• Ocean Systems Engineering
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• 제2권1호
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• pp.33-47
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• 2012

This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.

• Structural Engineering and Mechanics
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• 제35권6호
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• pp.699-715
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• 2010

This paper investigates the structural responses of axially restrained steel beams under fire conditions by a nonlinear finite element method. The axial restraint is represented by a linear elastic spring. Different parameters which include beam slenderness ratio, external load level and axial restraint ratio are investigated. The process of forming a mid-span plastic hinge at the mid-span under a rising temperature is studied. In line with forming a fully plastic hinge at mid-span, the response of a restrained beam under rising temperature can be divided into three stages, viz. no plastic hinge, hinge forming and rotating, and catenary action stage. During catenary action stage, the axial restraint pulls the heated beam and prevents it from failing. This study introduces definitions of beam limiting temperature $T_{lim}$, catenary temperature $T_{ctn}$ and warning time $t_{wn}$. Influences of slenderness ratio, load level and axial restraint ratio on $T_{lim}$, $T_{ctn}$ and $t_{wn}$ are examined.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1171-1176
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• 2004

To develop and improve a switchgear, the prediction of the pressure rising within the switchgear is very important. This study investigates the pressure rising characteristics of switchgear in order to evaluate the result of arc fault test. The pressure rising time at the four points of measurement calculated by CFD is well accord with the experimental results. The maximum pressure within the switchgear estimated by CFD is about 1.0bar, the pressure from experiment is 0.7 bar. The results of this study are able to be used to improve the performance of existing switchgear and to develop a new type switchgear.

• 대한기계학회논문집B
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• 제31권11호
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• pp.904-911
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• 2007

A measurement technique fur void fraction has been proposed using a time-resolved two-phase PIV system and the bubble dynamics has been investigated in gas-liquid two-phase flows. For the three-dimensional evaluation of the bubble information, both the images from the front and side views are simultaneously recorded into a high speed CCD camera by reflecting the side view image on a $45^{\circ}$ oriented mirror to be juxtaposed with the front view image. Then, a stereo-matching technique is applied to calculate the void fraction, bubble size and shape. To obtain the rising bubble velocities, the 2-frame PTV method was adopted. The present technique is applied to freely rising bubby flows in stagnant liquid. The results show that the increase of bubble flow rate gives rise to the increase of bubble size and rising velocity at first. If it goes over a certain level, the rising velocity becomes constant and the horizontal velocity grows bigger instead due to the obstruction of other bubbles.

• Journal of Electrical Engineering and Technology
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• 제6권5호
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• pp.677-683
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• 2011

The present paper describes the setup of standard partial discharge calibrator for measuring partial discharge and estimating uncertainties. The standard PD calibrator was designed and set up, consisting of a digital pulse generator, capacitor modules, and a digital oscilloscope controlled by software developed in the laboratory. Using this software, averages of charges and rising times and their standard deviations in the measured pulses can also be calculated. The standard PD calibrator generates five types of pulses: single, double, random, oscillating, and long-rising. The coefficient sensitivities to estimate the uncertainties of pulses were extracted in the model circuit of the standard PD calibrator. The uncertainties of charges and rising times in pulses of the standard PD calibrator were estimated with single pulses. These values were 0.3%-1.4% in charges and 1.9%-7.0% in rising time; however, these values are lower than the limit values in IEC 60270.

• 한국운동역학회지
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• 제17권2호
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• pp.103-112
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• 2007

The purpose of this study was to investigate the kinematic characteristics during rising from a chair. Six stroke patients and three healthy subjects participated in the study. Three dimensional kinematic analysis was used to get the duration, center of mass, and lower extremity angle. The stroke patients performed longer duration(0.28sec) than the healthy subjects in rising from a chair. The stroke subjects stayed longer time than the healthy subjects did in phase 2(From the initiation of knee extension to the reversal of trunk flexion to trunk extension)(t=-1.01, p=.04). The healthy subjects showed longer time than the stroke subjects in phase 3(from the reversal of trunk motion to extension to full standing position). The healthy subjects displayed larger value of center of mass in anterioposterior direction than stroke subjects(t=5.79, p=0.05). The center of mass in the mediolateral direction did not change during the completion of movement. However, the center of mass in the anterioposterior direction began to increase throughout the completion of movement. The center of mass in the vertical direction increased extensively in phase 3. The significant difference was not found in the maximum dorsiflexion in ankle, the initiation angle of knee, and the minimum angle of hip between stroke and healthy subjects. Even though statistical results did not show any significant angle difference in the lower extremity, the patterns of the change in the knee and hip angle during rising from a chair were different. The stroke subjects showed smaller angle of knee extension than the healthy subjects in phase 3. The stroke subjects flexed their trunk more than the healthy subjects in phase 2.

• 대한건축학회논문집:구조계
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• 제35권10호
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• pp.207-215
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• 2019

The aim of the research is analyzing the simple adiabatic temperature rising properties and the heat of hydration based on different placing timing of the mass concrete depending on various replacing ratios of blast furnace slag to comparative analyze the thermal cracking index and cracking possibility. As a result from the experiment, a suggested adiabatic temperature rising equation based on various blast furnace slag replacing ratios can be provide favorable correlation with over 0.99 of $R^2$ value by applying the initial induction period. With this relationship, more accurate prediction of the amount of the hydration heat rising and heating timing, and it is known that there is an approximately $13.1^{\circ}C$ of gap between plain concrete without blast furnace slag and concrete with 80 % of replacing blast furnace slag. To control the setting time and heat rising gap, the mix designs between top and bottom concrete casts were changed 15 cases, and D, E, H, I, and L models of controlling the heat of hydration showed 41.23 to $46.88^{\circ}C$ of core temperature and 0.98 to 1.27 of thermal cracking index. Therefore the cracking possibility was 15 to 52 % of favorable results of possibly controlling both the cracking due to the internal and external retainment and concrete temperature at early age.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2002년도 춘계학술대회 및 임시총회
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• pp.227-230
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• 2002

이 논문에서는 신경회로망을 이용한 원전 금속파편 시스템에 적용하여 진단 가능성을 제시한다. 첫 번째로, 오경보 감소에 대해 역전파 신경망을 적용하여 오경보 감소에 대한 가능성을 제시하였다. 즉, 전처리 단계에서 이동 평균 필터를 적용하여 저주파수인 배경잡음을 소거하였으며, 충격신호의 시작시간, 상승시간, 반주기, 전체시간을 신경망의 입력 값으로 사용하였다 발전소 운전가동시의 오경보 및 충격시험시의 신호를 적용한 결과 오경보가 1/4 이내로 줄어드는 유용한 결과를 보임을 알 수 있었다. 두 번째로 신경회로망 이론을 금속파편 진단(질량추정)에 적용하여 진단 가능성을 제시하였다. 신경회로망에서 사용된 알고리즘은 역전파 알고리즘(Back Propagation Network)을 사용하였으며, 세 가지의 입력변수(Rising Time, Half Period, Maximum amplitude)를 이용하였다. 영광 3호기 시운전시 강구의 충격 데이터로 미리 학습을 시킨 후 실제 금속파편 신호와 비교/분석하여 질량값을 추정하였다. 분석한 결과 비교적 만족할 만한 결과를 얻어 금속파편 진단에 신경회로망의 적용이 가능할 것으로 판단하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.373-376
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• 2006

In general, a method for generating irregular wave by combination of component waves obtained from linear wave theory is widely used. In these method, however, mean water surface elevation is rising from time to time because of nonlinear effect of wave. In this study, for the rising problem of mean water surface elevation and stabilization of calculation from time to time, mass transport velocity for horizontal velocity at wave source position is considered. The rising problem of mean water surface elevation is checked by comparing calculated wave profile from numerical technique proposed in this study with target wave profile at wave source position in numerical wave tank by using CADMAS-SURF code. And, by generating irregular wave, the validity of wave overtopping rate estimated from this numerical analysis is discussed by comparing computed results with measured results in hydraulic model experiments for vertical seawall located on a sloping sea bottom. As a results, the computations are validated against the previously experimental results by hydraulic model test and numerical results of this study and a good agreement is observed. Therefore, numerical technique of this study is a powerful tool for estimating wave overtopping rate over the crest of coastal structure.

• International Journal of Automotive Technology
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• 제4권3호
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• pp.109-117
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• 2003

The analysis and evaluation of the transient performance by the transient response specifications under various acceleration speeds and types based on driver's typical acceleration habit are implemented by the experimental study to provide the appropriate direction for the transient control in a gasoline engine. The concept of the transient response specifications which consist of delay time, rising time, maximum overshoot and settling time, and the analysis method using them are introduced to evaluate the characteristics of the transient performance quantitatively. Furthermore four acceleration speeds and four acceleration types are set respectively to realize the various transient states which are similar to the real drive. Several performance parameters in terms of engine speed, manifold absolute pressure, fuel injection duration and air excess ratio are measured simultaneously during the various acceleration using a throttle actuator controlled by a PC. The transient response specifications characterized well the transient performance for the various acceleration speed and types quantitatively. Delay and rising time with increment of the acceleration speed became shorter, but settling time did longer. Intensified acceleration type appeared to be the most economical in view of fuel consumption, and linear acceleration type was found to have the least harmful emission concentration.