• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.540-545
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• 2001

In case of small motors, coil bundle occupies a large portion of stator in view of mass and volume as well as dynamics. It is observed through modal test on the stator of an IPM BLDC (interior permanent magnet brushless direct current) motor that coil bundle wound on the stator core causes the first and second natural frequencies to decrease by about 20-30% compared with those of bare stator. Especially the third natural frequency is newly observed below 3 KHz, which is not observed on the bare stator. It is found that at the third mode the end-coil and the core vibrate out of phase in radial direction. In this paper, the stator is dynamically modeled in terms of the core and the coil bundle consisting of the end-coil and the slot coil based on the above observations for the prediction of dynamic properties. The core can easily be modeled using finite element method with its actual material properties and geometric shape. The concept of equivalent bending stiffness is used for modeling of the end-coil so that predictions may match with the measured natural frequencies for the end-coil cut out of the stator. Although the same concept can be applied to the slot coil, separation of the slot coil from the stator is impractical. Therefore, equivalent bending stiffness of the slot coil is determined through iterative comparisons with the measurements of natural frequencies of the stator with the slot coil in it.

• Nuclear Engineering and Technology
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• v.4 no.1
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• pp.39-45
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• 1972

In neutron shielding, the scattering effect is equally important as the attenuations in shielding materials. In the present study, the scattered dose equivalent was measured using a Rem counter for water, paraffin, borated paraffin, ordinary and heavy concrete, lead, iron, and tissue equivalent material in three different angles: 45$^{\circ}$, 90$^{\circ}$, and 135$^{\circ}$, respectively. The measurements were performed for the neutron, having the energies of 0.5, 1, 2, 5, and 18 MeV, which are produced from the Van do Graaff accelerator. The scattered dose equivalent ratios were increased with increasing the thickness of scattering materials and saturated at a certain thickness although they were different from one to other materials under study. The ratios were large for lead and iron while they were small for the hydrogen containing materials such as water and paraffin etc.

• Structural Engineering and Mechanics
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• v.21 no.6
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• pp.737-765
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• 2005

This paper presents a theoretical model for the behavior of partially confined axi-symmetric reinforced concrete members subjected to axial load. The analysis uses the theories of elasticity and plasticity to cover the full range of the concrete behavior. Analysis of the elastic range of the problem involves boundary conditions that are defined along a relatively simple geometry. However, extending the analysis into the plastic range involves difficulties that arise from the irregular geometry of the boundary between the plastic zone and the elastic zone, a boundary which is also changing as the axial load increases. The solution is derived by replacing the discrete steel ties with an equivalent tube of thickness $t_{eq}$ and by analyzing the concrete cylinder, which is uniformly confined by the equivalent tube. The equivalency criterion initiates from a theoretical analysis of the problem in its elastic range where further finite element analysis shows that this criterion is valid also for the plastic range of the cylinder material. According to the proposed model, the efficiency of the lateral reinforcement can be evaluated by the equivalent thickness $t_{eq}$. Comparison with published test results of confined reinforced concrete stress-strain curves shows good agreement between the test and the analytical results.

• Computers and Concrete
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• v.15 no.4
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• pp.485-501
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• 2015

Cooling by the flow of water through an embedded cooling pipe has become a common and effective artificial thermal control measure for massive concrete structures. However, an extreme thermal gradient induces significant thermal stress, resulting in thermal cracking. Using a mesoscopic finite-element (FE) mesh, three-phase composites of concrete namely aggregate, mortar matrix and interfacial transition zone (ITZ) are modeled. An equivalent probabilistic model is presented for failure study of concrete by assuming that the material properties conform to the Weibull distribution law. Meanwhile, the correlation coefficient introduced by the statistical method is incorporated into the Weibull distribution formula. Subsequently, a series of numerical analyses are used for investigating the influence of the correlation coefficient on tensile strength and the failure process of concrete based on the equivalent probabilistic model. Finally, as an engineering application, damage and failure behavior of concrete cracks induced by a water-cooling pipe are analyzed in-depth by the presented model. Results show that the random distribution of concrete mechanical parameters and the temperature gradient near water-cooling pipe have a significant influence on the pattern and failure progress of temperature-induced micro-cracking in concrete.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.65-68
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• 2000

A $\mu-oxo$ diiron(III) complex and two bis( $\mu-alkoxo)$ diiron(III) complexes with biomimetic tripodal ligand containing mixed N/O donor atoms were synthesized using a mononuclear iron(III) complex as starting material. Depending on the amounts and kinds of bases used, we obtained various kinds of diiron (III) complexes. The reaction of $[$Fe^{III}$(Hbbea)Cl_2]Cl$, 1, with an equivalent amount of $KO_2$ or NaOAc produced $[$Fe^{III}$_2O(Hb-bea)_2Cl_2]Cl_2$, 2. An additional equivalent amount of NaOBz or NaOAc converts complex 2 to complex 3 or complex 4 depending on the base used. The addition of two equivalent amounts of NaOBz orNaOAc directly converts complex 1 to $[$Fe^{III}$_2(bbea)_2(OBz)_2]Cl_2$, 3, or $[$Fe^{III}$_2(bbea)_2(OAc)_2]Cl_2$, 4, depending on the base used. Crystal data are as follows: [$Fe^{III}_2O(Hbbea)_2Cl_2]Cl_2$, 2: monoclinic space group $$P2_1/n$$, a = 8.421 (1) $\AA$, b = 18.416 (2) $\AA$, c = 13.736 (1) $\AA$, $\beta$ = 104.870 $(7)^{\circ}$, V = 2058.9 (4) $\AA^3$, Z = 2, R1 = 0.0469 and wR2 = 0.1201 for reflections with I > 2 ${\sigma}$(I).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.2
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• pp.262-268
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• 2019

Previous dynamic models of hysteresis motor use an extended induction machine equivalent circuit or somewhat different equivalent circuit with conventional one, which makes unsatisfiable results. In this paper, the hysteresis dynamic characteristics of the motor rotor are analyzed using the inverse Preisach model and the hysteresis motor equivalent circuit considering eddy current effect. The hysteresis loop for the rotor ring is analyzed under full-load voltage source static state. The calculated hysteresis loop is then approximated to an ellipse for simplicity of dynamic computation. The permeability and delay angle of the elliptic loop apply to the dynamic analysis model. As a result, it is possible to dynamically analyze the hysteresis motor according to the applied voltage and the rotor material. With this method, the motor speed, generated torque, load angle, rotor current as well as synchronous entry time, hunting effect can be calculated.

• Journal of Magnetics
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• v.16 no.2
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• pp.157-160
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• 2011

The magnetostrictive material is magnetized in magnetic field and produces a nonuniform demagnetizing field inside and outside it. The demagnetization is decided by the permeability of magnetostrictive material and its size. The magnetoelectric performances are determined by the synthesis of the applied and demagnetizing fields. An analytical model is proposed to predict the magnetoelectric voltage coefficient (MEVC) of magnetostrictive/piezoelectric laminate composite using equivalent circuit method, in which the nonuniform demagnetizing field is taken into account. The theoretical and experimental results indicate that the MEVC is positively connected with the permeability and the piezomagnetic coefficient of magnetostrictive material. To obtain the maximum MEVC, both the permeability and the piezomagnetic coefficient of magnetostrictive material should be taken into account in selecting the suitable magnetostrictive material.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.1
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• pp.49-55
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• 1996

In this paper, the characteristics of a double-sided linear pulse motor (DLPM) with permanent magnet are analysed using the method which combined the coenergy method and the equivalent magnetic circuit method. In the process of computation, the magnetic material nonlinealities of the permanent magnet, the primary and the secondary core are interpolated by the cubic spline method. Then, the equivalent magnetic circuit modelled by the permeance method including airgap reluctance, which is a function of displacement, is obtained. The static thrust which is the derivative of coenergy is computed by Newton Raphson method at each dispacement. And, in order to investigate the characteristics of the DLPM, the thrust shows as a function of displacement, input current and air gap. The simulation resuls are compared with experimental ones obtained from the DLPM with 2 phase and 4 poles.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.70-76
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• 2013

This study investigates structural durability through the analyses of stress, fatigue life and vibration damage at bike carrier basket. As model 2 has less stress and deformation than model 1 on static structural analysis, model 2 becomes more durable than model 1. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. The amplitude deformations become highest at maximum response frequency of 2400Hz in cases of models 1 and 2. As the values of maximum equivalent stresses become within the allowable material stresses at two holes at the upper parts on models 1 and 2, these models become safe. The structural result of this study can be effectively utilized with the design of bike carrier basket by investigating prevention and durability against fatigue or vibration damage.

• Journal of Welding and Joining
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• v.4 no.3
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• pp.32-42
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• 1986

In this study, the influence of carbon equivalents on friction welds of dissimilar steels was investigated. Four types of carbon steels with 10mm diameter were welded to a high-speed tool steel SKH 9. Main experimental results could be summarized as follows (1) Under constant friction pressure, the friction time increased almost linearly with the increasing burn-off length, while the forge length decreased almost linearly. (2) The maximum hardness in carbon steels increased almost linearly with the increasing carbon equivalent, but was much lower than that in the high speed steel. (3) After quenching and tempering of dissimilar steel friction welds, the hardness in carbon steel weldments became similar as that in the base metal, while the hardness in SKH 9 weld was still higher that of the base metal. (4) Relative movement in the friction phae occurred not at the interface of the weldments, but in the high speed steed steel near the interface. (5) For considered material combinations and welding parameters, most of fractures in tension and twisting tests occurred in the base metal. And welds with so high strength could produced in a wide range of welding parameters.