• 대한기계학회논문집A
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• 제20권1호
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• pp.79-87
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• 1996

SMC(Sheet Molding Compound) is made of unsaturated polyester resin and other additives reinforced with randomly distributed chopped fiberglass strands. Because of its higher stiffness per unit mass, SMC was used as a substitute for steel for automotive steel outer panels. Thus, understanding of flow characteristics during fabrication of SMC is of importance since the formation of weld line depends on material flow. In the present study, SMC compression molding simulations in the flat and T-shape molds were accomplished. During simulations, the preferential the preferential flow occurred at the low mold closing speed while plug flow was observed for the higher mold closing speed. When the preferential flow was observed, the weld line was seen at the final stage. For simulations, rigid-viscoplastic finite element method was applied. Self-contact algorithm was also applied in order to predict the formation of the weld line. Simulation results were compared to the experimental results available in the literature.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권2호
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• pp.124-130
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• 2005

In this paper, low-power design and implementation techniques for DWT(Discrete Wavelet Transform) of the JPEG2000 compression are proposed. In DWT block of the JPEG2000, linear phase 9 tap and 7 tap filters are used. For low-power implementation of those filters, processor technique for DA(Distributed Arithmetic) filter and minimization technique for number of addition in CSD(Canonic Signed Digit) filter are utilized. Proposed filter structure consists of 3 blocks. In the first CSD coefficient block, every possible 4 bit CSD coefficients are calculated and stored. In second processor block, multiplication is done by MUX and addition processor in terms of the binary values of filter coefficient. Finally, in third block, multiplied values are output and stored in flip-flop train. For comparison of the implementation area and power dissipation, proposed and conventional structures are implemented by using Verilog-HDL coding. In simulation, it is shown that 53.1% of the implementation area can be reduced comparison with those of the conventional structure.

• Geomechanics and Engineering
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• 제24권1호
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• pp.43-55
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• 2021

Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1-74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 디지털콘텐츠학회 논문지
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• 제5권3호
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• pp.199-204
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• 2004

저비트율에서도 우수한 화질을 제공하는 프랙탈 영상 압축 기법들이 갖고 있는 하나의 문제점은 복호화가 반복 처리를 통해 구현되며 그 복잡도가 각각의 영상에 따라 상이하다는 것이다. 이러한 문제를 해소하기 위해 본 논문은 복호 시간을 단축시키기 위해 반복 변환이 필요 없는 프랙탈 영상 복호 알고리즘을 제안하고 그 성능을 분석함에 그 목적이 있다. 제안된 프랙탈 복호 알고리즘은 복호기에서 사용할 초기 영상과 동일한 코드북 영상을 부호기에 보유하고 있는 상태에서 부호화 과정에서는 이 코드북 영상과 부호화하려는 영상의 유사성을 찾아 프랙탈 계수를 구한다. 이후, 수신단의 복호화 과정에서는 수신된 프랙탈 계수와 기설정된 초기 영상을 이용하여 반복 변환 없이 한 번에 영상을 복호함으로써 반복 변환 횟수의 역수배만큼 복호 소요 시간을 현저하게 단축시킬 수 있었다. 제안된 방법의 타당성과 보편성을 검증하기 위해 서로 다른 분포 특성을 갖는 복수의 정지 영상과 동영상을 대상으로 복호 소요 시간과 화질 측면에서 그 성능을 평가$\cdot$분석하였다.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.59.1-59.14
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• 2021

Objectives: This study compared the Biodentine, MTA Repair HP, and Bio-C Repair bioceramics in terms of bond strength to dentin, failure mode, and compression. Materials and Methods: Fifty-four slices obtained from the cervical third of 18 single-rooted human mandibular premolars were randomly distributed (n = 18). After insertion of the bioceramic materials, the push-out test was performed. The failure mode was analyzed using stereomicroscopy. Another set of cylindrically-shaped bioceramic samples (n = 10) was prepared for compressive strength testing. The normality of data distribution was analyzed using the Shapiro-Wilk test. The Kruskal-Wallis and Friedman tests were used for the push-out test data, while compressive strength was analyzed with analysis of variance and the Tukey test, considering a significance level of 0.05. Results: Biodentine presented a higher median bond strength value (14.79 MPa) than MTA Repair HP (8.84 MPa) and Bio-C Repair (3.48 MPa), with a significant difference only between Biodentine and Bio-C Repair. In the Biodentine group, the most frequent failure mode was mixed (61%), while in the MTA Repair HP and Bio-C Repair groups, it was adhesive (94% and 72%, respectively). Biodentine showed greater resistance to compression (29.59 ± 8.47 MPa) than MTA Repair HP (18.68 ± 7.40 MPa) and Bio-C Repair (19.96 ± 3.96 MPa) (p < 0.05). Conclusions: Biodentine showed greater compressive strength than MTA Repair HP and Bio-C Repair, and greater bond strength than Bio-C Repair. The most frequent failure mode of Biodentine was mixed, while that of MTA Repair HP and Bio-C Repair was adhesive.

• 인지과학
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• 제28권2호
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• pp.111-131
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• 2017

연결주의 모델은 계산주의적 관점에서 언어 처리를 연구하는 한 가지 접근법이다. 그리고 연결주의 모델 연구를 진행하는데 있어서 표상(representation)을 구축하는 것은, 모델의 학습 수준 및 수행 능력을 결정한다는 점에서 모델의 구조를 만드는 것만큼이나 중요한 일이다. 연결주의 모델은 크게 지역 표상(localist representation)과 분산 표상(distributed representation)이라는 두 가지 서로 다른 방식으로 표상을 구축해 왔다. 하지만 종래 연구들에서 사용된 지역 표상은 드문 목표 활성화 값을 갖고 있는 출력층의 유닛이 불활성화 하는 제한점을, 그리고 과거의 분산 표상은 표상된 정보의 불투명성에 의한 결과 확인의 어려움이라는 제한점을 갖고 있었으며 이는 연결주의 모델 연구 전반의 제한점이 되어 왔다. 본 연구는 이와 같은 과거의 표상 구축의 제한점에 대하여, 제한된 볼츠만 머신(restricted Boltzmann machine)이 갖고 있는 특징인 정보의 추상화를 활용하여 지역 표상을 가지고 분산 표상을 유도하는 새로운 방안을 제시하였다. 결과적으로 본 연구가 제안한 방법은 정보의 압축과 분산 표상을 지역 표상으로 역변환하는 방안을 활용하여 종래의 표상 구축 방법이 갖고 있는 문제를 효과적으로 해결함을 보였다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.32-38
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• 2004

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC $180^{\circ}C$, fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC $90{\circ}C$ and $60^{\circ}C$, fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.

• Geomechanics and Engineering
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• 제22권5호
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• pp.461-473
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• 2020

Natural rock mass contains defects of different shapes, usually filled with inclusions such as clay or gravel. The presence of inclusions affects the failure characteristics and mechanical properties of rock mass. In this study, the strength and failure characteristics of rock with inclusions were studied using the particle flow code under uniaxial compression. The results show that the presence of inclusions not only improves the mechanical properties of rock with defects but also increases the bearing capacity of rock. Circular inclusion has the most obvious effect on improving model strength. The inclusions affect the stress distribution, development of initial crack, change in crack propagation characteristics, and failure mode of rock. In defect models, concentration area of the maximum tensile stress is generated at the top and bottom of defect, and the maximum compressive stress is distributed on the left and right sides of defect. In filled models, the tensile stress and compressive stress are uniformly distributed. Failing mode of defect models is mainly tensile failure, while that of filled models is mainly shear failure.

• 한국해안·해양공학회논문집
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• 제28권5호
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• pp.303-311
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• 2016

낙동강 하구지역에 위치하고 있는 녹산지역과 장유지역에서 채취한 불교란 연약 점성토에 대한 물리적 특성시험과 압밀시험을 수행한 결과 다음과 같은 결론을 얻었다. 낙동강 하구지역 점성토의 주요 점토광물은 Kaolinite, Illite 계열로 분류되었다. 자연함수비는 녹산지역 및 장유지역이 각각 50.4~92.8%, 46.6~99.0%의 범위로 비슷하게 분포하고 있으며, 두 지역 모두 액성한계는 자연함수비($W_n$)보다 낮게 나타났다. 압축지수는 녹산지역이 0.44~1.57의 범위로 분포하고, 장유지역은 0.67~1.94의 범위로 분포하고 있어 녹산지역보다 장유지역이 다소 높게 나타났다. 이차압축지수 역시 장유지역이 0.027~0.092로 녹산지역 0.024~0.075보다 높은 것으로 나타났다. 회귀분석결과 함수비($W_n$)와 압축지수와의 관계는 선형적이며, 초기간극비와 압축지수와의 관계는 $C_c=0.80e_o-0.58$로 나타났다. $C_{\alpha}/C_c$비는 0.03~0.08로 다소 넓은 범위의 값을 나타내었다.