• 한국환경보건학회지
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• 제34권6호
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• pp.414-422
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• 2008

Methane is a potent greenhouse gas and methane emissions from landfill sites have been linked to global warming. In this study, LandGEM (Landfill Gas Emission Model) was applied to predict landfill gas quantity over time, and then this result was compared with the data surveyed on the site, Cheongju Megalo Landfill. LandGEM allows the input of site-specific values for methane generation rate (k) and potential methane generation capacity $L_o$, but in this study, k value of 0.04/yr and $L_o$ value of $100\;m^3$/ton were considered to be most appropriate for reflecting non-arid temperate region conventional landfilling like Cheongju Megalo Landfill. Relatively high discrepancies between the surveyed data and the predicted data about landfill gas seems to be derived from insufficient compaction of daily soil-cover, inefficient recovery of landfill gas and banning of direct landfilling of food waste in 2005. This study can be used for dissemination of information and increasing awareness about the benefits of recovering and utilizing LFG (landfill gas) and mitigating greenhouse gas emissions.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.540-549
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• 2018

This paper proposes the method of active distribution network expansion planning considering distributed generation integration and distribution network reconfiguration. The distribution network reconfiguration is taken as the expansion planning alternative with zero investment cost of the branches. During the process of the reconfiguration in expansion planning, all the branches are taken as the alternative branches. The objective is to minimize the total costs of the distribution network in the planning period. The expansion alternatives such as active management, new lines, new substations, substation expansion and Distributed Generation (DG) installation are considered. Distribution network reconfiguration is a complex mixed-integer nonlinear programming problem, with integration of DGs and active managements, the active distribution network expansion planning considering distribution network reconfiguration becomes much more complex. This paper converts the dual-level expansion model to Second-Order Cone Programming (SOCP) model, which can be solved with commercial solver GUROBI. The proposed model and method are tested on the modified IEEE 33-bus system and Portugal 54-bus system.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.15-21
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• 2009

High-order harmonic generation from a solid surface affected by the contrast of a laser pulse was studied using an oscillating mirror model. High-order harmonics generated from solid surfaces have unusual properties such as spectral redshift, and an intensity difference between even- and odd-order harmonics which is not reported for high-order harmonics generated by a gas medium. We confirmed that high-order harmonics from solid surfaces have selectivity of polarization as well as cut-off extension and the enhancement of conversion efficiency proportional to laser intensity. And the principle of operation and the characteristics of a plasma mirror system developed for achieving high contrast laser pulses to pursue the experimental realization of high-harmonic generation from solid surfaces are reported. Energy fluence on the plasma mirrors is tunable between $10\;J/cm^2$ and $1000\;J/cm^2$ and around 1000 shots are available before the plasma mirrors require replacement.

• 한국CDE학회논문집
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• 제7권3호
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• pp.148-156
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• 2002

Most Rapid Prototyping (RP) processes adopt a solid Computer Aided Design (CAD) model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; and eventually the stacked layers from a physical part of the model. A new RP process, the transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST), has been developed to reduce building time and to improve the surface finish of parts with the thick layers and a sloping surface. This paper describes the generation of Unit Shape Layer (USL), the cutting path data of the linen. hotwire cutter for the VLM-ST process. USL is a three-dimensional layer with a thickness of more than 1 mm and a side slope, and it is the basic unit of cutting and building in the VLM-ST process. USL includes data such as layer thickness, positional coordinates, side angles of each layer, hotwire cutting speed, the heat input to the hotwire, and reference shape. The procedure of generating USL is as follows: (1)Generation of the mid-slice from the CAD model, (2)Conversion of the mid-slice into a simply connected domain, (3)Generation to the reference shape for the mid-slice, (4)Calculation of the rotation angle of the hotwire of the cutting system.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.893-903
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• 2022

Recently, computer vision (CV)-based safety monitoring (i.e., object detection) system has been widely researched in the construction industry. Sufficient and high-quality data collection is required to detect objects accurately. Such data collection is significant for detecting small objects or images from different camera angles. Although several previous studies proposed novel data augmentation and synthetic data generation approaches, it is still not thoroughly addressed (i.e., limited accuracy) in the dynamic construction work environment. In this study, we proposed a game engine-driven synthetic data generation model to enhance the accuracy of the CV-based object detection model, mainly targeting small objects. In the virtual 3D environment, we generated synthetic data to complement training images by altering the virtual camera angles. The main contribution of this paper is to confirm whether synthetic data generated in the game engine can improve the accuracy of the CV-based object detection model.

• Communications for Statistical Applications and Methods
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• 제30권6호
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• pp.589-603
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• 2023

Deep generative models target to infer the underlying true data distribution, and it leads to a huge success in generating fake-but-realistic data. Regarding such a perspective, the data attributes can be a crucial factor in the data generation process since non-existent counterfactual samples can be generated by altering certain factors. For example, we can generate new portrait images by flipping the gender attribute or altering the hair color attributes. This paper proposes counterfactual disentangled variational autoencoder generative adversarial networks (CDVAE-GAN), specialized for data attribute level counterfactual data generation. The structure of the proposed CDVAE-GAN consists of variational autoencoders and generative adversarial networks. Specifically, we adopt a Gaussian variational autoencoder to extract low-dimensional disentangled data features and auxiliary Bernoulli latent variables to model the data attributes separately. Also, we utilize a generative adversarial network to generate data with high fidelity. By enjoying the benefits of the variational autoencoder with the additional Bernoulli latent variables and the generative adversarial network, the proposed CDVAE-GAN can control the data attributes, and it enables producing counterfactual data. Our experimental result on the CelebA dataset qualitatively shows that the generated samples from CDVAE-GAN are realistic. Also, the quantitative results support that the proposed model can produce data that can deceive other machine learning classifiers with the altered data attributes.

• 경영정보학연구
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• 제25권3호
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• pp.43-57
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• 2023

본 연구에서는 한국어 기반의 시를 창작하는 데 도움이 되는 문장들을 생성하는 인공지능을 개발하였다. 인공지능이 인간의 고유의 영역이라고 할 수 있는 창작에 대한 욕망과 창의력을 대신하는 것이 아니라, 인간이 창의력을 효율적으로 사용할 수 있도록, 창작에 밑바탕이 되는 문장들을 생성하는데 초점을 맞추었다. 시인들과의 인터뷰를 통해서 8개의 다른 데이터 세트로부터 문장을 학습하여 8가지 장르의 시가 생성될 수 있도록 만들었다. 이 연구는 한국어를 활용한 문학 작품 생성 기술을 개발하였다는 점에서 차별성이 있으며, 이 연구를 확장해서 수필과 산문 또는 소설과 같은 다양한 형태의 문학 작품을 창작하는 데 도움이 될 수 있다는 점에서 큰 의미가 있다.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.386-401
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• 2011

Mathematical models for various steps in coal gasification reactions were developed and applied to investigate the effects of operation parameters on dynamic behavior of gasification process. Chemical reactions considered in these models were pyrolysis, volatile combustion, water shift reaction, steam-methane reformation, and char gasification. Kinetics of heterogeneous reactions between char and gaseous agents was based on Random pore model. Momentum balance and Stokes' law were used to estimate the residence time of solid particles (char) in an up-flow reactor. The effects of operation parameters on syngas composition, reaction temperature, carbon conversion were verified. Parameters considered here for this purpose were $O_2$-to-coal mass ratio, pressure of reactor, composition of coal, diameter of char particle. On the basis of these parametric studies some quantitative parameter-response relationships were established from both dynamic and steady-state point of view. Without depending on steady state approximation, the present model can describe both transient and long-time limit behavior of the gasification system and accordingly serve as a proto-type dynamic simulator of coal gasification process. Incorporation of heat transfer through heterogenous boundaries, slag formation and steam generation is under progress and additional refinement of mathematical models to reflect the actual design of commercial gasifiers will be made in the near futureK.

• 한국과학교육학회지
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• 제25권5호
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• pp.595-602
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• 2005

이 연구의 목적은 과학학습에서 가설 생성력 향상에 미치는 삼원귀추모형(TAM)의 적용 효과를 검증하는 것이다. 이를 위해 TAM의 가설 생성 절차에 따른 가설 생성 활동 10개와 전통적인 방법에 따른 가설생성활동 10개를 개발하여 각각26명의 고등학생으로 구성된 TAM 집단과 27명의 전통 집단에 투입하였다. 가설 생성 활동 10개가 투입되는 과정에서 4개의 활동에서 학생들이 생성한 최종 가설의 설명도를 평가하였다. 또한 가설 생성력의 향상 정도를 검증하기 위해서 과학 지식 생성력 검사 A형과 B형을 사전과 사후에 각각 투입하여 연구 대상 학생들의 가설 생성력을 검사하였다. 연구 결과 TAM 집단이 생성한 가설의 설명도가 전통 집단의 가설보다 통계적으로 의미 있는 수준에서 높았다. 가설 생성력 검사에서는 TAM 집단과 전통 집단의 검사 점수가 사전 검사에서는 통계적으로 유의미한 수준에서 차이가 없었으나 사후에는 TAM집단이 의미 있게 높았다. 따라서 TAM을 적용한 가설 생성 활동은 전통적인 방법보다 가설 생성력 향상에 효과적이라고 할 수 있다.

• 한국산학기술학회논문지
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• 제21권9호
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• pp.210-217
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• 2020

여러 세대가 공존하는 다세대 기술 시장의 경우 성능, 가격 및 진입시점 등의 조정을 통해 다양한 진입모드가 가능하므로, 다세대 기술의 시장진입모드에 대한 이해가 중요하다. 본 연구에서는 다세대 기술의 시장진입모드에 대해 기술, 시간, 성능(또는 가격)의 다차원 관점에서 개념에 대해 정의하고, 다양한 진입모드의 종류에 대해 모형을 제시하고자 하였다. 문헌리뷰를 통해 다세대 기술의 시장진입모드의 정의 및 종류에 대한 모형을 제시하였고, 도출한 모형의 정합성을 반도체 및 스마트폰 시장 사례를 바탕으로 검증하였다. 다세대 기술의 시장진입모드는 6가지 종류(중간 성능 및 일찍 진입 모드, 높은 성능 및 일찍 진입 모드, 낮은 성능 및 일찍 진입 모드, 중간 성능 및 늦게 진입 모드, 높은 성능 및 늦게 진입 모드, 낮은 성능 및 늦게 진입 모드)로 모형화가 가능하였다. 본 연구를 토해 도출한 시장진입모드의 정의 및 종류에 대한 모형은 다세대 기술의 시장진입모드를 이해하는데 유용할 것이고, 다세대 기술 외에도 다른 특성의 시장에서도 적용 가능할 것이다.