基于扩散理论的华北春玉米生理成熟后籽粒脱水过程分析

玉米机收籽粒可以显著提高玉米的生产效率,是玉米生产的发展方向。生理成熟后的籽粒含水率是决定机收质量的关键,受品种、密度和气候等多种因素影响。准确估算生理成熟后玉米籽粒含水率,进而分析其主要影响因素,最终确定玉米收获时间和筛选适宜机收的品种,对玉米主产区华北的春玉米籽粒机收发展具有重要意义。因此,于2017年和2018年在河北省泊头、南大港、玉田和山西榆次进行了两年田间春玉米试验,每年设置7个共性品种,每个品种3个密度,对生理成熟后籽粒含水率、品种性状、气象和管理要素进行了监测,并利用基于扩散理论考虑空气温湿度的脱水模型对籽粒含水率进行了模拟,进而计算脱水曲线下的面积(AUDDC),用以筛选脱水优异的玉米品种。结果表明,基于扩散理论的籽粒脱水模型对玉米生理成熟后籽粒含水率的模拟效果较好;年份、地点和品种对生理成熟时籽粒含水率(M_0)和水分扩散速率(k)具有显著影响,密度对脱水参数影响不显著。逐步线性回归分析得到灌浆期参考作物蒸发蒸腾量(ET_0)、最高气温和灌水量对M_0具有显著的正效应,生理成熟后30 d内ET0和灌浆中后期降雨对k具有显著的正效应,全生育期降雨对k具有显著的负效应。品种性状中对M_0影响最大的为苞叶层数(正效应),对k影响最大的为叶片数(负效应)。通过模型计算得到,生理成熟后10d华北地区春玉米籽粒含水率可以下降到28%,籽粒含水率下降到25%的概率为50%。由模型计算得到各品种生理成熟后10 d内的AUDDC,与AUDDC平均值比较发现‘京农科728’‘张1453’‘华农887’‘广德5’和‘金科玉3306’为脱水表现优异的品种。     

泡桐木材流体渗透性与扩散性的研究

本文论述了泡桐木材流体渗透性,扩散性,吸着水与自由水的吸着与吸收动力学特性,密度和干缩性以及电镜观察结果;阐明了泡桐木材具有流体可渗透及可扩散路径,有着输导流体的天然机制,水、热处理难易一般;泡桐材本身并不具有隔潮耐湿性,但由于它密度低,胀缩小,变形和开裂的可能性亦小,用它干燥后制成的箱盒容器的密封性、隔潮耐湿性较好。     

Application of a modified rate equation to the acetylation of wood

A modified rate equation, in which the diffusion of reagent was taken into consideration, was proposed and applied to results reported previously for the acetylation of wood. The equation was fitted more successfully to the prolonged as well as the early stage of the reaction than a common first-order rate equation. Although the conclusions were virtually unchanged, the reliability was enhanced because reaction parameters such as the rate constant, ultimate extent of the reaction, and activation energy calculated for the modified equation were based on much more data than those reported previously. The equation proposed here may be applicable not only to acetylation but to other chemical modifications of cellulosic materials in heterogeneous systems.     

川南地区1989—2019年农业干旱危险性特征分析

旨在研究川南地区近30年农业干旱危险性特征。基于川南地区（内江市、自贡市、宜宾市、泸州市）1989—2019年夏季（6—8月）降水数据,组成了降水距平百分率和农业干旱危险性等级之间的模糊隶属函数,通过引入区间平均隶属度,将信息扩散理论与之结合,研究了川南经济区的农业干旱危险性特征。结果显示：轻、中度农业干旱危险性水平最大的都是泸州市,危险性水平分别达21.47%、15.32%;重度农业干旱危险性水平最大的是自贡市,其危险性水平达7.58%;严重农业干旱危险性水平最大的是宜宾市,其危险性水平达7.47%。     

Influence of processing temperature on the water vapour transport properties of wheat gluten based agromaterials

The influence of processing conditions (thermoforming temperature) on water vapour transport properties (permeability, sorption and diffusion) of wheat gluten-based films was studied in relation to structural properties (cross-linking degree of the wheat gluten matrix). Increasing temperature from 80 °C to 120 °C led to a significant decrease in material swelling in high moisture environment and a WVP reduction mainly due to a decrease in diffusivity but without important effect on the moisture sorption isotherms. This was attributed to a higher cross-linking degree of protein network for film thermoformed at 120 °C, with a limited mobility and less possibilities of rearrangement in high moisture conditions.     

《大学图书馆学报》期刊引用认同实证研究

引用认同是Howard D.White在2001年提出的,它同时对引用和施引期刊进行研究,获得了有关引用的全景,有助于了解期刊之间在研究领域、学术思想上的联系。以CSSCI《大学图书馆学报》2000-2009年的数据为研究对象,采用文献计量学的方法,从自引率、自被引率和同被引等方面来研究期刊的引用认同,分析比较了《大学图书馆学报》与图书情报领域其它期刊的关系密切程度,同时还引进了新期刊扩散因子的概念作为期刊影响因子的补充指标,对《大学图书馆学报》进行分析和评价,揭示该刊的学术水平和办刊质量,为该刊今后的发展及研究提供参考数据。     

一种纤维素酶产生菌的筛选方法

[目的]获得一种简单高效的纤维素酶产生菌的筛选方法。[方法]基于扩散原理,采用滤纸条扩散试验筛选纤维素酶产生菌。[结果]获得2株纤维素酶产生菌菌株X1和X2。经DNS法检验,菌株X1的FPA酶和CMC酶活力分别为12.3和8.3 U,菌株X2的FPA酶和CMC酶活力分别为8.8和7.8 U。[结论]滤纸条扩散试验可作为一种便捷高效的筛选高质量纤维素酶产生菌的方法。     

A comparison of regression methods for estimating soil-atmosphere diffusion gas fluxes by a closed-chamber technique

Continuous changes in methane (CH₄) and carbon dioxide (CO₂) concentrations inside a closed chamber were measured on the forest floor at three sites: a deciduous forest and a coniferous forest in Hokkaido, Japan, and a birch forest in West Siberia, Russian Federation. Flux estimations by three types of regression methods, exponential, nonlinear, and linear, were examined using field-collected concentration data. The pattern of change with time of the gas concentration in the headspace differed, mainly according to site but also, to a lesser extent, according to the gas. This was a function of both the chamber height and surface soil property relating to soil gas diffusion and the gas concentration profile. Flux estimations did not differ statistically between the exponential and nonlinear methods for either gas at any site, because both of those regression methods were based on diffusion theory. However, the flux values estimated by linear regression were significantly different from those estimated by the other two methods for both CH₄ and CO₂ at the deciduous forest site and for CO₂ at the coniferous forest site. Shortening the chamber deployment period improved the linearity of the curve, but did not completely eliminate the error. Our results suggest that linear regression is not a good model of the change in headspace concentration with time.     

What determines the temperature response of soil organic matter decomposition?

The temperature dependence of litter and soil organic matter (SOM) mineralisation is important because it determines how strong the feedback from the expected warmer climate may be on the atmospheric CO₂ concentration. We have used a simple, analytical model to investigate how three different mechanism (i) the rate at which decomposers take up substrate at their surface; (ii) the rate by which substrate diffuses up to the surface of the decomposer; and (iii) the rate at which substrate is made available in the environment interact to determine the temperature response. The mechanisms are characterised by activation energies; two for the uptake rate (i) and one for each of the other two (ii, iii). The model shows that the temperature dependence is the result of the number of processes that effectively contributes to the rate of mineralisation; this result should also be valid if other processes are included. Depending upon the relative magnitude of the four activation energies, the temperature response is mainly determined by one or two of the mechanisms. In a transition zone, where all activation energies are similar and the number of contributing processes changes, there can be either a sharp increase or a sharp decrease in the temperature response when activation energies change.     

土壤磷扩散规律及其能量特征的研究──Ⅰ．水分、质地、温度及其相互作用对磷扩散的影响

用＾３２Ｐ示踪扩散池和扩散管法测定了４种不同质地土壤在不同含水量和温度下的磷自扩散系数。结果表明，非饱和土壤磷扩散系数随土壤水分含量增加或土壤水吸力减小而增大，符合幂函 数Ｄａ＝ａＷ＾ｂ＝ａＳ＾－ｂ关系；质地对磷扩散的影响与土壤水分条件密切相关，在同一含水量下，轻质土壤Ｄａ值大于粘质土，Ｄａ与粘粒含量呈显著负相关，而同吸力下与此恰好相反。饱和土壤磷扩散系数比Ｄａ值通常大２－３个数量级，但不同土壤之