• Journal of Korea Game Society
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• v.19 no.4
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• pp.49-64
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• 2019

In this paper, we examined the concept of three types of double loot box respectively and analyzed each characteristics of double loot box by game case study. Those types are divided into the following three cases; 1) Double-mileage gacha 2) Double-limited period gacha 3) Kompu gacha. As the result, Double loot boxs are characterized as below: 1) Double loot box has a tendency to combine various type of loot boxes. 2) Double loot box's reward is hard to gain in game, or not to sell in game store. With these features, double loot box could be a gambling sales strategy. To solve this problem, this study suggested that it is essential to revise game self-regulations, enhance the professionalism of monitoring groups, and propel the self-effort of game companies.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.146-153
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• 2019

The exposure system is a device that transfers a circuit pattern to a desired location. To display patterns on a substrate without deforming the optical characteristics, the characteristics of the optical exposure system are very important. Therefore, to form a microcircuit pattern, a small divergence angle should impinge on the irradiation area. Also, since the light from the source must react uniformly with the photosensitizer, it must have high luminance efficiency and uniformity of illumination. In this paper a parabolic reflector and an aspherical lens were designed to solve the problem of narrow-angle implementation, and it was confirmed by simulation analysis after their arrangement that the beam angle, uniformity, and maximum illuminance satisfied the target performance.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.5
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• pp.101-108
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• 2019

The domestic duck industry is the sixth-largest among the livestock industries. However, 34.3% of duck houses were the duck houses arbitrarily converted from plastic greenhouses. This type of duck house was difficult to properly manage internal air temperature and humidity environment. Humidity environment inside duck houses is an important factor that directly affects the productivity and disease occurrence of the duck. Although the humidity environments of litters (bedding materials) affect directly the inside environment of duck houses, there are only few studies related to humidity environment of litters. In this study, evaporation rates from litters were evaluated according to air temperature, relative humidity, water contents of litters, and wind speed. The experimental chamber was made to measure evaporation rates from litters. Temperature and humidity controlled chamber was utilized during the conduct of the laboratory experiments. Using the measured data, a multi linear regression analysis was carried out to derive the calculation formula of evaporation rates from litters. In order to improve the accuracy of the multi linear regression model, the partial vapor pressure directly related to evaporation was also considered. Variance inflation factors of air temperature, relative humidity, partial vapor pressure, water contents of litters, and wind speed were calculated to identify multicollinearity problem. The Multiple $R^2$ and adjusted-$R^2$ of regression model were calculated at 0.76 and 0.71, respectively. Therefore, the regression models were developed in this study can be used to estimate evaporation rates from the litter of duck houses.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.391-405
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• 2019

Compared to the ambient vibration test mainly identifying the structural modal parameters, such as frequency, damping and mode shapes, the impact testing, which benefits from measuring both impacting forces and structural responses, has the merit to identify not only the structural modal parameters but also more detailed structural parameters, in particular flexibility. However, in traditional impact tests, an impacting hammer or artificial excitation device is employed, which restricts the efficiency of tests on various bridge structures. To resolve this problem, we propose a new method whereby a moving vehicle is taken as a continuous exciter and develop a corresponding flexibility identification theory, in which the continuous wheel forces induced by the moving vehicle is considered as structural input and the acceleration response of the bridge as the output, thus a structural flexibility matrix can be identified and then structural deflections of the bridge under arbitrary static loads can be predicted. The proposed method is more convenient, time-saving and cost-effective compared with traditional impact tests. However, because the proposed test produces a spatially continuous force while classical impact forces are spatially discrete, a new flexibility identification theory is required, and a novel structural identification method involving with equivalent load distribution, the enhanced Frequency Response Function (eFRFs) construction and modal scaling factor identification is proposed to make use of the continuous excitation force to identify the basic modal parameters as well as the structural flexibility. Laboratory and numerical examples are given, which validate the effectiveness of the proposed method. Furthermore, parametric analysis including road roughness, vehicle speed, vehicle weight, vehicle's stiffness and damping are conducted and the results obtained demonstrate that the developed method has strong robustness except that the relative error increases with the increase of measurement noise.

• Communications of Mathematical Education
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• v.33 no.3
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• pp.319-334
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• 2019

In this study, using the tasks related trigonometric functions, the degree of high school students' understanding of the function concept was examined through the level of Hitt(1998). First, the degree of the students' understanding was classified by level, then the concept understanding was reclassified by the process or the object. As a result, high school students' concept understanding showed incompleteness in three stages. It was possible to know that the process in the interpretation of the graph is the main perspective, and the operation of algebraic representation is regarded as important. Based on these results, it seems necessary to study the teaching-learning method which can understand trigonometric functions from various perspectives. It seems necessary to study a lesson model that can reach function concept's understanding level 5 that maintains consistency between problem solving and representation system.

• Steel and Composite Structures
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• v.31 no.5
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• pp.503-516
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• 2019

This work presents a dynamic investigation of functionally graded (FG) plates resting on elastic foundation using a simple quasi-3D higher shear deformation theory (quasi-3D HSDT) in which the stretching effect is considered. The culmination of this theory is that in addition to taking into account the effect of thickness extension (${\varepsilon}_z{\neq}0$), the kinematic is defined with only 4 unknowns, which is even lower than the first order shear deformation theory (FSDT). The elastic foundation is included in the formulation using the Pasternak mathematical model. The governing equations are deduced through the Hamilton's principle. These equations are then solved via closed-type solutions of the Navier type. The fundamental frequencies are predicted by solving the eigenvalue problem. The degree of accuracy of present solutions can be shown by comparing it to the 3D solution and other closed-form solutions available in the literature.

• Journal of Korean Society of Rural Planning
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• v.25 no.2
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• pp.1-13
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• 2019

The rural development policies and projects in Korea has been implemented with various related acts. For instance, these acts include Framework Act on the National Land, National Land Planning Utilization Act, Special Act on Balanced National Development, etc, enacted by each of adminstration. However, there are some limitations to encourage the variety of rural development policies due to duplication and overlapping between the relevant acts. Nowadays, the fields of rural development have been evolved and integrated not only by agricultural infrastructures but also in various fields such as multi-functional industry including rural tourism, green care, and cultural welfare, etc. Therefore, the current legal system may not effectively accept and support in various rural development policies and projects at all. This study tried to figure out the necessity of reorganization related legal system through the field survey to planners, residents and analysts regarding the correlation between legal systems and projects. For these reasons, this study tried to find out the problem of current legal system and then, suggested alternative methods related to the legal system for integrated rural development. The scope of the study is as follows; 1)correlation analysis between relevant laws and rural development projects. 2)field survey to figure out the legitimacy and validity for the reorganization of the legal system. At last the result of the research has suggested an alternative method to reorganize the legal system and proposed the new legal system with is good for integrated rural development.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.101-112
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• 2019

This study developed selection criteria of small-scales reservoirs, having under $300,000m^3$ storage capacity, for the Emergency Action Plan(EAP) establishment in order to reduce the disaster risks of the reservoir's failures. Those reservoirs are out of ranges of Korean EAP establishment standard, but have potential risk of disasters as they have often failed by the recent extreme rainfall events and earthquakes, causing economical and life losses. The problem of reservoir aging is also one of the reasons of them. In this study, the developed selection criteria of small reservoirs for EAP establishment are storage capacity, embankment height, reservoir age, heavy rain factor and earthquake factor. These criteria were selected based on the review of the existing EAP establishment guidelines, analysis of the past dam failure cases, and the previous related studies. The quantification of these criteria were conducted for the practical applications in the fields, and applied to 67 previous failures in order to investigate the relation of each criteria with these failures. The earthquake factor found to be the highest relations followed by heavy rain factors, combination of earthquake and heavy rain factors, and reservoir age. The classification was made as observation and review groups for EAP establishments based on overlapping numbers of each criteria. This classifications applied to 354 reservoirs designated as having the potential disaster risk by MOIS, and showed 38.4% of observation and 11.9% of review groups. Anticipatory monitoring and regular inspection should be made by professional facility managers for the observation group, and necessity of EAP establishment should be assessed for the review group based on the downstream status and financial budget.

• Health Policy and Management
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• v.28 no.4
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• pp.339-351
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• 2018

Background: The purpose of this study is to estimate empirically whether there is a difference in medical use among income groups, and if so, how much. This study applies econometric model to the most recent year of Korean Medical Panel, 2015. The model consists of outpatient service and inpatient service models. Methods: The probit model is applied to the model which indicate whether or not the medical care has been used. Two step estimation method using maximum likelihood estimation is applied to the models of outpatient visits, hospital days, and outpatient and inpatient out-of-pocket cost models, with disconnected selection problems. Results: The results show that there was the inequality favorable to the low income group in medical care use. However, after controlling basic medical needs, there were no inequities among income groups in the outpatient visit model and the model of probability of inpatient service use. However, there were inequities favorable to the upper income groups in the models of probability of outpatient service use and outpatient out-of-pocket cost and the models of the number of length of stay and inpatient out-of-pocket cost. In particular, it shows clearly how the difference in outpatient service and inpatient service utilizations by income groups when basic medical needs are controlled. Conclusion: This means that the income contributes significantly to the degree of inequality in outpatient and inpatient care services. Therefore, the existence of medical care use difference under the same medical needs among income groups is a problem in terms of equity of medical care use, so great efforts should be made to establish policies to improve equity among income groups.

• The Korean Journal of Archival Studies
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• no.41
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• pp.75-111
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• 2014

With the quantitative growth of research data, the issue of enormous preservation cost and sharing expansion, the organizations should prioritize the collections then select the data that are worthy of save. Therefore, today, it is important for the organizations to appraise the continuing value of produced records. Considering the universities and the public institutions such as governmentfunded research institutes as the heavy producer of the data, it becomes a rising problem for the records management that it does not go beyond the framework of "administrative records" and "public records". In this study, I looked into the background of the contention that the research records must be managed in a different perspective and checked the characteristics of research records in therms of the producers, research activities and records. Based on this analysis, I suggested the main issues and considerations about the subjects, criterias and methods in research records appraisal.