• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.158-160
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• 2022

Many office workers spend a lot of time performing repetitive office tasks in inefficient ways. We developed a user-friendly chatbot system based on Kakaotalk to automate repetitive tasks and used the chatbot in the real workplace. In the process of operating the chatbot, if several people use the chatbot at the same time, the server was down or could not respond. To address these issues, we performed code migration of programs used by chatbot back-end servers and tried several ways to improve server performance such as database redesign and load balancing. To determine how much each method affects performance improvement, we measured total request per second and average latency. After that, we proposed ways to improve the problems of using the chatbot in the work environment.

• Journal of the Korea Society of Computer and Information
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• v.28 no.4
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• pp.113-120
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• 2023

Smart farms are steadily increasing in research to minimize labor, energy, and quantity put into crops as IoT technology and artificial intelligence technology are combined. However, research on efficiently managing crop growth information in smart farms has been insufficient to date. In this paper, we propose a management technique that can efficiently monitor crop growth information by applying autonomous sensors to smart farms. The proposed technique focuses on collecting crop growth information through autonomous sensors and then recycling the growth information to crop cultivation. In particular, the proposed technique allocates crop growth information to one slot and then weights each crop to perform load balancing, minimizing interference between crop growth information. In addition, when processing crop growth information in four stages (sensing detection stage, sensing transmission stage, application processing stage, data management stage, etc.), the proposed technique computerizes important crop management points in real time, so an immediate warning system works outside of the management criteria. As a result of the performance evaluation, the accuracy of the autonomous sensor was improved by 22.9% on average compared to the existing technique, and the efficiency was improved by 16.4% on average compared to the existing technique.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1083-1095
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• 2023

Recently, the demand for low-voltage, high-capacity ESS is rapidly increasing due to the revitalization of the e-mobility industry, which is mainly powered by electricity. In addition, the demand for portable power banks is rapidly increasing due to the revitalization of leisure industries such as camping and fishing. The ESS with this structure consists of a small number of series cells and many parallel cells, resulting in a system with a large rated current. Therefore, the number of power devices for cell balancing configured in series is small, but a balancing device with a large current capacity is required. Construction of a constant temperature device in such a low-voltage, high-current ESS is difficult due to economic issues. The demand for an active balancing system that can solve the passive balancing heating problem is rapidly increasing. In this paper, propose a power feedback fly-back topology that can solve the balancing heating problem. The characteristic of the proposed topology is that a series-connected voltage sharing voltage is used as the input of the flyback converter, and the converter output is connected to one transformer. In this structure, the converter output for cell voltage balancing shares magnetic flux through one high-frequency transformer, so the cell voltage connected to the converter automatically converges to the same voltage.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.3
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• pp.41-49
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• 2024

In this paper, we validate simulation results for the design optimization of a Superconducting Fault Current Limiter (SFCL) intended for use in Medium Voltage Direct Current systems (MVDC). With the increasing integration of renewable energy and grid connections, researchers are focusing on medium-voltage systems for balancing energy in new and renewable energy networks, rather than traditional transmission or distribution networks. Specifically, for DC distribution networks dealing with fault currents that must be rapidly blocked, current-limiting systems like superconducting current limiters offer distinct advantages over the operation of DC circuit breakers. The development of such superconducting current limiters requires finite element analysis (FEM) and an extensive design process before prototype production and evaluation. To expedite this design process, the design outcomes are assimilated using a Reduced Order Model (ROM). This approach enables the verification of results akin to finite element analysis, facilitating the optimization of design simulations for production and mass production within existing engineering frameworks.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1270-1273
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• 2007

최근 인터넷의 급속한 발달은 온라인 뱅킹, 인터넷 쇼핑몰 등에서의 실물 경제행위를 온라인상으로 처리할 수 있는 환경을 제공하지만 온라인상의 업무처리는 개인정보유출, 개인정보의 위조 및 변조 등의 문제를 가지고 있다. 사용자가 CA에게서 받은 인증서의 공개키로 전자서명 함으로써 개인정보유출, 정보의 위조 및 변조 등의 문제를 해결한 PKI(Public Key Infrastructure)기반의 인증서 검증시스템이 제안되어 사용되고 있다. 인증서 상태검증 방법에는 CRL(Certificate Revocation List)기반의 검증방식, OCSP(Online Certificate Status Protocol)기반의 검증방식 등이 있다. CRL기반의 인증서 검증방식은 인증서 취소목록을 검색해서 인증서의 유효성 여부를 응답하는 방식으로 시간이 지남에 따라 크기 증가와 오프라인 방식으로 인해서 목록을 다운받는 시간의 부담으로 인해서 OCSP방식이 제안되었다. 하지만 OCSP 방식 역시 서비스의 요청이 집중될 경우 문제가 발생될 수 있다. 그래서 분산된 OCSP를 구축하고 각 서버의 부하의 균형을 유지하기 위해 로드밸런싱 기법을 사용하고 있지만 그 방법 역시 지속적인 서비스 제공이 불가한 문제를 가지고 있다. 본 논문에서는 서비스 요청의 집중으로 인한 시스템 마비나 각 응답서버의 부하가 불균형적임으로써 생길 수 있는 문제를 해결할 수 있는 방법을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.59-68
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• 2004

Thanks to the development of microelectromechanical systems(MEMS), wireless communication technology and microsensor technology, it was Possible to manufacture a very small and low costdata acquisition node with sensing function, processing function, wireless communication function and battery. Thus sensor networks begin to be prevailed. The sensor network is a spontaneous system which sets up automatically routing paths and transmits asignificant data to the destination. Sensor nodes requires low-power operation because most of them use a battery as operating power. Sensor nodes transmit a sensing data to the destination. Moreover, they play a router. In fact, because the later consumes more energy than the former, the low-power routing is very important. Sensor networks don't have a routing standard unlike general wireless Ad-hoc networks. So This paper proposes a low-power routing method for anting to sensor networks. It is based on AODV and adapts a method to drop probably RREQ depending on remaining power. We examined it through simulations. From simulation results, we could confirm to reduce power consumption about $10-20\%$ and distribute equally power consumption among nodes.

• Journal of Digital Contents Society
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• v.19 no.8
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• pp.1585-1592
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• 2018

Due to un-balancing weight allocation on the wheelchair the existing wheelchair system are faced with the risk of flipping or falling when a wheelchair goes up to a hill. In to order to be safer during riding the wheelchair, in this paper, we proposed a real-time new solution using the integrated Gyro Sensor and Tilt Sensor for controlling the balance. Because the typical property of wheelchair is for the special user who meets the difficulty in moving on foot the maintain the balance of wheel-chair systems have become important and helpful. In our method, we calculate the seat angle using information from Tilt Sensor. However, due to the law of inertia when a wheelchair is moving there is a deviation in the output value of Tilt Sensor. Therefore, we have to optimize the value of the angle by utilizing the acceleration that is the output of the Gyro Sensor. We took the advantages by using the combination of Gyro and Tilt sensors. Moreover, we also solved the consumption issue of the whole system. Through various experimentations with usage of ZigBee sensor module, the power consumption for the balancing system is reduced significantly.

• Journal of the Korea Society for Simulation
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• v.17 no.2
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• pp.63-74
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• 2008

The design of best efficient production process is common requirements of the production strategy department and the process planning department to maximize the revenue and accomplish target production volumes in the production periods. And they use several general methods for that-line-balancing, removing of the bottle-neck process, facility ramp-up, increasing of the worker's utilization, etc. But, those methods have depended on analytic, static and arithmetic calculations, yet. So, irregular work-waiting time causing the delay time isn't include in extracting production capacity, especially in the line production process. The work-waiting time is changed irregularly along the variation of each machine and very important for calculate real product lead-time and forecasting target production volumes. At this thesis, i'm going to mention the importance of the delay time of conveyor system which can be extracted by discrete-event simulation. And suggest it as a new main variable that must be considered at designing new production system. Then experimented and tested that's effects in the H-company case, conveyor based line production process.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.26-35
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• 2011

In these days, internet environment are very quickly development as well on-line service have been using a online for the mission critical business around the world. As the amount of information to be processed by computers has recently been increased there has been cluster computing systems developed by connecting workstations server using high speed networks for high availability. but cluster computing technology are limited for a lot of IT resources. So, grid computing is an expanded technology of distributed computing technology to use low-cost and high-performance computing power in various fields. Although the purpose of Grid computing focuses on large-scale resource sharing, innovative applications, and in some case, high-performance orientation, it has been used as conventional distributed computing environment like clustered computer until now because grid middleware does not have common sharable information system. In order to use grid computing environment efficiently which consists of various grid middleware, it is necessary to have application-independent information system which can share information description and services, and expand them easily. This paper proposed new database architecture and load balancing for high availability through Grid technology.

• The KIPS Transactions:PartA
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• v.14A no.1 s.105
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• pp.63-72
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• 2007

This paper introduces a load-balancing algorithm focusing on distributing web requests evenly into the web cluster servers. The load-balancing algorithms based on conventional periodic load-information update mechanism are not suitable for dynamic page applications, which are common in Cyber Foraging services, due to the problems caused by periodic synchronized load-information updating and the difficulties of work load estimation caused by embedded executing scripts of dynamic pages. Update-on-Finish algorithm solves this problem by using non-periodic load-update mechanism, and the web switch knows the servers' real load information only after their reporting and then distributes new loads according to the new load-information table, however it results in much communication overhead. Our proposed mechanism improve update-on-finish algorithm by using K-Percents-Finish mechanism and thus largely reduce the communication overhead. Furthermore, we consider the different capabilities of servers with a threshold Ti value and propose a load-balancing algorithm for servers with various capabilities. Simulation results show that the proposed K-Percents-Finish Reporting mechanism can at least reduce 50% communication overhead than update-on-finish approach while sustaining better load balancing performance than periodic mechanisms in related work.