Effect of soil moisture on microwave scattering for remote sensing

The main objective of remote sensing is to design space borne microwave sensors to sense a target and derive useful geophysical parameters. For this purpose, the knowledge of the target characteristics must be obtained through ground based remote sensing. In this paper, soil has been taken as the target. Various percentages of gravimetric soil moisture (m _g) have been taken for establishing its relation with the scattering coefficient (σ ₀) for both like polarizations at X-band frequencies. A linear model has been developed for correlating these two variables (i.e.m _g andσ ₀). Using this model, regression analysis has been done for obtaining different regression parameters and predicted values. Treating measurements from bare smooth soil fields with different soil moistures, the data were analysed to examine the effect of soil moisture on scattering co-efficient (σ ₀) at 9.50 GHz frequency in X-band. The scattering coefficient increases with increase in soil moisture content. Different regression parameters have been obtained, which show that the best look-angle is at 25° for HH-pol and 60° for VV-pol for observingσ ₀ from bare moist soil. Data analysis indicated that the basic cause and effect relationship between the sensor measurements and soil moisture can be extrapolated from theory and small-scale tests to larger resolution elements observed by the sensing aircraft. These results indirectly provide reference data for a satellite-borne remote sensor. From the results, the look angles suitable for operation with radar antennas can be suggested.     

Permanent deformation characteristics of silty sand subgrades from multistage RLT tests

Rutting is one of the main forms of distresses in thin flexible pavement structures, often associated with accumulation of permanent deformation in unbound granular layers and subgrade soils under traffic loading. Realistic prediction of surface rutting requires models that can reliably capture the cumulative plastic deformation of pavement unbound layers under repeated loads. This study presents an evaluation of three models that incorporate the time-hardening concept for prediction of permanent deformation of silty sand subgrade materials. A series of multistage repeated load triaxial (RLT) tests, in which the material underwent a wide range of continuous stress conditions, were carried out on two silty sand subgrades. The RLT tests were conducted at four different moisture contents in which pore suctions were measured throughout the test. In the modelling of the permanent deformations, the effective stress approach was used taking into account the effects of soil suctions. The material parameters of the predictive models were optimised using the RLT test data and the effect of moisture content (matric suction) on the permanent deformation characteristics of the materials and the predictive model parameters were investigated. Generally, it was observed that the modified models that are based on the shakedown approach performed reasonably well in capturing the permanent deformation behaviour of the selected subgrade materials with minor discrepancies between the models. This indicates that using multistage RLT tests can be an efficient approach for characterising the permanent deformation behaviour of subgrade soils.     

Effect of Moisture on the Thermal Conductivity of a Cementitious Composite

Measurements of the thermal conductivity of a cement-based composite material are performed as a function of moisture content from a dry state to a fully water-saturated state using an impulse technique. Then, the obtained data are analyzed using Brugemann and Wiener homogenization formulas. The validity of applied homogenization techniques is assessed comparing the measured and calculated results. On the basis of the experimental data and the homogenization analyses, the effects of total pore volume, pore distribution, and moisture content on the thermal conductivity are discussed.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

基于AIEM和实地观测数据对GNSS-R反演土壤水分的研究

介绍了用GPS反射信号反演土壤水分的原理及反演研究的进展,并用改进的积分方程模型(AIEM)和实地观测数据对利用GPS反射信号反演土壤水分的方法进行了分析,分析结果表明,由于单个频率的雷达信号受地表粗糙度、角度和地表类型(裸地和植被类型)的影响比较大,很难提出一个实用的通用物理算法.利用美国2002年土壤水分实验(SMEX02)实测数据对上述的反演算法进行了分析,分析结果表明,采用经验统计算法对单个站点观测比较实用,平均相关系数达到0 85以上.整个分析表明,利用GPS前向散射信号与噪声之比反演土壤水分在单个站点能够取得比较高的精度.     

不同掺量风化砂对宜昌市某公路膨胀土特性的影响研究

针对湖北省宜昌市小溪塔至鸦鹊岭一级公路改建工程项目中广泛存在的膨胀土及当地可以充分利用的风化砂展开试验研究,分别针对原状膨胀土和掺入10%～50%的风化砂改良膨胀土进行击实试验及膨胀性指标室内试验。通过在原状膨胀土中掺入不同含量的风化砂进行试验,可以发现掺风化砂可以改变膨胀土的含水特性和密实特性;掺不同含量的风化砂对膨胀土的膨胀性指标影响较大,可以显著抑制膨胀土的膨胀性,达到路基填料的标准。     

土壤界限含水率自动检测系统设计研究

为了解决传统土壤界限含水率检测中存在的需人工现场操作、耗时久、数据采集困难、数据传输实时性差等问题,设计了一种土壤界限含水率自动检测系统。该系统以西门子S7-200PLC为控制核心,由传送带、正方体容器、搅拌容器、电子秤、抹平系统、圆锥仪和加热箱等组成,使用MCGS组态软件进行数据监控,并采用采样烘干法测定含水率,液-塑限联合测定法测定液、塑性指数。实际应用中,该系统能够完成自动搅拌、多组数据同时测定和数据实时传送,基于含水率和液、塑性指数实现土体的分类以及地基土承载力的估算。该系统具有自动化程度高、操作简单及成本低廉的特点,能够广泛应用于各种土壤界限含水率的测定,对农业工程的设计和实施具有一定的参考价值。     

陶瓷涂覆包装材料对烟支防潮保润的影响研究

目的 研究不同材质包装烟盒对烟支含水率变化的影响。方法 对不同类型的包装纸进行定量、厚度、水蒸气透过率的测定,并用扫描电镜分析其微观形貌。将涂陶白卡纸,涂陶介质纸与普通包装成品卷烟拆包后置于自然环境、常温干燥环境、常温潮湿环境中,测定烟支含水率的变化,并对烟支中水溶性糖与关键化学成分的含量进行分析,对3种包装的烟支进行评吸。结果 3种包装纸的定量、厚度差别不大,在常温干燥与常温潮湿的环境下,涂陶介质包装盒展现出更好的防潮保润效果以及更高的感官评吸分值。结论 包装材料对烟支的含水率及综合感官有直接影响,本研究中的涂陶介质纸具有较好的防潮保润效果,在烟草包装领域具有推广价值。     

Effect of subgrade on piezoelectric energy harvesting under traffic loads

Piezoelectric energy harvesting in roads generated by traffic loads was theoretically and experimentally investigated, and an indoor model of a layered road for piezoelectric transformation was developed using the traffic load model groove. Elastic double-layer beams resting on the subgrade soil were used to consider piezoelectric energy harvesting under traffic loads. Based on the vibration differential equations of elastic double-layer beams, the electromechanical equation was obtained using the Fourier transform. The experimental results of the piezoelectric energy harvesting were close to the theoretical ones, which indicated that the proposed method was useful in predicting piezoelectric energy harvesting from roads under traffic loads. The results also show that the influence of the transducer position on the output voltage and power should be considered, and that the thickness of the concrete panel and the condition of the subgrade soil can affect the output voltage and output power of the piezoelectric transducer. Moreover, the electrical energy was proportional to the vibration frequency and the excitation load.     

Effect of aspect ratio on the compaction characteristics and micromorphology of copper powders by magnetic pulse compaction

Magnetic pulse compaction (MPC) technology has the advantages of near net shape, high efficiency and density. In this paper, the effect of aspect ratio on the deformation characteristics of copper powders compacted by MPC technology was studied. Specifically, the compaction velocity, volume strain, micromorphology and micro hardness of compacts at various aspect ratios were obtained. Results showed that the compaction velocity and volume strain increased and then decreased with the increase of aspect ratio. The maximum compaction velocity reached 10.28 m/s at aspect ratio of 1.2. At the same compaction moment, the volume strain was decreased as the aspect ratio increased. Then the relationship between compaction pressure and volume strain was revealed. The aspect ratio range of the optimal compaction effect was 0.6–1.0, and the fluctuation degree of relative density was only 1.03%. The aspect ratio had less effect on the micromorphology distribution in the axial direction of the compacts. The micro hardness value of the upper surface was higher than that of the lower surface, and the edge position was greater than the center position.     

Monitoring of the manufacturing process for ambroxol hydrochloride tablet using NIR-chemometric methods: compression effect on content uniformity model and relevant process parameters testing

This study aimed at using near-infrared (NIR) spectroscopy to monitor compaction pressure for simultaneously determining the tensile strength and content uniformity, as well as moisture and mean particle size of ambroxol hydrochloride tablets. The content uniformity, compression force and tensile strength of the laboratory samples were obtained by pressing a mixture of active principle and excipient components into tablets. To reduce the spectral baseline shift of the laboratory samples, the compaction pressure applied to the mixture was assessed by a variable pressure test. Production samples were added to the test and subjected to principal component analysis. The expanded partial least-squares (PLS) calibration model used to quantify the active content was more accurate than the model constructed from laboratory samples using the production tablets included in the calibration set. The model showed good predictability, with correlation coefficient (R) 0.9977. The validation and reliability of the content model were evaluated to determine trueness and reliability for the measurement of individual production tablets and the laboratory tablets with drug content ranging from 24 to 36?mg. The PLS calibration models for compression force and tensile strength were constructed using the same spectral set assuming both were highly related. These models yielded high R values (0.9955 and 0.9910). The R values of the moisture and mean particle size were 0.9994 and 0.9919, respectively. This study demonstrated that NIR spectroscopy combined with chemometric techniques can be successfully used to quantitatively monitor the tablet manufacturing process in the pharmaceutical industry.     

Effects of random heterogeneity of soil properties on bearing capacity

This study examines the effect of random heterogeneity of soil properties on bearing capacity. The stochastic soil property considered is the undrained shear strength and two major sources of uncertainty are identified with it: inherent spatial variability (modeled as a non-Gaussian, homogeneous stochastic field) and uncertainty in the estimation of its expected value (modeled as a random variable). The two sources of uncertainty are treated separately, before being eventually combined. A Monte Carlo simulation approach is followed in combination with non-linear finite element analysis. It is demonstrated that the inherent spatial variability of soil shear strength can drastically modify the basic form of the failure mechanism in this bearing capacity problem. Consequently, there is no ‘average’ failure mechanism (surface) in this problem, leading to the conclusion that Monte Carlo simulation is the only methodology capable of providing a solution to this geomechanics problem. It is further demonstrated that this behavior of the failure mechanism translates into a substantial reduction in the ultimate bearing capacity (in an average sense), compared to the corresponding deterministic (homogeneous soil) case. In addition, differential settlements are computed in the stochastic analysis, something impossible in a deterministic analysis of a symmetric problem. A parametric study is performed using fragility curves to investigate the effects of various probabilistic parameters involved in the problem. It is found that the coefficient of variation and the marginal probability distribution of the soil's shear strength (both controlling the amount of loose pockets in the soil mass) are the two most important parameters in reducing the bearing capacity (in an average sense) and producing substantial differential settlements in heterogeneous soils (compared to homogeneous soils). A technique is finally introduced for determining ‘overall’ fragility curves that account for both inherent soil spatial variability and uncertainty in the expected value of soil strength. Based on such ‘overall’ fragility curves obtained at failure (ultimate bearing capacity), nominal values of the bearing capacity of a heterogeneous soil deposit corresponding to an exceedance probability of 5% are established for a range of probabilistic characteristics.     

含水量对纸张导电性的影响研究

针对纸张输送、印刷以及其他工序中的静电问题,提出了利用纸张导电性来消除静电的方法。论述了纸张导电性对印刷过程良好运行的重要性,研究了影响纸张导电性的因素,确定了含水量是最重要的影响因素。研究了含水量与纸张导电性之间的关系,通过曲线拟合得到了关系方程。通过改变纸张的含水量可调节纸张的导电性,达到消除或减弱纸张所带静电的目的。     

Algorithm development for the application of ground-penetrating radar on asphalt pavement compaction monitoring

Ground-penetrating radar (GPR) is a promising non-destructive technique to be applied on monitoring the density change during asphalt pavement compaction. The utmost challenge of this application is the unknown effect of surface moisture, sprayed by the compactor during compaction, on GPR signals. To extract density information without the effect of surface moisture, a correction algorithm based on reference scan approach was developed. To evaluate the performance of the algorithm, a full-scale test site was constructed with compaction pass number from 0 to 10, and a large amount of GPR data were collected from the pavement with different surface moisture contents. A total of 22 cores were extracted for validation purposes. After applying the algorithm, it was found that the average density prediction error was reduced significantly. By using correction algorithm together with the density model, the density of asphalt pavement was obtained with high accuracy.     

环境湿度对瓦楞纸箱品质的影响

目的评价环境相对湿度对瓦楞纸箱质量的影响。方法在23℃和相对湿度为50%,70%,98%的环境中,比较3层、5层和7层瓦楞纸箱的抗压强度、耐破强度以及吸湿率等性能指标。结果瓦楞纸箱的吸湿率和含水率随环境湿度的升高而增大;当环境相对湿度在50%~70%时,瓦楞纸箱的耐破强度、边压强度及抗压强度等性能保持稳定;当环境相对湿度达到98%时,3层、5层和7层瓦楞纸箱的耐破强度比相对湿度50%条件下分别降低了53.8%,74.1%和76.3%,边压强度分别降低了71.4%,70.3%和77.5%,抗压强度和堆码层数显著下降;7层瓦楞纸箱的防潮耐压能力优于3层和5层。结论高湿度会引起瓦楞纸箱的性能指标显著降低,功能受损。     

Study of Laboratory and Field Tests Related to Soil Compaction Based on Proficiency Testing Schemes

The main objective of the paper is to present some understandings of laboratory and field tests related to soil compaction and useful for quality control purposes. The methodology of this study is different of other similar works because it is based on proficiency testing schemes （PTS）, involving several operators and test devices. The study was performed in the following test methods： laboratory Proctor compaction test; determination of density and unit weight of soil in place by the sand-cone method; and determination of density and water content of soil and soil-aggregate by nuclear methods. The paper describes the procedures followed for the PTS implementation. The statistical analysis is presented, firstly focusing on the repeatability and reproducibility of the test results. Secondly, beyond this analysis, the paper describes some studies related to practical aspects of the test methods： the influence of the manual or mechanical compaction devices in the modified Proctor test results; the comparison between direct transmission and the backscatter modes in the case of the wet density measurements obtained by the in situ nuclear method; the relationship concerning test results obtained by the nuclear and conventional methods used in the field quality control.     

间隙元素碳氮含量对2Cr21Ni12N气阀钢强度的影响

进行了(C N)含量对2Cr21Ni12N气阀钢强度性能的影响的实验研究，包括固溶态和时效态的室温和高温硬度实验，室温和高温拉伸性能的试验以及高温持久性能和高温弯曲疲劳性能实验。随着(C N)含量的增加，硬度和强度性能都不同程度地提高。     

Effect of soil compositions on the electrochemical corrosion behavior of carbon steel in simulated soil solution

In this study, effect of cations, Ca²⁺, Mg²⁺, K⁺, and anions, SO₄^2–, HCO₃^–, NO₃^– on electrochemical corrosion behavior of carbon steel in simulated soil solution was investigated through potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results indicate that the Ca²⁺and Mg²⁺ can decrease the corrosion current density of carbon steel in simulated soil solution, and K⁺, SO₄^2–, HCO₃^–, and NO₃^– can increase the corrosion density. All the above ions in the simulated soil solution can decrease its resistivity, but they have different effect on the charge transfer resistivity. This finding can be useful in evaluating the corrosivity of certain soil through chemical analysis, and provide data for construction engineers.     

Effect of aggregate structure on VOC gas adsorption onto volcanic ash soil

The understanding of the gaseous adsorption process and the parameters of volatile organic compounds such as organic solvents or fuels onto soils is very important in the analysis of the transport or fate of these chemicals in soils. Batch adsorption experiments with six different treatments were conducted to determine the adsorption of isohexane, a gaseous aliphatic, onto volcanic ash soil (Tachikawa loam). The measured gas adsorption coefficient for samples of Tachikawa loam used in the first three treatments, Control, AD (aggregate destroyed), and AD-OMR (aggregate destroyed and organic matter removed), implied that the aggregate structure of volcanic ash soil as well as organic matter strongly enhanced gas adsorption under the dry condition, whereas under the wet condition, the aggregate structure played an important role in gas adsorption regardless of the insolubility of isohexane. In the gas adsorption experiments for the last three treatments, soils were sieved in different sizes of mesh and were separated into three different aggregate or particle size fractions (2.0–1.0 mm, 1.0–0.5 mm, and less than 0.5 mm). Tachikawa loam with a larger size fraction showed higher gas adsorption coefficient, suggesting the higher contributions of macroaggregates to isohexane gas adsorption under dry and wet conditions.     

粘土含水量对固化剂配比的影响

本文通过石膏等外加剂对不同含水量粘土的固化试验以及ＸＲＤ和ＳＥＭ分析表明：粘土含水量不同，外加剂对水泥稳定土的作用效果不同。对于高含水量粘土，增加外加剂含量有利于形成较多的钙矾石，提高稳定土强度；粘土含水量较低时，应适当控制硫酸盐含量，避免过多的钙矾石造成体积膨胀而引起试样强度下降。在研制和生产水泥系固化剂时，一定要充分注意钙矾石增强和膨胀的双重作用，从而更合理地确定适应于不同含水量粘土的最佳固化剂组成。     

Effect of twin-screw extrusion parameters on mechanical hardness of direct-expanded extrudates

Mechanical properties of cereal (starch-based) extrudates are perceived by the final consumer as criteria of quality. We investigate one of the important characteristics of extrudates, mechanical hardness, which is one of the main texture parameters. Texture quality has an influence on taste sensory evaluation, and thus on the acceptability of the product. Characteristics that have great influence on acceptability are crispness, elasticity, hardness and softness. These attributes are narrowly related to, and affected by, the process parameters. A 2-level-4-factor factorial experimental design was used to investigate the influence of temperature of expansion, screw speed, feed moisture content and feed rate, and their interactions, on the mechanical hardness of extrudates. Feed moisture content, screw speed and temperature are found to influence, while feed rate does not have significant effect on extrudate hardness. Mechanical properties of specimens were measured by means of compression testing, based on the concept of nominal stress, using a universal testing machine and special grips that were constructed for this purpose.