The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produc...The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.展开更多
The Adaptive Quality Control Phantom (AQCP) is the computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to prod...The Adaptive Quality Control Phantom (AQCP) is the computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce any spatial distribution of gamma rays to perform the QC Tests such as the Collimator Hole Angulation (CHA) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for seven collimators were measured with the method by using a point source and computer-controlled cylindrical positioning. In this method the displacement of the image of a point source examined as the AQCP move point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS, LEUHR, MEGP-250, MEGP-300, MEGP-360 and HEPH collimators of SMV dual heads camera were measured to be 0.290°, 0.292°, 0.208°, 0.194°, 0.181°, 0.177°, 0.150°, respectively. The Root Mean Square (RMS) of CHA for LEGP, MEGP and HEGP collimators of GE Millennium MG were measured to be 0.154°, 0.220° and 0.202° respectively. It is to be added in this connection that the measured RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface +/– 1 mm has been varied +/– 0.04 degree.展开更多
In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrit...In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.展开更多
AIM:To elucidate the safety and visual quality of implantable collamer lens with central hole(ICL V4c)implantation for correcting moderate and high myopia for at least 5y.METHODS:This retrospective study was conducted...AIM:To elucidate the safety and visual quality of implantable collamer lens with central hole(ICL V4c)implantation for correcting moderate and high myopia for at least 5y.METHODS:This retrospective study was conducted on 58 patients(114 eyes)who were followed up for at least 5y after ICL V4c implantation.The observation was done before and on 1d,1mo,1 and 5y or more after the surgical procedure.The visual acuity,subjective refraction,intraocular pressure,vault,axial length,central hole position,pupil diameter,visual quality,and adverse events were analyzed.The visual quality includes aberration,the modulation transfer function cutoff frequency(MTF cutoff),objective scattering index(OSI),Stroller's ratio(SR),and visual quality questionnaire.RESULTS:The average follow-up period was 69.25±3.80mo(range 60–82mo)and the preoperative spherical equivalent(SE)was-8.66±1.97 D.At 5y after operation,the safety index was 1.01±0.02 and the efficacy index was 0.99±0.42 and SE was-0.65±0.63 D.The 59.6%of the eyes achieved an uncorrected distance visual acuity of 20/20,76.3%of the eyes had SE within±1.0 D at the last visit.The axial length increased by 0.29±0.71 mm 5y after the surgery(t=-3.843,P<0.001).The mean vault at the last follow-up was 510.59±245.61μm.The central hole was on the temporal side in 80 eyes(84.2%).The visual quality questionnaire showed that 98.2%patients were satisfied with the surgical procedure.Adverse events occurred in 4 eyes(3.5%),including the posttraumatic toric ICL rotation(2 eyes),iris incarceration(1 eye),and posttraumatic ICL displacement(1 eye)at the last follow-up.CONCLUSION:Long-term ICL V4c implantation is safe,effective,and stable for correcting moderate and to high myopia,and the visual quality with patients is excellent and satisfactory,but the progression of axial length still needs attention after surgery.展开更多
· AIM: To investigate the visual function and the relationship with vision-related quality of life(VRQOL)after macular hole repair surgery.· METHODS: Prospective case series. Thirty-six consecutive eyes in 3...· AIM: To investigate the visual function and the relationship with vision-related quality of life(VRQOL)after macular hole repair surgery.· METHODS: Prospective case series. Thirty-six consecutive eyes in 36 patients who underwent pars plana vitrectomy(PPV) and internal limiting membrane(ILM) peeling were included. The 25-item National Eye Institute Visual Function Questionnaire(VFQ-25) was answered by the participants before and 3 and 12 mo after operation. Follow-up visits examinations included best-corrected visual acuity(BCVA), clinical examination,and central macular thickness(CMT) measured by optical coherence tomography(OCT).·RESULTS: Macular-hole closure was achieved in 35 of36 eyes(97.2%). At baseline and months 3 and 12, the log MAR BCVAs(mean±SD) were 1.15±0.47, 0.68±0.53(P 【0.0001 versus baseline), and 0.55 ±0.49(P 【0.001 versus baseline, P =0.273 versus month 3), respectively; the CMTs(μm) were 330 ±81, 244 ±62(P 【0.001 versus baseline), and 225±58(P 【0.001 versus baseline, P =0.222 versus month 3), respectively; the median preoperative VFQ-25 composite score of 73.50(63.92-81.13) increased postoperatively to 85.50(80.04-89.63) at 3mo(P 【0.001)and 86.73(82.50-89.63) at 12mo(P 【0.001) respectively.The improved BCVA was correlated with improvements in five subscales(r =-0.605 to-0.336, P 【0.001 to P =0.046) at 12 mo.· CONCLUSION: PPV with ILM peeling improved anatomic outcome, visual function, and VRQOL. Theimproved BCVA was an important factor related to the improved VRQOL.展开更多
Revolution radius is one of the significant parameters in orbital drilling,which has great influence on many factors,such as the cutting area of front and side cutting edge,undeformed chip geometry,delamination and bu...Revolution radius is one of the significant parameters in orbital drilling,which has great influence on many factors,such as the cutting area of front and side cutting edge,undeformed chip geometry,delamination and burr at hole exit side,hole surface roughness,cutting tool force and deflection,chip removal and heat transmission.First,the influence of revolution radius on the factors is discussed theoretically in detail.Analysis results show that big revolution radius can reduce axial cutting force,restrain exit delamination and burr,and improve chip removal and heat transmission.Then,single factor test and orthogonal test are utilized in the two processing methods as machining unidiameter holes with several cutting tools and machining different diameter holes with one tool.Finally,the influence of revolution radius on cutting force and hole machining precision is studied.These results provide a profound foundation for future optimization of cutting control parameters.展开更多
Printed circuit boards(PCBs)are representative composite materials,and their high-quality drilling machining remains a persistent challenge in the industry.The finishing of the cutting edge of a microdrill is crucial ...Printed circuit boards(PCBs)are representative composite materials,and their high-quality drilling machining remains a persistent challenge in the industry.The finishing of the cutting edge of a microdrill is crucial to drill performance in machining fine-quality holes with a prolonged tool life.The miniature size involving submicron scale geometric dimensions,a complex flute shape,and low fracture toughness makes the cutting edge of microdrills susceptible to breakage and has been the primary limiting factor in edge preparation for microdrills.In this study,a newly developed cutting edge preparation method for microdrills was tested experimentally on electronic printed circuit boards.The proposed method,namely,shear thickening polishing,limited the cutting edge burrs and chipping on the cutting edge,and this in turn transformed the cutting edge’s radius from being sharp to smooth.Moreover,the edge–edge radius could be regulated by adjusting the processing time.PCB drilling experiments were conducted to investigate the influence of different cutting edge radii on wear,hole position accuracy,nail head value,and hole wall roughness.The proposed approach showed 20%enhancement in hole position accuracy,33%reduction in the nail head value,and 19%reduction in hole wall roughness compared with the original microdrill.However,a threshold is needed;without it,excessive shear thickening polishing will result in a blunt edge,which may accelerate the wear of the microdrill.Wear was identified as the primary factor that reduced hole quality.The study indicates that in printed circuit board machining,microdrills should effectively eliminate grinding defects and maintain the sharpness of the cutting edge as much as possible to obtain excellent drilling quality.Overall,shear thickening polishing is a promising method for cutting edge preparation of microdrills.Further research and optimization can lead to additional improvements in microdrill performance and contribute to the continued advancement of printed circuit board manufacturing.展开更多
A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefin...A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefinite-difference time-domain method,the parameters of the M-PCNC,including cavity thickness and width,lattice constant,and radii and numbers of holes,are optimized,with the quality factor Q and mode volume Vm as performance indicators.Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance.The optimized cavity possesses a high quality factor Q 1.45105 and an ultra-small mode=×volume Vm 0.01(λ/n)[Zeng et al.,Opt Lett 2023:48;3981–3984]in the telecommunications wavelength range.Light can be progres-=sively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure.Thereby,the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.展开更多
Mobile edge caching technology is gaining more and more attention because it can effectively improve the Quality of Experience (QoE) of users and reduce backhaul burden. This paper aims to improve the utility of mobil...Mobile edge caching technology is gaining more and more attention because it can effectively improve the Quality of Experience (QoE) of users and reduce backhaul burden. This paper aims to improve the utility of mobile edge caching technology from the perspectie of caching resource management by examining a network composed of one operator, multiple users and Content Providers (CPs). The caching resource management model is constructed on the premise of fully considering the QoE of users and the servicing capability of the Base Station (BS). In order to create the best caching resource allocation scheme, the original problem is transformed into a multi-leader multi-follower Stackelberg game model through the analysis of the system model. The strategy combinations and the utility functions of players are analyzed. The existence and uniqueness of the Nash Equilibrium (NE) solution are also analyzed and proved. The optimal strategy combinations and the best responses are deduced in detail. Simulation results and analysis show that the proposed model and algorithm can achieve the optimal allocation of caching resource and improve the QoE of users.展开更多
Mobile Edge Computing (MEC) has been considered a promising solution that can address capacity and performance challenges in legacy systems such as Mobile Cloud Computing (MCC). In particular, such challenges include ...Mobile Edge Computing (MEC) has been considered a promising solution that can address capacity and performance challenges in legacy systems such as Mobile Cloud Computing (MCC). In particular, such challenges include intolerable delay, congestion in the core network, insufficient Quality of Experience (QoE), high cost of resource utility, such as energy and bandwidth. The aforementioned challenges originate from limited resources in mobile devices, the multi-hop connection between end-users and the cloud, high pressure from computation-intensive and delay-critical applications. Considering the limited resource setting at the MEC, improving the efficiency of task offloading in terms of both energy and delay in MEC applications is an important and urgent problem to be solved. In this paper, the key objective is to propose a task offloading scheme that minimizes the overall energy consumption along with satisfying capacity and delay requirements. Thus, we propose a MEC-assisted energy-efficient task offloading scheme that leverages the cooperative MEC framework. To achieve energy efficiency, we propose a novel hybrid approach established based on Particle Swarm Optimization (PSO) and Grey Wolf Optimizer (GWO) to solve the optimization problem. The proposed approach considers efficient resource allocation such as sub-carriers, power, and bandwidth for offloading to guarantee minimum energy consumption. The simulation results demonstrate that the proposed strategy is computational-efficient compared to benchmark methods. Moreover, it improves energy utilization, energy gain, response delay, and offloading utility.展开更多
To improve the processing efficiency and the quality of orbital milling hole of aerospace Al-alloy, the big-pitch influence on cutting force and hole quality was studied experimentally. First, a program based on horiz...To improve the processing efficiency and the quality of orbital milling hole of aerospace Al-alloy, the big-pitch influence on cutting force and hole quality was studied experimentally. First, a program based on horizontal lathe was proposed based on kinematics analysis of orbital milling. Then, the cutting force at different stages and the hole quality with different pitches were measured. Results show that the axial force and radial force increase with the pitch amplification during orbital milling. However, the axial force in the orbital milling hole is about 8—10 times smaller than that in the conventional drilling. The diameter error of milling hole is 48—93 μm, and the surface roughness of milling hole is 1.2—1.7 μm. Finally, an orbital milling device with big pitch was designed.展开更多
The magnetisation of heavy holes in III-V semiconductor quantum wells with Rashba spin-orbit coupling (SOC) in an external perpendicular magnetic field is studied theoretically. We concentrate on the effects on the ...The magnetisation of heavy holes in III-V semiconductor quantum wells with Rashba spin-orbit coupling (SOC) in an external perpendicular magnetic field is studied theoretically. We concentrate on the effects on the magnetisation induced by the system boundary, the l^ashba SOC and the temperature. It is found that the sawtooth-like de Haas- van Alphen (dHvA) oscillations of the magnetisation will change dramatically in the presence of such three factors. Especially, the effects of the edge states and Rashba SOC on the magnetisation are more evident when the magnetic field is smaller. The oscillation center will shift when the boundary effect is considered and the Rashba SOC will bring beating patterns to the dHvA oscillations. These effects on the dHvA oscillations are preferably observed at low temperatures. With increasing temperature, the dHvA oscillations turn to be blurred and eventually disappear.展开更多
Next-generation cellular networks are expected to provide users with innovative gigabits and terabits per second speeds and achieve ultra-high reliability,availability,and ultra-low latency.The requirements of such ne...Next-generation cellular networks are expected to provide users with innovative gigabits and terabits per second speeds and achieve ultra-high reliability,availability,and ultra-low latency.The requirements of such networks are the main challenges that can be handled using a range of recent technologies,including multi-access edge computing(MEC),artificial intelligence(AI),millimeterwave communications(mmWave),and software-defined networking.Many aspects and design challenges associated with the MEC-based 5G/6G networks should be solved to ensure the required quality of service(QoS).This article considers developing a complex MEC structure for fifth and sixth-generation(5G/6G)cellular networks.Furthermore,we propose a seamless migration technique for complex edge computing structures.The developed migration scheme enables services to adapt to the required load on the radio channels.The proposed algorithm is analyzed for various use cases,and a test bench has been developed to emulate the operator’s infrastructure.The obtained results are introduced and discussed.展开更多
The adiabatic film effectivenessηof the counter-inclined film-holes fed by varying internal coolant intake on the turbine vane leading edge model was experimentally investigated.A semi-cylinder model was adopted to m...The adiabatic film effectivenessηof the counter-inclined film-holes fed by varying internal coolant intake on the turbine vane leading edge model was experimentally investigated.A semi-cylinder model was adopted to model the vane leading edge which was arranged with two-row holes,which located at±15°on both sides.The four Leading edge model with the combinations of hole-shape(simple holes and laid-back holes)and intake structure(plenum and impingement)were tested under four blowing ratios M of 0.5,1.0,1.5,and 2.0.Theηcontours were obtained by the transient measurement technique based on double thermochromic liquid-crystals.The results present that theηis sensitive to the M for the four studied leading edge cases.The addition of impingement enhances theηfor the two studied holes.The film jets make the coolant-flow closed to the target surface,resulting in higherηunder lower M.The core with higherηappears in the downstream area of hole-exit.Theηenhancement can be provided to almost the identical level by adding the impingement-holes and improving the hole-exit shaping in most areas.With increasing M,the jets with stronger exit normal momentum penetrate into the main-flow.The impingement addition may be a more effective program to upgrade theηrelatively to the exit shaping under larger M.Besides,the laid-back holes with impingement case produce the highest film cooling performance among the four cases,providing great potential in the leading edge especially under larger M.展开更多
文摘The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.
文摘The Adaptive Quality Control Phantom (AQCP) is the computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce any spatial distribution of gamma rays to perform the QC Tests such as the Collimator Hole Angulation (CHA) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for seven collimators were measured with the method by using a point source and computer-controlled cylindrical positioning. In this method the displacement of the image of a point source examined as the AQCP move point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS, LEUHR, MEGP-250, MEGP-300, MEGP-360 and HEPH collimators of SMV dual heads camera were measured to be 0.290°, 0.292°, 0.208°, 0.194°, 0.181°, 0.177°, 0.150°, respectively. The Root Mean Square (RMS) of CHA for LEGP, MEGP and HEGP collimators of GE Millennium MG were measured to be 0.154°, 0.220° and 0.202° respectively. It is to be added in this connection that the measured RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface +/– 1 mm has been varied +/– 0.04 degree.
文摘In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.
基金Supported by the Science and Technology Innovation Program of Hunan Province,China(No.2020SK50103)Hunan Clinical Medical Technology Innovation Guiding Project in 2020。
文摘AIM:To elucidate the safety and visual quality of implantable collamer lens with central hole(ICL V4c)implantation for correcting moderate and high myopia for at least 5y.METHODS:This retrospective study was conducted on 58 patients(114 eyes)who were followed up for at least 5y after ICL V4c implantation.The observation was done before and on 1d,1mo,1 and 5y or more after the surgical procedure.The visual acuity,subjective refraction,intraocular pressure,vault,axial length,central hole position,pupil diameter,visual quality,and adverse events were analyzed.The visual quality includes aberration,the modulation transfer function cutoff frequency(MTF cutoff),objective scattering index(OSI),Stroller's ratio(SR),and visual quality questionnaire.RESULTS:The average follow-up period was 69.25±3.80mo(range 60–82mo)and the preoperative spherical equivalent(SE)was-8.66±1.97 D.At 5y after operation,the safety index was 1.01±0.02 and the efficacy index was 0.99±0.42 and SE was-0.65±0.63 D.The 59.6%of the eyes achieved an uncorrected distance visual acuity of 20/20,76.3%of the eyes had SE within±1.0 D at the last visit.The axial length increased by 0.29±0.71 mm 5y after the surgery(t=-3.843,P<0.001).The mean vault at the last follow-up was 510.59±245.61μm.The central hole was on the temporal side in 80 eyes(84.2%).The visual quality questionnaire showed that 98.2%patients were satisfied with the surgical procedure.Adverse events occurred in 4 eyes(3.5%),including the posttraumatic toric ICL rotation(2 eyes),iris incarceration(1 eye),and posttraumatic ICL displacement(1 eye)at the last follow-up.CONCLUSION:Long-term ICL V4c implantation is safe,effective,and stable for correcting moderate and to high myopia,and the visual quality with patients is excellent and satisfactory,but the progression of axial length still needs attention after surgery.
文摘· AIM: To investigate the visual function and the relationship with vision-related quality of life(VRQOL)after macular hole repair surgery.· METHODS: Prospective case series. Thirty-six consecutive eyes in 36 patients who underwent pars plana vitrectomy(PPV) and internal limiting membrane(ILM) peeling were included. The 25-item National Eye Institute Visual Function Questionnaire(VFQ-25) was answered by the participants before and 3 and 12 mo after operation. Follow-up visits examinations included best-corrected visual acuity(BCVA), clinical examination,and central macular thickness(CMT) measured by optical coherence tomography(OCT).·RESULTS: Macular-hole closure was achieved in 35 of36 eyes(97.2%). At baseline and months 3 and 12, the log MAR BCVAs(mean±SD) were 1.15±0.47, 0.68±0.53(P 【0.0001 versus baseline), and 0.55 ±0.49(P 【0.001 versus baseline, P =0.273 versus month 3), respectively; the CMTs(μm) were 330 ±81, 244 ±62(P 【0.001 versus baseline), and 225±58(P 【0.001 versus baseline, P =0.222 versus month 3), respectively; the median preoperative VFQ-25 composite score of 73.50(63.92-81.13) increased postoperatively to 85.50(80.04-89.63) at 3mo(P 【0.001)and 86.73(82.50-89.63) at 12mo(P 【0.001) respectively.The improved BCVA was correlated with improvements in five subscales(r =-0.605 to-0.336, P 【0.001 to P =0.046) at 12 mo.· CONCLUSION: PPV with ILM peeling improved anatomic outcome, visual function, and VRQOL. Theimproved BCVA was an important factor related to the improved VRQOL.
基金Supported by the Major Science and Technology Project(2012ZX04003-031)
文摘Revolution radius is one of the significant parameters in orbital drilling,which has great influence on many factors,such as the cutting area of front and side cutting edge,undeformed chip geometry,delamination and burr at hole exit side,hole surface roughness,cutting tool force and deflection,chip removal and heat transmission.First,the influence of revolution radius on the factors is discussed theoretically in detail.Analysis results show that big revolution radius can reduce axial cutting force,restrain exit delamination and burr,and improve chip removal and heat transmission.Then,single factor test and orthogonal test are utilized in the two processing methods as machining unidiameter holes with several cutting tools and machining different diameter holes with one tool.Finally,the influence of revolution radius on cutting force and hole machining precision is studied.These results provide a profound foundation for future optimization of cutting control parameters.
基金support from the National Natural Science Foundation of China(Grant No.52175441)the Natural Science Foundation of Zhejiang Province,China(Grant No.LD22E050010)+4 种基金the travel scholarship from the China Scholarship Council(Grant No.202208330333)for secondment of Jiahuan Wang at London South Bank University(LSBU)for working closely with Prof.GoelSaurav Goel would like to acknowledge the funding support from UK Research and Innovation,UKRI(Grant Nos.EP/S036180/1 and EP/T024607/1)the feasibility study awards to LSBU from the UKRI National Interdisciplinary Circular Economy Hub(Grant No.EP/V029746/1)Transforming the Foundation Industries:A Network+(Grant No.EP/V026402/1)the International Exchange Cost Share Award by the Royal Society(Grant No.IEC\NSFC\223536).This work accessed the supercomputing service(Isambard-AI,Bristol,UK)via the Resource Allocation Panel and Kittrick(LSBU)-based computational resources.
文摘Printed circuit boards(PCBs)are representative composite materials,and their high-quality drilling machining remains a persistent challenge in the industry.The finishing of the cutting edge of a microdrill is crucial to drill performance in machining fine-quality holes with a prolonged tool life.The miniature size involving submicron scale geometric dimensions,a complex flute shape,and low fracture toughness makes the cutting edge of microdrills susceptible to breakage and has been the primary limiting factor in edge preparation for microdrills.In this study,a newly developed cutting edge preparation method for microdrills was tested experimentally on electronic printed circuit boards.The proposed method,namely,shear thickening polishing,limited the cutting edge burrs and chipping on the cutting edge,and this in turn transformed the cutting edge’s radius from being sharp to smooth.Moreover,the edge–edge radius could be regulated by adjusting the processing time.PCB drilling experiments were conducted to investigate the influence of different cutting edge radii on wear,hole position accuracy,nail head value,and hole wall roughness.The proposed approach showed 20%enhancement in hole position accuracy,33%reduction in the nail head value,and 19%reduction in hole wall roughness compared with the original microdrill.However,a threshold is needed;without it,excessive shear thickening polishing will result in a blunt edge,which may accelerate the wear of the microdrill.Wear was identified as the primary factor that reduced hole quality.The study indicates that in printed circuit board machining,microdrills should effectively eliminate grinding defects and maintain the sharpness of the cutting edge as much as possible to obtain excellent drilling quality.Overall,shear thickening polishing is a promising method for cutting edge preparation of microdrills.Further research and optimization can lead to additional improvements in microdrill performance and contribute to the continued advancement of printed circuit board manufacturing.
基金supported by the Open Fund of the State Key Laboratory of Advanced Optical Communication Systems and Networks (SJTU)(Grant No. 2023GZKF018)the Open Fund of IPOC (BUPT)(Grant No. IPOC2021B03)+4 种基金the National Natural Science Foundation of China (NSFC)(Grant No. 11974188)the China Postdoctoral Science Foundation (Grant Nos. 2021T140339 and 2018M632345)the Jiangsu Province Postdoctoral Science Foundation (Grant No. 2021K617C)the Postgraduate Research and Practice Innovation Program of Jiangsu Province (Grant No.KYCX22_0945)the Qing Lan Project of Jiangsu Province
文摘A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefinite-difference time-domain method,the parameters of the M-PCNC,including cavity thickness and width,lattice constant,and radii and numbers of holes,are optimized,with the quality factor Q and mode volume Vm as performance indicators.Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance.The optimized cavity possesses a high quality factor Q 1.45105 and an ultra-small mode=×volume Vm 0.01(λ/n)[Zeng et al.,Opt Lett 2023:48;3981–3984]in the telecommunications wavelength range.Light can be progres-=sively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure.Thereby,the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.
文摘Mobile edge caching technology is gaining more and more attention because it can effectively improve the Quality of Experience (QoE) of users and reduce backhaul burden. This paper aims to improve the utility of mobile edge caching technology from the perspectie of caching resource management by examining a network composed of one operator, multiple users and Content Providers (CPs). The caching resource management model is constructed on the premise of fully considering the QoE of users and the servicing capability of the Base Station (BS). In order to create the best caching resource allocation scheme, the original problem is transformed into a multi-leader multi-follower Stackelberg game model through the analysis of the system model. The strategy combinations and the utility functions of players are analyzed. The existence and uniqueness of the Nash Equilibrium (NE) solution are also analyzed and proved. The optimal strategy combinations and the best responses are deduced in detail. Simulation results and analysis show that the proposed model and algorithm can achieve the optimal allocation of caching resource and improve the QoE of users.
基金supported by the Chinese Scholarship Council(CSC)under MOFCOM(No.2017MOC010907)any opinions,findings,and conclusions are those of the authors and do not necessarily reflect the views of the above agency.
文摘Mobile Edge Computing (MEC) has been considered a promising solution that can address capacity and performance challenges in legacy systems such as Mobile Cloud Computing (MCC). In particular, such challenges include intolerable delay, congestion in the core network, insufficient Quality of Experience (QoE), high cost of resource utility, such as energy and bandwidth. The aforementioned challenges originate from limited resources in mobile devices, the multi-hop connection between end-users and the cloud, high pressure from computation-intensive and delay-critical applications. Considering the limited resource setting at the MEC, improving the efficiency of task offloading in terms of both energy and delay in MEC applications is an important and urgent problem to be solved. In this paper, the key objective is to propose a task offloading scheme that minimizes the overall energy consumption along with satisfying capacity and delay requirements. Thus, we propose a MEC-assisted energy-efficient task offloading scheme that leverages the cooperative MEC framework. To achieve energy efficiency, we propose a novel hybrid approach established based on Particle Swarm Optimization (PSO) and Grey Wolf Optimizer (GWO) to solve the optimization problem. The proposed approach considers efficient resource allocation such as sub-carriers, power, and bandwidth for offloading to guarantee minimum energy consumption. The simulation results demonstrate that the proposed strategy is computational-efficient compared to benchmark methods. Moreover, it improves energy utilization, energy gain, response delay, and offloading utility.
基金Supported by National Natural Science Foundation of China (No.50975141 and No.51005118)Aviation Science Fund (No.20091652018 and No.2010352005)
文摘To improve the processing efficiency and the quality of orbital milling hole of aerospace Al-alloy, the big-pitch influence on cutting force and hole quality was studied experimentally. First, a program based on horizontal lathe was proposed based on kinematics analysis of orbital milling. Then, the cutting force at different stages and the hole quality with different pitches were measured. Results show that the axial force and radial force increase with the pitch amplification during orbital milling. However, the axial force in the orbital milling hole is about 8—10 times smaller than that in the conventional drilling. The diameter error of milling hole is 48—93 μm, and the surface roughness of milling hole is 1.2—1.7 μm. Finally, an orbital milling device with big pitch was designed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60821061, 60776061, 10604010 and 60776063)
文摘The magnetisation of heavy holes in III-V semiconductor quantum wells with Rashba spin-orbit coupling (SOC) in an external perpendicular magnetic field is studied theoretically. We concentrate on the effects on the magnetisation induced by the system boundary, the l^ashba SOC and the temperature. It is found that the sawtooth-like de Haas- van Alphen (dHvA) oscillations of the magnetisation will change dramatically in the presence of such three factors. Especially, the effects of the edge states and Rashba SOC on the magnetisation are more evident when the magnetic field is smaller. The oscillation center will shift when the boundary effect is considered and the Rashba SOC will bring beating patterns to the dHvA oscillations. These effects on the dHvA oscillations are preferably observed at low temperatures. With increasing temperature, the dHvA oscillations turn to be blurred and eventually disappear.
基金This work was supported by Princess Nourah bint Abdulrahman University Researchers Supporting Project Number(PNURSP2022R308),Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘Next-generation cellular networks are expected to provide users with innovative gigabits and terabits per second speeds and achieve ultra-high reliability,availability,and ultra-low latency.The requirements of such networks are the main challenges that can be handled using a range of recent technologies,including multi-access edge computing(MEC),artificial intelligence(AI),millimeterwave communications(mmWave),and software-defined networking.Many aspects and design challenges associated with the MEC-based 5G/6G networks should be solved to ensure the required quality of service(QoS).This article considers developing a complex MEC structure for fifth and sixth-generation(5G/6G)cellular networks.Furthermore,we propose a seamless migration technique for complex edge computing structures.The developed migration scheme enables services to adapt to the required load on the radio channels.The proposed algorithm is analyzed for various use cases,and a test bench has been developed to emulate the operator’s infrastructure.The obtained results are introduced and discussed.
基金support of the National Natural Science Foundation of China(Grant No.51776173)the Innovation Capacity Support Plan in Shaanxi Province of China(Grant No.2019KJXX-065)+1 种基金the Scientific Research Plan Project of Key Laboratory of Shaanxi Provincial Education Department(Grant No.17JS070)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(Grant No.CX201913)。
文摘The adiabatic film effectivenessηof the counter-inclined film-holes fed by varying internal coolant intake on the turbine vane leading edge model was experimentally investigated.A semi-cylinder model was adopted to model the vane leading edge which was arranged with two-row holes,which located at±15°on both sides.The four Leading edge model with the combinations of hole-shape(simple holes and laid-back holes)and intake structure(plenum and impingement)were tested under four blowing ratios M of 0.5,1.0,1.5,and 2.0.Theηcontours were obtained by the transient measurement technique based on double thermochromic liquid-crystals.The results present that theηis sensitive to the M for the four studied leading edge cases.The addition of impingement enhances theηfor the two studied holes.The film jets make the coolant-flow closed to the target surface,resulting in higherηunder lower M.The core with higherηappears in the downstream area of hole-exit.Theηenhancement can be provided to almost the identical level by adding the impingement-holes and improving the hole-exit shaping in most areas.With increasing M,the jets with stronger exit normal momentum penetrate into the main-flow.The impingement addition may be a more effective program to upgrade theηrelatively to the exit shaping under larger M.Besides,the laid-back holes with impingement case produce the highest film cooling performance among the four cases,providing great potential in the leading edge especially under larger M.