Spontaneous Orientation Polarization of Anisotropic Equivalent Dipoles Harnessed by Entropy Engineering for Ultra‑Thin Electromagnetic Wave Absorber

The synthesis of carbon supporter/nanoscale high-entropy alloys(HEAs)electromagnetic response composites by carbothermal shock method has been identified as an advanced strategy for the collaborative competition engineering of conductive/dielectric genes.Electron migration modes within HEAs as manipulated by the electronegativity,valence electron configurations and molar proportions of constituent elements determine the steady state and efficiency of equivalent dipoles.Herein,enlightened by skin-like effect,a reformative carbothermal shock method using carbonized cellulose paper(CCP)as carbon supporter is used to preserve the oxygencontaining functional groups(O·)of carbonized cellulose fibers(CCF).Nucleation of HEAs and construction of emblematic shell-core CCF/HEAs heterointerfaces are inextricably linked to carbon metabolism induced by O·.Meanwhile,the electron migration mode of switchable electronrich sites promotes the orientation polarization of anisotropic equivalent dipoles.By virtue of the reinforcement strategy,CCP/HEAs composite prepared by 35%molar ratio of Mn element(CCP/HEAs-Mn_(2.15))achieves efficient electromagnetic wave(EMW)absorption of−51.35 dB at an ultra-thin thickness of 1.03 mm.The mechanisms of the resulting dielectric properties of HEAs-based EMW absorbing materials are elucidated by combining theoretical calculations with experimental characterizations,which provide theoretical bases and feasible strategies for the simulation and practical application of electromagnetic functional devices(e.g.,ultra-wideband bandpass filter).

Dual-functional poly(2-methyl-2-oxazoline)/poly(2-(dimethylamine)ethyl methacrylate)mixed brushes with switchable protein adsorption and antibacterial properties

Herein,binary mixed brushes consisting of poly(2-methyl-2-oxazoline)(PMOXA)and poly(2-(dimethylamine)ethyl methacrylate)(PDMAEMA)with different chain lengths were fabricated by successive grafting of NH_(2)-terminated PMOXA and SH-terminated PDMAEMA onto polydopamine-anchored substrates.The mixed-brush coating was characterized by variable-angle spectroscopic ellipsometry,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,zeta potential measurements,water contact angle,and atomic force microscopy.The mixed brushes showed tunable surface charge,wettability,and surface roughness,depending on the degree of PDMAEMA swelling under varying pH and ionic strength(Ⅰ).Then the adsorption behaviors of pepsin,bovine serum albumin(BSA),γ-globulin,and lysozyme,four very different proteins with regard to isoelectric point,on the mixed brushes coating were studied by using fluorescence microscopy and surface plasmon resonance.When the chain length of PDMAEMA was about twice as long as PMOXA,the mixed brushes not only had high adsorption capacity for pepsin,BSA,and y-globulin but also had a desorption efficiency of 86.9%,87.1%,and 93.5%,respectively.It is explained that electrostatic attraction between the protonated PDMAEMA and positively charged acidic proteins(pepsin and BSA,whose isoelectric points were below the pK_(a) of PDMAEMA)would drive the intensive adsorption(at pH 3,I=10^(-3)mol·L^(-1)for pepsin,and pH 5,I=10^(-5)mol·L^(-1)for BSA),while desorption was dominated by the hydrophilic PMOXA when PDMAEMA was shrinking(at pH 7,I=10^(-1)mol·L^(-1)for pepsin,and pH 9,I=10^(-1)mol·L^(-1)for BSA).Furthermore,the isoelectric precipitation led to the adsorption of neutral protein(γ-globulin,whose isoelectric point was near the pK_a of PDMAEMA)at pH 7,I=10^(-5)mol·L^(-1),while electrostatic repulsion and antifouling PMOXA triggered the desorption of y-globulin at pH 3,I-10^(-1)mol·L^(-1).However,alkaline protein(lysozyme,whose isoelectric point was higher than the pK_(a) of PDMAEMA)exhibited slight adsorption on PMOXA/PDMAEMA mixed brushes under test conditions,regardless of whether PMOXA or PDMAEMA occupied the outermost layer.The antibacterial property of the mixed brushes against Escherichia coli was investigated.PMOXA/PDMAEMA mixed brushes showed significant bactericidal activity at pH 3,I=10^(-3)mol·L^(-1),while the rinse of pH 9,I=10^(-1)mol·L^(-1)solution could remove most of the residual bacteria.This work not only enables controlled adsorption of proteins with different isoelectric points but also ensures that the surface of the coating is minimized from bacterial contamination.

Wavelength-interval switchable Brillouin–Raman random fiber laser through Brillouin pump manipulation

A wavelength-interval switchable Brillouin–Raman random fiber laser(BRRFL) based on Brillouin pump(BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity configuration, featuring multiwavelength output with wavelength interval of double Brillouin frequency shifts. Through simultaneously injecting the BP light and its first-order stimulated Brillouin-scattered light into the cavity, the laser output exhibits a wavelength interval of single Brillouin frequency shift. The wavelength-interval switching effect can be manipulated by controlling the power of the first-order stimulated Brillouin scattering light. The experimental results show the multiwavelength output can be switched between double Brillouin frequency shift multiwavelength emission with a broad bandwidth of approximately 60 nm and single Brillouin frequency shift multiwavelength emission of 44 nm. The flexible optically controlled random fiber laser with switchable wavelength interval makes it useful for a wide range of applications and holds significant potential in the field of wavelength-division multiplexing optical communication.

Recent advances in switchable surfactants for heavy oil production:A review

Surfactants are extensively employed in the cold production of heavy oil.However,producing heavy oil emulsions using conventional surfactants poses a challenge to spontaneous demulsification,necessitating the addition of demulsifiers for oil-water separation.This inevitably increases the exploitation cost and environmental pollution risk.Switchable surfactants have garnered much attention due to their dual capabilities of underground heavy oil emulsification and surface demulsification.This study focuses on the fundamental working principles and classification of novel switchable surfactants for oil displacement developed in recent years.It offers a comprehensive overview of the latest advances in the applications of switchable surfactants in the fields of enhanced oil recovery(EOR),oil sand washing,and oil-water separation.Furthermore,it highlights the existing challenges and future development directions of switchable surfactants for heavy oil recovery.

Improved Small Target Detection Method for SAR Image Based on YOLOv7

In order to solve the problems that the current synthetic aperture radar(SAR)image target detection method cannot adapt to targets of different sizes,and the complex image background leads to low detection accuracy,an improved SAR image small target detection method based on YOLOv7 was proposed in this study.The proposed method improved the feature extraction network by using Switchable Around Convolution(SAConv)in the backbone network to help the model capture target information at different scales,thus improving the feature extraction ability for small targets.Based on the attention mechanism,the DyHead module was embedded in the target detection head to reduce the impact of complex background,and better focus on the small targets.In addition,the NWD loss function was introduced and combined with CIoU loss.Compared to the CIoU loss function typically used in YOLOv7,the NWD loss function pays more attention to the processing of small targets,so as to further improve the detection ability of small targets.The experimental results on the HRSID dataset indicate that the proposed method achieved mAP@0.5 and mAP@0.95 scores of 93.5%and 71.5%,respectively.Compared to the baseline model,this represents an increase of 7.2%and 7.6%,respectively.The proposed method can effectively complete the task of SAR image small target detection.

Wide-Angle Scanning Antennas for Millimeter-Wave 5G Applications

The fifth generation(5G)network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range,which is impossible to achieve using current wireless services,including the sub-6 GHz band.In this work,we briefly review several existing designs of millimeter-wave phased arrays for 5G applications,beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one plane.We then move on to array systems that offer two-dimensional(2D)scan capability,which is highly desirable for a majority of 5G applications.Next,in the main body of the paper,we discuss two different strategies for designing scanning arrays,both of which circumvent the use of conventional phase shifters to achieve beam scanning.We note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly;furthermore,alternatives such as active phase shifters,which include radio frequency amplifiers,are both expensive and power-hungry.Given this backdrop,we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave range.The first of these is a Luneburg lens,which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan capability.Next,for second design,we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes,inserted between radiating slots in a waveguide to provide the desired phase shifts for scanning.Finally,we discuss several approaches to enhance the gain of the array by modifying the conventional array configurations.We describe novel techniques for realizing both one-dimensional(1D)and 2D scans by using a reconfigurable metasurface type of panels.

Diode-pumped wavelength-switchable visible Pr^(3+):YLF laser and vortex laser around 670 nm

Here we developed a novel wavelength-switchable visible continuous-wave(CW)Pr^(3+):YLF laser around 670 nm.In single-wavelength laser operations,the maximum output powers of 2.60 W,1.26 W,and 0.21 W,the maximum slope efficiencies of 34.7%,27.3%,and 12.3%were achieved with good beam qualities(M^(2)<1.6)at 670.4 nm,674.2 nm,and 678.9 nm,respectively.Record-high output power(2.6 W)and record-high slope efficiency(34.7%)were achieved for the Pr^(3+):YLF laser operation at 670.4 nm.This is also the first demonstration of longer-wavelength peaks beyond 670 nm in the^(3)P_(1)→^(3)F_(3)transition of Pr^(3+):YLF.In multi-wavelength laser operations,the dual-wavelength lasings,including 670.1/674.8 nm,670.1/679.1 nm,and 675.0/679.4 nm,were obtained by fine adjustment of one/two etalons within the cavity.Furthermore,the triple-wavelength lasings,e.g.672.2/674.2/678.6 nm and 670.4/674.8/679.4 nm,were successfully demonstrated.Moreover,both the first-order vortex lasers(LG_(0)^(+1)and LG_(0)^(-1)modes)at 670.4 nm were obtained by off-axis pumping.

Switchable dry adhesive based on shape memory polymer with hemispherical indenters for transfer printing

Transfer printing based on switchable adhesive is essential for developing unconventional systems,including flexible electronics,stretchable electronics,and micro light-emitting diode(LED)displays.Here we report a design of switchable dry adhesive based on shape memory polymer(SMP)with hemispherical indenters,which offers a continuously tunable and reversible adhesion through the combination of the preloading effect and the thermal actuation of SMP.Experimental and numerical studies reveal the fundamental aspects of design,fabrication,and operation of the switchable dry adhesive.Demonstrations of this adhesive concept in transfer printing of flat objects(e.g.,silicon wafers),three-dimensional(3D)objects(e.g.,stainless steel balls),and rough objects(e.g.,frosted glasses)in two-dimensional(2D)or 3D layouts illustrate its unusual manipulation capabilities in heterogeneous material integration applications.

Stimuli-responsive emulsions:Recent advances and potential applications

Responsive emulsions are the emulsions that can be reversibly switched on-demand between“stable”and“unstable”by environmental stimulus or trigger,which allows a simple and effective adjustment approach to achieve emulsification and demulsification.In recent years,stimuli-responsive emulsions acting as smart soft material are received considerable attention with the advantages of simple manipulation,good reversibility,low cost,easy treatment,and little effect on the system.In this paper,the recent research progress of emulsions that can respond to external stimuli,including pH,light,magnetic field,CO_(2)/N_(2) and dual responsive are reviewed.Also,the potential applications based on responsive emulsion are discussed,such as catalytic reactions,heavy oil recovery,polymer particles synthesis and optical sensor,aiming to summarize the latest achievements and put forward the possible development trends of responsive emulsions.

Switchable diurnal radiative cooling by doped VO_(2)

This paper presents design and simulation of a switchable radiative cooler that exploits phase transition in vanadium di-oxide to turn on and off in response to temperature.The cooler consists of an emitter and a solar reflector separated by a spacer.The emitter and the reflector play a role of emitting energy in mid-infrared and blocking incoming solar energy in ultraviolet to near-infrared regime,respectively.Because of the phase transition of doped vanadium dioxide at room tem-perature,the emitter radiates its thermal energy only when the temperature is above the phase transition temperature.The feasibility of cooling is simulated using real outdoor conditions.We confirme that the switchable cooler can keep a desired temperature,despite change in environmental conditions.

A thermal actuated switchable dry adhesive with high reversibility for transfer printing

Transfer printing based on switchable adhesive that heterogeneously integrates materials is essential to develop novel electronic systems,such as flexible electronics and micro LED displays.Here,we report a robust design of a thermal actuated switchable dry adhesive,which features a stiff sphere embedded in a thermally responsive shape memory polymer(SMP)substrate and encapsulated by an elastomeric membrane.This construct bypasses the unfavorable micro-and nano-fabrication processes and yields an adhesion switchability of over1000 by combining the peel-rate dependent effect of the elastomeric membrane and the thermal actuation of the sub-surface embedded stiff sphere.Experimental and numerical studies reveal the underlying thermal actuated mechanism and provide insights into the design and operation of the switchable adhesive.Demonstrations of this concept in stamps for transfer printing of fragile objects,such as silicon wafers,silicon chips,and inorganic micro-LED chips,onto challenging non-adhesive surfaces illustrate its potential in heterogeneous material integration applications,such as flexible electronics manufacturing and deterministic assembly.

Research progress in SAW filter banks

SAW （Surface Acoustic Wave） filter bank is a single input, single or multi-output device consisting of multi-SAW-filters with input interconnection network or switch circuits, and can be divided into two categories： channelizer （multi-output） and switchable （programmable, single output）. The tbrmer is mainly used in military channelized receiver for spectrum analysis; the latter has wide application in frequency synthesizer and frequency-hopping radar and communication system receiver as anti-jamming filter, and has been widely used in various military electronic equipments ever since the 1970s. Research abroad was done mainly by Americans, few documents on related work done by Japan and Russia are available. Domestic research started in the 1980s, mainly by No. 26 Research Institute, China Electronics Technology Group Co., Institute of Acoustics, Chinese Academy of Sciences, No. 23 and No. 25 Research Institute, China Spaceflight Tech. Group Co. This paper first briefly introduces Chinese and foreign research on SAW filter banks; then discusses research progress in device design, the input interconnection network or switch circuit and miniaturization; and ends in a brief perspective of developing trends in future.

Strategy for Synthesizing Novel Acetamidines as CO_2-Triggered Switchable Surfactants via Acetimidates

In this study, we developed a strategy for using the Scoggins procedure in the synthesis of acetamidines as novel C02-triggered switchable surfactants via acetimidates by effectively tuning the chemical equilibrium. The as-synthesized N'-alkyl-N,Ndiethylacetamidines exhibit excellent CO_2/N_2 switchability and their bicarbonate salts have the ability to emulsify oil-water mixtures.

Selective production of acetol or methyl lactate from cellulose over RuSn catalysts

Designing a catalytic system that could convert cellulose to switchable C3 alcohols or esters with controllable selectivity is highly desired to meet the rapidly changing market demand.Herein,we develop RuSn catalysts with the altering Sn loadings that can achieve acetol formation from cellulose hydrogenation at240℃in presence of H_(2)or yield methyl lactate production from cellulose conversion in methanol and water mixture at 200℃in presence of N_(2).The increased Sn contents from 3%to 6%lead to form different surface sites from Ru_(3)Sn_(7),Ru,and SnO_(x)to Ru_(3)Sn_(7)and SnO_(x).The integrated Ru_(3)Sn_(7),Ru,and SnO_(x)species on 1.5%Ru-3%Sn/SiO_(2)catalyze isomerization,retro-aldol condensation,and hydrogenation individual steps with coordinated reaction rates,resulting in the acetol formation with a high yield of 53.7 C%.Furthermore,the optimum combination of Ru_(3)Sn_(7)and SnO_(x)on 1.5%Ru-6%Sn/SiO_(2)contributes to the isomerization,retro-aldol condensation,dehydration,and 1,2-hydride shift,giving rise to the preferential production of methyl lactate at a 25.1 C%yield.These results illustrate the feasibility of controlling the selective conversion of cellulose to C3 acetol or methyl lactate by devising a tunable catalytic system,which guides the rational design of catalysts for the selective conversion of cellulose.

Jatropha curcas L. oil extracted by switchable solvent N, N-dimethylcyclohexylamine for biodiesel production

Biodiesel, which is a renewable and environmentally friendly fuel, has been studied widely to help remedy increasing environmental problems. One of the key processes of biodiesel production is oil extraction from oilseed materials. Switchable solvents can reversibly change from molecular to ionic solvents under atmospheric CO_2,and can be used for oil extraction. N, N-dimethylcyclohexylamine(DMCHA), a switchable solvent, was used to extract oil from Jatropha curcas L. oil seeds to produce biodiesel. The appropriate extraction conditions were:1:2 ratio of seed mass to DMCHA volume, 0.3–1 mm particle size, 200 r·min-1agitation speed, 60 min extraction time, and 30 °C extraction temperature. The extraction ratio was about 83%. This solvent extracted the oil more efficiently than hexane, and is much less volatile. By bubbling CO_2 under 1 atm and 25 °C for 5 h, the oil was separated, and DMCHA was recovered after releasing CO_2 by bubbling N_2 under 1 atm and 60 °C for 2 h. The residual solvent content in oil was about 1.7%. Selectivity of DMCHA was evaluated by detecting the protein and sugar content in oil. Using the oil with residual solvent to conduct transesterification process, the oil conversion ratio was approximately 99.5%.

Self-supported metal(Fe, Co, Ni)-embedded nitrogen-doping carbon nanorod framework as trifunctional electrode for flexible Zn-air batteries and switchable water electrolysis

To meet the practical demand of wearable/portable electronics, developing high-efficiency and durable multifunctional catalyst and in-situ assembling catalysts into electrodes with flexible features are urgently needed but challenging. Herein, we report a simple route to fabricate bendable multifunctional electrodes by in-situ carbonization of metal ion absorbed polyaniline precursor. Alloy nanoparticles encapsulated in graphite layer are uniformly distributed in the N-doping carbon nanorod skeleton. Profiting from the favorable free-standing structure and the cooperative effect of metallic nanoparticles, graphitic layer and N doped-carbon architecture, the trifunctional electrodes exhibit prominent activities and stability toward HER, OER and ORR. Notably, due to the protection of carbon layer, the electrocatalysts show the reversible catalytic HER/OER properties. The overall water splitting device can continuously work for 12 h under frequent exchanges of cathode and anode. Importantly, the bendable metal air batteries fabricated by self-supported electrode not only displays the outstanding battery performance,achieving a decent peak power density(125 mW cm^(-2)) and exhibiting favorable charge-discharge durability of 22 h, but also holds superb flexible stability. Specially, a lightweight self-driven water splitting unit is demonstrated with stable hydrogen production.

Tunable and Switchable Narrow Bandwidth Semiconductor-Saturable Absorber Mirror Mode-Locked Yb-Doped Fiber Laser Delivering Different Pulse Widths

The wavelength-tunable and switchable narrow bandwidth mode-locking operation is demonstrated in an all fiber laser based on semiconductor-saturable absorber mirror （SESAM）. Two narrow-band fiber Bragg gratings centered at 1029.9nm and 1032nm respectively with a polarization controller inserted between them are used to realize the wavelength switchable between 1029.9nm and 1032nm. The laser delivers different pulse widths of 7.5ps for 1030nm and 20ps for 1032nm. The maximum output power for both could reach -6.5mW at single pulse operation. The output wavelength couM be tuned to about 0.gnm intervals ranging from 1030.2nm to 1031.1 nm and from 1032.15nm to 1033.7nm with the temperature change of the fiber Bragg grating, respectively.

Colorless to black switching with high contrast ratio via the electrochemical process of a hybrid organic-inorganic perovskite

Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy.However,it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states.Herein,we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr_(3),which shows a high integrated contrast ratio of up to 73%from 400 to 800 nm.The perovskite solution can be used as the active layer to assemble the device,showing superior transmittance over the entire visible region in neutral states.By applying an appropriate voltage,the device undergoes reversible switching between colorless and black,which is attributed to the formation of lead and Br_(2)in the redox reaction induced by the electron transfer process in MAPbBr_(3).In addition,the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage.These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices.

A CO_(2)/N_(2)-Responsive Pickering Emulsion Stabilized by Novel Switchable Surface-Active Alumina Nanoparticles

This article reports the development of a novel switchable Pickering emulsion with rapid CO_(2)/N_(2) respon-siveness,which is stabilized using alumina nanoparticles hydrophobized in situ with a trace amount of a switchable superamphiphile via electrostatic interactions.With the introduction of CO_(2) for 30 s,the Pickering emulsion can be spontaneously demulsified with complete phase separation;the emulsion can then be reconstructed in response to N_(2) purging for 10 min followed by homogenization.Moreover,the stable Pickering emulsion can be stored for more than 60 days at room temperature with-out any visible change.The CO_(2)/N_(2)-responsive behavior of the switchable Pickering emulsion is attribu-ted to the reversible desorption/adsorption of the switchable surfactants on the surfaces of the alumina nanoparticles upon the alternative bubbling of CO_(2)or N_(2).Thanks to the simple fabrication of the surfac-tant and the hydrophobization of the alumina nanoparticles,this research has developed an extremely facile and cost-efficient method for preparing a rapidly CO_(2)/N_(2)-responsive switchable Pickering emul-sion.The dosage of the switchable surfactants has been significantly reduced by nearly 1500 times(from 150 to 0.1 mmol·L^(-1))as compared with the dosage used in previous studies.Moreover,the as-prepared CO_(2)/N_(2)-responsive switchable Pickering emulsion is environmentally friendly,mild,and nontoxic;thus,it holds great potential for practical applications with considerable economic and environmental benefits,such as oil transport,fossil fuel production,environmental gases detection,and the encapsulation and release of active ingredients.

Switching CO_(2) Electroreduction Selectivity Between C_(1) and C_(2) Hydrocarbons on Cu Gas-Diffusion Electrodes

Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.