探索传统村落活态再生之道——浙江黄岩乌岩头古村实践为例

基于对传统村落"活态再生"内涵阐释、理论文献的综述,从"文化定桩、功能注入、点穴启动、适用技术"四个方面,提出了对当下我国传统村落保护和利用的新思路和新方法;结合浙江省台州市黄岩区宁溪镇乌岩头古村实践案例,列举了"活态再生"具体改造方法及改造前后对比,体现了规划设计在实施乡村振兴战略过程中的重要引领角色,以期对当前我国各地相同或相似地形、地貌、气候条件和社会经济环境下的传统村落保护和利用工作有所借鉴。

UltrahighQ Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)microwave dielectric ceramics for temperature-stable millimeter-wave dielectric resonator antennas

Microwave dielectric ceramics should be improved to advance mobile communication technologies further.In this study,we prepared Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics with nonstoichiometric Sr^(2+)ratios based on our previously reported SrY_(2)O_(4) microwave dielectric ceramic,which has a low dielectric constant and an ultrahigh quality factor(Q value).The ceramic exhibited a 33.6% higher Q-by-frequency(Q×f)value(Q≈12,500)at x=0.02 than SrY_(2)O_(4).All Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited pure phase structures,although variations in crystal-plane spacings were observed.The ceramics are mainly composed of Sr-O,Y1-O,and Y_(2)-O octahedra,with the temperature coefficient of the resonant frequency(τ_(f))of the ceramic increasing with Y_(2)-O octahedral distortion.The ceramic comprises uniform grains with a homogeneous elemental distribution,clear grain boundaries,and no obvious cavities at x=0.02.The Sr_(1+x)Y_(2)O_(4+x)(x=0-0.04)ceramics exhibited good microwave dielectric properties,with optimal performance observed at x=0.02(dielectric constant(εr)=15.41,Q×f=112,375 GHz,and τ_(f)=-17.44 ppm/℃).The τ_(f) value was reduced to meet the temperaturestability requirements of 5G/6G communication systems by adding CaTiO_(3),with Sr_(1.02)Y_(2)O_(4.02)+2wt% CaTiO_(3) exhibiting ε_(r)=16.14,Q×f=51,004 GHz,andτf=0 ppm/℃.A dielectric resonator antenna prepared using Sr_(1.02)Y_(2)O_(4.02)+2wt%CaTiO_(3) exhibited a central frequency of 26.6 GHz,with a corresponding gain and efficiency of 3.66 dBi and 83.14%,respectively.Consequently,Sr_(1.02)Y_(2)O_(4).02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band(24.5-27.5 GHz)applications.

A Multilayered Magnetoelectric Transmitter with Suppressed Nonlinearity for Portable VLF Communication

Acoustically actuated magnetoelectric(ME)antenna based on the efficient oscillation of magnetic dipoles has recently been considered as a promising solution for portable very-low-frequency communications.However,the severe nonlinear dynamic behavior in the case of strong-field excitation results in insufficient radiation capability and poor communication performance for a conventional ME antenna.In this work,we propose to suppress the nonlinearity of an ME antenna by neutralizing the spring-hardening effect in amorphous Metglas and the spring-softening effect in piezoelectric ceramics through an ME multilayered transmitter(ME-MLTx)design.With a driving voltage of 50 V_(pp)at the resonance frequency of 21.2 kHz,a magnetic flux density as high as 108 fT at a distance of 100 m is produced from a single ME-MLTx.In addition,ME-MLTx performs a decreased mechanical quality factor(Q_(m))less than 40.65,and,thus,a broadened bandwidth of 500 Hz is generated.Finally,a communication link transmitting binary American Standard Code for Information Interchange-coded message is built,which allows for an error-free communication with a distance of 18 m and a data rate of 300 bit/s in the presence of heavy environment noise.The communication distance can be further estimated over 100 m when using a femtotesla-class-inductive magnetic field receiver.The obtained results are believed to bring ME antennas one step closer to being applicable in very-low-frequency communications.

Luminescent ionic lattice occupation and wide tunable emission spectra of La_(2)MgZrO_(6):Bi^(3+),Eu^(3+)double perovskite phosphors for white light LED

La_(2)Mg_(1-x/2)Zr_(1-x/2)O_(6):xBi^(3+)(x=0.01-0.035,abbreviated as LMZ:Bi^(3+))and La_(2-y)Mg_(0.99)Zr_(0.99)O_(6):0.02Bi^(3+),yEu^(3+)(y=0.1-0.11,abbreviated as LMZ:Bi^(3+),Eu^(3+))double-perovskite phosphors were prepared through high-temperature solid-phase method.The emission spectrum of LMZ:xBi^(3+)(x=0.01-0.035)phosphors excited at 353 nm is asymmetric in the range between 375 and 650 nm,showing strong green light.There are two luminescent centers of[Mg1/Zr2-O_(6)]and[Mg2/Zr1-O_(6)]for Bi^(3+)occupation,which were analyzed through different excitation wavelengths,Gaussian fitting peaks,fluorescence decay curves and Rietveld refinement of powder X-ray diffraction data.Through deep study of the luminescent lattices in the LMZ matrix,the green to blue tunning-emission is observed by different excitation wavelengths.In addition,red emission is obtained by co-doping Bi^(3+)/Eu^(3+),and adjustable emission was investigated by changing the content of Eu^(3+)in the co-doped phosphor formulation,so it is converted from green emission to red emission.The above results demonstrate how to tune emission color by co-doping rare earth ions in the double perovskite phosphor,which is attractive for future applications.

Lattice vibrational characteristics,crystal structures and dielectric properties of non-stoichiometric Nd_((1+x))(Mg_(1/2)Sn_(1/2))O_(3) ceramics

Non-stoichiometric Nd_((1+x))(Mg_(1/2)Sn_(1/2))O_(3)(-0.04=x≤0.04,NMS)ceramics were fabricated via a conventional solid-state reaction method.Crystal structures and morphologies were investigated by Xray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The main crystalline phase is monoclinic Nd(Mg_(1/2)Sn_(1/2))O_(3) with a double perovskite structure(P21/n space group)for the NMS system proved by XRD.The sample at x=0.01 has the best crystallinity and evenly distributed crystal grains observed by SEM.The optimum performances(ε_(r)=19.87,Q×f=41840 GHz,f=12.05 GHz)are obtained at x=0.01.Lattice vibrational modes of the Raman spectra were assigned and illustrated,in detail.The dielectric properties obtained by fitting infrared reflectance spectra with the help of four-parameter semi-quantum model are consistent with the calculated values by microscopic polarization and damping coefficients.The reverse translational vibration of the NdeMgO_(6),the F_(5u)^((5)) mode,provides the greatest contribution to the dielectric response.The relationships between crystal structures and dielectric properties were mainly established using lattice vibrational modes as a media.

Significant enhancement of blue photoluminescence intensity of Dy^(3+) modified Sr_(6)Ca_(4)(PO_(4))_(6)F_(2):Eu^(2+) phosphors

Blue-emitting phosphors Sr_(6)Ca_(4)(PO_(4))_(6) F_(2):Eu^(2+)(SCPF:Eu^(2+)),Sr_(6 )Ca_(4)(PO4)6 F_(2):Eu^(2+),Dy^(3+)(SCPF:Eu^(2+),Dy^(3+))and Sr_(6)Ca_(4)(PO4)6 F_(2):Eu^(2+),Dy^(3+),Si^(4+)(SCPF:Eu^(2+),Dy^(3+),Si^(4+)) with apatite structure were successfully synthesized by traditional solid-state reaction under reducing atmosphere.Eu^(2+),Dy^(3+) and Si^(4+)ions occupy the corresponding sites of Sr^(2+),Ca^(2+) and P5+.Strong broad blue photo luminescence band is exhibited in SCPF:Eu^(2+),Dy^(3+) phosphor ranging from 400 to 550 nm centered at 455 nm and Dy^(3+) ions are vital in creating traps.Emission intensity of Eu^(2+),Dy^(3+) co-doped SCPF:0.02 Eu^(2+),0.02 Dy^(3+) is about 1.8 times that of SCPF:0.02 Eu^(2+) and electron trap centers serve as energy transporting media.To further elucidate the formation and effect of the specific defect on the luminescence of SCPF:0.02 Eu^(2+),0.02 Dy^(3+) phosphor,the thermoluminescence properties,decay curves and thermal stability studies were performed while the Si^(4+)-P^(5+) charge compensated pho sphor SCPF:0.02 Eu^(2+),0.02 Dy^(3+),0.02 Si^(4+) was prepared as a contrast.All the results of present work indicate that Dy^(3+) co-doping can obviously enhance photoluminescence intensity of SCPF:0.02 Eu^(2+) by the electron traps generated by non-equivalence replacement of Dy^(3+)-Ca^(2+).

Study on properties of ultra-low dielectric loss mPPO/MTCLT composites prepared by injection molding

A novel category of polyphenylene oxide/high-impact polystyrene(PPO/HIPS)alloy was used as the polymer matrix(abbreviated as mPPO)and loaded with different volume fractions(0,10,20,30,40,50 vol.%)of MgTiO_(3)-Ca_(0.7)La_(0.2)TiO_(3)(abbreviated as MTCLT)ceramics to prepare composites by injection molding.Its micromorphology,density,dielectric,thermal and mechanical properties were analyzed in detail.The experimental results show that the composites possess a compact microstructure because HIPS increases the fluidity of PPO.Due to the excellent dielectric properties of both mPPO and MTCLT,the composites have an extremely low dielectric loss.The realization of the high ceramic filler fraction greatly limits the thermal expansion of the polymer chain by introducing the interphase,so that the coefficient of thermal expansion of the composite material could be as low as 21.8 ppm/°C.At the same time,the presence of ceramic particles could reinforce the mechanical property of the compos-ites.When the ceramic filler fraction is higher than 20 vol.%,the bending strength of the composite material is around 110 MPa.When the ceramic filler fraction is 40 vol.%,the composite possesses the best comprehensive performance.The dielectric constant is 6.81,the dielectric loss is 0.00104,the thermal expansion coefficient is as low as 25.3 ppm/°C,and the bending strength is 110.4 MPa.Due to its excellent properties,this material can be a good candidate in the field of microwave communication.