喷射成形中金属液滴凝固过程的计算机模拟

在群体动力学方法的基础上,提出了描述合金雾化液滴凝固过程动力学的数学模型,并将其与液滴的传热方程和运动方程相耦合,对A1—4．5％Cu(质量分数)合金液滴的冷却凝固过程进行了分析．结果表明,液滴冷却至一定温度时开始形核,随后晶粒长大;在形核过程中,晶粒尺寸分布区间较宽,形核后晶粒尺寸分布区间逐渐减小;液滴直径越小,冷却速度越快,晶粒数量密度越大,凝固结束时晶粒越细小．     

基于C51的氨含量监测系统软件设计

本文提出了使用C51高级语言将浮点数转换为BCD码的算法和实现过程。提出对具有指数特性的电化学传感器的快速校正算法。详细论述了存储、查询和打印函数的设计思想。     

定点距离最优化的遗传算法研究

本文研究了GIS城市道路网中任意两点节之间路径优化问题,提出了解决该问题的求解策略,解释实现该遗传算法的一些关键问题,力求为工程设计人员开发相关算法提供参考。     

“人口最优控制”的一点注记

本文给出时间连续按龄离散的人口发展模型最优性问题的充分条件,     

Quantile estimation in two-phase sampling

The estimation of quantiles in two-phase sampling with arbitrary sampling design in each of the two phases is investigated. Several ratio and exponentiation type estimators that provide the optimum estimate of a quantile based on an optimum exponent α are proposed. Properties of these estimators are studied under large sample size approximation and the use of double sampling for stratification to estimate quantiles can also be seen. The real performance of these estimators will be evaluated for the three quartiles on the basis of data from two real populations using different sampling designs. The simulation study shows that proposed estimators can be very satisfactory in terms of relative bias and efficiency.     

浮动衬套式节流缓冲机构及尺寸计算

介绍浮动衬套式节流缓冲机构的工作原理及浮动衬套的尺寸计算。     

几种常用消毒剂对烟草黑胫病菌生长的抑制

漂浮育苗是一项较先进的育苗技术,对育苗盘、池膜、剪叶器具和操作的严格消毒是培育无病壮苗的关键环节。为烟叶生产上更合理地选用消毒剂,研究采用浸泡法以甲霜灵为对照药剂,分析了几种常用消毒剂对烟草黑胫病菌菌丝生长和孢子囊产生的抑制作用,结果表明7%有效氯次氯酸钠AS、10%二氧化氯DP、30%有效氯漂白粉DP和高锰酸钾常规浓度,对烟草黑胫病菌均有一定的抑制作用,所有供试消毒药剂中高浓度处理对烟草黑胫病菌均有一定的抑制,并且其抑制作用好于或相当于甲霜灵。不同消毒药剂对烟草黑胫病菌孢子囊产生的抑制以甲霜灵处理抑制率最高。7%有效氯次氯酸钠AS、24%混脂酸·铜(商品名:毒消)EW、10%二氧化氯DP、30%有效氯漂白粉DP、高锰酸钾常规浓度处理、美国消毒剂AS中高浓度处理可有效抑制孢子囊的产生,但与甲霜灵差异不显著。     

集聚的需要--读《The Need For Concentration》

介绍了((The Need For Concentration》一文的作者及写作背景，对文章中关于住宅集聚密度与住宅拥挤之间关系的内容进行了阐述，结合我国目前规划的现实，提出了一些个人的看法。     

Rotifer Seasonal Succession and Copepod Predation in Lake Michigan

Phytoplankton and zooplankton population dynamics in southeastern Lake Michigan provide indirect evidence that selective Cyclops predation and food resource levels are important determinants of rotifer species succession. The spring rotifer community, dominated by the soft-bodied Synchaeta, declined in abundance by late spring and was succeeded by a summer assemblage dominated by spiny (Kellicottia, Keratella) and colonial (Conochilus) rotifers, and then by an autumn assemblage of spiny rotifers and the soft-bodied, evasive-swimming Polyarthra vulgaris. In contrast to Synchaeta, these latter forms are resistant to predation by Cyclops bicuspidatus thomasi, the major invertebrate predator in the study area. The density of Synchaeta was negatively correlated with the population density of late instar C. bicuspidatus thomasi and positively correlated with standing stocks of flagellates and small, non-flagellate (<30 μm on one dimension) phytoplankton. These results suggest that Cyclops predation and food resource levels were important factors affecting the abundance of this genus. Conservative estimates of predation mortality of Synchaeta by Cyclops can account for most of the estimated population death rates during spring and early summer when Synchaeta abundances declined markedly. The population dynamics of rotifers resistant to Cyclops predation, especially Keratella cochlearis and Kellicottia longispina, were positively correlated with Cyclops populations, suggesting that abundances of these populations were not predation-limited. A high correlation between egg ratios of these resistant species and phytoplankton standing stocks was found. However, no significant correlation was observed between estimated death rates of resistant species and Cyclops abundance, suggesting that population dynamics of these predation-resistant species were more affected by food resources than by cyclopoid predation.