• Title/Summary/Keyword: Step response

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Investigations on seismic response of two span cable-stayed bridges

  • Bhagwat, Madhav;Sasmal, Saptarshi;Novak, B.;Upadhyay, A.
    • Earthquakes and Structures
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    • v.2 no.4
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    • pp.337-356
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    • 2011
  • In this paper, cable-stayed bridges with single pylon and two equal side spans, with variations in geometry and span ranging from 120 m to 240 m have been studied. 3D models of the bridges considered in this study have been analysed using ANSYS. As the first step towards a detailed seismic analysis, free vibration response of different geometries is studied for their mode shapes and frequencies. Typical pattern of free vibration responses in different frequencies with change in geometry is observed. Further, three different seismic loading histories are chosen with various characteristics to find the structural response of different geometries under seismic loading. Effect of variation in pylon shape, cable arrangement with variation in span is found to have typical characteristics with different structural response under seismic loading. From the study, it is observed that the structural response is very much dependent on the geometry of the cable-stayed bridge and the characteristics of the seismic loading as well. Further, structural responses obtained from the study would help the design engineers to take decisions on geometric shapes of the bridges to be constructed in seismic prone zones.

A Review and Its Implications on School-based Crisis Response Team in the U.S. (미국의 학교기반 위기대응팀에 대한 고찰과 시사점)

  • Lee, Dong Hun;Jeong, Bo Young;Kang, Eun Jin;Myung, So Yeon
    • Korean Journal of Comparative Education
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    • v.27 no.1
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    • pp.1-28
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    • 2017
  • In this study, the school crisis response system and intervention are examined in the U.S. by reviewing Crisis Response Team(CRT) to give a direction for establishing and improving the school crisis response system in Korea. To do this, a literature review has been conducted focusing on domestic and foreign literature on the school - based crisis response system about the U.S. and Korea. The characteristics of the school-based CRT in the U.S. are as follows. First, in the U.S., the organizational structure and financial support for school - based crisis response has been stated by law so that the roles and responsibilities of region, district, school have been clearly defined. Second, in the event of a school crisis, the school have been shared the role of professional crisis response according to the Incident Command System and coordinates communication smoothly between each area of society through cooperation with CRT. Third, CRT prevents burnout by showing flexibility in team composition so that CRT members are not tired or overwhelmed by a crisis event, and focuses on strengthening the crisis capability of the school itself through cooperation between the school and CRT. Fourth, the school-based CRT in the U.S. conducts a step by step crisis intervention from prevention to prolonged post management. Based on these results, implications for the establishment and improvement of school-based crisis response system in Korea are discussed.

A study on the Crashworthiness Design of Bow Structure of Oil Carriers -Collision Behaviour of Simplified Models(1) (유조선 선수부의 내충돌 구조설계에 관한 연구 -이상화 모델의 충돌거동 분석(1))

  • 신영식;박명규
    • Journal of Ocean Engineering and Technology
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    • v.15 no.3
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    • pp.120-127
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    • 2001
  • The potential pollution problems resulting from tanker collision necessitate the requirement for an effective structural design and the development of relevant safety regulations. During a few decades, the great effort has been made by the international Maritime Organization and the Administration, etc, to reduce oil spillage from collision accidents. However there is still a need for investigation in the light of structural evaluation method for the experiments and rational analysis, and design development for an operational purpose of ships. This study aims for investigating a complicated structural response of bow structures of simplified models and oil carriers for assessing the energy dissipation and crushing mechanics of the striking vessels through a methodology of the numerical analysis for the various models and its design changes. Through these study an optimal bow construction absorbing great portion of kinetic energy at the least penetration depth prior to reach to the cargo area and an effective location of collision bulkhead are investigated. In order to obtain a rational results in this study, three stages of collision simulation procedures have been performed step by step as follows; 1) 16 simplified ship models are used to investigate the structural response against bow collision with variation of primary and secondary members. Mass and speed are also varied in four conditions. 2) 21 models consisted of 5 sizes of the full scaled oil carriers are used to perform the collision simulation with the various sizes and deadweight delivered in a recent which are complied with SOLAS and MARPOL. 3) 36 models of 100l oil carrier are used to investigate the structural response and its influence to the collision bulkhead against bow collision in variation with location of collision bulkhead, primary members, framing system and colliding conditions, etc. By the first study using simplified models the response of the bow collision is synthetically evaluated for the parameters influencing to the absorbed energy, penetration depth and impact force, etc.

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An effective load increment method for multi modal adaptive pushover analysis of buildings

  • Turker, K.;Irtem, E.
    • Structural Engineering and Mechanics
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    • v.25 no.1
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    • pp.53-73
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    • 2007
  • In this study, an effective load increment method for multi modal adaptive non-linear static (pushover) analysis (NSA) for building type structures is presented. In the method, lumped plastisicity approach is adopted and geometrical non-linearties (second-order effects) are included. Non-linear yield conditions of column elements and geometrical non-linearity effects between successive plastic sections are linearized. Thus, load increment needed for formation of plastic sections can be determined directly (without applying iteration or step-by-step techniques) by using linearized yield conditions. After formation of each plastic section, the higher mode effects are considered by utilizing the essentials of traditional response spectrum analysis at linearized regions between plastic sections. Changing dynamic properties due to plastification in the system are used on the calculation of modal lateral loads. Thus, the effects of stiffness changes and local mechanism at the system on lateral load distribution are included. By using the proposed method, solution can be obtained effectively for multi-mode whereby the properties change due to plastifications in the system. In the study, a new procedure for determination of modal lateral loads is also proposed. In order to evaluate the proposed method, a 20 story RC frame building is analyzed and compared with Non-linear Dynamic Analysis (NDA) results and FEMA 356 Non-linear Static Analysis (NSA) procedures using fixed loads distributions (first mode, SRSS and uniform distribution) in terms of different parameters. Second-order effects on response quantities and periods are also investigated. When the NDA results are taken as reference, it is seen that proposed method yield generally better results than all FEMA 356 procedures for all investigated response quantities.

New prototypes of target transfer functions for time domain specification (시간영역 설계명세를 위한 목표전달함수의 새로운 표준형)

  • Kim, Sin-Gu;Kim, Yeong-Cheol
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.8
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    • pp.889-897
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    • 1999
  • This paper deals with a problem searching a target transfer function to meet the time-domain specifications for feedback system with given plant transfer function. For the Type I system, we first define three forms of transient response to unit step input, which are named by F, M, S-type. These are charaacterized as follows ; F-type has fast initial response and slow approach to the steady sate after reaching at 90% of the steady state value, S-type has slow initial response but fast approach to the steady state, and M-type is denoted by highly smooth response between F-type and S-type. Three prototypes corresponding to each form are proposed, time. For the order $n{\geq}4$, after determining admissible root structures of target characteristic polynomials empirically and expressing such polynomial coefficients by using special parameters ${\gamma}_i$ and $\epsilon$, the optimal prototypes that minimize the integral of the squared of the modified errors(ISME) have been obtained. Since the step responses of these prototypes have almost same wave forms irrespective to the order, the desired settling time or the rise time can be converted into the equibalent time constant $\tau$ and thus it is easy to obtain a target transfer function. It is shown through a design example that the present prototype is very useful for meeting the time-domain specifications and has been compared with different methods with a viewpoint of pertinence.

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A Pilot Study on the Muscle Activities in Step Input Test as an Indicator of the Vehicle Characteristics

  • Kong, Yong-Ku;Jung, Myung-Chul;Lee, In-Seok;Hyun, Young-Jin;Kim, Chang-Su;Seo, Min-Tae
    • Journal of the Ergonomics Society of Korea
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    • v.32 no.3
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    • pp.217-227
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    • 2013
  • Objective: The purpose of this study was to analyze 'response time', 'peak response time' and 'overshoot value' for each muscle by applying the EMG signal to the vehicle response in ISO 7401 and to quantify the response of the driver according to vehicle characteristics by comparing vehicle characteristics and muscle responses of the driver. Background: The Open-loop test defined in international standards ISO 7401 is the only method for evaluating the performance of the vehicle. However, this test was focused only on mechanical responses, not driver's ones. Method: One skilled male driver(22 yrs. experience) was participated in this experiment to measure muscle activities of the driver in transient state. Then the seven muscle signals were applied to calculate 'response time', 'peak response time', and 'overshoot value'. Results: In the analyses of the EMG data, the effects of vehicle type and muscle were statistically significant on the 'response time' and 'peak response time'. Also, the effects of vehicle type, muscle, and lateral acceleration level were statistically significant on the 'overshoot value' in this study. According to the analyses of the vehicle motion data, vehicle motion variable(LatAcc, Roll, YawVel) was statistically significant on the 'response time' and vehicle type, vehicle motion variable, and lateral acceleration level were statistically significant on the 'peak response time', respectively. Conclusion: In the analyses of the 'response time' and 'overshoot value', the data of muscle activities(EMGs) was better index that could evaluate the vehicle characteristic and performance than the data of vehicle motion. In case of peak response time, both EMG and vehicle motion data were good index. Application: The EMGs data from a driver might be applicable as index for evaluation of various vehicle performances based on this study.

Automobile Dynamic Simulation using CAD/CAE (CAD/CAE 기법을 이용한 자동차 동역학적 시뮬레이션)

  • No, Chang-Su
    • 한국기계연구소 소보
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    • s.18
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    • pp.147-152
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    • 1988
  • The dynamic simulation for automobile running on bumpy road is introduced. The modeling method that is a very close approximation to automobile is presented. Because the output printed at every integration time step is lots of amount, to save the time of interpretation of dynamic response, the ouptput data are interactively processed by PLOT88, also a configuration of automobile is generated by animated graphic displays using PADL and APPLICON.

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Enhanced Startup Diagnostics of LCL Filter for an Active Front-End Converter

  • Agrawal, Neeraj;John, Vinod
    • Journal of Power Electronics
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    • v.18 no.5
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    • pp.1567-1576
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    • 2018
  • The reliability of grid-connected inverters can be improved by algorithms capable of diagnosing faults in LCL filters. A fault diagnostic method during inverter startup is proposed. The proposed method can accurately generate and monitor information on the peak value and the location of the peak frequency component of the step response of a damped LCL filter. To identify faults, the proposed method compares the evaluated response with the response of a healthy higher-order damped LCL filter. The frequency components in the filter voltage response are first analytically obtained in closed form, which yields the expected trends for the filter faults. In the converter controller, the frequency components in the filter voltage response are computed using an appropriately designed fast Fourier transform and compared with healthy LCL response parameters using a finite state machine, which is used to sequence the proposed startup diagnostics. The performance of the proposed method is validated by comparing analytical results with the simulation and experimental results for a three-phase grid-connected inverter with a damped LCL filter.

Comparative Study on Ground Response Analyses for Seismic Design of Geotechnical Structures (지반 구조물의 내진설계를 위한 지반응답해석 기법의 비교연구)

  • Hwang, Jae-Ik;Han, Jin-Tae;Cho, Jong-Seok;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.294-301
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    • 2005
  • Ground response analysis is one of the most important and most commonly encountered problems in geotechnical earthquake engineering. It is a prerequisite step for liquefaction assessment of saturated soil or the pseudo-static and dynamic analysis of geotechnical structures. A number of techniques have been developed for ground response analysis. In this study, ground response analyses were performed using the computer programs that are currently being used domestically. From these analyses, the analysis techniques applied to the programs were compared and analyzed. The results of ground response analyses were compared as follows: 1) 1-dimensional analysis vs. 2-dimensional analysis; 2) equivalent linear analysis vs. nonlinear analysis.

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Sensibility Evaluation of Internet Shoppers with the Sportswear Rustling Sounds (스포츠의류 마찰음 정보 제공에 따른 인터넷 구매자의 감성평가)

  • Baek, Gyeong-Rang;Jo, Gil-Su
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • 2009.05a
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    • pp.177-180
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    • 2009
  • This study investigates the perception of different fabrics by consumers when provided with a video clip with rustling sounds of the fabric. We utilized sportswear products that are currently on the market and evaluated the emotional response of internet shoppers by measuring the physiological and psychological responses. Three kinds of vapor-permeable water-repellent fabric were selected to generate video clips each containing the fabric rustling sound and images of exercise activities wearing the sportswear made of the respective fabric. The new experimental website contained the video clips and was compared with the original website which served as a control. 30 subjects, who had experience to buy clothing online, took part in the physiological and psychological response to the video clip. Electroen-cephalography (EEG) was used to measure the physiological response while the psychological response consisted of evaluating accurate perception of the fabric, satisfaction, and consumer interest. When we offered video clips with fabric's rustling sound on the website, subjects answered they could get more accurate and rapid information to decide to purchase the products than otherwise they do the shopping without such information. However, such rustling sounds somewhat annoy customers, as proved psychological and physiological response. Our study is a critical step in evaluating the consumer's emotional response to sportswear fabric which will promote selling frequency, reduce the return rate and aid development of new sportswear fabric further evolution of the industry.

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