Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely u...Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely utilized to investigate neuro biological markers after mild traumatic brain injury.This approach has emerged as a promising tool for investigating the pathogenesis of mild traumatic brain injury.G raph theory is a quantitative method of analyzing complex networks that has been widely used to study changes in brain structure and function.However,most previous mild traumatic brain injury studies using graph theory have focused on specific populations,with limited exploration of simultaneous abnormalities in structural and functional connectivity.Given that mild traumatic brain injury is the most common type of traumatic brain injury encounte red in clinical practice,further investigation of the patient characteristics and evolution of structural and functional connectivity is critical.In the present study,we explored whether abnormal structural and functional connectivity in the acute phase could serve as indicators of longitudinal changes in imaging data and cognitive function in patients with mild traumatic brain injury.In this longitudinal study,we enrolled 46 patients with mild traumatic brain injury who were assessed within 2 wee ks of injury,as well as 36 healthy controls.Resting-state functional magnetic resonance imaging and diffusion-weighted imaging data were acquired for graph theoretical network analysis.In the acute phase,patients with mild traumatic brain injury demonstrated reduced structural connectivity in the dorsal attention network.More than 3 months of followup data revealed signs of recovery in structural and functional connectivity,as well as cognitive function,in 22 out of the 46 patients.Furthermore,better cognitive function was associated with more efficient networks.Finally,our data indicated that small-worldness in the acute stage could serve as a predictor of longitudinal changes in connectivity in patients with mild traumatic brain injury.These findings highlight the importance of integrating structural and functional connectivity in unde rstanding the occurrence and evolution of mild traumatic brain injury.Additionally,exploratory analysis based on subnetworks could serve a predictive function in the prognosis of patients with mild traumatic brain injury.展开更多
The strength of the connection structure has always been a key issue in the structural design of a launch vehicle.In this paper,the finite element analysis method is used for the strength of typical connection structu...The strength of the connection structure has always been a key issue in the structural design of a launch vehicle.In this paper,the finite element analysis method is used for the strength of typical connection structures of a new launch vehicle.The research scope includes the inter-stage connection structure and the bundle connection structure.Aiming at establishing the strength of these two connection structures under flight conditions,we built a refined finite element model,simulated the bolt tensile test and obtained a calculation criteria,and carried out finite element analysis of the connection structures under flight conditions.As a result,we not only established the analysis and evaluation method of the connection structures based on the refined finite element modeling analysis,but also provided a fast numerical simulation design method for the development of the launch vehicle’s connection structures,which greatly improved the design efficiency and reduced the design risk.展开更多
Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were...Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.展开更多
The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differe...The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.展开更多
This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite eleme...This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite elements models）. Procedure for composition of a model based on usual production process is used in CBFEM. Its results are compared to those obtained by component method for portal frame eaves moment connection with good agreement. Design of moment resistant column base is demonstrated by a case loaded by two directional bending moments and normal force. Interaction of several connections in one complex joint is explained in the last example. This paper aims to provide structural engineers with a new tool to effectively analyze and design various joints of steel structures.展开更多
Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the se...Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the semi-rigid connections were used to model the bond angle variations between the C-Cbonds in graphene. The simulated results show that the equivalent space frame model with semi-rigid connections for graphene proposed in this article is a simple, efficient, and accurate model to evaluate the equivalent elastic properties of graphene. Though the present computational model of the semi-rigid connected space frame is only applied to characterize the mechanical behaviors of the space lattices of graphene, it has more potential applications in the static and dynamic analyses of graphene and other nanomaterials.展开更多
Interest in the engineering performance of bamboo is on the rise primarily due to its rapid regenerative qualities and high strength-to-weight ratio.It has been a standard,sustainable building material for thousands o...Interest in the engineering performance of bamboo is on the rise primarily due to its rapid regenerative qualities and high strength-to-weight ratio.It has been a standard,sustainable building material for thousands of years in Asia and South America,where it grows naturally.Although there are many examples of magnificent bamboo structures,standards and documentation on safe and reliable bamboo design are scarce,particularly for connection design.Traditional connections involve friction-tight lashings(eg.ropes and cords of dried grasses)and pin-and-socket connections such as dowels and pegs,but more recent advances have involved integration with steel hardware and concrete.This paper presents bamboo as a feasible alternative building material and presents a review of past,current and emerging technologies to join hollow bamboo culms in structural applications.The paper’s intent is to give an overview of the current state of bamboo connection technology and to promote developments in the emerging field of bamboo engineering.Recent technological advances and visionary architects have proven that it is possible to create safe structures that are not only sustainable but have tremendous potential for use in disaster relief and quick-build scenarios.展开更多
The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered fir...The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered first in the study area and the distributing curves of excess pore water pressure along with time and depth in the soil stratum are gained; the possibility of silt liquefaction is evaluated using the computing values and the affecting depth of liquefaction is given. This paper quantitatively analyzes the dynamic response of seafloor soil under the cyclic loading of waves and makes an inquiry into the instable mechanism of soil.展开更多
Epilepsy is a common neurological disorder, and its electrophysiology characteristic is abnormally high excitability and synchronization of the neural activity. This paper focuses on the study of medial temporal lobe ...Epilepsy is a common neurological disorder, and its electrophysiology characteristic is abnormally high excitability and synchronization of the neural activity. This paper focuses on the study of medial temporal lobe epilepsy with hippocampal sclerosis. The hippocampus plays an important role in short-term memory. However, little is known about the connectivity between hippocampal structures and adjacent brain regions. The functional and structural connectivity between patients and controls was investigated by using the techniques of functional magnetic resonance imaging and diffusion tensor imaging in the paper. Three pairs of ROIs related to working memory from BOLD-fMRI data were chosen. These ROIs were registrated from MNI space to individual space and the fiber bundle between two ROIs were traced in the DTI images. The results show that the number of fiber bundle of patients reduce among these ROIs, such as left hippocampus and right hippocampus, left hippocampus and left thalamus, left hippocampus and left frontal lobe and so on. And the number of fiber bundle of patients increase among these ROIs, such as left thalamus and right thalamus, right hippocampus and right thalamus. And the FA values of the fiber bundles of patients in some regions related to left hippocampus decrease. The cause of abnormal functional and structural connections due to the damage of hippocampus in medial temporal lobe epilepsy is studied from a new perspective.展开更多
Fibrous components and structural morphology of the connective tissue of the lamina cribrosa obtained from 35 normal human autopsy eyes were examined by histochemical staining, transmission electron microscopic and co...Fibrous components and structural morphology of the connective tissue of the lamina cribrosa obtained from 35 normal human autopsy eyes were examined by histochemical staining, transmission electron microscopic and computer-展开更多
Background:Autism spectrum disorder(ASD)is associated with altered brain development,but it is unclear which specific structural changes may serve as potential diagnostic markers,particularly in young children at the ...Background:Autism spectrum disorder(ASD)is associated with altered brain development,but it is unclear which specific structural changes may serve as potential diagnostic markers,particularly in young children at the age when symptoms become fully estab-lished.Furthermore,such brain markers need to meet the requirements of precision medicine and be accurate in aiding diagnosis at an individual rather than only a group level.Objective:This study aimed to identify and model brain-wide differences in structural connectivity using diffusion tensor imaging(DTI)in young ASD and typically developing(TD)children.Methods:A discovery cohort including 93 ASD and 26 TD children and two independent validation cohorts including 12 ASD and 9 TD children from three different cities in China were included.Brain-wide(294 regions)structural connectivity was measured using DTI(fractional anisotropy,FA)together with symptom severity and cognitive development.A connection matrix was constructed for each child for comparisons between ASD and TD groups.Pattern classification was performed on the discovery dataset and the resulting model was tested on the two independent validation datasets.Results:Thirty-three structural connections showed increased FA in ASD compared to TD children and associated with both autistic symptom severity and impaired general cognitive development.The majority(29/33)involved the frontal lobe and comprised five different networks with functional relevance to default mode,motor control,social recognition,language and reward.Overall,clas-sification achieved very high accuracy of 96.77%in the discovery dataset,and 91.67%and 88.89%in the two independent validation datasets.Conclusions:Identified structural connectivity differences primarily involving the frontal cortex can very accurately distinguish novel individual ASD from TD children and may therefore represent a robust early brain biomarker which can address the requirements of precision medicine.展开更多
Hybrid beamforming（ HBF） technology becomes one of the key technologies in the millimeter wave（ mm Wave）mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamform...Hybrid beamforming（ HBF） technology becomes one of the key technologies in the millimeter wave（ mm Wave）mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamforming（ DBF）. Two structures of HBF exist in the mm Wave mobile backhaul system,namely,the fully connected structures（ FCS） and partially connected structures（ PCS）. However,the existing methods cannot be applied to both structures. Moreover,the ideal phase shifter is considered in some current HBF methods,which is not realistic. In this paper,a HBF algorithm for both structures based on the discrete phase shifters is proposed in the mm Wave mobile backhaul systems. By using the principle of alternating minimization,the optimization problem of HBF is decomposed into a DBF optimization problem and an analog beamforming（ ABF） optimization problem.Then the least square（ LS） method is enabled to solve the optimization model of DBF. In addition,the achievable data rate for both structures with closed-form expression which can be used to convert the optimization model into a single-stream beamforming optimization model with per antenna power constraint is derived. Therefore,the ABF is easily solved. Simulation results show that the performance of the proposed HBF method can approach the full DBF by using a lower resolution phase shifter.展开更多
Dysfunction of brain-derived arginine-vasopressin（AVP） systems may be involved in the etiology of autism spectrum disorder（ASD）. Certain regions such as the hypothalamus, amygdala, and hippocampus are known to con...Dysfunction of brain-derived arginine-vasopressin（AVP） systems may be involved in the etiology of autism spectrum disorder（ASD）. Certain regions such as the hypothalamus, amygdala, and hippocampus are known to contain either AVP neurons or terminals and may play an important role in regulating complex social behaviors.The present study was designed to investigate the concomitant changes in autistic behaviors, circulating AVP levels, and the structure and functional connectivity（FC） of speci？c brain regions in autistic children compared with typically developing children（TDC） aged from 3 to5 years. The results showed：（1） children with ASD had a signi？cantly increased volume in the left amygdala and left hippocampus, and a signi？cantly decreased volume in the bilateral hypothalamus compared to TDC, and these were positively correlated with plasma AVP level.（2） Autistic children had a negative FC between the left amygdala and the bilateral supramarginal gyri compared to TDC. The degree of the negative FC between amygdala and supramarginal gyrus was associated with a higher score on the clinical autism behavior checklist.（3） The degree of negative FC between left amygdala and left supramarginal gyrus was associated with a lowering of the circulating AVP concentration in boys with ASD.（4） Autistic children showed a higher FC between left hippocampus and right subcortical area compared to TDC.（5） The circulating AVP was negatively correlated with the visual and listening response score of the childhood autism rating scale.These results strongly suggest that changes in structure and FC in brain regions containing AVP may be involved in the etiology of autism.展开更多
Chinese,as a logographic language,fundamentally differs from alphabetic languages like English.Previous neuroimaging studies have mainly focused on alphabetic languages,while the exploration of Chinese reading is stil...Chinese,as a logographic language,fundamentally differs from alphabetic languages like English.Previous neuroimaging studies have mainly focused on alphabetic languages,while the exploration of Chinese reading is still an emerging and fast-growing research field.Recently,a growing number of neuroimaging studies have explored the neural circuit of Chinese reading.Here,we summarize previous research on Chinese reading from a connectomic perspective.Converging evidence indicates that the left middle frontal gyrus is a specialized hub region that connects the ventral with dorsal pathways for Chinese reading.Notably,the orthography-to-phonology and orthography-to-semantics mapping,mainly processed in the ventral pathway,are more specific during Chinese reading.Besides,in addition to the left-lateralized language-related regions,reading pathways in the right hemisphere also play an important role in Chinese reading.Throughout,we comprehensively review prior findings and emphasize several challenging issues to be explored in future work.展开更多
Background:Protected areas(PA)are central to biodiversity,but their efficiency is challenged by human‑induced habitat loss and fragmentation.In the Fennoscandian boreal region,forestry with clearcutting is a threat to...Background:Protected areas(PA)are central to biodiversity,but their efficiency is challenged by human‑induced habitat loss and fragmentation.In the Fennoscandian boreal region,forestry with clearcutting is a threat to biodiversity causing the loss of mature forest elements and deterioration of ecological processes in forest landscapes,ultimately affecting PAs via declined structural connectivity.This paper aims to(1)determine PAs with high,red‑listed species concentrations;(2)estimate the change in forest habitat around these PAs on different spatial scales;and(3)determine if forest management intensity is higher around biologically most valuable PAs.Occurrences of red‑listed forest‑dwelling species in Finland were used to identify PAs harbouring these species and to produce site‑specific importance indices.CORINE landcover data was used as a baseline for the distribution of forests to assess the cover of clear‑cuttings from 2001 to 2019 with the Global Forest Change(GFC)data set in three buffer areas around the PAs with occurrences of red‑listed species.Results:The largest proportion of clear‑cuts occurred in 1 km and 10 km buffers around the PAs in the southern and middle boreal zones,being ca.20%.This indicates that the forest habitat is degrading fast at regional and landscape levels.On the positive side,the change in forest cover was lower around the biologically most important PAs compared to other PAs with red‑listed species.Conclusions:Open and free satellite‑data based assessments of the cover and change of forests provide reliable estimates about the rates at which mature and old‑growth forests are being converted into young managed ones in Finland mainly via clear‑cuts on different scales around PAs.The rate of clear‑cuts was lowest in adjacent buffer areas next to the most species‑rich PAs,which provides opportunities for biodiversity conservation efforts to be targeted to the remaining mature and old‑growth forests found in the vicinity of these areas.展开更多
For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contracti...For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contractions of generic anti-canonical hypersurfaces along the three rational curves can be deformed to smooth threefolds which is diffeomorphic to connected sums of S3 ~ S~. In this manner, we obtain complex structures with trivial canonical bundles on some connected sums of S^3 × S^3. This construction is an analogue of that made by Friedman [On threefolds with trivial canonical bundle. In： Complex Geometry and Lie Theory, volume 53 of Proc. Sympos. Pure Math., Amer. Math. Soc., Providence, RI, 1991, 103-134], Lu and Tian [Complex structures on connected sums of S^3× S^3. In： Manifolds and Geometry, Pisa, 1993, 284 293] who used only quintics in P^4.展开更多
基金supported by the National Natural Science Foundation of China,Nos.81671671(to JL),61971451(to JL),U22A2034(to XK),62177047(to XK)the National Defense Science and Technology Collaborative Innovation Major Project of Central South University,No.2021gfcx05(to JL)+6 种基金Clinical Research Cen terfor Medical Imaging of Hunan Province,No.2020SK4001(to JL)Key Emergency Project of Pneumonia Epidemic of Novel Coronavirus Infection of Hu nan Province,No.2020SK3006(to JL)Innovative Special Construction Foundation of Hunan Province,No.2019SK2131(to JL)the Science and Technology lnnovation Program of Hunan Province,Nos.2021RC4016(to JL),2021SK53503(to ML)Scientific Research Program of Hunan Commission of Health,No.202209044797(to JL)Central South University Research Program of Advanced Interdisciplinary Studies,No.2023Q YJC020(to XK)the Natural Science Foundation of Hunan Province,No.2022JJ30814(to ML)。
文摘Patients with mild traumatic brain injury have a diverse clinical presentation,and the underlying pathophysiology remains poorly understood.Magnetic resonance imaging is a non-invasive technique that has been widely utilized to investigate neuro biological markers after mild traumatic brain injury.This approach has emerged as a promising tool for investigating the pathogenesis of mild traumatic brain injury.G raph theory is a quantitative method of analyzing complex networks that has been widely used to study changes in brain structure and function.However,most previous mild traumatic brain injury studies using graph theory have focused on specific populations,with limited exploration of simultaneous abnormalities in structural and functional connectivity.Given that mild traumatic brain injury is the most common type of traumatic brain injury encounte red in clinical practice,further investigation of the patient characteristics and evolution of structural and functional connectivity is critical.In the present study,we explored whether abnormal structural and functional connectivity in the acute phase could serve as indicators of longitudinal changes in imaging data and cognitive function in patients with mild traumatic brain injury.In this longitudinal study,we enrolled 46 patients with mild traumatic brain injury who were assessed within 2 wee ks of injury,as well as 36 healthy controls.Resting-state functional magnetic resonance imaging and diffusion-weighted imaging data were acquired for graph theoretical network analysis.In the acute phase,patients with mild traumatic brain injury demonstrated reduced structural connectivity in the dorsal attention network.More than 3 months of followup data revealed signs of recovery in structural and functional connectivity,as well as cognitive function,in 22 out of the 46 patients.Furthermore,better cognitive function was associated with more efficient networks.Finally,our data indicated that small-worldness in the acute stage could serve as a predictor of longitudinal changes in connectivity in patients with mild traumatic brain injury.These findings highlight the importance of integrating structural and functional connectivity in unde rstanding the occurrence and evolution of mild traumatic brain injury.Additionally,exploratory analysis based on subnetworks could serve a predictive function in the prognosis of patients with mild traumatic brain injury.
文摘The strength of the connection structure has always been a key issue in the structural design of a launch vehicle.In this paper,the finite element analysis method is used for the strength of typical connection structures of a new launch vehicle.The research scope includes the inter-stage connection structure and the bundle connection structure.Aiming at establishing the strength of these two connection structures under flight conditions,we built a refined finite element model,simulated the bolt tensile test and obtained a calculation criteria,and carried out finite element analysis of the connection structures under flight conditions.As a result,we not only established the analysis and evaluation method of the connection structures based on the refined finite element modeling analysis,but also provided a fast numerical simulation design method for the development of the launch vehicle’s connection structures,which greatly improved the design efficiency and reduced the design risk.
基金Project(51178203)supported by the National Natural Science Foundation of China
文摘Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.
文摘The formation and the thermal stability of a connected hard skeleton structure(CHSS) in the matrix of Mg-5Al-2Sn-5Ca(ATX525) alloy were investigated by using X-ray diffractometer, scanning electron microscopy, differential scanning calorimeter, creep tester and isothermal treatment method. The results indicated that the CHSS composed of Mg2(Al,Ca) and Al2 Ca intermetallics was formed into a typical eutectic structure and no obvious change occurred when the samples were isothermally treated at 250 °C for 96 h and 350 °C for 72 h, respectively. It became a chained structure when isothermally treated at 450 °C for 48 h. The dissolution and reconstruction processes, however, were observed for the CHSS when the processing temperature was up to 550 °C. The creep life at the stress-temperature condition of 50MPa/200°C for the alloy treated at 450 °C for 48 h was as high as 510 h, and the strain at creep time of 100 h was as low as 0.03%, which indicated that the present alloy has not only a good thermal stability, but also a better heat resistance.
文摘This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite elements models）. Procedure for composition of a model based on usual production process is used in CBFEM. Its results are compared to those obtained by component method for portal frame eaves moment connection with good agreement. Design of moment resistant column base is demonstrated by a case loaded by two directional bending moments and normal force. Interaction of several connections in one complex joint is explained in the last example. This paper aims to provide structural engineers with a new tool to effectively analyze and design various joints of steel structures.
基金Funded by the Talent Foundation and Youth Foundation of Xi’an University of Architecture and Technology(Nos.DB12062 and QN1239)
文摘Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the semi-rigid connections were used to model the bond angle variations between the C-Cbonds in graphene. The simulated results show that the equivalent space frame model with semi-rigid connections for graphene proposed in this article is a simple, efficient, and accurate model to evaluate the equivalent elastic properties of graphene. Though the present computational model of the semi-rigid connected space frame is only applied to characterize the mechanical behaviors of the space lattices of graphene, it has more potential applications in the static and dynamic analyses of graphene and other nanomaterials.
文摘Interest in the engineering performance of bamboo is on the rise primarily due to its rapid regenerative qualities and high strength-to-weight ratio.It has been a standard,sustainable building material for thousands of years in Asia and South America,where it grows naturally.Although there are many examples of magnificent bamboo structures,standards and documentation on safe and reliable bamboo design are scarce,particularly for connection design.Traditional connections involve friction-tight lashings(eg.ropes and cords of dried grasses)and pin-and-socket connections such as dowels and pegs,but more recent advances have involved integration with steel hardware and concrete.This paper presents bamboo as a feasible alternative building material and presents a review of past,current and emerging technologies to join hollow bamboo culms in structural applications.The paper’s intent is to give an overview of the current state of bamboo connection technology and to promote developments in the emerging field of bamboo engineering.Recent technological advances and visionary architects have proven that it is possible to create safe structures that are not only sustainable but have tremendous potential for use in disaster relief and quick-build scenarios.
基金This project was financially supported by the National Science Foundation through Grant No.49476291
文摘The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered first in the study area and the distributing curves of excess pore water pressure along with time and depth in the soil stratum are gained; the possibility of silt liquefaction is evaluated using the computing values and the affecting depth of liquefaction is given. This paper quantitatively analyzes the dynamic response of seafloor soil under the cyclic loading of waves and makes an inquiry into the instable mechanism of soil.
基金National Natural Science Foundation of Chinagrant number: 6075107
文摘Epilepsy is a common neurological disorder, and its electrophysiology characteristic is abnormally high excitability and synchronization of the neural activity. This paper focuses on the study of medial temporal lobe epilepsy with hippocampal sclerosis. The hippocampus plays an important role in short-term memory. However, little is known about the connectivity between hippocampal structures and adjacent brain regions. The functional and structural connectivity between patients and controls was investigated by using the techniques of functional magnetic resonance imaging and diffusion tensor imaging in the paper. Three pairs of ROIs related to working memory from BOLD-fMRI data were chosen. These ROIs were registrated from MNI space to individual space and the fiber bundle between two ROIs were traced in the DTI images. The results show that the number of fiber bundle of patients reduce among these ROIs, such as left hippocampus and right hippocampus, left hippocampus and left thalamus, left hippocampus and left frontal lobe and so on. And the number of fiber bundle of patients increase among these ROIs, such as left thalamus and right thalamus, right hippocampus and right thalamus. And the FA values of the fiber bundles of patients in some regions related to left hippocampus decrease. The cause of abnormal functional and structural connections due to the damage of hippocampus in medial temporal lobe epilepsy is studied from a new perspective.
文摘Fibrous components and structural morphology of the connective tissue of the lamina cribrosa obtained from 35 normal human autopsy eyes were examined by histochemical staining, transmission electron microscopic and computer-
文摘Background:Autism spectrum disorder(ASD)is associated with altered brain development,but it is unclear which specific structural changes may serve as potential diagnostic markers,particularly in young children at the age when symptoms become fully estab-lished.Furthermore,such brain markers need to meet the requirements of precision medicine and be accurate in aiding diagnosis at an individual rather than only a group level.Objective:This study aimed to identify and model brain-wide differences in structural connectivity using diffusion tensor imaging(DTI)in young ASD and typically developing(TD)children.Methods:A discovery cohort including 93 ASD and 26 TD children and two independent validation cohorts including 12 ASD and 9 TD children from three different cities in China were included.Brain-wide(294 regions)structural connectivity was measured using DTI(fractional anisotropy,FA)together with symptom severity and cognitive development.A connection matrix was constructed for each child for comparisons between ASD and TD groups.Pattern classification was performed on the discovery dataset and the resulting model was tested on the two independent validation datasets.Results:Thirty-three structural connections showed increased FA in ASD compared to TD children and associated with both autistic symptom severity and impaired general cognitive development.The majority(29/33)involved the frontal lobe and comprised five different networks with functional relevance to default mode,motor control,social recognition,language and reward.Overall,clas-sification achieved very high accuracy of 96.77%in the discovery dataset,and 91.67%and 88.89%in the two independent validation datasets.Conclusions:Identified structural connectivity differences primarily involving the frontal cortex can very accurately distinguish novel individual ASD from TD children and may therefore represent a robust early brain biomarker which can address the requirements of precision medicine.
基金supported by the State Major Science and Technique Project(MJ-2014-S-37)the National Natural Science Foundation of China(61201134)the 111 Project(B08038)
文摘Hybrid beamforming（ HBF） technology becomes one of the key technologies in the millimeter wave（ mm Wave）mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamforming（ DBF）. Two structures of HBF exist in the mm Wave mobile backhaul system,namely,the fully connected structures（ FCS） and partially connected structures（ PCS）. However,the existing methods cannot be applied to both structures. Moreover,the ideal phase shifter is considered in some current HBF methods,which is not realistic. In this paper,a HBF algorithm for both structures based on the discrete phase shifters is proposed in the mm Wave mobile backhaul systems. By using the principle of alternating minimization,the optimization problem of HBF is decomposed into a DBF optimization problem and an analog beamforming（ ABF） optimization problem.Then the least square（ LS） method is enabled to solve the optimization model of DBF. In addition,the achievable data rate for both structures with closed-form expression which can be used to convert the optimization model into a single-stream beamforming optimization model with per antenna power constraint is derived. Therefore,the ABF is easily solved. Simulation results show that the performance of the proposed HBF method can approach the full DBF by using a lower resolution phase shifter.
基金support provided by the Department of Radiology,Peking University Third Hospital and the Brainnetome Center,Institute of Automation,Chines Academy of Sciences are highly appreciatedsupported by the UULM-PUHSC Joint Center for Neuroscience Fund(BMU20160563)
文摘Dysfunction of brain-derived arginine-vasopressin（AVP） systems may be involved in the etiology of autism spectrum disorder（ASD）. Certain regions such as the hypothalamus, amygdala, and hippocampus are known to contain either AVP neurons or terminals and may play an important role in regulating complex social behaviors.The present study was designed to investigate the concomitant changes in autistic behaviors, circulating AVP levels, and the structure and functional connectivity（FC） of speci？c brain regions in autistic children compared with typically developing children（TDC） aged from 3 to5 years. The results showed：（1） children with ASD had a signi？cantly increased volume in the left amygdala and left hippocampus, and a signi？cantly decreased volume in the bilateral hypothalamus compared to TDC, and these were positively correlated with plasma AVP level.（2） Autistic children had a negative FC between the left amygdala and the bilateral supramarginal gyri compared to TDC. The degree of the negative FC between amygdala and supramarginal gyrus was associated with a higher score on the clinical autism behavior checklist.（3） The degree of negative FC between left amygdala and left supramarginal gyrus was associated with a lowering of the circulating AVP concentration in boys with ASD.（4） Autistic children showed a higher FC between left hippocampus and right subcortical area compared to TDC.（5） The circulating AVP was negatively correlated with the visual and listening response score of the childhood autism rating scale.These results strongly suggest that changes in structure and FC in brain regions containing AVP may be involved in the etiology of autism.
基金supported by the Natural Science Foundation of China(81901826 and 61932008)the Natural Science Foundation of Shanghai(19ZR1405600 and 20ZR1404900)the Shanghai Municipal Science and Technology Major Project(2018SHZDZX01)。
文摘Chinese,as a logographic language,fundamentally differs from alphabetic languages like English.Previous neuroimaging studies have mainly focused on alphabetic languages,while the exploration of Chinese reading is still an emerging and fast-growing research field.Recently,a growing number of neuroimaging studies have explored the neural circuit of Chinese reading.Here,we summarize previous research on Chinese reading from a connectomic perspective.Converging evidence indicates that the left middle frontal gyrus is a specialized hub region that connects the ventral with dorsal pathways for Chinese reading.Notably,the orthography-to-phonology and orthography-to-semantics mapping,mainly processed in the ventral pathway,are more specific during Chinese reading.Besides,in addition to the left-lateralized language-related regions,reading pathways in the right hemisphere also play an important role in Chinese reading.Throughout,we comprehensively review prior findings and emphasize several challenging issues to be explored in future work.
基金supported by funding provided by the Finnish Ministry of the Environment(Evaluating the protected area network in the changing climate,SUMI,and the Finnish Ecosystem Observatory,FEO)the Strategic Research Council(SRC)at the Academy of Finland(Decision No 312559).
文摘Background:Protected areas(PA)are central to biodiversity,but their efficiency is challenged by human‑induced habitat loss and fragmentation.In the Fennoscandian boreal region,forestry with clearcutting is a threat to biodiversity causing the loss of mature forest elements and deterioration of ecological processes in forest landscapes,ultimately affecting PAs via declined structural connectivity.This paper aims to(1)determine PAs with high,red‑listed species concentrations;(2)estimate the change in forest habitat around these PAs on different spatial scales;and(3)determine if forest management intensity is higher around biologically most valuable PAs.Occurrences of red‑listed forest‑dwelling species in Finland were used to identify PAs harbouring these species and to produce site‑specific importance indices.CORINE landcover data was used as a baseline for the distribution of forests to assess the cover of clear‑cuttings from 2001 to 2019 with the Global Forest Change(GFC)data set in three buffer areas around the PAs with occurrences of red‑listed species.Results:The largest proportion of clear‑cuts occurred in 1 km and 10 km buffers around the PAs in the southern and middle boreal zones,being ca.20%.This indicates that the forest habitat is degrading fast at regional and landscape levels.On the positive side,the change in forest cover was lower around the biologically most important PAs compared to other PAs with red‑listed species.Conclusions:Open and free satellite‑data based assessments of the cover and change of forests provide reliable estimates about the rates at which mature and old‑growth forests are being converted into young managed ones in Finland mainly via clear‑cuts on different scales around PAs.The rate of clear‑cuts was lowest in adjacent buffer areas next to the most species‑rich PAs,which provides opportunities for biodiversity conservation efforts to be targeted to the remaining mature and old‑growth forests found in the vicinity of these areas.
文摘For a generic anti-canonical hypersurface in each smooth toric Fano 4-fold with rank 2 Picard group, we prove there exist three isolated rational curves in it. Moreover, for all these 4-folds except one, the contractions of generic anti-canonical hypersurfaces along the three rational curves can be deformed to smooth threefolds which is diffeomorphic to connected sums of S3 ~ S~. In this manner, we obtain complex structures with trivial canonical bundles on some connected sums of S^3 × S^3. This construction is an analogue of that made by Friedman [On threefolds with trivial canonical bundle. In： Complex Geometry and Lie Theory, volume 53 of Proc. Sympos. Pure Math., Amer. Math. Soc., Providence, RI, 1991, 103-134], Lu and Tian [Complex structures on connected sums of S^3× S^3. In： Manifolds and Geometry, Pisa, 1993, 284 293] who used only quintics in P^4.
