Influence of process parameters and aging treatment on the microstructure and mechanical properties of Al Si8Mg3 alloy fabricated by selective laser melting

Many studies have investigated the selective laser melting(SLM)of AlSi10Mg and AlSi7Mg alloys,but there are still lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM.In this work,a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM.The results showed that this new alloy exhibited excellent SLM processability with a lowest porosity of 0.07%.Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser power due to the precipitation of Mg_(2)Si nanoparticles from theα-Al matrix induced by high-intensity intrinsic heat treatment during SLM.The maximum microhardness and compressive yield strength of the alloy reached HV(211±4)and(526±12)MPa,respectively.After aging treatment at 150℃,the maximum microhardness and compressive yield strength of the samples were further improved to HV(221±4)and(577±5)MPa,respectively.These values are higher than those of most known aluminum alloys fabricated by SLM.This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.

Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds

One of the well-defined sexually dimorphic structures in the brain is the sexually dimorphic nucleus,a cluster of cells located in the preoptic area of the hypothalamus.The rodent sexually dimorphic nucleus of the preoptic area can be delineated histologically using conventional Nissl staining or immunohistochemically using calbindin D28K immunoreactivity.There is increasing use of the calbindin D28K-delineated neural cluster to define the sexually dimorphic nucleus of the preoptic area in rodents.Several mechanisms are proposed to underlie the processes that contribute to the sexual dimorphism(size difference)of the sexually dimorphic nucleus of the preoptic area.Recent evidence indicates that stem cell activity,including proliferation and migration presumably from the3rdventricle stem cell niche,may play a critical role in the postnatal development of the sexually dimorphic nucleus of the preoptic area and its distinguishing sexually dimorphic feature:a significantly larger volume in males.Sex hormones and estrogen-like compounds can affect the size of the sexually dimorphic nucleus of the preoptic area.Despite considerable research,it remains unclear whether estrogen-like compounds and/or sex hormones increase size of the sexually dimorphic nucleus of the preoptic area via an increase in stem cell activity originating from the 3rdventricle stem cell niche.

Erratum to:Influence of process parameters and aging treatment on the microstructure and mechanical properties of AlSi8Mg3 alloy fabricated by selective laser melting

Erratum to:International Journal of Minerals, Metallurgy and MaterialsVolume 29, Number 9, September 2022, Page 1770https://doi.org/10.1007/s12613-021-2287-1The original version of this article unfortunately contained a mistake due to the PDF file conversion through different softwares. The presentation of Fig. 13 in original version was incorrect.

Genetic Variation of the Novel Badnaviruses Infecting Nelumbo Nucifera Based on the RT/RNase H Coding Region Sequences

Lotus(Nelumbo nucifera Gaertn.)is an economically important perennial aquatic herb plant in China.Presently,viral diseases caused by Cucumber mosaic virus(CMV)and Dasheen mosaic virus(DsMV)are detected in lotus.In this study,the putatively novel badnaviruses from lotus plants(LBVs)were identified using next-generation sequencing of siRNAs and conventional Sanger sequencing based on the RT/RNase H coding region sequences.Lotus plants infected by LBVs harbored virus quasispecies.A unique recombination event of LBVs was found in a single lotus plant.Sap inoculation showed that LBVs could actively replicate in the lotus plants,but without a wide host range.The field survey of 43 lotus plants in Jiangsu Province showed a prevalence of 62.8%for LBVs,confirming that it is widely distributed in Jiangsu Province of China.

7075铝合金半固态触变挤压件的显微组织和力学性能

通过触变挤压工艺对热挤压态7075铝合金深腔圆筒形零件进行成形,分析等温温度和保温时间对成形件显微组织和力学性能的影响。通过正交试验优化T6热处理工艺参数,研究T6热处理对成形件显微组织和力学性能的影响。结果表明,通过触变挤压可以成功成形表面光滑的深腔圆筒形零件,成形温度和加热时间对成形件的金相组织有显著影响。T6热处理可以大大提高深腔圆筒形零件的力学性能,最优的T6热处理工艺参数为:465℃固溶16h,150℃时效16h。当半固态坯料在600℃加热10min后,成形的深腔圆筒形零件具有最佳的综合力学性能,其极限抗拉强度为573.57MPa,伸长率为13.44%,显微硬度为HV187.12。

形状记忆聚合物在4D打印技术中的应用进展

形状记忆聚合物(SMP)是一种典型的智能材料,其在特定条件下可以变形成临时形状,并在环境条件变化下固定该临时形状,再次受到刺激后可以主动回复到初始形状。在智能制造领域,智能材料与增材制造技术的结合催生了4D打印技术,实现了3D打印领域的跨越发展。当前主要发展的是形状记忆聚合物4D打印技术。文中重点介绍了4D打印SMP的实现方式以及各种刺激响应材料的特点,然后介绍了基于形状记忆聚合物的4D打印结构在航空航天、生物医疗和柔性机器人领域的应用研究,最后总结了4D打印形状记忆聚合物未来可能遇到的问题并展望了其未来可能的研究方向,旨在让更多人认识4D打印技术,促进其在各行业的应用发展。

Engineering the axial coordination of cobalt single atom catalysts for efficient photocatalytic hydrogen evolution

Improving the catalytic activity of non-noble metal single atom catalysts(SACs)has attracted considerable attention in materials science.Although optimizing the local electronic structure of single atom can greatly improve their catalytic activity,it often involves in-plane modulation and requires high temperatures.Herein,we report a novel strategy to manipulate the local electronic structure of SACs via the modulation of axial Co-S bond anchored onto graphitic carbon nitride(C_(3)N_(4))at room temperature(RT).Each Co atom is bonded to four N atoms and one S atom(Co-(N,S)/C_(3)N_(4)).Owing to the greater electronegativity of S in the Co-S bond,the local electronic structure of the Co atoms is available to be controlled at a relatively moderate level.Consequently,when employed for the photocatalytic hydrogen evolution reaction,the adsorption energy of intermediate hydrogen(H*)on the Co atoms is remarkably low.In the presence of the Co-(N,S)/C_(3)N_(4)SACs,the hydrogen evolution rates reach up to 10 mmol/(g·h),which is nearly 10 and 2.5 times greater than the rates in the presence of previously reported transition metal/C_(3)N_(4)and noble platinum nanoparticles(PtNPs)/C_(3)N_(4)catalysts,respectively.Attributed to the tailorable axial Co-S bond in the SAC,the local electronic structure of the Co atoms can be further optimized for other photocatalytic reactions.This axial coordination engineering strategy is universal in catalyst designing and can be used for a variety of photocatalytic applications.

广东省海珠区10~19岁青少年青春期健康知识自评及需求分析

目的了解广东省广州市海珠区10~19岁青少年青春期健康知识自评及需求情况,为在海珠区开展基于微信平台的青春期健康教育提供策略依据。方法抽取海珠区17所学校,整群抽取小学五、六年级、初中和高中各年级、职中和大学一、二年级各一班,采用自制调查问卷调查学生青春期健康知识自评及需求。结果学生自评青春期健康知识及格率为69.1%。在青春期健康知识自评及格率模型中,相对于小学生,初中生、高中生、大学生的OR值分别为2.277、1.778和2.213;相对于父亲文化水平为小学及初中的学生,父亲文化水平为高中及大学的学生的OR为1.432;相对于未接受过学校青春期健康教育的学生,接受过学校青春期健康教育的学生的OR值为3.406。学生希望获取的前2位青春健康知识是青春期生理(70.2%)和心理(70.7%)。小学和初中学生希望获得的第3位青春期健康知识为性自我保护,高中、职中和大学生希望获得的第3位青春期健康知识为性卫生保健。结论海珠区青少年自觉青春期健康知识掌握程度较低,基于微信公众号的青春期健康教育应重点开发青春期生理和心理以及性与生殖健康。

Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

The technology of direct reduction by adding sodium carbonate (Na2CO3 ) and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na2CO3 reacts with gangue minerals (SiO2 and Al2O3 ), forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na2CO3 also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product (metal iron powder) after briquetting can be used as the burden for steelmaking by an electric arc furnace to replace scrap steel.

Low-overpotential selective reduction of CO2 to ethanol on electrodeposited CuxAuy nanowire arrays

Direct electrochemical reduction of CO2 to multicarbon products is highly desirable, yet challenging. Here, we present a potentiostatic pulse-electrodeposition of high-aspect-ratio CuxAuy nanowire arrays (NWAs) as high-performance electrocatalysts for the CO2 reduction reaction (CO2RR). The surface electronic structure related to the Cu:Au ratio in the CuxAuy NWAs could be facilely modulated by controlling the electrodeposition potential and the as-fabricated CuxAuy NWAs could be directly used as the catalytic electrode for the CO2RR. The morphology of the high-aspect-ratio nanowire array significantly lowers the onset potential of the alcohol formation due to the diffusion-induced enhancement of the local pH and CO concentration near the nanowire surface. Besides, the properly adjusted surface electronic structure of the CuxAuy NWA enables the adsorption of CO and facilitates the subsequent CO reduction to ethanol via the C-C coupling pathway. Owing to the synergistic effect of morphology and electronic structure, the optimized CuxAuy NWA selectively reduces CO2 to ethanol at low potentials of -0.5——0.7 V vs. RHE with a highest Faradaic efficiency of 48%. This work demonstrates the feasibility to optimize the activity and selectivity of the Cu-based electrocatalysts toward multicarbon alcohols for the CO2RR via simultaneous adjustment of the electronic structure and morphology of the catalysts.

Quest for carbon and vanadium oxide based rechargeable magnesium-ion batteries

Rechargeable magnesium ion batteries are potential candidates to replace the lithium ion batteries due to their high volumetric energy density,dendrite free cycling,and low costs.In present work,we have critically reviewed the recent advances made in the field of cathode materials development to achieve the high reversible capacities and working potentials.In first part,carbon-based cathodes such as fluorinedoped graphene nanosheets and graphite fluoride(CF0.8)are discussed in terms of compatibilities of pos让ive electrode materials and electrolyte solutions for rechargeable magnesium-ion batteries.Whereas,the second part of this review focuses on crystal structure of vanadium oxide and its capability to accommodate the Mg^2+ions.Likewise,electrochemical performance of selected vanadium oxide based cathodes including VO2(B),FeVO4.0.9H2(X Mc)2.5+yVO9+δ,RFC/V2O5 and V2O5/Graphene composite,are discussed at different temperatures.To support the future research on magnesium ion batteries,particularly positive electrode material developments,several innovative research directions are proposed.

Constrained cooperative control design for distributed morphing wing systems

An efficient design method is proposed for the cooperative control problem of morphing wing systems with distributed structures and bounded control inputs. The multi-agent model of the distributed morphing wing system is established. The cooperative controllers with saturation constraints are presented. By introducing the concepts in consensus algorithms, the cooperative information links in the controllers are described by graphs, and the corresponding Laplacian matrix is defined. The design conditions of the cooperative controllers are proposed, in the form of linear matrix inequalities. For the case of undirected information links, the controller design conditions are simplified as algebraic inequalities, which highly reduce the computation cost. The designed controllers are implemented on a distributed morphing wing platform, and experiments are carried out. Simulation and experiment results show that the controllers can make all the actuating units in the morphing wing system cooperatively achieve the desired positions, which demonstrates the effectiveness of the proposed theory.

Preparation and properties of Ni-W-P-TiO_(2)nanocomposite coatings developed by a sol-enhanced electroplating method

Several Ni-W-P-TiO_(2) nanocomposite coatings were developed by the sol-enhanced electroplating method. The phase and elemental compositions of coatings were determined, and the surface and cross-section morphology were characterized. The mechanical and corrosion performance were systematically tested. The results revealed the addition of 5 ml·L^(-1) TiO_(2) sol caused a compact coating surface,while higher concentrations of TiO_(2) reduced the coating thickness and led to the inferior surface microstructure. The comparison in physiochemical properties of prepared coatings confirmed the superior performance of the Ni-W-P-TiO_(2) nanocomposite coating at 5 ml·L^(-1) TiO_(2) sol addition. Under this condition, the best mechanical properties were achieved when abrasive wear was the dominating wearresistance mechanism, and the best corrosion resistance was obtained due to its smooth and compact surface microstructure.

Advantages of Nanchong City in Developing Late-maturing Citrus and Countermeasures

Nanchong City has the advantages of developing late-maturing citrus in ecology,no-quarantine diseases and insect pests,base construction starting taking shape,production and management technology becoming increasingly mature,leaders paying close attention and market recognition,and significant income increase of fruit growers. However,there are also problems such as weak infrastructure and weak anti-disaster ability,inadequate technology extension system,unmatched cold chain warehouses,and uneven quality of seedlings. Therefore,it is recommended to make scientific plan in accordance with actual local situations,regulate fine variety breeding and market supervision,build orchards with high standard and strengthen management,do a good job of propaganda and branding,improve post-harvest processing,extend the industrial chain,and issue preferential policies to promote the development of citrus industry in Nanchong City.

A common genetic mechanism underlying susceptibility to posttraumatic stress disorder

We hypothesize that susceptibility to post-traumatic stress disorder(PTSD) may be determined in part by aberrant microtubule-associated protein tau expression in neurons of critical brain structures. The following lines of evidence support this hypothesis. First, epidemiologic data suggest the involvement of genetic factors in the susceptibility to PTSD. Second, the common features of both abnormal tau expression and PTSD include amygdalar and hippocampal atrophy, upregulation of norepinephrine biosynthetic capacity inthe surviving locus coeruleus neurons and dysfunction of N-methyl-D-aspartate-receptors. Finally, our experiments using r Tg4510 mice, a model that over-expresses human mutant tau and develops age-dependent tauopathy, demonstrate that these animals display circling behavior thought to be related to states of anxiety. To detect the potential molecular mechanisms underlying PTSD episodes, laser-assisted/capture microdissection can be used with microarray analysis as an alternative approach to identify changes in gene expression in excitatory and/or inhibitory neurons in critical brain structures(i.e., hippocampus and amygdala) in response to the onset of PTSD.

Wet-chemical synthesis and applications of amorphous metalcontaining nanomaterials

In the past decades,metal-containing nanomaterials have attracted increasing interests owing to their intriguing physicochemical properties and various promising applications.Recent research has revealed that the phase of metal-containing nanomaterials could significantly affect their properties and functions.In particular,nanomaterials with amorphous phase,which possess long-range disordered atomic arrangements,and the amorphous/crystalline heterophase nanostructures comprised of both amorphous and crystalline phases,have exhibited superior performance in various applications,e.g.,catalysis and energy storage.In this review,a brief overview of the recent progress on the wet-chemical synthesis and applications of amorphous and amorphous/crystalline heterophase metal-containing nanomaterials has been provided.Subsequently,on the basis of different categories of metal-containing nanomaterials,including metals,metal alloys,and metal compounds,their synthetic routes and promising applications will be highlighted.Finally,current challenges and some personal perspectives in this emerging research field will be proposed.

Stress relaxation properties of calcium silicate hydrate:a molecular dynamics study

The time-dependent viscoelastic response of cement-based materials to applied deformation is far from fully understood at the atomic level.Calcium silicate hydrate(C-S-H),the main hydration product of Portland cement,is responsible for the viscoelastic mechanism of cement-based materials.In this study,a molecular model of C-S-H was developed to explain the stress relaxation characteristics of C-S-H at different initial deformation states,Ca/Si ratios,temperatures,and water contents,which cannot be accessed experimentally.The stress relaxation of C-S-H occurs regardless of whether it is subjected to initial shear,tensile,or compressive deformation,and shows a heterogeneous characteristic.Water plays a crucial role in the stress relaxation process.A large Ca/Si ratio and high temperature reduce the cohesion between the calcium-silicate layer and the interlayer region,and the viscosity of the interlayer region,thereby accelerating the stress relaxation of C-S-H.The effect of the hydrogen bond network and the morphology of C-S-H on the evolution of the stress relaxation characteristics of C-S-H at different water contents was elucidated by nonaffine mean squared displacement.Our results shed light on the stress relaxation characteristics of C-S-H from a microscopic perspective,bridging the gap between the microscopic phenomena and the underlying atomic-level mechanisms.

A global invasion by the thrip,Frankliniella occidentalis:Current virus vector status and its management

Western flower thrip,Frankliniella occidentalis(Pergande),is among the most economically important agricultural pests globally,attacking a wide range of vegetable and horticultural crops.In addition to causing extensive crop damage,the species is notorious for vectoring destructive plant viruses,mainly belonging to the genera Orthotospovirus,Ilarvirus.AIphacarmovirus and Machlomovirus.Once infected by orthotospoviruses,thrips can remain virulent throughout their lifespan and continue transmitting viruses to host plants when and wherever they feed.These irruptive viral outbreaks in crops will permanently disrupt functional integrated pest management systems,and typically require a remedial treatment involving insecticides,contributing to further development of insecticide resistance.To mitigate against this continuing cycle,the most effective management is early and comprehensive surveillance of the pest species and recognition of plant viruses in the field.This review provides information on the pest status of F.occidentalis,discusses the current global status of the viruses vectored by this thrip species,examines the mechanisms involved in transmitting virus-induced diseases by thrips,and reviews different management strategies,highlighting the potential management tactics developed for various cropping systems.The early surveillance and the utilization of potential methods for control of both F occidentalis and viruses are proposed.

Association between serum somatostatin levels and glucose-lipid metabolism in the Jino ethnic minority and Han Chinese population

We aim to investigate the relationship between serum somatostatin(SST) levels and glucose-lipid metabolism at various stages of glucose tolerance in the Jino ethnic minority(n=111) and Han population(n=113) of Yunnan Province, southwest China.Anthropometric parameters and biochemical traits were measured. Serum SST and plasma glucagon levels were tested. Participants were divided into three subgroups: isolated fasting hyperglycemia(IFH), isolated post challenge hyperglycemia(IPH)and normal glucose tolerance(NGT). SST levels were found lower while glucagon levels were significantly higher in the Jino ethnic with IPH(P=0.0026 and P=0.0069, respectively). Fasting glucose and high density lipoprotein-cholesterol(HDL-C)levels were higher(P=0.0055 and P=0.0021, respectively) and fasting insulin levels and homeostasis model assessments β-cell function were lower(P=0.0479 and P=0.0007, respectively) in the Jino population. After adjusting for confounding factors, the serum SST level was associated with glucagon(P<0.0001) in both populations. The SST level was correlated with fasting Cpeptide(P=0.0267) in Jino and HDL-C levels in Han(P=0.0079). Our findings suggest that serum SST levels and plasma glucagon levels may vary in subjects with IPH between two ethnics.

Modelling and analysis of half-/full-bridge hybrid MMC when riding through DC-side pole-to-ground fault

In a modular multilevel converter-based high-voltage direct current(MMC-HVDC)system,the dc fault ride through(FRT)control is an effective way to deal with a dc-side pole-to-ground(PTG)fault.However,the setting of FRT duration brings potential hazards:1)MMC will face the risk of“secondary short circuit”if FRT duration is short;2)ac grid may have power angle stability issue if FRT duration is long.To avoid these hazards and provide theoretical guidance for the FRT duration setting,transient behaviour of dc fault current during the PTG FRT stage is explored in this work.Firstly,challenges of the transient analysis are summarised as non-linearity and high-order issues.In light of this,numerical and Hilbert-Huang Transformation methods are introduced to evaluate the non-linearity issue.It is found that the path of MMC from dc current to dc internal voltage is weakly non-linear.Hence,a linear transient model is built to analyse the dc fault current.By participation factor analysis,the order of the proposed model is further reduced,so that an analytical expression of the dc fault current is approximately derived.Based on the analytical expression,regularities and mechanism of dc fault current are fully revealed.Application of the transient analysis to the setting of FRT duration is elaborated in detail.Finally,the PSCAD/EMTDC simulation verifies the validity of the proposed model and analytical expression.