低能小型医用回旋加速器谐振腔的有限元分析

应用有限元方法分析了一台小型医用回旋加速器的谐振腔.以PC机为平台,采用ANSYS软件进行建模,对腔体的谐振频率、空载品质因数进行了研究,探讨了微调电容间距、网格剖分精度以及建模方法对计算结果的影响.回旋加速器谐振腔不是一个严格的封闭腔体,结构复杂.为减少计算量,根据其物理特性对腔体做了封闭处理,研究发现,这一简化的模型对计算精度的影响不大.计算结果和实际测量结果的误差在工程允许的范围之内,表明基于有限元的软件能够很好地计算类似回旋加速器高频谐振腔这样具有复杂边界的腔体结构,可用于加速器的物理设计及工程设计.     

The Differentiated Effect of Administrative Policy in China's Housing Market——Based on the Heterogeneous Households Multi-Agent Model

Since 2010, Chinese government has introduced a series of administrative policies to limit speculation in the housing market to stabilize price fluctuations and keep the housing market in a healthy state of development. In order to investigate whether administrative policy can play its due role, this paper constructs a comprehensive bottom-up housing market heterogeneous households multiagent model(HHMAM) to undertake research on the differentiated effect of administrative policy in different cities. The empirical studies find that: 1) Administrative policy that increases interest rates will cause housing prices to continue to decline in the long term, but they will resume a rising trend after reaching the lowest point; 2) If the government cancels a property-purchasing limitation, housing prices will continue to rise; and 3) investors tend to invest in 1~(st)-tier cities due to the high demand and greater likelihood of appreciation in these cities.     

Experimental studies on oxidizing removal of Cyclops of zooplankton

0 IntroductionCyclops couldn’t be effectively inactivated by theconventional disinfection such as chlorination due to itsstronger resistance to oxidation.In addition,the motilityof Cyclops makes it easily penetrate sand filter into theclean water tank in waterworks , even municipal servicepipe .Adult Cyclops , with body length of one to severalmillimeters, may be caught by naked eye to bring con-sumers unsanitary sense and may become disease trans-mission mediumas the host of pathogenic para…     

1546例泌尿生殖道支原体感染及药敏分析

目的:了解近年广州市性病门诊患者支原体感染及耐药情况,为临床选择敏感治疗药物提供参考依据。方法:对1 546例性病门诊患者进行了支原体培养,并对阳性标本进行10种抗生素药敏试验。采用支原体培养、鉴定及药敏一体化试剂盒进行检测。结果:1 546例中支原体阳性560例,阳性率为36.22%。解脲脲原体(Uu)、人型支原体(Mh)及Uu Mh混合感染的阳性率分别为28.85%、1.03%、6.34%。Uu感染敏感率最高的是交沙霉素(92.4%),其次是强力霉素(85.7%)、美满霉素(80.9%);耐药率最高的为环丙沙星(69.5%),其次是罗红霉素(63.3%)、阿奇霉素(61.2%)。Mh感染敏感率最高的是强力霉素(68.8%)、美满霉素(62.5%);耐药率最高的为环丙沙星、氧氟沙星、阿奇霉素、克拉霉素(均为50.0%)。Uu Mh混合感染敏感率最高的是强力霉素(39.8%)、美满霉素(35.7%);耐药率最高的为环丙沙星和罗红霉素(均为63.3%)、阿奇霉素(61.2%)。结论:性病门诊支原体感染主要为Uu引起;就广州市支原体感染而言,应将交沙霉素、强力霉素或美满霉素作为目前治疗泌尿生殖道支原体感染的首选抗生素。     

四川盆地北部二叠系茅口组沉积特征及油气意义

基于地震资料精细解释成果,结合野外剖面及室内薄片观察,通过分析主要岩石类型及古生物、地球化学和地震相特征,对四川盆地北部二叠系茅口组沉积相展布特征进行研究,依据生物(屑)灰岩、礁灰岩和硅质岩等岩相发育规律以及地震地层结构和地层厚度变化特征,认为茅口组发育了开阔台地、台地边缘及斜坡—盆地等沉积亚相,总结出了开阔海夹点礁、开阔海夹点滩、台地边缘滩和灰质—硅质盆地等4种沉积微相组合,明确了沉积相纵向演化和平面展布规律。结果表明,台地边缘高能生物滩平面上呈条带状在剑阁—元坝—龙岗一带规模发育,生物(屑)灰岩的晶间溶孔、粒间溶孔和生物体腔孔发育,物性好,是优质储集层发育带;川西海槽和广元—旺苍海槽茅四段的硅质岩和泥岩有机碳含量高,则是优质生油岩,优越的沉积环境为该区油气成藏提供了有利的生油和储集条件。     

单透镜分数傅里叶变换全息图

基于分数傅里叶变换理论并以分数阶这一重要参量为纽带,推导和分析了分数傅里叶变换与菲涅耳衍射之间的关系;提出了基于罗曼I型分数傅里叶变换系统的分数傅里叶变换全息图,并实现了其计算机生成及数字重现;研究表明,分数傅里叶变换是描述菲涅耳衍射的理想工具,分数傅里叶变换全息图可以同时记录物体和系统的信息,开拓了分数傅里叶变换和全息术的应用领域。     

考虑自动驾驶仪动态特性与攻击角约束的模糊自适应动态面末制导律

在大口径舰炮制导炮弹打击近岸机动目标的末制导段,考虑自动驾驶仪二阶动态特性与攻击角约束,基于模糊自适应逼近与动态面控制提出一种末制导律。构建二维弹目相对运动模型,运用扩张状态观测器估计目标加速度。为零化视线角的跟踪误差与视线角速率,采用自适应指数趋近律设计非奇异终端动态面滑模,设计模糊自适应系统逼近变结构项,削弱自动驾驶仪的控制指令抖振。通过Lyapunov第二法证明了闭环系统中视线角的跟踪误差与视线角速率均一致最终有界。仿真实验表明:该制导律使制导炮弹在打击具有不同加速度形式的目标时,均具备较好的末制导性能。     

A Survey on Algorithms for Computing Comprehensive Gröbner Systems and Comprehensive Gröbner Bases

Journal of Systems Science and Complexity - Weispfenning in 1992 introduced the concepts of comprehensive Gröbner system/basis of a parametric polynomial system, and he also presented an...     

怎样利用Visual Basic制作PowerPoint多媒体课堂时间显示器

针对现代多媒体课堂教学中,PowerPoint全屏放映时无法看到系统时间,影响教学效率这一问题,本文介绍了利用V isual Basic制作PowerPoint多媒体课堂时间显示器的设计思想和方法.