• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.227-233
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• 2009

We investigated the polarization-mode dispersion (PMD) tolerance for 40Gb/s non-return to zero (NRZ), duobinary NRZ, return to zero (RZ), carrier-suppressed RZ (CS-RZ), and duobinary-carrier-suppressed RZ (DCS-RZ) modulation formats with a forward error correction (FEC) coding. The power penalty has been calculated as a measure of the system performance due to PMD. After comparison of the PMD tolerance of various modulation formats, our results suggest that RZ signals have the best tolerance against the effect of first-order PMD only. The duobinary NRZ modulation format is most resilient to PMD when both first- and second-order PMD are considered. However, the duobinary NRZ modulation format is the most sensitive to the incident angle of the input signal to a fiber axis in the presence of first- and second-order PMD, leading to incident angle-dependent power penalty. The coding gain by FEC can cope with the power penalties induced by first- and second-order PMD up to a DGD value of 16ps.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.73-85
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• 2013

In this paper we present an alternative approach to addressing the problem of designing cloaks for radar targets, which have been dealt with in the past by using the transformation optics (TO) algorithm. The present design utilizes realistic materials, which can be fabricated in the laboratory, and are wideband as well as relatively insensitive to polarization and incident angle of the incoming wave. The design strategy, presented herein, circumvents the need to use metamaterials for cloak designs that are inherently narrowband, dispersive and highly sensitive to polarization and incident angle. A new interpretation of the TO algorithm is presented and is employed for the design of radar cross section-reducing absorbers for arbitrary targets, and not just for canonical shapes, e.g., cylinders. The topic of performance enhancement of the absorbers by using graphene materials and embedded frequency structure surfaces is briefly mentioned. The design procedure for planar absorbing covers is presented and their performance as wrappers of general objects is discussed. A number of test cases are included as examples to illustrate the application of the proposed design methodology, which is a modification of the classical TO paradigm.

• Journal of the Korea Society of Computer and Information
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• v.15 no.5
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• pp.75-81
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• 2010

Adaptive array antenna system estimates target signal, as making a null pattern toward the interference signal. However, receiving a coherent interference signal at adaptive array antenna system, as target signal is regarded as interference signal, the performance of system rapidly decreases. The main beam does not direct an incidence direction of target signal due to sensitivity in directivity error. This paper proposes beamforming algorithm which combines high order limit condition and directivity error modify method. And it minimizes degree of freedom and decreases interference signal and directivity error using proposed algorithm. This paper compares and analyzes the performance of proposed algorithm and general algorithm using simulation. In this paper, the proposed algorithm correctly estimates an incident angle, but general algorithm occurs an error of about $0.8^{\circ}$.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.102-111
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• 1998

This study was concerned with the development of a heavy duty rust-converting agent, the function of which is to form metal complex coatings, containing vinyl halide-acrylic terpolymer emulsion, defoamer, emulsifying agent, glass flakes, chelating agent such as gallotannic acid, gallic acid, and pyrogallic acid, and other additives. The resulted emulsion products(Sample No.1~No.5) were characterized through test either in the forms of emulsions, which include Viscosity, Penetration rate, Acidity and Film drying rate test, or in the forms of coated layer on rusty steel substrates by FT-IR, which include hardness, gloss, salt spray, adhesion and flame retardant test. The test results are as follows ; Penetration rate(0.1~0.4 mm/min), Solid content(70%), Acidity (pH 1.8~2.0), Specific gravity(1.30~1.35), Film drying rate(108min, RH 40% ; 150min, RH 80%), Gloss(83~92, incident angle $60^{\circ}$; 88~97, incident angle $85^{\circ}$), Pencil hardness(4H~5H), Adhesion (100/100), Salt spray test(>720Hr), LOI(%) value(38%), Vertical burning test(UL 94-v-l). According to the various performance of specimens show above, the evaluation of the availability of this heavy duty rust-converting agent can be concluded that all the samples(No.1~No.5) are capable of being used in the field of chemical plant and in the hazard areas of fire and explosion potential. It was observed that the properties of sample No.2, especially gloss and hardness, were much better than that of the other samples.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.21-29
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• 2016

In this paper, optical tracking and analysis was carried out to find the optical properties with respect to various geometric design parameters of collimator lens which is very efficient when collect the light. As a result, a whole, ellipse incident part can obtain a high light efficiency and a narrow beam angle, and angled cylinder incident part is confirmed to obtain high efficiency and a narrow beam angle at a certain height or more. When Transmission part have a specific surface which can reflect the light in forward direction, a good optical properties was confirmed.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.2
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• pp.185-194
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• 2016

It is essential for generating the synthetic image to test and evaluate a guided missile system in the hardware-in-the-loop simulation. In order to make the evaluation results to be more reliable, the extent of fidelity and rendering performance of the synthetic image cannot be left ignored. There are numerous challenges to simulate the LWIR sensor signature of sea surface depending on the incident angle, especially in the maritime environment. In this paper, we investigate the key factors in determining the apparent temperature of sea surface and propose the approximate formula consisting of optical characteristics of sea surface and sky radiance. We find that the greater the incident angle increases, the larger the reflectivity of sea surface, and the greater the water vapor concentration in atmosphere increases, the larger the amount of sky radiance. On the basis of this information, we generate the virtual maritime environment in LWIR region using the SE-WORKBENCH, physically based rendering software. The margin of error is under seven percentage points.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.8-12
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• 2016

A planar, light-weight, and low-cost notch filter structure is required for the KSTAR ECEI (Electron Cyclotron Emission Imaging) system to protect the mixer arrays from spurious plasma heating power. Without protection, this heating power can significantly degrade or damage the performance of the mixer array. To protect mixer arrays, a frequency selective surface (FSS) structure is the suitable choice as a notch filter to reject the spurious heating power. The FSS notch filter should be located between the lenses of the ECEI system. This paper presents a 170 GHz FSS notch filter for the KSTAR ECEI sensor application. The design of such an FSS notch filter is based on the single-sided square loop geometry, because that makes it relatively insensitive to the incident angle of incoming wave. The FSS notch filter exhibits high notch rejection with low pass-band insertion loss over a wide range of incident angles. This paper also reviews the simulated and measured results. The proposed FSS notch filter might be implemented in other millimeter-wave plasma devices.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.36-40
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• 2017

With an attempt to enhance the visibility of laser beam, we have investigated a black matrix with scattering particles by ray tracing simulations. As the scattering particle density is increased, the detected power by the receiver is increased, thereby enhancing the visibility. In reality, the visibility is reduced with increasing incident angle (away from the normal incidence) of laser beam, a phenomenon also observed by ray tracing simulations. It is due to the fact that the mean path is increased within a highly absorptive BM layer or a smaller number of rays hit the BM area when the incident angle is high. Embedding a number of scattering particles into BM may bring in crosstalk among pixels. However, it is negligible because scattered rays inside highly absorptive BM are re-scattered due to the high scattering particle density, decreasing the power of scattered rays into the active areas.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.835-836
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• 2014

In this paper, we have designed the collimator of different sizes structure for the development of stereo radiation detector. And we conducted a study of the optimal structure of collimator using the results of the Gamma-ray irradiation test associated with the change of the incident angle. According to the results of the performance analysis, and showed the results of the optimal incident angle 2. Results of the paper are used as basic data for designing the structure of the detector efficiency for radiation detection.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.177-191
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• 2019

The local topography has a significant effect on the characteristics of seismic ground motion. This paper investigates the influence of topographic effects on the seismic response of a train-bridge system. A 3-D finite element model with local absorbing boundary conditions is established for the local site. The time histories of seismic ground motion are converted into equivalent loads on the artificial boundary, to obtain the seismic input at the bridge supports. The analysis of the train-bridge system subjected to multi-support seismic excitations is performed, by applying the displacement time histories of the seismic ground motion to the bridge supports. In a case study considering a bridge with a span of 466 m crossing a valley, the seismic response of the train-bridge system is analyzed. The results show that the local topography and the incident angle of seismic waves have a significant effect on the seismic response of the train-bridge system. Leaving these effects out of consideration may lead to unsafe analysis results.