• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.27-37
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• 1983

A method of dynamic analysis is developed for torsional free vibrations of elliptical-box girder type or stiffening truss system suspension bridge. In this study, the method based on a finite element technique using a digital computer, is illustrated by two numerical examples, the Namhae Bridge which is located in Kyungsang nam-do opened on June, 1973, and the Mt. Chunma Bridge is simple span pedestrian's suspension bridge with lateral bracing system in Mt. Chunma, Kyungki-do, are used. In general, dynamic modes of complex suspension bridges are three-dimensional in form, i.e., coupling between vertical and torsional motions. However, introduced that amplitudes of oscillation are infinitesimal for coincidence with the purpose of it's use, thereupon, the torsional vibration analyses are treated without coupling terms. A sufficient number of natural frequencies and mode shapes for torsional free vibration are presented in this paper. In the case of Mt. Chunma Bridge, the natural frequencies and periods are computed with and without reinforcement, respectively, and compared their discrepancies. The influence of the auxiliary reinforcing cables is prevailing in the first few modes, namely, 1st and 2nd in symmetric and 1st, 2nd and 3rd in antisymmetric vibration, and conspicuous in the symmetric compared with the antisymmetric motion, but in the higher modes, this kind of simple accessory elucidates rether converse effects. In the Namhae Bridge, the results are compared with the Manual's obtained by wind tunnel test. It reveals commendable agreement.

• Journal of Preventive Medicine and Public Health
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• v.42 no.5
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• pp.298-304
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• 2009

Objectives : The aim of this study was to investigate the association of blood pressure levels with the common carotid artery intima-media thickness (CCA-IMT) and carotid plaques. Methods : Data were obtained from 2,635 subjects, aged 50 years and over, who participated in the Community Health Survey (a population-based, cross-sectional study) in Dong-gu, Gwangju city between 2007 and 2008. Participants were categorized into three groups according to blood pressure levels; normotensives (<120/80 mmHg), prehypertensives (120-139/80-89 mmHg), and hypertensives ($\geq$140/90 mmHg). Prehypertensives were further categorized as low prehypertensives (120-129/80-84 mmHg) and high prehypertensives (130-139/85-89 mmHg). Carotid intima-media thickness and plaques were evaluated with a high-resolution B-mode ultrasound. Statistical analyses were performed using chi-square test, ANOVA, and multiple logistic regression. Results : Prehypertensives had significantly greater maximal CCA-IMT values than normotensives, with a multivariate adjusted odds ratio of 1.78 (95% CI=1.36-2.32) for abnormal CCA-IMT (maximal CCA-IMT$\geq$1.0 mm), and 1.45 (95% CI=1.19-1.77) for carotid plaques. The multivariate adjusted odds ratio of low prehypertensives was 1.64 (95% CI=1.21-2.21) for abnormal CCA-IMT, and 1.30 (95% CI=1.04-1.63) for carotid plaques compared with normotensives. Subject with hypertension had higher frequency of abnormal CCA-IMT (odds ratio, 2.18; 95% CI=1.49-3.18), and carotid plaques (odds ratio, 1.98; 95% CI=1.46-2.67) compared with normotensives after adjustment for other cardiovascular risk factors. Conclusions : Our results indicate that there is a significant increase in the prevalence of carotid atherosclerosis in subjects with prehypertension (even in low prehypertensives) compared with normotensive subjects. Further studies are required to confirm the benefits and role of carotid ultrasonography in persons with prehypertension.

• Journal of Animal Environmental Science
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• v.14 no.1
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• pp.53-60
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• 2008

This study was carried out to measure and analyze the vibration levels and modes produced by a hopper type feeder used at laying hen farms, to prevent the vibration resonance and to reduce the vibration of the hopper type feeder (6-tier). The most vibration in a layer house were produced by hopper type feeder as shown the previous study. According to the measurement results, the ratio of transmissibility was as high as 100-638% for natural frequency of 170 Hz or less. And vibration simulations were taken by the results of vibration mode analysis and the weakest points to vibrations were determined accordingly. Then measurement and analysis were taken for those points. The quantities of vibration were 4.6354-4.9118 g($g=9.81^m/s^2$) by axis. In this study, it was found that hopper type feeder generated vibration as much as to influence the ratio of laying eggs of layer. And by the analysis of vibration on the weakest points, design methods and equipment were suggested for isolating/reducing of vibration by each axis.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.1
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• pp.42-52
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• 2012

In this paper, a waveguide antenna is designed and fabricated for side and rear radar sensor of vehicles in UWB (Ultra Wide Band) high band (center frequency : 9.5 GHz, -10 dB bandwidth : 600 MHz (6.4 %)). For the radar antenna, a probe fed rectangular waveguide antenna having simple structure and wide bandwidth is used. An important performance factor in this antenna is the isolation between transmitting (TX) and receiving (RX) waveguide antennas because this radar system uses TX and RX antennas separately. Thus the isolation between two antennas was simulated for E-plane and H-plane array. As a result, it was verified that the isolation of the H-plane array of the antennas is better than E-plane array, due to the TE10 mode. Therefore, H-plane arrayed waveguide antennas were mounted on a T-shaped radar module and performance of antennas was investigated. The -10 dB bandwidth of the TX and RX antenna mounted on T-shaped radar module was measured as 1000 MHz (10.52 %) and 1090 MHz (11.47 %) respectively and the isolation is less than -50 dB in the operation band. The peak gain is 7.65 dBi for the TX antenna and 7.26 dBi for the RX antenna and the beamwidth of H-plane of TX and RX antenna was measured as $64^{\circ}$ and $65^{\circ}$ respectively. Consequently, we verified that the proposed waveguide antenna is appropriate for a vehicle radar applications.

• Journal of Embryo Transfer
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• v.28 no.3
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• pp.243-250
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• 2013

Pyracantha is a genus of thorny evergreen large shrubs in the family of Rosaceae, with common names Firethorn or Pyracantha. It's extract has also been used in cosmetics as a skin-whitening agent and functioning through tyrosinase inhibition. Recent studies have shown that pyracantha extract possesses antioxidant activities and may significantly improve lipoprotein metabolism in rats. Although the mode of action of Pyracantha extract is not fully understood, a strong relationship was observed between antioxidant and apoptosis in some types of cells. Thus, the aim of this study was to evaluated the effect of pyracantha extract on blastocysts formation and their quality of the porcine parthenogenetic embryos. After parthenogenetic activation by chemicals, presumptive porcine parthenogenetic embryos were cultured in PZM-3 medium supplemented with extracts of pyracantha leaf, stalk and root for 6 day (1, 5 and $10{\mu}g/ml$, respectively). In our results, the frequency of blastocyst formation in pyracantha root extract ($5{\mu}g/ml$) treated group had increased that of other groups. Furthermore, blastocysts derived from pyracantha root extract ($5{\mu}g/ml$) treated group had increased the total cell numbers and reduced apoptotic index. Blastocyst development was significantly improved in the pyracantha root extract ($5{\mu}g/ml$) treated group when compared with the $H_2O_2$ treated group (p<0.05). Subsequent evaluation of the intracellular levels of ROS in pyracantha root extract ($5{\mu}g/ml$) treated groups under $H_2O_2$ induced oxidative stress were decreased (p<0.05). In conclusion, our results indicate that treatment of pyracantha root extract may improve in vitro development of porcine parthenogenetic embryos through its antioxidative and antiapoptotic effects.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.518-527
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• 2016

The present study considers the usage of concentrated forces to simulate real panel flutter. The concept of using concentrated forces have been validated for studying the flutter of wing structure in subsonic flow, yet its application in the supersonic region remained to be explored. Hence, a simply supported panel subjected to forces, equivalent to aerodynamic force is considered for studying supersonic panel flutter. The distributed aerodynamic forces are approximated to few concentrated forces by taking numerical integration. The aeroelastic equation is formulated using the classical small-deflection theory and the piston theory for linear panel flutter whereas for emulated panel flutter the flutter equation is derived by replacing the pressure due to aerodynamic loading with pressure from concentrated loading. Finally, flutter frequency, flutter dynamic pressure, and corresponding mode shape are found for emulated panel flutter and compared with linear panel flutter. Two important parameters, the number of concentrated forces and their location are discussed through numerical examples and optimization process respectively. So far, the flutter results acquired in this study are reasonable to suggest the feasibility of reproducing panel flutter using concentrated forces.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.179-187
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• 2014

The underlay protocol is a cognitive radio method in which secondary or cognitive users use the same frequency without affecting the quality of service (QoS) for the primary users. In addition, because of the broadcast characteristics of the wireless environment, some nodes, which are called eavesdropper nodes, want to illegally receive information that is intended for other communication links. Hence, Physical Layer Security is applied considering the achievable secrecy rate (ASR) to prevent this from happening. In this paper, a performance analysis of the amplify-and-forward scheme under an interference constraint and Physical Layer Security is investigated in the cooperative communication mode. In this model, the relays use an amplify-and- forward method to help transmit signals from a source to a destination. The best relay is chosen using an opportunistic relay selection method, which is based on the end-to-end ASR. The system performance is evaluated in terms of the outage probability of the ASR. The lower and upper bounds of this probability, based on the global statistical channel state information (CSI), are derived in closed form. Our simulation results show that the system performance improves when the distances from the relays to the eavesdropper are larger than the distances from the relays to the destination, and the cognitive network is far enough from the primary user.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.2 s.302
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• pp.27-36
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• 2005

This thesis proposed an effective encryption method for the DCT-based image/video contents and made it possible to operate in a high speed by implementing it as an optimized hardware. By considering the increase in the amount of the calculation in the image/video compression, reconstruction and encryption, an partial encryption was performed, in which only the important information (DC and DPCM coefficients) were selected as the data to be encrypted. As the result, the encryption cost decreased when all the original image was encrypted. As the encryption algorithm one of the multi-mode AES, DES, or SEED can be used. The proposed encryption method was implemented in software to be experimented with TM-5 for about 1,000 test images. From the result, it was verified that to induce the original image from the encrypted one is not possible. At that situation, the decrease in compression ratio was only $1.6\%$. The hardware encryption system implemented in Verilog-HDL was synthesized to find the gate-level circuit in the SynopsysTM design compiler with the Hynix $0.25{\mu}m$ CMOS Phantom-cell library. Timing simulation was performed by Verilog-XL from CadenceTM, which resulted in the stable operation in the frequency above 100MHz. Accordingly, the proposed encryption method and the implemented hardware are expected to be effectively used as a good solution for the end-to-end security which is considered as one of the important problems.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.77-86
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• 2008

Traditional cluster-based routing method is a representative method for increasing the energy efficiencies. In these cluster-based routing methods, the selected cluster head collect/aggregate the information and send the aggregated information to the base station. But they have to solve the unnecessary energy dissipation of frequent information exchange between the cluster head and whole member nodes in cluster. In this paper, we minimize the frequency of the information exchange for reducing the unnecessary transmit/receive frequencies as calculate the overlapped area or number of overlapped member nodes between the selected cluster head and previous cluster head in the setup phase. And besides, we consider the direction of super cluster head for optimal cluster formation. So, we propose the modified cluster selection scheme that optimizes the energy dissipation in the setup phase and reuses the saved energy in the steady phase efficiently that prolongs the whole wireless sensor network lifetime by uniformly selecting the cluster head.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.987-994
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• 2010

In this paper, a simple and effective active load-pull method is proposed, and the method to improve the efficiency of X-band power amplifier using harmonic control circuit is presented. The proposed active load-pull system mainly consists of directional coupler, phase shifter, short circuit, and power amplifier, and allows a user to access reflection coefficients near the edge of the Smith chart($\Gamma$=1) easily. The device used in this paper is Mitsubishi's GaAs FET MGF1801, and the operating frequency of the power amplifier is 9 GHz, The amplifier had output power of 21.65 dBm and drain efficiency of 24.9 % at class-A, and had output power of 21.46 dBm and drain efficiency of 53.3 % at class-AB. Harmonic control circuit is designed only second and third harmonic components because of the bandwidth limitation of the microwave components. The drain efficiency is improved as much as 6.4 % compared with class-AB power amplifier.