某边坡变形破坏机理的数值分析

某花岗岩矿岩土体主要有填土、粉质粘土、淤泥及淤泥质土、含泥中粗砂、粘土、残积砂质粘土,其下为花岗岩基岩。边坡最大高度75m,其中残积土层以上的土质边坡高度约50m。本文运用有限元强度折减法对该边坡的稳定性进行了研究,得出了潜在的破坏模式及各个滑动部分的安全系数。分析结果表明,本边坡存在3个潜在滑动面,其中两个为浅层滑动面,另一个为深层滑动面。两个浅层滑动面的稳定系数在1.13～1.17,处于临界状态。深层滑动面稳定性系数在1.29,目前尚处在相对稳定状态。根据分析结果,提出了如下加固措施:（1）对滑坡体进行削坡处理;（2）在其滑动面下方设置抗滑台阶;（3）采用预应力锚索框架梁结合肋柱进行加固处理。     

Fractional-order sliding mode control of uncertain QUAVs with time-varying state constraints

Nonlinear Dynamics - In this paper, a novel robust fractional-order sliding mode (FOSM)-based state constrained control scheme is designed for uncertain quadrotor UAVs (QUAVs). Model uncertainties...     

REAL‐t1, an Effective Approach for t1‐Noise Suppression in NMR Spectroscopy Based on Resampling Algorithm

Summaryof main observation and conclusionIn multidimensional(nD)NMR spectroscopy,t1noise usually appears as ridges along indirect dimen-sions,and affects observation of weak signals.The main source of t1noise is instrumental instability,which causes random variation of FID amplitude during data acquisitions and introduces random noise-like peaks into spectrum after Fourier transformation.A number of efforts have been devoted,in order to develop new method or to improve existing approaches for suppressing t1noise.Herein,we propose a novel t1noise suppression method based on resampling algorithm for data processing,shortenedas REAL-t1.The method was verified using simulated 2D spectra,and NOESY spectra of sucrose and protein GB1,showing that the spectral quality was improved in all cases.The performance of REAL-t1was also compared with another recently pro-posed method,which showed that these two methods provided similar performance while REAL-t1cost much shorter experimental time.     

改性ZSM-5分子筛催化裂解湛江等鞭金藻制取低碳烯烃(英)

研究了湛江等鞭金藻(Isochrysis zhanjiangensis)在改性ZSM-5分子筛上催化裂解制取低碳烯烃的过程.与热裂解过程相比,湛江等鞭金藻催化裂解可以得到更高的低碳烯烃选择性和收率.同时还研究了湛江等鞭金藻中不同油脂和藻渣的催化裂解.结果表明,微藻中的油脂能有效转化为烯烃,其中中性脂的烯烃收率最高,可达36.7%.不同溶剂抽提后得到的藻渣也可转化为低碳烯烃,但收率远低于微藻中的油脂.微藻中的油脂,特别是中性脂,是烯烃的主要贡献者,提高微藻中的中性脂含量能够得到更高的低碳烯烃收率.     

LEO空间目标的非协同共视观测及初轨确定

测角数据的初轨确定(IOD)是通过光学观测技术进行空间目标编目的 关键,然而对于低地球轨道(LEO)空间目标,地基光学观测所获得的数据弧长较短且不包含距离信息.因此,在进行IOD时,所得轨道的误差往往较大,难以应用于进一步的工作中.针对上述问题,研究了LEO空间目标的非协同共视观测技术及其初轨确定,并基于统计学提出了一种利用非协同共视观测技术定位空间目标的新方法.结合中国科学院空间目标与碎片观测网的光学测角数据进行了实验验证,结果表明,所提方法对Ajisai卫星定位的均方根(RMS)误差小于100 m,对空间碎片CZ-2C R/B定位的RMS误差小于200 m,优于传统的三角视差法.随后,将上述定位结果用于IOD,所得轨道半长轴的误差在1 km左右.     

A novel fast 3D measurement method based on phase-coded fringe projection

Optical Review - Fringe projection profilometry is widely used for the 3D measurement of real-world objects; however, quickly obtaining high-precision 3D measurements is an issue that needs to be...     

Properties of Natural Rubber Vulcanizates/Nanosilica Composites Prepared Based on the Method of In-situ Generation and Coagulation

Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO₂ particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO₂) were obtained. The composites C(NR/nSiO₂) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO₂) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO₂ in NR were investigated. The results obtained were compared with the NR/SiO₂ composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent (Si69) in C(NR/nSiO₂), the vulcanizate had better mechanical properties, higher wet resistance, and lower rolling resistance than those without Si69. In the composites C(NR/nSiO₂) and their vulcanizates, the SiO₂ particles’ average grain diameter was 60 nm, and the good-dispersion of the in-situ generated SiO₂ in the rubber matrix were a significant contribution to the satisfactory properties of C(NR/nSiO₂) composites and their vulcanizates.     

Multi-residue determination of plant growth regulators in apples and tomatoes by liquid chromatography/tandem mass spectrometry

A sensitive and rapid multi-residue analytical method for plant growth regulators (PGRs) (i.e., chlormequat, mepiquat, paclobutrazol, uniconazole, ethephon and flumetralin) in apples and tomatoes was developed using high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). A homogenised sample was extracted with a mixture of methanol/water (90:10, v/v) and adjusted to pH <3 with formic acid. Primary secondary amine (PSA) adsorbent was used to clean up the sample. The determination was performed using electrospray ionisation (ESI) and a triple quadrupole (QqQ) analyser. Under the optimised method, the results showed that, except for ethephon, the recoveries were 81.8-98.1% in apples and tomatoes at the spiked concentrations of 0.005 to 2 mg/kg, with relative standard deviations (RSDs) of less than 11.7%. The limits of quantification (LOQs) were lower than their maximum residue limits (MRLs). The procedure was concluded as a practical method to determine the PGR residues in fruit and vegetables and is also suitable for the simultaneous analysis of the amounts of samples for routine monitoring. The analytical method described herein demonstrates a strong potential for its application in the field of PGR multi-residue analysis to help assure food safety.     

Biosorption of americium-241 by Saccharomyces cerevisiae

The biosorption of radionuclide ²⁴¹Am from solution by Saccharomyces cerevisiae (S. cerevisiae), and the effects of experimental conditions on the adsorption were investigated. The preliminary results showed thatS. cerevisiae is a very efficient biosorbent. An average of more than 99% of the total ²⁴¹Am could be removed by S. cerevisiae of 2.1 g/l (dry weight) from ²⁴¹Am solutions of 17.54–4386.0 mg/l (2.22 MBq/l–555 MBq/l) with adsorption capacities of 7.45–1880.0 mg/g biomass (dry weight) (0.94 MBq/g–237.9 MBq/g). The adsorption equilibrium was achieved within 1 hour and the optimum pH ranged 1–3. No significant differences on ²⁴¹Am adsorption were observed at 10–45 °C, or in solutions containing Au³⁺ or Ag⁺, even 2000 times above ²⁴¹Am concentration. The relationship between concentrations and adsorption capacities of ²⁴¹Am indicated the biosorption process should be described by the Freundlich adsorption isotherm.     

螺栓材料应力与声速、温度关系的测定

基于应力－超声波速度关系方法已用于螺栓轴向应力的测量。而声速与被测材料的许多物理因素有关，如弹性模量，密度与温度。本文介绍了用于分析超声波速度－应力－温度三者关系的实验与计算方法，并给出了三种金属材料的结果。检测的质量。