Preparation and properties of open-cell zinc foams as human bone substitute material

Foamed zinc was prepared by infiltration casting process.The mechanical properties and corrosion resistance of the samples were studied,and the feasibility of the foamed zinc as a bone implant material was discussed.All the compression stress-strain curves of open-cell zinc foams with various cell size(1-4 mm)and porosity(55%-67%)show three stages:elastic stage,plastic stage,and densification stage.The compression strength increases with decreasing density.The smooth stress-strain response indicates a progressively deformation of open-cell zinc foam.In addition,the cell wall or edge bending and fracture are the dominated mechanisms for failure of open cell zinc foam.The immersion test for determining the corrosion rate of open cell zinc foam was conducted in simulated body fluid.It was found that zinc foam with a small cell size and high porosity showed a higher corrosion rate.In addition,open-cell zinc foams can effectively induce Ca-P deposition in immersion tests,showing good bioactivity.Therefore,the open cell zinc foam prepared in this experiment has a good potential application as a human bone substitute material.

基于POA优化FMD参数的滚动轴承早期故障诊断

早期滚动轴承故障较难诊断,且特征模式分解(FMD)输入参数滤波器长度L和模态分量个数n较难准确选择。因此,提出基于鹈鹕优化算法(POA)优化FMD参数的滚动轴承早期故障诊断方法。该方法以全体峭度的指标作为适应度函数,通过POA优化算法获取FMD优良参数组合,并且结合包络谱分析实现故障诊断。使用该方法对滚动轴承早期故障仿真信号和实验信号进行分析,结果表明:该方法通过优化FMD参数,可以从包络谱中得到故障特征频率及其倍频突出的幅值,进而诊断出滚动轴承早期故障类别;与基于固有时间尺度分解(ITD)和基于最小熵解卷积(MED)方法相比,包络谱中的故障特征频率及其倍频幅值更突出,在滚动轴承早期故障诊断中具有一定的应用前景和价值。

Bi@C nanosphere anode with Na^(+)-ether-solvent cointercalation behavior to achieve fast sodium storage under extreme low temperatures

The low ion transport is a major obstacle for low-temperature(LT)sodium-ion batteries(SIBs).Herein,a core-shell structure of bismuth(Bi)nanospheres coated with carbon(Bi@C)is constructed by utilizing a novel Bi-based complex(1,4,5,8-naphthalenetetracarboxylic dianhydride as the ligand)as the precursor,which provides an effective template to fabricate Bi-based anodes.At-40℃,the Bi@C anode achieves a high capacity,which is equivalent to 96%of that at 25℃,benefitting from the core-shell nanostructured engineering and Na^(+)-ether-solvent cointercalation process.The special Na+-diglyme cointercalation behavior may effectively reduce the activation energy and accelerate the Na+diffusion kinetics,enabling the excellent low-temperature performance of the Bi@C electrode.As expected,the fabricated Na_(3)V_(2)(PO_(4))_(3)//Bi@C full-cell delivers impressive rechargeability in the ether-based electrolyte at-40℃.Density functional theory calculations and electrochemical tests also reveal the fast reaction kinetic mechanism at LT,thanks to a much lower diffusion energy barrier(167 meV)and a lower reaction activation energy(32.2 kJ mol^(-1))of Bi@C anode in comparison with that of bulk Bi.This work provides a rational design of Bi-based electrodes for rechargeable SIBs under extreme conditions.

Tailoring crystal plane of short-process regenerated LiFePO_(4) towards enhanced rate properties

Captured by the environmental and economic value,the recycling of spent lithium iron phosphate(LFP)batteries has attracted numerous attentions.However,hydrometallurgical method still suffers from complex process,and hydrothermal method is limited by morphology control,ascribed to the strong polarity of water.Herein,supported by ethanol as crystal surface modifier,the regular(010)orientation and short b-axis are effectively tailored for regenerated LFP.As Li-storage cathode,the capacities of as-optimized LFP could reach up to 157.07 mA h g^(-1)at 1 C,and the stable capacity of 150.50 mA h g^(-1)could be remained with retention of 93.48%after 400 cycles at 1 C.Even at 10 C,their capacity could be still kept about 119.3 m A h g^(-1).Assisted by the detail analysis of adsorption energy,the clear growth mechanism is proposed,the lowest adsorbing energy(-4.66 eV)of ethanol on(010)crystal plane renders the ordered growth along(010)crystal plane.Given this,the work is expected to shed light on the tailoring mechanism of internal plane about regenerated materials,whilst providing effective strategies for highperformance regenerated LFP.

From charge storage mechanism to performance:A strategy toward boosted lithium/sodium storage through heterostructure optimization

Solving the problems of low electrical conductivity and poor cycling durability in transition metal oxidesbased anode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has already turned into an urgent requirement.In this paper,we successfully synthesized Co_(2)VO_(4)/Co compounds with Co-VMOF(metal-organic framework)as a sacrificial template and investigated their electrochemical mechanism in order to improve the electrochemical properties of LIBs and SIBs.The optimized heaping configuration and the existence of metallic Co catalyzed the formation of radical ions,thereby facilitating higher conductivity,shortening Li+and Na+transport paths,and providing more active sites.Co_(2)VO_(4)/Co constructed with 2-methylimidazole as a ligand showed a discharge capacity of 1605.1 mA h g^(-1)after 300 cycles at 0.1 A g^(-1)in LIB and 677.2 mA h g^(-1)in SIB.Density functional theory(DFT)calculation emphasizes the crucial role of Co_(2)VO_(4)/Co in enhancing electrode conductivity,decreasing the migratory energy barrier,and thereby strengthening electrochemical properties.This heterostructure building technique may pave the way for the development of high-performance LIBs and SIBs.Furthermore,the problem of the low first-loop coulombic efficiency faced by transition metal oxides is improved.

Controllable step-flow growth of GaN on patterned freestanding substrate

A new kind of step-flow growth mode is proposed,which adopts sidewall as step source on patterned GaN substrate.The terrace width of steps originated from the sidewall was found to change with the growth temperature and ammonia flux.The growth mechanism is explained and simulated based on step motion model.This work helps better understand the behaviors of step advancement and puts forward a method of precisely modulating atomic steps.

Artificial intelligence technology in rock mechanics and rock engineering

The scope and scale of rock engineering activities have witnessed continuous expansion,which makes the geological conditions of rock engineering increasingly complex,and there are more and more types of disasters occurring during the construction and operation processes.The uncertainty of engineering geological information and the unclear nature of rock mass failure and disaster mechanisms pose increasingly prominent challenges to the study of rock mechanics and engineering problems.The artificial intelligence technology develops driven by data and knowledge,especially the proposal of digital-twin technology and metaverse ideas.This has injected new innovative impetus for the development of rock mechanics and engineering intelligence,where data and knowledge have been greatly enriched and updated in recent years.This article proposes the construction idea of a rock mechanics and engineering artificial intelligence system based on the metaverse,including intelligent recognition of three-dimensional(3D)geological structures,intelligent recognition of 3D geostress,intelligent recognition of rock mechanical behavior,intelligent evaluation,monitoring and early warning of rock engineering disaster,intelligent design of rock engineering,and intelligent construction of rock engineering.Two typical engineering applications are used as case studies to illustrate the integrated method of applying this system to solve engineering problems with multiple tasks.

Recycled, Bio-Based, and Blended Composite Materials for 3D Printing Filament: Pros and Cons—A Review

In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.

Use of a 2-Dimensional Ionization Chamber Array to Measure Head Leakage of a Varian Truebeam^®Linear Accelerator

The purpose of this work is to evaluate the use of a two-dimensional (2D) planar ion chamber array to characterize leakage radiation from the head of the linear accelerator. Ion chamber arrays provide a benefit over a singular ion chamber measurement as they allow for the measurement of a larger area in order to isolate the point of maximum leakage dose and the small size of each individual ion chamber minimizes volume-averaging effects. A Varian Truebeam® undergoing acceptance testing was used for all measurements. The gantry was wrapped in Portal Pack for Localization (PPL) radiographic film in order to isolate the location of maximum leakage. A calibration curve was developed and used to determine dose-to-film. An Ion Chamber Profiler (IC Profiler™) manufactured by Sun Nuclear Corporation was used to confirm measurements by the PPL film. All measurements were normalized to leakage at 100 cm from the target relative to the central axis. Three points were investigated with the IC Profiler, including the top of the gantry, the Varian logo, and the side of the gantry. For the three locations, respectively, the PPL film and the IC profiler were measured 0.142% and 0.131%, 0.036% and 0.030%, and 0.014% and 0.019%. The good agreement between the PPL film and the IC Profiler provides confidence in the use of a more efficient and accurate ion chamber array for head leakage measurements.

高负荷轴流风扇中弯曲动叶的应用研究

本文采用弯曲叶片设计方法,对前期设计的大折转角高负荷轴流风扇的叶轮叶片进行根部正弯处理,弯角为30°。采用数值模拟方法,对比了直叶片和正弯叶片的叶轮流场,确定了弯叶片气动作用的有效性。结果表明设计工况下,利用径向叶片力,压制了由于旋转和叶栅高扩压度引起的轮毂分离流动。正弯动叶级效率提高了1.64%,静压升增大了10.74%。动叶吸力面根部分离区位置后移,强度减弱,静叶吸力面流动有明显改善,低速区均明显减小,通流能力增大,降低了叶栅内部流场中的能量损失。

一种机动无源光接入系统的应用研究

针对各种重大突发事件发生所导致信息实时传送阻断问题,研发了一种灵活应用的机动应急光接入系统,在硬件、软件及接口等技术基础上,进行了系统管理软件关键技术的设计,阐述了链路测试过程并进行了组网应用。测试结果表明:从源端到目的端的吞吐量为75.47Mb/s(TCP)和20.56Mb/s(UDP)。通过在不同地理位置,分别选择8km、13km和18km的传送距离进行语音、数据、图像及视频等多业务试用,信号传输正常、网络运行稳定。

高速线材Φ7.3 mm规格盘条的开发

针对市场对Φ7.3 mm规格免拉拔线材盘条的个性化需求,结合摩根五代高速线材轧机的特点,通过合理的孔型设计、导卫设计以及控制工艺的优化,实现了Φ7.3 mm规格高速线材免拉拔盘条的成功轧制,能够很好地满足用户使用需求,拓宽了摩根五代高速线材轧机产品大纲,为后续类似产品开发提供了参考。开拓了全新的市场,实现产业全流程的绿色生产。

CDDO-Me对三阴性乳腺癌细胞泛素特异性蛋白酶2a活性及细胞增殖的抑制作用

目的·在三阴性乳腺癌(triple negative breast cancer,TNBC)细胞中研究筛选得到的泛素特异性蛋白酶2a(ubiquitin-specific protease 2a,USP2a)抑制剂甲基巴多索隆(bardoxolone methyl,CDDO-Me)对USP2a活性及细胞增殖的影响。方法·利用泛素特异性蛋白酶抑制剂筛选系统筛选得到USP2a抑制剂CDDO-Me,采用分子对接分析技术预测CDDO-Me与USP2a的结合情况,采用细胞热迁移实验(cellular thermal shift assay,CETSA)检测CDDO-Me与3种TNBC细胞株内USP2a蛋白的结合情况。通过Western blotting检测USP2a的底物β连环素(β-catenin)和肿瘤坏死因子受体相关因子6(tumor necrosis factor receptor-associated factor 6,TRAF6)蛋白水平以及凋亡相关蛋白胱天蛋白酶3(caspase3)和聚腺苷二磷酸核糖聚合酶1[poly(ADP-ribose)polymerase1,PARP1]的变化。利用细胞活性检测试剂盒8(cell counting kit-8,CCK8)检测CDDO-Me对TNBC细胞增殖的影响。MDA-MB-468细胞瞬时转染pLVX(pLVX组)或pLVX-USP2a(pLVX-USP2a组)质粒,经CDDO-Me处理后,采用Western blotting检测β-catenin和TRAF6的蛋白水平,流式细胞术检测细胞周期以及台盼蓝拒染法检测活细胞数。结果·CDDO-Me在体外可以抑制USP2a活性,50%抑制浓度为3.84μmol/L。分子对接分析结果显示,CDDO-Me可以和USP2a的His456残基之间形成氢键,和Phe409、Tyr514残基之间具有疏水相互作用。CETSA实验结果显示,CDDO-Me能够和3种TNBC细胞中的USP2a蛋白结合。Western blotting结果显示,CDDO-Me可以下调USP2a底物β-catenin和TRAF6的蛋白水平,而相同浓度的CDDO-Me处理USP2a过表达的MDA-MB-468细胞,发现β-catenin和TRAF6蛋白水平未出现明显降低。CDDO-Me呈剂量依赖性抑制TNBC细胞的增殖,使细胞发生caspase3活化和PARP1的剪切并且导致细胞出现S期和G2/M期阻滞。与pLVX组相比,pLVX-USP2a组活细胞数目更多,细胞也未出现周期阻滞。结论·CDDO-Me可以抑制TNBC细胞中USP2a的活性,并且抑制TNBC细胞的增殖,诱导其凋亡。

高温高湿环境下调亏灌溉对番茄叶片光合和衰老特性的影响

为了研究调亏灌溉对高温高湿环境下设施番茄光合及衰老特性的影响,以番茄品种合作903为试验材料,在夏季玻璃温室内进行了试验,试验期间温室内的平均气温为31.45℃,平均相对湿度为69.95%。试验以开花至结果期番茄的潜在蒸散量(ET_(0))为CK,设置了4个灌溉处理:100%ET_(0)、90%ET_(0)、75%ET_(0)和50%ET_(0),测定番茄叶片的光合特性和衰老特性。结果表明,与100%ET_(0)处理相比,90%ET_(0)处理番茄叶片最大净光合速率(Pm)、叶绿素含量和可溶性蛋白含量分别显著升高70.64%、27.45%、49.25%,MDA含量显著降低15.97%,叶片衰老程度低,光合活性高,有利于番茄植株光合生产;50%ET_(0)处理番茄叶片叶绿素含量、光饱和点(LSP)分别降低了9.02%、25.44%,呼吸速率(Rd)和光补偿点(LCP)显著增高了36.69%、10.21%,叶片光合活性低。90%ET_(0)灌溉处理为夏季高温高湿环境下设施番茄的最佳灌溉量。

扩压叶栅缩放模化中表面粗糙度的影响及其修正方法

从扩压叶栅实验研究时的模化问题出发,研究表面粗糙度和基于弦长的雷诺数对叶型损失系数的影响并总结其影响规律。基于零压力梯度流动表面粗糙度影响的边界层理论及水力光滑条件下雷诺数改变对压气机性能的影响规律,综合考虑表面粗糙度k_(s)和雷诺数Re对叶型损失的影响,建立了扩压叶栅的叶型损失修正方法,初步解决了模化设计与母型之间性能换算的问题。

基于C51语言的星载嵌入式软件定时器管理方法

本文通过对星载51系列单片机定时器常见问题进行分析,归纳出三类典型问题,分别给出解决方案,并在此基础上总结出一套基于C51语言的星载嵌入式软件定时器管理方法,该方法可以解决因中断冲突和定时器进位而产生的问题,同时可推广到其他嵌入式领域的定时器使用中。

Excavation-induced deep hard rock fracturing:Methodology and applications

To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths.Evolution mechanisms of stress-induced disasters in deep hard rock excavations,such as spalling,deep cracking,massive roof collapse,large deformation and rockbursts,have been recognized.The analytical theory for the fracturing process of hard rock masses,including the three-dimensional failure criterion,stress-induced mechanical model,fracturing degree index,energy release index and numerical method,has been established.The cracking-restraint method is developed for mitigating or controlling rock spalling,deep cracking and massive collapse of deep hard rocks.An energy-controlled method is also proposed for the prevention of rockbursts.Finally,two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.

A new long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(PPO)/polybenzimidazole(PBI)amphoteric membrane for vanadium redox flow battery

A new amphoteric membrane was prepared by blending long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(S-L-PPO)and polybenzimidazole(PBI)for vanadium redox flow battery(VRFB)application.An acid-base pair structure formed between the imidazole of PBI and sulfonic acid of S-L-PPO resulted in lowered swelling ratio.It favors to reduce the vanadium permeation.While,the increased sulfonic acid concentration ensured that proton conductivity was still at a high level.As a result,a better balance between the vanadium ion permeation(6.1×10^-9 cm^2·s^-1)and proton conductivity(50.8 m S·cm^-1)in the S-L-PPO/PBI-10%membrane was achieved.The VRFB performance with S-L-PPO/PBI-10%membrane exhibited an EE of 82.7%,which was higher than those of pristine S-L-PPO(81.8%)and Nafion 212(78.0%)at 120 m A·cm^-2.In addition,the S-LPPO/PBI-10%membrane had a much longer self-discharge duration time(142 h)than that of Nafion 212(23 h).

Highly efficient production of 2,5-dihydroxymethylfuran from biomass-derived 5-hydroxymethylfurfural over an amorphous and mesoporous zirconium phosphonate catalyst

The development of high-efficiency and low-cost catalysts is very crucial for the MeerweinPonndorf-Verley (MPV) reduction of biomass-derived 5-hydroxymethylfurfural (HMF) into 2,5-dihydroxymethylfuran (DHMF). In this work, an amorphous and mesoporous zirconium phosphonate catalyst (Zr-DTMP), which is a zirconium-containing organic-inorganic nanohybrid, was successfully designed and synthesized by the simple assembly of zirconium tetrachloride (ZrCl4) and diethylene triaminepenta(methylene phosphonic acid)(DTMP). Satisfactorily, when Zr-DTMP was employed for the MPV reduction of HMF in the presence of 2-butanol (secBuOH), DHMF yield could be achieved as 96.5% in 3 h under a relatively mild reaction temperature of 140℃. Systematic investigations indicated that this high catalytic activity should be mainly due to the cooperative role of enhancive Lewis acid site (Zr4+) and Lewis base site (O2-) in activating the carbonyl group of HMF and dissociating the hydroxyl group of secBuOH, respectively. Additionally, Zr-DTMP showed excellent catalytic stability, when it was successively used 5 recycles, its surface characteristics and textural properties still remained almost unchanged, and so, the catalytic activity was not obviously affected. More interestingly, Zr-DTMP could also be applied for the selective reduction of other biomass-derived carbonyl compounds, such as 5-methylfurfural (MF), furfural (FF), levulinic acid (LA), ethyl levulinate (EL) and cyclohexanone (CHN), into the corresponding products with high yields, which is beneficial to the effective synthesis of various valuable bio-based chemicals.

基于等效替代下滚动轴承滚子接触载荷算法研究

传统的计算滚子接触载荷与接触变形的方法计算量庞大,易出现系统崩溃的情况。采用等效替代的方法,建立了3种等效数学模型,运用牛顿迭代原理求解出滚子的变形量,进而求得不同滚子在3种数学模型下的接触变形与接触载荷,按照从小到大再到小的顺序进行数值排列,得到任意滚子在不同时刻的接触变形及接触载荷的变化范围。与传统计算方法相比,提出的新方法计算生成的程序迅速,不易出现系统崩溃的情况,且计算结果满足传统方法的数值。