In this study,the corrosion behavior of the CuAl-NiC abradable seal coating system in chloride solution was investigated to systematically research the effect of porosity,multiphase,and multilayer structure on the cor...In this study,the corrosion behavior of the CuAl-NiC abradable seal coating system in chloride solution was investigated to systematically research the effect of porosity,multiphase,and multilayer structure on the corrosion failure.Through the composition and structure analysis,the corrosion process of the system was predicted and then verified with mercury intrusion porosimetry,cross-section SEM/EDS analysis,and electrochemical measurements.The results demonstrated that the interphase selective corrosion caused the porosity of the top layer to decrease first and then increase during the corrosion development.The interlayer galvanic corrosion,determined by the pore connectivity,is crucial for corrosion failure.展开更多
Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstr...Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstructed via computed tomography had satisfactory biocompatibility. However, the reverse modeling scaffolds were inflexible for customized design. Therefore, a top-down designing biomimetic bone scaffold with favorable mechanical performances and cytocompatibility is urgently demanded for orthopedic implants. An emerging additive manufacturing technique, selective laser melting, was employed to fabricate the trabecular-like porous Ti-6Al-4 V scaffolds with varying irregularities(0.05-0.5) and porosities(48.83%–74.28%) designed through a novel Voronoi-Tessellation based method. Micro-computed tomography and scanning electron microscopy were used to characterize the scaffolds’ morphology.Quasi-static compression tests were performed to evaluate the scaffolds’ mechanical properties. The MG63 cells culture in vitro experiments, including adhesion, proliferation, and differentiation, were conducted to study the cytocompatibility of scaffolds. Compressive tests of scaffolds revealed an apparent elastic modulus range of 1.93–5.24 GPa and an ultimate strength ranging within 44.9–237.5 MPa, which were influenced by irregularity and porosity, and improved by heat treatment. Furthermore, the in vitro assay suggested that the original surface of the SLM-fabricated scaffolds was favorable for osteoblasts adhesion and migration because of micro scale pores and ravines. The trabecular-like porous scaffolds with full irregularity and higher porosity exhibited enhanced cells proliferation and osteoblast differentiation at earlier time, due to their preferable combination of small and large pores with various shapes. This study suggested that selective laser melting-derived Ti-6Al-4 V scaffold with the trabecular-like porous structure designed through Voronoi-Tessellation method, favorable mechanical performance, and good cytocompatibility was a potential biomaterial for orthopedic implants.展开更多
Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improveme...Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks.展开更多
3-RRR planar parallel robots are utilized for solving precise material-handling problems in industrial automation applications.Thus,robust and stable control is required to deliver high accuracy in comparison to the s...3-RRR planar parallel robots are utilized for solving precise material-handling problems in industrial automation applications.Thus,robust and stable control is required to deliver high accuracy in comparison to the state of the art.The operation of the mechanism is achieved based on three revolute(3-RRR)joints which are geometrically designed using an open-loop spatial robotic platform.The inverse kinematic model of the system is derived and analyzed by using the geometric structure with three revolute joints.The main variables in our design are the platform base positions,the geometry of the joint angles,and links of the 3-RRR planar parallel robot.These variables are calcula ted based on Cayley-Menger determinants and bilateration to det ermine the final position of the platform when moving and placing objects.Additionally,a proposed fractional order proportional integral derivative(FOPID)is optimized using the bat optimization algorithm to control the path tracking of the center of the 3-RRR planar parallel robot.The design is compared with the state of the art and simulated using the Matlab environment to validate the effectiveness of the proposed controller.Furthermore,real-time implementation has been tested to prove that the design performance is practical.展开更多
Passive acoustic monitoring is emerging as a promising solution to the urgent, global need for new biodiversity assessment methods. The ecological relevance of the soundscape is increasingly recognised, and the afford...Passive acoustic monitoring is emerging as a promising solution to the urgent, global need for new biodiversity assessment methods. The ecological relevance of the soundscape is increasingly recognised, and the affordability of robust hardware for remote audio recording is stimulating international interest in the potential for acoustic methods for biodiversity monitoring.The scale of the data involved requires automated methods,however, the development of acoustic sensor networks capable of sampling the soundscape across time and space and relaying the data to an accessible storage location remains a significant technical challenge, with power management at its core. Recording and transmitting large quantities of audio data is power intensive,hampering long-term deployment in remote, off-grid locations of key ecological interest. Rather than transmitting heavy audio data, in this paper, we propose a low-cost and energy efficient wireless acoustic sensor network integrated with edge computing structure for remote acoustic monitoring and in situ analysis.Recording and computation of acoustic indices are carried out directly on edge devices built from low noise primo condenser microphones and Teensy microcontrollers, using internal FFT hardware support. Resultant indices are transmitted over a ZigBee-based wireless mesh network to a destination server.Benchmark tests of audio quality, indices computation and power consumption demonstrate acoustic equivalence and significant power savings over current solutions.展开更多
Triboelectric nanogenerators(TENGs)have potential to achieve energy harvesting and condition monitoring of oils,the“lifeblood”of industry.However,oil absorption on the solid surfaces is a great challenge for oil-sol...Triboelectric nanogenerators(TENGs)have potential to achieve energy harvesting and condition monitoring of oils,the“lifeblood”of industry.However,oil absorption on the solid surfaces is a great challenge for oil-solid TENG(O-TENG).Here,oleophobic/superamphiphobic O-TENGs are achieved via engineering of solid surface wetting properties.The designed O-TENG can generate an excellent electricity(with a charge density of 9.1μC m^(−2) and a power density of 1.23 mW m^(−2)),which is an order of magnitude higher than other O-TENGs made from polytetrafluoroethylene and polyimide.It also has a significant durability(30,000 cycles)and can power a digital thermometer for self-powered sensor applications.Further,a superhigh-sensitivity O-TENG monitoring system is successfully developed for real-time detecting particle/water contaminants in oils.The O-TENG can detect particle contaminants at least down to 0.01 wt%and water contaminants down to 100 ppm,which are much better than previous online monitoring methods(particle>0.1 wt%;water>1000 ppm).More interesting,the developed O-TENG can also distinguish water from other contaminants,which means the developed O-TENG has a highly water-selective performance.This work provides an ideal strategy for enhancing the output and durability of TENGs for oil-solid contact and opens new intelligent pathways for oil-solid energy harvesting and oil condition monitoring.展开更多
In vehicle ad-hoc networks(VANETs),the proliferation of wireless communication will give rise to the heterogeneous access environment where network selection becomes significant.Motivated by the self-adaptive paradigm...In vehicle ad-hoc networks(VANETs),the proliferation of wireless communication will give rise to the heterogeneous access environment where network selection becomes significant.Motivated by the self-adaptive paradigm of cellular attractors,this paper regards an individual communication as a cell,so that we can apply the revised attractor selection model to induce each connected vehicle.Aiming at improving the Quality of Service(QoS),we presented the bio-inspired handover decision-making mechanism.In addition,we employ the Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)for any vehicle to choose an access network.This paper proposes a novel framework where the bio-inspired mechanism is combined with TOPSIS.In a dynamic and random mobility environment,our method achieves the coordination of performance of heterogeneous networks by guaranteeing the efficient utilization and fair distribution of network resources in a global sense.The experimental results confirm that the proposed method performs better when compared with conventional schemes.展开更多
Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resista...Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resistance and low wear endurance became a fatal demerit in practical applications. In order to overcome these issues of high strength aluminum alloys, high density plasma nitriding is proposed as an effective surface treatment for duralumin. This process has a capability to control the RF- and DC-plasmas independently for nitriding. This enables us to temporally control and describe the plasma state by in-situ plasma diagnosis. This plasma diagnosis was instrumented to search for optimum processing condition to plasma nitriding the duralumin alloys of type A2011. Both type A2011 aluminum alloy plates and pipes were employed to describe the inner nitriding behavior for hardening the duralumin alloys by the present plasma nitriding.展开更多
MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At pre...MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.展开更多
Accurate localization is paramount for unmanned aerial vehicles (UAVs) spanning various technical and industrial domains, necessitating a comprehensive assessment of global navigation satellite system (GNSS) precision...Accurate localization is paramount for unmanned aerial vehicles (UAVs) spanning various technical and industrial domains, necessitating a comprehensive assessment of global navigation satellite system (GNSS) precision. This study investigates the performance of distinct GNSS constellations in determining the precise location of a building utilizing a high-precision GNSS receiver. The receiver, incorporating advanced multi-frequency and full-constellation positioning capabilities, was integrated with a smartphone via Bluetooth to enable the UAV’s acquisition of centimeter-level positioning data. Sequential utilization of single satellite systems—such as GPS-only, GLONASS-only, Galileo-only, SBAS-only, and BeiDou-only—facilitated the documentation of latitude and longitude coordinates for the designated building. Subsequent comparison of these coordinates with a specialized Geographic Information System (GIS) was conducted to evaluate their positional accuracy. The comparative analysis underscores significant variability in the precision offered by each satellite constellation, providing valuable insights for optimizing UAV navigation across GIS, IoT, construction, and other sectors requiring high-precision localization. This research underscores the significance of high-precision GNSS receivers in enhancing UAV-based geospatial assessments, emphasizing the critical selection of appropriate satellite systems for tailored localization tasks. The study contributes to advancing UAV navigation strategies, ensuring robust and accurate geospatial data collection within diverse operational frameworks.展开更多
Dynamic channel assignment(DCA)is significant for extending vehicular ad hoc network(VANET)capacity and mitigating congestion.However,the un-known global state information and the lack of centralized control make chan...Dynamic channel assignment(DCA)is significant for extending vehicular ad hoc network(VANET)capacity and mitigating congestion.However,the un-known global state information and the lack of centralized control make channel assignment performances a challenging task in a distributed vehicular direct communication scenario.In our preliminary field test for communication under V2X scenario,we find that the existing DCA technology cannot fully meet the communication performance requirements of VANET.In order to improve the communication performance,we firstly demonstrate the feasibility and potential of reinforcement learning(RL)method in joint channel selection decision and access fallback adaptation design in this paper.Besides,a dual reinforcement learning(DRL)-based cooperative DCA(DRL-CDCA)mechanism is proposed.Specifically,DRL-CDCA jointly optimizes the decision-making behaviors of both the channel selection and back-off adaptation based on a multi-agent dual reinforcement learning framework.Besides,nodes locally share and incorporate their individual rewards after each communication to achieve regional consistency optimization.Simulation results show that the proposed DRL-CDCA can better reduce the one-hop packet delay,improve the packet delivery ratio on average when compared with two other existing mechanisms.展开更多
In this paper, a multi-sensory quality evaluation using an array of instruments to measure different sensory qualities is established via communication network. The network is used to transmit quality data to evaluati...In this paper, a multi-sensory quality evaluation using an array of instruments to measure different sensory qualities is established via communication network. The network is used to transmit quality data to evaluation computer. And the network-induced delays between instruments and computer may have negative influence on final evaluation results. The main goal of this paper is to analyze network delays’ influence on evaluation results, and present a fuzzy-logic based solution to eliminate the impact and improve the precision of evaluation. And simulations are conducted to show the effectiveness of the proposed approach.展开更多
It has been shown before that liquids can slip at a solid boundary,which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid flow.T...It has been shown before that liquids can slip at a solid boundary,which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid flow.The amount of slip at the wall depends on the surface tension at the liquid-solid interface,which in turn depends on the chemical state of the surface and its roughness.In the present study a heterogeneous surface was obtained by coating half of a circular glass disc with a coating repellant to glycerol.A rotating glass disc was placed at a known/calibrated distance and the gap was filled with glycerol.With the mobile surface moving from the direction of slip to non-slip region it can be theoretically shown that a pressure build up can be achieved.The pressure gradient in the two regions is constant,similar to that in a Rayleigh step bearing,with the maximum pressure at the separation line.The heterogeneous disc was placed on a holder supported by a load cell thus the force generated by this pressure increase can be measured accurately.Tests were carried out at different sliding speeds and gaps and the load carried was measured and subsequently compared with theoretical calculations.This allowed the slip coefficient to be evaluated.展开更多
Purpose–The motion control of unmanned ground vehicles(UGV)is a challenge in the industry of automation.The purpose of this paper is to propose a fuzzy inference system(FIS)based on sensory information for solving th...Purpose–The motion control of unmanned ground vehicles(UGV)is a challenge in the industry of automation.The purpose of this paper is to propose a fuzzy inference system(FIS)based on sensory information for solving the navigation challenge of UGV in cluttered and dynamic environments.Design/methodology/approach–The representation of the dynamic environment is a key element for the operational field and for the testing of the robotic navigation system.If dynamic obstacles move randomly in the operation field,the navigation problem becomes more complicated due to the coordination of the elements for accurate navigation and collision-free path within the environmental representations.This paper considers the construction of the FIS,which consists of two controllers.The first controller uses three sensors based on the obstacles distances from the front,right and left.The second controller employs the angle difference between the heading of the vehicle and the targeted angle to obtain the optimal route based on the environment and reach the desired destination with minimal running power and delay.The proposed design shows an efficient navigation strategy that overcomes the current navigation challenges in dynamic environments.Findings–Experimental analyses are conducted for three different scenarios to investigate the validation and effectiveness of the introduced controllers based on the FIS.The reported simulation results are obtained using MATLAB software package.The results show that the controllers of the FIS consistently perform the manoeuvring task and manage the route plan efficiently,even in a complex environment that is populated with dynamic obstacles.The paper demonstrates that the destination was reached optimally using the shortest free route.Research limitations/implications–The paper represents efforts toward building a dynamic environment filled with dynamic obstacles that move at various speeds and directions.The methodology of designing the FIS is accomplished to guide the UGV to the desired destination while avoiding collisions with obstacles.However,the methodology is approached using two-dimensional analyses.Hence,the paper suggests several extensions and variations to develop a three-dimensional strategy for further improvement.Originality/value–This paper presents the design of a FIS and its characterizations in dynamic environments,specifically for obstacles that move at different velocities.This facilitates an improved functionality of the operation of UGV.展开更多
The morphological quantification of the proximal tibia of the knee joint is important in knee replacement.Accurate knowledge of these parameters provides the basis for design of the tibial prosthesis and its fixation....The morphological quantification of the proximal tibia of the knee joint is important in knee replacement.Accurate knowledge of these parameters provides the basis for design of the tibial prosthesis and its fixation.Ideally,a prosthesis that is suitable for the morphological characteristics of Chinese knees is needed.In this paper,a deep learning automatic network framework is designed to achieve automatic segmentation and automatic quantitative analysis of magnetic resonance images of the tibia.An enhanced feature fusion network structure is designed,including high and low-level feature fusion path modules to create accurate segmentation of the tibia.A new method of extracting feature points and lines from outline contours of the proximal tibia is designed to automatically calculate six clinical morphological linear parameters of the tibia in real-time.The final result is an automatic visualisation of the tibial contour and automated extraction of tibial morphometric parameters.Validation of the results from our system against a gold standard obtained by manual processing by expert clinicians showed the Dice coefficient to be 0.97,the accuracy to be 0.98,and the correlation coefficients for all six morphological parameters of the automatic quantification of the tibia are above 0.96.The gender-specific study found that the values of the proximal tibial linear parameters of internal and external tibial diameter,anterior and posterior diameter,lateral plateau length,lateral plateau width,medial plateau length,and medial plateau width in male patients are significantly greater than in female patients(all P values<0.01).The results enrich the use of deep learning in medicine,providing orthopaedic specialists with a valuable and intelligent quantitative tool that can assess the progression and changes in osteoarthritis of the knee joint.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51671198)。
文摘In this study,the corrosion behavior of the CuAl-NiC abradable seal coating system in chloride solution was investigated to systematically research the effect of porosity,multiphase,and multilayer structure on the corrosion failure.Through the composition and structure analysis,the corrosion process of the system was predicted and then verified with mercury intrusion porosimetry,cross-section SEM/EDS analysis,and electrochemical measurements.The results demonstrated that the interphase selective corrosion caused the porosity of the top layer to decrease first and then increase during the corrosion development.The interlayer galvanic corrosion,determined by the pore connectivity,is crucial for corrosion failure.
基金Acknowledgements The authors wish to express their thanks to the following organisations which have supported this research work. The Engineering and Physical Sciences Research Council, Rolls-Royce Plc,the European Union and participating companies in the ICAS-GT2 （Flow and Heat Transfer in the Rotating Cooling Air Systems of Gas Turbines 2） programme of research, funded by the 5th Framework of the GR0WTH programme of the European Union. We are also grateful to Mr. Nicolas Mich6 for operating the test rig.
基金financially supported by the Advanced Research Project of Army Equipment Development (No. 301020803)the Key Research and Development Program of Jiangsu (No. BE 2015161)+3 种基金the Young Scientists Fund of the National Natural Science Foundation of China (No. 51605473)the Jiangsu Provincial Research Foundation for Basic Research, China (No. BK 20161476)the Science and Technology Planning Project of Jiangsu Province of China (No. BE 2015029)the Science and Technology Support Program of Jiangsu (Nos. BE 2014009-1, BE 2014009-2 and BE 2016010-3)
文摘Porous metal scaffolds play an important role in the orthopedic field, due to their wide applications in prostheses implantation. Some previous studies showed that the scaffolds with trabecular bone structure reconstructed via computed tomography had satisfactory biocompatibility. However, the reverse modeling scaffolds were inflexible for customized design. Therefore, a top-down designing biomimetic bone scaffold with favorable mechanical performances and cytocompatibility is urgently demanded for orthopedic implants. An emerging additive manufacturing technique, selective laser melting, was employed to fabricate the trabecular-like porous Ti-6Al-4 V scaffolds with varying irregularities(0.05-0.5) and porosities(48.83%–74.28%) designed through a novel Voronoi-Tessellation based method. Micro-computed tomography and scanning electron microscopy were used to characterize the scaffolds’ morphology.Quasi-static compression tests were performed to evaluate the scaffolds’ mechanical properties. The MG63 cells culture in vitro experiments, including adhesion, proliferation, and differentiation, were conducted to study the cytocompatibility of scaffolds. Compressive tests of scaffolds revealed an apparent elastic modulus range of 1.93–5.24 GPa and an ultimate strength ranging within 44.9–237.5 MPa, which were influenced by irregularity and porosity, and improved by heat treatment. Furthermore, the in vitro assay suggested that the original surface of the SLM-fabricated scaffolds was favorable for osteoblasts adhesion and migration because of micro scale pores and ravines. The trabecular-like porous scaffolds with full irregularity and higher porosity exhibited enhanced cells proliferation and osteoblast differentiation at earlier time, due to their preferable combination of small and large pores with various shapes. This study suggested that selective laser melting-derived Ti-6Al-4 V scaffold with the trabecular-like porous structure designed through Voronoi-Tessellation method, favorable mechanical performance, and good cytocompatibility was a potential biomaterial for orthopedic implants.
文摘Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks.
文摘3-RRR planar parallel robots are utilized for solving precise material-handling problems in industrial automation applications.Thus,robust and stable control is required to deliver high accuracy in comparison to the state of the art.The operation of the mechanism is achieved based on three revolute(3-RRR)joints which are geometrically designed using an open-loop spatial robotic platform.The inverse kinematic model of the system is derived and analyzed by using the geometric structure with three revolute joints.The main variables in our design are the platform base positions,the geometry of the joint angles,and links of the 3-RRR planar parallel robot.These variables are calcula ted based on Cayley-Menger determinants and bilateration to det ermine the final position of the platform when moving and placing objects.Additionally,a proposed fractional order proportional integral derivative(FOPID)is optimized using the bat optimization algorithm to control the path tracking of the center of the 3-RRR planar parallel robot.The design is compared with the state of the art and simulated using the Matlab environment to validate the effectiveness of the proposed controller.Furthermore,real-time implementation has been tested to prove that the design performance is practical.
文摘Passive acoustic monitoring is emerging as a promising solution to the urgent, global need for new biodiversity assessment methods. The ecological relevance of the soundscape is increasingly recognised, and the affordability of robust hardware for remote audio recording is stimulating international interest in the potential for acoustic methods for biodiversity monitoring.The scale of the data involved requires automated methods,however, the development of acoustic sensor networks capable of sampling the soundscape across time and space and relaying the data to an accessible storage location remains a significant technical challenge, with power management at its core. Recording and transmitting large quantities of audio data is power intensive,hampering long-term deployment in remote, off-grid locations of key ecological interest. Rather than transmitting heavy audio data, in this paper, we propose a low-cost and energy efficient wireless acoustic sensor network integrated with edge computing structure for remote acoustic monitoring and in situ analysis.Recording and computation of acoustic indices are carried out directly on edge devices built from low noise primo condenser microphones and Teensy microcontrollers, using internal FFT hardware support. Resultant indices are transmitted over a ZigBee-based wireless mesh network to a destination server.Benchmark tests of audio quality, indices computation and power consumption demonstrate acoustic equivalence and significant power savings over current solutions.
基金want to thank Swedish Kempe Scholarship Project(No.JCK-1903.1)the Swedish Research Council for Environment,Agricultural Sciences and Spatial Planning(Formas,No.2019-00904)+1 种基金the Swedish Research Council(No.2019-04941)and the National Natural Science Foundation of China(Grant No.51905027).
文摘Triboelectric nanogenerators(TENGs)have potential to achieve energy harvesting and condition monitoring of oils,the“lifeblood”of industry.However,oil absorption on the solid surfaces is a great challenge for oil-solid TENG(O-TENG).Here,oleophobic/superamphiphobic O-TENGs are achieved via engineering of solid surface wetting properties.The designed O-TENG can generate an excellent electricity(with a charge density of 9.1μC m^(−2) and a power density of 1.23 mW m^(−2)),which is an order of magnitude higher than other O-TENGs made from polytetrafluoroethylene and polyimide.It also has a significant durability(30,000 cycles)and can power a digital thermometer for self-powered sensor applications.Further,a superhigh-sensitivity O-TENG monitoring system is successfully developed for real-time detecting particle/water contaminants in oils.The O-TENG can detect particle contaminants at least down to 0.01 wt%and water contaminants down to 100 ppm,which are much better than previous online monitoring methods(particle>0.1 wt%;water>1000 ppm).More interesting,the developed O-TENG can also distinguish water from other contaminants,which means the developed O-TENG has a highly water-selective performance.This work provides an ideal strategy for enhancing the output and durability of TENGs for oil-solid contact and opens new intelligent pathways for oil-solid energy harvesting and oil condition monitoring.
基金This research was supported in part by the National Natural Science Foundation of China under Grant Nos.61672082 and 61822101Beijing Municipal Natural Science Foundation Nos.4181002Beihang University Innovation&Practice Fund for Graduate(YCSJ-02-2018-05).
文摘In vehicle ad-hoc networks(VANETs),the proliferation of wireless communication will give rise to the heterogeneous access environment where network selection becomes significant.Motivated by the self-adaptive paradigm of cellular attractors,this paper regards an individual communication as a cell,so that we can apply the revised attractor selection model to induce each connected vehicle.Aiming at improving the Quality of Service(QoS),we presented the bio-inspired handover decision-making mechanism.In addition,we employ the Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)for any vehicle to choose an access network.This paper proposes a novel framework where the bio-inspired mechanism is combined with TOPSIS.In a dynamic and random mobility environment,our method achieves the coordination of performance of heterogeneous networks by guaranteeing the efficient utilization and fair distribution of network resources in a global sense.The experimental results confirm that the proposed method performs better when compared with conventional schemes.
文摘Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resistance and low wear endurance became a fatal demerit in practical applications. In order to overcome these issues of high strength aluminum alloys, high density plasma nitriding is proposed as an effective surface treatment for duralumin. This process has a capability to control the RF- and DC-plasmas independently for nitriding. This enables us to temporally control and describe the plasma state by in-situ plasma diagnosis. This plasma diagnosis was instrumented to search for optimum processing condition to plasma nitriding the duralumin alloys of type A2011. Both type A2011 aluminum alloy plates and pipes were employed to describe the inner nitriding behavior for hardening the duralumin alloys by the present plasma nitriding.
文摘MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.
文摘Accurate localization is paramount for unmanned aerial vehicles (UAVs) spanning various technical and industrial domains, necessitating a comprehensive assessment of global navigation satellite system (GNSS) precision. This study investigates the performance of distinct GNSS constellations in determining the precise location of a building utilizing a high-precision GNSS receiver. The receiver, incorporating advanced multi-frequency and full-constellation positioning capabilities, was integrated with a smartphone via Bluetooth to enable the UAV’s acquisition of centimeter-level positioning data. Sequential utilization of single satellite systems—such as GPS-only, GLONASS-only, Galileo-only, SBAS-only, and BeiDou-only—facilitated the documentation of latitude and longitude coordinates for the designated building. Subsequent comparison of these coordinates with a specialized Geographic Information System (GIS) was conducted to evaluate their positional accuracy. The comparative analysis underscores significant variability in the precision offered by each satellite constellation, providing valuable insights for optimizing UAV navigation across GIS, IoT, construction, and other sectors requiring high-precision localization. This research underscores the significance of high-precision GNSS receivers in enhancing UAV-based geospatial assessments, emphasizing the critical selection of appropriate satellite systems for tailored localization tasks. The study contributes to advancing UAV navigation strategies, ensuring robust and accurate geospatial data collection within diverse operational frameworks.
基金Beijing Municipal Natural Science Foundation Nos.L191001 and 4181002the National Natural Science Foundation of China under Grant Nos.61672082 and 61822101the Newton Advanced Fellow-ship under Grant No.62061130221.
文摘Dynamic channel assignment(DCA)is significant for extending vehicular ad hoc network(VANET)capacity and mitigating congestion.However,the un-known global state information and the lack of centralized control make channel assignment performances a challenging task in a distributed vehicular direct communication scenario.In our preliminary field test for communication under V2X scenario,we find that the existing DCA technology cannot fully meet the communication performance requirements of VANET.In order to improve the communication performance,we firstly demonstrate the feasibility and potential of reinforcement learning(RL)method in joint channel selection decision and access fallback adaptation design in this paper.Besides,a dual reinforcement learning(DRL)-based cooperative DCA(DRL-CDCA)mechanism is proposed.Specifically,DRL-CDCA jointly optimizes the decision-making behaviors of both the channel selection and back-off adaptation based on a multi-agent dual reinforcement learning framework.Besides,nodes locally share and incorporate their individual rewards after each communication to achieve regional consistency optimization.Simulation results show that the proposed DRL-CDCA can better reduce the one-hop packet delay,improve the packet delivery ratio on average when compared with two other existing mechanisms.
基金partially supported by National Natural Science Foundation of China,Project No.60274031International Cooperation Project of Science&Technology Commission of Shanghai Municipality,Project No.015107017Building Fund for Doctoral Disciplines of Shanghai Mouicipality
文摘In this paper, a multi-sensory quality evaluation using an array of instruments to measure different sensory qualities is established via communication network. The network is used to transmit quality data to evaluation computer. And the network-induced delays between instruments and computer may have negative influence on final evaluation results. The main goal of this paper is to analyze network delays’ influence on evaluation results, and present a fuzzy-logic based solution to eliminate the impact and improve the precision of evaluation. And simulations are conducted to show the effectiveness of the proposed approach.
文摘It has been shown before that liquids can slip at a solid boundary,which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid flow.The amount of slip at the wall depends on the surface tension at the liquid-solid interface,which in turn depends on the chemical state of the surface and its roughness.In the present study a heterogeneous surface was obtained by coating half of a circular glass disc with a coating repellant to glycerol.A rotating glass disc was placed at a known/calibrated distance and the gap was filled with glycerol.With the mobile surface moving from the direction of slip to non-slip region it can be theoretically shown that a pressure build up can be achieved.The pressure gradient in the two regions is constant,similar to that in a Rayleigh step bearing,with the maximum pressure at the separation line.The heterogeneous disc was placed on a holder supported by a load cell thus the force generated by this pressure increase can be measured accurately.Tests were carried out at different sliding speeds and gaps and the load carried was measured and subsequently compared with theoretical calculations.This allowed the slip coefficient to be evaluated.
文摘Purpose–The motion control of unmanned ground vehicles(UGV)is a challenge in the industry of automation.The purpose of this paper is to propose a fuzzy inference system(FIS)based on sensory information for solving the navigation challenge of UGV in cluttered and dynamic environments.Design/methodology/approach–The representation of the dynamic environment is a key element for the operational field and for the testing of the robotic navigation system.If dynamic obstacles move randomly in the operation field,the navigation problem becomes more complicated due to the coordination of the elements for accurate navigation and collision-free path within the environmental representations.This paper considers the construction of the FIS,which consists of two controllers.The first controller uses three sensors based on the obstacles distances from the front,right and left.The second controller employs the angle difference between the heading of the vehicle and the targeted angle to obtain the optimal route based on the environment and reach the desired destination with minimal running power and delay.The proposed design shows an efficient navigation strategy that overcomes the current navigation challenges in dynamic environments.Findings–Experimental analyses are conducted for three different scenarios to investigate the validation and effectiveness of the introduced controllers based on the FIS.The reported simulation results are obtained using MATLAB software package.The results show that the controllers of the FIS consistently perform the manoeuvring task and manage the route plan efficiently,even in a complex environment that is populated with dynamic obstacles.The paper demonstrates that the destination was reached optimally using the shortest free route.Research limitations/implications–The paper represents efforts toward building a dynamic environment filled with dynamic obstacles that move at various speeds and directions.The methodology of designing the FIS is accomplished to guide the UGV to the desired destination while avoiding collisions with obstacles.However,the methodology is approached using two-dimensional analyses.Hence,the paper suggests several extensions and variations to develop a three-dimensional strategy for further improvement.Originality/value–This paper presents the design of a FIS and its characterizations in dynamic environments,specifically for obstacles that move at different velocities.This facilitates an improved functionality of the operation of UGV.
基金National Natural Science Foundation of China(Project Nos.11772214 and 11972243)supported by the Shanxi Huajin Orthopaedic Public Foundation.
文摘The morphological quantification of the proximal tibia of the knee joint is important in knee replacement.Accurate knowledge of these parameters provides the basis for design of the tibial prosthesis and its fixation.Ideally,a prosthesis that is suitable for the morphological characteristics of Chinese knees is needed.In this paper,a deep learning automatic network framework is designed to achieve automatic segmentation and automatic quantitative analysis of magnetic resonance images of the tibia.An enhanced feature fusion network structure is designed,including high and low-level feature fusion path modules to create accurate segmentation of the tibia.A new method of extracting feature points and lines from outline contours of the proximal tibia is designed to automatically calculate six clinical morphological linear parameters of the tibia in real-time.The final result is an automatic visualisation of the tibial contour and automated extraction of tibial morphometric parameters.Validation of the results from our system against a gold standard obtained by manual processing by expert clinicians showed the Dice coefficient to be 0.97,the accuracy to be 0.98,and the correlation coefficients for all six morphological parameters of the automatic quantification of the tibia are above 0.96.The gender-specific study found that the values of the proximal tibial linear parameters of internal and external tibial diameter,anterior and posterior diameter,lateral plateau length,lateral plateau width,medial plateau length,and medial plateau width in male patients are significantly greater than in female patients(all P values<0.01).The results enrich the use of deep learning in medicine,providing orthopaedic specialists with a valuable and intelligent quantitative tool that can assess the progression and changes in osteoarthritis of the knee joint.
