• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.271-277
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• 2022

PBFT (Practical Byzantine Fault Tolerant) is a consensus algorithm that can achieve consensus by resolving unintentional and intentional faults in a distributed network environment and can guarantee high performance and absolute finality. However, as the size of the network increases, the network load also increases due to message broadcasting that repeatedly occurs during the consensus process. Due to the characteristics of the PBFT algorithm, it is suitable for small/private blockchain, but there is a limit to its application to large/public blockchain. Because PBFT affects the performance of blockchain networks, the industry should test whether PBFT is suitable for products and services, and academia needs a unified evaluation metric and technology for PBFT performance improvement research. In this paper, quantitative evaluation metrics and evaluation frameworks that can evaluate PBFT family consensus algorithms are studied. In addition, the throughput, latency, and fault tolerance of PBFT are evaluated using the proposed PBFT evaluation framework.

• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.61-71
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• 2009

The server redirection system replicates contents on replica servers in the distributed network environment. When users make a request for contents, the system can provide the contents much faster than the client-server network system. In the server redirection system, it is the most important to select the optimal replica server with user's information because many replica servers are geographically distributed. And, the system can serve contents to users flexibly if a redirector is well constructed. In this paper, the redirector makes a list of candidates suitable for user conditions by the decision tree method and calculates the availability of each replica server. And, the redirector selects the replica server with the highest availability. This paper also proposes an availability-based server redirection system that predicts the availability of each replica server in order to reduce the workload of replica servers and the repetitive communication messages between a redirector and replica servers. If a user accesses the network path for the replica server selected and noticed by the proposed system, the user can get contents effectively and efficiently.

• 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 Korea Society of Industrial Information Systems
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• v.28 no.2
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• pp.61-75
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• 2023

This study aims to evaluate the usability of a banking app that is frequently used by the elderly. To this end, the usability PACMAD(People At the Center of Mobile Application Development) model that can be used in mobile was explained and the usability evaluation was empirically verified for the elderly over 60 years of age. For this study, descriptive statistics and variance analysis were conducted using SPSS 25.0 for 165 elderly people who had experience using banking apps. Looking at the analysis results of this study, efficiency, satisfaction, and effectiveness showed relatively high scores, and learnability, memorability, error, and cognitive load showed relatively low scores. In addition, in the verification of differences by age, it was confirmed that there were differences in all variables by age. These results suggest that the elderly's usability evaluation of banking apps and differences by age could be confirmed, but there is also a limitation that comparison with the general public is difficult because the age is limited to the elderly.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.189-196
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• 2024

Frequent false positives alarm from the Intelligent Selective Control System have raised significant concerns. These persistent issues have led to declines in operational efficiency and market credibility among agents. Developing a new model or replacing the existing one to mitigate false positives alarm entails substantial opportunity costs; hence, improving the quality of the training dataset is pragmatic. However, smaller organizations face challenges with inadequate capabilities in dataset collection and refinement. This paper proposes an automatic human pose data collection system centered around a human pose estimation model, utilizing camera-based sensor fusion techniques and edge devices. The system facilitates the direct collection and real-time processing of field data at the network periphery, distributing the computational load that typically centralizes. Additionally, by directly labeling field data, it aids in constructing new training datasets.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.505-514
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• 2009

Aqueous potassium salt of serine was proposed as an alternative $CO_2$ absorbent to monoethanolamine (MEA) and its $CO_2$ absorption characteristics were studied. The experiment has been conducted using screening test equipment with NDIR type gas analyzer and vapor-liquid equilibrium apparatus. $CO_2$ absorption/desorption rate and net amount of $CO_2$ absorbed in cyclic process are the criteria to assess the $CO_2$ absorption characteristics in this study. Effective $CO_2$ loading of potassium salt of serine and MEA are 0.425 and 0.230 respectively. Cyclic capacities are 0.354 and 0.298 for potassium salt of serine and MEA. The absorption rate of the potassium serinate decreased sharply at $CO_2$ loading is 0.1 and were maintained approximately at half of MEA. To enhance the absorption rate of aqueous potassium salt of serine, small quantities of rate promoters, namely piperazine and tetraethylenepentamine were blended, so that rich $CO_2$ loading were increased by 13.7% and 18.7% respectively. The rich $CO_2$ loading of potassium salt of serine was 29.2% and 35.0% higher than those of aqueous sodium and lithium salt of serine, respectively. The absorption rate of potassium salt of valine and isoleucine which have similar molecular structures to serine were lower than that of serine because of the presence of bulky side group. Precipitation phenomena during $CO_2$ absorption were discussed by the aid of literatures.

• The Journal of the Korea Contents Association
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• v.8 no.12
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• pp.347-356
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• 2008

In this study, in order to evaluate the 4th local government heads and to grope for ways for development of the government, the researcher surveyed public officials in Daejeon, Chungnam and Chungbuk regions. The main contents of the survey were such as the leadership type and characteristics of the local government heads, their administrative characteristics, and evaluation of their pubic pledges. And for the surveyed questionnaires, the researcher did cross-tabulation and analysis of variance using the SPSS 12.0 statistics program. As the result of the analysis, on the basis of most indexes, the provincial governor of Chungcheongnam-do was found to have received more affirmative support than those of Chungcheongbuk-do and Daejeon Metropolitan City. Therefore, it seems that provincial governor of Chungbuk and mayor of Daejeon Metropolitan City need to benchmark the leadership of the provincial governor of Chungnam.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.694-701
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• 2012

The main purpose of this study is to evaluate of backwash system of hydrodynamic separator filter (HSF) with solar powered submerged pumps. It consists of a photovoltaic solar array, control electronics, battery, and two submersible pump powered by a 12 voltage DC motor. The laboratory scale study on treatable potential of micro particles using backwash HSF that was a combined with perlite filter cartridge and backwash nozzles. Since it was not easy to use actual storm water in the scaled-down hydraulic model investigations, it was necessary to reproduce ranges of particle sizes with synthetic materials. The synthesized storm runoff was made with water and addition of particles; ion exchange resin partices, silica gel particles, and commercial area manhole sediment particles. HSF was made of acryl resin with 250 mm of diameter filter chamber and overall height of 800 mm. Four case test were performed with different backwashing conditions and determined the SS removal efficiency with various surface loading rates. The operated range of surface loading rate was about 308~$1,250m^3/m^2/day$. It was found that SS removal efficiency of HSF using two submersible pumps improved by about 18% compared with HSF without backwash. Nonpoint control devices with solar water pumping systems would be useful for backwashing the filter in areas with not suppling electricity and reduce filter media exchange cost.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.3
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• pp.82-90
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• 2011

Multi-core system is becoming more general with development of microprocessors. Due to this change in performance improvement paradigm, switching conventional single thread applications with multi thread applications. Performance monitoring tools are used to optimize application performance because of complexity in development of multi thread applications. Conventional performance monitoring tools are focused on performance itself rather than user friendliness or real-time support. Real-time performance monitor identify the problem while multi-threaded applications should be performed as well as check real-time operating status of the application. So it can be used as an effective tool compared to non-real-time performance monitor that only with simple performance indicators to find the cause of the problem. In this paper, we propose RMPM(Real-time Multi-core Performance Monitor) which is real-time performance monitoring tool for multi-core system. Observation period is optimized by comparing relation between overhead due to performance evaluation period and accuracy. Our performance monitor shows not only amount of CPU usage of whole system, memory usage, network usage but also aspect of overhead distribution per thread of an application.

• Journal of KIISE
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• v.43 no.12
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• pp.1428-1436
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• 2016

A multipath routing in wireless sensor networks (WSNs) provides advantage such as reliability improvement and load balancing by transmitting data through divided paths. For these reasons, existing multipath routing protocols divide path appropriately or create independent paths efficiently. However, when the sink node moves to avoid hotspot problem or satisfy the requirement of the applications, the existing protocols have to reconstruct multipath or exploit foot-print chaining mechanism. As a result, the existing protocols will shorten the lifetime of a network due to excessive energy consumption, and lose the advantage of multipath routing due to the merging of paths. To solve this problem, we propose a multipath creation and maintenance scheme to support the mobile sink node. The proposed protocol can be used to construct local grid structure with restricted area and exploit grid structure for constructing the multipath. The grid structure can also be extended depending on the movement of the sink node. In addition, the multipath can be partially reconstructed to prevent merging paths. Simulation results show that the proposed protocol is superior to the existing protocols in terms of energy efficiency and packet delivery ratio.