363 research outputs found
Improved l1-SPIRiT using 3D walsh transform-based sparsity basis
l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency
Optimal Control Policies of Pests for Hybrid Dynamical Systems
We improve the traditional integrated pest management (IPM) control strategies and formulate three specific management strategies, which can be described by hybrid dynamical systems. These strategies can not only effectively control pests but also reduce the abuse of pesticides and protect the natural enemies. The aim of this work is to study how the factors, such as natural enemies optimum choice in the two kinds of different pests, timings of natural enemy releases, dosages and timings of insecticide applications, and instantaneous killing rates of pesticides on both pests and natural enemies, can affect the success of IPM control programmes. The results indicate that the pests outbreak period or frequency largely depends on the optimal selective feeding of the natural enemy between one of the pests and the control tactics. Ultimately, we obtain the only pest needs to be controlled below a certain threshold while not supervising pest
An Autonomous Path Planning Method for Unmanned Aerial Vehicle based on A Tangent Intersection and Target Guidance Strategy
Unmanned aerial vehicle (UAV) path planning enables UAVs to avoid obstacles
and reach the target efficiently. To generate high-quality paths without
obstacle collision for UAVs, this paper proposes a novel autonomous path
planning algorithm based on a tangent intersection and target guidance strategy
(APPATT). Guided by a target, the elliptic tangent graph method is used to
generate two sub-paths, one of which is selected based on heuristic rules when
confronting an obstacle. The UAV flies along the selected sub-path and
repeatedly adjusts its flight path to avoid obstacles through this way until
the collision-free path extends to the target. Considering the UAV kinematic
constraints, the cubic B-spline curve is employed to smooth the waypoints for
obtaining a feasible path. Compared with A*, PRM, RRT and VFH, the experimental
results show that APPATT can generate the shortest collision-free path within
0.05 seconds for each instance under static environments. Moreover, compared
with VFH and RRTRW, APPATT can generate satisfactory collision-free paths under
uncertain environments in a nearly real-time manner. It is worth noting that
APPATT has the capability of escaping from simple traps within a reasonable
time
Comprehensive ab initio study of effects of alloying elements on generalized stacking fault energies of Ni and NiAl
Excellent high-temperature mechanical properties of Ni-based single crystal
superalloys (NSCSs) are attributed to the yield strength anomaly of NiAl
that is intimately related to generalized stacking fault energies (GSFEs).
Therefore, clarifying the effects of alloying elements on the GSFEs is of great
significance for alloys design. Here, by means of ab initio density functional
theory calculations, we systematically calculated the GSFEs of different slip
systems of Ni and NiAl without and with alloying elements using the alias
shear method. We obtained that for Ni, except for magnetic elements Mn, Fe, and
Co, most of alloying elements decrease the unstable stacking fault energy
() of the and slip systems
and also decrease the stable stacking fault energy () of the
slip system. For NiAl, most of alloying elements in
groups IIIB-VIIB show a strong Al site preference. Except for Mn and Fe, the
elements in groups VB-VIIB and the first column of group VIII increase the
values of of different slip systems of NiAl. On the other
hand, the elements in groups IIIB-VIIB also increase the value of
. We found that Re is an excellent strengthening alloying element
that significantly increases the slip barrier of the tailing slip process for
Ni, and also enhances the slip barrier of the leading slip process of three
slip systems for NiAl. W and Mo exhibit similar effects as Re. We
predicted that Os, Ru, and Ir are good strengthening alloying elements as well,
since they show the strengthening effects on both the leading and tailing slip
process for Ni and NiAl
Searching for Variable Stars in the Open Cluster NGC 2355 and Its Surrounding Region
We have investigated the variable stars in the field surrounding NGC 2355
based on the time-series photometric observation data. More than 3000 CCD
frames were obtained in the V band spread over 13 nights with the Nanshan
One-meter Wide-field Telescope. We have detected 88 variable stars, containing
72 new variable stars and 16 known variable stars. By analyzing these light
curves, we classified the variable stars as follows: 26 eclipsing binaries, 52
pulsating stars, 4 rotating variables, and 6 unclear type variable stars for
which their periods are much longer than the time baseline chosen. Employing
Gaia DR2 parallax, kinematics, and photometry, the cluster membership of these
variable stars were also analyzed for NGC 2355. In addition to the 11 variable
members reported by Cantat-Gaudin et al. (2018), we identify 4 more variable
member candidates located at the outer region of NGC 2355 and showed
homogeneity in space positions and kinematic properties with the cluster
members. The main physical parameters of NGC 2355 estimated from the two-color
and color-magnitude diagrams are log(age/yr) = 8.9, E(B - V) = 0.24 mag, and
[Fe/H] = - 0.07 dex.Comment: 15 pages, 11 figures. 6 tables,Accepted for publication in A
OccuQuest: Mitigating Occupational Bias for Inclusive Large Language Models
The emergence of large language models (LLMs) has revolutionized natural
language processing tasks. However, existing instruction-tuning datasets suffer
from occupational bias: the majority of data relates to only a few occupations,
which hampers the instruction-tuned LLMs to generate helpful responses to
professional queries from practitioners in specific fields. To mitigate this
issue and promote occupation-inclusive LLMs, we create an instruction-tuning
dataset named \emph{OccuQuest}, which contains 110,000+ prompt-completion pairs
and 30,000+ dialogues covering over 1,000 occupations in 26 occupational
categories. We systematically request ChatGPT, organizing queries
hierarchically based on Occupation, Responsibility, Topic, and Question, to
ensure a comprehensive coverage of occupational specialty inquiries. By
comparing with three commonly used datasets (Dolly, ShareGPT, and WizardLM), we
observe that OccuQuest exhibits a more balanced distribution across
occupations. Furthermore, we assemble three test sets for comprehensive
evaluation, an occu-test set covering 25 occupational categories, an estate set
focusing on real estate, and an occu-quora set containing real-world questions
from Quora. We then fine-tune LLaMA on OccuQuest to obtain OccuLLaMA, which
significantly outperforms state-of-the-art LLaMA variants (Vicuna, Tulu, and
WizardLM) on professional questions in GPT-4 and human evaluations. Notably, on
the occu-quora set, OccuLLaMA reaches a high win rate of 86.4\% against
WizardLM
Research Progress on Structure, Function and Application of Tremella fuciformis Polysaccharide
Tremella fuciformis is rich in nutrients, and Tremella fuciformis polysaccharide is the most important functional active component with a variety of biological activities. Tremella fuciformis polysaccharides can be prepared by various methods, and the research on its structure is mainly focused on molecular weight, monosaccharide components, and glycosidic bond type. This review summarizes the preparation, structure, and biological activities of Tremella fuciformis polysaccharides, such as antioxidant, anti-tumor, immune regulation, memory improvement, anti-inflammation, blood sugar and blood lipid lowering, and its development and application in food, cosmetics, and medicine. In the future, it is necessary to optimize the preparation technology of Tremella fuciformis polysaccharides, analyze the advanced structure of Tremella fuciformis polysaccharides with modern analytical techniques, and conduct in-depth research on the function and mechanism of action of Tremella fuciformis polysaccharides, so as to provide theoretical reference for the deep processing and product development of Tremella fuciformis fuciformis
Structure-driven intercalated architecture of septuple-atomic-layer family with diverse properties from semiconductor to topological insulator to Ising superconductor
Motivated by the fact that septuple-atomic-layer MnBiTe can be
structurally viewed as the combination of double-atomic-layer MnTe
intercalating into quintuple-atomic-layer BiTe, we present a general
approach of constructing twelve septuple-atomic-layer - and
- monolayer family (\emph{i} = 1 to 6) by intercalating
MoS-type monolayer into InSe-type AZ monolayer. Besides
reproducing the experimentally synthesized -MoSiN,
-WSiN and -MnBiTe monolayer materials,
another 66 thermodynamically and dynamically stable were predicted,
which span a wide range of properties upon the number of valence electrons
(VEC). with the rules of 32 or 34 VEC are mostly semiconductors with
direct or indirect band gap and, however, with 33 VEC are generally metal,
half-metal ferromagnetism, or spin-gapless semiconductor upon whether or not an
unpaired electron is spin polarized. Moreover, we propose
-WSiP for the spin-valley polarization,
-TaSiN for Ising superconductor and -SrGaSe
for topological insulator.Comment: Maintext 9 pages; 5 figures; Supplementary Materials 8 figures and 4
table
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