• Journal of applied mathematics & informatics
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• 제9권2호
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• pp.531-542
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• 2002

In this paper we deal with a sequence of positive linear operators ${{R_n}}^{[$\beta$]}$ approximating functions on the unbounded interval [0, $\infty$] which were firstly used by K. balazs and J. Szabados. We give pointwise estimates in the framework of polynomial weighted function spaces. Also we establish a Voronovskaja type theorem in the same weighted spaces for ${{K_n}}^{[$\beta$]}$ operators, representing the integral generalization in Kantorovich sense of the ${{R_n}}^{[$\beta$]}$.

• 대한수학회지
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• 제33권2호
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• pp.249-258
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• 1996

Analysis by the method of characteristics shows that if f and $u_0$ are smooth and $u_0$ has compact support, then the Hamilton-Jacobi equation $$ (H-J) ^{u_t + f(u_x) = 0, x \in R, t > 0, } _{u(x, 0) = u_0(x), x \in R, } $$ has a unique $C^1$ solution u on some maximal time interval $0 \leq t < T$ for which $lim_{t \to T}u(x, t) exists uniformly; but this limiting function is not continuously differentiable.

• Communications for Statistical Applications and Methods
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• 제3권1호
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• pp.87-99
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• 1996

We construct bootstrap confidence intervals for reliability, R= P{X>Y}, where X and Y are independent normal random variables. One way ANOVA random effect models are assumed for the populations of X and Y, where standard deviations $\sigma_{x}$ and $\sigma_{y}$ are unequal. We investigate the accuracy of the proposed bootstrap confidence intervals and classical confidence intervals work better than classical confidence interval for small sample and/or large value of R.

• 호남수학학술지
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• 제42권4호
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• pp.747-755
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• 2020

The mathematical proof for establishing some new inequalities involving arithmetic, geometric, harmonic means for the arguments lying on the paths of triangular wave function (linear) and new parabolic function (curved) over the interval (0, 1) are discussed. The results representing an extension as well as strengthening of Ky Fan Type inequalities.

• 대한수학회지
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• 제49권5호
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• pp.1017-1030
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• 2012

We consider forced second order differential equation with $p$-Laplacian and nonlinearities given by a Riemann-Stieltjes integrals in the form of $$(p(t){\phi}_{\gamma}(x^{\prime}(t)))^{\prime}+q_0(t){\phi}_{\gamma}(x(t))+{\int}^b_0q(t,s){\phi}_{{\alpha}(s)}(x(t))d{\zeta}(s)=e(t)$$, where ${\phi}_{\alpha}(u):={\mid}u{\mid}^{\alpha}\;sgn\;u$, ${\gamma}$, $b{\in}(0,{\infty})$, ${\alpha}{\in}C[0,b)$ is strictly increasing such that $0{\leq}{\alpha}(0)<{\gamma}<{\alpha}(b-)$, $p$, $q_0$, $e{\in}C([t_0,{\infty}),{\mathbb{R}})$ with $p(t)>0$ on $[t_0,{\infty})$, $q{\in}C([0,{\infty}){\times}[0,b))$, and ${\zeta}:[0,b){\rightarrow}{\mathbb{R}}$ is nondecreasing. Interval oscillation criteria of the El-Sayed type and the Kong type are obtained. These criteria are further extended to equations with deviating arguments. As special cases, our work generalizes, unifies, and improves many existing results in the literature.

• Advances in Traditional Medicine
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• 제10권4호
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• pp.278-287
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• 2010

The present study was undertaken to evaluate the protective effect of ethanol (EtAS), ethyl acetate (EAAS) and aqueous (AQAS) extracts of Argyreia speciosa (AS) roots against Isoproterenol (ISO)-induced myocardial infarction in rats. The animals were exposed to isoproterenol (200 mg/kg. s.c) twice at an interval of 24 hrs. Cardioprotective effect was assessed by observing ECG parameters, serum marker enzymes and histopathology of the heart. Pretreatment of EAAS, and EtAS (200 mg/kg) resulted in a significant (P < 0.001) increase in P wave, QRS complex and R-R interval, whereas heart rate, QT interval and cardiac cycle were maintained near to normal values. EtAS and EAAS showed significant (P < 0.05; P < 0.001) reduction in all the tested diagnostic markers compared to ISO treated group. Histological studies on the structural changes of heart tissue supported the protective activity of AS. The result suggest that treatment of AS prior to ISO has a significant role in protecting the animals from ISO induced myocardial infarction.

• 한국물환경학회지
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• 제22권5호
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• pp.856-864
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• 2006

For estimating the minimum discharge to maintain a river, low flow analysis is required and long term runoff records are needed for the analysis. However, runoff data should be estimated to run a hydrologic model for ungaged river basin. For the reason, parameter estimation is crucial to simulate rainfall-runoff events for those basins using Tank model. In this study, only runoff data recorded for dry season are used for parameter estimation, which is different to other methods based on runoff data recorded for wet and dry seasons. The Harmony Search algorithm is used to determine the optimum parameters for Tank model. The coefficient of determination ($R^2$) is served as the objective function in the Harmony Search. In cases that recorded data are insufficient, the recording interval is changed and Empirical CDF is adopted to analyze the estimated parameters. The suggested method is applied to Yongdam dam, Soyanggang dam, Chungju dam and Seomjingang dam basins. As results, the higher $R^2s$ are obtained when the shorter recording interval, the better recorded data quality, and the more rainfall events recorded along with certain rainfall amount is. Moreover, when the total rainfall is higher than the certain amount, $R^2$ is high. Considering the facts found from this study for the low flow analysis, it is possible to estimate the parameters for Tank model properly with the desired confidence level.

• Journal of Preventive Medicine and Public Health
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• 제53권3호
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• pp.151-157
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• 2020

Objectives: The outbreak of coronavirus disease 2019 (COVID-19) is one of the main public health challenges currently facing the world. Because of its high transmissibility, COVID-19 has already caused extensive morbidity and mortality in many countries throughout the world. An accurate estimation of the basic reproduction number (R₀) of COVID-19 would be beneficial for prevention programs. In light of discrepancies in original research on this issue, this systematic review and meta-analysis aimed to estimate the pooled R₀ for COVID-19 in the current outbreak. Methods: International databases (including Google Scholar, Science Direct, PubMed, and Scopus) were searched to identify studies conducted regarding the R₀ of COVID-19. Articles were searched using the following keywords: "COVID-19" and "basic reproduction number" or "R₀." The heterogeneity among studies was assessed using the I² index, the Cochran Q test, and T². A random-effects model was used to estimate R₀ in this study. Results: The mean reported R₀ in the identified articles was 3.38±1.40, with a range of 1.90 to 6.49. According to the results of the random-effects model, the pooled R₀ for COVID-19 was estimated as 3.32 (95% confidence interval, 2.81 to 3.82). According to the results of the meta-regression analysis, the type of model used to estimate R₀ did not have a significant effect on heterogeneity among studies (p=0.81). Conclusions: Considering the estimated R₀ for COVID-19, reducing the number of contacts within the population is a necessary step to control the epidemic. The estimated overall R₀ was higher than the World Health Organization estimate.

• 한국임상수의학회지
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• 제25권4호
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• pp.280-285
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• 2008

한우에서 분만 전, 분만 시 및 분만 후의 body condition score(BCS)와 이후의 번식능력과의 상관관계를 조사하였다. 2년 6개월에 걸쳐 33두의 한우에서 얻은 73회의 분만 산차(평균 $2.0\pm0.9$)에 대한 BCS 평가를 위하여 분만 2개월 및 1개월 전, 분만 시, 그리고 분만 후 7개월까지 매 1개월 간격으로 수행하였다. 분만 전 현저한 BCS의 감소에 대해서도 조사하였다. 분만 후 임신까지의 간격과 분만 1개월 전, 분만 시 그리고 분만 1개월 및 2개월 후 BCS 사이의 상관관계에 대하여 Pearson correlation analysis를 이용하여 분석하였다. 분만 후 임신까지의 간격과 분만 전 BCS의 감소에 대한 상관관계도 또한 분석하였다. 분만 후 임신까지의 간격은 분만 1개월 전 BCS (r=0.389, P=0.0007) 및 분만 전 BCS의 감소(r=0.488, P<0.0001)와는 정의 상관관계를 나타내었으나, 분만 시(r=-0.070, P=0.56)그리고 분만 1개월(r=0.107, P=0.37) 및 2개월 후(r=0.102, P=0.39)의 BCS와는 유의적인 상관관계를 나타내지 않았다. 분만 전 BCS의 감소는 분만 1개월 전 BCS와 정의 상관관계를 나타내었다(r=0.587, P<0.0001). 본 연구의 결과는 한우에서 분만 1개월 전 BCS는 이후의 번식능력을 예측하는데 유용한 기준으로 활용될 수 있으며, 또한 분만 전 비만 및 과도한 BCS의 감소의 예방은 번식능력을 증진시킬 수 있음을 보여 준다.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.728-734
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• 2016

최근 들어 국민 식생활 문화가 개선되고 생활수준이 향상됨에 따라 소프트 아이스크림, 슬러시와 같은 일회용 냉동 유제품의 소비가 급증하고 있다. 이들 냉동 유제품은 소형 냉동 시스템에서 만들어진다. 소프트 아이스크림 제조기의 냉매로 그간 R-502가 주로 사용되어 왔으나 오존층 파괴와 관련하여 R-404A로 대체되고 있다. 본 연구에서는 냉각기 체적 2.8 리터인 R-404A를 사용하는 소프트 아이스크림 제조기에 대하여 최적화와 성능평가를 수행하였다. 최적화는 적정 냉매량 및 팽창 밸브의 개도를 찾는데 주안점을 맞춰 수행되었다. 최적 조건에서 아이스크림 제조 시간은 10분 5초, COP는 0.57로 나타났다. 이 제품에 대하여 무 간격 연속 판매 시험, 30초 간격 연속 판매 시험, 극한 시험을 수행하여 성능을 평가하였다. 무 간격 연속 판매는 20개까지 가능하였고 30초 간격 연속 판매는 무한대로 가능하였다. 또한 여름철 및 겨울철 환경에도 아이스크림 판매가 가능한 것으로 나타났다. 본 연구 결과는 냉동식품 제조기를 비롯한 여타 냉동 사이클의 최적화에도 활용될 수 있을 것이다.