• Title, Summary, Keyword: Vibration Control

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Seismic Response of Spatial Structure Subjected to Multi-Support Earthquake Load (다중지점 지진하중을 고려한 대공간구조물의 지진응답 분석)

  • Kim, Gee Cheol;Kang, Joo Won
    • Journal of Korean Society of Steel Construction
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    • v.25 no.4
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    • pp.399-407
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    • 2013
  • Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response for seismic design of spatial structure. Keel arch structure is used as an example structure because it has primary characteristics of spatial structures. In case of spatial structures with different ground condition and time lag, multiple support excitation may be subjected to supports of a keel arch structure. In this study, the response of the keel arch structure under multiple support excitation and with time lag are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic responses of spatial structure under multiple support excitation are different from those of spatial structure under simple excitation. And the seismic response of spatial structure with time lag are different from those of spatial structure without time lag. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation and time lag because the spatial structure supports may be different and very long span. It is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation.

Fabrication of Photocatalytic TiO2 thin Film Using Aerosol Deposition Method and its Filtration Characteristics (에어로졸 증착법을 이용한 광촉매 TiO2 박막 제조 및 박막의 여과 특성)

  • Choi, Wonyoul;Lee, Jinwoo;Kim, Shijun;Kim, Jongoh
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.1
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    • pp.5-11
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    • 2010
  • The objective of this study is to evaluate the effect of operational parameters such as rotation speed and vibrating milling time for the fabrication of photocatalytic $TiO_2$ thin film using aerosol deposition methods. $TiO_2$ powders produced in the range of 1,000-3,000 rpm of rotation speed of centrifugal separator are ineffective on the fabrication of $TiO_2$ thin film by aerosol deposition due to the problem of nozzle powder jam. $TiO_2$ powders controlled by vibrating milling had about 420 nm of average diameter after 2 hr of vibrating milling time. The result of XRD analysis indicated that $TiO_2$ powders had a anatase phase. Vibrating milling methods was considered to be an effective pre-treatment process for $TiO_2$ powder control. Consequently $TiO_2$ photocatalytic thin film with dispersion of anatase crystallites controled by vibrating milling was successfully fabricated by aerosol deposition. The permeation flux of $TiO_2$ photocatalytic thin film with the immobilized $TiO_2$ powder was higher than that of suspended $TiO_2$ powder. Therefore, $TiO_2$ photocatalytic thin film promises to be one of the effective methods for enhancing filtration performance for the treatment of organic pollutants.

Dynamic Model Prediction and Validation for Free-Piston Stirling Engines Considering Nonlinear Load Damping (자유피스톤 스털링 엔진의 비선형 부하 감쇠를 고려한 동역학 모델 예측 및 검증)

  • Sim, Kyuho;Kim, Dong-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.10
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    • pp.985-993
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    • 2015
  • Free-piston Stirling engines (FPSEs) have attracted much attention in the renewable energy field as a key device in the conversion from thermal to mechanical energy, and in the recycling of waste energy. Traditional Stirling engines consist of two pistons that are connected by a mechanical link, while FPSEs are formed as a vibration system by connecting each piston to a spring without a physical link. To ensure the correct design and control of operations, this requires elaborate dynamic-performance predictions. In this paper, we present the performance-prediction methodology using a linear and nonlinear dynamic analytical model considering the external load of FPSEs. We perform linear analyses to predict the operating point of the engine using the root locus technique. Using nonlinear analysis, we also predict the amplitude of pistons by performing numerical integration considering both the linear and nonlinear damping terms of the external load. We utilize the predicted dynamic behavior to predict the engine performance. In addition, we compare the experiment results and existing model predictions for RE-1000 to verify the reliability of the analytical model.

The Application of Unmanned Aerial Photograpy for Effective Monitoring of Marine Debris (해안표착물의 효율적인 모니터링을 위한 무선 조정 항공기 촬영기법의 적용)

  • Jang, Seon-Woong;Lee, Seong-Kyu;Oh, Seung-Yeol;Kim, Dae-Hyun;Yoon, Hong-Joo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.17 no.4
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    • pp.307-314
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    • 2011
  • This study proposed detection method of Marine debris using unmanned aerial photography. For unmanned aerial photography, a RC(Radio Control) helicopter which has good movability and economics was used. To a camera mounting, a gimbal equipment was attached to the bottom of the RC helicopter. The gimbal equipment is very useful because it is not seriously affected by vibration and rolling. In addition, we invented that digital image processing algorithm using Matlab program for detection of marine debris from photographs. Particularly, background subtraction in invented algorithm was applied. As a result, marine debris of a variety of forms from different sand states of coast were reliably detected. In the future, monitoring using proposed method was expected to contribute that the solution to representative problem of monitoring area selecting and estimate the total litter mass over the beach. Moreover, It is considered a greater application possibility to marine environmental observations.

An Implementation of Brain-wave DB building system for Artifacts prevention using Face Tracking (얼굴 추적 기반의 잡파 혼입 방지가 가능한 뇌파 DB구축 시스템 구현)

  • Shin, Jeong-Hoon;Kwon, Hyeong-Oh
    • Journal of the Institute of Convergence Signal Processing
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    • v.10 no.1
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    • pp.40-48
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    • 2009
  • Leading of the computer, IT technology has make great strides. As a information-industry-community was highly developed, user's needs to convenience about intelligence and humanization of interface is being increase today. Nowadays, researches with are related to BCI are progress put the application-technology development first in importance eliminating research about fountainhead technology with DB construction. These problems are due to a BCI-related research studies have not overcome the initial level, and not toward a systematic study. Brain wave are collected from subjects is a signal that the signal is appropriate and necessary in the experiment is difficult to distinguish. In addition, brain wave that it's not necessary to collect the experiment, serious eyes flicker, facial and body movements of an EMG and electrodes attached to the state, noise, vibration, etc. It is hard to collect accurate brain wave was caused by mixing disturbance wave in experiment on the environment. This movement, and the experiment of subject impact on the environment due to the mixing disturbance wave can cause that lowering cognitive and decline of efficiency when embodied BCI system. Therefore, in this paper, we propose an accurate and efficient brain-wave DB building system that more exactness and cognitive basis studies when embodied BCI system with brain-wave. For the minimize about brain wave DB with mixing disturbance, we propose a DB building method using an automatic control and prevent unnecessary action, put to use the subjects face tracking.

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Study on frequency response of implantable microphone and vibrating transducer for the gain compensation of implantable middle ear hearing aid (이식형 마이크로폰과 진동체를 갖는 인공중이의 이득 보상을 위한 주파수 특성 고찰)

  • Jung, Eui-Sung;Seong, Ki-Woong;Lim, Hyung-Gyu;Lee, Jang-Woo;Kim, Dong-Wook;Lee, Jyung-Hyun;Kim, Myoung-Nam;Cho, Jin-Ho
    • Journal of Sensor Science and Technology
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    • v.19 no.5
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    • pp.361-368
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    • 2010
  • ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

Validity of Linear Combination Approach based on Net Damping Analysis of Cable-Damper System (케이블-댐퍼 시스템의 전체감쇠비 해석을 통한 선형조합 접근법의 유효성)

  • Kim, Hyeon Kyeom;Hwang, Jae Woong;Lee, Myeong Jae
    • Journal of The Korean Society of Civil Engineers
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    • v.29 no.5A
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    • pp.467-475
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    • 2009
  • Existing studies have suggested Universal Curve only for supplemental damping by damper. Therefore net damping has been determined by means of arithmetic summation between intrinsic, aero-damping of cable and supplemental damping of damper. However linear combination approach by means of the arithmetic summation is not enough theoretical background. So validity of this approach should be verified in order to design adequate cable-damper system by engineers. This study establishes governing differential equation which can consider intrinsic, aero-damping and supplemental damping as well. And also analysis method is solved by combination of muller method and successive iteration method. Consequently, this study succeeds in verification for validity of linear combination approach. As a result of this study, linear combination approach is limitedly effective in case of low stiffness and optimum damping coefficient of damper, short distance from support to damper, lower vibration mode, low aero-damping, and normal windy environment. Whereas this study will be effective in case of opposite conditions, and existing studies or linear combination approach occur to further error. Meaning of this study presents exact solution for net damping of cable-damper system, and verifies linear combination approach by means of the analysis method. In the future, if monitoring of optimum damping coefficient of a damper against aero-damping is feasible on time, algorithm of this study will be available for control of cable and semi-active damper system such as magneto-rheological damper.

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Designing fuzzy systems for optimal parameters of TMDs to reduce seismic response of tall buildings

  • Ramezani, Meysam;Bathaei, Akbar;Zahrai, Seyed Mehdi
    • Smart Structures and Systems
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    • v.20 no.1
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    • pp.61-74
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    • 2017
  • One of the most reliable and simplest tools for structural vibration control in civil engineering is Tuned Mass Damper, TMD. Provided that the frequency and damping parameters of these dampers are tuned appropriately, they can reduce the vibrations of the structure through their generated inertia forces, as they vibrate continuously. To achieve the optimal parameters of TMD, many different methods have been provided so far. In old approaches, some formulas have been offered based on simplifying models and their applied loadings while novel procedures need to model structures completely in order to obtain TMD parameters. In this paper, with regard to the nonlinear decision-making of fuzzy systems and their enough ability to cope with different unreliability, a method is proposed. Furthermore, by taking advantage of both old and new methods a fuzzy system is designed to be operational and reduce uncertainties related to models and applied loads. To design fuzzy system, it is required to gain data on structures and optimum parameters of TMDs corresponding to these structures. This information is obtained through modeling MDOF systems with various numbers of stories subjected to far and near field earthquakes. The design of the fuzzy systems is performed by three methods: look-up table, the data space grid-partitioning, and clustering. After that, rule weights of Mamdani fuzzy system using the look-up table are optimized through genetic algorithm and rule weights of Sugeno fuzzy system designed based on grid-partitioning methods and clustering data are optimized through ANFIS (Adaptive Neuro-Fuzzy Inference System). By comparing these methods, it is observed that the fuzzy system technique based on data clustering has an efficient function to predict the optimal parameters of TMDs. In this method, average of errors in estimating frequency and damping ratio is close to zero. Also, standard deviation of frequency errors and damping ratio errors decrease by 78% and 4.1% respectively in comparison with the look-up table method. While, this reductions compared to the grid partitioning method are 2.2% and 1.8% respectively. In this research, TMD parameters are estimated for a 15-degree of freedom structure based on designed fuzzy system and are compared to parameters obtained from the genetic algorithm and empirical relations. The progress up to 1.9% and 2% under far-field earthquakes and 0.4% and 2.2% under near-field earthquakes is obtained in decreasing respectively roof maximum displacement and its RMS ratio through fuzzy system method compared to those obtained by empirical relations.

Biological Monitoring of Workers Exposed to Diisocyanates using Urinary Diamines (소변 중 디아민을 이용한 디이소시아네이트 노출 근로자의 생물학적 모니터링)

  • Lee, Jong Seong;Kim, Boowook;Shin, Jungah;Baek, JinEe;Shin, Jae Hoon;Kim, Ji-hye
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.26 no.2
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    • pp.178-187
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    • 2016
  • Objectives: Diisocyanates are a potent inducer of diseases of the airways, especially asthma. In this study, toluenediamine(TDA) and methylenedianiline(MDA) in urine were evaluated as biomarkers of exposure to tolunenediisocyanate(TDI) and methylenediphenyl diisocyanate(MDI), respectively. Methods: Workers exposed to TDI and MDI, as well as non-occupationally exposed subjects, were studied and pre- and post-shift urine samples were collected from 8 control subjects and 8 workers from a factory which manufactures polyurethane products for reducing noise and vibration in automobiles. Airborne TDI and MDI(n=8) were sampled on solvent-free glass filters impregnated with n-butylamine and detected by liquid chromatography atmospheric pressure ionization tandem mass spectrometry. Urinary TDA and MDA were detected as pentafluoropropionic acid anhydride(PFPA) derivatives by liquid chromatography electrospray ionization tandem mass spectrometry. Results: The median levels of urinary 2,6-TDA(p<0.001), 2,4-TDA(p=0.001), and MDA(p<0.001) of workers in post-shift samples were significantly higher than those of controls. The median levels of urinary 2,6-0TDA($0.63{\mu}g/g$ creatinine vs $0.34{\mu}g/g$ creatinine, p=0.017) and MDA($4.21{\mu}g/g$ creatinine vs $3.18{\mu}g/g$ creatinine, p=0.017) of workers in post-shift samples were significantly higher than those of the pre-shift samples. There were significant correlations between the urinary 2,6-TDA, 2,4-TDA, and MDA of workers in post-shift samples and the airborne 2,6-TDI(rho=0.952, p<0.001), 2,4-TDI(rho=0.833, p=0.001), and MDI(rho=0.952, p<0.001). Conclusions: These urinary diamines, metabolites of diisocyanates, in post-shift samples were useful biomarkers to assess occupational exposure to diisocyanates.

Measuring the Intrusive Feeling of a Lane Keeping Assistance System (차선 유지 보조 시스템으로 인해 발생하는 이질감의 계측에 대한 연구)

  • Park, Kyudong;Kwahk, Jiyoung;Han, Sung H.;Song, Minseok;Choi, Dong Gu;Jang, Hyeji;Kim, Dohyeon
    • Journal of the Ergonomics Society of Korea
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    • v.37 no.4
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    • pp.459-473
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    • 2018
  • Objective: The objective of this study is to investigate the intrusive feeling caused by a Lane Keeping Assistance System (LKAS) and measure it objectively through the sensor log data of a vehicle. Background: LKAS, one of the Advanced Driver Assistance System (ADAS), directly intervenes in the steering wheel control to assist the driver to keep the lane. Due to the torque generated by the LKAS, the driver has a different and undesirable feeling from a usual situation, which can affect the driving experience. Nevertheless, the performance of the LKAS in most studies focused only on how well the system keeps the lane. Method: Through an actual driving test using a test vehicle equipped with an LKAS, two ADAS experts and two human factor experts observed the intrusive feeling while collecting sensor log data at the same time. After the types of the intrusive feeling were classified, variables that could account for the feeling were derived. Then, this study compared the data collected from the vehicle with and without the intrusive feeling. Results: Three types of the intrusive feeling were observed: abrupt lateral change, steering wheel vibration, and heavy steering. The lateral speed (LS), the high-pass filtered steering angle (FSA), and the interrupt torque (IT) were then derived as the variables that could explain each feeling, respectively. It is found that the patterns of the derived variables are different in driving with and without the intrusive feeling. Conclusion and Application: The intrusive feeling found in this study can be used as a performance index in the development stage of the LKAS. It will be helpful to systematically reduce the intrusive feeling.