Optimisation of ultrasound assisted extraction of phenolic compounds from Sparganii rhizoma with response surface methodology

The present study reports on the extraction of phenolic compounds from sparganii rhizome. Box–Behnken Design (BBD), a widely used form of response surface methodology (RSM), was used to investigate the effect of process variables on the ultrasound-assisted extraction (UAE). Three independent variables including ethanol concentration (%), extraction time (min) and solvent-to-material ratio (mL/g) were studied. The results showed that the optimal UAE condition was obtained with an ethanol concentration of 75.3%, an extraction time of 40 min and a solvent-to-material ratio of 19.21 mL/g for total phenols, and an ethanol concentration of 80%, an extraction time of 33.54 min and solvent-to-material ratio of 22.72 mL/g for combination of ρ-hydroxybenzaldehyde, ρ-coumaric acid, vanillic acid, ferulic acid, rutin and kaempferol. The experimental values under optimal conditions were in good consistent with the predicted values, which suggested UAE is more efficient process as compared to solvent extraction.     

A normalised residence time transport equation for the numerical simulation of combustion with high-temperature air

This study concerns the numerical simulation of turbulent non-premixed combustion in highly preheated air streams. One of the objectives is to settle an efficient computational procedure to proceed with the numerical simulation of large-scale industrial devices. It is also expected that the availability of such a computational framework may facilitate comprehensive sensitivity analyses as well as the development of mathematical models able to represent turbulence-chemistry interactions (TCI) in such conditions. Based on the salient physical ingredients that characterise scalar mixing, propagation, and self-ignition processes, a turbulent combustion modelling framework is thus introduced and applied to the numerical simulation of well-documented laboratory flames. In the corresponding geometries, the bulk flow velocities of the reactants streams can reach rather large values, which lead the flame to lift from the burner rim. Partially premixed flame edges thus stabilise the whole flame structure and the temperature of the oxidising stream can be increased by vitiation with burned gases so as to promote the corresponding flame-stabilisation processes. For sufficiently large values of the vitiated airstream temperature, self-ignition mechanisms may be triggered thus leading to a competition between mixing, propagation, and ignition processes. In this context, the ratio of the residence time to the self-ignition delay is thought to be a relevant variable to delineate the possible influence of ignition phenomena. Therefore, a modelled transport equation for this normalised residence time is considered. The performance of the corresponding modelling proposal is analysed with special emphasis placed on its ability to reproduce ‘memory’ or ‘lagrangian’ effects related to thermal aging processes. In this respect, it is noteworthy that the present set of computations makes use of tabulated quantities associated to (i) steady laminar one-dimensional diffusion flamelets, so as to describe the composition of combustion products, (ii) steady laminar one-dimensional premixed flamelets, to describe the flame brush propagation, and (iii) temporal evolution of zero-dimensional homogeneous mixtures to account for the possible occurrence of self-ignition phenomena. In particular, the tabulated self-ignition time value is used to evaluate the increase in the normalised residence time. Finally, two modelling parameters are put into evidence and studied through a detailed sensitivity analysis.     

Spectroscopic Studies of the Stability of Doped Polythiophenes Under Air

Abstract

The stability of the doped state of conductive polythiophenes under air was investigated by the use of Infrared (IR) and UV-visible (UV) spectroscopies. Poly(3-methyl thiophene) doped with BF₃-ethyl ether (BFEE). shows higher stability due to its stereoregularity-chain structure. While the doped polythiophene (PT) degrades easily under the moisture.     

关于建立新型激励机制与综合应用激励手段的研究

本文从西方激励理论与我国企业现状出发．探索了建立适合改革中的企业管理体制的新型激励机制之路，指出新型激励机制中多种激励手段应有机地综合运用．首先对西方激励理论进行了分析．而后对“人”在管理中的地位进行了探讨．在分析我国激励机制中现存缺陷后．提出了从组织结构、企业文化、领导行为多个方面进行变革以建立新型激励机制的建议．     

关于物质激励与精神激励基础与结合研究

从激励的心理学理论基础出发进行分析；对需求、动机、行为等及其相互影响在激励实践中的作用进行了总结。精神激励和物质激励是两种主要的激励模式．它们都是从实践中来经过否定之否定而发展起来的．现代激励理论对两种激励基本上接受，但对两种激励的评价及侧重又各有不同．我国现行激励机制存在一些问题，尤以平均主义为甚．精神激励与物质激励的有机结合．是激励模式发展的未来．     

BAHADUR ASYMPTOTIC EFFICIENCY IN A SEMIPARAMETRIC REGRESSION MODEL

ＢＡＨＡＤＵＲＡＳＹＭＰＴＯＴＩＣＥＦＦＩＣＩＥＮＣＹＩＮＡＳＥＭＩＰＡＲＡＭＥＴＲＩＣＲＥＧＲＥＳＳＩＯＮＭＯＤＥＬ￥ＬＩＡＮＧＨＵＡ；ＣＨＥＮＧＰＩＮＧＡｂｓｔｒａｃｔ：ＴｈｅａｕｔｈｏｒＳｇｉｖｅＭＬＥθ１ＭＬｏｆθ１ｉｎｔｈｅｍｏｄｅｌＹ＝θ...     

产量──密度模型讨论

本文给出产量与密度函数关系     

An Invariant of Gauge Transformations of Contact Riemannian Structures

Ａｎ　Ｉｎｖａｒｉａｎｔ　ｏｆ　Ｇａｕｇｅ　Ｔｒａｎｓｆｏｒｍａｔｉｏｎｓ　ｏｆ　Ｃｏｎｔａｃｔ　Ｒｉｅｍａｎｎｉａｎ　ＳｔｒｕｃｔｕｒｅｓＬｉａｎｇＸｉｑｕａｎ（梁希泉）ａｎｄＬｉｕＸｉｍｉｎ（刘西民）（ＩｎｓｔｉｔｕｔｅｏｆＭａｔｈｅｍａｔｉｃｓ...     

聚合反应制备键合型纤维素-三(4-甲基苯基甲酸酯)衍生物类手性固定相

合成了带有甲基丙烯酰基的纤维素-三(4-甲基苯基甲酸酯)衍生物(CTMB),并通过聚合反应将其键合在具有双键的硅胶表面,得到手性固定相(CSP)。用所得到的CSP对9种对映体化合物(丁苯酞、酮基布洛芬、反-2,3-二苯环氧乙烷、安息香、安息香类似物、托葛尔碱、华法令、4,4′-二甲氧基-5,6,5′,6′-二次甲二氧基-2,2′-羰甲基甲酯联苯、4,4′-二甲氧基-5,6,5′,6′-二次甲二氧基-2-羰甲基甲酯-2′-羰甲基乙酯联苯)进行了拆分。考察了CSP制备过程中甲基丙烯酰氯的用量、键合方式以及硅胶     

Weyl谱定理的推广及改进

对Weyl关于二阶奇异微分方程边值问题谱性质的一个定理进行了推广和改进,使得所讨论的方程形式更一般且结果更详细．