• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.153-159
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• 2018

Many researches have been carried out on carbonation, a representative deterioration in underground structure. The carbonation of RC (Reinforced Concrete) structure can cause steel corrosion through pH drop in concrete pore water. However extension of service life in RC structures can be obtained through simple surface protection. Unlike the conventional deterministic maintenance technique, probabilistic technique can consider a variation of service life but it deals with only normal distributions. In the work, life time-probability distributions considering not only normal but also log distributions are induced, and repair cost estimation technique is proposed based on the induced model. The proposed technique can evaluate the repair cost through probabilistic manner regardless of normal or log distribution from initial service life and extended service life with repair. When the extended service life through repair has log distribution, repair cost is effectively reduced. The more reasonable maintenance strategy can be set up though actual determination of life-probability distribution based on long term tests and field investigations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.117-121
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• 2019

In this study, research and a demonstration for applying DC distribution systems to ships as an environmental and energy conservation solution in domestic and foreign countries were actively carried out. In order to apply a generator to a DC distribution system, a variable speed engine was used. Both engine speed and fuel consumption were reduced. In this paper, a DC generator for DC distribution was constructed using a diesel generator, a generator controller, a governor, and an AVR. A system configuration method for a generator, power quality test, and the power characteristics of a variable speed generator were analyzed. The voltage (250 - 440 VAC) and frequency (34 - 60 Hz) of the variable speed generator were set to 60 - 100 % of the rated value, and the engine was set to operate from 1100 - 1800 rpm. It was confirmed that the voltage, current, and frequency of the generator output fluctuated in a stable manner according to the power amount when changing the engine speed of the generator according to the load variation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.173-181
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• 2019

To estimate probabilistic distribution function from experimental data, kernel density estimation(KDE) is mostly used in cases when data is insufficient. The estimated distribution using KDE depends on bandwidth selectors that smoothen or overfit a kernel estimator to experimental data. In this study, various bandwidth selectors such as the Silverman's rule of thumb, rule using adaptive estimates, and oversmoothing rule, were compared for accuracy and conservativeness. For this, statistical simulations were carried out using assumed true models including unimodal and multimodal distributions, and, accuracies and conservativeness of estimating distribution functions were compared according to various data. In addition, it was verified how the estimated distributions using KDE with different bandwidth selectors affect reliability analysis results through simple reliability examples.

• Steel and Composite Structures
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• v.42 no.1
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• pp.49-57
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• 2022

This paper presents a study on the behavior of a bolted T-stub to square tube connection using Thread-fixed One-side Bolts (TOBs) through tests and numerical simulations. It outlines a research work of four connections with focus on the failure modes and strengths of the connection under tensile load. It was observed that the thread anchor failure caused by shear failure of hole threads controlled the final failure of the connection in the tests. Meanwhile, the out-of-plane deformation of tube wall resulted in the contact separation between hole threads and bolt threads, which in turn reduced the shear strength of hole threads. Finite element models (FEMs) allowing for the configuration details of the TOBs fixed connection are then developed and compared with the test results. Subsequently, the failure mechanism of hole threads and stress distribution of each component are analyzed based on FEM results. It was concluded that the ultimate strength of connection was not only concerned with the shear strength of hole threads, but also was influenced by the plastic out-of-plane deformation of tube wall. These studies lay a foundation for the establishment of suitable design methods of this type of connection.

• Journal of the Korean Home Economics Association
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• v.46 no.6
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• pp.75-87
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• 2008

The purposes of this study were to examine the attitude of undergraduates toward money and the differences in dining-out behavior among three groups of subjects divided by attitude toward money. Self-administrated questionnaires were completed by 387 undergraduates and data were analysed by frequency analysis, chi-square, t-test, one-way ANOVA, factor analysis, reliability analysis, duster analysis and discriminant analysis. Results of study were as follows. There appeared six different attitudes of money among the undergraduates investigated: money as a means of seizing power, money as a life pursuit, money as a tool for rational consumption, money as a barometer of success, money as a cause of anxiety, and distrust. The undergraduates showed several different attitudes of money according to gender, major, age and pocket money. Cluster analysis divided subjects into three groups by attitude toward money : low dependent group, moderately dependent group and high dependent group. Three groups of subjects classified by attitudes of money were different from one another in dining-out behavior as well. The low money-dependent group mainly spent less than 5,000 won on a dining-out, and relied on their own experience and recommendation from others on a dining-out information. In contrast, the high money-dependent group spent 20,000 won or more on dining-out, and the distribution of subjects acquiring dining-out information from various channels in that group was significantly higher than other groups.

• Ocean and Polar Research
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• v.36 no.4
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• pp.319-326
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• 2014

Mineral dust in the polar snow plays an important role both in the climate system of the Earth and in global biogeochemical cycles. Analysis of the concentration and the particle size distribution of mineral dust has been carried out in the snow from the Antarctic surface snow and the Greenland snowpit. Among the various particle size determination techniques, a Multisizer 3 Coulter Counter in a class 100 clean bench counted all particles between 1.1 and $30.0{\mu}m$ with a $50{\mu}m$ aperture tube. The aperture tube size, the concentration of electrolytes and the accuracy of the particle size distribution were determined in this study. The number concentrations from the Antarctic surface snow were 81,843 particles $mL^{-1}$, but those from the Greenland snowpit were 10,666 particles $mL^{-1}$. In the volume distribution, the distributions of mineral dust in both the Antarctic surface snow and the Greenland snowpit showed lognormal distribution in the size interval 1.1 to $6.0{\mu}m$ with the mode, 3.562 and $3.836{\mu}m$, respectively. The analysis technique using a coulter counter for mineral dust could be used for reconstructing paleoclimates from polar ice cores.

• The Journal of Society for e-Business Studies
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• v.23 no.2
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• pp.67-81
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• 2018

Technology commercialization is a reward process for companies' various trials and investment to develop technologies, which can be regarded as a way to figure out company's business performance. To successfully attain companies' purpose via technology commercialization, a variety of knowledge which triggers and completes business activities are needed. This paper suggests a methodology to analyze problems and solutions around the technology commercialization process in terms of knowledge distribution status, especially focused on Korean SMC cases. The knowledge map of this paper is constructed from the knowledge networks and identifies problems and solutions of the target process. A case study for applying proposed concepts to SMC's cases is also performed by checking knowledge distribution status and extracting practical implications. This paper's ideas can be regarded as one of references for SMCs to prepare technology commercialization with guaranteeing facilitated knowledge distribution and utilization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.514-522
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• 2007

Finite failure NHPP models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this parer, Goel-Okumoto and Yamada-Ohba-Osaki model was reviewed, proposes the Burr distribution reliability model, which making out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE, AIC statistics and Kolmogorov distance, for the sake of efficient model, was employed. Analysis of failure using real data set for the sake of proposing shape parameter of the Burr distribution was employed. This analysis of failure data compared with the Burr distribution model and the existing model(using arithmetic and Laplace trend tests, bias tests) is presented.

• Journal of the korean Society of Automotive Engineers
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• v.2 no.1
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• pp.39-50
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• 1980

This paper presents the variations obtained in heat flow rate and engine performance of a four-stroke cycle Diesel engine when there were changes in the temperature of cooling water, compression ratio, injection timing of fuel, and other factors. Heat dissipation of engine cylinder was calculated by the heat transfer coefficient of Nusselt's empirical equation and the analysis of distribution of temperature in cylinder barrel was obtained by the finite element method of two-dimensional steady state heat conduction. In this experiment, the out side temperature of cylinder liner was measured by the data logger, and the temperature distribution of liner was computed by the analysis of triangular finite element model under the assumption due to surface heat flux of cylinder inner surface. The results obtained by this study are as follows. Under the given operating condition, the temperature distribution of cylinder liner by using finite element method shows that the mean temperature of barrel is in accordance with the experimental results of Eichelberg and temperature difference is lower than 4.23.deg. C. The heat dissipation of engine decrease in accordance with the decrease of piston mean velocity, compression ratio, and the increase of coolant temperature. Influence on the delay of injection timing of fuel brings about the decrease of heat rejection over the cylinder at constant test conditions.

• Journal of Distribution Science
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• v.15 no.2
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• pp.47-51
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• 2017

Purpose - The purpose of the study was to find out factors having influence upon management of franchise convenience stores being distribution business by interview with franchisees in accordance with Delphi method and to investigate marketing strategy of increase income. Research design, data, and methodology - This study investigated not only franchisees but also head office's franchise consultants of convenience stores carefully by Delta technique to suggest actual solutions of practice and to be different from precedent studies. Delphi method's interview and questionnaire were used to investigate performance of franchisees. 120 franchisees were interviewed to consist of men and women. Results - FC visited franchise stores to investigate: Franchisees thought of keeping of exact information on commodity information and sales promotion events, and admitted of franchiser's effort of growth and development of stores and improper visit frequency of stores and low effort of solving of difficulty of franchisees. Conclusions - More than 80% of the franchisees cognized more than 70% of performance upon request of ordering from headquarters: Not only franchisees but also headquarters need to lessen gap of difference of cognition. Franchise headquarters was thought to give services below than common level, and service manual and operation manual were thought to be high. Headquarters need to give practical support service.