A study of factors influencing the accuracy of quantitative X-ray analysis of thin foil specimens

Needle-shaped specimens were used to determine experimental values of X-ray intensity ratios for L/K and M/L lines. These ratios can be used to determine k_AB factors for L and M lines. They also provide necessary data for absorption correction with the X-ray intensity ratio method. Recent theoretical calculations of k_AB factors are evaluated and new constants in the parametrization of ionization cross-sections for L and M lines are presented. The average X-ray production per unit thickness has been measured as a function of mass thickness for a stainless steel specimen using acceleration voltages of 100 and 200 kV. An increase in X-ray production by more than 20% was found at 100 kV for mass thicknesses up to 1 mg/cm² while at 200 kV the increase was about 5%. The contamination spot method for thickness measurements has also been investigated using needle-shaped specimens. The reported overestimate of thickness using this method can be explained by the formation of broad contamination layers around the deposited spots.     

The relative importance of multiple inelastic scattering in the quantification of EELS

A comparison is given of energy loss results obtained for the L and K edges of aluminium as a function of specimen thickness, crystallographic orientation and collection angle. It is demonstrated that as the thickness is increased post-loss elastic scattering is generally important in reducing the fraction of electrons collected. The implications for the quantification of EELS data are discussed while a comparison of the Fe/C ratio in cementite demonstrates the improved consistency which can be obtained when comparing K and L losses at lower energy separation than are the losses for aluminium.     

CO激光在非线性晶体ZnGeP2和GaSe中的混频效应（英文）

为了获得2.15～1 500μm的相干光源,研究了CO激光在高质量非线性晶体ZnGeP2和GaSe中的混频效应。为了提高转换效率,在激光锁模方式下对CO激光器的二次谐波、和频和差频的产生进行了研究。结果显示,利用GaSe晶体和ZnGeP2晶体,调Q多谱线CO激光辐射的谱线内倍频效率分别大于0.3%和1.1%。采用ZnGeP2晶体进行倍频时,可调谐锁膜CO激光器的转换效率为12.5%。模拟结果显示,二次谐波与和频产生的输出光谱相同。相邻谱线下,和频和差频的产生过程中,基波和一次谐波可以分别在4.0～5.0μm和100～≥1 200μm(太赫兹范围)形成振荡。利用锁模CO激光器在ZnGeP2晶体中的混频效应,可以得到2.15～≥1 500μm的相干光源,同时转换效率可达到甚至高于12.5%。     

Note: Development of target changeable palm-top pyroelectric x-ray tube

A target changeable palm-top size x-ray tube was realized using pyroelectric crystal and detachable vacuum flanges. The target metals can be exchanged easily by attaching them on the brass stage with carbon tape. When silver and titanium palates (area: 10 mm(2)) were used as targets, silver Lα and titanium K lines were clearly observed by bombarding electrons on the targets for 90 s. The intensities were the same or higher than those of previously reported pyroelectric x-ray tubes. Chromium, iron, nickel, copper, and zinc K lines in the x-ray tube (stainless steel and brass) disappeared by replacing the brass stage and the stainless steel vacuum flange with a carbon stage and a glass tube, respectively.     

The efficiency of X-ray production at low energies

The absolute efficiency of X-ray production has been determined for the K-lines of Al, Si and Cu; for the L-lines of Fe, Co, Cu, Ge and As; and for the M-lines of Hf, Ir, Pt, Au and Bi, using overvoltage ratios in the range 1–10. These emissions, with the exception of the Cu K, have critical excitation energies below 2.6 keV and are therefore typical of the lines used for X-ray microanalysis at low beam energies. For K-lines it is found that the experimental results are in good agreement with a Bethe, or a Casnati, cross-section model. For the L- and M-lines a Monte Carlo technique has been used to find an effective X-ray generation cross-section for each of the elements. The functional forms of these cross-sections are found to be in general agreement with proposed theoretical models.     

Experimental and theoretical determination of kAFe factors for quantitative X-ray microanalysis in the analytical electron microscope

Quantitative X-ray microanalysis in the analytical electron microscope involves the use of Cliff-Lorimer k_AB factors to relate measured X-ray intensities from elements A and B to their composition. This study has generated a wide range of these factors for both K and L X-ray lines. The values of the k factor for each element is ratioed to Fe, rather than to Si as has been common practice to date. The use of k_AFe rather than k_ASi factors reduces the uncertainty in the values due to variations in the efficiency of individual energy dispersive spectrometers, thus making the values more universally applicable. New calculations of the value of k_AFe have been made from first principles, encompassing all of the most recent values of the cross-section for X-ray ionization. Comparison of the experimental results with both the calculations and existing k factor data has been made. Close attention has been paid to minimizing the errors in both the experimental and theoretical calculations to reduce the overall error in quantification of X-ray energy dispersive spectra in the analytical electron microscope.     

基于图论的3K行星齿轮系传动比与传动效率分析

应用齿轮系的复接头图画表示法与基本回路方法，对3K行星齿轮系进行系统化的传动比、作用力矩与传动效率的分析，作为3K行星齿轮系分析与设计的依据。首先，采用复接头运动链图画表示法，有效地表示3K行星齿轮系的运动构造，所谓“复接头运动链图画表示法”就是齿轮系与其对应图画间具有一对一的对应关系，可以完全表示齿轮系的拓朴与运动构造；然后，以此图画表示法与基本回路方法推导在各种运动情况下3K行星齿轮系的传动比、作用力矩与传动效率方程式；最后，讨论了3K行星齿轮系传动比、作用力矩、功率流与传动效率的关系，并提出一系统化的方法，可以进行3K行星齿轮系传动比、作用力矩、功率流与传动效率分析。     

Shape error measurement using ray-tracing and fringe scanning methods: projection of grating displayed on a liquid crystal panel

We present an improved Hartmann test, which has high spatial resolution with respect to the measuring points, for measuring projection mirrors. In the method, grid lines with a sinusoidal transmittance distribution are displayed on a liquid crystal panel and illuminated with a collimated laser beam. The beam transmitted through the liquid crystal panel reflects off the mirror surface being tested and reaches a screen. A charge-coupled device camera detects the projected images, which contain information about the inclination of the surface being tested. Any error in the shape of the mirror surface is identified by integrating the inclination. To increase the spatial resolution, the fringe scanning method is performed by shifting the grid lines on the liquid crystal panel. The grid lines are optimized for the shape of the mirror being tested. Because the grid lines are displayed by an electrical method, the shifting operation is easy and rapid, and furthermore, the displacement can be done precisely. The shape error of an off-axis parabolic mirror made of plastic is measured by the proposed method.     

A hybrid genetic algorithm approach to mixed-model assembly line balancing

Assembly line balancing has been a focus of interest to academics in operation management for the last four decades. Mass production has saved huge costs for manufacturers in various industries for some time. With the growing trend of greater product variability and shorter life cycles, traditional mass production is being replaced in assembly lines. The current market is intensely competitive and consumer-centric. Mixed-model assembly lines are increasing in many industrial environments. This study deals with mixed-model assembly line balancing for n models, and uses a classical genetic algorithm approach to minimize the number of workstations. We also incorporated a hybrid genetic algorithm approach that used the solution from the modified ranked positional method for the initial solution to reduce the search space within the global space, thereby reducing search time. Several examples illustrate the approach. The software used for programming is C++ language .     

Friction reduction by metal sulfides in boundary lubrication studied by XPS and XANES analyses

In this work, the antiwear action of zinc dithiophosphate (ZnDTP) in combination with friction modifier agent molybdenum dithiocarbamate (MoDTC) has been investigated. A Cameron-Plint friction machine was used to generate large tribofilm areas in mild tribological conditions. Two analytical techniques, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy, have been employed to characterize the chemical species in tribofilms. XANES spectroscopy at the P K and L-edge, Mo L and M-edge and S K-edge was carried out in order to investigate phosphates and sulfides species in the tribofilms This was followed by XPS analysis in the same location in the tribofilms. Special attention has been paid to the peak fitting of Fe 2p, Zn 2p, S 2p, Mo 3d and O 1s photopeaks and Auger ZnLMM lines. The combined analyses have shown that the MoDTC+ZnDTP containing oil produces mainly shorter chain metal polyphosphate material in addition to ZnS and MoS₂. No zinc sulfate has been detected. XPS confirms that the formation of MoS₂ is enhanced by the presence of ZnDTP. For all additives combinations; no iron has been detected in the tribofilms. Analytical results are discussed and compared with theoretical predictions from the Chemical Hardness model for ZnDTP, MoDTC and ZnDTP+MoDTC tribofilms formation.     

Measuring the quantum efficiency of multielement photodetectors in the spectral range between 180 and 800 nm

An automatic system for measuring the quantum efficiency of multielement photodetectors applied in atomic emission spectral analysis is created. Results of measuring the quantum efficiency of BLPP-369 photodiode lines with different dopants and coating layers, and also lines of CCDs (Sony ILX-526A) are presented. It is shown that the quantum efficiency of photodiode lines between 180 and 360 nm is 0.3–0.5, which is 2–5 times greater than for ILX-526A CCDs with phosphor. The spread of quantum efficiency values of photodiodes in one BLPP-369 line is no more than 10%, and about 30% for lines from different batches.     

Taxus globosa S. cell lines: Initiation,selection and characterization in terms of growth,and of baccatin III and paclitaxel production

Of the initial six cell lines originating from explants of Taxus globosa, or Mexican yew (stem internode, leaves and meristematic tissue), three were selected for their microbial and oxidation resistance, two from leaves and the other from stem internode. A study of their behavior, both in terms of cell growth, and of baccatin III and paclitaxel production, was developed in suspension cultures with an initially standardized biomass (fresh weight 0.23 g/L) using modified Gamborg’s B5 medium, and an elicitor (methyl jasmonate), on either the first or seventh day of culture, at several levels (0, 0.1, 1, 10, 100 μM). In most of the conditions used, the three cell lines showed growth associated baccatin III production. The cell line from stem internode was the highest producer of baccatin III using 1 μM elicitor, sampling at 10 days (p < 0.01, 6.45 mg/L). This same line also had the highest biomass production (6.85 g/L, p < 0.01) at 10 days of culture but at the higher elicitor concentration of 10 μM. All three cell lines did not produce paclitaxel under experimental conditions used.     

Long-life vibration-free 4.5 K sorption cooler for space applications

A breadboard 4.5 K helium sorption cooler for use in vibration-sensitive space missions was developed and successfully tested. This type of cooler has no moving parts and is, therefore, essentially vibration-free. The absence of moving parts also simplifies scaling down of the cooler to small sizes, and it contributes to achieving a very long lifetime. In addition, the cooler operates with limited dc's so that hardly any electromagnetic interference is generated. This cooler is a favorite option for future missions such as ESA's Darwin mission, a space interferometer in which the sensitive optics and detectors can hardly accept any vibration. The system design consists of a hydrogen stage cooling from 80 to 14.5 K and a helium stage establishing 5 mW at 4.5 K. Both stages use microporous activated carbon as the adsorption material. The two cooler stages need about 3.5 W of total input power and are heat sunk at two passive radiators at temperatures of about 50 and 80 K-radiators which are constructed at the cold side of the spacecraft. We developed, built, and tested a demonstrator of the helium cooler. This demonstrator has four sorption compressor cells in two compressor stages. Test experiments on this cooler showed that it performs within all specifications imposed by ESA. The cooler delivered 4.5 mW at 4.5 K with a long-term temperature stability of 1 mK and an input power of 1.96 W. So far, the cooler has operated continuously for a period of 2.5 months and has not shown any sign of performance degradation.     

Efficient, high-spectral-resolution Bragg crystal x-ray polarimeter

Utilizing Bragg scattering near 90 degrees , an x-ray polarimeter is described that has high spectral resolution and reasonable efficiency. The latter is achieved by using a position-sensitive proportional counter to discriminate spatially resolved x rays dispersed by the crystal. This instrument has been used to measure the linear polarization of lines from one- and two-electron oxygen ions. For this study, aligned initial states have been populated in oxygen beams by various excitation processes in foil, gas, and thick solid targets. In spite of the small probability for the production and radiative decay of few-electron excited states in the presence of intense background radiation, the instrument resolution and efficiency are sufficient to permit polarization measurements.     

Simple bridge detector for use with a low-temperature capacitance thermometer, and thermometer performance limits

A simple high-resolution bridge circuit for use with a glass-ceramic capacitance thermometer is described. This circuit allows a linear readout of capacitance changes and has better than 1 mK resolution and short-term stability. Performance limits of the thermometer itself are also reported. Irreproducibility of thermometer calibration upon thermal cycling can be as large as 0.3 K, and changes in the calibration slope dC/dT are also observed. The bridge circuit described partially compensates for these shifts in dC/dT.     

Hard x-ray transmission crystal spectrometer at the OMEGA-EP laser facility

The transmission crystal spectrometer (TCS) is approved for taking data at the OMEGA-EP laser facility since 2009 and will be available for the OMEGA target chamber in 2010. TCS utilizes a Cauchois type cylindrically bent transmission crystal geometry with a source to crystal distance of 600 mm. Spectral images are recorded by image plates in four positions, one IP on the Rowland circle and three others at 200, 400, and 600 mm beyond the Rowland circle. An earlier version of TCS was used at LULI on experiments that determined the x-ray source size from spectral line broadening on one IP positioned behind the Rowland circle. TCS has recorded numerous backlighter spectra at EP for point projection radiography and for source size measurements. Hard x-ray source size can be determined from the source broadening of both K shell emission lines and from K absorption edges in the bremsstrahlung continuum, the latter being a new way to measure the spatial extent of the hard x-ray bremsstrahlung continuum.     

A closed-cycle cryostat for optical and M?ssbauer spectroscopy in the temperature range 4.2–300 K

A closed cycle cryostat intended for optical and M?ssbauer investigations in the temperature range 4.2–300 K is described. Samples are cooled owing to the operation of a two-stage closed-cycle cryogenic refrigerator (CR) based on the Gifford-MacMahon cycle (with a refrigerating capacity of 1 W at T = 4.2 K at the second stage). The minimum temperature reached at the second stage of the CR was 2.7 K. The methods for reducing vibrations transferred from the CR to a sample are described in detail. The design proposed makes it possible to reduce the vibrational broadening of the resonance M?ssbauer lines to a level of 10–15% at 5 K, thus exceeding the level of the best cryostat prototypes in the world.     

钻孔水力开采用气力提升装置的实验研究

为阐明进气方式对气力提升特性的作用规律,以普通河沙模拟井下矿层,利用小型输沙系统实验研究在恒定浸入率和供沙量下气孔数量与进气角度对扬水量、扬沙量及总效率的影响。结果表明:任一进气方式下扬水量、扬沙量及总效率并不随气量值增加呈现单调特性,前两者峰值所处位置大致接近,且较总效率峰值对应点右移。气孔数量和进气角度对扬水量及扬沙量影响较小,对总效率影响程度稍大。就整体而言,对应气孔数量和进气角度分别为4和90°时其扬沙量与总效率较其它进气方式上扬。另外,实验测得最高扬沙效率所对气相佛汝德数大致相同,约为2.5,且最佳扬沙效率所对应的气相佛汝德数随管径递增。     

NON-LINEAR NORMAL MODES AND NON-PARAMETRIC SYSTEM IDENTIFICATION OF NON-LINEAR OSCILLATORS

The Karhunen–Loeve (K–L) decomposition procedure is applied to a system of coupled cantilever beams with non-linear grounding stiffnesses and a system of non-linearly coupled rods. The former system possesses localized non-linear normal modes (NNMs) for certain values of the coupling parameters and has been studied in the literature using various asymptotic techniques. In this work, the K–L method is used to locate the regions of such localized motions. The method yields orthogonal modes that best approximate the spatial behaviour of the beams. In order to apply this method simultaneous time series of the displacements at several points of the system are required. These measurements are obtained by a direct numerical integration of the governing partial differential equations, using the assumed modes method. A two-point correlation matrix is constructed using the measured time-series data, and its eigenvectors represent the dominant K–L modes of the system; the corresponding eigenvalues give an estimate of the participations (energies) of these modes in the dynamics. These participations are used to estimate the dimensionality of the system and to identify regions of localized motion in the coupling parameter space. The same approach is applied to a system of non-linearly coupled rods. Through the comparison of system response reconstructions of the responses using a simple K–L mode and a number of physical modes, it is shown that the K–L modes can be used to create lower-order models that can accurately capture the dynamics of the original system.     

凝胶HPLC测定相思子毒素纳米粒包封率

目的建立相思子毒素的凝胶HPLC分析方法,用于测定相思子毒素纳米粒的包封率。方法采用TSKgel G2000SWXL凝胶色谱柱;流动相为20mmol/L PB,pH=7.3,流速为0.8mL/min;柱温为25℃;分析时间为20min;紫外检测波长为214 nm;进样量60μL。结果 2种纳米粒上清液对于相思子毒素的测定均无干扰;相思子毒素保留时间为10.35±0.55min(n=20);在浓度范围12.5-400μg/mL内,峰面积与相思子毒素含量成良好的线性关系:y=52.85676x-342.656,R=0.9999(n=6,P<0.0001);相思子毒素日内平均回收率为100.47%-107.73%,RSD为0.17%-0.25%;日间回收率为100.87%-106.33%,RSD为1.48%-2.18%;温度对于相思子毒素含量变化影响很小,5日内,相思子毒素样品在室温、4℃以及-20℃保存均较为稳定,检测浓度平均回收率为98.04%-106.86%,RSD<3%;蛋白的最低检测限为49.5ng。结论该方法专属性强,可用于相思子毒素纳米粒包封率和释药率的测定,也可用于较低含量相思子毒素的定量分析。