Mixing in Wave Processes Propagating in Gas Mixtures (Review)

A review is made of uptodate investigations in the field of physicomathematical modeling of mixing of solid particles with highvelocity gas flows arising under the action on shock waves, compression waves, and expansion waves on unstable dust deposits on the boundaries of channels or plates and in cavities, as well as on free clouds of particles. In particular, experiments in shock tubes with particles initially located in cavities and on surfaces are described. The experimental data presented in the form of distributions of particle concentrations at various points of space above the unstable layer, pressure distributions on the lower wall of the shock tube, etc., are used for verification of proposed mathematical models in regimes of single particles, interacting continua, and turbulent diffusion. An analysis of experimental and numerical data shows that the models considered sometimes allow adequate identification of the wave structure of motion of the mixture and the field of parameters inside and outside the layer.     

Adhesion Effects of Intermediate Layers on the Densification of Ceramic Powders

In the ceramic technology the first step to produce sintered bodies is the manufacturing of powders which then are densified. The adhesion mechanisms between the single particles and the agglomerates produced from them determine the densification process. Starting from theoretical considerations adhesion mechanisms, such as solid bridge formation, adhesive bonding and glide-promoting effects, are discussed in principle. Subsequently, the effects of surface-active substances on the densification behaviour of clay-ceramics and oxide-ceramic bodies are discussed. Further, the evaluation of the action of additives to the powder mixtures on the microstructure of the compacts, such as porsity and texture, leads to a compaction equation which describes the transition from the powder pile to a densified green body.     

Fissure evolution and evaluation of pressure-relief gas drainage in the exploitation of super-remote protected seams

Based on nonlinearity contact theory and the geological structure of the Xieqiao Coal Mine in the newly developed Huainan coal field, rock movements, mining fissures and deformation of overlying strata were simulated by using the interface unit of FLAC3D to evaluate the pressure-relief gas drainage in the exploitation of super-remote protected seams. The simulation indicates that the height of the water flowing fractured zone is 54 m in the overlying strata above the protective layer. The maximum relative swelling deformation of the C 13 coal seam is 0.232%,while the mining height is 3.0 m and the distance from the B8 roof to the C13 floor is 129 m, which provides good agreement with a similar experiment and in situ results. The feasibility of exploitation of a super-remote protective coal seam and the performance of the pressure-relief gas drainage in a super-remote protected layer are evaluated by comparisons with practice projects. It demonstrates that the relieved gas in the super-remote protected layers could be better drained and it is feasible to exploit the B8 coal seam before the C13 super-remote protected coal seam. The method is applicable for the study of rock movements, mining fissures and deformation of the overburden, using the interface unit to analyze the contact problems in coal mines.     

全化学法制备缓冲层和YBaCuO超导涂层

用化学溶液沉积法,尤其是金属有机物沉积法（MOD）制备第二代超导带材,包括缓冲层和YBaCuO涂层,在当前超导带材研究中具有重要的意义．因为其成本低、操作简单、便于规模化生产,可能成为制备高温超导带材最有前途的方法．文内详述了用化学气相沉积,化学溶液沉积,电泳共沉积以及超声雾化热分解等方法制备YBaCuO超导涂层的国内外进展,介绍了在LaAlO3单晶上以及金属基带上制备钙钛矿结构缓冲层的主要种类和特征,也介绍了当前研究的热点之一,导电缓冲层的作用、制备方法和研究进展．     

干密度对土工格栅与膨胀土界面拉拔性状的影响

采用高密度聚乙烯(HDPE)单向土工格栅与聚脂(PET)双向土工格栅,以及南水北调中线工程新乡段的膨胀性泥灰岩风化土,在填土尺寸为600 mm×600 mm×600 mm的大型叠环式剪切仪上进行拉拔试验,研究了干密度对土工格栅与膨胀土界面拉拔性状的影响.结果表明:干密度较大时,土工格栅刚体平动及其速率增大时的拉拔力较大,峰值拉拔力较大,峰值时土工格栅的变形量较大;干密度较大时,筋土界面摩阻力-相对位移曲线更偏于弹塑性特征,其界面切向刚度较小;干密度对界面似摩擦角的影响显著,而对似粘聚力的影响较小.     

应力吸收层沥青混合料的低温抗裂性能

通过对自主研发的Sampave等3种改性沥青结合料和不同级配的应力吸收层沥青混合料进行低温弯曲和低温蠕变试验,分析沥青结合料和矿料级配对应力吸收层沥青混合料低温抗裂性能的影响.结果表明:自主研发的Sampave特种改性沥青混合料具有优良的低温抗裂性能,但单一改性剂SBR改性沥青并不能达到应力吸收层沥青结合料的性能要求;矿料4.75 mm、0.075 mm筛孔通过率对其低温抗裂性能影响较敏感.     

The Mechanical Behaviour of Polyimide/Copper Laminates Part 2: Peel Energy Measurements

The mechanical peel behaviour of laminates consisting of polyimide films adhered to copper foil using a modified acrylic adhesive has been studied over a wide range of test rates and temperatures. The laminates were prepared from polyimide films which had been subjected to either a “high-thermal history” or a “low-thermal history” treatment during the production of the film. The measured peel energies of the laminates could be superimposed to give a master curve of peel energy versus the reduced rate of peel test, Ra_T, where R is the rate of peel test and a_T is the time-temperature shift factor. The appropriate shift factors were a function of the test temperature and were mainly deduced from tensile tests conducted on the bulk adhesive. The “high-thermal history” laminates gave higher peel energies and the locus of failure of the laminates was mainly by cohesive fracture through the adhesive layer. At low values of log₁₀ Ra_T, i.e. Low rates of peel and high test temperatures, the “low-thermal history” laminates also failed in the adhesive layer and possessed similar peel energies to those measured for the “high-thermal history” laminates. However, at high log₁₀ Ra_T values, the peel energies measured for the “low-thermal history” laminates were lower and showed a wider scatter. These arose from a different locus of failure occurring in these “low-thermal history” laminates when tested under these conditions. Namely, it was found that most of these laminates failed in a weak boundary layer in the outer regions of the “low-thermal history” polyimide film.     

土工格栅加筋包边填砂路堤模型试验研究

为探究包边填砂路堤荷载作用下的极限承载力特性、破坏形态规律及加筋性状,设计了土工格栅加筋包边填砂路堤结构,改装美国GCTS公司的USTX-2000动静三轴加载装置进行加载,通过改变加筋层数、筋材布置长度及包边土厚度对土工格栅包边填砂路堤进行一系列试验。对不同工况下包边填砂路堤的极限承载力、封层及坡面法向累积变形、位移变化进行研究。试验结果表明:土工格栅加筋和增加包边土厚度可以显著提高包边填砂路堤的极限承载力,并能减小封层中、封层右及坡顶、坡中的法向累积变形;无筋路堤的滑动面在路堤内呈折线状且并未通过坡脚侵入地基,在坡顶的黏土和砂芯交界处产生最大位移;土工格栅加筋及增加包边土厚度可以使滑动面向路堤内部迁移但形态不变,且最大位移处向路堤内部迁移。     

高温气候下沥青混凝土心墙连续碾压施工结合面温控试验研究

在夏季高温气候沥青混凝土心墙连续多层施工时,为减少等待结合面温度降至规范要求上限值90℃的时间,通过室内试验模拟结合面温度提高后心墙连续两层铺筑的情况,分别研究了结合面温度在90℃、100℃、110℃情况下沥青混凝土的压实性和变形情况,并进行了现场试验论证。室内试验结果表明:心墙沥青混凝土结合面温度降至100℃时,上层沥青混凝土的孔隙率为2.88%,下层沥青混凝土的最大侧向应变值为2.78%;结合面温度为110℃时,上层沥青混凝土的孔隙率为3.85%,下层沥青混凝土的最大侧向应变值为4.00%。现场试验结果表明:结合面温度为100℃时的上层沥青混凝土孔隙率和渗透系数均满足规范要求。因此,沥青混凝土心墙连续多层碾压时,结合面温度提高至100℃的施工质量可以得到保证。     

加筋劲性水泥土桩的应力应变与极限承载力研究

通过1个水泥土模型桩和2个劲性水泥土组合模型桩以及2个加筋劲性水泥土组合模型桩的静载荷试验,分析了组合桩的极限承载力、Q-S曲线及应力-应变曲线.分析表明:1土工格栅围箍面积越大,模型桩的应力应变变化速度越缓慢;2围箍面积越大,提高承载力的作用越明显;3加筋劲性水泥土组合桩的4根芯桩离桩心距离为40mm时,土工格栅的作用最明显,其极限承载力提高12.5%.