BioMEMS devices for drug delivery

Successful therapeutic outcomes following the administration of drugs, including small molecules and large biomolecules, require not only the selection of a proper drug but also its delivery to the proper site of action, with proper temporal presentation. Drug delivery is an extremely broad area of research, as each molecule presents its own absorption, distribution, metabolism, excretion, and toxicology (ADMET) profile. Moreover, timing of drug release may affect the efficacy of a pharmacologic agent. Any means by which drug delivery can be actuated and controlled is, therefore, of interest, and there should be no surprise that microelectromechanical systems (MEMS) have received considerable attention over the past decade in the drug delivery field. The ability to generate two-dimensional (2-D) and three-dimensional (3-D) material constructs accurately and reproducibly using MEMS may lead to substantial advances over conventional drug delivery systems.     

Engineering strategies for drug delivery

A drug is a molecule that changes physiological functions when absorbed into the cells or tissues of a living organism. It can be used to treat, cure, prevent, or diagnose diseases or to enhance physical or mental health. However, the discovery of a drug is an expensive, long, and challenging process. It can take 15 years for a big pharmaceutical company to spend more than US$500 million for developing a new drug. Despite the high cost, many drugs themselves can only provide the human being with modest desired effects. Moreover, almost all drugs can cause side effects when they act in the body. Therefore, there is a clear need to maximize the efficacy of a drug and simultaneously reduce its side effects. To achieve this goal, it is necessary to find a way to help drugs to primarily reach the target area of the body (e.g., solid tumors). Drug delivery is the right discipline for studying methods for administering drugs in a safe and efficient manner. The success of this discipline relies on different expertises from chemists, biologists, and engineers. In this special issue of IEEE Engineering in Medicine and Biology Magazine, we will particularly illustrate the significance of engineering knowledge in drug delivery through a collection of six articles from experts in the field.     

Fabrication of densely arrayed Si needles with large height for transdermal drug delivery system application

The effects of varying etching conditions for microneedle fabrication were investigated in order to form densely arrayed, sharply angled Si needles with large height for application in transdermal drug delivery systems (DDSs). A sharply angled needle shape could be fabricated by using 34.0 wt% KOH (representing a typical etching‐rate diagram at a highly alkaline etching solution concentration). The needle height could be increased by 20% by adding a compensation mask pattern or by increasing the KOH concentration to 51.0 wt%. The trade‐off relationship between the maximum needle height and the needle density was calculated. These experiments provided useful parameters for designing densely arrayed, sharply angled Si needles for transdermal DDS application. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An expert system for monitoring psychiatric treatment

A number of medical expert systems have been developed to address problems in health care, but there have been few applications to date for psychiatric practice. We have previously discussed design and implementation issues specific to this medical specialty, and have described OVERSEER, a prototype expert system for monitoring drug treatment in a psychiatric setting. Since its initial implementation, this prototype has been substantially modified based on clinical experience, and in this article we report on the operation and evaluation of the resulting “Clinical Evaluation and Monitoring System” (CEMS). CEMS addresses the essential elements of the clinical process-assessment, diagnosis, and treatment. The Pharmacotheraapy Guidelines contain information about psychiatric medications (e.g., dosages, therapeutic serum levels, indications and side effects), and they reflect the institutions' “standards of practice”. The Diagnostic Checklists (DCLs) provide an automated method for (1) assuring documentation of the key symptoms and behavioral issues noted in the patient assessment, and (2) noting the degree of change in each symptom/behavior at the time of the discharge (or other) evaluation. The Outcome Assessment module provides data about patients' functional, social, and vocational status at admission and discharge, and at three, six, and twelve months post-discharge     

An asynchronous pulse width modulator for DC-DC buck converter

This paper presents an asynchronous pulse width modulation (APWM) approach for the analysis of a new class of the switched mode power supply (SMPS). The proposed APWM significantly simplified the mathematical analysis by utilizing a binary comparator (BAPWM) and a distinctive delay cell instead of hysteretic comparator. By this way, the mathematical analysis can be extended to study the behavior of high-order self-oscillating modulators in terms of key parameters such as the harmonic distortion and the stability. The performance of the proposed BAPWM is deeply analyzed for different orders of loop filters (here up to third order) in both time and frequency domain. To verify the effectiveness of the proposed analytical derivations, the BAPWMs are employed in a classic synchronous DC-DC buck converter and its closed loop performance, in terms of stability, has been investigated. Then the converter is designed and simulated in 130-nm CMOS technology to convert input voltage of 5 to 3.3 V with maximum load current of 1 A, using Spectre simulator. From the post-layout simulation results, the peak efficiency conversion efficiency for 3.3 V output voltage is higher than 89%.     

The invention of the programmable implantable medication system

The author describes the genesis of his idea for a programmable implantable medication system and the problems encountered in going from idea to the first prototype. He discusses the funding, development, and marketing of his device. He provides some observations on the process of getting medical inventions into public use.     

基于SVPWM的异步电动机矢量控制调速系统软件设计

将SVPWM的调制技术应用于异步电机的矢量控制,并且引入SVPWM过调制以及抗积分饱和PI调节算法,以提高了调速系统的动态性能和调速精度。全数字控制利用高速处理器DSP芯片-TMSLF2407A实现了交流调速系统的全数字控制。实验结果充分验证了该设计方案的可行性和正确性。     

A robast digital control system for an asynchronous electric drive

Polynomial methods for synthesizing robast digital regulators of a frequency-controlled asynchronous electric drive are considered. It is shown that the use of robast regulators makes it possible to significantly reduce sensitivity to changing object parameters and increase the adjustment of disturbing actions. The possibility to create qualitative systems for an electric drive without a unit of compensating cross connections is grounded.     

异步电机SVPWM矢量控制系统仿真与实现

从异步电机矢量控制的基本理论出发,给出了M-T坐标系下的状态方程并分析了电压空间矢量PWM(SVPWM)的原理,然后在Matlab/Simulink环境下搭建起系统的仿真模型,仿真结果符合理论分析.最后在以TMS320F2812为核心的实验平台上实现了上述算法,实验结果表明电机工作正常,动态性能优越,有很强的实用性.     

异步联网送端系统紧急切机控制方法

在异步联网运行方式下,送、受端系统间相互支援能力弱,因直流紧急降功率所导致的送端系统频率稳定问题不容忽视。在分析系统频率特性的基础上,提出了具有预测性的送端系统紧急切机控制方法。该方法将依据B样条拟合曲面预测得到的系统暂态频率最大偏差作为紧急控制启动判据,实现在系统功率出现不平衡的前期就能准确启动切机控制,避免系统进入紧急状态;根据功率平衡控制原理和预测所得的暂态频率最大偏差求出紧急控制所需切机量,并依据电气距离确定机组切除顺序。以实际暂态频率最大偏差、频率到达稳态时间以及直流频率限制控制器(FLC)恢复至额定状态的时间为指标,与系统采用高频切机控制进行对比。通过算例验证了所提方法的有效性。     

Micromachined needle arrays for drug delivery or fluid extraction

Micromachined needle arrays have been designed, fabricated, and characterized. The design includes arrays of 25 needles with fluid coupling channels and dual structural supports. Numerical modeling of fluid flow characteristics was performed, demonstrating that the needle coupling channels redistribute flow when the input or output ports are fully restricted. Micromachining technologies have been used to batch fabricate hollow metallic fluid coupled needle arrays. The significance of this work includes the development of the hollow metallic micromachined needle arrays for biomedical applications, as well as a discussion of structural, fluidic, and biological design considerations. The micromachined needle array has many advantages, including (a) reduced trauma at penetration site (small size), (b) greater freedom of patient movement (minimal penetration), (c) a practically pain-free drug delivery device (distribution of force), (d) precise control of penetration depth (needle extension length), and (e) they can be stacked and packaged into a 3-D device for fluid transfer.     

Selection of the coordinate system for implementing algorithm of vector management of asynchronous electric drive

A brief history of the appearance and development of vector management is given. The results of studying the system of subordinate vector management with reference vectors of the principle magnetic linkage and the rotor magnetic linkage are considered based on physical and computer models using the Matlab Simulink software package. The results of calculating transition processes in the system aimed at comparing dynamic and energy parameters and giving recommendations on reference vector selection are demonstrated.     

An algorithm for direct torque control of field oriented asynchronous motor drives

Contents The dynamic behaviour of fully digital control systems is strictly related to the duration of the sampling interval. The minimum length of this period depends exclusively on the time needed for the execution of all the required operations. Therefore, the minimization of computing time is one of the most important goals to be achieved in order to improve the accuracy of electrical drives with fully digitalized control systems. The best results can be obtained using fast programming languages and short sets of computing instructions. This goal is achieved using a proper feeding algorithm for asynchronous motor drives called direct, because it links directly the requested torque and magnetic flux to the input voltages.

---

Ein Algorithmus zur direkten drehmomentregelung bei feldorientierten antrieben mit asynchronmotor

Übersicht Die Dynamik einer vollständig digitalen Regelung ist eng verbunden mit der Dauer des Abtast-Intervalles. Die Mindestdeuer der Periode hängt ausschließlich von der erforderlichen Rechenzeit ab. Deswegen ist die Minimierung der Rechenzeit eines der wichtigsten Ziele für die Genauigkeit elektrischer Antriebe mit vollständig digitaler Regelung. Die besten Ergebnisse können mit schnellen Programmiersprachen und kurzen Befehlssätzen erlangt werden. Das Ziel wird erreicht durch einen geeigneten Algorithmus für Asynchronmotoren. Dieser Algorithmus wird direkt genannt, weil er das elektromagnetische Moment und den magnetischen Fluss direkt mit den Eingangsspannungen verbindet.

---

List of symbols i_r instantaneous value of the rotor currents symmetrical component referred to the stator - i _s instantaneous value of the stator currents symmetrical component - l _r rotor leakage inductance referred to the stator phase - l _s stator phase leakage inductance - m number of stator phases - p pole-pairs number - r _r rotor phase resistance referred to stator phase - r _s stator phase resistance - v instantaneous value of the stator voltages symmetrical component - J, J _m total and motor inertia - L _m air-gap motor inductance - P rated power - T _el motor electromagnetic torque - T _L load torque - V _R rated voltage - instantaneous rotor position - _R rated angular speed     

840D系统的异步中断功能在机床断刀后的应用

利用840D系统的异步中断功能,可以实现机床在断刀后暂停当前的加工程序,转而执行中断程序,使机床移动到安全地方后执行手动换刀功能,当刀具更换完毕后继续执行断电程序自动返回断点继续加工。     

基于柔性直流输电的异步互联系统频率支援控制方法综述

利用基于电压源换流器的柔性直流输电(VSC-HVDC)的快速功率控制能力实现异步互联的交流电网间的频率支援,可以充分发挥全系统备用容量的调节能力,提高互联系统的安全性和稳定性。综述了国内外该领域的研究现状,详细介绍了基于通信的主从控制、利用电压传递频率波动的主从控制、附加频率调节的下垂控制以及基于虚拟同步机特性的控制等不同方法的基本原理。通过统一的仿真模型对比分析了各种方法的控制特点和性能,从工程应用角度总结了这些方法的优缺点以及进一步研究的方向。     

Unique high-bandwidth UV fiber delivery system for the OMEGAdiagnostics applications

A special fiber-optic signal delivery system for 351-nm pulse-shape measurements has been developed in the contest of a large laser fusion facility. To deliver a sufficient signal and preserve an overall bandwidth of >33 GHz over a distance of ~15 m, a seven-fiber bundle of gradient-index fiber was developed, fabricated, and tested, and is now applied in routine operation     

异步传输的分布式铁路10 kV电力监控系统

为解决提速铁路10 kV电力系统运行参数变化快、海量实时数据传输和处理困难的问题,设计研发了实时异步传输的电力远动监控系统.对铁路10 kV电力系统的运行、录波数据的远程传输和海量实时数据的处理进行了分析设计.提出了利用发布/订阅原理进行异步数据传输的模式,考虑到实时数据点多、变化快的特点.建立了实时数据交换的二级缓存...     

异步电动机直接转矩控制系统性能优化的研究

本文对传统直接转矩控制系统中的定子磁链模型切换以及磁链调节器、转矩调节器进行了优化设计，分别引入了积分滞环切换模型和多点滞环调节器，实现定子磁链模型的平滑切换，使系统能够快速准确的跟踪转速指令的变化，特别是大大减小了低速时转矩的脉动。仿真结果表明，改进后的直接转矩控制系统具有优良的动静态性能。     

基于模糊控制器的异步电机直接转矩控制

为改善交流异步电机伺服系统的动、静态品质,攀计了一种自适应模糊控制器来控制逆变器的开关,它是在传统的DTC技术基础上加入模糊控制器,使整个控制器具有较强的鲁棒性和自适应性。通过仿真实验,将其与常规的直接转矩控制系统进行比较,证实了这种模糊控制器具有更好的控制效果。     

并网异步风电机组有功功率的振荡频率分析

为了准确研究影响并网风电机组功率波动因素及规律,提出了不同运行工况以及不同风力机模型和参数对异步风电机组有功功率的振荡频率研究.首先,采用等效集中质量法,结合异步发电机电磁暂态模型,建立了不同风力机传动链等效的异步风电机组数学模型.其次,在风速扰动下,对不同传动链模型、传动链刚度系数以及不同风速扰动频率时机组有功功率振荡的频率进行仿真分析.最后,在电网三相短路故障情况下,针对等效两个质量决传动链模型,对不同传动链刚度系数和故障持续时间的机组有功功率振荡频率进行仿真.研究结果表明相同振荡频率下的有功功率幅值与风力机模型、传动链刚度系数以及故障持续时间密切相关.