Study on the Hydration and Physical Properties of Cement by M18 Polycarboxylate Superplasticizer Modified Graphene Oxide

Graphene oxide(GO)as a new nano-enhancer in cement-based materials has gained wide attention.However,GO is easy to aggregate in alkaline cement mortar with poor dispersibility.This hinders its application in practical infrastructure construction.In this work,GO-M18 polycarboxylate compound superplasticizer(GM)were obtained by compounding the M18 polycarboxylate superplasticizer with GO solution at different mass ratios.The dispersion of GM in alkaline solution was systematically studied.The phases and functional groups of GM were characterized by XRD and FTIR.The effects of GM on the cement mortar hydration and the formation of microstructure were investigated by measuring the heat of hydration,MIP,TG/DSC,and SEM.The results show that the long-chain structure of the M18 polycarboxylate superplasticizer can increase the interlayer spacing of GO and weaken the force between GO sheets.The modified GO can be uniformly dispersed in the cement slurry.GM can accelerate the early hydration process of cement,which can increase the content of Ca(OH)2 and decrease the grain size.It can optimize the pore size distribution of cement-based materials,increase the density of harmless and less harmful pores,thereby improving mechanical properties.Such methods can transform traditional cement-based materials into stronger,more durable composites,which prolong the life of cement-based materials and reduce the amount of cement used for later maintenance.This provides an idea for achieving sustainability goals in civil engineering.

Fundamental Limitation of Semantic Communications:Neural Estimation for Rate-Distortion

This paper studies the fundamental limit of semantic communications over the discrete memoryless channel.We consider the scenario to send a semantic source consisting of an observation state and its corresponding semantic state,both of which are recovered at the receiver.To derive the performance limitation,we adopt the semantic rate-distortion function(SRDF)to study the relationship among the minimum compression rate,observation distortion,semantic distortion,and channel capacity.For the case with unknown semantic source distribution,while only a set of the source samples is available,we propose a neural-network-based method by leveraging the generative networks to learn the semantic source distribution.Furthermore,for a special case where the semantic state is a deterministic function of the observation,we design a cascade neural network to estimate the SRDF.For the case with perfectly known semantic source distribution,we propose a general Blahut-Arimoto(BA)algorithm to effectively compute the SRDE.Finally,experimental results validate our proposed algorithms for the scenarios with ideal Gaussian semantic source and some practical datasets.

Resonant Beam Communications:A New Design Paradigm and Challenges

Resonant beam communications (RBCom), which adopts oscillating photons between two separate retroreflectors for information transmission, exhibits potential advantages over other types of wireless optical communications (WOC). However, echo interference generated by the modulated beam reflected from the receiver affects the transmission of the desired information. To tackle this challenge, a synchronization-based point-to-point RBCom system is proposed to eliminate the echo interference, and the design for the transmitter and receiver is discussed. Subsequently,the performance of the proposed RBCom is evaluated and compared with that of visible light communications(VLC)and free space optical communications (FOC). Finally, future research directions are outlined and several implementation challenges of RBCom systems are highlighted.

P-E hysteresis loop going slim in Ba0.3Sr0.7TiO3-modified Bi0.5Na0.5TiO3 ceramics for energy storage applications

(Ba0.3Sr0.7)x(Bi0.5Na0.5)1-xTiO3(BSxBNT,x=0.3–V0.8)ceramics were prepared to investigate their structure,dielectric and ferroelectric properties.BSxBNT ceramics possess pure perovskite structure accompanied from a tetragonal symmetry to pseudo-cubic one with the increase of x value,being confirmed by X-ray diffraction(XRD)and Raman results.The Tm corresponding to a temperature in the vicinity of maximum dielectric constant gradually decreases from 110℃(x=0.3)to-45℃(x=0.8),across Tm=36℃(x=0.5)with a maximum dielectric constant(ɛr=5920@1 kHz)around room temperature.The saturated polarization Ps gradually while the remnant polarization Pr sharply decreases with the increase of x value,making the P-E hysteresis loop of BSxBNT ceramics goes slim.A maximum difference between Ps and Pr(Ps-Pr)is obtained for BSxBNT ceramics with x=0.5,at which a high recoverable energy density(Wrec=1.04 J/cm3)is achieved under an applied electric field of 100 kV/cm with an efficiency ofη=77%.Meanwhile,the varied temperature P-E loops,fatigue measurements,and electric breakdown characteristics for the sample with x=0.5 indicate that it is promising for pulsed power energy storage capacitor candidate materials.

Vibration control for the solar panels of spacecraft: Innovation methods and potential approaches

Solar panels on spacecraft are typical kinds of flexible structures.Low‐frequency and large‐amplitude vibrations usually occur due to the inevitable disturbances of deployment impact,attitude/orbit maneuver,separation/docking impact,and so forth.These vibrations degrade the stability of the spacecraft platform,leading to a reduction in imaging quality and pointing direction accuracy.Vibration control is obligatory during flight missions.Here,we summarize the researches on vibration control of the solar panels.First,typical solar panels used in spacecraft and the specific difficulties in dynamic modeling and control design are introduced.Next,the researches on dynamic modeling methods,decentralized vibration control strategy,and in‐orbit vibration controller design technologies are presented sequentially.Finally,a practical example where our method was successfully applied in‐orbit is described.In conclusion,the theories,methods,and technologies presented in this review hold significant value for achieving high‐precision performance in large spacecraft.

Progress and perspectives in dielectric energy storage ceramics

Dielectric ceramic capacitors,with the advantages of high power density,fast chargedischarge capability,excellent fatigue endurance,and good high temperature stability,have been acknowledged to be promising candidates for solid-state pulse power systems.This review investigates the energy storage performances of linear dielectric,relaxor ferroelectric,and antiferroelectric from the viewpoint of chemical modification,macro/microstructural design,and electrical property optimization.Research progress of ceramic bulks and films for Pb-based and/or Pb-free systems is summarized.Finally,we propose the perspectives on the development of energy storage ceramics for pulse power capacitors in the future.

Experimental and numerical investigation on the thermal and mechanical behaviours of thermal barrier coatings exposed to CMAS corrosion

Calcium-magnesium-alumino-silicate(CMAS)corrosion is a critical factor which causes the failure of thermal barrier coating(TBC).CMAS attack significantly alters the temperature and stress fields in TBC,resulting in their delamination or spallation.In this work,the evolution process of TBC prepared by suspension plasma spraying(SPS)under CMAS attack is investigated.The CMAS corrosion leads to the formation of the reaction layer and subsequent bending of TBC.Based on the observations,a corrosion model is proposed to describe the generation and evolution of the reaction layer and bending of TBC.Then,numerical simulations are performed to investigate the corrosion process of free-standing TBC and the complete TBC system under CMAS attack.The corrosion model constructs a bridge for connecting two numerical models.The results show that the CMAS corrosion has a significant influence on the stress field,such as the peak stress,whereas it has little influence on the steady-state temperature field.The peak of stress increases with holding time,which increases the risk of the rupture of TBC.The Mises stress increases nonlinearly along the thick direction of the reaction layer.Furthermore,in the traditional failure zone,such as the interface of the top coat and bond coat,the stress obviously changes during CMAS corrosion.

Decoration of Terpyridine with Electron-Rich Unit TH DTAP: an Efficient Way to Explore Fluorescence Sensors for Recognizing Metal Ions

The electron-donating unit 2,3,4,6-tetrahydro-1,6-dithia-3a-azaphenalene (THDTAP) was introduced onto terpyridine (TPy) to give a donor-acceptor (D-A) type TPy-ligand (compound 2).Upon selective oxidation of two sulfur atoms on the THDTAP moiety of 2,the ligands 3-6 were created.The electronic structures of 2-6 were evaluated by theoretical,electrochemical,and spectroscopic investigations.The oxidation on the sulfur atoms brings significant influence on the electron-donating ability of THDTAP moiety,subsequently,leads to fine modulations on intramolecular charge-transfer (ICT) of 2-6 and the electronically excited states of the complexes of 2-6 with metal ions.Based on the optical response of 2-6 toward metal ions,the step-by-step recognition of Zn2+,Cd2+,and Ag+ ions is set up by employing 2 and 3 as combined fluorescence sensors.

Genomic basis of evolutionary adaptation in a warm-blooded fish

Few fishes have evolved elevated body temperatures compared with ambient temperatures,and only in opah(Lampris spp)is the entire body affected.To understand the molecular basis of endothermy,we analyzed the opah genome and identified 23 genes with convergent amino acid substitutions across fish,birds,and mammals,including slc8b1,which encodes the mitochondrial Na+/Ca2+exchanger and is essential for heart function andmetabolic heat production.Among endothermic fishes,44 convergent genes with suggestive metabolic functions were identified,such as glrx3,encoding a crucial protein for hemoglobin maturation.Numerous genes involved in the production and retention of metabolic heat were also found to be under positive selection.Analyses of opah’s unique inner-heat-producing pectoral muscle layer(PMI),an evolutionary key innovation,revealed that many proteins were co-opted from dorsal swimming muscles for thermogenesis and oxidative phosphorylation.Thus,the opah genome provides valuable resources and opportunities to uncover the genetic basis of thermal adaptations in fish.

Precipitation of Ti 2 Al phases at lamellar interfaces in a high-Nb-containing TiAl alloy during thermal exposure

The thermal stability of microstructures is crucial for determining the performance of alloys in extreme environments.In the present work,the microstructural evolution and precipitation behavior in a high Nb-containing Ti45Al8Nb alloy during thermal exposure at 950°C were investigated.It was found that excessα2 phases in the as-cast microstructure were unstable and tended to decompose during thermal expo-sure.Hexagonal Ti 2 Al phases precipitated at lamellar interfaces and had a[1¯10]_(γ)[11¯20]_(α2)[11¯20]_(Ti2Al),(002)_(γ)(1¯100)_(α2)(1¯100)_(Ti2Al)crystallographic orientation relationship(OR)with the matrix.Stacking faults(SFs)generated inα2 phases during theα2→γphase transformation provided favorable nucleation sites for Ti 2 Al phases.