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  • Title/Summary/Keyword: Active current density

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아크 용접에서 구동력에 따른 열 및 물질 유동에 관한 연구

  • 김원훈;나석주
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1996.11a
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    • pp.27-41
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    • 1996
  • In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

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Harvesting energy from acoustic vibrations of conventional and ultrasonic whistles

  • Hattery, Rebecca;Bilgen, Onur
    • Smart Structures and Systems
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    • v.19 no.6
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    • pp.615-624
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    • 2017
  • This paper experimentally investigates the feasibility of harvesting vibration energy from whistles using piezoelectric materials. The end goal of this research is to generate sufficient power from the whistle to power a small radio transmitter to relay a basic signal - for example, a distress call. First, the paper discusses the current literature in energy harvesting from acoustic resonance. Next, the concept of an active whistle is presented. Next, results from energy harvesting experiments conducted on conventional and ultrasonic whistles undergoing human-actuation and actuation by a pressure-regulated air supply are presented. The maximum power density of the conventional whistle actuated by a human at 100 dB sound pressure level is 98.1μW/cm3.

Performance Characteristics of Tubular Linear Iduction Motor (동기형 직선유도전동기의 동작특성)

  • Lee, Eun-Ung
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.3
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    • pp.153-162
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    • 1987
  • The purpose of this paper is to analysis and develop theoretically the characteristics of tubular linear induction motor, which is a special industrial motor that generates directly thrust force from electrical power. The Poisson equation about vector potential which is created by the application of Maxwell electromagnetic equation with the speed considered, results in modified Bessel equation by the assumption that is applied to each region of the experimental motor. Vector potential, magnetic flux density, secondary current, and thrust force according to its region respectively were found out by substituting boundary condition for this equation and rearranging. Besides, a attendant materials, that is, thermal characteristic, which is one of the characteristics under the operation of experimental motor each part's magnetic flux distribution characteristics within active zone, the required time for reciprocating motion, and variation of power factor vs. a slip were found.

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A Study on the Lateral Waveguiding & Beam Width Variation of DH Laser Diode (이중 헤테로 접합 레이저 다이오드의 횡방향 도파 및 빔폭 변화에 관한 연구)

  • 김은수;박한규
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.20 no.1
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    • pp.15-21
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    • 1983
  • In this paper, the theoretical analysis of lateral guiding mechanism in stripe geometry Double Heterojunction Laser Diode is performed. In the analysis, the spatial variations of gain form refractive index profile are modeled by the mathematical form of injected current density and the beam width variations dependence of active layer, stripe width & cavity length have been analyzed by perturbed mode equation.

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Characteristics of high energy density hybrid capacitor using metal oxide electrode (금속산화물 전극을 사용한 고 에너지밀도 하이브리드 커패시터 특성)

  • Yoon, Hong-Jin;Shin, Yoon-Sung;Lee, Jong-Dae
    • Journal of the Korean Applied Science and Technology
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    • v.28 no.3
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    • pp.329-334
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    • 2011
  • The electrochemical performances of an asymmetric hybrid capacitor were investigated using LiFePO4 as the positive electrode and active carbon fibers(ACF) as the negative electrode. The electrochemical behaviors of a nonaqueous hybrid capacitor were characterized by constant current charge/discharge test. The specific capacitance using LiFePO4/ACF electrode turned out to be 0.87F/cm2 and the unit cell showed excellent cycling performance. This hybrid capacitor was able to deliver a specific energy as high as 178 Wh/kg at a specific power of 1,068 W/kg.

PREPARATION OF NICKEL HYDROXIDE FOR NICKEL-CADMIUM CELL

  • Sasaki, Yasushi;Yamashita, Tsugito
    • Journal of Surface Science and Engineering
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    • v.29 no.6
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    • pp.724-727
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    • 1996
  • Electrolytic impregnation of nickel hydroxide into porous sintered nickel plaque from various nickel solutions were carried out at room or high temperatures and current density range of 2.5mA cm2 to 25mA cm2. The morphology of the deposited surface was observed with an electron microscope and the surface products were analyzed by means of X-ray diffraction method. Nickel hydroxide was deposited in nickel nitrate electrolyte, while deposits from sulphate or chloride solutions were almost metallic nickel. The loading level of nickel hydroxide from nitrate solutions was 1.6gcm3 void volume and the appearance of the surface was good quality. Discharge capacity of prepared electrodes in nickel nitrate electrolyte was larger than that of the others bath. It was considered that the cell capacity was dependent on the surface roughness of active material.

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Research on the Energy Hole Problem Based on Non-uniform Node Distribution for Wireless Sensor Networks

  • Liu, Tang;Peng, Jian;Wang, Xiao-Fen;Yang, Jin;Guo, Bing
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.9
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    • pp.2017-2036
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    • 2012
  • Based on the current solutions to the problem of energy hole, this paper proposed a nonuniform node distribution clustering algorithm, NNDC. Firstly, we divide the network into rings, and then have an analysis and calculation on nodes' energy consumption in each ring of the network when clustering algorithm is applied to collect data. We also put forward a scheme of nonuniform node distribution on the basis of the proportion of nodes' energy consumption in each ring, and change nodes' active/hibernating states under density control mechanism when network coverage is guaranteed. Simulation shows NNDC algorithm can satisfyingly balance nodes' energy consumption and effectively avoid the problem of energy hole.

MOGABA: Monitoring of Gamma-ray Bright AGN with KVN 21-m radio telescopes at 22 and 43GHz

  • Lee, Sang-Sung;Yang, Ji-Hae;Byun, Do-Young;Sohn, Bong-Won
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.59.2-59.2
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    • 2011
  • We introduce an ongoing project for monitoring total flux density at 22 and 43GHz, linearly polarized flux, and polarization angle at 22GHz of Gamma-ray bright AGN (Active Galactic Nuclei) with KVN (Korean VLBI Network) 21-m radio telescopes. The project started in May, 2011 with an effective monitoring cycle of 4 days, observing four main objects (3C 454.3, BL Lac, 3C 273, and 3C 279). More objects were included in the source list when they had flared in Gamma-ray. In this paper, we report the current status of the project and preliminary results for the monitoring observations.

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Electrochamical Properties of LiFePO4 Electrodes for Lithium Polymer Battery (리튬 폴리머 전지 LiFePO4의 전기화학적 특성)

  • Kong, Ming-Zhe;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.05b
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    • pp.5-9
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    • 2005
  • LiFePO4 is a potential candidate for the cathode material of the lithium polymer batteries. LiFePO4 cathode active materials were synthesized by coating on the LiFePO4 was tried using TiO2 and corbon in oreder to increase cyclic performance and electronic conductivity. Highly dispersed on the particles enhances the electronic conductivity and increases the capacity. For lithium polymer battery applications, LiFePO4/SPE/Li and LiFePO4-TiO2/SPE/Li 'cells were characterized electrochemically by cyclic volatammetry and charge/discharge cycling. The LiFePO4-carbon-TiO2 cathode in PVDF-PC-EC-LiCIO4 electrolyte showed high capacity at high current density.

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Heteroface AlGaAs/GaAs Solar Cells grown by MBE (MBE에 의해 성장된 Heteroface AlGaAs/GaAs 태양전지)

  • 장호성;임성규
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.1
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    • pp.46-50
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    • 1990
  • Heteroface AlGaAs/GaAs drift solar cells with an active area conversion efficiency of 15.9% under one sun and AM 1.5 condition have been grown by molecular beam epitaxy(MBE). These drift solar cells have graded doping profiles in the base and emitter regions. The cells have a short circuit current density (Jsc) of 19.00 mA/cm\ulcorner an open circuit voltage(Voc) of 0.93 V, and f fill factor(FF) of 0.78, respectively. Conventional solar cells with fixed doping profiles were also grown by MBE for comparison with the drift solar cells. Even though the fabrication cost of MBE grown solar cell is higher, the expected highest conversion efficiency of the single or multiple cells could compensate for the increased cost, particularly in case of space applications.

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