什么是视频处理器,它为什么重要

高清视频是一件非常美妙的事情。谁不喜欢漂亮的图像和数字环绕声呢?谁不愿意换掉27或32英寸的CRT显示器以追求新型高清电视呢?现在是和低分辨率和因低质量标清信号而导致图像     

Analysis of the high temperature characteristics of InGaAs-AlGaAsstrained quantum-well lasers

The effect of high temperature on the threshold gain and threshold current density of an In_0.15Ga_0.85As strained quantum-well laser is examined both theoretically and experimentally. It is found that the nonlinearity of the gain-versus-current relationship increases with temperature. The implications of this result on laser cavity design for optimal high-temperature performance are discussed. The effect of high temperature on modulation bandwidth is also considered. While the numerical results are specific to an In_0.15 Ga_0.85As strained quantum-well laser, qualitatively they apply to all quantum-well lasers     

Regional seroprevalence of Cryptosporidium parvum-specific IgG of cats in the United States

The objective of this study was to determine the regional prevalence of Cryptosporidium parvum-specific IgG in the sera of cats in the United States. The continental United States was partitioned into eight regional areas. Serum samples from 75 cats from each region were assayed for C. parvum-specific IgG using an indirect enzyme-linked immunosorbent assay (ELISA). Age, sex, breed, and indoor/outdoor status were examined as possible risk factors for developing a positive C. parvum-specific IgG antibody titer. The presence of gastro-intestinal signs and Toxoplasma gondii-specific IgG in the serum were also evaluated for association with C. parvum seropositivity. Of the 600 samples assayed, 50 (8.3%) were positive for C. parvum-specific IgG. Regional seroprevalence ranged from 1.3% in the mid-Atlantic states to 14.7% in the south-eastern states. The oldest group of cats (>10 years) had the highest seroprevalence (15.3%). The prevalence of C. parvum-specific IgG was higher among male (10.1%) than among female cats (6.9%), although, the difference was not statistically significant (p = 0.17). Seropositivity was not associated with pure-bred status. C. parvum-specific IgG antibodies was detected most frequently in T. gondii-specific IgG seropositive cats, outdoor cats, and cats with gastro-intestinal signs. These results suggest that cats in the United States are commonly exposed to C. parvum.     

The oxidation behaviour of a niobium-chromium-nickel alloy

The oxidation behaviour of an 80wt.% Nb, 16wt.% Cr, 4wt.% Ni alloy has been studied in the temperature range 855–1197°C using kinetic, electron-probe, and X-ray techniques. The Arrhenius plot resembles that for pure niobium. The rate-controlling step is thought to be diffusion through a layer of Nb₂O₅ at the oxide-metal interface and the variation of the oxidation rate with time and temperature is explained in terms of the behaviour of this layer.     

Effects of an organizer on memory for prose.

112 undergraduates read a literature text preceded by either a comparative advance organizer or a placebo introduction. Three hypotheses regarding the interactive effects of the organizer treatment and reasoning skills were tested: the assimilation, the schema plus correction, and the assimilation plus correction hypotheses. Findings favor the assimilation plus correction view, which holds that schema-implied text units are assimilated and obscured in the final text encoding, whereas ideas representing unexpected, schema-modifying information are enhanced. The dominant treatment effect was assimilatory loss of detail associated with implied information. Positive effects on schema-modifying information were observed for Ss with good reasoning skills, as assessed by the Diagramming Relationships and Inference Tests from the Kit of Factor-Referenced Cognitive Tests. Possible explanantions for the results are discussed in terms of reconstructive views of recall, adaptive learning and changes in semantic memory representation, and perceived structural importance of target ideas. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A sensitive method for the determination of chlorine-36 in foods using accelerator mass spectrometry

A method using accelerator mass spectrometry (AMS) has been developed to offer a more sensitive alternative to scintillation techniques for the determination of chlorine-36 (³⁶Cl) in foods. The main problem in method development was the potential interference of the sulfur-36 (³⁶S) isobar. This was overcome by reducing the sulfur level of acid digests of food by precipitation of chloride as silver chloride, then purification by washing, dissolution and reprecipitation to present silver chloride as the AMS target. The limit of detection was around 0.1 Bq kg^?1 and the limit of quantitation was around 0.2 Bq kg^?1. The AMS method was only semi-quantitative at the lowest levels of interest. To test the method a few samples of milk (five) and blackberries (three) collected from near two nuclear power stations as potential sources of contamination were analysed. Blackberries spiked at 0.2 Bq kg^?1 and milk spiked at 0.1 Bq kg^?1 could be distinguished from method blanks. There was no ³⁶Cl detectable in the unspiked samples.     

Raman and optical absorption studies of proton bombarded CsI

CsI single crystals, which have the simple cubic structure, have been bombarded with 1 MeV protons at a temperature close to 300 K. Optical absorption and Raman studies have identified most of the defects created. These include F and F₂ centres, and V centres having absorption bands at 2.7 eV and 3.4 eV, which grow together during irradiation. The Raman studies identify these latter centres as having the structure. Isochronal and isothermal annealing experiments show a mutual decay of the F-type centres and these V centres in a second order reaction with an activation energy of 1.28 eV. The results are discussed in relation to the excitonic mechanism of defect production and the formation of interstitial iodine aggregates of various types in alkali iodides.