Reductions in non-point source pollution through different management practices for an agricultural watershed in the Three Gorges Reservoir Area

Non-point source water pollution generated by agricultural production is considered a major environmental issue in the Three Gorges Reservoir Area （TGRA） of China. The Annualised Agricultural Non-Point Source Pollution （AnnAGNPS） model was selected to assess the impact of the application of various management treats, including seven crops, five fertilizer levels and three-group management practice scenarios, on water quality from Heigou River Watershed in TGRA. The scenario subsets include conservation tillage practice （CTP）, conservation reserve program （CRP） and conversion of cropland into forestland program （CCFP）. Results indicated that tea can not be replaced by other crops because comparatively tea resulted in a higher sediment yield. CTP with no-tillage was more effective to reduce sediment yield, but could increased nutrient loss. CRP reduced sediment yield significantly, but slightly benefited on nutrient loss. CCFP reduced not only sediment yield but also the nutrient loss significantly. The conversion of cropland with a slope greater than 10° into forestland was found to be the best scenario as the sediment yield export is less than 5 tons/ha and nutrient loss is within the permissible limit.

基于PointCloudTransformer和优化集成学习的三维点云分类

针对三维点云的不规则性和无序性所导致的难于提取特征并进行分类的问题,提出了一种融合深度学习和集成学习的三维点云分类方法。首先,训练深度学习点云分类网络PointCloudTransformer,并使用主干网络提取点云特征,进而训练基分类器,获得基分类器集合;然后,针对集成学习算法设计基分类器选择模型,模型的优化目标为基分类器组合的差异性和平均总体精度。为了降低集成规模,本文基于增强后的白鲸优化算法提出了二元多目标白鲸优化算法,并使用该算法优化基分类器选择模型,获得集成剪枝方案集合;最后,采用多数投票法集成每个基分类器组合在测试集点云特征上的分类结果,获得最优基分类器组合,从而构建基于多目标优化剪枝的集成学习点云分类模型。在点云分类数据集上的实验结果表明,本文方法使用了更小的集成规模,获得了更高的集成精度,能够对多类别三维点云进行准确分类。

多尺度特征融合对比学习结合PointMetaBase的点云分割

点云场景边界的精确分割对提升三维点云整体分割精度和小目标的分割精度都非常重要。针对现有三维点云语义分割算法中存在的对点云场景边界分割不准确的问题,设计了一种新的多尺度特征融合对比学习方法,并将其集成到PointMetaBase网络上,提出了MFFCL-PMB三维点云语义分割网络。该网络将解码器各层的输入和输出平行多路径地输入多尺度特征提取网络,其次将多尺度特征进行拼接融合,最后由边界搜索模块确定点云场景边界点,在边界点对应的多尺度融合特征上进行对比学习,使网络学习到使特征区分度更大的权重。MFFCL-PMB在数据集S3DIS的测试集区域5上的mIoU为70.9%,相比原始的PointMetaBase,在边界上的mIoU增加了1.4%,内部区域mIoU增加了1.2%,总体mIoU增加了1.2%,边界mIoU增量比内部区域增加的mIoU更大,说明MFFCL-PMB有效增强了PointMetaBase在边界上的分割表现并提高了网络在点云总体上的语义分割性能。

Regulated multi-sited practice for physicians in China: incentives and barriers

The multi-sited practices (MSP) policy in China is expected to exert found implications upon uneven distribution of high-quality medical resources,coupled with the widespread phenomenon of physician's informal practices on multiple sites.Since 2009,the Chinese government has upheld a policy that allows medical doctors to take on secondary jobs for the purpose of encouraging talented physicians to work in medical institutions and underdeveloped areas where their expertise is badly needed.This paper focuses on the MSP policy in China by examining how it has been implemented at the national and provincial levels through a review of government documents,statistical information,academic papers,and newspaper accounts.Despite the MSP policy is to offer incentive to physicians at first-tier public hospitals to work in primary care centers or areas where their expertise,the evidence is hard to find.This paper identifies several outstanding challenges to the MSP policy:(1) The importance of the MSP policy which is made by the central government is perceived differently at the provincial level by health officials and hospital administrators;(2) Interest in implementing the policy varies among physicians and hospitals;(3) Concerns about quality control and legal responsibilities for medical doctors to take on secondary jobs are widespread.China's MSP policy differs from the 'dual practice' policy in many countries because of its top-down approach,with its emphasis on government's role and administrative intervention.This paper's findings may be useful for other developing countries where medical expertise is unevenly distributed due to market forces.On the special occasion of the Alma Ata Declaration's 40th anniversary and for the sake of promoting Universal Health Coverage,this paper also aims at sharing with other countries China's experience in trying to develop an adequate force of primary care professionals.At the end of this paper,a four-point proposal is made for policy makers in China.

基于PointNet++的沙质海岸点云形变监测分析

沙质海岸因其特殊的物理结构,极易受到气候变化的影响而遭受海水侵蚀发生形变。为了获取沙质海岸的形变信息,通常采用M3C2算法计算研究区的形变量,但该方法仅考虑点云间邻域关系,缺失对点云全局的特征描述,因此,本实验采用荷兰Kijkduin地区监测的为期7个月的一公里海岸点云数据作为研究对象,通过PointNet++深度学习算法提取不同尺度点云的局部特征和全局特征,构建点云特征向量的距离度量计算研究区内点云的形变量。实验结果发现,研究区内西部和中部形变量显著,最大月平均形变量为0.3051 m,并根据形变量的变化分析出沙质海岸的形变量与降雨量和温度有密切关系。该研究方法体系充分考虑到点云的局部特征和全局特征,从而实现沙质海岸点云的高效形变监测,对沙质海岸的防护具有重要意义。

基于特征融合的改进型PointPillar点云目标检测

针对PointPillar在自动驾驶道路场景下对点云稀疏小目标检测效果差的问题,通过引入一种多尺度特征融合策略和注意力机制,提出一种点云目标检测网络Pillar-FFNet。针对网络中的特征提取问题,设计了一种基于残差结构的主干网络;针对馈入检测头的特征图没有充分利用高层特征的语义信息和低层特征的空间信息的问题,设计了一种简单有效的多尺度特征融合策略;针对主干网络提取的特征图中信息冗余的问题,提出了一种卷积注意力机制。为验证所提算法的性能,在KITTI和DAIR-V2X-I数据集上进行实验。实验结果表明,所提出的算法在KITTI数据集上与PointPillar相比,汽车、行人和骑行者的平均精度最大提高分别为0.84%,2.13%和4.02%;在DAIR-V2X-I数据集上与PointPillar相比,汽车、行人和骑行者的平均精度最大提高分别为0.33%,2.09%和4.71%,由此证明了所提方法对点云稀疏小目标检测的有效性。

Sedimentation retention basin utilization for best management practice

Approaches to the artificial impoundment and theoretical design of sedimentation retention basin are reviewed with particular attention to best management practice(BMP) to control agriculture and surface runoff. Sediments retention basins are the small version of farm pond used where a criteria of farm pond is not met. Such basin traps the pollutants and suspended solids prior to entry into streams and lakes. The study is focused with special reference to the assessment and control of non point source pollution(NPSP) from the sub basin area of Tai Lake in the Xishan County of Wuxi City of China. The author suggested two different approaches to conduct this study including theoretical design for sedimentation retention basin and computation of flow, sediment transport and deposition during the artificial impoundment of retention basin for BMP's utilization. Theoretical design will provide a useful function as a first line defense against the movement of sediments and transport of pollutants into the Tai Lake while the assessment of sediments deposition will help to make its proper use and periodic cleanup.

Simulation on damage effectiveness of hexagonal prism aimable warhead with multi-point synchronous initiations

In order to study the impacts of warhead geometry and initiation pattern on the lethality of aimable warhead, multi-point synchronous initiated hexagonal prism and cylindrical warheads were compared through numerical simulation, combined with theoretical formulas of fragment decelera- tion and target plugging. Enhancements of fragment velocity, kinetic energy and density toward the target and target destructions were analyzed. The results show that hexagonal prism warhead can produce dense fragment beams and enhance average velocity and kinetic energy with asymmetric eight-point initiation by 24. 13% and 54. 52% respectively, which are higher than those of the isomet- ric or same weight cylindrical warhead. The effective fragments are still relatively concentrated in an area of 8 m × 2 m for the hexagonal prism warhead when the distance between warhead and target is 40 m.

Multi-Point Forming Technology for Sheet Metal

Multi-point forming (MPF) is an advanced manufacturing technology for three-dimensional sheet metal parts. In this paper, the MPF integrated system is described that can form a variety of part shapes without the need for solid dies, and given only geometry and material information about the desired part. The central component of this system is a pair of matrices of punches, and the desired discrete die surface is constructed by changing the positions of punches though the CAD and control system. The basic MPF process is introduced and the typical application examples show the applicability of the MPF technology. Wrinkle and dimple are the major forming defects in MPF process, numerical simulation is a feasible way to predict forming defects in MPF. In conventional stamping, the mode to form sheet metal with blankholder is an effective way to suppress wrinkling; the same is true in MPF. A MPF press with flexible blankholder was developed, and the forming results indicated the forming stability of this technique. Based on the flexibility of MPF, varying deformation path MPF and sectional MPF were explored that cannot be realized in conventional stamping. By controlling each punch in real-time, a sheet part can be manufactured along a specific forming path. When the path of deformation in MPF is designed properly, forming defects will be avoided completely and lager deformation is achieved. A work piece can be formed section by section though the sectional MPF, and this technique makes it possible to manufacture large size parts in a small MPF press. Some critical experiments were performed that confirmed the validity of two special MPF techniques.

Multi-point Contact of the High-speed Vehicle-turnout System Dynamics

The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.

Existence Results of Third Order Multi-Point Boundary Value Problem at Resonance

A kind of third order multi-point boundary value problems, x＇＇＇（ ι） = f（ t, x （ t ）, x＂ （ t ）, x＇＇＇ （ t ） ） ＋ m 2 e（t）,t∈（0, 1）,x（0）=ax（ξ）,x＇（0）-0,x（l）= ^m2∑j=1 βjx（ηj）, fεC[0, 1]×R^3, e（t）∈L^1[0, 1],a≥0, is considered, all theβj＇s have not the same sign, 0〈ξ〈 l, 0〈η1〈 η2〈… 〈ηm.2〈 1. By using the coincidence degree theory, some existence theorems for the problems at resonance are obtained.

SOLUTIONS TO A SECOND-ORDER MULTI-POINT BOUNDARY VALUE PROBLEM AT RESONANCE

This article deals with the following second-order multi-point boundary value problem x″（t）=r（t,x（t）,x′（t））＋e（t）,t∈（0,1）x′（0）=m∑i=1aix′（ξi）,x（1）=n∑j=1βjx（ηj）, Under the resonance conditions m∑i=1ai=1,n∑j=1βj=1,n∑j=1βjηj=1 , by applying the coincidence degree theory, some existence results of the problem are established. The emphasis here is that the dimension of the linear operator is two. In this paper, we extend and improve some previously known results like the ones in the references.

Analysis for the Deployment of Single-Point Mooring Buoy System Based on Multi-Body Dynamics Method

Deployment of buoy systems is one of the most important procedures for the operation of buoy system. In the present study, a single-point mooring buoy system which contains surface buoy, cable segments with components, anchor and so on is modeled by applying multi-body dynamics method. The motion equations are developed in discrete node description and fully Cartesian coordinates. Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board. The trajectories and velocities of different nodes without current and with current in buoy system are obtained. The transient tension force of each part of the cable is analyzed in the process of deployment. Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration. This work is helpful for design and deployment planning of buoy system.

Numerical simulation on the process of multi-point forming for tube

To apply the multi-point forming technology to the field of tube processing,the process of multi-point forming for tube is studied.Numerical simulation for the process of multi-point forming for tube is achieved by using elastic-plastic FEM in ABAQUS.During simulation,reasonable coefficient of mass scaling and friction model of penalty function are used.The influence of several major technological parameters on the process is analyzed.When the tube diameter is 60 mm and the forming curvature radius is 1000 mm,the distortion rate of cross-section and the absolute forming error gradually decrease with the increasing of tube wall thickness;However,when the tube wall thickness is constant,the smaller the curvature radius,the larger the distortion rate of cross-section,but as to forming part,its absolute forming error becomes smaller.

PointPCA:一种三维空间点云的特征提取算法

点云是一个庞大点的集合而且拥有重要的几何结构。由于其庞大的数据量,不可避免地就会在某些区域内出现一些相似点,这就使得在进行特征提取时提取到一些重复的信息,造成计算冗余,降低训练的准确率。针对上述问题,提出了一种新的神经网络——PointPCA,可以有效地解决上述问题;在PointPCA中,总共分为三个模块:a)采样模块,提出了一种average point sampling(APS)采样方法,可以有效地规避一些相似的点,得到一组近似代表这组点云的新的点集;b)特征提取模块,采用分组中的思想,对这组新的点的集合进行多尺度空间特征提取;c)拼接模块,将每一尺度提取的特征向量拼接到一起组合为一个特征向量。经过实验表明,PointPCA比PointNet在准确率方面提升了4.6%,比PointNet++提升了1.1%;而且在mIoU评估测试中也有不错的效果。

A STUDY OF A FULLY COUPLED TWO-PARAMETER SYSTEM OF SEQUENTIAL FRACTIONAL INTEGRO-DIFFERENTIAL EQUATIONS WITH NONLOCAL INTEGRO-MULTIPOINT BOUNDARY CONDITIONS

In this article, we discuss the existence and uniqueness of solutions for a coupled two-parameter system of sequential fractional integro-differential equations supplemented with nonlocal integro-multipoint boundary conditions. The standard tools of the fixed-point theory are employed to obtain the main results. We emphasize that our results are not only new in the given configuration, but also correspond to several new special cases for specific values of the parameters involved in the problem at hand.

Analysis on the Seismic Response of Soil Slopes Based on the Multi-point Input Method

In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters of the target and the contact surface of the external media are identical,i. e., single point input. However, earthquake energy has an attenuation phenomenon in wave propagation,so a wide range of soil slopes and the external medium contact surface of different input points on motion are not identical. If we consider single point input only, it may not correspond with reality, so it is necessary to carry out research on multi-point input methods. Based on the 2-D slope model,single-point input and multi-point input are performed respectively to analyze and compare their similarities and differences in the perspectives of the characteristics of seismic response of soil layer and plastic zone distribution to provide a reference for the seismic design of slopes. The results show that in the perspective of soil seismic response analysis,the peak acceleration output and peak velocity output under multi-point input are greater than the peak values under single point input at the same monitoring point,the peak appearing time is also earlier than that of the single point input; in terms of the plastic zone distribution,the multi-point effect is manifested as the presence of more obvious tensile shear failures; in the perspective of safety coefficient,the safety coefficient under each multi-point input is smaller than that of single point input,a difference of about 7 % or so. In summary,multi-point input is more reasonable and practical than single point input,so multi-point input should be considered in seismic design.

Practical points that gastrointestinal fellows should know in management of COVID-19

Pandemics obligate providers to transform their clinical practice.An extensive effort has been put to find out feasible approaches for gastrointestinal diseases and also to manage coronavirus disease 2019(COVID-19)related gastrointestinal conditions.Diarrhea,hepatitis,and pancreatitis can be seen in the COVID-19 course.Endoscopic procedures increase the risk of contamination for medical staff and patients despite precautions,therefore indications should be tailored to balance risks vs benefits.Furthermore,whether the immunosupression in inflammatory bowel diseases,liver transplantation,and autoimmune liver diseases increases COVID-19 related risks and how to modify immunosupression are topics of ongoing debate.This review aims to provide most up to date practical approaches that a gastrointestinal fellow should be aware on the problems and management of gastrointestinal and hepatobiliary diseases during the COVID-19 pandemic.

Existence of Solutions to Multi-point BVP with p-Laplacian at Resonance

This paper is concerned with the existence of solutions for the following multipoint boundary value problem at resonance{(Φp (x'))' + f(t,x)=0,0 < t < 1,x' (0)=x'(ξ) x(1)=m-3 ∑i=1 βi x(η i),where βi∈ R,m-3 ∑i=1 β i=1,0 < η 1 < η 2 < ··· < ηm-3 < 1,m-3 ∑i=1 βiηi=1,0 < ξ < 1.An existence theorem is obtained by using the extension of Mawhin's continuation theorem.Since almost all the multi-point boundary value problem at resonance in previous papers are for the linear operator without p-Laplacian by the use of Mawhin's continuation theorem,our method is new.

Solvability of Non-homogeneous Mixed Type Multi-point BVPs for Second Order Differential Equations with p-Laplacian

A class of multi-point boundary value problems are studied.Easily verified suffcient conditions to guarantee the existence of at least one solutions of above mentioned BVPs are established.The examples are presented to illustrate the main results.