对牛奶成分近红外光谱分析方法的研究

研究牛奶成分近红外光谱测量的基本方法,探讨了在用偏最小二乘(PLS)方法建立系统校正模型过程中,采用直接正交(DO)数据预处理方法滤除牛奶漫反射光谱中与待测组分质量浓度无关的干扰信息的可行性,并与多元散射校正(MSC)及二阶微分(SOD)等光谱数据预处理方法进行比较．实验结果表明：相对于DO处理前,PLS模型的实际预测偏差(RMSEP)明显改善,最佳主成分数降低;相对于其他数据预处理方法,DO处理后系统PLS模型的RMSECV及RMSEP相对较低．DO数据预处理方法是近红外光谱分析中,从复杂重叠光谱中提取净信号信息、滤除噪音、进一步改善对原始光谱数据解释的有效途径．     

近红外光谱法检测小麦粉中灰分含量的研究

采用化学法测定67个小麦粉样品的灰分含量,利用波通DA7200型近红外光谱分析仪采集样品近红外光谱,选择合适的光谱区间及光谱预处理方法,采用偏最小二乘法(PLS)和留一法交叉验证方式建立定标模型.50个定标样品的近红外光谱经二阶导数预处理,由PLS法获得的定标模型的决定系数(R2)为0.897 0.利用17个验证集样品进行外部检验,预测值与真实值之间的相关系数(R2)为0.909 4,预测集标准偏差(SEP)为0.098 0.实验表明,近红外光谱法应用于小麦粉灰分的测定是可行的.     

干扰校正组合法在近红外检测牛奶中的应用

以牛奶近红外透射光谱为研究对象,探讨不同干扰信息消除方法对牛奶主要成分定量检测模型的影响,对比分析了采用扩展多元散射校正、标准正交变换、正交信号校正、扣标准液校正法和小波变换处理后光谱的建模效果,并对干扰校正方法组合后的效果进行了评价.结果表明,使用干扰校正组合方法能更有效地消除无关信息对模型的影响,与最佳单一方法的结果相比,脂肪和蛋白质的预测精度分别提高了31.6%和30.0%.该研究为建立稳健的近红外牛奶检测模型提供了有效的预处理方法,对牛奶品质在线快速检测具有参考价值.     

基于近红外光谱技术测定小麦籽粒淀粉含量

采用化学方法测定78个小麦样品中的淀粉含量,运用近红外光谱仪采集小麦样品近红外光谱.用光学处理和数学处理等手段对模型的影响进行了探讨.结果显示,反相离散多元校正(Inverse MSC)与二阶导数结合对光谱数据进行预处理后,运用偏最小二乘法(PLS)所建分析模型的预测效果最优,其相关系数为0.951 7.以17个验证集样品进行外部检验,得小麦籽粒中淀粉含量的模型预测值与化学值之间的相关系数为0.978 6.     

基于近红外光谱无损快速检测面粉品质的研究

提出一种基于近红外光谱技术结合偏最小二乘法对面粉品质进行无损快速检测的方法．配制含滑石粉的面粉样品30个,采集样品在12500～4000cm^-1范围内的近红外漫反射光谱,选择最优的光谱预处理方法和光谱范围,采用偏最小二乘法（PLS）建立定量分析模型．结果表明所建定量分析模型的相关性能比较高,预测相关系数和预测均方根误差均符合要求．研究发现,近红外光谱技术用于快速无损检测面粉掺假是可行的．     

近红外光谱法测定油炸方便面中水分含量的研究

应用近红外光谱技术测定了油炸方便面中的水分.通过比较各种数据处理方法,以80份样品建立方便面水分的近红外定标模型,40份样品作为验证样品集进行了验证.结果表明:以SNV(标准正态变量转化法)预处理后采用PLS(偏最小二乘法)建模效果最好.该方法得到的定标集样品的相关系数Rc和预测标准误差SEC分别为0.985 0、0.237 3;验证集样品的相关系数Rv和预测标准误差SEP分别为0.986 0、0.232 2.验证结果表明利用近红外光谱技术能快速测定油炸方便面中的水分.     

近红外光谱法快速定量分析那格列奈

采用近红外漫反射光谱分析技术和化学计量学的方法对那格列奈进行快速无损的定量分析.采集41份不同浓度系列的那格列奈样品测量近红外漫反射光谱,用多元散射校正结合一阶导数的光谱预处理方法,结合偏最小二乘法(PLS)建立那格列奈的定量分析模型.结果表明:交叉验证均方根误差(RMSECV)为0.448 5,决定系数R2为0.999 8;预测均方根误差(RMSEP)为0.196 0.方法精密度RSD为1.1%(n=6),加标回收率为95.55%.结果表明,用近红外光谱分析技术对那格列奈进行定量分析结果准确可靠,方法简便快速,可推广用于此类样品的工业在线分析.     

数据预处理方法对油页岩含油率近红外光谱分析的影响

为提高利用近红外光谱(NIRS)分析技术进行油页岩含油率的原位检测时的建模精度,需要采用适当的方法进行数据预处理。本研究利用实际和合成油页岩样品,结合光谱和矩阵2类数据预处理方法,研究不同方法及其组合对油页岩光谱数据一致性、样品含油率偏最小二乘法(PLS)的模型精度的影响。结果表明:在11种光谱数据预处理方法中,一阶导数、正则化、中心化以及适当的组合(如平滑、消噪和消基线后分别加中心化)等光谱预处理方法,可提高相同样品光谱数据间的一致性;在11种光谱预处理和3种矩阵处理的组合方法中,3种数据预处理组合方法(中心化、一阶导数2种光谱预处理+中心化矩阵预处理、一阶导数光谱预处理+正则化矩阵预处理)可提高合成样品含油率PLS模型的精度。     

正交信号校正算法及其在光谱处理中的应用

基于正交投影的正交信号校正(OSC)算法是近年来在光谱处理上很活跃的一种方法.本文介绍了OSC算法的基本原理,并对S.Wold、Fearn等人的比较成熟的5种正交信号校正算法作了比较详细的介绍.利用谷物的近红外数据,采用5种不同的OSC算法对谷物中的湿度、油含量、蛋白质和淀粉含量的预报情况进行了比较,并讨论了OSC组分数对预处理结果的影响.结果表明,各种正交信号校正算法基本上都能取得比单纯使用PLS更好的结果.     

正交信号校正算法及其在光谱处理中的应用

基于正交投影的正交信号校正(OSC)算法是近年来在光谱处理上很活跃的一种方法。本文介绍了OSC算法的基本原理，并对S．Wold、Feam等人的比较成熟的5种正交信号校正算法作了比较详细的介绍。利用谷物的近红外数据，采用5种不同的OSC算法对谷物中的湿度、油含量、蛋白质和淀粉含量的预报情况进行了比较，并讨论了OSC组分数对预处理结果的影响。结果表明，各种正交信号校正算法基本上都能取得比单纯使用PLS更好的结果。     

Structural evolution and stability of mechanically alloyed Fe-Ni nanocrystalline

The structural evolution and stability of Fe100-xNix(x=10, 20, 35, 50) alloys prepared by mechanical alloying were investigated through X-ray diffraction analysis and transmission electron microscopy. The intrinsic conditions of preparation determining phase stability in nanocrystalline were clarified. After being milled for 120 h, the powders of Fe90Ni10 and Fe80Ni20 consist of a single α(bcc) phase, Fe30Ni30 powders are a single γ(fcc), and for Fe65Ni35 powders there is co-existence of α and γ phases. The as-milled Fe80Ni20 powders annealed at 680 ℃ exhibits the stability of high-temperature γ phase at room temperature, which is consistent with the theoretical prediction.     

Influence of interfacial strength on the fracture toughness of glass-ceramic matrix composites

Nine kinds of glass-ceramic matrix composites with different compositions and interfacial strength (τ _s) were prepared. The influence of τ _s on the fracture toughness(K _1c) of composites was studied. It was discoved that, for the system no chemical reaction taking place at the interface, K _1c increased proportionally with τ _s increasing at the first stage, then decreased when τ _s reached a certain value. According to this result, a model of relationship between τ _s, thermal mismatch (Δα _r) and K _1c was built up. If a chemical reaction took place and a new phase was formed in the interface, the K _1c of composite was effected by the combination of τ _s, chemical bonding, radial interfacial stress and other factors. Project supported by the National Natural Science Foundation of China Synopsis of the first author Wang Lingsen, professor, born in 1938, current research field: special ceramic and ceramic matrix composite, etc.     

基于扩展有限元的混凝土三点弯曲梁断裂性能数值模拟研究

基于扩展有限元法,模拟了不同宽度混凝土三点弯曲梁的断裂破坏过程,得到了荷载-裂缝口位移曲线;对不同宽度、缝高比、跨高比的三点弯曲梁断裂过程进行模拟并利用双K断裂准则得出了不同宽度、缝高比、跨高比等条件下的应力强度因子,研究了这三种参数的变化对应力强度因子的影响。研究结果表明:当跨高比、缝高比等于0.4,梁宽在100~250 mm范围内变化时,其起裂断裂韧度K_Icⁱⁿⁱ、失稳断裂韧度K_Ic^un基本保持不变;当梁宽不变,跨高比等于4,缝高比从0.2增大到0.5时,起裂断裂韧度K_Icⁱⁿⁱ、失稳断裂韧度K_Ic^un呈现先增大后减小的趋势;当梁宽不变,缝高比等于0.4,跨高比从2.5增大到3.5时,起裂断裂韧度K_Icⁱⁿⁱ保持不变,失稳断裂韧度K_Ic^un将逐渐增大但幅度很小;当跨高比不变,缝高比等于0.4,梁宽在100~250 mm的范围内变化时,起裂断裂韧度K_Icⁱⁿⁱ、失稳断裂韧度K_Ic^un均呈现先增大后减小的趋势,表明小跨高比的K_Icⁱⁿⁱ、K_Ic^un在梁宽度方向存在一定的尺寸效应。     

Synthesis of γ-Al2O3 nanoparticles by chemical precipitation method

Highly pure active γ-Al₂O₃ nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al₂O₃ nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)₃ sols are produced by using 0.1 mol/L Al(NO₃)₃ · 9H₂O and 0.16 mol/L (NH₄)₂CO₃ · H₂O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 °C, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80°C for 8 h, final calcined at 800 °C for 1 h in the air, and high purity active γ-Al₂O₃ nanoparticles can be prepared with cubic in crystal system, O _H ⁷ -FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131. 35 m²/g in BET specific surface area, 7 – 11 nm in pore diameter, and not lower than 99.93% in purity. Foundation item: Project(03JJY3015) supported by the Natural Science Foundation of Hunan Province     

明光路车站基坑连续墙变形规律分析研究

城市地铁车站基坑施工对周围环境产生较大影响,往往造成严重后果。本文采用数值计算和监测数据分析的方法对合肥地铁明光路基坑开挖过程中的地下连续墙墙体深层水平位移的进行分析,并将两种方法获得的结果进行对比分析,得出结论表明:在基坑开挖过程中地连墙水平位移呈现中间大、两头小的弓肚形态,最而大位移点随基坑开挖深度加大而逐渐下降,大致位于基坑深度三分之一到三分之二范围处;地连墙水平位移增量与开挖深度程正比,与土层的性质也直接影响到支护体的变形。该结果将对合肥市地铁车站基坑支护结构设计提供重要的借鉴作用。     

Experiments and reaction characteristics of liquid phase simultaneous removal of SO<Subscript>2</Subscript> and NO

Experiments of simultaneous removal of SO₂ and NO from simulated flue gas, using NaClO₂ solution as the absorbent, were carried out in a self-designed bubble reactor, and high simultaneous removal efficiencies of SO₂ and NO were obtained under the optimal experimental conditions. The mechanism of simultaneous removal based on NaClO₂ acid solutions was proposed by analyzing the removal products. Possibility and limitation of the desulfurization and denitrification using NaClO₂ acid solutions were calculated by thermodynamic methods. Experimental results of reaction kinetics for simultaneous desulfurization and denitrification indicated that the oxidation-absorption processes of SO₂ and NO were divided into two zones, namely the fast and slow reaction zones. In the slow reaction zones both were zero order reactions, and in the fast reaction zones, the reaction order, rate constant and activation energy of SO₂ reaction with absorbent were 1.4, 1.22 (mol·L⁻¹)^−0.4·s⁻¹ and 66.25 kJ·mol⁻¹, respectively, and 2, 3.15×10³ (mol·L⁻¹) ⁻¹·s⁻¹, and 42.50 kJ·mol⁻¹ for NO reaction, respectively. Supported by the National High-Tech Research and Development Program of China (“863” Project) (Grant No. 2007AA061803)     

Low-temperature sintering and microwave dielectric properties of Li2MgTi3O8 ceramics doped with BaCu（B2O5）

The influences of BaCu(B₂O₅) (BCB) addition on sintering, microstructure and microwave dielectric properties of Li₂MgTi₃O₈ ceramics were investigated using X-ray diffractometry, scanning electron microscopy and microwave dielectric measurements. The experimental results show that a small amount of BaCu(B₂O₅) addition can effectively reduce the sintering temperature to 900 °C, and induce only a limited degradation of the microwave dielectric properties. Typically, the best microwave dielectric properties of ɛ _r=24.5, Q×f =24 622 GHz, τ _f=4.2×10⁻⁶ °C⁻¹ are obtained for 1.0% BCB-doped Li₂MgTi₃O₈ ceramics sintered at 900 °C for 3 h. The BCB-doped Li₂MgTi₃O₈ ceramics can be compatible with Ag electrode, which may be a strong candidate for low temperature co-fired ceramics applications.     

Frequency up-conversion luminescence properties and mechanism of Tm<Superscript>3+</Superscript>/Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped oxyfluorogermanate glasses

Oxyfluoride glasses were developed with composition 60GeO 2 ·10AlF 3 ·25BaF 2 ·(1.95-x)GdF 3 · 3YbF 3 ·0.05TmF 3 ·xErF 3 (x=0.02,0.05,0.08,0.11,0.14,0.17)in mole percent.Intense blue(476 nm),green(524 and 546 nm)and red(658 nm)emissions which identified from the 1G 4 →3H 6 transition of Tm3+and the(2H 11/2 ,4S 3/2 )→4I 15/2 ,4F 9/2 →4I 15/2 transitions of Er3+,respectively,were simultaneously observed under 980 nm excitation at room temperature.The results show that multicolor luminescence including white l...     

Investigation on extremal and critical characteristics of ignition time for H<Subscript>2</Subscript>/O<Subscript>2</Subscript> combustion system and their applications

The L, H and C curves in P-T phase are proposed to describe the minimal, maximal and critical characteristics of ignition time of H₂/O₂ combustion system, respectively. The features of H₂/O₂(Air) combustion system, including explosion or not as well as the time delay to achieve its explosion status, can be well shown by explosion limits and these proposed curves. These curves can be described by 1.2k ₁=k _s [M_s], (k ₁₁/k ₁₀+1)k ₁=k _s [M_s], and 2k ₁=k _s [M_s], respectively, which provide a physical explanation for these curves and give another way to establish them. Based on the contour of ignition time, the Z-type explosion limits can be explained by thermal explosion theory. Furthermore, the ignition distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system, which is very reasonable.     

不同再燃技术降低燃煤锅炉NOx排放的对比分析

目前降低NO_x生成与排放技术中,再燃技术具有改造费用低、锅炉运行效率高、降低NO_x排放效率显著等特点。通过分析超细粉、生物质气、天然气和H₂作为再燃燃料的机理、影响因素、优缺点和实际应用情况,比较了不同再燃技术降低NO_x排放的技术参数和经济性,发现H₂再燃技术降低燃煤锅炉NO_x排放具有较大优越性。