水下不分散混凝土试验与抗裂性能分析

针对目前混凝土在水下浇筑过程中出现的分散严重、无法达到预定强度、浇筑完成后电通量高的问题,对影响混凝土抗分散性、强度的因素进行了试验研究及理论分析．首先采用了调整外加剂、增加掺和料的方式,对使用2种类型的外加剂制作的6组配合比的混凝土试件进行了试验研究,找出了影响混凝土电通量与氯离子渗透性的关键影响因素,并对混凝土内含裂纹初始起裂角随裂纹倾角的变化规律进行了研究,找出了影响混凝土抗裂强度的因素,并将混凝土水下悬浊物含量降低至预定范围之内;通过对陆上和水下工程的验证性应用成功研制了水下不分散混凝土,并对其性能作进一步深化研究．所推荐的不分散混凝土配合比,已经成功得到工程应用的验证,可借鉴和推广应用到类似的水下浇筑、修复等工程的施工中．     

Theoretical Calculations of Strain—Induced Splittings and／or Shifts of t2^32E and t2^34A2 Levels for MgO：Cr^3＋

Under various uniaxial stresses, both strains with low symmetry and isotropic strains of crystals take place. The former gives the strain-induced low-symmetry crystal fields and accordingly splittings of levels; the latter gives the isotropic parts of strain-induced crystal fields and accordingly shifts of levels. By using the wavefunctions obtained from the diagonalization of the complete d^3$ energy matrix in a regular octahedral field, the relevant matrix elements and accordingly strain-induced splittings and/or shifts of t₂³²E and t₂³⁴A₂ for MgO:Cr³⁺ have been calculated. Their physical origins have been thoroughly analyzed and revealed. It is the admixtures of basic wavefunctions resulted from the spin-orbit interaction and/or Coulomb interaction and/or Kramers degeneracy that make strain-induced splittings of levels nonzero. In contrast with this, strain-induced shifts come mainly from the zero-order approximate wavefunctions. It is found that there are nonvanishing matrix elements of operators T₂ξ, T₂η and T₂ζ between wavefunctions with positive M_s and those with negative M_s', which have important effects on strain-induced splittings of levels. The shifts of t₂³²E under both hydrostatic pressure and uniaxial pressure have been uniformly calculated. The important results of Y_c, Z_c, P_c, Q_c and 〈t₂|| C(A₁)|| t₂〉have been evaluated.     

混合规划处理流水车间调度问题

针对不确定条件下流水车间调度问题(F low shop schedu ling),研究了含有随机参数和灰色参数的混合机会约束规划模型的建立及求解方法。提出了灰色模拟的概念和方法,为含有灰色参数的机会约束规划提供了求解途径。通过理论推导及仿真实例,结合遗传算法,验证了基于随机模拟和灰色模拟的混合机会约束规划的调度模型及求解方法的有效性。     

Determination of pozzolanic activity of materials by thermal analysis

The results of pozzolanic activity determination using DTA-TG method are presented. This feature was characterised by Ca(OH)₂ residue determination in cement pastes admixtured with siliceous earth, consuming the calcium ions from hydrolysis of cement clinker minerals. The rate of pozzolanic reaction was thus estimated. Some results for fly ash containing pastes were also given. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structure of interparticle space in great noncrystalline packings of Lennard-Jones atoms and its influence on diffusional mobility of admixture particles

Models of 100,000 atoms interacting with Lennard-Jones potential have been constructed using the Monte Carlo method at different densities and temperatures. In these models, the structure of empty space is investigated in which the test particle with a diameter smaller than the diameter of matrix atoms can move. The percolation thresholds, when “infinite” cavities penetrating all model space arise, are found. A change of density and temperature of matrix preparation leads to a non trivial redistribution of volume between cavities of different type. By the method of molecular dynamics it is found that the usual (Einsteinian) law of diffusion is established rather quickly, on average. However, the laws for test particles moving in cavities of different type are more complex and specific to each kind of cavities. It should result in different course of chemical reaction in different local areas of a matrix.     

喷射混凝土新型增稠速凝剂研究

不同水泥的增稠对比试验表明：喷射混凝土新型增调速凝剂（IVA）具有良好的增稠效果经扫描电镜的观察分析,其增稠原理是IVA分子的吸附“架桥”和液相膜空间网络综合作用;不同水泥、不同水灰比时凝结时间测定表明IVA具有良好的速凝适应性;强度试验证实IVA对水泥各龄期强度发展有利;在矿山巷道的应用表明IVA能明显减少喷射混凝土回弹．图3,表4,参4     

影响高性能混凝土工作性和强度的主要因素的正交试验研究

研究结果表明：水胶比、减水剂掺量及胶凝材料总量对砼坍落度影响显著,碎石粗骨料种类对砼强度有显著影响．结果选择出一个具有良好坍落度（２００ｍｍ）和较高强度（８０．５ＭＰａ）的砼配合比,而其水泥用量只有４５０ｋｇ／ｍ３．图１,表３,参４．     

Effect of Some Aromatic Admixtures on the Raman Line Intensity of Solid Cyclohexane at 77 K

The dependence of the intensity of Raman line components of E_g symmetry of cyclohexane, frozen rapidly down to 77 K, on the concentration of admixtures of benzene or naphtalene was studied quantitatively. The admixture of benzene was found to facilitate to a larger extent the overcooling of phase I of solid cyclohexane than admixture of naphtalene.     

Reparameterization of hybrid functionals based on energy differences of states of different multiplicity

 Low-spin/high-spin energy splittings for Fe(II) transition-metal complexes – particularly in weak ligand fields – cannot be well described by density functional methods. Different density functionals yield results which differ by up to 1 eV in transition-metal complexes with sulfur-rich first coordination spheres. We attribute this failure to the fact that the high-spin state is systematically favoured in Hartree–Fock-type theories, because Fermi correlation is included in the exact exchange, while Coulomb correlation is not. We thus expect that the admixture of exact exchange to a given density functional will heavily influence the energy splitting between states of different multiplicity. We demonstrate that the energy splitting depends linearly on the coefficient of exact exchange admixture. This remarkable result is found for all the Fe(II)–S complexes studied. From this observation we conclude in connection with experimental results that Becke's 20% admixture should be reduced to about 15% if meaningful energetics are sought for transition-metal compounds. We rationalize that this reduction by 5% will not affect the quality of the hybrid functional since we arrive at a slightly modified functional, which lies between the pure density functional and the hybrid density functional, which both give good results for “standard” systems. Received: 13 July 2001 / Accepted: 31 August 2001 /  Published online: 16 November 2001     

减缩剂掺加对混凝土性能的影响

对比研究了减缩剂单掺及与减水剂复掺对混凝土早期收缩、水化热、开裂性能、抗压强度及劈拉强度的影响.试验结果表明,减缩剂内掺有效抑制了混凝土早期收缩,单掺和复掺下24h减缩率分别达到了58%和50%;减缩剂延缓了水化热峰值的出现,降低了水化热峰值,使得水化反应平缓进行,有利于缓解温差收缩裂缝;减缩剂的掺入对混凝土的抗压和劈拉强度有不利影响,但明显提高了混凝土的抗裂性能;试验中也发现,复掺减缩剂和减水剂能降低单掺减缩剂对混凝土强度的不利影响,将这种不利影响控制在10%以内.