• Earthquakes and Structures
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• 제15권5호
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• pp.513-528
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• 2018

A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems could have different impacts. These kinds of earthquakes can damage the tanks readily. Hence, the seismic behaviour and vibration of cylindrical liquid storage tanks, subjected to earthquakes, is of paramount importance, and it is investigated in this paper. The Finite Element Method is used to evaluate seismic response in addition to the reduction of excessive liquid sloshing in the tank when subjected to the long-period ground motion. The non-linear stress-strain behaviour pertaining to polymers and rubbers is implemented while non-linear contact elements are employed to describe the 3-D surface-to-surface contact. Therefore, Nonlinear Procedures are used to investigate the fluid-structure interactions (FSI) between liquid and the tank wall while there is incompressible liquid. Part I, examines the effect of the flexibility of the isolation system and the tank aspect ratio (height to radius) on the tank wall radial displacements of the tank wall and the liquid sloshing heights. Maximum stress and base shear force for various aspect ratios and different base-isolators, which are subjected to three seismic conditions, will be discussed in Part II. It is shown that the composite-base isolator is much more effective than other isolators due to its high flexibility and strength combined. Moreover, the base isolators may decrease the maximum level pertaining to radial displacement.

• 한국관개배수논문집
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• 제18권1호
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• pp.68-80
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• 2011

To provide a operation rule curve for reservoir with low ratio of watershed area to paddy field area, Duckyong reservoir with watershed area of $15.8km^2$ and paddy field area of 1,071ha was selected, in which 4 meters are being heightened and full water levels will be increased from EL.26.0m to EL.30.0m, total water storages from 365.6M $m^3$ to 708.0M $m^3$. There was no operation rule curve that satisfied over 90% reliability of water supply in reservoir with watershed area of 1.48 times of paddy field area. The differences between observed and simulated reservoir daily water storages were minimized to determine parameters for simulating reservoir inflow in case of paddy field area of 550ha from 1991 to 2010. A operation rule curve was drawn to have a maximum storage with total water storage, which was in paddy field area of 700ha with ratio of 2.3 between watershed area and paddy field area. This case showed that annual irrigation water supply was 668M $m^3$ and instream flow of 57M $m^3$, water supply reliability of 55.6% in normal operation, and annual irrigation water supply was 605M $m^3$ and instream flow of 38M $m^3$, water supply reliability of 95.6% in withdrawal limited operation. Water supply reliabilities showed 35.6% without flood regulation and 17.8% with flood regulation in existing reservoir before heightening.

• 한국수소및신에너지학회논문집
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• 제9권3호
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• pp.101-110
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• 1998

Ti-Cr-V 합금에서 Ti의 일부를 Zr으로 치환하는 것에 의한 수소저장 특성의 변화에 대하여 연구하였다. Zr 의 치환은 평탄압력과 히스테리시스를 감소시키나 생성된 $Cr_2Zr$상은 평탄성을 악화시키며 수소저장량의 저하를 초래하였다. 그러나, Ti/Cr의 조성비를 조절하여 $Cr_2Zr$상의 생성을 억제함으로써 수소저장용량이 매우 큰 합금을 얻을 수 있었다. 또한, 열처리에 의해 수소저장량과 유효수소저장량의 감소없이 평탄성을 크게 향상시킬 수 있었다.

• 한국식품영양과학회지
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• 제31권2호
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• pp.184-188
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• 2002

시료 달걀의 난황 속에는 올레산과 팔미트산이 가장 많이 함유되어 있었고, 저장 1, 2주에 그 함량이 최고점으로 도달 하였으며, 3주 때는 감소하였다. 일반란의 경우 저장기간이 길어질수록 팔미트산과 올레산은 증가 후 다시 감소하였고, 리놀레산은 증가하였다. 인삼란의 경우 팔미트산과 스테아르산이 감소 경향을 보였다. DHA란의 팔미트산과 올레산의 변화는 없었으나, 리놀레산이 증가하였다 감골란은 올레산이 급격히 감소의 경향을 보이는 반면, 팔미트산은 증가 후 감소의 경향을 반복하였다. 저장기간이 길어짐에 따라 포화 지방산의 함량은 감소하고 불포화지방산의 함량은 증가하는 경향을 보였다. 구입 당시 모든 달걀에 나타나지 않았던 DHA가 저장기간 동안에 극미량 검출되었다. 한편, n-6/n-3 비율은 일반란이 저장 1~3주, 감골란은 구입 당시, DHA란은 저장 0~3주의 저장기간 동안 섭취 권장 범위에 해당되었다. 저장기간 동안 다중불포화지방산, 단일불포화지방산과 포화 지방산의 비 (P/M/S)가 DHA란은 변화가 없었고, 인삼란은 점차 증가하는 경향을 보였다. P/M/S비는 3주 저장한 일반란, 2주 저장한 인삼란과 0~3주 저장기간의 DHA란에서 적정권장 수준을 나타내었다.

• 한국환경농학회지
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• 제15권4호
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• pp.434-441
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• 1996

저장중인 사과에 발생하는 병해를 방지하기 위하여 postharvest 약제로서 benomyl과 bitertanol을 사과에 처리한 후 CA 및 저온저장시켜 저장중 약제의 분해양상, 잔류량의 변화 및 약제의 안전성 평가 그리고 약제의 사과 내로의 침투율을 조사하였다. CA저장에서 약제의 분해양상은 사과의 저장 초기에는 느린 속도로 분해되나 저장 후반기로 갈수록 빠르게 분해되며, 저온저장에서는 이와는 반대로 저장 후기보다 초기에 빠른 분해양상이 나타났다. Benomyl과 bitertanol이 표준살포농도로 처리된 사과에서의 초기농도는 2.24 및 1.54mg/kg으로 나타났으며, CA저장에서는 저장후 135 및 96일, 저온저장에서는 115 및 70일에 MRL인 1mg/kg에 이르렀다. Benomyl과 bitertanol의 분해반감기는 CA저장에서 124 및 130일이고, 저온저장에서는 101 및 111일로 나타나서 CA저장보다는 저온저장에서 보다 더 빠른 분해가 이루어졌다. Benomyl과 bitertanol이 처리된 사과에서의 침투율을 조사한 결과 두 약제 모두 과육부보다는 과피에 주로 잔류되어 있었다.

• Journal of Power Electronics
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• 제18권2호
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• pp.343-355
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• 2018

A wide-voltage-conversion range bidirectional DC-DC converter is proposed in this paper. The topology is comprised of one typical LC energy storage component and a special common grounded asymmetric H-bridge with four active power switches/anti-parallel diodes. The narrow output PWM voltage is generated from the voltage difference between two normal (wider) output PWM voltages from the asymmetric H-bridge with duty cycles close to 0.5. The equivalent switching frequency of the output PWM voltage is double the actual switching frequency, and a wide step-down/step-up ratio range is achieved. A 300W prototype has been constructed to validate the feasibility and effectiveness of the proposed bidirectional converter between the variable low voltage side (24V~48V) and the constant high voltage side (200V). The slave active power switches allow ZVS turn-on and turn-off without requiring any extra hardware. The maximum conversion efficiency is 94.7% in the step-down mode and 93.5% in the step-up mode. Therefore, the proposed bidirectional topology with a common ground is suitable for energy storage systems such as renewable power generation systems and electric vehicles with a hybrid energy source.

• Journal of Information Processing Systems
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• 제18권6호
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• pp.803-812
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• 2022

With the increasing number of mobile device users worldwide, utilizing mobile edge computing (MEC) devices close to users for content caching can reduce transmission latency than receiving content from a server or cloud. However, because MEC has limited storage capacity, it is necessary to determine the content types and sizes to be cached. In this study, we investigate a caching strategy that increases the hit ratio from small base stations (SBSs) for mobile users in a heterogeneous network consisting of one macro base station (MBS) and multiple SBSs. If there are several SBSs that users can access, the hit ratio can be improved by reducing duplicate content and increasing the diversity of content in SBSs. We propose a Deep Q-Network (DQN)-based caching strategy that considers time-varying content popularity and content redundancy in multiple SBSs. Content is stored in the SBS in a divided form using maximum distance separable (MDS) codes to enhance the diversity of the content. Experiments in various environments show that the proposed caching strategy outperforms the other methods in terms of hit ratio.

• 태양에너지
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• 제15권3호
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• pp.15-27
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• 1995

본 연구는 상변화물질로써 무기염수화물계 물질인 피로인산나트륨($Na_4P_2O_7{\cdot}10H_2O$)이 채워져 있는 직육면체형 잠열축열조 내에서 축열과정시 일어나는 상변화물질의 온도특성, 열전달현상, 축열량 등을 실험적으로 측정하고 그 결과들을 수치해석결과들과 비교 검토한 것이다. 축열과정시 상변화물질인 피로인산나트륨은 용융상태가 액체상태가 아닌 gel상태이므로 액체상태에서의 주된 열전달현상으로 나타나는 자연대류 유동현상이 일어나지 않아 전도에 의한 열전달현상이 지배적인 것으로 나타났다. 무기염수화물계 상변화물질은 공극율(공기 함유율)이 작을수록 열용량이 커지므로 축열과정시 공극율이 큰 경우보다 온도가 서서히 상승되었으며, 실험으로 측정된 온도값과 수치해석적인 방법으로 계산된 온도값은 최대 15%의 차이가 났다.

• 정보저장시스템학회논문집
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• 제10권1호
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• pp.23-26
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• 2014

In this paper, we present a novel approach for tuning the resonant frequency of torsionally driven vertical comb actuators. The tuning unit composed of thermal actuator, scissor mechanism and V-shape shaft enables continuous and reversible resonant frequency tuning. The proposed method is based on the stiffness alteration of the V-shape shaft. It is experimentally verified that the resonant frequency of the torsional microscanner is shifted up to 1.59 kHz from 1.51 kHz showing the maximum tuning ratio of 5.29%.

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.38-42
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• 2006

We report the random pattern characteristics of the super resolution near field structure(Super-RENS) write once read-many(WORM) disc at a blue laser optical system(laser wavelength 405nm, numerical aperture 0.85) and the Super-RENS read only memory(ROM) disc at a blue laser optical system(laser wavelength 659nm, numerical aperture 0.65). We used the WORM disc of which carrier-to-noise ratio(CNR) of 75nm is 47dB and ROM disc of which carrier-to-noise ratio(CNR) of 173nm is 45dB. We controlled the equalization(EQ) characteristics and used advanced partial-response maximum likelihood(PRML) technique. We obtained bit error rate(bER) of 10-3 level at 50GB WORM disc and bite error rate of 10-4 level at 50GB level ROM disc. This result shows high feasibility of Super-RENS technology for practical use.