Optimal design of viscoelastic dampers using eigenvalue assignment   总被引：1，自引：0，他引：1  

Sang‐Hyun Lee  Dong‐In Son  Jinkoo Kim  Kyung‐Won Min 《地震工程与结构动力学》2004,33(4):521-542

In this study a procedure for determining the optimum size and location of viscoelastic dampers is proposed using the eigenvalue assignment technique. Natural frequencies and modal damping ratios, required to realize a given target response, are determined first by the convex model. Then the desired dynamic structural properties are realized by optimally distributing the damping and stiffness coefficients of viscoelastic dampers using non‐linear programming based on the gradient of eigenvalues. This optimization method provides information on the optimal location as well as the magnitude of the damper parameters. The proposed procedure is applied to the retrofit of a 10‐story shear frame, and to a three‐dimensional structure with an asymmetric plan. The analysis results confirm that the responses of model structures retrofitted by the proposed method correspond well with the given target response. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Probabilistic approach for active control of structures: experimental verification     

Jae‐Seung Hwang  Kyung‐Won Min  Sang‐Hyun Lee  Hongjin Kim 《地震工程与结构动力学》2005,34(3):207-225

In our previous study (Earthquake Engineering and Structural Dynamics 2003; 32 :2301), we have developed a probabilistic algorithm for active control of structures. In the probabilistic control algorithm, the control force is determined by the probability that the structural energy exceeds a specified target critical energy, and the direction of a control force is determined by the Lyapunov controller design method. In this paper, an experimental verification of the proposed probabilistic control algorithm is presented. A three‐story test structure equipped with an active mass driver (AMD) has been used. The effectiveness of the control algorithm has been examined by exciting the test structure using a sinusoidal signal, a scaled El Centro earthquake and a broadband Gaussian white noise; and, especially, experiments on control have been performed under different conditions to that of system identification in order to prove the stability and robustness of the proposed control algorithm. The experimental results indicate that the probabilistic control algorithm can achieve a significant response reduction under various types of ground excitations even when the modeling error exists. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Submarine groundwater discharge revealed by aerial thermal infrared imagery: a case study on Jeju Island,Korea          下载免费PDF全文

Eunhee Lee  Ki‐mook Kang  Sung Pil Hyun  Kil‐Yong Lee  Heesung Yoon  Seung Hee Kim  Yongcheol Kim  Zhen Xu  Duk‐jin Kim  Dong‐Chan Koh  Kyoochul Ha 《水文研究》2016,30(19):3494-3506

Submarine groundwater discharge (SGD) is a global phenomenon that carries large volumes of groundwater and dissolved chemical species such as nutrient, metals, and organic compounds to coastal zones. We report the influence of SGD on the coastal waters of Jeju Island, Korea, using high‐resolution aerial thermal infrared (TIR) mapping techniques and field investigations. An aircraft‐based system was implemented using a cost‐effective TIR camera for aerial TIR mapping. Ground‐based calibrations and system integration with GPS/IMU (global positioning system/inertial measurement unit) were performed for the aerial systems. The aerial surveys showed distinct low‐temperature signatures of SGD along the coasts of Jeju Island, revealing large groundwater inputs from the coastal aquifers to the ocean. Multiple aerial surveys over a range of seasons and tidal stages revealed that SGD rates dynamically affect the sea surface temperature (SST) of the coastal zone. The in‐situ measurements supported that SGD has a substantial influence on the coastal water chemistry as well as SST. Our observations highlight the extent to which aerial‐based TIR mapping can serve as a powerful tool for studying SGD and other coastal processes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Assessment of the Accuracy of Close Distance Photogrammetric JRC Data     

Dong Hyun Kim  George Poropat  Ivan Gratchev  Arumugam Balasubramaniam 《Rock Mechanics and Rock Engineering》2016,49(11):4285-4301

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Learning the hard way: a case study of an attempt at agricultural transformation in response to climate change     

E. Jakku  P. J. Thorburn  N. A. Marshall  A-M. Dowd  S. M. Howden  E. Mendham  K. Moon  C. Brandon 《Climatic change》2016,137(3-4):557-574

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Application of 2D numerical model to unsteady performance evaluation of vertical-axis tidal current turbine     

Zhen Liu  Hengliang Qu  Hongda Shi  Gexing Hu  Beom-Soo Hyun 《中国海洋大学学报(英文版)》2016,15(6):977-986

Tidal current energy is renewable and sustainable, which is a promising alternative energy resource for the future electricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2×10~5 and 0.01 s are selected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio(TSR) determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coefficients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analysis of the vertical tidal stream turbine.  相似文献   

Assessment of soil washing for simultaneous removal of heavy metals and low-level petroleum hydrocarbons using various washing solutions     

Deok Hyun Moon  Jae-Woo Park  Agamemnon Koutsospyros  Kyung Hoon Cheong  Yoon-Young Chang  Kitae Baek  Raehyun Jo  Jeong-Hun Park 《Environmental Earth Sciences》2016,75(10):884

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Investigation of the impacts of local-scale hydrogeologic conditions on sinkhole occurrence in East-Central Florida,USA     

Han Xiao  Yong Je Kim  Boo Hyun Nam  Dingbao Wang 《Environmental Earth Sciences》2016,75(18):1274

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Distribution of chaetognaths (Aphragmophora: Sagittidae) in Korean waters     

Bo Ram Lee  Hyun Woo Kim  Wongyu Park 《Ocean Science Journal》2016,51(3):447-454

The distribution of chaetognaths was investigated at 10 stations in the southern part of Korean waters (line S), at six stations in the eastern part of Korean waters (line E) and at 8 stations in the western part of Korean waters (line W). Ten species were present at the stations at line S and Flaccisagitta enflata and Zonosagitta bedoti were dominant among these species. Mean densities at line S ranged from 7 inds.m^-3 to 27 inds.m^-3. Five chaetognath species were found at the stations at line E and Zonosagitta nagae and Parasagitta elegans were the most abundant. Mean densities ranged from 1 to 10 inds.m-3. Four chaetognath species were present at line W and Aidanosagitta crassa and chaetognath juveniles were dominant in this line. Mean densities ranged from 21 to 199 inds.m^-3. The density of chaetognaths was highest at line W while the diversity of chaetognaths was highest at line S. Individuals of chaetognaths were divided into two groups, a group of line E and a mixed group of lines W and E. This study suggests that F. enflata is a warm water species; Z. nagae is a mixed water species; P. elegans is a cold water species; and A. crassa is a less saline water species. The mtCOI of F. enflata, which was a dominant species in the sampling area, was analyzed. F. enflata that are present in waters around Korean were genetically divided into two groups, which may be influenced by various oceanic factors.  相似文献   

Thermal effects on the growth and fatty acid composition of four harmful algal bloom species: Possible implications for ichthyotoxicity     

Bonggil Hyun  Se-Jong Ju  Ah-Ra Ko  Keun-Hyung Choi  Seung Won Jung  Pung-Guk Jang  Min-Chul Jang  Chang Ho Moon  Kyoungsoon Shin 《Ocean Science Journal》2016,51(3):333-342

Little is known regarding how harmful algal bloom species respond to different temperatures in terms of fatty acid production. This study examined the effects of temperature on the growth rates, cell volumes, and fatty acid concentrations and compositions of four harmful algal bloom species (HABs), Akashiwo sanguinea, Alexandrium tamarense, Chattonella ovata, and Prorocentrum minimum. The HABs species were cultured at 15, 20, 25, and 30°C in a nutrient-enriched medium. Three of the species maintained optimal growth rates over a wide range of temperatures, but A. tamarense did not. The cell volumes of each species showed little change over the temperature range. The total fatty acid concentrations in A. sanguinea, A. tamarense and C. ovata decreased as the temperature increased, but P. minimum showed no trend in this respect. Polyunsaturated fatty acids (PUFAs), the key biochemical components that maintain cell membrane fluidity and which are associated with toxicity, decreased in both concentration and proportion of total fatty acids as temperature increased, except in A. sanguinea, in which the proportion of PUFAs to the total fatty acids increased. These reductions in PUFA concentration and proportion could reduce cell membrane fluidity and toxicity in HABs; however, enhanced growth and/or ruptured cells, which are considered more toxic than intact cells, could compensate for the reduced per-cell toxicity. This phenomenon might impact on the marine ecosystem and aquaculture industry.  相似文献