Effects of particle nonsphericity and radiation polarization on retrieving dust properties from MODIS observations

The scattering and radiative properties of mineral dust aerosols at violet-to-blue (0.412, 0.441, and 0.470 μm) and red (0.650 μm) wavelengths are investigated. To account for the effect of particle nonsphericity on the optical properties of dust aerosols, in the present study, these particles are assumed to be spheroids. A combination of the T-matrix method and an improved geometric optics method is applied to the computation of the single-scattering properties of spheroidal particles with size parameters ranging from the Rayleigh to geometric optics regimes. For comparison, the Lorenz–Mie theory is employed to compute the optical properties of spherical dust particles that have the same volumes as their nonspherical counterparts. The differences between the phase functions of spheroidal and spherical particles lead to quite different lookup tables involved in retrieving dust aerosol properties. Moreover, the applicability of a hybrid approach based on the spheroid model for the phase function and the sphere model for the other phase matrix elements is also demonstrated. The present sensitivity study, employing the moderate resolution imaging spectroradiometer (MODIS) measurements and the fundamental principle of the Deep Blue algorithm, illustrates that neglecting the nonsphericity of dust particles usually leads to an underestimate of retrieved aerosol optical depth; although, depending on the scattering angle, an overestimate is noted in some cases. Furthermore, the effect of including full polarization treatment in forward radiative transfer simulation on dust property retrieval is also investigated. It is found that the effect of radiation polarization on the Deep Blue dust property retrieval is not negligible if the retrieval is based on two violet—blue channels centered at 0.412 and 0.470 μm.     

New PAMA Technology Helps Tackle the New Challenges of China Automotive Sector

Polyalkylmethacrylate (PAMA) based viscosity index improver (VII) and pour point depressant (PPD), with the versatile chemistry and unique performance characteristics, are widely used in advanced formulations, enabling fluids to meet rheological requirement of modern specifications. This paper will be dedicated to the application of PAMA in helping China automotive lubricant formulators tackle the challenges of improving fuel economics from using lower viscosity fluids, of better protection strengthten in t...     

Aerosol properties over bright-reflecting source regions

Retrieving aerosol properties from satellite remote sensing over a bright surface is a challenging problem in the research of atmospheric and land applications. In this paper we propose a new approach to retrieve aerosol properties over surfaces such as arid, semiarid, and urban areas, where the surface reflectance is usually very bright in the red part of visible spectrum and in the near infrared, but is much darker in the blue spectral region (i.e., wavelength <500 nm). In order to infer atmospheric properties from these data, a global surface reflectance database of 0.1/spl deg/ latitude by 0.1/spl deg/ longitude resolution was constructed over bright surfaces for visible wavelengths using the minimum reflectivity technique (e.g., finding the clearest scene during each season for a given location). The aerosol optical thickness and aerosol type are then determined simultaneously in the algorithm using lookup tables to match the satellite observed spectral radiances. Examples of aerosol optical thickness derived using this algorithm over the Sahara Desert and Arabian Peninsula reveal various dust sources, which are important contributors to airborne dust transported over long distances. Comparisons of the satellite inferred aerosol optical thickness and the values from ground-based Aerosol Robotic Network (AERONET) sun/sky radiometer measurements indicate good agreement (i.e., within 30%) over the sites in Nigeria and Saudi Arabia. This new algorithm, when applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Sea-viewing Wide Field of view Sensor (SeaWiFS), and Global Imager (GLI) satellite data, will provide high spatial resolution (/spl sim/1 km) global information of aerosol optical thickness over bright surfaces on a daily basis.     

Effects of interfacial structure on the magnetic properties of ultrathin Fe/Pt(111) films with Ag buffer layer

For Fe/Pt(111) grown at 180 K, the easy axis of magnetization changes from out-of-plane to in-plane while the surface structure changes from fcc(111) to bcc(110). The Curie temperature for 1 ML Fe/Pt(111) is close to room temperature. After insertion of submonolayer Ag, no significant change for the Curie temperature is observed. By thermally annealing Ag/Pt(111) at 550 K to form a Ag-Pt surface alloy, we demonstrate that the Curie temperature of the deposited Fe films is elevated to be higher than room temperature. For an ultrathin Fe/Ag/Fe/Pt(111) sandwich system, the strong interaction between the two Fe layers is superior due to the effect of the double Fe/Ag interfaces. This causes that the easy axis of the magnetization switches back to the in-plane direction during the deposition of Fe overlayer on the surface of a Ag/Fe/Pt(111) film.     

Journal co-citation analysis of semiconductor literature

The purpose of this study is to map semiconductor literature using journal co-citation analysis. The journal sample was gathered from the INSPEC database from 1978 to 1997. In the co-citation analysis, the data compiled were counts of the number of times two journal titles were jointly cited in later publications. It is assumed that the more two journals are cited together, the closer the relationship between them. The journal set used was the 30 most productive journals in the field of semiconductors. Counts of co-citations to the set of semiconductor journals were retrieved from SciSearch database, accessed through Dialog. Cluster analysis and multi-dimensional scaling were employed to create two-dimensional maps of journal relationships in the cross-citation networks. The following results were obtained through this co-citation study: The 30 journals fall fairly clearly into three clusters. The major cluster of journals, containing 17 titles, is in the subject of physics. The second cluster, consisting of 9 journals, includes journals primarily on material science. The remaining cluster represents research areas in the discipline of electrical and electronic engineering. All co-cited journals share similar co-citation profiles, reflected in high positive Pearson correlation. Two hundred and ninety-six pairs (68%) correlate at greater than 0.70. This shows that there is strong relationship between semiconductor journals. Five individual journals in five paired sets with co-citation frequency over 100,000 times include Physical Review B, Condensed Matter; Physical Review Letters; Applied Physics Letters; Journal of Applied Physics; and Solid State Communications. This revised version was published online in August 2006 with corrections to the Cover Date.     

The properties of transparent semiconductor Zn1 − xTixO thin films prepared by the sol-gel method

Transparent semiconductor thin films of Zn_1 − xTi_xO (0 ≦ x ≦ 0.12) were deposited on alkali-free glass substrates by the sol-gel method. The effects of Ti addition on the crystallization, microstructure, optical properties and resistivity of ZnO thin films were investigated. The as-coated films were preheated at 300 °C, and then annealed at 500 °C in air ambiance. X-ray diffraction results showed all polycrystalline Zn_1 − xTi_xO thin films with preferred orientation along the (002) plane. Ti incorporated within the ZnO thin films not only decreased surface roughness but also increased optical transmittance and electrical resistivity. In the present study, the Zn_0.88Ti_0.12O film exhibited the best properties, namely an average transmittance of 91.0% (an increase of ~ 12% over the pure ZnO film) and an RMS roughness value of 1.04 nm.     

A Bibliometric Study of Semiconductor Literature, 1978–1997

Semiconductor is the key element for information industry. The present study investigated the growth of semiconductor literature based on the database of INSPEC. Well-established bibliometric techniques, such as Bradford-Zipf's plot and Lotka's law have been employed to further explore the characteristics of semiconductor literature. Quantitative results on the literature growth, form of publication, research treatment, publishing country and language, author productivity and affiliate are reported. Moreover, from the Bradford-Zipf's plot, 25 core journals in semiconductor were identified and analyzed.     

Transparent semiconductor zinc oxide thin films deposited on glass substrates by sol–gel process

Transparent semiconductor ZnO thin films were spin-coated onto alkali-free glass substrates by a sol–gel process. The influence of ZnO sols synthesized via different solvents (2-ME, EtOH or IPA) on the surface morphologies, microstructures, optical properties and resistivities of the obtained films were investigated. The as-coated films were annealed in ambient air at 500 °C for 1 h. X-ray diffraction results showed all polycrystalline ZnO thin films to have preferred orientation along the (0 0 2) plane. The surface morphologies, optical transmittances and resistivity values of the sol–gel derived ZnO thin films depended on the solvent used. The ZnO thin films synthesized with IPA as the solvent exhibited the highest average transmittance 92.2%, an RMS roughness of 4.52 nm and a resistivity of 1.5 × 10⁵ Ω cm.     

Performance and Selection of Pour Point Depressants

1 IntroductionParaffinic mineral oil base stocks contain waxy hydro-carbons that come out of solution when temperature de-creases.The lower the molecular weight of the paraffinand the higher its level of branching,thelower the precipi-tation temperature.Initially,tiny crystals are for medwhich diffract light making the solution hazy to the nakedeye.The temperature at which this occurs is called thecloud point.When temperature is further lowered,addi-tional wax precipitates,the crystals grow i…     

Variance and Covariance Computations for 2-D ARMA Processes

An algorithm is presented to compute the variance of the output of a two-dimensional (2-D) stable auto-regressive moving-average (ARMA) process driven by a white noise bi-sequence with unity variance. Actually, the algorithm is dedicated to the evaluation of a complex integral of the form , where and G(z₁,z₂) = B(z₁, z₂) / A(z₁, z₂) is stable (z₁,z₂)-transferfunction. Like other existing methods, the proposed algorithmis based on the partial-fraction decomposition G(z₁,z₂)G(z ₁ ^-1 , z ₂ ^-1 ) = X(z₁, z₁) / A(z₁,z₂)+ X(z ₁ ^-1 , z ₂ ^-1 ) / A(z ₁ ^-1 , z ₂ ^-1 ). However,the general and systematic partial-fraction decomposition schemeof Gorecki and Popek [1] is extended to determine X(z₁,z₂).The key to the extension is that of bilinearly transforming thediscrete (z₁, z₂)-transfer function G(z₁,z₂)into a mixed continuous-discrete (s₁, z₂)-transferfunction . As a result, the partial-fraction decomposition involves only efficient DFT computations for the inversion of a matrix polynomial, and the value of I is finally determined by the residue method with finding the roots of a 1-D polynomial. The algorithm is very easy to implement and it can be extended to the covariance computation for two 2-D ARMA processes.