• Title/Summary/Keyword: Periodic response

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Recent Progress in Flexible Energy Harvesting Devices based on Piezoelectric Nanomaterials (압전나노소재 기반의 플렉서블 에너지 하베스팅 소자 연구동향)

  • Park, Kwi-Il
    • Journal of Powder Materials
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    • v.25 no.3
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    • pp.263-272
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    • 2018
  • Recent developments in the field of energy harvesting technology that convert ambient energy resources into electricity enable the use of self-powered energy systems in wearable and portable electronic devices without the need for additional external power sources. In particular, piezoelectric-effect-based flexible energy harvesters have drawn much attention because they can guarantee power generation from ubiquitous mechanical and vibrational movements. In response to demand for sustainable, permanent, and remote use of real-life personal electronics, many research groups have investigated flexible piezoelectric energy harvesters (f-PEHs) that employ nanoscaled piezoelectric materials such as nanowires, nanoparticles, nanofibers, and nanotubes. In those attempts, they have proven the feasibility of energy harvesting from tiny periodic mechanical deformations and energy utilization of f-PEH in commercial electronic devices. This review paper provides a brief overview of f-PEH devices based on piezoelectric nanomaterials and summarizes the development history, output performance, and applications.

대향분출류가 있는 맥동연소기의 비 정상 점화현상

  • 이창진
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1997.04a
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    • pp.259-265
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    • 1997
  • An analytical study has been peformed to investigate the unsteady ignition characteristics of pulse combustion. In many combustion applications, strain rate of the flow can significantly affect the combustion features; ignition, extinction, and reignition. In the pulse combustion, two jets (hot combustion gases and fresh mixtures) coming from the opposite side of the combustor will collide in the combustor forming a stagnation region where the chemical reaction is suppressed by the strain rate until this becomes below the critical value. In this research, the method of large activation energy asymptotic is adopted with one step irreversible kinetics to examine the ignition response to the periodic variation of the strain rate of flow. The results show the variation of the maximum value of strain rate can determine whether the ignition or extinction occur.

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Predictive Characteristics of the Oculomotor System to the Periodic Signal (주기신호에 대한 안구운동의 예측 특성)

  • 이상효
    • Journal of Biomedical Engineering Research
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    • v.2 no.2
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    • pp.145-150
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    • 1981
  • In this paper, we measured the tracking response time of horizontal eye movement to the target moving according to the square waveform to investigate the predictive characteristics of the human oculomotor system. And in the experiment we used the square waves with an amplitude of 5 degree and frequencies o.1, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2 Hz. Random occurrences of the human eye movement reponse time were analyzed using a finite Markov chain process and we found the results as follows. From both the experimental and theoretical results, we found the trend showing that Predictive characteristics moved from the transient state to the steady state.

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Permanence of a Three-species Food Chain System with Impulsive Perturbations

  • Baek, Hunki;Lee, Hung-Hwan
    • Kyungpook Mathematical Journal
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    • v.48 no.3
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    • pp.503-514
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    • 2008
  • We investigate a three-species food chain system with Lotka-Volterra functional response and impulsive perturbations. In [23], Zhang and Chen have studied the system. They have given conditions for extinction of lowest-level prey and top predator and considered the local stability of lower-level prey and top predator eradication periodic solution. However, they did not give a condition for permanence, which is one of important facts in population dynamics. In this paper, we establish the condition for permanence of the three-species food chain system with impulsive perturbations. In addition, we give some numerical examples.

Torque Ripple Minimization of PMSM Using Parameter Optimization Based Iterative Learning Control

  • Xia, Changliang;Deng, Weitao;Shi, Tingna;Yan, Yan
    • Journal of Electrical Engineering and Technology
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    • v.11 no.2
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    • pp.425-436
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    • 2016
  • In this paper, a parameter optimization based iterative learning control strategy is presented for permanent magnet synchronous motor control. This paper analyzes the mechanism of iterative learning control suppressing PMSM torque ripple and discusses the impact of controller parameters on steady-state and dynamic performance of the system. Based on the analysis, an optimization problem is constructed, and the expression of the optimal controller parameter is obtained to adjust the controller parameter online. Experimental research is carried out on a 5.2kW PMSM. The results show that the parameter optimization based iterative learning control proposed in this paper achieves lower torque ripple during steady-state operation and short regulating time of dynamic response, thus satisfying the demands for both steady state and dynamic performance of the speed regulating system.

Influence of cable loosening on nonlinear parametric vibrations of inclined cables

  • Wu, Qingxiong;Takahashi, Kazuo;Chen, Baochun
    • Structural Engineering and Mechanics
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    • v.25 no.2
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    • pp.219-237
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    • 2007
  • The effect of cable loosening on the nonlinear parametric vibrations of inclined cables is discussed in this paper. In order to overcome the small-sag limitation in calculating loosening for inclined cables, it is necessary to first derive equations of motion for an inclined cable. Using these equations and the finite difference method, the effect of cable loosening on the nonlinear parametric response of inclined cables under periodic support excitation is evaluated. A new technique that takes into account flexural rigidity and damping is proposed as a solution to solve the problem of divergence. The regions of inclined cables that undergo compression are also indicated.

Physiological Response of a White Mutant of Ganoderma lucidurn Induced by Light and Temperature (영지버섯 백색변이주의 광 및 온도에 의한 생리적 반응)

  • Cho, Soo-Muk;Seo, Geon-Sik;Yoo, Ick-Dong;Shin, Gwan-Chull
    • Microbiology and Biotechnology Letters
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    • v.22 no.2
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    • pp.115-119
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    • 1994
  • White mutant of Ganoderma lucidum(G4142) induced the non-basediocarpous basidiospores(NBB) from the aerial mycelia on agar media by the light illumination. Light was found to be necessary for NBB formation, but it also inhibited the growth of mycelium. The best sporulation was obtained at the periodic exposure of 16 hour light and 8 hour dark. Blue and yellow light were the most effective on sporulation, however, near UV and red light did not induce any spores. Effective light intensity for NBB bearing was about 1,000 lux as white light. Even after 16 days of culture, this strain did not form the pinhead nor chlamydospore. Optimum temperature for the mycelial growth and NBB formation were 30$\circ $C. Ganoderma lucidum G4142 exhibited the formation of stroma after five days of incubation at 30$\circ $C.

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Behavior of Non-premixed Flame Front in an Acoustically-Driven Dump Combustor (가진된 덤프 연소기 내에서의 비예혼합 화염 거동)

  • Park, Jung-Kyu;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
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    • 2000.05a
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    • pp.142-151
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    • 2000
  • Dump combustor is a combustor having a dump plane to make coherent structures. A non-premixed flame dump combustor of simple geometry was constructed. We conducted basic experiments such as frequency response on the combustor to confirm the characteristics of the phenomena as a typical dump combustion and unsteady combustion. Furthermore we visualized the flame front behavior by CH chemiluminescence and high speed motion analysis. In spite of the lack of another data such as velocity, species concentration and temperature, the results showed not only the periodic motion of flame front but the ignition process of vortex ring flame. Also we could check out Rayleigh criterion by combining the visualization data with the pressure data.

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A Theoretical Study of Ultrasound Scattering by Blood (혈액에 의한 초음파 산란의 이론적 고찰)

  • 최재준;홍승홍
    • Journal of Biomedical Engineering Research
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    • v.2 no.1
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    • pp.15-20
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    • 1981
  • In this study, the scattering of ultrasound by blood is theoretically studied. At first, the Chernow equation which represents acoustic propagation inside the region of inhomogenieties is modified to be fitted for blood. Then, scattering amplitude and scattering Cross-section at the far-field region are obtained from this equation. In this case, hemotocrit is assumed to be less than 26 per cent, and the red blood cell is modeled as independent scatterer. This study also develops a practical approximation for the backscattering of periodic sinewave bursts by a volume of randomly distributed scatterers, i.e., whole red blood cells. This expression for the received backscattering ultrasound pressure after the n-th burst of narrowband transducer is obtained from an ideal continuous wave transducer's response.

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Analysis of a Communication Network for Control Systems in Nuclear Power Plants and a Case Study

  • Lee, Sung-Woo;Gwak, Kwi?Yil
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.338-341
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    • 2005
  • In this paper, a real-time communication method using a PICNET-NP(Plant Instrumentation and Control Network for Nuclear Power Plant) is proposed with an analysis of the control network requirements of DCS (Distributed Control System) in nuclear power plants. The method satisfies deadline in case of worst data traffics by considering aperiodic and periodic real-time data and others. In addition, the method was used to analyze the data characteristics of the DCS in existing nuclear power plant. The result shows that use of this method meets the response time requirement(100ms).

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