• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.457-464
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• 2000

In this paper, we describe the results of various calculations performed for a design of the thickness gauges that use the gamma-ray backscattering method. The radiation source is assumed to be the $_{24}$1Am(60keV gamma-ray) and the detector is a single crystal scintillator in a cylindrical form. The source is located at the center of the detector with the collimator of a cylindrical shape. First, when gamma-rays are incident on a material with a constant angle, we compute the variations of the spectrum for the photons scattered into different angular intervals. Next, we compute for an optimal size for the collimator cylinder for a fixed detector size and an optimal distance from the detector to the material. Finally, we compute the number of observed photons for different thickness of two different materials, a plastic film and an Al foil.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.82-82
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• 2012

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool to investigate the electronic structure of a single-crystalline solid. After the development of a two-dimensional electron detector, it became a basic experimental method in solid state physics comparable to other powerful tools such as x-ray and neutron scatterings. In this tutorial, I talk briefly on the basic principle of ARPES and its recent and future direction of development.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.5-6
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• 2002

The new spectrometer for X-ray Induced Electron Emission Spectroscopy (XIEES) .has been recently developed in KRISS in collaboration with PTI (Russia). The spectrometer allows to perform research using the XAFS, SXAFS, XANES techniques (D.C.Koningsberger and R.Prins, 1988) as well as the number of techniques from XIEES field(L.A.Bakaleinikov et all, 1992). The experiments may be carried out with registration of transmitted through the sample x-rays (to investigate bulk samples) or/and total electron yield (TEY) from the sample surface that gives the high (down to several atomic mono-layers in soft x-ray region) near surface sensitivity. The combination of these methods together give the possibility to obtain a quantitative information on elemental composition, chemical state, atomic structure for powder samples and solids, including non-crystalline materials (the long range order is not required). The optical design of spectrometer is made according to Johannesson true focusing schematics and presented on the Fig.1. Five stepping motors are used to maintain the focusing condition during the photon energy scan (crystal angle, crystal position along rail, sample goniometer rail angle, sample goniometer position along rail and sample goniometer angle relatively of rail). All movements can be done independently and simultaneously that speeds up the setting of photon energy and allows the using of crystals with different Rowland radil. At present six curved crystals with different d-values and one flat synthetic multilayer are installed on revolver-type monochromator. This arrangement allows the wide range of x-rays from 100 eV up to 25 keV to be obtained. Another 4 stepping motors set exit slit width, sample angle, channeltron position and x-ray detector position. The differential pumping allows to unite vacuum chambers of spectrometer and x-ray generator avoiding the absorption of soft x-rays on Be foil of a window and in atmosphere. Another feature of vacuum system is separation of walls of vacuum chamber (which are deformed by the atmospheric pressure) from optical elements of spectrometer. This warrantees that the optical elements are precisely positioned. The detecting system of the spectrometer consists of two proportional counters, one scintillating detector and one channeltron detector. First proportional counter can be used as I/sub 0/-detector in transmission mode or by measuring the fluorescence from exit slit edge. The last installation can be used to measure the reference data (that is necessary in XANES measurements), in this case the reference sample is installed on slit knife edge. The second proportional counter measures the intensity of x-rays transmitted through the sample. The scintillating detector is used in the same way but on the air for the hard x-rays and for alignment purposes. Total electron yield from the sample is measured by channeltron. The spectrometer is fully controlled by special software that gives the high flexibility and reliability in carrying out of the experiments. Fig.2 and fig.3 present the typical XAFS spectra measured with spectrometer.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1354-1357
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• 2002

In this paper, we propose a suboptimal receiver combining adaptive array antenna and orthogonal decision-feedback detector in DS/CDMA system. Adaptive array antenna can cancel out undesired signal using beamforming scheme. However, if there are interfering signals from undesired users with the same incident angle as that of a desired user, an adaptive array antenna cannot suppress them. The proposed receiver can cancel out remaining interference from users having nearly the same beam pattern. And we employ Orthogonal Decision-Feedback Detector (ODFD) as multiuser detection. The ODFD performs as good as the decorrelating decision -feedback detector (DDD) with much less complexity. Simulation results show that the proposed system provides a significantly enhanced performance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.270-274
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• 2008

The microwave sensor in which the sensitivity was excellent and a structure is simple was developed and it manufactured. And the sensing range that uses the developed product was confirmed. When the developed microwave sensor was set up in the ceiling of a building, we confirmed that the amplitude of the sensitive area increased as the tilting angle was enlarged. The sensitive area became a greatest in case the tilting angle was 65 degree. According to the height of a ceiling, because the sensing range is determined, in case of using in the building in which the height of a ceiling is enough secured it is determined to secure the more wide sensitive area. Moreover, the configuration of the circuit having the simple structure makes the miniaturization of a product, and the light weight possible. It is considered to have the price competitive power which it reduces the manufacturing cost, is sufficient.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.201-210
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• 2018

This paper proposes a new start-up method for a load commutated inverter (LCI) in a large synchronous gas-turbine generator. The initial rotor position for start-up torque is detected by the proposed initial angle detector, which consists of an integrator and a phase-locked loop. The initial rotor position is accurately detected within 150ms, and the angle difference between the real position and the detected position is less than 1%. The LCI system operates in two modes (forced commutation mode and natural commutation mode) according to operating speed range. The proposed controllers include a forced commutation controller for the low-speed range, a PI speed controller and a PI current controller, where the forced commutation controller is connected to the current controller in parallel. The current controller is modeled by Matlab/Simulink, where a six-pulse delay of the thyristor and a processing delay are considered by using a zero-order hold. The performance of the proposed start-up method is evaluated in Matlab/Psim at standstill and at low speed. To verify the feasibility of the method, a 5kVA LCI system prototype is implemented, and the proposed initial angle detector and the system performance are confirmed by experimental results from standstill to 900rpm.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.383-390
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• 2006

Having its roots in medical applications, industrial gamma ray CT has opened up new roads far investigating and modeling industrial processes. Using a line of research related to industrial gamma ray CT, the authors set up a system of single source and detector gamma transmission tomography for wood timber and a packed bed phantom. The hardware of the CT system consists of two servo motors, a data logger, a computer, a radiation source and a radiation detector. One motor simultaneously moves the source and the detector for a parallel beam scanning, whereas the other motor rotates the scan table at a preset projection angle. The image is reconstructed from the measured projections by the filtered back projection method. The phantom was designed to simulate a cross section of a packed bed with a void. The radiation source was 20mCi of Cs-137 and the detector was a 1 inch $\times$ 1 inch NaI (TI) scintillator shielded by a lead collimator. The experimental gamma ray CT image has sufficient resolution to reveal air holes and the density distribution inside the phantom. The system could possibly be applied to a packed bed column or a pipe flow in a petrochemical plant.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2601-2606
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• 2020

In this study, we expanded the performance of the existing EXVol code and performed empirical experiments and calculations. A high-resolution gamma spectroscopy system was constructed, and a standard point source and a standard volume source were measured with an HPGe detector with 43.1% relative efficiency. EXVol was verified by quantitative comparison of the detection efficiencies determined by measurements and calculations. To introduce the concept of the detector scanning that occurs in the actual measurement into the EXVol code, a collimator was placed between the source and detector. The detection efficiency was determined in the asymmetric arrangement of the source and detector with a collimator. A collimator made of lead with a diameter of 15 mm and a thickness of 50 mm was installed between the source and the detector to determine the detection efficiency at a specific location. The calculation result was contour plotted so that the distribution of detection efficiency could be visually confirmed. The relative deviation between the measurements and calculations for the coaxial and asymmetric structures was 10%, and that for the collimation structure was 20%. The results of this study can be applied to research using γ-ray measurements.

• The Journal of the Korea Contents Association
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• v.21 no.1
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• pp.119-128
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• 2021

The most typical method to generate traffic information is installing vehicle detectors and collecting various traffic variables. The information collection accuracy of a vehicle detector affects the reliability of the generated traffic information. The most universal vehicle detector is an image detector. This study installed a magnetic detector in the same position as an image detector and evaluated the accuracy of traffic volume and speed data depending on a variety of environment. Based on the evaluation, more errors occurred as the image detector was placed farther from the camera, whereas more errors were found to occur during the night rather than the day. Although rainfall did not affect the collection of traffic volume, it negatively affected speed data collection. Therefore, an analysis of the camera's view angle and its optimization depending on the camera installation position and height are required to enhance the currently operated image detector performance. It is judged that a separate performance evaluation criterion should be prepared in a bad weather environment.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.01a
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• pp.235-238
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• 2017

This study was to develop a portable digital radiography (PDR) system with a function measuring the X-ray source-with-detector angle (SDA) and to evaluate the imaging performance for the diagnosis of chest imaging. The SDA device consisted of an Arduino, an accelerometer and gyro sensor, and a Bluetooth module. According to different angle degrees, five anatomical landmarks on chest images were assessed using a 5-point scale. Mean signal-to-noise ratio and contrast-to-noise ratio were 182.47 and 141.43. Spatial resolution (10% MTF) and entrance surface dose were 3.17 lp/mm ($157{\mu}m$) and 0.266mGy. The angle values of SDA device were not significant difference as compared to those of the digital angle meter. In chest imaging, SNR and CNR values were not significantly different according to different angle degrees (repeated-measures ANOVA, p>0.05). The visibility scores of the border of heart, 5th rib and scapula showed significant differences according to different angles (rmANOVA, p<0.05), whereas the scores of the clavicle and 1st rib were not significant. It is noticeable that the increase in SDA degree was consistent with the increase of visibility score. Our PDR with SDA device would be useful to be applicable to clinical radiography setting according to the standard radiography guideline at various fields.