Reaction thrust of water jet for conical nozzles

Clear knowledge on the reaction thrust of water jet is valuable for better design of water jet propulsion system. In
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions．     

量子代数D（—）函子的系数扩张

令A=Z[ν]m,其中m是ν-1和某奇素数p生成的理想,ν是未定元.A′=Q（ν）是a的分式域,（aij）nxn是对称Cartan矩阵,令U′是A′上相伴于对称Cartan矩阵（aij）nxn的量子代数.U是U′的由Ei（N）,Fi（N）,Ki,Ki-1（i=1,2,…,N≥0）生成的A子代数,则U是A-Hopf代数.本文讨论了U中函子D（—）的系数扩张的若干性质,即对A代数Γ,如上函子的基环从A扩张到Γ时,函子Dr（—）具有的性质.     

提高洪水作业预报精度的方法浅析

面对实用预报方案,如何提高洪水作业预报精度,是衡量洪水预报质量和效率的关键。依据预报计算的影响因素、预报要素的特征、方案参数的物理属性分析,论证了预报修正系数的理论依据,并分析了预报修正系数确定的技术和方法。     

电导法测定水溶液中NaBr与KBr的活度系数

应用电导法分别测定水溶液中NaBr、KBr的电导率,以及混合电解质NaBr和KBr的电导率;计算了电解质的活度系数。结果表明,温度一定时,在稀溶液范围内,活度系数随浓度的增加而降低;浓度一定时,随温度的升高而降低;混合电解质的活度系数与单一电解质的活度系数相近,并不存在简单的加和关系。     

完全沉淀被测组分所需沉淀剂的用量条件

以难溶盐的溶解度与活度积、活度系数的关系为依据,探讨完全沉淀被测离子所需沉淀剂的具体用量条件,并推导出相应的计算关系式,使沉淀剂的用量更加明确、具体和具有实用性．     

沥青路面抗滑集料微观纹理系数计算及试验——基于扫描电镜法

目前常用于评价集料抗滑性能的磨光值试验存在不少弊端.文章采用扫描电镜法试验获取集料的微观形貌,提出集料微观纹理系数,进而评价集料的抗滑性能.试验研究结果表明,该方法比磨光值试验能更快捷、简便、直观地评价集料的抗滑性能.     

基于同类型日思路的节假日电力负荷预测方法

针对节假日负荷预测的特点,从同类型日与基准日的选择思路进行了分析,并据此提供了相应的实用预测方法,使预测较为准确,为电力行业从事预测的人员提供算法参考。     

Measurement of boiling heat transfer coefficient in liquid nitrogen bath by inverse heat conduction method

Inverse heat conduction method （IHCM） is one of the most effective approaches to obtaining the boiling heat transfer coefficient from measured results. This paper focuses on its application in cryogenic boiling heat transfer. Experiments were conducted on the heat transfer of a stainless steel block in a liquid nitrogen bath, with the assumption of a 1D conduction condition to realize fast acquisition of the temperature of the test points inside the block. With the inverse-heat conduction theory and the explicit finite difference model, a solving program was developed to calculate the heat flux and the boiling heat transfer coefficient of a stainless steel block in liquid nitrogen bath based on the temperature acquisition data. Considering the oscillating data and some unsmooth transition points in the inverse-heat-conduction calculation result of the heat-transfer coefficient, a two-step data-fitting procedure was proposed to obtain the expression for the boiling heat transfer coefficients. The coefficient was then verified for accuracy by a comparison between the simulation results using this expression and the verifying experimental results of a stainless steel block. The maximum error with a revised segment fitting is around 6%, which verifies the feasibility of using IHCM to measure the boiling heat transfer coefficient in liquid nitrogen bath.     

Enhancement of solubility and mass transfer coefficient of salicylic acid through hydrotropy

This study deals with the effect of hydrotropes on the solubility and mass transfer coefficient of salicylic acid. The solubility and mass transfer studies were performed using the hydrotropes, i.e., sodium acetate, sodium salicylate, citric acid, and urea at concentrations of 0-3.0 mol/L and system temperatures of 303-333 K. It was found that the solubility and mass transfer coefficient of salicylic acid increases with increase in hydrotrope concentration and also with system temperature. All hydrotropes used in this work showed an enhancement in solubility and mass transfer coefficient to different degrees. The maximum enhancement factor values were determined for all hydrotropes used in this study. The highest value was 28.08 for solubility studies and 10.42 for mass transfer studies. The performance of hydrotropes was measured in terms of the Setschenow constant （Ks）. The highest value observed was 0.696.     

变温条件下半导体霍尔系数及载流子浓度的测量

利用简单的加热装置改装HL—IV型霍尔效应实验仪,利用改装后实验仪器测量不同温度条件下的半导体霍尔系数及其载流子浓度。