According to the development characteristics of three types of reservoirs, this paper analyzes the main characteristics of salt-resistant polymer, and forms a highly targeted setting method for the ...key parameters of numerical simulation. At the same time, according to the actual situation of the salt-resistant test area, different injection parameter schemes are predicted, and the optimal design scheme is determined. Finally, the numerical simulation method of salt-resistant polymer flooding in three types of reservoirs is preliminarily formed.
Microstructure and mechanical properties of FSW joint of 6061-T6 alloy.
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•The grain size, hardness and impact absorbing energy of weld nugget zone was smallest.•Friction stir welding ...induced compressive residual stresses in weld nugget zone.•The particles in aluminum alloy matrix can impede the propagation of fatigue crack.
This paper studied the microstructural and mechanical evolution of friction stir welded (FSW) 6061-T6 aluminum alloy, the influence of notch locations on impact and fatigue crack growth (FCG) behavior were evaluated. The results show that the grain size, hardness and impact absorbing energy of weld nugget zone (WNZ) was smaller than those of base material and heat affected zone. Longitudinal residual stresses dominated all the zones of the joint, FSW induced compressive stresses in WNZ. The particles in aluminum alloy matrix can impede the propagation of fatigue crack. The microstructural inhomogeneity and crack closure contribute to the fluctuation FCG rate.
As the most straightforward synthetic strategy for cyclic polymers in theory, the traditional homodifunctional bimolecular ring-closure methods showed limited success for preparing pure cyclic ...polymers in practice even after several decades of development. A breakthrough was achieved in this paper to develop a successful homodifunctional bimolecular ring-closure method using a self-accelerating double strain-promoted azide–alkyne click reaction as the intermolecular and subsequent intramolecular coupling reactions. Because of the self-accelerating property of coupling reaction, this novel approach eliminated the usage of equimolar quantities between telechelic polymers and small molecule linkers, which was the prerequisite of traditional homodifunctional bimolecular ring-closure methods for pure cyclic polymers. More importantly, this approach could use an excess amount of small linkers to increase the intermolecular coupling reaction rate, further resulting in a significantly enhanced preparation efficiency of cyclic polymers.
Scanning electron microscope, atomic force microscope and other equipment play an important role in the fields of topography restoration and detection. However, these devices are generally used in ...nanometer-scale measurement scenarios. For wafer topography quality control scenarios ranging from microns to hundreds of microns, these technologies have problems such as high cost and slow detection speed. Therefore, developing new, low-cost, and high-precision methods is necessary. To address this problem, a wafer surface reconstruction framework is proposed based on the shape-from-focus principle. In view of the characteristics of the large area and micro-small height of the wafer, to solve the limitations of the existing shape from focus framework, which is generally based on a single field, we created a multi-field image sequence rapid acquisition system and proposed the use of pulse control methods to achieve rapid acquisition of large area images. On the other hand, this paper proposes a dual filtering framework combining the Levy flight filtering principle with the SOR algorithm in point cloud filtering to achieve a balance between smoothing the depth map and maintaining the detailed structure, reducing the impact of noise, and improving the morphology restoration accuracy. To avoid splicing seams between fields, the progressive detection multifield stitching technique is used to complete large-area depth data stitching. Experiments were conducted on both synthetic and real objects to verify the effectiveness of the proposed method. In terms of synthesized images, the accuracy of the three methods significantly improved after applying the proposed method framework. After applying the Tenenbaum method framework, its correlation and peak signal-to-noise ratio improved by 7.5% and 38.2%, respectively, and its root mean square error was reduced by 40.7%. The excellent accuracy reconstruction results of the proposed method was verified through accuracy evaluation experiments. The height errors of the three methods used were all higher than 1 μm. However, after using the proposed method framework, the maximum error was only 0.24 μm. The experimental results indicated that this method overcomes the area limitation of traditional SFF and is suitable for applying wafer surface morphology measurements.
The influences of aging treatments on microstructures and the corrosion properties of an Al–Cu–Li alloy were investigated through an immersion test in intergranular corrosion (IGC) solutions, a ...potentiodynamic polarization test, and electrochemical impedance spectra (EIS), combined with scanning and transmission electron microscopy. The results demonstrated that the Al–Cu–Li alloy displayed outstanding comprehensive mechanical properties and IGC resistance after treating with pre-strain deformation and a double aging process (PDA). Both the PDA and pre-strain followed by creep aging (PCA) treatments significantly increased the number densities of T1 and θ’ precipitates in the grain interior. The increase in precipitates in the grain interior greatly reduced the Cu-rich precipitates on the grain boundaries and inhibited the formation of a precipitate-free zone (PFZ). The electrochemical characteristics of the Al–Cu–Li alloy were influenced by the precipitates in the grain interior and grain boundaries. The studied alloy gained high IGC resistance due to the refinement of its microstructure, and the main corrosion mode was intra-granular pitting corrosion; thus, the corrosion diffusion rate was slowed down.
An Al–Mg–Si alloy with three types of grain structure (fully, partly, and none recrystallized grains) were prepared to determine the effects of grain structure related precipitation on corrosion ...resistance and corrosion fatigue property in this paper. Corrosion immersion tests, corrosion fatigue tests were conducted for the purpose. Through the investigations, a mechanism different from the existent mechanisms for expounding the corrosion behavior of Al–Mg–Si alloys is proposed in this paper. It was found that low angel grain boundaries (LAGBs) with continuous Mg-Si segregation play a dominant role on the penetration depth of corrosion; while the intragranular dislocations induced precipitates determine the corrosion morphology on the surface of the sample; in addition, the high angel grain boundaries (HAGBs) and precipitation free zones (PFZs) in the periphery do not decrease the corrosion resistance of the experimental alloy in the conditions of this paper. Furthermore, a deeper penetration of corrosion rather than the severer attack of corrosion on the surface results in a shorter corrosion fatigue life, as well as a corrosion dominated fracture failure during corrosion fatigue tests.These results may supplement the existing corrosion mechanisms of Al–Mg–Si alloy.
In this paper, an efficient application mapping approach is proposed for the co-optimization of reliability, communication energy, and performance (CoREP) in network-on-chip (NoC)-based ...reconfigurable architectures. A cost model for the CoREP is developed to evaluate the overall cost of a mapping. In this model, communication energy and latency (as a measure of performance) are first considered in energy latency product (ELP), and then ELP is co-optimized with reliability by a weight parameter that defines the optimization priority. Both transient and intermittent errors in NoC are modeled in CoREP. Based on CoREP, a mapping approach, referred to as priority and ratio oriented branch and bound (PRBB), is proposed to derive the best mapping by enumerating all the candidate mappings organized in a search tree. Two techniques, branch node priority recognition and partial cost ratio utilization, are adopted to improve the search efficiency. Experimental results show that the proposed approach achieves significant improvements in reliability, energy, and performance. Compared with the state-of-the-art methods in the same scope, the proposed approach has the following distinctive advantages: 1) CoREP is highly flexible to address various NoC topologies and routing algorithms while others are limited to some specific topologies and/or routing algorithms; 2) general quantitative evaluation for reliability, energy, and performance are made, respectively, before being integrated into unified cost model in general context while other similar models only touch upon two of them; and 3) CoREP-based PRBB attains a competitive processing speed, which is faster than other mapping approaches.
A robotic system for the automatic wire pulling of coreless motor winding is designed, including the design of an opening-closing control system and a micro-gripper’s tip structure with a ...double-armed elastic-beam structure for the support part and an enveloping clamping structure for the tip part. The micro-gripper captures the electrode wire from the root, encircles the wire after the envelope region is closed, and the thin and flexible electrode wire is pulled to the top of the electrode pad by the movement of the micro-gripper and released. The mechanical index of the micro-gripper is simulated to obtain the optimal structural parameters. The experimental results show that the electrode wire’s maximum bearing force is about 0.3 N. Under this reaction force, the deformation of the tip-envelope region of the micro-gripper is about 27.5 μm, which is sufficient for electrode wire pulling micro-manipulation. By comparison with the steel micro-gripper, the silicon micro-gripper has more advantages in shape integrity, machinability and mechanical properties.
Imbalanced class data are commonly observed in pattern analysis, machine learning, and various real-world applications. Conventional approaches often resort to resampling techniques in order to ...address the imbalance, which inevitably alter the original data distribution. This paper proposes a novel classification method that leverages optimal transport for handling imbalanced data. Specifically, we establish a transport plan between training and testing data without modifying the original data distribution, drawing upon the principles of optimal transport theory. Additionally, we introduce a non-convex interclass regularization term to establish connections between testing samples and training samples with the same class labels. This regularization term forms the basis of a regularized discrete optimal transport model, which is employed to address imbalanced classification scenarios. Subsequently, in line with the concept of maximum minimization, a maximum minimization algorithm is introduced for regularized discrete optimal transport. Subsequent experiments on 17 Keel datasets with varying levels of imbalance demonstrate the superior performance of the proposed approach compared to 11 other widely used techniques for class-imbalanced classification. Additionally, the application of the proposed approach to water quality evaluation confirms its effectiveness.
In this paper, a multi-objective, i.e., reliability, communication energy, performance, co-optimization model oriented mapping approach is proposed to find optimal mappings when applications are ...mapped onto network-on-chip (NoC) based reconfigurable architectures. A co-optimization model, defined as reliability efficiency model (REM), is developed to evaluate the overall reliability efficiency of a mapping. In REM, reliability efficiency is defined as the reliability profit at the same energy latency product. Based on REM, a mapping approach, referred to as priority and compensation factor oriented branch and bound (PCBB), is introduced to figure out the best mapping pattern. Two techniques, priority allocation and compensation factor utilization, are adopted to make a tradeoff between search efficiency and accuracy. Experimental results show that the proposed approach has three major contributions compared to state-of-the-art approaches. (1) PCBB is highly efficient in finding best mappings, with a 3x and 720x speedup compared to branch and bound (BB) and simulated annealing (SA). (2) PCBB is able to dynamically remap after the reconfiguration of the architecture. (3) General quantitative evaluation for reliability, communication energy and performance are made respectively before integrated into the unified model REM, whereas other similar models only touch upon two of them quantitatively.
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