• Journal of Information Science Theory and Practice
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• v.10 no.spc
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• pp.96-111
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• 2022

With the rapid development of the Fourth Industrial Revolution and digital transformation, scientific and technological innovation measures are being devised to overcome Korea's low-growth, high-cost structure. Accordingly, by examining the R&D investment evaluation system of R&D PIE (R&D Platform for Investment and Evaluation), which has been promoted by the Korean government in response to the Fourth Industrial Revolution, from the perspective of R&D transformation, this study aims to explore a new path for a sustainable national science and technology innovation system following digital transformation. In particular, from the perspective of R&D PIE, a MLP (Multi-level Perspective), which had been conducted as an abstract theoretical study, was attempted with specific cases and analysis for each of the three layers: niche, landscape, and regime. In conclusion, R&D PIE was intended to elevate the abstract R&D investment evaluation system to a platform that leads innovation in the digital space of the Fourth Industrial Revolution. In addition, it was confirmed that the R&D PIE could be replaced or enhanced as a platform for innovation in response to the Fourth Industrial Revolution, thereby providing an alternative to job creation and an escape from economic crisis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.945-964
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• 2014

In this paper, we investigate the performance of Signal to Leakage and Noise Radio (SLNR) based user scheduling in uplink of multi-cell with large-scale antenna system. Large antenna array is desired to improve the performance in future system by providing better beamforming capability. However, some studies have found that the signal channel is 'hardened' (becomes invariant) when the antenna number goes extremely large, which implies that the signal channel aware user scheduling may have no gain at all. With the mathematic tool of order statistics, we analyzed the signal and interference terms of SLNR in a homogeneous multicell network. The derived distribution function of signal and interference shows that the leakage channel's variance is much more influential than the signal channel's variance in large-scale antenna regime. So even though the signal channel is hardened, the SLNR-based scheduling can achieve remarkable multiuser diversity (MUD) gain due to the fluctuation of the uplink leakage channel. By providing the final SINR distribution, we verify that the SLNR-based scheduling can leverage MUD in a better way than the signal channel based scheduling. The Monte Carlo simulations show that the throughput gain of SLNR-based scheduling over signal channel based scheduling is significant.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.120-127
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• 2007

The purpose of this study is experimentally to analyze that the fuel mass fractions of multi-component mixed fuels have an effect on the characteristics of spray ignition and combustion under the ambient conditions of diesel combustion fields. The characteristics of ignition and combustion were investigated by chemiluminescence images and direct photography. The experiments were conducted in the RCEM(rapid compression expansion machine) with optical access. Multi-component fuels mixed with i-octane, n-dodecane and n-hexadecane are injected in RCEM by the electronic control of common rail injector. Experimental conditions set up 42, 72 and 112 MPa in injection pressure, 700, 800 and 900 K in ambient gas temperature. The results show that the ignition delay was dependent on high cetane number. In case of low ambient temperature, the more low boiling point fuels were mixed, the lower luminance regime had a remarkable effect and also shortened diffusion combustion by increasing heat release rate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.182-183
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• 2014

Hemispherical dimples with diameter, ø=$60{\mu}m$ and depth, d= $30{\mu}m$ were created on the metal and ceramics surfaces using INYA 10 watt Laser of 1064 nm wavelength. This study reports the influence of dimple pitch on friction and wear behavior rather than dimple size, depth and density. LST was performed on the specimens with dimple pitch and density in the range of 80 to-$200{\mu}m$ and 44 to 7 %, respectively. Surface topography was analyzed by using roughness measurement, scanning electron microscopy (SEM), and optical microscopy. Friction and wear characteristics were analyzed on textured surfaces at lubricating environment to observe the effect of surface texturing on reduction of friction and wear. Reduction on coefficient of friction was achieved by more than 70% due to the dual behavior of dimples as wear (debris) traps and lubricant reservoirs. Wear reduced significantly for the textured surface as compared to the polished surface. Moreover, the friction coefficient of the textured specimens reduced with increasing load and speed which may be attributed to the transition of lubrication regime.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.131-135
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• 2010

We report on the design of a three-axis missile autopilot using multi-objective control synthesis via linear matrix inequality techniques. This autopilot design guarantees $H_2/H_{\infty}$ performance criteria for a set of finite linear models. These models are linearized at different aerodynamic roll angle conditions over the flight envelope to capture uncertainties that occur in the high-angle-of-attack regime. Simulation results are presented for different aerodynamic roll angle variations and show that the performance of the controller is very satisfactory.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.87-94
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• 2007

Tilt rotor-wing concept to show enhanced performance in low speed mission is presented. Three types of stud wings on the existing tilt rotor configuration are suggested and their characteristics are compared. Aerodynamic analysis indicates that the stud wing concept gives significant performance improvement on the endurance and range in the low speed regime when compared with the tilt rotor. Penalties of the stud wing are discussed from the perspectives of conversion corridor, structural weight, configuration design, and cross wind stability. This study concludes that the advantage of the stud wing in general UAV mission performance is so significant as to surpass the penalties in other perspectives investigated.

• Progress in Superconductivity
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• v.1 no.2
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• pp.141-145
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• 2000

Different twist pitches of multi filamentary BSCCO 2223 tapes using high resistivity sheath were fabricated to investigate the effect of twist pitches on the microstructure and critical current property. A conductor with a high resitstivity matrix is possible to allow larger twist pitch for reducing ac losses and reduce eddy current losses simultaneously. The $J_{ct}$ values of 10 mm and 5 mm twisted tapes drop faster than that of untwisted and 20 mm twisted tapes under increasing magneticfield, especially in low field regime (0 $\sim$ 0.03 T). It suggests that weak links in the former are more serious than in the latter, which is in accordance with the microstructure analysis.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.177-185
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• 1999

The airfoil design optimization procedures based on the Navier-Stokes equations were developed, This procedure enables more realistic and practical transonic airfoil designs. The modified Hicks-Henne functions were used to generate the shape of airfoils. Five Hick-Henne functions were used to design upper surface of airfoil only. To enhance the ability of Hick-Henne function to generate various airfoil shape with limited number of functions, the positions of control points were adjusted through optimization procedure. The design procedure was applied to the single-point design for the drag minimization problem with lift and area constraints. The result shows the capability of the procedure to generate much realistic airfoils with very small drag-creep in the low transonic regime. This is mainly due to the viscosity effect of Navier-Stokes flow analysis. However, in the higher transonic range tile drag-creep appears. The multi-point design is shown to be an effective way to avoid the drag-creep and improve off-design performance which is very similar in the Euler design.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.205-209
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• 1998

A synthesis of fuzzy variable structure control is proposed to design a high-angle-of-attack flight system for a modification version of the F-18 aircraft. The knowledge of the proportional, integral, and derivative control is combined into the fuzzy control that addresses both the highly nonlinear aerodynamic characteristics of elevators and the control limit of thrust vectoring nozzles. A simple gain scheduling method with multi-layered fuzzy rules is adopted to obtain an appropriate blend of elevator and thrust vectoring commands in the wide operating range. Improving the computational efficiency, an accelerated kernel for on-line fuzzy reasoning is also proposed. The resulting control system achieves the good flying quantities during a high-angle-of- attack excursion. Thus the fuzzy logic can afford the control engineer a flexible means of deriving effective control laws in the nonlinear flight regime.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.1-8
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• 2009

Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.