Study on Hydrodynamic Pressure in Grinding Contact Zone Considering Grinding Parameters and Grinding Wheel Specifications

AbstractIn the grinding process, coolant lubricant is used to lubricate and mainly to transmit the heat generated in the contact zone. Grinding wheel accelerates a portion of the coolant lubricant into the contact zone. As e resault of the wedge effect between grinding wheel and workpiece in the contact zone a hydrodynamic pressure is generated, which influences the grinding results. In this paper, a new model for the hydrodynamic pressure of the coolant in the contact zone is presented. The simulation results show that the hydrodynamic pressure is proportion to grinding wheel velocity, and in inverse proportion to the minimum gap between wheel and workpiece. Furthermore, it could be investigated that the specification of the grinding wheel can affect the value of this pressure. The experimental results correspond to the simulation results, which show the validity of the simulation

A Context-Aware Smartphone-Based 3D Indoor Positioning Using Pedestrian Dead Reckoning

The rise in location-based service (LBS) applications has increased the need for indoor positioning. Various methods are available for indoor positioning, among which pedestrian dead reckoning (PDR) requires no infrastructure. However, with this method, cumulative error increases over time. Moreover, the robustness of the PDR positioning depends on different pedestrian activities, walking speeds and pedestrian characteristics. This paper proposes the adaptive PDR method to overcome these problems by recognizing various phone-carrying modes, including texting, calling and swinging, as well as different pedestrian activities, including ascending and descending stairs and walking. Different walking speeds are also distinguished. By detecting changes in speed during walking, PDR positioning remains accurate and robust despite speed variations. Each motion state is also studied separately based on gender. Using the proposed classification approach consisting of SVM and DTree algorithms, different motion states and walking speeds are identified with an overall accuracy of 97.03% for women and 97.67% for men. The step detection and step length estimation model parameters are also adjusted based on each walking speed, gender and motion state. The relative error values of distance estimation of the proposed method for texting, calling and swinging are 0.87%, 0.66% and 0.92% for women and 1.14%, 0.92% and 0.76% for men, respectively. Accelerometer, gyroscope and magnetometer data are integrated with a GDA filter for heading estimation. Furthermore, pressure sensor measurements are used to detect surface transmission between different floors of a building. Finally, for three phone-carrying modes, including texting, calling and swinging, the mean absolute positioning errors of the proposed method on a trajectory of 159.2 m in a multi-story building are, respectively, 1.28 m, 0.98 m and 1.29 m for women and 1.26 m, 1.17 m and 1.25 m for men