• Structural Engineering and Mechanics
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• 제14권2호
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• pp.209-221
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• 2002

In this paper a fracture criterion is proposed for cracked cylindrical samples of high-strength prestressing steels of different yield strength. The surface crack is assumed to be semi-elliptical, a geometry very adequate to model sharp defects produced by any subcritical mechanism of cracking: mechanical fatigue, stress-corrosion cracking, hydrogen embrittlement or corrosion fatigue. Two fracture criteria with different meanings are considered: a global (energetic) criterion based on the energy release rate G, and a local (stress) criterion based on the stress intensity factor $K_I$. The advantages and disadvantages of both criteria for engineering design are discussed in this paper on the basis of many experimental results of fracture tests on cracked wires of high-strength prestressing steels of different yield strength and with different degrees of strength anisotropy.

• Journal of Animal Science and Technology
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• 제59권2호
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• pp.3.1-3.7
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• 2017

Background: The modelling of lactation curve provides guidelines in formulating farm managerial practices in dairy cows. The aim of the present study was to determine the suitable non-linear model which most accurately fitted to lactation curves of five lactations in 134 Gir crossbred cows reared in Research-CumDevelopment Project (RCDP) on Cattle farm, MPKV (Maharashtra). Four models viz. gamma-type function, quadratic model, mixed log function and Wilmink model were fitted to each lactation separately and then compared on the basis of goodness of fit measures viz. adjusted $R^2$, root mean square error (RMSE), Akaike's Informaion Criteria (AIC) and Bayesian Information Criteria (BIC). Results: In general, highest milk yield was observed in fourth lactation whereas it was lowest in first lactation. Among the models investigated, mixed log function and gamma-type function provided best fit of the lactation curve of first and remaining lactations, respectively. Quadratic model gave least fit to lactation curve in almost all lactations. Peak yield was observed as highest and lowest in fourth and first lactation, respectively. Further, first lactation showed highest persistency but relatively higher time to achieve peak yield than other lactations. Conclusion: Lactation curve modelling using gamma-type function may be helpful to setting the management strategies at farm level, however, modelling must be optimized regularly before implementing them to enhance productivity in Gir crossbred cows.

• 소성∙가공
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• 제11권1호
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• pp.69-74
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• 2002

In addition to lightweight and moldable characteristics, polymeric foams possess an excellent energy absorbing capability that can be utilize for a wide range of commercial applications, especially in the crashworthiness of the automobiles. The purpose of the present study is to develop experimental methodology to characterize the pressure dependent yield behavior of the energy absorbing polymeric foams. For the compression test in a triaxial stress sate, a specially designed device was placed in a hydraulic press to produce and control oil pressure. For the test material, the polyurethane foams of two different densities were used. The displacement of the specimen, the load subjected to the specimen, and oil pressure applied to the specimen were measured and controlled. Stress strain curves and yield stresses for the four different oil pressure were obtained. It was found from the present experiments that the polyurethane foams exhibited significant increases in yield stress with applied pressure or mean normal stress. Based on this observation, a yield criteria which included the effect of the stress invariant were established for the polymeric foams. The obtained experimental constants which constituted the pressure-dependent yield criterion were verified.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.81-86
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• 2001

The concrete bridge decks are in need of replacement and rehabilitation due to decreasing load carrying capacity. In this study, to propose a strengthening technique that improves usability and structural performance of the bridge deck and to propose an efficient strengthening design technique which satisfies both the strength End serviceability of the bridge deck, this paper shows the failure characteristics of the strengthened bridge decks and proposes an empirical yield criterion. Therefore, strengthening efficiency was proposed based on the experiment and yield line analysis result. The yield line theory which adopts the modified criteria of Johansen is considered to predict the ultimate strength about all strengthening material(Carbon Fiber Sheet, Carbon Fiber Rod, Grid Type Carbon Fiber).

• 품질경영학회지
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• 제32권4호
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• pp.184-195
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• 2004

Current companies 집중 on how to operate and select projects to achieve the best result. 6sigma projects are chosen in the best suitable concept, which are solved by the 6Sigma experts according to the priority. And every project has to be launched not the view of individual management factors but the total factors, Big Y. Therefore, a process needs to be treated to connect the vital few factors in various processes to improve the yield, which is the main performance criteria in a manufacturing industry This report is to make the total optimization through the Vital-Few mapping between quality characteristics and process factors in a manufacturing line. Accordingly, it means to secure lower variance by making the CTP(Critical To Process) optimization and finally to improve the yield.

• Plant Resources
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• 제3권3호
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• pp.206-210
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• 2000

A total of 20 soybean recommended varieties which were developed until late 1980's in Korea was evaluated at Suwon. Comprehensive evaluation and correlation analysis were conducted on the agronomic characters. Great variations were found in these genotypes for branch number, pod number, and grain yield per plant. The variation in number of pods/plant ranged from 53 to 164, and in grain yield from 25.9 to 68.8 g. The coefficient of variation for most of the characters had a wide range. In correlation coefficient, grain yield per plant showed a positive phenotypic association with weight of pods, pod number of branches, and weight of stem. Multiple regression analysis was done to formulate selection criteria. It indicated that stout and medium-stature genotypes with more branches, resulting in varieties with more pods per plant but with medium-size seeds are available to obtain high-yielding varieties.

• 한국유기농업학회지
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• 제22권4호
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• pp.841-854
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• 2014

This study aimed to analyze the selection criteria and priority settings for solid culture medium used in hydroponic crop production in farm households. Expert brain storming was carried out to extract solid culture medium selection criteria for hydroponic farming. As a result, 3 criteria of economy (cost), productivity, and environment, and 9 factors were extracted. A questionnaire survey of hydroponic farm households was conducted in Gyeonggi, Gangwon, and Chooncheong provinces. AHP analysis of the hydroponic solid culture medium selection criteria identified productivity as the most important criterion, chosen by 58.7% of the respondents, followed by economy (28.4%) and environment (12.9%). The 9 factors were rated by the respondents in the following decreasing order of importance: 1, crop yield (28.3%); 2, pest occurrence (18.5%); 3, maintenance/management costs (12.0%); 4, convenience of maintenance/management (13.4%); 5, initial investment cost (11.6%); 6, material energy consumption (6.5%); 7, waste recyclability (4.0%); 8, waste disposal costs (3.4%); and 9 environmental emissions (1.81%). These results imply that hydroponic farm households consider cultivation-related quality factors more important than economic factors, such as price of culture medium or installation cost.

• 대한토목학회논문집
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• 제31권4D호
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• pp.571-576
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• 2011

일반적으로 도로구조물들은 포화상태라는 가정 하에 설계되고 있으나 실제 도로구조물의 재료인 입상지반재료는 대부분 불포화 상태에 존재하고 있다. 이러한 부분을 반영하기 위하여 본 논문에서는 다져진 입상지반재료를 대상으로 삼축압축시험과 함수특성곡선 시험 결과를 활용하여 다양한 조건에서의 불포화 전단강도를 추정하였다. 이를 바탕으로 비선형 모형을 활용한 2차원 유한요소해석을 실시하고 Mohr-Coulomb항복조건을 통하여 항복하중을 규명하였다. 또한, 입상재료의 항복하중에 대한 도로구조물 표층두께의 변화에 따른 영향을 확인하였다. 해석 결과 입상지반재료의 불포화토 이론을 고려하여 포장 혹은 비포장 도로의 지지력을 예측할 수 있음을 보여주고 있다.

• 한국도로학회논문집
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• 제18권3호
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• pp.21-32
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• 2016

PURPOSES : In this paper, the analytical solutions suggested to simulate the behavior of rheological fluids were rigorously re-derived and investigated for fixed conditions to evaluate the applicability for the solutions on a mini-cone slump test of cement paste. The selected solutions with proper boundary conditions can be used as reference solutions to evaluate the performance of numerical simulation approaches, such as the discrete element method. METHODS : The slump, height, and spread radius for the given boundary and yield stress conditions that are determined by five different analytical solutions are compared. RESULTS : The analytical solution based on fluid mechanics for pure shear flow shows similar results to that for intermediate flow at low yield stresses. The fluid mechanics-based analytical solution resulted in a very similar trend to the geometry-based analytical solution. However, it showed a higher slump at high yield stress and lower slump at low yield stress ranges than the geometry-based analytical model. The analytical solution based on the mini-cone geometry was not significantly affected by the yield criteria, such as von Mises and Tresca. CONCLUSIONS : Even though differences among the analytical solutions in terms of slump and spread radius existed, the difference can be considered insignificant when the solutions were used as reference to evaluate the appropriateness of numerical approaches, such as the discrete element method.

• Applied Biological Chemistry
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• 제16권3호
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• pp.137-145
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• 1973

수량(收量) 등급별(等級別) 영양기준설정(榮養基準設定)을 위하여 전국적(全國的)으로 실시된 수도삼요소시험중(水稻三要素試驗中) 3 개년간(個年間)$(1967{\sim}1969)$의 고(藁) 또는 수분석결과(穗分析結果)에 의(依)하여 수량등급별(收量等級別)로 생육시기별(生育時期別) N,P,K 및 Si의 함량(含量)을 조사(調査)하였다. 수량증가(收量增加)에 따라 양분농도(養分濃度)가 증가(增加)하는 경향은 N>P>K>Si의 순(順)으로 감소(減少)하였다. 그 경향(傾向)은 양분(養分)에 따라서 해에 따라 생육시기별(生育時期別) 보다는 정조수량등급(正租收量等級)에 양분(養分)의 농도변화(濃度變化)가 더 밀접(密接)한 관계(關係)를 보였다.