• 한국국방경영분석학회지
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• 제10권1호
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• pp.23-39
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• 1984

Consider a failure model for a stochastic system. A shock is any perturbation to the system which causes a random amount of damage to the system. Any of the shocks can cause the system to fail at shock times. The amount of damage at each shock is a function of the sum of the magnitudes of damage caused from all previous shocks. The times between shocks form a sequence of independent and identically distributed random variables. The system must be replaced upon failure at some cost but it also can be replaced before failure at a lower cost. The long term expected cost per unit time criterion is used. Structural relationships of the optimal replacement policy under the appropriate regularity conditions will be developed. And these relationships will provide theoretical background for the algorithm development.

• Communications for Statistical Applications and Methods
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• 제22권2호
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• pp.137-146
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• 2015

Singh (2013) considered the dual problem to the calibration of design weights to obtain a new generalized linear regression estimator (GREG) for the finite population total. In this work, we have made an attempt to suggest a way to use the dual calibration of the design weights in case of multi-auxiliary variables; in other words, we have made an attempt to give an answer to the concern in Remark 2 of Singh (2013) work. The same idea is also used to generalize the GREG estimator proposed by Deville and S$\ddot{a}$rndal (1992). It is not an easy task to find the optimum values of the parameters appear in our approach; therefore, few suggestions are mentioned to select values for such parameters based on a random sample. Based on real data set and under simple random sampling without replacement design, our approach is compared with other approaches mentioned in this paper and for different sample sizes. Simulation results show that all estimators have negligible relative bias, and the multivariate case of Singh (2013) estimator is more efficient than other estimators.

• Communications for Statistical Applications and Methods
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• 제3권3호
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• pp.161-168
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• 1996

This paper describes a sampling method, which can be used instead of the simple random sampling without replacement(SRSWOR). This method, circular sampling, assumes that the sampling units of the population are arranged in circular format, and randomly selects as many as samples of contiguous units. Therefore this method gathers information quicker and easier than STSWOR. In certain circumstances, the reliability of this method is better than that of STSWOR. And of circular sampling would be applied to nonprobability could be determined. methods, the reliability of the sample results in terms of probability could be determined.

• Communications for Statistical Applications and Methods
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• 제20권5호
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• pp.357-366
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• 2013

This paper defines an improvement for estimating the population mean of a study variable using auxiliary information and known values of certain population parameter(s), when there is a non-response in a study as well as on auxiliary variables. Under a simple random sampling without a replacement (SRSWOR) scheme, the mean square error (MSE) of all proposed estimators are obtained and compared with each other. Numerical illustration is also given.

• Journal of the Korean Data and Information Science Society
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• 제20권5호
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• pp.779-786
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• 2009

로또복권은 이미 전 세계적으로 인기가 가장 높은 복권중의 하나이다. 우리나라의 경우 전체 45개의 번호 중 6개의 번호를 선택하는 방법으로 로또복권이 발행하고 있으며, 로또복권의 발행을 통해 얻은 수익 중 일부분을 복지사업에 지원하는 등 다양한 분야에 대한 지원 사업으로 사회 환원에도 적극적으로 앞장서고 있다. 하지만 이런 장점에도 불구하고 로또복권의 1등 당첨번호들이 과연 무작위로 선택되었는가 하는 의혹은 발행초기부터 지금까지도 끊이지 않고 제기되어 오고 있다. 따라서 본 연구에서는 로또복권의 총 331회의 1등 당첨번호들에 대하여 주관 사업체별, 그리고 로또복권의 가격변화로 구분하여 다변량 중심극한정리와 몬테카를로 모의실험을 이용한 검정 방법으로 당첨번호들에 대한 무작위성 검정을 실시하였다. 그 결과 모든 경우에서 당첨번호들이 무작위성을 만족하였다.

• 품질경영학회지
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• 제52권1호
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• pp.43-56
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• 2024

Purpose: The injection molding process, crucial for plastic shaping, encounters difficulties in sustaining product quality when replacing injection machines. Variations in machine types and outputs between different production lines or factories increase the risk of quality deterioration. In response, the study aims to develop a system that optimally adjusts conditions during the replacement of injection machines linked to molds. Methods: Utilizing a dataset of 12 injection process variables and 52 corresponding sensor variables, a predictive model is crafted using Decision Tree, Random Forest, and XGBoost. Model evaluation is conducted using an 80% training data and a 20% test data split. The dependent variable, classified into five characteristics based on temperature and pressure, guides the prediction model. Bayesian optimization, integrated into the selected model, determines optimal values for process variables during the replacement of injection machines. The iterative convergence of sensor prediction values to the optimum range is visually confirmed, aligning them with the target range. Experimental results validate the proposed approach. Results: Post-experiment analysis indicates the superiority of the XGBoost model across all five characteristics, achieving a combined high performance of 0.81 and a Mean Absolute Error (MAE) of 0.77. The study introduces a method for optimizing initial conditions in the injection process during machine replacement, utilizing Bayesian optimization. This streamlined approach reduces both time and costs, thereby enhancing process efficiency. Conclusion: This research contributes practical insights to the optimization literature, offering valuable guidance for industries seeking streamlined and cost-effective methods for machine replacement in injection molding.

• 지질공학
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• 제26권4호
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• pp.485-495
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• 2016

본 연구에서는 방파제 하부지반을 저치환율 재료로 보강 및 개량하기 위한 치환율과 재하중 방치기간을 확률론적 최적화 기법을 이용하여 분석하였다. 해석에 필요한 확률변수의 불확실성을 최소화하기 위하여 사전자료를 활용한 베이지안 갱신결과 최대 39.8% 포인트까지 불확실성이 감소하였고, 특히 사전함수의 표본수가 더 많은 구간의 감소폭이 컸다. 치환율 결정을 위하여 저치환율 단면 중 15~40% 범위에서 일계신뢰도법 및 몬테카를로 시뮬레이션 방법에 의해 해석한 결과 목표파괴확률을 만족하는 치환율은 심층고결처리 및 쇄석다짐말뚝 구간에서 각각 20% 및 25% 이상으로 나타났다. 치환율에 대한 최적화를 위하여 생애주기비용 분석을 실시한 결과 목표파괴확률을 만족하는 범위 내에서 최적 치환율이 산정되었으며, 두 구간에서 각각 20% 및 30%가 가장 경제적인 것으로 결정되었다. 재하중의 방치기간에 대한 확률론적 해석결과 3개월 이상인 경우 모두 목표파괴확률을 만족하는 것으로 나타났다.

• Asian-Australasian Journal of Animal Sciences
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• 제10권4호
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• pp.408-415
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• 1997

Data from 5,311 ewes and 13,076 lambing from 1977 through 1994 were used to analyse both annual and cumulative outputs in terms on total number of lambs born, total lamb weight weaned and total wool produced per ewe for ewe longevity 1 to 8 depending on their productive life in the flock. Ewes at Khushab produced 0.08 more lambs per parturition than ewes at Khizerabad; however, 0.39 less lambs were weaned at Khushab than at Khizerabad. Similarly, cumulative number of lambs born was more at Khushab flock than Khizerabad flock (p < .01). However, total weight of lambs weaned was greater at Khizerabad than Khushab flock (p < .01) for each ewe longevity. Most ewes (35%) were sold/replaced just after their first parturition (i. e. ewe longevity 1). The overall mean for annual sale/replacement was 32 and 23% at Khushab and Khizerabad, respectively. Distribution of growth and reproductive traits from 1977-94 did not show upward or downward trend inspite of heavy sale/replacement except yearly variation. Lack of any genetic progress over the year suggested that random breeding was employed without any scientific selection programme. Annual means for lambs born, lambs weaned and weight of lambs weaned per ewe present in the flock were the highest for ewe longevity 2 compared with other ewe longevity groups. Relative efficiency in terms of net income was highest for ewe longevity 5 followed by ewe longevity 4 and 6 in both flocks.

• 한국멀티미디어학회논문지
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• 제8권7호
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• pp.943-952
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• 2005

본 연구는 이동환경에서 연속 미디어 객체에 대한 사용자 요구들에 대하여 효율적으로 자원을 관리하기 위하여, 사용자의 이동성 정보를 반영하는 협력적 프록시 캐슁 정책을 제안한다. 제안된 정책은 담당영역 내에서 사용자의 요구들을 참조하여 캐슁하는 기존의 프록시 캐슁 정책과는 다르게 인접한 영역의 많은 사용자 요구 정보들을 이용하여 캐슁 객체를 선택함으로써 이동환경에서 발생하는 사용자들의 임의접근 요구들을 충분히 반영할 수 있도록 한다. 그리고 제안된 캐슁 정책을 위해서 각 프록시에서 발생한 요구정보의 가중치와 재생량을 기반으로 하는 재배치 기법을 제안한다. 그래서 객체단위와 세그먼트 단위로 재배치 기법을 수행하여 캐슁 정책의 성능을 평가하였다. 그 결과, 이동환경에서 적절한 세그먼트의 크기, 사용자의 이동성 비율 그리고 가중치가 협력적 캐슁의 성능에 영향을 미치는 중요한 요인이 된다는 것을 알았다.

• 임상간호연구
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• 제26권3호
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• pp.365-373
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• 2020

Purpose: The purpose of this study was to evaluate the effect of preoperative warming to prevent hypothermia in surgery for patients undergoing total hip replacement arthroplasty under spinal anesthesia. Methods: A randomized experimental study was conducted. Data were collected at an S University hospital in Gyeonggido from December 3, 2019 to March 31, 2020. A random allocation program was used to randomize participants into intervention and control groups. A total of 90 participants were assigned to the study: 30 people were randomized to a pre-warming group using Bair Hugger forced-air warming blankets(Model 505) 30 minutes before surgery, 30 to a pre-warming group 15 minutes before surgery, or 30 to a control group. The findings from 88 participants were analyzed. For data analysis, χ2 test and ANOVA were used utilizing the SPSS 21.0 program. Results: The pre-warming group 30 minutes before surgery had significantly higher body temperature than the control group, from 30 minutes after inducing anesthesia to the end of anesthesia. Body temperature over anesthesia time showed significant differences among the three groups, but there were no statistically significant differences in interactions between time and groups. Conclusion: Warming patients' body for 30 minutes before surgery was effective in maintaining normal body temperature while preventing intraoperative hypothermia.