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31.
LiNbO3:Fe晶体中光写入阵列平面光波导的实验实现 总被引:6,自引:6,他引:6
采用两束相干平行光形成的干涉光场辐照LiNbO3: Fe晶体,通过光折变效应在晶体中写入了阵列平面光波导.分别采用马赫-曾德干涉仪光路和光栅衍射法测量了阵列平面光波导的横向折射率分布和周期,并对所写入的阵列平面光波导进行了初步的导光测试.实验结果表明,用这种方法写入阵列平面光波导简便可行. 相似文献
32.
33.
We have derived an upper bound on the K-π transition amplitude of the penguin operator using hadronic sum rules. Combined with an anomalous-commutator contribution, this sets lower and upper limits on the physical K → 2π amplitude of the penguin operator. Applying this result to CP-violating effects, we find that the Gilman-Hagelin lower limit on ?′/? decreases by an order of magnitude. 相似文献
34.
The properties of water layers on bare marble and on marble samples covered with various amounts of tetradecylammonium chloride (TDACl) after flotation were investigated by thermal analysis methods. The dependences of the layer thickness, activation energy, enthalpy and entropy of the bonded watervs. the amount of TDACl previously deposited on the marble surface were determined. The results obtained and the literature data were used to propose an interpretation of the changes caused in these parameters by the coverage of the marble surface with TDACl molecules. A correlation between these parameters and the changes in water structure and marble flotatibility is also presented.
Zusammenfassung Eigenschaften von Wasserfilmen auf unbeschichteten und mit Tetradecylammoniumchlorid (TDACl) in unterschiedlichen Mengen bedeckten Marmorproben wurden nach Flotation thermoanalytisch untersucht. Die Abhängigkeit der Schichtdicke, der Aktivierungsenergie und der Enthalpie und Entropie des gebundenen Wassers von der Menge des vorhergehend auf die Marmoroberfläche aufgebrachten TDACl wurden ermittelt. Die durch die Bedeckung der Marmoroberfläche mit TDACl verursachten Veränderungen dieser Parameter werden anhand der erhaltenen Resultate und von Literaturangaben interpretiert. Beziehungen zwischen diesen Parameters und Veränderungen der Wasserstrukturen und der Flotierbarkeit des Marmors werden angegeben.
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35.
A. Bartnik H. Fiedorowicz R. Jarocki J. Kostecki M. Szczurek A. Biliński O. Chernyayeva J. W. Sobczak 《Applied Physics A: Materials Science & Processing》2010,99(4):831-836
Extreme ultraviolet (EUV) radiation is the electromagnetic radiation ranging from vacuum ultraviolet to soft X-rays. A single
EUV photon carries enough energy to ionize any atom or molecule. The penetration depth of the radiation in any material is
very short, ranging from tens to hundreds nanometers. Intense EUV pulses can remove material from the surface or modify its
morphology or/and chemical structure. In this work, the radiation from a laser-plasma EUV source based on a double-stream
gas-puff target was used for surface modification of polyethylene terephthalate (PET). The PET samples were irradiated with
the EUV pulses emitted from krypton plasma and focused with a gold-plated ellipsoidal collector. The spectrum of the focused
radiation covered the wavelength range from 9 to 70 nm. The PET samples were irradiated for 1 s–2 min at a 10-Hz repetition
rate. Surface morphology of polymer samples after irradiation was investigated using a scanning electron microscope. Changes
in chemical surface structure of the irradiated samples were investigated using an X-ray photoelectron spectroscopy. Different
kinds of surface microstructures were obtained depending on the EUV fluence in a single pulse and the total EUV fluence. XPS
measurements also revealed a modification of the chemical structure. 相似文献
36.
对文献^[1]中用弹簧秤直观显示摩擦力的实验进行了改进,成功地解决了原实验在滑动摩擦力的测量过程中不易读数的问题。 相似文献
37.
Using the formalism of relativistic acoustic geometry we study the expanding chiral fluid in the regime of broken chiral symmetry near the QCD chiral phase transition temperature Tc. The dynamics of pions below Tc is described by the equation of motion for a massless scalar field propagating in curved spacetime similar to an open FRW universe. The metric tensor depends locally on the soft pion dispersion relation and the four-velocity of the fluid. In the neighbourhood of the critical point an analogue trapped region forms with the analogue trapped horizon as its boundary. We show that the associated surface gravity diverges near the critical point as κ∼(Tc−T)−1. Hence, if the horizon forms close to the critical temperature the analogue Hawking temperature may be comparable with or even larger than the background fluid temperature. 相似文献
38.
We study a supersymmetric model in curved background spacetime. We calculate the effective action and the vacuum expectation value of the energy momentum tensor using a covariant regularization procedure. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density and pressure. Assuming the presence of a cosmic fluid in addition to the vacuum fluctuations of the supersymmetric field an effective equation of state is derived in a self-consistent approach at one loop order. The net effect of the vacuum fluctuations of the supersymmetric fields in the leading adiabatic order is a renormalization of the Newton and cosmological constants. 相似文献
39.
A system of charged bosons at finite temperature and chemical potential is studied in a general-relativistic framework. We assume that the boson fields interact only gravitationally. At sufficiently low temperature the system exists in two phases: the gas and the condensate. By studying the condensation process numerically we determine the critical temperature Tc at which the condensate emerges. As the temperature decreases, the system eventually settles down in the ground state of a cold boson star. 相似文献
40.
Reimers JR Solomon GC Gagliardi A Bilić A Hush NS Frauenheim T Di Carlo A Pecchia A 《The journal of physical chemistry. A》2007,111(26):5692-5702
A review is presented of the nonequilibrium Green's function (NEGF) method "gDFTB" for evaluating elastic and inelastic conduction through single molecules employing the density functional tight-binding (DFTB) electronic structure method. This focuses on the possible advantages that DFTB implementations of NEGF have over conventional methods based on density functional theory, including not only the ability to treat large irregular metal-molecule junctions with high nonequilibrium thermal distributions but perhaps also the ability to treat dispersive forces, bond breakage, and open-shell systems and to avoid large band lineup errors. New results are presented indicating that DFTB provides a useful depiction of simple gold-thiol interactions. Symmetry is implemented in DFTB, and the advantages it brings in terms of large savings of computational resources with significant increase in numerical stability are described. The power of DFTB is then harnessed to allow the use of gDFTB as a real-time tool to discover the nature of the forces that control inelastic charge transport through molecules and the role of molecular symmetry in determining both elastic and inelastic transport. Future directions for the development of the method are discussed. 相似文献