• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.189-206
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• 2003

During tunnel excavation in urban area a systematic monitoring is important for the purpose of determination of support type and quantity, as well as for the control of stability of both surface structures and the tunnel itself due to the frequently, and in many cases, abruptly changing ground condition. In Austria absolute displacement monitoring methods have replaced relative displacement measurements by geodetic methods to a large extent. Prompt detection of weak ground ahead of the tunnel face as well as better adjustment of excavation and support to the geotechnical conditions is possible with the help of the improved methods of data evaluation on sites. Deformation response of the ground to excavation starts ahead of the tunnel face, therefore, the deformation and state of the tunnel advance core is the key factor of the whole deformation process after excavation. In other words, the rigidity and state of the advance core play a determining role in the stability of both surface structures and the tunnel itself. This paper presents the results from detailed three-dimensional numerical studies, exploring vertical displacements, vector orientations and extrusions on tunnel face during the progressive advancement for the shallow tunnel in various geotechnical conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.433-441
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• 2004

국내 발파 현장에서 사용되고 있는 폭약류에 강력한 폭굉력을 충분하게 발휘하기 위해서는 뇌관(Blasting cap, Detonator)의 역할이 중요하다. 그리고 이 뇌관의 정밀성에 따라 발파 효율의 차이가 있게된다. 초기의 도화선 및 공업뇌관에서 시작하여 현재 정밀성 면에서는 MS(Milli Second)뇌관의 경우 20ms또는 25ms의 정밀한 시차로 순차적으로 기폭함으로써 발파효과의 극대화와 소음 및 진동제어에 큰 효과를 이루었으나, 최근 개발된 진자뇌관의 경우 자체 IC회로를 내징하여 $1{\sim}2ms$의 초정밀시차(오차범위 $0.1{\sim}0.2ms$이내)의 구현이 가능해짐에 따라 이를 적절히 조합하여 설계함으로써 각종 제어발파, 파쇄도 향상, 암손상영역 저감 등의 효과에 대해 국외에서 연구가 진행되고 있는 것으로 알려지고 있다. 그러나 우리나라와 같이 도심지 발파 및 터널이나 노천 현장 근거리에 보안물건이 위치해 있어 진동제어가 절실히 필요한 상황에서 진동제어에 효과가 있는 것으로 알려진 전자뇌관에 대한 연구가 이루어지고 있지 않은 상황에서 본 연구는 앞으로 이루어질 전사뇌관에 대한 수많은 연구에 기초자료를 제공하고자 실시하였다. 본 연구에서는 이를 위해 국내에서 최초로 2003년 9월 23일 강원도 양구 지역읜 00터널에 전자뇌관을 이용한 시험발파를 실시하였고, 발파에 의한 진동 등을 조사하여 그 효율성을 검토하였다. 이를 위해 전자뇌관의 특성과 장점을 최대한 살리기 위하여 각공을 발파하는 방식, 즉 1지발에 1공을 발파하는 방식을 채택하고 비전기 뇌관과 전자뇌관으로 설계를 하여 각각의 발파효율을 비교하여 보았다. 그 결과 발파신동의 경우 비전기뇌관을 이용하여 1공씩을 1지발로 발파를 한 경우에는 18${\sim}$56%의 진동저감 효과가 있었고, 번 설계에 의해 진해오딘 발파에 비하여는 최대 70% 이상의 진동저감 효과가 있는 것으로 나타났다.

• KIEAE Journal
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• v.16 no.3
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• pp.89-94
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• 2016

Purpose: This study aimed at developing an artificial neural network (ANN) model to predict the optimal start moment of the setback temperature during the normal occupied period of a building. Method: For achieving this objective, three major steps were conducted: the development of an initial ANN model, optimization of the initial model, and performance tests of the optimized model. The development and performance testing of the ANN model were conducted through numerical simulation methods using transient systems simulation (TRNSYS) and matrix laboratory (MATLAB) software. Result: The results analysis in the development and test processes revealed that the indoor temperature, outdoor temperature, and temperature difference from the setback temperature presented strong relationship with the optimal start moment of the setback temperature; thus, these variables were used as input neurons in the ANN model. The optimal values for the number of hidden layers, number of hidden neurons, learning rate, and moment were found to be 4, 9, 0.6, and 0.9, respectively, and these values were applied to the optimized ANN model. The optimized model proved its prediction accuracy with the very storing statistical correlation between the predicted values from the ANN model and the simulated values in the TRNSYS model. Thus, the optimized model showed its potential to be applied in the control algorithm.

• Journal of Hydrogen and New Energy
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• v.19 no.6
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.787-790
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• 2003

A rf triode magnetron sputtering system is designed and installed its construction in vacuum chamber. In order to calibrate the rf triode magnetron sputtering for thin films deposition processes, the effects of different glow discharge conditions were investigated in terms of the deposition rate measurements. The basic parameters for calibrating experiment in this sputtering system are rf power input, gas pressure, plasma current, and target-to-substrate distance. Because a knowledge of the deposition rate is necessary to control film thickness and to evaluate optimal conditions which are an important consideration in preparing better thin films, the deposition rates of copper as a testing material under the various sputtering conditions are investigated. Furthermore, a triode sputtering system designed in our team is simulated by the SIMION program. As a result, it is sure that the simulation of electron trajectories in the sputtering system is confined directly above the target surface by the force of $E{\times}B$ field. Finally, some teats with the above 4 different sputtering conditions demonstrate that the deposition rate of rf triode magnetron sputtering is relatively higher than that of the conventional sputtering system. This means that the higher deposition rate is probably caused by a high ion density in the triode and magnetron system. The erosion area of target surface bombarded by Ar ion is sputtered widely on the whole target except on both magnet sides. Therefore, the designed rf triode magnetron sputtering is a powerful deposition system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.555-560
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• 2016

Recently, many countries have placed great attention on energy security and climate changes. Governments are promoting the construction of renewable energy projects with regulatory support in Korea. Despite an increasing penetration of renewable resources, however, the photovoltaic and wind power are underutilized due to the endemic problems such as difficulties of output control and intermittent output. The Energy Storage System (ESS) is proposed as a good solution for solving the problems and has been studied in both the private business and the government. However, because of inefficient aspects, the research has been carried out for improving high costs and a small capacity. In addition, the ESS is currently installed for using only one purpose which is frequency regulation or transmission congestion relief such that has an economic limitation. Therefore, methods which are becoming economically justifiable to increase the penetration of the ESS is required. Thus, this paper presents in terms of operation efficiency to improve economic feasibility of the ESS currently used. mainly, there are two aspects for the operation efficiency. Firstly, it is intended to improve the utilization rate through a process that can utilize the ESS for various purposes. It is necessary to be able to use for other purposes by classifying and clustering for increasing the efficiency of availability. The clustering method is proposed to conduct the grouping the ESS. Especially, it is proposed to utilize ESS for frequency regulation service which is the one of ancillary services in the power system. Through case studies, it is confirmed to secure the necessary resources by clustering small size ESS.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.49-57
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• 2016

The aim of this study was to investigate the fundamental properties of pyroclastic flow deposit (PFD), and evaluate the fresh and strength properties of concrete mixed with PFD by indoor tests. The fresh properties, strength properties, shrinkage properties, and durability of the concrete mixed with PFD were also evaluated by outdoor plant tests. the harmful alkali-silica reaction did not occur by mixing concrete with PFD. ages. Moreover, no difficulty was found to be associated with concrete manufacture in the plant because no change in air contents and noticeable slump loss occurred by mixing concrete with PFD. The strength properties, shrinkage properties, and durability of the concrete mixed with PFD were also compared with those of normal concrete. With a suitable temperature control and curing method of concrete, the concrete mixed with PFD is considered to be useful in the construction material field.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.1
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• pp.78-87
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• 2009

An attribute-based signature scheme is a signature scheme where a signer's private key is associate with an attribute set and a signature is associated with an access structure. Attribute-based signature schemes are useful to provide anonymity and access control for role-based systems and attribute-based systems where an identity of object is represented as a set of roles or attributes. In this paper, we formally define the definition of attribute-based signature schemes and propose the first efficient attribute-based signature scheme that requires constant number of pairing operations for verification where a policy is represented as a disjunctive normal form (DNF). To construct provably secure one, we introduce a new interactive assumption and prove that our construction is secure under the new interactive assumption and the random oracle model.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.25-34
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• 2011

In this paper, In this paper, we propose a Cooperative Routing Protocol (CooRP) for supporting network convergence and transmission services efficiently in mobile ad-hoc wireless sensor networks with Rayleigh fading environments. The main contributions and features of this paper are as follows. First, the routing routes are decided on route stability based on entropy concepts using mobility of nodes within the direction guided line region to increase the operational lifetime of routes as well as reduce control overhead for route construction. Second, a cooperative data transmission strategy based on the constructed stable routing route is used to increase packet delivery ratio with advanced SNR. Third, a theoretical analysis for cooperative data transmission of the proposed CooRP with outage probability is presented. The performance evaluation of the proposed CooRP is performed via simulation using OPNET and analysis. The results of performance evaluation show that the proposed CooRP by using stable routing routes and cooperative transmission can increase packet delivery ratio efficiently.

• The Journal of the Korea Contents Association
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• v.15 no.10
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• pp.587-596
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• 2015

3D scanners are applied to many industries, such as manufacturing, construction, and shipbuilding. Recently, 3D scanner is used in 3D imaging of worksite in order to control and guide earthmoving heavy equipments, which provides basic information for intelligent excavation. This study compares the accuracy and productivity between total stations and high-resolution 3D scanners. The analysis results show that 3D scanner has high accurate rate of greater than 99 percent and has low error rate of less than 2.0mm compared to total stations. In terms of productivity, 3D scanner saves 71 percent of measuring time compared to the total station. This study confirms that 3D scanner can measure the earthwork sites with high accuracy and better productivity.