Design of a two-phase loop thermosyphon for telecommunications system (I)

A two-phase loop thermosyphon system is developed for the B-ISDN telecommunications system and its performance is evaluated, both experimentally and by visualization techniques. The design of the thermosyphon system proposed is aimed to cool multichip modules (MCM) upto heat flux of 8 W/cm². The results indicate that in the loop thermosyphon system, cooling heat flux is capable of 12 W/cm² with two condensers under the forced convection cooling of the condenser section with acetone or FC-87 as the working fluid. The instability of the working fluid flow within the loop is observed using the visualization techniques and temperature fluctuation is stabilized with orifice insertion.     

Fabrication of suspended micro-structures using diffsuser lithography on negative photoresist

We report the results of diffuser lithography applied to a negative-type thick photoresist to fabricate 3-dimensional microstructures suspended on supports. When UV light passes through a diffuser film, the direction of the light is randomized because of the irregular surface of the diffuser. By exposing through a diffuser on a Cr-mask, a circular or an elliptical cross-section of exposed region can be formed on a spin-coated photoresist. When applied to a negative-type thick photoresist, diffuser lithography gives a 3-dimensional circular cross-section of the exposed and cross-linked regions, which could be used for making suspended microstructures. The size of the exposed region has been controlled by the dose of the UV light. The current study clearly shows that the depth of exposed region of photoresist is affected by the geometry of the pattern. By controlling the depth of the exposed region using different pattern size, beam structures suspended on the support structures could be fabricated by single exposure process. The characteristics of the diffuser lithography process were investigated on a negative type photopolymer, SU-8, with different doses of UV-light and different geometry.     

Dynamic load analysis and design methodology of LCD transfer robot

The objective of the present study is to develop a design methodology for the large scale heavy duty robot to meet the design requirements of vibration and stress levels in structural components resulting from exposure of system modules to LCD (Liquid Crystal Display) processing environments. Vibrations of the component structures significantly influence the motion accuracy and fatigue damage. To analyze and design a heavy duty robot for LCD transfer, FE and multi-body dynamic simulation techniques have been used. The links of a robot are modeled as flexible bodies using modal coordinates. Nonlinear mechanical properties such as friction, compliance of reducers and bearings were considered in the flexible multi-body dynamics model. Various design proposals are investigated to improve structural design performances by using the dynamic simulation model. Design sensitivity analyses with respect to vibration and stresses are carried out to search an optimal design. An example of an 8G (8th-Generation) LTR (LCD Transfer Robot) is illustrated to demonstrate the proposed methodology. Finally, the results are verified by real experiments including vibration testing.     

A study on the characteristic of parameters by the response surface method in final wafer polishing

As the level of Si-wafer surface directly affects device line-width capability, process latitude, yield, and throughput in fabrication of microchips, it needs to have ultra precision surface and flatness. Polishing is one of the important processing having influence on the surface roughness in manufacturing of Si-wafers. The surface roughness in final wafer polishing is mainly affected by the many process parameters. For decreasing the surface, the control of polishing parameters is very important. In this paper, the optimum condition selection of ultra precision wafer polishing and the effect of polishing parameters on the surface roughness were evaluated by using central composite designs such as the Box-Behnken method. Moreover, in accordance with variation of process variables, there is a temperature change on pad surface. And so, this paper also researches that this temperature variation affects surface roughness of Si-wafer.     

Experimental study on heat transfer characteristics of internal heat exchangers for CO2 system under cooling condition

This paper presents the heat transfer characteristics of the internal heat exchanger (IHX) for CO₂ heat pump system. The influence on the IHX length, the mass flow rate, the shape of IHX, the operating condition, and the oil concentration was investigated under a cooling condition. Four kinds of IHX with a coaxial type and a micro-channel type, a mass flow meter, a pump, and a measurement system. With increasing of the IHX length, the capacity, the effectiveness, and the pressure drop increased. For the mass flow rate, the capacity of micro-channel IHX are higher about 2 times than those of coaxial IHX. The pressure drop was larger at cold-side than at hot-side. In the transcritical CO₂ cycle, system performance is very sensitive to the IHX design. Design parameters are closely related with the capacity and the pressure drop of CO₂ heat pump system. Along the operating condition, the performance of CO₂ IHXs is different remarkably. For oil concentration 1, 3, 5%, the capacity decreases and the pressure drop increased, as compared with oil concentration 0%. This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang Prof. Young-Chul Kwon received his B.S. degree in Precision Mechanical Engineering from Pusan National University, Korea, in 1989. He then received his M.S. and Ph.D. degrees from POSTECH, in 1991 and 1996, respectively. Dr. Kwon is currently a Professor at the Division of Mechanical Engineering at Sunmoon University in Chungnam, Korea. He serves as a chief of the Institute of Automation and Energy Technology. Dr. Kwon’s research interests include heat exchanger, CO₂ cycle, heat pump, and energy recovery ventilator for HVAC&R. Mr. Dae-Hoon Kim is currently Doctoral student at the Mechanical Engineering from Hanyang University in Seoul, Korea. His research topics include experimental and numerical of CO₂ heatpump system. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Prof. Jae-Heon Lee received his B.S. degree in Mechanical Engineering from Seoul National University, Korea, in 1971. He then received his M.S. and Ph. D. degree from Seoul National University in 1977 and 1980, respectively. Dr. Lee is currently a Professor at the school of Mechanical Engineering at Hanyang University in Seoul, Korea. Dr. Lee is currently a president at the Korea Institute research interests include simulation of thermal fluid and Plant engineering and construction. Dr. Jun-Young Choi received his B.S. degree in Mechanical Engineering from Yonsei University, Republic of Korea, in 1989. He then received his M.S. and Ph. D. degrees from Yonsei University in 1991 and 1999, respectively. Dr. Choi is currently a chief researcher with the 18 years experience on the energy performance testing of HVAC/R product. He is now assigned to the Energy Technology Center at Basic Industry Division at Korea Testing Laboratory. He has been involved in the development of Design and Manufacturing Technology for Air-Conditioner E.E.R. and Performance Testing Equipment for Cooling and Heating System with Non-CFCs, and natural refrigerants. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Dr. Sang Jae Lee received his Ph.D. degree in Mechanical Engineering from Hanyang University, KOREA, in 2008. Dr. Lee is currently a Researcher at the Korea Institute of Industrial Technology in Cheonan, Korea. Dr. Lee’s research interests CO₂ heatpump system, liquid desiccant air conditioning system and Micro heat exchanger.     

Development of an automated progressive design system with multiple processes (piercing, bending, and deep drawing) for manufacturing products

This paper describes the research work involved in developing an automated progressive design system with multiple processes such as piercing, bending, and deep drawing for manufacturing products. This approach to make a progressive, flexible working system is based on knowledge-based rules. The knowledge required for this system is formulated from plasticity theories, experimental results, and the empirical knowledge of field experts. The system consists of three main modules: shape treatment, strip layout, and die layout modules. The system is founded on knowledge-based rules and is designed in consideration of several factors, such as the material and thickness of a product, the piercing, bending and deep drawing sequence, and the complexities of blank geometry and punch profiles. The system then generates the strip layout drawing for an automobile product. The die layout module carries out the die design for each process from the results of the strip layout module. The results obtained using the modules enable the designers of manufacturing products with multiple processes to be more efficient in this field.     

立体停车库监控系统

本文简单介绍了多层升降横移式立体车库的结构形式.详细介绍了PLC控制系统和监控系统功能,通过PLC和上位机组成的监控系统实现了立体车库的控制和实时监控管理功能.     

Effect of Antimony Addition on Electrical and Optical Properties of Tin Oxide Film

Antimony-doped tin oxide films were prepared on Corning glass substrate by chemical vapor deposition from a gas mixture of SnCl₄–SbCl₅–H₂O. The electrical conductivity and optical transmission of tin oxide films were studied with antimony doping. The film conductivity increased largely without losing optical transparency with a small addition of antimony. The increase of the conductivity was attributed mainly to more electrons donated by pentavalent Sb ions in the SnO₂ lattice. Large additions of antimony, however, diminished the conductivity, optical transparency, and crystallinity of the film. The diminution was found to be caused by fine Sb₂O₅ phases codeposited with SnO₂.     

Spring-back characteristics of fiber metal laminate (GLARE) in brake forming process

The brake forming process has been considered as a feasible method for producing fiber metal laminate (GLARE) stringer. However, the spring-back developed during brake forming leads to serious problems in the final dimensional tolerance of the stringer. A series of experiments were performed to examine the effect of tool design and process parameters on the spring-back of GLARE. The parameters studied include punch radius, punch speed, forming load, and forming temperature. This paper shows that both design and process parameters can significantly affect the amount of spring-back. Scanning electron microscopy (SEM) was also carried out for the observation of delamination or cracking in the bent zone.     

An investigation of local heat transfer characteristics in a ventilated disc brake with helically fluted surfaces

Local Nusselt numbers in the cooling flow passage of the automobile disc brake with helically fluted surfaces are presented. The flat surface in the flow passage is modified to the helically fluted surface for the purpose of enhancing the heat transfer rate, thereby reducing the thermal stress and deformation in the disc brake. Thermochromic liquid crystals and shroud-transient technique are used to measure spatially-resolved surface temperature distributions, which are used to deduce local Nusselt numbers. The Reynolds number Re ranges from 30,000 to 70,000, the helix angle θ is fixed at 45° and the dimensionless streamwise distance z/d ranges from 1.5 to 4.5. The results show that in general, local Nusselt numbers monotonically decrease with a distance away from both windward and leeward crests of the helical flute and reach a minimum value near its valley for all Re’s and z/d’s tested. The local Nusselt numbers on the helically fluted grooves are maximum 51.6 to 93.7% higher than values measured on the flat surface. The heat transfer enhancement magnitudes become more pronounced with smaller Re and z/d. The largest enhancement occurs at the windward side of the helical flute at z/d=1.5 and Re=30,000. It is also found that at Re=30,000 the average Nusselt numbers on the helically fluted surface are maximum 37% higher than those on the flat surface. The numerical results show that with 10 braking cycles, the temperatures with helically fluted surface are maximum 44.3%, 36.8%, and 36.6% lower than those with the flat surface in the inlet, the center, and the outlet, respectively.