Creep behavior of cold-rolled nanocrystalline pure copper

The creep of cold rolled nanocrystalline Cu has been investigated at 20–50 °C. The most reasonable stress exponent is found to be 2, the corresponding activation energy is 0.82 eV. The results imply that the creep is possibly associated with grain boundary sliding. The increase of threshold stress after rolling is associated with the increase of microstrain.     

Effect of texture and grain size on the mechanical properties of warm-worked cadmium,zinc and zinc-0·35% aluminium alloy

Changes in the grain size and crystallographic texture during warm working and their influence on the room temperature mechanical properties are investigated on Cd, Zn and a Zn-Al alloy. The yield strength increase in the early stages of working in extruded cadmium is accounted for based on the development of a basal texture while in rolled zinc and zinc alloy, the properties are affected more by the grain size. Cadmium exhibits ductile fracture at all extrusion ratios whereas the fracture mode in zinc and the alloy changes from cleavage at small rolling strains to ductile at higher deformation strains.     

固液分离机中岩屑颗粒沉降规律研究

岩屑在钻井液中的沉降速度、沉降阻力、流动分布等已成为钻井工艺设计中的重要参数。岩屑在钻井液中的运动十分复杂，这些参数很难用纯解析方法获得。文章从岩屑颗粒与液相介质之间的相互作用入手，采用理论分析和试验研究相结合的方法，参照经验公式,讨论了固液动态压滤分离机中岩屑颗粒的沉降规律，对动压机内颗粒的受力情况、轴向沉降、离心力场沉降等问题进行了理论探讨和研究，得出了岩屑颗粒离心沉降末速度。     

Linear flaw detection in woven textiles using model-based clustering

We combine image-processing techniques with a powerful new statistical technique to detect linear pattern production faults in woven textiles. Our approach detects a linear pattern in preprocessed images via model-based clustering. It employs an approximate Bayes factor which provides a criterion for assessing the evidence for the presence of a defect. The model used in experimentation is a (possibly highly elliptical) Gaussian cloud superimposed on Poisson clutter. Results are shown for some representative examples, and contrasted with a Hough transform. Software for the statistical modeling is available.     

Performance analysis of a greedy algorithm for inferring Boolean functions

We analyzed average case performance of a known greedy algorithm for inference of a Boolean function from positive and negative examples, and gave a proof to an experimental conjecture that the greedy algorithm works optimally with high probability if both input data and the underlying function are generated uniformly at random.     

高产梳棉机生条定量问题的探讨

统计了30年来梳棉机高产化进程中生条定量变化情况，资料表明生条定量只是略有增加。提高产量的主要措施是提高道夫速度(生条输出速度)。根据实际情况建议将生条定量范围做如下划分：4．0g／m以下为轻定量，4．0g/m～5．2g/m为中定量，5．2g/m以上为重定量。     

A submicron mild steel produced by simple warm deformation

One simple deformation process, through which a submicron ferrite grained mild steel was fabricated, was introduced. According to the transmission electron microscope images of the microstructures, most of the boundaries formed during the process might be low angle boundaries, which means that most of the ultrafine grains are subgrains. This deformation process is attractive because: (1) the necessary strain was only 1.5, (2) the deformation resistance decreased due to higher rolling temperature, and (3) the as warm-rolled mild steel had a microstructure with equiaxed grains of 0.7 μm in average diameter. The result of mechanical tests indicates that better properties, with comparison to its coarse-grained counterpart, were obtained, including doubled yield strength, high hardness, good work hardening and reliable elongation. Cross effect was observed during tensile process and interpreted from point view of conventional dislocation movement.     

Materials Design of Microstructure in Grain Boundary and Second Phase Particles

A concept of microstructure design for materials or materials microstructure engineering is proposed. The argument was suggested based on literature review and some our new research work on second phase strengthening mechanisms and mechanical property modeling of a particulate reinforced metal matrix composite. Due to development of computer technology, it is possible now for us to establish the relationship between microstructures and properties systematically and quantitatively by analytical and numerical modeling in the research scope of computerization materials. Discussions and examples on intellectual optimization of microstructure are presented on two aspects:grain boundary engineering and optimal geometry of particulate reinforcements in two-phase materials.     

MFI zeolite as a support for automotive catalysts with reduced Pt sintering

The noble metals used as catalysts in automotive exhaust systems are subject to sintering at extreme temperatures, leading to deterioration of catalytic activity. Zeolite with the MFI (ZSM5) structure is examined as a support for Pt particulate catalysts. The MFI structure is composed of agglomerates of single-crystal zeolite with interstitial mesoporosity. Pt fixed within these mesopores is shown through high-temperature aging tests in air to be highly resistant to sintering due to the mechanical constraints on particle size imparted by the mesoporous structure. The deterioration of catalytic activity after aging is significantly lower than that for comparable γ-alumina supported catalyst.     

Controller-integrated predictive oscillation compensation for machine tools with parallel kinematics

Since computerised numerical control (CNC) systems were introduced into the field of mechanical engineering, the manufacturing technology made significant progress. In spite of drastic improvements, mainly in terms of productivity and precision (e.g. finishing surface quality), opportunities for further advancements for the manufacturing processes still exist. One possible method for increasing precision is to adopt a machine structure with parallel kinematics. This kinematic structure can enhance the system dynamics, because the moving mass is divided among all actuators, contrary to the conventional, cartesian machine structures. The problem, which still exists even with this new structural solution, is the machine oscillation that appears during machining. This oscillation may decrease the machining accuracy. This paper highlights a new possible method to compensate the machine oscillation by using a controller-integrated compensation principle. Because of this principle, additional mechanical components (e.g. piezo stacks, actuators) are not necessary. This compensation concept was developed and verified under Matlab/SIMULINK and then installed into the machining centre Dyna-M. The kinematic structure of Dyna-M is defined as a hybrid-kinematic and also one of the typical parallel structures. The obtained results show up to 60% reduction of the machine oscillation and prove the practical usability of this compensation system.