon die. The force measured by the microsensor is further referred to as “y-force” To Al-metalized test pads with the integrated microsensors, AlSi1 wire of 25 μm diameter was bonded using a wedge/wedge autobonder. Measurements of the vibration amplitudes and the y-force during bonding were conducted for nine different bonding parameter settings of force and ultrasound (us) amplitude. They confirm a theory for the friction cleaning phase as it was described earlier and will be partially presented here. Compared to earlier measurements of Au-ball-bonds, the results largely show the same behavior and imply that us wedge bonding and thermosonic ball bonding are similar processes. Furthermore, the data approves former interpretations of the bonding process starting with a stiction phase. A clear break off point was found in all pad amplitude measurements, which is followed by a friction plateau that implicates the need of a minimum friction cleaning power.The discussion made in this paper is interesting for a bond process control system. The transversal force reflects the important stages of the bond process and contains the information to suit as a control signal. But it is impractical to measure the transversal force in situ under the wedge in industrial production, where chip, substrate and bonding table create a complex setup with a high geometric variety. An indirect measurement of the transversal force via the tool tip amplitude opens up new possibilities for gaining an efficient control variable, because the geometry and the properties of the bonding machine are well defined. As a first step it is shown by correlating vibration measurements with microsensor signals, that the tool tip amplitude measured by laser vibrometer contains all of the necessary information needed to control the bond process. From that point, process integrable measurement systems - which are cheaper, more handy and more fail safe than the laser vibrometer - might be developed.     

Constellation expanded active interference cancellation technique for suppression of out-of-band radiation in OFDM based cognitive radios

Cognitive radio is a novel technology to address the problem of spectrum under-utilization, by allowing the secondary users to dynamically use the spectrum of the primary users. OFDM is a potential candidate for the physical layer of cognitive radio, due to its inherent features of spectrum shaping, spectrum analysis and robustness to multipath. OFDM based cognitive radio, however suffers from out-of-band radiation (OOBR). In cognitive radio, suppression of OOBR is much more important as the interference to the primary users needs to be kept to the minimum possible level. In the literature, time and frequency characteristics of the transmitted signal have been exploited to minimize the OOBR. In this paper, we investigate the possibility of combining merits of the constellation expansion (CE) technique and the active interference cancellation (AIC) technique for suppression of OOBR. We show through simulations that the joint technique based on CE and AIC achieves much better OOBR reduction, with a slight degradation in error performance.     

A mathematical model for slip phenomenon in a cavity-filling process of nanoimprint lithography

Squeeze flow theory has been used as an effective tool to clarify how and which process conditions determine cavity-filling behavior in nanoimprint lithography (NIL). Conventional squeeze flow models used in NIL research fields have assumed no-slip conditions at the solid-to-liquid boundaries, that is, at the stamp-to-polymer or polymer-to-substrate boundaries. The no-slip assumptions are often violated, however, in micrometer- to nanometer-scale fluid flow. It is therefore necessary to adopt slip or partial slip boundary conditions. In this paper, an analytical mathematical model for the cavity-filling process of NIL that takes into account slip or partial slip boundary conditions is derived using squeeze flow theory. Velocity profiles, pressure distributions, imprinting forces, and evolutions of residual thickness can be predicted using this analytical model. This paper also aims to elucidate how far the slip phenomenon is able to promote the process rate.     

基于空间一致性的复杂场景钢坯端面字符定位

复杂场景中的字符目标定位是进行字符目标提取与识别的关键步骤,字符目标定位的准确程度决定着后续字符识别的正确与否。本文提出了一种基于空间一致性特征的复杂场景钢坯字符目标定位新方法。先对复杂场景钢坯图像进行分割,跟踪并标记分割图中每一个连通区域,然后根据钢坯端面字符在空间位置上排列的一致性,提取连通区域目标的质心点特征,并寻找排列成一条线的质心点,同时比较它们之间的区域面积及相互距离等特征,快速定位目标字符。对多幅实际复杂场景钢坯端面字符图像进行处理,结果表明我们提出的方法具有可行性和实用性。