The detection of human body temperature is one of the important indicators to reflect the physical condition. In order to accurately judge the state of the human body, a high-performance temperature sensor with fast response, high sensitivity, and good linearity characteristics is urgently needed. In this paper, the positive temperature characteristics of graphene-polydimethylsiloxane (PDMS) composite with high sensitivity were studied. Besides, doping polyaniline (PANI) with special negative temperature characteristics as the temperature compensation of the composite finally creatively solved the problem of sensor nonlinearity from the material level. Thus, the PANI:graphene and PDMS hybrid temperature sensor with extraordinary linearity and high sensitivity is realized by establishing the space-gap model and mathematical theoretical analysis. The prepared sensor exhibits high sensitivity (1.60%/°C), linearity (R2 = 0.99), accuracy (0.3 °C), and time response (0.7 s) in the temperature sensing range of 25-40 °C. Based on this, the fabricated temperature sensor can combine with the read-out circuit and filter circuit with a high-precision analog digital converter (ADC) to monitor real-time skin temperature, ambient temperature, and respiratory rate, et al. This high-performance temperature sensor reveals its great potential in electronic skin, disease diagnosis, medical monitoring, and other fields.
In view of the non-conductivity and brittleness of thermal barrier coating materials, the problems of conventional electromachining and machining can not be used. The processing technology of thermal barrier coating materials is studied. The regression model of processing technology based on response surface method is established. The influence of process parameters on the experimental results is of great significance in the field of processing key components of ceramic coatings. The main research work of this thesis is as follows: The regression equation based on response surface method is established, the parameters of laser processing and rotary cutting are analyzed, and the influence of processing precision of various process parameters is analyzed. The electrolyte assisted UV laser processing is designed and carried out.
Abstract Modular multilevel converter (MMC) has a wide range of applications in the field of HVDC. However, some of the electricity in MMC is coupled, which makes the design of control system more difficult and have a negative impact on the stable operation of the system. This paper puts forward a strategy to eliminate the coupling control, this method compensates the current cross-coupling terms of the d-axis and the q-axis in the dq coordinate system, SOGI(Second Order Generalized Integrator) and Q-PR(Quasi-PR) controller are used to accurately control the double frequency circulation in the internal unbalanced current, the coupling caused by the internal unbalance current and the sub-capacitor module voltage is compensated in the three-phase coordinate system. Finally, the simulation verification is carried out in PSCAD, which is compared with the traditional control method to verify that the proposed method can achieve complete power decoupling.
At this stage, with the continuous use of new energy sources, how to improve the utilization of new energy and the stability of micro grid has become the most important issue. In the electricity market environment, consider the effects of user side respond and energy storage systems on microgrids, a proper load transfer at the user side under the condition of a time-sharing optical storage price micro grid joint optimization operation strategy, to use for new energy sources and high stability of micro grid. Firstly, the mathematical model of the user and the energy storage system with the load response under the time-sharing electricity price is established, and an integrated system model is also established. Based on this, the optimal operation strategy of the system is proposed. The model and strategy are applied to an actual photovoltaic micro grid system in Gansu, to verify the validity of the model and strategy.
For the traditional laser processing method, processing defects such as recasting layer, microcrack and high concentration of heat affected zone are inevitably generated, which reduces the surface quality and service life of the microstructure. In this paper, the electrolyte jet assisted laser micromachining technology is proposed. This technology applies the laser beam and the corrosive electrolyte jet beam coaxially to the workpiece. At the same time as the laser acts, the corrosive electrolyte jet continuously scour, cool and slightly corrode the processing area. The effect can reduce the thickness of the recast layer, reduce the number of microcracks, and eliminate the high concentration of the heat affected zone. In this paper, the causes of recasting layer in laser processing are analyzed firstly. The material removal mechanism involved in the laser jet assisted laser micromachining and the mechanism of laser coupled electrolyte jet beam are studied. The flow field in the laser jet assisted laser drilling process is established. And the mathematical model of the temperature field; the effects of laser pulse energy, laser repetition frequency, electrolyte concentration and electrolyte jet velocity on the thickness of material recast layer were studied, and the basic processing technology of electrolyte jet assisted laser micromachining was preliminarily mastered, laying the foundation for further research on electrolyte jet assisted laser micromachining technology.
A copper-catalyzed oxygen trifluoromethylation of o -vinyl- N -alkylamide using Togni reagent as the trifluoromethyl precursor is demonstrated for the efficient synthesis of trifluoromethyl-containing iminoisobenzofurans.
Thinly bedded marls are widely developed in the oil shale-bearing series of the Lower Jurassic Badaowan Formation in the Dachanggou Basin (Northwest China). In this study, the characteristics, genesis, and hydrocarbon prospects of marls in a lacustrine organic-rich shale series were analyzed via X-ray diffractometry, element geochemistry, carbon and oxygen isotope analysis, total organic carbon content analysis, rock pyrolysis, and sedimentary analysis. The results show that the main carbonate component of marl is siderite, which is mainly present in areas with lithologic changes at the top and bottom of organic shale, and that the development of a thick siderite-rich marl is closely related to the presence of the thick oil shale. The elemental indicators of the sedimentary environment show that the low initial organic matter abundance and low clastic input were conducive to the formation of siderite and that the water body in the marl development period provided an oxic–suboxic environment, although the formation of siderite was still disturbed by oxygen in the relatively reduced bottom sediments. The carbonate carbon isotopes in the marl are clearly positive, indicating that δ13C-rich carbonate provided by methanogens decomposing sedimentary organic matter contributed to the siderite formation. These siderite-rich marls formed in a relatively restricted environment; i.e., they were deposited close to a rich organic layer, with a sufficient methanogenic metabolite CO2 content and a small amount of terrigenous clastic input. These factors reached an appropriate balance, thus forming a narrow zone (partial shallow lake and delta front facies). Although the hydrocarbon generation potential of the marl is low relative to that of other source rocks, the thin marl that is widespread in continental shallow-water organic-rich sedimentary systems can improve the fracturing ability of shale reservoirs, which is of far-reaching significance for the development of shale oil and gas in continental shallow-water sedimentary systems.
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