Background:Benign paroxysmal positional vertigo(BPPV)is characterized by vertigo lasting from seconds to minutes,induced by head movements.Objectives:Our study aimed to investigate the clinical significance of the cal...Background:Benign paroxysmal positional vertigo(BPPV)is characterized by vertigo lasting from seconds to minutes,induced by head movements.Objectives:Our study aimed to investigate the clinical significance of the caloric vestibular and video head-impulse tests(vHIT)diagnosing the disorder.Methods:68 patients suffering from posterior canal BPPV(25 male,43 females,mean age±SD,54.5±13.2 years)and 56 patients with a normal functioning vestibular system as control were investigated.Bithermal caloric test and vHIT was performed during the same medical check-up.Canal paresis(CP%),gain(GA)and asymmetry(GA%)parameters were calculated.Results:The Dix-Hallpike manoeuvre was only positive in 4%of this population.The CP%parameter was only pathologic in two patients,and there was no significant difference between control and BPPV patients(p=0.76).The GA value was never under 0.8 in this population,but GA%was abnormal in 63.2%.A significant difference comparing the GA%values to the control group was seen(p=0.034).There was no correlation detected between the CP%and GA%values in BPPV.Regarding the GA%value,61%sensitivity and 76%specificity was seen.Conclusion:The Dix-Hallpike manoeuvre was not often positive in the non-acute phase of BPPV;therefore,objective testing is essential.The caloric test does not have clinical significance in BPPV,but vHIT can be helpful based on the GA%parameter。展开更多
This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcathete...This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcatheter heart valve replacement(TAVR)procedures.In order to facilitate this exploration,it derives pertinent formulas for 3D multi-material isogeometric hyperelastic analysis based on Hounsfield unit(HU)values,thereby unlocking foundational capabilities for isogeometric analysis in calcified aortic valves.A series of uniaxial and biaxial tensile tests is executed to obtain an accurate constitutive model for calcified active valves.To mitigate discretization errors,methodologies for reconstructing volumetric parametric models,integrating both geometric and material attributes,are introduced.Applying these analytical formulas,constitutive models,and precise analytical models to isogeometric analyses of calcified valves,the research ascertains their close alignment with experimental results through the close fit in displacement-stress curves,compellingly validating the accuracy and reliability of the method.This study presents a step-by-step approach to analyzing themechanical characteristics of patient-specific valves obtained fromCT images,holding significant clinical implications and assisting in the selection of treatment strategies and surgical intervention approaches in TAVR procedures.展开更多
Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to a...Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys.In this study,the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography(micro XCT)and a standard leak test.The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance.Instead,micro XCT shows distinct advantages by enabling more comprehensive analysis.It reveals the presence of a low atomic number impregnates sealant within casting defects,which has low grey contrast and allows for visualizing primary leakage paths in 3D.The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT.This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.展开更多
The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory e...The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.展开更多
Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and ...Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces （i.e. damage）. Acoustic emission （AE） monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.展开更多
Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test compa...Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test comparison analyzes the acoustic emission load and CT images for an effective observation on the entire process, from crack propagation to the samples＇ destruction. The box dimension of the coal samples＇ acoustic emission series and the CT images were obtained through calculations by using the authors＇ own program. The results show that the fractal dimension of both the acoustic emission energy and CT image increase rapidly, indicating coal and rock mass has entered a dangerous condition. Hence, measures should be taken to unload the pressure of the coal and rock mass. The test results provide intuitive observation data for the coal meso-damage model. The test contributes to in-depth studies of coal or rock crack propagation mechanisms and provides a theoretical basis for rock burst mechanism.展开更多
基金supported by EFOP-3.6.3-VEKOP-16-2017-00009 Project and by theÚNKP-20-4-I New National Excellence Program of The Ministry for Innovation and Technology from the Source of The National Research,Development and Innovation Fund.
文摘Background:Benign paroxysmal positional vertigo(BPPV)is characterized by vertigo lasting from seconds to minutes,induced by head movements.Objectives:Our study aimed to investigate the clinical significance of the caloric vestibular and video head-impulse tests(vHIT)diagnosing the disorder.Methods:68 patients suffering from posterior canal BPPV(25 male,43 females,mean age±SD,54.5±13.2 years)and 56 patients with a normal functioning vestibular system as control were investigated.Bithermal caloric test and vHIT was performed during the same medical check-up.Canal paresis(CP%),gain(GA)and asymmetry(GA%)parameters were calculated.Results:The Dix-Hallpike manoeuvre was only positive in 4%of this population.The CP%parameter was only pathologic in two patients,and there was no significant difference between control and BPPV patients(p=0.76).The GA value was never under 0.8 in this population,but GA%was abnormal in 63.2%.A significant difference comparing the GA%values to the control group was seen(p=0.034).There was no correlation detected between the CP%and GA%values in BPPV.Regarding the GA%value,61%sensitivity and 76%specificity was seen.Conclusion:The Dix-Hallpike manoeuvre was not often positive in the non-acute phase of BPPV;therefore,objective testing is essential.The caloric test does not have clinical significance in BPPV,but vHIT can be helpful based on the GA%parameter。
基金National Key Research and Development Project during the 14th Five-year Plan Period(2023YFF0905800)Science and Technology Program of Jiangxi Provincial Education Department(GJJ160879)。
基金supported by the Natural Science Foundation of China(Project Nos.52075340 and 61972011)the Shanghai Special Research Project on Aging Population and Maternal and Child Health(Project No.2020YJZX0106).
文摘This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcatheter heart valve replacement(TAVR)procedures.In order to facilitate this exploration,it derives pertinent formulas for 3D multi-material isogeometric hyperelastic analysis based on Hounsfield unit(HU)values,thereby unlocking foundational capabilities for isogeometric analysis in calcified aortic valves.A series of uniaxial and biaxial tensile tests is executed to obtain an accurate constitutive model for calcified active valves.To mitigate discretization errors,methodologies for reconstructing volumetric parametric models,integrating both geometric and material attributes,are introduced.Applying these analytical formulas,constitutive models,and precise analytical models to isogeometric analyses of calcified valves,the research ascertains their close alignment with experimental results through the close fit in displacement-stress curves,compellingly validating the accuracy and reliability of the method.This study presents a step-by-step approach to analyzing themechanical characteristics of patient-specific valves obtained fromCT images,holding significant clinical implications and assisting in the selection of treatment strategies and surgical intervention approaches in TAVR procedures.
文摘Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys.In this study,the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography(micro XCT)and a standard leak test.The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance.Instead,micro XCT shows distinct advantages by enabling more comprehensive analysis.It reveals the presence of a low atomic number impregnates sealant within casting defects,which has low grey contrast and allows for visualizing primary leakage paths in 3D.The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT.This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277150,41977219)Henan Provincial Science and Technology Research Project(Grant No.222102320271).
文摘The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.
基金financial support for much of the early development of the AE analysis methods was provided by the U.S. Department of Energy (DOE) (Grant No. DE-FE0002760)
文摘Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces （i.e. damage）. Acoustic emission （AE） monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.
文摘Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test comparison analyzes the acoustic emission load and CT images for an effective observation on the entire process, from crack propagation to the samples＇ destruction. The box dimension of the coal samples＇ acoustic emission series and the CT images were obtained through calculations by using the authors＇ own program. The results show that the fractal dimension of both the acoustic emission energy and CT image increase rapidly, indicating coal and rock mass has entered a dangerous condition. Hence, measures should be taken to unload the pressure of the coal and rock mass. The test results provide intuitive observation data for the coal meso-damage model. The test contributes to in-depth studies of coal or rock crack propagation mechanisms and provides a theoretical basis for rock burst mechanism.
