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The MELCOR 2.1 computer code has been used to simulate the large-scale aerosol behavior experiment in the Containment System Test Facility (CSTF) vessel. The test LA2 of the Light Water Aerosol Containment Experiments (LACE) was designed to simulate the containment conditions and aerosol behaviors in the high-steam-concentration environment under a postulated severe accident. In this study, the Aerosol Condensation model’s (ACD) and Hygroscopic Model’s (HM) ability of the aerosol behavior prediction has been evaluated by the simulation of LA2 based on MELCOR 2.1 code. It has been found that the size distribution and depletion rate of dry aerosols are affected by the mass of water aerosol. The different masses of water aerosol in ACD and HM models are due to the different relative humidity calculated by these two models. The simulation models with different control volumes setup were evaluated to study the effect of water aerosol mass on aerosol depletion rate. The results show that higher water aerosol mass results are calculated and better airborne aerosol masses are predicted under the multi-control volume models. Based on this research①, it can be concluded that good results of aerosol deposition in the vessel are severely affected by the accuracy of water aerosol mass. The improvement of water aerosol mass results by the MELCOR code’s simulation should be thoroughly studied.

Strongly swirling flow is widely encountered in engineering applications. However, accurate prediction of the flow is still challenging for turbulence modeling. The present study reports the assess...

In this paper, we propose a robust human sleep posture recognition method via multidimensional feature representation and learning based on millimeter-wave (mmw) radar. Firstly, through time-frequency processing of the radar echo signal reflected by the human body, the range spectrum, Doppler spectrum, range-Doppler spectrum, azimuth angle spectrum and elevation angle spectrum of the estimated target are obtained. By setting a fixed frame window length and splicing the above feature spectrums, 5 single-channel 2D radar features are obtained, and combining them in parallel can get a variety of different multi-channel 2D radar feature representations. Finally, a lightweight multi-channel convolutional neural network (CNN) with Inception-Residual module (IRM) is designed to learn and classify multidimensional features. Extensive experiments were carried out using the developed mmw radar system, and a large amount of data was obtained to train and test the classifier. The results show that the proposed sleep posture recognition method can effectively distinguish different sleep postures and achieve better robust performance and generalization compared to other methods.

In this paper, a multi-dimensional feature learning method is proposed to improve the classification accuracy and generalization performance of human behavior recognition on millimeter-wave radar. First, through the process of the radar echo reflected by the human body, we get the spectrums of range-Doppler, Doppler, the azimuth angle and the elevation angle. Then, a fixed frame-length sliding window method is used to capture 6 single-channel image features and 6 three-channel image features that can effectively represent human behaviors. Finally, a lightweight convolutional neural network (CNN) is used to learn and classify multidimensional behavior features. In order to evaluate the effectiveness of the proposed method, a dataset of six classes of human behaviors are collected by 3 people at multiple positions. The experimental results show that, compared with other features, the combined feature of range-time map (RTM), Doppler-time map (DTM) and azimuth-elevation-time map (AETM) has best classification performance for 6 human behaviors. In addition, the data of person A is used to train for a classification model, and the model is used to classify the behavior of people B and C, respectively. The recognition accuracy rates for untrained people B and C are 91.7% and 86.7%, respectively.

One of the most important issues in radar-based pattern recognition is how to efficiently obtain a large amount of reliable labeled data to train the classification model. We train classification models based on simulated samples to classify measured samples across domains to solve the problem of labeled data acquisition in human motion recognition. First, we use the motion capture dataset of Carnegie Mellon University (CMU MOCAP) to simulate the frequency modulated continuous wave (FMCW) radar echo signals of 41 target points of human body. Then generate an amount of simulated labeled data to perform supervised learning to train a Convolutional Neural Network (CNN) classification model. Firstly, a millimeter-wave radar with a two-dimensional antenna array is utilized to transmit FMCW signals and receive the echo signals of human motions. Then data processing is performed on the intermediate frequency (IF) sampling data to gain measured data. Experiment results show that there are similar characteristics in feature spectrograms between those generated by simulation and measurement. Applying the model trained on simulation data to classify the measured data based on a multi-channel CNN with multi-dimensional features method, we achieve test accuracy rate of 94.4%, which proves the feasibility and practicability for cross-domain human motion recognition.

China Fusion Engineering Test Reactor (CFETR) is aimed to meet the technical gaps between International Thermonuclear Experimental Reactor (ITER) and future fusion DEMO reactors, tritium self-sufficiency must be guaranteed for the operation of fusion reactors. Helium Cooled Ceramic Breeder (HCCB) blanket is one of the promising candidate blanket schemes for CFETR. Tritium generated in Li4SiO4 pebble bed is carried out by purge gas, it is crucial to study the tritium behavior in the blanket from the tritium fuel cycle point of view. In this paper, the effective diffusivity of tritium in purge gas is conducted based on Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) coupled simulation considering the influence of the pebble bed structure. The flow characters analysis of purge gas is carried out by CFD simulation as well, which includes velocity field distribution, pressure field distribution and pressure drop. Based on the macro parameters conducted above, the tritium transport process in blanket including tritium permeation into coolant, tritium inventory in blanket and tritium carried out by purge gas is simulated based on a 2D model set up in COMSOL Multiphysics, the results can be the reference for the design of Tritium Extraction System (TES) and Coolant Purification System (CPS).

In the early 20th century, the interpretation of the poem "Wei Jiao Zhongqing Qi Zuo" or "For Jiao Zhongqing's Wife" was mainly based on the social context at the time, which, however, might deviate from the original purpose of the female writing in the work. The poem once witnessed several modifications from the late Eastern Han Dynasty to the Southern Dynasties when the development of traditional Confucian code of ethics took off. The rewritings of female writing in literature works were to adapt to the male-dominated moral codes and discourse system at that time. Based on that, the female writing in the poem was processed, and evidence would be that from the perspective of content, the persona of Liu (Jiao's wife) portrayed in the poem changed greatly while characters like Jiao Zhongqing and Mother Jiao (Jiao's mother) were enriched. In addition, some new plots and characters were created for example, Brother Liu (Liu's brother) and Mother Liu (Liu's mother). In regard to the narrative strategy, the processed version intentionally emphasized the absence of "father" and "unrighteousness" of the brother to serve to the plot of suicide for love of Liu. This type of narrative poems conveying both criticism and praise was a tool used to complete and consolidate the ethical discourse and restrain women's influence on men, and it also echoed the traditional view of women passed from the Qin and Han Dynasties which for sure further confined women's free choice.

GaFeO

GaFeO3-type iron oxides are promising multiferroics due to the coexistence of large spontaneous magnetization and polarization near room temperature. However, the high leakage current and difficulties associated with synthesizing single crystals make it difficult to achieve two important features in the system: a large ferroelectric polarization switching and magnetoelectric coupling at a high-temperature region. Herein, we report successful achievement of these features by preparing high-quality Sc-doped GaFeO3 single crystals (ScxGa1-x/2Fe1-x/2O3 with x = 0-0.3) using the floating zone method. The x ≥ 0.05 crystals exhibit a leakage current 104 times lower than the x = 0 crystals, highlighting the importance of Sc doping. Because of the reduced leakage current, the Sc-doped crystals exhibit large ferroelectric polarization switching along the c-axis with a remanent polarization of 22-25 μC/cm2, which is close to the theoretically predicted polarization value of 25-28 μC/cm2. In addition, the Sc-doped crystals exhibit ferrimagnetism with magnetic anisotropy along the a-axis. Furthermore, a magnetic-field-induced modulation of polarization is observed in the x = 0.15 crystal even at a relatively high temperature, i.e., 100 K.

The steady impinging jets applied in turbomachine have been comprehensively studied but the pulsating jets still need to be further researched. The flow field and heat transfer characteristics of pulsating impinging jet impinging on a flat plate have been simulated using the improved very large eddy simulation established with SST k–ω model. Two time-mean Reynolds numbers (6,000 and 23,000) in the conditions of frequency = 10Hz and steady state at the constant jet–to–surface distance (6D) were considered. The velocity, vortices, and Nusselt number distributions on the plate surface were investigated to emphasize on the vortex structures in the flow and its relation to the heat transfer. The investigation has revealed the advantage of the improved very large eddy simulation for predicting the dynamical generating process of flow structures in pulsating jets. Calculated results showed pairs of vortices were organized and induced from the jet exit, and propagated along with the jet region periodically. The vortices grew with the entrainment towards the ambient fluid and resulted in accelerated interaction in the wall jet region. Meanwhile, the vortices had strong interaction with the core region and weakened velocity in the core region. Results showed that the time–mean local Nusselt number of pulsating jet was lower in the stagnation region at both investigated Re numbers but not reduced in the wall jet region.

Due to the low nuclear safety risk, low initial investment cost and short construction period, integrated small nuclear reactors have received wide attention from all over the world. As advanced new type of nuclear reactors, the technologies of integrated small nuclear reactors are in the process of exploration and development. Steam generators are used as the heat transfer system for energy exchange between the primary and secondary circuit in reactors, and their heat transfer analysis is very important for reactor design and development. Due to the simple structure, strong heat exchange capacity and timely load following, Once-Through Steam Generators (OTSGs) are the mainly used steam generators in the design of integrated small nuclear reactors. RELAP5/MOD4.0 is a commercial software developed by Innovative System Software, LLC for transient analysis of light water reactors (LWR). After years of development and improvement, RELAP5 has been a basic tool for analysis and calculation of various simulators of nuclear power plants. However, when RELAP5 models steam generators, only structural models related to straight pipes can be established, which is very inconvenient for the heat transfer research of Once-Through Steam Generators. In this paper, Once-Through Steam Generators with specified structural parameters are taken as the research object. The heat transfer calculation is performed on the simplified inclined tube models by RELAP5 code and the theoretical calculation of the spiral tube heat transfer models is also carried out. Comparing the steam outlet temperature on the primary and secondary sides, the heat exchange power, the average heat transfer coefficient and the tube length of different heat exchange zones under given primary and secondary side inlet fluid conditions, it is confirmed that the RELAP5 heat transfer calculation is verified for simplifying Once-Through Steam Generators with inclined tube models.

As key heat transfer system in small and medium size pressurized water reactors, once-through steam generators are important parts of energy exchange between primary and secondary circuits, and are very important for the design and operation of reactors. However, two-phase flow and heat transfer in once-through steam generators are very complicated. When a reactor experience power rising and descending transient, the heat removal of once-through steam generator, the flow rate, the inlet fluid temperature and outlet steam temperature will all change accordingly. Especially when a reactor is running at a low power, the flow rate of the secondary side of OTSG is extremely small and the single-phase region of the secondary side of OTSGs is also too small. The two-phase flow instability may occur, which has a serious impact on reactor operation and safety. So, a reasonable power-up and power-down transient scheme is required to ensure operational stability when starting up and shutting down a reactor. RELAP5/MOD4.0 is a commercial software developed by Innovative System Software, LCC for transient analysis of light water reactors (LWR). After years of development and improvement, RELAP5 has been a basic tool for analysis and calculation of various simulators of nuclear power plants. Scholars all over the world have carried out a large number of analysis of two-phase flow stability using RELAP5, and the results are reliable. This paper takes once through steam generators with given structural parameters as the research object, and uses RELAP5 as the calculation tool. The influencing factors of flow instability are discussed in this paper, and the operating parameters of the fluid on the primary and secondary sides are designed to satisfy the flow stability under different powers. And a set of power-up and power-down schemes for stable operation is proposed.

The principal component analysis (PCA) is used to analyze the high dimensional chemistry data of laminar premixed/stratified flames under strain effects. The first few principal components (PCs), which have larger contribution ratios, are chosen as the tabulated scalars to build the look-up chemistry table. Prior tests show that the strained premixed flame structure can be well reconstructed. To highlight the physical meanings of the tabulated scalars in the stratified flames, a modified PCA method is developed, where the mixture fraction is used to replace one of the PCs with the highest correlation coefficient with a mixture fraction. The other two tabulated scalars are then modified with the Schmidt orthogonalization. The modified tabulated scalars not only have clear physical meanings, but also contain passive scalars. The PCA method has good commonality, and can be extended for building the thermo-chemistry table including strain rate effects when different fuels are used.

LaO3/2-GaO3/2-ZrO2 ternary glasses have been prepared by aerodynamic levitation technique. The highest refractive index of glass system is 1.976 and the Abbe number of glass system reaches 49.9 for 30LaO3/2-62.5GaO3/2-7.5ZrO2 glass. Glasses have high transmittance of over 80% from ultraviolet light to the middle infrared light region. The maximum of infrared cutoff wavelength reaches to 10.6 μm. After ZrO2 doping, the acid corrosion resistance of glass is increased and the hardness of glass is improved from 7.14 GPa to 7.72 GPa ZrO2 adding increases the transforming temperature and crystallization temperature of glasses and improves the thermal stability of the glasses. The proper amount of ZrO2 doping improves the corrosion resistance, hardness, thermal and optical properties of the glass at the same time, which indicates that LaO3/2-GaO3/2-ZrO2 ternary glasses may have the potential to be used in a variety of endoscopes, especially those that need to be used in harsh environments.

The subject of heat transfer behaviors of steam generator is of great interest for better heat transfer efficiency and safety in industry. On most previous study, the models of SG based on RELAP5 used heat structures as the power generation, which is different from heating by primary side. This paper investigates the distinctions of different heat transfer methods on the thermal-hydraulic parameters by RELAP5. Two different heat transfers are selected, case 1 is uniformly heated by heat structure and case 2 is heated by the primary side of SG. The results show that the onset position of critical heat flux for case 2 is ahead of that for case 1. Besides, the temperature of tube wall corresponding to position of critical heat flux increases abruptly in case 1, and the wall temperature in superheated region in case 1 increases faster than that in case 2 when the water becomes fully superheated vapor. Then instability distinctions for two heat transfer cases are studied in this investigation. It is detected the fluid flow heated by second method is more stable than the first one, and the system has a higher ultimate thermal power when density wave oscillation occurs for case 2.

In x Ga1− x Sb is a ternary alloy with tunable properties. The wavelength of In x Ga1− x Sb can be varied in the range of 1.7– 6.8 μm, which is in the infrared (IR) region and makes that In x Ga1− x Sb can be used as a substrate for IR detector and thermophotovoltaic (TPV). The phase diagram reveals that there is a large temperature gap between liquidus and solidus lines, which leads to constitutional supercooling and the formation of crystal defects during the solidification process of InGaSb crystal. Moreover, convection caused by gravity will increase the inhomogeneity of transport in the liquid region near the crystal growth interface, which makes it quite difficult to grow In x Ga1− x Sb crystal. The convection will be restrained in microgravity environment, and thus, it is very beneficial for crystal growth. This article introduces the effect of microgravity on the growth of In x Ga1− x Sb crystal and the results of the space growth experiment of In x Ga1− x Sb ternary crystal with a high concentration of In in SJ10 recoverable scientific experimental satellite.

In the present study, a detailed assessment investigation of Very-Large Eddy Simulation (VLES) method is performed using the open-source toolbox OpenFOAM for the simulation of turbulent separated flow. The VLES method is a unified simulation approach enabling a seamless evolution from Reynolds-Averaged Navier-Stokes (RANS) to quasi Direct Numerical Simulation (quasi-DNS) depending on the numerical resolution. Two VLES models, i.e. VLES-k-e and VLES-k-ω, are implemented in OpenFOAM and applied in the present study. In order to assess the performance of VLES models based on the framework of OpenFOAM, four classic separated flow are selected and investigated in details, including the flow past a triangular bluff body at Re ​= ​45,000, the flow past a backward facing step at Re ​= ​40,000, the periodic hill flow at Re ​= ​10,595, and the flow past a circular cylinder at Re ​= ​41,300. The comparisons between VLES simulation results and experiments give an indication on the adequacy and accuracy of the VLES modelling method based on the OpenFOAM toolbox. The VLES-k-ω model performs slightly better than the VLES-k-e model on a relatively low mesh resolution, especially in predicting the turbulent separation flow induced by the pressure gradient on a smooth surface. The results also demonstrate the reliability and accuracy of the VLES modelling based on OpenFOAM platform for complex separated flow simulations.