• Communications of the Korean Mathematical Society
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• v.18 no.3
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• pp.569-580
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• 2003

The Lotka-McKendrick equation which describes the evolution of a single population under the phenomenological conditions is developed from the well-known Malthus’model. In this paper, we introduce the Lotka-McKendrick equation for the description of the dynamics of a population. We apply a discontinuous Galerkin finite element method in age-time domain to approximate the solution of the system. We provide some numerical results. It is experimentally shown that, when the mortality function is bounded, the scheme converges at the rate of $h^2$ in the case of piecewise linear polynomial space. It is also shown that the scheme converges at the rate of $h^{3/2}$ when the mortality function is unbounded.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.123-133
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• 2001

An important goal in diesel engine research is the development of a means to reduce the emission of oxides of nitrogen ($NO_x$) and soot particulate. A phenomenological model based on the multizone concept is used in the current paper to analyze and compare the effects of exhaust gas recirculation (EGR) and split fuel injection on emission from a compression-ignited, direct-injection engine. The present results show that $NO_x$ can be reduced with a minimum penalty of soot particle emission with cooled EGR. Compared with EGR, split fuel injection has a higher soot penalty at a given level of $NO_x$ reduction.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.71-76
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• 2002

In this study low cycle fatigue (LCF) behavior of 12Cr steel at high temperature are described. Secondly, comparisons between predicted lives and experimental lives are made for the several sample life prediction models. Two minute hold period in either tension or compression reduce the number of cycles to failure by about a factor of two. Twenty minute hold periods in compression lead to shorter lives than 2 minute hold periods in compression. Experiments showed that life predictions from classical phenomenological models have limitations. More LCF experiments should be pursued to gain understanding of the physical damage mechanisms and to allow the development of physically-based models which can enhance the accuracy of the predictions of components. From a design point-of-view, life prediction has been judged acceptable for these particular loading conditions but extrapolations to thermo-mechanical fatigue loading, for example, require more sophisticated models including physical damage mechanisms.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.33-43
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• 1994

A series of tensile tests have been performed to investigate the hardening behavior of rolled steel sheets. Tensile tests consist of three stages. At the 1st stage, full size tensile specimens were prestrained in the direction of rolling, then mid-sized tensile specimens were cut from the gauge sections of the full size specimens at angles to the rolling direction. At the 2nd stage, mid-sized specimens were prestrained by predetermined magnitudes of strains and miniature tensile specimens were prepared from each of the mid-sized specimens at every 10 degrees. At the final stage, from tests on miniature tensile specimens the hardening behavior of the prestrained sheets has been investigated. According to the experimental results, orthotropic symmetry is reserved during tensile elongation, and one of the orthotropy axes is continuously rotated to specimen axis. Existing theories seem to fail to explain the rotation of orthotropy axis. A new phenomenological model is proposed to explain the strain induced rotation of orthotropy axes.

• Journal of Korean Academy of Nursing
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• v.31 no.6
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• pp.1055-1066
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• 2001

The Purpose of this study is to understand the meaning and the essence of suffering as viewpoint and to find the meaning and structure of the experience from encounters with patients in their terminal stages of illness. Method: A descriptive design based on the phenomenological approach model developed by Collaizzi was used. The period of data collection was from August to November of 2000. Data collection was conducted by open-ended and audio-taped interviews. The participants were nine female nurses who were willing to take part in this study. Results: Results of this study were classified into five main categories. The main category clusters were "difficulty in experiencing suffering," "professional challenges to expert nurses," "formation of empathic relationships," "expanding consciousness through suffering," and "alleviation of the patient's suffering." Conclusion: In conclusion, the implications for providing nursing care to end-stage patients in the throes of suffering is both rewarding and stressful. However, sharing these research results may help other nurses discover and experience deeper meanings in their own practice and careers.deeper meanings in their own practice and careers.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.69-77
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• 1996

We analyzed wideband propagation characteristics of a microstrip transmission line based on FR-4 composite substrate using the wideband complex dielectric constant model and the phenomenological loss equivalence method. The loss calculated by constant relative permittivity and loss tangent is greatly overestimatd compared to that calculated by the frequency-dependent complex relative permittivity. This wideband analysis can be helpful to characterize high-speed and high-density transmission lines associated with the wideband dielectric characteristics and shows that the FR-4 composite substrate has high potential of high frequency circuit applications in terms o fthe propagation loss.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.42-42
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• 1999

본 연구에서는 극 저 에너지 이온 주입에 관한 연구를 위하여 새로이 제안된 PLDAM(phenomenological local damage accumulation model)을 효과적인 분자동역학 이온 주입 분포 계산 방법(highly efficient molecular dynamics (MD) schemes)에 적용하여 극 저 에너지 이온 주입에 관하여 연구하였다. PLDAM은 셀에 축적된 에너지와 이온 발생 순서(history of recoil event) 및 열 전도를 고려하여 실리콘 자기 이완과 재결합을 고려하고 있다. 효과적인 분자동역학 이온 주입방법으로는 MDRANGE code를 사용하였다. 국부적인 격자결함을 고려하지 않은 MDRANGE의 결과는 불순물 분포의 실험치와 꼬리 부분에서 많은 차이를 보여주었다. 그러나 본 연구에서 사용된 국부적인 격자결함 축적을 고려한 MDRANGE의 결과는 극 저 에너지 이온 주입 실험치와 잘 일치하였다. 또한 본 연구에서는 <100> 실리콘 기판 위의 0.1$\mu\textrm{m}$$\times$0.1$\mu\textrm{m}$ 영역에 도즈에 해당하는 이온만큼을 주입하여 불순물 분포를 계산하였다. 붕소와 비소의 경우에, 도즈와 이온주입 에너지가 증가하에 따라서 국부적으로 축적된 격자결함이 불순물의 분포에 미치는 영향이 커지는 것을 알 수 있었다. 특별히 이온 주입 에너지와 함께 무관하게 도즈 1014/cm2 이상에서는 국부적으로 축적된 격자 결함이 불순물의 분포에 크게 영향을 미치는 것으로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.131-140
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• 1993

The activation energy for high temperature creep is associated with stresses, temperatures, straians And the creep strain appears to be a function of a temperature, compensated time, namely $te^{-}$.DELTA.H/RT/, and the stress. In fact this functional relation appears to be isomorphic to material structure by x-ray analyses. Applying this functional relation, the dependance of activation energy for A17075 creep was investigated. The activation energy for creep is insensitive to stress, temperature, structure, and strain. And phenomenological model agrees with experimental creep data.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.84-86
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• 2001

본 연구에서는 플랜트의 계측신호로 부터 특징 패턴 파형들을 감지하고 패턴감지 정보로부터 플랜트의 운전상황 및 고장을 알아내도록 하는 새로운 기법을 제시하고, 이러한 기법의 실현에 필요한 신호처리 기초 연구를 수행하였다. 또한 보령화력 1.2호기 500MW급 드럼형 보일러및 제어 시스템을 대상으로 보일러 플랜트의 dynamics 모델링과 운전 시뮬레이션을 통하여 여러 운전 패턴및 고장 상황을 발생시켜 고장감지 앨고리즘들의 개발 및 시험과정에 적용하였다. 본 연구에서 수행한 보일러 및 보일러 제어계통에 대한 모델링 및 시뮬레이션은 실제 수행한 발전소 시험 데이터와 비교할 때 높은 일치도를 보이는 결과를 보였다.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.162-167
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• 2016

As the simple empirical and phenomenological model applied to the analysis of leakage and explosion of chemical substances does not regard numerous variables, such as positional density of installations and equipment, turbulence, atmospheric conditions, obstacles, and wind effects, there is a significant gap between actual accident consequence and computation. Therefore, the risk management of a chemical plant based on such a computation surely has low reliability. Since a process plant is required to have outcomes more similar to the actual outcomes to secure highly reliable safety, this study was designed to apply the CFD (computational fluid dynamics) simulation technique to analyze a virtual prediction under numerous variables of leakages and explosions very similarly to reality, in order to review the computation technique of the practical safety distance at a process plant.