• Journal of the Korean Applied Science and Technology
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• v.26 no.1
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• pp.45-50
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• 2009

Three-dimensional, statistical-mechanical formulations of problems are usually untractable analytically, and therefore they are commonly solved numerically. However, their one-dimensional counterparts are always to be solved analytically. In general analytical solutions sheds more insights to the problems than numerical solutions. Hence, solutions of one-dimensional problems may provide key properties to the problems, when they are extended to three dimensions. In this article, thermodynamic properties of one-dimensional fluid comprising molecules of rigid rods are analyzed statistical-mechanically. Molecules of rigid rods are characterized with repulsive or excluded volume effect. It is observed that this feature is well reflected in thermodynamic functions such as Helmholtz free energy. volumetric equation of state. chemical potential, entropy, etc.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.166-173
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• 2001

Composite materials consists of two or more different material layers. The usefulness of clad metal rods forms the possibilities of combination of properties of different metals. Copper clad aluminum composite materials are being used for economic and structural purpose. In this study, composite billet consists of commercially pure copper and aluminum(A6061) and experimental conditions consist of the combinations of clad thickness, extrusion ratio, and semi-cone angle of die. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios, semi-cone angles of die, and composition rate of Cu:Al.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.677-680
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• 2004

This study investigates the buckling evaluation of connecting rods used in the diesel engine through finite element analysis. The Rankine formula, which is modified from classical Euler‘s formula, has been widely accepted in automotive industry to evaluate the buckling of connecting rods. Apparently, this formula is most suitable for the straight and idealized rod shape, and over-simplifies the geometric complexity associated with connecting rods. The subspace iteration method in FEA is used to predict the critical buckling stress of a connecting rod with certain slenderness ratio. To create models with various slenderness ratios for shank portion in the rod, the automatic meshing preprocessor was implemented. Results from FEA were verified by the experiments, in which the embedded strain gages measured for the connecting rod running at 4000rpm. The result indicates that the buckling prediction curve through FEA and experiment is effectively different from the curve of classical Rankine formula.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.247-250
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• 2004

A ground resistance is a good index of performance in a grounding system, but it does not reflect the performance in transient states. Recently long vertical ground rods in urban areas are often installed. But because of the inductance of long ground rods the ground impedance at high frequency might be greater than its resistance at low frequency. In this paper, a ground impedance of deeply driven ground rod has been measured in the frequency range from 10 kHz to 50 MHz. As a result, the ground impedances of a deeply driven ground rods are almost constant at the frequency range less than 100 kHz. However at high frequency the ground impedance showed the strong frequency dependance.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.233-235
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• 2003

To obtain a low ground resistance in high resistivity soil or in insufficient place such as downtown, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flows into the grounding system, the ground impedance is significantly increased. This paper presents how the impulse current works on the long vertical ground rods with a different length. As a result, it can be estimated what the waveform is composed of and how the GPR is affected by the rate of current change.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.3
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• pp.89-98
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• 1998

Some analytic results for a solenoid eddy current coil to test nondestructive conducting materials are described in this paper. Normalized impedance of solenoid coil encircling cylindrical conducting tubes or tow-conductor rods is analyzed. Electrical and magnetic properties such as conductivity, permeability and exciting frequency as well as the geometric ones of fill factor or radius ratio of the conductor are also considered. Impedance characteristics of the models obtained by numerical analysis are examined. Validation of the model is carried out using several samples of non-ferromagnetic conducting tubes and 2-conductor rods.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.149-158
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• 1994

Powder forged Connecting Rods have become attractive for use in automotive engines. The powder forging process offers beneficial material utilization as well as the minimization of finishing operations over that of conventionally forged rods. In the present work, the sintering behavior of Fe-2Cu-0.6C, optimum preform design and forgeability of various forging variables were investigated. Our data were generated using a newly proposed sub-scale con-rod developed specifically to simulate the powder forging process. We obtain optimum condition of sintering and powder forging process.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.8 no.2
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• pp.75-86
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• 2004

In this study, a recursive algorithm for generating the equations of motion of a chain of rigid rods is presented. The methods rests upon the idea of replacing the rigid body by a dynamically equivalent constrained system of particles. The concepts of linear and angular momentums are used to generate the rigid body equations of motion without either introducing any rotational coordinates or the corresponding transformation matrices. For open-chain, the equations of motion are generated recursively along the serial chains. For closed-chain, the system is transformed to open-chain by cutting suitable kinematic joints with the addition of cut-joints kinematic constraints. An example of a closed-chain of rigid rods is chosen to demonstrate the generality and simplicity of the proposed method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.568-572
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• 2000

This paper describes the experimental results of a transient impedance characteristics of grounding rods to a square pulse and standard lightning impulse current. The test were performed on single grounding rod($\phi$ 10mm, 1m) and triple-grounding rods( $\phi$ 10mm, 1m) of equilateral triangles with 5m spacing. For measurements of transient impedance, a pulse generator which can produce square wave of 30ns rise time and 20U Pulse duration was designed and fabricated. In the experiment, transient impedance of the grounding systems have been investigated from the recorded potential and current waveforms. The results showed that the value of the transient impedance is quite higher than the stationary resistance, and provide useful information for the value of a grounding system considered transient characteristics under a high frequency condition such as lightning stokes and ground-fault.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.535-538
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• 2002

Cube-textured Ni substrates for YBCO coated conductors were fabricated by cold-rolling and annealing of Ni powder compacts. To establish the optimum sintering temperature, tensile test was performed for the Ni rod sintered at various temperatures. The Ni rods prepared at above 100$0^{\circ}C$ showed good mechanical properties due to the complete densification of the Ni rods. The Ni rods were rolled to final thickness of 100 ${\mu}{\textrm}{m}$ and then annealed at 100$0^{\circ}C$ for various annealing time for texture development. The texture analysis made by 2 $\theta$ scan and pole-figure showed that the cube texture was developed in a short time of a few munitues. The FWHM of in-plane and out of plane texture of the prepared Ni tapes was 8-10$^{\circ}$. The AEM surface roughness of the Ni tapes was as smooth as 3 nm.