一种“KooN”结构的马尔可夫简并建模和简化计算的方法

IEC61508等标准提出了几种计算安全仪表系统需求时平均失效概率的方法,但是,对于具有冗余配置的复杂系统,随着组件数量的增加,系统的中间状态数量快速增长,用户难以构建马尔可夫模型,即便借助计算机来建模运算也较为耗时。提出了一种同型“K oo N”简并状态的马尔可夫建模的通用方法,首先是根据降级状态进行判断,将符合条件的状态进行简并,然后对标记为危险失效状态的概率进行计算。通过严格的理论推导,该简并状态方法可以在不损失精度的前提下简化马尔可夫建模。     

箱形横梁的水压爆破拆除

某电影院大厅内钢筋混凝土箱形横梁长25m,断面尺寸1 6m×2 4m,用水压爆破拆除。通过梁的受力分析得知,为避免横梁的挠度过大,在吊梁拆除后必须另补支撑,以确保水压爆破正常进行。文中对水压爆破炸药用量的计算公式进行了比较和简评。在参考计算结果和考虑厅内环境的基础上,并结合以往水压爆破工程的经验,确定了合理、有效的药量,保证了主体结构的绝对安全。     

Thermodynamic calculation and microstructure characterization of spinel formation in MgO–Al2O3–C refractories

In this paper, by simulating the gas phase conditions inside the MgO–Al₂O₃–C refractories during continuous casting process and combining with thermodynamic analysis, as well as SEM analysis, the gas-gas and gas-solid formation of MA spinel were clarified in carbon containing refractories. Thermodynamic calculations showed that gas partial pressure of CO, O₂ and Mg could meet the formation and stable existence conditions of MA spinel in MgO–Al₂O₃–C refractories under service environment, and nitrogen could not affect the formation of MA spinel at 1550 °C in the thermodynamic condition. The formation processes of MA spinel were analyzed experimentally under embedding carbon atmosphere. The carbon-coated alumina powders in MgO–Al₂O₃–C refractories prevented the direct contact between magnesia and alumina. Mg gas was formed by carbon thermal reaction, then reacted with alumina (gas-solid) and gas containing aluminum (gas-gas) to generate MA spinel. Through gas-gas or gas-solid reaction, the formation of MA spinel was effectively controlled. By means of SEM analysis, a two-layer structure with dense outer spinel layer and loose inner layer was formed in MgO–Al₂O₃–C refractories.     

α钛富氧层增厚动力学模型

为了实现在工业化生产中对α钛富氧层厚度预测和控制,通过实验研究α钛富氧层在高温空气环境中的形成及增厚过程,讨论热处理温度和时间的影响作用,建立高温(750~850℃)空气环境下关于温度、时间的富氧层增厚动力学模型。结果表明:当恒温热处理温度为750~850℃时,α钛富氧层厚度x与保温时间t0.5呈正比例关系,且升高热处理温度可显著提高富氧层增厚速度。在此温度范围内,氧原子的扩散激活能约为203473 J/mol,计算曲线与实验数据吻合性较好。结合文献中已有的扩散系数方程和实验测得的富氧层厚度数据,推导得到5个富氧层增厚动力学方程,其中3个方程的计算曲线与实验数据吻合性较好,可为实际生产中预估富氧层厚度提供理论支持。     

钨中空位及其团簇的能量学和动力学性质参数

在总结前人钨中空位及其团簇的能量学和动力学行为的研究成果基础上，采用第一性原理方法系统计算了钨中空位及其团簇的结合能和扩散能垒。研究发现，交换关联泛函PW91和PBE较PBEsol、AM05和LDA更适合用于计算钨空位的能量学性质。基于第一性原理计算结果对文献中单空位形成能、双空位作用性质等争议性问题进行了讨论，并对钨经验势进行了评估。研究结果表明，钨中孤立单空位间总是相互排斥，而空位团簇（V_n>3）对单空位具有很强的吸引作用，其结合能随着所含空位个数增多呈现波动性增大的趋势。空位团簇稳定结构可通过最小化Wigner-Seitz表面积来确定，其结合能与V_n与V_n-1之间的Wigner-Seitz面积之差呈正比。     

Theoretical study on a kind of cyclization mechanism of boron trichloride and hexamethyldisilazane to form the borazine ring for SiBCN ceramics precursor

Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl₃) and hexamethyldisilazane (HN(SiMe₃)₂) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl₃ and HN(SiMe₃)₂ to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl₃ and HN(SiMe₃)₂ alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl₃ with more heat released compared to that for the introduction of HN(SiMe₃)₂. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions.     

Improved one-dimensional beam model for unbalanced composite single-lap joint

An analytical nonlinear solution was provided for unbalanced composite single-lap joint (CSLJ) using an improved one-dimensional beam model, which incorporated the effect of bending–tension coupling. The bending–tension coupling stiffness was introduced to characterize the coupling bending and tension behavior induced by the un-symmetric stacking sequence of composite laminates. The governing differential equations captured the bending–tension coupling behavior and the geometrically nonlinear features were constructed based on the displacement compatibility conditions of flexible interface. The transverse deformation in overlap region, edge moment factors and adhesive stress distributions for the unbalanced CSLJ with inflexible, intermediate flexibility and flexible adhesive can be determined by the present one-dimensional beam model. The accuracy of the present model was validated by the comparison with nonlinear finite element model. The effect of bending–tension coupling on edge moment factors and peak values of adhesive stresses was shed light on with the present model.     

深水油区多油田组合开发及产量接替优化

对由多个油田组成的海外深水开发项目区块，高效开发的关键是针对不同油田的特点，统筹规划不同油田投产次序和产量接替的组合方式，实现有效开发时间内的整个开发项目的最大收益。文中基于深水油田特点及开发要求，通过3个方面的研究来实现深水油区不同油田组合的储量动用及产量接替优化。一是建立深水油田储量分级评价标准，并利用数学综合评价方法确定不同油田的储量等级；二是通过分析深水油田产量运行主控因素，建立不同等级储量的关键开发指标预测模型，可作为不同油田组合开发下产量运行计算的基础；三是建立满足不同限制条件、开发效益最大的数学模型，并利用过程控制理论进行计算，优化得到不同储量等级油田的组合方式和逐次动用程序。将本文方法应用在XF深水油区的开发部署中，基于油田实际数据，进行了不同条件下、多个油田储量动用及产量接替方式的计算，优化结果符合实际开发需求，提高了深水油田开发决策的科学性。