低密度聚乙烯熔体挤出胀大的实验和数值模拟预测

对一种国产低密度聚乙烯 ( LDPE)进行了经过长毛细管的挤出胀大流动实验测量 ,得到了挤出胀大比和流动曲线 .测定了材料的线性和非线性粘弹性 ,并用 PSM模型进行了表征 ,同时数值模拟了 LDPE熔体的挤出胀大流动 .预测结果与实验基本吻合 ,但在较高剪切速率下两者间还存在一定的偏差 。

己酮可可碱对实验性自身免疫性脑脊髓炎的影响

目的 观察己酮可可碱抑制急性 EAE豚鼠发病、病情程度 ,以及对血清 TNF、IL-6活性和 PRL水平的影响。方法 将 EAE模型豚鼠随机分为处理组和对照组 ,分别肌注己酮可可碱 30 mg/( kg·d)和等容量生理盐水 ,观察发生 EAE的数目、临床评分、病灶计数及检测血清 TNF、IL-6活性及血清 PRL水平 ,并对数据进行显著性检验和相关性分析。结果 处理组豚鼠发病数减少 ,临床表现及病理变化明显减轻 ,血清 TNF、IL-6活性及 PRL水平较对照组显著降低。结论 己酮可可碱可能通过抑制 TNF活性抑制 EAE的发病。

The bacterial genotoxicity test：issues to be considered in the performance of the test and their recent advances

The bacterial genotoxicity test is widely used as an initial screening to determing the genotoxic potential of chemicals for hazard identification.Firstly,I will state about technical issues in the performance of the test,which may largely affect the results of the mutagenicity of test compounds of lead to low concordance with the results between inter-and intra-laboratories.The second issue of my speech will be a brief review on bacterial tester strains that are highly sensitive to the mutagenicity of particular classes of mutagens.These strains are often used to efficiently explore environmental mutagens and to study the mechanisms of mutagenesis.Finally,I will present our recent study on the use of human S9 fractions in the genotoxicity tests to comprehensively evaluate the genotoxic effect to humans.In addition,genetically-engineered tester strains expressing human drug-metabolizing enzymes will be introduced.

Integrated identification method of rheological model of sandstone in Sanmenxia bauxite

Based on the uniaxial compression creep experiments conducted on bauxite sandstone obtained from Sanmenxia,typical creep experiment curves were obtained.From the characteristics of strain component of creep curves,the creep strain is composed of instantaneous elastic strain,ε（me）,instantaneous plastic strain,ε（mp）,viscoelastic strain,ε（ce）,and viscoplastic strain,ε（cp）.Based on the characteristics of instantaneous plastic strain,a new element of instantaneous plastic rheology was introduced,instantaneous plastic modulus was defined,and the modified Burgers model was established.Then identification of direct screening method in this model was completed.According to the mechanical properties of rheological elements,one- and three-dimensional creep equations in different stress levels were obtained.One-dimensional model parameters were identified by the method of least squares,and in the process of computation,Gauss-Newton iteration method was applied.Finally,by fitting the experimental curves,the correctness of direct method model was verified,then the examination of posterior exclusive method of the model was accomplished.The results showed that in the improved Burgers models,the rheological characteristics of sandstone are embodied properly,microscopic analysis of creep curves is also achieved,and the correctness of comprehensive identification method of rheological model is verified.

Modification of the linear viscoelastic deformation prediction model of asphalt mixture

A deformation prediction model for the dynamic creep test is deduced based on the linear viscoelastic（LVE）theory.Then,the defect of the LVE deformation prediction model is analyzed by comparing the prediction of the LVE deformation model with the experimental data.To improve accuracy,a modification of the LVE deformation prediction model is made to simulate the nonlinear property of the deformation of asphalt mixtures,and it is verified by comparing its simulation results with the experimental data.The comparison results show that the LVE deformation prediction model cannot simulate the nonlinear property of the permanent deformation of asphalt mixtures,while the modified deformation prediction model can provide more precise simulations of the whole process of the deformation and the permanent deformation in the dynamic creep test.Thus,the proposed modification greatly improves the accuracy of the LVE deformation prediction model.The modified model can provide a better understanding of the rutting behavior of asphalt pavement.

Experiment of dynamic property and transient magnetic effects of coal during deformation and fracture

Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following： the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.

Special epoxy silicone adhesive for inertial confinement fusion experiment

The effects of toughener and coupling agent on special epoxy silicone adhesive were discussed by researching the surface morphology characters, thermal properties and shear strength of the adhesive. The results indicate that silicone coupling agent (KH-550) can improve the shear strength of the epoxy silicone adhesive effectively. The mass fraction of the toughener in the epoxy silicone adhesive plays an important role in its properties. When the mass fraction of the toughener is less than 14%, the shear strength of the adhesive is low. When the mass fraction of the toughener is over 33%, thermal properties and shear strength of the adhesive decrease with the increasing of the toughener. The mass fraction of toughener of 25% results in good integral properties of the epoxy silicone adhesive. The morphologic analysis indicates that the micro-phase separation exists in the epoxy molecular chain and the silicone molecular chain of the epoxy silicone adhesive.

Deformation of ductile cuttings from sandstone in compaction process and experimental study of influence on porosity

Deformation of ductile cuttings from sandstone in the mechanical compaction process was designed through the "experimental system of triaxial rock deformation",and the influence on porosity was studied by looking into the deformation characteristics of ductile cuttings. The design indexes are as follows: simulated depth 0- 4 000 m,interval depth 500 m,and pressure range 0- 120 MPa at interval of 1. 5 MPa. The experimental results show that the porosity decreases as buried depth increases,indicating a negative relationship between them. The amount of compression was mainly obtained by porosity reduction and cutting deformation. Deformation of ductile cuttings is mainly ductile deformation; and deformation of crystal fragments is mainly expressed as brittle fracture,resulting in decrease of particle size. The research is of certain value for the exploration and development of oil and gas.

Information Moment for Chinese Character Recognition

Moment invariants firstly introduced by M. K Hu in 1962, has some shortcomings. After counting a large number of statistical distribution information of Chinese characters,the authors put forward the concept of information moments and demonstrate its invariance to translation,rotation and scaling.Also they perform the experiment in which information moments compared with moment invaiants for the effects of similar Chinese characters and font recognition.At last they show the recognition rate of 88% by information moments,with 70% by moment inariants.

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.

美他多辛作用的研究

目的:因美他多辛对乙醇性肝病的生化机理有积极作用,同时用于急性和慢性乙醇中毒、乙醇性肝病,但该药的致突变作用未见报道,本文在于检测美他多辛致突变性。方法:通过微生物回复突变试验、小鼠微核试验、哺乳动物培养细胞染色体试验证明。结果:美他多辛的三个试验结果均呈阴性。结论:美他多辛在用于治疗急性和慢性乙醇中毒、乙醇性肝病无致突变性。

Experimental and theoretical study on thermal and moisture characteristics of new-type bamboo structure wall

Thermal and moisture characteristics of the bamboo structure wall were tested in natural climate and three representative variation processes of heat and moisture： heating from solar radiation in summer at normal temperature and humidity, heating from solar radiation in summer at normal temperature and high humidity after rain, humidifying from brash in summer at high temperature and normal humidity. The results show that, in summer, the largest temperature difference between external and internal surface of the 28 mm-thick bamboo plywood wall is 11.73℃ （at 15：40） and the largest strain difference is 136 μm/m （at 18：50）, both in ambient and indoor conditioned environment. In heating process, lengthways of the wall surface are in contracting strain while transverse ways are in expanding strain at initial stage and in contracting strain during later period. When the high temperature wall is humidified by rain, the surface temperature drops, moisture content increases and the expanding strain is presented on the surface during the whole process. Temperature and moisture content are two important factors which affect thermal and moisture stress （TMS） of the bamboo structure wall. The TMS is not only related to temperature and moisture content, but also greatly affected by temperature gradient, moisture content gradient and rates of changing.

Hot compression deformation characteristics of Mg-Mn alloys

The hot deformation behaviors of solution treated Mg-1.8Mn-0.4Er-0.2Al alloys were investigated by means of compression tests on Gleeble-1500 in strain rate range of 0.01-10s-1,deformation temperature range of 250-450℃ and a true strain of 0.6.The constitutive relationships among flow stress,strain rate and deformation temperature were described by Arrhenius-type equations,based on the fact that the material constants could be calculated under a wide range of strains.The results show that the flow stress of the experimental alloy decreases with temperature increasing and strain rate decreasing.Under the experimental conditions,the products of constant α and n in the constitutive equation are stable within certain strains,and the deformation activation energy ranges from 160 to 220 kJ/mol.It is proved that the values of calculated flow stress are close to the experimental results with average error of 2.01%.

Influence of Tacking Sequence on Residual Stress and Distortion of Single Sided Fillet Submerged Arc Welded Joint

Submerged arc welding （SAW） is advantageous for joining high thickness materials in large structure due to high material deposition rate. The non-uniform heating and cooling generates the thermal stresses and subsequently the residual stresses and distortion. The longitudinal and transverse residual stresses and angular distortion are generally measured in large panel structure of submerged arc welded fillet joints. Hence, the objective of this present work is to quantify the amount of residual stress and distortion in and around the weld joint due to positioning of stiffeners tack. The tacking sequence influences the level of residual stress and proper controlling of tacking sequences is required to minimize the stress. In present study, an elasto-plastic material behavior is considered to develop the thermo mechanical model which predicts the residual stress and angular distortion with varying tacking sequences. The simulated result reveals that the tacking sequence heavily influences the residual stress and deformation pattern of the single sided fillet joint. The finite element based numerical model is calibrated by comparing the experimental data from published literature. Henceforth, the angular distortions are measured from an in-house developed experimental set-up. A fair agreement between the predicted and experimental results indicates the robustness of the developed numerical model. However, the most significant conclusion from present study states that tack weld position should be placed opposite to the fillet weld side to minimize the residual stress.

Rheological characterization of A201 aluminum alloy

The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted.Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the solidus and liquidus temperatures, the melting range and the sensitivity of the solid fraction at the thixoforming temperatures.The rheology of aluminium alloy A201 was examined using a high temperature Searle rheometer.The flow behaviour was analyzed with concentric cylinders of graphite to avoid chemical interactions with the liquid or semi-solid aluminium.The rotational body was grooved to prevent a phenomenon called wall slippage.Continuous cooling experiment was used to observe the shear rate effects on the flow behaviour.It can be seen that the viscosity level decreases at higher shear rates.Shear rate jump experiment was carried out to evaluate the steady state flow curve within the analyzed shear rate range from 60 s-1 to 260 s-1.It is found that the power law indexes are-1.35 and-1.49 for 35% and 45% solid fraction, respectively.Finally, some mechanical property data of as-cast and as-thixoformed A201 alloy are included indicating the potential for high strength applications.

Experimental study on creep of high-performance concretes

In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.

Visco-elastoplastic damage constitutive model for compressed asphalt mastic

In order to describe the three-stage creep behavior of compressed asphalt mastic, a visco-elastoplastic damage constitutive model is proposed in this work. The model parameters are treated as quadratic polynomial functions with respect to stress and temperature. A series of uniaxial compressive creep experiments are performed at various stress and temperature conditions in order to determine these parameter functions, and then the proposed model is validated by comparison between the predictions and experiments at the other loading conditions. It is shown that very small permanent deformation at low stress and temperature increases rapidly with elevated stress or temperature and the damage may initiate in the stationary stage but mainly develops in the accelerated stage. Compared with the visco-elastoplastic models without damage, the predictions from the proposed model is in better agreement with the experiments, and can better capture the rate-dependency in creep responses of asphalt mastic especially below its softening point of 47 ℃

Experimental study on freezing of liquids under static magnetic field

Freezing processes of several liquids under static magnetic field(SMF) less than 50 mT were investigated. Central temperature of liquid samples held in glass test tubes immersed in a liquid bath was measured and collected. Nucleation temperature and phase transition time were obtained from freezing curves. Normality tests were performed for nucleation temperature of these liquids with/without magnetic field and normality distributions were justified. Analysis of variances was carried out for nucleation temperature of these liquids with magnetic field flux density as the influencing factor. Results showed that no significant difference was found for deionized water with or without SMF. However, differences exist in 0.9% NaCl solution and 5% ethylene glycol solution with and without SMF. Nucleation temperature of 0.9% NaCl with SMF is lower than that without SMF, while its phase transition time is shorter than that without SMF. Nucleation temperature of 5% ethylene glycol with SMF is higher than that without SMF, while its phase transition time is not modified with SMF.