In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are...In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are based on the concept of ice nucleation active surface site density (<i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;">). It is usually assumed that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> is independent of time and aerosol size distribution, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> that the surface properties of aerosols of the same species do not vary with size. However, the independence of </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> on aerosol size for every species has been questioned. This study presents the results of ice nucleation processes of ATD laboratory-generated aerosol (particle diameters of 0 - 3 μm). Ice nucleation in the condensation mode was performed in a Dynamic Filter Processing Cham- ber at temperatures of </span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;">18<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and </span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span><span style="font-family:Verdana;">22<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, with a saturation ratio with respect to water of 1.02. Results show that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> increased by lowering the nucleation temperature, and was also dependent on the particle size. The </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> of particles collected on the filters, after a 0.5 μm D</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> cut-off cyclone, resulted statistically higher with respect to the values obtained from the particles collected on total filters. The results obtained suggest the need for further investigation of </span><i><span style="font-family:Verdana;">n</span></i><sub><span style="font-family:Verdana;">s</span></sub><span style="font-family:Verdana;"> dependence of same composition aerosol particles with a view to support weather and climate predictions.</span></span></span>展开更多
In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assiste...In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.展开更多
In contrast to the conventional etching that makes nanoparticles rounder and our previous sharpening etching mode that causes serrated edges,here,we developed a new boring etching mode that targets the faces of Au nan...In contrast to the conventional etching that makes nanoparticles rounder and our previous sharpening etching mode that causes serrated edges,here,we developed a new boring etching mode that targets the faces of Au nanoplates to make holes.The critical factors are the pre-incubation step with the ligand 2-mercapto-5-benzimidazolecarboxylic acid(MBIA)and the subsequent removal of excess ligands in the solution.Thus,etching is focused onto the few sites with initial loss of ligands,which cannot be quickly replaced.The choice of ligand MBIA is also of importance,as it carries negative charge and repels each other.Its inability of forming a dense layer probably plays a critical role in the site-selectivity for faces,because ligands at the higher curvature edges and corners are expected to have less repulsion.The etching results from the comproportionation reaction between Au3+and Au0 in the nanoplates,where Br-coordination to Au and the extra stabilization from cetyltrimethylammonium bromide(CTAB)are essential.We believe that the ability of boring holes is an important tool for future synthetic designs.展开更多
ZrCo alloy holds great promise for hydrogen isotope storage,yet its susceptibility to poisoning by impurity gases,especially CO,poses a challenge.This susceptibility arises due to the electron acceptor nature of the s...ZrCo alloy holds great promise for hydrogen isotope storage,yet its susceptibility to poisoning by impurity gases,especially CO,poses a challenge.This susceptibility arises due to the electron acceptor nature of the surface Co element and the formation of the d-πfeedback bond,thereby impeding the surface hydrogen dissociation.Accordingly,we propose a novel local activity modulation strategy,where substituent elements are sacrificed to protect the active Co sites for hydrogen dissociation.Considering CO absorption capacity,solid solubility,and hydrogen affinity,we selected V,Cr,and Mn as microalloying elements and successfully prepared the single-phase ZrCo_(0.97)(VCrMn)_(0.03)alloy.Compared to pristine ZrCo,ZrCo_(0.97)(VCrMn)_(0.03)demonstrates significantly enhanced poisoning resistance.Notably,the hydrogenation kinetics of ZrCo_(0.97)(VCrMn)_(0.03)is 2.4 times higher than that of ZrCo in 4 bar H_(2)+5000 ppm CO.Interestingly,the controllable in situ formation of the Co_(2)C phase shell structure during cycling further safeguards the surface reactivity of ZrCo_(0.97)(VCrMn)_(0.03).Consequently,its capacity retention ratio after 25 cycles has been improved to 74.5%from 55.3%of the ZrCo alloy.These findings suggest that micro-alloying engineering could be a promising strategy for surface activity modulation to enhance the anti-poisoning properties of hydrogen storage materials.展开更多
This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable int...This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable intelligent surfaces(DARISs)as-sisted physical layer security(PLS)scheme denoted by DARISs-PLS to protect the secrecy message trans-mission.We formulate a secrecy rate maximization problem for the proposed DARISs-PLS scheme by considering a power budget constraint for the two ac-tive reconfigurable intelligent surfaces(ARISs)and AP.To address the formulated optimization problem,we jointly optimize the reflecting coefficients for the two ARISs and the beamforming at the AP in an it-erative manner by applying Dinkelbach based alter-nating optimization(AO)algorithm and a customized iterative algorithm together with the semidefinite re-laxation(SDR).Numerical results reveal that the pro-posed DARISs-PLS scheme outperforms the dou-ble passive reconfigurable intelligent surfaces-assisted PLS method(DPRISs-PLS)and single ARIS-assisted PLS method(SARIS-PLS)in terms of the secrecy rate.展开更多
This paper explores a UAV-mounted active Reconfigurable Intelligent Surface(aRIS)network designed to enhance secure downlink communication for multiple users while mitigating the impact of multiple Eavesdroppers(EVs)....This paper explores a UAV-mounted active Reconfigurable Intelligent Surface(aRIS)network designed to enhance secure downlink communication for multiple users while mitigating the impact of multiple Eavesdroppers(EVs).The focus is on optimizing the UAV’s trajectory,the Base Station’s(BS)transmit beamforming,and the power-Amplified Programmable Reflecting Elements(APREs)of the aRIS to maximize the minimum secrecy rate in the presence of EVs.This is a complex non-convex problem due to multiple optimization variables,high-dimensional matrix operations,and log-determinant objective functions,which makes it challenging to solve.Hence,a Successive Convex Approximation(SCA)-based optimization strategy is developed to efficiently solve the subproblems related to the UAV’s trajectory,aRIS’s APREs,and BS’s beamforming.By leveraging slack variables and approximation techniques,we solve the nonconvex subproblems by a sequence of convex subproblems.Simulation results demonstrate that the proposed UAV-aRIS network significantly outperforms its passive RIS counterpart in improving communication security,highlighting the effectiveness of the optimization strategy.展开更多
CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programined reaction. The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones. Model studie...CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programined reaction. The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones. Model studies were performed to better understand the oxidation state, reactivities and stabilities of partially oxidized Pd surfaces under CO oxidation reaction condi tions using an in situ infrared reflection absorption spectrometer （IRAS）. Three O/Pd（100） model surfaces, chemisorbed oxygen covered surface, surface oxide and bulk-like surface oxide, were prepared and characterized by low-energy electron diffraction （LEED） and Auger electron spectroscopy （AES）. The present work demonstrates that the oxidized palladium surface is less active for CO oxidation than the metallic surface, and is unstable under the reaction conditions with sufficient CO.展开更多
Discovering new methods and principles in the inequivalent growth of equivalent facets is of great significance for going beyond symmetrical nanocrystals and for out-of-box exploration. In this work, we demonstrate th...Discovering new methods and principles in the inequivalent growth of equivalent facets is of great significance for going beyond symmetrical nanocrystals and for out-of-box exploration. In this work, we demonstrate that a middle ground exists between the traditional weak ligands and the strong ligands with unusual growth modes. By modifying the seed concentration during the growth of pentagonal Au nanorods, the typical weak ligand cetyltrimethylammonium bromide(CTAB) is made strong, leading to notches of restricted growth and even the active surface growth mode. In-depth investigation in the link between growth kinetics and ligand packing reveals the principle of their interplay —— that the on-off dynamics of the ligands only allows for a certain limit of materials deposition rate. Beyond this limit, the growth materials build up and are then diverted elsewhere, leading to inequivalent growth. The fact that a freshly grown surface has few ligands promotes the active surface growth, focusing the growth materials onto a few sites. We believe that the knowhow of interfering ligand packing via growth kinetics would offer a powerful tool of synthetic control, where the facet-and curvature-dependent ligand packing is expected to be useful synthetic handles.展开更多
Passive surface-wave utilization has been intensively studied as a means of compensating for the short-age of low-frequency information in active surface-wave measurement, In general, passive surface-wave methods cann...Passive surface-wave utilization has been intensively studied as a means of compensating for the short-age of low-frequency information in active surface-wave measurement, In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range, To reduce the amount of field work, we pro-pose a strategy for a high-frequency passive surface-wave survey that imposes active sources during con-tinuous passive surface-wave observation; we call our strategy ＂mixed-source surface-wave （MSW） measurement,＂ Short-duration （within 10 min） passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels： namely, inside a school, along a road, and along a railway, Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation, The spatial autocorrelation （SPAC） method and the multichannel analysis of passive surface waves （MAPS） method based on cross-correlations were performed on the recorded time sequences, The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis, We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement,展开更多
SrTiO_3 nano-crystal samples with floccule or flake crystal morphology,which were indexed as a perovskite-type crystal structure based on the results of XRD and TEM,were successfully prepared by one-step liquid reacti...SrTiO_3 nano-crystal samples with floccule or flake crystal morphology,which were indexed as a perovskite-type crystal structure based on the results of XRD and TEM,were successfully prepared by one-step liquid reaction method.And the growth mechanism of the SrTiO_3 nano-crystals under the liquid condition with/without adding the surface active agent was investigated.It was found that adding the surface active agent contributes to the processing in which the ions gathering bodies transit to a more stable phase through the chemical reaction and form the flake SrTiO_3 nano-crystals.展开更多
Five new zwitterionic surfactants with long chain alkyl betaine structure incorporated with hydroxylpropyl group have been synthesized. Their structures were identified by elemental analysis, IR (HNMR)-H-1, and (CNMR)...Five new zwitterionic surfactants with long chain alkyl betaine structure incorporated with hydroxylpropyl group have been synthesized. Their structures were identified by elemental analysis, IR (HNMR)-H-1, and (CNMR)-C-13. Surface tension experiments showed that these surfactants have higher surface activity than those without hydroxypropyl group. The values of CMC and gamma(CMC) of these surfactants have been determined.展开更多
The oxidation heat of coal is the direct reason leading to coal spontaneous combustion. When coal is exposed in oxygen atmosphere, the physical adsorption and chemisorption happened, and then which resulting chemical ...The oxidation heat of coal is the direct reason leading to coal spontaneous combustion. When coal is exposed in oxygen atmosphere, the physical adsorption and chemisorption happened, and then which resulting chemical reaction followed heat between coal and oxygen. Owing to the complexity and uncertain of molecular structure of coal,it was only reduced that bridge bonds, side chains and O 2 containing functional groups in coal may be prone to oxidation in last year, but not to deeply investigate into the structures and the type of the active radicals. In this paper, according to the last achievements in coal structure research, the hypomethylether bond, hypoalkyl bond of α carbon atom with hydroxyl and α carbon atom with hypomethy side chain and hypomethyl bonds linking up two aromatic hydrocarbon in bridge bonds, and methoxy,aldehyde and alkyls of α carbon atom with hydroxy in side bonds are inferred to be free radical easily to lead to oxidize coal under the ambient temperature and pressure. The order from strong to weak of oxide activation of the seven surface active groups is aldehyde side chains, hypomethylether bonds, hypoalkyl bonds of α carbon atom with hydroxyl, hypoalkyl bonds of α carbon atom with hypomethyl, hypomethyl bonds linking up two aromatic hydrocarbon,methoxy, alkyls side chains of α carbon atom with hydroxyl. Because of the two unsaturated molecular tracks of O 2, unpaired electron clouds of the part of surface active groups of coal enter molecular tracks of O 2 to lead to chemisorb on the conjugate effect and induced effect of surface active groups, and then chemical reaction followed heat happens in them. On the basis of change of bond energy, weighted average method is adopted to count the reaction heat value of each mol CO,CO 2 and H 2O. The property of coal spontaneous combustion is different for the different number and oxidability of the active structure in the coal resulting in the different oxidation heat.展开更多
In this paper,we propose an active reconfigurable intelligent surface(RIS)enabled hybrid relaying scheme for a multi-antenna wireless powered communication network(WPCN),where the active RIS is employed to assist both...In this paper,we propose an active reconfigurable intelligent surface(RIS)enabled hybrid relaying scheme for a multi-antenna wireless powered communication network(WPCN),where the active RIS is employed to assist both wireless energy transfer(WET)from the power station(PS)to energyconstrained users and wireless information transmission(WIT)from users to the receiving station(RS).For further performance enhancement,we propose to employ both transmit beamforming at the PS and receive beamforming at the RS.We formulate a sumrate maximization problem by jointly optimizing the RIS phase shifts and amplitude reflection coefficients for both the WET and the WIT,transmit and receive beamforming vectors,and network resource allocation.To solve this non-convex problem,we propose an efficient alternating optimization algorithm with the linear minimum mean squared error criterion,semidefinite relaxation(SDR)and successive convex approximation techniques.Specifically,the tightness of applying the SDR is proved.Simulation results demonstrate that our proposed scheme with 10 reflecting elements(REs)and 4 antennas can achieve 17.78%and 415.48%performance gains compared to the single-antenna scheme with 10 REs and passive RIS scheme with 100 REs,respectively.展开更多
（2-acrylamido） ethyl tetradecyl dimethylammonium bromide （AMC14AB） was polymerized in aqueous solu- tion to form the homopolymer P（AMC14AB）. The physicochemical properties of P（AMC14AB） in aqueous solution wer...（2-acrylamido） ethyl tetradecyl dimethylammonium bromide （AMC14AB） was polymerized in aqueous solu- tion to form the homopolymer P（AMC14AB）. The physicochemical properties of P（AMC14AB） in aqueous solution were mainly studied with fluorescent probe method, surface tension measurement and conductom- etry. The experimental results show that the aggregation morphology of P（AMC14AB） in aqueous solution is unimolecular micelle as expected. Being different from conventional multimolecular micelle systems, the unimolecular micelle system of P（AMC14AB） not only shows critical micellar concentration （CMC=0）, （i.e. once added to pure water, the surface tension decreases immediately in spite how small the density is）, but also the surface tension stays almost the same with the concentration increasing. That is to say, there is no mutational point on the relationship curve between surface tension and concentration. Furthermore, the unimolecular micelle system of P（AMC14AB） has no Krafft temperature, i.e. at any temperature, so long as it is dissolved in water, the unimolecular micelles will form. Besides this, for the solubilization of hydrophobic organic substances, the unimolecular micelle system of P（AMC14AB） is obviously different from the common multimolecular micelle system, having no turning point on the relationship curve between toluene solubi- lizaion amount and P（AMC14AB） concentration, and the solubilizing ability of the unimolecular-micelle system of P（AMC14AB） for hydrophobic organic substances is much higher than that of the conventional multimolecular micelle solutions of common surfactants, such as centyl trimethyl ammonium bromide.展开更多
Active intelligent reflecting surface(IRS)is a novel and promising technology that is able to overcome the multiplicative fading introduced by passive IRS.In this paper,we consider the application of active IRS to non...Active intelligent reflecting surface(IRS)is a novel and promising technology that is able to overcome the multiplicative fading introduced by passive IRS.In this paper,we consider the application of active IRS to nonorthogonalmultiple access(NOMA)networks,where the incident signals are amplified actively through integrating amplifier to reflecting elements.More specifically,the performance of active/passive IRS-NOMA networks is investigated over large and small-scale fading channels.Aiming to characterize the performance of active IRSNOMA networks,the exact and asymptotic expressions of outage probability for a couple of users,i.e.,near-end user n and far-end user m are derived by exploiting a 1-bit coding scheme.Based on approximated analyses,the diversity orders of user n and user m are obtained for active IRS-NOMA.In addition,the system throughput of active IRS-NOMA is discussed in the delay-sensitive transmission.The simulation results are carried out to verify that:i)The outage behaviors of active IRS-NOMAnetworks are superior to that of passive IRS-NOMAnetworks;ii)As the reflection amplitude factors increase,the active IRS-NOMAnetworks are capable of furnishing the enhanced outage performance;and iii)The active IRS-NOMA has a larger system throughput than passive IRS-NOMA and conventional communications.展开更多
A novel surface active monomer （surfmer） containing poly（ethylene glycol） chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP （N-vinylpyrrolidone） and with ...A novel surface active monomer （surfmer） containing poly（ethylene glycol） chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP （N-vinylpyrrolidone） and with NVP and VEP （5-tert-butylperoxy-5-methyl-2-hexene-3-yne monomer） led to formation of corresponding surface-active copolymers. The capability of application of resulted copolymers as surface active macroinitiators of emulsion polymerization of styrene and as components of polymeric scaffolds was investigated.展开更多
Synthesis and surface active properties of the oxyethylenated fatty alcohol 2-hydroxypropyl sulfonates were investigated.Of all surface active compounds studied,those with a 2-hydroxypropyl (HP) moiety in the molecule...Synthesis and surface active properties of the oxyethylenated fatty alcohol 2-hydroxypropyl sulfonates were investigated.Of all surface active compounds studied,those with a 2-hydroxypropyl (HP) moiety in the molecule are more surface-active than the corresponding compounds without it.展开更多
An experimental double-layer active frequency-selective surface（AFSS） for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface（FSS）, a PIN diodes arra...An experimental double-layer active frequency-selective surface（AFSS） for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface（FSS）, a PIN diodes array, and a DC bias network. The AFSS elements incorporating switchable PIN diodes are discussed. By means of controlling the DC bias network, it is possible to switch the frequency response for reflecting and transmitting. Measured and simulated data validate that when the incidence angle varies from 0°to 30° the AFSS produces more than-11.5 dB isolation across6–18 GHz when forward biased. The insertion loss（IL） is less than 0.5 dB across 10–11 GHz when reverse biased.展开更多
Mesoporous carbon supports mitigate platinum(Pt)sulfonic poisoning through nanopore-confined Pt deposition,yet their morphological impacts on oxygen transport remain unclear.This study integrates carbon support morpho...Mesoporous carbon supports mitigate platinum(Pt)sulfonic poisoning through nanopore-confined Pt deposition,yet their morphological impacts on oxygen transport remain unclear.This study integrates carbon support morphology simulation with an enhanced agglomerate model to establish a mathematical framework elucidating pore evolution,Pt utilization,and oxygen transport in catalyst layers.Results demonstrate dominant local mass transport resistance governed by three factors:(1)active site density dictating oxygen flux;(2)ionomer film thickness defining shortest transport path;(3)ionomer-to-Pt surface area ratio modulating practical pathway length.At low ionomer-to-carbon(I/C)ratios,limited active sites elevate resistance(Factor 1 dominant).Higher I/C ratios improve the ionomer coverage but eventually thicken ionomer films,degrading transport(Factors 2–3 dominant).The results indicate that larger carbon particles result in a net increase in local transport resistance by reducing external surface area and increasing ionomer thickness.As the proportion of Pt situated in nanopores or the Pt mass fraction increases,elevated Pt density inside the nanopores exacerbates pore blockage.This leads to the increased transport resistance by reducing active sites,and increasing ionomer thickness and surface area.Lower Pt loading linearly intensifies oxygen flux resistance.The model underscores the necessity to optimize support morphology,Pt distribution,and ionomer content to prevent pore blockage while balancing catalytic activity and transport efficiency.These insights provide a systematic approach for designing high-performance mesoporous carbon catalysts.展开更多
A novel C/Pb composite has been successfully prepared by electmless plating to reduce the hydrogenevolution and achieve the high reversibility of the anode of lead-carbon battery （LCB）. The depositedlead on the surf...A novel C/Pb composite has been successfully prepared by electmless plating to reduce the hydrogenevolution and achieve the high reversibility of the anode of lead-carbon battery （LCB）. The depositedlead on the surface of C/Pb composite was found to be uniform and adherent to carbon surface. Becauselead has been stuck on the surface of C/Pb composite, the embedded structure suppresses the hydrogenevolution of lead-carbon anode and strengthens the connection between carbon additive and sponge lead.Compared with the blank anode, the lead-carbon anode with C/Pb composite displays excellent charge-discharge reversibility, which is attributed to the good connection between carbon additives and leadthat has been stuck on the surface of C/Pb composite during the preparation process. The addition of CIPb composite maintains a solid anode structure with high specific surface area and power volume, andthereby, it plays a significant role in the highly reversible lead-carbon anode.展开更多
文摘In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are based on the concept of ice nucleation active surface site density (<i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;">). It is usually assumed that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> is independent of time and aerosol size distribution, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> that the surface properties of aerosols of the same species do not vary with size. However, the independence of </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> on aerosol size for every species has been questioned. This study presents the results of ice nucleation processes of ATD laboratory-generated aerosol (particle diameters of 0 - 3 μm). Ice nucleation in the condensation mode was performed in a Dynamic Filter Processing Cham- ber at temperatures of </span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;">18<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and </span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span><span style="font-family:Verdana;">22<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, with a saturation ratio with respect to water of 1.02. Results show that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> increased by lowering the nucleation temperature, and was also dependent on the particle size. The </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> of particles collected on the filters, after a 0.5 μm D</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> cut-off cyclone, resulted statistically higher with respect to the values obtained from the particles collected on total filters. The results obtained suggest the need for further investigation of </span><i><span style="font-family:Verdana;">n</span></i><sub><span style="font-family:Verdana;">s</span></sub><span style="font-family:Verdana;"> dependence of same composition aerosol particles with a view to support weather and climate predictions.</span></span></span>
基金supported in part by the National Natural Science Foundation of China under Grant 62071253,Grant 62371252 and Grant 62271268in part by the Jiangsu Provincial Key Research and Development Program under Grant BE2022800in part by the Jiangsu Provincial 333 Talent Project.
文摘In this paper,we examine an illegal wireless communication network consisting of an illegal user receiving illegal signals from an illegal station and propose an active reconfigurable intelligent surface(ARIS)-assisted multi-antenna jamming(MAJ)scheme denoted by ARIS-MAJ to interfere with the illegal signal transmission.In order to strike a balance between the jamming performance and the energy consumption,we consider a so-called jamming energy efficiency(JEE)which is defined as the ratio of achievable rate reduced by the jamming system to the corresponding power consumption.We formulate an optimization problem to maximize the JEE for the proposed ARIS-MAJ scheme by jointly optimizing the jammer’s beamforming vector and ARIS’s reflecting coefficients under the constraint that the jamming power received at the illegal user is lower than the illegal user’s detection threshold.To address the non-convex optimization problem,we propose the Dinkelbach-based alternating optimization(AO)algorithm by applying the semidefinite relaxation(SDR)algorithm with Gaussian randomization method.Numerical results validate that the proposed ARIS-MAJ scheme outperforms the passive reconfigurable intelligent surface(PRIS)-assisted multi-antenna jamming(PRIS-MAJ)scheme and the conventional multiantenna jamming scheme without RIS(NRIS-MAJ)in terms of the JEE.
基金the financial support from the National Natural Science Foundation of China(Nos.91956109,92356310,and 22075137)Zhejiang Provincial Natural Science Foundation of China:Major Program(No.2022XHSJJ002)+1 种基金Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(No.TD2022004)Foundation of Westlake University.
文摘In contrast to the conventional etching that makes nanoparticles rounder and our previous sharpening etching mode that causes serrated edges,here,we developed a new boring etching mode that targets the faces of Au nanoplates to make holes.The critical factors are the pre-incubation step with the ligand 2-mercapto-5-benzimidazolecarboxylic acid(MBIA)and the subsequent removal of excess ligands in the solution.Thus,etching is focused onto the few sites with initial loss of ligands,which cannot be quickly replaced.The choice of ligand MBIA is also of importance,as it carries negative charge and repels each other.Its inability of forming a dense layer probably plays a critical role in the site-selectivity for faces,because ligands at the higher curvature edges and corners are expected to have less repulsion.The etching results from the comproportionation reaction between Au3+and Au0 in the nanoplates,where Br-coordination to Au and the extra stabilization from cetyltrimethylammonium bromide(CTAB)are essential.We believe that the ability of boring holes is an important tool for future synthetic designs.
基金financially supported by the National Key Research and Development Program of China(2022YFE03170002)the National Natural Science Foundation of China(52071286,U203020852171223)。
文摘ZrCo alloy holds great promise for hydrogen isotope storage,yet its susceptibility to poisoning by impurity gases,especially CO,poses a challenge.This susceptibility arises due to the electron acceptor nature of the surface Co element and the formation of the d-πfeedback bond,thereby impeding the surface hydrogen dissociation.Accordingly,we propose a novel local activity modulation strategy,where substituent elements are sacrificed to protect the active Co sites for hydrogen dissociation.Considering CO absorption capacity,solid solubility,and hydrogen affinity,we selected V,Cr,and Mn as microalloying elements and successfully prepared the single-phase ZrCo_(0.97)(VCrMn)_(0.03)alloy.Compared to pristine ZrCo,ZrCo_(0.97)(VCrMn)_(0.03)demonstrates significantly enhanced poisoning resistance.Notably,the hydrogenation kinetics of ZrCo_(0.97)(VCrMn)_(0.03)is 2.4 times higher than that of ZrCo in 4 bar H_(2)+5000 ppm CO.Interestingly,the controllable in situ formation of the Co_(2)C phase shell structure during cycling further safeguards the surface reactivity of ZrCo_(0.97)(VCrMn)_(0.03).Consequently,its capacity retention ratio after 25 cycles has been improved to 74.5%from 55.3%of the ZrCo alloy.These findings suggest that micro-alloying engineering could be a promising strategy for surface activity modulation to enhance the anti-poisoning properties of hydrogen storage materials.
基金supported in part by the National Natural Science Foundation of China under Grant 62071253,Grant 62371252 and Grant 62271268in part by the Jiangsu Provincial Key Research and Development Program under Grant BE2022800in part by the Jiangsu Provincial 333 Talent Project.
文摘This paper considers a multi-antenna ac-cess point(AP)transmitting secrecy message to a single-antenna user in the presence of a single-antenna illegal eavesdropper(Eve)and proposes a double ac-tive reconfigurable intelligent surfaces(DARISs)as-sisted physical layer security(PLS)scheme denoted by DARISs-PLS to protect the secrecy message trans-mission.We formulate a secrecy rate maximization problem for the proposed DARISs-PLS scheme by considering a power budget constraint for the two ac-tive reconfigurable intelligent surfaces(ARISs)and AP.To address the formulated optimization problem,we jointly optimize the reflecting coefficients for the two ARISs and the beamforming at the AP in an it-erative manner by applying Dinkelbach based alter-nating optimization(AO)algorithm and a customized iterative algorithm together with the semidefinite re-laxation(SDR).Numerical results reveal that the pro-posed DARISs-PLS scheme outperforms the dou-ble passive reconfigurable intelligent surfaces-assisted PLS method(DPRISs-PLS)and single ARIS-assisted PLS method(SARIS-PLS)in terms of the secrecy rate.
基金co-supported by Technology Key Project of Guangdong Province,China(No.HZJBGS-2021001)the Shanghai Sailing Scholar,China(No.23YF1412700)+1 种基金the National Natural Science Foundation of China(No.61901254)the Shanghai Technical Service Computing Center of Science and Engineering,Shanghai University,China.
文摘This paper explores a UAV-mounted active Reconfigurable Intelligent Surface(aRIS)network designed to enhance secure downlink communication for multiple users while mitigating the impact of multiple Eavesdroppers(EVs).The focus is on optimizing the UAV’s trajectory,the Base Station’s(BS)transmit beamforming,and the power-Amplified Programmable Reflecting Elements(APREs)of the aRIS to maximize the minimum secrecy rate in the presence of EVs.This is a complex non-convex problem due to multiple optimization variables,high-dimensional matrix operations,and log-determinant objective functions,which makes it challenging to solve.Hence,a Successive Convex Approximation(SCA)-based optimization strategy is developed to efficiently solve the subproblems related to the UAV’s trajectory,aRIS’s APREs,and BS’s beamforming.By leveraging slack variables and approximation techniques,we solve the nonconvex subproblems by a sequence of convex subproblems.Simulation results demonstrate that the proposed UAV-aRIS network significantly outperforms its passive RIS counterpart in improving communication security,highlighting the effectiveness of the optimization strategy.
基金supported by the National Basic Research Program of China(2010CB732303,2013CB933102)the Major Project of Chinese Ministry of Education(309019)+2 种基金the National Natural Science Foundation of China(21033006,21073149,21273178)the Program for Changjiang Scholars and Innovative Research Team in University(IRT1036)the Ph.D Programs foundation of Chinese Ministry of Education(20110121110010)
文摘CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programined reaction. The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones. Model studies were performed to better understand the oxidation state, reactivities and stabilities of partially oxidized Pd surfaces under CO oxidation reaction condi tions using an in situ infrared reflection absorption spectrometer （IRAS）. Three O/Pd（100） model surfaces, chemisorbed oxygen covered surface, surface oxide and bulk-like surface oxide, were prepared and characterized by low-energy electron diffraction （LEED） and Auger electron spectroscopy （AES）. The present work demonstrates that the oxidized palladium surface is less active for CO oxidation than the metallic surface, and is unstable under the reaction conditions with sufficient CO.
基金supported by the National Natural Science Foundation of China (21703104, 21673117, 91956109)Jiangsu Provincial Foundation for Specially-Appointed Professor, Jiangsu Science and Technology Plan (BK20211258)+2 种基金Fellowship of China Postdoctoral Science Foundation (2019M661810)Nanjing Tech University (39837102, 39837131, 39837140)SICAM Fellowship from Jiangsu National Synergetic Innovation Centre for Advanced Materials。
文摘Discovering new methods and principles in the inequivalent growth of equivalent facets is of great significance for going beyond symmetrical nanocrystals and for out-of-box exploration. In this work, we demonstrate that a middle ground exists between the traditional weak ligands and the strong ligands with unusual growth modes. By modifying the seed concentration during the growth of pentagonal Au nanorods, the typical weak ligand cetyltrimethylammonium bromide(CTAB) is made strong, leading to notches of restricted growth and even the active surface growth mode. In-depth investigation in the link between growth kinetics and ligand packing reveals the principle of their interplay —— that the on-off dynamics of the ligands only allows for a certain limit of materials deposition rate. Beyond this limit, the growth materials build up and are then diverted elsewhere, leading to inequivalent growth. The fact that a freshly grown surface has few ligands promotes the active surface growth, focusing the growth materials onto a few sites. We believe that the knowhow of interfering ligand packing via growth kinetics would offer a powerful tool of synthetic control, where the facet-and curvature-dependent ligand packing is expected to be useful synthetic handles.
文摘Passive surface-wave utilization has been intensively studied as a means of compensating for the short-age of low-frequency information in active surface-wave measurement, In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range, To reduce the amount of field work, we pro-pose a strategy for a high-frequency passive surface-wave survey that imposes active sources during con-tinuous passive surface-wave observation; we call our strategy ＂mixed-source surface-wave （MSW） measurement,＂ Short-duration （within 10 min） passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels： namely, inside a school, along a road, and along a railway, Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation, The spatial autocorrelation （SPAC） method and the multichannel analysis of passive surface waves （MAPS） method based on cross-correlations were performed on the recorded time sequences, The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis, We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement,
文摘SrTiO_3 nano-crystal samples with floccule or flake crystal morphology,which were indexed as a perovskite-type crystal structure based on the results of XRD and TEM,were successfully prepared by one-step liquid reaction method.And the growth mechanism of the SrTiO_3 nano-crystals under the liquid condition with/without adding the surface active agent was investigated.It was found that adding the surface active agent contributes to the processing in which the ions gathering bodies transit to a more stable phase through the chemical reaction and form the flake SrTiO_3 nano-crystals.
文摘Five new zwitterionic surfactants with long chain alkyl betaine structure incorporated with hydroxylpropyl group have been synthesized. Their structures were identified by elemental analysis, IR (HNMR)-H-1, and (CNMR)-C-13. Surface tension experiments showed that these surfactants have higher surface activity than those without hydroxypropyl group. The values of CMC and gamma(CMC) of these surfactants have been determined.
文摘The oxidation heat of coal is the direct reason leading to coal spontaneous combustion. When coal is exposed in oxygen atmosphere, the physical adsorption and chemisorption happened, and then which resulting chemical reaction followed heat between coal and oxygen. Owing to the complexity and uncertain of molecular structure of coal,it was only reduced that bridge bonds, side chains and O 2 containing functional groups in coal may be prone to oxidation in last year, but not to deeply investigate into the structures and the type of the active radicals. In this paper, according to the last achievements in coal structure research, the hypomethylether bond, hypoalkyl bond of α carbon atom with hydroxyl and α carbon atom with hypomethy side chain and hypomethyl bonds linking up two aromatic hydrocarbon in bridge bonds, and methoxy,aldehyde and alkyls of α carbon atom with hydroxy in side bonds are inferred to be free radical easily to lead to oxidize coal under the ambient temperature and pressure. The order from strong to weak of oxide activation of the seven surface active groups is aldehyde side chains, hypomethylether bonds, hypoalkyl bonds of α carbon atom with hydroxyl, hypoalkyl bonds of α carbon atom with hypomethyl, hypomethyl bonds linking up two aromatic hydrocarbon,methoxy, alkyls side chains of α carbon atom with hydroxyl. Because of the two unsaturated molecular tracks of O 2, unpaired electron clouds of the part of surface active groups of coal enter molecular tracks of O 2 to lead to chemisorb on the conjugate effect and induced effect of surface active groups, and then chemical reaction followed heat happens in them. On the basis of change of bond energy, weighted average method is adopted to count the reaction heat value of each mol CO,CO 2 and H 2O. The property of coal spontaneous combustion is different for the different number and oxidability of the active structure in the coal resulting in the different oxidation heat.
基金supported in part by the National Natural Science Foundation of China (No.62071242 and No.61901229)in part by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22 0967)in part by the Open Research Project of Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology (No.NJUZDS2022-008)
文摘In this paper,we propose an active reconfigurable intelligent surface(RIS)enabled hybrid relaying scheme for a multi-antenna wireless powered communication network(WPCN),where the active RIS is employed to assist both wireless energy transfer(WET)from the power station(PS)to energyconstrained users and wireless information transmission(WIT)from users to the receiving station(RS).For further performance enhancement,we propose to employ both transmit beamforming at the PS and receive beamforming at the RS.We formulate a sumrate maximization problem by jointly optimizing the RIS phase shifts and amplitude reflection coefficients for both the WET and the WIT,transmit and receive beamforming vectors,and network resource allocation.To solve this non-convex problem,we propose an efficient alternating optimization algorithm with the linear minimum mean squared error criterion,semidefinite relaxation(SDR)and successive convex approximation techniques.Specifically,the tightness of applying the SDR is proved.Simulation results demonstrate that our proposed scheme with 10 reflecting elements(REs)and 4 antennas can achieve 17.78%and 415.48%performance gains compared to the single-antenna scheme with 10 REs and passive RIS scheme with 100 REs,respectively.
文摘（2-acrylamido） ethyl tetradecyl dimethylammonium bromide （AMC14AB） was polymerized in aqueous solu- tion to form the homopolymer P（AMC14AB）. The physicochemical properties of P（AMC14AB） in aqueous solution were mainly studied with fluorescent probe method, surface tension measurement and conductom- etry. The experimental results show that the aggregation morphology of P（AMC14AB） in aqueous solution is unimolecular micelle as expected. Being different from conventional multimolecular micelle systems, the unimolecular micelle system of P（AMC14AB） not only shows critical micellar concentration （CMC=0）, （i.e. once added to pure water, the surface tension decreases immediately in spite how small the density is）, but also the surface tension stays almost the same with the concentration increasing. That is to say, there is no mutational point on the relationship curve between surface tension and concentration. Furthermore, the unimolecular micelle system of P（AMC14AB） has no Krafft temperature, i.e. at any temperature, so long as it is dissolved in water, the unimolecular micelles will form. Besides this, for the solubilization of hydrophobic organic substances, the unimolecular micelle system of P（AMC14AB） is obviously different from the common multimolecular micelle system, having no turning point on the relationship curve between toluene solubi- lizaion amount and P（AMC14AB） concentration, and the solubilizing ability of the unimolecular-micelle system of P（AMC14AB） for hydrophobic organic substances is much higher than that of the conventional multimolecular micelle solutions of common surfactants, such as centyl trimethyl ammonium bromide.
基金supported by the National Natural Science Foundation of China Grant 61901043.
文摘Active intelligent reflecting surface(IRS)is a novel and promising technology that is able to overcome the multiplicative fading introduced by passive IRS.In this paper,we consider the application of active IRS to nonorthogonalmultiple access(NOMA)networks,where the incident signals are amplified actively through integrating amplifier to reflecting elements.More specifically,the performance of active/passive IRS-NOMA networks is investigated over large and small-scale fading channels.Aiming to characterize the performance of active IRSNOMA networks,the exact and asymptotic expressions of outage probability for a couple of users,i.e.,near-end user n and far-end user m are derived by exploiting a 1-bit coding scheme.Based on approximated analyses,the diversity orders of user n and user m are obtained for active IRS-NOMA.In addition,the system throughput of active IRS-NOMA is discussed in the delay-sensitive transmission.The simulation results are carried out to verify that:i)The outage behaviors of active IRS-NOMAnetworks are superior to that of passive IRS-NOMAnetworks;ii)As the reflection amplitude factors increase,the active IRS-NOMAnetworks are capable of furnishing the enhanced outage performance;and iii)The active IRS-NOMA has a larger system throughput than passive IRS-NOMA and conventional communications.
文摘A novel surface active monomer （surfmer） containing poly（ethylene glycol） chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP （N-vinylpyrrolidone） and with NVP and VEP （5-tert-butylperoxy-5-methyl-2-hexene-3-yne monomer） led to formation of corresponding surface-active copolymers. The capability of application of resulted copolymers as surface active macroinitiators of emulsion polymerization of styrene and as components of polymeric scaffolds was investigated.
文摘Synthesis and surface active properties of the oxyethylenated fatty alcohol 2-hydroxypropyl sulfonates were investigated.Of all surface active compounds studied,those with a 2-hydroxypropyl (HP) moiety in the molecule are more surface-active than the corresponding compounds without it.
基金Project supported by the National Basic Resarch Program of China(Grant No.2014CB339800)the National Natural Science Foundation of China(Grant No.11173015)
文摘An experimental double-layer active frequency-selective surface（AFSS） for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface（FSS）, a PIN diodes array, and a DC bias network. The AFSS elements incorporating switchable PIN diodes are discussed. By means of controlling the DC bias network, it is possible to switch the frequency response for reflecting and transmitting. Measured and simulated data validate that when the incidence angle varies from 0°to 30° the AFSS produces more than-11.5 dB isolation across6–18 GHz when forward biased. The insertion loss（IL） is less than 0.5 dB across 10–11 GHz when reverse biased.
基金supported by the Program of Ministry of Science and Technology of China(No.2023YFB2504200)support of Shanghai Rising-Star Program(Grant No.24QB2703200)the Major Science and Technology Projects of Yunnan Province(No.202302AH360001).
文摘Mesoporous carbon supports mitigate platinum(Pt)sulfonic poisoning through nanopore-confined Pt deposition,yet their morphological impacts on oxygen transport remain unclear.This study integrates carbon support morphology simulation with an enhanced agglomerate model to establish a mathematical framework elucidating pore evolution,Pt utilization,and oxygen transport in catalyst layers.Results demonstrate dominant local mass transport resistance governed by three factors:(1)active site density dictating oxygen flux;(2)ionomer film thickness defining shortest transport path;(3)ionomer-to-Pt surface area ratio modulating practical pathway length.At low ionomer-to-carbon(I/C)ratios,limited active sites elevate resistance(Factor 1 dominant).Higher I/C ratios improve the ionomer coverage but eventually thicken ionomer films,degrading transport(Factors 2–3 dominant).The results indicate that larger carbon particles result in a net increase in local transport resistance by reducing external surface area and increasing ionomer thickness.As the proportion of Pt situated in nanopores or the Pt mass fraction increases,elevated Pt density inside the nanopores exacerbates pore blockage.This leads to the increased transport resistance by reducing active sites,and increasing ionomer thickness and surface area.Lower Pt loading linearly intensifies oxygen flux resistance.The model underscores the necessity to optimize support morphology,Pt distribution,and ionomer content to prevent pore blockage while balancing catalytic activity and transport efficiency.These insights provide a systematic approach for designing high-performance mesoporous carbon catalysts.
基金the financial support provided by the National Natural Science Foundation of China (No.21573093)the National Key Research and Development Program (No.2017YFB0307501)Guangdong Innovative and Entrepreneurial Research Team Program (No.2013C092)
文摘A novel C/Pb composite has been successfully prepared by electmless plating to reduce the hydrogenevolution and achieve the high reversibility of the anode of lead-carbon battery （LCB）. The depositedlead on the surface of C/Pb composite was found to be uniform and adherent to carbon surface. Becauselead has been stuck on the surface of C/Pb composite, the embedded structure suppresses the hydrogenevolution of lead-carbon anode and strengthens the connection between carbon additive and sponge lead.Compared with the blank anode, the lead-carbon anode with C/Pb composite displays excellent charge-discharge reversibility, which is attributed to the good connection between carbon additives and leadthat has been stuck on the surface of C/Pb composite during the preparation process. The addition of CIPb composite maintains a solid anode structure with high specific surface area and power volume, andthereby, it plays a significant role in the highly reversible lead-carbon anode.
