Morphological structure, other than chemical composition is of great significance to design and fabricate superior electromagnetic (EM) wave absorption materials. Hollow CoS 2 nanobubble prisms with hierarchical porous structure are well preserved via a subsequent sulfuration process from hollow nanorods-like ZIF-67 as a precursor. The hollow CoS 2 nanobubble prisms provide advanced microwave absorbing property. With a low filler loading of 25 wt%, the minimum reflection loss of hollow CoS 2 nanobubble prisms reaches À 54.9 dB at 5 GHz, while the effective absorption frequency band is 14.2 (3.8-18) GHz. Moreover, the microwave absorbing mechanism of porous architecture and chemical component is discussed systematacially. This work elaborates the importance in investigating porous architectures for microwave absorption in the possible field of future, providing an excellent example to study and develop advanced microwave absorbers.
Self-localization of sensor nodes is one of the important technologies in wireless sensor networks. APIT is a range-free localization algorithm; it has the advantages of high localization accuracy and low communication overhead. However, the localization coverage of APIT is low, and when the proportion of anchor nodes is low, APIT is prone to OutToIn and InToOut error. To solve the above problems, this paper proposed a new point-in-triangulation test method based on cosine theorem according to APIT's basic idea to prevent OutToIn and InToOut error, and added RSSI model to locate the unknown nodes which are judged outside the triangles through trilateral measurement method to improve the localization coverage. Simulation results shows that compared with APIT algorithm, the new algorithm has higher localization accuracy and coverage.
In wire electro-discharge machining with high traveling speed(WEDM-HS), the emulsion is used as working liquid. Because there exists a functional electrolyte, this affects the surface quality of workpiece machined. An investigation has been made into the machining feasibility when the gas or air is employed as processing medium. The first cut on workpiece is done with emulsion, and then air or distilled water is used for the second cut and multi-cuts. After machining, the surface quality and mechanical performance of the specimen under different conditions are compared. The experimental results show that air and distilled water have little influence on the surface roughness, but they can improve the mechanical performance such as the increase of hardness and the decrease of surface cracks. An orthogonal design is adopted to optimize the electric parameters and cutting passes so as to obtain the best integrative result. The experiment with air as medium reveals that it is a feasible and effective way for eliminating the electrolytic layer and improving the surface integrity of workpiece.
A new method for on-line fabrication of micro tool-electrodes is presented in this paper.
The method is base on the machining mechanism of electrochemical micromachining. By exchanging
the polarities of the tool-electrodes and workpiece repeatedly, micro tool-electrode appropriate for
electrochemical micromachining can be obtained through mutual machining. Because the processes
are carried out on-line, the position error and clamp error caused by twice-clamp of tool-electrodes
can be avoided, and the machining precision can be improved greatly. This method will be very
important to electrochemical generating micromachining. Experiments are carried out, and a
tool-electrode with the pinpoint of 20μm can be machined stably.
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