• 한국소음진동공학회논문집
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• 제26권3호
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• pp.340-349
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• 2016

A coupled room system consists of adjacent rooms and apertures where the sound energy is exchanged between the two rooms. Acoustically, a coupled room system shows a non-exponential decay profile. Most of the related researches have been to analyze the acoustic properties of two-room coupled system so far whereas three-room coupled system were seldom studied. In this regard, this paper aims to analyse the distribution of sound pressure level, sound decay curve of three-room coupled system and sound energy flow between them by using the acoustic diffusion model and to further verify them through experiments. Firstly, the sound pressure level distribution and mean sound pressure level in the steady-state condition are analyzed at various frequencies and source locations. Good agreements are observed in both experiments and analysis results. Secondly, two double slope effect quantifiers of sound attenuation, LDT/EDT and LDT/T10 are compared at various frequencies and for different source locations. The result indicates that LDT/T10, less affected by the early reflection patterns than LDT/EDT, is more suitable to the analysis and experiments of a multi-slope sound decay curve. Lastly, the sound energy flow in each room is analyzed based on the acoustic diffusion model. After the early decay stage, the sound energy is observed to flow from the room with a long reverberation time to the room with a short one.

• 농업과학연구
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• 제45권4호
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• pp.811-821
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• 2018

This study focused on the improvement of blueberry delivery service using pre-cooled ice and $SO_2$ pads to prevent an increase in the fruit temperature as well as decay. To maintain the fruit quality during low temperature storage, the effect of a $SO_2$ pad and modified atmosphere packaging was also examined. Harvested blueberries were precooled at $15^{\circ}C$, sorted, and packaged. And the fruits were placed in a similar environment as that for the parcel service. Part of the fruits were stored at $0^{\circ}C$ for long term storage. The air temperature in the delivery box increased along with an increase in the simulated delivery time regardless of the treatment. However, the rate of temperature increase was lower in the ice pad treatment. No significant difference was not found after 48 h. The oxygen concentration in the box ranged between 10.5 - 14.5% in the ice pad treatment, which was higher than that of the untreated control (7.5 - 11.9%) whereas the $CO_2$ concentration was lower in the ice pad treatment. No differences were found in the occurrence of off-flavor, decay, and sensory quality loss during the 48 hours of the parcel service simulation. The combined treatment of the $SO_2$ pad and modified atmosphere packaging (MAP) using a perforated film increased the shelf-life of the blueberry fruits, the overall quality such as firmness, and the soluble solid content was not different between the treatments except for the decay incidence. No decayed fruit was found in the combined treatment. However, the percentage of decayed fruit in the control was 25% on day 15 of storage and 75% on day 33 of storage, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.198-202
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• 1987

The regulator problem can be considered as some impulsive disturbance rejection one. In this point of view, the rate of decay is one of important factors for regulation and depends on how negative the real parts of the eigenvalues of closed-loop system. The algorithm that the closed-loop system has eigenvalues lying within a vertical. strip is useful for rapid disturbance rejection. This paper presents a design method for a linear quadratic regulator of two-time scale system with eigenvalues in a vertical strip by use of time-scale separation property.

• Journal of Korean Vacuum Science & Technology
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• 제4권2호
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• pp.41-43
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• 2000

We present a study of exciton relaxation in GaAs/AIGaAs quantum well structures by using time-resolved photoluminescence techniques.03 observed that light-hole exciton has a longer decay time than heavy-hole exciton, which results from the difference of the exciton population factor. We considered the thermal population time to explain the observed exciton dynamics.

• 분석과학
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• 제13권4호
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• pp.539-543
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• 2000

The quantitative aspects of 2D carbon-13 INADEQUATE (Incredible Natural Abundance DoublE QUAntum Transfer Experiment) experiment were studied on the basis of the time needed in various concentrations of samples. In order to evaluate the quantitative time of this experiment, eight compounds were selected (M. W. ca. 150-500). The effect on time needed of various concentrations showed exponential decay function, Y=$8.15X^{-0.64}$.

• Ocean and Polar Research
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• 제25권1호
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• pp.63-74
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• 2003

The build-up of the heat field in shallow coastal water due to a point source has been investigated using an analytical solution of a time-integral form derived by extending the solutions by Holley(1969) and also presented in Harleman (1971). The uniform water depth is assumed with non-isotropic turbulent dispersion. The alongshore-flow is assumed to be uni-directional, spatially uniform and oscillatory. Due to the presence of the oscillatory alongshore-flow, the heat build-up occurs in an oscillatory manner, and the excess temperature thereby fluctuates in that course and even in the quasi-steady state. A series of calculations reveal that proper choices of the decay coefficient as well as dispersion coefficients are critical to the reliable prediction of the excess temperature field. The dispersion coefficients determine the absolute values of the excess temperature and characterize the shoreline profile, particularly within the tidal excursion distance, while the decay coefficient determines the absolute value of the excess temperature and the convergence rate to that of the quasi-steady state. Within the e-folding time scale $1/k_d$ (where $k_d$ is the heat decay coefficient), heat build-up occurs more than 90% of the quasi-steady state values in a region within a tidal excursion distance (L), while occurs increasingly less the farther we go to the downstream direction (about 80% at 1.25L, and 70% at 1.5L). Calculations with onshore and offshore discharges indicate that thermal spreading in the direction of the shoreline is reduced as the shoreline constraint which controls the lateral mixing is reduced. The importance of collecting long-term records of in situ meteorological conditions and clarifying the definition of the heat loss coefficient is addressed. Interactive use of analytical and numerical modeling is recommended as a desirable way to obtain a reliable estimate of the far-field excess temperature along with extensive field measurements.

• 한국식품저장유통학회지
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• 제16권3호
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• pp.327-332
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• 2009

관행, 저농약 및 유기농 재배한 참다래 과실의 저온저장 중 품질변화를 조사하였다. 경도는 저장초기 심하게 감소한 다음 연화되는 경향을 보였는데 연화 속도는 유기농 과실에서 다소 빨랐다. 당도는 저장 중 증가하는 경향을 보인 반면, 산함량은 감소하였고, pH는 변화가 없었다. 환원당 함량은 전분함량이 감소하면서 저장초기 크게 증가하는 경향을 보였다. 유기농 과실은 저장 중 부패율이 관행재배나 저 농약재배에 비해 유의하게 높았고, 병을 유기하는 병원균은 잿빛곰팡이, 연부병, 꼭지썩음병 순으로 높았다. 호흡량과 함께 에틸렌발생량이 증가하면서 과실이 연화되었는데, 호흡량과 에틸렌함량은 유기농 과실에서 다소 높은 경향을 나타내었다. 유기농 과실은 연화와 함께 부패과 증가로 관행재배나 저 농약재배에 비해 저장력이 감소되었다.

• 한국대기환경학회지
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• 제30권2호
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• pp.95-109
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• 2014

In this study, the concentration of odorants released from albumin (EA) and yolk (EY) portions of boiled egg samples were determined as a function of storage time. The concentrations were measured at storage days of 0, 1, 3, 6, and 9 under room temperature. As such, odorants produced during both fresh and decay conditions were measured through time. A total of 19 compounds were selected as the main target odorants along with 12 reference compounds. GC-MS (for VOC) and GC-PFPD system (for sulfur gases) equipped with thermal desorption (TD) system were employed for odorant analysis in this work. The initial concentrations measured from the chamber system were converted into flux terms ($ng{\cdot}g^{-1}{\cdot}min^{-1}$). The EA showed the highest concentration of $H_2S$ (234 $ng{\cdot}g^{-1}{\cdot}min^{-1}$) at EA-0, and the concentrations of AT (Acetone) was also seen clearly in the range of 11.7 (EA-0) to 58.6 $ng{\cdot}g^{-1}{\cdot}min^{-1}$ (EA-9). The EY showed similar patterns. EtAl (Ethyl alcohol) increased 9.47 (EA-1) to 96.7 $ng{\cdot}g^{-1}{\cdot}min^{-1}$ (EA-9) in EA samples. Ketone, alcohol, sulfur groups generally exhibited high concentrations compared to other odorants. These data were also compared in relation to olfactometry related dilution-to-threshold (D/T) ratio by air dilution sensory (ADS) test and sum of odor intensity (SOI).

• 한국수자원학회논문집
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• 제34권4호
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• pp.289-301
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• 2001

비보존성 오염물질의 종확산에 관한 단계분리 유한차분 모형을 낙동강에 적용하여, 1991년에 발생한 페놀누출 사고에 따른 종확산 모의계산을 수행하였다. Preissmann의 4점 음해법에 근거한 부정류 계산모형으로부터 산정된 계산결과를 종확산 모형의 입력자료로 사용하였다. 종확산계수의 산정을 위한 경험식 및 1차 반응의 감쇠계수에 따른 종확산 계산결과의 민감도를 분석하였다. 하류 지점에서의 첨두농도 발생 시각은 사용된 종확산계수 식에 따라 상당히 달라짐을 알 수 있었다. 또한 농도 분포형은 감쇠계수에 따라 변하지 않는 반면, 농도값은 감쇠계수에 상당히 좌우되는 것으로 나타났다. 최적화 기법을 사용하여 흐름 모형 및 종확산 모형을 보정하였으며, 낙동강에 위치한 주요 취수지점들에 대한 첨두농도 발생시각을 모의하여 제시하였다.

• Nuclear Engineering and Technology
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• 제25권1호
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• pp.8-19
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• 1993

강제순환 냉각상실사고시 조밀화된 저장계통의 사용후 핵연료에서 생성된 붕괴열의 제거를 확인하기 위한 자연순환 해석모델이 개발되었다 채택된 수치기법은 ADI방법에 근거하였다. 사용후 핵연료의 붕괴열 생성율은 ANS-79 붕괴열 모델에 따라 계산되었으며, 보수적인 붕괴열 생성량 입력을 위해 chopped sine곡선에 따른 비균일 표면열속이 가정되었다. 저장조내 국부비등의 발생 가능성을 조사하기 위해서 민감도분석이 수행되었으며, 이는 핵연료간 거리 비, 열 생성량 및 핵연료 봉 반지름 등의 여러 변수를 변경시킴으로서 이루어졌다. 이 모델의 적용결과는 적절한 냉각시간 후의 조밀화된 사용후 핵연료 다발을 통한 자연대류 유량이 안전하고 효과적인 방식으로 저장조의 온도준위를 조절할 수 있음을 보여주고 있으며, 또한 사용후 핵연료봉 재배치를 위한 냉각시간에 관한 허용기준이 얻어졌다.