• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.127-135
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• 2009

Most traffic information that drivers receive while driving are stored in their short-term memory and disappear within a few seconds. Contemporary modeling approaches using a dummy variable can't fully explain this phenomenon. As such, this study proposes to use utility functions of real-time in-vehicle traffic safety information (IVTSI), analyzing its safety impacts based on empirical data from an on-site driving experiment at signalized intersection approach with a limited visibility. For this, a driving stability evaluation model is developed based on driver's driving speed choice, applying an ordered probit model. To estimate the specified utility functions, the model simultaneously accounts for various factors, such as traffic operation, geometry, road environment, and driver's characteristics. The results show three significant facts. First, a normal density function (exponential function) is appropriate to explain the utility of IVTSI proposed under study over time. Second, the IVTSI remains in driver's short-term memory for up to nearly 22 second after provision, decreasing over time. Three, IVTSI provision appears more important than the geometry factor but less than the traffic operation factor.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.429-440
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• 2015

This study was to investigate factors influencing the school adjustment according to gender and body mass index (BMI) of middle school students who participated in the 2nd-wave Korea Children and Youth Panel Study (KCYPS). This study used a crosssectional design with secondary analysis with KCYPS. The variables were parental interest, behavioral problem, aggression, attention problem, somatic symptom, social withdrawal, depression, and academic achievement. The data were analyzed with descriptive statistics, Pearson's correlation coefficients, and multiple regressions. School adjustment was significantly associated with academic achievement high, explaining 11.3~19.1% of the variance in boys. School adjustment was significantly associated with attention problem, explaining 14.9~42.4% of the variance in girls. Factors influencing school adjustment were significantly different according to gender and BMI. To improve the school adjustment, it is necessary to develop gender-specific school adjustment promotion programs according to BMI.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.173-178
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• 2017

As research on the practical use of robots has continued since the past, advancements into each field of society are being continuously tried in modern society, breaking bounds from the previous experimental environment. However, in order for robots to be applied to the real environment, the production cost, which is considered to be the biggest disadvantage of commercializing the existing robot platform, and the adaptability issue in working environments in terms of human standards must be considered. This paper proposes a robot of biped walking form, which conforms to the degree of freedom and the size of human beings. By replacing the encoder with a combined module of potentiometer, the high cost of production is reduced, and by adopting a modular design that is easy to replace parts, the maintenance cost of robots is reduced. Finally, stability was verified by applying a walking pattern to two dummy robots of different sizes and motor arrangements. In this paper, after developing the real biped walking robots, the performance and usability were verified through walking experiments and applying the walking pattern using the developed robots.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.2
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• pp.33-40
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• 2016

Due to the growth of social network systems (SNS), big data are realized and Hadoop was developed as a distributed platform for analyzing big data. Enterprises analyze data containing users' sensitive information by using Hadoop and utilize them for marketing. Therefore, researches on data encryption have been done to protect the leakage of sensitive data stored in Hadoop. However, the existing researches support only the AES encryption algorithm, the international standard of data encryption. Meanwhile, Korean government choose ARIA algorithm as a standard data encryption one. In this paper, we propose a HDFS data encryption scheme using ARIA algorithms on Hadoop. First, the proposed scheme provide a HDFS block splitting component which performs ARIA encryption and decryption under the distributed computing environment of Hadoop. Second, the proposed scheme also provide a variable-length data processing component which performs encryption and decryption by adding dummy data, in case when the last block of data does not contains 128 bit data. Finally, we show from performance analysis that our proposed scheme can be effectively used for both text string processing applications and science data analysis applications.

• Journal of the Korea Convergence Society
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• v.10 no.3
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• pp.193-201
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• 2019

The public's interest regarding multi-household houses, one of the small-scale housings used as profit earning property, has been increasing. Previous studies regarding price, such as the rent and sales price of multi-household houses', however, were difficult to find. Thus, this study set forth to find out what characteristics influence the sales price of multi-household houses so as to provide further suggestions to investors' decision makings and developers' strategy establishments. The data was retrieved from multi-household sales transacted in Changwon City. Through empirical analysis, this paper found that prices were high in Euichang-gu and Seongsan-gu, and meaningful variables in terms of locations were distance from major trade areas(-), distance from main streets(-), and Corner site(+). Meaningful variables related to household characteristics were total floor area(+), Studio type(+), Southern exposure(+), Building age(-), and Full-furnished(+).

• Explosives and Blasting
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• v.42 no.1
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• pp.23-33
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• 2024

Recently, various techniques and patented methods on blasting operation are being newly developed. In this study, test construction of the MDS blasting method was performed, and the fragmentation size and the occurrence rate of rocks exceeding 300mm were measured and analyzed in comparing to normal blasting method. Test construction was performed three times each for normal and the MDS at the same bench for each round, and fragmentation size(P80) and occurrence rate of rocks exceeding 300mm(S30) were measured using digital image processing. A sieve bucket was also manufactured on-site to sort oversized rock particles from muck piles, and their weights and equivalents were measured to calculate actual values. As a result, the fragmentation size decreased of 21.0% with the MDS compared to normal, and 100-S30 decreased of 10.1%, with actual values decreasing of 7.6%. Although there were variations in blasting effects for each round due to differences in rock quality at site, overall, the MDS proved to be more effective compared to normal blasting method under equivalent conditions.

• Journal of Korean Society of Transportation
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• v.34 no.5
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• pp.465-475
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• 2016

Since inaccurate demand estimation for recent urban rail construction may result in financial burden to cities, precise prediction for operating cost as well as construction costs is necessary to avoid or reduce budget loss of the local or central government. The operating cost is directly related to the public fare and affect a policy to determine the rate system. Therefore, there is a pressing need to develop an estimating model for reliable operating cost of urban railway. This study introduces a new model to estimate the operating cost with new variables. It provides a better prediction in accuracy and reliability compared to the existing model, considering the feature of urban railway. For verification of our model, railway operation data from a few cities for the last five years were comprehensively examined to determine variables that affect the operating cost. The operating cost was estimated in a dummy regression model using five independent variables, which were average distance between stations, daily trains distance, total passenger capacity of a train in a train, driving mode(manned/unmanned), and investment type(financial/private).

• KDI Journal of Economic Policy
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• v.34 no.3
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• pp.95-131
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• 2012

This study examines whether the executive turnover and the executive resignation during the term of office affect the performance of Korean state-owned enterprises. The executive turnover in the paper means the comprehensive change of the executives which includes the change after the term of office, the change after consecutive terms and the change during the term of office. The 'resignation' was named for the executive change during the term of office to distinguish from the executive turnover. The study scope of the paper is restrained to the comprehensive executive change itself irrespective of the term of office and the resignation during the term of office. Therefore the natural change of the executive after the term of office or the change after consecutive terms is not included in the study. Spontaneous resignation and forced resignation are not distinguished in the paper as the distinction between the two is not easy. The paper uses both the margin of return on asset and the margin of return on asset adjusted by industry as proxies of the performance of state-owned enterprises. The business nature of state-owned enterprise is considered in the study, the public nature not in it. The paper uses the five year (2004 to 2008) samples of 24 firms designated as public enterprises by Korean government. The analysis results are as follows. First, 45.1% of CEOs were changed a year during the sample period on the average. The average tenure period of CEOs was 2 years and 3 months and 49.9% among the changed CEOs resigned during the term of office. 41.6% of internal auditors were changed a year on the average. The average tenure period of internal auditors was 2 years and 2 months and 51.0% among the changed internal auditors resigned during the term of office. In case of outside directors, on average, 38.2% were changed a year. The average tenure period was 2 years and 7 months and 25.4% among the changed internal directors resigned during the term of office. These statistics show that numerous CEOs resigned before the finish of the three year term in office. Also, considering the tenure of an internal auditor and an outside director which diminished from 3 years to 2 years by an Act on the Management of Public Institutions (applied to the executives appointed since April 2007), it seems most internal auditors resigned during the term of office but most outside directors resigned after the end of the term. Secondly, There was no evidence that the executives were changed during the term of office because of the bad performance of prior year. On the other hand, contrary to the normal expectation, the performance of prior year of the state-owned enterprise where an outside director resigned during the term of office was significantly higher than that of other state-owned enterprises. It means that the clauses in related laws on the executive dismissal on grounds of bad performance did not work normally. Instead it can be said that the executive change was made by non-economic reasons such as a political motivation. Thirdly, the results from a fixed effect model show there were evidences that performance turned negatively when CEOs or outside directors resigned during the term of office. CEO's resignation during the term of office gave a significantly negative effect on the margin of return on asset. Outside director's resignation during the term of office lowered significantly the margin of return on asset adjusted by industry. These results suggest that the executive's change in Korean state-owned enterprises was not made by objective or economic standards such as management performance assessment and the negative effect on performance of the enterprises was had by the unfaithful obeyance of the legal executive term.

• Journal of Mushroom
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• v.15 no.3
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• pp.150-154
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• 2017

A self-propelled turner was developed to produce mushroom compost at low costs and high efficiency, and the uniformity of compost produced by an excavator, compost mixer, and self-propelled turner was compared. The material of the compost was mixed with rice straw and chicken manure at a dry weight ratio of 3:1. After the final turning, internal temperature distribution, water content of the compost pile, ash ratio, and uniformity of the compost pile were examined. After the compost was completed, the water content was $69.9{\pm}0.54%$, $72.1{\pm}0.15%$, and $74.5{\pm}0.82%$, respectively. The length of rice straw was $47.5{\pm}15.4cm$, $24.9{\pm}10.1cm$, and $31.0{\pm}10.6cm$, respectively. The ash content in the dry weight of each compost was $25.0{\pm}6.2%$, $33.6{\pm}4.2%$, and $28.2{\pm}1.1%$, respectively. The deviation in the length of rice straw was affected by the linear velocity of the spinner in the compost mixer and the self-propelled turner, which were 21.5 m/sec and 9 m/sec, respectively. As a result, the most uniform mushroom compost was produced by the self-propelled turner.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.9 no.1
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• pp.119-132
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• 2014

This study analyzed the failure prediction model of the firms listed on the KOSDAQ by considering whether there are embezzlement, malpractice and the largest shareholder changes or not. This study composed a total of 166 firms by using two-paired sampling method. For sample of failed firm, 83 manufacturing firms which delisted on KOSDAQ market for 4 years from 2009 to 2012 are selected. For sample of normal firm, 83 firms (with same item or same business as failed firm) that are listed on KOSDAQ market and perform normal business activities during the same period (from 2009 to 2012) are selected. This study selected 80 financial ratios for 5 years immediately preceding from delisting of sample firm above and conducted T-test to derive 19 of them which emerged for five consecutive years among significant variables and used forward selection to estimate logistic regression model. While the precedent studies only analyzed the data of three years immediately preceding the delisting, this study analyzes data of five years immediately preceding the delisting. This study is distinct from existing previous studies that it researches which significant financial characteristic influences the insolvency from the initial phase of insolvent firm with time lag and it also empirically analyzes the usefulness of data by building a firm's fail prediction model which considered embezzlement/malpractice and the largest shareholder changes as dummy variable(non-financial characteristics). The accuracy of classification of the prediction model with dummy variable appeared 95.2% in year T-1, 88.0% in year T-2, 81.3% in year T-3, 79.5% in year T-4, and 74.7% in year T-5. It increased as year of delisting approaches and showed generally higher the accuracy of classification than the results of existing previous studies. This study expects to reduce the damage of not only the firm but also investors, financial institutions and other stakeholders by finding the firm with high potential to fail in advance.