• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.1
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• pp.63-67
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• 2009

Current mismatch in a charge pump causes degradation in spectral purity of the phase locked loops(PLLs), such as reference spurs. The current mismatch can be reduced by increasing the output resistance of the charge pump, as in a cascoded output stage. However as the supply voltage is lowered, it is hard to stack transistors. In this paper, a new method for reducing the current mismatch is proposed. The proposed method is based on a feed-forward compensation for the channel length modulation effect of the output stage. The new method has been demonstrated through simulations on typical $0.18{\mu}m$ CMOS circuits.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.85-93
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• 2016

In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

• 한국벤처창업학회:학술대회논문집
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• 2019.11a
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• pp.107-112
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• 2019

21세기 4차 산업혁명 시대에 급변하는 산업과 기술 발전으로 인해 기존의 직업과 일자리의 위협과 변화가 커짐에 따라 청소년의 진로에 대한 준비는 더욱 절실해졌다. 청소년들은 급격한 기술 발전과 시장의 변화로 인한 기존 직업 소멸, 일생에서의 직업 활동기간의 비약적인 증가가 맞물려서 평생 한 번은 창직이나 창업을 해야만 하는 시대를 살고 있다. 이에 대비하기 위해 진로 및 직업활동에 대한 기회를 발견하고, 급변하는 시대와 시장의 다양한 문제들을 창의적으로 해결하고, 남들과 다르게 자신만의 방법으로 다방면의 경험과 지식을 쌓기 위한 자기주도적 학습력이 필수가 되었다. 본 연구는 그동안 다루어지지 않았던 청소년의 기회발견, 창의성 역량, 자기주도 학습력이 진로결정 자기효능감에 미치는 영향에 대해 청소년 진로교육 사례를 중심의 연구이다. 청소년에게 기회발견, 창의성 역량, 자기주도 학습력이 기업가정신의 매개로 하여 진로결정 자기효능감에 어떠한 영향을 미치는지에 대한 것이 주요 연구목적이다. 분석결과, 첫째로 기회발견, 창의성 역량, 자기주도 학습력은 진로결정 자기효능감에 유의한 영향을 미치는 것으로 나타났다. 둘째, 기업가정신의 향상 정도에 따라 진로결정 자기효능감에 매개 역할을 부분적으로 하고 있음이 확인되었다. 이와 같은 결과는 앞으로 청소년의 진로 및 기업가정신 교육에 중요한 자료가 될 것이며, 향후 청소년 진로 및 기업가정신 교육 프로그램의 연구개발을 위해 관련 연구가 확대 되어야 할 것이다.

• The KIPS Transactions:PartB
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• v.16B no.6
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• pp.489-496
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• 2009

Hierarchical Task Network(HTN) planning, a typical planning method for effectively taking advantage of domain-specific control knowledge, has been widely used in complex real applications for a long time. However, it still lacks theoretical formalization and standardization, and so there are some differences among existing HTN planners in terms of principle and performance. In this paper, we present an effective way to translate a HTN planning domain specification into the corresponding standard PDDL specification. Its main advantage is to allow even many domain-independent classical planners to utilize domain-specific control knowledge contained in the HTN specifications. In this paper, we try our translation-based approach to three different domains such as Blocks World, Office Delivery, Hanoi Tower, and then conduct some experiments with a forward-chaining heuristic state-space planner, FF, to analyze the efficiency of our approach.

• Journal of the Korea Society for Simulation
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• v.15 no.2
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• pp.1-12
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• 2006

As the needs of intelligent systems increase, there have been diverse approaches that combine artificial intelligence (AI) and simulation in the last decade. RG-DEVS, which is the basis for this paper, embedded AI planning techniques into the simulation modeling methodology of DEVS, in order to specify dynamically a simulation model. However, a hierarchy concept, which is used for various types of problem solving systems. is not included in the planning of RG-DEVS. The hierarchy concept reduces the computational cost of planning by reducing the search space, and also makes it easy to apply the hierarchical process flow of a target system to planning. This paper proposes Hierarchical RG-DEVS (HRG-DEVS) in an attempt to insert hierarchical planning capability into RG-DEVS. For the verification of the proposed modeling methodology, HRG-DEVS is applied to model the block's world problem of ABSTRIPS, which is a classical planning problem.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.12
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• pp.1769-1776
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• 2022

Automatically summarizing long sentences is an important technique. The BART model is one of the widely used models in the summarization task. In general, in order to generate a summarization model of a specific domain, fine-tuning is performed by re-training a language model trained on a large dataset to fit the domain. The fine-tuning is usually done by changing the number of nodes in the last fully connected layer. However, in this paper, we propose a fine-tuning method by adding an attention layer, which has been recently applied to various models and shows good performance. In order to evaluate the performance of the proposed method, various experiments were conducted, such as accumulating layers deeper, fine-tuning without skip connections during the fine tuning process, and so on. As a result, the BART model using two attention layers with skip connection shows the best score.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.479-479
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• 2011

전 세계는 현재 이상기후와 국지적인 돌발호우 및 가뭄으로 많은 어려움을 겪고 있다. 우리나라도 예외가 아니어서 지난 겨울에 많은 폭설로 여러 지역에서 도로단절, 농작물 피해 및 공공 시설물의 파괴 등 날로 기후변화에 따른 피해가 증가하고 있다. 또한 지난 몇 해 전에도 강원도지역 가뭄으로 인한 식수 및 농업용수 부족으로 인근 지역의 식수원 및 농작물 피해를 겪어야만 했다. 이러한 수자원의 변화에 능동적으로 대처할 수 있는 방법은 여러 가지가 있겠으나, 대규모 저수지 및 랩을 신설하는 것이 가장 수자원확보에 용이한 방법이다 그러나, 대규모 저수지 및 댐을 건설할 수 있는 적지의 감소로 수자원확보가 예전보다 수월하지 않다. 이러한 대안으로 기존 수자원시설물의 개량 혹은 재개발로 수자원의 일부인 농업용수를 확보하는 경제적인 방안이 활용되고 있다. 농업용 저수지중 콘크리트 댐으로 구성된 제체 높이를 17.0m에서 3.1m 높여 20.1m로 증고하여, 환경용수를 포함한 유효저수량을 184만 $m^3$을 추가 확보하여 하류 수혜구역 485.9ha에 농업용수 공급 및 갈수기 하류하천의 환경용수를 제공할 수 있도록 계획하였다. 경상북도 남동단에 형산강 지류에 위치한 OO 저수지는 기계천을 중심으로 형산강에 도달하며 동쪽으로는 포항시 신광변, 북쪽으로는 포항시 죽장면과 경계를 이루고 있다. OO 저수지는 기존 저수지 콘크리트 범 상류면 보강 및 내측 덧쌓기, 하류면 보강 및 외측 덧 쌓기, 기존 저수지 하류에 신설탬을 설치하는 안으로 비교하여 결정하였으며, 저수지 제체 입지 여건 등을 종합적으로 비교 검토한 결과 콘크리트 댐 상류면에 보강 및 내측 덧쌓기 안이 가장 시공성에 있어 효율적이며 경제적이므로 선정하여 계획하였다.

• Polymer(Korea)
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• v.37 no.4
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• pp.411-419
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• 2013

Various biomaterials have been widely used for biomedical applications, including bio-organs, medical devices, and clinical devices like vessel, blood pumps, artificial kidneys and hearts, even in contact with blood. The issue of blood compatibility has been studied intensively to prevent negative effects such as thrombosis due to the implanted devices. The use of lotus-leaf-like structured surfaces has been extended to an increasing number of applications such as contamination prevention and anticorrosion applications. Various methods such as template, sol-gel transition, layer-by-layer, and other methods, developed for the fabrication of lotus-leaf-like surfaces have been reported for major industrial applications. Recently, the non-wettable character of these surfaces has been shown to be useful for biomedical applications ranging from blood-vessel replacement to antibacterial surface treatment. In this review, we provide a summary of current and future research efforts and opportunities in the development and medical applications of lotus-leaf-like structure surfaces.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.581-587
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• 2004

Conventional power spectrum methods based on FFT, AR method are not appropriate for analyzing biomedical signals whose spectral characteristics change rapidly. On the other hand, time-frequency analysis has more desirable characteristics of a time-varying spectrum. In this study, we investigated the spectral components of heart rate variability(HRV) in time-frequency domain using time frequency analysis methods. In the various time-frequency kernels functions, we studied the suitable kernels for the analysis of HRV using synthetic HRV signals. First, we evaluated the time/frequency resolution and cross term reduction of various kernel functions. Then, from the instantaneous frequency, obtained from time-frequency distribution, the method extracting frequency components of HRV was proposed. Subjects were 17 healthy young men. A coin-stacking task was used to induce mental stress. For each subjects, the experiment time was 3 minutes. Electrocardiogram, measured during the experiment, was analyzed after converted to HRV signal. In the results, emotional stress of subjects produced an increase in sympathetic activity. Sympathetic activation was responsible for the significant increase in the LF/HF ratio. Subjects were divided into two groups with task ability. Subjects who have higher mental stress have lack of task ability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.103-110
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• 2011

This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.