• Current Optics and Photonics
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• v.2 no.5
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• pp.474-481
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• 2018

We propose a polarization phase-shifting technique to investigate the thickness of $Ta_2O_5$ thin films deposited on BK7 substrates, using a modified Sagnac interferometer. Incident light is split by a polarizing beam splitter into two orthogonal linearly polarized beams traveling in opposite directions, and a quarter-wave plate is inserted into the common path to create an unbalanced phase condition. The linearly polarized light beams are transformed into two circularly polarized beams by transmission through a quarter-wave plate placed at the output of the interferometer. The proposed setup, therefore, yields rotating polarized light that can be used to extract a relative phase via the self-reference system. A thin-film sample inserted into the cyclic path modifies the output signal, in terms of the phase retardation. This technique utilizes three phase-shifted intensities to evaluate the phase retardation via simple signal processing, without manual adjustment of the output polarizer, which subsequently allows the thin film's thickness to be determined. Experimental results show that the thicknesses obtained from the proposed setup are in good agreement with those acquired by a field-emission scanning electron microscope and a spectroscopic ellipsometer. Thus, the proposed interferometric arrangement can be utilized reliably for non-contact thickness measurements of transparent thin films and characterization of optical devices.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.597-606
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• 2021

Due to the characteristics of the farmland in Korea, forward and reverse shift is the most used. The fatigue of farmers is caused by forward and reverse shifting with a manual transmission. Therefore, it is necessary to improve the convenience of forward and backward shifting. This study was a basic study on the development of a current control system for forward and reverse shifting of agricultural tractors using proportional control valves and a controller. A test bench was fabricated to evaluate the current control accuracy of the control system, and the stability of the controller was evaluated through CPU (central processing unit) load measurements. A controller was selected to evaluate the stability of the proportional valve controller. The stability evaluation was performed by comparing and analyzing the command current of the controller and the actual current measured. The command current was measured using a CAN (controller area network) communication device and DAQ (data acquisition). The actual current was measured with a current probe and an oscilloscope. The control system and stability evaluation was performed by measuring the CPU load on the controller during control operations. The average load factor was 12.27%, and when 5 tasks were applied, it was shown to be 70.65%. This figure was lower than the CPU limit of 74.34%, when 5 tasks were applied and was judged to be a stable system.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.4
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• pp.457-466
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• 2021

This paper describes the design of model-based fault diagnosis software to apply to the propulsion system in tracked amphibious assault vehicle which consists of an engine, a transmission, a cooling system, and two waterjets. This software includes specific functions to detect the failures regarding sensor malfunctions, mechanical malfunctions, control errors, and communication errors. This software generates the proper malfunction codes which are classified as the warning and caution. In order to validate the fault diagnosis software, the manual and automatic test are performed using the test program with 32 test cases. Test results show that the designed fault diagnosis software is reliable and effective for applying to the propulsion system.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.1
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• pp.37-43
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• 2022

Drones, one of the 4th industrial technologies that are expanding from military use to industrial use, are being actively used in the search missions of the National Police Agency and finding missing persons, thereby reducing interest in a wide area and the input of large-scale search personnel. However, legal review of police drone operation is continuously required, and the importance of advanced system for related operations and analysis of captured images in connection with search techniques is increasing at the same time. In this study, in order to facilitate recording, preservation, and monitoring in the concept of precise search and monitoring, it is possible to achieve high efficiency and secure golden time when precise search is performed by constructing spatial information based on photo rather than image data-based search. Therefore, we intend to propose a spatial information construction technique that reduces the resulting data volume by adjusting the unnecessary spatial information completion rate according to the size of the subject. Through this, the scope of use of drone search missions for large-scale areas is advanced and it is intended to be used as basic data for building a drone operation manual for police searches.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.525-530
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• 2024

The need for an environmental monitoring system that obtains and provides environmental information in real time is increasing. In particular, in the case of water quality management in public waters, regular management must be conducted through manual and automatic measurement by law, and air pollution also requires regular measurement and management to reduce fine dust and exhaust gas in connection with the realization of carbon neutrality. In this study, we implemented a system that can measure and monitor water pollution and air pollution information in real time. A hovercraft capable of moving on land and water simultaneously was used as a measurement tool. Water quality measurement and air pollution measurement sensors were installed on the hovercraft body, and a communication module was installed to transmit the information to the monitoring system in real time. The structure of a hovercraft for environmental measurement was designed, and a LoRa module capable of low-power, long-distance communication was applied as a real-time information transmission communication module. The operational performance of the proposed system was confirmed through actual hardware implementation.

• Clinical Endoscopy
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• v.55 no.5
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• pp.674-682
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• 2022

Background/Aims: Endoscopic channels are difficult to clean and can cause infection transmission. We examined the effectiveness of a newly developed channel-cleaning ball brush (BB), which is sucked into the endoscopic channel and scrapes and cleans the lumen as it passes through. Methods: The upper and lower gastrointestinal endoscopes used for patient examinations were randomly selected as the conventional brush (CB) or BB group. After manual cleaning, the presence or absence of carbohydrates, proteins, adenosine triphosphate, and hemoglobin was assessed. Results: Fifty-six and 58 endoscopes were cleaned with the CB and BB, respectively. Carbohydrate and protein were detected in one (1.8%) and two endoscopes (3.4%) in the CB and BB groups, respectively (p=1.000). Hemoglobin was observed in one (1.8%) and three endoscopes (5.2%) in the CB and BB groups, respectively (p=0.636). The adenosine triphosphate levels were 10.6±15.9 and 12.5±14.3 relative light units in the CB and BB groups, respectively (p=0.496). Twenty-seven (48.2%) and 19 (32.8%) endoscopes were positive for microbial cultures in the CB and BB groups, respectively (p=0.136). Conclusions: The efficacy of BB was not significantly different from that of CB in the endoscopic channel-cleaning process.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.1
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• pp.1-9
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• 2020

Objectives: The purpose of this case study is to assess workers' exposure to carbon nanotubes(CNTs) and characterize particles aerosolized during the process of producing CNT-enabled polytetrafuoroethylene(PTFE) composites at a worksite in Korea. Methods: Personal breathing zone and area samples were collected for determining respirable concentrations of elemental carbon(EC) using NIOSH(National Institute for Occupational Safety and Health) Method 5040. Personal exposure to nano-sized particles was measured as the number concentration and mean diameter using personal ultrafine particle monitors. The number concentration by particle size was measured using optical particle sizers(OPS) and scanning mobility particle sizers(SMPS). Transmission electron microscopy (TEM) area samples were collected on TEM grids and analyzed to characterize the size, morphology, and chemistry of the particles. Results: Respirable EC concentrations ranged from 0.04 to 0.24 ㎍/㎥, which were below 23% of the exposure limit recommended by NIOSH and lower than background concentrations. Number concentrations by particle size measured using OPS and SMPS were not noticeably elevated during CNT-PTFE composite work. Instant increase of number concentrations of nano-sized particles was observed during manual sanding of CNT-PTFE composites. Both number concentrations and mean diameters did not show a statistically significant difference between workers handing CNT-added and not-added materials. TEM analyses revealed the emission of free-standing CNTs and CNT-PTFE aggregate particles from the powder supply task and composite particles embedded with CNTs from the computer numerical control(CNC) machining task with more than tens of micrometers in diameter. No free-standing CNT particles were observed from the CNC machining task. Conclusions: Significant worker exposure to respirable CNTs was not found, but the aerosolization of CNTs and CNT-embedded composite particles were observed during handing of CNT-PTFE powders and CNC machining of CNT-PTFE composites. Considering the limited knowledge on the toxicity of CNTs and CNT composite particles to date, it seems prudent to take a precautionary approach for the protection of workers' health.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.2
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• pp.107-115
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• 2011

Purpose: To design and fabricate the distributed auto edging machine for the development. Methods: We got the necessary data needed in design by using CAD. Based on the these data, we fabricated the trial product for the development of the distributed auto edging machine. Results: The patternless mode could be operated by receiving the eyesize data from the auto lay-outer with the RS232C transmission system and the pattern mode could be operated by setting the pattern on the left side of the machine. The distributed auto edging machine were composed with combinations of many elements; head, auto arm, pattern clamp and grinding wheels. The head part controlled the grinding of ophthalmic lens by operating the vertical and horizontal motors. The wheels part was comprised of glass mode, plastic mode, V-bevel mode and polish mode. The slide in the auto arm was equipped on the below of the patten and the slide could hold up the pattern which was rotated by fixed shaft. The pattern clamp could move the head part to the up and down or right or left way by the manual operation of optometrists. Conclusions: We could succeed in making the trial product by applying it to the development of the distributed auto edging machine which could be used as the patternless mode and pattern mode, selectively. Therefore, it was confidently expected that this product was very helpful for the optometrists to dispense the ophthalmic lens because of its cost-efficiency and convenience.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.180-198
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• 2019

In recent years, countries like Europe and Japan have been involved in many researches on the Low-Crested Structure (LCS) which is the method to protect beach erosion and it is regarded as an alternative to the submerged breakwaters, and compiled its results and released the design manual. In the past, studies on LCS have focused on two-dimensional wave transmission and calculating required weight of armor units, and these were mainly examined and discussed based on experiments. In this study, three-dimensional numerical analysis is performed on permeable LCS. The open-source CFD code olaFlow based on the Navier-Stokes momentum equations is applied to the numerical analysis, which is a strongly nonlinear analysis method that enables breaking and turbulence analysis. As a result, the distribution characteristics of the LCS such as water level, water flow, and turbulent kinetic energy were examined and discussed, then they were carefully compared and examined in the case of submerged breakwaters. The study results indicate that there is a difference between the flow patterns of longshore current near the shoreline, the spatial distribution of longshore and on-offshore directions of mean turbulent kinetic energy in case of submerged breakwaters and LCS. It is predicted that the difference in these results leads to the difference in sand movement.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.384-388
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• 2019

In winter season, the snow and ice accretion on the bottom of the high speed railway rolling stock and boogie part has fallen at a high speed from the ballast section (gravel section for the transmission of the rolling stock load received by sleepers and fixing sleepers), causing the gravel to be scattered, thereby damaging the railway rolling stock structures and facilities. In order to solve these problems, the gravel scattering prevention net, manual de-icing, and movable hot air machine were used, but their efficiency was low. For the more efficient de-icing than ever before, an optimum material for de-icing fluid for high speed railway rolling stock was developed by evaluating the ice melting capacity, kinematic viscosity, evaporation of the material used as a chemical de-icing fluid. Four kinds of organic acid salts (sodium formate, sodium acetate, potassium formate and potassium acetate) and two different alcohols (propylene glycol, glycerol) were used as evaluation materials. Potassium formate, potassium acetate, and propylene glycol had similar ice melting capacities in the indoor test, but the propylene glycol showed the best ice melting capacity in spraying the system simulation test. This is because the kinematic viscosity of propylene glycol was 2.989029 St, which is higher than those of other materials therefore, it could stay longer on the ice and de-icing. In addition, potassium formate and potassium acetate were difficult to be used since the crystals precipitated and adversely affected the appearance of the rolling stock. The propylene glycol is the most optimum as an de-icing fluid for the high speed railway rolling stock.