Restricted Maximum Likelihood Estimates in Finite Mixture Models

ＲｅｓｔｒｉｃｔｅｄＭａｘｉｍｕｍＬｉｋｅｌｉｈｏｏｄＥｓｔｉｍａｔｅｓｉｎＦｉｎｉｔｅＭｉｘｔｕｒｅＭｏｄｅｌｓ￥（陈家骅，成平）ＣｈｅｎＪｉａｈｕａ（ＤｅｐａｒｔｍｅｎｔｏｆＳｔａｔｉｓｔｉｃｓ＆ＡｃｔｕａｒｉａｌＳｃｉｅｎｃｅ，Ｕｎｉｖｅｒｓｉ...     

Multi-element analysis of iron ore pellets by Laser-induced Breakdown Spectroscopy and Principal Components Regression

Laser-induced Breakdown Spectroscopy (LIBS) in combination with Principal Components Regression (PCR) has been applied to determine the elemental composition of a series of run-of-mine (ROM) iron ore samples. The samples were presented for measurement both as compressed pellets and as loose chipped material. The present paper details the results of the measurements of the compressed pellets. Results from ore chips will be reported separately. LIBS spectral data was recorded in three separate spectral regions to measure major, minor and trace components of the iron ore sample pellets. Background stripping, normalization and spectral cleaning were applied to minimize the relative standard deviations of the LIBS data. PCR analysis was then applied to produce calibration models for iron, aluminum, silicon, manganese, potassium and phosphorous. These calibration models were then validated using independent LIBS measurements. Robust calibration models were determined for iron, aluminum, silicon and potassium, whilst the results for manganese were encouraging. Phosphorous, present at low levels in the ores measured, remained the most difficult element to determine accurately. The combination of LIBS and PCR shows potential for in-situ on-line determination of ore composition.     

Applications of High-Resolution Mass Spectrometry in Studies of Brown Carbon

Brown carbon is a hotspot in the field of atmospheric carbonaceous aerosol research. It has significant influence on regional radiative forcing and exerts climatic effects due to its apparent absorbance in the near ultraviolet-visible region. Brown carbon is mainly derived from incomplete combustion of biomass or coal, as well as secondary sources, such as a series of atmospheric photochemical reactions from volatile organic compounds. Although the composition of brown carbon is complex, high-resolution mass spectrometry, with its ultra-high mass resolution and precision, enables elucidation of the characteristics of the organic components of brown carbon at the molecular level. Here, high-resolution mass spectrometry combined with traditional analytical methods was used for the study of brown carbon. The development of high-resolution mass spectrometry for brown carbon separation is reviewed, as well as compositional analysis, source apportionment, and formation mechanism of brown carbon based on high-resolution data. In addition, the issues and prospects for the application of high-resolution mass spectrometry to evaluate brown carbon are discussed.     

采用GC-MS技术分析合成己烯-1中间产品组成

己烯-1是重要的化工原料,应用范围非常广,利用乙烯作为原料合成己烯-1是一种在国内同行业中处于领先地位的新技术。为了全面了解合成中各个环节的情况,需要对各部分的中间产品的组成进行分析,以便确定最佳的工艺参数。气相色谱-质谱联用(GC-MS)技术集色谱的高分辨能力与质谱的高鉴定能力于一体,依据化合物的质谱碎片定性,可以不需要标准品的对比,在定性分析中具有专属性强的特点,适合于未知组分的分析。本次实验中采用GC-MS技术对合成己烯-1中间产品的各个组分进行了详细的定性分析,取得了满意的结果。     

完备格中的成分理论

在完备格中引入了元素的成分概念．基于此,引入了元素的宽度的概念．在分配格的情形证明了元素的成分集对有限并运算封闭且有某种遗传性．证明了元素的有限宽度的成分之集是定向集．称没有非平凡成分的元素为颗粒．称每个非零元素都可表示为其颗粒成分之并的完备格为颗粒表示格．证明了拓扑空间是局部连通的充要条件是其开集格为颗粒表示格．     

顶空固相微萃取-气相色谱-质谱法分析扶芳藤叶挥发性成分

采用顶空固相微萃取-气相色谱-质谱法分析了扶芳藤叶挥发性成分,鉴定了90种化合物,主要挥发成分及其含量为:萜类(25种,45.82%)、酯类(20种,18.26%)、脂肪烃(20种,15.06%)、芳烃化合物(3种,7.31%)、酸酐(1种,4.91%)、酮类(4种,4.2%)、卤代烃类(7种,1.52%),为进一步开发和利用扶芳藤提供基础数据。     

湖南省各地市州居民生活水平比较分析

本文结合恩格尔系数研究居民生活水平的优点，采用聚类分析法与主成分分析法对2004年湖南省各地市州居民生活水平进行比较分析，给出了这些城市居民生活水平的综合得分及其排序，从而更真实地衡量湖南省各地市州居民生活水平．     

凹叶厚朴各部位挥发油成分比较研究

采用顶空固相微萃取(HS-SPME)提取凹叶厚朴不同部位的挥发油成分,气相色谱-质谱(GC-MS)分析其组成.结果显示:根鉴定出19个化合物,其中4(14),11-桉叶二烯(26.04％),(1S-顺)-1,4-二甲基-7-(1-甲基亚乙基)-奠(24.94％),石竹烯(9.41％),β-桉叶醇(7.28％)为主要成分...     

X射线荧光光谱法测定黏土中的主次组分

采用熔融玻璃片制样,选用标准样品,以经验α系数和散射线内标法校正元素谱线重叠干扰和基体效应,使用ZSX Primus Ⅱ X射线荧光光谱仪对黏土样品中的Al₂O₃、SiO₂、Fe₂O₃、CaO、MgO、K₂O、Na₂O、MnO、P₂O₅、TiO₂、Cu、Cr等组分进行测定,分析结果与标准值和化学值相吻合,12次测定的相对标准偏差小于10%.     

扁蓄种子的营养成分

对子午岭扁蓄种子的营养成分进行分析 ,扁蓄种子中含有丰富的氨基酸、维生素和种类比较齐全的矿物元素 ;种子油含大量人体所必需的不饱和脂肪酸。扁蓄种子和种子油具有较高的营养价值 ,在食物、香料和医药等领域具有潜在的开发利用前景。