氯离子对9Cr马氏体钢静态腐蚀和应力腐蚀行为的影响

目的研究9Cr马氏体钢在非服役条件下的腐蚀行为。方法运用传统电化学测试和微区扫描振动电极(SVET)技术研究材料的静态腐蚀行为,采用慢应变速率动态拉伸腐蚀试验与传统电化学测试技术相结合的方法研究材料的应力腐蚀行为。结果获得常温下氯离子对马氏体钢静态腐蚀行为的影响规律,以及慢拉伸过程中材料表面钝化膜生成和破裂过程。结论马氏体钢在氯化钠溶液中的腐蚀为阳极溶解型,且随着氯离子浓度的上升,局部腐蚀电流密度增大。常温下材料在含氯离子环境中发生弹性变形时,表面生成的钝化膜使材料的抗腐蚀性能升高。当材料进入塑性变形阶段后,由于金属表面缺陷的增多、颈缩区体积的收缩,以及钝化膜与基体金属塑性变形能力的差异,钝化膜逐渐溶解并发生破裂。     

Integrated planning method of green hydrogen supply chain for hydrogen fuel cell vehicles

To satisfy the growing refueling demand of hydrogen fuel cell vehicles (HFCVs) with carbon-free hydrogen supply, this paper proposes an integrated planning method of green hydrogen supply chain. First, the k-shorted path method is introduced to analyze HFCV refueling load considering vehicle travel habits and routing diversity. Second, based on it, a two-stage integrated planning model is established to minimize the total investment and operation cost. The construction of hydrogen refueling stations, electrolysis-based hydrogen generation stations and hydrogen pipelines are coordinated with their operating constraints, constituting the green hydrogen supply chain, in which hydrogen storage is also an important part for consideration to address variable renewable power. Then, the proposed model is reformulated as a mixed integer linear programing (MILP) problem solved efficiently. Finally, the case studies are carried out on an urban area in Xi'an China to verify the validity and correctness of the proposed method. The results show that the integrated planning can realize synergy benefits. The influence of electricity prices and k values is also discussed.     

HYDRA model: Simulation of salt intrusion in coastal aquifers using Visual Basic and GIS

A GIS-linked tool, which simulates salt intrusion in coastal aquifers, is presented. The tool was created by means of Microsoft Visual Basic ver. 6 programming language, and was linked to the GIS program MapInfo ver. 7. The Visual Basic code applies the Galerkin finite element method using triangular elements. The code is divided into two distinct parts: one for the simulation of the phenomenon in steady-state and one in transient state. For steady-state simulation the system of non-linear equations is solved using a Gauss–Seidel iterative solver. When simulating a transient phenomenon, a modified Newton–Raphson iterative solver is used. All spatial data, such as aquifer and boundary geometry or well location, are introduced and managed in the GIS environment. Temporal data, such as pumping or recharge time series, are introduced in a relational database or spreadsheet, such as Microsoft Access or Microsoft Excel. The result is a user-friendly computer tool, which incorporates the advantages provided by GIS and relational databases in the simulation of such complex physical systems.     

The characteristics of air void and frost resistance of RCC with fly ash and expansive agent

In order to assure the outer concrete of Longtan dam in China possesses excellent of frost resistance, the losses of strength, mass and air void characteristics of roller compacted concrete (RCC) containing fly ash, superplasticizer and a novel MgO-bearing expansive agent (HNM) were studied using the freezing–thawing method ASTM C666. The results show that there is a linear correlation between strength and mass losses in RCC subjected to cycles of freezing and thawing.There is a relationship between the air void spacing factor and the frost resistance of RCC. However, for RCC containing fly ash and superplasticizer a spacing factor of 0.25 mm is not necessary. Using a water:binder ratio of 0.48 in RCC containing 50% fly ash and 8% HNM a durability factor of over D₃₀₀ can be achieved provided the spacing factor is less than 0.4 mm.     

h-graphs: A new representation for tree decompositions of graphs

In geometric constraint solving, 2D well constrained geometric problems can be abstracted as Laman graphs. If the graph is tree decomposable, the constraint-based geometric problem can be solved by a Decomposition–Recombination planner based solver. In general decomposition and recombination steps can be completed only when steps on which they are dependent have already been completed. This fact naturally defines a hierarchy in the decomposition–recombination steps that traditional tree decomposition representations do not capture explicitly.In this work we introduce h-graphs, a new representation for decompositions of tree decomposable Laman graphs, which captures dependence relations between different tree decomposition steps. We show how h-graphs help in efficiently computing parameter ranges for which solution instances to well constrained, tree decomposable geometric constraint problems with one degree of freedom can actually be constructed.     

An open-source compiler and PCB synthesis tool for digital microfluidic biochips

This paper describes a publicly available, open source software framework designed to support research efforts on algorithms and control for digital microfluidic biochips (DMFBs), an emerging laboratory-on-a-chip (LoC) technology. The framework consists of two parts: a compiler, which converts an assay, specified using the BioCoder language, into a sequence of electrode activations that execute out the assay on the DMFB; and a printed circuit board (PCB) layout tool, which includes algorithms to reduce the number of control pins and PCB layers required to drive the chip from an external source. The framework also includes a suite of visualization tools for debugging, and a collection of front-end algorithms that generate mixing/dilution trees for sample preparation.     

Indirect Z-scheme hydrogen production photocatalyst based on two-dimensional GeC/MoSi2N4 van der Waals heterostructures

The stacked two-dimensional materials with suitable band gap are crucial for photocatalytic hydrogen production. Here, using first-principles calculations, the GeC/MoSi₂N₄ heterojunction with a band gap of 1.80 eV is calculated thoroughly. The indirect band alignment of Z-scheme and high carrier mobility boost the separation of electron-hole pairs, allowing more electrons and holes participating in the reactions. Additionally, the band-edge potential perfectly satisfies the requirements for redox potential of water splitting. Furthermore, the Gibbs free energy (−0.552 eV) close to zero indicates the heterojunction can conduct HER exceedingly well, providing a guarantee for photocatalytic hydrogen production. Remarkably, the light absorption coefficient peak is about 1.39 × 10⁵ cm⁻¹ within the visible light range enables the heterojunction to absorb more visible light from the spectrum. In short, results demonstrate the GeC/MoSi₂N₄ heterojunction is a promising photocatalyst for visible light water splitting, which will pave the way for the development of water splitting hydrogen production.