• Journal of the Korean Institute of Gas
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• v.23 no.5
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• pp.8-14
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• 2019

Although the rate of city gas supply in South Korea has grown significantly, the fields related to gas meters have not yet escaped from the initial method of service (e.g. measurement, safety checks, billing, etc). As smart gas meters are actively developed and researched, the introduction of smart gas meters requires rational performance evaluation methods and standards to verify reliability and safety. The purpose of this paper is to make a prototype of the performance evaluation to test the performance of the smart gas meter and to derive the performance evaluation method by conducting the demonstration operation so that the smart gas meter can be smoothly distributed in South Korea.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4006-4024
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• 2017

Internet of Things (IoT) will transform our daily life by making different aspects of life smart like smart home, smart workplace, smart health and smart city etc. IoT is based on network of physical objects equipped with sensors and actuators that can gather and share data with other objects or humans. Secure communication is required for successful working of IoT. In this paper, a total of 13 lightweight cryptographic algorithms are evaluated based on their implementation results on 8-bit, 16-bit, and 32-bit microcontrollers and their appropriateness is examined for resource-constrained scenarios like IoT. These algorithms are analysed by dissecting them into their logical and structural elements. This paper tries to investigate the relationships between the structural elements of an algorithm and its performance. Association rule mining is used to find association patterns among the constituent elements of the selected ciphers and their performance. Interesting results are found on the type of element used to improve the cipher in terms of code size, RAM requirement and execution time. This paper will serve as a guideline for cryptographic designers to design improved ciphers for resource constrained environments like IoT.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.2
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• pp.43-52
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• 2019

The recent technological developments of smart devices, multiple services are provided to enhance the users' quality of life including smart city, smart energy, smart car, smart healthcare, smart home, and so on. Academia and industries try to provide the users with convenient services upon seamless technological research and developments. Also, whenever and wherever a variety of services can be used without any limitation on the place and time upon connecting with different types of devices. However, security weaknesses due to integrations of multiple technological elements have been detected resulting in the leakage of user information, account hacking, and privacy leakage, threats to people's lives by device operation have been raised. In this paper, safer communication framework is suggested by device control and user authentication in the mobile network environment. After implementations of registration and authentication processes by users and devices, safe communication protocol is designed based on this. Also, renewal process is designed according to the safe control of the device. In the performance evaluation, safety was analyzed on the attack of protocol change weakness occurred in the existing system, service halt, data leakage, illegal operation control of message, and so on, which confirmed the enhanced speed approximately by 8% and 23% in the communication and verification parts, respectively, compared to the existing system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.1
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• pp.74-82
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• 2019

The revolution of industry 4.0 is enabling us to build an intelligent connection society called smart cities. The use of renewable energy in particular solar energy is extremely important for modern society due to the growing power demand in smart cities, but its difficult to monitor and manage in each buildings since need to be deploy low energy sensors and information need to be transfer via wireless sensor network (WSN). The Internet of Things (IoT) / low-power wide-area (LPWA) is an emerging WSN technology, to collect and monitor data about environmental and physical electrical / electronics devices conditions in real time. However, providing power to IoT sensor end devices and other public electrical loads such as street lights, etc is an important challenging role because the sensor are usually battery powered and have a limited life time. In this paper, we proposes an efficient solar energy-based power management scheme for smart city based on IoT technology using LoRa wide-area network (LoRaWAN). This approach facilitates to maintain and prevent errors of solar panel based energy systems. The proposed solution maximizing output the power generated from solar panels system to distribute the power to the load and the grid. In this paper, we proved the efficiency of the proposed system with Simulink based system modeling and real-time emulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.415-423
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• 2021

Citizen participation and Living Lab are attracting interest as one of the major strategies for the success of smart cities. In a Living Lab, citizens, who are the end-users of technology, participate in the search for alternatives to define and solve problems and repeat experiments to verify alternatives in a circular process. The purpose of this research was to present an operating model of a citizen-participating online community platform to improve urban problems, implement and test it, and show its applicability. To this end, an operation model of a citizen-participating online community platform was proposed to improve urban problems. An online platform was designed and implemented to reflect the functions pursued by the operation model. Finally, a pilot test for the function was performed using the Oma Elementary School case located in Ilsan, Goyang-si, Gyeonggi-do. The operating model was designed with the city's pedestrian environment and children. As a result, the sharing and communicating process of urban issues among community members worked appropriately according to the designed intention. The Living Lab coordinator could visualize and view urban issues posted by users on a map based on location information. Visualizing the urban problem as a heat map confirmed that urban problems were concentrated in a specific area.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.6
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• pp.109-119
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• 2021

Thermal environment of city is getting worse due to severe urban heat island caused by climate change and urbanization. Green roof improves the urban thermal environment and save the cooling energy in buildings. This study presented a green roof combined with a storage system that stores rain-water and supplies water through a wick and evaluated the temperature reduction effect as surface temperature and amount of evapotranspiration. For about a week, the surface temperature using a infrared thermal imager and the evapotranspiration by recording change of module weight were measured at intervals of 30 minutes from sunrise to sunset. The results show that the mean surface temperature of the green roof was 15.4 degrees lower than that of the non-green roof from 12:00 P.M. to 14:00 P.M. There was no significant difference between mean surface temperature of green roof with and without storage system immediately after rain, but more than a week after rain, there was a difference with average of 2.49 degrees and maximum of 4.72 degrees. The difference in daily amount of evapotranspiration was measured to be 1.66 times on average. As drought stress increased over time, the difference in daily amount of evapotranspiration and surface temperature between with/without storage system increased simultaneously. The results of the study show a more excellent cooling effect of green roof combined with the rainwater storage system.

• Journal of the Korean Society of School Health
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• v.28 no.3
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• pp.200-210
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• 2015

Purpose: This study aimed to examine the use of smart phones and their relationship with self-efficacy and academic achievement among students in 5th to 6th grade. Methods: 954 students in $5^{th}$ to $6^{th}$ grade were selected from three elementary schools in K City through purposive sampling. Data of 591 respondents were analyzed by $x^2$ test, ANOVA, correlation analysis and multiple regression analysis using the SPSS/WIN program. Results: First, 64% of the students possessed a smart phone and female students used their phone more than male students. 47.5% of the students said they first used a smartphone in their $5^{th}$ grade and 11.7% said in their 6th grade. Second, heavier use of smart phones was related to a lower level of self-efficacy (p<.001). Third, the more the students used a smart phone, the less they achieved in academic performance (Korean language: p<.001, mathematics: p<.01). Finally, the biggest factor influencing smart phone addiction was longer use of smart phones. In addition, lower self-efficacy and lower ability to adapt to difficult tasks were the factors influencing the increase in smart phone addiction. Less use of smart phones and higher self-efficacy resulted in higher achievement in academic performance. Conclusion: It is essential to decrease students' use of smart phones and improve their self-efficacy and academic performance. Intervention programs to reduce the use of smart phones should include a profound interest, a personality-oriented educational environment and sufficient dialogues with students at home, schools and the local society, beyond simple regulations to prevent adverse effects.

• Journal of Intelligence and Information Systems
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• v.14 no.3
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• pp.109-131
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• 2008

Ubiquitous Smart Space(USS) like u-City has been expected to create a high added value. However, developing USS has a high risk because it should use future technologies and development methodologies that have been never tried in the past. Hence, it has to be considered thoroughly in the very first stage of development. Moreover, USS usually uses several ubiquitous computing technologies combinationally because of the nature of USS. Despite of this, existing technology selection methodologies or technology evaluation methodologies only focus on a single technology. This leads us to develop a methodology of optimal technology combination for developing a specific USS. The purpose of this paper is to propose the methodology and to apply it to develop a real USS. We use portfolio theory and constraint satisfaction problem to determine an optimal technology combination. We also apply our methodology to the national ubiquitous computing project which carries out at present to validate it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7902-7909
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• 2015

The needs for smart city management technology has been increased for efficiently managing huge and complex social infrastructures. Thus, this research introduces smart bridge facility management system based on sensor and BIM technologies so that the inadequacy of current facility maintenance system and the limitations of data objectivity, consistency and expandability can be improved. For which, current trends on sensor and BIM technologies and standard information system were investigated to derive system develop requirements, and a scenario was suggested to discuss how to utilize the suggested system. Research outcomes are expected to be utilized as a preliminary research for developing the real application framework for bridge facility management.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.3
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• pp.148-159
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• 2013

An analysis of the throughput and stability region of random access systems is currently of interest in research and industry. This study evaluated the performance of a multiuser random access channel with a retransmission gain. The channel was composed of a media access control (MAC) determined by the transmission probabilities and a multiuser communication channel characterized by the packet reception probabilities as functions of the number of packet transmissions and the collision status. The analysis began with an illustrative two-user channel, and was extended to a general multiuser channel. For the two-user channel, a sufficient condition was derived, under which the maximum throughput was achieved with a control-free MAC. For the channel with retransmission gain, the maximum steady throughput was obtained in a closed form. The condition under which the random access channel can acquire retransmission gain was also obtained. The stability region of the general random access channel was derived. These results include those of the well-known orthogonal channel, collision channel and slotted Aloha channel with packet reception as a special instance. The analytical and numerical results showed that exploiting the retransmission gain can increase the throughput significantly and expand the stability region of the random access channel. The analytical results predicted the performance in the simulations quite well.