Recording head field for SPT head combined with hard/soft magnetic composite pillar array media

The head field distribution for hard/soft magnetic composite pillar array media (CPA media) is significantly different from that of the conventional patterned media. The head field distribution for a CPA media-single-pole-type (SPT) head system which assumes 1 Tbits/in² recording is calculated by the three dimensional finite elements method. One of the features of the system is that a magnetic flux concentrates in a hard magnetic unit. The system is found to yield 80% of the field strength of SPT head and continuous SUL media system.     

Pressure Distribution in a Semi-infinite Horizontal Aquifer with Steep Gradients Due to Steady Recharge and/or Drainage: The Exact Explicit Solution

Groundwater flow with steep gradients in a vertical plane of infinite horizontal extension due to arbitrary non-symmetric strip sources and/or sinks can be described by the 2D Laplace equation. Notwithstanding the strongly nonlinear character of the free surface boundary condition, the exact analytical solution to this problem is developed in a closed form by employing neither the Dupuit assumption nor any other form of linearization. The first section of the development, still including the unsteady case, leads via conformal mapping and transformation procedures to a singular integro-differential-equation for the transient groundwater table. From this point onwards we restrict ourselves to the steady case for which the exact solution of the 2D Laplace equation for the pressure head and the location of the groundwater table was achieved. The solution is expressed exclusively in algebraic terms without the need for iterative procedures. It can not only be applied to real world phenomena, including a simple solution of the inverse problem, but also provide a new transparency regarding the solution characteristics and may serve as a standard for investigating numerical solutions and the domain of validity of simplified approaches. The computer program can be downloaded from www.tu-dresden.de/fghhihm/hydrologie.html     

柔性头部模型与大挠度板接触撞击力的预报方法

针对被撞击板是大挠度的特点,提出了模拟函数预报撞击力的方法,根据撞击系统的动量守恒原理推导出了撞击力的预报方程,用恢复系数考虑头皮对撞击缓冲的影响.得到了头部与发动机罩板大变形、非线性、瞬态撞击过程的响应函数.分析结果与鸿巢敦宏、石川博敏的试验数据进行了对比,结果显示有较好的一致性,表明该方法能够较好地描述柔性球体模型与大挠度板接触撞击的响应过程.同时还利用该预报方程分析了各种因素对接触撞击力的影响.     

拦截高超声速飞行器的三维有限时间制导律设计

由于高超声速飞行器具有飞行速度快、机动能力强等特点,因此,传统的制导方式难以保证拦截弹拦截高超声速飞行器时的制导精度。为了减小弹目相对速度,降低对拦截弹的过载能力要求,按照前向制导方式,设计了有限时间收敛的三维前向滑模制导律。该制导律采用了连续的快速双幂次趋近律,不仅保证收敛速度快,同时削弱了传统制导律中存在的抖振现象。在此基础上为了处理系统扰动的上界未知的问题,又设计了自适应滑模制导律,该制导律既可以处理未知上界的外部扰动又可以保证第一种制导律所具有的良好特性。运用李雅普诺夫稳定性理论对所设计的滑模制导律进行了理论证明,最后,通过数值仿真验证了所设计制导律的有效性及优越性。     

范德华力对磁头/硬盘薄膜气体润滑动态特性的影响

利用摄动法分析了纳米间隙下范德华力对磁头动态飞行特性的影响规律.结果表明,在飞行高度低于5 nm后,范德华力降低了磁头的承载能力和飞行高度,使飞行高度和俯仰气膜刚度降低,对侧翻气膜刚度没有明显影响.范德华力对磁头滑块飞高振幅的影响主要在于特征振动频率区间,因此,通过磁头设计提高磁头特征振动频率,可以减弱范德华力对飞高振幅的影响.     

加速度计的全组合标定方法

阐述了在重力场上用全组合法标定单加速度计的方法,并且推导了加速度计全组合标定法测试原理。这种方法剔出了测试设备的确定性角位置误差对加速度计误差模型系数标定精度的影响,提高了加速度计的标定精度。结合上述的理论分析,对某型号加速度计进行了实际测试和误差分析,实验结果证明本方法对于提高加速度计标定精度是非常有效的。     

单水库在线发电调度策略设计与分析

考察单水库电站的多时段发电调度问题,决策者在每个时段初决策该时段的发电量,目标是使得在整个调度期内总发电量最大。针对在每个时段决策时缺乏当前及后续时段来水信息的情形,运用在线理论建立在线发电调度模型,设计给出了竞争比为2/(2-β(1-Ф))的在线发电调度策略,其中,β∈(0,1)表示每个时段最大来水导致的水头最大增幅与水库有效水头最大落差的比值,Ф∈(0,1)表示最低与最高有效水头数值之比。针对各时段可获知当前时段来水信息的情形,给出了在线调度策略,并证明了其竞争比为1+(1-Ф)/(1+Ф)。     

单自由度冲击扰动下模拟磁头／磁盘系统接触回复特性的实验研究

采用自制的试验装置研究了单自由度冲击扰动下磁头 /磁盘系统的接触回复特性 ,分析了不同载荷下球形模拟磁头跳跃振动回复系数和接触时间与输入速度之间的关系 .结果表明 :当载荷较小时 ,回复系数随着输入速度的减小而增加 ,而当载荷较大时 ,回复系数随着输入速度的减小而减小 .在不同载荷条件下 ,接触时间均随输入速度的减小而缩短 ,但小载荷下接触时间缩短的幅度较大 .球形模拟磁头的回复特性和接触时间与载荷、输入速度及润滑膜特性有关 ,增大载荷和选择合适的润滑剂均可抑制跳跃振动     

Influence of the projectile composition and shape during an impact

Slug impact is considered a potential risk for pressurized water reactors in the event of a severe accident. The German team of FZK investigates this issue through the reduced-scale experiments BERDA, whose goal is to quantify the maximum mechanical energy that the upper head of a PWR is able to withstand. As these tests are performed with a material different from the one that would intervene in a real accident, the French team of CEA studies the influence of the slug material with the SKIPPY mock-ups. In order to understand better the impact process, relevant theoretical study has been conducted with the EUROPLEXUS code Published in Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 3–15, May 2006.     

Anthelmintic Effect of Leucaena leucocephala Extract and Its Active Compound,Mimosine, on Vital Behavioral Activities in Caenorhabditis elegans

Helminth infections continue to be a neglected global threat in tropical regions, and there have been growing cases of anthelmintic resistance reported towards the existing anthelmintic drugs. Thus, the search for a novel anthelmintic agent has been increasing, especially those derived from plants. Leucaena leucocephala (LL) is a leguminous plant that is known to have several pharmacological activities, including anthelmintic activity. It is widely known to contain a toxic compound called mimosine, which we believed could be a potential lead candidate that could exert a potent anthelmintic effect. Hence, this study aimed to validate the presence of mimosine in LL extract and to investigate the anthelmintic effect of LL extract and mimosine on head thrashing, egg-laying, and pharyngeal pumping activities using the animal model Caenorhabditis elegans (C. elegans). Mimosine content in LL extract was confirmed through an HPLC analysis of spiking LL extract with different mimosine concentrations, whereby an increasing trend in peak heights was observed at a retention time of 0.9 min. LL extract and mimosine caused a significant dose-dependent increase in the percentage of worm mortality, which produced LC50s of 73 mg/mL and 6.39 mg/mL, respectively. Exposure of C. elegans to different concentrations of LL extract and mimosine significantly decreased the head thrashing, egg-laying, and mean pump amplitude of pharyngeal pumping activity. We speculated that these behavioral changes are due to the inhibitory effect of LL extract and mimosine on an L-type calcium channel called EGL-19. Our findings provide evidential support for the potential of LL extract and its active compound, mimosine, as novel anthelmintic candidates. However, the underlying mechanism of the anthelmintic action has yet to be elucidated.