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Revisiting the normal stiffness–permeability relations for shale fractures under true triaxial stress 认领 引用 被引量：2
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作者 Fudong Li Derek Elsworth +6 位作者 Xia-Ting Feng Tianyu Chen Jun Zhao Yingchun Li Jianyu Zhang Qiong Wu Guanglei Cui 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2025年第8期5001-5017,共17页
Understanding the relationship between normal stiffness and permeability in rock fractures under high and true-triaxial in situ stress conditions is critical to assess hydro-mechanical coupling in the Earth's crus... Understanding the relationship between normal stiffness and permeability in rock fractures under high and true-triaxial in situ stress conditions is critical to assess hydro-mechanical coupling in the Earth's crust.Previous data on stiffness–permeability relations are measured under uniaxial stress states as well as under normal stress.However,many projects involve faulted formations with complex three-dimensional(3D)stress states or significant changes to the original stress state.We rectified this by following the permeability evolution using a true-triaxial stress-permeability apparatus as well as independently applying a spectrum of triaxial stresses from low to high.The relationship between permeability and fracture normal stiffness was quantified using constraints based on the principle of virtual work.The impacts of fracture-lateral and fracture-normal stresses on permeability and normal stiffness evolution were measured.It was found that permeability decreases with increasing fracture-lateral and fracture-normal stresses as a result of Poisson confinement,independent of the orientation of the fracture relative to the stresses.The lateral stresses dominated the evolution of normal stiffness at lower normal stresses(σ3=10 MPa)and played a supplementary role at higher normal stresses(σ3>10 MPa).Moreover,correlations between the evolution of permeability and normal stiffness were extended beyond the low-stiffness,high-permeability region to the high-stiffness,low-permeability region under high fracture-lateral stresses(10–80 MPa)with fracture-normal stress(10–50 MPa)conditions.Again,high lateral stresses further confined the fracture and therefore reduced permeability and increased normal stiffness,which exceeded the previous reported stiffness under no lateral stress conditions.This process enabled us to identify a fundamental change in the flow regime from multi-channel to isolated channelized flow.These results provide important characterizations of fracture permeability in the deep crust,including recovery from deep shale-gas reservoirs. 展开更多
关键词 Fracture permeability Deformation Fracture normal stiffness True-triaxial stress Principle of virtual work
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Changes in liver and spleen stiffness after transjugular intrahepatic portosystemic shunt and their relationship with prognosis 认领 引用
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作者 Xiao-Fang Liu Xiao-Chun Huang +4 位作者 Qian-Jun Ye Li-Jing Yuan Gui-Fang Gao Jin-Yu Li Dui-Ping Feng 《World Journal of Gastrointestinal Surgery》 SCIE 2025年第8期338-349,共12页
BACKGROUND The impact of transjugular intrahepatic portosystemic shunt(TIPS)on liver and spleen stiffness remains unclear,as does the association between preoperative liver and spleen stiffness and prognosis following... BACKGROUND The impact of transjugular intrahepatic portosystemic shunt(TIPS)on liver and spleen stiffness remains unclear,as does the association between preoperative liver and spleen stiffness and prognosis following TIPS.AIM To investigate changes in liver and spleen stiffness after TIPS and examines the relationship between these parameters and the prognosis of post-TIPS patients.METHODS A total of 76 patients with liver cirrhosis and portal hypertension who underwent TIPS were included.Liver and spleen stiffness was assessed using the sound touch quantify(STQ)value,determined via point shear wave elastography in ultrasound imaging.Cox regression analysis was employed to evaluate the relationship between liver and spleen stiffness and cumulative survival in TIPS patients.RESULTS The liver STQ value demonstrated a marginally decreasing trend over time(P=0.052),while the spleen STQ value showed a significantly decreasing trend(P=0.025).Spleen STQ was positively correlated with portal pressure gradient(PPG)levels(rs=0.327,P=0.025).Cox regression analysis indicated that older age[hazard ratio(HR)=1.063,95%CI:0.997-1.133,P=0.060]and a higher liver STQ value(HR=1.051,95%CI:1.009-1.095,P=0.018)were associated with an increased mortality risk after TIPS.No significant correlation was found between liver or spleen stiffness and overt hepatic encephalopathy post-TIPS.The liver STQ value[area under the receiver operating characteristic curve(AUC)=0.724(95%CI:0.563-0.884)]showed superior predictive performance compared to the Child-Pugh score[AUC=0.699(95%CI:0.529-0.870)]and was comparable to the model for end-stage liver disease score[AUC=0.746(95%CI:0.591-0.902)].CONCLUSION Following TIPS,spleen stiffness exhibited a more pronounced change than liver stiffness and was positively associated with PPG.Preoperative liver stiffness serves as a prognostic indicator for survival in patients undergoing TIPS. 展开更多
关键词 Liver and spleen stiffness Sound touch quantify Portal pressure gradient Transjugular intrahepatic portosystemic shunt Prognosis
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PROPERTY DEGRADATION OF ANISOTROPIC COMPOSITELAMINATES WITH MATRIX CRACKING(Ⅰ)──CONSTITUTIVE RELATION DEVELOPING FOR (θ_m/90_n)_s CRACKED LAMINATES BY STIFFNESS PARTITION 认领 引用 被引量：1
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作者 华玉 王兴国 郦正能 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1998年第3期279-287,共9页
The study on property degradation of damaged composite laminates is extendedto anisotropic laminates with matrix cracking. In (I) of the paper, an idea of 'stiffnesspatition' is proposed to deal with the puzzl... The study on property degradation of damaged composite laminates is extendedto anisotropic laminates with matrix cracking. In (I) of the paper, an idea of 'stiffnesspatition' is proposed to deal with the puzzle that the in-plane normal response iscoupled with the shear response of the laminates. For (θm/90n.), laminates containingtransversely cracked layers under general in-plane loading, the constitutive relationsare derived and the effective stiffnesses are expressed as the function of crack density. 展开更多
关键词 composite laminate anisotropy damage constitutive relation,stiffness partition
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Relationship between arterial stiffness and cognitive function in outpatients with dementia and mild cognitive impairment compared with community residents without dementia 认领 引用
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作者 Ai Hirasawa Kumiko Nagai +4 位作者 Taiki Miyazawa Hitomi Koshiba Mami Tamada Shigeki Shibata Koichi Kozaki 《Journal of Geriatric Cardiology》 SCIE CAS CSCD 2022年第8期594-602,共9页
BACKGROUND It is unclear whether the dementia patients with Alzheimer’s disease(AD)and vascular dementia(VaD)and mixed dementia(MIX,including AD and VaD)would have more developed arterial stiffness as compared with l... BACKGROUND It is unclear whether the dementia patients with Alzheimer’s disease(AD)and vascular dementia(VaD)and mixed dementia(MIX,including AD and VaD)would have more developed arterial stiffness as compared with local residents without dementia.The aim of this study was to assess arterial stiffness and cognitive function in different types of dementia pa-tients[AD,VaD,MIX and mild cognitive impairment(MCI)]and community residents without dementia.METHODS This was a single-center,cross-sectional observational study.We studied a cohort of 600 elderly outpatients with a complaint of memory loss,who were divided into four groups(AD,VaD,MIX and MCI).In addition,they were compared with 55 age-matched local residents without dementia(Controls).We assessed arterial stiffness by brachial-ankle pulse wave velocity(baPWV)and the global cognitive function by the Mini-Mental State Examination(MMSE).RESULTS The baPWV was higher in AD,VaD and MIX than in MCI and in Controls(P<0.05).The baPWV was higher in MCI than in Controls(P=0.021),while MMSE were compatible between them(P=0.119).The higher baPWV predicted the presence of AD,VaD,MIX and MCI with the odds ratio of 6.46,8.74,6.16 and 6.19,respectively.In contrast,there were no difference in baPWV among three different types of dementia(P=0.191).The linear relationship between baPWV and MMSE was observed in the elderly with MMSE≥23(R=0.452,P=0.033),while it was not in dementia patients(MMSE<23).CONCLUSIONS The findings suggest that MCI and dementia patients have stiffer arteries as compared with age-matched local residents,although global cognitive function may be comparable between MCI and the local residents. 展开更多
关键词 arterial impairment stiffness
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CONSTITUTIVE RELATION AND STIFFNESS DEGRADATION OF CRACKED ANISOTROPIC COMPOSITE LAMINATES(II)─DETERMINATION OF RESOLVED STIFFNESS AND INVESTIGATION OF STIFFNESS DEGRADATION FOR CRACKED LAMINATES 认领 引用
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作者 王兴国 华玉 郦正能 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1998年第6期555-561,共7页
The study on properly degradation of damaged,.onlj,osile laminates is extendedto anisotropic laminates with matrix cracking. In (II) of the paper, a solution forpartitioned stiffness is given to complete the constitut... The study on properly degradation of damaged,.onlj,osile laminates is extendedto anisotropic laminates with matrix cracking. In (II) of the paper, a solution forpartitioned stiffness is given to complete the constitutive relations developed in (I) Thestiffness degradation in cracked laminates is calculated and the results arediscussed. 展开更多
关键词 composite laminate anisotropy damage stiffness partition,property degradation
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Analysis of the Relationship Between the Meshing Stiffness and the Inherent Characteristics of Planetary Gear Transmission Mechanism 认领 引用 被引量：1
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作者 Qiang Zhang Rong He +1 位作者 Yudong Zhang Jin Xu 《Journal of Beijing Institute of Technology》 EI CAS 2019年第4期811-818,共8页
According to the relationship between the meshing stiffness and the inherent characteristics of a seven-speed three-row coupled planetary transmission mechanism,a equivalent concentrated mass dynamics model of the pla... According to the relationship between the meshing stiffness and the inherent characteristics of a seven-speed three-row coupled planetary transmission mechanism,a equivalent concentrated mass dynamics model of the planetary transmission mechanism is established.The natural frequency of the planetary gear train at a specific gear is calculated and extracted.The relationship between the meshing stiffness of each row and the natural frequency of the system is analyzed,thereby avoiding possible resonance behavior by changing the meshing stiffness.These results show that the meshing stiffness,in its range of possible values,has nearly no effect on the low order natural frequency(<4.000.Hz),and that the time-varying meshing stiffness mainly affects the natural frequencies of the higher-and middle-order parts of the system.Changes of the natural frequencies lead to the change of the system's corresponding vibration mode,which will change the vibration situation of the system. 展开更多
关键词 planetary transmission dynamics meshing stiffness inherent characteristics
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Relationship of rolling bearing stiffness with diameter of roller 认领 引用
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作者 GUO Maolin +3 位作者 WANG Gang ZHANG Rui 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2002年第3期316-317,共2页
The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relatio... The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relationship of roller bearing stiffness with roller diameter was studied using Hz contacting theory. It is concluded that conclusion in experience formula is only approximate result of data processing under special conditions, and the relation between stiffness of roller bearing and roller diameter must be taken into consideration while designing or selecting roller bearings. 展开更多
关键词 stiffness roller diameter roller bearing
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Seminar on 70 Years of China-Africa and China-Arab Diplomatic Relations Held in Beijing 认领 引用
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《China International Studies》 2026年第3期F0002-F0002,共1页
On June 17,the Seminar on 70 Years of China-Africa and China-Arab Diplomatic Relations:Jointly Building a Community with a Shared Future was held in Beijing.China's Vice Foreign Minister Miao Deyu attended and del... On June 17,the Seminar on 70 Years of China-Africa and China-Arab Diplomatic Relations:Jointly Building a Community with a Shared Future was held in Beijing.China's Vice Foreign Minister Miao Deyu attended and delivered an address at the opening ceremony of the seminar.President of the China Institute of International Studies(CIIS)Chen Bo hosted the opening ceremony. 展开更多
关键词 years diplomatic relations China Arab relations seminar community shared future China Africa relations
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Assessment of Arterial Stiffness Index in Hypertensive Patients in Relation to Their Treatment Status Attending a Tertiary Care Center in South India 认领 引用
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作者 Shourya Kola Melvin George +4 位作者 Suresh Kumar Srinivasamurthy Sandhiya Selvarajan Kadhiravan Tamilarasu Rathinam Palamalai Swaminathan Adithan Chandrasekaran 《Pharmacology & Pharmacy》 2014年第4期413-418,共6页
Objectives: To assess the arterial stiffness index (ASI) and pulse wave velocity (PWV) in patients with hypertension and to compare with age matched healthy controls;to assess and compare the ASI and PWV in relation t... Objectives: To assess the arterial stiffness index (ASI) and pulse wave velocity (PWV) in patients with hypertension and to compare with age matched healthy controls;to assess and compare the ASI and PWV in relation to the treatment status. Methods: The study was observational-cross sectional. Group one included chronic hypertensive patients on regular treatment for more than 2 months;group two included newly diagnosed hypertensive patients and group three had age matched healthy controls with normal blood pressure. The hypertensives subjects with other comormid conditions such as renal disease, diabetes were excluded from the study. The study was approved by the Institute Ethics Committee. The subjects were interviewed and explained the purpose of the study. All subjects gave written informed consent. The noninvasive periscope device was used to measure PWV, ASI and pulse pressure. Results: PWV, ASI and pulse pressure were statistically higher in hypertensive patients when compared to controls. Further, carotid-femoral PWV was correlated with mean arterial pressure in hypertensive subjects and was found to be statistically significant. Conclusion: PWV, ASI and pulse pressure are significantly higher in chronic and newly diagnosed non-diabetic hypertensives as compared to controls irrespective of their treatment status. 展开更多
关键词 Pulse Wave Velocity Arterial Stiffness Index Hypertension Antihypertensives
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Water Swelling-induced Stiffness Enhancement of Polymer Hydrogels 认领 引用 被引量：1
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作者 Yi Yu Wei Zhou +1 位作者 Tao Chen Wei Lu 《Chinese Journal of Polymer Science》 SCIE EI CAS CSCD 2026年第6期1749-1759,I0012,共11页
Polymer hydrogels with variable stiffness demonstrate immense practical application value,particularly when utilizing water as a trigger medium,which significantly expands their prospects in soft robotics,bioelectroni... Polymer hydrogels with variable stiffness demonstrate immense practical application value,particularly when utilizing water as a trigger medium,which significantly expands their prospects in soft robotics,bioelectronics,and artificial muscles.However,existing water-induced stiffening hydrogel rely on ionic liquids and inorganic salts,posing leakage risks during prolonged use.Here,we proposed a strategy for mechanically strengthening hydrogel through water-induced phase separation.By designing a polymer matrix featuring hydrophilic oligomeric ethylene glycol methacrylate(OEGMA)and hydrophobic methyl methacrylate(MMA)moieties,this poly[methyl methacrylate-co-poly(ethylene glycol)methacrylate][P(MMAx-co-OEGMAy)]hydrogel exhibited reversible stiffness switching across four orders of magnitude(from 1.88×10-2MPa to201.63 MPa)upon water stimulation.This abrupt stiffness enhancement stemmed from strong hydrogen bonding between water molecules and hydrophilic OEGMA segments,facilitating spontaneous aggregation and phase separation of hydrophobic MMA segments.The resulting hydrophobic MMA domains formed dynamic physical crosslinking points,thereby enhancing the hydrogel's stiffness.Furthermore,the hydrogel exhibited a time-dependent,multi-stage stiffness enhancement during water swelling.As proof of concept,it was employed as a shape-memory component to explore its application in the controllable programming of multi-stage complex shapes,offering novel design insights for developing environmentally friendly,high-mechanical-performance smart hydrogel materials. 展开更多
关键词 Polymer hydrogel Water-induced phase separation Stiffness enhancement Hydrogen bonding Shape memory
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An improved nonlinear vibration absorber with adjustable stiffness and rotating mass 认领 引用 被引量：1
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作者 Ke-Fan Xu Zhuo-Da Zhou +1 位作者 Ye-Wei Zhang Li-Qun Chen 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第3期146-157,共12页
A novel approach for vibration reduction is proposed by improving an adjustable stiffness nonlinear vibration absorber(NVA)with a rotating mass system.The adjustable stiffness is realized by a buckling Euler beam and ... A novel approach for vibration reduction is proposed by improving an adjustable stiffness nonlinear vibration absorber(NVA)with a rotating mass system.The adjustable stiffness is realized by a buckling Euler beam and an active control system.The rotating mass is consisted of a primary mass block and two rotating mass blocks.The dynamic responses are analyzed based on nonlinear output frequency response functions.The results indicate that,in comparison to the adjustable stiffness NVA,the enhanced NVA can efficiently suppress the resonance in steady state response.Moreover,the new vibration absorber can improve the robustness of the adjustable stiffness NVA.The mass ratio and the angular velocity are two key parameters of the new vibration absorber with optimal values for effective vibration reduction.The new vibration absorber introduces new possibilities for incorporating the adjustable stiffness and the rotating mass system in the design of NVA. 展开更多
关键词 Nonlinear vibration absorber Adjustable stiffness Rotating mass Vibration reduction
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On a broadband vibration isolator with tunable stiffness:from quasi-zero-stiffness to zero-stiffness behavior 认领 引用 被引量：2
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作者 N.A.SAEED Lei HOU +3 位作者 Haiming YI A.A.SHUKUR S.M.ALAMRY S.M.EL-SHOURBAGY 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2026年第2期255-282,共28页
A novel vibration isolation system designed for superior performance in low-frequency environments is proposed in this work.The isolator is based on a unique hexagonal arrangement of linear springs,allowing for an adj... A novel vibration isolation system designed for superior performance in low-frequency environments is proposed in this work.The isolator is based on a unique hexagonal arrangement of linear springs,allowing for an adjustable geometric configuration via the initial inclination angle.Based on the principle of Lagrangian mechanics,the equation of motion governing the structural dynamics is rigorously derived.The system is modeled as a strongly nonlinear single-degree-of-freedom dynamical system,loaded with a normalized payload and subject to harmonic base excitation.To analyze the steady-state response,the harmonic balance method is employed,providing accurate predictions of the payload's vibration amplitude and displacement transmissibility as functions of both the base excitation amplitude and frequency.The analysis reveals a direct relationship between the isolator's geometric and stiffness parameters and its load-bearing capacity,leading to the identification of three distinct operational regimes.Depending on the unloaded initial inclination angle,the equivalent stiffness ratio,and the payload design configuration,the system can exhibit one of three vibration isolation modes:(i)the quasizero stiffness(QZS)isolation mode,(ii)the zero linear stiffness with controllable nonlinear stiffness,and(iii)the full-band perfect zero stiffness.The vibration isolation performance of the proposed structure is thoroughly discussed for all three oscillation modes in terms of frequency response curves,displacement transmissibility,and time-domain responses.The key novel finding is that this structure can operate as a full-band,high-performance vibration isolator when the initial inclination angle is designed to be a right angle,enabling full isolation of the maximum possible payload.Moreover,the analytical results and numerical simulations demonstrate that the isolator's displacement transmissibility T with the unit dB tends to-∞as the air-damping coefficient approaches zero,enabling ideal vibration isolation across the entire excitation frequency range.These analytical insights are validated through comprehensive numerical simulations,which show excellent agreement with the theoretical predictions. 展开更多
关键词 nonlinear vibration isolation quasi-zero stiffness(QZS)structure full-band vibration isolator harmonic balance method displacement transmissibility
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Toward a Constructive China-U.S.Relationship of Strategic Stability 认领 引用
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作者 HE WEIWEN 《China Today》 2026年第6期19-21,共3页
Now,constructiveness prevails as the vision of the constructive China-U.S.relationship of strategic stability has been agreed upon by the two leaders.U.S.President Donald Trump’s China visit from May 13-15,2026 was a... Now,constructiveness prevails as the vision of the constructive China-U.S.relationship of strategic stability has been agreed upon by the two leaders.U.S.President Donald Trump’s China visit from May 13-15,2026 was a resounding success and marks a milestone in the world’s most important bilateral relationship.As Chinese President Xi Jinping said,2026 will be a“historic,landmark year”that opens up a new chapter in China-U.S.relations. 展开更多
关键词 historic year milestone China U S relations strategic stability constructive relationship bilateral relationship
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Active vibration isolation based on absolute-relative dynamic stiffness control via multi-sensor information fusion 认领 引用
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作者 Zhiwei Huang Jiulin Wu +4 位作者 Fuxiang Zhang Rui Zhou Hu Li Xuedong Chen Wei Jiang 《ENGINEERING Mechanical Engineering》 SCIE CAS CSCD 2026年第2期129-152,共24页
The requirements for isolating outer vibration and suppressing inner disturbances are increasingly stringent and even approaching extreme limits in integrated circuit manufacturing,precision measurement,scientific exp... The requirements for isolating outer vibration and suppressing inner disturbances are increasingly stringent and even approaching extreme limits in integrated circuit manufacturing,precision measurement,scientific experiments,etc.In comparison with passive isolation,active control methods can significantly enhance vibration isolation performance.However,different control strategies are mainly effective in different frequency domains,and performance may deteriorate in some frequency domains due to sensor noises.Active vibration isolation based on absolute-relative dynamic stiffness control via multi-sensor information fusion is proposed in this paper.This method can substantially improve vibration attenuation capability and position stability performances in broad bandwidth,with a particular focus on improving the resonance peak suppression capability in the ultra-low frequency domain.First,the effects of different control strategies on vibration isolation in different frequency domains are analyzed,and the hybrid control strategy is proposed by using both absolute relative signal feedback.Considering the noise characteristics of absolute velocity sensors and relative displacement sensors,different filters are accordingly adopted to improve vibration isolation performance.A one-dimensional experimental platform is established to conduct vibration control experiments under different configurations.The results demonstrate that vibration isolation performance across a wide frequency range can be significantly improved,and the proposed method further proves effective for micro-vibration systems.Typically,transmissibility can be reduced to as low as -30 dB at 1 Hz and -48 dB at 2 Hz,with guarantee of less than -50 dB within 10-50 Hz.Additionally,compliance results show 10-40 dB performance improvements across the broad frequency range(0.1-100 Hz)compared with the passive system. 展开更多
关键词 active vibration control dynamic stiffness multi-sensor information fusion absolute velocity feedback relative displacement feedback
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Design of a nonlinear stiffness metastructure isolator for powered wearable devices vibration isolation 认领 引用
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作者 Shikai Jin Wenjie Ge +2 位作者 Bin Liu Zhuo Wang Ning Chen 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第3期86-103,共18页
The vibration control performance of powered wearable devices(PWDs)directly affects the health and comfort of the wearer.Effective vibration isolation technology has become a fundamental aspect of next-generation wear... The vibration control performance of powered wearable devices(PWDs)directly affects the health and comfort of the wearer.Effective vibration isolation technology has become a fundamental aspect of next-generation wearable device design.This study proposes a highly integrated nonlinear stiffness metastructure vibration isolator design for PWDs to address vibration isolation requirements in such scenarios.In this paper,we systematically analyze and experimentally verify the static characteristics of the proposed metastructure vibration isolator through numerical analysis,analytical model and experimental methods,and deeply discuss its dynamic transmissibility characteristics.Among them,we analytically derive and calculate the cantilever beam oscillator of the metastructure vibration isolator and verify the numerical results.Utilizing the mode superposition method,we examine the variations in vibration transmissibility under different operating conditions and geometric parameters.Experimental results are consistent with the numerical calculation results and demonstrate that the isolator exhibits excellent vibration attenuation within the vibration isolation frequency range of 53-61 Hz,achieving a minimum vibration transmissibility of−38 dB.The metastructure vibration isolation system presented in this study successfully achieves the anticipated vibration suppression performance,offering a novel approach to vibration isolation design for PWDs. 展开更多
关键词 Powered wearable devices Nonlinear stiffness Vibration isolator Metastructure
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Analytical solution for longitudinal seismic response of variable stiffness tunnel with isolation layers under shear waves 认领 引用
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作者 LIU Xiang YANG Jiao-jiao +3 位作者 LI Kui-chen LU Tong JIANG An-nan FANG Qian 《Journal of Central South University》 SCIE EI CAS CSCD 2026年第6期2844-2867,共24页
Seismic isolation design typically emphasizes transverse responses of tunnels,with comparatively limited research on longitudinal isolation responses.Previous analytical solutions for isolation response are inapplicab... Seismic isolation design typically emphasizes transverse responses of tunnels,with comparatively limited research on longitudinal isolation responses.Previous analytical solutions for isolation response are inapplicable to variable stiffness tunnels.To address research gaps,analytical solutions for longitudinal seismic responses of variable stiffness tunnels with isolation layers are proposed.The solution can be applied to engineering practice.The mechanical model of isolation layers is developed using the Kelvin model.The variable stiffness tunnel is simplified as two semi-infinite beams embedded in homogeneous and isotropic soil layers.Governing equations are solved using integral transformations and continuity conditions.Analytical expressions are obtained by introducing displacement phase angles to simulate traveling wave effects.The proposed analytical solutions are validated through comparisons with results from existing literature and verified using numerical simulations.Parametric sensitivity analyses are conducted to investigate effects of tunnels with and without an isolation layer,isolation layer thickness and elastic modulus,tunnel stiffness ratio,and wavelength and amplitude of shear waves on seismic responses of variable stiffness tunnels.Changes in stiffness have a more significant effect on internal forces than displacements.Additionally,isolation layer's thickness and elastic modulus can be optimized through our method to balance structural performance and economic efficiency. 展开更多
关键词 isolation layer variable stiffness tunnel analytical solution seismic response shear waves
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Stiffness evaluation and experimental test of a novel redundantly actuated parallel machining robot 认领 引用
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作者 Hanliang Fang Jian Wang +2 位作者 Shuyi Ge Fufu Yang Jun Zhang 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2026年第1期413-422,共10页
Parallel machining robot is a new type of robotized equipment for high-efficiency machining structural com-ponents with complex geometries.Terminal rigidity is of great importance index for such type of equipment,whic... Parallel machining robot is a new type of robotized equipment for high-efficiency machining structural com-ponents with complex geometries.Terminal rigidity is of great importance index for such type of equipment,which affects their load capacity and working accuracy.Before a parallel machining robot can be used for heavy-load and high-efficiency machining,its terminal rigidity should be evaluated systematically.The present study is to quantitatively reveal the stiffness properties of a previously invented Z4 redundantly actuated parallel ma-chining robot(RAPMR).For this purpose,two critical issues,i.e.,stiffness modelling and index construction,are clarified to carry out stiffness evaluation of the Z4 RAPMR.Firstly,drawing on the screw theory,a semi-analytic stiffness model of the proposed RAPMR is established at a component level.Secondly,a set of virtual work-based stiffness indices is constructed to evaluate the terminal rigidity of parallel robots.Those indices have a consistent physical unit in describing linear and angular terminal rigidity.With these indices,the local and the global stiffness performance of the Z4 RAPMR are predicted.Thirdly,a laboratory prototype of the proposed RAPMR is fabricated.And the experimental test is performed to verify the correctness of the established stiffness model.The present work is expected to provide fundamental information for further light-weight design and rigidity enhancement. 展开更多
关键词 Parallel machining robot Redundantly actuated Terminal rigidity Stiffness model Experimental test
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Impact of biochar particle size and content on small strain stiffness characteristics of amended expansive clay 认领 引用
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作者 GAO Zhiao KONG Lingwei +4 位作者 WANG Yong QIN Hui SHANG Zhaowei LIN Huanwen ZHOU Yuan 《Journal of Mountain Science》 SCIE CSCD 2026年第7期3459-3476,共18页
Biochar-modified clay has garnered growing interest in geotechnical engineering,yet existing research has predominantly focused on swelling-shrinkage behavior,strength,and hydraulic conductivity,with comparatively lit... Biochar-modified clay has garnered growing interest in geotechnical engineering,yet existing research has predominantly focused on swelling-shrinkage behavior,strength,and hydraulic conductivity,with comparatively little attention given to stiffness evolution.This study systematically investigates the effects of biochar particle size(<0.075mm,0.075-0.425 mm,and 0.425-2 mm)and mass content(0%,5%,10%,and 15%)on the small-strain stiffness characteristics of amended expansive clay under varying effective consolidation stresses.Microstructural changes were examined using scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).Results indicate that finer biochar particles markedly enhance initial stiffness but also accelerate its degradation with strain,whereas coarser particles attenuate stiffness reduction more slowly.Increasing biochar content generally promotes more brittle behavior.A modified Hardin-Drnevich model accurately captures the maximum shear modulus and its decay behavior across all biochar contents,with prediction errors within 15%.A logarithmic relationship between dimensionless confining pressure and reference shear strain reveals that higher confining pressures mitigate the influence of biochar content on normalized stiffness attenuation.Microstructural analyses show that fine biochar particles fill interaggregate pores,leading to a pronounced stiffening effect,while medium and coarse particles bond with soil particles through surface adsorption,enhancing stiffness via interparticle adhesion.These findings offer practical guidance for sustainable soil improvement strategies in mountain and slope environments,where stiffness-dependent deformation is critical. 展开更多
关键词 Biochar particle size Biochar content Expansive clay Small strain stiffness Microstructure
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Effect of percussive massage treatment and static stretching on muscle tone,stiffness,and strength recovery after exercise-induced muscle fatigue:A randomized controlled study 认领 引用
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作者 Gangrui Chen Zhongke Gu +2 位作者 Dongling Xin Yuxuan Qi Jiansong Dai 《Sports Medicine and Health Science》 CAS CSCD 2026年第5期524-530,共7页
The aim of this study was to compare the effects of percussive massage treatment and static stretching on muscle tone,stiffness,and strength recovery following exercise fatigue.Sixty subjects were randomly divided int... The aim of this study was to compare the effects of percussive massage treatment and static stretching on muscle tone,stiffness,and strength recovery following exercise fatigue.Sixty subjects were randomly divided into three groups:a control group(CG,n=20),a static stretching group(SSG,n=20),and a percussive massage treatment group(PMTG,n=20).Following exercise-induced muscle fatigue,interventions were applied,including supine rest,static stretching,and percussive massage treatment.Muscle tone,stiffness,and muscle strength indicators were assessed at five time points:before the exercise(Pre-exercise),immediately after exercise(Post-exercise),immediately after therapy intervention(Post-0),24 hours(h)after therapy intervention(Post-24 h),and 48 h after therapy intervention(Post-48 h).Results:At Post-0,muscle tone and stiffness in both the control group and static stretching group were significantly higher than Pre-exercise,while in the percussive massage treatment group,there were no statistically significant differences compared to Pre-exercise.At Post-48 h,peak torque in the control group was significantly lower than Pre-exercise.In contrast,the percussive massage treatment group and static stretching group showed no significant differences at Post-48 h compared to Pre-exercise.These findings indicated that percussive massage therapy is immediately effective in mitigating muscle tone and stiffness after exercise fatigue,whereas static stretching and percussive massage therapy facilitate the recovery of muscle strength within 48 h. 展开更多
关键词 Percussive massage therapy Static stretching Muscle tone and stiffness Muscle strength
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Liver stiffness at baseline as a marker of hepatocellular carcinoma in cirrhosis:A matched analysis 认领 引用
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作者 Varun Mehta Manjeet Kumar Goyal +5 位作者 Yogesh Kumar Gupta Abhinav Gupta Manisha Khubber Tanisha Sehgal Prabhav Mehta Omesh Goyal 《World Journal of Gastrointestinal Pathophysiology》 2026年第2期28-38,共11页
BACKGROUND Early hepatocellular carcinoma(HCC)detection in cirrhosis remains suboptimal despite semi-annual ultrasound and alpha-fetoprotein surveillance.Advanced fibrosis is a central driver of hepatocarcinogenesis,a... BACKGROUND Early hepatocellular carcinoma(HCC)detection in cirrhosis remains suboptimal despite semi-annual ultrasound and alpha-fetoprotein surveillance.Advanced fibrosis is a central driver of hepatocarcinogenesis,and liver stiffness measurement(LSM)is a non-invasive measure of liver stiffness that may be associated with HCC risk.AIM To evaluate whether LSM by transient elastography(TE)is associated with the presence of HCC among patients with established cirrhosis.METHODS A retrospective,matched case-control study at a tertiary liver center including adults with cirrhosis and a valid TE(≥10 valid acquisitions,interquartile range60%)was conducted.Cirrhotic patients with diagnosed HCC per standard guidelines were frequency matched for age,sex,etiology,and Child-Pugh class with controls(cirrhotic patients without HCC).Multivariable logistic regression tested the association between LSM and HCC.Discrimination and cut-off points were assessed using receiver operating characteristic(ROC)analysis and Youden’s index.RESULTS A total of 262 patients(133 with HCC;129 controls)were enrolled.Median LSM was higher in the HCC cohort than in controls(31.7 kPa vs 22.6 kPa;P<0.001).Multivariate regression analysis revealed that only LSM was significantly associated with HCC(adjusted odds ratio 1.09;95%CI:1.05-1.13;P=0.0001).A cut-off of≥47 kPa had excellent discriminatory power(area under the ROC curve:0.88;95%CI:0.84-0.93).CONCLUSION A liver stiffness threshold of approximately 47 kPa may serve as a marker associated with risk of HCC,justifying intensified screening in high-risk cirrhosis;prospective validation,integration with multivariable risk models,and cost-effectiveness analyses remain essential. 展开更多
关键词 Hepatocellular carcinoma Liver cirrhosis Liver fibrosis Liver stiffness Elastography Liver stiffness measurement Hepatocellular carcinoma Cirrhosis Risk stratification Portal hypertension
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