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Lead-based reactor coolant has high thermal conductivity, good thermal expansion and strong natural circulation ability, which has outstanding advantages in safety, economy and miniaturization. At the same time, lead-bismuth reactors have potential applications in small nuclear power sources, marine reactors and so on. Difference from land-based nuclear power plants, marine nuclear power plants will produce swaying, heaving, tilting and other movements due to their long-term operation in the ocean environment. In order to study the thermal-hydraulic characteristics of the lead-bismuth reactor system under marine conditions, an experimental study was conducted by building a lead-bismuth experimental circuit based on a heaving motion platform. Under the influence of heaving motion, the flow rate of lead-bismuth circuit fluctuates and the flow resistance and heat transfer characteristics change. In this paper, the flow resistance and heat transfer characteristics of liquid lead-bismuth eutectic in a vertical circular tube under forced circulation under heaving conditions are investigated experimentally. The range of Reynolds number (Re) in the flow resistance experiment is 23 500-261 280, and the range of Peclet number (Pe) in the flow heat transfer experiment is 524.4 450. The results show that: The peak value of instantaneous additional pressure drop caused by heaving motion is lower than the theoretical value; The heaving motion causes periodic fluctuations in the flow rate of the circuit, and the maximum fluctuation is up to 16% in the low Re region; In the low Re region, the heaving condition makes the time-averaged frictional resistance coefficient of the pipe increase slightly; The relationship between the fluctuation of loop flow caused by undulating motion and the undulating acceleration and Re was obtained by fitting, which is in good agreement with the experimental results. This method can be used to predict the fluctuation of flow rate in the reactor at different coolant flow rates by heaving motion. In the scope of this experimental working condition, although the fluctuation causes the fluctuation of the flow rate, the instantaneous temperature difference between the inlet and outlet of the experimental section and the instantaneous heat transfer coefficient h of the experimental section do not fluctuate significantly, and the fluctuation has little impact on the instantaneous heat transfer characteristics. In the forced circulation, the heaving motion does not affect the heat transfer characteristics of the circuit. The results of this study can provide data reference for the engineering design of lead-bismuth reactor.

Lead-cooled fast reactor (LFR) is known as a typical reliable new type reactor by the US Department of Energy (DOE), and the potential accidents of LFR are necessary to assess. Steam generator tube rupture (SGTR) accident can cause high-pressure hyperbaric steam-water jetting into liquid lead bismuth eutectic (LBE) pool, and leads to a rapid pressure rising in the reactor primary system together with a potential pressure wave crashing the structures. This paper focuses on the computational fluid dynamics (CFD) analyses of SGTR experimental research on the LIFUS5/MOD2 experiment facility. A two-dimensional symmetrical slice with 1 million 570 thousand structured mesh was established for the experimental reaction vessel, and each side except the injection nozzle were set as adiabatic no slip boundary in order to achieve the non-decompression process. In the aspect of multiphase model settings, the Eulerian-Eulerian two-phase flow model was adopted to track the steam-LBE interface in the transient simulation, and the CSF surface tension polynomial together with Lee substituted evaporation model were considered. In addition, the injection of high-pressure water in each time step was separated to two parts: latent heat and injected steam, so as to calculate both endothermic and jet of flash evaporation simultaneously. Among them, the latent heat was realized by user-defined functions (UDF), and the injected steam was adopted as compressible real gas with R-K gas state equation. Based on the above settings, three established thermal-hydraulics phenomena including pressure rising of LBE environment together with pressure wave spreading, level fluctuation of liquid environment with argon entrainment and level rising of liquid environment and diffusion of injected steam were analyzed. From the results a conclusion can be reached that CFD numerical simulation has little error on calculating pressure rising with pressure wave spreading. In addition, the peak value of pressure wave rises with back pressure of water increasing, and the pressure of partial steam cavity is lower than that of LBE pool around it, in turn inhibits the occurrence of its explosion. Meanwhile, LBE in the middle firstly washes up and impacts the structures, and then entrains the argon when it falls back, in turn causes the combination of argon and steam cavity, or the secondary segmentation to small argon bubbles. Moreover, the diffusion of the steam cavity along the radial direction becomes more intense with the increase of the axial height, accompanies by the steam cavity divided from the center to the edge along the radius.

This study introduces the low‐volume core (LVC) fabrication method, which enables the monolithic molding of compact, complex, versatile, and intelligent soft robotic systems. This method uses thin and flexible thermoplastic sheets to mold internal chambers in soft fluidic actuators, valves, and circuits. The LVC fabrication method creates low‐volume networks in soft actuators (LV‐net actuators) that can be made with compact and complex geometries, enabling both low actuation volume input and multi‐degree‐of‐freedom actuators. LVC fabrication can also be used for compact, completely soft, and monolithic logic components (valves with low‐volume core, also called as LV valves) to provide directional resistance as well as a switching mechanism that enables fluidic logic in soft systems. The compatibility of the fabrication methods for both soft actuators and valves facilitates the creation of compact, integrated, and versatile soft robotic systems with embodied intelligence. This study introduces two examples of such intelligent soft robotic systems that integrate both LV‐net actuators and LV valves to demonstrate capability for complex system fabrication. [ABSTRACT FROM AUTHOR]

The geometrical measurement precision of laser spots is affected by the deviation between the parameters of the laser altimeter and the laboratory measurement results, and the inversion accuracy of surface object height is also limited. The measurement parameters and the load state can be obtained by calibration of the laser altimeter system. Usually, ground detectors are deployed to calibrate the measurement parameters of the laser altimeter, including the divergence angle and the energy distribution of the laser beam. A calibration method for a laser footprint spot without a calibration field was proposed in this paper, focused on the airborne large-footprint laser altimeter system. The geometric parameters of the laser spot were calibrated through the laser echo waveforms of a specific terrain. The experimental results show that geometric calibration of the large-footprint laser altimeter can be achieved in the area of the step surface. The divergence angle of the laser beams obtained from the six experimental areas is 4.604 ± 0.359 mRad, and the consistency of the energy distribution from each laser spot reaches 92.67%. A new method of on-orbit calibration and verification is provided for the satellite laser altimeter system. [ABSTRACT FROM AUTHOR]

Training employees to become image ambassadors is an important manifestation of an organization's internal branding. However, most tourism destination marketing studies consider external image-building and pay little attention to the brand ambassador behavior of internal members. This study investigates 208 front-line employees in two tourist attractions and constructs a structural equation model including workplace friendship, employee well-being, employee helping behavior, and employee brand ambassador behavior. The results show that: (1) workplace friendship has a significant promoting effect on employee brand ambassador behavior; (2) employee helping behavior mediates the relationships between workplace friendship and employee well-being, and between workplace friendship and employee brand ambassador behavior; (3) employee well-being mediates the relationship between workplace friendship and employee brand ambassador behavior; (4) employee helping behavior and employee well-being play a chain-mediating role in the relationship between workplace friendship and employee brand ambassador behavior. Our findings not only enrich the theoretical understanding of outcomes of workplace friendship, but also provide important guidance for tourist attractions regarding internal brand marketing. [ABSTRACT FROM AUTHOR]

Due to the difference in surface reflectivity, the laser measurement waveform data recorded in full waveform have a saturation phenomenon. When the signal is saturated, the echo waveform produces peak clipping and pulse spreading, which seriously restrict the accuracy of laser measurement results and the usability of data. Therefore, we conducted a ranging investigation on the "peak clipping" phenomenon of the saturated waveform and found a nonlinear time delay in the range, which is between the two extreme cases of saturated "dead time" and Gaussian fitting peak time as pulse signal reception time. Subsequently, based on the consistent relationship between the geometric characteristics of the high- and low-gain channels of the space-borne laser altimeter, we constructed a laser waveform saturation compensation model, namely, the laser pulse flight time delay compensation and the laser waveform peak intensity compensation, and carried out the data saturation compensation and validation with the dual-channel measurement data from the GaoFen-7 (GF-7) satellite. The experimental results showed that the saturation compensation model (SCM) proposed in this paper could restore the features of the saturated waveform signal and effectively improve the accuracy of the laser ranging. The accuracy of the laser waveform fitting result after saturation compensation improved from 0.7 ns (0.11 m) to 0.14 ns (0.02 m), which greatly improved the usability of the saturated laser measurement waveform data. [ABSTRACT FROM AUTHOR]

The regeneration mechanism of sulfated Cu/SAPO-34 catalysts in reducing atmospheres (5% H2/Ar and NH3/Ar at 600 °C) was investigated by using a series of characterization methods. Hydrogen regeneration improved the catalysts' NH3-SCR activity from 150 to 550 °C remarkably, while ammonia regeneration exhibited relatively less obvious promotion effect. The TPR of hydrogen and EPR spectra data show that the regeneration process affects the amount and the coordination of the active isolated Cu2+ species significantly. The desulfation increases the amount of isolated copper ions and improves the catalytic activity of SCR. [ABSTRACT FROM AUTHOR]

The improved low temperature SCR activity and operating window of MnTiS0.05 caused by the greatly enhanced L-H route owing to the replacement of Ti4+ by S4+ to form Ti O S band. • S is doped into TiO 2 via the replacement of Ti4+ by S4+ to form Ti O S bond. • Brønsted acid sites and redox property are enhanced due to more active species. • Reactivity and amount of ad-NH 3 and ad-NO x species are improved. • L-H route occurred on the S-doped catalyst is more significant than E-R route. • MnTiS0.05 exhibits the best SCR performance and widest operating window. A series of S-doped MnO x /TiO 2 catalysts were prepared by sol-gel method for the purpose of enhancing SCR performance. The obtained catalyst with mole ratio of S:Ti = 0.05:1 exhibited the best low temperature SCR performance and the widest active temperature window. According to the results of various analyses, the proper S was doped into TiO 2 lattice via the replacement of Ti4+ by S4+ to generate Ti O S bond, along with increasing surface area, more surface Mn4+ species and more active oxygen species (O 2 −). These enhanced properties improved the Brønsted acid sites and redox property of the properly S-doped MnO x /TiO 2 catalyst. These advantages of S doping can essentially benefit the de-NO x ability of MnO x /TiO 2 catalysts. Meanwhile, the in situ DRIFT experiments revealed that the adsorbed NH 4 + and gas-phase NO 2 species were greatly increased after proper S-doping, along with the enhanced reactivity of the adsorbed NH 3 and NO x species. Both E-R and L-H mechanisms occurred on the S-doped catalysts, while the promoting effect of S-doping was performed by facilitating the L-H route during SCR reaction. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) was applied to simulate the direct shear tests of irregular ballast stones by constructing clump particles, where irregular clumped-particles have similar particle size distribution (PSD) with those of the real ballast stone. With these clumped particles, the interlock of ballast stones in the direct shear test is investigated. The nonlinear contact force model with Mohr–Coulomb is adopted to model the interaction of the clumped particles. With different normal loads, the simulated microscopic characteristics in the direct shear test were linked with that of tests. The results demonstrate that DEM numerical simulations can produce interrelated responses of the ballast behavior, including the critical state response and are in good agreement with experimental observations. The shear resistance value increases with the normal stress application, indicating that the lateral confinement of ballast bed leading to less vertical settlement and more track stability. In addition, the DEM can further provide details of the microstructure evolutions during shearing processes. [ABSTRACT FROM AUTHOR]

• The thermal–hydraulic characteristics of lead–bismuth eutectic in a vertical tube under rolling conditions are numerically investigated. • It is concluded that the frictional resistance coefficient and heat transfer correlations now used are not suitable for the ship-based LFR. • Comparison with water coolant shows that the enhancement of radial secondary flow is the main cause for the change of heat transfer ability of coolant. The investigation of flow and heat transfer of lead–bismuth eutectic (LBE) under rolling conditions is vital to the application of LBE cooled reactor in offshore engineering. In this paper, mature numerical method for modelling low Prandtl number liquid metal is used for LBE flow in a vertical tube under rolling conditions. Reynolds stress turbulent model is chosen to consider the complex secondary flow caused by additional force. It is found that the transverse additional force is the main reason accounting for the enhancement of heat transfer and secondary flow. The transient maximum heat transfer ability can be enlarged by 18% under condition of rolling angle of 30° and period of 8 s. And 10 times transverse additional force caused by rolling angle of 30° and period of 8 s is enough to change the flow resistance characteristic of LBE. Comparisons with water coolant indicate that the intensity of radial secondary flow play an important role in determining the heat transfer characteristic of fluid under rolling conditions. The high density and low Prandtl number also make the features of LBE under rolling conditions different from those of water. The empirical correlations used in system code now could not predict the flow and heat transfer of LBE under rolling conditions. Special attention should be paid to safety design criteria of the off-shore LBE cooled reactor. This paper may contribute to the thermal–hydraulic design of off-shore liquid metal cooled reactors. [ABSTRACT FROM AUTHOR]