Textured Asymmetric Membrane Electrode Assemblies of Piezoelectric Phosphorene and Ti_(3)C_(2)T_(x)MXene Heterostructures for Enhanced Electrochemical Stability and Kinetics in LIBs

Black phosphorus with a superior theoretical capacity(2596 mAh g^(-1))and high conductivity is regarded as one of the powerful candidates for lithium-ion battery(LIB)anode materials,whereas the severe volume expansion and sluggish kinetics still impede its applications in LIBs.By contrast,the exfoliated two-dimensional phosphorene owns negligible volume variation,and its intrinsic piezoelectricity is considered to be beneficial to the Li-ion transfer kinetics,while its positive influence has not been discussed yet.Herein,a phosphorene/MXene heterostructure-textured nanopiezocomposite is proposed with even phosphorene distribution and enhanced piezo-electrochemical coupling as an applicable free-standing asymmetric membrane electrode beyond the skin effect for enhanced Li-ion storage.The experimental and simulation analysis reveals that the embedded phosphorene nanosheets not only provide abundant active sites for Li-ions,but also endow the nanocomposite with favorable piezoelectricity,thus promoting the Li-ion transfer kinetics by generating the piezoelectric field serving as an extra accelerator.By waltzing with the MXene framework,the optimized electrode exhibits enhanced kinetics and stability,achieving stable cycling performances for 1,000 cycles at 2 A g^(-1),and delivering a high reversible capacity of 524 m Ah g^(-1)at-20℃,indicating the positive influence of the structural merits of self-assembled nanopiezocomposites on promoting stability and kinetics.

BUCKLING ANALYSIS UNDER COMBINED LOADING OF THIN-WALLED PLATE ASSEMBLIES USING BUBBLE FUNCTIONS

Bubble functions are finite element modes that are zero on the boundary of the element but nonzero at the other point. The present paper adds bubble functions to the ordinary Complex Finite Strip Method(CFSM) to calculate the elastic local buckling stress of plates and plate assemblies. The results indicate that the use of bubble functions greatly improves the convergence of the Finite Strip Method(FSM) in terms of strip subdivision, and leads to much smaller storage required for the structure stiffness and stability matrices. Numerical examples are given, including plates and plate structures subjected to a combination of longitudinal and transverse compression, bending and shear. This study illustrates the power of bubble functions in solving stability problems of plates and plate structures.

Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary

Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor-and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water(salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield(ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching(NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water(salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon(14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.

Hierarchical lichee-like Fe_(3)O_(4) assemblies and their high heating efficiency in magnetic hyperthermia

A nontoxic and biocompatible thermoseed is developed for the magnetic hyperthermia.Two kinds of thermoseed materials:hierarchical hollow and solid lichee-like Fe_(3)O_(4) assemblies,are synthesized by a facile hydrothermal method.The crystal structure of Fe_(3)O_(4) assemblies are characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Moreover,the prepared Fe_(3)O_(4) assemblies are used as a magnetic heat treatment agent,and their heating efficiency is investigated.Compared to solid assembly,hollow lichee-like Fe_(3)O_(4) assembly exhibits a higher specific absorption rate of 116.53 W/g and a shorter heating time,which is ascribed to its higher saturation magnetization,larger initial particle size,and the unique hierarchical hollow structure.Furthermore,the magnetothermal effect is primarily attributed to Neel relaxation.Overall,we propose a facile and convenient approach to enhance the heating efficiency of magnetic nanoparticles by forming hollow hierarchical assemblies.

Bureaucratic Factors Impeding the Delivery of Infrastructure at the Metropolitan Municipal and District Assemblies (MMDAs) in Ghana

Decentralisation of infrastructure delivery to sub-national governments has become commonplace in governments worldwide especially in developing countries such as Ghana. This is due to the benefits of decentralisation in improving public service delivery. However, decentralised infrastructure delivery is marred with numerous challenges that render most local governments incapable of providing infrastructure within their localities. This paper explored the bureaucratic factors that impede infrastructure delivery at the MMDAs in Ghana. A questionnaire survey with 121 construction professionals in the Departments of Works (DoWs) of the MMDAs within the Ashanti and Greater Accra Regions of Ghana was conducted. The results indicated six (6) major components of the bureaucratic factors that impede the delivery of infrastructure at the MMDAs: Central government bureaucracy;Minimal control of MMDAs;Political influence;MMDA project funding;Lack of capacity of MMDAs;and Political interference. This paper calls for a more committed central government to the establishment of adequate decentralised structures and implementation of major reforms that would remove the bureaucratic obstacles in the delivery of infrastructure at the MMDAs, to ensure effective infrastructure delivery at the MMDAs.

General Assemblies of CAS and CAE held in Beijing

The tenth general assembly ofthe Chinese Academy of Sciences(CAS) and the fifth general assem-bly of the Chinese Academy ofEngineering (CAE) were held fromJune 5 to June 9 in Beijing.

Preparation of Nano-porous Materials(Ⅰ) by Polymerization of Amphiphile Self-assemblies

The polymerization of amphiphilic self assemblies is a promising method to synthesize nano structured materials with novel properties. These materials have many attractive features for their application in biomedical area and materials science, such as catalysis, separation, surface modification, and therapeutics areas. A general review on the polymerization of lipids and surfactant self assemblies to amphiphilic self assemblies is given in this paper with 49 references. The polymerization and the subsequently resulted structure of lipids in different morphologies are summarized. The polymerization of polymerizable surfactants(surfmers) in emulsion and liquid crystalline phases are also discussed. The potential application of new nano porous materials is briefly described.

DESIGN REUSE METHOD FOR ASSEMBLIES IN CONCEPT DESIGN

Aiming at difficult sorting and retrieving complicated structure assembliesin assembly lib, a method for compartmentalizing assembly design resource by conceptual productstructure model is presented. The similar assembly retrieval mechanisms of symbol assembly relationgraph matching and symbol assembly relation graph similarity are discussed. The method is validatedby taking valve rod assemblies as example.

Surface-enhanced Raman scattering properties of highly ordered self-assemblies of gold nanorods with different aspect ratios

Gold nanorods with aspect ratios of from 1 （particles） to 31.6 were synthesized by the seed-mediated method and packed in a highly ordered structure on a large scale on silicon substrates through capillary force induced self-assembly behaviour during solvent evaporation. The gold nanorod surface exhibits a strong enhancing effect on Raman scattering spectroscopy. The enhancement of Raman scattering for two model molecules （2-naphthalenethiol and rhodamine 6C） is about 5-6 orders of magnitude. By changing the aspect ratio of the Au nanorods, we found that the enhancement factors decreased with the increase of aspect ratios. The observed Raman scattering enhancement is strong and should be ascribed to the surface plasmon coupling between closely packed nanorods, which may result in huge local electromagnetic field enhancements in those confined junctions.

Enhancement of current density using effective membranes electrode assemblies for water electrolyser system

The goal of this study was to develop and design a composite proton exchange membrane（PEM） and membrane electrode assembly（MEA） that are suitable for the PEM based water electrolysis system. In particular,it focuses on the development of sulphonated polyether ether ketone（SPEEK） based membranes and caesium salt of silico-tungstic acid（Cs Si WA） matrix compared with one of the transition metal oxides such as titanium dioxide（TiO2）, silicon dioxide（SiO2） and zirconium dioxide（ZrO2）. The resultant membranes have been characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ion exchange capacity（IEC）, water uptake and atomic force microscopy. Comparative studies on the performance of MEAs were also conducted utilizing impregnation-reduction and conventional brush coating methods. The PEM electrolysis performance of SPEEK-Cs Si WA-ZrO2 composite membrane was more superior than that of other membranes involved in this study. Electrochemical characterization shows that a maximum current density of 1.4 A/cm^2 was achieved at 60 °C, explained by an increased concentration of protonic sites available at the interface.

Microstructural Evolution and Cracking of Pb-free Ball Grid Array Assemblies under Thermal Cycling

Two kinds of CBGA （ceramic ball grid array） assemblies were made by reflow soldering process using two different Pb-free solders. Microstructural evolution and cracks induced by thermal cycling in CBGA assemblies were examined by scanning electron microscopy （SEM） and finite element method （FEM）. Before thermal cycling, intermetallic compounds （IMCs） Cu6Sn5 and Ag3Sn were observed at the solder interface between Cu and Ag metallizations, respectively. After thermal cycling, another IMC Cu3Sn was observed near the Cu pad in both two assemblies and the layers of Cu6Sn5 and Ag3Sn became thicker. As a result of thermal cycling, cyclic stress and strain were accumulated in the solder joint leading to fatigue cracking. Both experiments and FEM revealed that cracks preferred to initiate at the corner of each solder joint. Multi-modes of the crack propagation were found in the two assemblies. Based on Coffin-Manson equation, the thermal fatigue life was calculated and the predicted life showed good agreement with the experimental results.

Preparation of Nano-porous Materials(Ⅱ) by Cross-linking of Amphiphilic Self-assemblies

Amphiphilic block copolymers can exhibit rich and complex morphologies in aqueous solutions, but these structures are usually delicate, easily disturbed by composition change or temperature change. In this work, the use of different methods to cross link block copolymer self assemblies in the presence of a selective solvent and to stabilize the structures is reviewed. In addition, the cross linking reaction kinetics of block copolymer amphiphilic self assemblies is briefly discussed.

Photoelectrochemical Studies on High Specific Capacitance-Photoactive Interfaces Based on Poly 3,4- Ethylenedioxythiophene/Metal Oxides Assemblies

Inorganic/organic interfaces (IOI) consist of TiO2/PEDOT (poly 3,4-ethylenedioxythiophene) and [PMo12O40]3- or MoO3/PEDOT were subject to photoelectrochemical studies in both aqueous nanosuspensions and in thin solid films. The effects PEDOT modifier caused on the photoelectrochemical behavior of the IOI were investigated using [Fe(CN)6]4- as the photoactive hydrated electron donor agent. Results show that native PEDOT or PEDOT doped with MoO3 thin films increased charge storage capability evident by the high capacitive current. In the case of nano suspensions composed of TiO2/PEDOT the adsorption process of [Fe(CN)6]3- (photolysis product) control of the photoactivity outcome of the IOI assemblies. TiO2/PEDOT shows a lower heterogeneous photochemical response than native TiO2 in short term photolysis times. At longer photolysis times the IOI shows photoactivity greater than that of native TiO2. The interface activities were explained by analyzing the IOI junction characteristics, such as electron affinity, work function and hole/electrons barrier heights. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4-and PEDT contributed to the stability of native TiO2 surfaces.

Performance Investigation of Membrane Electrode Assemblies for High Temperature Proton Exchange Membrane Fuel Cell

Different types of ABPBI (poly(2,5-benzimidazole)) membranes and polymer binders were evaluated to investigate the performance of MEAs for high temperature proton exchange membrane fuel cell (HT-PEMFC). The properties of the prepared MEAs were evaluated and analyzed by polarization curve, electrochemistry impedance spectroscopy (EIS), cyclic voltammetry (CV) and durability test. The results showed that MEA with modified ABPBI membrane (AM) has satisfactory performance and durability for fuel cell application. Compare to conventional PBI or Nafion binders, polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) are more attractive as binders in the catalyst layer (CL) of gas diffusion electrode (GDE) for HT-PEMFC.

The Compactions of Elasto-Plastic and Visco-Plastic Granular Assemblies

In this paper, the compactions of the elasto-plastic and the visco-plastic granular assemblies are simulated using the finite element method. Governing equations for motion and deformation for particles, including coupling of rigid body motion and deformation for deformable bodies, are investigated. An implicit discrete element method for block systems is developed to make visco-plastic analysis for the assemblies. Among particles, three different contact types, cohering, rubbing and sliding, are taken into account. To verify accuracy and efficiency of the numerical method, some numerical example is simulated and the results are in a satisfactory agreement with the solutions in literatures. The effects of frictional condition, the initial solid volume ratio, the number of particles in the assembly, and different types of compact- tion on the compaction of the elasto-plastic and the visco-plastic aggregates are investigated. It is demonstrated that the effect of frictional condition, the initial solid volume ratio, the number of particles in the assembly, and different types of compaction on the global behavior of the elasto-plastic the visco-plastic granular assemblies under compacting are considerable. The numerical model is extended to simulate the compaction of aggregates consisting of mixed particles of different viscous incompressible materials. It is indicated that, with minor modification, the method could be used in a variety of problems that can be represented using granular media, such as asphalt, polymers, aluminum, snow, food product, etc.

Supramolecular flow chemistry: Construction of multiscale supramolecular assemblies by micro/nanofluidic techniques

The rapid and precise fabrication of multiscale supramolecular assemblies using micro/nanofluidic techniques has emerged as a dynamic area of research in supramolecular chemistry, materials chemistry, and organic chemistry. This review summarizes the application of micro/nanofluidic techniques in constructing supramolecular assemblies, including nanoscale supramolecular assemblies such as macrocycles and cages, microscale supramolecular assemblies such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), and macroscale supramolecular assemblies such as supramolecular hydrogels. Compared to conventional synthesis methods, micro/nanofluidic techniques for the production of supramolecular assemblies have significant advantages, including enhanced safety, high reaction rates, improved selectivity/yield, and scalability. Additionally, micro/nanofluidic systems facilitate the creation of precisely controllable micro/nanoconfined environments, allowing for a unique flow behavior that improves our understanding of the supramolecular self-assembly process. Such systems may also lead to the development of novel supramolecular assemblies that differ from those generated via traditional methods.

Topology optimization of modular structures with multiple assemblies and applications to airborne shelves

This work is devoted to the aeronautical application of topology optimization for modular structures with multiple assemblies that consist of repeated standard modules and optional reinforcements.These kinds of structures are widely used owing to their transportability,reconfigurability,low manufacturing and service costs.In this work,the design of airborne shelves with modular structures characterized by the standard module configuration is formulated for the first time as a topology optimization problem of multiple assemblies and multiple load cases subjected to the volume constraint.It is shown that the weighted compliance design of multiple assemblies is a compromising solution compared to the optimization result of each individual assembly of standard modules.Meanwhile,the performance of optimized airborne shelves with the modular structures can effectively be ameliorated with the help of reinforcements.

Phenazine-based supramolecular photosensitizing assemblies:A“smart”selectivity control on catalytic activity of Pd(Ⅱ)nanoparticles

Photosensitizing supramolecular assemblies based on a phenazine derivative(PPA)have been developed,which show a strong affinity toward Pd2+ions to generate supramolecular ensemble PPA@Pd nanoparticles(NPs).The PPA@Pd NPs catalyse the Suzuki cross-coupled reaction under mild conditions(aerial conditions,mixed aqueous media,and visible light radiations).Although PPA@Pd NPs exhibit a strong affinity for arylboronic acid and could catalyse homocoupling of arylboronic acid,the preference of PPA assemblies for aryl halide directed the course of reactions toward the formation of cross-coupled products.The electron-rich PPA assemblies not only facilitate the oxidative addition step through photoinduced electron transfer to Pd^(2+)ions but also bring the reactants closer to the catalytic sites by selective interactions with aryl halides in the presence of arylboronic acid under visible light irradiation.The efficiency of PPA@Pd NPs to catalyse the Suzuki crosscoupled reaction has been demonstrated for the synthesis of unsymmetrically substituted terphenyl derivatives.

DNA functionalized plasmonic nanoassemblies as SERS sensors for environmental analysis

Surface-enhanced Raman scattering(SERS)is among the most widely applied analytical techniques due to its easy execution and extreme sensitivity.Target molecules can be detected and distinguished based upon the fingerprint spectra that arise when absorbed on the SERS substrates surface,particularly on the SERS-active hotspots.Thus,rational fabricating the enhancing substrates plays a key role in broadening SERS application.Programmable DNA functionalized plasmonic nanoassemblies,where DNA acts as both structure basis and functional unit,combine the specificity of DNA recognition,and modulate the assembly of plasmonic nanoparticles(NPs).Specifically designed DNA not only improves the selectivity to target molecules but also promotes the sensitivity of the optical signals through precisely regulating the distance between the molecule and the substrate.A variety of DNA-functionalized SERS sensors have been reported and obtained well performance in the analysis of heavy metal ions in water,toxins,pesticide residues,antibiotics,hormones,illicit drugs,or other small molecules.This review places an emphasis on the design and sensing strategies of the DNA-functionalized plasmonic nanoassemblies,as well as basic principles of Raman enhancement,and recent advances for environmental analysis.The current challenges and potential trends in the development of DNAfunctionalized SERS sensors for environmental pollutant monitoring in complicated scenarios are subsequently discussed.

Rotor orientation direction controls geometric curvature and chirality for assemblies of motor amphiphiles in water

Control over geometric curvature and chirality of assemblies in pure aqueous media is key to the design of responsive materials and molecular machines.Here we show how aggregate geometric curvature and chirality of motor amphiphiles could be switched from bicontinuous calabashes to nanoribbons or from vesicles to nanoribbons by modulating rotor orientation direction with dual light/heat stimuli to influence spontaneous curvature in assemblies.The photoisomerization and thermal helix inversion processes of molecular motors have been studied at the molecular level,and the transformation of supramolecular assemblies has been investigated at the microscopic level.The morphological evolution of the calabash-shaped assembly can be kinetically captured,suggesting that the bicontinuous calabash-shaped structures are different from the bowl-shaped aggregates based on solvent-driven assembly upon the addition of non-solvent or solvent.The investigation of dual optical/thermal control of rotor orientation can provide a new strategy for tuning the geometric curvature and chirality of nanoassemblies at the nanoscale,arriving ultimately the clusteroluminescence through-space electronic communication at responsive supramolecular nanosystems.