• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1764-1773
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• 2018

A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are $46.1{\times}46.1{\times}46.1mm^3$ and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4-2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.2
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• pp.157-162
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• 2022

The purpose of the direct cortical and subcortical stimulation technique is to prevent false positives caused by transcranial electrical motor evoked potentials (TceMEP) in surgery on patients with brain tumors that have occurred around the motor cortex and to preserve the correct mapping of motor areas during surgery and the corticospinal tract. In addition, it reduces the trial and error that occurs during the intraoperative neurophysiological monitoring (INM) process and minimizes the test time, so that accurate information is communicated to the surgeon with quick feedback on the test results. The most important factors of this technique are, first, examination at a stimulus threshold of a certain intensity, and second, maintaining anesthesia depth at an appropriate level to prevent false positives from occurring during surgery. The third is the installation of a multi-level channel recording electrode on the opposite side of the area of operation to measure the TceMEP waveform and the response to direct cortical and subcortical stimulation in as many muscles as possible. If these conditions are maintained, it is possible to predict causes that may occur in other factors, not false positives, from the INM test.

• Journal of IKEEE
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• v.26 no.2
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• pp.287-291
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• 2022

In general, as the amplitude and phase information of the physical layer channel impulse response change rapidly in time and frequency according to the high-speed movement of the vehicles in V2X communication systems, it is difficult to accurately estimate these channels at the receiving end. In order to effectively overcome this problem, midamble-based channel estimation methods in which mid-ambles are periodically inserted into a packet have been recently considered. However, as the number of midambles increases, we suffer from the spectral efficiency loss. To relieve such a loss, in this paper, we propose a new bidirectional averaging channel estimation method that combines the existing data pilot-based channel estimation methods and the mid-ambles. Finally, through the simulation results, we demonstrate that the proposed method outperforms the existing mid-amble method in terms of packet error rate with fewer number of mid-ambles.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.11-18
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• 2022

Recently, as flexible electronic device-related technologies have received worldwide attention, the development of wiring and bonding technologies using liquid metals is required in order to improve problems such as formability in the manufacturing process of flexible devices and performance and durability in the bending state. In response to these needs, various studies are being conducted to use gallium and gallium-based alloys (eutectic Ga-In and eutectic Ga-In-Sn, etc.) liquid metals, with low viscosity and excellent electrical conductivity without toxicity, as low-temperature bonding materials. In this paper, the latest research trends of low-temperature bonding technology using gallium and gallium-based alloys are summarized and introduced. These technologies are expected to become important base technologies for practical use in the fields of manufacturing flexible electronic devices and low-temperature bonding in microelectronic packages in the future.

• Advances in nano research
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• v.11 no.6
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• pp.581-593
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• 2021

This model is proposed to describe the buckling behavior of Carbon Nanotubes (CNTs) embedded in an elastic medium taking into account the combined effects of the magnetic field, the temperature, the nonlocal parameter, the number of walls. Using Eringen's nonlocal elasticity theory, thin cylindrical shell theory and Van der Waal force (VdW) interactions, we develop a system of partial differential equations governing the buckling response of CNTs embedded on Winkler, Pasternak, and Kerr foundations in a thermal-magnetic environment. The pre-buckling stresses are obtained by applying airy's stress function and an adjacent equilibrium criterion. To estimate the nonlocal critical buckling load of CNTs under the simultaneous effects of the magnetic field, the temperature change, and the number of walls, an optimization technique is proposed. Furthermore, analytical formulas are developed to obtain the buckling behavior of SWCNTs embedded in an elastic medium without taking into account the effects of the nonlocal parameter. These formulas take into account VdW interactions between adjacent tubes and the effect of terms involving differences in tube radii generally neglected in the derived expressions of the critical buckling load published in the literature. Most scientific research on modeling the effects of magnetic fields is based on beam theories, this motivation pushes me to develop a cylindrical shell model for studying the effect of the magnetic field on the static behavior of CNTs. The results show that the magnetic field has significant effects on the static behavior of CNTs and can lead to slow buckling. On the other hand, thermal effects reduce the critical buckling load. The findings in this work can help us design of CNTs for various applications (e.g. structural, electrical, mechanical and biological applications) in a thermal and magnetic environment.

• Journal of IKEEE
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• v.27 no.3
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• pp.319-326
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• 2023

In this paper, simulation and experimental results are presented, including the implementation of a digital controller for robust output voltage control of a single-phase voltage source inverters (VSIs) and total harmonic distortion (T.H.D.v) analysis. Typically, the VSIs uses a proportional integral (PI) controller for the current controller on the inner loop and a proportional resonant (PR) controller for the voltage controller on the outer loop to control the output voltage. However, non-linear loads still produce high-order odd harmonic distortion. Therefore, in this paper, a proportional multiple resonance (PMR) controller with a resonance controller for odd harmonic frequencies is proposed to suppress harmonic distortion. Analyze the frequency response of controllers for VSI plants and design PMR controllers. Through simulation, the total harmonic distortion characteristics of the output voltage are compared and verified when PI and PMR are used as voltage controllers. Both linear and non-linear loading conditions were considered. Finally, the effectiveness of the PMR controller was demonstrated by applying it to a 3kW VSIs prototype.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.2
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• pp.109-115
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• 2023

In this paper, we demonstrated the orientation characteristics of liquid crystals using UV-treated FSAM as alignment layer. Moreover we confirmed the FSAM properties before and after UV treatment on indium tin oxide (ITO) glass substrates using physicochemical analysis. The hydrophobic property of the FSAM surface is change to hydrophilic through UV treatment. After UV treatment the LC molecules also were uniformly and horizontally aligned on the FSAM surfaces and the pretilt angle was obviously changed 90° degrees to 0° degrees. EO characteristic of TN cell which was fabricated with UV-treated FSAM was faster response time compare to conventional PI layer. The FSAM before and after UV treatment has a superior application potential as the LC alignment layer for LCD, potentially replacing the conventional polyimide layer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1706-1712
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• 2022

Recently, the safety of chemical substances has gained attention due to incidents occurring in petrochemical industrial complexes, such as gas leaks and fires. In particular, industrial complexes in Ulsan and Yeosu (South Korea) are valuable as they significantly contribute to the petrochemical industry, but accidents may occur due to chemical leakage. Therefore, in this study, sensor nodes are configured at an interval of 20 [m] based on outdoor facilities standards to respond to chemical accidents, and exposure consideration of 8 h (TWA) and 15 min (STEL) are proposed in TLVs. The proposed system pre-processes data collected in multi-hop communication at a cycle of 0.6-0.75 [s] using Python and stores it in the MySQL database through SQL and a real-time remote monitoring system that updates the stored data once every 5 s is implemented by linking MySQL and Grafana.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.351-353
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• 2021

In recent years, while the demand for electricity is rapidly increasing, fire accidents due to negligence in management of switchboards. In particular, switchboards for industrial and electrical resource control can cause serious problems. Thus, for the safety management of power switchboard, a secondary response is conducted to control firing when a specific condition value is satisfied, but in this case, it is highly likely that a considerable amount of time has elapsed after firing. In this paper, we propose a method to acquire big data for the development of a switchboard temperature and power control system that can actively respond to the current situation by monitoring and learning the temperature of the switchboard's busbar connection in real time. Specifically, a method for periodically acquiring and managing data such as temperature and power from various scattered sensors is proposed.

• Journal of IKEEE
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• v.27 no.4
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• pp.494-500
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• 2023

Image processing is currently used in various fields. Among them, autonomous vehicles, medical image processing, and robot control require fast image processing response speeds. To fulfill this requirement, hardware design for real-time processing is being actively researched. In addition to the size of the input image, the hardware processing speed is affected by the size of the inactive video periods that separate lines and frames in the image. In this paper, we design three different scaler structures based on the type of line memories, which is closely related to the inactive video periods. The structures are designed in hardware using the Verilog standard language, and synthesized into logic circuits in a field programmable gate array environment using Xilinx Vivado 2023.1. The synthesized results are used for frame rate analysis while comparing standard image sizes that can be processed in real time.