• 한국음향학회지
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• 제24권1호
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• pp.21-28
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• 2005

본 논문에서는 장방형 콘서트홀에서 무대천장높이 변화가 객석의 음향성능에 미치는 영향에 대하여 조사하였다. 먼저 컴퓨터 시뮬레이션을 사용하여 객석부에서의 음향 특성을 조사하기 위하여 대표적 장방형 콘서트홀인 Boston Symphony Hall (이하 BSH)의 단순화 모델을 적용하였다. 또한 신축된 400석 규모의 장방형 홀의 축소모형 $(1.2m{\times}0.68m{\times}0.31m)$ 실험과 축소모형의 시뮬레이션을 통하여 무대부 천장높이의 변화에 따른 객석에서의 음향특성의 영향을 측정하였다. 실험 결과, 컴퓨터 시뮬레이션과 축소모형실험 및 축소모형실험의 시뮬레이션에서 모두 무대천장높이가 낮아질수록 잔향시간이 증가하는 경향을 보였으며, 무대천장 높이에 따른 잔향시간의 변화율은-0.09[sec/m]$\~$-0.061[sec/m]로 나타났다.

• 수산해양기술연구
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• 제22권1호
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• pp.1-5
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• 1986

In order to improve the net-mouth height of dragged gears, the authors devised models of floatingcollars of nylon cloth instead of floats and experimented with 4 types-A type (length 65em, breadth 3em), B type (length 65em, breadth 4em), C type (length 65em, breadth 5em) and D type (length 65 em, breadth 6em) attached respectively to the front edge of square of a model net after preliminary experimentation. These various types of floating collars were experimented in a circulating water channel to evaluate the characteristics of net-mouth height and hydrodynamic resistance and the effect of the length of bridles were also examined. The results obtained were as follows: 1. In case of attaching floats, the model net-mouth height reduced from 80 em to 20 em when current velocity was increased from 0.25m/see to 1m/sec. 2. In case of attaching floating collars, the model net-mouth heights were maintained 70 em, 71 em, 80 em, 78 em in maximum and 55 em, 63 em, 69 em, 73 em in minimum respectively even the current volocity was increased from 0.25 m/see to 1 m/see. 3. The model net-mouth height was reduced to 10 em maximum according to the current velocity and types of floating collars when the bridles were shortened 3~4 mm in length. 4. Hydrodynamic resistance of D type only was increased to 700 g in maximum and those of A, B, C type were reduced to 460 g in maximum at current velocity beyond 0.5 m/ see when bridles were shortened 3-4 mm in length. 5. But the model net-mouth heights became higher in accordance with breadth of floating coliars, B type was the best for this model net in case that hydrodynamic resistance was taken into account.

• Journal of Microbiology and Biotechnology
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• 제33권9호
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• pp.1238-1249
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• 2023

In this study, we sought to investigate the production and optimization of biosurfactants by soil fungi isolated from petroleum oil-contaminated soil in Saudi Arabia. Forty-four fungal isolates were isolated from ten petroleum oil-contaminated soil samples. All isolates were identified using the internal transcribed spacer (ITS) region, and biosurfactant screening showed that thirty-nine of the isolates were positive. Aspergillus niger SA1 was the highest biosurfactant producer, demonstrating surface tension, drop collapsing, oil displacement, and an emulsification index (E₂₄) of 35.8 mN/m, 0.55 cm, 6.7 cm, and 70%, respectively. This isolate was therefore selected for biosurfactant optimization using the Fit Group model. The biosurfactant yield was increased 1.22 times higher than in the nonoptimized medium (8.02 g/l) under conditions of pH 6, temperature 35℃, waste frying oil (5.5 g), agitation rate of 200 rpm, and an incubation period of 7 days. Model significance and fitness analysis had an RMSE score of 0.852 and a p-value of 0.0016. The biosurfactant activities were surface tension (35.8 mN/m), drop collapsing (0.7 cm), oil displacement (4.5 cm), and E₂₄ (65.0%). The time course of biosurfactant production was a growth-associated phase. The main outputs of the mathematical model for biomass yield were Yx/s (1.18), and µ_max (0.0306) for biosurfactant yield was Y_p/s (1.87) and Y_p/x (2.51); for waste frying oil consumption the So was 55 g/l, and Ke was 2.56. To verify the model's accuracy, percentage errors between biomass and biosurfactant yields were determined by experimental work and calculated using model equations. The average error of biomass yield was 2.68%, and the average error percentage of biosurfactant yield was 3.39%.

• 품질경영학회지
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• 제40권1호
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• pp.49-59
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• 2012

In computer simulation models the output from the computer code is often deterministic, i.e., running the code twice with the same values for the input variables would give the same output. It is discussed why the response surface method with polynomial approximation for the true response function is a good approximation to the computer experiments model. A sequential strategy to find the proper reduced quadratic polynomial model is illustrated with a case study in the military war game computer simulation model.

• 한국IT서비스학회지
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• 제11권1호
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• pp.125-139
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• 2012

Machine-to-Machine(M2M) refers to technologies allowing both wireless and wired systems to communicate with other devices. The enhancement of wireless technologies and the reduced cost of wireless connection have contributed toward the development of M2M market. M2M market currently focuses on public sector services, As M2M can offer scalable and flexible services, M2M services are expected to be applied in various fields. However there are still some doubts on whether the demand for M2M services will be increased. This study investigates the feasibility of M2M services from the perspective of operators. Operators evaluate that M2M services will show high marketability but low profitability in general. In addition, operators predict that M2M services will show both marketability and profitability in the area of car maintenance, insurance, telematics, home and office security, shop floor maintenance, and real-time locating services for children protection. This study may offer some ideas of M2M business models based on empirical feasibility studies.

• 한국터널지하공간학회 논문집
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• 제20권3호
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• pp.609-623
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• 2018

건물하중의 영향을 받는 상태의 기존터널에 근접해서 터널보다 깊은 심도로 지반을 굴착하는 경우에 흙막이벽체의 거동이 기존터널의 존재로 인해 큰 영향을 받는 것으로 알려져 있다. 그런데 지상 구조물에 의해 받는 영향에 대한 연구 예가 많지 않다. 따라서 본 연구에서는 기존터널에 근접하여 지반을 굴착할 때 기존터널이 상부구조의 영향을 받는 상태에서 건물 위치에 따른 터널의 거동을 대형모형실험과 수치해석을 실시하여 측정하였다. 이를 위해 지표면에 건물하중이 없는 경우와 건물하중이 3가지 이격거리에 위치한 경우(0 m, 1D, 2D)에 대하여 각각 대형모형실험을 수행하였다. 본 논문에서는 흙막이벽체와 기존구조물의 영향을 받고 있는 터널의 거동에 대하여 연구하였다. 1 : 10의 축척으로 2.0 m (폭)${\times}$6 m (높이)${\times}$4.0 m (길이)의 크기를 가진 대형토조에서 실험을 수행하였다. 그 결과 흙막이벽체 배면에 있는 인접터널의 안정성은 근접굴착에 의해 뚜렷하게 영향을 받는 것으로 나타냈다.

• 한국물환경학회지
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• 제33권4호
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• pp.441-448
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• 2017

Microcystis aeruginosa (M. aeruginosa) is a cyanobacterium species that can form harmful algal blooms in freshwater bodies worldwide. The use of Artemisia asiatica extracts to control M. aeruginosa inhibition will be environmentally friendly and promising. Artemisia asiatica extracts removed successfully upto 88% of M. aeruginosa pH 8 at $25^{\circ}C$ of temperature. These results was indicated that the amount of 2.24 g/L Artemisia asiatica extracts was removed 1g dryweight/L of M. aeruginosa. The kinetic data showed substrate inhibition kinetics and maximum growth rate was obtained when the M. aeruginosa was grown in medium containing 2.5 g/L of initial concentration of Artemisia asiatica extracts. In the various growth control models, Luong model showed the highest correlation coefficient of 0.9916. Therefore, the Luong model was the most suitable control model for the growth control of M. aruginosa using Artemisia asiatica extracts. In conclusion, the growth control of M. aruginosa using Artemisia asiatica extracts can be applied in the field without controlling the temperature and pH of rivers and streams, and it is possible to control the growth of M. aruginosa efficiently in a short time. The natural extract, Artemisia asiatica extracts, can be a promising inhibition due to its high efficiency and low dose requirements.

• ETRI Journal
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• 제15권3_4호
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• pp.35-45
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• 1994

In this paper we develop an approximation formalism on the queue length distribution for general queueing models. Our formalism is based on two steps of approximation; the first step is to find a lower bound on the exact formula, and subsequently the Chernoff upper bound technique is applied to this lower bound. We demonstrate that for the M/M/1 model our formula is equivalent to the exact solution. For the D/M/1 queue, we find an extremely tight lower bound below the exact formula. On the other hand, our approach shows a tight upper bound on the exact distribution for both the ND/D/1 and M/D/1 queues. We also consider the $M+{\Sigma}N_jD/D/1$ queue and compare our formula with other formalisms for the $M+{\Sigma}N_jD/D/1$ and M+D/D/1 queues.

• 한국터널지하공간학회 논문집
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• 제7권4호
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• pp.285-294
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• 2005

본 연구에서는 저토피 구간에서 기존터널 하부에 새로운 터널이 경사로 교차하여 신설할 때 하부 터널굴착으로 인하여 발생하는 교차부 주변지반과 상부터널의 거동을 분석하였다. 4.0m (폭), 3.8m (높이), 4.1m (길이) 크기의 콘크리트로 제작된 대형토조에서 모래를 이용하여 상대밀도기 일정한 모형지반을 3.4m높이로 조성하였고, 상하터널의 교차 각도가 $56^{\circ}$인 경우에 대하여 대형모형실험을 실시하였다. 또한, 모형실험과 동일한 조건으로 수치해석을 실시하여 실험결과와 연관하여 분석하였다. 연구결과 교차부 주변지반은 하부터널 종방향의 응력 전이로 인하여 교차 전과 교차 후에 응력과 지반변위의 차이가 발생하였다. 모형실험 결과로부터 교차 전 후의 하부터널굴착에 따른 종방향 응력전이가 상부터널에 의하여 차단됨을 알 수 있었다.

• Communications for Statistical Applications and Methods
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• 제24권1호
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• pp.43-65
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• 2017

We propose a flexible cure rate survival model by assuming that the number of competing causes of the event of interest has the Poisson distribution and the time for the event follows the gamma-G family of distributions. The extended family of gamma-G failure-time models with long-term survivors is flexible enough to include many commonly used failure-time distributions as special cases. We consider a frequentist analysis for parameter estimation and derive appropriate matrices to assess local influence on the parameters. Further, various simulations are performed for different parameter settings, sample sizes and censoring percentages. We illustrate the performance of the proposed regression model by means of a data set from the medical area (gastric cancer).