• Title/Summary/Keyword: MHD

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ASYMPTOTIC BEHAVIOR OF SOLUTIONS FOR THE GENERALIZED MHD AND HALL-MHD SYSTEMS IN ℝn

  • Zhu, Mingxuan
    • Bulletin of the Korean Mathematical Society
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    • v.55 no.3
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    • pp.735-747
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    • 2018
  • This paper deals with the asymptotic behavior of solutions to the generalized MHD and Hall-MHD systems. Firstly, the upper bound for the generalized MHD and Hall-MHD systems is investigated in $L^2$ space. Then, the effect of the Hall term is analyzed. Finally, we optimize the upper bound of decay and obtain their algebraic lower bound for the generalized MHD system by using Fourier splitting method.

An Experimental Study on Magnetohydrodynamic Flow in MHD Propulsion System (MHD 추진장치내의 자기유체 유동에 관한 실험적 연구)

  • 노창주;김윤식;공영경;이성근
    • Journal of Advanced Marine Engineering and Technology
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    • v.17 no.3
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    • pp.50-59
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    • 1993
  • Usually ship is propelled by the conventional propeller. When the conventional propeller is used for ship's propulsion, reduction of propeller noise is big issue in some special vessel. In order to reduce the acoustic noise of the propeller, novel propulsion system named as MHD propulsion system has been studied among researchers. In this paper, thruster characteristic analysis and system analysis of MHD propulsion system have been carried out. Firstly basic experimental apparatus is designed, fabricated and installed and test is carried out. Test results are compared with numerical analysis. It is confirmed that test results agreed with numerical results satisfactorily.

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Potential of MHD in Improving the Performance of and Generating Power in Scramjets (MHD의 스크램제트 성능 개선과 전력 생산 잠재력)

  • Parent, Bernard;Choi, Jeong-Yeol
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.310-313
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    • 2008
  • Magnetohydrodynamics (MHD) devices have received considerable attention in recent years as a means to either improve the propulsive characteristics of hypersonic cruise missiles or as a means to generate power at low cost in drag and weight aboard scramjet powered vehicles. Based on more complete physical models than previously used, it is here argued that the use of MHD is not valuable in improving the performance of hypersonic propulsion systems through prevention of boundary layer separation or power bypass. This is due to the inevitable high amount of Joule heating accompanying MHD flow control having considerable undesired adverse effects on the engine performance. On the other hand, preliminary estimates indicate that MHD is likely to succeed in generating high amounts of power with little additional drag to feed megawatt-class energy weapons on-board scramjet engines.

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Performance of Space-Time Trellis Codes with Minimum Hamming Distance Mapping on Fast Fading Channels (빠른 페이딩 채널에서 MHD 매핑을 응용한 STTC 부호의 성능평가)

  • Jin, Ik-Soo
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.9 no.2
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    • pp.96-103
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    • 2010
  • This paper studies the performance of STTC with minimum Hamming distance (MHD) mapping in order to improve the bit error rate (BER) performance. Unfortunately, the MHD mapping used in trellis coded modulation (TCM) or multiple trellis coded modulation (MTCM) cannot be directly applied to STTC because the trellis structure of STTC is generally different from that of TCM or MTCM. Therefore, we need a simple modification to apply the MHD mapping concept in STTC. The core of the modification assigns information bits with a Hamming distance in proportion to the sum of the Euclidean distance to trellis branch of STTC. To the best knowledge, this combination has not been considered yet. The BER performance is examined with simulations and the performance of MHD mapping is compared to that of well known natural mapping and Gray mapping on both fast Rayleigh as well as fast Rician fading channels. It is shown that the performance of MHD mapping is much better than that of natural mapping or Gray mapping over fast Rician fading channels, especially.

Present Research Status of MHD Electrical Power Generation

  • Shioda, Susumu
    • Proceedings of the KIEE Conference
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    • pp.3-8
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    • 1989
  • Recent research activities for open and closed cycle MHD electrical power generations are reviewed. World first full scale 500MWe natural gas fired open cycle MHD is now under construction in USSR. Coal-fired open cycle MHD researches are in the stage of proof of concept and retrofitting of old coal power stations with MHD is planned in US and other countries. Basic research for closed MHD is most actively pursued in Japan, which potentially can provide a very high efficiency and a simple and reliable system.

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Simulations on Incompressible MHD Turbulence

  • CHO JUNGYEON
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.275-279
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    • 2001
  • The study of incompressible magnetohydrodynamic (MHD) turbulence gives useful insights on many astrophysical problems. We describe a pseudo-spectral MHD code suitable for the study of incompressible turbulence. We review our recent' works on direct three-dimensional numerical simulations for MHD turbulence in a periodic box. In those works, we use a pseudo-spectral code to solve the incompressible MHD equations. We first discuss the structure and properties of turbulence as functions of scale. The results are consistent with the scaling law recently proposed by Goldreich & Sridhar. The scaling law is based on the concept of scale-dependent isotropy: smaller eddies are more elongated than larger ones along magnetic field lines. This scaling law substantially changes our views on MHD turbulence. For example, as noted by Lazarian & Vishniac, the scaling law can provide a fast reconnection rate. We further discuss how the study of incompressible MHD turbulence can help us to understand physical processes in interstellar medium (ISM) by considering imbalanced cascade and viscous damped turbulence.

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A Study on the Disk Type MHD Generator Using a Shock Tube (충격파관을 이용한 DISK형 MHD발전기에 관한 연구)

  • 배철오;신명철;김윤식;길경석
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.3 no.2
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    • pp.447-453
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    • 1999
  • In MHD power generation system, enthalpy of the working gas is convened to electric power directly through expansion in generator channel. It means that electric power can be generated without a moving mechanical linkage such as turbine blades. The principle of MHD generation is based on Faraday'law of induction that eletromotive force(u$\times$B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In this paper, helium gas seeded with cesium is used as working gas. There are two types of generator in MHD generation; linear type faraday and disk type hall generator. Rogowski coils having the bandwidth of the 100(Hz) ~ 20(kHz) were used for measuring current flowing MHD disk channel. Optimum load resistor value of the MHD generator studied was 2.5[$\Omega$]. Disk type hall generator's generation performance is the main target of this paper, which superiors to linear type Faraday generator in many points. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

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Automatic Conversion between MHD Metadata and XDS.b Metadata (IHE MHD 메타데이터와 IHE XDS.b 메타데이터의 자동 변환)

  • Jeon, Hyeongseok;Lee, Jangsoo;Park, Dongwook;Do, Hyoungho;Lee, Sungkee
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.298-300
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    • 2013
  • IHE(Integrating the Healthcare Enterprise)의 XDS.b(Cross-Enterprise Document Sharing.b) 프로파일은 의료기관간 환자의 전자진료기록을 공유하기 위해 개발되었으나 모바일 환경을 고려하지 않았다. 이를 보완하고자 IHE에서는 모바일기기에서도 전자진료기록을 공유할 수 있는 MHD(Mobile access to Health Documents) 프로파일을 개발했다. XDS.b 메타데이터는 ebXML(electronic business XML)을 사용하고 MHD 메타데이터는 JSON(JavaScript Object Notation)을 사용하므로 MHD와 XDS.b를 연동하기 위해서는 MHD 메타데이터를 XDS.b 메타데이터로 변환이 필요하다. 본 논문에서는 MHD 메타데이터를 XDS.b 메타데이터로 변환하는 규칙을 정의했다.

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MHD (Magnetohydrodynamic) Micropump Using Lorentz Force (로렌츠 힘을 이용한 MHD(Magnetohydrodynamic) 마이크로펌프)

  • 장재성;이승섭
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.11
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    • pp.93-99
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    • 1998
  • We present a novel micropump of which pumping mechanism is based upon MHD (Magnetohydrodynamic) principle. The MHD micropump uses Lorentz force as pumping source. In the MHD micropump, Lorentz force is applied into initially stagnant conducting fluid to drive it in magnetic and electric field to flow in both directions. The performance of the MHD micropump is obtained by measuring the pressure head difference and flow rate as applied voltage changes from 10 to 60 V DC at 0.19 and 0.44 Tesla. The pressure head difference is 18 mm at 38 mA and the flow rate is 63 ${\mu}{\ell}$ /min at 1.8 mA when the inside diameter of inlet/outlet tube is 2 mm and the magnetic flux density is 0.44 Tesla.

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Numerical Analysis and Experimental Investigation of Duct Flows of an MHD Propulsion System (사각형의 MHD 추진 덕트 내부유동에 관한 수치해석 및 실험적 연구)

  • J.W. Lee;S.J. Lee;C.M. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.1
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    • pp.83-93
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    • 1995
  • A numerical and experimental investigation on the flow characteristics in the rectangular duct of an MHD propulsion system has been carried out. In numerical analysis, three-dimensional, steady-state, viscous, incompressible electrically conducting fluid flow under the influence of uniformly applied magnetic and electric fields was treated using a finite-difference technique. It was found from the numerical study that when the Lorentz force is weak, the typical parabolic velocity profile under a laminar flow condition changes to an M shaped profile near the electrode region and that the pressure increases linearly from the inlet toward the outlet of the MHD duct under constant electro-magnetic field. In experiment, thrust of the MHD propulsion system can be controlled easily by varying electrode current. The measured pressure gradient along the MHD duct is proportional to the Lorentz force, which is in agreement with the numerical results.

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