• 한국농촌간호학회지
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• 제2권2호
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• pp.111-119
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• 2007

Purpose: In this study consumers' preference for housing for elderly people was analyzed as well as the recognition by elders of silver town facilities, and their preference for service provided by silver town. The study was done to provide basic data for the development of silver town facilities that are low in cost and high in efficiency. Methods: A sample research was used in this study to analyze the understanding of old age, silver town, and service preference. Results: First, interest and intention to live in silver town was very positive, however low cost was also preferred and that is quite different to current silver towns of Korea. Second, women have more understanding of, requests for, and intention to move into silver town facilities than men. Women's demands for silver town facilities must be reflected in the development strategy of silver towns. Third, the most important part of activating silver town facilities is price strategy. Government political support is required in order to keep silver town move-in costs affordable. Fourth, silver towns must function as total service complex towns. Conclusion: This study is meaningful as efficient operation of silver town is suggested rather than facility degradation to achieve price reduction. This result is important to the development of silver towns based on consumer preference, as it suggests a development direction that is focused on securing differentiated services and programs.

• Journal of Power Electronics
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• 제19권2호
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• 한국경영정보학회:학술대회논문집
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• 한국경영정보학회 2007년도 추계학술대회
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• pp.527-532
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• 2007

Differentiation strategies have been suggested as the critical sources of competitive advantage in B2C industry where customers can switch internet shopping mall with one click with virtually no transaction cost. Indeed, competition on low pricing cannot be a viable strategy in B2C industry. Moreover, cultivating customer loyalty to attain profitability is still a challenging task for most internet shopping mall. In this study, we provide empirical analysis results on key managerial variables that indicate the difference between the product categories in terms of customer perception on relative value importance. We first identified comprehensive managerial variables and organized them in terms of customer decision stage. Next, with reference to extant literatures on product characteristics based e-commerce strategy, hypotheses are developed to formalize the customer value differences on the key managerial variables. Empirical testing results indicated that there are significant differences on customer perceived value of the key managerial variables between the product groups. The findings provide useful insight for further study on e-commerce differentiation strategy.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.209-217
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• 2013

This paper presents a control strategy of 4 wheel drive (4WD) vehicles. Proposed control strategy has simple structure and can easily apply to various vehicles with low cost and time. It is consist of feedforward control for traction ability, fedback control for minimizing the wheel speed difference and yaw control for lateral stability. In addition, to integrate the traction and stability control, a blending function is applied. To evaluate the feasibility of the proposed control strategy, actual vehicle experiment is conducted after deciding the tuning parameter through the simulation. The simulation is accomplished by CarSim and Matlab/Simulink and the actual vehicle test is conducted using full size Sports Utility Vehicle (SUV) equipped rear wheel based solenoid type 4WD device.

• Journal of Power Electronics
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• 제17권4호
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• pp.874-883
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• 2017

T-type isolated DC/DC converters have recently attracted attention due to their numerous advantages, including few components, low cost, and symmetrical operation of transformers. This study proposes an improved control strategy for increasing the efficiency of T-type isolated DC/DC converters. Under the proposed strategy, the primary circulating current flows through the auxiliary switches (metal-oxide-semiconductor field-effect transistors) instead of their body diodes in free-wheeling periods. Such feature can reduce conduction losses, thereby improving the efficiency of T-type isolated DC/DC converters. The operation principles and performances of T-type isolated DC/DC converters under the proposed control strategy are analyzed in detail and verified through the simulation and experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권10호
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• pp.3534-3553
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• 2021

The low cost of Bluetooth technology has led to its wide usage in indoor positioning. However, some inherent shortcomings of Bluetooth technology have limited its further development in indoor positioning, such as the unstable positioning state caused by the fluctuation of Received Signal Strength Indicator (RSSI) and the low transmission frequency accompanied by a poor real-time performance in positioning and tracking moving targets. To address these problems, an indoor fusion positioning algorithm of Bluetooth technology and pedestrian dead reckoning (PDR) based on a particle filter with dynamic adjustment of weights calculation strategy (BPDW) will be proposed. First, an orderly statistical filter (OSF) sorts the RSSI values of a period and then eliminates outliers to obtain relatively stable RSSI values. Next, the Group-based Trilateration algorithm (GTP) enhances positioning accuracy. Finally, the particle filter algorithm with dynamic adjustment of weight calculation strategy fuses the results of Bluetooth positing and PDR to improve the performance of positioning moving targets. To evaluate the performance of BPDW, we compared BPDW with other representative indoor positioning algorithms, including fingerprint positioning, trilateral positioning (TP), multilateral positioning (MP), Kalman filter, and strong tracking filter. The results showed that BPDW has the best positioning performance on static and moving targets in simulation and actual scenes.

• 한국정보과학회논문지:데이타베이스
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• 제31권2호
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• pp.122-131
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• 2004

이전의 연구들에서 제안된 많은 색인 방법들은 저차원과 동적인 환경을 가정하고 제안되었다. 그러나 최근의 많은 데이타베이스 응용분야들은 대용량, 고차원 그리고 정적인 환경에 대한 처리를 요구하고 있다. 따라서 기존의 저차원이고 동적인 환경에서 제안되었던 색인 구축 전략들은 특히 데이타 및 공간 분할에 있어서 새로운 환경에 잘 적응하지 못한다. 본 연구에서 우리는 이러한 사실들을 지적하였고, 새로운 환경에 적응하는 색인 구축 시 적용되는 새로운 분할 전략을 성능 모델에 근거하여 제안하였다. 우리의 접근 방법은 기본적으로 정적인 환경에서 색인 구축에 사용되는 패킹이라는 기법을 적용하였다. 그리고 고차원 환경에서 질의 성능의 기대 값을 제시하는 민코프스키-합 비용모델에 대한 관찰 결과를 이용하였다. 이러한 것들에 바탕을 두어 우리는 데이타 및 공간을 균등하게 분할하는 것보다 불균등하게 분할하는 것이 좋을 것이라는 예측을 비용 모델에 대한 관찰 결과로써 도출하였다. 그리고 이러한 결과를 이용한 불균등 분할 방법과 성능 모델들을 제시하였다. 이 연구의 결론으로서 균등 분할 방법보다 불균등 분할 방법이 고차원 환경에서 더 효율적인 방법임을 성능 모델 및 실험을 통하여 보여주었다. 그리고, 어떻게 불균등하게 분할하는 것이 좋은지에 대한 명확한 계량적 기준들을 제시하였다.

• Journal of Information Processing Systems
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• 제17권3호
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• pp.489-504
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• 2021

By distributing computing tasks among devices at the edge of networks, edge computing uses virtualization, distributed computing and parallel computing technologies to enable users dynamically obtain computing power, storage space and other services as needed. Applying edge computing architectures to Internet of Vehicles can effectively alleviate the contradiction among the large amount of computing, low delayed vehicle applications, and the limited and uneven resource distribution of vehicles. In this paper, a predictive offloading strategy based on the MEC load state is proposed, which not only considers reducing the delay of calculation results by the RSU multi-hop backhaul, but also reduces the queuing time of tasks at MEC servers. Firstly, the delay factor and the energy consumption factor are introduced according to the characteristics of tasks, and the cost of local execution and offloading to MEC servers for execution are defined. Then, from the perspective of vehicles, the delay preference factor and the energy consumption preference factor are introduced to define the cost of executing a computing task for another computing task. Furthermore, a mathematical optimization model for minimizing the power overhead is constructed with the constraints of time delay and power consumption. Additionally, the simulated annealing algorithm is utilized to solve the optimization model. The simulation results show that this strategy can effectively reduce the system power consumption by shortening the task execution delay. Finally, we can choose whether to offload computing tasks to MEC server for execution according to the size of two costs. This strategy not only meets the requirements of time delay and energy consumption, but also ensures the lowest cost.

• Journal of Multimedia Information System
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• 제6권3호
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• pp.131-138
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• 2019

With the rapid evolution of communication technology, it became possible to overcome the spatial and temporal limitations faced by humans to some extent. Furthermore, the quality of personal life was revolutionized with the emergence of the personal communication device commonly known as the smart phone. In terms of defense networks, however, due to restrictions from the military and security perspectives, the use of smart phones has been prohibited and controlled in the army; thus, they are not being used for any defense strategy purposes as yet. Despite the current consideration of smart phones for military communication, due to the difficulties of network configuration and the high cost of the necessary communication devices, the main tools of communication between soldiers are limited to the use of flag, voice or hand signals, which are all very primitive. Although these primitive tools can be very effective in certain cases, they cannot overcome temporal and spatial limitations. Likewise, depending on the level of the communication skills of each individual, communication efficiency can vary significantly. As the term of military service continues to be shortened, however, types of communication of varying efficiency depending on the levels of skills of each individual newly added to the military is not desirable at all. To address this problem, it is essential to prepare an intuitive network configuration that facilitates use by soldiers in a short period of time by easily configuring the strategy network at a low cost while maintaining its security. Therefore, in this article, the author proposes a Zigbee-based local strategic network by using Opnet and performs a simulation accordingly.

• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2006년도 추계학술대회
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• pp.409-418
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• 2006

The purpose of this paper is to present a low cost u-City portal development idea and to propose an exclusive system architecture using 3-D interface layers. 3-D interface layers consist of reused ideas of data from existed public data produced from GIS in order to reduce Produce Processes. 3-D interface layers implement a u-City portal systems that tags from physical spaces 1 ink to mobiles from ubiquitous networks between electronic spaces and physical spaces. Primary produce of this study exhibits an exclusive architecture of a u-City portal for speedy and low cost web 3-D interface layers and GIS data, and for implementation interface of 3-D types on USN of physical spaces. Secondary produce of this study represents that a 3-D u-City portal system has visualized speedy implementation characteristics for implementation of the application systems to execute an ubiquitous concept by returning electronic space to physical space, and to present the low cost 3-D u-City portal than an existed 3-D u-city development strategy. Therefore continuous expansion and study of the 3-D interface physical space under a 상황인지(Context Awareness)ubiquitous will appear the innovated u-City portal systems.