• Wind and Structures
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• 제10권5호
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• pp.421-435
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• 2007

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

• Macromolecular Research
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• 제15권5호
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• pp.396-402
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• 2007

The dielectric properties and various pattern-forming states of dual-frequency material in a nematic phase, as well as its mixture containing low concentrations of reactive monomers, are reported. The dielectric relaxation behaviors of nematic MLC 2048 are presented and compared to its mixture containing both mesogenic and nonmesogenic reactive monomers. The sign-inversion frequency of the dielectric anisotropy was significantly shifted on the addition of small amounts of the reactive monomers. However, all three mixtures used in this study essentially exhibited the same field-induced instabilities at different frequencies and voltage domains of the applied electric field. A broad band of modulated states were found to exist above a critical voltage and within a voltage dependent frequency band in the vicinity of the sign-inversion frequency, $f_I$, of the dielectric anisotropy. As the $f_I$ of the mixtures shifted, so did the bands of the modulated state of the different mixtures and the temperatures, which were well matched with the measured $f_I$ value.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.140-147
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• 2003

There are many problems in the prediction of soil dynamic behaviors because undrained excess pore water pressure builds up and then the strain softening behavior is occurred simultaneously. A few analytical methods based on the dynamic constitutive model have been proposed but the model hardly predict the excess pore water pressure directly. In this study, the verification on the disturbed state concept (DSC) model, proposed by Dr, Desai was performed. Some laboratory tests such as conventional triaxial tests and cyclic triaxial tests were carried out to determine DSC Parameters and then disturbance values are determined by the proposed equation. Through this verification, it is proved that the disturbed state concept can express reliably the soil dynamic characteristics such as excess pore water pressure and strain softening behavior. It is also found that the critical disturbance which is determined at the minimum curvature of disturbance function can be a the specific index.

• Nuclear Engineering and Technology
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• 제41권9호
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• pp.1205-1214
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• 2009

The critical heat flux (CHF) levels that occurred due to exponential heat inputs for varying periods to a 1.0-mm diameter horizontal cylinder immersed in various liquids were measured to develop an extended database on the effect of high subcoolings for quasi-steady-state and transient maximum heat fluxes. Two main mechanisms of CHF were found. One mechanism is due to the time lag of the hydrodynamic instability (HI) which starts at steady-state CHF upon fully developed nucleate boiling, and the other mechanism is due to the explosive process of heterogeneous spontaneous nucleation (HSN) which occurs at a certain HSN superheat in originally flooded cavities on the cylinder surface. Steady-state CHFs were divided into three regions for lower, intermediate and higher subcooling at pressures resulting from HI, transition and HSN, respectively. HSN consistently occurred in the transient boiling CHF conditions that correspond to a short period. It was also found that the transient boiling CHFs gradually increased, then rapidly decreased and finally increased again as the period became shorter.

• 사회복지연구
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• 제44권1호
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• pp.267-302
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• 2013

최근 들어, 사회복지 프로그램을 집행하는 데 있어서 정부, 시민사회, 시장의 협업을 표방하는 파트너십이 전세계적인 추세로 떠오르고 있다. 특히 제 3섹터, 비영리단체, NGO로 불리는 시민사회단체는 국가의 경직성과 시장의 이윤추구가 갖는 한계를 넘어 공공서비스를 전달하기에 가장 적합한 행위자로 주목받고 있다. 이 같은 시민사회의 공공정책 주류화 현상은 기존의 시민사회 개념에 대한 재정립을 요구한다. 근대사회에서 시민사회단체는 국가와 시장에 대한 비판기능을 수행하는 자발적 결사체로 정의되어 왔다. 그러나 시민사회의 독자성와 자율성을 지향하는 전통 시민사회 이론은 탈경계, 혼종성, 상호의존을 특징으로 하는 복지다원주의 시대의 시민사회를 설명하는 데 한계를 가지고 있다. 그러나 현재 국가-시민사회 파트너십에 대한 연구들은 대부분 규범적 전망 제시나 개별 사례연구에 머물러 있고, 파트너십 체계에서 시민사회의 위치를 종합적으로 이론화하는 데에는 이르지 못하고 있다. 이에 본 연구는 민관파트너십 시대에 시민사회의 역할에 이론화를 시도했다. 이를 위해 먼저 본 논문은 시민사회 고전이론을 (1) 토크빌 중심의 기능주의/자유주의적 전통(견제와 균형자로서의 시민사회), (2) 맑스, 알튀세르, 푸코를 필두로 한 갈등주의/(후기)구조주의적 전통(이데올로기적 국가장치로서의 시민사회), (3) 그람시, 하버마스에서 출발한 갈등주의/비판이론적 전통(헤게모니 투쟁의 장으로서의 시민사회)으로 나누고, 각 전통의 특성과 공통점을 일별했다. 이어서 본 연구는 본격적으로 국가-시민사회 복지파트너십 관련 동서양의 문헌과 논쟁들을 포괄적으로 검토하면서, 파트너십에서 시민사회의 위치와 정체성을 해석하는 시각을 다음 세 가지 관점으로 나누어 살펴보았다: (1) 주류적 관점(민주적 파트너로서의 시민사회); (2) 비판적 관점(그림자 정부로서의 시민사회); (3) 대안적 관점(지속적 미시저항의 장으로서의 시민사회)이 그것이다. 또한 각 관점의 대표학자와 주요개념, 한계와 특성을 분석하고, 위 이론적 관점과 시민사회 고전이론 사이의 연결점을 짚어보았다. 이와 같은 복지파트너십 문헌들의 이론화 작업을 통해 향후 민관파트너십의 정치역학을 관찰하고자 하는 후속연구들에 참고가 될 만한 분석틀을 제공하고자 했다.

• 산업기술연구
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• 제19권
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• pp.253-260
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• 1999

Two thermodynamic models were used to predict the partial molar volumes of solutes in supercritical carbon dioxide at infinite dilution: (1) the Peng-Robinson equation of state with various mixing rules including those based on $EOS/G^E$ (2) the Kirkwood Buff fluctuation integral with the hard sphere expansion (HSE) method. The Kirkwood-Buff fluctuation integral method, in which an equation of state for pure component and molecular parameters are required, produced better results especially near the critical point than the Peng-Robinson equation of state with the several mixing rules based an $EOS/G^E$. When the $EOS/G^E$ mixing rules were used, poorer results were obtained compared with the classical mixing rule and Kirkwood-Buff model.

• 한국지반공학회지:지반
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• 제10권1호
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• pp.7-18
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• 1994

본 연구에서는 단조하중과 반복하중에 대한 점토지반의 거동을 표현할 수 있는 새로운 구성모델을 제안하였다. 제안된 모델은 과압밀상태에서의 응력-변형률 관계를 쌍곡선식으로 가정하고 한계상태이론과 결합시켜 비배수 응력경로를 예측한다. 에너지분산식을 이용하여 개발된 이 구성모델은 단조하중 작용시에 미약한 과압밀상태 및 과다한 과압밀상태의 점성토거동을 표현할 수 있다. 또한 반복하중하에서의 거동을 나타내기 위하여 단조하중에 대하여 개발된 구성모델에 비배수 경로간격비 이동함수를 도입하였다. 이를 위하여 한개의 추가적인 모델계수가 필요하며 그 값은 합리적 방법으로 실험결과로부터 산정될 수 있다. 본 구성모델은 비교적 쉽고 정확하게 반복하중을 받는 점성토지반의 비배수 거동에 대한 실험결과를 예측한다.

• Structural Engineering and Mechanics
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• 제44권6호
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• pp.801-814
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• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• Smart Structures and Systems
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• 제7권4호
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• pp.289-302
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• 2011

In marine clay deposits, naturally formed or artificially reclaimed, the evaluation and monitoring of the consolidation process has been a critical issue in civil engineering practices due to the time frame required for completing the consolidation process, which range from several days to several years. While complementing the conventional iconographic method suggested by Casagrande and recently developed in-situ techniques that measure the shear wave, this study suggests an alternative experimental procedure that can be used to evaluate the consolidation state of marine clay deposits using the shear wave velocity. A laboratory consolidation testing apparatus was implemented with bimorph-type piezoelectric bender elements to determine the effective stress-shear wave velocity (${\sigma}^{\prime}-V_s$) relationship with the marine clays of interest. The in-situ consolidation state was then evaluated by comparing the in-situ shear wave velocity data with the effective stress-shear wave velocity relationships obtained from laboratory experiments. The suggested methodology was applied and verified at three different sites in South Korea, i.e., a foreshore site in Incheon, a submarine deposit in Busan, and an estuary delta deposit in Busan. It is found that the shear wave-based experimental procedure presented in this paper can be effectively and reliably used to evaluate the consolidation state of marine clay deposits.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.605-616
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• 2014

When the periodic cellular structure is loaded or swelling beyond the critical value, the structure may undergo a pattern transformation owing to the local elastic instabilities, thus leading to structural collapse and the structure changing to a new configuration. Based on this deformation-triggered pattern, we have proposed the novel composite gel materials. This designed material is a type of architectural material possessing special mechanical properties. In this study, the mechanical behavior of the composite gel periodic structure with various gel inclusions is studied further through numerical simulations. When pattern transformation occurs, it results in a different elastic relationship compared with the material at untransformed state. Based on the obtained nominal stress versus nominal strain behavior, the Poisson's ratio and corresponding deformed structure patterns, we investigate the performance of designed composite materials and the effects of the uniformly distributed gel inclusions on composite materials. A better understanding of the characteristics of these composite gel materials is a key to develop its potential applications on new soft machines.