Ultimate Bearing Capacity Analysis of High Strength Single Angle Compression Member Eccentrically at One End

To analyze mechanical behavior of Q460 high strength single angle steel struts with an eccentric load at one end in transmission towers, experimental analysis and theoretical calculation were carried out to study the overall stability and local buckling of members. Spherical hinge bearing and double knife edge bearing were applied at axial end of specimens. Influence of some factors on bearing capacity of compression members with eccentricities at both ends was analyzed, such as the end supporting conditions and residual stresses. It was shown that whether spherical hinge bearing or double knife edge bearing was used at axial end, the mechanical behavior can be accurately presented and the residual stresses affected the ultimate load carrying capacity by about 5％ or less. Compared with different methods, such as experiment method、finite element method, method in the Guide for American Design of Latticed Steel Transmission Structure（ASCE101997）and method in Chinese Technical Regulation of Design for Tower and Pole Structure of Overhead Transmission Line (DL/T51542002), it was found that the calculated strength of high strength steel member by standard calculation method in DL/T51542000 was over conservative. According to the research results, the revised formulas of ASCE were proposed with dividing actual material strength by the resistance coefficient of rR=1.111. Therefore, the experimental results can provide reference for designing high strength Q460 single angle steel members compressed eccentrically at one end.     

Experimental Analysis of Construction Time Space Effect for Large Span and Flat Multi Arch Tunnel

For the large span and flat, together with the interaction effect of construction and disturbance of surrounding rock, the mechanical of large span and flat multi arch tunnel is very complicated, and the time space effect is different from that of two lane multi arch tunnel or separated tunnel. Adopting the “CTSSSRH”, the 3 D dynamic process of the tunnel construction was simulated. Analyzing the rule of surrounding rock displacement and stress with excavation, the time space effect of large span and flat multi arch tunnel was proposed.     

Performance and Microstructure of Ultra Low Ion Permeability Cementitious Materials

Microstructure and macro performance of Ultra Low Ion Permeability Cementitious Materials (ULIPCM) were investigated by Micro hardness, MIP and SEM EDXA. It was shown that the compressive strength of ULIPCM was more than 80 MPa, flexural strength was more than 11.0 MPa, and elastic modulus was in the range of 38.0 to 42.0 GPa at the age of 28 days; chloride diffusion coefficient was lower than 0.8×10－13m2·s－1, conductive charge for 6 hours was lower than 300 coulombs; sulfate attack resistance was good; shrinkage at the age of 28 days was lower than 400×10－6. Compared with ordinary concrete with which thickness of interfacial transition zone is 60 to 100 μm, the thickness of interfacial transition zone of ULIPCM was lower than 30 μm. Penetration paths of corrosive medium were effectively interrupted in ULIPCM. And pore structure parameters, such as porosity and the most probable pore radius of ULIPCM, were also obviously optimized in ULIPCM. Besides, few CH crystals were in the ULIPCM aggregate and the interfacial transition zone of ULIPCM. And the orientation of CH crystals was poor.     

Dynamic characteristic analysis of an all terrain vehicle body

The body is a key part of all terrain vehicles (ATV). Its dynamic characteristics greatly effect the vibration of the ATV assembly. Simulation and experimental methods are combined to analyze ATV body vibration characteristics. A computer aided design(CAD) model is built using UG4.0. A finite element method(FEM) model of an ATV body and a body with an engine are created using Hypermesh. The FEM model is imported to Msc.Nastran to calculate the free mode. The simulation model is verified by the experimental modal result. The results indicate that after the frame with engine, the first bending mode increases due to the engine increasing the body stiffness, while the first torsion mode decreases due to the engine mass. The effects on the dynamic response of the road and engine excitation are analyzed respectively. Vibration characteristic improvement methods and suggestions regarding the body are provided.     

Robust adaptive control for nonlinear chaotic systems

Tracking control of a nonlinear uncertain Chua's chaotic system is studied. With coordinate transform, Chua's chaotic system is transformed to a general form of a strict feedback control system. Combining the backstepping method with robust control technology, an adaptive parameter control law for a robust output feedback control scheme is developed for output tracking of nonlinear unknown systems. It is shown that the derived robust adaptive controller based on Lyapunov stability theory can guarantee global uniformly bounded ultimate property for all states of the closed loop system, and lead to tracking error decreasing at exponential speed. The simulation results show the effectiveness of the proposed approach.     

Waste FR 4 printed circuit board recycling technology based on supercritical fluid carbon dioxide

To create a model for recycling technology, a waste FR 4 printed circuit board (PCB) recycling process employing supercritical fluid CO2 (SCF CO2) is studied using central composite design. The influence of temperature and treatment time on the PCB delamination ratio, latitudinal tensile strength of glass fiber sheets, and their synthesized effect are analyzed. The optimal temperature and treatment time for FR 4 PCB recycling with SCF CO2 are found by building a quadratic polynomial equation model of output parameters in recycling technology. The accuracy of the derived optimal temperature and treatment time is validated by a series of experiments.     

A Hilbert fractal antenna and portable monitoring system for partial discharge detection in gas insulated substations

We design a third Hilbert fractal antenna for partial discharge (PD) monitoring in gas insulated substations (GIS) based on fractal principles, and analyze the Hilbert antenna impedance characteristics using an equivalent inductance method of parallel transmission lines. The PD experiment of metal protrusion defect is conducted employing fractal and microstrip antennae. The test results show that the characteristic of the Hilbert fractal antenna has good performance and can detect the PD signal for online monitoring in GIS. A portable online monitoring and locating system for GIS is established using the Hilbert fractal antenna and LabVIEW. The locating accuracy of the PD source in the laboratory meets the requirements of the PD site location.     

Theory and approach to reactive power flow tracing

Based on an analysis of the characteristics of reactive power supplies and reactive loads, this paper presents a method for forming a lossless reactive network using an equivalent technique of modeling the branch admittance as a reactive power supply and the branch power loss as a virtual load. A downstream distribution matrix for a power system is constructed based on its reactive lossless network, and the analytical model and its algorithm for tracing reactive power flow (TRPF) is proposed. A method dealing with the abnormal downstream distribution matrix of active power flow also is discussed. The main advantage of the proposed method is that the matrix theory is used to analyze the TRPF model directly and no assumption on the flow distribution is needed. Case studies of the IEEE14 Bus and IEEE30 Bus systems demonstrate the accuracy and the validity of the proposed method.     

Dynamic analysis and optimization of gear trains in a megawatt level wind turbine

Through coupling vibration analysis of the transmission system of a 1.5 MW wind turbine gearbox, a torsional vibration model of a gear drive system in wind turbines is established. The fourth order Runge Kutta integration method is applied to calculate the dynamic response of a gear system caused by wind loads, time varying meshing stiffness, and system damping. The harmonic balance method is used to find the analytic solution. Based on the solution, a mathematical model for optimum gear system design is established. The model aims at minimizing the vibration acceleration of the planet gear and the total mass of the gear transmission system. The optimization toolbox in MATLAB program is adopted to obtain the optimal solution. A calculated example shows that the primary natural frequency of the gear system has been raised, the dynamic properties of the gear train have been improved remarkably, and the total mass of the gear train has been decreased.