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1.
2.
Jaehoon Lee Seongha Kim Yonghoon Kim Yunje Oh Seongtaek Hwang Jichai Jeong 《Lightwave Technology, Journal of》2003,21(2):521-527
Optically preamplified receiver performance according to the vestigial sideband (VSB) filtering has been numerically investigated for 40-Gb/s optical signals modulated with nonreturn-to-zero, duobinary nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed RZ, and duobinary carrier-suppressed RZ formats. The VSB filtering enables the spectral widths of NRZ, duobinary NRZ, and RZ signals to be reduced without severe power penalties at the receiver. On the other hand, carrier-suppressed RZ and duobinary carrier-suppressed RZ signals have no large advantages over VSB filtering because of the characteristics of their signals. Our results suggest that RZ signals are the most suitable modulation format for VSB filtering, without considering the filter loss, because of the tolerance of the intersymbol interference and a large spectral width. However, duobinary NRZ signals are the most suitable modulation format for VSB filtering, considering the filter loss, because of their narrow spectral width. 相似文献
3.
In this paper, we present design features, implementation, and validation of a satellite simulator subsystem for the Korea Multi‐Purpose Satellite‐2 (KOMPSAT‐2). The satellite simulator subsystem is implemented on a personal computer to minimize costs and trouble on embedding onboard flight software into the simulator. An object‐oriented design methodology is employed to maximize software reusability. Also, instead of a high‐cost commercial database, XML is used for the manipulation of spacecraft characteristics data, telecommand, telemetry, and simulation data. The KOMPSAT‐2 satellite simulator subsystem is validated by various simulations for autonomous onboard launch and early orbit phase operations, anomaly operation, and science fine mode operation. It is also officially verified by successfully passing various tests such as the satellite simulator subsystem test, mission control element system integration test, interface test, site installation test, and acceptance test. 相似文献
4.
A compact dipole antenna for the terrestrial digital multimedia broadcasting (TDMB) application is presented. The length of the antenna is about 0.06λ at the TDMB resonance frequency of 190 MHz. Miniaturization of the antenna is achieved by using meander structures and lumped elements. The proposed antenna has two resonance frequencies and covers the TDMB band from 174 MHz to 216 MHz in Korea. The antenna has good impedance bandwidth and radiation characteristics for the TDMB. The experimental results of the designed dipole antenna are presented and analyzed. 相似文献
5.
KS Choi JJ Nah CU Choi YJ Ko HJ Sohn G Libeau SY Kang YS Joo 《Canadian Metallurgical Quarterly》2003,96(1):1-16
An experimental competitive enzyme-linked immunosorbent assay (morbillivirus cELISA) using a recombinant N antigen (rRPV N) expressed in a baculovirus and a ruminant morbillivirus (RPV and PPRV)-specific monoclonal antibody (P-13A9) was developed for simultaneous detection of rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) antibodies and its diagnostic performance was evaluated. A set of known reference antisera against RPV and PPRV belonging to different lineages, experimental sera from cattle vaccinated for a RPV of Asian lineage, and field sera from cattle and sheep/goat populations known to be positive (West Africa) and negative (Korea) for RPV and PPRV were used for the evaluation. Morbillivirus cELISA results on the panel of experimental RPV and PPRV antisera showed high correlation (r=0.97) between the whole virus and the rRPV N antigens, suggesting that the rRPV N contains a ruminant morbillivirus-specific antigenic determinant recognized by the P-13A9 and it may be suitable as an ELISA antigen in place of the whole virus. Morbillivirus cELISA detected anti-RPV and anti-PPRV antibodies in all reference RPV and PPRV antisera containing VN titers >/=1:8, suggesting that the assay can simultaneously detect antibodies against RPV and PPRV. Anti-RPV antibody was detected by morbillivirus cELISA in vaccinated cattle as early as the VNT and continued to be detectable by both the cELISA and the VNT until termination of the study. When applied to field samples from Africa, morbillivirus cELISA showed good agreement with a RP cELISA kit (kappa value of 0.86) in bovine sera and with a peste des petits ruminant cELISA kit (kappa value of 0.81) in caprine/ovine sera. Usefulness of morbillivirus cELISA using the rRPV N protein was discussed. 相似文献
6.
A novel reconfigurable microstrip patch antenna with frequency and polarization diversities is proposed. A U‐slot is incorporated into a square patch, and a PIN diode is utilized to switch the slot on and off, which realizes the frequency diversity characteristic. The polarization diversities among linear polarization (LP), right‐hand circular polarization (RHCP), and left‐hand circular polarization (LHCP) are also obtained by switching three PIN diodes on the slot and the truncating corners of a square patch on and off. The antenna design and experimental results are presented. 相似文献
7.
Joon‐Seop Kim Min‐Chul Hong Yeon Hwa Nah Yeonhee Lee Seunghee Han Hyun Eui Lim 《应用聚合物科学杂志》2002,83(11):2500-2504
The wetting properties of polystyrene‐based ionomers treated with plasma source ion implantation (PSII) were investigated by the measurement of water contact angles. When sulfonated ionomers were aged for a few days, the hydrophobic recovery for the ionomers became much slower than that for the nonionic polymers. However, when the samples were aged over 20 days, the water contact angle of the ionomers converged with that of the nonionic polymer. Thus, it was concluded that the ionic interaction between the ionic groups and the presence of ionic groups together resulted in the slow hydrophobic recovery and that the aging effect was significant for the ionomers. For the methacrylate ionomer of low ion content, on the other hand, it was found that the PSII treatment produced only a small change in hydrophobic recovery behavior. Thus, it was suggested that the low ionic content coupled with the small size of the ionic unit might cause changes only of a very insignificant degree in hydrophobic recovery behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2500–2504, 2002 相似文献
8.
Depolymerization of the biopolymer chitosan by an autoclaving process at 121°C and 15 psi was investigated using various treatments. Acetic acid was found to be the most effective solvent in decreasing chitosan viscosity among the six organic acids tested. The rate of viscosity decrease increased with increasing chitosan concentration. The viscosity of 1% chitosan in 1% acetic acid decreased rapidly to 91% of the initial viscosity following the initial 15 min of autoclaving. This decreased gradually to 93% and 94% in 30 and 60 min, respectively, without being adversely affected by the chitosan solution volume. The degree of deacetylation was comparable before and after autoclaving for 60 min. Chitosan at three molecular weights (Mr = 1597, 1110, and 789 kDa) decreased in molecular weight by 46%–51% in the 15‐min treatment, 55%–60% in the 30‐min treatment, and 60%–62% in the 60‐min treatment. The addition of 0.1%–1.0% (v/v) concentrations of hydrogen peroxide to the chitosan solution autoclaved for 15 min decreased viscosity by 94%–98% and molecular weight by 69%–83%. This process is a simple, timesaving, homogeneous depolymerization procedure, and it is possible to prepare partially hydrolyzed chitosan with specified molecular weights by regulating the time of treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1890–1894, 2003 相似文献
9.
Changyong Choi Su Young Chae Tai‐Hyoung Kim Jung Keon Kweon Chong Su Cho Mi‐Kyeong Jang Jae‐Woon Nah 《应用聚合物科学杂志》2006,99(6):3520-3527
Diblock copolymers with different poly(ε‐caprolactone) (PCL) block lengths were synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of monomethoxy poly(ethylene glycol) (mPEG‐OH, MW 2000) as initiator. The self‐aggregation behaviors and microscopic characteristics of the diblock copolymer self‐aggregates, prepared by the diafiltration method, were investigated by using 1H NMR, dynamic light scattering (DLS), and fluorescence spectroscopy. The PEG–PCL block copolymers formed the self‐aggregate in an aqueous environment by intra‐ and/or intermolecular association between hydrophobic PCL chains. The critical aggregation concentrations of the block copolymer self‐aggregate became lower with increasing hydrophobic PCL block length. On the other hand, reverse trends of mean hydrodynamic diameters were measured by DLS owing to the increasing bulkiness of the hydrophobic chains and hydrophobic interaction between the PCL microdomains. The partition equilibrium constants (Kv) of pyrene, measured by fluorescence spectroscopy, revealed that the inner core hydrophobicity of the nanoparticles increased with increasing PCL chain length. The aggregation number of PCL chain per one hydrophobic microdomain, investigated by the fluorescence quenching method using cetylpyridinium chloride as a quencher, revealed that 4–20 block copolymer chains were needed to form a hydrophobic microdomain, depending on PCL block length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3520–3527, 2006 相似文献
10.
Because silica has strong filler–filler interactions, a silica‐filled rubber compound shows a poor filler dispersion compared to a carbon black‐filled one. Improvement of the filler dispersion in silica‐filled styrene–butadiene rubber (SBR) compounds was studied using low molecular weight polybutadiene (liquid PBD) with the high content of 1,2‐unit. By adding the liquid PBD to the silica‐filled SBR compound, the filler dispersion and flow property are improved. The cure time and cure rate become faster as the 1,2‐unit content of the liquid PBD increases for the compounds containing the liquid PBD. The crosslink density increases linearly with increase in the 1,2‐unit content of the liquid PBD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3135–3140, 2003 相似文献