Atmospheric correction of ocean-color sensors: effects of the Earth's curvature

We investigate the influence of the curvature of the Earth on a proposed atmospheric-correction scheme for the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) by simulating the radiance exiting the top of a spherical-shell atmosphere and inserting the result into the proposed correction algorithm. The error in the derived water-leaving reflectance suggests that the effects of the curvature are negligible for solar zenith angles (θ(0)) ≤ 70°. Furthermore, for θ(0) > 70° the error in atmospheric correction can usually be reduced if the molecular-scattering component of the top of the atmosphere reflectance (ρ(r)) is computed with a spherical-shell atmosphere radiative transfer code. Also, for θ(0) > 70° the error in atmospheric correction in a spherical-shell atmosphere, when ρ(r) is computed with a spherical-shell model, can be predicted reasonably well from computations made with plane-parallel atmosphere radiative transfer codes. This implies that studies aimed at improving atmospheric correction can be made assuming plane-parallel geometry and that the investigator can be confident when θ(0)> 70° that any improvements will still be valid for a spherical-shell atmosphere as long as ρ(r) is computed in spherical-shell geometry. Finally, a scheme for computing ρ(r) in a spherical-shell atmosphere in a relatively simple manner is developed.     

Wide angular aperture holograms in photorefractive crystals by the use of orthogonally polarized write and read beams

We demonstrate a method of simultaneous holographic recording and readout in photorefractive crystals that provides high write-read beam isolation and wide angular bandwidth. The method uses orthogonally polarized read and write beams and parallel tangent diffraction geometry near the equal curvature condition to provide spatially separable, orthogonally polarized diffracted output beams with high isolation and wide Bragg-matched angular bandwidth. The available angular bandwidth of this read-write technique is analyzed, simulated, and experimentally investigated. The measured angular bandwidth internal to the crystal is approximately 18° × 6° for our 45°-cut BaTiO(3) crystal, yet the entire hologram still demonstrates high Bragg selectivity. In contrast, traditional nonparallel-tangent geometries yield angular apertures of the order of 1° × 4°.     

Angle-dependent light emission from aligned multiwalled carbon nanotubes under CO(2) laser irradiation

This paper reports the light emission from aligned multiwalled carbon nanotubes (MWNTs) under continuous wave CO(2) laser (λ = 10.6?μm) irradiation. Results indicate that the light emission is dependent on the angle θ between the laser incident direction and the nanotube axis. The relative intensity of the light emission at certain wavelengths shows a Lorentzian feature when θ varies from 0° to 90°. The Lorentzian fitting curve displays a distinct tendency between shorter (λ<600?nm) and longer wavelength (λ>700?nm). A minimum intensity was observed at θ(m) close to 67° under shorter wavelength, whereas a maximum intensity was shown at θ(m) of about 60° at longer wavelength. These results show the anisotropic property of aligned MWNTs.     

Retroreflecting ellipsometer for measuring the birefringence of optical disk substrates

A retroreflecting ellipsometer has been constructed for measuring the birefringence of optical disk substrates. In contrast to conventional ellipsometers with two mechanical arms, this system has only one arm along which both the incident and reflected beams travel. This construction eliminates the mechanical limitations of conventional ellipsometers, thereby permitting normal incidence on the sample. In addition, the single arm is adjustable in two dimensions, with the polar incident angle, θ(inc), varying from 0° to 70°, and the azimuthal incident angle, Φ(inc), varying from 0° to 360°. The condition of normal incidence permits accurate measurement of in-plane birefringence. The adjustability of both θ(inc) and Φ(inc) is necessary for the measurement of possible tilts of the index ellipsoid, and also for the variation of birefringence through the substrate thickness. Measurement results showing the useful features of the equipment are presented. The optics of the hemispherical assembly used for retroreflection as well as for the elimination of undesirable refractions are also studied by use of the ZEMAX lens design program.     

Colors of transparent submicron suspensions on approaching the Rayleigh regime

The features of scattered and transmitted light by dilute suspensions of transparent submicron particles are investigated both in the spectral and in the perceived colorimetric domains, as a function of effective particle diameter D, particle-host refractive-index mismatch m, and scattering angle θ. Our results show that the wavelength λ-dependence of the scattering and extinction cross sections remains quite similar well beyond the Rayleigh regime up to particle sizes of a few hundreds nm, but only for specific scattering angles that depend on D and m, and tend to 90° on approaching the Rayleigh regime. Close to this limit (D/λ<1), a simple criterion that relates the perceived scattering color at θ=90° and the ratio of the sample extinction coefficients at two properly selected wavelengths is demonstrated. A comparison between computed and measured data is presented.     

Dependence of the spectral resolution of an X-ray diffractor on the shape and curvature of the reflecting surface

Dependence of the spectral resolution of a focusing X-ray diffractor on the shape of the reflecting crystallographic planes was theoretically studied in the point source approximation. An analytical expression describing the resolution as a function of the crystal curvature in the focusing circle plane was derived. An optimum radius of the curvature ensuring the best spectral resolution was determined for a nonsymmetric diffractor scheme.     

Synthesis,crystal structure and thermal analysis of a new stilbazolium salt crystal

A new organic crystal of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS·H₂O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232°C.     

Quantifying ligand binding to large protein complexes using electrospray ionization mass spectrometry

An electrospray ionization mass spectrometry (ESI-MS) method for quantifying protein-ligand complexes that cannot be directly detected by ESI-MS is described. The proxy protein ESI-MS method combines direct ESI-MS binding measurements with competitive protein-ligand binding. To implement the method, a proxy protein (P(proxy)), which interacts specifically with the ligand of interest with known affinity and can be detected directly by ESI-MS, is used to quantitatively monitor the extent of ligand binding to the protein of interest. A mathematical framework for establishing the association constant (K(a)) for protein-ligand binding by the proxy protein ESI-MS method, implemented with a P(proxy) containing a single ligand binding site, is given. A modified form of the proxy protein ESI-MS method, which accounts for real-time changes in ligand concentration, is also described. The reliability of these methods is demonstrated for the interactions between the 180 kDa wildtype homotrimeric tailspike protein of the bacteriophage P22 and its endorhamnosidase point mutant (D392N) with its ligands comprising two and three O-antigen repeats from Salmonella enterica serovar Typhimurium: octasaccharide ([α-Gal-(1→2)-[α-Abe-(1→3)]-α-Man-(1→4)-α-Rha](2)) and dodecasaccharide ([α-Gal-(1→2)-[α-Abe-(1→3)]-α-Man-(1→4)-α-Rha](3)). A 27 kDa single chain antibody, which binds to both ligands, served as P(proxy). The results of binding measurements performed at 10 and 25 °C are in excellent agreement with K(a) values measured previously using a fluorescence quenching assay.     

煤制气再燃中NH2与NO反应的物化研究

对煤制气再燃低NOx燃烧过程进行分析,采用量子化学密度泛函理论(DFT)研究NH2自由基与NO的反应机理。全参数优化了各反应物、中间体、过渡态和产物的几何构型,并计算了它们的能量,通过振动频率分析证实中间体和过渡态的真实性。同时用内禀反应坐标(IRC)计算以进一步确定过渡态。为了得到更精确的能量信息,在QCISD(T)水平上计算了单点能。对NH2自由基与NO反应机理进行分析比较,并通过模拟NH2自由基与NO的反应,得出通道NH2+NO→IM1→TS1→IM3→N2+H2O的活化能最低(206.1kJ/mol),为最佳反应通道。揭示其微观机理,对进一步认识再燃脱氮的本质和主要过程提供了重要的理论依据和实践指导。     

Hydrothermally synthesized titanate nanostructures: impact of heat treatment on particle characteristics and photocatalytic properties

The role titanate particle structure plays in governing its characteristics upon calcining and their ensuing influence on photocatalytic performance was investigated. Titanate nanotubes and nanoribbons were prepared by hydrothermal treatment of Aeroxide P25 and then calcined at temperatures in the range 200 - 800 °C. Heat treatment directly transformed the nanotubes to anatase while nanoribbon transformation to anatase occurred via a TiO(2)(B) intermediate phase. The nanoribbon structure also provided an increased resistance to sintering, allowing for retention of the original {010} facet of the titanate nanosheets up to 800 °C. The changing material properties with calcining were found to influence the capacity of the particles to photodegrade oxalic acid and methanol. The nanotubes provided an optimum photoactivity following calcination at 500 °C with this point representing a transition between the relative dominance of crystal phase and surface area on performance. The comparatively smaller initial surface area of the nanoribbons consigned this characteristic to a secondary role in influencing photoactivity with the changes to crystal phase dominating the continually improving performance with calcination up to 800 °C. The structural stability imparted by the nanoribbon architecture during calcination, in particular its retention of the {010} facet at temperatures >700 °C, advanced its photocatalytic performance compared with the nanotubes. This was especially the case for methanol photooxidation whose primary degradation mechanism relies on hydroxyl radical attack and was facilitated by the {010} facet. The effect was not as pronounced for oxalic acid due to its higher adsorption on TiO(2) and therefore greater susceptibility to oxidation by photogenerated holes. This study demonstrates that, apart from modulating sintering effects and changes to crystal phase, the titanate nanostructure influences particle crystallography which can be beneficial for photocatalytic performance.     

Degenerate bifurcations and catastrophe sets via frequency analysis

We present some bifurcation conditions using the well-known stability analysis of feedback systems. A general ordinary differential equation system is formulated in two parts: one that considers the linear part and the other that includes the memoryless nonlinear part, in a similar way as the describing function. The bifurcation conditions are obtained using the results of the generalized Nyquist stability criterion (GNSC) with some explicit formulae derived from some properties of the complex variable

We analyse simultaneously both static and dynamic (Hopf) bifurcations and their degeneracies in a rich example, a continuous stirred-tank reactor (CSTR), in which two consecutive, irreversible, first-order reactions A→B→C occur     

Analysis of forces in rectangular-pole geometries using numerical integration techniques

The force and stiffness characteristics for rectangular-pole geometries are derived as a function of the parameters gap width, pole width and pole displacement. The Schwarz-Christoffel transformation technique is employed, with the simpler cases giving directly integrable solutions, or solutions in terms of elliptic integrals. For the most general case, numerical integration is used to determine the transformation and the force characteristics. The analysis shows that the restoring force and initial stiffness for the finite-width geometry are bounded by those for the infinite-width and line-potential geometries, and that the unbalance force and stiffness vary linearly with pole-width.     

On the interaction between a screw dislocation and a circular coated inclusion with interfacial cracks

Summary The problem of the elastic interaction between a screw dislocation, which is located at an arbitrary point inside either the matrix or the inclusion, and a circular coated inclusion with interfacial cracks is dealt with. An efficient and concise method for a complex multiply connected region is developed, in terms of which the general solutions to the problem are derived. As an illustrative example, explicit series form solutions for complex potentials are presented in the case of one interfacial crack. Based on the complex potentials, image forces on the screw dislocation are then calculated using the Peach-Koehler formula. The equilibrium position of the dislocation is discussed in detail for various crack geometries, coating layer thicknesses and material constant combinations. It is shown that the influence of interfacial cracks on the motion of the dislocation near the coated inclusion is significant. The present solutions contain a number of previously known results as special cases.     

Machinable REPM with Excellent Intrinsic Coercive ForcePrepared by DS Technology

To obtain excellent magnetic properties of machinable REPM prepared by directional solidification (DS) technology Space A, a composition area with θ=0°~5° where easy axis is parallel to solidified direction of alloys, has been established in Zr-Sm-La-Co-Cu-Fe system. In 2/17+1/5+Co, and 2/17+1/5 region near Co phase of Space A, one obtains:Vf = 80.933 - 2.739Zr - 1.828Sm - 0.773Co - 0.147Cu + 0.415Fe + 0.218LaNonequilibrium solidification process of alloys in 2/17+1/5+Co region, is as follows: L→Co,L→2/17, L+2/17→1/5 and L→1/(5-x)+1/(5+x). The product of partially completed peritectic reaction, and 1/(5-x) and 1/(5+x) phases can all be transformed into a homogeneous 1/5 phase after solution treatment in 1413 K for 5 h. Containing 3~6% Co phase magnetically hardened by 0.5~2.5% V, the DS magnets have been achieved with both improved toughness and excellent coercive force of 520 kA/m.     

Diffraction Efficiency and Angular Selectivity of Volume Phase Holograms Recorded in Photorefractive Materials

The recording and replay of volume phase gratings in photorefractive crystals is investigated for both transmission and reflection geometries. Differential equations are derived and solved for a range of parameters including the length of the crystal, the magnitude, spatial distribution and phase angle of the refractive index modulation, the beam ratio at recording, and the angular range at replay. The recording process is assumed to reach a steady-state limit before replay with a weak probe beam. Solution of the repaly equations is mainly by numerical integration, although analytic solutions are derived for special cases. It is found that in certain cases the diffraction efficiency can be greatly increased by replaying the hologram at an angle different from the recording angle.     

水热法合成4A沸石的相变/纳米聚合生长过程及其机理研究

用廉价的硅铝系渣料为原料,通过水热法合成了4A沸石,根据不同时间的晶化反 应产物,用XRD、SEM等表征手段对4A沸石的形成机理及晶体长大过程进行了研究,结果 表明:①该反应过程的机理属前驱体固相→硅酸根或铝酸根液相→P型沸石晶相→P型沸石 向A型沸石的相变→A型沸石向P型沸石逆相变;②4A沸石晶体的长大是通过纳米聚合生 长的结果.     

Analysis of the Phenomena of Diamond Synthesis by Seeding with Diamond

Synthesizing diamond single crystal by diamond seed particles which were electroplated with nickel film as catalyst under high pressure and high temperature （HPHT） was described. The microstructure of nickel film after synthesis and morphology of grown diamond were investigated by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The phase structure in nickel film were graphite, NiC, Ni, and diamond structure hadn＇t been found. A lot of recrystallized graphite pits appear in interface between the inner surface of nickel film and the surface diamond. It is shown that the new-grown diamond was developed epitaxially on the crystal planes of seeds. Also, the new-grown diamond grew by two-dimensional nucleation and by a layer growth mechanism. The growth process of crystal was microaggregate→step→expansion→new crystal layers, and the flat growth interface transformed into a cellular interface at the same time.     

On the spherical X-ray wave focusing upon backscattering from a biaxially bent crystal

It is shown that a spherical X-ray wave incident at the Bragg angle θ_B≈π/2 onto a biaxially bent crystal exhibits independent diffraction in two mutually perpendicular planes. An analytical formula for the size of the diffraction reflection region in the backscattering mode is derived and the analytical expression for the wave intensity distribution at the two-dimensional focus is refined.     

Precipitation phenomena in and electrical resistivity of high-temperature treated langatate (La3Ta0.5Ga5.5O14)

La(3)Ta(0.5)Ga(5.5)O(14) (LTG) single crystals, which have no phase transition up to the melting point, were heat-treated in air at temperatures from 1000°C to 1450°C for 10 h. LaTaO(4) (LT) and LaGaO(3) (LG), which coexist with LTG in the three-phase region on the Ga-poor side, precipitated on the surface of the crystal for heat treatments above 1300°C because of Ga evaporation during the heat treatment. The Ga-poor state near the surface of the 1450°C heat-treated specimen was confirmed by electron probe micro-analysis measurements. The electrical resistivity of LTG single crystals decreased by heat treatment in the range of 1000°C to 1200°C for 10 h in air, where no precipitation was observed, whereas the resistivity increased with heat treatment over 1400°C for 10 h in air. The electrical resistivity of the Ga-poor surface region was higher than that of the interior.