• Smart Structures and Systems
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• 제13권2호
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• pp.281-303
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• 2014

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

• 한국초지조사료학회지
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• 제18권3호
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• pp.259-266
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• 1998

A field experiment was carried out to determine the effects of mechanical and chemical drying agents at mowing on the field drying rate and hay quality of orchardgrass dominant pasture plants. The mower conditioner /chemical drying agent ($K_2CO_3$ 2% conditioning, $K_2CO_3$ 2% + conditioning and control) were treated at different harvest stages (late boot, heading and bloom stage) for hastening hay manufacture in 1996. After field dry, four square bales were made by hay baler, and the visual estimation and nutritive value of hay were evaluated after storing two months. The field drying rate of pasture plants was higher with delayed stage of harvest, and mechanical and mechanical + chemical, but chemical alone was very low. In mower conditioning, the duration of field dry was shortened by 0.5 to 1 day compared with $K_2CO_3$ and 1.5 to 2 days compared with control. The dry matter loss of hay was reduced by late harvest and mechanical, and mechanical + chemical, but the score by chemical alone was very low. The visual score (leafiness, green color, odor and softness) of hay after storage was high in mechanical and mechanical + chemical, but the score by chemical alone was very low. Nutritive value (ADF, NDF, digestibility, and relative feed value) of hay was also high with treatment of mechanical and mechanical + chemical, but the quality by chemical alone was similar compared with control. The quality of hay was very low when harvested at bloom stage. In conclusion, mower conditioning can enhance the field drying rate of orchardgrass dominant pasture plants, however the drying efficiency of chemical drying agent was very low. Harvesting at early heading to heading stage was recommened for manufacture of high quality hay.

• Wind and Structures
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• 제31권1호
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• pp.21-29
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• 2020

The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and high-frequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

• 전자공학회논문지
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• 제50권1호
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• pp.254-260
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• 2013

본 논문에서는 IPMSM(Interior Permanent Magnet Synchronous Motor)의 약계자 제어에 따른 전자기적특성을 다룬다. IPMSM의 운전 속도 영역을 확장하기 위해 약계자 전류제어가 일반적으로 사용되며 약계자 운전 중에는 전기강판의 자기적 포화에 의해 쇄교자속의 왜형이 발생하게 된다. 따라서 정현파 전류 입력을 위한 전압 파형은 왜형을 갖게 된다. 약계자 전류 증가에 따라 이러한 전압 왜형은 더욱 크게 발생되며 기본파 전압에 비해 상당한 크기의 고조파 전압을 필요로 하게 된다. 이러한 현상을 ２차원 유한요소 해석을 이용하여 확인하였으며 시험을 통해 검증하였다. 본 연구 결과를 통해 IPMSM의 특성 분석에 사용되는 d-q축 등가회로 파라미터 즉, 영구자석에 의한 쇄교자속, d－q축 인덕턴스는 산정 단계에서 기본파 물리량으로 계산되므로 약계자 운전시 발생하는 전압 왜형을 예측할 수 없음을 알 수 있다. 결국 주어진 전압에서 얻을 수 있는 속도 예측에 오차를 수반하게 되며 전압고조파에 대한 대책이 필요하다.

• Earthquakes and Structures
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• 제22권1호
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• pp.53-64
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• 2022

This study proposes an intelligent semi-active isolation system combining a variable-stiffness control device and ground motion characteristic prediction. To determine the optimal control parameter in real-time, a genetic algorithm (GA)-fuzzy control law was developed in this study. Data on various types of ground motions were collected, and the ground motion characteristics were quantified to derive a near-fault (NF) characteristic ratio by employing an on-site earthquake early warning system. On the basis of the peak ground acceleration (PGA) and the derived NF ratio, a fuzzy inference system (FIS) was developed. The control parameters were optimized using a GA. To support continuity under near-fault and far-field ground motions, the optimal control parameter was linked with the predicted PGA and NF ratio through the FIS. The GA-fuzzy law was then compared with other control laws to verify its effectiveness. The results revealed that the GA-fuzzy control law could reliably predict different ground motion characteristics for real-time control because of the high sensitivity of its control parameter to the ground motion characteristics. Even under near-fault and far-field ground motions, the GA-fuzzy control law outperformed the FPEEA control law in terms of controlling the isolation layer displacement and the superstructure acceleration.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.619-624
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• 1987

A study on distribution automation system suitable to distribution system of KEPCO has started since 1984, and the field trial system for ADS will be operated for testing. This paper will describe project and planning for field trial of KEPCO.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.1-5
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• 2008

The purpose of this study is to ensure an amicable material quality control in the construction site through investigating a process which can impact the construction material quality. For it, a worker interview and questionnaire survey was conducted through a direct field visit. The visited construction sites are composed of 79% construction site and 21% engineering site. As the respondents of questionnaire survey, the quality control workers were 72% of total respondents. Next, the construction worker, handymen, field representatives and others formed 7%. The interview with the quality control staff was conducted with the items including the construction site quality control guide, incoming inspection and material management. Through this survey, the problems of quality control by progress phase were derived. It could be known that the management and measures by each phase were urgently required. It also was indicated that a selection of low-priced material caused by low price bidding could badly impact the construction and safety. Also, in relation to the opinions such as the insufficient quality control and heavy work-load, the improvements are required. For the effective quality control in the construction site, the material quality control procedures suitable for the phase of construction progress must be presented in the present quality control. Also, the standards for it need to be established.

• Structural Engineering and Mechanics
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• 제83권4호
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• pp.537-549
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• 2022

In this paper, a novel multi-feature model predictive control (MPC) framework with real-time and adaptive performances is proposed for intelligent structural control in which some drawbacks of the algorithm including, complex control rule and non-optimality, are alleviated. Hence, Linear Programming (LP) is utilized to simplify the resulted control rule. Afterward, the Whale Optimization Algorithm (WOA) is applied to the optimal and adaptive tuning of the LP weights independently at each time step. The stochastic control rule is also achieved using Kalman Filter (KF) to handle noisy measurements. The Extreme Learning Machine (ELM) is then adopted to develop a data-driven and real-time control algorithm. The efficiency of the developed algorithm is then demonstrated by numerical simulation of a twenty-story high-rise benchmark building subjected to earthquake excitations. The competency of the proposed method is proven from the aspects of optimality, stochasticity, and adaptivity compared to the KF-based MPC (KMPC) and constrained MPC (CMPC) algorithms in vibration suppression of building structures. The average value for performance indices in the near-field and far-field (El earthquakes demonstrates a reduction up to 38.3% and 32.5% compared with KMPC and CMPC, respectively.

• 대한방사선기술학회지:방사선기술과학
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• 제44권1호
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• pp.1-8
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• 2021

The purpose of this study was to analyze the effect of automatic exposure control (AEC) control factors in digital radiography systems based on the fine contrast images using coin phantoms. The AEC control factors were targeted at the range of dominent zone, sensitivity, and density. The dominent zone was divided into cases where a single coin was used to cover the field configuration, and cases where seven coins were used to cover the field configuration. The sensitivity was classified into three stages (200, 400, 800) and the density was classified into three stages (2.5, 0, 2.5). Image quality was evaluated by signal to noise ratio (SNR) and contrast to noise ratio (CNR). Then, the automatically exposed tube current was measured. As a result, the X-ray image of seven coins obtained a result value of about 1.2 times higher for SNR and 1.9 times higher for CNR than the X-ray image for one coin. The tube current was also about 1.6 times higher. In conclusion, In AEC, the higher the field configuration and dominent zone are matched and the higher the density, the lower the sensitivity, which increases the tube current and CNR, which increases the image quality. Therefore, it is judged that the appropriate setting of the range of dominent zone, sensitivity, and density of the control, which is the AEC control factor, could improve the fine contrast of images.

• 한국음향학회지
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• 제31권4호
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• pp.214-224
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• 2012

The objective of this paper is to design multichannel spherical loudspeaker array by considering various positioning methods such as Gaussian grid, Lebedev grid and packing method. For the spatial sound manipulation, which is to make desired sound field by controling multiple sound sources, the Kirchhoff-Helmholtz integral states that sound fields can be reproduced in terms of infinite control sources on the integral surface. But since we cannot control infinite number of sources for the implementation, we have to allocate finite number of sound sources which can approximately act as infinite number of sources. To manipulate sound field inside of a sphere (which is typical example of three dimensional array) by controlling sound sources on the surface, three methods of allocating sound sources, which are Gaussian grid, Lebedev grid and packing method, are reviewed. For each geometry, the performances of manipulation rendered by time-reversal operator and higher-order ambisonics are compared.