• Electrical & Electronic Materials
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• v.10 no.7
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• pp.659-667
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• 1997

The influence of SiO$_2$on the microstructure and electrical properties of zinc oxide varistor was investigated. Zn$_2$SiO$_4$third phase in the sintered body was found at grain boundaries, multiple grain junctions, and occasionally within ZnO grains. This phase acted as a grain growth inhibitor, which retard the grain growth of the ZnO matrix by impeding migration on the grain boundaries. As SiO$_2$ addition increases, average grain size decreased from 40.6${\mu}{\textrm}{m}$ to 26.9${\mu}{\textrm}{m}$ due to the pinning effect by Zn$_2$SiO$_4$ and drag effect by Si segregation at grain boundaries, the breakdown voltage consequently increased. When SiO$_2$ addition is increased, interface state density decreased, however, the barrier height increased by decrease of donor concentration, as a result, the nonlinear exponent increased and leakage current decreased. While, as SiO$_2$ addition increase, it was found that the apparent dielectric loss factor shows a tendency of decrease. Wholly, electrical properties of zinc oxide varistor can be said to be improved by SiO$_2$addition.

• Journal of Magnetics
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• v.16 no.4
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• pp.328-331
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• 2011

Here, we describe a dual spin valve structure with distinct switching fields for two pinned layers. A device with this structure has a staircase of three distinct magnetoresistive states. The multiple resistance states are achieved by controlling the exchange coupling between two ferromagnetic pinned layers and two adjacent anti-ferromagnetic pinning layers. The maximum magnetoresistance ratio is 7.9% for the current-perpendicular-to-plane and 7.2% for the current-in-plane geometries, with intermediate magnetoresistance ratios of 3.9% and 3.3%, respectively. The requirements for using this exchange-biased stack as a three-state memory device are also discussed.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.188-193
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• 2004

The purpose of this paper is concerned with a development of an air-powered handpiece for surgical operation. The handpiece is the tool of surgical instruments and it can be used to interchange multiple attachments for drilling, pinning, sawing, driving screws and reaming. Most of domestic medical instruments bring in overseas and the air-powered handpiece imported from foreign countries at 100％ too. Therefore we develop new air powered handpiece. we research in 2D and 3D modeling, design of air line, analyze structure. The air-powered handpiece composes of body, power supply air-line, elements for mechanical power transmission, attachment, and surgical tools. The handpiece is developed by several processes that 3D design, machining, heat treatment and coating. The developed handpiece is experimented to confirm check the efficiency.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1361-1363
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• 1997

Zinc oxide-based MOV was fabricated with $SiO_2$ additive ranging from 0.5 to 4.0 mol%, and the microstructure and electrical characteristics were investigated. $Zn_2SiO_4$ phase formed by $SiO_2$ additive was distributed at ZnO grains, grain boundaries, and multiple grain junctions. As the content of $SiO_2$ additive increases, average grain size decreased from 40.6 to $26.9{\mu}m$ due to the Pinning effect by $Zn_2SiO_4$ at grain boundaries Breakdown voltage and nonlinear exponent increased, and leakage current decreased in the range of $11.2{\sim}6.14{\mu}A$ with an increasing $SiO_2$. Donor concentration and interface state density decreased, and barrier height increased in the range of $0.71{\sim}1.04eV$ with an increasing $SiO_2$. While, as the content of $SiO_2$ additive, apparent dielectric constant decreased, peak frequency of dissipation factor decreased in the range of $6.45{\times}10^5{\sim}3.00{\times}10^5Hz$, and dissipation peak was $0.31{\sim}0.22$ at Peak frequency.

• Archives of Plastic Surgery
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• v.34 no.3
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• pp.409-412
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• 2007

Purpose: Percutaneous Kirschner wire fixation is common method for hand fracture. It is simple but has risk of ascending infection through the pin and bony injury by multiple drilling. Ascending infection through pin tract is mostly superficial and can be treated with antibiotics and aseptic dressing. This is a case review of subacute osteomyelitis on phalangeal bones after Kirschner wire fixation with literature review. Methods: A 40-years-old man with distal phalangeal fracture on right second finger is presented. He went to a local clinic and had percutaneous Kirschner wire fixation under local anesthesia. He was transferred to our hospital for ulcerative wound on DIP joint at 4 weeks after operation. Radiography showed osteolytic change around medulla of middle and distal phalanges, leading to diagnosis of a subacute osteomyelitis. We treated it with amputation at the level of shaft of middle phalanx. Results: The postoperative course was uneventful. We thought several possible reasons for osteomyelitis in our case. First, it could resulted from ascending infection through the wire. Second, it could be resulted from a bony burn by repeated drilling. And bony necrosis could be a consequence of arterial insufficiency caused by 2 pin insertion. Conclusion: We suggest that a precise pinning based on accurate anatomical understanding is required for a percutaneous Kirschner wire fixation. The frequency of drilling should be minimized. Careful observation and patient education for pin site care are essential.

• Journal of Yeungnam Medical Science
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• v.20 no.1
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• pp.28-35
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• 2003

Purpose: To evaluate physeal remodeling after internal fixation of slipped capital femoral epiphysis, We performed a retrospective review of the medical records and radiographs of 14 children (17 cases) who had had slipped capital femoral epiphysis. Materials and Methods: We reviewed 14 patients who had slipped capital femoral epiphysis. They were divided two groups. Group I were in situ pinning with single screw and group II were corrective osteotomy with multiple pinning. We identified physeal remodeling camparing with their preoperative, postoperative and last follow-up radiographs with measuring physeal-shaft angle. Results: Early closure of the physis was observed in 6 cases among 14 patients (17 hips). Compared with their postoperative radiographs, the last follow up radiographic study revealed that physeal remodeling was observed in 4 patients (4 hips) at group I (mean, $7.8^{\circ}$), in 2 patients (3 hips) at group II (mean, $10.7^{\circ}$). Conclusion: In this study, physeal remodeling was observed in 4 patients (4 hips) in group I and 2 patients (3 hips) in group II. The incidence of physeal remodeling was related with degree of epiphyseal slippage, and age was not related with physeal remodeling potential.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.592-607
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• 2006

This paper proposes a technique to select processors and hardware IPs and to map the tasks into the selected processing elements, aming to achieve high performance with minimal system cost when multitask applications with real-time constraints are run on a multicore SoC. Such technique is called to 'Hardware-Software Cosynthesis Technique'. A cosynthesis technique was already presented in our early work [1] where we divide the complex cosynthesis problem into three subproblems and conquer each subproblem separately: selection of appropriate processing components, mapping and scheduling of function blocks to the selected processing component, and schedulability analysis. Despite good features, our previous technique has a serious limitation that a task monopolizes the entire system resource to get the minimum schedule length. But in general we may obtain higher performance in multitask multicore system if independent multiple tasks are running concurrently on different processor cores. In this paper, we present two mapping techniques, task mapping avoidance technique(TMA) and task mapping pinning technique(TMP), which are applicable for general cases with diverse operating policies in a multicore environment. We could obtain significant performance improvement for a multimedia real-time application, multi-channel Digital Video Recorder system and for randomly generated multitask graphs obtained from the related works.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.19-23
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• 2023

The Second-generation high-temperature superconducting (HTS) Rare-Earth Barium Copper Oxide (REBCO) wire is a composite laminate having a multi-layer structure (8 or more layers). HTS wires will undergo multiple loads including the bending-tension loads during winding, high current density, and high magnetic fields. In particular, the wires are subjected to bending stress and magnetic field stress because HTS wires are wound around a circular bobbin when making a high-field magnetic. Each of the different laminated wires inevitably exhibits damage and fracture behavior of wire due to stress deformation, mismatches in thermal, physical, electrical, and magnetic properties. Therefore, when manufacturing high-field magnets and other applications, it is necessary to calculate the stress-strain experienced by high-temperature superconducting wire to present stable operating conditions in the product's use environment. In this study, the finite element model (FEM) was used to simulate the strain-stress characteristics of the HTS wire under high current density and magnetic field, and bending loads. In addition, the result of obtaining the neutral axis of the wire and the simulation result was compared with the theoretical calculation value and reviewed. As a result of the simulation using COMSOL Multiphysics, when a current of 100 A was applied to the wire, the current value showed the difference of 10^-9. The stress received by the wire was 501.9 MPa, which showed a theoretically calculated value of 500 MPa and difference of 0.38% between simulation and theoretical method. In addition, the displacement resulted is 30.0012 ㎛, which is very similar to the theoretically calculated value of 30 ㎛. Later, the amount of bending stress by the circular mandrel was received for each layer and the difference with the theoretically obtained the neutral axis result was compared and reviewed. This result will be used as basic data for manufacturing high-field magnets because it can be expanded and analyzed even in the case of wire with magnetic flux pinning.