高效液相色谱法测定玉米中的游离酚和结合酚

建立了高效液相色谱法同时测定玉米中游离酚和结合酚的检测方法,包括原儿茶酸、龙胆酸、对羟基苯甲酸、绿原酸、香草酸、咖啡酸、丁香酸、表儿茶素、香豆酸、阿魏酸、芥子酸、芦丁、橙皮素、槲皮素。有机溶剂提取玉米中的游离酚,碱法提取玉米中的结合酚,以ZORBAX Eclipse Plus Phenyl-Hexyl(4.6 mm×250mm,5μm)为分析柱,乙腈(A)和含0.4%乙酸的超纯水(B)为流动相梯度洗脱,采用二极管阵列检测器280 nm波长检测。14种酚类化合物在一定浓度范围内与其峰面积呈良好的线性关系,相关系数为0.999 4~0.999 9,加标回收率为90%~108%,相对标准偏差为0.03%~3.59%。试验结果表明,该方法能用来同时测定玉米中的游离酚和结合酚。     

不同水解方法对刺梨渣多酚含量及活性的影响

该研究以刺梨渣为原料,分别经酸水解、碱水解以及酶水解得到刺梨渣提取液,测定提取液中多酚含量组成及体外抗氧化能力,并比较酚类物质与抗氧化能力之间的相关性。结果表明,刺梨渣提取液中游离多酚、游离黄酮含量最高（分别为84.44 mg RE/g和136.67 mg RE/g）;碱水解得到的结合酚、结合黄酮含量最高（2.04 mg RE/g和5.89 mg RE/g）。抗氧化分析结果表明,游离酚抗氧化能力最强,对DPPH·、ABTS+·清除能力、还原铁离子和铜离子的能力分别达到854.87 μmol TE/g、995.35 μmol TE/g、336.24 μmol TE/g、1 212.08 μmol TE/g。皮尔逊相关性分析结果表明,多酚含量与抗氧化活性呈较强的正相关（P＜0.05）。综上可知,刺梨渣富含酚类物质,且碱水解处理刺梨渣能释放更多的结合酚,具有较强的抗氧化活性。     

考虑风电出力不确定性与半绝对离差风险的机组组合模型

在风电-火电系统中,若机组组合策略不当,风电出力的不确定性会引起电力系统的实际运行成本严重偏离期望成本,称之为决策风险.为了降低潜在的决策风险,运用情景生成与情景削减的方法表征风电出力的不确定性,并采用半绝对离差(lower semi-absolute deviation,LSAD)来衡量决策风险,即仅考虑实际运行成本高于期望成本的情形,提出了考虑风电出力不确定性与决策风险的机组组合模型,模型以最小化各个情景的半绝对离差风险期望值为优化目标(decision risk minimization,DRM).算例对比了不考虑决策风险的机组组合模型与考虑决策风险的机组组合模型,计算结果表明DRM模型能够降低潜在的决策风险.最小化运行成本期望将会增大决策风险,而最小化决策风险会导致运行成本期望的增加,计算结果表明DRM模型能够较好地处理风电出力的不确定性带来的运行成本期望与决策风险之间的矛盾关系,为决策者在不确定条件下进行决策提供新的思路.     

Graphics processing unit‐accelerated bounding for branch‐and‐bound applied to a permutation problem using data access optimization

Branch‐and‐bound (B&B) algorithms are attractive methods for solving to optimality combinatorial optimization problems using an implicit enumeration of a dynamically built tree‐based search space. Nevertheless, they are time‐consuming when dealing with large problem instances. Therefore, pruning tree nodes (subproblems) is traditionally used as a powerful mechanism to reduce the size of the explored search space. Pruning requires to perform the bounding operation, which consists of applying a lower bound function to the subproblems generated during the exploration process. Preliminary experiments performed on the Flow‐Shop scheduling problem (FSP) have shown that the bounding operation consumes over 98% of the execution time of the B&B algorithm. In this paper, we investigate the use of graphics processing unit (GPU) computing as a major complementary way to speed up the search. We revisit the design and implementation of the parallel bounding model on GPU accelerators. The proposed approach enables data access optimization. Extensive experiments have been carried out on well‐known FSP benchmarks using an Nvidia Tesla C2050 GPU card. Compared to a CPU‐based single core execution using an Intel Core i7‐970 processor without GPU, speedups higher than 100 times faster are achieved for large problem instances. At an equivalent peak performance, GPU‐accelerated B&B is twice faster than its multi‐core counterpart. Copyright © 2013 John Wiley & Sons, Ltd.     

油桃采后结合态香气变化规律及其与可溶性糖的关联性

以‘瑞光1号’油桃为研究对象,研究其采后常温（20 ℃）和低温（1 ℃）贮藏下游离态和结合态香气物质变化规律。采用酶解法释放结合态香气物质,利用顶空固相微萃取法结合气相色谱-质谱联用对油桃游离态和结合态香气物质分别进行定性和定量分析,并研究结合态香气物质与可溶性糖之间的相关性。结果表明,油桃果实常温和低温贮藏条件下游离态和结合态香气物质种类存在很大差异。常温贮藏下检测到油桃中游离态香气物质37 种,结合态香气物质30 种,其中8 种物质以游离态和结合态2 种形式存在。游离态香气物质第4天下降至最低值后第6天有所上升,第8天含量有所下降,结合态香气物质第6天降至最低值后第8天有所上升。低温贮藏下检测到游离态香气物质21 种,结合态香气物质32 种,其中7 种物质以游离态和结合态2 种形式存在。随着低温贮藏时间延长,游离态香气物质含量下降,结合态香气物质呈现先上升后下降的趋势。相关性分析表明结合态香气物质含量与果实中可溶性糖含量之间显著相关,与蔗糖的相关系数最高。     

Three-dimensional modelling of in-furnace coal/coke combustion in a blast furnace

A three-dimensional mathematical model of the combustion of pulverized coal and coke is developed. The model is applied to the region of lance-blowpipe-tuyere-raceway-coke bed to simulate in-furnace phenomena of pulverized coal injection in an ironmaking blast furnace. The model integrates not only pulverized coal combustion model in the blowpipe-tuyere-raceway-coke bed but also coke combustion model in the coke bed. The model is validated against the measurements under different conditions. The comprehensive in-furnace phenomena are investigated in the raceway and coke bed, in terms of flow, temperature, gas composition, and coal burning characteristics. The underlying mechanisms for the in-furnace phenomena are also analysed. The simulation results indicate that it is important to include recirculation region in the raceway and the coke bed reactions for better understanding in-furnace phenomena. The model provides a cost-effective tool for understanding and optimizing the in-furnace flow-thermo-chemical characteristics of the PCI operation in full-scale blast furnaces.     

Chitosan—A versatile semi-synthetic polymer in biomedical applications

This review outlines the new developments on chitosan-based bioapplications. Over the last decade, functional biomaterials research has developed new drug delivery systems and improved scaffolds for regenerative medicine that is currently one of the most rapidly growing fields in the life sciences. The aim is to restore or replace damaged body parts or lost organs by transplanting supportive scaffolds with appropriate cells that in combination with biomolecules generate new tissue. This is a highly interdisciplinary field that encompasses polymer synthesis and modification, cell culturing, gene therapy, stem cell research, therapeutic cloning and tissue engineering. In this regard, chitosan, as a biopolymer derived macromolecular compound, has a major involvement. Chitosan is a polyelectrolyte with reactive functional groups, gel-forming capability, high adsorption capacity and biodegradability. In addition, it is innately biocompatible and non-toxic to living tissues as well as having antibacterial, antifungal and antitumor activity. These features highlight the suitability and extensive applications that chitosan has in medicine. Micro/nanoparticles and hydrogels are widely used in the design of chitosan-based therapeuticsystems. The chemical structure and relevant biological properties of chitosan for regenerative medicine have been summarized as well as the methods for the preparation of controlled drug release devices and their applications.     

溶剂法制备碳纳米管结合胶及其微观结构的研究

利用溶剂法制备碳纳米管结合胶,确定了制备高质量碳纳米管结合胶的实验参数：橡胶／甲苯溶液的质量浓度为0．020g／mL,橡胶与碳纳米管的质量比为4：1,反应时间为7h。用扫描探针显微镜对天然橡胶、碳纳米管及其结合胶的微观形貌进行研究,得到了碳纳米管结合胶的清晰结构。碳纳米管结合胶的结构为天然橡胶分子在定向紧密排列的碳纳米管的两侧沿着纳米管的表面与碳纳米管结合形成环状的闭合结构,随着纳米管管径的增大,结合胶的结构趋向于炭黑结合胶的结构。     

均匀圆阵二维波达角估计的Cramer-Rao界

均匀圆阵(UCA)是一种应用广泛的具有二位波达角估计能力的平面阵列。为了从理论上分析不同阵列参数下到达波方位角(AOA)、仰角估计精度,推导了均匀圆阵二维波达角估计的性能界,以此为基础分析了阵列孔径、阵元个数、快拍数以及来波仰角高低与到达角估计精度的关系,并通过对UCA-MUSIC算法计算机仿真验证了推导结果的正确性。研究结果为波达角估计类算法提供了可供参考的性能下界,圆阵设计时也不再需要大量的Monte Carlo仿真试验确定阵列参数,可直接从估计精度表达式中获得。     

Rashba效应对量子线中强耦合束缚极化子性质的影响

采用改进的线性组合算符和幺正变换相结合的方法,研究了Rashba效应对半导体量子线中强耦合束缚极化子性质的影响。计算了Rashba效应的影响下量子线中强耦合束缚极化子的基态能量、有效质量和振动频率。数值分析结果表明:基态能量随库仑束缚势的增加而减少,随受限强度的增加而增大,而且在Rashba效应影响下,基态能量和有效质量比随库仑束缚势的变化曲线由原来的一条分裂为上下两条;振动频率随束缚势、受限强度和耦合强度的增加而加快;有效质量比随库仑束缚势和受限强度的增强而变大。