• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.292-301
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• 2014

The objective of this study was to design and develop a broadband ultrasonic transducer that has both wide bandwidth and high sensitivity to measure broadband echoes related to identifying fish species. A broadband ultrasonic transducer providing a nearly flat transmitting response band of 40.2-75.5 kHz with a -12 dB bandwidth of 35.3 kHz was achieved by integrating 12 tonpilz transducer elements operating at different resonance frequencies. The average transmitting voltage response, receiving sensitivity, and figure of merit values in this frequency band were 168.4 dB (re $1{\mu}Pa/V$ at 1 m), -196.8 dB (re $1V/{\mu}Pa$), and -28.4 dB, respectively. The results suggest that bandwidth and sensitivity can be widened and improved by adjusting the array pattern and the structure of tonpilz transducer elements.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.302-312
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• 2014

This article describes the design and performance characteristics of a broadband ultrasonic mosaic transducer. We focus on the improved bandwidth in the high frequency band of a previously designed broadband ultrasonic transducer (Lee et al., 2014). The improvement in the pulse-echo bandwidth was achieved by employing twelve $2{\times}2$ element subarrays, operating at different resonance frequencies, and utilizing the mosaic array concept. We found that the -6 dB and -12 dB bandwidths of the newly developed broadband ultrasonic mosaic transducer, were up to 155% and 170% of the previously designed model, with a quality factor of 1.71 and 1.25, respectively. The averaged TVR (transmitting voltage response), SRT (receiving sensitivity), and FOM (figure of merit) values in a nearly flat transmitting response band, from 45 to 105 kHz providing a -12 dB bandwith of 60 kHz, were 163.3 dB (re $1{\mu}Pa/V$ at 1 m), -192.8 dB (re $1V/{\mu}Pa$), and -30.9 dB, respectively.

• Journal of Chest Surgery
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• v.22 no.1
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• pp.106-115
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• 1989

Clinical results with the xenograft cardiac valves were reviewed for 212 patients who underwent heart valve replacement from January 1981 to December 1987. One hundred and twenty-four Carpentier-Edwards k 88 Ionescu Shiley valves were used. Overall operative mortality was 11 out of 212[5.1%]: 5 out of 153[3.39o] for mitral valve replacement [MVR], 2 out of 34[5.9%] for aortic valve replacement [AVR], 0 out of 4[0%] for Tricuspid valve replacement [TVR], and 4 out of 21[19.1%] for double valve replacement [DVR;MVR+ AVR]. Two hundred and one operative survivors were followed up for a total of 824.3 patient-years [a mean 3.9*1.8 yrs], and the follow up was 78.1%. The linealized complication rates were 0.1% emboli / patient-year, 1.0% endocarditis/ patient-year and 2.2% overall valve failure / patient-year. A linealized rate of primary tissue failure was 0.7*/o/ patient-year. The actuarial survival rates including the operative mortality were 92*2.8% at 4 years and 85*4.3% at 7 years after surgery using the Xenograft cardiac valves. Probabilities of freedom from thromboembolism and overall valve failure were 73*11.0% and 69*2.4% at 7 years after surgery using the Xenograft cardiac valves respectively. The intrinsic durability of the Xenograft cardiac valves appears to be relatively well satisfactory over the long term [4 to 7 years] and the risk of failure appears well balanced by the advantages of a low incidence of thromboembolism and no mandatory anticoagulant therapy.

• Journal of Chest Surgery
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• v.14 no.3
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• pp.247-253
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• 1981

A total and consecutive 46 patients have undergone cardiac valvular surgery including 8 open mitral commissurotomy and 38 mitral, aortic, mitral-aortic, mitral-tricuspid, tricuspid valve replacements using 46 artificial valves in a period between September 1976 and July 1981. They were 19 males and 27 females with the age ranging from 16 to 50 (mean 32.6) years. Out of 46 valves replaced, 6 were prosthetic valves and 40 were tissue valves, and 33 were replaced in mitral, 9 in aortic and 3 In tricuspid position. Isolated replacements were 33 mitral valves, 6 aortic valves and 1 tricuspid valve; double valve replacements were 6 mitral-aortic valves and 2 mitral-tricuspid valves. . Early mortality within 30 days after operation was noted in 4 cases; 3 after MVR and 1 after open mitral commissurotomy. Causes of death were thrombus obstruction of Beall-Surgitool, Cerebral air embolism, acute renal shut down due to low output syndrome, and left upper pUlmonary vein rupture after open mitral commissurotomy (early mortality 8.7%). 3 late deaths were noted during the follow-up period from 2 to 59 months; 1 due to cerebral hemorrhage from warfarin overdose 3 months, 1 due to miliary tuberculosis 9 months, and another 1 due to cardiac failure after open mitral commissurotomy 42 months postoperatively. Total survival rate 59 months after valvular surgery was 84.8%; there were no early and late death in the group of AVR, TVR and double valve replacements. Preoperative NYHA Class III & IV were 35 cases (76%) out of total 46 cases, and 38 cases (94.8%) out of 39 survival cases were included In NYHA Class I & II during the follow-up period.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.94-101
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• 2014

In this work, we present an underwater acoustic transducer with a cavity-type head mass to achieve a wide frequency bandwidth. We analyzed the effects of design variables on the transducer characteristics, and optimized the structure of the Tonpilz transducer based on the analysis results. Further, validity of the design was verified by manufacturing a prototype of the transducer and measuring its properties. The designed transducer had a far wider -6 dB fractional bandwidth which is 131 % than that of a single mode transducer, and the measured results were confirmed to be in good agreement with the analysis results.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.377-387
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• 1999

A piezoelectric flextentional deep-water sonar transducer has been designed using a coupled FE-HEM. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state frequency response for TX displacement modes, directivity patterns, resonance frequencies, TVRs. While the conventional barrel-stave typed sonar transducer of the piezoelectric material is designed, the external surface of the transducer is modified in order to allow the same hydrostatic pressure to be applied onto the inner and the outer surfaces of the transducer. With this modification for deep-water application, a new resonance mode is generated at lower frequency. This lower resonance mode can be adjusted according to the degree of the outer surface modification.

• Journal of Chest Surgery
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• v.16 no.3
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• pp.289-294
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• 1983

The report is concerned to our experience of 12 cases of open heart surgery under the extracorporeal circulation at the Department of Thoracic and Cardiovascular Surgery, Chosun University Hospital during the period between Nov, 1979 and April, 1983. 1. There were 4 cases of congenital anomaly and 8 cases of acquired heart disease. 2. There were 6 male and 6 female patients with a mean age of 20 years. [range 9 to 33 years]. 3. The cases induced 2 ventricular septal defect, 2 atrial septal defects and 8 acquired valvular heart diseases. 4. The surgical managements were 2 primary repair for atrial septal defect and 2 patch closure for ventricular septal defect, 1 triple valve replacement [AVR MVR TVR], 1 aortic valve replacement, 4 double valve replacement [AVR MVR] and 2 open mitral commissurotomy for pure mitral stenosis. 5. The average cardiopulmonary bypass time was 61.5 minutes for congenital heart disease and 201.4 minutes for acquired valvular heart disease and the average aortic cross clamping time was 36.75 minutes for the former and 165.6 minutes for the latter. 6. Postoperatively, there were 1 Alopecia, 1 Electric burn and 1 wound infection as complication. 7. Overall operative mortality was 8.3%. 7. All patients received valve replacement were recommended anticoagulation with persantin.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• Korean Journal of Applied Biomechanics
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• v.25 no.4
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• pp.383-391
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• 2015

Objective : The purpose of this study was to investigate the effects of dynamic squats with slope-whole body vibration (WBV) on the trunk and lower limb in muscle activities. Method : 9 healthy women (age: $21.1{\pm}0.6years$, height: $160.5{\pm}1.4cm$, body weight: $50.5{\pm}2.4kg$) were recruited for this study. Muscle activities in the trunk and lower limb muscles, including biceps femoris (BF), rectus femoris (RF), rectus abdominum (RA), gastrocnemius (GCM), iliocostalis lumborum (IL) and tibialis anterior (TA), were recorded using an EMG measurement system. The test was performed by conducting dynamic squats with slope-WBV using frequency (10Hz, 50Hz), amplitude (0.5mm), and degree ($0^{\circ}$, $5^{\circ}$). Experimental method consisted of 2-pre-sessions and 1-test-session for 20 seconds. Results : The results showed that the muscle activities of the trunk and low limb muscles increased significantly with the $5^{\circ}$ slope and lower frequency (10Hz) except for in the TA. From this result, we confirmed that the slope and WBV could efficiently affect stimulation, enhancing muscle activities by facilitating neural control trail and muscle chain tightness. Conclusion : Utilizing the slope-WBV device while squatting could give positive effects on muscle activation in the trunk and lower limb muscles and provide neural stimulation, enhancing muscle chain of control subsystem through TVR (tonic vibration reflex).

• KEPCO Journal on Electric Power and Energy
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• v.4 no.1
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• pp.33-38
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• 2018

This study applied upgrades to the processes of a 10 MW wet amine $CO_2$ capture pilot plant and conducted performance evaluation. The 10 MW $CO_2$ Capture Pilot Plant is a facility that applies 1/50 of the combustion flue gas produced from a 500 MW coal-fired power plant, and is capable of capturing up to 200 tons of $CO_2$. This study aimed to quantitatively measure efficiency improvements of post-combustion $CO_2$ capture facilities resulting from process upgrades to propose reliable data for the first time in Korea. The key components of the process upgrades involve absorber intercooling, lean/rich amine exchanger efficiency improvements, reboiler steam TVR (Thermal Vapor Recompression), and lean amine MVR (Mechanical Vapor Recompression). The components were sequentially applied to test the energy reduction effect of each component. In addition, the performance evaluation was conducted with the absorber $CO_2$ removal efficiency maintained at the performance evaluation standard value proposed by the IEA-GHG ($CO_2$ removal rate: 90%). The absorbent used in the study was the highly efficient KoSol-5 that was developed by KEPCO (Korea Electric Power Corporation). From the performance evaluation results, it was found that the steam consumption (regeneration energy) for the regeneration of the absorbent decreased by $0.38GJ/tonCO_2$ after applying the process upgrades: from $2.93GJ/ton\;CO_2$ to $2.55GJ/tonCO_2$. This study confirmed the excellent performance of the post-combustion wet $CO_2$ capture process developed by KEPCO Research Institute (KEPRI) within KEPCO, and the process upgrades validated in this study are expected to substantially reduce $CO_2$ capture costs when applied in demonstration $CO_2$ capture plants.