Effects of stabilizing heat treatment on microstructures and creep behavior of Zn-10Al-2Cu-0.02Ti alloy

The microstructures of as-extruded and stabilizing heat-treated Zn-10Al-2Cu-0.02Ti alloys were observed by scanning electron microscopy,transmission electron microscopy,electron probe microanalysis and X-ray diffraction analysis techniques.The change in structure after heat treatment and its effects on room temperature creep behavior were investigated by creep experiments at constant stress and slow strain rate tensile tests.The results show that after stabilizing heat treatment（（350℃,30 min,water-cooling）＋（100℃,12 h,air-cooling））,the amount of α＋η lamellar structure decreases,while the amount of cellular and granular structure increases.The heat-treated Zn-10Al-2Cu-0.02Ti alloy exhibits better creep resistance than the as-extruded alloy,and the rate of steady state creep decreases by 96.9% after stabilizing heat treatment.

黑梁煤矿通风系统设计研究

通过对黑梁煤矿地质条件、瓦斯等级、开拓方式、风井布置等进行分析,建立了高效、可靠、经济、简单的通风系统,保证了国家财产和井下工作人员的生命安全,对同类其他煤矿通风系统的建立具有借鉴意义。

高墩大跨连续刚构桥及其双肢薄壁高墩计算分析

该文结合山区、黄土地区合理桥型的选择,收集了国内外具代表性的高墩大跨连续刚构桥下部结构的数据资料,提出了双肢薄壁墩刚度更精确的计算图式,推导了计入几何非线性的墩顶水平位移计算公式、墩身合理刚度,并讨论了双肢中距与稳定性的关系。

Analysis on stability of strategic alliance: A game theory perspective

Strategic alliance has suffered much instabilities since its first implementation. Scholars have carried out many em- bedded, precise and comprehensive researches from both theory and empiricism. Here we try to find certain stable solutions by employing game theory, in an attempt to construct theoretical bases for strategic alliance, which people called “one of the most important organizational innovation in the end of the 20th century” (Shi, 2001), to exploit its advantages in the process of glob- alization. Finally, this article puts forward some advices for its success.

Influence of Polymer Binder on the Physical Properties and Stability of Engineering Spoil on a Slope

An experiment was performed to study the influence of polymer binders on the physical properties,and stability against a simulated rainfall,of a slope consisting of engineering spoil.Results showed that low polymer binder concentrations(≤500g/m3) could enhance the air permeability and moisture-retaining capacity of the engineering spoil;however,adding more polymer binder made the hardness of the engineering spoil increase and then decline.With the increase of polymer binder concentrations,the surface(0-5cm) permeability of the engineering spoil decreased but the permeability of the lower layers(5-10cm) increased.Polymer binders might reduce runoff and sediment,but the effect becomes weaker with the increase of rainfall.The results of this study have significance for engineering practices.Further experiments are needed to study the effects of binders under other conditions,such as natural rainfall,different slopes,different rock types,different degrees and spoil weathering and different added material,and the chemical interaction between soil and polymer binders.

Effect of heat treatment on microstructure and dimensional stability of ZL114A aluminum alloy

The effects of heat treatment process on microstrucature, micro-yield strength and dynamic dimensional stability of ZL114A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile testing and thermal cycling on-line measuring method. Fine dispersed eutectic Si phases are observed, and long strip eutectic Si and massive primary Si phases decrease in ZL114A alloy after high-temperature and long-time solution treatment, which result in the increase of micro-plastic deformation resistance. With the increasing of aging temperature, aging precipitation behaviour of ZLll4A alloy transforms from precipitation of GP zone and fl＇ phases simultaneously at lower temperature to precipitation of stable Mg2Si phases at higher temperature. Because coherent strengthening is the main strengthen mechanism for micro-plastic deformation, precipitation of stable Mg2Si phases is unfavorable to the improvement of micro-plastic deformation resistance. Micro-yield strength cannot characterize dimensional stability comprehensively, and dynamic dimensional stability under alternative temperature should also be tested cooperatively for better evaluation of dimensional stability.

The protection, development, research and use of intangible cultural heritage in Hebei province

Hebei has a long history, rich cultural heritage, which not only has a lot of tangible cultural heritage, but also has many valuable cultural heritages. This non- material cultural heritage not only is a spiritual wealth and a precious wisdom of Hebei children, but also a treasure of Chinese civilization. Protection of intangible cultural heritage, maintaining national cultural heritage, is an important cultural foundation of enhancing the bond of national emotional, promoting and safeguarding national unity and social stability, and is also a necessary requirement to building an advanced socialist culture, promoting a cultural province construction, building a ＂harmonious Hebei ＂, and achieving better and faster development of Hebei. Conscientiously implement the approach of ＂protection and rescue first, rational use, inheritance and development ＂, and do a really good job of intangible cultural heritage protection, management and rational use.

Comparative Studies of Thermal Stability of Coal Tar Pitches

In the present work, three medium softening point coal tar pitches were used for comparative thermal stability and under-storage stability investigation. Powders of the pitches were found to be different under storage： one of the pitches was caked and slumped after 7-day or longer storage. For thermal stability investigation the soft temperature treatment （265℃） of coal tar pitches was used. Detailed study of initial and treated pitches was carried out. Experimental results demonstrated that LMW-HC （high low-molecular-weight hydrocarbons） and oxygen content influence pitch quality characteristics in a negative way under long-term storage and lead to highest properties change after thermal stability treatment.

Study for reasonable value of friction coefficient between main cable and saddle

The value of friction coefficient between the main cable and saddle, relates to not only the anti-slippage stability of three-tower suspension bridge, but also the reasonable stiffness of the middle tower and the magnitude of rigidity of the whole bridge. First, the paper does some comparative studies about the relevant provisions of international norms, and then, summarizes the relevant load test results both at home and abroad. Finally, the paper draws the appropriate anti-slippage safety factor for the most unfavorable load in accordance with international load standards, and discusses the rationality and feasibility of the friction coefficient of 0.2 between main cable and saddle.

Fluid–solid coupling analysis of rock pillar stability for concealed karst cave ahead of a roadway based on catastrophic theory

In order to study the mechanism of water inrush from a concealed, confined karst cave, we established a fluid–solid coupling model of water inrush from a concealed karst cave ahead of a roadway and a strength reduction method in a rock pillar for preventing water inrush based on catastrophic theory. Fluid–solid coupling effects and safety margins in a rock pillar were studied. Analysis shows that rock pillar instability, exerted by disturbance stress and seepage stress, is the process of rock pillar catastrophic destabilization induced by nonlinear extension of plastic zones in the rock pillar. Seepage flow emerges in the rock pillar for preventing water inrush, accompanied by mechanical instability of the rock pillar. Taking the accident of a confined karst cave water-inrush of Qiyi Mine as an example, by studying the safety factor of the rock pillar and the relationship between karst cave water pressure and thickness of the rock pillar,it is proposed that rock pillar thickness with a safety factor equal to 1.5 is regarded as the calculated safety thickness of the rock pillar, which should be equal to the sum of the blasthole depth, blasting disturbance depth and the calculated safety thickness of the rock pillar. The cause of the karst water inrush at Qiyi Mine is that the rock pillar was so small that it did not possess a safety margin. Combining fluid–solid coupling theory, catastrophic theory and strength reduction method to study the nonlinear mechanical response of complicated rock engineering, new avenues for quantitative analysis of rock engineering stability evaluation should be forthcoming.

A Criterion for Stability of Synchronization and Application to Coupled Chua's Systems

We investigate synchronization in an array network of nearest-neighbor coupled chaotic oscillators. By using of the Lyapunov stability theory and matrix theory, a criterion for stability of complete synchronization is deduced. Meanwhile, an estimate of the critical coupling strength is obtained to ensure achieving chaos synchronization. As an example application, a model of coupled Chua＇s circuits with linearly bidirectional coupling is studied to verify the validity of the criterion.

SELECTION OF HORIZONTAL DISTANCE X BETWEEN ROADWAY AND THE EDGE OF ITS UPPER PILLAR

The horizontal distance X between roadway and the edge of its upper pillar is considered as an important parameter for layout of roadway in floor strata or in the adjacent coal seam. Based on the research achievements of rockstrata pressure, this paper illustrates the quantitative relationship among the mining situation of upper searn, the rockstrata properties around roadway, the vertital distanee Z (between roadway and its upper pillar), and the horizontai distance X (between roadway and the edge of its upper pillar), and provides a main basiS for the selection of value X and the relative location between roadway and its upper seam.

Impact of the Integrated Management Systems on the Achievement of Stable Quality and Safety of Biscuit Products

The implementation of Integrated Management System （IMS） of the quality management and safety is aiming to provide production of biscuit products corresponding to particular specification and client＇s requirements. This paper explores the possibilities of achieving stable sensory and microbiological parameters of the biscuits, through the implementation of IMS. An analysis was carried out of the factors affecting the achievement of stable quality. The achievement of the stability of the parameters of 150 different lots of biscuits has been measured before, during and after the implementation of IMS in the manufacturing company The performed water activity analysis and sensory analysis confirmed that despite the dynamic changes in the internal and external environments as well as the significant changes in the requirements of the standards and the legislation, the implemented IMS has allowed the maintenance of the stable quality and safety of the biscuit products.

Stable High-Energy Density Super-Atom Clusters of Aluminum Hydride

With the concept of super-atom, first principles calculations propose a new type of super stable cage clusters AlnH3n that are much more energetic stable than the well established clusters, AlnHn＋2. In the new clusters, the aluminum core-frame acts as a super-atom with n vertexes and 2n A1-A1 edges, which allow to adsorb n hydrogen atoms at the top-site and 2n at the bridge-site. Using Al12H36 as the basic unit, stable chain structures, （Al12H36）m, have been constructed following the same connection mechanism as for （A1H3）n linear polymeric structures. Apart from high hydrogen percentage per molecule, calculations have shown that these new clusters possess large heat of formation values and their combustion heat is about 4.8 times of the methane, making them a promising high energy density material.

Stability and Electronic Properties of Metal-N4 and Metal-N2 Complexes

Nitrogen molecules Nx have been the subject of much recent research because of their potential as high-energy materials. Many nitrogen molecules dissociate with very low barriers, including molecules such as acyclic N4 that are essentially unbound. A number of studies have reported the ability of heteroatoms to stabilize complex nitrogen molecules. In the present study, the energetic and electronic properties of scandium（Ⅰ） and titanium（Ⅱ） complexes with N2 and N4 are calculated and discussed. Dissociation energies and singlet-triplet energies are determined by theoretical calculations using second-order perturbation theory （MP2） in conjunction with the Dunning basis sets.

Structural, thermodynamics and elastic properties of Mg_(17)Al_(12), Al_2Y and Al_4Ba phases by first-principles calculations

Structural stabilities, thermodynamics stabilities, elastic properties and electronic structures of Mgl7Al12, Al2Y and AlaBa phases were analyzed by first-principles calculations with Castep and Drool3 program based on the density functional theory. The calculated results of heat of formation indicate that AI2Y phase has the strongest alloying ability. The calculated thermodynamic properties show that the thermal stability of these compounds gradually increases in the order ofMgl7Al12, A12Y and Al4Ba phases. Y or Ba addition to the Mg-Al alloys could improve the heat resistance. The calculated bulk modulus B, shear modulus G, elastic modulus E and Poisson ratio v show that the adding Y or Ba to Mg-Al alloys could promote the brittleness and stiffness, and reduce tenacity and plasticity by forming Al4Ba and Al2Y phases. The calculated cohesive energy and density of state （DOS） show that Al2Y has the strongest structural stability, then AlaBa and finally Mg17Al12. The calculated electronic structures show that Al2Y has the strongest structure stability because of the strong ionic bonds and covalent bonds combined action.

一种轮足组合式擦玻璃机器人机构设计研究

为提高擦玻璃装置的实用性和自动化水平,提出了一种新型轮足组合式擦玻璃机器人,能够实现自主越障和双向清洗功能,并通过改善整体运动性能提高清洗效率。通过对机器人清洗和越障状态进行力学分析,得到了保持安全稳定性的条件,为机器人合理的机构设计、选型和控制提供依据。

Flow computations of multi-stages by URANS and flux balanced mixing models

The quasi-steady methods based on mixing models have been widely applied to flow computations of turbomachinery multi- stages in aerospace engineering. Meanwhile, the unsteady numerical simulation has also been used due to its ability in obtaining time-dependent flow solutions. In the paper, two different mixing treatments and the corresponding flux balanced ones are presented to exchange the flow solutions on the interfaces between adjacent blade rows. The four mixing treatments are then used for flow computations of a subsonic 1.5-stage axial turbine and a quasi-l.5-stage transonic compressor rotor. The results are compared with those by unsteady numerical method, which is implemented by using the sliding mesh technique. The effects of the quasi-steady and unsteady computation methods on the conservation of flow solutions across the interfaces are presented and addressed. Furthermore, the influence of mixing treatments on shock wave and flow separation of the transonic compressor rotor is presented in detail. All the results demonstrate that the flux balanced mixing treatments can be used for multi-stage flow computations with improved performance on interface conservation, even in the complex flows.

Qualitative analysis for a Wolbachia infection model with diffusion

We consider a reaction-diffusion model which describes the spatial Wolbachia spread dynamics for a mixed population of infected and uninfected mosquitoes. By using linearization method, comparison principle and Leray-Schauder degree theory, we investigate the influence of diffusion on the Wolbachia infection dynamics.After identifying the system parameter regions in which diffusion alters the local stability of constant steadystates, we find sufficient conditions under which the system possesses inhomogeneous steady-states. Surprisingly,our mathematical analysis, with the help of numerical simulations, indicates that diffusion is able to lower the threshold value of the infection frequency over which Wolbachia can invade the whole population.

Lag Synchronization Between Two Coupled Networks via Open-Plus-Closed-Loop and Adaptive Controls

In this paper,we study lag synchronization between two coupled networks and apply two types of control schemes,including the open-plus-closed-loop(OPCL) and adaptive controls.We then design the corresponding control algorithms according to the OPCL and adaptive feedback schemes.With the designed controllers,we obtain two theorems on the lag synchronization based on Lyapunov stability theory and Barbalat's lemma.Finally we provide numerical examples to show the effectiveness of the obtained controllers and see that the adaptive control is stronger than the OPCL control when realizing the lag synchronization between two coupled networks with different coupling structures.