• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.45-46
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• 2006

In recent years, micro powder injection molding $(\mu-PIM)$ is being explored as an economical fabrication method for microcomponents in microsystems technology (MST). Technical and economic comparison was performed for $\mu-PIM$ processes. Molding experiment and simulation during the filling process were performed to evaluate several different geometries and processing conditions. The influence of material parameters and process conditions on mold filling were examined as a function of features size using microchannels as an example. It was found that the heat conductivity and viscosity of feedstock, geometry and mold temperature were the most critical parameters for complete filling of micro features.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1577-1581
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• 2014

This paper presents a method to minimize torque ripple of a V-type IPMSM using the PSO (Particle Swarm Optimization) method with FEM. The proposed algorithm includes one objective function and three design variables for a notch on the surface of a rotor. The simulation model of the V-type IPMSM has 3-phases, 8-poles and 48 slots with 2 notches on the one-pole rotor surface. The arc-angle, length and width of the notch are optimized to minimize the torque ripple of the motor. The cogging torque of the model is reduced by 55.6% and the torque ripple is decreased by 15.5 %. Also, the efficiency of the motor is increased by 15.5 %.

• Journal of Welding and Joining
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• 제20권1호
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• pp.83-90
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• 2002

Metal Transfer in gas metal arc (GMA) welding is a complex phenomenon affected by many parameters of the welding conditions and material properties. In this research, the correlation equation between the welding condition and detaching droplet size and detaching velocity in GMA welding was studied via recession analysis on the results of numerical analysis using the volume-of-fluid (VOF) method. Welding parameters and material properties were grouped into three dimensionless numbers and detaching droplet size was expressed as the function of them. Second order and exponential multi-variable correlation forms were assumed, and the coefficients of these equations were calculated for globular and spray modes as well as entire transfer modes. Applying correlation equation into available experimental data, it shows good agreement.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.596-599
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• 2004

The robotic $CO_2$ welding is a manufacturing process to produce high quality joints for metal and it could provide a capability of full automation to enhance productivity. Despite the widespread use in the various manufacturing industries, the full automation of the robotic $CO_2$ welding has not yet been achieved partly because the mathematical model for the process parameters of a given welding task is not fully understood and quantified. Several mathematical models to control welding quality, productivity, microstructure and weld properties in arc welding processes have been studied. However, it is not an easy task to apply them to the various practical situations because the relationship between the process parameters and the bead geometry is non-linear and also they are usually dependent on the specific experimental results. Practically, it is difficult, but important to know how to establish a mathematical model that can predict the result of the actual welding process and how to select the optimum welding condition under a certain constraint. In this research, an attempt has been made to develop an intelligent algorithm to predict the weld geometry (top-bead width, top-bead height, back-bead width and back-bead height) as a function of key process parameters in the robotic $CO_2$welding. To achieve this above objective, Taguchi method was employed using five different process parameters (tip gap, gas flow rate, welding speed, arc current, welding voltage) as a guide for optimization of process parameters.

• 한국항공우주학회지
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• 제41권6호
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• pp.458-464
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• 2013

본 논문에서는 무인 항공기의 활주로 자동 접근 알고리즘에 대해 기술하였다. 본 연구에서 자동 접근의 주요 목적은 야간에 항공기의 안전한 착륙을 돕기 위함이다. 자동 접근 기능을 사용하게 되면 항공기가 어느 위치에 있던 초기 위치를 기준으로 경로 명령이 생성된다. 경로 명령은 최단거리를 가지는 원호-직선-원호로 구성되어있다. 경로 명령을 통해 생성된 경로를 따라 이동한 다음 활주로에 접근하도록 알고리즘을 설계하였다. 항공기의 다양한 초기 위치에 대한 경로 생성 알고리즘의 시뮬레이션을 통해 1차 검증을 하였으며 이를 기반으로 실제 비행시험을 수행하여 본 연구에서 제안한 알고리즘의 타당성을 실증적으로 검증하였다.

• 한국정보통신학회논문지
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• 제13권11호
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• pp.2433-2440
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• 2009

전력 공급과 전기안전은 전체 시스템과 네트워크에 대한 필수적인 요소이다. 전기안전기술은 u-IT, u-City 기반 기술의 발전과 함께 전력 u-IT 융복합화 제품개발은 제품에 대한 평가와 인증에 관한 연구가 필요하다. 본 논문에서는 전력기기와 u-IT기기의 융복합화 제품을 u-City에 적용시킬 전기안전 통합감시시스템을 개발하기 위해, 전력기기 단말에서 가장 많이 사용되는 아울렛에서 접속불량 검출장치가 내장된 전력 u-IT 융복합화 기기를 만들었다. 또한 전기안전 통합감시시스템에서의 원격 안전점검을 위한 ZigBee, RFID의 센서를 이용하여 통신모듈과 제품의 기능에 대한 성능 평가를 하고, 누전, 고전압, Arc, 화재 검출 센서 진단 시스템에서 성능 실험 및 평가를 하여 적합판정을 받은 제품은 KS, 전기안전제품 인증을 한다.

• 대한기계학회논문집
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• 제7권3호
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• pp.263-269
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• 1983

Underwater welding by a gravity arc welding process was investigated by using six types of coated electrodes and SM41A steel plates of 10 mm thickness as base metal and it was ascertained that this process may be put to practical use. Main results obtained are summarized as follows: 1. Angle of electrode affects no influence on bead appearance and the proper range of welding current and diameter of electrode for the high titanium oxide type is relatively wider than that for the ilmenite type. And the lime titania type, high titanium oxide type and ilmenite type of domestic coated arc welding electrodes of .phi.4 mm could attain the soundest underwater welded joints which contain no welding imperfection. 2. According to macro-structure, micro-structure and hardness distribution inspectionson underwater welded joint, the area between the HAZ and the surface of the weld in neighbourhood of the bond has the maximum hardness value. The structure of these parts is martensite and bainite. Other parts contain mocro-ferrite, micro-pearlite structure, which contain soundness of welded joint free from weld imperfection. 3. On consideration of both tensile strength of more than 100% joint efficiency and sufficient impact value, the welding condition which can get optimal welding strength is heat input of 1,400-1,500 J/mm, current of 200-215 ampere (voltage of 32-33 volts) in the case of lime titania type electrode. 4. Underwater welding strength (tensile strength, impact strength) depends on heat input (or current) quantitatively and they have the relationship of parabolic function. Each experimental equation has a high reliability and its percent of mean error is 4.14%. 5. It is suggested that the optimal design of weld strength by welding condition (current, heat input) could be utilized for a quality control of underwater welding.

• 대한기계학회논문집B
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• 제26권3호
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• pp.432-438
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• 2002

In order to design and analyze the performance of an axial-flow pump it is necessary to know the flow deviation, deflection angle and pressure loss coefficient as a function of the angle of incidence for the hydrofoil section in use. Because such functions are unique to the particular section, however, general correlation formulae are not available for the multitude of hydrofoil profiles, and such functions must be generated by either experiment or numerical simulation for the given or selected hydrofoil section. The purpose of present study is to generate design correlations for hydrofoils with double circular arc (DCA) camber by numerical analysis using a commercial code, FLUENT. The cascade configuration is determined by a combination of the inlet blade angle, blade thickness, camber angle, and cascade solidity, and a total of 90 cascade configurations are analyzed in this study. The inlet Reynolds number based on the chord and the inlet absolute velocity is fixed at 5${\times}$10$\^$5/. Design correlations are formulated, based on the data at the incidence angle of minimum total pressure loss. The correlations obtained in this way show good agreement with the experiment data collected at NASA with DCA hydrofoils.

• 대한공간정보학회지
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• 제1권2호
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• pp.167-175
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• 1993

본 연구에서는 교통모형의 기술적인 단점을 보완하기 위하여 교통모형과 지리정보시스템을 결합하는데 있어서 교통모형의 입력자료를 지리정보시스템의 위상구조에서 추출하여 교통모형의 단점을 극복해 보는데 있다. 또한, 그래픽 기능을 이용하여 교통모형의 결과치를 화면상에서 직접 보여줌으로서 의사결정과정에 효율적으로 대처할 수 있을 것으로 보인다. 이 시스템은 특정도시나 지역에 쓰여질 수 있고, 하드웨어 발달에 따른 컴퓨터 사용시간 및 자료 입력시의 오류의 절감과 지리정보시스템의 교통에로의 응용을 가능케 할 것이며, 여행자 정보시스템(ATIS: Advanced Traveler Information Systems)에 활용할 수 있는 주행안내시스템(Route Guidence System) 또는 차량항법시스템(Vehicle Navigation System)의 기초적 자료 및 시스템 개발에 기여할 것이다.

• Clinical and Experimental Reproductive Medicine
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• 제40권4호
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• pp.155-162
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• 2013

Objective: Stress is known to be an inhibitor of the reproductive hypothalamic-pituitary-gonadal (HPG) axis. However, the neural and molecular connections between stress and reproduction are not yet understood. It is well established that in both humans and rodents, kisspeptin (encoded by the kiss1 gene) is a strong stimulator of the HPG axis. In the present study we hypothesized that endocannabinoids, an important neuromodulatory system in the brain, can act on the HPG axis at the level of kiss1 expression to inhibit reproductive function under stress. Methods: Adult male Wistar rats were unilaterally implanted with an intracerebroventricular cannula. Afterwards, the animals were exposed to immobilization stress, with or without the presence of the cannabinoid CB1 receptor antagonist AM251 (1 ${\mu}g/rat$). Blood samples were collected through a retro-orbital plexus puncture before and after stress. Five hours after the stress, brain tissue was collected for reverse transcriptase-quantitative polymerase chain reaction measurements of kiss1 mRNA. Results: Immobilization stress (1 hour) resulted in a decrease in the serum luteinizing hormone concentration. Additionally, kiss1 gene expression was decreased in key hypothalamic nuclei that regulate gonadotrophin secretion, the medial preoptic area (mPOA), and to some extent the arcuate nucleus (ARC). A single central administration of AM251 was effective in blocking these inhibitory responses. Conclusion: These findings suggest that endocannabinoids mediate, at least in part, immobilization stress-induced inhibition of the reproductive system. Our data suggest that the connection between immobilization stress and the HPG axis is kiss1 expression in the mPOA rather than the ARC.