基于NDTI指数的MODIS火情监测研究

在分析燃烧热点光谱辐射特征的基础上,提出基于MODIS红外辐射的NDTI指数火情监测模型,给出了该监测模型的详细算法,并通过几起较大森林火灾对该模型进行了分析和验证。这种双通道比值指数和NDVI指数一样具有衰减仪器噪声和抵消常规大气影响的优点。MWIR 4μm火点辐射通道和LWIR 11μm背景分量通道的组合突出了火点信息。研究表明,选择合适的NDTI门限,NDTI指数能够准确检测火点。MODIS NDTI火情指数模型可以推广到同类探测器的应用中,例如NOAA AVHRR、GOES VAS以及即将运行的NPP VIIRS和中国风云3号FY-3平台,特别是MODIS的下一代多光谱探测器NPOESS NPP VIIRS设计继承了MODIS的优势,为NDTI算法模型提供了广阔的应用前景。

基于MODIS热红外辐射的归一化差异火点指数NDTI研究

本研究使用MODIS红外辐射遥感数据在分析了异常热点光谱辐射特性的基础上,提出一个新的火情监测模型NDTI火点指数,并通过几起较大森林火灾对该模型进行了分析和验证,给出了该监测模型的详细算法。这种双通道比值指数和NDVI一样具有衰减仪器噪声和抵消常规大气影响的优点。研究表明,4μm火点辐射通道和11μm背景分量通道的组合突出了火点信息,选择合适的NDTI门限,NDTI指数能够准确检测火点,识别率可达到93%。根据对实时接收轨道的有限实测,由于使用极少的数据集数学运算操作,NDTI模型比MODIS推荐火情算法在计算速度上快两倍以上。EOS MODIS探测器具有多光谱和高光谱以及对热点监测动态范围宽的特点,MODIS的下一代多光谱探测器NPOESS NPP VIIRS同样继承了MODIS的优势,为NDTI算法模型提供了广阔的应用前景。

新铌酸盐Ba_5NdTi_3Nb_7O_(30)的合成与介电性能

The New Niobate Ba5NdTi3Nb7O30 was synthesized by solid state reaction at 1250℃ for 48h. The crystal structure and dielectric properties of Ba5NdTi3Nb7O30 were determined by X ray powder diffraction and dielectric measurements. The results show that Ba5NdTi3Nb7O30 belongs to ferroelectric phase of tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.24424(4)nm, c=0.39476(2)nm, calculated density 5.719g·cm-3. Ba5NdTi3Nb7O30 belongs to relaxor ferroelectrics. The phase transition temperature (Tc) of Ba5NdTi3Nb7O30 from ferroelectric to paraelectric is found to shift toward higher temperature side at higher frequency, and Tc is 90℃ at 1kHz. At room temperature, the dielectric constant (εr) and dielectric loss of Ba5NdTi3Nb7O30 decrease with the increase of frequency, and Ba5NdTi3Nb7O30 ceramic have high dielectric constant 489 at 1kHz.

新铌酸盐Sr_5NdTi_3Nb_7O_(30)的合成与介电特性

一些铁电铌酸盐具有优良的电光性能和非线性光学性能,因此该类化合物的人工合成、结构与性能的研究受到了重视,其中钨青铜结构的系列晶体(例如SBN、KNSBN、SCNN)在材料的制备和器件的设计方面都取得了很大进展,它们在实时全息存储、集成光学与光信号处理等领域具有广泛的应用前景[1].

类钙钛矿新铌酸盐Ba_5NdTi_2Nb_3O_(18)的合成、结构与介电特性

为满足现代通信技术的小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理、电子等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构Ba(Zn1/3Ta2/3)O3、钨青铜结构Ba6-3xLn8+2xTi18O54等实用化的高性能材料[1-5].

Perylene diimide self-assembly: From electronic structural modulation to photocatalytic applications

As an emerging organic semiconductor,perylene diimide(PDI)self-assembly has attracted tremendous attention in the aspects of solar cells,sensors,fluorescence probes and n-transistors,etc.In term of photocatalysis,various photocatalysts based on PDI self-assembly exhibit some unique properties,such as intrinsicΠ-Πstacking structure,fast internal charge transfer,band-like electronic structure,flexible structural modifiability,well-defined morphological adjustability and excellent light absorption.This paper mainly presents recent progress on PDI self-assembly regarding how to regulate the electronic structure of PDI self-assembly.In addition,the photocatalytic applications of PDI self-assembly and its complexes were reviewed,such as environmental remedy,energy productions,organic synthesis and photodynamic/photothermal therapy,further highlighting related photocatalytic mechanisms.Finally,the review contents and some perspectives on photocatalytic research of PDI selfassembly were summarized,and some key scientific problems were put forward to direct related photocatalytic research in future.

Effects of 1,7-Bromine Substitution at Bay Area on Self-assembly Behavior and Photo Physical Properties of Perylene Diimide

N,N'-bis( n-dodecyl)-3,4: 9,10-tetracarboxyl-diimide( 1,7-H-PDI-C12) and its bay position 1,7-Br substituted derivative have been synthesized and characterized by1H-NMR,13C-NMR,FT-IR,and X-ray diffraction( XRD). A comparison of the two samples by measuring their photo physical properties using UV visible absorption and fluorescence emission spectra revealed that bay substitutions of bromine do not have significant effect on the perylene diimide( PDI) photo physical properties in solution. However,the solid state fluorescence properties were enhanced by brominating at bay areas. The solid fluorescence quantum yield of 1,7-Br-PDI-C12 was 2. 83%( Фf= 2. 83%) and 1,7-H-PDI-C12 was only 0. 02%( Фf= 0. 02%). This behavior was also reflected in the steady-state fluorescence spectra. This work shows that solid state photo physical properties of PDI could be improved without changing the other properties by simply using bromine substitution at bay areas. These types of materials are useful intermediate for further synthesis of PDI with tunnable optoelectronic properties.

Recent advances in rylene diimide polymer acceptors for all-polymer solar cells

In recent years, a large library of n-type polymers have been developed and widely used as acceptor materi- als to replace fullerene derivatives in polymer solar cells （PSCs）, stimulating the rapid expansion of research on so-called all-polymer solar cells （aPSCs）. In particular, rylene diimide-based n-type polymer acceptors have attracted broad research interest due to their high electron mobility, suitable energy levels, and strong light-harvesting ability in the visible region. Among various polymer acceptors, rylene diimide-based poly- mers presented best performances when served as the acceptor materials in aPSCs. Typically, a record power conversion efficiency （PCE） of 7.7% was very recently achieved from an aPSC with a rylene diimide polymer derivative as the acceptor component. In this review, we highlight recent progress of n-type polymers orig- inated from two significant classes of rylene diimide units, namely naphthalene diimide （NDI） and perylene diimide （PDI）, as well as their derivatives for aPSC applications.

Synthesis,characterization,and activity of a covalently anchored heterogeneous perylene diimide photocatalyst

The consecutive two‐photon photocatalytic behavior of perylene diimide(PDI)enables it to catalyze photoreduction reactions that are thermodynamically unfavorable via single‐photon processes.In this work,we developed a heterogeneous PDI photocatalyst by covalently binding PDI molecules on the surface of nanosilica.This photocatalyst structure overcomes the intrinsic limitation of the low solubility of PDI,but retains its consecutive two‐photon photocatalytic property.Detailed characterization of the photocatalyst by techniques such as thermogravimetric analysis,solid‐state nuclear magnetic resonance spectroscopy,and Fourier transform infrared spectroscopy indicated that the PDI molecules were anchored covalently on the surface of nanosilica.The obtained photocatalyst reduced aryl halides under visible‐light irradiation in polar organic solvent and in water.The present study provides a promising strategy to realize two‐photon activity of PDI in common solvents for photocatalytic applications.

All-organic covalent organic frameworks/perylene diimide urea polymer S-scheme photocatalyst for boosted H_(2) generation

Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.

Hydrochloric acid‐mediated synthesis of ZnFe_(2)O_(4) small particle decorated one‐dimensional Perylene Diimide S‐scheme heterojunction with excellent photocatalytic ability

The recyclable and stable ZnFe_(2)O_(4) small particle decorated one‐dimensional perylene diimide(PDI)S‐scheme heterojunction(1D PDI/ZnFe_(2)O_(4))is prepared by the hydrochloric acid‐mediated(HCl‐mediated)strategy,interestingly,the morphology of the 1D PDI/ZnFe_(2)O_(4) can also be effectively regulated by HCl‐mediated process,the existence of HCl can regulate PDI into a uniform rod structure,while the co‐existence of HCl and PDI can limit ZnFe_(2)O_(4) to become the uniform small particles.More importantly,based on the 1D rod structure of PDI and the small size effect of ZnFe_(2)O_(4),carriers can migrate to the surface more easily,which can improve the photocatalytic activity.Meanwhile,due to the appropriate energy level structure,the S‐scheme heterojunction structure is formed between PDI and ZnFe_(2)O_(4),which eliminates meaningless photo‐generated charge carriers through recombination and introduces strong redox to further enhance the photodegradation effect,thereby,1D PDI/ZnFe_(2)O_(4) exhibits excellent photocatalytic ability,under the visible light irradiation,the degradation rate of tetracycline(TC)with 1D PDI/ZnFe_(2)O_(4)(66.67%)is 9.18 times that with PDI(7.26%)and 9.73 times that with ZnFe_(2)O_(4)(6.85%).This work proposes new ideas for the assembly of magnetic organic‐inorganic S‐scheme heterojunction photocatalysts.

Effect of Fluorination on Aggregate Structure of Perylene Diimide

The effect of fluorination on the aggregate structure of a novel fluorinated perylene diimide, N, N'-diperfluorophenyl-3, 4, 9, 10-perylenetetracarboxylic diimide 1, was investigated by UV-Vis absorptions and the conformation simulations from AM1 semi-empirical quantum mechanics modeling. The results showed that in the solid film 1 molecules stacked with the perfluorinated phenyl groups straightly over or below the perylene cores of the adjacent 1 molecules.

Self-assembled helical nanostructures from an asymmetrical perylene diimide

An asymmetrical perylene diimide 3, N-（4-methoxyphenyl）-N＇-（4-nitrophenyl）-perylene-3,4,9,10-tetracarboxylic diimide, was synthesized, and its self-assembly and dissociation behaviors in chloroform was studied in detail by UV-vis and fluorescence spectroscopies. The resulting unique helical nanostructures from 3 were proposed to be self-assembled via the cooperative actions of π-π stacking, steric hindrance and electrophile-nucleophile type pairing.

Synthesis and Fluorescence Quenching of Copolymer Containing3, 4, 9, 10-Perylenetetracarboxyl Diimide Side Chains

A photoluminescence material, copolymer of N-vinylcarbazole (VCz) and N,N'- bisallyl-3, 4. 9, 10-ferylenetetracarboxyl diimide (APTC) chromophores P(VCz-APTC) was synthesized. The fluorescence quenching of P(VCz-APTC) by fullerene (C-60) and triethylamine was also studied.

Synthesis and Crystal Structure of N,N′-4-aminomethyl-pyromellitic diimide

The title compound N,N′-4-aminomethyl-pyromellitic diimide （4-pmpmd） crystallizes in monoclinic, space group P21/c with a = 4.785（1）, b = 6.200（1）, c = 29.907（2） A, β = 93.583（11）°, V= 885.5（2） A^3, Dc = 1.494 g/cm^3, Z= 2, C22H14N4O4, Mr = 398.37,/t（MoKα） = 0.106 mm^-1 and F（000） = 412, and its structure was refined to R = 0.0469 and wR = 0.1017 for 1194 observed reflections （F0 〉 4σ（F0））. The X-ray diffraction shows the existence of the staggered strong intermolecular C-H…O （DA） hydrogen bonds between adjacent molecules, the intermo- lecular C-H…π hydrogen bonds and the weak π…π stacking interactions, leading to the formation of multi-dimensional supramolecular network based on the Z-mode conformation of the title compound.

Optical Waveguide and Nonlinear Properties of Bi_3NdTi_3O_(12) Thin Films

Neodymium-substituted bismuth titanate （Bi3NdTi3O12, BNT） thin films were prepared on quartz substrates by a metal-organic solution deposition process. The crystalline structure was evaluated by X-ray diffraction. Waveguide property was investigated by using prism coupling technique and optical transmittance measurement. The optical nonlinearities of the film were measured by the top-hat Z-scan techniques and a large positive nonlinear refractive index, nonlinear refractive coefficient and two-photon absorption coefficient were determined to be 3.84×10^7 esu, 0.7523 cm^2/GW and 4.81×10^4 cm/GW, respectively. These results reveal that the BNT film may be a kind of new multifunctional materials.

Photoactive Naphthalene Diimide Functionalized Titanium-Oxo Clusters with High Photoelectrochemical Responses

Photoactive functionalized titanium-oxo clusters(TOCs)are regarded as an important model compound for dye-sensitized titanium dioxide solar cells.However,the dyes used for sensitizing TOCs are still limited.Herein,two cyclic TOCs are reported,namely,[Ti_(6)(μ_(3)-O)_(2)(Oi-Pr)_(8))(LA)_(2)]·i-PrOH(S1)and[Ti_(6)(μ_(3)-O)2(Oi-Pr)_(8))(LV)_(2)]·i-PrOH(S2),which are functionalized by photoactive naphthalene diimide(NDI)chromophores.Their molecular structures and photophysical and photochemical properties were systematically studied.As shown by ultraviolet-visible(UV-vis)spectra and photocurrent study results,the band gap and the photocurrent response of S1 and S2 were derived from NDI ligands which extend the absorption edge of S1 and S2 approaching 500 nm and afford high photocurrent densities of 2.12μA/cm^(2)and 1.95μA/cm^(2)for S1 and S2,respectively,demonstrating the significance of the photoactive ligand in modulating photoresponse of TOCs.This work is expected to enrich the structural library of photoactive TOCs and provide insights into understanding the structure-property relationships of sensitized clusters.

SYNTHESIS,CHARACTERIZATION OF DIAMIDE-DIIMIDE-DIAMINES BASED ON L-CYSTEINE AMINO ACID AND THEIR EFFECT ON THE THERMAL PROPERTIES OF DIGLYCIDYL ETHER OF BISPHENOL-A(DGEBA)

The curing behavior of diglycidyl ether of bisphenol-A(DGEBA) with aromatic diamide-diimide-diamines having aryl ether,sulfone and methylene linkages was studied by differential scanning calorimetry(DSC).Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine(S) in a mixture of acetic acid and pyridine(3:2 V/V) followed by activation with thionyl chloride(SOCl_2) and then condensation with excess of diamines.Structural characterization...

乙烯与乙烯基三乙氧基硅烷共聚物的制备与表征

采用一系列结构不同的α-二亚胺镍催化剂,在倍半乙基氯化铝(EASC)作用下,以配位共聚的方法制备乙烯和乙烯基三乙氧基硅烷(VTEoS)共聚物。研究了VTEoS的浓度、催化剂用量、n(Al)/n(Ni)、乙烯压力、聚合时间、溶剂以及催化剂结构对共聚反应的影响,得到了最优化的聚合条件。通过核磁共振(NMR)、哀减全反射傅里叶变换红外光谱(ATR-FTIR)、热失重分析(TGA)、焙烧法、聚合物膜的接触角测试等方法分别表征了聚合物的结构、热稳定性、硅质量分数和聚合物膜的表面性能。结果表明,以C4为催化剂,二氯甲烷为溶剂时,共聚活性(以1 mol Ni计)最高达9.10×10^(5) g/(mol·h),共聚物中硅的质量分数为0.74%~3.39%。含硅单体的引入,能够提高聚合物的热稳定性和疏水性能。

乙烯与乙烯基五甲基二硅氧烷的配位共聚

后过渡金属催化剂具有独特的“链行走”机理以及对极性基团的耐毒性等特点,可用于催化α-烯烃与极性单体共聚,得到结构与性能优异的功能化聚烯烃.本文以α-二亚胺镍(Ⅱ)配合物(C1~C6)为催化剂,在倍半乙基氯化铝(EASC)作用下,以乙烯和乙烯基五甲基二硅氧烷(VPMDSO)为单体进行配位共聚,制备了一系列共聚物.考察了VPMDSO单体浓度、催化剂用量、Al/Ni摩尔比、乙烯压力、聚合时间、溶剂以及催化剂结构对配位共聚反应的影响,得到了最优的聚合条件.通过核磁共振氢谱(1H NMR)、傅里叶变换红外光谱(FTIR)、凝胶渗透色谱(GPC)、热失重分析(TGA)及接触角测试等表征了聚合物的微观结构、热稳定性、硅含量和表面性能.研究结果表明,α-二亚胺镍(Ⅱ)配合物催化活性可达1.26×10^(6)g·mol_(Ni)^(-1)·h^(-1),共聚物中硅含量为0.25%~0.87%(质量分数),与聚乙烯(PE)相比,共聚物的表面能降低、疏水性提高.