• 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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.879-885
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• 2014

In this paper, we designed and fabricated wideband 3-axis isotropic antenna for the Electro-Magnetic Fields(EMFs) measurement. Each part of proposed 3-axis antenna has isotropic characteristics and arbitrary axis of proposed 3-axis antenna could be selectable using RF switch. Also, a resistor was inserted in each axis of proposed 3-axis antenna for improving antenna gain and noise suppression characteristics, and port impedance of each dipole antenna were matched by balun. For the performance verification of antenna, GTEM Cell which generates standard electromagnetic field was used for the derivation of antenna factor and receiver sensitivity. As a result, fabricated 3-axis isotropic antenna has receiver sensitivity of 0.12~4.2 mV/m and typical VSWR of 3.3:1 within a wide operation frequency range from 0.03 MHz to 3 GHz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4891-4895
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• 2010

RF coil is an important component of the Magnetic Resonance Imaging (MRI) system and the performance of RF coil is one of major factors for high SNR images. Sensitivity and RF field uniformity are parameters for evaluating RF coil performance. Since the B1 field is induced by RF coil, MR signal is strongly affected by RF coil structure and arrangement. In receiving MR signal, the RF coil sensitivity to MR Signal is also determined by the induced B1 field of RF coil. Therefore, the spatial distribution of B1 field must be verified. In this work, we performed computer simulation of the basic RF coil structures using Matlab and verified their sensitivity and uniformity through their B1 field distribution. This work will be useful for the advanced multi-channel RF coil design.

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1053-1059
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• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1151-1158
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• 2011

Proximity magnetic sensor is able to detect the object target accurately in close range and it has been widely used in the underwater guided weapon system because there is no countermeasures from the target. In order to increase the damage of target by shock wave due to explosion of the underwater guided weapon system, the maximum detection range of the proximity magnetic sensor needs to be increased. In this paper, we describe the techniques of the optimum transmitting and receiving coils design using the Finite Element Method for the output power enhancement of the transmitter and the sensitivity improvement of the receiver. Finally, the proposed design techniques of the transmitter and the receiver were verified using a experimental setup and a prototype.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.215-220
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• 2013

In this paper, the signal reception environment of the satellite communications was analyzed on urban, suburban and rural environment. The correct analysis of received environment is very important in the satellite communications because the presence of various attenuation factors. Analyze attenuation factor through the simulation and that apply to each receiving environment. The urban and suburban various received sensitivity is determined according to building height and density. Moreover, attenuation occurs in rural areas due to the mountainous and vegetation. In this paper, we analysis of variety receiving environment according to movement of the ground station and the satellites can be utilized to provide stable multimedia services.

• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.200-209
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• 2015

An underwater sound surveillance system detects and tracks enemy ships in real-time using hydrophone arrays, in which seabed-mounted sensor arrays play a pivotal role. In this paper the conceptual design of seabed-mounted, cylindrical hydrophone arrays for use in shallow coastal waters is performed via finite element calculations. To stabilize the receiving characteristics under the ocean ambient noise, a technique for whitening the ambient noise spectrum using a metal baffle is proposed. Optimization of the array configuration is performed to achieve the directivity in the vertical and azimuthal directions. And the effects of the sonar dome shape and material on the structural vibration and sound scattering properties are studied. It is demonstrated that a robust hydrophone array, having a sensitivity deviation less than 4 dB over the frequency range of interest, can be obtained through the whitening of the ambient noise, the optimization of the array configuration, and the design of acoustically transparent sonar domes.

• Journal of Preventive Medicine and Public Health
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• v.29 no.1 s.52
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• pp.67-78
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• 1996

The purpose of this study was examine the general characteristics of relapsed pulmonary tuberculous patients (i.e. age, sex, weight, occupation, previous forms of treatment, drug sensitivity, and the frequency of relapse) in order to improve future treatments of tuberculosis as well as to perpetuate health education. The data was obtained from the medical records of 186 relapsed pulmonary tuberculosis patients who were registered for treatment at various public health offices in Seoul during the year of 1994. The major findings obtained from the study were as follows; 1) The male to female ratio of relapsed pulmonary tuberculous patients was about 7:3, more specifically 23.7% of the men and 30.9% of the women were between 20 and 29 years of age. 2) Comparing initial less aggravated states to relapsed states, patients with minimal X-ray findings later proved moderately advanced X-ray findings. Furthermore, patients with negative sputum AFB findings later proved positive sputum AFB findings. 3) Of the 186 patients studied, 91.9% suffered, relapse and 8.1% suffered 2 or more relapses. Of the patients who suffered at least 1 relapse, 54.8% received short-term treatment, 26.9% received long-term treatment, and 18.3% received treatment of an unknown during their initial tuberculosis treatment periods. 4) fifty five point four percent of the patients had no reaction to the drug treatment(not available), 25.9% of the patients had sensitive reaction to the drug treatment, 18.7% of the patients had resistant reaction to the- drug treatment. Drug resistance was higher in patients that exhibited positive X-ray findings as well as in patients that exhibited positive sputum AFB findings. furthermore, patients receiving treatment of an unknown nature(35.5%) exhibited higher drug resistance than those receiving short-term treatment(13.6%) and long-term treatment(17.0%). 5) Of the 160 patients who suffered relapses, 8.8% suffered a relapse within 1 year after treatment and 91.2% suffered a relapse at least 1 year after treatment. Furthermore, our study showed that women, under 30, who received short-term treatment and encounterd complications during their primary treatment suffered relapses faster than any other groups studied. In addition, minimal X-ray findings and sputum AFB findings were not correlated to the time relapse occured. Therefore, the seater efforts are needed to prevent relapsed pulmonary tuberculosis.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.223-230
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• 2002

In this paper, we induced that the noise powers and bit error rate of direct detection receiver taking account of ISI (intersymbol interference) in the 2,000 km optical transmission system. And we evaluated the sensitivity in the vrious bit rate system. We verified that the proposed calculation method is applicable to the exact optical system. And we confirmed that the signal distortion due to both chromatic dispersion and nonlinear effects compensated by using of MSSI (Mid-Span Spectral Inversion) method, and yet the sensitivity of a higher bit rate system is reduced, because of the increase of ISI and then the decrease of the average receiving power, compared with a the lower bit rate system.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.419-433
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• 2016

One of the important severe accident management measures in the Light Water Reactors is water injection to the reactor core. The related phenomena are investigated by performing experiments and computer simulations. One of the most widely known is the QUENCH test-program. A number of analyses on QUENCH tests have also been performed by different computer codes for code validation and improvements. Unfortunately, any deterministic computer simulation is not free from the uncertainties. To receive the realistic calculation results, the best estimate computer codes should be used for the calculation with combination of uncertainty and sensitivity analysis of calculation results. In this article, the QUENCH-03 and QUENCH-06 experiments are modelled using ASTEC and RELAP/SCDAPSIM codes. For the uncertainty and sensitivity analysis, SUSA3.5 and SUNSET tools were used. The article demonstrates that applying the best estimate approach, it is possible to develop basic QUENCH input deck and to develop the two sets of input parameters, covering maximal and minimal ranges of uncertainties. These allow simulating different (but with the same nature) tests, receiving calculation results with the evaluated range of uncertainties.