Impact of aerosols on the forecast accuracy of solar irradiance calculated by a numerical weather prediction model

The impact of aerosols on the forecast accuracy of solar irradiance calculated by a fine-scale, one day-ahead, and operational numerical weather prediction model (NWP) is investigated in this study. In order to investigate the impact of aerosols only, the clear sky period is chosen, which is defined as when there are no clouds in the observation data and in the forecast data at the same time. The evaluation of the forecast accuracy of the solar irradiance is done at a single observation point that is sometimes affected by aerosol events. The analysis period is one year from April 2010 to March 2011. During the clear sky period, the root mean square errors (RMSE) of the global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI) are 40.0?W?m^?2, 84.0?Wm^?2, and 47.9?W?m^?2, respectively. During one extreme event, the RMSEs of the GHI, DNI, and DHI are 70.1?W?m^?2, 211.6?W?m^?2, and 141.7?W?m^?2, respectively. It is revealed that the extreme events were caused by aerosols such as dust or haze. In order to investigate the impact of the aerosols, the sensitivity experiments of the aerosol optical depth (AOD) for the extreme events are executed. The best result is obtained by changing the AOD to 2.5 times the original AOD. This changed AOD is consistent with the satellite observation. Thus, it is our conclusion that an accurate aerosol forecast is important for the forecast accuracy of the solar irradiance.     

Growth, microhardness, dielectric and photoconductivity characterization of a highly polarizable NLO material: Sodium p-nitrophenolate dihydrate (NO2-C6H4-ONa.2H2O)

Sodium p-nitrophenolate dihydrate (NPNa.2H₂O) is a highly polarisable non linear optical material. It has a d_eff about 1.45 times than that of potassium titanyl phosphate. Single crystals of (NPNa.2H₂O) have been grown successfully by slow solvent evaporation having water and methanol as solvent. The structure of the crystal is verified by single X-ray analysis. Optical absorption shows that the crystal is highly transparent between 1500 and 300 nm. Microhardness of the crystal is found to increases with increase in load and the hardness number is found to be high for methanol grown crystal as compared to the water grown crystal. Electrical conductivity as evaluated from the cole-cole plot is found to be 1.26 × 10⁻⁵ mho m⁻¹. The dielectric constant of the crystal is low and independent at higher frequencies. The crystal has prominent photoconduction in the presence of trap energy levels formed by the Na⁺ ions. The SHG efficiency of the crystal is studied by performing Kurtz powder test and the results of scanning electron microscope analysis indicate that the major part of the crystal surface is free from inclusion and dislocation.     

超短超强激光与稀薄等离子体相互作用中后孤立子的观测

开展了超短超强激光与稀薄等离子体相互作用实验,在实验中采用等离子体单色成像法观测等离子体发光图像,捕捉到了近乎对称的环形等离子体发光结构. 在对实验结果进行分析并与理论预言进行比较后确认这是由激光-等离子体相互作用形成的后孤立子云外围的高密度等离子体壳层发光所致. 同时通过对等离子体通道的观测还发现,孤立子的形成对超短超强激光在稀薄等离子体中的传输产生了非常大的影响. 关键词： 超短超强激光 稀薄等离子体 单色成像 后孤立子     

Influence of local waste burning on atmospheric aerosol properties in urban environment

Aerosols affect the radiative energy budget on both the regional and global scales. The wavelength-dependent aerosol optical depth (AOD) is a fundamental determinant of the amount by which extra-terrestrial incoming sunlight and outgoing terrestrial radiation are being attenuated in the atmosphere. The present study addresses the influence of local waste burning on aerosol characteristics, black carbon (BC) aerosol mass concentration and spectral solar irradiance using ground-based measurements over the tropical urban environment of Hyderabad, India. AOD has been observed to be maximum during burning days compared to normal days. Aerosol size spectra suggest bimodal distributions during pre-and post-burning periods and trimodal distributions during burning periods. Angstrom wavelength exponent estimated from spectral variation of AOD suggested dominance of accumulation mode particle loading during burning days compared to normal days. Diurnal variation of BC on normal days showed a broad nocturnal peak during ∼20:00 to ∼24:00 h with a maximum value of BC aerosol concentration of ∼14,000 ng m⁻³ whereas on local waste burning days enormous increases in BC concentrations have been observed with a peak at ∼60,000 ng m⁻³. Relative attenuation of global solar irradiance during burning days has been found to be of the order of 30% in the visible and 28% in the near-infrared regions. The results are discussed in detail in this paper.     

Examination of the laser-induced variations in the chemical etch rate of a photosensitive glass ceramic

Previous studies in our laboratory have reported that the chemical etch rate of a commercial photosensitive glass ceramic (Foturan^TM, Schott Corp., Germany) in dilute hydrofluoric acid is strongly dependent on the incident laser irradiance during patterning at λ=266 nm and λ=355 nm. To help elucidate the underlying chemical and physical processes associated with the laser-induced variations in the chemical etch rate, several complimentary techniques were employed at various stages of the UV laser exposure and thermal treatment. X-ray diffraction (XRD) was used to identify the crystalline phases that are formed in Foturan following laser irradiation and annealing, and monitor the crystalline content as a function of laser irradiance at λ=266 nm and λ=355 nm. The XRD results indicate the nucleation of lithium metasilicate (Li₂SiO₃) crystals as the exclusive phase following laser irradiation and thermal treatment at temperatures not exceeding 605 °C. The XRD studies also show that the Li₂SiO₃ density increases with increasing laser irradiance and saturates at high laser irradiance. For our thermal treatment protocol, the average Li₂SiO₃ crystal diameters are 117.0±10.0 nm and 91.2±5.8 nm for λ=266 nm and λ=355 nm, respectively. Transmission electron microscopy (TEM) was utilized to examine the microscopic structural features of the lithium metasilicate crystals. The TEM results reveal that the growth of lithium metasilicate crystals proceeds dendritically, and produces Li₂SiO₃ crystals that are ∼700–1000 nm in length for saturation exposures. Optical transmission spectroscopy (OTS) was used to study the growth of metallic silver clusters that act as nucleation sites for the Li₂SiO₃ crystalline phase. The OTS results show that the (Ag⁰)_x cluster concentration has a dependence on incident laser irradiance that is similar to the etch rate ratios and Li₂SiO₃ concentration. A comparison between the XRD and optical transmission results and our prior etch rate results show that the etch rate contrast and absolute etch rates are dictated by the Li₂SiO₃ concentration, which is in turn governed by the (Ag⁰)_x cluster concentration. These results characterize the relationship between the laser exposure and chemical etch rate for Foturan, and permit a more detailed understanding of the photophysical processes that occur in the general class of photostructurable glass ceramic materials. Consequently, these results may also influence the laser processing of other photoactive materials. PACS  42.62.-b; 61.43.Fs; 81.05.Kf; 81.10.-h; 83.80.Ab     

Memory effect and cathodoluminescent properties of YAG:Nd<Superscript>3+</Superscript> nanoceramics

The cathodoluminescent properties of nanoceramics based on neodymium-doped yttrium–aluminum garnet (YAG:Nd³⁺) are studied in a wide optical spectral range (from UV to IR). It is shown that the spectral positions of the emission bands of nanoceramics are identical to that of single crystal, but the bands of nanoceramics are broadened by no more than 15% from the half bandwidths of single crystal. The intensity of cathodoluminescence bands in nanoceramics is lower, and the lifetimes of radiative levels are shorter. It is found for the first time that electron-beam irradiation of nanoceramics increases the cathodoluminescence intensity of bands in visible and UV ranges (by two or more times). Preliminary electron beam irradiation of YAG:Nd³⁺ nanoceramics samples leads to the increase of cathodoluminescence efficiency. Such effect retains for a long time (a year and more) and can be compared to the memory effect. This effect is not observed in single crystal. We propose a model describing this effect in nanoceramics.     

Ni熔体凝固过程中临界晶核和亚临界晶核的分子动力学模拟

本文用分子动力学模拟研究了Ni熔体以不同冷速凝固后微观结构的演变规律, 并通过理论计算确定出了Ni熔体凝固后获得理想非晶的临界条件. 模拟结果发现冷速小于10¹¹ K/s时, Ni 熔体凝固后形成晶态组织; 冷速在10¹¹ K/s到10^14.5 K/s之间时, Ni熔体凝固后形成由晶态结构与非晶态结构组成的混合组织. 冷速小于10¹⁰ K/s, Ni 熔体凝固后形成的晶态组织具有fcc结构; 冷速在10¹⁰ K/s到10^14.5 K/s之间时, Ni熔体凝固后组织中的晶态由fcc和hcp结构层状镶嵌排列构成. 通过分析模拟结果和计算结果, 确定出了Ni熔体凝固后形成理想非晶的临界冷速为10^14.5 K/s. 并发现Ni熔体中临界晶核(冷速等于10^14.5 K/s)和亚临界晶核(冷速大于10^14.5 K/s) 均由fcc和hcp组成层状偏聚结构, 这表明Ni熔体中生长的晶体、临界晶核和晶胚的结构是相同的. 关键词： 分子动力学模拟 晶体团簇 临界冷速 结构     

Crystal shape effect on nuclear orientation thermometry at ultra-low temperatures

Absolute temperature measurement (T < 100 mK region) from anisotropy of gamma radiations emitted from oriented⁶⁰Co nuclei in a single crystal of hcp cobalt is found to depend on the shape of the crystal. This dependence is attributed to some closure magnetic domains not oriented along thec-axis of the disc shaped crystal studied. A long rectangular strip of cobalt crystal is found to give correct angular distribution ofγ-radiations and, therefore, suitable for thermometry.     

Photophysical and nonlinear optical properties of zincphthalocyanines with peripheral substitutions

Photophysical and nonlinear optical properties of zinc phthalocyanines (ZnPc) bearing peripheral phenoxy substituents containing different functionalized groups were studied. Fluorescence spectra corresponding to the optical transition S₁ → S₀ are found to be appeared at 684 or 686.4 nm. Z-scan technique reveals large nonlinearities, where the absorptive and refractive effects are separately evaluated. Saturation absorption of ZnPc-1 was observed at 632.8 nm, with a very large nonlinear absorption coefficient β = −1.36 × 10⁻² cm/W. However a strong nonlinear refractive effect was found in all ZnPcs (1-4). Transmitted versus incident irradiance measurements carried out on ZnPc-1 and ZnPc-2, showed a very clear optical limiting behavior with irradiance thresholds around be 44 W/cm² and 90 W/cm² respectively.     

M factor and kurtosis parameter of super-Gaussian beams passing through an axicon

The effects of axicons on the M² factor and kurtosis parameter of super Gaussian beams(SGBs) are studied in detail. The closed-form expression for the M² factor of SGBs after passing through an axicon is derived, and the reason why the convergent and divergent axicons give rise to the same increase of the M² factor is explained physically from the similarity of the resulting irradiance distributions. The analytical propagation equation of the K parameter of SGBs passing through an axicon followed by a paraxial optical ABCD system is given, some interesting special cases are discussed. In particular, it is found that even for the Gaussian special case theK parameter is no longer a constant due to the effect of the axicon. Numerical examples are also given to illustrate our analytical results.     

Generation of 532 nm laser radiation and phase matching properties of organic nonlinear optical material

Organic nonlinear optical single crystal of l-asparagine-l-tartaric acid (LAsT) was grown by slow evaporation technique at room temperature. The grown crystal was confirmed by single crystal X-ray diffraction and FT-IR studies. The direct band gap energy was found to be 5.4 eV. The SHG efficiency of the sample is 3 times higher than that of KDP crystal. The laser damage threshold of the grown crystal was 5.7 GW/cm². The grown crystal was thermally stable up to 141 °C. Low dielectric constant at higher frequency was found by dielectric measurements. The activation energy was calculated from Arrhenius relation and it was found to be 0.088 eV. Negative photoconducting nature was obtained by photoconductivity measurements.     

Study of TL properties of LaAlO3:Ce,Dy crystals for UV dosimetry

Thermoluminescence properties of lanthanum aluminum oxide (LaAlO₃) crystals doped with optically active rare earth ions have been investigated for ultraviolet dosimetry purposes. Single crystals co-doped with 5.0 at.% of Ce³⁺ and 1.0 at.% of Dy³⁺ ions have two thermoluminescent (TL) peaks at 151 °C and 213 °C which can be sensitized after 1 h of UV exposure. The material shows very high TL output and linear response for UV spectral irradiance ranging from 0.04 to 1.20 mJ cm⁻², that corresponds to 10 times the TL response of the Al₂O₃:C oxides. From 0.62 to 148.0 mJ cm⁻² the dependence is linear with the logarithm of the spectral irradiance. The investigation demonstrates that LaAlO₃:Ce,Dy crystals are very attractive to be investigated as UV dosimeters.     

Emission properties of laser ablation of SnO2: Sb transparent conducting film and KTiOPO4 crystal

Optical emission spectra of Nd:YAG laser ablation of KTiOPO₄ (KTP) crystal and SnO₂:Sb transparent conducting thin film were recorded and analyzed in vacuum and in air. The integral intensities of spectral lines from laser-ablated KTP crystal were obtained as functions of distance from the target surface and laser power density in vacuum and in air. The ambient gas effects on pulsed laser ablation of target were discussed. We also performed laser ablation of SnO₂:Sb transparent conducting thin film in air and the electron temperature and full-width at half-maximum (FWHM) of atomic and ionic spectral lines in the plasma were quantified using Boltzmann plot method and Lorentzian fit, respectively. Integral intensities of atomic and ionic Sn spectral lines were also obtained as functions of distance from the target surface and laser irradiance. The intensity ratio of ionic and atomic Sn spectral lines as a function of laser power density was got which gives some information about the variation of ionization ratio with laser irradiance in the plasma produced by high-power laser.     

Preferential orientation of planar Ni(CN)2-4 complex ions in a NaCl lattice: Evidence from EPR studies

Anomalous intensity distribution in the EPR spectrum from tetragonal [Ni(CN)₄.Cl₂]^5- complex in γ-irradiated NaCl:Ni(CN)^2-₄ has been observed. A detailed EPR study revealed that the planar Ni(CN)^2-₄ complex preferentially enters the lattice with the plane parallel to the {100} growth planes of the crystal. Consequently, regions in the crystal could be found where the complex ions are predominantly oriented parallel to one of the three {100} planes of the crystal. Possible mechanisms of incorporation of the ions are discussed.     

Microscopic stability mechanisms of a charge-ordered phase of La1.5Sr0.5NiO4

Using a pairwise potential approximation and a shell model, computer simulation is performed of a charge-ordered crystal phase of La_1.5Sr_0.5NiO₄, in which Ni²⁺ and Ni³⁺ ions are arranged in staggered rows in perovskite layers. This phase is found to be stable, and, in the process of its formation, the contribution to the lowering of the total crystal energy from the charge rearrangement is smaller than that from the relaxation of the crystal structure (the structure of NiO₂ layers, first of all) caused by this rearrangement. The decrease in the total energy is due to the long-range Coulomb interaction, predominantly the attraction between Ni³⁺ and oxygen ions in NiO₂ layers.     

Preparation and Raman Spectrum of Rutile Single Crystals Using Floating Zone Method

With anatase-type titanium dioxide as the raw materials, the futile type titanium dioxide single crystal is prepared using the floating zone method. The results of XRD measurement show that the grown crystal is highly crystalline with a futile structure, which has orientation to the c-axis. The four Raman vibration characteristic peaks （143, 240, 450 and 610 cm^-1） at room temperature show that the crystalline structure of the single crystal is a typical futile phase, meanwhile a new Raman peak at around 690 cm^-1 is found. The results of the Raman measurement at various temperatures for the single crystal show that the Raman frequency shifts are different.     

Strong signature of the active Sun in 100 years of terrestrial insolation data

Terrestrial solar irradiance data of the Smithsonian Astrophysical Observatory from 1905 to 1954 and of Mauna Loa Observatory from 1958 to 2008 are analyzed. The analysis shows that, with changing solar activity, the atmosphere modifies the solar irradiance on the percentage level, in all likelihood via cosmic ray intensity variations produced by the active sun. The analysis strongly suggests that cosmic rays cause a large part of the atmospheric aerosols. These aerosols show specific absorption and scattering properties due to an inner structure of hydrated ionic centers, most probably of O₂^‐ and O₂⁺ produced by the cosmic rays.     

锆英石的抗γ射线辐照能力和Rietveld结构精修

为研究放射性核素固化介质备选矿物锆英石的抗γ射线辐照结构稳定性,以澳大利亚锆英石为研究对象,通过⁶⁰Co源γ射线辐照装置对样品施以1728 kGy的γ射线辐照.利用X射线荧光光谱仪、扫描电子显微镜和X射线衍射仪对样品的元素含量、γ射线辐照前后的微观形貌及物相变化进行表征,同时利用Rietveld方法对γ射线辐照前后的样品进行了结构精修.结果表明:澳大利亚锆英石经1728 kGy剂量的γ射线辐照后未发生物相变化,射线辐照前后样品的晶胞参数仅发生了10^-4 量级的变 关键词： 锆英石 γ射线 辐照 Rietveld结构精修     

铌酸锶钠锂单晶电光、热电、介电和压电性能

文本研究了用提拉法生长的铌酸锶钠锂(Sr₄NaLiNb₁₀O₃₀)晶体的电光、热电、介电和压电性能。其半波电压与温度的关系与晶体中锂含量密切相关。测得其室温下的热电系数与Ba～0.5的Sr_1-xBa_xNb₂O₆晶体相当,～7×10^-8C/cm²·K。已极化的晶体几乎检测不到退极化现象。将其作成热电器件,其探测度D^*不小于1.7×10⁷Hz^1/2·cm/W。文中还描述了其介电和某些压电性能。 关键词：     

Simulation of earth background radiation characteristic for satellite borne laser warning system

The earth background radiation is a kind of main background interference for satellite borne laser warning system in the space environment, and it is so necessary that the radiation characteristic be studied. In this paper, the mathematic model of the earth background radiation is established, the input parameters of 6S model are analyzed and set, and the simulation of earth background radiation is carried on aiming at the alarm wavelength 1.315 μm and the waveband 0.9-1.7 μm which is the responsive bandwidth of the detector. The results show that: with the increase of zenith angle, the irradiance from ground reflection increases, but the irradiances of atmospheric path radiation and surface-atmosphere interaction at the satellite level decrease; comparing with other two parts, the irradiance from ground reflection weighs most, and the corresponding percentages for 1.315 μm and 0.9-1.7 μm are 75.89% and 73.99%, respectively. The total irradiance at the satellite level from earth background radiation has exceeded the detection sensitivity of the system (about 1 mW/cm²), which may arouse the false alarm. So, the special technique of background suppression must be studied.