• Journal of Korean Vacuum Science & Technology
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• v.4 no.4
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• pp.112-121
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• 2000

The paper investigates electrical discharge properties in neon gas mixed with xenon. The breakdown temperature T$\sub$b/ and voltage V$\sub$b/ are obtained in terms of the gas mixture ratio X. It is shown that the breakdown voltage decreases, reaches the minimum value at X=0.02 and then increases again, as the mixture ratio X increases from zero to unity. Therefore, mixing the neon gas with a few percent of xenon is the most beneficial to reduce the breakdown voltage. Plasma density at breakdown in neon gas mixed with xenon is described in terms of the gas mixture ratio. The optimum value of mixture ratio for highest plasma density is found to be Xm=0.03. A preliminary experiment of AC-PDP is carried out for neon gas mixed with a few percent of xenon to verify some of the theoretical models. The experimental data agree qualitatively well with theoretical predictions.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1193-1195
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• 1995

The superconducting properties of YBaCuO thin films prepared by pulsed laser deposition(PLD) have been investigated. The x-ray diffraction patterns of the films are substantially different from one another. The YBaCuO thin films manufactured at the 20% of Argon mixture ratio were indicated $T_c$(zero)=88.2 K, $T_c$(onset)=92.1 K, and $J_c=9.0{\times}10^4A/cm^2$(at 77.3K).

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.239.2-239.2
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• 2015

Graphene is a most interesting material due to its unique and outstanding properties. However, semi-metallic properties of graphene along with zero bandgap energy structure limit further application to optoelectronic devices. Recently, many researchers have shown that band gap can be induced in the Bernal stacked bilayer graphene. Several methods have been used for the controlled growth of the Bernal staked bilayer graphene, but it is still challenging to control the growth process. In this paper, we synthesize the large area Bernal stacked bilayer graphene using multi heating zone low pressure chemical vapor deposition (LPCVD). The synthesized bilayer graphenes are characterized by Raman spectroscopy, optical microscope (OM), scanning electron microscopy (SEM). High resolution transmission electron microscopy (HRTEM) is used for the observation of atomic resolution image of the graphene layers.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.41-43
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• 1996

This paper describes on concerning electromagnetical and thermal behaviors during normal transition in Bi-2223/Ag superconducting multifilamentary tapes by conduction cooling. Some experiments were carried with operating temperature, 10-40K, and transport current as parameters in zero magnetic field. Sample tapes are transited normally with heater to intiate a quench. The voltage and temperature properties which accord to normal transition are measured by voltage taps and thermocouples attached to sample tapes, we also calculated longitudinal and transverse directions normal-zone propagation velocities from the voltage traces.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.123-130
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• 1995

This study presents model synthesis and performance investigation of a new brake system using electro-rheological(ER) fluids. Field-dependent Bingham properties characterized by non-zero yield stresses of the ER fluids are experimentally distilled. These properties are then incorporated with the governing equation of the proposed brake system which features design simplicity, fast response and salient controllability. After analyzing system performance with respect to design parameters such as electrode gap and length, an appropriate size of the brake is designed and fabricated. Both simulation and experimental works are undertaken in order to determine the feasibility and efficiency of the proposed brake system. The system performances are justified by evaluating field-dependent braking torques as well as braking times.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.628-628
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• 2013

Graphene, a single layer of graphite, has raised extensive interest in a wide scientific community for its extraordinary thermal, mechanical, electrical and other properties [1,2]. However, because of zero-band gap of graphene, it is difficult to apply for electronic applications. To overcome this problem, chemical doping is one of way to opening grahene bandgap. According to experimental results, by changing doping concentration and doping time, it is possible to control work function of graphene. We can obtain results through raman spectroscopy, UPS, Sheet resistance. Moreover, electronic properties of doped graphene were studied by making field effect transistors. We were able to control the doping concentration, dirac point of graphene and work function of graphene by formng n-type, p-type doping materials. In this research, the chemicals of diazonium salts, viologen, etc. were used for extrinsic doping.

• Journal of the Korean Operations Research and Management Science Society
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• v.20 no.1
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• pp.115-130
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• 1995

This paper considers a single machine nonpreemptive scheduling problem with a given common due date. In the problem, the optimal job sequence is sought to minimize the sum of earliness/tardiness and flow time measures in the situation where all jobs are available at time zero, and weights per unit length of earliness/tardiness and flow time are V and W, respectively. Some dominant solution properties are characterized to deriva both an optimal starting time for an arbitrary sequence and sequence improvement rules. The optimal schedule is found to the case W .geq. V/. By the way, it is difficult to find the optimal schedule for the case W < V. Therefore, the derived properties are put on together to construct a heuristic solution algorithm for the case W < V, and its effectiveness is rated at the mean relative error of about 3% on randomly generated numerical problems.

• Geomechanics and Engineering
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• v.3 no.4
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• pp.323-337
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• 2011

Israel's coastal region consists, mainly, of Pleistocene and Holocene sands with varying degrees of calcareous cementation, known locally as "kurkar". Previous studies of these materials emphasized the difficulty in their geotechnical characterization, due to their extreme variability. Consequently, it is difficult to estimate construction stability, displacements and deformations on, or within these soils. It is suggested that SPT and Menard pressuremeter tests may be used to characterize the properties of these materials. Values of elastic modulus obtained from pressuremeter tests may be used for displacement analyses at different strain levels, while accounting for the geometric dimensions (length/diameter ratio) of the test probe. A relationship was obtained between pressuremeter modulus and SPT blow count, consistent with published data for footing settlements on granular soils. Cohesion values, for a known friction angle, are estimated, by comparing field pressuremeter curves to curves from numerical (finite element or finite difference) analyses. The material analyzed in the paper is shown to be strain-softening, with the initial cohesion degrading to zero on development of plastic shear strains.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.741-750
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• 2018

Antoine showed that the properties of Armendariz and NI are independent of each other. The study of Armendariz and NI rings has been doing important roles in the research of zero-divisors in noncommutative ring theory. In this article we concern a new class of rings which generalizes both Armendariz and NI rings. The structure of such sort of ring is investigated in relation with near concepts and ordinary ring extensions. Necessary examples are examined in the procedure.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.125-127
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• 2005

In this paper, we propose a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption. This scheme is applied to the sample-data representation of a nonlinear system with constant state tine-delay. The mathematical expressions of the discretization scheme are presented and the effect of the time-discretization method on key properties of nonlinear control system with state tine-delay, such as equilibrium properties and asymptotic ability, is examined. The proposed scheme provides a finite-dimensional representation for nonlinear systems with state time-delay enabling existing controller design techniques to be applied to then. The performance of the proposed discretization procedure is evaluated using a nonlinear system. For this nonlinear system, various sampling rates and time-delay values are considered.