• Fashion & Textile Research Journal
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• 제3권2호
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• pp.168-173
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• 2001

In order to overcome the disadvantage of the conventional two bath dyeing method of wool/cotton blends, it had prompted significant effort to the development of the one bath dyeing method which can accomplish savings in energy, water usage and time. To improve the dyeability of cotton toward direct dyes in a non-electrolytic and acidic dyebath, cotton component was pretreated with cationizing agent containing chlorohydrine group in aqueous solution of sodium hydroxide. This study was carried out to investigate almost equal color strength between wool component and cationized cotton component when wool/cationized cotton blends was dyed with acid dye/direct dye by the one bath two step method in a non-electrolytic and acidic dyebath.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.531-546
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• 2011

The backward differentiation formula (BDF) method is applied to a three-dimensional reactor kinetics calculation for efficient yet accurate transient analysis with adaptive time step control. The coarse mesh finite difference (CMFD) formulation is used for an efficient implementation of the BDF method that does not require excessive memory to store old information from previous time steps. An iterative scheme to update the nodal coupling coefficients through higher order local nodal solutions is established in order to make it possible to store only node average fluxes of the previous five time points. An adaptive time step control method is derived using two order solutions, the fifth and the fourth order BDF solutions, which provide an estimate of the solution error at the current time point. The performance of the BDF- and CMFD-based spatial kinetics calculation and the adaptive time step control scheme is examined with the NEACRP control rod ejection and rod withdrawal benchmark problems. The accuracy is first assessed by comparing the BDF-based results with those of the Crank-Nicholson method with an exponential transform. The effectiveness of the adaptive time step control is then assessed in terms of the possible computing time reduction in producing sufficiently accurate solutions that meet the desired solution fidelity.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제13권3호
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• pp.305-319
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• 2000

Numerical solution lot frictional contact problems of nonlinearly deformable bodies having large deformation is presented. The contact conditions on the possible contact points are expressed by using the contact error vector, and the iterative scheme is used to reduce the contact error vector monotonically toward zero. At each iteration the solution consists of two steps : The first step is to revise the contact force by using the contact error vector given by the previous geometry, and the second step is to compute the displacement and the contact error vector by solving the equilibrium equation with the contact force given at the first step. Convergence of the iterative scheme to the correct solution is analyzed, and the numerical simulations we performed with a rigid-plastic membrane and a nonlinear elastic beam.

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.235-244
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• 1998

The solutions of orbital maneuver problem using the sliding mode control in the presence of the erath gravitational perturbations is obtained. Especially, the optimization of consuming fuel for maneuver is performed. The impulsive solution to Lambert's problem using the combined equation method to minimize total ${\Delta}V is used for the desired orbit and the maneuver times. Two-step sliding mode control method is introduced for satisfying the boundary conditions of finite-thrust rendezvous problem at the end of maneuver time. Using the new approach to the orbit maneuver problem, two-step sliding mode control, orbit maneuvers are processed. The solutions to a rendezvous using the optimal control are obtained, and they are compared to the results by two-step sliding control.According to the new approach for orbit maneuver, the thrust-coast-thrust type controller is obtained to make satellite to track desired Lambert's orbit, and the total ${\Delta}V$ required for maneuver is resonable in comparison with the impulsive solution to Lambert's problem. The final state variables, also are close to the boundary conditions at the end of maneuver times.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제14권3호
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• pp.175-187
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• 2010

This paper presents the numerical valuation of the two-asset step-down equitylinked securities (ELS) option by using the operator-splitting method (OSM). The ELS is one of the most popular financial options. The value of ELS option can be modeled by a modified Black-Scholes partial differential equation. However, regardless of whether there is a closedform solution, it is difficult and not efficient to evaluate the solution because such a solution would be represented by multiple integrations. Thus, a fast and accurate numerical algorithm is needed to value the price of the ELS option. This paper uses a finite difference method to discretize the governing equation and applies the OSM to solve the resulting discrete equations. The OSM is very robust and accurate in evaluating finite difference discretizations. We provide a detailed numerical algorithm and computational results showing the performance of the method for two underlying asset option pricing problems such as cash-or-nothing and stepdown ELS. Final option value of two-asset step-down ELS is obtained by a weighted average value using probability which is estimated by performing a MC simulation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제17권3호
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• pp.102-108
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• 2018

The objective of this study is to develop the mechanical properties of an AlSiCu aluminum alloy using the two-step solution heat treatment. The microstructure of the gravity casting specimen represents a typical dendrite structure with a secondary dendrite arm spacing (SDAS) of 40 um. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases is generated. The eutectic Si phases are fragmented and globularized with the solution heat treatment. The $Al_2Cu$ intermetallic phase is also resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ may be an optimal condition to enhance the mechanical properties of the AlSiCu aluminum alloy.

• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.9-18
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• 1999

The present study is aimed to investigate flow characteristics of two-dimensional backward-fac-ing step by numerical approach. A convection conservation difference scheme based upon SOLA algorithm is used for the solution of the two-dimensional incompressible Navier-Stokes equations to simulate the laminar transitional and trubulent flow conditions at which the experimental data can be available for the backlward-facing step. The twenty kinds of reynolds number are used for the calculations. In an effort to demonstrate that the reported solutions are dependent on the mesh refinement computations are performed on seven different meshes of uniformly increasing refinement. also to investigate the result of inflow dependence two kinds of the inflow profile are chosen for the laminar flow. Irregular grid is adopted to minimize the errors on the satis-faction fo the discretized continuity. As criterion of benchmarking the result of numerical simula-tion reattachment lengthis used for the selected Reynolds numbers. The results of the present study prove the fact that the numerical predictions agree well with the experimental data and the flow characteristics are shown at the backward-facing step.

• Computational Structural Engineering
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• 제8권4호
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• pp.65-74
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• 1995

Direct method developed for the inelastic analysis of planar frames subjected to monotonic loads is extended to cyclic loads. Two frame elements for Direct Method(inelastic truss and inelastic beam) are developed. The accuracy and reliability of the preposed method is verified by comparing the analysis results of example with step-by-step analysis. Direct Method is superior to Step-by-step analysis in view of reliability of solution and analysis cost.

• Textile Coloration and Finishing
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• 제12권1호
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• pp.44-51
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• 2000

The conventional one bath exhaust dyeing system of nylon]/cotton blends with acid dye/direct dye involves a lot of neutral salt which affect dyeability of acid dyes. Because of conventional one bath exhaust dyeing system of nylonl/cotton blends with acid dye/direct dye needs acid dyes adjusted at a neutral liquor, suitable acid dye is limited. To improve dyeing property of nylon/cotton blends, cotton component was pretreated with cationizing agent containing chlorohydrine group in aqueous solution of sodium hydroxide. This study was carried out to investigate dyeing possibilities of nylon/cationized cotton blends with acid dye/direct dye in a non-neutral salt dyebath by one bath two step method. The concentration of direct dye was 1.0%, 0.7%, 0.3%o.w.f. respectively at a non, 1%, 3%owf of reserving agent for being almost equal color strength between nylon and 3% cationized cotton when nylon/3% cationized cotton blends was dyed with acid dye/direct dye at concentration of acid dye(1%o.w.f.) by one bath two step method.

• Nuclear Engineering and Technology
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• 제41권7호
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• pp.885-892
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• 2009

This manuscript will discuss a numerical method where the six equations of two-phase flow, the solid heat conduction equations, and the two equations that describe neutron diffusion and precursor concentration are solved together in a tightly coupled, nonlinear fashion for a simplified model of a nuclear reactor core. This approach has two important advantages. The first advantage is a higher level of accuracy. Because the equations are solved together in a single nonlinear system, the solution is more accurate than the traditional "operator split" approach where the two-phase flow equations are solved first, the heat conduction is solved second and the neutron diffusion is solved third, limiting the temporal accuracy to $1^{st}$ order because the nonlinear coupling between the physics is handled explicitly. The second advantage of the method described in this manuscript is that the time step control in the fully implicit system can be based on the timescale of the solution rather than a stability-based time step restriction like the material Courant limit required of operator-split methods. In this work, a pilot code was used which employs this tightly coupled, fully implicit method to simulate a reactor core. Results are presented from a simulated control rod movement which show $2^{nd}$ order accuracy in time. Also described in this paper is a simulated rod ejection demonstrating how the fastest timescale of the problem can change between the state variables of neutronics, conduction and two-phase flow during the course of a transient.