Applied Mechanics and Materials Vols. 249-250

Abstract: In order to improve the performance of interstellar autonomous navigation system, an interstellar autonomous navigation system using X-ray pulsar and stellar angle measurement is proposed. In this system, an X-ray detector, which is fixed on a gimbaled axis, is adopted. The detector can point at the different X-ray pulsars that are visible. By augmenting the clock error and the clock drift error as a component of the spacecraft state, the proposed system can correct the clock error of the atomic clock onboard. Furthermore, the observability of the corresponding system is investigated, and the result shows that the system is completely observable at most of time. The proposed system can provide an improved performance than traditional version of celestial navigation system (CNS). Through consequentially measure the difference pulsars, the proposed system can have a satisfactory performance. The proposed navigation system provides a prospective way for the realization of the deep space autonomous navigation system.

Abstract: Magnetic code is widely used in check, securities, tax invoice, etc. However, the traditional recognizing and reading method of magnetic code is mostly based on correlation coefficient and it takes significant time and cost. After analyzing the characteristics of magnetic code signals in E-13B standard, this paper has proposed a new algorithm based on the peak-valley location and amplitude (PVLA) to simplify the calculation and system design. Firstly, the magnetic code signal is separated into magnetic ink character signals by the thresholds of peak and valley. Secondly, the features of the peak-valley location (PVL) and peak-valley amplitude(PVA) of each magnetic ink character signal are extracted and normalized, then the nearest neighbor recognition algorithm based on the vectors of peak-valley location and amplitude is utilized to recognize the magnetic code. The recognition results and statistical parameters from a large number of experiments show that the new method has higher recognition rate and better robustness. In addition, the new algorithm only involves additions and subtractions, so it has a lower computation cost.

Abstract: Gas identification represents a big challenge for improving detection and pattern recognition of each gas by using inexpensive gas sensor. This paper presents a gas detector system which is built to monitor, and measure gas pollutant emissions in the air and also used to detect different gases. The pollutants are ethane (C2H6) and methane (CH4) which are located beside the fertilizer factories in Alexandria Egypt and some other gases as hydrogen (H2), propane (C3H8) and isobutane (C4H10).The gas sensors TGS-2611, TGS-816, TGS-2620 and TGS-823 from Figaro Engineering Inc. are used to build agas detector system and it is located in the site of measurements. The data of each sensor is transmitted and received wirelessly using XBee module (DigiXBee 802.15.4) and microcontroller PIC 18F4620. The system is controlled and monitored by using programmable logic controllerPLC Step 7-200 from Siemens and Supervisory Control and Data Acquisition SCADA systems respectively. The principal component analysis PCA method is applied for clustering and distinguishing among different gases. The results indicate thatmethane can be detected using TGS-2611 better than other sensors.Isobutane can be detected by using TGS-2620 and TGS-2611 better than others. Propane can be detected by using TGS-816 and TGS-823 better than others. Hydrogen can be detected using TGS-2620, TGS-816 and TGS-823 better than others

Abstract: This paper investigates the regenerative chatter in a plunge grinding process. The effect of the contact force on the onset of chatter vibration is clarified by a proposed continuation algorithm, and the boundary for the chatter-free region in which the grinding process is stable is obtained. By varying the rotational speed of the workpiece continuously, the chatter vibration with the values of the system parameters being near the boundary is suppressed, namely, the chatter-free region is expanded by this spindle speed variation control strategy.

Abstract: CFRP/AL stacks are widely used in modern aircraft manufacturing industry. Thrust force is the most important element which will cause delamination in the drilling of stack. This paper developed a thrust force dynamic analysis model for drilling of CFRP/AL stack, by firstly, representing the drilling process into a five-stage model. Secondly, the dynamic thrust force is decomposed into two parts (sub models for CFRP and AL drilling). Thirdly, the thrust force components on both tool major cutting edge and chisel edge is developed according to the analysis on infinitesimal cutting unit in both sub models for CFRP and AL drilling. Lastly, several experiments are performed to compare the result of thrust force analysis, which proves that the purposed model can analyze the dynamic thrust force in drilling of CFRP well.

Abstract: An optimal selection model of the lurk orbit on which a satellite will park waiting for instructions aiming at a non-cooperative space target is presented. The model uses factors including orbit maneuver satisfaction degree in special cases and orbit utilization value in ordinary uses taking into account orbit maintenance cost, orbit availability and the resulting elusiveness. These factors are derived from dynamics characteristics of the space target orbit and the optional lurk orbits. The model is employed to select the optimal lurk orbit from several optional orbits for a satellite taking aim at a non-cooperative space target so as to secure ordinary utilization and effective respond when receiving instruction to perform tasks concerning the space target. In the presented work, lurk orbit selection processes in an application example are analyzed using the model. It is seen that the optimal selection model effectively solves lurk orbit selection

Abstract: Considering the effect of axial loads in the rail, this study presents a hybrid approach to investigate the dynamic responses of vehicle-track-foundation system. In this model, the vehicle is taken as a multi-rigid-body subsystem, and the ballastless track is simulated as Euler beam supported by two-layer elastic foundation. The coupled dynamic equations of system with axial loads are derived based on D’Alembert’s and Hamilton’s principles. The proposed methodology is validated through the real example to be numerically analyzed. The results show that the tensile force in rail is tending to have the amplitude of vibration decrease, and the compress force would bring the amplitude of vibration going up. So a rational axial loading is necessary to suppress the vibration of vehicle-track-foundation system when the car moving at a high speed.

Abstract: In this study, thermodynamic performances of ammonia-water Rankine (AWR) cycle and regenerative Rankine (AWRR) cycle are comparatively investigated. Special attention is focused on the effects of ammonia concentration and turbine inlet pressure on the performance of system using heat sources of high temperature of 300 oC and low temperature of 150 oC. The behavior of important system variables including mass flow ratio of working fluid, net work production, and thermal efficiency are closely examined. Results show that performance characteristics for heat sources of high and low temperatures are quite different each other. For the high-temperature source, the thermal efficiency has a minimum in AWR system while it has a maximum in AWRR with respect to ammonia concentration in the range of 65% to 75%. For low-temperature source, however, the thermal efficiency decreases with ammonia concentration in the range of ammonia concentration higher than 95% for both AWR system and AWRR system and the effect of regenerator is negligible.

Abstract: Subjects related to strength and durability of structures such as oil and gas transmission pipelines areof great importance. Considering the special characteristics of these structures including their construction and harsh working environment, they are especially prone to different types of damages. Repair welding is a viable optiontomitigatesuch damages and for restoration of the strength and resistance of these structures. In this paper, anumerical coupled thermo-mechanical finite element modelling approachis conducted tosimulatethewelding and the repair welding process. The results of the studyshow that repair weldsmay wellhave adverseeffects on the residual stress magnitudeand on its distribution. This might in turnpotentially put the integrity of the pipeline at risk.

Abstract: In order to solve the problems such as more restriction conditions, complicated interference and longer design periods in the design process of segment erector for Tunnel Boring Machine, it is necessary to study on the dynamics simulation of TBM segment erector. The 3D virtual assembling model of a tunnel segment erector is built based on Pro/E software according to its design parameters such as structure and size. The model is simplified and optimized reasonably and various constraints are applied under variety working conditions. The dynamics characteristics of drives and the forces of each part are obtained and they will provide a boundary condition for strength check and basis for the power system design which is important for the further optimal design. The simulation results also provide an important reference for the mechanism design and type selection design for the power system of segment erector and design cycle is shortened for TBM segment erector.