Rapid detection and risk assessment of soil contamination at lead smelting site based on machine learning

A general prediction model for seven heavy metals was established using the heavy metal contents of 207soil samples measured by a portable X-ray fluorescence spectrometer(XRF)and six environmental factors as model correction coefficients.The eXtreme Gradient Boosting(XGBoost)model was used to fit the relationship between the content of heavy metals and environment characteristics to evaluate the soil ecological risk of the smelting site.The results demonstrated that the generalized prediction model developed for Pb,Cd,and As was highly accurate with fitted coefficients(R^(2))values of 0.911,0.950,and 0.835,respectively.Topsoil presented the highest ecological risk,and there existed high potential ecological risk at some positions with different depths due to high mobility of Cd.Generally,the application of machine learning significantly increased the accuracy of pXRF measurements,and identified key environmental factors.The adapted potential ecological risk assessment emphasized the need to focus on Pb,Cd,and As in future site remediation efforts.

网络式多媒体监控系统

简要介绍了视频信号在网络中传输时遇到的问题，提出了把有线电视网同局域网结合起来的解决方案。并通过实例一基于网络的多媒体监控系统来说明该方案的可行性。

Improving Efficiency by Doping PtOEP into Spiro Light-Emitting Devices

To investigate effective means of improving the efficiency of organic light-emitting devices （OLEDs） by making full use of ,triplet emission, a phosphorescent material Pt （II） Octaethylporphine （PtOEP） is doped into polymer host polyspirobifluorene （Spiro） to allow radiative recombination of triplet excitons. The current and brightness characteristics of the devices are tested and the electroluminescent spectra are described. Both fluorescence and phosphorescence are ob- served,and an obvious increase in external quantum efficiency is realized compared to undoped devices when different phosphorescent dopant concentrations are tried. Thus,the phosphorescent emission from triplet excited states might be an effective way to increase the efficiency of OLEDs when the concentration of the phosphorescent dopant is properiy controlled.

美开发出可集热的太阳能保温纸

美国研究、开发出一种新型纸张太阳能保温纸。

描绘想像中的童话

可能是Bryce作者Eric的特意安排,使我们可以轻而易举的创造各种自然景观,难怪有人说:“使用Bryce让人亲身体会上帝的造物伟大。”在三维软件中除去材质还有光线,而Bryce中的光源就是Sky＆Fag。强一些的光源被称为日光,弱一些的光源被称为月光,还可Sky＆Fag工作板中调整雾是浓众还是稀薄,云的分布,这所有对自然因素的调节就能让Bryce的像质的光感更自然。

切莫小觑“灯下黑”

划根火柴,点亮油灯,灯下总有光线暗淡之处,老百姓俗称其为“灯下黑”。及至社会发展,科学进步,用上电灯、日光灯,甚至无影灯,灯座处仍暗淡依然。无独有偶,一些位高权重的领导身边,往往有人倚仗领导之势,行腐败之实。

Synthesis of a novel organic nonlinear optical chromophore and the Testing for μ_gβ Value

A novel second-order nonlinear optical chromophore （DCDHF-2-V） was synthesized from 3-Hydroxy-3-methyl-2-butanae, propanedinitrile and 4-diethylaminobenzaldehyde by aldol condensation reaction. Molecular structural characterization was investigated by elemental analysis, FTIR, and 1H-NMR spectra. The melting point obtained from DSC thermogram was almost 251 ℃, and the compound shows a thermal stability up to 270 ℃. Second-order NLO properties of the chromophore were measured by solvatochromic method. From the quantum-mechanical two-level model, it can be obtained that the μgβ value of DCDHF-2-V is 6520×10^-48esu atthe wavelength of 1064 nm.

Beam shaping with limited amplitude weight values for satellite active phased array antenna

To gain the tradeoff between lower sidelobe and higher power amplifiers efficiency,a transmitting beam shaping scheme with limited amplitude weight values for satellite active phased array antenna is presented. The scheme is implemented by a dual coding genetic algorithm(GA). Phase and amplitude of array weight vectors for beam shaping are encoded by real coding and finite length binary coding,respectively,which,maintaining accuracy of results,reduces the amplitude dynamic range and improves the efficiency of power amplifiers. The presented algorithm,compared with complex-coded GA,increases the convergence rate due to the search space's decrease. In order to overcome the prematurity and obtain better global optimization or quasi-global optimization,a new dual coding GA based on "species diversity retention" strategy and adaptive crossover and mutation probability are presented.

Low Distortion 1.31μm AlGaInAs/InP MQW DFB Laser Module for CATV Systems

A high power and low distortion 1.31 μm AlGaInAs/InP multiquantum well distributed feedback laser diode (MQW DFB LD) with RWG structure has been developed by MOCVD technique. The fiber output power of butterfly packaged module with optic isolator P f is more than 10 mW, threshold current is in the range of (13～20) mA, slope efficiency, E s>0.30 W/A and side mode suppression ratio, R S,M,S >35 dB. The composite second order, O C,S <-61 dBc and composite triple beat, B C,T <-65 dBc are obtained by test frequencies of (45～550) MHz with 60 PAL channels. In the test conditions the carrier to noise ratio, R C,N >51 dB.

Variation of Two-photon Absorption Cross Sections and Optical Limiting of Compounds Induced by Static Electric Field

By numerically solving the Maxwell-Bloch equations using an iterative predictor-corrector finite-difference time-domain technique, we investigate propagating properties of a few-cycle laser pulse in a 4,4＇-bis（di-n-butylamino） stilbene （BDBAS） molecular medium when a static electric field exists. Dynamical two-photon absorption （TPA） cross sections are obtained and optical limiting （OL） behavior is displayed. The results show that when the static electric field intensity increases, the dynamical TPA cross section is enhanced and the OL behavior is improved. Moreover, both even- and odd-order harmonic spectral components are generated with existence of the static electric field because it breaks the inversion symmetry of the BDBAS molecule. This work provides a method to modulate the nonlinear optical properties of the BDBAS compounds.

Study on Tribological Properties of CVT Fluid Containing Inert and Active Functional Elements

The lubricating characteristics of CVTF(continuously variable transmission fluid) mixed with a multi-functional complex additive were studied. The said complex additive contained an organic borate ester and a new type of friction improver comprising phosphorus element and poly-methylmethacrylate(PMMA), and a viscosity index improver. The viscosity-pressure characteristics were evaluated by a high-pressure quartz viscometer, and the anti-wear property was investigated by a four-ball friction tester. The mechanism of lubrication by the CVTF was studied using X-ray photoelectron spectroscopy(XPS). The results showed that CVTF T10, which contained a multi-functional complex additive, exhibited excellent properties, featuring greater solidification pressure and pressure-viscosity coefficient, improved oil film strength, and low wear value. These attributes meet the special CVTF requirements for "high friction and low wear" that make it possible to provide both traction and lubrication. The lubricating mechanism was varied using different functional elements, such as inert and active elements. Sulfur and phosphorus are active extreme pressure elements that can react on the metal friction surface and produce an extreme pressure lubrication film. Boron is an inert functional element and does not react upon the metal surface; boron is only adsorbed onto the metal surface to act as a lubricant for adsorption film and fillers.

Tribological Performance of Two Potential Environmentally Friendly Ashless Vegetable Oil Additives

Two potential novel environmentally friendly ashless vegetable oil additives, 2-mercaptobenzothiazole derivatives, di-n-dodecyl-[2-（2-benzothiazolyl）thio]ethylborane （LBN） and di-n-dodecylthio-[2-（2-benzothiazolyl） thio]ethylborane （LBNS）, were synthesized and their tribological performance as additives in rapeseed oil （RSO） was evaluated using a four-ball wear tester. Their anti-corrosive properties and thermal stability were also examined. The worn surface of the steel ball was analyzed by means of scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. The results showed that 2-mercaptobenzothiazole derivatives exhibited excellent anti-corrosive property and high thermal stability. Moreover, they both had good load-carrying capacities and anti-wear and friction-reducing properties. The PR values of samples decreased in the following order： LBNS〉 LBN〉RSO. The results of XPS examination illustrated that the excellent tribological behavior of the prepared compounds used as additives in RSO was attributed to the formation of a protective lubrication film on the worn surface, which consisted of an adsorption layer and a reaction layer containing Fe3O4, FeS, Fe2（SO4）3, FeB, and organic nitrogen-containing compounds.

SYNTHESIS AND CHARACTERIZATION OF NOVEL SOL-GEL DOPED ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL MATERIALS

hydroxy-4-nitro azobenzene (NHA) and 4-amino-4-nitro azobenzene (DO3) were prepared respectively from p-nitrophenylamine as a precursor compound. Two kinds of doped organic/inorganic hybrid nonlinear optical (NLO) materials containing NHA and DO3 were synthesized by Sol-Gel process. The preparation and properties of two NLO materials were studied and characterized by FTIR, 1H-NMR, UV-VIS, SEM, DSC and SHG measurements. The results show that the maximum doping amounts of NHA and DO3 in two doped hybrid NLO materials are 7.2(wt)% and 11.3(wt)% respectively, and the corresponding second-order NLO coefficients (d33 values) are 2.91×10 8esu and 6.14×10 8esu. Two doped NLO materials have relatively good RT stability, after 90 days at RT the d33 values can maintain about 85% of their initial values, but after 10h at 100℃ can only maintain about 50% of their initial values. In this report, the reasons for high-temperature instability of doped materials were discussed, and the possible improvements were also suggested.

狄更斯的观察力

狄更斯十分重视细节的真实性。在1848年4月22日给好朋友约翰·福斯特的信中,狄更斯赞美了后者所著《高士密斯传》后,又提出了一点质疑: “在第三部(这是最美的一部)

尽职尽责

据说驼鸟有一习性,就是一旦遇到危险的情况,它就埋首沙堆,来个“眼不见心不烦”,管它屁股还是露在外面。——因此,驼鸟的行为成了被人嘲笑的行为。而且在人类社会中这种“驼鸟行为”并不为少,有的还有过之而无不及,并形成“驼鸟政策”。

分床睡6绝招

“我们3岁的女儿有她自己的床,可她仍然喜欢跟我们睡在一起。可是,我们想让她自己一个入睡,我们该怎么办呢?”这是一位读者的来信,相信这种情况你也会遇到。试试我们为你量身定做的小绝招吧！

Synthesis of Ordered Multivalent Mn-TiO2 Nanospheres with Tunable Size： A High Performance Visible-Light Photocatalyst

A facile and reproducible method has been developed for the synthesis of ordered anatase Mn-TiO2 nanospheres with controllable sizes in the range 200-300 nm by simply varying the amount of manganese（lI） chloride added. The samples were characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, scanning electron microscope （SEM）, and transmission electron microscope （TEM） measurements, and it was found that the manganese exists in multivalent forms （Mn4＋/Mn3＋） and substitutes for some of the Ti4＋ in the anatase TiO2 lattice. The presence of Mn significantly influences the morphology and high-temperature stability of TiO2, and extends its light absorption range. Surface photovoltage and photocurrent measurements revealed that an electronic interaction between the Mn and TiO2 was present, in which Mn served as an electron acceptor and effectively inhibited the charge recombination in TiO2; this is thought to be responsible for the highly efficient photocatalytic activity of the material in the degradation of rhodarnine B （RhB） under visible-light irradiation （λ 〉 420 nm）.

Progress in next-generation organic electroluminescent materials:material design beyond exciton statistics

Exciton(or spin)statistics is a physical principle based on the statistics of spin multiplicity.In electroluminescence,injected electrons and holes have randomized spin states,and usually form singlet or triplet excitons in the ratio of 1:3.Exciton statistics determines that the upper limit of internal quantum efficiency is 25%in fluorescent devices,since only singlet exciton can decay radiatively.However,both experimental and theoretical evidence indicate that the actual efficiency can exceed the exciton statistics limit of 25%by utilizing materials with special electronic structure and optimized device structures.These results bring light to break through the exciton statistics limit and develop new-generation fluorescent materials with low cost and high efficiency.Recently,the exciton statistics,which has attracted great attention in the past decade,is being rejuvenated due to the discovery of some fluorescent materials with abnormally high efficiencies.In view of their significance in theoretical research of organic semiconductors and developing new-generation OLED materials,such materials are widely investigated in both academic institutions and industry.Several key issues still require further clarification for this kind of materials,such as the molecular design concepts.Herein,we review the progress of the materials with efficiency exceeding the exciton statistics limit,and the routes to improve exciton utilization efficiency.In the end,we present an innovative pathway to fully harvest the excitons in fluorescent devices,namely,"hot exciton"model and relevant fluorescence material with hybridized local and charge-transfer(HLCT)excited state.

Metal-organic framework film for fluorescence turn-on H2S gas sensing and anti-counterfeiting patterns

Hydrogen sulphide(H2 S)is a common air pollutant,which is produced in various industry processes.Therefore,it is of crucial importance to detect H2 S in real time.Many fluorescent sensors were reported aiming at detecting H2 S in solution;however,the fluorescence sensing of gaseous H2 S has not yet been reported.In this work,we utilized the post-functionalized fluorescent film,MIL-100(In)@Eu3+/Cu2+film,realizing fluorescence turn-on sensing of gaseous H2 S at room temperature for the first time with the limit of detection as low as 0.535 ppm,which is comparable to some reported fluorescent probes for S2-ions and semiconductor based gaseous H2 S sensors.The sensor was designed due to the strong affinity of H2 S with Cu2+.With the formation of CuS,the"antenna effect"between the ligand and Eu3+recovered,resulting in the fluorescence turn-on of Eu3+emission.Additionally,we proposed a new method to realize multi-colour anti-counterfeiting patterns with lanthanide ions ink,taking advantage of the extraordinary smooth surface and uncoordinated carboxylate groups within the MIL-100(In)film.