A broadband circularly polarized (CP) antenna with compact size is proposed. The composed of a loop feeding structure which provides sequential phase, four driven patches, and parasitic patches. are capacitively coupled by the loop, generate one CP mode due to sequentially rotated patches introduced produce additional mode. By combining axial ratio (AR) bandwidth greatly broadened. An prototype fabricated validate simulated results. Experimental results show that achieves broad impedance...

The single Helmholtz resonator obtains only one absorption peak in the broad frequency range, which limits its application reducing noise with multiple spectra. This paper reports an acoustic multi-layer resonance metamaterial, can achieve peaks at given low-frequency targets. Meanwhile, through adjusting structural parameters of resonator, impedance be altered correspondingly to realize multi groups specific frequencies. In this paper, order fine performance frequencies 100 and 400 Hz for a...

In order to manufacture high-speed rubber tracks, it is urgent develop natural composites with excellent thermal and mechanical properties. this paper, was filled milled carbon fiber (CF) which synergistically modified by dopamine silane coupling agent (SCA), including KH560, KH570 KH590. Firstly, the polydopamine initial platform formed on CF surface through self-polymerization of dopamine. Subsequently, SCA grafted improve interface properties between filler matrix. Eventually, co-modified...

This paper presents a multi-Helmholtz unit series–parallel acoustic metamaterial with segmented noise control effect designed by taking advantage of the adjustable frequency band an metamaterial, aiming to change main spectrum characteristics under different driving conditions military equipment such as tanks. Based on transfer matrix method, theoretical model that can predict hybrid structure multiple Helmholtz resonator (HR) units is established, and its feasibility verified through finite...

In this study, polysaccharides were extracted at a rate of 87.5% ± 1.5% from native dandelion roots, and the root (DRPs) then chemically modified to obtain sulfated (SDRPs) with degree substitution 1.49 0.07. The effects modification conditions, physicochemical characterizations, structural characteristics, antioxidant properties, hypoglycemic activity, proliferative on probiotics DRP derivatives further investigated. Results showed that optimum conditions for sulfation DRPs included...

Novel acoustic absorbers were fabricated by the compression and microperforation of porous metal, which aimed to develop practical for noise reduction. Sound absorbing coefficients five investigated measured AWA6128A detector according standing wave method, their trends consistent with normal sound absorption principle metal absorber that microperforated panel absorber. The results proved same length cavity, performance could be obviously improved microperforation. When cavity was 20 mm,...

Rubber is widely applied in the field of electrical engineering due to its high elasticity. However, poor thermal conductivity can cause localized overheating and eventual failure. This issue be addressed through adding fillers with conductivity. In this study, natural rubber selected as matrix, while braided carbon fiber (B-CF), known for excellent conductivity, serves reinforcing phase. research defines cubic Bessel curves, establishes a curvilinear coordinate system, examines orthogonal...

An acoustic metamaterial absorber of parallel–connection square Helmholtz resonators is proposed in this study, and its sound absorption coefficients are optimized to reduce the noise for given conditions factory. A two–dimensional equivalent simulation model built obtain initial value parameters a three–dimensional finite element constructed simulate performance cell, which aims improve research efficiency. The optimal cells obtained through particle swarm optimization algorithm,...

Acoustic metamaterials based on Helmholtz resonance have perfect sound absorption characteristics with the subwavelength size, but bandwidth is narrow, which limits practical applications for noise control broadband. On basis of Fabry-Perot principle, a novel absorber acoustic metamaterial by parallel connection multiple spiral chambers (abbreviated as MSC-AM) proposed and investigated in this research. Through theoretical modeling, finite element simulation, sample preparation experimental...

To achieve the broadband sound absorption at low frequencies within a limited space, an optimal design of joint simulation method incorporating finite element and cuckoo search algorithm was proposed. An acoustic metamaterial multiple parallel hexagonal Helmholtz resonators with sub-wavelength dimensions designed optimized in this research. First, initial geometric parameters investigated metamaterials were confirmed according to actual noise reduction requirements reduce optimization burden...

To improve the mechanical properties of aramid fiber (AF) reinforced epoxy resin (EP) composites without damaging strength AF body, in this paper, poly(ethyleneimine) (PEI) and aminoated carbon nanotubes (NH2-CNTs) were successfully deposited on surface layer by using poly(dopamine) (PDA) as initial layer. The modified fibers PDA-AF, PEI-PDA-AF, NH2-CNTs-PEI-PDA-AF prepared. microstructure chemical composition at different modification stages systematically characterized. interfacial...

In order to improve the interface and mechanical properties of aramid fiber (AF)-reinforced epoxy resin (EP) composites (AF/EPs), surface modification AF was carried out with atmospheric pressure air plasma, effects plasma treatment time discharge power on AF/EPs were investigated. The results show that, when 10 min 400 W, showed best effect. Compared unmodified material, total content active groups increased by 82.4%; contact angle between EP decreased 20%; interfacial energy work adhesion...

Al-PTFE (aluminum-polytetrafluoroethene) is regarded as one of the most promising reactive materials (RMs). In this work, Ni (Nickel) was added to composites for purpose improving energy density and damage effect. To investigate thermal behavior, mechanical properties reaction characteristics Al-Ni-PTFE composites, an mixture Al-Ni were prepared by ultrasonic mixing. Six types specimens with different component mass ratios molding sintering. Simultaneous analysis experiments carried out...

Magnesium hydride (MgH2) was doped into PTFE/Al to improve the energy release characteristics of material system and strive for better application in military engineering. Five types PTFE/Al/MgH2 reactive materials with different MgH2 content were prepared by molding sintering method. The dynamic mechanical properties studied performing split-Hopkinson pressure bar (SHPB) tests scanning electron microscope characterizations. thermal behavior, reaction energy, process mechanism systematically...

Polygonatum cyrtonema Hua polysaccharides (PCP) have beneficial effects on lipid metabolism and oxidative stress. Here, PCP extraction was optimized using response surface methodology (RSM), the antioxidant lipid-lowering of its main component, PCP1, were evaluated in vitro. The maximum yield 11.05% at an temperature 72°C, liquid-to-solid ratio 21, time 96 min, two rounds. PCP1 purified by column chromatography showed significant scavenging activity against 1,1-diphenyl-2-picrylhydrazyl...

Increasing absorption efficiency and decreasing total thickness of the acoustic absorber is favorable to promote its practical application. Four compressed porous metals with compression ratios 0%, 30%, 60%, 90% were prepared assemble four-layer gradient metals, which aimed develop high-efficiency thin thickness. Through deriving structural parameters thickness, porosity, static flow resistivity for theoretical models sound coefficients constructed through transfer matrix method according...