• Title/Summary/Keyword: Body force density

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Evaluation of Global Force and Interaction Body Force Density in Permanent Magnet Employing Virtual Air-gap Concept (가상공극개념을 이용한 연구자석의 전체전자기력과 상호체적력밀도 계산)

  • Lee, Se-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.2
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    • pp.278-284
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    • 2009
  • The global force and interaction body force density were evaluated in permanent magnets by using the virtual air-gap scheme incorporating the finite-element method. Until now, the virtual air-gap concept has been successfully applied to calculate a contact force and a body force density in soft magnetic materials. These force calculating methods have been called as generalized methods such as the generalized magnetic charge force density method, the generalized magnetizing current force density method, and the generalized Kelvin force density method. For permanent magnets, however, there have been few research works on a contact force and a force density field. Unlike the conventional force calculating methods resulting in surface force densities, the generalized methods are novel methods of evaluating body force density. These generalized methods yield the actual total force, but their distributions have an irregularity, which seems to be random distributions of body force density. Inside permanent magnets, however, a smooth pattern was obtained in the interaction body force density, which represents the interacting force field among magnetic materials. To evaluate the interaction body force density, the intrinsic force density should be withdrawn from the total force density. Several analysis models with permanent magnets were tested to verify the proposed methods evaluating the interaction body force density and the contact force, in which the permanent magnet contacts with a soft magnetic material.

An Observation of Unified Force Expression in The Cylindrical Magnetic Material with a Vertical Current Running Through Its Center (전류가 관통하는 원통형 자성체에 미치는 전자기력식의 통일성에 대한 고찰)

  • Choi, Hong-Soon
    • Journal of the Korean Magnetics Society
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    • v.21 no.5
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    • pp.174-179
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    • 2011
  • Magnetic force calculation methods such as Maxwell stress, virtual work principle, equivalent magnetic charge, and equivalent magnetizing current are widely used until now. The force density is still controversial issue even though it is common sense that all of these methods have legitimate results. The surface force densities of each method are quite different with each other in the point of numerical result and final expression. In this paper, it is shown that a unified expression of body force density is derived using virtual air-gap scheme for an analytic model in which cylindrical magnetic material with a vertical current runs through its center.

The study on effects of porosity, strain and grain size on B-H Hysteresis Ioop (기공율, 응력 및 입자 크기가 B-H Hysteresis loop 특성에 미치는 영향 연구)

  • 김성재;정명득;백종규
    • Journal of the Korean Magnetics Society
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    • v.4 no.2
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    • pp.89-93
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    • 1994
  • Effects of density, inner-stress, and grain size on B-H hysteresis loop properties of Mg-ferrite were investigated. As the sintered bulk density increase, coercive force($H_c$) decreasand squareness ratio increase. Coercive force was very dependent on inner-stress in sintered body, so coercive force increase from 1.95[Oe] to 4.35[Oe] when inner stress present in bulk, however, the squareness ratio was almost not changed Coercive force and squareness ratio were independent on grain size of sintered body which is between 6-11[$\mu\textrm{m}$]

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On the Physical Meaning of Maxwell Stress Tensor (맥스웰 응력텐서의 물리적 의미의 고찰)

  • Choi, Hong-Soon;Park, Il-Han;Moon, Won-Kyu
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.725-734
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    • 2009
  • Maxwell stress tensor is one of the methods which are generally used for electromagnetic force calculation. In this paper, it is presented that Maxwell stress tensor T and n${\cdot}$T have no physical meaning and therefore should not be used as sources of mechanical force for deformations or dynamics. The divergence of Maxwell stress tensor ${\nabla}{\cdot}T$ is the one which can acquire a physical identity and is electromagnetic body force density by an action at a distance like a gravity. This result can be derived from the principle of power balance, and also verified by some thought experiments. The virtual air-gap approach is proposed as a valid solution for the calculation of the body force.

Vehicle Interior Noise Analysis Using Frequency Response Function Based Substructural Method (주파수응답함수의 부분구조합성 법을 이용한 차 실내소음 예측)

  • 허덕재;박태원
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.4
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    • pp.5-12
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    • 2001
  • This paper presents the simulation methodology of the interior noise of vehicle using the frequency response function based hybrid modeling of the system which consists of multi-subsystem models obtained by the test or analysis. The complex systems such as a trimmed body of high modal density and a powertrain were modeled by using experimental data, and a sub-frame of a vehicle of low modal density was modeled by finite element data. Modeling of the whole system was executed and validated in the two stages. The first stave is combining the trimmed body and the sub-frame, and the second stage is attaching the powertrain, which is a exciting source, to the combined model of the first stage. The input force to the system was modeled as an equivalent force in the virtual space, which was obtained from impedance method using the FRFs of the powertrain and the responses. The interior noise predicted by the proposed method was very close to the direct measurement, which showed feasibility of the proposed modeling procedure. Since the methodology is easily applied to both the transfer path analysis of structure-borne noise and the analysis of noise contribution of a sub-system, it is expected to be a strong tool for design change of a vehicle in the earlier stare.

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Influence of Lifetime Sports Activity Based on a Ground Reaction Force on Bone Mineral Density in Korean Adults (지면반력에 근거한 과거 신체활동정도가 골밀도에 미치는 영향 -아이오와에 거주하는 한인을 대상으로-)

  • Lee Eun Nam;Clark Mary Kathleen
    • Journal of Korean Academy of Nursing
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    • v.35 no.3
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    • pp.621-630
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    • 2005
  • Purpose: The purpose of this study was to -retrospectively describe the childhood sports activity level of Korean adult men and women and to determine whether a higher level of childhood sports activity was positively associated with adult bone mineral density. Methods: A cross-sectional study of 100 Korean men (n=40) and women (n=60) was completed. Participants completed a detailed lifetime sports activity questionnaire and had their bone mineral density of the femur and lumbar spine measured using dual energy x-ray densitometry (DEXA). All sports activities were classified into four categories of peak strain score on the basis of ground reaction forces (GRF). Results: During the age of high school, women and men who participated in a high intensity sports activity demonstrated higher bone density in the femur site after adjustment for the effects of body weight, fat body mass, lean body mass, the level of calcium intake, and breast feeding period than those who did not participate in sports activity at all. Conclusion: These results highlight the need to participate in high intensity sports activity during high school age as a means of increasing peak bone mass in the femur site.

Computation of Stratified Flows using Finite Difference Lattice Boltzmann Method

  • Kang, Ho-Keun;Kim, Won-Cheol
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.4
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    • pp.511-519
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    • 2003
  • A stratified flow is simulated using the finite difference lattice Boltzmann method (FDLBM). The effect of body force (gravity) in a simple one-dimensional model with the lattice BGK 9 velocity is examined. The effect of body force in the compressible fluid is greatly different from that of the incompressible fluid In a compressible fluid under gravitational force, the density stratification is not sufficient and the entropy stratification is essential. The numerical simulation of a line sink compressible stratified flow in two-dimensional channel is also carried out. The results show that selective withdrawal is established when the entropy of the upper part increases. and the simulated results using FDLB method are satisfactory compared with the theoretical one.

Green Body Behaviour of High Velocity Pressed Metal Powder

  • Jonsen, P.;Haggblad, H.A.;Troive, L.;Furuberg, J.;Allroth, S.;Skoglund, P.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.22-23
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    • 2006
  • High velocity compaction (HVC) is a production technique with capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts. Investigated here are green body data such as density, tensile strength, radial springback, ejection force and surface flatness. Comparisons are performed with conventional compaction using the same pressing conditions. Cylindrical samples of a pre-alloyed water atomized iron powder are used in this experimental investigation. The HVC process in this study resulted in a better compressibility curve and lower ejection force compared to conventional quasi static pressing. Vertical scanning interferometry measurements show that the HVC process gives flatter sample surfaces.

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산화아연 압전 나노전력발전소자 기반 에너지 하베스팅

  • Kim, Sang-U
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.49-49
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    • 2010
  • Nanopiezotronics is an emerging area of nanotechnology with a variety of applications that include piezoelectric field-effect transistors and diodes, self-powered nanogenerators and biosystems, and wireless nano/biosensors. By exploiting coupled piezoelectric and semiconducting characteristics, it is possible for nanowires, nanobelts, or nanorods to generate rectifying current and potential under external mechanical energies such as body movement (handling, winding, pushing, and bending) and muscle stretching, vibrations (acoustic and ultrasonic waves), and hydraulic forces (body fluid and blood flow). Fully transparent, flexible (TF) nanogenerators that are operated by external mechanical forces will be presented. By controlling the density of the seed layer for ZnO nanorod growth, transparent ZnO nanorod arrays were grown on ITO/PES films, and a TF conductive electrode was stacked on the ZnO nanorods. The resulting integrated TF nanodevice (having transparency exceeding 70 %) generated a noticeable current when it was pushed by application of an external load. The output current density was clearly dependent on the force applied. Furthermore, the output current density depended strongly on the morphology and the work function of the top electrode. ZnO nanorod-based nanogenerators with a PdAu, ITO, CNT, and graphene top electrodes gave output current densities of approximately $1-10\;uA/cm^2$ at a load of 0.9 kgf. Our results suggest that our TF nanogenerators are suitable for self-powered TF device applications such as flexible self-powered touch sensors, wearable artificial skins, fully rollable display mobile devices, and battery supplements for wearable cellular phones.

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Simulation of Neutral Flow around Plasma Actuator

  • Jung Suk-Young;Ahn Chang-Soo;Hong Seung-Kyu
    • 한국전산유체공학회:학술대회논문집
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    • 2006.05a
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    • pp.306-308
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    • 2006
  • Numerical simulations were carried out of the effects of momentum and heat produced by a plasma actuator on neutral flow. Momentum and heat generated during plasma discharge were modeled as a body force and heat source using results of experiments and DSMC of particle. These force and heat model were inserted into a Navier-Stokes equation and the flow around the plasma actuator could be explored by solving fluid dynamics only. Fluid simulation showed that force produced in DSMC generated a jet flow in the vicinity of the plasma actuator and heat accounted for density change.

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