• Journal of Power Electronics
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• v.19 no.3
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• pp.702-713
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• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1470-1476
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• 2020

This paper describes a design of a lightweight security system-on-chip (SoC) suitable for the implementation of security protocols for IoT and mobile devices. The security SoC using Cortex-M0 as a CPU integrates hardware crypto engines including an elliptic curve cryptography (ECC) core, a SHA3 hash core, an ARIA-AES block cipher core and a true random number generator (TRNG) core. The ECC core was designed to support twenty elliptic curves over both prime field and binary field defined in the SEC2, and was based on a word-based Montgomery multiplier in which the partial product generations/additions and modular reductions are processed in a sub-pipelining manner. The H/W-S/W co-operation for elliptic curve digital signature algorithm (EC-DSA) protocol was demonstrated by implementing the security SoC on a Cyclone-5 FPGA device. The security SoC, synthesized with a 65-nm CMOS cell library, occupies 193,312 gate equivalents (GEs) and 84 kbytes of RAM.

• Journal of Digital Convergence
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• v.19 no.6
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• pp.233-238
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• 2021

Recently, blockchain technology accumulates and stores all transactions. Therefore, in order to verify the contents of all transactions, the data itself is compressed, but the scalability is limited. In addition, since a separate verification algorithm is used for each type of transaction, the verification burden increases as the size of the transaction increases. Existing blockchain cannot participate in the network because it does not become a block sink by using a server with a low specification. Due to this problem, as the time passes, the data size of the blockchain network becomes larger and it becomes impossible to participate in the network except for users with abundant resources. Therefore, in this paper, we are improved transaction as studied the zero knowledge proof algorithm for general operation verification. In this system, the design of zero-knowledge circuit generator capable of general operation verification and optimization of verifier and prover were also conducted.

• Journal of Appropriate Technology
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• v.7 no.2
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• pp.225-234
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• 2021

The purpose of this paper is to examine commercialization model of appropriate technology through the case of the Lao-Korea Science and Technology Center (LKSTC). LKSTC has developed washing, water treatment, and sterilization technology in the agrifood sector and three types of pico-hydro generator, Pico-solar hybrid system, and energy remote monitoring technology in the renewable energy sector. Commercialization of appropriate technology was successfully carried out through the establishment of Kaipan community business, school enterprises, and social enterprise. The policy implications are as follows. First, the commercialization of appropriate technology in developing countries should enhance the linkage with the regional development policies of the recipient countries. Second, in order to minimize market risk, innovative technology development and local startup networks should be properly established. Finally, the mid and long term efforts are needed to increase the sustainability of the business.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.94-107
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• 2022

Accidents prevention and mitigation is the highest priority of nuclear power plant (NPP) operation, particularly in the aftermath of the Fukushima Daiichi accident, which has reignited public anxieties and skepticism regarding nuclear energy usage. To deal with accident scenarios more effectively, operators must have ample and precise information about key safety parameters as well as their future trajectories. This work investigates the potential of machine learning in forecasting NPP response in real-time to provide an additional validation method and help reduce human error, especially in accident situations where operators are under a lot of stress. First, a base-case SGTR simulation is carried out by the best-estimate code RELAP5/MOD3.4 to confirm the validity of the model against results reported in the APR1400 Design Control Document (DCD). Then, uncertainty quantification is performed by coupling RELAP5/MOD3.4 and the statistical tool DAKOTA to generate a large enough dataset for the construction and training of neural-based machine learning (ML) models, namely LSTM, GRU, and hybrid CNN-LSTM. Finally, the accuracy and reliability of these models in forecasting system response are tested by their performance on fresh data. To facilitate and oversee the process of developing the ML models, a Systems Engineering (SE) methodology is used to ensure that the work is consistently in line with the originating mission statement and that the findings obtained at each subsequent phase are valid.

• Journal of radiological science and technology
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• v.45 no.3
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• pp.255-262
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• 2022

In this study, by analyzing the examination time for each procedure, the appropriate workload of radiologic technologist is analyzed based on the actual examination time in the current clinical setting by comparing with the examination time in the radiology field setting of the health insurance review and assessment service. In addition, this result is introduced into the calculation of relate value units; it was attempted to provide accurate and objective evidence in the field of radiology. From May 2020 to December 2021, the study retrospectively investigated the examination times recorded in the electronic medical record and picture archiving and communication system at 5 tertiary general hospitals and 1 general hospital. The total of 16 examination parts are applied in this study, including the head, sinuses, chest, ribs, abdomen, pelvis, cervical, thoracic, lumbar, shoulder, elbow, wrist, hip, femur, knee, and ankle. The minimum number of images that could be obtained per radiation generator was 3.6 images for one hour, and the maximum was 6.4 images. When 50% median of procedure time is calculated, the minimum number of images that could be obtained was 16.7 images and maximum was 35.3 images; in addition, minimum examination time is 1.7 minutes, and maximum time is 3.6 minutes. In conclusion, it is judged that there will be insufficient explanation time for basic infection instructions such as hand hygiene during the examinations in current clinical practice. It is believed that radiologic technologists will contribute to providing higher-quality of radiation examination services to the public by complying with guidelines for work and setting appropriate workload on their own.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.4
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• pp.222-227
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• 2022

In this paper, we implemented a Korean text generation and classification model based on a deep learning algorithm that can be applied to various industries. It consists of two implemented GAN-based Korean handwriting generation models and CNN-based Korean handwriting classification models. The GAN model consists of a generator model for generating fake Korean handwriting data and a discriminator model for discriminating fake handwritten data. In the case of the CNN model, the model was trained using the 'PHD08' dataset, and the learning result was 92.45. It was confirmed that Korean handwriting was classified with % accuracy. As a result of evaluating the performance of the classification model by integrating the Korean cursive data generated through the implemented GAN model and the training dataset of the existing CNN model, it was confirmed that the classification performance was 96.86%, which was superior to the existing classification performance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.55-64
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• 2023

Gas turbine engines are widely used as prime movers of generator and propulsion system in warships. This study addresses the problem of designing a DS-based PID controller for speed control of the LM-2500 gas turbine engine used for propulsion in warships. To this end, we first derive a dynamic model of the LM-2500 using actual sea trail data. Next, the PRC (process reaction curve) method is used to approximate the first-order plus time delay (FOPTD) model, and the DS-based PID controller design technique is proposed according to approximation of the time delay term. The proposed controller conducts set-point tracking simulation using MATLAB (2016b), and evaluates and compares the performance index with the existing control methods. As a result of simulation at each operating point, the proposed controller showed the smallest in %OS, which means that the rpm does not change rapidly. In addition, IAE and IAC were also the smallest, showing the best result in error performance and controller effort.

• Journal of Wellbeing Management and Applied Psychology
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• v.5 no.4
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• pp.51-56
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• 2022

Purpose: By applying an ultrasonic mechanical device to the liquid fertilizer storage in the pig dropping treatment plant, the initial odor of the odor source is reduced, and the air dilution drainage of the complex odor is fundamentally recognized to facilitate odor treatment on the mechanical and chemical biological treatment devices at the rear. Research design, data and methodology: The odor concentration on the site boundary was measured to confirm the state of reduction. In order to prevent the spread of odor from the collection of the pig dropping treatment plant, it was measured by installing an ultrasonic generator inside the installation wall after installing the sealing wall. Results: The average value of the March and April measurement data remained close to neutral at 8.2 after 8.6 treatment before pH treatment, decreased 97.3% from 462 mg/L before SS treatment to 10.5 mg/L after treatment, and the composite odor was reduced by 85% from 20 to 3 before treatment. It was confirmed that ammonia (NH3) was reduced by 99% from 5.8 ppm to 0.09 ppm, and general bacteria were also reduced by 99% from 3,200 CFU/mL to 57 CFU/mL Conclusion: Applying the ultrasonic air ejector hybrid system and zigzag air complex module development product to resource circulation centers or sewage treatment facilities is thought to reduce inconvenience to residents due to odors caused.

• Progress in Medical Physics
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• v.33 no.4
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• pp.53-62
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• 2022

In this study, we have investigated the shielding evaluation methodology for facilities using kV energy generators. We have collected and analysis of safety evaluation criteria and methodology for overseas facilities using radiation generators. And we investigated the current status of shielding evaluation of domestic industrial radiation generators. According to the statistical data from the Radiation Safety Information System, as of 2022, a total of 7,679 organizations are using radiation generating devices. Among them, 6,299 facilities use these devices for industrial purposes, which accounts for a considerable portion of radiation. The organizations that use these devices evaluate whether the exposure dose for workers and frequent visitors is suitable as per the limit regulated by the Nuclear Safety Act. Moreover, during this process, the safety shields are evaluated at the facilities that use the radiation generating devices. However, the facilities that use radiating devices having energy less than or equal to 6 MV for industrial purposes are still mostly evaluated and analyzed according to the National Council on Radiation Protection and Measurements 49 (NCRP 49) report published in 1976. We have investigated the technical standards of safety management, including the maximum permissible dose and parameters assessment criteria for facilities using radiation generating devices, based on the NCRP 49 and the American National Standards Institute/Health Physics Society N.43.3 reports, which are the representative reports related to radiation shielding management cases overseas.