The cavitation dynamics and mechanical stress in viscoelastic tissues, as the primary mechanisms of some ultrasound therapies, are extremely complex due to the interactions of cavitation bubble with adjacent bubbles a...The cavitation dynamics and mechanical stress in viscoelastic tissues, as the primary mechanisms of some ultrasound therapies, are extremely complex due to the interactions of cavitation bubble with adjacent bubbles and surrounding tissues.Therefore, the cavitation dynamics and resultant mechanical stress of two-interacting bubbles in the viscoelastic tissues are numerically investigated, especially focusing on the effects of the adjacent bubble. The results demonstrate that the mechanical stress is highly dependent on the bubble dynamics. The compressive stress and tensile stress are generated at the stage of bubble expansion and collapse stage, respectively. Furthermore, within the initial parameters examined in this paper, the effects of the adjacent bubble will distinctly suppress the radial expansion of the small bubble and consequently lead its associated stresses to decrease. Owing to the superimposition of two stress fields, the mechanical stresses surrounding the small bubble in the direction of the neighboring bubble are smaller than those in other directions. For two interacting cavitation bubbles, the suppression effects of the nearby bubble on both the cavitation dynamics and the stresses surrounding the small bubble increase as the ultrasound amplitude and the initial radius of the large bubble increase, whereas they decrease with the inter-bubble distance increasing. Moreover, increasing the tissue viscoelasticity will reduce the suppression effects of the nearby bubble, except in instances where the compressive stress and tensile stress first increase and then decrease with the tissue elasticity and viscosity increasing respectively. This study can provide a further understanding of the mechanisms of cavitation-associated mechanical damage to the adjacent tissues or cells.展开更多
In dentistry,orthodontic root resorption is a long-lasting issue with no effective treatment strategy,and its mechanisms,especially those related to senescent cells,remain largely unknown.Here,we used an orthodontic i...In dentistry,orthodontic root resorption is a long-lasting issue with no effective treatment strategy,and its mechanisms,especially those related to senescent cells,remain largely unknown.Here,we used an orthodontic intrusion tooth movement model with an L-loop in rats to demonstrate that mechanical stress-induced senescent cells aggravate apical root resorption,which was prevented by administering senolytics(a dasatinib and quercetin cocktail).展开更多
In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoi...In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.展开更多
A significant negative aspect in the operation of bridge-type cranes are the technical problems associated with wear of the wheels and the crane track,which causes crane skewing.The main causes of crane skewing includ...A significant negative aspect in the operation of bridge-type cranes are the technical problems associated with wear of the wheels and the crane track,which causes crane skewing.The main causes of crane skewing include unevenness of the crane track,unequal loading of the traction drives depending on the position of the crane trolley,slips and different sizes of travel wheels and combinations of these causes.Firstly,this paper presents a design solution that can be used to detect the magnitude of mechanical stress and deformation of the steel structure of the crane,caused by the effects of skewing.The mechanical stress generated by the transverse forces of the deformed geometric shape of the crane bridge structure is recorded by mechanical stress detectors installed in the inner corners of the crane bridge.The resulting electrical signal from element mechanical voltage detectors,loaded by axial forces,can be used for feedback control of separate crane travel drives controlled by frequency converters.Secondly,this paper presents the calculation of the lateral transverse forces according to CSN 270103 and the determination of the values of mechanical stresses of the deformed steel structure of the crane bridge of a two-girder bridge crane using the finite element method in the program MSC.MARC 2019.Finally,this paper presents the structural and strength design of mechanical stress detectors and the conclusions of laboratory tests of axial force loading of mechanical stress detectors on the test equipment.At the same time,it presents records of the measured axial forces acting in the mechanical stress detectors,arising from the deformation and warping of the crane bridge by the known magnitude of the axial force acting on the crossbeam and from the deformation of the crane bridge caused by the crane operating modes.展开更多
This paper challenges the concept that the essential element in wound healing is to offload pressure. We suggest a change in approach that recognizes the integumentary system as one which, like all other body systems,...This paper challenges the concept that the essential element in wound healing is to offload pressure. We suggest a change in approach that recognizes the integumentary system as one which, like all other body systems, adapts to the stresses put upon it. We use a clinical case example to illustrate the use of intentional mechanical stress to promote wound healing and include a review of the relevant literature. The intent of this publication is to call for a new look at clinical practice regarding wound healing and to call for future research directed at investigation of this theory.展开更多
This research presents an experimental study of analysis of stress strain state SSS of X-60 pipe weld joints employing magnetic anisotropy indicator of mechanical stresses Stress Vision (IMS) using of “before and af...This research presents an experimental study of analysis of stress strain state SSS of X-60 pipe weld joints employing magnetic anisotropy indicator of mechanical stresses Stress Vision (IMS) using of “before and after” comparison approach taking readings on pipe base metal, weld area and heat affected zone (HAZ) before and after hydrotest. Test results were compared with X-ray testing results for welded joints and with metallographic testing. Test results demonstrate the relevance of applied test conditions and redistribution of residual stresses. A new equation was established for estimating the residual (technological) and operating stresses in other pipelines with a tolerance of 15% in the field of elastic deformation (up to the yield point), according to Hooke law.展开更多
Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propos...Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propose a thermal expansion method to estimate stresses in multi-layer blood vessels under healthy and pathological conditions.The proposed method provides a relatively simple and convenient means to predict reliable in vivo mechanical stresses with accurate residual stress.The method is first verified with the opening-up process and the pressure-radius responses for single and multi-layer vessel models.It is then applied to study the stress variation in a human carotid artery at different hypertension stages and in a plaque of vascular stenosis.Our results show that specific or optimal residual stresses exist for different blood pressures,which helps form a homogeneous stress distribution across vessel walls.High elastic shear stress is identified on the shoulder of the plaque,which contributes to the tearing effect in plaque rupture.The present study indicates that the proposed numerical method is a capable and efficient in vivo stress evaluation of patient-specific blood vessels for clinical purposes.展开更多
The investigation explores the mechanical stress and electromagnetic performance for a wind-driven synchronous reluctance generator(SRG).The change in the mechanical stress due to the presence of centripetal force,win...The investigation explores the mechanical stress and electromagnetic performance for a wind-driven synchronous reluctance generator(SRG).The change in the mechanical stress due to the presence of centripetal force,wind speed,and rotor speed are evaluated for different thickness of tangential and radial ribs.Moreover,the variation in the electromagnetic feature such as the q−and d−axes flux,reactance ratio,inductance,torque and torque ripple are discussed for different thickness of tangential and radial ribs.Increasing both tangential and radial ribs thickness has an effect on the electromagnetic performance,but it is observed that effect is significantly more with the variation of tangential rib thickness.Similarly,the mechanical stress analysis for rotor design has been explored in this paper.It is observed that high concentration of peak stress on the rotor ribs,which limits the range of rotor speed.展开更多
The mechanical stress distribution and the stress concentrations of the superheater outlet header of a 600MW supercritical boiler were analyzed by the finite element method. The results showed that the stress concentr...The mechanical stress distribution and the stress concentrations of the superheater outlet header of a 600MW supercritical boiler were analyzed by the finite element method. The results showed that the stress concentrated at the inside conjunction area between the pipe and the header cylinder , and the value of the maximum mechanical stress concentration factor is 2.51.展开更多
The residual mechanical stress in SiO<sub>2</sub> films results in the degradation of mobilitiesin MOSFETs. Based on the edge force approximation in SiO<sub>2</sub> films, the stress field in M...The residual mechanical stress in SiO<sub>2</sub> films results in the degradation of mobilitiesin MOSFETs. Based on the edge force approximation in SiO<sub>2</sub> films, the stress field in MOS devicesis calculated. The results here are in agreement with those measured by the Raman spectrummethod.展开更多
Vascular remodeling is the essential pathogenic process of various cardiovascular disorders,including hypertension,atherosclerosis,stroke,and restenosis after vein graft.The main characterization of vascular remodelin...Vascular remodeling is the essential pathogenic process of various cardiovascular disorders,including hypertension,atherosclerosis,stroke,and restenosis after vein graft.The main characterization of vascular remodeling is abnormal variations of vascular cell phenotype,morphological structure and functions such as migration,hypertrophy,proliferation and apoptosis.Numerous researches revealed that mechanical stress,including shear stress and cyclic stretch,participates in physiological vascular homeostasis,or pathophysiological vascular remodeling.The understanding of mechanobiological mechanism in vascular remodeling will play a unique role in understanding human physiology and disease,and will generate important theoretical and clinical significance [2].Non-coding RNAs are newly recognized RNAs which cannot be translated into proteins but are involved in epigenetic modification of gene regulation.The studies revealed that non-coding RNAs,such as microRNAs(miRNAs)and long noncoding RNAs(long ncRNAs,IncRNA),as well as small interfering RNAs(siRNAs),piwi-interacting RNAs(piRNAs),small nucleolar RNAs(snoRNAs),play essential roles in the regulation of various processes,such as metabolism,development,cell proliferation,cell apoptosis,cell differentiation,oncogenesis and vascular homeostasis[5].However,the roles of non-coding RNAs in the cardiovascular system under mechanical stresses are still not clarified.Our recent researches detected the mechanical regulation of IncRNAs and miRNAs in vascular remodeling.LncRNAs are non-protein-coding transcripts that are longer than 200 nucleotides(nt),which is an arbitrary cut-off value that distinguishes these transcripts from other small RNAs.Unlike the well-established mechanism of microRNA action,the functional mode of IncRNAs is not fully understood.Increasing evidence shows that IncRNAs modulate gene expression via a multilevel-regulated pathway.Given their large number and complicated functional modes,lncRNAs are emerging as important regulators of a variety of cellular responses,developmental processes and diseases.Using a gene microarray,we screened the differences in the IncRNAs and mRNAs between spontaneously hypertensive rats(SHR)and Wistar Kyoto rats(WKY).The results showed that 68 IncRNAs and 255 mRNAs were up-regulated in the aorta of SHR,while 167 IncRNAs and 272 mRNAs were down-regulated.Expressions of the screened IncRNAs,including XR007793,were validated by real-time PCR.A co-expression network was composed,and gene function was analysed using Ingenuity Pathway Analysis.In vitro,vascular smooth muscle cells(VSMCs)were subjected to cyclic stretch at a magnitude of 5%(physiological normotensive cyclic stretch)or 15%(pathological hypertensive cyclic stretch)by Flexercell-5000TM.15%-cyclic-stretch increased XR007793 expression.XR007793 knockdown attenuated VSMC proliferation and migration and inhibited co-expressed genes such as signal transducers and activators of transcription 2(stat2),LIM domain only 2(lmo2)and interferon regulatory factor 7(irf7)[4].Illuminating the role of IncRNAs in vascular remodeling induced by hyper mechanical stretch may provide deeper insight into the mechanobiological mechanism underlying hypertension,and contribute to identifying potential targets for hypertension therapy.miRNAs are endogenous,non-coding,single-stranded RNAs of 18-22 nucleotides that constitute a novel class of gene regulators.miRNAs bind to their target genes within their 3’-untranslated regions(3’-UTRs),leading to direct degradation of mRNA or translational repression by a complete,i.e.in plants,or incomplete,i.e.in animals,complement respectively.Our resent works revealed several important mechano-responsive miRNA and their potential effects in vascular remodeling.Forexample,miRNA-33 is regulated by cyclic stretch in the grafted vessels,which targets to BMP3 and subsequent modulates smad signaling pathway.The miRNA-33-BMP3-smad pathway protects against venous VSMC proliferation in response to arterial cyclic stretch.Therefore,miRNA-33 may be a potential therapeutic target in autologous vein grafted surgery,and locally overexpression of miR-33 may attenuates neointimal hyperplasia of grafted human saphenous vein [3].The unpublished data revealed that 15%cyclic stretch also significantly elevated the expression of miRNA-124-3p which bound to the 3’UTR of Lmna mRNA,and then negatively regulated protein expression of lamin A/C which is the important skeletal proteins in nucleus.In addition to primary intracellular locations of miRNAs,our recent study showed that miRNAs can be secreted and protected extracellularly via inclusion into membrane-derived vesicles including microparticles.Microparticles are extracellular vesicles ranging from 0.1 to 1μm in size and have been shown to deliver various bioactive molecules,i.e.,chemokines,enzymes and miRNAs,to recipient cells.Increasing evidence shows that microparticles play a pivotal role in many pathological processes,such as cancer,inflammatory diseases and cardiovascular disease.Our present study showed that platelet-derived microparticles(PMPs),which are released by active platelets,are important vehicles for communication and play crucial roles in inducing abnormal EC proliferation in hypertension.In briefly,EC proliferation was increased in renal hypertensive rats established by abdominal aortic coarctation compared to control rats and that elevated thrombin in plasma promoted platelet activation,which may induce the release of PMPs.miRNA array and qPCR revealed a higher level of miRNA-142-3p in platelets and PMPs.In vitro,PMPs delivered miRNA-142-3p into ECs and enhanced EC proliferation via Bcl-2-associated transcription factor 1(BCLAF1)and its downstream genes.These results indicated that PMPs deliver miRNA-142-3p from activated platelets into ECs and that miRNA-142-3p may play important roles in EC dysfunction under hypertensive conditions and might be a novel therapeutic target for maintaining EC homeostasis in hypertension[1].These results provide possible mechanisms by which non-coding RNAs regulate cellular functions under different mechanical stresses,and suggest a novel potential therapeutic approach for vascular remodeling.The further studies on noncoding RNAs may provide new insight into understanding the mechanism of vascular remodeling in different various cardiovascular disorders,and may provide novel targets for the maintenance of vascular homeostasis.展开更多
This imaginary transformation from Sméagol to Gollum is a dramatization of the illusive repercussions of mechanical stress affecting bone. This paper presents the main ideas of mechanical stress and bone remodell...This imaginary transformation from Sméagol to Gollum is a dramatization of the illusive repercussions of mechanical stress affecting bone. This paper presents the main ideas of mechanical stress and bone remodelling from a novel’s perspective. The object of this study is to provide evidence for new ways to explore bone’s functional adaptation to mechanical stress made through the copious interpretation and integration of new and existing literature. It tackles the underlying biology of bone cells and how they detect and react to strain stimuli. The different types of mechanical demands in daily activities are sifted through and any misconceptions found fallible in literature are refined. A personal experience of a stress fracture is reviewed to parallel the implications that lead to the incident with the findings on the link between mechanical stress and bone remodelling. Some factors regarding age, gender and ethnicity and the interplay with mechanical stress influencing bone remodelling are considered. Brief overviews of three new medical novelties in bone healing are outlined, hoping that these interventions of proper medical techniques can be a change for the better: one from Gollum to Sméagol rather than vice versa.展开更多
In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a waf...In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a wafer-scale-based (WaferICTM) rapid prototyping platform for electronic systems. This technique will be embedded into the structure of the WaferIC, and will be used as a preventive measure to protect the wafer from possible damages that can be caused by excessive thermomechanical stress. The paper also presents spatial and spatiotemporal algorithms and the experimental results from an IR images collection campaign conducted using an IR camera.展开更多
This work aims to describe the behavior of the interface using the method of load transfer between fiber and matrix in a composite material. Our contribution is to track the Evolution of the thermomechanical behavior ...This work aims to describe the behavior of the interface using the method of load transfer between fiber and matrix in a composite material. Our contribution is to track the Evolution of the thermomechanical behavior by establishing a new mathematical model that describes the variation of shear stress along the interface. This model has been implemented in code in C++. The results revealed that the shear of the interface increases with temperature. This increase is partly due to the difference in expansion coefficient between fiber and matrix. The composite studied is T300/914;Carbon-Epoxy.展开更多
The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducte...The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.展开更多
Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunological response. The present study investigated the impact of a 3-min mechanical perturbation mimicking t...Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunological response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopus japonicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immune connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity functions. Therefore, these effects should be considered for developing better husbandry procedures.展开更多
We present an accurate through silicon via(TSV) thermal mechanical stress analytical model which is verified by using finite element method(FEM). The results show only a very small error. By using the proposed analyti...We present an accurate through silicon via(TSV) thermal mechanical stress analytical model which is verified by using finite element method(FEM). The results show only a very small error. By using the proposed analytical model, we also study the impacts of the TSV radius size, the thickness, the material of Cu diffusion barrier, and liner on the stress. It is found that the liner can absorb the stress effectively induced by coefficient of thermal expansion mismatch. The stress decreases with the increase of liner thickness. Benzocyclobutene(BCB) as a liner material is better than Si O2. However,the Cu diffusion barrier has little effect on the stress. The stress with a smaller TSV has a smaller value. Based on the analytical model, we explore and validate the linear superposition principle of stress tensors and demonstrate the accuracy of this method against detailed FEM simulations. The analytic solutions of stress of two TSVs and three TSVs have high precision against the finite element result.展开更多
In order to study mechanical stress on root from orthodontic tooth movement by sliding mechanics, a 3-dimensional finite element model incorporating all layers of a human mandibular dental arch with orthodontic applia...In order to study mechanical stress on root from orthodontic tooth movement by sliding mechanics, a 3-dimensional finite element model incorporating all layers of a human mandibular dental arch with orthodontic appliance has been developed to simulate mechanical stress on root from the orthodontic tooth movement. Simulated orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis was applied to the crown of the teeth. The finite element analysis showed when or- thodontic forces were applied to the tooth, the stress was mainly concentrated at the neck of the tooth decreasing uniformly to the apex and crown. The highest stress on the root was 0.621 N/mm2 for cer- vical margin of the canine, and 0.114 N/mm2 for apical region of the canine. The top of canine crown showed the largest amount of displacement (2.417 μm), while the lowest amount of displacement was located at the apical region of canine (0.043 μm). In conclusion, this model might enable one to simulate orthodontic tooth movements clinically. Sliding force at 2 N is ideal to ensure the bodily or- thodontic tooth movement. The highest stress concentration in the roots was always localized at the cervical margin when orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis, so there may be the same risk of root resorption when orthodontic force of 2 N at 0, 30 and 45 degree was used in clinic cases.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.11904042)the Natural Science Foundation of Chongqing,China (Grant No.cstc2019jcyj-msxmX0534)the Science and Technology Research Program of Chongqing Municipal Education Commission,China (Grant No.KJQN202000617)。
文摘The cavitation dynamics and mechanical stress in viscoelastic tissues, as the primary mechanisms of some ultrasound therapies, are extremely complex due to the interactions of cavitation bubble with adjacent bubbles and surrounding tissues.Therefore, the cavitation dynamics and resultant mechanical stress of two-interacting bubbles in the viscoelastic tissues are numerically investigated, especially focusing on the effects of the adjacent bubble. The results demonstrate that the mechanical stress is highly dependent on the bubble dynamics. The compressive stress and tensile stress are generated at the stage of bubble expansion and collapse stage, respectively. Furthermore, within the initial parameters examined in this paper, the effects of the adjacent bubble will distinctly suppress the radial expansion of the small bubble and consequently lead its associated stresses to decrease. Owing to the superimposition of two stress fields, the mechanical stresses surrounding the small bubble in the direction of the neighboring bubble are smaller than those in other directions. For two interacting cavitation bubbles, the suppression effects of the nearby bubble on both the cavitation dynamics and the stresses surrounding the small bubble increase as the ultrasound amplitude and the initial radius of the large bubble increase, whereas they decrease with the inter-bubble distance increasing. Moreover, increasing the tissue viscoelasticity will reduce the suppression effects of the nearby bubble, except in instances where the compressive stress and tensile stress first increase and then decrease with the tissue elasticity and viscosity increasing respectively. This study can provide a further understanding of the mechanisms of cavitation-associated mechanical damage to the adjacent tissues or cells.
基金supported by JST,CREST Grant Number JPMJCR22L5,Japan。
文摘In dentistry,orthodontic root resorption is a long-lasting issue with no effective treatment strategy,and its mechanisms,especially those related to senescent cells,remain largely unknown.Here,we used an orthodontic intrusion tooth movement model with an L-loop in rats to demonstrate that mechanical stress-induced senescent cells aggravate apical root resorption,which was prevented by administering senolytics(a dasatinib and quercetin cocktail).
文摘In this research,mechanical stress,static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented.The kinematic relations are developed based on higherorder sinusoidal shear deformation theory.Thickness stretching formulation is accounted for more accurate analysis.The total transverse deflection is divided into bending,shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction.The axisymmetric formulations are derived through principle of virtual work.A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions.To explore effect of thickness stretching model on the static results,a comparison between the present results with the available results of literature is presented.As an important output,effect of micro-scale parameter is studied on the static stress and strain distribution.
文摘A significant negative aspect in the operation of bridge-type cranes are the technical problems associated with wear of the wheels and the crane track,which causes crane skewing.The main causes of crane skewing include unevenness of the crane track,unequal loading of the traction drives depending on the position of the crane trolley,slips and different sizes of travel wheels and combinations of these causes.Firstly,this paper presents a design solution that can be used to detect the magnitude of mechanical stress and deformation of the steel structure of the crane,caused by the effects of skewing.The mechanical stress generated by the transverse forces of the deformed geometric shape of the crane bridge structure is recorded by mechanical stress detectors installed in the inner corners of the crane bridge.The resulting electrical signal from element mechanical voltage detectors,loaded by axial forces,can be used for feedback control of separate crane travel drives controlled by frequency converters.Secondly,this paper presents the calculation of the lateral transverse forces according to CSN 270103 and the determination of the values of mechanical stresses of the deformed steel structure of the crane bridge of a two-girder bridge crane using the finite element method in the program MSC.MARC 2019.Finally,this paper presents the structural and strength design of mechanical stress detectors and the conclusions of laboratory tests of axial force loading of mechanical stress detectors on the test equipment.At the same time,it presents records of the measured axial forces acting in the mechanical stress detectors,arising from the deformation and warping of the crane bridge by the known magnitude of the axial force acting on the crossbeam and from the deformation of the crane bridge caused by the crane operating modes.
文摘This paper challenges the concept that the essential element in wound healing is to offload pressure. We suggest a change in approach that recognizes the integumentary system as one which, like all other body systems, adapts to the stresses put upon it. We use a clinical case example to illustrate the use of intentional mechanical stress to promote wound healing and include a review of the relevant literature. The intent of this publication is to call for a new look at clinical practice regarding wound healing and to call for future research directed at investigation of this theory.
文摘This research presents an experimental study of analysis of stress strain state SSS of X-60 pipe weld joints employing magnetic anisotropy indicator of mechanical stresses Stress Vision (IMS) using of “before and after” comparison approach taking readings on pipe base metal, weld area and heat affected zone (HAZ) before and after hydrotest. Test results were compared with X-ray testing results for welded joints and with metallographic testing. Test results demonstrate the relevance of applied test conditions and redistribution of residual stresses. A new equation was established for estimating the residual (technological) and operating stresses in other pipelines with a tolerance of 15% in the field of elastic deformation (up to the yield point), according to Hooke law.
基金The authors would like to thank Prof.Shu Takagi and Prof.Huaxiong Huang for their instructive comments.The authors would also like to acknowledge Jianda Yang for assisting with FEM simulations.This work was supported by the National Natural Science Foundation of China(Grants 11372191,11232010,11650(Grant 91111138)the National Institute of Health(Grant 2R01DC005642-10A1).
文摘Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propose a thermal expansion method to estimate stresses in multi-layer blood vessels under healthy and pathological conditions.The proposed method provides a relatively simple and convenient means to predict reliable in vivo mechanical stresses with accurate residual stress.The method is first verified with the opening-up process and the pressure-radius responses for single and multi-layer vessel models.It is then applied to study the stress variation in a human carotid artery at different hypertension stages and in a plaque of vascular stenosis.Our results show that specific or optimal residual stresses exist for different blood pressures,which helps form a homogeneous stress distribution across vessel walls.High elastic shear stress is identified on the shoulder of the plaque,which contributes to the tearing effect in plaque rupture.The present study indicates that the proposed numerical method is a capable and efficient in vivo stress evaluation of patient-specific blood vessels for clinical purposes.
基金This work was sponsored by a Defense University from the National Defense of Ethiopia.
文摘The investigation explores the mechanical stress and electromagnetic performance for a wind-driven synchronous reluctance generator(SRG).The change in the mechanical stress due to the presence of centripetal force,wind speed,and rotor speed are evaluated for different thickness of tangential and radial ribs.Moreover,the variation in the electromagnetic feature such as the q−and d−axes flux,reactance ratio,inductance,torque and torque ripple are discussed for different thickness of tangential and radial ribs.Increasing both tangential and radial ribs thickness has an effect on the electromagnetic performance,but it is observed that effect is significantly more with the variation of tangential rib thickness.Similarly,the mechanical stress analysis for rotor design has been explored in this paper.It is observed that high concentration of peak stress on the rotor ribs,which limits the range of rotor speed.
文摘The mechanical stress distribution and the stress concentrations of the superheater outlet header of a 600MW supercritical boiler were analyzed by the finite element method. The results showed that the stress concentrated at the inside conjunction area between the pipe and the header cylinder , and the value of the maximum mechanical stress concentration factor is 2.51.
文摘The residual mechanical stress in SiO<sub>2</sub> films results in the degradation of mobilitiesin MOSFETs. Based on the edge force approximation in SiO<sub>2</sub> films, the stress field in MOS devicesis calculated. The results here are in agreement with those measured by the Raman spectrummethod.
基金supported by grants from the National Natural Science Foundation of China ( 11625209,11572199,31670958)
文摘Vascular remodeling is the essential pathogenic process of various cardiovascular disorders,including hypertension,atherosclerosis,stroke,and restenosis after vein graft.The main characterization of vascular remodeling is abnormal variations of vascular cell phenotype,morphological structure and functions such as migration,hypertrophy,proliferation and apoptosis.Numerous researches revealed that mechanical stress,including shear stress and cyclic stretch,participates in physiological vascular homeostasis,or pathophysiological vascular remodeling.The understanding of mechanobiological mechanism in vascular remodeling will play a unique role in understanding human physiology and disease,and will generate important theoretical and clinical significance [2].Non-coding RNAs are newly recognized RNAs which cannot be translated into proteins but are involved in epigenetic modification of gene regulation.The studies revealed that non-coding RNAs,such as microRNAs(miRNAs)and long noncoding RNAs(long ncRNAs,IncRNA),as well as small interfering RNAs(siRNAs),piwi-interacting RNAs(piRNAs),small nucleolar RNAs(snoRNAs),play essential roles in the regulation of various processes,such as metabolism,development,cell proliferation,cell apoptosis,cell differentiation,oncogenesis and vascular homeostasis[5].However,the roles of non-coding RNAs in the cardiovascular system under mechanical stresses are still not clarified.Our recent researches detected the mechanical regulation of IncRNAs and miRNAs in vascular remodeling.LncRNAs are non-protein-coding transcripts that are longer than 200 nucleotides(nt),which is an arbitrary cut-off value that distinguishes these transcripts from other small RNAs.Unlike the well-established mechanism of microRNA action,the functional mode of IncRNAs is not fully understood.Increasing evidence shows that IncRNAs modulate gene expression via a multilevel-regulated pathway.Given their large number and complicated functional modes,lncRNAs are emerging as important regulators of a variety of cellular responses,developmental processes and diseases.Using a gene microarray,we screened the differences in the IncRNAs and mRNAs between spontaneously hypertensive rats(SHR)and Wistar Kyoto rats(WKY).The results showed that 68 IncRNAs and 255 mRNAs were up-regulated in the aorta of SHR,while 167 IncRNAs and 272 mRNAs were down-regulated.Expressions of the screened IncRNAs,including XR007793,were validated by real-time PCR.A co-expression network was composed,and gene function was analysed using Ingenuity Pathway Analysis.In vitro,vascular smooth muscle cells(VSMCs)were subjected to cyclic stretch at a magnitude of 5%(physiological normotensive cyclic stretch)or 15%(pathological hypertensive cyclic stretch)by Flexercell-5000TM.15%-cyclic-stretch increased XR007793 expression.XR007793 knockdown attenuated VSMC proliferation and migration and inhibited co-expressed genes such as signal transducers and activators of transcription 2(stat2),LIM domain only 2(lmo2)and interferon regulatory factor 7(irf7)[4].Illuminating the role of IncRNAs in vascular remodeling induced by hyper mechanical stretch may provide deeper insight into the mechanobiological mechanism underlying hypertension,and contribute to identifying potential targets for hypertension therapy.miRNAs are endogenous,non-coding,single-stranded RNAs of 18-22 nucleotides that constitute a novel class of gene regulators.miRNAs bind to their target genes within their 3’-untranslated regions(3’-UTRs),leading to direct degradation of mRNA or translational repression by a complete,i.e.in plants,or incomplete,i.e.in animals,complement respectively.Our resent works revealed several important mechano-responsive miRNA and their potential effects in vascular remodeling.Forexample,miRNA-33 is regulated by cyclic stretch in the grafted vessels,which targets to BMP3 and subsequent modulates smad signaling pathway.The miRNA-33-BMP3-smad pathway protects against venous VSMC proliferation in response to arterial cyclic stretch.Therefore,miRNA-33 may be a potential therapeutic target in autologous vein grafted surgery,and locally overexpression of miR-33 may attenuates neointimal hyperplasia of grafted human saphenous vein [3].The unpublished data revealed that 15%cyclic stretch also significantly elevated the expression of miRNA-124-3p which bound to the 3’UTR of Lmna mRNA,and then negatively regulated protein expression of lamin A/C which is the important skeletal proteins in nucleus.In addition to primary intracellular locations of miRNAs,our recent study showed that miRNAs can be secreted and protected extracellularly via inclusion into membrane-derived vesicles including microparticles.Microparticles are extracellular vesicles ranging from 0.1 to 1μm in size and have been shown to deliver various bioactive molecules,i.e.,chemokines,enzymes and miRNAs,to recipient cells.Increasing evidence shows that microparticles play a pivotal role in many pathological processes,such as cancer,inflammatory diseases and cardiovascular disease.Our present study showed that platelet-derived microparticles(PMPs),which are released by active platelets,are important vehicles for communication and play crucial roles in inducing abnormal EC proliferation in hypertension.In briefly,EC proliferation was increased in renal hypertensive rats established by abdominal aortic coarctation compared to control rats and that elevated thrombin in plasma promoted platelet activation,which may induce the release of PMPs.miRNA array and qPCR revealed a higher level of miRNA-142-3p in platelets and PMPs.In vitro,PMPs delivered miRNA-142-3p into ECs and enhanced EC proliferation via Bcl-2-associated transcription factor 1(BCLAF1)and its downstream genes.These results indicated that PMPs deliver miRNA-142-3p from activated platelets into ECs and that miRNA-142-3p may play important roles in EC dysfunction under hypertensive conditions and might be a novel therapeutic target for maintaining EC homeostasis in hypertension[1].These results provide possible mechanisms by which non-coding RNAs regulate cellular functions under different mechanical stresses,and suggest a novel potential therapeutic approach for vascular remodeling.The further studies on noncoding RNAs may provide new insight into understanding the mechanism of vascular remodeling in different various cardiovascular disorders,and may provide novel targets for the maintenance of vascular homeostasis.
文摘This imaginary transformation from Sméagol to Gollum is a dramatization of the illusive repercussions of mechanical stress affecting bone. This paper presents the main ideas of mechanical stress and bone remodelling from a novel’s perspective. The object of this study is to provide evidence for new ways to explore bone’s functional adaptation to mechanical stress made through the copious interpretation and integration of new and existing literature. It tackles the underlying biology of bone cells and how they detect and react to strain stimuli. The different types of mechanical demands in daily activities are sifted through and any misconceptions found fallible in literature are refined. A personal experience of a stress fracture is reviewed to parallel the implications that lead to the incident with the findings on the link between mechanical stress and bone remodelling. Some factors regarding age, gender and ethnicity and the interplay with mechanical stress influencing bone remodelling are considered. Brief overviews of three new medical novelties in bone healing are outlined, hoping that these interventions of proper medical techniques can be a change for the better: one from Gollum to Sméagol rather than vice versa.
文摘In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a wafer-scale-based (WaferICTM) rapid prototyping platform for electronic systems. This technique will be embedded into the structure of the WaferIC, and will be used as a preventive measure to protect the wafer from possible damages that can be caused by excessive thermomechanical stress. The paper also presents spatial and spatiotemporal algorithms and the experimental results from an IR images collection campaign conducted using an IR camera.
文摘This work aims to describe the behavior of the interface using the method of load transfer between fiber and matrix in a composite material. Our contribution is to track the Evolution of the thermomechanical behavior by establishing a new mathematical model that describes the variation of shear stress along the interface. This model has been implemented in code in C++. The results revealed that the shear of the interface increases with temperature. This increase is partly due to the difference in expansion coefficient between fiber and matrix. The composite studied is T300/914;Carbon-Epoxy.
文摘The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.
基金financially supported by the 863 High Technology Project of the Ministry of Science and Technology (No. 2012AA10A412-4)the Special Funds for the Basic B & D Program in the Central Non-profit Research Institutes (No. 2010-cb-03)+1 种基金Science and Technology Development Planning Project of Shandong Province (No. 2012GGA06021)Science and Technology Development Fund of Shinan district of Qingdao (No. 2011-5-023-QT)
文摘Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunological response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopus japonicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immune connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity functions. Therefore, these effects should be considered for developing better husbandry procedures.
基金supported by the National Natural Science Foundation of China(Grant No.61334003)the Kunshan Innovation Institute of Xidian University
文摘We present an accurate through silicon via(TSV) thermal mechanical stress analytical model which is verified by using finite element method(FEM). The results show only a very small error. By using the proposed analytical model, we also study the impacts of the TSV radius size, the thickness, the material of Cu diffusion barrier, and liner on the stress. It is found that the liner can absorb the stress effectively induced by coefficient of thermal expansion mismatch. The stress decreases with the increase of liner thickness. Benzocyclobutene(BCB) as a liner material is better than Si O2. However,the Cu diffusion barrier has little effect on the stress. The stress with a smaller TSV has a smaller value. Based on the analytical model, we explore and validate the linear superposition principle of stress tensors and demonstrate the accuracy of this method against detailed FEM simulations. The analytic solutions of stress of two TSVs and three TSVs have high precision against the finite element result.
文摘In order to study mechanical stress on root from orthodontic tooth movement by sliding mechanics, a 3-dimensional finite element model incorporating all layers of a human mandibular dental arch with orthodontic appliance has been developed to simulate mechanical stress on root from the orthodontic tooth movement. Simulated orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis was applied to the crown of the teeth. The finite element analysis showed when or- thodontic forces were applied to the tooth, the stress was mainly concentrated at the neck of the tooth decreasing uniformly to the apex and crown. The highest stress on the root was 0.621 N/mm2 for cer- vical margin of the canine, and 0.114 N/mm2 for apical region of the canine. The top of canine crown showed the largest amount of displacement (2.417 μm), while the lowest amount of displacement was located at the apical region of canine (0.043 μm). In conclusion, this model might enable one to simulate orthodontic tooth movements clinically. Sliding force at 2 N is ideal to ensure the bodily or- thodontic tooth movement. The highest stress concentration in the roots was always localized at the cervical margin when orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis, so there may be the same risk of root resorption when orthodontic force of 2 N at 0, 30 and 45 degree was used in clinic cases.
