• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.600-608
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• 2017

The presence of piping in a levee body allows water seepage to occur by producing a large cavity or water tunnel within it, ultimately resulting in the failure of the river levee and differential settlement. In order to properly cope with river levee failure due to piping and establish a proper remediation method for this problem, it is necessary to analyze the failure mechanism of the river levee due to piping. Therefore, this study analyzed the shape and mechanism of river levee failure due to piping through small-scale and large-scale models and evaluated the seepage pressure distribution characteristics in the hydraulic well, which has been suggested as a remediation method for piping. According to the results of this study, as the safety factor for the piping in the river levee decreased, the river levee failure shape was more clearly shown through the small-scale model test. In the large-scale model test, the type of local damage to the levee due to the piping was identified and the evaluation showed that the hydraulic well had the largest effect on the inhibition of piping below the center of the well. A follow-up study is needed to confirm the reliability of the results. However, it is thought that this study can be utilized as the baseline data for research into the piping-induced river levee failure mechanism and for the preparation of a remediation method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.511-517
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• 2016

Current oil-type potential transformers for trains are filled with insulating oil, which could have problems like explosions due to rising inner pressure during train operation. Therefore, mold and dry-type potential transformers are being developed to prevent explosions. One problem in manufacturing mold-type transformers is preventing void formation around the coiled core inside the mold during epoxy filling, which could cause an electrical spark. Micro voids can remain in the resin after filling, and macro voids can occur due to the structure shape. A transformer that is being developed has a cavity at the junction of the core and the coil for better performance, and when highly viscous epoxy flows inside the cavity channel, macro voids can form inside it. Therefore, in this study, the free-surface flow of the mold filling procedure was analyzed numerically by applying the VOF method. The results were used to understand the phenomena of void formation inside the cavity and to modify the process conditions to reduce voids.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.561-568
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• 2016

The purpose of this study was to investigate the influence of SNS addiction tendency, pathological narcissism, social support, and stress among university students. Data were collected via questionnaires from 385 students and were analyzed by descriptive statistics, t-test, ANOVA, Scheffe's test, Pearson's correlation coefficients, and Stepwise multiple regression analysis using SPSS/WIN 19.0 program. The levels of SNS addiction tendency depended on gender, SNS usage time, SNS over-usage, health problem, and household economic status. SNS addiction tendency was significantly correlated with pathological narcissism, social support, and stress. Influential factors that affect SNS addiction tendency were pathological narcissism, SNS usage time, SNS over-usage, gender, social support, and academic performance, which explained about 39.4% of the variance. The results of this study indicate that nursing interventions are necessary to improve SNS addiction tendency, and also suggesting that such variables should be carefully considered in intervention programs for university students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.9-16
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• 2016

Wireless sensor networks (WSN) are composed of sensor nodes and a base station. The sensor nodes deploy a non-accessible area, receive critical information, and transmit it to the base station. The information received is applied to real-time monitoring, distribution, medical service, etc.. Recently, the WSN was extended to mobile wireless sensor networks (MWSN). The MWSN has been applied to wild animal tracking, marine ecology, etc.. The important issues are mobility and energy consumption in MWSN. Because of the limited energy of the sensor nodes, the energy consumption for data transmission affects the lifetime of the network. Therefore, efficient data transmission from the sensor nodes to the base station is necessary for sensing data. This paper, proposes an energy consumption model using two-tier clustering in mobile sensor networks (TTCM). This method divides the entire network into two layers. The mobility problem was considered, whole energy consumption was decreased and clustering methods of recent researches were analyzed for the proposed energy consumption model. Through analysis and simulation, the proposed TTCM was found to be better than the previous clustering method in mobile sensor networks at point of the network energy efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.507-517
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• 2017

This study suggests that the diversity of parks is necessary because the number of children, who are the main users in children's parks, is decreasing and the use of parks by older people is increasing. In particular, the present aging society is trying to propose a multi-purpose park to solve the problem of the elderly leisure. To do this, this study surveyed domestic and foreign children's parks and selected study sites to understand the usage patterns of children's parks. As a result of surveying the location of the park to select the study sites, most children's parks were found mostly in single family housing areas and multi-family housing areas. As a result of the survey, it was found that the children's parks consisted of streets and areas by the 'City Parks and Greenery Act' and they were uniform. This paper presents basic data for the development of a model for producing a multipurpose park that can be used for children's parks by the elderly. The subjects of this study were selected from 7 districts of Daegu city, which were classified into single family housing areas and multi-family housing areas. As a result, the arrangement of various facilities in the children's park is insufficient, and it was uniform without a design motive and contents. Therefore, the utilization rate of various age groups could be increased by developing a multi-purpose park model for a children's park.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.657-666
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• 2017

In this study, factor analysis was performed to reduce the friction in the elevation motion of a stand for a 50-inchtelevision. Pipe type cross-section control was used for accurate positioning control of the piston rod. The pipe type was also compared with a labyrinth-type crosssection for the orifice. The frictional force was then reduced using gas seal lip technology. Specifications were chosen, and a volume compensation experiment was carried out using an apparatus for compensating the volume of the cylinder, which is compressed by the volume of the piston rod. Based on CAE and experimental considerations, the labyrinth-type orifice is preferred for reducing friction. For the gas seal lip technology, outer and inner diameters of ${\Phi}20$ and ${\Phi}8$ for the hollow rod were more appropriate when assuming the weight of a 50-inch television to be 30kgf. The third is that the result of total consideration in stability problem and performance of volume compensation for specification decision and volume compensation experiment is determined the final speculation of hollow rod ?8x?4 and riveting system. The last is that the labyrinth orifice is not founded that of the ${\O}0.4{\sim}0.6$ orifice both tests on 300 mm intervals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.85-92
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• 2018

Reductions of the electricity charge are achieved by demand management of the load. The demand management method of the load using ESS involves peak shifting, which shifts from a high demand time to low demand time. By shifting the load, the peak load can be lowered and the energy charge can be saved. Electricity charges consist of the energy charge and the basic charge per contracted capacity. The energy charge and peak load are minimized by Linear Programming (LP) and Quadratic Programming (QP), respectively. On the other hand, each optimization method has its advantages and disadvantages. First, the LP cannot separate the efficiency of the ESS. To solve these problems, the charge and discharge efficiency of the ESS was separated by Mixed Integer Linear Programming (MILP). Nevertheless, both methods have the disadvantages that they must assume the reduction ratio of peak load. Therefore, QP was used to solve this problem. The next step was to optimize the formula combination of QP and LP to minimize the electricity charge. On the other hand, these two methods have disadvantages in that the charge and discharge efficiency of the ESS cannot be separated. This paper proposes an optimization method according to the situation by analyzing quantitatively the advantages and disadvantages of each optimization method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.117-122
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• 2018

A large-capacity three-phase system air conditioner recently includes an inverter circuit to reduce power consumption. The inverter circuit uses a DC voltage that comes from DC-link power capacitor with the function of rectifying, which means AC voltage to DC voltage using a diode. An electrolytic capacitor is generally used to satisfy the voltage ripple and current ripple conditions of a DC-link power capacitor used for rectifying. Reducing the capacitance of the capacitor decreases the size, weight, and cost of the circuit. This paper proposes an algorithm to reduce the input ripple current by combining the minimum point estimation phase locked loop (PLL) phase control and the average voltage d axis current control technique. When this algorithm was used, the input ripple current decreased by almost 90%. The current ripple of the DC-link capacitor decreased due to the decrease in input ripple current. The capacitor capacity can be reduced but the electrolytic capacitor has a heat generation problem and life-time limitations because of its large equivalent series resistance (ESR). This paper proposes a method to select a film capacitor considering the current ripple at DC-link stage instead of an electrolytic capacitor. The capacitance was selected considering the voltage limitation, RMS (Root Mean Square) current capacity, and RMS current frequency analysis. A $1680{\mu}F$ electrolytic capacitor can be reduced to a $20{\mu}F$ film capacitor, which has the benefit of size, weight and cost. These results were verified by motor operation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.143-153
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• 2018

Environmental regulations, which are discussed through the International Maritime Organization, focus on two aspects: the economic supply of fuel oil and, ultimately, securing next-generation energy sources. At present, there are limitations in relation to the basic quality of fuel oil and the direct relation through basic quality when applied to ships and traps in relation to environmental regulations, and the standard for the basic quality of fuel oil is generally used. There are many cases where the composition is very complicated, and the interpretation and analysis of basic quality deviate from the range of the basic standard. In other words, it is difficult to classify and apply the problem when analyzing it in connection with fuel quality and ship operations. In this paper are various factors for the basic quality of fuel oil, and a proposed possibility for the scope of the standard.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.463-471
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• 2018

The career stress of college students is a more serious problem caused by the difficulty of finding a job these days, and various management strategies are needed. The purpose of this study was to investigate the effects of part-time job experience, social support, and ego-resilience on career stress in order to suggest ways to manage career stress. The subjects were 457 college students. Multiple regression analysis was used. First, there were no significant differences in ego-resilience, social support, and career stress according to the experience of part-time job. However, employment pressure, a sub-scale of career stress, was higher among college students who had part-time jobs. Second, the experience of part-time work had a significant effect on career stress. College students without a part-time job showed higher career stress than those who had. Third, the effect of social support on career stress was more effective for college students who did not have part-time jobs. Fourth, ego-resilience showed no effect on career stress. However, an interaction effect between the part-time job experience and gender was found. Based on these findings, college students without part-time work experience should be offered counseling management through social support and a program is needed to enhance ego-resilience in female students.