采用直接转换I/Q解调器的基站接收器设计

直接转换(或低中频)接收器设计已经出现很多年了.由于简单和成本低,因此这类接收器广泛用于蜂窝电话和无绳电话.直到最近,直接转换接收器集成电路才达到了基站的性能要求.下一代基站对低成本的无止境追求将人们的注意力引向了直接转换架构.这种架构可以灵活地满足多种射频(RF)标准的要求,并简化系统设计.     

推广新型生产设备 促进行业节能减排——再生常压连续脱硫设备、技术及应用现场会在成都召开

<正>为继续在行业中大力推广废橡胶(含废旧轮胎)粉碎、脱硫、压延等工艺和专业配套工装方面的创新成果,使该行业更符合"低碳"循环经济产     

Inherently X-ray opaque polyurethane microspheres for biomedical applications

In this work synthesis and characterization of inherently X-ray opaque, nonresorbable polyurethane microspheres with well-calibrated particles in a defined range of sizes suitable for embolization is reported. In order to impart X-ray opacity to the polyurethane, a bifunctional monomer, namely, 4,4′-isopropylidenediphenol (BPA) was iodinated and this iodinated compound was used as one of the monomers during polyurethane synthesis. The resultant X-ray opaque polyurethane was converted into microspheres using an oil-in-water emulsion and solvent evaporation technique. Microspheres obtained had diameters in the range of 200–500?µm, were noncytotoxic and free from X-ray attenuating additives. In vivo X-ray fluoroscopic imaging carried out in a rabbit cadaver model showed that these microspheres were sufficiently X-ray opaque to be visualized under fluoroscopic conditions.     

It's others, not the police: Smoking, reprimand, and fines among adults of Korean descent in California.

Objective: This study assesses the association of immediate social and legal reprimand and current smoking status among Californians of Korean descent. Design: Data were drawn from a population-based probability sample using a telephone survey conducted by bilingual, professional interviewers (N = 2085). About 85.0% of eligible respondents completed interviews and 86.3% of participants preferred to be interviewed in Korean. Main Outcome Measure: Smoking status was measured using Centers for Disease Control and Prevention criteria, ever smoked 100 cigarettes and currently smoke every day or some days. Results and Conclusion: Reports of immediate criticism by others in several settings was associated with nonsmoking, but likelihood of immediate legal penalties was unrelated. Participants were far less likely to expect legal than social sanction. Results were replicated after controlling for reinforcers of smoking and ecologically relevant variables including models of smoking, primary group social support for smoking, acculturation, sex, acculturation by sex (male) interaction, age, and education. It may be efficacious to target public health interventions encouraging appropriate social sanctions of smoking in public among persons of Korean descent, and to encourage strict enforcement of legal penalties for smoking in public places. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

关注战略性新兴资源 促橡胶行业可持续发展——“2010中国杜仲产业化论坛”在京举行

<正>杜仲树是我国特有的绿色资源,经过几十年的努力,我国已经在杜仲树的种植、杜仲胶的提取以及综合应用等方面取得了长足进步。由于杜仲树特有的医用和保健功能以及提取出来的杜仲胶有独特的橡-塑二重性、优良的共混性和集成性等综合性能,     

Photoconductive and ellipsometric studies of spray pyrolysed CdS thin films

The influence of annealing temperature on photoconductivity of spray pyrolysed CdS films has been investigated. The annealing of films at 373K resulted in maximum photoconductivity. The photoconductivity at all wavelengths was found to decrease with increase of annealing temperature and became a minimum at 473K. For films annealed at or above 523K, the photoconductivity for wavelengths ⩾560 nm decreased considerably. The results are discussed with the help of ellipsometric data, visible and IR spectra of these samples. Also the variation in photoconductivity of these samples were studied during heating to analyse the effect of trapping.     

Effect of Cu and Fe addition on electrical properties of Ni–Mn–Co–O NTC thermistor compositions

The effect of addition of Cu and Fe on the electrical properties of Ni–Mn–Co–O based NTC thermistor compositions is studied. Compositions with very low resistivity were prepared by co-doping of very small amounts of Cu along with Co in NiMn₂O₄, without affecting the sensitivity very much. Compositions with high resistivity and good sensitivity were achieved by co-doping Fe with Co in NiMn₂O₄. The effect of sintering temperature on electrical properties was investigated and it was found that the resistivity and material constant increase with sintering temperature. The reliability characteristics of the compositions were studied by the accelerated thermal aging method. All the compositions exhibited very good reliability.     

Strain rate-dependant mechanical properties of OFHC copper

The mechanical properties of high purity copper have been extensively studied in the literature, with yield and flow stresses measured as a function of strain rate, grain size, and temperature. This paper presents a comprehensive study of the strain rate and grain size dependence of the mechanical properties of OFHC copper, including an investigation of the previously observed upturn in rate dependence of flow stress at high rates of strain (≥500 s^?1). As well as a comprehensive review of the literature, an experimental study is presented investigating the mechanical properties of OFHC copper across a range of strain rates from 10^?3 to 10⁵ s^?1, in which the copper samples were designed to minimize the effects of inertia in the testing. The experimental data from this study are compared with multiple sources from the literature varying strain rate and grain size to understand the differences between experimental results on nominally the same material. It is observed that the OFHC copper in this study showed a similar increase in flow stress with strain rate seen by other researchers at high strain rates. The major contribution to the variation between experimental results from different studies is most likely the starting internal structure for the materials, which is dependent on cold working, annealing temperature, and annealing time. In addition, the experimental variation within a particular study at a given strain rate may be due to small variations in the internal structure and the strain rate history.     

Optical constants of CdS thin films prepared by spray pyrolysis

CdS thin films were prepared by spray pyrolysis techniques. Variable angle spectroscopic ellipsometry was used for optical constant calculations. Multiple angle measurements were taken in the most sensitive angle of incidence region. The sensitive regions of angle of incidence were obtained theoretically using 3-dimensional graph ofδψ andδΔ. Real partn and imaginary partk of the complex refractive index of the samples were calculated in the wavelength range 470–650 nm, taking into account surface roughness. Bruggeman’s effective medium approximation is used for analysis of the surface rough layer of the thin films.