• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.338-344
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• 2022

It is necessarily required in developing Si-based anode materials for lithium ion batteries, and the related researches are actively working especially in Si-carbon composite material. On the other hand, the photovoltaic and semiconductor industries discard huge amount of Si resources, facing the environmental issue. In this study, recycled Si resource is adopted to obtain Si-carbon composite for LIB(Lithium-Ion Batteries). In order to improve high-capacity retention characteristics and cycle stability of a Si anode material for the LIB, two differenct composites having a mass ratio of silicon and pitch of 1:1 and 2:1 are synthesized and electrochemical characteristics of the anode material manufactured by simple self-assembly method. This result in excellent initial capacity with stable cycle life, and confirming the potential use of recycled Si material for LIB.

• Journal of Creative Information Culture
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• v.7 no.4
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• pp.235-242
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• 2021

Recently, many human activity recognition(HAR) researches using smartphone sensor data have been studied. HAR can be utilized in various fields, such as life pattern analysis, exercise measurement, and dangerous situation detection. However researches have been focused on recognition of basic human behaviors or efficient battery use. In this paper, exercising activities performed indoors and outdoors were defined and recognized. Data collection and pre-processing is performed to recognize the defined activities by SVM, random forest and gradient boosting model. In addition, the recognition result is determined based on voting class approach for accuracy and stable performance. As a result, the proposed activities were recognized with high accuracy and in particular, similar types of indoor and outdoor exercising activities were correctly classified.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.11
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• pp.291-296
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• 2021

The development of the Internet of Things(IoT) requires large computational resources for tasks from numerous devices. Mobile Edge Computing(MEC) has attracted a lot of attention in the IoT environment because it provides computational resources geographically close to the devices. Task offloading to MEC servers is efficient for devices with limited battery life and computational capability. In this paper, we assumed an industrial IoT environment requiring high reliability. The complexity of optimization problem in industrial IoT environment with many devices and multiple MEC servers is very high. To solve this problem, the problem is divided into two. After selecting the MEC server considering the queue status of the MEC server, we propose an offloading decision algorithm that optimizes reliability and energy consumption using genetic algorithm. Through experiments, we analyze the performance of the proposed algorithm in terms of energy consumption and reliability.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.1-6
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• 2021

In this study, we developed AMI terminals of 1 (reader): N (small transmitter). Currently, the government is focusing on the Gas AMI demonstration project to advance the outdated metering system of the urban gas industry, led by the government-sponsored ministries. The supply of gas AMI meters has the advantage of resolving uncertainties in privacy violations and measurement information and preparing for consumer safety through gas leakage detection. In the case of existing AMI meters, readers and transmitters were 1:1 methods, while this technology can be extended to multiple generations with a 1:N method, and a technology that can extend battery life by implementing a low-power design is applied. We hope that this research will contribute to the gas AMI supply project in the future.

• Resources Recycling
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• v.31 no.3
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• pp.27-39
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• 2022

The global demand for lithium-ion batteries (LIBs) has been continuously increasing since the 1990s along with the growth of the portable electronic device market. Of late, the rapid growth of the electric vehicle market has further accelerated the demand for LIBs. The demand for the LIBs is expected to surpass the supply of lithium from natural resources in the near future, posing a risk to the global lithium supply chain. Moreover, the continuous accumulation of end-of-life LIBs is expected to cause serious environmental problems. To solve these problems, recycling the spent LIBs must be viewed as a critical technological challenge that must be urgently addressed. In this study, recycling LIBs using pyrometallurgical processes and post-processes for efficient lithium recovery are briefly reviewed along with the major accomplishments in the field and current challenges.

• Industry Promotion Research
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• v.7 no.3
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• pp.65-70
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• 2022

The purpose of this study was to investigate the child counselling process of a 5-year old girl with anger problem. Her mother had difficult on caring a child. The researcher conducted 47 session of child counseling through child-centered play therapy once per week during 14months for 40 minutes. Parent consultation session follwed for 10 minutes. The child expressed her aggression, control, desire of affection and power during the sessions. As a result, the child's anger decreased, and child-mother relationship improved. Finally, the child successfully adapted new school life. The mother reported that raising children was much easier than before. This study is meaningful that it is a case study of a child's intervention in counseling prior to her entering elementary school. This study showed her adaptive school lifestyle during the beginning of the first year.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.28-32
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• 2023

Recently, the use of stable lithium nanostructures as substrates and electrodes for secondary batteries can be a fundamental alternative to the development of next-generation system semiconductor devices. However, lithium structures pose safety concerns by severely limiting battery life due to the growth of Li dendrites during rapid charge/discharge cycles. Also, enabling long cyclability of high-voltage oxide cathodes is a persistent challenge for all-solid-state batteries, largely because of their poor interfacial stabilities against oxide solid electrolytes. For the development of next-generation system semiconductor devices, solid electrolyte nanostructures, which are used in high-density micro-energy storage devices and avoid the instability of liquid electrolytes, can be promising alternatives for next-generation batteries. Nevertheless, poor lithium ion conductivity and structural defects at room temperature have been pointed out as limitations. In this study, a low-dimensional Graphene Oxide (GO) structure was applied to demonstrate stable operation characteristics based on Li+ ion conductivity and excellent electrochemical performance. The low-dimensional structure of GO-based solid electrolytes can provide an important strategy for stable scalable solid-state power system semiconductor applications at room temperature. The device using uncoated bare NCA delivers a low capacity of 89 mA h g-1, while the cell using GO-coated NCA delivers a high capacity of 158 mA h g−1 and a low polarization. A full Li GO-based device was fabricated to demonstrate the practicality of the modified Li structure using the Li-GO heterointerface. This study promises that the lowdimensional structure of Li-GO can be an effective approach for the stabilization of solid-state power system semiconductor architectures.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.39-44
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• 2023

In this study, the particle size of Si polycrystals was controlled through wet-sedimentation method, and changes in the capacity and cyclic characteristics of the Si anode material according to the particle size were observed. After wet-sedimentation of Si particles pulverized by a vibration mill, the non-uniform particle distribution of Si was uniformly controlled. The d₅₀ of a sample in which Si was sedimented for 24 hours decreased to 0.50 ㎛. As a result of the electrochemical characteristic analysis, the Rct value representing the resistance in the electrode was significantly reduced due to the decrease in particle size. The unclassified Si sample exhibited a discharge capacity of 2,869 mAh/g in the first cycle, and decreased to 85.7 mAh/g after 100 cycles. The sample in which Si was classified for 24 hours showed a capacity of 3,394 mAh/g initially, and maintained a capacity of 1,726 mAh/g after 100 cycles. As the size of the Si particles decreased, the discharge capacity increased and the cycle life was also increased.

• Journal of the Korea Society of Computer and Information
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• v.14 no.7
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• pp.123-132
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• 2009

The perforrnance and portability of mobile applications can be greatly increased by adopting proxy modiles which exists between the conventional system and the device. When mobile devices collaborate with the conventional computers, there are problems to address: a battery life problem, limited input and output methods, and intermittent wireless connection. Those issues are magnified in the multimedia collaboration environment since it works in a real-time condition and the size of the message in the system is big in many cases. Additionally, because multimedia collaboration system softwares are too heavy and complex for mobile devices, it is veη hard to integrate them with conventional systems. In this paper, we describe our design and its implementation of a novel approach to map events (i.e. messages) using a proxy for mobile applications. We adopt a proxy to provide a content adaptation (i.e. transcoding) where the message contents are customized. Also, we design a mobile version publish/subscribe system to provide communication service for mobile device in loosely coupled and flexible manner. We present our empirical results which show that our design can be efficiently implemented and integrated with a conventional multimedia collaboration system.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.47-54
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• 2024

In this study, ZIF67/rGO was used to minimize the battery life degradation due to the insulating properties of sulfur and the elution of lithium polysulfide. ZIF67 wrapped in rGO creates more space within the carbon sponge and can hold a large amount of sulfur. The sulfur@ZIF67/rGO composite was synthesized and prepared as a sponge to enhance the sulfur retention capacity. The result showed a high initial capacity, with a value of about 1093 mAh g^-1 and a capacity retention rate of 84% after 100 cycles. The high interaction with sulfur through the complexation of cobalt and carbon confirmed that ZIF67/rGO exhibits high performance as a carrier for sulfur, the anode active material of lithium-sulfur batteries, and the high initial capacity and improved capacity retention rate were confirmed.