POINTWISE CONVERGENCE RATE OF VANISHING VISCOSITY APPROXIMATIONS FOR SCALAR CONSERVATION LAWS WITH BOUNDARY

This article is concerned with the pointwise error estimates for vanishing vis- cosity approximations to scalar convex conservation laws with boundary.By the weighted error function and a bootstrap extrapolation technique introduced by Tadmor-Tang,an optimal pointwise convergence rate is derived for the vanishing viscosity approximations to the initial-boundary value problem for scalar convex conservation laws,whose weak entropy solution is piecewise C 2 -smooth with interaction of elementary waves and the ...

Reinvestigation of the scaling law of the windblown sand launch velocity with a wind tunnel experiment

Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions.The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand particle,which has been investigated by the experimental measurement and numerical simulation.However,the obtained results in literatures are inconsistent.Some researchers have discovered a relation between average launch velocity and wind shear velocity,while some other researchers have suggested that average launch velocity is independent of wind shear velocity.The inconsistence of launch velocity leads to a controversy in the scaling law of the sand transport rate in the windblown case.On the contrary,in subaqueous case,the scaling law of the sand transport rate has been widely accepted as a cubic function of fluid shear velocity.In order to explain the debates surrounding the windblown case and the difference between windblown and subaquatic cases,this study reinvestigates the scaling law of the vertical launch velocity of windblown transported sand particles by using a dimensional analysis in consideration of the compatibility of the characteristic time of sand particle motion and that of air flow.Then a wind tunnel experiment is conducted to confirm the revisited scaling law,where the sand particle motion pictures are recorded by a high-speed camera and then the launch velocity is solved by the particle tracking velocimetry.By incorporating the results of dimensional analysis and wind tunnel experiment,it can be concluded that,the ratio of saltons number to reptons number determines the scaling law of sand particle launch velocity and that of sand transport rate,and using this ratio is able to explain the discrepancies among the classical models of steady sand transport.Moreover,the resulting scaling law can explain the sand sieving phenomenon:a greater fraction of large grains is observed as the distance to the wind tunnel entrance becomes larger.

Study on numerical simulation of organic pollutant transport in groundwater northwest of Laixi

The construction and hydrogeological area in the low hill, which is northwest of Laixi City and in the east of Shandong Province more precisely, is one of Dagu River's groundwater source. Regarding COD as the typical pollutant according to general situation of groundwater pollution in aforementioned area, a three-dimensional advection-dispersion model was established to simulate the transport of organic pollutants under two accident conditions. In addition, the effect of corresponding dispersity was analyzed. The results show that COD transport is mainly in accordance with the direction of groundwater flow, pollutant concentration and its gradient as well as the rule of narrower pollution range in deeper stratum. Moreover, COD is mainly transported and diffused in groundwater of sandy soil in the first and second layers. However, under accident condition II, the pollutant concentration begins to decay gradually after its transport and diffusion tends to be stable. Besides, in terms of dominance, dispersion is to transverse transport of pollutants what advection is to longitudinal transport. If considering random dispersion, the final results see higher peak concentration of COD and longer transverse distance from pollution center compared to transport route. What's more, the pollution plume changes and concentration isocline becomes slightly irregular.

Nonlinear Analysis of Bedload Transport Rate of Paroxysm Debris Flow

The evolution characteristics of bedload transport feature of paroxysm debris flow have been studied by means of both theory analysis and experimental data.The analysis based on the flume experiment data of a sand pile model as well as a large amount of field data of debris flow clearly shown that the statistical distribu- tion for the main variable of the sand pile made of non-uniform sand (according the sand pile experiment,φ≥2.55) conform to the negative power law,that means the non-uniform sand syste...

RENEWAL OF BASIC LAWS AND PRINCIPLES FOR POLAR CONTINUUM THEORIES (Ⅵ)—CONSERVATION LAWS OF MASS AND INERTIA

The purpose is to reestablish the coupled conservation laws, the local conservation equations and the jump conditions of mass and inertia for polar continuum theories. In this connection the new material derivatives of the deformation gradient, the line element, the surface element and the volume element were derived and the generalized Reynolds transport theorem was presented. Combining these conservation laws of mass and inertia with the balance laws of momentum, angular momentum and energy derived in our previous papers of this series, a rather complete system of coupled basic laws and principles for polar continuum theories is constituted on the whole. From this system the coupled nonlocal balance equations of mass, inertia, momentum, angular momentum and energy may be obtained by the usual localization.

Transport properties of CrP

CrP has many exotic physical properties due to a four-fold degenerate band crossing at the Y point of the Brillouin zone,which is protected by the nonsymmorphic symmetry of the space group.We carried out the heat capacity,electrical and thermal transport measurements on CrP and extracted the electron thermal conductivity.Due to the difference in energy and momentum relaxation time during electron-phonon inelastic scattering,the normalized Lorentz number decreases below about 160 K.Below 25.6 K,the normalized Lorentz number begins to recover,which is due to the dominance of elastic scattering between electrons and defects at low temperatures.

Mixture flow of particles and power-law fluid in round peristaltic tube

The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.

权宜之计抑或权利扩张:学前教育立法中的托育服务

国家在2023年重拾学前教育立法工作,并公布了《学前教育法(草案)》,学前教育与托育服务被法条明文分离切割。实际上托育服务自20世纪末式微之后,并非无法可依,而是在一定程度上寄身于学前教育立法以获取发展空间与法律支持,尤其是在地方立法中呈现出类型多样的立法模式。尽管对于部分地方立法将托育服务纳入学前教育制度的立法技术,在特定历史阶段下应肯定其必要性与合理性,但作为填补立法空白的权宜之计,该立法技术也日渐暴露出了覆盖范围有限、“过度学习”风险、保障水平较低等诸多现实问题。有鉴于此,托育服务专项立法势在必行,其根本实现路径是从基本权利保护的视角出发,承认获得托育服务权是一项有别于受教育权的基本权利,明确权能内涵,具体化相对应的各类国家义务。

国外典型国家综合性交通运输立法经验及启示

目前,我国综合性交通运输立法空缺,《交通运输法》已列入国家立法计划。为开展好我国综合性交通运输立法工作,采用对比分析方法,研究了国外典型国家综合性交通运输立法主要经验,分析了各国综合性交通运输法律,即美国综合交通运输系列法案、日本《交通政策基本法》、法国《国内交通基本法》和韩国《国家综合交通运输体系效率法》的立法思路和重点制度。在此基础上,结合我国综合性交通运输立法现状与需求,提出了加强我国综合性交通运输立法、起草《交通运输法》的建议。研究认为,我国综合性交通运输立法要加快步伐,满足国内综合交通运输体系建设的需要,需厘清立法思路,确立重点法律制度,包括明确交通运输发展总要求、确立综合交通运输管理体制、建立促进综合交通融合发展的制度、建立综合交通运输体系保障机制、明确综合交通安全绿色发展原则等。

《仲裁法》如何更加国际化——基于《仲裁法(修订)(征求意见稿)》主要条款的考察

《仲裁法(修订)(征求意见稿)》通过大幅修订,力求促进我国仲裁制度的进一步国际化发展。以《示范法》和《纽约公约》为国际化对标标准,《仲裁法(修订)(征求意见稿)》在仲裁庭权力和仲裁裁决的司法审查、临时仲裁、法院协助取证等方面基本符合国际标准,但应进一步细化具体措施的实施标准和配套规则,以期为仲裁实践提供更为清晰的指引。此外,此次修订在仲裁机构法律地位、仲裁员任职资格与责任等方面还未达到国际化标准,可以进一步提升意思自治程度,深化仲裁机构改革、引入仲裁员责任有限豁免制度。

基于“认知—技术—法治”框架的交通知识产权“走出去”研究

知识产权治理已成为交通现代化治理和交通国际合作的重要内容,交通知识产权“走出去”能促进交通运输行业自立自强、实现交通运输技术创新、扩大交通运输对外开放、促进交通企业可持续发展、推动构建人类命运共同体。本文基于“认知—技术—法治”框架分析交通知识产权“走出去”的现状及面临的主要问题,借鉴美欧日在国际交通知识产权竞争中的经验,探究推动交通知识产权“走出去”的路径与对策。提出中国应该积极参与全球交通知识产权治理,主动参与国际规则制定,缩小与相关国家或地区在知识产权制度、保护、运用、管理、服务等方面的差距,消除或减少我国交通企业“走出去”的知识产权障碍,为交通领域知识产权全球治理贡献中国智慧与方案。

抚养权直接执行的理论阐释与实现路径

抚养权执行难是长期困扰司法实践的难题。《中华人民共和国民事强制执行法(草案)》所创设的抚养权直接执行制度是纾解该难题的关键举措。为保障预期立法目的的实现,应从正当性及可行性上补强理论阐释。在正当性方面,明确抚养权判决系具备执行内容的形成判决。在可行性方面,执行标的为交出子女的行为而非子女人身,直接执行并不侵害被执行人的意志自由。针对抚养权直接执行适用中如何正确考量子女意愿的困境,需要以子女对执行行为本身的认识作为判断是否继续采取直接执行的标准。据此,提出抚养权直接执行的实现路径,即赋予执行机关考量未成年子女意愿的义务;建立有效收集未成年子女真实意愿的机制;明确未成年子女“拒绝意思”的认定标准。

《中华人民共和国学位法》制定中的若干重要法律问题

2024年4月26日,全国人大常委会审议通过的《中华人民共和国学位法》(以下简称《学位法》)是我国教育法律体系中的一个重要里程碑,其影响深远。《学位法》制定过程中涉及若干重要的法律问题:一是《学位法》在我国教育法律体系中的地位;二是国家学位制度与大学学位制度的关系;三是《学位法》立法的目的、立法依据和适用范围;四是学位授予单位资格的取得和丧失的条件与程序;五是学位评定委员会与学术委员会的关系;六是校学位评定委员会、院系评定委员会分会与答辩委员会的关系;七是学位撤销的条件与程序;八是有关学位纠纷的法律解决;九是对国外大学学位的认证,等等。对以上法律问题的分析与思考,对理解和适用《学位法》至关重要。同时,作为教育法律体系的一部分,《学位法》并没有穷尽所有细节,主要是确定了原则和框架,为学位工作的具体操作提供坚实的法律基础。总之,一部公正、透明、有利于学术发展的《学位法》对促进学术交流、提升教育质量、维护学位制度的权威性具有重要作用。

民国初年民事“第一法源”的确立——民初大理院对“现行律民事有效部分”的形塑

学界普遍认为《大清现行刑律》民事部分的效力由1912年4月3日南京临时参议院的决议所确立,但梳理史料却能得出不同的结论。原因在于,该决议由南方政权作出且并未被北洋政府承认,故民事法源的空白未在立法层面得到解决。“现行律民事有效部分”的确立,离不开大理院在“司法兼营立法”过程中的塑造。民初民事“第一法源”的确立,大致经历了通过《大清民律草案》的尝试与挫败、大理院确立“现行律民事有效部分”的地位、剥离《大清现行刑律》刑法属性及该律地位的巩固等阶段。纵观民事“第一法源”的确立,自清末兴起的“诸法合体说”起了关键作用,大理院根据该观点将《大清现行刑律》区分为不同的部门法,既解决了“无法可依”的困境,又避免另立新民法将会遭受的阻力。

含粗骨料尾砂膏体长距离管输流变特性及阻力预测

为探明质量浓度、粗骨料含量、灰砂质量比和水化时间对膏体长距离管输流变特性的影响,本文基于正交设计开展流变实验,采用回归分析建立流变参数预测模型,在此基础上通过理论推导建立管道阻力预测模型,采用现场实测数据验证阻力预测结果的可靠性。结果表明:含粗骨料尾砂膏体属于宾汉流体,质量浓度和粗骨料含量对膏体流变参数的影响最显著;屈服应力随质量浓度的增大呈指数增长,随粗骨料含量的增加呈指数减小,随水化时间的增加呈线性增长,与灰砂质量比的关系不大;塑性粘度随质量浓度的增大呈指数增长,随粗骨料含量的增加呈线性减小,随灰砂质量比和水化时间的增加呈线性增长;建立的流变参数预测模型平均误差小于4.3%,基于宾汉流变模型建立的管道阻力模型预测值比现场实测值偏大12.5%,满足工程应用的精度要求。

我国货运结构调整的理论认识和实践难点

为探寻货运结构调整理论原点,认识货运结构发展演变规律,探究梳理了货运结构调整的理论源头和发展规律,总结了我国货运结构调整面临的难题,进而提出货运结构调整的工作重点。研究认为,供需交易决定货运结构的形成、货运结构调整工作主线在供给侧;公路是货运占比最大运输方式、公路货运比重长期持续上升是难以改变的世界性规律,而以铁路、水路为主的多式联运优势主要在特定细分货运市场;我国货运结构调整面临公路货运结构比重偏高、多式联运发展相对滞后、运输组织方式尚不适应等难题,有关政策应重点平衡总体局部关系、把握主辅配合关系、善用推拉关系,以多式联运发展带动运输结构优化调整。

从动物防疫角度浅谈实验动物运输的法律规定

实验动物运输活动应按照相关法律规定做好动物防疫工作,以防止实验动物疫病远距离跨地区传播。本文从动物防疫的角度概括了国内机构通过道路运输实验动物,尤其是向无规定动物疫病区运输实验动物,在运输前、中、后不同环节应遵循的法律规定及相关要求,并指出运输环节易出现的违规问题及处罚规定,提出了动物防疫部门应加强运输实验动物的动物卫生监管及相关法律法规宣传,实验动物运输机构应加强动物防疫相关法规的学习,做到依法运输实验动物。本文为相关单位及人员做好实验动物卫生防疫工作提供参考。

穿心电加热管道仿真和集输规律分析

随着外围油田深入开发,零散区块不断开采,穿心电加热技术得到了广泛应用。由于电线插入后管道内流体流动和传热的规律尚不明确,因此现场主要依靠保持电加热系统高功率运行来保证原油的安全输送,能耗浪费严重。针对穿心电加热管道的环空结构,基于质量、动量和能量守恒定律,分析电线插入管道后带来的摩擦和加热效应,建立了穿心电加热管道稳态温度和压力计算模型。结合智能算法校核摩阻和总传热系数,实现了不同功率下穿心电加热管道沿线水热力参数的准确计算;同时分析了含水率、输量、起点温度、功率和加热方式对电加热管道温度、压力、维温功率和维温能耗的影响情况。利用大庆油田电加热管道现场数据对模型进行了验证,结果显示:压力平均误差为7%,温度平均误差为4.16%,能够对生产起到指导作用,基本满足生产需要;此外,增大输量有助于节能降耗,全线维温是最节能的运行方式。

人权保障视角下的治安管理处罚程序创新与优化

2023年9月1日公布的《中华人民共和国治安管理处罚法(修订草案)》对现行《中华人民共和国治安管理处罚法》作出了较大幅度的修改,其中涉及“处罚程序”章节的修改合计29处,主要修改内容包括以“立案”取代“受理”等7个方面。这对治安管理处罚程序的规则优化和体系完善具有积极的推动作用,应予以充分肯定。从良法善治的标准看,《中华人民共和国治安管理处罚法(修订草案)》在基本权利保障规范、正当程序原则条款设计、控权机制优化等方面还需要进一步改进:一是应将行政拘留纳入听证范围,并将集体讨论作为处十日以上行政拘留决定的必经程序;二是需要明确集体讨论程序的启动程序、参加人员构成、讨论形式及效力等内容;三是继续优化行政程序控权机制,明确和扩大程序条款的规范效力,赋予当事人必要的拒绝权。

冷链运输车空调冷风机运行自适应PID控制方法研究

冷链运输车空调冷风机运行环境复杂,导致传统的比例积分微分(PID)控制过程难以准确设定控制参数。为解决这一问题,设计冷链运输车空调冷风机运行自适应PID控制方法。首先,通过分析冷链运输车空调冷风机工作过程,选取多个控制参数,以降低复杂度。然后,设计基于自适应PID控制器的控制模型,以送风温度和送风压力作为控制量,将冷、热水流量及风机转速作为被控制量,求解控制量和被控制量的传递函数。最后,根据传递函数与期望值间的耦合关系,对控制分量的增减进行调整,以实现冷链运输车空调冷风机运行的自适应PID控制。试验结果表明,该方法能够使冷链运输车内温度保持稳定。该方法控制精准度高、鲁棒性强、实用价值高,可以确保货物在整个冷链运输过程中的质量和安全。