• International journal of advanced smart convergence
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• v.9 no.2
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• pp.157-163
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• 2020

Recently the blockchain technology has been actively studied due to its great potentiality. The smart contract is a key mechanism of the blockchain system. Due to the short history of the smart contract, many issues have not been solved yet. One main issue is vulnerability and another main issue is cost optimization. While the vulnerability of smart contract has been actively studied, the cost optimization has been rarely studied. In this paper, we propose two cost optimization methods for smart contracts running on the blockchain system. Triggering a function in a smart contract program code may require costs and it is repeated continuously. So the minimization of costs required to trigger a function of smart contract while maintaining the performance equally is very important. The proposed two methods minimize the usage of expensive permanent variables deployed on the blockchain system. We apply the proposed two methods to three prevalent blockchain platforms: Ethereum, Klaytn and Tron. Evaluation experiments verify that the proposed scheme significantly reduces the costs of functions in the smart contract written with Solidity.

• International Journal of Computer Science & Network Security
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• v.21 no.7
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• pp.108-118
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• 2021

This paper aims to presents the overview of research in the sustainable smart cities development domain. It investigates the key challenges of the sustainable smart cities development that faced by the developers from different countries. The qualitative research method via the interview is conducted to collect the data. 10 experts on the sustainable smart cities development project were interviewed in this study. The results indicate that there are 12 sustainable smart cities development challenges named: (1) budgetary constraint; (2) lack of resources; (3) lack of institutional capacity to deliver technology; (4) lack of systems integration; (5) social acceptability; (6) lack of awareness level in the smart city development among residents; (7) the need to drive towards content development; (8) lack of strategically approach in the smart city transformation; (9) disagreement on standardizing the smart city model; (10) lack of overarching institution to create the governance structure; (11) lack of sustainable focused strategies; and (12) lack of the smart city operational framework. Furthermore, the solutions framework for these challenges was proposed as the guidelines to overcome or minimize them.

• International journal of advanced smart convergence
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• v.13 no.2
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• pp.265-275
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• 2024

Smart factory is a remarkable development from traditional manufacturing systems to data-based smart manufacturing systems that can connect and process data continuously, collected from machines, production equipment to production and business processes, capable of supporting workers in making decisions or performing work automatically. Smart factory is the key and center of the fourth industrial revolution, combining improvements in traditional manufacturing activities with digital technology to help factories achieve greater efficiency, contributing to increased revenue and reduce operating costs for businesses. Besides, the importance of smart factories is to make production more quality, efficient, competitive and sustainable. Businesses in Vietnam are in the process of learning and applying smart factory models. However, the number of businesses applying the pine factory model is still limited due to many barriers and difficulties. Therefore, in this paper we conduct a survey to assess the needs and current situation of businesses in applying smart factories and propose some specific solutions to develop and promote application of smart factory model in Vietnamese businesses.

• Journal of Power Electronics
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• v.18 no.3
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• pp.841-852
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• 2018

This paper presents a dual-algorithm search method (GWO-GSO) combining grey wolf optimization (GWO) and golden-section optimization (GSO) to realize maximum power point tracking (MPPT) for photovoltaic (PV) systems. First, a modified grey wolf optimization (MGWO) is activated for the global search. In conventional GWO, wolf leaders possess the same impact on decision-making. In this paper, the decision weights of wolf leaders are automatically adjusted with hunting progression, which is conducive to accelerating hunting. At the later stage, the algorithm is switched to GSO for the local search, which play a critical role in avoiding unnecessary search and reducing the tracking time. Additionally, a novel restart judgment based on the quasi-slope of the power-voltage curve is introduced to enhance the reliability of MPPT systems. Simulation and experiment results demonstrate that the proposed algorithm can track the global maximum power point (MPP) swiftly and reliably with higher accuracy under various conditions.

• Smart Structures and Systems
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• v.23 no.6
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• pp.669-682
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• 2019

Vibration mitigation of cables or hangers is one of the crucial problems for cable supported bridges. Previous research focused on the behaviors of cable with dampers or crossties, which could help engineering community apply these mitigation devices more efficiently. However, less studies are available for hybrid applied cross-ties and dampers, especially lack of both analytical and experimental verifications. This paper studied damping and frequency of two parallel identical cables with a connection cross-tie and an attached damper. The characteristic equation of system was derived based on transfer matrix method. The complex characteristic equation was numerically solved to find the solutions. Effects of non-dimensional spring stiffness and location on the maximum cable damping, the corresponding optimum damper constant and the corresponding frequency of lower vibration mode were further addressed. System with twin small-scale cables with a cross-link and a viscous damper were tested. The damping and frequency from the test were very close to the analytical ones. The two branches of solutions: in-phase modes and the out-of-phase modes, were identified; and the two branches of solutions were different for damping and frequency behaviors.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.763-765
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• 2003

본 논문에서는 RFC 1760 표준 S/KEY 일회용 패스워드 인증 스킴이 서버 스푸핑 공격 재시도 공격 오프라인 패스워드 공격, 능동적 공격 등 여러 가지 공격에 취약함에 대해서 설명하고 이들 공격에 안전한 스마트 카드를 이용한 새로운 스킴을 제안한다. 본 논문에서 제안한 스킴은 스마트 카드를 이용한 안전한 S/KEY 일회용 패스워드 인증 스킴으로 기존의 S/KEY 일회용 패스워드 인증 스킴의 보안 문제점을 개선하였으며 상호 인증을 가능하게 하는 새로운 스킴으로 여러 가지 안전성 향상을 보인다.

• International journal of advanced smart convergence
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• v.11 no.3
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• pp.42-48
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• 2022

Currently, the world is facing severe inflation due to Corona and the war in Ukraine, and it is causing a lot of difficulties for us. Companies are facing a lot of restrictions on their economic activities compared to the past due to supply chain problems and foreign exchange rates. In this situation, many countries have been implementing various smart factory promotion projects to secure competitiveness through productivity improvement in the manufacturing industry. In this study, the contents of smart factory promotion in major countries were reviewed, and problems raised about the implementation of smart factory in Korea, which are being implemented based on this, were described. It is most reasonable to judge the success of a smart factory by the achievement of the performance indicators presented at the time of the project. Therefore, based on the performance index of the business, which is a key factor in determining the success or failure of a smart factory, we investigated whether the company's smart factory promotion can be carried out successfully through examples

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.2
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• pp.25-36
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• 1999

In this paper we propose a one-time password mechanism that solves the problems of the S/KEY: the limitation of a usage and the need of storage for keys. because of using a cryptographic algorithm the proposed mechanism has no the limitation of a usage. Also because of producing the key for an authentication from a user's password it is easy to manage the authentication key and is possible to share the session key between a client and a server after the authentication process. In addition the proposed mechanism is easy to protect and manage the authentication information because of using a smart card and is adopted by the system that needs a noe-way authentication from a client to a server without the challenge of a server.

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.3
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• pp.168-174
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• 2010

User authentication is an important requirement to provide secure network service. Therefore, many authentication schemes have been proposed to provide secure authentication, such as key agreement and anonymity. However, authority of scheme is limited to one's self. It is inefficient when authenticated users grant a certification to other users who are in an organization which has a hierarchical structure, such as a company or school. In this paper, we propose the first authentication scheme to use Attributes-Based Re-encryption that creates a certification to other users with specified attributes. The scheme, which has expanded from Rhee et al. scheme, has optimized computation performance on a smart card, ensuring the user's anonymity and key agreement between users and server.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.323-331
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• 2014

This research is based on real-time service model that uses lock screen of smart devices which is mostly exposed to device users. The potential for lock screen space is immense due to their exposing time for user. The effect can be maximized by offering useful information contents on lock screen. This service model offers real-time keyword with abridged sentence. They match real-time keyword with news by using text matching algorithm and extracts kernel sentence from news to provide short sentence to user. News from the lock screen to match real-time query sentence, and then only to the original core of the ability to move a user evaluation was conducted after adding. The report provided a key statement users feel the lack of original Not if you go to an average of 5.71%. Most algorithms allow only real-time zoom key sentence extracted keywords can accurately determine the reason for that was confirmed.