Interactions of simazine, metsulfuron-methyl, and tetracycline with biochars and soil as a function of molecular structure

Purpose

Biochars are increasingly recognized as effective, inexpensive, and environmentally friendly sorbents for abating organic contaminants. In this study, the sorption and competitive sorption characteristics of simazine (SZ), metsulfuron-methyl (ME), and tetracycline (TC) to corn straw biochars and soil were examined to understand the interactions of herbicides and antibiotics with biochars and the potential role of biochars as engineered sorbents.

Materials and methods

Biochars were obtained by pyrolyzing corn straw at 400, 500, and 600 °C for 6 h under oxygen-limited conditions and were characterized via elemental analysis, N₂-BET surface area determination, ¹³C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. Soil was collected from North Tanggu Farm in Tianjin, and its organic carbon, cation exchange capacity, and particle size distribution were analyzed. The batch sorption experiments were performed to obtain the sorption isotherms of SZ, ME, and TC to biochars and soil.

Results and discussion

The biochars that were pyrolyzed at higher temperatures had higher sorption affinities for SZ, ME, and TC, which may be due to the enhancement of hydrophobic interactions, charge transfer (π–π*) interactions, and pore-filling mechanism. The sorption affinities for these compounds to all biochars decreased in the order SZ?>?TC?>?ME, indicating that the neutral molecule with a stronger hydrophobicity is more easily adsorbed by biochars. For soil, the decrease of the sorption affinities followed the order TC?>?SZ?>?ME due to the high sorption affinity of TC with clays in the soil. Moreover, the sorption affinities of TC by biochars were lower than by soil, indicating that corn straw biochars may be not an ideal sorbent for the immobilization of TC. Biochars were much more effective in sorbing SZ and ME than soil, indicating that corn straw biochars can potentially prevent transport of the herbicides to surface and ground water. Nevertheless, the presence of TC significantly hinders biochar adsorption of SZ and ME, implying that the coexisting contaminants should be considered when developing biochars as engineered sorbents.

Conclusions

The observations in this study demonstrated that the sorption of organic contaminants by biochars is dependent on the properties of the biochars and the molecular structures of the contaminants. Corn straw biochars effectively retain SZ and ME and hinder their transportation to surface and ground water; however, the coexisting contaminants should be considered. Our results will be helpful for designing biochars as engineered sorbents for environmental applications.     

A simulation model of 3D migration of Cs-137 in soils

This paper presents an algorithm and its numerical realization for a simulation model of migration of radiocesium in a certain volume of soil, including non-uniform contamination and pronounced inclination of the soil surface. The model can also be used to predict the redistribution of soil toxicants.     

轴流泵3D实体造型的自动实现

针对目前轴流泵三维(3D)实体造型缺乏自动实现的特点，提出了一种自动实现轴流泵3D实体造型的方法。该方法将数据文件作为水力设计软件和三维造型软件Pro/Engineer之间的桥梁，利用叶片表面离散点表达方式灵活的特点，来构造任意形式的叶片柱面截线的平面展开图，以此生成具有足够精度的叶片特征曲线。在该方法中，轮毂利用二次开发工具Pro/Toolkit和特征描述法直接完成造型；叶片则由特征曲线混成叶片的正背面，再融合叶片的所有表面得到封闭曲面，根据封闭曲面得到实体造型。这种方法的特点是：充分利用了Pro/Toolkit快速灵活的优势，所完成的造型程序适用性强，精度高，可实现任意形式的轴流叶轮的三维自动实体造型。文中给出了叶轮实体造型实例。     

番茄三维形态结构的参数提取及模拟

为了实现番茄植株形态的三维动态重建,通过对其形态结构的周期监测与统计分析,提取番茄主茎器官的形态结构变化规律与主要模型参数。模型中形态结构的演变被看作是生长轴由于节间累积而不断的延伸,果实个数应用二项分布进行随机模拟,番茄叶子典型结构采用马尔可夫过程进行模拟,模型采用悬臂梁弯曲模型实现了叶倾角的动态模拟,并利用计算机图形学技术定义了器官的几何形状,而器官几何尺寸的变化应用贝塔（Beta）分布进行了模拟。模型实现了器官及植株的三维动态模拟并具有较高的逼真效果,器官动态生长与田间测量拟合较好。结果表明模型中引     

双吸式叶轮内流三维数值模拟及性能预测

以时均化的N-S方程和考虑旋转与曲率影响的修正的k- 湍流模型为基础,在贴体坐标系中运用SIMPLEC算法,对双吸式离心叶轮内流进行三维湍流数值模拟。计算得到叶轮内的速度、压力场分布,预估了扬程、水力效率并与试验值进行对比。计算结果表明,在双吸式叶轮中,从叶轮进口到出口压力逐渐增加;在叶片区域,处于前盖板和对称面之间的中间截面上,叶片工作面附近的压力明显大于背面附近的压力,且从对称面到前盖板各中间截面上的压力梯度显著增加;流动关于对称面对称,在对称面上不存在轴向速度;设计工况下叶轮出口断面上压力分布明显比其它工况均匀, 因此水力效率最高。     

利用3D模型模拟天空与叶面散射对玉米冠层截光率的影响

该文利用并行蒙特卡罗光线跟踪模型定量分析了天空散射与叶片散射对玉米冠层截光率的影响.模拟试验表明:相同辐射强度时,冠层截获的光强与受剑照射的叶片在天空散射时都比直接辐射时多;当太阳高度角小于60°时,冠层在阴大截获的总光强小于晴大,但至少60%的叶片在阴大截获的光强大于晴大时截获的光强;叶片散射对冠层光分布的影响与波长...     

植物三维建模ICP点云配准优化

构建精确三维模型无损获取植物表型特征信息,对研究农作物的精准化种植、可视化管理和智能化操控具有实际意义。针对当前植物三维建模过程点云数据量大、配准精度不高的问题,该研究提出基于轻量化处理的迭代最近点算法（Iterative Closest Point,ICP）点云配准优化方法。首先以人机交互算法对获取的植株点云图像进行背景滤除,然后利用高效近邻搜索算法判别点云的离群点进行噪声去噪;通过引入辅助特征坐标参数解决ICP算法配准过程中易陷于局部最优解的问题,获取多组点云的精确配准;最后提出体素化网格法,在保证点云三维形态特征的前提下有效滤除冗余点云数据点。试验结果表明,单株和多植株的精简配准效果良好,表型清晰明显,细节易区分,精简后的植株点云冗余数据减少96.90%～97.35%。精简后的植物点云表型可有效重构植株的形态特征,单植株的株高误差为0.20%～0.45%,冠幅误差为0.17%～0.47%,多植株的株高误差为0.25%～0.60%,冠幅误差为0.42%～0.80%。优化后的ICP算法实现滴水莲点云数据精准融合时间为124.3 s,较暴力算法提升26.75%,冗余点云数据精简96.90%～97.20%,为植物表型的三维建模轻量化处理提供参考。     

超临界CO2干燥罗非鱼片的传质模型和数值模拟

为了探讨超临界CO2干燥罗非鱼的机理,该文基于微分床的质量守恒定律建立了超临界CO2干燥罗非鱼片的传质数学模型,通过Matlab软件对其干燥过程进行了数值模拟,分析了干燥室内超临界CO2中的溶质质量分数和罗非鱼片中的溶质质量分数随干燥时间和干燥床高度变化的规律,揭示溶质在超临界CO2干燥过程中的传质模式。结果表明:在超临界CO2干燥罗非鱼片的过程中,溶质传质主要以对流扩散为主,而以轴向扩散为辅;数值模拟的结果与试验值拟合良好(R2=0.97),相对偏差的绝对值在10%以内,说明建立的传质数学模型能较好的模拟超临界CO2干燥罗非鱼片的过程。研究结果可为超临界CO2干制罗非鱼片的工业化生产的过程控制提供参考。     

番茄的结构-功能模型 Ⅰ：基于有限态自动机的3D形态构建

根据番茄的形态结构特点及其演变规则,应用有限态自动机的数学理论,研究建立了番茄动态发展的随机结构模型。该模型建立在对番茄结构的宏观抽象和生理年龄(PHYAGE)与生长年龄(GA)这两个最重要的基本概念之上,利用“事件驱动”的状态转移机制模拟了番茄生长过程、分枝过程和死亡过程,其中利用了二项随机分布模拟番茄的动态生长,离散的Markov链用于模拟番茄的分枝模式。番茄的有限态自动机模型完成了对主茎上节间长度、果实个数以及叶子结构的随机模拟。并利用试验统计分析获得的参数结果,模拟出番茄在不同生长阶段的3D结构。该动态的番茄结构模型,为与生理生态模型进行接口建立互影响、互反馈的结构-功能模型打下了基础。     

基于X3D的虚拟植物建模与可视化研究

本文在阐述X3D虚拟现实技术的基础上,介绍并分析了基于X3D虚拟植物建模的关键技术和优势,进一步探讨了基于X3D虚拟现实技术植物建模的原理与方法,最后,针对国内外应用现状,提出了应用中出现的问题,并为未来的研究方向进行了展望。     

大田玉米长势的三维图像监测与建模

基于双目立体视觉对大田间玉米生长参数进行测量,并建立玉米三维生长模型,以实现大田玉米生长参数的实时测量和生长过程的三维虚拟显示。以上次测量的平均株高平面为测量区域基准面,利用大津法提取测量区域的玉米叶片。对测量区域进行均匀网格分割,通过对左右网格的匹配,求得覆盖面积和平均颜色。对网格的形心,通过左右视觉的对应进行三维重建,获得形心点云的三维数据和平均株高。利用标杆的测量方法佐证了三维株高测量的正确性。利用上述测量参数,构建了玉米的三维生长模型,并利用OpenGL实现了玉米生长过程的三维虚拟显示。为下一步玉米生物量的实时无损检测以及更精确的玉米三维虚拟建模奠定了基础。     

2D25卧式柴油机冷却水套结构的CFD模拟优化

针对高效低污染卧式柴油机的技术要求,为了设计合理的冷却系统,结合冷却水流动试验,采用计算流体动力学(CFD)三维模拟的方法建立了冷却水流动仿真模型,分析了2D25卧式柴油机强制冷却闭式循环系统的冷却水套结构对冷却水流场的影响,优化了卧式两缸柴油机冷却水套结构。研究结果表明:合理布局缸体进水孔方案可以改善缸体水套内冷却水的流动和冷却效果,减少流动损失,降低水泵的功率损耗。合理设计和布置缸盖入水孔,可以大大提高缸盖水套内冷却水的整体流动速度,减小各缸冷却效果的差异,改善热负荷高的鼻梁区以及排气侧的冷却效果。对原冷却水套结构优化后,水套整体平均流速提高了40%,整体平均换热系数提高了41.7%,在公共水腔和缸体水套上方没有出现原方案的水流撞击和大漩涡,热负荷最高的缸盖底面和鼻梁区冷却水流速和换热明显增强,各缸均匀性变好。     

Long-time 3D CFD modeling of sedimentation with dredging in a hydropower reservoir

Purpose

The purpose of the current study was to present a 3D computational fluid dynamics (CFD) model that can be used to predict long-term (11 years) bed changes in a reservoir due to sedimentation and dredging and that can be done with a reasonable computational time (18 h) on a desktop computer.

Materials and methods

The numerical model solved the Navier-Stokes equations on a 3D non-orthogonal unstructured grid to find the water velocities and turbulence. The convection-diffusion equation for suspended sediment transport was solved to find the sediment deposition pattern. Bed changes were computed and used to adjust the grid over time. Thereby, bed elevations over time were computed. The effect of dredging was also included in the model, and how this affected the bed elevation changes. The main feature of the numerical model enabling a reasonable computational time was implicit numerical methods giving the possibility to use long time steps.

Results and discussion

The results were compared with annually measured bed elevation changes in the reservoir over 11 years. This gave 11 figures of bed elevation changes, due to the combined effect of sedimentation and dredging. Comparing the annually computed and measured bed changes, there was a fair agreement for most of the years. The main deposition patterns were reproduced. The amount of sediments removed in three dredging campaigns were also computed numerically and compared with the measured values. Parameter tests were done for the grid size, fall velocity of the sediments, cohesion, and sediment transport formula. The deviation between computed and measured dredged sediment volumes was less than 16% for all these four parameters/formulas.

Conclusions

The 3D CFD numerical model was able to compute water flow, sediment transport, and bed elevation changes in a hydropower reservoir over a time period of 11 years. Field measurements showed reasonable agreement with the computed bed elevation changes. The results were most sensitive to the sediment particle fall velocity and cohesion of the bed material.

     

低温水热法制备竹生物炭及其对有机物的吸附性能

竹是一类常见的生物质资源,竹加工中产生的废弃物是制生物炭的理想原料。该研究采用水热炭化法,在较低的水热温度下制备竹生物炭,并通过Na OH浸泡和N2氛围下高温煅烧2种方法,对竹生物炭进行进一步改性,所得产品用于去除水溶液中2-萘酚和刚果红。结果显示:仅采用水热炭化得到的竹生物炭产品得率大于54%,表面官能团丰富,均能吸附水溶液中的2-萘酚和刚果红,其中160℃3 h下制备的样品对2-萘酚吸附效果最好,200℃7 h下制备的样品对刚果红吸附效果最好;改性处理会降低终产品得率并影响表面官能团,Na OH浸泡改性处理能增加竹生物炭对2-萘酚和刚果红的吸附容量,N2氛围下高温煅烧改性则不能提高竹生物炭对这2种物质的吸附效果。研究结果可为废弃生物质制炭及生物炭在水污染物吸附分离中的应用提供参考。     

小型农用履带底盘多体动力学建模及验证

多体动力学建模及仿真是研究履带车辆动力学性能的重要手段,其分析结果是否可信取决于所建立的动力学模型是否准确。该文以自主研制的小型农用履带底盘为对象,运用极限理论和瞬态运动分析法建立了履带底盘的运动学方程,运用拉格朗日法建立了履带底盘的动力学方程,在此基础上,结合履带底盘的拓扑结构分析建立了其多体动力学模型,并通过不同路面环境下履带底盘直线行驶的实车试验与仿真结果的对比分析验证了模型的有效性、可信度。结果表明:硬质、松软2种路面环境下履带底盘直线行驶时的平均速度、侧向偏移量、驱动轮转矩和履带张紧力等仿真分析数据与实车试验结果的相对误差分别为5.00%、2.27%,3.86%、6.83%,3.15%、4.66%,0.15%、0.62%,吻合度较好,说明所建立的履带底盘动力学模型准确度较高。该研究可为后期履带底盘动力学性能的深入研究提供参考模型。     

Study on the binding of propiconazole to protein by molecular modeling and a multispectroscopic method

Propiconazole (PCZ) is an N-substituted triazole used as a fungicide on fruits, grains, seeds, hardwoods, and conifers. Although the triazole fungicides have shorter half-lives and lower bioaccumulation than the organochlorine pesticides, possible detrimental effects on the aquatic ecosystem and human health also exist. To evaluate the toxicity of PCZ at the protein level, its effects on human serum albumin (HSA) were characterized by molecular modeling and multispectroscopic method. On the basis of the fluorescence spectra, PCZ exhibited remarkable fluorescence quenching, which was attributed to the formation of a complex. The thermodynamic parameters ΔH and ΔS were calculated to be -14.980 KJ/mol and 26.966 J/(mol K), respectively, according to the van't Hoff equation, which suggests hydrophobic and electrostatic interactions are the predominant intermolecular forces in stabilizing the PCZ-protein complex. Furthermore, HSA conformation was slightly altered in the presence of PCZ. These results indicated that PCZ indeed affected the conformation of HSA.     

离散单元法在土壤机械特性动态仿真中的应用进展

简述了离散单元法的基本原理及其国内外发展现状，介绍了目前地面力学研究领域中离散单元法在土壤机械特性动态仿真中的应用情况，分析了离散单元法在土壤动态行为仿真中应用的可行性，指出离散单元法应用于土壤这样的多相不连续复合体系中，以离散单元的总体行为来描述土壤动态行为具有独特的优越性，提出了离散单元法在土壤动态特征研究中的发展趋势和近期需要解决的关键问题。     

基于三维X-CT图像的结皮土壤孔隙结构特征与渗透率

地表结皮广泛存在于干旱半干旱地区的表层土壤,对水土保持和生态环境有着重要的影响.该研究采用X射线断层扫描成像技术(X-CT)和图像分析方法,获取并分析了3个含表层结皮的土样(孔隙率分别为0.196、0.144和0.093)三维孔隙结构特征,并利用格子玻尔兹曼方法计算了各土样沿深度方向不同土层的渗透率.孔隙结构分析发现,...     

土方作业动态切削的可视实时仿真

针对液压挖掘机驾驶模拟器土方作业仿真中缺乏时变负载——土壤切削阻力,基于Delta3D视景仿真引擎和多体动力学实时交互软件Vortex搭建了系统软件框架,实现了挖掘机车辆动力学特性的真实模拟,并建立了铲斗与土壤的交互仿真平台。根据挖掘机铲斗的实际作业情况,将土壤假定为刚塑性体,并引入地形倾角、加速力、土壤对铲斗侧面摩擦力等参数,推导并修正了Reece提出的土壤切削基本方程,实现了土方作业中土壤动态切削的可视实时仿真。将模型导入到某驾驶模拟器中,进行3次交互作业,获得了土壤相对于铲斗的切削阻力,并对影响切削阻力的因素进行了分析。仿真平台逼真度高、交互性强,实现了铲斗与土壤交互作业具有物理学行为的拟实模拟,可为操作培训人员和产品开发人员提供可视化和交互性的手段,提高培训效果和产品开发效率。