• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1606-1608
• /
• 1994

A performance of the torch greatly depends on the plasma gas and the cooling gas. The plasma gas constricted by the nozzle concentrates electric power and momentum, so it can eject molten metal from a cut. As an electric arc constricted in a nozzle is more constricted through thermal pinch by the cooling gas, it is possible to transfer larger thermal concentration to the workpiece. The optimized parameter value in this study was given below. Plasma gas pressure is $4[kgf/cm^2]$ and gas mass flow is $30[{\ell}/min]$. Cooling gas pressure is $6[kgf/cm^2]$ and gas mass flow is $120[{\ell}/min]$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.497-500
• /
• 1999

This paper reports on the fabrication and characteristics of recessed gate GaN MESFETs fabricated using a photoelectrochemical wet etching method. The unique etching process utilizes photo-resistive mask and KOH based etchant. GaN MESFETs with successfully recessed gate structure was characterized in terms of dc and RF performance. The fabricated GaN MESFET exhibits a current saturation at $V_{DS}$ = 4 V and a pinch-off at $V_{GS}$ =-3V The peak drain current of the device is about 230mA/mm at 300 K and the value is remained almost same for 500K operation. The $f_{T}$ and $f_{max}$ from the device are 6.357Hz and 10.25 GHz, respectively.y.y.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.19 no.4
• /
• pp.491-501
• /
• 2021

This paper aims to evaluate the mechanical integrity for Spent Nuclear Fuel (SNF) cladding under lateral loads during transportation. The evaluation process requires a conservative consideration of the degradation conditions of SNF cladding, especially the hydride effect, which reduces the ductility of the cladding. The dynamic forces occurring during the drop event are pinch force, axial force and bending moment. Among those forces, axial force and bending moment can induce transverse tearing of cladding. Our assessment of 14 × 14 PWR SNF was performed using finite element analysis considering SNF characteristics. We also considered the probabilistic procedures with a Monte Carlo method and a reliability evaluation. The evaluation results revealed that there was no probability of damage under normal conditions, and that under accident conditions the probability was small for transverse failure mode.

• Journal of Welding and Joining
• /
• v.26 no.4
• /
• pp.61-65
• /
• 2008

The static force balance model (SFBM) has been used to analyze drop transfer in gas metal arc welding. Although the SFBM is capable of predicting the detaching drop size in the globular mode with reasonable accuracy, discrepancy between the calculated and experimental results increases with current. In order to reduce discrepancy, the SFBM is modified by considering the momentum of the molten metal flow, which is generated by the pinch pressure. The momentum increases with smaller drop size and becomes compatible to the electromagnetic force. The modified force balance model (MFBM) predicts the experimental results more accurately, and extends its application to the projected mode.

• Proceedings of the KIEE Conference
• /
• 1997.07a
• /
• pp.288-290
• /
• 1997

The electromagnetic theory is applicated on the field of electromagnetic continuous casting(EMC). This paper treats the stream phenomena of high frequency current on the solid-loop coil of which consists the hollow conductor. The governing equation is derived from elctromagnetic field theory and the characteristics are analyzed by FEM. The results may be availabe data on designing the optimum shape of the coil for the improved pinch effect.

• 제어로봇시스템학회:학술대회논문집
• /
• 1989.10a
• /
• pp.819-824
• /
• 1989

This paper proposes a new method for the discovery and design of an optimal heat exchanger network. The method is based upon the concept of pinch, a problem reduction technique and the heuristics developed in this work. It generates subproblems in a logical way and solves the subproblems by the heuristics to synthesize an optimal network structure. It is thought that the heuristics can preserve the minimum utility consumption, the minimum number of heat exchanger units, and the minimum number of stream splittings needed for a given problem. The minimum heat exchanger area for the optimal network can then be obtained by adjusting the temperatures associate with the heat exchanger in the optimal network structure. The method is applied to the problems appeared in the literatures. The results show the reductions in the number of heat exchanger units for some problems.

• Progress in Superconductivity and Cryogenics
• /
• v.8 no.4
• /
• pp.34-38
• /
• 2006

Cycle analysis was performed in order to find the optimum design point of the LNG Boil-off gas re-liquefaction system. Thermodynamic analysis revealed the system could be defined by three state variables. Thus the system performance could be described by the three cold endpoint temperatures of the three-pass heat exchanger. This enabled us to investigate the cycle performance in terms of the heat exchanger parameters. To get access to the cycle states of higher system performances, larger heat exchangers were found necessary. Also the thermal pinch in cryogenic heat exchangers was found to act as a limiting factor to the system performance.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.222-224
• /
• 1996

This paper treats the stream phenomena of high frequency current on the solid-loop coil of which consists the hollow conductor. The governing equation is derived from electromagnetic field theory and the characteristics are analyzed by FEM with 2-D and 3-D. The results may be available data on designing the optimum shape of the coil for the improved pinch effect.

• Journal of Welding and Joining
• /
• v.11 no.1
• /
• pp.73-79
• /
• 1993

The phenomenon of metal transfer has been investigated for different transfer modes using a digital high speed motion analyzer and an arc shadow-graphing system based on a laser source and related optical system. It was observed that the pinch instability phenomenon did not occur for the globular transfer mode, since the liquid globule was then spherical rateher than a cylindrical liquid bar. On increasing the ratio of carbon dioxide to argon, the transition current from globular to spray transfer generally increased, but it is interesting that the transition was observed to occur at the lowest current in a 5% CO$_{2}$-95% argon gas mixture. For pure carbon dioxide and helium shielding gases, the drop frequency increased slowly with increasing current. At high currents or an argon based shielding gas, the length of liquid bar decreased as the carbon dioxide content increased. The acceleration of a droplet within the arc was determined using the gas drag force theory and was found to be greater than the experimental results.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2173-2175
• /
• 1999

This paper presents the development of closing switch for high voltage and current in detail. Design concept of INPIStron triggered by the gas puffing, voltage hold-off, current capacity, insulating and electrode material, rise time etc, are described. Also for the dptimized design of the electrical triggering switch, pin, ring, wire brush, surface discharge and HCP(Hypo-Cycloidal Pinch) trigger are considered.