oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 331 )

2018 ( 6649 )

2017 ( 6819 )

2016 ( 7318 )

Custom range...

Search Results: 1 - 10 of 298100 matches for " 滕李军 "
All listed articles are free for downloading (OA Articles)
Page 1 /298100
Display every page Item
一种改进的CSGC频谱分配算法
,
哈尔滨工业大学学报 , 2014, DOI: 10.11918/j.issn.0367-6234.2014.11.020
Abstract: 基于图论着色的频谱分配算法未充分考虑用户实际带宽需求,针对这一问题,本文在原算法基础上提出了一种改进的CSGC频谱分配算法.该算法引入了空闲频谱和用户请求两个时间因子,通过设置用户优先级函数,在进行二次频谱分配时最大限度地满足用户需求.仿真结果表明,该算法不仅保留了原CSGC算法的性能,而且大幅度提高了频谱利用率.
分布式光纤振动传感系统中数据采集及信号处理系统设计
李彩华,云田,
地震工程与工程振动 , 2012,
Abstract: 本文主要介绍了一套分布式光纤振动传感系统中的数据采集及信号处理系统,该系统设计采用高性能的运算放大电路完成光电信号调理,以高精度差动模数转换器AD9246完成模数转换工作,并选用高性能FPGA作为核心逻辑控制器,并以低功耗的OMAP-L137作为CPU负责振动数据计算、网络通讯等工作,从而使该φ-OTDR分布式光纤振动传感系统测量范围扩展到25km范围。本文通过计算相邻测点振动增量方法检测是否发生了振动入侵,提高了分布式光纤振动入侵检测的灵敏度。该设计方法提高分布式光纤振动传感系统的信噪比,使得该系统振动检测灵敏度提高、抗干扰能力增强,因此该分布式光纤振动传感系统可以用于实际工程的振动监控。
箍筋约束混凝土单轴受压塑性损伤本构模型
,祚华,李安,陈亮
工程力学 , 2014,
Abstract: 基于所建立的素混凝土单轴塑性损伤模型,研究箍筋约束作用对混凝土单轴受压作用下损伤行为的影响,引入损伤约束因子来综合体现在约束作用下不同物理量对材料损伤演化规律的影响,将单轴受压混凝土的塑性段分成塑性第一阶段和塑性第二阶段,确定了方形箍筋和圆形箍筋约束下混凝土的损伤演化方程,并给出相应的塑性变形关系的经验公式,建立了箍筋约束混凝土的单轴受压塑性损伤本构模型。通过与单轴荷载作用下约束混凝土的试验结果对比分析,验证了所建模型的有效性,结果表明所建模型能较好反映混凝土材料在约束作用下的本构关系。
基于ABAQUS的混凝土材料子程序开发与应用
,祚华,王孝锋,和雪峰
建筑结构学报 , 2009,
Abstract: 为了对复杂高层结构进行数值模拟,初步探讨了ABAQUS显式动力模块下的用户材料子程序(VUMAT)的开发过程,给出了可应用于VUMAT接口的单参数混凝土弹塑性模型的显式计算表达式,通过对梁单元的应用初步验证了该材料模型的有效性。最后结合工程实例对数值模拟和振动台试验结果进行了对比分析研究。分析结果表明,所建立的分析模型不但能够较为准确地判断高层结构在大震作用下的屈服顺序及薄弱部位,而且能够方便地考虑结构塑性阶段的损伤扩展情况。
MIMO系统中基站天线递增选择算法
,郑权龙,
北京理工大学学报 , 2014,
Abstract: 在散射体丰富的环境中,信道容量受终端移动的影响很大,为此提出一种基于动态的多入多出(MIMO)散射无线信道模型,分析了移动终端对该无线信道容量的影响,并讨论了在移动过程中进行天线选择为系统性能带来的提升。仿真结果表明,信道容量随着天线单元间距的增大而增大,随散射信号扩展角度的变大而增加,移动环境下的信道容量要小于准静态环境下的信道容量,且动态天线选择能够有效提升系统容量。
有限维修能力下舰载机可修复件库存优化模型
Optimization of carrier-based aircraft repairable spares inventory systems under limited maintenance ability

张帅,,吕卫民,克难
- , 2015, DOI: 10.13700/j.bh.1001-5965.2014.0393
Abstract: 摘要 舰载机保障受维修渠道约束,维修能力有限.为使Palm定理和Metric理论适用于舰载机可修复件优化配置,基于排队理论,将有限维修渠道的实际维修时间与维修等待时间之和等效为无限维修渠道的平均维修时间,建立专业渠道、通用渠道和混合渠道的维修供应渠道修正模型.根据维修供应渠道修正模型,给出了两层级备件项的供应渠道备件数均值和方差模型.结合实例应用,分析了备件需求率和维修渠道数对维修时间的影响.对比分析了"有限维修渠道模型"和"无限维修渠道模型"库存方案的应用效果,并给出了各自的适用条件,结果表明了修正模型的有效性.
Abstract:The repair capability of carrier-based aircraft is constrained by finite repair channels. To make Palm's theorem and Metric theory applicable to the optimal allocation of carrier-base aircraft repairable spares, the modified accommodative models of repair and supply channels under conditions of dedicated channels, general channels and hybrid channels were researched and proposed by making the sum of actual repair time and waiting time under finite repair channels equal to the repair time under infinite repair channels based on the queuing theory. According to the modified accommodative models, the mean and variance models of two indenture spares in repair and supply channels were found. Combined with the application instance, the impact of spares demand rate and the amount of repair channels on the repair time were analyzed. The application effect of the stockpiles programs under the finite repair channels model and infinite repair channels model were compared and analyzed. The applicable conditions of each model were given. And the results show that the modified accommodative models are effective.
基于SE-DEA模型的生态环境可持续发展评价——以闽江源流域为例
,剑仑,应春,黄海棠
草业科学 , 2014, DOI: 10.11829\j.issn.1001-0629.2014-0302
Abstract: ?以生态环境投入产出的角度为基础,结合现有研究成果改进的可持续发展指标体系,采用三阶段SE-DEA模型,对闽江流域进行了可持续发展能力分析与评价。结果表明,近10年来(2003-2012年),闽江源流域生态环境可持续发展呈波浪式递增态势,但可持续发展能力偏弱;第三产业、科技投入、城镇化水平、工业产业和劳动力成为影响生态环境可持续发展的主要因素。生态环境的过度投入既造成资源的浪费,也是环境恶化的主导因素;科技进步、城镇化水平不断推进和劳动力水平的提升是实现生态可持续发展的助推器;推动产业升级,发展生态产业是生态环境可持续发展的有效途径。
外源性FGF-2对高糖环境下内皮祖细胞功能的影响
,陆晨晖,陆骊工,张海军,,茂全
- , 2018, DOI: 10.16118/j.1008-0392.2018.01.008
Abstract: 目的 观察外源碱性成纤维细胞生长因子-2(basic fibroblast growth factor-2, FGF-2)对高糖环境下内皮祖细胞(endothelial progenitor cells, EPCs)功能的影响。方法 体外分离和培养小鼠EPCs,并采用流式细胞分析和免疫荧光染色进行细胞鉴定,分别在高糖(30mmol/L)和高糖(30mol/L)+FGF-2(30、50、100、150、300ng/mL)条件下干预培养,正常EPCs作为空白对照组,TUNEL检测细胞凋亡,Transwell小室和基质胶在体外观察EPCs的迁移和成管能力;Western印迹法检测活化β-catenin和总β-catenin的表达,构建小鼠后肢缺血模型,分别注射空白组、正常组、高糖组及高糖+FGF2(150ng/mL)组EPCs,使用激光多普勒血流仪观察小鼠缺血后肢血流恢复情况。结果 高糖组EPCs比空白对照组凋亡率显著增高(P<0.01),迁移和血管形成能力显著降低(P<0.01);高糖+FGF-2组EPCs与高糖组相比,细胞凋亡显著减少(P<0.05),迁移和血管形成能力显著增强(P<0.05),且在150ng/mL FGF-2时效果最强(P<0.01)。Western印迹法分析表明,高糖组较空白对照组活化β-catenin/总β-catenin显著下降(P<0.01),而高糖+FGF-2组与高糖组相比则显著升高(P<0.05)。体内实验显示,高糖组小鼠缺血后肢较正常组血流恢复显著减少,而高糖+FGF-2组较高糖组显著增加。结论 外源性FGF-2处理可能通过激活Wnt/β-catenin信号通路发挥对高糖下受损EPCs的功能修复作用。
Objective To investigate the effects of exogenous basic fibroblast growth factor-2 (FGF-2) on the damaged biological activity of endothelial progenitor cells (EPCs) induced by high glucose. Methods Bone marrow endothelial progenitor cells from C57BL/6 mice was isolated,then cultured in vitro and identified by flow cytometry and immunofluorescence staining. EPCs were treated with high glucose (30 mmol/L) and high glucose + FGF-2 (30, 50, 100, 150 and 300 ng/mL) respectively, and normal EPCs were taken as a blank control. The cell apoptosis was detected by TUNEL, the migration and tube formation ability of EPCs in vitro were observed by Transwell chamber and Matrigel reagent; the expression of activated β-catenin and total β-catenin was detected by Western blot. Mouse hind limb ischemia model was constructed; and the ischemic hind limb mice were injected with EPCs obtained from blank, normal high glucose and high glucose +FGF2 (150 ng/mL) groups, respectively. The blood flow recovery was observed by laser Doppler flowmetry in mice with ischemic hind limbs. Results EPCs in high glucose group were significantly higher than those in blank control group(P<0.01), and migration and tube formation ability significantly decreased(P<0.01). Compared with high glucose group, cell apoptosis significantly decreased and the migration and tube formation ability significantly increased in the high glucose + FGF-2 group; and the effect of 150 ng/mL FGF-2 was the strongest (P<0.05,P<0.01). Western blotting analysis showed that the ratio of activated β-catenin/total β-catenin in the high glucose group was significantly lower than that in the control group, while the ratio in high glucose + FGF-2 groups was significantly higher than that in the high glucose group. In vivo experiments showed that the blood flow recovery of the ischemic hind limbs of
任务准备期内的军用飞机瞬时可用度
Instantaneous availability of military aircraft during mission preparation period

,克难,杨春周,孙媛,季颖
- , 2017, DOI: 10.13700/j.bh.1001-5965.2016.0279
Abstract: 摘要 军用飞机是一种复杂的可修系统,其瞬时可用度计算是装备综合保障领域研究的难点。本文构建了基于作战任务和飞机技术状态驱动的随机维修网络(SMTN),SMTN中各项活动的维修时间服从不同分布,定义了SMTN的矩母函数并求解系统维修度函数的数字特征,将得到的期望和方差分别代入不同分布形式函数进行验证,从而选定符合实际情况的SMTN的维修度函数,并对任务准备期内的军用飞机可用度进行仿真。在计算过程中基于蒙特卡罗技术设计了一种新方法,在提高计算效率的同时,可以较好地反映维修保障过程的逻辑性、拓扑性和随机性,仿真结果可以真实反映装备在任务准备期内瞬时可用度的波动规律。该方法可以广泛应用到各种复杂的可修系统,为装备的使用决策提供依据,为保障系统的保障效能评估提供量化指标,对于综合保障领域“动态”指标的研究有着一定探索价值。
Abstract:Military aircraft is a complex repairable system, instantaneous availability analysis of it is a difficult problem in the integrated logistics support field. The stochastic maintenance task net (SMTN) based on mission requirement and technical condition of the military aircraft is constructed, and the maintenance function distribution types of activities in the SMTN are different. The moment generating function is defined, and the numerical characteristics of the system maintenance distribution function are solved. The functions are verified by substituting expectation and variance into different distribution functions, and the maintenance functions that meet the actual situation are selected. And the military aircraft availability in the mission preparation period is simulated. In the calculation process, a new method is designed based on the Monte Carlo method, which can increase calculation efficiency and well reflects the logic, topology and randomness of the maintenance process. The simulation result can truly reflect the fluctuation of the instantaneous availability of military aircraft in the mission preparation period. This method can be widely applied to complex repairable systems to provide basis for decision-making of the use of equipment and to provide quantitative indicators for support effectiveness evaluation of support system, and is of certain exploration value on the research of "dynamic" indicator in the integrated logistics support field.
GaAs/AlGaAs光子平行存贮器的性能
夏永伟,学公,国花,樊志,王守武
半导体学报 , 1996,
Abstract: 本文报告用PnpN型GaAs/AlGaAs结构的光电双稳器件形成的光子平行存贮器单元器件和4×4阵列器件的特性.单元器件的最小维持功耗小于30μW.使器件从“关闭”态翻转到“导通”态所需的光触发功率小于80μW.单元面积160×160μm、间距40μm的存贮器4×4原理性阵列已经研制成功,这是0.85μm波长范围的光子平行存贮器的首次报道.
Page 1 /298100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.