WELL-POSEDNESS IN CRITICAL SPACES FOR THE FULL COMPRESSIBLE MHD EQUATIONS

In this paper we prove local well-posedness in critical Besov spaces for the full compressible MHD equations in R^N, N≥ 2, under the assumptions that the initialdensity is bounded away from zero. The proof relies on uniform estimates for a mixed hyperbolic/parabolic linear system with a convection term.

Critical Temperature of Deconfinement in a Constrained Space Using a Bag Model at Vanishing Baryon Density

The geometry of fireballs in relativistic heavy ion collisions is approximated by a static box,which is infinite in two directions while finite in the other direction.The critical temperature of deconfinement phase transition is calculated explicitly in the MIT bag model at vanishing baryon density.It is found that the critical temperature shifts to a value higher than that in an unconstrained space.

伪辛空间上全迷向子空间的Critical问题

利用伪辛空间的性质和计数定理在伪辛空间上研究了全迷向子空间的Critical问题,得到了相应的计数公式和Critical指数.

酉空间上全迷向子空间的Critical问题

利用酉空间上全迷向子空间的性质及计数定理在酉空间上研究了全迷向子空间的Critical问题,得到了相应的计数公式和Critical指数.

EXISTENCE OF NODAL SOLUTION FOR SEMI-LINEAR ELLIPTIC EQUATIONS WITH CRITICAL SOBOLEV EXPONENT ON SINGULAR MANIFOLD

In this article, we prove that semi-linear elliptic equations with critical cone Sobolev exponents possess a nodal solution.

THE EXISTENCE OF A NONTRIVIAL WEAK SOLUTION TO A DOUBLE CRITICAL PROBLEM INVOLVING A FRACTIONAL LAPLACIAN IN R^N WITH A HARDY TERM

In this paper,we consider the existence of nontrivial weak solutions to a double critical problem involving a fractional Laplacian with a Hardy term:(−Δ)s u−γu|x|2s=|u|2∗s(β)−2 u|x|β+[Iμ∗Fα(⋅,u)](x)fα(x,u),u∈H˙s(R n),(0.1)(1)where s∈(0,1),0≤α,β<2s<n,μ∈(0,n),γ<γH,Iμ(x)=|x|−μ,Fα(x,u)=|u(x)|2#μ(α)|x|δμ(α),fα(x,u)=|u(x)|2#μ(α)−2 u(x)|x|δμ(α),2#μ(α)=(1−μ2n)⋅2∗s(α),δμ(α)=(1−μ2n)α,2∗s(α)=2(n−α)n−2s andγH=4 sΓ2(n+2s4)Γ2(n−2s4).We show that problem(0.1)admits at least a weak solution under some conditions.To prove the main result,we develop some useful tools based on a weighted Morrey space.To be precise,we discover the embeddings H˙s(R n)↪L 2∗s(α)(R n,|y|−α)↪L p,n−2s2 p+pr(R n,|y|−pr),(0.2)(2)where s∈(0,1),0<α<2s<n,p∈[1,2∗s(α))and r=α2∗s(α).We also establish an improved Sobolev inequality,(∫R n|u(y)|2∗s(α)|y|αdy)12∗s(α)≤C||u||θH˙s(R n)||u||1−θL p,n−2s2 p+pr(R n,|y|−pr),∀u∈H˙s(R n),(0.3)(3)where s∈(0,1),0<α<2s<n,p∈[1,2∗s(α)),r=α2∗s(α),0<max{22∗s(α),2∗s−12∗s(α)}<θ<1,2∗s=2nn−2s and C=C(n,s,α)>0 is a constant.Inequality(0.3)is a more general form of Theorem 1 in Palatucci,Pisante[1].By using the mountain pass lemma along with(0.2)and(0.3),we obtain a nontrivial weak solution to problem(0.1)in a direct way.It is worth pointing out that(0.2)and 0.3)could be applied to simplify the proof of the existence results in[2]and[3].

Critical Dimension for Stable Self-Gravitating Stars in AdS

We study the self-gravitating stars with a linear equation of state, P = aρ, in AdS space, where a is a constant parameter. There exists a critical dimension, beyond which the stars are always stable with any central energy density; below which there exists a maximal mass configuration for a certain central energy density and when the central energy density continues to increase, the configuration becomes unstable. We find that the critical dimension depends on the parameter a, it runs from d = 11.1429 to 10.1291 as a varies from a = 0 to 1. The lowest integer dimension for a dynamically stable self-gravitating configuration should be d = 12 for any a E [0, 1] rather than d = 11, the latter is the case of self-gravitating radiation configurations in AdS space.

基于CRITIC和云模型的航天标准化师评价方法研究

针对目前航天标准化师评价方法存在的问题,建立了基于CRITIC和云模型的评价模型。首先,采用文献成熟的评价指标构建了航天标准化师评价指标体系;其次,用CRITIC法对专家评分进行处理,并确定了评价指标的权重;然后,建立了云模型评价方法对航天标准化师进行评价;最后,对模型进行了实例分析。结果表明:该模型是一种合理科学的评价优选模型,能够针对航天标准化师的评价工作取得合理和有效的结果。

基于CRITIC—熵权法的地下空间照明环境评价指标研究

地下空间光环境质量对于提升安全性和舒适性至关重要,光环境评价是改善地下光环境质量的关键,评价指标构成了光环境评价研究的核心基础。本文聚焦地下空间的照明环境,以重庆三峡地下购物中心为研究对象,分别提取影响地下空间照明环境的主观和客观因素,利用CRITIC权重法和熵权法赋权并计算各个影响因素对地下空间光环境的重要性。

基于CiteSpace的急危重症患者救治新体系的可视化分析

目的 基于CiteSpace了解急危重症患者救治的研究现状、研究热点和未来发展趋势。方法 检索2020至2023年CNKI数据库中的相关文献,通过CiteSpace分析急危重症患者救治的研究现状、热点及趋势。结果 研究共获得文献199篇;研究合作不密切,关键词集中于院前急救、转运和阶梯型治疗,其中院前急救和患者转运是研究前沿。结论 近年来,随着急危重症患者数量的增加,相关救治研究也呈增长趋势。未来需加强研究合作,提升研究质量,并持续推动救治体系的建立与完善,以促进急危重症救治领域的发展。

SPACE-R意外掉落事故的临界安全分析

当空间热离子反应堆发生意外掉落事故时,必须采取反应性控制措施保证反应堆处于次临界状态。SPACE-R是设计目标为40kWe、10a寿命的空间核反应堆。适合SPACE-R意外掉落事故的反应性控制方案有:在燃料空腔内加入控制材料及在慢化剂中放入可燃毒物棒。利用MCNP程序分别对两种方案下反应堆的反应性进行计算,可知两种方案均对SPACE-R在意外掉落事故下的反应性有一定的改善。经综合考虑得出一个最终设计方案,能满足意外掉落事故的临界安全验收准则。

STEADY-STATE RESPONSE OF A TIMOSHENKO BEAM ON AN ELASTIC HALF-SPACE UNDER A MOVING LOAD

By introducing the equivalent stiffness of an elastic half-space interacting with a Timoshenko beam, the displacement solution of the beam resting on an elastic half-space subjected to a moving load is presented. Based on the relative relation of wave velocities of the half-space and the beam, four cases with the combination of different parameters of the half-space and the beam, the system of soft beam and hard half-space, the system of sub-soft beam and hard half- space, the system of sub-hard beam and soft half-space, and the system of hard beam and soft half-space are considered. The critical velocities of the moving load are studied using dispersion curves. It is found that critical velocities of the moving load on the Timoshenko beam depend on the relative relation of wave velocities of the half-space and the beam. The Rayleigh wave velocity in the half-space is always a critical velocity and the response of the system will be infinite when the load velocity reaches it. For the system of soft beam and hard half-space, wave velocities of the beam are also critical velocities. Besides the shear wave velocity of the beam, there is an additional minimum critical velocity for the system of sub-soft beam and hard half-space. While for systems of （sub-） hard beams and soft half-space, wave velocities of the beam are no longer critical ones. Comparison with the Euler-Bernoulli beam shows that the critical velocities and response of the two types of beams are much different for the system of （sub-） soft beam and hard half-space but are similar to each other for the system of （sub-） hard beam and soft half space. The largest displacement of the beam is almost at the location of the load and the displacement along the beam is almost symmetrical if the load velocity is smaller than the minimum critical velocity （the shear wave velocity of the beam for the system of soft beam and hard half-space）. The largest displacement of the beam shifts behind the load and the asymmetry of the displacement along the beam increases with the increase of the load velocity due to the damping and wave racliation. The displacement of the beam at the front of the load is very small if the load velocity is larger than the largest wave velocity of the beam and the half space. The results of the present study provide attractive theoretical and practical references for the analysis of ground vibration induced by the high-speed train.

EFFECT OF SURFACE ENERGY ON DISLOCATION-INDUCED FIELD IN HALF-SPACE WITH APPLICATION TO THIN FILM-SUBSTRATE SYSTEMS

In this work the elastic field of an edge dislocation in a half-space with the effect of surface energy has been obtained. The elastic field is then used to study the image force on the dislocation, the critical thickness for dislocation generation in epitaxial thin films with strain mismatch and the yielding strength of thin films on substrates. The results show that the image forces on the dislocation deviate from the conventional solutions when the distance of the dislocation from the free surface is smaller than several times of the characteristic length. Also due to the effect of surface energy, the critical thickness for dislocation generation is smaller than that predicted by the conventional elastic solutions and the extent of the deviation depends on the magnitude of mismatch strain. In contrast, the effect of surface energy on the yielding strength for many practical thin films can be neglected except for some soft ones where the characteristic length is comparable to the thickness.

Accidents during Tanker Accident in Confined Spaces

One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to happen, that＇s why this paper is focusing on differentiating between the manual ＆ more developed equipments used specially in rescuing the crew in such an adequate time, to save the workers＇ life. The manual way is called ＂MUCKY CRANE＂ which is used for rescue purposes onboard tankers, in any of the confined spaces, should be replaced by excel crane which is air or hydraulic driven machine, to achieve better results. As safety precautions measures taken in such tasks are not enough for the required objective achievement. Such safety procedures have been discussed and critical situations have been pointed out.

The Basics of Flat Space Cosmology

We present a new model of cosmology which appears to show great promise. Our flat space cosmology model, using only four basic and reasonable assumptions, derives highly accurate Hubble parameter H0, Hubble radius R0 and total mass M0 values for our observable universe. Our model derives a current Hubble parameter of , in excellent agreement with the newly reported (lower limit) results of the 2015 Planck Survey. Remarkably, all of these derivations can be made with only these basic assumptions and the current CMB radiation temperature . The thermodynamic equations we have generated follow Hawking’s black hole temperature formula. We have also derived a variety of other useful cosmological formulae. These include angular velocity and other rotational formulae. A particularly useful hyperbolic equation, , has been derived, which appears to be an excellent fit for the Planck scale as well as the current observable universe scale. Using the flat space Minkowski relativistic formula for Doppler effect, and a formula for staging our cosmological model according to its average mass-energy density at every Hubble time (universal age) in its expansion, a persuasive argument can be made that the observable phenomena attributed to dark energy are actually manifestations of Doppler and gravitational redshift. Finally, a theory of cosmic inflation becomes completely unnecessary because our flat space cosmology model is always at critical density.

微型反应堆高速撞击下核临界安全的初步分析

微型反应堆可作为月球表面动力、航天器动力等用于太空探索,反应堆发射前需要对发射事故的影响进行安全分析。反应堆高空坠落并撞击到混凝土是主要的临界安全分析场景,高速撞击后反应堆可能重返临界。本文以两种简化的反应堆模型高速撞击场景为例,利用连续介质力学有限元程序ABAQUS与粒子输运蒙特卡罗程序耦合,完成了纯燃料堆芯垂直撞击地面和带径向反射层和屏蔽层圆柱堆30°倾角撞击地面的模拟,预测了两种场景反应堆高速撞击下keff随时间变化的物理特性。结果表明:纯燃料反应堆垂直撞击地面的keff增加最高可达1000×10^(-5),而具有反射层和屏蔽层反应堆30°倾角撞击地面的keff增加最高为200×10^(-5)。均匀密度变化条件下,采用表面非结构网格与内部非结构网格的蒙卡程序的计算结果符合较好,内部非结构网格能够更真实地捕捉材料的非均匀密度变化效应。本文的研究为微型反应堆高速撞击下的临界安全研究奠定了重要基础。

Sequential Vision and Disorienting Experience of Garden Space in Asian Context:Comparative Analysis Based on the Residence of Ena de Silva and Xixi Villa

The blending of Eastern and Western cultures brought about by colonization was an important reason for the changes in Asian architecture in the 20th century.The passive input of Western design concepts into the local tradition caused a long swing in the design direction.The process of regionalism and global modernism from opposition to gradual integration can be found in the development of a series of Asian architectures.Based on the two architectural works of Geoffrey Bawa and Ge Ruliang,this paper discusses how Asian architects make in-depth regional expressions through garden space.

论空间转向:关于空间形式、空间批评与地理批评的概述

空间形式几乎是所有时代和所有文化共有的文学经验与文学阐释的重要方面。空间首先是一个物理的观念,极早成为欧几里得几何学的基本内容。欧洲物理学、哲学、形而上学关于空间及其属性的争论持续了2000多年。空间、地理空间、社会空间、空间形式、空间批评、空间转向是一组相互关联的人文观念。1945年约瑟夫·弗兰克提出了现代文学中的空间形式。空间批评发生于1950-1980年代,巴什拉尔、勒菲弗尔、福柯、詹明信、曼德尔、哈维等从人文地理学、马克思主义、文化批评理论等角度越来越多地关注了空间理论。“空间转向”发生于1990年前后。21世纪初期,其革新的学者范式及其方法迅速从人文地理学扩展/散播到哲学、文学、艺术研究诸领域。

页岩凝析气受限空间相态及开发特征研究

涪页10井的钻探获取了东岳庙段典型陆相页岩相关特征参数,其页岩储层介孔和大孔发育,非均质性较强,主要孔隙分布在10nm左右。纳米孔中受限流体的临界参数偏移使得受限空间下凝析气的流体性质与常规室内实验测试结果存在差异。为更合理地开采页岩凝析气,结合室内相态实验、受限流体临界参数偏移计算和数值模拟,开展页岩凝析气相态特征分析和开采特征研究,明确凝析气的相态变化规律和开采特征。考虑临界参数偏移的凝析气相态特征计算表明:随着孔隙半径减小,体系组分的临界温度、临界压力降低,相图向左下收缩,露点压力降低,气相黏度降低,偏差因子增加,反凝析液饱和度逐渐降低。通过机理模型分析了临界参数偏移对衰竭开采效果的影响,结果表明:随着孔隙半径减小,天然气采收率基本不变,凝析油采收率逐渐增加,孔隙半径减小至10nm,凝析油采收率增加9.93%。研究结果对页岩凝析气藏开发具有指导意义。

城市浅埋隧道自然排烟竖井临界间距研究

竖井间距会改变竖井内外压差,当竖井内外压差为0时,隧道火灾烟气将无法排出,此时竖井对应位置为竖井临界间距。由竖井内外口压差理论分析,给出竖井临界间距理论模型,再采用FDS模拟进行仿真验证。结果表明:设置竖井可明显降低隧道温度,竖井间距为临界间距时,温度下降幅度接近150℃,人员疏散路径温度低于60℃,竖井排烟效率在55%~80%,可有效进行竖井排烟;当竖井间距大于竖井临界间距时,隧道内烟气压强小于竖井出口处风压,竖井排烟效率低于50%。