• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.10-14
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• 1990

Variable Structure System(VSS) la being extended to a new control system of ac servo machines for its merits of simple mechanism and robustness. This paper has studied about applying VSS to position control for brushless servo motor. But VSS has the chattering problem of control input. This chattering phenomenon cause acoustic noises, torque ripple and increase harmonics of the current. One of the useful way to eliminate this defect of VSS, linearlizing the switching function is discussed here. Though the conventional method of linearizing the switching function diminishes the chattering, it may degrade the robustness of the system. In this paper, new linearized switching function which shows robust performance to the parametric variation and reduces chattering simultaneously is introduced and assured by simulation.

• Archives of Reconstructive Microsurgery
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• 제5권1호
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• pp.62-69
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• 1996

Lateral arm flap has been used for the reconstruction of the various defects in hand, head and neck region. This flap is highly dependable as a free flap because of its thin flap thickness, constant vascular anatomy and possibility of osteocutaneous flap and fascial flap. Recently, many authors tried extended approach for vascular pedicle and distal flap extension for bigger defects. In this study, we review previous articles and 14 cases used lateral arm flaps for coverage of the varying defect on head and neck, upper and lower extremities succesfully. In conclusion, lateral arm flap has constant anatomical structure and can overcome the disadvantages such as short pedicle length and limited flap size, then the range of its application can be very widened.

• Journal of Korean Neurosurgical Society
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• 제56권6호
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• pp.509-512
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• 2014

Primary intraosseous meningioma is a rare tumor, and atypical pathologic components both osteolytic lesion and dura and soft tissue invasion is extremely rare. A 65-year-old woman presented with a 5-month history of a soft mass on the right frontal area. MR imaging revealed a 4 cm sized, multilobulated, strongly-enhancing lesion on the right frontal bone, and CT showed a destructive skull lesion. The mass was adhered tightly to the scalp and dura mater, and it extended to some part of the outer and inner dural layers without brain invasion. The extradural mass and soft tissue mass were totally removed simultaneously and we reconstructed the calvarial defect with artificial bone material. The pathological study revealed an atypical meningioma as World Health Organization grade II. Six months after the operation, brain MR imaging showed that not found recurrence in both cranial and spinal lesion. Here, we report a case of primary osteolytic intraosseous atypical meningioma with soft tissue and dural invasion.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.319-323
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• 2007

Acoustic emission (AE) was originally developed for non-destructive testing of static structure, but over the year its application has been extended to health monitoring of rotating machines and bearings. It offers the advantage of earlier defect detection in comparison with monitoring bearing. This study was diagnosed low-speed machine which had a fault bearing for early detection by AE. And the artificial faults in a experimentation bearing was made for the bearing signals from difference speed and load were compared and analyzed by AE.

• 한국경영과학회지
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• 제20권1호
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• pp.27-34
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• 1995

In this paper, we have developed a model to determine the input quantity to be processed at each stage of a multi-stage production system in which the yield at each stage may be random and may need reworking at this stage. Yield randomness. especially in a semiconductor industry, is a most challenging problem for production control. The demand for flnal product is uncertain. We have extended the model proposed in Park and Kim[9] to consider a multiple number of reworkings which can be done at any stage prior to or tat the stage whose output in bad, depending on the level of the defect.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.74-75
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• 2008

TIGBT has some merits which are lower on-state voltage drop and smaller cell pitch, but also has a defect which is relatively lower breakdown voltage in comparison with planar IGBT. This lower breakdown voltage is due to the electric field which is concentrated on beneath the vertical gate. Therefore in this paper, new trench IGBT structure is proposed to improve breakdown voltage In the new proposed structure, a narrow oxide beneath the trench gate edge where the electric field is concentrated is extended into rectangular shape to decrease the electric field. As a result, breakdown voltage is improved to 23%.

• 품질경영학회지
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• 제25권1호
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• pp.56-68
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• 1997

The object of multiresponse optimization is to determine conditions on hte independent variables that lead to optimal or nearly optimal values of the response variables. Derringer and Suich (1980) extended Harrington's (1965) procedure by introducing more general transformations of the response into desirability functions. The core of the desirability a, pp.oach condenses a multivariate optimization into a univariate one. But because of the subjective nature of this a, pp.oach, inexperience on the part of the user in assessing a product's desirability value may lead to inaccurate results. To compensate for this defect, a weighted desirability function is introduced which takes into consideration the vriances of the responses.

• Restorative Dentistry and Endodontics
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• 제37권4호
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• pp.228-231
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• 2012

Invasive cervical resorption is a relatively uncommon form of external root resorption. It is characterized by invasion of cervical region of the root by fibrovascular tissue derived from the periodontal ligament. This case presents an invasive cervical resorption occurring in maxillary lateral incisor, following damage in cervical cementum from avulsion and intracoronal bleaching procedure. Flap reflection, debridement and restoration with glass ionomer cement were performed in an attempt to repair the defect. But after 2 mon, more resorption extended apically. Considering root stability and recurrence potential, we decided to extract the tooth. Invasive cervical resorption in advanced stages may present great challenges for clinicians. Therefore, prevention and early detection must be stressed when dealing with patients presenting history of potential predisposing factors.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1116-1122
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• 2005

A finite element method was used to simulate the wave propagation of laser-generated ultrasound and its interaction with surface breaking cracks in an elastic material. Thermoelastic laser line source on the material surface was approximated as a shear dipole and loaded as nodal forces in the plane-strain finite element (FE) model. The shear dipole- FE model was tested for the generation of ultrasound on the surface with no defect. The model was found to generate the Rayleigh surface wave. The model was then extended to examine the interaction of laser generated ultrasound with surface-breaking cracks of various depths. The crack-scattered waves were monitored to size the crack depth. The proposed model clearly reproduced the experimentally observed features that can be used to characterize the presence of surface-breaking cracks.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.