• 대한치과기공학회지
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• 제30권2호
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• pp.87-92
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• 2008

Purpose: In this study, we tried to compare marginal accuracy when produce ceramic crown using all ceramic materials and existent metal-ceramic system. Material and methods: All-ceramic systems were E-max (Ivoclar/Vivadent, Lichtenstein), Lava(3M, U.S.A.) and Wol-ceram(Teamziereis, Germany). Metal-ceramic system(PFG) was composed of Au-Pt alloy (Metalor, Switzerlandand) and overlying ceramic(D-sign, Ivoclar/Vivadent, Lichtenstein). We fabricated metal master die with upper diameter of 7.95mm, bottom diameter of 9.00mm, height of 5.00mm, and taper of $6^{\circ}$. All ceramic system used 0.5mm thickness ceramic coping, while metalceramic system used 0.3 thickness metal coping. By adding dentin and enamel ceramics on each coping, a crown with a proximal thickness of 1.0 mm and occlusal thickness of 2.0mm was fabricated. Pressure of 2kg was applied for 10 seconds on each crown with static load compressor. Before and after cementation, we measured the marginal gap at 4 points of each crown using optical microscope. The data was analyzed using a Student's t test and repeated-measures of analyses of variance(ANOVA) followed by a Bonferroni test. A p value<0.05 was considered significant. Results: As experiment results, marginal accuracy of wol-ceram and Lava is no good when compared with marginal accuracy of PFG. But marginal accuracy of E.max is good when compared with PFG. This result showed not significant. The marginal accuracy of E.max is good when compared with marginal accuracy of wol-ceram and Lava. Conclusion: The marginal accuracy of E.max is very good when compared with marginal accuracy of another group.

• 한국환경과학회지
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• 제23권1호
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• pp.39-46
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• 2014

This study surveyed Abies koreana to identify the correlation between its vegetation structure according to its slope direction and seedling establishment in a bid to build basic research data on the changes and conservation of the A. koreana in Hallasan Mountain. The findings of its vegetation structure revealed that in both areas, Importance value was given to the A. koreana for its tree layer, the Taxus cuspidata for its shrub layer, and the Sasa quelpaertensis for its herb layer. However, in the Youngsil area with the tree layer, high importance was given to deciduous broad-leaved trees such as Prunus maximowiczii, Quercus mongolica, and the young species of the A. koreana in the shrub layer that can maintain the A. koreana forest's greater importance in the Jindallebat than in the Youngsil. Thus, the A. koreana forest in the Jindallebat is believed to lastlonger. The findings of correlation between the quantity of seedlings and their location by area revealed that in each tiny quadrat, the A. koreana seedling averaged 5.3 in the Youngsil and 2.9 in the Jindallebat. Both areas were all found to have a positive correlation in terms of rock exposure ratio and dead tree ratio as well as a negative correlation with regard to the cover degree of S. quelpaertensis, the canopy gap, the total vegetation, and the herb layer. It was found that the cover degree of the herb layer in the Youngsil and the S. quelpaertensis in the Jindallebat had the largest impact on the A. koreana seedlings.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.41-45
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• 2016

The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.

• 한국전기전자재료학회논문지
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• 제25권6호
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• pp.451-455
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• 2012

To compare an electrical and optical characteristics of indium tin oxide (ITO) and carbon nanotube (CNT) electrode on flexible and reflective display, we fabricate two charged particle-type display panels under the same panel condition of which the width of ribs is 10 ${\mu}m$, the cell size is $300{\mu}m{\times}300{\mu}m$, the q/m value of the white particles is -4.3 ${\mu}C/g$ and that for the black is +1.3 ${\mu}C/g$, and the cell gap is 75 ${\mu}m$, 125 ${\mu}m$, and 175 ${\mu}m$. We use plastic substrates coated with ITO and CNT electrode. To evaluate optical property, we measure a response time of particles using a laser and a photodiode. Threshold and driving voltages of CNT electrode according to the sheet resistance of 300, 600, 1,000 (ohm/sq) are compared with ITO electrode of 10 (ohm/sq). A response time of the CNT panel is similar to that of ITO panel, but the threshold and driving voltages of CNT panel are higher than that of ITO panel, inducing a large bombardment of the particles and shortening the lifetime of the panel. High difference of a threshold and a driving voltage of CNT panel will induce an particle clumping, resulting degradation of the panel. A bending radius of the fabricated CNT panel is 18 ${\mu}m$.

• 한국실내디자인학회논문집
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• 제13권5호
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• pp.82-89
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• 2004

Today, people are bombarded with information, high-technology and multimedia. With that in mind, museum can no longer attract visitor with traditional concept, so it must find some solution or stimulation to attract their attention back. New museum is becoming a experimental space for new culture, new education, and most of all a place to fulfill one's satisfaction of life. Over the past centuries, Guggenheim Foundation has done a great job in providing place for art and place to get emotional stimulation. Out of all of their museums, Frank L. Wright's Solomon R. Guggenheim in New York and frank O. Gehry's Guggenheim Museum in Bilbao had most unique character yet share similar feature to be recognized as the architectural landmark of the 20th & 21st century Although there are close to 50 years of gap between two museums, their unique, attractive, site-specific, emotional value comes from the two most innovative architect of the past and present century. For Wright the Guggenheim was his last project but it had one of the greatest impact on his career and for Gehry the museum gave him confidence that anything is possible. This study will focus on the spatial organization as well as the architectural formation of both museum to compare and analyze. The goal of the research is to give fundamental data which will reveal emotional elements as well as concepts from each work. The content of this research will mainly focused on their architectural philosophy and it will reveal their concept on human emotion as well as the characteristics of the spatial organization. The result of the study will be a valuable reference for people designing art & cultural facilities in the future.

• The Journal of Advanced Prosthodontics
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• 제12권5호
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• pp.316-321
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• 2020

PURPOSE. The stress distribution and microgap formation on an implant abutment structure was evaluated to determine the relationship between the direction of the load and the stress value. MATERIALS AND METHODS. Two types of three-dimensional models for the mandibular first molar were designed: bone-level implant and tissue-level implant. Each group consisted of an implant, surrounding bone, abutment, screw, and crown. Static finite element analysis was simulated through 200 N of occlusal load and preload at five different load directions: 0, 15, 30, 45, and 60°. The von Mises stress of the abutment and implant was evaluated. Microgap formation on the implant-abutment interface was also analyzed. RESULTS. The stress values in the implant were as follows: 525, 322, 561, 778, and 1150 MPa in a bone level implant, and 254, 182, 259, 364, and 436 MPa in a tissue level implant at a load direction of 0, 15, 30, 45, and 60°, respectively. For microgap formation between the implant and abutment interface, three to seven-micron gaps were observed in the bone level implant under a load at 45 and 60°. In contrast, a three-micron gap was observed in the tissue level implant under a load at only 60°. CONCLUSION. The mean stress of bone-level implant showed 2.2 times higher than that of tissue-level implant. When considering the loading point of occlusal surface and the direction of load, higher stress was noted when the vector was from the center of rotation in the implant prostheses.

• Earthquakes and Structures
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• 제11권6호
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• pp.1123-1141
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• 2016

To explore the application of traditional tuned mass dampers (TMDs) to the earthquake induced vibration control problem, a pounding tuned mass damper (PTMD) is proposed by adding a viscoelastic limitation to the traditional TMD. In the proposed PTMD, the vibration energy can be further dissipated through the impact between the attached mass and the viscoelastic layer. More energy dissipation modes can guarantee better control effectiveness under a suite of excitations. To further reduce mass ratio and enhance the implementation of the PTMD control, multiple PTMDs (MPTMD) control is then presented. After the experimental validation of the proposed improved Hertz based pounding model, the basic equations of the MPTMD controlled system are obtained. Numerical simulation is conducted on the benchmark model of the Canton Tower. The control effectiveness of the PTMD and the MPTMD is analyzed and compared under different earthquake inputs. The sensitivity and the optimization of the design parameters are also investigated. It is demonstrated that PTMDs have better control efficiency over the traditional TMDs, especially under more severe excitation. The control performance can be further improved with MPTMD control. The robustness can be enhanced while the attached mass for each PTMD can be greatly reduced. It is also demonstrated through the simulation that a non-uniformly distributed MPTMD has better control performance than the uniformly distributed one. Parameter study is carried out for both the PTMD and the MPTMD systems. Finally, the optimization of the design parameters, including mass ratio, initial gap value, and number of PTMD in the MPTMD system, is performed for control improvement.

• Computers and Concrete
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• 제20권5호
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• pp.545-553
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• 2017

A pounding tuned mass damper (PTMD) can be considered as a passive device, which combines the merits of a traditional tuned mass damper (TMD) and a collision damper. A recent analytical study by the authors demonstrated that the PTMD base on the energy dissipation during impact is able to achieve better control effectiveness over the traditional TMD. In this paper, a PTMD prototype is manufactured and applied for seismic response reduction to examine its efficacy. A series of shaking table tests is conducted in a three-story building frame model under single-dimensional and two-dimensional broadband earthquake excitations with different excitation intensities. The ability of the PTMD to reduce the structural responses is experimentally investigated. The results show that the traditional TMD is sensitive to input excitations, while the PTMD mostly has improved control performance over the TMD to remarkably reduce both the peak and root-mean-square (RMS) structural responses under single-dimensional earthquake excitation. Unlike the TMD, the PTMD is found to have the merit of maintaining a stable performance when subjected to different earthquake loadings. In addition, it is also indicated that the performance of the PTMD can be enhanced by adjusting the initial gap value, and the control effectiveness improves with the increasing excitation intensity. Under two-dimensional earthquake inputs, the PTMD controls remain outperform the TMD controls; however, the oscillation of the added mass is observed during the test, which may induce torsional vibration modes of the structure, and hence, result in poor control performance especially after a strong earthquake period.

• 한국항행학회논문지
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• 제19권4호
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• pp.338-344
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• 2015

국가 직무능력 표준 (NCS; national competency standards)은 직무를 수행하기 위해 요구되는 능력에 대한 체계화 및 표준화이다. NCS는 특정 직무능력인 능력단위 요소로 구체화하고 표준화하여 학습모듈을 개발한다. 기존 교육과정은 NCS 능력단위 요소를 교육 훈련에 활용하기 위해서 갭 분석 (gab analysis)이 필수적이다. 기존에 갭 분석은 전문가가 주관적으로 평가하였다. 전문가에 의한 갭 분석은 심리적 요소에 의해 주관적 결정, 정확성 결여, 시간 및 공간적 비효율성 문제가 제기되었다. 본 논문은 주관적 평가의 문제 해결을 위해 자동화 평가모델을 제시하였다. 본 논문은 기존 교육과정과 능력단위 요소 간 갭 분석을 위해, 색인어 추출, 단어빈도수-역 빈도수 기반 특징 값 추출, 코사인 유사도 알고리즘을 이용하였다. 또한, 기존 교육과정과 NCS 능력단위요소 사이 유사도 매핑 테이블을 제시하였다. 본 논문의 평가모델은 구조적 특징이나 속도 면에서 개선된 알고리즘을 통해 보완해야 한다.

• 한국멀티미디어학회논문지
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• 제12권3호
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• pp.362-371
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• 2009

고품질의 액정디스플레이를 개발하는데 있어서 제일 중요한 기술은 빛을 반사하는 망점의 균일한 분포를 갖는 도광판(BLU)을 만드는 것이다. 망점의 균일한 분포는 연속계조 영상을 이진영상으로 해프토닝하는 방법을 통해 만들고 있다. 여러 해프토닝 방법들 중에서 주거리 기반의 오차확산 기법이 균일한 망점의 분포를 보여주고 있다. 그러나 이 방법은 각 화소의 주거리 범위가 주위 하소의 주거리와 겹치거나 틈이 많이 벌어지는 문제가 발생하게 된다. 이에 본 논문에서는 주거리 기반의 오차 확산 방법을 개선한 가변적 주거리 기반의 오차 확산 방법을 제안한다. 해당 화소 및 주변 화소의 주거리를 활용한 가변적 주거리를 정의하며 주거리는 방향에 따라 다른 값을 가지게 된다. 이 가변적 주거리 알고리즘은 망점들 간의 간격에 대한 고른 분포를 얻을 수 있게 되었다.