To demonstrate flexible and tandem device applications,a low-temperature Cu_(2)ZnSnSe_(4)(CZTSe)deposition process,combined with efficient alkali doping,was developed.First,high-quality CZTSe films were grown at 480℃...To demonstrate flexible and tandem device applications,a low-temperature Cu_(2)ZnSnSe_(4)(CZTSe)deposition process,combined with efficient alkali doping,was developed.First,high-quality CZTSe films were grown at 480℃by a single co-evaporation,which is applicable to polyimide(PI)substrate.Because of the alkali-free substrate,Na and K alkali doping were systematically studied and optimized to precisely control the alkali distribution in CZTSe.The bulk defect density was significantly reduced by suppression of deep acceptor states after the(NaF+KF)PDTs.Through the low-temperature deposition with(NaF+KF)PDTs,the CZTSe device on glass yields the best efficiency of 8.1%with an improved Voc deficit of 646 mV.The developed deposition technologies have been applied to PI.For the first time,we report the highest efficiency of 6.92%for flexible CZTSe solar cells on PI.Additionally,CZTSe devices were utilized as bottom cells to fabricate four-terminal CZTSe/perovskite tandem cells because of a low bandgap of CZTSe(~1.0 eV)so that the tandem cell yielded an efficiency of 20%.The obtained results show that CZTSe solar cells prepared by a low-temperature process with in-situ alkali doping can be utilized for flexible thin-film solar cells as well as tandem device applications.展开更多
In recent years,additive manufacturing(AM)has gained popularity in the aerospace,automobile,and medical industries due to its ability to produce complex profiles with minimal tolerances.Micro-milling is recommended fo...In recent years,additive manufacturing(AM)has gained popularity in the aerospace,automobile,and medical industries due to its ability to produce complex profiles with minimal tolerances.Micro-milling is recommended for machining AM-based parts to improve surface quality and form accuracy.Therefore,the machinability of a titanium alloy(Ti6Al4V)manufactured using selective laser melting(SLM)is explored and compared to that of wrought Ti6Al4V in micro-milling.The experimental results reveal the surface topology,chip morphology,burr formation,and tool wear characteristics of both samples.The micro-milling of AM-based Ti6Al4V generates a surface roughness of 19.2 nm,which is 13.9%lower than that of wrought workpieces,and this component exhibits less tool wear.SLM-based Ti6Al4V produces continuous chips,while wrought Ti6Al4V yields relatively short chips.Additionally,SLM-fabricated Ti6Al4V exhibits smaller burrs after micro-milling than wrought Ti6Al4V.Despite the higher hardness of SLM-based Ti6Al4V,it demonstrates better machinability than wrought Ti6Al4V,resulting in better surface quality with lower tool wear levels and shorter burr heights.This study provides valuable insights into future research on postprocessing AM-based titanium parts,especially using micro-milling.展开更多
Developing countries are facing the problem of environmental degradation.Environmental degradation is caused by the use of non-renewable energy consumptions for economic growth but the consequences of environmental de...Developing countries are facing the problem of environmental degradation.Environmental degradation is caused by the use of non-renewable energy consumptions for economic growth but the consequences of environmental degradation cannot be ignored.This primary purpose of this study is to investigate the nexus between energy consumption,economic growth and CO_(2) emission in Pakistan by using annual time series data from 1965 to 2015.The estimated results of ARDL indicate that energy consumption and economic growth increase the CO_(2) emissions in Pakistan both in short run and long run.Based on the estimated results it is recommended that policy maker in Pakistan should adopt and promote such renewable energy sources that will help to meet the increased demand for energy by replacing old traditional energy sources such as coal,gas,and oil.Renewable energy sources are reusable that can reduce the CO_(2) emissions and also ensure sustainable economic development of Pakistan.展开更多
This paper addresses the control law design for synchronization of two different chaotic oscillators with mutually Lipschitz nonlinearities. For analysis of the properties of two different nonlinearities, an advanced ...This paper addresses the control law design for synchronization of two different chaotic oscillators with mutually Lipschitz nonlinearities. For analysis of the properties of two different nonlinearities, an advanced mutually Lipschitz condition is proposed. This mutually Lipschitz condition is more general than the traditional Lipschitz condition. Unlike the latter, it can be used for the design of a feedback controller for synchronization of chaotic oscillators of different dynamics. It is shown that any two different Lipschitz nonlinearities always satisfy the mutually Lipschitz condition. Applying the mutually Lipschitz condition, a quadratic Lyapunov function and uniformly ultimately bounded stability, easily designable and implementable robust control strategies utilizing algebraic Riccati equation and linear matrix inequalities, are derived for synchronization of two distinct chaotic oscillators. Furthermore, a novel adaptive control scheme for mutually Lipschitz chaotic systems is established by addressing the issue of adaptive cancellation of unknown mismatch between the dynamics of different chaotic systems. The proposed control technique is numerically tested for synchronization of two different chaotic Chua＇s circuits and for obtaining identical behavior between the modified Chua＇s circuit and the R6ssler system.展开更多
Injuries deeper than the platysma are considered as penetrating neck injuries,constituting approximately 5%-10%of all trauma.Many vital organs are at risk from a penetrating neck injury.These injuries in zone 1 have t...Injuries deeper than the platysma are considered as penetrating neck injuries,constituting approximately 5%-10%of all trauma.Many vital organs are at risk from a penetrating neck injury.These injuries in zone 1 have the highest mortality,because the injuries are close to the vital organs and difficult to access surgically.A 41-year-old male,a car mechanic by profession,presented to the emergency department with a penetrating neck injury on the right side.CT scan demonstrated a metallic foreign body in zone 1 between the right internal jugular vein and the common carotid artery.The patient was asymptomatic,and the foreign body was removed surgically.This case shows a rare presentation of a penetrating neck injury with a foreign body located in zone 1,where no vital internal structure was injured.As of now,no previous case report has been identified on such presentation.Thus,it will provide a valuable addition to the pre-existing literature.展开更多
Additive manufacturing,particularly 3D printing,has revolutionized the manufacturing industry by allowing the production of complex and intricate parts at a lower cost and with greater efficiency.However,3D-printed pa...Additive manufacturing,particularly 3D printing,has revolutionized the manufacturing industry by allowing the production of complex and intricate parts at a lower cost and with greater efficiency.However,3D-printed parts frequently require post-processing or integration with other machining technologies to achieve the desired surface finish,accuracy,and mechanical properties.Ultra-precision machining(UPM)is a potential machining technology that addresses these challenges by enabling high surface quality,accuracy,and repeatability in 3D-printed components.This study provides an overview of the current state of UPM for 3D printing,including the current UPM and 3D printing stages,and the application of UPM to 3D printing.Following the presentation of current stage perspectives,this study presents a detailed discussion of the benefits of combining UPM with 3D printing and the opportunities for leveraging UPM on 3D printing or supporting each other.In particular,future opportunities focus on cutting tools manufactured via 3D printing for UPM,UPM of 3D-printed components for real-world applications,and post-machining of 3D-printed components.Finally,future prospects for integrating the two advanced manufacturing technologies into potential industries are discussed.This study concludes that UPM is a promising technology for 3D-printed components,exhibiting the potential to improve the functionality and performance of 3D-printed products in various applications.It also discusses how UPM and 3D printing can complement each other.展开更多
An interferometer based optical sensor for displacement measurement is reported. This method requires quite simple signal processing as well as least electronic components. Referring to this technique, two photodiodes...An interferometer based optical sensor for displacement measurement is reported. This method requires quite simple signal processing as well as least electronic components. Referring to this technique, two photodiodes spatially shifted by 90 degrees were used. The output of photodiodes was converted into rectangular signals which were extracted in LabVIEW using the data acquisition card without using an analog to digital converters （ADC）. We have also processed the signals in C＋＋ after acquiring via parallel port. A Michelson interferometer configuration was used to produce linear fringes for the detection of displacements. The displacement less than 100nm could be measured using this technique.展开更多
基金financially supported by the Korea Institute of Energy Research(KIER)(grant no.C3-2401,2402,2403)the National Research Foundation(grant no.2022M3J1A1063019)funded by the Ministry of Science and ICT
文摘To demonstrate flexible and tandem device applications,a low-temperature Cu_(2)ZnSnSe_(4)(CZTSe)deposition process,combined with efficient alkali doping,was developed.First,high-quality CZTSe films were grown at 480℃by a single co-evaporation,which is applicable to polyimide(PI)substrate.Because of the alkali-free substrate,Na and K alkali doping were systematically studied and optimized to precisely control the alkali distribution in CZTSe.The bulk defect density was significantly reduced by suppression of deep acceptor states after the(NaF+KF)PDTs.Through the low-temperature deposition with(NaF+KF)PDTs,the CZTSe device on glass yields the best efficiency of 8.1%with an improved Voc deficit of 646 mV.The developed deposition technologies have been applied to PI.For the first time,we report the highest efficiency of 6.92%for flexible CZTSe solar cells on PI.Additionally,CZTSe devices were utilized as bottom cells to fabricate four-terminal CZTSe/perovskite tandem cells because of a low bandgap of CZTSe(~1.0 eV)so that the tandem cell yielded an efficiency of 20%.The obtained results show that CZTSe solar cells prepared by a low-temperature process with in-situ alkali doping can be utilized for flexible thin-film solar cells as well as tandem device applications.
基金Supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant No.15221322)National Natural Science Foundation of China(Grant No.U19A20104)+1 种基金Shenzhen Municipal Science and Technology Program(Grant No.JCYJ20210324131214039)State Key Laboratory of Ultra-precision Machining Technology and the Research Committee of The Hong Kong Polytechnic University of China(Project Code:RHD5)。
文摘In recent years,additive manufacturing(AM)has gained popularity in the aerospace,automobile,and medical industries due to its ability to produce complex profiles with minimal tolerances.Micro-milling is recommended for machining AM-based parts to improve surface quality and form accuracy.Therefore,the machinability of a titanium alloy(Ti6Al4V)manufactured using selective laser melting(SLM)is explored and compared to that of wrought Ti6Al4V in micro-milling.The experimental results reveal the surface topology,chip morphology,burr formation,and tool wear characteristics of both samples.The micro-milling of AM-based Ti6Al4V generates a surface roughness of 19.2 nm,which is 13.9%lower than that of wrought workpieces,and this component exhibits less tool wear.SLM-based Ti6Al4V produces continuous chips,while wrought Ti6Al4V yields relatively short chips.Additionally,SLM-fabricated Ti6Al4V exhibits smaller burrs after micro-milling than wrought Ti6Al4V.Despite the higher hardness of SLM-based Ti6Al4V,it demonstrates better machinability than wrought Ti6Al4V,resulting in better surface quality with lower tool wear levels and shorter burr heights.This study provides valuable insights into future research on postprocessing AM-based titanium parts,especially using micro-milling.
文摘Developing countries are facing the problem of environmental degradation.Environmental degradation is caused by the use of non-renewable energy consumptions for economic growth but the consequences of environmental degradation cannot be ignored.This primary purpose of this study is to investigate the nexus between energy consumption,economic growth and CO_(2) emission in Pakistan by using annual time series data from 1965 to 2015.The estimated results of ARDL indicate that energy consumption and economic growth increase the CO_(2) emissions in Pakistan both in short run and long run.Based on the estimated results it is recommended that policy maker in Pakistan should adopt and promote such renewable energy sources that will help to meet the increased demand for energy by replacing old traditional energy sources such as coal,gas,and oil.Renewable energy sources are reusable that can reduce the CO_(2) emissions and also ensure sustainable economic development of Pakistan.
基金supported by the Higher Education Commission of Pakistan through the Indigenous 5000 Ph.D.Fellowship Program(Phase II,Batch II)
文摘This paper addresses the control law design for synchronization of two different chaotic oscillators with mutually Lipschitz nonlinearities. For analysis of the properties of two different nonlinearities, an advanced mutually Lipschitz condition is proposed. This mutually Lipschitz condition is more general than the traditional Lipschitz condition. Unlike the latter, it can be used for the design of a feedback controller for synchronization of chaotic oscillators of different dynamics. It is shown that any two different Lipschitz nonlinearities always satisfy the mutually Lipschitz condition. Applying the mutually Lipschitz condition, a quadratic Lyapunov function and uniformly ultimately bounded stability, easily designable and implementable robust control strategies utilizing algebraic Riccati equation and linear matrix inequalities, are derived for synchronization of two distinct chaotic oscillators. Furthermore, a novel adaptive control scheme for mutually Lipschitz chaotic systems is established by addressing the issue of adaptive cancellation of unknown mismatch between the dynamics of different chaotic systems. The proposed control technique is numerically tested for synchronization of two different chaotic Chua＇s circuits and for obtaining identical behavior between the modified Chua＇s circuit and the R6ssler system.
文摘Injuries deeper than the platysma are considered as penetrating neck injuries,constituting approximately 5%-10%of all trauma.Many vital organs are at risk from a penetrating neck injury.These injuries in zone 1 have the highest mortality,because the injuries are close to the vital organs and difficult to access surgically.A 41-year-old male,a car mechanic by profession,presented to the emergency department with a penetrating neck injury on the right side.CT scan demonstrated a metallic foreign body in zone 1 between the right internal jugular vein and the common carotid artery.The patient was asymptomatic,and the foreign body was removed surgically.This case shows a rare presentation of a penetrating neck injury with a foreign body located in zone 1,where no vital internal structure was injured.As of now,no previous case report has been identified on such presentation.Thus,it will provide a valuable addition to the pre-existing literature.
基金supported by the State Key Laboratories in Hong Kong,China,from the Innovation and Technology Commission(project code:BBR3)of the Government of the Hong Kong Special Administrative Region,Chinathe Research Office(project codes:BBXM and BBX)of The Hong Kong Polytechnic University,China+1 种基金the Project of Strategic Importance(project codes:1-ZE0G and SBBD)of The Hong Kong Polytechnic University,Chinaand the Research Committee(project code:RMAC)of The Hong Kong Polytechnic University,China。
文摘Additive manufacturing,particularly 3D printing,has revolutionized the manufacturing industry by allowing the production of complex and intricate parts at a lower cost and with greater efficiency.However,3D-printed parts frequently require post-processing or integration with other machining technologies to achieve the desired surface finish,accuracy,and mechanical properties.Ultra-precision machining(UPM)is a potential machining technology that addresses these challenges by enabling high surface quality,accuracy,and repeatability in 3D-printed components.This study provides an overview of the current state of UPM for 3D printing,including the current UPM and 3D printing stages,and the application of UPM to 3D printing.Following the presentation of current stage perspectives,this study presents a detailed discussion of the benefits of combining UPM with 3D printing and the opportunities for leveraging UPM on 3D printing or supporting each other.In particular,future opportunities focus on cutting tools manufactured via 3D printing for UPM,UPM of 3D-printed components for real-world applications,and post-machining of 3D-printed components.Finally,future prospects for integrating the two advanced manufacturing technologies into potential industries are discussed.This study concludes that UPM is a promising technology for 3D-printed components,exhibiting the potential to improve the functionality and performance of 3D-printed products in various applications.It also discusses how UPM and 3D printing can complement each other.
文摘An interferometer based optical sensor for displacement measurement is reported. This method requires quite simple signal processing as well as least electronic components. Referring to this technique, two photodiodes spatially shifted by 90 degrees were used. The output of photodiodes was converted into rectangular signals which were extracted in LabVIEW using the data acquisition card without using an analog to digital converters （ADC）. We have also processed the signals in C＋＋ after acquiring via parallel port. A Michelson interferometer configuration was used to produce linear fringes for the detection of displacements. The displacement less than 100nm could be measured using this technique.
