• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.270-277
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• 2021

In the power ultrasound fields, the flange position for fixing the transducer is an important factor influencing on electro-mechanical efficiency of the transducer. We suggested a practical method that can determine the installation position of the flange for different resonance modes of the bolt-clamped type Langevin ultrasonic transducer. A semicircular wedge-shaped jig was manufactured and moved along the lateral surface of the transducer. The vibration characteristics were examined after a constant pressure was applied to the semicircular wedge-shaped jig. By observing the change of the input admittance of the transducer depending on the position of the pressure application, the optimum position for the flange installation could be determined. The resonant modes of the transducer were calculated by a Mason's equivalent circuit, and the particle velocity distribution for each resonance mode was calculated by a transmission line model. Since the optimum positions determined from an experimental result show a good correspondence with the node positions of the vibration modes calculated by the transmission line model, the validity of the suggested method was verified.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.2
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• pp.109-116
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• 2010

We consider an information system where its throughput deteriorates due to security threats and evaluate information security investment portfolios. We assume that organizations adopt information security countermeasures (or portfolios consisted of countermeasures) to lessen the damage resulted from the productivity (or throughput) deterioration. A probability model is used to derive the system throughput and the average number of repairs according to the occurrence rate of security threats. Considering the revenue from throughput, the repair cost, and the investment for the security system, the net present value for each portfolio is derived. Organizations can compare information security investment portfolios and select the optimal portfolio.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.53-60
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• 2021

High voltage CV cables have been widely installed underground due to their convenience and urban aesthetics. However, cable accidents have occurred frequently owing to poor construction and natural degradations. This paper proposes the method to measure the multi parameter measurement for optimum diagnostics of high voltage cable connection parts and verifies its technical usefulness. This measurement is intended to diagnose degradations of cable connection parts by using simultaneous vibration and thermography as well as partial discharge(PD). The experiment in a shielded laboratory was carried out to verify the usefulness of the multi parameter measurement. The experiment defined the degradation of the cable connection part as 12 types, and produced each degradation sample. As a result of experiment, it was possible to check the correlation of vibration signals with regard to progress in some defects. In the case of thermography, the coherence with regard to the progress of some defects was found. We figure that the proposed method would be useful also in the noise environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.419-419
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• 2021

수자원 관리 패러다임은 공급 위주에서 수요관리로 전환되고 있다. 가용한 수자원은 한정적이나 급속한 인구증가와 도시화로 인한 물 수요의 증가로 수요관리의 효율성이 중시되고 있기 때문이다. 기존 상수도시스템은 노후화로 가동효율이 점차 낮아지고 있으며, 인력으로 월 또는 격월로 소비자의 물 사용량을 검침해 실시간 관리가 불가능하여 수요와 공급의 불균형을 초래한다. 이러한 문제를 해결할 대안으로 IT 기술과 전통적인 물관리 기술을 접목한 Smart Water Grid는 양방향 통신장치를 이용해 실시간으로 소비자의 물 사용량을 모니터링한다. 물 사용 특성을 잘 파악하면 보다 정확한 물 수요 예측이 가능하다. 특히 소비자들의 시간별, 평일, 주말, 그리고 주별 물 사용 특성을 파악하면 미래 물 수요 예측에 도움이 된다. 예측된 물 수요량에 따라 물 공급 배분 계획을 수립하여 운영 효율성을 높일 수 있다. 물 수요예측 방법 중 k-mean 군집분석은 시간별 물 사용량을 이용해 서로 유사한 여러 개의 부분집합으로 할당하여 분류하는 Machine learing 방법으로 물 사용의 유사성을 파악할 수 있다. SWG 연구단은 2019년 Vietnam Hai Duong province에 SWG Pilot plant를 구축하고 27개의 Smart water meter를 설치하여 운영하고 있다. 이에 본 연구에서는 소비자의 물 사용 특성을 분석하기 위해 27개 SWM로부터 수신된 2019년 11월 14일부터 2020년 12월 3일까지 1시간 단위의 물 사용량 데이터를 수집하였다. 그리고 k-mean 군집 방법을 이용해 시간별, 평일, 주말, 그리고 주별 물 사용 특성을 분석하였다. 이 때 최적의 군집 개수 결정을 위해 Elbow 방법을 적용하였다. 분석 결과 각 소비자의 물 사용량 특성에 따라 평균 물 수요패턴 추정이 가능하며, 향후 물 수요 예측에 도움이 될 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.457-457
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• 2022

최근 기후변화로 인한 위기가 인류의 생존을 위협하면서 전 지구적으로 기후변화에 대응하기 위한 탄소 중립 대책을 모색하고 있으며, 지속가능한 신재생에너지에 대해 주목하고 있다. 산업통상자원부는 2034년까지 총 발전량 중 신재생에너지의 비율을 25.8%까지 증가시키는 것을 목표로 신재생에너지의 발전 비율을 증가시키기 위한 다양한 노력을 기울이고 있다. 특히, 신재생에너지 중 가장 많은 비중을 차지하고 있는 태양광 발전은 비교적 광범위한 부지를 필요로 하고 있으며, 환경 및 지형적 영향이 크게 작용하는 만큼 발전 시설 부지 선정 및 운용 계획을 위한 면밀한 분석이 필수적이다. 그러나, 태양광 발전 활용 계획을 수립하기 위해 고려할 수 있는 지상 관측 일사량 및 일조량 데이터는 상당히 제한적이며 관측 밀도가 조밀하지 않다는 한계점이 있다. 본 연구에서는 천리안위성의 후속으로 발사된 천리안2위성의 산출물인 일사량 데이터를 활용하여 한반도 영역에서의 일사량에 대한 시·공간적 분석을 수행하였으며, 이를 기반으로 각 지역적 특성을 파악하고, 토지 피복 유형에 따른 태양광 발전의 효율 정도를 분석·평가하였다. 본 연구의 결과는 계측 지역 및 미계측 지역에서의 시공간적인 태양광 에너지의 효율성에 대한 정보를 제공함에 따라 태양광 발전을 위한 관련 시설물들의 최적 설치 위치 및 규모 등에 대한 설계 기준 마련에 활용될 수 있을 것으로 판단된다.

• Geotechnical Engineering
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• v.11 no.2
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• pp.29-36
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• 1995

Load testis are executed on model reticulated root piles (RRP) to figure out the optimum slanting angle in the piles installation. One set of model RRP consists of 8 slanting piles which are installed in circular patterns forming two concentric circles, each of which is made by 4 piles. Each pile which is a steel bar of 5m in diameter and 300mm in length is coated to become a pile of 6.5mm in diameter. The slanting angle of the model RRP varies from 0$^{\circ}$ to 20$^{\circ}$ Comparing ultimate bearing capacities of the model RRP of different installation angles, it is observed that the ultimate capacities of the RRP increase as the installation angle increases until 15$^{\circ}$, and the optimum slanting angle of the RRP is around 15$^{\circ}$ The ultimate bearing capacity of the 15$^{\circ}$-RRP is found to be 22% bigger than that of the vertical RRP and 120% bigger than that of the circular surface footing whose diameter is same with the circle formed by outer root piles'heads. However, it is noticed that when the slanting angle of the RRP is increased over 15$^{\circ}$, the ultimate capacity starts to be reduced. The ultimate capacity of 20$^{\circ}$-RRP is even smaller than that of the vertical RRP by as much as 5%. From the observation of the load settlement curve obtained during the RRP load tests, it is known that as the slanting angle gets bigger the load -settlement behavior becomes more ductile.

• Journal of Animal Environmental Science
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• v.13 no.2
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• pp.105-112
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• 2007

This research was carried out to test and analyse the capability of a fan for development of a sprayer in actual livestock farm. A fan was designed and made to be able to spray agricultural chemicals within 140mm in a maximum scattering range and 100m in an effective scattering range. Accordingly, its' flow rate was $3,600\;m^3/min$, and static pressure was 100 mmAq for a wide area sprayer to be sprayed widely and far. Fan performance, which was given $600\;m^3/min$ flow rate and 500 mmAq total pressure, was tested fur basic experiment. As the result, the axial power showed minimum error, which be designed to keep the fan performance. And power efficiency was the maximum. Sound level was 92.1dB that wasn't enough to environmental standard. If we take the sealed place into consideration, sound level is suitable for environmental standard.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.802-810
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• 2006

For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.110-118
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• 2003

Spacer dampers maintain the constant gaps between each conductor in a bundle conductor-transmission line, and are installed at proper intervals to keep a line from all sorts of damages derived from the vibration energy caused by mechanical or electrical external factors. It is most important to embody a technology which considers difficulties of maintenance and repair, and has optimum elements in order to prevent accidents such as destruction by fire or the snapping of a wire by the effect of vibration phenomenon coming from transmission lint In the resent thesis, therefore, the analysis of vibratory characteristics of spacer damper is set up by analytical methods such as the analysis of conductor motion's governing equation, the equation of spacer damper's motion, spacer damper-fastened wire's motion in a span and the numerical analysis of finite difference method. Furthermore, the installation distance between spacer dampers was scrutinized by simulations of various vibration phenomena which change at any time as actual conditions do, and hereafter difference method. Furthermore, the installation distance between spacer dampers was scrutinized by simulations of various vibration phenomena which change at any time as actual conditions do, and hereafter we will be able to analyze all kinds of vibration phenomena coming from a boltless spacer damper with 6 bundle conductor for 765kV transmission line based on new analytical methods.

• Tunnel and Underground Space
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• v.32 no.2
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• pp.120-130
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• 2022

In this study, the applicability of the microseismic monitoring system based on the underground mine communication system has been verified by operation test in the domestic underground mine. The microseismic data consists of wavelet data and meta-data for mine safety management, and both data should be transferred, stored, analyzed and managed with proper method according to the purpose and size of each data. In order to select the optimal communication system for the microseismic monitoring system considering the underground environment as well as properties of data, various types of communication system have been tested and compared during operation test after installing the optical cable communication system, 2.4 GHz and 900 MHz wireless communication system through the underground mine tunnel and overground area of the test site. The integrated microseismic monitoring software, which was developed to secure the stability of data management and ease of use, has been updated according to findings from operation test. Through the operation test of the microseismic monitoring system including the communication system and the monitoring software, the technical basis was established corresponding to various requirements of the domestic mine for adoption of the microseismic monitoring system.