• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.1-5
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• 2020

As the world gradually advances to an aging society, the quality of human life is valued. Among them, 'quality of sleep' is very closely related to quality of life. Recently, Korea expanded health insurance coverage for "sleep disorders". Particularly, as the number of sleep multiple tests and prescriptions for sleep aids has increased rapidly, much attention has been focused on the related medical service environment. Therefore, this study looked at an in-depth interview of 11 hospitals to see what treatment delivery system is being established when the government applies health insurance for 'sleep disorders'. In conclusion, the organizations with the most average number of sleep polyp tests per day were found to have more sleep polyp labs (hardware) and more full-time specialists. Also, the polysomnography lab (hardware) and the specialist's full-time status (software) did not necessarily result in a "positive pressure regulator prescription" that can solve "sleep apnea" caused by "sleep ailments". Rather, it was found that the number of days of sleep multiple laboratories (hardware), the number of full-time specialists (software) or the specialty majors (software) had a greater impact. In particular, the higher the specialist's full-time personnel (software) index (=6.000), the higher the sleep-inducing agent prescription rate(=1.000), and the lower the specialist's full-time personnel (software) index (=1.000), the higher the sleep-inducer's prescription rate(= 0.010) Was low. In addition, even if the professional full-time personnel(software) index was the same (=1.000), the hospital type was lower as it was closer to the public hospital(=0.067) and higher at the specialized hospital (= 0.933). In the case of university hospitals, when the full-time specialists (software) are in the same condition (= 1.000), the frequency of use of the sleep laboratory (=1.000) and the sleep test rate (= 1.000) were all the same.

• 한국공간구조학회논문집
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• 제13권3호
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• pp.83-90
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• 2013

A series of wind tunnel tests were conducted on 7 super-tall buildings with various polygon cross-sections, including triangle, square, pentagon, hexagon, octagon, dodecagon, and circular. The primary purpose of the present study is to investigate the effect of increasing number of sides on aerodynamic characteristics for super-tall buildings. Wind tunnel tests were conducted under the turbulent boundary layers whose power-law exponent is 0.27. Fluctuating wind pressures from more than 200 pressure taps were recorded simultaneously, and time series of overturning moments were calculated considering tributary area of each pressure tap. The results show that the overturning moment coefficients and the spectral values decrease with increasing number of sides, and the largest mean and fluctuating overturning moments were found for the triangular super-tall building, and the largest spectral values were found for the square super-tall building. The analysis should be conducted more in detail, but currently it can be roughly said that there seems to be a little differences in the aerodynamic characteristics for the super-tall buildings whose number of sides is larger than 5 or 6.

• 한국지반공학회지:지반
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• 제11권1호
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• pp.113-126
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• 1995

점성토의 변형특성을 연구하기 위하여 공진주(RC)시험과 비틀전단(75)시험을 저변형률 및 중간 변형률하에서 실시하여 변형률의 크기,진동주파수,하중반복회수의 영향을 살펴보았다. 소 성지수가 이들의 영향을 평가하는데 중요한 변수임을 알 수 있었다. 실험에 사용된 시료로는 불 교란 실트 및 점토와 실험실에서 다져진 노상토를 사용하였다. 선형한계변형률이하에서 전단탄 성계수는 하중반복회수와 변형률의 크기에 영향을 받지 않았으며, RC시험에서 얻은 최소감소비가 1.1%에서 1.7%영역에서 존재하였다. 점성토의 선형한계변형률은 구속압과 소성지수에 따라 증가하였으며 사질토와 비교하여 넘은 선형영역을 보였다. 반복한계변형률이상의 변형률하에서는 전단탄성계수는 하중반복회수에 따라 감소하였지만 감쇠비는 영향을 받지 않았다. 진동주파수의 영향에 의해 RC시험에서 얻은 점성토의 전단탄성계수와 감쇠비는 RC시험결과보다 컸다. 전단탄성계수는 진동주파수의 대수증가에 따라 선형적으로 증가하였고 감쇠비의 경우 2Hz이하의 저주파수영역에서는 영향을 받지 않았다.

• Environmental Analysis Health and Toxicology
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• 제30권sup호
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• pp.8.1-8.5
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• 2015

Objectives The objective of this study was to evaluate the biodegradation potential of four perfluorooctane sulfonic acid (PFOS) alternatives that were developed at Changwon National University. While PFOS has been used widely in industrial and consumer products, it is known to be a persistent organic pollutant. Therefore, greener alternatives are highly desirable. Methods Biodegradation tests were run for 28 days using standard test protocols. The biochemical oxygen demand was measured daily throughout the experimental period, and the data were used to calculate the biodegradation rates. Microorganisms were isolated from the some of the tests that showed evidence of biodegradation. Results $C_8H_8F_9KO_3S$, which has the same number of carbons as the parent compound PFOS but a reduced number of fluorines, showed the highest biodegradation rate followed by $C_{10}H_8F_{13}KO_3S$. Chemical alternatives with lower number of carbons did not biodegrade readily in the experiments. Conclusions Together, these results suggest that it may be advantageous to develop PFOS alternatives with 8 carbons, the same as PFOS, but a reduced number of fluorines; as such, chemicals are more susceptible to biodegradation than the parent compound.

• 한국지반공학회논문집
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• 제20권5호
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• pp.87-98
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• 2004

본 연구에서는 현장타설말뚝에 보강재를 정착시킴으로써 주변지반의 강성을 높이고 보강재의 저항력에 의해 지지력을 향상시키기 위한 연구를 수행하였다. 보강형 및 무보강 현장타설말뚝에 대하여 보강효과에 영향을 미치는 인자들인 보강재의 단수, 경사, 배열에 따른 일련의 실내모형실험 및 3차원 수치해석을 수행하였다. 또한 보강효과의 검증과 실제 현장에서의 적용성을 알아보기 위하여 현장재하시험을 수행하였다. 실내모형실험 및 수치해석 결과, 보강재3단, 8개, 40$^{\circ}$ 경사의 교차배열에서 최적의 보강효과가 발현됨을 알 수 있었다. 1/8 모형재하실험에서는 압축, 인발, 수평 모두 보강재에 의한 지지력 증가효과가 나타났으며, 변위 25mm를 기준으로 압축 및 수평실험에서는 100% 이상의 보강효과가 나타났다. 또한 무보강 현장타설말뚝의 하중 단계에 따른 변위와 주면마찰력 검토결과, 철탑기초와 같은 대규모 현장타설말뚝 설계 시 사용되는 주면마찰력 값인 풍화암 10t/$\textrm{m}^2$, 연암 15t/$\textrm{m}^2$ 보다 큰 주면마찰력 값을 얻을 수 있었다. 1/2 모형재하실험에서는 약 25m의 변위가 발생하였을 때 인발하중 650ton에서 파괴가 일어났으며, 약 22%의 보강재에 의한 지지력 증가효과가 있는 것으로 나타났다.

• Wind and Structures
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• 제6권2호
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• pp.127-140
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• 2003

An investigation into the effect of corner cuts on the Strouhal number of rectangular cylinders with various dimensional ratios and various angles of attack is described. The Strouhal number given as a function of corner cut size is obtained directly from the aerodynamic behavior of the body in a uniform flow through a series of wind-induced vibration tests. For a quick verification of the validity of the Strouhal numbers obtained in this way, they are compared with the approximated the Strouhal numbers based on Shiraishi's early research. The test results show that the Strouhal number of the model with various corner cuts has a fluctuating trend as the angle of attack changes. For each cutting ratio as the angle of attack increases at each cutting ratio above $15^{\circ}$, the Strouhal number decreases gradually, and these trends are more evident for larger corner cut sizes. However, a certain corner cut size which is effective in reducing the wind-induced vibration can be identified by larger Strouhal numbers than those of other corner cut sizes. Three distinct characteristics of Strouhal number variation can be identified in three regions which are termed as Region I, II, and III based on the general trend of the test results. It is also found that the corner cut is effective in one region (Region-II) and less effective in another one (Region-III) when only the vortex-induced vibration occurs.

• Computers and Concrete
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• 제26권3호
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• pp.239-255
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• 2020

Experimental and discrete element method were used to investigate the effects of joint number and its angularities on the shear behaviour of joint's bridge area. A new shear test condition was used to model the gypsum cracks under shear loading. Gypsum samples with dimension of 120 mm×100 mm×50 mm were prepared. the length of joints was 2cm. in experimental tests, the joint number is 1, 2 and 3 and its angularities change from 0° to 90° with increment of 45°. Assuming a plane strain condition, special rectangular models are prepared with dimension of 120 mm×100 mm. similar to joints configuration in experimental test, 9 models with different joint number and joint angularities were prepared. This testing show that the failure process is mostly governed by the joint number and joint angularities. The shear strengths of the specimens are related to the fracture pattern and failure mechanism of the discontinuities. The shear behaviour of discontinuities is related to the number of induced tensile cracks which are increased by increasing the rock bridge length. The strength of samples decreases by increasing the joint number and joint angularities. Failure pattern and failure strength are similar in both of the experimental test and numerical simulation.

• 대한의용생체공학회:의공학회지
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• 제32권2호
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• pp.134-143
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• 2011

The selection of meaningful clinical tests and its reference values from a high-dimensional clinical data with imbalanced class distribution, one class is represented by a large number of examples while the other is represented by only a few, is an important issue for differential diagnosis between similar diseases, but difficult. For this purpose, this study introduces methods based on the concepts of both discernibility matrix and function in rough set theory (RST) with two discretization approaches, equal width and frequency discretization. Here these discretization approaches are used to define the reference values for clinical tests, and the discernibility matrix and function are used to extract a subset of significant clinical tests from the translated nominal attribute values. To show its applicability in the differential diagnosis problem, we have applied it to extract the significant clinical tests and its reference values between normal (N = 351) and abnormal group (N = 101) with either cholecystitis or cholelithiasis disease. In addition, we investigated not only the selected significant clinical tests and the variations of its reference values, but also the average predictive accuracies on four evaluation criteria, i.e., accuracy, sensitivity, specificity, and geometric mean, during l0-fold cross validation. From the experimental results, we confirmed that two discretization approaches based rough set approximation methods with relative frequency give better results than those with absolute frequency, in the evaluation criteria (i.e., average geometric mean). Thus it shows that the prediction model using relative frequency can be used effectively in classification and prediction problems of the clinical data with imbalanced class distribution.

• 대한조선학회논문집
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• 제57권5호
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• pp.262-270
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• 2020

An outdoor free-running model test system was designed for assessing ship maneuverability with test uncertainty. The test model was a surface combatant of tumblehome hull geometry. The straight forward tests were conducted first to obtain the relationship between the propeller revolution rate and advance speed. During the outdoor tests, the propeller revolution rate to achieve a certain Froude number condition was higher than that in the indoor free-running model tests. Turning circle and zigzag tests for evaluating ship maneuverability criteria were carried out at the propeller revolution rate determined by the straight forward test results. The random and systematic standard uncertainties of maneuvering criteria were obtained by repeated tests and comparison with the indoor free-running model test results, respectively. The test uncertainty was largely dominated by the systematic standard uncertainty, while the random standard uncertainty was small with good repeatability.

• 한국지반환경공학회 논문집
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• 제14권1호
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• pp.61-68
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• 2013

본 연구에서는 지반보강재로서 폐타이어 사용에 따른 환경영향을 평가하기 위하여 실내실험 및 현장시험시공을 수행하였다. 실내실험을 통하여 폐타이어의 용출특성에 가장 큰 영향을 미치는 폐타이어의 입경과 배수조건을 변화시켜가며 유출수의 pH, 탁도, TOC, Zn 농도를 분석하였다. 또한, 현장시험시공을 통하여 폐타이어를 이용한 보강토 옹벽 시공 후 하부 집수정의 수질을 분석하였다. 입경에 따른 용출실험 결과 폐타이어 입경이 증가할수록 용출농도가 감소하는 것을 확인할 수 있었으며, 이는 비표면적의 차이 때문으로 판단된다. 배수조건에 따른 용출실험 결과 배수조건인 경우 시간이 경과할수록 용출농도가 감소하여 주변 환경에 큰 영향을 미치지 않을 것으로 판단되나, 비배수 조건인 경우 시간이 경과할수록 용출농도가 증가하는 현상을 발견할 수 있었다. 1년간의 현장모니터링 결과 폐타이어로 보강된 옹벽으로부터 발생되는 침출수는 전반적으로 용출농도가 높지 않은 것으로 나타났으며, 침출수 발생 초기에 농도가 증가하다가 이후 점점 감소하여 원수인 우수와 비슷해지는 경향을 나타내었다. 따라서 폐타이어를 지반보강재로 사용함에 따라 발생하는 환경적 영향은 무시할 수 있는 수준임을 알 수 있었다.