• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.21-28
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• 2021

In order to develop a Korea Positioning System (KPS) as part of key national infrastructure, independent navigation signal design is essential. The designed signal candidates must coexist with existing or planned GNSS signals within the limited frequency band. This requires a RF compatibility assessment, which can be performed using the Spectral Separation Coefficient (SSC) and Effective Carrier to Noise Density Ratio (Effective C/N0), for navigation signals. Thus, in this paper, the analysis of RF compatibility between the designed signal candidates and the existing GNSS signals is carried out based on analytical and numerical techniques.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.315-320
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• 2024

In order to maximize the function and increase the compatibility of silicone hydrogel lens, this study compared and analyzed the properties of Amino modified silicone oil using mini and microemulsion technique, respectively. Optical and physical properties were evaluated by spectral transmittance, refractive index, water content, oxygen transmittance and contact angle measurements to evaluate the performance of the manufactured hydrogel lens. The spectral transmittance results revealed the copolymerization method lens showed 31 % of the visible light area, which did not satisfy the basic optical properties. However, the lens using the mini and microemulsion materials showed more than 90 % of the visible light area, satisfying the optical characteristics. In addition, all physical properties were superior to a basic hydrogel lens. The mini and microemulsion techniques effectively improved the stability and function of the ophthalmic hydrogel lens and are considered a promising ways of manufacturing an ophthalmic hydrogel contact lens with increased compatibility and stability.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.171-182
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• 2018

For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen's nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results' accuracy in current work.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.1094-1099
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• 2002

In this paper, a numerical method for vehicle-track interaction analysis is developed to evaluate vertical dynamic force subjected to rail surface. A vehicle is modelled by lumped masses system and track by multi layered continuous beam system. The equation of motion of vehicle and track interaction system is derived by considering compatibility condition at the contact points between wheel and rail. The input vibration source is given by the empirical formula of power spectral density of track irregularity, which is suggested by FRA. Using this method, dynamic impact factors with the train speed are evaluated.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.825-837
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• 2017

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

• Journal of the Korean Society of Tobacco Science
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• v.30 no.1
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• pp.25-32
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• 2008

In this study, we compared three different pretreatment methods, such as block digestion, microwave digestion and solvent injection, coupled with Octopole Reaction System(ORS)-ICP-MS was used for the quantification of heavy metals in mainstream smoke of 2R4F reference cigarette, and then evaluated those efficiencies in the recovery, repeatability and reproducibility. In all methods, volatile heavy metals, As, showed the highest CV value, and Cd showed the lowest one. However, the solvent injection method showed the most stable recovery rate and CV value of 2.36 %. This method showed also advantages in time-consuming and compatibility with ICP-MS system. This results demonstrate that solvent injection method can be recommended as a superior pretreatment procedure to be able to reduce contaminants and spectral interference as well as loss of the elements interested.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.4
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• pp.286-292
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• 2004

This paper presents a polyphase filtered orthogonal frequency division multiplexing (PF-OFDM) technique. The proposed structure uses a modified discrete Fourier transform (MDFT) transmultiplexer to achieve greater spectral efficiency than an OFDM system, while preserving backward compatibility with it. The prototype PF-OFDM filter has excellent time and frequency localization properties, which matte it possible to eliminate a guard interval (or cyclic prefix) and easily suppress interchannel interference (ICI). This modulation technique uses a single DFT structure, in contrast to a MDFT transmultiplexer, which requires two DFT polyphase filter banks. The PF-OFDM modulation is .justified over multipath Rayleigh fading channels.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.346-349
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• 2008

A metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) is proposed as an effective UV sensing device for integration with a GaN n-channel MISFET on auto-doped p-type GaN grown on a silicon substrate. Due to the high hole barrier of the metal-p-GaN contact, the dark current density of the fabricated MSM PD was less than $3\;nA/cm^2$ at a bias of up to 5 V. Meanwhile, the UV/visible rejection ratio was 400 and the cutoff wavelength of the spectral responsivity was 365 nm. However, the UV/visible ratio was limited by the sub-bandgap response, which was attributed to defectrelated deep traps in the p-GaN layer of the MSM PD. In conclusion, an MSM PD has a high process compatibility with the n-channel GaN Schottky barrier MISFET fabrication process and epitaxy on a silicon substrate.

• Journal of Pharmaceutical Investigation
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• v.40 no.6
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• pp.367-372
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• 2010

Rabeprazole sodium (RPN) is known to be very unstable at acidic condition or some acidic pharmaceutical excipients such as acrylic acid polymer (carbomer 934) with carboxylic acids. Thus, degradation mechanism of binary blends of rabeprazole with pharmaceutical excipients in a solid state without using solvents at three different ratios (3:1, 1:1 and 1:3) was investigated using Fourier transform infrad (FTIR) spectroscopy. Alkalizer (MgO), neutral hydroxypropymethylcellulose (HPMC 4000) were also tested for comparison. The binary blends were stored under accelerated conditions ($40^{\circ}C$/75% relative humidity) for two weeks. The concentration of thioether rabeprazole from the binary blends with acidic carbomer 934 increased as the rabeprazole concentration decreased. In addition, the degradation half-life of rabeprazole as well as the relative peak area ratios obtained from FTIR spectra of S=O stretching at $1094.1\;cm^{-1}$ decreased consistently as the fraction of carbomer 934 increased due to its sensitivity between the basic benzimidazole nitrogen and carboxylic acid group of carbomer 934. The physical appearance also turned into strong brown color in the presence of carbomer 934. In contrast, there were no significant changes in the degradation kinetics of rabeprazole with MgO and HPMC 4000 in a solid state. This present study demonstrated that the solid-state compatibility test with the aid of HPLC chromatographic and FTIR spectral analyses could offer a valuable methodology to select suitable pharmaceutical excipients and to elucidate the degradation mechanism of RPN for drug formulations at the early formulation stages.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.512-519
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• 2012

To design a new Navigation Satellite System signal, we should analyze the influence of inter-system interference to existing Global Navigation Satellite Systems(GNSS). Various GNSS systems such as GSP, GALILEO, Compass use same frequence band and incur inter-system interference due to the overlapping spectrums. In this paper, we consider L2 Band for new Navigation Satellite System and propose the BOCcos(15,2.5) signal what has least Spectral Separation Coefficient with GPS L2 system. Assuming 4 stationary satellite over Korea, we simulate the effect of interference. As a result, proposed system shows very small mutual interference effect and negligible effective signal to noise ratio(SNR) loss, compared to the interferences between GNSS systems in L1 Band.