粒子的不同属性对声波散射和吸收的影响

利用有限元软件COMSOL模拟了声波打在不同属性粒子上的散射现象,并且研究了粒子对声波的吸收,其中考虑了粘滞损失、热传导损失和散射。结论是不同属性粒子对声波的散射效果不同,而且不同属性粒子对声波的吸收也不同,其中阻抗越大,粒子对声波的吸收越小。

粒子群属性聚类的位置隐私保护

针对基于位置服务中连续查询情况下,用户自身属性信息很容易被攻击者获取,并通过关联获得用户位置隐私的情况,提出了一种利用粒子群聚类加速相似属性用户寻找,并由相似属性匿名实现用户位置泛化的隐私保护方法。该方法利用位置隐私保护中常用的可信中心服务器,通过对发送到中心服务器中的查询信息进行粒子群属性聚类,在聚类的过程中加速相似属性用户的寻找过程,由相似属性用户完成位置泛化,以此实现位置隐私保护。实验结果证明,这种基于粒子群属性聚类的隐私保护方法具有高于同类算法的隐私保护能力,以及更快的计算处理速度。

用光子的观点看光的波动现象

光具有波粒二象性 ,波动现象 (干涉、衍射等 )用电磁波动理论得到了圆满解释 ,但没有用粒子属性去解释波动现象 .测不准关系是以普朗克常数和波粒二象性为基础的一条客观规律 ,它适用于一切微观粒子 ,包括光子在内 。

Anisotropic gold nanoparticles: Preparation and applications in catalysis

Despite the high amount of scientific work dedicated to the gold nanoparticles in catalysis, most of the research has been performed utilising supported nanoparticles obtained by traditional impreg‐nation of gold salts onto a support, co‐precipitation or deposition‐precipitation methods which do not benefit from the recent advances in nanotechnologies. Only more recently, gold catalyst scien‐tists have been exploiting the potential of preforming the metal nanoparticles in a colloidal suspen‐sion before immobilisation with great results in terms of catalytic activity and the morphology con‐trol of mono‐and bimetallic catalysts. On the other hand, the last decade has seen the emergence of more advanced control in gold metal nanoparticle synthesis, resulting in a variety of anisotropic gold nanoparticles with easily accessible new morphologies that offer control over the coordination of surface atoms and the optical properties of the nanoparticles （tunable plasmon band） with im‐mense relevance for catalysis. Such morphologies include nanorods, nanostars, nanoflowers, den‐dritic nanostructures or polyhedral nanoparticles to mention a few. In addition to highlighting newly developed methods and properties of anisotropic gold nanoparticles, in this review we ex‐amine the emerging literature that clearly indicates the often superior catalytic performance and amazing potential of these nanoparticles to transform the field of heterogeneous catalysis by gold by offering potentially higher catalytic performance, control over exposed active sites, robustness and tunability for thermal‐, electro‐and photocatalysis.

Facile and Efficient Method for the Adsorption and Separation of Lanthanum Rare Earth Metal Oxide Using Iron（Ⅱ） Sulfide Nanoparticles Coated on Magnetite

A novel iron sulphide adsorbent using magnetite embedded with nanosized Fe3O4 was prepared and applied to separation lanthanum （Ⅲ） from aqueous solution. This adsorbent combines the advantages of magnetic nanoparticle with magnetic separability and high affinity toward rare earth metals, which provides distinctive merits including easy preparation, high adsorption capacity, easy isolation from sample solutions by the application of an external magnetic field. The adsorption behaviors of lanthanum （Ⅲ） from an aqueous medium, using iron sulphide magnetite nanoparticles were studied using equilibrium batch and column flow techniques. The effect ofpH, contents of loaded iron sulphide nanoparticles, ionic strength, adsorbent dose, contact time, and temperature on adsorption capacity of the magnetic beads was investigated. All of the results suggested that the FeS/Fe3O4 Nanoparticles could be excellent adsorbents for La（Ⅲ） contaminated water treatment.

Ultrasmall Ag^＋-rich nanoclusters as highly efficient nanoreservoirs for bacterial killing

Metallic silver （Ag） and its ability to combat infection have been known since ancient history. In the wake of nanotechnology advancement, silver＇s efficacy to fight broad spectrum bacterial infections is further improved in the form of Ag nanoparticles （NPs）. Recent studies have ascribed the broad spectrum antimicrobial properties of Ag NPs to dissociation of Ag＊ ions from the NPs, which may not be entirely applicable when the size of Ag NPs decreases to the sub-2 nm range [denoted Ag nanoclusters （NCs）]. In this paper we report that ultrasmall glutathione （GSH）-protected Ag^＋-rich NCs （Ag^＋-R NCs for short, with a predominance of Ag＋ species in the NCs） have much higher antimicrobial activities towards both gram-negative and gram-positive bacteria than the reference NC, GSH-Ag^＋-R NCs. They have the same size and surface ligand, but with different oxidation states of the core silver. This interesting finding suggests that the undissociated Ag^＋-R NCs armed with abundant Ag^＋ ions on the surface are highly active in bacterial killing, which was not observed in the system of their larger counterpart, Ag NPs.

Effective Approach for the Synthesis of Monodisperse Magnetic Nanocrystals and M-Fe3O4 （M = Ag, Au, Pt, Pd） Heterostructures

Monodisperse and size-tunable magnetic iron oxide nanoparticles （NPs） have been synthesized by thermal decomposition of an iron oleate complex at 310 ℃ in the presence of oleylamine and oleic acid. The diameters of the as-synthesized iron oxide NPs decrease with increasing concentrations of iron oleate complex and oleic acid/oleylamine. In addition, the size-dependent crystallinity and magnetic properties of iron oxide NPs are presented. It is found that larger iron oxide NPs have a higher degree of crystallinity and saturation magnetization. More importantly, various M-iron oxide heterostructures （M = Au, Ag, Pt, Pd） have been successfully fabricated by using the same synthesis procedure. The iron oxide NPs are grown over the pre-made metal seeds through a seed-mediated growth process. The physicochemical properties of Au-Fe3O4 heterostructures have been characterized by X-ray diffraction （XRD）, superconducting quantum interference device （SQUID） magnetometry and UV-vis spectroscopy. The as-synthesized Au-Fe3O4 heterostructures show a red-shift in surface plasmon resonance peak compared with Au NPs and similar magnetic properties to Fe3O4 NPs. The heterojunction effects present in such nanostructures offer the opportunity to tune the irphysicochemical properties. Therefore, this synthesis process can be regarded as an efficient way to fabricate a series of heterostructures for a variety of applications.

Optical properties of dyes with/without metal nanoparticles doped in a highly ordered nanostructure

Highly ordered nanocomposite arrays of Rh6G-Au-AAO are formed by filling anodized aluminum oxide （AAO） with Rhodamine 6G （Rh6G） and gold nanoparticles. The optical properties of Rh6G-Au-AAO are studied by visible absorptive and fluorescent spectroscopy. Compared with the fluorescence spectra of Rh6G-Au in the solution environment, the fluo- rescence peak intensities of Rh6G-Au-AAO are significantly enhanced, the maximum enhancement rate is 5.5, and a constant blue shift of-12 nm of peak positions is presented. The effects come from the spatial confinement of AAO and the inhibition of the fluorescence quenching effect induced by gold nanoparticles. The results show that the nanocomposite structures of fluorescence molecules-metal nanoparticles-AAO have a considerable potential in engineering molecular assemblies and creating functional materials of superior properties for future nanoDhotonics.

Core@shell sub-ten-nanometer noble metal nanoparticles with a controllable thin Pt shell and their catalytic activity towards oxygen reduction

Reducing Pt loading, while improving electrocatalytic activity and the stability of Pt-based nanostructured materials, is currently a key challenge in green energy technology. Herein, we report the controllable synthesis of tri-metallic （Au@Ag@Pt） and bimetallic （Ag@Pt） particles consisting of a controllable thin Pt shell, via interface-mediated galvanic displacement. Through oil-ethanol-H2O interface mediation, the controllable ＂out to in＂ displacement of Ag atoms to Pt enables the formation of a thin Pt shell on monodisperse sub-ten-nanometer Au@Ag and Ag nanocrystals. The synthesized nanoparticles with a thin Pt shell exhibited potential catalytic activity towards the oxygen reduction reaction （ORR） due to the high exposure of Pt atoms.

Experimental characterization of the bipolar effect on P-hit single-event transients in 65 nm twin-well and triple-well CMOS technologies

Single-event charge collection is controlled by drift, diffusion and the bipolar effect. Previous work has established that the bipolar effect is significant in the p-type metal-oxide-semiconductor field-effect transistor(PMOS) in 90 nm technology and above. However, the consequences of the bipolar effect on P-hit single-event transients have still not completely been characterized in 65 nm technology. In this paper, characterization of the consequences of the bipolar effect on P-hit single-event transients is performed by heavy ion experiments in both 65 nm twin-well and triple-well complementary metal-oxide-semiconductor(CMOS) technologies. Two inverter chains with clever layout structures are explored for the characterization. Ge(linear energy transfer(LET) = 37.4 Me V cm^2/mg) and Ti(LET = 22.2 Me V cm^2/mg) particles are also employed. The experimental results show that with Ge(Ti) exposure, the average pulse reduction is 49 ps(45 ps) in triple-well CMOS technology and 42 ps(32 ps) in twin-well CMOS technology when the bipolar effect is efficiently mitigated. This characterization will provide an important reference for radiation hardening integrated circuit design.

Carbon-CeO interface confinement enhances the chemical stability of Pt nanocatalyst for catalytic oxidation reactions

Noble metals are downsized to nano-/subnanoscale to improve their catalytic activity and atom-economy.However,the stabilities in chemical state and catalytic performance of these nanocatalysts often suffer during harsh conditions.For Pt nanoparticles(NPs)supported on CeO2,activated oxygen diffused from the support over-stabilizes the active sites of Pt,degrading its performance at mild temperature.In this work,Pt nanocatalysts with unique structure of triple-junction are synthesized by selectively growing Pt NPs on the carbon-CeO2 interface.Impressively,the Pt NPs exhibit much enhanced catalytic stability and high activity for CO oxidation at mild temperature.The enhancement is attributed to electron donation from graphitized carbon and the confinement effect from the high-density nanopores of the CeO2 support.The triple-junction of Pt-C-CeO2,combining the merits of CeO2 for activating O2 and electron donating capability of carbon,provides new inspiration to the fabrication of high-performance nanocatalysts.

Research on magnetic metallization of microorganism cells using electroplating technique

Spirulina platensis were chosen as templates to produce microscopic helical soft-core magnetic particles by way of depositing ferromagnetic alloy onto their surface using electroplating technique,and the process of electroplating ferromagnetic alloy onto microorganism cells was studied.The morphology and appearance of the coated Spirulina platensis were analyzed with optical microscopy and scanning electron microscopy,respectively,and the ingredients and phase structure of the alloy coating were analyzed with energy dispersive X-ray detector(EDX) and X-ray diffractive analysis(XRD),respectively.The result showed that the particles were successfully coated with uniform metal coating and their initial helical shape was perfectly replicated.The coating was NiFe alloy,and its phase structure was face-centered cubic structure.The magnetic properties of the coated particles were tested with vibrating sample magnetometer(VSM),and the result showed that the particles were ferro-magnetic,which means the magnetic electroplating of the microorganism cells was successfully achieved.The electrochemical reaction mechanism of the magnetic plating process was also analyzed;the result showed that the deposition of NiFe on the microorganism cells was anomalous codeposition,and that Fe2+ ion was preferential deposited when magnetic stirring was applied.

Particle size polydispersity of the rheological properties in magnetorheological fluids

Dispersion of metal particles in fluids can be used to manufacture magnetorheologic fluids(MRF).Properties of these dispersion systems are mainly determined by the arrangements and contacts among particles.In this paper,particles with smaller sizes than those in the target dispersion system are added using iron particles dispersed in silicon oil as a model to control the arrangements and contacts.The result suggests that these small-sized particles have a significant effect on the viscoelastic properties of the dispersion.The maximum packing density and the fluid viscosity depend mainly on the adhesion of small particles,which is directly related to the fraction of small particles in the model dispersion system.Under a magnetic field,the yield stress of the dispersion system is proportional to the concentration of iron particles,suggesting that the yield stress relies directly on the presence of small particles.These small particles in the fluid determine the difference in stress of the magnetorheological fluid(MRF) with or without a magnetic field.

Optimization of Pyrolysis Properties using TGA and Cone Calorimeter Test

The present paper describes an optimization work to obtain the properties related to a pyrolysis process in the solid material such as density, specific heat, conductivity of virgin and char, heat of pyrolysis and kinetic parameters used for deciding pyrolysis rate. A repulsive particle swarm optimization algorithm is used to obtain the pyrolysis-related properties. In the previous study all properties obtained only using a cone calorimeter but in this paper both the cone calorimeter and thermo gravimetric analysis (TGA) are used for precisely optimizing the pyrolysis properties. In the TGA test a very small mass is heated up and conduction and heat capacity in the specimen is negligible so kinetic parameters can first be optimized. Other pyrolysis-related properties such as virgin/char specific heat and conductivity and char density are also optimized in the cone calorimeter test with the already decided parameters in the TGA test.