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Design and Implementation of True Random Noise Radar System
Woo-Ki Min,Cheol-Hoo Kim,Constantin A. Lukin,Jeong-Phill Kim 한국전자파학회JEES 2009 Journal of Electromagnetic Engineering and Science Vol.9 No.3
The design theory and experimental results of a true random noise radar system are presented in this paper. Target range information can be extracted precisely by correlation processing between the delayed reference and the signal received from a target, and the velocity information by the Doppler processing with successive correlation data. A K-band noise radar system was designed using random FM noise signal, and the characteristics of the fabricated system were examined with laboratory and outdoor experiments. A C-band random FM noise signal was generated by applying a low-frequency white Gaussian noise source to VCO(Voltage Controlled Oscillator), and a K-band Tx noise signal with 100 ㎒ bandwidth was obtained by using a following frequency multiplier. Two modified waveguide horn arrays were designed and fabricated, and used for the Tx and Rx antennas. The required amount of Tx/Rx isolation was attained by using a coupling cancellation circuit as well as keeping them apart with predetermined spacing. A double down-conversion scheme was used in the Rx and reference channels, respectively, for easy post processing such as correlation and Doppler processing. The implemented noise radar performance was examined with a moving bicycle and a very high-speed target with a velocity of 150 ㎧. The results extracted by the Matlab simulation using the logging data were found to be in a reasonable agreement with the expected results.
A . Oltchev,J . Constantin,G . Gravenhorst,A . Ibrom,주영특,김영채 한국산림과학회 1996 한국산림과학회지 Vol.85 No.2
The SLODSVAT consists of interrelated submodels that simulate : the transfer of radiation, water vapour, sensible heat, carbon dioxide and momentum in two canopy layers determined by environmental conditions and ecophysiological properties of the vegetation ; uptake and storage of water in the $quot;root-stem-leaf$quot; system of plants ; interception of rainfall by the canopy layers and infiltration and storage of rain water in the four soil layers. A comparison of the results of modeling experiments and field micro-climatic observations in a spruce forest(Picea abies [L].Karst) in the Soiling hills(Germany) shows, that the SLODSVAT can describe and simulate the short-term(diurnal) as well as the long-term(seasonal) variability of water vapour and sensible heat fluxes adequately to natural processes under different environmental conditions. It proves that it is possible to estimate and predict the transpiration and evapotranspiration rates for spruce forest ecosystems on the patch and landscape scales for one vegetation period, if certain meteorological, botanical and hydrological information for the structure of the atmospheric boundary layer, the canopy and the soil are available.
Gořalík Marek,Jurča Marek,Bubulinca Constantin,Babayan Vladimír A.,Vilčáková Jarmila,Kazantseva Natalia E.,Sáha Petr 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.5
This work is focused on the optimization of electromagnetic and mechanical properties of magnetic polymer composites for EMI applications as radio absorbers (RAs). Polymer composites with a dual-phase polymer matrix, vinyl-terminated polydimethylsiloxane (PDMS) in epoxy (ER), were investigated for fabricating highlyfilled manganese zinc ferrite (MnZn) and carbonyl iron (CI) composites with respect to radio-absorption and mechanical properties. The dielectric and magnetic properties of the composites were determined by the type, concentration as well as the polymer matrix composition. Increase of the filler and the PDMS concentration leads to an increase in magnetic losses due to a decrease in the demagnetizing field. The electromagnetic properties of the composites were evaluated in the RF band using the impedance method (1 MHz–3 GHz). Based on the complex permittivity (ε*) and the complex permeability (μ*), the reflection loss RL (dB) of single-layer metal-backed RAs were calculated. The RAs with a MnZn ferrite demonstrated a larger bandwidth to thickness ratio in comparison with the CI-based RAs due to a proper ratio between ε* and μ* which leads to the better impedance matching conditions. According to the mechanical analyses (DMA, Charpy impact strength) the significant increase of stiffness up to 125% and the impact strength up to 150% was achieved due to the optimal composition of the polymer matrix and the filler.
Enhancing the H<sub>2</sub>O Megamaser Detection Rate Using Optical and Mid-infrared Photometry
Kuo, C. Y.,Constantin, A.,Braatz, J. A.,Chung, H. H.,Witherspoon, C. A.,Pesce, D.,Impellizzeri, C. M. V.,Gao, F.,Hao, Lei,Woo, J.-H.,Zaw, Ingyin American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>Water megamasers from circumnuclear disks in galaxy centers provide the most accurate measurements of supermassive black hole masses and uniquely probe the subparsec accretion processes. At the same time, these systems offer independent crucial constraints of the Hubble constant in the nearby universe, and thus, the arguably best single constraint on the nature of dark energy. The chances of finding these golden standards are, however, abysmally low, at less than or similar to 3% overall for any level of water maser emission detected at 22 GHz and less than or similar to 1% for those exhibiting disk-like configuration. We provide here a thorough summary of the current state of detection of water megamaser disks along with a novel investigation of the likelihood of increasing their detection rates based on a multivariate parameter analysis of the optical and mid-infrared (mid-IR) photometric properties of the largest database of galaxies surveyed for 22 GHz emission. We find that galaxies with water megamaser emission tend to be associated with strong emission in all Wide-field Infrared Survey Explorer mid-IR wavelengths, with the strongest enhancement in the W4 band, at 22 mu m, as well as with previously proposed and newly found indicators of active galactic nucleus strength in the mid-IR, such as red W1 - W2 and W1 - W4 colors, and the integrated mid-IR luminosity of the host galaxy. These trends offer a potential boost of the megamaser detection rates to 6%-15%, or a factor of 2-8 relative to the current rates, depending on the chosen sample selection criteria, while fostering real chances for discovering. 20 new megamaser disks.</P>
Engineering magnetic type radio-absorbers based on composites with a dual-phase polymer matrix
Marek Gořalík,Marek Jurča,Constantin Bubulinca,Vladimír A. Babayan,Jarmila Vilčáková,Natalia E. Kazantseva,Petr Sáha 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.4
This work is focused on the optimization of electromagnetic and mechanical properties of magnetic polymer composites forEMI applications as radio absorbers (RAs). Polymer composites with a dual-phase polymer matrix, vinyl-terminated polydimethylsiloxane(PDMS) in epoxy (ER), were investigated for fabricating highlyfilled manganese zinc ferrite (MnZn) andcarbonyl iron (CI) composites with respect to radio-absorption and mechanical properties. The dielectric and magnetic propertiesof the composites were determined by the type, concentration as well as the polymer matrix composition. Increase ofthe filler and the PDMS concentration leads to an increase in magnetic losses due to a decrease in the demagnetizing field. Theelectromagnetic properties of the composites were evaluated in the RF band using the impedance method (1 MHz–3 GHz). Based on the complex permittivity (ε*) and the complex permeability (μ*), the reflection loss RL (dB) of single-layer metalbackedRAs were calculated. The RAs with a MnZn ferrite demonstrated a larger bandwidth to thickness ratio in comparisonwith the CI-based RAs due to a proper ratio between ε* and μ* which leads to the better impedance matching conditions. According to the mechanical analyses (DMA, Charpy impact strength) the significant increase of stiffness up to 125% andthe impact strength up to 150% was achieved due to the optimal composition of the polymer matrix and the filler.
Flexural analysis of steel fibre-reinforced concrete members
Constantin E. Chalioris,Thomas A. Panagiotopoulos 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.1
A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for the SFC under compression and tension which include post-peak and post-cracking softening parts. A new compressive stress-strain model for SFC is employed that has been derived from test data of 125 stress-strain curves and 257 strength values providing the overall compressive behaviour of various SFC mixtures. The proposed sectional analysis is verified using existing experimental data of 42 SFC beams, and it predicts the flexural capacity and the curvature ductility of SFC members reasonably well. The developed approach also provides rational and more accurate compressive and tensile stress-strain curves along with bending moment versus curvature curves with regards to the predictions of relevant existing models.
AN IMPROVED ANALYSIS FOR DETERMINATION OF MONOVINYL AND DIVINYL PROTOPORPHYRIN IX
Kim, Jin-Seog,Rebeiz, Constantin A. Korean Society of Photoscience 1995 Journal of Photosciences Vol.2 No.2
For studying chlorophyll biosynthetic heterogeneity of plants, it is necessary to establish a technique for microassay of a putative monovinyl and divinyl protoporphyrin IX. Precise determination of the amounts of monovinyl and divinyl protoporphyrin IX is difficult with optical electronic spectroscopy even at 77$\circ$C. Such a problem could be solved by conversion of protoporphyrin IX to protoporphyrin IX dimethylester with diazomethane and subsequent Mg insertion into protoporphyrin IX dimethylester by reaction with a Grignard solution. The proportion of monovinyl and divinyl Mg-protoporphyrin IX dimethylester formed was measured instead of direct measuring that of protoporphyrin IX by low-temperature spectrofluorometry. The relative proportions of monovinyl and divinyl of protoporphyrin IX, Mg-protoporphyrin IX, and Mgprotoporphyrin IX dimethylester have not changed during the chemical conversion steps. This analysis system could be useful for the study of the monovinyl and divinyl chlorophyll biosynthetic routes in plants.
Origin of Chlorophyll α Biosynthetic Heterogeneity in Higher Plants
Jin Seog Kim,Constantin A . Rebeiz 생화학분자생물학회 1996 BMB Reports Vol.29 No.4
In this study, the origin of the monovinyl chlorophyll a carboxylic biosynthetic route was investigated in barley (Hordeum uulgare L.) and com (Zea mays L.). Protoporphyrin IX accumulated in vivo or in vitro was found to be all of the divinyl form. Furthermore, the conversion of divinyl protopotphyrin IX to monovinyl protoporphyrin IX in vitro was not observed. In contrast, the biosynthesis and accumulation of monovinyl Mg-protoporphyrin IX and its methyl ester occurred in etiolated leaves and divinyl Mg-protoporphyrin IX was convertible to monovinyl Mg-protoporphyrin IX in vitro. These results suggest that the monovinyl chlorophyll a carboxylic biosynthetic route in plants may originate from the divinyl Mg-protoporphyrin IX pool.