镧系裂变产物(La、Ce、Pr和Nd)在α-U表面偏析行为的第一原理研究

镧系裂变产物引起的燃料肿胀及包壳脆化是UZr金属燃料服役中的主要问题。其快速扩散通常借助于裂变气体释放通道,实验可观察到镧系裂变产物会在UZr金属燃料氙气泡处偏析。为理解裂变产物扩散机理及表面偏析现象,本文采用第一原理方法,对低温α-U中(100)、(112)、(001)、(021)、(110)、(010)表面的原子结构及形成能进行了研究,并讨论了常见镧系裂变产物La、Ce、Pr和Nd在不同表面的偏析行为。计算结果表明,(110)表面的形成能最低,为1.75 J/m^(2),(112)、(021)和(001)表面的形成能次之,为1.81~1.83 J/m^(2),(010)和(100)表面的形成能最高,分别为1.96 J/m^(2)和2.04 J/m^(2)。4种裂变产物在6种表面都表现出明显的偏析效应,对于同一种表面,其偏析驱动力排序为:La>Ce>Pr>Nd。对于同一种镧系裂变产物,偏析能随层间距的增加而减小。此外,采用Mc-Lean方程从热力学上评估了4种裂变产物在α-U表面的占据率,结果表明在服役温度范围内,4种镧系裂变产物均表现出明显的表面偏析。

钍基熔盐反应堆内化学研究进展和展望

熔盐反应堆是第四代核能系统中唯一使用液态燃料的反应堆,在钍基熔盐反应堆研制和运行中有许多直接与化学相关的关键问题,堪比“化学堆”。于是,因熔盐反应堆研发和运行的需要诞生了放射化学在裂变能利用中的一门新分支学科——熔盐反应堆化学。本实验室利用加速器驱动的中子源和γ能谱分析技术开展了钍基熔盐反应堆化学研究。本文介绍了钍铀转换中间核素~(233)Pa和裂变产物~(131)I及~(95)Nb在熔盐反应堆模拟燃料盐中分布和行为的研究进展。基于对美国橡树岭国家实验室(ORNL)的熔盐反应堆实验装置运行中的燃料盐、锕系元素和裂变产物等相关若干问题分析,提出了在钍基熔盐反应堆框架内熔盐反应堆内化学方面应该进一步开展的研究内容,包括钍基熔盐反应堆运行的化学检测和诊断、影响熔盐氧化还原电势的因素、熔盐氧化还原电势检测的新技术等。熔盐反应堆化学研究的进一步深入将拓展熔盐反应堆化学实践和理论,使钍基熔盐反应堆化学水平提升到新高度,为未来钍基熔盐反应堆高效安全运行提供科学技术方面的支撑和保障。

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.

Soliton Fission and Fusion in (2+l)-Dimensional Boiti-Leon-Pempinelli System

By means of a special Painleve—Baecklund transformation and a multilinearvariable separation approach, an exact solution with arbitrary functions of the (2+1)-dimensionalBoiti-Leon-Pempinelli system (BLP) is derived. Based on the derived variable separation solution, weobtain some special soliton fission and fusion solutions for the higher dimensional BLP system.

MEASUREMENT OF PROMPT NEUTRON SPECTRA OF ^（238）U FISSION INDUCED BY 10．17 AND 12．12 MeV NEUTRONS

Erperimental method to measure the prompt neutron spectra of 238U fissioninduced by fast neutrons has been developed at HI-13 Tandem Van de Grab Accelerator Laboratory of CIAE. These techniques employ a multi-segment fission chamberand tab liquid scintillator neutron detectors. TOF (time of flight) techniques are usedfor prilnny neutrons to select the fission evellts induced by monoenergetic neutronfrom 'H(d, n) reactions instead of breakup neutrons from 'H(d, up) reactions. Thefission neutron TOF spectra are measured in coincidence with the fission fragmellts todistinguish fission neutrons from other secondals neutrons. The method perests measurements to a forly good accuracy under large neutron and gamma ray baCkgroulld.The tecboques are described and experimelltal spectra are presented.

Performance of EDAB-HCl Acid Blended System as Fracturing Fluids in Oil Fields

Due to the high price and formation damage of the guargum fracturing fluid, many oilfields are more and more interested in surfactant based fracturing fluids. The rheological properties of erucicamide dimethyl amidopropyl betaine （EDAB）-HC1 acid blended system and its suitability as fracturing fluid were investigated in this work. The effects of pH, concentration of EDAB, and temperature on the rheological properties of the blended system were studied. The results show that addition of EDAB improved the viscosity of the system from less than 10 mPa. s to about 400 mPa. s, which could retard the acid-rock reaction to about one half at 60℃ and one quarter at 90℃ comparing to straight HC1 acid, suggesting that there is sufficient time for the blended fluid to react with formation rock when it is used as fracturing fluid in an oil field. Core flow tests demonstrated that the EDAB-acid blended fluid could divert itself from high permeability formation core to low permeability one, thus ensuring proper acid placement in the target reservoirs.

Crust Shortening of the Daliangshan Tectonic Zone in the Cenozoic Era and Its Implications

The Daliangshan tectonic zone is a rhombic area to the east of the Anninghe and Zemuhe fault zones in the middle segment of the Xianshuihe-Xiaojiang fault system along the southeast margin of the Qinghai-Xizang （Tibet） Plateau. Since the Cenozoic era, the neotectonic deformation in the Daliangshan tectonic zone has presented not only sinistral slip and reverse faulting along the Daliangshan fault zone, but also proximate SN-trending crust shortening. It is estimated that the average crust shortening in the Daliangshan tectonic zone is 10.9 ± 1.6 km, with a shortening rate of 17.8 ± 2.2% using the method of balanced cross-sections. The crust shortening from folding occurred mainly in the Miocene and the Pliocene periods, lasting no more than 8.6 Ma. Based on this, a crust shortening velocity of 1.3 ± 0.2 mm/a can be estimated. Compared with the left offset along the Daliangshan fault zone, it is recognized that crust shortening by folding plays an important part in transferring crustal deformation southeastward along the Xianshulhe-Xiaojiang fault system.

Notes on Multi-linear Variable Separation Approach

The multi-linear variable separation approach method is very useful to solve (2+1)-dimensional integrable systems. In this letter, we extend this method to solve (1+1)-dimensional Boiti system, (2+1)-dimensional Burgers system, (2+1)-dimensional breaking soliton system, and (2+1)-dimensional Maccari system. Some new exact solutions are obtained and the universal formula obtained from many (2+1)-dimensional systems is extended or modified.

Asymptotic analysis of mode Ⅰ propagating crack-tip field in a creeping material

Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasi-statically growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions can be unified.

Gravity and GPS Measurements at South-West Part of Baikal Rift

Measurements of non-tidal variations of gravity （Ag）, which were obtained from 1992 to 2012 at the Talaya seismic station （located in the south-western part of the Baikal region）, are interpreted together with GPS （Global Position System） observation data, which were obtained from 2000 to 2013 at the same station. An absolute gravimeter was used for gravity observation. The strongest precision requirements concern tidal gravity prediction. It is the reason why we investigated tidal effect by LCR （LaCoste ＆ Romberg） gravimeter from 1996 to 1997 at the same station. We use tested tidal model for correction of gravity change. The linear component of gravity variations corresponds to changes in the elevation of the site. The correlation coefficient is close to the normal value of the vertical gradient of gravity. At this site, coseismic gravity variations at the time of the Kultuk earthquake （August 27, 2008, Mw = 6.5） were caused by a combined effect of the change of the site＇s elevation and deformation of the crust. Our estimations of the coseismic effects are consistent with results obtained by modeling based on the available seismic data.

览物不知深 观道妙于浅——读油画家邵珠春的画

画家邵珠春邵珠春,出生于1979年,山东枣庄人。2001-2005年就读于山东师范大学美术学院油画专业。毕业后任教于枣庄师范,2010年至今就读于首都师范大学美术学院,艺术硕士。主要参展:2011作品《无聊夏日系列》参加"岁月90年"——央美、清华、人大、民大、首师大五校研究生作品联展,获优秀奖;作品《三彩马之裂变系列Ⅰ、Ⅱ》参加"变化"——中美国际美术交流展。2011年作品《无聊夏日系列之九》《无聊夏日系列之十二》参加2011"大学时代——中国艺术院校优秀作品展"。

Collective rotations of fission isomers in actinide nuclei

Using the total-Routhian-surface （TRS） method, the rotational behaviors of fission isomers in the second well of actinide nuclei 234-242U, 236-244pu and 238-246Cm were investigated. The pairing-deformation-frequency self-consistent TRS calculations repro- duced reasonably the experimental moments of inertia extracted from spectroscopic data. It is calculated that, in these largely elongated （β2 ≈0.65 and β4≈ 0.03） fission isomers, the ν1/2-[981] neutron and π1/2＋[651] proton align simultaneously at rotational frequency hω≈0.4 - 0.6 MeV （corresponding to spin I≈80h）, which leads to clear upbending in moments of inertia （MoI＇s）. Our calculations have indicated that the hexadecapole deformation f14 influenced significantly the frequency of the rotational alignment of the proton 1/2＋[651] orbit.

Applying terahertz time-domain spectroscopy to probe the evolution of kerogen in close pyrolysis systems

Terahertz time-domain spectroscopy (THz-TDS) has been used to probe the evolutionary paths of kerogen in selected black mudstone. The evolutionary regime of kerogens (for instance, the immaturity, early maturity, middle maturity, late maturity, and catagenesis stages) can be indicated by the absorption coefficient in the THz region. The present study of identification based on THz-TDS was in good agreement with programmed pyrolysis experiments and suggests that THz technology can act as a nondestructive, contact-free tool for probing the ability to generate hydrocarbons from kerogens.

Abnormality diagnosis of cracks in the concrete dam based on dynamical structure mutation

A method of the fuzzy cross-correlation factor exponent in dynamics is researched and proposed to diagnose abnormality of cracks in the concrete dam. Moreover, the Logistic time series changing from period-doubling bifurcation to chaos is tested first using this method. Results indicate that it can distinguish inherent dynamics of time series and can detect mutations. Considering that cracks in the concrete dam constitute an open, dissipative and complex nonlinear dynamical system, a typical crack on the downstream face of a concrete gravity arch dam is analyzed with the proposed method. Two distinct mutations are discovered to indicate that the abnormality diagnosis of cracks in the concrete dam is achieved dynamically through this method. Furthermore, because it can be directly utilized in the measured crack opening displacement series to complete abnormality diagnosis, it has a good prospect for practical applications.

Angular momentum dependence of quasifission dynamics in the reaction ^(48)Ca+^(244)Pu

The quasifission dynamics in the reaction ^(48)Ca+^(244)Pu is investigated in the framework of time-dependent Hartree-Fock(TDHF)theory. The calculations are performed in three-dimensional Cartesian coordinate without any symmetry restrictions. The full Skyrme energy functional is incorporated in our TDHF implementation. The quasifission dynamics is quite sensitive to the angular momentum of colliding system. The contact time of quasifission decreases as a function of angular momentum and then forms a plateau with small oscillations. The quasifission process is accompanied by an important multi-nucleon transfer. The quantum shell effect plays a crucial role in the mass and charge of quasifission fragments. The mass-angle distribution of the fragments is calculated, which can be compared directly with future experiments.