用于氢化的铜铬氧化物催化剂的研究

通过铜铬氧化物催化剂用于豆油的选择氢化,研究了制备方法及氢化条件对催化剂活性的影响.在所用的五种催化剂中,以Adkins法制备的催化剂活性最好,碳酸氢铵法次之.文中还对催化剂焙烧气氛、焙烧温度、焙烧时间、铜铬原子比对催化剂活性的影响以及氢化温度、催化剂用量、搅拌速度、氢流速等对反应的影响进行了较详细的讨论.     

精铸件结构优化设计实践

以6种典型的精密铸件为例，利用“6个千方百计”原则对产品结构进行优化设计，同时辅助有限元分析对优化结果进行再验证。通过减少大平面、避免深长孔、采用加强筋等优化措施，有效地避免了夹砂、鼓包、跑火、缩孔、裂纹等铸造缺陷，实现了少无切削和减轻铸件质量。     

Practice characteristics that lead to 21st century learning outcomes

Abstract The key research question for this study was to ask whether or not innovative teaching practices would lead to the development of learning outcomes essential for preparing the younger generation for the challenges of life in the knowledge society of the 21st century, and if so, how are the pedagogical features related to the different learning outcomes. Preliminary analyses of the case study data collected from the SITES M2 Study in Hong Kong reveal that where the development of more significant learning gains were observed, the cases possess characteristics additional to the criteria defined in the Study for selection of innovation. More importantly, it was found that the impact of the pedagogical practices was not determined simply by the aggregation of characteristics of the practices per se , nor on the technologies used, but on whether 'empowerment' permeates the curriculum goal and process. Further, this paper claims that these affective and socio-cognitive learning outcomes are more important as preparation for lifelong learning in the 21st century than 'knowledge management competencies'.     

Analogue implementation of a neural network controller for UPSinverter applications

An analogue neural-network controller for UPS inverter applications is presented. The proposed neural-network controller is trained off-line using patterns obtained from a simulated controller, which had an idealized load-current-reference. Simulation results show that the proposed neural-network controller can achieve low total harmonic distortion under nonlinear loading condition and good dynamic responses under transient loading condition. To verify the performance of the proposed NN controller, a hardware inverter with an analogue neural network (NN) controller (using mainly operational amplifiers and resistors) is built. Additionally, for comparison purposes, a PI controller with optimized parameters is built. Experimental results confirm the simulation results and show the superior performance of the NN controller especially under rectifier-type loading condition. Implementing the analogue neural-network controller using programmable integrated circuits is also discussed     

Heating energy use management in residential buildings by temperature control

This paper presents the results of analytical investigations to determine the potential heating energy savings that can be achieved in residential buildings by controlling the house temperature through either night setback or night setback plus day zone setback. A typical U.S. single family house is analyzed for different levels of thermal integrity of the building envelope (i.e., levels of insulation, window glazing, and infiltration). Reduced infiltration, insulated interior walls, and various window orientations are also considered. Results are given for four major U.S. climate zones—cool, temperate, hot-humid, and hot-arid. The analysis shows that both types of setbacks are most effective in loose houses, with the greatest absolute savings for the cool climates, and the greatest percent savings for the hot climates. However, the benefits from thermostat setbacks are smaller for tighter houses, and may actually be counterproductive owing to corollary effects such as increased peak loads and degradation of system efficiency.     

Microstructure investigations of ball milled materials

HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.     

Lysophosphatidylcholine is involved in the antigenicity of oxidized LDL

Lysophosphatidylcholine (LPC) is formed by hydrolysis of PC in low density lipoprotein (LDL) and cell membranes by phospholipase A2 or by oxidation. Oxidized (ox) LDL activates endothelial cells, an effect mimicked by LPC. oxLDL also has the capacity to activate T and B cells, and antibody titers to oxLDL are related to the degree of atherosclerosis. The antigen in oxLDL responsible for its immune-stimulatory capacity is not well characterized, and we hypothesized that LPC was involved. We demonstrate herein the presence of antibodies against LPC, both of the IgG and IgM isotype, in 210 healthy individuals. This antibody reactivity was not specifically related to oxidation of the fatty acid moiety in LPC, since LPC containing only palmitic acid showed antibody titers equivalent to those of LPC containing unsaturated fatty acids. Antibody titers to PC were low compared with LPC, and hydrolysis of PC at the sn-2 position is thus essential for immune reactivity. There was a close correlation between anti-oxLDL and anti-LPC antibodies. Furthermore, LPC competitively inhibited anti-oxLDL reactivity, which indicates that LPC may explain a significant part of the immune-stimulatory properties of oxLDL. LPC, being a lipid, is not likely to be an antigen itself. Instead, LPC could form immunogenic complexes with peptides, which may induce and potentiate immune reactions in the vessel wall. This study adds to the evidence that LPC is an important component of oxLDL and emphasizes the potential role of phospholipase A2 in atherosclerosis.     

Physical fitness, physical activity, and functional limitation in adults aged 40 and older

PURPOSE: A cohort of middle-aged and older men and women were followed for an average of 5.5 yr to examine the association between physical fitness, physical activity, and the prevalence of functional limitation. METHODS: The participants received medical assessments between 1980 and 1988 and responded to a mail-back survey regarding functional status in 1990. RESULTS: Among 3495 men and 1175 women over 40 yr of age at baseline, 350 (7.5%) reported at least one functional limitation in daily or household activities at follow-up. The prevalence of functional limitation was higher among women than men. Physically fit and physically active participants reported less functional limitation than unfit or sedentary participants. After controlling for age and other risk factors, the prevalence of functional limitation was lower for both moderately fit (odds ratio = 0.4, 95% CI = 0.2-0.6) and high fit men (odds ratio = 0.3, 95% CI = 0.2-0.4), compared with low fit men. Corresponding figures for women were 0.5 (0.3-0.7) and 0.3 (0.2-0.5) for moderately fit and high fit women. The association between physical activity and functional limitation was similar to the data for physical fitness. CONCLUSIONS: These data support a protective effect of physical fitness and physical activity on functional limitation among older adults and extend this protective effect to middle-aged men and women.