Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehens...Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehensive review of commonly employed coalbed methane extraction technologies.It then delves into several critical issues in the current stage of CBM exploration and development in China,including the compatibility of existing technologies with CBM reservoirs,the characteristics and occurrence states of CBM reservoirs,critical desorption pressure,and gas generation mechanisms.Our research indicates that current CBM exploration and development technologies in China have reached an internationally advanced level,yet the industry is facing unprecedented challenges.Despite progress in low-permeability,high-value coal seams,significant breakthroughs have not been achieved in exploring other types of coal seams.For different coal reservoirs,integrated extraction technologies have been developed,such as surface pre-depressurisation and segmented hydraulic fracturing of coal seam roof strata.Additionally,techniques like large-scale volume fracturing in horizontal wells have been established,significantly enhancing reservoir stimulation effects and coalbed methane recovery rates.However,all of these technologies are fundamentally based on permeation.These technologies lack direct methods aimed at enhancing the diffusion rate of CBM,thereby failing to fully reflect the unique characteristics of CBM.Current CBM exploration and development theories and technologies are not universally applicable to all coal seams.They do not adequately account for the predominantly adsorbed state of CBM,and the complex and variable gas generation mechanisms further constrain CBM development in China.Finally,continuous exploration of new deep CBM exploration technologies is necessary.Integrating more effective reservoir stimulation technologies is essential to enhance technical adaptability concerning CBM reservoir characteristics,gas occurrence states,and gas generation mechanisms,ultimately achieving efficient CBM development.We conclude that while China possesses a substantial foundation of deep fractured CBM resources,industry development is constrained and requires continuous exploration of new CBM exploration and development technologies to utilize these resources effectively.展开更多
Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-ba...Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-based solid waste expanding agent.First,the mechanism of directional fracturing blasting by the IESF was analyzed,and the criterion of directional crack initiation was established.On this basis,laboratory experiments and numerical simulations were conducted to systematically evaluate the directional fracturing blasting performance of the IESF.The results indicate that the IESF presents an excellent directional fracturing effect,with average surface undulation differences ranging from 8.1 mm to 22.7 mm on the fracture surfaces.Moreover,during concrete fracturing tests,the stresses and strains in the fracturing direction are measured to be 2.16-3.71 times and 8 times larger than those in the nonfracturing direction,respectively.Finally,the IESF technique was implemented for no-pillar mining with gob-side entry retaining through roof cutting and pressure relief in an underground coal mine.The IESF technique effectively created directional cracks in the roof without causing severe roadway deformation,achieving an average cutting rate and maximum roadway deformation of 94%and 197 mm,respectively.These on-site test results verified its excellent directional rock fracturing performance.The IESF technique,which is safe,efficient,and green,has considerable application prospects in the field of rock mechanics and engineering.展开更多
Professor Paul Crosthwaite,from the School of Literature,Languages,and Cultures at the University of Edinburgh,is a prominent scholar in the interdisciplinary field of literature and economics.He is a co-editor of the...Professor Paul Crosthwaite,from the School of Literature,Languages,and Cultures at the University of Edinburgh,is a prominent scholar in the interdisciplinary field of literature and economics.He is a co-editor of the Palgrave Studies in Literature,Culture,and Economics series and The Cambridge Companion to Literature and Economics(2022).In recent years,he has significantly influenced the intersection of literature and economics,advocating particularly for a shift towards the Economic Humanities.This interview covers:1.The definition and theoretical origin of the Economic Humanities;2.The internal heterogeneity and critical limitations of the New Economic Criticism,and the theoretical advantages and potential development of the Economic Humanities;3.What research paradigms do Environmental Humanities,Medical Humanities,and Digital Humanities provide for the Economic Humanities;4.How literary researchers can work at the interface of the Economic Humanities research.As a novel interdisciplinary interface between literature and economics,Professor Paul Crosthwaite’s concept of the Economic Humanities not only pioneers methodological tools for interdisciplinary studies of literature and economics but also underscores the interpretative potential and disciplinary benefits of literary viewpoints on economics.This underscores the vital role of literature in human knowledge,meriting attention from the literary research academia.展开更多
According to the measurement principle of the traditional interferometer,a narrowband signal model is established and used,however,for wideband signals or multiple signals,this model is invalid.For the problems of dir...According to the measurement principle of the traditional interferometer,a narrowband signal model is established and used,however,for wideband signals or multiple signals,this model is invalid.For the problems of direction finding with interferometer for wideband signals and multiple signals scene,a frequency domain phase interferometer is proposed and the concrete implementation scheme is given.The proposed method computes the phase difference in frequency domain,and finds multi-target results with judging the spectrum amplitude changing,and uses the frequency phase difference to compute the arrival angle.Theoretical analysis and simulation results show that the proposed method effectively solves the problem of the angle estimation with phase interferometer for wideband signals,and has good performance in multiple signals scene with nonoverlapping spectrum or partially overlapping.In addition,the wider the signal bandwidth,the better direction finding performance of this algorithm.展开更多
Interval-valued pre-aggregation functions are a hot topic in the research of aggregation functions and have received considerable attention in recent years.As a special class of interval-valued pre-aggregation functio...Interval-valued pre-aggregation functions are a hot topic in the research of aggregation functions and have received considerable attention in recent years.As a special class of interval-valued pre-aggregation functions,(light)interval-valued pre-t-norms were initially proposed by Wang and Hu,but their properties were not further discussed by the authors.The main purpose of this paper is to study in depth the properties and generation of(light)intervalvalued pre-t-norms.Firstly,several properties of(light)interval-valued pre-t-norms and their relationship with(light)pre-t-norms are presented.Then,two different generation methods for(light)interval-valued pre-t-norms are introduced.Finally,it demonstrates a specific application of(light)interval-valued pre-t-norms in constructing interval-valued directional monotonic fuzzy implications,namely,using the(light)interval-valued pre-t-norm IT,interval-valued fuzzy negations IN,and(light)interval-valued pre-t-conorm IS to construct interval-valued QL-directional monotonic operations.展开更多
Columnar grains offer considerable advantages in terms of microstructure for resisting high-temperature low-cycle fatigue. In additive manufacturing, the formation of fine columnar grains is common. However, post-heat...Columnar grains offer considerable advantages in terms of microstructure for resisting high-temperature low-cycle fatigue. In additive manufacturing, the formation of fine columnar grains is common. However, post-heat treatment often transforms these grains into equiaxed grains. This study aimed to tailor the grain morphology by controlling the precipitation of carbides. By balancing the restraining effects of carbide pinning and grain growth, we achieved carbide-assisted in situ-directional recrystallization. This process preserved the columnar grains created via laser powder bed fusion, even after high-temperature heat treatment. The approach emphasizes promoting the longitudinal growth of columnar grains while preventing their broadening. Additionally, we characterized the evolution of carbides and γ′ precipitates and examined their role in nucleation and growth during recrystallization. This study supports the viability of carbide-assisted in situ-directional recrystallization in additive manufacturing alloys, introducing an innovative strategy for microstructure customization. The implementation of carbon stabilization (CS) treatment to control the carbide distribution led to a 40 % improvement in the creep life at 900 ℃ and 150 MPa.展开更多
Mental healthcare in Ethiopia is underutilized due to a lack of resources and skilled practitioners.Psychological counselling offers unique intervention possibilities because of its focus on a wide range of mental hea...Mental healthcare in Ethiopia is underutilized due to a lack of resources and skilled practitioners.Psychological counselling offers unique intervention possibilities because of its focus on a wide range of mental health and social justice issues.This literature review tracks the historical development of the profession of psychological counselling in Ethiopia to establish what has been achieved to date and the development challenges.Key achievements include recognition of the profession by the Ministry of Education,growing public awareness,and increasing capacity of practitioners skilled in psychological counselling.Challenges include limited contextually relevant training,poor representation of the profession within Ministry of Health policies,poor public and government mental health literacy,and a lack of regulatory frameworks.Postgraduate training would benefit from more culturally,contextually,and linguistically appropriate evidence-based,indigenous psychology practices.The profession would benefit from engagement in government policy development that promotes mental health,and professional regulatory bodies to hold practitioners accountable to professional standards and ethical practice.展开更多
Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small targe...Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small target detection method based on the tensor nuclear norm and direction residual weighting was proposed.Based on converting the infrared image into an infrared patch tensor model,from the perspective of the low-rank nature of the background tensor,and taking advantage of the difference in contrast between the background and the target in different directions,we designed a double-neighborhood local contrast based on direction residual weighting method(DNLCDRW)combined with the partial sum of tensor nuclear norm(PSTNN)to achieve effective background suppression and recovery of infrared small targets.Experiments show that the algorithm is effective in suppressing the background and improving the detection ability of the target.展开更多
Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity forma...Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys,considering variations in Cu content and solidification rate.The results indicate that the Cu content primarily influences the growth of microporosity.To validate the model,directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal rates.The experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model,thus confirming the validity of the model.The alloy’s liquidus temperature,dendrite morphology,and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity morphology.The withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates,resulting in different microporosity characteristics.展开更多
In this paper, the problem of pre-specified performance fault-tolerant cluster consensus control and fault direction identification is solved for the human-in-the-loop(HIL) swarm unmanned aerial vehicles(UAVs) in the ...In this paper, the problem of pre-specified performance fault-tolerant cluster consensus control and fault direction identification is solved for the human-in-the-loop(HIL) swarm unmanned aerial vehicles(UAVs) in the presence of possible nonidentical and unknown direction faults(NUDFs) in the yaw channel.The control strategy begins with the design of a pre-specified performance event-triggered observer for each individual UAV.These observers estimate the outputs of the human controlled UAVs, and simultaneously achieve the distributed design of actual control signals as well as cluster consensus of the observer output.It is worth mentioning that these observers require neither the high-order derivatives of the human controlled UAVs' output nor a priori knowledge of the initial conditions. The fault-tolerant controller realizes the pre-specified performance output regulation through error transformation and the Nussbaum function. It should be pointed out that there are no chattering caused by the jump of the Nussbaum function when a reverse fault occurs. In addition, to provide a basis for further solving the problem of physical malfunctions, a fault direction identification algorithm is proposed to accurately identify whether a reverse fault has occurred. Simulation results verify the effectiveness of the proposed control and fault direction identification strategies when the reverse faults occur.展开更多
In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ra...In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ratios(λ)were prepared using pulsed electrodeposition in this paper and unidirectional tensile experiments were carried out at room temperature with different currents and their applied directions.The experimental results show that the nanocrystalline Ni foil produces an obvious electroplasticity effect after applying the current field,and when 300<λ<1100,the current weakens the size effect of nanocrystalline Ni foils to a certain extent,and the angle between the current direction and the deformation direction also affects the mechanical response of nanocrystalline Ni foils,and when the angle between the current direction and the deformation direction is 0°,electroplasticity effect is the best,and the current has the most significant effect of abating the size effect of the material.The mechanism of unidirectional tensile deformation of nanocrystalline Ni foils under the effect of pulsed current was analyzed using TEM and TKD.It was found that the applied pulse current increased the activity of the nanocrystalline boundaries,promoted the movement of dislocations,and reduced the tendency of dislocation entanglement.The higher the peak current density and the smaller the angle between the direction of the current and the direction of deformation,the smaller the grain boundary orientation difference,the more dispersed the grain orientation,and the lower the density of geometrically necessary dislocations(GND)in the deformed nanocrystalline foil,the more significant the effect on material plasticity improvement.展开更多
Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single...Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single-crystal(SC) superalloys, with limited research on its influence on the high-temperature mechanical properties of DS superalloys. This study systematically investigated the effect of RX on the high-temperature tensile properties of a DS DZ409 superalloy. The results show that at 650℃, the yield strength decreases almost linearly with an increase in RX fraction. A significant reduction in elongation is observed as the RX fraction increases from 0% to 4.9%. However, beyond this point, further increase in RX fraction leads to minimal changes in elongation. At 950℃, both yield strength and elongation decrease as the RX fraction increases from 0% to 4.9%. At 650℃, fractures in the RX DS superalloys exhibit a mixed mode of transgranular and intergranular cleavage fracture, while at 950℃, it features a combination of ductile and intergranular dimple fractures. The failure mechanism of the RX DS superalloy is associated with the introduction of transverse grain boundaries(GBs) during RX. In the early stages of tensile testing at intermediate and high temperatures, cracks can easily initiate at these GBs. Subsequently, the cracks propagate along the GBs into the DS matrix, ultimately leading to failure of the DS superalloy.展开更多
We proposed a new technique route of directional solidification for the manufacture of super slab.A 7-t laboratory-scale thick slab was casted and characterised for trial.To further understand the process,the evolutio...We proposed a new technique route of directional solidification for the manufacture of super slab.A 7-t laboratory-scale thick slab was casted and characterised for trial.To further understand the process,the evolution of the multiple physical fields during the directional solidification was simulated and verified.Similar to the convectional ingot casting,a negative segregated cone of equiaxed grains was formed at the bottom,and a seriously positive segregated region was formed beneath the top surface of the slab.Specific measures on the lateral walls,base plate,and free surface were strongly recommended to ensure that the slab is relatively directionally casted.A water-cooling copper base plate accelerates the solidification rate and the columnar growth along the vertical direction.It inhibits the sedimentation of equiaxed grains and enlarges the columnar zone.Based on the simulation analysis,it can be concluded that the directional solidification technique route is promising to manufacture super slab with lower segregation level,and less porosities and inclusions.展开更多
The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidenc...The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.展开更多
The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient ...The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient to account for ozone transport at different altitudes.To further understand the characteristics of ozone transport,we applied theWeather Research and Forecasting(WRF)model and the Comprehensive Air Quality Model with Extensions(CAMx)based on flux calculation method.The results showed that the simulated flux calculation method was suitable for revealing the evolutionary trend of ozone fluxes.Monthly inflows,outflows,and total net fluxes ranged from-32985.45 to 37361.46 t/d and indicated strong transport and significant spatial and temporal variations of ozone in the urban boundary segments.Vertical distribution analysis of the net ozone fluxes demonstrated that the net fluxes varied with the altitude,and the altitude at which the corresponding peaks were located had a strong correlation with the neighborhood and season.It was noteworthy that there were three main transport directions throughout the year,namely northwest-southeast(NW-SE),southeast-northwest(SE-NW),and southwestnortheast(SW-NE).Additionally,the ozone flux was mainly affected by temperature,wind speed,and ozone concentration,with the correlation coefficient varying by season and altitude,up to 0.78.Moreover,the correlation analysis of ozone flux and wind direction in each city further verified the accuracy of the transport direction.This paper can provide scientific and technological support for the study of ozone generation mechanisms and the solution of urban/interregional ozone pollution problems.展开更多
Pneumatic down-the-hole hammer, serving as rock-breaking tool, possesses appeal for directional drilling due to its high rate of penetration. However, corresponding experimental studies on existing hammers for directi...Pneumatic down-the-hole hammer, serving as rock-breaking tool, possesses appeal for directional drilling due to its high rate of penetration. However, corresponding experimental studies on existing hammers for directional drilling have rarely been reported, and a model for evaluating their output performance is absent. This study proposes a novel structure of self-rotating pneumatic hammer(NSH)with a built-in rotational mechanism, which converts partial impact energy of the piston to rotate the drill bit and, consequently, enables dual functions of impact and rotate drill bit. The energy is converted via a screw key-groove mechanism, and the wedge-shaped teeth mechanism ensures that the drill bit rotates clockwise during the piston moves downward. The computational fluid dynamics method is applied to simulate the dynamic response of airflow and piston during the operation of Φ127NSH.Meanwhile, a test bench is established to record data concerning chamber pressure and piston displacement, as well as recording its operational status and rock fragmentation during drilling into granite. The results showed that the maximum error between simulated and experimental data is 8.2%.The Φ127NSH successfully achieves dual impact and rotary drilling functions, and granite smoothly feeds and forms a continuous shear rock zone. In addition, the effects of torque load, engagement distance in rotation sleeves, and well deviation angle towards the performance of NSH were studied in detail. The designed Φ127NSH operates at an impact velocity of 3.98 m/s, impact frequency of 12.55 Hz, and rotational speed of 29.51 r/min under a mass-flow rate of 0.18 kg/s, torque load of 400 N·m, engagement distance of 40 mm, and well deviation angle of 0°. The torque load adversely affects the NSH output performance. Increasing the engagement distance improves impact performance while reducing rotational performance. The performance variation of the NSH is minimal when drilling directional wells with varying deviation angles.展开更多
Let X be a real uniformly convex and uniformly smooth Banach space and C a nonempty closed and convex subset of X.Let Π_(C):X→C denote the generalized metric projection operator introduced by Alber in[1].In this pap...Let X be a real uniformly convex and uniformly smooth Banach space and C a nonempty closed and convex subset of X.Let Π_(C):X→C denote the generalized metric projection operator introduced by Alber in[1].In this paper,we define the Gâteaux directional differentiability of Π_(C).We investigate some properties of the Gâteaux directional differentiability of Π_(C).In particular,if C is a closed ball,or a closed and convex cone(including proper closed subspaces),or a closed and convex cylinder,then,we give the exact representations of the directional derivatives of Π_(C).By comparing the results in[12]and this paper,we see the significant difference between the directional derivatives of the generalized metric projection operator Π_(C) and the Gâteaux directional derivatives of the standard metric projection operator PC.展开更多
The convergence of materials science and biotechnology has catalyzed the development of innovative platforms,including nanotechnology,smart sensors,and supramolecular materials,significantly advancing the progress in ...The convergence of materials science and biotechnology has catalyzed the development of innovative platforms,including nanotechnology,smart sensors,and supramolecular materials,significantly advancing the progress in the field of life sciences[1−7].Among them,supramolecular materials have garnered increasing attention in life sciences owing to their distinctive self-assembly capabilities and intelligent responsiveness[8−12].展开更多
The directional annealing technique is widely used to prepare columnar grains or single crystals.To investigate the effect of hot zone temperature and temperature gradient on the growth of columnar crystals,Ti43Al all...The directional annealing technique is widely used to prepare columnar grains or single crystals.To investigate the effect of hot zone temperature and temperature gradient on the growth of columnar crystals,Ti43Al alloys were heat treated by the directional annealing technique and their mechanical properties were tested.The results show that columnar grains with a maximum size of 22.29 mm can be obtained at a hot zone temperature of 1,350℃ and a temperature gradient of 8 K·mm^(-1).During the directional annealing process,Ti43Al alloys are heated toαsingle-phase domain to start the phase transformation.Columnar grains with a microstructure of fully lamellar colonies are obtained at different hot zone temperatures and temperature gradients.The distribution of the orientation difference for theα2 phase was found to be more random,suggesting that the growth of the columnar crystals may be stochastic in nature.Tensile testing results show that the strength and elongation of directional annealed Ti43Al alloy at 1,400℃-8 K·mm^(-1) are 411.23 MPa and 2.29%,and the remaining directional annealed alloys show almost plasticity.展开更多
The publisher regrets that the article type for this publication was incorrectly labeled as a Research Article.The correct designation should be Review Article.This correction does not affect the content or conclusion...The publisher regrets that the article type for this publication was incorrectly labeled as a Research Article.The correct designation should be Review Article.This correction does not affect the content or conclusions of the article.The publisher apologizes for any inconvenience caused.展开更多
基金supported by the National Natural Science Foundation of China(52074045,52274074)the Science Fund for Distinguished Young Scholars of Chongqing(CSTB2022NSCQ-JQX0028).
文摘Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehensive review of commonly employed coalbed methane extraction technologies.It then delves into several critical issues in the current stage of CBM exploration and development in China,including the compatibility of existing technologies with CBM reservoirs,the characteristics and occurrence states of CBM reservoirs,critical desorption pressure,and gas generation mechanisms.Our research indicates that current CBM exploration and development technologies in China have reached an internationally advanced level,yet the industry is facing unprecedented challenges.Despite progress in low-permeability,high-value coal seams,significant breakthroughs have not been achieved in exploring other types of coal seams.For different coal reservoirs,integrated extraction technologies have been developed,such as surface pre-depressurisation and segmented hydraulic fracturing of coal seam roof strata.Additionally,techniques like large-scale volume fracturing in horizontal wells have been established,significantly enhancing reservoir stimulation effects and coalbed methane recovery rates.However,all of these technologies are fundamentally based on permeation.These technologies lack direct methods aimed at enhancing the diffusion rate of CBM,thereby failing to fully reflect the unique characteristics of CBM.Current CBM exploration and development theories and technologies are not universally applicable to all coal seams.They do not adequately account for the predominantly adsorbed state of CBM,and the complex and variable gas generation mechanisms further constrain CBM development in China.Finally,continuous exploration of new deep CBM exploration technologies is necessary.Integrating more effective reservoir stimulation technologies is essential to enhance technical adaptability concerning CBM reservoir characteristics,gas occurrence states,and gas generation mechanisms,ultimately achieving efficient CBM development.We conclude that while China possesses a substantial foundation of deep fractured CBM resources,industry development is constrained and requires continuous exploration of new CBM exploration and development technologies to utilize these resources effectively.
基金supported by the National Natural Science Foundation of China(Grant No.52404155)State Key Laboratory of Mining Disaster Prevention and Control(Shandong University of Science and Technology)+1 种基金Ministry of Education(Grant No.JMDPC202402)supported by the opening project of State Key Laboratory of Explosion Science and Safety Protection(Beijing Institute of Technology).The opening project number is KFJJ24-20M.
文摘Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-based solid waste expanding agent.First,the mechanism of directional fracturing blasting by the IESF was analyzed,and the criterion of directional crack initiation was established.On this basis,laboratory experiments and numerical simulations were conducted to systematically evaluate the directional fracturing blasting performance of the IESF.The results indicate that the IESF presents an excellent directional fracturing effect,with average surface undulation differences ranging from 8.1 mm to 22.7 mm on the fracture surfaces.Moreover,during concrete fracturing tests,the stresses and strains in the fracturing direction are measured to be 2.16-3.71 times and 8 times larger than those in the nonfracturing direction,respectively.Finally,the IESF technique was implemented for no-pillar mining with gob-side entry retaining through roof cutting and pressure relief in an underground coal mine.The IESF technique effectively created directional cracks in the roof without causing severe roadway deformation,achieving an average cutting rate and maximum roadway deformation of 94%and 197 mm,respectively.These on-site test results verified its excellent directional rock fracturing performance.The IESF technique,which is safe,efficient,and green,has considerable application prospects in the field of rock mechanics and engineering.
文摘Professor Paul Crosthwaite,from the School of Literature,Languages,and Cultures at the University of Edinburgh,is a prominent scholar in the interdisciplinary field of literature and economics.He is a co-editor of the Palgrave Studies in Literature,Culture,and Economics series and The Cambridge Companion to Literature and Economics(2022).In recent years,he has significantly influenced the intersection of literature and economics,advocating particularly for a shift towards the Economic Humanities.This interview covers:1.The definition and theoretical origin of the Economic Humanities;2.The internal heterogeneity and critical limitations of the New Economic Criticism,and the theoretical advantages and potential development of the Economic Humanities;3.What research paradigms do Environmental Humanities,Medical Humanities,and Digital Humanities provide for the Economic Humanities;4.How literary researchers can work at the interface of the Economic Humanities research.As a novel interdisciplinary interface between literature and economics,Professor Paul Crosthwaite’s concept of the Economic Humanities not only pioneers methodological tools for interdisciplinary studies of literature and economics but also underscores the interpretative potential and disciplinary benefits of literary viewpoints on economics.This underscores the vital role of literature in human knowledge,meriting attention from the literary research academia.
文摘According to the measurement principle of the traditional interferometer,a narrowband signal model is established and used,however,for wideband signals or multiple signals,this model is invalid.For the problems of direction finding with interferometer for wideband signals and multiple signals scene,a frequency domain phase interferometer is proposed and the concrete implementation scheme is given.The proposed method computes the phase difference in frequency domain,and finds multi-target results with judging the spectrum amplitude changing,and uses the frequency phase difference to compute the arrival angle.Theoretical analysis and simulation results show that the proposed method effectively solves the problem of the angle estimation with phase interferometer for wideband signals,and has good performance in multiple signals scene with nonoverlapping spectrum or partially overlapping.In addition,the wider the signal bandwidth,the better direction finding performance of this algorithm.
基金the National Natural Science Foundation of China(Grant No.12171294)。
文摘Interval-valued pre-aggregation functions are a hot topic in the research of aggregation functions and have received considerable attention in recent years.As a special class of interval-valued pre-aggregation functions,(light)interval-valued pre-t-norms were initially proposed by Wang and Hu,but their properties were not further discussed by the authors.The main purpose of this paper is to study in depth the properties and generation of(light)intervalvalued pre-t-norms.Firstly,several properties of(light)interval-valued pre-t-norms and their relationship with(light)pre-t-norms are presented.Then,two different generation methods for(light)interval-valued pre-t-norms are introduced.Finally,it demonstrates a specific application of(light)interval-valued pre-t-norms in constructing interval-valued directional monotonic fuzzy implications,namely,using the(light)interval-valued pre-t-norm IT,interval-valued fuzzy negations IN,and(light)interval-valued pre-t-conorm IS to construct interval-valued QL-directional monotonic operations.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0705300)the National Natural Science Foundation of China(Grant No.51974057)the Fundamental Research Funds for the Central Universities。
文摘Columnar grains offer considerable advantages in terms of microstructure for resisting high-temperature low-cycle fatigue. In additive manufacturing, the formation of fine columnar grains is common. However, post-heat treatment often transforms these grains into equiaxed grains. This study aimed to tailor the grain morphology by controlling the precipitation of carbides. By balancing the restraining effects of carbide pinning and grain growth, we achieved carbide-assisted in situ-directional recrystallization. This process preserved the columnar grains created via laser powder bed fusion, even after high-temperature heat treatment. The approach emphasizes promoting the longitudinal growth of columnar grains while preventing their broadening. Additionally, we characterized the evolution of carbides and γ′ precipitates and examined their role in nucleation and growth during recrystallization. This study supports the viability of carbide-assisted in situ-directional recrystallization in additive manufacturing alloys, introducing an innovative strategy for microstructure customization. The implementation of carbon stabilization (CS) treatment to control the carbide distribution led to a 40 % improvement in the creep life at 900 ℃ and 150 MPa.
文摘Mental healthcare in Ethiopia is underutilized due to a lack of resources and skilled practitioners.Psychological counselling offers unique intervention possibilities because of its focus on a wide range of mental health and social justice issues.This literature review tracks the historical development of the profession of psychological counselling in Ethiopia to establish what has been achieved to date and the development challenges.Key achievements include recognition of the profession by the Ministry of Education,growing public awareness,and increasing capacity of practitioners skilled in psychological counselling.Challenges include limited contextually relevant training,poor representation of the profession within Ministry of Health policies,poor public and government mental health literacy,and a lack of regulatory frameworks.Postgraduate training would benefit from more culturally,contextually,and linguistically appropriate evidence-based,indigenous psychology practices.The profession would benefit from engagement in government policy development that promotes mental health,and professional regulatory bodies to hold practitioners accountable to professional standards and ethical practice.
基金Supported by the Key Laboratory Fund for Equipment Pre-Research(6142207210202)。
文摘Aiming at the problem that infrared small target detection faces low contrast between the background and the target and insufficient noise suppression ability under the complex cloud background,an infrared small target detection method based on the tensor nuclear norm and direction residual weighting was proposed.Based on converting the infrared image into an infrared patch tensor model,from the perspective of the low-rank nature of the background tensor,and taking advantage of the difference in contrast between the background and the target in different directions,we designed a double-neighborhood local contrast based on direction residual weighting method(DNLCDRW)combined with the partial sum of tensor nuclear norm(PSTNN)to achieve effective background suppression and recovery of infrared small targets.Experiments show that the algorithm is effective in suppressing the background and improving the detection ability of the target.
基金financially supported by the National Natural Science Foundation of China(Grant No.51875211)the Beijing Natural Science Foundation(Grant No.L223001)。
文摘Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys,considering variations in Cu content and solidification rate.The results indicate that the Cu content primarily influences the growth of microporosity.To validate the model,directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal rates.The experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model,thus confirming the validity of the model.The alloy’s liquidus temperature,dendrite morphology,and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity morphology.The withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates,resulting in different microporosity characteristics.
基金supported in part by the National Natural Science Foundation of China(62173028,62233015,62173024)the Guangdong Basic and Applied Basic Research Foundation(2024A1515011493)+3 种基金the Science,Technology&Innovation Project of Xiongan New Area(2023XAGG0062)Beijing Natural Science Foundation(4232060)the International Scientists Project,Beijing Natural Science Foundation(IS23065)the Brazilian Research Council(303289/2022-8)
文摘In this paper, the problem of pre-specified performance fault-tolerant cluster consensus control and fault direction identification is solved for the human-in-the-loop(HIL) swarm unmanned aerial vehicles(UAVs) in the presence of possible nonidentical and unknown direction faults(NUDFs) in the yaw channel.The control strategy begins with the design of a pre-specified performance event-triggered observer for each individual UAV.These observers estimate the outputs of the human controlled UAVs, and simultaneously achieve the distributed design of actual control signals as well as cluster consensus of the observer output.It is worth mentioning that these observers require neither the high-order derivatives of the human controlled UAVs' output nor a priori knowledge of the initial conditions. The fault-tolerant controller realizes the pre-specified performance output regulation through error transformation and the Nussbaum function. It should be pointed out that there are no chattering caused by the jump of the Nussbaum function when a reverse fault occurs. In addition, to provide a basis for further solving the problem of physical malfunctions, a fault direction identification algorithm is proposed to accurately identify whether a reverse fault has occurred. Simulation results verify the effectiveness of the proposed control and fault direction identification strategies when the reverse faults occur.
基金Project(51975167)supported by the National Natural Science Foundation of China。
文摘In order to gain a deeper understanding of the effect of pulsed current on the mechanical properties and size effect of nanocrystalline Ni foils,nanocrystalline Ni foils with different grain thickness-to-grain size ratios(λ)were prepared using pulsed electrodeposition in this paper and unidirectional tensile experiments were carried out at room temperature with different currents and their applied directions.The experimental results show that the nanocrystalline Ni foil produces an obvious electroplasticity effect after applying the current field,and when 300<λ<1100,the current weakens the size effect of nanocrystalline Ni foils to a certain extent,and the angle between the current direction and the deformation direction also affects the mechanical response of nanocrystalline Ni foils,and when the angle between the current direction and the deformation direction is 0°,electroplasticity effect is the best,and the current has the most significant effect of abating the size effect of the material.The mechanism of unidirectional tensile deformation of nanocrystalline Ni foils under the effect of pulsed current was analyzed using TEM and TKD.It was found that the applied pulse current increased the activity of the nanocrystalline boundaries,promoted the movement of dislocations,and reduced the tendency of dislocation entanglement.The higher the peak current density and the smaller the angle between the direction of the current and the direction of deformation,the smaller the grain boundary orientation difference,the more dispersed the grain orientation,and the lower the density of geometrically necessary dislocations(GND)in the deformed nanocrystalline foil,the more significant the effect on material plasticity improvement.
基金supported by the National Science and Technology Major Project(No.HT-J2019-VI-0020-0136)the National Youth Talent Support Program,and the Fundamental Research Funds for the Central Universities(No.xtr072024004).
文摘Surface recrystallization(RX) is a typical grain defect observed in directionally solidified(DS) Ni-based superalloys. Most studies have focused on the RX behavior and its impact on the mechanical properties of single-crystal(SC) superalloys, with limited research on its influence on the high-temperature mechanical properties of DS superalloys. This study systematically investigated the effect of RX on the high-temperature tensile properties of a DS DZ409 superalloy. The results show that at 650℃, the yield strength decreases almost linearly with an increase in RX fraction. A significant reduction in elongation is observed as the RX fraction increases from 0% to 4.9%. However, beyond this point, further increase in RX fraction leads to minimal changes in elongation. At 950℃, both yield strength and elongation decrease as the RX fraction increases from 0% to 4.9%. At 650℃, fractures in the RX DS superalloys exhibit a mixed mode of transgranular and intergranular cleavage fracture, while at 950℃, it features a combination of ductile and intergranular dimple fractures. The failure mechanism of the RX DS superalloy is associated with the introduction of transverse grain boundaries(GBs) during RX. In the early stages of tensile testing at intermediate and high temperatures, cracks can easily initiate at these GBs. Subsequently, the cracks propagate along the GBs into the DS matrix, ultimately leading to failure of the DS superalloy.
基金the National Natural Science Foundation of China(No.52074182)Joint Funds of the National Natural Science Foundation of China(No.U23A20612).
文摘We proposed a new technique route of directional solidification for the manufacture of super slab.A 7-t laboratory-scale thick slab was casted and characterised for trial.To further understand the process,the evolution of the multiple physical fields during the directional solidification was simulated and verified.Similar to the convectional ingot casting,a negative segregated cone of equiaxed grains was formed at the bottom,and a seriously positive segregated region was formed beneath the top surface of the slab.Specific measures on the lateral walls,base plate,and free surface were strongly recommended to ensure that the slab is relatively directionally casted.A water-cooling copper base plate accelerates the solidification rate and the columnar growth along the vertical direction.It inhibits the sedimentation of equiaxed grains and enlarges the columnar zone.Based on the simulation analysis,it can be concluded that the directional solidification technique route is promising to manufacture super slab with lower segregation level,and less porosities and inclusions.
基金financial support from the Ministry of Education,Culture,Sports,Science and Technology (MEXT),Japan
文摘The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.
基金supported by the National Natural Science Foundation of China(No.52200120)the R&D Program of Beijing Municipal Education Commission(No.KM202310011003)。
文摘The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient to account for ozone transport at different altitudes.To further understand the characteristics of ozone transport,we applied theWeather Research and Forecasting(WRF)model and the Comprehensive Air Quality Model with Extensions(CAMx)based on flux calculation method.The results showed that the simulated flux calculation method was suitable for revealing the evolutionary trend of ozone fluxes.Monthly inflows,outflows,and total net fluxes ranged from-32985.45 to 37361.46 t/d and indicated strong transport and significant spatial and temporal variations of ozone in the urban boundary segments.Vertical distribution analysis of the net ozone fluxes demonstrated that the net fluxes varied with the altitude,and the altitude at which the corresponding peaks were located had a strong correlation with the neighborhood and season.It was noteworthy that there were three main transport directions throughout the year,namely northwest-southeast(NW-SE),southeast-northwest(SE-NW),and southwestnortheast(SW-NE).Additionally,the ozone flux was mainly affected by temperature,wind speed,and ozone concentration,with the correlation coefficient varying by season and altitude,up to 0.78.Moreover,the correlation analysis of ozone flux and wind direction in each city further verified the accuracy of the transport direction.This paper can provide scientific and technological support for the study of ozone generation mechanisms and the solution of urban/interregional ozone pollution problems.
基金supported by the Natural Science Foundation of Jilin Province(YDZJ202101ZYTS143).
文摘Pneumatic down-the-hole hammer, serving as rock-breaking tool, possesses appeal for directional drilling due to its high rate of penetration. However, corresponding experimental studies on existing hammers for directional drilling have rarely been reported, and a model for evaluating their output performance is absent. This study proposes a novel structure of self-rotating pneumatic hammer(NSH)with a built-in rotational mechanism, which converts partial impact energy of the piston to rotate the drill bit and, consequently, enables dual functions of impact and rotate drill bit. The energy is converted via a screw key-groove mechanism, and the wedge-shaped teeth mechanism ensures that the drill bit rotates clockwise during the piston moves downward. The computational fluid dynamics method is applied to simulate the dynamic response of airflow and piston during the operation of Φ127NSH.Meanwhile, a test bench is established to record data concerning chamber pressure and piston displacement, as well as recording its operational status and rock fragmentation during drilling into granite. The results showed that the maximum error between simulated and experimental data is 8.2%.The Φ127NSH successfully achieves dual impact and rotary drilling functions, and granite smoothly feeds and forms a continuous shear rock zone. In addition, the effects of torque load, engagement distance in rotation sleeves, and well deviation angle towards the performance of NSH were studied in detail. The designed Φ127NSH operates at an impact velocity of 3.98 m/s, impact frequency of 12.55 Hz, and rotational speed of 29.51 r/min under a mass-flow rate of 0.18 kg/s, torque load of 400 N·m, engagement distance of 40 mm, and well deviation angle of 0°. The torque load adversely affects the NSH output performance. Increasing the engagement distance improves impact performance while reducing rotational performance. The performance variation of the NSH is minimal when drilling directional wells with varying deviation angles.
文摘Let X be a real uniformly convex and uniformly smooth Banach space and C a nonempty closed and convex subset of X.Let Π_(C):X→C denote the generalized metric projection operator introduced by Alber in[1].In this paper,we define the Gâteaux directional differentiability of Π_(C).We investigate some properties of the Gâteaux directional differentiability of Π_(C).In particular,if C is a closed ball,or a closed and convex cone(including proper closed subspaces),or a closed and convex cylinder,then,we give the exact representations of the directional derivatives of Π_(C).By comparing the results in[12]and this paper,we see the significant difference between the directional derivatives of the generalized metric projection operator Π_(C) and the Gâteaux directional derivatives of the standard metric projection operator PC.
基金supported by the National Natural Science Foundation of China(22101043)the Fundamental Research Funds for the Central Universities(N2205013,N232410019,N2405013)+3 种基金Natural Science Foundation of Liaoning Province(2023-MSBA-068)the Opening Fund of State Key Laboratory of Heavy Oil Processing(SKLHOP202203006)the Key Laboratory of Functional Molecular Solids,Ministry of Education(FMS2023005)Northeastern University。
文摘The convergence of materials science and biotechnology has catalyzed the development of innovative platforms,including nanotechnology,smart sensors,and supramolecular materials,significantly advancing the progress in the field of life sciences[1−7].Among them,supramolecular materials have garnered increasing attention in life sciences owing to their distinctive self-assembly capabilities and intelligent responsiveness[8−12].
基金supported by the National Natural Science Foundation of China(Grant Nos.52074229,52371035)the Key R&D Plan of Sichuan Province(Grant No.SC2022A1C01J)the State Key Lab of Advanced Metals and Materials(Grant No.2020-ZD05).
文摘The directional annealing technique is widely used to prepare columnar grains or single crystals.To investigate the effect of hot zone temperature and temperature gradient on the growth of columnar crystals,Ti43Al alloys were heat treated by the directional annealing technique and their mechanical properties were tested.The results show that columnar grains with a maximum size of 22.29 mm can be obtained at a hot zone temperature of 1,350℃ and a temperature gradient of 8 K·mm^(-1).During the directional annealing process,Ti43Al alloys are heated toαsingle-phase domain to start the phase transformation.Columnar grains with a microstructure of fully lamellar colonies are obtained at different hot zone temperatures and temperature gradients.The distribution of the orientation difference for theα2 phase was found to be more random,suggesting that the growth of the columnar crystals may be stochastic in nature.Tensile testing results show that the strength and elongation of directional annealed Ti43Al alloy at 1,400℃-8 K·mm^(-1) are 411.23 MPa and 2.29%,and the remaining directional annealed alloys show almost plasticity.
文摘The publisher regrets that the article type for this publication was incorrectly labeled as a Research Article.The correct designation should be Review Article.This correction does not affect the content or conclusions of the article.The publisher apologizes for any inconvenience caused.
