Instrumented oscillographic study on impact toughness of an axle steel DZ2 with different tempering temperatures

Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.

Fabricating AC/DC nanogenerators based on single ZnO nanowires by using a nanomanipulator in a scanning electron microscope

Single zinc oxide nanowires(ZnO NWs)are promising for nanogenerators because of their excellent semiconducting and piezoelectric properties,but characterizing the latter efficiently is challenging.As reported here,an electrical breakdown strategy was used to construct single ZnO NWs with a specific length.With the high operability of a nanomanipulator in a scanning electron microscope,ZnO-NW-based twoprobe and three-probe structures were constructed for fabricating AC/DC nanogenerators,respectively.For a ZnO NW,an AC output of between−15.31 mV and 5.82 mV was achieved,while for a DC nanogenerator,an output of24.3 mV was realized.Also,the three-probe structure’s output method was changed to verify the distribution of piezoelectric charges when a single ZnO NW is bent by a probe,and DC outputs of different amplitudes were achieved.This study provides a low-cost,highly convenient,and operational method for studying the AC/DC output characteristics of single NWs,which is beneficial for the further development of nanogenerators.

Research on safety control technology of high-speed railway combined test based on threatening event analysis

Purpose–Safety management is a key point and poses a challenge in joint testing.To detect and address potential accidents’hidden dangers early,this paper conducts research on the safety control technology for high-speed railway joint tests by incorporating the concept of hazardous events.Design/methodology/approach–Aiming at ensuring the safety of high-speed railway combined inspections and trials,this paper starts from the dual prevention mechanism.It introduces the concept of threatening events,defines them and analyzes the differences between threatening events and railway accidents.The paper also proposes a cause model for threatening events in high-speed railway combined inspections and trials,based on three types of hazard sources.Furthermore,it conducts research on the control strategies for these threatening events.Findings–The research on safety control technology for high-speed railway combined operation and testing,based on the analysis of threatened events,offers a new perspective for safety management in these operations.It also provides theoretical and practical support for the transition from passive prevention to active risk pre-control,which holds significant theoretical and practical value.Originality/value–The innovation mainly includes the following three aspects:(1)Building on the traditional dual prevention mechanism,which includes risk hierarchical management and control as well as hidden danger investigation and management,a triple prevention mechanism is proposed.This new mechanism adds the management of threatening events as the third line of defense.The aim is to more comprehensively identify and address potential security risks,thereby enhancing the efficiency and effectiveness of security management.(2)In this paper,the definition of a railway threatening event is clarified,and the causative model of a high-speed railway threatening event based on three kinds of danger sources is proposed.(3)This paper puts forward the control strategy of the high-speed railway combined operation and trial,which includes five key links:identification,reporting,analysis,rectification and feedback,which provides a new perspective for the safety management of the high-speed railway combined operation and trial and has important theoretical and application value.

Quantitative and Comprehensive Prediction of Shale Oil Sweet Spots in Qingshankou Formation, Songliao Basin

The mud shale of Qingshankou Formation in Songliao Basin is the main rock source and contains rich shale oil resources. The successful development of shale oil depends on evaluating and optimizing the “sweet spots”. To accurately identify and optimize the favorable sweet spots of shale oil in Qingshankou Formation, Songliao Basin, the original logging data were preprocessed in this paper. Then the thin mud shale interlayer of Qingshankou Formation was identified effectively by using the processed logging data. Based on the artificial neural network method, the mineral content of mud shale in Qingshankou Formation was predicted. The lithofacies were identified according to the mineral and TOC content. Finally, a three-dimensional (3-D) model of total organic carbon (TOC), vitrinite reflectance (Ro), mineral content, and rock of Qingshankou Formation in Songliao Basin was established to evaluate and predict the favorable sweet spots of shale oil in the study area. The results show that there are a lot of calcareous and siliceous thin interlayers in Qingshankou Formation, and TOC content is generally between 2% and 3%. Ro is the highest in Gulong sag, followed by Sanzhao sag. The lithofacies mainly consists of felsic shale and mixed shale, mainly in the first member of Qingshankou Formation. Comprehensive analysis shows that shale oil development potential is enormous in the eastern part of Sanzhao Sag and the northern part of Gulong Sag.

A comparative single-pulse shock tube experiment and kinetic modeling study on pyrolysis of cyclohexane,methylcyclohexane and ethylcyclohexane

The pyrolysis of cyclohexane,methylcyclohexane,and ethylcyclohexane have been studied behind reflected shock waves at pressures of 5 and10 bar and at temperatures of 930-1550 K for 0.05%fuel diluted by Argon.A single-pulse shock tube(SPST)is used to perform the pyrolysis experiments at reaction times varying from 1.65 to 1.74 ms.Major products are obtained and quantified using gas chromatography analysis.A flame ionization detector and a thermal conductivity detector are used for species identification and quantification.Kinetic modeling has been performed using several detailed and lumped chemical kinetic mechanisms.Differences in modeling results among the kinetic models are described.Reaction path analysis and sensitivity analysis are performed to determine the important reactions controlling fuel pyrolysis and their influence on the predicted concentrations of reactant and product species profiles.The present work provides new fundamental knowledge in understating pyrolysis characteristics of cyclohexane compounds and additional data set for detailed kinetic mechanism development.

3D characterization of porosity and minerals of low-permeability uranium-bearing sandstone based on multi-resolution image fusion

In the process of in situ leaching of uranium,the microstructure controls and influences the flow distribution,percolation characteristics,and reaction mechanism of lixivium in the pores of reservoir rocks and directly affects the leaching of useful components.In this study,the pore throat,pore size distribution,and mineral composition of low-permeability uranium-bearing sandstone were quantitatively analyzed by high pressure mercury injection,nuclear magnetic resonance,X-ray diffraction,and wavelength-dispersive X-ray fluorescence.The distribution characteristics of pores and minerals in the samples were qualitatively analyzed using energy-dispersive scanning electron microscopy and multi-resolution CT images.Image registration with the landmarks algorithm provided by FEI Avizo was used to accurately match the CT images with different resolutions.The multi-scale and multi-mineral digital core model of low-permeability uranium-bearing sandstone is reconstructed through pore segmentation and mineral segmentation of fusion core scanning images.The results show that the pore structure of low-permeability uranium-bearing sandstone is complex and has multi-scale and multi-crossing characteristics.The intergranular pores determine the main seepage channel in the pore space,and the secondary pores have poor connectivity with other pores.Pyrite and coffinite are isolated from the connected pores and surrounded by a large number of clay minerals and ankerite cements,which increases the difficulty of uranium leaching.Clays and a large amount of ankerite cement are filled in the primary and secondary pores and pore throats of the low-permeability uraniumbearing sandstone,which significantly reduces the porosity of the movable fluid and results in low overall permeability of the cores.The multi-scale and multi-mineral digital core proposed in this study provides a basis for characterizing macroscopic and microscopic pore-throat structures and mineral distributions of low-permeability uranium-bearing sandstone and can better understand the seepage characteristics.

Microscale deformation behavior of sandstone mineral particles based on XCT scanning

This work aimed to quantify the physical and mechanical behavior of three-dimensional microstructures in rocks under uniaxial compression.A high-precision in situ XCT(X-ray transmission computed tomography)technology was applied to investigating the behavior of mineral grains in sandstone:the movement,the rotation deformation,and the principal strains between fault zone and non-fault zone.The results indicate that after unloading,the shear strain of mineral grains is periodic in the radial direction,the strain of mineral grains in the fracture zone is about 30 times of the macro strain of the specimen,which is about 5 times in the non-fracture zone,and the shear strain near the fault zone is larger than the compressive strain,and there is the shear stress concentration feature.

碳酸类护肤品的功效评测

二氧化碳是一种人体可产生的气体,无毒、无害,且对人体的生理功能具有重要作用,利用二氧化碳改善身体健康目前已有广泛的应用。含有二氧化碳或在使用过程中能够产生二氧化碳的碳酸类护肤品已成为目前护肤品行业关注的热点产品之一。产品中存在的或使用时产生的二氧化碳能进入皮肤,引起波尔效应,进而达到护肤的目的。使用VISIACR皮肤检测仪和MoistureMeterSC皮肤表面水含量测量仪详细研究了碳酸类护肤品对血液循环、毛孔、护肤品吸收的影响,并对碳酸类护肤品对皮肤的深层清洁作用进行了探讨。结果显示,碳酸类护肤品可暂时性改善皮肤局部微循环,促进毛孔扩张,进而为后续护肤产品中功效成分的吸收提供条件。同时,碳酸类护肤品导致的短暂性的毛孔扩张有利于黑头排出体外,达到皮肤深层清洁的目的。碳酸类护肤品有望通过加速皮肤血液循环、促进功效成分吸收、有效清除皮肤深层的垃圾和废物,从根本上解决基本皮肤问题。

Fatigue Life Prediction of Gray Cast Iron for Cylinder Head Based on Microstructure and Machine Learning

Conventional fatigue tests on complex components are difficult to sample,time-consuming and expensive.To avoid such problems,several popular machine learning(ML)algorithms were used and compared to predict fatigue life of gray cast iron(GCI)with the complex microstructures.The feature analysis shows that the fatigue life of GCI is mainly influenced by the external environment such as the stress amplitude,and the internal microstructure parameters such as the percentage of graphite,graphite length,stress concentration factor at the graphite tip,matrix microhardness and Brinell hardness.For simplicity,collected datasets with some of the above features were used to train ML models including back-propagation neural network(BPNN),random forest(RF)and eXtreme gradient boosting(XGBoost).The comparison results suggest that the three models could predict the fatigue lives of GCI,while the implemented RF algorithm is the best performing model.Moreover,the S–N curves fitted by the Basquin relation in the predicted data have a mean relative error of 15%compared to the measured data.The results have demonstrated the advantages of ML,which provides a generic way to predict the fatigue life of GCI for reducing time and cost.

Research on the pressure variation law and enhancing CBM extraction application effect of CO_(2) phase transition jet coal seam fracturing technology

Due to the limited permeability and high methane content of the majority of China’s coal seams,significant coal mining gas disasters frequently occur.There is an urgent need to artificially improve the permeability of coalbed methane(CBM)reservoirs,enhance the recovery efficiency of CBM and prevent mine gas accidents.As a novel coal rock fracture technology,the CO_(2) phase transition jet(CPTJ)has been widely used due to its advantages of safety and high fragmentation efficiency.In this study,to ascertain the effects of the pressure of CPTJ fracturing,the influence of its jet pressure on cracked coal rock was revealed,and its effect on CBM extraction was clarified.In this research,the law of CPTJ pressure decay with time was investigated using experimental and theoretical methods.Based on the results,the displacement and discrete fracture network law of CPTJ fracturing coal rock under different jet pressure conditions were studied using particle flow code numerical simulation.Finally,field experiments were conducted at the Shamushu coal mine to assess the efficiency of CPTJ in enhancing CBM drainage.The results showed that the pressure of the CPTJ decreased exponentially with time and significantly influenced the number and expansion size of cracks that broke coal rock but not their direction of development.CPTJ technology can effectively increase the number of connected microscopic pores and fractures in CBM reservoirs,strongly increase the CBM drainage flow rate by between 5.2 and 9.8 times,and significantly reduce the CBM drainage decay coefficient by between 73.58%and 88.24%.

Bioactive hydrogels for bone regeneration

Bone self-healing is limited and generally requires external intervention to augment bone repair and regeneration.While traditional methods for repairing bone defects such as autografts,allografts,and xenografts have been widely used,they all have corresponding disadvantages,thus limiting their clinical use.Despite the development of a variety of biomaterials,including metal implants,calcium phosphate cements(CPC),hydroxyapatite,etc.,the desired therapeutic effect is not fully achieved.Currently,polymeric scaffolds,particularly hydrogels,are of interest and their unique configurations and tunable physicochemical properties have been extensively studied.This review will focus on the applications of various cutting-edge bioactive hydrogels systems in bone regeneration,as well as their advantages and limitations.We will examine the composition and defects of the bone,discuss the current biomaterials for bone regeneration,and classify recently developed polymeric materials for hydrogel synthesis.We will also elaborate on the properties of desirable hydrogels as well as the fabrication techniques and different delivery strategies.Finally,the existing challenges,considerations,and the future prospective of hydrogels in bone regeneration will be outlined.

Targeted delivery of a STING agonist to brain tumors using bioengineered protein nanoparticles for enhanced immunotherapy

Immunotherapy is emerging as a powerful tool for combating many human diseases.However,the application of this life-saving treatment in serious brain diseases,including glioma,is greatly restricted.The major obstacle is the lack of effective technologies for transporting therapeutic agents across the blood-brain barrier(BBB)and achieving targeted delivery to specific cells once across the BBB.Ferritin,an iron storage protein,traverses the BBB via receptor-mediated transcytosis by binding to transferrin receptor 1(TfR1)overexpressed on BBB endothelial cells.Here,we developed bioengineered ferritin nanoparticles as drug delivery carriers that enable the targeted delivery of a small-molecule immunomodulator to achieve enhanced immunotherapeutic efficacy in an orthotopic glioma-bearing mouse model.We fused different glioma-targeting moieties on self-assembled ferritin nanoparticles via genetic engineering,and RGE fusion protein nanoparticles(RGE-HFn NPs)were identified as the best candidate.Furthermore,RGE-HFn NPs encapsulating a stimulator of interferon genes(STING)agonist(SR717@RGE-HFn NPs)maintained stable self-assembled structure and targeting properties even after traversing the BBB.In the glioma-bearing mouse model,SR717@RGE-HFn NPs elicited a potent local innate immune response in the tumor microenvironment,resulting in significant tumor growth inhibition and prolonged survival.Overall,this biomimetic brain delivery platform offers new opportunities to overcome the BBB and provides a promising approach for brain drug delivery and immunotherapy in patients with glioma.

Single-cell transcriptomic profiling unravels the adenoma-initiation role of protein tyrosine kinases during colorectal tumorigenesis

The adenoma-carcinoma sequence is a well-accepted roadmap for the development of sporadic colorectal cancer.However,cellular heterogeneity in aberrant epithelial cells limits our understanding of carcinogenesis in colorectal tissues.Here,we performed a single-cell RNA sequencing survey of 54,788 cells from patient-matched tissue samples,including blood,normal tissue,para-cancer,polyp,and colorectal cancer.

SERS光谱对肾结石患者尿液的无标记检测

近年来,肾结石的发病率逐渐升高,严重影响了患者的生活质量。因此,有必要开发一种强大的肾结石患者筛查技术。本文采用表面增强拉曼散射(SERS)技术对24例肾结石患者尿液和16例正常志愿者尿液进行检测,并成功记录了其光谱。同时分析两组SERS光谱的差谱,表明两组尿液在SERS光谱上存在细微但不可忽略的差异。利用主成分分析(PCA)算法考察两组SERS光谱中多个变量的相关性从而降维,并结合线性判别分析(LDA)算法区分正常人尿液样本和肾结石患者尿液样本,结果表明灵敏度和特异性分别为88%和81%。最后,计算受试者工作特征(ROC)曲线的面积为0.94,进一步证明了基于PCA-LDA诊断算法的有效性.

不同温度下酿酒酵母细胞分裂周期蛋白Cdc5在有丝分裂中的分子动力学研究

【目的】探究不同温度下酿酒酵母细胞分裂周期蛋白Cdc5蛋白在有丝分裂中的分子动力学变化。【方法】本研究以酿酒酵母(Saccharomyces cerevisiae)为材料,采用活细胞成像的方法,探究Cdc5蛋白在不同温度下在酿酒酵母有丝分裂过程中的精细分子动力学变化;通过测量OD595绘制生长曲线图,看其宏观的分裂情况是否与微观下Cdc5蛋白的分子动力学变化一致;利用流式细胞术检测细胞的细胞周期变化的情况。【结果】在胞质分裂时,Cdc5蛋白从母细胞进入子细胞,并在芽颈处发生聚集。25℃条件下细胞中Cdc5蛋白在芽颈处的聚集时间长,37℃条件下Cdc5蛋白在芽颈处聚集时间短,两者间存在显著差异;但两个温度下,细胞中Cdc5蛋白的表达量没有显著性差异。同时,温度也会影响Cdc5蛋白在降解过程中的动力学行为,包括Cdc5蛋白在母细胞与子细胞中荧光强度峰值出现的次数和时间。生长曲线结果显示,酿酒酵母单一细胞分裂周期的变化影响了其宏观的细胞生长,且酵母分裂速度越快,子细胞长宽比越小;细胞周期结果表明,37℃下Cdc5蛋白的动力学变化与酿酒酵母细胞周期变化一致,酿酒酵母细胞周期从G_(0)/G_(1)期进入S期,亦加速了酿酒酵母的分裂。【结论】本研究首次探究了不同温度下酿酒酵母有丝分裂中Cdc5蛋白的精细分子动力学及对应的酵母的宏观生长情况,结果表明温度会对Cdc5蛋白的动力学产生影响,且其精细分子动力学与酿酒酵母的分裂速度成正相关,该结果为进一步研究其在细胞有丝分裂中的功能提供了前期研究基础。

Prediction of Primary Frequency Regulation Capability of Power System Based on Deep Belief Network

The primary frequency response ability plays a crucial role in the rapid recovery and stability of the power grid when the grid is disturbed to generate a power imbalance.In order to predict the primary frequency control ability of power system,a new model is proposed based on deep belief networks.The key feature of the proposed model lies in the fact that it considers three key factors,i.e.,disturbance information,system state feature,and unit operation mode.Through this way,it predicts the primary frequency control ability of the power system accurately.The simulation results on real power system data verify the feasibility and accuracy of the proposed model.