内燃机车曲轴中频淬火过程的数值模拟

借助 ANSYS大型有限元分析软件 ,实现了 16 V2 4 0曲轴淬火过程的计算机模拟 ,模拟结果可直观地显示出任一时刻曲轴表面及内部的温度分布、冷却曲线以及淬火结束后的残余应力分布 ,并能预测淬硬层深度。同时对比了轴颈内圆角处进行淬火和不进行淬火两种工艺的效果 ,为现场提供了用虚拟现实方法详尽分析和研究淬火工艺的工具。     

NEURAL NETS SPEED FLOW CALCULATION

Neural Nets Successfully Solve Complex Fluid Flow Problem. Much research is being done in the area of neural networks, and industry is actively seeking successful application to real world problems. We describe here a successful application. We have used neural networks to model complex coolant flow patterns, such as those encountered in design of hypersonic aircraft. Previous calculation methods, while reasonably accurate, are iterative and extremely time consuming. Our new approach uses a hierarchical neural network architecture to model coolant flow distribution in multiple heat exchanger panels. This method is direct, fast, and accurate.     

基于AutoCAD2000的图解法确定工艺转角

提出了基于AutoCAD2 0 0 0的图解法求解机械加工过程中工艺转角的问题 ,并针对具体的应用实例给出了圆满的解答 ,并验证了其精度。     

��Ȼ����Һ���÷����̽

求文针对我国天然气凝液如何利用问题,结合新技术进展,进行了初步探讨,认为原料较多的场合,应以催化脱氢或芳构化作为当前的主要加工方向。对原料较少的场合,也提出一些看法。     

Lactic acid production from dining‐hall food waste by Lactobacillus plantarum using response surface methodology

BACKGROUND: Food waste generally has a high starch content and is rich in nutritional compounds, including lipids and proteins. It therefore represents a potential renewable resource. In this study, dining‐hall food waste was used as a substrate for lactic acid production, and response surface methodology was employed to optimise the fermentation conditions. RESULTS: Lactic acid biosynthesis was significantly affected by the interaction of protease and temperature. Protease, temperature and CaCO₃ had significant linear effects on lactic acid production, while α‐amylase and yeast extract had insignificant effects. The optimal conditions were found to be an α‐amylase activity of 13.86 U g^?1 dried food waste, a protease activity of 2.12 U g^?1 dried food waste, a temperature of 29.31 °C and a CaCO₃ concentration of 62.67 g L^?1, which resulted in a maximum lactic acid concentration of 98.51 g L^?1 (88.75% yield). An increase in inoculum size would be appropriate for accelerating the depletion of initial soluble carbohydrate to enhance the efficiency of α‐amylase in dining‐hall food waste fermentation. CONCLUSION: A suitable regression model for lactic acid production was developed based on the experimental results. Dining‐hall food waste was found to be a good substrate for lactic acid fermentation with high product yield and without nutrient supplementation. Copyright © 2008 Society of Chemical Industry     

Restraining the associations of anthracene fluorophore by chemically linking to poly(methyl methacrylate)

Associations (dimer or aggregate) of anthracene (An) fluorophores tend to interrupt the monomer emission and reduce the quantum yield (Φ_PL); therefore, poly(methyl methacrylate) (PMMA) chain was used in this study to chemically link to anthracene and to block the mutual associations among the anthracene fluorophores. With this aim, the target polymers were prepared by anionic polymerizations with 9,10‐dibromoanthracene/s‐butyllithium as initiating system to proceed polymerizations of methyl methacrylate (MMA) directly or in the presence of 1,1‐diphenylethylene (DPE). Use of DPE before addition of MMA produces stable initiating anionic species and avoids potential side reactions during polymerization; however, it also introduces four β‐phenylene rings around the central anthracene ring, which interfere with the corresponding emission pattern and reduce the Φ_PL (32%) value due to potential interactions between phenylene rings and anthracene. On the contrast, polymerization without participation of DPE results in polymer with central anthracene ring directly connected to two PMMA chains, which gives clean vibronic emission pattern with limited association emissions and enhanced Φ_PL (52%) value. Physical blending of anthracene by PMMA is less efficient to restrain the associations and results in a film of lower Φ_PL (20%). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polysaccharide‐based artificial extracellular matrix: Preparation and characterization of three‐dimensional,macroporous chitosan,and heparin composite scaffold

Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Stress in Dairy Farming and the Adoption of New Technology.

Previous studies have identified a number of different farm stressors and have reported gender and age differences in levels of stress. This study aimed to determine stress experienced by New Zealand dairy farmers, particularly in relation to adoption of new technology and its relationship to age and gender. Measures of farm stress and adoption of technology were completed by 985 dairy farmers. The highest levels of stress were reported for time pressures, machinery breakdown, weather, and government policies. Stress related to new technologies occurred rarely. Women reported more stress and higher levels of stress for understanding new technologies. There was also an increase in severity of stress with age related to new technologies. Overall, stress levels were moderate and may reflect favorable economic conditions. The findings suggest a need to tailor stress interventions to meet specific needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

高酸性气田压力容器无损检测

通过对压力容器四种常规无损检测方法进行分析对比,阐述了高酸性气田压力容器对接接头的无损检测方法和比例,在满足国内外现行标准规范的前提下,应加大超声波检测比例,对接触高酸性气体介质的焊缝内表面进行100%磁粉检测或渗透检测,最大限度地检测出焊缝内表面或近表面裂纹,确保高酸性气田地面建设工程的安全。     

Using a weight-of-evidence approach for management of watersheds.

This research used a weight-of-evidence approach to evaluate sources of contaminants in a drinking water watershed that serves as part of the City of Boston's water supply. The approach incorporated land use analysis using GIS, sanitary surveys, traditional water quality monitoring and microbial source tracking (MST) tools. Case-study tributaries were selected based on elevated faecal coliform counts. Land use analysis and sanitary surveys were used to identify suspected microbial sources, including residential septic systems, agricultural animal operations, commercial/industrial operations and wildlife activity. Sampling sites were selected to hydrologically isolate potential contamination sources. Samples were collected seasonally over 1 year and analysed for traditional and MST parameters. Results demonstrated that both septic systems and a horse stable were contributing microbial loads in the first tributary. In the second tributary, septic systems from the townhouses were contributing microbial loads while a plant nursery was contributing organic matter. This evidence was used to evaluate best management practices to mitigate the contamination.