Background Virtual reality technology has been widely used in surgical simulators,providing new opportunities for assessing and training surgical skills.Machine learning algorithms are commonly used to analyze and eva...Background Virtual reality technology has been widely used in surgical simulators,providing new opportunities for assessing and training surgical skills.Machine learning algorithms are commonly used to analyze and evaluate the performance of participants.However,their interpretability limits the personalization of the training for individual participants.Methods Seventy-nine participants were recruited and divided into three groups based on their skill level in intracranial tumor resection.Data on the use of surgical tools were collected using a surgical simulator.Feature selection was performed using the Minimum Redundancy Maximum Relevance and SVM-RFE algorithms to obtain the final metrics for training the machine learning model.Five machine learning algorithms were trained to predict the skill level,and the support vector machine performed the best,with an accuracy of 92.41%and Area Under Curve value of 0.98253.The machine learning model was interpreted using Shapley values to identify the important factors contributing to the skill level of each participant.Results This study demonstrates the effectiveness of machine learning in differentiating the evaluation and training of virtual reality neurosurgical performances.The use of Shapley values enables targeted training by identifying deficiencies in individual skills.Conclusions This study provides insights into the use of machine learning for personalized training in virtual reality neurosurgery.The interpretability of the machine learning models enables the development of individualized training programs.In addition,this study highlighted the potential of explanatory models in training external skills.展开更多
In recent years,statistics have indicated that the number of patients with malignant brain tumors has increased sharply.However,most surgeons still perform surgical training using the traditional autopsy and prosthesi...In recent years,statistics have indicated that the number of patients with malignant brain tumors has increased sharply.However,most surgeons still perform surgical training using the traditional autopsy and prosthesis model,which encounters many problems,such as insufficient corpse resources,low efficiency,and high cost.With the advent of the 5G era,a wide range of Industrial Internet of Things(IIOT)applications have been developed.Virtual Reality(VR)and Augmented Reality(AR)technologies that emerged with 5G are developing rapidly for intelligent medical training.To address the challenges encountered during neurosurgery training,and combining with cloud computing,in this paper,a highly immersive AR-based brain tumor neurosurgery remote collaborative virtual surgery training system is developed,in which a VR simulator is embedded.The system enables real-time remote surgery training interaction through 5G transmission.Six experts and 18 novices were invited to participate in the experiment to verify the system.Subsequently,the two simulators were evaluated using face and construction validation methods.The results obtained by training the novices 50 times were further analyzed using the Learning Curve-Cumulative Sum(LC-CUSUM)evaluation method to validate the effectiveness of the two simulators.The results of the face and content validation demonstrated that the AR simulator in the system was superior to the VR simulator in terms of vision and scene authenticity,and had a better effect on the improvement of surgical skills.Moreover,the surgical training scheme proposed in this paper is effective,and the remote collaborative training effect of the system is ideal.展开更多
Objective:To judge the efficacies of neural stem cell(NSC)transplantation on functional recovery following contusion spinal cord injuries(SCIs).Data sources:Studies in which NSCs were transplanted into a clinically re...Objective:To judge the efficacies of neural stem cell(NSC)transplantation on functional recovery following contusion spinal cord injuries(SCIs).Data sources:Studies in which NSCs were transplanted into a clinically relevant,standardized rat model of contusion SCI were identified by searching the PubMed,Embase and Cochrane databases,and the extracted data were analyzed by Stata 14.0.Data selection:Inclusion criteria were that NSCs were used in in vivo animal studies to treat contusion SCIs and that behavioral assessment of locomotor functional recovery was performed using the Basso,Beattie,and Bresnahan lo-comotor rating scale.Exclusion criteria included a follow-up of less than 4 weeks and the lack of control groups.Outcome measures:The restoration of motor function was assessed by the Basso,Beattie,and Bresnahan locomotor rating scale.Results:We identified 1756 non-duplicated papers by searching the aforementioned electronic databases,and 30 full-text articles met the inclusion criteria.A total of 37 studies reported in the 30 articles were included in the meta-analysis.The meta-analysis results showed that transplanted NSCs could improve the motor function recovery of rats following contusion SCIs,to a moderate extent(pooled standardized mean difference(SMD)=0.73;95%confidence interval(CI):0.47–1.00;P<0.001).NSCs obtained from different donor species(rat:SMD=0.74;95%CI:0.36–1.13;human:SMD=0.78;95%CI:0.31–1.25),at different donor ages(fetal:SMD=0.67;95%CI:0.43–0.92;adult:SMD=0.86;95%CI:0.50–1.22)and from different origins(brain-derived:SMD=0.59;95%CI:0.27–0.91;spinal cord-derived:SMD=0.51;95%CI:0.22–0.79)had similar efficacies on improved functional recovery;however,adult induced pluripotent stem cell-derived NSCs showed no significant efficacies.Furthermore,the use of higher doses of transplanted NSCs or the administration of immunosuppressive agents did not promote better locomotor function recovery(SMD=0.45;95%CI:0.21–0.70).However,shorter periods between the contusion induction and the NSC transplantation showed slightly higher efficacies(acute:SMD=1.22;95%CI:0.81–1.63;subacute:SMD=0.75;95%CI:0.42–1.09).For chronic injuries,NSC implantation did not significantly improve functional recovery(SMD=0.25;95%CI:–0.16 to 0.65).Conclusion:NSC transplantation alone appears to be a positive yet limited method for the treatment of contusion SCIs.展开更多
Vertically stacked heterostructures have received extensive attention because of their tunable electronic structures and outstanding optical properties.In this work,we study the structural,electronic,and optical prope...Vertically stacked heterostructures have received extensive attention because of their tunable electronic structures and outstanding optical properties.In this work,we study the structural,electronic,and optical properties of vertically stacked GaS-SnS_(2)heterostructure under the frame of density functional theory.We find that the stacked GaS-SnS_(2)heterostructure is a semiconductor with a suitable indirect band gap of 1.82 eV,exhibiting a type-Ⅱband alignment for easily separating the photo-generated carriers.The electronic properties of GaS-SnS_(2)hetero structure can be effectively tuned by an external strain and electric field.The optical absorption of GaS-SnS_(2)heterostructure is more enhanced than those of the GaS monolayer and SnS_(2)monolayer in the visible light region.Our results suggest that the GaS-SnS_(2)hetero structure is a promising candidate for the photocatalyst and photoelectronic devices in the visible light region.展开更多
Two-dimensional(2 D)materials are playing more and more important roles in both basic sciences and industrial applications.For 2 D materials,strain could tune the properties and enlarge applications.Since the growth o...Two-dimensional(2 D)materials are playing more and more important roles in both basic sciences and industrial applications.For 2 D materials,strain could tune the properties and enlarge applications.Since the growth of 2 D materials on substrates is often accompanied by strain,the interaction between 2 D materials and substrates is worthy of careful attention.Here we demonstrate the fabrication of strained monolayer silver arsenide(AgAs)on Ag(111)by molecular beam epitaxy,which shows one-dimensional stripe structures arising from uniaxial strain.The atomic geometric structure and electronic band structure are investigated by low energy electron diffraction,scanning tunneling microscopy,x-ray photoelectron spectroscopy,angle-resolved photoemission spectroscopy and first-principle calculations.Monolayer AgAs synthesized on Ag(111)provides a platform to study the physical properties of strained 2 D materials.展开更多
With the merits of non-contact,highly efficient,and parallel computing,optoelectronic synaptic devices combining sensing and memory in a single unit are promising for constructing neuromorphic computing and artificial...With the merits of non-contact,highly efficient,and parallel computing,optoelectronic synaptic devices combining sensing and memory in a single unit are promising for constructing neuromorphic computing and artificial visual chip.Based on this,a N:ZnO/MoS_(2)-heterostructured flexible optoelectronic synaptic device is developed in this work,and its capability in mimicking the synaptic behaviors is systemically investigated under the electrical and light signals.Versatile synaptic functions,including synaptic plasticity,long-term/short-term memory,and learning-forgetting-relearning property,have been achieved in this synaptic device.Further,an artificial visual memory system integrating sense and memory is emulated with the device array,and the visual memory behavior can be regulated by varying the light parameters.Moreover,the optoelectronic co-modulation behavior is verified by applying mixed electric and light signals to the array.In detail,a transient recovery property is discovered when the electric signals are applied in synergy during the decay of the light response,of which property facilitates the development of robust artificial visual systems.Furthermore,by superimposing electrical signals during the light response process,a differentiated response of the array is achieved,which can be used as a proof of concept for the color perception of the artificial visual system.展开更多
Local signaling events at synapses or axon terminals are communicated to the nucleus to elicit transcriptional responses,and thereby translate information about the external environment into internal neuronal represen...Local signaling events at synapses or axon terminals are communicated to the nucleus to elicit transcriptional responses,and thereby translate information about the external environment into internal neuronal representations.This retrograde signaling is critical to dendritic growth,synapse development,and neuronal plasticity.Here,we demonstrate that neuronal activity induces retrograde translocation and nuclear accumulation of endosomal adaptor APPL1.Disrupting the interaction of APPL1 with Importin ocl abolishes nuclear accumulation of APPL1,which in turn decreases the levels of histone acetylation.We further demonstrate that retrograde translocation of APPL1 is required for the regulation of gene transcription and then maintenance of hippocampal late-phase long-term potentiation.Thus,these results illustrate an APPLl-mediated pathway that contributes to the modulation of synaptic plasticity via coupling neuronal activity with chromatin remodeling.展开更多
Opportunity networks provide a chance to offload the tremendous cellular traffic generated by sharing popular content on mobile networks. Analyzing the content spread characteristics in real opportunity environments c...Opportunity networks provide a chance to offload the tremendous cellular traffic generated by sharing popular content on mobile networks. Analyzing the content spread characteristics in real opportunity environments can discover important clues for traffic offloading decision making. However, relevant published work is very limited since it is not easy to collect data from real environments. In this study, we elaborate the analysis on the dataset collected from a real opportunity environment formed by the users of Xender, which is one of the leading mobile applications for content sharing. To discover content transmission characteristics, scale, speed, and type analyses are implemented on the dataset. The analysis results show that file transmission has obvious periodicity, that only a very small fraction of files spread widely, and that application files have much higher probability to be popular than other files. We also propose a solution to maximize file spread scales, which is very helpful for forecasting popular files. The experimental results verify the effectiveness and usefulness of our solution.展开更多
Hydrogen can be trapped in the bulk materials in four forms:interstitial molecular H_2,interstitial atom H,O^-H^+(2Si=O–H)^+,Si-H^-(4Oˉ≡Si H)^-to affect the electronic and optical properties of amorphous silica.The...Hydrogen can be trapped in the bulk materials in four forms:interstitial molecular H_2,interstitial atom H,O^-H^+(2Si=O–H)^+,Si-H^-(4Oˉ≡Si H)^-to affect the electronic and optical properties of amorphous silica.Therefore,the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory.Initially,the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom.However,the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy.Subsequently,the optical properties such as absorption spectra,conductivity and loss functions were analyzed.It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 e V while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 e V.However,the neutral hydrogen defects just improved the intensity of absorption spectrum.This may give insights into understanding the mechanism of laser-induced damage for optical materials.展开更多
Graphene on insulator is the foundation of its practical applications in electronic information technology.However,fabrication of graphene on insulating substrates suffers from small size and limited quality by direct...Graphene on insulator is the foundation of its practical applications in electronic information technology.However,fabrication of graphene on insulating substrates suffers from small size and limited quality by direct growth of graphene on dielectric substrates,and the method of transferring graphene onto insulating substrates is not so compatible with the large-scale production in industry.Here,we report the fabrication of high-quality,large-area,single-crystal graphene on crystalline magnesium oxide(MgO),which has a dielectric constant of 7–10.Magnesium and oxygen are intercalated at the interface of epitaxial graphene/Ru(0001)and form crystalline structure after high-temperature annealing.The graphene/MgO/Ru(0001)sample was characterized by low energy electron diffraction(LEED),scanning tunneling microscopy(STM),X-ray photoelectron spectroscopy(XPS),and scanning transmission electron microscopy(STEM).LEED pattern shows that the magnesium oxide displays crystalline structure,and STM studies show clearly that the top layer is graphene.STEM characterization of as-intercalated sample demonstrates that the MgO intercalation layer,with a thickness of up to 2.3 nm,has a crystal structure of rock salt MgO,and the out-of-plane crystal orientation is[001].Our work provides a new route for fabrication of graphene on high dielectric constant insulators,which may have potential applications in future electronics.展开更多
To realize high performance flexible transparent electronics with extreme environmental adaptivity,Ag nanowires(Ag NWs)electrodes should simultaneously meet the requirements of high-temperature tolerance,chemical and ...To realize high performance flexible transparent electronics with extreme environmental adaptivity,Ag nanowires(Ag NWs)electrodes should simultaneously meet the requirements of high-temperature tolerance,chemical and mechanical robustness.Herein,a scalable Ag NWs bundle micro-meshes embedded in polyimide(Ag BMs/ePI)conducting film via a facile spray coating and transfer method is reported.Due to the synergistic effect of bundle micromesh and embedded architecture,the Ag BMs/ePI electrode exhibits high thermal stability(370℃ and 400℃ under ambient and nitrogen atmosphere conditions,respectively),low sheet resistance variation(<4%),good corrosion and deformation resistance.As an electrical heater,the Ag BMs/ePI can achieve~204℃ with the fast thermal response time of~8 s at 8 V,and exhibits good heating stability under bent condition.This work offers a promising platform for the emerging flexible transparent electronics to adapt extreme environments,especially for those devices which require high-temperature processing.展开更多
基金Supported by the Yunnan Key Laboratory of Opto-Electronic Information Technology,Postgraduate Research Innovation Fund of Yunnan Normal University (YJSJJ22-B79)the National Natural Science Foundation of China (62062069,62062070,62005235)。
文摘Background Virtual reality technology has been widely used in surgical simulators,providing new opportunities for assessing and training surgical skills.Machine learning algorithms are commonly used to analyze and evaluate the performance of participants.However,their interpretability limits the personalization of the training for individual participants.Methods Seventy-nine participants were recruited and divided into three groups based on their skill level in intracranial tumor resection.Data on the use of surgical tools were collected using a surgical simulator.Feature selection was performed using the Minimum Redundancy Maximum Relevance and SVM-RFE algorithms to obtain the final metrics for training the machine learning model.Five machine learning algorithms were trained to predict the skill level,and the support vector machine performed the best,with an accuracy of 92.41%and Area Under Curve value of 0.98253.The machine learning model was interpreted using Shapley values to identify the important factors contributing to the skill level of each participant.Results This study demonstrates the effectiveness of machine learning in differentiating the evaluation and training of virtual reality neurosurgical performances.The use of Shapley values enables targeted training by identifying deficiencies in individual skills.Conclusions This study provides insights into the use of machine learning for personalized training in virtual reality neurosurgery.The interpretability of the machine learning models enables the development of individualized training programs.In addition,this study highlighted the potential of explanatory models in training external skills.
基金supported by the Yunnan Key Laboratory of Optoelectronic Information Technology,and grant funded by the National Natural Science Foundation of China(62062069,62062070,and 62005235)Taif University Researchers Supporting Project(TURSP-2020/126)Taif University,Taif,Saudi Arabia.Jun Liu and Kai Qian contributed equally to this paper。
文摘In recent years,statistics have indicated that the number of patients with malignant brain tumors has increased sharply.However,most surgeons still perform surgical training using the traditional autopsy and prosthesis model,which encounters many problems,such as insufficient corpse resources,low efficiency,and high cost.With the advent of the 5G era,a wide range of Industrial Internet of Things(IIOT)applications have been developed.Virtual Reality(VR)and Augmented Reality(AR)technologies that emerged with 5G are developing rapidly for intelligent medical training.To address the challenges encountered during neurosurgery training,and combining with cloud computing,in this paper,a highly immersive AR-based brain tumor neurosurgery remote collaborative virtual surgery training system is developed,in which a VR simulator is embedded.The system enables real-time remote surgery training interaction through 5G transmission.Six experts and 18 novices were invited to participate in the experiment to verify the system.Subsequently,the two simulators were evaluated using face and construction validation methods.The results obtained by training the novices 50 times were further analyzed using the Learning Curve-Cumulative Sum(LC-CUSUM)evaluation method to validate the effectiveness of the two simulators.The results of the face and content validation demonstrated that the AR simulator in the system was superior to the VR simulator in terms of vision and scene authenticity,and had a better effect on the improvement of surgical skills.Moreover,the surgical training scheme proposed in this paper is effective,and the remote collaborative training effect of the system is ideal.
基金supported by the National Natural Science Foundation of China,No.81171147“Key Medical Talents of Qiangwei Project” Research Foundation of Health Department of Jiangsu Province of China,No.ZDRCA2016010+1 种基金“Xingwei Project” Key Personal Medical Research Foundation of Health Department of Jiangsu Province of China,No.RC201156Jiangsu Provincial Key Discipline of Medicine of China,No.XK201117(all to LXL)
文摘Objective:To judge the efficacies of neural stem cell(NSC)transplantation on functional recovery following contusion spinal cord injuries(SCIs).Data sources:Studies in which NSCs were transplanted into a clinically relevant,standardized rat model of contusion SCI were identified by searching the PubMed,Embase and Cochrane databases,and the extracted data were analyzed by Stata 14.0.Data selection:Inclusion criteria were that NSCs were used in in vivo animal studies to treat contusion SCIs and that behavioral assessment of locomotor functional recovery was performed using the Basso,Beattie,and Bresnahan lo-comotor rating scale.Exclusion criteria included a follow-up of less than 4 weeks and the lack of control groups.Outcome measures:The restoration of motor function was assessed by the Basso,Beattie,and Bresnahan locomotor rating scale.Results:We identified 1756 non-duplicated papers by searching the aforementioned electronic databases,and 30 full-text articles met the inclusion criteria.A total of 37 studies reported in the 30 articles were included in the meta-analysis.The meta-analysis results showed that transplanted NSCs could improve the motor function recovery of rats following contusion SCIs,to a moderate extent(pooled standardized mean difference(SMD)=0.73;95%confidence interval(CI):0.47–1.00;P<0.001).NSCs obtained from different donor species(rat:SMD=0.74;95%CI:0.36–1.13;human:SMD=0.78;95%CI:0.31–1.25),at different donor ages(fetal:SMD=0.67;95%CI:0.43–0.92;adult:SMD=0.86;95%CI:0.50–1.22)and from different origins(brain-derived:SMD=0.59;95%CI:0.27–0.91;spinal cord-derived:SMD=0.51;95%CI:0.22–0.79)had similar efficacies on improved functional recovery;however,adult induced pluripotent stem cell-derived NSCs showed no significant efficacies.Furthermore,the use of higher doses of transplanted NSCs or the administration of immunosuppressive agents did not promote better locomotor function recovery(SMD=0.45;95%CI:0.21–0.70).However,shorter periods between the contusion induction and the NSC transplantation showed slightly higher efficacies(acute:SMD=1.22;95%CI:0.81–1.63;subacute:SMD=0.75;95%CI:0.42–1.09).For chronic injuries,NSC implantation did not significantly improve functional recovery(SMD=0.25;95%CI:–0.16 to 0.65).Conclusion:NSC transplantation alone appears to be a positive yet limited method for the treatment of contusion SCIs.
基金Project supported by the National Natural Science Foundation of China(Grant No.1186040026)the Incubation Project for High-Level Scientific Research Achievements of Hubei Minzu University,China(Grant No.4205009)the Fund of the Educational Commission of Hubei Province,China(Grant No.T201914)。
文摘Vertically stacked heterostructures have received extensive attention because of their tunable electronic structures and outstanding optical properties.In this work,we study the structural,electronic,and optical properties of vertically stacked GaS-SnS_(2)heterostructure under the frame of density functional theory.We find that the stacked GaS-SnS_(2)heterostructure is a semiconductor with a suitable indirect band gap of 1.82 eV,exhibiting a type-Ⅱband alignment for easily separating the photo-generated carriers.The electronic properties of GaS-SnS_(2)hetero structure can be effectively tuned by an external strain and electric field.The optical absorption of GaS-SnS_(2)heterostructure is more enhanced than those of the GaS monolayer and SnS_(2)monolayer in the visible light region.Our results suggest that the GaS-SnS_(2)hetero structure is a promising candidate for the photocatalyst and photoelectronic devices in the visible light region.
基金Supported by the National Key Research&Development Program of China(Grant Nos.2016YFA0202300 and 2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.61888102,11604373,61622116,and 51872284)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB30000000 and XDB28000000)the University of Chinese Academy of Sciences。
文摘Two-dimensional(2 D)materials are playing more and more important roles in both basic sciences and industrial applications.For 2 D materials,strain could tune the properties and enlarge applications.Since the growth of 2 D materials on substrates is often accompanied by strain,the interaction between 2 D materials and substrates is worthy of careful attention.Here we demonstrate the fabrication of strained monolayer silver arsenide(AgAs)on Ag(111)by molecular beam epitaxy,which shows one-dimensional stripe structures arising from uniaxial strain.The atomic geometric structure and electronic band structure are investigated by low energy electron diffraction,scanning tunneling microscopy,x-ray photoelectron spectroscopy,angle-resolved photoemission spectroscopy and first-principle calculations.Monolayer AgAs synthesized on Ag(111)provides a platform to study the physical properties of strained 2 D materials.
基金supported by the National Natural Science Foundation of China(No.62174068).
文摘With the merits of non-contact,highly efficient,and parallel computing,optoelectronic synaptic devices combining sensing and memory in a single unit are promising for constructing neuromorphic computing and artificial visual chip.Based on this,a N:ZnO/MoS_(2)-heterostructured flexible optoelectronic synaptic device is developed in this work,and its capability in mimicking the synaptic behaviors is systemically investigated under the electrical and light signals.Versatile synaptic functions,including synaptic plasticity,long-term/short-term memory,and learning-forgetting-relearning property,have been achieved in this synaptic device.Further,an artificial visual memory system integrating sense and memory is emulated with the device array,and the visual memory behavior can be regulated by varying the light parameters.Moreover,the optoelectronic co-modulation behavior is verified by applying mixed electric and light signals to the array.In detail,a transient recovery property is discovered when the electric signals are applied in synergy during the decay of the light response,of which property facilitates the development of robust artificial visual systems.Furthermore,by superimposing electrical signals during the light response process,a differentiated response of the array is achieved,which can be used as a proof of concept for the color perception of the artificial visual system.
基金This work was supported by the National Natural Science Foundation of China(81671049 and 91732102 to S.Q.31900722 to Y.W.)+4 种基金Natural Science Foundation of Zhejiang Province for Distinguished Young Scholars(LR16C090001 to S.Q.)Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences(2018PT31041)Fundamental Research Funds for the Central Universities of China(2019XZZX001-01-1A to S.Q.)the Chinese Ministry of Education Project 111 Program(B13026 to S.Q.)Key Realm R&D Program of Guangdong Province(2019B030335001).
文摘Local signaling events at synapses or axon terminals are communicated to the nucleus to elicit transcriptional responses,and thereby translate information about the external environment into internal neuronal representations.This retrograde signaling is critical to dendritic growth,synapse development,and neuronal plasticity.Here,we demonstrate that neuronal activity induces retrograde translocation and nuclear accumulation of endosomal adaptor APPL1.Disrupting the interaction of APPL1 with Importin ocl abolishes nuclear accumulation of APPL1,which in turn decreases the levels of histone acetylation.We further demonstrate that retrograde translocation of APPL1 is required for the regulation of gene transcription and then maintenance of hippocampal late-phase long-term potentiation.Thus,these results illustrate an APPLl-mediated pathway that contributes to the modulation of synaptic plasticity via coupling neuronal activity with chromatin remodeling.
基金Project supported by the National Natural Science Foundation of China(Nos.61433012 and 61602156)the Project of Science and Technology in Henan Province,China(No.142102210435)+1 种基金the Project of the Basic and Frontier Technology in Henan Province,China(No.142300410147)the PhD Foundation of Henan Polytechnic University,China(No.B2012-099)。
文摘Opportunity networks provide a chance to offload the tremendous cellular traffic generated by sharing popular content on mobile networks. Analyzing the content spread characteristics in real opportunity environments can discover important clues for traffic offloading decision making. However, relevant published work is very limited since it is not easy to collect data from real environments. In this study, we elaborate the analysis on the dataset collected from a real opportunity environment formed by the users of Xender, which is one of the leading mobile applications for content sharing. To discover content transmission characteristics, scale, speed, and type analyses are implemented on the dataset. The analysis results show that file transmission has obvious periodicity, that only a very small fraction of files spread widely, and that application files have much higher probability to be popular than other files. We also propose a solution to maximize file spread scales, which is very helpful for forecasting popular files. The experimental results verify the effectiveness and usefulness of our solution.
基金Project supported by the Science and Technology of Hubei Provincial Department of Education(No.B2017098)
文摘Hydrogen can be trapped in the bulk materials in four forms:interstitial molecular H_2,interstitial atom H,O^-H^+(2Si=O–H)^+,Si-H^-(4Oˉ≡Si H)^-to affect the electronic and optical properties of amorphous silica.Therefore,the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory.Initially,the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom.However,the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy.Subsequently,the optical properties such as absorption spectra,conductivity and loss functions were analyzed.It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 e V while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 e V.However,the neutral hydrogen defects just improved the intensity of absorption spectrum.This may give insights into understanding the mechanism of laser-induced damage for optical materials.
基金This study was financially supported by the National Key Research&Development Program of China(Nos.2019YFA0308500,2018YFA0305800 and 2016YFA0202300)the National Natural Science Foundation of China(Nos.61888102 and 61925111)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB30000000 and XDB28000000)the CAS Key Laboratory of Vacuum Physics.
文摘Graphene on insulator is the foundation of its practical applications in electronic information technology.However,fabrication of graphene on insulating substrates suffers from small size and limited quality by direct growth of graphene on dielectric substrates,and the method of transferring graphene onto insulating substrates is not so compatible with the large-scale production in industry.Here,we report the fabrication of high-quality,large-area,single-crystal graphene on crystalline magnesium oxide(MgO),which has a dielectric constant of 7–10.Magnesium and oxygen are intercalated at the interface of epitaxial graphene/Ru(0001)and form crystalline structure after high-temperature annealing.The graphene/MgO/Ru(0001)sample was characterized by low energy electron diffraction(LEED),scanning tunneling microscopy(STM),X-ray photoelectron spectroscopy(XPS),and scanning transmission electron microscopy(STEM).LEED pattern shows that the magnesium oxide displays crystalline structure,and STM studies show clearly that the top layer is graphene.STEM characterization of as-intercalated sample demonstrates that the MgO intercalation layer,with a thickness of up to 2.3 nm,has a crystal structure of rock salt MgO,and the out-of-plane crystal orientation is[001].Our work provides a new route for fabrication of graphene on high dielectric constant insulators,which may have potential applications in future electronics.
基金supported by the Guangdong Basic and Applied Basic Research Foundation program (Grant No.2020A1515110292)Shandong Provincial Natural Science Foundation (Grant No.ZR2020QF080)Qilu Young Scholar program (Grant No.11500089963022),China.
文摘To realize high performance flexible transparent electronics with extreme environmental adaptivity,Ag nanowires(Ag NWs)electrodes should simultaneously meet the requirements of high-temperature tolerance,chemical and mechanical robustness.Herein,a scalable Ag NWs bundle micro-meshes embedded in polyimide(Ag BMs/ePI)conducting film via a facile spray coating and transfer method is reported.Due to the synergistic effect of bundle micromesh and embedded architecture,the Ag BMs/ePI electrode exhibits high thermal stability(370℃ and 400℃ under ambient and nitrogen atmosphere conditions,respectively),low sheet resistance variation(<4%),good corrosion and deformation resistance.As an electrical heater,the Ag BMs/ePI can achieve~204℃ with the fast thermal response time of~8 s at 8 V,and exhibits good heating stability under bent condition.This work offers a promising platform for the emerging flexible transparent electronics to adapt extreme environments,especially for those devices which require high-temperature processing.
