• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.318-321
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• 2003

In order to generate the extrusion die surface of non-symmetric H- and U-shaped sections, an automatic surface construction method based on B-spline surface and scalar field theory is proposed in this study. The isothermal lines and stream lines designed in the scalar field are introduced to find the control points which are used in constructing B-spline surfaces. Intersected points between the isothermal lines and stream lines are used to construct B-spline surfaces. The inlet and outlet profiles are precisely described with B-spline curves by using the centripetal method for uniform parameterization. The extrusion die surface is generated by using the cubic curve interpolation in the u- and v-directions. A quantitative measure for the control of surface is suggested by introducing the tangential vectors at the inlet and outlet sections.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.211-217
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• 2009

The numerical program has been developed for the purpose of the complicate geometries application using CIP method. The non-staggered, non-orthogonal, and unstructured grid system can be also used for the various geometries in the program. For validating CIP solver, the lid-driven cavity flow and solitary wave propagation flow are carried out. Test results show a good agreement with the verified results. The dynamic solver was used for the behavior of moving body. Interface process between the two solvers is introduced. The research was performed on the flow problem around torpedo and log and the flow problem in a tank in order to analyze the three phase flow problem Although the comparison to the verified results was not quantitatively performed, the trend of the results was reasonable.

• 한국정밀공학회지
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• 제17권6호
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• pp.199-209
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• 2000

Particles reinforced MMCs have higher specific modulus, higher specific strength, better properties at elevated temperatures and better wear resistance than monolithic metals. But the coefficient of thermal expansion(CTE) of Al6061 is 5 times larger than that of SiCp. The discrepancy of CTE makes some residual stresses inside of MMCs. This work investigates Si$C_p$/Al6061 composites at high temperatures in the microscopic view by three-dimensional elasto-plastic finite element analyses and compares the analytical results with the experimental ones. The theoretical model is not able to consider the nonuniform shape of particle. So the shape of particle is assumed to be perfect global shape. And also particle distribution is not homogeneous in experimental specimen. It is assumed to be homogeneous in simulation model. The type of particle distribution is face-centered cubic array(FCC array). Furthermore, non-homogeneous distribution is modeled by combination of several volume fractions.

• Wind and Structures
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• 제12권1호
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• pp.77-88
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• 2009

A pulsed impinging jet is used to simulate the gust front of a thunderstorm downburst. This work concentrates on investigating the peak transient loading conditions on a 30 mm cubic model submerged in the simulated downburst flow. The outflow induced pressures are recorded and compared to those from boundary layer and steady wall jet flow. Given that peak winds associated with downburst events are often located in the transient frontal region, the importance of using a non-stationary modelling technique for assessing peak downburst wind loads is highlighted with comparisons.

• International Journal of Precision Engineering and Manufacturing
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• 제3권1호
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• pp.49-56
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• 2002

The Z-map is a special farm of discrete non-parametric representation in which the height values at grid points on the xy-plane are stored as a 2D array z[ij]. While the z-map is the simplest farm of representing sculptured surfaces and is the most versatile scheme for modeling non-parametric objects, its practical application in industry (eg, tool-path generation) has aroused much controversy over its weaknesses, namely its inaccuracy, singularity (eg, vertical wall), and some excessive storage needs. Much research or the application of the z-map can be found in various articles, however, research on the systematic analysis of sculptured surface shape representation via the z-map model is rather rare. Presented in this paper are the following: shape modeling power of the simple z-map model, exact (within tolerance) z-map representation of sculptured surfaces which have some feature-shapes such as vertical-walls and real sharp-edges by adopting some complementary z-map models, and some application examples.

• 대한산업공학회지
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• 제22권4호
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• pp.741-751
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• 1996

The three dimensional cutting-stock problem is to maximize the total value of pieces which are smaller cubics-cut from a original cubic stock. This paper suggests a method to maximize the total value of different size cut pieces using the orthogonal non-guillotine cut technique. We first formulated a zero-one integer programming, then developed a Lagrangeon relaxation method far the problem. The solutions were given by using a brunch-end-bound technique associates with Lagrangean relaxation, which guarantees an optimal solution.

• Computers and Concrete
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• 제22권6호
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• pp.501-514
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• 2018

The paper presents the thermo-mechanically induced non-linear response of multiwall carbon nanotube reinforced laminated composite beam (MWCNTRCB) supported by elastic foundation using higher order shear deformation theory and von-Karman non-linear kinematics. The elastic properties of MWCNT reinforced composites are evaluated using Halpin-Tsai model by considering MWCNT reinforced polymer matrix as new matrix by dispersing in it and then reinforced with E-glass fiber in an orthotropic manner. The laminated beam is supported by Pasternak elastic foundation with Winkler cubic nonlinearity. A generalized static analysis is formulated using finite element method (FEM) through principle of minimum potential energy approach.

• 대한환경공학회지
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• 제34권8호
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• pp.557-565
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• 2012

본 연구는 초기 강우시 축사주변 지역을 대상으로 강우 유출수와 함께 배출되는 비점오염물질의 특성에 대하여 분석하였다. 강우량에 따른 유출특성 중 수리 수문-농도곡선 분석결과 유량이 증가함에 따라 농도가 점점 증가하는 경향을 보였으며, 첨두 유량이 발생한 후에는 급격히 감소하였다. 축사주변지역에서의 유량평균가중농도(EMCs)는 TSS EMC 146.80~424.95 mg/L, COD EMC 11.64~55.66 mg/L, BOD EMC 6.66~49.88 mg/L, T-N EMC 7.650~43.825 mg/L, T-P EMC 0.711~3.855 mg/L였다. 또한 TSS와 BOD, COD, T-N 그리고 T-P의 오염물질별 상관계수를 분석해보면 0.53~0.95를 나타내었으며, 정량화된 EMCs와 강우 유출량($m^3$) 등 다른 요소들간의 회귀분석을 통한 상관관계를 분석한 결과는 3차 다항식으로 설명되었으며, 물질별 결정계수는 TSS 0.767~0.835, T-N은 0.773~0.901로 비교적 높게 분석되었다, 이는 두 항목간 상관관계가 높다는 것을 의미하며, 강우유출량이 많을수록 EMC가 증가한다는 것을 의미한다. 이는 추후 강우유출량을 모니터링하면 유출량에 따른 유량가중평균농도를 예측할 수 있을 것으로 판단된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1901-1904
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• 2003

MPC or model predictive control is representative of control methods which are able to handle physical constraints. Closed-loop stability can therefore be ensured only locally in the presence of constraints of this type. However, if the system is neutrally stable, and if the constraints are imposed only on the input, global aymptotic stability can be obtained; until recently, use of infinite horizons was thought to be inevitable in this case. A globally stabilizing finite-horizon MPC has lately been suggested for neutrally stable continuous-time systems using a non-quadratic terminal cost which consists of cubic as well as quadratic functions of the state. The idea originates from the so-called small gain control, where the global stability is proven using a non-quadratic Lyapunov function. The newly developed finite-horizon MPC employs the same form of Lyapunov function as the terminal cost, thereby leading to global asymptotic stability. A discrete-time version of this finite-horizon MPC is presented here. The proposed MPC algorithm is also coded using an SQP (Sequential Quadratic Programming) algorithm, and simulation results are given to show the effectiveness of the method.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.301-314
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• 2015

Aiming at accurately distinguishing modeless component and natural vibration mode terms from data series of nonlinear and non-stationary processes, such as Vortex-Induced Vibration (VIV), a new empirical mode decomposition method has been developed in this paper. The key innovation related to this technique concerns the method to decompose modeless component from non-stationary process, characterized by a predetermined 'maximum intrinsic time window' and cubic spline. The introduction of conceptual modeless component eliminates the requirement of using spurious harmonics to represent nonlinear and non-stationary signals and then makes subsequent modal identification more accurate and meaningful. It neither slacks the vibration power of natural modes nor aggrandizes spurious energy of modeless component. The scale of the maximum intrinsic time window has been well designed, avoiding energy aliasing in data processing. Finally, it has been applied to analyze data series of vortex-induced vibration processes. Taking advantage of this newly introduced empirical decomposition method and mode identification technique, the vibration analysis about vortex-induced vibration becomes more meaningful.