Motor noise generation and prediction for high spinning speed hard disk drive

The acoustic level of a hard disk drive is an important specification. This is especially so for enterprise HDD which is required to operate under a high spinning speed. In order to reduce the acoustics level of a HDD, an in depth understanding behind the mechanisms whereby the noise is being generated in a HDD should be established. This paper will study the acoustics characteristics of a high speed permanent magnet brushless DC motor (PM BLDC) and investigate the physics underlying the generation of noise associated with a motor. An analysis procedure of the PM BLDC motor noise generating mechanisms is proposed. Through finite element analysis and experimental verification, the results indicate that the major noise source for the high speed PM BLDC motor is due to the presence of electromagnetic (EM) torque ripples. Furthermore, it has been observed that the noise radiated by a HDD can be amplified when its structural dynamics are close to the frequency components of the noise source. Finally, a methodology which discusses the steps involved in the prediction of motor radiated noise will be presented.     

A new criterion of delay-dependent asymptotic stability for Hopfield neural networks with time delay.

In this brief, the problem of global asymptotic stability for delayed Hopfield neural networks (HNNs) is investigated. A new criterion of asymptotic stability is derived by introducing a new kind of Lyapunov-Krasovskii functional and is formulated in terms of a linear matrix inequality (LMI), which can be readily solved via standard software. This new criterion based on a delay fractioning approach proves to be much less conservative and the conservatism could be notably reduced by thinning the delay fractioning. An example is provided to show the effectiveness and the advantage of the proposed result.     

PVP对溶剂热合成FeS2(Pyrite)的形貌控制研究

采用溶剂热合成技术,以FeSO4和(NH2)2CS为反应前驱物,在聚乙烯吡略烷酮(PVP)作表面活性剂的醇-水体系中获得了晶粒完整的FeS2(Pyrite)粉体.借助X射线衍射(XRD)和透射电镜(TEM)对合成样品的晶相组成、分散性、形貌进行了分析与表征,结果表明,以PVP为表面活性剂可以显著提高产物的分散性,适当调节PVP的用量可以有效调控FeS2晶体的大小与形貌.     

以EPROM查表反馈实现的抗干扰细分电路

介绍了新颖的以EPROM查表技术为核心的四细分辩向电路。由于采用了记忆元件及反馈回路,它能有效地滤除各种不符合相序的干扰脉冲信号,同时其它性能参数(如测量速度等)不受影响。该电路可用于光栅、激光干涉仪等输出非调制信号的增量式测量装置的信号处理。     

Characterization of a Thermostable and Surfactant-Tolerant Chondroitinase B from a Marine Bacterium Microbulbifer sp. ALW1

Chondroitinase plays an important role in structural and functional studies of chondroitin sulfate (CS). In this study, a new member of chondroitinase B of PL6 family, namely ChSase B6, was cloned from marine bacterium Microbulbifer sp. ALW1 and subjected to enzymatic and structural characterization. The recombinant ChSase B6 showed optimum activity at 40 °C and pH 8.0, with enzyme kinetic parameters of K_m and V_max against chondroitin sulfate B (CSB) to be 7.85 µg/mL and 1.21 U/mg, respectively. ChSase B6 demonstrated thermostability under 60 °C for 2 h with about 50% residual activity and good pH stability under 4.0–10.0 for 1 h with above 60% residual activity. In addition, ChSase B6 displayed excellent stability against the surfactants including Tween-20, Tween-80, Trion X-100, and CTAB. The degradation products of ChSase B6-treated CSB exhibited improved antioxidant ability as a hydroxyl radical scavenger. Structural analysis and site-directed mutagenesis suggested that the conserved residues Lys248 and Arg269 were important for the activity of ChSase B6. Characterization, structure, and molecular dynamics simulation of ChSase B6 provided a guide for further tailoring for its industrial application for chondroitin sulfate bioresource development.     

环江油田巴19区块长7段钙夹层评价与大斜度井分段压裂优化

为实现最大化油藏接触,提高油藏产出水平,长庆环江油田巴19区块长7油藏采用大斜度井开发方式。在初期压裂改造中,由于忽视了层内钙质夹层对压裂缝高的影响,导致实际裂缝的几何形态与设计产生巨大偏差,出现了邻井裂缝串通及生产高含水等问题。本文通过研究油藏剖面测井特征,在细分层位基础上分析纵向应力分布,研究“复合层效应”影响裂缝缝高延伸的关键因素,优化了分段压裂方案,获得了更好的水力裂缝几何形态和尺寸。技术调整后现场压裂工艺质量获得提高,长7段油藏压裂改造质量优良率100%,大大提高了该区块的开发水平。     

上海外滩通道综合改造工程中特大基坑的分幅施工技术

在城市核心区进行群坑施工时,降水、临时封堵墙拆除等施工是关键,也是上海外滩地区综合改造工程中的难题。因此,针对“共墙”结构特点,采用了分幅施工技术,不权成功地解决了施工难题,又确保了施工中的安全与进度。     

Optical Fiber Cavity Ring Down Measurement of Refractive Index With a Microchannel Drilled by Femtosecond Laser

A microchannel was inscribed in the fiber of a ring cavity which was constructed using two 0.1% : 99.9% couplers and a 10-m fiber loop. Cavity ring down spectroscopy was used to measure the refractive index (RI) of gels infused into the microchannel. The ring down time discloses a nonlinear increase with respect to RI of the gel and sensitivity up to 300 mus/RI unit and an index resolution of 1.4 times10^-4 was obtained.     

基于动态逆的队形保持控制器设计

研究了无人机之间存在气动耦合的编队飞行系统模型。对模型运用时标分离原则将其划分为快变和慢变两个子系统,并且快变子系统的输出作为慢变子系统的输入参与控制。两个子系统分别用动态逆设计控制器,并在慢回路用干扰观测器补偿逆误差和模型的不确定性。通过仿真说明所设计的紧密队形保持动态逆控制器是非常有效的。