Applied Mechanics and Materials Vols. 34-35

Abstract: In order to improve the wear resistance of debris-ejecting blade of driller, cemented carbide welding coatings were prepared by arc-welding technology. The abrasive wear behavior and wear mechanisms of cemented carbide welding coatings were researched under both dry and water friction conditions. The research results show that the wear rates of the coatings increase with the increase of loads and sliding speeds. The influence of sliding speeds on wear rates of the coatings becomes intense as the increase of loads. The wear rates of the coatings under water friction conditions are bigger than those under dry friction conditions. The main wear mechanisms of the coatings are micro-cutting and multi-plastic deformation wear of matrix metal, and micro-cracking and brittle fracture as well as spalling of WC particles.

Abstract: The work of vibration test has significant meanings for the researches and applications of 3-dimension and 5-direction braided composites. This article discusses the effects of added mass with different weight on the modal test of 3-dimension and 5-direction braided composites. The comparison of the modal parameters of 3-dimension and 5-direction braided composites tested by different weight of mass reveals that the additional mass is a mostly influence factor for vibration property of 3-dimension and 5-direction braided composites. The results of frequency response and force response curves show that smaller mass accelerometer is more effective for a wider range of frequencies around the resonance frequency, a higher natural frequency and a larger peak in these points. Force-response curves show that force response amplitude increases with the increase of additional mass weight, and the larger additional mass, the shorter time taken for reaching stationary state. The errors of natural frequency and damping ratio increase when the weight of additional mass increases. With the increase of modal orders, relative errors of modal characteristics have slighter decreasing degrees. The results derived from this article will provide a useful reference for precise modal analysis of 3-dimension and 5-direction braided composites.

Abstract: This paper presents a novel Multi-Degree-of-Freedom magnetic levitation sphere driving joint. It analyses the relevance theory of air-gap magnetic energy of the mechanic and electric energy transformation while the magnetic levitation force and electromagnetic torque were generated by driving joint, which based on the principles of state reconstruction. It achieves state synchronization suspension control and self-test feedback control without sensor of the rotor. The simulation experiment shows that the state synchronization suspension control owns high precision and interference immunity.

Abstract: In order to study the high-temperature performance of composite structure asphalt concrete specimens, cylindrical and plate double-layer specimens with two asphalt mixtures are prepared to conduct uniaxial repeated load permanent deformation test and wheel tracking test. The deformation behavior and mechanical characteristics are analyzed and the relationship between rut deformation and mechanical parameters are also discussed. In addition, according to finite element analysis, the deformation mechanism of composite structures under the same loads was discussed. The results and analysis indicate that the deformation behaviors of the specimens with different structures are different significantly despite the same total thickness. Among those specimens, S（4/6）has the smallest deformation and corresponding mechanical parameter εp/Fn is also the smallest under the same load. The maximum shear stresses and their occurrence in different positions for different composite structures have discrepancies. The maximum shear stress of S（4/6）is smaller than other structures, which appears in the upper layer having better high temperature performance. This is the reason that the resistance to permanent deformation of S（4/6） is best among the three composite structures.

Abstract: Centrifugal compressors are widely used to compressor gas in many different processes within the petroleum and chemical industry. Two vibration types of concern in industrial compressors are synchronous and subsynchronous vibration. The latter, more troubling type of vibration, occurs when non-conservative whirling forces(Cross-coupling) act to excite a lateral natural frequency, which lies below the running speed(subsynchronous vibration). In this paper, more attention is paid to impellers from a rotordynamic standpoint and a synthesis gas compress in ammonia plant is analyzed in order to diagnosis the root cause of vibration fault using the best available resources for seals and bearing. Logarithmic decrement predictions for the full rotor model consisting of all the stages and seals are conducted under different bearing structure. On this basis, a resolvent to improve the rotordynamic stability is presented. The field application result indicates that this method is effective.

Abstract: Regular expression was the foundation of advanced language and compiler. It can be recognized by finite automaton. In this paper, combined with operator priority analysis and the rules of regular expression, the table of priority relationship between operators involved in regular expression has be constructed. Based on the table, realized the automatic convert from regular expression to finite automaton, and the program is given. It provided a new reference of regular expression convert to finite automaton.

Abstract: Simulating and researching for characteristics of channel is essential when designing a wireless communications system. Based on the research of existed simulating methods, this paper proposed the Rayleigh-Normal simulating model which looks received signal as the linear combination of Rayleigh stochastic process and Normal stochastic process. This method was used to simulate the first-order statistical characteristics of Rayleigh model, Ricean model, Nakagami model, Lognormal model and so on, the simulating results prove that Rayleigh-Normal simulating model is a correct and valid simulating model for wireless channel.

Abstract: The useful properties of cellular solids depend on the material from which they are made, their relative density, and their internal geometrical structure. Based on two simple models (two-dimensional honeycomb and three-dimensional prism)of cellular structures, equivalent Young’s modulus related to the relative density is derived, and the theoretical results are found to be in good agreement with experimental data of open cell aluminum foams. And the results provide evidence that the three-dimensional prism model is reasonable, which two models are approximately true at low density.

Abstract: Geographic profiling uses locations of series crimes to detect the most probable residence of the offender. However, because of shortage of other information, the method doesn't perform well. To Solve this problem, the concept of geographic profiling was extended and a concept of human geographic profiling (HGP) was put forward to take offender’s bias, victims’ characteristics, and geographical circumstances into account. The physical geographic profiling (PGP) was obtained by combining an improved “spatial mean” method and an improved criminal geographic targeting (CGT) model by using a precisely deduced "Combination Function". Afterwards, HGP and PCG were combined by the same function. The resultant product was a three-dimentional probability map. Simulation result indicated high accuracy rates among which the lowest is 66% under an ideal situation. The introduction of HGP and deduction of combination function are discussed originally and are of great importance in this paper.