DETERMINATION OF EQUILIBRIUM MOISTURE OF SOME CHINESE AND AUSTRALIAN COALS BY PULSE PROTON NMR

The varying temperature pulse proton NMR method was adopted to determine the e-quilibrium moisture content of several Chinese and Australian coals. The pulse proton NMR spec-trometry is sensible to the hydrogen at different physical state which occurs for water when temperature changes through 273 K. The equilibrium water,with some interactions to the coal surface, will not transform from one phase to another while the free water does. The measured results are reasonable comparing to the conventional gravimetric method.

The Equilibrium Moisture Content of Five Lesser Utilized Species of Ghana Contrasted with Three European Species

Equilibrium moisture contents (EMC) of wood species are very necessary in the utilization of these in service. This study investigated the EMC of five lesser utilized species of Ghana and compared it with that of three European species. Sixteen randomly sampled specimens of each of the eight species (heartwood and sapwood) with dimensions 3 cm × 3 cm × 3 cm were exposed at various relative humidity conditions of 30%, 45%, 60%, 75% and 90% in a temperature and humidity-controlled climate chamber at a temperature of 25°C in accordance to German standard DIN 52182. The species are Albies alba, Fagus sylvatica and Picea abies which are European species and Amphimas pterocarpoides, Antiaris toxicaria, Canarium schweinfurthii, Celtis zenkeri and Cola gigantea are wood species from Ghana. Internal wood temperature and humidity were measured with datalogger. Samples were considered to have reached equilibrium at any given humidity when the daily weight changes were less than 0.1 mg according to German standard DIN 52183. After the last measurements of the weight changes, the samples were dried at 103°C until there was a constant weight. The five tropical hardwoods had low sorption values recorded and high sorption values for the European species and this could be attributed to differences in the microstructure of these woods.

Basic density, extractive content and moisture sorption properties of Pinus pinaster wood infected with the pinewood nematode, Bursaphelenchus xylophilus

The pinewood nematode（PWN）, Bursaphelenchus xylophilus, has become one of the most severe threats to pine forest worldwide. Nematodes, migrating through resin canals and feeding on the living cells, induce rapid metabolic changes in ray parenchyma cells, create cavitation areas, decrease xylem water content and oleoresin exudation, and cause necrosis of parenchyma and cambial cells. This study focused on the impact of PWN infection on technological parameters of wood and evaluated the impact of anatomic and biochemical incidences of tree defense reactions on basic density, extractive content and moisture sorption properties of Pinus pinaster wood.Samples of infected and uninfected wood were studied.The presence of nematodes reduced wood basic density by2 % and decreased the total content of extractives in infected wood as compared with uninfected（5.98 and8.90 % of dry wood mass, respectively）. Extractives in infected trees had inverse distribution along the trunk as compared with uninfected trees. The adsorption isotherms for infected and uninfected wood had similar positioning.We recorded differences（some statistically significant） in the equilibrium moisture content of infected and uninfected wood under varying environmental conditions. Despite the verified differences in wood basic density, extractive content and moisture sorption properties, the overall conclusion is that the PWN had a slight impact on these characteristics of wood.

Hygroexpansion of Wood during Moisture Adsorption and Desorption Processes

In order to investigate the shrinking and swelling behavior of wood at a non-equilibrium state, the moisture sorptlon processes of wood under constant and changing conditions were studied. For the static sorption experiment, Chinese fir （Cunninghamia lanceolata） specimens were subjected to the adsorption processes at 25℃, 10 different relative humidity environments and the moisture contents were measured at distinct time intervals of adsorption processes. For the dynamic sorption experiment, the specimens were exposed to periodically and linearly varying relative humidity between 45% and 75% at 25℃. Moisture content as well as radial and tangential dimensional changes in response to the changing relative humidity were measured. The main results from the experiments indicated that： the moisture sorption isotherms of Chinese fir at equilibrium state and different stages of adsorption processes could be characterized by S-shape curves. From the non-equilibrium state to the equilibrium state, the sigmoid moisture sorption isotherms changed from smooth, gradually increasing values to a steep rise at 100% humidity. Furthermore, under dynamic conditions with a constant temperature and a linearly and periodically varying relative humidity, the moisture content as well as radial and tangential dimensional changes of the specimens generally waved but lagged behind the relative humidity change.

Determination of Moisture Sorption Isotherm Characteristics of Dehydrated Sorghum Flour （＂Ogi＂）

Dehydrated sorghum flour （＂ogi＂） is useful as additional ingredient in certain food and pharmaceutical formulation, this could be obtained by soaking sorghum in water for 3 to 4 days, wet milling the soaked material, and fermentation for another 3 to 4 days. Typically, the fermented product is boiled into a pap or cooked into a stiff porridge. However, the fermented product can not be easily handled or stored and does not have a long shelf life （typically less than a week）. Dehydrating the fermented product into flour is one of the ways that is being employed to overcome these problems. Equilibrium moisture content （EMC） of dehydrated sorghum flour （aka ＂ogi＂） was therefore determined at two temperatures of 25℃ and 40℃ and four salt solutions. Zinc chloride （ZnCl2）, potassium acetate （KC2H3O2）, calcium chloride （CaCl2） and sodium chloride （NaCl） salts were prepared to correspond to equilibrium relative humidities of 10.0% to 75.4%. The moisture sorption characteristics of the sorghum product showed the characteristics S-shaped sorption isotherm curve that is typically obtained for agricultural products. The equilibrium data and the monomolccular layer moisture content values were estimated using the Brunauer-Emmett-Teller （BET） equation. The moisture content range for optimum storage of the dehydrated sorghum flour lies between 2.84% to 3.69% at 25℃ and 6.84% and 7.67% at 40℃. The information obtained from this study will help in the design and selection of storage and packaging systems for dehydrated sorghum flour.

The Equilibrium and Growth Stability of Winter Wheat Root and Shoot Under Different Soil Water Conditions

The equilibrium between root, shoot and growth stability under different soil water conditions were investigated in a tube experiment of winter wheat. The water supplying treatments included： sufficient irrigation at whole growth phase, moderate deficiency irrigation at whole growth phase, serious deficiency irrigation at whole growth phase, sufficient irrigation at jointing stage, tillering stage, flowering stage, and fillering respectively, after moderate and serious water deficit during their previous growth stage. Root and shoot biomass were measured. On the basis of the cooperative root-shoot interactions model, the equilibrium and growth stability were studied on the strength of the kinetics system theory. There was only one varying equilibrium point between the root and shoot over the life time of the winter wheat plant. Water stress prolonged the duration of stable growth, the more serious the water deficit, the longer the period of stable growth. The duration of stable growth was shortened and that of unstable growth was prolonged after water recovery. The growth behavior of the plants exposed to moderate water deficit shifted from stable to unstable until the end of the growth, after rewatering at flowering. In the life-time of the crop, the root and shoot had been adjusting themselves in structure and function so as to maintain an equilibrium, but could not achieve the equilibrium state for long. They were always in an unbalanced state from the beginning to the end of growth. This was the essence of root-shoot equilibrium. Water stress inhibited the function of root and shoot, reduced root shoot interactions, and as a result, the plant growth gradually tended to stabilize. Rewatering enhanced root shoot interactions, prolonged duration of instable growth. Rewatering at flowering could upset the inherent relativity during the long time of stable growth from flowering to filling stage, thus leading to unstable growth and enhanced dry matter accumulating rate in the whole plant.

降雨条件下层状土坡三维边坡稳定性分析

降雨是诱发滑坡的重要因素之一,在降雨型滑坡的研究中,关于土壤水分剖面形状动态变化对三维边坡稳定性的影响有待进一步考虑。鉴于此,在前人工作的基础上,本文采用含修正形状系数的形状曲线描述土壤水分剖面的变化,结合非饱和土的水力特性,计算等效渗透系数,推导出改进入渗模型并拓展至双层土体入渗。利用GRASS GIS建立三维边坡模型,选取椭球面作为三维滑动面,通过蒙特卡洛法模拟椭球面参数,确定试算滑动面,采用Hovland三维极限平衡法计算考虑雨水入渗影响的三维边坡安全系数。根据湿润锋面、土层间界面和潜在滑动面三者的相对位置关系,将栅格单元柱分为5种情况考虑。通过算例分析验证所提出的降雨条件下三维边坡稳定性分析方法的可行性,结果表明:蒙特卡洛模拟试算样本数的最佳取值可定为2500次;最小三维边坡安全系数随着降雨历时的增加而减小,减小幅度为0.055~0.126。

七参数多项式方程拟合氦等离子体处理面粉的水分吸着等温线

为了解释小麦面粉经过冷等离子体处理后面团吸水率增加的成因,采用120 W低压强射频氦冷等离子体处理面粉0~180 s,随着等离子体处理时间增加,小麦面粉吸水率、电导率、水和蔗糖溶剂保持力(SRC)值及糊化衰减值显著增加,深入探究这些指标变化原因,我们提出一个七参数多项式M=A+B·t+C·t^(2)+D·t^(3)+E·ERH+F·ERH^(2)+G·ERH^(3)(M是平衡水分%,ERH是小数表示的平衡相对湿度,t是温度℃,A~G是参数),能够拟合氦冷等离子体处理面粉的水分吸着等温线,拟合度指标优于修正Chung-Pfost(常用)和四参数多项式(不含温度项)方程。七参数多项式方程能够清晰显示面粉样品水分吸附与解吸等温线之间的滞后环,随着温度增加,滞后环下移,且滞后度随ERH增加呈现抛物线形状,抛物线顶点在ERH 40%~50%。冷等离子体处理将单分子层吸附位点转变为多分子吸附位点的区域提前了,由ERH 50%转变为40%。用Dent模型分析显示,氦冷等离子体处理能够降低面粉单分子层含水量和扩展压强,增加毛细管壁弹性,水分子与化学成分形成氢键的能力加大,促进水分子向面粉颗粒均匀分布和渗透。红外光谱扫描显示面粉中淀粉粒表面短程有序化程度及淀粉与蛋白的作用程度增大。氦冷等离子体技术在改善面粉加工品质具有应用潜力。

高压注入条件下N_(2)对含水煤中CH_(4)置换效应的影响

为了揭示高压注入条件下N_(2)对不同含水率煤中CH_(4)置换效应影响,基于含水率为0.75%、1.5%和3%的3种煤样,开展了高压注N_(2)置换CH_(4)实验。实验结果表明:随着煤含水率的增加,煤吸附CH_(4)和N_(2)的能力表现出逐渐减弱的趋势,N_(2)的吸附量始终小于CH_(4)的吸附量,且N_(2)置换CH_(4)的能力逐步下降;在本实验压力条件下,CH_(4)预吸附平衡压力超出0.75 MPa越大,其N_(2)利用率越低。同时随煤含水量的增加,CH_(4)置换率、N_(2)注置比均出现逐步减小的趋势,因此可得CH_(4)置换率、N_(2)注置比均与煤的含水量呈负相关关系。实验含水煤样更好的还原井下处于潮湿环境中的原煤,通过CH_(4)置换率和N_(2)注置比的反馈得出,过大的注气压力并不能得到良好的注气效果,反而会降低该置换源气体的利用率,因此对井下注N_(2)置换煤层CH_(4)的工程技术来说,为避免盲目提高注气压力而造成N_(2)的置换效率下降的现象,建议井下煤层注N_(2)置换CH_(4)时,CH_(4)吸附平衡压力控制在0.75 MPa最佳。

温度影响下不同级配生土材料吸湿性能的研究

采用饱和盐溶液法,研究了9种级配生土材料在不同温湿度环境下的吸湿性能。研究结果表明,当环境温度在10~30℃之间时,生土材料的平衡含湿量随着温度的升高呈现出先增大后降低的趋势,在20~25℃区间内平衡含湿量达到最大。低温环境下,级配对生土材料吸湿量的影响相对较小,吸湿速率相对较慢。当土、沙、石比例为28∶67∶6时,生土材料吸湿性能相对较差(最大平衡含湿量约为2.66%);而当土、沙、石比例为45∶13∶42时,生土材料吸湿性能相对较好(最大平衡含湿量约为3.95%)。由此可见,小粒径成分含量高的生土材料展现出更好的吸湿性能。此外,采用数据拟合的方法对不同吸湿性能预测模型进行分析,最终修正了温度因子对预估数值的影响,且修正系数与温度之间符合二次函数关系α=-0.0656t2+0.4185t+0.3033,相关性系数高达0.9354。上述结论为生土材料平衡环境温湿度性能的量化计算提供了科学便捷的方法。

油纸绝缘微水扩散的稳态分布

针对目前缺乏关于任意温度下油纸绝缘中微水稳态分布研究的情况,提出了基于参数拟合的曲面拟合法。利用该方法及现有若干温度点下的分布曲线,分0～60°C和60～1 000°C二区域地拟合出可表征温度、绝缘油及绝缘纸的水分体积分数3者间稳态关系的曲面,从而获得任意温度点下油纸绝缘微水扩散的稳态分布曲线。计算所得曲线与实际数据的比较结果表明该法具有很高的精度。

特高煤级煤平衡水条件下的吸附实验

鉴于国内外对镜质组最大反射率Ro(max)大于4.0%的特高煤级煤的吸附特性研究的空白,作者系统地采集了12个Ro(max)>4.0%的煤样进行了平衡水条件下的高压等温吸附实验,分析了特高煤级煤样的朗格缪尔常数与Ro(max)、显微煤岩组分、比孔容和比表面积的关系,发现了煤的朗格缪尔体积随煤级变化的拐点是在Ro(max)为4.5%左右。在上述研究的基础上,文中探讨了煤的吸附特征及机理。

干制荔枝果肉吸附等温线及热力学性质

为了解干制“乌叶”荔枝果肉含水率与水分活度、贮藏温度之间的复杂关系，并为干制“乌叶”荔枝果肉贮藏条件的确定提供技术依据，运用吸附原理，在水分活度为0.112～0.976范围内，研究了干制“乌叶”荔枝果肉在20、30和40℃时的水分吸附等温线；采用8种模型对试验数据进行拟合，通过比较模型决定系数（R2）和均方根误差确定用于描述干制“乌叶”荔枝果肉吸附等温线的最适模型；通过不同温度下干制“乌叶”荔枝果肉的吸附等温线数据获得净等量吸附热、焓变、熵变和自由能等热力学性质。结果表明，干制“乌叶”荔枝果肉的水分吸附呈Ⅲ型等温线，在相同水分活度时，平衡含水率随温度的升高而下降。Peleg模型用于描述吸附等温线是较适合的，决定系数为R2为0.9950～0.9979，均方根误差为1.9431～2.7102。热力学性质显示，净等量吸附热随含水率的增加而降低，在较高含水率时趋近于0。焓变与净等量吸附热有相同的值，其范围为0.95～186.98 kJ/mol。熵变随含水率的增加而降低，并没有表现出对温度的依赖性。自由能随含水率和温度的增加而减小。焓-熵补偿理论适用于干制“乌叶”荔枝果肉中的水分吸附过程，此水分吸附过程是焓驱动的。研究结果为干制“乌叶”荔枝果肉的加工和贮藏稳定性提供理论依据。

低煤级煤平衡水条件下的吸附实验

基于13个镜质组最大反射率小于0.65%的低煤级煤样平衡水条件下的高压等温吸附实验,分析了低煤级煤的朗格缪尔常数与平衡水分、煤级、显微煤岩组分、比孔容和比表面积之间的关系,揭示了低煤级煤的吸附特征与中、高煤级煤之间的差异,探讨了低煤级煤的吸附机理。

贮藏条件对糙米水分变化的影响规律

为探讨贮藏条件对糙米含水率随时间变化规律,以环境温度和相对湿度为影响因素,采用全因素组合试验方法设计试验,应用静力学法进行了试验研究。利用SAS软件处理试验结果,建立了贮藏环境温度和相对湿度对糙米含水率随时间变化影响规律的数学模型,经检验方程显著性水平小于0.001。研究结果表明,贮藏过程中的环境温度和相对湿度对糙米含水率的变化影响显著,所建立的数学模型可以描述和预测糙米含水率在贮藏仓内的变化规律,指导糙米加工及安全贮藏。

基于平衡水分模型的稻谷含水率实时监测系统

基于静力学谷物平衡水分模型,利用无线传感器网络及嵌入式技术设计了仓储中稻谷含水率实时监测系统。通过试验验证改进Henderson、改进Chung-Pfost和改进Owin模型及对应参数的稻谷含水率预测误差和精度,结果表明改进Chung-Pfost模型具有准确预测的精度,且当参数A=363.06、B=0.180 4、C=26.674时该模型的预测精度较高。通过测试传感器节点的传输质量,表明系统能够实现数据稳定的传输。

平衡含水率法预测死可燃物含水率的研究进展

死可燃物含水率预报是森林火险天气预报的重要内容,准确预测死可燃物含水率是做好森林火险天气预报和火行为预报的关键。平衡含水率法预测死可燃物含水率在物理上十分可靠,若研究对象可精确描述,理论上其含水率的预测是准确的。因此,该方法是重要的可燃物含水率预测方法。本文对该方法的理论基础和应用情况进行综述。结果表明:1)平衡含水率的预测模型主要有4种,其中Simard模型、Van Wagner模型和Anderson模型都是统计模型,其应用具有一定的局限性;而Nelson模型为半物理模型,在预测可燃物含水率上的效果好,应用广。2)可燃物类型影响平衡含水率,但具体机理还没有系统研究。3)对时滞的影响因子研究相对较少。可燃物的种类、物理性质对时滞都有影响。4)现有平衡含水率法中,Catchpole等的方法因采用Nelson的半物理模型而具普适性,有良好的应用前途。5)平衡含水率法在实际预测中得到广泛应用,是美国火险等级系统和加拿大森林火险等级系统及其他类似系统中可燃物含水率预测的主要方法。

采用水分解吸方程估算我国稻谷安全水分

对静态称重法测定的我国稻谷主产区15个品种（包括3个粳稻、10个籼稻、2个糯稻）的解吸等温线数据,分别采用Brunauer-Emmett-Teller（BET）、Guggenhein-Anderson-de Boer（GAB）、修正Chung-Pfost（MCPE）、修正Henderson（MHE）、修正Oswin（MOE）及Strohman-Yoerger（STYE）6个数学模型进行拟合,MCPE被判定为稻谷最佳解吸等温线模型。稻谷的解吸特性受产地影响较小。以M=f（hr,t）形式表达的平均解吸等温线方程MCPE的3个参数C1、C2及C3各是502.485、45.276及0.186。在70%相对湿度下,推导10、15、20、25、30及35℃条件下15个稻谷品种平均解吸值,分别是14.83%、14.49%、14.13%、13.88%、13.61%及13.35%。尤其是在RH 70%、30~35℃条件下,稻谷解吸水分范围是13.61%~13.35%,与规定的稻谷安全储藏水分13.5%近似。

几种细小可燃物失水过程中含水率的变化规律

对樟子松落叶、水曲柳落叶、水曲柳细、粗枝在Z0℃、78％相对湿度条件下的失水过程进行测定．获取相应过程动态方程所需参数——平衡含水率和水份交换导度。据此建立了相应条件下4种可燃物含水率时间动态方程。介绍了有关计算方法。并对平衡含水率Mc及比例系数片进行了讨论.为林火预测预报提供了理论基础。

玉米平衡水分测定及等温线方程确定

采用静态称重法对6个玉米品种的吸附/解吸等温线进行测定,并用6个非线性回归方程描述吸附/解吸等温线,修正Chung-Pfost方程(MCPE)、修正Henderson方程(MHE)、修正Oswin方程(MOE)及Strohman-Yoerger方程(STYE)均在ERH 11.3%～96%范围内适合描述玉米等温线,其中最佳数学模型是MCPE,以M=f(ERH,t)形式表达的M=-1/C3×ln[-1/C1×(t+C2)ln(ERH)],C1、C2及C3参数对吸附数据分别是863.159、108.443及0.216,对解吸数据分别是581.393、35.840、0.235,平均数据是655.792、59.035、0.225。分析MCPE方程预测的6个玉米品种解吸或吸附等温线之间的差异,6个品种解吸等温线之间有差异,但是6个品种吸附等温线之间没有差异。解吸与吸附等温线之间存在滞后现象。