In this study,water soluble CuO nanostructures having nanobelt,nanorod,or spindle morphologies were synthesized using aqueous solutions of Cu(NO_(3))_(2)·3H_(2)O and NaOH by adjusting the type of surface modifier...In this study,water soluble CuO nanostructures having nanobelt,nanorod,or spindle morphologies were synthesized using aqueous solutions of Cu(NO_(3))_(2)·3H_(2)O and NaOH by adjusting the type of surface modifier and reaction temperature.The effect of morphologies of these various CuO nanostructures as water‐based lubricant additives on tribological properties was evaluated on a UMT‐2 micro‐friction tester,and the mechanisms underlying these properties are discussed.The three different morphologies of CuO nanostructures exhibited excellent friction‐reducing and anti‐wear properties.Tribological mechanisms differed in the initial stage of frictional interactions,but in the stable stage,a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs,leading to improved tribological properties.展开更多
CONSPECTUS:Additive Manufacturing(AM)technology produces three-dimensional components in a layer-by-layer fashion and offers numerous advantages over conventional manufacturing processes.Driven by the growing needs of...CONSPECTUS:Additive Manufacturing(AM)technology produces three-dimensional components in a layer-by-layer fashion and offers numerous advantages over conventional manufacturing processes.Driven by the growing needs of diverse industrial sectors,this technology has seen significant advances on both scientific and engineering fronts.Fusion-based processes are the mainstream techniques for AM of metallic materials.As the metals go through melting and solidification during the printing processes,the final microstructure and hence the properties of the printed components are highly sensitive to the printing conditions and can be very different from those of the feedstock.It is critical to understand the process-microstructure-property relationship for the accelerated optimization of the processing conditions and certification of the printed components.While experimentation has been used widely to acquire a mechanistic understanding of this subject matter,numerical modeling has become increasingly helpful in achieving the same purpose.In this Account,the authors review their ongoing collaborative effort to establish a multiphysics modeling framework to predict the process-microstructure-property relationship in fusion-based metal AM processes.The framework includes three individual modules to simulate the dominating physics that dictate the process dynamics and microstructure evolution during printing as well as the responses of the printed microstructure to specific mechanical loadings.The process model uses the material properties and processing conditions as the inputs and simulates the laser-material interaction,multiphase thermo-fluid flow,and fluid-driven powder motion.It has successfully revealed the physical causes of depression zone shape variation as well as powder motion during the laser powder bed fusion process.The microstructure model uses the thermal history of the printing process and the material chemistry as the inputs and predicts the nucleation and growth of multiple grains in the multipass and multilayer printing processes.It has been used to understand the effects of inoculation and thermal conditions on grain texture evolution.The property models use microstructure data from simulations,experimental measurements,or statistical analyses as the inputs and leverage various computational tools to predict the mechanical response of the AM materials.These models have been used to quantitatively evaluate the effects of grain structure,residual strain,and pore and void defects on their properties and performance.While this and many other modeling works have significantly grown our collective knowledge of the process-microstructure-property relationship in fusion-based metal AM processes,efforts should be further invested in developing advanced theories and algorithms for the governing physics,leveraging data-driven approaches,accelerating simulation speed,and calibrating/validating models with controlled experimental measurements,among other aspects.展开更多
The limitations in electronics in arithmetic, algebraic & logic processing are well known. Very high speed performance (above GHz) are not expected at all in conventional electronic mechanism. To achieve high spee...The limitations in electronics in arithmetic, algebraic & logic processing are well known. Very high speed performance (above GHz) are not expected at all in conventional electronic mechanism. To achieve high speed performance we may think on the introduction of optics instead of electronics for information, processing and computing. Non-linear optical material is a successful candidate in this regard to play a major role in the optically controlled switching systems and therefore in all-optical parallel computation these materials can show a very good potential aspect. In this paper, we have proposed a new method of an optical half adder as well as full adder circuit for binary addition using non-linear and linear optical materials.展开更多
2,5-Furandicarboxylic(FDCA) is a potential substitute for petroleum-derived terephthalic acid, and aerobic oxidation of5-hydroxymethylfurfural(HMF) provides an efficient route to synthesis of FDCA. On an activated car...2,5-Furandicarboxylic(FDCA) is a potential substitute for petroleum-derived terephthalic acid, and aerobic oxidation of5-hydroxymethylfurfural(HMF) provides an efficient route to synthesis of FDCA. On an activated carbon supported ruthenium(Ru/C) catalyst(with 5 wt% Ru loading), HMF was readily oxidized to FDCA in a high yield of 97.3% at 383 K and 1.0 MPa O_2 in the presence of Mg(OH)_2 as base additive. Ru/C was superior to Pt/C and Pd/C and also other supported Ru catalysts with similar sizes of metal nanoparticles(1–2 nm). The Ru/C catalysts were stable and recyclable, and their efficiency in the formation of FDCA increased with Ru loadings examined in the range of 0.5 wt%–5.0 wt%. Based on the kinetic studies including the effects of reaction time, reaction temperature, O_2 pressure, on the oxidation of HMF to FDCA on Ru/C, it was confirmed that the oxidation of HMF to FDCA proceeds involving the primary oxidation of HMF to 2,5-diformylfuran(DFF) intermediate, and its sequential oxidation to 5-formyl-2-furancarboxylic acid(FFCA) and ultimately to FDCA, in which the oxidation of FFCA to FDCA is the rate-determining step and dictates the overall formation rate of FDCA. This study provides directions towards efficient synthesis of FDCA from HMF, for example, by designing novel catalysts more efficient for the involved oxidation step of FFCA to FDCA.展开更多
For A Zm and n ∈ Zm, let σA（n） be the number of solutions of equation n =x ＋ y, x, y ∈ A. Given a positive integer m, let Rm be the least positive integer r such that there exists a set A Zm with A ＋ A = Zm ...For A Zm and n ∈ Zm, let σA（n） be the number of solutions of equation n =x ＋ y, x, y ∈ A. Given a positive integer m, let Rm be the least positive integer r such that there exists a set A Zm with A ＋ A = Zm and σA（n） ≤ r. Recently, Chen Yonggao proved that all Rm ≤ 288. In this paper, we obtain new upper bounds of some special type Rkp2.展开更多
基金The authors acknowledge the financial support provided by National Natural Science Foundation of China(Nos.51775168,21671053,51875172,51605143,and 51605469)Scientific and Technological Innovation Team of Henan University(No.19IRTSTHN024)Key Scientific Research Project of Colleges and Universities in Henan Province(No.20A150003)。
文摘In this study,water soluble CuO nanostructures having nanobelt,nanorod,or spindle morphologies were synthesized using aqueous solutions of Cu(NO_(3))_(2)·3H_(2)O and NaOH by adjusting the type of surface modifier and reaction temperature.The effect of morphologies of these various CuO nanostructures as water‐based lubricant additives on tribological properties was evaluated on a UMT‐2 micro‐friction tester,and the mechanisms underlying these properties are discussed.The three different morphologies of CuO nanostructures exhibited excellent friction‐reducing and anti‐wear properties.Tribological mechanisms differed in the initial stage of frictional interactions,but in the stable stage,a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs,leading to improved tribological properties.
基金support provided by the National Science Foundation under Grant No.CMMI-2119671.
文摘CONSPECTUS:Additive Manufacturing(AM)technology produces three-dimensional components in a layer-by-layer fashion and offers numerous advantages over conventional manufacturing processes.Driven by the growing needs of diverse industrial sectors,this technology has seen significant advances on both scientific and engineering fronts.Fusion-based processes are the mainstream techniques for AM of metallic materials.As the metals go through melting and solidification during the printing processes,the final microstructure and hence the properties of the printed components are highly sensitive to the printing conditions and can be very different from those of the feedstock.It is critical to understand the process-microstructure-property relationship for the accelerated optimization of the processing conditions and certification of the printed components.While experimentation has been used widely to acquire a mechanistic understanding of this subject matter,numerical modeling has become increasingly helpful in achieving the same purpose.In this Account,the authors review their ongoing collaborative effort to establish a multiphysics modeling framework to predict the process-microstructure-property relationship in fusion-based metal AM processes.The framework includes three individual modules to simulate the dominating physics that dictate the process dynamics and microstructure evolution during printing as well as the responses of the printed microstructure to specific mechanical loadings.The process model uses the material properties and processing conditions as the inputs and simulates the laser-material interaction,multiphase thermo-fluid flow,and fluid-driven powder motion.It has successfully revealed the physical causes of depression zone shape variation as well as powder motion during the laser powder bed fusion process.The microstructure model uses the thermal history of the printing process and the material chemistry as the inputs and predicts the nucleation and growth of multiple grains in the multipass and multilayer printing processes.It has been used to understand the effects of inoculation and thermal conditions on grain texture evolution.The property models use microstructure data from simulations,experimental measurements,or statistical analyses as the inputs and leverage various computational tools to predict the mechanical response of the AM materials.These models have been used to quantitatively evaluate the effects of grain structure,residual strain,and pore and void defects on their properties and performance.While this and many other modeling works have significantly grown our collective knowledge of the process-microstructure-property relationship in fusion-based metal AM processes,efforts should be further invested in developing advanced theories and algorithms for the governing physics,leveraging data-driven approaches,accelerating simulation speed,and calibrating/validating models with controlled experimental measurements,among other aspects.
文摘The limitations in electronics in arithmetic, algebraic & logic processing are well known. Very high speed performance (above GHz) are not expected at all in conventional electronic mechanism. To achieve high speed performance we may think on the introduction of optics instead of electronics for information, processing and computing. Non-linear optical material is a successful candidate in this regard to play a major role in the optically controlled switching systems and therefore in all-optical parallel computation these materials can show a very good potential aspect. In this paper, we have proposed a new method of an optical half adder as well as full adder circuit for binary addition using non-linear and linear optical materials.
基金supported by the National Natural Science Foundation of China(21373019,21433001,21690081)
文摘2,5-Furandicarboxylic(FDCA) is a potential substitute for petroleum-derived terephthalic acid, and aerobic oxidation of5-hydroxymethylfurfural(HMF) provides an efficient route to synthesis of FDCA. On an activated carbon supported ruthenium(Ru/C) catalyst(with 5 wt% Ru loading), HMF was readily oxidized to FDCA in a high yield of 97.3% at 383 K and 1.0 MPa O_2 in the presence of Mg(OH)_2 as base additive. Ru/C was superior to Pt/C and Pd/C and also other supported Ru catalysts with similar sizes of metal nanoparticles(1–2 nm). The Ru/C catalysts were stable and recyclable, and their efficiency in the formation of FDCA increased with Ru loadings examined in the range of 0.5 wt%–5.0 wt%. Based on the kinetic studies including the effects of reaction time, reaction temperature, O_2 pressure, on the oxidation of HMF to FDCA on Ru/C, it was confirmed that the oxidation of HMF to FDCA proceeds involving the primary oxidation of HMF to 2,5-diformylfuran(DFF) intermediate, and its sequential oxidation to 5-formyl-2-furancarboxylic acid(FFCA) and ultimately to FDCA, in which the oxidation of FFCA to FDCA is the rate-determining step and dictates the overall formation rate of FDCA. This study provides directions towards efficient synthesis of FDCA from HMF, for example, by designing novel catalysts more efficient for the involved oxidation step of FFCA to FDCA.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10901002 10771103)
文摘For A Zm and n ∈ Zm, let σA（n） be the number of solutions of equation n =x ＋ y, x, y ∈ A. Given a positive integer m, let Rm be the least positive integer r such that there exists a set A Zm with A ＋ A = Zm and σA（n） ≤ r. Recently, Chen Yonggao proved that all Rm ≤ 288. In this paper, we obtain new upper bounds of some special type Rkp2.
