Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-const...Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-constant subsegment stiffness structure for tendon-driven quasi continuum robots(TDQCRs) comprising rigid-flexible coupling subsegments.Aiming at real-time control applications, we present a novel static-to-kinematic modeling approach to gain a comprehensive understanding of the TDQCR model. The analytical subsegment-based kinematics for the multisection manipulator is derived based on screw theory and product of exponentials formula, and the static model considering gravity loading,actuation loading, and robot constitutive laws is established. Additionally, the effect of tension attenuation caused by routing channel friction is considered in the robot statics, resulting in improved model accuracy. The root-mean-square error between the outputs of the static model and the experimental system is less than 1.63% of the arm length(0.5 m). By employing the proposed static model, a mapping of bending angles between the configuration space and the subsegment space is established. Furthermore, motion control experiments are conducted on our TDQCR system, and the results demonstrate the effectiveness of the static-to-kinematic model.展开更多
BACKGROUND Acute bleeding due to esophageal varices(EVs)is a life-threatening complication in patients with cirrhosis.The diagnosis of EVs is mainly through upper gastrointestinal endoscopy,but the discomfort,contrain...BACKGROUND Acute bleeding due to esophageal varices(EVs)is a life-threatening complication in patients with cirrhosis.The diagnosis of EVs is mainly through upper gastrointestinal endoscopy,but the discomfort,contraindications and complications of gastrointestinal endoscopic screening reduce patient compliance.According to the bleeding risk of EVs,the Baveno VI consensus divides varices into high bleeding risk EVs(HEVs)and low bleeding risk EVs(LEVs).We sought to identify a non-invasive prediction model based on spleen stiffness measurement(SSM)and liver stiffness measurement(LSM)as an alternative to EVs screening.AIM To develop a safe,simple and non-invasive model to predict HEVs in patients with viral cirrhosis and identify patients who can be exempted from upper gastrointestinal endoscopy.METHODS Data from 200 patients with viral cirrhosis were included in this study,with 140 patients as the modelling group and 60 patients as the external validation group,and the EVs types of patients were determined by upper gastrointestinal endoscopy and the Baveno Ⅵ consensus.Those patients were divided into the HEVs group(66 patients)and the LEVs group(74 patients).The effect of each parameter on HEVs was analyzed by univariate and multivariate analyses,and a noninvasive prediction model was established.Finally,the discrimination ability,calibration ability and clinical efficacy of the new model were verified in the modelling group and the external validation group.RESULTS Univariate and multivariate analyses showed that SSM and LSM were associated with the occurrence of HEVs in patients with viral cirrhosis.On this basis,logistic regression analysis was used to construct a prediction model:Ln[P/(1-P)]=-8.184-0.228×SSM+0.642×LSM.The area under the curve of the new model was 0.965.When the cut-off value was 0.27,the sensitivity,specificity,positive predictive value and negative predictive value of the model for predicting HEVs were 100.00%,82.43%,83.52%,and 100%,respectively.Compared with the four prediction models of liver stiffness-spleen diameter to platelet ratio score,variceal risk index,aspartate aminotransferase to alanine aminotransferase ratio,and Baveno VI,the established model can better predict HEVs in patients with viral cirrhosis.CONCLUSION Based on the SSM and LSM measured by transient elastography,we established a non-invasive prediction model for HEVs.The new model is reliable in predicting HEVs and can be used as an alternative to routine upper gastrointestinal endoscopy screening,which is helpful for clinical decision making.展开更多
With the development of artificial intelligence,stiffness sensors are extensively utilized in various fields,and their integration with robots for automated palpation has gained significant attention.This study presen...With the development of artificial intelligence,stiffness sensors are extensively utilized in various fields,and their integration with robots for automated palpation has gained significant attention.This study presents a broad range self-powered stiffness sensor based on the triboelectric nanogenerator(Stiff-TENG)for variable inclusions in soft objects detection.The Stiff-TENG employs a stacked structure comprising an indium tin oxide film,an elastic sponge,a fluorinated ethylene propylene film with a conductive ink electrode,and two acrylic pieces with a shielding layer.Through the decoupling method,the Stiff-TENG achieves stiffness detection of objects within 1.0 s.The output performance and characteristics of the TENG for different stiffness objects under 4 mm displacement are analyzed.The Stiff-TENG is successfully used to detect the heterogeneous stiffness structures,enabling effective recognition of variable inclusions in soft object,reaching a recognition accuracy of 99.7%.Furthermore,its adaptability makes it well-suited for the detection of pathological conditions within the human body,as pathological tissues often exhibit changes in the stiffness of internal organs.This research highlights the innovative applications of TENG and thereby showcases its immense potential in healthcare applications such as palpation which assesses pathological conditions based on organ stiffness.展开更多
predicting high-risk esophageal varices based on liver and spleen stiffness".Acute bleeding caused by esophageal varices is a life-threatening complication in patients with liver cirrhosis.Due to the discomfort,c...predicting high-risk esophageal varices based on liver and spleen stiffness".Acute bleeding caused by esophageal varices is a life-threatening complication in patients with liver cirrhosis.Due to the discomfort,contraindications,and associated complications of upper gastrointestinal endoscopy screening,it is crucial to identify an imaging-based non-invasive model for predicting high-risk esophageal varices in patients with cirrhosis.展开更多
The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic ...The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic stiffness and its effect mechanism have been rarely incorporated in open studies of the rotor system.Therefore,this study theoretically reveals the effect mechanism of dynamic stiffness on the rotor system.Then,the numerical study and experimental verification are conducted on the dynamic stiffness characteristics of a squirrel cage,which is a common support structure for aero-engine.Moreover,the static stiffness experiment is also performed for comparison.Finally,a rotor system model considering the dynamic stiffness of the support structure is presented.The presented rotor model is used to validate the results of the theoretical analysis.The results illustrate that the dynamic stiffness reduces the critical speed of the rotor system and may lead to a new resonance.展开更多
Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)c...Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)conditions associated with large thickness of fault surrounding rock mass.In this study,the rock friction experiments were conducted to understand the fault activation modes under the CNS conditions.Two major parameters,i.e.the initial normal stress and loading rate,were considered and calibrated in the tests.To reveal the response mechanism of fault activation,the local strains near the fault plane were recorded,and the macroscopic stresses and displacements were analyzed.The testing results show that the effect of displacement-controlled loading rate is more pronounced under the CNS conditions than that under constant normal load(CNL)conditions.Both the normal and shear stresses drop suddenly when the stick-slip occurs.The decrease and increase of the normal stress are synchronous with the shear stress in the regular stick-slip scenario,but mismatch with the shear stress during the chaotic stick-slip process.The results are helpful for understanding the fault sliding mode and the prediction and prevention of fault slip.展开更多
Overconstrained mechanism has the advantages of large bearing capacity and high motion reliability,but its force analysis is complex and difficult because the mechanism system contains overconstraints.Considering the ...Overconstrained mechanism has the advantages of large bearing capacity and high motion reliability,but its force analysis is complex and difficult because the mechanism system contains overconstraints.Considering the limb axial deformation,taking typical 2SS+P and 7-SS passive overconstrained mechanisms,2SPS+P and 7-SPS active overconstrained mechanisms,and 2SPS+P and 7-SPS passive-input overconstrained mechanisms as examples,a new force analysis method based on the idea of equivalent stiffness is proposed.The equivalent stiffness matrix of passive overconstrained mechanism is derived by combining the force balance and deformation compatibility equations with consideration of axial elastic limb deformations.The relationship between the constraint wrench magnitudes and the external force,limb stiffness is established.The equivalent stiffness matrix of active overconstrained mechanism is derived by combining the force balance and displacement compatibility equations.Here,the relationship between the magnitudes of the actuated wrenches and the external force,limb stiffness is investigated.Combining with the equivalent stiffness of the passive overconstrained mechanism,an analytical relationship between the actuated forces of passive-input overconstrained mechanism and the output displacement,limb stiffness is explored.Finally,adaptability of the equivalent stiffness to overconstrained mechanisms is discussed,and the effect of the limb stiffness on overconstrained mechanisms force distribution is revealed.The research results provide a theoretical reference for the design,research and practical application of overconstrained mechanism.展开更多
A novel implementation of negative stiffness elements(NSEs)is proposed,utilizing industrial grade nitrogen gas springs as pre-stressed stiffness elements in a configuration with lever arms.This NSE is combined with an...A novel implementation of negative stiffness elements(NSEs)is proposed,utilizing industrial grade nitrogen gas springs as pre-stressed stiffness elements in a configuration with lever arms.This NSE is combined with an inerter to form a stiff dynamic absorber(SDA)for vertical seismic protection of structures with base isolation.The SDA is optimized to minimize vertical accelerations while ensuring static structural integrity,excellent damping performance and containment of relative displacements.The introduction of gas springs in place of conventional linear springs addresses important practical limitations through features of non-linearity and industrial grade manufacturing.The proposed implementation is dimensioned for a 50-ton structure and evaluated numerically for 25 actual earthquake records,in comparison with a linear SDA model and an equivalent conventional damper(CD).Individual and averaged results of acceleration and displacement time histories demonstrate vastly superior response compared to CD regarding induced accelerations for similar displacements.Performance equivalency with the linear SDA model indicates the stability of the gas spring implementation while guaranteeing predictability,tested endurance,proper tolerances,and off-axis motion resistance without requiring additional guiding components,as opposed to conventional springs.These features render the proposed implementation a promising solution for the realization of NSEs in seismic protection.展开更多
Objective This study aimed to investigate the association between fruit and vegetable intake and arterial stiffness.Methods We conducted a cohort-based study comprising 6,628 participants with arterial stiffness infor...Objective This study aimed to investigate the association between fruit and vegetable intake and arterial stiffness.Methods We conducted a cohort-based study comprising 6,628 participants with arterial stiffness information in the Prediction for Atherosclerotic Cardiovascular Disease Risk in China(China-PAR)project. A semi-quantitative food-frequency questionnaire was used to assess baseline(2007–2008) and recent(2018–2021) fruit and vegetable intake. We assessed changes in fruit and vegetable intake from2007–2008 to 2018–2021 in 6,481 participants. Arterial stiffness was measured using the arterial velocity–pulse index(AVI) and arterial pressure-volume index(API). Elevated AVI and API values were defined according to diverse age reference ranges.Results Multivariable-adjusted linear regression models revealed that every 100 g/d increment in fruit and vegetable intake was associated with a 0.11 decrease in AVI(B =-0.11;95% confidence interval [CI]:-0.20,-0.02) on average, rather than API(B = 0.02;95% CI:-0.09, 0.13). The risk of elevated AVI(odds ratio [OR] = 0.82;95% CI: 0.70, 0.97) is 18% lower in individuals with high intake(≥ 500 g/d) than in those with low intake(< 500 g/d). Furthermore, maintaining a high intake in the past median of 11.5years of follow-up was associated with an even lower risk of elevated AVI compared with a low intake at both baseline and follow-up(OR = 0.64;95% CI: 0.49, 0.83).Conclusion Fruit and vegetable intake was negatively associated with arterial stiffness, emphasizing recommendations for adherence to fruit and vegetable intake for the prevention of arterial stiffness.展开更多
Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods ...Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods for determining joint normal stiffness were introduced and reviewed,among which MethodⅠ(the indirect measurement method),MethodⅡ(the direct determination method),MethodⅢ(the across-joint strain gauge measurement method)and MethodⅣ(the deformation measuring ring method)are via destructive uniaxial compression testing,while MethodⅤ(the best fitting method),MethodⅥ(the rapid evaluation method)and MethodⅦ(the effective modulus method)are through wave propagation principles and nondestructive ultrasonic testing.Subsequently,laboratory tests of intact and jointed sandstone specimens were conducted following the testing requirements and pro-cedures of those seven methods.A comparison among those methods was then performed.The results show that Method I,i.e.the benchmark method,is reliable and stable.MethodⅡhas a conceptual drawback,and its accuracy is acceptable at only very low stress levels.Relative errors in the results from MethodⅢare very large.With MethodⅣ,the testing results are sufficiently accurate despite the strict testing environment and complicated testing procedures.The results from MethodⅤare greatly unstable and significantly dependent on the natural frequency of the transducers.The joint normal stiffness determined with MethodⅥis stable and accurate,although data processing is complex.MethodⅦcould be adopted to determine the joint normal stiffness corresponding to the rock elastic deformation phase only.Consequently,it is suggested that MethodsⅠ,ⅣandⅥshould be adopted for the mea-surement of joint normal stiffness.The findings could be helpful in selecting an appropriate method to determine joint normal stiffness and,hence,to better solve discontinuous rock mass problems.展开更多
This research proposes a novel type of variable stiffness tuned particle damper(TPD)for reducing vibrations in boring bars.The TPD integrates the developments of particle damping and dynamical vibration absorber,whose...This research proposes a novel type of variable stiffness tuned particle damper(TPD)for reducing vibrations in boring bars.The TPD integrates the developments of particle damping and dynamical vibration absorber,whose frequency tuning principle is established through an equivalent theoretical model.Based on the multiphase flow theory of gas-solid,it is effective to obtain the equivalent damping and stiffness of the particle damping.The dynamic equations of the coupled system,consisting of a boring bar with the TPD,are built by Hamilton’s principle.The vibration suppression of the TPD is assessed by calculating the amplitude responses of the boring bar both with and without the TPD by the Newmark-beta algorithm.Moreover,an improvement is proposed to the existing gas-solid flow theory,and a comparative analysis of introducing the stiffness term on the damping effect is presented.The parameters of the TPD are optimized by the genetic algorithm,and the results indicate that the optimized TPD effectively reduces the peak response of the boring bar system.展开更多
Mechanical metamaterials such as auxetic materials have attracted great interest due to their unusual properties that are dictated by their architectures.However,these architected materials usually have low stiffness ...Mechanical metamaterials such as auxetic materials have attracted great interest due to their unusual properties that are dictated by their architectures.However,these architected materials usually have low stiffness because of the bending or rotation deformation mechanisms in the microstructures.In this work,a convolutional neural network(CNN)based self-learning multi-objective optimization is performed to design digital composite materials.The CNN models have undergone rigorous training using randomly generated two-phase digital composite materials,along with their corresponding Poisson's ratios and stiffness values.Then the CNN models are used for designing composite material structures with the minimum Poisson's ratio at a given volume fraction constraint.Furthermore,we have designed composite materials with optimized stiffness while exhibiting a desired Poisson's ratio(negative,zero,or positive).The optimized designs have been successfully and efficiently obtained,and their validity has been confirmed through finite element analysis results.This self-learning multi-objective optimization model offers a promising approach for achieving comprehensive multi-objective optimization.展开更多
BACKGROUND Older men are more vulnerable to fatal falls than women,and gait disturbances contribute to the risk of falls.Studies have assessed the association between arterial stiffness and gait dysfunction,but the re...BACKGROUND Older men are more vulnerable to fatal falls than women,and gait disturbances contribute to the risk of falls.Studies have assessed the association between arterial stiffness and gait dysfunction,but the results have been inconclusive.This study aimed to conduct a cross-sectional analysis to evaluate the association between brachial–ankle pulse wave velocity(baPWV)and gait assessment in older men.METHODS Data from the 2014–2015 Korea Institute of Sport Science Fitness Standards project were used for the analysis.The inclusion criteria were men aged>65 years with gait assessment[the 30-s chair stand test(30s-CST),the timed up and go(TUG)test,the figure-of-8 walk(F8W)test,the 2-min step test(2MST),and the 6-min walk test(6MWT)]and baPWV measurement data.Generalized linear regression analysis was conducted with multiple confounding factor adjustments,including lower extremity isometric strength.RESULTS A total of 291 participants were included in the analysis.The mean age was 71.38±4.40 years.The mean values were as follows:(1)30s-CST,17.48±5.00;(2)TUG test,6.01±1.10 s;(3)F8W test,25.65±4.71 s;(4)2MST,102.40±18.83 per 2 min;and(5)6MWT,500.02±85.65 m.After multivariable adjustment,baPWV was associated with the 6MWT(β=−0.037,95%CI:−0.072–−0.002),TUG test(β=0,95%CI:0.000–0.001),and F8W test(β=0.002,95%CI:0.000–0.004).baPWV was not associated with the 30s-CST and 2MST.CONCLUSIONS The current study showed a statistically significant association between gait assessments and arterial stiffness,independent of lower extremity strength.However,this association was modest.Future prospective studies are needed to elucidate the complex relationship between arterial stiffness and gait dysfunction.展开更多
In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due ...In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.展开更多
In order to provide more insights into the damage propagation composite wind turbine blades(blade)under cyclic fatigue loading,a stiffness degradation model for blade is proposed based on the full-scale fatigue testin...In order to provide more insights into the damage propagation composite wind turbine blades(blade)under cyclic fatigue loading,a stiffness degradation model for blade is proposed based on the full-scale fatigue testing of a blade.A novel non-linear fatigue damage accumulation model is proposed using the damage assessment theories of composite laminates for the first time.Then,a stiffness degradation model is established based on the correlation of fatigue damage and residual stiffness of the composite laminates.Finally,a stiffness degradation model for the blade is presented based on the full-scale fatigue testing.The scientific rationale of the proposed stiffness model of blade is verified by using full-scale fatigue test data of blade with a total length of 52.5 m.The results indicate that the proposed stiffness degradation model of the blade agrees well with the fatigue testing results of this blade.This work provides a basis for evaluating the fatigue damage and lifetime of blade under cyclic fatigue loading.展开更多
BACKGROUND Intrahepatic cholestasis of pregnancy(ICP)is a rare but severe complication for both the mother and the unborn child.The diagnosis is primarily based on elevated serum levels of bile acids.In a large ICP co...BACKGROUND Intrahepatic cholestasis of pregnancy(ICP)is a rare but severe complication for both the mother and the unborn child.The diagnosis is primarily based on elevated serum levels of bile acids.In a large ICP cohort,we here study in detail liver stiffness(LS)using transient elastography(TE),now widely used to noninvasively screen for liver cirrhosis within minutes.AIM To specifically explore LS in a large cohort of women with ICP compared to a control group with uncomplicated pregnancy.METHODS LS and hepatic steatosis marker controlled attenuation parameter(CAP)were measured in 100 pregnant women with ICP using TE(Fibroscan,Echosens,Paris,France)between 2010 and 2020.In 17 cases,LS could be measured postpartum.450 women before and 38 women after delivery with uncomplicated pregnancy served as control group.Routine laboratory,levels of bile acids and apoptosis marker caspase-cleaved cytokeratin 18 fragment(M30)were also measured.RESULTS Women with ICP had significantly elevated transaminases but normal gammaglutamyl transferase(GGT).Mean LS was significantly increased at 7.3±3.0 kPa compared to the control group at 6.2±2.3 kPa(P<0.0001).Postpartum LS decreased significantly in both groups but was still higher in ICP(5.8±1.7 kPa vs 4.2±0.9 kPa,P<0.0001),respectively.In ICP,LS was highly significantly correlated with levels of bile acids and M30 but not transaminases.No correlation was seen with GGT that even increased significantly after delivery in the ICP group.Bile acids were mostly correlated with the liver apoptosis marker M30,LS and levels of alanine aminotransferase,aspartate aminotransferase,and bilirubin.In multivariate analysis,LS remained the sole parameter that was independently associated with elevated bile acids.CONCLUSION In conclusion,LS is significantly elevated in ICP which is most likely due to toxic bile acid accumulation and hepatocyte apoptosis.In association with conventional laboratory markers,LS provides additional non-invasive information to rapidly identify women at risk for ICP.展开更多
Background: Analysis of arterial stiffness (AS) is a good marker of early arterial disease and an important determinant of cardiovascular risk, independent of other traditional cardiovascular risk factors. Carotid-fem...Background: Analysis of arterial stiffness (AS) is a good marker of early arterial disease and an important determinant of cardiovascular risk, independent of other traditional cardiovascular risk factors. Carotid-femoral pulse wave velocity (CfPWV) is the gold standard to evaluate arterial stiffness. There is evidence that patients with rheumatoid arthritis (RA) have a higher arterial stiffness than their age-matched healthy counterparts and thus have higher cardiovascular (CV) risk. However, data on arterial stiffness in African rheumatoid arthritis patients is scarce. Objectives: To determine the patterns of arterial stiffness in rheumatoid arthritis patients in a sub-Saharan African setting, using CfPWV and Augmentation index (AIx). Method: We conducted a case-control study, at the Douala general hospital over four months (February to May 2018) on 63 subjects among which 31 RA patients matched for age and sex with 32 healthy subjects. AIx and CfPWV were determined non-invasively by radial pulse wave analysis and carotid femoral wave analysis respectively, using a sphygmocor Atcor device (SphygmoCor, PWV Medical, Sydney, Australia). Results: The mean age of RA patients was 47 ± 14 years with most of them being females (n = 26, 83.9%). CfPWV was significantly higher in RA patients compared to the control group (mean: 8.85 ± 2.1 vs 7.45 ± 1.38;p ≤ 0.01) as well as was AIx (Median: 33 [26 - 43] vs 26 [20 - 31];p = 0.01). RA (OR: 6.105;95% CI: 1.52 - 24.54;p 1.34;95% CI: 1.14 - 5.17;p = 0.05), elevated CRP levels (OR: 4.01;95% CI: 1.16 - 13.68;p = 0.03) and Hypertension (OR: 5.75;95% CI: 1.24 -11.60;p Conclusion: Arterial stiffness, a well-recognized marker of cardiovascular risk is increased among patients suffering from rheumatoid arthritis when compared to a healthy control group.展开更多
Truck frames should be designed and fabricated with enough rigidity to avoid excessive deflections. Finite element analysis (FEA) plays an important role in all stages of frame designs. While being accurate, 3D solid ...Truck frames should be designed and fabricated with enough rigidity to avoid excessive deflections. Finite element analysis (FEA) plays an important role in all stages of frame designs. While being accurate, 3D solid element FEA models are built upon frame configuration details which are not feasible in the preliminary design stage, partially because of limited available design data of frames and heavy computation costs. This research develops 1D beam element FEA models for simulating frame structures. In this paper, the CAD model of a truck frame is first created. The solid element FEA analysis, which is adopted as the baseline in this study, is subsequently conducted for the stiffness of the frame, Next, beam element FEA analysis is performed for validating the feasibility of the beam element FEA model by comparing the results from the solid and beam element FEA models. It is found that the beam element FEA model can predict the frame stiffness with acceptable accuracy and reduce the computation cost significantly.展开更多
Background and objective:Liver stiffness measurement(LSM)may effectively correlate to the presence of liver fibrosis,but it is controversial to use for the prediction of clinical outcomes.Therefore,we aimed to evaluat...Background and objective:Liver stiffness measurement(LSM)may effectively correlate to the presence of liver fibrosis,but it is controversial to use for the prediction of clinical outcomes.Therefore,we aimed to evaluate the predictive value of liver stiffness for the regression of liver fibrosis.Methods:In this study,we collected data from a clinical cohort of patients who are received anti-virus therapies for 48 weeks.180 naive chronic hepatitis B(CHB)patients,who received paired LSM and liver biopsy with pre-and post-treatments were analyzed.Two methods(FibroScan and iLivTouch)test LSM.Result:The area under the receiver operating characteristics curve(AUROC)of changing LSM for fibrosis regression is higher in advanced fibrosis patients(F5/6)than in moderate fibrosis patients(F3/4)in both FibroScan(0.719,95%CI,0.590–0.848;P=0.003;vs 0.617,95%CI,0.379–0.856,P=0.282)and iLivTouch(0.707,95%CI,0.567–0.847;P=0.011;vs 0.583,95%CI,0.422–0.744;P=0.377).A higher kappa value was received in advanced stage than in moderate stage both in FibroScan(0.392,P=0.001 vs 0.265,P=0.053)and iLivTouch(0.326,P=0.019 vs 0.030,P=0.833).Cut-off set as 4.10 kPa(sen,69.4%;spe,73.9%)in FibroScan,as 4.25 kPa(sen,56.8%;spe,72.2%)in iLivTouch.Conclusion:The changing LSM can be used for predicting the liver fibrosis regression in advanced stage of CHB patients.展开更多
The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, an...The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, and stability. For very large compressions, the tangent stiffness in the direction of the compression can even become negative, which can be regarded as physical nonsense. So in many cases rubber materials exposed to great compression cannot be analyzed, or the analysis could lead to very poor convergence. Problems with the standard geometric stiffness matrix can even occur with a small strain in the case of plastic yielding, which eventuates even greater practical problems. The authors demonstrate that amore precisional approach would not lead to such strange and theoretically unjustified results. An improved formula that would eliminate the disadvantages mentioned above and leads to higher convergence rate and more robust computations is suggested in this paper. The new formula can be derived from the principle of virtual work using a modified Green-Lagrange strain tensor, or from equilibrium conditions where in the choice of a specific strain measure is not needed for the geometric stiffness derivation (which can also be used for derivation of geometric stiffness of a rigid truss member). The new formula has been verified in practice with many calculations and implemented in the RFEM and SCIA Engineer programs. The advantages of the new formula in comparison with the standard formula are shown using several examples.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.61973167)the Jiangsu Funding Program for Excellent Postdoctoral Talent。
文摘Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-constant subsegment stiffness structure for tendon-driven quasi continuum robots(TDQCRs) comprising rigid-flexible coupling subsegments.Aiming at real-time control applications, we present a novel static-to-kinematic modeling approach to gain a comprehensive understanding of the TDQCR model. The analytical subsegment-based kinematics for the multisection manipulator is derived based on screw theory and product of exponentials formula, and the static model considering gravity loading,actuation loading, and robot constitutive laws is established. Additionally, the effect of tension attenuation caused by routing channel friction is considered in the robot statics, resulting in improved model accuracy. The root-mean-square error between the outputs of the static model and the experimental system is less than 1.63% of the arm length(0.5 m). By employing the proposed static model, a mapping of bending angles between the configuration space and the subsegment space is established. Furthermore, motion control experiments are conducted on our TDQCR system, and the results demonstrate the effectiveness of the static-to-kinematic model.
基金Supported by the Shaanxi Provincial Key Research and Development Plan,No.2020SF-159.
文摘BACKGROUND Acute bleeding due to esophageal varices(EVs)is a life-threatening complication in patients with cirrhosis.The diagnosis of EVs is mainly through upper gastrointestinal endoscopy,but the discomfort,contraindications and complications of gastrointestinal endoscopic screening reduce patient compliance.According to the bleeding risk of EVs,the Baveno VI consensus divides varices into high bleeding risk EVs(HEVs)and low bleeding risk EVs(LEVs).We sought to identify a non-invasive prediction model based on spleen stiffness measurement(SSM)and liver stiffness measurement(LSM)as an alternative to EVs screening.AIM To develop a safe,simple and non-invasive model to predict HEVs in patients with viral cirrhosis and identify patients who can be exempted from upper gastrointestinal endoscopy.METHODS Data from 200 patients with viral cirrhosis were included in this study,with 140 patients as the modelling group and 60 patients as the external validation group,and the EVs types of patients were determined by upper gastrointestinal endoscopy and the Baveno Ⅵ consensus.Those patients were divided into the HEVs group(66 patients)and the LEVs group(74 patients).The effect of each parameter on HEVs was analyzed by univariate and multivariate analyses,and a noninvasive prediction model was established.Finally,the discrimination ability,calibration ability and clinical efficacy of the new model were verified in the modelling group and the external validation group.RESULTS Univariate and multivariate analyses showed that SSM and LSM were associated with the occurrence of HEVs in patients with viral cirrhosis.On this basis,logistic regression analysis was used to construct a prediction model:Ln[P/(1-P)]=-8.184-0.228×SSM+0.642×LSM.The area under the curve of the new model was 0.965.When the cut-off value was 0.27,the sensitivity,specificity,positive predictive value and negative predictive value of the model for predicting HEVs were 100.00%,82.43%,83.52%,and 100%,respectively.Compared with the four prediction models of liver stiffness-spleen diameter to platelet ratio score,variceal risk index,aspartate aminotransferase to alanine aminotransferase ratio,and Baveno VI,the established model can better predict HEVs in patients with viral cirrhosis.CONCLUSION Based on the SSM and LSM measured by transient elastography,we established a non-invasive prediction model for HEVs.The new model is reliable in predicting HEVs and can be used as an alternative to routine upper gastrointestinal endoscopy screening,which is helpful for clinical decision making.
基金This work is supported by the grant from the National Natural Science Foundation of China under Grants 62104125 and 62311530102,Guangdong Innovative and Entrepreneurial Research Team Program(2021ZT09L197)Guangdong Basic and Applied Basic Research Foundation(2020A1515110887)+1 种基金Tsinghua Shenzhen International Graduate School-Shenzhen Pengrui Young Faculty Program of Shenzhen Pengrui Foundation(No.SZPR2023005)Shenzhen Science and Technology Program(JCYJ20220530143013030).
文摘With the development of artificial intelligence,stiffness sensors are extensively utilized in various fields,and their integration with robots for automated palpation has gained significant attention.This study presents a broad range self-powered stiffness sensor based on the triboelectric nanogenerator(Stiff-TENG)for variable inclusions in soft objects detection.The Stiff-TENG employs a stacked structure comprising an indium tin oxide film,an elastic sponge,a fluorinated ethylene propylene film with a conductive ink electrode,and two acrylic pieces with a shielding layer.Through the decoupling method,the Stiff-TENG achieves stiffness detection of objects within 1.0 s.The output performance and characteristics of the TENG for different stiffness objects under 4 mm displacement are analyzed.The Stiff-TENG is successfully used to detect the heterogeneous stiffness structures,enabling effective recognition of variable inclusions in soft object,reaching a recognition accuracy of 99.7%.Furthermore,its adaptability makes it well-suited for the detection of pathological conditions within the human body,as pathological tissues often exhibit changes in the stiffness of internal organs.This research highlights the innovative applications of TENG and thereby showcases its immense potential in healthcare applications such as palpation which assesses pathological conditions based on organ stiffness.
基金the Shaanxi Provincial Key Research and Development Plan,No.2020SF-159.
文摘predicting high-risk esophageal varices based on liver and spleen stiffness".Acute bleeding caused by esophageal varices is a life-threatening complication in patients with liver cirrhosis.Due to the discomfort,contraindications,and associated complications of upper gastrointestinal endoscopy screening,it is crucial to identify an imaging-based non-invasive model for predicting high-risk esophageal varices in patients with cirrhosis.
基金the National Natural Science Foundation of China(Nos.11872148 and U1908217)the Fundamental Research Funds for the Central Universities of China(Nos.N2224001-4 and N2003013)the Basic and Applied Basic Research Foundation of Guangdong Province of China(No.2020B1515120015)。
文摘The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic stiffness and its effect mechanism have been rarely incorporated in open studies of the rotor system.Therefore,this study theoretically reveals the effect mechanism of dynamic stiffness on the rotor system.Then,the numerical study and experimental verification are conducted on the dynamic stiffness characteristics of a squirrel cage,which is a common support structure for aero-engine.Moreover,the static stiffness experiment is also performed for comparison.Finally,a rotor system model considering the dynamic stiffness of the support structure is presented.The presented rotor model is used to validate the results of the theoretical analysis.The results illustrate that the dynamic stiffness reduces the critical speed of the rotor system and may lead to a new resonance.
基金supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China(Grant No.U1865203)the National Natural Science Foundation of China(Grant Nos.52109142 and 41941018).
文摘Fault activation has been the focus of research community for years.However,the studies of fault activation remain immature,such as the fault activation mode and its major factors under constant normal stiffness(CNS)conditions associated with large thickness of fault surrounding rock mass.In this study,the rock friction experiments were conducted to understand the fault activation modes under the CNS conditions.Two major parameters,i.e.the initial normal stress and loading rate,were considered and calibrated in the tests.To reveal the response mechanism of fault activation,the local strains near the fault plane were recorded,and the macroscopic stresses and displacements were analyzed.The testing results show that the effect of displacement-controlled loading rate is more pronounced under the CNS conditions than that under constant normal load(CNL)conditions.Both the normal and shear stresses drop suddenly when the stick-slip occurs.The decrease and increase of the normal stress are synchronous with the shear stress in the regular stick-slip scenario,but mismatch with the shear stress during the chaotic stick-slip process.The results are helpful for understanding the fault sliding mode and the prediction and prevention of fault slip.
基金National Natural Science Foundation of China(Grant Nos.52075467,51875495)Key Project of Natural Science Foundation of Hebei Province of China(Grant No.E2017203335)Hebei Provincial Science and Technology Project of China(Grant No.206Z1805G)。
文摘Overconstrained mechanism has the advantages of large bearing capacity and high motion reliability,but its force analysis is complex and difficult because the mechanism system contains overconstraints.Considering the limb axial deformation,taking typical 2SS+P and 7-SS passive overconstrained mechanisms,2SPS+P and 7-SPS active overconstrained mechanisms,and 2SPS+P and 7-SPS passive-input overconstrained mechanisms as examples,a new force analysis method based on the idea of equivalent stiffness is proposed.The equivalent stiffness matrix of passive overconstrained mechanism is derived by combining the force balance and deformation compatibility equations with consideration of axial elastic limb deformations.The relationship between the constraint wrench magnitudes and the external force,limb stiffness is established.The equivalent stiffness matrix of active overconstrained mechanism is derived by combining the force balance and displacement compatibility equations.Here,the relationship between the magnitudes of the actuated wrenches and the external force,limb stiffness is investigated.Combining with the equivalent stiffness of the passive overconstrained mechanism,an analytical relationship between the actuated forces of passive-input overconstrained mechanism and the output displacement,limb stiffness is explored.Finally,adaptability of the equivalent stiffness to overconstrained mechanisms is discussed,and the effect of the limb stiffness on overconstrained mechanisms force distribution is revealed.The research results provide a theoretical reference for the design,research and practical application of overconstrained mechanism.
基金European Union′s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant No.INSPIRE-813424(“INSPIRE-Innovative Ground Interface Concepts for Structure Protection”)。
文摘A novel implementation of negative stiffness elements(NSEs)is proposed,utilizing industrial grade nitrogen gas springs as pre-stressed stiffness elements in a configuration with lever arms.This NSE is combined with an inerter to form a stiff dynamic absorber(SDA)for vertical seismic protection of structures with base isolation.The SDA is optimized to minimize vertical accelerations while ensuring static structural integrity,excellent damping performance and containment of relative displacements.The introduction of gas springs in place of conventional linear springs addresses important practical limitations through features of non-linearity and industrial grade manufacturing.The proposed implementation is dimensioned for a 50-ton structure and evaluated numerically for 25 actual earthquake records,in comparison with a linear SDA model and an equivalent conventional damper(CD).Individual and averaged results of acceleration and displacement time histories demonstrate vastly superior response compared to CD regarding induced accelerations for similar displacements.Performance equivalency with the linear SDA model indicates the stability of the gas spring implementation while guaranteeing predictability,tested endurance,proper tolerances,and off-axis motion resistance without requiring additional guiding components,as opposed to conventional springs.These features render the proposed implementation a promising solution for the realization of NSEs in seismic protection.
基金supported by the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences[2021-I2M-1-010 and 2019-I2M-2-003]the National High Level Hospital Clinical Research Funding [2022-GSP-GG-1, 2022-GSP-GG-2]+3 种基金Research Unit of Prospective Cohort of Cardiovascular Diseases and Cancers,CAMS (2019RU038)National Natural Science Foundation of China [82030102, 12126602, 91857118]the National Key Research and Development Program of China [2021YFC2500500]the National Clinical Research Center for Cardiovascular Diseases,Fuwai Hospital,Chinese Academy of Medical Sciences [NCRC2020006]。
文摘Objective This study aimed to investigate the association between fruit and vegetable intake and arterial stiffness.Methods We conducted a cohort-based study comprising 6,628 participants with arterial stiffness information in the Prediction for Atherosclerotic Cardiovascular Disease Risk in China(China-PAR)project. A semi-quantitative food-frequency questionnaire was used to assess baseline(2007–2008) and recent(2018–2021) fruit and vegetable intake. We assessed changes in fruit and vegetable intake from2007–2008 to 2018–2021 in 6,481 participants. Arterial stiffness was measured using the arterial velocity–pulse index(AVI) and arterial pressure-volume index(API). Elevated AVI and API values were defined according to diverse age reference ranges.Results Multivariable-adjusted linear regression models revealed that every 100 g/d increment in fruit and vegetable intake was associated with a 0.11 decrease in AVI(B =-0.11;95% confidence interval [CI]:-0.20,-0.02) on average, rather than API(B = 0.02;95% CI:-0.09, 0.13). The risk of elevated AVI(odds ratio [OR] = 0.82;95% CI: 0.70, 0.97) is 18% lower in individuals with high intake(≥ 500 g/d) than in those with low intake(< 500 g/d). Furthermore, maintaining a high intake in the past median of 11.5years of follow-up was associated with an even lower risk of elevated AVI compared with a low intake at both baseline and follow-up(OR = 0.64;95% CI: 0.49, 0.83).Conclusion Fruit and vegetable intake was negatively associated with arterial stiffness, emphasizing recommendations for adherence to fruit and vegetable intake for the prevention of arterial stiffness.
基金supported by the Shenzhen Fundamental Research Program(Grant No.JCYJ20220818095605012)the National Natural Science Foundation of China(Grant No.51909026)the Fund of Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization(Grant No.2020-08).
文摘Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods for determining joint normal stiffness were introduced and reviewed,among which MethodⅠ(the indirect measurement method),MethodⅡ(the direct determination method),MethodⅢ(the across-joint strain gauge measurement method)and MethodⅣ(the deformation measuring ring method)are via destructive uniaxial compression testing,while MethodⅤ(the best fitting method),MethodⅥ(the rapid evaluation method)and MethodⅦ(the effective modulus method)are through wave propagation principles and nondestructive ultrasonic testing.Subsequently,laboratory tests of intact and jointed sandstone specimens were conducted following the testing requirements and pro-cedures of those seven methods.A comparison among those methods was then performed.The results show that Method I,i.e.the benchmark method,is reliable and stable.MethodⅡhas a conceptual drawback,and its accuracy is acceptable at only very low stress levels.Relative errors in the results from MethodⅢare very large.With MethodⅣ,the testing results are sufficiently accurate despite the strict testing environment and complicated testing procedures.The results from MethodⅤare greatly unstable and significantly dependent on the natural frequency of the transducers.The joint normal stiffness determined with MethodⅥis stable and accurate,although data processing is complex.MethodⅦcould be adopted to determine the joint normal stiffness corresponding to the rock elastic deformation phase only.Consequently,it is suggested that MethodsⅠ,ⅣandⅥshould be adopted for the mea-surement of joint normal stiffness.The findings could be helpful in selecting an appropriate method to determine joint normal stiffness and,hence,to better solve discontinuous rock mass problems.
基金Project supported by the National Natural Science Foundation of China(Nos.12172014 and 11972050)。
文摘This research proposes a novel type of variable stiffness tuned particle damper(TPD)for reducing vibrations in boring bars.The TPD integrates the developments of particle damping and dynamical vibration absorber,whose frequency tuning principle is established through an equivalent theoretical model.Based on the multiphase flow theory of gas-solid,it is effective to obtain the equivalent damping and stiffness of the particle damping.The dynamic equations of the coupled system,consisting of a boring bar with the TPD,are built by Hamilton’s principle.The vibration suppression of the TPD is assessed by calculating the amplitude responses of the boring bar both with and without the TPD by the Newmark-beta algorithm.Moreover,an improvement is proposed to the existing gas-solid flow theory,and a comparative analysis of introducing the stiffness term on the damping effect is presented.The parameters of the TPD are optimized by the genetic algorithm,and the results indicate that the optimized TPD effectively reduces the peak response of the boring bar system.
文摘Mechanical metamaterials such as auxetic materials have attracted great interest due to their unusual properties that are dictated by their architectures.However,these architected materials usually have low stiffness because of the bending or rotation deformation mechanisms in the microstructures.In this work,a convolutional neural network(CNN)based self-learning multi-objective optimization is performed to design digital composite materials.The CNN models have undergone rigorous training using randomly generated two-phase digital composite materials,along with their corresponding Poisson's ratios and stiffness values.Then the CNN models are used for designing composite material structures with the minimum Poisson's ratio at a given volume fraction constraint.Furthermore,we have designed composite materials with optimized stiffness while exhibiting a desired Poisson's ratio(negative,zero,or positive).The optimized designs have been successfully and efficiently obtained,and their validity has been confirmed through finite element analysis results.This self-learning multi-objective optimization model offers a promising approach for achieving comprehensive multi-objective optimization.
基金supported by the Korea Sport Promotion Foundation。
文摘BACKGROUND Older men are more vulnerable to fatal falls than women,and gait disturbances contribute to the risk of falls.Studies have assessed the association between arterial stiffness and gait dysfunction,but the results have been inconclusive.This study aimed to conduct a cross-sectional analysis to evaluate the association between brachial–ankle pulse wave velocity(baPWV)and gait assessment in older men.METHODS Data from the 2014–2015 Korea Institute of Sport Science Fitness Standards project were used for the analysis.The inclusion criteria were men aged>65 years with gait assessment[the 30-s chair stand test(30s-CST),the timed up and go(TUG)test,the figure-of-8 walk(F8W)test,the 2-min step test(2MST),and the 6-min walk test(6MWT)]and baPWV measurement data.Generalized linear regression analysis was conducted with multiple confounding factor adjustments,including lower extremity isometric strength.RESULTS A total of 291 participants were included in the analysis.The mean age was 71.38±4.40 years.The mean values were as follows:(1)30s-CST,17.48±5.00;(2)TUG test,6.01±1.10 s;(3)F8W test,25.65±4.71 s;(4)2MST,102.40±18.83 per 2 min;and(5)6MWT,500.02±85.65 m.After multivariable adjustment,baPWV was associated with the 6MWT(β=−0.037,95%CI:−0.072–−0.002),TUG test(β=0,95%CI:0.000–0.001),and F8W test(β=0.002,95%CI:0.000–0.004).baPWV was not associated with the 30s-CST and 2MST.CONCLUSIONS The current study showed a statistically significant association between gait assessments and arterial stiffness,independent of lower extremity strength.However,this association was modest.Future prospective studies are needed to elucidate the complex relationship between arterial stiffness and gait dysfunction.
基金The authors would like to acknowledge the financial support provided by the National Natural Science Foundation of China(Grant No.41977240)the Fundamental Research Funds for the Central Universities(Grant No.B200202090).
文摘In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.
基金supported by the Science and Technology Programs of Gansu Province,China(Nos.21JR1RA248,20JR10RA264)the Young Scholars Science Foundation of Lanzhou Jiaotong University,China(Nos.2020039,2020017)the Special Funds for Guiding Local Scientific and Technological Development by the Central Government,China(No.22ZY1QA005)。
文摘In order to provide more insights into the damage propagation composite wind turbine blades(blade)under cyclic fatigue loading,a stiffness degradation model for blade is proposed based on the full-scale fatigue testing of a blade.A novel non-linear fatigue damage accumulation model is proposed using the damage assessment theories of composite laminates for the first time.Then,a stiffness degradation model is established based on the correlation of fatigue damage and residual stiffness of the composite laminates.Finally,a stiffness degradation model for the blade is presented based on the full-scale fatigue testing.The scientific rationale of the proposed stiffness model of blade is verified by using full-scale fatigue test data of blade with a total length of 52.5 m.The results indicate that the proposed stiffness degradation model of the blade agrees well with the fatigue testing results of this blade.This work provides a basis for evaluating the fatigue damage and lifetime of blade under cyclic fatigue loading.
文摘BACKGROUND Intrahepatic cholestasis of pregnancy(ICP)is a rare but severe complication for both the mother and the unborn child.The diagnosis is primarily based on elevated serum levels of bile acids.In a large ICP cohort,we here study in detail liver stiffness(LS)using transient elastography(TE),now widely used to noninvasively screen for liver cirrhosis within minutes.AIM To specifically explore LS in a large cohort of women with ICP compared to a control group with uncomplicated pregnancy.METHODS LS and hepatic steatosis marker controlled attenuation parameter(CAP)were measured in 100 pregnant women with ICP using TE(Fibroscan,Echosens,Paris,France)between 2010 and 2020.In 17 cases,LS could be measured postpartum.450 women before and 38 women after delivery with uncomplicated pregnancy served as control group.Routine laboratory,levels of bile acids and apoptosis marker caspase-cleaved cytokeratin 18 fragment(M30)were also measured.RESULTS Women with ICP had significantly elevated transaminases but normal gammaglutamyl transferase(GGT).Mean LS was significantly increased at 7.3±3.0 kPa compared to the control group at 6.2±2.3 kPa(P<0.0001).Postpartum LS decreased significantly in both groups but was still higher in ICP(5.8±1.7 kPa vs 4.2±0.9 kPa,P<0.0001),respectively.In ICP,LS was highly significantly correlated with levels of bile acids and M30 but not transaminases.No correlation was seen with GGT that even increased significantly after delivery in the ICP group.Bile acids were mostly correlated with the liver apoptosis marker M30,LS and levels of alanine aminotransferase,aspartate aminotransferase,and bilirubin.In multivariate analysis,LS remained the sole parameter that was independently associated with elevated bile acids.CONCLUSION In conclusion,LS is significantly elevated in ICP which is most likely due to toxic bile acid accumulation and hepatocyte apoptosis.In association with conventional laboratory markers,LS provides additional non-invasive information to rapidly identify women at risk for ICP.
文摘Background: Analysis of arterial stiffness (AS) is a good marker of early arterial disease and an important determinant of cardiovascular risk, independent of other traditional cardiovascular risk factors. Carotid-femoral pulse wave velocity (CfPWV) is the gold standard to evaluate arterial stiffness. There is evidence that patients with rheumatoid arthritis (RA) have a higher arterial stiffness than their age-matched healthy counterparts and thus have higher cardiovascular (CV) risk. However, data on arterial stiffness in African rheumatoid arthritis patients is scarce. Objectives: To determine the patterns of arterial stiffness in rheumatoid arthritis patients in a sub-Saharan African setting, using CfPWV and Augmentation index (AIx). Method: We conducted a case-control study, at the Douala general hospital over four months (February to May 2018) on 63 subjects among which 31 RA patients matched for age and sex with 32 healthy subjects. AIx and CfPWV were determined non-invasively by radial pulse wave analysis and carotid femoral wave analysis respectively, using a sphygmocor Atcor device (SphygmoCor, PWV Medical, Sydney, Australia). Results: The mean age of RA patients was 47 ± 14 years with most of them being females (n = 26, 83.9%). CfPWV was significantly higher in RA patients compared to the control group (mean: 8.85 ± 2.1 vs 7.45 ± 1.38;p ≤ 0.01) as well as was AIx (Median: 33 [26 - 43] vs 26 [20 - 31];p = 0.01). RA (OR: 6.105;95% CI: 1.52 - 24.54;p 1.34;95% CI: 1.14 - 5.17;p = 0.05), elevated CRP levels (OR: 4.01;95% CI: 1.16 - 13.68;p = 0.03) and Hypertension (OR: 5.75;95% CI: 1.24 -11.60;p Conclusion: Arterial stiffness, a well-recognized marker of cardiovascular risk is increased among patients suffering from rheumatoid arthritis when compared to a healthy control group.
文摘Truck frames should be designed and fabricated with enough rigidity to avoid excessive deflections. Finite element analysis (FEA) plays an important role in all stages of frame designs. While being accurate, 3D solid element FEA models are built upon frame configuration details which are not feasible in the preliminary design stage, partially because of limited available design data of frames and heavy computation costs. This research develops 1D beam element FEA models for simulating frame structures. In this paper, the CAD model of a truck frame is first created. The solid element FEA analysis, which is adopted as the baseline in this study, is subsequently conducted for the stiffness of the frame, Next, beam element FEA analysis is performed for validating the feasibility of the beam element FEA model by comparing the results from the solid and beam element FEA models. It is found that the beam element FEA model can predict the frame stiffness with acceptable accuracy and reduce the computation cost significantly.
基金supported by the National Science and Technology Major Project,The People’s Republic of China(2018ZX10302204,2014ZX10005001)the National Natural Science Foundation of China(81730109,82274305)。
文摘Background and objective:Liver stiffness measurement(LSM)may effectively correlate to the presence of liver fibrosis,but it is controversial to use for the prediction of clinical outcomes.Therefore,we aimed to evaluate the predictive value of liver stiffness for the regression of liver fibrosis.Methods:In this study,we collected data from a clinical cohort of patients who are received anti-virus therapies for 48 weeks.180 naive chronic hepatitis B(CHB)patients,who received paired LSM and liver biopsy with pre-and post-treatments were analyzed.Two methods(FibroScan and iLivTouch)test LSM.Result:The area under the receiver operating characteristics curve(AUROC)of changing LSM for fibrosis regression is higher in advanced fibrosis patients(F5/6)than in moderate fibrosis patients(F3/4)in both FibroScan(0.719,95%CI,0.590–0.848;P=0.003;vs 0.617,95%CI,0.379–0.856,P=0.282)and iLivTouch(0.707,95%CI,0.567–0.847;P=0.011;vs 0.583,95%CI,0.422–0.744;P=0.377).A higher kappa value was received in advanced stage than in moderate stage both in FibroScan(0.392,P=0.001 vs 0.265,P=0.053)and iLivTouch(0.326,P=0.019 vs 0.030,P=0.833).Cut-off set as 4.10 kPa(sen,69.4%;spe,73.9%)in FibroScan,as 4.25 kPa(sen,56.8%;spe,72.2%)in iLivTouch.Conclusion:The changing LSM can be used for predicting the liver fibrosis regression in advanced stage of CHB patients.
文摘The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, and stability. For very large compressions, the tangent stiffness in the direction of the compression can even become negative, which can be regarded as physical nonsense. So in many cases rubber materials exposed to great compression cannot be analyzed, or the analysis could lead to very poor convergence. Problems with the standard geometric stiffness matrix can even occur with a small strain in the case of plastic yielding, which eventuates even greater practical problems. The authors demonstrate that amore precisional approach would not lead to such strange and theoretically unjustified results. An improved formula that would eliminate the disadvantages mentioned above and leads to higher convergence rate and more robust computations is suggested in this paper. The new formula can be derived from the principle of virtual work using a modified Green-Lagrange strain tensor, or from equilibrium conditions where in the choice of a specific strain measure is not needed for the geometric stiffness derivation (which can also be used for derivation of geometric stiffness of a rigid truss member). The new formula has been verified in practice with many calculations and implemented in the RFEM and SCIA Engineer programs. The advantages of the new formula in comparison with the standard formula are shown using several examples.
