• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.648-656
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• 2009

We perform an analysis of the characteristics of the time-reversal pulse in Rayleigh or Ricean fading channel environments. We verify it by using Monte Carlo simulation. In a time-reversal system, each antenna in the time-reversal array receives signals from the transmitter and reverse the received signal in the time axis and then resend it to the original transmitter. We assume that the channel characteristics varies very slowly and the spatial separation between the antennas is not large. Hence the signals received by each antenna are correlated. In this paper, the effect of the correlation on the time-reversed pulse is examined, which includes the spatial properties of the time-reversal pulse such as the focus size, and spatial power distribution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.614-622
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• 2004

In this paper, we propose the frequency diversity scheme for performance improvement of a OFDM system without decreasing the spectral efficiency. In the proposed scheme, information bit is encoded to symbol by a simple procedure, and the encoded symbol is transmitted through the two lowest correlated sub-channels with the particular phase difference. At the receiver, a frequency diversity gain is obtained by a simple signal processing. We also suggest optimum phase difference value to minimize the performance degradation which resulted from a phase difference estimation error and bit/symbol mapping method to minimize BER. As results, at the point of performance improvement, the proposed scheme is excellent even though it requires a little increase of system complexity because of an additional encoding and decoding. In particular, we confirmed through computer simulation that on the same channel environment and bandwidth efficiency, the 27x/1Rx STBC-OFDM system adopting the proposed frequency diversity scheme outperforms the conventional 27x/1Rx STBC-OFDM system performance

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7C
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• pp.921-930
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• 2004

In this paper, a robust video transmission system is proposed. To effectively prevent the corruption of video stream and its propagation in spatial and temporal domains, a version of turbo code, so-called as byte-aligned variable-length turbo code, is applied. Protection performance of the proposed turbo code is first evaluated by applying it to GOB-based variable-size ITU-T H.263+ video packets, where the protection level is statically controlled based on the joint source-channel criteria. This protection is then extended to support the adaptation of code ratio to best match the time-varying channel condition. The time-varying Rayleigh fading channel is modelled considering the correlation of the fading channel. The resulting performance comparison with the static turbo code as well as the conventional RCPC code clearly demonstrates the possibility of the proposed adaptation approach for the time-varying correlated Rayleigh-fading channel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1395-1404
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• 1994

Transverse bed slope in bend is a subject of scientific investigation since it provides the necessary information for channel design and protection of hydraulic structures (bank, bridge, etc), and study of river morphology. In this paper, selected models were examined and compared for the value of prediction of the transverse bed slope in curved alluvial channels(project area), by using field data, and fitting model was proposed. All models that related the local transverse bed slope to mean flow characteristics were alike in the sense that they predicted the local transverse bed slope to be proportional to the ratio between depth and radius of curvature. The difference among the models was related with the factor of proportionality, K. Also, measured transverse bed slope was correlated to mean velocity, maximum depth, and density Froude number in channel bend. In this paper selected models were compared for the prediction of the transverse bed slope using Odgaard's experiment (obtained in Sacramento River bend), so Odgaard89 model was closely related with real transverse bed slope.

• Nutrition Research and Practice
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• v.6 no.5
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• pp.414-420
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• 2012

Forty guinea pigs were divided into four groups and fed 0.04% cholesterol based control diet, plus 0.05% simvastatin, and statin plus 0.1% CoQ10 or 10% Ardisia Japonica Blume (AJB) leave powder for 4 weeks. Plasma total cholesterol levels decreased significantly in all groups fed the statin-containing diet compared with that in guinea pigs fed the control diet (P < 0.01). Plasma and liver triglycerides decreased significantly in the statin plus CoQ10 group compared with those in the control (both P < 0.05). Maximum platelet aggregation was significantly higher in the statin plus CoQ10 group than that in the other groups (P < 0.05). Na-K ATPase activity increased in the statin group and decreased in the statin plus CoQ10 group (P < 0.01). Na-K co-transport and Na passive transport decreased significantly in the control group compared with those in the other groups (both P < 0.05). Intracellular Na was highest in the statin group and lowest in the statin plus CoQ10 group and was correlated with Na-K ATPase activity. Thiobarbituric acid reactive substance production in platelet-rich plasma and liver tended to decrease in the statin plus CoQ10 group compared with those in the other groups. Plasma glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase increased significantly in the statin group compared with those in the control (P < 0.05). These result suggest that antioxidant rich AJB did not have positive effects on cardiovascular disease parameters. The statin plus CoQ10 seemed to decrease cholesterol more efficiently than that of statin alone.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1084-1093
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• 2012

For large multihop networks, large time synchronization (TS) errors can accumulate with conventional methods, such as TPSN, RBS, and FTSP, since they need a large number of hops to cover the network. In this paper, a method combining Concurrent Cooperative Transmission (CCT) and Semi- Cooperative Spectrum Fusion (SCSF) is proposed to reduce the number of hops to cover the large network. In CCT, cooperating nodes transmit the same digitally encoded message in orthogonal channels simultaneously, so receivers can benefit from array and diversity gains. SCSF is an analog cooperative transmission method where different cooperators transmit correlated information simultaneously. The two methods are combined to create a new distributed method of network TS, called the Cooperative Analog and Digital (CANDI) TS protocol, which promises significantly lower network TS errors in multi-hop networks. CANDI and TPSN are compared in simulation for a line network.

• Journal of Biomedical Engineering Research
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• v.31 no.4
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• pp.285-291
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• 2010

Recently, advance on various modalities of diagnosing, prostate volume estimation became possible not only by the existing two-dimension medical images data but also by the three-dimensional medical images data. In this study, magnetic resonance image (MRI), computer tomography (CT) and ultrasound (US) were employed to evaluate prostate phantom volume measurements for estimation, comparison and analysis. For the prostate phantoms aimed at estimating the volume, total of 17 models were developed by using devils-tongue jelly and changing each of the 5ml of capacity from 20ml to 100ml. For the volume estimation through 2D US, the calculation of the diameter with C9-5Mhz transducer was conducted by ellipsoid formula. For the volume estimation through 3D US, the Qlab software (Philips Medical) was used to calculate the volume data estimated by 3D9-3Mhz transducer. Moreover, the images by 16 channels CT and 1.5 Tesla MRI were added by the method of continuous cross-section addition and each of imaginary prostate model's volume was yielded. In the statistical analysis for comparing the availability of volume estimation, the correlation coefficient (r) was more than 0.9 for all indicating that there were highly correlated, and there were not statistically significant difference between each of the correlation coefficient (p=0.001). Therefore, the estimation of prostate phantom volume using three-dimensional modalities of diagnosing was quite closed to the actual estimation.

• Journal of The Korean Astronomical Society
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• v.50 no.4
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• pp.125-129
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• 2017

We investigate the solar cycle variation of microwave and extreme ultraviolet (EUV) intensity in latitude to compare microwave polar brightening (MPB) with the EUV polar coronal hole (CH). For this study, we used the full-sun images observed in 17 GHz of the Nobeyama Radioheliograph from 1992 July to 2016 November and in two EUV channels of the Atmospheric Imaging Assembly (AIA) $193{\AA}$ and $171{\AA}$ on the Solar Dynamics Observatory (SDO) from 2011 January to 2016 November. As a result, we found that the polar intensity in EUV is anti-correlated with the polar intensity in microwave. Since the depression of EUV intensity in the pole is mostly owing to the CH appearance and continuation there, the anti-correlation in the intensity implies the intimate association between the polar CH and the MPB. Considering the report of Gopalswamy et al. (1999) that the enhanced microwave brightness in the CH is seen above the enhanced photospheric magnetic field, we suggest that the pole area during the solar minimum has a stronger magnetic field than the quiet sun level and such a strong field in the pole results in the formation of the polar CH. The emission mechanism of the MPB and the physical link with the polar CH are not still fully understood. It is necessary to investigate the MPB using high resolution microwave imaging data, which can be obtained by the high performance large-array radio observatories such as the ALMA project.

• YAKHAK HOEJI
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• v.40 no.1
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• pp.102-111
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• 1996

LB10522 is a new parenteral broad spectrum cephalosporin with a catechol moiety at C-7 position of beta-lactam ring. This compound can utilize tonB-dependent iron transp ort system in addition to porin proteins to enter bacterial periplasmic space and access to penicillin-binding proteins (PBPs) which are the lethal targets of ${\beta}$-lactam antibiotics. The chelating activity of LB10522 to metal iron was measured by spectrophotometrically scanning the absorbance from 200 to 900nm. When $FeCl_3$ was added, optical density was increased between 450 and 800nm. LB10522 was more active against gram-negative strains in iron-depleted media than in iron-replete media. This is due to the increased expression of iron transport channels in iron-depleted condition. LB10522 showed a similar activity against E. coli DC2 (permeability mutant) and E. coli DCO (wild type strain) in both iron-depleted and iron-replete media, indicating a minimal permeaility barrier for LB10522 uptake. LB10522 had high affinities to PBP 3 and PBP 1A, 1B of E. coli. By blocking these proteins, LB10522 caused inhibition of cell division and the eventual death of cells. This result was correlated well with the morphological changes in E. coli exposed to LB10522. Although the in vitro MIC of LB10522 against P. aeruginosa 1912E mutant (tonB) was 8-times higher than that of the P. aeruginosa 1912E parent strain, LB10522 showed a similar in vivo protection efficacy against both strains in the mouse systemic infection model. This result suggested that tonB mutant, which requires a high level of iron for normal growth, might have a difficulty in surviving in their host with an iron-limited environment.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.329-337
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• 1999

Thyroid hormone-induced cellular dysfunctions may be associated with changes in the intracellular $Ca^{2+}$ concentration. The ryanodine receptor, a $Ca^{2+}$ release channel of the SR, is responsible for the rapid release of $Ca^{2+}$ that activates cardiac muscle contraction. In the excitation-contaction coupling cascade, activation of ryanodine receptors is initiated by the activity of sarcolemmal $Ca^{2+}$ channels, the dihydropyridine receptors. In hyperthyroidism left ventricular contractility and relaxation velocity were increased, whereas these parameters were decreased in hypothyroidism. The mechanisms for these changes have been suggested to include alterations in the expression and/or activity levels of various proteins. In the present study, quantitative changes of ryanodine receptors and the dihydropyridine receptors, and the functional consequences of these changes in various thyroid states were investigated. In hyperthyroid hearts, $[^3H]ryanodine$ binding and ryanodine receptor mRNA levels were increased, but protein levels of ryanodine were not changed significantly. However, the above parameters were markedly decreased in hypothyroid hearts. In case of dihydropyridine receptor, there were a significant increase in the mRNA and protein levels, and [3H]nitrendipine binding, whereas no changes were observed in these parameters of hypothyroid hearts. Our findings indicate that hyperthyroidism is associated with increases in ryanodine receptor and dihydropyridine receptor expression levels, which is well correlated with the ryanodine and dihydropyridine binding. Whereas opposite changes occur in ryanodine receptor of the hypothyroid hearts.