神经网络法在使用裂解气相色谱鉴别中草药中的应用

将以误差反向传播为训练算法的前馈式人工神经网络（ＢＰ－ＡＮＮ）首次艇于中草药的裂解气相色谱谱图解析。重点考察了如何表征和提取复杂的裂解色谱图中有价值信息,用于主成分分析方法处理后输入到有数经优化的神经网络中。实验证明,该广阔示仅可以正确识别样品所属种类,耐用对一示同实验时间、数据残缺等原因造成的噪音具有优异的抗干扰能力。     

LT50m缩比模型悬索舱体系统的风振分析

在新一代大型射电望远镜（LT）的悬索舱体系统中增加了抑制风激振动的下拉结构控制索系，并分析了50m缩比模型的风振响应。首先，由非线性静力分析确定结构初始静态参考位形和初应力；其次，针对结构特点模拟作用在悬索和馈源舱上的随机风荷。在上述研究的基础上，在时域中模拟分析下拉索系对结构风振的抑制效果，同时通过典型节点时域响应的FFT变换，给出响应自功率谱图，进一步描述了振动控制的效果。     

离子色谱法测定饲料中的甜菜碱

建立了离子色谱法测定饲料中甜菜碱的方法。向饲料样品中加水并超声提取,加入三氯甲烷剧烈振摇,离心取上清液,以离子色谱非抑制电导检测器测定其中的甜菜碱。结果表明,甜菜碱的质量浓度在50~1000 mg/L的范围内与电导率线性关系良好,相关系数为0.9995。甜菜碱的定量限为41 mg/kg,优于国家标准的定量限(200mg/kg),加标回收率为102.4%,重现性的相对标准偏差为1.19%(n=5)。该法可应用于饲料行业的例行检测。     

Co—Mo／Al2O3型重整预加氢催化剂的研制

考察了不同方法制备的Ｃｏ－Ｍｏ／Ａｌ２Ｏ３型重整预加氢催化剂对石油加氢脱硫活性的影响，选出了一种工业生产步骤简单，金属含量容易控制，并且不腐蚀设备的碱必等量共浸法制备的ＤＳ－９４８催化剂。该催化剂在温度３５０℃，压力３．０ＭＰａ，液体空速６．０ｈ＾－１，体积氢油比７０的条件下，满足了双金属重整催化剂对精制石油脑油杂质含量的要求。     

三层前向人工神经网络全局最优逼近

提出了求解不等式约束非线性优化问题的群体复合形进化算法 ,提出的算法能充分利用目标函数值的信息、优化搜索过程具有较强的方向性和目标性 ,收敛速度较快 ,且是全局优化算法 ;将群体复合形进化算法应用于三层前向人工神经网络逼近 ,提出了三层前向人工神经网络全局最优逼近算法 ;将三层前向人工神经网络全局最优逼近算法应用于实例 ,表明了提出的全局最优逼近算法的有效性 .     

催化动力学光度法测定锅炉给水中异抗坏血酸钠

基于催化动力学过程，研究了新型锅炉给水除氧剂异抗坏血酸钠的分光光度法测定。试验表明，这一方法操作简便，快速、准确提高，可测至5μg.L^-1异抗坏血酸钠。     

Application of microwave heating for the fast extraction of fat content from the poultry feeds

A rapid method has been developed to extract and quantitatively measure the total oil content in poultry feeds using a domestic microwave oven. The optimized extraction procedure involves the replicate (6×) extraction of 5 g of ground feed with 12 ml of hexane for 20 s in a 900 W oven. Each replicate involves the collection of the resulting miscella and its replacement with fresh solvent for re-extraction. The collected extracts were centrifuged and transferred to a vial. The solvent was evaporated to a constant weight and the residual lipid weighed. In comparison to conventional Soxhlet extraction method, lipid contents obtained using the optimized microwave procedure was not significantly different. However, FTIR analysis indicated that the microwave procedure was superior in minimizing the formation of free fatty acids (FFA) relative to the Soxhlet procedure if the temperature of the sample was kept within the range of 45–50 °C. This simple, sequential extraction procedure is rapid, highly efficient and provides a simple mean of quantitating the lipid content of poultry feed in less than 40 min without the need for specialized microwave oven.     

GC×GC-ECD: a promising method for the determination of dioxins and dioxin-like PCBs in food and feed

There is a need for cost-efficient alternatives to gas chromatography (GC)–high-resolution mass spectrometry (HRMS) for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food and feed. Comprehensive two-dimensional GC–micro electron capture detection (GC×GC-μECD) was tested and all relevant (according to the World Health Organisation, WHO) PCDD/Fs and PCBs could be separated when using a DB-XLB/LC-50 column combination. Validation tests by two laboratories showed that detectability, repeatability, reproducibility and accuracy of GC×GC-μECD are all statistically consistent with GC-HRMS results. A limit of detection of 0.5 pg WHO PCDD/F tetrachlorodibenzo-p-dioxin equivalency concentration per gram of fish oil was established. The reproducibility was less than 10%, which is below the recommended EU value for reference methods (less than 15%). Injections of vegetable oil extracts spiked with PCBs, polychlorinated naphthalenes and diphenyl ethers at concentrations of 200 ng/g showed no significant impact on the dioxin results, confirming in that way the robustness of the method. The use of GC×GC-μECD as a routine method for food and feed analysis is therefore recommended. However, the data evaluation of low dioxin concentrations is still laborious owing to the need for manual integration. This makes the overall analysis costs higher than those of GC-HRMS. Further developments of software are needed (and expected) to reduce the data evaluation time. Combination of the current method with pressurised liquid extraction with in-cell cleanup will result in further reduction of analysis costs. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Liquid chromatographic method development for anabolic androgenic steroids using a monolithic column Application to animal feed samples

An isocratic HPLC method for the determination with screening purposes of anabolic androgenic steroids (AASs: fluoxymesterone, boldenone, nortestosterone, metandrostenolone, norethindrone, methyltestosterone and bolasterone), used as growth promoting agents, in finishing pig feed samples has been developed and validated. The separation was achieved by using a reversed-phase Chromolith RP-18e column at controlled temperature, UV-detection at 245 nm and epitestosterone as internal standard. The method development involved optimization of different aqueous-organic mobile phases using methanol or acetonitrile as organic modifiers, flow-rate and temperature. The optimum separation for these compounds was achieved at 40 °C using ultrapure water:acetonitrile (71:29, v/v) as mobile phase and 3 mL min⁻¹ flow-rate, allowing the separation of AASs with baseline resolution in about 15 min. The optimized method was applied to the analysis of AASs in finishing pig feed samples. Prior to HPLC, sample preparation procedure was used by leaching using acetonitrile, saponification in a basic medium and solid-phase extraction using polymeric Abselut Nexus cartridges. Method validation has been carried out according to the European Commission Decision 2002/657/EC. The extraction efficiencies, decision limits (CCα) and detection capabilities (CCβ) for these compounds were in the range 83-96%, 27-37 and 32-47 μg kg⁻¹ range, respectively. The within-laboratory reproducibility at 1, 1.5 and 2 CCβ concentration levels were smaller than 13, 10 and 8%, respectively. Finally, the proposed method was successfully applied to nine different kinds of animal feed.