Arc plasma torch is an effective tool for spheroidization of metallic powders.However,as most conventional plasma torches were not specifically designed for plasma spheroidization,they may exhibit the disadvantages of...Arc plasma torch is an effective tool for spheroidization of metallic powders.However,as most conventional plasma torches were not specifically designed for plasma spheroidization,they may exhibit the disadvantages of the radial injection of powders,large fluctuations in the arc voltage,large gas flow rate,and disequilibrium between multiple plasma jets during the spheroidization process.Therefore,this paper presents a triple-cathode cascade plasma torch(TCCPT)for plasma spheroidization.Its structural design,including three cathodes,a common anode,and three sets of inter-electrodes,are detailed to ensure that powders can be inserted into the plasma jet by axial injection,the arc voltage fluctuations are easily maintained at a low level,and the plasma torches can work at a relatively small gas flow rate.Experimental results showed that the proposed TCCPT exhibits the following characteristics:(1)a relatively small arc voltage fluctuation within 5.3%;(2)a relatively high arc voltage of 75 V and low gas flow rate range of10-30 SLM;(3)easy to be maintained at the equilibrium state with the equilibrium index of the three plasma jets within 3.5 V.Furthermore,plasma spheroidization experiments of SUS304 stainless steel powers were carried out using the proposed TCCPT.Results verified that the proposed TCCPT is applicable and effective for the spheroidization of metallic powders with wide size distribution.展开更多
Lactobacilli have been consistently associated with dental caries for decades;however, knowledge of this group of bacteria in the etiology of the disease is limited to quantitative elucidation. Nowadays, explicit iden...Lactobacilli have been consistently associated with dental caries for decades;however, knowledge of this group of bacteria in the etiology of the disease is limited to quantitative elucidation. Nowadays, explicit identification of oral Lactobacillus species is possible, despite their taxonomic complexity. Here we describe a combined approach involving both cultivation and genetic methods to ascertain and characterize the diversity and abundance of the Lactobacillus population in the oral cavities of children with severe early childhood caries (S-ECC). Eighty 3- to 6-year-old children (40 S-ECC and 40 caries free) who were seeking dental care at the Pediatric Dental Clinic of Bellevue Hospital in New York City were invited to participate in this study. Clinical data on sociodemographic information and oral health behavior were obtained from the primary caregiver. The data included a detailed dental examination, children’s medical history, and a questionnaire survey. Combined non-stimulated saliva and supragingival plaque samples were collected from each child and cultivated on selective media for quantitative measures of lactobacilli levels. The procedure for Lactobacillus species screening will include the random selection of 50 colonies per plate, ex- traction of DNA from each colony, and genotyping by arbitrarily primed polymerase chain reaction (AP-PCR). Each unique Lactobacillus AP-PCR genotype will be selected for taxonomic assessment by 16S rRNA gene sequencing analysis. Lactobacillus species will be identified by comparing the 16S rRNA sequences with the Ribosomal Database and the Human Oral Microbiome Database. Meanwhile, the same set of clinical samples will be independently subjected to genomic DNA isolation, 16S rRNA amplification with Lactobacillus genus-specific primers, sequencing, and taxonomic identification, both at genus and species levels with a customized pipeline. The distribution and phylogenetic differences of these Lactobacillus species will be compared between children with or without S-ECC. One of the main objectives of this study is to establish a study protocol for the identification and characterization of lactobacilli in the oral cavity. Future caries risk assessments can include lactobacilli counts (quantitative) and the presence/absence of specific cario- genic genetic signatures of a Lactobacillus species (qualitative) associated with S-ECC.展开更多
Polygalae Radix,which has a long history of medical use in traditional Chinese medicine,is multifunctional such as tranquilize mind,relieve swelling and remove phlegm.It has been demonstrated that Polygalae Radix olig...Polygalae Radix,which has a long history of medical use in traditional Chinese medicine,is multifunctional such as tranquilize mind,relieve swelling and remove phlegm.It has been demonstrated that Polygalae Radix oligosaccharide ester is the main active component which excutes the neuropharmacological activities like antidepression,anti-dementia and neuroprotection.In this review,the chemical structure,pharmacology,pharmacokinetics and processing mechanism of Polygalae Radix oligosaccharide ester are summarized so as to provide reference for its further development and utilization.展开更多
This paper discusses the transformation of art education in anticipation of the future school,and emphasizes the key role of art education in cultivating students’creativity,aesthetic ability,thinking ability,and mee...This paper discusses the transformation of art education in anticipation of the future school,and emphasizes the key role of art education in cultivating students’creativity,aesthetic ability,thinking ability,and meeting social needs.The shortcomings and delays in the traditional art education mode have become evident,prompting the need to explore innovative educational methods.Digital art education is emerging as a means to offer a more immersive art experience through virtual and augmented reality technologies while broadening students’cultural horizons.Interdisciplinary integration combines art with science,engineering,mathematics,and other disciplines to cultivate students’comprehensive literacy and innovative thinking.The innovative spirit and the application of educational technology help students overcome difficulties and continuously improve their work.The article also emphasizes the alignment between art education and social needs,the importance of social support and resources,and the training and development of teachers.展开更多
Bacterial biofilms have emerged as potential critical triggers in the pathogenesis of bisphosphonate(BP)-related osteonecrosis of the jaw(ONJ) or BRONJ. BRONJ lesions have shown to be heavily colonized by oral bacteri...Bacterial biofilms have emerged as potential critical triggers in the pathogenesis of bisphosphonate(BP)-related osteonecrosis of the jaw(ONJ) or BRONJ. BRONJ lesions have shown to be heavily colonized by oral bacteria, most of these difficult to cultivate and presents many clinical challenges. The purpose of this study was to characterize the bacterial diversity in BRONJ lesions and to determine host immune response. We examined tissue specimens from three cohorts(n530); patients with periodontal disease without a history of BP therapy(Control, n510), patients with periodontal disease having history of BP therapy but without ONJ(BP, n55) and patients with BRONJ(BRONJ, n515). Denaturing gradient gel electrophoresis of polymerase chain reaction(PCR)-amplified 16 S r RNA gene fragments revealed less bacterial diversity in BRONJ than BP and Control cohorts. Sequence analysis detected six phyla with predominant affiliation to Firmicutes in BRONJ(71.6%), BP(70.3%) and Control(59.1%). Significant differences(P,0.05) in genera were observed, between Control/BP, Control/BRONJ and BP/BRONJ cohorts. Enzyme-linked immunosorbent assay(ELISA)results indicated that the levels of myeloperoxidase were significantly lower, whereas interleukin-6 and tumor necrosis factor-alpha levels were moderately elevated in BRONJ patients as compared to Controls. PCR array showed significant changes in BRONJ patients with downregulation of host genes, such as nucleotide-binding oligomerization domain containing protein 2, and cathepsin G, the key modulators for antibacterial response and upregulation of secretory leukocyte protease inhibitor, proteinase 3 and conserved helix–loop–helix ubiquitous kinase. The results suggest that colonization of unique bacterial communities coupled with deficient innate immune response is likely to impact the pathogenesis of ONJ.展开更多
Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM),...Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM),scanning electron micros-copy (SEM),and X-ray diffraction (XRD). The corrosion resistance of the various anodized alloys was evaluated by a fast corrosion test using the solution of hydrochloric acid and potassium dichromate. The results showed that the addition of KF resulted in the presence of NaF in the anodic film. The thickness of the anodic film formed under a constant current density of 20 mA/cm2 for 16 min at 60°C exceeded 100 μm. The growth of the anodic film could be divided into three stages based on the anodizing time; the growth rate was much faster during stage II than in stages I and III. The anodic film exhibited the highest corrosion resistance for the AZ91 alloy,which is attributed to the fact that the anodization was maintained until the end of stage II.展开更多
The by-product of coal combustion,coal fly ash(CFA),has become one of the world’s most emitted solid wastes,and bulk utilization while achieving high value-added products is the focus of current research.Using CFA to...The by-product of coal combustion,coal fly ash(CFA),has become one of the world’s most emitted solid wastes,and bulk utilization while achieving high value-added products is the focus of current research.Using CFA to prepare zeolite cannot only reduce environmental pressure,but also obtain high value-added products,which has a good market prospect.In this paper,the research progress of hydrothermal synthesis method of CFA zeolites is reviewed in detail and summarized several other synthetic methods of CFA zeolites.This review also presents an overview of CFA zeolites application in environmental applications like water treatment,gas adsorption and soil remediation.However,a considerable number of literature data have documented using CFA zeolites for water treatment,whereas research on CFA zeolites application to gas adsorption and soil remediation is still limited.In addition,the current status of basic research on the industrial production of CFA zeolites is briefly summarized,and the development trend of the synthetic zeolite of CFA is prospected.After the feasibility analysis of the industrial production of CFA zeolite,it is concluded that the only two methods with high feasibility for industrial application are two-step hydrothermal and alkali melting methods,and the industrial production technology still needs to be studied in depth.展开更多
Large-scale flapping-wing flying robotic birds have huge application potential in outdoor tasks,such as military reconnaissance,environment exploring,disaster rescue and so on.In this paper,a multiple modes flight con...Large-scale flapping-wing flying robotic birds have huge application potential in outdoor tasks,such as military reconnaissance,environment exploring,disaster rescue and so on.In this paper,a multiple modes flight control method and system are proposed for a large-scale robotic bird which has 2.3 m wingspan and 650 g mass.Different from small flapping wing aerial vehicle,the mass of its wings cannot be neglected and the flapping frequency are much lower.Therefore,the influence of transient aerodynamics instead of only mean value are considered in attitude estimation and controller design.Moreover,flight attitude and trajectory are highly coupled,and the robot has only three actuators----one for wings flapping and two for tail adjustment,it is very difficult to simultaneously control the attitude and position.Hence,a fuzzy control strategy is addressed to determine the command of each actuator by considering the priority of attitude stabilization,trajectory tracking and the flight safety.Then,the on-board controller is designed based on FreeRTOS.It not only satisfies the strict restrictions on mass,size,power and space but also meets the autonomous,semi-autonomous and manual flight control requirements.Finally,the developed control system was integrated to the robotic prototype,HIT-phoenix.Flight experiments under different environment conditions such as sunny and windy weather were completed to verify the control method and system.展开更多
Chemically functionalized gas-filled bubbles with a versatile micro/nano-sized scale have witnessed a long history of developments and emerging applications in disease diagnosis and treatments.In combination with ultr...Chemically functionalized gas-filled bubbles with a versatile micro/nano-sized scale have witnessed a long history of developments and emerging applications in disease diagnosis and treatments.In combination with ultrasound and image-guidance,micro/nanobubbles have been endowed with the capabilities of biomedical imaging,drug delivery,gene transfection and diseaseoriented therapy.As an external stimulus,ultrasound(US)-mediated targeting treatments have been achieving unprecedented efficiency.Nowadays,US is playing a crucial role in visualizing biological/pathological changes in lives as a reliable imaging technique and a powerful therapeutic tool.This review retrospects the history of ultrasound,the chemistry of functionalized agents and summarizes recent advancements of functional micro/nanobubbles as US contrast agents in preclinical and transclinical research.Latest ultrasound-based treatment modalities in association with functional micro/nanobubbles have been highlighted as their great potentials for disease precision therapy.It is believed that these state-of-the-art micro/nanobubbles will become a booster for ultrasound medicine and visualizable guidance to serve future human healthcare in a more comprehensive and practical manner.展开更多
With the development of the offshore fossil energy industry,the designing life of many offshore oil and gas facilities will end.The decommissioning of these facilities has become an urgent task due to unpre-dictable c...With the development of the offshore fossil energy industry,the designing life of many offshore oil and gas facilities will end.The decommissioning of these facilities has become an urgent task due to unpre-dictable costs,high risks,and environmental protection issues of public concern.Decision-making,as the core in the pre-decommissioning stage,plays a decisive role in the cost,risk,and impact of the entire de-commissioning.Therefore,the multi-attribute decision-making model has attracted much attention from industry and academia.An efficient,accurate,and simply using multi-attribute decision-making model can enable governments,energy companies,other marine users,and environmental protection organi-zations to reasonably fulfill their concerns.It is of great significance to all parties.This review mainly studies the multi-attribute decision-making models that have been used in the decommissioning of off-shore oil and gas facilities,and conducts a more detailed interpretation of them,including the relevant regulations,frameworks,methodology,preferences and advantages and disadvantages of different mod-els.In addition,a more comprehensive review of the cost assessment model,an important part of the decision-making model,is carried out,including the general framework and methodology of the cost as-sessment model,and the accuracy of the models is explored.And then the current evaluation method of accuracy of the cost assessment model raises the author’s personal doubts.At the end of the article,this paper names two core problems of the current decision-making model,that is,the lack of basic data and the incomplete MCDA(Multi-criteria Decision Analysis)method.This review can provide a comprehen-sive reference and feasible research directions for future scholars who aims to study the decommissioning of offshore oil and gas facilities especially in the North Sea in the UK and point out the direction for the industry to improve its current multi-attribute decision-making models.展开更多
Summary What is already known about this topic?Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)reinfection by variants is being reported commonly and has caused waves of epidemic in many countries.Because o...Summary What is already known about this topic?Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)reinfection by variants is being reported commonly and has caused waves of epidemic in many countries.Because of dynamic zero policy,the SARSCoV-2 reinfection was less reported in China.What is added by this report?SARS-CoV-2 reinfections were observed in Guangdong Province between December 2022 and January 2023.This study estimated that the reinfection incidence was 50.0%for the original strain primary infections,35.2%for the Alpha or Delta variants,and 18.4%for the Omicron variant;The reinfection incidence within 3-6 months after primary infection by Omicron variant was 4.0%.Besides,96.2%reinfection cases were symptomatic while only 7.7%sought medical attention.What are the implications for public health practice?These findings suggest a reduced likelihood of an Omicron-driven epidemic resurgence in the short term but emphasize the importance of maintaining vigilant surveillance of emerging SARS-CoV-2 variants and conducting population-based antibody level surveys to inform response preparedness.展开更多
We present a method to precisely determine the hyperfine structure constants of the rubidium 5D_(5/2) and 7S_(1/2) states in a cascade atomic system. The probe laser is coupled to the 5S_(1/2)→ 5P_(3/2) hyperfine tra...We present a method to precisely determine the hyperfine structure constants of the rubidium 5D_(5/2) and 7S_(1/2) states in a cascade atomic system. The probe laser is coupled to the 5S_(1/2)→ 5P_(3/2) hyperfine transition, while the coupling laser is scanned over the 5P_(3/2)→ 5D_(5/2)(7S_(1/2)) transition. The high-resolution double-resonance optical pumping spectra are obtained with two counter-propagating laser beams acting on rubidium vapor. The hyperfine splitting structures are accurately measured by an optical frequency ruler based on the acousto-optic modulator, thus, the magnetic dipole hyperfine coupling constant A and quadrupole coupling constant B are determined. It is of great significance for the atomic hyperfine structure and fundamental physics research.展开更多
基金the supports of the Key R&D Program of Advanced Technology of Sichuan Science and Technology Department(No.2020YFG0111)。
文摘Arc plasma torch is an effective tool for spheroidization of metallic powders.However,as most conventional plasma torches were not specifically designed for plasma spheroidization,they may exhibit the disadvantages of the radial injection of powders,large fluctuations in the arc voltage,large gas flow rate,and disequilibrium between multiple plasma jets during the spheroidization process.Therefore,this paper presents a triple-cathode cascade plasma torch(TCCPT)for plasma spheroidization.Its structural design,including three cathodes,a common anode,and three sets of inter-electrodes,are detailed to ensure that powders can be inserted into the plasma jet by axial injection,the arc voltage fluctuations are easily maintained at a low level,and the plasma torches can work at a relatively small gas flow rate.Experimental results showed that the proposed TCCPT exhibits the following characteristics:(1)a relatively small arc voltage fluctuation within 5.3%;(2)a relatively high arc voltage of 75 V and low gas flow rate range of10-30 SLM;(3)easy to be maintained at the equilibrium state with the equilibrium index of the three plasma jets within 3.5 V.Furthermore,plasma spheroidization experiments of SUS304 stainless steel powers were carried out using the proposed TCCPT.Results verified that the proposed TCCPT is applicable and effective for the spheroidization of metallic powders with wide size distribution.
基金supported by the National Institute of Dental and Craniofacial Research(R01DE019455).
文摘Lactobacilli have been consistently associated with dental caries for decades;however, knowledge of this group of bacteria in the etiology of the disease is limited to quantitative elucidation. Nowadays, explicit identification of oral Lactobacillus species is possible, despite their taxonomic complexity. Here we describe a combined approach involving both cultivation and genetic methods to ascertain and characterize the diversity and abundance of the Lactobacillus population in the oral cavities of children with severe early childhood caries (S-ECC). Eighty 3- to 6-year-old children (40 S-ECC and 40 caries free) who were seeking dental care at the Pediatric Dental Clinic of Bellevue Hospital in New York City were invited to participate in this study. Clinical data on sociodemographic information and oral health behavior were obtained from the primary caregiver. The data included a detailed dental examination, children’s medical history, and a questionnaire survey. Combined non-stimulated saliva and supragingival plaque samples were collected from each child and cultivated on selective media for quantitative measures of lactobacilli levels. The procedure for Lactobacillus species screening will include the random selection of 50 colonies per plate, ex- traction of DNA from each colony, and genotyping by arbitrarily primed polymerase chain reaction (AP-PCR). Each unique Lactobacillus AP-PCR genotype will be selected for taxonomic assessment by 16S rRNA gene sequencing analysis. Lactobacillus species will be identified by comparing the 16S rRNA sequences with the Ribosomal Database and the Human Oral Microbiome Database. Meanwhile, the same set of clinical samples will be independently subjected to genomic DNA isolation, 16S rRNA amplification with Lactobacillus genus-specific primers, sequencing, and taxonomic identification, both at genus and species levels with a customized pipeline. The distribution and phylogenetic differences of these Lactobacillus species will be compared between children with or without S-ECC. One of the main objectives of this study is to establish a study protocol for the identification and characterization of lactobacilli in the oral cavity. Future caries risk assessments can include lactobacilli counts (quantitative) and the presence/absence of specific cario- genic genetic signatures of a Lactobacillus species (qualitative) associated with S-ECC.
文摘Polygalae Radix,which has a long history of medical use in traditional Chinese medicine,is multifunctional such as tranquilize mind,relieve swelling and remove phlegm.It has been demonstrated that Polygalae Radix oligosaccharide ester is the main active component which excutes the neuropharmacological activities like antidepression,anti-dementia and neuroprotection.In this review,the chemical structure,pharmacology,pharmacokinetics and processing mechanism of Polygalae Radix oligosaccharide ester are summarized so as to provide reference for its further development and utilization.
基金This paper is one of the promotion achievements of the 2018 key project of the National Educational Technology Research Planning Project of the Central Audio-Visual Education Museum“Practical Research on Promoting High School Students’Art Performance Literacy by Information Technology”(Project number:184420013)One of the promotion achievements of Zhongshan Education and Scientific Research 2020 general project“Research on the Aesthetic Education Function of Famous Illustrations in Chinese Textbooks for Primary and Secondary Schools Published by People’s Education Press”(Project number:B2020175)One of the learning and training achievements of the“Guangdong Provincial Famous Principal Wan Fei Workshop.”This abstract is selected from author Yihong Li for the“National Training Program”early 2021 Middle School Art Backbone Teacher Workshop(A314)teaching topic“The Transformation of Art Education Towards the Future School.”。
文摘This paper discusses the transformation of art education in anticipation of the future school,and emphasizes the key role of art education in cultivating students’creativity,aesthetic ability,thinking ability,and meeting social needs.The shortcomings and delays in the traditional art education mode have become evident,prompting the need to explore innovative educational methods.Digital art education is emerging as a means to offer a more immersive art experience through virtual and augmented reality technologies while broadening students’cultural horizons.Interdisciplinary integration combines art with science,engineering,mathematics,and other disciplines to cultivate students’comprehensive literacy and innovative thinking.The innovative spirit and the application of educational technology help students overcome difficulties and continuously improve their work.The article also emphasizes the alignment between art education and social needs,the importance of social support and resources,and the training and development of teachers.
基金supported by NIH grants CA172894, CA180277, DE020891New York University Research Funds
文摘Bacterial biofilms have emerged as potential critical triggers in the pathogenesis of bisphosphonate(BP)-related osteonecrosis of the jaw(ONJ) or BRONJ. BRONJ lesions have shown to be heavily colonized by oral bacteria, most of these difficult to cultivate and presents many clinical challenges. The purpose of this study was to characterize the bacterial diversity in BRONJ lesions and to determine host immune response. We examined tissue specimens from three cohorts(n530); patients with periodontal disease without a history of BP therapy(Control, n510), patients with periodontal disease having history of BP therapy but without ONJ(BP, n55) and patients with BRONJ(BRONJ, n515). Denaturing gradient gel electrophoresis of polymerase chain reaction(PCR)-amplified 16 S r RNA gene fragments revealed less bacterial diversity in BRONJ than BP and Control cohorts. Sequence analysis detected six phyla with predominant affiliation to Firmicutes in BRONJ(71.6%), BP(70.3%) and Control(59.1%). Significant differences(P,0.05) in genera were observed, between Control/BP, Control/BRONJ and BP/BRONJ cohorts. Enzyme-linked immunosorbent assay(ELISA)results indicated that the levels of myeloperoxidase were significantly lower, whereas interleukin-6 and tumor necrosis factor-alpha levels were moderately elevated in BRONJ patients as compared to Controls. PCR array showed significant changes in BRONJ patients with downregulation of host genes, such as nucleotide-binding oligomerization domain containing protein 2, and cathepsin G, the key modulators for antibacterial response and upregulation of secretory leukocyte protease inhibitor, proteinase 3 and conserved helix–loop–helix ubiquitous kinase. The results suggest that colonization of unique bacterial communities coupled with deficient innate immune response is likely to impact the pathogenesis of ONJ.
基金The work was financially supported by the National Natural Science Foundation of China (No.50541003) and the Aeronautic ScienceFoundation of China (No.04H51002).
文摘Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM),scanning electron micros-copy (SEM),and X-ray diffraction (XRD). The corrosion resistance of the various anodized alloys was evaluated by a fast corrosion test using the solution of hydrochloric acid and potassium dichromate. The results showed that the addition of KF resulted in the presence of NaF in the anodic film. The thickness of the anodic film formed under a constant current density of 20 mA/cm2 for 16 min at 60°C exceeded 100 μm. The growth of the anodic film could be divided into three stages based on the anodizing time; the growth rate was much faster during stage II than in stages I and III. The anodic film exhibited the highest corrosion resistance for the AZ91 alloy,which is attributed to the fact that the anodization was maintained until the end of stage II.
基金supported by the National Natural Science Foundation of China(No.51904278)the Fundamental Research Program of Shanxi Province(No.202103021223277)+1 种基金the Taiyuan University of Science and Technology Doctoral Research Fund(No.20212025)the Natural Science Foundation of Shanxi Province(No.20210302123218).
文摘The by-product of coal combustion,coal fly ash(CFA),has become one of the world’s most emitted solid wastes,and bulk utilization while achieving high value-added products is the focus of current research.Using CFA to prepare zeolite cannot only reduce environmental pressure,but also obtain high value-added products,which has a good market prospect.In this paper,the research progress of hydrothermal synthesis method of CFA zeolites is reviewed in detail and summarized several other synthetic methods of CFA zeolites.This review also presents an overview of CFA zeolites application in environmental applications like water treatment,gas adsorption and soil remediation.However,a considerable number of literature data have documented using CFA zeolites for water treatment,whereas research on CFA zeolites application to gas adsorption and soil remediation is still limited.In addition,the current status of basic research on the industrial production of CFA zeolites is briefly summarized,and the development trend of the synthetic zeolite of CFA is prospected.After the feasibility analysis of the industrial production of CFA zeolite,it is concluded that the only two methods with high feasibility for industrial application are two-step hydrothermal and alkali melting methods,and the industrial production technology still needs to be studied in depth.
基金supported by the National Natural Science Foundation of China(No.U1613227,61803125)Guangdong Special Support Program of China(No.2017TX04X0071)the Basic Research Program of Shenzhen of China(Nos.JCYJ20180507183610564,JCYJ20190806144416980)。
文摘Large-scale flapping-wing flying robotic birds have huge application potential in outdoor tasks,such as military reconnaissance,environment exploring,disaster rescue and so on.In this paper,a multiple modes flight control method and system are proposed for a large-scale robotic bird which has 2.3 m wingspan and 650 g mass.Different from small flapping wing aerial vehicle,the mass of its wings cannot be neglected and the flapping frequency are much lower.Therefore,the influence of transient aerodynamics instead of only mean value are considered in attitude estimation and controller design.Moreover,flight attitude and trajectory are highly coupled,and the robot has only three actuators----one for wings flapping and two for tail adjustment,it is very difficult to simultaneously control the attitude and position.Hence,a fuzzy control strategy is addressed to determine the command of each actuator by considering the priority of attitude stabilization,trajectory tracking and the flight safety.Then,the on-board controller is designed based on FreeRTOS.It not only satisfies the strict restrictions on mass,size,power and space but also meets the autonomous,semi-autonomous and manual flight control requirements.Finally,the developed control system was integrated to the robotic prototype,HIT-phoenix.Flight experiments under different environment conditions such as sunny and windy weather were completed to verify the control method and system.
基金This research was financially supported by the National Natural Science Foundation of China(21575106,82072057).
文摘Chemically functionalized gas-filled bubbles with a versatile micro/nano-sized scale have witnessed a long history of developments and emerging applications in disease diagnosis and treatments.In combination with ultrasound and image-guidance,micro/nanobubbles have been endowed with the capabilities of biomedical imaging,drug delivery,gene transfection and diseaseoriented therapy.As an external stimulus,ultrasound(US)-mediated targeting treatments have been achieving unprecedented efficiency.Nowadays,US is playing a crucial role in visualizing biological/pathological changes in lives as a reliable imaging technique and a powerful therapeutic tool.This review retrospects the history of ultrasound,the chemistry of functionalized agents and summarizes recent advancements of functional micro/nanobubbles as US contrast agents in preclinical and transclinical research.Latest ultrasound-based treatment modalities in association with functional micro/nanobubbles have been highlighted as their great potentials for disease precision therapy.It is believed that these state-of-the-art micro/nanobubbles will become a booster for ultrasound medicine and visualizable guidance to serve future human healthcare in a more comprehensive and practical manner.
文摘With the development of the offshore fossil energy industry,the designing life of many offshore oil and gas facilities will end.The decommissioning of these facilities has become an urgent task due to unpre-dictable costs,high risks,and environmental protection issues of public concern.Decision-making,as the core in the pre-decommissioning stage,plays a decisive role in the cost,risk,and impact of the entire de-commissioning.Therefore,the multi-attribute decision-making model has attracted much attention from industry and academia.An efficient,accurate,and simply using multi-attribute decision-making model can enable governments,energy companies,other marine users,and environmental protection organi-zations to reasonably fulfill their concerns.It is of great significance to all parties.This review mainly studies the multi-attribute decision-making models that have been used in the decommissioning of off-shore oil and gas facilities,and conducts a more detailed interpretation of them,including the relevant regulations,frameworks,methodology,preferences and advantages and disadvantages of different mod-els.In addition,a more comprehensive review of the cost assessment model,an important part of the decision-making model,is carried out,including the general framework and methodology of the cost as-sessment model,and the accuracy of the models is explored.And then the current evaluation method of accuracy of the cost assessment model raises the author’s personal doubts.At the end of the article,this paper names two core problems of the current decision-making model,that is,the lack of basic data and the incomplete MCDA(Multi-criteria Decision Analysis)method.This review can provide a comprehen-sive reference and feasible research directions for future scholars who aims to study the decommissioning of offshore oil and gas facilities especially in the North Sea in the UK and point out the direction for the industry to improve its current multi-attribute decision-making models.
基金Supported by the Key-Area Research and Development Program of Guangdong Province(2022B1111020006)the Natural Science Foundation of China(82341034).
文摘Summary What is already known about this topic?Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)reinfection by variants is being reported commonly and has caused waves of epidemic in many countries.Because of dynamic zero policy,the SARSCoV-2 reinfection was less reported in China.What is added by this report?SARS-CoV-2 reinfections were observed in Guangdong Province between December 2022 and January 2023.This study estimated that the reinfection incidence was 50.0%for the original strain primary infections,35.2%for the Alpha or Delta variants,and 18.4%for the Omicron variant;The reinfection incidence within 3-6 months after primary infection by Omicron variant was 4.0%.Besides,96.2%reinfection cases were symptomatic while only 7.7%sought medical attention.What are the implications for public health practice?These findings suggest a reduced likelihood of an Omicron-driven epidemic resurgence in the short term but emphasize the importance of maintaining vigilant surveillance of emerging SARS-CoV-2 variants and conducting population-based antibody level surveys to inform response preparedness.
基金supported by the National Key R&D Program of China(No.2017YFA0304203)the National Natural Science Foundation of China(Nos.61575116,61705122,61728502,91736209,and 11434007)+3 种基金the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT13076)the Program for Sanjin Scholars of Shanxi Provincethe Applied Basic Research Project of Shanxi Province(No.201701D221004)the Fund for Shanxi‘1331 Project’Key Subjects Construction
文摘We present a method to precisely determine the hyperfine structure constants of the rubidium 5D_(5/2) and 7S_(1/2) states in a cascade atomic system. The probe laser is coupled to the 5S_(1/2)→ 5P_(3/2) hyperfine transition, while the coupling laser is scanned over the 5P_(3/2)→ 5D_(5/2)(7S_(1/2)) transition. The high-resolution double-resonance optical pumping spectra are obtained with two counter-propagating laser beams acting on rubidium vapor. The hyperfine splitting structures are accurately measured by an optical frequency ruler based on the acousto-optic modulator, thus, the magnetic dipole hyperfine coupling constant A and quadrupole coupling constant B are determined. It is of great significance for the atomic hyperfine structure and fundamental physics research.
