制造发展的三个范式:制造发展规律的研究

基于对人类社会发展历史和科学技术发展内在规律的认识,本文详细分析了制造发展的三个范式,论证了原子及近原子尺度制造是制造范式III的核心使能技术。文章回顾了国内外各机构对原子级制造研发规划现状,指出我国目前处于原子级制造技术发展的重要战略机遇期,并从设计、材料、加工和检测等角度分析了原子级制造的技术体系内涵;梳理了原子级表面制造、原子级结构制造、原子级测量与表征等领域的研究进展,呈现了当前具有原子级制造能力的部分代表性技术,包括原子级切削、原子级抛光、电化学加工、等离子体原子级加工技术、原子精准操控以及原子分辨测量与表征技术,并对原子级制造战略规划提出发展建议。

Nanometric Cutting Mechanism of Cerium-Lanthanum Alloy

Cerium-lanthanum alloy is widely used in the green energy industry,and the nanoscale smooth surface of this material is in demand.Nanometric cutting is an effective approach to achieving the ultra-precision machining surface.Molecular dynamics(MD)simulation is usually used to reveal the atomic-scale details of the material removal mechanism in nanometric cutting.In this study,the effects of cutting speed and undeformed chip thickness(UCT)on cutting force and subsurface deformation of the cerium-lanthanum alloy during nanometric cutting are analyzed through MD simulation.The results illustrate that the dislocations,stacking faults,and phase transitions occur in the subsurface during cutting.The dislocations are mainly Shockley partial dislocation,and the increase of temperature and pressure during the cutting process leads to the phase transformation ofγ-Ce(FCC)intoβ-Ce(HCP)andδ-Ce(BCC).β-Ce is mainly distributed in the stacking fault area,whileδ-Ce is distributed in the boundary area between the dislocation atoms andγ-Ce atoms.The cutting speed and UCT affect the distribution of subsurface damage.A thicker deformed layer including dislocations,stacking faults and phase-transformation atoms on the machined surface is generated with the increase in the cutting speed and UCT.Simultaneously,the cutting speed and UCT significantly affect the cutting force,material removal rate,and generated subsurface state.The fluctuations in the cutting force are related to the generation and disappearance of dislocations.This research first studied the nanometric cutting mechanism of the cerium-lanthanum ally,providing a theoretical basis for the development of ultra-precision machining techniques of these materials.

Association of MBOAT7 rs641738 polymorphism with hepatocellular carcinoma susceptibility:A systematic review and meta-analysis

BACKGROUND The MBOAT7 rs641738 single-nucleotide polymorphism(SNP)has been proven to influence various liver diseases,but its association with hepatocellular carcinoma(HCC)susceptibility has been debated.To address this discrepancy,we conducted the current systematic review and meta-analysis.AIM To perform a systematic review and meta-analysis on association of MBOAT7 SNP and HCC susceptibility.METHODS We performed a systematic review in PubMed,Web of Science,Scopus,and EMBASE;applied specific inclusion and exclusion criteria;and extracted the data.Meta-analysis was conducted with the meta package in R.Sensitivity and subgroup analyses were also performed.This meta-analysis was registered in PROSPERO(CRD42023458046).RESULTS Eight studies were included in the systematic review,and 12 cohorts from 6 studies were included in the meta-analysis.Our meta-analysis revealed an association between the MBOAT7 SNP and HCC susceptibility in both the dominant[odds ratio(OR):1.14,95%confidence interval(95%CI):1.02-1.26,P=0.020]and recessive(OR:1.21,95%CI:1.05-1.39,P=0.008)models.Subgroup analysis revealed that stratification of the included patients by geographical origin showed a significant association in Asia(OR:1.20,95%CI:1.03-1.39).CONCLUSION This meta-analysis underscores the contribution of the MBOAT7 rs641738 SNP to hepatocarcinogenesis,especially in Asian populations,which warrants further investigation.

Formulae for secondary electron yield from insulators and semiconductors

The processes and characteristics of secondary electron emission in insulators and semiconductors were studied, and the formulae for the maximum yield(δ_m) at W_(pOm)≤ 800 eV and the secondary electron yield from insulators and semiconductors δ at the primary incident energy of 2 keV≤ W_(pO) < 10 keV(δ_(2-10)) and10 keV ≤ W_(pO)≤100 keV(δ_(10-100)) were deduced. The calculation results were compared with their corresponding experimental data. It is concluded that the deduced formulae can be used to calculate δ_(2-100)at W_(pOm)≤ 800 eV.

人参抗血液和心血管系统衰老作用研究新进展

人参皂苷(Ginsenosides, GS)是人参的主要的抗衰老成分,衰老是体内外多因素共同作用于机体后的综合表现,GS在抗血液和心血管系统衰老中起到重要作用。Rg1可激活端粒酶并抑制端粒长度缩短而延缓造血干细胞衰老;GS明显降低血管平滑肌细胞(Vascular smooth muscle cells, VSMCs)增殖力并增加PPAR-γ表达,减少自由基产生,增加NO释放,对心血管系统起保护作用;人参提取物可减少负性细胞因子表达,延缓血管老化;人参三七川芎提取物通过下调NAD(P)H氧化酶p47phox表达而使ROS产生减少,延缓血管紧张素Ⅱ诱导的内皮细胞衰老;人参皂甙Rbl和人参皂甙Re均可减少缺血再灌注(Ischemia reperfusion, IR)心肌细胞的凋亡;人参皂甙Rb1可能具有抑制缺血再灌注心肌细胞凋亡的作用,从而减轻心肌IR损伤;实验表明人参皂甙Rb1对老龄大鼠心肌收缩有抑制作用。本文综述了近期有关于GS抗血液及心血管系统衰老作用及其机制的研究进展,将为其临床防治血液及心血管系统衰老相关疾病提供理论依据。

Ultra-precision machining of cerium-lanthanum alloy with atmosphere control in an auxiliary device

Cerium–lanthanum alloys are the main component of nickel–metal hydride batteries,and they are thus an important material in the greenenergy industry.However,these alloys have very strong chemical activity,and their surfaces are easily oxidized,leading to great difficulties in their application.To improve the corrosion resistance of cerium–lanthanum alloys,it is necessary to obtain a nanoscale surface with low roughness.However,these alloys can easily succumb to spontaneous combustion during machining.Currently,to inhibit the occurrence of fire,machining of this alloy in ambient air needs to be conducted at very low cutting speeds while spraying the workpiece with a large amount of cutting fluid.However,this is inefficient,and only a very limited range of parameters can be optimized at low cutting speeds;this restricts the optimization of other cutting parameters.To achieve ultraprecision machining of cerium–lanthanum alloys,in this work,an auxiliary machining device was developed,and its effectiveness was verified.The results show that the developed device can improve the cutting speed and obtain a machined surface with low roughness.The device can also improve the machining efficiency and completely prevent the occurrence of spontaneous combustion.It was found that the formation of a build-up of swarf on the cutting tool is eliminated with high-speed cutting,and the surface roughness(Sa)can reach 5.64 nm within the selected parameters.Finally,the oxidation processes of the cerium–lanthanum alloy and its swarf were studied,and the process of the generation of oxidative products in the swarf was elucidated.The results revealed that most of the intermediate oxidative products in the swarf were Ce^(3+),there were major oxygen vacancies in the swarf,and the final oxidative product was Ce^(4+).

Black phosphorus inverter devices enabled by in-situ aluminum surface modification

Two-dimensional black phosphorus (BP) generally exhibits a hole-dominated transport characteristic when configured as field-effect transistor devices. The effective control of charge carrier type and concentration is very crucial for the application of BP in complementary electronics. Herein, we report a facile and effective electron doping methodology on BP, through in situ surface modification with aluminum (Al). The electron mobility of few-layer BP is found to be largely enhanced to ~ 10.6 cm^2·V^–1·s^–1 by over 6 times after aluminum modification. In situ photoelectron spectroscopy characterization reveals the formation of Al–P covalent bond at the interface, which can also serve as local gate to tune the transport properties in BP layers. Finally, a spatially-controlled aluminum doping technique is employed to establish a p–n homojunction on a single BP flake, and hence to realize the complementary inverter devices, where the highest gain value of ~ 33 is obtained.

Sub-nanometer finishing of polycrystalline tin by inductively coupled plasma-assisted cutting

Polycrystalline tin is an ideal excitation material for extreme ultraviolet light sources.However,the existence of grain boundary(GB)limits the surface roughness of polycrystalline tin after single-point diamond turning(SPDT).In this work,a novel method termed inductively coupled plasma(ICP)-assisted cutting was developed for the sub-nanometer finishing of polycrystalline tin.The relationship between ICP power,processing time,and modification depth was established by thermodynamic simulation,and the fitted heat transfer coefficient of polycrystalline tin was 540 W/(m2·K).The effects of large-thermal-gradient ICP treatment on the microstructure of polycrystalline tin were studied.After 0.9 kW ICP processing for 3.0 s,corresponding to the temperature gradient of 0.30 K/μm,the grain size of polycrystalline tin was expanded from a size of approximately 20-80μm to a millimeter scale.The Taguchi method was used to investigate the effects of rotational speed,depth of cut,and feed rate on SPDT.Experiments conducted based on the ICP system indicated that the plasma-assisted cutting method promoted the reduction of the influence of GB steps on the finishing of polycrystalline tin,thereby achieving a surface finish from 8.53 to 0.80 nm in Sa.The results of residual stress release demonstrated that the residual stress of plasma-assisted turning processing after 504 h stress release was 10.7 MPa,while that of the turning process without the ICP treatment was 41.6 MPa.

Molecular dynamics study on surface formation and phase transformation in nanometric cutting of β-Sn

Atomic motion and surface formation in the nanometric cutting process ofβ-Sn are investigated using molecular dynamics(MD).A stagnation region is observed that changes the shape of the tool edge involved in nanometric cutting,resulting in a fluctuation in the cutting forces.It is found that single-crystal tin releases the high compressive stress generated under the tool pressure through slip and phase transformation.The tin transformation proceeds from aβ-Sn structure to a bct-Sn structure.The effects of the cutting speed,undeformed chip thickness(UCT)and tool edge radius on material removal are also explored.A better surface is obtained through material embrittlement caused by a higher speed.In addition,a smaller UCT and sharper tool edge help reduce subsurface damage.

Nanometric polishing of lutetium oxide by plasma-assisted etching

Plasma-assisted etching,in which the irradiation of hydrogen plasma and inorganic acid etching are integrated,is proposed as a novel polishing method for sesquioxide crystals.By means of this approach,low damage and even damage-free surfaces with a high material removal rate can be achieved in lutetium oxide surface finishing.Analysis of transmission electron microscopy and X-ray photoelectron spectroscopy reveal that plasma hydrogenation converts the sesquioxide into hydroxide,which leads a high efficient way to polish the surfaces.The influences of process conditions on the etching boundary and surface roughness are also qualitatively investigated using scanning electron microscope and white light interferometry.The newly developed process is verified by a systematic experiment.