• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.75-84
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• 2021

The authors had presented two previous papers[1,2] on Helicopter/Rotorcraft develoment in Europe and US. Meanwhile, the next generation rotorcrafts, currently under development in US and Europe, have new configurations (tilt-rotor, coaxial, compound) of rotor-type vertical takeoff/landing rotorcrafts to overcome the disadvantages of traditional helicopters. For developing these new types of rotorcrafts, the upgraded conceptual design/comprehensive programs are required. In US and Europe, they are already developing new program tools with their technologies and database obtained during more than last half centuries. For us, many academia, research institutes and industrial engineers have experienced and developed core technologies on rotorcrafts (aerodynamics, structural analysis, flight dynamics, and noise analysis etc.) comparable to US and Europe during last couple of decades of developing helicopters and various configurations of rotorcrafts. In this paper, the pros and cons of conceptual design/comprehensive tools currently used in US and Europe have been summarized. Furthermore, the possibilities and problems to develope our own design and analysis tools have been studied.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.496-501
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• 2022

In this study, an anode material for lithium secondary batteries was manufactured using petroleum-based residual oil, which is a petroleum refining by-product. Among petroleum-based residual oils, pyrolysis fuel oil (PFO), fluidized catalyst cracking-decant oil (FCC-DO), and vacuum residue (VR) were used as carbon precursors. The physicochemical characteristics of petroleum-based residual oil were confirmed through Matrix-assisted laser desorption/ionization Time-of-Flight (MALDI-TOF) and elemental analysis (EA), and the structural characteristics of anode materials manufactured from residual oil were evaluated using X-ray crystallography (XRD) and Raman spectroscopic techniques. VR was found to contain a wide range of molecular weight distributions and large amounts of impurities compared to PFO and FCC-DO, and PFO and FCC-DO exhibited almost similar physicochemical characteristics. From the XRD analysis results, carbonized PFO and FCC-DO showed similar d₀₀₂ values. However, it was confirmed that FCC-DO had a more developed layered structure than PFO in Lc (Length of a and c axes in the crystal system) and La values. In addition, FCC-DO showed the best cycle characteristics in electrochemical characteristics evaluation. According to the physicochemical and electrochemical results of the petroleum-based residual oil, FCC-DO is a better carbon precursor for a lithium secondary battery than PFO and VR.

• Korean Journal of Cognitive Science
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• v.33 no.3
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• pp.135-154
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• 2022

The purpose of this study was to confirm that the property generalization to social categories with low coherence is stronger when stress due to COVID-19 is perceived as high, compared to when stress is perceived as low. To this end, this study selected categories with high coherence(nun, soldier, flight attendant) and categories with low coherence(wedding planner, interpreter, florist), and recruited 336 participants to perform a category-based inductive generalization task(inferring how many properties repeatedly observed by some category members would appear across all category members), and measured their perceived COVID-19 stress. As a result, this study showed that when the cohesion of social categories is high, the effect of property generalization is stronger than when it is low, and the effect of property generalization is stronger in those who perceive stress due to Corona 19 higher than those who perceive it as low. In addition, this study confirmed that people who perceive COVID-19 stress strongly tend to generalize strongly to properties that are repeatedly observed in the low coherence category. This study is important in that it shows that there is a cognitive mechanism that is at the root of the phenomenon that stereotypes and prejudices deepen and discriminatory behaviors increase after the outbreak of COVID-19, such as COVID-19 stress and the resulting increase in attribute generalization tendency.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.510-516
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• 2021

Recently, the range of utilization and demand for unmanned aerial vehicle (UAV) has been continuously increasing, and research on the construction of a separate operating system for low-altitude UAV is underway through the development of a management system separate from manned aircraft. Since low-altitude UAVs also fly in the airspace, it is essential to establish technical standards and certification systems necessary for the operation of the aircraft, and research on this is also in progress. If the operating standards and certification requirements of the aircraft are presented, a test method to confirm this should also be presented. In particular, the accuracy of small UAV's navigation required during flight is required to be more precise than that of a manned aircraft or a large UAV. It was necessary to calculate a separate navigation error. In this study, we presented a test method for deriving navigation errors that can be applied to UAVs that have difficulty in acquiring long-term operational data, which is different from existing manned aircraft, and conducted verification tests.

• The Korean Journal of Nuclear Medicine Technology
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• v.27 no.2
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• pp.111-127
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• 2023

Purpose: Gallium-68 (⁶⁸Ga) is increasingly used in nuclear medicine imaging for various conditions such as lymphoma and neuroendocrine tumors by labeling tracers like Prostate Specific Membrane Antigen (PSMA) and DOTA-TOC. However, compared to Fluorine-18 (¹⁸F) used in conventional nuclear medicine imaging, ⁶⁸Ga has lower spatial resolution and relatively higher Signal to Background Ratio (SBR). Therefore, this study aimed to investigate the optimized parameters and reconstruction methods for PET/CT imaging using the ⁶⁸Ga radiotracer through model-based image evaluation. Materials and Methods: Based on clinical images of ⁶⁸Ga-PSMA PET/CT, a NEMA/IEC 2008 PET phantom model was prepared with a Hot vs Background (H/B) ratio of 10:1. Images were acquired for 9 minutes in list mode using DMIDR (GE, Milwaukee WI, USA). Subsequently, reconstructions were performed for 1 to 8 minutes using OS-EM (Ordered Subset Expectation Maximization) + TOF (Time of Flight) + Sharp IR (VPFX-S), and BSREM (Block Sequential Regularized Expectation Maximization) + TOF + Sharp IR (QCFX-S-400), followed by comparative evaluation. Based on the previous experimental results, images were reconstructed for BSREM + TOF + Sharp IR / 2 minutes (QCFX-S-2min) with varying β-strength values from 100 to 700. The image quality was evaluated using AMIDE (freeware, Ver.1.0.1) and Advanced Workstation (GE, USA). Results: Images reconstructed with QCFX-S-400 showed relatively higher values for SNR (Signal to Noise Ratio), CNR (Contrast to Noise Ratio), count, RC (Recovery Coefficient), and SUV (Standardized Uptake Value) compared to VPFX-S. SNR, CNR, and SUV exhibited the highest values at 2 minutes/bed acquisition time. RC showed the highest values for a 10 mm sphere at 2 minutes/bed acquisition time. For small spheres of 10 mm and 13 mm, an inverse relationship between β-strength increase and count was observed. SNR and CNR peaked at β-strength 400 and then decreased, while SUV and RC exhibited a normal distribution based on sphere size for β-strength values of 400 and above. Conclusion: Based on the experiments, PET/CT imaging using the ⁶⁸Ga radiotracer yielded the most favorable quantitative and qualitative results with a 2 minutes/bed acquisition time and BSREM reconstruction, particularly when applying β-strength 400. The application of BSREM can enhance accurate quantification and image quality in ⁶⁸Ga PET/CT imaging, and an optimization process tailored to each institution's imaging objectives appears necessary.

• The Korean Journal of Air & Space Law and Policy
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• v.21 no.1
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• pp.169-189
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• 2006

In 2007, KSLV(Korea Small Launching Vehicle) that we made at Goheung National Space Center is going to launch and promotes of our space exploration systematically and 'Space Exploration Promotion Act' was enter into force. 'Space Exploration Promotion Act' article 3, section 1, as is prescribing "Korean government keeps the space treaties contracted with other countries and international organizations and pursues after peaceful uses of outer space." The representative international treaties are Outer Space Treaty (1967) and Liability Convention (1972) etc. In Liability convention article 2, "A launching State shall be absolutely liable to pay compensation for damage caused by its space object on the surface of the earth or to aircraft in flight. The important content of the art. 2 is the responsible entity is the 'State' not the 'Company'. According by Korean Space Exploration Act art. 14, person who launches space objects according to art. 8 and art. 11 must bear the liability for damages owing to space accidents of the space objects. Could Korean government apply the Products Liability Act which is enter into force from July 1, 2002 to space launching person? And what is the contact type between Korea Aerospace Research Institute(KARl) and Russia manufacturer. Is that a Co-Development contract or Licence Product contract? And there is no exemption clause to waive the Russia manufacturer's liability which we could find it from other similar contract condition. If there is no exemption clause to the Russia manufacturer, could we apply the Korean Products Liability Act to Russia one? The most important legal point is whether we could apply the Korean Products Liability Act to the main component company. According by the art. 17 of the contract between KARl and the company, KARl already apply the Products Liability Act to the main component company. For reference, we need to examine the Appalachian Insurance co. v. McDonnell Douglas case, this case is that long distance electricity communication satellite of Western Union Telegraph company possessions fails on track entry. In Western Union's insurance company supplied to Western Union with insurance of $ 105 millions, which has the satellite regard as entirely damage. Five insurance companies -Appalachian insurance company, Commonwealth insurance company, Industrial Indemnity, Mutual Marine Office, Northbrook Excess & Surplus insurance company- went to court against McDonnell Douglases, Morton Thiokol and Hitco company to inquire for fault and strict liability of product. By the Appalachian Insurance co. v. McDonnell Douglas case, KARl should waiver the main component's product liability burden. And we could study the possibility of the adapt 'Government Contractor Defense' theory to the main component company.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.11-15
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• 2016

Proton Exchange Membrane Fuel Cells (PEMFC) instead of batteries is appropriate for long time flight of unmanned aero vehicles (UAV). In this work, $NaBH_4$ hydrolysis system supplying hydrogen to PEMFC was studied. In order to decrease weight of $NaBH_4$ hydrolysis system, enhancement of hydrogen yield, recovery of condensing water and maintenance of stable hydrogen yield were studied. The hydrogen yield of 3.4% was increased by controlling of hydrogen pressure in hydrolysis reactor. Condensing water formed during air cooling of hydrogen was recovered into storage tank of $NaBH_4$ solution. In this process the condensing water dissolved $NaBH_4$ powder and then addition of $NaBH_4$ solution decreased system weight of 14%. $NaBH_4$ hydrolysis system was stably operated with hydrogen yield of 96% by 2.0g Co-P-B catalyst for 10 hours at 2.0L/min hydrogen evolution rate.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.318-323
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• 2007

Electronic photofragmentation spectrum of protonated tyrosine-alanine dipeptide ions(YAH+) was obtained in the wavenumber region of 34500~36700 cm-1 using a quadrupole ion trap time-of-flight mass spectrometer (QIT-TOFMS). YAH+ ions were produced by electrospray ionization, stored in the ion trap and then irradiated by ultraviolet laser pulses which induced photofragmentation of the ions. The electronic photofragmentation spectrum was obtained by monitoring the photodissociation yields of YAH+ ions as a function of the laser wavelength. The spectrum exhibited two broad peaks which were assigned as S1 and S2 by theoretical calculations using a time-dependent density functional method. The broad widths of the peaks in the spectrum were explained by the overlaps of the peaks originated from various conformers of YAH+ ions which were present in the gas phase at room temperature and also by the contributions of the hot bands.

• Composites Research
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• v.33 no.5
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• pp.275-281
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• 2020

The mechanical property related to lap shear strength of the joint structure between carbon fiber reinforced polymer (CFRP) composite and metal (Ni-Cr Alloy) under varying environmental conditions (temperature and humidity) was studied in order to apply to the aircraft fan blade. Room temperature dry (RTD), elevated temperature wet (ETW), and cold temperature dry (CTD) environmental conditions were chosen for investigation based on the flight conditions of aircraft. Lap shear strength tests were conducted according to ASTM Standard D3528 to evaluate the shear strength. The microstructure characteristic of failure zone was analyzed by SEM images to check the adhesive shear strength with the three environmental conditions. In comparison with shear strength for the RTD condition, the shear strength in the ETW condition was reduced by 72.8% while those for the CTD condition increased by 56.5%. The moisture absorption and high temperature in ETW condition strongly had an affect on mechanical property of adhesive, while cold temperature could enhance the adhesive shear strength due to the higher brittleness.