• Journal of Power Electronics
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• v.19 no.1
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• pp.168-178
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• 2019

Discrete space vector modulation (DSVM) is an effective method to improve the steady-state performance of the finite control set predictive control for permanent magnet synchronous motor drive systems. However, it requires complex computations due to the presence of numerous virtual voltage vectors. This paper proposes an improved finite control set model-free predictive control using DSVM to reduce the computational burden. First, model-free deadbeat current control is used to generate the reference voltage vector. Then, based on the principle that the voltage vector closest to the reference voltage vector minimizes the cost function, the optimal voltage vector is obtained in an effective way which avoids evaluation of the cost function. Additionally, in order to implement double-objective control, a two-level decisional cost function is designed to sequentially reduce the stator currents tracking error and the inverter switching frequency. The effectiveness of the proposed control is validated based on experimental tests.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.14-17
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• 2022

Due to the development of IT technology and the on-going Coronavirus disease, non-face-to-face services have been activated. To overcome the inconvenience of non-face-to-face service, service providers have adopted chatbots as a way to feel like a human being. As the increasing chatbot services, chatbot builders have emerged, which can help non-developers to build them. Although its popularity has increased, its performance evaluation has not been conducted on such chatbot builders. In this paper, we implement a prototype chatbot that classifies hospital departments in the medical field using Dialogflow and Rasa, which are popular chatbot builders. By measuring the accuracy of the chatbot's classification of medical subjects, we evaluated the level of accuracy that the most used chatbot builder can have when they are used to build a chatbot service. The simulation results showed that Dialogflow had 87%, 65%, and 60%, and Rasa did 64%, 70%, and 63% in surgery dermatology, and otolaryngology, respectively.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2120-2134
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• 2022

A hypothetical core destructive accident (HCDA) has received widespread attention as one of the most serious accidents in sodium-cooled fast reactors. This study combined recent advantages in numerical methods to realize realistic modeling of the complex fluid-structure interactions during HCDAs in a full-scale sodium-cooled fast reactor. The multi-material arbitrary Lagrangian-Eulerian method is used to describe the fluid-structure interactions inside the container. Both the structural deformations and plug rises occurring during HCDAs are evaluated. Two levels of expansion energy are considered with two different reactor models. The simulation results show that the container remains intact during an accident with small deformations. The plug on the top of the container rises to an acceptable level after the sealing between the it and its support is destroyed. The methodology established in this study provides a reliable approach for evaluating the safety feature of a container design.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.503-508
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• 2020

The three-dimensional precision numerical analysis was performed using the finite element model applied with the railway track model consisting of rails, As a result of analyzing the track deformation level of the existing tunnel due to the excavation work adjacent to the urban transit, it was found that the evaluation criteria (allowed values) of conventional railways lines were satisfied. Based on the numerical analysis, it was analyzed that the results of the prediction of the tunnel structural stability of due to the excavation work and the level of the tunnel deformation occurring at the actual site could be approximated as closely as possible.

• Applied Biological Chemistry
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• v.40 no.5
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• pp.433-437
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• 1997

The jujube alcoholic beverage, one of Korean traditional wine was manufactured by varying the additional levels of jujube fruits from 1.89 to 7.57% on the basis of raw material and the quality of wine was anaylzed by physical, chemical and sensory evaluation. Fermentation temperature of wines Increased to the highest value of $24{\sim}26^{\circ}C$ in the 2nd day of fermentation. Jujube fruits effected the increase in total acid contents. Both reducing and total sugar contents were on the peak values of $13{\sim}53%$ and $43{\sim}51%$ after the 2nd brewing stage$(1{\sim}1.5day) and continuously decreased afterwards. Ethyl alcohol concentrations were rapidly increased In $1{\sim}3days$ of fermentation and their increasing rates were affected with the added amount of jujube. Amylase activity was on the highest value in $2{\sim}2.5{\;}days$ and decreased afterwards. According to the sensory evaluation of the overall quality Dacchusul could be classified into 2 groups. The superior group was composed of E, C, B, D and the inferior group included A and F. However the highest sensory quality was observed from E which was added at the level of 7.57% jujube fruit.

• The Journal of the Convergence on Culture Technology
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• v.5 no.4
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• pp.401-406
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• 2019

The three-dimensional precision numerical analysis was performed using the finite element model applied with the railway track model consisting of rails, sleepers, and track elastic springs(ballast, rail pad). As a result of analyzing the track deformation level of the existing tracks due to the excavation work adjacent to the railway facilities, it was found that the track irregularity evaluation criteria (allowed values) of both conventional and high-speed railways lines were satisfied. Based on the numerical analysis using the track model, it was analyzed that the results of the prediction of the track irregularity due to the excavation work and the level of the track deformation occurring at the actual site could be approximated as closely as possible.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.10-22
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• 2022

According to the Space Development Promotion Basic Plan, more than 110 satellites are expected to be deployed by 2031. Accordingly, the operation concept and technology for satellites constellation are required, compared to the existing few multi-satellite operations. It is essential to automate and optimize the mission operation system, for efficient operation of the satellite constellation, and preparations are urgently needed for the operation of satellite constellation in domestic as well. In this study, the development direction and strategy of the mission operation system applying automation and optimization for efficient operation of the satellite constellation are proposed. The framework for evaluating the automation level and priority of the mission operation system was developed, to identify the tasks to which automation should be applied preferentially.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3950-3960
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• 2024

As a solution to the problem of spent nuclear fuels (SNFs), the disposal of SNF has gained attention from nations using nuclear energy because of hazards posed to the ecosystem. Among many proposed solutions, the most promising method is to dispose of SNF in a deep geological repository (DGR) which utilizes the multi-barrier concept developed by Finland and Sweden. Here, a new fully-coupled Thermal-Hydraulic (TH) code HADES (High-level rAdionuclide Disposal Evaluation Simulator) is developed using the MOOSE framework. This new code suggests basic numerical tools, such as a non-linear solver and finite element discretization, to assess the safety performance of disposal systems. The new TH code considered various TH behavior using Richards' flow approach, assuming gas pressure is constant. The HADES showed promising results when it was compared to various TH codes validated from DECOVAELX-THMC projects. When the single-canister model was utilized to estimate the TH behavior of the Korean Reference disposal System, although it showed significant saturation reduction due to the evaporation of water, the temperature was maintained under the thermal criteria limit, which is 100 ℃. In addition, the new code estimated temperature and degree of saturation of the multi-canisters model, considering two or three canisters, it showed a slightly lower temperature, 5 ℃, than the single-canister model. From these results, the following are concluded: (1) the new TH code contribute to an additional integrity by estimating TH behavior of KRS; (2) however, due to limitations in single-canister simulation, it is recommended to use multi-canisters simulation to estimate TH behavior accurately. Therefore, this model is anticipated not only to help licensing applications and estimation of various multi-physics phenomena and multi-canister at the disposal site.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.5
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• pp.277-284
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• 2012

To meet the usage of discrete wavelet transform (DWT) on potable devices, this paper implements 2-level DWT using a reference many-core processor architecture and determine the optimal many-core processor. To explore the optimal many-core processor, we evaluate the impacts of a data-per-processing element ratio that is defined as the amount of data mapped directly to each processing element (PE) on system performance, energy efficiency, and area efficiency, respectively. This paper utilized five PE configurations (PEs=16, 64, 256, 1,024, and 4,096) that were implemented in 130nm CMOS technology with a 720MHz clock frequency. Experimental results indicated that maximum energy and area efficiencies were achieved at PEs=1,024. However, the system area must be limited 140mm2 and the power should not exceed 3 watts in order to implement 2-level DWT on portable devices. When we consider these restrictions, the most reasonable energy and area efficiencies were achieved at PEs=256.

• Asian Journal for Public Opinion Research
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• v.4 no.4
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• pp.246-259
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• 2017

The purpose of this study is to evaluate the effects of critical friends on self-esteem and the academic oral presentation ability of undergraduate students. A pretest was conducted in the first week of the semester. A pre-academic oral presentation preparation was held from the second week to the seventh week and followed by pedagogical speech activities from the eighth week to the eleventh week. The research instruments are Academic oral presentation behavior and self-esteem evaluation forms. The samples were 37 third year undergraduate students, who were purposively selected from the educational technology class at the Chulalongkorn University. The statistics used for analyzing quantitative data are frequencies, means, standard deviations, one sample t-tests, and Pearson's Product-Moment Correlations. It was found that the 37 third year undergraduate teacher students had higher self-esteem at the statistically significant level of .05 and academic oral presentation scores after the activity were statistically significant at the .05 level.