In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate ...In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate rail geometric deformations caused by settlement within a vehicle-track-tunnel coupled system.The model integrates the geometric deformations of the track,attributed to settlement,as track irregularities.A novel“cyclic model”algorithm was employed to enhance computational efficiency without compromising on precision,a claim that was rigorously validated.The model’s capability extends to analyzing the time-history responses of vehicles traversing settlement-affected areas.The research primarily focuses on how settlement wavelength,amplitude,and vehicle speed influence operational performance.Key findings indicate that an increase in settlement wavelength can improve vehicle performance,whereas a rise in amplitude can degrade it.The study also establishes settlement thresholds,based on vehicle operation comfort and safety.These insights are pivotal for maintaining and enhancing the safety and efficiency of subway systems,providing a valuable framework for urban infrastructure management and long-term maintenance strategies in metropolitan transit systems.展开更多
Amid urbanization and the continuous expansion of transportation networks,the necessity for tunnel construction and maintenance has become paramount.Addressing this need requires the investigation of efficient,economi...Amid urbanization and the continuous expansion of transportation networks,the necessity for tunnel construction and maintenance has become paramount.Addressing this need requires the investigation of efficient,economical,and robust tunnel reinforcement techniques.This paper explores fiber reinforced polymer(FRP)and steel fiber reinforced concrete(SFRC)technologies,which have emerged as viable solutions for enhancing tunnel structures.FRP is celebrated for its lightweight and high-strength attributes,effectively augmenting load-bearing capacity and seismic resistance,while SFRC’s notable crack resistance and longevity potentially enhance the performance of tunnel segments.Nonetheless,current research predominantly focuses on experimental analysis,lacking comprehensive theoretical models.To bridge this gap,the cohesive zone model(CZM),which utilizes cohesive elements to characterize the potential fracture surfaces of concrete/SFRC,the rebar-concrete interface,and the FRP-concrete interface,was employed.A modeling approach was subsequently proposed to construct a tunnel segment model reinforced with either SFRC or FRP.Moreover,the corresponding mixed-mode constitutive models,considering interfacial friction,were integrated into the proposed model.Experimental validation and numerical simulations corroborated the accuracy of the proposed model.Additionally,this study examined the reinforcement design of tunnel segments.Through a numerical evaluation,the effectiveness of innovative reinforcement schemes,such as substituting concrete with SFRC and externally bonding FRP sheets,was assessed utilizing a case study from the Fuzhou Metro Shield Tunnel Construction Project.展开更多
Down syndrome(DS)is a genetic condition characterized by intellectual disability,delayed brain development,and early onset Alzheimer’s disease.The use of primary neural cells and tissues is important for understandin...Down syndrome(DS)is a genetic condition characterized by intellectual disability,delayed brain development,and early onset Alzheimer’s disease.The use of primary neural cells and tissues is important for understanding this disease,but there are ethical and practical issues,including availability from patients and experimental manipulability.Moreover,there are significant genetic and physiological differences between animal models and humans,which limits the translation of the findings in animal studies to humans.Advancements in induced pluripotent stem cells(iPSC)technology have revolutionized DS research by providing a valuable tool for studying the cellular and molecular pathologies associated with DS.Induced pluripotent stem cells derived from cells obtained from DS patients contain the patient’s entire genome including trisomy 21.Trisomic iPSCs as well as their derived cells or organoids can be useful for disease modeling,investigating the molecular mechanisms,and developing potential strategies for treating or alleviating DS.In this review,we focus on the use of iPSCs and their derivatives obtained from DS individuals and healthy humans for DS research.We summarize the findings from the past decade of DS studies using iPSCs and their derivatives.We also discuss studies using iPSC technology to investigate DS-associated genes(e.g.,APP,OLIG1,OLIG2,RUNX1,and DYRK1A)and abnormal phenotypes(e.g.,dysregulated mitochondria and leukemia risk).Lastly,we review the different strategies for mitigating the limitations of iPSCs and their derivatives,for alleviating the phenotypes,and for developing therapies.展开更多
To examine the feasibility of using a computer tool for stratifying the severity of Coronavirus Disease 2019(COVID-19)based on computed tomography(CT)images.We retrospectively examined 44 confirmed COVID-19 cases.All ...To examine the feasibility of using a computer tool for stratifying the severity of Coronavirus Disease 2019(COVID-19)based on computed tomography(CT)images.We retrospectively examined 44 confirmed COVID-19 cases.All cases were evaluated separately by radiologists(visually)and through an in-house computer software.The degree of lesions was visually scored by the radiologist,as follows,for each of the 5 lung lobes:0,no lesion present;1,<1/3 involvement;2,>1/3 and<2/3 involvement;and 3,>2/3 involvement.Lesion density was assessed based on the proportion of ground-glass opacity(GGO),consolidation and fibrosis of the lesions.The parameters obtained using the computer tool included lung volume(mL),lesion volume(mL),lesion percentage(%),and mean lesion density(HU)of the whole lung,right lung,left lung,and each lobe.The scores obtained by the radiologists and quantitative results generated by the computer software were tested for correlation.A Chi-square test was used to test the consistency of radiologist-and computer-derived lesion percentage in the right/left lung,upper/lower lobe,and each of the 5 lobes.The results showed a strong to moderate correlation between lesion percentage scores obtained by radiologists and the computer software(r ranged from 0.7679 to 0.8373,P<0.05),and a moderate correlation between the proportion of GGO and mean lesion density(r=-0.5894,P<0.05),and proportion of consolidation and mean lesion density(r=0.6282,P<0.05).Computer-aided quantification showed a statistical significant higher lesion percentage for lower lobes than that assessed by the radiologists(x^2=8.160,P=0.004).Our experiments demonstrated that the computer tool could reliably and accurately assess the severity and distribution of pneumonia on CT scans.展开更多
The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transform...The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.展开更多
To explore the feasibility and superiority of iodine delivery rate(IDR)and tube voltage determined by patients'body mass index(BMI)in coronary CT angiography(CCTA),a total of 1567 patients undertaking CCTA during ...To explore the feasibility and superiority of iodine delivery rate(IDR)and tube voltage determined by patients'body mass index(BMI)in coronary CT angiography(CCTA),a total of 1567 patients undertaking CCTA during Feb.and Dec.2016 were enrolled and divided into two groups.In the control group,the IDR and tube voltage were fixed,while in the experimental group,the IDR and tube voltage were determined by patients,BMI.The volume of iodinated contrast media(ICM),extravasation rate,extravasation volume,extravasation recovery interval,incidence rate of adverse reactions,effective dose(ED)and image quality of the two groups were compared.The experiments demonstrated that the ICM volume,extravasation rate,extravasation volume,extravasation recovery interval,incidence of adverse reactions and ED were lower or shorter in the experimental group than in the control group,and the differences were statistically significant(all P<0.05).However,there were no significant differences in the mean CT value,image noise,signal to noise ratio and contrast to noise ratio between the two groups(all P<0.05),which were consistent with the diagnosticians*subjective evaluation outcomes.Our findings suggested that in CCTA,it is feasible to determine the IDR and tube voltage based on patients'BMI;low tube voltage and IDR are superior to the fixed tube voltage and IDR and are worthy of clinical promotion.展开更多
The corrosion behavior of 5 wt%Cr steel tempered at different temperatures was investigated by immersion testing and electrochemical testing in a CO_2 aqueous environment. When the tempering temperature exceeded 500℃...The corrosion behavior of 5 wt%Cr steel tempered at different temperatures was investigated by immersion testing and electrochemical testing in a CO_2 aqueous environment. When the tempering temperature exceeded 500℃, the corrosion rate increased. The corrosion layers consisted of Cr-rich compounds, which affected the corrosion behaviors of the steels immersed in the corrosive solution. The results of electrochemical experiments demonstrated that 5 wt%Cr steels with different microstructures exhibited pre-passivation characteristics that decreased their corrosion rate. Analysis by electron back-scattered diffraction showed that the frequency of high-angle grain boundaries(HAGBs) and the corrosion rate were well-correlated in specimens tempered at different temperatures. The corrosion rate increased with increasing HAGB frequency.展开更多
Objective:To research on consistency of identifying solitary pulmonary masses with CT. Methods:Three observers with different working backgrounds in imaging diagnosis individually interpreted the same group images of ...Objective:To research on consistency of identifying solitary pulmonary masses with CT. Methods:Three observers with different working backgrounds in imaging diagnosis individually interpreted the same group images of solitary pulmonary mass, by 12 indexes of objective signs. The differences in interpretation resulted in ante- and post-interpretations were assessed by the x2 test. The agreement of two interpretations from the same observer was confirmed with the kappa test. A double-blind method was adopted for analysis. Results:The agreement rates of ante- and post-interpreting from the three observers were respectively 82.65%(486/588) 80.27%(472/588) and 84.86% (499/588) while their interpreting results were generally accordant without significant difference(x2 = 4.975, df = 2, P = 0.083) however there was difference between the observer 2 and observer 3(x2 = 4.875, df = 1, P = 0.027). There were five indexes with k > 0.40 of ante- and post-interpreting results of the three observers, including clarity of nodule borderline, presence of sentus, uniformity of density, existence of cavity and calcification in pathological region, among them, the agreement rate of interpreting borderline and cavity was higher(k > 0.07); the blood vessel convergence poorer(0 < k ≤ 0.40); the other six CT signs of interpretation were slightly different. Conclusion:The ability to identify solitary pulmonary mass was inconsistent, and needs to be improved further.展开更多
To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure,the influences of cold deformation and annealing parameters on the microstructure evolution and mec...To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure,the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316 L austenitic stainless steel were investigated.The samples were first cold-rolled,and then samples deformed to different extents were annealed at different temperatures.The microstructure evolutions were analyzed by optical microscopy,scanning electron microscopy(SEM),magnetic measurements,and X-ray diffraction(XRD):the mechanical properties are also determined by tensile tests.The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel.The micro/nanometric microstructure was obtained after reversion annealing at 820–870°C for 60 s.Nearly 100% reversed austenite was obtained in samples annealed at 850°C,where grains with a diameter ≤ 500 nm accounted for 30% and those with a diameter > 0.5 μm accounted for 70%.The micro/nanometer-grain steel exhibited not only a high strength level(approximately 959 MPa) but also a desirable elongation of approximately 45%.展开更多
Based on the survey on wild plants in 21 counties( cities) in Yichun Area,89 species of 32 families of wild vegetables were collected. The species,parts,edible parts,distribution and current development and use of wil...Based on the survey on wild plants in 21 counties( cities) in Yichun Area,89 species of 32 families of wild vegetables were collected. The species,parts,edible parts,distribution and current development and use of wild vegetables in Yichun Area were expounded. Then,existing problems of wild vegetables in Yichun Area were discussed. Finally,pertinent recommendations were put forward.展开更多
The corrosion behavior and mechanism of 3Ni weathering steel in a simulated oceanic atmospheric environment are investigated in order to comprehend the impacts of La,as determined through electrochemical analysis and ...The corrosion behavior and mechanism of 3Ni weathering steel in a simulated oceanic atmospheric environment are investigated in order to comprehend the impacts of La,as determined through electrochemical analysis and rust layer characterization.The results of this study demonstrate that the addition of La enhances the corrosion resistance of 3Ni weathering steel in the marine atmospheric environment,thereby reducing the corrosion rate and improving the protection of the rust layer.The influence of La on corrosion resistance can be attributed to two primary factors.Firstly,La functions as a grain refiner,minimizing the potential difference of the micro-regions on the substrate surface,thereby significantly reducing the corrosion of bare steel in the marine environment.Secondly,La inhibits the process of Fe_(3)O_(4) oxidation back toγ-FeOOH during corrosion at the local site,thus decreasing the formation ofγ-FeOOH and enhancing the charge transfer resistance.This research work may serve as a reference for expanding the application of rare earth elements in the field of weathering steel.展开更多
Lead-free bismuth sodium titanate(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)and related solid solutions are potential piezoelectric materials for such applications as actuators and transducers if their excellent strain responses a...Lead-free bismuth sodium titanate(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)and related solid solutions are potential piezoelectric materials for such applications as actuators and transducers if their excellent strain responses and piezoelectric properties can be optimized.In this work,a large strain response of 0.61%is achieved in lead-free(0.94-x%)(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)-x%NaNbO_(3)(x=0 e6,BNT-6BT-xNN)ceramics with the composition of x=3.5 in a pseudo-cubic structure.Coexistence of ferroelectric(FE)and relaxor(RE)domain structures is observed in all the unpoled ceramics and the enhanced strain response is believed to be related to the evolution of the ergodic relaxor(ER)and non-ergodic(NR)states thanks to the substitution of antiferroelectric NN.BNT-6BT-3.5NN is a critical composition near the FE/NR/ER phase boundary close to room temperature(RT)and its high strain response arises from a synergistic combination of a reversible electric-field-induced phase transition and an active domain switching in the mixed NR/ER state.This work provides new insights into the dynamic interplay between mesoscopic domains and macroscopic electrical properties in the BNT-based piezoceramics.展开更多
The phase transformation behavior during continuous cooling of high-strength spring steels containing different amounts of Cr was studied.Furthermore,the effects of combining Cr with V as well as austenite deformation...The phase transformation behavior during continuous cooling of high-strength spring steels containing different amounts of Cr was studied.Furthermore,the effects of combining Cr with V as well as austenite deformation on the transformation kinetics were investigated in the method of dilatometry and metallography hardness.The results showed that,with the increase of Cr,the pearlite transformation field was enlarged,the ferrite transformation field was narrowed,and the entire phase field shifted to the right.With the addition of V,the start transformation temperature of undercooling austenite( A_(r3))was gradually increased,but the ferrite and pearlite transformation fields were not affected.Besides,the minimum critical cooling rate of martensitic transformation was also reduced.In addition,the dynamic continuous cooling transformation( CCT) curve moves to the top left compared with the static CCT curve.The transformed microstructures showed that the addition of V and the deformation not only refined the overall transformed microstructures but also reduced the lamellar spacing of pearlite.The alloying elements Cr and V promoted the Vickers hardness.However,the effect of Cr on the Vickers hardness of martensite was stronger and the influence of V on that of pearlite was stronger.Moreover,the Vickers hardness affected by the austenite deformation was more complex and strongly depended on the transformed microstructures.展开更多
304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained(NG/UFG)structure.Transmission electron microscopy,electron ...304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained(NG/UFG)structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline(60-100 nm)and ultrafine(100-500 nm)grains,submicron size(500-1000 nm)grains and micron size(>1000 nm)grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test.展开更多
To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray dif...To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray diffraction and nanoindentation test have been used to detect the residual stress and micro-property.The samples with deformation rate of 0-5.59%or annealing at 550℃ are analyzed.The results show that,due to the coupling effect of thermal expansion and cold contraction and the volume expansion of microstructural transformation from austenite to ferrite,compressive residual stress was found inside the hot-rolled samples.With the increase in cold compression deformation,the dislocation density increased and the microhardness increased gradually,and there is no obvious rule for the change of mean nano-hardness in micro-zone for the center of samples.However,the uniformity of nano-hardness in the micro-zone increased first and then decreased,and the value of residual stress has obvious corresponding relationship with the uniformity of micro-zone property.The cold compression deformation with appropriate reduction rate can reduce residual stress and improve nano-hardness uniformity of the hot-rolled samples,but more deformation(such as reduction rateε=5.59%)makes residual stress increase and makes uniformity of nano-hardness deteriorate.展开更多
Hardware electronic synapse and neuro-inspired computing system based on phase change random access memory(PCRAM)have attracted an extensive investigation.However,due to the intrinsic asymmetric reversible phase trans...Hardware electronic synapse and neuro-inspired computing system based on phase change random access memory(PCRAM)have attracted an extensive investigation.However,due to the intrinsic asymmetric reversible phase transition,the defective weight update of PCRAM synapses in aspects of tuning range,linearity and continuity has long required a system-level complexity of circuits and al-gorithms.The cell-level improvements to a great extent may slim the system thus achieving efficient computing.We report in this work the great enhancement of Ge_(2)Sb_(2)Te_(5)(GST)based PCRAM synapses by combining materials engineering and pulse programming.It is found that carbon doping in GST retards the rate of phase changing thus increasing the controllability of the conductance,while non-linear programmable pulse excitations can eventually lead to a reliable synaptic potentiation and depression.A set of improved programmable pulse schemes for spike-timing dependent plasticity was then demonstrated,suggesting its potential superiority in flexible programming and reliable data collection.Our methods and results are of great significance for implementing PCRAM electronic synapses and high-performance neuro-inspired computing.展开更多
In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen press...In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen pressure,the best conditions were found to be 650-700℃and 0.5 Pa.To further improve the quality of hetero-epitaxialβ-Ga_(2)O_(3),the sapphire substrates were pretreated for atomic terraced surface by chemical cleaning and high temperature annealing.From the optical transmittance measurements,the films grown at 600-750℃exhibit a clear absorption edge at deep ultraviolet region around 250-275 nm wavelength.High resolution transmission electron microscope(HRTEM)images and X-ray diffraction(XRD)patterns demonstrate thatβ-Ga_(2)O_(3)(-201)//Al_(2)O_(3)(0001)epitaxial texture dominated the epitaxial oxide films on sapphire substrate,which opens up the possibilities of high power electric devices.展开更多
1.Introduction Advanced high-strength steels with good ductility are essen-tial to the manufacturing,structural safety,and light-weighting of load-bearing structures in many industries[1-3].Austenitic stain-less steel...1.Introduction Advanced high-strength steels with good ductility are essen-tial to the manufacturing,structural safety,and light-weighting of load-bearing structures in many industries[1-3].Austenitic stain-less steel(ASS)exhibits high ductility due to the TRIP and/or TWIP effect that can alleviate stress concentration,prevent void nucle-ation,enhance work hardening,and postpone necking[4-6].The yield strength of conventional ASS is generally low(∼200-500 MPa),and their deformation resistance is insufficient for many load-bearing applications[6].Previous studies reported the in-creased yield strength in various austenitic steels through grain refinement,dislocation strengthening,precipitation strengthening,and heterogeneous hardening[7-14].A single strengthening mech-anism,however,is typically insufficient to obtain ultrahigh yield strength over 1 GPa in austenitic steel[12].展开更多
Lead-free piezoelectric sodium bismuth titanate((Bi0.5Na0.5)TiO3,BNT)thin films were epitaxially grown onto(001)-,(110)-,and(111)-oriented Nb:SrTiO3(STO)single crystal substrates prepared by sol-gel processing.Highly ...Lead-free piezoelectric sodium bismuth titanate((Bi0.5Na0.5)TiO3,BNT)thin films were epitaxially grown onto(001)-,(110)-,and(111)-oriented Nb:SrTiO3(STO)single crystal substrates prepared by sol-gel processing.Highly oriented growth in(001),(110),and(111)BNT thin films was obtained in this work benefiting from the lattice match between the BNT film and the STO substrate.The different growth models in thin films with various orientations result in various surface morphologies dependent on the film orientation.The piezoresponse of the BNT thin films was represented exhibiting a strong orientation dependence that(110)>(001)>(111).This is contributed by the various domain switching contribution related to the crystal symmetry and polarization distribution in the three oriented thin films.展开更多
基金funded by the Scientific Research Startup Foundation of Fujian University of Technology (GY-Z21067 and GY-Z21026).
文摘In the realm of subway shield tunnel operations,the impact of tunnel settlement on the operational performance of subway vehicles is a crucial concern.This study introduces an advanced analytical model to investigate rail geometric deformations caused by settlement within a vehicle-track-tunnel coupled system.The model integrates the geometric deformations of the track,attributed to settlement,as track irregularities.A novel“cyclic model”algorithm was employed to enhance computational efficiency without compromising on precision,a claim that was rigorously validated.The model’s capability extends to analyzing the time-history responses of vehicles traversing settlement-affected areas.The research primarily focuses on how settlement wavelength,amplitude,and vehicle speed influence operational performance.Key findings indicate that an increase in settlement wavelength can improve vehicle performance,whereas a rise in amplitude can degrade it.The study also establishes settlement thresholds,based on vehicle operation comfort and safety.These insights are pivotal for maintaining and enhancing the safety and efficiency of subway systems,providing a valuable framework for urban infrastructure management and long-term maintenance strategies in metropolitan transit systems.
基金funded by the Scientific research startup Foundation of Fujian University of Technology(GY-Z21067 and GY-Z21026).
文摘Amid urbanization and the continuous expansion of transportation networks,the necessity for tunnel construction and maintenance has become paramount.Addressing this need requires the investigation of efficient,economical,and robust tunnel reinforcement techniques.This paper explores fiber reinforced polymer(FRP)and steel fiber reinforced concrete(SFRC)technologies,which have emerged as viable solutions for enhancing tunnel structures.FRP is celebrated for its lightweight and high-strength attributes,effectively augmenting load-bearing capacity and seismic resistance,while SFRC’s notable crack resistance and longevity potentially enhance the performance of tunnel segments.Nonetheless,current research predominantly focuses on experimental analysis,lacking comprehensive theoretical models.To bridge this gap,the cohesive zone model(CZM),which utilizes cohesive elements to characterize the potential fracture surfaces of concrete/SFRC,the rebar-concrete interface,and the FRP-concrete interface,was employed.A modeling approach was subsequently proposed to construct a tunnel segment model reinforced with either SFRC or FRP.Moreover,the corresponding mixed-mode constitutive models,considering interfacial friction,were integrated into the proposed model.Experimental validation and numerical simulations corroborated the accuracy of the proposed model.Additionally,this study examined the reinforcement design of tunnel segments.Through a numerical evaluation,the effectiveness of innovative reinforcement schemes,such as substituting concrete with SFRC and externally bonding FRP sheets,was assessed utilizing a case study from the Fuzhou Metro Shield Tunnel Construction Project.
基金supported by Shenzhen Science and Technology Planning Project(Grant No.JCYJ20210324093209024)Stable Support Project of Shenzhen(Grant No.20220812182215001).
文摘Down syndrome(DS)is a genetic condition characterized by intellectual disability,delayed brain development,and early onset Alzheimer’s disease.The use of primary neural cells and tissues is important for understanding this disease,but there are ethical and practical issues,including availability from patients and experimental manipulability.Moreover,there are significant genetic and physiological differences between animal models and humans,which limits the translation of the findings in animal studies to humans.Advancements in induced pluripotent stem cells(iPSC)technology have revolutionized DS research by providing a valuable tool for studying the cellular and molecular pathologies associated with DS.Induced pluripotent stem cells derived from cells obtained from DS patients contain the patient’s entire genome including trisomy 21.Trisomic iPSCs as well as their derived cells or organoids can be useful for disease modeling,investigating the molecular mechanisms,and developing potential strategies for treating or alleviating DS.In this review,we focus on the use of iPSCs and their derivatives obtained from DS individuals and healthy humans for DS research.We summarize the findings from the past decade of DS studies using iPSCs and their derivatives.We also discuss studies using iPSC technology to investigate DS-associated genes(e.g.,APP,OLIG1,OLIG2,RUNX1,and DYRK1A)and abnormal phenotypes(e.g.,dysregulated mitochondria and leukemia risk).Lastly,we review the different strategies for mitigating the limitations of iPSCs and their derivatives,for alleviating the phenotypes,and for developing therapies.
基金supported by the Science and Technology Project of Shaanxi Province(No.2018SF-264)The National Natural Science Foundation of China(81701691)Natural and Science Foundation of Shaanxi Province(2019JM-361)。
文摘To examine the feasibility of using a computer tool for stratifying the severity of Coronavirus Disease 2019(COVID-19)based on computed tomography(CT)images.We retrospectively examined 44 confirmed COVID-19 cases.All cases were evaluated separately by radiologists(visually)and through an in-house computer software.The degree of lesions was visually scored by the radiologist,as follows,for each of the 5 lung lobes:0,no lesion present;1,<1/3 involvement;2,>1/3 and<2/3 involvement;and 3,>2/3 involvement.Lesion density was assessed based on the proportion of ground-glass opacity(GGO),consolidation and fibrosis of the lesions.The parameters obtained using the computer tool included lung volume(mL),lesion volume(mL),lesion percentage(%),and mean lesion density(HU)of the whole lung,right lung,left lung,and each lobe.The scores obtained by the radiologists and quantitative results generated by the computer software were tested for correlation.A Chi-square test was used to test the consistency of radiologist-and computer-derived lesion percentage in the right/left lung,upper/lower lobe,and each of the 5 lobes.The results showed a strong to moderate correlation between lesion percentage scores obtained by radiologists and the computer software(r ranged from 0.7679 to 0.8373,P<0.05),and a moderate correlation between the proportion of GGO and mean lesion density(r=-0.5894,P<0.05),and proportion of consolidation and mean lesion density(r=0.6282,P<0.05).Computer-aided quantification showed a statistical significant higher lesion percentage for lower lobes than that assessed by the radiologists(x^2=8.160,P=0.004).Our experiments demonstrated that the computer tool could reliably and accurately assess the severity and distribution of pneumonia on CT scans.
基金financially supported by the National Natural Science Foundation of China (No.51474031)
文摘The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.
文摘To explore the feasibility and superiority of iodine delivery rate(IDR)and tube voltage determined by patients'body mass index(BMI)in coronary CT angiography(CCTA),a total of 1567 patients undertaking CCTA during Feb.and Dec.2016 were enrolled and divided into two groups.In the control group,the IDR and tube voltage were fixed,while in the experimental group,the IDR and tube voltage were determined by patients,BMI.The volume of iodinated contrast media(ICM),extravasation rate,extravasation volume,extravasation recovery interval,incidence rate of adverse reactions,effective dose(ED)and image quality of the two groups were compared.The experiments demonstrated that the ICM volume,extravasation rate,extravasation volume,extravasation recovery interval,incidence of adverse reactions and ED were lower or shorter in the experimental group than in the control group,and the differences were statistically significant(all P<0.05).However,there were no significant differences in the mean CT value,image noise,signal to noise ratio and contrast to noise ratio between the two groups(all P<0.05),which were consistent with the diagnosticians*subjective evaluation outcomes.Our findings suggested that in CCTA,it is feasible to determine the IDR and tube voltage based on patients'BMI;low tube voltage and IDR are superior to the fixed tube voltage and IDR and are worthy of clinical promotion.
基金financially supported by the National Key R & D Program of China (No. 2017YFB0304900)the National Science and Technology Major Project of China (No. 2014E-3604)
文摘The corrosion behavior of 5 wt%Cr steel tempered at different temperatures was investigated by immersion testing and electrochemical testing in a CO_2 aqueous environment. When the tempering temperature exceeded 500℃, the corrosion rate increased. The corrosion layers consisted of Cr-rich compounds, which affected the corrosion behaviors of the steels immersed in the corrosive solution. The results of electrochemical experiments demonstrated that 5 wt%Cr steels with different microstructures exhibited pre-passivation characteristics that decreased their corrosion rate. Analysis by electron back-scattered diffraction showed that the frequency of high-angle grain boundaries(HAGBs) and the corrosion rate were well-correlated in specimens tempered at different temperatures. The corrosion rate increased with increasing HAGB frequency.
文摘Objective:To research on consistency of identifying solitary pulmonary masses with CT. Methods:Three observers with different working backgrounds in imaging diagnosis individually interpreted the same group images of solitary pulmonary mass, by 12 indexes of objective signs. The differences in interpretation resulted in ante- and post-interpretations were assessed by the x2 test. The agreement of two interpretations from the same observer was confirmed with the kappa test. A double-blind method was adopted for analysis. Results:The agreement rates of ante- and post-interpreting from the three observers were respectively 82.65%(486/588) 80.27%(472/588) and 84.86% (499/588) while their interpreting results were generally accordant without significant difference(x2 = 4.975, df = 2, P = 0.083) however there was difference between the observer 2 and observer 3(x2 = 4.875, df = 1, P = 0.027). There were five indexes with k > 0.40 of ante- and post-interpreting results of the three observers, including clarity of nodule borderline, presence of sentus, uniformity of density, existence of cavity and calcification in pathological region, among them, the agreement rate of interpreting borderline and cavity was higher(k > 0.07); the blood vessel convergence poorer(0 < k ≤ 0.40); the other six CT signs of interpretation were slightly different. Conclusion:The ability to identify solitary pulmonary mass was inconsistent, and needs to be improved further.
基金supported by the National Natural Science Foundation of China(Grant No.51474031)
文摘To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure,the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316 L austenitic stainless steel were investigated.The samples were first cold-rolled,and then samples deformed to different extents were annealed at different temperatures.The microstructure evolutions were analyzed by optical microscopy,scanning electron microscopy(SEM),magnetic measurements,and X-ray diffraction(XRD):the mechanical properties are also determined by tensile tests.The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel.The micro/nanometric microstructure was obtained after reversion annealing at 820–870°C for 60 s.Nearly 100% reversed austenite was obtained in samples annealed at 850°C,where grains with a diameter ≤ 500 nm accounted for 30% and those with a diameter > 0.5 μm accounted for 70%.The micro/nanometer-grain steel exhibited not only a high strength level(approximately 959 MPa) but also a desirable elongation of approximately 45%.
文摘Based on the survey on wild plants in 21 counties( cities) in Yichun Area,89 species of 32 families of wild vegetables were collected. The species,parts,edible parts,distribution and current development and use of wild vegetables in Yichun Area were expounded. Then,existing problems of wild vegetables in Yichun Area were discussed. Finally,pertinent recommendations were put forward.
基金G.Niu,R.Yuan,H.B.Wu,C.J.Shang,and X.P.Mao appreciate the support from the National Key R&D Program of China(No.2021YFB3701700)G.Niu appreciates the support from the National Natural Science Foundation of China(No.52304389)the China Postdoctoral Science Foundation(No.2022M720402).
文摘The corrosion behavior and mechanism of 3Ni weathering steel in a simulated oceanic atmospheric environment are investigated in order to comprehend the impacts of La,as determined through electrochemical analysis and rust layer characterization.The results of this study demonstrate that the addition of La enhances the corrosion resistance of 3Ni weathering steel in the marine atmospheric environment,thereby reducing the corrosion rate and improving the protection of the rust layer.The influence of La on corrosion resistance can be attributed to two primary factors.Firstly,La functions as a grain refiner,minimizing the potential difference of the micro-regions on the substrate surface,thereby significantly reducing the corrosion of bare steel in the marine environment.Secondly,La inhibits the process of Fe_(3)O_(4) oxidation back toγ-FeOOH during corrosion at the local site,thus decreasing the formation ofγ-FeOOH and enhancing the charge transfer resistance.This research work may serve as a reference for expanding the application of rare earth elements in the field of weathering steel.
基金supported by the Natural Science Foundation of China(Grant No.51902246,12161141012,and 12174299)the China National Key R&D Program(Grant No.2021YFB3201800 and 2020YFC0122100)+5 种基金the Natural Science Fundamental Research Project of Shaanxi Province of China(No.2019JQ590)the Key R&D Program of Shaanxi Province of China(2020GY-271)the Fundamental Research Funds for the Central Universities(xzd012020059)the“111 Project”of China(B14040)the Natural Sciences&Engineering Research Council of Canada(NSERC,Discovery Grant No.RGPIN-2017-06915)Xijiang Innovation Team Introduction Program of Zhaoqing(Jiecheng).
文摘Lead-free bismuth sodium titanate(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)and related solid solutions are potential piezoelectric materials for such applications as actuators and transducers if their excellent strain responses and piezoelectric properties can be optimized.In this work,a large strain response of 0.61%is achieved in lead-free(0.94-x%)(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)-x%NaNbO_(3)(x=0 e6,BNT-6BT-xNN)ceramics with the composition of x=3.5 in a pseudo-cubic structure.Coexistence of ferroelectric(FE)and relaxor(RE)domain structures is observed in all the unpoled ceramics and the enhanced strain response is believed to be related to the evolution of the ergodic relaxor(ER)and non-ergodic(NR)states thanks to the substitution of antiferroelectric NN.BNT-6BT-3.5NN is a critical composition near the FE/NR/ER phase boundary close to room temperature(RT)and its high strain response arises from a synergistic combination of a reversible electric-field-induced phase transition and an active domain switching in the mixed NR/ER state.This work provides new insights into the dynamic interplay between mesoscopic domains and macroscopic electrical properties in the BNT-based piezoceramics.
文摘The phase transformation behavior during continuous cooling of high-strength spring steels containing different amounts of Cr was studied.Furthermore,the effects of combining Cr with V as well as austenite deformation on the transformation kinetics were investigated in the method of dilatometry and metallography hardness.The results showed that,with the increase of Cr,the pearlite transformation field was enlarged,the ferrite transformation field was narrowed,and the entire phase field shifted to the right.With the addition of V,the start transformation temperature of undercooling austenite( A_(r3))was gradually increased,but the ferrite and pearlite transformation fields were not affected.Besides,the minimum critical cooling rate of martensitic transformation was also reduced.In addition,the dynamic continuous cooling transformation( CCT) curve moves to the top left compared with the static CCT curve.The transformed microstructures showed that the addition of V and the deformation not only refined the overall transformed microstructures but also reduced the lamellar spacing of pearlite.The alloying elements Cr and V promoted the Vickers hardness.However,the effect of Cr on the Vickers hardness of martensite was stronger and the influence of V on that of pearlite was stronger.Moreover,the Vickers hardness affected by the austenite deformation was more complex and strongly depended on the transformed microstructures.
基金supported by the National Natural Science Foundation of China(Grant No.51474031)
文摘304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained(NG/UFG)structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline(60-100 nm)and ultrafine(100-500 nm)grains,submicron size(500-1000 nm)grains and micron size(>1000 nm)grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test.
基金support from Guangxi Science and Technology Major Project of China(Grant No.AA18242012-1).
文摘To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray diffraction and nanoindentation test have been used to detect the residual stress and micro-property.The samples with deformation rate of 0-5.59%or annealing at 550℃ are analyzed.The results show that,due to the coupling effect of thermal expansion and cold contraction and the volume expansion of microstructural transformation from austenite to ferrite,compressive residual stress was found inside the hot-rolled samples.With the increase in cold compression deformation,the dislocation density increased and the microhardness increased gradually,and there is no obvious rule for the change of mean nano-hardness in micro-zone for the center of samples.However,the uniformity of nano-hardness in the micro-zone increased first and then decreased,and the value of residual stress has obvious corresponding relationship with the uniformity of micro-zone property.The cold compression deformation with appropriate reduction rate can reduce residual stress and improve nano-hardness uniformity of the hot-rolled samples,but more deformation(such as reduction rateε=5.59%)makes residual stress increase and makes uniformity of nano-hardness deteriorate.
基金This work was supported by Key R&D Program of Shaanxi Province of China(2020GY-271 and 2018ZDXM-GY-150)the Fundamental Research Funds for the Central Universities(xjj2018016)+3 种基金the“111 Project”of China(B14040),the Open Project of State Key Laboratory of Electronic Thin Films and Integrated Devices(KFJJ201902)the Open Project of State Key Laboratory of Information Functional Materials(SKL-201908)the Natural Sci-ences and Engineering Research Council of Canada(NSERC,Dis-covery Grant No.RGPIN-2017-06915)the National Natural Science Foundation of China(91964204 and 61634008).
文摘Hardware electronic synapse and neuro-inspired computing system based on phase change random access memory(PCRAM)have attracted an extensive investigation.However,due to the intrinsic asymmetric reversible phase transition,the defective weight update of PCRAM synapses in aspects of tuning range,linearity and continuity has long required a system-level complexity of circuits and al-gorithms.The cell-level improvements to a great extent may slim the system thus achieving efficient computing.We report in this work the great enhancement of Ge_(2)Sb_(2)Te_(5)(GST)based PCRAM synapses by combining materials engineering and pulse programming.It is found that carbon doping in GST retards the rate of phase changing thus increasing the controllability of the conductance,while non-linear programmable pulse excitations can eventually lead to a reliable synaptic potentiation and depression.A set of improved programmable pulse schemes for spike-timing dependent plasticity was then demonstrated,suggesting its potential superiority in flexible programming and reliable data collection.Our methods and results are of great significance for implementing PCRAM electronic synapses and high-performance neuro-inspired computing.
基金the National Natural Science Foundation of China(61674165,61604167,61574160,61704183,61404159,11604366)the Natural Science Foundation of Jiangsu Province(BK20170432,BK20160397,BK20140394)+2 种基金the National Key R&D Program of China(2016YFB0401803)the Strategic Priority Research Program of the Chinese Academy of Science(XDA09020401)XRD,AFM and TEM experiments were performed at the Platform for Characterization&Test,Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO),Chinese Academy of Sciences.
文摘In this work,we have successfully grown high quality epitaxialβ-Ga_(2)O_(3)thin films onβ-Ga_(2)O_(3)(100)and Al_(2)O_(3)(0001)substrates using pulsed laser deposition(PLD).By optimizing temperature and oxygen pressure,the best conditions were found to be 650-700℃and 0.5 Pa.To further improve the quality of hetero-epitaxialβ-Ga_(2)O_(3),the sapphire substrates were pretreated for atomic terraced surface by chemical cleaning and high temperature annealing.From the optical transmittance measurements,the films grown at 600-750℃exhibit a clear absorption edge at deep ultraviolet region around 250-275 nm wavelength.High resolution transmission electron microscope(HRTEM)images and X-ray diffraction(XRD)patterns demonstrate thatβ-Ga_(2)O_(3)(-201)//Al_(2)O_(3)(0001)epitaxial texture dominated the epitaxial oxide films on sapphire substrate,which opens up the possibilities of high power electric devices.
基金the support from the National Natural Science Foundation of China (Nos.51774033 and 51474031)。
文摘1.Introduction Advanced high-strength steels with good ductility are essen-tial to the manufacturing,structural safety,and light-weighting of load-bearing structures in many industries[1-3].Austenitic stain-less steel(ASS)exhibits high ductility due to the TRIP and/or TWIP effect that can alleviate stress concentration,prevent void nucle-ation,enhance work hardening,and postpone necking[4-6].The yield strength of conventional ASS is generally low(∼200-500 MPa),and their deformation resistance is insufficient for many load-bearing applications[6].Previous studies reported the in-creased yield strength in various austenitic steels through grain refinement,dislocation strengthening,precipitation strengthening,and heterogeneous hardening[7-14].A single strengthening mech-anism,however,is typically insufficient to obtain ultrahigh yield strength over 1 GPa in austenitic steel[12].
基金supported by the Natural Science Foundation of China(Grant No.51902246)the Natural Science Fundamental Research Project of Shaanxi Province of China(No.2019JQ590)the Fundamental Research Funds for the Central Universities,and the“111 Project”of China(B14040).
文摘Lead-free piezoelectric sodium bismuth titanate((Bi0.5Na0.5)TiO3,BNT)thin films were epitaxially grown onto(001)-,(110)-,and(111)-oriented Nb:SrTiO3(STO)single crystal substrates prepared by sol-gel processing.Highly oriented growth in(001),(110),and(111)BNT thin films was obtained in this work benefiting from the lattice match between the BNT film and the STO substrate.The different growth models in thin films with various orientations result in various surface morphologies dependent on the film orientation.The piezoresponse of the BNT thin films was represented exhibiting a strong orientation dependence that(110)>(001)>(111).This is contributed by the various domain switching contribution related to the crystal symmetry and polarization distribution in the three oriented thin films.
