New dust aerosol identification method for spaceborne lidar measurements

Classification is a critical step in the backscatter lidar data processing to accurately retrieve extinction and backscatter profiles of atmospheric aerosols and clouds. Different schemes, such as the probability distribution functions (PDFs) method, have been used in the cloud and aerosol classification. In this paper, we attempt to use the support vector machine (SVM) to discriminate aerosols from clouds, with a focus on dust aerosol classification in China. To demonstrate the feasibility of the SVM classifier, we chose dust storms that occurred in the Gobi and Taklimakan deserts and observed by the CALIPSO lidar in spring time 2007. The results show that the SVM can correctly identify the dust storms.     

双视场米散射激光雷达探测对流层气溶胶

介绍了自行研制的用来探测对流层大气气溶胶消光特性的双视场米散射激光雷达.该激光雷达采用两个具有独立接收视场的探测通道分别接收高低层532 nm的大气回波信号,可以兼顾低层大视场角低探测盲区和高层小视场角高探测高度的要求.叙述了该雷达系统的总体结构和技术参量以及数据处理方法,给出了合肥地区(东经117.16°,北纬31.90°)大气气溶胶消光系数廓线和对流层光学厚度的探测结果.测量结果表明,该雷达具备昼夜连续观测对流层大气气溶胶的能力,可以很好地反映气溶胶粒子的时间和空间分布特征.      

Mixing angles,mass matrix and CP violation in the Kobayashi-Maskawa model

We analyze the K_L ? K_S mass difference Δm and CP-violating parameters η_+? and η₀₀ in terms of the mixing angles of the six-quark Kobayashi-Maskawa model. In contrast to previous analyses, we include a parameter to allow for uncalculable contributions of low-mass intermediate states to the mass matrix. As a result, Δm provides only weak constraints on the mixing angles but stronger constraints may possibly be obtained using data on η₀₀.     

Influence of temperature variations on the entropy and correlation of the Grey-Level Co-occurrence Matrix from B-Mode images

In this work, the feasibility of texture parameters extracted from B-Mode images were explored in quantifying medium temperature variation. The goal is to understand how parameters obtained from the gray-level content can be used to improve the actual state-of-the-art methods for non-invasive temperature estimation (NITE). B-Mode images were collected from a tissue mimic phantom heated in a water bath. The phantom is a mixture of water, glycerin, agar-agar and graphite powder. This mixture aims to have similar acoustical properties to in vivo muscle. Images from the phantom were collected using an ultrasound system that has a mechanical sector transducer working at 3.5 MHz. Three temperature curves were collected, and variations between 27 and 44 °C during 60 min were allowed. Two parameters (correlation and entropy) were determined from Grey-Level Co-occurrence Matrix (GLCM) extracted from image, and then assessed for non-invasive temperature estimation. Entropy values were capable of identifying variations of 2.0 °C. Besides, it was possible to quantify variations from normal human body temperature (37 °C) to critical values, as 41 °C. In contrast, despite correlation parameter values (obtained from GLCM) presented a correlation coefficient of 0.84 with temperature variation, the high dispersion of values limited the temperature assessment.     

Parameters S, T, and U of radiative corrections and masses of scalar leptoquarks in the minimal model featuring four-color symmetry

The contributions to the parameters S, T, and U of radiative corrections are discussed within the minimal model featuring four-color symmetry of the Pati-Salam type. A numerical analysis of these contributions is given for the Higgs mechanism of mass generation for scalar leptoquarks and the simplest version of scalar-leptoquark mixing. It is shown that up-to-date experimental data on S, T, and U are compatible with the existence of relatively light scalar leptoquarks (of masses about 1 TeV or below), still lighter scalar leptoquarks (of masses below 1 TeV) improving the agreement of theoretical results with experimental data on S, T, and U.     

Jet analysis in lepton-hadron scattering from QCD

For deep inelastic lepton-hadron scattering we deduce from QCD perturbation theory the cross sections $\text{d}\text{σ}\text{d}\text{T}$ and $\text{d}\text{σ}\text{d}\text{S}$ in terms of the collective jet variables thrust T and spherocity S. We find that the shape of these cross sections depends mainly on the total hadronic energy W. While present data are consistent with the cross sections calculated they do not yet prove or disprove the presence of three-jet contributions. We predict that these contributions will be clearly visible for W ? 12 to 15 GeV.     

Surface anchoring and pitch variation in thin smectic C* layers in an electric field

The variations of the pitch of smectics C* in thin planar layers in an external electric field and their dependence on the surface anchoring are investigated theoretically. The proposed mechanism of the change in the number of half-turns of the helical structure in a finite-thickness layer upon a change in the applied field is the slip of the director on the surface of the layer through the potential barrier of surface anchoring. The equations describing the pitch variation in an external field and, in particular, the hysteresis in the jumpwise variations of the pitch for opposite directions of field variation are given and analyzed for arbitrary values of the field. For weak fields, it is found that the pitch variation in the layer is of a universal nature and is determined by only one dimensionless parameter, S _d= K ₂₂/dW, where K ₂₂ is the Frank torsion modulus, W is the surface anchoring potential, and d is the layer thickness. The possibility of direct determination of the form of the anchoring potential from the results of corresponding measurements is considered. Numerical calculations for the deviation of the director from the direction of alignment on the layer surface and pitch variations, as well as the points of pitch jumps and hysteresis in the field, are made for the Rapini model anchoring potential for values of the parameters for which the pitch variation weakly depends on the direction of the field applied in the plane perpendicular to the spiral axis of smectics C*. The changes in the pitch variation in stronger fields are discussed, and the optimal conditions for observing the discovered effects are formulated.     

Surface morphology of epitaxial lattice-matched Ba0.7Sr0.3O on Si(0 0 1) and vicinal Si(0 0 1)-4°[1 1 0] substrates

Exploring ways for self-organized structuring of insulating thin films, we investigated the possibility to produce replicas of step trains, given by a vicinal Si(0 0 1)-4°[1 1 0] surface, in layers of crystalline and perfectly lattice-matched Ba_0.7Sr_0.3O. For this purpose, we carried out high-resolution spot profile analyses in low-energy electron diffraction (SPA-LEED) both on flat Si(0 0 1) and on Si(0 0 1)-4°[1 1 0]. Oxide layers were generated by evaporating the metals in oxygen ambient pressure with the sample at room temperature. Our G(S) analysis of these mixed oxide layers reveals a strong influence of local compositional fluctuations of Sr and Ba ions and their respective scattering phases, which appears as an unphysically large variation of layer distances. Nevertheless, we are able to show that quite smooth and closed oxide films are obtained with an rms roughness of about 1 ML. These Ba_0.7Sr_0.3O films directly follow the step train of Sr-modified vicinal Si surfaces that form (1 1 3) oriented facets after adsorption of a monolayer of Sr. This proves that self-organized structuring of insulating films can indeed be an effective method.     

Corrosion and erosion monitoring in plates and pipes using constant group velocity Lamb wave inspection

Recent improvements in tomographic reconstruction techniques generated a renewed interest in short-range ultrasonic guided wave inspection for real-time monitoring of internal corrosion and erosion in pipes and other plate-like structures. Emerging evidence suggests that in most cases the fundamental asymmetric A₀ mode holds a distinct advantage over the earlier market leader fundamental symmetric S₀ mode. Most existing A₀ mode inspections operate at relatively low inspection frequencies where the mode is highly dispersive therefore very sensitive to variations in wall thickness. This paper examines the potential advantages of increasing the inspection frequency to the so-called constant group velocity (CGV) point where the group velocity remains essentially constant over a wide range of wall thickness variation, but the phase velocity is still dispersive enough to allow accurate wall thickness assessment from phase angle measurements. This paper shows that in the CGV region the crucial issue of temperature correction becomes especially simple, which is particularly beneficial when higher-order helical modes are also exploited for tomography. One disadvantage of working at such relatively high inspection frequency is that, as the slower A₀ mode becomes faster and less dispersive, the competing faster S₀ mode becomes slower and more dispersive. At higher inspection frequencies these modes cannot be separated any longer based on their vibration polarization only, which is mostly tangential for the S₀ mode while mostly normal for the A₀ at low frequencies, as the two modes become more similar as the frequency increases. Therefore, we propose a novel method for suppressing the unwanted S₀ mode based on the Poisson effect of the material by optimizing the angle of inclination of the equivalent transduction force of the Electromagnetic Acoustic Transducers (EMATs) used for generation and detection purposes.     

Estimates of radiation over clouds and dust aerosols: Optimized number of terms in phase function expansion

The bulk-scattering properties of dust aerosols and clouds are computed for the community radiative transfer model (CRTM) that is a flagship effort of the Joint Center for Satellite Data Assimilation (JCSDA). The delta-fit method is employed to truncate the forward peaks of the scattering phase functions and to compute the Legendre expansion coefficients for re-constructing the truncated phase function. Use of more terms in the expansion gives more accurate re-construction of the phase function, but the issue remains as to how many terms are necessary for different applications. To explore this issue further, the bidirectional reflectances associated with dust aerosols, water clouds, and ice clouds are simulated with various numbers of Legendre expansion terms. To have relative numerical errors smaller than 5%, the present analyses indicate that, in the visible spectrum, 16 Legendre polynomials should be used for dust aerosols, while 32 Legendre expansion terms should be used for both water and ice clouds. In the infrared spectrum, the brightness temperatures at the top of the atmosphere are computed by using the scattering properties of dust aerosols, water clouds and ice clouds. Although small differences of brightness temperatures compared with the counterparts computed with 4, 8, 128 expansion terms are observed at large viewing angles for each layer, it is shown that 4 terms of Legendre polynomials are sufficient in the radiative transfer computation at infrared wavelengths for practical applications.     

Vacuum insertion and nonperturbative effects for exclusive nonleptonic decays of charmed mesons and kaons

We re-examine QCD sum rules forS-wave charmonium. Dimension 6, 8 contributions for both³ S ₁,¹ S ₀ waves are taken into account using the factorisation model and found to be reasonably small. A good fit to the data requires the confinement parameterφto be much bigger than the generally accepted value.     

The influence of the sintering temperature on the structural and the magnetic properties of doped manganites: La0.95Ag0.05MnO3 and La0.75Ag0.25MnO3

La_1−xAg_xMnO₃ samples were synthesized by standard sol-gel method with Ag concentrations of x=0.05 and 0.25. The samples from each concentration were pressed and sintered at 1000, 1200 and 1400 °C for 24 h in air for a systematic study. They were examined structurally by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) and magnetically by Magnetic Properties Measurements System (MPMS). AFM and SEM analyses show that surface morphology changes with Ag concentration and sintering temperature (T_S). It was observed that high temperature sintering leads Ag to leave material as determined from EDS analyses. XRD spectra exhibited that the crystal structure changes with Ag concentration while showing pronounced change with the sintering temperature. From the magnetic measurements, the Curie temperatures (T_C) and the isothermal magnetic entropy changes (−ΔSM) were calculated. It was observed that T_C increases with Ag concentration and decreases with T_S. The maximum −ΔSM was calculated to be 7.2 J/kg K under the field change of 5 T for the sample sintered at 1000 °C with x=0.25.     

Electrical properties of KTiOPO4 single crystal in the temperature range from −100 °C to 100 °C

The electrical property of a KTiOPO₄ single crystal was studied by means of a dielectric spectroscopy method in the temperature range from −100 to 100 °C. Dielectric dispersion began at a temperature, T_S=−80 °C. It is believed that this dielectric dispersion is related to the ionic hopping conduction, which arises mainly from the jumping of K⁺ ions. The activation energy concerned with hopping conduction is E_a∼0.20 eV above T_S. T_S=−80 °C can be the minimum temperature for the hopping K⁺ ion.     

Surface anchoring and temperature variations of the pitch in thin cholesteric layers

The temperature variations of the cholesteric pitch in thin planar layers of cholesterics and their dependence on the surface anchoring force are investigated theoretically. It is shown that the temperature variations of the pitch in a layer are of a universal character. This is manifested in the fact that they depend not separately on the parameters of the sample but only on one dimensionless parameter S _d =K ²²/dW, where K ₂₂ is the torsional modulus in the Frank elastic energy, W is the height of the surface-anchoring potential, and d is the thickness of the layer. The investigation is performed the parameter S _d in a range where the change per unit number of cholesteric half-turns within the thickness of the layer accompanying a change in the temperature is due to the slipping of the director on the surface of the layer through the potential barrier for surface anchoring. The critical values of the parameter S _d (which are most easily attained experimentally by varying the thickness of the layer), determining the region of applicability of the approach employed, are presented. The temperature variations of the free energy of the layer and the pitch of the cholesteric helix in the layer as well as the temperature hysteresis in the variations of the pitch with increasing and decreasing temperature are investigated for the corresponding values of S _d . Numerical calculations of the quantities mentioned above are performed using the Rapini anchoring potential.     

Silicon carbonitride by remote microwave plasma CVD from organosilicon precursor: Growth mechanism and structure of resulting Si:C:N films

The remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) from bis(dimethylamino)methylsilane precursor was used for the synthesis of silicon carbonitride (Si:C:N) films. The effect of thermal activation on the RP-CVD process was examined by determining the mass- and the thickness-based film growth rate and film growth yield, at different substrate temperature (T_S). It was found that the mechanism of the process depends on T_S and for low substrate temperature regime, 30 °C ≤ T_S ≤ 100 °C, RP-CVD is limited by desorption of film-forming precursors, whereas for high substrate temperature regime, 100 °C < T_S ≤ 400 °C, RP-CVD is a non-thermally activated and mass-transport limited process. The Si:C:N films were characterized by X-ray photoelectron and Fourier transform infrared spectroscopies, as well as by atomic force microscopy. The increase of T_S enhances crosslinking in the film via the formation of nitridic Si-N and carbidic Si-C bonds. On the basis of the structural data a hypothetical crsosslinking reactions contributing to silicon carbonitride network formation have been proposed.     

Anisotropy of the linear and quadratic magnetic birefringence in rare-earth semiconductors (γ-Ln2S3 (Ln=Dy3+, Pr3+, Gd3+, La3+)

The field and angular dependence of the magnetic linear birefringence (MLB) in noncentrosymmetric cubic (symmetry class T _d) rare-earth (RE) semiconductors γ-Ln₂S₃ (Ln=Dy³⁺, Pr³⁺, Gd³⁺, La³⁺) was studied. The field dependence of the MLB in Dy₂S₃ and Pr₂S₃ is a combination of two contributions, quadratic and linear with respect to the magnetic induction B, both possessing a strong anisotropy. The quadratic birefringence related to the Cotton-Mouton effect manifestations at a wavelength of λ=633 nm is characterized in Dy₂S₃ by the value of β=1.5 deg/(cm T²) and the anisotropy parameter a=?0.7 and in Pr₂S₃, by β=0.2 deg/(cm T²) and a=2. The non-reciprocal MLB caused by the magnetic-field-induced spatial dispersion reaches γ 0.55 and 0.71 deg/(cm T) in Dy₂S₃ and Pr₂S₃, respectively. The relationship between parameters A and g of the γ_ijkl tensor describing contributions of the B _ik_j type to the dielectric tensor ε_ij(ω, k, B) is A=2g in Dy₂S₃ (as well as in boracite crystals containing 3d ions), which is characteristic of the second-order magnetoelectric permittivity manifestations in the optical frequency range. In Pr₂S₃, the relationship A=3.3g is evidence of manifestations of the additional quadrupole mechanism. A comparison of the Cotton-Mouton and Faraday effects in Ln₂S₃ and in magnetic semiconductors Cd_1?x Mn_xTe shows a principal difference between these systems and indicates that both phenomena in Ln₂S₃ are determined by the optical transitions in RE ions rather than by the interband or exciton transitions. This is also confirmed by the comparison of the Cotton-Mouton effect manifestations in Ln₂S₃, in dielectric Dy₃Ga₅O₁₂ and Dy₃Al₅O₁₂ single crystal cubic garnets, and in Dy₂O₃. An analysis of the non-reciprocal MLB mechanisms related to manifestations of the local interconfiguration optical transitions 4f ^N→ 4f ^N?15d in RE ions showed that this phenomenon, in contrast to the Cotton-Mouton and Faraday effects, is caused by the presence of odd components of the crystal field acting upon the RE ion in Ln₂S₃. In Gd₂S₃, as well as in diamagnetic Ln₂S₃, neither the Cotton-Mouton effect nor the non-reciprocal MLB are manifested at T=294 K, which is explained by different microscopic mechanisms of the magnetooptical phenomena for ions in the S-state and diamagnetic ions, on the one hand, and RE ions with nonzero orbital moment, on the other hand.     

Uncertainties in the space-based measurements of CO2 columns due to scattering in the Earth's atmosphere

During the next decade satellites may be expected to provide a promising new source of CO₂ data. However, in order for the column-integrated CO₂ measurements to be useful for sources/sinks inversions, the requirements on these measurements are very demanding. In this paper we therefore quantify the largest error source for such CO₂ measurements in the near-infrared wavelength range , namely the effect of aerosols and thin cirrus clouds in the atmosphere. The errors are provided for the most common used observation geometries, nadir observations over land and sunglint observations over the ocean. It is estimated that for dust aerosols the aerosol optical thickness must be known within ±0.05 for errors below ±0.5% in the CO₂ total column. For other aerosol types the requirements are less strict (e.g. ±0.15 for sulfate aerosols). In the case of thin cirrus clouds over land the cirrus optical thickness must be known to ±0.05 over land surfaces and ±0.015 for sunglint observations over the ocean in case of moderate windspeed.     

Classical and quantum pumping in closed systems

Pumping of charge (Q) in a closed ring geometry is not quantized even in the strict adiabatic limit. The deviation form exact quantization can be related to the Thouless conductance. We use the Kubo formalism as a starting point for the calculation of both the dissipative and the adiabatic contributions to Q. As an application we bring examples for classical dissipative pumping, classical adiabatic pumping, and in particular we make an explicit calculation for quantum pumping in case of the simplest pumping device, which is a three site lattice model. We make a connection with the popular S-matrix formalism which has been used to calculate pumping in open systems.     

Berry phase in the gravitational quantum well and the Seiberg-Witten map

We explicitly compute the geometrical Berry phase for the noncommutative gravitational quantum well for different SW maps. We find that they lead to different partial contributions to the Berry phase. For the most general map we obtain that Δγ(S)∼η³, in a segment S of the path in the configuration space where is the fundamental momentum scale for the noncommutative gravitational quantum well. For the full closed path, we find, through an explicit computation, that γ(C)=0. This result is consistent with the fact that physical properties are independent of the SW map and shows that these maps do not introduce degeneracies or level crossing in the noncommutative extensions of the gravitational quantum well.     

Spectral manifestations of nonradiative processes in azulene

The linewidths for S₁ ← S₀ (at 14 652 cm⁻¹) and S₂ ← S₀ (at 28 048 cm⁻¹) of azulene in a naphthalene host crystal at 1.2°K are presented along with measurements of the line narrowing due to perdeuteration of the azulene. The results are related to current ideas of nonradiative processes in azulene and azulene-d₈.