• 한국기계가공학회지
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• 제11권4호
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• pp.160-167
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• 2012

This paper is concerned with a particular fracture mechanics parameter ${\Delta}K_{th}$, known as the 'threshold stress intensity range', or 'fatigue threshold'. This threshold ${\Delta}K_{th}$ constitutes, as it were, a hinge between the notion of crack initiation and the notion of crack growth. It has often been thought that, like the endurance limit, it could be an intrinsic criterion of the material. The study was conducted on a SA-508 pressure vessel steel used in the nuclear power industry. This material exhibits a typical threshold effect in the range of the crack growth rates which were determined; that is, below approximately $da/dN=10^{-6}mm/cycle$, the slope of the da./dN versus ${\Delta}K$ curve is almost vertical. The value of ${\Delta}K_{th}$ was determined at a growth rate of $10^{-7}$ mm/cycle according to the ASTM Standard for threshold testing. The fatigue threshold values are in the range 21 $kg/mm^{3/2}$ to 12 $kg/mm^{3/2}$ depending on the stress ratio effect.

• East Asian Economic Review
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• 제22권3호
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• pp.307-336
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• 2018

This paper proposes a monetary aggregate "Liquidity" that could serve as a useful indicator for gauging the appropriateness of monetary policy. If liquidity rises above a certain threshold, it is signaling that monetary policy is losing traction due to structural and other impediments even when the inflation gap remains open. This indicator supplements the financial cycle approach but adds value by providing a benchmark that is derived from the national account, and not based on its own trend. Over the last two decades, each time this measure rose above the threshold range, it was followed by a decline in GDP growth. The latter was greater when accompanied by a high physical asset value to GDP, e.g., an elevated property market.

• 한국시뮬레이션학회논문지
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• 제19권3호
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• pp.119-125
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• 2010

시뮬레이션 출력 분석 방법인 이동 블록 부트스트랩이나 정상 부트스트랩, 그리고 임계값 부트스트랩은 자기상관성이 존재하는 데이터에 적용 가능한 표본 재추출 방법론들이다. 이러한 부트스트랩 방법들은 데이터의 정상성을 가정하여 적용해 왔다. 그러나 실제 자료 또는 시뮬레이션 출력에 계절성이나 추세를 동반하여 그 정상성을 보장할 수 없는 경우에는 부트스트랩을 시뮬레이션 출력 분석에 적용하지 못하였다. 시뮬레이션 출력 분석 기법 중 자기상관성을 가장 잘 묘사하는 방법은 임계값 부트스트랩 방법이다. 임계값 부트스트랩은 자료의 임계값을 기준으로 주기를 형성하여 재추출하는 방법으로써 계절성이 존재하는 데이터에 부트스트랩을 적용한다면 임계값 부트스트랩과 유사한 정확도를 얻을 수 있다. 본 논문에서는 계절성이 존재하는 시계열 자료에 대한 부트스트랩 적용 가능성을 제시 및 검증해보고자 한다.

• Journal of Medicine and Life Science
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• 제20권3호
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• pp.107-114
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• 2023

Epidemiological control of coronavirus disease 2019 (COVID-19) is needed to estimate the infection period of confirmed cases and identify potential cases. The present study, targeting confirmed cases for which the time of COVID-19 symptom onset was disclosed, aimed to investigate the relationship between intervals (day) from symptom onset to testing the cycle threshold (CT) values of real-time reverse transcription-polymerase chain reaction. Of the COVID-19 confirmed cases, those for which the date of suspected symptom onset in the epidemiological investigation was specifically disclosed were included in this study. Interval was defined as the number of days from symptom onset (as disclosed by the patient) to specimen collection for testing. A locally weighted regression smoothing (LOWESS) curve was applied, with intervals as explanatory variables and CT values (CTR for RdRp gene and CTE for E gene) as outcome variables. After finding its non-linear relationship, a polynomial regression model was applied to estimate the 95% confidence interval values of CTR and CTE by interval. The application of LOWESS in 331 patients identified a U-shaped curve relationship between the CTR and CTE values according to the number of interval days, and both CTR and CTE satisfied the quadratic model for interval days. Active application of these results to epidemiological investigations would minimize the chance of failing to identify individuals who are in contact with COVID-19 confirmed cases, thereby reducing the potential transmission of the virus to local communities.

• 대한화장품학회지
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• 제22권2호
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• pp.141-152
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• 1996

Many eastern females concern themselves about the condition and the color of their skin. The purpose of the present study is to classify the skin trouble and the change of the facial color due to hormonal cycle in female. We examined the actual cricumstances by questionnaires, and made patch tests of methyl nicotinate, representing rubefacient, to estimate the epidermal penetratin rate, and measured the facial color change during the menstrual cycle period to invest the correlation factors between skin trouble due to cosmetics and facial color change. Fifty-two percent of subjects had skin trouble relating to cosmetics. One second of subjects with skin trouble due to cosmetic complained the change of sysptom by menstrual cycle. The changes of systptom were related on premenstrual period. The skin trouble developed mainly on the first trimester of the pregnancy. In patch test of methyl nicotinate, most cases showed decreased threshold of the reaction on minstruation, and other cases showed increased reactivity of the skin of menstruation. In facial color measurements, it proves in the appearance of red spot, darkness, increasing the value and turning the hue to yellowish, Also it demonstrates that premenstruation hue turn red and value level decrease. During the period, facial color turns pale and hue progress to yellow. This fact coincides with the questionnaire. We have quqntified through questionnaire, which demonstrates it has good correlation with done to the subjects among the internal environment factors hormonal cycle influences the facial color change and the skin trouble due to cosmetics. Through this paper the development of an more fragmented make-up and skin care products is required to increase the interest to females, to make true the creation of beauty.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.259-268
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• 2007

A knock detection circuit that is based on the signal of an accelerometer installed on the engine block of a spark ignition automotive engine has a band-pass filter with a certain frequency as a parameter to be calibrated. A new statistical method for the determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The method uses both the cylinder pressure and block vibration signals and is divided into two steps. In both steps, a new recursive trigonometric interpolation method that calculates the frequency contents of the signals is applied. The new trigonometric interpolation method developed in this paper improves the performance of the Discrete Fourier Transformation, allowing a flexible choice of the size of the moving window. In the first step, the frequency contents of the cylinder pressure signal are calculated. The knock is detected in the cylinder of the engine cycle for which at least one value of the maximal amplitudes calculated via the trigonometric interpolation method exceeds a threshold value indicating a considerable amount of oscillations in the pressure signal; this cycle is selected as a knocking cycle. In the second step, the frequency analysis is performed on the block vibration signal for the cycles selected in the previous step. The knock detectability, which is an individual cylinder attribute at a certain frequency, is verified via a statistical hypothesis test for testing the equality of two mean values, i.e. mean values of the amplitudes for knocking and non-knocking cycles. Signal-to-noise ratio is associated in this paper with the value of t-statistic. The frequency with the largest signal-to-noise ratio (the value of t-statistic) is chosen for implementation in the engine knock detection circuit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.274-276
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• 2002

This paper proposes a current differential relaying algorithm for power transformers using the third difference function of a differential current. The algorithm observes the instants when the wave-shape of the differential current is changed due to the change of the magnetization inductance. If the value of the third difference is bigger than the threshold, the output of a current differential relay is blocked for a cycle. In the cases of magnetic inrush and overexcitation, the blocking signal is maintained: however, for internal faults, reset in a cycle. The test results clearly show that the algorithm successfully distinguishes internal faults from magnetizing inrush.

• 한국산업정보학회논문지
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• 제20권5호
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• pp.107-115
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• 2015

Residential building owners are turning toward renovating their existing buildings to improve old and inefficient HVAC systems. Due to the renovation, much of the added costs will inevitably be passed on to tenants by increasing rent rates. This increment often increases the vacancy rate in the buildings. To balance the interests of both owners and tenants, this paper suggested a method to determine an appropriate rental rate increment for the HVAC system renovation. A case study on residential buildings was conducted to determine a balanced point where the rental rate increment that offsets the amount tenants are willing to pay for the renovation. To calculate all costs incurred by the renovation, life-cycle cost analysis was carried out. Therefore, this paper ultimately provides a threshold value of rental rate increment such that building owners can make a reasonable decision on the HVAC system renovation.

• 대한임상검사과학회지
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• 제52권4호
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• pp.335-341
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• 2020

본 연구는 Cobas TaqMan MTB 검사(CTM test, Roche Diagnostics, Basel, Switzerland)와 항산균 도말염색검사의 연관성을 확인하고 그에 따른 반정량적 판정기준을 확립하고자 하였다. 2015년 1월부터 2015년 12월까지 삼성서울병원 진단검사의학과에 의뢰된 8,389개의 검체에 대해 결핵균 도말 검사, 배양 검사 및 CTM 검사를 동시에 실시하였으며, 그 결과를 분석하여 AFB 염색과주기의 연관성을 후향적으로 분석하였다. CTM 검사의 임계 값(Ct)값으로, 결핵균 검출방법의 반정량적 판정기준을 설정 하였다. CTM 검사의 135개의 양성 표본에 대한 Ct값은 항산균 도말염색과 반비례적 상관관계가 있었다(rs=-0.545, P<0.01). CTM 검사와 항산균 염색 등급의 음의 상관관계가 입증되었으며, 임상 기준에 이러한 기준을 적용하여 임상적 의의를 검증하였다. 이 연구의 반정량적 기준은 병원에서 활동성 결핵 및 감염을 일으킬 수 있는 환자의 빠른 진단의 판단에 도움이 될 것으로 사료된다.

• Clinical and Experimental Reproductive Medicine
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• 제48권3호
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• pp.255-261
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• 2021

Objective: This study aimed to investigate sperm motility and its changes after preparation as predictors of pregnancy in intrauterine insemination (IUI) cycles. Methods: In total, 297 IUI cycles from January 2012 to December 2017 at a single tertiary hospital were retrospectively analyzed. Patient and cycle characteristics, and sperm motility characteristics before and after processing were compared according to clinical pregnancy or live birth as outcomes. Results: The overall clinical pregnancy rate per cycle was 14.5% (43/297) and the live birth rate was 10.4% (30/289). Patient and cycle characteristics were similar between pregnant and non-pregnant groups. Sperm motility after preparation and the total motile sperm count before and after processing were comparable in terms of pregnancy outcomes. Pre-preparation sperm motility was significantly higher in groups with clinical pregnancy and live birth than in cycles not resulting in pregnancy (71.4%±10.9% vs. 67.2%±11.7%, p=0.020 and 71.6% ±12.6% vs. 67.3%±11.7%, p=0.030, respectively). The change in sperm motility after processing was significantly fewer in the non-pregnant cycles, both when the comparison was conducted by subtraction (post-pre) and division (post/pre). These relationships remained significant after adjusting for the female partner's age, anti-Müllerian hormone level, and number of pre-ovulatory follicles. According to a receiver operating characteristic curve analysis, an initial sperm motility of ≥72.5% was the optimal threshold value for predicting live birth after IUI. Conclusion: Initial sperm motility, rather than the motility of processed sperm or the degree of change after preparation, predicted live birth after IUI procedures.