Real time power management strategy for fuel cell hybrid electric bus based on Lyapunov stability theorem

The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB.     

疫情下电磁场理论课程的网络教学

本文主要总结了新冠疫情期间作者的电磁场理论课程在线教学经验。对比分析了录播和直播的优缺点后,选择录播教学方式。基于超星网络教学平台,展示了录播网络教学的具体措施,包括网上答疑和学习效果检查以及在线批改作业等。给出了网络教学可以为线下教学继续使用的方法和手段,为疫情结束后的正常教学提供了新的网络教学补充措施。     

基于误差估值累加开环校正的诱导式欺骗检测方法

诱导式卫星欺骗干扰可诱导航空器逐渐偏离预定航迹，难以被发现，因此及时有效地检测干扰是飞行安全的保障。在现有紧组合导航体制基础上，设计了一种基于误差估值累加开环校正的紧组合导航结构，并证明了其性能与传统闭环校正紧组合导航性能等效。在此结构中，将紧组合导航系统与自适应序贯概率比检测方法结合，提出了一种基于误差估值累加开环校正的诱导式欺骗检测方法，融合紧组合导航信息与其他不受欺骗影响的导航信息，构建欺骗检测统计量进行诱导式欺骗检测。仿真结果表明，开环校正结构可避免随时间累加的惯性导航系统误差所导致的组合导航滤波器发散问题，同时欺骗检测方法可进一步提高算法对“最坏”情形下微小诱导式欺骗的检测效果。     

Structural,electrical, and linear/nonlinear optical characteristics of thermally evaporated molybdenum oxide thin films

Homogeneous thin films of Molybdenum oxide (MoO₃) were grown on quartz and glass substrates using the thermal evaporation method. XRD results showed that the MoO₃ powder has a polycrystalline structure with an orthorhombic crystal system whereas the MoO₃ thin films have amorphous nature. SEM images showed that the MoO₃ thin films have a nearly uniform surfaces with worm-like shape grains. The film thickness influences on the linear and nonlinear optical characteristics of MoO₃ thin films that were examined using spectrophotometric measurements and from which, the linear optical constants of the MoO₃ thin films were estimated. The electronic transition type was determined as a direct allowed one. The values of the optical band gap were obtained to be in the range of 3.88–3.72 eV. The dispersion parameters, third-order nonlinear optical susceptibility, and the nonlinear refractive index of the MoO₃ thin films were determined and interpreted in the light of the single oscillator model. The temperature dependence of the DC electrical conductivity and the corresponding conduction mechanism for the MoO₃ films were investigated at temperatures ranging from 303 to 463 K.     

高光谱成像用高帧频CMOS图像传感器北大核心

针对高帧频、全局曝光和光谱平坦等成像应用需求,设计了一款高光谱成像用CMOS图像传感器。其光敏元采用PN型光电二极管,读出电路采用5T像素结构。采用列读出电路以及高速多通道模拟信号并行读出的设计方案来获得低像素固定图像噪声(FPN)和非均匀性抑制。芯片采用ASMC 0.35μm三层金属两层多晶硅标准CMOS工艺流片,为了抑制光电二极管的光谱干涉效应,后续进行了光谱平坦化VAE特殊工艺,并对器件的光电性能进行了测试评估。电路测试结果符合理论设计预期,成像效果良好,像素具备积分可调和全局快门功能,最终实现的像素规模为512×256,像元尺寸为30μm×30μm,最大满阱电子为400 ke^(-),FPN小于0.2%,动态范围为72 dB,帧频为450 f/s,相邻10 nm波段范围内量子效率相差小于10%,可满足高光谱成像系统对CMOS成像器件的要求。     

一种用于电气设备状态监测的新式FBG传感器北大核心CSCD

为了监测绕组变压器的静态应力场和发生短路等故障时的动态应力变化,设计了一种用于电气设备状态监测的新式FBG传感器。该传感器由聚醚醚酮材料封装的FBG构成,通过内部圆锥形空腔结构实现将轴向应力集中于FBG敏感位置。通过仿真对不同压力强度下传感器结构的应力场部分及形变趋势进行了计算与分析,论证了设计的合理性。实验分别对静态载荷和动态冲击进行测试,结果显示,在静态压载测试中,当100 N相似文献   

Synthesis and characterizations of highly responsive H2S sensor using p-type Co3O4 nanoparticles/nanorods mixed nanostructures

High-quality p-type semiconducting Co₃O₄ with mixed morphology of nanoparticles/nanorods are synthesized using a hydrothermal route for high response and selective hydrogen sulphide (H₂S) sensor application. XRD and Raman studies revealed the crystal structure and molecular bonding for obtained Co₃O_4, respectively. The nanoparticles/nanorods-like structures were confirmed for Co₃O₄ using FESEM and TEM analysis. The EDS and XPS spectra analysis were carried out for elemental composition and chemical atomic states of Co₃O₄. The Co₃O₄ sensor is investigated for gas sensing properties in dynamic conditions. The sensor exhibited the highest selectivity towards H₂S among various hydrogen-contained gases at 225 °C. The sensor revealed a high response of 357% and 44% for 100 and 10 ppm H₂S gas concentrations, respectively. The Co₃O₄ sensor exhibited a systematic dynamic resistance response for 100–10 ppm range H₂S gas. The excellent dynamic resistance repeatability of the sensor was shown towards 25 ppm H₂S gas. The response of Co₃O₄ sensor was investigated at different operating temperatures and H₂S concentrations. The sensor stability and H₂S sensing mechanism for the Co₃O₄ sensor have been reported. Highly uniform and mixed nanostructures of Co₃O₄ can be the potential sensor material for real-time high-performance H₂S sensor application.     

基于平均飞行航迹的CCO减噪效用研究

近年来，通过优化飞行程序降低机场飞机噪声影响成为机场环境保护的重要研究方向。文章首先建立了基于飞机“噪声-功率-距离”数据的噪声计算模型，介绍了平均飞行航迹以及连续爬升运行(Continuous Climb Opera-tion, CCO)离场程序的相关理论，最后以大型国际机场为实例，使用飞机平均飞行航迹进行噪声预测，运用综合噪声模型计算出噪声影响面积并绘制噪声影响等值线图，比较了CCO离场相对常规的标准仪表离场(Standard Instru-ment Departure, SID)的降噪效果。结果表明，CCO离场程序可有效降低机场噪声影响，在高噪声级影响区域的降噪效果更佳。     

条形药包爆破震动场的试验研究

通过时条形药包周围实测爆破震动数据采用数值计算方法进行处理，作出了条形药包周围的爆破震动场，使我们对条形药包的爆破地震效应有了全面的认识，从而在实际工程爆破中能够有针对性地进行安全防护。分析研究认为：条形药包周围的震动场由一系列同心椭圆形等震线组成。在爆破近区由于位置因素的影响，等震线的长轴与药包轴线重合；在远区的震动主要受波动干涉作用的影响，致使长轴与药包轴线垂直，因此不能采用集中药包的计算方法。     

Fabrication of high-efficiency Yb:Y2O3 laser ceramics without photodarkening

High-efficiency Yb:Y₂O₃ laser ceramics were fabricated using the vacuum-sintering plus hot isostatic pressing (HIP) without sintering additives. High-purity well-dispersed nanocrystalline Yb:Y₂O₃ powder was synthesized using a modified co-precipitation method in-house. The green bodies were first vacuum sintered at a temperature as low as 1430°C and then HIPed at 1450°C. Finally, the samples were air annealed at 800°C for 10 h. Although no sintering aids were used, full density of the samples with excellent optical homogeneity and an inline transmission of 80% at 400 nm could be obtained. Moreover, photodarkening phenomenon was not detected in the ceramics. Preliminary laser experiment with the fabricated ceramics in a two-mirror cavity has demonstrated 32 W continuous-wave (CW) output at ∼1077 nm with an optical-to-optical conversion efficiency of 58.2%. To the best of our knowledge, this is so far the highest CW output power and optical-to-optical conversion efficiency achieved with the Yb³⁺-doped sesquioxide ceramics in a simple two-mirror cavity.