Semi-empirical schemes for the x-ray mass absorption coefficients used in XRF analysis

X-ray mass absorption coefficients play an important role in the accu racy of any XRF intensity calculation. It is necessary to determine the proper schemes for providing satisfying values μ/ρ. In this work we examined and compared various schemes. A program based on the existing schemes to provide more accurate and convenient μ/ρ values was then introduced. The results from the program appears to be tolerable.

Estimation of mass transfer coefficient in ozone absorption by linear least square fitting and Simplex search methods

For physical ozone absorption without reaction,two parametric estimation methods,i.e.the common linear least square fitting and non-linear Simplex search methods,were applied,respectively,to determine the ozone mass transfer coefficient during absorption and both methods give almost the same mass transfer coefficient.While for chemical absorption with ozone decomposition reaction,the common linear least square fitting method is not applicable for the evaluation of ozone mass transfer coefficient due to the difficulty of model linearization for describing ozone concentration dissolved in water.The nonlinear Simplex method obtains the mass transfer coefficient by minimizing the sum of the differences between the simulated and experimental ozone concentration during the whole absorption process,without the limitation of linear relationship between the dissolved ozone concentration and absorption time during the initial stage of absorption.Comparison of the ozone concentration profiles between the simulation and experimental data demonstrates that Simplex method may determine ozone mass transfer coefficient during absorption in an accurate and high efficiency way with wide applicability.

Recovery of carbon monoxide from flue gases by reactive absorption in ionic liquid imidazolium chlorocuprate(I): Mass transfer coefficients

Recovery of carbon monoxide from flue gases by selective absorption of carbon monoxide in an imidazolium chlorocuprate（l） ionic liquid is considered in this work as an alternative to the use of molecular volatile solvents such as aromatic hydrocarbons. The present work evaluates the CO mass transfer rates from the gas phase to the ionic liquid solutions in the absence of chemical reaction. To that end, carbon dioxide was employed as an inert model gas and absorption experiments were performed to assess the influence of different process variables in a batch reactor with fiat gas-liquid interface. The experimental mass transfer coefficients showed significant var- iation with temperature, （3.4-10.9） × 10^-7 m·s^-1 between 293 and 313 K; stirring speed, （10.2- 33.1）× 10^-7 m.s 1 between 100 and 300 r·min^-1; and concentration of copper（1）, （6.6-10.2） × 10^-7 m·s^-1 between 0.25 and 2 mol· L^- 1. In addition, the mass transfer coefficients were eventually found to follow a poten- tial proportionality of the type kL ∝μ^-0.5 and the dimensionless correlation that makes the estimation of the mass transfer coefficients possible in the studied range of process variables was obtained： Sh=10^-2.64 Re^1.07 , Sc^0.75,These results constitute the first step in the kinetic analysis of the reaction between CO and imidazolium chlorocuprate（I） ionic liquid that determines the design of the separation units.

Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

Effect of surfactant type on interfacial area and liquid mass transfer for CO_2 absorption in a bubble column

The effect of different surfactants(n-octyltrimethylammonium bromide(OTABr),sodium dodecyl benzene sulfonate(SDBS) and Tween 80) with different critical micelle concentrations(CMC) on the CO_2 absorption into aqueous solutions in a bubble column is analyzed in the present work.The presence of these surfactants increased the gas-liquid interfacial area,and decreased the liquid phase mass transfer coefficient,but with significant different extent.The results indicated that the CMC can be a key parameter affecting the mass transfer of CO_2 absorption into a dilute aqueous solution of a surfactant.Sardeing's model was used to fit the experimental data successfully by re-correlating the parameters.

Aqueous ammonia solution cooling absorption refrigeration driven by fishing boat diesel exhaust heat

A solution cooling absorption（SCA）approach is proposed to modify the aqueous ammonia absorption refrigerat-ion cycle using the strong solution from the absorber to cool the forepart of the absorption in the cycle for reclaiming some portion of absorption heat.As a consequence of raised temperature at the inlet,the strong solution partially boils at the outlet of the solution heat exchanger,and diminishes the thermal heat consumption of the heat source.The calculation results show that the coefficient of performance（COP）of this modified cycle is about 28.3% higher than that of the traditional cycle under typical conditions;while the required heat transfer area of the total heat exchangers of the cycle is somewhat less than that of the traditional one.The capacity of refrigeration with the new absorption cycle is more than doubled in contrast to the adsorption scheme with an identical configuration.It is sufficient to supply a fishing boat the chilling capacity for preservation of fishing products with the modified cycle chiller driven by its diesel engine exhaust.

A convenient method for measuring gas-liquid volumetric mass transfer coefficient in micro reactors

The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO_(2) and the chemical absorption method of sodium carbonate solution-CO_(2) were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO_(2) and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the p H value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.

Predictions of equilibrium solubility and mass transfer coefficient for CO_(2) absorption into aqueous solutions of 4-diethylamino-2-butanol using artificial neural networks

In the present work,artificial neuron network(ANN)based models for predicting equilibrium solubility and mass transfer coefficient of CO_(2) absorption into aqueous solutions of high performance alternative 4-diethylamino-2-butanol(DEAB)solvent were successfully developed.The ANN models show an outstanding predictive performance over the predictive correlations proposed in the literature.In order to predict the equilibrium solubility,the ANN model were developed based on three input parameters of operating temperature,concentration of DEAB and partial pressure of CO_(2).An outstanding prediction performance of 2.4%average absolute deviation(AAD)can be obtained(comparing with 7.1–8.3%AAD from the literature).Additionally,a significant improvement on predicting mass transfer coefficient can also be achieved through the developed ANN model with 3.1%AAD(comparing with 14.5%AAD from the existing semi-empirical model).The mass transfer coefficient is considered to be a function of liquid flow rate,liquid inlet temperature,concentration of DEAB,inlet CO_(2) loading,outlet CO_(2) loading,concentration of CO_(2) along the height of the column.

Zn吸收边附近质量衰减系数测量

物质材料的光子质量衰减系数的准确值可为不同领域提供基本数据。由于单能X射线辐射装置能量连续可调、光子数可测,产生的X射线单能窄束,使其成为研究质量衰减系数(μ/ρ)的理想器件。研究了在8~20 keV能量范围内,Zn样品在K吸收边附近(9~11 keV),以0.1 keV步长,基于单能X射线装置的质量衰减系数测量方法,并利用实验得到的测量值与NIST理论值进行比较分析。结果表明,在K吸收边跳跃附近会产生1个最大偏差,偏差在远离吸收边时会减小。实测曲线与NIST-XCOM及NIST-FFAST曲线基本一致,测量值与NIST-XCOM理论值最大偏差不超过10.51%。

Modeling of mass transfer characteristics of bubble column reactor with surfactant present

Danckwert’s method was used to determine the specific interfacial area, a, and the individual mass transfer coefficient, kL, during absorption of CO2 in a bubble column with an anionic surfactant in the carbonate-bicarbonate buffer solution and NaAsO2 as catalyst, the presence of which decreases the specific interfacial area and the individual mass transfer coefficient. The specific interfacial area and the individual mass transfer coefficient increase with increasing su- perficial gas velocity. The specific interfacial area decreases whereas the individual mass transfer coefficient increases with increasing temperature. The results of experiments were used to determine the dependence of a, kL, and kLa on the surface tension, the temperature of the absorption phase, and the superficial velocity of the gas. The calculated results from the correlation were found to be within 10% deviation from the actual experimental results.

Quantitative energy-dispersive X-ray fluorescence analysis for unknown samples using full-spectrum least-squares regression

The full-spectrum least-squares(FSLS) method is introduced to perform quantitative energy-dispersive X-ray fluorescence analysis for unknown solid samples.Based on the conventional least-squares principle, this spectrum evaluation method is able to obtain the background-corrected and interference-free net peaks, which is significant for quantization analyses. A variety of analytical parameters and functions to describe the features of the fluorescence spectra of pure elements are used and established, such as the mass absorption coefficient, the Gi factor, and fundamental fluorescence formulas. The FSLS iterative program was compiled in the C language. The content of each component should reach the convergence criterion at the end of the calculations. After a basic theory analysis and experimental preparation, 13 national standard soil samples were detected using a spectrometer to test the feasibility of using the algorithm. The results show that the calculated contents of Ti, Fe, Ni, Cu, and Zn have the same changing tendency as the corresponding standard content in the 13 reference samples. Accuracies of 0.35% and 14.03% are obtained, respectively, for Fe and Ti, whose standard concentrations are 8.82% and 0.578%, respectively. However, the calculated results of trace elements (only tens of lg/g) deviate from the standard values. This may be because of measurement accuracy and mutual effects between the elements.

Gamma and X-ray radiation compatibility of Ti–Ta–Hf–Zr alloys used for coronary stent applications

We have studied the gamma and X-ray radiation compatibility of Ti-based alloys such as Ti–37 Ta–26 Hf–13 Zr-24(wt%) [Alloy 1], Ti–40 Ta–22 Hf–11.7 Zr-26.3(wt%) [Alloy 2], Ti–45 Ta–18.4 Hf–10 Zr-26.6(wt%) [Alloy3], Ti–50 Ta–15 Hf–8 Zr-27(wt%) [Alloy 4], Ti–55 Ta–12 Hf–7 Zr-26(wt%) [Alloy 5], and Ti–60 Ta–10 Hf–5 Zr-25(wt%) [Alloy 6]. Gamma and X-ray radiation compatibility is studied by evaluating the mass attenuation coefficient,mean free path, HVL, TVL effective atomic number,effective electron density, exposure buildup factor, and relative dose. We have compared these parameters for studied alloys with that of arteries. The alloys Ti–55 Ta–12 Hf–7 Zr-26 and Ti–60 Ta–10 Hf–5 Zr-25 have added properties such as gamma/X-ray radiation compatibility,high elastic admissible strain, high mechanical strength,and excellent biocompatibility. Hence, we may suggest that, among Ti–Ta–Hf–Zr alloys, these alloys are best materials for coronary stent applications.

AN INCREMENTAL METHOD OF X-RAY DIFFRACTION QUANTITATIVE PHASE ANALYSIS OF SAMPLESCONTAINING AMORPHOUS MATERIAL

A new method for quantitative X-ray diffraction phase analysis of a powder misture has been developed according to Popovic's doping method. The weight fraction of amorphous material in the analysed sample is obtained. For a multicomponent system in which (n-2) pure phases are added into an n-phase compnent sample and theweight fractions of all n phases can be determined by the method. The test results of confirmation agree well with the theory.

Wood Moisture Content Measurement by X-Ray Exposure Method

Although quite a numer of papers can be found up to now dealing with the subject of the measurement ofwood density by using the X-ray exposure methods, direet scanning or radiographic photography, the following two aspects,which are very important from both theorctical and engineering application points of view, have not yet been properly handled. One is that the elementary analyses or the experimental measurement on the mass attenuation coefficients were notspecified in regard to spectnun energv distridutions [1]. In this connection, the ambiguities in the specification of the coeffiecients and in turn for thc results among studies arise when only one of the two parameters, namely wave length and applied voltage, of detining the energy spectrum of X-ray is given. The oher is that the relationships between the relative intensity and the sample thickness as well the wood moisture content [2], which are the critical factors for the design and theselection of X-ray apparatus, were not sufficiently examined. In addition, the knowledge of the measurelnent of woodmiosture content by using the direct X-ray scanning method is also almost unavaible now. In the study, the direct X-rayscanning method of measuring wood moisture content was at first investigated theoretically with respect to the relationshipbetween the mass attenuation coefficients of wood (beech, Fagus Sylvatica) and the maximum spectrum energy of X-ray.Secondly, the dependence of the relative intensity on the sample thickness and on the wood moisture content was analysed.The main advantage of the method is on-site nondestructive measuring of wood moisture content in the processes such asdrying, impregnation and unsteady mass diffusion. Specifically for the application in the area of biomechanics, the methodcan also bc used for understanding the water pathway within wood, for example, the water around the knots and the relation between the stress distribution and the local moisture content of wood.

用于XTES的铋吸收体对单色X射线的响应研究

超导转变边缘探测器(TES)是目前为止已知的具有最佳的能量分辨率的X射线探测器。金属Bi因其具有较好的X射线吸收率和低比热容而被广泛用于XTES的吸收体。通过电镀的方法制备了一种由Bi构成的XTES吸收体薄膜,使用Ti和Au作为导电层在Si上提供电流通路。研究了电镀法制备Bi金属XTES吸收体对单能X射线的吸收效率,使用高纯锗探测器测量通过吸收材料前后的单能X射线光子数,以全能峰面积衡量不同厚度电镀Bi吸收体对单能X射线的吸收效率。研究结果对促进先进探测器的国产化具有重要意义。

基于核磁共振技术对水泥砂浆高温后孔隙结构及水分迁移特征的研究

为研究高温后水泥砂浆内部水分迁移特征,将水泥砂浆试件300、400、500℃高温处理后表面镀蜡(留有一个上表面),随后将试件未镀蜡一端置于液面下2 cm进行自渗吸试验。采用核磁共振(NMR)技术T_(2)谱及核磁共振成像研究高温作用后水泥砂浆试件水分迁移情况及特征。结果表明,随着处理温度升高,试件胶凝孔和气孔或裂隙占比增大,而毛细孔占比逐渐降低,试件吸水质量减小,吸水质量前24 h内快速增加,随后减缓并趋于稳定。同时,高温作用影响毛细管吸水率,当处理温度小于等于400℃时,高温可增大毛细管吸水率;当处理温度大于400℃时,高温反而削弱毛细管吸水率。通过引入毛细吸收系数S来表征毛细管吸水率,S在6 h前大于10,而在6 h后减小超过2个数量级。另外,水分迁移存在优先孔径,在毛细孔中迁移的优先孔径为10~480 nm,在气孔或者裂隙中迁移的优先孔径为1680~16800 nm,且随浸水时间增加,水分更倾向由大孔传输到较小孔隙中。最后,通过核磁共振成像可实时观测到水分迁移位置由外到内,迁移速度与试件处理温度呈正相关。

Heat and mass transfer through spiral tubes in absorber of absorption heat pump system for waste heat recovery

Heat and mass transfer of a LiBr/water absorption heat pump system(AHP)was experimentally studied during working a heating-up mode.The examination was performed for a single spiral tube,which was simulated for heat transfer tubes in an absorber.The inside and outside of the tube were subjected to a film flow of the absorption liquid and exposed to the atmosphere,respectively.The maximum temperature of the absorption liquid was observed not at the entrance but in the region a little downward from the entrance in the tube.The steam absorption convective heat transfer coefficient between the liquid film flowing down and the inside wall of the temperature and the film temperature at the maximum temperature location and the bottom.The film heat and mass transfer coefficients rose with increasing Reynolds number of the liquid film stream.The coefficients showed opposite trend to the empirical correlation reported for laminar film flow on a straight smooth tube in a refrigeration mode in the past work.The fact can be caused due to a turbulent promotion effect of the liquid in a spiral tube.

基于GEANT4模拟含铋辐射防护材料制备及性能研究

基于GEANT4软件,采用蒙特卡罗方法设计了一种柔性、轻质、无铅的含铋辐射防护面料。建立仿真模型,研究了铋粉质量分数、铋粉粒径对防护材料辐射防护性能的影响,并与实际制备结果进行比较,发现铋元素可以大大提高防护材料的辐射防护效率,当铋粉的质量分数为70.0%、铋粉粒径为1μm、涂层厚度为400μm时,防护面料的辐射防护性能较为优异。

臭氧在水中的吸收和自分解

研究了臭氧在水中的吸收和自分解特性，探讨了ｐＨ值和气速对溶解臭氧平衡浓度的影响。实验测定了臭氧在鼓泡反应器中的传质系数。

伽玛射线测量径流泥沙含量算法中质量吸收系数优选及其对测量误差影响的分析

质量吸收系数是伽玛射线测量径流泥沙含量理论计算公式中由伽玛射线记数率确定泥沙含量的基本参数。该文研究了确定质量吸收系数的多点法和单点法。在多点法中 ,提出了确定质量吸收系数的回归方法 ,推导了由大量 (多点 )试验数据计算质量吸收系数的回归公式。采用大量实测数据由回归公式确定的质量吸收系数准确且精度较高 ,能在很大程度上消除随机误差的影响。而单点法通过几个特殊的取值点 (单点 )来估算质量吸收系数 ,具有参数确定快速、物理概念明确的优点。另外 ,该文从理论上分析了质量吸收系数变化对泥沙含量测量精度的影响 ,结果表明质量吸收系数的相对变化与泥沙含量的相对变化成正比例关系 ,且比例系数为 1。从而确定了两种方法的有效性、优缺点和应用方法。