Electronic structure and ultraviolet spectra of p-C_(6)H_(4)-C_(20)

Geometry optimization of p-C_(6)H_(4)-connected cyclo[20]carbon(p-C_(6)H_(4)-C_(20))was carried out at M062X/6-311G(d,p)level,three kinds of bond orders(Mayer,Laplacian,and Wiberg),electron-hole distributions,localized orbital locators(LOL),and infrared(IR)spectrum were also performed at the same level.Based on TD-DFT M062X/6-311G(d,p)method,the first 20 excited states and ultraviolet(UV)spectra of p-C_(6)H_(4)-C_(20) were calculated.Calculation results of π-electron delocalization analyses prove thatπ-electron delocalization of p-C_(6)H_(4)-C_(20) is more likely to occur on shorter C-C bonds rather than longer C-C bonds,and inside/outside of the ring plane rather than above/below the ring plane.Two absorption peaks of p-C_(6)H_(4)-C_(20) locate at about 319 nm and 236 nm,respectively.

Microstructure and mechanical properties of Mg_(94)Zn_2Y_4 extruded alloy with long-period stacking ordered structure

The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.

基于次序统计量的4鸭问题求解

次序统计量是数理统计基本概念章节的一个教学难点.通过4鸭问题,介绍次序统计量解决该问题的一种解题思路,融入次序统计量概率密度函数的梳理,为次序统计量内容的讲授丰富教学思路.

Synthesis of a new ordered mesoporous NiMoO_4 complex oxide and its efficient catalytic performance for oxidative dehydrogenation of propane

Highly ordered mesoporous NiMoO4 material was successfully synthesized using mesoporous silica KIT-6 as hard template via vacuum nanocasting method. The structure was characterized by means of XRD, TEM, N2 adsorption-desorption, Raman and FT-IR. The mesoporous NiMoO4 with the coexistence of a-NiMoO4 and fl-NiMoO4 showed well-ordered mesoporous structure, a bimodal pore size distribution and crystalline framework. The catalytic performance of NiMoOa was investigated for oxidative dehydrogenation of propane. It is demonstrated that the mesoporous NiMoO4 catalyst with more surface active oxygen species showed better catalytic performance in oxidative dehydrogena- tion of propane in comparison with bulk NiMoO4.

Existence of solutions of nonlinear two-point boundary value problems for 4nth-order nonlinear differential equation

Studies the existence of solutions of nonlinear two point boundary value problems for nonlinear 4n-th-order differential equationy (4n)=f(t,y,y′,y″,...,y (4n-1))(a)with the boundary conditions g 2i(y (2i)(a),y (2i+1)(a))=0,h 2i(y (2i)(c),y (2i+1)(c))=0,(i=0,1,...,2n-1)(b) where the functions f, g i and h i are continuous with certain monotone properties. For the boundary value problems of nonlinear nth order differential equationy (n)=f(t,y,y′,y″,...,y (n-1))many results have been given at the present time. But the existence of solutions of boundary value problem (a),(b) studied in this paper has not been covered by the above researches. Moreover, the corollary of the important theorem in this paper, i.e. existence of solutions of the boundary value problem.y (4n)=f(t,y,y′,y″,...,y (4n-1)) a 2iy (2i)(a)+a 2i+1y (2i+1)(a)=b 2i,c 2iy (2i)(c)+c 2i+1y (2i+1)(c)=d 2i,(i=0,1,...2n-1)has not been dealt with in previous works.

Effect of Ordering on Embrittlement of Ni4Mo Alloy in Hydrogen Gas

The fracture behavior of disordered and ordered Ni4Mo alloy was investigated by tensile tests in hydrogen gas or during hydrogen charging. The results show that the ductility of the disordered alloy decreased slightly with the hydrogen pressure increasing, while that of the ordered alloy decreased rapidly with the hydrogen pressure increasing. However, the ductility of both disordered and ordered alloys reduced similarly seriously with the charging current density increasing. Therefore, the mechanism of order-induced embrittlement of Ni4 Mo alloy in hydrogen gas is supposed to be that atomic order accelerates the kinetics of the catalytic reaction for the dissociation of molecular H2 into atomic H.

Fourth-Order Adjoint Sensitivity Analysis of an OECD/NEA Reactor Physics Benchmark: II. Mathematical Expressions and CPU-Time Comparisons for Computing 4^th-Order Sensitivities

This work extends to fourth-order previously published work on developing the adjoint sensitivity and uncertainty analysis of the numerical model of a polyethylene-reflected plutonium (acronym: PERP) OECD/NEA reactor physics benchmark. Previous works showed that the third-order sensitivities of the PERP leakage response with respect to these total microscopic cross sections are far larger than the corresponding 1st-order and 2nd-order ones, thereby having the largest impact on the uncertainties induced in the PERP benchmark’s response. This finding has motivated the development of the original 4th-order formulas presented in this work, which are valid not only for the PERP benchmark but can also be used for computing the 4th-order sensitivities of response of any nuclear system involving fissionable material and internal or external neutron sources. Subsequent works will use the adjoint-based mathematical expressions obtained in this work to compute exactly and efficiently the numerical values of the largest fourth-order sensitivities of the PERP benchmark’s response to the total microscopic cross sections, and use them for a pioneering fourth-order uncertainty analysis of the PERP benchmark’s response.

Co_(3)O_(4) with ordered pore structure derived from wood vessels for efficient Hg^(0) oxidation

Catalytic oxidation of Hgo to Hg~O is an efficient way to remove Hg^(0) from coal-fired flue gas.The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg^(0) oxidation efficiency.Therefore,in the present work,wood vessels were used as sacrificial template to obtain Co_(3)O_(4) with ordered pore structure.SEM and BET results show that,when the mass concentrations of Co(NO_(3))_(2)·6H_(2)O was 20%,the obtained catalyst(Co_(3)O_(4) [20%Co(NO_(3))_(2)])possesses better pore structure and higher surface area.It will expose more available surface active sites and lower the mass transfer resistance.Furthermore,XPS results prove that Co_(3)O_(4) [20%Co(NO_(3))_(2)]has the highest ratio of chemisorbed oxygen which plays an important role in Hg^(0) oxidation process.These results lead to a better Hg^(0) oxidation efficiency of Co_(3)O_(4) [20%Co(NO_(3))_(2)],which is about 90%in the temperature range of 200 to 350℃,Furthermore,Co_(3)O_(4) [20%Co(NO_(3))_(2)]has a stable catalytic activity,and its Hg^(0) oxidation efficiency maintains above 90%at 250℃even after 90 h test,A probable reaction mechanism is deduced by the XPS results of the fresh,used and regenerated catalyst of Co_(3)O_(4) [20%Co(NO3)2].Chemisorbed oxygen can react with Hg^(0) forming HgO with the reduction of Co^(3+)to Co^(2)+.And lattice oxygen and gaseous oxygen can supplement the consumption of chemisorbed oxygen to oxidize Co^(2+)to Co^(3+).

Explicit High-Order Method to Solve Coupled Nonlinear Schrödinger Equations

Models of the coupled nonlinear Schrödinger equations submit various critical physical phenomena with a typical equation for optical fibres with linear refraction. In this article, we will presuppose the Compact Finite Difference method with Runge-Kutta of order 4 (explicit) method, which is sixth-order and fourth-order in space and time respectively, to solve coupled nonlinear Schrödinger equations. Many methods used to solve coupled nonlinear Schrödinger equations are second order in time and need to use extra-technique to rise up to fourth-order as Richardson Extrapolation technique. The scheme obtained is immediately fourth-order in one step. This approach is a conditionally stable method. The conserved quantities and the exact single soliton solution indicate the competence and accuracy of the article’s suggestion schemes. Furthermore, the article discusses the two solitons interaction dynamics.

Enhanced activation of peroxymonosulfate by Fe/N co-doped ordered mesoporous carbon with dual active sites for efficient removal of m-cresol

The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.

Eigenvalue Computation of Regular 4th Order Sturm-Liouville Problems

In this paper we present and test a numerical method for computing eigenvalues of 4th order Sturm-Liouville (SL) differential operators on finite intervals with regular boundary conditions. This method is a 4th order shooting method based on Magnus expansions (MG4) which use MG4 shooting as the integrator. This method is similar to the SLEUTH (Sturm-Liouville Eigenvalues Using Theta Matrices) method of Greenberg and Marletta which uses the 2nd order Pruess method (also known as the MG2 shooting method) for the integrator. This method often achieves near machine precision accuracies, and some comparisons of its performance against the well-known SLEUTH software package are presented.

NiCr_(2)O_(4)化合物的磁相变临界行为

采用标准固相法制备NiCr_(2)O_(4),并对其结构、磁性能和磁相变临界行为进行研究.研究结果表明:NiCr_(2)O_(4)具有尖晶石结构;当温度低于居里温度TC时,随着磁场强度增加,磁化强度趋于饱和;当温度高于TC,随着磁场强度增加,磁化强度线性增加,NiCr_(2)O_(4)呈顺磁特征;长程和短程铁磁相互作用共存于NiCr_(2)O_(4).

Molecular Structure, Vibrational Analysis and First Order Hyperpolarizability of 4-Methyl-3-Nitrobenzoic Acid Using Density Functional Theory

The Fourier Transform Infrared (FTIR) and FT-Raman spectra of 4-methyl-3-nitrobenzoic acid have been recorded in the range 4000 - 400 cm-1 and 3500 - 50 cm-1, respectively. The optimized geometry of the molecule, its vibrational frequencies along with corresponding intensities have been computed using the Density Functional Theory (DFT) employing B3LYP/6-311++G basis set. The scaled values of harmonic vibrational frequencies obtained in the computations have been compared with their experimental counter parts. The scaling factors have been refined to reproduce the frequencies with an RMS error of 11.68 cm-1 between the experimental and computed frequencies. The theoretically constructed spectra agree satisfactorily with those of experimental spectra. First order hyperpolarizability constants have also been evaluated.

镁含量对Ni/MgAl_(2)O_(4)催化剂甲烷干重整反应性能的影响

本研究采用溶剂蒸发自组装法制备了不同Mg含量的镁铝尖晶石(MgAl_(2)O_(4))载体,随后负载了金属Ni,并将该催化剂(Ni/x-MAO)应用于甲烷干重整制合成气反应。结合X射线衍射、氮气物理吸附-脱附和透射电镜等表征对催化剂的结构性质进行了分析,发现适量Mg的加入(10%-15%)有利于提高载体的比表面积,并形成耐高温的有序介孔结构。该结构可以将Ni颗粒限域在孔道内,有利于形成高分散、小晶粒的活性物种,其在高温反应下不易烧结。同时,H2-TPR和XPS结果表明,10%-15%的Mg含量有利于增强Ni与MgAl_(2)O_(4)的金属-载体相互作用,有效抑制Ni烧结,且其表面的活性氧物种有效抑制了积炭生成。在性能评价中,10%-15%Mg含量的Ni/MgAl_(2)O_(4)催化剂呈现出优异的CH4和CO_(2)转化率,在180 h的长周期活性评价期间,Ni/15-MAO催化剂的CH4和CO_(2)转化率分别保持在92.6%和92.5%左右,同时积炭量仅为0.89%,且反应后的Ni颗粒尺寸变化不大。

可控合成具有增强光催化性能的CeO_(2)纳米中空球/g-C_(3)N_(4)纳米复合材料

以Ce(NO_(3))_(3))·6H_(2))O和三聚氰胺为原料,采用简单的原位聚苯乙烯球模板法成功合成了一种新型CeO_(2)纳米中空球/g-C_(3)N_(4)纳米复合材料。将其用于紫外光催化降解对硝基苯胺(PNA)。结果表明,当CeO_(2)的复合质量分数为2.5%时,PNA降解效率达到90.26%。动力学拟合结果表明,PNA光催化降解过程符合拟一级反应动力学特征。与g-C_(3)N_(4)(k=0.0060 min^(-1))和CeO_(2)(k=0.0023 min^(-1))相比,CeO_(2)纳米中空球/g-C_(3)N_(4)复合材料光催化降解PNA的反应速率常数(k=0.0110 min^(-1))分别提高了1.8倍和4.8倍。CeO_(2)和g-C_(3)N_(4)复合后形成的异质结构促进了光生载流子的分离,延长了光生载流子的寿命,从而显著提高了光催化性能。

非线性4n阶常微分方程的非线性三点边值问题解的存在性

利用“上下解”的方法 ,讨论了非线性 4n阶常微分方程 y( 4n) =f(t,y,y′,y″ ,… ,y( 4n-1) )满足条件 g2i(y( 2i) (a) ,y( 2i+ 1) (a) ) =0 i=0 ,1 ,… ,2n - 3 g4n-4(y( 4n-4) (a) ,y( 4n-3 ) (a) ,y( 4n-2 ) (a) ,y( 4n-1) (a) ) =0 g4n-3 (y(b) ,y′(b) ,… ,y( 4n-6) (b) ) =0 g4n-2 (y( 4n-5) (b) ,y( 4n-4) (b) ) =0 g4n-1(y( 4n-3 ) (b) ,y( 4n-2 ) (b) ) =0 g2i+ 1(y( 2i+ 1) (c) ,y( 2i+ 2 ) (c) ) =0 i=0 ,1 ,… ,2n- 4 g4n-5(y( 4n-5) (c) ,y( 4n-4) (c) ,… ,y( 4n-1) (c) ) =0的非线性三点边值问题解的存在性 .

UV/PS降解水中2,4-二氯苯酚及毒性评价研究

比较采用PS,UV/PS 2种工艺降解2,4-DCP的去除效果、一级反应动力学;考察不同氧化剂(PS)剂量、不同初始浓度的2,4-DCP、腐殖酸条件对该光解反应速率常数的影响以及采用发光菌青海弧菌-Q67来评价2,4-DCP和光解过程中间产物溶液对生态环境的毒性评价.实验结果表明,单独PS工艺光解2,4-DCP去除率仅有4%,而UV/PS光解2,4-DCP去除率高达96.4%,充分说明UV/PS工艺可高效去除2,4-DCP,且其反应基本遵循拟一级反应动力学,一级反应动力学常数为35.1×10^(-3)min^(-1).UV/PS降解2,4-DCP的降解率和反应速率常数随着氧化剂(PS)的增加而增大,随着2,4-DCP初始浓度增大而降低.随着腐殖酸初始浓度的增大,有先增大后变小的过程.毒性评价实验中,随着2,4-DCP光解45min,发光菌抑制率降低,溶液对环境毒性在降低,且从长期时间规律来看,同一氧化时间溶液对发光菌相对抑制率与发光菌接触时间没有关系.

一步合成聚苯胺/Fe_3O_4磁性纳米吸附剂去除Cr(Ⅵ)的应用

采用一步加热法合成聚苯胺/Fe_3O_4磁性纳米颗粒(PANI-Fe_3O_4),处理模拟含Cr(Ⅵ)废水,探讨吸附时间和吸附温度对Cr(Ⅵ)去除效果的影响。结果表明,反应时间90 min达到吸附饱和状态,吸附温度25℃时可达到较好的吸附效果。在常温下,Cr(Ⅵ)最大吸附量可达200. 2 mg/g,符合准二级动力学模型和Langmuir等温吸附模型。

EH-4系统中工频干扰的处理与改进

EH-4系统处理50 Hz工频干扰的方法一是在采集数据时进行硬件陷波,二是在利用标定文件标定功率谱时进行数字陷波.这两种陷波在没有工频干扰时会过度丢失有用信息,在强干扰下陷波不彻底,且没有对三次以上高次谐波进行压制.针对这两点不足,本文采用在50 Hz及其谐波影响频段范围内设置0权值的改进parzen窗加权平均法来取代IMAGEM窄带等权平均法对功率谱进行平滑估算,从而有效消除工频干扰.实例应用表明该方法简单有效,可以提高数据质量.

7-羟基-4-甲基香豆素的二阶NLO性质对晶体结构的依赖性

研究了7种香豆素衍生物的二阶非线性光学性质,在理论和实验上分析了7 羟基 4 甲基香豆素的二阶非线性光学性质对晶体结构的依赖性,表明这是一类热稳定性高、透光性好的化合物,分子在晶体中的趋向对二阶非线性光学响应有重要影响,改良其晶体结构是提高这类材料综合性能的主要手段.