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Search Results: 1 - 10 of 18573 matches for " 卢紫莼 "
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暗霉素的快原子轰击(FAB)质谱
方一苇,,林桂坚
化学学报 , 1985,
Abstract:
苯并-3-氮杂环庚酮-1衍生物及N-二烷氧基磷酰基-N-取代苯乙基甘氨酸衍生物的电子电离质谱
,严琳,徐梦山,奚士康,赵玉芬,方一苇
分析化学 , 1986,
Abstract: 应用高分辨质谱,准确质量测定和亚稳态离子的测定结果,对五个苯并-3-氮杂环庚酮-1衍生物及六个N-二烷氧基磷酰基-N-取代苯乙基甘氨酸衍生物的断键机理进行了研究。在EIMS条件下,前者的分子离子峰比后者强;N原子上发生电离的几率最大;除磷酰基上取代基为甲基的两个化合物外,其他九个化合物均含有m/z110(CH5O3NP)碎片离子;由于受磷酰基的影响,这些化合物都发生C—N键特征断裂。
边界约束二次规划问题的分解方法
战杰,
计算数学 , 1999,
Abstract:
机械变速器换档的接合过程建模及特性分析
Modeling and characteristic analysis of engaging process during gear shifting of mechanical transmissions

陈红旭,,王立军,田光宇
- , 2018,
Abstract: 接合套和接合齿圈的接合过程是影响机械变速器换档品质的关键阶段。针对在接合过程中,当接合套和接合齿圈在齿端倒角处接触时碰撞发生,其相对速度会发生突变,相应的耦合关系及动力学方程也会发生改变的现象,为了得到机械变速器整个接合过程的精确数学模型和特性,运用多体动力学理论和混杂系统方法建立了描述接合过程的混杂自动机模型。在该模型中,用3个微分方程组描述接合过程中接合套和接合齿圈在不同耦合关系下的动力学特性;引入泊松恢复系数,建立了4个差分方程组描述碰撞过程接合齿圈转速、接合套轴向运动速度和转速产生的突变。基于该混杂自动机模型,在MATLAB环境下进行了仿真分析,得到了接合过程中接合套和接合齿圈的轨迹、接合时间和最大冲击,分析了换档力、接合套相对接合齿圈的初始转速和位置对接合性能(时间和最大冲击)的影响。研究结果表明:接合套和接合齿圈的相对位置对接合时间和冲击有显著影响;当接合套和接合齿圈的转速差在一定范围内时,接合时间较短,过大的转速差则会使接合时间呈指数上升;接合套和接合齿圈的转速差越大,冲击越大;增大换档力可缩短接合时间,但会增大冲击。在设计机械式自动变速器的控制系统时,应根据机械变速器换档过程的特性,选取最佳的换档力、相对转速、相对位置作为控制参数,进而缩短动力中断时间,减小换档冲击。
The engaging process of engaging sleeve and clutch gear is the key phase influencing the gear shifting performance of mechanical transmissions. During an engaging process, collision occurred when engaging sleeve and clutch gear contacted at the end of the tooth chamfer, their relative speed suddenly changed, and their coupling relationship and dynamic equations also changed. In order to obtain an accurate mathematical model and characteristics of the engaging process of mechanical transmission, a hybrid automaton model was built to describe the engaging process through multi-body dynamics theory and hybrid system methodology. In this model, three sets of differential equations were built to describe the dynamic characteristics of engaging sleeve and clutch gear under different coupling relationships during an engaging process. Poisson recovery coefficient was introduced to build four sets of difference equations to describe the rotational speed of clutch gear, the axial movement speed of engaging sleeve and the sudden change of rotational speed during the collision process. Based on the hybrid automaton model, simulation analysis was carried out in the MATLAB environment. The trajectories, the engaging duration and the maximum impact of engaging sleeve and clutch gear during their engaging process were obtained. The effects of the shifting force and the initial rotational speed and position of engaging sleeve relative to clutch gear on engaging performance were analyzed. The results show that the relative position of engaging sleeve and clutch gear has significant effect on the engaging duration and the maximum impact. If the rotational speed difference of engaging sleeve and clutch gear is within limit, the engaging duration is relatively short, and a big rotational speed difference will cause an exponential rise of engaging duration, a bigger rotational speed difference of engaging sleeve and clutch gear will cause a bigger engaging impact. When increasing the shifting force, the engaging duration will
在CD-ROM上的LCMARC记录传输至普通计算机
,杨宗英
现代图书情报技术 , 1988,
Abstract: 利用光盘上的LCMARC记录进行西文书刊编目有很大的优越性:数据全、查找快、功能强并方便使用。但CD-ROM仅限于IBM-PC/XT及兼容机使用。为此,我们编写了LCPRE程序,把CD-ROM上的LCMARC记录转换成标准的LCMARC通讯磁带格式。现已用于我馆HP 3000计算机的管理集成系统中。
高分辨率视频会议中基于模板的自适应编码算法
,叶德建
中国图象图形学报 , 2007, DOI: 10.11834/jig.20071028
Abstract: 如今,对高分辨率的便携计算机视频会议系统的需求日益高涨。虽然便携计算机使用方便、局域网带宽充足,能够为工作学习带来许多益处,然而计算资源的紧张却直接影响了高分辨率视频会议的效果。针对这个问题提出了自适应模板编码算法(template―basedcodingalgorithm,TBCA),不仅能比传统自适应算法提高10%的计算资源利用率,还减少了近一倍的参数调整频率。TBCA已被实现在校园网会议系统(campusvideomeetingsystem,CVMS)中,成功地提高了用户体验。
DECOMPOSITION METHOD FOR QUADRATIC PROGRAMMING PROBLEM WITH BOX CONSTRAINTS
边界约束二次规划问题的分解方法

Lu Zanjie,Wei Ziluan,
战杰
,

计算数学 , 1999,
Abstract: A Decomposition method for solving quadratic programming (QP) with boxconstraints is presented in this paper. It is similar to the iterative method forsolving linear system of equations. The main ideas of the algorithm are to splitthe Hessian matrix Q of the oP problem into the sum of two matrices N and Hsuch that Q = N H and (N - H) is symmetric positive definite matrix ((N, H)is called a regular splitting of Q)5]. A new quadratic programming problem withHessian matrix N to replace the original Q is easier to solve than the originalproblem in each iteration. The convergence of the algorithm is proved under certainassumptions, and the sequence generated by the algorithm converges to optimalsolution and has a linear rate of R-convergence if the matrix Q is positive definite,or a stationary point for the general indefinite matrix Q, and the numerical resultsare also given.
船舶在碎冰区航行的离散元模型及冰载荷分析
,刘煜,孙珊珊,云亮,季顺迎
力学学报 , 2013, DOI: 10.6052/0459-1879-13-020
Abstract: 采用离散元模型对碎冰区浮冰与船舶结构的相互作用进行了数值研究。碎冰由三维圆盘单元构成,并考虑其在海流作用下的浮力、拖曳力和附加质量。船体结构由一系列三角形单元组合构造。通过海冰与船体单元间的接触判断和接触力计算,确定海冰与船体结构之间的相互作用。采用以上离散单元模型对不同冰况(冰速、冰厚、冰块尺寸和密集度)以及航速条件下,海冰对船体的动力作用过程进行了数值分析,对比分析了以上因素对船体冰载荷的影响,可为冰区船舶的安全运行和结构设计提供一定的借鉴作用。
卷烟主流烟气的中性香气成分分析
洪华俏,,易克,董道竹,练文柳,向阳
湖南农业大学学报(自然科学版) , 2008,
Abstract: 采用同时蒸馏萃取法,从卷烟主流烟气中萃取中性香气成分,对其进行气相色谱(GC)分析和气相色谱/质谱(GC/MS)鉴定.结果表明,在萃取时间为2 h,水浴温度为60 ℃的条件下,同时蒸馏萃取法能提取和分离出主流烟气中多种主要中性香气成分.在提取得到的中性香气成分中,质谱鉴定出了72种,其中:烃类17种,醛类7种,酮类23种,醇类9种,酯类8种,醌类1种,含氧杂环类2种,含氮化合物5种.所测标样的回收率为70.9%~85.4%.提取的25种含量较高的中性香气成分中,除植醇外,相对标准偏差均在10%以下.
沙尘天气对呼吸系统疾病日入院人数影响的时间序列研究(1995~2003年)
,,周义,黄文清,王彤,耿红,张剑
环境科学学报 , 2006,
Abstract: 为了探讨沙尘天气,特别是沙尘暴对人群呼吸系统健康的影响,对过去9年(1995~2003)沙尘暴高发地区甘肃省武威市的6所大中型医院沙尘天气高发季节(3月1日~5月31日)每日呼吸系统疾病入院人数进行了调查.采用半参数广义相加模型(Semi-parametricgeneralizedadditivemodel,GAM),在控制了长期趋势、日历效应(calendareffect)以及气象因子等混杂因素后,考虑到具体年份的差异,分别对每年建立GAM回归模型(滞后7d)并进行分析.然后应用Meta-分析方法的固定效应模型对各年GAM分析结果(即相对危险度RR)进行效应量合并,计算合并效应量(RR+),以此表示沙尘天气对呼吸系统疾病日入院人数的综合影响.结果表明:(1)对于沙尘暴的影响,各年呼吸系统疾病日入院相对危险度(RR)合并效应量(RR+)随沙尘暴滞后天数的不同而不同,且在滞后3、4、5d时每天的RR+均有统计学意义,其RR+分别为1.40(95%CI为1.06~1.86)、1.34(95%CI为1.01~1.77)、1.73(95%CI为1.35~2.23);(2)扬沙天气在其滞后第6天RR+有统计学意义(RR+为1.14(95%CI为1.01~1.30);(3)浮尘天气与扬沙天气类似,也在其滞后第6天RR+有统计学意义,其RR+为1.12(95%CI为1.00~1.25).(4)沙尘天气对人群健康的影响,可根据滞后不同天的RR+值变化,分为滞后早期效应、滞后中期效应和滞后后期效应三类;(5)沙尘天气引发和加重的呼吸系统疾病主要为各种肺炎、上呼吸道感染和感冒以及急、慢性支气管炎.这些结果表明,呼吸系统日入院人数沙尘天气,特别是沙尘暴与有关联系,且均表现为滞后效应,而且沙尘暴的影响强度大于扬沙天气或浮尘天气的影响.
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