PMD in high-bit-rate transmission and means for its mitigation

Polarization-mode dispersion (PMD) prevents the cost-effective upgrading of fiber networks to 40 and sometimes even to 10 Gbit/s. This paper reviews recent progress in its mitigation and compensation and points out where more research is needed. Electronic PMD mitigation is preferable at 10 Gbit/s, due to its low cost, even though it is accompanied by a considerable residual penalty. A lot of work takes place in the field of optical PMD compensation. Among the numerous detection methods for first-order PMD, we prefer a purely electronic, hence low-cost, arrival time detection method, with a linear readout and ps-sensitivity. Surprisingly, the most easily detectable higher order of PMD is the third order, indicated by a slope steepness difference. Both methods rely on a polarization scrambler at the transmitter side, which can be shared. Regarding PMD compensators, LiNbO/sub 3/ devices are probably needed to guarantee a sufficient speed. A distributed PMD compensator allows to integrate a number of polarization transformers and differential group delay sections on one chip, thereby exactly emulating the way how the fiber accumulates, but in reverse order and orientation. We report on progress in using these devices, including their use for PMD compensation in a 40-Gbit/s carrier-suppressed return-to-zero differential phase-shift keying experiment. More work is needed to perfection the device, and to implement a fast endless polarization control. The theory of the distributed PMD compensator lends itself to a new definition of higher order PMD by a Fourier expansion of mode conversion, as an alternative to the familiar Taylor expansion of the PMD vector.     

Scalability and process induced variation analysis of polarity controlled silicon nanowire transistor

In this paper, we present scalability and process induced variation analysis of polarity gate silicon nanowire field-effect transistor. 3D simulation results show that the PGFET offers significant reduction in short channel effects and variability due to utilization of uniform lightly doped silicon nanowire (SiNW) as compare to highly doped silicon nanowire in junctionless transistors. The performance parameters were evaluated for different device geometries, such as variation in SiNW radius, equivalent oxide thickness, channel length and spacer length. Sensitivity analysis shows that the PGFET exhibits less dependence towards gate length in comparison to other device parameters. It is seen that ON to OFF current ratio variation with silicon nanowire thickness is lower for PGFET as compared to JLFET. The threshold voltage roll-off and sensitivity towards intrinsic delay in PGFET is much lower than its counterpart device.     

一起发电机内漏氢事件分析处理及预防

河南许昌热电厂2号机组在运行中,发电机内冷水箱含氢量超高报警,经分析检查为发电机励磁机端定子绝缘引水管交叉接触,管壁振动磨损,造成氢气泄漏。在检修中更换了引水管,并提出相应的防范措施,为同类故障的处理提供参考。     

基于网络分析法(ANP)的水电工程风险分析及其应用

水电工程项目在开发建设过程中往往面临着来自技术、经济、自然和社会环境等诸多方面的风险和干扰,其风险因素又难以量化且他们之间相互关联、相互影响,本文针对此问题,提出了基于网络分析法(ANP)对水电工程风险进行分析.建立了风险因素多准则、多层次的ANP结构模型,并对模型的求解进行了详细的阐述.最后,以某水电工程为例,应用此方法求得风险因素总排序,结果表明ANP能够比较有效地处理多种风险因素之间复杂影响关系,从而发现了其主要关键的风险因素,为工程项目的风险控制和管理提供了重要的参考.     

电力隧道渗漏水成因分析及控制技术

介绍电力隧道渗漏水及其他缺陷的特点,制定了针对性的应急预案。在电力隧道运营期渗漏水治理方面,提出要控制隧道的不均匀沉降,采用注浆等方式加固隧道周围土体的控制技术。     

Triple‐junction effect and its electric field relaxation in three dielectrics

This paper analyzes the electric field distribution near a wedge‐like edge in arrangements consisting of three dielectrics using analytical and numerical methods. The electric potential behaves exponentially as rⁿ (r is the distance from the edge) near the edge, leading to an infinitely high field with decreasing r for all cases. The value of the analytically derived exponent n agreed well with that obtained from the numerical field calculations. It has also been demonstrated that rounded contact of the spacer with a zero contact angle can make the electric field constant without showing an exponential rise near the edge. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 1– 8, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20670     

Analysis of independent gate operation in Si nano tube FET and threshold prediction model using 3D numerical simulation

In this paper, silicon nanotube field effect transistors (SiNT-FETs) are investigated for independent gate operation using 3D numerical simulation. The parameters, \(\mathrm{I_{ON} , I_{OFF}, V_{T}}\), and the unity gain cut-off frequency \(\mathrm{(f_{T}}\)) are studied in the independent-gate mode. The SiNT-FET we have considered has two gates, namely outer and inner gates, and can be simultaneously driven or independently driven. The physical gate oxide thicknesses of the outer and inner gates of the device are to be converted into effective gate oxide thicknesses due to the non-Euclidean geometry associated with the tube structure. The effective gate oxide thicknesses are different for the same outer and inner physical gate oxide thickness. Since the inner and outer gates are asymmetric, the device parameters extracted at the outer and inner gates are different. Since the independent gate operation allows dynamic threshold voltage adjustment, a model to predict the threshold voltage also known as the threshold voltage sensitivity model is developed for the SiNT device by modifying the double gate FinFET model. These models are verified by TCAD simulation results to validate their accuracy.     

小山电站2号机推力轴承漏油原因分析及处理

分析了松江河发电厂小山电站2号机推力轴承漏油的原因是由于油的紊流和推力轴承密封结构不合理造成的,在检修期间,通过降低油槽油位、改变推力油槽密封结构等方法对推力轴承漏油进行了综合性的处理,最终解决了推力轴承漏油的缺陷,保证了机组的安全稳定运行。     

锅炉暖风器泄漏原因分析及解决措施

包头第三热电厂300 MW机组锅炉一、二次风暖风器经常发生泄漏,疏水回收不畅。对其进行改造：将暖风器改为套管结构,更换了换热器,提高了暖风器标高。改造后,空预器入口风温能维持在20℃以上,再未发生暖风器泄漏事故,疏水回收顺畅,且降低了一次风机、送风机的电耗。     

回转式空气预热器漏风原因分析及解决对策

针对回转式空气预热器的漏风率高的问题,文章介绍了一种回转式空气预热器检修的方法,提出了降低回转式空气预热器漏风率的10种对策。通过与习惯的做法比较,现行的方法效果突出,推广应用证实,漏风率可控制在6%~7%。     

浅述漏风对锅炉的危害及消除措施

漏风对锅炉运行的经济性和设备的安全性都有很大影响,该文指出漏风对设备的危害,分析了漏风对经济性的影响,列举了常见的漏风部位,提出了消除漏风的措施和建议。     

柠檬酸化学清洗中沉淀的产生及其控制

针对采用柠檬酸进行热力设备化学清洗时易产生沉淀的问题,通过试验模拟实际清洗条件,研究了沉淀的类型、产生的条件、沉淀产生的机理,并提出了控制措施。研究表明:柠檬酸清洗产生沉淀是因为清洗液中高浓度的Fe2+与未电离的柠檬酸结合形成柠檬酸亚铁,超过了其溶度积常数而产生沉淀。在一定的清洗条件下(初始柠檬酸浓度、pH值、温度),影响沉淀的主要因素为Fe2+浓度,因此,建议:在采用柠檬酸化学清洗前,根据实际清洗系统条件,通过试验确定极限Fe2+浓度;也可加入专用防沉淀剂抑制沉淀的产生。     

海水作为冷却介质的汽轮机凝汽器泄漏原因及对策

分析了海水作为冷却介质的汽轮机凝汽器发生泄漏的原因,指出了可能导致的危害及如何采取科学有效的措施进行处理,并针对可能导致泄漏的因素提出了预防措施,确保机组能长期安全稳定运行。     

频谱分析仪测量相位噪声及测量不确定度分析

相位噪声是电子测量中的一个重要指标,相噪指标的好坏直接影响着整个系统的性能。测试相位噪声的方法有几种,然而,每种测试方法都有各自的优缺点。因此,根据实际的需要来选择适当的测试方法就尤为重要。本文主要是通过实验来讨论用频谱分析来测量相位噪声的方法,并对其测量的结果,应用不确定度理论给出了相应的测量不确定度的分析。     

A new modeling of loading margin and its sensitivities using rectangular voltage coordinates in voltage stability analysis

This paper presents new mathematical models to compute the loading margin, as well as to perform the sensitivity analysis of loading margin with respect to different electric system parameters. The innovative idea consists of evaluating the performance of these methods when the power flow equations are expressed with the voltages in rectangular coordinates. The objective is to establish a comparative process with the conventional models expressed in terms of power flow equations with the voltages in polar coordinates. IEEE test system and a South-Southeastern Brazilian network are used in the simulations.     

420t/h锅炉省煤器泄漏原因分析及其改造方案的探讨

连州发电厂420t／h燃煤锅炉投产运行了两年多,其省煤器泄漏现象相当严重。为此,对省煤器泄漏的原因进行了分析,详细分析了烟气流速、飞灰浓度和受热面布置形式等对省煤器磨损的影响。根据发电厂的实际情况,对省煤器的改造进行了探讨,提出采用膜式省煤器可以较好地解决泄漏问题,并给出具体实施方案。     

Improvement of a Fourier coefficient estimation method using an adaptive algorithm and its performance analysis

There are many applications where it is necessary to estimate accurately the amplitude and phase of signals when the information regarding the frequencies is obtained in advance. This paper presents a new algorithm for estimating more accurately Fourier coefficients of a signal contaminated by additive noise where sinusoidal frequencies of interest are not distributed uniformly. In the proposed method, Fourier coefficients are adaptive parameters. It uses averaged gradient signals and has almost the same acquisition time as the conventional LMS algorithm with more accurate estimation. The performance analysis of the proposed method is presented and its validity and limits are verified under various conditions by computer simulations. It is shown that the proposed method has especially better performance than the LMS algorithm when both the number of frequencies and the step size parameter, µ, are large. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(1): 52–60, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10362     

靶场光电经纬仪测量数据的误差分析及数据处理

光电经纬仪是在现代靶场测量中广泛应用的一种测量仪器,但是光电经纬仪在跟踪飞行目标的过程中,会因各种原因产生测角误差,影响弹道的测量精度。采用卡尔曼滤波的方法可以对光测数据进行有效的处理,提高其测量精度。本文通过对光电经纬仪测量数据的误差分析,建立了误差模型,并对测量数据进行了卡尔曼滤波,生成滤波数据弹道曲线。从而得到较为准确完整的弹道测试数据和外推数据,提高弹道数据获取的精度,最大限度地延伸弹道测量设备跟踪距离。     

"W"火焰锅炉炉膛负压波动大的原因分析与对策

介绍了“W”火焰锅炉燃烧系统的设计特点,该锅炉运行过程中出现了炉膛负压波动大、燃烧不稳定的问题。对该炉实际运行情况的分析研究表明:锅炉控制系统的稳定性偏低、燃烧调整不平衡、燃煤煤种偏离设计煤种过大以及各煤粉管道风煤比偏差过大是造成炉膛负压波动大的关键问题。通过优化调整燃烧、加强燃用煤质管理、减小各煤粉管道风煤比偏差、增加炉膛卫燃带的敷设面积、加大磨煤机出力裕度,保证满负荷运行中合理的煤粉细度等措施,基本消除了炉膛负压波动大的问题,同时还降低了锅炉飞灰可燃物质量分数。     

An integrated course in fundamental engineering and Englishcomposition using interactive and process learning methodologies

At the University of Arizona, the electrical and computer engineering faculty teamed up with English composition instructors and used process-oriented teaching strategies to teach a combined English/engineering course to freshmen. The six credit-hour course combined three credit hours of introductory engineering and three credit hours of English composition, both required courses in the curriculum. The combined course is a creative problem-solving class that emphasizes the use of critical reading, thinking, and writing as appropriate learning strategies for technical material. The authors found that the seminar/lecture/laboratory approach produced an increased awareness of learning processes and resulted in more collaborative learning and holistic thinking