用改进的基向量法重建光谱反射比

如何从已知物体表面颜色的三刺激值及其照明条件和观察条件准确地重建其光谱反射比，是彩色图像研究领域尚待解决的一个重要课题．本文首先介绍了两种前人提出的方法，即“伪逆矩阵法”和“Wiener方法”，然后，分析了这两种方法的优缺点，指出了共同存在的问题，即所重建的光谱反射系数有可能超出实际可能的范围（0，1），进而提出了一种新的改进的基向量法．最后，文中还给出此改进的算法和上述两种算法的特性模拟仿真．从仿真的结果中可以看出，改进的算法不仅在精度上较上述两种算法更精确，而且能够保证所重建的光谱反射比能够满足其实际可能的范围（0，1）．因而，用本文中所给出的改进的基向量法重建物体表面的光谱反射比，较上述两种前人提出的算法更能满足工业实际需要．     

Kinetic and thermodynamic study of Eu(III) sorption on natural red earth in South China

We did a kinetic and thermodynamic study of Eu(III) sorption on natural red earth (NRE) in South China as a function of contact time, pH values, ionic strength, humic acid (HA) and temperature under ambient conditions. Linear and nonlinear regression methods in selecting the optimum sorption isotherm were applied on the experimental data. The results suggest that sorption of Eu(III) on NRE can be described by a pseudo-second-order rate equation and strongly dependent on ionic strength at pH<7. Sorption of Eu(III) on NRE increased with increasing temperature, two-parameter and three-parameter isotherms were applied to analysis the equilibrium adsorption data, and a comparison of linear and nonlinear regression methods was done. The thermodynamic parameters (ΔH⁰, ΔS⁰ and ΔG⁰) of Eu(III) sorption on NRE at different temperatures were calculated from the temperature-dependent sorption isotherms, indicating that the sorption process of Eu(III) was spontaneous. The results showed that the nonlinear method is a better way to obtain the isotherm parameters and the data were in good agreement with the Freundlich isotherm model.     

Improving the Hawkyard method for generating reflectance functions

An iterative method was developed by Hawkyard in 1993 for generating reflectance functions, based on a given set of tristimulus values. In a recent article by Dupont (Col Res Appl 2002;27:88–99), many methods for generating reflectance functions were compared, and it was shown that the Hawkyard method is one of the best methods. However, one of the weak points of the Hawkyard method is its iterative nature. In addition, one important issue for the Hawkyard method is its convergence, which has not been addressed. In this article, this issue is examined. The necessary and sufficient condition to achieve convergence, using the Hawkyard method, is given. The method is then modified to make it an analytical method. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 283–287, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20126     

煤中全硫测定方法的研究

介绍了中国国标规定的4种煤中全硫的测定方法主要有艾士卡法、高温燃烧中和法、库仑滴定法和红外光谱法。采用不同方法对5种标准煤样进行全硫测定对比实验,结果表明：艾士卡法的准确度最高,艾士卡法、库仑滴定法、红外光谱法的测定值无显著性差异,与标准值的相关性均较好,且均在标煤的不确定度范围内;高温燃烧中和法测定结果与标准值的相关性最差,测定低硫标煤时结果偏高,偏离标煤的不确定度,测定高硫煤样时结果偏低。通过对比4种方法的原理、适用煤种、优缺点及应用场合,有针对性地提出减小测量误差的措施,如严格按照标准采样、制样、测样,加强质量管理,定期用标样对仪器进行检定和校验等,最大限度确保检测数据的真实性、准确性和可靠性。     

Comparison of finite difference and control volume methods for solving differential equations

Comparisons are made between the finite difference method (FDM) and the control volume formulation (CVF). An analysis of truncation errors for the two methods is presented. Some rules-of-thumb related to the accuracy of the methods are included. It is shown that the truncation error is the same for both methods when the boundary conditions are of the Dirichlet type, the system equations are linear and represented in Cartesian coordinates. A technique to analyze the accuracy of the methods is presented. Two examples representing different physical situations are solved using the methods. The FDM failed to conserve mass for a small number of nodes when both boundary conditions include a derivative term (i.e. either a Robin or Neumann type boundary condition) whereas the CVF method did conserve mass for these cases. The FDM is more accurate than the CVF for problems with interfaces between adjacent regions. The CVF is (ΔX) order of accuracy for a Neumann type boundary condition whereas the FDM is (ΔX)² order.     

Studies on carboxymethyl cellulose. Quantitative analysis of the huggins constant k′

The Huggins constant k′ was measured for sodium carboxymethyl cellulose (NaCMC) solutions by an isoionic dilution technique for various ionic strengths. The value of k′ is found to increase with decreasing ionic strength. The electrostatic potential at the effective surface of the macromolecule was calculated due to the method of Mason et al. and that of Lifson and it has been observed that there is an agreement between the two methods of deriving the potential.     

Reconstruction of reflectance spectra using weighted principal component analysis

The weighted principal component analysis technique is employed for reconstruction of reflectance spectra of surface colors from the related tristimulus values. A dynamic eigenvector subspace based on applying certain weights to reflectance data of Munsell color chips has been formed for each particular sample and the color difference value between the target, and Munsell dataset is chosen as a criterion for determination of weighting factors. Implementation of this method enables one to increase the influence of samples which are closer to target on extracted principal eigenvectors and subsequently diminish the effect of those samples which benefit from higher amount of color difference. The performance of the suggested method is evaluated in spectral reflectance reconstruction of three different collections of colored samples by the use of the first three Munsell bases. The resulting spectra show considerable improvements in terms of root mean square error between the actual and reconstructed reflectance curves as well as CIELAB color difference under illuminant A in comparison to those obtained from the standard PCA method. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 360–371, 2008     

Measurement of bile acid synthesis in man by release of14CO2 from [26-14C]cholesterol: Comparison to isotope dilution and assessment of optimum reference cholesterol specific activity

Bile acid synthesis can be measured as release of¹⁴CO₂ from [26-¹⁴C]cholesterol divided by cholesterol specific activity, but this method has not been validated in human subjects. We made twelve comparisons of this CO₂ method to standard isotope dilution in six normal subjects and found a mean discrepancy of 6%. Linear regression analysis of one value with respect to the other revealed a correlation coefficient of 0.83 (P<0.001), a Y-intercept close to zero (−4.98) and a slope close to 1 (1.06), suggesting good correspondence between the two methods. To assess the potential for error arising from use of serum cholesterol to estimate specific activity of cholesterol used for bile acid synthesis, we compared synthesis measured using serum free cholesterol specific activity to that measured using bile cholesterol specific activity, which is known to be near isotopic equilibrium with the precursor pool used for bile acid synthesis. Synthesis calculated in these two ways differed by less than 10%. The data indicate that the CO₂ method using either serum or bile cholesterol specific activity provides a valid estimate of bile acid synthesis in man.     

A technique for monitoring the quality of used frying oils

The objective of this work was to develop a practical method for monitoring the quality of oils during the frying process. A special effort was made to find a technique that would not be affected by dilution, since replenishment with fresh oil to varying degrees is a frequent necessity. Nine analytical methods, i.e., measurements of viscosity, polymers, change in dielectric constant, polar compounds, dimers, free fatty acids, smoke point, carbonyls and cyclic monomers, as well as certain combinations of these measurements were evaluated. Since each single method was influenced by replenishment with fresh oil, combinations of two methods were studied in an attempt to produce a single value unaffected by dilution. The ratio polymer/FOS (polymers according to Peled’s technique of methylation and extraction and change in dielectric constant by Foodoil Sensor readings) proved not only to be adequate for monitoring the quality of the used oil, but also was affected minimally by replenishment.     

Determination of frozen-in stresses in thermoplastic injection mouldings

A method and apparatus for providing an overall numerical value of the frozen-in stresses in injection mouldings was developed and compared with existing methods. The developed technique was more rapid and could be employed on either opaque or transparent samples and was more suitable for production quality control purposes. Frozen-in stress values of a number of different thermoplastics moulded under varying conditions of melt temperature and pressure were determined. Some results on the influence of melt flow pattern are also included.     

降低不稳直顶缓倾斜中厚矿床采掘比的途径

圆柱切底全面崩落法和长柱切底全面崩落法,适合开采不稳直顶缓倾斜中厚矿体。前者的主要开采特点是:先在矿层下盘以留圆柱的房柱法切底回采,然后向上钻凿平行炮孔,崩落上部矿体。长柱切底全面崩落法与前者的主要区别在于以长柱代替圆柱,它适用于倾角较大和岩矿稳定性较差的条件。两种方法均具有生产能力高,采掘比低,贫化损失较小,改善通风条件等优点。     

重铬酸钾法与氧化微回流法测定COD的对比试验研究

分别采用重铬酸钾法与氧化微回流法测定相同条件下邻苯二甲酸氢钾标准溶液的COD值,对比两种方法的测试结果表明,氧化微回流法操作简便,结果准确,与国标法不存在显著性差异。     

聚氨酯用羟基化合物羟值的分析

综述了聚氨酯用羟基化合物羟值的分析方法,并对各种方法进行了分析比较。基于醇羟基和酚羟基化合物的特殊性,分析方法有类似又有区别,实际工作中要区别对待。     

Comparison of bile acid synthesis determined by isotope dilution versus fecal acidic sterol output in human subjects

Fecal acidic sterol output has been found to be much lower than bile acid synthesis determined by isotope dilution (J. Lipid Res. 17: 77, 1976). Because of this confusing discrepancy, we compared these 2 measurements done simultaneously on 13 occasions in 5 normal volunteers. In contrast to previous findings, bile acid synthesis by the Lindstedt isotope dilution method averaged 16.3% lower than synthesis simultaneously determined by fecal acidic sterol output (95% confidence limit for the difference −22.2 to −10.4%). When one-sample determinations of bile acid pools were substituted for Lindstedt pools, bile acid synthesis by isotope dilution averaged 5.6% higher than synthesis by fecal acidic sterol output (95% confidence limits −4.9 to 16.1%). These data indicate that the 2 methods yield values in reasonably close agreement with one another. If anything, fecal acidic sterol outputs are slightly higher than synthesis by isotope dilution.     

气提法测定多组分混合溶剂体系的无限稀释活度系数

运用加连预饱和釜技术将气提法适用范围扩展到多组分混合溶剂体系的无限稀释活度系数的测定.据此获得了298.15K温度条件下甲醇—丙酮—苯三元体系各组分的Y~∞i(j,k)值,用UNIQUAC方程关联,结果良好.     

Interfacial tension measurement between immiscible polymers: improved deformed drop retraction method

This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size.     

用ICP-AES测定蜂蜜中硒元素

采用高压硝化罐法处理蜂蜜样品,正交试验法找出最佳硝化条件.用ICP-AES法和AAS法测定蜂蜜中硒元素的含量.经比较发现,用2种方法测定蜂蜜中硒元素的含量值接近,无显著性差异,但ICP-AES法较AAS法具有较多优点,简单、灵敏度高、准确性好.     

碘光谱法测定非离子表面活性剂的临界胶束浓度

考察了碘光谱法测定非离子表面活性剂在水溶液中的临界胶束浓度（ｃｍｃ）的影响因素。欲得正确结果，须将碘－胶束溶液（不同浓度）放置，待碘的分配达到平衡（例如２４ｈ）后再进行测定，这样测得ＴｒｉｔｏｎＸ－１００、ＴｒｉｔｏｎＸ－３０５和单分散的纯化合物Ｃ１２Ｈ２５Ｏ（Ｃ２Ｈ４Ｏ）６Ｈ的ｃｍｃ分别为２．４×１０－４、３．５×１０－４和８．４×１０－５ｍｏｌ·ｄｍ－３，与文献中用表面张力法测得的结果一致。若按Ｒｏｓｓ和Ｏｌｉｖｅｒ将预先配好的溶液稀释后１小时内测定的方法，则所得结果偏低。只要测定时碘－胶束溶液已达平衡，则碘浓度在４～１２ｍｇ／１００ｍｌ范围内对ｃｍｃ的测定结果无明显的影响。文献中提到的碘浓度对ｃｍｃ测定值的影响可能是由于碘的分配未达平衡所致。     

Predicting Temperature-Dependent Activity Coefficients at Infinite Dilution Using Tensor Completion

Knowledge of thermodynamic properties of mixtures is essential in many fields of science and engineering. However, the experimental data is usually scarce, so prediction methods are needed. Matrix completion methods have proven to be very successful in predicting thermodynamic properties of binary mixtures. In this approach, the experimental data is organized in a matrix whose rows and columns correspond to the two components, and whose entries indicate the value of the studied thermodynamic property at fixed conditions. In the present work, we extend the concept to tensor completion methods (TCMs). This allows to account for the variation of the studied property depending on the chosen conditions. The feasibility is demonstrated by applying a TCM to predict activity coefficients at infinite dilution. The third dimension of the tensor is used to describe the influence of the temperature. The TCM is shown to yield better predictions than the well-established UNIFAC method. Furthermore, the proposed TCM is able to learn and unveil the physical law describing the temperature dependence of activity coefficients from the scarce experimental mixture data only.     

Performance of symmetric polygonal fins with and without tip loss — A comparison of different methods of prediction

No analytical solution exists for estimating the efficiency of symmetric polygonal fins (SPFs) circumscribing circular tubes. Performance of such fins is conventionally determined from either of the two approximate techniques, namely, the equivalent annulus method and the sector method. The present work aims to judge the relative merits and applicability of these two methods critically. To this end, the results obtained from the approximate techniques have compared with those obtained from a semi‐analytical technique. It has been noted that, with the increase of the tip heat loss, the accuracy of prediction from any of the approximate methods decreases. For the sector method, a modification has been suggested. The prediction from the modified version of the sector method is always more accurate than that from the equivalent annulus method. It has been further illustrated that though the approximate techniques can be employed for the prediction of efficiency, they cannot be used to predict the tip temperatures accurately.