• Communications for Statistical Applications and Methods
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• 제15권2호
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• pp.161-171
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• 2008

This study discusses Johnson's $S_U$-normal distribution capturing a wide range of non-normality in various regression models. We provide the likelihood inference using Johnson's $S_U$-normal distribution, and propose a likelihood ratio (LR) test for normality. We also apply the $S_U$-normal distribution to the binary and censored regression models. Monte Carlo simulations are used to show that the LR test using the $S_U$-normal distribution can be served as a model specification test for normal error distribution, and that the $S_U$-normal maximum likelihood (ML) estimators tend to yield more reliable marginal effect estimates in the binary and censored model when the error distributions are non-normal.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.724-727
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• 1995

Dynamic deformation behavior under the high strain rate loading condition obtained with the aid of Split Hopkinson Pressure Bar(SHPB) technique is simulated by DYNA2D (an hydrodynamic code). A constitutive equation such as Johnson-Cook model is used by adjusting various parameters to fit experimentally determined dynamic stress-strain relationship.

• Journal of the Korean Statistical Society
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• 제36권1호
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• pp.129-148
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• 2007

Frailty estimates from the proportional hazards frailty model often lead us to conjecture the heterogeneity in frailty such that the variance of the frailty varies over different covariate groups (e.g. male group versus female group). For such systematic heterogeneity in frailty, we consider a regression model for the variance components in the proportional hazards frailty model, denoted by the MLFM. However, in many cases, the observed data do not show any statistically significant preference between the homogeneous frailty model and the heterogeneous frailty model. In this paper, we propose a Bayesian model averaging procedure with the reversible jump Markov chain Monte Carlo which selects the appropriate model automatically. The resulting regression coefficient estimate ignores the model uncertainty from the frailty distribution in view of Bayesian model averaging (Hoeting et al., 1999). Finally, the proposed model and the estimation procedure are illustrated through the analysis of the kidney infection data in McGilchrist and Aisbett (1991) and a simulation study is implemented.

• 한국항공우주학회지
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• 제50권7호
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• pp.465-470
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• 2022

본 논문은 알루미늄 6061의 고속 충격 해석과 고속 충격 시험 결과를 비교 검증하여 금속 재료의 고속 충격에 의한 거동 특성을 연구하였다. 고속 충격 해석을 위해 만능재료시험기를 이용한 준정적 시험과 Hopkinson bar를 이용한 동적 시험을 통해 Huh-Kang 모델과 Johnson-Cook 파손 모델의 계수를 구했다. LS-DYNA 프로그램 해석을 이용하여 관통 속도와 형상을 결과로 예측했고 고속 충격 시험기를 이용한 시험 결과와 비교하였다. 이를 바탕으로 항공기 가스터빈 엔진 블레이드 컨테인먼트 평가 연구에 적용하고자 한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권6호
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• pp.539-545
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• 2013

In this paper, a behavioral current-voltage model with intermediate states is proposed for analog applications of unipolar resistive memories, where intermediate resistance values between SET and RESET state are used to store analog data. In this model, SET and RESET behaviors are unified into one equation by the blending function and the percentage volume fraction of each region is modeled by the Johnson-Mehl-Avrami (JMA) equation that can describe the time-dependent phase transformation of unipolar memory. The proposed model is verified by the measured results of $TiO_2$ unipolar memory and tested by the SPECTRE circuit simulation with CMOS read and write circuits for unipolar resistive memories. With the proposed model, we also show that the behavioral model that combines the blending equation and JMA kinetics can universally describe not only unipolar memories but also bipolar ones. This universal behavioral model can be useful in practical applications, where various kinds of both unipolar and bipolar memories are being intensively studied, regardless of polarity of resistive memories.

• 한국기계가공학회지
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• 제13권5호
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• pp.50-56
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• 2014

A technique based on the finite element method (FEM) is used in the simulation of metal cutting process. This offers the advantages of the prediction of the cutting force, the stresses, the temperature, the tool wear, and optimization of the cutting condition, the tool shape and the residual stress of the surface. However, the accuracy and reliability of prediction depend on the flow stress of the workpiece. There are various models which describe the relationship between the flow stress and the strain. The Johnson-Cook model is a well-known material model capable of doing this. Low-alloy steel is developed for a dry storage container for used nuclear fuel. Related to this, a process analysis of the plastic machining capability is necessary. For a plastic processing analysis of machining or forging, there are five parameters that must be input into the Johnson-Cook model in this paper. These are (1) the determination of the strain-hardening modulus and the strain hardening exponent through a room-temperature tensile test, (2) the determination of the thermal softening exponent through a high-temperature tensile test, (3) the determination of the cutting forces through an orthogonal cutting test at various cutting speeds, (4) the determination of the strain-rate hardening modulus comparing the orthogonal cutting test results with FEM results. (5) Finally, to validate the Johnson-Cook material parameters, a comparison of the room-temperature tensile test result with a quasi-static simulation using LS-Dyna is necessary.

• 대한기계학회논문집A
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• 제32권9호
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• pp.740-753
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• 2008

The conventional Split Hopkinson Pressure Bar (C-SHPB) technique with aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials such as hot temperature degraded POM (Poly Oxy Methylene) and PP (Poly Propylene) to obtain more distinguishable experimental signals is used to obtain a dynamic behavior of material deformation under a high strain rate loading condition. An experimental modification with Pulse shaper is introduced to reduce the nonequilibrium on the dynamic material response during a short test period to increase the rise time of the incident pulse for two polymeric materials. For the dynamic stress strain curve obtained from SHPB experiment under high strain rate, the Johnson-Cook model is applied as a constitutive equation, and we verify the applicability of this constitutive equation to the probabilistic reliability estimation method. The methodology to estimate the reliability using the probabilistic method such as the FORM and the SORM has been proposed, after compose the limit state function using Johnson-Cook model. It is found that the failure probability estimated by using the SORM is more reliable than those of the FORM, and the failure probability increases with the increase of applied stress. Moreover, it is noted that the parameters of Johnson-Cook model such as A and n, and applied stress affect the failure probability more than the other random variables according to the sensitivity analysis.

• Steel and Composite Structures
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• 제19권6호
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• pp.1467-1481
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• 2015

This paper presents a contribution to improving an analytical thermo-mechanical modeling of Oxley's machining theory of orthogonal metals cutting, which objective is the prediction of the cutting forces, the average stresses, temperatures and the geometric quantities in primary and secondary shear zones. These parameters will then be injected into the developed model of Karas et al. (2013) to predict temperature distributions at the tool-chip-workpiece interface. The amendment to Oxley's modified model is the reduction of the estimation of time-related variables cutting process such as cutting forces, temperatures in primary and secondary shear zones and geometric variables by the introduction the constitutive equation of Johnson-Cook model. The model-modified validation is performed by comparing some experimental results with the predictions for machining of 0.38% carbon steel.

• 대한간호학회지
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• 제16권2호
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• pp.36-43
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• 1986

The main purpose of this study was to explore the effect of the stress of hospitalization on the sleep pattern. Additionaly, this study was also to demonstrate how Johnson's nursing model may be applied to as nursing process. 104 hospitalized patients on surgical and medical wards were asked to rate 49 stress producing events associated with experience of hospitalization and sleep pattern scale. Five university hospitals were used as the setting for this study. Data for the study were collected by patient interview during hospitalization, self-reports and review of charts. For the analysis of the data, the pearson's correlation analysis of covariance and regression analysis were used. The results of this study were stated as follows; 1. The mean of the hospital stress scores was 111.261(S.D.=26.160). This means that the level of the hospitalization stress is high. The mean of the sleep pattern scores was 12.204(S.D. =2.615) This means that the characteristic's of the sleep pattern is poor. 2. The relationship between the hospitalization stress and sleep pattern was statistically significant at .01 level. 3. The effect of the hospitalization stress influenced strongly on the sleep pattern after sex, trait anxiety as covariates controlled. 4. The hospitalization stress revealed a 12% pre-diction as an influenced factor for the sleep pattern. Therefore, It can he said that the hospital stress did contribute significantly to the characteristics of the sleep pattern. Johnson's model can he also said that it is useful for the the assessment and diagnosis in nursing process.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1098-1108
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• 2022

The effect of the material hardening model of the canister on a finite element vertical cask drop simulation is investigated for the strain-based acceptance evaluation. Three different hardening models are considered in this paper: the isotropic hardening model, the strain rate-dependent Johnson-Cook (J-C) hardening model, and the modified J-C model which are believed to be the most accurate. By comparing the results using the modified J-C model, it is found that the use of the J-C model provides similar or larger stresses and strains depending on the magnitudes of the strain and strain rate. The use of the isotropic hardening model always yields larger stresses and strains. For the strain-based acceptance evaluation, the use of the isotropic hardening model can produce highly conservative assessment results. The use of the J-C model, however, produces satisfactory results.