• 비파괴검사학회지
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• 제24권5호
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• pp.532-537
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• 2004

전자기장을 유도하는 원리를 기초로 한 새로운 비파괴탐상법인 FEF법을 개발하였다. 이 탐상법은 전자기장을 유도하는 유도선과 이를 감지하는 감지부로 구성되어 있고, 비접촉 방식으로 탐상을 실시한다. 본 연구는 알루미늄합금, 스테인레스강과 인코넬 합금강의 재료에 방전 가공한 결함에 대하여 결함 검출 및 결함 깊이에 대한 평가를 실시하였다. 결함이 없는 영역에서의 측정전압은 lift-off에 의존한다. 결함영역에서 탐촉자가 결함에 가까이 접근할수록 전압은 증가하고, 결함위치에서 최고전압으로 측정되며, 이 최고치는 결함의 깊이에 따라 변화한다. 각 재료에 대한 전압분포 같은 경향으로 측정된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1824-1827
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• 2003

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in two high voltage motors. Two 6.6kV motors were installed with 80pF capacitive couplers at the terminal box. The PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantifies such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). Off-line PD measurements were conducted on one 4.16kV motor. The motor was energized to 2.4kV, 3.0kV, 3.5kV and 4.16kV, respectively. The PD levels in pC were measured with a conventional digital PD detector. The comparison of positive to negative PD indicates whether the defect elements of PD are within the insulation or on the insulation surface. Discharge at conductor surface was discovered in No. 1 motor. Internal discharges were generated in phase A, B and C of No. 2 motor, Slot discharges occurred in three phases of No. 3 motor.

• Computers and Concrete
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• 제33권5호
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• pp.481-496
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• 2024

Internal erosion around pipes can lead to the failure of earth dams through various mechanisms. This study investigates the displacement patterns in earth dam models under three different failure modes due to internal erosion, using digital image correlation (DIC) methods. Three failure modes—erosion along a pipe (FM1), pipe leakage leading to soil erosion (FM2), and erosion in a pipe due to defects (FM3)—are analyzed using two- and three-dimensional image- processing techniques. The internal displacement of the cross-sectional area and the surface displacement of the downstream slope in the dam models are monitored using an image acquisition system. Physical model tests reveal that FM1 exhibits significant displacement on the upper surface of the downstream slope, FM2 shows focused displacement around the pipe defect, and FM3 demonstrates increased displacement on the upstream slope. The variations in internal and surface displacements with time depend on the segmented area and failure mode. Analyzing the relationships between internal and surface displacements using Pearson correlation coefficients reveals various displacement patterns for the segmented areas and failure modes. Therefore, the image-based characterization methods presented in this study may be useful for analyzing the displacement distribution and behavior of earth dams around pipes, and further, for understanding and predicting their failure mechanisms.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제40권
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• pp.2.1-2.7
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• 2018

With the development of computer-aided design/computer-aided manufacturing (CAD/CAM) technology, it has been possible to reconstruct the cranio-maxillofacial defect with more accurate preoperative planning, precise patient-specific implants (PSIs), and shorter operation times. The manufacturing processes include subtractive manufacturing and additive manufacturing and should be selected in consideration of the material type, available technology, post-processing, accuracy, lead time, properties, and surface quality. Materials such as titanium, polyethylene, polyetheretherketone (PEEK), hydroxyapatite (HA), poly-DL-lactic acid (PDLLA), polylactide-co-glycolide acid (PLGA), and calcium phosphate are used. Design methods for the reconstruction of cranio-maxillofacial defects include the use of a pre-operative model printed with pre-operative data, printing a cutting guide or template after virtual surgery, a model after virtual surgery printed with reconstructed data using a mirror image, and manufacturing PSIs by directly obtaining PSI data after reconstruction using a mirror image. By selecting the appropriate design method, manufacturing process, and implant material according to the case, it is possible to obtain a more accurate surgical procedure, reduced operation time, the prevention of various complications that can occur using the traditional method, and predictive results compared to the traditional method.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권1호
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• pp.1-11
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• 2012

Purpose: The purpose of this study was to evaluate the bone regeneration capacity of silk fibroin (SF) when combined with beta tricalcium phosphate (${\beta}$-tricalcium phosphate [TCP]) and rh-bone morphogenetic protein (BMP) in vivo by micro-computed tomography (CT), soft x-ray, and histological analysis. Methods: A total of 56 critical size defects formed by a trephine bur made on 28 adult female Spague-Dawley rats were used for this study and the defect size was 5.0 mm in diameter. The defects were transplanted with (1) no graft material (raw defect), (2) autogenous bone, (3) SF ($10{\mu}g$), (4) SF-BMP ($10{\mu}g$, $0.8{\mu}g$ each), and (5) SF+${\beta}$-TCP ($10{\mu}g$). At 4 and 8 weeks after operation, the experimental animals were sacrificed. Samples were evaluated with soft x-ray, histological examinations and 3-dimensional micro-CT analysis. Results: In the 3-dimensional micro-CT evaluation, bone volume and bone surface data were higher in the SF-BMP ($12.8{\pm}1.5$, $138.6{\pm}45.0$ each) (P<0.05) and SF-TCP ($12.3{\pm}1.5$, $144.9{\pm}30.9$ each) group than in the SF group ($6.1{\pm}3.3$, $77.2{\pm}37.3$ each) (P<0.05), except for the autogenous group ($15.0{\pm}3.0$, $190.7{\pm}41.4$ each) at 4 weeks. At 8 weeks, SF-BMP ($16.8{\pm}3.5$, $173.9{\pm}34.2$ each) still revealed higher (P<0.05) bone volum and surface, but SF-TCP ($11.3{\pm}1.5$, $1132.9{\pm}52.1$ each) (P=0.5, P=0.2) revealed the same or lower amount compared with the SF group ($13.8{\pm}2.7$, $127.5{\pm}44.8$ each). The % of bone area determined by radiodensity was higher in the SF-TCP ($31.4{\pm}9.1%$) and SF-BMP ($36.2{\pm}16.2%$) groups than in the SF ($19.0{\pm}10.4$) group at the period of 4 weeks. Also, in the histological evaluation, the SF-BMP group revealed lower inflammation reaction, lower foreign body reaction and higher bone healing than the SF group at postoperative 4 weeks and 8 weeks. The SF-TCP group revealed lower inflammation at 4 weeks, but accordingly, as the TCP membrane was absorbed, inflammatory and foreign body reaction are increased at 8 weeks. Conclusion: The current study provides evidence that the silk fibrin can be used as an effective grafted material for tissue engineering bone generation through a combination of growth factor or surface treatment.

• 제어로봇시스템학회논문지
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• 제22권1호
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• pp.59-65
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• 2016

As modern electronic devices get smaller and smaller, high-resolution, large Field-Of-View (FOV), fast, and cost-effective 3-dimensional (3-D) measurement is requested more and more. In particular, defect inspection machines using machine-vision technology nowadays require 3-D inspection as well as the conventional 2-D inspection. Phase Measuring Profilometry (PMP) is one of the fast non-contact 3-D shape measuring methods currently being extensively investigated in the electronic component manufacturing industry. The PMP system is well known and is successfully applied to measuring complex surface profiles with varying reflectance properties. However, for highly reflective surfaces, such as Ball Grid Arrays (BGAs), it has difficulty accurately measuring 3-D shapes. In this paper, we propose a new fast optical system that can eliminate the highly reflective saturated regions in BGA ball images. This is achieved by utilizing four Low Intensity Grating (LIG) images together with the conventional High Intensity Grating (HIG) images. Extensive experiments using BGA samples show a repeatability of under ${\pm}20um$ in standard deviation, which is suitable for most 3-D shape measurements of BGAs.

• 한국재료학회지
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• 제28권2호
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• pp.101-107
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• 2018

Li-incorporated ZnO thin films were deposited by using ultrasonic-assisted spray pyrolysis deposition (SPD) system. To investigate the effect of Li-incorporation on the performance of ZnO thin films, the structural, electrical, and optical properites of the ZnO thin films were analyzed by means of X-ray diffraction (XRD), field-emssion scanning electron microscopy (FE-SEM), Hall effect measurement, and UV-Vis spectrophotometry with variation of the Li concentraion in the ZnO sources. Without incorporation of Li element, the ZnO surface showed large spiral domains. As the Li content increases, the size of spiral domains decreased gradually, and finally formed mixed small grain and one-dimensional nanorod-like structures on the surface. This morphological evolution was explained based on an anti-surfactant effect of Li atoms on the ZnO growth surface. In addition, the Li-incorporation changed the optical and electrical properties of the ZnO thin films by modifying the crystalline defect structures by doping effects.

• Archives of Plastic Surgery
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• 제39권4호
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• pp.323-328
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• 2012

Background Among the various methods for correcting nasal deformity, the composite graft is suitable for the inner and outer reconstruction of the nose in a single stage. In this article, we present our technique for reconstructing the ala and columella using the auricular chondrocutaneous composite graft. Methods From 2004 to 2011, 15 cases of alar and 2 cases of columellar reconstruction employing the chondrocutaneous composite graft were studied, all followed up for 3 to 24 months (average, 13.5 months). All of the patients were reviewed retrospectively for the demographics, graft size, selection of the donor site and outcomes including morbidity and complications. Results The reasons for the deformity were burn scar (n=7), traumatic scar (n=4), smallpox scar (n=4), basal cell carcinoma defect (n=1), and scar contracture (n=1) from implant induced infection. In 5 cases of nostril stricture and 6 cases of alar defect and notching, composite grafts from the helix were used ($8.9{\times}12.5$ mm). In 4 cases of retracted ala, grafts from the posterior surface of the concha were matched ($5{\times}15$ mm). For the reconstruction of the columella, we harvested the graft from the posterior scapha ($9{\times}13.5$ mm). Except one case with partial necrosis and delayed healing due to smoking, the grafts were successful in all of the cases and there was no deformity of the donor site. Conclusions An alar and columellar defect can be reconstructed successfully with a relatively large composite graft without donor site morbidity. The selection of the donor site should be individualized according to the 3-dimensional configuration of the defect.

• 한국지리정보학회지
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• 제4권4호
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• pp.61-71
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• 2001

오늘날 측량장비개발의 급속한 발전과 더불어 정밀도가 많이 향상되고 있고, 컴퓨터를 이용한 지형공간정보체계기술의 발달로 보다 정밀한 3차원 지형의 재현이 가능하게 되었다. 그런데 실제 현장에서 이루어지고 있는 면적 및 체적산출방법에 있어서는, 재래적인 측량방법인 평판측량을 통해서 지형을 만들어낸 후 구적기나 기타 다른 방법을 통해서 2차원 물량을 산출해 내고 거기에 일정량의 경사보정계수를 곱하여 3차원 물량을 산출하는 방법을 사용하고 있다. 본 연구에서는 재래적인 측량방법 및 물량산출방법에 대한 비효율성 및 비정밀성을 제시하고, 현대측량장비인 광파거리측량기와 GPS장비를 이용해서 불규칙삼각형방식과 격자형방식으로 측량을 실시하고, 두 측량데이터를 가지고 각각 방법에 따라 3차원 지형모델을 구축한 후 2차원 및 지표면적을 산출하였다. 그 후 재래적인 측량방법을 이용한 면적산출량을 기준으로 불규칙삼각형방식과 격자형방식으로 산출한 면적산출량을 비교 분석함으로써 보다 정밀하고 효율성이 높은 지표면적 산출방법을 제시하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.306-306
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• 2011

Three dimensional(3D) topological insulators(TIs) of Bi binary alloys are characterized by a bulk energy gap with strong spin-orbit coupling and metallic surface states protected by time-reversal symmetry. It was reported that film forms of such materials were advantageous over bulk forms due to less defect density and better crystallinity. So far, the films have been prepared on several substrates including semiconductors and graphene. But, there were no studies on metal substrates. For electronic transport experiments and device applications, it is necessary to know epitaxial relation between TIs and metal electrodes. In this study, Atomically flat films of Bi2Se3 were grown on a Au(111) metal substrate by in-situ molecular beam epitaxy. Using home-built scanning tunneling microscope, we observed hexagonal atomic structures which corresponded to the outmost selenium atomic layer of Bi2Se3. Triangular-shaped defects known as Selenium vacancy were also found.