Forming-Precision-Driven Structure Design of Hydraulic Press: Methodology and Case Study

The structure stiffness of presses has great effects on the forming precision of workpieces, especially in near-net or net shape forming. Conventionally the stiffness specification of presses is empirically determined, resulting in poor designs with insufficient or over sufficient stiffness of press structures. In this paper, an approach for the structure design of hydraulic presses is proposed, which is forming-precision-driven and can make presses costeffective by lightweight optimization. The approach consists of five steps:(1)the determination of the press stiffness specification in terms of the forming precision requirement of workpieces;(2)the conceptual design of the press structures according to the stiffness and workspace specifications, and the structure configuration of the press;(3)the prototype design of the press structures by equivalently converting the conceptual design to prototypes;(4)the selection of key structure parameters by sensitivity analysis of the prototype design; and(5)the optimization of the prototype design. The approach is demonstrated and validated through a case study of the structure design of a 100 MN hydraulic press.

NANO-BEARING:THE DESIGN OF A NEW TYPE OF AIR BEARING WITH FLEXURE STRUCTURE

A new type of air bearing with flexure structure is introduced. The new bearing is designed for precision mechanical engineering devices such as mechanical watch movement. The new design uses the flexure structure to provide 3D damping to absorb shocks from all directions. Two designs are presented： one has 12 T-shape slots in the radian direction while the other has 8 spiral slots in the radian direction. Both designs have flexure mountings on the axial directions. Based on the finite element analysis （FEA）, the new bearing can reduce the vibration （displacement） by as much as 8.37% and hence, can better protect the shafts.

A Precise Description of the Electronic Structures and Spin-Allowed Transition Properties of PF and Its Cation:All-Electron Configuration-Interaction Investigations Including Relativistic Effect

The electronic structures of PF and PF＋ are calculated with the high-level configuration interaction method. To improve the precision of calculations, the spin-orbit coupling effect, the scalar relativistic effect, and the Davidson correction（q-Q） are also considered. The spectroscopic parameters of bound states are derived by the electronic structures of PF and PF＋, which are in good accordance with the measurements. The transition dipole moments of spin-allowed transitions are evaluated, and the radiative lifetimes of several A S states of PF and PF＋ are obtained.

Dynamic crosslinked polymeric nano-prodrugs for highly selective synergistic chemotherapy

To achieve highly selective synergistic chemotherapy attractive for clinical translation,the precise polymeric nano-prodrugs(PPD-NPs)were successfully constructed via the facile crosslinking reaction between p H-sensitive poly(ortho ester)s and reduction-sensitive small molecule synergistic prodrug(Pt(IV)-1).PPD-NPs endowed the defined structure and high drug loading of cisplatin and demethylcantharidin(DMC).Moreover,PPD-NPs exhibited steady long-term storage and circulation via the crosslinked structure,suitable negative potentials and low critical micelle concentration(CMC),improved selective tumour accumulation and cellular internalization via dynamic size transition and surficial amino protonation at tumoural extracellular p H,promoted efficient disintegration and drug release at tumoural intracellular p H/glutathione,and enhanced cytotoxicity via the synergistic effect between cisplatin and DMC with the feed ratio of 1:2,achieving significant tumour suppression while decreasing the side effects.Thus,the dynamic crosslinked polymeric nano-prodrugs exhibit tremendous potential for clinically targeted synergistic cancer therapy.

Progress on the use of satellite technology for gravity exploration

In this paper, the technological progress on Chinese gravity exploration satellites is presented. Novel features such as ultra-stable structure, high accurate thermal control, drag-free and attitude control, micro-thrusters, aerodynamic configuration, the ability to perform micro-vibration analyses, microwave ranging system and mass center trimmer are described.

Integrating Homogeneous and Heterogeneous Catalysis in a Copper Nanocluster with Lewis Acid–Base Sites for Chemical Conversion of CO_(2) and Propargylamine

It remains a significant challenge to develop a catalyst that merges the advantages of homogeneous and heterogeneous catalysis with high reactivity and great recyclability.Herein,an atomically precise Cu_(6)-NH_(2) nanocluster with distorted octahedral Cu_(6) core and NH_(2)-functionalized ligands has been developed as the first homo/heterogeneous catalyst to catalyze the cyclization reaction of propargylic amines with carbon dioxide(CO_(2))under mild conditions.As a homogeneous catalyst,Cu_(6)-NH_(2) shows excellent catalytic activity with high turnover frequency due to highly accessible active sites.The definite coordination geometry and homogeneity nature of active centers make it convenient to investigate the structure–activity relationship at the atomic level through experiments and theory calculations.In addition,the nanocluster exhibits excellent stability,great recrystallizability,and reusability in five catalytic cycles,in which its catalytic performance has no obvious decrease.Moreover,Cu_(6)-NH_(2) incorporates Lewis acid and base sites in metal and ligand,respectively,which can promote catalytic efficiency in a synergistic effect in the absence of any cocatalysts.Importantly,Cu_(6)-NH_(2) can realize direct conversion of CO_(2) in simulated flue gas into oxazolidinones with high efficiency.The metal-ligand cooperative effect and integrated advantages of homogeneous and heterogeneous catalysis would provide new perspectives to achieve advanced metal nanocluster catalysts for CO_(2) conversion.

Tailor-Made Dynamic Fluorophores:Precise Structures Controlling the Photophysical Properties

Organic fluorophores with dynamic conformations in the excited state have played a significant role in applications of organic functional dyes.Among them,dihydrophenazine-based dynamic fluorophores involving a photoinduced structural planarization process in the excited state exhibited large Stokes shifts and conformation-dependent multicolor emissions.With the developments of synthetic strategies,precise modifications on dihydrophenazinebased scaffolds have successfully afforded a variety of precise molecular structures of varying sizes and compositions,which have delicately modulated their photophysical properties.Herein,this Perspective summarizes the precise modulations of dihydrophenazine-based dynamic fluorophores,including the development of the synthetic methodologies,and tailor-made molecular models to reveal the luminescence−structure relationships.

Bulky Thiolate-Protected Silver Nanocluster Ag_(213)(Adm-S)_(44)Cl_(33)with Excellent Electrocatalytic Performance toward Oxygen Reduction

Atomically precise gold and/or silver nanoclusters play a key role in crystallography and coordination chemistry.Compared with gold nanoclusters,silver nanoclusters become unstable and difficult to crystallize due to the high reactivity ofmetal silver.Herein,we report a silver nanocluster Ag_(213)(Adm-S)_(44)Cl_(33)(Ag_(213))coprotected by bulky thiolates and chlorides.The low surface thiolate coverage(about 45%)endows Ag_(213)with high catalytic activity.Supported on activated carbon,Ag_(213)nanoclusters exhibit excellent electrocatalytic oxygen reduction performance with Eonset and E_(1/2)values of 0.89 and 0.72 V,respectively,close to the values of commercial Pt/C catalyst.This is the first report on the electrocatalytic oxygen reduction reaction of nanoclusters with more than 100 silver atoms.Ag_(213)with the diameter of 2.75 nm comprises a core–shell structure Ag_(7)@Ag_(32)@Ag_(77)@Ag_(97).The strong plasmonic absorption band at 454 nm reveals the metallic nature of Ag_(213).Interestingly,halide is of importance.Chloride facilitates the formation of Ag_(213)and Ag_(56)(Adm-S)_(33)Cl_(16)(Ag_(56)^(Cl))while bromide can promote the formation of Ag_(56)(Adm-S)_(33)Br_(16)(Ag_(56)Br).This work provides an example for the study of largesized metal nanoclusters and nanocluster-based electrocatalysts.

Atomically precise copper nanoclusters as ultrasmall molecular aggregates:Appealing compositions,structures,properties,and applications

Metal nanoclusters(NCs)are ultrasmall molecular aggregates consisting of dozens to hundreds of metal atoms consolidated by organic ligands,which represent an emerging area of nanoscience.Amide a myriad of metal NCs,copper NCs(CuNCs)comprise a low-cost,high-value subclass that has attracted great attention.The variable copper cores and diversity of protecting ligands have rendered CuNCs interesting molecular aggregates featuring structural and compositional versatility,hence showing distinctive properties and potential applications.In the present review,we have summarized the progress on atomically precise CuNCs that exhibit a range of appealing properties and applications in different fields.This review is expected to provide not only an overview of the current development on atomically precise CuNCs,but also possible directions for the future design of novel CuNCs for fundamental studies and practical applications.

Catalytic Conversion of C_(1) Molecules on Atomically Precise Metal Nanoclusters

Metal nanoclusters with accurate compositions and precise crystalline structures hold remarkable attention in serving as a unique model catalyst for well-defined correlations between structure and catalytic activity.More importantly,these metal nanoclusters exhibit strong quantum confinement effects,which differ from their larger nanoparticles in a number of catalytic reactions.This review focuses on recent advances of atomically precise metal nanoclusters for C_(1) compound conversion(C_(O),CO_(2),CH_(4),and HCOOH),including thermally-driven catalysis,photocatalysis,and electrocatalysis.The reaction mechanisms are discussed at an atomic-or even electron-level.It is anticipated that the progress in this research area could be extended to catalytic applications of metal nanoclusters in C_(1) chemistry.