Investigating spatial and temporal variations of soil moisture content in an arid mining area using an improved thermal inertia model

Mining operations can usually lead to environmental deteriorations. Underground mining activities could cause an extensive decrease in groundwater level and thus a dramatic variation in soil moisture content（SMC）. In this study, the spatial and temporal variations of SMC from 2001 to 2015 at two spatial scales（i.e., the Shendong coal mining area and the Daliuta Coal Mine） were analyzed using an improved thermal inertia model with a long-term series of Landsat TM/OLI（TM=Thematic Mapper and OLI=Operational Land Imager） data. Our results show that at large spatial scale（the Shendong coal mining area）, underground mining activities had insignificant negative impacts on SMC and that at small spatial scale（the Daliuta Coal Mine）, underground mining activities had significant negative impacts on SMC. Trend analysis of SMC demonstrated that areas with decreasing trend of SMC were mainly distributed in the mined area, indicating that underground mining is a primary cause for the drying trend in the mining region in this arid environment.

Opto-thermal Moisture Content and Moisture Depth Profile Measurements in Organic Materials

Opto-thermal transient emission radiometry(OTTER) is a infrared remote sensing technique, which has been successfully used in in vivoskin moisture content and skin moisture depth profiling measurements. In present paper, we extend this moisture content measurement capability to analyze the moisture content of fruit(tomato, grape, etc.) skins, and to study the relationship between fruits ripening process and their surface moisture and moisture depth profiles.

Research on the Estimation Model of Soil Moisture Content Based on the Characteristics of Thermal Infrared Data

With the portable Fourier Transform Infrared Spectroscopy (FTIR), the reflectance spectra of soil samples with different moisture content are measured in laboratory for expounding the characteristic of radiation in the thermal infrared part of the spectrum with different soil moisture content. A model of estimating the moisture content in soil is attempted to make based on Moisture Diagnostic Index (MDI). In general,the spectral characteristic of soil emissivity in laboratory includes the following aspects.Firstly,in the region of 8.0-9.5 μm,along with the increase of soil moisture content,the emissivity of soil increases to varying degrees. The spectral curves are parallel relatively and have a tendency to become horizontal and the absorbed characteristic of reststrahlen is also weakened relatively with the increase of soil moisture in this region.Secondly,in the region of 11.0-14.0 μm,the emissivity of soil has a tendency of increasing.There is an absorption value near about 12.7 μm. As the soil moisture content increases,the depth of absorption also increases. This phenomenon may be caused by soil moisture absorption. Methods as derivative, difference and standardized ratio transformation may weaken the background noise effectively to the spectrum data. Especially using the ratio of the emissivity to the average of 8-14 μm may obviously enhance the correlation between soil moisture and soil emissivity. According to the result of correlation analysis, the 8.237 μm is regarded as the best detecting band for soil moisture content. Moreover,based on the Moisture Diagnostic Index ( MDI) in the 8.194-8.279 μm, the logarithmic model of estimating soil moisture is made.

Microstructure and Properties Characterization of WC-Co-Cr Thermal Spray Coatings

WC-Co-Cr coatings are widely employed due to their improved wear resistance and mechanical properties, however, the properties and performance of these coatings are compromised by the processing parameters of each spraying technique. Therefore, this study is aimed to evaluate and determine the effect of the deposition parameters on the properties and microstructural characteristics of WC-Co-Cr coatings using a more economical thermal spray technique. In particular, the influence of flame spray parameters on the microstructure, crystal structure, hardness, and sliding wear resistance of WC- Co-Cr coatings was examined. Two parameters were considered: Type of flame (reducing, neutral and oxidizing), and the spray torch nozzle exit area. Results indicated that WC particles undergo considerable degree of decarburization and dissolution during spraying, showing substantial amounts of W2C, W, and Co3W3C, for all the considered conditions. However, the extent of phase transformation depended largely on the flame chemistry. The microstructure of the coatings was mainly affected by the spray nozzle. Regarding the sliding wear behavior, the coatings with uniform distribution of hard particles provided the best wear resistance. The decomposition of WC into W2C phase seems to have meaningless significance in the mass loss, nevertheless, the WC phase transformation to metallic tungsten and η-phase (Co3W3C) produce higher wear rates due to deficiency of carbide particles and embrittlement of the binder phase which induces cracking and delamination of the splats.

Thermal Diffusion in Masson Pine Wood

In order to analyze the effects of the temperature gradient on moisture movement during the highly intensive microwave-vacuum drying, thermal diffusion of Masson pine wood was studied. Internal distribution of temperature and moisture in Masson pine samples sealed by epoxy resin and aluminum foil was measured, the magnitude of thermal diffusion was calculated and the influencing factors of thermal diffusion were discussed. Results showed that with the transfer of moisture toward the low temperature in wood, opposite temperature and moisture gradient occurred. The initial moisture content （MC）, temperature and time are important factors affecting this process; the thermal diffusion is in proportion to wood temperature, its initial moisture and time. The temperature and distance from hot surface is strongly linearly correlated, and the relationship between MCs at different locations and distance from the hot end surface changes from logarithmically form to exponentially form with the increase in experimental time.

Soil Thermal Diffusivity of a Gleyic Solonetz Soil Estimated by Different Methods in the Brazilian Pantanal

The soil temperature is an important microclimatic factor due to the interactions between soil and plant, and the energy exchange with the atmosphere. The soil energy exchange is affected by the incident solar radiation, type of coverage and mainly by the soil thermal properties. Among the soil thermal properties, the soil thermal diffusivity is highlighted because it affects the soil temperature profile and soil heat flux transport and distribution. Thus, the aim of this study was to evaluate different estimates of soil thermal diffusivity of a Gleyic Solonetz soil in the Brazilian Pantanal. The soil thermal diffusivity was determined by the amplitude, logarithmic, arctangent and the phase methods between 0.01 and 0.03 m, 0.01 and 0.07 m and 0.01 and 0.15 m depth. The soil thermal diffusivity estimated by the four methods showed significant differences and varied over the study period as a function of volumetric soil water content. The soil thermal diffusivity estimated by logarithmic methodshowed better performance at different depths, followed by the method of phase.

Effect of Low Content Chlorophyll on Distribution Properties of Absorbed Light Energy in Leaves of Mutant Rice

This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, and analyzed the difference of absorbed light distributionbetween the two rice varieties in a day. The results showed that the mutant had poor absorbedlight because of its little light absorption coefficient, but higher electron transportg ratecould partly reduce the disadvantageous effect of deficient absorbed light in mutant. Comparedwith wild-type rice, the mutant had less excess excitation energy and the fraction of absorbedlight allocated to photochemical process was more.

火电灵活性改造中大量补水除氧技术探讨

针对灵活性改造中常遇到的大量补水工况,探讨了真空热力除氧关键技术。结合凝汽器热力除氧一般原理和关键环节,对某300MW机组的实测结果进行了分析。分析结果表明,凝汽器在切缸运行工况可以胜任大量补水除氧的任务。相较于常规的凝汽器热力除氧,机组运行大量补水时喷淋除氧布置、管束流场规划、循环水运行、抽真空设备等方面需要进行一定程度的优化。

S波段变频微波方腔干燥PET切片的研究

目的针对聚对苯二甲酸乙二醇酯(PET)材料传统干燥方式能耗高、效率低等不足,运用微波干燥材料具有速度快、效率高、易于控制的特点,研究微波深度干燥PET技术并研制实验装置。方法提出微波变频和变功率加热干燥技术,通过主动调整频率改善微波均匀性,结合微波变功率技术,控制PET材料温度在170~180℃,提升PET材料温度均匀性,并防止“热失控”现象的发生。结果当干燥时间为2 h时,实现了PET深度干燥,能耗率为1.03 kW·h/kg,含水率降低至0.01%以下,达到了后续包装材料注塑加工的要求。结论微波变频变功率加热技术适用于低含水率PET的深度干燥,比传统干燥方式能耗低并且时间短。

电渗热固结处理顶管废弃泥浆的减量化研究

针对顶管废弃泥浆渗透性差、含水率高、承载力低等特点,采用电渗热固结法对其进行减量化研究,并探究不同温度条件下电渗热固结的处理效果。选取EKG电极板作为电极,分析在40℃、60℃、80℃等不同加热温度下,泥浆固化过程中的排水量、排水速率、温度、电流等参数的变化趋势,对比电渗热固结前后泥浆的物理力学特性变化。结果表明:电渗热固结能够有效促进泥浆的排水,提高固结效率,降低含水率,增强固化泥浆的承载力和抗剪强度;在其加热到一定程度时,裂缝进展过快,泥浆导电性减弱,加热效率降低,且加热的温度越高,加热效率越低;电渗热固结对顶管废弃泥浆减量化应用具有一定的有效性与可行性。本文的研究成果可为其实际工程应用提供借鉴与参考。

花生硬脂的性质研究

为解决花生硬脂(peanut stearin,PeS)目前存在的研究不足、应用局限及附加值低等问题,以工厂中花生油冬化产物(3种PeS)为原料,对其理化性质进行分析,并利用差示扫描量热法、X射线衍射及偏光显微镜对其热力学性质、同质多晶性质和晶体微观形态进行研究。结果表明:PeS的脂肪酸组成以油酸(O,31.56%~35.77%)、亚油酸(L,33.40%~35.98%)、棕榈酸(P,11.94%~14.11%)和硬脂酸(St,7.00%~8.83%)为主,此外,还含有部分二十碳及以上的超长链脂肪酸(9.33%~12.12%);PeS的碘值(Ⅳ)为85.33~93.53 g/100 g;0~25℃时PeS的滑动熔点随Ⅳ的降低而升高;PeS分别在-30~0℃和0~25℃出现了2个较强、较宽的吸热峰,在-20~20℃出现了1个较宽的放热峰;PeS晶型为β′型,晶体形态为羽毛叶片状,晶簇呈花瓣状聚集;15℃时PeS的等温结晶行为均为一步结晶,但其滞后期有所不同。PeS通过与其他硬脂混合或酯交换,可用作塑性脂肪的基料油。

考虑有机质含量及分解度的草炭土导热系数模型改进

土壤导热系数是决定土层传热性能的主要参数,影响到地温分布、土壤环境及作物生长。高有机质土的导热系数受到有机质组分直接影响,而目前土壤导热系数模型缺乏对有机质含量及分解度的考虑。该研究采用稳态比较法测定了未冻结及冻结状态下的草炭土导热系数,分析了不同层位原状草炭土性质对导热系数的影响,对比了10余种土体导热系数计算模型对草炭土的适用性,并以此提出了改进模型。结果表明:1)各层位草炭土在未冻结状态下导热系数相近(0.51~0.66 W/(m·K)),而冻结后导热系数层间差异明显(1.00~1.62 W/(m·K)),表明冻结极大地改变了土体物质组成,而有机质含量及分解度显著影响着土体的传热性质;2)考虑了干密度及组分权重的土体导热系数模型对草炭土的预测适用性更佳,但准确度仍然难以达到理想效果;3)基于土体性质的影响程度及计算模型的原理,引入草炭土有机质含量O_(c)及分解度D_(d)计算草炭土导热系数,建立了改进模型,提高了参数模型准确率(R^(2)>0.75)。研究成果可为季冻草炭土分布区的农业耕作及工程建设提供参数依据,同时可作为高有机质土体热物理性质研究的理论参考。

传统广式烤鸭烫皮工艺中蛋白质变性与品质关系分析

以樱桃谷鸭为原料,研究了烫皮过程温度变化和烫皮前后的水分、色泽、蛋白变性、显微结构等变化规律。结果表明:90~95℃,5 s的烫皮程度已达到传统烫皮感官要求,鸭皮表面温度到达80℃以上,皮内温度达到45℃以上;晾皮失水速度差异不显著(P>0.05),与鸭皮中的蛋白质变性程度测定(DSC)实验结果一致,显示该温度下蛋白发生变性、聚集。进一步探究90℃烫皮条件,结果表明,90℃烫皮7 s(90℃-7 s)晾皮3 h(含水量22.01%)比90℃烫皮9 s(90℃-9 s)晾皮4 h(含水量20.52%)膨化效果更好;DSC数据也显示90℃-7 s蛋白质热聚集程度大于烫皮5 s(P<0.05),90℃-9 s的样品蛋白质存在凝胶结构。综上所述,传统广式烤鸭鸭皮脆化与膨化的核心是控制烫皮后鸭皮中蛋白质处于变性聚集的状态及此状态下皮的水分含量,研究结果为探究传统广式烤鸭烫皮机理并为其烫皮工艺改良提供理论支持和技术参考。

银含量对快速热冲击下Sn−xAg−0.5Cu焊点显微组织和力学性能的影响

使用高频感应加热设备研究Ag含量对快速热冲击下Sn−xAg−0.5Cu焊点的显微组织和剪切强度的影响。结果表明,Ag含量的增加使焊点表面更致密光滑,减少焊点内部长条状Cu6Sn5金属间化合物(IMC)的产生,从而提高焊点的抗氧化性。Ag能够加快焊点界面IMC层的生长速度,Cu6Sn5层的生长速度由体扩散和晶界扩散共同决定,Cu3Sn层的生长速度由体扩散和界面反应共同决定。在快速热冲击环境下,焊点的断裂模式从韧性断裂转变为脆性断裂,而高Ag含量使得焊点的断裂模式转变时间更短,降低焊点的抗热疲劳性能。

绝缘纸在矿物油与菜籽油基天然酯中的加速热老化特性分析

天然酯较矿物绝缘油具有燃点高、可降解性好并且能延缓绝缘纸热老化速率等优点,作为提升变压器寿命或短时过载能力的液体绝缘介质正受到广泛关注。本文选取我国食用油中占比较大的菜籽油作为基油制备天然酯绝缘液,通过试验比较不同含水量绝缘纸在菜籽油基天然酯和矿物油中的加速热老化特性,并研究了氧气对绝缘纸在两种不同绝缘液中的加速热老化特性的影响。结果表明:在相同温度下,含水量是影响绝缘纸热老化速率的主要因素,氧气会降低菜籽油基天然酯对低含水量绝缘纸热老化速率的抑制作用。结合绝缘纸在绝缘液热老化过程中比强度与聚合度的实测数据,导出得到考虑含水量和氧气影响的绝缘纸纤维素分解反应数学模型,应用该模型可以对绝缘纸在绝缘液中的热老化过程和寿命进行预测。

考虑压力和含水率影响的小麦粮堆导热特性数值研究

【目的】研究小麦粮堆压力—导热特性和含水率—导热特性的规律。【方法】使用孔隙率测定装置来测定小麦粮堆在不同压力(0 kPa、50 kPa、100 kPa、200 kPa、300 kPa)、不同含水率(8.50%、11.21%、14.45%、16.97%、20.72%)下的孔隙率,并在COMSOL有限元数值模拟软件中进行模拟分析。【结果】得到压力、含水率对粮堆孔隙率产生的影响,通过建立小麦粮堆的压力—导热特性数值模型,模拟不同压力和含水率下小麦颗粒的导热特性,得到粮堆压力—导热特性的规律。【结论】小麦颗粒的等效导热系数与孔隙率基本呈线性分布。单元体颗粒的等效导热系数范围为0.1095~0.1572 W/(m·K),粮堆等效导热系数随上覆压力的增大而增大,当含水率为8.5%~20.72%,上覆压力为300 kPa时,导热系数增大17.5%~27.5%。

模拟干旱下杨树树干液流特征及其对环境因子的响应

[目的]研究干旱对杨树人工林树干液流的影响,可以深入理解杨树人工林对全球降水格局改变的响应。[方法]于2018年9月—2020年11月以东台林场10年生杨树(Populus deltoides)人工林为对象,采用穿透雨移除法模拟干旱处理:CK(对照)、D_(1)(30%穿透雨移除)、D_(2)(50%穿透雨移除),利用热扩散探针技术连续测定杨树人工林的液流变化,结合同步监测的环境因子,揭示杨树人工林对环境因子的响应规律。[结果](1)3个处理下杨树人工林树干液流年变化曲线呈现单峰型,与饱和蒸汽压差、光合有效辐射的年际变化曲线相似。树干液流速率在夏季达到峰值,接着随着时间推移逐渐下降,到达林木休眠期时液流密度趋近于0;(2)模拟干旱下,随着截流程度增大,树干液流随之降低。D_(1)和D_(2)生长季液流密度平均值比对照组显著下降了24%~39%(p<0.05);(3)混合效应模型表明饱和蒸汽压差和土壤温度与液流变化极显著相关(p<0.01),大气温度,降雨量和土壤温度与液流变化显著相关(p<0.05)。[结论]移除30%的穿透雨提高了各环境因子对液流变化的解释程度,即干旱条件下会提高树干液流对环境变化的敏感性,其中土壤含水量对液流变化的解释率最高。未来仍需继续探讨树木自身性状对环境的响应。

压力和含水率对小麦粮堆导热特性的影响

基于瞬态热线法,设计了粮堆导热特性试验装置,研究了小麦粮堆在压力0~73.9 kPa、含水率8.50%~20.72%时导热系数的变化规律。结果表明:当含水率一定时,导热系数与压力呈线性增长关系;当含水率分别为8.50%和20.72%时,随着压力从0增大至73.9 kPa,导热系数分别增长21.1%和36.6%。当压力为0时导热系数k1与含水率呈线性增长关系;导热系数随压力变化率c1与含水率呈线性增长关系;当压力一定时,导热系数与含水率呈线性增长关系;当压力分别为0、73.9 kPa时,随着含水率从8.50%增大至20.72%,导热系数分别增长50.6%和69.2%。含水率为0时的导热系数不随压力变化,为0.074 W·m^(-1)·K^(-1)。导热系数随着含水率的变化率c_(2)与压力呈线性增长关系。

冻结过程土体导热系数影响因素及预测模型研究

为探究土体导热系数的基本规律,采用瞬态平面热源法测试了冻结过程土体导热系数。研究了土体在不同温度、含水率和干密度物理指标下导热系数变化规律,分析了这三个物理指标动态变化对土体导热系数的影响机制。基于试验数据,建立了DT、RF、GBDT、AdaBoost、SVR、BPNN共六种机器学习模型以预测土体导热系数,通过四个性能指标评估了六种机器学习模型的预测能力,并与三种经验模型进行了对比。此外,基于RF和GBDT进行了特征重要性分析。结果表明:未冻结阶段土体导热系数无显著变化。剧烈相变阶段,因含水率和干密度的不同,土体导热系数随温度的降低分别呈现出减小和增大的趋势,其中增大的趋势随着含水率的增加而增加。冻结阶段,因测试过程中土样的水分蒸发和迁移,土体导热系数随着温度的降低而减小。土体导热系数均随干密度和含水率的增加而增加。根据评估结果,六种机器学习模型中RF的表现较好(RMSE=0.036,MAE=0.028,R^(2)=0.993,AD=0.004),明显优于三种经验模型,RF相较于经验模型也能更准确地预测出其他地区的土体导热系数,建议使用RF预测冻结过程土体导热系数。特征重要性分析表明含水率、温度和孔隙率是影响冻结过程土体导热系数的重要因素。

高含水油泥热干化处理设备研究与应用进展

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