Transport and Pinning Properties of FeSe北大核心CSCD

利用固相反应法合成了FeSe超导体,根据名义组分和热处理工艺的不同共得到四组FeSe样品,利用X射线衍射仪(XRD)和物性测试系统(PPMS)分别对样品的晶体结构和电输运性能进行表征,并分析了磁通钉扎特性.XRD测试结果表明所有的样品主相均为β-FeSe四方相,同时在样品中也存在少量杂相,包括α-FeSe和Fe,不同名义组分和不同热处理工艺对晶体结构的影响较小.电阻率测试结果表明所有的样品均发生了超导转变,Tc大约为9K,在零场下的转变宽度约为3K,但是四个样品的正常态电阻率明显不同,通过测试四个样品在不同磁场下的电阻率随温度的变化曲线,随着磁场的增加,电阻率曲线出现展宽效应,分析表明FeSe的磁通钉扎行为是由于在不同磁场下热激活磁通蠕动引起的,其上临界磁场可达23T.     

Fluorescence and Nonlinear Optical Properties of Organic Dye in Inorganic Glass and Xerogel Matrices

ＦｌｕｏｒｅｓｃｅｎｃｅａｎｄＮｏｎｌｉｎｅａｒＯｐｔｉｃａｌＰｒｏｐｅｒｔｉｅｓｏｆＯｒｇａｎｉｃＤｙｅｉｎＩｎｏｒｇａｎｉｃＧｌａｓａｎｄＸｅｒｏｇｅｌＭａｔｒｉｃｅｓＺＨＡＮＧＱｉｎｙｕａｎＪＩＡＮＧＺｈｏｎｇｈｏｎｇ（ＳｈａｎｇｈａｉＩｎｓｔ...     

Laser-Induced Growth Device and Optical Properties of ZnO MicrocrystalsEI北大核心CSCD

ZnO is third-generation semiconductors which can be used as the carrier of ultraviolet photoluminescence and multiresonance mode laser. In recent years, ZnO microcrystals prepared by optical vapor supersaturation precipitation (OVSP) have shown important advantages in photocatalysis, efficient multi-color light source and efficient electroluminescence. However, the high preparation cost and low production efficiency hinder the development of the large-scale device. In this work, we designed and built a set of growth devices with a working wavelength of 1 080 nm and a power of 18% (@2 500 W) laser heating. The height of the raw material rod was 6. 5 mm, and the diameter was 8 mm. The results show that the morphology, structure, and luminescence properties of the products prepared by this device are very close to those prepared by the OVSP method, and the production efficiency is greatly improved (similar to 500 %). The growth device successfully prepared acceptor-rich ZnO single crystal micro rods with complete hexagonal cross-section morphology. The diameter and length of ZnO micro rods are about 3. 8 and 10 similar to 20 mu m, respectively. Raman spectra show that the Raman peaks of ZnO micro rods are sharp, and the Raman mode at 437 cm(-1) indicates that the ZnO micro rods are hexagonal wurtzite structures with good crystallinity. By analysing the PL spectra of ZnO micro rods, it was found that the ZnO microtubes prepared by the OVSP method had a similar ultraviolet bimodal structure, indicating that there exists an abundant zinc-vacancies acceptor. In the 80 similar to 280 K range, with the increase of temperature, the fluorescence intensity of ZnO microrods appears "thermal quenching-negative thermal quenching-thermal quenching" behavior. The negative thermal quenching behavior in the range of 166 similar to 200 K is related to the intermediate state energy level (trap center) at 477 meV below the conduction band bottom, and the thermal quenching phenomenon in the range of 200 similar to 280 K is related to the non-radiative recombination center at 600 meV below the conduction band bottom. The appearance of both is related to the prepared ZnO microrod oxygen vacancy (V-o) defect. The laser growth device developed in this paper has high feasibility and practicability. This preparation method lays a technical foundation for the rapid batch growth of ZnO single crystal micro rods with rich acceptors and is also of great significance for its application in optoelectronic devices.     

Absorption and Emission Properties of a New Two-photon Absorption Dye

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｔｗｏ ｐｈｏｔｏｎａｂｓｏｒｐｔｉｏｎ (ＴＰＡ )ｉｓａｎｉｍｐｏｒｔａｎｔｎｏｎｌｉｎｅａｒａｂｓｏｒｐｔｉｏｎｐｒｏｃｅｓｓｉｎｂｏｔｈｂａｓｉｃａｎｄａｐｐｌｉｅｄｒｅｓｅａｒｃｈｅｓ.Ｆｏｒｍａｎｙｙｅａｒｓ,ｄｕｅｔｏｔｈｅｒｅｌａｔｉｖｅｌｙｓｍａｌｌＴＰＡｃｒｏｓｓ ｓｅｃｔｉｏｎｓｏｆｍｏｓｔｍａｔｅｒｉａｌｓ,ｔｗｏ ｐｈｏｔｏｎｐｒｏｃｅｓｓｅｓｗｅｒｅｆｏｕｎｄｌｉｍｉｔｅｄａｐｐｌｉｃａｔｉｏｎｓ.Ｌａｔｅｌｙ ,ｇｒｅａｔｐｒｏｇｒｅｓｓｅｓｈａｖ…     

Intermolecular Interactions. Absorption and Fluorescence Spectra of α-Naphthol

In the ground state, -naphthol interacts with water via oxygen, whereas with alcohols (ethanol and isopropanol) and acetonitrile it interacts via hydrogen from the hydroxyl group. In the excited state, -naphthol interacts much more weakly. An analysis of the dependences of positions of electronic-vibrational transitions on the solvent basicity and acidity demonstrates their nonlinearity. For the parameters describing the solvation ability of the solvent, linear dependences are observed for the following series of solvents: isopropanol, ethanol, acetonitrile, and water. The possible values of the acid number (pA*) for the excited -naphthol molecule fall within the interval from 0.4 to 1.4 depending on the chosen maximum of the absorption band. In fluorescence spectra, the band intensities differ for neutral and ionic modifications of the molecule. The fluorescence efficiency of the neutral molecule is by an order of magnitude higher than that of the ionic modification. Possible channels of quenching of the ionic modification are discussed.     

Fluorescein and Phenolphthalein—Correlation of Fluorescence and Photoelectric Properties

Two phthalein dyes in aqueous polyvinyl alcohol solutions of pH 8.5 have been investigated: fluorescein and phenolphthalein. Competitive pathways of deactivation of their energetically excited states have been followed by the use of spectroscopic and photoelectric techniques. Radiative, nonradiative, and charge separation processes followed by electron transfer have been measured by absorption, fluorescence, and photoacoustic spectroscopy accompanied by photovoltage/photocurrent generation in a photoelectrochemical cell. It is shown that, despite their being only a slight difference in molecular structure between the two dyes, their spectral as well as photoelectric behavior is significantly different.     

Properties of Movement and Boiling of Speckles Produced by Moving Objects Illuminated with Partially COherent Light

Properties of movement and the boiling of dynamic partially coherent speckles are investigated.Theoretical analysis of the correlation functions shows that in front of and behind the Fraunhofer plane,the directions of the movement of the dynamics partially coherent speckles are the samp and opposite to that of the object,respectively,The boiling occurs according to a parabolic factor with respect to time separation τ.These properties are observed experimentally by using an elaborately chosen extended source to meet the requirement of intensity and coherence.The boiling of the speckles is measured with the photon counting system,which is refitted for the automatic data acquistition,and the experimental results are confirmed by the theory.     

UV-vis Absorption and PL Properties of Self-Assembled Silicon Nanotubes

Silicon nanotubes （SiNTs） are novel one-dimensional nanomaterials, which have potential applications in nano- photoelectric devices, sensors and field-emission devices. The self-assembled silicon nanotubes have clear structures without metal catalysts. The structures are confirmed by TEM and HRTEM, and the UV-vis absorption spectra with an absorption peak near 685nm and PL spectra with widened strong emission near 436nm are measured by UV-vis spectrometer and spectroftuorophotometer.     

Improved Luminescence Properties and Thermal Stability of ZnS Quantum Dots by Organic and Inorganic Passivation

ZnS quantum dots(QDs) synthesized in water and ethanol solutions were coated with polystyrene (PS) and SiO2 shells,respectively.The band edge emission was enhanced by nearly five times after PS coating and by about thirteen times after SiO2 coating,because the surface trap states were removed.From the photoluminescence properties of ZnS QDs coated with PS and SiO2 shells we have detected the improvement of thermal stability.This is due to the fact that the surface passivation can prevent the further growth of the ZnS QDs and the diffusion of oxygen on the surface of ZnS QDs during thermal oxidation.     

Study on the Non-Uniformity Calibration of Space-Born Differential Optical Absorption SpectrometerSCIEI北大核心CSCD

Space-borne differential optical absorption spectrometer is a nadir viewing wide field imaging spectrometer, which adopts two-dimensional CCD detector arrays. The pixel response non-uniformity exists in each column of spatial dimension, which will introduce high-frequency instrument-related spectral structures in the measurement data. However, the non-uniformity calibration of space-born imaging spectrometer is difficulty due to two factors: the spectral smile effect and the large field of view. For this reason, a method of non-uniformity calibration is discussed in detail. The result shows that the spectral smile effect and non-uniformity of full FOV image are corrected effectively, and high-frequency instrument-related structures in the measurement data are removed.     

Study on the Relationship between the Depth of Spectral Absorption and the Content of the Mineral Composition of BiotiteSCIEI北大核心CSCD

The mineral composition of rock is one of the main factors affecting the spectral reflectance characteristics, and it' s an important reason for generating various rock characteristic' spectra. This study choose the rock samples provided by Jet Propulsion Laboratory (JPL) (including all kinds of mineral percentage of rocks, and spectral reflectances range from 0. 35 to 2. 50 Elm wavelength measured by ASD spectrometer), and the various types of mineral spectral reflectances contained within the rocks are the essential data. Using the spectral linear mixture model of rocks and their minerals, firstly, a simulation study on the mixture of rock and mineral composition is achieved, the experimental results indicate that rock spectral curves using the model which based on the theory of the linear mixture are able to simulate better and preserve the absorption characteristics of various mineral components well. Then, 8 samples which contain biotite mineral are picked from the rock spectra of igneous, biotite contents and the absorption depth characteristics of spectral reflection at 2. 332 tan, furthermore, a variety of linear and nonlinear normal statistical models are used to fit the relationship between the depth of absorption spectra and the content of the mineral composition of biotite, finally, a new simulation model is build up with the Growth and the Exponential curve model, and a statistical response relationship between the spectral absorption depth and the rock mineral contents is simulated by using the new model, the fitting results show that the correlation coefficient reaches 0. 998 4 and the standard deviation is 0. 572, although the standard deviation using Growth and Exponential model is less than the two model combined with the new model fitting the standard deviation, the correlation coefficient of the new model had significantly increased, which suggesting that the new model fitting effect is closer to the measured values of samples, it proves that the simulation results of new model is closer to the measured value.     

Microwave Absorption Properties of Nickel–Zinc Ferrites Synthesized by Different Means

Ferromagnetic resonance (FMR) characteristics are investigated for Ni_xZn_{1 ? x}Fe₂O₄ ferrites (where x = 0.25, 0.5) synthesized using different organic complexation agents. The microstructure of the synthesized ferrites is studied, and the effect complexation agents have on their microstructure and FMR characteristics is determined.     

Simultaneous Determination of Sn and S in Methyltin Mercaptide by Microwave-Assisted Acid Digestion and ICP-OESSCIEI北大核心CSCD

Methyltin mercaptide is widely used as one of the best heat stabilizer in the polyvinylchloride (PVC) thermal processing due to its excellent stability, good transparency, high compatibility and weather resistance. The content of sulfur and tin significantly affects its quality and performance, so it is of great significance to develop an analytical method for the simultaneous determination of sulfur and tin. Inductively coupled plasma atomic emission spectrometry (ICP-OES) has been a powerful analytical tool for a myriad of complex samples owing to its advantages of the low detection limits, rapid and precise determinations over wide dynamic ranges, freedom from chemical inter-element interferences, the high sample throughput and above all, simultaneous multi-elements analysis. Microwave technique as a well-developed method for sample preparation can dramatically reduce the digestion time and the loss of volatile elements compared with the traditional open digestion. Hereby, a microwave-assisted acid digestion (MW-AAD) procedure followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis was developed for the simultaneous determination of Sn and S in methyltin mercaptide. This method has the advantages of simplicity, rapidness, good accuracy, green and less use of samples. Parameters affecting the MW-AAD such as the digestion solution and digestion time were optimized by using a chemical analyzed reference sample (DX-181) to attain tin and sulfur quantitative recoveries. HNO3-HCl-HClO4(v/v/v=9 : 3 : 1) and 10 min were the optimum digestion solution and digestion time, respectively. Under optimum conditions, the standard addition method and the standard calibration curve method were both been used to detect Sn and S in DX-181. There was no significant difference between two methods and the relative deviations to the chemical analysis values were both less than 2%. Additionally, the accuracy of the MW-AAD method was examined by analyzing three methyltin mercaptide samples (DX-181, DX-990, DX-960). The results were satisfactory with the relative deviations (<3%) and the recoveries of standard addition (99%-102%).     

Determination of Trace Elements in Marine Cetaceans by ICP-MS and Health Risk AssessmentSCIEI北大核心CSCD

The liver, kidney and muscle samples from seven cetaceans were digested by microwave digestion, and trace elements amounts of V, Cd, Cu, Zn, As, Cr, Ni, Mn, Se, Hg and Pb were determined by inductively coupled plasma mass spectrometry (ICP-MS), and the health risk assessment for Zn, Cu, Cd, Hg, Se in the liver was conducted. The results of international lobster hepatopancreas standard (TORT-2) showed acceptable agreement with the certified values, and the relative standard deviation (RSD) of eleven kinds of trace elements were less than 3.54%, showing that the method is suitable for the determination of trace elements in cetaceans. The experimental results indicated that different tissues and organs of the dolphins had different trace elements, presenting the tissue specificity. There is a certain inter-species difference among different dolphins about the bioaccumulation ability of the trace elements. The distribution of trace elements in whales presented a certain regularity: the contents of most elements in liver, kidney were much higher than the contents of muscle tissues, Cu, Mn, Hg, Se, and Zn exhibit the higher concentrations in liver, while Cd was mainly accumulated in kidney. And according to the health risk assessment in liver, the exceeding standardrate of selenium and copper in seven kinds of whales was 100%, suggesting that these whales were suffering the contamination of trace elements. The experimental results is instructive to the study of trace elements in cetaceans, while this is the first report for the concentrations in organs of Striped dolphin, Bottlenose dolphin, Fraser's Dolphin and Risso's dolphin in China, it may provide us valuable data for the conservation of cetaceans.     

Comparison and Analysis of IR Spectra of Four Dendrobium SpeciesEI北大核心CSCD

In this paper, Fourier transform infrared spectroscopy (FTIR) was used to compare the five dendrobium species' infrared absorption spectra of stem powder. The stem of Dendrobium is rich in saccharides. The saccharides of Dendrobium Officinale, Dendrobium Paxt and Dendrobium wardianum Warner are complex in composition. And the sugar units are mainly galactopyranose, grape pyranose, mannopyranose, arabinopyranose and xypyranose. The sugar components in the stem of Dendrobium strongylanthum Rchb. f. were simple. The sugar units were galactopyranose, grape pyranose and mannopyranose. Dendrobium wardianum Warner had the same chemical structure as Dendrobium strongylanthum Rchb. Dendrobium Officinale had the same chemical structure as Dendrobium devonianum Paxt. The species of Dendrobium could be identified by the characteristic absorption peak of the polysaccharide fingerprint absorption region.     

Biosorption and Biomineralization of Uranium(VI) from Aqueous Solutions by Landoltia PunctataSCIEI北大核心CSCD

The biosorption and biomineralization characteristics of uranium by the duckweed Landoltia punctata was investigated in aqueous solutions enriched with 1 to 250 mg . L-1 of U(VI) supplied as uranyl nitrate [UO2(NO3)(2) center dot 6H(2)O]. The maximum uranium removal for the plant cultivar occurred at pH 4 similar to 5 of solution and their uranium removal efficiencies exceeded 90% after 24 h. In kinetics studies, the dried powder of duckweed can finished nearly 80% adsorption within 5 min, the batch adsorption equilibrium can be reached within 24 h for the living and dried powder of duckweed, Both for the living and dried powder of duckweed, the experimental data were well fitted by the pseudo-second-order rate model with the degree of fitting (r) higher than 0.99. The adsorption isotherms could be better described by the Freundlich model than the Langmuir model. In addition, Fourier transform infrared spectroscopy (FTIR) revealed that the surface of Landoltia punctata possess many active groups such as hydroxyl, carboxyl, phosphate and amide groups, the hydroxyl, amino groups involved in adsorption of U(VI) by living and dried powder of Landoltia punctata, and the phosphate groups also participated in the adsorption behavior of U(VI) by the living Landoltia punctata. The living Landoltia punctata reduction part of U(VI) to U(IV) was observed by XPS analysis. SEM and energy dispersive X-ray spectroscopy (EDS) of duckweed from 10 similar to 200 mg . L-1 uranium treatments indeed showed root surface of living Landoltia punctata formed a significant portion of U precipitates with nanometer sized schistose structures that consisted primarily U and P, not containing C. Inorganic phosphate was released by the root cells of Landoltia punctata during the experiments providing ligands for formation of insoluble U(VI) and U(IV) phosphates. The distinct uranium peaks in the EDS spectra of the cluster on the root surface can be observed after biosorption and the uranium and phosphorus mass ratio of the cluster spot was measured to be 82.5% and 8.76% of the total component weight, respectively, and the atomic percentage of 30.89% and 25.19%, respectively. It is worth noting that the phosphorus mass ratio and the atomic rate of the control group is only 0.24% and 0.11%, respectively. But there was no similar crystals observed on the surface of dried powder of Landoltia punctata after biosorption. The present work suggests that living and dried powder of Landoltia punctata can remove more than 90% U(VI) from solution simultaneously precipitated together with phosphate by the living Landoltia punctata, and the dried powder of Landoltia punctata adsorption U(VI) is mainly through the effect of electrostatic attraction, ion exchange and complexation coordination, etc. Here, for the first time, the presence of U immobilization mechanisms within one aquatic plant is reported using Landoltia punctata.     

Year Discrimination of Mild Aroma Chinese Liquors Using Three-Dimensional Fluorescence Spectroscopy Combined with Parallel Factor and Neural NetworkSCIEI北大核心CSCD

Three-dimensional fluorescence spectroscopy coupled with parallel factor analysis and neural network was applied to the year discrimination of mild aroma Chinese liquors. The excitation-emission fluorescence matrices (EEMs) of 120 samples with various years were measured by FLS920 fluorescence spectrometer. The trilinear decomposition of the data array was performed and the loading scores of and the excitation-emission profiles of four components were also obtained. The scores were employed as the inputs of the BP neural networks and the PARAFAC-BP identification model was constructed. 10 samples were collected from 10, 20 and 30 years of liquors respectively, and 30 samples were selected as the test sets. The remaining 90 samples were used as the training sets to build the training model. The year prediction of unknown samples was also carried out, and the prediction accuracy was 90%, 100% and 100%, respectively. Meanwhile, the discrimination analysis method and the multi way partial least squares discriminant analysis were compared, namely PARAFAC-BP and NPLS-DA. The results indicated that parallel factor combined with the neural network (PARAFAC-BP) has higher prediction accuracy. The proposed method can effectively extract the spectral characteristics, and also reduce the dimension of the input variables of neural network. A good year discrimination result was finally achieved.     

Isospin Symmetry Breaking Effects on the Properties of Asymmetrical Nuclear Matter and β-Stable Matter

We have studied the influences of isospin symmetry breaking of nucleon–nucleon interaction on the various properties of asymmetrical nuclear matter and -stable matter. For asymmetrical nuclear matter, it is found that by including this isospin symmetry breaking, the changes of bulk properties increase by increasing both density and asymmetry parameter. However, these effects on the total energy and equation of state of -stable matter are ignorable. For asymmetrical nuclear matter, the validity of the empirical parabolic law in the isospin symmetry breaking case is shown. It is observed that the isospin symmetry breaking of nucleon–nucleon interaction affects the -equilibrium conditions in -stable matter.     

Structural and Magnetic Properties of Nd（Fe,Mo）12Nx Compounds Produced by Strip-Casting Method

The strip casting （SC） technique is employed to fabricate Nd（Fe,Mo）12Nx magnets. The crystallographic structure, intrinsic and permanent magnetic properties, as well as the microstruetures of the compound are investigated. There are prominent advantages for the SC Nd-Fe-Mo ailoys and their nitrides when compared with the samples prepared by the conventional casting （CC） method： （1） SC technique rebounds to the formation of the compounds crystallizing in a ThMn12-type structure. A single-phased host alloy Nd（Fe,Mo）12 can be directly prepared by strip casting without any isothermal annealing. Accordingly, lower energy cost and less rare earth demand notablely benefit the manufacture processing from a point of economizing. （2） The intrinsic magnetic properties, such as Curie temperature To, saturation magnetization Ms and anisotropy field Ha of the SC sample exceed the CC sample due to a phase forming condition with less-Mo-depended. （3） The microstructure studies also demonstrate that the SC compound contains finer grains, better-proportioned phase distribution than the CC compound. Optimized finM particles are observed aligned in their easy axis and the energy product of powder sample is up to （BH）max - 22 MGOe （176 kJ/m3）.