• 한국수자원학회논문집
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• 제43권3호
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• pp.265-273
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• 2010

본 연구에서는 기존의 수위만을 고려하여 작성된 수위-유량관계곡선식을 개선하기 위하여 경심, 하상경사, 수심 등 비교적 쉽게 취득할 수 있는 하천의 수리특성인자를 활용하여 유량을 산정할 수 있는 방법을 제안하였다. 알버타대학에서 제공된 보고서 내용 중 수리실험실 및 자연하천의 수리자료를 활용하여 평균유속 공식인 Manning식과 Chezy식으로부터 하천의 수리학적 특성이 반영된 조도계수 n값과 C값을 산정하고 이를 토대로 유량을 산정하였다. 제안된 유량산정 방법은 실측치에 근사하여 정확도가 개선됨을 확인하였으며 기존의 수위-유량관계곡선식에서 추정된 유량과 비교하고 그 적용성을 검토하였다.

• 대한기계학회논문집A
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• 제33권2호
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• pp.99-107
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• 2009

This study produced a design curve and fatigue limit for a variation in volume ratio and reduction ratio of TiNi/Al composites. In many cases, stress-life curve does not indicate fatigue limit, so it was presented by probabilistic-stress-life curve. Goodman diagram was used to analyze the fatigue strength of materials with a finite life determined by repeated load and the fatigue strength of endurance limit with an infinite life. The fatigue experiment was conducted using the scenk-type plane bending specimen in same shape. The result of the fatigue test, which had been conducted under consistent stress amplitude, was examined. (i) The optimal condition for TiNi/Al in accordance with hot pressing (ii) Impacts of fatigue limit caused by a variation in reduction ratio and volume ratio of TiNi/Al composites (iii) Probability distribution for fatigue limit of TiNi/Al2024 and TiNi/Al6061.

• 한국안전학회지
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• 제21권6호
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• pp.20-25
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• 2006

In the design of class 1 components to apply ASME code section III NB, a fatigue is considered as one of the important failure mechanisms. Fatigue analysis procedure and standard fatigue design curve(S-N curve) is suggested in ASME code, which had to be performed to meet the integrity of components at the design step. As the plant life extension for operating power plants and the long-lived plant design, however, are being progressed, the fact which the existing ASME fatigue design curve can not consider fatigue effects sufficiently comes to the fore. To find the technical solution for these problems, a number of researches and discussion are continued up to now. In this study, the detailed fatigue analyses using the 3 dimensional modeling for the fatigue-weakened components were performed to develop the optimized fatigue analysis procedure and their results are compared with other reference solutions.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.129-135
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• 1997

Previous studies has shown that the curve of low-cycle fatigue life was not expressed with the single line subjected to Manson-Coffin's law type and bent to short life in low ${\Delta}{\varepsilon}_p$ region. The main cause of this phenomenon has been considered that the localization of plastic strain in the crack initiation process fosters the crack initiation. In this study, the low-cycle fatigue life was investigated for each specimens omitted crack initiation process and it was found that fatigue life curve in log(${\Delta}{\varepsilon}_p$)-log($N_f$)was bent in low ${\Delta}{\varepsilon}_p$ region as ever. Therefore, the main cause of appearance of knee point in fatigue life curve is not found in the crack initiation process but in the crack propagation process. In the crack propagation process, the localization of the plastic strain in the vicinity of crack tip and the influence of test environment on the crack propagation rate were observed and these inclinations were more remarkable in low ${\Delta}{\varepsilon}_p$ region. Hence, it was concluded that these two phenomena in the crack propagation process were proved to the main cause which accelerates the crack propagation in low ${\Delta}{\varepsilon}_p$ region and bent the fatigue life curve in result.

• 한국가스학회지
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• 제14권5호
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• pp.19-25
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• 2010

본 연구에서는 o-xylene+n-pentanol 및 m-xylene+n-hexanol 계의 인화점을 Tag 개방식 장치(ASTM D1310-86)를 이용하여 측정하였다. 실험값은 Raoult의 법칙, van Laar 및 Wilson 식을 이용한 계산된 값들과 비교하였다. 그 결과, 최적화법에 의한 예측값이 Rauolt의 법칙에 의한 계산 보다 실험값에 더욱 근접하였다. 또한, van Laar 식을 사용한 최적화법이 Wilson 식에 의한 최적화법 보다 실험값에 대한 모사성이 우수하였다.

• International Journal of Industrial Entomology and Biomaterials
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• 제9권2호
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• pp.273-277
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• 2004

Variation in the size of the silk filament will determine the uniformity and quality of the silk reeled. In the present study, an attempt has been made to study the filament size variation in 6 multivoltine parental breeds and 9 multivoltine ${\times}$ bivoltine hybrids in all three seasons of a year. All multivoltine breeds and multivoltine ${\times}$ bivoltine hybrids showed variation in filament size throughout its length from the outer layer to inner layer. Results of the present study indicated that the size of the filament decreased from outer to inner layer. The decrease in filament size was sudden in some breeds/hybrids whereas it was gradual in other. Relationship between filament length to that of slope, average filament size to slope, and maximum filament size to slope was determined based on regression analysis. Regression analysis revealed significant positive correlation between slope vs average filament length (r=0.92$^{**}$) in multivoltine${\times}$bivoltine hybrids. Among parental breeds, 96C showed lowest slope of the curve (b-value: -0.00428) and 96A showed highest slope of the curve (b-value: -0.00269). Among 9 hybrids, PM${\times}$N $B_4$ $D_2$ recorded lowest slope value (b-value: -0.00328) and BL24${\times}$N $B_4$ $D_2$ showed highest value for slope of the curve (b-value: -0.00234). The breed 96C, which showed lowest slope value can be utilized for future breeding programmes to breed strains with less size deviation. Three multivoltine${\times}$bivoltine hybrids viz., PM${\times}$N $B_4$ $D_2$, 96E${\times}$CSR19 and BL67${\times}$CS $R_{101}$ , which showed less slope values (b-values: -0.00328, -0.00300 and -0.00297 respectively) can be utilized for commercial exploitation to produce uniform silk.k.

• Asian-Australasian Journal of Animal Sciences
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• 제27권9호
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• pp.1250-1253
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• 2014

The objective of this study was to estimate the parameters of Gompertz growth curves with the measurements of body conformation, real-time ultrasound longissimus dorsi muscle area (LMA) and backfat thickness (BFT) in Hanwoo cows. The Hanwoo cows (n = 3,373) were born in 97 Hanwoo commercial farms in the 17 cities or counties of Gyeongbuk province, Korea, between 2000 and 2007. A total of 5,504 ultrasound measurements were collected for the cows at the age of 13 to 165 months in 2007 and 2008. Wither height (HW), rump height (HR), the horizontal distance between the top of the hips (WH), and girth of chest (GC) were also measured. Analysis of variance was conducted to investigate variables affecting LMA and BFT. The effect of farm nested in location was included in the statistical model, as well as the effects of HW, HR, WH, and GC as covariates. All of the effects were significant in the analysis of variance for LMA and BFT (p<0.01), except for the HR effect for LMA. The two ultrasound measures and the four body conformation traits were fitted to a Gompertz growth curve function to estimate parameters. Upper asymptotic weights were estimated as $54.0cm^2$, 7.67 mm, 125.6 cm, 126.4 cm, 29.3 cm, and 184.1 cm, for LMA, BFT, HW, HR, WH, and GC, respectively. Results of ultrasound measurements showed that Hanwoo cows had smaller LMA and greater BFT than other western cattle breeds, suggesting that care must be taken to select for thick BFT rather than an increase of only beef yield. More ultrasound records per cow are needed to get accurate estimates of growth curve, which, thus, helps producers select animals with high accuracy.

• 한국항공우주학회지
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• 제36권6호
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• pp.541-549
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• 2008

피로해석은 반복하중 하에서의 항공우주 구조물에 대한 구조적 파괴를 예방하기 위해 수행된다. 본 논문에서는 틸트로터형 무인 항공기에 대하여 피로수명에 대한 평가를 하였다. 먼저 틸트로터형 무인항공기의 기동에 맞는 하중 스펙트럼을 생성해 내었으며, F.C.L. 부품중 하나인 플랩퍼론 연결부위에 대하여 피로해석을 수행 하였다. 틸트로터형 무인항공기는 크게 두 가지 기동 형태로 나눌 수 있는데, 이 착륙시의 헬리콥터 형태와 순항시의 고정익 형태가 되겠다. 전체적인 피로하중 스펙트럼을 만들기 위해서 헬리콥터 형태에는 FELIX를, 고정익 형태에서는 TWIST를 사용하였다. 한편으로는, S-N 실험점이 해석에 사용될 때 재료수명의 전 영역에 대한 S-N 회귀식을 얻기 위하여 크리깅 메타 모델이 사용되었다. 그리고 최소 자승법을 이용한 이차 회귀식에 대한 S-N 커브 역시 생성하였다. 더욱이 이 커브들이 갖고 있는 정확도를 측정하기 위하여 결정 계수법을 사용하였다. 마지막으로는 플랩퍼론 연결 부위에 대한 피로수명 결과를 MSC. Fatigue와 비교하였다.

• 대한전자공학회논문지
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• 제18권1호
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• pp.16-24
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• 1981

Delay-lock loop(DLL)는 상단관련이 있는 두 파형 사이의 지연차이를 추적하는한 최적장치이다. 본 논문에서는 지연시간이 n- 로 확장된 한 DLL의 구조와 동기상실 주파수등 저역주파수대의 성능이 해석되었다. 본 DLL은 correlator와 개선된 PN 신호장치로 구성되었으며,상관 특성은 확장된 S-커브의 형태를 가지고 있다. 잡음이 크더라도 추적범위와 초기동기시간이 좋은 특성을 가지고 있다. 3- DLL을 1- DLL과 비교하면 직렬동기방식에서 초기동기시간이 3배나 빠르며, doppler shift에 대한 저항이 2배나 큰 것으로 나타났다.

• 한국환경보건학회지
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• 제22권3호
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• pp.49-55
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• 1996

Water parsley(Oenanthe javanica(Blume) DC) was raised with varying population density(S) in the laboratory aquarium unit to determine the growth equation. The population density was measure after 7 days. The resultant growth curve was well fit to the equation 1/S = A+B (1/S0) with a high correlation coefficient ($R^2$ = 0.999). The maximum specific absorption rate was $9.011 \times 10^{-5}$ kg $NO_x-N/kg$ water parsley$\cdot$day and $1.31 \times 10^{-5}$ kg $PO_4-P/kg$ water parsley$\cdot$day when the average population density was $2.62 kg/m^2$. The relationship between population density and nutrient absorption rate, the absorption rate of $NO_x-N$ was 5.04~5.24 mg/l$\cdot$day when the population density was $7.51~10.0 $mg/m^2\cdot day$ and the absorption rate of $PO_4-P$ was 0.56~0.78 mg/l$\cdot$day when the population density was 5.02~10.0 $kg/m^2\cdot day$. Taking into account the nutrient absorption rate and growth rate, the population density between $7.0 kg/m^2\cdot day$ and $8.0 kg/m^2 \cdot day$ was selected. The removal rate of nutrient was investigated after 7 days culture. Removal rate of $NO_x-N$ was 95.6~99.95% with initial concentration of 35 mg $NO_x-N/l$, and the removal rate of $PO_4-P$ was also high, indicating 80.24~98.9% with initial concentration of 5.95 mg $PO_x-P/l$.