• Title, Summary, Keyword: mode effects

Search Result 2,438, Processing Time 0.045 seconds

Mode effects in concurrent mixed-mode surveys (병행적 혼합조사의 모드효과 분석)

  • Baek, Jeeseon;Min, Kyung A
    • The Korean Journal of Applied Statistics
    • /
    • v.29 no.5
    • /
    • pp.787-806
    • /
    • 2016
  • Mixed-mode (MM) designs in which data are collected by different modes in one design have become increasingly popular. An MM data collection has several advantages such as reductions of coverage error, non-response and cost. However, MM designs may introduce mode effects that are confounded by selection effects and measurement effects, which can make MM data quality poor. In order to investigate mode effects, SRI implemented a concurrent mixed-mode experiment in 2014 where respondents could choose between a self-administrated Web survey and a self-administrated paper survey. This paper separately estimates selection effects and measurement effects. We found that measurement effects on some items are large.

Higher-mode effects for soil-structure systems under different components of near-fault ground motions

  • Khoshnoudian, Faramarz;Ahmadi, Ehsan;Sohrabi, Sina;Kiani, Mahdi
    • Earthquakes and Structures
    • /
    • v.7 no.1
    • /
    • pp.83-99
    • /
    • 2014
  • This study is devoted to estimate higher-mode effects for multi-story structures with considering soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15, and 25-story shear buildings are idealized by using nonlinear stick models. The ratio of base shears for the soil-MDOF structure system to those obtained from the equivalent soil-SDOF structure system is selected as an estimator to quantify the higher-mode effects. The results demonstrate that the trend of higher-mode effects is regular for pulse component and has a descending variation with respect to the pulse period, whereas an erratic pattern is obtained for high-frequency component. Moreover, the effect of pulse component on higher modes is more significant than high-frequency part for very short-period pulses and as the pulse period increases this phenomenon becomes vice-versa. SSI mechanism increases the higher-mode effects for both pulse and high-frequency components and slenderizing the super-structure amplifies such effects. Furthermore, for low story ductility ranges, increasing nonlinearity level leads to intensify the higher-mode effects; however, for high story ductility, such effects mitigates.

Modal Analysis of the Bell Type Shell with Thickness and Asymmetric Effects (鐘形셀의 두께變化 및 非對稱效果에 따른 振動모우드 解析에 관한 硏究)

  • 정석주;공창덕;염영하
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.10 no.3
    • /
    • pp.383-391
    • /
    • 1986
  • Mode shapes and natural frequencies of the bell type shell are analyzed numerically by the finite element method. The impulse hammer method and the Fast Fourier Transform analyzer are used for the experimental test. All types of mode shapes are expressed by the computer graphics. Numerical solutions are good agreement with the experimental results. The sustaining sound of the typical bell-type shell depend upon the first flexural mode (0-2 mode) and the second flexural mode (0-3 mode), and their mode shapes are independent upon thickness Dangjwas, holes, and added mass effects. Asymmetric effects by Dangjwas, holes and added mass give rise to beat frequencies, and the added mass is found to be most effective.

An analysis of an elastic solid incorporating a crack under the influences of surface effects in plane & anti-plane deformations

  • Kim, Chun Il
    • Interaction and multiscale mechanics
    • /
    • v.4 no.2
    • /
    • pp.123-137
    • /
    • 2011
  • We review a series of crack problems arising in the general deformations of a linearly elastic solid (Mode-I, Mode-II and Mode-III crack) and, perhaps more significantly, when the contribution of surface effects are taken into account. The surface mechanics are incorporated using the continuum based surface/interface model of Gurtin and Murdoch. We show that the deformations of an elastic solid containing a single crack can be decoupled into in-plane (Mode-I and Mode-II crack) and anti-plane (Mode-III crack) parts, even when the surface mechanics is introduced. In particular, it is shown that, in contrast to classical fracture mechanics (where surface effects are neglected), the incorporation of surface elasticity leads to the more accurate description of a finite stress at the crack tip. In addition, the corresponding stress fields exhibit strong dependency on the size of crack.

Effects of Failure Mode II on Crack Initiation and Crack propagation Steps Using Multilevel Fatigue Loading Test (다단계 피로하중 실험을 통한 균열 발생 및 전파단계에서 파괴모드 II 영향 분석)

  • Hong, Seok Pyo;Park, Sae Min;Kim, Ju Hee
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.41 no.9
    • /
    • pp.853-860
    • /
    • 2017
  • To evaluate the effects of mode II on the crack initiation and propagation stages, the effects in the fatigue threshold region under a mixed-mode I+II loading state was experimentally investigated. In the case of mixed-mode I + II, during the crack initiation stage, as the loading application angle (${\theta}$) increased, cracks occurred in the lower load owing to the effects of mode II, while the crack propagation rate decreased. The effects of mode II were experimentally investigated in the crack propagation stage by means of multilevel loading direction variation. Following mixed-mode I+II ($0^{\circ}{\rightarrow}{\theta}{\rightarrow}60^{\circ}$), as the load application angle increased, the fatigue crack propagation rate decreased, as did the fatigue crack propagation rate, which occurred later. Following mixed-mode I + II in case of(${\theta}{\geq}75^{\circ}$), the fatigue crack propagation rate was found to increase, while the fatigue life decreased.

Nonlinear Pushover Analysis Considering Higher Mode Effects (고차모드의 효과를 고려한 비선형정적평가방법)

  • Eom, Tae-Sung;Lee, Hye-Rin;Park, Hong-Gun
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • /
    • pp.153-160
    • /
    • 2005
  • A new nonlinear static analysis method, Effective Modal Pushover Analysis (EMPA) which can evaluate earthquake responses such as story drift and plastic rotation of plastic hinges addressing higher mode effects was developed. Unlike existing nonlinear static procedure based on properties of fundamental vibration mode, the EMPA performs nonlinear static analysis using multiple effective modes constructed by direct combination of natural vibration modes. Therefore higher mode effects can be efficiently considered. In the present study, procedures of the EPMA evaluating inelastic earthquake responese were established and the results were verified by nonlinear time history analysis. The EMPA can be applied to seismic evaluation of high-rise buildings and irregular buildings where higher mode effects become conspicuous.

  • PDF

Speed Control of Linear Induction Motor using Sliding Mode Controller Considering the End Effects

  • Boucheta, A.;Bousserhane, I.K.;Hazzab, A.;Sicard, P.;Fellah, M.K.
    • Journal of Electrical Engineering and Technology
    • /
    • v.7 no.1
    • /
    • pp.34-45
    • /
    • 2012
  • In the present paper, the mover speed control of a linear induction motor (LIM) using a sliding mode control design is proposed, considering the end effects. First, the indirect field-oriented control LIM is derived, considering the end effects. The sliding mode control design is then investigated to achieve speed- and flux-tracking under load thrust force disturbance. The numerical simulation results of the proposed scheme present good performances in comparison to that of the classical sliding mode control.

Analysis of Parameter Effects on the Small-Signal Dynamics of Buck Converters with Average Current Mode Control

  • Li, Ruqi;O'Brien, Tony;Lee, John;Beecroft, John;Hwang, Kenny
    • Journal of Power Electronics
    • /
    • v.12 no.3
    • /
    • pp.399-409
    • /
    • 2012
  • In DC-DC Buck converters with average current mode control, the current loop compensator provides additional design freedom to enhance the converter current loop performance. On the other hand, the current loop circuit elements append substantial amount of complexity to not only the inner current loop but also the outer voltage loop, which makes it demanding to quantify circuit and operating parameter effects on the small-signal dynamics of such converters. Despite the difficulty, it is shown in this paper that parameter effects can be analyzed satisfactorily by using an existing small-signal model in conjunction with a newly proposed simplified alternative. As a result of the study, new insight into average current mode control is uncovered and discussed quantitatively. Measurable experimental results on a prototype averaged-current-mode-controlled Buck converter are provided to facilitate the analytical study with good correlation.

A Study on Failure Mode and Effect Analysis (FMEA) for Preoperative Risk Prevention (오류유형 영향분석(FMEA)을 적용한 수술준비 위험예방활동의 효과)

  • Kim, Chang Hee;Lee, Mi Hyang
    • Journal of Korean Academy of Nursing Administration
    • /
    • v.22 no.5
    • /
    • pp.415-423
    • /
    • 2016
  • Purpose: The purpose of this research was to provide patients with safe preoperative preparatory procedures by removing any risk factors from the preparatory procedures by using failure mode and effects analysis, which is a prospective risk-managing tool. Methods: This was a research design in which before and after conditions of a single group were studied, Failure mode and effects analysis were applied for the preparatory procedures done before operations. Results: The preparation omission rate before the operation decreased from 2.70% to 0.04%, and operation cancellation rate decreased from 0.48% to 0.08%. Conclusion: Failure mode and effects analysis which remove any risk factors for patients in advance of the operation is effective in preventing any negligent accidents.

Effects of Refraction of Ultrasonic Beam on B-mode Tomograms (B-mode 단층상에서의 초음파 빔의 굴절 영향)

  • 최종수
    • Journal of Biomedical Engineering Research
    • /
    • v.2 no.2
    • /
    • pp.141-144
    • /
    • 1981
  • This paper descirbes about effects of refraction of ultrasonic beam on B-mode tomogram. Both compution based on Snell's law and the experiments performed using B-mode scanner and schlieren optical method are discussed on a circular phantom immersed in water. In these results, if the discrepancy of sound velocity is more than 0. 6%, the distortion of the B-mode image becomes conspicuous and a target beyound the phantom may disappear or displayed as two targets depending on the velocity of the phantom.

  • PDF