Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dyna...Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.展开更多
To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at dif...To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain ratesε were systematically studied through compression tests and microscopic observations. The increase in ε eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473?573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10?3 s?1; however, at 1×10?2 s?1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ε inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.展开更多
The compressibility of stale waste is studied based on the investigation into the composition and properties of stale waste in the Chongqing City. Stale waste sampled at a landfill closed for over 8 a was analyzed ind...The compressibility of stale waste is studied based on the investigation into the composition and properties of stale waste in the Chongqing City. Stale waste sampled at a landfill closed for over 8 a was analyzed indoors for its natural density, natural water content, relative density, grain size distribution curve, uniformity coefficient and curvature coefficient. Indoor compression tests for the stale waste were performed to find out the void ratio and its dependence upon applied pressure, compressibility coefficient, constrained modulus and volume compressibility coefficient. From the experimental data, the curvature coefficient and the preconsolidation pressure of the stale waste were worked out. The results indicates that the stale waste is of high compressibility, which is different from the other kinds of common soil, and is underconsolidated soil. The measured compressibility parameters are applicable to settlement calculation of closed landfills.展开更多
Carbon is an important alloying element in improving high temperature mechanical properties of various metallic materials.The effects of carbon on high temperature mechanical properties of aβ-stabilized Ti?45Al?3Fe?2...Carbon is an important alloying element in improving high temperature mechanical properties of various metallic materials.The effects of carbon on high temperature mechanical properties of aβ-stabilized Ti?45Al?3Fe?2Mo(molar fraction,%)alloy were studied through compressive and creep tests.The results show that the carbon addition(0.5%,molar fraction)obviously enhances the high temperature compressive strength and creep resistance of theβ-stabilized Ti?45Al?3Fe?2Mo alloy.A lot of nano-scaled Ti3AlC carbides precipitate in theβ-stabilized alloy and these carbides pin the dislocations,and greatly increase the high temperature properties.At the same time,the carbon addition decreases the amount of?phase,refines the lamellar spacing,and causes solution strengthening,which also contribute to the improvement of the high temperature properties.展开更多
High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperatu...High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 ℃ was selected as the test temperature; for the resin sand used for cast non-ferrous alloy, 800 ℃ was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%.展开更多
Fibrous porous ceramics are attractive for use as thermal insulation materials.However,the intrinsic brit-tleness of rigid materials has remained challenging and severely restricts their applications.Here,we demonstra...Fibrous porous ceramics are attractive for use as thermal insulation materials.However,the intrinsic brit-tleness of rigid materials has remained challenging and severely restricts their applications.Here,we demonstrated a facile method for fabricating elastic fibrous porous ceramics(EFPCs)with high com-pressive strength and low thermal conductivity through ordinary press filtration and subsequent heat treatment.The quasi-layered structure and the well-bonded bridging fibers between layers are the key points for the elasticity of EFPCs.The advanced EFPCs exhibited low density(∼0.126 g cm^(−3)),high com-pressive stress(∼0.356 MPa),and low thermal conductivity(∼0.026 W m^(−1) K^(−1)).Compared with rigid porous fibrous materials,the EFPCs had deformability and excellent shape recovery.In contrast to flexible materials,the EFPCs possessed high compressive stress,thus endowing them with good resistance to de-formation.The emergence of this fascinating material may provide new insights for candidate materials in thermal insulation and other fields.展开更多
The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials s...The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields.Herein,high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres(FAHMs)by the protein gelling technique.Owing to their unique shell-pore structure inspired by shell-protected biomaterials,the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength(32.3–42.9 MPa)which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere.Moreover,their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs,and the resultant monoliths demonstrated superior integrated performances for multifunctional applications,such as broadband sound insulation,efficient thermal insulation,and high-temperature fire resistance(>1300℃).On this basis,mullite-based porous ceramic lattices(porosity 68.28%–84.79%)with a hierarchical porous structure were successfully assembled by direct ink writing(DIW),which exhibited significantly higher compressive strength(3.02–10.77 MPa)than most other ceramic lattices with comparable densities.This unique shell-pore structure can be extended to other porous materials,and our strategy paves a new way for cost-effective,scalable and green production of multifunctional materials with well-defined microstructure.展开更多
Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix propo...Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix proportion design method for RHPC using 100 % CRA and natural sand. Five groups of RHPC mixes with five strength grades（40, 50, 60, 70 and 80 MPa） were produced using CRA with four quality classes, and their workability, 28 d compressive strengths and frost resistances（measured by the compressive strength loss ratio and the relative dynamic modulus of elasticity） were tested. Relationships between the 28 d compressive strength, the frost resistance and the CRA quality characteristic parameter, water absorption, were then developed. The criterion of a CRA maximum water absorption limit value for RHPC was suggested, independent of its source and quality class. The results show that all RHPC mixes achieve the expected target workability, strength, and frost durability. The research results demonstrate that the application of the proposed method does not require trial testing prior to use.展开更多
Compression tests A ere conducted in the two phase Ti46Al8.5Nb0.2W alloy with a cast microstructure under the strain rates ranging from 2x10(-5) s(-1) to 10(-2) s(-1) at temperatures ranging front 900degreesC to 1100d...Compression tests A ere conducted in the two phase Ti46Al8.5Nb0.2W alloy with a cast microstructure under the strain rates ranging from 2x10(-5) s(-1) to 10(-2) s(-1) at temperatures ranging front 900degreesC to 1100degreesC. It was found that there exist approximately linear relationships between the flow stress and the logarithm of strain rate at different temperatures. The strain rate dependence was analzed by the thermal activation theory and dislocation climbing is regarded as the controlling mechanism during high temperature compression tests.展开更多
The construction of CKE road embankments is undertaken over soft soils,which include peats,organic soils,clays and sludge.The moisture content of peat is up to 700%and void ratio is up to 11.99.It's very easy for ...The construction of CKE road embankments is undertaken over soft soils,which include peats,organic soils,clays and sludge.The moisture content of peat is up to 700%and void ratio is up to 11.99.It's very easy for the embankments of high moisture content,high void ratio and of the high compression nature to cause too much settlement and loss of stability.Embankment stability during construction and residual settlement of pavement during service period are two major challenges to be faced of the design and construction.This paper outlines the site investigation,laboratory tests and monitoring data in a few selected existing preloading areas,and presents the back-analysis results of the modified secondary compression indices of in-situ soft materials.It is found that the early monitoring data after primary settlement completion are a more reliable approach to estimate the residual settlements within a nominated duration.展开更多
We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability...We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability of the PACs for oil/water separation were investigated and characterized via extensive ex-periments.The PACs material had favourable properties including mechanical strength and chemical durability compared with fabric-based materials and organic sponge-based materials previously reported in literature for oil/water separation.It is believed that the PACs material and methodology presented in this work may provide wastewater remediation industry with a promising alternative for dealing with the catastrophic ocean oil pollu-tion and other oil contamination.展开更多
Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studie...Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.展开更多
The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were exe...The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.展开更多
The true stress-true strain curves of Ti-6Al-2Zr-IMO-IV alloy with hydrogen were obtained by hot compression test. The microstructures of the alloy before and after thermo-compression were observed. The apparent activ...The true stress-true strain curves of Ti-6Al-2Zr-IMO-IV alloy with hydrogen were obtained by hot compression test. The microstructures of the alloy before and after thermo-compression were observed. The apparent activation energies of deformation were calculated for the alloy with and without hydrogen. The behavior and mechanism of deformation for hydrogenated Ti-6A1-2Zr-IMO-IV alloy at high temperature were analyzed. The relationship between hydrogenation time and hydrogen content at 800 ℃ can be expressed as the equation： CH（t）=1.2-1.2exp（-t/120）. The true stress-true strain curves of hot compression for Ti-6Al-2Zr-IMO-IV alloy with hydrogen first move down and then move up as hydrogen content increases. Appropriate hydrogen content can reduce the peak of flow stress to minimal value. The apparent activation energies of deformation of the alloy with 0.47% hydrogen content and without hydrogen were calculated as 140 kJ·mol^-1 and 390 kJ-mol^-1, respectively, at 800 ℃ and at strain rate 8.3×10^4 s^-1. The apparent activation energy of deformation increases when the strain rate enhances from 8.3×10^-4 s^-1 to 8.3×10^-2 s^-1.展开更多
In the process of image transmission, the famous JPEG and JPEG-2000 compression methods need more transmission time as it is difficult for them to compress the image with a low compression rate. Recently the compresse...In the process of image transmission, the famous JPEG and JPEG-2000 compression methods need more transmission time as it is difficult for them to compress the image with a low compression rate. Recently the compressed sensing（CS） theory was proposed, which has earned great concern as it can compress an image with a low compression rate, meanwhile the original image can be perfectly reconstructed from only a few compressed data. The CS theory is used to transmit the high resolution astronomical image and build the simulation environment where there is communication between the satellite and the Earth. Number experimental results show that the CS theory can effectively reduce the image transmission and reconstruction time. Even with a very low compression rate, it still can recover a higher quality astronomical image than JPEG and JPEG-2000 compression methods.展开更多
High-strength concrete and shape steel are combined to form composite shear wall members to address the cross-section oversize of core tube shear walls at the bottom of tall and super-tall buildings.However,the existi...High-strength concrete and shape steel are combined to form composite shear wall members to address the cross-section oversize of core tube shear walls at the bottom of tall and super-tall buildings.However,the existing investigation focus on rectangular shear walls,and insufficient study has been conducted on L-shaped shear walls.To better understand the seismic performance of L-shaped-section steel reinforced high-strength concrete(f cu≥60 MPa)shear walls(LSRHCW),four such specimens with distinct dimensions,reinforcement ratios and concrete strengths were tested under cyclic loading and high axial compression ratio(n=0.5),and the lateral cyclic loading direction makes an angle of 45°with the wall limb length direction.The influence of improving concrete strength and reducing the steel and reinforcement ratios on the seismic performance is investigated.The results show that under high axial compression ratio,the specimens fail in flexure-shear mode due to strength reduction caused by concrete crushing,and exhibit excellent deformation performance(maximum drift ratio capacity,3.03%).The wall specimens built with different strength concrete and shape steel ratios demonstrate comparable strength,deformation and initial stiffness.This suggests that the reinforcement ratio of LSRHCWs can be effectively reduced by upgrading concrete strength,while still maintaining their seismic performance.展开更多
The development of compressible supercapacitors strongly relies on the design of electrode materials combining superior compressibility,high conductivity with the stable electrochemical cycling performance.In this wor...The development of compressible supercapacitors strongly relies on the design of electrode materials combining superior compressibility,high conductivity with the stable electrochemical cycling performance.In this work,we report a facile yet scalable strategy to construct a highly compressible supercapacitor by integrating the current collector,active materials and the separator into one device.We use the highly compressive melamine foam(MF)as scaffold and the Ti_(3)C_(2)T_(x)nanosheets as the active materials.Filling the few-layer Ti_(3)C_(2)T_(x)nanosheets into the skeleton of MF by capillary force followed by freeze-drying yields the MF/Ti_(3)C_(2)T_(x)composite with superior structural integrity that can be compressed at a large strain of 50%for 100 cycles.The electrochemical performances of the all-in-one supercapacitor were systematically investigated under diverse compression strains.The improved conductivity and reduced ion diffusion length allow the all-in-one supercapacitor to exhibit fast ion and electron kinetics even at high strain of 60%,delivering a maximal volumetric specific energy of 0.37 mWh∙cm^(-3)at power density of 0.42 mW∙cm^(-3)and extraordinary cycling performance during the 2,500 compression cycles.展开更多
In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knoc...In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knock in practical working process.The objective of this work is to comprehensively investigate the application of high compression ratio on a gasoline engine based on the Miller cycle with boost pressure and split injection.In this work,the specific optimum strategies for CR10 and CR12 were experimentally investigated respectively on a single cylinder DISI engine.It was found that a high level of Miller cycle with a higher boost pressure could be used in CR12 to achieve an effective compression ratio similar to CR10,which could eliminate the knock limits at a high compression ratio and high load.To verify the advantages of the high compression ratio,the fuel economy and power performance of CR10 and CR12 were compared at full and partial loads.The result revealed that,compared with CR10,a similar power performance and a reduced fuel consumption of CR12 at foil load could be achieved by using the strong Miller cycle and split injection.At partial load,the conditions of CR12 had very superior fuel economy and power performance compared to those of CR10.展开更多
Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit...Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit of storage capacity.Adiabatic compressed air energy storage(A-CAES)systems typically compress air from ambient temperature in the charge phase and expand the air back to ambient temperature in the discharge phase.This papers explores the use of an innovative operating scheme for an A-CAES system aimed at lowering the total cost of the system for a given exergy storage capacity.The configuration proposed considers preheating of the air before compression which increases the fraction of the total exergy that is stored in the fom of high-grade heat in comparison to existing designs in which the main exergy storage medium is the compressed air itself.Storing a high fraction of the total exergy as heat allows reducing the capacity of costly pressure stores in the system and replacing it with cheaper thermal energy stores.Additionally,a configuration that integrates a system based on the aforementioned concept with solar thermal power or low-medium grade waste heat is introduced and thoroughly discussed.展开更多
Magnesium phosphate bone cement has become a widely used orthopedic implant due to the advantages of fast-setting and high early strength. However, developing magnesium phosphate cement possessing applicable injectabi...Magnesium phosphate bone cement has become a widely used orthopedic implant due to the advantages of fast-setting and high early strength. However, developing magnesium phosphate cement possessing applicable injectability, high strength, and biocompatibility simultaneously remains a significant challenge. Herein, we propose a strategy to develop high-performance bone cement and establish a trimagnesium phosphate cement (TMPC) system. The TMPC exhibits high early strength, low curing temperature, neutral pH, and excellent injectability, overcoming the critical limitations of recently studied magnesium phosphate cement. By monitoring the hydration pH value and electroconductivity, we demonstrate that the magnesium-to-phosphate ratio could manipulate the components of hydration products and their transformation by adjusting the pH of the system, which will influence the hydration speed. Further, the ratio could regulate the hydration network and the properties of TMPC. Moreover, in vitro studies show that TMPC has outstanding biocompatibility and bone-filling capacity. The facile preparation properties and these advantages of TMPC render it a potential clinical alternative to polymethylmethacrylate and calcium phosphate bone cement. This study will contribute to the rational design of high-performance bone cement.展开更多
基金Project (14JJ6047) supported by the Natural Science Foundation of Hunan Province,ChinaProject (51274092) supported by the National Natural Science Foundation of ChinaProject (20120161110040) supported by the Doctoral Program of Higher Education ofChina
文摘Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.
基金Projects(51231002,51271054,51571058,50671023)supported by the National Natural Science Foundation of China
文摘To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain ratesε were systematically studied through compression tests and microscopic observations. The increase in ε eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473?573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10?3 s?1; however, at 1×10?2 s?1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ε inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.
基金Application and Foundation Research Fund of Chongqing Construction Committee,2001.
文摘The compressibility of stale waste is studied based on the investigation into the composition and properties of stale waste in the Chongqing City. Stale waste sampled at a landfill closed for over 8 a was analyzed indoors for its natural density, natural water content, relative density, grain size distribution curve, uniformity coefficient and curvature coefficient. Indoor compression tests for the stale waste were performed to find out the void ratio and its dependence upon applied pressure, compressibility coefficient, constrained modulus and volume compressibility coefficient. From the experimental data, the curvature coefficient and the preconsolidation pressure of the stale waste were worked out. The results indicates that the stale waste is of high compressibility, which is different from the other kinds of common soil, and is underconsolidated soil. The measured compressibility parameters are applicable to settlement calculation of closed landfills.
基金Project(2014CB6644002)supported by the National Basic Research Program of ChinaProject(2016YFB0700302)supported by the National Major Scientific Research Development Program,ChinaProject(2017JJ2311)supported by the Hunan Natural Science Foundation of China
文摘Carbon is an important alloying element in improving high temperature mechanical properties of various metallic materials.The effects of carbon on high temperature mechanical properties of aβ-stabilized Ti?45Al?3Fe?2Mo(molar fraction,%)alloy were studied through compressive and creep tests.The results show that the carbon addition(0.5%,molar fraction)obviously enhances the high temperature compressive strength and creep resistance of theβ-stabilized Ti?45Al?3Fe?2Mo alloy.A lot of nano-scaled Ti3AlC carbides precipitate in theβ-stabilized alloy and these carbides pin the dislocations,and greatly increase the high temperature properties.At the same time,the carbon addition decreases the amount of?phase,refines the lamellar spacing,and causes solution strengthening,which also contribute to the improvement of the high temperature properties.
基金financially supported by the National Natural Science Foundation of China(No.51405002)
文摘High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 ℃ was selected as the test temperature; for the resin sand used for cast non-ferrous alloy, 800 ℃ was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%.
基金financially supported by the National Key Research and Development of China (No.2021YFB3400200)the National Natural Science Foundation of China (Nos.12090031 and 11602125)the Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Fibrous porous ceramics are attractive for use as thermal insulation materials.However,the intrinsic brit-tleness of rigid materials has remained challenging and severely restricts their applications.Here,we demonstrated a facile method for fabricating elastic fibrous porous ceramics(EFPCs)with high com-pressive strength and low thermal conductivity through ordinary press filtration and subsequent heat treatment.The quasi-layered structure and the well-bonded bridging fibers between layers are the key points for the elasticity of EFPCs.The advanced EFPCs exhibited low density(∼0.126 g cm^(−3)),high com-pressive stress(∼0.356 MPa),and low thermal conductivity(∼0.026 W m^(−1) K^(−1)).Compared with rigid porous fibrous materials,the EFPCs had deformability and excellent shape recovery.In contrast to flexible materials,the EFPCs possessed high compressive stress,thus endowing them with good resistance to de-formation.The emergence of this fascinating material may provide new insights for candidate materials in thermal insulation and other fields.
基金financially supported by the National Natural Science Foundation of China(Grant No.51802347)the Natural Science Foundation of Hubei Province(Grant No.2022CFB939).
文摘The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields.Herein,high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres(FAHMs)by the protein gelling technique.Owing to their unique shell-pore structure inspired by shell-protected biomaterials,the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength(32.3–42.9 MPa)which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere.Moreover,their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs,and the resultant monoliths demonstrated superior integrated performances for multifunctional applications,such as broadband sound insulation,efficient thermal insulation,and high-temperature fire resistance(>1300℃).On this basis,mullite-based porous ceramic lattices(porosity 68.28%–84.79%)with a hierarchical porous structure were successfully assembled by direct ink writing(DIW),which exhibited significantly higher compressive strength(3.02–10.77 MPa)than most other ceramic lattices with comparable densities.This unique shell-pore structure can be extended to other porous materials,and our strategy paves a new way for cost-effective,scalable and green production of multifunctional materials with well-defined microstructure.
基金Funded by the National Natural Science Foundation of China(No.51278073)Prospective Joint Research Project of Jiangsu Province(No.BY2015027-23)State Key Laboratory for Geo Mechanics and Deep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK1704)
文摘Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix proportion design method for RHPC using 100 % CRA and natural sand. Five groups of RHPC mixes with five strength grades（40, 50, 60, 70 and 80 MPa） were produced using CRA with four quality classes, and their workability, 28 d compressive strengths and frost resistances（measured by the compressive strength loss ratio and the relative dynamic modulus of elasticity） were tested. Relationships between the 28 d compressive strength, the frost resistance and the CRA quality characteristic parameter, water absorption, were then developed. The criterion of a CRA maximum water absorption limit value for RHPC was suggested, independent of its source and quality class. The results show that all RHPC mixes achieve the expected target workability, strength, and frost durability. The research results demonstrate that the application of the proposed method does not require trial testing prior to use.
文摘Compression tests A ere conducted in the two phase Ti46Al8.5Nb0.2W alloy with a cast microstructure under the strain rates ranging from 2x10(-5) s(-1) to 10(-2) s(-1) at temperatures ranging front 900degreesC to 1100degreesC. It was found that there exist approximately linear relationships between the flow stress and the logarithm of strain rate at different temperatures. The strain rate dependence was analzed by the thermal activation theory and dislocation climbing is regarded as the controlling mechanism during high temperature compression tests.
文摘The construction of CKE road embankments is undertaken over soft soils,which include peats,organic soils,clays and sludge.The moisture content of peat is up to 700%and void ratio is up to 11.99.It's very easy for the embankments of high moisture content,high void ratio and of the high compression nature to cause too much settlement and loss of stability.Embankment stability during construction and residual settlement of pavement during service period are two major challenges to be faced of the design and construction.This paper outlines the site investigation,laboratory tests and monitoring data in a few selected existing preloading areas,and presents the back-analysis results of the modified secondary compression indices of in-situ soft materials.It is found that the early monitoring data after primary settlement completion are a more reliable approach to estimate the residual settlements within a nominated duration.
基金Fund by the Science and Technology Programme Project of Bengbu City(No.2023gx01)the Key Technologies R&D Program of CNBM(No.2021HX0809)。
文摘We presented a novel porous alumina ceramics(PACs)with superoleophilicity and superoleo-phobicity when immersed in different oil-water environments.The wettability,separation efficiency,permeation flux and reusability of the PACs for oil/water separation were investigated and characterized via extensive ex-periments.The PACs material had favourable properties including mechanical strength and chemical durability compared with fabric-based materials and organic sponge-based materials previously reported in literature for oil/water separation.It is believed that the PACs material and methodology presented in this work may provide wastewater remediation industry with a promising alternative for dealing with the catastrophic ocean oil pollu-tion and other oil contamination.
基金the National Natural Science Foundation of China(No.50776094)the National High Technology Research and Development Program(863)of China(No.2006AA05Z135)
文摘Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.
基金Project(50979032)supported by the National Natural Science Foundation of China
文摘The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.
基金supported by the National Natural Science Foundation of China(No.50671028)
文摘The true stress-true strain curves of Ti-6Al-2Zr-IMO-IV alloy with hydrogen were obtained by hot compression test. The microstructures of the alloy before and after thermo-compression were observed. The apparent activation energies of deformation were calculated for the alloy with and without hydrogen. The behavior and mechanism of deformation for hydrogenated Ti-6A1-2Zr-IMO-IV alloy at high temperature were analyzed. The relationship between hydrogenation time and hydrogen content at 800 ℃ can be expressed as the equation： CH（t）=1.2-1.2exp（-t/120）. The true stress-true strain curves of hot compression for Ti-6Al-2Zr-IMO-IV alloy with hydrogen first move down and then move up as hydrogen content increases. Appropriate hydrogen content can reduce the peak of flow stress to minimal value. The apparent activation energies of deformation of the alloy with 0.47% hydrogen content and without hydrogen were calculated as 140 kJ·mol^-1 and 390 kJ-mol^-1, respectively, at 800 ℃ and at strain rate 8.3×10^4 s^-1. The apparent activation energy of deformation increases when the strain rate enhances from 8.3×10^-4 s^-1 to 8.3×10^-2 s^-1.
文摘In the process of image transmission, the famous JPEG and JPEG-2000 compression methods need more transmission time as it is difficult for them to compress the image with a low compression rate. Recently the compressed sensing（CS） theory was proposed, which has earned great concern as it can compress an image with a low compression rate, meanwhile the original image can be perfectly reconstructed from only a few compressed data. The CS theory is used to transmit the high resolution astronomical image and build the simulation environment where there is communication between the satellite and the Earth. Number experimental results show that the CS theory can effectively reduce the image transmission and reconstruction time. Even with a very low compression rate, it still can recover a higher quality astronomical image than JPEG and JPEG-2000 compression methods.
基金supported by the National Key Research and Development Program of China(No.2020YFB190140201).
文摘High-strength concrete and shape steel are combined to form composite shear wall members to address the cross-section oversize of core tube shear walls at the bottom of tall and super-tall buildings.However,the existing investigation focus on rectangular shear walls,and insufficient study has been conducted on L-shaped shear walls.To better understand the seismic performance of L-shaped-section steel reinforced high-strength concrete(f cu≥60 MPa)shear walls(LSRHCW),four such specimens with distinct dimensions,reinforcement ratios and concrete strengths were tested under cyclic loading and high axial compression ratio(n=0.5),and the lateral cyclic loading direction makes an angle of 45°with the wall limb length direction.The influence of improving concrete strength and reducing the steel and reinforcement ratios on the seismic performance is investigated.The results show that under high axial compression ratio,the specimens fail in flexure-shear mode due to strength reduction caused by concrete crushing,and exhibit excellent deformation performance(maximum drift ratio capacity,3.03%).The wall specimens built with different strength concrete and shape steel ratios demonstrate comparable strength,deformation and initial stiffness.This suggests that the reinforcement ratio of LSRHCWs can be effectively reduced by upgrading concrete strength,while still maintaining their seismic performance.
基金This work was supported by the National Natural Science Foundation of China(No.51772181)the Fundamental Research Funds for the Central Universities(No.2019TS006)+1 种基金the Natural Science Basic Research Plan of Shaanxi Province(No.2019JLP-12)Shaanxi Sanqin Scholars Innovation Team.
文摘The development of compressible supercapacitors strongly relies on the design of electrode materials combining superior compressibility,high conductivity with the stable electrochemical cycling performance.In this work,we report a facile yet scalable strategy to construct a highly compressible supercapacitor by integrating the current collector,active materials and the separator into one device.We use the highly compressive melamine foam(MF)as scaffold and the Ti_(3)C_(2)T_(x)nanosheets as the active materials.Filling the few-layer Ti_(3)C_(2)T_(x)nanosheets into the skeleton of MF by capillary force followed by freeze-drying yields the MF/Ti_(3)C_(2)T_(x)composite with superior structural integrity that can be compressed at a large strain of 50%for 100 cycles.The electrochemical performances of the all-in-one supercapacitor were systematically investigated under diverse compression strains.The improved conductivity and reduced ion diffusion length allow the all-in-one supercapacitor to exhibit fast ion and electron kinetics even at high strain of 60%,delivering a maximal volumetric specific energy of 0.37 mWh∙cm^(-3)at power density of 0.42 mW∙cm^(-3)and extraordinary cycling performance during the 2,500 compression cycles.
基金the National Natural Science Foundation of China (Grant Nos.91641203,51476114,and 91741119)the National Key Research and Development Program of China(2017YFB0103400)。
文摘In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knock in practical working process.The objective of this work is to comprehensively investigate the application of high compression ratio on a gasoline engine based on the Miller cycle with boost pressure and split injection.In this work,the specific optimum strategies for CR10 and CR12 were experimentally investigated respectively on a single cylinder DISI engine.It was found that a high level of Miller cycle with a higher boost pressure could be used in CR12 to achieve an effective compression ratio similar to CR10,which could eliminate the knock limits at a high compression ratio and high load.To verify the advantages of the high compression ratio,the fuel economy and power performance of CR10 and CR12 were compared at full and partial loads.The result revealed that,compared with CR10,a similar power performance and a reduced fuel consumption of CR12 at foil load could be achieved by using the strong Miller cycle and split injection.At partial load,the conditions of CR12 had very superior fuel economy and power performance compared to those of CR10.
基金This work has been supported by the UK Engineering and Physical Sciences Research Council(EPSRC)through the NexGen-TEST(EP/LO14211/1),IMAGES(EP/K002228/1)and RESTLESS(EP/N001893/1)projects.
文摘Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit of storage capacity.Adiabatic compressed air energy storage(A-CAES)systems typically compress air from ambient temperature in the charge phase and expand the air back to ambient temperature in the discharge phase.This papers explores the use of an innovative operating scheme for an A-CAES system aimed at lowering the total cost of the system for a given exergy storage capacity.The configuration proposed considers preheating of the air before compression which increases the fraction of the total exergy that is stored in the fom of high-grade heat in comparison to existing designs in which the main exergy storage medium is the compressed air itself.Storing a high fraction of the total exergy as heat allows reducing the capacity of costly pressure stores in the system and replacing it with cheaper thermal energy stores.Additionally,a configuration that integrates a system based on the aforementioned concept with solar thermal power or low-medium grade waste heat is introduced and thoroughly discussed.
基金supported by grants from The National Key Research and Development Program of China(2022YFB4601402)the National Natural Science Foundation of China(32201109,51772233,51861145306)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(2022B1515120052,2021A1515110557)the Self-innovation Research Funding Project of Hanjiang Laboratory(HJL202202A002).
文摘Magnesium phosphate bone cement has become a widely used orthopedic implant due to the advantages of fast-setting and high early strength. However, developing magnesium phosphate cement possessing applicable injectability, high strength, and biocompatibility simultaneously remains a significant challenge. Herein, we propose a strategy to develop high-performance bone cement and establish a trimagnesium phosphate cement (TMPC) system. The TMPC exhibits high early strength, low curing temperature, neutral pH, and excellent injectability, overcoming the critical limitations of recently studied magnesium phosphate cement. By monitoring the hydration pH value and electroconductivity, we demonstrate that the magnesium-to-phosphate ratio could manipulate the components of hydration products and their transformation by adjusting the pH of the system, which will influence the hydration speed. Further, the ratio could regulate the hydration network and the properties of TMPC. Moreover, in vitro studies show that TMPC has outstanding biocompatibility and bone-filling capacity. The facile preparation properties and these advantages of TMPC render it a potential clinical alternative to polymethylmethacrylate and calcium phosphate bone cement. This study will contribute to the rational design of high-performance bone cement.
