Profile measurement is a key technical enabler in the manufacturing of highly curved freeform surfaces due to their complex geometrical shape. A current optical probe was used to measure nearly rotary freeform surfaces with the help of one rotation axis, because the probe needs to measure along the normal vector of the surface under the limitation of the numerical aperture (NA). This kind of measuring system generally has a high cost due to the high-precision, multi-axis platform. In this paper, we propose a low-cost, dual-axis rotation scanning method for a highly curved freeform surface with an arbitrary shape. The optical probe can scan the surface profile while always keeping consistent with the normal vector of the measuring points with the help of the double rotation axis. This method can adapt to the changes in curvature in any direction for a highly curved freeform surface. In addition, the proposed method provides a system error calibration technique for the rotation axis errors. This technique can be used to avoid the dependence of the measuring system on the high-precision platform. The three key system errors that affect the measurement accuracy such as installation error of the B-axis, A-axis, and XZ perpendicularity error are first analyzed through establishing an error model. Then, the real error values are obtained by the optimal calculation in the calibration process. Finally, the feasibility of the measurement method is verified by measuring one cone mirror and an F-theta mirror and comparing the results to those obtained using commercial equipment. The maximum measurable angle of the system is ±90°, the maximum measurable diameter is 100 mm, and the measurement accuracy of the system reaches the micron level in this paper.
The present paper reports the influence of hot working conditions on the microstructure of Ti 2 AlNb/TC11 dissimilar joint. Linear friction welding technique was used to fabricate the joints. The microhardness and tensile properties of the joints have been tested. It was found that the fine structure of linear friction welds underwent abnormal grain growth and abnormal grain boundary phase growth in the post-weld solution heat treated condition. This phenomenon significantly deteriorated the ductility of the joint. After appropriate hot work, abnormal big grains/phases disappeared, and the joint exhibited good tensile properties due to its fine structures.
The skyrocketing popularity of health monitoring has spurred increasing interest in wearable electrochemical biosensors. Compared with the traditionally rigid and bulky electrochemical biosensors, flexible and stretchable devices render a unique capability to conform to the complex, hierarchically textured surfaces of the human body. With a recognition element (e.g., enzymes, antibodies, nucleic acids, ions) to selectively react with the target analyte, wearable electrochemical biosensors can convert the types and concentrations of chemical changes in the body into electrical signals for easy readout. Initial exploration of wearable electrochemical biosensors integrates electrodes on textile and flexible thin-film substrate materials. A stretchable property is needed for the thin-film device to form an intimate contact with the textured skin surface and to deform with various natural skin motions. Thus, stretchable materials and structures have been exploited to ensure the effective function of a wearable electrochemical biosensor. In this mini-review, we summarize the recent development of flexible and stretchable electrochemical biosensors, including their principles, representative application scenarios (e.g., saliva, tear, sweat, and interstitial fluid), and materials and structures. While great strides have been made in the wearable electrochemical biosensors, challenges still exist, which represents a small fraction of opportunities for the future development of this burgeoning field.
Abstract As a non-renewable resource, mineral resources occupy a very important role in human production and life. They are closely related to human beings. This article aims to analyse the status of mineral resource development and the distribution of mineral resources, and expound Relevant geological environment of the mine where the resource is located and some accompanying hazards, and put forward relevant suggestions and specific measures to protect the geological environment in view of the problems found. From the improvement of the utilization rate of minerals, the implementation of mine environmental protection and environmental supervision and other methods to protect the geological environment, I hope that we can provide some suggestions to our country on address environmental protection and development and utilization of mineral resources.
Aim at the unilateral penalty for treating intermediate density elements in traditional topology optimization, a bi-directional interpolation model (BDIM) is developed to treat intermediate density elements during the topology optimization process. By introducing a threshold, the BDIM model can rationally treat intermediate density elements through penalizing and promoting them toward void and solid elements bilaterally. The mathematical model based BDIM is established for optimizing heat conduction problems and the optimization criteria is derived according to gradient projection method. Corresponding numerical examples are presented to demonstrate the validity of this proposed approach, with the global optimizing results based BDIM model laying a reliable foundation for the subsequent shape and size optimizations in thermal engineering design.
In this paper, a new type of Delta robot with only two degrees of freedom is proposed on the basis of multi - degree - of - freedom delta robot. In order to meet our application requirements, we have carried out structural design and analysis of the robot. Through SolidWorks modeling, combined with 3D printing technology to determine the final robot structure. In order to achieve the precise control of the robot, the kinematics analysis of the robot was carried out. The SimMechanics toolbox of MATLAB is used to establish the mechanism model, and the kinematics mathematical model is used to simulate the robot motion control in Matlab environment. Finally, according to the design mechanism, the working space of the robot is drawn by the graphic method, which lays the foundation for the motion control of the subsequent robot.
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