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In this paper, the concept of well array operating enhanced geothermal system (EGS) is proposed in response to the existing challenges in EGS commercialization. A well array operating EGS is characterized by well sharing, which substantially reduces drilling cost and maximizes mass flow rate. Following a thorough discussion of conditions for representing an EGS by a 2D model, the life time performance of a well array operating EGS is investigated based on 2D finite element modeling. The accuracy of the presented numerical results is quantified by systematic tests of mesh, element order and time step dependence, and by direct comparison with an analytical solution for 2D porous flow, which is derived in the paper as well. This paper demonstrates that 2D modeling is not only capable of accurately solving a wide range of EGS problems at low computational cost, but also a powerful tool for quantitatively estimating 3D numerical modeling errors, which are usually not adequately addressed in previous studies. The modeling results of the well array operating EGS presented in this paper may serve as a benchmark for testing future EGS models.

In order to identify quickly and accurately the load state of structures in some complex environments, a non-iterative inversion method based on finite element method and Newmark method is proposed. By exploring the relationship between measurement data and loads that need to be identified, the error function is established. Based on the least square method and the matrix decomposition scheme, the formulas are derived without iteration process. To improve the inversion accuracy and efficiency in the identification of dynamic loads, the basis function expansion and the singular value decomposition method are adopted. Several different structures are considered to verify the influence of some factors on the inversion results, such as the basis function expansion, the computational time, the measurement noise, the number of measurement points and the location of measurement points. Numerical examples show that the present method can obtain the stable and accurate identifying results.

A large-sized CuZr-based bulk metallic glass (BMG) composite with enhanced mechanical properties is prepared successfully. With the addition of Ta to CuZr-based alloys, the critical composite size changes and the microstructure diversifies. The composite with 0.5 at.% Ta addition has the largest critical size with the microstructure of single CuZr(B2) phase uniformly dispersing in amorphous matrix. This composite exhibits good mechanical properties, i.e., large compressive plasticity and work-hardening ability, which should be attributed to the uniformly distributed CuZr(B2) phase. The increased critical size of CuZr-based BMG composite can be explained by the fact that proper Ta addition can suppress the precipitation of crystalline phases other than B2 CuZr phase during solidification. This study may be helpful for the fabrication of large-sized BMG composites with excellent mechanical properties.

Nanoparticles (∼20 nm) of tetragonal (P42/mnm) cobalt fluoride (CoF2) has been synthesized by precipitation using cobalt nitrate and ammonium fluoride solution at room temperature, followed by annealing at 400 °C under argon atmosphere. The morphology and structure have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The electrochemical lithiation of CoF2 and its structural and valence changes during conversion have been investigated. Electrochemical measurements revealed a discharge specific capacity close to theoretical specific capacity of 553 mAh g−1 and charge specific capacities ranging from 250 to 450 mAh g−1 in the first cycle, depending on the type of conductive carbon addictive used. Lithiation of CoF2 occurs without any intercalation, but via conversion reaction CoF2 + 2Li+ + 2e− → Co(0) + 2LiF. During lithiation, CoF2 is fully reduced to Co(0) and breaks down into smaller particles of ∼2 nm. Upon recharging, CoFx is formed instead of CoF2. XPS and EELS studies show that only the surface of the electrode is reconverted back to CoFx during recharging. In addition, recharging to form CoFx commences at the interface between the cobalt and lithium fluoride. These results offer the experimental evidence explaining the lack of cycle stability of metal fluorides that undergo a conversion reaction with lithium such as cobalt fluoride. In addition, they also provide insight into the reactions during conversion and reconversion. Finally, it is shown that the morphology of the conductive carbon addictives used in electrode fabrication plays a crucial role in determining the capacity retention ability for materials that undergo a conversion reaction with lithium.

Association rule mining is one of the most important areas in data mining, which has received a great deal of attention. The purpose of association rule mining is the discovery of association relationships or correlations among a set of items.In this paper, we present an efficient way to find the valid association rules among the infrequent items, which is seldom mentioned and whose importance often get ignored by other researchers. We design a new data structure, called Transactional Co-Occurrence Matrix, in short TCOM, by two passing of the original transactional database. Then the occurrence count of the itemsets and valid association rules will be mined based on TCOM, which combines the advantages of both transactional oriented (horizontal) layout and item oriented (vertical) layout of the database. It turns out that any itemsets could be randomly accessed and counted without full scan of either the original database or the TCOM, which significantly improves the efficiency of the mining processes.