• Design & Manufacturing
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• v.11 no.2
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• pp.29-36
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• 2017

In this study, the non-contact type bicycle generator system considering the recharge is developed to use the eco-friendly energy source when the bicycle is operating. The following three main factors are considered in this study. One of factors is that the intensity of the rotating magnet is in the range of 2,700~4,300 [Gause]. The next factor is that the separation distance of rotating magnet and bicycle rim is in the range of 1.5-3.0 mm. The last factor is that the pedaling speed is in the range of 55 RPM [Wheel speed 5.6Km]~150 RPM [Wheel speed 15.25Km] consirering with the 5 staged gear transmission. The obtained results are as followed. (1) The generator output voltage gradually increases from 3V to 10V with the pedaling speed increases, at the separation distance is less than 2.5 mm and the operating voltage of the LED lamp is generated at a pedaling speed of 60 RPM or more. (2) The output current of the generator increases from 20mA to 40mA with the pedaling speed increases, at a separation distance is less than 2.0 mm and the operating current of the LED lamp is generated at a pedaling speed of 60 RPM or more. (3) When the separation distance was 3.0 mm, the output voltage and current are significantly lower than those of the bicycle LED lamp is generated. (4) The charging time is expected to be 12.24 ~ 17.65 hours when the magnitude of the magnet is 3,400[Gauss] at a pedaling speed of 55 RPM or more. (5) As a result of this study, it is thought that the non-contact type bicycle generator system considering the recharge can replace the conventional friction power generation system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.626-631
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• 2018

An emergency evacuation support system is used to maintain evacuation routes by pressurizing a space inside screens. In cases of fire, it is important to understand the thermal distributions in the tunnel for preventing system failure. In this study, we numerically investigated the effect of fire on an emergency evacuation support system in a large fabric store with some fire scenarios with different combustibles. The critical temperature for system failures was assumed to be $200^{\circ}C$. As a result, the highest temperature was predicted in the ceiling part due to the effect of a ceiling jet, and the fire safety of the screen was secured at distances of 20 to 30 m according to the heat release rate. To prevent the inflow of smoke into the system, it is necessary to maintain more than 5 Pa if positive pressure inside the smoke screen. The results of this study could be useful for designing an emergency evacuation support system.

• Journal of Powder Materials
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• v.29 no.2
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• pp.110-117
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• 2022

The grain growth behavior in the (1-x)K_0.5Na_0.5NbO₃-xCaZrO₃ (KNNCZ-x) system is studied as a function of the amount of CZ and grain shape. The (1-x)K_0.5Na_0.5NbO₃-xCaZrO₃ (KNNCZ-x) powders are synthesized using a conventional solid-state reaction method. A single orthorhombic phase is observed at x = 0 - 0.03. However, rhombohedral and orthorhombic phases are observed at x = 0.05. The grain growth behavior changes from abnormal grain growth to the suppression of grain growth as the amount of CaZrO₃ (CZ) increases. With increasing CZ content, grains become more faceted, and the step-free energy increases. Therefore, the critical growth driving force increases. The grain size distribution broadens with increasing sintering time in KNNCZ-0.05. As a result, some large grains with a driving force larger than the critical driving force for growth exhibit abnormal grain growth behavior during sintering. Therefore, CZ changes the grain growth behavior and microstructure of KNN. Grain growth at the faceted interface of the KNNCZ system occurs via two-dimensional nucleation and growth.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.429-435
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• 2020

This paper describes the experimental study of reverse-Brayton refrigeration system for application to high temperature superconductivity electric devices and LNG re-liquefaction. The reverse-Brayton refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa, cooling capacity of 2 kW at 77 K, and neon as a working fluid. The refrigeration system is developed with multi scroll compressor, turbo expander and plate heat exchanger. From experiments, the performance characteristics of used components is measured and discussed for 77-120 K of operating temperature. The developed refrigeration system shows the cooling capacity of 1.23 kW at 77 K and 1.64 kW at 110 K.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.635-642
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• 2020

The purpose of this study was to analysis the effects of shielding area of field configuration with changing of sensitivity and density on tube current (milliampere-seconds, mAs) and image quality in automatic exposure control (AEC) system. The equipment used a digital radiography device (Digital Diagnost, Philips, Netherlands), which has a integral type with an X-ray tube and an indirect digital detector. The AEC system conditions were consisted of 9 setting environments, that mode changing of the sensitivity (S200, S400, S800) and the density (+2.5, 0, -2.5). The tube current evaluated automatically exposed mAs under 81 combination conditions crossed by AEC conditions in fixed at 40 kVp. The image quality evaluated the radiographic images that selected valid images by visual assessment the radiographic images of the self-produced conical pyramid phantom and then measured their signal to noise ratio (SNR). As a result, the maximum tube current was 60.0 mAs that automatically exposed conditions were the 100% of shielding area and the sensitivity of S200 and the density of +2.5. The minimum tube current was 0.9 mAs with non-shielding area and the sensitivity of S800 and the density of -2.5. When the shielded area 0% with the sensitivity of S200 and the density of +2.5, the maximum SNR was the highest as 25.2. But when the shielded area 25% with the sensitivity of S800 and the density of -2.5, the minimum SNR was the lowest as 4.7.

• Environmental Engineering Research
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• v.10 no.5
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• pp.227-238
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• 2005

The characteristics of nitrogen removal by the free cell and the immobilized cell of R. capsulatus were investigated. Denitrification by R. capsulatus cells resulted in reduction of ORP with the rapid depletion of DO and the increase of pH. Without accumulation of nitrite, the removal efficiencies of ${NO_3}^-$-N for the free cell and the immobilized cell were 99.1 and 99.3%, respectively. During the three-month experiment of goldfish breeding equipped with a water-purification biofilter, the average values of pH and total cell numbers present in an aquarium were not significantly different between water-purification system and the control. The average concentrations of ${NH_4}^+$-N and ${PO_4}^{2-}$-P in water-purification system were relatively low, compared to that in the control. Goldfish died at $11^{th}$, $16^{th}$, $43^{rd}$, and $67^{th}$ days in the control, while goldfish died at $10^{th}$, $20^{th}$, and $39^{th}$ days in the water-purification system. On the days of goldfish's death, the total concentrations of nitrogenous compounds except for ${NO_2}^--N$ were higher than those on the other days of the experiment, especially with the concentrations of ${NH_4}^+$-N ranging from 7.4 to 13.5 mg/L. The water-purification system also showed the less turbidity of water with more active movement of goldfish than the control. PVA gel beads showed almost the full denitrifying ability even after the long-term experiment. As a result, the water-purification system was effective to remove nitrogenous compounds with better survival of goldfish.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.309-315
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• 2018

Currently, the commercialization of the $5^{th}$ Generation (5G) service is becoming more prevalent in domestic communication network technology. This has reduced communication delay time and enabled large-capacity data transmission and video streaming services in real-time. In order to keep pace with these developments, K-water has introduced a smart process control system in water purification plants to monitor the status of the water purification process. However, since wireless networks are based on the public Long Term Evolution (LTE) network, communication delay time remains high, and high-resolution video services are limited. This is because communication networks still have a closed structure due to expense and security issues. Therefore, with 5G in its current form, it is very difficult to accommodate future services without improving the infrastructure of its communication networks. In recognition of these problems, this study implemented the authentication and management function of wireless networks on a wired network management system in the K-water Bansong water purification plant. The results confirmed that wired Local Area Network (LAN) services give a higher security performance than an expensive commercial wireless LAN system. This was achieved by using an Internet Protocol (IP) address management system of wired networks and the packet filtering function of the Layer2 (L2) switch. This study also confirmed that it is possible to create a wireless LAN service that is 3.7 times faster than the existing LTE communication network.

• Progress in Medical Physics
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• v.17 no.1
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• pp.32-39
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• 2006

To assess the ability of an extravasation detection accessory (EDA) system to detect clinically important extravascular injection of iodinated contrast material delivered with an automated power injector. Fifty patients referred for contrast material enhanced body computed tomography studied in a prospective, observation study in which the EDA system was used to identify and interrupt any injection associated with clinically Important extravasation. The presence or absence of extravasation was definitively established with multi-detector CT at the injection site (injection rate, $2.0{\sim}2.5$ mL/sec). There were two true positive, extravasation volumes $22{\sim}25$ mL. The EDA system had sensitivity in the detection of clinically important extravasation. The EDA system is easy to use, safe, and accurate In the monitoring of intravenous injections for extravasation, which may prove especially useful in CT applications.

• Journal of Power Electronics
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• v.5 no.3
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• pp.233-239
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• 2005

In this paper, a new conceptual circuit configuration of a 3-phase voltage source, soft switching AC-DC-AC converter using an IGBT module, which has one ARCPL circuit and one ARDCL circuit, is presented. In actuality, the ARCPL circuit is applied in the 3-phase voltage source rectifier side, and the ARDCL circuit is in the inverter side. And more, each power semiconductor device has a novel clamp snubber circuit, which can save the power semiconductor device from voltage and current across each power device. The proposed soft switching circuits have only two active power semiconductor devices. These ARCPL and ARDCL circuits consist of fewer parts than the conventional soft switching circuit. Furthermore, the proposed 3-phase voltage source soft switching AC-DC-AC power conversion system needs no additional sensor for complete soft switching as compared with the conventional 3-phase voltage source AC-DC-AC power conversion system. In addition to this, these soft switching circuits operate only once in one sampling term. Therefore, the power conversion efficiency of the proposed AC-DC-AC converter system will get higher than a conventional soft switching converter system because of the reduced ARCPL and ARDCL circuit losses. The operation timing and terms for ARDCL and ARCPL circuits are calculated and controlled by the smoothing DC capacitor voltage and the output AC current. Using this control, the loss of the soft switching circuits are reduced owing to reduced resonant inductor current in ARCPL and ARDCL circuits as compared with the conventional controlled soft switching power conversion system. The operating performances of proposed soft switching AC-DC-AC converter treated here are evaluated on the basis of experimental results in a 50kVA setup in this paper. As a result of experiment on the 50kVA system, it was confirmed that the proposed circuit could reduce conduction noise below 10 MHz and improve the conversion efficiency from 88. 5% to 90.5%, when compared with the hard switching circuit.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.4
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• pp.181-191
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• 2016

A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.