• Journal of Astronomy and Space Sciences
• /
• v.26 no.4
• /
• pp.451-466
• /
• 2009

While substorms are known to generally occur under southward IMF conditions, they can sometimes occur even under northward IMF conditions. In this paper, we studied the substorms that occurred in May, 2000 to 2002 to examine some statistical characteristics of the IMF and solar wind associated with northward IMF substorms. We focused on the cases where two or more substorms occurred successively under northward IMF conditions. Also, by checking Sym-H index associated with each of the substorms we determined whether or not there is any association of such northward IMF substorm occurrence with storm times. We also examined statistical properties at geosynchronous altitude in terms of magnetic field dipolarization and energetic particle injection. The following results were obtained. (i) Most of the northward IMF substorms occurred under average solar wind conditions. The majority of them occurred within 2 hrs duration of northward IMF Bz state, but there are also a nonnegligible number of substorms that occurred after a longer duraiton of northward IMF Bz state. (ii) While most of the substorms occurred as isolated from a magnetic storm time, those that occurred in a magnetic storm time show a higher average value of IMF and solar wind than that for the isolated substorms. (iii) About 55% of the substorms were associated with the IMF clock angle that can possibly allow dayside reconnection, and the other 45% were associated with more or less pure northward IMF conditions. Therefore, for the latter cases, the energy input from the solar wind into the magnetosphere should be made by other way than the dayside reconnection. (iv) For most of the substorms, the magnetic field dipolarizations and energetic particle injections at geosynchronous altitude were identified to be generally weak. But, several events indicated strong magnetic field dipolarizations and energetic particle injections.

• Journal of Intelligence and Information Systems
• /
• v.17 no.4
• /
• pp.241-254
• /
• 2011

Financial time-series forecasting is one of the most important issues because it is essential for the risk management of financial institutions. Therefore, researchers have tried to forecast financial time-series using various data mining techniques such as regression, artificial neural networks, decision trees, k-nearest neighbor etc. Recently, support vector machines (SVMs) are popularly applied to this research area because they have advantages that they don't require huge training data and have low possibility of overfitting. However, a user must determine several design factors by heuristics in order to use SVM. For example, the selection of appropriate kernel function and its parameters and proper feature subset selection are major design factors of SVM. Other than these factors, the proper selection of instance subset may also improve the forecasting performance of SVM by eliminating irrelevant and distorting training instances. Nonetheless, there have been few studies that have applied instance selection to SVM, especially in the domain of stock market prediction. Instance selection tries to choose proper instance subsets from original training data. It may be considered as a method of knowledge refinement and it maintains the instance-base. This study proposes the novel instance selection algorithm for SVMs. The proposed technique in this study uses genetic algorithm (GA) to optimize instance selection process with parameter optimization simultaneously. We call the model as ISVM (SVM with Instance selection) in this study. Experiments on stock market data are implemented using ISVM. In this study, the GA searches for optimal or near-optimal values of kernel parameters and relevant instances for SVMs. This study needs two sets of parameters in chromosomes in GA setting : The codes for kernel parameters and for instance selection. For the controlling parameters of the GA search, the population size is set at 50 organisms and the value of the crossover rate is set at 0.7 while the mutation rate is 0.1. As the stopping condition, 50 generations are permitted. The application data used in this study consists of technical indicators and the direction of change in the daily Korea stock price index (KOSPI). The total number of samples is 2218 trading days. We separate the whole data into three subsets as training, test, hold-out data set. The number of data in each subset is 1056, 581, 581 respectively. This study compares ISVM to several comparative models including logistic regression (logit), backpropagation neural networks (ANN), nearest neighbor (1-NN), conventional SVM (SVM) and SVM with the optimized parameters (PSVM). In especial, PSVM uses optimized kernel parameters by the genetic algorithm. The experimental results show that ISVM outperforms 1-NN by 15.32%, ANN by 6.89%, Logit and SVM by 5.34%, and PSVM by 4.82% for the holdout data. For ISVM, only 556 data from 1056 original training data are used to produce the result. In addition, the two-sample test for proportions is used to examine whether ISVM significantly outperforms other comparative models. The results indicate that ISVM outperforms ANN and 1-NN at the 1% statistical significance level. In addition, ISVM performs better than Logit, SVM and PSVM at the 5% statistical significance level.

• Korean Journal of Materials Research
• /
• v.5 no.1
• /
• pp.42-54
• /
• 1995

$Ta_2O_5$ thin film IS a promising material for the high dielectrics of ULSI DRAM. In this study, $Ta_2O_5$ thin film was grown on p-type( 100) Si wafer by thermal metal organic chemical vapo deposition ( MCCVD) method and the effect of operating varialbles including substrate temperature( $T_s$), bubbler temperature( $T_ \sigma$), reactor pressure( P ) was investigated in detail. $Ta_2O_5$ thin film were analyzed by SEM, XRD, XPS, FT-IR, AES, TEM and AFM. In addition, the effect of various anneal methods was examined and compared. Anneal methods were furnace annealing( FA) and rapid thermal annealing( RTA) in $N_{2}$ or $O_{2}$ ambients. Growth rate was evidently classified into two different regimes. : (1) surface reaction rate-limited reglme in the range of $T_s$=300 ~ $400 ^{\circ}C$ and (2: mass transport-limited regime in the range of $T_s$=400 ~ $450^{\circ}C$.It was found that the effective activation energies were 18.46kcal/mol and 1.9kcal/mol, respectively. As the bubbler temperature increases, the growth rate became maximum at $T_ \sigma$=$140^{\circ}C$. With increasing pressure, the growth rate became maximum at P=3torr but the refractive index which is close to the bulk value of 2.1 was obtained in the range of 0.1 ~ 1 torr. Good step coverage of 85. 71% was obtained at $T_s$=$400 ^{\circ}C$ and sticking coefficient was 0.06 by comparison with Monte Carlo simulation result. From the results of AES, FT-IR and E M , the degree of SiO, formation at the interface between Si and TazO, was larger in the order of FA-$O_{2}$ > RTA-$O_{2}$, FA-$N_{2}$ > RTA-$N_{2}$. However, the $N_{2}$ ambient annealing resulted in more severe Weficiency in the $Ta_2O_5$ thin film than the TEX>$O_{2}$ ambient.

• Radiation Oncology Journal
• /
• v.17 no.1
• /
• pp.1-8
• /
• 1999

Purpose : Experimental studies have implicated the wild type p53 In cellular response to radiation. Whether altered p53 function can lead to changes in clinical radiocurability remains an area of ongoing study. This study was performed to investigate whether any correlation between change of p53 and outcome of curative radiation therapy in patients with head and neck cancels. Methods : Immunohistochemical analysis with a mouse monoclonal antibody (DO-7) specific for human p53 was used to detect to overexpression of protein in formalin fixed, paraffin-embedded tumor sample from 55 head and neck cancer patients treated with curative radiation therapy (median dose of 7020 cGy) from February 1988 to March 1996 at 51. Mary's Hospital. Overexpression of p53 was correlated with locoregional control and survival using Kaplan-Meier method. A Cox regression multi-variate analysis was peformed that included all clinical variables and status of p53 expression. Results : Thirty-seven (67.2$\%$) patients showed overexpression of p53 by immunohistochemical staining in their tumor. One hundred percent of oral cavity, 70$\%$ of laryngeal, 66.7$\%$ of oropharyngeal, 66.7$\%$ of hypopharyngeal cancer showed p53 overexpression (P=0.05). The status of p53 had significant relationship with stage of disease (P=0.03) and history of smoking (P=0.001). The overexpression of p53 was not predictive of response rate to radiation therapy. The locoregional control was not significantly affected by p53 status. Overexpression of p53 didn't have any prognostic implication for disease free survival and overall survival. Primary site and stage of disease were significant prognostic factors for survival. Conclusions : The p53 overexpression as detected by immunohistochemical staining had significant correlation with stage, primary site of disease and smoking habit of patients. The p53 overexpression didn't have any predictive value for outcome of curative radiation therapy in a group of head and neck cancers.

• Food Science and Preservation
• /
• v.23 no.4
• /
• pp.502-509
• /
• 2016

The seasonal appearance and the chemical composition characteristics of cladode of Opuntia humifusa were investigated in this study. The minor (horizontal) and major (vertical) axes, the width, and weight of O. humifusa cladode were compared for its appearance features. Moisture, crude protein, ash, fat, color, dietary fiber, mineral, and amino acids contents were measured for the comparison of their chemical composition characteristics. The cladode of O. humifusa harvested in summer showed higher values of minor and major axis, width, and weight than those harvested in winter. According to the results of Hunter color index, cladode of O. humifusa harvested in summer showed the highest lightness level (Hunter L value). In the meanwhile, cladode of O. humifusa harvested in spring showed the highest Hunter a (redness) and b (yellowness) values. Cladode of O. humifusa harvested in summer had the lowest crude protein and crude fat contents, while it showed the highest crude ash content. The total contents of moisture and dietary fiber were significantly greater than summer-harvested cladode of O. humifusa followed by spring- and winter-harvested cladode of O. humifusa. The major mineral content of all seasonal cladode of O. humifusa was $Ca^{2+}$. Glutamic acid and aspartic acid were the major amino acids in all seasonal samples. Contrary, the contents of total amino acids and free amino acids were the lowest in summer-harvested cladode of O. humifusa. Taken together, it was concluded that the appearance and chemical quality of cladode of O. humifusa was versatile depending on the harvesting season.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.34 no.4
• /
• pp.389-393
• /
• 2001

For an effective utilization, quality stability of instant powdered oyster soup made of canned oyster processing waste water (IPSW) was determined. Instant powdered soup from oyster hot-water extracts (IPSE) was also prepared by mixing hot-water extract powder (15 g) with table salt (5 g), cream powder (19 g), milk replacer (12 g), wheat flour (20 g), corn flour (15 g), starch (5 g), glucose (7.5 g) and onion powder (1.5 g). In preparing IPSW, mixed powder from wash water and boiling liquid waste, instead of powder from hot-water extracts and table salt, was added (powder from boiling liquid waste: powder from wash water= 12: 8) and other additives were added in proportion to those in the IPSE. The moisture content, water activity, peroxide value and fatty acid composition showed little changes during storage of the IPSW. The pH, volatile basic nitrogen content and brown pigment formation increased slightly, while white index decreased slightly during storage of IPSW. No significant difference was observed in the changes of food component during storage between IPSW and IPSE. According to a sensory evaluation, the change in quality of IPSW was negligible during 12 months of storage. from the results of the chemical experiment and sensory evaluation, IPSW packed with laminated film bag (OPP, $20{\mu}m/PE,\;20{\mu}m/paper,\;45g/m^3/PE,\;20{\mu}\;m/Al,\;7{\mu}\;m/PE,\;20{\mu}m$) was revealed to be preserved in good quality during 12 months of storage.

• Management & Information Systems Review
• /
• v.36 no.4
• /
• pp.21-32
• /
• 2017

Motivated by the recent cases of negligent social responsibility as manifested by foreign luxury fashion brands in Korea, this study investigates whether agency costs depend on the sustainability of different types of corporate governance. Agency costs refer either to vertical costs arising from the relationship between stockholders and managers, or to horizontal costs associated with the potential conflicts between majority and minority stockholders. The firms with luxury fashion brand could spend large sums of money on maintenance of magnificent brand image, thereby increasing the agency cost. On the contrary, the firms may hold down wasteful spending to report a gaudily financial achievement. This results in mitigation of the agency cost. Agency costs are measured by the value of the principal component. First, three ratios are constructed: asset turnover, operating expense to sales, and earnings before interest, tax, and depreciation. Then, the scores of each of these ratios for individual firms in the sample are differenced from the ratios for the benchmark firm of S-OIL. S-OIL was designated as the best superior governance model firm for 2013 by CGS. We perform regression analysis of each agency cost index, luxury fashion brand dummy and a set of control variables. The regression results indicate that the agency costs of the firms with luxury fashion brand exceed those of control group in the fashion industry in the part of operating expenses, but the agency cost falls short of those of control group in the part of EBITD, thus the aggregate agency costs are not differential of those of the control group. In sensitivity test, the results are same that the agency cost of the firms are higher than those of the matching control group with PSM(propensity matching method). These results are corroborated by an additional analysis comparing the group of the companies with the best brands with the control group. The results raise doubts about the effectiveness of management of the firms with luxury fashion brand. This study has a limitation that the research has performed only for 2013 and this paper suggests that there is room for improvement in the current research methodology.

• Journal of the Korean earth science society
• /
• v.39 no.3
• /
• pp.241-249
• /
• 2018

As the international trade increases, vessel traffics around the Korean Peninsula are also increasing. Maritime accidents hence take place more frequently in the southern coast of Korea where many big and small ports are located. Accidents involving ship collision and sinking result in a substantial human and material damage as well as the marine environmental pollution. Therefore, it is necessary to locate the ships quickly when such accidents occur. In this study, we suggest a new ship detection index by comparing and analyzing the reflectivity of each channel of the Korea MultiPurpose SATellite-2 (KOMPSAT-2) images of the area around the Gwangyang Bay. A threshold value of 0.1 is set based on a histogram analysis, and all vessels are detected when compared with RGB composite images. After selecting a relatively large ship as a representative sample, the distribution of spatial reflectivity around the ship is studied. Uniform shadows are detected on the northwest side of the vessel. This indicates that the sun is in the southeast, the azimuth of the actual satellite image is $144.80^{\circ}$, and the azimuth angle of the sun can be estimated using the shadow position. The reflectivity of the shadows is 0.005 lower than the surrounding sea and ship. The shadow height varies with the position of the bow and the stern, perhaps due to the relative heights of the ship deck and the structure. The results of this study can help search technology for missing vessels using optical satellite images in the event of a marine accident around the Korean Peninsula.

• Sleep Medicine and Psychophysiology
• /
• v.7 no.1
• /
• pp.27-33
• /
• 2000

Objectives: The sensitivity and accuracy of thermistor airflow signal has been debated. The purposes of this study were to compare apnea-hypopnea index(AHI) detected from a conventional thermistor signal and a nasal pressure transducer of airflow(NPT), to evaluate the value of NPT for the diagnosis of upper airway resistance syndrome(UARS), and to measure airway pressure fluctuations which produced respiratory arousals in UARS by naso-oro-esophageal manometer catheter. The subjects were 30 patients with obstructive sleep apnea syndrome [mild(540), 10), and 6 UARS patients. Airway resistance arousal in this study was defined as arousals which were not associated with apnea or hypopnea of thermistor signal, but showed significant decrease of nasal airflow pressure just before arousal and a prompt recovery of nasal airflow pressure after arousal. The airway pressure fluctuations were measured during 260 airway resistance arousals observed in 10 patients with OSAS, 2 with UARS. Results: Mean AHIs of patients with OSAS were 33.4 by thermistor and 48.4 by NPT. The AHIs of mild, moderate and severe OSAS groups were 10.2, 32.1, 65.4 respectively by thermistor and 23.1, 45.9, 76.4 by NPT. The mean AHI of patients with UARS was 3.2 by thermistor and 10.8 by NPT. The mean AHI of patients with nonspecific arousals was 2.7 by thermistor and 4.4 by NPT. The mean airway pressure changes during respiratory arousals of different groups were $8.7\;cmH_2O$ in mild OSAS, $11.4\;cmH_2O$ in moderate OSAS, $24.7\;cmH_2O$ in severe OSAS and $6.6\;cmH_2O$ in UARS. Conclusion: The nasal pressure transducer of airflow was more sensitive and accurate for assessing respiratory disturbances of patients with OSAS and was extremely helpful for the diagnosis of UARS without esophageal pressure monitoring. From the results, we would like to propose carefully the NPT diagnostic criteria for sleep disordered breathing as follows: NPT-AHI 5-15 $\rightarrow$ UARS, 15-35 $\rightarrow$ mild OSAS, 35-55 $\rightarrow$ moderate OSAS and >55 $\rightarrow$ severe OSAS.

• Journal of Korean Society of Forest Science
• /
• v.105 no.2
• /
• pp.247-252
• /
• 2016

This study was conducted to evaluate the technical efficiency of Annual Chestnut production in South Korea. In this study, technical efficiency is the maximum possible production for which a certain amount of costs is inputted. For analysis on the technical efficiency we used output-oriented BCC Model, and then we analyzed correlation among input costs, production, gross income, net income, and market price per unit in order to determine the cause of variation in the technical efficiency. As study materials, we used statistics for the forestry production costs for 7 years from 2008 to 2014. The study results showed that the maximum possible production and actual production in 2008, 2009, and 2010 were 1,568 kg, 1,745 kg, and 1,534 kg by hectares in the order which were the same values. Consequently, the technical efficiency of those was all evaluated as 1.00. On the other hand, actual production from 2011 to 2014 was 1,270 kg 1,047 kg, 1,258 kg, and 1,488 kg by hectares in the order and the maximum possible production was 1,524 kg, 1,467 kg, 1,635 kg, and 1,637 kg by hectares in the analysis. From those values, the technical efficiency was evaluated in the following order:0.83, 0.71, 0.75, 0.91. The lowest value of the technical efficiency was 0.71 in 2012, and the values of this increased gradually since 2013. It is indicated that the cause of variation in the technical efficiency was related to the relationship between production and market price, and there was a negative correlation with r = -0.821 (p<0.05). The level of maximum available production per unit area was between 1,488kg in lower limit and 1,745 kg in upper limit, and the average was turned out as 1,548 kg.