• Journal of Korean Society for Quality Management
• /
• v.20 no.1
• /
• pp.22-32
• /
• 1992

This thesis compares life test acceptance sampling plans under lifetime has an exponential distribution. Various practical considerations may lead a user adopt a two-stage, or double sampling, test procedure. Hewett and Spurrier(1983) provided a survey of two-stage methods, as well as examples of experiments for which a two-stage procedure would be appropriate. The plans are compared in terms of the expected number of failures, and the expected time required to reach a dicision. Computational experiments are conducted and the results are tabulated to provide guidelines for selecting an appropriate plan for a given situation.

• Journal of Korean Society for Quality Management
• /
• v.23 no.4
• /
• pp.13-27
• /
• 1995

This paper considers the design of life test sampling plans based on Type II censored accelerated life tests. The lifetime distribution of products is assumed to be exponential. An estimator of acceleration factor between use condition stress and an accelerated level of stress higher than use condition stress is assumed to be known. The critical value for lot acceptance and the number of failure before censoring which satisfy the producer's and consumer's risk requirements are determined. The properties of the proposed life test sampling plans are investigated.

• Journal of Korean Society for Quality Management
• /
• v.22 no.1
• /
• pp.96-112
• /
• 1994

This article studies the design of Bayesian single attribute acceptance sampling plans under dependent production processes. An economic model is constructed by extending the mathematical model developed for non-Bayesian cases for Bayesian cases. The mathematical structure of the model is analyzed and it is used to prove that optimization of the model can be achieved by applying the solution method developed for non-Bayesian models directly. The effect of dependence patterns and the types of prior distributions on the design of sampling plans is also investigated through a computational study.

• Journal of Korean Institute of Industrial Engineers
• /
• v.21 no.2
• /
• pp.255-265
• /
• 1995

Due to advances in automated manufacturing systems and automatic inspection equipment, complete inspection has drown increased attention recently and has become a widespread practice. In a complete inspection plan all of the items are subject to acceptance inspection If an item fails to meet the predetermined specifications, it is rejected. In this paper, economic complete inspection plans are developed in situations where rejected items are reworked Complete inspections based on the performance variable of interest or a variable which is correlated with the performance variable are considered. Cost models are constructed which involve cost incurred by imperfect quality rework cast and quality inspection cost Methods of finding the optimal complete inspection plans are presented and numerical examples are given.

• Journal of Korean Society for Quality Management
• /
• v.10 no.2
• /
• pp.25-33
• /
• 1982

We discuss a model for acceptance/rejection decision regarding finite populations. The model is based on a beta-binomial prior distribution and additive costs -- relative sampling costs, relative sorting costs and costs of accepted defectives. A substantial part of the paper is devoted to constructing a Bayes sequential sampling acceptance plan (BSSAP) for attributes under the model. It is shown that the Bayes fixed size sampling acceptance plans (BFSAP) are better than the Hald's (1960) single sampling acceptance plans based on a uniform prior. Some tables and examples are provided for comprisons of the minimum Bayes risks of the BSSAP and those of the BFSAP based on a uniform prior and the model.

• Journal of Korean Society for Quality Management
• /
• v.24 no.2
• /
• pp.25-43
• /
• 1996

This paper presents the optimal and practical constant-stress accelerated life test plans for the lognormal lifetime distribution tinder assumptions of intermittent inspection and Type-I censoring. In an optimal plan, the low stress level and the proportions of test units allocated at each stress are determined under given inspection scheme and number of inspections such that the asymptotic variance of the maximum likelihood estimator of a certain quantile at use condition is minimized. Although the practical plan adopts the same design criterion, it involves three rather than two overstress levels in order to compromise the practical deficiencies of the optimal plan. Computational experiments are conducted to choose an allocation plan and a inspection scheme of the practical plan and to compare with test plans over a range of parameter values.

• Journal of Korean Society for Quality Management
• /
• v.39 no.2
• /
• pp.313-319
• /
• 2011

In design verification and process validation stages, reliability demonstration tests(RDT's) are common practice in industry, A new two-stage RDT that is known to be more efficient than a corresponding single-stage one in terms of expected test duration for Weibull distribution is proposed. Zero or one failure two-stage plans to minimize expected test duration under Type I and hybrid censoring subject to satisfying consumer's risk at a specified reliability target are developed and a numerical example is provided to illustrate the proposed two-stage RDT plans and compared with other one- and two-stage plans.

• Radiation Oncology Journal
• /
• v.33 no.3
• /
• pp.242-249
• /
• 2015

Purpose: The purpose of this study is to compare the dosimetry of electron beam (EB) plans and three-dimensional helical tomotherapy (3DHT) plans for the patients with left-sided breast cancer, who underwent breast conserving surgery. Materials and Methods: We selected total of 15 patients based on the location of tumor, as following subsite: subareolar, upper outer, upper inner, lower lateral, and lower medial quadrants. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clip plus 1 cm margin. The conformity index (CI), homogeneity index (HI), quality of coverage (QC) and dose-volume parameters for the CTV, and organ at risk (OAR) were calculated. The following treatment techniques were assessed: single conformal EB plans; 3DHT plans with directional block of left anterior descending artery (LAD); and 3DHT plans with complete block of LAD. Results: 3DHT plans, regardless of type of LAD block, showed significantly better CI, HI, and QC for the CTVs, compared with the EB plans. However, 3DHT plans showed increase in the $V_{1Gy}$ at skin, left lung, and left breast. In terms of LAD, 3DHT plans with complete block of LAD showed extremely low dose, while dose increase in other OARs were observed, when compared with other plans. EB plans showed the worst conformity at upper outer quadrants of tumor bed site. Conclusion: 3DHT plans offer more favorable dose distributions to LAD, as well as improved target coverage in comparison with EB plans.

• Journal of Radiation Protection and Research
• /
• v.44 no.1
• /
• pp.32-42
• /
• 2019

Background: There have been much efforts to develop the proper and realistic machine Quality Assurance (QA) reflecting on real Volumetric Modulated Arc Therapy (VMAT) plan. In this work we propose and test a special VMAT plan of plan-class specific (pcsr) QA, as a machine QA so that it might be a good solution to supplement weak point of present machine QA to make it more realistic for VMAT treatment. Materials and Methods: We divided human body into 5 treatment sites: brain, head and neck, chest, abdomen, and pelvis. One plan for each treatment site was selected from real VMAT cases and contours were mapped into the computational human phantom where the same plan as real VMAT plan was created and called plan-class specific reference (pcsr) QA plan. We delivered this pcsr QA plan on a daily basis over the full research period and tracked how much MLC movement and dosimetric error occurred in regular delivery. Several real patients under treatments were also tracked to test the usefulness of pcsr QA through comparisons between them. We used dynalog file viewer (DFV) and Dynalog file to analyze position and speed of individual MLC leaf. The gamma pass rate from portal dosimetry for different gamma criteria was analyzed to evaluate analyze dosimetric accuracy. Results and Discussion: The maxRMS of MLC position error for all plans were all within the tolerance limit of < 0.35 cm and the positional variation of maxPEs for both pcsr and real plans were observed very stable over the research session. Daily variations of maxRMS of MLC speed error and gamma pass rate for real VMAT plans were observed very comparable to those in their pcsr plans in good acceptable fluctuation. Conclusion: We believe that the newly proposed pcsr QA would be useful and helpful to predict the mid-term quality of real VMAT treatment delivery.

• Journal of the Korean housing association
• /
• v.16 no.6
• /
• pp.65-72
• /
• 2005

The purpose of this study is to get preeminent data from comparative analysis of multi-family housing unit plans between Korea and China nowadays. Even though Korea and China belong to common cultured band in Asia, there are many different Housing aspects and unit plans. Through this study we want to grasp the characteristics of both nation's apartment unit plans and to contribute for advance into the China apartment market. Analysis target is constructing and lotting out apartment at South Korea and China in 2004, and the space syntax model is used as an analysis tool. First, analyze kind, number and special quality of each room by use area, and second, analyze area and scale of the rooms. Through the integration analysis we know the grade of rank and centrality of each rooms, and search difference of South Korean and Chinese apartment.