阴极保护用阳极

介绍了牺牲阳极材料中镁基、锌基、铝基阳极的化学成分和性能特点，以及多种外加电流阴极保护用阳极材料的特点。通过对石墨阳极、高硅铸铁阳极和铅银合金阳极、镀铂阳极和混合金属氧化物阳极的性能比较，认为混合金属氧化物阳极是最为理想和最有前途的辅助阳极材料。     

消失模样性能对铝合金液充型速度及间隙压力影响的数值计算

采用计算机模拟技术研究了聚苯乙烯模样汽化潜热及发气性对消失模铸造铝合金液充填速度及金属液／模样间隙压力的影响。结果表明，模样汽化潜热与发气性均严重影响铝合金液的充型速度及间隙压力。     

智能化密集烤房控制器的设计与实现

密集烤房是烟叶烘烤加工的专用设备;针对密集烤房原理和烟叶烘烤工艺要求,以AT89C55WD单片机为核心研制了密集烤房控制器;控制器可自动检测装烟室温、湿度,并根据预先设定的工艺曲线自动控制助燃设备和通风排湿设备,实现了烟叶烘烤全过程自动控制,干、湿球温度控制精度士1℃.控制器具有内置多条专家曲线并可快捷修改、人机界面友好、硬件软件设计模块化等特点,适于用不同特性烟叶烘烤;介绍了工作原理、控制器构成、硬件软件设计并给出了应用效果.     

A priori and a posteriori analysis for a locking-free low order quadrilateral hybrid finite element for Reissner–Mindlin plates

This paper proposes a quadrilateral finite element method of the lowest order for Reissner–Mindlin (R–M) plates on the basis of Hellinger–Reissner variational principle, which includes variables of displacements, shear stresses and bending moments. This method uses continuous piecewise isoparametric bilinear interpolation for the approximation of transverse displacement and rotation. The piecewise-independent shear stress/bending moment approximation is constructed by following a self-equilibrium criterion and a shear-stress-enhanced condition. A priori and reliable a posteriori error estimates are derived and shown to be uniform with respect to the plate thickness t. Numerical experiments confirm the theoretical results.     

Optimization of stress modes by energy compatibility for 4‐node hybrid quadrilaterals

Optimal hybrid stress quadrilaterals can be obtained by adopting appropriate stresses and displacements, and satisfying the energy compatibility condition is shown to be an ultimate key to obtaining optimal stress modes. By using compatible isoparametric bilinear (Q₄) displacements and 5‐parameter energy compatible stresses of the combined hybrid finite element CH(0‐1), a robust 4‐node plane stress element ECQ₄ is derived. Equivalence to another hybrid stress element LQ₆ with 9‐parameter complete linear stresses based on a modified Hellinger–Reissner principle is established. A convergence analysis is given and numerical experiments show that elements ECQ₄/LQ₆ have high performance, i.e. are accurate at coarse meshes, insensitive to mesh distortions and free from locking. Copyright © 2003 John Wiley & Sons, Ltd.     

非渗透钻井液体系在梨树断陷的研究与应用

梨树断陷碎屑岩储层多为低孔低渗致密碎屑岩储层,存在井壁稳定性差和储层保护难度大的钻井技术难点。为增强井壁稳定性和储层保护效果,开展了非渗透钻井液的研究与应用工作。根据钻井液抗温性、抑制性、储层伤害等室内试验评价结果,表明非渗透钻井液抗温稳定性好,防塌能力强,返排压力低,能够有效封堵地层孔隙,渗透率恢复率达到80%以上,表皮因数较低,具有储层保护的效果。     

ASYMPTOTIC INFERENCES FOR AN AR(1) MODEL WITH A CHANGE POINT: STATIONARY AND NEARLY NON‐STATIONARY CASES

This article examines the asymptotic inference for AR(1) models with a possible structural break in the AR parameter β near the unity at an unknown time k₀. Consider the model y_t = β₁y_{t − 1}I{t ≤ k₀} + β₂y_{t − 1}I{t > k₀} + ϵ_t, t = 1,2, … ,T, where I{ ⋅ } denotes the indicator function. We examine two cases: case I | β₁ | < 1,β₂ = β_2T = 1 − c ∕ T; and case II β₁ = β_1T = 1 − c ∕ T, | β₂ | < 1, where c is a fixed constant, and {ϵ_t,t ≥ 1} is a sequence of i.i.d. random variables, which are in the domain of attraction of the normal law with zero means and possibly infinite variances. We derive the limiting distributions of the least squares estimators of β₁ and β₂ and that of the break‐point estimator for shrinking break for the aforementioned cases. Monte Carlo simulations are conducted to demonstrate the finite‐sample properties of the estimators. Our theoretical results are supported by Monte Carlo simulations.     

影响急性缺血性脑卒中血管内治疗预后的相关因素分析

【摘要】 随着多项大型临床试验研究结果发布，血管内治疗（或联合静脉溶栓）被推荐为颅内大血管闭塞所致急性缺血性脑卒中患者首选治疗措施。然而，血管内再通治疗预后受到一系列因素影响。该文就影响血管内治疗预后的可能因素作一综述。

     

智能变电站光纤回路描述方案研究

阐述了现在智能变电站光纤回路在运维和管理中存在的问题。针对智能变电站特点,从智能变电站建设、运维和管理角度提出了一套适用于智能变电站的光纤回路描述和管理方案。方案从智能变电站虚回路描述、过程层光纤路径描述、交换机配置描述、光纤回路标签命名等几个方面分别进行了阐述。该方案可直接应用于现有智能变电站的建设和管理,提高智能变电站的工程质量和光纤回路的管理水平。