• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.90-95
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• 2007

In order to investigate the optimum condition of the autofrettage process for the diesel engine injection pipe, different values of autofrettage pressure, pressure rising time, pressure holding time, and repetition of autofrettage process were applied. Autofrettage was preformed by applying the hydrostatic internal pressures of 603 MPa, 535 MPa, 500 MPa on the fuel injection pipe, corresponding to theoretically 50%, 30%, and 20% overstrain levels, respectively. The autofrettage residual stresses in the injection pipe were experimentally determined by using X-ray diffractometer. As the overstrain level increased, the magnitude of compressive residual stress at the bore increased. It was found that the rising time to reach the autofrettage pressure, holding time at the autofrettage pressure, and repeating application of the autofrettage pressure on the pipe had no significant influence on the residual stress distributions.

• 한국군사과학기술학회지
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• 제14권6호
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• pp.1121-1128
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• 2011

The HEMP has very short rising time with several tens of kV/m, and very dangerous to almost of the electronics. And the certain level of EMP shielding effectiveness is necessary for mos t of the systems andequipment. In EMP shielding effectiveness, the peak value and the rising time in the system are the most considerable parameters. In order to find out these parameters, we need to estimate the pulse shape in time domain. In this paper, we propose the methods to estimate the penetrated pulse in time domain using measured shielding effectiveness and digital filter modeling technique. The validity of the Digital filter modeling technique is verified by the HFSS.

• 융복합기술연구소 논문집
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• 제1권1호
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• pp.18-23
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• 2011

Shaping an input command through considering the resonant modes of multi degrees of freedom system, it is possible to realize the wanted motion, without exciting the uncontrollable modes of the flexible system. But, an increase of modes to be considered brings inevitably about the time delay due to an excessive rising time. On the purpose of reducing the rising time, only the interesting and dominant modes can be considered to determine the timing pulses of input shaper. In this paper, an effect of shaper by the partial modes is analysed for a specific system and the input shapers by the partial modes are analysed for three d.o.f damped system, using Matlab simulation.

• 벤처창업연구
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• 제7권2호
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• pp.101-111
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• 2012

ALC(Autoclaved lightweight concrete) 제조공정 중에서 예비양생이 완료된 반 경화제품(cake)인 상태에서 탈형을 실시할 때 적절한 탈형 시기가 지난 후에 탈형을 하게 되면 보습력이 떨어지고 절단 시 피아노선이 절단되어 제품에 균열이 발생할 우려가 있다. 이에 본 연구에서는 탈형 시기의 관리기준이 되는 경도(hardness)에 관한 예측을 하기 위해 관련된 변수들 간에 상호관련성을 찾고자 다중회귀분석(multiple regression analysis)을 이용한 연구를 진행하였다. ALC 제조공정의 V/T(Vibration Time)대기, V/T동작, 발포 높이, 경화시간, 타설 온도, Rising, C/S비의 독립변수(Independent variables)들이 종속변수(Dependent variables)인 경도(hardness)에 어떠한 관련성이 있는지를 다중 회귀분석을 이용한 연구를 진행하였다.

• 한국인터넷방송통신학회논문지
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• 제19권1호
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• pp.29-35
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• 2019

4차 산업 혁명이 진행되며 많은 회사들의 스마트 팩토리에 대한 관심이 커지고 있으며 센서의 중요성 또한 대두되고 있다. 정보를 수집하기 위한 센서에서 고장이 발생하면 공장을 최적화하여 운영할 수 없기 때문에 이에 따른 손해가 발생할 수 있다. 이를 위해 센서의 상태를 진단하여 센서의 고장을 진단하는 일이 필요하다. 본 논문에서는 디지털 센서의 고장유형 중 Rising time과 Falling time 고장을 딥러닝 알고리즘 RNN의 LSTM을 통해 신호를 분석하여 고장을 진단하는 모델을 제안한다. 제안한 방식의 실험 결과를 정확도와 ROC 곡선 그래프의 AUC(Area under the curve)를 이용하여 Rule 기반 고장진단 알고리즘과 비교하였다. 실험 결과, 제안한 시스템은 Rule 기반 고장진단 알고리즘 보다 향상되고 안정된 성능을 보였다.

• 한국안전학회지
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• 제9권1호
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• pp.76-82
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• 1994

Combustion phenomena(characteristics) of organic solvents including various alcohols Immobilized on ceramic balls were studied. Experiments were performed by burning methyl, ethyl, and propyl alcohol immobilized on sands (particle size 0.35mm) and coramic balls(particle size 1~5mm) to measure mass burning rate, height burning rate and combustion temperature. The longer time from ignition to extinguishment was resualted from the larger particle size of ceramic balls and the smaller size of ceramic balls exhibited the higher mass burning rate. Of alcohols tested the relative magnitude of facilitation of combustion was methyl >ethyl >propyl. Combustion temperatare of alcohols, without regard to the types of alcohols, was not increased with smaller ceramic balls(up to 3mm of particle size). However, with larger ceramic balls, combustion temperatare of alcohols was increased by 40~5$0^{\circ}C$ and the highest combustion temperatare was obtained with sands(particle size 0.35mm). Also, second rising was occurred at the combustion time of I5-20min. and this second rising time was increased with the smaller particle. These results will be able to be used for petrochemical industries using particles to evaluate the danger of fire and explosion.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 춘계학술발표논문집
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• pp.450-453
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• 2009

Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites. Compare economic estimation of SiC ceramic heater with sheathe heater are as followings. (1) Temperature rising time of sheath heater is 1.1 times faster than SiC ceramic heater. (2) Heating insulation of SiC ceramic heater is 2.7 times larger than sheath heater. If SiC ceramic heater is one body type of a product application, contact resistance will decrease. I think that temperature initial rising time is faster than now. The more SiC ceramic heater is used for a long time, the more economic benefit is larger in the view point of heat insulation.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1174-1180
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• 2015

We investigate in this paper the radiated electromagnetic waves together with the discharge characteristics of Trichel pulse of negative DC corona discharge in air in pin-to-plate and wire-to-plate configurations. The feature of the current pulse and the frequency spectrum of the electromagnetic radiations were measured under various pressures and gas gaps. The results show that the repetition frequency and the amplitude of Trichel pulse current depend on the discharge conditions, but the rising time of the pulse relates only to the radius of needle or wire and keeps constant even if the other conditions (including the discharge current, the gas gap and the gas pressure) change. There exists the characterized spectrum of electromagnetic waves from negative corona discharge in Trichel pulse regime. These characterized radiations do not change their frequency at a given cathode geometry even if the averaged current, the gas gap or the air pressure changes, but the amplitude of radiations changes accordingly. The characterized electromagnetic radiations from Trichel pulse corona relate to the formation or the rising edge of current pulse. It confirms that the characterized radiations from Trichel pulse supply information of discharge system and provide a potential method for detecting charged targets.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.469-470
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• 2008

We have studied electro-optic characteristics as a function of splay elastic constants ($K_{11}$) in the fringe-field switching (FFS) mode using the LC with positive dielectric anisotropy. When $K_{11}$ is increased from 7.7pN to 11.7pN, a maximum transmittance is slightly increased and rising time become a little bit fast. However, operating voltage and threshold voltage is independent. In opposition to rising time, decay time is not affected by $K_{11}$. We already know that $K_{11}$ affects tilt angle of liquid crystals. Therefore, on the occasion of high $K_{11}$, liquid crystals are mainly affected by twist deformation because the higher $K_{11}$, the less tilt angle. In the FFS device, high $K_{11}$ is favorable to reduce tilt angle in on state and thus improve rising response time.

• 한국가시화정보학회지
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• 제8권3호
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• pp.41-48
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• 2010

A visualization study to evaluate bubble motion in a tab water filled cylindrical tank with a varying flow rate of compressed air is conducted. The flow rate of compressed air varies from 1 to 5 L/min. Time resolved images are acquired by a high speed camera in 10 bit gray level at 100 fps and the measurement volume is irradiated by a 230 W halogen lamp. It is observed that there are three different regions; the bubble formation region, the rising bubble region and the free surface region. During the rise of bubble, the shape is changed as if an elastic body. Based on the binarized bubble image, the mean diameters of rising bubbles are estimated at beneath of the free surface. As the gas flow rate increases, the mean diameter is increased and the rising velocity also increases with buoyancy force.