Experimental Determination of Micromachined Discrete and Continuous Device Spring Constants Using Nanoindentation Method

A rapid and accurate static and quasi-static method for determining the out-of-plane spring constants of cantilevers and a micromachined vibratory sensor is presented. In the past much of the effort in nanoindentation application was to investigate the thin-film mechanical properties. In this paper, we have utilized the nanoindentation method to measure directly some micromachined device (e.g. microgyroscope) spring constants. The cantilevers and devices tested were fabricated using the MUMPS process and an SOI process (patent pending). Spring constants are determined using a commercial nanoindentation apparatus UMIS-2000 configured with both Berkovich and spherical indenter tip that can be placed onto the device with high accuracy. Typical load resolution is: 20 N to 0.5 N and a displacement resolution of 0.05 nm. Information was deduced from the penetration depth versus load curves during both loading and unloading.     

Heterogeneous InSb quantum well transistors on silicon for ultra-high speed, low power logic applications

The heterogeneous integration of InSb quantum well transistors onto silicon substrates is investigated for the first time. 85 nm gate length FETs with f_T = 305 GHz at V_ds = 0.5 V and DC performance suitable for digital logic are demonstrated on material with a buffer just 1.8 mum thick. An initial step towards integrating InSb FETs with mainstream Si CMOS for high-speed energy-efficient logic applications has been achieved.     

Toroidal structures due to anisotropy of DNA-like molecules

We suggest that toroidal structures in the state of psi-condensation of DNA may be caused by anisotropy on a meso-scale of several thousand A, the conformation of a DNA-molecule being determined by its elasticity and neutralization of phosphate charge. We model a molecule of B-DNA on an anisotropic elastic rod subject to a torque, and make the numerical simulation of the model that reveals that under appropriate conditions, which may be effected in experimental setting by changing the concentration of polymeric solutions, there are toroidal structures having the size of a few persistence lengths, in agreement with the experimental data. On changing the elastic modulii or characteristics of the counterion layer, we see the toroidal structures turn into the spherical ones. To understand the function of anisotropy it would be interesting to investigate the Z-DNA as regards psi-condensation.     

Performance Analysis of Split-Winding Doubly Salient Permanent Magnet Motor for Wide Speed Operation

In this paper, various flux-weakening techniques available for wide speed operation of the doubly salient permanent magnet (DSPM) motor are reviewed. A new split-winding topology capable of widening the speed range is proposed, which is valid not only for the DSPM motor with stationary PMs, but also for that with rotary PMs. Based on the parameters obtained by finite element analysis, the performance of the proposed DSPM motor is analyzed. The results show that this motor combines the features of wide speed range, high efficiency, simple structure, and low cost.     

A new design method and half-step operation for ultrasonic stepping motors

In this paper, a systematic design method and a new half-step operation are proposed for ultrasonic stepping motors (USMs) which are based on the principle of spatially shifted standing vibrations. With emphasis on the combination of the order of vibration mode, the number of spatial phase shifts, the number of electrodes, and the number of simultaneously excited electrodes, the design equations and constraints are newly derived, hence, proposing the design procedure. The finite-element method and impedance measurement are also employed to investigate the vibration of the stator. By borrowing the control idea of electromagnetic stepping motors, the half-step operation is newly applied to this USM so that the step size can be further halved. An 80-step USM is prototyped. The proposed design method and half-step operation are well supported by experimentation.     

聚磁式场调制永磁风力发电机工作原理与静态特性

提出一种新型聚磁式场调制永磁(Flux-Concentrating Field-Modulated Permanent-Magnet,FCFMPM)电机,该电机外转子采用聚磁式永磁体结构改善气隙磁通密度,定子采用开口槽结构提高空间利用率.基于磁齿轮效应,定子齿对转子永磁磁场进行调制,产生极对数少、运行速度快的谐波磁场,由该谐波磁场作为有效励磁的FCFMPM电机具有低速、大转矩密度的特点.在深入分析电机工作原理的基础上,运用二维有限元方法计算了其静态特性,包括空载永磁磁链、空载感应电动势、电感、定位力矩和电磁转矩等.研制了一台5kW实验样机,并与商业化小型永磁直驱风力发电机做比较.仿真和实验结果表明,所提电机具有转矩密度大、定位力矩小、外特性硬等特点,特别适用于如风力发电等低速、直驱系统.     

Cyanobacteria,Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons

The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.