This article provides an overview of the current development status of prestressed segmental precast and assembled piers,Emphasis was placed on analyzing the stress characteristics of bridge piers under impact.The con...This article provides an overview of the current development status of prestressed segmental precast and assembled piers,Emphasis was placed on analyzing the stress characteristics of bridge piers under impact.The concept of recoverable functional design and its application prospects were elaborated,and finally,the research on the impact resistance performance of prestressed segmental precast and assembled pierswas discussed.Research has shown that optimizing design and material selection can effectively enhance the impact resistance and structural durability of bridge piers.At the same time,the introduction of the concept of recoverable functionality provides new ideas for the rapid repair and functional recovery of bridge piers,which helps to improve the recovery efficiency of bridges after extreme events.Future research should focus on the evaluation methods of impact resistance performance,new connection technologies,in-depth application of recoverable functional design,a combination of impact simulation experiments and numerical analysis,and exploration of comprehensive disaster prevention and reduction strategies.These research results will also promote the further development and innovation of prefabricated assembly technology in bridge engineering,bringing new ideas and methods to the field of engineering construction.展开更多
This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and...This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.展开更多
To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyur...To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn.展开更多
Granite is well known as an acid aggregate. An active mineral filler produced in the laboratory is first used as an anti-stripping filler in the granite asphalt concrete. Four aggregate gradations were chosen in this ...Granite is well known as an acid aggregate. An active mineral filler produced in the laboratory is first used as an anti-stripping filler in the granite asphalt concrete. Four aggregate gradations were chosen in this study,and the effects of the active mineral filler and aggregates on the rutting resistance performance and fatigue properties of granite asphalt concrete were investigated by means of rutting test and four-point bending fatigue test. The results indicate that the dynamic stability of granite asphalt concrete increase significantly with the addition of active mineral filler and the fatigue properties can also be improved especially at lower strain level. Meanwhile,the results demonstrate that granite asphalt concrete has better rutting resistance performance and fatigue properties than limestone asphalt concrete.展开更多
In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To ex...In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.展开更多
The resistance performance and motion stability of deep sea remotely operated vehicles(ROVs)subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method com...The resistance performance and motion stability of deep sea remotely operated vehicles(ROVs)subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method combined with the six-degree-of-freedom equation of motion to quickly and accurately predict them.In the modeling process,we consider the complexity of ROV geometry and thus reduce the model to a series of regular geometries to maximize the position and weight of the original components.The grid and value slots of an ROV are divided,and the surface is reconstructed.The forward,backward,transverse,floating,and submerged resistance of ROVs are simulated and compared with existing experimental forces to determine the accuracy of the calculation method.Then,the oblique navigation of the ROV on the horizontal and vertical planes is studied.Furthermore,the motion response of the ROV to direct horizontal motion,heave,pitch,and yaw are studied.The force,moment,and motion time curves are obtained.The stability of ROV motion is analyzed to provide technical support for the safety of ROVs.展开更多
We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated...We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.展开更多
Copper is a versatile material,commonly utilized in power transmission and electronic devices,but its relative high reactivity necessitates a long-lasting protective technique.Here,we report a method that combines pla...Copper is a versatile material,commonly utilized in power transmission and electronic devices,but its relative high reactivity necessitates a long-lasting protective technique.Here,we report a method that combines plasma-enhanced non-equilibrium magnetron sputtering physical vapor deposition(PEUMS-PVD)and anodization to construct a self-healing three-dimensional Ti/Al-doped TiO_(2)nanotubes/Ti_(3)AlC_(2)coating on the surface of Cu substrates.This novel strategy enhances the corrosion resistance of copper substrates in marine environments,with corrosion current densities of up to 4.5643×10^(−8)A/cm^(2).Among them,the doping of nano-aluminum particles makes the coating self-healing.The mechanistic analysis of the corrosion behaviors during early immersion experiments was conducted using electrochemical noise,and revealed that during the initial stages of coating immersion,uniform corrosion predominates,with a minor occurrence of localized corrosion.展开更多
Inorganic buffer layers such as SiO2 or TiO2 and transparent conductive indium-tin-oxide （ITO） films were prepared on polyethylene terephthalate （PET） substrates by ion assisted deposition （IAD） at room temperat...Inorganic buffer layers such as SiO2 or TiO2 and transparent conductive indium-tin-oxide （ITO） films were prepared on polyethylene terephthalate （PET） substrates by ion assisted deposition （IAD） at room temperature, and the effects of SiO2 and TiOzon the bending resistance performance of flexible ITO films were investigated. The results show that ITO films with SiO2 or TiO2 buffer layer have better resistance stabilities compared to ones without the buffer layer when the ITO films are inwards bent at a bending radius more than 1.2 cm and when the ITO films are outwards bent at a bending radius from 0.8 cm to 1.2 cm. 1TO films with SiO2 buffer layer have better resistance sta- bilities compared to ones with TiO2 buffer layer after the ITO fdms are bent several hundreds of cycles at the same bending radius, for the adhesion of SiO2 is stronger than that of TiO2. The compressive stress resulted from inward bending leads to the formation of more defects in the ITO films compared with the tensile stress arising from outward bending. SiO2 and TiO2 buffer layers can effectively improve the crystallinity of ITO films in （400）, （440） directions.展开更多
The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area betw...The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.展开更多
Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and ...Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.展开更多
In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes wit...In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter. The filling ratio is50%. The visualization investigation is conducted to observe the oscillation and circulation flow in the CLPHP. In order to investigate the effects of inclination angles to thermal performance in the ammonia CLPHP, four case tests are studied. The trends of temperature fluctuation and thermal resistance as the input power increases at different inclination angles are highlighted. The results show that it is very easy to start up and circulate for the ammonia CLPHP at an inclining angle.The thermal resistance is low to 0.02 K/W, presenting that heat fluxes can be transferred from heating section to cooling section very quickly. It is found that the thermal resistance decreases as the inclination angle increases. At the horizontal operation, the ammonia CLPHP can be easy to start up at low input power, but hard to circulate. In this case, once the input power is high,the capillary tube in heating section will be burnt out, leading to worse thermal performance with high thermal resistance.展开更多
[Objective]This experiment was conducted on Pseudosciaena crocea to study the effects of mannan oligosaccharides on growth and antibacterial ability. [Method]1 500 experimental fishes were divided into five groups. Th...[Objective]This experiment was conducted on Pseudosciaena crocea to study the effects of mannan oligosaccharides on growth and antibacterial ability. [Method]1 500 experimental fishes were divided into five groups. The control group（ C） contained no mannan oligosaccharides,the treatment groups were contained 100,200,400,800 mg /kg of konjac mannan oligosaccharides in basal diet,respectively. The experiment continued 4 months. [Result]The results showed that Konjac Mannan oligosaccharides could significantly improve weight gain Pseudosciaena crocea. Compared with control group,Test 2 group intestine protease activity increased by 45. 74%,hepatopancreatic lipase activity increased by 31. 37%,amylase activity increased by 27. 16%. Comparison with the control group,the test group serum SOD activity was significantly higher than that in the control group（ P 〈0. 05）. Lysozyme（ LZM） activity,spleen and serum test group was significantly higher than that in the control group（ P 〈0.05）. Pseudosciaena crocea were infected by Anguillarum,compared with control group,the survival rate is higher than that of the control group（ P 〈0. 05） when the dosage of 200 mg /kg,400 mg /kg. [Conclusion]According to the test results,the Konjac Mannan oligosaccharides in the basal diet suitable dosage were 200 mg /kg.展开更多
We have investigated the factors affecting the current spreading length（CSL） in GaN-based light-emitting diodes（LEDs） by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LE...We have investigated the factors affecting the current spreading length（CSL） in GaN-based light-emitting diodes（LEDs） by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LEDs,the effects of both indium tin oxide（ITO） and n-GaN are taken into account for the first time,and a new Q factor is introduced to explain the effects of different current flow paths on the CSL.The calculations and simulations show that the CSL can be enhanced by increasing the thickness of the ITO layer and resistivity of the n-GaN layer,or by reducing the resistivity of the ITO layer and thickness of the n-GaN layer.The results provide theoretical support for calculating the CSL clearly and directly.For vertical-structure LEDs,the effects of resistivity and thickness of the CSL on the internal quantum efficiency（IQE） have been analyzed.The theoretical expression relating current density and the parameters（resistivity and thickness）of the CSL is obtained,and the results are then verified by simulation.The IQE under different current injection conditions is discussed.The effects of CSL resistivity play a key role at high current injection,and there is an optimal thickness for the largest IQE only at a low current injection.展开更多
We investigate influences of series resistances on the performance of 1.55 μm waveguide-type germanium photodetectors（Ge-PDs） on a silicon-on-insulator substrate. The current-voltage characteristics, responsivities...We investigate influences of series resistances on the performance of 1.55 μm waveguide-type germanium photodetectors（Ge-PDs） on a silicon-on-insulator substrate. The current-voltage characteristics, responsivities,saturation photo-current characteristics, electrical reflection coefficients, and photodetection frequency responses of Ge-PDs, having different series resistances, are measured, and their equivalent circuit models are established. By analyzing the resulting circuit model parameters, we determine how much Ge-PD series resistances influence Ge-PD saturation photo-currents and photodetection bandwidth. These results should be of great use for optimization of Ge-PD fabrication processes and device parameters for target applications.展开更多
The seemingly useless reeds are prepared as thermal insulation materials,which not only meet the requirements of environmental sustainability but also enhance the added value of reeds,creating new economic benefits.Th...The seemingly useless reeds are prepared as thermal insulation materials,which not only meet the requirements of environmental sustainability but also enhance the added value of reeds,creating new economic benefits.The hydrophobicity of raw biomass surfaces leads to problems such as weak bonding strength and non-dense structure in the formed materials,as well as issues related to the residual insect infestations on the surface.In this study,reed straw was used as the raw material,and foamed geopolymer was used as the binder to prepare building insulation materials based reed.To improve the interfacial adhesion performance between reed straw and foamed geopolymer,a thermochemical modification method-thermal carbonization,was proposed.In this study,the mechanical properties and hydraulic properties of the studied materials with different degrees of surface thermal modification were tested,especially the fire resistance performance,and weathering resistance performance rarely found in published literature.When the surface thermal modification condition of reed straw was 250℃(30 min),the comprehensive performance of reed-based building insulation materials was the best,when the studied material density was 321.3 kg/m^(3);the compressive strength was 0.59 MPa;the thermal conductivity was 0.101 W/(m·K);the pH was 11.27;the moisture absorption rate was 25.1%,and the compressive strength loss rate in wet-dry cycles was 18.5%.In addition,it had excellent fire resistance performance and weathering resistance performance.This new material can be widely used to improve the thermal insulation of traditional buildings and as sandwich filler in prefabricated buildings,such as preparing insulating walls.展开更多
The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, ...The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5 % cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density （MDD） and a higher optimum moisture content （OMC）. Moreover, the unconfined compressive strength （UCS）, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pave- ment design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% （5 % cement content in the mixture）. Furthermore, it needs to be noted that the cement treated aggre- gate which contains crushed clay bricks should be cautiously used in the cold region due to its insuffi- cient frost resistance performance.展开更多
基金supported by the Zhejiang Provincial Natural Science Foundation of China under Grant No.LTGG23E080001Scientific Research Foundation of Hangzhou City University under Grant Nos.X-202107 and X-202109Zhejiang Engineering Research Center of Intelligent Urban Infrastructure under Grant No.IUI2023-ZD-14.
文摘This article provides an overview of the current development status of prestressed segmental precast and assembled piers,Emphasis was placed on analyzing the stress characteristics of bridge piers under impact.The concept of recoverable functional design and its application prospects were elaborated,and finally,the research on the impact resistance performance of prestressed segmental precast and assembled pierswas discussed.Research has shown that optimizing design and material selection can effectively enhance the impact resistance and structural durability of bridge piers.At the same time,the introduction of the concept of recoverable functionality provides new ideas for the rapid repair and functional recovery of bridge piers,which helps to improve the recovery efficiency of bridges after extreme events.Future research should focus on the evaluation methods of impact resistance performance,new connection technologies,in-depth application of recoverable functional design,a combination of impact simulation experiments and numerical analysis,and exploration of comprehensive disaster prevention and reduction strategies.These research results will also promote the further development and innovation of prefabricated assembly technology in bridge engineering,bringing new ideas and methods to the field of engineering construction.
文摘This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.
基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20200494)China Postdoctoral Science Foundation(Grant No.2021M701725)+3 种基金Jiangsu Postdoctoral Research Funding Program(Grant No.2021K522C)Fundamental Research Funds for the Central Universities(Grant No.30919011246)National Natural Science Foundation of China(Grant No.52278188)Natural Science Foundation of Jiangsu Province(Grant No.BK20211196)。
文摘To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn.
基金Department of Transportation in Hubei Province,China and Headguarters of Ma-Wu Expressway in Hubei Province for its financial support of this work.
文摘Granite is well known as an acid aggregate. An active mineral filler produced in the laboratory is first used as an anti-stripping filler in the granite asphalt concrete. Four aggregate gradations were chosen in this study,and the effects of the active mineral filler and aggregates on the rutting resistance performance and fatigue properties of granite asphalt concrete were investigated by means of rutting test and four-point bending fatigue test. The results indicate that the dynamic stability of granite asphalt concrete increase significantly with the addition of active mineral filler and the fatigue properties can also be improved especially at lower strain level. Meanwhile,the results demonstrate that granite asphalt concrete has better rutting resistance performance and fatigue properties than limestone asphalt concrete.
基金This work was supported by the Shandong Natural Science Foundation(Grant No.ZR2022ME008)the Shenzhen Science and Technology Program(KCXFZ20201221173409026)+2 种基金the Young Scholars Program of Shandong University(YSPSDU,No.2018WLJH73)the Open Project of State Key Laboratory of Clean Energy Utilization,Zhejiang University(Program No.ZJUCEU2020011)the Shandong Natural Science Foundation(Grant No.ZR2021ME118).
文摘In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.
文摘The resistance performance and motion stability of deep sea remotely operated vehicles(ROVs)subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method combined with the six-degree-of-freedom equation of motion to quickly and accurately predict them.In the modeling process,we consider the complexity of ROV geometry and thus reduce the model to a series of regular geometries to maximize the position and weight of the original components.The grid and value slots of an ROV are divided,and the surface is reconstructed.The forward,backward,transverse,floating,and submerged resistance of ROVs are simulated and compared with existing experimental forces to determine the accuracy of the calculation method.Then,the oblique navigation of the ROV on the horizontal and vertical planes is studied.Furthermore,the motion response of the ROV to direct horizontal motion,heave,pitch,and yaw are studied.The force,moment,and motion time curves are obtained.The stability of ROV motion is analyzed to provide technical support for the safety of ROVs.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CBA00602,2010CB934200,2011CB921804,2011CB707600,2011AA010401,and 2011AA010402the National Natural Science Foundation of China under Grant Nos61322408,61334007,61376112,61221004,61274091,61106119,61106082,and 61006011
文摘We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.
基金Projects(42106051,42006046,U2106206) supported by the National Natural Science Foundation of ChinaProject(22373501D) supported by Hebei Provincial Key R&D Program,China。
文摘Copper is a versatile material,commonly utilized in power transmission and electronic devices,but its relative high reactivity necessitates a long-lasting protective technique.Here,we report a method that combines plasma-enhanced non-equilibrium magnetron sputtering physical vapor deposition(PEUMS-PVD)and anodization to construct a self-healing three-dimensional Ti/Al-doped TiO_(2)nanotubes/Ti_(3)AlC_(2)coating on the surface of Cu substrates.This novel strategy enhances the corrosion resistance of copper substrates in marine environments,with corrosion current densities of up to 4.5643×10^(−8)A/cm^(2).Among them,the doping of nano-aluminum particles makes the coating self-healing.The mechanistic analysis of the corrosion behaviors during early immersion experiments was conducted using electrochemical noise,and revealed that during the initial stages of coating immersion,uniform corrosion predominates,with a minor occurrence of localized corrosion.
基金supported by the National Eleventh Five-Year Pre-research Project of China (No.51302060203)
文摘Inorganic buffer layers such as SiO2 or TiO2 and transparent conductive indium-tin-oxide （ITO） films were prepared on polyethylene terephthalate （PET） substrates by ion assisted deposition （IAD） at room temperature, and the effects of SiO2 and TiOzon the bending resistance performance of flexible ITO films were investigated. The results show that ITO films with SiO2 or TiO2 buffer layer have better resistance stabilities compared to ones without the buffer layer when the ITO films are inwards bent at a bending radius more than 1.2 cm and when the ITO films are outwards bent at a bending radius from 0.8 cm to 1.2 cm. 1TO films with SiO2 buffer layer have better resistance sta- bilities compared to ones with TiO2 buffer layer after the ITO fdms are bent several hundreds of cycles at the same bending radius, for the adhesion of SiO2 is stronger than that of TiO2. The compressive stress resulted from inward bending leads to the formation of more defects in the ITO films compared with the tensile stress arising from outward bending. SiO2 and TiO2 buffer layers can effectively improve the crystallinity of ITO films in （400）, （440） directions.
基金This project is supported by National Innovation Foundation for TechnologyBased Firms, China (No.01C26213300872).
文摘The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.
文摘Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.
基金supported by the National Natural Science Foundation of China (No. 51176190)
文摘In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter. The filling ratio is50%. The visualization investigation is conducted to observe the oscillation and circulation flow in the CLPHP. In order to investigate the effects of inclination angles to thermal performance in the ammonia CLPHP, four case tests are studied. The trends of temperature fluctuation and thermal resistance as the input power increases at different inclination angles are highlighted. The results show that it is very easy to start up and circulate for the ammonia CLPHP at an inclining angle.The thermal resistance is low to 0.02 K/W, presenting that heat fluxes can be transferred from heating section to cooling section very quickly. It is found that the thermal resistance decreases as the inclination angle increases. At the horizontal operation, the ammonia CLPHP can be easy to start up at low input power, but hard to circulate. In this case, once the input power is high,the capillary tube in heating section will be burnt out, leading to worse thermal performance with high thermal resistance.
基金Funded by Key Project of Shanghai Science and Technology Committee(10 jc140620011320501200)
文摘[Objective]This experiment was conducted on Pseudosciaena crocea to study the effects of mannan oligosaccharides on growth and antibacterial ability. [Method]1 500 experimental fishes were divided into five groups. The control group（ C） contained no mannan oligosaccharides,the treatment groups were contained 100,200,400,800 mg /kg of konjac mannan oligosaccharides in basal diet,respectively. The experiment continued 4 months. [Result]The results showed that Konjac Mannan oligosaccharides could significantly improve weight gain Pseudosciaena crocea. Compared with control group,Test 2 group intestine protease activity increased by 45. 74%,hepatopancreatic lipase activity increased by 31. 37%,amylase activity increased by 27. 16%. Comparison with the control group,the test group serum SOD activity was significantly higher than that in the control group（ P 〈0. 05）. Lysozyme（ LZM） activity,spleen and serum test group was significantly higher than that in the control group（ P 〈0.05）. Pseudosciaena crocea were infected by Anguillarum,compared with control group,the survival rate is higher than that of the control group（ P 〈0. 05） when the dosage of 200 mg /kg,400 mg /kg. [Conclusion]According to the test results,the Konjac Mannan oligosaccharides in the basal diet suitable dosage were 200 mg /kg.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2014AA032608)the National Natural Science Foundation of China(Grant No.61404101)the China Postdoctoral Science Foundation(Grant No.2014M562415)
文摘We have investigated the factors affecting the current spreading length（CSL） in GaN-based light-emitting diodes（LEDs） by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LEDs,the effects of both indium tin oxide（ITO） and n-GaN are taken into account for the first time,and a new Q factor is introduced to explain the effects of different current flow paths on the CSL.The calculations and simulations show that the CSL can be enhanced by increasing the thickness of the ITO layer and resistivity of the n-GaN layer,or by reducing the resistivity of the ITO layer and thickness of the n-GaN layer.The results provide theoretical support for calculating the CSL clearly and directly.For vertical-structure LEDs,the effects of resistivity and thickness of the CSL on the internal quantum efficiency（IQE） have been analyzed.The theoretical expression relating current density and the parameters（resistivity and thickness）of the CSL is obtained,and the results are then verified by simulation.The IQE under different current injection conditions is discussed.The effects of CSL resistivity play a key role at high current injection,and there is an optimal thickness for the largest IQE only at a low current injection.
基金supported in part by the National Research Foundation of Korea through the Korean Ministry of Science,ICTFuture Planning under Grant No.2015R1A2A2A01007772in part by the Materials and Parts Technology Research and Development Program through the Korean Ministry of Trade,Industry & Energy under Project No.10065666
文摘We investigate influences of series resistances on the performance of 1.55 μm waveguide-type germanium photodetectors（Ge-PDs） on a silicon-on-insulator substrate. The current-voltage characteristics, responsivities,saturation photo-current characteristics, electrical reflection coefficients, and photodetection frequency responses of Ge-PDs, having different series resistances, are measured, and their equivalent circuit models are established. By analyzing the resulting circuit model parameters, we determine how much Ge-PD series resistances influence Ge-PD saturation photo-currents and photodetection bandwidth. These results should be of great use for optimization of Ge-PD fabrication processes and device parameters for target applications.
基金supported by the National Natural Science Foundation of China(No.52076070,No.52008166)the Natural Science Foundation of Hunan Province(No.2021JJ30256,No.2022JJ30139)。
文摘The seemingly useless reeds are prepared as thermal insulation materials,which not only meet the requirements of environmental sustainability but also enhance the added value of reeds,creating new economic benefits.The hydrophobicity of raw biomass surfaces leads to problems such as weak bonding strength and non-dense structure in the formed materials,as well as issues related to the residual insect infestations on the surface.In this study,reed straw was used as the raw material,and foamed geopolymer was used as the binder to prepare building insulation materials based reed.To improve the interfacial adhesion performance between reed straw and foamed geopolymer,a thermochemical modification method-thermal carbonization,was proposed.In this study,the mechanical properties and hydraulic properties of the studied materials with different degrees of surface thermal modification were tested,especially the fire resistance performance,and weathering resistance performance rarely found in published literature.When the surface thermal modification condition of reed straw was 250℃(30 min),the comprehensive performance of reed-based building insulation materials was the best,when the studied material density was 321.3 kg/m^(3);the compressive strength was 0.59 MPa;the thermal conductivity was 0.101 W/(m·K);the pH was 11.27;the moisture absorption rate was 25.1%,and the compressive strength loss rate in wet-dry cycles was 18.5%.In addition,it had excellent fire resistance performance and weathering resistance performance.This new material can be widely used to improve the thermal insulation of traditional buildings and as sandwich filler in prefabricated buildings,such as preparing insulating walls.
基金supports from the program for New Century Excellent Talents in University,Ministry of Education of China (No.NCET -08-0748 )the Special Fund for Scientific Research of Central Colleges , Chang'an University ( No. CHD2011TD014 )Traffic Science and Technology Talents Training Plan , Ministry of Transport of China ( No . 2012-16 )
文摘The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5 % cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density （MDD） and a higher optimum moisture content （OMC）. Moreover, the unconfined compressive strength （UCS）, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pave- ment design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% （5 % cement content in the mixture）. Furthermore, it needs to be noted that the cement treated aggre- gate which contains crushed clay bricks should be cautiously used in the cold region due to its insuffi- cient frost resistance performance.
