• Composites Research
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• v.33 no.3
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• pp.169-175
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• 2020

The compression and tension test were performed to evaluate the stiffnesses of the conical composite lattice structures and results of test were compared with finite element analysis results. Because of difficulty to perform simple tension and compression test due to conical shape, suitable specimens and jig for test were made. Subelements extracted from the structure were prepared for compression test. Compression test of subelement was performed and compressive strains in fiber direction were measured. Compressive stiffness of the helical rib was verified by finite element analysis results. For stiffness of hoop rib, hoop ring specimens were extracted from the structure. Tension test of hoop ring specimen was performed to apply bending deformation to hoop rib. Stiffness of hoop rib was verified by finite element model considering various fiber volume fraction in thickness direction.

• Journal of Ocean Engineering and Technology
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• v.34 no.1
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• pp.19-25
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• 2020

This paper proposes the optimal shape of an LNG fuel tank with a lattice pressure vessel (LPV) design for a tugboat. The LPV is a Type C tank with a design philosophy of "design by analysis," which facilitates greater variability of shape compared with other traditional Type C tanks. Further, compared with conventional cylindrical fuel tanks, the LPV provides better volumetric efficiency. Considering the shape of a fuel tank room, a trapezoidal shape of the LPV is concluded as the most optimal design. This study performs two major analyses of the LPV: structural and heat transfer analyses. First, a design procedure of the LPV based on structural analyses is elaborated. The finite element method is used for the analyses. Furthermore, the results guarantee that the maximum stresses by applied loads do not exceed an allowable stress limitation. Second, the heat transfer analysis of the LPV is conducted. LNG boil-off gas generation is analyzed based on various insulation materials and the degree of acuum.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.122-131
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• 2011

In this paper, the design and analysis of a reconfigurable modular structure, which reforms itself according to the change of the environment and realize appropriate forms and motions, are dealt with. This modular is a free structure from the restrictions with constraints about fixed environment and has various forms and motions by combining units. The form of this unit has a shape of a square with 7 centimeters side each, and has a structure which can be combined in a chain-shape or a lattice-shape. Additionally, The structure has a mobility by being equipped with wheels so that it can be combined for itself. In this paper, all the wireless controllers, sensor system, and communicating method between modules according to module structures were suggested and transformation method to be transformed to shape of snakes, caterpillars were presented. Moreover, simulations for each method were performed to show the validity of the motions including motor torque analysis. All the motions suggested were realized and experimented, whereby the availability of the designed mechanism and algorithm was verified with the result of experiments.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.57-64
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• 2022

A study on propllers for unmaned aerial vehicles is conducted using the open softwares. Since the shape of the propeller is closely related to the thurst characteristics of the propulsion system, adopting an appropriate propeller will significantly reflect stable aerodynamic performances. In this study, propellers for unmanned aerial vehicles were modeled by using OpenVSP and Propel for comparison, the thrust characteristics according to the number of blades and the diameter of the propeller were analyzed. In addition, the tendency of thrust characteristics according to various propeller pitch angles was confirmed. Based on the analysis results of this study, the applicability of the propeller shape to the design of the unmanned aerial vehicle was confirmed. It is shownthat the analysis results of this study can be utilized when modeling the propeller shape in research such as a conceptual design of unmanned aerial vehicle. In this case, it should be noted that OpenVSP does not involve the viscous effect of air.

• The Pure and Applied Mathematics
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• v.22 no.3
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• pp.245-261
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• 2015

The notion of a parabolically semistandard tableau is a generalisation of Young tableau, which explains combinatorial aspect of various Howe dualities of type A. We prove a Jacobi-Trudi type formula for the character of parabolically semistandard tableaux of a given generalised partition shape by using non-intersecting lattice paths.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.623-628
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• 2002

A meshfree formulation for the calculation of energy band structure is presented. The conventional meshfree shape function is modified to handle the periodicity of Bravais lattice, and applied to the calculation of real-space electronic-band structure. Numerical examples include the Kronig-Penney model potential and the empirical pseudopotentials of diamond and zinc-blonde semiconductors. Results demonstrate that the meshfree method be a promising one as a real-space technique for the calculations of diverse physical band structures.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.251-255
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• 1999

Local field distribution in the mixed state of type II superconductors has been numerically calculated and compared with $^{11}$B NMR spectra for YNi$_2B_2C$ single crystals. We find that only small distortion of vortex positions from the perfect lattice points is enough to smear out the low frequency shoulder. As the vortices are further distorted, the line shape changes from an asymmetric shape with a high frequency tail to a symmetric Gaussian line shape. It is found that the second moment of the field distribution has a major contribution from the high frequency tail. Consequently, a linewidth of the full width at half maximum calculated from the second moment assuming for a Gaussian line shape is overestimated.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.210-217
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• 2011

Recently, research on evaluating thermal comfort by using CFD has been vigorously active. This research evaluates not only distribution of temperature and air flow analysing but also thermal comfort in indoor space by applying human model. But research of human model's shape, Grid characteristic and turbulence model has not yet been studied. In this paper, human model's shape, physical characteristic of variable Grid, and change of turbulence model has been studies by CFD. In this study. FLUENT is used for analysis and PMV(predicted Mean Vote), PPD(Predicted Percentage Dissatisfied) and EHT(Equivalent Homogeneous Temperature} are used for evaluation and comparison of thermal comfort. As a result, it shows that shape of CSP and lattice features does not affect on global flow field or evaluation on PMV, PPD. However, it demonstrates more precise result from evaluation of thermal comfort by equivalent temperature when it used detailed human model considering prism grid.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.226-227
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• 2003

광자 크리스탈 (Photonic Crystals)은 서로 다른 유전체의 주기적인 구조로 이루어져 있으며, 전자기파가 특정한 주파수 범위에서 전파하지 못하고 차단되는 영역인 광자 밴드갭 (Photonic Band Gap)이 존재한다. 이러한 광자 밴드갭의 존재로 인하여 빛의 흐름을 조절할 수 있다는 점 때문에 반사거울, 휘어진 도파로(bent waveguide), 레이저, 채널 드롭핑 필터(channel dropping filter) 등 여러 가지 다양한 분야에 응용될 수 있다. (중략)

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.11
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• pp.1405-1416
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• 1995

An effective algorithm for implementation of unmanned surveillance system which detects moving object from image sequences, predicts the direction of it, and drives the camera in real time is proposed. Outputs of proposed algorithm are coordinates of location of moving object, and they are converted to the values according to camera model. As a pre- processing, extraction of moving object and shape discrimination are performed. Existence of the moving object or scene change is detected by computing the temporal derivatives of consecutive two or more images in a sequence, and this result of derivatives is combined with the edge map from one original gray level image to obtain the position of moving object. Shape discri-mination(Target identification) is performed by analysis of distribution of projection profiles in x and y directions. To reduce the prediction error due to the fact that the motion cha- racteristic of walking man may have an abrupt change of moving direction, an order adaptive lattice structured linear predictor is proposed.