To study the safety and stability of large slopes, taking the right side slope of the Yuxi’an tunnel of the Yuchu Expressway Bridge in Yunnan Province as an example, limit equilibrium and finite element analysis were...To study the safety and stability of large slopes, taking the right side slope of the Yuxi’an tunnel of the Yuchu Expressway Bridge in Yunnan Province as an example, limit equilibrium and finite element analysis were applied to engineering examples to calculate the stability coefficient of the slope before and after excavation in the natural state. After comparative analysis, it was concluded that the former had a clear mechanical model and concept, which could quickly provide stability results;the latter could accurately determine the sliding surface of the slope and simulate the stress state changes of the rock and soil mass. The stability coefficients calculated by the two methods were within the stable range, but their values were different. On this basis, combined with the calculation principles, advantages and disadvantages of the two methods, a comprehensive analysis method of slope stability based on the limit equilibrium and finite element methods was proposed, and the rationality of the stability coefficient calculated by this method was judged for a slope case.展开更多
Steel slag is characterized by high strength,good wear resistance and micro-expansion.This study aims at exploring the potential of steel slag in cement stabilized aggregates,mainly including mechanical properties,shr...Steel slag is characterized by high strength,good wear resistance and micro-expansion.This study aims at exploring the potential of steel slag in cement stabilized aggregates,mainly including mechanical properties,shrinkage and compensation mechanisms.For this purpose,the compressive strength and compressive resilient modulus of cement stabilized aggregates with different steel slag contents(CSMS)were initially investigated.Subsequently,the effects of steel slag and cement on dry shrinkage,temperature shrinkage,and total shrinkage were analyzed through a series of shrinkage test designs.Additionally,in combination with X-ray diffraction(XRD)and Scanning electron microscope(SEM),the characteristic peaks and microscopic images of cement,steel slag and cement-steel slag at different hydration ages were analyzed to identify the chemical substances causing the expansion volume of steel slag and reveal the compensation mechanism of CSMS.The results show that the introduction of 20%steel slag improved the mechanical properties of CSMS by 16.7%,reduced dry shrinkage by 21%,increased temperature shrinkage by 5.8%and reduced its total shrinkage by 19.2%.Compared with the hydration reaction of cement alone,the composite hydration reaction of steel slag with cement does not produce new hydrates.Furthermore,it is noteworthy that the volume expansion of the f-CaO hydration reaction in steel slag can compensate for the volume shrinkage of cement-stabilized macadam.This research can provide a solid theoretical basis for the application and promotion of steel slag in cement-stabilized macadam and reduce the possibility of shrinkage cracking.展开更多
In this paper,the electromagnetic performance of variable flux memory(VFM)machines with series-magnetic-circuit is investigated and compared for different rotor topologies.Based on a V-type VFM machine,five topologies...In this paper,the electromagnetic performance of variable flux memory(VFM)machines with series-magnetic-circuit is investigated and compared for different rotor topologies.Based on a V-type VFM machine,five topologies with different interior permanent magnet(IPM)arrangements are evolved and optimized under same constrains.Based on two-dimensional(2-D)finite element(FE)method,their electromagnetic performance at magnetization and demagnetization states is evaluated.It reveals that the iron bridge and rotor lamination region between constant PM(CPM)and variable PM(VPM)play an important role in torque density and flux regulation(FR)capabilities.Besides,the global efficiency can be improved in VFM machines by adjusting magnetization state(MS)under different operating conditions.展开更多
Enzyme immobilization has attracted great attention for improving the performance of enzymes in industrial applications.This work was designed to create a new support for Candida rugosa lipase(CRL)immobilization.A por...Enzyme immobilization has attracted great attention for improving the performance of enzymes in industrial applications.This work was designed to create a new support for Candida rugosa lipase(CRL)immobilization.A porous poly(vinyl acetate–divinyl benzene)microsphere coated by a zwitterionic polymer,poly(maleic anhydride-alt-1-octadecene)and N,N-dimethylethylenediamine derivative,was developed for CRL immobilization via hydrophobic binding.The catalytic activity,reaction kinetics,stabilities and reusability of the immobilized CRL were investigated.It demonstrated the success of the zwitterionic polymer coating and subsequent CRL immobilization on the porous microsphere.The immobilized lipase(p2-MS-CRL)reached27.6 mg·g^-1 dry carrier and displayed a specific activity 1.5 times higher than free CRL.The increase of Vmax and decrease of Kmwere also observed,indicating the improvement of catalytic activity and enzyme-substrate affinity of the immobilized lipase.Besides,p2-MS-CRL exhibited significantly enhanced thermal stability and pH tolerance.The improved performance was considered due to the interfacial activation regulated by the hydrophobic interaction and stabilization effect arisen by the zwitterionic polymer coating.This study has thus proved the advantages of the zwitterionic polymer-coated porous carrier for lipase immobilization and its potential for further development in various enzyme immobilizations.展开更多
The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field dis...The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.展开更多
The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” ...The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” soft soil. Thus, the construction of expressways in this area is likely to cause subgrade settlement. The manuscript investigated the influence of the design parameters of precast pipe piles on the soft ground treatment in the Jianghan Plain based on the case of the soft soil subgrade project of the Xiaogan south section of the Wuhan city ring expressway, China. Midas GTS NX 2019 finite element software was used to analyse the settlement pattern of the subgrade under the variations in pile length, pile spacing and pile diameter. The results show that precast pipe piles are effective in reducing the settlement of soft soil subgrades with a high compressibility and water content;the soft foundation settlement decreases with increasing pile length and pile diameter and decreasing pile spacing. As the pile tip is embedded in the bearing stratum, the settlement of the soft foundation is greatly affected by the variations in pile length and pile spacing while slightly influenced by the variation in pile diameter;in combination with the curve fitting obtained from the real-time monitoring data, the analysis concludes that the soft foundation treatment plan with a pile length of 15 m, pile spacing of 1.2 m to 1.5 m and pile diameter of 0.6 m can better contain the soft soil subgrade settlement in this section.展开更多
Grid-forming(GFM)converters can provide inertia support for power grids through control technology,stabilize voltage and frequency,and improve system stability,unlike traditional grid-following(GFL)converters.Therefor...Grid-forming(GFM)converters can provide inertia support for power grids through control technology,stabilize voltage and frequency,and improve system stability,unlike traditional grid-following(GFL)converters.Therefore,in future“double high”power systems,research on the control technology of GFM converters will become an urgent demand.In this paper,we first introduce the basic principle of GFM control and then present five currently used control strategies for GFM converters:droop control,power synchronization control(PSC),virtual synchronous machine control(VSM),direct power control(DPC),and virtual oscillator control(VOC).These five strategies can independently establish voltage phasors to provide inertia to the system.Among these,droop control is the most widely used strategy.PSC and VSM are strategies that simulate the mechanical characteristics of synchronous generators;thus,they are more accurate than droop control.DPC regulates the active power and reactive power directly,with no inner current controller,and VOC is a novel method under study using an oscillator circuit to realize synchronization.Finally,we highlight key technologies and research directions to be addressed in the future.展开更多
This paper studied the stress corrosion cracking(SCC)of EV31A in 0.1 M Na 2 SO 4 saturated with Mg(OH)2 using linearly increasing stress tests,compared with pure Mg and WE43B.All three materials were susceptible to SC...This paper studied the stress corrosion cracking(SCC)of EV31A in 0.1 M Na 2 SO 4 saturated with Mg(OH)2 using linearly increasing stress tests,compared with pure Mg and WE43B.All three materials were susceptible to SCC.SCC susceptibility increased with decreasing applied stress rate.The threshold stress was 0.3×(yield stress)for pure Mg,0.6×(yield stress)for EV31A,and 0.8×(yield stress)for WE43B.The SCC velocities at an applied stress rate of 7.3×10^(-4)MPa s^(-1)were 7.2×10^(-8)m s^(−1)for pure Mg,5.6×10^(-9)m s^(-1)for WE43B,and 1.5×10^(-9)m s^(-1)for EV31A.展开更多
We analyzed the sequence alignment on 25 AA rice and 24 non-AA rice chloroplasts using two length diversity markers (ORF 100 and ORF29-TrnCGCA) and four sequence markers existed in introns of rps16 gene and TrnTUGU-Tr...We analyzed the sequence alignment on 25 AA rice and 24 non-AA rice chloroplasts using two length diversity markers (ORF 100 and ORF29-TrnCGCA) and four sequence markers existed in introns of rps16 gene and TrnTUGU-TrnLUAA spacer to explore the chloroplast diversity of different types of rice using PCR amplification and sequencing. Results showed that in terms of the length of ORF100 and ORF29-TrnCGCA, chloroplast DNA (cp DNA) of Hainan ordinary wild rice, Dongxiang ordinary wild rice, Hepu ordinary wild rice and three-line cytoplasmic male sterile wild rice were indica-type, Chaling ordinary wild rice, Fusui ordinary wild rice, Niwara wild rice, Brazilian upland rice and Lemont were japonica-type among in AA genome. Besides, all non-AA wild rice was japonica-type. There were 4 indica-japonica markers utilizing introns of rps16 gene and TrnTUGU-TrnLUAA. We found that all the ordinary wild rice in Chaling and Fusui of AA genome presented as japonica specific sites, while the others owned two indica and japonica specific sites, respectively. There were two indica-japonica sites separately and a 6-base specific fragment in three-line cytoplasmic male sterile materials except Yuetai A, simultaneously, 2-base difference from Hainan wild rice. Moreover, Brazilian upland rice and Lemont were entire japonica specific sites. Result of three markers indicated that the cp DNA of non-AA wild rice was japonica-type and result of one marker showed indica-type. Sequencing results also suggested that wild rice existed many polymorphic base sites, CCDD genome, wart wild rice and malay wild rice had their own specific sites. In conclusion, significant differentiation trend of indica-japonica exhibits in chloroplast of ordinary wild rice, and non-AA wild rice is generally japonica-type. The cytoplasmic polymorphism level of three-line sterile lines is low. It is worth considering whether the cytoplasm of Honglian-type sterile line Yuetai A comes from Hainan ordinary wild rice. Furthermore, genetic polymorphisms in wild rice are far more than in cultivar.展开更多
In this paper,the problem of controllability of Boolean control networks(BCNs)with multiple time delays in both states and controls is investigated.First,the controllability problem of BCNs with multiple time delays i...In this paper,the problem of controllability of Boolean control networks(BCNs)with multiple time delays in both states and controls is investigated.First,the controllability problem of BCNs with multiple time delays in controls is considered.For this controllability problem,a controllability matrix is constructed by defining a new product of matrices,based on which a necessary and sufficient controllability condition is obtained.Then,the controllability of BCNs with multiple time delays in states is studied by giving a necessary and sufficient condition.Subsequently,based on these results,a controllability matrix for BCNs with multiple time delays in both states and controls is proposed that provides a concise controllability condition.Finally,two examples are given to illustrate the main results.展开更多
A ductility-dip-cracking(DDC)-concentrated zone(DCZ) in a width of about 3 mm was observed adjacent to the AISI 316 L/52 Mw fusion boundary(FB) in 52 Mw. The morphology, microstructure, mechanical and thermal properti...A ductility-dip-cracking(DDC)-concentrated zone(DCZ) in a width of about 3 mm was observed adjacent to the AISI 316 L/52 Mw fusion boundary(FB) in 52 Mw. The morphology, microstructure, mechanical and thermal properties and corrosion behavior in simulated primary water of DDC/DCZ were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM), 3 D X-ray tomography(XRT), 3 D atom probe(3 DAP), slow strain rate tensile(SSRT) testing and thermal dilatometry. The results indicate that DDCs are random-shaped and disc-like cavities with corrugated structure of inner surface and are parallel in groups along straight high-angle boundaries of columnar grains, ranging from micrometers to millimeters in size. Large-size M_(23)C_6 carbides dominate on the grain boundaries rather than MC(M=Nb, Ti), and thus the bonding effect of carbides is absent for the straight grain boundaries.The impurity segregation of O is confirmed for the inner surfaces of DDC. The oxide film formed on the inner surface of DDC(about 50 nm) is approximately twice as thick as that on the matrix(about 25 nm)in simulated primary water. The yield strength, tensile strength and elongation to fracture of 52 MwDCZ(400 MPa, 450 MPa and 20 %, respectively) are lower than those of 52 Mw-MZ(460 MPa, 550 MPa and 28 %, respectively). The intrinsic high-restraint weld structure, the additional stress/strain caused by the thermal expansion difference between AISI 316 L and 52 Mw as well as the detrimental carbide precipitation and the resulting grain boundary structure all add up to cause the occurrence of DCZ in the dissimilar metal weld.展开更多
A novel porous heterostructured Nd_(0.8)Sr_(1.2)CoO_(4)±/Nd_(0.5)Sr_(0.5)CoO_(3-δ)(NSC_(214/113))cathode for intermediate tem-perature solid oxide fuel cells(IT-SOFCs)is developed to significantly enhance oxygen...A novel porous heterostructured Nd_(0.8)Sr_(1.2)CoO_(4)±/Nd_(0.5)Sr_(0.5)CoO_(3-δ)(NSC_(214/113))cathode for intermediate tem-perature solid oxide fuel cells(IT-SOFCs)is developed to significantly enhance oxygen reduction reaction(ORR)kinetics.Compared to single-phase materials,the fabricated porous heterostructured NSC 214/113 shows optimized electrochemical properties,including a better conductivity,20 times faster surface oxygen exchange kinetics,and a comparatively lower area-specific resistance(0.065Ωcm^(2) at 800℃).The single cell with Ni-YSZ|YSZ-GDC|NSC_(214/113) configuration exhibits a high peak power density of 1.10 W cm^(−2) at 800℃,superior to other cells reported in literature with similar heterostructured cathodes.Moreover,the underlying mechanism of the ORR performance enhancement is further investigated,revealing that the formation of heterojunction can lead to a narrowed energy bandgap and a decrease of Co oxidation state,which further induce better conductivity,more available electrons and oxygen vacancies to enhance the ORR process.Taken together,our research also provides new insights into potential application of artificial intelligence(AI)method involved in materials in-telligent identification,cell state estimation,system diagnostic and optimization.The revolutionary force of AI,especially in the field of new electrode material development is now advancing in its full swing.More and greater breakthroughs are still expected.展开更多
Background This study aimed to assess whether pregnancy and puerperium were associated with the risk of brain arteriovenous malformation(bAVM)haemorrhage.Methods A retrospective review was conducted in Xiangya Hospita...Background This study aimed to assess whether pregnancy and puerperium were associated with the risk of brain arteriovenous malformation(bAVM)haemorrhage.Methods A retrospective review was conducted in Xiangya Hospital,Central South University from January 2012 to December 2021.A case-crossover design was adopted to calculate the incidence density of bAVM-related haemorrhage among female patients in risk(pregnancy and puerperium)and control(non-pregnancy and non-puerperium)periods,according to four scenarios observed in different populations scenario I:patients with haemorrhagic bAVM of all ages;scenario II:patients with haemorrhagic bAVM of all ages,with at least one previous pregnancy;scenario III:patients with haemorrhagic bAVM who are of reproductive age(15-45 years);scenario IV:patients with haemorrhagic bAVM of reproductive age(15-45 years),with at least one previous pregnancy.Next,a comprehensive literature aggregation(up to April 2022)was performed for evidence synthesis.Results Among the 311 female patients with haemorrhagic bAVM,a significant haemorrhage risk during pregnancy and puerperium was found in Scenarios I(relative risk[RR],2.08;95%CI,1.28 to 3.39),II(RR,3.21;95%CI,1.95 to 5.31)and IV(RR,2.92;95%CI,1.73 to 4.93);however,a suggestive risk was found in scenario III(RR,1.62;95%CI,0.99 to 2.67).Evidence synthesis revealed a consistent haemorrhage risk among patients of all ages(RR,3.15;95%CI,1.93 to 5.15)and those of reproductive age(RR,1.29;95%CI,0.89 to 1.86).Conclusion Compared with most previous studies,a higher but relatively moderate risk for bAVM-related haemorrhage was identified during pregnancy and puerperium.Individualised prevention and treatment strategies should be preferred when neurosurgeons make clinical decisions.展开更多
Alloy 690TT tube samples with different scratch depths were repaired by grinding treatments using abra-sive papers of two different particle sizes.The microstructure and stress corrosion cracking(SCC)behavior were stu...Alloy 690TT tube samples with different scratch depths were repaired by grinding treatments using abra-sive papers of two different particle sizes.The microstructure and stress corrosion cracking(SCC)behavior were studied in detail.During grinding,the plastic accumulation zone vulnerable to SCC was removed.Meanwhile,some residual slip steps remained in the scratched area.Corrosion tests lasting 1000,2000,3000,and 4000 h show that the sensitivity and risk of SCC in the scratched area are decreased by grind-ing.Treatment using abrasive particles of a smaller size is more effective.Nevertheless,deep scratches remained hazardous even after the grinding.展开更多
文摘To study the safety and stability of large slopes, taking the right side slope of the Yuxi’an tunnel of the Yuchu Expressway Bridge in Yunnan Province as an example, limit equilibrium and finite element analysis were applied to engineering examples to calculate the stability coefficient of the slope before and after excavation in the natural state. After comparative analysis, it was concluded that the former had a clear mechanical model and concept, which could quickly provide stability results;the latter could accurately determine the sliding surface of the slope and simulate the stress state changes of the rock and soil mass. The stability coefficients calculated by the two methods were within the stable range, but their values were different. On this basis, combined with the calculation principles, advantages and disadvantages of the two methods, a comprehensive analysis method of slope stability based on the limit equilibrium and finite element methods was proposed, and the rationality of the stability coefficient calculated by this method was judged for a slope case.
基金National Natural Science Foundation of China(Grant No.52078051)Fundamental Research Funds for the Central Universities(Grant No.310821163502)+1 种基金Technology Innovation Project of Shandong Department of Industry and Information(Grant No.Lugongxinji 2020-8)the Transportation Department of Shandong Province(Grant No.Lujiaokeji 2017-28).
文摘Steel slag is characterized by high strength,good wear resistance and micro-expansion.This study aims at exploring the potential of steel slag in cement stabilized aggregates,mainly including mechanical properties,shrinkage and compensation mechanisms.For this purpose,the compressive strength and compressive resilient modulus of cement stabilized aggregates with different steel slag contents(CSMS)were initially investigated.Subsequently,the effects of steel slag and cement on dry shrinkage,temperature shrinkage,and total shrinkage were analyzed through a series of shrinkage test designs.Additionally,in combination with X-ray diffraction(XRD)and Scanning electron microscope(SEM),the characteristic peaks and microscopic images of cement,steel slag and cement-steel slag at different hydration ages were analyzed to identify the chemical substances causing the expansion volume of steel slag and reveal the compensation mechanism of CSMS.The results show that the introduction of 20%steel slag improved the mechanical properties of CSMS by 16.7%,reduced dry shrinkage by 21%,increased temperature shrinkage by 5.8%and reduced its total shrinkage by 19.2%.Compared with the hydration reaction of cement alone,the composite hydration reaction of steel slag with cement does not produce new hydrates.Furthermore,it is noteworthy that the volume expansion of the f-CaO hydration reaction in steel slag can compensate for the volume shrinkage of cement-stabilized macadam.This research can provide a solid theoretical basis for the application and promotion of steel slag in cement-stabilized macadam and reduce the possibility of shrinkage cracking.
基金supported by the CRRC Zhuzhou Institute Company Ltd.and in part by Key R&D projects in Hunan+1 种基金ChinaNo.2022GK2062。
文摘In this paper,the electromagnetic performance of variable flux memory(VFM)machines with series-magnetic-circuit is investigated and compared for different rotor topologies.Based on a V-type VFM machine,five topologies with different interior permanent magnet(IPM)arrangements are evolved and optimized under same constrains.Based on two-dimensional(2-D)finite element(FE)method,their electromagnetic performance at magnetization and demagnetization states is evaluated.It reveals that the iron bridge and rotor lamination region between constant PM(CPM)and variable PM(VPM)play an important role in torque density and flux regulation(FR)capabilities.Besides,the global efficiency can be improved in VFM machines by adjusting magnetization state(MS)under different operating conditions.
基金Supported by the National Natural Science Foundation of China(21621004,21878222).
文摘Enzyme immobilization has attracted great attention for improving the performance of enzymes in industrial applications.This work was designed to create a new support for Candida rugosa lipase(CRL)immobilization.A porous poly(vinyl acetate–divinyl benzene)microsphere coated by a zwitterionic polymer,poly(maleic anhydride-alt-1-octadecene)and N,N-dimethylethylenediamine derivative,was developed for CRL immobilization via hydrophobic binding.The catalytic activity,reaction kinetics,stabilities and reusability of the immobilized CRL were investigated.It demonstrated the success of the zwitterionic polymer coating and subsequent CRL immobilization on the porous microsphere.The immobilized lipase(p2-MS-CRL)reached27.6 mg·g^-1 dry carrier and displayed a specific activity 1.5 times higher than free CRL.The increase of Vmax and decrease of Kmwere also observed,indicating the improvement of catalytic activity and enzyme-substrate affinity of the immobilized lipase.Besides,p2-MS-CRL exhibited significantly enhanced thermal stability and pH tolerance.The improved performance was considered due to the interfacial activation regulated by the hydrophobic interaction and stabilization effect arisen by the zwitterionic polymer coating.This study has thus proved the advantages of the zwitterionic polymer-coated porous carrier for lipase immobilization and its potential for further development in various enzyme immobilizations.
基金Supported by National Key R&D Program of China(Grant No.2016YFF0203000)State Key Program of National Natural Science Foundation of China(Grant No.11834008)+5 种基金National Natural Science Foundation of China(Grant Nos.11774167,61571222)Fundamental research funds for the Central Universities(Grant No.020414380001)State Key Laboratory of Acoustics,Chinese Academy of Science(Grant No.SKLA201809)Key Laboratory of Underwater Acoustic Environment,Chinese Academy of Sciences(Grant No.SSHJ-KFKT-1701)AQSIQ technology R&D program(Grant No.2017QK125)Innovative Talents Program of Far East NDT New Technology&Application Forum
文摘The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.
文摘The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” soft soil. Thus, the construction of expressways in this area is likely to cause subgrade settlement. The manuscript investigated the influence of the design parameters of precast pipe piles on the soft ground treatment in the Jianghan Plain based on the case of the soft soil subgrade project of the Xiaogan south section of the Wuhan city ring expressway, China. Midas GTS NX 2019 finite element software was used to analyse the settlement pattern of the subgrade under the variations in pile length, pile spacing and pile diameter. The results show that precast pipe piles are effective in reducing the settlement of soft soil subgrades with a high compressibility and water content;the soft foundation settlement decreases with increasing pile length and pile diameter and decreasing pile spacing. As the pile tip is embedded in the bearing stratum, the settlement of the soft foundation is greatly affected by the variations in pile length and pile spacing while slightly influenced by the variation in pile diameter;in combination with the curve fitting obtained from the real-time monitoring data, the analysis concludes that the soft foundation treatment plan with a pile length of 15 m, pile spacing of 1.2 m to 1.5 m and pile diameter of 0.6 m can better contain the soft soil subgrade settlement in this section.
基金supported by the National Natural Science Foundation of China(No.52177122)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA 21050100)the Youth Innovation Promotion Association CAS(No.2018170)。
文摘Grid-forming(GFM)converters can provide inertia support for power grids through control technology,stabilize voltage and frequency,and improve system stability,unlike traditional grid-following(GFL)converters.Therefore,in future“double high”power systems,research on the control technology of GFM converters will become an urgent demand.In this paper,we first introduce the basic principle of GFM control and then present five currently used control strategies for GFM converters:droop control,power synchronization control(PSC),virtual synchronous machine control(VSM),direct power control(DPC),and virtual oscillator control(VOC).These five strategies can independently establish voltage phasors to provide inertia to the system.Among these,droop control is the most widely used strategy.PSC and VSM are strategies that simulate the mechanical characteristics of synchronous generators;thus,they are more accurate than droop control.DPC regulates the active power and reactive power directly,with no inner current controller,and VOC is a novel method under study using an oscillator circuit to realize synchronization.Finally,we highlight key technologies and research directions to be addressed in the future.
基金YL wishes to thank The University of Queensland,the University of Science and Technology Beijing,and China Scholarship Council for their support during his study abroad year.
文摘This paper studied the stress corrosion cracking(SCC)of EV31A in 0.1 M Na 2 SO 4 saturated with Mg(OH)2 using linearly increasing stress tests,compared with pure Mg and WE43B.All three materials were susceptible to SCC.SCC susceptibility increased with decreasing applied stress rate.The threshold stress was 0.3×(yield stress)for pure Mg,0.6×(yield stress)for EV31A,and 0.8×(yield stress)for WE43B.The SCC velocities at an applied stress rate of 7.3×10^(-4)MPa s^(-1)were 7.2×10^(-8)m s^(−1)for pure Mg,5.6×10^(-9)m s^(-1)for WE43B,and 1.5×10^(-9)m s^(-1)for EV31A.
文摘We analyzed the sequence alignment on 25 AA rice and 24 non-AA rice chloroplasts using two length diversity markers (ORF 100 and ORF29-TrnCGCA) and four sequence markers existed in introns of rps16 gene and TrnTUGU-TrnLUAA spacer to explore the chloroplast diversity of different types of rice using PCR amplification and sequencing. Results showed that in terms of the length of ORF100 and ORF29-TrnCGCA, chloroplast DNA (cp DNA) of Hainan ordinary wild rice, Dongxiang ordinary wild rice, Hepu ordinary wild rice and three-line cytoplasmic male sterile wild rice were indica-type, Chaling ordinary wild rice, Fusui ordinary wild rice, Niwara wild rice, Brazilian upland rice and Lemont were japonica-type among in AA genome. Besides, all non-AA wild rice was japonica-type. There were 4 indica-japonica markers utilizing introns of rps16 gene and TrnTUGU-TrnLUAA. We found that all the ordinary wild rice in Chaling and Fusui of AA genome presented as japonica specific sites, while the others owned two indica and japonica specific sites, respectively. There were two indica-japonica sites separately and a 6-base specific fragment in three-line cytoplasmic male sterile materials except Yuetai A, simultaneously, 2-base difference from Hainan wild rice. Moreover, Brazilian upland rice and Lemont were entire japonica specific sites. Result of three markers indicated that the cp DNA of non-AA wild rice was japonica-type and result of one marker showed indica-type. Sequencing results also suggested that wild rice existed many polymorphic base sites, CCDD genome, wart wild rice and malay wild rice had their own specific sites. In conclusion, significant differentiation trend of indica-japonica exhibits in chloroplast of ordinary wild rice, and non-AA wild rice is generally japonica-type. The cytoplasmic polymorphism level of three-line sterile lines is low. It is worth considering whether the cytoplasm of Honglian-type sterile line Yuetai A comes from Hainan ordinary wild rice. Furthermore, genetic polymorphisms in wild rice are far more than in cultivar.
基金supported by the Natural Science Foundation of Chongqing,China(No.CSTB2022NSCQ-MSX2869)the Science and Technology Research Program of Chongqing Municipal Education Commission,China(No.KJQN202200524)+1 种基金the Research Project of National Center for Applied Mathematics in Chongqing,China(No.ncamc2022-msxm05)the Program of Chongqing Normal University,China(No.21XLB045)。
文摘In this paper,the problem of controllability of Boolean control networks(BCNs)with multiple time delays in both states and controls is investigated.First,the controllability problem of BCNs with multiple time delays in controls is considered.For this controllability problem,a controllability matrix is constructed by defining a new product of matrices,based on which a necessary and sufficient controllability condition is obtained.Then,the controllability of BCNs with multiple time delays in states is studied by giving a necessary and sufficient condition.Subsequently,based on these results,a controllability matrix for BCNs with multiple time delays in both states and controls is proposed that provides a concise controllability condition.Finally,two examples are given to illustrate the main results.
基金financially supported by the National Key Research and Development Program of China (2016YFE0105200)Key Research Program of Frontier Sciences,Chinese Academy of Sciences (QYZDY-SSW-JSC012)
文摘A ductility-dip-cracking(DDC)-concentrated zone(DCZ) in a width of about 3 mm was observed adjacent to the AISI 316 L/52 Mw fusion boundary(FB) in 52 Mw. The morphology, microstructure, mechanical and thermal properties and corrosion behavior in simulated primary water of DDC/DCZ were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM), 3 D X-ray tomography(XRT), 3 D atom probe(3 DAP), slow strain rate tensile(SSRT) testing and thermal dilatometry. The results indicate that DDCs are random-shaped and disc-like cavities with corrugated structure of inner surface and are parallel in groups along straight high-angle boundaries of columnar grains, ranging from micrometers to millimeters in size. Large-size M_(23)C_6 carbides dominate on the grain boundaries rather than MC(M=Nb, Ti), and thus the bonding effect of carbides is absent for the straight grain boundaries.The impurity segregation of O is confirmed for the inner surfaces of DDC. The oxide film formed on the inner surface of DDC(about 50 nm) is approximately twice as thick as that on the matrix(about 25 nm)in simulated primary water. The yield strength, tensile strength and elongation to fracture of 52 MwDCZ(400 MPa, 450 MPa and 20 %, respectively) are lower than those of 52 Mw-MZ(460 MPa, 550 MPa and 28 %, respectively). The intrinsic high-restraint weld structure, the additional stress/strain caused by the thermal expansion difference between AISI 316 L and 52 Mw as well as the detrimental carbide precipitation and the resulting grain boundary structure all add up to cause the occurrence of DCZ in the dissimilar metal weld.
文摘A novel porous heterostructured Nd_(0.8)Sr_(1.2)CoO_(4)±/Nd_(0.5)Sr_(0.5)CoO_(3-δ)(NSC_(214/113))cathode for intermediate tem-perature solid oxide fuel cells(IT-SOFCs)is developed to significantly enhance oxygen reduction reaction(ORR)kinetics.Compared to single-phase materials,the fabricated porous heterostructured NSC 214/113 shows optimized electrochemical properties,including a better conductivity,20 times faster surface oxygen exchange kinetics,and a comparatively lower area-specific resistance(0.065Ωcm^(2) at 800℃).The single cell with Ni-YSZ|YSZ-GDC|NSC_(214/113) configuration exhibits a high peak power density of 1.10 W cm^(−2) at 800℃,superior to other cells reported in literature with similar heterostructured cathodes.Moreover,the underlying mechanism of the ORR performance enhancement is further investigated,revealing that the formation of heterojunction can lead to a narrowed energy bandgap and a decrease of Co oxidation state,which further induce better conductivity,more available electrons and oxygen vacancies to enhance the ORR process.Taken together,our research also provides new insights into potential application of artificial intelligence(AI)method involved in materials in-telligent identification,cell state estimation,system diagnostic and optimization.The revolutionary force of AI,especially in the field of new electrode material development is now advancing in its full swing.More and greater breakthroughs are still expected.
基金supported by the grants from the Hunan Province Nature Science Foundation,China(2021JJ30911,2021JJ31077,2021JJ31121)Financial Science and Technology Project of Hunan Province,China(422000008)Central South University Case Database Construction Project for Graduate Students,China(2020ALK24).
文摘Background This study aimed to assess whether pregnancy and puerperium were associated with the risk of brain arteriovenous malformation(bAVM)haemorrhage.Methods A retrospective review was conducted in Xiangya Hospital,Central South University from January 2012 to December 2021.A case-crossover design was adopted to calculate the incidence density of bAVM-related haemorrhage among female patients in risk(pregnancy and puerperium)and control(non-pregnancy and non-puerperium)periods,according to four scenarios observed in different populations scenario I:patients with haemorrhagic bAVM of all ages;scenario II:patients with haemorrhagic bAVM of all ages,with at least one previous pregnancy;scenario III:patients with haemorrhagic bAVM who are of reproductive age(15-45 years);scenario IV:patients with haemorrhagic bAVM of reproductive age(15-45 years),with at least one previous pregnancy.Next,a comprehensive literature aggregation(up to April 2022)was performed for evidence synthesis.Results Among the 311 female patients with haemorrhagic bAVM,a significant haemorrhage risk during pregnancy and puerperium was found in Scenarios I(relative risk[RR],2.08;95%CI,1.28 to 3.39),II(RR,3.21;95%CI,1.95 to 5.31)and IV(RR,2.92;95%CI,1.73 to 4.93);however,a suggestive risk was found in scenario III(RR,1.62;95%CI,0.99 to 2.67).Evidence synthesis revealed a consistent haemorrhage risk among patients of all ages(RR,3.15;95%CI,1.93 to 5.15)and those of reproductive age(RR,1.29;95%CI,0.89 to 1.86).Conclusion Compared with most previous studies,a higher but relatively moderate risk for bAVM-related haemorrhage was identified during pregnancy and puerperium.Individualised prevention and treatment strategies should be preferred when neurosurgeons make clinical decisions.
基金jointly supported by National Natural Science Foundation of China (No. 51771211)National Key R&D Program(2019YFB1900904)the open-ended fund of the CAS Key laboratory of Nuclear Materials and Safety Assessment (Institute of Metal Research, Chinese Academy of Sciences, China)(No.2021NMSAKF01)
文摘Alloy 690TT tube samples with different scratch depths were repaired by grinding treatments using abra-sive papers of two different particle sizes.The microstructure and stress corrosion cracking(SCC)behavior were studied in detail.During grinding,the plastic accumulation zone vulnerable to SCC was removed.Meanwhile,some residual slip steps remained in the scratched area.Corrosion tests lasting 1000,2000,3000,and 4000 h show that the sensitivity and risk of SCC in the scratched area are decreased by grind-ing.Treatment using abrasive particles of a smaller size is more effective.Nevertheless,deep scratches remained hazardous even after the grinding.
