晶粒生长过程的蒙特卡罗模拟方法

计算机模拟晶粒生长所用的模型及模拟方法大体可分3种:蒙特卡罗(Monte Carlo)方法或改进的蒙特卡罗方法(简称MC法)、使用连续扩散界面场模型以及将细胞状的晶粒结构看作Laguere棋盘形布局来处理的Laguerre模型.特别是应用于模拟焊接热影响区(HAZ)晶粒长大的二维和三维过程取得了较好结果,但在生长模型的边界处理等方面有待继续完善,特别是晶粒生长与晶化温度、时间、气氛等参数密切相关,这种复杂工艺条件下的晶粒生长过程的模拟,是当前该领域正待解决的难题.     

新型热泵热水器的控制器设计

热泵热水器是一种新型的供热设备,是一种可替代锅炉的供暖设备和热水装置。它通过制冷剂温差吸热和压缩机压缩制热后,与水换热,从而提高了热效率并且能较充分利用能源。热泵热水器必须拥有完善而可靠的控制系统。热泵热水器的控制系统由触摸屏与PLC构成。根据对热泵热水器工作原理、系统控制要求及硬件环境设计了触摸屏界面及PLC控制程序。     

Liquid film dryout model for predicting critical heat flux in annular two-phase flow

Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux （CHF） is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model： onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed.     

液态金属热输运过程的分子动力学模拟

采用分子动力学模拟方法对平板间液态金属的流动换热过程进行模拟.研究液态金属的微观热输运过程,左右两侧平板采用Cu原子作为恒温固壁,液态金属Pb处于平板间,以FCC结构为初始排列.模拟结果表明,在平板间的液态金属温度分布呈线性变化;不同温度下液态金属在恒温平板间的热输运模拟过程表明,平板间液态金属的热导率随温度的升高而增加,呈现线性变化.当在系统上施加一个重力加速度时,平板间未出现明显的自然对流,表明在微尺度下,边界阻力和粘滞力抑制了液态金属的自然对流.     

Prostate Specific Antigen in Cord Blood

Recent studies have demonstrated the presence of prostate specific antigen (PSA) in cord blood of male as well as female babies. The placental progesterone and estradiol up-regulate the synthesis and secretion of PSA in Placenta. This PSA is presumed to play a role in intrauterine growth of fetus by virtue of its proteolytic action on several substrates including insulin-like-growth-factor-binding-protein-3, insulin chains and Interleukin-2. This study was planned with the objective of correlating the levels of PSA in cord blood to gestation at delivery, the type of delivery and gender of the fetus. Fifty-seven cord blood samples were collected from the umbilical cord during delivery or mid-trimester abortion and analyzed for PSA using ‘Active PSA DSL-9700 ultra sensitive’ kit employing two-site immuno-radiometric assay principle and having a detection limit of 0.001 ng/ml. Mean PSA levels in cord blood were found to be 0.112 ± 0.027 ng/ml. The concentration of PSA in cord blood was found to be higher in case of higher gestational age, male baby and operative delivery. 50 % of cord bloods for female babies had PSA below detection limit (range <0.001–0.460 ng/ml), while all the male samples had detectable PSA (range 0.11–0.973 ng/ml). Higher Progesterone levels found in prenatal maternal blood in case of male babies may be responsible for the higher cord blood PSA. Mean cord blood PSA was 0.150 ± 0.150 ng/ml in forceps delivery and 0.078 ± 0.012 ng/ml in normal vaginal delivery. Forceps delivery causes much more stress and strain as compared to a normal vaginal delivery, resulting in increased levels of adrenal glucocorticoids, and therefore, higher cord blood PSA.     

技巧啦啦操底座运动员托举专项力量训练方案设计探析

采用文献资料法、专家访谈法和录像分析法等研究方法,对技巧啦啦操底座运动员专项力量训练内容和手段进行深入研究,通过训练研究得出：对技巧啦啦操底座运动员的上肢、肩带、腰腹和下肢进行专项力量训练可有效提高其专项能力,可有效提高其托举难度和稳定性。     

谈地源热泵系统在暖通空调中的应用

随着经济的发展和人们生活水平的提高,公共建筑和住宅的供暖和空调已经成为普遍的要求.作为中国传统供热的燃煤锅炉不仅能源利用率低,而且还会给大气造成严重的污染,因此在一些城市中燃煤锅炉在被逐步淘汰,而燃油、燃气锅炉则运行费用很高.地源热泵就是一种在技术上和经济上都具有较大优势的解决供热和空调的替代方式.     

低品位碳酸锰规模化生产电解金属锰新工艺研究

为有效利用低品位碳酸锰矿,变废为宝,该工艺以低品位碳酸锰矿为原料,规模化生产电解金属锰。生产结果表明。采用本工艺生产,碳酸锰浸出率达到90％以上,硫酸、SDD等消耗指标均达到行业先进水平,电解直流电耗达到6500kwh／t。     

采用Conconi场地测试法评估优秀竞走运动员专项能力的可行性研究

目的:通过两种测试方法的比较,建立优秀竞走运动员专项有氧能力的场地评价方法。研究对象为国家竞走队运动员8人;方法:采用实验室递增负荷测试和conconi场地测试。结果:实验室递增负荷测试,优秀竞走运动员的最大血乳酸值为11.50±1.51mmol/L,10min乳酸清除率为0.37±0.15,乳酸阈走速为12.44±0.59km/h,心率阈走速为13.30±0.91km/h。通过conconi测试获得的优秀竞走运动员的心率阈值为168.8±3.2次/min,个体无氧阈走速为13.40±0.27km/h;两种测试方法比较,心率阈值不存在显著性差异,个体无氧阈走速也不存在显著性的差异,两组值存在高度正相关。结论:从获取竞走运动员心率阈和个体无氧阈走速方面看,场地conconi测试可以取代实验室递增负荷测试,且更接近运动实际。     

湿热环境下军体教学的综合创新与实践

随着新时期战争形态的发展,各种特殊环境下体能训练,成为军队医学院校军体教学的主题,要求军校学员在具备充沛体能的基础上,更要具备各种环境的适应能力。在湿热环境下学员的体能较常温下降明显,身体各方面的运动能力也明显降低。教学中对学员采用自然热环境训练,则存在诸多限制和不便,而在模拟热环境训练则具有良好的可控性。为院校的5公里武装越野、形体和柔韧教学开创了新思路。