• Structural Engineering and Mechanics
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• 제19권2호
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• pp.231-236
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• 2005

This study considers the buckling of orthotropic cylindrical thin shells with material nonhomogeneity in the thickness direction, under torsion, which is a power function of time. The dynamic stability and compatibility equations are obtained first. Applying Galerkin's method then applying Ritz type variational method to these equations and taking the large values of loading parameters into consideration, analytic solutions are obtained for critical parameter values. Using those results, the effects of the periodic and power variations of Young's moduli and density, ratio of Young's moduli variations, loading parameters variations and the power of time in the torsional load expression variations are studied via pertinent computations. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question.

• Earthquakes and Structures
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• 제25권6호
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• pp.429-442
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• 2023

To study the seismic vulnerability of the composite material structure of adobe and timber, we collected and statistically analysed empirical observation samples of 542,214,937 m² and 467,177 buildings that were significantly impacted during the 179 earthquakes that occurred in mainland China from 1976 to 2010. In multi-intensity regions, combined with numerical analysis and a probability model, a non-linear continuous regression model of the vulnerability, considering the empirical seismic damage area (number of buildings) and the ratio of seismic damage, was established. Moreover, a probability matrix model of the empirical seismic damage mean value was provided. Considering the coupling effect of the annual and seismic fortification factors, an empirical seismic vulnerability curve model was constructed in the multiple-intensity regions. A probability matrix model of the mean vulnerability index (MVI) was proposed, and was validated through the above-mentioned reconnaissance sample data. A matrix model of the MVI of the regions (19 provinces in mainland China) based on the parameter (MVI) was established.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.871-884
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• 2015

In the present study, separate and combined effects of rotary inertia, shear deformation and material non-homogeneity (MNH) on the values of natural frequencies of the simply supported beam are examined. MNH is characterized considering the parabolic variations of the Young's modulus and density along the thickness direction of the beam, while the value of Poisson's ratio is assumed to remain constant. At first, the equation of the motion including the effects of the rotary inertia, shear deformation and MNH is provided. Then the solutions including frequencies of the first three modes for various combinations of the parameters of the MNH, depth to length ratios, and shear corrections factors are reported. To show the accuracy of the present results, two comparisons are carried out and good agreements are found.

• 한국안전학회지
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• 제27권3호
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• pp.63-70
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• 2012

In the hazardous areas where explosive gases, vapor or mists exist, electrical apparatus and installations must be the explosion-proof construction to prevent or limit the danger of the ignition of potentially explosive atmosphere. In Korea, nine types of protection have been specified in the government regulations at present: flameproof enclosure, pressurization, oil immersion, increased safety, intrinsic safety, non-incendive, powder filling, encapsulation, and special types. Among these types, the intrinsic safety has the construction which limit or by-pass igniting the electric energy using electronic devices. This type has lots of merits but at the same time requires a high-degree of technology. In this paper, we investigated several dominating factors which affect the minimum ignition energy; this energy plays a very important role in design and evaluation of the intrinsic safety type electrical apparatus. Electrode material, which is one of the most important factors, was intensively studied for the five sorts of material(Al, Cd, Mg, Sn, and Zn) with performing experiment in a low-voltage inductive circuit using IEC-type(International Electro-technical Commission) spark apparatus. The experimental results show that the minimum ignition energy of electrode material is varied: highest in Cd and lowest in Sn. We also confirmed the effect of electrode make-and-break speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.579-580
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• 2008

• 대한기계학회논문집A
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• 제27권8호
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• pp.1273-1280
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• 2003

In this paper, transparent dynamic photoelastic experimental hybrid method for propagating cracks in orthotropic material was developed. Using transparent dynamic photoelastic experimental hybrid method, we can obtain stress intensity factor and separate the stress components from only isochromatic fringe patterns without using isoclinics. When crack is propagated with constant velocity, the contours of stress components in the vicinity of crack tip in orthotropic material are similar to those of isotropic material or orthotropic material with stationary crack under the static load. Dynamic stress intensity factors are decreased as crack growths. It was certified that the dynamic photoelastic experimental hybrid method was very useful for the analysis of the dynamic fracture mechanics.

• 자원ㆍ환경경제연구
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• 제23권1호
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• pp.91-132
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• 2014

본 논문은 한국, 미국, 영국의 제조업 및 전기 가스 수도사업에서 ICT 확산이 노동 및 에너지 수요에 어떠한 영향을 미치는지 연구하였다. 제조업에 대해서는 ICT 자본, 비ICT 자본, 노동, 전기, 연료, 재료를 생산요소로 가정하고, 전기 가스 수도사업에 대해서는 ICT 자본, 비 ICT 자본, 노동, 에너지 재료를 생산요소로 가정하여 요소 간 대체관계를 분석하였다. 모리시마 대체탄력성 추정결과 및 요소의 상대적 가격변화를 고려할 때, 3개 국가의 제조업 및 전기 가스 수도사업에서 ICT 자본은 노동을 대체하여 노동 수요를 감소시키는 것으로 나타났다. ICT 자본에 비해 전기 및 연료의 가격증가율이 높은 미국과 영국의 제조업에서 ICT 자본은 전기 및 연료를 대체하여 에너지 수요를 감소시키는 것으로 나타났다. 한국의 제조업에서 ICT 자본과 전기 및 연료가 대체관계에 있으나, 요소의 상대적 가격변화를 고려하면 ICT 자본이 에너지 수요 감소에 기여했다고 보기 어렵다. 3개 국가의 전기 가스 수도사업에서 ICT 자본은 에너지 재료를 거의 탄력적으로 대체하여 에너지 재료 수요를 감소시키는 것으로 분석되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1394-1397
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• 1995

In the hazardous areas where explosive gases, vapor or mists exist, electrical apparatus and installations must be of explosion-proof construction to prevent or limit the danger of the ignition of potentially explosive atmosphere. In Korea, nine types of protection have been specified in the government regulations at present: flameproof enclosure, pressurization, oil immersion, increased safety, intrinsic safety, non-incendive, sand filling, encapsulation, and special types. Among these types, the intrinsic safety has the construction which limit or by-pass igniting the electric energy using electronic devices. This type has lots of merits but at the same time requires a high-degree of technology. In this paper, we investigated several dominating factors which affect the minimum ignition energy: this energy plays a very important role in design and evaluation of the intrinsic safety type electrical apparatus. Eletrode material, which is one of the most important factors, was intensively studied for the five sorts of material(Al, Cd, Mg, Sn, and Zn) with performing experiment in a low-voltage inductive circuit using IEC-type spark apparatus. The experimental results show that the minimum ignition energy of electrode material is varied: highest in Cd and lowest in Sn. We also confirmed the effect of eletrode make-and-break speed and magnetic field magnitude.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1652-1657
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• 2021

Nuclear materials can be utilized not only for peaceful uses, but also for military purposes; hence, the international community has devoted itself to the control, management and safeguarding of nuclear materials. Nuclear materials are of varying degrees of usability for development of nuclear weapons. Thus, several methods for assessing the attractiveness of nuclear materials for nuclear weapons purposes have been proposed. When these methods are applied to unirradiated depleted, natural, and low-enriched uranium (DU, NU, and LEU), they are certainly classified as non-attractive nuclear materials. However, when nuclear material attractiveness is to be evaluated for potential radiological dispersal device (RDD) uses, it is required to develop a different method for the different aspects and factors. In the present study, we derived a novel method for evaluating nuclear material attractiveness for use in RDD development. To this end, the specific activity and dose coefficient were identified as the two sub-factors, and, in consideration of those, the mass causing detrimental health effects was determined to be the main factor impacting on nuclear materials attractiveness. Based on this factor, the attractiveness of unirradiated DU, NU, and LEU for RDD use was qualitatively compared with that of ¹³⁷Cs.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.613-617
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• 2006

개별 하천에 존재하는 하상재료는 상류의 지질특성과 유수에 의한 작용력의 특성을 반영하고 있으며 유수에 의한 작용력은 하상경사와 유량규모에 지배적인 영향을 받는다. 산본 황일(山本 晃一)(1994)에 의하면 자연하천에서 동일한 경사를 가지는 하도 구간은 하상재료, 소류력, 저수로 폭, 수심 등이 대체로 동일한 값을 나타내고 있으며, 하도 특성을 지배하는 주요인자로 각 하천의 평균연최대유량, 하상재료의 대표입경, 하상경사 등을 설정하고 있다. 하상재료는 하도의 물리적, 생태적 특성을 지배하는 대표적인 인자로 의미가 있으나 국내에서는 이와 관련된 연구가 미비한 실정이다. 본 연구에서는 국내 하천의 하도 특성을 분석하는 기초연구로서 대표하천에 대한 하상재료를 채취하여 분석하였으며 이를 분급도와 하상경사와의 관계로 도시하여 하상재료 분포 특성을 분석하였으며 이를 일본 하천의 하상재료 특성과 비교하였다. 분석결과에 의하면 분급도, 무차원 소류력, 하상경사와의 관계 분석을 통해서 자갈과 모래하천은 그 특성이 뚜렷이 구분됨을 확인할 수 있었으며, 하상경사와 대표입경의 관계도 모래와 자갈을 구분하여 접근하여야 함을 확인하였다.