• International Journal of CAD/CAM
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• v.7 no.1
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• pp.51-60
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• 2007

This paper presents an algorithm of optimal cutting tool selection for machining of the point-based surface that is defined by a set of surface points rather than parametric polynomial surface equations. As the ball-end and fillet-end mills are generally used for finish machining in a 3-axis computer numerical control machine, the algorithm is applicable for both cutters. The optimum tool would be as large as possible in terms of the cutter radius and/or corner radius which maximise (s) the material removal rate (i.e., minimise (s) the machining time), while still being able to machine the entire point-based surface without gouging any surface point. The gouging are two types: local and global. In this paper, the distance between the cutter bottom and surface points is used to check the local gouging whereas the shortest distance between the surface points and cutter axis is effectively used to check the global gouging. The selection procedure begins with a cutter from the tool library, which has the largest cutter radius and/or corner radius, and then adequacy of the point-density is checked to limit the accuracy of the cutter selection for the point-based surface within tolerance prior to the gouge checking. When the entire surface is gouge-free with a chosen cutting tool then the tool becomes the optimum cutting tool for a list of cutters available in the tool library. The effectiveness of the algorithm is demonstrated considering two examples.

• International Journal of Advanced Culture Technology
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• v.11 no.4
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• pp.263-272
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• 2023

We investigated and analyzed students' perceptions of their choice of science subjects in the high school credit system and the reasons for their choice. To achieve this, the selection of science subjects was investigated for the second year of S high school over the past three years. Students selected an average of 1.54 science subjects, and it was found that the rate of selection of science subjects was gradually increasing by year. Students chose high in the order of life science I, earth science I, chemistry I, physics I, etc. in the science subject group. Students who wish to enter the natural and engineering fields chose life science I, chemistry I, physics I, etc., while, students who wish to enter the humanities society chose society and culture, life science I, ethics and thought, etc. On the other hand, the reason for choosing science subjects was 'related to college admission', followed by 'aptitude and interest', 'career and real life help', etc. physics I, chemistry I, etc., were high in the subjects selected according to the 'related to college admission'. The subjects selected according to 'aptitude and interest' were high in life science I, earth science I, etc. Physics I, chemistry I, etc. are recognized as subjects necessary for college entrance, and life science I, earth science I, etc., are found to be related to their interests and aptitudes.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.461-463
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• 2002

Image quality and selection of optimized window for good quality reconstruction in coronary angiography using multi-detector row CT (MDCT) have not been studied by heart rate and its variation. Therefore, the effect of heart rate and its variation was systemically analyzed. Eighty-three patients were undergone contrast-enhanced coronary angiography using MDCT. In this study, sixty cases were enrolled. Two radiologists graded image quality as follows: 4, excellent; 3, good; 2, fair; l, bad. The starting points of the reconstruction window were chosen at seventy and forty percent of R wave interval. Optimized window was scored as 1 when 40% reconstruction was better quality than 70%, as 2 when 40% reconstruction is same as 70%, and as 3 when 70% reconstruction was better than 40%. Regression analysis was performed. The range of variation of beats per minute (BPM) was well correlated with image quality (r=-0.55, p=0.000), however correlation with optimized window percentage was not statistically significant (p=0.969). By contraries, median value of BPM was comparatively well correlated with optimized window grade (r=-0.24, p=0.086). Median value of BPM was not well correlated with image quality (r=0.l70, p=0.l97). Image quality is more affected by variation of heart rate (VHR) than by higher heart rate. Selection of optimized reconstruction window for good image quality is mainly affected by heart rate and there is a tendency that systolic phase reconstruction is better in image quality than diastolic reconstruction in higher heart rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3A
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• pp.141-150
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• 2012

The WiMedia Alliance has specified a Distributed Medium Access Control (D-MAC) protocol based on UWB for high speed wireless home networks and WPANs. In this paper, firstly, a time slot reservation protocol for relay transmission is proposed. Furthermore, we propose a novel relay node selection algorithm adaptive to current UWB link transmission rate. The proposed relay node selection algorithm has compatibility with current WiMedia D-MAC standard and is executed at each device according to the SoQ as a QoS criterion.

• Architectural research
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• v.11 no.2
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• pp.19-26
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• 2009

The effect of rebirthing technique on the genetic algorithm (GA)-based size optimization is investigated. The GA mimics the principles of nature and it can gradually improve structural design through biological operations such as fitness, selection, crossover and mutation. However, premature optimum has been often detected in the generic GA with continuous design variable. Since then, the so-called rebirthing technique has been proposed to avoid this problem. However, the performance of the rebirthing technique has not been reported. Therefore, the size optimizations of spatial structures are tackled to investigate the performance of the rebirthing technique on the generic GA. From numerical results, it is well proved that the rebirthing technique is very effective to produce the optimum values regardless of the values of parameters used in the GA operations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.467-472
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• 2008

One of the maindisadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is the Peak to Average Power Ratio (PAPR) problem. To reduce PAPR and improve the error performance of the OFDM signal over a fading channel, an OFDM system combining an Adaptive Symbol Selection Scheme (ASSS) and channel estimation can be used. Because of the side information of ASSS, however, the data rate decreases in the conventional ASSS OFDM system. In this letter, to overcome this impairment, we propose a technique to transmit side information by using pilot tones, and demonstrate that the proposed technique can give reasonable bit error rate (BER) performance.

• Current Optics and Photonics
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• v.1 no.4
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• pp.289-294
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• 2017

A high-performance time-division multiplexing (TDM) -based multiuser (MU) multiple-input multipleoutput (MIMO) system for efficient indoor visible-light communication (VLC) is presented. In this work, a MIMO technique based on RGB light-emitting diodes (LEDs) with selection combining (SC) is utilized for data transmission. That is, the proposed scheme employs RGB LEDs for parallel transmission of user data and transmits MU data in predefined slots of a time frame with a simple and efficient design, to schedule the transmission times for multiple users. Simulation results demonstrate that the proposed scheme offers an approximately 6 dB gain in signal-to-noise ratio (SNR) at a bit error rate (BER) of $3{\times}10^{-5}$, as compared to conventional MU single-input single-output (SISO) systems. Moreover, a data rate of 66.7 Mbps/user at a BER of $10^{-3}$ is achieved for 10 users in indoor VLC environments.

• Korean Journal of Agricultural Science
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• v.40 no.2
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• pp.169-176
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• 2013

The price and revenue of rice are expected to decrease due to increasing rice imports, decreasing consumption and the discontinuance of the government's rice procurement. This degenerating profitability is leading to a rise in the cultivation of upland-crops such as beans, fodder crops and fruits in paddy fields. However, there is a lack of research on the selection of rice substitute crops which are adaptable to the relevant region through profitability analysis. This research, therefore, analyzed investment profitability of rice substitute crops for Cheorwon-gun area in Kangwon province. The study applied net present value (NPV) and internal rate of return (IRR), which fit for mutually exclusive investments that make one selection to the exclusion of other crops. Target crops are green house plants in Cheorwon-gun area. Financial analysis showed paprika and cucumber have investment feasibility for automated vinyl greenhouses and conventional plastic greenhouses respectively.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.419-420
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• 2006

In the new video coding standard H.264/AVC, motion estimation (ME) is allowed to search multiple reference frames for improve the rate-distortion performance. The complexity of multi-frame motion estimation increases linearly with the number of used reference frame. However, the distortion gain given by each reference frame varies with the video sequence, and it is not efficient to search through all the candidate frames. In this paper, we propose a fast mult-frame selection method using all zero coefficient block (AZCB) prediction and sum of difference (SAD) of neighbor block. Simulation results show that the speed of the proposed algorithm is up to two times faster than exhaustive search of multiple reference frames with similar quality and bit-rate.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.153-161
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• 2021

This study examined whether the probability of a tax investigation by the general construction industry could reduce the entertainment expenses in order to confirm whether a tax investigation can reduce excessive discretionary expenses of firms. Among the general construction industry listed on the KOSPI and KOSDAQ from 2011 to 2018, 274 firms with sales exceeding 10 billion won in the previous year were targeted at the tax audit selection rate and the tax audit detection rate, which is a proxy for the possibility of a tax investigation. The effect of the ratio of entertainment expenses to sales and the increase rate of entertainment expenses was verified. As a result of the analysis, both the selection rate and the detection rate of the tax investigation have a significant negative effect on the proxy variable of the discretionary expenses measured as the proportion of entertainment expenses and the increase rate of entertainment expenses. The results of this study showed that the tax investigation is a means to curb the excessive expenditure of the firm's discretionary expenses, thus suggesting the direction for the taxation policy and the effectiveness of the tax investigation.