论高校学业考试“分数膨胀”及其应对策略——兼谈高校“等级制”取代“百分制”改革

长期以来,我国高校学业考试"分数膨胀"问题饱受诟病,严重地损害了高校人才培养的质量。然而,在现实利益面前,无论是对于学生、管理者还是高校教师来说,给予学生"高分"都是一个"最不坏"的选择。或者说,高校学业考试"分数膨胀"是高校内部各利益相关者功利主义心态"膨胀"的结果。而当下,我国高校实施的"等级制"取代"百分制"的学业评价体系改革,并不能从根本上解决高校学业考试"分数膨胀"问题。而要有效解决这一问题,必须从高校教学管理入手,为教师营造良好的教学管理氛围,从而让教师真正地"挺起腰杆"评分。

Swelling characteristics of East-Africa black cotton soil based on computer molecular simulation

Black cotton soil in East Africa is not a stable engineering material for highway and railroad projects. Its strong swelling potential when it absorbs water causes distresses in subgrade of highway and railroad, and thus leads to failures of the projects. This paper presents study on the swelling characteristics of black cotton soil in East Africa. Lab tests were conducted to obtain its basic engineering properties, and the results show that black cotton soil contains high amount of montmorillonite and exchangeable cations and is strong expansive soil. Molecular modelling was exploited to further investigate water absorption ability of montmorillonite. Three different molecular models of montmorillonite were constructed and used for simulations, among which Types I and II montmorillonite represent the expansive soil montmorillonite in China, and Types II and III montmorillonite represent black cotton soil montmorillonite in East Africa. The results showed that the interlayer cations of Type III montmorillonite possessed the strongest water absorption ability based on analysis of radial distribution function(RDF) of cations. Interlayer compensatory cations of Na+ enhance the hydration ability of the other major cations, thus resulting in the strong swelling potential of East-Africa black cotton soil.

Study of the features of outburst caused by rock cross-cut coal uncovering and the law of gas dilatation energy release

To study the law of gas dilatation energy release of rock cross-cut coal uncovering face, according to the analysis of the physical parameters distribution features of coal and rock mass in front of crosscut face,the equations of elastic potential of coal and gas dilatation energy theory were set up to process a contrast calculation of the sizes of two kinds of energy. The results show that gas dilatation energy is the uppermost energy source causing outburst occurrence. Furthermore, the mathematical model of spherical flow field gas dilatation energy release was established and MATLAB software was applied to make a numerical calculation analysis on the law of gas dilatation energy release. The results indicate that the gas dilatation energy is closely related to gas parameters and its energy index does reflect the possibility of coal seam outburst.

Molecular Dynamics Simulation for the Binary Mixtures of High Pressure Carbon Dioxide and Ionic Liquids

Molecular dynamics simulation with an all-atom force field has been carded out on the two binary sys- tems of [bmim][PF6]-CO2 and [bmim][NO3]-CO2 to study the transport properties, volume expansion and micro- structures. It was found that addition of CO2 in the liquid phase can greatly decrease the viscosity of ionic liquids （ILs） and increase their diffusion coefficient obviously. Furthermore, the volume expansion of ionic liquids was found to increase with the increase of the mole fraction of CO2 in the liquid phase but less than 35% for the two simulated systems, which had a significant difference with CO2 expanded organic solvents. The main reason was that there were some void spaces inter and intra the molecules of ionic liquids. Finally, site to site radial distribution functions and corresponding number integrals were investigated and it was found that the change of microstructures of ILs bv addition CO2 had a great influence on the orooerties of ILs.

Effects of Magnesia Fines Addition and Spinel with Different Compositions on Thermal Expansion Behavior of Alumina Magnesia Castables

Effects of magnesia fines addition （ 4%, 6% and 8% in mass ） and spinel with different compositions （alumina-rich, magnesia-rich and stoichiometric spi-nel） on thermal expansion behavior of alumina magne-sia castables were researched using tabular corundum, magnesia fines, spinel fines, p-A12O3, Secar-71 cement and SiO2 fume as main starting materials. The results show that： （1） thermal expansion coefficients of speci- mens with 4 mass% and 6 mass% magnesia fines have the similar change tendency, increasing slightly with temperature rising ; when magnesia addition is 8 mass% , the thermal expansion coefficient increases ob-viously at Ⅰ 050 ℃ and reaches the peak at 1 350 ℃ ; （2） when MgO content is the same, the specimen with magnesia-rich spinel has the lowest thermal expansion coefficient; （3） for the castables specimens with the same MgO content, the specimen with magnesia has higher thermal expansion coefficient than that with pre-synthesized spin, el, which is related with the secondary spinelization dttriag the heating process.

Determinants of Export Performance in East Africa Countries

The main objectives of this study are to identify and analyze variables which have impact on export performances of seven East Africa countries and suggest possible solutions to improve export performance in East Africa. Usingdata from World Development Indicators database we conducted panel data analysis for the period of 1990-2014.Empirical results show that labor force, industrialization, foreign direct investment, and exchange rate have positiveimpact on export value. On the other hand, inflation has negative impact on export performance while GDP growthis the only variable that does not affect the export value of East Africa countries. Finally, we suggest somerecommendations, including the need of replacing agricultural exports by the industrial export, improving infrastructural facility as well as the quality of human capital and the need of policies for attracting internationalinvestors.

Investigation on thermophysical properties of reactive powder concrete

The thermophysical properties,such as thermal conductivity,thermal diffusivity,specific heat capacity and linear thermal expansion of reactive powder concrete(RPC) with different steel fiber volumetric fractions are investigated by means of high temperature tests. The thermophysical characteristics of RPC with different fiber volumes under different temperatures are analyzed and compared with those of the common high-strength concrete and high-performance concrete. The empirical relationships of thermophysical properties with temperature and fiber volume are identified. By the heat transfer and solid physics methods,the microscopic physical mechanism of heat transfer process and heat conduction properties of RPC are investigated,and the theoretical formulas of specific heat capacity and thermal expansion coefficient are derived,respectively. The effects of temperature and steel fibers on the specific heat capacity and the thermal expansion coefficient are quantitatively analyzed and the discriminant conditions are provided. It is shown that the experimental results are consistent with the theoretical prediction.

Anisotropic Hardy-Lorentz spaces and their applications

Let p ∈(0, 1], q ∈(0, ∞] and A be a general expansive matrix on Rn. We introduce the anisotropic Hardy-Lorentz space H^(p,q)_A(R^n) associated with A via the non-tangential grand maximal function and then establish its various real-variable characterizations in terms of the atomic and the molecular decompositions, the radial and the non-tangential maximal functions, and the finite atomic decompositions. All these characterizations except the ∞-atomic characterization are new even for the classical isotropic Hardy-Lorentz spaces on Rn.As applications, we first prove that Hp,q A(Rn) is an intermediate space between H^(p1,q1)_A(Rn) and H^(p2,q2)_A(R^n) with 0 < p1 < p < p2 < ∞ and q1, q, q2 ∈(0, ∞], and also between H^(p,q1)_A(Rn) and H^(p,q2)_A(R^n) with p ∈(0, ∞)and 0 < q1 < q < q2 ∞ in the real method of interpolation. We then establish a criterion on the boundedness of sublinear operators from H^(p,q)_A(R^n) into a quasi-Banach space; moreover, we obtain the boundedness of δ-type Calder′on-Zygmund operators from H^(p,∞)_A(R^n) to the weak Lebesgue space L^(p,∞)(R^n)(or to H^p_A(R^n)) in the ln λcritical case, from H^(p,q)_A(R^n) to L^(p,q)(R^n)(or to H^(p,q)_A(R^n)) with δ∈(0,(lnλ)/(ln b)], p ∈(1/(1+,δ),1] and q ∈(0, ∞], as well as the boundedness of some Calderon-Zygmund operators from H^(p,q)_A(R^n) to L^(p,∞)(R^n), where b := | det A|,λ_:= min{|λ| : λ∈σ(A)} and σ(A) denotes the set of all eigenvalues of A.

FEM analysis on the effect of cobalt content on thermal residual stress in polycrystalline diamond compact(PDC)

Thermal residual stress in Polycrystalline Diamond Compacts （PDCs） is mainly caused by the mismatch in the Coefficients of Thermal Expansion （CTE） between the polycrystalline diamond （PCD） layer and WC-Co substrate. In the PCD layer, the CTE of cobalt exhibit magnitudes four times larger than those of diamond. Cobalt content in the PCD layer has important effects on the thermal residual stress of PDCs. In this work, the effects of cobalt content on thermal residual stress in PCDs were investi- gated by the Finite Element Method （FEM）. The simulation results show that the thermal residual stress decreases firstly, and then increases with increasing cobalt content （1 vo1.%-20 vol.%）, which reaches a minimum value when the cobalt content is about 10 vol.%. The FEM analysis results are in agreement with our experimental results. It will provide an effective method for further designing and optimizing PDC properties.