It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size...It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.展开更多
Driver distraction is a leading cause of traffic accidents,with fatigue being a significant contributor.This paper introduces a novel method for detecting driver distraction by analyzing facial features using machine ...Driver distraction is a leading cause of traffic accidents,with fatigue being a significant contributor.This paper introduces a novel method for detecting driver distraction by analyzing facial features using machine deep learning and 68 face model.The proposed system assesses driver tiredness by measuring the distance between key facial landmarks,such as the distance between the eyes and the angle of the mouth,to evaluate signs of drowsiness or disengagement.Real-time video feed analysis allows for continuous monitoring of the driver’s face,enabling the system to detect behavioral cues associated with distraction,such as eye closures or changes in facial expressions.The effectiveness of this method is demonstrated through a series of experiments on a dataset of driver videos,which proves that the approach can accurately assess tiredness and distraction levels under various driving conditions.By focusing on facial landmarks,the system is computationally efficient and capable of operating in real-time,making it a practical solution for in-vehicle safety systems.This paper discusses the system’s performance,limitations,and potential for future enhancements,including integration with other in-vehicle technologies to provide comprehensive driver monitoring.展开更多
One of the main causes of cancer-related morbidity and mortality globally is hepatocellular carcinoma(HCC).At every stage of the disease,HCC may now be treated using a variety of therapy techniques.Nevertheless,despit...One of the main causes of cancer-related morbidity and mortality globally is hepatocellular carcinoma(HCC).At every stage of the disease,HCC may now be treated using a variety of therapy techniques.Nevertheless,despite the abundance of effective therapeutic choices,the prognosis for patients with HCC is still typically dismal.Prognostic indicators are crucial when assessing prognosis and tracking tumor metastases or recurrence.There are many prognostic markers in HCC.We mainly focused on newly reported prognostic markers such as MEX3A,apolipoprotein B,alpha-fetoprotein,circulating tumor cells,SAMD13,Agrin,and Glypican-3 in the pathogenesis of HCC.Further,we highlighted how these prognostic markers correlated to clinical parameters such as tumor node metastasis,tumor diameter,differentiation,hepatocirrhosis,vascular invasion,and others in HCC.Therefore,identifying specific prognostic biomarkers of HCC helps to provide a great opportunity to improve the prognosis in patients with HCC and provide therapeutic targets.展开更多
Flow characteristics around a wall-mounted square cylinder have been numerically simulated at aspect ratios (AR) ranging from 4 to 7 at Re =10 000. Four turbulence models have been compared in terms of drag coefficien...Flow characteristics around a wall-mounted square cylinder have been numerically simulated at aspect ratios (AR) ranging from 4 to 7 at Re =10 000. Four turbulence models have been compared in terms of drag coefficient (C_D). The closest result has been provided by two turbulence models, namely, k-ε Realizable and k ?ω Shear Stress Transport (SST). Hence, these models were utilized to present the flow patterns of pressure distributions, turbulent kinetic energy values, velocity magnitude values with streamlines, streamwise velocity components, crossstream velocity components and spanwise velocity components on different planes. Flow stagnation has been attained in front of the cylinder. Pressure values peaked for the upstream region. Over the cylinders, the tip vortex structure was dominant owing to the influence of the free end. Flow separation from the top front edge of the body has been obtained. The dividing streamline affected by the flow separation was highly effective in the wake region and moved nearer to the body when the aspect ratio was decreased;the reason was the wake shrinkage owing to the decreasing aspect ratio. Upwash and downwash have been seen in the cylinder wake. These two models presented similar flow patterns and drag coefficients. These drag coefficients are in good agreement with those in previous studies.展开更多
Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider...Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.展开更多
A two-dimensional large eddy simulation numerical model is proposed to study the transient vortex flow and pressure oscillation of a large-aspect-ratio solid rocket motor.The numerical model is validated through exper...A two-dimensional large eddy simulation numerical model is proposed to study the transient vortex flow and pressure oscillation of a large-aspect-ratio solid rocket motor.The numerical model is validated through experimental data,finite element analysis and cumulative error analysis.The numerical simulations are executed to obtain the characteristics of the vortex-acoustic and pressure oscillation.The results show that the burning surface regression decreases the motor aspect ratio,increasing the corresponding natural frequency from 260 Hz to 293 Hz.The pressure oscillation phenomenon is formed due to the vortex-acoustic coupling.Decreasing the corner vortex shedding intensity shows negative effects on the dimensionless amplitude of the pressure oscillation.The head cavity without the injection can decrease the vortex-acoustic coupling level at the acoustic pressure antinode.The modified motor with head cavity can obtain a lower dimensionless oscillating pressure amplitude 0.00149 in comparison with 0.00895 of the original motor.The aspect ratio and volume of the head cavity without the injection have great effects on the pressure oscillation suppression,particularly at the low aspect ratio or large volume.The reason is that the mass in the region around the acoustic pressure antinode is extracted centrally,reducing the energy contribution to the acoustic system.With the volume increasing,the acoustic energy capacity increases.展开更多
Rechargeable magnesium batteries(RMBs)are a cutting-edge energy storage solution,with several advantages over the state-of-art lithiumion batteries(LIBs).The use of magnesium(Mg)metal as an anode material provides a m...Rechargeable magnesium batteries(RMBs)are a cutting-edge energy storage solution,with several advantages over the state-of-art lithiumion batteries(LIBs).The use of magnesium(Mg)metal as an anode material provides a much higher gravimetric capacity compared to graphite,which is currently used as the anode material in LIBs.Despite the significant advances in electrolyte,the development of cathode material is limited to materials that operate at low average discharge voltage(<1.0 V vs.Mg/Mg^(2+)),and developing high voltage cathodes remains challenging.Only a few materials have been shown to intercalate Mg^(2+)ions reversibly at high voltage.This review focuses on the structural aspects of cathode material that can operate at high voltage,including the Mg^(2+)intercalation mechanism in relation to its electrochemical properties.The materials are categorized into transition metal oxides and polyanions and subcategorized by the intrinsic Mg^(2+)diffusion path.This review also provides insights into the future development of each material,aiming to stimulate and guide researchers working in this field towards further advancements in high voltage cathodes.展开更多
Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dep...Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dependent syntactic trees, which improves the classification performance of the models to some extent. However, the technical limitations of dependent syntactic trees can introduce considerable noise into the model. Meanwhile, it is difficult for a single graph convolutional network to aggregate both semantic and syntactic structural information of nodes, which affects the final sentence classification. To cope with the above problems, this paper proposes a bi-channel graph convolutional network model. The model introduces a phrase structure tree and transforms it into a hierarchical phrase matrix. The adjacency matrix of the dependent syntactic tree and the hierarchical phrase matrix are combined as the initial matrix of the graph convolutional network to enhance the syntactic information. The semantic information feature representations of the sentences are obtained by the graph convolutional network with a multi-head attention mechanism and fused to achieve complementary learning of dual-channel features. Experimental results show that the model performs well and improves the accuracy of sentiment classification on three public benchmark datasets, namely Rest14, Lap14 and Twitter.展开更多
High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effect...High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques.This study proposes a novel cutting-based process,namely elliptical vibration chiseling(EV-chiseling),for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio.Unlike conventional cutting,EV-chiseling superimposes a microscale EV on a backward-moving tool.The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation.Thanks to the tool’s backward movement,the chip is left on the material surface to form a microstructure rather than falling off.Since one microstructure is generated in one vibration cycle,the process can be highly efficient using ultrafast(>1 kHz)tool vibration.A finite element analysis model is established to explore the process mechanics of EV-chiseling.Next,a mechanistic model of the microstructured surface generation is developed to describe the microstructures’aspect ratio dependency on the process parameters.Then,surface texturing tests are performed on copper to verify the efficacy of EV-chiseling.Uniformed micro ribs with a spacing of 1–10μm and an aspect ratio of 2–5 have been successfully textured on copper.Compared with the conventional EV-cutting that uses a forward-moving tool,EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times.The experimental results also verify the accuracy of the developed surface generation model of microstructures.Finally,the effects of elliptical trajectory,depth of cut,tool shape,and tool edge radius on the surface generation of micro ribs have been discussed.展开更多
To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, is...To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, isothermal compression experiments were performed under the deformation temperature range from 1073 to 1473 K, the reduction rates from 25% to 75% and the strain rates from 0.01 to 10 s^(−1). The variations of deformability features (i.e., aspect ratios, size distributions, and morphologies) of MnS inclusions with those isothermal compression parameters were revealed. The evaluation of the probable maximum aspect ratio of MnS inclusions at the three different positions in the cross-section of the billet after hot rolling was examined using the statistical analysis of extreme values. Results showed that the number densities of MnS inclusions at three different positions (edge, 1/2 radius and center) in the cross-section of the steel billet only fluctuated slightly when the deformation parameters varied in the isothermal compression, while the average inclusion aspect ratios in all cases generally have a negative correlation with the deformation temperature and positive correlations with the reduction ratio and the strain rate. Statistical analysis reveals that larger inclusions deform more easily during hot rolling. The effect of rolling temperature on the extreme value of the aspect ratio of inclusions is the smallest, while the effects of initial size, reduction ratio and strain rate are more significant.展开更多
This study aims to determine the environmental aspects and impacts of the phase relating to the operation of Manantali’s hydroelectric structures and facilities according to the requirements of the ISO 14001 version ...This study aims to determine the environmental aspects and impacts of the phase relating to the operation of Manantali’s hydroelectric structures and facilities according to the requirements of the ISO 14001 version 2015 standard. To do this, the mapping of the different work areas made it possible to identify all the activities within the framework of the farm. Based on the mapping, environmental measurements made including noise level, brightness, electric and magnetic fields, total particles, PM10, PM2.5, PM1 showed the work areas with the exposure limit values exceeded. The inventories of the waste produced show eighteen (18) types of waste, 67% of which are special industrial waste (SIW), 28% are ordinary industrial waste (OIW) and 5% are inert industrial waste (IIW). The identification and assessment of environmental aspects and impacts made it possible to determine sixteen (16) positive and negative significant environmental aspects (ESAs). The positive AES must be maintained, and for the negative ones, mitigation and mitigation measures must be put in place in order to manage them effectively. This will ultimately improve environmental management in the operation of hydroelectric structures and facilities.展开更多
Objective: Describe the psychosocial aspects of male infertility at the hospital of the Sino-Guinean Friendship. Patients and method: It is a prospective study of a descriptive type covering a period of 6 months. The ...Objective: Describe the psychosocial aspects of male infertility at the hospital of the Sino-Guinean Friendship. Patients and method: It is a prospective study of a descriptive type covering a period of 6 months. The study covered 17 patients, all received for a desire to conceive after at least one year of regular sexual intercourse without contraception. The data were collected from patient interviews using a pre-established questionnaire. Results: The average age of the patients was 32.07 years with extremes of 23 years and 42 years. During this study, 64.70% of patients were no longer participating in community ceremonies. The patients’ relationships with their spouse and family deteriorated in 52.94% and 47.06%, respectively. Conversely, relations with the family of origin remained unchanged in 70.59 percent of cases. The reduction in economic activity was by 13 patients (76.48%). Conclusion: Male infertility causes a real psychic earthquake in men with its corollaries of negative feelings. The rather complex moral repercussions of male infertility affect not only the individual, his/her partner, and family, but also economic activity.展开更多
Introduction: Sickle cell disease is the most widespread genetic disorder in the world. This study aimed to investigate the epidemiological, clinical, biological, and therapeutic aspects of sickle cell anemia in Marad...Introduction: Sickle cell disease is the most widespread genetic disorder in the world. This study aimed to investigate the epidemiological, clinical, biological, and therapeutic aspects of sickle cell anemia in Maradi, Niger. Methodology: This was a retrospective descriptive study carried out at the Centre Hospitalier Régional (CHR) of Maradi over 12 months, from September 2021 to August 2022. Results: This study included 246 patients with sickle cell anemia. The average age was 7.9 years, ranging from 0 to 16 years, and a sex ratio of 1.2. We observed kinship in 54.9% of the parents of sickle cell patients. Among the fathers, 62.6% were primarily blue-collar workers, while 87.4% of the mothers were housewives. Clinically, we observed pallor in 78.5% of the patients, jaundice in 43.5%, splenomegaly in 12.6%, and hepatomegaly in 11.8%. The most common vaso-occlusive crises involved osteoarticular pain (34.6%), followed by hand-foot syndrome (26.4%) and abdominal pain (20.3%). The SS form predominated biologically, representing 93.5% of cases, while double heterozygotes SC represented 6.5%. Most patients (56.5%) presented with severe anemia, with moderate anemia observed in 38.6% of cases. All patients received folic acid. Level I and II analgesics were used in 82.6% and 46.7% of patients, respectively, and patients received non-steroidal anti-inflammatory drugs in 72.3% of cases. A small proportion of patients (7.8%) were on background treatment with Hydrea. Conclusion: The results of our study are similar to those often described in sickle cell anemia.展开更多
The aspect ratio of the structure has a significant impact on the overall stability of the ultra high-rise building. A large aspect ratio of the structure increases the risk of overturning and reduces the lateral stif...The aspect ratio of the structure has a significant impact on the overall stability of the ultra high-rise building. A large aspect ratio of the structure increases the risk of overturning and reduces the lateral stiffness of the structure, leading to significant tensile and compressive stresses in the isolated bearings. To study the effect of aspect ratio on the seismic response and overturning resistance of a new staggered story isolated structure, three models with different aspect ratios were established. Nonlinear time-history analysis of the three models was conducted using ETABS finite element software. The results indicate that the overturning moment and overturning resistance moment of the superstructure in the new staggered story isolated structure increase with an increasing aspect ratio. However, the increase in the overturning moment of the superstructure is much greater than the increase in the overturning resistance moment, resulting in a decrease in the overturning resistance ratio of the superstructure with an increasing aspect ratio. The overturning moment and overturning resistance moment of the substructure in the new staggered story isolated structure decrease with an increasing aspect ratio. However, the decrease in the overturning moment of the substructure is greater than the decrease in the overturning resistance moment, leading to an increase in the overturning resistance ratio of the substructure with an increasing aspect ratio. The decrease in the overturning resistance ratio of the superstructure in the new staggered story isolated structure is much greater than the increase in the overturning resistance ratio of the substructure. Therefore, as the aspect ratio of the overall structure increases, the overturning resistance ratio of the superstructure and the entire structure decreases.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12202294 and 12022208)the Project funded by China Postdoctoral Science Foundation (Grant No.2022M712243)the Fundamental Research Funds for the Central Universities (Grant No.2023SCU12098).
文摘It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.
文摘Driver distraction is a leading cause of traffic accidents,with fatigue being a significant contributor.This paper introduces a novel method for detecting driver distraction by analyzing facial features using machine deep learning and 68 face model.The proposed system assesses driver tiredness by measuring the distance between key facial landmarks,such as the distance between the eyes and the angle of the mouth,to evaluate signs of drowsiness or disengagement.Real-time video feed analysis allows for continuous monitoring of the driver’s face,enabling the system to detect behavioral cues associated with distraction,such as eye closures or changes in facial expressions.The effectiveness of this method is demonstrated through a series of experiments on a dataset of driver videos,which proves that the approach can accurately assess tiredness and distraction levels under various driving conditions.By focusing on facial landmarks,the system is computationally efficient and capable of operating in real-time,making it a practical solution for in-vehicle safety systems.This paper discusses the system’s performance,limitations,and potential for future enhancements,including integration with other in-vehicle technologies to provide comprehensive driver monitoring.
文摘One of the main causes of cancer-related morbidity and mortality globally is hepatocellular carcinoma(HCC).At every stage of the disease,HCC may now be treated using a variety of therapy techniques.Nevertheless,despite the abundance of effective therapeutic choices,the prognosis for patients with HCC is still typically dismal.Prognostic indicators are crucial when assessing prognosis and tracking tumor metastases or recurrence.There are many prognostic markers in HCC.We mainly focused on newly reported prognostic markers such as MEX3A,apolipoprotein B,alpha-fetoprotein,circulating tumor cells,SAMD13,Agrin,and Glypican-3 in the pathogenesis of HCC.Further,we highlighted how these prognostic markers correlated to clinical parameters such as tumor node metastasis,tumor diameter,differentiation,hepatocirrhosis,vascular invasion,and others in HCC.Therefore,identifying specific prognostic biomarkers of HCC helps to provide a great opportunity to improve the prognosis in patients with HCC and provide therapeutic targets.
文摘Flow characteristics around a wall-mounted square cylinder have been numerically simulated at aspect ratios (AR) ranging from 4 to 7 at Re =10 000. Four turbulence models have been compared in terms of drag coefficient (C_D). The closest result has been provided by two turbulence models, namely, k-ε Realizable and k ?ω Shear Stress Transport (SST). Hence, these models were utilized to present the flow patterns of pressure distributions, turbulent kinetic energy values, velocity magnitude values with streamlines, streamwise velocity components, crossstream velocity components and spanwise velocity components on different planes. Flow stagnation has been attained in front of the cylinder. Pressure values peaked for the upstream region. Over the cylinders, the tip vortex structure was dominant owing to the influence of the free end. Flow separation from the top front edge of the body has been obtained. The dividing streamline affected by the flow separation was highly effective in the wake region and moved nearer to the body when the aspect ratio was decreased;the reason was the wake shrinkage owing to the decreasing aspect ratio. Upwash and downwash have been seen in the cylinder wake. These two models presented similar flow patterns and drag coefficients. These drag coefficients are in good agreement with those in previous studies.
基金funded by the National Natural Science Foundation of China(Grant No.52108435)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202404320)+1 种基金Chongqing Jiaotong University Postgraduate Research and Innovation Project(2024S0013)Chongqing Jiaotong University Undergraduate Innovation and Entrepreneurship Project(S202410618019).
文摘Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.
基金supported by the Natural Science Foundation of Hunan Province of China(No.2023JJ40672)the Innovation Science Fund Project of National University of Defense Technology,China(No.ZK2023-039)。
文摘A two-dimensional large eddy simulation numerical model is proposed to study the transient vortex flow and pressure oscillation of a large-aspect-ratio solid rocket motor.The numerical model is validated through experimental data,finite element analysis and cumulative error analysis.The numerical simulations are executed to obtain the characteristics of the vortex-acoustic and pressure oscillation.The results show that the burning surface regression decreases the motor aspect ratio,increasing the corresponding natural frequency from 260 Hz to 293 Hz.The pressure oscillation phenomenon is formed due to the vortex-acoustic coupling.Decreasing the corner vortex shedding intensity shows negative effects on the dimensionless amplitude of the pressure oscillation.The head cavity without the injection can decrease the vortex-acoustic coupling level at the acoustic pressure antinode.The modified motor with head cavity can obtain a lower dimensionless oscillating pressure amplitude 0.00149 in comparison with 0.00895 of the original motor.The aspect ratio and volume of the head cavity without the injection have great effects on the pressure oscillation suppression,particularly at the low aspect ratio or large volume.The reason is that the mass in the region around the acoustic pressure antinode is extracted centrally,reducing the energy contribution to the acoustic system.With the volume increasing,the acoustic energy capacity increases.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS-2024-00446825)by the Technology Innovation Program(RS-2024-00418815)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘Rechargeable magnesium batteries(RMBs)are a cutting-edge energy storage solution,with several advantages over the state-of-art lithiumion batteries(LIBs).The use of magnesium(Mg)metal as an anode material provides a much higher gravimetric capacity compared to graphite,which is currently used as the anode material in LIBs.Despite the significant advances in electrolyte,the development of cathode material is limited to materials that operate at low average discharge voltage(<1.0 V vs.Mg/Mg^(2+)),and developing high voltage cathodes remains challenging.Only a few materials have been shown to intercalate Mg^(2+)ions reversibly at high voltage.This review focuses on the structural aspects of cathode material that can operate at high voltage,including the Mg^(2+)intercalation mechanism in relation to its electrochemical properties.The materials are categorized into transition metal oxides and polyanions and subcategorized by the intrinsic Mg^(2+)diffusion path.This review also provides insights into the future development of each material,aiming to stimulate and guide researchers working in this field towards further advancements in high voltage cathodes.
文摘Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dependent syntactic trees, which improves the classification performance of the models to some extent. However, the technical limitations of dependent syntactic trees can introduce considerable noise into the model. Meanwhile, it is difficult for a single graph convolutional network to aggregate both semantic and syntactic structural information of nodes, which affects the final sentence classification. To cope with the above problems, this paper proposes a bi-channel graph convolutional network model. The model introduces a phrase structure tree and transforms it into a hierarchical phrase matrix. The adjacency matrix of the dependent syntactic tree and the hierarchical phrase matrix are combined as the initial matrix of the graph convolutional network to enhance the syntactic information. The semantic information feature representations of the sentences are obtained by the graph convolutional network with a multi-head attention mechanism and fused to achieve complementary learning of dual-channel features. Experimental results show that the model performs well and improves the accuracy of sentiment classification on three public benchmark datasets, namely Rest14, Lap14 and Twitter.
基金support for this research provided by the National Natural Science Foundation of China(Grant No.52105458)Beijing Natural Science Foundation(Grant No.3222009)+1 种基金Huaneng Group Science and Technology Research Project(No:HNKJ22-H105)China Postdoctoral Science Foundation(Grant No.2022M711807)。
文摘High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques.This study proposes a novel cutting-based process,namely elliptical vibration chiseling(EV-chiseling),for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio.Unlike conventional cutting,EV-chiseling superimposes a microscale EV on a backward-moving tool.The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation.Thanks to the tool’s backward movement,the chip is left on the material surface to form a microstructure rather than falling off.Since one microstructure is generated in one vibration cycle,the process can be highly efficient using ultrafast(>1 kHz)tool vibration.A finite element analysis model is established to explore the process mechanics of EV-chiseling.Next,a mechanistic model of the microstructured surface generation is developed to describe the microstructures’aspect ratio dependency on the process parameters.Then,surface texturing tests are performed on copper to verify the efficacy of EV-chiseling.Uniformed micro ribs with a spacing of 1–10μm and an aspect ratio of 2–5 have been successfully textured on copper.Compared with the conventional EV-cutting that uses a forward-moving tool,EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times.The experimental results also verify the accuracy of the developed surface generation model of microstructures.Finally,the effects of elliptical trajectory,depth of cut,tool shape,and tool edge radius on the surface generation of micro ribs have been discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.52074198,52374342 and U21A20113)also supported by the Department of Science and Technology of Hubei Province(Grant No.2023AFB603 and No.2023DJC140).
文摘To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, isothermal compression experiments were performed under the deformation temperature range from 1073 to 1473 K, the reduction rates from 25% to 75% and the strain rates from 0.01 to 10 s^(−1). The variations of deformability features (i.e., aspect ratios, size distributions, and morphologies) of MnS inclusions with those isothermal compression parameters were revealed. The evaluation of the probable maximum aspect ratio of MnS inclusions at the three different positions in the cross-section of the billet after hot rolling was examined using the statistical analysis of extreme values. Results showed that the number densities of MnS inclusions at three different positions (edge, 1/2 radius and center) in the cross-section of the steel billet only fluctuated slightly when the deformation parameters varied in the isothermal compression, while the average inclusion aspect ratios in all cases generally have a negative correlation with the deformation temperature and positive correlations with the reduction ratio and the strain rate. Statistical analysis reveals that larger inclusions deform more easily during hot rolling. The effect of rolling temperature on the extreme value of the aspect ratio of inclusions is the smallest, while the effects of initial size, reduction ratio and strain rate are more significant.
文摘This study aims to determine the environmental aspects and impacts of the phase relating to the operation of Manantali’s hydroelectric structures and facilities according to the requirements of the ISO 14001 version 2015 standard. To do this, the mapping of the different work areas made it possible to identify all the activities within the framework of the farm. Based on the mapping, environmental measurements made including noise level, brightness, electric and magnetic fields, total particles, PM10, PM2.5, PM1 showed the work areas with the exposure limit values exceeded. The inventories of the waste produced show eighteen (18) types of waste, 67% of which are special industrial waste (SIW), 28% are ordinary industrial waste (OIW) and 5% are inert industrial waste (IIW). The identification and assessment of environmental aspects and impacts made it possible to determine sixteen (16) positive and negative significant environmental aspects (ESAs). The positive AES must be maintained, and for the negative ones, mitigation and mitigation measures must be put in place in order to manage them effectively. This will ultimately improve environmental management in the operation of hydroelectric structures and facilities.
文摘Objective: Describe the psychosocial aspects of male infertility at the hospital of the Sino-Guinean Friendship. Patients and method: It is a prospective study of a descriptive type covering a period of 6 months. The study covered 17 patients, all received for a desire to conceive after at least one year of regular sexual intercourse without contraception. The data were collected from patient interviews using a pre-established questionnaire. Results: The average age of the patients was 32.07 years with extremes of 23 years and 42 years. During this study, 64.70% of patients were no longer participating in community ceremonies. The patients’ relationships with their spouse and family deteriorated in 52.94% and 47.06%, respectively. Conversely, relations with the family of origin remained unchanged in 70.59 percent of cases. The reduction in economic activity was by 13 patients (76.48%). Conclusion: Male infertility causes a real psychic earthquake in men with its corollaries of negative feelings. The rather complex moral repercussions of male infertility affect not only the individual, his/her partner, and family, but also economic activity.
文摘Introduction: Sickle cell disease is the most widespread genetic disorder in the world. This study aimed to investigate the epidemiological, clinical, biological, and therapeutic aspects of sickle cell anemia in Maradi, Niger. Methodology: This was a retrospective descriptive study carried out at the Centre Hospitalier Régional (CHR) of Maradi over 12 months, from September 2021 to August 2022. Results: This study included 246 patients with sickle cell anemia. The average age was 7.9 years, ranging from 0 to 16 years, and a sex ratio of 1.2. We observed kinship in 54.9% of the parents of sickle cell patients. Among the fathers, 62.6% were primarily blue-collar workers, while 87.4% of the mothers were housewives. Clinically, we observed pallor in 78.5% of the patients, jaundice in 43.5%, splenomegaly in 12.6%, and hepatomegaly in 11.8%. The most common vaso-occlusive crises involved osteoarticular pain (34.6%), followed by hand-foot syndrome (26.4%) and abdominal pain (20.3%). The SS form predominated biologically, representing 93.5% of cases, while double heterozygotes SC represented 6.5%. Most patients (56.5%) presented with severe anemia, with moderate anemia observed in 38.6% of cases. All patients received folic acid. Level I and II analgesics were used in 82.6% and 46.7% of patients, respectively, and patients received non-steroidal anti-inflammatory drugs in 72.3% of cases. A small proportion of patients (7.8%) were on background treatment with Hydrea. Conclusion: The results of our study are similar to those often described in sickle cell anemia.
文摘The aspect ratio of the structure has a significant impact on the overall stability of the ultra high-rise building. A large aspect ratio of the structure increases the risk of overturning and reduces the lateral stiffness of the structure, leading to significant tensile and compressive stresses in the isolated bearings. To study the effect of aspect ratio on the seismic response and overturning resistance of a new staggered story isolated structure, three models with different aspect ratios were established. Nonlinear time-history analysis of the three models was conducted using ETABS finite element software. The results indicate that the overturning moment and overturning resistance moment of the superstructure in the new staggered story isolated structure increase with an increasing aspect ratio. However, the increase in the overturning moment of the superstructure is much greater than the increase in the overturning resistance moment, resulting in a decrease in the overturning resistance ratio of the superstructure with an increasing aspect ratio. The overturning moment and overturning resistance moment of the substructure in the new staggered story isolated structure decrease with an increasing aspect ratio. However, the decrease in the overturning moment of the substructure is greater than the decrease in the overturning resistance moment, leading to an increase in the overturning resistance ratio of the substructure with an increasing aspect ratio. The decrease in the overturning resistance ratio of the superstructure in the new staggered story isolated structure is much greater than the increase in the overturning resistance ratio of the substructure. Therefore, as the aspect ratio of the overall structure increases, the overturning resistance ratio of the superstructure and the entire structure decreases.
