One-dimensional horizontal infiltration experiment for determining permeability coefficient of loamy sand

A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil permeability. In order to confirm the acceptability of the one-dimensional horizontal infiltration method（one-D method） for simultaneously determining both the saturated and unsaturated permeability coefficients of loamy sand, we first measured the cumulative infiltration and the wetting front distance under various infiltration heads through a series of one-dimensional horizontal infiltration experiments, and then analyzed the relationships of the cumulative horizontal infiltration with the wetting front distance and the square root of infiltration time. We finally compared the permeability results from Gardner model based on the one-D method with the results from other two commonly-used methods（i.e., constant head method and van Genuchten model） to evaluate the acceptability and applicability of the one-D method. The results showed that there was a robust linear relationship between the cumulative horizontal infiltration and the wetting front distance, suggesting that it is more appropriate to take the soil moisture content after infiltration in the entire wetted zone as the average soil moisture content than as the saturated soil moisture content. The results also showed that there was a robust linear relationship between the cumulative horizontal infiltration and the square root of infiltration time, suggesting that the Philip infiltration formula can better reflect the characteristics of cumulative horizontal infiltration under different infiltration heads. The following two facts indicate that it is feasible to use the one-D method for simultaneously determining the saturated and unsaturated permeability coefficients of loamy sand. First, the saturated permeability coefficient（prescribed in the Gardner model） of loamy sand obtained from the one-D method well agreed with the value obtained from the constant head method. Second, the relationship of unsaturated permeability coefficient with soil water suction for loamy sand calculated using Gardner model based on the one-D method was nearly identical with the same relationship calculated using van Genuchten model.

Preparation of Aluminum Matrix Composite by Pressureless Infiltration Process

he Al_2O_3 particle reinforced aluminum matrix composite was prepared by using a new pressureless infiltration process. The microstructure of (Al_2O_3)p/Al was analyzed. The tension and the thermal conductivity of the composite were studied as well.

Description and reconstruction of one-dimensional photonic crystal by digital signal processing theory

A method of describing one-dimensional photonic crystals （1DPCs） based on Z-domain digital signal processing theory is presented. The analytical expression of the target band gap spectrum in the digital domain is obtained by the autocorrelation of its impulse response. The feasibility of this method is verified by reconstructing two simple 1DPC structures with a target photonic band gap obtained by the traditional transfer matrix method. This method provides an effective approach to function-guided designs of interference-based band gap structures for photonic applications.

Experimental determination of threshold pressure and permeability based on equation-solving method for liquid metal infiltration processes

A new method for determining two key parameters(threshold pressure and permeability)for fabricating metal matrix composites was proposed based on the equation-solving method.An infiltration experimental device was devised to measure the infiltration behavior precisely with controllable infiltration velocity.Two experiments with alloy Pb-Sn infiltrating into Al2O3 preform were conducted independently under two different pressures so as to get two different infiltration curves.Two sets of coefficients which are functions of threshold pressure and permeability can be obtained through curve fitting method.By solving the two-variable equation set,two unknown variables were determined.It is shown that the determined threshold pressure and permeability are very close to the calculated ones and are also verified by another independent infiltration experiment.The proposed method is also feasible to determine the key infiltration parameters for other metal matrix composite systems.

A Numerical Study of Densification Behavior of Silicon Carbide Matrix Composites in Isothermal Chemical Vapor Infiltration

We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the reaction. Thereby, we established mathematical models on two scales, respectively, preform and reactor. These models were used for the numerical simulation of the process of ceramic matrix composites densified by isothermal chemical vapor infiltration(ICVI). The models were used to carry out a systematic study on the influence of process conditions and the preform structure on the densification behaviors. The most important findings of our study are that the processing time could be reduced by about 50% without compromising the quality of the material, if the processing temperature is 950-1 000 ℃ for the first 70 hours and then raised to 1 100 ℃.

Effects of infiltration parameters on mechanical and microstructural properties of tungsten wire reinforced Cu_(47)Ti_(33)Zr_(11)Ni_6Sn_2Si_1 metallic glass matrix composites

Cu47Ti33Zr11Ni6Sn2Si1-based bulk metallic glass matrix composites reinforced with tungsten wires were fabricated by infiltration process at different temperatures （850, 900, 950 and 1000 °C） and time （10, 20 and 30 min） in a quartz or a steel tube. The mechanical tests were carried out by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that the maximum strength and total strain of the composite are 1778 MPa and 2.8% fabricated in steel tube at 900 °C for 10 min, and 1582 MPa and 3.6% fabricated in quartz tube at 850 °C for 10 min, respectively.

Fate of nitrogen in subsurface infiltration system for treating secondary effluent

The concentration of total nitrogen(TN) is reported to vary between 20 and 35 mg/L in domestic wastewater. In raw wastewater, ammonia nitrogen eNHt4-NT is the main nitrogen form, accounting for 70%e82% of the TN concentration. Organic nitrogen, nitrite nitrogen eNOà2-NT,and nitrate nitrogen eNOà3-NT are present as well. For years, due to the lack of regulatory limits on nitrogen concentration in surface waters,nitrogen from secondary effluent has posed a significant threat to the health of aquatic ecosystems. Researchers have made substantial efforts to reduce the nitrogen concentration in secondary effluent. As a kind of advanced wastewater treatment technology, the subsurface infiltration(SI)system has been widely used, owing to its advantages, which include low operation cost, easy maintenance, and low energy consumption. This review discusses the fate of various forms of nitrogen in SI treatment, including organic nitrogen, NHt4-N, NOà2-N, and NOà3-N. Major biological processes involved in nitrogen removal and the main factors influencing its transformation are suggested. Finally, it is shown that ammonification followed by nitrification-denitrification plays a major role in nitrogen removal. Further research needs to focus on the emission characteristics of gaseous nitrogen(generated from the nitrification, denitrification, and completely autotrophic nitrogen-removal over nitrite(CANON) processes) with respect to their greenhouse effects.

Quantification of irrigation water transport processes in ZiZiphus jujuba garden using water stable isotopes

ZiZiphus jujuba,which is native to China,has become one of the main crops widely planted in the western Loess Plateau because of its drought and flood-tolerance,adaptability,and higher nutritional value of the fruit.The irrigation water infiltration in Z.jujuba gardens is complex,and understanding its mechanisms is essential for efficient water use and sustainable agriculture.This knowledge helps ensure the long-term success of jujuba cultivation.This paper describes a field experiment that investigates the infiltration process of irrigation water from Z.jujuba garden and quantifies the contribution of irrigation water to soil water at different depths using the MixSIAR model.According to the FC(Field water holding Capacity)of Z.jujuba,irrigation experiments with three volumes of 80%FC,60%FC,and 40%FC are set up in this study.The study finds that water retention is better in Z.jujuba garden soils with a higher proportion of coarse gravel in the soil particle composition.Soil water content exhibits a gradient change after irrigation,with deeper wetting front transport depth observed with increased irrigation water.Additionally,there is correlation between soil temperature and soil water content.The soil water in Z.jujuba garden generally exhibits a preferential flow signal in the 0-40 cm range.Below 40 cm,a piston flow pattern dominates.The rate of soil water infiltration increases with the amount of irrigation water.In the 0-40 cm range of the soil vertical profile,irrigation water was the main contributor to soil water.Z.jujuba demonstrated flexibility in water uptake,primarily absorbing soil water at depths of 0-40 cm.For optimal growth of Z.jujuba at this stage,40%FC irrigation is recommended.The results are expected to be valuable future irrigation practices and land use planning for Z.jujuba garden in arid zones,supporting sustainable agricultural development and water management.

连续纤维增强碳化硅陶瓷基复合材料低成本制备工艺研究进展

连续纤维增强陶瓷基复合材料具有低密度、高强度、耐高温等优异性能,已被广泛应用于航空航天、国防军工和新兴民用等领域,但连续纤维增强陶瓷基复合材料制备工艺大多存在成本较高、周期过长等问题,限制其应用和推广,发展低成本制备工艺是推动连续纤维增强陶瓷基复合材料广泛应用的关键。本文简要介绍了连续纤维增强陶瓷基复合材料制备工艺现状,总结了反应熔渗、纳米浆料浸渗瞬时共晶、浆料浸渗结合热压等低成本工艺的研究现状,围绕制备工艺优化、复合材料微观结构和性能等方面进行综述,提出了低成本制备工艺的未来研究方向,如熔盐法制备超高温陶瓷界面和反应诱导相分离制备具有孔隙结构均匀的多孔基体,可显著提升连续纤维增强陶瓷基复合材料的综合性能。

基于W-OH的矿区重构冻土阻水层功能评价模拟研究

为缓解高寒矿区扰动土体难以形成冻土带来的不利影响,选取5种W-OH浓度(0%、1.5%、2.5%、3.5%、4.5%)喷施于扰动土体底部,重构矿区冻土阻水层,进行抗压试验、入渗试验和模拟降雨试验,分别从物理性能、入渗产流产沙、经济性3个层面进行重构阻水层评价分析,采用层次分析法和专家打分法选出8个影响重构阻水层的主要因子,构建重构阻水层功能评价体系,根据综合评分选出该地区最佳的重构阻水层方案。结果表明:(1)W-OH增强了煤矸石固结体的强度,特别是4.5%W-OH浓度时效果最明显。(2)W-OH浓度上升导致重构阻水层入渗率降低,稳渗历时延长,累计入渗量减少。(3)在降雨条件下,W-OH浓度升高降低了煤矸石固结体的稳定入渗率,增加了平均产流率和平均产沙率,并且平均产流率和平均产沙率都同W-OH浓度、坡度存在正相关关系。(4)4.5%W-OH浓度方案功能综合评分最高,但在实际施工中,4.5%W-OH浓度方案易堵塞喷头,故推荐使用评分次之的3.5%W-OH浓度方案重构矿区冻土阻水层。研究结果可为W-OH在高寒矿区重构冻土阻水层应用提供理论依据。

金刚石与硅烧结制备金刚石碳化硅陶瓷基复合材料研究

为了提高金刚石材料的耐磨性和使用寿命,以Si_(3)N_(4)为基体材料,利用CVD生长的金刚石粉作为增强相制备了金刚石/碳化硅陶瓷基复合材料。对SiC/Ce-SiC/Si_(3)N_(4)陶瓷基复合材料的烧结过程进行研究,探讨烧结温度、保温时间等对其显微结构及力学性能的影响。结果表明,随着烧结温度的升高,复合材料的致密度不断提高,当烧结温度为1000℃时,复合材料的致密度最高,达98.7%,烧结温度越高,SiC颗粒团聚现象越严重,且晶粒尺寸越小,在保温时间为20 min时,复合材料达到致密化状态,此时复合材料中含有较多的SiC颗粒。通过优化工艺参数可制备出具有优异性能的金刚石/碳化硅陶瓷基复合材料,满足航空航天领域的使用要求。

基于高密度电阻率成像技术的MICP浆液入渗过程监测研究

微生物诱导碳酸钙沉淀(MICP)技术是一种生态环保、前景广阔的土体改性方法,其改性效果与浆液的入渗特征密切相关。为此,提出将高密度电阻率成像(ERT)技术用于MICP浆液入渗过程监测。文章通过开展模型试验,对石英砂试样进行混合一步注浆法MICP处理,同时对试样持续进行ERT监测及电导率分析,获取了试样的三维电阻率变化特征,处理完成后测定了试样中碳酸钙含量的空间分布。结果表明:(1)MICP反应过程中,砂土与注浆液电导率随尿素分解而逐渐升高;(2)注浆液的迁移分布对砂土内部低电阻区的分布规律起主导作用,而碳酸钙沉淀的影响较小;(3)在MICP处理过程中,碳酸钙沉淀的生成与注浆液的迁移渗透相互作用,共同影响改性效果;(4)ERT技术可有效监测MICP处理区电阻率的时空演化特征,准确反映注浆液渗透迁移情况,进而评价改性效果。研究结果表明,采用ERT技术监测MICP改性土体过程具有可行性,为评价和优化微生物矿化改性效果提供了新的技术思路和方向。

树脂渗透剂的制备及其后处理对3DP成型件抗压性能的影响

在利用三维粉末黏结(3DP)工艺成型标准圆柱件时,为了制备3DP工艺后处理环节所需的树脂渗透剂,以抗压强度为指标,利用响应面法中的Box-Behnken设计了实验方案,确定了优化配比方案。以此为后处理剂扫描电子显微镜(SEM)、能谱仪(EDS)和抗压强度测试讨论了渗透参数(渗透次数、渗透方式以及渗透间隔时间)对3DP工艺成型件的抗压性能的影响。结果表明,制备的树脂渗透剂可有效改善成型件的抗压性能。在渗透处理时,采用浸润的渗透形式,通过多次浸润、渗透间隔时间逐次递增的方式,可以有效提高成形件的抗压性能。

Flexible one-dimensional photonic crystal films composed of chalcogenide glass and water-soluble polymer for curvature sensing

Curvature sensing plays an important role in structural health monitoring,damage detection,real-time shape control,modification,etc.Developing curvature sensors with large measurement ranges,high sensitivity,and linearity remains a major challenge.In this study,a curvature sensor based on flexible one-dimensional photonic crystal(1D-PC)films was proposed.The flexible 1D-PC films composed of dense chalcogenide glass and water-soluble polymer materials were fabricated by solution processing.The flexible 1D-PC film curvature sensor has a wide measurement range of 33-133 m-1and a maximum sensitivity of0.26 nm/m^(-1).The shift of the transmission peak varies approximately linearly with the curvature in the entire measurement range.This kind of 1D-PC film curvature sensor provides a new idea for curvature sensing and measurement.

自然语言处理中的价值观渗透问题——以ChatGPT为例

[研究目的]以ChatGPT为例,探讨自然语言处理中的价值观渗透方式和固化机理,探索在自然语言处理技术广泛应用的背景下,预防不可控信息的传播,巩固主流价值体系的方法路径。[研究方法]以描述性研究为基础,从ChatGPT驱动下价值观渗透的四种方式入手,研判可能出现的舆情传播态势。结合价值观的本身特点,综合科技哲学、伦理学等相关学科知识,整合提出目前存在的价值观渗透、固化风险,并提出相应的对策。[研究结论]通过与ChatGPT的结合,价值观能以数据投喂、自主示弱、自我优化、语言景观等方式强化其渗透过程中的隐蔽性,在渗透之后,将会通过隐性教化、知识内部分野和去实践化等方式进行固化,从而扩大影响。研究结合多领域知识,提出应对此种情况的三项基本原则:辩证扬弃、针锋相对和复合规制,力求促进情报搜集和舆情控制工作健康平稳发展。

Integrated rainfall-runoff process with shallow water model by mass varied smoothed particle hydrodynamics:Infiltration effect implementation

Rainfall-runoff modeling is essential for addressing a wide range of issues in urban drainage system design and operation in both scientific research and engineering practice.Recently,it has become increasingly attractive to use the smoothed particle hydrodynamics(SPH)method to model rainfall-runoff because of its inherent features such as mesh-free and automatic adaptiveness for wet-dry interfaces.However,one of its inadequacies is the lack of an infiltration effect within rainfall-runoff modeling.Hence,we propose a new methodology that innovatively integrates the infiltration effect into the shallow water equation(SWE)system with the SPH method(SPH-SWE)to represent a more complete rainfall-runoff process.In the proposed method,the mass-varied SPH-SWE(MVSPH-SWE)method is enhanced by integrating the infiltration model.A naked area treatment(NAT)method is subsequently proposed to improve the modeling efficiency and accuracy.The obtained numerical results are validated using experimental data from the literature.The results demonstrate that the proposed method is accurate and reliable.The achievements and findings of this study are expected to improve and extend the use of existing hydrological process models.

不同渗糖工艺对低糖化枇杷果脯品质的影响

目的:评价不同渗糖工艺对低糖化枇杷果脯的影响,筛选适宜低糖化枇杷果脯的渗糖工艺。方法:采用常压、超声、微波和真空渗糖工艺对枇杷果脯进行处理,以感官评定、总糖含量、复水率、色差、维生素C含量、多酚含量和抗氧化能力为评价指标,评估不同渗糖工艺对枇杷果脯品质的影响。结果:微波渗糖的感官评分、维生素C含量和抗氧化性能最佳,储存后色差较小,复水率较低;超声处理在总糖含量和复水率两方面表现出一定优势。结论:低糖化枇杷果脯的渗糖工艺以微波处理效果最佳,其次可以选用超声处理。

响应面法优化百香果果脯微波渗糖工艺

以百香果为主要原料,采用微波渗糖技术将其制成果脯,考查了柠檬酸添加量、百香果原汁添加量、糖液质量分数、微波渗糖时间对果脯感官评分的影响,结合响应面试验优化微波渗糖的加工工艺。结果表明,在柠檬酸质量浓度为0.75 g/L,百香果原汁添加量为15%,糖液质量分数为15%,微波渗糖时间为25 min条件下,所制得百香果果脯颜色为玫红色,透亮无杂质,软硬度、酸甜度均适中,微黏牙,具有百香果浓郁的风味特征,品质和口感达到最佳,感官评分为93分。经理化指标检测,水分含量、总糖含量和总酸含量均符合相关的国家标准要求。

纤维增强热塑性树脂基复合材料固相复合成型工艺研究进展

纤维增强热塑性树脂基复合材料具有比强度比模量高、结构可设计等优点,广泛应用于汽车、航空航天等领域。本文综述了国内外纤维增强热塑性复合材料固相复合成型工艺的研究现状,分析了不同固相复合成型工艺的成型过程与原理,总结了所制备复合材料的微观结构、力学性能等特点,阐述了此类工艺存在的问题和挑战,并对固相复合工艺的研究方向和发展趋势进行了展望。