• 응용통계연구
• /
• 제19권3호
• /
• pp.395-406
• /
• 2006

임상시험 연구나 역학 연구에서 환자들의 예후는 흔히 생존을 추정을 통해 수량화 되곤 한다. 하지만 코호트 분석이나 완전분석에 의한 생존율 추정량들은 수년 전에 진단된 환자에 크게 의존하기 때문에 실제 생존율보다 더 낮게 추정하곤 한다. 본 연구에서는 최근의 생존정보를 잘 반영하는 생존을 추정을 위해 기간분석 방법을 통한누적한계 추정량을 제안하였고, 그 방법을 1993년 1월-1997년 12월 사이에 조사된 서울시 암등록 자료(Ahn등, 2002)에 적용하여 결과를 고찰하였다.

• 한국국방경영분석학회지
• /
• 제6권2호
• /
• pp.129-149
• /
• 1980

In medical follow-up, equipment lifetesting, various military situations, and other fields, one often desires to calculate survival probability as a function of time, p(t). If the observer is able to record the time of occurrence of the event of interest (called a 'death'), then an empirical, non-parametric estimate may simply by obtained from the fraction of survivors after various elapsed times. The estimation is more complicated when the data are truncated, i.e., when the observer loses track of some individuals before death occurs. The product-limit method of Kaplan and Meier is one way of estimating p(t) when the mechanism causing truncation is independent of the mechanism causing death. This paper proposes jackknife estimators of logistic trans-formation and compares it to the product-limit method. A computer simulation is used to generate the times of death and truncation from a variety of assumed distributions.

• 한국ITS학회 논문지
• /
• 제23권3호
• /
• pp.17-28
• /
• 2024

본 연구에서는 고속도로 VDS 검지기 데이터를 활용하여 터널 구간과 일반 구간의 도로용량을 산정하여 비교하였으며, 터널 특성 요인에 따라 분류된 터널유형별 터널 진입 전 대비 터널 내부 도로용량 감소율을 분석하였다. 터널 구간과 일반 구간의 도로 용량을 비교하기 위해 5분 단위 VDS 검지기 데이터에 Product Limit Method(PLM)을 적용하였다. PLM으로 도출된 터널 구간 및 일반 구간의 도로 용량을 비교한 결과, 터널 구간은 일반 구간 대비 도로 용량이 약 6.5% 감소하였다. 터널 유형 분류를 위해 터널 연장과 터널 내 차로수를 변수로 활용하였으며, 각 기준에 의해 분류된 터널 집단별 도로 용량 감소율에는 차이가 있었다.

• 대한기계학회논문집
• /
• 제18권7호
• /
• pp.1685-1696
• /
• 1994

In this paper, a new forming process of the large-size forgings within the limit of forming loads is developed by introducing the incremental forging method and combined forming method. For the development of the forming process, various related processes are proposed and modelling experiments of plasticine and corresponding numerical simulation ate carried out. Thus, an optimal process considering the productivity and economical efficiency is recommended from the study of formability and forming loads, etc. The selected process is subjected to a modelling experiment of lead and 1/7 scale prototype experiment of the real material so as to verify the effectiveness of a selected process as well as to determine the design parameters. The developed process is then applied the forging product of dome shape. Dome-shaped forgings can be produced by the developed process within the limit loads and with the simple tools.

• 소성∙가공
• /
• 제8권5호
• /
• pp.482-490
• /
• 1999

7000 series Al alloy with good mechanical properties has been focused with tendency to reduce the components weight of aircraft and automobile. However, it is difficult to manufacture a sound extruded product because of segregation, grain growth, casting defect, surface defect, decreasing extrudability and so on. The objective of this study is to manufacture a new 7000 al alloy more than the extrudability of A7N01 and A7003 through controlling the weight (%) Mg, Zn, Si. Hot extrusion experiments on the axisymmetric rod are performed in 500℃ and also performed analysis of the same process using unmerical analysis method, a coupled rigid-thermoviscoplastic finite element method. Extrusion limit diagram was obtained for the developed alloy by FE-simulation in order to define the relationship of extrusion speed and initial billet temperature.

• Environmental Engineering Research
• /
• 제12권5호
• /
• pp.203-210
• /
• 2007

Since the emissions composition from the household products have potentially been associated with health risks for building occupants, the chemical composition emitted from the products should be surveyed. The current study identified the emission composition for 42 liquid household products, using a purge-and-trap method. This evaluation was done by classifying the household products into five product classes (deodorizers, household cleaners, color removers, pesticides, and polishes). Nineteen compounds were chosen on the basis of selection criteria. The quality control program for purge-and-trap and analytical systems included tests of laboratory blank Tenax traps and blank water samples, and the determination of calibration equation, measurement precision, method detection limit (MDL), and recovery. The number of chemicals varied according to the product categories, ranging from 4 for the product category of bleaches to 12 for the product categories of air fresheners and nail color removers. For all product categories, the emission composition and concentrations varied broadly according to product. It is noteworthy that most household products emit limonene: 19 of 25 cleaning products; 5 of 6 deodorizers; 1 of 3 pesticides; 3 of 3 color removers; and 4 of 5 polishes. It was suggested that the use of household products sold in Korea could elevate the formation of secondary toxic pollutants in indoor environments, by the reaction of limonene with ozone, which entered indoor environments or might be generated by indoor sources such as electronic air cleaning devices and copying machines.

• 분석과학
• /
• 제36권5호
• /
• pp.250-257
• /
• 2023

The development of a spectrofluorimetric method for the determination of trimethoprim according to the reaction between O-phthalaldehyde (OPA) in highly alkaline media, and 2-mercaptoethanol (2ME) and this reaction gives fluorescent product measured at (458) nm when excited at (342) nm. The optimization of the analytical parameters that influence intensity was investigated. The intensity of fluorescence of the formed product was linearly related to the concentration of trimethoprim in the (100-1200) ng mL^-1 range. The limit of detection and limit of quantification were estimated to be (22.54) ng mL^-1 and (75.15) ng mL^-1 respectively. The utility of the proposed methods was successfully verified by analysis of trimethoprim in pure and real pharmaceutical preparations with high accuracy, the recovery percentages Re%, were found to be (100.5) % and (99.76) % for pure drug and pharmaceutical preparations respectively.

• 한국환경과학회지
• /
• 제4권1호
• /
• pp.91-103
• /
• 1995

The reaction rate, equilibrium, and flow injection analysis methods were fundamentally evaluated for the determination of aqueous ammonia. The selected indophenol blue method was based on the formation of indophenol blue in which ammonium ion reacted with hypochlorite and phenol in alkaline solution. In the optimized reaction condition, the reaction followed 1st order reaction kinetics and the final product was stable. The absorbance measurements before and after the equilibrium were utilized for the reaction rate and equilibrium methods. The reaction rate methods, based on the relative analytical signals for the possibility of eliminating interferents, were shown to have good linear calibration curves but the detection limit and the calibration sensitivity were poorer than those in the equilibrium method. The detection limits were 32-49 pub and 24 pub for the reaction rate and equilibrium methods, respectively In the flow injection analysis, the absorbance was measured before the equilibrium reached and thus resulted in 30% reduction of calibration sensitivity. However, the detection limit was 11 ppb, indicating that the peak-to-peak noise for the blank was remarkably improved. Compared to the manual methods, the optimized experimental condition in a closed reaction system reduced the blank absorbance and the inclusion of ammonia from the atmosphere was prevented. In addition, highly reproducible mixing of sample and reagents and analytical data extracted from continuous recording showed excellent reproducibility.

• International Journal of CAD/CAM
• /
• 제13권1호
• /
• pp.1-11
• /
• 2013

Just by adjusting the control points iteratively, progressive iterative approximation (PIA) presents an intuitive and straightforward scheme such that the resulting limit curve (surface) can interpolate the original data points. In order to obtain more flexibility, adjusting only a subset of the control points, a new method called local progressive iterative approximation (LPIA) has also been proposed. But to this day, there are two problems about PIA and LPIA: (1) Only an approximation process is discussed, but the accurate convergence curves (surfaces) are not given. (2) In order to obtain an interpolating curve (surface) with high accuracy, recursion computations are needed time after time, which result in a large workload. To overcome these limitations, this paper gives an explicit matrix expression of the control points of the limit curve (surface) by the PIA or LPIA method, and proves that the column vector consisting of the control points of the PIA's limit curve (or surface) can be obtained by multiplying the column vector consisting of the original data points on the left by the inverse matrix of the collocation matrix (or the Kronecker product of the collocation matrices in two direction) of the blending basis at the parametric values chosen by the original data points. Analogously, the control points of the LPIA's limit curve (or surface) can also be calculated by one-step. Furthermore, the $G^1$ joining conditions between two adjacent limit curves obtained from two neighboring data points sets are derived. Finally, a simple LPIA method is given to make the given tangential conditions at the endpoints can be satisfied by the limit curve.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1994년도 박판성형기술의 진보
• /
• pp.173-184
• /
• 1994

A method of obtaining deformation severity of axisymmetric shape deep-drawn products was developed. Strain states of products produced by single or multi-stage drawing were predicted by using finite element analysis. This method used minimization of potential energy between the known shape of final product and the unknown in initial blank. And that was done numerically by nonlinear finite element method. Deformation theory of plasticity was used for practical purposes. From predicted strain states of drawn parts, deformation severity was found by using forming limit diagrams.