• The KIPS Transactions:PartD
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• v.15D no.6
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• pp.755-766
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• 2008

Recently, NAND flash memory is becoming into the spotlight as a next-generation storage device because of its small size, fast speed, low power consumption, and etc. compared to the hard disk. However, due to the distinct characteristics such as erase-before-write architecture, asymmetric operation speed and unit, disk-based systems and applications may result in severe performance degradation when directly implementing them on NAND flash memory. Especially when a B-tree is implemented on NAND flash memory, intensive overwrite operations may be caused by record inserting, deleting, and reorganizing. These may result in severe performance degradation. Although ${\mu}$-tree has been proposed in order to overcome this problem, it suffers from frequent node split and rapid increment of its height. In this paper, we propose Log-Structured B-Tree(LSB-Tree) where the corresponding log node to a leaf node is allocated for update operation and then the modified data in the log node is stored at only one write operation. LSB-tree reduces additional write operations by deferring the change of parent nodes. Also, it reduces the write operation by switching a log node to a new leaf node when inserting the data sequentially by the key order. Finally, we show that LSB-tree yields a better performance on NAND flash memory by comparing it to ${\mu}$-tree through various experiments.

• The KIPS Transactions:PartD
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• v.11D no.2
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• pp.293-304
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• 2004

Recently, caching for the database-backed web applications has received much attention. The results of frequent queries could be cached for repeated reuse or for efficient processing of the relevant queries. Since the emergence of XML as a standard for data exchange on the web, today's web applications are to retrieve information from the remote XML sources across the network, and thus it is desirable to maintain the XML query results in the cache for the web applications. In this paper, we describe implementation of an XML query processing system that supports cache-answerability of XML queries, and evaluate its performance. XML path expression, which is one of the core features of XML query languages including XQuery, XPath, and XQL was considered as the XML query. Their result is maintained as an XML materialized view in the XML cache. The algorithms to rewrite the given XML path expression using its relevant materialized view proposed in [13] were implemented with RDBMS as XML store. The major issues of implementation are described in detail. The results of performance experiments conducted with the implemented system showed effectiveness of cache-answerability of XML queries. Comparison with previous research in terms of performance is also Provided.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.2
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• pp.41-56
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• 2019

Cloud manufacturing is a new concept of manufacturing process that works like a single factory with connected multiple factories. The cloud manufacturing system is a kind of large-scale CPS that produces products through the collaboration of distributed manufacturing facilities based on technologies such as cloud computing, IoT, and virtualization. It utilizes diverse and distributed facilities based on centralized information systems, which allows flexible composition user-centric and service-oriented large-scale systems. However, the cloud manufacturing system is composed of a large number of highly heterogeneous subsystems. It has difficulties in interconnection, data exchange, information processing, and system verification for system construction. In this paper, we derive the user requirements of various aspects of the cloud manufacturing system, such as functional, human, trustworthiness, timing, data and composition, based on the CPS Framework, which is the analysis methodology for CPS. Next, by analyzing the user requirements we define the system requirements including scalability, composability, interactivity, dependability, timing, interoperability and intelligence. We map the defined CPS system requirements to the requirements of oneM2M, which is the platform standard for IoT, so that the support of the system requirements at the level of the IoT platform is verified through Mobius, which is the implementation of oneM2M standard. Analyzing the verification result, finally, we propose a large-scale cloud manufacturing platform based on oneM2M that can meet the cloud manufacturing requirements to support the overall features of the Cloud Manufacturing CPS with dependability.

• Journal of the Korea Society for Simulation
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• v.22 no.1
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• pp.9-20
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• 2013

Defense M&S for weapons effectiveness is a realistic way to support virtual warfare similar to real warfare. As the war paradigm becomes platform-centric to network-centric, people try to utilize smartphones as the source of sensor, and command/control data in the simulation-based weapons effectiveness analysis. However, there have been limited researches on integrating smartphones into the weapon simulators, partly due to high modeling cost - modeling cost to accomodate client-server architecture, and re-engineering cost to adapt the simulator on various devices and platforms -, lack of efficient mechanisms to exchange large amount of simulation data, and low-level of security. In this paper, we design and implement Smartphone Adaptor to utilize smartphones for the simulationbased weapons effectiveness analysis. Smartphone Adaptor automatically sends sensor information, GPS and motion data of a client's smartphone to a simulator and receives simulation results from the simulator on the server. Also, we make it possible for data to be transferred safely and quickly through JSON and SEED. Smartphone Adaptor is applied to OpenSIM (Open simulation engine for Interoperable Models) which is an integrated simulation environment for weapons effectiveness analysis, under development of our research team. In this paper, we will show Smartphone Adaptor can be used effectively in constructing a Live simulation, with an example of a chemical simulator.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.494-507
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• 2021

With the increasing use of TBM, research has recently been conducted in Korea to analyze TBM data with machine learning techniques to predict the ground in front of TBM, predict the exchange cycle of disk cutters, and predict the advance rate of TBM. In this study, classification prediction of rock characteristics of slurry shield TBM sites was made by combining traditional rock classification techniques and machine learning techniques widely used in various fields with machine data during TBM excavation. The items of rock characteristic classification criteria were set as RQD, uniaxial compression strength, and elastic wave speed, and the rock conditions for each item were classified into three classes: class 0 (good), 1 (normal), and 2 (poor), and machine learning was performed on six class algorithms. As a result, the ensemble model showed good performance, and the LigthtGBM model, which showed excellent results in learning speed as well as learning performance, was found to be optimal in the target site ground. Using the classification model for the three rock characteristics set in this study, it is believed that it will be possible to provide rock conditions for sections where ground information is not provided, which will help during excavation work.

• Journal of Convergence for Information Technology
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• v.10 no.11
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• pp.64-76
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• 2020

The purpose of this study is to empirically analyze the mediating effect of job stress and Job engagement in job satisfaction between WFC(Work-Family Conflict) and quality of LMX(eader-member exchange) relationship of married female workers based on JD-R(Job Demands-Resources) model. A total of 945 people were targeted using the 7th panel data from the Korean Longitudinal Survey of Women and a structural equation model was used to verify the causal relationship and mediating effect of each variable using spss 23.0 and AMOS 21.0. As a result of the study, it was confirmed that WFC did not directly affect job satisfaction, and it was found that job satisfaction was negatively affected through job stress related to WFC. It was found that the quality of the LMX relationship had a positive effect on job satisfaction and reduced job stress, thus positively affecting job satisfaction. Job engagement was found to mediate the relationship between LMX and job satisfaction. This study is meaningful in that the search for multidimensional psychological and contextual factors that lead to job performance and job demands of married female workers are conducted.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.4
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• pp.456-462
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• 2011

As the ARRA enacted recently in the United States, the interest in EHR systems have been increased in the field of medical industry. The passage of the ARRA presents a program that provides incentives to office-based physicians and hospitals adapting the EHR systems to guarantee interoperability with various medical standards. Thanks to the incentive program, a great number of EHR systems have been developed and lots of office-based physicians and hospitals have adapted the EHR systems certified by CCHIT. Keeping pace with the rapid changes in the market of healthcare, some enterprises try to push in to the United States healthcare market based on the experience acquired by developing EHR systems for hospitals in Korea. However, the developed system must be customized because of the different medical environment between Korea and the United States. In this paper, therefore, we design and develop an integrated EHR platform to guarantee the interoperability between different medical information systems based on medical standard technologies. In the developed platform, an integrated system has been composed by integrating various basic techniques such as data transmission standards and its methods, medical standard terminologies and its usage, and knowledge management for medical decision-making support. Moreover, medical data can be processed electronically by adapting an HL7 interface engine and the terminologies for exchanging medical information and the standardization of medical information. We develop SeniCare, an EHR system for supporting ambulatory care of the office-based physicians, based on the platform, and we verify the usability of the platform by confirming whether SeniCare satisfies the criteria of "meaningful use" issued by CMS or not.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.514-520
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• 2018

Presence service provides various information about users such as locations, status of on/offline and network access methods, and number of presence resources required by each users increases largely in mobile environment. Therefore an effective method which can reduce load of presence servers is needed. In this paper, a large scale distributed presence service system which can distribute effectively total presence system load of presence servers using message control session has been presented. This large scale distributed presence service system provides various presence information for massive volumes of users. In this study, a new message control session architecture which can dynamically distribute loads of the presence servers to multiple servers has been presented, and a new presence information data architecture for controlling load of the presence servers has been designed. In this architecture, each presence server can exchange current load level in real time to get variance of the total system load change according to user numbers, and can distribute system load to maintain load level of each server evenly. The performance of the proposed large scale distributed presence service system has been analysed by experiments. The results has been showed that average presence resource subscription processing time reduced from 42.6% to 73.6%, and average presence notification processing time reduced from 37.6% to 64.8%.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.576-579
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• 2011

Wireless sensor network are widely all over different fields. Because of its distinguished characteristics, we must take account of the factor of energy consumed when designing routing protocol. Wireless sensor networks consist of small battery powered devices with limited energy resources. Once deployed, the small sensor nodes are usually inaccessible to the user, and thus replacement of the energy source is not feasible. Hence, energy efficiency is a key design issue that needs to be enhanced in order to improve the life span of the network. In BCDCP, all sensors sends data from the CH (Cluster Head) and then to the BS (Base Station). BCDCP works well in a smallscale network however is not preferred in a large scale network since it uses much energy for long distance wireless communication. TBRP can be used for large scale network, but it weakness lies on the fact that the nodedry out of energy easily since it uses multi-hops transmission data to the Base Station. Here, we proposed a routing protocol. A Cluster Based Energy Efficient Tree Routing Protocol (CETRP) in Wireless Sensor Networks (WSNs) to prolong network life time through the balanced energy consumption. CETRP selects Cluster Head of cluster tree shape and uses maximum two hops data transmission to the Cluster Head in every level. We show CETRP outperforms BCDCP and TBRP with several experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.378-386
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• 2013

In this paper, we propose a multi-way relaying system, in which N communicating nodes interchange their information one another by the help of a multiple-antenna non-regenerative relay station (RS). While the conventional multi-way relaying requires 2N transmission phases to complete the data exchange, the proposed system completes the mission with N phases composed of one multiple access phase and N-1 broadcast phases. For effective broadcast transmission, the proposed system pairs users for signal transmission with a new RS beamforming matrix not to interfere with the nodes of different pairs and a self-interference canceler at each node. The performance evaluation in terms of the average sum rate shows that the proposed system outperforms the conventional one with more significant gain when the number of RS antennas is comparable to the number of communicating nodes. The proposed schemes can be applicable to marine communications where the ships need to share their information with extended coverage.