落实物理学科素养裂变建模科学复习——以“动量与能量结合的模型”为例

针对2019年物理高考复习的现状,提出以模型裂变的方式,用弹簧连接两物体的模型,理解两连接体之间的力与运动、能量与动量之间的变化及相关联系,在这个模型基础上理解物理学中三个代表性模型,用这三个模型在实际应用中解决所有相关实际问题,达到提升学生核心素养,提高应用物理知识解决问题的能力,达到一举多得的多种模式归一的复习模型。

历史语言学族群史观的演变及其解释模型

历史语言学跟民族学、历史学一样都关注族群历史起源研究。历史语言学在其发展进程中先后建立起两种解释语言历史演变的模型——裂变模型和聚变模型。这两种模型反映了历史语言学家对族群历史起源研究的思考。它们的先后建立反映出历史语言学族群史观的一次重要嬗变。

族群历史溯源研究的语言学模型

历史语言学在发展进程中建立起两种解释语言历史演变的模型——裂变模型和聚变模型。这两种模型同时也包含着语言学家对族群历史溯源研究的深刻思考。语言裂变从本质上来说是由族群裂变引发的,语言聚变则是长期而又复杂的族群经济文化互动造成的。

超重核^(274-319)119同位素链的α衰变与自发裂变的竞争

基于统一裂变模型和自发裂变公式,计算了^(274-319)119同位素链的衰变和自发裂变的竞争关系。结果表明在A=283~297区间,核素以衰变为主要衰变模式,在A>297和A<283,核素则是以自发裂变为主要的衰变模式。通过对衰变模式的预测为实验工作提供一定的理论参考。

Pb同位素链(178≤A≤220)的α衰变的理论研究

利用统一裂变模型(UFM),在考虑预形成因子的情况下系统地研究了Pb同位素链(178≤A≤220)的α衰变情况,并利用包含离心势的推广的Royer(G−Royer)公式和the Viola-Seaborg Semi-empirical relationship(VSS)公式做了计算.通过理论计算值与实验值的对比分析,结果表明离心势在原子核的α衰变过程中起着非常重要的作用.同时实验值与理论值良好的一致性表明统一裂变模型、G−Royer公式和VSS公式对于Pb同位素链的α衰变的预测是可靠的,并给出了部分Pb同位素的α衰变半衰期的预测值.

钨(W)同位素链(158

在统一裂变模型下系统的研究了钨同位素链(158<A<180)的α衰变情况,并与两个解析公式UDL和VSS计算结果进行对比分析。计算结果表明,钨同位素链的α衰变半衰期跨度较大从10^(-2.6)-10^(26)s,中子数较小的钨的同位素α衰变较为明显,随着中子数的增大,α衰变半衰期逐渐增大,其核素以其他的衰变方式为主。

ANALYSIS OF STRESS FIELD NEAR CRACK TIP BASED ON ELECTRIC SATURATION MODEL

Within the framework of nonlinear eleetroelasticity, the stress field near to the crack tip in an infinite piezoelectric media subject to a far field uniform loading is studied by using an electrical strip saturation model and the complex variable method. And the emphasis is placed on the stress field near to the crack tip. The obtained solutions show that the normalized stress components at an arbitrary point near to the crack tip are determined by the angle of the point. Moreover, the stress components are independent of the distance from the point to the ori- gin of the coordinate. The distributions of in-plane stress components near to the crack tip are analyzed based on numerical results for PZT-SH. Compared with some related solutions, results show that the solutions are valid.

Study of Pre-equilibrium Fission Based on Diffusion Model

In terms of numerical method of Smoluchowski equation the behavior of fission process in diffusion model has been described and analyzed, including the reliance upon time, as well as the deformation parameters at several nuclear temperatures in this paper. The fission rates and the residual probabilities inside the saddle point are calculated for fissile nucleus n＋^238U reaction and un-fissile nucleus p＋^208Pb reaction. The results indicate that there really exists a transient fission process, which means that the pre-equillbrium fission should be taken into account for the fissile nucleus at the high temperature. Oppositely, the pre-equilibrlum fission could be neglected for the un-fissile nucleus. In the certain case the overshooting phenomenon of the fission rates will occur, which is mainly determined by the diffusive current at the saddle point. The higher the temperature is, the more obvious the overshooting phenomenon is. However, the emissions of the light particles accompanying the diffusion process may weaken or vanish the overshooting phenomenon.

Failure characteristics and its influencing factors of rock-like material with multi-fissures under uniaxial compression

The compression test on rock-like specimens with prefabricated closed multi-fissures made by pulling out the embedded metal inserts in the precured period was done on the servo control uniaxial loading instrument. The influence of fissure inclination angle and distribution density on the failure characteristics of fissure bodies was researched. It was found that, the fissure inclination angle was the major influencing factor on the failure modes of fissure bodies. The different developmental states of micro-cracks would appear on specimens under different fissure inclination angles. However, the influence of fissure distribution density on the failure mode of fissure bodies was achieved by influencing the transfixion pattern of fissures. It was shown by the sliding crack model that, the effective shear, which drove the relative sliding of the fissure, was a function of fissure inclination angle and friction coefficient of the fissure surface. The strain-softening model of fissure bodies was established based on the mechanical parameters that were obtained by the test of rock-like materials under the same experimental condition. And the reliability of experimental results was identified by using this model.

Crack evolution behavior of rocks under confining pressures and its propagation model before peak stress

The understanding of crack propagation characteristics and law of rocks during the loading process is of great significance for the exploitation and support of rock engineering.In this study,the crack propagation behavior of rocks in triaxial compression tests was investigated in detail.The main conclusions were as follows:1)According to the evolution characteristics of crack axial strain,the differential stress?strain curve of rocks under triaxial compressive condition can be divided into three phases which are linear elastic phase,crack propagation phase,post peak phase,respectively;2)The proposed models are applied to comparison with the test data of rocks under triaxial compressive condition and different temperatures.The theoretical data calculated by the models are in good agreement with the laboratory data,indicating that the proposed model can be applied to describing the crack propagation behavior and the nonlinear properties of rocks under triaxial compressive condition;3)The inelastic compliance and crack initiation strain in the proposed model have a decrease trend with the increase of confining pressure and temperature.Peak crack axial strain increases nonlinearly with the inelastic compliance and the increase rate increases gradually.Crack initiation strain has a linear relation with peak crack axial strain.

Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels—mechanism and discussion of characteristic parameters

The mechanism of the zonal disintegration phenomenon(ZDP) was realized based on the analysis of the stressedstrained state of the rock mass in the vicinity of the maximum stress zone, which resides in the creep instability failure of rock mass due to the development of a plastic zone and transfer of the maximum stress zone within the rock mass.Some characteristic parameters of the ZDP are discussed theoretically.In first instance, the analytical critical depth condition for the occurrence of ZDP was obtained, which depends on the characteristics and stress concentration coefficient of the rock mass.Secondly, based on creep theory, the expression of the outer radius of the undisturbed zones in the deep rock mass was obtained with the use of an improved Burgers rheological model, which indicated that the radius depends on the characteristics of the rock mass and the depth of excavation and increases quasi-linearly with the rise of creep compliance of the rock mass.Finally, the formula for the distance of the most remote fissured zone away from the working periphery was derived, which increases logarithmically with the increase in the ratio of the in-situ stress and ultimate strength of rock mass.The distances between fissured zones are discussed in qualitative terms.

Half-Lives for Alpha Radioactivity of Elements with 104 ≤Z≤120 within Unified Fission Model

α decay half-lives are calculated using the Qα values obtained by Semi-empirical Shell Model in the framework of the Unified Fission Model （UFM） with the Coulomb repulsion, nuclear attraction due to proximity potential, and rotational energy due to angular momentum transfer of a particle. In addition, the calculated and experimental half-lives of 425 nuclei are compared to check the validity of the model applied on α decay. The calculated half-lives of decay are in good agreement with the experimental data. Finally, some useful predications on the α decay half-lives are provided for future experiments.

Role of N/Z in Pre-scission Neutrons as an Observable of Nuclear Friction

A dynamical Langevin model is employed to evaluate the excess of the neutron emission in the fission ofheavy nuclei ^(240)Cf,^(246)Cf,^(254)Cf,^(240)U relative to the standard statistical-model prediction at various saddle-to-scissionfriction strengths.It is shown that when the neutron-to-proton ratio N/Z of the system increases,the sensitivityof the excess to the friction decreases substantially,and it almost disappears for ^(240)U.We suggest that using thosecompound systems with low N/Z favors an accurate determination for the saddle-to-scission friction strength based onthe measurement of the pre-scission neutron multiplicity.

Exact Solution of Fractional Diffusion Model with Source Term used in Study of Concentration of Fission Product in Uranium Dioxide Particle

The exact solution of fractional diffusion model with a location-independent source term used in the study of the concentration of fission product in spherical uranium dioxide （U02） particle is built. The adsorption effect of the fission product on the surface of the U02 particle and the delayed decay effect are also considered. The solution is given in terms of Mittag-Leffler function with finite Hankel integral transformation and Laplace transformation. At last, the reduced forms of the solution under some special physical conditions, which is used in nuclear engineering, are obtained and corresponding remarks are given to provide significant exact results to the concentration analysis of nuclear fission products in nuclear reactor.

Model on surface borehole squeezing deformation fracture

As a good method to solve the problem of high methane on the workface and inthe goaf,drawing coal strata methane through a surface borehole is used.However,theexcavation affected the overlying rock strata greatly.When the excavation face passedthrough the surface borehole position,the surface borehole fractures fast.This problemwas seriously related to the unformed squeeze effect.Therefore,a squeezing deformationfracture model based on the rock strata squeezing effect was set up.At the same time,a3DEC simulation model is presented to confirm the theory.The result shows that the modelis reliable and has a good engineering application value.

中子诱发^（233，235，238）U裂变机制的多通道理论研究

用改进的多通道和无规颈断裂模型，计算了能量Ｅｎ＝０—６ＭｅＶ的中子诱发２３３Ｕ、２３５Ｕ裂变和Ｅｎ＝１．３—５．３ＭｅＶ中子诱发２３８Ｕ裂变的碎片的质量分布、动能分布和瞬发中子数分布，理论计算在定量上与实验符合较好．

核裂变现象及其研究现状

通过介绍核裂变的发现及意义、核裂变后现象及其模型理论研究现状,为众多物理学专业、甚至文史类专业的大学生揭开了核裂变这层神秘的面纱,为从事核物理的科学研究、课堂教学以及与大众化的科普活动相结合提供了很好的尝试。

中能质子入射的裂变产物质量分布计算

采用量子分子动力学 (QMD)、统计衰变模型 (SDM)和半经验的多模裂变模型方法计算了能量在 2 0 0MeV附近的中能质子入射重核引起裂变的裂变产物质量分布 ,得到了与实验相符合的结果 ;

10.6MeV/u^(84)Kr+^(27)Al反应中角动量对断点前粒子多重性的影响

用推广的裂变扩散模型研究了角动量对１０．６ＭｅＶ／ｕ８４Ｋｒ（２７Ａｌ，二体裂变）反应断点前粒子多重性的影响，发现阶点前粒子多重性和断点时间随着角动量的减小逐渐增大，而且绝大多数粒子是在鞍点前发射的。对实验中二体裂变反应发生的角动量范围进行权重平均，得到了与实验一致的断点前粒子多重性。同时还研究了影响断点前粒子多重性和断点时间的诸多因素。

断前粒子发射的同位素效应

用推广的裂变扩散模型研究了2 8Si+16 4,16 7,170 Er→192 ,195,198Pb反应中测量的断前中子、质子和α粒子多重性的激发函数 .发现扩散模型能很好地拟合这些轻粒子多重性随裂变系统激发能和Pb同位素的变化趋势 .表明断前粒子发射存在一个同位素效应 .进而在一个考虑了裂变过程中摩擦效应的统计模型的框架内 ,在In和Er这两个元素的同位素链中 ,考察了同位素效应与裂变碎片质量不对称性和裂变系统尺度的关系 .计算结果表明 :同位素效应的存在不依赖于裂变系统的大小和不对称性 .此外 ,当裂变系统具有高的中质比时 ,轻带电粒子发射将不再敏感于裂变延迟时间的长短 ,而中子发射则非常敏感 .这个结果暗示对那些特别丰中子的裂变系统 ,轻带电粒子 (质子和α粒子 )的多重性对于研究热核裂变过程中的摩擦强度不是一个好的探针 .