UWB:个人无线局域网络的高速公路多频带OFDM VS.直接序列DS--两大技术特性的综合剖析

大约3年前,美国联邦通信委员会发布一份历史性的Report&Order报告,将3.1GHz～10.6GHz的7,500MHz频谱配置给超宽带(UltraWideBand,UWB)装置使用。这份报告为产业和学术界带来许多创新与技术进步的机会,业界也纷纷成立各种组织,例如多频带OFDM联盟(Multi-band OFDM Alliance)、UWB论坛以及IEEE802.15.3a特别工作小组,希望为UWB技术建立共同的标准。     

Effect of manuring and frequency of cutting on the yield of leaf protein from some fodder grasses

A study to find out the effect of manuring and the frequency of cutting on the yield of leaf protein was conducted with four fodder grasses. The study revealed that Cenchrus glaucus was superior to the other grasses tried and it gave the maximum yield of dry matter and extractable protein. Farm yard manure at 10 tons/ha along with ammonium sulphate at 33 kg N/ha proved to be the best in giving the highest yield of dry matter and leaf protein. For all the grasses the maximum yield was found to range within the first three cuttings.     

Fluid catalytic cracking: Selectivity and product yield patterns

Fluid catalytic cracking, a common secondary process employed in the petroleum industry, is used to convert heavier feedstocks into products such as liquefied Petroleum Gas (LPG), motor gasoline, diesel etc. The present study focuses on developing a three lump fraction kinetic model to estimate the yield of C5 up to 370°C cut (motor gasoline and middle distillates). A Micro Activity Test (MAT) apparatus was used to estimate the parameters in the kinetic model. The study is useful in evolving a procedure to simulate plant performance using experimental data obtained in the MAT apparatus for a particular catalyst and feedstock in terms of the product yield pattern.     

Adiabatic gas absorption in packed columns with large thermal effects

The performance of packed bed adiabatic gas absorbers has been analyzed using the enthalpy and material balance equations incorporating a new parameter, f_r, defined as the fraction of the heat of absorption that is accounted for in the gas stream. An experimental programme to evaluate f_r was carried out and the data correlated. It was found that f_r was dependent on the thermo-physical properties and the hydrodynamic conditions. It is postulated that the mechanism by which this heat transfer occurs is by turbulence at the interface and by entrainment.     

Measures and interpretations of vigilance performance: evidence against the detection criterion

Operators' performance in a vigilance task is often assumed to depend on their choice of a detection criterion. When the signal rate is low this criterion is set high, causing the hit and false alarm rates to be low. With increasing time on task the criterion presumably tends to increase even further, thereby further decreasing the hit and false alarm rates. Virtually all of the empirical evidence for this simple interpretation is based on estimates of the bias measure beta from signal detection theory. In this article, I describe a new approach to studying decision making that does not require the technical assumptions of signal detection theory. The results of this new analysis suggest that the detection criterion is never biased toward either response, even when the signal rate is low and the time on task is long. Two modifications of the signal detection theory framework are considered to account for this seemingly paradoxical result. The first assumes that the signal rate affects the relative sizes of the variances of the information distributions; the second assumes that the signal rate affects the logic of the operator's stopping rule. Actual or potential applications of this research include the improved training and performance assessment of operators in areas such as product quality control, air traffic control, and medical and clinical diagnosis.     

Effect of pretreatment on the anodic behaviour of lead alloys for use in electrowinning operations. I

Lead alloys are widely used as anodes in electrowinning operations, for the recovery of metals such as zinc, copper and chromium. When lead alloys are used as such it takes a long time for the build up of a compact, adherent and protective lead dioxide film. During the initial period prior to the build up of the compact layer of lead dioxide, the rate of anodic dissolution is very high, leading to a decrease in the purity of the cathode deposit. In order to minimize the duration of the conditioning of the anode, it is customary to build up a compact lead dioxide layer by pretreating the anodes in suitable electrolytes. An attempt is made to evaluate the performance of the pretreated electrodes by potentiodynamic methods.