方阵的相似占优与非异性

利用方阵的对角占优性判断方阵的非异性迄今已有不少结果,本文拟从方阵的行(列)占优[即每行(列)中的占优元素位于不同列(行)]这一条件来进行讨论,先引入相似占优与相似对角占优等概念,进而给出方阵为非异的充分必要条件,井推广[1]中的一些结论。     

广义严格对角占优矩阵的判定方法

基于对角占优矩阵和α-对角占优矩阵的概念,给出了广义严格对角占优矩阵的新的判定方法,推广并改进了文献已有的结果.     

一个带有比例接种疫苗丧失率的双菌株传染病模型的稳定性

讨论了带有比例接种疫苗丧失率的双菌株传染病模型,给出了该模型基本再生数和侵入再生数的表达式,分析了无病平衡点、菌株占优平衡点、共存平衡点的存在性和稳定性.     

广义Ostrowski对角占优矩阵与非奇异H-矩阵的判定

设A=(aij)∈Cn×n,若α∈(0,1),使i∈N+,有|aii|≥Riα(A)S1i-α(A)成立,则称A为Ostrowski对角占优矩阵;推广Ostrowski对角占优矩阵的概念到广义Ostrowski对角占优矩阵;得到了判别非奇异H-矩阵的一个判定方法.进一步丰富和完善了Ostrowski对角占优矩阵和非奇异H-矩阵的理论.     

对角占优矩阵和块对角占优矩阵的判定

基于α-对角占优矩阵概念,给出了广义严格对角占优矩阵新的判定条件,改进和推广了先前有关文献的相应结果.     

广义α-双链对角占优矩阵的判定

设A=(aij)∈Cn×n,若α∈(0,1),i,j∈N,i≠j,有|aii | |ajj|≥Rαi (A)Rαj(A)S1-αi(A)S1 -αj(A)成立,则称A为α-双链对角占优矩阵.为给出H-矩阵的判别条件,首先推广α-双链对角占优矩阵到广义α-双链对角占优矩阵,然后得到了判别广义α-双链对角占优矩阵的一个充分条件,改进和推广了已有的结论,进一步丰富了广义α-双链对角占优矩阵和非奇H-矩阵的理论.     

严格积γ-对角占优矩阵的三角-schur补

为了深入研究schur补的适用范围,引入了三角-schur补(diagonal-schur补是其当θ=π/2时的特殊情况),利用严格积γ-对角占优矩阵的矩阵性质,证明得到了严格积γ-对角占优矩阵的三角-schur补仍是严格积γ-对角占优矩阵,最后应用数值例子进行了验证.     

严格γ-对角占优矩阵的三角-schur补

为了进一步研究一类特殊矩阵严格γ-对角占优矩阵的相关schur补性质,本文对其在schur补及diagonal-schur补概念的基础上进行了推广从而得到三角-schur补.利用该矩阵本身的性质证明了严格γ-对角占优矩阵的三角-schur补仍然是严格γ-对角占优矩阵(其中当θ=π/2时,diagonal-schur补是三角schur补的一种特殊情况),最后利用数值算例验证了其有效性.     

永磁无刷直流电机在打草机设计中的应用研究

结合永磁无刷直流电机设计和应用,以Φ300 mm、DC36 V打草机为例,从电池包空载放电时间、切割效率、单电池包工作时间、抗过载性及结构优化设计等五个方面分析永磁无刷直流电机与永磁有刷直流电机的区别,得出永磁无刷直流电机性能占优的结论。     

非奇异H-矩阵的一个新的判别定理

为得到H-矩阵的一个简捷判别方法,首先将Ostrowski对角占优矩阵的概念推广到广义Ostrowski对角占优矩阵.结合不等式的放缩技巧,得到了判别非奇异H-矩阵的一个判定方法.从而改进和推广了相应的结果,并给出相应的数值例子说明结果的有效性.     

预处理对六种黄酒酿造原料酿造特性的研究

为探究不同黄酒酿造原料的酿造特性,以红谷、张杂谷、圆糯米、黍米、金米、粳大米等六种谷物为原料进行浸泡和蒸饭实验,监测浸泡过程中不同原料质构和色泽的动态变化;比较了浸泡后六种米浆水的有机酸和氨基酸组成;并对蒸饭中挥发性风味物质的含量进行分析。结果表明,浸泡过程中六种谷物的颜色和质构参数存在显著差异（P＜0.05）。红谷米浆水的总氨基酸含量最高（976.49 mg/L）,乙酸、酒石酸和柠檬酸含量显著高于其他谷物米浆水的相应含量（P＜0.05）。六种谷物蒸饭样品中共检出165种挥发性成分,其中红谷蒸饭中酸类（11.75 μg/100 g）和酚类含量（10.54 μg/100 g）远高于其他谷物。综上所述,红谷米浆水中氨基酸含量以及蒸米中酸类香气成分较高,这有利于发酵醪的进一步微生物发酵。     

Quantification of skin penetration of antioxidants of varying lipophilicity

Antioxidants play a vital role in protecting the skin from environmental distress. As the skin is constantly exposed to harmful UV radiation, endogenous antioxidants present in the superficial layers of the skin neutralize reactive oxygen species. Over time, antioxidants become depleted and loss their protective effect on the skin. Therefore, supplementing skin with topical antioxidant can help replenish this loss and fight the oxidative stress. The objective of this study was to deliver antioxidants topically and quantify the amount permeated in the stratum corneum and underlying skin. Polyphenols (catechin, resveratrol and curcumin) and vitamin (retinol) with various lipophilic properties were delivered via porcine ear skin, using propylene glycol as a vehicle. The amount in the stratum corneum and underlying skin was quantified using tape stripping and skin extraction methods, respectively, and samples were analysed via HPLC. All four antioxidants permeated into the skin from the propylene glycol vehicle. The order of the amount of antioxidant in the stratum corneum was catechin > resveratrol~ retinol> curcumin, whereas that in the underlying skin was retinol > catechin~ resveratrol~ curcumin. Of the total amount of polyphenols in the skin, approximately 90% was retained in the stratum corneum whereas 10% was quantified in the underlying skin. In contrast, 10% of retinol was retained in the stratum corneum whereas 90% permeated in the underlying skin. Polyphenols (catechin, resveratrol and curcumin) showed high concentration in the stratum corneum whereas retinol showed high accumulation in the underlying layers of the skin.     

水氯镁石脱水研究的进展及展望

本文介绍了几十年以来水氯镁石脱水研究的进展，给出了该项研究在热力学、动力学以及相平衡领域中的最新成果，并介绍了脱水过程中关键技术难题以及该项目研究目前存在的问题。同时，预测了该研究项目工业应用前景。     

木瓜蛋白酶的提取及应用研究进展

本文主要介绍木瓜蛋白酶的组成,重点阐述提取方法、提取工艺的研究进展,进一步介绍木瓜蛋白酶在食品工业特别是在食品加工中的应用,并对其在医药、化工及未来食品加工方面的应用前景进行展望。     

Mechanisms of oxidative browning of wine

Oxidative browning is a long-standing problem in winemaking and sulphur dioxide is the generally used antioxidant to control wine browning. However, concerns over its ability to induce severe allergic reactions have created a great need for its reduction or replacement in recent years. Furthermore, ascorbic acid seems unsuccessful as an alternative antioxidant in winemaking. So a comprehensive understanding of the chemistry of wine browning is essential to study new antioxidant(s) for the protection of wine from browning. The review systematically outlines the mechanisms of wine browning including enzymic and non-enzymic browning happening in winemaking and discusses the central roles performed by iron and copper in the chemistry of wine oxidation. Iron and copper might play a central role in initiating wine non-enzymic browning, and this has important implications in studying antioxidant substitute for sulphur dioxide in wine.     

葵花籽油中酸价测量结果的不确定度评价

目的 分析食用油中酸价测定的不确定度来源并建立不确定度评定方法, 为检验数据的可靠性和准确性提供参考。方法 依据GB 5009.229-2016《食品安全国家标准 食品中酸价的测定》和JJF 1059.1-2012《测量不确定度评定与表示》建立数学模型, 计算各变量的不确定度, 最终计算扩展不确定度。结果 结果显示, 样品中酸价的扩展不确定度为U=1.764×10?3 mg/g, 样品中酸价含量为(0.16±0.002) mg/g(置信水平95%, 包含因子k=2)。结论 在测定过程中, 测量重复性对总的不确定度影响最大, 其次是滴定管的体积。     

葡萄酒中单宁含量调查与口感关系的分析

目的 通过测定不同产地、不同品种、不同类型的524支进出口葡萄酒中单宁的含量,进一步分析葡萄酒中的单宁与口感质量的关系。方法 将样品用蒸馏水稀释100倍,以没食子酸为标准物质,采用分光光度法对葡萄酒中的单宁进行定量分析。结果 该方法简单可靠,试剂用量少,操作方便,快速准确,仪器设备简单。在0 mg/L~5.0 mg/L范围内线性关系良好,相关系数为0.9999;单宁添加回收率在86.7%~120%之间,平均回收率达103.8%。产地方面,意大利的红葡萄酒中单宁含量最高,平均为2.70 g/L;品种方面,黑皮诺酿造的红葡萄酒中单宁含量较多,平均含量为3.15 g/L;国产葡萄酒方面,云南产区的葡萄酒中单宁含量相对较高,平均为2.51 g/L。结论 葡萄酒中单宁含量与葡萄品种、产地、酒类型有关;柔顺指数超过5.0的葡萄酒,口感与品质良好。     

Mechanism of Prevention of Aggregation of Proteins: A Case Study of Aggregation of α-Globulin in Glycerol

The precipitation of proteins due to the changes in pH has been a major limiting factor in their utility especially when the precipitation is concurrent with irreversible aggregation. In the present study, an attempt is made to see the effect of glycerol on the pH-induced aggregation of α- globulin which is the major protein fraction (11S) from Sesame (Sesamum indicum L.) seeds. A second order polynomial relation existed between the cosolvent concentration and precipitation which was prevented in presence of the cosolvent. Similarly, there was a second order polynomial relation between 8-anilino 1-naphthalene sulfonic acid (ANS) binding of the protein (as indicated by fluorescence emission at 466 nm) and the cosolvent concentration. The relative precipitation in presence of glycerol is however linearly proportional to the changes in surface hydrophobicity as seen by behavior of ANS with the protein in presence of the cosolvent. A possible role of the cosolvents in prevention of aggregation due to hydrophobicity of the protein is envisaged and the relation between the different parameters is discussed.     

不同品种小米对黄酒风味影响的研究

为探究不同品种的小米原料对黄酒的挥发性风味成分的影响，该实验利用顶空固相微萃取（HS-SPME）提取技术和气相色谱-质谱联用（GC-MS）检测技术，测定了不同品种小米酿制的黄酒中的风味物质的种类和含量。结果表明，从5个品种小米黄酒共检测出222种风味物质，黄金1号、小香谷、大金苗、晋谷21及东方亮所酿小米黄酒分别检测出56、92、98、81、74种风味物质，酯类和醇类化合物为小米黄酒的主要风味物质，5个品种小米黄酒中共有的风味物质为β-苯乙醇、辛酸乙酯、己酸乙酯、丁二酸二乙酯、乙酸乙酯，各个品种的小米黄酒都有其独特的风味物质。说明不同品种小米对黄酒酿制中产生的挥发性风味成分种类与含量都有较大的影响，进而影响小米黄酒的综合口感。     

Determination of aflatoxins in by-products of industrial processing of cocoa beans

This study has examined the occurrence of aflatoxins in 168 samples of different fractions obtained during the processing of cocoa in manufacturing plants (shell, nibs, mass, butter, cake and powder) using an optimised methodology for cocoa by-products. The method validation was based on selectivity, linearity, limit of detection and recovery. The method was shown to be adequate for use in quantifying the contamination of cocoa by aflatoxins B₁, B₂, G₁ and G₂. Furthermore, the method was easier to use than other methods available in the literature. For aflatoxin extraction from cocoa samples, a methanol–water solution was used, and then immunoaffinity columns were employed for clean-up before the determination by high-performance liquid chromatography. A survey demonstrated a widespread occurrence of aflatoxins in cocoa by-products, although in general the levels of aflatoxins present in the fractions from industrial processing of cocoa were low. A maximum aflatoxin contamination of 13.3?ng?g^?1 was found in a nib sample. The lowest contamination levels were found in cocoa butter. Continued monitoring of aflatoxins in cocoa by-products is nevertheless necessary because these toxins have a high toxicity to humans and cocoa is widely consumed by children through cocoa-containing products, like candies.