Nucleate and film boiling on a microheater under pulse heating in a microchannel

Using MEMS technology, a Pt microheater (60 × 100 µm²) fabricated on a glass wafer is placed in a silicon-based microchannel of trapezoidal cross section. With the aid of a high-speed CCD and based on Pt's linear temperature-resistance characteristic, flow boiling phenomena and temperature response on the surface of the microheater in the microchannel under pulse heating are observed and recorded. At a given mass flux, nucleate boiling and film boiling begin to appear on the microheater with increasing heat flux. A flow boiling map, showing the effects of heat and mass flux on nucleate and film boiling regimes on the microheater at a pulse heating width of 2 ms, is presented. It is found that nucleate boiling is changed to film boiling as the heat flux supplied to the microheater is increased. Furthermore, increasing mass flux increases the heat flux required for the incipience of nucleate boiling and film boiling on the microheater in the microchannel.     

塑料新材料进展与加工助剂

塑料原材料、加工助剂和塑料加工机械是构成塑料产业的三大基本要素。市场的需求是促进塑料产业持续发展的动力,新产品的不断涌现是功能型加工助剂的催生素,作者从介绍塑料新产品的角度描述了功能型加工助荆的重要性、概况和发展趋势。     

基于磁流变技术的车用减震器

磁流变液具有响应快、可控性强、能耗低、工作温度范围宽等特点,已成功应用在车辆减振控制领域。介绍了磁流变技术的发展概况,对其流变特性及磁流变减震器的力学模型及其工作模式进行了分析,对今后的研究重点进行了探讨。     

Modeling of a magneto-rheological (MR) fluid damper using a self tuning fuzzy mechanism

A magneto-rheological (MR) fluid damper is a semi-active control device that has recently begun to receive more attention in the vibration control community. However, the inherent nonlinear nature of the MR fluid damper makes it challenging to use this device to achieve high damping control system performance. The development of an accurate modeling method for a MR fluid damper is necessary because of its unique characteristics. Our goal was to develop an alternative method for modeling an MR fluid damper by using a self tuning fuzzy (STF) method based on neural technique. The behavior of the researched damper is directly estimated through a fuzzy mapping system. To improve the accuracy of the STF model, a back propagation and a gradient descent method are used to train online the fuzzy parameters to minimize the model error function. A series of simulations were done to validate the effectiveness of the suggested modeling method when compared with the data measured from experiments on a test rig with a researched MR fluid damper. Finally, modeling results show that the proposed STF interference system trained online by using neural technique could describe well the behavior of the MR fluid damper without need of calculation time for generating the model parameters. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Kyoung Kwan Ahn received the B.S. degree in the Department of Mechanical Engineering from Seoul National University in 1990, the M. Sc. degree in Mechanical Engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1992 and the Ph.D. degree from Tokyo Institute of Technology in 1999, respectively. He is currently a Professor in the School of Mechanical and Automotive Engineering, University of Ulsan, Ulsan, Korea. His research interests are design and control of smart actuator using smart material, fluid power control and active damping control. He is a Member of IEEE, ASME, SICE, RSJ, JSME, KSME, KSPE, KSAE, KFPS, and JFPS. Dinh Quang Truong received the B.S degree from the department of Mechanical Engineering from Hochiminh City University of Technology in 2001. From 2003 to 2006, he worked in the lab of machine design — Mechanical Department of Hochiminh City University of Technology. He is currently Ph.D. candidate at University of Ulsan. His research interests focus on designing and control of new hydraulic actuators, applications to hybrid vehicles with saving energy.     

淀粉基纳米复合浆料与常用浆料性能对比

研究淀粉基纳米复合浆料的基本性能.通过测试淀粉基纳米复合浆料、聚酯浆料、PVA、氧化淀粉、醚化淀粉浆膜的机械性能,并分析对比其浆膜拉伸曲线.认为:虽然淀粉基纳米复合浆料浆膜的断裂强度较低,但由于其具有较高的断裂功和对涤纶纤维较好的黏附性,仍然为部分取代PVA创造了基础条件.指出:淀粉改性的方向是提高浆膜的断裂功,使普通淀粉由脆性材料转变为韧性材料;要进一步提高淀粉基纳米复合浆料的断裂强度,以达到完全取代PVA的目标.     

聚四氟乙烯膜裂成纱工艺参数的优化

探讨聚四氟乙烯(PTFE)膜裂成纱的工艺优化.在单因素工艺参数试验的基础上,选取总牵伸倍数、捻系数、薄膜厚度进行三因素三水平正交工艺试验.结果表明:聚四氟乙烯膜裂成纱的较理想工艺参数为总牵伸1.8倍,捻系数190,薄膜厚度40μm.     

弹性环式挤压油膜系统新的三维动力学模型

建立考虑外层油膜剪切效应的弹性环式挤压油膜系统的新的三维动力学模型.该模型采用Hirs整体流动理论和Moody壁面摩擦因数方程,在考虑壁面摩擦及外层油膜剪切效应影响的基础上,通过油膜连续方程、平衡方程获取弹性环式挤压油膜系统的控制方程,更为合理.通过数值算例分析,证明由新模型能较大幅度地改进弹性环式挤压油膜系统的动态性能.     

横向槽宽度对气膜孔冷却性能数值研究

应用数值模拟的方法,研究了带横向槽气膜孔冷却结构的槽宽度变化对其平均冷却效率的影响.在吹风比为0.5,1.0,1.5和2.0的条件下,对槽宽度为1.75D,2.5D,3.5D和4.5D四种冷却结构进行了数值模拟,通过分析气膜孔下游的反向涡对、平均冷却效率和壁面冷却效率大于0.343的区域,得出了气膜孔出口开槽宽度变化对二次流的贴壁性能和平均冷却效率的影响规律,并分析了槽宽度变化对平均冷却效率影响的机理.     

研磨轮损耗自动修正系统设计与应用

基于手动修正研磨轮损耗在TFT-LCD基板玻璃研磨加工过程中存在诸多缺陷,设计了一种应用于TFT-LCD基板玻璃研磨加工过程的自动修正系统,并对该系统原理及实际应用进行了详细的介绍。     

The effect of myofibrillar/sarcoplasmic protein ratios on the properties of round scad muscle protein based film

The effect of the ratios of myofibrillar protein (MP) to sarcoplasmic protein (SP) from round scad (Decapterus maruadsi) muscle on the properties of the resulting films was investigated. Tensile strength (TS) of films decreased with increasing SP content (p < 0.05). Films prepared from MP/SP ratio of 10:0 (w/w) exhibited the highest TS (p < 0.05). Elongation at break (EAB) of films prepared with SP content greater than 30% had the decreased EAB (p < 0.05). Water vapor permeability (WVP) of films increased when SP content increased up to 20% and decreased with increasing SP content up to 30% (p < 0.05). Solubility of films decreased but protein solubility increased with increasing SP contents (p < 0.05). The a*-value and ΔE* of film increased with increasing SP content. Films with all MP/SP ratios exhibited the negligible transmission to the light in UV range. Therefore, it is suggested that the type and ratio of proteins in fish muscle, both SP and MP, influenced the properties of film from round scad muscle. Results suggested that the removal of sarcoplasmic protein from fish muscle by thorough washing was an effective means to improve the mechanical properties as well as color of the fish muscle protein-based film.