• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.6
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• pp.479-486
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• 2021

In this paper, an ultra small phase locked loop (PLL) with a single capacitor loop filter has been proposed by adding a signal sensing circuit (SSC). In order to extremely reduce the size of the PLL, the passive element loop filter, which occupies the largest area, is designed with a very small single capacitor (2pF). The proposed PLL is designed to operate stably by the output of the internal negative feedback loop including the SSC acting as a negative feedback to the output of the single capacitor loop filter of the external negative feedback loop. The SSC that detects the PLL output signal change reduces the excess phase shift of the PLL output frequency by adjusting the capacitance charge of the loop filter. Although the proposed structure has a capacitor that is 1/78 smaller than that of the existing structure, the jitter size differs by about 10%. The PLL is designed using a 1.8V 180nm CMOS process and the Spice simulation results show that it works stably.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.578-592
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• 2021

This study performed to investigate the propagation characteristics of overpressure, impulse, vibration in underwater blasting. The difference between air blasting and underwater blasting is that noise and vibration propagate through water as a medium. In some cases, the noise and vibration propagates through various media (rock, water, air, etc.). In this study, the underwater blasting was simulated using AUTODYN, and the propagation characteristics of overpressure, impulse and vibration induced by blasting were analyzed. We mainly focused on the effect of mesh size on the overpressure, impulse and peak particle velocity from the underwater blasting simulation. The numerical results indicated that the overpressure and peak particle velocity tended to decrease as the mesh size increased, while the impulse increased with the mesh size. The results also indicated that the mesh dependence varied depending on the explosive charge and scaled distance.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.3
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• pp.7-18
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• 2022

Secondary batteries used in electric vehicles have a potential risk of ignition and explosion. Various safety measures are being taken to prevent these risks. A numerical study was performed using a computational fluid dynamics code on the cases where pressure relief vents that can reduce the blast overpressures of batteries were installed in the through-compression test room, short-circuit drop test room, combustion test room, and immersion test room in facilities rleated to battery used in electric vehicles. This study was conducted using the weight of TNT equivalent to the energy release from the battery, where the the thermal runaway energy was set to 324,000 kJ for the capacity of the lithium-ion battery was 90 kWh and the state of charge (SOC) of the battery of 100%. The explosion energy of TNT (△H_TNT) generally has a range of 4,437 to 4,765 kJ/kg, and a value of 4,500 kJ/kg was thus used in this study. The dimensionless explosion efficiency coefficient was defined as 15% assuming the most unfavorable condition, and the TNT equivalent mass was calculated to be 11 kg. The internal explosion generated in a test room shows the very complex propagation behavior of blast waves. The shock wave generated after the explosion creates reflected shock waves on all inner surfaces. If the internally reflected shock waves are not effectively released to the outside, the overpressures inside are increased or maintained due to the continuous reflection and superposition from the inside for a long time. Blast simulations for internal explosion targeting four test rooms with pressure relief vents installed were herein conducted. It was found that that the maximum blast overpressure of 34.69 bar occurred on the rear wall of the immersion test room, and the smallest blast overpressure was calculated to be 3.58 bar on the side wall of the short-circuit drop test room.

• Korean Journal of Artificial Intelligence
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• v.9 no.1
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• pp.1-7
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• 2021

In this paper, We focused the issue of creating a socially problematic nurse schedule. The nurse schedule should be prepared in consideration of three shifts, appropriate placement of experienced workers, the fairness of work assignment, and legal work standards. Because of the complex structure of the nurse schedule, which must reflect various requirements, in most hospitals, the nurse in charge writes it by hand with a lot of time and effort. This study attempted to automatically create an optimized nurse schedule based on legal labor standards and fairness. We developed an I/O Q-Learning algorithm-based model based on Python and Web Application for automatic nurse schedule. The model was trained to converge to 100 by creating an Fairness Indicator Score(FIS) that considers Labor Standards Act, Work equity, Work preference. Manual nurse schedules and this model are compared with FIS. This model showed a higher work equity index of 13.31 points, work preference index of 1.52 points, and FIS of 16.38 points. This study was able to automatically generate nurse schedule based on reinforcement Learning. In addition, as a result of creating the nurse schedule of E hospital using this model, it was possible to reduce the time required from 88 hours to 3 hours. If additional supplementation of FIS and reinforcement Learning techniques such as DQN, CNN, Monte Carlo Simulation and AlphaZero additionally utilize a more an optimized model can be developed.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.191-196
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• 2023

In this paper, for the application of ultrasonic cleaners for cleaning dentures and transparent braces, Pb(Mn_1/3Nb_2/3)O₃-Pb(Ni_1/3 Nb_2/3)O₃-Pb(Zr,Ti)O₃ [PMN-PNN-PZT] system ceramics were manufactured and their dielectric and piezoelectric properties were investigated. Overall the best properties suitable for the device applications such as ultrasonic cleaner were obtained from the ceramics sintered at 920℃: bulk density of 7.8 g/cm³, the dielectric constant (ε_r) of 1,689, piezoelectric charge constant (d₃₃) of 433 pC/N, planar electromechanical coupling factor (k_p) of 0.64, mechanical quality factor (Qm) of 835, S₁₁^E of 13.37 (10^-12 N/m²), and Curie temperature of 315℃ By using the physical properties of this composition, the ultrasonic cleaner was designed and simulated using the commercial ATILA software. For the three-layered ceramics with the dimension of 25 mm × 25 mm × 2.5mm, an excellent displacement of 8.998 10^-3 m) and the sound pressure of 147.68 dB were recorded.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.769-776
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• 2023

In this paper, we designed an MLSA(Match-line Sense Amplifier) for low-power CAM(Content Addressable Memory). By using the MLSA and precharge controller, we reduced power consumption during CAM operation by employing a selective match-line charging technique to mitigate power consumption caused by mismatch. Additionally, we further reduced power consumption due to leakage current by terminating precharge early when a mismatch occurs during the search operation. The designed circuit exhibited superior performance compared to the existing circuits, with a reduction of 6.92% and 23.30% in power consumption and propagation delay time, respectively. Moreover, it demonstrated a significant decrease of 29.92% and 52.31% in product-delay-product (PDP) and energy-delay-product (EDP). The proposed circuit was validated using SPECTRE simulation with TSMC 65nm CMOS process.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2021-2030
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• 2017

In this paper, the unipolar corona-needle charger was developed and its capabilities were both numerically and experimentally investigated. The experimental corona discharges and particle losses in the charger were obtained at different corona voltage, aerosol flow rate and particle diameter for positive and negative coronas. Inside the charger, the electric field and charge distribution and the transport behavior of the charged particle were predicted by a numerical simulation. The experimental results yielded the highest ion number concentrations of about $1.087{\times}10^{15}ions/m^3$ for a positive corona voltage of about 3.2 kV, and $1.247{\times}10^{16}ions/m^3$ for a negative corona voltage of about 2.9 kV, and the highest $N_it$ product for positive and negative coronas was found to about $7.53{\times}10^{13}$ and $8.65{\times}10^{14}ions/m^3$ s was occurred at the positive and negative corona voltages of about 3.2 and 2.9 kV, respectively, and the flow rate of 0.3 L/min. The highest diffusion loss was found to occur at particles with diameter of 30 nm to be about 62.50 and 19.33 % for the aerosol flow rate of 0.3 and 1.5 L/min, respectively, and the highest electrostatic loss was found to occur at particles with diameters of 75 and 50 nm to be about 86.29 and 72.92 % for positive and negative corona voltages of about 2.9 and 2.5 kV, respectively. The numerical results for the electric field distribution and the charged particles migration inside the charger were used to guide the description of the electric field and the behavior of charged particle trajectories to improve the design and refinement of a unipolar corona-needle charger that otherwise could not be seen from the experimental data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.49-60
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• 2005

The Back Bone of gearing portion between Core Network System which is used in wire and wireless system is No.7 Protocol. ISUP( ISDN User Part), INAP handling in Intelligent Network and MAP gearing method for linking each Network Element System in mobile network have use of No.7 signaling. Therefore, it is require for system to detect the problem - operating problem occurs in Core Network which use No.7 signaling or the existing problem that is not recognized - in shortest time. This paper study out analyzing and measuring system for No.7 protocol and analyzing out system whether out of order or not. It can abstract No.7 Signaling Message and analyze system performance and report it. This system is connected in system No.7 HW Module which is in charge of No.7 Signaling. It is not offer Emulator function and Simulation function for any scenario but offer monitoring No.7 signaling. This system perform the function about No.7 MTP, ISUP, INAP and MAP and is offered several wire and wireless network Operator. It can detect and correct SW system, HW system and operating system problem. From now on, this system may offer the function about A-interface which is gearing between BSC and MSC, so it will perform to analyze generally and prompt effective operating for Core Network system.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.359-365
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• 2021

A heavy particle accelerator is a device that accelerates particles using high energy and is used in various fields such as medical and industrial fields as well as research. However, secondary neutrons and particle fragments are generated by the high-energy particle beam, and among them, the neutrons do not have an electric charge and directly interact with the nucleus to cause radiation of the material. Quantitative evaluation of the radioactive material produced in this way is necessary, but there are many difficulties in actual measurement during or after operation. Therefore, this study compared and evaluated the generated radioactive material in the concrete shield for protons and carbon ions of specific energy by using the simulation code FLUKA. For the evaluation of each energy of proton beam and carbon ion, the reliability of the source term was secured within 2% of the relative error with the data of the NASA Space Radiation Laboratory(NSRL), which is an internationally standardized data. In the evaluation, carbon ions exhibited higher neutron flux than protons. Afterwards, in the evaluation of radioactive materials under actual operating conditions for disposal, a large amount of short-lived beta-decay nuclides occurred immediately after the operation was terminated, and in the case of protons with a high beam speed, more radioactive products were generated than carbon ions. At this time, radionuclides of ⁴⁴Sc, ³H and ²²Na were observed at a high rate. In addition, as the cooling time elapsed, the ratio of long-lived nuclides increased. For nonparticulate radionuclides, ³H, ²²Na, and for particulate radionuclides, ⁴⁴Ti, ⁵⁵Fe, ⁶⁰Co, ¹⁵²Eu, and ¹⁵⁴Eu nuclides showed a high ratio. In this study, it is judged that it is possible to use the particle accelerator as basic data for facility maintenance, repair and dismantling through the prediction of radioactive materials in concrete according to the cooling time after operation and termination of operation.