Nonlinear dynamic behavior of stiffened plate under instantaneous loading

The stiffened plate subjected to both geometric and material nonlinearities under instantaneous loading is investigated by a finite element method. The effects of the two nonlinearities on the dynamic behavior of the structure are discussed. The two nonlinearities behave in different ways: the geometric nonlinearity tends to reinforce the structure stiffness owing to the resistance of the membrane forces against the bending deformation and decreases the vibration period and amplitude; while the material one possesses the function of softening the stiffness and increases the vibration period and amplitude. Thus, the dynamic behavior depends on the property of the nonlinearity which the structure experiences.     

The complexity of some reachability problems for a system on a finite group

We consider a system defined as the product of a finite set of periodic systems on cyclic groups. It is of interest to determine if certain subgroups and unions of subgroups of the state set are reachable from a specified initial state, and in particular to determine the computational complexity of verifying such reachability. These questions are motivated by certain problems that arise in the modelling and control of discrete event systems and certain forms of periodic scheduling. Our main result is that deciding whether or not the union of a certain set of subgroups is reachable or not is NP-complete.     

Order–disorder phase transition induced by swift ions in MgAl2O4 and ZnAl2O4 spinels

Grazing X-ray diffraction was used to study in details the behaviour of two spinels, ZnAl₂O₄ and MgAl₂O₄ irradiated by swift ions. Such an irradiation allows to have an important irradiated depth and then accurate diffraction diagrams. Rietveld refinement done on these diagrams clearly show an order–disorder transition due to a melting of cations under irradiation in these two spinels. More especially, these results clearly exhibit that no new phase is created under irradiation in MgAl₂O₄. Raman spectroscopy, sensitive to the crystallographic space group, seems to confirm this analysis.     

富氧氮氧化硅薄膜退火的研究

利用红外吸收(IR)谱和X射线光电子谱(XPS)对富氧氮氧化硅(oxygen-rich SiOxNy)及其在600、750和900℃下退火后样品的微结构进行了研究.实验中除观察到N、H的释放外,首次发现退火会导致SiOxNy中O的释放,同时还发现退火温度不同,H、O、N元素的释放量以及微结构的变化都不相同,根据这些现象,提出了5个化学反应过程并予以解释.     

MECHANISM OF SOUND GENERATION BY FLOW OVER TWO CAVITIES IN TWO DIMENSIONS

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DH-2001综合地化录井仪的研制

地化录井仪是一种采用岩石热解法快速定量评价生油岩和储油岩的设备。文章介绍了DH - 2 0 0 1综合地化录井仪的组成和功能 ,阐述了仪器硬件和软件的设计思想。实际应用证明 ,该仪器的设计先进、实用     

Al-Cu-Fe系初生准晶相凝固过程的电子显微分析

采用包括金相（OM），粉末X射线衍射（XRD），扫描电子显微镜（SEM）观察和透射电子显微（TEM）分析等方法，研究了铸态Al592.Cu36.8Fe3.0Si1.0合金（700℃保温2．5h后水淬）的显微组织及相组成。发现铸锭中存在4种相：准晶I相，τ3相（或φ相），θ－Al2Cu相和η－AlCu相，凝固过程可描述为：初生晶是准晶Ⅰ相；在保温过程中发生包晶或共晶反应（L＋i→τ3(或φ）或L→τ3（或φ）＋i)形成的τ3相（或φ相），呈微畴结构；而剩余液体水淬形成θ－Al2Cu相和η－AlCu 相。     

碳酸二甲酯的市场需求和生产技术进展

介绍了碳酸二甲酯的价格、生产情况及国内外市场需求 ,指出碳酸二甲酯在我国具有极大的市场潜力。综述了生产碳酸二甲酯的三类主要方法 ,介绍了光气法、酯交换法和氧化羰基化法的各种具体方法及尚未实现工业化仍在研究中的其他方法。并对各种工业化的生产方法从技术、经济和清洁性的角度进行了分析 ,指出适合我国采用的工业合成方法是气相氧化羰基化法和甲醇与 CO2 直接合成法     

岩石工程力学特性参数测定装置设计

岩石工程力学特性参数测定装置实现了对试验载荷的恒速率加载 ,可对压模的吃深和试验载荷进行连续记录 ,记录的数据可实时显示及处理 ,且动态显示试验岩石的特性曲线 (试验载荷—轴向应变 )。该装置体积小、可移动性强 ,且能一机多用。文章详细阐述该装置机械结构、电路和系统软件的设计等     

rried out. The Lagrange multipliers are

boundary conditions. A cell structure which is independent to the nodes is used to evaluate the integrals of EFG