The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser forming is the combination of five common technologies: lasers, rapid prototyping (RP), computer-aided ...design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing workpiece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. In the present work, a type of direct laser deposition process, called laser metal deposition shaping (LMDS), has been employed and developed to fabricate metal parts. Through the comprehensive experiments, it is found that this process is affected by many factors. Besides the processing parameters, scanning pattern is the one that strongly influences the quality and precision of as-fabricated parts. In comparison with the forming effects of different scanning patterns, the most suitable one can be selected to carry out this laser forming process. Finally, with the suitable scanning patterns, the high performance of the formed alloys is confirmed after the above studies.
With the expanding reach of physics, xenon-based detectors such as PandaX-4T in the China Jinping Underground Laboratory aim to cover an energy range from sub-keV to multi-MeV. A linear response of ...the photomultiplier tubes (PMTs) is required for both scintillation and electroluminescence signals. Through a dedicated bench test, we investigated the cause of the non-linear response in the Hamamatsu R11410-23 PMTs used in PandaX-4T. The saturation and suppression of the PMT waveform observed during the commissioning of PandaX-4T were caused by the high-voltage divider base. The bench test data validated the de-saturation algorithm used in the PandaX-4T data analysis. We also confirmed the improvement in linearity of a new PMT base design, which will be used to upgrade the PMT readout system in PandaX-4T.
At present, laser processing has been widely used, but the traditional laser processing can not rapidly adapt to current market demands, so the virtual prototyping technology based on laser ...processing is put forward. In this paper, the research status of the virtual prototyping technology based on laser processing is summarized and the structure figure of laser processing virtual prototyping system is established. Then the virtual prototyping technology based on metal part direct rapid prototyping is studied, which includes the structure parameterization designs of coaxial powder feeding device and powder nozzle and the simulation of the gas-solid two-phase flow in the coaxial powder feeding device and the temperature distribution during the deposition process of metal powder.
Laser forming based on Rapid Prototyping (RP) is a state-of-the-art technology, which creates part by focusing an industrial laser beam on the surface of processing workpiece to create a molten pool ...of metal. A small stream of powdered alloy sprayed from a nozzle is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. The LMDS apparatus consists of four primary components: energy supply system, motion control system, powder delivery system, and computer control system. These components have their specified functions, but work in association with each other. Among them, powder delivery system is the most important one that considerably determines the quality of the as-fabricated metal part. Through the experiments, it is proved that the coaxial powder delivery system can provide uniform and steady powder stream, and possesses the omnidirectional characteristic which results in the smooth appearance and consistent geometry of the deposited part. (5 pages)
In large-scale Data Center Network, how to effectively monitor, find bottlenecks and potential points of failure has become a new research to optimize network performance. However, it is difficult to ...give an accurate network performance evaluation. Because factors affecting network are numerous and network are not equally effected by different factors. Aiming at above problems, this paper proposes an evaluation index system of network performance. Furthermore, the paper puts forward an evaluation method of network performance based on objective weights determination for data center network, short for PE-OWD. First, this method dynamically calculates performance weights based on objective weights determination. Then the method normalizes data using the distribution of historical parameters. And finally the method builds a more refined health evaluation model of network performance. In this paper, according to the Tianhe2 network environment, we evaluate the indexes of network equipment performance. The experimental results verify the effectiveness of the evaluation method of network performance.
In order to investigate the effect on manufacturing quality of focus position misalignment between laser beam and powder convergence in laser metal deposition shaping (LMDS) processing, several ...experiments including single-track monolayer, straight thin-wall and ring thin-wall were made. The measurements and analysis on shape, size and surface quality of the experiment parts were carried out. An omnidirectional detecting method to check the misalignment of focus position was brought forward and tested. The results indicate that the misalignment of focus position directly affects the quality of shaping parts and shows the regularity, the detecting method can easily detect the focus position misalignment on random direction and angle and guide the adjustment on them.
Waveform digitizers are key readout instruments in particle physics experiments. In this paper, we present a waveform digitizer for the PandaX dark matter experiments. It supports both ...external-trigger readout and triggerless readout, accommodating the needs of low rate full-waveform readout and channel-independent low threshold acquisition, respectively. This digitizer is a 8-channel VME board with a sampling rate of 500 MS/s and 14-bit resolution for each channel. A digitizer system consisting of 72 channels has been tested in situ of the PandaX-4T experiment. We report the system performance with real data.
In this study,EU-1 zeolite was successfully synthesized via a quasi-solid state approach and assembled to catalyst for the C 8 aromatics isomerization process.The catalytic properties were tuned ...through careful modification of the acidity of EU-1 zeolites and metal-doping of the catalyst.It was shown that EU-1 was an excellent candidate for the C 8 aromatics isomerization process due to its unique structure.In addition,steam treatment of EU-1 at 450-500 ℃ could optimize the acidic properties of the catalyst,hence enhance its catalytic performance.The effect of the amount of Pt on ethylbenzene conversion was studied and the optimum amount was determined to be about 0.3-0.4 wt%.It was confirmed that EU-1 zeolite prepared via a quasi-solid state approach and then dealuminated by steam treatment had better activity and selectivity than conventional mordenite（MOR） zeolite and could be an excellent candidate for C 8 aromatics isomerization.
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