• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.182-190
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• 2021

Computational simulations of turbulent flows around a model ship have been performed to investigate an influence of TVD schemes on the accuracy of advective terms associated with ship resistances. Several TVD schemes including upwind, second-order upwind, vanLeer, and QUICK as well as a nonTVD linear scheme were studied by examining temporal and spatial characteristics of accuracy transition in adjacent cells to the hull. Even though vanLeer scheme was the most accurate among TVD schemes in both structured and unstructured grid systems, the ratio of accuracy switch from 2^nd order to 1^st order in vanLeer scheme was considerable compared with the 2^nd order linear scheme. Also, the accuracy transition was observed to be overally scattered in the unstructured grid while the accuracy transition in the structured grid appeared relatively clustered. It concluded that TVD schemes had to be carefully used in computational simulations of turbulent flows around a model ship due to the loss of accuracy despite its attraction of numerical stability.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.261-265
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• 2011

An adaptive wavelet transformation method with high order accuracy is proposed to allow efficient and accurate flow computations. While maintaining the original numerical accuracy of a conventional solver, the scheme offers efficient numerical procedure by using only adapted dataset. The main algorithm includes 3rd order wavelet decomposition and thresholding procedure. After the wavelet transformation, 3rd order of spatial and temporal accurate high order interpolation schemes are executed only at the points of the adapted dataset. For the other points, high order of interpolation method is utilized for residual evaluation. This high order interpolation scheme with high order adaptive wavelet transformation was applied to unsteady Euler flow computations. Through these processes, both computational efficiency and numerical accuracy are validated even in case of high order accurate unsteady flow computations.

• Korean Journal of Clinical Pharmacy
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• v.17 no.1
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• pp.1-5
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• 2007

A computerized chemotherapy order system (CCOS) was developed to improve the accuracy and efficiency of prescriptions for pharmacy medication scheduling at a teaching hospital, Asan Medical Center, Seoul, Korea. We evaluated the system by comparing prescriptions before and after the implementation of the system and by analyzing the effects of the system on dosing accuracy (only against 5-FU), prescription change, overdoses above maximum limit and medication disposal in non computerized program group (control group) and CCOS group. In terms of dosing accuracy, prescription error rate (%) was significantly decreased in CCOS groups compared with the control group. The rate of prescription changes was also significantly decreased in CCOS groups. Regarding overdoses above maximum limit, we found that there was no prescription order exceeding the dosage limit in CCOS groups in contrast to significant overdoses in control group. In terms of medication disposal, there was no significant difference between 2 groups. We suggest that the computerized chemotherapy order system for chemotherapy may bean important and useful tool for minimizing prescribing errors in the hospitals.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.429-438
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• 2017

Cranke-Nicolson scheme in native OpenFOAM source libraries was not able to provide 2nd order temporal accuracy of velocity and pressure since the volume flux of convective nonlinear terms was 1st accurate in time. In the present study the simplest way of getting the volume flux with 2nd order accuracy was proposed by using old fluxes. A possible numerical instability originated from an explicit estimation of volume fluxes could be handled by introducing a weighting factor which was determined by observing the ratio of the finally corrected volume flux to the intermediate volume flux at the previous step. The new calculation of volume fluxes was able to provide temporally accurate velocity and pressure with 2nd order. The improvement of temporal accuracy was validated by performing numerical simulations of 2D Taylor-Green vortex of which an exact solution was known and 2D vortex shedding from a circular cylinder.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.99-106
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• 2005

Performance of first, second and third order accurate methods for calculation of in viscid fluxes in fluid flow governing equations are investigated here. For the purpose, an upwind method based on Roe's scheme is used to solve 2-dimensional Euler equations. To increase the accuracy of the method two different schemes are applied. The first one is a second and third order upwind-based algorithm with the MUSCL extrapolation Van Leer (1979), based on primitive variables. The other one is an upwind-based algorithm with the Chakravarthy extrapolation to the fluxes of mass, momentum and energy. The results show that the thickness of shock layer in the third order accuracy is less than its value in second order. Moreover, applying limiter eliminates the oscillations near the shock while increases the thickness of shock layer especially in MUSCL method using Van Albada limiter.

• Journal of the Korea Safety Management & Science
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• v.13 no.2
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• pp.169-177
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• 2011

In this paper, the author devised new decision recommendation ordering method of items attributed by age to improve accuracy of recommender system. In conventional recommendation system, recommendation order is decided by high order of preference prediction. However, in this paper, recommendation accuracy is improved by decision recommendation order method that reflect age attribute of target customer and neighborhood in preference prediction. By applying decision recommendation order method to recommender system, recommendation accuracy is improved more than conventional ordering method of recommendation.

• Journal of the Korean Data and Information Science Society
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• v.11 no.1
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• pp.103-110
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• 2000

Suppose that there is a population of hidden objects of which the total number N is unknown. From such data, we derive second-order approximations to the stopping time with fixed proportional accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2607-2615
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• 2011

The purpose of this study is to increase efficiency and accuracy in operation of CPR(Cardiopulmonary Resuscitation) through comparing accuracy in CPR between group with verbal order and group with non-verbal order given carrying out CPR. This study performed convenience sampling targeting 62 students(31 people for group with non-verbal order, 31 people for group with verbal order) at university where is located in G Province. Survey period was carried out from October 7, 2010 to October 21. Analytical method was made by using SPSS WIN(Version 12.0). As a result of research, the group with non-verbal order was indicated to be higher in accuracy of CPR on artificial respiration and chest compression in several spheres than the group with verbal order. Based on this, the non-verbal order method needs to try to be applied to performing education and skills of CPR in the future. And, even a continuous research is needed on effectiveness between verbal order method and non-verbal order method in an emergency situation.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.452-460
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• 2005

Based on an introduced optimal trajectory planning method, this paper mainly deals with the accuracy analysis during the function approximation process of the optimal trajectory planning method. The basis functions are composed of Hermit polynomials and Fourier series to improve the approximation accuracy. Since the approximation accuracy is affected by the given orders of each basis function, the accuracy of the optimal solution is examined by changing the combinations of the orders of Hermit polynomials and Fourier series as the approximation basis functions. As a result, it is found that the proper approximation basis functions are the $5^{th}$ order Hermit polynomials and the $7^{th}-10^{th}$ order of Fourier series.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.410-415
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• 2001

An analytical and numerical examination of second-order fractional-step methods and boundary condition for the incompressible Navier-Stokes equations is presented. In this study, the compatibility condition for pressure Poisson equation and its boundary conditions, stability, and numerical accuracy of canonical fractional-step methods has been investigated. It has been found that satisfaction of compatibility condition depends on tentative velocity and pressure boundary condition, and that the compatible boundary conditions for type D method and approximately compatible boundary conditions for type P method are proper for divergence-free velocity for type D and approximately divergence-free for type P method. Instability of canonical fractional-step methods is induced by approximation of implicit viscous term with explicit terms, and the stability criteria have been founded with simple model problems and numerical experiments of cavity flow and Taylor vortex flow. The numerical accuracy of canonical fractional-step methods with its consistent boundary conditions shows second-order accuracy except $D_{MM}$ condition, which make approximately first-order accuracy due to weak coupling of boundary conditions.