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Search Results: 1 - 10 of 69053 matches for " 芮雄丽 "
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不对称速率双向中继系统的中继选择及功率分配
杨洁,曹雪虹,,陈瑞
南京邮电大学学报(自然科学版) , 2014,
Abstract: 研究了不对称速率双向放大转发中继系统中的中继选择及功率分配问题。以中断概率作为约束条件,以系统总发射功率最低为目标,通过将几何规划问题转化成凸优化问题推导了功率分配的闭式解。在此基础上,提出了最小化最低总功率的中继选择标准。最后给出了中继选择与功率分配联合优化策略及实施步骤。仿真结果表明在给定的中断概率门限下,文中的联合优化策略能显著降低系统的功率消耗。
一种总发射功率最小化的协作MAC协议
Cooperative MAC protocol based on total transmission power minimization

,曹雪虹,杨洁,陈瑞
- , 2015,
Abstract: 针对能量受限的无线传感器网络,提出了一种能降低网络能耗的跨层协作MAC(Medium Access Control)协议。文中首先分析了直接传输和协作传输下的总发射功率,理论分析表明,在一定的误码率限制下,引入合适的中继节点能降低网络总的发射功率。在802.11DCF(Distributed Coordination Function)的基础上,通过监听邻居节点控制包,获得各信道的状态信息,并选出使总发射功率最小的最佳中继,同时扩展CTS(Clear To Send)、增加HTS(Helper ready To Send),完成自适应的协作传输。仿真表明,该MAC协议能有效降低网络能耗,延长网络寿命。
A cooperative medium access control (MAC) protocol based on total transmission power minimization is proposed to reduce the network energy consumption in energy limited wireless sensor networks. With theoretical analysis, appropriate relay nodes can reduce the total transmission power of the network and the bit error rate of the destination node constrained at a certain target level. Based on the 802.11 distributed coordination function (DCF), the channel state informations (CSIs) are estimated according to the strength of control frames and the best relay by minimizing the total transmission power of the network is selected. Furthermore, to design an adptive cooperative transmission scheme, the frame format of clear to send (CTS) is extended and a helper ready to send (HTS) frame is introduced. Simulation results show that the proposed MAC protocol can effectively reduce the energy consumption and extend the network lifetime
随机微分方程的几种参数估计方法
Some methods of parameter estimation for stochastic differential equations

蔡昕,
- , 2017, DOI: 10.7523/j.issn.2095-6134.2017.05.001
Abstract: 摘要 提出3种基于离散观测数据的随机微分方程参数估计的方法。第1种方法应用于线性随机微分方程。推导出这类方程的真解的相关运算服从的分布,使观测数据的运算也服从此分布,由此来估计漂移系数与扩散系数中的未知参数。第2种方法用于It?型随机微分方程。推导出Euler-Maruyama格式的数值解的相关运算服从的分布,使观测数据的运算服从此分布,由此来估计参数。第3种方法用于Stratonovich型随机微分方程。推导出中点格式的数值解的相关运算服从的分布,使观测数据的运算服从此分布,以此来估计参数。数值实验验证了这3种方法的有效性。数值实验显示,Euler-Maruyama格式参数估计的误差约为O(h0.5)阶,中点格式参数估计的误差约为O(h)阶,其中h是数值方法的时间步长。我们提出的3种估计方法均比文献中已有的EM-MLE方法更精确。
整体装配式预应力板柱节点摩擦性能的试验研究
,,,谢灵慧,
- , 2017,
Abstract: 通过对6个整体装配式预应力板柱结构节点试件的试验研究,分析了板柱节点灌缝的胶结材料(如细石混凝土)强度、预应力大小、外加剂等因素对板柱节点界面摩擦性能的影响,并对比了板柱节点处存在细石混凝土胶结材料与否时的差异.试验结果表明:板柱节点处灌缝细石混凝土会显著提高节点摩擦性能,与不灌缝的节点试件相比,摩擦性能提高幅度在35%以上.细石混凝土的强度、施加预应力大小、外加剂种类也会不同程度影响节点的摩擦性能.当细石混凝土立方体抗压强度由30 MPa增加到40 MPa时,界面摩擦性能提高约9.8%.预应力从300 kN增大到450 kN时,节点界面摩擦性能提高约55.1%,膨胀剂添加后对节点界面摩擦性能也有提高作用,但是幅度很小.
The influences of cement-based material (such as fine aggregate concrete) strength,prestressing,additive admixture and other factors on the friction performances of the integral prefabricated prestressed slab-column joint structures were analyzed through experimental study on 6 joints. The difference between the slab column joints with and without fine stone concrete cement material was also compared. The results show that fine stone concrete at the slab column joints can significantly improve the friction performance. The friction performance was increased by more than 35% when compared with that of the joint specimen without filling materials. Cement material strength,prestress and additive admixture can affect the friction performance of the node to various degrees. When the cubic strength of the fine aggregate concrete increased from 30 MPa to 40 MPa,the friction performance at the joint interface increased by about 9.8%. When the prestress increased from 300 kN to 450 kN,the friction performance of the joint interface increased by around 55.1%. The expansion agent can also improve the friction performance of the joint interface,but the effects are just a little.
上证综合指数日收盘价的短期预测——基于ARIMA模型的实证分析
Short Term Forecast ofDaily Closing Price of Shanghai Composite Index—Empirical Analysis Based on ARIMA Model
 [PDF]

周小, 吴志
Advances in Social Sciences (ASS) , 2016, DOI: 10.12677/ASS.2016.54088
Abstract:
上海证券交易所作为国内两大交易所之一,它编制的上证综合指数能有效反映在该交易所上市的股票价格的变动情况。通过建立合适的时间序列模型,对该指数变化趋势进行预测分析具有重要意义。文章对历史数据进行处理,通过R语言进行模型选择及估计,实现上证综合指数日收盘价格的短期预测,为股票市场投资者提供相关参考。
Shanghai stock exchange is one of the two major exchanges, its establishment of the Shanghai Composite Index can effectively respond to changes in the stock price listed on the exchange. Through the establishment of a suitable time series model, it is important to predict and analyze the trend of the index change. By dealing with the historical data and using R to select the model and estimate the parameters, this article achieved the short-term closing price forecasting of the Shanghai Composite Index, and this will provide the relevant reference for the trend analysis of stock market.
低温冻结预处理对胡萝卜渗糖速度及果脯质量的影响
汉明,汤伟,陈中
食品科学 , 1996,
Abstract: ?利用低温冻结预处理方法,以胡萝卜为主要原料,研究在不同条件下的渗糖速度及果脯质量。结果表明:采用低温冻结预处理样品的吸糖速度大大快于热烫和未经处理的样品,其收缩变形小,具有良好的色、香、味及质构,有利于缩短果脯生产周期,提高产品质量。
低通滤波器LPF对谐波检测电路影响的研究
Research on the Impact of Low Pass Filter LPF on Harmonics Detection Circuit
 [PDF]


Smart Grid (SG) , 2012, DOI: 10.12677/sg.2012.21002
Abstract: 本文对基于瞬时无功功率理论的谐波电流检测法进行了研究,并利用MATLAB/SIMULINK就其中的低通滤波器对谐波电流检测效果的影响进行了仿真实验。结果表明LPF的截止频率、阶数和类型对检测电路的动态响应过程、检测精度都有很大影响,从而为谐波检测电路中LPF的选取提供了指导。
This paper has researched the harmonics current detection method based on instantaneous reactive power theory, and the impact which low pass filter has on harmonics current detecting has been simulated by MAT-LAB/ SIMULINK. The simulation results show that the dynamic response and the detection precision can be greatly influ-enced by the cut-off frequency, order and type of the low pass filter in the harmonics detection circuit. Thus this can provide guidance for the selection of LPF in harmonics detection circuit.
乙烯氧乙酰化固定床反应器的模拟与催化剂分布优化
赵振兴,,陈甘棠
化工学报 , 1994,
Abstract: 采用拟均相一维和二维模型对乙烯氧乙酰化工业固定床反应器进行了数学模拟,结果表明:反应器进口气温即为热点温度,可以进一步提高催化剂活性和生产能力.当催化剂活性达到现活性的3倍时,传统的反应器将出现热失控(飞温).采用分段填装高活性催化剂的优化分布,可以大大降低反应器的热敏感性,提高反应转化率和选择性.例如,用两段填装催化剂平均活性(?)=2的反应器代替一段填装催化剂的反应器时,热点温度降低了13.9℃,乙烯转化率和乙烯转化为醋酸乙烯的选择性分别提高了1.46%和1.41%.
流动人口生殖健康权利意识及影响因素分析
张开宁,,邓睿,
中国公共卫生 , 2008, DOI: 10.11847/zgggws2008-24-11-59
Abstract: ?目的了解云南省昆明市流动人口生殖健康权利意识及其影响因素。方法在昆明市某区2个街道办事处共20个居民小组采用多阶段分层抽样抽取519名年龄18~49岁并在昆明市居住3个月以上的流动人口(非昆明市户口)进行问卷调查及个人深入访谈。结果绝大多数流动人口生殖健康权利意识亟待提高。多因素Logistic回归分析结果显示:影响流动人口生殖健康权利意识的主要因素有受教育水平、职业和网络朋友3个变量。结论亟需开展对流动人口生殖健康权利意识的教育与促进工作。初中及以下文化程度者、从事非技术工作或一般性技术工作者、家庭主妇应该成为教育的重点人群。
含油污泥体膨颗粒调剖剂的研究
,刘国良,赵振兴,田立志
环境工程 , 2006, DOI: 10.13205/j.hjgc.200603020
Abstract: 研究了利用含油污泥制备体膨颗粒深部调剖剂的技术。试验表明,在单体浓度20%、干泥含油率14%、污泥占单体质量110%、交联剂占单体质量0.14%、反应温度35℃条件下,聚合产物性能较好。胶块造粒过程中需加入适量减阻剂,粒度可根据实际要求调整。含油污泥体膨颗粒调剖剂在自来水中和0.5%NaCl水溶液中的膨胀倍数分别为40倍和15倍,膨胀后强度和弹性好。
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