• 대한조선학회논문집
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• 제57권2호
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• pp.80-87
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• 2020

As the Arctic sea ice decreases due to various reasons such as global warming, the demand for ships and offshore structures operating in the Arctic region is steadily increasing. In the case of sea ice, the anisotropy is caused by the uncertainty inside the material. For most of the research, nevertheless, estimating the ice load has been treated deterministically. With regard to this, in this paper, a four-point bending strength analysis of an ice specimen was attempted using a stochastic finite element method. First, spatial distribution of the material properties used in the yield criterion was assumed to be a multivariate Gaussian random field. After that, a direct method, which is a sort of stochastic finite element method, and a sensitivity method using the sensitivity of response for random variables were proposed for calculating the probabilistic distribution of ice specimen strength. A parametric study was conducted with different mean vectors and correlation lengths for each material property used in the above procedure. The calculation time was about ten seconds for the direct method and about three minutes for the sensitivity methods. As the cohesion and correlation length increased, the mean value of the critical load and the standard deviation increased. On the contrary, they decreased as the friction angle increased. Also, in all cases, the direct and sensitivity methods yielded very similar results.

• Structural Engineering and Mechanics
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• 제45권5호
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• pp.595-611
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• 2013

This paper aims to compare three collocation point methods associated with the odd order stochastic response surface method (SRSM) in a systematical and quantitative way. The SRSM with the Hermite polynomial chaos is briefly introduced first. Then, three collocation point methods, namely the point method, the root method and the without origin method underlying the odd order SRSMs are highlighted. Three examples are presented to demonstrate the accuracy and efficiency of the three methods. The results indicate that the condition that the Hermite polynomial information matrix evaluated at the collocation points has a full rank should be satisfied to yield reliability results with a sufficient accuracy. The point method and the without origin method are much more efficient than the root method, especially for the reliability problems involving a large number of random variables or requiring complex finite element analysis. The without origin method can also produce sufficiently accurate reliability results in comparison with the point and root methods. Therefore, the origin often used as a collocation point is not absolutely necessary. The odd order SRSMs with the point method and the without origin method are recommended for the reliability analysis due to their computational accuracy and efficiency. The order of SRSM has a significant influence on the results associated with the three collocation point methods. For normal random variables, the SRSM with an order equaling or exceeding the order of a performance function can produce reliability results with a sufficient accuracy. The order of SRSM should significantly exceed the order of the performance function involving strongly non-normal random variables.

• 폴리머
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• 제38권6호
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• pp.714-719
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• 2014

라이신과 글루코오스에서부터 제조된 카프로락탐과 모폴리논을 음이온 개환중합법을 이용하여 나일론 6-모폴리논 랜덤 공중합체를 합성함으로써 바이오매스 기반의 새로운 나일론을 제조할 수 있었으며 또한 친수성이 향상된 나일론 6을 제조할 수 있었다. 중합 조건을 적절하게 조절함으로써, 점도평균분자량 30000 g/mol과 수율 80%의 공중합체를 제조할 수 있었다. 모폴리논을 공중합 단량체로 사용함으로써 나일론 6의 친수성을 높게 향상시킬 수 있었다. 제조된 나일론 6-모폴리논 랜덤공중합체를 시차주사 열량계(DSC), 열중량 분석기(TGA), X-선 회절분석기(XRD), 점도계, 접촉각 측정기와 같은 분석방법으로 그 특성을 분석하였다.

• Macromolecular Research
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• 제11권2호
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• pp.80-86
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• 2003

The polymerization of a cyclopolymerizable disubstituted dipropargyl ether, his(3-trimethylsilyl-2-propynyl)ether (BTPE), was attempted by various transition metal catalysts. The yield for the polymerization of BTPE was generally low, which is possibly due to the steric hindrance of bulky substituents. In general, the catalytic activities of Mo-based catalysts were found to be greater than those of W-based catalysts. The highest yield was obtained when the MoCl$_{5}$,-EtAlCl$_2$(1:2) catalyst system was used. The copolymerization of BTPE and diethyl dipropargylmalonate yielded a random copolymer with conjugated polymer backbone. However the polymers were partially desilylated, depending on the reaction conditions. The thermal and morphological properties of the resulting polymers were also discussed.d.

• Animal cells and systems
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• 제3권1호
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• pp.73-78
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• 1999

Although there are several methods for the preparation of mitochondrial DNA (mtDNA) from mammalian tissues, most are relatively long ultracentrifugation or manipulations by a small-scale method. We escribed a rapid method for large-scale extraction of mtDNA from human placental and horse liver tissues. The method is based on the preparation and homogenization of tissues, urification of crude mitochondria by differential centrifugations and isolation of mtDNA by alkaline Iysis. It was improved from Pre-existing methods by replacing some steps with simpler ones and discarding many others. This method gives a high yield of pure mtDNA(approximately 1-5mg from one placenta; ca. 400-600 g wet weight), depending on its sources (fresh tissue gave better results than frozen one). The resulting mtDNA indicated that this method can yield mtDNA in sufficient purity and quantity to identify the direct restriction analysis on agarose gel, random-primed labeling as a probe, and end labeling. Therefore, the method is ideal for obtaining good mtDNA samples to conduct routine restriction fragment length polymorphism (RFLP) analyses of natural populations for genetic studies.

• The Journal of Asian Finance, Economics and Business
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• 제8권11호
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• pp.223-234
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• 2021

This study aims to examine whether operating cash flows influence banks' financial stability in Pakistan. The study employed annual panel data collected from annual reports of 20 commercial banks listed on the Pakistan Stock Exchange for the year 2011 to 2019. Free cash flow yield was taken as the dependent variable while cash flow ratio was selected as the independent variable, and net interest margin, income diversification, asset quality, financial leverage, the cost to income ratio, advance net of provisions to total assets ratio, capital ratio, financial performance, breakup value per share and bank size were taken as control variables. The study performed ordinary least square technique, random and fixed effects models, Hausman test, Lagrange multiplier test, descriptive and correlation analysis. Results showed that operating cash flows and net interest margin significantly and positively influenced banks' financial stability while the cost to income ratio and advances net of provisions to total assets ratio significantly and negatively associated with banks' financial stability. To improve financial stability, banks should become more cost-effective and enhance their liquidity levels by lowering lending activities. In the future, it would be useful to compare commercial and investment banks, also Islamic and conventional banks in the same research setting.

• Journal of Animal Science and Technology
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• 제48권2호
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• pp.143-150
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• 2006

본 연구는 현재 유전평가에 사용하는 모델보다 많은 장점을 지니고 있는 임의회귀 검정일 모형(Random regression test-day model)을 이용할 때 마지막 세대의 불완전한 검정기록이 유전능력에 어떤 영향을 주는지 알아보고자 실시하였다.이용된 재료는 유우군능력검정사업을 통하여 수집된 2000년 1월부터 2005년 6월까지의 825,157개의 초산의 검정일 자료를 이용하였으며, 유전모수와 종모우의 육종가 추정은 REMLF90, BLUPF90을 이용하였다.

• 생명과학회지
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• 제29권8호
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• pp.916-921
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• 2019

본 연구는 내열성, 에탄올내성 및 에탄올생산성이 향상된 새로운 생물시스템을 육종하기 위해 DNA 복제 시 교정기능이 결여된 변이주(proofreading-deficient mutant)를 이용한 무작위적 돌연변이(random mutagenesis)를 유도하였다. DNA polymerase ${\delta}$와 ${\varepsilon}$의 catalytic subunit를 코드하고 있는 POL3와 POL2 유전자가 변이된 AMY410 균주(pol2-4)와 AMY126 균주(pol3-01)를 이용하여 $30^{\circ}C$, $38^{\circ}C$, $48^{\circ}C$에서 내열성 변이를 유도하였다. AMY410 균주와 AMY126 균주는 $38^{\circ}C$ 이상의 온도에서는 거의 자랄 수가 없기 때문에, 배양 온도를 점차 높여가며 변이를 유도한 결과, $40^{\circ}C$에서도 잘 자라는 AMY410-Ht와 AMY126-Ht 균주를 선별할 수 있었다. 또한 AMY410-Ht와 AMY126-Ht 균주의 에탄올내성을 추가로 획득하기 위해 6%와 8% 에탄올이 함유된 배지에서 변이를 유도하였고, 8% 에탄올 농도에서 내성을 가지는 AMY410-HEt 균주와 AMY126-HEt 균주를 분리하였다. 특히 AMY126-HEt 균주는 10% 에탄올 농도에서도 내성을 가짐을 확인할 수 있었다. AMY126-HEt 균주의 에탄올생산성의 증가를 위한 변이는 고농도 당(glucose)의 첨가에 의해 유도되었고, 50 g/l의 고농도 glucose를 함유한 배지에서 24.7 g/l의 에탄올(95% 이론적 전환수율)을 생산할 수 있는 고효율 에탄올 생산균주(AMY126-HEt3)를 최종 분리하였다. 따라서, 본 연구를 통해서 교정기능이 결여된 균주(proofreading-deficient mutant)를 사용한 돌연변이법으로 산업적으로 유용한 다양한 형질을 가진 생물시스템의 구축이 가능함을 확인하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제30권8호
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• pp.1105-1116
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• 2017

Objective: A meta-analysis was conducted to evaluate the effects of supplemental fat containing saturated free fatty acids (FA) on milk performance of Holstein dairy cows. Methods: A database was developed from 21 studies published between 1991 and 2016 that included 502 dairy cows and a total of 29 to 30 comparisons between dietary treatment and control without fat supplementation. Only saturated free FA (>80% of total FA) was considered as the supplemental fat. Concentration of the supplemental fat was not higher than 3.5% of diet dry matter (DM). Dairy cows were offered total mixed ration, and fed individually. Statistical analysis was conducted using random- or mixed-effects models with Metafor package in R. Results: Sub-group analysis showed that there were no differences in studies between randomized block design and Latin square/crossover design for dry matter intake (DMI) and milk production responses to the supplemental fat (all response variables, $p{\geq}0.344$). The supplemental fat across all studies improved milk yield, milk fat concentration and yield, and milk protein yield by 1.684 kg/d (p<0.001), 0.095 percent unit (p = 0.003), 0.072 kg/d (p<0.001), and 0.036 kg/d (p<0.001), respectively, but tended to decrease milk protein concentration (mean difference = -0.022 percent unit; p = 0.063) while DMI (mean difference = 0.061 kg/d; p = 0.768) remained unchanged. The assessment of heterogeneity suggested that no substantial heterogeneity occurred among all studies for DMI and milk production responses to the supplemental fat (all response variables, $I^2{\leq}24.1%$; $p{\geq}0.166$). Conclusion: The effects of saturated free FA were quantitatively evaluated. Higher milk production and yields of milk fat and protein, with DMI remaining unchanged, indicated that saturated free FA, supplemented at ${\leq}3.5%$ dietary DM from commercially available fat sources, likely improved the efficiency of milk production. Nevertheless, more studies are needed to assess the variation of production responses to different saturated free FA, either C16:0 or C18:0 alone, or in combination with potentially optimal ratio, when supplemented in dairy cow diets.

• Asian-Australasian Journal of Animal Sciences
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• 제17권1호
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• pp.102-108
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• 2004

The present experiment was conducted to assess the efficacy of methionine hydroxy analogue free fatty acid (MHAFA) in comparison to DL-methionine (DL-Met) utilizing day-old commercial broiler chicks (n=300). The chicks were randomly distributed into 30 groups of 10 chicks each. Three dietary treatments, viz. D1-maize-soybean meal based basal diet (Control), D2- control diet supplemented with DL- methionine to meet its requirements and D3-control supplemented with MHA-FA @ 1.54 times of DL-methionine used in D2, were formulated. Each dietary treatment was offered to 10 replicated groups of chicks following completely random design (CRD). The chicks fed on supplemental DL-Met had significantly higher (p<0.01) gain in body weight, followed by MHA-FA group and control during 0-3 weeks of age. During overall growth period (0-6 weeks), chicks in DL-Met and MHA-FA groups grew better (p<0.01) than those in control. Feed conversion ratio (FCR) improved (p<0.01) on supplementation of either DL- Met or MHA-FA in the basal (Control) diet during 0-3 weeks of age. The FCR for overall period, however, did not differ statistically (p>0.05) amongst the treatments. The eviscerated yields emanated from diets with DL-Met or MHA-FA were higher (p<0.01) than that in Control. Abdominal fat pad was also more (p<0.01) in broilers fed control diet than in DL-Met or MHA-FA supplemented group. Breast yield was higher (p<0.05) in MHA-FA fed broilers than those fed DL-methionine supplemented or un-supplemented diets. The efficacy of MHA-FA in comparison to DL-Met for growth was 62.11, 64.82 and 63.88% and for feed efficiency was 62.98, 67.73 and 64.01% at 0-3, 3-6 and 0-6 weeks of age, respectively, while it was 65.85, 71.40 and 67.49% for eviscerated yield, abdominal fat pad reduction and breast yield at 6 weeks of age, respectively.