Three-dimensional numerical analysis of plant-soil hydraulic interactions on pore water pressure of vegetated slope under different rainfall patterns

Understanding the pore water pressure distribution in unsaturated soil is crucial in predicting shallow landslides triggered by rainfall,mainly when dealing with different temporal patterns of rainfall intensity.However,the hydrological response of vegetated slopes,especially three-dimensional(3D)slopes covered with shrubs,under different rainfall patterns remains unclear and requires further investigation.To address this issue,this study adopts a novel 3D numerical model for simulating hydraulic interactions between the root system of the shrub and the surrounding soil.Three series of numerical parametric studies are conducted to investigate the influences of slope inclination,rainfall pattern and rainfall duration.Four rainfall patterns(advanced,bimodal,delayed,and uniform)and two rainfall durations(4-h intense and 168-h mild rainfall)are considered to study the hydrological response of the slope.The computed results show that 17%higher transpiration-induced suction is found for a steeper slope,which remains even after a short,intense rainfall with a 100-year return period.The extreme rainfalls with advanced(PA),bimodal(PB)and uniform(PU)rainfall patterns need to be considered for the short rainfall duration(4 h),while the delayed(PD)and uniform(PU)rainfall patterns are highly recommended for long rainfall durations(168 h).The presence of plants can improve slope stability markedly under extreme rainfall with a short duration(4 h).For the long duration(168 h),the benefit of the plant in preserving pore-water pressure(PWP)and slope stability may not be sufficient.

Reviews on Post-earthquake Reconstruction of Qiang Culture: Three-dimensional Pattern

Through the introduction of disaster situation of Qiang Culture after Wenchuan Earthquake, the paper emphasized that carriers of Qiang Culture had been seriously damaged, the inheritance of Qiang Culture had been affected, and the environment for Qiang Culture was difficult to recover. It highlighted that three-dimensional reconstruction of Qiang Culture should stress the core task and timely and effectively rescue endangered cultural heritages of Qiang Nationality from the perspectives of material and spiritual life. It had explained focuses of three-dimensional pattern construction in detail. In terms of spatial reconstruction, it should reconstruct native culture and history while material culture was constructed, and reconstruct Qiang culture highland by depending on aborigines; in terms of cluster reconstruction, it should give support to large tourism enterprises and perfect tourism chain; in terms of ecological reconstruction, it should enhance construction and demonstration of "ecological protection pilot area of Qiang culture"; in terms of development reconstruction, it should realize coordinated unity between protection and development according to classification protection, characteristic protection and key protection, so as to form the virtuous circle of post-disaster recovery protection and sustainable development.

Automatic three-dimensional reconstruction based on four-view stereo vision using checkerboard pattern

An automatic three-dimensional(3D) reconstruction method based on four-view stereo vision using checkerboard pattern is presented. Mismatches easily exist in traditional binocular stereo matching due to the repeatable or similar features of binocular images. In order to reduce the probability of mismatching and improve the measure precision, a four-camera measurement system which can add extra matching constraints and offer multiple measurements is applied in this work. Moreover, a series of different checkerboard patterns are projected onto the object to obtain dense feature points and remove mismatched points. Finally, the 3D model is generated by performing Delaunay triangulation and texture mapping on the point cloud obtained by four-view matching. This method was tested on the 3D reconstruction of a terracotta soldier sculpture and the Buddhas in the Mogao Grottoes. Their point clouds without mismatched points were obtained and less processing time was consumed in most cases relative to binocular matching. These good reconstructed models show the effectiveness of the method.

Perceptible landscape patterns reveal invisible socioeconomic profiles of cities

Urban landscape is directly perceived by residents and is a significant symbol of urbanization development.A comprehensive assessment of urban landscapes is crucial for guiding the development of inclusive,resilient,and sustainable cities and human settlements.Previous studies have primarily analyzed two-dimensional landscape indicators derived from satellite remote sensing,potentially overlooking the valuable insights provided by the three-dimensional configuration of landscapes.This limitation arises from the high cost of acquiring large-area three-dimensional data and the lack of effective assessment indicators.Here,we propose four urban landscapes indicators in three dimensions(UL3D):greenness,grayness,openness,and crowding.We construct the UL3D using 4.03 million street view images from 303 major cities in China,employing a deep learning approach.We combine urban background and two-dimensional urban landscape indicators with UL3D to predict the socioeconomic profiles of cities.The results show that UL3D indicators differs from two-dimensional landscape indicators,with a low average correlation coefficient of 0.31 between them.Urban landscapes had a changing point in2018–2019 due to new urbanization initiatives,with grayness and crowding rates slowing,while openness increased.The incorporation of UL3D indicators significantly enhances the explanatory power of the regression model for predicting socioeconomic profiles.Specifically,GDP per capita,urban population rate,built-up area per capita,and hospital count correspond to improvements of 25.0%,19.8%,35.5%,and 19.2%,respectively.These findings indicate that UL3D indicators have the potential to reflect the socioeconomic profiles of cities.

Generative deep-learning-embedded asynchronous structured light for three-dimensional imaging

Three-dimensional(3D)imaging with structured light is crucial in diverse scenarios,ranging from intelligent manufacturing and medicine to entertainment.However,current structured light methods rely on projector-camera synchronization,limiting the use of affordable imaging devices and their consumer applications.In this work,we introduce an asynchronous structured light imaging approach based on generative deep neural networks to relax the synchronization constraint,accomplishing the challenges of fringe pattern aliasing,without relying on any a priori constraint of the projection system.To overcome this need,we propose a generative deep neural network with U-Net-like encoder-decoder architecture to learn the underlying fringe features directly by exploring the intrinsic prior principles in the fringe pattern aliasing.We train within an adversarial learning framework and supervise the network training via a statisticsinformed loss function.We demonstrate that by evaluating the performance on fields of intensity,phase,and 3D reconstruction.It is shown that the trained network can separate aliased fringe patterns for producing comparable results with the synchronous one:the absolute error is no greater than 8μm,and the standard deviation does not exceed 3μm.Evaluation results on multiple objects and pattern types show it could be generalized for any asynchronous structured light scene.

医院净化空调系统的平疫结合设计探究

近期研究发现,优化医院净化空调系统对提高医院的传染病防控能力起到了关键作用。为向新阶段医院净化空调系统的平疫结合设计提供参考,文章采用文献研究法、模拟法对A医院的净化空调系统改造情况进行分析。以对洁净度要求较高的重症监护室(intensive care unit,ICU)为例,分析该区域净化空调系统在气流组织的平疫结合设计、空气处理措施及配套自动控制系统等方面的优化情况。利用广联达GQI软件建立优化系统的三维模型。研究结果能够为今后需要对净化空调系统进行平疫结合改造的医院提供有益参考,有助于提高医院对传染病的防控能力。

锻造炉周边风场对厂区建筑群自然热压通风的影响研究

文章针对锻造炉周边风场对厂区建筑群自然热压通风的影响效果展开研究。设定建筑周边风场参数条件后,以划分建筑通风气流模式为基础,设定风场强度与建筑通风量对应关系;构建热压计算模型,利用该模型获取建筑群自然通风量。实验结果表明,厂区建筑群周边风场的风压受多种因素影响,在室内热源强度的影响条件下,建筑贯流通风模式相比单侧通风模式和浮力通风模式,产生的自然热压通风量更高。

The spring Yellow Sea fog：synoptic and air–sea characteristics associated with different airflow paths

The fog occurs frequently over the Yellow Sea in spring（April–May）, a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provided associated with the fog for the period of 1960–2006. The sea fog is categorized by airflow pathways of backward trajectory cluster analysis with the surface observations derived from international comprehensive oceanatmosphere dataset（I_COADS） I_COADS datasets and contemporaneous wind fields from the National Centers for Environmental Prediction（NCEP）/National Center for Atmospheric Research（NCAR） reanalysis. On the basis of the airflow paths, the large-scale lower-tropospheric circulation patterns and the associated surface divergence,the distribution of a vertical humidity, the horizontal water vapor transportation and the air-sea temperature difference are investigated and the major findings are summarized as follows.（1） Four primary clusters of the airflow paths that lead to spring sea fog formation are identified. They are originated from the northwest, east,southeast and southwest of the Yellow Sea, respectively.（2） Springtime Yellow Sea fog occurs under two typical weather patterns： the Yellow Sea high（YSH） and cyclone and anticyclone couplet（CAC）. Each pattern appears by about equal chance in April but the YSH occurrence drops to around one third and the CAC rises to around two third of chance in May.（3） The common feature in the two types of synoptic conditions is that surface divergence center is located over the Yellow Sea.（4） For the YSH type of fog, water vapor comes mainly from local evaporation with a well-defined dry layer present in the lower atmosphere; for the CAC type of fog, however, water vapor comes mainly from areas outside the Yellow Sea with a thick surface layer of high humidity.（5） With the differences in weather patterns and its associated vertical distribution of the humidity and the transportation of water vapor, there are two types of sea fogs. Most fogs of the CAC types are ＂warm＂ fog, while fogs of YSH type have nearly equal chance to be ＂warm＂ and ＂cold＂ fog.

Nasal airflow of patient with septal deviation and allergy rhinitis

A numerical simulation of a patient’s nasal airflow was developed via computational fluid dynamics.Accordingly,computerized tomography scans of a patient with septal deviation and allergic rhinitis were obtained.The three-dimensional(3D)nasal model was designed using InVesalius 3.0,which was then imported to(computer aided 3D interactive application)CATIA V5 for modification,and finally to analysis system(ANSYS)flow oriented logistics upgrade for enterprise networks(FLUENT)to obtain the numerical solution.The velocity contours of the cross-sectional area were analyzed on four main surfaces:the vestibule,nasal valve,middle turbinate,and nasopharynx.The pressure and velocity characteristics were assessed at both laminar and turbulent mass flow rates for both the standardized and the patient’s model nasal cavity.The developed model of the patient is approximately half the size of the standardized model;hence,its velocity was approximately two times more than that of the standardized model.

Influence of indoor airflow on airborne disease transmission in a classroom

It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow,measured in air change per hour(ACH).However,increasing ACH did not effectively prevent the spread of COVID-19.To better understand the role of ACH and airflow large-scale patterns,a comprehensive fully transient computational fluid dynamics(CFD)simulation of two-phase flows based on a discrete phase model(DPM)was performed in a university classroom setting with people present.The investigations encompass various particle sizes,ventilation layouts,and flow rates.The findings demonstrated that the particle size threshold at which particles are deemed airborne is highly influenced by the background flow strength and large-scale flow pattern,ranging from 5µm to 10µm in the cases investigated.The effects of occupants are significant and must be precisely accounted for in respiratory particle transport studies.An enhanced ventilation design(UFAD-CDR)for university classrooms is introduced that places a premium on mitigating airborne disease spread.Compared to the baseline design at the same ACH,this design successfully reduced the maximum number density of respiratory particles by up to 85%.A novel airflow-related parameter,Horizontality,is introduced to quantify and connect the large-scale airflow pattern with indoor aerosol transport.This underscores that ACH alone cannot ensure or regulate air quality.In addition to the necessary ACH for air exchange,minimizing horizontal bulk motion is essential for reducing aerosol transmissibility within the room.

阻尼式脉动气流分选装置的流场分析

实现颗粒按密度为主导的分离是气流分选研究的关键.对于传统气流分选,运动颗粒的空气动力学特性,即颗粒的沉降末速是影响气流分选的主要因素.理论上在稳定的上升流中,无法实现颗粒按密度为主导的分离.阻尼式脉动气流分选机气流在局部产生加速效应,可以使颗粒按密度分离.通过阻尼式脉动气流分选机流场模拟实验,揭示了气流在阻尼块附近的流场特性,得出了气流在阻尼块上部区域存在明显加速效应的结论,为脉动气流分选效果优于传统气流分选提供了理论依据.实验室实际物料分选实验表明,阻尼式脉动气流分选装置比传统气流分选机有更优越的分选效果,总分选效率提高6%～8%.

塑料大棚气流场模拟及作物蒸腾量计算

为了分析塑料大棚内气流场的特征和计算与作物蒸腾量有关的通风参数,该文通过计算流体动力学模拟了塑料大棚内自然通风量,建立了华东地区常见塑料大棚内平均风速和外部风速之间的线性关系,根据能量平衡和紊流扩散模型建立了一个计算作物蒸腾量的数学模型,并利用棚外的常规气象资料和棚内的实测温度计算了棚内作物蒸腾量。通过将作物蒸腾量的计算值和实测值进行比较,结果发现作物蒸腾量的计算值与实测值比较一致,逐日蒸腾量间的决定系数为0.7756,累积蒸腾量间的决定系数为0.9983,模拟累计值与实测累计值之间标准误差为1.16mm,最大绝对误差为4.82mm;结果表明,所建立的计算方程参数较少,推求的风速参数比较适用于普通塑料大棚。该研究可满足大棚内作物水分管理、温室大棚设计规划和区域水资源管理等方面的需要。

循环吸气支气管内瞬态气流运动特性的仿真研究

人体支气管内的瞬态气流运动对气溶胶在支气管内的沉积产生重要影响,深入认识支气管内的瞬态气流运动特性,对于分析气溶胶在人体支气管内的沉积模式具有重要作用。应用计算流体动力学方法,对人体轻度运动强度下Weibel模型的3级到6级支气管内的瞬态气流运动特性进行了数值仿真,讨论了支气管对称平面、横截面内的瞬态气流组织形式。研究结果表明:在支气管的对称平面内,支气管分叉处产生气流分离现象;在吸气加速阶段,在3级支气管横截面内,没有产生涡流运动;在吸气加速阶段,4级支气管内,呈现出具有内壁附近区域速度高、外壁区域附近速度低的倾斜的抛物线特点的速度分布形式;5级支气管内,形成由两个涡流到四个涡流又到两个涡流的涡流演变过程。在6级支气管横截面内,在吸气加速阶段,和4级支气管横截面相似,在对称平面上下形成两个对称旋转的涡流运动,两个涡流中心分别处于上下平面的中心位置。

华北平原对流风暴的个例分析

应用较详细的卫星云图、多普勒雷达和探空资料对一次强对流风暴进行了综合分析研究。

置换通风在纺织厂应用的探讨

从置换通风的基本理论和纺织厂空气调节的具体情况出发 ,借助CFD手段 ,研究了采用置换通风时纺织厂各车间的送风量的确定、能源消耗、气流组织、温度分布以及空气品质等问题。结果表明 :大多数车间在应用置换通风系统后有较为明显的节能效果 。

体育馆类高大空间的气流组织设计难点及对策

文中讨论了体育馆类高大空间气流组织的主要形式及设计难点 ,并从工程应用的角度给出了相应对策 :指出用计算流体动力学 (CFD)的方法进行体育馆类高大空间的气流组织设计具有很大优势 。

自然通风下栽培番茄的单栋温室内气流场稳态模拟

从N av ier-S tokes方程出发,运用CFX软件对外界风向与屋脊平行和相夹45°两种情形下温室内气流场进行了稳态模拟研究。结果显示,对于前者,气流从山墙门和侧窗的上部进入,从侧窗的下部流出,气流在温室内沿中心纵截面分布的对称性较好,在温室的后半部气流逐渐扩散,紊流加强;对于后者,气流从山墙门和迎风侧窗处进入,两股气流相遇后受棚面形状及作物的影响而形成各种涡流,最后从背风侧窗处流出。气流在接触到栽培作物时流速迅速减小,作物冠层边界受到周围空间气流的影响,但在作物冠层内受周围空间气流影响不大。

空调室内气流组织和空气品质的数值研究进展

介绍了室内空气品质问题的提出、评价,以及改善的方法.从计算流体力学角度对空调室内气流组织和空气品质的研究进展进行了综述,并对尚待解决的问题进行了展望.

CFD技术在洁净室气流组织设计中的应用

本文运用CFD技术作为辅助工具对一ISO5级洁净室内的气流组织进行设计。我们采用CFD技术对光刻胶研发实验室内的气流组织和微尘污染进行了研究。研究中采用了k-ε模型,并用FLUENT软件进行求解。对多种洁净室的气流组织方案进行了数值模拟,并选择优化方案建造了实验室,对此实验室测试了多组数据并与数值模拟的结果进行比较,表明数值模拟的结果是准确的。说明了CFD技术是洁净室设计的可靠辅助工具。

大棚结构型式比较分析

运用三维不可压缩流体的紊流模型,分别对拱型、屋脊型和斜顶型大棚内部气流场进行了精细的数值模拟,并在此基础上进一步计算了大棚的1次换气时间。从模拟结果可以看出,不同型式的大棚,其内部回流区的范围和流速分布形态明显不同,大棚的型式对其内部气流流态有显著的影响。在大棚尺寸和进出口条件相同的情况下,斜顶型大棚换气时间最短,拱型大棚次之,屋脊型大棚换气时间最长。从大棚内部气流流态好坏和1次换气时间长短角度看,斜顶型大棚结构型式较佳。