Air-breathing mode laser propulsion with a long-pulse TE CO_2 laser

Air-breathing mode laser propulsion experiment with a long-pulse transversely excited(TE) CO2 laser is carried out,and its ignition problem is solved with the ignition needle of lightcraft.Owing to the ignition needle,an order of magnitude reduction in the ignition threshold is demonstrated.The result is compared with previous study.The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy(6-14 J) and pulse width(20,32,and 40μs) is discussed.     

Theoretical Study of Interesting Fine-Structure Splittings Based on a Scenario for Precise Calculations

Based on the multi-configuration Dirac-Fock self-consistent field method, a scenario has been presented to calculate the fine-structure energy levels of C^2＋ and Si^2＋ excited states （31 D2 and 33D1,2,3）. The Breit interactions and quantum electrodynamics corrections are added as perturbations. The present calculation results are found to be in excellent agreement with the experimental data. By means of the precise calculation procedure, we elucidate that four competitive mechanisms influence the interesting fine-structure splittings in C^2＋ and Si^2＋, such as spin-orbit interactions, relativistic corrections of exchange interactions, the Breit interactions and electron correlation effects. Furthermore, the mechanism of relativistic correction of exchange interactions has been studied clearly. We elucidate that the inner shell 2p1/2,3/2 orbitals are essential to relativistic corrections of exchange interactions which are crucial for the final anomalous fine-structure splittings.     

Equiangular-spiral bent lightpipes with arbitrary bent angle

A recent study proposed the concept of a leakage-free bent lightpipe with an equiangular-spiral shape [S.-C. Chu, J.-L. Chern, Opt. Lett. 30 (2005) 3006]. This paper extends the design of a leakage-free equiangular-spiral bent lightpipe with arbitrary-bend-angle and addresses in detail the mathematical formalism required to build such an equiangular-spiral bent lightpipe. Furthermore, a comparison of the proposed equiangular-spiral bent lightpipe and a conventional circular bent lightpipe is provided. Numerical verifications are discussed, and experimental explorations with different bent shapes and angles are carried out for comparison. Results show that equiangular-spiral bent lightpipes with different bent angles exhibit a theoretical 100% transmission with more than 76% efficiency when practically propagating, which is much better than conventional circular bent lightpipes. The output irradiance distributions of bent lightpipes with different bent shapes are also investigated.     

Near-field-smoothing of periodic chirped pulse with applied angular dispersion

Periodic chirped pulse (PCP) with applied angular dispersion has been approved to be an efficient beam smoothing method in inertial confinement fusion. In this paper, the propagation characteristics of dispersed PCP in near field is analyzed theoretically and calculated numerically, and the results indict dispersed PCP is a motion beam, which can be applied to improve beam uniformity in near field. An experiment is carried out to validate the near-field-intensity smoothing effect of PCP.     

A flexible carbon nanotube field emitter fabricated on a polymer substrate by a laser separation method

The fabrication of a sparsely networked carbon nanotube (CNT) thin film on a polycarbonate substrate as the conductor electrode and the emitting cathode by a newly proposed laser separation method is reported. Based on this approach, numerous surface protruding tube tips can be structured straightforwardly, which results in favorable field-emission characteristics. A flexible field emitter with a low turn-on voltage of 1.0 V/μm can be obtained. This method also demonstrates the abilities for fabricating a film with precision patterns and varying CNT concentrations as well as the flexibility of direct film formation on a curved surface. Moreover, all fabrication steps are executed in the ambient environment and at room temperature.     

DYNAMIC CHARACTERISTICS IN INCOMPRESSIBLE HYPERELASTIC CYLINDRICAL MEMBRANES

In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inner surface. A second-order nonlinear ordinary differential equation that approximately describes the radial oscillation of the inner surface of the membrane with respect to time is obtained. Some interesting conclusions are proposed for different materials, such as the neo-Hookean material, the Mooney-Rivlin material and the Rivlin-Saunders material. Firstly, the bifurcation conditions depending on the material parameters and the pressure loads are determined. Secondly, the conditions of periodic motion are presented in detail for membranes composed of different materials. Meanwhile, numerical simulations are also provided.     

Deep‐Ultraviolet Nonlinear Optics in a Borate Framework with 21‐Ring Channels

A new borate LiBa₃(OH)[B₉O₁₆][B(OH)₄], which combines the uniform porosity of open‐frameworks with the extraordinary NLO properties of borates, has been obtained under hydrothermal conditions by using mixed lithium and barium ions as templates. The framework displays an acs‐type net with large 21‐ring channels. The second harmonic generation (SHG) measurement shows that it is a type I phase‐matchable material with a strong SHG signal intensity about 3.1 times that of KDP (KH₂PO₄). UV/Vis–NIR diffuse reflectance analysis indicates that the compound has a wide transparency range with the short‐wavelength absorption edge below 200 nm. These characteristics reveal that the compound is a promising deep‐UV nonlinear optical material.     

Analysis of hybrid donor layer in organic solar cells based on SubPc and rubrene

In this paper, photovoltaic characteristics of ITO/PEDOT:PSS/SubPc:Rubrene (mixed ratio R by weight)/C₆₀/Bphen/Ag organic solar cells (OSCs) are analyzed in detail. The intrinsic properties of a SubPc:rubrene doped layer on device performance were discussed based on theoretical analysis of the experimental OSCs. The ratio R was 0, 0.25, 0.5, and 0.75,1, respectively. The results showed that when R was 0.75 performing the best, which owned the highest short circuit current (J _sc ) 6.61 mA/cm² and highest power conversion efficiency (PCE) 2.44%, the FF was 41% and the open circuit current (V _oc ) was 0.905 V. The suitable HOMO level, absorption capacity, carrier transport ability and exciton diffusion length (L _D ) of organic material are very important for the performance of the device.     

A fluorine-contained copolymer ultra-thin film: Stability and electrochemical corrosion behavior

A novel fluorine-contained random copolymer (2,3,4,5,6-pentafluorostyrene)-r-poly(4-vinyl benzocyclobutene) (P(PFSt-r-4-VBCB)) was synthesized, and then spin-coated onto Si substrates followed by thermal cross-linking to produce the copolymer ultra-thin films. Although the surface modification with the P(PFSt-r-4-VBCB) film was simple and did not rely on special surface chemical reactions, the film could decrease the surface energy significantly, more importantly; the film demonstrated excellent stability and corrosion resistance. This random copolymer film could find broad applications in modifying various solid surfaces to enhance the properties such as corrosion resistance and solvent resistance.     

Fine tuning the assembly and gel behaviors of PEGylated polypeptide conjugates by the copolymerization of l‐alanine and γ‐benzyl‐l‐glutamate N‐carboxyanhydrides

Tuning the secondary structure of polypeptide is an effective strategy to modulate the assembly behaviors of polypeptide‐based copolymers. In this study, ring‐opening polymerization of l ‐alanine (Ala) and γ‐benzyl‐l ‐glutamate (BLG) N‐carboxyanhydrides was adopted using mPEG‐NH₂ as the initiator to prepare mPEG‐poly(l ‐alanine‐co‐γ‐benzyl‐l ‐glutamate) (PEAB) copolymers with various Ala to BLG ratios. ¹H NMR spectra and GPC test confirmed their well‐defined chemical structures. FT‐IR spectra indicated that at the powder state, all copolymers adopted both β‐sheet and α‐helical conformations. With the content of PBLG increased, the crystallization temperature and melting points of PEAB copolymers first rose then fell indicated by DSC curves. The self‐assembly of PEAB copolymers in dilute aqueous solution studied by DLS, TEM and circular dichroism spectra showed that PEAB copolymers self‐assembled into nanostructures with diverse morphologies and sizes due to distinct polypeptide conformations. Rheological analysis indicated that the alteration of the polypeptide composition can effectively modulate the modulus of PEAB assemblies in concentrated solutions. In all, copolymerization of two hydrophobic amino acid N‐carboxyanhydrides into the polypeptide block maybe an effective approach for modulating the assembly properties of PEGylated polypeptide. Besides, nanosilver‐encapsulated PEA or PEAB hydrogel showed promising antibacterial effect against Staphylococcus aureus and Bacillus subtillis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1512–1523