A TIME DOMAIN METHOD FOR QUASI-STATIC ANALYSIS OF VISCOELASTIC THIN PLATES

Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.

An h-adaptive Discontinuous Galerkin Method for Laminar Compressible Navier-Stokes Equations on Curved Mesh

An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adaptivity.The elements where the vorticity is larger than a pre-defined upper limit are refined,and those where the vorticity is smaller than a pre-defined lower limit are coarsened if they have been refined.A high-order geometric approximation of curved boundaries is adopted to ensure the accuracy.Numerical results indicate that highly accurate numerical results can be obtained with the adaptive method at relatively low expense.

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation: A Soil Column Method

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3- -N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process.

Effect of preparation method on the bimetallic NiCu/SAPO-11 catalysts for the hydroisomerization of n-octane

The bimetallic NiCu/SAPO-11 catalysts were prepared by co-impregnation, sequential impregnation, coprecipitation, and mechanical mixing methods. Powder X-ray diffraction, nitrogen adsorption-desorption,temperature-programmed desorption of ammonia, transmission electron microscopy, temperatureprogrammed reduction of hydrogen, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the catalysts. The catalytic performance of the catalysts was assessed by the hydroisomerization of n-octane. Results indicated that the conversion of n-octane and selectivity to n-octane isomers were related to the preparation methods of the catalysts. The catalysts with Ni-Cu alloy effectively restrained the hydrogenolysis reaction that decreases the selectivity of isomerization. The catalyst prepared by the mechanical mixing of NiO and CuO hardly formed Ni-Cu alloy, showing obvious hydrogenolysis and low selectivity to n-octane isomers. The unbalance between the metal and acid sites resulted in the low conversion of n-octane and selectivity to n-octane isomers. Among all the catalysts,the catalyst prepared by the co-impregnation method exhibited high catalytic activity and selectivity to n-octane isomers.

Measurement of ^(232)Th(n,2n)^(231)Th reaction cross-sections at neutron energies of 14.1 MeV and 14.8 MeV using neutron activation method

In this study, the activation cross-sections were measured for ^(232)Th(n,2n)^(231)Th reactions at neutron energies of 14.1 and 14.8 MeV, which were produced by a neutron generator through a T(d,n)~4He reaction. Induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. In the cross-section calculations, corrections were made regarding the effects of gamma-ray attenuation, dead-time, fluctuation of the neutron flux, and low energy neutrons. The measured cross-sections were compared with the literature data, evaluation data(ENDF-B/VII.1, JENDL-4.0 and CENDL-3.1), and the results of the model calculation(TALYS1.6).

Numerical Investigations of a New N-body Simulation Method

Numerical investigation of a new similarity method (the Aldar-Kose method) for N-body simulations is described. Using this method we have carried out numerical simulations for two tasks: 1) calculation of the temporal behavior of different physical parameters of active galactic nuclei (AGN) containing a super massive black hole (SMBH), an accretion disk, and a compact stellar cluster;2) calculation of the stellar capture rate to the central SMBH without accretion disk. The calculations show good perspectives for applications of the similarity method to optimize the evolution model calculations of large stellar systems and of AGN.

CFD-Based Load Calculation Method for Monopile Support Configuration of Offshore Wind Turbine

An unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on the Fluent software platform.Firstly,the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution.Then the wave evolution is simulated by solving the unsteady incompressible Navier-Stokes(N-S)equations coupled with the volume of fluid method.For the small amplitude wave with reasonable wave parameters,the numerical wave result agrees well with that of the given wave model.Finally,a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under the combined action of wave and wind.The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with that of the Morison formula.The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under the combined action of small amplitude wave and wind.

n 的多项式为系数的幂级数和函数注记

研究了以n的多项式为系数的幂级数的和函数的求解问题,给出了这类幂级数和函数的一种求解方法,并得到了其和函数的通用计算公式,通过实例验证了公式的正确性.文中还得到了两个关于组合数的等式.

一种消除周期性毛刺相位误差的互补格雷码双N步相移法

互补格雷码双N步相移法因其具有鲁棒性好、检测精度高等特点在条纹投影轮廓术领域成为研究热点。然而,传统互补格雷码双N步相移法存在检测效率低以及未消除周期性毛刺相位误差的问题。针对这些问题,本文对传统互补格雷码双N步相移法进行改进消除周期性毛刺相位误差,首先通过相机捕获形变条纹图像并计算出两组截断相位,然后利用两组截断相位的相关性消除检测数据中的相位差、周期性毛刺相位误差,再对两组截断相位进行融合,最后通过互补格雷码相位展开法对融合后的截断相位进行相位展开。实验得出本文方法在检测效率不变的情况下,能有效消除周期性毛刺相位误差,得到高精度展开相位,相比于未消除周期性毛刺相位误差的互补格雷码双N步相移法,本文检测方法精度提高了约24.57%,相比于互补格雷码N步相移法,本文检测方法精度提高了约6.29%。

Fe_(3)N磁性纳米粒子的制备及其应用研究进展

Fe_(3)N作为一种磁性纳米粒子,同时具有纳米粒子和磁性物质的特殊性质,由于其优异的机械强度、耐腐蚀抗氧化能力等特点,近年来广泛应用于磁流体、电极材料和催化等领域。本文论述了Fe_(3)N磁性纳米材料的结构,在对Fe_(3)N的制备方法进行综述的基础上,详细介绍了物理和化学两种制备方法,并总结了Fe_(3)N磁性纳米材料在各领域中的应用,同时对Fe_(3)N磁性纳米材料未来研究应用进行了展望。

C_(4)F_(7)N/CO_(2)混合气体在GIS环保型母线中的应用研究

文章对C_(4)F_(7)N/CO_(2)混合气体的特性进行研究,并对其制气方法和混合比测试方法进行了理论分析和应用,在此基础上进行了型式试验验证,为后续在某变电站110 kVGIS环保型母线中的实际应用提供了佐证和试验支撑。研究表明,C_(4)F_(7)N/CO_(2)混合气体能正常满足环保型母线的应用,研究结果可为新型环保GIS设备的研制和应用提供参考。

N掺杂二氧化钛光催化降解甲基橙染料废水的试验研究

试验以尿素为氮源,采用溶胶-凝胶法合成N掺杂二氧化钛(N-TiO_(2)),使用X射线衍射仪和X射线光电子能谱仪对其结构进行表征,然后探索N-TiO_(2)光催化降解甲基橙染料废水的最佳工艺条件。结果显示,最佳工艺条件下,反应体系pH为8,催化剂添加量为7 g/L,甲基橙初始浓度为10 mg/L,催化剂循环使用次数小于4次,甲基橙降解率可达98%,N-TiO_(2)具有优异的光催化活性和稳定性。

基于等效结构应力法的高强钢焊接结构低温主S-N曲线

现有的疲劳S-N曲线已不再适用于北极的低温环境,为了评估北极海洋工程设备材料的低温疲劳寿命,有必要建立金属结构尤其是焊接结构的低温疲劳S-N曲线。本文基于等效结构应力法,计算出Q690高强钢管环焊缝的主S-N曲线,并通过共振疲劳试验对该方法进行了验证。在此基础上,结合大量的高强钢焊接结构试验结果,将温度敏感因子c引入到低温疲劳主S-N曲线的推导中,首次建立了基于低温金属焊接结构的主S-N曲线,并对文献中的疲劳S-N试验数据和ASME中的修正方法进行了对比和验证。结果表明,等效结构应力法能够较准确地计算出焊缝疲劳S-N曲线,推导出的金属焊接结构低温主S-N曲线与试验曲线吻合较好,能够满足低温地区工程要求,可为高强钢焊接结构在北极地区低温环境中的广泛应用提供理论指导。该方法可以为金属焊接结构的低温疲劳研究节省大量的成本,减少非标准试验操作造成的不必要的误差。这对北极海洋工程设备的设计、安全运行和疲劳评估具有重要意义。

The synthesis of B,N-carbon dots by a combustion method and the application of fluorescence detection for Cu^2+

Heteroatom doping is an efficient approach to regulate the fluorescence properties of carbon dots.Using aminophenylboronic acid as the raw material,a combustion method was developed for the synthesis of boron,nitrogen-doped carbon dots（B,N-carbon dots）.The B,N-carbon dots emitted green fluorescence and displayed high resistance to both photo bleaching and ionic strength.A facile fluorescence sensing approach for Cu^2＋ was fabricated via static fluorescence quenching.Under optimal conditions,a rapid detection of Cu^2＋ could be completed in 2 min with a linearity ranging from 1 μmol/L to 25 μmol/L and a detection limit of 0.3 μmol/L Furthermore,the proposed method showed potential applications for the detection of Cu^2＋ in natural water samples.

基于n-MFSK调制的激光致声空-水跨介质通信方法

为了改善空中平台和水下目标之间的激光致声通信技术,采用了一种多进制多频移键控(n-MFSK)调制方式来提升激光致声空-水跨介质通信速率的方法。在借助激光致声热膨胀效应实现空-水界面处的光声转换基础上,分别采用长脉冲法和重复频率法进行了调制及仿真验证,得到了在调制频率数量为2的情况下,2-MFSK调制可在2-FSK调制基础上将通信速率提高1倍的结果。结果表明,长脉冲法主要通过激光阵列结合频率叠加的方式实现n-MFSK调制,重复频率法则通过控制激光器频率变化进而在时域上以分配时间段的方式实现n-MFSK调制;随着调制频率数量增加,相对于n-FSK调制,n-MFSK调制下通信速率更高,并可改善频带利用率,但声压级和水中传输距离会随符号码元持续时间内调制频率数量增加而减小。该研究为未来激光致声空-水跨介质通信实际应用提供了参考。

Study of n-γ discrimination in low energy range(above 40 keVee) by charge comparison method with a BC501A liquid scintillation detector

A VME-based experiment system for n-y discrimination using the charge comparison method was established.A data acquisition program for controlling the programmable modules and processing data online via VME64X bus was developed through the use of Lab VIEW.The two-dimensional（2D） scatter plots of the charge in the slow component vs.the total charge from ^（241）Am-Be and 252Cf neutron sources are presented.The 2D scatter plots of the energy vs.the ratio of the charge in the slow component to the total charge of the pulses are also presented.The quality of n-γ discrimination was checked by the figure-of-merit,and the results showed good performance of n-γ discrimination at the low energy range.Neutrons and γ-rays were separated above 50 keVee（electron-equivalent energy）.The quality of n-γ discrimination has been improved compared with others＇ results at five energies（150,250,350,450,550 keVee）.

Determination of neutron capture cross sections of ^(232)That 14.1 MeV and 14.8 MeV using the neutron activation method

The ^232Th（n,γ）^233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method.The neutron flux was determined using the monitor reaction^27Al（n,α）^24Na.The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector.The experimentally determined cross sections were compared with the data in the literature,and the evaluated data of ENDF/B-Ⅶ.1,JENDL-4.0u＋,and CENDL-3.1.The excitation functions of the ^232Th（n,γ）^233Th reaction were also calculated theoretically using the TALYS1.6 computer code.

Transition prediction of a hypersonic boundary layer over a cone at small angle of attack——with the improvement of e^N method

The problem of transition prediction for hypersonic boundary layers over a sharp cone has been studied in this work. The Mach number of the oncoming flow is 6, the cone half-angle is 5o,and the angle of attack is 1o. The conventional eN method is used, but the transition location so obtained is obviously incorrect. The reason is that in the conventional method, only the amplifying waves are taken into account, while in fact, for different meridians the decay processes of the disturbances before they begin to grow are different. Based on our own previous work, new interpretation and essential improvement for the eN method are proposed. Not only the amplification process but also the decay process is considered. The location, where by linear stability theory, the amplitude of disturbance wave is amplified from its initial small value to 1%, is considered to be the transition location. The new result for transition prediction thus obtained is found to be fairly satisfactory. It is also indicated that for the calculation of base flow, boundary layer equations can be used for a small angle of attack. Its computational cost is much smaller than those for DNS.

一锅煮分步方法合成N-苯基苯甲酰胺

以苯甲醛和苯胺为原料,通过一锅煮的分步方法先形成亚胺,然后利用过氧化二苯甲酰/二甲亚砜体系,高效合成出N-苯基苯甲酰胺。该合成操作采用一锅煮的方法且简单,反应条件温和,适合本科生的有机化学综合性实验教学。本实验包含有机化合物的制备、分离纯化和结构表征为一体的综合性实验过程,有利于学生理解形成亚胺可以对氨基进行保护从而高效氧化合成酰胺的过程。