A “Multiplicative Coboundary” theorem for some sequences of random matrices

Schmidt(¹⁰) showed that if the family of distributions of the partial sums of a strictly stationary random sequence is tight, then that random sequence is a coboundary. Here an analog of that result is proved for some sequences of random matrices, with partial sums replaced by matrix products.     

空调热泵系统R22替代的理论分析及试验研究

空调热泵系统Ｒ２２替代的理论分析及试验研究杨昭,马一太,吕灿仁,陈东（天津大学热能研究所大津３０００７２）关键词替代物;可燃性;空调;热泵１前言制冷工质Ｒ２２因优良的热力学性质已被广泛应用。但因其ＯＤＰ值为０．０５５且ＧＷＰ值为０．３６,在１９９４年...     

冷热兼供热泵空调器的性能模拟与分析

针对冷热兼供热泵空调器的特点,建立了冷热兼供热泵空调器稳态运行的数学模型,对该系统进行了较全面的模拟分析,并将模拟结果和实验数据进行了比较,两者吻合良好．同时应用该软件对不同设备参数和不同工况下性能进行分析,得到若干有用的结果．     

液体燃料爆炸抛撒过程分析

该文建立了描述液体燃料空气炸药云雾运动规律的模型,给出了云雾膨胀过程３个阶段的速度—半径关系或速度—时间关系,以及云雾中燃料液滴的尺寸估计。     

气垫调压室的体型优化计算

以总容积最小为目标,建立了气垫调压室体型优化的数学模型,采用遗传算法求解该模型,从而为合理选择调压室截面积、气室高度、室内水体高度及初始气体压力等基本参数提供了科学依据．给出了计算实例,所得结果与经验估算值相比,工程效益较为显著,设计安全度高．     

用环形扩散管和滤纸联用采样技术采集空气中氨和铵盐

建立了环形扩散管和滤纸采样夹联用，分形态同时采集空气中所态氨和颗粒态铵盐的方法。在同一气流中，采用涂渍１．５％草酸乙醇水溶液的环形扩散管采集气态氨，用浸渍上述试剂的玻璃纤维纸和慢速定量滤纸分别采集颗粒安和第一层滤纸上的铵盐挥发产生的氨气。用靛酚蓝比色法分别测定氨和铵盐。当采气流速为１．０Ｌ／ｍｉｎ时，采样效率高于９８．２％。将本法测得的氨气和铵盐的总量与标准采样方法的测定结果比较。无显著性差异（Ｐ     

Production of oxygen enriched air by rapid pressure swing adsorption

A novel rapid pressure swing adsorption (RPSA) process is described for production of 25–50% oxygen enriched air. The embodiment consists of one or more pairs of adsorbent layers contained in a single adsorption vessel. The layers undergo simultaneous pressurization-adsorption and simultaneous depressurization-purge steps. A total cycle time of 6–20 seconds is used. The process yields a very large specific oxygen production rate and a reasonable oxygen recovery for production of 20–50 mole% oxygen enriched gas.It is demonstrated by a simple mathematical model of isothermal single adsorbate pressure swing ad(de)sorption concept on a single adsorbent particle that the specific production rate of a PSA process cannot be indefinitely increased by reducing the cycle time of operation when adsorbate mass transfer resistances are finite.     

Catalytic wet air oxidation of oleic acid on ceria-supported platinum catalyst.effect of pH

Summary Catalytic wet air oxidation (CWAO) of oleic acid was carried out in a batch reactor on platinum supported ceria catalyst (Pt/CeO₂). Oleic acid is a water insoluble linear unsaturated fatty acid of 18 carbon atoms. To increase the homogeneity of the solution by saponification, the influence of NaOH additions in oleic acid CWAO mechanism and catalyst performances have been investigated. The oxidation of such molecule occurs by two types of mechanisms: successive carboxy-decarboxylation which leads essentially to CO₂and/or C-C bonds splitting in the alkyl chain inducing a high formation of acetic acid. With or without NaOH, the 5%Pt/CeO₂catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially saponified which increases the solubility of the reactant before it to be oxidized. Finally the oxidation is slightly delayed by the presence of NaOH. The catalyst characterizations show no significant difference before and after reaction.</o:p>     

Effect of pressure on oxygen enrichment of liquid crystalline cellulose ether membranes at elevated temperature

Cholesteric liquid crystalline triheptyl cellulose (THC)/ethyl cellulose binary blend membranes were prepared and the effect of pressure on their oxygen enrichment at elevated temperature was investigated using a constant pressure-variable volume method. The oxygen enrichment increased with the increase of transmembrane pressure difference or with slight increase of the THC content in the blend membranes. The oxygen concentration through the membranes increased linearly with decreasing pressure ratio. Air was directly separated through a 17 m-thick THC/EC(1.5/98.5) membrane to prepare an oxygen-enriched air containing 39.5% oxygen at the flux of 6.99×10^–4 cm³ (STP)/s.cm² at the pressure difference of 0.43 MPa and 85 °C.     

A central limit theorem for age- and density-dependent population processes

Consider a population consisting of one type of individual living in a fixed region with area A. In [8], we constructed a stochastic population model in which the death rate is affected by the age of the individual and the birth rate is affected by the population density P_A(t), i.e., the population size divided by the area A of the given region. In [8], we proposed a continuous deterministic model which in general is a nonlinear Volterra type integral equation and proved that under appropriate conditions the sequence P_A(t) would converge to the solution P(t) of our integral equation in the sense that

$\text{lim}\text{→∞}\text{P}\text{sup}\text{0?s?t}\text{|P}{}_{\mathrm{A}}\text{(s) ? P(s)|>ε}\text{=0}\text{for every}\text{ε > 0}$

.In this paper, we obtain a “central limit theorem” for the random element √A(P_A(t)?P(t)). We prove that under appropriate conditions √A(P_A(t)?P(t)) will converge to a Gaussian process. (See Theorem 3.4 for the explicit formula of this Gaussian process.)