• The Korean Journal of Applied Statistics
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• v.23 no.5
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• pp.943-953
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• 2010

From a mixture distribution of the score random variable for credit evaluation, there are many methods of estimating optimal thresholds. Most the research news is based on the assumption of normal distributions. In this paper, we extend non-normal distributions such as Weibull, Logistic and Gamma distributions to estimate an optimal threshold by using a hypotheses test method and other methods maximizing the total accuracy and the true rate. The type I and II errors are obtained and compared with their sums. Finally we discuss their e ciency and derive conclusions for non-normal distributions.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.40-46
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• 2005

In order to consider the statistical properties of probability variables which are used in structural analysis, the conventional approach of using safety factors based on past experience, are usually used to estimate the safety of a structure. The real structures could only be analyzed with the error in estimation of loads, materials and dimensional characteristics. Errors should be considered systematically in the structural analysis. In this paper, we estimated the probability of failure of two pressure vessels, simultaneously, using computational analysis. One pressure vessel, theoretically, had no stiffener whereas the other had. This paper also discusses sensitivity values of random variables in the rounded parts of the pressure vessel which had ring-style stiffener in the center of the external area which had ring-style stiffener. Finally, we show that the reliability index, and the probability of failure, can be calculated to particular tolerance limits.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.441-452
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• 2011

Purpose: Identify the factors that influence following up control and reuse intention of patient who used dental health care institution after dental heath care service and in order to prepare the method which improve the quality of dental health service which dental heath care institution service afford. Methods: Data were collected through random sampling from June 20th to August 20th 2010 (for 60 days). Once we explained the purpose of our survey to people who experienced the dental service within one year, we distributed the questionnaires to someone who volunteered to respond and they answered all questions by themselves based on the actual experience of dental health care organizations. Even if the survey was conducted for 610 people, only 585 properly answered questionnaires were analyzed because responses which had many unanswered questions and had errors in responsive way were excluded. Results: Result of multiple regression analysis, the value of dental clinic service, the following up control after dental treatment, the technique and kindness of dentist, the environment of treatment, type of dental service and the kindness of dental staff is significant main cause to intention of reuse dental clinic. Conclusion: In order to increase the rate of patient reuse, enhance the value of service with following up control after health treatment and the high quality of dental health service.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.1
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• pp.353-356
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• 2016

Background: This study used receiver operating characteristic curve to analyze Surveillance, Epidemiology and End Results (SEER) for glassy cell carcinoma data to identify predictive models and potential disparities in outcome. Materials and Methods: This study analyzed socio-economic, staging and treatment factors. For risk modeling, each factor was fitted by a generalized linear model to predict the cause specific survival. Area under the receiver operating characteristic curves (ROCs) were computed. Similar strata were combined to construct the most parsimonious models. A random sampling algorithm was used to estimate modeling errors. Risk of glassy cell carcinoma death was computed for the predictors for comparison. Results: There were 79 patients included in this study. The mean follow up time (S.D.) was 37 (32.8) months. Female patients outnumbered males 4:1. The mean (S.D.) age was 54.4 (19.8) years. SEER stage was the most predictive factor of outcome (ROC area of 0.69). The risks of cause specific death were, respectively, 9.4% for localized, 16.7% for regional, 35% for the un-staged/others category, and 60% for distant disease. After optimization, separation between the regional and unstaged/others category was removed with a higher ROC area of 0.72. Several socio-economic factors had small but measurable effects on outcome. Radiotherapy had not been used in 90% of patients with regional disease. Conclusions: Optimized SEER stage was predictive and useful in treatment selection. Underuse of radiotherapy may have contributed to poor outcome.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.684-693
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• 2011

Measurement time delay in the transfer alignment is very important. It has been well known that the time delay degrades the alignment performance and makes some navigation errors on the transfer alignment of slave INS(SINS). Therefore there are many schemes to eliminate that time delay but the compensation technique through the estimation by Kalman filter through modeling the time delay as a random constant is generally used. In the case of change over measurement time delay or the large measurement time delay, estimation performance in the existing compensation technique is degraded because model of time delay is not correct any more. In this paper, we propose the method to keep the time delay almost constant even though in the abnormal communication state and very small through feedback compensation using double buffer. Double buffer consists of two moving window to temporarily store measurements from master INS and slave INS in real time.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.737-752
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• 2014

As condition-based maintenance (CBM) has risen as a new trend, there has been an active movement to apply information technology for effective implementation of CBM in power plants. This motivation is widespread in operations and maintenance, including monitoring, diagnosis, prognosis, and decision-making on asset management. Thermal efficiency analysis in nuclear power plants (NPPs) is a longstanding concern being updated with new methodologies in an advanced IT environment. It is also a prominent way to differentiate competitiveness in terms of operations and maintenance costs. Although thermal performance tests implemented using industrial codes and standards can provide officially trustworthy results, they are essentially resource-consuming and maybe even a hind-sighted technique rather than a foresighted one, considering their periodicity. Therefore, if more accurate performance monitoring can be achieved using advanced data analysis techniques, we can expect more optimized operations and maintenance. This paper proposes a framework and describes associated methodologies for in-situ thermal performance analysis, which differs from conventional performance monitoring. The methodologies are effective for monitoring, diagnosis, and prognosis in pursuit of CBM. Our enabling techniques cover the intelligent removal of random and systematic errors, deviation detection between a best condition and a currently measured condition, degradation diagnosis using a structured knowledge base, and prognosis for decision-making about maintenance tasks. We also discuss how our new methods can be incorporated with existing performance tests. We provide guidance and directions for developers and end-users interested in in-situ thermal performance management, particularly in NPPs with large steam turbines.

• Speech Sciences
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• v.12 no.4
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• pp.183-195
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• 2005

In the present study, we investigated development of verb inflections or endings in 3- to 5-year old Korean-speaking children using 28 action verbs for both comprehension and production tasks. For each verb, a l0-second long motion picture and a sheet of paper with three random-ordered color pictures representing 'before, in the middle of, at the end of' the action were generated. A past tense inflection' -et ta,' two present progressive verb endings '-enta' & '-ko itta.' a future tense ending '-elyeko hanta' were tested. In the comprehension task, children were asked to point to a picture correctly representing the tense of a presented verb. In the production task, children were asked to produce a verb with correctly marking the tense of a presented picture. The order of the two tasks were counterbalanced across the children, and the motion pictures were only presented in the first task. Across the ages, the performance accuracies on both comprehension and production tasks were the highest for the past tense marking followed by two present progressive and future tense markings. For each verb endings, the changes of accuracies across ages were analyzed in both tasks. The types of errors for production tasks were also reported.

• Journal of Families and Better Life
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• v.33 no.2
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• pp.35-51
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• 2015

The purpose of this study was to provide information for research about residents' opinion toward the physical environments of elderly facilities, through the analysis and investigation on the research methodology of foreign academic journal articles from 1990 to 2014. The study results were as follows: Firstly, purposive sampling was a large majority of both facilities and elderly residents. In quantitative studies, many researchers have conducted simple random, cluster, or stratified sampling. Diverse facilities in area, size, location, and etc. should be considered for participation. The qualifications for residents' participation should be considered as well, so that they all could have autonomy for study participation. Secondly, questionnaire and semi-structured guide were likely to be used in independent and resident care facilities. On the other hand in assisted living and long-term care facilities, open questions and visual material were used as well. A compatible scale should be developed so that elderly having variable functional level could participate independently in the study. Thirdly, in data collection process, compliance with research ethics and well trained interviewer's skill were important for residents' active responses and minimization of response errors. Enough research period of time and mixed study in data collection will decrease the response error.

• Structural Engineering and Mechanics
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• v.56 no.5
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• pp.871-897
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• 2015

This paper presents a novel method based on sensitivity of structural response for identifying both the system parameters and input excitation force of a bridge. This method, referred to as "Adjoint Variable Method", is a sensitivity-based finite element model updating method. The computational cost of sensitivity analyses is the main concern associated with damage detection by these methods. The main advantage of proposed method is inclusion of an analytical method to augment the accuracy and speed of the solution. The reliable performance of the method to precisely indentify the location and intensity of all types of predetermined single, multiple and random damages over the whole domain of moving vehicle speed is shown. A comparison study is also carried out to demonstrate the relative effectiveness and upgraded performance of the proposed method in comparison to the similar ordinary sensitivity analysis methods. Moreover, various sources of error including the effects of noise and primary errors on the numerical stability of the proposed method are discussed.