提高微波晶体管S参数测量精确度的实用技术

介绍了矢量网络分析仪测量微波晶体管S参数时的主要误差 ,给出了基于测试夹具校准件的制作方法和它的特性测量     

Power characteristics of a variable hydraulic transformer

The flow control of hydraulic transformers is a great challenge.To meet this challenge,a new kind of hydraulic transformer,variable hydraulic transformer(VHT),is proposed in this work.This paper focuses on the power characteristics of the newly proposed VHT,including instantaneous power,average power,power pulsation,and efficiency.In the analyses,the concepts of efficiency,input power,output power,starting angle,and ceasing angle are defined or redefined.To investigate the power characteristics,their models are derived by considering the governing factors such as the control angle of the swash plate and the structure of the port plate.This work highlights that the load flow can be adjusted by adjusting the control angle of the swash plate,and the power characteristics at the B-port produce a remarkable change.In addition,the VHT has a starting angle and a ceasing angle,and these two angles can be adjusted by the influencing factors.The results reveal that the power pulsation and the jump points of the instantaneous power are the primary causes of a less smooth work.Then,it is shown that the control angle of the port plate,the control angle of the swash plate,and the pressures at the ports are the three key elements for a stable operation.The results also reveal that the adjustment of the influencing factors can improve the efficiency.     

Optimal deployment schedule of an active twist rotor for performance enhancement and vibration reduction in high-speed flights

The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions.The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input.An advanced Particle Swarm assisted Genetic Algorithm (PSGA) is employed for the optimizer.A rotorcraft Computational Structural Dynamics (CSD) code CAMRAD Ⅱ is used to perform the rotor aeromechanics analysis.A Computation Fluid Dynamics (CFD) code is coupled with CSD for verification and some physical insights.The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation.The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases.A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration.The mechanism of reduction to the performance gains is identified illustrating the section airloads,angle-of-attack distribution,and elastic twist deformation predicted by the present approaches.     

依托学会 注重服务 提高高职学报整体办刊水平——陕西省高职高专教育学会学报工作委员会学术活动综述

陕西省高职高专教育学会学报工作委员会，依托陕西省高校学报研究会、全国高职高专学报研究会等行业学会组织，团结本省高职高专院校学报20多个会员单位，根据会员学报办刊现状和实际需求开展学报编辑规范化建设、学报编辑学研究和学术讲座等一系列学术活动，注重学会服务功能，推动以特色栏目为主要特征的高职高专学报创新实践，有效地提高了陕西省高职高专院校学报的整体办刊水平。     

新型功率传递系统构建方案研究

通过对SYSTEMⅡ功率传递系统构成原理的分析研究,提出了利用1806双通道功率计配合通过式功率座和终端式功率座构成测试系统的新方案,新方案去除了老方案中的必备设备1805射频控制器,对于1805损坏或因其他原因没有1805构成测试系统的实验室来讲,也是一个不错的选择。     

Impact of DORIS ground antennas environment on their radio signal quality

Among the factors which may disrupt the DORIS measurements quality, the ground antennas environment is of high importance. For a set of 15 selected DORIS beacon, the differences between the effective and theoretical power received on-board the satellites (SPOT-5 and Envisat) have been analyzed in terms of spatial direction around the antenna. Such antenna maps have also been established regarding the Doppler residuals of the least-square precise orbit adjustment. Thanks to 360° views from the antennas and aerial views of the sites, the impact of the signal obstructions (trees, roofs, antennas …) on power attenuation and Doppler residuals is discussed. Depending on the nature of the obstructed object, the attenuation level can reach more than 5 dB, and the residual RMS of the orbit adjustment may be doubled from the nominal value, reaching 1 mm/s locally. The nature of the ground at the foot of the antennas has been correlated to DORIS signal quality at high elevation: reflections on flat surfaces (e.g. roofs) affect the signal more significantly than reflections on natural ground (e.g. soil). In particular, a modeling of the multipath phenomenon affecting Fairbanks site has been established and fits remarkably with the observations. Finally, an evaluation of the direct impact of obstructing objects on the orbit has also been performed. The example of a scaffolding at Kauai site displays a few millimeters error in the along-track position of the satellite.     

Experimental investigation of flow and distortion mitigation by mechanical vortex generators in a coupled serpentine inlet-turbofan engine system

The performance of compact, aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow distortions at the duct exit. An experimental investigation was conducted to study the flow field and passive suppression of flow separation and Aerodynamic Interface Plane (AIP) distortion in a serpentine air inlet duct. Tests were performed by a turbofan engine at several Engine Operating Points (EOPs) from 56% (idle) to 100% (max). A large total pressure deficit region arose at the upper part of the AIP, which was associated with the upper surface flow separation. Using the new mechanical S-type vortex generators in two longitudinal positions (VG1 and VG2), separation and loss were diminished at the upper part of the duct and AIP. The VG2 arrangement attained the maximum reductions in distortion coefficients which were 73.72%, 60.7% and 37.8% in DC(90°), DC(60°) and ΔP_C/P metrics, respectively. In the next step of the study, some unsteady aspects of the flow field were analyzed inside the duct. The separation onset and reattachment points were determined by the standard deviation of static pressure on the upper surface. The AIP spectral distribution showed that the boundary of low pressure and high pressure recovery regions was dominated by the maximum fluctuations. Furthermore, the PSD diagram of several probes at AIP revealed the vortex shedding frequency and its higher harmonics at separation region. The energy content of distinct unsteady spectral features in the bare configuration was significantly reduced using VGs, which showed the improvement of flow at the duct exit.     

USB在雷达功率测试中的应用研究

介绍了外设使用USB口进行雷达功率测试的优点，USB通信机制和外设开发过程，一种雷达功率测试模块的设计结构和性能指标，以及应用软件开发及其通信用的两个关键API函数。     

一种基于单定向耦合器比较法的8 mm小功率校准系统

介绍了一种基于单定向耦合器比较法组建的8mm小功率校准系统,讨论了校准原理、系统组成、校准不确定度,通过分析和实验证明系统作为8mm小功率座的校准是可行的.     

某型飞机发电机供电系统一起典型故障的分析

分析了在维修过程中某型飞机发电机供电系统的一起典型故障的原因,详述该故障排除的过程,以及通过此故障的排除获得的两点启示。