Analysis of Thermoelectric Generator Performance by Use of Simulations and Experiments

A method that enables accurate determination of contact resistances in thermoelectric generators and which gives detailed insight into how these reduce module performance is presented in this paper. To understand the importance taking thermal and electrical contact resistances into account in analysis of thermoelectric generators, full-scale modules were studied. Contact resistances were determined by means of non-linear regression analysis on the basis of results from 3D finite element simulations and experiments in a setup in which heat flow, voltage, and current were measured. Statistical evaluation showed that the model and the identified contact resistances enabled excellent prediction of performance over the entire range of operating conditions. It was shown that if contact resistances were not included in the analysis the simulations significantly over-predicted both heat flow and electric power output, and it was concluded that contact resistance should always be included in module simulations. The method presented in this paper gives detailed insight into how thermoelectric modules perform in general, and also enables prediction of potential improvement in module performance by reduction of contact resistances.     

International harmonization of grid connection guidelines: adequate requirements for the prevention of unintentional islanding

Islanding is still one of the major controversial subjects in the international harmonization of grid connection requirements for distributed generation, and particularly photovoltaics. As long as islanding is not intended in order to back up a loss of mains, it should be avoided. The present study reviews the theory of unintentional islanding and assesses the probability of occurrence of the phenomenon, based on previous studies and theoretical considerations. While islanding is virtually impossible if only a small number of distributed generation units is connected to a distribution grid, with higher distributed generation densities, the possibility of islanding becomes realistic. The risk associated with unintentional islanding is estimated, and adequate requirements for functional safety of protection devices are determined in order to ensure the necessary additional degree of safety to be introduced by an islanding prevention device. Finally, a fundamental set of requirements with regard to islanding, to be included in an international grid connection guideline, is derived from the study. Copyright © 2003 John Wiley & Sons, Ltd.     

如何利用远程二极管温度传感器准确量度温度如何量度温度

由于芯片温度是一个关键的参数,因此部分电子设备设有特别的装置,以量度芯片的温度.在一般情况下,系统设计工程师都喜欢采用二极管或连接成二极管的晶体管,将之置于靠近芯片热点的位置,以量度芯片温度.     

Nanoparticle‐Based Antivirulence Vaccine for the Management of Methicillin‐Resistant Staphylococcus aureus Skin Infection

With the rising threat of antibiotic‐resistant bacteria, vaccination is becoming an increasingly important strategy to prevent and manage bacterial infections. Made from deactivated bacterial toxins, toxoid vaccines are widely used in the clinic as they help to combat the virulence mechanisms employed by different pathogens. Here, the efficacy of a biomimetic nanoparticle‐based antivirulence vaccine is examined in a mouse model of methicillin‐resistant Staphylococcus aureus (MRSA) skin infection. Vaccination with nanoparticle‐detained staphylococcal α‐hemolysin (Hla) effectively triggers the formation of germinal centers and induces high anti‐Hla titers. Compared to mice vaccinated with control samples, those vaccinated with the nanoparticle toxoid show superior protective immunity against MRSA skin infection. The vaccination not only inhibits lesion formation at the site of bacterial challenge but also reduces the invasiveness of MRSA, preventing dissemination into other organs. Overall, this biomimetic nanoparticle‐based toxin detainment strategy is a promising method for the design of potent antivirulence vaccines for managing bacterial infections.     

Accuracy of q-space related parameters in MRI: simulations and phantom measurements

The accuracy of q-space measurements was evaluated at a 3.0-T clinical magnetic resonance imaging (MRI) scanner, as compared with a 4.7-T nuclear magnetic resonance (NMR) spectrometer. Measurements were performed using a stimulated-echo pulse-sequence on n-decane as well as on polyethylene glycol (PEG) mixed with different concentrations of water, in order to obtain bi-exponential signal decay curves. The diffusion coefficients as well as the modelled diffusional kurtosis K(fit) were obtained from the signal decay curve, while the full-width at half-maximum (FWHM) and the diffusional kurtosis K were obtained from the displacement distribution. Simulations of restricted diffusion, under conditions similar to those obtainable with a clinical MRI scanner, were carried out assuming various degrees of violation of the short gradient pulse (SGP) condition and of the long diffusion time limit. The results indicated that an MRI system can not be used for quantification of structural sizes less than about 10 microm by means of FWHM since the parameter underestimates the confinements due to violation of the SGP condition. However, FWHM can still be used as an important contrast parameter. The obtained kurtosis values were lower than expected from theory and the results showed that care must be taken when interpreting a kurtosis estimate deviating from zero.     

Chemical Imaging of Explosions – Mapping BO2 Light Emission

This work describes chemical imaging of BO₂ formed during ballistic initiation of 1 : 1 by weight powder‐mixtures of boron (B) and potassium nitrate (KNO₃) contained within a polyethylene spherical projectile (25 mm diameter). Initiation was achieved by impact of the gas‐gun‐launched B/KNO₃‐filled projectile with an anvil in a windowed, air‐filled chamber. To monitor the subsequent chemical reaction, a two‐camera, optically‐filtered method to map discrete chemical emission from the BO₂ molecule was used. This technique distinguishes incandescence of hot particles produced during the event from discrete chemical emission by BO₂ near a wavelength of 546 nanometers (nm). The dependence of delay in BO₂ chemical emission (that exceeded particle incandescence) with impact velocity was investigated and chemical emission movies which ratio the intensity of discrete to thermal emission are discussed. Emission spectra (300–1000 nm wavelength) were recorded during the impact event, and used to determine a grey‐body temperature of the hot particles during the time when BO₂ emission was most intense.     

A Review of Literature on Transformation Processes in South African Townships

The paper provides a literature review of research published on South Africa??s black townships in order to answer certain questions: how have the townships changed? In what directions are they changing? Which groups in the townships benefit from these changes? Which groups of actors who push for change in the townships can be identified? To what extent are these residential areas becoming multifunctional, shifting from their role as dormitory settlements to providing their residents with a higher quality of life than in the past? What new social and ethnic antagonisms arise in turn? The paper reviews township literature in four periods: up to the 1970s, the 1980s, the 1990s and 2000s (the bulk of the review is however on the last 20?years).     

基于SEMI(R)F57-0301标准下,新一代化学品输送过程中,阀门管接件及其材料的选择、设计、生产和测试

本文高度阐述了含氟聚合物阀门应用在半导体行业超高纯水系统和液体化学分配系统,阀门的选择、设计、生产和测试的问题.针对半导体工业发展的需求,以SEMI F57-0301为标准,对更加苛刻的应用进行了预先考虑和阐述.所阐述方法和理论同样适用于流量计,过滤器,调节阀等组件.