• Journal of Sensor Science and Technology
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• v.21 no.2
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• pp.103-108
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• 2012

Radiofrequency(RF) signal is a key medium to the most of the present wireless communication devices including RF identification devices(RFID) and smart sensors. However, the most critical barrier to overcome in RFID application is in the failure rate in detection. The most notable improvement in the detection was from the introduction of EPC Class1 Gen2 protocol, but the fundamental problems in the physical properties of the RF signal drew less attention. In this work, we focused on the physical properties of the RF signal in order to understand the failure rate by noting the existence of the ground planes and noise sources in the real environment. By using the mathematical computation software, Maple, we simulated the distribution of the electromagnetic field from a dipole antenna when ground planes exist. Calculations showed that the dark area can be formed by interference. We also constructed a test system to measure the failure rate in the detection of a RFID transponder. The test system was composed of a fixed RFID reader and an EPC Class1 Gen2 transponder which was attached to a scanner to sweep in the x-y plane. Labview software was used to control the x-y scanner and to acquire data. Tests in the laboratory environment showed that the dark area can be as much as 43 %. One who wants to use RFID and smart sensors should carefully consider the extent of the dark area.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.1
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• pp.112-122
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• 2024

Recently, as unmanned aerial vehicle technology such as drones has developed, there are many environmental, social and economic benefits, but if there is malicious intent against important national facilities such as airports, public institutions, power plants, and the military, it can seriously affect national safety and people's lives. It can cause damage. To respond to these drone threats, attempts are being made to introduce detection equipment such as RF scanners. In particular, power transmission towers installed in substations, power plants, and Korea's power system can affect detection performance if the transmission tower is located in the RF scanner detection path. In the experiment, a commercial drone was used to measure the signal intensity emitted from the drone and confirm the attenuation rate. The average and maximum attenuation rates showed similar trends in the 2.4 GHz and 5.8 GHz bands, and were also affected by the density of the structure.

• Korean Journal of Pharmacognosy
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• v.12 no.3
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• pp.119-124
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• 1981

In our country, in order to cure diseases, a large number of crude drug preparations has been available. Nevertheless, the development of crude drug preparations have been inhibited, because the quality control is not completed so far. Therefore, we have eontinued on studing the quality control method by Zig-zag TLC. profile analysis. The water extract of 'Samyo-Tang' and componental crude drug (Glycyrrhizae Radix, Ephedrae Herba, Armenicae Semen) were developed on Silica gel $60F_{254}\;plate\;(E.\;Merck)$ useing elution solvent. The developed plate were examined useing Dual Wavelength Zig-zag Scanner (Shimadzu). According to the results of the experiment, it could be summarized as follow: 1) Original patterns of TLC profiles of 'Samyo-Tang' componental crude drug and mixing two crude drugs of 'Samyo-Tang' were observed. 2) Original patterns TLC profile of each extract after spraying with 2% ninhydrine were observed. 3) In the extract of addition and subtraction of Ephedrae Herba, peak area of Rf 0.48 and Rf 0.60 were varied quantitatively.

• Journal of electromagnetic engineering and science
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• v.10 no.4
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• pp.244-249
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• 2010

Recent development of magnetic resonance imaging (MRI) equipment enables interventional radiology (IVR) as diagnosis and treatment under MRI usage. In this paper, a new methodology for magnetic resonance (MR) scanner to apply not only diagnostic equipment but for treatment one is discussed. The temperature measuring procedure under MR is to measure phase shift of $T_1$, which is the longitudinal relaxation time of proton, for the position inside a sample material with the application of pulsed RF for heating inside the sample as artificial dielectrics. The result shows the possibility to apply MR as temperature measuring equipment and as a heating equipment for applying such as hyperthermia heating modality.

• Investigative Magnetic Resonance Imaging
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• v.18 no.1
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• pp.52-58
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• 2014

Purpose : To establish a pH measurement system for a mouse tumor study using a clinical scanner, to develop the $^1H$ and 31P radio frequency (RF) coil system and to test pH accuracy with phantoms. Materials and Methods: The $^1H$ and the $^{31}P$ surface coils were designed to acquire signals from mouse tumors. Two coils were positioned orthogonally for geometric decoupling. The pH values of various pH phantoms were calculated using the $^1H$ decoupled $^{31}P$ MR spectrum with the Henderson-Hasselbalch equation. The calculated pH value was compared to that of a pH meter. Results: The mutual coil coupling was shown in a standard $S_{12}$. Coil coupling ($S_{12}$) were -73.0 and -62.3 dB respectively. The signal-to-noise ratio (SNR) obtained from the homogeneous phantom $^1H$ image was greater than 300. The high resolution in vivo mice images were acquired using a $^{31}P$-decoupled $^1H$ coil. The pH values calculated from the $^1H$-decoupled $^{31}P$ spectrum correlated well with the values measured by pH meter ($R^2$=0.97). Conclusion: Accurate pH values can be acquired using a $^1H$-decoupled $^{31}P$ RF coil with a clinical scanner. This two-surface coil system could be applied to other nuclear MRS or MRI.

• Investigative Magnetic Resonance Imaging
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• v.23 no.3
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• pp.179-201
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• 2019

Portable low-cost magnetic resonance imaging (MRI) systems have the potential to enable "point-of-care" and timely MRI diagnosis, and to make this imaging modality available to routine scans and to people in underdeveloped countries and areas. With simplicity, no maintenance, no power consumption, and low cost, permanent magnets/magnet arrays/magnet assemblies are attractive to be used as a source of static magnetic field to realize the portability and to lower the cost for an MRI scanner. However, when taking the canonical Fourier imaging approach and using linear gradient fields, homogeneous fields are required in a scanner, resulting in the facts that either a bulky magnet/magnet array is needed, or the imaging volume is too small to image an organ if the magnet/magnet array is scaled down to a portable size. Recently, with the progress on image reconstruction based on non-linear gradient field, static field patterns without spatial linearity can be used as spatial encoding magnetic fields (SEMs) to encode MRI signals for imaging. As a result, the requirements for the homogeneity of the static field can be relaxed, which allows permanent magnets/magnet arrays with reduced sizes, reduced weight to image a bigger volume covering organs such as a head. It offers opportunities of constructing a truly portable low-cost MRI scanner. For this exciting potential application, permanent magnets/magnet arrays have attracted increased attention recently. A magnet/magnet array is strongly associated with the imaging volume of an MRI scanner, image reconstruction methods, and RF excitation and RF coils, etc. through field patterns and field homogeneity. This paper offers a review of permanent magnets and magnet arrays of different kinds, especially those that can be used for spatial encoding towards the development of a portable and low-cost MRI system. It is aimed to familiarize the readers with relevant knowledge, literature, and the latest updates of the development on permanent magnets and magnet arrays for MRI. Perspectives on and challenges of using a permanent magnet/magnet array to supply a patterned static magnetic field, which does not have spatial linearity nor high field homogeneity, for image reconstruction in a portable setup are discussed.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.181-185
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• 1997

The ion sources for induction linac driven heavy ion fusion were fabricated and their omittance characteristics were investigated. For to kinds of ion sources, i. e. a carbon vacuum arc ion source and a cusp field rf ion source, the emittance was measured with a double slit beam scanner. The required normalized omittance of an ion source for heavy ion fusion is 10$^{-7}$ - 5$\times$10$^{-7}$ $\pi$ m-rod, and the measured emittances of the ion beams from carbon vacuum arc ion source and cusp field rf ion source (Ne$^{+}$) were 2$\times$10$^{-6}$ $\pi$ m-rad and 4$\times$10$^{-7}$ $\pi$ m-rad, respectively.y.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.261-266
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• 2010

In this paper, we report the changes of electrical, structural and optical characteristics in $Ge_2Sb_2Te_5$ thin films according to an increase of Si content. The Si-doped $Ge_2Sb_2Te_5$ thin films were prepared by rf-magnetron co-sputtering method. Isothermal annealing was carried out at $N_2$ atmosphere. The crystallization speed (v) of amorphous thin films was evaluated by detecting the reflection response signals using a nano-pulse scanner (wavelength = 658 nm) with illumination power of 1~17 mW and pulse duration of 10~460 ns. Structural phase changes were evaluated by XRD, and the optical transmittance was measured in the wavelength range of 300~3000 nm using UV-vis-NIR spectrophotometer. The sheet resistance (RS) of the thin films was measured using 4 point probe. Conclusivlely, the v-value decreased with an increase of Si content, while the RS-values of both crystalline and amorphous phases were increased. In particular, fcc-to-hexagonal transition was suppressed by the added Si atoms.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.817-818
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• 2006

In Magnetic Resonance Imaging(MRI), the QRS complex of ECG is used as a trigger signal for MRI scan. But, gradient and RF(radio frequency) artifacts which are caused to static and dynamic field in MRI scanner cause interference in the ECG. Also, the signal shape of theses artifacts can be similar to the QRS-complex, causing possible misinterpretation during patient monitoring and false gating of the MRI. In case of using general FIR or IIR band-pass filters for minimizing the artifacts, artifact-reduction-ratio is not excellent. So, an adaptive real-time digital filter is proposed for reduction of noise by gradient and RF(radio frequency) artifacts. The proposed filter for MRI-Gating is based on the noise-canceller with NLMS(Normalized Least Mean Square) algorithm. The reference signals of the adaptive noise canceller are a combination of the noisy three channel ECG signals. In conclusions, the proposed method showed the acceptable quality of ECG signal with sufficient SNR for gating the MRI and possibility of real time implementation.

• Journal of the Korean Society of Radiology
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• v.11 no.1
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• pp.49-54
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• 2017

As the Radiofrequency(RF) increases with the magnetic field strength, the wavelength of the RF excitation field becomes smaller, which leads to more the thermal effect in the human-body placed in the electric field. MRI scanner used was GE signa 1.5T, HDx 3.0T and Philips 3.0T with same routine clinical sequence protocol. Therefore temperature was measured before and after each scan. Taken the temperatures in the ear with ear infra-red type thermometer(Braun co). 3.0T were temperature increases more than $0.15^{\circ}C$ and GE 3.0T MRI equipment about $0.14^{\circ}C$ higher than the Philips 3.0T MRI(p<0.012). Psychogenic status was investigated by the survey respondents about their status can not just answer therefore, a little different from the expected. In our study of Thermal effect of clinical MRI with clinical protocol sequence, we found that the 3.0T in the body-temperature rise was greater than the 1.5T. Therefore, in clinical 3.0T examine the dangerous situation caused by the temperature rise occurred (burns, impaired thermoregulatory mechanism in patients with high-temperature damage, exhaustion occurs due to excessive sweating), not to appear the more watched the patient's condition with procedure.