This study proposes a novel impact driver mechanism (IDM)-assisted displacement sensor based on the time-sharing-control-based measurement method and the IDM-assisted mechanism. This innovation enables traditional capacitive displacement sensors to break through their range limits and to be used for feedback control in the positioning system of precision instruments, such as scanning probe microscopes and astronomical telescopes. To allow the IDM to drive a larger mass sensor probe, a flexible isolation structure is designed based on the dynamic mass isolation principle and together form the IDM-assisted probe. The IDM-assisted probe together with the combination fixture form the IDM-assisted mechanism. Through the utilization of the time-sharing-control-based measurement method, the IDM-assisted displacement sensor achieves a large measuring range by working in synergy with the positioning system. The IDM-assisted sensor is designed and manufactured. Experimental results show that the IDM-assisted sensor can achieve displacement measurements with a resolution of 0.3 nm $_{\mathbf{RMS}}$ and a range of 1.6 mm. The IDM-assisted sensor has been applied to the feedback control of a designed positioning system and experimental results have shown that it effectively improves the nonlinearity of the positioning system, reducing it from 10 $\% $ to 1 $\% $ .
In this article, we propose a high-quality ratio-metric measurement (HQRM) method based on an analog-to-digital converter (ADC) for high-precision sensors, which shows significant improvement in resolution and stability as well as the sensor's ability to adapt to rapidly changing experimental environments. The traditional ratio-metric measurement (TRM) method based on ADC is introduced in detail for comparison. Circuits of the two ratio-metric measurement methods are designed and tested, and the experimental results show that the HQRM has much better suppression capability to the output noise and drift caused by the excitation source compared with the TRM. A precision capacitive displacement sensor with two ratio-metric methods is tested as an example, and it is found that the sensor's output noise and drift caused by the excitation source are significantly better suppressed with the HQRM in the full bandwidth range and the full-scale range, so the resolution of the sensor is improved from 3.79 nm(rms) to 1.51 nm(rms), and the temperature drift is reduced from 0.75 nm/°C to nearly zero even with drastic temperature changes. Furthermore, this method is expected to function efficiently for other amplitude-modulated types of high-precision sensors.
The design life of the main step-up transformer in AP1000 Nuclear Power Plant is 60 years,which is significantly larger than in regular plants.The main focus of this paper is on the life expectancy of transformer.This paper shows the methods to detect the degree of aging in the transformers and then presents various factors that will affect the life expectancy of the transformer.Through analysis,the author proposes methods and steps to alleviate the aging problem and effectively prolong the life expectancy of the main transformer.
The formation of linear explosion formed penetrator(LEFP) from linear shaped charge detonated from one end point was studied both theoretically and experimentally, and a numerical simulation was also carried out. By decomposing the detonation velocity vector into spherical and slide components, the theoretical model described the tip velocity change of LEFP. The numerical model illustrated the formation of LEFP and the tip velocity agreed with the theoretical model. The validation of the theoretical and numerical models was verified by experiment, in which steel targets were used to show the effect of LEFP. The results showed that average tip velocity was 2658.4 m/s at 100 mm to the charge mouth. The theoretical and numerical velocity values and distribution curve were very close to the experimental ones. This work may further develop the theory of LEFP and linear shaped charge.
Most exiting piezoelectric polymers have low glass transition temperature, so they can only opereture at lower temperature (<150 °C). Once the operate temperature is exceeded, the piezoelectric performance of the device rapidly decreases. At higher temperatures, dense chain motion can interfere with the orientation of dipoles, thus limiting the development of polmer based high-temperature piezoelectric sensors. High-temperature piezoelectric sensor devices are entirely made of inorganic materials, however, inorganic materials are rigid and can only under small strains. Therefore, the enhancement the temperature resistance of piezoelectric polmers and constructing piezoelectric asymmetric structure are the key to the manufacturing of flexible high-temperature resistant piezoelectric/pyroelectric dual functional sensors. In this study, polyacrylonitrile (PAN) nanofiber film was prepared by electrospinning, then heat treating PAN nanofiber film by program temperature control. The effects of the different heat-treatment temperatures on the mechanical and electrical performance of PAN nanofiber film are studied systematically. The results of the study show that, PAN high temperature resistant flexible nanofiber film sensors can be used in high temperature environment (> 500 ℃). Its output performance increases with the increase of heat treatment temperature (< 260 ℃) and then basically remains unchanged (260-450 ℃). Finally, the output performance decreased (> 450 ℃). When the heat treatment temperature reaches 260 ℃, the output voltage was up to 10.08 V, and current reached 2.89 μA. Compared to the PAN membranes without heat treatment, its output voltage and current were increased by 3.54 times and 2.83 times, respectively. At the same time, the output of the PAN high temperature resistant flexible nanofiber film sensors almost unchanged in the high-temperature environment. For the first time, the heat-treated PAN nanofiber film has a pyroelectric effect, and the pyroelectric output open-circuit voltage and short-circuit current increase with the increasing of the temperature gradient. Besides, the PAN nanofiber film sensors have durability for over 5000 cycles under room temperature(25 °C), and it also has durability for over 5000 cycles under high temperature (400 °C). Overall, good flexible, high-temperature resistance, and bifunctional sensing ability make PAN flexible nanofiber film sensors expect to be widely used in high temperature environments such as fire safety, aerospace and other harsh environment.
SF6 gas is widely used in many fields because of its good insulating property and arc-extinguishing property. However, the emission of SF6 waste gas also accelerates global temperature warming. The insulating performance of the SF6 gas gap is a core property of its efficient utilization and exhaust gas treatment. Therefore, it is very important to study the influencing factors of the insulating performance of the SF6 gas gap. Due to the inevitable dust particles in the production and maintenance environment of SF6 gas equipment, this article studies the influence of dust particles on the insulating performance of SF6 gas in a small gap at atmospheric pressure. The experimental results indicate that in the laboratory environment, the dust particles are numerous and large in size, they adhere to the surface of electrodes, which results in a non-negligible local enhancement of the electric field between small-gap electrodes and reduces the insulating performance of SF6 gas; in a Class 1000 clean room environment, the dust particles are few in number and small in size, which can hardly change the uniform electric field between electrodes and have little influence on the insulating performance of SF6 gas in a small gap. Thus, the dust particles have a non-negligible influence on the insulating performance of SF6 gas in a small gap at atmospheric pressure, and the insulating performance of SF6 gas in a small gap can be changed by controlling the content of dust particles in the gas. This provides valuable guidance for the utilization of SF6 gas and the treatment of SF6 waste gas.
SUV39H1, the first identified histone lysine methyltransferase in human, is involved in chromatin modification and gene regulation. SUV39H1 contains a chromodomain in its N-terminus, which potentially plays a role in methyl-lysine recognition and SUV39H1 targeting. In this study, the structure of the chromodomain of human SUV39H1 was determined by X-ray crystallography. The SUV39H1 chromodomain displays a generally conserved structure fold compared with other solved chromodomains. However, different from other chromodomains, the SUV39H1 chromodomain possesses a much longer helix at its C-terminus. Furthermore, the SUV39H1 chromodomain was shown to recognize histone H3K9me2/3 specifically.
Study on the critical paths for the schedule control of nuclear power projects has been performed for reactor M310,based on the experiences from Daya Bay project and Ling Ao project.The study shows that the critical paths for the nuclear power project are from NI civil work,NI erection,commissioning of single systems directly serving the CFT to the joint-test.For NI civil work,the critical path is the main civil work of the reactor building,pre-stressing,handover of room s for important areas,and key CW-erection interfaces;there are four critical paths for NI erection;For startup,two stages can be identified: commissioning of 16 single systems directly serving the CFT and joint-test.
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