• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.1-12
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• 2021

Technologies for an MVDC(medium voltage direct current) distribution system are being considered as an effective alternative to overcome the interconnection delay issues of PV systems. However, the implementation of a DC distribution system might lead to economic problems because of the development of DC devices. Therefore, this paper deals with the scale of a PV plant based on its capacity and proposes hosting-capacity models for PV systems to establish a network to evaluate the feasibility of an MVDC distribution system. The proposed models can be classified as AC and DC distribution systems by the power-supply method. PV systems with hundreds of MW, dozens of MW, and a few MW can be categorized as large-scale, medium-scale, and small-scale models, respectively. This paper also performed modeling for an economic evaluation of MVDC distribution system by considering both the cost of AC and DC network construction, converter replacement, operation, etc. The profit was composed of the SMP and REC rate of a PV plant. A simulation for economic evaluation was done for the MVDC distribution system using the present worth and equal-principal costs repayment method. The results confirmed that the proposed model is a useful tool to evaluate economic issues of a DC distribution system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.45-50
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• 2017

Micro-service Architecture is a service architecture optimized for large-scale distributed systems such as real-time realistic broadcasting systems, so that are fiercely adopted by Global leading service platform vendors such as Netflix and Twitter due to the merit of horizontal performance scalability enabling the scale-out technique. In addition, micro-service architecture makes it possible to execute image processing and real-time data analysis using an asynchronous-based processing that are difficult to handle in Web API such as REST. In this paper, an event stream processing framework applicable to asynchronous based micro services is proposed in the sense that the accountability of event processing order is not guaranteed in the events such as IoT sensor data analysis or cloud-based image editing because these are the situations where the real-time media editing generates multiple event streams and asynchronous processes in the platform.

• Korea Real Estate Review
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• v.27 no.3
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• pp.7-22
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• 2017

Establishing greater reliability in property appraisal is critical because it promotes the public interest. Reliability is composed of competence and ethics. In particular, the ethics of property appraisal has individual and corporational aspects. This study aimed to evaluate how the ethical climate of a firm is affected by the scale of appraisal firms, thereby validating the effect of the 'Large Appraisal Firm System'. Hence, the ethical climate of appraisal firms, an indicator of inherent ethical value recognition, was investigated, divided into recognition of social responsibility and exclusion of self-interest. The study results showed that the ethical management systems of appraisal firms encourage the appraisers of such firms to be conscious of their social responsibility and to exclude self-interest in their work. The degree of such influence, however, differs according to the scale of appraisal firms. Based on these results, further research on the maintenance and operation of the ethical management systems of appraisal firms is required to enhance the reliability of property appraisal.

• Journal of Intelligence and Information Systems
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• v.29 no.3
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• pp.125-144
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• 2023

Recently, the use of Large Language Models (LLMs) such as ChatGPT has been increasing in various fields such as interactive commerce and mobile financial services. However, LMMs, which are mainly created by learning existing documents, can also learn various human biases inherent in documents. Nevertheless, there have been few comparative studies on the aspects of bias and discrimination in LLMs. The purpose of this study is to examine the existence and extent of nine types of discrimination (Age, Disability status, Gender identity, Nationality, Physical appearance, Race ethnicity, Religion, Socio-economic status, Sexual orientation) in LLMs and suggest ways to improve them. For this purpose, we utilized BBQ (Bias Benchmark for QA), a tool for identifying discrimination, to compare three large-scale language models including ChatGPT, GPT-3, and Bing Chat. As a result of the evaluation, a large number of discriminatory responses were observed in the mega-language models, and the patterns differed depending on the mega-language model. In particular, problems were exposed in elder discrimination and disability discrimination, which are not traditional AI ethics issues such as sexism, racism, and economic inequality, and a new perspective on AI ethics was found. Based on the results of the comparison, this paper describes how to improve and develop large-scale language models in the future.

• Journal of the Korea Safety Management & Science
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• v.11 no.3
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• pp.19-26
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• 2009

It is becoming more and more important to develop safety-critical systems with special attention. Examples of the safety-critical systems include the mass transportation systems such as high speed trains, airplanes, ships and so forth. Safety critical issues can also exist in the development of atomic power plants that are attracting a great deal of attention recently as oil prices are sky-rocketing. Note that the safety-critical systems are in general large-scale and very complex for which case the effects of adopting the systems engineering (SE) approach has been quite phenomenal. Furthermore, safety-critical requirements should necessarily be realized in the design phase and be effectively maintained thereafter. In light of these comments, we have considered our approach to developing safety-critical systems to be based on the method combining the systems engineering and safety management processes. To do so, we have developed a design environment by constructing a whole life cycle model in two steps. In the first step, the integrated process model was developed by integrating the SE (ISO/IEC 15283) and systems safety (e.g., hazard analysis) activities and implemented in a computer-aided SE tool environment. The model was represented by three hierarchical levels: the life-cycle level, the process level, and the activity level. As a result, one can see from the model when and how the required SE and safety processes have to be carried out concurrently and iterately. Finally, the design environment was verified by the computer simulation.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.1
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• pp.33-49
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• 2003

Recently, there have been large storage demands for manipulating multimedia data. To solve the tremendous storage demands, one of the major researches is the SAN(Storage Area Network) that provides the local file requests directly from shared-disk storage and also eliminates the server bottlenecks to performance and availability. SAN also improve the network latency and bandwidth through new channel interface like FC(Fibre Channel). But to manipulate the efficient storage network like SAN, traditional local file system and distributed file system are not adaptable and also are lack of researches in terms of a metadata structure for large-scale inode object such as file and directory. In this paper, we describe the architecture and design issues of our shared-disk file system and provide the efficient bitmap for providing the well-formed block allocation in each host, extent-based semi flat structure for storing large-scale file data, and two-phase directory structure of using Extendible Hashing. Also we describe a detailed algorithm for implementing the file system's device driver in Linux Kernel and compare our file system with the general file system like EXT2 and shard disk file system like GFS in terms of file creation, directory creation and I/O rate.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.5
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• pp.199-212
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• 2008

Software simulation has been widely used for the design and application development of a large-scale wireless sensor network. The degree of details of the simulation must be high to verify the behavior of the network and to estimate its execution time and power consumption of an application program as accurately as possible. But, as the degree of details becomes higher, the simulation time increases. Moreover, as the number of sensor nodes increases, the time tends to be extremely long. We propose an optimal-synchronous parallel discrete-event simulation method to shorten the time in a large-scale sensor network simulation. In this method, sensor nodes are partitioned into subsets, and each PC that is interconnected with others through a network is in charge of simulating one of the subsets. Results of experiments using the parallel simulator developed in this study show that, in the case of the large number of sensor nodes, the speedup tends to approach the square of the number of PCs participating in the simulation. In such a case, the ratio of the overhead due to parallel simulation to the total simulation time is so small that it can be ignored. Therefore, as long as PCs are available, the number of sensor nodes to be simulated is not limited. In addition, our parallel simulation environment can be constructed easily at the low cost because PCs interconnected through LAN are used without change.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1091-1101
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• 2012

Device-to-device (D2D) communication is expected to offer local area services with low transmit power and short link distance, even not via any infrastructures. These advantages will lead to the deployment of D2D systems in a massive scale, where the order of magnitude of D2D user density is higher than that of cellular user density. Network-assisted D2D systems, where D2D resources are managed by cellular networks, are unable to support the large number of D2D devices, due to the signaling overhead for control signals. In this case, no coordination can be an answer. This paper considers uncoordinated D2D systems, which is implemented with a number of D2D devices in a large scale. By analyzing the transmission capacity of D2D systems, we found a feasibility condition under which the uncoordinated D2D communications possibly coexist within cellular networks, sharing the uplink spectrum. In addition, we provide guidelines for the operational points of massive D2D communications, giving some knowledge about proper transmit power level and link distance of uncoordinated D2D.

• The Journal of Information Systems
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• v.15 no.1
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• pp.1-20
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• 2006

Peer-to-peer systems (P2P) are rapidly growing in importance on the Internet environment, quickly extending the range of their usage. However, peer-to-peer systems have not been widely applied in electronic commerce because they have not been established as an appropriate business model. Therefore, we firstly review the previous research relevant to peer-to-peer systems, and then analyze the business models for P2P systems presented by previous researchers. Furthermore, this study categorizes major issues in terms of the technical and business model aspects. On the basis of these reviews, we develop P2P electronic commerce systems based on the file sharing method between users, focusing on user interface friendliness. A developed P2P electronic commerce systems are programmed by using the C# based on the Microsoft.net solution. A database is implemented using the MSSQL2000. A main application technology is designed that P2P electronic commerce systems make it possible. for user to extend into BtoB Solution by using WSDL (Web Services Description Language), UDDI (Universal Description, Discovery, and Integration) and the XML that is a document for users. User interface is made as form of Internet messenger for a user's convenience and is possible to develop into a commodity transaction system based on XML. In this study, it is possible for the P2P electronic commerce system to have extended application to fields such as Internet shopping mall and property transaction in a nonprofit organization, a public institution and a large scale nonprofit institution that have a similar structure as compared with a structure of a nonprofit educational institution.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.2
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• pp.63-81
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• 2008

WiMAX has been introduced as a competitive alternative for metropolitan broadband wireless access technologies. It is connection oriented and it can provide very high data rates, large service coverage, and flexible quality of services (QoS). Due to the large number of connections and flexible QoS supported by WiMAX, the uplink access in WiMAX networks is very challenging since the medium access control (MAC) protocol must efficiently manage the bandwidth and related channel allocations. In this paper, we propose and investigate a cost-effective WiMAX bandwidth management scheme, named the WiMAX partial sharing scheme (WPSS), in order to provide good QoS while achieving better bandwidth utilization and network throughput. The proposed bandwidth management scheme is compared with a simple but inefficient scheme, named the WiMAX complete sharing scheme (WCPS). A maximum entropy (ME) based analytical model (MEAM) is proposed for the performance evaluation of the two bandwidth management schemes. The reason for using MEAM for the performance evaluation is that MEAM can efficiently model a large-scale system in which the number of stations or connections is generally very high, while the traditional simulation and analytical (e.g., Markov models) approaches cannot perform well due to the high computation complexity. We model the bandwidth management scheme as a queuing network model (QNM) that consists of interacting multiclass queues for different service classes. Closed form expressions for the state and blocking probability distributions are derived for those schemes. Simulation results verify the MEAM numerical results and show that WPSS can significantly improve the network’s performance compared to WCPS.