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The wave functions, energy levels and matrix elements of Yb+ ions are calculated using the relativistic configuration interaction plus core polarization (RCICP) method. The static and dynamic electric dipole polarizabilities of the ground state and low-lying excited states are determined. Then, the magic wavelengths of the magnetic sublevel 6s1/2,m = 1/2 → 5d3/2,m = ±3/2,±1/2 and 6s1/2,m = 1/2 → 5d5/2,m = ±5/2,±3/2,±1/2 transitions in the linearly, right-handed, and left-handed polarized light are further determined. The dependence of the magic wavelengths upon the angle between the direction of magnetic field and the direction of laser polarization is analyzed.

Underwater navigation plays an important role in the exploration of current marine resources. But the underwater environment is complicated, traditional fault-tolerant control of the unmanned underwater vehicle has a high dependence on the accuracy of the dynamic model in the design of the control rate, which is difficult to deal with the uncertainty and external disturbance of this system. Therefore, an adaptive fault-tolerant control algorithm based on the residual drive is proposed. The motion state reference model is generated by BP neural network, and the residual between the reference model and the actual state is used as a feedback parameter. The thrust distributor is established with a simple dynamic model, and the control strategy is reconstructed by adjusting distribution weight to achieve the purpose of adaptive fault-tolerant control. Taking a typical fixed-angle propulsion system as an example, the algorithm is modeled, analyzed, and simulated. Simulation results show that the algorithm can track target parameters well without relying on an accurate dynamic model and automatically adapt to a variety of abnormal working conditions.

Most existing visual roughness perception algorithms are pixel-wised operations, which lead to unstable roughness measurements. To address this problem, a novel visual roughness perception in the maximum variance direction of image patches is proposed in this article. Specifically, each patch is assumed to be a point in a multi-dimensional Euclidean space. To improve the signal-to-noise ratio of roughness, all points are projected onto its maximum variance direction based on principal component analysis. In this direction, the variance of these points is characterized as roughness. A new roughness metric dataset is constructed by scanned images of sandpapers with different mesh sizes to verify the effectiveness of the proposed algorithm. Experiments on the dataset show the proposed method outperforms many computer vision-based methods, such as the gray-level co-occurrence matrix approach and the G a approach.

Weak signal detection has become an important means of mechanical fault detections. In order to solve the problem of poor signal detection performance in classical tristable stochastic resonance system (CTSR), a novel unsaturated piecewise linear symmetric tristable stochastic resonance system (PLSTSR) is proposed. Firstly, by making the analysis and comparison of the output and input relationship between CTSR and PLSTSR, it is verified that the PLSTSR has good unsaturation characteristics. Then, on the basis of adiabatic approximation theory, the Kramers escape rate, the mean first-passage time (MFPT), and output signal-to-noise ratio (SNR) of PLSTSR are deduced, and the influences of different system parameters on them are studied. Combined with the adaptive genetic algorithm to synergistically optimize the system parameters, the PLSTSR and CTSR are used for numerically simulating the verification and detection of low-frequency, high-frequency, and multi-frequency signals. And the results show that the SNR and output amplitude of the PLSTSR are greatly improved compared with those of the CTSR, and the detection effect is better. Finally, the PLSTSR and CTSR are applied to the bearing fault detection under Gaussian white noise and Levy noise. The experimental results also show that the PLSTSR can obtain larger output amplitude and SNR, and can detect fault signals more easily, which proves that the system has better performance than other systems in bearing fault detection, and has good theoretical significance and practical value.

The electronic properties of pseudo-twin boundary in γ-TiAl intermetallic and the influence of interstitial alloying atoms on them are investigated through ab initio calculation. Similar to true twin boundary, there exist three-central bonds at the pseudo-twin boundary, which are discussed by local energy scheme combined with electron localization function and quantum theory of atoms in molecules schemes. The effect of interstitial atoms C, N, H and O on slipping energy is separated into the contributions of affinity of interstitial atoms to host atoms and the multi-center bonds. In shearing process of pseudo-twin configuration, a local true twin boundary is formed in the neighbor layer of the initial pseudo-twin boundary, resulting in a plateau formed in stacking fault energy curve.

Shape memory alloy (SMA) has been widely used in different applications due to its unique shape memory property. However, when used as an actuator, it exhibits a hysteresis behavior in its relation between temperature and strain, which is highly nonlinear and difficult to control. Although studies have been conducted on establishing various constitutive models of SMA, it is still difficult to achieve the precise control of the SMA wire with the existing models. In this work, a new promising approach regarding the SMA control task as a reinforcement learning (RL) problem is proposed to address this issue, which does not require accurate mathematical models. Both RL and an improved method named deep reinforcement learning (DRL) are used to solve the problem of precise control of a 1D SMA wire actuator, respectively. The simulation results indicate that with the DRL method, the agent can precisely control the output deformation of the SMA wire after only ten episodes of training. Compared with the DRL method, the RL agent can also achieve the same training target but with hundreds of training.

The electromagnetic radiation of household appliances and radioactivity of stone materials from residences were determined using integrated magnetometer and γ-ray spectrometer techniques. The radiation levels of desktop computers were greater than that of notebook computers, while microwave ovens and induction cookers produced low-frequency electromagnetic fields during the operation. The safety distances for hair drier, desk lamp, and patch board were ca. 50 cm, whereas those of the rest appliances were ca. 30 cm. Radioactive tests of stones collected from certain regions were conducted. The specific activities of 226Ra, 232Th, and 40K were used to calculate internal exposure indexes (I Ra) and external exposure indexes (I γ). Moreover, both the I Ra and I γ for wall coatings were putty < tile adhesive, thereby the I Ra and I γ for bathroom furniture were ceramic facet < pottery basin < flush toilet. Natural radionuclides widely exist in interior decorations, indicating that humans in open radioactive environments receive background radiation all the time.

The telescopes and the infrastructures may alter the local wind environment around the observatory and further affect the observing environment. After the completion of site testing, it is necessary to analyze the wind environment of the entire site and plan the telescope layout to make use of the excellent conditions scientifically and rationally. Taking a typical observatory as an example, the effect of topographical features on wind environment and the mutual interference between telescope enclosures are analyzed by using Computational Fluid Dynamics (CFD) method. The CFD simulations are compared with the seeing data from Differential Image Motion Monitor (DIMM), the results are in good agreement, which verifies the effectiveness of the CFD method. The results of wind environment analysis can provide reasonable suggestions for site layout and construction, improving the observing environment and the image quality., 9 pages, 15 figures

By carrying out the green transition and upgrading of heavy chemical industry in Jiangsu, it is conducive to improving the industrial competitiveness and the level of clean production of key industries; it is conducive to establishing the system and mechanism of ecological priority and green development of the Yangtze River economic belt, and promoting high-quality development. Based on the development practice of heavy chemical industry in Jiangsu Province, this study analyzes its negative effects on the high-quality development of the Yangtze River economic belt. This paper puts forward the index of green transition of industry, establishes the measurement and evaluation model of green transition of heavy chemical industry in Jiangsu Province. Based on the empirical research results, this paper puts forward the green transition path of Jiangsu heavy chemical industry.

As one of the most attractive non-radiative power transfer mechanisms without cables, efficient magnetic resonance wireless power transfer (WPT) in the near field has been extensively developed in recent years, and promoted a variety of practical applications, such as mobile phones, medical implant devices and electric vehicles. However, the physical mechanism behind some key limitations of the resonance WPT, such as frequency splitting and size-dependent efficiency, is not very clear under the widely used circuit model. Here, we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics, which starts from a completely different avenue (utilizing loss and gain) to introduce novel functionalities to the resonance WPT. From the perspective of non-Hermitian photonics, the coherent and incoherent effects compete and coexist in the WPT system, and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity–time symmetry. Based on this basic physical framework, some optimization schemes are proposed, including using nonlinear effect, using bound states in the continuum, or resorting to the system with high-order parity-time symmetry. Moreover, the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection. Therefore, the non-Hermitian physics can not only exactly predict the main results of current WPT systems, but also provide new ways to solve the difficulties of previous designs.

Ion extraction time is one of the key parameters for an ion extraction process. Particle-in-cell (PIC) simulation can provide a detailed description on the charged-particle behaviours during the ion extraction process in a decaying plasma. However, the PIC modelling is a very time-consuming task with very small space step (~ Debye length) and time step (~ inverse of plasma frequency), as well as a massive number of macro-particles, especially for the cases in multi-dimensions and large geometrical sizes. In this paper, based on the sheath expansion and ion-acoustic rarefaction wave propagation model, a similarity relation of ion extraction time with different geometrical sizes of the ion extraction regions is established. The theoretical analysis shows that, by changing the magnitude of the externally applied voltage to keep the ion extraction flux equal, the ion extraction time is proportional to the geometrical size ratio. Then, the PIC simulations on the ion extraction process are conducted, which show that there exists a good consistency with the theoretical analysis and previous experimental data. This research is helpful for promoting numerical simulations facing actual ion extraction processes with large geometrical sizes and provides theoretical guidance for improving the ion extraction efficiencies in applications.

To evaluate performances of a back-illuminated scientific CMOS (sCMOS) camera for astronomical observations, comparison tests between Andor Marana sCMOS and Andor iKon-L 936 CCD cameras were conducted in a laboratory and on a telescope. The laboratory tests showed that the readout noise of the sCMOS camera is about half lower, the dark current is about 17 times higher, the dynamic range is lower in the 12-bit setting and higher in the 16-bit setting, and the linearity and bias stability are comparable relative to those of the CCD camera. In field tests, we observed the open cluster M67 with the sCMOS and CCD cameras on a 60 cm telescope. Unlike the CCD camera, the sCMOS camera has a dual-amplifier architecture. Since a 16-bit image of the sCMOS camera is composed of two 12-bit images sampled with 12-bit high gain and low gain amplifiers simultaneously, it is not real 16-bit output data. The evaluation tests indicated that the dual-amplifier architecture of the sCMOS camera leads to a decline of photometric stability by about six times around specific pixel counts. For photometry of bright objects with similar magnitudes that require high frame rates, the sCMOS camera under 12-bit setting is a good choice. Therefore, the sCMOS camera is fitted with survey observations of variable objects requiring short exposure times, mostly less than 1 s, and high frame rates. It also satisfies the requirements for an offset guiding instrument owing to its high sensitivity, high temporal resolution and high stability.

The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing ∼11.8 years of the Fermi Large Area Telescope (Fermi-LAT) data in this study. We found that its photon flux was approximately three times higher than that of the previous study in the 0.2–100 GeV band, and the corresponding significance level ∼ 8.15σ was approximately four times higher than before. The light curves of 15 and 45 time bins from the whole time all showed two active periods, and the variability of the second period was more significant than that of the first period. The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT. Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis, we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region. For Arp 220, there was no significant variability in the γ-ray emission.

Since the quantum concept of parity-time (PT) symmetry has been introduced into the conventional inductor–capacitor resonance, strategies based on exceptional points (EP) based strategies redefine our understanding of sensitivity limitation. This considerable enhancement of sensitivity originated in exploration of the non-Hermitian physics in photonics, acoustics and electronics, which exhibits a substantial application to the miniaturization of implanted electronic sensors in medicine field. By continuously accessing the EP, the spectral response of reader ∆ω follows a dependency of Δω ∼ κ 2/3 to a weakly coupling rate (|κ| ≈ 0), which may approach the theoretical limit of sensitivity in a second-order EP system. In this paper, we experimentally demonstrate a high-order (higher than second-order) PT symmetric system for weak coupling detection, in which a third-order EP can be employed to fulfill the sensitivity of Δω ∼ κ 1/2. Particularly, we introduce the incoming wave as an effective gain to balance the loss and obtain a pair of purely real eigenfrequencies. There are absence of imaginary parts despite corresponding real parts shifts dramatically by using a neutral resonator, without a broadening of the reflection spectrum so that maintaining a high resolution on the sensitivity. This work may reveal the physical mechanics of a small perturbation at a high-order EP and promote applications in implanted medicine devices.

Based on the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) method and the corresponding program package GRASP2018, a new program for calculating the polarizabilities is developed. As the first application, the static electric-dipole polarizabilities of the ground state 2s2 1 S 0 and excited state 2s2p 3 P 0 of beryllium are calculated. By means of these polarizabilities, the blackbody radiation (BBR) shift of the 2s2p 3 P 0 → 2s2 1 S 0 clock transition is determined. The present results agree very well with other available theoretical results.

The direct and resonant single-photon photoionization of W63+ ions from their ground state 1s 22s 22p 63s 2 S 1/2 and four lowly-excited states 1s 22s 22p 63p 2 P 1/2,3/2 and 1s 22s 22p 63d 2 D 3/2,5/2 has been studied within the framework of the relativistic R-matrix method and the multiconfigurational Dirac–Fock method. Special attention has been paid to obtaining direct and resonant ionization limits and to identifying possible resonant symmetries of W63+ ions. To this end, the photoionization cross-sections have been calculated using the Dirac Atomic R-matrix Code package. Direct and resonant ionization limits were obtained for the ground-state photoionization of W63+ ions, and the resonant peaks identified were found to be associated with the resonances 1s 22s 22p 53lnl′ and 1s 22s2p 63lnl′ (l, l′ = s, p, d) for the fine-structured energy level or configuration at the level of fine structure or configuration. For excited-state photoionization, however, the resonant ionization limits and resonant peaks were hardly distinguishable due to much more densely spaced resonant peaks and a complicated resonant structure, although the respective direct ionization limits are obtained. We expect that this work will remedy the current lack of fundamental studies of the photoionization of W63+ ions and be helpful in the diagnosis and simulation of fusion plasmas in conjunction with the available photoionization data for tungsten ions in other charge states.

This paper proposes a detailed design of a novel bias shape memory alloy (SMA) actuated repeatable launch locking protective device (RLLPD) for the magnetically suspended flywheel (MSFW) during the launching state. The proposed SMA actuated RLLPD consists of two bias SMA-spring actuators. One is designed to realize locking/unlocking and the other is intended for triggering. Besides, self-locking blocks are employed to ensure that the MSFW can be safely locked under the vibration of the launching process. Considering the locking method by compressing the flywheel against the mechanical bearing, there are at least three or four locking points to maintain the balance and enhance the locking reliability of the flywheel. Additionally, a force amplifying linkage mechanism is employed using one bias SMA-spring actuator to actuate the movement of two clamps, further reducing the total weight of the RLLPD and amplifying the locking strength. Furthermore, the recovery envelope curve which represents the recovery ability of SMA wire under various spring rate is proposed and computed using thermodynamics constitutive model. Simulation results indicate that the recovery envelope curve coincides with the austenite unloading curve. The thermodynamics constitutive model of SMA considering functional fatigue is utilized to calculate the evolution rate of functional fatigue of SMA wire in the RLLPD. The functional fatigue evolution rate computation algorithm and results are presented. After the design and simulation, a prototype of the locking device is fabricated and tested. According to the performance results, the SMA-actuated locking device can release a preload up to 1000 N. The simulation and experimental results indicate that the life cycle of the locking device is more than 50 times.

In this paper, a novel variable camber guide vane (VCGV) actuated with a shape memory alloy (SMA) plate is proposed to achieve active real-time control. An analytical model is proposed to describe the relationship of SMA plates with different thicknesses between the deflection angle and temperature. Then, a numerical model of the VCGV is established to design the shape of the VCGV. Moreover, experiments of this actuator and VCGV are conducted to explore the variation of deflection angles over time for the VCGV. Results show that the deflection angle of the VCGV can be actively controlled from 0° to 8.2°. This work is expected to widen the applications of SMAs in variable guide vanes.

China’s economic development accelerates the process of urbanization, accompanied by formaldehyde pollution in indoor environment. we summarized the recent research on the pollution and impact factor of indoor formaldehyde in China, and elaborated the shortcomings of the existing research and the future research direction from the perspective of source emission, environmental fate and human health effects.

Indoor formaldehyde is widely existed which poses a threat to residents’ physical health. In order to eliminate the risk of formaldehyde pollutant, individuals usually adopt formaldehyde air purifiers. In this empirical study, we aim to investigate individuals’ adoption intention of formaldehyde air purifier from the perspective of consumption values. Grounded in the Protective Action Decision Model, our research framework underlines the mechanism through which one’s personal knowledge and risk perception affect the perceived functional and non-functional values of formaldehyde air purifiers and subsequently impact the adoption intention. A survey is conducted to validate our model. This research contributes to the literature by enriching current understanding of individuals’ protective behavioral intention in the context of indoor formaldehyde.

With the rapid development of science and technology, the application of computer vision is more and more widely, and there are great changes in all walks of life. New retail can rely on this advantage to improve the intelligent settlement of supermarket and reduce the workload of supermarket staff. In this paper, we use deep learning to train the goods that need to be settled, and identify the goods in the video during the settlement. At the settlement interface, Alipay two-dimensional code is generated to sweep the code for customers. QT is used to display the process of commodity identification and settlement.

Apply vague adaptive optimization method to find new natural rubber species. It is advisable to accelerate the promotion of wind-resistant and high-yield natural rubber species’ plantation in the dominant areas of western Guangdong Province, which are Reyan 7-33-97, Yunyan 77-2, Dafeng-95, Yunyan 77-4, Haiken 1, PR 107, RRIM 600, RRII 208 and other species.

The unipolar diode-like domain wall currents in LiNbO3 single-crystal nanodevices are not only attractive in terms of their applications in nonvolatile ferroelectric domain wall memory, but also useful in half-wave and full-wave rectifier systems, as well as detector, power protection, and steady voltage circuits. Unlike traditional diodes, where the rectification functionality arises from the contact between n-type and p-type conductors, which are unchanged after off-line production, ferroelectric domain wall diodes can be reversibly created, erased, positioned, and shaped, using electric fields. We demonstrate such functionality using ferroelectric mesa-like cells, formed at the surface of an insulating X-cut LiNbO3 single crystal. Under the application of an in-plane electric field above a coercive field along the polar Z axis, the domain within the cell is reversed to be antiparallel to the unswitched bottom domain via the formation of a conducting domain wall. The wall current was rectified using two interfacial volatile domains in contact with two side Pt electrodes. Unlike the nonvolatile inner domain wall, the interfacial domain walls disappear to turn off the wall current path after the removal of the applied electric field, or under a negative applied voltage, due to the built-in interfacial imprint fields. These novel devices have the potential to facilitate the random definition of diode-like elements in modern large-scale integrated circuits.

In order to solve the problems of unbalanced energy consumption and shortened network lifetime caused by the uneven distribution of cluster heads (CHs)in wireless sensor networks, a Limited IST and Random Uniform Clustering Algorithm (LIRUCA) is proposed. The algorithm comprehensively considers the energy of nodes, the distance to the sink, and the correlation between nodes when selecting CHs, and limits the intra-cluster communication distance, thus improving the uniformity of CH distribution. Compared with LEACH, EBCRP, and LEACH-improved protocols, results of simulation experiments show that the LIRUCA algorithm can effectively improve the uniformity of clustering, reduce the energy consumption, and prolong the network lifetime.

The Nanshan One-meter Wide-field Telescope (NOWT) is a prime focus system located at Nanshan Station of Xinjiang Astronomical Observatories (XAO). The field of view(FOV) was designed to 1.5 degree *1.5 degree, and Johnson-Cousins UBVRI system was chosen as the main Filter set. The telescope has been providing observation services for astronomers since Sept. 2013. Variable source searching and time-domain surveys are the main scientific goals. The system's test results are reported including linearity, dark current, bias, readout noise and gain of the CCD camera. The accurate instrumental calibration coefficients in UBVRI bands was driven with Landolt standard stars during photometric nights. Finally, the limiting magnitudes are given with signal-to-noise ratios and various exposure times for observers., Comment: 11 pages, 14 figures, 8tables

Natural occurring boron has two stable isotopes: boron-10 and boron-11. Boron-10 has high thermal neutron cross section in a wide range of energy and the product of boron-10’s neutron reaction contains alpha particles. So, it is a good material for neutron absorbing and neutron detecting. In order to enrich boron-10 from natural boron, several methods had been proven to be feasible: chemical exchange distillation, cryogenic distillation and ion exchange resin method. The market now places higher demands on the economics of the separation method, so study on production of boron-10 by gas diffusion method is carried out. Using BF3 as processing gas, it is feasible to enrich high abundance of boron-10 by gas diffusion. The single stage separation effect and the hydraulic status of single stage was estimated. Binary gas diffusion cascades were designed and compared. Under given production requirements, the scale of the cascade was estimated and optimized. Finally, step cascade was picked for the production of 96% boron-10. Based on the cascade design, economic estimation of this separation method was conducted, and the target product cost was calculated. This study laid a good foundation for the expansion of boron isotope separation methods.

The weldability of ASTM B708 R05252 tantalum sheet was analyzed, and the mechanical properties, bending properties and corrosion resistance of tantalum sheet were tested by GTAW butt welding. Test results show that butt joints by this welding procedure perform good mechanical property, and the metallographic microstructures &corrosion resistance of the welding joint are normal. It expresses the great significance of formulating the welding procedures of tantalum pressure vessels.

According to the fluorescence characteristics of hydrocarbon inclusions under the microscope, the interpenetration relationship with the occurrence veins, and the homogenization temperature, the hydrocarbon inclusions developed in the Cambrian-Ordovician reservoir in Yingmian 7 area can be divided into four periods, which correspond to four hydrocarbon accumulation events respectively. The periods of accumulation determined by the analysis of homogenization temperature and burial history are as follows: late Caledonian to early Hercyian low mature heavy oil filling, late Hercyian medium mature normal oil filling, early Himalayan high mature light oil filling and late Himalayan over mature natural gas filling. Among them, periods of I, II hydrocarbon inclusions distribution range is limited, only visible in part of the wells in Yingmai 7 area; periods of III, IV hydrocarbon inclusions in Yingmai 7 area are widely distributed, which reveals the Himalayan period of the two-stage oil and gas filling on the reservoir formation.

Over the past decade, time-domain astronomy in optical bands has developed rapidly with the operations of some wide-field survey facilities. However, most of these surveys are conducted with only a single band, and simultaneous color information is usually unavailable for the objects monitored during the survey. Here we present introductions to the system of Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), which consists of an array of four optical telescopes installed on a single equatorial mount. Such a system is designed to get multiband photometry simultaneously for stars and transients discovered during the survey. The optics of each telescope is a modified Hamilton-Newtonian system, covering the wavelengths from 400 to 900 nm, with a field of view (FoV) of about 4.5 deg2 and a plate scale of 1.86"/pixel when combining with a 4K*4K QHY4040 CMOS detector. The TMTS system can have a FoV of about 9 deg2 when monitoring the sky with two bands (i.e., SDSS g and r filters) at the same time, and a maximum FoV of ~18 deg2 when four telescopes monitor different sky areas in monochromatic filter mode. For an exposure time of 60 s, the average 3{\sigma} detection limit of the TMTS system can reach at ~19.4 mag in Luminous filter and at ~18.7 mag in SDSS r filter. The preliminary discovery obtained during the first few months' survey is briefly discussed. As this telescope array is located at the Xinglong Observatory of NAOC, it can have an excellent synergy with the spectroscopic survey by the LAMOST (with a FoV of about 20 deg2) at the same site, which will benefit the studies of stellar and binary physics besides the transient sciences., Comment: 27 pages, 21 figures

The improved sub-equation method is used to obtain the exact analytical solution of (2 + 1) - dimensional BBM Equation. Some traveling wave solutions such as soliton solution and periodic wave solution of trigonometric function are obtained. Practice shows that the sub-equation method is widely used in nonlinear evolution equations.

Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions is one of the basic tasks of it. As one of three potential sites to host 12-meter Large Optical/infrared Telescope (LOT), Muztagh-ata site which is located on the Pamirs Plateau in west China's Xinjiang began its site-testing task in the spring of 2017. In this paper, we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature, barometric pressure, relative humidity, wind speed and direction, recorded by automatic weather station with standard meteorological sensors for two-year long. We also show the monitoring results of sky brightness during this period., 16 pages, 19 figures

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade. Based on satellite remote sensing data, along with geographical, logistical and political considerations, three candidate sites were chosen for ground-based astronomical performance monitoring. These sites include: Ali in Tibet, Daocheng in Sichuan and Muztagh-ata in Xinjiang. Up until now, all three sites have continuously collected data for two years. In this paper, we will introduce this site testing campaign, and present its monitoring results obtained during the period between March 2017 and March 2019.

The Large Optical/infrared Telescope (LOT) is a ground-based 12m diameter optical/infrared telescope, which is proposed to be built in the western part of China in the next decade. To select the best site which satisfies the construction and future operation of LOT, data monitoring and comparing are required for all the candidate sites. The comparison of most of the instruments was done at Xinglong Observatory. These instruments include weather station, all sky camera, sky background meter and differential image motion monitor (DIMM). This paper introduces the instruments used in LOT site monitoring and the instruments comparisons. The results show that the instrument is stable and the data uniformity of the identical instruments is good. This paper provides a fundamental description of LOT site monitoring.

High precision force sensors usually include flexible structures, which are prone to cause unnecessary mechanical vibrations, due to their low stiffness and high sensitivity. Aimed at the adverse problem, this paper proposes a novel two-degree-of-freedom passive damping system dedicated to the vibration suppression of a dual-axis precision force sensor. The damping system consists of two identical eddy current dampers (ECDs), each of which utilizes a double-layer Halbach-array permanent magnet structure and a middle-layer copper plate to generate a large damping force. Analytical models are established to predict the damping characteristic and dynamic behavior of the sensor system, with further verification through finite element simulation. Experiments are implemented to demonstrate the effectiveness of the damping design to suppress the sensor vibration in comparison with three different configurations (without ECD, with a single ECD, and dual ECDs). The results indicate the excellent damping characteristics of the developed ECD. This feature can be also extended to the vibration suppression of the planar XY positioning stages.

From 2008 to 2018, the Chinese government has issued more than 200 policies on new energy automobile industry at the national, provincial and municipal levels in the past ten years. These policies systematically guide the new energy automobile industry to develop vigorously from the aspects of comprehensive promotion, energy-saving layout, price, charging equipment and batteries, subsidies, tax exemption, loans and investment, etc. The implementation of the support policy in the relevant areas of the development of new energy automobile industry will have a tremendous impact on the environmental protection, taxation, employment, scientific research, Power industry and related industries in the relevant areas, thus bringing the regional economic development to a new climax.

The Coude Echelle Spectrograph (CES) was originally mounted on Xinglong 2.16 m telescope in 1994. When the High Resolution Fiber-fed Spectrograph (HRS) was commissioned at Xinglong 2.16 m telescope, the red path of CES was moved to Lijiang 1.8 m telescope, following some redesign and reinstallation. The CES of Lijiang 1.8 m telescope has the spectral resolution (R = λ/Δλ) ranging from 20000 to 50000 corresponding to different slit widths. With a 2k × 2k PI CCD, CES has a wavelength coverage between 570 nm to 1030 nm. In particular, the resolution of 37000 at 0.5 mm slit corresponds to 1.3″ on the sky. The limiting magnitude is V = 11.5 with the use of the tip-tilt feedback system, and the S/N is about 40 for 1 hour exposure at 600 nm (R = 37000). During the installation of CES, the tip-tilt mirror technology had successfully fulfilled high precision guiding and tracking for high resolution spectral observation and significantly improved the observation efficiency.

In this paper, a novel method is proposed to enhance ion extraction flux from collision-free decaying plasma by injecting an energetic electron beam from the cathode surface. A numerical model accounting for initial plasma generation and plasma-wall interactions is established and implemented into an electrostatic particle-in-cell (PIC) code. The model and the modified code are validated by comparing the results without an electron beam injection against known experimental scaling. Based on this validation, simulations with an externally injected electron beam are conducted. Our results show a significant enhancement of the ion extraction flux, as well as a corresponding reduction of the ion extraction time, e.g., by a factor of 3 when the beam current is 600 A/m2. The analysis on spatiotemporal evolution of the electric potential during the plasma expansion process shows the formation of a standing wave in the bulk plasma. Interaction of this wave with the bulk electrons provides an efficient heating mechanism. Higher mean energy of plasma electrons leads to higher ion-acoustic speed, and thus, results in the enhancement of the ion extraction flux.

Dark sector may couple to the Standard Model via one or more mediator particles. We discuss two types of mediators: the dark photon $A^{\prime}$ and the dark scalar mediator $\phi$. The total cross-sections and various differential distributions of the processes $e^{+} e^{-} \rightarrow q \bar{q} A^{\prime}$ and $e^{+} e^{-} \rightarrow q \bar{q} \phi$ ($q=u,~d,~c,~s$ and $b$ quarks) are discussed. We focus on the study of the invisible $A^{\prime}$ due to the cleaner background at future $e^{+} e^{-}$ colliders. It is found that the kinematic distributions of the two-jet system could be used to identify (or exclude) the dark photon and the dark scalar mediator, as well as to distinguish between them. We further study the possibility of a search for dark photons at a future CEPC experiment with $\sqrt{s}=$ 91.2 GeV and 240 GeV. With CEPC running at $\sqrt{s}=$ 91.2 GeV, it would be possible to perform a decisive measurement of the dark photon (20 GeV $< m_{A^{\prime}}, Comment: 17 pages, 10 figures, to be published in Chinese Physics C

Synopsis The electron impact excitation total and differential cross sections, Stokes parameters, and coherence pa-rameters of Zn atom from the ground state 41S0 to the excited state 41P1 were systematically calculated using the fully relativistic distorted wave method. The calculated results are compared with the experimental data and other theoretical results, good agreement is obtained.

Energy levels, transition probabilities, collision sections, and collision excitation rate coefficients of NII ion have been calculated using Flexible Atomic Code, which is based on the multiconfiguration Dirac–Fock method. The ratios of line intensity, I567.96 nm/I500.52 nm, where the 567.96 and 500.52 nm are two strong spectral lines from the core current channel of lightning, have been calculated by using the collisional-radiative model, in which the line intensity is proportional to the collision excitation rate coefficients from the ground state to the excited state and the transition probability from the high excited state to the low excited state. The temperatures of six lightning plasma channels were then obtained, and they are consistent with temperatures obtained by diagnosing the actual spectrum with the multispectral line method.

A general framework for observatory control software would help to improve the efficiency of observation and operation of telescopes, and would also be advantageous for remote and joint observations. We describe a general framework for observatory control software, which considers principles of flexibility and inheritance to meet the expectations from observers and technical personnel. This framework includes observation scheduling, device control and data storage. The design is based on a finite state machine that controls the whole process.

With regard to detection of insulation faults in power transformers, acoustic emission (AE) method has been widely recognized and applied due to its advantages of anti-electromagnetic interference and ability of locating partial discharge (PD) position. AE sensors are usually installed on the transformer wall. Thus the transformer wall is an important medium for PD ultrasonic detection, but it is often overlooked. In this manuscript, three - dimensional multiphysics model was established and simulated to research the propagation characteristics in transformer wall. Furthermore, Piezoelectric Transducer (PT) is used to detect PD ultrasonic signals and verify simulation results in the laboratory. To ensure accuracy of detection, an optical fiber sensor based on Sagnac interference principle was designed and adopted. The variation of ultrasonic signal amplitude with distance reveals characteristics of ultrasonic signal propagating in transformer wall. The sound pressure distribution on upper and lower surfaces of simulation model proves that ultrasonic waves propagate in form of symmetrical Lamb waves in transformer wall. What's more, the AE amplitude attenuated due to absorption and refraction loss, and local fluctuations on account of acoustic interference. Thus, stable signal detected by AE sensor doesn't represent the absence of PD in transformer. To improve reliability of AE detection, it is proposed in this manuscript that repeated movement of AE sensor is necessary to obtain suitable measurement position. Similarly, PD can be located well after the placement adjustment of AE sensor. In addition, this study is expected to provide a theoretical analysis and fiber sensor for problem of sensor placement in AE detection.

Using the Debye shielding model, the effects of plasma shielding on the dielectronic recombination processes of the H-like helium ions are investigated. It is found that plasma shielding causes a remarkable change in the Auger decay rate of the doubly excited 2p 2 3 P 2 state. As a result, the dielectronic recombination cross sections from the doubly excited 2p 2 3 P 2 state increases with the decreasing Debye shielding length.