• 해양환경안전학회지
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• 제20권1호
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• pp.11-17
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• 2014

본 연구에서는 연승 수하식 양식시설의 파랑 중 해조류의 꼬임 현상에 영향을 미치는 연승줄의 간격, 계류 블록의 이동에 따른 양식장 형상변화 등을 수리모형실험을 통해 검토하고자 하였다. 실험결과로부터 해조류의 꼬임현상은 연승간격이 감소함에 따라 낮은 파고에서도 발생하였으며, 연승줄 간격이 클수록 보다 큰 파랑조건에서도 해조류 꼬임현상이 발생하지 않는 안정한 상태를 유지하였다. 이는 해조류의 꼬임 현상은 연승간격에 민감하게 영향을 받음을 나타낸다. 또한 블록 중량 및 주기가 길어짐에 따라 전체적으로 계류블록이 이동하기 시작한 임계파고가 커지는 경향을 나타내었다. 입사파랑 조건과 계류 블록 중량을 달리한 실험결과로부터 전면 블록 중량이 3.0 ton에서 8.0 ton으로 증가함에 따라 안정성이 크게 확보되는 결과를, 반대로 후면에서는 블록의 거동이 거의 발생하지 않았다. 이때 전면 계류삭의 최대 장력은 약 3.0 ton/m을 나타내었다.

• 한국전산유체공학회지
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• 제14권2호
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• pp.59-67
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• 2009

An accurate prediction of the bypass flow is of great importance in the VHTR core design concerning the fuel thermal margin. Nevertheless, there has not been much effort in evaluating the amount and the distribution of the core bypass flow. In order to evaluate the behavior and the distribution of the coolant flow, a unit-cell experiment was carried out. Unit-cell is the regular triangular section which is formed by connecting the centers of three hexagonal blocks. Various conditions such as the inlet mass flow rate, block combinations and the size of bypass gap were examined in the experiment. CFD analysis was carried out to analyze detailed characteristics of the flow distribution. Commercial CFD code FLUENT 6.3 was validated by comparing with the experimental results. In addition, SST model and standard k-$\varepsilon$ model were validated. The results of CFD simulation show good agreements with the experimental results. SST model shows better agreement than standard k-$\varepsilon$ model. Results showed that block combinations and the size of the bypass gap have an influence on the bypass flow ratio but the inlet mass flow rate does not.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1405-1407
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• 2009

We prepared polystyrene-b-poly(2-vinyl pyridine) (PSb-P2VP) lamellar films which is hydrophobic block-hydrophilic polyelectrolyte block polymer have 57 kg/mol-b-57 kg/mol. The result of UV-visible absorption spectra supported that effect of poly(ethylene oxide) on the band gap tuning of PS-P2VP photonic gel like salt effect.

• Wind and Structures
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• 제30권5호
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• pp.485-497
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• 2020

A study, using potential water wave theory, is conducted on the oblique water wave motion over two fixed submerged rectangular blocks (breakwaters) placed over a finite step bottom. We have considered infinite and semi-infinite fluid domains. In both domains, the Fourier expansion method is employed to obtain the velocity potentials explicitly in terms of the infinite Fourier series. The unknown coefficients appearing in the velocity potentials are determined by the eigenfunction expansion matching method at the interfaces. The derived velocity potentials are used to compute the hydrodynamic horizontal and vertical forces acting on the submerged blocks for different values of block thickness, gap spacing between the two blocks, and submergence depth of the upper block from the mean free surface. In addition, the wave load on the vertical wall is computed in the case of the semi-infinite fluid domain for different values of blocks width and the incident wave angle. It is observed that the amplitudes of hydrodynamic forces are negligible for larger values of the wavenumber. Furthermore, the upper block experiences a higher hydrodynamic force than the lower block, regardless of the gap spacing, submergence depth, and block thickness.

• Restorative Dentistry and Endodontics
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• 제41권1호
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• pp.37-43
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• 2016

Objectives: The purpose of this study was to compare the marginal and internal fit of nano-composite CAD-CAM restorations. Materials and Methods: A full veneer crown and an mesio-occluso-distal (MOD) inlay cavity, which were prepared on extracted human molars, were used as templates of epoxy resin replicas. The prepared teeth were scanned and CAD-CAM restorations were milled using Lava Ultimate (LU) and experimental nano-composite CAD/CAM blocks (EB) under the same milling parameters. To assess the marginal and internal fit, the restorations were cemented to replicas and were embedded in an acrylic mold for sectioning at 0.5 mm intervals. The measured gap data were pooled according to the block types and measuring points for statistical analysis. Results: Both the block type and measuring point significantly affected gap values, and their interaction was significant (p = 0.000). In crowns and inlays made from the two blocks, gap values were significantly larger in the occlusal area than in the axial area, while gap values in the marginal area were smallest (p < 0.001). Among the blocks, the restorations milled from EB had a significantly larger gap at all measuring points than those milled from LU (p = 0.000). Conclusions: The marginal and internal gaps of the two nano-composite CAD/CAM blocks differed according to the measuring points. Among the internal area of the two nano-composite CAD/CAM restorations, occlusal gap data were significantly larger than axial gap data. The EB crowns and inlays had significantly larger gaps than LU restorations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.261-261
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• 2010

Photonic band gap (PBG) materials have been of great interest due to their potential applications in science and technology. Their applications can be further extended when PBG becomes tunable against various chemical and electrical stimuli. In recent, it was found that tunable photonic band gap materials can be achieved by incorporating stimuli-responsive smart gels into PBG materials. For example, the characteristic volume phase transition of gels in response to the various external stimuli including temperature, pH, ionic strength, solvent compositions and electric field were recently combined with the unique optical properties of photonic crystals to form unprecedented highly responsive optical components. Since these responsive photonic crystals are capable of reversibly converting chemical or electrical energy into characteristic optical signals, they have been considered as a good platform for label-free chemical or biological detection, actuators or optical switches as well as a model system for investigating gel swelling behavior. Herein, we report block copolymer photonic gels self-assembled from polystyrene-b-poly (2-vinyl pyridine) (PS-b-P2VP) block copolymers. In this talk, we are going to demonstrate that selective swelling of lamellar structure can be effectively utilized for fabricating PBG materials with extremely large tunability. Optical properties and their applications will be discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권8호
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• pp.1964-1981
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• 2012

In this paper a reversible data hiding scheme based on histogram shifting of host image blocks is presented. This method attempts to use full available capacity for data embedding by dividing the image into non-overlapping blocks. Applying histogram shifting to each block requires that extra information to be saved as overhead data for each block. This extra information (overhead or bookkeeping information) is used in order to extract payload and recover the block to its original state. A method to eliminate the need for this extra information is also introduced. This method uses maximum gap that exists between histogram bins for finding the value of pixels that was used for embedding in sender side. Experimental results show that the proposed method provides higher embedding capacity than the original reversible data hiding based on histogram shifting method and its improved versions in the current literature while it maintains the quality of marked image at an acceptable level.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.342-349
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• 2012

고 에너지 물질 초음속 화염의 전파에 대한 gap의 효과를 이해하기 위하여 characteristic acoustic impedance theory와 수치해석이 적용되었다. 여러 개의 gap이 위치하고 있는 화약의 한 끝에 초음속 화염이 발생되도록 하여, 여러 gap에 전파되나가는 연속적인 화염에 대한 이해를 시도 하였다. 현재의 높은 차원의 다물질 해석은 SNU-Hydropack code에 포함되어 있는 복잡한 경계면 추적 알고리즘의 타당성에 대한 의미 있는 결과를 제시했다.

• 한국전자파학회논문지
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• 제12권3호
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• pp.432-438
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• 2001

본 논문은 Defected Ground Structure(DGS)를 DC block에 적용한 후 DC block의 부분인 λ/4-결합 선로의 간격과 길이의 변화를 EM 시뮬레이션과 실제 제작을 통하여 알라보았다. 그 결과 일반적인 DC block을 사용할때와 동일 출력 조건하에서 DGS 구조의 DC block의 λ/4-결합선로사이의 간격이 0.1 mm에서 0.46 mm로 0.36 mm만큼 늘어나고λ/4-결합 선로의 길이는 71.7 mm에서 13.32 mm로 4.5 mm만큼 줄어드는 것을 알 수 있었다. 또한 Blocking 캐패시터, 일반적인 DC block, DGS 구조의 DC block을 사용하는 세 종류의 전력증폭기를 제작한 후 특성을 확인해 보았다. 먼저 각 증폭기의 산란 파라미커 특성을 살펴본 결과 3.2$\pm$0.05 GHz의 주파수 대역에서 세 증폭기 모두 유사한 이득 특성과 산란 파라미터 특성을 갖음을 알수 있었다. 그리고 3.2 GHz의 CW 신호를 인가하여 주신호의 출력 전력이 25dBm 일 때 하모닉 특성을 스펙트럼 분석기로 분석한 결과 캐패시티를 사용시에는 주신호와 2차 하모닉 성분과의 차이가 -44.83dBc 일반적인 DC block과 DGS DC block 사용시에는 -66.84와 -64.33 dBc로서 일반적인 DC block 사용시와 DGS block 사용시에 하모닉 특성이 거의 일치함을 확인하였다.

• Tribology and Lubricants
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• 제20권4호
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• pp.209-217
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• 2004

Lubrication characteristics between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump play an important role in volumetric efficiency and durability of pump. In this paper, a finite element method is presented for the computation of the pressure distribution between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump. Also, a Runge-Kutta method is applied to simulate the cylinder block dynamics of three-degrees of freedom motion. From the results of computation, we can draw two major conclusions. One is related to the fluid film characteristics between a cylinder block and a valve plate and the other is related to the average leakage that is determined by the pressure gradient and the clearance near the discharge port. The numerical results of cylinder block dynamics were compared with the experimental results using eddy-current type gap sensors those are fixed at a pump housing.