• Journal of Broadcast Engineering
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• v.20 no.1
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• pp.92-109
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• 2015

Broadcast encryption is a cryptographic primitive that allows a sender to securely broadcast a message to a set of receivers. The most influential broadcast encryption system was proposed in 2001 by Naor, Naor, Lotspiech, based on a pseudo-random generator and the Subset Difference (SD) method. In this paper, we suggest a new broadcast encryption system that is based on secret sharing and SD methods. On an efficiency aspect, our system achieves O(r) transmission cost, O($log^2n$) storage cost, and O(1) computational cost for the number n of users and the number r of revoked users. Compared to O(log n) computational cost in the previous SD method, our system has the advantage that it needs only constant-sized computational cost for decryption, regardless of the number n or r. On a security aspect, our system can achieve tighter security reduction than the previous SD method and the gap of security loss is about O(n log n). Moreover, our result shows that it is possible to give the effect of the SD method while using an information-theoretically secure key distribution technique as in the Complete Subtree method.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.9
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• pp.1064-1072
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• 1999

The well-known Dimension Exchange Method(DEM) to quantized loads may result in difference in assigned loads to processors as large as logn~units, in the worst case, after balancing for a hypercube of size n. In order to limit the increase of the accumulation of these differences, this paper proposes a method that limits the accumulation of the difference by redistributing an unit load (odd or even) of the same type, if possible, when there is a load distribution between two processors. We reduced the maximum difference to LCEIL logn over {2} RCEIL . The result shows the simulation experiments which show about 30% improvement in speedup compare to the DEM.

• Kyungpook Mathematical Journal
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• v.48 no.2
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• pp.173-181
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• 2008

We give the necessary and sufficient conditions for the asymptotic stability of the linear delay difference equation $x_{n+1}\;-\;a^2x_{n-1}\;+\;bx_{n-k}\;=\;0$, n = 0, 1,$\cdots$, where a and b are arbitrary real numbers and k is a positive integer greater than 1. The obtained conditions are given in terms of parameters a and b of difference equations. The method of proof is based on arithematic of complex numbers as well as properties of analytic functions.

• Journal of applied mathematics & informatics
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• v.8 no.3
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• pp.683-691
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• 2001

A linearized finite-difference scheme is used to transform the initial/boundary-value problem associated with the nonlinear Schrodinger equation into a linear algebraic system. This method is developed by replacing the time and the nonlinear term by an appropriate parametric linearized scheme based on Taylor’s expansion. The resulting finite-difference method is analysed for stability and convergence. The results of a number of numerical experiments for the single-soliton wave are given.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.46-54
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• 2007

In this paper, we introduce the performance of improved symbol timing detection by the superposed difference type symbol timing detection method in the OFDM system. Also, we represent the maximum detection probability of symbol synchronization timing at each received delay signal in multipath channel delay profile in the correlation and difference type symbol timing detection methods. The computer simulation results show that the correlation symbol timing detection method have maximum detection probability at the lead of the nth received delay signal of highest amplitude, but the difference type symbol timing detection method always have maximum detection probability at the lead of the first received delay signal in the channel delay spread of $70nsec{\sim}217nsec$. The simulation results indicate the possibility of the perfect detection of OFDM symbol synchronization timing and it fit well with the results of improved S/N to the eb/n0 and the performance of symbol timing detection of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.7
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• pp.481-491
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• 1989

A compensation strategy for the phase-difference control method, which has been reported as a new driving method of a 2-phase inverter-fed induction motor, is proposed. The phase-difference control method extends the control range of the speed and eliminates the harmonic contents of the output voltage of the 2-phase inverter-fed induction motor. However, the phase-difference angle becomes narrower, motor efficiency deceases more and pulsating torque increases more. As the counterplan for these shortcomings of the phase-difference control method, a hybrid control method which combines the phase-difference control with the voltage control is proposed. The algorithm to realize a hybrid method is presented. As an example, a model composed of 5 regions has been analyzed by computer simulation in terms of motor performance and the results have been compared with experimental results.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.318-324
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• 2016

In order to study the effect of barley, Italian ryegrass (IRG), and legume mixture on nitrogen fixation and transfer to grasses on spring paddy field, an experiment was carried out from Oct. 2006 to June 2007 in Naju, Korea. A split plot design with three replications was used for the experiment. One reference plot was assigned for each treatment to determine nitrogen fixation. Main plots consisted of Chinese milk vetch, crimson clover, forage pea, and hairy vetch with barley, respectively. Subplot treatment were barley or IRG with four seeding ratio of legumes (50:50, 60:40, 70:30, and 80:20). To estimate N fixation by legumes, $^{15}N$ isotope dilution technique was used. $^{15}N$ fertilizer [$(^{15}NH_4)_2SO_4$ solution at 99.8 atom N] was uniformly applied to $600cm^2$ in the middle of each plot on April 15, 2007. Plots were harvest by hand on June 8, 2007. Dried sample were ground to a fine power and analyzed for total N isotope N. $^{15}N$ was determined using elemental analyzer-isotope ratio mass spectrometry. The calculation of N transfer was determined with the isotope dilution method. The content of N was higher in legumes than that in barley or Italian ryegrass. Nitrogen level in forage pea was significantly higher than that of other legumes. There were significantly differences in N content between legumes in IRG mixture. Atom % $^{15}N$ excess was significantly different in legumes with barley. The 60:40 sub plot had higher (p<0.05) atom % $^{15}N$ than other seeding ratio treatments. The enrichment ranged from 0 to 0.58. Compared to barley, the enrichment of IRG with its accompanied legumes was higher, ranging from 0.38 to 1.0. The N derived from the atmosphere (Ndfa) ranged from 0% to 49.5% with barley-legume mixture. It ranged from 0 to 60.5% in IRG-legume plots. N transfer from legumes to neighboring grasses was 12.3 to 90.9 kg/ha for barley-legume mixture and 31.7 to 107.8 kg/ha for IRG plots. IRG plots showed higher N transfer for IRG-legume mixture in general based on difference method. Based on $^{15}N$ dilution method, the N transfer was 0 to 36.1 kg/ha for barley-legume mixture and 0 to 50.6 kg/ha for IRG plots. There was a tendency toward higher N transfer on the difference method than that of the $^{15}N$ dilution method.

• Journal of the Korean Society of Tobacco Science
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• v.24 no.1
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• pp.32-37
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• 2002

This study was carried out to investigate the effects of suckers on chemical components with vertical and horizontal hanging method during stalk-cut curing in burley tobacco. The elongation and dry weights of suckers were increased until 14 days in vertical hanging method, and until 7days in horizontal hanging method after the beginning of curing. The contents of nicotine, protein-N and $NH_4$-N were decreased at treatment of more suckers during the curing. However, there was no significant difference by the hanging method. Solanone, damascenone, megastigmatrienone and 4-methyl phenol were increased gradually during curing. Those were increased with treatment of fewer suckers compared to treatment of more suckers. There was no significant difference by the hanging method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1179-1182
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• 2016

In this paper, a new method to reduce the size of ROM in the direct digital frequency synthesizer (DDFS) is proposed. This method use the sine-linear phase difference method and differential PCM. The new ROM compression method can reduce the ROM size by using the two ROM. The quantized value of sine-linear phase difference is saved by the ROM1 of the $2^N$ sample period. The ROM2 save the difference between the original sine-linear phase difference value and the saved sample value of the ROM1. The ROM compression ratio of 37% is achieved by this method. Also, the power consumption is decreased according to the ROM size reduction.

• Journal of Climate Change Research
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• v.6 no.3
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• pp.175-184
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• 2015

In this study GC and PAS were used to calculate $N_2O$ concentration of exhaust gas from Wood Chip combustion system. Fuel supplied to the incinerator was collected and analyzed and then the analysis result was used to calculate $N_2O$ emissions. Tier 3 and Tier 4 Method were used to calculate the $N_2O$ emissions. Plant's Specific emission factor of $N_2O$ by Tier 3 Method was 0.35 kg/TJ, while default emission factor of Wood?Wood Waste proposed by 2006 IPCC G/L was 4 kg/TJ. So the $N_2O$ emission factor of this study was 3.65 kg/TJ lower compared to the IPCC G/L. The total emissions calculated by Plant's specific emission factor was 4.22 kg during the measuring period, but by Tier 4 Method it was 7.88 kg. This difference in emissions was caused by the difference of continuous measuring and intermittent sampling. It would be necessary to apply continuous measuring to calculate emissions of $Non-CO_2$ gas whose the density distribution is relatively high. However currently, according to the target management guideline of greenhouse gas and energy, the continuous measuring method to calculate greenhouse gas emission is applied only to $CO_2$. Therefore for reliable greenhouse gas emission calculation it would be necessary to apply continuous measuring to calculate $Non-CO_2$ gas emission.