• Journal of the Chungcheong Mathematical Society
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• v.37 no.1
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• pp.27-40
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• 2024

In this paper, we consider the higher-order HartreeFock equations. The higher-order linear Schrödinger equation was introduced in [5] as the formal finite Taylor expansion of the pseudorelativistic linear Schrödinger equation. In [13], the authors established global-in-time Strichartz estimates for the linear higher-order equations which hold uniformly in the speed of light c ≥ 1 and as their applications they proved the convergence of higher-order Hartree-Fock equations to the corresponding pseudo-relativistic equation on arbitrary time interval as c goes to infinity when the Taylor expansion order is odd. To achieve this, they not only showed the existence of solutions in L² space but also proved that the solutions stay bounded uniformly in c. We address the remaining question on the convergence of higherorder Hartree-Fock equations when the Taylor expansion order is even. The distinguished feature from the odd case is that the group velocity of phase function would be vanishing when the size of frequency is comparable to c. Owing to this property, the kinetic energy of solutions is not coercive and only weaker Strichartz estimates compared to the odd case were obtained in [13]. Thus, we only manage to establish the existence of local solutions in H^s space for s > $\frac{1}{3}$ on a finite time interval [-T, T], however, the time interval does not depend on c and the solutions are bounded uniformly in c. In addition, we provide the convergence result of higher-order Hartree-Fock equations to the pseudo-relativistic equation with the same convergence rate as the odd case, which holds on [-T, T].

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.200-209
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• 2018

This study proposed a method to select existing facilities as a landmark in order to reset accumulated errors of dead reckoning in a tunnel difficult to receive GNSS signals in automated driving. First, related standards and regulations were reviewed in order to survey 'variety' on shapes and installation locations as a feature of facilities. Second, 'recognition' on facilities was examined using image and Lidar sensors. Last, 'regularity' in terms of installation locations and intervals was surveyed through related references. The results of this study selected a fire fighting box / lamp (50m), an evacuation corridor lamp (300m), a lane control system (500m), a maximum / minimum speed limit sign and a jet fan as a candidate landmark to reset positioning errors. Based on those facilities, it was determined that error correction was possible. The results of this study are expected to be used in repositioning of automated driving vehicles in a tunnel.

• Journal of Nutrition and Health
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• v.41 no.4
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• pp.307-316
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• 2008

The purpose of the study was to investigate nutritional status of chronic obstructive pulmonary disease (COPD) patients and to find out the differences according to the stages of disease. From March to October, 2006, 41 stable male patients of mild to severe COPD patients were recruited from Seoul National University hospital. The patients' of body weight and fat free mass were assessed by bioelectrical impedance analysis. The nutritional status of the patients was also assessed by 3-day recall, index of nutritional quality (INQ), dietary diversity score (DDS), dietary variety score (DVS), food group index pattern and dietary quality index (DQI). The total of 41 patients were classified into three groups, stage I, stage II and stage III groups according to the classification of Global Initiative for Chronic Obstructive Lung Disease (GOLD) standard. The mean age of the patients in each stage were 67.2-66.9 years showing no significant difference. The ratio of $FEV_1$/FVC were $57.5{\pm}7.3$, $46.9{\pm}7.6$ and $38.2{\pm}6.8%$, respectively showing significant differences according to the stages of disease. The fat free mass of the stage II ($48.2{\pm}4.7kg$) and III ($47.3{\pm}4.5kg$) was significantly lower than that of stage I ($53.1{\pm}6.9kg$) patients. There were significant correlation of fat free mass with $FEV_{1}$, and BMI (body mass index) with $FEV_{1}$/FVC ratio (p < 0.05). COPD patients showed the diet-related clinical symptoms of anorexia, dyspnea, dyspepsia, and chewing difficulty. Daily intakes of calorie, K, vitamin $B_2$ and folate of the patients were very low ($83.8{\pm}20.7%$, $58.9{\pm}14.4%$, $70.7{\pm}19.6%$ and $74.4{\pm}10.2%$, respectively) however, they did not significantly different according to the stages of disease. Daily intake of calcium was significantly lower in the stage III patients (p < 0.05). The mean scores of dietary variety score was significantly lower in the stage III patients (p < 0.001). Dietary quality index of the patients were not different among the stages of disease and the scores indicated poor quality of diet. As a summary, we found that body fat free mass, regularity of exercise, frequency of having snacks and dietary variety score were significantly associated with the severity of chronic obstructive pulmonary disease.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.1
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• pp.13-21
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• 2023

As problems such as difficulties in securing stable energy resources and global warming due to the emission of greenhouse gases due to the use of fossil fuels have emerged, interest in the development of renewable energy is increasing. Since the tidal phenomenon has a regularity that occurs regularly with a certain period, it is possible to predict accurately in advance, which has a advantage in terms of energy recovery. Therefore, various methods have been devised to utilize the tide as an energy source. Tidal power using barrages is a representative method that is widely operated, but the promotion of tidal power generation projects is being delayed or stopped due to the decrease in the level of water in the tidal basin, changes in water quality and in the ecosystem. In this study, a field experiment was conducted to develop and verify the performance of a tidal power device applicable to sea areas where dykes are already installed. As a result of carrying out four cases of experiments using two water tanks, pipe lines, open channels, weirs, and water turbine and generator, the possibility of developing a power generation system capable of 10 kW output or more and 60% efficiency or more was confirmed. These research results can be used for small-scale tidal power by utilizing the existing dykes.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.3
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• pp.1-15
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• 2016

This study has analyzed predication capabilities leveraging multi-variate model, logistic regression model, and artificial neural network model based on financial information of medium-small sized companies list in KOSDAQ. 83 delisted companies from 2009 to 2012 and 83 normal companies, i.e. 166 firms in total were sampled for the analysis. Modelling with training data was mobilized for 100 companies inlcuding 50 delisted ones and 50 normal ones at random out of the 166 companies. The rest of samples, 66 companies, were used to verify accuracies of the models. Each model was designed by carrying out T-test with 79 financial ratios for the last 5 years and identifying 9 significant variables. T-test has shown that financial profitability variables were major variables to predict a financial risk at an early stage, and financial stability variables and financial cashflow variables were identified as additional significant variables at a later stage of insolvency. When predication capabilities of the models were compared, for training data, a logistic regression model exhibited the highest accuracy while for test data, the artificial neural networks model provided the most accurate results. There are differences between the previous researches and this study as follows. Firstly, this study considered a time-series aspect in light of the fact that failure proceeds gradually. Secondly, while previous studies constructed a multivariate discriminant model ignoring normality, this study has reviewed the regularity of the independent variables, and performed comparisons with the other models. Policy implications of this study is that the reliability for the disclosure documents is important because the simptoms of firm's fail woule be shown on financial statements according to this paper. Therefore institutional arragements for restraing moral laxity from accounting firms or its workers should be strengthened.