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41.
求得了带有集中质量的分布质量弹性转轴系统横向自由振动的频率方程和振型函数的精确解析表达式,及其与不转动轴系统自由振动的频率方程和振型函数及转动角速度之间的精确解析关系 相似文献
42.
《Drying Technology》2007,25(7):1237-1242
Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model. 相似文献
43.
一种蒸发式冷凝器的新型设计方法 总被引:3,自引:0,他引:3
蒸发式冷凝器设计方法的粗糙和繁琐限制其广泛应用,特别是限制其应用于民用和小型商用建筑中。针对上述问题,作者通过实验研究了蒸发式冷凝器的影响因素(进风湿球温度、最小截面风速和喷淋水量)对蒸发式冷凝器热质交换的影响。同时提出了一种新型设计方法,此方法简单,精度较高。适合工程设计、选型和生产应用。 相似文献
44.
关于彩涂压型钢板构件设计中的选材问题 总被引:5,自引:1,他引:4
近年来 ,在彩涂压型钢板构件设计应用中 ,由于不重视、不了解如何合理选材 ,在实际工程的材料订货中也都不提出对材料性能的技术要求 ,致使供货材质、材性不能满足使用要求 ,存在降低彩板构件承载力或减少其使用寿命的隐患 ,应引起设计人员的注意。同时对当前如何按使用条件及材料供应条件合理地选定彩板材料的性能技术要求 ,包括基板钢材的级别及力学性能、板厚及公差控制要求、镀锌层质量与彩涂层类别以及参照的技术标准等 ,提出了一些建议 ,供设计应用参考。最后还对板的强度、厚度以及镀铝锌板的选用问题进行了讨论 相似文献
45.
介绍了一种烟道气中SO2在线检测系统,该系统可以实现24h不间断地监测烟道气中SO2的体积分数和质量浓度,同时将信息经网络传送给环保有关部门,具有一定的新颖性、可靠性、准确性。 相似文献
46.
A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method. 相似文献
47.
Sylvia V A Uzochukwu Esther Balogh Owen G Tucknot Mervyn J Lewis Patrick O Ngoddy 《Journal of the science of food and agriculture》1994,64(4):405-411
Palm wine and pasteurised palm sap volatiles were collected, concentrated on a Tenax GC and analysed by gas chromatography and gas chromatography-mass spectrometry. Eighty-two components were identified: 47 esters, 9 alcohols, 5 acids, 6 carbonyls, 2 acetals, 4 terpenes and 9 hydrocarbons. These had all been found previously in conventional wines. Odour evaluation of the separated palm wine components as they eluted suggested that no one compound is responsible for the characteristic palm wine odour. The acetates of higher alcohols and the ethyl esters of straight-chain aliphatic C6-C10 acids seemed to be important and may play a big role in imparting the fruity nuances of characteristic palm wine odour. Their association with alcohols seemed also to be necessary for the expression of typical palm wine odour. The qualitative difference between palm sap aroma and palm wine aroma appeared to be due mainly to the presence of these esters and alcohols in palm wine and their apparent absence from palm sap, as well as to the presence of some low-boiling esters and alcohols in palm sap and their apparent absence from palm wine. 相似文献
48.
K. Scott 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(3):257-266
This paper presents a relatively straightforward approach to the modelling of electrochemical reactors operated in batch or continuous modes. The models are based on ideal flow assumptions of either well-mixed or plug flow and incorporate reaction rate models based on electrochemical kinetics and mass transport at one electrode. General characteristics of the reactor models are described, particularly with regard to the need for good mass transport in metal recovery applications. An example is given on the use of the model in the recovery of a heavy metal (Cd2+) from an acidified solution containing Cd(II) and Fe(III) ions. The reaction rate model is based on experimental data. 相似文献
49.
The elastodynamic response of a rectangular Mindlin plate subjected to a distributed moving mass is investigated. The set of governing characteristic partial differential equations that include the effects of shear deformation and rotary inertia is expressed in its dimensionless form. A finite difference algorithm is employed to transform the differential equations into a set of linear algebraic equations. Simply supported edge conditions were used as an illustrative example. The analysis is also valid for other edge conditions. It is found that the maximum shearing forces, bending and twisting moments occur almost the same time. Also, the values of the maximum deflections are higher for Mindlin plates than for non-Mindlin plates. 相似文献
50.
Chen Bao-ming Zhang Li-qiangDepartment of Air-conditioning Refrigeration Engineering Shandong Institute of Architecture andEngineering Jinan China e-mail:chenbm @ sdai.edu.cnWang Bu-xuanDepartment of Thermal Engineering Tsinghua University Beijing China 《水动力学研究与进展(B辑)》2003,15(6)
The influences of Soret effect and Dufour effect on the natural convection and heat and mass transfer for a porous enclosure were investigated by means of the penalty finite element method. Numerical results indicate that the Soret and Dufour effects have significant influences on heat and mass transfer in the presence of large temperature gradient and concentration gradient. 相似文献