• Proceedings of the Korean Society of Computer Information Conference
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• 2013.01a
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• pp.9-12
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• 2013

리눅스 기반 안드로이드 단말에서는 CFS(Completely Fair scheduler)가 사용되고 있다. 그리고 CFS는 태스크의 nice값 조절을 통해서 응용프로그램의 CPU 점유율을 제어할 수 있다. 하지만 안드로이드를 업그레이드할 때마다 수많은 태스크의 nice값을 적절하게 맞추는 일은 매우 어려운 일이다. 이러한 문제를 해결하기 위하여 안드로이드 단말은 리눅스의 cgroup(control group)을 사용하여 태스크들을 그룹으로 나눈다. 고성능과 빠른 응답 특성이 필요한 태스크들을 apps 그룹에 할당하여 높은 CPU 점유율을 보장하고, 그렇지 않은 태스크들을 background 그룹에 할당한다. 하지만 안드로이드의 버전이 업그레이드 되면서 각 그룹에 속한 태스크들에도 변화가 생긴다. 그 결과 동일하게 제작된 태스크들의 CPU 점유율이 달라지게 되고 예기치 못한 성능 저하가 발생할 수 있다. 본 연구에서는 안드로이드 버전 향상에 따라 동종 태스크들이 이전 버전에서보다 성능이 하락하는 현상의 원인을 파악하였다. 아울러 분석과 실험을 통하여 태스크의 nice 값보다 그룹 스케줄링 메커니즘이 어떻게 태스크의 CPU 점유율을 결정 짓는지 규명하였다.

• KIISE Transactions on Computing Practices
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• v.24 no.2
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• pp.67-76
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• 2018

BLE (Bluetooth Low Energy) has been extensively used for communication between mobile applications and wearable devices in IoT (Internet of Things). In developing Android applications, wearable devices, on which the applications can run, should be available because the existing Android SDK does not support any BLE emulation facility. In this study, we have designed and implemented the first Android BLE emulator. Using this, we are able to develop and test BLE-based Android applications even when without wearable devices. We have also proposed an automatic generation method of Android BLE scenarios based on graph model. We have shown that the method is useful for systematically testing BLE application protocols by running the generated scenarios on the Android BLE emulator.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.1-10
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• 2017

The high costs of electric vehicle supply equipment (EVSE) and installation are currently a stumbling block to the proliferation of electric vehicles (EVs). The cost-effective solutions are needed to support the expansion of charging infrastructure. In this paper, we develope EV charging system based on the big data analysis of the power consumption patterns. The developed EV charging system is consisted of the smart EV outlet, gateways, powergates, the big data management system, and mobile applications. The smart EV outlet is designed to low costs of equipment and installation by replacing the existing 220V outlet. We can connect the smart EV outlet to household appliances. Z-wave technology is used in the smart EV outlet to provide the EV power usage to users using Apps. The smart EV outlet provides 220V EV charging and therefore, we can restore vehicle driving range during overnight and work hours.

• KIISE Transactions on Computing Practices
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• v.22 no.11
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• pp.567-575
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• 2016

With the popularity of smartphone, user's location information is of great interest as mobile apps based on the location information are increasing. In this paper, we are interested in analyzing user's speed data based on the location information. It is not uncommon to observe locations with great measurement errors, removing them is necessary. The distribution of speed can be considered as a mixture model in accordance with transportation means. We identify a tail part as a component of a mixture model and fit a simple parametric model to the tail part of the speed distribution.

• Journal of Korea Multimedia Society
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• v.21 no.8
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• pp.982-990
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• 2018

In recent years, many wearable devices and mobile apps related to life care have been developed, and a service for measuring the movement during walking and showing the amount of exercise has been provided. However, they do not measure walking in detail, so there may be errors in the total calorie consumption. If the user's behavior is measured by a multi-axis sensor and learned by a machine learning algorithm to recognize the kind of behavior, the detailed operation of walking can be autonomously distinguished and the total calorie consumption can be calculated more than the conventional method. In order to verify this, we measured activities and created a model using a machine learning algorithm. As a result of the comparison experiment, it was confirmed that the average accuracy was 12.5% or more higher than that of the conventional method. Also, in the measurement of the momentum, the calorie consumption accuracy is more than 49.53% than that of the conventional method. If the activity recognition is performed using the wearable device and the machine learning algorithm, the accuracy can be improved and the energy consumption calculation accuracy can be improved.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.319-324
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• 2011

Recently, development of app for smartphone is much and many apps provide information by reproduced with achieved information from internet site. There is a need of method dependent on reproduced data by app. For solving these requirements, this paper first identifies problems such as lower hardware performance and limited bandwidth when legacy web pages are accessed by smart phones. This paper suggests three methods, "real time," "cache," and "static" to develop application programs for smart phones by considering identified problems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.703-705
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• 2013

외부 데이터베이스를 사용해서 서비스하는 스마트폰 어플리케이션은 네이티브 앱과 모바일 웹을 병행하여 서비스 한다. 일반적인 어플리케이션 환경에서는 외부 데이터베이스에 리소스 및 연산 결과 등의 모든 정보를 담아 두고 접근하여 활용하는 방식을 사용하였다. 반면에 스마트폰 어플리케이션 환경에서 네이티브 앱을 활용하면 디바이스 내부에 외부 데이터베이스의 정보 및 리소스를 저장하여 활용한다. 이 경우 네이티브 앱에서 연산을 수행하고 변경되는 데이터가 발생하면 외부 데이터베이스에 접근하여 업데이트를 수행한다. 그 이유는 병행 접근이 가능한 서비스의 경우 차후에 현재 접근한 네이티브 앱이 아닌 모바일 웹으로 접근하였을 때를 대비해서 최근의 데이터를 항상 유지해야 하기 때문이다. 많은 사용자를 보유한 서비스의 경우 빈번히 발생하는 데이터 업데이트 문제로 많은 자원 소모가 발생된다. 본 논문에서는 앞서 언급한 문제를 해결하고 네이티브 앱과 모바일 웹간의 데이터 연동을 위하여 외부 데이터베이스의 접근을 최소화 하는 기법을 제안한다. 실시간으로 사용자들끼리 정보를 주고받아 상호작용하는 서비스의 빈도가 상당히 낮거나 없는 스마트폰 어플리케이션 환경에서는 서버 접근을 최소화 하는 것이 좋은 방법이다. 제안의 핵심은 네이티브 앱과 모바일 웹의 기본적인 접속 정보만 외부 데이터베이스에 업데이트하여 차후 접속하는 타입이 현재와 다른 경우에만 최근에 변경된 데이터를 외부 데이터베이스에 업데이트하여 서버의 부하를 최소화 하는 것이다. 이 기술을 활용하면 서비스 업체의 경우 서버 유지비용을 낮출 수 있으며 사용자는 빈번히 일어나는 서버와의 통신에 소요되는 비용 및 끊김 현상으로 인한 불편함을 최소화할 수 있을 것으로 사료된다.

• International Journal of Advanced Culture Technology
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• v.4 no.3
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• pp.13-19
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• 2016

The growth of mobile devices in Internet of Things (IoT) leads to a number of remote and controlling system related IoT applications. For instance, home automation controlling system uses client system such web apps on smartphone or web service to access the home server by sending control commands. The home server receives the command, then controls for instance the light system. The web service gateway responsible for handling clients' requests attests an internet latency when an increasing number of end users requests submit toward it. Therefore, this web service gateway fails to detect several commands, slows down predefined actions which should be performed without human intervention. In this paper, we investigate the performance of a web server-side platgorm based event-driven, non-blocking approach called Node.js against traditional thread-based server side approach to handle a large number of client requests simultaneously for remote and controlling system in IoT remote monitoring applications. The Node.JS is 40% faster than the traditional web server side features thread-based approach. The use of Node.js server-side handles a large number of clients' requests, then therefore, reduces delay in performing predefined actions automatically in IoT environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.140-142
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• 2016

Recently, rapid innovation of Smartphone is changing the paradigm of our daily life. Smartphone users, opinion experts more than 99 percent of the economically active population is using, it has reached the saturation past the early stages of formation. Smartphone is equipped with a general purpose OS possible the implementation of high performance environment similar level as a personal computer. Thus, it is a mobile communication terminal scalable which can be removed or installed various applications. Such extensibility, it is possible to use different applications through the Apps store. Also, it is also possible various services which are location based service. In this research, we aim to analyze factors influencing of cloud computing service on reusing intention of smartphone. In addition, we aim to analyze the causal relationship from perceived value to reusing intention. This study suggests practical and theoretical implications based on the results.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.107-113
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• 2017

Open platform technology in the banking industry is anticipated to impact the market very positively together with the activation of Fin Tech services. The domestic environment of payment services has been rapidly changing into the mobiles and multiple new payment services have been introduced from a variety of vendors. However, the convenience of payment always causes worsening the security, and the accidents on the security have been continued to occur such as leakage of personal information, hacking and so on upon the expansion of the industry and the market size. This study aims to analyze the status of Fin Tech open platforms and various problems of the related standard technologies, and to suggest the possible solutions. Upon the analysis results, it was confirmed that multiple solutions were required to improve the main security protocols of open platforms and to process the security functions diversely. In conclusion, the results of this study will be helpful to determine the direction of the solution on the security issues in the open platform environment of the current industry.