• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.294-305
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• 2022

Recently, drones have been widely used to solve environmental problems such as environmental protection and natural disaster monitoring. This study focuses on the problem of the search altitude of drones when using drones to search for air pollution in order to maintain the urban air environment. In particular, when exploring air pollution in cities using drones, various experiments are conducted to determine the appropriate search altitude for each air pollution source and each communication module. Through the experiment, the maximum measurable altitude for the most common air pollutants, such as CO (carbon monoxide), NO₂ (nitrogen dioxide), O₃ (ozone), and P10, P2.5 (fine dust), was identified, and the effective search altitude for each air pollution source was determined. As a result of the experiment, three types of drone search altitudes including legally measurable altitudes were suggested. The communication module measurable altitude was 60m to 120m depending on the communication module, and the effective measurable altitude was analyzed from 10m to 100m.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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• pp.1640-1648
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• 2014

This paper proposes a switching frequency reduction method for MMC (Modular Multilevel Converter) utilizing redundancy operation of sub-module, which can offer reduction of voltage harmonics and switching loss. The feasibility of proposed method was verified through computer simulations with PSCAD/EMTDC software. Based on simulation analysis, a hardware scaled-model of 10kVA, DC-1000V MMC was designed and manufactured in the lab. Various experiments were conducted to verify the feasibility of proposed method in the actual hardware system. The hardware scaled-model can be effectively utilized for analyzing the performance of MMC according to the modulation scheme and redundancy operation.

• Journal of Multimedia Information System
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• v.8 no.4
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• pp.203-210
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• 2021

Deep leaning convolutional neural networks (CNN) have successfully been applied to image super-resolution (SR). Despite their great performances, SR techniques tend to focus on a certain upscale factor when training a particular model. Algorithms for single model multi-scale networks can easily be constructed if images are upscaled prior to input, but sub-pixel convolution upsampling works differently for each scale factor. Recent SR methods employ multi-scale and multi-path learning as a solution. However, this causes unshared parameters and unbalanced parameter distribution across various scale factors. We present a multi-scale single-path upsample module as a solution by exploiting the advantages of sub-pixel convolution and interpolation algorithms. The proposed model employs sub-pixel convolution for the highest scale factor among the learning upscale factors, and then utilize 1-dimension interpolation, compressing the learned features on the channel axis to match the desired output image size. Experiments are performed for the single-path upsample module, and compared to the multi-path upsample module. Based on the experimental results, the proposed algorithm reduces the upsample module's parameters by 24% and presents slightly to better performance compared to the previous algorithm.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2113-2119
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• 2024

This study presents the development and characterization of a prototype TL/OSL reader for the retrospective dose assessment of individuals in radiological emergencies. The reader is portable, semi-automatic, and capable of accurate measurements. The dimension of the reader is 25 × 25 × 37 cm³ and the weight is about 15 kg. The reader consists of a sample moving stage, a heating module, an optical stimulation module, a detection module, a data acquisition (DAQ) unit, a nitrogen gas control module, and a PC with a GUI program. The reader has three measurement modes: TL, CW_OSL, and custom mode. The reader was characterized using commercial thermal luminescence dosimeters (TLD, LiF:Mg,Cu,Si) and optically stimulated dosimeters (OSLD, Al₂O₃:C), as well as fortuitous materials, such as display glasses and resistors of mobile phone. The results showed that the reader is capable of measuring signals with a detection limit of up to 0.02 mGy using a commercial dosimeter. In the dose recovery test using fortuitous materials, the reconstructed doses obtained three days post-irradiation closely aligned with the initially administered doses. As a result, this study suggests that the developed TL/OSL reader is a promising instrument for emergency dose assessment at accident sites.

• Journal of the Korean Mathematical Society
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• v.59 no.4
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• pp.733-756
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• 2022

In this paper, we introduce the notion of Gorenstein quasiresolving subcategories (denoted by 𝒢𝒬𝓡_𝒳 (𝓐)) in term of quasi-resolving subcategory 𝒳. We define a resolution dimension relative to the Gorenstein quasi-resolving categories 𝒢𝒬𝓡_𝒳 (𝓐). In addition, we study the stability of 𝒢𝒬𝓡_𝒳 (𝓐) and apply the obtained properties to special subcategories and in particular to modules categories. Finally, we use the restricted flat dimension of right B-module M to characterize the finitistic dimension of the endomorphism algebra B of a 𝒢𝒬_𝒳-projective A-module M.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.4
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• pp.262-275
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• 2012

This paper develops a multistage scheduling algorithm for the module operation of the LCD(Liquid Crystal Display) production systems and tests the efficiency of the proposed algorithm. The module operation is a multistage form composed of multiple sub operations of processes, and each stage is consists of multiple lines with the same kinds of machines. This paper presents a mathematical modeling reflecting the constraints of the LCD module operation and develops a multistage scheduling algorithm based on tabu search metaheuristic approach. For this purpose, an production order is assigned to a line of the sub operations and a sequence of the assigned order is rearranged to draw an efficient schedule. Simulation experiments test performance measures and show the efficiency of the proposed algorithm.

• Bulletin of the Korean Mathematical Society
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• v.57 no.3
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• pp.691-707
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• 2020

In this paper, we introduce and study the notions of weakly ⊕-supplemented modules, weakly D2 modules and weakly D2-covers. A right R-module M is called weakly ⊕-supplemented if every non-small submodule of M has a supplement that is not essential in M, and module M_R is called weakly D2 if it satisfies the condition: for every s ∈ S and s ≠ 0, if there exists n ∈ ℕ such that sⁿ ≠ 0 and Im(sⁿ) is a direct summand of M, then Ker(sⁿ) is a direct summand of M. The class of weakly ⊕-supplemented-modules and weakly D2 modules contains ⊕-supplemented modules and D2 modules, respectively, and they are equivalent in case M is uniform, and projective, respectively.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.33-33
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• 2017

본 연구는 온실 $CO_2$ 공급용 Membrane Module이 대기 중 $CO_2$를 포집하는 과정에서 유해병원균을 제거할 수 있는지 알아보기 위해 실험을 진행하였다. 본 실험은 Membrane Module과 유해병원균의 유무로 총 4개의 실험구, 포집하는 시간에 따라 1 min, 3 min, 5 min, 각각 3회씩, 총 36회의 실험을 진행하였다. 실험은 경상대학교 내 온실($W{\times}D{\times}H$, $3000{\times}4000{\times}2500mm$)에서 진행하였고, 유해병원균은 잎점무늬병을 일으키는 병원균(Phoma sp.)을 사용하였다. 온실에 Membrane System을 설치하고 Membrane Module을 통해 외부공기 또는 유해병원균이 포함된 공기를 분리하여 온실 내로 공급하고, 공급한 $CO_2$ 내에 유해병원균의 유무는 에어샘플러를 이용하여 온실 내의 공기를 포집 후 배지에 배양하여 확인하였다. 유해병원균은 PDA배지를 이용하여 포집한 뒤 항온항습기(HB-105SG-O, HANBAEK SCIENTIFIC CO., Korea)에 $25^{\circ}C$, 50%로 48시간 배양하였다. PDA배지 내에 배양된 미생물은 Colony Counter(HYC-560, CORETECH, Korea)로 측정하였다. 결과 값을 분석하기 위해서 IBM SPSS Statistics의 이원분산분석(two-way ANOVA)을 이용하여 통계분석 하였다. 결과 값은 유해병원균을 공급하고 Membrane Module을 사용하지 않았을 때, CFU(Colony-Forming Unit)가 가장 높았고, 유해병원균을 공급하고 Membrane Module을 사용했을 때 CFU가 가장 낮았다. 통계분석을 실시한 결과, Membrane Module을 사용하지 않은 실험구에는 유의한 차이가 나타났고, Membrane Module을 사용한 실험구에는 유의한 차이가 나타나지 않았다. 따라서 Membrane Module이 대기 중 $CO_2$를 분리하여 온실에 공급하는 과정에서 공기 중에 포함된 유해병원균을 제거 할 수 있다고 판단된다.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.36-42
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• 2001

This paper presents the operational planning systems of automated container terminals. The proposed system is composed of berth allocation module, yard planning module, resource allocation module, sequencing module, and simulation module. All the sub-modules except resource allocation module are built into integrated simulation model using simulation package AutoMod. Simulation experiments are performed according to the number of AGVs and AGV allocation policies.

• Tribology and Lubricants
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• v.36 no.3
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• pp.153-160
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• 2020

In this paper, we present a hydrostatic bearing design and rotordynamic analysis of a pump-and-drive turbine module for a 250-kW supercritical CO₂ cycle application. The pump-and-drive turbine module consists of the pump and turbine wheel, assembled to a shaft supported by two hydrostatic radial and thrust bearings. The rated speed is 21,000 rpm and the rated power is 143 kW. For the bearing operation, we use high-pressure CO₂ as the lubricant, which is supplied to the bearing through the orifice restrictor. We calculate the bearing stiffness and flow rate for various orifice diameters, and then select the diameter that provides the maximum bearing stiffness. We also conduct a rotordynamic analysis based on the design parameters of the pump-and-drive turbine module. The predicted Campbell diagram shows that there is no critical speed below the rated speed, owing to the high stiffness of the bearings. Furthermore, the predicted damping ratio indicates that there is no unstable mode. We conduct the operating tests for the pump and drive turbine modules within the supercritical CO₂ cycle test loop. The pressurized CO₂, at a temperature of 136℃, is supplied to the turbine and we monitor the shaft vibration during the test. The test results show that there is no critical speed below the rated speed, and the shaft vibration is controlled to below 3 ㎛.