• 한국소음진동공학회논문집
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• 제18권7호
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• pp.725-731
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centre (NS, 1942) ground motion histories with different peak ground acceleration (PGA) ranging from 0.06 g to 0.50 g. For model updating, flexural stiffness values of structural members (walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions (i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of Inputs for updating (j.e. transfer function and natural frequencies) The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters (i.e. flexural stiffness values).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.441-447
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• 2002

KSR-III(Korea Sounding Rocket - III), which is being developed by Space Technology R&D Division of KARI(Korea Aerospace Research Institute) will be launched in late 2002. It is a three-stage, liquid propellant rocket which can reach 250 km altitude and will carry out observation of ozone layer and scientific experiments, such as microgravity experiment, and atmospheric measurement. KSR-III is believed to be an intermediate to the launch vehicle capable of carrying a satellite to its orbit. Space Test Department of KARI performed GVT(Ground Vibration Test) fer KSR-III EM at Rocket Test Building of KARI. GVT is very important for predicting the behavior of rocket in its operation, developing flight control program and performing aerodynamic analysis. This paper gives an introduction of rocket GVT configuration and information on test procedures, techniques and results of It. In this test. to simulate free-free condition, test object hung in the air laterally by 4 bungee cords specially devised. For the excitation of test object, pure random signal by two electromagnetic shakers was used and total 22 frequency response functions were achieved. Polyreference parameter estimation was performed to identify the modal parameters with MIMO(Multi-Input-Multi-Output) method. As the result of the test, low frequency mode shapes and modal parameters below 60Hz were identified

• 한국지열·수열에너지학회논문집
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• 제6권1호
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• pp.9-16
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• 2010

The aim of this study is to verify the performance of water-to-air multi-heat pump system with a vertical U-tube GLHX(U-tube system) and a double tube GLHX(double tube system), which were installed in a school building located in Asan. For analyzing the performance of the GSHP system, we monitored various operating da~ including the water temperature of inlet and outlet of the ground heat exchanger, mass flow rate, and power consumption. Daily average COP of the single U-tube system and the double tube system were 4.5 and 4.2 at cooling mode and were 3.5 and 3.8 at heating mode. As a result, We know that performance of water-to-air multi-heat pump unit is reliable at actual condition operated in a part load conditions for all day.

• 수산해양기술연구
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• 제46권2호
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• pp.157-163
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• 2010

The indirect target strength (TS) estimation method which uses the Kirchhoff ray mode model (KRM model) was discussed to apply for a biomass estimation in the water of mixed species. TS of 25 live scorpion fishes for 120kHz were measured by a tethered method and of others dominant 5 species in the marine ranching ground of Jeju coastal water including a scorpion fish were also estimated by KRM model. The measurement TS of scorpion fish well agreed with the theoretical values and the standard formula of scorpion fish was estimated as $TS_{120kHz}=20Log\;(L)-72.9$ ($r^2=0.67$). TScm values estimated on trial to each sample of dominant 5 species were from -69.3dB to -75.1dB at 120kHz and they were in the general range of swimbladdered fish. It was clarified that TS by KRM model can be used to estimate fish biomass estimation by increasing a sample number and is more effective under the condition that there is rare TS information for inhabiting species in mixed-species area.

• 한국ITS학회 논문지
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• 제18권3호
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• pp.58-67
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• 2019

한전의 저압전송전선로로 이용되고 있는 지중저압접속함은 지중선로의 분기나 접속을 목으로 하고 있다. 지중저압접속함은 거리의 미관을 고려하는 효용성에 비하여 여름철 집중호우나 도로의 침수에 의하여 감전사고가 발생하는 등 안전대책이 필요하다. 본 논문에서는 지중저압접속함 내부에 온습도, $CO_2$, 수위, 가속도, 진동 센서를 장착하고 센서 데이터를 지그비모듈을 이용하여 지상으로 데이터를 전송한다. 지상과의 통신을 위한 안테나(볼티드 안테나)를 제안하여 이를 통한 데이터 수신을 확인하였다. 전송된 데이터는 LF 모드 및 HEX모드에서 완벽한 수신 성공률이 확인되었으며, 볼티드 안테나는 난환경 사태에서 실험한 결과 지중상태와 수중상태의 차이는 보이고 있으나, 지중저압접속함으로부터 10m 정도 떨어진 지상과의 통신에는 충분히 수신감도라고 판단되었다. 수신된 데이터는 PC기반의 GUI를 통해 확인할 수 있었다.

• 화약ㆍ발파
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• 제37권3호
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• pp.34-42
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• 2019

여러 가지 Type의 다양한 작업방식으로 사용이 가능한 전자뇌관 시스템이 개발되어 실용화되었다. 새롭게 개발된 HEBS (Hanwha Electronic Blasting System) II 장비는 Scanning, Logging 및 Tagging의 3가지 모드에서 작업이 가능하도록 기능 구현이 되어있으며, 현장 여건에 적합한 기능을 선택하면 된다. 금번 시험발파에서는 기존 비전기뇌관 사용 시와 비교하여 발파진동, 파쇄입도, Digging time 개선사항과 전자뇌관의 대표적인 작업방법인 Scanning 모드, Logging 모드, Tagging 모드의 작업 효율성을 동일현장에서 비교하였다. 발파진동은 약 45%, 파쇄입도는 약 31%가 감소하였으며, Digging time도 약 13%가 감소되는 것으로 나타났다. 이 결과는 새로운 시스템이 현장의 작업조건 하에서도 Scanning 모드와 Logging 모드, Tagging모드를 불문하고 공히 우수한 작업 효율성을 지니고 있음을 말해준다.

• 설비공학논문집
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• 제21권5호
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• pp.297-304
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• 2009

The aim of this study is to investigate the cooling performance of ground source multi-heat pump systems with a vertical single U-tube GLHX(U-tube system) and a vertical double tube GLHX(double tube system), which were installed in a school building located in Cheonan. All systems were operated in a part load conditions for all day, and the maximum COP of the single U-tube system and the double tube system were 6.2 and 5.2 at cooling mode, respectively. The double tube GLHX designed by the GLHEPRO, commercial program, was estimated to have the same performance as the U-tube GLHX, because the inlet temperatures of each outdoor unit heat exchanger for the former was similar to the latter. However, it is needed to prove the long tenn performance. It is suggested that the new algorithms to control the flow rate of secondary fluid for GLHX according to load variation have to be developed in order to enhance the performance of the system.

• Structural Engineering and Mechanics
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• 제40권4호
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• pp.517-539
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• 2011

This paper presents the seismic responses of a 1:5-scale five-story reinforced concrete building model, which represents a residential apartment building that has a high irregularity of weak story, soft story, and torsion simultaneously at the ground story. The model was subjected to a series of uni- and bi-directional earthquake simulation tests. Analysis of the test results leads to the following conclusions: (1) The model survived the table excitations simulating the design earthquake with the PGA of 0.187 g without any significant damages, though it was not designed against earthquakes; (2) The fundamental mode was the torsion mode. The second and third orthogonal translational modes acted independently while the torsion mode showed a strong correlation with the predominant translational mode; (3) After a significant excursion into inelastic behavior, this correlation disappeared and the maximum torsion and torsion deformation remained almost constant regardless of the intensity of the two orthogonal excitations; And, (4) the lateral resistance and stiffness of the critical columns and wall increased or decreased significantly with the large variation of acting axial forces caused by the high bi-directional overturning moments and rocking phenomena under the bi-directional excitations.

• 한국전자파학회논문지
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• 제27권11호
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• pp.949-958
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• 2016

본 논문은 다중대역 및 다중모드의 레이다 기능을 갖는 새로운 SDR(Software Defined Radar) 플랫폼의 개발 결과를 제시한다. SDR 하드웨어 플랫폼은 다중대역의 S, X, 그리고 K 밴드의 교체 가능한 RF 송수신기 및 안테나 모듈과 프로그램 가능한 신호처리기 모듈로 구현된다. 소프트웨어 플랫폼은 다중모드의 CW, Pulse, FMCW, LFM Chirp 파형 발생과 적응 가능한 신호처리 알고리즘 라이브러리 모듈 및 개방형 API 소프트웨어 모듈로 구현된다. SDR 플랫폼의 레이다 통합시험을 통하여 동작 성능을 실시간으로 검증하였으며, 또한 현장 활용시험을 통하여 지상 표적 및 비행체 드론 표적을 성공적으로 탐지하여 시험 결과를 제시하였다.

• Journal of Power Electronics
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• 제17권3호
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• pp.744-755
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• 2017

With the high penetration of various sustainable energy sources, the control and protection of Microgrids has become a challenging problem considering the inherent current limitation feature of inverter-based Distributed Generators (DGs) and the bidirectional power flow in Microgrids. In this paper, a hybrid control and protection scheme is proposed, which combines the traditional inverse-time overcurrent protection with the biased differential protection for different feeders with different kinds of loads. It naturally accommodates various control strategies such as P-Q control and V-f control. The parameter settings of the protection scheme are analyzed and calculated through a fast Fourier transform algorithm, and the stability of the control strategy is discussed by building a small signal model in MATLAB. Different operation modes such as the grid-connected mode, the islanding mode, and the transitions between these two modes are ensured. A Microgrid model is established in PSCAD and the analysis results show that a Microgrid system can be effectively protected against different faults such as the single phase to ground and the three phase faults in both the grid-connected and islanded operation modes.