• Annals of Clinical Neurophysiology
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• v.20 no.2
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• pp.105-108
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• 2018

Persistent left superior vena cava (PLSVC) is a common venous anomaly of the thorax and usually drains into the right atrium. Less often it drains into the left atrium and has previously been related to ischemic stroke. We report a case of PLSCV that founded during ischemic stroke evaluation in a 77-year-old woman which was detected on transesophageal echocardiography (TEE) and transcranial Doppler ultrasonography (TCD) with saline agitated test and computed tomography.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.426-434
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• 2015

In this paper we proposed a dada-aided Doppler estimation method for underwater acoustic communication. The training sequence is non-dedicate, hence it can be designed for Doppler estimation as well as channel equalization. We assume the channel has been equalized and consider only flat-fading channel. First, based on the training symbols the theoretical received sequence is composed. Next the least square principle is applied to build the objective function, which minimizes the error between the composed and the actual received signal. Then an iterative approach is applied to solve the least square problem. The proposed approach involves an outer loop and inner loop, which resolve the channel gain and Doppler coefficient, respectively. The theoretical performance bound, i.e. the Cramer-Rao Lower Bound (CRLB) of estimation is also derived. Computer simulations results show that the proposed algorithm achieves the CRLB in medium to high SNR cases.

• International Journal of Computer Science & Network Security
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• v.23 no.5
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• pp.121-127
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• 2023

A 500 km/h linear motor high speed terrestrial transportation service is planned to launch 2027 in Japan. In order to support 5G service in the train, the Sub-carrier spacing frequency of 30 kHz is planned to be used instead of common 15 kHz sub-carrier spacing to mitigate Doppler effect in such high-speed transportation. In addition, to increase the cell size of 5G mobile system, plural Base Station antenna will transmit the identical Down Link (DL) signal to form the expanded cell size along the train rail. In this situation, forward and backward antenna signals will be Doppler shifted by reverse direction respectively and the receiver in the train might suffer to estimate accurate Channel Transfer Function (CTF) for its demodulation. In this paper, Delay and Doppler Profiler (DDP) based Channel Estimator is proposed and it is successfully implemented in signal processing simulation system. Then the simulated performances are compared with the conventional Time domain linear interpolated estimator. According to the simulation results, QPSK modulation can be used even under severe channel condition such as 500 km/h, 2 path reverse Doppler Shift condition, although QPSK modulation can be used less than 200 km/h with conventional Channel estimator.

• International Journal of Computer Science & Network Security
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• v.23 no.9
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• pp.8-16
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• 2023

In Japan, high-speed ground transportation service using linear motors at speeds of 500 km/h is scheduled to begin in 2027. To accommodate 5G services in trains, a subcarrier spacing frequency of 30 kHz will be used instead of the typical 15 kHz subcarrier spacing to mitigate Doppler effects in such high-speed transport. Furthermore, to increase the cell size of the 5G mobile system, multiple base station antennas will transmit identical downlink (DL) signals to form an expanded cell size along the train rails. In this situation, the forward and backward antenna signals are Doppler-shifted in opposite directions, respectively, so the receiver in the train may suffer from estimating the exact Channel Transfer Function (CTF) for demodulation. In a previously published paper, we proposed a channel estimator based on Delay and Doppler Profiler (DDP) in a 5G SISO (Single Input Single Output) environment and successfully implemented it in a signal processing simulation system. In this paper, we extend it to 2×2 MIMO (Multiple Input Multiple Output) with spatial multiplexing environment and confirm that the delay and DDP based channel estimator is also effective in 2×2 MIMO environment. Its simulation performance is compared with that of a conventional time-domain linear interpolation estimator. The simulation results show that in a 2×2 MIMO environment, the conventional channel estimator can barely achieve QPSK modulation at speeds below 100 km/h and has poor CNR performance versus SISO. The performance degradation of CNR against DDP SISO is only 6dB to 7dB. And even under severe channel conditions such as 500km/h and 8-path inverse Doppler shift environment, the error rate can be reduced by combining the error with LDPC to reduce the error rate and improve the performance in 2×2 MIMO. QPSK modulation scheme in 2×2 MIMO can be used under severe channel conditions such as 500 km/h and 8-path inverse Doppler shift environment.

• Korean Journal of Clinical Laboratory Science
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• v.55 no.3
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• pp.219-226
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• 2023

Transcranial doppler ultrasonography (TCD) applies a low frequency of 2 MHz to measure the blood flow velocity and waveform within the skull. Medical technologists at several hospitals are conducting these examinations, and education is being imparted in many schools and academic societies. However, the skill of the tester is of utmost importance when performing TCD. Technicians who are conducting the procedure for the first time have trouble locating the blood vessels, and some experienced personnel are worried because too many blood vessels are present. Since this procedure does not directly look at and measure blood vessels, there are several limitations and difficulties. Therefore, this study aims to provide some help by introducing precautions and suggestions for TCD technicians conducting the test.

• Ocean and Polar Research
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• v.33 no.2
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• pp.171-183
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• 2011

Despite technological developments and application advances of Acoustic Doppler Current Profilers (ADCPs), no standard procedure has been adopted or accepted for calibration of ADCPs. Limitations of existing facilities for calibrating ADCPs, the complexity of ADCP instruments, and rapid changes in ADCP technology are some of the reasons why a standard procedure has not been adopted. However, there is increasing realization of the need for effective Quality Assurance (QA) and as part of that the importance of standardized calibration. In this study, the significance of calibration and QA plans for ADCPs is discussed and the calibration facilities for ADCPs at home and abroad are reported. Furthermore, the method for calibrating ADCPs using a towed car and its limitations are discussed. This study contributes to discussions surrounding the establishment of standard procedures for calibrating ADCPs and QA plans, and the construction of calibration facilities in the future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.484-486
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• 2018

MF-CW(Multi-Frequency Continuous Wave)operated on Electro-Optical Tracking System to measure slant range of space launch vehicle and aircraft at Naro Space Center. In this paper, we compared and analyzed the difference exactly measured slant range using the laser lightwave range measuring equipment with measured on the transponder and described the accuracy of slant range.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.119-125
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• 2003

We demonstrate parametric resonance in a magneto-optical trap. When we modulate the intensity of the cooling laser at about twice the resonant frequency of the trap, the atoms in the trap are divided into two parts and oscillate with 180 degree phase difference with the finite length due to nonlinearity of the trap potential. These are the effects of general nonlinear dynamics, called the Hopf bifurcation, or limit cycle motion. The amplitude and the phase of the oscillations are measured and compared with the theoretical calculations based on simple Doppler cooling theory. The experimental results are in excellent agreement with the simulation results based on the simple Doppler cooling theory.

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.9.1-9.11
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• 2023

Objectives: This study evaluated the effect of adjacent gingival blood flow on detection of pulpal blood flow (PBF) using ultrasound Doppler flowmetry (UDF) through animal study. Materials and Methods: The study included 36 right and left maxillary the third incisors and canines in 9 experimental dogs. The study included 2 main steps: In the first step, the pulse sound level (PSL) was recorded on the cervical part of each tooth without flap elevation (Group 1), with flap elevation (Group 2), and after it was repositioned in place (Group 3). In the second step, the PSL was recorded on the cervical part of each tooth (Group 4), after pulpotomy (Group 5), after partial pulp extirpation (Group 6), after complete extirpation (Group 7), and after canal filling (Group 8). In Groups 5-8, the study was performed with and without flap elevation in the left and right teeth, respectively. The PSL was graded as follows: 0, inaudible; 1, heard faintly; and 2, heard well. The difference between each group was analyzed using Friedman's test with Wilcoxon signed-rank tests (α = 0.05). Results: In step 1, the PSL results were Group 1 > 2 and 3. In step 2, there was no significant difference between the groups when the flap was not elevated, while PSL results were Group 4 > 5 ≥ 6 and 7 ≥ 8 when the flap was elevated. Conclusions: PBF is affected by gingival blood flow when measured with UDF. UDF measurements require isolation of gingiva from the tooth.

• Annals of Clinical Neurophysiology
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• v.1 no.1
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• pp.76-79
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• 1999

The most significant factor in pathogenesis of vascular headaches like migraine and cluster headache is dynamic changes of diameters of the cerebral arteries. TCD is a valuable noninvasive tool to assess the cerebral hemodynamic status by measuring the flow velocities of the intracranial cerebral arteries around the circle of Willis. TCD can evaluate flow velocities and vasoreactivity of the patients with a vascular headache during the ictal phase as well as during intericatal phase. Distribution of the changes recorded differ between types of headaches and also between the major ictal symptoms. The changes suggest the presence of prolonged vasospasm interictally and more marked relaxation of the cerebral arteries. TCD can be used to monitor the long-term clinical course of patients with vascular headache by correlation the symptomatic improvement and TCD data before and after long-term pharmacological prophylactic treatments. During the ictal phases large intervention. The results may be used in selecting and evaluating the agents for abortive therapy for acute attacks. In conclusion TCD can quantitatively evaluate vascular headaches when making diagnosis and classification and can provide guidelines to choose more individualized therapeutic options for both acute and long-term treatment.