Reliable polarization control of VCSELs through monolithically integrated surface gratings: a comparative theoretical and experimental study

Vertical cavity surface-emitting lasers (VCSELs) with a well-defined and predictable polarization of the emitted light are sought for a number of applications. In this paper, we show that one can define and stabilize the polarization of single- and multimode oxide-confined VCSELs with a monolithically integrated dielectric surface grating. In recent years, we have developed a three-dimensional, fully vectorial model for VCSELs, which proved to nicely reproduce the experimental results of quite complex structures, such as noncircular devices and phase-coupled VCSEL arrays. This software allows for the first time to analyze the effects of a dielectric grating in the output facet cap layer and its capability to fix the polarization of the emitted light. It is here employed as a design tool, yielding excellent agreement with the experimental data. Since the simulations predict the polarization behavior to be sensitively dependent on the grating parameters, hundreds of VCSELs with 99 different parameter sets, two grating orientations and active diameters of 4 and 7 /spl mu/m have been analyzed. Even VCSELs with eight or more coexisting modes turned out to be linearly polarized with an orthogonal polarization suppression ratio in excess of 15 dB. Theoretical and experimental emission far-fields are compared, and it is shown that diffraction side lobes can be prevented with properly chosen grating parameters which simultaneously ensure full polarization stability.     

Springrobot: a prototype autonomous vehicle and its algorithms for lane detection

This work presents the current status of the Springrobot autonomous vehicle project, whose main objective is to develop a safety-warning and driver-assistance system and an automatic pilot for rural and urban traffic environments. This system uses a high precise digital map and a combination of various sensors. The architecture and strategy for the system are briefly described and the details of lane-marking detection algorithms are presented. The R and G channels of the color image are used to form graylevel images. The size of the resulting gray image is reduced and the Sobel operator with a very low threshold is used to get a grayscale edge image. In the adaptive randomized Hough transform, pixels of the gray-edge image are sampled randomly according to their weights corresponding to their gradient magnitudes. The three-dimensional (3-D) parametric space of the curve is reduced to the two-dimensional (2-D) and the one-dimensional (1-D) space. The paired parameters in two dimensions are estimated by gradient directions and the last parameter in one dimension is used to verify the estimated parameters by histogram. The parameters are determined coarsely and quantization accuracy is increased relatively by a multiresolution strategy. Experimental results in different road scene and a comparison with other methods have proven the validity of the proposed method.     

500 kV大胜关长江大跨越输电线路导地线换线施工

介绍了大胜关长江大跨越二期工程导地线的换线施工方法,即采用旧地线"一牵一"张力牵引光缆过江,采用旧导线"一牵一"张力牵引D26牵引绳过江、D26牵引绳"一牵二"张力牵引新导线过江。针对大跨越不封航换线施工时所涉及到的主要施工难点,提出了相对应的解决方法,对今后类似的大跨越改造工程有积极的指导作用。     

输电工程中后注浆灌注桩的试验研究及应用

后注浆桩作为2008版桩基规范推荐的一种新型桩基础型式,具有可靠性高、承载力增幅大、经济效益显著等特点。由于缺少参数,无法在输电线路工程中直接采用。通过后注浆抗拔、受水平作用的真型试验,得到了计算公式和计算参数,并对试验的过程进行了描述。试验数据表明对于输电线路以抗拔受力为主的条件下,后注浆桩比普通桩承载力可以提高30%~50%,造价可节省15%~35%,具有广阔的推广应用前景。对受压、抗拔、受水平作用下的参数进行了推荐,方便以后工程中的应用。     

SCR 脱硝催化剂再生技术试验研究

对选择性催化还原法(SCR)脱硝催化剂再生工艺进行研究。用X射线晶体衍射(XRD),X射线荧光光谱(XRF),X射线光电子能谱(XPS)和比表面积分析等方法对再生前、后的催化剂进行了表征;采用模拟烟气在自制脱硝反应装置上对催化剂再生效果进行了评价。研究发现:通过鼓泡或超声波辅助的稀H2SO4清洗可有效去除催化剂中的有毒物质并恢复比表面积,且鼓泡的综合效果更好;以乙醇胺为助溶剂,可根据所需钒的补充量配制不同浓度的偏钒酸铵水溶液,采用浸渍-干燥-煅烧工艺,可实现活性物质钒氧化物的补充,使催化剂的脱硝效率恢复至92%;用溶解性较好的硝酸铈代替偏钒酸铵,向失活催化剂中添加活性物质氧化铈,可拓宽脱硝反应的温度区间,并将催化剂的脱硝效率最高值提至90%。     

Towards long-term economic welfare in deregulated electricity markets: Testing capacity mechanisms in an experimental setting

A number of mechanisms have been suggested for capacity adequacy. A study using laboratory experiments both of procurement of long-term strategic reserve contracting and of centralized auctioning for capacity contracts suggests that the centralized auctioning process stabilizes laboratory markets and provides economic welfare comparable to a free market. The strategic reserve contracting process does not seem to improve either of the two aspects compared to a non-regulated market.     

适应于双馈风电场送出线不对称故障的时域距离保护

目前,双馈风电场不对称短路电流特性对风电场送出线距离保护的影响以及相关优化策略的研究,主要是在计及Crowbar保护动作的基础上进行的,少有研究系统发生不对称故障后计及RSC控制的短路电流特性对传统距离保护的影响。基于此,分析了系统发生不对称接地故障后,计及Crowbar保护和RSC控制两种运行工况下的短路电流特性,解析推导了这两种运行工况下离散傅里叶算法提取基频分量产生的误差表达式。在此基础上分析双馈风机短路电流特性对传统距离保护的影响,从而提出了不受风电场短路电流特性影响的具有抗过渡电阻能力的时域距离保护。最后在Matlab/Simulink平台上建立DFIG电磁暂态仿真模型,仿真分析了风电场送出线发生单相经过渡电阻接地后,计及Crowbar保护动作和RSC控制两种运行工况下传统距离保护和时域距离保护的动作特性。     

风场及其送出线保护配置与整定研究

现有风场及其送出线保护多从保障风机或各元件自身安全角度进行简单配置整定,可能存在保护范围不明确,选择性和灵敏性未进行系统校验等问题。结合风电故障特征,给出了风电场提供故障电流最大值的简化计算公式,提出了兼顾风机安全与系统可靠性的风场及送出线保护配置与整定原则。并以吉林某风场为例,尝试给出了风机、箱变、集电线、母线、主变在内的风场及其送出线保护的配置原则,定量化校验了集电线路电流保护配置与整定的合理性。     

An experimental and theoretical framework for manufacturing prosthetic sockets for transtibial amputees.

Selective laser sintering (SLS) is a powerful manufacturing technology that does not require part-specific tooling or significant human intervention and provides the ability to easily generate parts with complex geometric designs. The present work focuses on developing a manufacturing framework using this technology to produce subject-specific transtibial amputee prosthetic sockets made of Duraform PA, which is a nylon-based material. The framework includes establishing an overall socket design (using the patellar-tendon bearing approach), performing a structural analysis using the finite element method (FEM) to ensure structural reliability during patient use, and validating the results by comparing the model output with experimental data. The validation included quantifying the failure conditions for the socket through a series of bending moment and compression tests. In the case study performed, the FEM results were within 3% of the experimental failure loads for the socket and were considered satisfactory.     

Relay setting considerations and operational experience of a long500 kV transmission line

The large capacitive susceptance, large load magnitude, and substantial phase unbalance before and after a single-pole trip operation have a substantial effect on the performance of the protective relaying systems of the Minneapolis-Duluth 500 kV line. Computer simulation studies show that correct operation of the relays can be assured if these effects are taken into consideration in determining relay settings. The selection, performance, and operation of the primary and secondary relay system are discussed, indicating that the relaying protection used achieved substantial security and dependability     

变压器、配网线路后备保护配置、整定方面的改进措施

通过对变压器10 kV侧及10 kV配网线路相间过流远后备灵敏度的计算、统计、分析,提出增加变压器和配网线路保护配置:增设负序过电流保护作为10 kV系统相间短路后备保护的补充,使对同一点故障的灵敏度及切除率由11.67%提高到76.56%.并给出合理的整定计算方法,指出改进后的保护配置对提高远、近后备灵敏度是一种行之有效的手段.     

变压器、配网线路后备保护配置、整定方面的改进措施

通过对变压器10kV侧及10kV配网线路相间过流远后备灵敏度的计算、统计、分析,提出增加变压器和配网线路保护配置:增设负序过电流保护作为10kV系统相间短路后备保护的补充,使对同一点故障的灵敏度及切除率由11.67%提高到76.56%。并给出合理的整定计算方法,指出改进后的保护配置对提高远、近后备灵敏度是一种行之有效的手段。     

超高压线路简化整定计算的原则和方法

随着超高压电网的逐步强大和继电保护技术的不断进步,简化线路后备保护的整定计算是切实可行的.提出了超高压线路后备保护的简化整定计算原则和距离保护及定时限零序保护简化整定计算的方法,重点讨论了距离I段可靠系数、零序补偿系数、距离Ⅱ段灵敏系数和距离保护躲最小负荷阻抗的计算方法.同时简单介绍了线路后备保护整定计算中选择运行方式的优化方法.采用这些原则和方法,既保证了整定值的正确、科学和合理,又能够提高整定计算工作的效率.     

超高压线路简化整定计算的原则和方法

随着超高压电网的逐步强大和继电保护技术的不断进步,简化线路后备保护的整定计算是切实可行的。提出了超高压线路后备保护的简化整定计算原则和距离保护及定时限零序保护简化整定计算的方法,重点讨论了距离Ⅰ段可靠系数、零序补偿系数、距离Ⅱ段灵敏系数和距离保护躲最小负荷阻抗的计算方法。同时简单介绍了线路后备保护整定计算中选择运行方式的优化方法。采用这些原则和方法,既保证了整定值的正确、科学和合理,又能够提高整定计算工作的效率。     

一种仿生机器鼠的跟踪与避障策略

针对一种新型仿生机器鼠平台的运动规划问题主要包括跟踪、避障等问题,依据仿生机器鼠的双目视觉系统以及多自由度的机械结构,根据驱动电机的特性,建立仿生机器鼠的扭腰、抬身、攀爬等动力学模型,采用"记忆"目标鼠的特征、"学习"最优避障路径、"推断"目标鼠的运动方向等方法,实现了仿生机器鼠的跟踪与避障行为,提出了一种基于仿生学原理的仿生机器鼠的跟踪与避障策略。在一种新型仿生机器鼠平台上的实验结果表明,相比与基于虚拟阻抗模型的控制方法,该跟踪与避障策略能够更好地实现仿生机器鼠的跟踪与避障行为,从而验证了策略的可行性与有效性。     

An experimental study of the effectiveness of an additive for fuel oil

An available multifunctional additive for low-grade fuel oil is proposed. Its effect on the service properties of fuel oil is experimentally studied, and results from this study are presented.     

配电网理论线损计算分析系统的研究与开发

文章详细介绍了《配电网理论线损计算分析系统》的算法选择、模型建立以及系统的实现。该系统已在西宁供电局、海东供电局投入运行,大大提高了理论线损计算的工作效率和工作质量,使理论线损计算工作走向了制度化,规范化和标准化。为网络规划,网络调压,经济运行提供了准确可靠的技术信息。对确定降损目标,实现科学的降低线损和电网技术改造具有重要的指导作用。     

贵阳电网110kV线路优化保护配置及整定计算的探讨

对贵阳地区电网运行现状的分析,针对其110kV线路保护的配置情况和整定计算,提出了优化方案。方案中,通过对110kV线路配置光纤电流差动保护,强化主保护,简化后备保护的整定原则,能够进一步提高110kV线路保护可靠性,有效地减轻维护工作难度,提高继电保护整定计算的工作效率,对运行方式的安排也提高了灵活性。     

Conceiving an easy-to-understand and automated polarimeter: application to a study of collagen

In this paper, the authors describe the design and the experimentation of a polarimeter aimed at characterizing the properties of some scattering materials (e.g., a scattering liquid containing a foreign body, or skin components, such as collagen). The polarimeter presents the advantage of offering an easy understanding of Stokes and Mueller formalism. Thus, it is typically suited for university students in physics (Master's level), giving them a clear understanding of polarization and birefringence. Another application is possible in schools of engineering, where students may use their design abilities to improve the apparatus performance. Apparatus automation was performed as well, providing easier use for experiment (commodity of use, reproducibility, and possible multiplication of measurements). The apparatus was tested in transillumination and backscattering modes. More generally, measurements can be performed with angles varying from 0/spl deg/ to 150/spl deg/ between the propagation direction and the line from the sensor to the sample material. In addition, the sensor can be either a photodiode (results presented here) or a two-dimensional (2-D) sensor charge-coupled device (CCD) camera. As an application, the apparatus was used to differentiate irradiated and nonirradiated collagen.     

Locating faults in a transformer winding: An experimental study

Based on terminal measurements on a single, continuous-disc winding of a transformer, it is demonstrated how faults introduced at different positions along the winding could be localized with reasonable accuracy. Fault in the present context represents a discrete change, e.g. short-circuiting a few turns within a disc (i.e. predominantly an inductive change) and/or addition of some tens of pico-Farad capacitance between a disc and ground (i.e. predominantly a capacitive change). Open-circuit and short-circuit natural frequencies are determined by sweep frequency measurements, in addition to measuring effective resistance, shunt capacitance and inductance, at the terminals. The proposed method aims at utilizing the measured data to iteratively synthesize a lumped-parameter ladder network, corresponding to each set of measurement. Comparison of such synthesized circuits with a reference (or fault-free) circuit reveals the location, quantum, and nature of fault. Results presented demonstrate the potential of this method.