Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in t...Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes.The disordered particle arrangement is harmful to the cyclic performance and structural stability,yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified.Herein,we have designed three kinds of LiNi_(0.83)Co_(0.06)Mn_(0.11)O_(2) cathode materials with different primary particle orientations by regulating the precursor coprecipitation process.Combining finite element simulation and in-situ characterization,the Li^(+)transport and structure evolution behaviors of different materials are unraveled.Specifically,the smooth Li^(+)diffusion minimizes the reaction heterogeneity,homogenizes the phase transition within grains,and mitigates the anisotropic microstructural change,thereby modulating the crack evolution behavior.Meanwhile,the optimized structure evolution ensures radial tight junctions of the primary particles,enabling enhanced Li^(+)diffusion during dynamic processes.Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance.This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.展开更多
Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium alloys.To investigate the influences of specimen orientation,the corrosion tes...Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium alloys.To investigate the influences of specimen orientation,the corrosion tests and(corrosion)fatigue crack growth tests were conducted.The rolled and transverse surfaces of the materials show distinct corrosion rate differences in the stable corrosion stage,but the truth is the opposite for the initial stage of corrosion.In air,specimen orientations have a significant influence on the plastic deformation mechanisms near the crack tip,which results in different fatigue fracture surfaces and cracking paths.Compared with R-T specimens,N-T specimens show a slower fatigue crack growth(FCG)rate in air,which can be attributed to crack closure effects and deformation twinning near the crack tip.The corrosion environment will not significantly change the main plastic deformation mechanisms for the same type of specimen.However,the FCG rate in phosphate buffer saline(PBS)is one order of magnitude higher than that in air,which is caused by the combined effects of hydrogen-induced cracking and anodic dissolution.Owing to the similar corrosion rates at crack tips,the specimens with different orientations display close FCG rates in PBS.展开更多
The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and...The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and resultant peak particle velocity(PPV)generates.With the orientation sequence of holes blasts on site,the superimposition angle of wave changes and hence results in significant variation in resultant PPV.The orientation with respect to the initiation of blasts resulting in lowest PPV needs to be identified for any site.By knowing the PPV contour of vibration waves in mine sites,it is possible to reduce the vibration on the structures by changing the initiation sequence.In this paper,experimental blasts were conducted at two different mine sites and the PPV values were recorded at different ori-entations from the blast site and its initiation sequence.The PPV contours were drawn to identify the orientation with least and highest PPV generation line.It was found that by merely changing the initi-ation sequence of blasts with respect to the sensitive structure or point of interest,the PPV values can be reduced significantly up to 76.9%.展开更多
Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter conten...Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter content, bedding planes, natural fractures, porosity and stress regime among others), external factors like wellbore orientation and stimulation design play a role. In this study, we present a series of true triaxial hydraulic fracturing experiments conducted on Lushan shale to investigate the interplay of internal factors (bedding, natural fractures and in situ stress) and external factors (wellbore orientation) on the growth process of fracture networks in cubic specimens of 200 mm in length. We observe relatively low breakdown pressure and fracture propagation pressure as the wellbore orientation and/or the maximum in situ stress is subparallel to the shale bedding plane. The wellbore orientation has a more prominent effect on the breakdown pressure, but its effect is tapered with increasing angle of bedding inclination. The shale breakdown is followed by an abrupt response in sample displacement, which reflects the stimulated fracture volume. Based on fluid tracer analysis, the morphology of hydraulic fractures (HF) is divided into four categories. Among the categories, activation of bedding planes (bedding failure, BF) and natural fractures (NF) significantly increase bifurcation and fractured areas. Under the same stress regime, a horizontal wellbore is more favorable to enhance the complexity of hydraulic fracture networks. This is attributed to the relatively large surface area in contact with the bedding plane for the horizontal borehole compared to the case with a vertical wellbore. These findings provide important references for hydraulic fracturing design in shale reservoirs.展开更多
The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolec...The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolecular chains remain elusive.Herein,we propose a novel electrospinning technique that can efficiently modulate molecular chain orientation by controlling the electric field.In contrast to the typical electrospinning method,this technique can piecewise control the electric field by applying high voltage to the metal ring instead of the needle.Benefiting from this change,a new electric field distribution can be realized,leading to a non-monotonic change in the drafting force.As a result,the macromolecular chain orientation of polyethylene oxide(PEO)nanofibers was significantly improved with a recordhigh infrared dichroic ratio.This was further confirmed by the sharp decrease in the PEO jet fineness of approximately 80%and the nanofiber diameter from 298 to 114 nm.Interestingly,the crystallinity can also be adjusted,with an obvious drop from 74.9%to 31.7%,which is different from the high crystallinity caused by oriented chains in common materials.This work guides a new perspective for the preparation of advanced electrospun nanofibers with optimal orientation–crystallinity properties,a merited feature for various applications.展开更多
With the rapid rise in perovskite solar cells(PSCs)performance,it is imperative to develop scalable fabrication techniques to accelerate potential commercialization.However,the power conversion efficiencies(PCEs)of PS...With the rapid rise in perovskite solar cells(PSCs)performance,it is imperative to develop scalable fabrication techniques to accelerate potential commercialization.However,the power conversion efficiencies(PCEs)of PSCs fabricated via scalable two-step sequential deposition lag far behind the state-of-the-art spin-coated ones.Herein,the additive methylammonium chloride(MACl)is introduced to modulate the crystallization and orientation of a two-step sequential doctorbladed perovskite film in ambient conditions.MACl can significantly improve perovskite film quality and increase grain size and crystallinity,thus decreasing trap density and suppressing nonradiative recombination.Meanwhile,MACl also promotes the preferred face-up orientation of the(100)plane of perovskite film,which is more conducive to the transport and collection of carriers,thereby significantly improving the fill factor.As a result,a champion PCE of 23.14%and excellent longterm stability are achieved for PSCs based on the structure of ITO/SnO_(2)/FA_(1-x)MA_xPb(I_(1-y)Br_y)_3/Spiro-OMeTAD/Ag.The superior PCEs of 21.20%and 17.54%are achieved for 1.03 cm~2 PSC and 10.93 cm~2 mini-module,respectively.These results represent substantial progress in large-scale two-step sequential deposition of high-performance PSCs for practical applications.展开更多
The crystal plasticity finite element method(CPFEM)is widely used to explore the microscopic mechanical behavior of materials and understand the deformation mechanism at the grain-level.However,few CPFEM simulation st...The crystal plasticity finite element method(CPFEM)is widely used to explore the microscopic mechanical behavior of materials and understand the deformation mechanism at the grain-level.However,few CPFEM simulation studies have been carried out to analyze the nanoindentation deformation mechanism of polycrystalline materials at the microscale level.In this study,a three-dimensional CPFEM-based nanoindentation simulation is performed on an Inconel 718 polycrystalline material to examine the influence of different crystallographic parameters on nanoindentation behavior.A representative volume element model is developed to calibrate the crystal plastic constitutive parameters by comparing the stress-strain data with the experimental results.The indentation force-displacement curves,stress distributions,and pile-up patterns are obtained by CPFEM simulation.The results show that the crystallographic orientation and grain boundary have little influence on the force-displacement curves of the nanoindentation,but significantly influence the local stress distributions and shape of the pile-up patterns.As the difference in crystallographic orientation between grains increases,changes in the pile-up patterns and stress distributions caused by this effect become more significant.In addition,the simulation results reveal that the existence of grain boundaries affects the continuity of the stress distribution.The obstruction on the continuity of stress distribution increases as the grain boundary angle increases.This research demonstrates that the proposed CPFEM model can well describe the microscopic compressive deformation behaviors of Inconel 718 under nanoindentation.展开更多
The propagation mechanism of microcracks in nanocrystalline single crystal systems under uniaxial dynamic and static tension is investigated using the phase-field-crystal method.Both dynamic and static stretching resu...The propagation mechanism of microcracks in nanocrystalline single crystal systems under uniaxial dynamic and static tension is investigated using the phase-field-crystal method.Both dynamic and static stretching results show that different orientation angles can induce the crack propagation mode,microscopic morphology,the free energy,crack area change,and causing fracture failure.Crack propagation mode depends on the dislocation activity near the crack tip.Brittle propagation of the crack occurs due to dislocation always at crack tip.Dislocation is emitted at the front end of the crack tip and plastic deformation occurs,which belongs to ductile propagation.The orientation angles of 9°and 14°are brittleductile mixed propagation,while the orientation angles of 19°and 30°are brittle propagation and no dislocation is formed under dynamic tension.The vacancy and vacancy connectivity phenomenon would appear when the orientation angle is14°under static tension,and the crack would be ductile propagation.While the orientation angle is 19°and 30°,the crack propagates in a certain direction,which is a kind of brittle propagation.This work has some practical significance in preventing material fracture failure and improving material performance.展开更多
Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the ...Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg_(17)Al_(12) precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy(TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg_(17)Al_(12) precipitates and the matrix were revealed: ■, and ■.Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential.展开更多
Smartphones are usually packed with a large number of features.An increasing number of researchers are paying attention to the technological capabilities of smartphones,which is a new topic and research interest.This ...Smartphones are usually packed with a large number of features.An increasing number of researchers are paying attention to the technological capabilities of smartphones,which is a new topic and research interest.This paper proposes a method using smartphones and digital photogrammetry to measure the discontinuity orientation of a rock mass.Smartphone photos satisfying a certain overlap rate provide an efficient method for generating point cloud models of rock outcrops based on image matching.Using the target and the generated point cloud model allows for determining actual geographic coordinates and the measurement of discontinuity orientations.The method proposed has been applied to two different study areas.The discontinuity orientations measured by the proposed method are compared with those measured by the manual method in two cases.The results show a good agreement,verifying the reliability and accuracy of the proposed method.The main contribution of this paper is to use knowledge of coordinate rotation to determine the actual geographic location of the model through a square target.The equipment used in this study is simple,and photogrammetric field surveys are easy to carry out.展开更多
Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction(RD)...Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction(RD),and free-end torsion of a tubular specimen machined along the thickness direction(ND)were conducted.The experimental results were used to evaluate an elastic-viscoplastic self-consistent model with the consideration of twinning and detwinning(EVPSC-TDT)on magnesium(Mg)alloys.The EVPSC-TDT model provides stress-strain curves and the hardening rates in close agreement with the experimental results of all the 11 loading cases.The model adequately predicts the textures after fracture of all the 11 loading cases and the evolutions of tension twins with increasing strains for tension in the ND,compression in the RD,and torsion along the ND.The Swift effect was observed in the experiment and was properly simulated by the model.展开更多
Mg-6.75Zn-0.57Zr-0.4Y-0.18Gd(wt.%)sheet with typical basal texture was produced by cross rolling and annealing.Room temperature tensile tests were subsequently conducted along rolling direction(RD),transverse directio...Mg-6.75Zn-0.57Zr-0.4Y-0.18Gd(wt.%)sheet with typical basal texture was produced by cross rolling and annealing.Room temperature tensile tests were subsequently conducted along rolling direction(RD),transverse direction(TD),and diagonal direction(RD45).Deformation mechanism and orientation evolution during the tension were investigated by quasi-in-situ electron backscatter diffraction observation and in-grain misorientation axis analysis.The results indicate that the activation of deformation mechanism mainly depends on the initial grain orientation.For RD sample,prismatic<a>slip plays an important role in the deformation of grains with<0001>axis nearly perpendicular to the RD.With the<0001>axis gradually tilted towards the RD,basal<a>slip becomes the dominant deformation mode.After the tensile fracture,the initial concentrically distributed{0001}pole is split into double peaks extending perpendicular to the RD,and the randomly distributed{1010}pole becomes parallel to the RD.The evolution in{0001}and{1010}poles during tension is related to the lattice rotation induced by basal<a>slip and prismatic<a>slip,respectively.TD and RD45 samples exhibit similar deformation mechanism and orientation evolution as the RD sample,which results in the nearly isotropic mechanical properties in the annealed cross-rolled sheet.展开更多
Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in G...Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in Garai et al.,2022),there are contours of measured vibration velocities in 4 directions(every 90?)and an incorrect interpretation between them.By placing all measured vibration velocity values(Gerai et al.,2022)at well-defined points on a single figure,it was not possible to precisely determine the type of vibration velocity,such as radial,tangential and vertical vibration velocities,with their different shapes.An incorrect conclusion was also drawn about the direction of the highest vibration velocity.The paper by Garai et al.(2022)measured the vibrational velocity of the medium through which the seismic wave passed,but used the incorrect term shock wave.The shock wave would have destroyed the seismic measuring instruments.A superposition of the vibrational velocity was considered,but not combined with the vibrational frequency of the seismic wave.This paper presents a method for selecting the time delay between successively initiated explosive charges to the measured frequency of the seismic wave,so that the direction of initiation of the explosive charges does not affect the vibration velocity of the ground through which the seismic wave passes.The theoretical and measured shapes and waveforms of radial velocity and tangential velocity in an opencast lignite mine are then presented.Moreover,the conditions for the formation of shock wave,transition wave and seismic waves are presented.展开更多
The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd...The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd–Fe–B magnets with varying Co content(Co = 0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20℃–500℃. It was found that, the coefficient of thermal expansion(CTE) increases with the increase of Co contents, while the anisotropy of thermal expansion decreases.The introduction of Co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of nonoriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd–Fe–B with controllable CTE.展开更多
Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to 100....Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to 100.Three variations of the solid volume fraction c={0.1,0.2,0.3}with four Hermans orientation factors S={−0.5,0,0.5,1}are studied.It has been found that changes in S cause prominent variations in the Nusselt number.In general,Nusselt number increases with the decrease of S.For all three aspect ratios,the Nusselt number remains a linear function of S at different c and Re.Therefore,it is concluded that,for heat transfer from prolate muti-particle system,the effects of orientations cannot be ignored.A new correlation for Nusselt number has been developed for arrays of prolate particles using the simulation data as a function of Re,c,S and ar.展开更多
BACKGROUND Oesophagogastroduodenoscopy is the gold standard investigation for the upper gastrointestinal(UGI)tract.Orientation during endoscopy is challenging and United Kingdom training focusses on technical competen...BACKGROUND Oesophagogastroduodenoscopy is the gold standard investigation for the upper gastrointestinal(UGI)tract.Orientation during endoscopy is challenging and United Kingdom training focusses on technical competence and procedural safety.The reported location of UGI pathologies is crucial to post-endoscopic planning.AIM To evaluate endoscopists’ability to spatially orientate themselves within the UGI tract.METHODS A cross sectional descriptive study elicited,using an anonymised survey,the ability of endoscopists to orientate themselves within the UGI tract.The primary outcome was percentage of correct answers from all surveyed;secondary outcomes were percentage of correct answers from experienced vs novice endoscopists.Pearson’sχ2 test was applied to compare groups.RESULTS Of 188 respondents,86 were experienced endoscopists having completed over 1000 endoscopies.44.4%of respondents correctly identified the anterior stomach and 47.3%correctly identified the posterior of the second part of the duodenum(D2).Experienced endoscopists were significantly more likely than novice to identify the anterior stomach correctly[61.6%vs 31.3%,X2(1,n=188)=11.10,P=0.001].There was no significant difference between the two groups in identifying the posterior of D2.CONCLUSION The majority of endoscopists surveyed were unable to identify key landmarks within the UGI tract.Endoscopic orientation appears to improve with experience yet there are some areas still not well recognised.This has potential considerable impact on post-endoscopic management of patients with posterior duodenal ulcers being more likely to perforate and associated with a higher rebleeding risk.We suggest the development of a consensus statement on endoscopic description.展开更多
As China’s economy shifts from high-speed development to high-quality development,China’s urbanization also shifts from incremental expansion to stock optimization,providing a new direction for the transformation of...As China’s economy shifts from high-speed development to high-quality development,China’s urbanization also shifts from incremental expansion to stock optimization,providing a new direction for the transformation of urban villages.At present,the reconstruction work office of urban villages in small towns is mainly promoted based on government-led and villager main body in the initial exploration stage.From the perspective of policy orientation,to solve the main problems in urban villages in small towns,Zhuangqian Xiongjia Village,Fengcheng City was taken as an example,and the micro-transformation strategies of urban villages were put forward from the perspective of satisfying the appeals of the government,village committee and villagers,so as to provide some references for the transformation of urban villages in other small towns across the country.展开更多
Introduction: Over time, new sexual practices other than the common ones are frequently described. This work aimed to determine the sexual orientation and its associated factors among adolescents attending school in t...Introduction: Over time, new sexual practices other than the common ones are frequently described. This work aimed to determine the sexual orientation and its associated factors among adolescents attending school in two big cities in Cameroon. Methodology: A cross-sectional study with prospective data collection took place from November 2021 to April 2022 in eight secondary schools (four in Yaoundé and four in Douala). We conducted non-probability, consecutive sampling on school-going, sexually active adolescents between the ages of 14 and 19 years. A self-administered questionnaire to students was used to study their sexual orientations and practices. Univariate and multivariate analyses made it possible to find the associated factors using the chi-square test. Results: We included 1274 adolescents with an average age of 18 years;majority were boys (54.8%) for a sex ratio of 1.21. Most (49.7%) were from two-parent families. Cisgender was the most common self-gender identity (89.6%). The main sexual orientation was heterosexuality (82.3%), followed by bisexuality (9.7%) and homosexuality (8%). The average age at first sexual intercourse (coitarche) was 15 years and the coitarche was consenting in 84.1%. Sexual practices included: kissing (94.7%), fondling (93.4%), vaginal penetration (80.6%), oral sex (40.4%), masturbation (22.8%), fisting (18.4%), and anal penetrations (17.5%). The majority of sexual intercourse acts (55.8%) took place without protection;24.6% of adolescents practiced them with a person of the same sex and 18.4% with several others simultaneously. The factors associated with heterosexuality were age ≤17 years (aOR: 2.44 [1.36 - 4.40];p = 0.003), self-identification opposite to primary sexual characteristics (aOR: 12.05 [5.13 - 28.29];p 0.001), absence of consent during the first coitus (aOR: 7.09 [3.61 - 13.93];p 0.001) and a history of sexual intercourse with a person of the same sex (aOR: 94.17 [43.36 - 183.39];p 0.001). Conclusion: Although most adolescents are heterosexual in the school environment, the authors raise the importance of providing guidance in the aspect of sexual orientation particularly on the psychological and behavioral level considering age, self-gender identity, sexual consent, and using protection during the sexual experience.展开更多
This present theoretical paper tries to highlight,i.e.,how education plays an important role in the process of social change through inculcating value within the youngsters of our higher education particularly in this...This present theoretical paper tries to highlight,i.e.,how education plays an important role in the process of social change through inculcating value within the youngsters of our higher education particularly in this COVID-19 unpredicted situation.It is very potential instrument,a powerful medium of bringing about changes in the society through more than 65%of the youngsters in the higher education of our country.Changes brought about by value-oriented education are permanent and transcendent in nature.This paper suggests that with the help of new communication media,technology,modern methodology,and latest instructional materials,education brings about changes in the society during this COVID-19 situation.This paper also highlights that the NEP(1986)characterizes higher education as a crucial factor for survival,providing the Indian people with an opportunity to reflect on the critical,social,economic,cultural,moral and spiritual issues facing humanity.This paper further argues that higher education in this COVID-19 also is the main instrument for development and it is the time to change the ways and come forward for value orientation through universities and colleges by the government.It has the important task of preparing leaders for different walks of life-social,intellectual,political,cultural,scientific,and technological.展开更多
基金supported by National Natural Science Foundation of China (52070194,52073309)Natural Science Foundation of Hunan Province (2022JJ20069)。
文摘Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes.The disordered particle arrangement is harmful to the cyclic performance and structural stability,yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified.Herein,we have designed three kinds of LiNi_(0.83)Co_(0.06)Mn_(0.11)O_(2) cathode materials with different primary particle orientations by regulating the precursor coprecipitation process.Combining finite element simulation and in-situ characterization,the Li^(+)transport and structure evolution behaviors of different materials are unraveled.Specifically,the smooth Li^(+)diffusion minimizes the reaction heterogeneity,homogenizes the phase transition within grains,and mitigates the anisotropic microstructural change,thereby modulating the crack evolution behavior.Meanwhile,the optimized structure evolution ensures radial tight junctions of the primary particles,enabling enhanced Li^(+)diffusion during dynamic processes.Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance.This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.
基金the National Natural Science Foundation of China(Nos.52175143 and 51571150)。
文摘Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium alloys.To investigate the influences of specimen orientation,the corrosion tests and(corrosion)fatigue crack growth tests were conducted.The rolled and transverse surfaces of the materials show distinct corrosion rate differences in the stable corrosion stage,but the truth is the opposite for the initial stage of corrosion.In air,specimen orientations have a significant influence on the plastic deformation mechanisms near the crack tip,which results in different fatigue fracture surfaces and cracking paths.Compared with R-T specimens,N-T specimens show a slower fatigue crack growth(FCG)rate in air,which can be attributed to crack closure effects and deformation twinning near the crack tip.The corrosion environment will not significantly change the main plastic deformation mechanisms for the same type of specimen.However,the FCG rate in phosphate buffer saline(PBS)is one order of magnitude higher than that in air,which is caused by the combined effects of hydrogen-induced cracking and anodic dissolution.Owing to the similar corrosion rates at crack tips,the specimens with different orientations display close FCG rates in PBS.
文摘The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and resultant peak particle velocity(PPV)generates.With the orientation sequence of holes blasts on site,the superimposition angle of wave changes and hence results in significant variation in resultant PPV.The orientation with respect to the initiation of blasts resulting in lowest PPV needs to be identified for any site.By knowing the PPV contour of vibration waves in mine sites,it is possible to reduce the vibration on the structures by changing the initiation sequence.In this paper,experimental blasts were conducted at two different mine sites and the PPV values were recorded at different ori-entations from the blast site and its initiation sequence.The PPV contours were drawn to identify the orientation with least and highest PPV generation line.It was found that by merely changing the initi-ation sequence of blasts with respect to the sensitive structure or point of interest,the PPV values can be reduced significantly up to 76.9%.
基金supported by the National Natural Science Foundation of China(Grant Nos.52064006 and 52004072)It was.also supported by the program(Grant No.202006050112)of China Scholarship Council(CSC)for the first author's visit at the Helm-holtz Centre Potsdam,GFZ German Research Centre for Geosciences.
文摘Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter content, bedding planes, natural fractures, porosity and stress regime among others), external factors like wellbore orientation and stimulation design play a role. In this study, we present a series of true triaxial hydraulic fracturing experiments conducted on Lushan shale to investigate the interplay of internal factors (bedding, natural fractures and in situ stress) and external factors (wellbore orientation) on the growth process of fracture networks in cubic specimens of 200 mm in length. We observe relatively low breakdown pressure and fracture propagation pressure as the wellbore orientation and/or the maximum in situ stress is subparallel to the shale bedding plane. The wellbore orientation has a more prominent effect on the breakdown pressure, but its effect is tapered with increasing angle of bedding inclination. The shale breakdown is followed by an abrupt response in sample displacement, which reflects the stimulated fracture volume. Based on fluid tracer analysis, the morphology of hydraulic fractures (HF) is divided into four categories. Among the categories, activation of bedding planes (bedding failure, BF) and natural fractures (NF) significantly increase bifurcation and fractured areas. Under the same stress regime, a horizontal wellbore is more favorable to enhance the complexity of hydraulic fracture networks. This is attributed to the relatively large surface area in contact with the bedding plane for the horizontal borehole compared to the case with a vertical wellbore. These findings provide important references for hydraulic fracturing design in shale reservoirs.
基金partly supported by the grants(51973027 and 52003044)from the National Natural Science Foundation of Chinathe Fundamental Research Funds for the Central Universities(2232020A-08)+5 种基金International Cooperation Fund of Science and Technology Commission of Shanghai Municipality(21130750100)Major Scientific and Technological Innovation Projects of Shandong Province(2021CXGC011004)supported by the Chang Jiang Scholars Programthe Innovation Program of Shanghai Municipal Education Commission(2019-01-07-00-03-E00023)to Prof.Xiaohong QinYoung Elite Scientists Sponsorship Program by China Association for Science and Technology,State Key Laboratory for Modification of Chemical Fibers and Polymer Materials(KF2216)Donghua University Distinguished Young Professor Program to Prof.Liming Wang。
文摘The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers.However,understanding and significantly tuning the orientation of fiber macromolecular chains remain elusive.Herein,we propose a novel electrospinning technique that can efficiently modulate molecular chain orientation by controlling the electric field.In contrast to the typical electrospinning method,this technique can piecewise control the electric field by applying high voltage to the metal ring instead of the needle.Benefiting from this change,a new electric field distribution can be realized,leading to a non-monotonic change in the drafting force.As a result,the macromolecular chain orientation of polyethylene oxide(PEO)nanofibers was significantly improved with a recordhigh infrared dichroic ratio.This was further confirmed by the sharp decrease in the PEO jet fineness of approximately 80%and the nanofiber diameter from 298 to 114 nm.Interestingly,the crystallinity can also be adjusted,with an obvious drop from 74.9%to 31.7%,which is different from the high crystallinity caused by oriented chains in common materials.This work guides a new perspective for the preparation of advanced electrospun nanofibers with optimal orientation–crystallinity properties,a merited feature for various applications.
基金supported by the National Key Research and Development Program of China(2022YFB3803300)the National Natural Science Foundation of China(51673214)the State Key Laboratory of Powder Metallurgy,Central South University,China。
文摘With the rapid rise in perovskite solar cells(PSCs)performance,it is imperative to develop scalable fabrication techniques to accelerate potential commercialization.However,the power conversion efficiencies(PCEs)of PSCs fabricated via scalable two-step sequential deposition lag far behind the state-of-the-art spin-coated ones.Herein,the additive methylammonium chloride(MACl)is introduced to modulate the crystallization and orientation of a two-step sequential doctorbladed perovskite film in ambient conditions.MACl can significantly improve perovskite film quality and increase grain size and crystallinity,thus decreasing trap density and suppressing nonradiative recombination.Meanwhile,MACl also promotes the preferred face-up orientation of the(100)plane of perovskite film,which is more conducive to the transport and collection of carriers,thereby significantly improving the fill factor.As a result,a champion PCE of 23.14%and excellent longterm stability are achieved for PSCs based on the structure of ITO/SnO_(2)/FA_(1-x)MA_xPb(I_(1-y)Br_y)_3/Spiro-OMeTAD/Ag.The superior PCEs of 21.20%and 17.54%are achieved for 1.03 cm~2 PSC and 10.93 cm~2 mini-module,respectively.These results represent substantial progress in large-scale two-step sequential deposition of high-performance PSCs for practical applications.
基金Supported by National Natural Science Foundation of China(Grant Nos.52130511,52075174).
文摘The crystal plasticity finite element method(CPFEM)is widely used to explore the microscopic mechanical behavior of materials and understand the deformation mechanism at the grain-level.However,few CPFEM simulation studies have been carried out to analyze the nanoindentation deformation mechanism of polycrystalline materials at the microscale level.In this study,a three-dimensional CPFEM-based nanoindentation simulation is performed on an Inconel 718 polycrystalline material to examine the influence of different crystallographic parameters on nanoindentation behavior.A representative volume element model is developed to calibrate the crystal plastic constitutive parameters by comparing the stress-strain data with the experimental results.The indentation force-displacement curves,stress distributions,and pile-up patterns are obtained by CPFEM simulation.The results show that the crystallographic orientation and grain boundary have little influence on the force-displacement curves of the nanoindentation,but significantly influence the local stress distributions and shape of the pile-up patterns.As the difference in crystallographic orientation between grains increases,changes in the pile-up patterns and stress distributions caused by this effect become more significant.In addition,the simulation results reveal that the existence of grain boundaries affects the continuity of the stress distribution.The obstruction on the continuity of stress distribution increases as the grain boundary angle increases.This research demonstrates that the proposed CPFEM model can well describe the microscopic compressive deformation behaviors of Inconel 718 under nanoindentation.
基金Project supported by the National Natural Science Foundation of China(Grant No.52074246)。
文摘The propagation mechanism of microcracks in nanocrystalline single crystal systems under uniaxial dynamic and static tension is investigated using the phase-field-crystal method.Both dynamic and static stretching results show that different orientation angles can induce the crack propagation mode,microscopic morphology,the free energy,crack area change,and causing fracture failure.Crack propagation mode depends on the dislocation activity near the crack tip.Brittle propagation of the crack occurs due to dislocation always at crack tip.Dislocation is emitted at the front end of the crack tip and plastic deformation occurs,which belongs to ductile propagation.The orientation angles of 9°and 14°are brittleductile mixed propagation,while the orientation angles of 19°and 30°are brittle propagation and no dislocation is formed under dynamic tension.The vacancy and vacancy connectivity phenomenon would appear when the orientation angle is14°under static tension,and the crack would be ductile propagation.While the orientation angle is 19°and 30°,the crack propagates in a certain direction,which is a kind of brittle propagation.This work has some practical significance in preventing material fracture failure and improving material performance.
基金financially supported by the National Natural Science Foundation of China (Project No.51871036,52071040 and 51421001)the open funding of International Joint Laboratory for Light Alloys (MOE),Chongqing University。
文摘Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship(OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg_(17)Al_(12) precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy(TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg_(17)Al_(12) precipitates and the matrix were revealed: ■, and ■.Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential.
基金supported by the National Natural Science Foundation of China(Grant No.51769014),which is gratefully acknowledged.
文摘Smartphones are usually packed with a large number of features.An increasing number of researchers are paying attention to the technological capabilities of smartphones,which is a new topic and research interest.This paper proposes a method using smartphones and digital photogrammetry to measure the discontinuity orientation of a rock mass.Smartphone photos satisfying a certain overlap rate provide an efficient method for generating point cloud models of rock outcrops based on image matching.Using the target and the generated point cloud model allows for determining actual geographic coordinates and the measurement of discontinuity orientations.The method proposed has been applied to two different study areas.The discontinuity orientations measured by the proposed method are compared with those measured by the manual method in two cases.The results show a good agreement,verifying the reliability and accuracy of the proposed method.The main contribution of this paper is to use knowledge of coordinate rotation to determine the actual geographic location of the model through a square target.The equipment used in this study is simple,and photogrammetric field surveys are easy to carry out.
基金supported by the U.S.National Science Foundation(CMMI-1762312)the support of China Scholarship Council(CSC).
文摘Comprehensive experiments including monotonic tension and monotonic compression of specimens taken from a rolled AZ31B Mg thick plate along five different material orientations with respect to the rolled direction(RD),and free-end torsion of a tubular specimen machined along the thickness direction(ND)were conducted.The experimental results were used to evaluate an elastic-viscoplastic self-consistent model with the consideration of twinning and detwinning(EVPSC-TDT)on magnesium(Mg)alloys.The EVPSC-TDT model provides stress-strain curves and the hardening rates in close agreement with the experimental results of all the 11 loading cases.The model adequately predicts the textures after fracture of all the 11 loading cases and the evolutions of tension twins with increasing strains for tension in the ND,compression in the RD,and torsion along the ND.The Swift effect was observed in the experiment and was properly simulated by the model.
基金the financial support from the National Natural Science Foundation of China(NSFC)with projects Nos.51874367,51574291.
文摘Mg-6.75Zn-0.57Zr-0.4Y-0.18Gd(wt.%)sheet with typical basal texture was produced by cross rolling and annealing.Room temperature tensile tests were subsequently conducted along rolling direction(RD),transverse direction(TD),and diagonal direction(RD45).Deformation mechanism and orientation evolution during the tension were investigated by quasi-in-situ electron backscatter diffraction observation and in-grain misorientation axis analysis.The results indicate that the activation of deformation mechanism mainly depends on the initial grain orientation.For RD sample,prismatic<a>slip plays an important role in the deformation of grains with<0001>axis nearly perpendicular to the RD.With the<0001>axis gradually tilted towards the RD,basal<a>slip becomes the dominant deformation mode.After the tensile fracture,the initial concentrically distributed{0001}pole is split into double peaks extending perpendicular to the RD,and the randomly distributed{1010}pole becomes parallel to the RD.The evolution in{0001}and{1010}poles during tension is related to the lattice rotation induced by basal<a>slip and prismatic<a>slip,respectively.TD and RD45 samples exhibit similar deformation mechanism and orientation evolution as the RD sample,which results in the nearly isotropic mechanical properties in the annealed cross-rolled sheet.
文摘Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in Garai et al.,2022),there are contours of measured vibration velocities in 4 directions(every 90?)and an incorrect interpretation between them.By placing all measured vibration velocity values(Gerai et al.,2022)at well-defined points on a single figure,it was not possible to precisely determine the type of vibration velocity,such as radial,tangential and vertical vibration velocities,with their different shapes.An incorrect conclusion was also drawn about the direction of the highest vibration velocity.The paper by Garai et al.(2022)measured the vibrational velocity of the medium through which the seismic wave passed,but used the incorrect term shock wave.The shock wave would have destroyed the seismic measuring instruments.A superposition of the vibrational velocity was considered,but not combined with the vibrational frequency of the seismic wave.This paper presents a method for selecting the time delay between successively initiated explosive charges to the measured frequency of the seismic wave,so that the direction of initiation of the explosive charges does not affect the vibration velocity of the ground through which the seismic wave passes.The theoretical and measured shapes and waveforms of radial velocity and tangential velocity in an opencast lignite mine are then presented.Moreover,the conditions for the formation of shock wave,transition wave and seismic waves are presented.
基金the National Key Research and Development Program of China (Grant No. 2021YFB3502900)the National Natural Science Foundation of China (Grant No. 51871063)+1 种基金the Key Technology Research and Development Program of Shandong Province, China (Grant No. 2019JZZY020210)the Major Projects in Inner Mongolia Autonomous Region, China。
文摘The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd–Fe–B magnets with varying Co content(Co = 0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20℃–500℃. It was found that, the coefficient of thermal expansion(CTE) increases with the increase of Co contents, while the anisotropy of thermal expansion decreases.The introduction of Co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of nonoriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd–Fe–B with controllable CTE.
基金supported by the HPC Platform of Xi’an Jiaotong Universitysupport by the Natural Science Foundation of China (21978228,22078255)+2 种基金support by Shaanxi Creative Talents Promotion Plan-Technological Innovation Team (2019TD-039)the Fundamental Research Funds for the Central Universities (Creative Team Plan No.cxtd2017004 in Xi’an Jiaotong University)the China Scholarship Council (CSC,2017GXZ021009).
文摘Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to 100.Three variations of the solid volume fraction c={0.1,0.2,0.3}with four Hermans orientation factors S={−0.5,0,0.5,1}are studied.It has been found that changes in S cause prominent variations in the Nusselt number.In general,Nusselt number increases with the decrease of S.For all three aspect ratios,the Nusselt number remains a linear function of S at different c and Re.Therefore,it is concluded that,for heat transfer from prolate muti-particle system,the effects of orientations cannot be ignored.A new correlation for Nusselt number has been developed for arrays of prolate particles using the simulation data as a function of Re,c,S and ar.
文摘BACKGROUND Oesophagogastroduodenoscopy is the gold standard investigation for the upper gastrointestinal(UGI)tract.Orientation during endoscopy is challenging and United Kingdom training focusses on technical competence and procedural safety.The reported location of UGI pathologies is crucial to post-endoscopic planning.AIM To evaluate endoscopists’ability to spatially orientate themselves within the UGI tract.METHODS A cross sectional descriptive study elicited,using an anonymised survey,the ability of endoscopists to orientate themselves within the UGI tract.The primary outcome was percentage of correct answers from all surveyed;secondary outcomes were percentage of correct answers from experienced vs novice endoscopists.Pearson’sχ2 test was applied to compare groups.RESULTS Of 188 respondents,86 were experienced endoscopists having completed over 1000 endoscopies.44.4%of respondents correctly identified the anterior stomach and 47.3%correctly identified the posterior of the second part of the duodenum(D2).Experienced endoscopists were significantly more likely than novice to identify the anterior stomach correctly[61.6%vs 31.3%,X2(1,n=188)=11.10,P=0.001].There was no significant difference between the two groups in identifying the posterior of D2.CONCLUSION The majority of endoscopists surveyed were unable to identify key landmarks within the UGI tract.Endoscopic orientation appears to improve with experience yet there are some areas still not well recognised.This has potential considerable impact on post-endoscopic management of patients with posterior duodenal ulcers being more likely to perforate and associated with a higher rebleeding risk.We suggest the development of a consensus statement on endoscopic description.
文摘As China’s economy shifts from high-speed development to high-quality development,China’s urbanization also shifts from incremental expansion to stock optimization,providing a new direction for the transformation of urban villages.At present,the reconstruction work office of urban villages in small towns is mainly promoted based on government-led and villager main body in the initial exploration stage.From the perspective of policy orientation,to solve the main problems in urban villages in small towns,Zhuangqian Xiongjia Village,Fengcheng City was taken as an example,and the micro-transformation strategies of urban villages were put forward from the perspective of satisfying the appeals of the government,village committee and villagers,so as to provide some references for the transformation of urban villages in other small towns across the country.
文摘Introduction: Over time, new sexual practices other than the common ones are frequently described. This work aimed to determine the sexual orientation and its associated factors among adolescents attending school in two big cities in Cameroon. Methodology: A cross-sectional study with prospective data collection took place from November 2021 to April 2022 in eight secondary schools (four in Yaoundé and four in Douala). We conducted non-probability, consecutive sampling on school-going, sexually active adolescents between the ages of 14 and 19 years. A self-administered questionnaire to students was used to study their sexual orientations and practices. Univariate and multivariate analyses made it possible to find the associated factors using the chi-square test. Results: We included 1274 adolescents with an average age of 18 years;majority were boys (54.8%) for a sex ratio of 1.21. Most (49.7%) were from two-parent families. Cisgender was the most common self-gender identity (89.6%). The main sexual orientation was heterosexuality (82.3%), followed by bisexuality (9.7%) and homosexuality (8%). The average age at first sexual intercourse (coitarche) was 15 years and the coitarche was consenting in 84.1%. Sexual practices included: kissing (94.7%), fondling (93.4%), vaginal penetration (80.6%), oral sex (40.4%), masturbation (22.8%), fisting (18.4%), and anal penetrations (17.5%). The majority of sexual intercourse acts (55.8%) took place without protection;24.6% of adolescents practiced them with a person of the same sex and 18.4% with several others simultaneously. The factors associated with heterosexuality were age ≤17 years (aOR: 2.44 [1.36 - 4.40];p = 0.003), self-identification opposite to primary sexual characteristics (aOR: 12.05 [5.13 - 28.29];p 0.001), absence of consent during the first coitus (aOR: 7.09 [3.61 - 13.93];p 0.001) and a history of sexual intercourse with a person of the same sex (aOR: 94.17 [43.36 - 183.39];p 0.001). Conclusion: Although most adolescents are heterosexual in the school environment, the authors raise the importance of providing guidance in the aspect of sexual orientation particularly on the psychological and behavioral level considering age, self-gender identity, sexual consent, and using protection during the sexual experience.
文摘This present theoretical paper tries to highlight,i.e.,how education plays an important role in the process of social change through inculcating value within the youngsters of our higher education particularly in this COVID-19 unpredicted situation.It is very potential instrument,a powerful medium of bringing about changes in the society through more than 65%of the youngsters in the higher education of our country.Changes brought about by value-oriented education are permanent and transcendent in nature.This paper suggests that with the help of new communication media,technology,modern methodology,and latest instructional materials,education brings about changes in the society during this COVID-19 situation.This paper also highlights that the NEP(1986)characterizes higher education as a crucial factor for survival,providing the Indian people with an opportunity to reflect on the critical,social,economic,cultural,moral and spiritual issues facing humanity.This paper further argues that higher education in this COVID-19 also is the main instrument for development and it is the time to change the ways and come forward for value orientation through universities and colleges by the government.It has the important task of preparing leaders for different walks of life-social,intellectual,political,cultural,scientific,and technological.
