lower beam
3.The formula for lower limit of natural frequency of tapered pier of continuous beam bridge were derived by the combination of Rayleigh and Southwell method. The natural frequency of tapered pier was composed of the sum of frequency of each subsystem consisted in inertia component and deformable component. Then finite element analysis was used to establish models to verify the approach.
4.The machine adopts athreeroller symmetrical structure,The upper roller makes vertical movement at a symmetrical position in the center between the two lower rollers.The hydraulic driving is achieved through the action of the oil in the hydraulic cylider on the piston,The two lower rollers make rotation,and provide the plates with torque through the engagement between the gear of the moderator and the lower roller,several groups of support rollers are devised on the lower side of the two lower rollers to enhance the rigidity of the lower rollers,and enablesvertical adjustment.Onthe upper side of the upper roller,there is a rigid beam and the upper roller,there are several groups of support rollers to enhance the rigidity of the upper roller.The machine is fit for bending the workpiece in shape and with excessive width.
7.Result: In the reconstruction of a simulated Phantom data, OSEM gives better images with higher spacial resolution and lower noise, as compared with traditional FBP method especially under noisy acquisition situation in fan-beam scanning, and in a certain extension the image quality is proportional to the product of the iterative number and the subset order, while computing time is only related to the iterative number.
