101 research outputs found
Real-time Routes Design Research of DIY tour Based on Greedy Algorithm
Compared with group tour, DIY tour is characterized by flexible time arrangements and uncertain routes planning. This paper has mainly employed partial greedy algorithm based on time series in designing real-time routes in DIY tours. As restaurant and accommodation are featured by time window constraint, thus the design is divided into several time partitions in line with 24-hour clock, and each partition has its tour behaviors including sighting, restaurant and accommodation. In each partition and its joint, the paper has availed partial optimal strategy of greedy algorithm so as to complete the overall routes design
EFFECT OF HARVESTING QUOTA AND PROTECTION ZONE IN A REACTION-DIFFUSION MODEL ARISING FROM FISHERY MANAGEMENT
A reaction-diffusion logistic population model with spatially nonhomogeneous harvesting is considered. It is shown that when the intrinsic growth rate is larger than the principal eigenvalue of the protection zone, then the population is always sustainable; while in the opposite case, there exists a maximum allowable catch to avoid the population extinction. The existence of steady state solutions is also studied for both cases. The existence of an optimal harvesting pattern is also shown, and theoretical results are complemented by some numerical simulations for one-dimensional domains
Modular development of deep potential for complex solid solutions
The multicomponent oxide solid solution is a versatile platform to tune the
delicate balance between competing spin, charge, orbital, and lattice degrees
of freedom for materials design and discovery. The development of
compositionally complex oxides with superior functional properties has been
largely empirical and serendipitous, in part due to the exceedingly complex
chemistry and structure of solid solutions that span a range of length scales.
The classical molecular dynamics (MD), as a powerful statistical method to
investigate materials properties over large spatial and temporal scales, often
plays a secondary role in computer-aided materials discovery because of the
limited availability and accuracy of classical force fields. Here, we introduce
the strategy of ``modular developing deep potential" (ModDP) that enables a
systematic development and improvement of deep neural network-based model
potential, termed as deep potential, for complex solid solutions with minimum
human intervention. The converged training database associated with an
end-member material is treated as an independent module and is reused to train
the deep potential of solid solutions via a concurrent learning procedure. We
apply ModDP to obtain classical force fields of two technologically important
solid solutions, PbSrTiO and HfZrO. For both
materials systems, a single model potential is capable of predicting various
properties of solid solutions including temperature-driven and
composition-driven phase transitions over a wide range of compositions. In
particular, the deep potential of PbSrTiO reproduces a few
known topological textures such as polar vortex lattice and electric dipole
waves in PbTiO/SrTiO superlattices, paving the way for MD
investigations on the dynamics of topological structures in response to
external stimuli.Comment: 32 pages, 9 figure
Dendrimer-entrapped gold nanoparticles as potential CT contrast agents for blood pool imaging
The purpose of this study was to evaluate dendrimer-entrapped gold nanoparticles [Au DENPs] as a molecular imaging [MI] probe for computed tomography [CT]. Au DENPs were prepared by complexing AuCl4- ions with amine-terminated generation 5 poly(amidoamine) [G5.NH2] dendrimers. Resulting particles were sized using transmission electron microscopy. Serial dilutions (0.001 to 0.1 M) of either Au DENPs or iohexol were scanned by CT in vitro. Based on these results, Au DENPs were injected into mice, either subcutaneously (10 μL, 0.007 to 0.02 M) or intravenously (300 μL, 0.2 M), after which the mice were imaged by micro-CT or a standard mammography unit. Au DENPs prepared using G5.NH2 dendrimers as templates are quite uniform and have a size range of 2 to 4 nm. At Au concentrations above 0.01 M, the CT value of Au DENPs was higher than that of iohexol. A 10-μL subcutaneous dose of Au DENPs with [Au] ≥ 0.009 M could be detected by micro-CT. The vascular system could be imaged 5 and 20 min after injection of Au DENPs into the tail vein, and the urinary system could be imaged after 60 min. At comparable time points, the vascular system could not be imaged using iohexol, and the urinary system was imaged only indistinctly. Findings from this study suggested that Au DENPs prepared using G5.NH2 dendrimers as templates have good X-ray attenuation and a substantial circulation time. As their abundant surface amine groups have the ability to bind to a range of biological molecules, Au DENPs have the potential to be a useful MI probe for CT
Development of Eighteen Microsatellite Markers in Anemone amurensis (Ranunculaceae) and Cross-Amplification in Congeneric Species
Polyploidy plays an important role in the evolution of plant genomes. To enable the investigation of the polyploidy events within the genus Anemone, we developed eighteen microsatellite markers from the hexaploid species A. amurensis (Ranunculaceae), and tested their transferability in five closely related species. The number of total alleles (NA) for each resulting locus varied from one to eight. The polymorphism information content (PIC) and Nei’s genetic diversity (NGD) for these microsatellites ranged from 0.00 to 0.71 and 0.00 to 0.91, respectively. For each population, the NA was one to seven, and the values of PIC and NGD varied from 0.00 to 0.84 and 0.00 to 0.95, respectively. In addition, most of these microsatellites can be amplified successfully in the congeneric species. These microsatellite primers provide us an opportunity to study the polyploid evolution in the genus Anemone
Channel Acquisition for HF Skywave Massive MIMO-OFDM Communications
In this paper, we investigate channel acquisition for high frequency (HF)
skywave massive multiple-input multiple-output (MIMO) communications with
orthogonal frequency division multiplexing (OFDM) modulation. We first
introduce the concept of triple beams (TBs) in the space-frequency-time (SFT)
domain and establish a TB based channel model using sampled triple steering
vectors. With the established channel model, we then investigate the optimal
channel estimation and pilot design for pilot segments. Specifically, we find
the conditions that allow pilot reuse among multiple user terminals (UTs),
which significantly reduces pilot overhead. Moreover, we propose a channel
prediction method for data segments based on the estimated TB domain channel.
To reduce the complexity, we are able to formulate the channel estimation as a
sparse signal recovery problem due to the channel sparsity in the TB domain and
then obtain the channel by the proposed constrained Bethe free energy
minimization (CBFEM) based channel estimation algorithm, which can be
implemented with low complexity by exploiting the structure of the TB matrix
together with the chirp z-transform (CZT). Simulation results demonstrate the
superior performance of the proposed channel acquisition approach.Comment: 30 pages, 4 figure
A universal interatomic potential for perovskite oxides
With their celebrated structural and chemical flexibility, perovskite oxides
have served as a highly adaptable material platform for exploring emergent
phenomena arising from the interplay between different degrees of freedom.
Molecular dynamics (MD) simulations leveraging classical force fields, commonly
depicted as parameterized analytical functions, have made significant
contributions in elucidating the atomistic dynamics and structural properties
of crystalline solids including perovskite oxides. However, the force fields
currently available for solids are rather specific and offer limited
transferability, making it time-consuming to use MD to study new materials
systems since a new force field must be parameterized and tested first. The
lack of a generalized force field applicable to a broad spectrum of solid
materials hinders the facile deployment of MD in computer-aided materials
discovery (CAMD). Here, by utilizing a deep-neural network with a
self-attention scheme, we have developed a unified force field that enables MD
simulations of perovskite oxides involving 14 metal elements and conceivably
their solid solutions with arbitrary compositions. Notably, isobaric-isothermal
ensemble MD simulations with this model potential accurately predict the
experimental phase transition sequences for several markedly different
ferroelectric oxides, including a 6-element ternary solid solution,
Pb(InNb)O--Pb(MgNb)O--PbTiO. We
believe the universal interatomic potential along with the training database,
proposed regression tests, and the auto-testing workflow, all released
publicly, will pave the way for a systematic improvement and extension of a
unified force field for solids, potentially heralding a new era in CAMD.Comment: 18 pages, 4 figure
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