• Asian-Australasian Journal of Animal Sciences
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• 제20권11호
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• pp.1761-1769
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• 2007

This experiment was conducted to determine the extent to which susceptibility to cortisol-induced follicle shutdown is influenced by fleece phentotype. Twenty Finewool (10 sheep low fibre diameter, low coefficient of fibre diameter-LL and 10 low fibre diameter, high coefficient of variation of fibre diameter-LH) and twenty Strongwool (10 low fibre diameter, low coefficient of variation of fibre diameter-HL and 10 high fibre diameter and high coefficient of variation of fibre diameter-HH) sheep of 9 months of age were individually penned in an animal house and were injected intramuscularly with an aqueous suspension of hydrocortisone acetate at a rate of 1.42 mg/kg body weight for a period of two weeks. Fibre diameter was measured from clipped tattooed patch wool samples. Follicle activity was measured by histological changes in skin biopsies taken weekly. Blood samples were collected at two-week intervals and plasma cortisol measured. Increased plasma cortisol concentration significantly (p<0.05) reduced clean wool production and mean fibre diameter dropped to its lowest level four weeks after commencement and two weeks after the cessation of cortisol injection. Elevation of plasma cortisol concentration significantly (p<0.0001) increased the percentage of inactive follicles two weeks after injection started. High fibre diameter groups (Strongwool sheep; i.e. HL+HH) had significantly (p<0.0001) higher percentage of follicle shutdown than low fibre diameter groups (Finewool sheep; i.e. LL+LH). Average percentage of shutdown follicles for Finewool (LL+LH) and Strongwool (HL+HH) Merino sheep was $9.8{\pm}0.9$ and $13.5{\pm}0.9$ respectively. Shutdown of primary follicles was more pronounced in Finewool than Strongwool sheep. There was no significant effect of coefficient of variation of fibre diameter on propensity to follicle shutdown induced by exogenous cortisol. It is concluded that elevation in plasma cortisol concentration is inhibitory to the normal activity of follicles in Strongwool sheep but that variation in fibre diameter has little or no effect.

• 한국자원식물학회지
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• 제11권3호
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• pp.264-271
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• 1998

This study was conducted to investigate morphological characteristics of Korean local garlic varieties and to define the genetic variability and the correlations amongthe characters associated with yield. The plant height, the leaf sheath diameter, the nubmer of leaves, and bulb weight were significantly increased in the garlic plants from heavier seed bulbs. The proportation of six clove bulbs was more than 60% in Seosan variety and this was not realted with the number of cloves in seed bulb. While more than 70% bulbs in Jeoksung and Danyang varieties cultivated in paddy field were composed of 6 or 7 cloves, majority of the bulbs of Euisung and Danyang varieties cultivated in upland were composed of bulbs with 7 cloves or more. The highest genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were observed in bulb weight. GCV and PCV also showed high value in leaf sheath diameter. Thus, there is a greater scope for selection of these characters. The small difference between PCV and GCV values in plant height indicates that the environmental influence would be limited in this character. High heritability was observed of plant height (56.76%) and bulb weight (45.95%). And the weight per bulb (34.24%) exhibited highest genitic advance followed by leaf sheath diameter (18.8%) and plant height (9.61%), and those would be the ideal characters for selelction.

• 물과 미래
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• 제29권4호
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• pp.223-231
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• 1996

보다 효율적인 관로운영에 필수적인 통수능 변화 및 영향인자 산정을 위하여 국내 도송수강관에 대하여 124개의 Hazen Williams및 Darcy-Weisbach 마찰계수를 실측, 분석하였다. 그 결과 국내 도송수강관은 국외의 마찰계수 변화형태와 유사한 경향을 보이며 관경이 클수록 (Diameter>1100mm) 통수능은 관령에 많은 영향을 받으나 관경이 작을수록 관경과 관령에 동시에 영향을 받는다는 사실을 알았다. 또한 Hazen Williams의 C 값은 외국에 비해 약 5-10 정도 작은 것으로 나타났으며, 조도높이의 성장률은 약 0.41 mm/년으로 관의 통수능이 외국에 비해 빨리 저하한다는 사실이 밝혀져 그 원인 파악 및 통수능 산정기준을 재 검토해야 할 것으로 판단되었다. For the most efficient operation of water mains, 124 head losses in domestic water supply steel mains were measured to provide the values of friction coefficient and the variable affecting the deterioration rate of Hazen Williams' and Darcy-Weisbach's friction coefficient. The experimental results show that pipe age is governing the friction coefficient of large mains (Diameter > 1100 mm). On the other hands, pipe age and pipe diameter are affecting the variation of carrying capacity for small mains (Diameter < 1100 mm). The friction coefficient of water mains in foreign countries is higher than that in Korea by about 5 to 10 in Hazen Williams' C value. The growing rate of roughness height of domestic water main is about 0.41 mm/year which is higher than the average of United States of America. So further study is required to find out what causes the serious deterioration rate.

• 한국지열·수열에너지학회논문집
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• 제17권4호
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• pp.15-27
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• 2021

In this study, the effect of design factors in a pump station on the pressure variations which are the main cause of water hammering has been investigated by numerical simulations. As design factors, the flow rate, Young's modulus, diameter, thickness, roughness coefficient of pipeline are considered. The relationships between the pressure variations and the design factors are analyzed. The results show that the pressure variation increases sensitively with the flow rate and Young's modulus, and increases gradually with the thickness and roughness coefficient of pipe, whereas it decreases with the pipe diameter. The wavelength of the pressure wave becomes longer for a smaller Young's modulus, a smaller pipe thickness and a bigger pipe diameter. These relationships are nondimensionalized, and logarithmic curve-fitted functions are proposed by regression analysis. Most effective factors on the nondimensional pressure variation is Young's modulus. Flow rate, roughness coefficient, relative thickness and pipe diameters are the next impact factors.

• Journal of Forest and Environmental Science
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• 제32권3호
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• pp.280-290
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• 2016

Stem diameter variability is an essential inventory result that provides useful information in forest management decisions. Little has been done to explore the modelling potentials of standard deviation (SDD) and coefficient of variation (CVD) of diameter at breast height (dbh). This study, therefore, was aimed at developing and testing models for predicting SDD and CVD in stands of Pinus caribaea Morelet (pine) in south west Nigeria. Sixty temporary sample plots of size $20m{\times}20m$, ranging between 15 and 37 years were sampled, covering the entire range of pine in south west Nigeria. The dbh (cm), total and merchantable heights (m), number of stems and age of trees were measured within each plot. Basal area ($m^2$), site index (m), relative spacing and percentile positions of dbh at $24^{th}$, $63^{rd}$, $76^{th}$ and $93^{rd}$ (i.e. $P_{24}$, $P_{63}$, $P_{76}$ and $P_{93}$) were computed from measured variables for each plot. Linear mixed model (LMM) was used to test the effects of locations (fixed) and plots (random). Six candidate models (3 for SDD and 3 for CVD), using three categories of explanatory variables (i.e. (i) only stand size measures, (ii) distribution measures, and (iii) combination of i and ii). The best model was chosen based on smaller relative standard error (RSE), prediction residual sum of squares (PRESS), corrected Akaike Information Criterion ($AIC_c$) and larger coefficient of determination ($R^2$). The results of the LMM indicated that location and plot effects were not significant. The CVD and SDD models having only measures of percentiles (i.e. $P_{24}$ and $P_{93}$) as predictors produced better predictions than others. However, CVD model produced the overall best predictions, because of the lower RSE and stability in measuring variability across different stand developments. The results demonstrate the potentials of CVD in modelling stem diameter variability in relationship with percentiles variables.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.297-302
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• 2000

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structure, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection is developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect in internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. finally a prediction model of the coefficient of flow convection is proposed using experimental results from the developed device. According to the proposed prediction model, the coefficient of flow convection increases with increase in flow velocity and decreases with increase in pipe diameter and thickness. Also, the coefficient of flow convection is largely affected by the type of pipe materials.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.459-464
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• 2009

가압 삼상슬러리 기포탑에서 탑의 직경변화에 따라 기체-액체 물질전달 특성을 고찰하였다. 기체 유속, 운전압력, 액체점도, 슬러리상에서 고체입자의 양 그리고 탑의 직경이 기체-액체 부피물질전달계수에 미치는 영향을 결정하였다. 운전변수들이 물질전달계수에 미치는 영향은 기포탑의 직경이 변화함에 따라 다르게 나타났다. 기체-액체 부피물질전달계수는 기체유속이나 운전압력이 증가함에 따라 증가하였으나, 기포탑의 직경, 액체의 점도 그리고 슬러리상에 고체입자의 농도가 증가함에 따라 감소하였다. 기체-액체 물질전달계수가 기체유속 증가에 따라 증가하는 경향과 액체의 점도가 증가함에 따라 감소하는 경향은 기포탑의 직경이 증가함에 따라 점차 감소하였다. 그러나, 운전압력과 슬러리상에 포함된 고체입자의 농도가 기체-액체 물질전달계수에 미치는 영향은 기포탑의 직경이 변화함에 따라 큰 영향을 받지 않았다. 본 연구의 실험범위에서 기체-액체 물질전달계수는 다음 식과 같은 실험변수의 상관식으로 나타낼 수 있었다. $k_La=0.02D^{-0.26}U_G^{0.28}P^{0.43}{\mu}_L^{-0.04}S_c^{-0.35}$.

• 한국염색가공학회지
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• 제9권5호
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• pp.1-9
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• 1997

In the single yarn spinning process by the ring spinning system, the finer the fineness of yarn and the lower the twist coefficient, the lower the breaking strength and breaking elongation. The change of yarn specific volume to yarn number agreed with Peirce's formula in the range of Ne 50 to 70, but above that range the values of the experiment are higher than that of the formula. The change of diameter of yarn to the reciprocal of the square root of yarn number agreed with Peirce's formula in the range of under 0.14, but above that value the values of the experiment are higher than that of the formula. In breaking strength variation according to twist constant of single yarn, as the twist coefficient increased, breaking strength increased. At 5.8∼6.0 of twist coefficient the maximum breaking strength was shown, but above that value breaking strength decreased. Breaking elongation also showed a similar tendency. But at 6.0∼6.5 of twist coefficient the maximum breaking elongation was shown. Also spinning tension increased as twist coefficient increased. Twist coefficient, breaking strength and breaking elongation according to the number of coils stayed almost the same. Yarn spinning tension according to the number of coils at the maximum of diameter was the lowest value. The speed of the traveller at the maximum of diameter was the highest value.

• 한국구조물진단유지관리공학회 논문집
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• 제27권1호
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• pp.64-70
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• 2023

본 연구에서는 1.04배 드릴비트 직경 및 1.02배 드릴비트 직경 시 앵커의 신뢰성시험을 수행하였다. 각 변수별 시험을 통해 앵커의 표준편차 및 변동계수를 검토하였고, 기준시험 결과와 비교 평가하였다. 1.04배 드릴비트 직경을 가진 M12 및 M16 앵커의 신뢰성시험결과, 극한 인장하중 허용기준 변동계수 값인 20% 이내의 값을 나타내어 시험기준을 만족하였다. 또한, 1.04배 드릴비트 직경을 가진 앵커의 성능은 기준시험 대비 M12 앵커는 약 74%, M16 앵커는 약 55% 정도로 나타나 앵커의 내력이 다소 부족한 성능을 나타냈지만, 설계강도 대비 약 253% 및 210%로 나타나 1.04배 드릴비트 직경에 설치된 앵커의 인발성능은 충분히 확보하고 있음을 알 수 있었다. 1.02배 드릴비트 직경을 가진 M12 및 M16 앵커의 신뢰성시험결과, 극한인장하중 허용기준 변동계수 값인 20% 이내의 값을 나타내어 시험기준을 만족하였다. 또한, 1.02배 드릴비트 직경을 가진 앵커의 성능은 기준시험 대비 M12 앵커는 약 48%, M16 앵커는 약 53% 정도로 나타나 다소 부족한 성능을 나타냈지만, 설계강도 대비 약 136% 및 168% 로 나타나 1.02배 드릴비트 직경에 설치된 앵커의 인발성능은 충분히 확보하고 있음을 알 수 있었다.

• 대한기계학회논문집B
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• 제32권1호
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• pp.39-46
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• 2008

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk.