The development of low-temperature hardening silicone ceramer coatings for the corrosion protection of metals

The process parameters for the formulation of two different hybrid ceramic-polymer (ceramer), barrier-type coatings for the corrosion protection of metals are discussed. The coating formulations were characterized in the liquid, gel, and solid phases using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and Secondary Ion Mass Spectroscopy (SIMS), respectively. The coatings were applied to 6061-T6 aluminum alloy, hardened in ambient conditions, and analyzed with X-ray photoelectron spectroscopy (XPS). Thermal stability of the coatings was analyzed in inert and oxidative atmosphere using thermogravimertic analysis. The final surface morphology was studied using Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). The nanoindentation technique supported by SEM revealed the nanomechanical properties of the coatings. The effectiveness as a barrier-type coating was studied using electrochemical polarization experiments and immersion experiments in saline solution.     

A passive auxiliary circuit achieves zero-voltage-switching in full-bridge converter over entire conversion range

A passive auxiliary circuit is proposed to achieve zero-voltage-switching (ZVS) over the entire conversion range in a full-bridge (FB) pulse-width modulated (PWM) converter (FBZVS converter) with minimum conduction loss penalty. The stored energy in the auxiliary circuit is minimal under the full-load condition. It increases progressively as the load current decreases. The proposed auxiliary circuit is passive, simple and can be viewed as an add-on to the conventional FBZVS converter. The principle of operation is described and the performance is demonstrated on a 100 kHz, 500 W prototype.     

Quantile estimation based on nomination sampling

Nomination sampling is a sampling process in which every observation is the maximum of a random sample from some distribution. If all samples are taken from a single underlying CDF, F, data can be viewed as consisting of pairs (X_i,K_i) where K_i is the size of sample i and, given K_i=k_i, X_i is distributed according to CDF F^ki. R.A. Boyles and F.J. Samaniego (1986) developed a nonparametric maximum-likelihood estimator of F. In the present work, their approach is extended to obtain estimates of the quantiles of F and to study the limit theory and consistency properties of these estimates. These results generalize the results of T.R. Willemain (1980), who discussed the estimation of the median of F based on nomination samples     

Analysis of a solar water heating system with n-tanks in series

A straightforward analysis of a solar water heating system with n-tanks connected in series has been presented. The long-term performance of the system has also been studied. On the basis of numerical calculations made for four successive days, the following conclusions have been drawn:

1. (1) The fluctuation in temperature variation decreases with increase of the number of tanks connected in series.

2. (2) The variation becomes smooth after the second successive day, which is more desirable from the point of view of users.

     

Life cycle cost analysis of HPVT air collector under different Indian climatic conditions

In this communication, a study is carried out to evaluate an annual thermal and exergy efficiency of a hybrid photovoltaic thermal (HPVT) air collector for different Indian climate conditions, of Srinagar, Mumbai, Jodhpur, New Delhi and Banglore. The study has been based on electrical, thermal and exergy output of the HPVT air collector. Further, the life cycle analysis in terms of cost/kWh has been carried out. The main focus of the study is to see the effect of interest rate, life of the HPVT air collector, subsidy, etc. on the cost/kWh HPVT air collector. A comparison is made keeping in view the energy matrices. The study reveals that (i) annual thermal and electrical efficiency decreases with increase in solar radiation and (ii) the cost/kWh is higher in case of exergy when compared with cost/kWh on the basis of thermal energy for all climate conditions. The cost/kWh for climate conditions of Jodhpur is most economical.     

Analysis of different configurations of flat plate water collectors connected in series

This paper presents the analytical study of flat plate collector based on the computer‐based thermal models considering two different cases, case A (fully covered by glass) and case B (fully covered by photovoltaic (PV) module). These models are developed based on energy balance equations. An analytical expression for characteristic equation for photovoltaic–thermal flat plate collector has been derived as a function of design and climatic parameters. This paper shows the detailed analysis of energy, exergy and electrical energy by varying the number of collectors by considering four weather conditions (A, B, C and D type) for five different cities (New Delhi, Bangalore, Mumbai, Srinagar and Jodhpur) of India. It is observed that the collectors fully covered by PV module combine the production of hot water in addition to electricity generation and it is beneficial in terms of exergy, thermal energy and electrical energy gain. Copyright © 2008 John Wiley & Sons, Ltd.     

GPRS的服务质量及其测量

(GN Nettest)　　一、GPRS简介　　通用分组无线服务 ( GPRS)系统扩展了当前世界上最流行的第二代移动系统一基于语音的 GSM的应用 ,使其能够收发基于分组的数据 ;同时保留了无线接口的基本内容 ,如时分多路复用和频率分配方案 ,以使 GPRS和 GSM能够共存于同一网络上。　　 1 .特性　　传统的 GSM拨号数据接入为用户提供了最大960 0波特的速率。GPRS能够结合多个 GSM时隙 ,在上行链路和下行链路上 ,最多可以使用八个 GSM时隙 ,提供最高 1 70 kbit/sec的带宽。此外 ,GPRS采用全新的 IP网络“一直在线”接入模式 :移动用户开…