• Journal of the Korea Institute of Military Science and Technology
• /
• v.11 no.5
• /
• pp.23-33
• /
• 2008

In this paper, we verify the performance of LDPC coded OFDM/DS system by Monte-Carlo simulation of BER on Eb/No. The simulation results show that LDPC coded OFDM/DS has a strong anti-jamming characteristic over pulse-noise jammer and partial-band noise jammer. The performance of LDPC coded OFDM/DS system is evaluated on both faded waveforms and non-faded waveforms. For non-faded waveforms, high coding gain is attained due to LDPC, even when waveforms have short PN sequence and JSR is only 5dB. Especially, the increase in the repeated number of LDPC decoding enhances coding gain. However, faded waveforms cannot achieve sufficient average effect when PN sequence is short. High coding gain of faded waveforms can be achieved by extending length of PN sequence. In addition, we compare LDPC coded OFDM/DS system with Convolutional coded OFDM/DS system. The simulation results illustrate that when LDPC coded OFDM/DS system with short PN sequence has sufficient average effects, the system shows lower BER than Convolutional coded OFDM/DS system with long PN sequence.

• Journal of applied mathematics & informatics
• /
• v.14 no.1_2
• /
• pp.461-471
• /
• 2004

In recent years, large volumes of data are transferred between a computer system and various subsystems through digital logic circuits and interconnected wires. And there always exist potential errors when data are transferred due to electrical noise, device malfunction, or even timing errors. In general, parity checking circuits are usually employed for detection of single-bit errors. However, it is not sufficient to enhance system reliability and availability for efficient error detection. It is necessary to detect and further correct errors up to a certain level within the affordable cost. In this paper, we report a generation of 3-distance code using the characteristic matrix of a PBCA.

• Journal of the Korean Mathematical Society
• /
• v.46 no.1
• /
• pp.41-49
• /
• 2009

Let $\zeta$ be a fixed complex number. In this paper, we study the quantity $S(\zeta,\;n):=mas_{f{\in}{\Lambda}_n}\;|f(\zeta)|$, where ${\Lambda}_n$ is the set of all real polynomials of degree at most n-1 with coefficients in the interval [0, 1]. We first show how, in principle, for any given ${\zeta}\;{\in}\;{\mathbb{C}}$ and $n\;{\in}\;{\mathbb{N}}$, the quantity S($\zeta$, n) can be calculated. Then we compute the limit $lim_{n{\rightarrow}{\infty}}\;S(\zeta,\;n)/n$ for every ${\zeta}\;{\in}\;{\mathbb{C}}$ of modulus 1. It is equal to 1/$\pi$ if $\zeta$ is not a root of unity. If $\zeta\;=\;\exp(2{\pi}ik/d)$, where $d\;{\in}\;{\mathbb{N}}$ and k $\in$ [1, d-1] is an integer satisfying gcd(k, d) = 1, then the answer depends on the parity of d. More precisely, the limit is 1, 1/(d sin($\pi$/d)) and 1/(2d sin($\pi$/2d)) for d = 1, d even and d > 1 odd, respectively.

• The Journal of Fisheries Business Administration
• /
• v.46 no.3
• /
• pp.31-49
• /
• 2015

This study examines whether or not the South Korean major fishery product import markets; Frozen Pollock, Frozen Long Arm Octopus, and Frozen Hairtail are integrated. We are utilizing the Multivariate and Bivariate Johansen Co-integration test to see if the law of one price(LOP) holds in each market or not. The empirical results show that even though import prices from different countries affect each other in each South Korean major fishery product import market, there is no evidence of LOP in any fishery product import market, which means that none of the markets are integrated. Based on these results, we could expect that the three major fishery product import markets show monopolistic competition among import countries. we would also see whether or not any country plays the role of a price leader in any of the markets. Based on weak exogeneity test results, we might expect that the United States and Malaysia are price leaders in the South Korean Frozen Pollock Import Market and Frozen Long Arm Octopus Import Market, respectively; however, we need to study more on this in the future.

• Nuclear Engineering and Technology
• /
• v.54 no.9
• /
• pp.3478-3487
• /
• 2022

In this study, we incorporate an anisotropic scattering scheme involving spherical harmonics into the method of characteristics (MOC). The neutron transport solution in a light water reactor can be significantly improved because of the impact of an anisotropic scattering source with the MOC flat source approximation. Several problems are selected to verify the proposed scheme and investigate its effects and accuracy. The MOC anisotropic scattering source is based on the expansion of spherical harmonics with Legendre polynomial functions. The angular flux, scattering source, and cross section are expanded in terms of the surface spherical harmonics. Later, the polynomial is expanded to achieve the odd and even parity of the source components. Ultimately, the MOC angular and scalar fluxes are calculated from a combination of two sources. This paper presents various numerical examples that represent the hot and cold conditions of a reactor core with boron concentration, burnable absorbers, and control rod materials, with and without a reflector or baffle. Moreover, a small critical core problem is considered which involves significant neutron leakage at room temperature. We demonstrate that an anisotropic scattering source significantly improves solution accuracy for the small core high-leakage problem, as well as for practical large core analyses.

• Applied Chemistry for Engineering
• /
• v.21 no.2
• /
• pp.230-237
• /
• 2010

A homologous series of linear liquid crystal dimers, ${\alpha},{\omega}$-bis(4-nitroazobenzene-4'-carbonyloxy)alkanes (NATWESn, n = 2~8, 10, the number of methylene units in the spacer) have been synthesized, and the thermal behavior of the series has been investigated. All the dimers formed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This behavior was rationalized in terms of the change in the average shape of the spacer on varing the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of NATWESn were very similar to those of the corresponding ether compounds, while they were significantly different from those of the monomesogenic compounds, 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-nitrophenylazo) phenoxycarbonylalkanoyloxy}ethylene]s. The results were discussed in terms of the 'irtual trimer model'by Imrie.

• Applied Chemistry for Engineering
• /
• v.22 no.4
• /
• pp.358-366
• /
• 2011

A homologous series of linear liquid crystal dimers, the ${\alpha},{\omega}$-bis(4-cyano-azobenzene-4'-oxy)alkanes (CATWETn, where n, the number of methylene units in the spacer, is 2~10) were synthesized, and their thermotropic liquid crystalline phase behavior were investigated. The CATWETn with n of 3 and 6 exhibited monotropic nematic phases, whereas other derivatives showed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This phase transition behavior was rationalized in terms of the change in the average shape of the spacer on varying the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of CATWETn were similar to those for the methoxy-, nitro-, and pentyl-substituted dimers, while they were significantly different from those for the monomesogenic compounds, 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s. The results were discussed in terms of 'virtual trimer model' by Imrie.

• Journal of Embryo Transfer
• /
• v.20 no.2
• /
• pp.185-190
• /
• 2005

This study was performed to investigate the effects of multiple superovulation and parity on embryo production in Hanwoo cows. Donors were superovulate 4 times $1\~2$ months interval and inserted CIDR plus (with the capsule of estradiol benzoate 10mg) on Day 10 from standing heat for 9 days and injected 2.5ml FSH (Antorin R-10) 2 times in a day on 6th day to 10th day from insertion of CIDR and the doses of FSH were decreasing 0.5ml on every 2 times. On 3th day of FSH injection, 25ml $PGF_2{\alpha}$ were injected i.m. and on 4th day, CIDR was removed. After 2 days from removing CIDR, AI was performed 2 times 12 hour apart with 2 straws of Korean Proved frozen Semen and simultaneously 200ug/ml GnRH was injected and embryos were recovered on 7th day from Al. The response rates of superovulated donors were $85.7\%,\;90.5\%,\;62.5\%,\;100\%$ from 1 to 4 times of superovulation, respectively. There were significant differences among No. of superovulation times (P<0.05). The results of transferable embryos were 3.7, 3.4, 3.4, 5.7 from 1 to 4 times of superovualtion, respectively. There were no differences among No. of superovulation times. The results of transferable embryos were 2.5, 3.0, 5.3, 3.0, 3.4 form heifer, first born to 4 the born, respectively. There were significant differences among the parities of donors (P<0.05). These results suggested that even 4 times of superovulations of Hanwoo donors could be able to recover transferable embryos, it might be used the donors maximally and improved the adaptation of embryo transfer to farms safely.

• Journal of Nutrition and Health
• /
• v.37 no.9
• /
• pp.809-816
• /
• 2004

The purpose of this study was to evaluate the effect of maternal nutritional status and health behaviors on the concentrations of minerals (Zn, Fe, Ca) and the immunological substances (lactoferrin, sIgA, Iysozyme) in breast milk. Breast milk was collected from 193 healthy Korean women from obstetric clinics and postpartum care centers in Seoul. : 99 colostrum (1 - 5 days postpartum), 33 transitional milk (6 - 10 days postpartum), 61 mature milk (11 - 50 days postpartum). The concentrations of minerals and immunological substance were highest in colostrum and decreased with lactational period. Concentrations of Zn and Fe reduced significantly from colostrum to mature milk, however, Ca concentration stayed constant throughout the lactational period. Contents of lactoferrin, sIgA, and lysozyme were significantly lower in mature milk than in colostrum. Mother's nutritional status, assessed by prepregnancy BMI, had an effect only on colostrum, but not on transition and mature milk. Fe concentration of colostrum was significantly lower in underweight (prepregnancy BMI < 18.5) than in overweight mothers (prepregnancy BMI $\geq$ 23.0). Also lower tendency was observed for sIgA and lysozyme contents, even though the difference was not statistically significant. Pregnancy weight gain had no effect on the breast milk component. Since nutritional factors had some effect on colostrum, the health behaviors of mothers providing colostrum were assessed. The mother's behavior of smoking, drinking, morning sickness, parity, disease, nutrient supplement use had no significant effect on the breast milk component, however, Zn, sIgA, and lysozyme were the somewhat affected components by maternal health behavior.

• 전자공학회논문지 IE
• /
• v.43 no.2
• /
• pp.80-86
• /
• 2006

The wireless communication based on LDPC and adaptive spatial-subcarrier coded modulation using MQAM for orthogonal frequency division multiplexing (OFDM) wireless transmission by using instantaneous channel state information and employing multiple antennas at both the transmitter and the receiver. Adaptive coded modulation is a promising idea for bandwidth-efficient transmission on time-varying, narrowband wireless channels. On power limited Additive White Gaussian Noise (AWGN) channels, low density parity check (LDPC) codes are a class of error control codes which have demonstrated impressive error correcting qualities, under some conditions performing even better than turbo codes. The paper demonstrates OFDM with LDPC and adaptive modulation applied to Multiple-Input Multiple-Output (MIMO) system. An optimization algorithm to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge is used. The experimental results are shown the potential of our proposed system.