Fatigue test of MEMS device : a monolithic inkjet print

A testing system was developed to improve the reliability of printhead and several printheads were tested. We developed a thermally driven monolithic inkjet printhead comprising dome-shaped ink chambers, thin film nozzle guides, and omega-shaped heaters integrated on the top surface of each chamber. To perform a fatigue test of an inkjet printhead, the testing system automatically detects a heating failure using a Wheatstone bridge circuit. Various models were designed and tested to develop a more reliable printhead. Two design parameters of the width of reinforcing layer and heater were investigated in the test. Specially, the reinforcing layer was introduced to improve the fatigue life of printhead. The life-span of heater with a reinforcing layer was longer than that without a reinforcing layer. The wider the heater was, the longer the life of printhead was.     

A compliance control strategy for robot manipulators under unknown environment

In this paper, a compliance control strategy for robot manipulators that employs a self-adjusting stiffness function is proposed. Based on the contact force, each entry of the diagonal stiffness matrix corresponding to a task coordinate in the operational space is adaptively adjusted during contact along the corresponding axis. The proposed method can be used for both the unconstrained and constrained motions without any switching mechanism which often causes undesirable instability and/or vibrational motion of the end-effector. The experimental results involving a two-link direct drive manipulator interacting with an unknown environment demonstrates the effectiveness of the proposed method.     

Atomization characteristics of a double impinging F-O-O-F type injector with four streams for liquid rockets

This paper presents atomization characteristics of a double impinging F-O-O-F type injector with four streams. A phase Doppler particle analyzer was employed to measure the droplet-size and water was used as the inert simulant liquid instead of reactive propellant liquids. The droplet mean diameter (SMD) and size distribution were measured to investigate the effects of the momentum ratio and pressure drop variations. This experimental results can be used during the preliminary design stage of a impinging stream type injector for liquid rockets.     

Oxidation characteristics of airborne carbon nanoparticles by NO(2)

The oxidation characteristics of airborne carbon nanoparticles were investigated at various temperatures and NO(2) concentrations. Airborne carbon nanoparticles were generated by spark-discharging method using nitrogen as a carrier gas. Monodisperse carbon particles classified using a differential mobility analyzer were introduced into a tube furnace with NO(2) for oxidation reaction. The size distributions of oxidized carbon aerosol particles were measured using a scanning mobility particle spectrometer system which consisted of a differential mobility analyzer and a condensation particle counter. The result was that as NO(2) concentrations and reaction temperatures increased, the surface oxidation rate of carbon aerosol particles increased. For NO(2) gas, the activation energy of the oxidation reaction was approximately 76.3 kJ/mol. The activation energy of the oxidation reaction for the mixture of NO(2) and O(2) gases was 65.9 kJ/mol, which is smaller than that for only NO(2) gas.     

Effect of various processing methods on the interfacial reactions in SiCp/2024 Al composites

SiC_p/2024 Al composites were prepared using various processing techniques, such as spray forming, powder metallurgical hot pressing, thixoforming, and compocasting. The interfacial characterizations of these composites were performed using scanning electron microscopy, Auger electron spectrometry, transmission electron microscopy, and X-ray diffraction on reaction products extracted using the electrochemical dissolution. The value of these combined techniques in elucidating the morphologies of the interfacial reaction products was also demonstrated. The influence that each fabrication process has on the extent of the interfacial reaction was studied. Adequate process parameters to fabricate SiC_p/Al alloy composites were proposed based on thermodynamic considerations.     

Analysis of deformation texture inhomogeneity and stability condition of shear components in f.c.c. metals

The texture of cold rolled aluminum sheet has been known to vary through the thickness due to inhomogeneous deformation during rolling. The copper texture is obtained in the center layer that is plane strain compressed while the shear texture in the surface layer, which is approximated by major 001 011 and minor 111 112 and 111 110 components. The stability condition of these components was calculated based on the full constraint Taylor-Bishop-Hill theory and could be described by a parameterdɛ₁₃/dɛ₁₁ with the suffixes 1 and 3 indicating the rolling and thickness directions, respectively.     

寻找失落的家园——韩国首尔市兰芝岛世界杯公园生态恢复设计

在20世纪70—90年代韩国经济高速成长时期,兰芝岛曾经是首尔市最主要的垃圾填埋场,因紧邻2002年世界杯足球赛上岩赛场而成为整个比赛场地的重要组成部分。在世界杯足球赛体育场馆建设过程中,兰芝岛被改造成为一座环境亲和型的城市公园。通过对兰芝岛垃圾山垃圾的形成、土地利用方式的选择和公园建设过程的回顾,总结了首尔世界杯公园的规划途径和公园设计过程中受污染场地受损生态系统修复所使用的基本方法,并指出对中国城市公园建设的借鉴意义。     

Performance of the smoke extraction system for fires in the Busan–Geoje immersed tunnel

A new partial smoke extraction system for the Busan–Geoje immersed tunnel was investigated experimentally using simulated tunnel fires. The tests were performed in a 1:20-scale model tunnel with a smoke extraction duct between two traffic tubes. The fire corresponded to a 5-MW full-scale fire, based on Froude modeling. Isothermal and thermal experimental models were considered. The performance of the partial smoke extraction system was quantified under natural and longitudinal ventilation conditions. The results showed that the smoke extraction efficiency of the natural ventilation was 30% better than with longitudinal ventilation, because of smoke stratification in the tunnel. Additionally, the efficiency obtained from the thermal model was comparable to that from the isothermal model under both ventilation conditions. The results suggested that the use of a partial smoke extraction system without longitudinal ventilation improved the initial visibility during tunnel fires.     

Reuse potential of municipal wastewater treatment facility effluents for sustainable water resource management in Ulsan,Korea

Effluent qualities of five municipal wastewater treatment facilities (MWWTFs) in Ulsan were evaluated to examine their reuse potential. Effluent from Yongyeon (Y) MWWTF, Onsan (O) MWWTF and Bangeojin (B) MWWTFs can be used as cooling water without further treatment. As evident from Langelier saturation index and Ryzner index values, reuse of treated effluent from OMWWTF and BMWWTFs is recommended by controlling the pH to reduce the scale-forming potential of effluent. However, effluents from these MWWTFs need additional treatment to remove residual dissolved constituents before reuse as boiler water. Besides, effluent from Hoiya (H) MWWTF and Unyang (U) MWWTFs can be reused for agricultural irrigation without any additional treatment. Based on the scientific results obtained from this investigation, proper application of technology and promotion of public awareness to change the traditional mindset for treated effluent reuse could immensely contribute towards conserving local water resources and addressing global environmental problems on a regional basis.     

Lubrication characteristics of dual piston ring in bent-axis type piston pumps

The bent-axis type of piston pump driven by the piston rod works by the piston rod driving the cylinder block; because of this the taper angle of the piston rod and the swivel angle between the cylinder block and the shaft are important design factors. If these factors cannot satisfy the conditions for optimum design, the friction loss between the cylinder bore and the piston increases, and the pump can fail to work under conditions of severe friction and wear. Since the piston reciprocates in the cylinder bore with high velocity, at the same time rotating on its own axis and revolving on the center of the cylinder block, a decrease of the volume efficiency is generated because of the leakage between the cylinder bore and the piston. Therefore, to prevent this, the piston ring is designed to be at the end of the piston, and the friction characteristics between the piston ring and the cylinder bore require further research due to their great influence on the performance of the piston pump. Thus, in this paper, the elastohydrodynamic lubrication (EHL) analysis of the film thickness, the pressure distribution, and the friction force, have been studied between the piston ring and the cylinder bore in the bent-axis type of piston pump. The analyzed results show that the friction force is influenced by the rotating speed and the discharge pressure.