水热沉积电压对C-AlPO_4涂层显微结构的影响

以方石英型磷酸铝(C-A1PO4)粉体为原料,异丙醇为溶剂,碘为荷电介质,采用水热电泳沉积方法在涂有SiC涂层的碳纤维增强碳(C/C-SiC复合材料表面制备了C-A1PO4外涂层.借助X射线衍射和扫描电镜表征了涂层的晶相组成和显微结构.研究了沉积电压对C-A1PO4涂层显微结构的影响,并测试了涂层的抗氧化性能.结果表明:在180～220V范围内,水热沉积电压对涂层的显微结构有较大的影响,220V时制备的涂层致密均匀.涂层的沉积量以及涂层与基体的结合强度随着沉积电压的升高而增加;单位面积沉积量与时间的二次方根之间符合线性关系.与包埋法制备的SiC涂层相比,水热电泳沉积法制备的C-A1PO4涂层具有更好的抗氧化性能,涂层样品在1500℃的空气中氧化37h后质量损失仅为0.53%.     

注射成型中浇口形式对塑件质量的影响

用生产实例介绍了不同浇口形式及位置对塑料熔体在型腔中的填充模式和注射成型后塑件的内在机械物理性能及表观质量的影响。     

Meteorological wind energy potential in the Alps using ERA40 and wind measurement sites in the Tyrolean Alps

The peculiarities of meteorological wind potential in alpine settings compared to flatland and offshore sites are studied. Four data sources are used: Global reanalysis ERA40 from ECMWF, long‐term stations in the Tyrolean Alps, spatially dense measurements near the best site and Doppler sodar wind profiles. Due to the decrease of density with height, alpine sites suffer from a nearly linear decrease of harvestable power with altitude, which is more than offset by the increase of wind speed at altitudes above 1.5 km MSL. ERA40 data show higher potential on the northern than on the southern side of the Alps. The best locations are not isolated peaks but ridges within wide orographic channels. The best potential sites in the Tyrolean part of the Alps have median wind speeds of up to 7.1 m s^?1 and extractable potentials between 2900 and 1600 kWh per year and per square meter of rotor area. The profile of horizontal wind speed at ridge sites is often not logarithmic but approximately constant within the height of a wind turbine due to a (nearly) complete absence of upwind fetch. Also, the turbulence intensity is independent of height. Icing can cause considerable downtimes. Copyright © 2010 John Wiley & Sons, Ltd.     

开放式数控系统实验教学平台研究

针对目前机电一体化专业机电综合性实验相对薄弱的问题,构建基于PMAC运动控制器的开放式数控实验教学平台.在此基础上进行伺服随动控制、控制系统校正环节设计、机电系统控制性能分析等实验教学工作,加深了数控实验教学内容,改善了机电综合实验和相关课程的教学效果.     

Selective iodine imaging using K-edge energies in computerized x-ray tomography

Iodine is commonly used as a contrast material in computerized x-ray tomography. In some cases the determination of the iodine distribution in the image may be prevented by the presence of bone or tissue variations within the tomographic slice. This paper describes a method for quantitative selective imaging of the iodine concentration in the slice. The method employs scans using three heavily filtered x-ray beams, two having mean energies which straddle the iodine K edge (33 keV) and another at a slightly higher energy. The results are independent of tissue and bone over a broad range of projection path lengths. It is shown that, for separation of iodine from one other material, a two-beam K-edge approach requires less integral dose than a two-beam technique at conventional CT energies for slice diameters up to 30 cm. For selective iodine imaging in the presence of more than one other material, the three-spectrum K-edge technique is a necessity. Exposure requirements and beam-hardening corrections are discussed in detail and a computer-simulated CT image generated by the proposed scheme is presented.     

Correlation of cerebral blood flow with outcome in head injured patients

In order to determine the relationship of cerebral blood flow (CBF) to the clinical outcome of head injury, serial determinations of CBF were performed by the intravenous Xenon technique in 24 patients. The patients were of mixed injury severity and were classified into four groups depending on the neurological exam at the time of each CBF study. All eight patients who were lethargic on admission demonstrated increases in their minimally depressed CBF as they improved to normal status. Eleven patients in deep stupor or coma ultimately recovered. Ten of these patients initially had moderate to profound decreases in CBF which improved as recovery occurred. The single exception was an adolescent whose initial CBF was high but became normal at recovery. Five comatose patients died. In four of these, already depressed CBF fell even lower, while one adolescent with initially increased CBF developed very low CBF preterminally. The data presented in this report demonstrated a good correlation between CBF and clinical outcome. In every one of the adult survivors, depressed CBF increased as the patient recovered to normal status. All adults who died showed a deterioration of CBF as the neurological status worsened. The only exceptions were two adolescents who initially showed high CBF values. In the adolescent who died, CBF dropped to low levels while in the survivor a normal CBF was achieved. Thus in adults a traumatic brain injury was associated with depressed CBF which increased with recovery or decreased further with deterioration while the reaction to injury was quite different in the younger brain.     

Influence of the number of questions on the student''s achievement in tests of anatomy

The authors compare student's achievement in tests with low and moderately high number of questions requiring short answers. Five groups of Medical School students underwent their regular Anatomy evaluation tests, which consisted of 13 questions (one group), 15 (two groups) and 25 (two groups). In each group five questions were chosen at random, average scores being calculated from their marks. These scores were statistically compared to the ones calculated from the marks given to the full-length evaluation tests; it became quite evidente that averages go up when the number of questions is increased. Putting the averages in terms of A, B, C and D scores (very good, good, regular and insufficient), it was noted that failure to reach at least the C score is inversely proportional to the number of questions. The results are discussed in terms of determining the most proper number of questions to be given in a test.     

Warm IgM anti-IT causing autoimmune haemolytic anaemia

A patient with autoimmune haemolytic anaemia due to an autoagglutinin of anti-IT specificity is reported. The antibody was of the IgM class and bound complement; unexpectedly, it reacted optimally at 37 degrees C. A prozone was noted when testing serial dilutions of the patient's serum against appropriate red cells in saline, but was not found when testing an eluate prepared from the patient's red cells. Investigations suggested that the prozone was due to a blocking antibody of high molecular weight, which appeared to be specific for I and IT.     

Medical equipment costs: those you see and those you pay

On day 21.5 a pregnant rat received a single injection of [1-14C]glycerol. The purpose was to study the transfer of glycerol through the placenta from the maternal to fetal plasma. From 3-20 min after injection the specific activity of glycerol in maternal and fetal plasma was measured. The results indicate that the mother can provide this molecule to the fetus. Similar results were obtained with the rabbit on day 28 of pregnancy. The possibility of the conversion of plasma glycerol to glucose has been investigated in the rat and rabbit fetus. This molecule was chosen chiefly to see whether the gluconeogenic pathway was functioning in the fetus above the triose phosphate step. At two stages of fetal development the capacity of the fetus to incorporate [1-14C]glycerol into glucose plus glycogen has been shown in the two species. In the rat fetus the conversion of [1-14C]glycerol to [14C]glucose increases from 19.5 to 21.5 days of gestation. For the rabbit this parameter increases from 25 to 28 days of gestation. On day 25 in the rabbit and day 19.5 in the rat the liver glycogen was labeled, but it did not accumulate the [14C]glucose from [1-14C]glycerol during the time that we have studied. In contrast, on day 28 in the rabbit and day 21.5 in the rat the incorporation of radioactivity increased as function of the time. However, the relative importance of glycerol as precursor of the glucose plus glycogen in the fetus remains to be elucidated.