• Journal of radiological science and technology
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• v.45 no.2
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• pp.171-177
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• 2022

The purpose of this study was to investigate the effect of the characteristics of patients who underwent spinal nerve block on the fear of injection and the risk of radiation. Subjects were 137 patients (67 males, 70 females) who visited the Department of Anesthesiology and Pain Medicine in Cheongju. The method was conducted as a research study using a total of 28 questionnaires consisting of patient characteristics, experience characteristics of nerve block surgery, nerve block fear scale, and radiation risk perception scale. The reliability of the questionnaire response was secured with a Cronbach's alpha coefficient of 0.6 or higher. For statistical analysis, correlation was tested by descriptive statistics, frequency analysis, independent sample T-test, and Pearson and Spearman correlation coefficients by measurement scale and factor. As a result, the fear scale of nerve block was significantly higher in women than in men (p<0.05). The fear scale of nerve block injection was significantly higher in the first-visit patients than in the second-visited patients (p<0.05). However, there was no significant difference among all variables in radiation risk perception. In conclusion, patients undergoing spinal nerve block were more aware of the fear of injection than the risk of radiation exposure during the procedure.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.5
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• pp.65-76
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• 2001

In this paper, performance of frequency-based watermarking methods is compared, which are used to protect copyright of image data. For performance comparison of each transform method, a test image is transformed into frequency domain by a full- and block-discrete cosine transforms and wavelet transform, and after general image processing, robustness of each transform is evaluated with using the same watermark signals. Simulation results show that the watermarking method based on DCTs are more robust than WT. Especially, $8{\times}8$ BDCT is most robust for JPEG lossy compression and sharpening, while $8{\times}8$ FDCT is best. for smoothing and scaling. In addition, watermarking based on BDCT shows decreasing robustness for a larger block size, compared with general image processing.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.55-62
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• 2008

Adaptive modulation and Coding(AMC) scheme is promising technique to support the demands for high data rates and wideband proposed for 4G mobile communication system standards. In this paper, adaptive modulation and coding(AMC) based on OFDM system is analyzed through simulation for single user case and compared with SISO-OFDM and SFBC(Space frequency block coding)-OFDM. The performance analysis in terms of capacity for downlink system environments with different values of constellation size under multipath fading channel is done. The adaptive modulation and coding technique is based on perfect estimation channel. It has been observed that SFBC(Space-frequency block coding)-OFDM system gives better performance in terms of capacity.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.322-326
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• 2008

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. There is a kind of specimen, one is a reference block having 1/4T, 1/2T, 3/4T side drilled holes as main run piping material of the steam generator in nuclear power plants. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously. Further more we have studied the reconstruction method of the amplitude and phase images, the enhancement method of the defect images' contrast.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.4
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• pp.177-185
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• 2019

In this paper, we propose and evaluate a FDE combined with STBC transmission structure to cancellation of ISI in underwater acoustic communication. To achieve this purpose, underwater acoustic channels are modeled and the simulation results are presented. In case of STBC-FDE, the transmission rate is less about 4% than STBC-OFDM, but the SER performance is better than STBC-OFDM that is larger from 4.4% to 16.8% at the SNR of 15dB than STBC-OFDM.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.386-396
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• 1996

The dynamic characteristics of a condenser are numerically studied for the control of air-conditioning systems. The important factors, such as the refrigerant flow rate and refrigerant temperature, air velocity and air temperature at the condenser inlet, are incorporated into the analysis. This study was focused on the analysis of dynamic responses by transfer function method in the condenser. Block diagrams were made through analytic transfer function, and dynamic responses are evaluated on Bode diagrams in the frequency response. These results may be used for determining an optimum design parameters in an actual component and total systems. Also, the mathematical models, frequency response and steady state response may be used to increase understanding, to obtain useful information for its commercialization, to evaluate the hardware and the optimum design parameters, the design control system and to determine the best controller setting for the refrigeration and air conditioning systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3B
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• pp.232-238
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• 2006

We propose a novel call admission control scheme which improves the handoff drop and the new call block probabilities of high priority services, minimizing the negative impact on low priority services, in multimedia service cellular networks. This paper proposes three schemes to solve this problem; the packing scheme in which available channels of a cell distributed to each frequency channel are concentrated on one frequency channel and a high transmission rate service is assigned to the frequency channel; the queuing scheme in which the queue is used for high transmission rate calls; and the power reallocation scheme in which the power assigned to calls under service is temporarily reduced and a high transmission rate service is allowed. The simulation results revealed that our scheme improved the drop and the block probabilities of the high priority services compared with the conventional scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.560-568
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• 1998

Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.1-11
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• 2016

We investigate compressive sensing techniques to estimate sparse channel in Orthogonal Frequency Division Multiplexing(OFDM) systems. In the case of large channel delay spread, compressive sensing may not be applicable because it is affected by length of measurement vectors. In this paper, we increase length of measurement vector adding pilot information to OFDM data block. The increased measurement vector improves probability of finding path delay set and Mean Squared Error(MSE) performance. Simulation results show that signal recovery performance of a proposed scheme is better than conventional schemes.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3
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• pp.129-135
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• 2007

In this paper. we propose a prewhitening method for the km reverberation to enhance the target signal. The proposed algorithm uses the dechirping method which inversely compensates the frequency chirp rate of LFM and transforms the LFM reverberation to have stationary frequency property in each data block. Also, using the left and right adjacent beam signals as reference signals. we model frequency response of each data block by AR coefficients. From these coefficients, we implement inverse filter and prewhiten the LFM reverberation of the center beam efficiently.