• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.850-855
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• 2013

This paper proposes a novel design for a compact, high-isolation WCDMA indoor repeater antenna. The proposed antenna consists of a patch antenna and metamaterial absorber. The required WCDMA bandwidth is obtained by utilizing the coupling between the main and the parasitic patches. In addition, high isolation is achieved using the metamaterial absorber, which has an absorption of about 98% at 2.1 GHz. Overall, the proposed antenna has a gain of over 7 dBi, a Voltage Standing Wave Ratio (VSWR) of less than 2, more than 85 dB of isolation between the service and donor antennas over the WCDMA band and a total volume of the proposed antenna only $70mm{\times}70mm{\times}43.8mm$.

• Journal of Korean Society of Transportation
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• v.16 no.3
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• pp.25-36
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• 1998

고속도로의 Tollgate는 상습 정체지역으로 개선방안이 시급히 요구되어진다. 이에 본 연구는 요금징수소 정체 해결의 기본자료로서 중요한 역할을 수행할 요금징수소의 평균 서비스시간 산정, 설계교통량 결정 및 서비스수준 결정 규정을 제시하였다. 연구방법으로는 공간적인 연구범위인 경주 Tollgate의 교통류 특성을 비데오 카메라로 촬영하여 이를 서비 스시간 측정기를 사용하여 포화서비스시간을 분석하였다. 이를 통하여 포화교통류율을 산정 하였고, 또한 중차량 포화서비스시간을 산정하여 중차량 보정 및 승용차 환산계수를 제시하 였다. 설문지 조사를 통한 운전자의 서비스수준 결정인자와 방법에 대해 조사하고 SPSS를 사용하여 분석하였다. 그리고 설계교통량 결정을 위해서 대기행렬대수 및 대기행렬 지속시 간을 매개변수로 하여 경제성 분석을 실시하였으며, 이를 통하여 게이트 수 결정 방법을 제 시하였다.

• Journal of applied mathematics & informatics
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• v.39 no.1_2
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• pp.31-43
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• 2021

A homogeneous circular disk undergoing a contact force is considered to investigate the thermo-elastic characteristics, and the inquiry is based on the variations of outer surface temperature and angular velocity. The intensity of stresses grows with the increase of outer surface temperature, and the circumferential strain reacts more sensitively to the change of outer surface temperature than the radial strain. In general, higher angular velocity produces; (i) larger expansion in the radial direction, (ii) smaller displacement in the circumferential, (iii) diminished intensity in the stresses. It is demonstrated that outer surface temperature and angular velocity are critical factors in the determination of thermo-elastic characteristics of homogeneous circular disks subjecting to a contact force. The results obtained can be applied on the design of a homogeneous circular cutter to promote proper and reliable thermos-elastic characteristics in service by the proper operation of these parameters.

• International Journal of Computer Science & Network Security
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• v.22 no.1
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• pp.55-60
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• 2022

Churn prediction is a critical long-term problem for many business like music, games, magazines etc. The churn probability can be used to study many aspects of a business including proactive customer marketing, sales prediction, and churn-sensitive pricing models. It is quite challenging to design machine learning model to predict the customer churn accurately due to the large volume of the time-series data and the temporal issues of the data. In this paper, a parallel artificial neural network is proposed to create a highly-accurate customer churn model on a large customer dataset. The proposed model has achieved significant improvement in the accuracy of churn prediction. The scalability and effectiveness of the proposed algorithm is also studied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.779-784
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• 2011

Freeway FFS (Free-Flow Speed) under the state of LOS (Level of Service) A has been regarded as a homogeneous state to all levels of traffic volume. The features of low-density FFS is served as the basic data for a decision on limited maximal speed, accident analysis, simulation modeling etc. A few researches for the macroscopic characteristics of design and operation speed have been reported, and any study for the microscopic features of freeway free-flow speed under the state of low density has not been done. Therefore, the characteristics of low-density FFS according to the level of traffic volume (1-3 veh/30 sec) and daily hour periods (0-5, 6-8, 9-11, 12-19, 20-23) is microscopically analyzed in this study with huge volume and speed data. It was found that speed distributions are changed and show different behaviors under the conditions of traffic volume levels and daily time periods. V85s (85th percentile speed) at early morning and night periods decrease when levels of traffic volume increase, whereas V85s at day time do not show considerable differences. Especially, FFSs of levels of traffic volume at early morning and night periods, despite low density, is analyzed as heterogeneity, but homogeneity at day time.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2004.11a
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• pp.19-24
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• 2004

The Necessity of extending the local library become inevitable because of the swift increasing the volume of information and enlarging the accessibility and increasing the requirements approached to the latest information, caused by continuous development of communication techniques. But these requirements have been concentrated at the quantitative growth to some extent such as an unique and mammoth library at an region or some few independent libraries, never to be considered enough for the users' convinience so that these locational conditions impede the utilization of library As to this matter, this is a basic research what's the best selection of arrangement for establishing public libraries in the future according to the planning regional area and this is the purpose to present a standard of planning regional area in consideration with user's easyaccesibility and also the facilities selecting activities of user's character and set up a planning the basic data about facilities arrangement and space scale before unfolding it's own public service activities of public library as the role of the regional and social information center

• Steel and Composite Structures
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• v.39 no.4
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• pp.419-433
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• 2021

In composite structures, shear connectors are crucial components to resist the relative slip between the steel and concrete, and thereby to achieve the composite actions. In the service stage, composite structures are usually in elastic state, so the elastic stiffness of the shear connection is a quite important parameter in the structural analysis of composite structures. Nevertheless, the existing studies mainly focus on the load-slip relationship rather than the tangent stiffness at the initial elastic stage. Furthermore, when composite beams subjected to torque or local load, shear connections are affected by both tensile force and shear force. However, the stiffness of shear connections under combined effects appears not to have been discussed hitherto. This paper investigates the initial elastic stiffness of stud connections under combined effects of biaxial forces. The initial expression and the relevant parameters are obtained by establishing a simplified analytical model of the stud connection. Afterwards, parametric finite element analysis is performed to investigate the effects of the relevant factors, including the stud length, stud diameter, elastic modulus of concrete, elastic modulus of steel and volume ratio of reinforcement. The feasibility of the proposed modelling has been proved by comparing with sufficient experimental tests. Based on the analytical analysis and the extensive numerical simulations, design equations for predicting the initial elastic stiffness of stud connections are proposed. The comparison between the equations and the data of finite element models demonstrates that the equations are accurate enough to serve for engineering communities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1460-1465
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• 2016

Lots of costs threaten the sustainability of the national health-guarantee system. Despite research by the national center for disease control and prevention on health care dynamics with its auditing systems, there are still restrictions of time limitation, sample limitation, and, target diseases limitation. Against this backdrop, using huge volume of total data, many technologies could be fully adopted to the preliminary forecasting and its target-disease expanding of health. With structured data from the national health insurance and unstructured data from the social network service, we attempted to design a model to predict disease. The model can enhance national health and maximize social benefit by providing a health warning service. Also, the model can reduce the advent increase of national health cost and predict timely disease occurrence based on Big Data analysis. We researched related medical prediction cases and performed an experiment with a pilot project so as to verify the proposed model.

• Journal of the Korean Chemical Society
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• v.67 no.5
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• pp.378-392
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• 2023

The purpose of this study is to analyze the pre-service chemistry teachers' cognition of the nature of model in process of designing and developing models using technology. For this purpose, 19 pre-service chemistry teachers' in the 3rd grade of a education college located in the central region observe experimental phenomena related to Boyle's law presented in the 7th grade science textbook and researchers required the design and development of a model related to the observed experimental results using technology. Based on previous studies, the nature of model were classified into two aspect: 'Representational aspect' and 'Explanatory aspect'. The 'Representational aspect' was classified into 'Representation', 'Abstraction', and 'Simplification', and the 'Explanatory aspect' was classified into 'Analysis', 'Interpretation', 'Reasoning', 'Explanation', and 'Quantification'. The pre-service chemistry teachers' cognition were analyzed by the classification. As a result of the study, the 'Representation' of the 'expressive aspect' was uniformized in the form of space that changes in volume, and the pressure was expressed as the Brightness inside the cylinder or frequency of color change of particles for 'Abstraction'. In the case of 'Simplification', the particle collision was expressed as a perfectly elastic collision, but there was a group that could not simply indicate the type of particle. In the 'Explanatory aspect', in the case of 'Analysis', volume was classified as a manipulated variable, and in the case of 'Interpretation', most groups analyzed the change in pressure through the collision of gas particles. However, the cognition involved in 'Reasoning' was not observed much. In the case of 'Explanation', there were groups that did not succeed in explanation because the area where the particles collided was not set or incorrectly set, and in the case of 'Quantification', there was a group that formulated the number of collisions per unit time, and on the contrary, there was a group that could not quantify the number of collisions because they could not be expressed in numbers.

• Journal of Distribution Science
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• v.14 no.3
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• pp.73-83
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• 2016

Purpose - The parcel delivery service(courier) industry all over the world has been expanding its market so far, but its growth has been declining in recent years. In this situation, most parcel delivery companies are having trouble with managing themselves because of the pressure from the customer to increase service level and decrease the rate. The purpose of this study is to provide ways to improve competitive advantages of the parcel delivery service industry by evaluating the multi-period operating efficiency of Korea, Japan and global service providers. Research design, data, and methodology - The data for the period of 2011 to 2014 were collected from the annual reports published by parcel delivery companies. In this study, we analyze the marketability (revenue), profitability (operating profits), and management conditions (net profits) of parcel service companies by combining information on human resources (number of employees) and material resources (total assets and equity). Therefore, the number of employees, total assets, and equity are selected as input variables, and revenue, operating profits, and net profits as the output variables. In this study, DEA (Data Envelopment Analysis) is used to measure the comparative efficiency and MPI (Malmquist Productivity Index) is used to analyze the trend of change of the efficiency for a multi-year period. Results - The operational efficiency scores of medium-sized parcel delivery companies in Korea are higher than other larger competitors such as Korean, Japan and Global larger companies. As of 2014, Logen(1.878) was found to be the most efficient parcel delivery enterprise, followed by KGB (1.224), and Kyoungdong(1.002). Otherwise, Hanjin(0.235), CJ(0.262), Hyundai Logistics(0.657), DHL(0.611), UPS(0.766), FedEx(0.498), TNT(0.350), Yamato(0.762) and Sagawa(0.520), larger sized companies, were done inefficiently. The productivity of parcel delivery companies is influenced by endogenous factors as well as exogenous ones such as changes in business environment and technological advances. Conclusions - Korean medium-sized companies have relatively high efficiency scores in operation. That is why they still survive the competitive market in Korea where market restructuring on the industry has been expected to be conducted for many years. The reason why medium-sized couriers had higher efficient scores than larger couriers is that most of couriers spend more operating expenses versus unit price of delivery which is the amount of money that is needed in order to send a package by parcel service. So the delivery unit price must be taken into account by all the expenses associated with the cost of fuel, labor and maintenance expenses for facilities, etc. therefore, the unit price must be increased to strengthen business competitive power. In order for the industry to have more competitive advantage, the companies need to make profits by increasing demand volume and raising the delivery rate to provide high-quality delivery service to customers. And both endogenous and exogenous change must take precedence in order to strengthen their competitiveness.