气固两相流风机的三元计算与二元计算的比较

在单相耦合模型的基础上，采用合适的粒子反弹模型和磨损模型，分析、推导、编制了三元粒子运动、碰撞的程序，并与二元粒子程序进行了比较，验证了该三元程序的优越性，为气固两相流离心风机叶轮的研制提供了一个行之有效的理论工具。     

电极熔蚀导致的气体开关绝缘子性能劣化

气体开关导通时,电极材料熔融或汽化并从电极表面移出,导致开关绝缘子被染污,并可能诱发开关内绝缘闪络事故,直接影响气体开关寿命和脉冲功率系统稳定性。在开关内嵌入有机玻璃圆环,收集黄铜电极熔蚀产物,并研究其对开关绝缘子表面形貌和沿面绝缘强度的影响。实验结果表明,电极熔蚀会产生大量金属蒸汽和溅射液滴,且熔蚀产物具有明显的轴向分布特性,其中,金属蒸汽冷凝并附着在绝缘子表面,形成细微的金属粉末;溅射液滴轰击绝缘子表面,在局部区域形成密集的表面裂纹和金属颗粒嵌入物。在两种电极熔蚀产物的共同作用下,开关绝缘子表面绝缘电阻下降,闪络场强降低;同时,绝缘子表面轴向不同区域的绝缘电阻差别很大,引起绝缘子表面电压分布不均和局部电场增强,最终导致开关绝缘子闪络电压降低,闪络概率增大。     

LTD模块气体开关电极材料烧蚀性能实验

针对直线变压器驱动源(LTD)对开关的长寿命需求,基于前期研制的200kV低抖动多间隙气体开关电极几何参数以及开关通流水平,详细开展了不同电极材料(钼、黄铜、铜钨合金、高密度石墨、304和321不锈钢)的烧蚀性能实验。实验结果表明,在单次电荷转移量15.4mC,脉冲电流20kA条件下,体积烧蚀速率从大到小依次为:石墨、黄铜、铜钨合金、钼、不锈钢。电极烧蚀微观形貌分析表明,不锈钢是用于LTD开关相对较好的电极材料。根据不锈钢电极的体积烧蚀速率,可知理论上LTD开关的运行寿命可以超过1×106次,但前提是开关外壳需保持足够的绝缘强度。     

Resource block Filtered-OFDM for future spectrally agile and power efficient systems

Spectrum sharing is a common paradigm in future communication systems and a spectrally agile baseband waveform with minimal out-of-band emissions is a critical component. In this paper, we propose a new multicarrier modulation technique, called resource block Filtered-OFDM (RB-F-OFDM) and present the transceiver design. This waveform can be used over channels with non-contiguous spectrum fragments and exhibits very low adjacent channel interference, which is required for cognitive radio systems with multi channel carrier aggregation capabilities. As such, regulatory based very stringent adjacent channel leakage ratio (ACLR) and adjacent channel selectivity (ACS) requirements can be met. We show that the transceiver complexity may be reduced by utilizing an efficient polyphase implementation that is commonly used in the filter bank multicarrier (FBMC) modulation. In addition, some efficient peak-to-average power ratio (PAPR) reduction techniques can be naturally applied. The new design is backwards compatible with legacy OFDM based systems. Simulation results to evaluate the performance, including measured bit error rate (BER) in multipath channels, are provided.     

Analytical solution of coupled soil erosion and consolidation equations by asymptotic expansion approach

In this work, one-dimensional approximation of internal erosion taking place in a soil made from sand and clay mixture was considered. The clay phase that is susceptible to experience erosion under water flow discharge was assumed to be small. A new erosion law fixing the initiation threshold of erosion and integrating the effect of soil consolidation on internal erosion was proposed. Conversely, the effect of erosion on elastic soil deformation was also integrated through damage mechanics concepts. Asymptotic expansion of the coupled equations in terms of a perturbation parameter linked to the total amount of internal erosion that is likely to occur has been performed. This has enabled to view the internal erosion phenomenon occurring inside the soil as a perturbation affecting the classical soil consolidation equation, and further to evaluate the critical discharge gradient for which internal erosion starts. Equations at order zero that are provided by the asymptotic expansion were exactly integrated while an adequate finite difference scheme was introduced to solve the equations at order one. A parametric study was conducted after that in order to assess effects of the main factors on internal erosion and soil deformation.     

Design optimization of guide vane for mitigating elbow erosion using computational fluid dynamics and response surface methodology

A 90° elbow equipped with guide vanes was developed with the intent of reducing elbow erosion. Numerical models were formed to predict the maximum erosion rate of elbow and Face-1, and the response surface methodology was used to study the relationship between the erosion rate and structural parameters of guide vane. A second-order response surface model was established to determine the relationship between R₁ and variables, and a reduced cubic (RC) polynomial model was obtained to reveal the relationship between R₂ and the three factors. The numerical results show that the low-speed region is expended and the maximum discrete particle matter (DPM) concentration is reduced after installing the guide vane. This internal component provides a shelter for the elbow from the direct impact of high-speed solids.     

利用统计方法对土壤侵蚀中自然环境和人类活动影响程度的比较

黄土高原的土壤侵蚀是黄河泥沙的主要来源，灾害性的水土流失既是生态环境脆弱的集中体现，又深受社会活动的影响．我们应用统计方法，包括果类分析、逐步回归、多元化一元等方法，对土壤侵蚀中自然侵蚀和人类活动加速侵蚀哪方面影响比重大这一问题进行了研究。我们的结论是，在不同的环境背景下，人类活动影响的比重是不同的；从全地区来看，人类活动对侵蚀的影响要小于自然环境的作用。     

PEOS功率倍增装置的物理设计与等离子枪实验

对PEOS功率倍增装置进行了物理设计与模拟计算并进行了脉冲等离子体枪实验。给出装置参数的选择方法,包括电路参数与PEOS参数的选择。为得到要求的功率倍增和能量传输效率,分析指出注入等离子体密度n_p与速度v_d的乘积要大而n_p相对要小,v_d要大;而且为断路快、阴极半径r要适当小;模拟计算结果证实了这一分析。对装置关键部件脉冲等离子体枪进行设计、研制和实验,在距枪60cm处测得碳离子速度v_d～5×10~(?)cm/s,离子密度n_p～4×10(?)/cm。     

浙江省东阳市紫色土坡面土壤侵蚀和降雨因子关系的初步研究

紫色土分布区是我国南方水土流失区的重要组成部分。本文通过对东阳市紫色土坡面土壤侵蚀和降雨因子之间的相关分析,建立了利用降雨量和平均降雨强度对土壤流失量进行预测预报的回归方程,为紫色土地区土壤过度侵蚀的治理提供了定量方法,并为紫色土的综合开发利用提供了科学根据.     

基于高储能密度电容退化数据的可靠性评估

 根据强激光能源模块高储能密度电容器在工作过程中，受到连续冲击而使退化失效具有累积效应的特点，提出了利用产品运行过程中性能参数退化的信息，用复合Poisson过程对退化轨道建模并进行可靠性评估的方法。给出了模型参数的矩估计和电容器的平均退化量、可靠度、平均寿命等可靠性指标评估的Bootstrap仿真过程。并通过实例说明了该评估方法在工程中的应用。基于电容退化信息的可靠性评估方法，可以在极少甚至没有寿命数据的情况下给出客观可信的评估结果，在理论和应用上都具有重要的价值。