• 한국소음진동공학회논문집
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• 제21권4호
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• pp.299-306
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• 2011

This study investigated the SIP-method as a low-vibration, low-noise engineering method. The ground vibrations caused by the SIP-method were measured and analyzed in each step. From the analysis results, quantitative ground vibration values and reliable vibration estimation equations were proposed. Furthermore, the ground vibrations caused by the SIP-method were compared with the ground vibrations caused by other methods presented by existing studies. Based on the vibration estimation equation with 50 % reliability, the ground vibration values by the SIP-method at the distance of 10~150 m corresponded to 17~57 % of the ground vibration values by the equation proposed by Attewell & Famer, and 14~96 % of the ground vibration values by the equation proposed by Prof. Park in his study using a diesel drop hammer. These results showed that the ground vibration reduction effect of the SIP-method was higher those of other general engineering methods. Finally, the permissible scope of work using the SIP-method which meets the domestic vibration standards was presented.

• International Journal of Aeronautical and Space Sciences
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• 제16권3호
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• pp.445-450
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• 2015

Generally, Low Earth Orbit (LEO) satellites are used to collect image or video from earth's surface. The collected data are stored on-board and/or transmitted to the main ground station directly or via polar ground station using terrestrial line. Today, an intersatellite link between a LEO and a GEO satellite allows transmission of the collected data to the main ground station through the GEO satellite. In this study, an approach for a continuous communication starting from LEO through GEO to ground station is proposed by determining the optimum ground station locations. In doing so, diverse ground stations help to determine the GEO orbit as well. Cross-correlation of the long term daily rainfall averages are multiplied with the logarithmic correlation of the sites to calculate the joint correlation of the diverse ground station locations. The minimum values of this joint correlation yield the optimum locations of the ground stations for Q/V-band communication and satellite control operations. Results for several case studies are listed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.769-775
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• 2008

The objective of this report is to determine the difference of thermal response that grouted two different materials, and compare the simulation result of the length of total ground heat exchanger length that using the ground thermal conductivity. And also to know heat exchange variation of ground heat exchanger temperature that measured with various test depth. The result shows that the test hole grouted with water permeable material got better thermal response than grouted with water impermeable material. However, with consideration of ingnore for the initial 12 hour data, the test hole grouted with impermeable material has larger thermal conductivity than the other. By former thermal conductivity, simulated data by engineering program shows only 3.4% difference or less. This result shows that ground thermal conductivity is not the main variables for the design program of ground heat exchanger. At the cooling or heating mode, base on the depth of -150m, the ground heat exchanger has best temperature at $-90{\sim}-60m$ and than getting worse because of entering water heat exchanged with leaving water in the same hole.

• 한국기계가공학회지
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• 제10권2호
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• pp.73-78
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• 2011

The existent cutting insert have occupied most product of grinding style, because it has a problem of accuracy and manufacturing process. The product has a concept but development is difficult, because grinding and manufacturing by press are impossible. But by development and stabilization of a technology, preference of non-ground insert increases gradually. And then insert that grinding is impossible is developed availably as non-ground product by using developed equipment and software. In this paper reports some experimental results on the machining performance of non-ground Cutting inserts. Three kinds of Cutting inserts were manufactured without using grinding process. Machining experiments were carried out to compare the machining performance of non-ground inserts with that of ground ones. The experimental results indicate that the cutting forces and tool wear and surface roughnesses of machined surface of both ground and non-ground inserts are comparable.

• Geomechanics and Engineering
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• 제4권1호
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• pp.1-18
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• 2012

The spatial variation of ground motion in Kolkata Metropolitan District (KMD) has been estimated by generating synthetic ground motion considering the point source model coupled with site response analysis. The most vulnerable source was identified from regional seismotectonic map for an area of about 350 km radius around Kolkata. The rock level acceleration time histories at 121 borehole locations in Kolkata for the vulnerable source, Eocene Hinge Zone, due to maximum credible earthquake (MCE) moment magnitude 6.2 were generated by synthetic ground motion model. Soil investigation data of 121 boreholes were collected from the report of Soil Data Bank Project, Jadavpur University, Kolkata. Surface level ground motion parameters were determined using SHAKE2000 software. The results are presented in the form of peak ground acceleration (PGA) at rock level and ground surface, amplification factor, and the response spectra at the ground surface for frequency 1.5 Hz, 3 Hz, 5 Hz and 10 Hz and 5% damping ratio. Site response study shows higher PGA in comparison with rock level acceleration. Maximum amplification in some portion in KMD area is found to be as high as 3.0 times compared to rock level.

• 한국안전학회지
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• 제20권3호
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• pp.143-151
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• 2005

In this study, it is demonstrated that how the effect of the Near Fault Ground Motion affects the response of the structure. Considering the general characteristic of Near Fault Ground Motion the characteristics of Near Fault Ground Motions is analysed by elastic response spectrums, and the inelastic response spectrum is evaluated with the ductility and the yield strength to consider the inelastic behavior which couldn't be simulated through the elastic response spectrum. The result of this study shows that the effect of Near Fault Ground Motion should be considered in the long period range of long span structures but the domestic seismic design code was developed based on Far Fault Ground Motions, so the effects of Near Fault Ground Motions, which is very serious especially in large structures with a long period, are not considered. Therefore, the effect of the Near Fault Ground Motion has to be examined especially in the seismic performance evaluation of long period structure.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.953-977
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• 2016

Modern performance-based design methods require ways to determine the factual behavior of structures subjected to earthquakes. Drift ratio demands are important measures of structural and/or nonstructural damage of the structures in performance-based design. In this study, global drift ratio and interstory drift ratio demands, obtained by nonlinear time history analysis of three generic RC frames using code-compatible ground motion record sets, are statistically evaluated. Several ground motion record sets compatible with elastic design spectra defined for the local soil classes in Turkish Earthquake Code are used for the analyses. Variation of the drift ratio demands obtained from ground motion records in the sets and difference between the mean of drift ratio demands calculated for ground motion sets are evaluated. The results of the study indicate that i) variation of maximum drift ratio demands in the sets were high; ii) different drift ratio demands are calculated using different ground motion record sets although they are compatible with the same design spectra; iii) the effect of variability due to random causes on the total variability of drift ratio demands is much larger than the effect of variability due to differences between the mean of ground motion record sets; iv) global and interstory drift ratio demands obtained for different ground motion record sets can be accepted as simply random samples of the same population at %95 confidence level. The results are valid for all the generic frames and local soil classes considered in this study.

• International Journal of Contents
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• 제15권1호
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• pp.32-38
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• 2019

In an environment where a large number of weapons are operated compared to a large number of ground targets, it is important to monitor and manage the targets to set up a fire plan, and through their multilateral analysis, to equip them with a priority order process for targets having a high threat level through the quantitative calculation of the threat level. Existing studies consider the anti-aircraft and anti-ship targets only, hence, it is impossible to apply the existing algorithm to ground weapon system development. Therefore, we proposed an effective threat evaluation algorithm for multiple ground targets in multi-target and multi-weapon environments. Our algorithm optimizes to multiple ground targets by use of unique ground target features such as proximity degree, sorts of weapons and protected assets, target types, relative importance of the weapons and protected assets, etc. Therefore, it is possible to maximize an engagement effect by deducing an effective threat evaluation model by considering the characteristics of ground targets comprehensively. We carried out performance evaluation and verification through simulations and visualizations, and confirmed high utility and effect of our algorithm.

• 한국지반환경공학회 논문집
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• 제20권9호
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• pp.5-11
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• 2019

최근 국내 도심지 지반침하 및 함몰이 빈번히 발생함에 따라 지반침하에 대한 불안감 또한 증가하고 있다. 그로 인해 GPR를 통한 지하 공동 탐지 지반함몰 모사실험 지반의 거동을 확인하기 위한 수치해석 등의 연구가 진행되고 있다. 국내의 경우 공동위험도 평가를 최근에 마련하였으나 현재의 지반상태 파악에 초점을 두었기 때문에 향후 발생할 수 있는 지반침하 및 함몰에 대한 예측을 정량적으로 하기 힘들다. 따라서 본 연구에서는 지반침하/함몰의 기하학적 변수인 공동크기와 토피두께를 변화시키며 총 30개의 case에 대한 수치해석을 수행하였다. 이 결과를 바탕으로 현재의 상태 뿐 아니라 향후 발생할 시기를 정량적으로 예측할 수 있는 방법을 제시하였다.

• 전력전자학회논문지
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• 제26권2호
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• pp.90-95
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• 2021

In contrast to AC grounding systems, the ground electrode in DC systems continuously maintains positive or negative polarity. Ground electrodes with (+) polarity proceeds by oxidation reaction. Thus, the DC current should flow opposite to the polarity of the leakage current flowing through the (+) ground electrode by using a compensation electrode, and the current flowing through the (+) ground electrode can be 0A. However, according to protecting the (+) ground electrode, the compensation electrode corrodes and gets damaged. Thus, the (+) ground electrode must be protected from corrosion, and the service life of the compensation electrode must be extended. As an alternative, the average value of the current flowing through the compensation electrode should be equal with the value of the leakage current flowing through the (+) ground electrode by using the square waveform. Throughout the experiment, the degree of corrosion on the compensation electrode is analyzed by the frequency of the compensation electrode for a certain time. In the experiment, the frequencies of the square waveform are considered for 0.1, 1, 10, 20, 50, 100 Hz, and 1 kHz. Through experiments and analysis, the optimal frequency for reducing the electrolytic damage of the (+) electrode and compensation electrode in an LVDC grounding environment is determined.