• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.22-28
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• 2013

It is important to begin left ventricular assist device (LVAD) treatment at appropriate time for heart failure patients who expect cardiac recovery after the therapy. In order to predict the optimal timing of LVAD implantation, we predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used LVAD-implanted cardiovascular system model which consist of 8 Windkessel compartments for the simulation study. The time-varying compliance theory was used to simulate ventricular pumping function in the model. The ventricular systolic dysfunction was implemented by increasing the end-systolic ventricular compliance. Using the mathematical model, we predicted cardiac responses such as left ventricular peak pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous and pulsatile LVAD. Left ventricular peak pressure, which indicates the ventricular loading condition, decreased maximally at the 1st level heart-failure under pulsatile LVAD therapy and 2nd level heart-failure under continuous LVAD therapy. We conclude that optimal timing for pulsatile LVAD treatment is 1st level heart-failure and for continuous LVAD treatment is 2nd level heart-failure when considering LVAD treatment as "bridge to recovery".

• Journal of Industrial Technology
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• v.38 no.1
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• pp.9-13
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• 2018

FRP(Fiber Reinforced Plastic) ships are easy to manufacture and repair. Also they are more durable and cheaper than steel wires and neck lines. Therefore FRP ships are widely used in small ships. In Korea, the amount of waste FRP ships is increasing. It is expected that a large amount of waste FRP ships will be generated. Waste FRP ships are emerging as a social problem, such as the difficulty in preserving the marine environment. To improve this, a waste FRP ship melting process system has been developed. In order to construct an effective waste FRP ship processing system, it is necessary to study the treatment facilities location problem. In this paper, we suggest mathematical model to solve optimal location problem of waste FRP Ships and discuss on results by applying it to nine regions selected as candidates for treatment facilities.

• Education of Primary School Mathematics
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• v.8 no.2 s.16
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• pp.115-128
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• 2004

This study is based on the observation of preceded research that problem based instruction is effective in acquiring advanced mathematical knowledge but is not effective for raising mathematical achievement. The treatment of this experimental research is named 'revised problem based instruction' because it adds an expository session to the original problem based instruction. Then the purpose of this study is to make sure that revised problem based instruction is effective in raising mathematical achievement of underachievers.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.2
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• pp.263-267
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• 2001

Beef samples of loin eye area from New Zealand, USA and three quality grades of Hanwoo were analyzed using near infrared spectrophotometer with reference values from laboratory optical Chromameter to determine effective spectrum range and mathematical treatment for determination of color values. $R^2s$ of prediction models were not improved much by calibrating with whole light range (400~2500 nm) compared to using visible range (400~1100 nm). Standard errors of calibration and prediction were influenced by possible bias due to sampling non-homogeneous sample sources. However, partial differentiation in the first order was more stable against sampling biases than second derivatives of the spectra. Lightness value was little different among the five sample sources of beef. Beef samples from USA were brighter and more reddish than beefs of Hanwoo or from New Zealand (p<0.05). Yellowness of USA beef was the highest followed by beef from New Zealand, which was also higher than Hanwoo beefs of three quality grades (p<0.05).

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.845-862
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• 2010

In a recent paper, M.A. Noor et al. (Hindawi publishing corporation, Mathematical Problems in Engineering, Volume 2008, Article ID 696734, 11 pages, doi:10.1155/2008/696734) proposed the variational homotopy perturbation method (VHPM) for solving higher dimentional initial boundary value problems. In this paper, we consider the proposed method for analytic treatment of the linear and nonlinear ordinary differential equations, homogeneous or inhomogeneous. The results reveal that the proposed method is very effective and simple and can be applied for other linear and nonlinear problems in mathematical.

• The Mathematical Education
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• v.41 no.1
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• pp.45-58
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• 2002

This study was conducted to investigate the gender-related effects of two instructional programs on spatial visualization skills of ninth grade students. Two instructional programs were developed for this study: a web-based virtual reality program and a paper-based program. 194 ninth graders from two middle schools in Seoul participated in this study. Six classes were divided into experimental groups and control groups. The Middle Grades Mathematics Projects (MGMP) Spatial Visualization Test was used to measure spatial visualization skills. The data analysis indicated that both the web-based and paper-based programs were effective to improve spatial visualization skills to treatment groups. Although boys'test mean scores were higher than girls' in the pretest, when deleting the effect of covariance of pretest, there were no statistical significance in the post-test. Girls in the treatment groups favored the paper-based spatial visualization program. These results imply that spatial training may benefit girls' performance more than that of boys and mode of instructional programs can create gender-related differences regarding spatial visualization skills.

• Nonlinear Functional Analysis and Applications
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• v.26 no.3
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• pp.629-648
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• 2021

In this paper, we study a within-host mathematical model of HCV infection and carry out mathematical analysis of the global dynamics and bifurcations of the model in different parameter regimes. We explore the effect of reverse transcriptase inhibitors (RTI) on spontaneous HCV clearance. The model can produce all clinically observed patient profiles for realistic parameter values; it can also be used to estimate the efficacy and/or duration of treatment that will ensure permanent cure for a particular patient. From the results of the model, we infer possible measures that could be implemented in order to reduce the number of infected individuals.

• Communications of the Korean Mathematical Society
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• v.12 no.1
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• pp.177-192
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• 1997

The basic theory of the quasi-birth-and-death process is extended to a process which is inhomogeous in levels. Several key results in the standard homogeneous theory hold in a more general context than that usually stated, in particular not requiring positive recurrence. Theser results are subsumed under our development. The treatment is entirely probabilistic.

• Bulletin of the Korean Mathematical Society
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• v.47 no.2
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• pp.221-229
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• 2010

Some new $\check{C}$eby$\check{s}$ev type inequalities have been developed by working on functions whose first derivatives are absolutely continuous and the second derivatives belong to the usual Lebesgue space $L_{\infty}[a,\;b]$. A unified treatment of the special cases is also given.

• Bulletin of the Korean Mathematical Society
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• v.49 no.3
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• pp.495-510
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• 2012

Let $X_1$, $X_2$,${\ldots}$, $X_n$ be a sequence of independent and identically distributed random variables with common distribution function $F$. Convergence rates for the moments of extremes are studied by virtue of second order regularly conditions. A unified treatment is also considered under second order von Mises conditions. Some examples are given to illustrate the results.