• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.87-93
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• 2010

This paper describes an improved location determination scheme based on the triangulation method calculating a target position. The proposed scheme uses coordinates of intersection points of three circles each generated by measurement of an observer. The target position obtained from the proposed scheme has higher accuracy not only at the vicinity, but also at the periphery of the observation area. The maximum error and the average error with the proposed scheme are reduced by 40.89% and 40.30%, respectively, with respect to conventional methods.

• Journal of the Korea Society for Simulation
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• v.12 no.2
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• pp.35-44
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• 2003

The effectiveness of buffer cache replacement algorithms is critical to the performance of I/O systems. In this paper, we propose the degree of inter-reference gap (DIG) based block replacement scheme that retains merits of the least recently used (LRU) such as simple implementation and good cache hit ratio (CHR) for general patterns of references, and improves CHR further. In the proposed scheme, cache blocks with low DIGs are distinguished from blocks with high DIGs and the replacement block is selected among high DIGs blocks as done in the low inter-reference recency set (LIRS) scheme. Thus, by having the effect of the partitioning the cache memory dynamically based on DIGs, CHR is improved. Trace-driven simulation is employed to verified the superiority of the DIG based scheme and shows that the performance improves up to about 175% compared to the LRU scheme and 3% compared to the LIRS scheme for the same traces.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.78-84
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• 2022

In this paper, to improve further the bit-error rate (BER) performance of the stronger channel user in non-uniform source non-orthogonal multiple access (NOMA) with symmetric superposition coding (SSC), we propose a smart bit-to-symbol (BTS) mapping of SSC. First, the analytical expression for the total allocated power of the proposed BTS mapping scheme is derived, and then we show that the BER of the proposed BTS mapping scheme improves further, compared to that of the existing BTS mapping scheme. Moreover, based on the simulations, the signal-to-noise (SNR) gain of the proposed BTS mapping scheme over the existing BTS mapping scheme is calculated. In result, the proposed BTS mapping could be a candidate scheme for non-uniform source SSC NOMA with the SNR gain.

• Atmosphere
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• v.24 no.2
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• pp.151-158
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• 2014

This study investigated a method for the discrimination of precipitation type using thickness of geopotential height at 1000~850 hPa and improved Matsuo's scheme over South Korea using 7 upper-level observations data during winter time from 2003 to 2008. With this research, it was suggested that thickness between snow and rain should range from 1281 to 1297 gpm at 1000~850 hPa. This threshold was suitable for determining precipitation type such as snow, sleet and rain and it was verified by investigation at 7 upper-level observation and 10 surface observation data for 3 years (2009~2011). In addition, precipitation types were separated properly by Matsuo's scheme and its improved one, which is a fuction of surface air temperature and relative humidity, when they lie in mixed sectors. Precipitation types in the mixed sector were subdivided into 5 sectors (rain, rain and snow, snow and rain, snow, and snow cover). We also present the decision table for monitoring and predicting precipitation types using model output of Korea Local Analysis and Prediction System (KLAPS) and observation data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3C
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• pp.297-303
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• 2009

Integral imaging is a well-known 3D image recording and display technique. The huge size of integral imaging data requires a compression scheme to store and transmit 3D scenes. In the conventional compression scheme, the data amount of elemental images depends on the various recording condition such as the positional location of a 3D object, the illumination and specification of the lenslet array even if an identical pickup system is used. In this paper, to reduce the dependence of the image characteristics of elemental images on the pickup conditions, a compression scheme using block division on the elemental image of integral imaging is proposed. The proposed scheme provides an improved compression ratio by considering the local similarity of elemental images picked up from three-dimensional objects according to a positional location. To test the proposed scheme, various elemental images are picked up and a compression process is then carried out u sing a standard MPEG-4. Based on compression ratio results, the proposed compression scheme is improved by approximately 9% compared with the conventional compression method.

• Journal of Internet Computing and Services
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• v.21 no.5
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• pp.39-48
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• 2020

Recently, the study and development of environment-friendly energy technique have increased in worldwide due to environmental pollution and energy resources problems. In vehicle industry, the development of electric vehicle(EV) is now on progress, and also, many other governments support the study and development and make an effort for EV to become widely available. In addition, though they strive to construct the EV infra such as a charge station for EV, the techniques related to managing charge demand and peak power are not enough. The standard of EV communication has been already established as ISO/IEC 15118, however, most of implemented EVs and EV charge stations do not support any communication between each of them. In this paper, an improved slow charge scheme for non-communication EVs is proposed and designed by using predicting charge demand. The proposed scheme consists of distributed charge model and charge demand prediction. The distributed charge model is designed to manage to distribute charge power depending on available charge power and charge demand. The charge demand prediction is designed to be used in the distributed charge model. The proposed scheme is based on the collected data which were from EV slow charge station in business building during the past 1 year. The system-level simulation results show that the waiting time of EV and the charge fee of the proposed scheme are better than those of the conventional scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.6
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• pp.1551-1560
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• 2016

With the advancement of wearable devices and wireless body are networks, smart healthcare systems based on such technologies have been emerging to effectively monitor patient health and disease progression. In order to implement viable smart healthcare systems, the security and privacy of patient's personal health information must be considered. Yang et al. proposed a privacy-preserving authentication scheme using key-insulation technique for remote health monitoring system, however, key-insulation technique is not properly adapted to their scheme which in turn causes a security pitfall contrary to their assertions. Besides, Yang et al.'s scheme does not guarantee user anonymity against healthcare service provider. Therefore, in this paper, we discuss the security concerns for Yang et al.'s scheme and present an improved anonymous authentication scheme.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.229-239
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• 2009

To solve user authentication problem, many remote user authentication schemes using password and smart card at the same time have been proposed. Due to the increasing of interest in personal privacy, there were some recent researches to provide user anonymity. In 2004, Das et al. firstly proposed an authentication scheme that guarantees user anonymity using a dynamic ID. In 2005, Chien et al. pointed out that Das et al.'s scheme has a vulnerability for guaranteing user anonymity and proposed an improved scheme. However their authentication scheme was found some weaknesses about insider attack, DoS attack, and restricted replay attack. In this paper, we propose an enhanced scheme which can remove vulnerabilities of Chien et al.'s scheme. The proposed authentication protocol prevented insider attack by using user's Nonce value and removed the restricted replay attack by replacing time stamp with random number. Furthermore, we improved computational efficiency by eliminating the exponentiation operation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2148-2150
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• 2015

This paper proposes an adaptive cooperative scheme in the cell boundary. The user location and the suitable cooperative transmission scheme are considered in the proposed scheme. If the user is located in the cell boundary, the quality of communication is degraded. Two base stations are used to obtain diversity in the conventional schemes. But the quality of communication is not sufficiently improved because the user is still distant from the base stations. So, the scheme is proposed that the relays and the adaptive cooperative scheme are used considering the location of the user. By the simulation, it is proved that the proposed scheme is better than the conventional scheme.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3171-3181
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• 2021

This research serves to advance the development of engineering computational fluid dynamics (CFD) computing efficiency for the analysis of pressurized water reactor (PWR) core using rod-type fuel assemblies with mixing vanes (one kind of typical PWR core). In this research, a CFD scheme based on the reconstruction of the initial fine flow field (RIF CFD scheme) is proposed and analyzed. The RIF scheme is based on the quantitative regulation of flow velocities in the rod-type PWR core and the principle that the CFD computing efficiency can be improved greatly by a perfect initialization. In this paper, it is discovered that the RIF scheme can significantly improve the computing efficiency of the CFD computation for the rod-type PWR core. Furthermore, the RIF scheme also can reduce the computing resources needed for effective data storage of the large fluid domain in a rod-type PWR core. Moreover, a flow-ranking RIF CFD scheme is also designed based on the ranking of the flow rate, which enhances the utilization of the flow field with a closed flow rate to reconstruct the fine flow field. The flow-ranking RIF CFD scheme also proved to be very effective in improving the CFD efficiency for the rod-type PWR core.