• Advances in Energy Research
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• 제1권1호
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• pp.53-78
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• 2013

Methane carbon dioxide reforming (MCDR) is a promising way of utilizing greenhouse gas for hydrogen-rich fuel production. Compared with other types of reactors, Compact Reformers (CRs) are efficient for fuel processing. In a CR, a thin solid plate is placed between two porous catalyst layers to enable efficient heat transfer between the two catalyst layers. In this study, the physical and chemical processes of MCDR in a CR are studied numerically with a 2D numerical model. The model considers the multi-component gas transport and heat transfer in the fuel channel and the porous catalyst layer, and the MCDR reaction kinetics in the catalyst layer. The finite volume method (FVM) is used for discretizing the governing equations. The SIMPLEC algorithm is used to couple the pressure and the velocity. Parametrical simulations are conducted to analyze in detail the effects of various operating/structural parameters on the fuel processing behavior.

• 한국공작기계학회논문집
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• 제14권6호
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• pp.117-124
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• 2005

This study developes the vibration model to estimate the vibration energy of compact disc player's mainbase assembly which is supported by dampers and springs, and this model is verified by experiment. From frequency response function, we investigate the natural frequency and mode shape in the up/down direction for mainbase assembly. In order to determine the analysis frequency band, we investigate the excitation frequency of road from the vehicle test. As the characteristics of dampers and springs are changed, we carry out the sensitivity analysis of vibration energy for mainbase assembly which include optical pick-up and feeding system. And we found out that the properties of damper were dominant element in the vibration energy of mainbase assembly's CG(center of gravity).

• 한국세라믹학회지
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• 제31권4호
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• pp.347-358
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• 1994

Creep densification and grain growth of alumina powder compacts during high temperature processing were investigated. The creep densification and grain growth of alumina powder compacts during various sintering processes were analyzed by employing the consitutive model by Kwon and Kim. Theoretical results from the constitutive model were compared with various experimental data of alumina powder compacts in the literature including pressureless sintering, sinter forging and hot pressing. The proposed constitutive equations were implemented into finite element analysis program (ABAQUS) to simulate densification for more complicated geometry and loading conditions. The effects of friction between die and powder compact or punch and powder compact during sinter forging and hot pressing are investigated by using the finite element method. Also, high temperature forming processing of alumina compact with complicated shape was simulated.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.403-411
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• 2007

This article describes a methodology based on experiments and 1D modeling work related to the exhaust system analysis of a small two-stroke engine. The primary goal of this work was to understand how the design criteria of a compact exhaust system influenced the exhaust port pressure, since its evolution controls not only engine performance but also exhaust emissions. On the experimental side, a fully instrumented 50cc two-stroke engine was used to check the behavior of three different exhaust systems. A problem related to instantaneous pressure measurements in unsteady, hot flow was detected and solved during the study. To build the 1D model of the three exhaust systems, experimental information on the steady flow and the impulse test rigs was obtained under controlled conditions in specific facilities. Accurate comparisons between measured and calculated exhaust port instantaneous pressures were obtained from the following different exhaust system configurations: a straight duct, a tapered pipe and the three compact exhaust systems. The last step in the method used this model to analyze the pressure waves inside the exhaust system and detect the influence of the geometric parameters. The results should lead to improvements in the design process of complex compact exhaust systems in two-stroke engines.

• 한국대기환경학회지
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• 제16권6호
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• pp.653-663
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• 2000

A lot of hazardous wastes are discharged as by-products of working process by industrial development. Hazardous wastes is physical characteristics of difficult destruction at hight temperature. Numerical simulation and combustion experiment performed of dump incinerator for hazardous waste incineration. For the numerical simulation, the SIMPLEST algorithm was used to ensure rapid converge A K-$\varepsilon$ model was incorporate for the enclosure of turbulence flow. Combustion model was used by ESCRS (extended simple chemically reacting system) model available of CHEMKIN thermodynamic data for the source term of species conservation equation or energy equation. Radiation model is used by six flux model. A parametric screening studies was carried out through numerical simulation and experiment. Residence time and concentration in the incinerator was strongly dependent on the parameters of mixture velocity, mixture equilibrium ratio, surrogate velocity and surrogate equilibrium ratio.

• 한국전산유체공학회지
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• 제8권3호
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• pp.50-55
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• 2003

Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In the present work, the accuracy of a Fractional step method, which is widely used in LES simulation, has been increased to the fourth-order accurate compact Pade discretization. To validate the present code, the flow-field past a cylinder was simulated and compared with experiment. A good agreement with experiment was achieved.

• 한국측량학회지
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• 제33권3호
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• pp.193-202
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• 2015

The greenbelt of South Korea has been under the process of adjustment and removal since its first designated year. This research is aimed at predicting the effect that the removal of the greenbelt has on urban growth. The SLEUTH model was executed via three calibration phases using historical data between 1990 and 2010. The urban growth of Busan Metropolitan City was predicted under its historical trend, as well as two different scenarios including development and compact development up to the year 2030. The accuracy of model, as verified by ROC, was 85.7%. The historical trend scenario showed the smallest increase, with the urban area expanding from 175.96 km² to 214.68 km² in 2030. Scenario 2, the development scenario, showed the most increase, with a 39.9% growth rate from 2010 to 2030. However, according to scenario 3, the compact development scenario, the urban area decreased in comparison to scenario 2. Accordingly, it is necessary to have effective urban growth management to provoke eco-friendly development on the removed areas, and to strengthen the non-removed areas for sustainable development. The results obtained in this study showed that the SLEUTH model can be useful for predicting urban growth, and that it can help policy makers establish proper urban planning as a decision-support tool for sustainable development.

• 설비공학논문집
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• 제28권8호
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• pp.316-324
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• 2016

This study investigated a compact regenerative evaporative cooler (REC). To achieve practical applications of an REC, it is very important to consider the compactness as well as the cooling performance. Therefore, a prototype of the REC was designed and fabricated to improve the compactness by reducing the length through the insertion of fins in both the dry and wet channels. The REC prototype was tested in terms of performance evaluation under various operating conditions. An analytical model was also developed to analyze the effects of the axial conduction through the solid body of the REC, the wetness of the surface in the wet channel, and the thermal capacity of the evaporation water flow. The model was validated by comparing the results of a simulation with experimental data. The numerical simulation was based on the model to analyze the performance of the REC and to suggest methods to improve the cooling performance of the REC. Finally, the performance of the present REC was compared to that obtained in previous experimental studies. The results showed that the REC prototype in the present study is the most compact and achieves the highest cooling performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권3호
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• pp.755-778
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• 2024

In recent years, the number of devices being connected to the internet has grown enormously, as has the intrusive behavior in the network. Thus, it is important for intrusion detection systems to report all intrusive behavior. Using deep learning and machine learning algorithms, intrusion detection systems are able to perform well in identifying attacks. However, the concern with these deep learning algorithms is their inability to identify a suitable network based on traffic volume, which requires manual changing of hyperparameters, which consumes a lot of time and effort. So, to address this, this paper offers a solution using the extended compact genetic algorithm for the automatic tuning of the hyperparameters. The novelty in this work comes in the form of modeling the problem of identifying attacks as a multi-objective optimization problem and the usage of linkage learning for solving the optimization problem. The solution is obtained using the feature map-based Convolutional Neural Network that gets encoded into genes, and using the extended compact genetic algorithm the model is optimized for the detection accuracy and latency. The CIC-IDS-2017 and 2018 datasets are used to verify the hypothesis, and the most recent analysis yielded a substantial F1 score of 99.23%. Response time, CPU, and memory consumption evaluations are done to demonstrate the suitability of this model in a fog environment.

• 한국산학기술학회논문지
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• 제14권8호
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• pp.4077-4085
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• 2013

본 연구는 서울시를 대상으로 압축도시 계획요소가 지역주민들의 쇼핑통행에 어떤 영향을 미치는지 분석하는데 연구의 목적이 있다. 이를 위해 본 연구에서는 압축도시 계획요소를 토지이용특성와 교통환경특성으로 구분하고 서울시 가구통행실태조사 데이터를 이용하여 분석을 수행하였으며, 분석방법은 임의절편로짓모형을 이용하였다. 분석결과 주거밀도가 높을수록 근린 내 쇼핑통행이 많아지는 것으로 나타났다. 또한 주거밀도와 토지이용혼합도가 높을수록 쇼핑통행수단 선택에서 승용차보다 대중교통, 보행, 자전거를 이용할 확률이 높은 것으로 나타났으며 대중교통시설의 접근성이 높을수록 승용차보다 대중교통을 이용할 확률이 높아지는 것으로 나타났다. 따라서 고밀 복합용도 개발을 유도하고 대중교통시설 접근성을 높이는 압축도시 개발정책은 쇼핑목적의 자동차이용을 줄이고 대중교통이용과 자전거, 보행활동을 활성화하는데 있어 긍정적인 영향을 미칠 것으로 판단된다.