• Investigative Magnetic Resonance Imaging
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• v.6 no.2
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• pp.158-165
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• 2002

Purpose : To evaluate the effect of Gd-DTPA on signal intensity of diffusion-weighted magnetic resonance(MR) image and apparent diffuse coefficient (ADC) in dog brain with hype racute stroke. Materials and methods : Experimental canine model of hyperacute cerebral infarction was made by selective intraarterial embolization with particulate embolic material. Diffusion-weighted MR imaging was performed in five dogs at 1 hour after the embolization of internal carotid artery. After intravenous bolus injection of Gd- DTPA, additional 11 diffusion-weighted MR images were serially obtained from 2 minutes to 90 minutes after injection in each dog. The author evaluated findings of hyperacute cerebral infarction on diffusion-weighted MR imaging, and calculated mean signal intensity and mean ADC in infarcted region and contralateral normal region. Statistical analysis of mean signal intensity, mean ADC and contrast-noise ratio before and after Gd-DTPA injection was performed. Results : Hyperacute cerebral infarction developed in all five dogs on diffusion-weighted MR images obtained 1 hour after embolization. The area of hyperacute infarction had steady increase in signal intensity on diffusion-weighted MR image and decrease in ADC. In normal perfusion area, decrease in signal intensity was observed at 2 minutes the Gd-DTPA injection, whereas ADC did not changed. Conclusion : Intravenous injection of Gd-DTPA had no influence on ADC in both hyperacute infarction and normally perfused are a, but caused initial transient signal reduction in normally perfused area on diffusion-weighted MR image due to susceptibility effect of Gd-DTPA. It is important to calculate ADC in evaluating the effect of diffusion after injection of Gd-DTPA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1507-1514
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• 2015

Non-orthogonal multiple access (NOMA) is a promising candidate for 5G networks. NOMA achieves superior spectral efficiency than conventional orthogonal multiple access (OMA), as in NOMA multiple users uses the same time and frequency resources. Multiple-input-multiple-output (MIMO) is one another promising technique that can enhance system performance. In this paper we present a spectral and energy efficient multiple antenna based NOMA scheme, known as spatially modulated NOMA. In the proposed scheme the cell edge users are multiplexed in spatial domain, which means the information to cell edge users is conveyed using the transmit antenna indices. In NOMA the performance of cell edge users are deeply effected as it treats signals of others as noise. The proposed scheme achieves superior spectral efficiency than the conventional NOMA. The number of decoding steps involved in decoding NOMA signal reduces by one as cell edge user is multiplexed in spatial domain. The proposed scheme is more energy efficient as compare to conventional NOMA. All of the three gains high spectral, energy efficiency and one step reduction in decoding comes at cost of multiple transmit antennas at base station.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.557-563
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• 2009

This study is on the properties of inorganic porous calcium silicate material made from silica powder through the autoclaving curing, the results of this study should be utilized fundamental data for the development of noise reduction porous solid material using siliceous byproduct generated by various manufacture process. For the manufacture of autoclave curing specimen, various calcareous materials used and siliceous materials used silica powder. In this study, properties in density and compressive strength according to the change of W/B and C/S ratio, microscopy for the shape of pore, SEM and XRD for the examination of hydrate after autoclave curing are carried out respectively. The test results shown that the more slurry density decrease, the more W/B increase at the fresh state, this tendency shown similar to in hardened state. Among the specimens of C/S ratio, the compressive strength of C/S ratio of 0.85 gave the highest the compressive strength. In the results of XRD, tobermorite generated by autoclaving curing was created all of specimens regardless of C/S ratio. To ascertain pore structure, we compared with existing porous calcium silicate product(ALC, organic sound absorbing porous material). The results of microscope observation, pore structure of specimen of this study was similar to that of existing inorganic sound absorbing foam concrete. therefore, we could conformed a possibility of sound absorbing porous solid material on the basis of the results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.331-340
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• 2006

In this Paper, we propose to extend the TSS-LS(Two-Step Search scheme with Linear search based Second step) scheme which was already proposed by the authors for coherent UWB(Ultra Wide Band) systems, to rapid and reliable acquisition of noncoherent UWB systems in multipath channels. The proposed noncoherent TSS-LS employing simple energy window banks utilizes two different thresholds and search windows to achieve fast acquisition. Furthermore, the linear search is adopted for the second step in the proposed scheme to correctly find the starting point in the range of effective delay spread of the multipath channels, and to obtain reliable BER(Bit Error Rate) performance of the noncoherent UWB systems. Simulation results with multipath channel models by IEEE 802.15.3a show that the proposed two-step search scheme can achieve significant reduction of the required mean acquisition time as compared to general search schemes. ]n addition, the proposed scheme achieves quite good BER performance for large signal-to-noise ratios, which is favorably comparable to the case of ideal perfect timing.

• International Journal of Highway Engineering
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• v.7 no.3 s.25
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• pp.31-42
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• 2005

This study evaluates the physical mechanical properties, durability and sound absorbtion of porous concrete for pavement according to content of silica fume and steel fiber to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of Korea National Housing Corporation as for every factor of mixture but in the case of the flexural strength, more than 0.6vol.% of steel fiber satisfied the Japan Concrete Institute proposition values. The mixture of silica fume and steel fiber presents the excellent intensity, though. The case when silica fume and steel fiber are used simultaneously presents the strongest durability because the durability shows the similar tendency to the dynamic characteristics. The case when 10wt.% of silica fume and 0.6vol.% of steel fiber are used at the same time shows that the loss rate of mass by Cantabro test became 27% better and freeze-thaw resistance became 60% better. As for the characteristics of sound absorption of porous concrete for pavement, Noise Reduction Coefficient is 0.48 to prove that it possesses almost 50% sound absorption.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3121-3129
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• 2009

Conventional marine radar systems utilize pulse radar which is capable of high-power transmissions and is effective for remote detection purposes. A pulse radar is most commonly used on medium or large vessels due to its expensive installation and maintenance costs. I propose the use of a Frequency Modulated Continuous Wave (FMCW) radar system operated at low-power and high-resolution instead of the conventional pulse-radar based system. The transmitted and received signals of the FMCW radar system were theoretically analyzed and radar signal processing design and simulation experiments were performed to detect the range and speed. Intermediate Frequency (IF) signal mixed with virtual transmit and receive signals were generated to perform FMCW radar signal processing simulations where the IF signal underwent noise reduction through a lowpass filter. The maximum frequency was derived through the sample interval of the FFT size instead of using A/D converter. This maximum frequency was used to get the frequency range and frequency speed which were in turn used to calculate the range and speed. The virtual beat frequency generated using MATLAB is utilized to analyze the beat frequency used in the actual FMCW radar system signal processing. The differences in the range and speed of the beat frequency signals are processed and analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.128-134
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• 2014

Recently, design and construction of street tunnels tend to focus on cost reduction and preservation of nature. Accordingly, research is actively being carried out to quickly detect fires when they occur in tunnels, which have partially closed structures. Among such research, fire detection methods using optical fiber sensors have a wide bandwidth and fast transmission speed, while using light as a medium. Therefore, it does not receive electrical interference and there is almost no loss of information during transmission, while also having little noise as well. In relation to this, a fire monitoring system that can accurately detect the location of fires in real time using shape memory alloy and optical cables was developed in this study. In order to verify the developed method, light loss measurement test was conducted according to indoor temperature changes, while also conducting fire simulation tests by installing test beds in common underground zones with different external environments of temperature and distance. Upon carrying out experiments, the fire monitoring system developed in this study was found to be able to detect fires in long distance sections in real time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.96-106
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• 2014

The increased vibration level of the railway bridge could make significant noise and, also, cause structural damages such as fatigue cracks. Related to these subjects, a spherical elastomeric bridge bearing, which is layered by hemispherical rubber and steel plates, was investigated in terms of its vibration performance. Several different shape factors could be considered by changing the curvature of hemispherical surface and size in rubber and steel plate thicknesses in the manufacturing stage. The performance of the spherical elastomeric bearing for the reduction in vibration was compared with that of the conventional bearing by performing vibration experiments on a scale-downed model. The rubber material characteristics and spherical shape are found to be important parameters in reducing the bridge vibration.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.193-198
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• 2004

In general, the function of intake structure, whether it be a open channel, a fully wetted tunnel, a sump or a tank is to supply an evenly distributed flow to a pump station. An even distribution of flow, characterized by strong local flow, can result in formation of surface or submerged vortices, and with certain low values of submergence, my introduce air into pun, causing a reduction of capacity and efficiency, an increase in vibration and additional noise. This study investigated experimentally the formation of the vortex to understand the mechanism of vortex formation and to prevent the formation of vortex in the sump model using by the model test and PIV tool. Sump model was manufactured to 1/8 scale with the drawing of W intake pumping station. from the results of model test and PIV, the vortex were occurred the in the whole section. Thus, sump model tests with the anti-vortex device might be considered to prevent the formation of vortex in the sump model.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.189-197
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• 2015

As enforced the regulation of fuel efficiency, the electrification of automotive components in internal combustion vehicle has been applied instead of hydraulic pressure. A typical example of such parts is the EPS (electric power steering), and it is applied to most automotive at present. In electric power steering system, the core component is motor. The reduction of cogging torque and torque ripple is required to improve steering feeling and reduce NVH (Noise Vibration Harshness) in EPS. Generally the skewed design of stator or rotor is applied in order to reduce cogging torque and torque ripple. This paper propose the design and analysis methodology of Brusheless PMSM (Permanent Magnet Synchronous Motor) which is applied to skewed stator. The proposed methodology is as follows: First Intial Design PMSM with skewed stator for EPS, Second Optimal design using RSM (Response surface method), Third Performance Analysis such as Phase Back EMF, Inductance, Load torque using FEA (Finite Element Method). Finally, the reliability of proposed design methodology will be verified through the experiments of prototype sample.