• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.83-92
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• 2005

Fluid conductivity logging has been applied in the boreholes to identify the permeable fi:actures and estimate the origin of saline groundwater in coast area. Fluid replacement technique measures the fluid electrical conductivity with depth at different times in a well after the borehole is first washed out with different water by passing a tube to the borehole bottom. Then formation water flows into the borehole through aquifer such as permeable fractures or porous formation during ambient or pumping condition. Measured conductivity profiles with times therefore indicate the locations of permeable zone or fractures within the open hole or the fully slotted casing hole. As a result of fluid conductivity logging for three boreholes in the study area, it is interpreted that saline groundwater is caused by seawater intrusion through fractured rock, although the effect by land reclamation partially remains. We are planning the quantitative analysis to estimate the hydraulic characteristics using fluid replacement technique, and this approach might be usefully utilized for assessing the characteristics of seawater intrusion, the design of optimal pumping, and estimating the hydraulic properties in coastal aquifer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.630-637
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• 2018

Harmony search (HS) is a recently developed metaheuristic optimization algorithm. HS is inspired by the process of musical improvisation and repeatedly searches for the optimal solution using three operations: random selection, memory recall (or harmony memory consideration), and pitch adjustment. HS has been applied by many researchers in various fields. The increasing complexity of real-world optimization problems has created enormous challenges for the current technique, and improved techniques of optimization algorithms and HS are required. We propose an improved clustering harmony search (ICHS) that uses a clustering technique to group solutions in harmony memory based on their objective function values. The proposed ICHS performs modified harmony memory consideration in which decision variables of solutions in a high-ranked cluster have higher probability of being selected than those in a low-ranked cluster. The ICHS is demonstrated in various optimization problems, including mathematical benchmark functions and water distribution system pipe design problems. The results show that the proposed ICHS outperforms other improved versions of HS.

• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.225-230
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• 2006

Fluid replacement and conductivity logging have been applied to three boreholes in coastal aquifer in order to identify permeable fractures and to estimate the origin of saline groundwater. Fluid replacement technique measures and monitors the change of borehole fluid conductivity with depth under ambient or pumping condition after replacing the original borehole fluid with different one (by pumping out original one and injecting simultaneously new one at the hole bottom). After the replacement of borehole fluid, the change of fluid conductivity can be the direct indicator of the intake flow of formation water through aquifer such as permeable fractures or porous formations. The conductivity profiles measured with times therefore indicate the locations of permeable zone or fractures within the open hole or the fully slotted casing hole. As a result of fluid conductivity logging for three boreholes at coastal area in Yeonggwang, Jeonam Province, it is interpreted that the seawater intrusion in this area is not by remnant saline groundwater after land reclamation but mainly by intrusion of saline water through fractured rock. This approach might be useful for assessing the characteristics of seawater intrusion, the design of optimal pumping, the mitigation of seawater intrusion using freshwater injection, and estimating the hydraulic characteristics in coastal aquifer.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.353-360
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• 2007

We practiced fresh water injection test to identify its applibility as a method of seawater intrusion mitigation technique, and monitored the change of borehole fluid conductivity and the behavior of injected fresh water using borehole multichannel electrical conductivity monitoring and well-logging, and DC resistivity and SP monitoring at the surface. Well-logging and multichannel EC monitoring showed the decrease of fluid conductivity due to fresh water injection. We note that such an injection effect lasts more than several month which means the applibility of fresh water injection as a seawater intrusion control technique. Although SP monitoring did not show meaningful results because of weather condition during monitoring and the defects of electrodes due to long operation time, DC resistivity monitoring showed its effectiveness and applicability as a monitoring and assessment techniques of injection test by means of imaging the behavior and the front of fresh water body in terms of the increase of resistivity with reasonable resolution. In conclusion, we note that geophysical techniques can be an effective method of monitoring and evaluation of fresh water injection test, and expect that fresh water injection may be an practical method for the mitigation of seawater intrusion when applied with optimal design of injection well distribution and injection rate based on geophysical evaluation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.227-233
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• 2022

The 3D-printing technique is used for manufacturing objects by adding multiple layers, and it is relatively easy to manufacture objects with complex shapes. The 3D concrete printing technique, which incorporates 3D printing into the construction industry, does not use a formwork when placing concrete, and it requires less workload and labor, so economical construction is possible. However, 3D-printed concrete is expected to have a lower strength than that of molded concrete. In this study, the properties of 3D-printed concrete were analyzed. To fabricate the 3D-printed concrete samples, the extrusion path and shape of the samples were designed with Ultimaker Cura. Based on this, G-codes were generated to control the 3D printer. The optimal concrete mixing proportion was selected considering such factors as extrudability and buildability. Molded samples with the same dimensions were also fabricated for comparative analysis. The properties of each sample were measured through a three-point bending test and uniaxial compression test, and a comparative analysis was performed.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.334-339
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• 2008

Construction that over 70% of the structure consists of concrete gets bigger and higher gradually and the demand of that is increasing as well. However, it's not easy to supply young and skilled persons on construction site because of social avoidance phenomena about 3D occupation, so it causes serious problems like aging and shortage of technicians. To solve the problems, executives related to the construction field make a management effort in various ways such as construction period shortening, labor productivity improvement and good quality but recently, they have an increasing interest in the necessity of the modularization of the high-rise building and the automation of the engineering development for the strengthening of international competitive power as more active and long-term alternatives. Therefore, this study is to propose the roadmap in order to make lots of efforts in developing construction technologies of high-rise buildings by performing a foundation study, the strategy for 4-step research development, on modularized construction system of concrete structure of high-rise buildings through domestic and foreign preceding research analyses associated with optimal design modularization technique, module factory automation and assembly automation of modularized objects.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.195-202
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• 2006

Thin-walled structures are efficiently utilized an automobiles, aircraft, satellite and ship as well as needed light weight simultaneously. This paper presents new shape of automobile hood reinforcement that rotating parts as engine, transmission are protected by thin-walled structures. The automobile hood is concerned about the resonance occurs due to the frequency of the rotating parts. The hood must be designed by supporting the stiffness of design loads and considering the natural frequencies. Hence, it is sustained the stiffness and considered the vibration by resonance. It is deep related to ride. Therefore, the topology, shape and size optimization methods are used to design the automobile hood. Topology technique is applied to determine the layout of a structural component optimum size with maximized natural frequency by volume reduction. In this research, The optimal structure layout of an inner reinforcement of an automobile hood for the natural frequency of a designated mode is obtained by using topology optimization method. The optimum size and the optimum shape are determined by PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.39-47
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• 1998

A fourth-order $\Sigma$-$\Delta$ modulator is designed and implemented in 0.6 $\mu\textrm{m}$ CMOS technology. The modulator is verified by introducing nonlinear factors such as DC gain and slew rate in system model that determines the transfer function in S-domain and in time-domain. Dynamic range is more than 110 dB and the peak SM is 102.6 dB at a clock rate of 2.8224 MHz for voiceband signal. The structure of a ∑-$\Delta$ modulator is a modified fourth-order ∑-$\Delta$ modulator using direct feedback loop method, which improves performance and consumes less power. The transmission zero for noise is located in the first-second integrator loop, which reduces entire size of capacitors, reduces the active area of the chip, improves the performance, and reduces power dissipation. The system is stable because the output variation with respect to unit time is small compared with that of the third integrator. It is easy to implement because the size of the capacitor in the first integrator, and the size of the third integrator is small because we use the noise reduction technique. This paper represents a new design method by modeling that conceptually decides transfer function in S-domain and in Z-domain, determines the cutoff frequency of signal, maximizes signal power in each integrator, and decides optimal transmission-zero frequency for noise. The active area of the prototype chip is 5.25$\textrm{mm}^2$, and it dissipates 10 mW of power from a 5V supply.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.67-73
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• 2016

Recently, wireless power transmission has attracted much interest and is the subject of much research in industry and academia. As its name implies, it is a technology which involves transferring power without wires. This paper presents the design of an ICT-based wireless power transmission system. The proposed system consists of a wireless transceiver unit and high-efficiency coil unit, which can increase both the transmission efficiency and the effective power distance. In particular, the wireless transceiver unit was designed to work with the ICT technique to enable real-time remote monitoring. Also, studies were done relating to the effect of reducing the standby power. The optimal frequency of IGBT devices used in industrial wireless power systems of 20[KHz] was utilized. The values of $23.9[{\mu}H]$ and $2.64[{\mu}F]$ were selected for L and C, respectively, through many field experiments designed to optimize the system design. In addition, an output current controlling algorithm was developed for the purpose of reducing the standby power. The results presented in this paper represent a 75[%] to 85[%] higher power transmission efficiency with a 10[%] increase in the effective power transmission distance compared with the existing systems. As a result, the proposed system exhibits a lower standby power and maintenance costs. Also, the designed wireless transceiver unit facilitates fault detection by means of user acquired data with the development of the ICT applied program.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6360-6367
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• 2015

The location selection of the element that should guarantee easy visual perception, like the landmark, is the a topic that appears much in the design process. Recently, a graph analysis technique using computers has been applied in order to evaluate the visibility of the visual element, but the analytic frame is flat and the setting of the visual pont and the matrix are fixed so there were great limitations in obtaining the results of the practical analysis. Thus, this study presented Nondirectional Multi-Dimensional Calculation (MDVC-N), an analytic methodology available for the analysis of the dynamic visual point in the 3D environment. It thus attempted to establish the analytic application using the 3D computer graphics technology and designed a script structure to set the visual point and the matrix. In addition to that, this study tried to verify the analytic methodology by applying the complex land as an example model, where buildings in various heights of terrains with a high-differences are located, verifying the same analytic methodology. It thus tried to identify the visual characteristics of each alternative location. The following results were gained from the study. 1) The visibility can be measured quantitatively trough the application of the 6-alternatives. 2) Using the 3dimensional graph, intuitive analysis was possible. 3) It attempted to improve the analytic applicability by calculating the results corrected as a variable behavior from the local integration variable of the space syntax.