An efficient multipaction suppression method in microwave components for space application

Multipaction,caused by the secondary electron emission phenomenon,has been a challenge in space applications due to the resulting degradation of system performance as well as the reduction in the service life of high power components.In this paper we report a novel approach to realize an effective increase in the multipaction threshold by employing micro-porous surfaces.Two micro-porous structures,i.e.,a regular micro-porous array fabricated by photolithography pattern processing and an irregular micro-porous array fabricated by a direct chemical etching technique,are proposed for suppressing the secondary electron yield(SEY) and multipaction in components,and the benefits are validated both theoretically and experimentally.These surface processing technologies are compatible with the metal plating process,and offer substantial flexibility and accuracy in topology design.The suppression effect is quantified for the first time through the proper fitting of the surface morphology and the corresponding secondary emission properties.Insertion losses when using these structures decrease dramatically compared with regular millimeter-scale structures on high power dielectric windows.SEY tests on samples show that the maximum yield of Ag-plated samples is reduced from 2.17 to 1.58 for directly chemical etched samples.Multipaction testing of actual C-band impedance transformers shows that the discharge thresholds of the processed components increase from 2100 W to 5500 W for photolithography pattern processing and 7200 W for direct chemical etching,respectively.Insertion losses increase from 0.13 d B to only 0.15 d B for both surface treatments in the transmission band.The experimental results agree well with the simulation results,which offers great potential in the quantitative anti-multipaction design of high power microwave components for space applications.     

双边市场中平台企业兼容策略选择研究

为了研究双边市场中平台企业的兼容策略选择,构建了反映不同兼容策略的双边市场模型.假设一个垄断者同时拥有两个存在横向差异的平台,运用两阶段博弈的思想分析了平台两边用户的兼容策略选择,发现两边都希望平台是完全兼容的;进而分析了平台企业的兼容策略选择,发现如果没有新用户的进入,平台之间的任何兼容策略都是无差异的,但如果存在新用户的进入,则完全兼容是垄断者的最优策略选择.     

软件与信息技术服务业上市公司生命周期研发投入及影响因素研究

以114家我国软件与信息技术服务业上市公司2010-2015年的数据为样本,利用产业经济学增长率分类法对样本公司所处生命周期进行划分,实证研究了软件与信息技术服务业上市公司在生命周期不同阶段研发投入强度差异性以及影响因素.研究结果表明,样本公司的研发投入强度在生命周期的成长-成熟-衰退阶段呈现“倒U型”的状态.企业生命周期不同阶段企业规模、资本结构、盈利能力对研发投入强度有不同程度的影响.     

基于模糊证据推理的汽车制造产业网络环境复杂性测度

环境复杂性是汽车制造产业网络复杂性的主要诱因。利用指标波动程度测度复杂性的思想,建立表征汽车制造产业网络外部环境的指标体系,构建指标变动程度的模糊信度结构模型,运用模糊证据推理算法结合熵值理论对多指标进行信息融合,并利用灰色关联分析方法评估复杂性测度结果。通过2002~2012年汽车行业数据的实证研究,结果表明:经济环境与国际环境的波动是导致汽车制造产业网络复杂性的最主要因素,技术环境和市场环境次之;近10年来我国汽车制造产业网络外部环境经历了两次较大波动,总体复杂性呈现增长趋势。本研究可为汽车产业环境复杂性测度及应对提供思路参考。     

Parametric study for the treatment of tannery dye wastewater by electro-oxidation

Degradation of tannery effluents is a difficult operation because of their intricate chemical structures. Most of the conventional approaches are becoming ineffective because of the wide variation in the composition of tannery effluent. Dyes from the wastewater is also dangerous, as the wastewater has negative impact on the health of human being, plants and aquatic animals. For the first time once through continuous approach was employed for the removal of Acid yellow 110 tannery dye in electro-oxidation process on Mix Metal Oxide of ruthenium and iridium on titanium sheet electrode. The effects of pH, time (t) and current (i) on % color removal and energy consumed were investigated in a batch setup and found the optimum condition with the help of RSM design. The values of the responses Y₁ and Y₂ were found to be 93.08% and 1.07 kWh/m³ respectively at the optimum condition. Toxicity Bioassay analysis, GC-MS analysis and the kinetic study were performed at optimum condition. At the flow rates of 10–40 ml/min once through continuous experiments was conducted to found the feasibility of the process at pilot scale or industrial scale application.     

Evolutionary stability of auction and supply chain contracting: An analysis based on disintermediation in the Indian tea supply chains

The purpose of this paper is to show that evolutionary stable market equilibrium is achievable through complete disintermediation of auctioneers if the option of bargaining-based supply chain contracting exists. The paper analyzes the evolutionary dynamics of a market that caters both the scopes of auction-intermediation and supply chain contracting to a set of homogeneous buyers and sellers. The motivation of this work developed from the contradiction between the theoretical framework of Lu and McAfee (1996) that identifies auction to be evolutionary stable over bargaining and the real instance of sustained disintermediation of auctioneers in the world’s largest tea industry in India where supply chain contracting is the other option of trading.     

棉花双关税后进口价格、期货价格与现货价格的感知及传导研究—基于VAR模型

随着我国棉花市场开放程度逐渐提高,探索国内外棉花价格感知和传导机制也愈显重要.国内外棉花价格传递必然受进出口贸易政策的影响,研究征收双关税后的棉花进口价格与国内期、现货价格之间的传递效应,对完善和优化我国棉花价格传导和形成机制更具现实意义.通过VAR模型、格兰杰因果检验、脉冲响应和方差分解等方法检验和探讨三者间的价格感...     

Erosion of oil&gas industry choke valves using computational fluid dynamics and experiment

As part of several years research activity with erosion in chokes, Norsk Hydro ASA has developed a model to estimate erosion and lifetime of chokes by incorporating erosion models into particulate flow models. This model has been verified with the results from flow and erosion testing of two different types of chokes, Needle&Seat and External Sleeve. The erosion tests with both the modified Needle&Seat choke and the External Sleeve choke gave peak erosion rates only two or three times larger than calculated. This is assumed to be near the uncertainty of the erosion model alone. This is very satisfactory for such complex flow geometries. The model and the experiments demonstrated that the External Sleeve choke is much more prone to erosion attack, at the given low pressure conditions.     

人力资本钳制的契约分析

为增强企业竞争，企业需要进行专用性人力资本投资，由于契约的不完全性和人力资本的特性，可能产生钳制(hold—up)问题，导致企业事前投资激励不足。本通过一种重新谈判机制的契约设计，提出了一种解决方案。     

A machine learning approach to process improvement in a telecommunications company

Redesigning and improving business processes to better serve customer needs has become a priority in service industries as they scramble to become more competitive. This paper describes an approach to process improvement that is being developed collaboratively by applied researchers at US WEST, a major telecommunications company, and the University of Colorado. Motivated by the need to streamline and to add more quantitative power to traditional quality improvement processes, the new approach uses an artificial intelligence (AI) statistical tree growing method that uses customer survey data to identify operations areas where improvements are expected to affect customers most. This AI/statistical method also identifies realistic quantitative targets for improvement and suggests specific strategies (recommended combinations of actions) that are predicted to have high impact. This research, funded in part by the Colorado Advanced Software Institute (CASI) in an effort to stimulate profitable innovations, has resulted in a practical methodology that has been used successfully at US WEST to help set process improvement priorities and to guide resource allocation decisions throughout the company.