• Advances in aircraft and spacecraft science
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• v.10 no.5
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• pp.419-437
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• 2023

This paper presents the study of the effects of rigid-body motion simultaneously with the presence of the effects of temporal variation due to the existence of morphing speed on the aeroelastic stability of the two-stage telescopic wings, and hence this is the main novelty of this study. To this aim, Euler-Bernoulli beam theory is used to model the bending-torsional dynamics of the wing. The aerodynamic loads on the wing in an incompressible flow regime are determined by using Peters' unsteady aerodynamic model. The governing aeroelastic equations are discretized employing a finite element method based on the beam-rod model. The effects of rigid-body motion on the length-based stability of the wing are determined by checking the eigenvalues of system. The obtained results are compared with those available in the literature, and a good agreement is observed. Furthermore, the effects of different parameters of rigid-body such as the mass, radius of gyration, fuselage center of gravity distance from wing elastic axis on the aeroelastic stability are discussed. It is found that some parameters can cause unpredictable changes in the critical length and frequency. Also, paying attention to the fuselage parameters and how they affect stability is very important and will play a significant role in the design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.85-91
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• 2018

Recently, there have been a lot of casualties due to fires in high-rise buildings. The toxic gases and smokes generated by fires in high-rise buildings spread rapidly through the elevator shaft and stairwell, due to the stack effect, and can cause critical casualties. To reduce the number of casualties, smoke control systems have been introduced. Smoke control systems play an essential role in preventing the spread of smoke in high-rise buildings and securing the evacuation route. Also, in high-rise buildings, evacuation by an elevator is considered to be indispensable. However, the pressure field in the shaft is strongly disturbed when the elevator is moving and this can affect the performance of the smoke control system. Therefore, in this study, we experimentally and numerically analyzed the effect of elevator movement on the pressure difference between the vestibule and living room by building a model using the sandwich pressurization method based on the performance based design. To consider the leakage areas in high-rise buildings, e.g. the windows, fire door and elevator, the National Fire Safety Codes and area ratio were used. The elevator speed in the model building was varied between 20 m/s and 100 m/s corresponding to a real elevator speed of 7 m/s~17 m/s. As a result, the relationship between the pressure difference and elevator speed was found to be ${\Delta}P=40{\cdot}{\exp}$(-Ves /-104.7)-23.735. This result can be used to take into consideration the effect of elevator movement when designing smoke control systems.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.566-573
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• 2017

The chine of high speed vessels does not only play a role in changing position when planing but also helps balancing the hull. It also has a great influence on resistance performance. However, designing a chine requires a lot of experience because it is influenced by various factors such as displacement, transom shape, draft and width. Such a design is not based on an empirical formula, but the purpose of this study is to provide basic guidelines regarding the shape of chine through calculation. This design was developed using Yacht-one, a commercial design program, and analysis was performed using Star-CCM+, also a commercial analysis program. Analysis of the hull selected in this study was carried out by Dynamic Fluid Body Interaction (DFBI) method. Analysis of the chine was carried out at chine angles of 15, 16, 17, and 19degrees, at a speed of 30knots. The result indicated that the highest trim occurred at 16 degrees among the four chine angles considered, and the highest heave occurred at 15degree. In terms of resistance performance, minimum resistance was observed at 16 degrees. Consequently, for minimum ship resistance, it is necessary to complete calculations in accordance with the chine angles, ${\pm}2$ degrees from the initial chine angle, which should be carried out a the design stage.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.32 no.1
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• pp.115-132
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• 2021

This study collected data on COVID-19 research papers published in international journals by Korean authors from WoS. Bibliographical analysis was performed on subject categories, institutions, funder distribution and so on. In addition, open access and journal review speed were also analyzed, which play an important role in facilitating academic publishing and distribution. The results showed that COVID-19-related papers published in international journals by Korean authors in 2020 included more papers on some specific fields, such as medicine, biology, and multidisciplinary. These researchers have published lots of papers not only in foreign journals but also in domestic English journals. 94% of papers were open access, and gold open access, which is available immediately after publication, was about 70% of the total. The COVID-19 orthopedic papers produced by Korean researchers were collected from PubMed and analyzed, and the average of review days was about 24 days. The analysis, including open access and review speed, showed that there has been an atmosphere of cooperation in the academic publishing ecosystem after the COVID-19 crisis. It would be desirable to continue this cooperation and address chronic problems in academic publishing system, such as promoting the publication of gold open access and reviewing efficiency.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.119-126
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• 2009

This paper describes the non-stringed guitar composed of laser strings, frets, sound synthesis algorithm and a processor. The laser strings that can depict stroke and playing arpeggios comprise laser modules and photo diodes. Frets are implemented by voltage divider. The guitar body does not need to implement physically because commuted waveguide synthesis is used. The proposed frets enable; players to represent all of chords by the chord glove as well as guitar solo. Sliding, hammering-on and pulling-off sounds are synthesized by using parameters from the voltage divider. Because the pitch shifting corresponds to the time-varying propagation speed in the digital waveguide model, the proposed model can synthesize vibrato as well. After transformation of signals from the laser strings and frets into parameters for synthesis algorithm, the digital signal processor, TMS320F2812, performs the real-time synthesis algorithm and communicates with the DAC. The demonstration movieclip available via the Internet shows one to play a song, 'Arirang', synthesized by proposed algorithm and interfaces in real-time. Consequently, we can conclude that the proposed synthesis algorithm is efficient in guitar solo and there is no problem to play the non-stringed guitar in real-time.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.143-150
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• 2018

With the rapid development of RF based high speed wireless communication technology, devices that can be applied to IoT networks based on RF bandwidth are rapidly spreading, nevertheless, the development speed of the RF communication is not possible to keep up with the spread of the RF band for wireless communication. In this situation, OWC technology that uses visible light source as a transmitter is attracting attention as a technology that can overcome the band exhaustion problem of RF based wireless communication technology. Although, due to the distortion of the LED illumination shape by camera exposure time and LED blinking period, the LED illumination detection rate is degraded and the RoI setting is inaccurate. In this paper, we propose an adaptive median filter applied LED illumination detection algorithm for low rate CamCom, it is possible to detect a clear RoI and LED illumination. This research will be able to play a role as a complementary material of RF based wireless communication technology efficiently.

• The Journal of Korean Academy of Sensory Integration
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• v.21 no.3
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• pp.39-53
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• 2023

Objective : The purpose was the effect of sensory integration therapy combined with an eye tracker on the sensory processing and visual perception of children with developmental disabilities. Methods : It was a single-subject study with a multiple baseline design between subjects, and the intervention applied sensory integration therapy combined with an eye tracker. Visual-motor speed and saccadic eye movements were assessed at each session of baseline and intervention periods. As pre- and post-evaluation, sensory profile, Korean-Developmental Test of Visual Perception and Trail Making Test were conducted. The results of each session evaluation and pre- and post-evaluation researched the effectiveness of the intervention through visual analysis and trend line analysis. Results : As a result of the evaluation for each session, the slope of the trend line for all children in visual-motor speed and saccadic eye movement increased sharply during the intervention compared to the baseline. As a result of the pre- and post-evaluation, the sensory processing of movement, body position, and visual changed from more than that of peers to a level similar to that of peers. In visual perception, all children's ability of Visual Closure increased. As a result of Trail Making Test conducted to confirm the improvement of children's visual tracking and visual-motor abilities, all children showed a decrease in performance time after the test compared to before. Conclusion : It was confirmed that sensory integration therapy combined with an eye tracker for developmental disabilities has effect on sensory processing and visual perception. It is expected to play an important role clinically as it can stimulate children's interest and motivation in line with recent technological improvements and the spread of smart devices.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.159-163
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• 2007

Micron size Co-alloy 800 (T800) powder is coated on the high temperature, oxidation and corrosion resistant super alloy Inconel 718 substrate by the optimal high velocity oxy-fuel (HVOF) thermal spray coating process developed by this laboratory. For the study of durability improvement of high speed spindle operating without lubricants, friction and sliding wear behaviors of the coatings are investigated both at room and at an elevated temperature of $1000^{\circ}F(538^{\circ}C)$. Friction coefficients, wear traces and wear debris of coatings are drastically reduced compared to those of non-coated surface of Inconel 718 substrate both at room temperature and at $538^{\circ}C$. Friction coefficients and wear traces of both coated and non-coated surfaces are drastically reduced at higher temperature of $538^{\circ}C$ compared with those at room temperature. At high temperature, the brittle oxides such as CoO, $Co_{3}O_{4}$, $MoO_2$ and $MoO_3$ are formed rapidly on the sliding surfaces, and the brittle oxide phases are easily attrited by reciprocating slides at high temperature through oxidation and abrasive wear mechanisms. The brittle solid oxide particles, softens, melts and partial-melts play roles as solid and liquid lubricants reducing friction coefficient and wear. These show that the coating is highly recommendable for the durability improvement coating on the machine component surfaces vulnerable to frictional heat and wear.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.5
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• pp.495-505
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• 2012

Modeling the effects of high-rise buildings on thermo-dynamic conditions and meteorological fields over a coastal urban area was conducted using the modified meso-urban meteorological model (Urbanized MM5; uMM5) with the urban canopy parameterization (UCP) and the high-resolution inputs (urban morphology, land-use/land-cover sub-grid distribution, and high-quality digital elevation model data sets). Sensitivity simulations was performed during a typical sea-breeze episode (4~8 August 2006). Comparison between simulations with real urban morphology and changed urban morphology (i.e. high-rise buildings to low residential houses) showed that high-rise buildings could play an important role in urban heat island and land-sea breeze circulation. The major changes in urban meteorologic conditions are followings: significant increase in daytime temperature nearly by $1.0^{\circ}C$ due to sensible heat flux emitted from high density residential houses, decrease in nighttime temperature nearly by $1.0^{\circ}C$ because of the reduction in the storage heat flux emitted from high-rise buildings, and large increase in wind speed (maximum 2 m $s^{-1}$) during the daytime due to lessen drag-force or increased gradient temperature over coastal area.

• Knowledge Management Research
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• v.21 no.1
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• pp.137-150
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• 2020

This study analyzes not only the direct impact of R&D investment on corporate growth for 578 private firms in 2007-2016, but also whether corporate innovation activities play a role as a mediating parameter between R&D investment and corporate growth. For this purpose, we classify companies into IT and non-IT companies and measure the mediating effect by dividing innovation activities into the number of registered patents, applied patents, and sum of them. In addition, this study is based on both the systemGMM which is considered to be effective in solving the endogenous problems caused by the cross-sectional analysis in previous studies and ML-SEM which is a new method recently, and then compares two results. According to the empirical results, innovation activities has a role as partly mediating parameter on sales growth in non-IT companies. On the other hands, in IT companies, the increase in R&D investment leads to a decrease in sales of the company, and the increase in innovation activities increases the sales of the company. However, it was confirmed that IT companies also had positive effects by adjusting the lag of the R&D. In other words, this suggests that securing patents is more important than R&D investment for direct sales growth of IT companies. It is also evidence that immediate introduction of technology is necessary to respond to the speed of technological change since the cycle time of technologies of the IT field is relatively shorter compared to that of other fields.