Foodborne disease is a worldwide il ness and over 1 bil ion people get diseased every year. In China, thousands of foodborne diseases occur every year. It is proved that prevention is the most crucial for control ing ...Foodborne disease is a worldwide il ness and over 1 bil ion people get diseased every year. In China, thousands of foodborne diseases occur every year. It is proved that prevention is the most crucial for control ing foodborne disease. In the research, food safety monitoring system, laws and early warning system in the US and EU were introduced to explore the successful experience and monitoring or control mode suitable for China.展开更多
Background: Floorball training offers a motivating and socially stimulating team activity for older adults, and 12 weeks of floorball training twice a week among men aged 65—76 years have been shown to have positive ...Background: Floorball training offers a motivating and socially stimulating team activity for older adults, and 12 weeks of floorball training twice a week among men aged 65—76 years have been shown to have positive effects on a number of physiological parameters important for health. However, the effect of long-term participation in floorball training among male elderly has not been investigated. The aim of the present study was to examine the effect of 26-month self-organized regular participation in floorball training on cardiovascular fitness, body composition, blood lipids, glucose control, and physical function among recreationally active men aged 66—78 years.Methods: After completing a 12-week randomized and controlled intervention with floorball and petanque training in the autumn 2014 or spring2015, 15 subjects chose to participate in floorball training(floorball group, FG), whereas 16 subjects resumed their usual lifestyle(control group,CG). FG took part in self-organized floorball training 1.7 sessions of 40 min/week, and CG continued their normal recreationally active lifestyle during a 26-month follow-up period. At baseline and after the follow-up period subjects were tested for cardiovascular fitness, glucose control(resting blood samples), body composition dual-energy X-ray absorptiometry(DXA-scanning), and functional capacity.Results: In FG, the decline in maximal oxygen uptake(VO_(2max)) during the follow-up period was lower(242 ± 379 mL/min, p = 0.01), blood glycosylated hemoglobin(HbA1c) increased less(—1.6 ± 2.9 mmol/L, p = 0.02), and leg bone mineral density increased more(0.03 ± 0.05 g/cm^2,p = 0.02) than those in CG. The effects on body mass, total lean body mass, fat mass, blood lipids, and physical function were similar in FG and CG.Conclusion: Approximately twice weekly floorball sessions with 40 min/session over 26-month appear to reduce age-related decline in cardiovascular fitness and glucose control and improve leg bone mineral density, suggesting that long-term participation in floorball training can be considered as a health-enhancing activity in recreationally active male elderly.展开更多
A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pul...A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.展开更多
Information-Centric Networking(ICN) has recently emerged as a result of the increased demand to access contents regardless of their location in the network services. This new approach facilitates content distribution ...Information-Centric Networking(ICN) has recently emerged as a result of the increased demand to access contents regardless of their location in the network services. This new approach facilitates content distribution as a service of the network with lower delay and higher security in comparison with the current IP network. Applying ICN in current IP infrastructure leads to major complexities. One approach to deploy ICN with less complexity is to integrate ICN with Software Defined Networking(SDN). The SDN controller manages the content distribution, caching, and routing based on the users' requests. In this paper, we extend these context by addressing the ICN topology management problem over the SDN network to achieve an improved user experience as well as network performance. In particular, a centralized controller is designed to construct and manage the ICN overlay. Experimental results indicate that this adopted topology management strategy achieves high performance, in terms of low failure in interest satisfaction and reduced download time compared to a plain ICN.展开更多
Based on planar Si dual-base transistor conception, a novel mesa dual-base heterojunc- tion bipolar transistor ( HBT) is designed and fabricated. Molecule beam extension. selective wet chemical etching, common contact...Based on planar Si dual-base transistor conception, a novel mesa dual-base heterojunc- tion bipolar transistor ( HBT) is designed and fabricated. Molecule beam extension. selective wet chemical etching, common contact photolithography and metal lift-off technique are adopted in the process. The device has particular and distinct voltage-controlled negative differential resistance (NDR) and photo-controlled NDR. The highest peak-to-vally current rate of the voltage-controlled NDR is larger than 148 and the peak current varies with the increase of collector voltage. The device features high speed and high frequency characteristics derived from HBT and intrinsic bistability and self-latching characteristics due to NDR. A single dual-base HBT can be seen as an integration of NDR device, HBT and photoconductive device. Compared with common HBT.the groove is the key factor producing NDR.展开更多
The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids spe...The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids species retrieved from GenBank. A phylogenetic tree was constructed based on the partial control region sequences. The results of phyloge- netic analysis are consistent with those of conventional systematics. Compared to previous studies, the structure of the 5’-end of mitochondrial control region was analyzed. The terminal associated sequence motif and its complementary motif were i- dentified at the 5’-end of the sequences. A conserved sequence block, named as CM5’d, was identified in the 5’-end of con- trol region sequences in all Pleuronectids. Another central conserved sequence block, named as CSB-F, was detected in the central conserved blocks.展开更多
This paper points out the drawbacks of traditional financial governance. After introducing Chinese and western economists' researches on firm financial governance theory, we put forward modern finn financial governan...This paper points out the drawbacks of traditional financial governance. After introducing Chinese and western economists' researches on firm financial governance theory, we put forward modern finn financial governance system, which is based on the core of finance-rights allocation. In our opinion, the theory of finance-rights is the important cornerstone of the theory of financial finance-rights theory. Financial governance structure system is the basic framework of the research of financial governance.展开更多
Cloud computing can offer a very powerful, reliable, predictable and scalable computing infrastructure for the execution of MAS (multi-agent systems) implementing complex agent-based applications such when modelling...Cloud computing can offer a very powerful, reliable, predictable and scalable computing infrastructure for the execution of MAS (multi-agent systems) implementing complex agent-based applications such when modelling, simulation and real-time running of complex systems must be provided. Multi-agent systems appears as an adequate approach to current challenges in many areas. Between important qualities of MAS also belongs to, that they are open, interoperable, and heterogenous systems. The agent is active, a program entity, has its own ideas how to perform the tasks of the own agenda. Agents: perceive, behave "reasonably", act in the environment, communicate with other agents. Cloud infrastructures can offer an ideal platform where run MAS systems simulations, applications and real-time running because of its large amount of processing and memory resources that can be dynamically configured for executing large agent-based software at unprecedented scale. Cloud computing can help chemical and food companies drive operational excellence; meet growing and changing customer demands; accelerate new product innovation and ramp-to-volume manufacturing in key markets; reduce IT spending; manage and mitigate supply chain risks; and enable faster and more flexible delivery of new IT system. Production type of SOC (service-oriented computing) can be inspired by a "Cloud", for the production of "Cloud" offers an attractive and natural solutions in several computing trends such as delivery system over the Internet, use of utilities, flexibility, virtualization, a "grid" distributed computing, outsourcing, Web 2.0, etc.. Production of the "Cloud" is also considered as a new multidisciplinary field that includes "network" production, virtual manufacturing, agile manufacturing, and of course cloud computing. Examples of cloud computing and MAS applications in food and chemistry development and industry, proposition of using multi-agent systems in the control of batch processes, modified ACO (ant colony optimization) approach for the diversified service allocation and scheduling mechanism in cloud paradigma, examples of applications in a business area were studied in the paper.展开更多
The paper presents an innovative renewable energy-load management technology, which is currently being developed as a prototype, in preparation for potential large-scale implementation in power systems. The new techno...The paper presents an innovative renewable energy-load management technology, which is currently being developed as a prototype, in preparation for potential large-scale implementation in power systems. The new technology employs controlled motion of large weights, which are being maneuvered (up and down) through the system peak/off-peak demand pattern. The load management scheme is similar to the pumping storage systems, but uses large weights instead of water and, therefore, is more suited to the operating environment in Saudi Arabia, in which water is relatively scarce. A portion of the off-peak valley-filling energy is supplied from wind-driven generators, which adds to the green energy component of the scheme. The controlled motion aspect of the new technology is based on partial implementation of previously published ideas by the authors as well as a registered patent. The paper describes the theoretical and analytical features of the introduced renewable energy-load management technology, and dwells on its practical implementation features.展开更多
Intensive in-depth development of resources, centralized purchasing and gradually expand under the category of environment, this paper studies how to use information technology tools to construction quality supervisio...Intensive in-depth development of resources, centralized purchasing and gradually expand under the category of environment, this paper studies how to use information technology tools to construction quality supervision and management system that focuses on the quality of supervision and project management, quality control process management, quality monitoring statistics report management, platform management-related content in four areas. Through the construction quality supervision and management system, to better enhance the quality of electric power enterprise management level, to ensure that the material quality, quantity of time and supplies. strengthening quality supervision and management can not only effectively reduce material procurement costs, but also enhance the competitiveness of enterprises.展开更多
This paper deals with utilization possibility of a kinematical couple of screw-matrix in minimachine mechatronic concept which is assigned to move within the pipes having less than 25 mm of the inner diameter. The pri...This paper deals with utilization possibility of a kinematical couple of screw-matrix in minimachine mechatronic concept which is assigned to move within the pipes having less than 25 mm of the inner diameter. The principle of the movement for a straightforward motion consists in transformation of the actuator rotary movement through a screw and a nut to the linear motion. It causes a change of distance between the front and rear parts of the minimachine modules. Due to minimization of the dimensions, the electrical control and power supply components are placed outside of the minimachine operating area. The control module is based on a programmable integrated circuit (PIC).展开更多
Parameters of the power source used to control PV-10 piezoelectric crystal valve are following DC output voltage: 0 - 120 V, continuously controllable, linear enlargement factor of input direct current voltage: appr...Parameters of the power source used to control PV-10 piezoelectric crystal valve are following DC output voltage: 0 - 120 V, continuously controllable, linear enlargement factor of input direct current voltage: approximate 25 times, the accuracy of DC output voltage: ±5%, manual control and automatic control.展开更多
A curriculum is a complex system that includes a set of core competencies, objectives, contents, methodological and evaluation criteria, regulation among other things. In order to represent a curriculum as a piece of ...A curriculum is a complex system that includes a set of core competencies, objectives, contents, methodological and evaluation criteria, regulation among other things. In order to represent a curriculum as a piece of software the common tools used are databases, trees and lists of courses. However, none of these tools can capture the deep and complex relationships among the elements of a curriculum. To avoid this problem, a more complete representation of an engineering curriculum using ontologies has been developed. This paper presents the construction of an ontology for undergraduate electrical engineering curriculum domain at Universidad Nacional de Colombia, which aims to represent, organize, formalize and standardize the knowledge of this domain, so that it can be shared and reused by different groups of people in the field of education and engineering. The ontology includes four curriculum aspects: knowledge in electrical engineering, skills in engineering, electrical engineering curriculum and regulation. For the ontology development, Methontology was selected as methodology and Protege as implementation tool. In addition, there is a proposal of documentation for this methodology, based on principles of quality management systems. This ontology is designed in order to be used in any field of engineering.展开更多
Molybdenum ditelluride (MoTe2) has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taki...Molybdenum ditelluride (MoTe2) has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taking advantage of high-κ screening effect, we have fabricated back-gated MoTe2 transistors on an Al2O3 high-κ dielectric and systematically investigated the electronic and optoelectronic proper- ties. A high current on/off ratio exceeding 106 is achieved in the Al2O3-based MoTe2 transistors, and the hole mobility is demonstrated to be 150 cm2 V^-1 s^-1, compared to 0.2-20 cm^2 V^-1 s^-1 ever obtained from back-gated MoTe2 transistors in the literatures. Moreover, a considerable hole concentration of 1.2 × 10^13 cm 2 is attained in our Al2O3-based MoTe2 transistors owing to the strong gate control capa- bility, leading to a high on-state hole current of 6.1 μA μm^-1. After optimization, our Al2O3-based MoTe2 phototransistor exhibits outstanding photodetective performance, with a high responsivity of 543 AW^-1 and a high photogain of 1,662 at 405 nm light illumination, which are boosted around 419 times compared to the referential SiO2-based control devices. The mechanisms of photoconductivity in the Al2O3-based MoTe2 phototransistors have been analyzed in detail, and the photogating effect is considered to play an important role. This work may provide useful insight to improve carrier mobility in two-dimensional layered semiconductors and open opportunities to facilitate the development of high-performance photodetectors in the future.展开更多
Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control ...Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control of physical process parameters has not been fully realized with high precision resolution, and requires optimization in order to achieve a wider range of potential applications. Furthermore, the combination of composite insulating oxide layers alternating with semiconducting layers and metals can provide various types of novel applications and eventually provide unique and advanced levels of multifunctional nanoscale devices. Semiconducting TiO2 nanotubes have potential applications in photovoltaic devices. The combination of nanostructured semiconducting materials with nested metal nanotubes has the potential to produce novel multi functional vertically-ordered three-dimensional nanodevices. Platinum growth by ALD has been explored, covering the initial stages of the thin film nucleation process and the synthesis of high aspect ratio nanotube structures. The penetration depth of the Pt into porous templates having various pore sizes and aspect ratios has been investigated. Several multi-walled nested TiO2-Pt nanotubes in series have been successfully fabricated using microporous Si templates. These innovative nested nanostructures have the potential to produce novel multifunctional vertically-ordered three-dimensional nanodevices in photovoltaic and sensing technologies.展开更多
文摘Foodborne disease is a worldwide il ness and over 1 bil ion people get diseased every year. In China, thousands of foodborne diseases occur every year. It is proved that prevention is the most crucial for control ing foodborne disease. In the research, food safety monitoring system, laws and early warning system in the US and EU were introduced to explore the successful experience and monitoring or control mode suitable for China.
文摘Background: Floorball training offers a motivating and socially stimulating team activity for older adults, and 12 weeks of floorball training twice a week among men aged 65—76 years have been shown to have positive effects on a number of physiological parameters important for health. However, the effect of long-term participation in floorball training among male elderly has not been investigated. The aim of the present study was to examine the effect of 26-month self-organized regular participation in floorball training on cardiovascular fitness, body composition, blood lipids, glucose control, and physical function among recreationally active men aged 66—78 years.Methods: After completing a 12-week randomized and controlled intervention with floorball and petanque training in the autumn 2014 or spring2015, 15 subjects chose to participate in floorball training(floorball group, FG), whereas 16 subjects resumed their usual lifestyle(control group,CG). FG took part in self-organized floorball training 1.7 sessions of 40 min/week, and CG continued their normal recreationally active lifestyle during a 26-month follow-up period. At baseline and after the follow-up period subjects were tested for cardiovascular fitness, glucose control(resting blood samples), body composition dual-energy X-ray absorptiometry(DXA-scanning), and functional capacity.Results: In FG, the decline in maximal oxygen uptake(VO_(2max)) during the follow-up period was lower(242 ± 379 mL/min, p = 0.01), blood glycosylated hemoglobin(HbA1c) increased less(—1.6 ± 2.9 mmol/L, p = 0.02), and leg bone mineral density increased more(0.03 ± 0.05 g/cm^2,p = 0.02) than those in CG. The effects on body mass, total lean body mass, fat mass, blood lipids, and physical function were similar in FG and CG.Conclusion: Approximately twice weekly floorball sessions with 40 min/session over 26-month appear to reduce age-related decline in cardiovascular fitness and glucose control and improve leg bone mineral density, suggesting that long-term participation in floorball training can be considered as a health-enhancing activity in recreationally active male elderly.
文摘A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.
文摘Information-Centric Networking(ICN) has recently emerged as a result of the increased demand to access contents regardless of their location in the network services. This new approach facilitates content distribution as a service of the network with lower delay and higher security in comparison with the current IP network. Applying ICN in current IP infrastructure leads to major complexities. One approach to deploy ICN with less complexity is to integrate ICN with Software Defined Networking(SDN). The SDN controller manages the content distribution, caching, and routing based on the users' requests. In this paper, we extend these context by addressing the ICN topology management problem over the SDN network to achieve an improved user experience as well as network performance. In particular, a centralized controller is designed to construct and manage the ICN overlay. Experimental results indicate that this adopted topology management strategy achieves high performance, in terms of low failure in interest satisfaction and reduced download time compared to a plain ICN.
基金Supported by "973" National Key Basic Research Program ( No. 2002CB311905) andYoung Teacher Foundation of Tianjin University.
文摘Based on planar Si dual-base transistor conception, a novel mesa dual-base heterojunc- tion bipolar transistor ( HBT) is designed and fabricated. Molecule beam extension. selective wet chemical etching, common contact photolithography and metal lift-off technique are adopted in the process. The device has particular and distinct voltage-controlled negative differential resistance (NDR) and photo-controlled NDR. The highest peak-to-vally current rate of the voltage-controlled NDR is larger than 148 and the peak current varies with the increase of collector voltage. The device features high speed and high frequency characteristics derived from HBT and intrinsic bistability and self-latching characteristics due to NDR. A single dual-base HBT can be seen as an integration of NDR device, HBT and photoconductive device. Compared with common HBT.the groove is the key factor producing NDR.
基金the Shandong Foundation of Sciences(No.Y2000D04) the National Key Basic Research Program from the Ministry of Science and Technology of China(No.G19990437).
文摘The 5’-end of the mitochondrial control region sequences of three flatfishes (Pleuronectiformes: Pleuronectidae) were amplified and sequenced. These sequences were compared with those of other three Pleuronectids species retrieved from GenBank. A phylogenetic tree was constructed based on the partial control region sequences. The results of phyloge- netic analysis are consistent with those of conventional systematics. Compared to previous studies, the structure of the 5’-end of mitochondrial control region was analyzed. The terminal associated sequence motif and its complementary motif were i- dentified at the 5’-end of the sequences. A conserved sequence block, named as CM5’d, was identified in the 5’-end of con- trol region sequences in all Pleuronectids. Another central conserved sequence block, named as CSB-F, was detected in the central conserved blocks.
文摘This paper points out the drawbacks of traditional financial governance. After introducing Chinese and western economists' researches on firm financial governance theory, we put forward modern finn financial governance system, which is based on the core of finance-rights allocation. In our opinion, the theory of finance-rights is the important cornerstone of the theory of financial finance-rights theory. Financial governance structure system is the basic framework of the research of financial governance.
文摘Cloud computing can offer a very powerful, reliable, predictable and scalable computing infrastructure for the execution of MAS (multi-agent systems) implementing complex agent-based applications such when modelling, simulation and real-time running of complex systems must be provided. Multi-agent systems appears as an adequate approach to current challenges in many areas. Between important qualities of MAS also belongs to, that they are open, interoperable, and heterogenous systems. The agent is active, a program entity, has its own ideas how to perform the tasks of the own agenda. Agents: perceive, behave "reasonably", act in the environment, communicate with other agents. Cloud infrastructures can offer an ideal platform where run MAS systems simulations, applications and real-time running because of its large amount of processing and memory resources that can be dynamically configured for executing large agent-based software at unprecedented scale. Cloud computing can help chemical and food companies drive operational excellence; meet growing and changing customer demands; accelerate new product innovation and ramp-to-volume manufacturing in key markets; reduce IT spending; manage and mitigate supply chain risks; and enable faster and more flexible delivery of new IT system. Production type of SOC (service-oriented computing) can be inspired by a "Cloud", for the production of "Cloud" offers an attractive and natural solutions in several computing trends such as delivery system over the Internet, use of utilities, flexibility, virtualization, a "grid" distributed computing, outsourcing, Web 2.0, etc.. Production of the "Cloud" is also considered as a new multidisciplinary field that includes "network" production, virtual manufacturing, agile manufacturing, and of course cloud computing. Examples of cloud computing and MAS applications in food and chemistry development and industry, proposition of using multi-agent systems in the control of batch processes, modified ACO (ant colony optimization) approach for the diversified service allocation and scheduling mechanism in cloud paradigma, examples of applications in a business area were studied in the paper.
文摘The paper presents an innovative renewable energy-load management technology, which is currently being developed as a prototype, in preparation for potential large-scale implementation in power systems. The new technology employs controlled motion of large weights, which are being maneuvered (up and down) through the system peak/off-peak demand pattern. The load management scheme is similar to the pumping storage systems, but uses large weights instead of water and, therefore, is more suited to the operating environment in Saudi Arabia, in which water is relatively scarce. A portion of the off-peak valley-filling energy is supplied from wind-driven generators, which adds to the green energy component of the scheme. The controlled motion aspect of the new technology is based on partial implementation of previously published ideas by the authors as well as a registered patent. The paper describes the theoretical and analytical features of the introduced renewable energy-load management technology, and dwells on its practical implementation features.
文摘Intensive in-depth development of resources, centralized purchasing and gradually expand under the category of environment, this paper studies how to use information technology tools to construction quality supervision and management system that focuses on the quality of supervision and project management, quality control process management, quality monitoring statistics report management, platform management-related content in four areas. Through the construction quality supervision and management system, to better enhance the quality of electric power enterprise management level, to ensure that the material quality, quantity of time and supplies. strengthening quality supervision and management can not only effectively reduce material procurement costs, but also enhance the competitiveness of enterprises.
文摘This paper deals with utilization possibility of a kinematical couple of screw-matrix in minimachine mechatronic concept which is assigned to move within the pipes having less than 25 mm of the inner diameter. The principle of the movement for a straightforward motion consists in transformation of the actuator rotary movement through a screw and a nut to the linear motion. It causes a change of distance between the front and rear parts of the minimachine modules. Due to minimization of the dimensions, the electrical control and power supply components are placed outside of the minimachine operating area. The control module is based on a programmable integrated circuit (PIC).
文摘Parameters of the power source used to control PV-10 piezoelectric crystal valve are following DC output voltage: 0 - 120 V, continuously controllable, linear enlargement factor of input direct current voltage: approximate 25 times, the accuracy of DC output voltage: ±5%, manual control and automatic control.
文摘A curriculum is a complex system that includes a set of core competencies, objectives, contents, methodological and evaluation criteria, regulation among other things. In order to represent a curriculum as a piece of software the common tools used are databases, trees and lists of courses. However, none of these tools can capture the deep and complex relationships among the elements of a curriculum. To avoid this problem, a more complete representation of an engineering curriculum using ontologies has been developed. This paper presents the construction of an ontology for undergraduate electrical engineering curriculum domain at Universidad Nacional de Colombia, which aims to represent, organize, formalize and standardize the knowledge of this domain, so that it can be shared and reused by different groups of people in the field of education and engineering. The ontology includes four curriculum aspects: knowledge in electrical engineering, skills in engineering, electrical engineering curriculum and regulation. For the ontology development, Methontology was selected as methodology and Protege as implementation tool. In addition, there is a proposal of documentation for this methodology, based on principles of quality management systems. This ontology is designed in order to be used in any field of engineering.
基金supported by the National Key Research and Development Program of China(2016YFA0302300,016YFA0200400)the National Science and Technology Major Project of China(2016ZX02301001)+1 种基金the National Natural Science Foundation of China(61306105)the Tsinghua University Initiative Scientific Research Program
文摘Molybdenum ditelluride (MoTe2) has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taking advantage of high-κ screening effect, we have fabricated back-gated MoTe2 transistors on an Al2O3 high-κ dielectric and systematically investigated the electronic and optoelectronic proper- ties. A high current on/off ratio exceeding 106 is achieved in the Al2O3-based MoTe2 transistors, and the hole mobility is demonstrated to be 150 cm2 V^-1 s^-1, compared to 0.2-20 cm^2 V^-1 s^-1 ever obtained from back-gated MoTe2 transistors in the literatures. Moreover, a considerable hole concentration of 1.2 × 10^13 cm 2 is attained in our Al2O3-based MoTe2 transistors owing to the strong gate control capa- bility, leading to a high on-state hole current of 6.1 μA μm^-1. After optimization, our Al2O3-based MoTe2 phototransistor exhibits outstanding photodetective performance, with a high responsivity of 543 AW^-1 and a high photogain of 1,662 at 405 nm light illumination, which are boosted around 419 times compared to the referential SiO2-based control devices. The mechanisms of photoconductivity in the Al2O3-based MoTe2 phototransistors have been analyzed in detail, and the photogating effect is considered to play an important role. This work may provide useful insight to improve carrier mobility in two-dimensional layered semiconductors and open opportunities to facilitate the development of high-performance photodetectors in the future.
文摘Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control of physical process parameters has not been fully realized with high precision resolution, and requires optimization in order to achieve a wider range of potential applications. Furthermore, the combination of composite insulating oxide layers alternating with semiconducting layers and metals can provide various types of novel applications and eventually provide unique and advanced levels of multifunctional nanoscale devices. Semiconducting TiO2 nanotubes have potential applications in photovoltaic devices. The combination of nanostructured semiconducting materials with nested metal nanotubes has the potential to produce novel multi functional vertically-ordered three-dimensional nanodevices. Platinum growth by ALD has been explored, covering the initial stages of the thin film nucleation process and the synthesis of high aspect ratio nanotube structures. The penetration depth of the Pt into porous templates having various pore sizes and aspect ratios has been investigated. Several multi-walled nested TiO2-Pt nanotubes in series have been successfully fabricated using microporous Si templates. These innovative nested nanostructures have the potential to produce novel multifunctional vertically-ordered three-dimensional nanodevices in photovoltaic and sensing technologies.