• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.137-146
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• 2019

The ultrasonic phased arrays are used for treating tumors in the human body by the focus control of the acoustic pressure at the desired position. The magnitude and phase of the surface acoustic pressure in each ultrasonic transducer is controlled by the magnitude and phase of the applied voltage to it. In this paper, the relationship between the applied voltage and the surface acoustic pressure of the ultrasound transducer is modelled, and the desired voltage is realized by PWM technique. The validity of the proposed method is verified by computer simulation of the focus control of a ultrasonic phased array composed of 61 ultrasonic transducers.

• The Journal of the Acoustical Society of Korea
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• v.26 no.8
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• pp.426-431
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• 2007

In this paper we have studied the underwater vector channel modeling for MIMO(Multiple Input Multiple Output) to increase the performance and efficiency for ultrasound communication in underwater channel environments. Also we have analyzed the MIMO techniques using the proposed channel modeling. For underwater MIMO channel modeling. experiments were done in real channel environments and the data were analyzed to estimate parameters such as fading, Doppler, time delay, angle of arrival, and receiving power. These were used for modeling of underwater vector channel modeling for MIMO. Additionally, we have analyzed the performance of MIMO systems using our proposed channel models. As a result we could see that the BER has decreased severely with the same SNR when using the MIMO system.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.17-22
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• 2010

The aim of this study is to research applicable possibility of DSI (Dry Sorbent Injection) technique in $SO_2$ removal process using lab-scale facility based on 500MW in capacity coal-fired thermal power plant operated by South Korea N. Power Co., Ltd. To increase the $SO_2$ removal efficiency, it is considered the mixing enhancement as different shapes called lobed-plate and stepplate tested ultimately for optimum shape. Also it tested to analysis $SO_2$ removal efficiency by numbers of injection holes. At experimental it showed the $SO_2$ removal efficiency is higher using mixing enhancement than not installed mixing enhancement and case on the step-plate was shown the most $SO_2$ removal efficiency. Also, $SO_2$ removal efficiency was higher recording which will increase the injection holes case on not installed mixing enhancement. But, the $SO_2$ removal efficiency was higher 4 injection holes case on installed mixing enhancement.

• The Journal of Korean Physical Therapy
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• v.22 no.1
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• pp.33-38
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• 2010

Purpose: This study investigated the effect of taping therapy on metacarpophalangeal (MCP) disorders of the thumb. Methods: Twenty eight patients were enrolled in this study. They were randomly assigned to experimental (n=16) or a control group (n=12). The experimental and control groups received Ultrasound (Gymna Pulson 200) operating at a frequency of 3MHz and an intensity of $1.0W/cm^2$ with a 100% duty cycle for 10 minutes. The experimental group received, additionally, taping using Kinesiotape on the injured thumb. The following parameters were measured:pain during rest and flexion of the thumb, tenderness, range of motion (ROM), pinch and spherical grip power pre- and post-treatment. This study was carried out 3 days per week throughout the 2-week treatment. Results: There were significant improvements in pain during rest and flexion of the thumb, tenderness, ROM, pinch and spherical grip power between pre- and post-treatment times in both groups (p<0.05). However, there was a significant difference in all parameters between the experimental and control groups (p<0.05). Finally, the satisfaction level after intervention was significantly higher in the experimental group than in the control group (p<0.05). Conclusion: Taping is effective for treating pain and dysfunction in patients with thumb disorders.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.150-157
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• 2017

Three types of piezoelectric single crystals [PMN-PT (Generation I $[Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3]$), PMN-PZT (Generation II $[Pb(Mg_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3]$), PMN-PZT-Mn (Generation III)] were grown by the solid-state single crystal growth (SSCG) method, and their dielectric and piezoelectric properties were measured and compared. Compared to (001) PMN-PT and PMN-PZT single crystals, the (001) PMN-PZT-Mn single crystals exhibited a higher transition temperature between the rhombohedral and tetragonal phases ($T_{RT}=144^{\circ}C$), as well as a higher coercive electric field ($E_C=6.3kV/cm$) and internal bias field ($E_I=1.6kV/cm$). The (011) PMN-PZT-Mn single crystals showed the highest coercive electric field ($E_C=7.0kV/cm$), and the highest stability of $E_C$ and $E_I$ during 60 cycles of polarization measurement. These results demonstrate that both Mn doping (for higher electromechanical quality factor ($Q_m$)) and a (011) crystallographic orientation (for higher coercive electric field and stability) are necessary for high power transducer applications of these piezoelectric single crystals. Specifically, the (011) PMN-PZT-Mn single crystal (Gen. III) had the highest potential for application in the fields of SONAR transducers, high intensity focused ultrasound (HIFU), ultrasonic motors, and others.

• Korean Journal of Radiology
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• v.25 no.2
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• pp.199-209
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• 2024

Objective: This study aimed to compare therapeutic efficacy and technical outcomes between adjustable electrode (AE) and conventional fixed electrode (FE) for radiofrequency ablation (RFA) of benign thyroid nodules. Materials and Methods: Between 2013 and 2021, RFA was performed on histologically proven benign thyroid nodules. For the AE method, AE length ≥ 1 cm with higher power and < 1 cm with lower power were utilized for ablating feeding vessels and nodules, especially those near anatomical structures, respectively. The therapeutic efficacy (volume reduction rate [VRR], complication rate, and regrowth rate) and technical outcomes (total energy delivery, ablated volume/energy, RFA time, and ablated volume/time) of FE and AE were compared. Continuous parameters were compared using a two-sample t-test or Mann-Whitney U test, and categorical parameters were compared using a chi-squared test or Fisher's exact test. Results: A total of 182 nodules (FE: 92 vs. AE: 90) in 173 patients (mean age ± standard deviation, 47.0 ± 14.7 years; female, 90.8% [157/173]; median follow-up, 726 days [interquartile range, 441-1075 days]) were analyzed. The therapeutic efficacy was comparable, whereas technical outcomes were more favorable for AE. Both electrodes demonstrated comparable overall median VRR (FE: 92.4% vs. AE: 84.9%, P = 0.240) without immediate major complications. Overall regrowth rates were comparable between the two groups (FE: 2.2% [2/90] vs. AE: 1.1% [1/90], P > 0.99). AE demonstrated a shorter median RFA time (FE: 811 vs. AE: 627 seconds, P = 0.009). Both delivered comparable median energy (FE: 42.8 vs. AE: 29.2 kJ, P = 0.069), but AE demonstrated higher median ablated volume/energy and median ablated volume/time (FE: 0.2 vs. AE: 0.3 cc/kJ, P < 0.001; and FE: 0.7 vs. AE: 1.0 cc/min, P < 0.001, respectively). Conclusion: Therapeutic efficacy between FE and AE was comparable. AE demonstrated better technical outcomes than FE in terms of RFA time, ablated volume/energy, and ablated volume/time.

• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.737-746
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• 2009

Given the increased interest in ubiquitous computing, wireless sensor network has been researched widely. The localization service which provides the location information of mobile user, is one of important service provided by sensor network. Many methods to obtain the location information of mobile user have been proposed. However, these methods were developed for only one mobile user so that it is hard to extend for multiple mobile users. If multiple mobile users start the localization process concurrently, there could be interference of beacon or ultrasound that each mobile user transmits. In the paper, we propose APL(Adaptive Power Control based Resource Allocation Technique for Efficient Localization Technique), the localization technique for multiple mobile nodes based on adaptive power control in mobile wireless sensor networks. In APL, collision of localization between sensor nodes is prevented by forcing the mobile node to get the permission of localization from anchor nodes. For this, we use RTS(Ready To Send) packet type for localization initiation by mobile node and CTS(Clear To Send) packet type for localization grant by anchor node. NTS(Not To Send) packet type is used to reject localization by anchor node for interference avoidance and STS(Start To Send) for synchronization between 모anchor nodes. At last, the power level of sensor node is controled adaptively to minimize the affected area. The experimental result shows that the number of interference between nodes are increased in proportion to the number of mobile nodes and APL provides efficient localization.

• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.1-10
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• 2012

This paper proposes design space exploration methodology of many-core processors including multimedia specific instructions to support high-performance and low power ultrasound imaging for portable devices. To explore the impact of multimedia instructions, we compare programs using multimedia instructions and baseline programs with a same many-core processor in terms of execution time, energy efficiency, and area efficiency. Experimental results using a $256{\times}256$ ultrasound image indicate that programs using multimedia instructions achieve 3.16 times of execution time, 8.13 times of energy efficiency, and 3.16 times of area efficiency over the baseline programs, respectively. Likewise, programs using multimedia instructions outperform the baseline programs using a $240{\times}320$ image (2.16 times of execution time, 4.04 times of energy efficiency, 2.16 times of area efficiency) as well as using a $240{\times}400$ image (2.25 times of execution time, 4.34 times of energy efficiency, 2.25 times of area efficiency). In addition, we explore optimal PE architecture of many-core processors including multimedia instructions by varying the number of PEs and memory size.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.213-218
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• 2017

Recently, as the number of high-risk pregnancies increases, the use of new techniques such as Doppler, which have higher acoustic power than in the past, has been increasingly used in prenatal diagnosis and guidelines have been set up by various organizations to prevent excessive exposure. Therefore, in this study, we tried to investigate the temperature change of the body surface for each test mode according to the long time ultrasound examination and to examine the exposure time which is not influenced by the thermal effect. B mode, C mode, and PD mode according to time, and the temperature difference between exposed and unexposed sites were compared. As a result, the B mode showed a significant difference in the temperature change from 10 minutes, 50 minutes after exposed, 20 minutes from the C mode, and 30 minutes from the PD mode (p<0.01). In all three modes, the temperature difference was different (p<0.000), and PD mode was the most sensitive to temperature change. Also, it was found that the temperature rise time was shortened with the increase of the ultrasonic exposure time. Therefore, it is recommended that ultrasonography to observe the embryo or fetus should be used only for diagnostic purposes, avoiding excessive test time.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.426-431
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• 2007

When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material in real time. In this paper a realtime detection of the brazing defect of thin Inconel plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (23 kHz) ultrasonic transducer was used to infuse the welded Inconel plates with a short pulse of sound for 280 ms. The ultrasonic source has a maximum power of 2 kW. The surface temperature of the area under inspection is imaged by an infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the bound between the two faces of the Inconel plates near the defective brazing point and heated up highly, are observed. And the weak thermal signal is observed at the defect position of brazed plate also. Using the image processing technology such as background subtraction average and image enhancement using histogram equalization, the position of defective brazing regions in the thin Inconel plates can be located certainly.