155 research outputs found
Optimal design of blade parameters for fracturing tea-picking machine
The blade is one of the most critical components in the fracturing tea-picking machine, and this study is conducted to optimize the blade's working parameters. In this study, the effects of blade width, blade thickness, and cutting angle on the maximum fracturing force of tea stems were analyzed using the L9 (34) standard orthogonal table, with the maximum fracturing force used as the evaluation index. The results indicate that the main factors affecting the maximum fracturing force (MFF) of tea stems are cutting angle (CA), blade width (BW), and blade thickness (BT) in that order. Furthermore, microscopic observation of the fracture surface revealed that compared with the thickness of the other two blades, the thickness of 0 mm caused the cross-section uneven and had lots of burrs, correspondingly resulting in the section's oxidation and the deterioration of tea leaf quality. Therefore, the optimal combination of design parameters was a cutting angle of 90°, a blade width of 2.0 mm, and a blade thickness of 0.5 mm. The findings of this study can provide reference for blade design to reduce the fracturing force of tea-picking machines, lower the working power consumption, and improve the quality of freshly plucked tea leaves
Complexity and approximation ratio of semitotal domination in graphs
A set is a semitotal dominating set of a graph ifâ
âit is a dominating set of andâ
âevery vertex in is within distance 2 of another vertex of â. âTheâ
âsemitotal domination number is the minimumâ
âcardinality of a semitotal dominating set of â.
âWe show that the semitotal domination problem isâ
âAPX-complete for bounded-degree graphsâ, âand the semitotal domination problem in any graph of maximum degree can be approximated with an approximationâ
âratio of
A molecular simulation analysis of producing monatomic carbon chains by stretching ultranarrow graphene nanoribbons
Atomistic simulations were utilized to develop fundamental insights regarding
the elongation process starting from ultranarrow graphene nanoribbons (GNRs)
and resulting in monatomic carbon chains (MACCs). There are three key findings.
First, we demonstrate that complete, elongated, and stable MACCs with fracture
strains exceeding 100% can be formed from both ultranarrow armchair and zigzag
GNRs. Second, we demonstrate that the deformation processes leading to the
MACCs have strong chirality dependence. Specifically, armchair GNRs first form
DNA-like chains, then develop into monatomic chains by passing through an
intermediate configuration in which monatomic chain sections are separated by
two-atom attachments. In contrast, zigzag GNRs form rope-ladder-like chains
through a process in which the carbon hexagons are first elongated into
rectangles; these rectangles eventually coalesce into monatomic chains through
a novel triangle-pentagon deformation structure under further tensile
deformation. Finally, we show that the width of GNRs plays an important role in
the formation of MACCs, and that the ultranarrow GNRs facilitate the formation
of full MACCs. The present work should be of considerable interest due to the
experimentally demonstrated feasibility of using narrow GNRs to fabricate novel
nanoelectronic components based upon monatomic chains of carbon atoms.Comment: 11 pages, 6 figures, Nanotechnology accepted versio
Optimizing glycerosome formulations via an orthogonal experimental design to enhance transdermal triptolide delivery
Triptolide exerts strong anti-inflammatory and immunomodulatory effects; however, its oral administration might be associated with side effects. Transdermal administration can improve the safety of triptolide. In this study, glycerosomes were prepared as the transdermal vehicle to enhance the transdermal delivery of triptolide. With entrapment efficiency and drug loading as dependent variables, the glycerosome formulation was optimized using an orthogonal experimental design. Phospholipid-to-cholesterol and phospholipid-to-triptolide mass ratios of 30:1 and 5:1, respectively and a glycerol concentration of 20 % (v/v) were used in the optimization. The glycerosomes prepared with the optimized formulation showed good stability, with an average particle size of 153.10 ± 2.69 nm, a zeta potential of â45.73 ± 0.60 mV and an entrapment greater than 75 %. Glycerosomes significantly increased the transdermal delivery of triptolide compared to conventional liposomes. As efficient carriers for the transdermal delivery of drugs, glycerosomes can potentially be used as an alternative to oral triptolide administration
Intelligent Reflecting Surface Assisted Anti-Jamming Communications Based on Reinforcement Learning
Malicious jamming launched by smart jammer, which attacks legitimate
transmissions has been regarded as one of the critical security challenges in
wireless communications. Thus, this paper exploits intelligent reflecting
surface (IRS) to enhance anti-jamming communication performance and mitigate
jamming interference by adjusting the surface reflecting elements at the IRS.
Aiming to enhance the communication performance against smart jammer, an
optimization problem for jointly optimizing power allocation at the base
station (BS) and reflecting beamforming at the IRS is formulated. As the
jamming model and jamming behavior are dynamic and unknown, a win or learn fast
policy hill-climbing (WoLF-PHC) learning approach is proposed to jointly
optimize the anti-jamming power allocation and reflecting beamforming strategy
without the knowledge of the jamming model. Simulation results demonstrate that
the proposed anti-jamming based-learning approach can efficiently improve both
the IRS-assisted system rate and transmission protection level compared with
existing solutions.Comment: This paper appears in the Proceedings of IEEE Global Communications
Conference (GLOBECOM) 2020. A full version appears in IEEE Transactions on
Wireless Communications. arXiv:2004.1253
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