• 지능정보연구
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• 제16권1호
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• pp.57-69
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• 2010

uTSN(ubiquitous Transportation Sensor Network)의데이터수집환경은기존ITS(Intelligent Transportation System) 환경과 커다란 차이가 있다. 지점 혹은 구간 검지체계를 근간으로 불연속적인 데이터를 수집하는 ITS 환경과 달리, 유비쿼터스 교통환경에서는 연속적인 개별차량 데이터의 취득이 가능하다. 또한 대응전략 구사에 있어서도, 구간단위 제어나 정보제공만 가능했던 ITS와 달리, 유비쿼터스 환경에서는 개별차량단위의 미세제어가 가능하다. 이러한 환경변화에 맞추어 수집데이터의 가공방식도 새로이 개발되어야 한다. 연속류 uTSN 환경에서 수집된 개별차량 위치와 개별차량 속도 데이터를 대상으로, 가공의 1차적 목적인 교통상황 판단을 위한 가공 방안을 제시하였다. uTSN으로부터 수집된 개별차량 단위 데이터를 기존 ITS와 같은 방식으로 집락하여 가공한다고 하면 그 미세한 정보는 다 손실되고 평균적 추세만 남게 된다. 본 연구에서는 수집 데이터에 담겨있는 미세한 정보를 손실하지 않음과 동시에 교통상황판단에 효과적인 정보를 생성하는 가공방식으로서, 3차원 속도, 교통량, 밀도 프로파일, 차량군 프로파일, 충격파 프로파일 생성을 제안하였다. 특히 밀도, 차량군, 충격파 정보는 교통상황 판단에 효과적이나 기존 ITS환경에서는 생성이 불가능하였던 것들이다. 본 연구에서는 모든 차량에 센서가 부착되어 있을 경우를 가정한 가공방안을 제시하였고, 장착율이 100%가 아닐 경우, 장착율에따라수집데이터를전수화하여프로파일작성하는방안을향후과제로남겨둔다.

• Design & Manufacturing
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• 제17권4호
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• pp.63-71
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• 2023

In order to increase the extrusion production speed of aluminum, extrusion die cooling technology using liquid nitrogen has recently attracted a lot of attention. Increasing the extrusion speed increases the temperature of the bearing area of extrusion dies and the extrusion profile, which may cause defects on the surface of extruded profile. Extrusion die cooling technology is to directly inject liquid nitrogen through a cooling channel formed between the die and the backer inside the die-set. The liquid nitrogen removes heat from the die-set, and gaseous nitrogen at the exit of the channel, covers the extrusion profile of an inert atmosphere reducing the oxidation and the profile temperature. The aim of this study is to evaluate the cooling capacity by applying die cooling to extrusion of Al-Mn-based aluminum alloy flat tubes, and to investigate the effects of die cooling on the change in extrusion characteristics of flat tubes. Cooling capacity was confirmed by observing the temperature change of the extrusion profile depending on whether or not die cooling is applied. To observe changes in material characteristics due to die cooling, surface observation is conducted and microstructure and precipitate analysis are performed by FE-SEM on the surface and longitudinal cross section of the extruded flat tubes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.903-904
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• 2006

This paper deals with analysis of linear switched reluctance motor at high speed. First, we defined turn-on position at inductance profile. Second, in turn-on section, we analyzed characteristic of linear switched reluctance motor according to speed. Also, we used finite element method at analysis process.

• 한국정밀공학회지
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• 제17권6호
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• pp.111-118
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• 2000

The design of reference trajectory with respect to drag acceleration is necessary to decelerate from hypersonic speed safely after atmosphere re-entry of space vehicle. The re-entry guidance design involves trajectory optimization, generation of a reference drag acceleration profile with the satisfaction of 6 trajectory constraints during the re-entry flight. This reference drag acceleration profile can be considered as the reference trajectory. The cost function is composed of the accumulated total heating on vehicle due to the reduction of weight. And a regularization is needed to prevent optimal drag profile from varying too fast and achieve realized trajectory. This paper shows the relations between velocity, drag acceleration and altitude in drag acceleration profile, and how to determine the reference trajectory.

• 한국정밀공학회지
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• 제33권10호
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• pp.781-787
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• 2016

We introduce FEST (Flight Environment Simulation Test) procedures for precise guided missiles to reliably improve systems. Flight vibration specification was established based on power spectral density curves calculated from flight test data of a high speed precise guided missile. A FEST pre-profile was developed according to flight vibration specification and delivered to a precise guided missile assembly. Vibration responses were measured by installing accelerometers on electronic components vulnerable to dynamic forces. The FEST profile was adjusted by comparing the vibration responses and the flight vibration specification. Subsequently, the FEST profile was repeatedly modified through trial and error, because the responses were similar to the flight environment. The modified FEST profile enabled performance testing of assembled precise guided missiles under simulated flight conditions on the ground, where unexpected errors could be corrected before the flight tests, leading to cost and risk reduction in the development of the precise guided missile system.

• 한국생산제조학회지
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• 제24권2호
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• pp.231-237
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• 2015

The pin-gear drive is a special form of fixed-axle gear mechanism. A large wheel with cylindrical pin teeth is called a pinwheel. As pinwheels are rounded, they have a simple structure, easy processing, low cost, and easy overhaul compared with general gears. They are also suitable for low-speed, heavy-duty mechanical transmission and for occasions with more dust, poor lubrication, etc. This paper introduces a novel slewing ring bearing with an external pinwheel gear set (e-PGS). First, we consider the exact cam pinion profile of the e-PGS with the introduction of a profile shift. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of the e-PGS can be lowered significantly by increasing the profile shift coefficient.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.585-592
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• 2009

The performance of screw compressor depends on lots of design parameters of rotor profile, such as length of seal line, wrap angle, blow hole, suction and discharge port size, number of rotor lobe, etc. The optimum rotor profile makes it possible to increase the compression efficiency with low energy consumption, and to minimize the loss of power. In this research, a new rotor profile design and performance analysis are done by computer simulation. It is expected that the volumetric efficiency is improved because the internal leakage is reduced due to the minimization of blow hole and clearance, and the stiffness of rotors is increased due to the reduction of length to diameter ratio. Also, the specific power consumption will be secured for use ranging from low to high operation speed.

• 한국전산유체공학회지
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• 제16권1호
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• pp.22-29
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• 2011

In this study, the glass fiber drawing from a silica preform in the furnace for the optical fiber manufacturing process is numerically simulated by considering the radiative heating of cylindrically shaped preform. The one-dimensional governing equations of the mass, momentum, and energy conservation for the heated and softened preform are solved as a set of the boundary value problems along with the radiative transfer approximation between the muffle tube and the deformed preform shape, while the furnace heating is modeled by prescribing the temperature distribution of muffle tube. The temperature-dependent viscosity of silica plays an important role in formation of preform neck-down profile when the glass fiber is drawn at high speed. The calculated neck-down profile of preform and the draw tension are found to be reasonable and comparable to the actual results observed in the optical fiber industry. This paper also presents the effects of key operating parameters such as the muffle tube temperature distribution and the fiber drawing speed on the preform neck-down profile and the draw tension. Draw tension varies drastically even with the small change of furnace heating conditions such as maximum heating temperature and heating width, and the fine adjustment of furnace heating is required in order to maintain the appropriate draw tension of 100~200 g.

• 한국환경과학회지
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• 제21권2호
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• pp.145-152
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• 2012

The mean wind speed and turbulence intensity profiles in the atmospheric boundary layer were extracted from a LIDAR remote sensing campaign in order to apply for CFD validation. After considering the semi-steady state field data requirements to be used for CFD validation, a neutral atmosphere campaign period, in which the main wind direction and the power-law exponent of the wind profile were constantly maintained, was chosen. The campaign site at the Pohang Accelerator Laboratory, surrounded by 40~50m high hills, with an apartment district spread beyond the hills, is to be classified as a semi-complex terrain. Nevertheless, wind speed profiles measured up to 100m above the ground fitted well into a theoretical-experimental logarithmic-law equation. The LIDAR remote-sensing data of the sub-layer of the atmospheric boundary layer has been proven to be superior to the data obtained by conventional extrapolation of the wind profile with 2 or 3 anemometer measurements.

• 한국기계가공학회지
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• 제15권4호
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• pp.101-108
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• 2016

Endmill fillet cutting at the corner was conducted with the online measurement of cutting forces and tool deflection by a tool dynamometer and an eddy current sensor system. The profile of the machined surface was also compared with the CAD profile with a Coordinate Measuring Machine (CMM) and CALYPSO software. It was found that the end mill cutter with four blades has a better surface profile than that with two blades, and the cutting forces and tool deformation were increased as the cutting speed was increased. When the tool located at the degree $45^{\circ}$ corner was found to conduct the maximum cutting force than started to the point of the workpiece. As it was compared with the CMM and ANOVA analysis result in the case that the cutting force and tool deformation was the maximum, it was found that the result was affected by the spindle speed and the number of blades.