2,663 research outputs found
Novel 3D Geometry-Based Stochastic Models for Non-Isotropic MIMO Vehicle-to-Vehicle Channels
This paper proposes a novel three-dimensional (3D) theoretical regular-shaped
geometry-based stochastic model (RS-GBSM) and the corresponding
sum-of-sinusoids (SoS) simulation model for non-isotropic multiple-input
multiple-output (MIMO) vehicle-to-vehicle (V2V) Ricean fading channels. The
proposed RS-GBSM, combining line-of-sight (LoS) components, a two-sphere model,
and an elliptic-cylinder model, has the ability to study the impact of the
vehicular traffic density (VTD) on channel statistics, and jointly considers
the azimuth and elevation angles by using the von Mises Fisher distribution.
Moreover, a novel parameter computation method is proposed for jointly
calculating the azimuth and elevation angles in the SoS channel simulator.
Based on the proposed 3D theoretical RS-GBSM and its SoS simulation model,
statistical properties are derived and thoroughly investigated. The impact of
the elevation angle in the 3D model on key statistical properties is
investigated by comparing with those of the corresponding two-dimensional (2D)
model. It is demonstrated that the 3D model is more accurate to characterize
real V2V channels, in particular for pico cell scenarios. Finally, close
agreement is achieved between the theoretical model, SoS simulation model, and
simulation results, demonstrating the utility of the proposed models
[2-(Piperidin-1-yl)ethylÂamine]dithioÂcyanatoÂzinc(II)
In the mononuclear title compound, [Zn(NCS)2(C7H16N2)], the ZnII atom is four-coordinated by two N atoms of the chelating 2-(piperidin-1-yl)ethylÂamine ligand and two N atoms from two thioÂcyanate ligands in a distorted tetraÂhedral geometry. In the crystal structure, molÂecules are linked through interÂmolecular N—H⋯S hydrogen bonds, forming chains along the b axis
Research of the active reflector antenna using laser angle metrology system
Active reflector is one of the key technologies for constructing large
telescopes, especially for the millimeter/sub-millimeter radio telescopes. This
article introduces a new efficient laser angle metrology system for the active
reflector antenna of the large radio telescopes, with a plenty of active
reflector experiments mainly about the detecting precisions and the maintaining
of the surface shape in real time, on the 65-meter radio telescope prototype
constructed by Nanjing Institute of Astronomical Optics and Technology (NIAOT).
The test results indicate that the accuracy of the surface shape segmenting and
maintaining is up to micron dimension, and the time-response can be of the
order of minutes. Therefore, it is proved to be workable for the sub-millimeter
radio telescopes.Comment: 10 pages, 15 figure
Timing of Drought Affected the Growth, Physiology, and Mortality of Mongolian Pine Saplings
Background and Objectives: More frequent and severe droughts are occurring due to climate change in northern China. In addition to intensity and duration, the timing of droughts may be decisive for its impacts on tree growth, mortality, and the whole forest ecosystem. The aim of this study was to compare the effect of drought occurring in the early- and mid-growing season on the growth and physiology of Mongolian pine (Pinus sylvestris var. mongolica Litv.) saplings. Materials and Methods: Four-year-old container saplings that were about to sprout were exposed to three treatments: (i) regular irrigation throughout the growing season (CTRL), (ii) no irrigation in the early growing season (weeks 1–5) followed by regular irrigation (EGD), (iii) no irrigation in the mid growing season (weeks 5–10), and regular irrigation in the early and late growing season (MGD). We measured the root and shoot growth, sapling mortality, and the physiological changes in the roots and needles periodically. Results: Drought in the mid growing season was more harmful than in the early growing season in terms of chlorophyll fluorescence, electrolyte leakage of needles, needle length, stem diameter increment, and sapling mortality. The high mortality in the mid growing season might be attributed to the joint effect of drought and high temperature. Drought in the early growing season decreased root growth, and the starch and soluble sugars in roots as much as the drought in the mid growing season. Abscisic acid concentration increased in fine roots, but decreased in old needles after drought. Conclusions: Special attention should be paid on forest sites susceptible to drought during afforestation in the face of ongoing climate change
Timing of Drought Affected the Growth, Physiology, and Mortality of Mongolian Pine Saplings
Background and Objectives: More frequent and severe droughts are occurring due to climate change in northern China. In addition to intensity and duration, the timing of droughts may be decisive for its impacts on tree growth, mortality, and the whole forest ecosystem. The aim of this study was to compare the effect of drought occurring in the early- and mid-growing season on the growth and physiology of Mongolian pine (Pinus sylvestris var. mongolica Litv.) saplings. Materials and Methods: Four-year-old container saplings that were about to sprout were exposed to three treatments: (i) regular irrigation throughout the growing season (CTRL), (ii) no irrigation in the early growing season (weeks 1–5) followed by regular irrigation (EGD), (iii) no irrigation in the mid growing season (weeks 5–10), and regular irrigation in the early and late growing season (MGD). We measured the root and shoot growth, sapling mortality, and the physiological changes in the roots and needles periodically. Results: Drought in the mid growing season was more harmful than in the early growing season in terms of chlorophyll fluorescence, electrolyte leakage of needles, needle length, stem diameter increment, and sapling mortality. The high mortality in the mid growing season might be attributed to the joint effect of drought and high temperature. Drought in the early growing season decreased root growth, and the starch and soluble sugars in roots as much as the drought in the mid growing season. Abscisic acid concentration increased in fine roots, but decreased in old needles after drought. Conclusions: Special attention should be paid on forest sites susceptible to drought during afforestation in the face of ongoing climate change
Exploring the Optimal Cycle for Quantum Heat Engine using Reinforcement Learning
Quantum thermodynamic relationships in emerging nanodevices are significant
but often complex to deal with. The application of machine learning in quantum
thermodynamics has provided a new perspective. This study employs reinforcement
learning to output the optimal cycle of quantum heat engine. Specifically, the
soft actor-critic algorithm is adopted to optimize the cycle of three-level
coherent quantum heat engine with the aim of maximal average power. The results
show that the optimal average output power of the coherent three-level heat
engine is 1.28 times greater than the original cycle (steady limit). Meanwhile,
the efficiency of the optimal cycle is greater than the Curzon-Ahlborn
efficiency as well as reporting by other researchers. Notably, this optimal
cycle can be fitted as an Otto-like cycle by applying the Boltzmann function
during the compression and expansion processes, which illustrates the
effectiveness of the method
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