This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled a...This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled as an Euler Bernoulli beam resting on the Pasternak foundation incorporating variability in subgrade parameters along the tunnel’s length.A random analysis method using random field theory is introduced to evaluate the tunnel’s longitudinal responses to excavation.Next,a risk assessment index system is established.The normalized relative depth between the excavation and the shield tunnel is used as a risk index,while the maximum longitudinal deformation,the maximum circumferential opening,and the maximum longitudinal bending moment serve as performance indicators.Based on these,a method for analyzing the longitudinal fragility of shield tunnels under excavation-induced disturbances is proposed.Finally,the technique is applied to a case study involving a foundation pit excavation above a shield tunnel,which is the primary application scenario of this method.Vulnerability curves for different performance indicators are derived,and the effects of tunnel stiffness and subgrade stiffness on the tunnel vulnerability are explored.The results reveal significant differences in vulnerability curves depending on the performance index used.Compared to the maximum circumferential opening and the maximum longitudinal bending moment,selecting the maximum longitudinal deformation as the control index better ensures the tunnel’s usability and safety under excavation disturbances.The longitudinal vulnerability of the shield tunnel nonlinearly decreases with the increase of the tunnel stiffness and subgrade stiffness,and the subgrade stiffness has a more pronounced effect.Parametric analyses suggest that actively reinforcing the substratum is more effective on reducing the risk of tunnel failure due to adjacent excavations than passive reinforcement of the tunnel structure.展开更多
Assessing the vulnerability of a platform is crucial in its design.In fact,the results obtained from vulnerability analyses provide valuable information,leading to precise design choices or corrective solutions that e...Assessing the vulnerability of a platform is crucial in its design.In fact,the results obtained from vulnerability analyses provide valuable information,leading to precise design choices or corrective solutions that enhance the platform's chances of surviving different scenarios.Such scenarios can involve various types of threats that can affect the platform's survivability.Among such,blast waves impacting the platform's structure represent critical conditions that have not yet been studied in detail.That is,frameworks for vulnerability assessment that can deal with blast loading have not been presented yet.In this context,this work presents a fast-running engineering tool that can quantify the risk that a structure fails when it is subjected to blast loading from the detonation of high explosive-driven threats detonating at various distances from the structure itself.The tool has been implemented in an in-house software that calculates vulnerability to various impacting objects,and its capabilities have been shown through a simplified,yet realistic,case study.The novelty of this research lies in the development of an integrated computational environment capable of calculating the platform's vulnerability to blast waves,without the need for running expensive finite element simulations.In fact,the proposed tool is fully based on analytical models integrated with a probabilistic approach for vulnerability calculation.展开更多
Introduction Twisted arteries and veins disrupt normal blood flow and elevate the risk for clinical complications such as thrombosis,heart attack,stroke,and organ dysfunction.Veins should remain mechanically stable fo...Introduction Twisted arteries and veins disrupt normal blood flow and elevate the risk for clinical complications such as thrombosis,heart attack,stroke,and organ dysfunction.Veins should remain mechanically stable for normal function.However,compared to arteries,veins are more vulnerable to collapse because they are thin-walled and under lower lumen pressure.Twisted veins have been shown to occur with head turning or after inadvertent twist during various vascular surgeries.In vivo and cadaver studies have demonstrated that turning the head to one side can result in torsion and compression of the internal jugular vein and can compromise cranial drain-展开更多
Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become ex...Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-展开更多
Groundwater is a finite resource which is being overexploited due to increase in demand over the years leading to decrease in its potentiality.As it is known that ground water is the only major source of drinking wate...Groundwater is a finite resource which is being overexploited due to increase in demand over the years leading to decrease in its potentiality.As it is known that ground water is the only major source of drinking water for both urban and rural India its proper management is very essential for its sustainability. In the present study,DRASTIC model is展开更多
Climate change is becoming a serious issue nowadays.There are profound environmental,economic and political implications of global warming. Ecosystems,from mountains to oceans and from the poles to the tropics,are und...Climate change is becoming a serious issue nowadays.There are profound environmental,economic and political implications of global warming. Ecosystems,from mountains to oceans and from the poles to the tropics,are undergoing rapid change.The cost will be borne by all,but especially by the展开更多
China Cardiovascular Disease Report 2017(Summary)pointed out that at present,cardiovascular diseases(CVD)account for the highest number of deaths among urban and rural residents.In the middle or later stages of athero...China Cardiovascular Disease Report 2017(Summary)pointed out that at present,cardiovascular diseases(CVD)account for the highest number of deaths among urban and rural residents.In the middle or later stages of atherosclerosis,the plaques become increasingly unstable with high chance to rupture,which may lead acute death from coronary heart diseases.Medical imaging and image-based computational modeling have been used in recent years to quantify ather-osclerotic plaque morphological and biomechanical characteristics and predict the coronary plaque growth and rupture processes.Analyzing the vulnerability of plaques effectively could lead to better patient screening strategies and enable physicians to adopt timely and necessary intervention or conservative treatment.Earlier investigations of vulnerable plaques were mostly based on histopathological data.With the accumulation of experience in pathology and the gradual enrichment of autopsy materials,the criteria for the diagnosis of vulnerable plaques appeared in 2001,mainly manifested as the necrotic lipid nuclei,fibrous caps that are infiltrated by a large number of macrophages,and fibrous cap thickness less than 65μm.Because of the obvious importance of the thin fibrous cap in the study of plaque vulnerability,it has been a focus of attention by many investigations.Watson,M.G.et al.are concerned about the formation of early fibrous caps in recent years.The presentation of local maximum stress on plaque further confirmed the importance of thin fibrous cap.The development of medical images has greatly promoted the study of coronary atherosclerosis.Compared with autopsy ex vivo,medical image could provide plaque data under in vivo conditions and greatly promote the study of coronary atherosclerosis.Huang XY et al.used ex vivo magnetic resonance imaging(MRI)to study the relationship between plaque wall stress(PWS)and death caused by coronary artery disease.Due to technical limitations and the accessibility of the coronary artery in the body,MRI is not widely used for in vivo coronary studies.Interventional intravascular ultrasound(IVUS),with an image resolution of 150-200μm,has been used in research and clinical practice to identify plaques,quantify plaque morphology,and characterize plaque components.More recently,optical coherence tomography(OCT),with its resolution of 5-10μm,has emerged as an imaging modality which can be used to detect thin fibrous caps and improve diagnostic accuracy.It is commonly believed that mechanical forces play an important role in plaque progression and rupture.Image-based biomechanical plaque models have been developed and used to quantify plaque mechanical conditions and seek their linkage to plaque progression and vulnerability development activities.Based on recent advances in imaging and modeling,this paper attempts to provide a brief review on plaque research,including histological classification,image preparation,biomechanical modeling and analysis methods including medical imaging techniques represented by intravascular ultrasound(IVUS)and optical coherence tomography(OCT),computational modeling and their applications in plaque progression and vulnerability analyses and predictions.The clinical application and future development direction are also briefly described.We focus more on human coronary plaque modeling and mainly included results from our group for illustration purpose.We apologize in advance for our limitations.展开更多
The gradual hybrid anti-worm （GHAW） was presented. percentage of vulnerable hosts present in the network. For GHAW It changed its confrontation scheme in real time according to the its process of countering maliciou...The gradual hybrid anti-worm （GHAW） was presented. percentage of vulnerable hosts present in the network. For GHAW It changed its confrontation scheme in real time according to the its process of countering malicious internet worms was modeled. The performance of GHAW on two factors was also estimated： confronting validity against worms and consumption of network resources. Factors governing its performance, specifically the transformation threshold and the transformation rate, were analyzed. The simulation experiments show that GHAW has dynamical adaptability to changes of network conditions and offers the same level of effectiveness on confronting internet worms as the divide-and-rule hybrid anti-worm, with significantly less cost to network resources. The experiments also indicate that the transformation threshold is the key factor affecting the performance of GHAW.展开更多
Survivability is defined as the capability of a platform to avoid or withstand a man-made hostile environment. Military aircraft in particular, but also other kinds of platforms subjected to external, impacting threat...Survivability is defined as the capability of a platform to avoid or withstand a man-made hostile environment. Military aircraft in particular, but also other kinds of platforms subjected to external, impacting threats, are commonly designed according to increasing survivability requirements. The concept of survivability was first formalized by R. Ball in 1985 in its seminal work on combat aircraft survivability.On the basis of the theory presented in his work, many computer programs have been developed which implement the modelling techniques and computations required by vulnerability assessments. However,a clear and general view of the operative computational procedures is still lacking. Moreover, to date only a limited number of applications to helicopter platforms have been investigated in the survivability field,even though these platforms experience numerous flight conditions exposing the system to different types of threats. In this context, this work aims at establishing a multi-purpose general framework for the vulnerability assessment of different types of platforms subjected to external threats, with a focus on helicopters. The in-house software specifically developed for this application is here described in detail and employed to present a case study on a representative military helicopter.展开更多
A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerabili...A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerability,were calculated.The current vulnerability was used to identify the current vulnerable area through calculating the distance between the current transmitted power and initial transmitted power;and the forecast vulnerability under variation of power injection was used to predict the vulnerable area of next step and verify the current vulnerable area.Numerical simulation was performed under variant operating conditions with IEEE-30 bus system,which shows that almost area of 90% overlaps between current vulnerable area and forecasting vulnerable area,the overlapped area is termed as inherent vulnerable area of grid.When considering N-1 contingency,the assessment results of this method proposed agree with those of optimal power flow.When considering N-2 contingency,optimal power flow fails to obtain correct results,while the method based on energy framework gives reliable results.展开更多
The research of groundwater vulnerability is the basic work to protect the groundwater. For utilizing groundwater resource continuably, groundwater vulnerability evaluation is necessary. Useful reference to protect, e...The research of groundwater vulnerability is the basic work to protect the groundwater. For utilizing groundwater resource continuably, groundwater vulnerability evaluation is necessary. Useful reference to protect, exploit and utilize on groundwater resource are provided rationally. According to the real condition of Sanjiang Plain, the indexes system is established based on the traditional DRASTIC model. The new system includes the following seven indexes： Depth of Water, Net Recharge, Aquifer Media, Soil Media, Conductivity of the Aquifer, Land Utilizing Ratio and Populace Density. The related analysis appears that the system is rather reasonable. Because traditional methods, such as analytic hierarchy process and fuzzy mathematics theory, can＇t be avoided human interference in selection of weights, they could lead to an imprecise result. In order to evaluate the groundwater vulnerability reasonably, entropy weight coefficient method is applied for the first time, which provides a new way to groundwater vulnerability evaluation. The method is a model whose weights are insured by the calculation process, so the artificial disturb can be avoided. It has been used to evaluate the groundwater vulnerability in Sanjiang Plain. The satisfied result is acquired. Comparably, the same result is acquired by the other method named projection pursuit evaluation based on real-coded accelerating genetic algorithm. It shows that entropy weight coefficient method is applicable on groundwater vulnerability evaluation. The evaluation result can provide reference on the decision-making departments.展开更多
The appropriate fuze-warhead coordination method is important to improve the damage efficiency of air defense missiles against aircraft targets. In this paper, an adaptive fuze-warhead coordination method based on the...The appropriate fuze-warhead coordination method is important to improve the damage efficiency of air defense missiles against aircraft targets. In this paper, an adaptive fuze-warhead coordination method based on the Back Propagation Artificial Neural Network(BP-ANN) is proposed, which uses the parameters of missile-target intersection to adaptively calculate the initiation delay. The damage probabilities at different radial locations along the same shot line of a given intersection situation are calculated, so as to determine the optimal detonation position. On this basis, the BP-ANN model is used to describe the complex and highly nonlinear relationship between different intersection parameters and the corresponding optimal detonating point position. In the actual terminal engagement process, the fuze initiation delay is quickly determined by the constructed BP-ANN model combined with the missiletarget intersection parameters. The method is validated in the case of the single-shot damage probability evaluation. Comparing with other fuze-warhead coordination methods, the proposed method can produce higher single-shot damage probability under various intersection conditions, while the fuzewarhead coordination effect is less influenced by the location of the aim point.展开更多
Security vulnerability of denial of service (DoS) in time out-medium access control (T-MAC) protocol was discussed and analysis of power consumption at each stage of T-MAC protocol was carried out. For power efficient...Security vulnerability of denial of service (DoS) in time out-medium access control (T-MAC) protocol was discussed and analysis of power consumption at each stage of T-MAC protocol was carried out. For power efficient authentication scheme which can provide reliability, efficiency, and security for a general T-MAC communication, a novel synchronization and authentication scheme using authentication masking code was proposed. Authentication data were repeated and masked by PN sequence. The simulation results show that the proposed approach can provide synchronization and authentication simultaneously for nodes in wireless sensor network (WSN). 63 bits AMC code gives above 99.97% synchronization detection and 93.98% authentication data detection probability in BER 0.031 7.展开更多
Damage assessment of the wing under blast wave is essential to the vulnerability reduction design of aircraft. This paper introduces a critical relative distance prediction method of aircraft wing damage based on the ...Damage assessment of the wing under blast wave is essential to the vulnerability reduction design of aircraft. This paper introduces a critical relative distance prediction method of aircraft wing damage based on the back-propagation artificial neural network(BP-ANN), which is trained by finite element simulation results. Moreover, the finite element method(FEM) for wing blast damage simulation has been validated by ground explosion tests and further used for damage mode determination and damage characteristics analysis. The analysis results indicate that the wing is more likely to be damaged when the root is struck from vertical directions than others for a small charge. With the increase of TNT equivalent charge, the main damage mode of the wing gradually changes from the local skin tearing to overall structural deformation and the overpressure threshold of wing damage decreases rapidly. Compared to the FEM-based damage assessment, the BP-ANN-based method can predict the wing damage under a random blast wave with an average relative error of 4.78%. The proposed method and conclusions can be used as a reference for damage assessment under blast wave and low-vulnerability design of aircraft structures.展开更多
Integrated with an improved architectural vulnerability factor （AVF） computing model, a new architectural level soft error reliability analysis framework, SS-SERA （soft error reliability analysis based on SimpleSca...Integrated with an improved architectural vulnerability factor （AVF） computing model, a new architectural level soft error reliability analysis framework, SS-SERA （soft error reliability analysis based on SimpleScalar）, was developed. SS-SERA was used to estimate the AVFs for various on-chip structures accurately. Experimental results show that the AVFs of issue queue （IQ）, register update units （RUU）, load store queue （LSQ） and functional unit （FU） are 38.11%, 22.17%, 23.05% and 24.43%, respectively. For address-based structures, i.e., levell data cache （LID）, DTLB, level2 unified cache （L2U）, levell instruction cache （LII） and ITLB, AVFs of their data arrays are 22.86%, 27.57%, 14.80%, 8.25% and 12.58%, lower than their tag arrays＇ AVFs which are 30.01%, 28.89%, 17.69%, 10.26% and 13.84%, respectively. Furthermore, using the AVF values obtained with SS-SERA, a qualitative and quantitative analysis of the AVF variation and predictability was performed for the structures studied. Experimental results show that the AVF exhibits significant variations across different structures and workloads, and is influenced by multiple microarchitectural metrics and their interactions. Besides, AVFs of SPEC2K floating point programs exhibit better predictability than SPEC2K integer programs.展开更多
Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a v...Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a variety of analysis programs for battlefield targets to traditional weapons have been developed,but a comprehensive assessment methodology for targets'vulnerability to laser is still missing.Based on the shotline method,this paper proposes a method that equates laser beam to shotline array,an efficient vulnerability analysis program of target to laser is established by this method,and the program includes the circuit board and the wire into the vulnerability analysis category,which improves the precision of the vulnerability analysis.Taking the UAV engine part as the target of vulnerability analysis,combine with the"life-death unit method"to calculate the laser penetration rate of various materials of the UAV,and the influence of laser weapon system parameters and striking orientation on the killing probability is quantified after introducing the penetration rate into the vulnerability analysis program.The quantitative analysis method proposed in this paper has certain general expansibility,which can provide a fresh idea for the vulnerability analysis of other targets to laser.展开更多
英语中的“heel”,就是汉语里的“脚后跟”,无可争议。但成语“the heel of Achilles”(或“Achilles’s heel”),在《新英汉词典》里的释义是“唯一致命的弱点”,一般也可译成“致命弱点'、“要害”、“可乘之隙”,都与“脚后跟”...英语中的“heel”,就是汉语里的“脚后跟”,无可争议。但成语“the heel of Achilles”(或“Achilles’s heel”),在《新英汉词典》里的释义是“唯一致命的弱点”,一般也可译成“致命弱点'、“要害”、“可乘之隙”,都与“脚后跟”不相干。有例句为证:展开更多
A multidisciplinary approach was applied to a detailed study of groundwater contamination by a Chemical Complex(CQE),near a coastal lagoon—an important wetland locally known as"Ria de Aveiro"(NW Portugal).T...A multidisciplinary approach was applied to a detailed study of groundwater contamination by a Chemical Complex(CQE),near a coastal lagoon—an important wetland locally known as"Ria de Aveiro"(NW Portugal).The study includes 3D lithostratigraphic modeling,the estimate of groundwater recharge using different methods,a geophysical (electromagnetic) survey,and a groundwater samp-展开更多
Background Current bottleneck of patient-specific coronary plaque model construction is the resolution of in vivo medical imaging.The threshold of cap thickness of vulnerable coronary plaques is 65 microns,while the r...Background Current bottleneck of patient-specific coronary plaque model construction is the resolution of in vivo medical imaging.The threshold of cap thickness of vulnerable coronary plaques is 65 microns,while the resolution of in vivo coronary intravascular ultrasound(IVUS)images is 150-200 microns,which is not enough to identify vulnerable plaques with thin caps and construct accurate biomechanical plaque models.Optical coherence tomography(OCT)with a 15-20μm resolution has the capacity to identify thin fibrous cap.IVUS and OCT images could complement each other and provide for more accurate plaque morphology,especially,fibrous cap thickness measurements.A modeling approach combining IVUS and OCT was introduced in our previous publication for cap thickness quantification and more accurate cap stress/strain calculations.In this paper,patient baseline and follow-up IVUS and OCT data were acquired and multimodality image-based Fluidstructure interaction(FSI)models combining 3D IVUS,OCT,angiography were constructed to better quantify human coronary atherosclerotic plaque morphology and plaque stress/strain conditions and investigate the relationship of plaque vulnerability and morphological and mechanical factors.Methods Baseline and 10-Month follow-up in vivo IVUS and OCT coronary plaque data were acquired from one patient with informed consent obtained.Co-registration and segmentation of baseline and follow-up IVUS and OCT images were performed for modeling use.Baseline and follow-up 3D FSI models based on IVUS and OCT were constructed to simulate the mechanical factors which integrating plaque morphology were employed to predict plaque vulnerability.These 3D models were solved by ADINA(ADINA R&D,Watertown,MA,USA).The quantitative indices of cap thickness,lipid percentage were classified according to histological literatures and denoted as Cap Index and Lipid Index.Cap Index,Lipid Index and Morphological Plaque Vulnerability Index(MPVI)were chosen to quantify plaque vulnerability,respectively.Random forest(RF)which was based 13 extracted features including morphological and mechanical factors was used for plaque vulnerability classification and prediction.Over sampling scheme and a 5-fold crossvalidation procedure was employed in all 45 slices for training and testing sets.Single and all different combinations of morphological and mechanical risk factors were used for plaque progression prediction.Results When Cap Index was used as the measurement,minimum cap thickness(MCT)was the best single predictor which area under curve(AUC)is 0.782 0;the combination of MCT,critical plaque wall strain(CPWSn),critical wall shear stress(CWSS)and cap wall shear stress(CapWSS)was the best predictor with ACU=0.868 6.When Lipid Index was used as the measurement,the lipid percentage(LP)was the best single predictor which AUC value is 0.857 8;the combination of Mean cap thickness(MeanCT),LP,CWSS and cap plaque wall stress(CapPWS)and was the best predictor with ACU=0.9821.When MPVI was used as the measurement,MCT was the best single predictor which AUC value is 0.782 9;the combination of MCT,LP,plaque area(PA),CPWSn and CapWSS was the best predictor with ACU=0.872 9.Conclusions Combinations of morphological and mechanical risk factors had higher prediction accuracy,compared to the prediction of single factors and other combination of morphological factors.展开更多
基金Project(52178402) supported by the National Natural Science Foundation of China。
文摘This paper proposes a longitudinal vulnerability-based analysis method to evaluate the impact of foundation pit excavation on shield tunnels,accounting for geological uncertainties.First,the shield tunnel is modeled as an Euler Bernoulli beam resting on the Pasternak foundation incorporating variability in subgrade parameters along the tunnel’s length.A random analysis method using random field theory is introduced to evaluate the tunnel’s longitudinal responses to excavation.Next,a risk assessment index system is established.The normalized relative depth between the excavation and the shield tunnel is used as a risk index,while the maximum longitudinal deformation,the maximum circumferential opening,and the maximum longitudinal bending moment serve as performance indicators.Based on these,a method for analyzing the longitudinal fragility of shield tunnels under excavation-induced disturbances is proposed.Finally,the technique is applied to a case study involving a foundation pit excavation above a shield tunnel,which is the primary application scenario of this method.Vulnerability curves for different performance indicators are derived,and the effects of tunnel stiffness and subgrade stiffness on the tunnel vulnerability are explored.The results reveal significant differences in vulnerability curves depending on the performance index used.Compared to the maximum circumferential opening and the maximum longitudinal bending moment,selecting the maximum longitudinal deformation as the control index better ensures the tunnel’s usability and safety under excavation disturbances.The longitudinal vulnerability of the shield tunnel nonlinearly decreases with the increase of the tunnel stiffness and subgrade stiffness,and the subgrade stiffness has a more pronounced effect.Parametric analyses suggest that actively reinforcing the substratum is more effective on reducing the risk of tunnel failure due to adjacent excavations than passive reinforcement of the tunnel structure.
文摘Assessing the vulnerability of a platform is crucial in its design.In fact,the results obtained from vulnerability analyses provide valuable information,leading to precise design choices or corrective solutions that enhance the platform's chances of surviving different scenarios.Such scenarios can involve various types of threats that can affect the platform's survivability.Among such,blast waves impacting the platform's structure represent critical conditions that have not yet been studied in detail.That is,frameworks for vulnerability assessment that can deal with blast loading have not been presented yet.In this context,this work presents a fast-running engineering tool that can quantify the risk that a structure fails when it is subjected to blast loading from the detonation of high explosive-driven threats detonating at various distances from the structure itself.The tool has been implemented in an in-house software that calculates vulnerability to various impacting objects,and its capabilities have been shown through a simplified,yet realistic,case study.The novelty of this research lies in the development of an integrated computational environment capable of calculating the platform's vulnerability to blast waves,without the need for running expensive finite element simulations.In fact,the proposed tool is fully based on analytical models integrated with a probabilistic approach for vulnerability calculation.
基金supported by a CAREER award(0644646)from NSFa research grant (R01HL095852)and an MBRS-RISE fellowship(5R25GM060655-12)from the NIHa collaboration grant (11229202)from NNSF of China
文摘Introduction Twisted arteries and veins disrupt normal blood flow and elevate the risk for clinical complications such as thrombosis,heart attack,stroke,and organ dysfunction.Veins should remain mechanically stable for normal function.However,compared to arteries,veins are more vulnerable to collapse because they are thin-walled and under lower lumen pressure.Twisted veins have been shown to occur with head turning or after inadvertent twist during various vascular surgeries.In vivo and cadaver studies have demonstrated that turning the head to one side can result in torsion and compression of the internal jugular vein and can compromise cranial drain-
基金partially supported by the National 973 Basic Research Program of China (No.2013CB733803)the National Natural Science Foundation of China(NSFC)(No.11272091)
文摘Introduction Stroke or heart attack,the leading cause of death and disability worldwide,is usually caused by rupture of atheromatous plaque.Therefore,the identification of vulnerable atheroma pre rupture has become extremely important for patient risk stratification.Previous studies have shown that the vulnerable plaque,i.e.one that is prone to rupture with thromboembolic complications,is often associated with a thin fibrous cap,a large lipid core and a high inflammatory burden.The mechanism of plaque rupture is not entirely clear but is thought to be a multi-factorial process involving thinning and weakening of the fibrous cap by enzymes secreted by activa-
文摘Groundwater is a finite resource which is being overexploited due to increase in demand over the years leading to decrease in its potentiality.As it is known that ground water is the only major source of drinking water for both urban and rural India its proper management is very essential for its sustainability. In the present study,DRASTIC model is
文摘Climate change is becoming a serious issue nowadays.There are profound environmental,economic and political implications of global warming. Ecosystems,from mountains to oceans and from the poles to the tropics,are undergoing rapid change.The cost will be borne by all,but especially by the
基金supported in part by NIH grant ( R01 EB004759)Jiangsu Province Science and Technology Agency grant ( BE2016785)
文摘China Cardiovascular Disease Report 2017(Summary)pointed out that at present,cardiovascular diseases(CVD)account for the highest number of deaths among urban and rural residents.In the middle or later stages of atherosclerosis,the plaques become increasingly unstable with high chance to rupture,which may lead acute death from coronary heart diseases.Medical imaging and image-based computational modeling have been used in recent years to quantify ather-osclerotic plaque morphological and biomechanical characteristics and predict the coronary plaque growth and rupture processes.Analyzing the vulnerability of plaques effectively could lead to better patient screening strategies and enable physicians to adopt timely and necessary intervention or conservative treatment.Earlier investigations of vulnerable plaques were mostly based on histopathological data.With the accumulation of experience in pathology and the gradual enrichment of autopsy materials,the criteria for the diagnosis of vulnerable plaques appeared in 2001,mainly manifested as the necrotic lipid nuclei,fibrous caps that are infiltrated by a large number of macrophages,and fibrous cap thickness less than 65μm.Because of the obvious importance of the thin fibrous cap in the study of plaque vulnerability,it has been a focus of attention by many investigations.Watson,M.G.et al.are concerned about the formation of early fibrous caps in recent years.The presentation of local maximum stress on plaque further confirmed the importance of thin fibrous cap.The development of medical images has greatly promoted the study of coronary atherosclerosis.Compared with autopsy ex vivo,medical image could provide plaque data under in vivo conditions and greatly promote the study of coronary atherosclerosis.Huang XY et al.used ex vivo magnetic resonance imaging(MRI)to study the relationship between plaque wall stress(PWS)and death caused by coronary artery disease.Due to technical limitations and the accessibility of the coronary artery in the body,MRI is not widely used for in vivo coronary studies.Interventional intravascular ultrasound(IVUS),with an image resolution of 150-200μm,has been used in research and clinical practice to identify plaques,quantify plaque morphology,and characterize plaque components.More recently,optical coherence tomography(OCT),with its resolution of 5-10μm,has emerged as an imaging modality which can be used to detect thin fibrous caps and improve diagnostic accuracy.It is commonly believed that mechanical forces play an important role in plaque progression and rupture.Image-based biomechanical plaque models have been developed and used to quantify plaque mechanical conditions and seek their linkage to plaque progression and vulnerability development activities.Based on recent advances in imaging and modeling,this paper attempts to provide a brief review on plaque research,including histological classification,image preparation,biomechanical modeling and analysis methods including medical imaging techniques represented by intravascular ultrasound(IVUS)and optical coherence tomography(OCT),computational modeling and their applications in plaque progression and vulnerability analyses and predictions.The clinical application and future development direction are also briefly described.We focus more on human coronary plaque modeling and mainly included results from our group for illustration purpose.We apologize in advance for our limitations.
基金Project(61070194) supported by the National Natural Science Foundation of ChinaProject([2009]1886) supported by the Information Security Industrialization Fund from NDRC of China in 2009+1 种基金Project(CJ[2010]341) supported by the Major Achievements Transfer Projects of MOF and MIIT of China in 2010Project(2011FJ2003) supported by the Natural Science Foundation of Hunan Province, China
文摘The gradual hybrid anti-worm （GHAW） was presented. percentage of vulnerable hosts present in the network. For GHAW It changed its confrontation scheme in real time according to the its process of countering malicious internet worms was modeled. The performance of GHAW on two factors was also estimated： confronting validity against worms and consumption of network resources. Factors governing its performance, specifically the transformation threshold and the transformation rate, were analyzed. The simulation experiments show that GHAW has dynamical adaptability to changes of network conditions and offers the same level of effectiveness on confronting internet worms as the divide-and-rule hybrid anti-worm, with significantly less cost to network resources. The experiments also indicate that the transformation threshold is the key factor affecting the performance of GHAW.
文摘Survivability is defined as the capability of a platform to avoid or withstand a man-made hostile environment. Military aircraft in particular, but also other kinds of platforms subjected to external, impacting threats, are commonly designed according to increasing survivability requirements. The concept of survivability was first formalized by R. Ball in 1985 in its seminal work on combat aircraft survivability.On the basis of the theory presented in his work, many computer programs have been developed which implement the modelling techniques and computations required by vulnerability assessments. However,a clear and general view of the operative computational procedures is still lacking. Moreover, to date only a limited number of applications to helicopter platforms have been investigated in the survivability field,even though these platforms experience numerous flight conditions exposing the system to different types of threats. In this context, this work aims at establishing a multi-purpose general framework for the vulnerability assessment of different types of platforms subjected to external threats, with a focus on helicopters. The in-house software specifically developed for this application is here described in detail and employed to present a case study on a representative military helicopter.
基金Project(51007006) supported by the National Natural Science Foundation of ChinaProject(20090185120023) supported by the Ph.D Programs Foundation for New Teacher of Ministry of Education of China
文摘A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerability,were calculated.The current vulnerability was used to identify the current vulnerable area through calculating the distance between the current transmitted power and initial transmitted power;and the forecast vulnerability under variation of power injection was used to predict the vulnerable area of next step and verify the current vulnerable area.Numerical simulation was performed under variant operating conditions with IEEE-30 bus system,which shows that almost area of 90% overlaps between current vulnerable area and forecasting vulnerable area,the overlapped area is termed as inherent vulnerable area of grid.When considering N-1 contingency,the assessment results of this method proposed agree with those of optimal power flow.When considering N-2 contingency,optimal power flow fails to obtain correct results,while the method based on energy framework gives reliable results.
基金Supported by the National Natural Science Foundation of China(30400275)the Tackle Key Problems of Heilongjiang Province(the Hobbledehoy Science Fund of Heilongjiang Province)(QC04C28)
文摘The research of groundwater vulnerability is the basic work to protect the groundwater. For utilizing groundwater resource continuably, groundwater vulnerability evaluation is necessary. Useful reference to protect, exploit and utilize on groundwater resource are provided rationally. According to the real condition of Sanjiang Plain, the indexes system is established based on the traditional DRASTIC model. The new system includes the following seven indexes： Depth of Water, Net Recharge, Aquifer Media, Soil Media, Conductivity of the Aquifer, Land Utilizing Ratio and Populace Density. The related analysis appears that the system is rather reasonable. Because traditional methods, such as analytic hierarchy process and fuzzy mathematics theory, can＇t be avoided human interference in selection of weights, they could lead to an imprecise result. In order to evaluate the groundwater vulnerability reasonably, entropy weight coefficient method is applied for the first time, which provides a new way to groundwater vulnerability evaluation. The method is a model whose weights are insured by the calculation process, so the artificial disturb can be avoided. It has been used to evaluate the groundwater vulnerability in Sanjiang Plain. The satisfied result is acquired. Comparably, the same result is acquired by the other method named projection pursuit evaluation based on real-coded accelerating genetic algorithm. It shows that entropy weight coefficient method is applicable on groundwater vulnerability evaluation. The evaluation result can provide reference on the decision-making departments.
文摘The appropriate fuze-warhead coordination method is important to improve the damage efficiency of air defense missiles against aircraft targets. In this paper, an adaptive fuze-warhead coordination method based on the Back Propagation Artificial Neural Network(BP-ANN) is proposed, which uses the parameters of missile-target intersection to adaptively calculate the initiation delay. The damage probabilities at different radial locations along the same shot line of a given intersection situation are calculated, so as to determine the optimal detonation position. On this basis, the BP-ANN model is used to describe the complex and highly nonlinear relationship between different intersection parameters and the corresponding optimal detonating point position. In the actual terminal engagement process, the fuze initiation delay is quickly determined by the constructed BP-ANN model combined with the missiletarget intersection parameters. The method is validated in the case of the single-shot damage probability evaluation. Comparing with other fuze-warhead coordination methods, the proposed method can produce higher single-shot damage probability under various intersection conditions, while the fuzewarhead coordination effect is less influenced by the location of the aim point.
文摘Security vulnerability of denial of service (DoS) in time out-medium access control (T-MAC) protocol was discussed and analysis of power consumption at each stage of T-MAC protocol was carried out. For power efficient authentication scheme which can provide reliability, efficiency, and security for a general T-MAC communication, a novel synchronization and authentication scheme using authentication masking code was proposed. Authentication data were repeated and masked by PN sequence. The simulation results show that the proposed approach can provide synchronization and authentication simultaneously for nodes in wireless sensor network (WSN). 63 bits AMC code gives above 99.97% synchronization detection and 93.98% authentication data detection probability in BER 0.031 7.
基金supported by the Natural Science Foundation of Shaanxi Province (Grant No. 2020JQ-122)the Fund support of Science and Technology on Transient Impact Laboratory。
文摘Damage assessment of the wing under blast wave is essential to the vulnerability reduction design of aircraft. This paper introduces a critical relative distance prediction method of aircraft wing damage based on the back-propagation artificial neural network(BP-ANN), which is trained by finite element simulation results. Moreover, the finite element method(FEM) for wing blast damage simulation has been validated by ground explosion tests and further used for damage mode determination and damage characteristics analysis. The analysis results indicate that the wing is more likely to be damaged when the root is struck from vertical directions than others for a small charge. With the increase of TNT equivalent charge, the main damage mode of the wing gradually changes from the local skin tearing to overall structural deformation and the overpressure threshold of wing damage decreases rapidly. Compared to the FEM-based damage assessment, the BP-ANN-based method can predict the wing damage under a random blast wave with an average relative error of 4.78%. The proposed method and conclusions can be used as a reference for damage assessment under blast wave and low-vulnerability design of aircraft structures.
基金Projects(60970036,60873016,61170045)supported by the National Natural Science Foundation of ChinaProjects(2009AA01Z102,2009AA01Z124)supported by the National High Technology Development Program of China
文摘Integrated with an improved architectural vulnerability factor （AVF） computing model, a new architectural level soft error reliability analysis framework, SS-SERA （soft error reliability analysis based on SimpleScalar）, was developed. SS-SERA was used to estimate the AVFs for various on-chip structures accurately. Experimental results show that the AVFs of issue queue （IQ）, register update units （RUU）, load store queue （LSQ） and functional unit （FU） are 38.11%, 22.17%, 23.05% and 24.43%, respectively. For address-based structures, i.e., levell data cache （LID）, DTLB, level2 unified cache （L2U）, levell instruction cache （LII） and ITLB, AVFs of their data arrays are 22.86%, 27.57%, 14.80%, 8.25% and 12.58%, lower than their tag arrays＇ AVFs which are 30.01%, 28.89%, 17.69%, 10.26% and 13.84%, respectively. Furthermore, using the AVF values obtained with SS-SERA, a qualitative and quantitative analysis of the AVF variation and predictability was performed for the structures studied. Experimental results show that the AVF exhibits significant variations across different structures and workloads, and is influenced by multiple microarchitectural metrics and their interactions. Besides, AVFs of SPEC2K floating point programs exhibit better predictability than SPEC2K integer programs.
基金National Natural Science Foundation of China(Grant Nos.62005276,62175234)the Scientific and Technological Development Program of Jilin,China(Grant No.20230508111RC)to provide fund for this research。
文摘Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a variety of analysis programs for battlefield targets to traditional weapons have been developed,but a comprehensive assessment methodology for targets'vulnerability to laser is still missing.Based on the shotline method,this paper proposes a method that equates laser beam to shotline array,an efficient vulnerability analysis program of target to laser is established by this method,and the program includes the circuit board and the wire into the vulnerability analysis category,which improves the precision of the vulnerability analysis.Taking the UAV engine part as the target of vulnerability analysis,combine with the"life-death unit method"to calculate the laser penetration rate of various materials of the UAV,and the influence of laser weapon system parameters and striking orientation on the killing probability is quantified after introducing the penetration rate into the vulnerability analysis program.The quantitative analysis method proposed in this paper has certain general expansibility,which can provide a fresh idea for the vulnerability analysis of other targets to laser.
文摘A multidisciplinary approach was applied to a detailed study of groundwater contamination by a Chemical Complex(CQE),near a coastal lagoon—an important wetland locally known as"Ria de Aveiro"(NW Portugal).The study includes 3D lithostratigraphic modeling,the estimate of groundwater recharge using different methods,a geophysical (electromagnetic) survey,and a groundwater samp-
基金supported in part by a Jiangsu Province Science and Technology Agency grant ( BE2016785)
文摘Background Current bottleneck of patient-specific coronary plaque model construction is the resolution of in vivo medical imaging.The threshold of cap thickness of vulnerable coronary plaques is 65 microns,while the resolution of in vivo coronary intravascular ultrasound(IVUS)images is 150-200 microns,which is not enough to identify vulnerable plaques with thin caps and construct accurate biomechanical plaque models.Optical coherence tomography(OCT)with a 15-20μm resolution has the capacity to identify thin fibrous cap.IVUS and OCT images could complement each other and provide for more accurate plaque morphology,especially,fibrous cap thickness measurements.A modeling approach combining IVUS and OCT was introduced in our previous publication for cap thickness quantification and more accurate cap stress/strain calculations.In this paper,patient baseline and follow-up IVUS and OCT data were acquired and multimodality image-based Fluidstructure interaction(FSI)models combining 3D IVUS,OCT,angiography were constructed to better quantify human coronary atherosclerotic plaque morphology and plaque stress/strain conditions and investigate the relationship of plaque vulnerability and morphological and mechanical factors.Methods Baseline and 10-Month follow-up in vivo IVUS and OCT coronary plaque data were acquired from one patient with informed consent obtained.Co-registration and segmentation of baseline and follow-up IVUS and OCT images were performed for modeling use.Baseline and follow-up 3D FSI models based on IVUS and OCT were constructed to simulate the mechanical factors which integrating plaque morphology were employed to predict plaque vulnerability.These 3D models were solved by ADINA(ADINA R&D,Watertown,MA,USA).The quantitative indices of cap thickness,lipid percentage were classified according to histological literatures and denoted as Cap Index and Lipid Index.Cap Index,Lipid Index and Morphological Plaque Vulnerability Index(MPVI)were chosen to quantify plaque vulnerability,respectively.Random forest(RF)which was based 13 extracted features including morphological and mechanical factors was used for plaque vulnerability classification and prediction.Over sampling scheme and a 5-fold crossvalidation procedure was employed in all 45 slices for training and testing sets.Single and all different combinations of morphological and mechanical risk factors were used for plaque progression prediction.Results When Cap Index was used as the measurement,minimum cap thickness(MCT)was the best single predictor which area under curve(AUC)is 0.782 0;the combination of MCT,critical plaque wall strain(CPWSn),critical wall shear stress(CWSS)and cap wall shear stress(CapWSS)was the best predictor with ACU=0.868 6.When Lipid Index was used as the measurement,the lipid percentage(LP)was the best single predictor which AUC value is 0.857 8;the combination of Mean cap thickness(MeanCT),LP,CWSS and cap plaque wall stress(CapPWS)and was the best predictor with ACU=0.9821.When MPVI was used as the measurement,MCT was the best single predictor which AUC value is 0.782 9;the combination of MCT,LP,plaque area(PA),CPWSn and CapWSS was the best predictor with ACU=0.872 9.Conclusions Combinations of morphological and mechanical risk factors had higher prediction accuracy,compared to the prediction of single factors and other combination of morphological factors.
