5,465 research outputs found
An investigation of air and water dual adjustment decoupling control of surface heat exchanger
The terminal equipment of central cooling system accounts for a significant proportion of the total system's energy consumption. Therefore, it is important to reduce the terminal equipment energy consumption in central air conditioning system. In this study, the difference of the effect of the chilled water flow rate and air supply rate on the surface cooler during the heat transfer process is taken into full account. Matlab/Simulink simulation software is used to model and simulate the heat transfer of surface cooler of the main terminal equipment of air conditioning system. Simulation tests and experimental validations are conducted by using variable chilled water flow rate and variable air supply rate control mode separately. The experiment results show that the simulation model can effectively predict the heat transfer performance of heat exchanger. Further, the study introduced a dual feedback control mode, which synchronously regulates the chilled water flow rate and air supply rate. Also, under certain conditions, the complex heat transfer process of the surface cooler can be decoupled, and single variable control pattern is used to separately regulate the chilled water flow rate and air supply rate. This can effectively shorten the system regulation time, reduce overshoot and improve control performance
Quasi-16-day periodic meridional movement of the equatorial ionization anomaly
Based on the daytime location of the equatorial ionization anomaly (EIA)
crest derived from GPS observations at low latitude over China during the
2005–2006 stratospheric sudden warming (SSW), a quasi-16-day periodic
meridional movement of EIA crest with the maximum amplitude of about 2
degrees relative to the average location of EIA crest has been revealed. In
addition, periodic variations that are in phase with the meridional EIA
movement are also revealed in the equatorial electrojet (EEJ) and F2 layer
peak height (<i>hm</i>F2) over Chinese ionosonde stations Haikou and Chongqing. The
quasi-16-day periodic component in Dst index is weak, and the 16-day
periodic component does not exist in F10.7 index. Such large-scale periodic
meridional movement of EIA crest is likely related to the globally enhanced
stratospheric planetary waves coupled with anomalous stratospheric zonal
wind connected with SSW. In addition, such large-scale periodic movement of
EIA should be global, and can affect the ionospheric morphology around the
low-latitude belt near the EIA region. Further case analysis, simulation and
theoretical studies must proceed in order to understand the periodic
movements of EIA connected with the different periodic atmospheric
variations
Data taking strategy for the phase study in
The study of the relative phase between strong and electromagnetic amplitudes
is of great importance for understanding the dynamics of charmonium decays. The
information of the phase can be obtained model-independently by fitting the
scan data of some special decay channels, one of which is . To find out the optimal data taking strategy for a scan experiment
in the measurement of the phase in , the
minimization process is analyzed from a theoretical point of view. The result
indicates that for one parameter fit, only one data taking point in the
vicinity of a resonance peak is sufficient to acquire the optimal precision.
Numerical results are obtained by fitting simulated scan data. Besides the
results related to the relative phase between strong and electromagnetic
amplitudes, the method is extended to analyze the fits of other resonant
parameters, such as the mass and the total decay width of .Comment: 13 pages, 7 figure
Ecohydrological optimality in the Northeast China Transect
The Northeast China Transect (NECT) is one of the International
Geosphere-Biosphere Program (IGBP) terrestrial transects, where there is a
significant precipitation gradient from east to west, as well as a vegetation
transition of forest–grassland–desert. It is remarkable to understand vegetation distribution and dynamics under climate change in this transect. We take canopy cover (M), derived from Normalized Difference Vegetation Index (NDVI), as an index to describe the properties of vegetation
distribution and dynamics in the NECT. In Eagleson's ecohydrological optimality
theory, the optimal canopy cover (M*) is determined by the trade-off
between water supply depending on water balance and water demand depending on
canopy transpiration. We apply Eagleson's ecohydrological optimality method
in the NECT based on data from 2000 to 2013 to get M*, which is compared with M from NDVI to further discuss the sensitivity of M* to vegetation properties and climate factors. The result indicates that the average M* fits the actual M well (for forest, M*  =  0.822 while M  =  0.826; for grassland, M*  =  0.353 while M  =  0.352; the
correlation coefficient between M and M* is 0.81). Results of water balance also match the field-measured data in the references. The sensitivity analyses show that M* decreases with the increase of leaf area index (LAI), stem fraction and temperature, while it increases with the increase of leaf angle and precipitation amount. Eagleson's ecohydrological optimality method offers a quantitative way to understand the impacts of climate change on canopy cover and provides guidelines for ecorestoration projects
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Pointhuman: Reconstructing Clothed Human From Point Cloud Of Parametric Model
It is very difficult to accomplish the 3D reconstruction of the clothed human body from a single RGB image, because the 2D image lacks the representation information of the 3D human body, especially for the clothed human body. In order to solve this problem, we introduced a priority scheme of different body parts spatial information and proposed PointHuman network. PointHuman combines the spatial feature of the parametric model of the human body with the implicit functions without expressive restrictions. In PointHuman reconstruction framework, we use Point Transformer to extract the semantic spatial feature of the parametric model of the human body to regularize the implicit function of the neural network, which extends the generalization ability of the neural network to complex human poses and various styles of clothing. Moreover, considering the ambiguity of depth information, we estimate the depth of the parameterized model after point cloudization, and obtain an offset depth value. The offset depth value improves the consistency between the parameterized model and the neural implicit function, and accuracy of human reconstruction models. Finally, we optimize the restoration of the parametric model from a single image, and propose a depth perception method. This method further improves the estimation accuracy of the parametric model and finally improves the effectiveness of human reconstruction. Our method achieves competitive performance on the THuman dataset.Shenzhen Science and Technology Projects under Grant JCYJ20200109143035495 and Natural Science Foundation of Fujian Province (2022J011275)
Analytical solution for transient radial interaction between energy piles and soils: Thermo-elastic cavity expansion analysis
Bearing capacity of energy piles may be affected by the Radial Interaction between Energy Piles and Soils (RIEPS) such as energy pile expansion and transient radial heat conduction. This paper proposes a cavity-expansion-based solution to investigate the thermo-elastic RIEPS. Transient temperature distributions are shown by assuming heat conduction in the radial direction and constant temperature at the pile-soil interface. With the temperature distributions, a thermo-elastic solution is obtained to capture the changes in stresses and displacements around energy piles. It is found that the solution under the combined thermal-mechanical loading pattern is the linear superposition of those under the thermal loading and mechanical loading patterns. Hence, the stresses, strains and displacements in soils are determined by the competitive relationships between thermal and mechanical loading patterns. The expression for radial stress change at the pile-soil interface is discussed by the cavity expansion analysis and comparison with field data. For typical soil and pile parameters, the expression could be quite general considering transient temperature distributions and soil/pile moduli. This paper can benefit to the capacity design of energy piles by taking the RIEPS into account
The DArk Matter Particle Explorer mission
The DArk Matter Particle Explorer (DAMPE), one of the four scientific space
science missions within the framework of the Strategic Pioneer Program on Space
Science of the Chinese Academy of Sciences, is a general purpose high energy
cosmic-ray and gamma-ray observatory, which was successfully launched on
December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE
scientific objectives include the study of galactic cosmic rays up to
TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the
search for dark matter signatures in their spectra. In this paper we illustrate
the layout of the DAMPE instrument, and discuss the results of beam tests and
calibrations performed on ground. Finally we present the expected performance
in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart.
Phy
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