• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.298-302
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• 2008

주어진 작은 크기의 칩 내부에 많은 기능 (예: 멀티미디어, 음성/영상 등)을 작동시키기 위해서는 고집적(high-integration)의 회로가 구현되게 된다. 이러한 고집적 회로는 작동할 때 상당한 양의 전력 소모를 유발하게 되어 결국 배더리 수명을 단축시키는 상황을 가지게 한다. 더욱 심각한 상황은 고 밀도의 칩 안에서의 많은 전력 소모는 열의 발생을 더욱 가속화 시키게 되며, 결국 칩 작동의 신뢰성(reliability)을 상당히 잃게 만든다. 본 연구에서는 칩의 작동에 따른 열 발생으로 유발되는 칩의 온도 상승을 감지하는 센서회로 구현에 관한 것이다. FPGA 칩은 주 목적의 기능을 수행하는 회로들을 구현함과 동시에 추가적으로 열 감지 센서 회로를 구현할 자원을 FPGA가 제공을 해 주어야 하는데, 주목적의 회로 공간(즉, 자원) 사용으로 인해 열 센서 회로 구현 자원이 충분하지 않을 경우나 여러 지역에 사용 가능한 자원이 소규모로 흩어진 경우 등 센서 구현을 위한 자원 탐색 및 구현 가능성에 대해 점검하는 알고리즘이 필요하다. 본 연구는 이러한 알고리즘을 개발하여 그 효용성을 실험을 통해 보이고 있다. 제안한 알고리즘의 특징은 Branch-and-Bound에 기반을 두고 있으며, 알고리즘의 수행 시간 단축을 위한 효과적인 search tree pruning 기법을 제안하고 있다.

• Coupled systems mechanics
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• v.6 no.2
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• pp.189-206
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• 2017

Tanks are used to store a wide variety of liquids such as oil, gasoline and water. It is reported that, a large number of tanks have been damaged during severe earthquakes. Therefore, understanding their behavior under earthquake is an important subject for structural engineers. In this paper, a comprehensive study is presented on dynamic response of tanks. A parametric study has been completed on the rectangular storage tanks with aid of finite element method (FEM). Various parameters are investigated, such as; liquid height, density and earthquake with different peak ground acceleration (PGA). When investigating these parameters, modal and time history method is used. Six different earthquake records are used for time history analysis. The analysis results show that when the PGA increases by 10.7 times, the maximum displacements, stress, sloshing and base shear increase by 11.4, 22.6, 5.46 and 17.8 times, respectively and when the liquid height increases by two times, the absolute maximum values of stress, displacements, base shear and sloshing increase 1.65, 2.04, 2.05 and 1.34. Furthermore, values of sloshing increase with decrease in density.

• Earthquakes and Structures
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• v.15 no.5
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.453-463
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• 2018

Three points bending flexural test was modelled numerically to study the crack propagation in the pre-cracked beams. The pre-existing double internal cracks inside the beam models were considered to investigate the crack propagation and coalescence paths within the modelled samples. Notch configuration effects on the failure stress were considered too. This numerical analysis shown that the propagation of wing cracks emanating from the tips of the pre-existing internal cracks caused the final breaking of beams specimens. It was also shown that when two notches were overlapped, they both mobilized in the failure process and the failure stress was decreased when the notches were located in centre line. However, the failure stress was increased by increasing the bridge area angle. Finally, it was shown that in all cases, there were good agreements between the discrete element method results and, the other numerical and experimental results. In this research, it is tried to improve the understanding of the crack propagation and crack coalescence phenomena in brittle materials which is of paramount importance in the stability analyses of rock and concrete structures, such as the underground openings, rock slopes and tunnel construction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.3
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• pp.156-164
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• 2010

Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use not only the advantages of the transfer matrix method but also well established classic control theories. The approach is applied to a gas turbine combustion system, which shows the validity and effectiveness of the approach.

• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.320-325
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• 1982

Utilyzing the solution prepared for the sulfur determination, the amounts of iron, copper and cobalt in the sulfide ore were determined by X-ray fluorescence spectrometry. The samples were dissolved with the mixed solutions of ,$Br_2\;and\;HNO_3$ and a major constituent of $SiO_2$was repelled from the solution by HF treatment several times. The analytical results agreed with the data obtained by conventional methods within ${\pm}$1.5% for Fe of the range of 20 to 50%, ${\pm}$1.0% for Cu of 10 to 15%, and ${\pm}$0.4% for Co of 1 to 5%. The present method was tolerably found to be reproducible.

• Korean Journal of Adult Nursing
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• v.19 no.4
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• pp.567-582
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• 2007

Purpose: The purpose of this study was to explore the utilization of the Transtheoretical Model(TTM) for Korean nursing studies on health behaviors and identify the strategies for improvement of further studies. Methods: From a main and seven branch journals on the Korean Society of Nursing Science, a total of 26 studies, which had been conducted based upon the TTM, were selected. The selected studies were analyzed from the September of 2006 to the February of 2007 by the criteria; name of journal, year of publication, health behavior, population, sampling, sample size, research design, instrument (translation process, reliability and validity), and statistical analysis. Results: TTM on the Korean nursing studies was mainly applied for smoking cessation or exercise with elderly or middle aged women. The research findings could not be generalized with the limitation of the use of non representative samples. The most frequently used research design was a cross-sectional survey. Some studies had a lack of reliable and valid instruments, so that the internal validity of the study findings may be threatened. Statistically related problems increased type I error and decreased power. Conclusion: Korean nursing studies based on TTM can be the beginning stage in quality and quantity.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.30.1-30.1
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• 2016

We have estimated a metallicity map of the Large Magellanic Cloud (LMC) using the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind, high-spatial resolution map of metallicity up to a radius of $4^{\circ}-5^{\circ}$, derived using large area photometric data and calibrated using spectroscopic data of Red Giant Branch (RGB) stars. The RGB is identified in the V, (V - I) colour- magnitude diagrams of small subregions of varying sizes in both data sets. The slope of the RGB is used as an indicator of the mean metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The mean metallicity of the LMC is found to be [Fe/H] = -0.37 dex (${\sigma}[Fe/H]=0.12$) from MCPS data, and [Fe/H] = -0.39 dex (${\sigma}[Fe/H]=0.10$) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc ($-0.049{\pm}0.002$ dex kpc-1 to $-0.066{\pm}0.006$ dex kpc-1). This metallicity gradient of the LMC disk, though shallow, resembles the gradient seen in spiral galaxies, and similar to that found in our Galaxy.

• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.1-8
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• 2015

Thermoelectric (TE) technology is becoming increasingly important in applications of solid-state cooling and renewable energy sources. $Bi_2Te_3$-based TE materials are widely used in small-scale cooling and temperature control applications; however, higher levels of TE performance are required for new applications such as large-scale cooling (e.g., domestic refrigerators or air conditioners) and for highly efficient power generation system. Recently, the TE performance of $Bi_2Te_3$-based materials has been remarkably enhanced by the introduction of nanostructuring technologies which can be used to prepare TE raw materials. Because it takes into account the theoretical and experimental characteristics, nanostructuring has been shown to be one of the most promising ways to realize the simultaneous control of the electronic and thermal transport properties. In this review, emphasis is placed on bulk-type nanostructured $Bi_2Te_3$-based TE materials. Nanostructuring technologies for enhanced TE performance are summarized, and a few important strategies are presented.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.720-724
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• 2003

Aluminum nitride (AlN) powders were synthesized by using a mixture of an aluminum nitrate or sulfate salt and carbon (mole ratio of $Al^{3+}$ to carbon=L : 30). The AlN was obtained by calcining the mixture under a flow of nitrogen in the temperature range 1100-1$600^{\circ}C$ and then burning out the residual carbon. The process of conversion of the salt to AlN was monitored by XRD and $^{27}$ Al magic-angle spinning (MAS) NMR spectroscopy. The salt decomposed to ${\gamma}$-alumina and then converted to AlN without phase transition from ${\gamma}$-to-$\alpha$-alumina. $^{27}$ Al MAS NMR spectroscopy shows that the formation of AlN commenced at 110$0^{\circ}C$. AlN powders obtained from the sulfate salt were superior to those from the nitrate salt in terms of homogeneity and crystallinity. A very small amount of AlN whiskers was obtained by calcining a mixture of an aluminum sulfate salt and carbon at 115$0^{\circ}C$ for 40 h, and the growth of the whiskers is well explained by the particle-to-particle self-assembly mechanism.