• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.309-316
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• 1995

RF (radio-frequency) probes of Nuclear Magnetic Resonance are one of the important factors and should be designed and built properly depending upon the geometry of the samples and the information. In general there are two kinds of rf probes : one encircles the sample while the other is placed on the surface of the sample. However, in case that the samples on human internal organs have a tube shape, the two kinds of rf probes, as specified above, are usually unsuitable for the internal imaging due to the degradation of signal-to-noise ratios (SNR's). In this case a probe should be positioned as close to the area as possible by putting the probe in the tubelike sample to improve filling factor In the present study inside-out probes have been constructed in the three different shapes such as an anti-solenoidal, a saddle and a dual surface types. RF-field distributions have also been calculated depending upon the geometrical changes of anti-solenoid probes. Moreover, the performance of the inside-out probes has been checked by measuring SNR's of the images acquired. The inside-out probes constructed in this study produced better SWR's and rf-field uniformity in the area close to the probes in comparing with any other commercial probes. There is a high feasibility that the constructed probes in the present study are applicable to the diagnosis of human bodies.

• Korean Journal of Construction Engineering and Management
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• v.11 no.2
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• pp.106-115
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• 2010

Recently, as the size of construction projects are getting bigger and higher, more effective managing methods are required in management areas such as duration reduction, cost reduction and quality management. In the current construction industry, conjunction with IT(Information Technology) is being noticed as a solution to support these needs. Various IT solutions such as Bar Code, Personal digital assistant(PDA), global positioning system(GPS), radio frequency identification(RFID) are being developed. In this research, among the various IT solutions, the Real Time Locating System(RTLS) which is acknowledged as a technology with high applicational potential is analyzed. Based on this analysis, a locating system to apply in construction sites is developed and validated. The locating system is developed to prevent construction disasters through real-time management of workers and equipment, which enables effective application in the area of construction safety management. Moreover, applications of the locating system in many different areas like construction material realtime monitoring, construction automation, construction quality management, maintenance management are expected.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.1-8
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• 2006

In this paper, we suggested a new antenna structure for the RFID(Radio Frequency IDentification) reader. The conventional RFID reader uses a loop antenna. The central area of a loop antenna shows a low magnetic field strength, especially for the case of a large loop antenna diameter. We proposed a parallel-fed multiple loop antenna. Simulation and measurement were carried out for a single loop antenna, series-fed and parallel-fed multiple loop antennas. Simulation results show that we can obtain 0.40A/m, 0.68A/m, 1.98A/m of magnetic field strengths at the central point of a reader antenna for a single loop antenna, series-fed and parallel-fed multiple loop antennas, respectively. We measured the $79mm{\time}48mm$ tag area averaged induced voltages with applying 20Vp-p same source signals to reader antennas through the resistors. Measured tag area averaged induced voltages at the central point of a reader antennas were 0.76V, 1.45V, 4.04V for a single loop antenna series-fed and parallel-fed multiple loop antennas, respectively. The results show that we can get high induced voltage which can grantee a longer reading distance with a proposed parallel-fed multiple loop antenna.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.730-736
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• 2014

Test standards for electrical and electronic equipment required for ship operations is applying the IEC-60533 standard. However, although a test procedure and a specified regulation are clearly defined in the deck and bridge zone and general power distribution zone, they are not regulated in the special power distribution zone with ship propulsion system. For these reasons, the costs for additional research and development have been invested. In this paper, we was measured power noise in a special power distribution zone in ship and we were compared and analyzed values measured. The actual experiments are performed on the ship of Korea Maritime and Ocean University. As a result, the acquired data on Hanbada shows that loop antenna with low frequency band(160kHz) and ultra log antenna with high frequency band(1.97GHz)occur about 6-8dB differences and about 8.7 difference respectively. Also, the acquired data on Hannara shows that each loop antenna of 1MHz, 11MHz, and 25MHz occurs about 7dB difference about 4-5dB differences respectively. so standard of Special distribution zone must be specified by comparative analysis of data obtained by the experiment more.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.243-244
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• 2013

Over the past 15 years, several groups have incorporated radio-frequency quadrupole (RFQ) based instruments before the accelerator in accelerator mass spectrometry (AMS) systems for ion-gas interactions at low kinetic energy (＜40 eV). Most AMS systems arebased on a tandem accelerator, which requires negative ions at injection. Typically, AMS sensitivity abundance ratios for radioactive-to-stable isotope are limited to Xr/Xs ＞10^-15, and the range of isotopes that can be analyzed is limited because of theneed to produce rather large negative ion beams and the presence of atomic isobaric interferences after stripping. The potential of using low-kinetic energy ion-gas interactions for isobar suppression before the accelerator has been demonstrated for several negative ion isobar systems with a prototype RFQ system incorporated into the AMS system at IsoTrace Laboratory, Canada (Ontario, Toronto). Requisite for any such RFQ system applied to very rare isotope analysis is large transmission of the analyte ion. This requires proper phase-space matching between the RFQ acceptance and the ion beam phase space (e.g. 35 keV, ${\varphi}3mm$, +-35 mrad), and the ability to control the average ion energy during interactions with the gas. A segmented RFQ instrument is currently being designed at Korea Institute for Science and Technology (한국과학기술연구원, KIST). It will consist of: a) an initial static voltage electrode deceleration region, to lower the ion energy from 35 keV down to ＜40 eV at injection into the first RFQ segment; b) the segmented quadrupole ion-gas interaction region; c) a static voltage electrode re-acceleration region for ion injection into a tandem accelerator. Design considerations and modeling will be discussed. This system should greatly lower the detection limits of the 6 MV AMS system currently being commissioned at KIST. As an example, current detection sensitivity of 41Ca/Ca is limited to the order of 10^-15 while the 41Ca/Ca abundance in modern samples is typically 41Ca/Ca~10^-14 - 10^-15. The major atomic isobaric interference in AMS is 41K. Proof-of-principal work at IsoTrace Lab. has demonstrated that a properly designed system can achieve a relative suppression of KF3-/41CaF3- ＞4 orders of magnitude while maintaining very high transmission of the 41CaF3- ion. This would lower the 41Ca detection limits of the KIST AMS system to at least 41Ca/Ca~10^-19. As Ca is found in bones and shells, this would potentially allow direct dating of valuable anthropological archives and archives relevant to our understanding of the most pronounced climate change events over the past million years that cannot be directly dated with the presently accessible isotopes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.323-332
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• 2009

In this paper, we introduce a modified short-circuited stub bandpass filter suitable for ultra-wideband(UWB) applications utilizing low temperature co-fired ceramic(LTCC) technology. By modifying the conventional short-circuited stub bandpass filter structure with stubs and connecting lines of lower characteristic impedances, the number of stubs has been reduced from 5 to 2 on a high dielectric constant substrate($\varepsilon_r$ = 40). A wireless local area network (WLAN) stopband in the frequency range of 5.15 to 5.825 GHz has been inserted into the filter characteristic using three short-circuited coupled lines. The filter has been measured with an insertion loss less than 1.0 dB and return loss better than 10 dB in the pass bands. A bandwidth ratio of 109.49 % has been achieved. Measurement results agree well with simulation results. The dimensions of the filter are $4{\times}8{\times}0.57\;mm^3$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.25-32
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• 2006

This study examined the possibility of using dark-striped field mice as a biological indicator for the environmental radio-surveillance. For this study, dark-striped field mice were caught from five areas of Kyonggi, Kyongsang, Chungchong and Cholla provinces. The external morphological characteristics and isoenzymic types of dark-striped field mice were studied after they were captured. Among the external morphological characteristics, the dark-brown coat, dark back stripe, head-to-tail length, tail length, and ear length matched the taxonomical characteristics of dark-striped field mice. The analyses on L-lactate dehydrogenase, aspartate aminotransferase, and malate dehydrogenese revealed that one species of dark-striped field mice, called Apodemus agrarius, was inhabitated throughout a wide range of Korea. On the other hand, the frequency of micronuclei in peripheral polychromatic erythrocytes to survived mice after irradiation also analyzed. The LD50/30 of A. cgrarius and ICR mice were approximately 5 Gy and 7.9Gy, respectively. The results of the study reveal that wild A. asrarius have a high potential as a biological monitoring system to determine the impact of radiation in areas such as those within the vicinity of nuclear power plants.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.661-667
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• 2018

Tactical communication radio systems that employ software defined radios(SDRs) have been developed for achieving high-speed data transmissions and voice communications. Such systems possess multiband and multichannel features, and can potentially replace several existing radio systems. This paper proposes a design for wideband antennas by incorporating a diplexer matching network for tactical vehicles. The proposed antenna design includes two radiators(upper and lower) and a diplexer matching network connected to the end of the feed line such that the LC matching networks are interleaved in the lower radiator and spring mount. By employing the diplexer matching network, the designed antenna can perform wideband impedance matching for the fifty ohm feed line. The designed LC networks aid in varying the effective electrical length of the antenna according to the operation frequency. The primary objective behind adjusting the electrical length is to vary the current distribution above and below the LC networks. The proposed antenna was fabricated and tested in an open site. The obtained evaluation results show that the designed antenna can achieve a relative bandwidth of 190% with a VSWR value of 3.5:1, and can attain good antenna gains over VHF and UHF bands.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.2
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• pp.276-284
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• 2020

This paper proposes a new convolutional neural network (CNN) based spectrum sensing technique for cognitive radio communications. The proposed technique determines the existence of the primary user (PU) by using energy detection without any prior knowledge of the PU's signal. In the proposed method, the received signal is high-rate sampled to sense the entire spectrum bands of interest. After that, fast Fourier transform (FFT) of the signal converts the time domain signal to frequency domain spectrum and by stacking those consecutive spectrums, a 2 dimensional signal is made. The 2 dimensional signal is cut by the sensing channel bandwidth and inputted to the CNN. The CNN determines the existence of the primary user. Since there are only two states (existence or non-existence), binary classification CNN is used. The performance of the proposed method is examined through computer simulation and indoor experiment. According to the results, the proposed method outperforms the conventional threshold-based method by over 2 dB.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.307-313
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• 2022

As the development of renewable energy expands internationally to cope with global warming and climate change, the share of wind power generation has been gradually increasing. Although wind farms can produce electric power for 24 h a day compared to solar power plants, Their interfere with the operation of nearby radars or communication equipment must be analyzed because large-scale wind power turbines are installed. This study analyzed whether a land radio station can receive sufficient signals when a ship sailing outside the offshore wind farm transmits distress signals on the VHF band. Based on the geographic information system digital map around the target area, wind turbine CAD model, and wind farm layout, the area of interest and wind farm were modeled to enable numerical analysis. Among the high frequency analysis techniques suitable for radio wave analysis in a wide area, a dedicated program applying physical optics (PO) and shooting and bouncing ray (SBR) techniques were used. Consequently, the land radio station could receive the electromagnetic field above the threshold of the VHF receiver when a ship outside the offshore wind farm transmitted a distress communication signal. When the line of sight between the ships and the land station are completely blocked, the strength of the received field decreases, but it is still above the threshold. Hence, although a wind farm is a huge complex, a land station can receive the electromagnetic field from the ship's VHF transmitter because the wave length of the VHF band is sufficiently long to have effects such as diffraction or reflection.