• Structural Engineering and Mechanics
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• 제81권2호
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• pp.179-194
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• 2022

The bending, buckling and free vibration responses of functionally graded material (FGM) beams are investigated semi-analytically by the scaled boundary finite element method (SBFEM) in this paper. In the concepts of the SBFEM, the dimension of computational domain can be reduced by one, therefore only the axial dimension of the beam is discretized using the higher order spectral element, which reduces the amount of calculation and greatly improves the calculation efficiency. The governing equation of FGM beams is derived in detail by the means of the principle of virtual work. Compared with the higher-order beam theory, fewer parameters and simpler control equations are used. And the governing equation is transformed into a first-order ordinary differential equation by introducing intermediate variables. Analytical solutions of the governing equation can be obtained by pade series expansion in the direction of thickness. Numerical example are compared with the numerical solutions provided by the previous researchers to verify the accuracy and applicability of the proposed method. The results show that the proposed formulations can quickly converge to the reference solutions by increasing the order of higher order spectral elements, and high accuracy can be achieved by using a small number of the elements. In addition, the influence of the structural sizes, material properties and boundary conditions on the mechanical behaviors of FG beams subjected to different load types is discussed.

• 에너지공학
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• 제2권3호
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• pp.268-275
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• 1993

수치해석 방법에 의해 큐백시의 스토커 소각로 유동장을 분석하였다. 수치모사의 변수는 큐백시의 스토커 소각로를 중심으로 한 5가지 내부 형상, 1차공기 속도, 2차공기 속도 및 주입각, 출구면적을 고려하였다. 검사체적에 기초한 Patankar의 유한차분 방법을 사용한 본 논문에서는 power-law scheme과 SIMPLEC 알고리즘을 사용했으며 난류 유동은 표준 k-e 모델을 이용했다. 소각로 유동장 분석을 위해서 재순환 영역의 크기, 난류 점성계수 및 이차공기의 질량분율 분포, 압력강하를 계산했다. 계산 결과는 물리적 의미에 잘 맞게 나타났으며, 큐백시의 스토커 소각로가 다른 내부 형상의 소각로에 비해 상부에 강한 난류를 가진 재순환 영역을 형성하였다.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.846-855
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• 2020

A loose part monitoring system is used to detect unexpected loose parts in a reactor coolant system in a nuclear power plant. It is still necessary to develop a new methodology for the localization and mass estimation of loose parts owing to the high estimation error of conventional methods. In addition, model-based diagnostics recently emphasized the importance of a model describing the behavior of a mechanical system or component. The purpose of this study is to propose a new localization and mass-estimation method based on finite element analysis (FEA) and optimization technique. First, an FEA model to simulate the propagation behavior of the bending wave generated by a metal sphere impact is validated by performing an impact test and a corresponding FEA and optimization for a downsized steam-generator structure. Second, a novel methodology based on FEA and optimization technique was proposed to estimate the impact location and mass of a loose part at the same time. The usefulness of the methodology was then validated through a series of FEAs and some blind tests. A new feature vector, the cross-correlation function, was also proposed to predict the impact location and mass of a loose part, and its usefulness was then validated. It is expected that the proposed methodology can be utilized in model-based diagnostics for the estimation of impact parameters such as the mass, velocity, and impact location of a loose part. In addition, the FEA-based model can be used to optimize the sensor position to improve the collected data quality in the site of nuclear power plants.

• 대한지리학회지
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• 제28권3호
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• pp.193-199
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• 1993

기후를 대기의 종합상태라 볼 때에 어느 지역의 기후요소의 변동 크기는 그 지역의 기후의 특성을 나타내는 하나의 지표가 된다. 특히 우리나라 하계 우기인 6,7,8월 동안의 강우량(1920년~1985년)의 변화경향성, 다우년과 과우년의 발생빈도, 그리고 주기 등에 대해 남한 전역의 표준강우량 및 서울, 대구, 부산, 목포, 강릉, 전주의 6개 지점의 강우를 서로 비교하였다. 그리고 남서기류의 영향이 우리나라의 하계 강우에 어떠한 영향을 미치는지 알아보기 위해 남한의 표준강우량 및 6개 지점의 강우와 인도 하계 몬순(monson) 강우와의 상관관계를 조사하였다. 남한 전역의 표준강우량의 평균은 611.6mm이고 표준편차는 165.5mm로서 평균의 21%이다. 6개 지점별 강수량의 평균은 지역에 따라 차이가 심하고 다우년과 과우년의 발생횟수 역시 지역에 따라 차이가 심하다. 변화경향성을 조사한 통계량 r는 남한 전역의 표준강우량의 경우 0.07이며 각 지점별 강우의 경우에도 비슷한 통계량 크기를 나타냈으며 이러한 값들은 통계적으로 유의하지 않다. 즉, 변화경향성은 없다. 우리나라 하계강우의 주기는 2.4~2.5년, 3.1~3.6년 그리고 7.3년으로 나타났다. 우리나라 하계강우와 인도 하계몬순 강우와의 상관은 대구와 전주같은 내륙지방에서는 크게 나타나고, 그 외 해안에 인접한 지역에서는 잘 나타나지 않고 있다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.432-435
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• 2002

We have developed and proposed the heavy ion CT system which consists of fluorescent screen and CCD camera equipped with image intensifier. In our system, we have measured the residual range of particles that passed a phantom and reconstructed the CT image for the distribution of relative stopping power by filtered back projection method with Shepp '||'&'||' Logan filter. The heavy ion $\^$12/C accelerated up to 400 MeV/u by HIMAC (Heavy Ion Medical Accelerator in Chiba) was used. Intensity of the beam output changes like macro pulse, the period being 3.3 sec and the width being 2 sec. The series of data was acquired in synchronizing with the pulse, leading to the improvement of S/N in the CT image. The fundamental performance was experimentally evaluated in the proposed system. The spatial resolution was estimated to be about 1 mm and the density resolution (electron density referred to water) to be about 0.01.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2349-2356
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• 2014

The recycling technology by the catalytic conversion is one of the most promising techniques for the $CO_2$ treatment of coal burning power plant flue gases. The conversion of $CO_2$ to valuable product of $CH_4$ can be used as a fuel to run the turbine for electricity generation. Through this technique, the amount of coal needed for the combustion in a gas turbine can be reduced as well as $CO_2$ emissions. Therefore, a series of catalysts based on cerium oxide doped with copper, nickel and manganese were prepared by impregnation method. From the characterization analysis, it showed that the prepared catalysts calcined at $400^{\circ}C$ were amorphous in structure with small particle size in the range below 100 nm. Meanwhile, the catalyst particles were aggregated and agglomerated with higher surface area of $286.70m^2g^{-1}$. By increasing the calcination temperature of catalysts to $1000^{\circ}C$, the particle sizes were getting bigger (> 100 nm) and having moderate crystallinity with lower surface area ($67.90m^2g^{-1}$). From the catalytic testing among all the prepared catalysts, Mn/Ce-75/$Al_2O_3$ calcined at $400^{\circ}C$ was assigned as the most potential catalyst which gave 49.05% and 56.79% $CO_2$ conversion at reaction temperature of $100^{\circ}C$ and $200^{\circ}C$, respectively.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.562-571
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• 2003

발전용원자로에서 뱃치방식으로 환경으로 배출된 액체유출물 내에 함유된 방사능 평가 결과에 오차를 유발하는 시료채취, 제조, 방사능 계측, 유출물 배출체적 측정 등 다양한 인자를 분석하였다. 환경배출 방사능 평가에 포함된 많은 인자들은 단일 측정에 의해 얻어지고 환경배출 방사능의 참값을 알 수 없음에 따라, 평가결과의 오차를 예측하는 것은 원칙적으로 불가능하다. 이에 따라 1993년 ISO가 권고한 측정의 불확도 표현지침에 근거하여 액체폐기물 배출방사능에 대한 불확도 평가모델을 수립하고 가상적인 조건에 대한 액체유출물 환경배출 방사능 평가결과의 불확도를 평가하였다. 그 결과, 액체유출물을 통한 환경배출 방사능 평가결과에 불확도를 유발하는 인자의 상대적인 기여도는 배출폐액의 체적, 시료의 체적, 총방사능 계측값의 순서를 갖는 것으로 나타났다. 또한 개별 변수의 확률분포와 특성값을 토대로 몬테칼로 모사법을 적용하여 최종 환경배출 방사능 평가결과의 확률분포를 해석함으로써, 지금까지 단일 값을 평가 및 보고되었던 발전용 원자로의 액체상 방사성물질 환경배출량이 실제로는 일정한 확률분포를 갖고 있음을 확인하였다.

• 한국정보시스템학회지:정보시스템연구
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• 제19권2호
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• pp.23-36
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• 2010

The focus of this study is to analyze between South Korea and China in terms of diversity in Management Information Systems research. As a result, there is herding phenomenon regarding researches in both of the countries compared to other previous studies. There also seemed to be lack of in-depth study of basic theories and connection to related field of study considering the broad topics of management information, unlike other international journals that pursue diversity in control referencing various methodologies, analysis units and many citations. Therefore, both South Korea and China should stabilize theoretical base of MIS through securing independent field of MIS along with founding the fundamentals by searching in diversified fields, methodologies and analysis units with focused topics. The upshot here is that with respect to diversity in MIS from both countries, to alleviate herding phenomenon, enforcing accuracy of data collection and reducing convenience pursuit should be implemented. Also as criteria to select a topic, different kinds of consulting concepts and taking social issues into consideration that helps tool development and analysis power should be done. Through varied methodologies, tool development and analysis power should be assisted and analysis unit should be shifted to organization unit for Korea and team or individual for China only to augment the accessibility. As a limitation for the paper is that the data used in this analysis is secondary data. In addition, although time period used in both countries were the same, object of analysis had homogeneity in Korean case while Chinese one having heterogeneity from 19 different journals. For the future studies, multicultural comparison or time series analysis and their comparison in deeper approach with regard to object of analysis and methodologies can contribute to further MIS diversity.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.949-959
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• 2021

The current study aims to explore the shielding properties of multi-component borate-based glass series. Seven glass-samples with composition of (80-y)H₃BO₃-10ZnO-10Na₂O-yBaO where (y = 0, 5, 10, 15, 20, 25 and 30 mol.%) were synthesized by melt-quench method. Various shielding features for photons, neutrons, and protons were determined for all prepared samples. XCOM, Phy-X program, and SRIM code were performed to determine and explain several shielding properties such as equivalent atomic number, exposure build-up factor, specific gamma-ray constants, effective removal cross-section (Σ_R), neutron scattering and absorption, Mass Stopping Power (MSP) and projected range. The energy ranges for photons and protons were 0.015-15 MeV and 0.01-10 MeV, respectively. The mass attenuation coefficient (μ/ρ) was also determined experimentally by utilizing two radioactive sources (¹⁶⁶Ho and ¹³⁷Cs). Consistent results were obtained between experimental and XCOM values in determining μ/ρ of the new glasses. The addition of BaO to the glass matrix led to enhance the μ/ρ and specific gamma-ray constants of glasses. Whereas the remarkable reductions in Σ_R, MSP, and projected range values were reported with increasing BaO concentrations. The acquired results nominate the use of these glasses in different radiation shielding purposes.

• 대한지리학회지
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• 제38권
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• pp.15-36
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• 1988

In this paper, I consider the development of methods in contemporary human geography in terms of a dialectical relation of action and structure, and try to draw a new horizon of method toward which geographical research and spatial theory would develop. The positivist geography which was dominent during 1960s has been faced both with serious internal reflections and strong external criticisms in the 1970s. The internal reflections that pointed out its ignorance of spatial behavior of decision-makers and its simplication of complex spatial relations have developed behavioural geography and systems-theoretical approach. Yet this kinds of alternatives have still standed on the positivist, geography, even though they have seemed to be more real and complicate than the previous one, The external criticisms that have argued against the positivist method as phenomenalism and instrumentalism suggest some alternatives: humanistic geography which emphasizes intention and action of human subject and meaning-understanding, and structuralist geography which stresses on social structure as a totality which would produce spatial phenomena, and a theoretical formulation. Human geography today can be characterized by a strain and conflict between these methods, and hence rezuires a synthetic integration between them. Philosophy and social theory in general are in the same in which theories of action and structural analysis have been complementary or conflict with each other. Human geography has fallen into a further problematic with the introduction of a method based on so-called political ecnomy. This method has been suggested not merely as analternative to the positivist geography, but also as a theoretical foundation for critical analysis of space. The political economy of space with has analyzed the capitalist space and tried to theorize its transformation may be seen either as following humanistic(or Hegelian) Marxism, such as represented in Lefebvre's work, or as following structuralist Marxism, such as developed in Castelles's or Harvey's work. The spatial theory following humanistic Marxism has argued for a dialectic relation between 'the spatial' and 'the social', and given more attention to practicing human agents than to explaining social structures. on the contray, that based on structuralist Marxism has argued for social structures producing spatial phenomena, and focused on theorising the totality of structures, Even though these two perspectives tend more recently to be convergent in a way that structuralist-Marxist. geographers relate the domain of economic and political structures with that of action in their studies of urban culture and experience under capitalism, the political ecnomy of space needs an integrated method with which one can overcome difficulties of orthhodox Marxism. Some novel works in philosophy and social theory have been developed since the end of 1970s which have oriented towards an integrated method relating a series of concepts of action and structure, and reconstructing historical materialism. They include Giddens's theory of structuration, foucault's geneological analysis of power-knowledge, and Habermas's theory of communicative action. Ther are, of course, some fundamental differences between these works. Giddens develops a theory which relates explicitly the domain of action and that of structure in terms of what he calls the 'duality of structure', and wants to bring time-space relations into the core of social theory. Foucault writes a history in which strategically intentional but nonsubjective power relations have emerged and operated by virtue of multiple forms of constrainst wihthin specific spaces, while refusing to elaborate any theory which would underlie a political rationalization. Habermas analyzes how the Western rationalization of ecnomic and political systems has colonized the lifeworld in which we communicate each other, and wants to formulate a new normative foundation for critical theory of society which highlights communicatie reason (without any consideration of spatial concepts). On the basis of the above consideration, this paper draws a new norizon of method in human geography and spatial theory, some essential ideas of which can be summarized as follows: (1) the concept of space especially in terms of its relation to sociery. Space is not an ontological entity whch is independent of society and has its own laws of constitution and transformation, but it can be produced and reproduced only by virtue of its relation to society. Yet space is not merlely a material product of society, but also a place and medium in and through which socety can be maintained or transformed.(2) the constitution of space in terms of the relation between action and structure. Spatial actors who are always knowledgeable under conditions of socio-spatial structure produce and reproduce their context of action, that is, structure; and spatial structures as results of human action enable as well as constrain it. Spatial actions can be distinguished between instrumental-strategicaction oriented to success and communicative action oriented to understanding, which (re)produce respectively two different spheres of spatial structure in different ways: the material structure of economic and political systems-space in an unknowledged and unitended way, and the symbolic structure of social and cultural life-space in an acknowledged and intended way. (3) the capitalist space in terms of its rationalization. The ideal development of space would balance the rationalizations of system space and life-space in a way that system space providers material conditions for the maintainance of the life-space, and the life-space for its further development. But the development of capitalist space in reality is paradoxical and hence crisis-ridden. The economic and poltical system-space, propelled with the steering media like money, and power, has outstriped the significance of communicative action, and colonized the life-space. That is, we no longer live in a space mediated communicative action, but one created for and by money and power. But no matter how seriously our everyday life-space has been monetalrized and bureaucratised, here lies nevertheless the practical potential which would rehabilitate the meaning of space, the meaning of our life on the Earth.