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871.
Dang Thi Thanh Le Do Dang Trung Nguyen Duc Chinh Bui Thi Thanh Binh Hoang Si Hong Nguyen Van Duy Nguyen Duc Hoa Nguyen Van Hieu 《Current Applied Physics》2013,13(8):1637-1642
The design of core–shell heteronanostructures is powerful tool to control both the gas selectivity and the sensitivity due to their hybrid properties. In this work, the SnO2–ZnO core–shell nanowires (NWs) were fabricated via two-step process comprising the thermal evaporation of the single crystalline SnO2 NWs core and the spray-coating of the grainy polycrystalline ZnO shell for enhanced ethanol sensing performance. The as-obtained products were investigated by X-ray diffraction, scanning electron microscopy, and photoluminescence. The ethanol gas-sensing properties of pristine SnO2 and ZnO–SnO2 core–shell NW sensors were studied and compared. The gas response to 500 ppm ethanol of the core–shell NW sensor increased to 33.84, which was 12.5-fold higher than that of the pristine SnO2 NW sensor. The selectivity of the core–shell NW sensor also improved. The response to 100 ppm ethanol was about 14.1, whereas the response to 100 ppm liquefied petroleum gas, NH3, H2, and CO was smaller, and ranged from 2.5 to 5.3. This indicates that the core–shell heterostructures have great potential for use as gas sensing materials. 相似文献
872.
A. Yu. Cherny A. E. Dorokhov Nguyen Suan Han V. N. Pervushin V. I. Shilin 《Physics of Atomic Nuclei》2013,76(3):382-396
The bound-state generating functional is constructed in gauge theories. This construction is based on the Dirac Hamiltonian approach to gauge theories, the Poincaré group classification of fields and their nonlocal bound states, and the Markov-Yukawa constraint of irreducibility. The generating functional contains additional anomalous creations of pseudoscalar bound states: para-positronium in QED and mesons inQCDin the two-gamma processes of the type of γ + γ → π 0 +para-positronium. The functional allows us to establish physically clear and transparent relations between the perturbativeQCD to its nonperturbative low-energy model by means of normal ordering and the quark and gluon condensates. In the limit of small current quark masses, the Gell-Mann-Oakes-Renner relation is derived from the Schwinger-Dyson and Bethe-Salpeter equations. The constituent quark masses can be calculated from a self-consistent nonlinear equation. 相似文献
873.
Thi Tran Minh Ben Pham Van Thai Dang Van Hien Nguyen Thi 《Optical and Quantum Electronics》2013,45(2):147-159
This study has been carried out on the optical properties of polyvinyl-pyrrolidone (PVP), the energy transition process in nanocomposite of PVP capped ZnS:Mn nanocrystalline and the influence of the PVP concentration on the optical properties of the PVP capped ZnS:Mn nanocrystalline thin films synthesized by the wet chemical method. The microstructures of the samples were investigated by X-ray diffraction, the atomic absorption spectroscopy, and transmission electron microscopy. The results showed that the prepared samples belonged to the sphalerite structure with the average particle size of about 2–3 nm. The optical properties of samples are studied by measuring absorption, photoluminescence (PL) spectra and time-resolved PL spectra in the wavelength range from 200 to 700 nm at 300 K. From data of the absorption spectra, the absorption edge of PVP polymer was found about of 230 nm. The absorption edge of PVP capped ZnS:Mn nanoparticles shifted from 322 to 305 nm when the PVP concentration increases. The luminescence spectra of PVP showed a blue emission with peak maximum at 394 nm. The luminescence spectra of ZnS:Mn–PVP exhibits a blue emission with peak maximum at 437 nm and an orange–yellow emission of ion Mn2+ with peak maximum at 600 nm. While the PVP coating did not affect the microstructure of ZnS:Mn nanomaterial, the PL spectra of the PVP capped ZnS:Mn samples were found to be affected strongly by the PVP concentration. 相似文献
874.
Yang Liu Hsiangkuo Yuan Andrew M. Fales Tuan Vo‐Dinh 《Journal of Raman spectroscopy : JRS》2013,44(7):980-986
Local pH environment has been considered to be a potential biomarker for tumor diagnosis because solid tumors contain highly acidic environments. A pH‐sensing nanoprobe based on surface‐enhanced Raman scattering (SERS) using nanostars under near‐infrared excitation has been developed for potential biomedical applications. To theoretically investigate the effect of protonation state on SERS spectra of p‐mercaptobenzoic acid (pMBA), we used the density functional theory (DFT) with the B3LYP functional to calculate Raman vibrational spectra of pMBA‐Au/Ag complex in both protonated and deprotonated states. Vibrational spectral bands were assigned with DFT calculation and used to investigate SERS spectral changes observed from experiment when varying pH value between five and nine. The SERS peak position of pMBA at ~1580 cm−1 was identified to be a novel pH‐sensing index, which has small but noticeable downshift with pH increase. This phenomenon is confirmed and well‐explained with theoretical simulation. The study demonstrates that SERS is a sensitive tool to monitor minor structural changes due to local pH environment, and DFT calculations can be used to investigate Raman spectra changes associated with minor differences in molecular structure. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
875.
J. S. Sanghera L. B. Shaw L. E. Busse V. Q. Nguyen P. C. Pureza B. C. Cole B. B. Harrison I. D. Aggarwal R. Mossadegh F. Kung D. Talley D. Roselle R. Miklos 《Fiber and Integrated Optics》2013,32(3):251-274
Chalcogenide glass fibers based on sulphide, selenide, telluride, and their rare earth doped compositions are being actively pursued both at the Naval Research Laboratory in Washington, D.C. (NRL) and worldwide. Great strides have been made in reducing optical losses using improved chem ical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, current singlemode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy spectroscopy, fiber infrared (IR) sources lasers, amplifiers, and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements the optical quality of the fibers and the performance of the fibers in existing future applications. 相似文献
876.
Duc Minh Nguyen Thanh Nam Nguyen Thierry Chartier Monique Thual 《Fiber and Integrated Optics》2013,32(4):225-238
Abstract A novel and simple procedure to improve the accuracy of the measurement of the third-order Kerr non-linear coefficient of optical fibers based on self-phase modulation is described. It includes an efficient method to identify the chirp of the input pulse. A standard single-mode fiber and a highly non-linear microstructure chalcogenide fiber have been measured. The accuracy of the measurement is increased to ±5% instead of ±19% with the classical self-phase modulation method in this case. 相似文献
877.
Xuan Hien Nguyen 《偏微分方程通讯》2013,38(3):257-280
In this paper, we describe the construction of new examples of self-translating surfaces under the mean curvature flow. We find the new surfaces by desingularizing the intersection of a grim reaper and a plane to obtain approximate solutions, then we solve a perturbation problem to find the exact solutions. Our work is inspired from Kapoulea' construction of minimal surfaces but differs from it by our more abstract and direct study of the linear operator, via Fredholm operators. 相似文献
878.
Nguyen Minh Tri 《偏微分方程通讯》2013,38(1-2):325-354
ABSTRACT We study the Cauchy Problem associated to a class of quasilinear Schrödinger equations which have been derived as models of several physical phenomenas. We prove local existence in arbitrary space dimension N without any smallness condition on the initial data. 相似文献
879.
880.
Triet Minh Le Quan Hoang Pham Trong Duc Dang Tuan Huy Nguyen 《Journal of Computational and Applied Mathematics》2013
We consider the problem of determining the temperature u(x,t), for (x,t)∈[0,π]×[0,T) in the parabolic equation with a time-dependent coefficient. This problem is severely ill-posed, i.e., the solution (if it exists) does not depend continuously on the given data. In this paper, we use a modified method for regularizing the problem and derive an optimal stability estimation. A numerical experiment is presented for illustrating the estimate. 相似文献