越南发现的巴地市沉船初议

2020年以来,中国收藏界和文博市场出现了大批由越南商贩销售而来的唐代低温铅绿釉印花器物和白釉瓷器,引起学界关注及对相关问题的讨论。这些器物据传出水于越南南部的一条沉船,但并非正式发掘的器物。①经越南社会科学院皇城考古研究所杜长江(DOTruongGiang)博士核实,该沉船位于今胡志明市东南约百里的巴地市近海(图1),因此权且称之为“巴地市沉船”。

Environmentally Tough and Stretchable MXene Organohydrogel with Exceptionally Enhanced Electromagnetic Interference Shielding Performances

Conductive hydrogels have potential applications in shielding electromagnetic(EM)radiation interference in deformable and wearable electronic devices,but usually suffer from poor environmental stability and stretching-induced shielding performance degradation.Although organohydrogels can improve the environmental stability of materials,their development is at the expense of reducing electrical conductivity and thus weakening EM interference shielding ability.Here,a MXene organohydrogel is prepared which is composed of MXene network for electron conduction,binary solvent channels for ion conduction,and abundant solvent-polymer-MXene interfaces for EM wave scattering.This organohydrogel possesses excellent anti-drying ability,low-temperature tolerance,stretchability,shape adaptability,adhesion and rapid self-healing ability.Two effective strategies have been proposed to solve the problems of current organohydrogel shielding materials.By reasonably controlling the MXene content and the glycerol-water ratio in the gel,MXene organohydrogel can exhibit exceptionally enhanced EM interference shielding performances compared to MXene hydrogel due to the increased physical cross-linking density of the gel.Moreover,MXene organohydrogel shows attractive stretching-enhanced interference effectiveness,caused by the connection and parallel arrangement of MXene nanosheets.This well-designed MXene organohydrogel has potential applications in shielding EM interference in deformable and wearable electronic devices.

Simulation of meso factors influencing fracture performance of dense-graded asphalt concrete at low temperature

In order to characterize the impacts of key factors onthe low-temperature fracture performance of dense-gradedasphalt concrete, the virtual bending fracture test is simulatedby using the discrete dement method （DEM） and emulationsoftware PFC3D （particle flow code in three-dimension）. Avirtual specimen generation procedure consisting of aggregategradation, irregular clumps, asphalt mortar and air voidcontent is performed based on the random generation algorithmand irregular coarse aggregates library. Then, the virtualfracture test is conducted after adding the micro mechanicalcontact models to the specimen, and the validity of virtualmodeling is verified by the comparison of simulation test dataand lab test data. Additionally, an orthogonal test is designedto investigate the impacts of the volume fraction of coarseaggregates and air voids, stiffness of coarse aggregates andasphait mortar, internal bond strength of asphalt mortar anddistribution of coarse aggregates and air voids on low-temperature fracture performance based on virtual simulation.The results show that all the factors have effects on fractureperformance to various degrees, while the value of the bondstrength of asphalt mortar is found to be the most importantdeterminant of tensile strength and strain-energy density. Thevolume fraction of coarse aggregates is considered to be themost important determinant of tensile strain. Therefore, toobtain a high low-temperature fracture performance of dense-graded asphalt concrete, it is important to consider themicrostructure and properties of asphalt mortar and aggregates.

Effect of Sintering Temperature on Aging Resistance and Mechanical Properties of 3Y-TZP Dental Ceramic

In order to investigate the effect of sintering temperature on aging properties and mechanical properties of 3Y-TZP dental ceramic in simulated oral environment, 3Y-TZP nanopowder compacts were pressurelessly sintered at 1 350℃, 1 400 ℃, 1 450 ℃,1 500 ℃, respectively, then were treated by soaking in artificial saliva （65 ℃, pH=7） for two months. The treated specimens sintered at 1 350 ℃ showed there was no phase transformation but whose strength and toughnesswere significantly improved （P〈0.05）, while those sintered at 1 400 ℃- 1 500 ℃ revealed a small amount of phase transformation and insignificant mechanical reinforcement （P〉0.05）. No microcracks were detected but increment in lattice volume was found in all specimens. Lowering sintering temperature favors aging resistance and mechanical reinforcement of 3Y-TZP in a simulated oral environment.

Effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge in atmospheric airflow

In this paper,an asymmetric electrode geometry(the misalignment between the ends of highvoltage and grounded electrodes)is proposed in order to investigate the effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge(DBD).The results show that diffuse discharge manifests in the misaligned region and the micro-discharge channel in the aligned region moves directionally.Moreover,the diffuse discharge area increases with the decrease of the discharge gap and pulse repetition frequency,which is consistent with the variation of the moving velocity of the micro-discharge channel.When airflow is introduced into the discharge gap in the same direction as the transverse electric field,the dense filamentary discharge region at the airflow inlet of asymmetric electrode geometry is larger than that of symmetric electrode geometry.However,when the direction of the airflow is opposite to that of the transverse electric field,the dense filamentary discharge region of asymmetric electrode geometry is reduced.The above phenomena are mainly attributed to the redistribution of the space charges induced by the transverse electric field.

Observation of source/drain bias-controlled quantum transport spectrum in junctionless silicon nanowire transistor

We investigate the influence of source and drain bias voltages(V_(DS))on the quantum sub-band transport spectrum in the 10-nm width N-typed junctionless nanowire transistor at the low temperature of 6 K.We demonstrate that the transverse electric field introduced from V_(DS) has a minor influence on the threshold voltage of the device.The transverse electric field plays the role of amplifying the gate restriction effect of the channel.The one-dimensional(1D)-band dominated transport is demonstrated to be modulated by V_(DS) in the saturation region and the linear region,with the sub-band energy levels in the channel(E_(channel))intersecting with Fermi levels of the source(E_(fS))and the drain(E_(fD))in turn as V_(g) increases.The turning points from the linear region to the saturation region shift to higher gate voltages with V_(DS) increase because the higher Fermi energy levels of the channel required to meet the situation of E_(fD)=E_(channel).We also find that the bias electric field has the effect to accelerate the thermally activated electrons in the channel,equivalent to the effect of thermal temperature on the increase of electron energy.Our work provides a detailed description of the bias-modulated quantum electronic properties,which will give a more comprehensive understanding of transport behavior in nanoscale devices.

An efficient molten-salt electro-deoxidation strategy enabling fast-kinetics and long-life aluminum-selenium batteries

Aluminum-selenium(Al-Se)batteries have been considered as one of the most promising energy storage systems owing to their high capacity,energy density,and cost effectiveness,but Se falls challenges in addressing the shuttle effect of soluble intermediate product and sluggish reaction kinetics in the solid-solid conversion process during cycling.Herein,we propose an unprecedented design concept for fabricating uniform Se/C hollow microspheres with controllable morphologies through low-temperature electro-deoxidation in neutral NaCl-AlCl_(3) molten salt system.Such Se/C hollow microspheres are demonstrated to hold a favorable hollow structure for hosting Se,which can not only suppress the dissolution of soluble intermediate products into the electrolyte,thereby maintaining the structural integrity and maximizing Se utilization of the active material,but also promote the electrical/ionic conductivity,thus facilitating the rapid reaction kinetics during cycling.Accordingly,the as-prepared Se/C hollow microspheres exhibit a high reversible capacity of 720.1 mAh g^(−1)at 500 mA g^(−1).Even at the high current density of 1000 mA g^(−1),Se/C delivers a high discharge capacity of 564.0 mAh g^(−1),long-term stability over 1100 cycles and high Coulombic efficiency of 98.6%.This present work provides valuable insights into short-process recovery of advanced Se-containingmaterials and value-added utilization for energy storage.

Synergistic effect of cobalt and niobium in Co_(3)-Nb-O_(x)on performance of selective catalytic reduction of NO with NH_(3)

Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)shows average activity,however,it exhibits a poor N_(2)selectivity.Nb_(2)O_(5)is not active for NH_(3)-SCR.However,the mixed Co_(3)-Nb-O_(x) catalyst shows higher NO conversion and N_(2)selectivity than the single Co_(3)O_(4)and Nb_(2)O_(5)catalysts at 100–300℃.The results of temperature programmed reduction by H_(2)and X-ray photoelectron(XP)spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co^(3+) and Oa,adjusting the activity for catalytic oxidation to a moderate level.This suppresses the formation of undesired N_(2)O from the over-oxidation of NH_(3).Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity,ensuring the high catalytic activity and N2 selectivity in NH3-SCR.

Short-term cold storage of blowfly Lucilia sericata embryos

The developmental rate under low temperatures and cold tolerance were investigated in embryos of the blowfly Lucilia sericata. The larvae of this species are now widely used in maggot debridement therapy. Embryonic development was dependent on temperature, with a lower developmental threshold of 9.0℃. The duration of the egg stage at a rearing temperature of 25℃was 14 h, and a low temperature of 12.5℃ successfully prolonged this period to 66 h. Embryonic stages differed markedly in their cold tolerance; young embryos were less tolerant to cold than old ones. Late embryonic stages are suitable for cold storage at 5℃ and the storage for 72 h did not decrease the hatching rate by more than 50%. In the mass-rearing process required for maggot debridement therapy, either of these two simple protocols would be beneficial.

Experiments on the effect of the pressure on the mineral transformation of coal ash under the different reaction atmosphere

This paper investigated the effect of the pressures,reaction atmospheres and coal ash species on the ash fusibility with high-pressure thermogravimetric analysis(PTGA)apparatus and X-ray diffraction(XRD)analysis.Each specimen analyzed by XRD was observed for the mineral conversion and formation of new minerals with the pressures under different atmospheres.These results indicate that the pressure restrains the transformation and decomposition of minerals.Many low-temperature minerals are still present under the elevated pressure.The different reaction atmospheres have different effects on the formation of coal ash minerals.Under the N_(2)atmosphere,the present microcline may decrease the melting temperature of coal ash.And later,it transforms into sanidine at high pressure;thus,the melting temperature of coal ash may increase.Under the CO_(2)atmosphere,the minerals such as microcline,lomonitite,geothite and illite are still present with the increase in pressure;this may reduce the melting temperature.While under the H_(2)O atmosphere,there are magnetite and anorthoclase,which may produce the low-temperature eutectics decreasing the melting temperature.The coal ash abundance in basic oxides or higher SiO_(2),Fe_(2)O_(3),K_(2)O and Na_(2)O has lower melting temperature.While the ash sample with more SiO_(2)and Al_(2)O_(3)and less Fe_(2)O_(3)and basic oxides may lead to higher melting temperature.