• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2010년도 제39회 하계학술대회 초록집
• /
• pp.291-291
• /
• 2010

Electron-beam lithography (EBL) process is a versatile tool for a fabrication of nanostructures, nano-gap electrodes or molecular arrays and its application to nano-device. However, it is not appropriate for the fabrication of sub-5 nm features and high-aspect-ratio nanostructures due to the limitation of EBL resolution. In this study, the precision assembly and alignment of DNA molecule was demonstrated using sub-5 nm nanostructures formed by a combination of conventional electron-beam lithography (EBL) and plasma ashing processes. The ma-N2401 (EBL-negative tone resist) nanostructures were patterned by EBL process at a dose of $200\;{\mu}C/cm2$ with 25 kV and then were ashed by a chemical dry etcher at microwave (${\mu}W$) power of 50 W. We confirmed that this method was useful for sub-5 nm patterning of high-aspect-ratio nanostructures. In addition, we also utilized the surface-patterning technique to create the molecular pattern comprised 3-(aminopropyl) triethoxysilane (APS) as adhesion layer and octadecyltrichlorosilane (OTS) as passivation layer. DNA-templated gold nanoparticle chain was attached only on the sub-5 nm APS region defined by the amine groups, but not on surface of the OTS region. We were able to obtain DNA molecules aligned selectively on a SiO2/Si substrate using atomic force microscopy (AFM).

• 대한기계학회논문집A
• /
• 제25권10호
• /
• pp.1678-1683
• /
• 2001

The mobility of tracked vehicles is mainly influenced by the interaction between tracks and soil, so that the characteristics of their interactions are quite important fur the tracked vehicle study. In particular, the track tension is closely related to the maneuverability of tracked vehicles and the durability of tracks and suspension systems. In order to minimize the excessive load on the tracks and to prevent the peal-off of tracks from the road-wheels, the Dynamic Track Tensioning System (DTTS) which maintains the optimum track tension throughout the maneuver is required. It consists of track tension monitoring system, track tension controller and hydraulic system. In this paper, a dynamic track tensioning system is developed for tracked vehicles which are subject to various maneuvering tasks. The track tension is estimated based on the idler assembly model. Using the monitored track tension and con sidering the highly nonlinear hydraulic units, fuzzy logic controllers are designed in order to control the track tension. The track tensioning performance of the proposed DTTS is verified through the simulation of the Multi -body Dynamics tool.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.250-253
• /
• 2002

The operation of surface and edge finishing is the last and essential process of parts machining, because a product is completed as an assembly. Therefore, the quality of the finished parts has a direct effect upon the performance of the product. Especially, the edge quality depending on the burr control process is very important. A number of deburring processes have been developed for macro burrs such as barreling, brushing, chemical methods, etc. However, micro burr removal when piercing a very thin plate is very difficult, because this badly deteriorates the surface quality of the processed part. When ultrasonic wave is propagated in liquids, it forms an infinitude of micro bubbles. These bubbles generate extremely strong force, which removes micro burrs. In ultrasonic micro deburring, the problem is that burrs are not removed completely, because only components of the explosive force directly act on the burrs, which is not enough. An attempt was made to remove the burrs using ultrasonic vibration in water with SiC as an abrasive agent. Because of the abrasive, smoother edges have been achieved. There are many control parameters in ultrasonic deburring such as abrasive size, ultrasonic frequency and amplitude, distance between tool and workpiece, tilt angle of workpiece etc. This study focuses on how distance and tilt angle influence deburring effect. A number of experiments for these parameters have been carried out, and then the effect of each parameter analyzed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
• /
• pp.980-985
• /
• 1988

In this paper, a control system of the PUMA 560 robot manipulator using a PC (Personal Computer) is presented. The hardware of the designed control system is composed of IBM-PC/AT, interface board, selection board, interrupt generating circuit, and the servo control unit of the PUMA controller. A robot control library is developed using assembly and C language, and is composed of several low-level functions and arm interface routines, world model routines, arm kinematics routines, and motion command service routines. Using the designed library, joint interpolated motion and Cartesian interpolated motion of the PUMA robot manipulator are realized. In the future, our system is expected to be a very helpful basis and a useful tool for developing various control algorithms of robot manipulator using sensory information.

• 한방안이비인후피부과학회지
• /
• 제30권3호
• /
• pp.166-181
• /
• 2017

Objectives : The study was done to verify the relation between early-onset androgenetic alopecia(AGA) and metabolic syndrome(MetS). Methods : Data were collected through electronic database including KoreaMed, National Assembly Library, KMBASE, NDSL, KCI, KERIS, Google Scholar, Pubmed, Cochrane CENTRAL and EBSCO MEDLINE. A total of 13 case-control studies related to the MetS of early-onset alopecia patients were used for the systematic review and meta-analysis. Risk of bias of included studies were assessed by RoBANS tool. RevMan5.3, CMA3 were used for the meta-analysis. Results : In 13 evaluated articles, most frequent bias was the participant selection bias that was found in 10 articles. Significant association between early-onset AGA and MetS was found in 10(76.9%) out of 13 articles in the systematic review. In meta-analysis, early-onset male AGA was associated with increased risk of metabolic syndrome(OR: 3.73, 95% CI:2.49 -5.61). Conclusions : AGA, particularly early -onset male AGA, is significantly associated with MetS. Therefore all patients with early onset male AGA should be suggested to take preventive treatment to reduce the risk of MetS and various problems associated with it.

• 반도체디스플레이기술학회지
• /
• 제5권3호
• /
• pp.29-32
• /
• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(Printed Circuit Boards), Thermal control of the reflow process is required in order to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD(Computational Fluid Dynamics) tool for predicting flow and temperature distributions. Porous plate was installed to prevent leakage flow which was one of the major problem of temperature uniformity in the reflow process. There is a separation region where the flow is turned. Outside wall made of porous plate is to prevent and minimize separation region for acquiring uniform temperature during operation. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• 한국시뮬레이션학회논문지
• /
• 제12권3호
• /
• pp.41-53
• /
• 2003

The major components of an engine are engine block (or cylinder block), cylinder head, crank shaft, connecting rod and cam shaft. Thus the engine shop usually consists of six sub-lines, five machining lines and one assembly line. Flow line is the typical concept of layout for machining these parts, especially for engine block. In order to design an engine block machining line, several factors should be considered such as yearly production target, working hours, machines, tools, material handling equipments and so on. If the designers of manufacturing line were unaware of some factors those would be influenced on the system performance, it would make greater problems in the phase of mass production. Therefore the initial design of engine block machining line should be verified carefully. Simulation is the most powerful tool for analyzing the initial layout. This paper introduces the major factors those should be considered for designing the machining line and their effects on the system performance. 3D simulation models are developed with QUEST. Using the simulation model developed the initial layout is analyzed, and we suggest some ideas for improvement.

• 한국CDE학회논문집
• /
• 제3권3호
• /
• pp.201-209
• /
• 1998

To develop timely an optimal fan, a design system and a new manufacturing process used step by step have to be integrated. A small sized optimal fan for refrigerators, that was the goal on this project, was developed by the following principal processes. All processes are technologically linked in many directions: The existing fan was measured through reverse engineering. The measured data was used for the basic source of 3D design. The performance tests were carried and used as the data for the evaluation of the existing fan. Flow analysis by FANS-3D/sup [1]/ was performed at the given information (pressure drop and flow rate) to find out the configuration of optimal fan design. The flow patterns were investigated to measure the performance of fan through numerical experiment. The grid point data obtained by the above analysis turned into 3D high efficiency fan model by using CATIA. The product was manufactured by RP process (SLS, SLA) and tested the characteristic curves of the developed fan to compare with the existing fan. The modification of fan design were all examined to see any change in performance and checked to find any deficiency in assembling the fan into a duct. After the plastics flow analysis of the injection molding cycle to ensure acceptable quality fan, an optimal mold was processed by using tool-path for the newly designed fan.

• 한국기계가공학회지
• /
• 제13권4호
• /
• pp.99-105
• /
• 2014

The domestic airline industry undertakes the production of finished products by assembling existing self-described components via a design process which involves assembly and production steps, after which many of the finished products are exported. However, high reliability and stability must be guaranteed, because customers require high-precision components at the time of manufacturing. In the aircraft parts industry, the mass production of high-value-added parts is limited. Therefore, a small production scale depending on the part is used, as many types of conventional CNC lathe machines with X-axis and Z-axis as well as Z-axis and C-axis CNC milling are used. The parts also rely on high-pressure air to increase production. The most important factors are good stability during processing, as high-precision parts are required, as noted above. It was found that as the C-axis rotation speed increased, the diameter of the cutting tool decreased with a decrease in the surface roughness, while the workpiece rotation speed increased with an increase in the surface roughness.

• 한국기계가공학회지
• /
• 제12권2호
• /
• pp.121-126
• /
• 2013

Precision machine tools for high dignity cutting are needed for efforts to improve machining accuracy. However, there are many factors to improve machining accuracy. This study investigated how machining accuracy changes when variation and unbalance amount in rotational speed domain is decreased. Machining accuracy of initial machine tools depends on manufacturing and assembly of parts such as bearing. And then, vibration and noise vary with volume of unbalance amount when it is rotation, so it effects unbalance amount. Also vibration and noise increased by unbalance shorten spindle's life and it especially makes worse boring accuracy. Therefore, this study studied the change of roundness and cylindricity of workpiece when it decreases variation and unbalance in rotational speed domain.