The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design,in which the band gaps play a paramount role.Aiming at providing better designs for these foundation...The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design,in which the band gaps play a paramount role.Aiming at providing better designs for these foundations,this study first proposes and validates the analytical formulas to approximate the bounds of the first few band gaps.In addition,the mapping relations linking the frequencies of different band gaps are presented.Furthermore,an optimal design method for these foundations is developed,which is validated through an engineering example.It is demonstrated that ensuring the superstructure’s resonance zones are completely covered by the corresponding periodic foundation’s band gaps can achieve satisfactory vibration attenuation effects,which is a good strategy for the design of rubber concrete layered periodic foundations.展开更多
As one of the most concerned digital technologies in recent years,blockchain and distributed ledger technology are an important driving force for a new round of technological development.It is currently in the process...As one of the most concerned digital technologies in recent years,blockchain and distributed ledger technology are an important driving force for a new round of technological development.It is currently in the process of accelerating its evolution and maturity,and has gradually integrated with other digital technologies.It has been applied in many industries,providing decentralized solutions for various industries,realizing innovative storage models,and building a new trust system.As blockchain technology is officially incorporated into China’s new information infrastructure category,the application fields of blockchain have expanded rapidly,gradually extending from the financial field and government affairs to other fields in the real economy.At the same time,with the continuous development of the globalized economy,blockchain technology will also have a profound impact on international technological and economic development.Therefore,for the healthy and orderly development and real implementation of the blockchain industry,standardize the application of blockchain,effectively break through the cognitive and technical barriers between different countries,industries and systems on a global scale,prevent application risks,the development of the global blockchain industry needs standardization basis,which is particularly important and urgent.A sound standard system is an important key to the successful development of technology,and formulating the right standard at the right time for technology development helps ensure the ease of use and interoperability of the technology.From the perspective of international standardization,this article first introduces the general situation of ISO,ITU-T,IEEE,W3C and other international standardization organizations,and sorts out the status quo of the blockchain standardization working groups of mainstream international standardization organizations.All blockchain-related standards under development have been analyzed for the characteristics of international blockchain technology standards and industry application standards.Through data analysis,the overlaps,differences and conflicts in the field of international blockchain standard formulation are sorted out,and suggestions for blockchain standardization work in the application and development of blockchain technology standardization by international organizations and industries are put forward.The plans and layouts of future international standards are summarized to help the development of the international standardization of blockchain.展开更多
Electrochemical water splitting represents one of the most promising technologies to produce green hydrogen,which can help to realize the goal of achieving carbon neutrality.While substantial efforts on a laboratory s...Electrochemical water splitting represents one of the most promising technologies to produce green hydrogen,which can help to realize the goal of achieving carbon neutrality.While substantial efforts on a laboratory scale have been made for understanding fundamental catalysis and developing high-performance electrocatalysts for the two half-reactions involved in water electrocatalysis,much less attention has been paid to doing relevant research on a larger scale.For example,few such researches have been done on an industrial scale.Herein,we review the very recent endeavors to bridge the gaps between fundamental research and industrial applications for water electrolysis.We begin by introducing the fundamentals of electrochemical water splitting and then present comparisons of testing protocol,figure of merit,catalyst of interest,and manufacturing cost for laboratory and industry-based water-electrolysis research.Special attention is paid to tracking the surface reconstruction process and identifying real catalytic species under different testing conditions,which highlight the significant distinctions of corresponding electrochemical reconstruction mechanisms.Advances in catalyst designs for industry-relevant water electrolysis are also summarized,which reveal the progress of moving the practical applications forward and accelerating synergies between material science and engineering.Perspectives and challenges of electrocatalyst design strategies are proposed finally to further bridge the gaps between lab-scale research and large-scale electrocatalysis applications.展开更多
This paper analyzes the evolving trends in China’s rural poverty from 1988 to 2018 and how income growth and income gaps contributed to poverty reduction using rural household data from the China Household Income Pro...This paper analyzes the evolving trends in China’s rural poverty from 1988 to 2018 and how income growth and income gaps contributed to poverty reduction using rural household data from the China Household Income Project(CHIP).We find that after China’s reform and opening up policy introduced in 1978,China’s rural poverty has been reduced substantially due primarily to income growth,although this poverty-reducing effect was partially offset by widening income gaps.During the progress of this poverty reduction,however,income distribution replaced income growth as the key driver.For the extremely poor in particular,their poverty status hinged upon income distribution.As revealed by our empirical analysis of income sources,wage income became the chief source of income for rural households,contributing a rising share to poverty reduction in the countryside.The contribution of net income from government transfer to poverty reduction has increased in recent years,and this contribution has been increased with the deepening level of poverty.Calculation of the pro-poor growth index suggests that the poor population primarily benefited from the trickle-down effect of economic growth,and the economic growth pattern has yet to lean towards pro-poor growth.展开更多
Daily and weekly reporting events of climate change and impacts on populations, cultures, economies and politics at local, national, regional and international scales suggest the need to construct databases that will ...Daily and weekly reporting events of climate change and impacts on populations, cultures, economies and politics at local, national, regional and international scales suggest the need to construct databases that will be useful in future scientific inquiry and global human/environmental policies. That need is evident in constructing a geographic or locational knowledge base that examines countries, regions and cities. This study constructs a database on the impacts of climate change using Google Scholar entries for 200 countries and capital cities. A series of maps reveal the vast unevenness in the database, especially between Global North and Global South countries. The discussion explores these sharp differences and suggests future research topics for much-needed global, interdisciplinary and international research.展开更多
China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits. However, the annual productivity of China's apple is significantly l...China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits. However, the annual productivity of China's apple is significantly lower than that of other dominant apple producing countries. In addition, apple production is based on excessive application of chemical fertilizers and the nutrient use efficiency (especially nitrogen) is therefore low and the nutrient emissions to the environment are high. Apple production in China is considerably contributes to farmers' incomes and is important as export product. There is an urgent need to enhance apple productivity and improve nutrient use efficiencies in intensive apple production systems in the country. These can be attained by improved understanding of production potential, yield gaps, nutrient use and best management in apple orchards. To the end, priorities in research on apple production systems and required political support are described which may lead to more sustainable and environmental-friendly intensification of apple production in China.展开更多
The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically ...The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically placed in a host material. Numerical simulations show that the low-frequency gaps of flexural wave exist in the thin plates. The width of the first gap decreases monotonically as the matrix density increases, The frequency response of the finite periodic thin plates is simulated by the finite element method, which provides attenuations of over 20dB in the frequency range of the band gaps. The findings will be significant in the application of phononic crystals.展开更多
Periodic arrays of resonant shunted piezoelectric patches are employed to control the wave propagation in a two-dimensional (2D) acoustic metamaterial. The performance is characterized by the finite element method. ...Periodic arrays of resonant shunted piezoelectric patches are employed to control the wave propagation in a two-dimensional (2D) acoustic metamaterial. The performance is characterized by the finite element method. More importantly, we propose an approach to solving the conventional issue of the nonlinear eigenvalue problem, and give a convenient solution to the dispersion properties of 2D metamaterials with periodic arrays of resonant shunts in this article. Based on this modeling method, the dispersion relations of a 2D metamaterial with periodic arrays of resonant shunted piezos are calculated. The results show that the internal resonances of the shunting system split the dispersion curves, thereby forming a locally resonant band gap. However, unlike the conventional locally resonant gap, the vibrations in this locally resonant gap are unable to be completely localized in oscillators consisting of shunting inductors and piezo-patches.展开更多
Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly ...Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8+δ (Bi2212) and YBa2Cu3O7-x (YBCO) along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the (100) plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a (110) surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.展开更多
The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with...The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2μm to 40 #m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d 〈5 μm), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 μm〈 d 〈10 μm); (3) a region for large gaps that adhered to Paschen's curve (d 〉10μm). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.展开更多
A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we...A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we find a strong consistency between the variation of the TD number(the average value of the temperature in each heat transfer channel is averaged after taking the absolute values) with the change of the height of gaps and the variation of the TD number with the change of Ra number in partitioned convection.For a given thickness of partition, heights of gaps are approximately equal to 0.5 or 1 time of the thermal boundary layer thickness λθ at different Ra numbers.TD number representing temperature characteristics is almost the constant value, which means that TD number is a function of d/λθ only.Analysis of local temperature field of area in gaps shows that the temperature distribution in the gaps are basically the same when d/λθ is certain.The heat transfer Nu number of the system at d/λθ≈ 0.5 is larger than that of d/λθ≈ 1, both of them have the same scaling law with Ra number and Nu^Ra^0.25.展开更多
The genebank at ICRISAT maintains 8020 accessions of sorghum from 16 West and Central African countries. Geographical gaps and diversity were assessed in the collection. Using the passport data of 3991 accessions for ...The genebank at ICRISAT maintains 8020 accessions of sorghum from 16 West and Central African countries. Geographical gaps and diversity were assessed in the collection. Using the passport data of 3991 accessions for which georeferenced data were available, a total of386 districts(gaps) located in 11 West and Central African countries were identified as geographical gaps. Burkina Faso with 140 and Nigeria with 118 districts were identified as countries with major geographical gaps. The collection of 43 accessions of wild species represented only three species belonging to Sorghum bicolor ssp. drummondii and ssp.verticilliflorum, S. hevisonii, and S. macrochaeta, highlighting the need for collection missions aimed exclusively at enriching the collection of wild relatives. Accessions having characterization data(7630) were used to assess diversity. The first three principal components contributed to >60% of variation. Maximum diversity was observed in the collection from Nigeria for both qualitative and quantitative traits. Mean values indicated significant differences between basic and intermediate races for the traits studied. Among the races, accessions of guinea-caudatum for qualitative traits and those of caudatum for quantitative traits were highly diverse. The low intensity of the sorghum collection and the many geographical gaps in the collection underline the importance of launching collection missions to fill the gaps, particularly in regions of predominantly guinea sorghums.Genotyping of possible duplicate accessions is needed to identify duplicates in the collection. It is suggested that all passport information including georeferenced data of collection sites should be collected when samples are collected in gaps.展开更多
In this paper, modified two-dimensional peri- odic lattice materials with local resonance phononic band gaps are designed and investigated. The design concept is to introduce some auxiliary structures into conventiona...In this paper, modified two-dimensional peri- odic lattice materials with local resonance phononic band gaps are designed and investigated. The design concept is to introduce some auxiliary structures into conventional pe- riodic lattice materials. Elastic wave propagation in this kind of modified two-dimensional lattice materials is studied us- ing a combination of Bloch's theorem with finite element method. The calculated frequency band structures of illus- trative modified square lattice materials reveal the existence of frequency band gaps in the low frequency region due to the introduction of the auxiliary structures. The mechanism underlying the occurrence of these frequency band gaps is thoroughly discussed and natural resonances of the auxiliary structures are validated to be the origin. The effect of geo- metric parameters of the auxiliary structures on the width of the local resonance phononic band gaps is explored. Finally, a conceptual broadband vibration-insulating structure based on the modified lattice materials is designed and its capabil- ity is demonstrated. The present work is anticipated to be useful in designing structures which can insulate mechanical vibrations within desired frequency ranges.展开更多
The accelerated population growth of the elderly(individuals aged 60 years or more)across the globe has many indications,including changes in demography,health,the psycho-social milieu,and economic security.This trans...The accelerated population growth of the elderly(individuals aged 60 years or more)across the globe has many indications,including changes in demography,health,the psycho-social milieu,and economic security.This transition has given rise to varied challenges;significant changes have been observed in regard to developing strategies for health care systems across the globe.The World Health Organization(WHO)is also engaging in initiatives and mediating processes.Furthermore,advocacy is being conducted regarding a shift toward the salutogenic model from the pathogenic model.The concept behind this move was to shift from disablement to enablement and from illness to wellness,with the notion of mental health promotion(MHP)being promoted.This article attempts to discuss the MHP of elderly individuals,with special reference to the need to disseminate knowledge and awareness in the community by utilizing the resources of the health sector available in the WHO South-East Asia Region countries.We have tried to present the current knowledge gap by exploring the existing infrastructure,human resources,and financial resources.There is much to do to promote the mental health of the elderly,but inadequate facilities are available.Based on available resources,a roadmap for MHP in elderly individuals is discussed.展开更多
Incidence and consequences of spinal cord injuries: World- wide, every year 250,000-500,000 people suffer from spinal cord injury (SCI; www.who.int, 2013). Traumatic lesions of the spinal cord lead to primary and s...Incidence and consequences of spinal cord injuries: World- wide, every year 250,000-500,000 people suffer from spinal cord injury (SCI; www.who.int, 2013). Traumatic lesions of the spinal cord lead to primary and secondary injury mechanisms, which result in axon damage, loss of signal conduction, demyelination of axons and long-lasting deficits in motor and sensory func- tion. The extent of the damage and the subsequent functional loss depend on the spinal level and the severity of the primary injury. Furthermore, pathophysiological and pathomorpholog- ical responses in acute and chronic SCI share similar but also different requirements for treatment.展开更多
A periodic pipe system composed of steel pipes and rubber hoses with the same inner radius is designed based on the theory of phononic crystals. Using the transfer matrix method, the band structure of the periodic pip...A periodic pipe system composed of steel pipes and rubber hoses with the same inner radius is designed based on the theory of phononic crystals. Using the transfer matrix method, the band structure of the periodic pipe is calculated considering the structural-acoustic coupling. The results show that longitudinal vibration band gaps and acoustic band gaps can coexist in the fluid-filled periodic pipe. The formation of the band gap mechanism is further analyzed. The band gaps are validated by the sound transmission loss and vibration-frequency response functions calculated using the finite element method. The effect of the damp on the band gap is analyzed by calculating the complex band structure. The periodic pipe system can be used not only in the field of vibration reduction but also for noise elimination.展开更多
With the idea of the phononic crystals, the beams with periodic structure are designed. Flexural vibration through such periodic beams composed of two kinds of materials is studied. The emphasis is laid on the effects...With the idea of the phononic crystals, the beams with periodic structure are designed. Flexural vibration through such periodic beams composed of two kinds of materials is studied. The emphasis is laid on the effects of rotary inertia and shear deformation. Based on the vibration equation, plane wave expansion method is provided. The acceleration frequency responses of such beams with finite structure are simulated by the finite element method. The frequency ranges of sharp drops in the calculated acceleration frequency response curves are in good agreement with those in the band structures. The findings will be significant in the application of the periodic beams.展开更多
基金National Natural Science Foundation of China under Grant Nos.52078395 and 52178301the Open Projects Foundation of the State Key Laboratory for Health and Safety of Bridge Structures under Grant No.BHSKL19-07-GF+1 种基金the Dawn Program of Knowledge Innovation Project from the Bureau of Science and Technology of Wuhan Municipality under Grant No.2022010801020357the Science Research Foundation of Wuhan Institute of Technology under Grant No.K2021030。
文摘The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design,in which the band gaps play a paramount role.Aiming at providing better designs for these foundations,this study first proposes and validates the analytical formulas to approximate the bounds of the first few band gaps.In addition,the mapping relations linking the frequencies of different band gaps are presented.Furthermore,an optimal design method for these foundations is developed,which is validated through an engineering example.It is demonstrated that ensuring the superstructure’s resonance zones are completely covered by the corresponding periodic foundation’s band gaps can achieve satisfactory vibration attenuation effects,which is a good strategy for the design of rubber concrete layered periodic foundations.
基金supported by the Key R&D Program of Zhejiang Province(2021C01105)the Key R&D Program of Guangdong Province(2020B0101090003)+1 种基金the National Key R&D Program of China(2021YFB2701100)These supports are gratefully acknowledged.
文摘As one of the most concerned digital technologies in recent years,blockchain and distributed ledger technology are an important driving force for a new round of technological development.It is currently in the process of accelerating its evolution and maturity,and has gradually integrated with other digital technologies.It has been applied in many industries,providing decentralized solutions for various industries,realizing innovative storage models,and building a new trust system.As blockchain technology is officially incorporated into China’s new information infrastructure category,the application fields of blockchain have expanded rapidly,gradually extending from the financial field and government affairs to other fields in the real economy.At the same time,with the continuous development of the globalized economy,blockchain technology will also have a profound impact on international technological and economic development.Therefore,for the healthy and orderly development and real implementation of the blockchain industry,standardize the application of blockchain,effectively break through the cognitive and technical barriers between different countries,industries and systems on a global scale,prevent application risks,the development of the global blockchain industry needs standardization basis,which is particularly important and urgent.A sound standard system is an important key to the successful development of technology,and formulating the right standard at the right time for technology development helps ensure the ease of use and interoperability of the technology.From the perspective of international standardization,this article first introduces the general situation of ISO,ITU-T,IEEE,W3C and other international standardization organizations,and sorts out the status quo of the blockchain standardization working groups of mainstream international standardization organizations.All blockchain-related standards under development have been analyzed for the characteristics of international blockchain technology standards and industry application standards.Through data analysis,the overlaps,differences and conflicts in the field of international blockchain standard formulation are sorted out,and suggestions for blockchain standardization work in the application and development of blockchain technology standardization by international organizations and industries are put forward.The plans and layouts of future international standards are summarized to help the development of the international standardization of blockchain.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)supported by National R&D Program through the National Research Foundation of Korea(NRF),grant number 2021M3H4A1A01079300the Korea Research Institute of Chemical Technology Core Research Program funded by the Korea Research Council for Industrial Science and Technology,grant number KS2222-10.
文摘Electrochemical water splitting represents one of the most promising technologies to produce green hydrogen,which can help to realize the goal of achieving carbon neutrality.While substantial efforts on a laboratory scale have been made for understanding fundamental catalysis and developing high-performance electrocatalysts for the two half-reactions involved in water electrocatalysis,much less attention has been paid to doing relevant research on a larger scale.For example,few such researches have been done on an industrial scale.Herein,we review the very recent endeavors to bridge the gaps between fundamental research and industrial applications for water electrolysis.We begin by introducing the fundamentals of electrochemical water splitting and then present comparisons of testing protocol,figure of merit,catalyst of interest,and manufacturing cost for laboratory and industry-based water-electrolysis research.Special attention is paid to tracking the surface reconstruction process and identifying real catalytic species under different testing conditions,which highlight the significant distinctions of corresponding electrochemical reconstruction mechanisms.Advances in catalyst designs for industry-relevant water electrolysis are also summarized,which reveal the progress of moving the practical applications forward and accelerating synergies between material science and engineering.Perspectives and challenges of electrocatalyst design strategies are proposed finally to further bridge the gaps between lab-scale research and large-scale electrocatalysis applications.
文摘This paper analyzes the evolving trends in China’s rural poverty from 1988 to 2018 and how income growth and income gaps contributed to poverty reduction using rural household data from the China Household Income Project(CHIP).We find that after China’s reform and opening up policy introduced in 1978,China’s rural poverty has been reduced substantially due primarily to income growth,although this poverty-reducing effect was partially offset by widening income gaps.During the progress of this poverty reduction,however,income distribution replaced income growth as the key driver.For the extremely poor in particular,their poverty status hinged upon income distribution.As revealed by our empirical analysis of income sources,wage income became the chief source of income for rural households,contributing a rising share to poverty reduction in the countryside.The contribution of net income from government transfer to poverty reduction has increased in recent years,and this contribution has been increased with the deepening level of poverty.Calculation of the pro-poor growth index suggests that the poor population primarily benefited from the trickle-down effect of economic growth,and the economic growth pattern has yet to lean towards pro-poor growth.
文摘Daily and weekly reporting events of climate change and impacts on populations, cultures, economies and politics at local, national, regional and international scales suggest the need to construct databases that will be useful in future scientific inquiry and global human/environmental policies. That need is evident in constructing a geographic or locational knowledge base that examines countries, regions and cities. This study constructs a database on the impacts of climate change using Google Scholar entries for 200 countries and capital cities. A series of maps reveal the vast unevenness in the database, especially between Global North and Global South countries. The discussion explores these sharp differences and suggests future research topics for much-needed global, interdisciplinary and international research.
基金the project "Cash Crops Research Network of China" of the Center for Resources, Environment and Food Security, China Agricultural UniversityProfessor Oene Oenema from Alterra Wageningnen University, the Netherlands, for his financial support of the research
文摘China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits. However, the annual productivity of China's apple is significantly lower than that of other dominant apple producing countries. In addition, apple production is based on excessive application of chemical fertilizers and the nutrient use efficiency (especially nitrogen) is therefore low and the nutrient emissions to the environment are high. Apple production in China is considerably contributes to farmers' incomes and is important as export product. There is an urgent need to enhance apple productivity and improve nutrient use efficiencies in intensive apple production systems in the country. These can be attained by improved understanding of production potential, yield gaps, nutrient use and best management in apple orchards. To the end, priorities in research on apple production systems and required political support are described which may lead to more sustainable and environmental-friendly intensification of apple production in China.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 51307) and the National Natural Science Foundation of China (Grant No 50575222).
文摘The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically placed in a host material. Numerical simulations show that the low-frequency gaps of flexural wave exist in the thin plates. The width of the first gap decreases monotonically as the matrix density increases, The frequency response of the finite periodic thin plates is simulated by the finite element method, which provides attenuations of over 20dB in the frequency range of the band gaps. The findings will be significant in the application of phononic crystals.
基金the National Natural Science Foundation of China(Grant Nos.50905182 and 51175501)
文摘Periodic arrays of resonant shunted piezoelectric patches are employed to control the wave propagation in a two-dimensional (2D) acoustic metamaterial. The performance is characterized by the finite element method. More importantly, we propose an approach to solving the conventional issue of the nonlinear eigenvalue problem, and give a convenient solution to the dispersion properties of 2D metamaterials with periodic arrays of resonant shunts in this article. Based on this modeling method, the dispersion relations of a 2D metamaterial with periodic arrays of resonant shunted piezos are calculated. The results show that the internal resonances of the shunting system split the dispersion curves, thereby forming a locally resonant band gap. However, unlike the conventional locally resonant gap, the vibrations in this locally resonant gap are unable to be completely localized in oscillators consisting of shunting inductors and piezo-patches.
基金Supported by the National Natural Science Foundation of Chinathe National Key Research and Development Program of China under Grant No 2016YFA0300203
文摘Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8+δ (Bi2212) and YBa2Cu3O7-x (YBCO) along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the (100) plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a (110) surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.
基金supported by Research Funds of State Key Laboratory of Electrical Insulation and Power Equipment (Xi'an Jiaotong University) of China (No.EIPE14107)
文摘The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2μm to 40 #m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d 〈5 μm), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 μm〈 d 〈10 μm); (3) a region for large gaps that adhered to Paschen's curve (d 〉10μm). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11772362 and 11452002)the Special Scientific Research Fund for Super Computing in the Joint Fund of the National Natural Science Foundation of China and the People’s Government of Guangdong Province,China(Phase Ⅱ,nsfc2015_570)
文摘A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we find a strong consistency between the variation of the TD number(the average value of the temperature in each heat transfer channel is averaged after taking the absolute values) with the change of the height of gaps and the variation of the TD number with the change of Ra number in partitioned convection.For a given thickness of partition, heights of gaps are approximately equal to 0.5 or 1 time of the thermal boundary layer thickness λθ at different Ra numbers.TD number representing temperature characteristics is almost the constant value, which means that TD number is a function of d/λθ only.Analysis of local temperature field of area in gaps shows that the temperature distribution in the gaps are basically the same when d/λθ is certain.The heat transfer Nu number of the system at d/λθ≈ 0.5 is larger than that of d/λθ≈ 1, both of them have the same scaling law with Ra number and Nu^Ra^0.25.
文摘The genebank at ICRISAT maintains 8020 accessions of sorghum from 16 West and Central African countries. Geographical gaps and diversity were assessed in the collection. Using the passport data of 3991 accessions for which georeferenced data were available, a total of386 districts(gaps) located in 11 West and Central African countries were identified as geographical gaps. Burkina Faso with 140 and Nigeria with 118 districts were identified as countries with major geographical gaps. The collection of 43 accessions of wild species represented only three species belonging to Sorghum bicolor ssp. drummondii and ssp.verticilliflorum, S. hevisonii, and S. macrochaeta, highlighting the need for collection missions aimed exclusively at enriching the collection of wild relatives. Accessions having characterization data(7630) were used to assess diversity. The first three principal components contributed to >60% of variation. Maximum diversity was observed in the collection from Nigeria for both qualitative and quantitative traits. Mean values indicated significant differences between basic and intermediate races for the traits studied. Among the races, accessions of guinea-caudatum for qualitative traits and those of caudatum for quantitative traits were highly diverse. The low intensity of the sorghum collection and the many geographical gaps in the collection underline the importance of launching collection missions to fill the gaps, particularly in regions of predominantly guinea sorghums.Genotyping of possible duplicate accessions is needed to identify duplicates in the collection. It is suggested that all passport information including georeferenced data of collection sites should be collected when samples are collected in gaps.
基金supported by the National Natural Science Foundation of China (90916007)
文摘In this paper, modified two-dimensional peri- odic lattice materials with local resonance phononic band gaps are designed and investigated. The design concept is to introduce some auxiliary structures into conventional pe- riodic lattice materials. Elastic wave propagation in this kind of modified two-dimensional lattice materials is studied us- ing a combination of Bloch's theorem with finite element method. The calculated frequency band structures of illus- trative modified square lattice materials reveal the existence of frequency band gaps in the low frequency region due to the introduction of the auxiliary structures. The mechanism underlying the occurrence of these frequency band gaps is thoroughly discussed and natural resonances of the auxiliary structures are validated to be the origin. The effect of geo- metric parameters of the auxiliary structures on the width of the local resonance phononic band gaps is explored. Finally, a conceptual broadband vibration-insulating structure based on the modified lattice materials is designed and its capabil- ity is demonstrated. The present work is anticipated to be useful in designing structures which can insulate mechanical vibrations within desired frequency ranges.
文摘The accelerated population growth of the elderly(individuals aged 60 years or more)across the globe has many indications,including changes in demography,health,the psycho-social milieu,and economic security.This transition has given rise to varied challenges;significant changes have been observed in regard to developing strategies for health care systems across the globe.The World Health Organization(WHO)is also engaging in initiatives and mediating processes.Furthermore,advocacy is being conducted regarding a shift toward the salutogenic model from the pathogenic model.The concept behind this move was to shift from disablement to enablement and from illness to wellness,with the notion of mental health promotion(MHP)being promoted.This article attempts to discuss the MHP of elderly individuals,with special reference to the need to disseminate knowledge and awareness in the community by utilizing the resources of the health sector available in the WHO South-East Asia Region countries.We have tried to present the current knowledge gap by exploring the existing infrastructure,human resources,and financial resources.There is much to do to promote the mental health of the elderly,but inadequate facilities are available.Based on available resources,a roadmap for MHP in elderly individuals is discussed.
基金funded by the DGUV(Deutsche Gesetzliche Unfallversicherung)BMBF(German Federal Ministry for Education and Research)+1 种基金DSQ(German Paraplegia Foundation)Manchot Foundation and Research Commission of the Medical Faculty of the Heinrich-Heine-University Düsseldorf
文摘Incidence and consequences of spinal cord injuries: World- wide, every year 250,000-500,000 people suffer from spinal cord injury (SCI; www.who.int, 2013). Traumatic lesions of the spinal cord lead to primary and secondary injury mechanisms, which result in axon damage, loss of signal conduction, demyelination of axons and long-lasting deficits in motor and sensory func- tion. The extent of the damage and the subsequent functional loss depend on the spinal level and the severity of the primary injury. Furthermore, pathophysiological and pathomorpholog- ical responses in acute and chronic SCI share similar but also different requirements for treatment.
基金Supported by the National Natural Science Foundation of China under Grant No 11372346
文摘A periodic pipe system composed of steel pipes and rubber hoses with the same inner radius is designed based on the theory of phononic crystals. Using the transfer matrix method, the band structure of the periodic pipe is calculated considering the structural-acoustic coupling. The results show that longitudinal vibration band gaps and acoustic band gaps can coexist in the fluid-filled periodic pipe. The formation of the band gap mechanism is further analyzed. The band gaps are validated by the sound transmission loss and vibration-frequency response functions calculated using the finite element method. The effect of the damp on the band gap is analyzed by calculating the complex band structure. The periodic pipe system can be used not only in the field of vibration reduction but also for noise elimination.
基金This project is supported by National Key Basic Research Program of China (973 Program, No.51307).
文摘With the idea of the phononic crystals, the beams with periodic structure are designed. Flexural vibration through such periodic beams composed of two kinds of materials is studied. The emphasis is laid on the effects of rotary inertia and shear deformation. Based on the vibration equation, plane wave expansion method is provided. The acceleration frequency responses of such beams with finite structure are simulated by the finite element method. The frequency ranges of sharp drops in the calculated acceleration frequency response curves are in good agreement with those in the band structures. The findings will be significant in the application of the periodic beams.