低温多效蒸发海水淡化系统热力分析

建立了喷射器低温多效蒸发海水淡化系统的数学模型,计算分析了各种温度损失随温度的变化,并研究了顶值盐水温度、蒸发器效数和动力蒸汽等参数对系统的造水比和生产单位质量淡水所需传热面积的影响。结果表明各种温度损失在末效蒸发器内显著增加;喷射器低温多效蒸发系统的热力特性明显优于多效蒸发系统;通过增加顶值盐水温度、蒸发器效数和动力蒸汽温度,可以实现系统的优化运行。     

Dendrite morphology of several steady state unidirectionally solidified iron base alloys

The experimental data are presented of the dendrite morphology of steady state unidirectionally solidified steels. The dendrite arm spacings were correlated with the equation A =KR ^mG^mwhereR is the growth rate and G the temperature gradient. The exponentsm andn for the primary arms are fairly close to the theoretical values (m = -0.25,n = -0.5). For the secondary arms they are about the same (-0.4). The primary arm spacings do not depend much on composition. The secondary arm spacings, however, decrease at fixed carbon content with increasing content of substitutional elements, and they were found to be smaller in a steel freezing as ferrite compared to steels freezing as austenite. All the authors were with Max-Planck Institut für Eisenforschung, 4 Düsseldorf 1, Max-Planck-Str. 1, Germany, at the time this investigation was carried out.     

吸收式热泵多效蒸发海水淡化热力性能研究

提出了两级吸收式热泵多效蒸发海水淡化工艺流程,并建立了系统的数学模型。计算分析了溴化锂溶液浓度和加热蒸汽温度对系统的造水比、生产单位淡水所需传热面积和吸收式热泵的热力系数的影响。研究结果表明,系统的造水比和吸收式热泵的热力系数随加热蒸汽温度和LiBr浓溶液浓度的降低而增大,生产单位质量淡水所需传热面积随加热蒸汽温度的降低而急剧增加;通过调整溴化锂溶液的浓度,能够实现对不同品质热源的利用;该系统不仅能够保证淡水不被溴化锂污染,而且其造水比明显优于喷射泵多效蒸发系统和多效蒸发系统。     

Skills training as treatment for juvenile delinquents.

Viewing skills deficits as parameters of juvenile offender dysfunctioning, and considering skills training as a treatment modality represent relatively new strategies for rehabilitation. Data from a police diversion project (the Dallas Police Department's Youth Services Program) are presented, indicating that levels of certain physical, emotional, and intellectual skills are related to rearrest recidivism for juvenile offenders. The results of providing skills training as a treatment program for both the juvenile offenders and their parents are presented, and implications for rehabilitation strategies are discussed. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phylogenetic and physiological diversity of sulphate-reducing bacteria isolated from a salt marsh sediment

Xenopus blastula cells activate different mesodermal genes as a concentration-dependent response to activin, which behaves like a morphogen. To understand how cells recognize morphogen concentration, we have bound naturally labeled activin to cells and related this to choice of gene activation. We find that the increasing occupancy of a single receptor type can cause cells to switch gene expression. Cells sense ligand concentration by the absolute number of occupied receptors per cell (100 and 300 molecules of bound activin induce Xbra and Xgsc, respectively, i.e., 2% and 6% of the total receptors) and not by a ratio of occupied to unoccupied receptors. The long duration of occupancy explains a previously described ratchet effect. Our results suggest a new concept of morphogen gradient formation and interpretation that is particularly well suited to the needs of early development.     

Determination of diffusion controlled reaction rates at a solid/liquid interface using scanning electron microscopy

A high‐resolution method has been developed for the determination of localized values of interfacial reaction rate and mass transfer coefficient in aqueous solution. Scanning electron microscopy has been successfully applied to this problem through the measurement of electroplated film thickness formed under limiting current conditions. The method involves the calculation of local values of reaction rate via Faraday's laws and subsequent conversion of the data to absolute values of mass transfer coefficient. The technique has been verified in an undisturbed, turbulent flow regime (rotating cylinder electrode) through the use of Sherwood group dimensionless analysis. The resulting relationship shows comparable accuracy relative to electrochemical measurements. Favourable comparison has also been made with the generally accepted rotating cylinder correlation of Eisenberg, Tobias and Wilke. Differential rates of mass transfer to a single surface under conditions of disturbed flow have also been examined at a high spatial resolution using the stepped rotating cylinder electrode geometry. In this case, reaction rates have been measured as a function of circumferential distance within a recirculation zone situated immediately downstream of a backward‐facing step.