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Crack propagation with different radius local random damage based on peridynamic theory

《结构与土木工程前沿（英文）》 2021年 第15卷 第5期   页码 1238-1248 doi: 10.1007/s11709-021-0695-y

摘要： Drawing from the advantages of Classical Mechanics, the peridynamic theory can clarify the crack propagation mechanism by an integral solution without initially setting the factitious crack and crack path. This study implements the peridynamic theory by subjecting bilateral notch cracked specimens to the conditions of no local damage, small radius local damage, and large radius local damage. Moreover, to study the effects of local stochastic damage with different radii on the crack propagation path and Y-direction displacement, a comparison and contact methodology was adopted, in which the crack propagation paths under uniaxial tension and displacement in the Y-direction were compared and analyzed. This method can be applied to steel structures under similar local random damage conditions.

关键词： peridynamics     stochastic damage     bilateral notch crack    

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Peridynamics versus XFEM: a comparative study for quasi-static crack problems

Jinhai ZHAO, Hesheng TANG, Songtao XUE

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 548-557 doi: 10.1007/s11709-017-0434-6

摘要： Peridynamics (PD) is a nonlocal continuum theory based on integro-differential equations without spatial derivatives. The fracture criterion is implicitly incorporated in the PD theory and fracture is a natural outcome of the simulation. However, capturing of complex mixed-mode crack patterns has been proven to be difficult with PD. On the other hand, the extended finite element method (XFEM) is one of the most popular methods for fracture which allows crack propagation with minimal remeshing. It requires a fracture criterion which is independent of the underlying discretization though a certain refinement is needed in order to obtain suitable results. This article presents a comparative study between XFEM and PD. Therefore, two examples are studied. The first example is crack propagation in a double notched specimen under uniaxial tension with different crack spacings in loading direction. The second example is the specimens with two center cracks. The results show that PD as well as XFEM are well suited to capture this type of behaviour.

关键词： XFEM     peridynamic     bilateral crack     parallel double cracks     nonlocal theory    

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Mechanical responses of pristine and defective hexagonal boron-nitride nanosheets: A molecular dynamics investigation

Mohammad SALAVATI, Arvin MOJAHEDIN, Ali Hossein Nezhad SHIRAZI

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 623-631 doi: 10.1007/s11709-020-0616-5

摘要： In this work we conducted classical molecular dynamics (MD) simulation to investigate the mechanical characteristics and failure mechanism of hexagonal boron-nitride (h-BN) nanosheets. Pristine and defective structure of h-BN nanosheets were considered under the uniaxial tensile loadings at various temperatures. The defective structure contains three types of the most common initial defects in engineering materials that are known as cracks, notches (with various length/size), and point vacancy defects (with a wide range of concentration). MD simulation results demonstrate a high load-bearing capacity of extremely defective (amorphized) h-BN nanosheets. Our results also reveal that the tensile strength decline by increasing the defect content and temperature as well. Our MD results provide a comprehensive and useful vision concerning the mechanical properties of h-BN nanosheets with/without defects, which is very critical for the designing of nanodevices exploiting the exceptional physics of h-BN.

关键词： hexagonal boron-nitride     mechanical properties     crack     notch     point defects     molecular dynamics    

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Chidamide inhibits the NOTCH1-MYC signaling axis in T-cell acute lymphoblastic leukemia

《医学前沿（英文）》 2022年 第16卷 第3期   页码 442-458 doi: 10.1007/s11684-021-0877-y

摘要： T-cell acute lymphoblastic leukemia (T-ALL) is one of the most dangerous hematological malignancies, with high tumor heterogeneity and poor prognosis. More than 60% of T-ALL patients carry NOTCH1 gene mutations, leading to abnormal expression of downstream target genes and aberrant activation of various signaling pathways. We found that chidamide, an HDAC inhibitor, exerts an antitumor effect on T-ALL cell lines and primary cells including an anti-NOTCH1 activity. In particular, chidamide inhibits the NOTCH1-MYC signaling axis by down-regulating the level of the intracellular form of NOTCH1 (NICD1) as well as MYC, partly through their ubiquitination and degradation by the proteasome pathway. We also report here the preliminary results of our clinical trial supporting that a treatment by chidamide reduces minimal residual disease (MRD) in patients and is well tolerated. Our results highlight the effectiveness and safety of chidamide in the treatment of T-ALL patients, including those with NOTCH1 mutations and open the way to a new therapeutic strategy for these patients.

关键词： T-cell acute lymphoblastic leukemia     HDAC inhibitor     chidamide     NOTCH1     MYC     ubiquitination    

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Parametric equations for notch stress concentration factors of rib–deck welds under bending loading

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 595-608 doi: 10.1007/s11709-021-0720-1

摘要： The effective notch stress approach for evaluating the fatigue strength of rib–deck welds requires notch stress concentration factors obtained from complex finite element analysis. To improve the efficiency of the approach, the notch stress concentration factors for three typical fatigue-cracking modes (i.e., root–toe, root–deck, and toe–deck cracking modes) were thoroughly investigated in this study. First, we developed a model for investigating the effective notch stress in rib–deck welds. Then, we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib–deck weld on the notch stress concentration factors. On this basis, the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors. Finally, we employed the proposed formulas in a case study. The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results. The results of the case study demonstrate the feasibility and reliability of the proposed formulas. It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib–deck welds.

关键词： notch stress concentration factor     rib–deck weld     parametric analysis     regression analysis     parametric equation    

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Demand response based congestion management in a mix of pool and bilateral electricity market model

Ashwani KUMAR, Charan SEKHAR

《能源前沿（英文）》 2012年 第6卷 第2期   页码 164-178 doi: 10.1007/s11708-012-0187-9

摘要： The independent system operator (ISO) is a key element in the deregulated structure with one of the responsibilities of transmission congestion management (CM). The ISO opts market based solutions to manage congestion receiving bids from generation companies (GENCOs) as well as distribution companies (DISCOMs) to reschedule their generation and relocate demand. The nodal prices increases during the congestion hours and the demand response to nodal prices will be an effective tool for the control of congestion. In this paper, demand response-based CM has been proposed for a mix of pool and bilateral electricity market model. The linear bid curves have been considered for demand bids to respond to the congestion in the network. The bilateral demand has been obtained with minimum deviations in their preferred schedule. The impact of flexible alternating current transmission system (FACTS) devices viz static var compensator (SVC) and thyristor controlled series compensator (TCSC) has also been considered for demand management during congestion. Multi-line congestion cases have been considered to study the impact on demand response without and with FACTS devices. The proposed approach has been tested on the IEEE 24 bus test system.

关键词： bid function     congestion management (CM)     demand response     pool+bilateral electricity market     static var compensator (SVC)     thyristor controlled series compensator (TCSC)    

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Role of Wnt and Notch signaling in regulating hair cell regeneration in the cochlea

null

《医学前沿（英文）》 2016年 第10卷 第3期   页码 237-249 doi: 10.1007/s11684-016-0464-9

摘要：

Sensory hair cells in the inner ear are responsible for sound recognition. Damage to hair cells in adult mammals causes permanent hearing impairment because these cells cannot regenerate. By contrast, newborn mammals possess limited regenerative capacity because of the active participation of various signaling pathways, including Wnt and Notch signaling. The Wnt and Notch pathways are highly sophisticated and conserved signaling pathways that control multiple cellular events necessary for the formation of sensory hair cells. Both signaling pathways allow resident supporting cells to regenerate hair cells in the neonatal cochlea. In this regard, Wnt and Notch signaling has gained increased research attention in hair cell regeneration. This review presents the current understanding of the Wnt and Notch signaling pathways in the auditory portion of the inner ear and discusses the possibilities of controlling these pathways with the hair cell fate determiner Atoh1 to regulate hair cell regeneration in the mammalian cochlea.

关键词： inner ear     cochlea     hair cell     regeneration     Wnt     Notch     signaling pathways    

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Unidirectional and stage-dependent roles of Notch1 in Wnt-responsive Lgr5

Hui Jiang, Shan Zeng, Wenli Ni, Yan Chen, Wenyan Li

《医学前沿（英文）》 2019年 第13卷 第6期   页码 705-712 doi: 10.1007/s11684-019-0703-y

摘要： Wnt and Notch signaling play crucial roles in the determination of the prosensory domain and in the differentiation of hair cells (HCs) and supporting cells during mouse inner ear development; however, the relationship between the two signaling pathways in the mouse cochlea remains largely unknown. Here, we investigated the interactions between Notch and Wnt signaling on the basis of the bidirectional regulation of Notch1 specifically in Wnt-responsive Lgr5 progenitors during different cochlear development stages. We found that the downregulation of Notch1 in Lgr5 cells from embryonic day (E) 14.5 to E18.5 can drive the quiescent Lgr5 cells to re-enter the cell cycle and differentiate into extra HCs, whereas the upregulation of Notch1 expression did not affect the proliferation or differentiation of otic progenitor cells. No effect was observed on the upregulation or downregulation of Notch1 in Lgr5 cells from E10.5 to E14.5. We concluded that the roles of Notch1 in Wnt-responsive Lgr5 cells are unidirectional and stage dependent and Notch1 serves as a negative regulator for Lgr5 progenitor activation during cochlear differentiation. Our findings improved the understanding of the interactions between Notch and Wnt signaling in cochlear development.

关键词： inner ear     cochlear     Wnt     Notch     Lgr5     auditory system    

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Numerical investigation on the dryout point of annular flow in the upward narrow annuli with bilateral

SU Guanghui, QIU Suizheng, DUAN Feng, XIAO Zejun, HUANG Yanping

《能源前沿（英文）》 2007年 第1卷 第3期   页码 264-272 doi: 10.1007/s11708-007-0037-3

摘要： Based on the fundamental conservation principles—the mass, momentum, and energy conservation equtions of liquid films and the momentum conservation equation of vapor core, a theoretical three-fluid model has been developed to predict the dryout point of upward annular flow in vertical narrow annuli with bilateral heating. The range of the parameters are: pressure from 0.5 to 5.0 MPa; mass flow rate from 30 to 150 kg/(m · s); gap size from 1.2 to 2.0 mm. Through numerically solving the model, the relationships among the parameters of the critical quality (), critical heat flux (), mass flow rate, system pressure, and the ratio of heat flux on the inner wall of the outer tube to that on the outer wall of the inner tube (/) are obtained and analyzed. The predicted results accurately match with the experimental data. For a fixed , will increase with the decreases in the gap size and the tube curvature when the dryout point occurs on the outer wall of the inner tube. However, for a fixed , when the dryout point occurs on the inner wall of the outer tube, the parametric trend is reverse. When the dryout point on the inner and outer walls occurs simultaneously, reaches a peak value, and the ratio of / at this position changes with the gap size and the tube curvature.
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Dynamic crack propagation in plates weakened by inclined cracks: an investigation based on peridynamics

A. SHAFIEI

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 527-535 doi: 10.1007/s11709-018-0450-1

摘要： Peridynamics is a theory in solid mechanics that uses integral equations instead of partial differential equations as governing equations. It can be applied to fracture problems in contrast to the approach of fracture mechanics. In this paper by using peridynamics, the crack path for inclined crack under dynamic loading were investigated. The peridynamics solution for this problem represents the main features of dynamic crack propagation such as crack bifurcation. The problem is solved for various angles and different stress values. In addition, the influence of geometry on inclined crack growth is studied. The results are compared with molecular dynamic solutions that seem to show reasonable agreement in branching position and time.

关键词： peridynamics     inclined crack     dynamic fracture     crack branching    

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Prevention of laryngeal webs through endoscopic keel placement for bilateral vocal cord lesions

null

《医学前沿（英文）》 2018年 第12卷 第3期   页码 301-306 doi: 10.1007/s11684-017-0549-0

摘要：

Transoral microresection for treatment of vocal cord lesions involving the anterior commissure may result in anterior glottic webs. In this study, we retrospectively reviewed 54 patients who underwent microsurgery for bilateral lesions involving the anterior commissure and categorized them into two groups. The keel placement and control groups received endoscopic keel placement and mitomycin C, respectively. During the follow-up of at least 1 year, the laryngeal web formation rate significantly decreased in the keel placement group compared with that in the control group (18.6% versus 54.5%, <0.05). Furthermore, the voice handicap index-10 scores for patients without web formation decreased in both the keel placement and control groups ( <0.0001 and <0.001, respectively). A pseudomembrane covering the vocal cords was detected in 16.3% (7 of 43) cases after keel removal. A total of 100% (7 of 7) of these cases and 2.8% (1 of 36) of the other cases formed laryngeal webs ( <0.0001). Endoscopic keel placement could be an effective method for preventing anterior glottic webs after surgery for bilateral vocal cord diseases involving the anterior commissure. The pseudomembrane observed at the time of keel removal may imply a high risk of web formation.

关键词： glottic stenosis     glottic web     laryngeal keel     silastic sheets     anterior commissure    

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Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

《结构与土木工程前沿（英文）》 2009年 第3卷 第3期   页码 323-329 doi: 10.1007/s11709-009-0041-2

摘要： Changes of the material fracture energy consumption with crack propagation can be described by a crack extension resistance curve, one of the fundamental fracture criteria in crack mechanics. Recently, experimental observation of the fracture behavior in concrete was used to develop a new fracture criterion, the crack extension resistance curve, to analyze crack propagation during the entire concrete fracture process. The variation of the crack extension resistance is mainly associated with the energy consumption in the fracture process zone ahead of the stress-free crack tip. The crack extension resistance is then a function of the softening curve, which is a basic mechanical property in the fracture process zone. The relationship between the softening curve and the crack extension resistance curve is then analyzed based on results of three-point bending beams tests. The results indicate that the characteristic points of the crack extension resistance curve is closely related to the characteristic point on used tension softening curve.

关键词： concrete     fracture process zone     crack extension GR resistance     tension softening curve    

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Regeneration of hair cells in the mammalian vestibular system

null

《医学前沿（英文）》 2016年 第10卷 第2期   页码 143-151 doi: 10.1007/s11684-016-0451-1

摘要：

Hair cells regenerate throughout the lifetime of non-mammalian vertebrates, allowing these animals to recover from hearing and balance deficits. Such regeneration does not occur efficiently in humans and other mammals. Thus, balance deficits become permanent and is a common sensory disorder all over the world. Since Forge and Warchol discovered the limited spontaneous regeneration of vestibular hair cells after gentamicin-induced damage in mature mammals, significant efforts have been exerted to trace the origin of the limited vestibular regeneration in mammals after hair cell loss. Moreover, recently many strategies have been developed to promote the hair cell regeneration and subsequent functional recovery of the vestibular system, including manipulating the Wnt, Notch and Atoh1. This article provides an overview of the recent advances in hair cell regeneration in mammalian vestibular epithelia. Furthermore, this review highlights the current limitations of hair cell regeneration and provides the possible solutions to regenerate functional hair cells and to partially restore vestibular function.

关键词： utricle     hair cell     regeneration     Atoh1     Notch     Wnt    

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Fracture resistance on aggregate bridging crack in concrete

ZHANG Xiufang, XU Shilang

《结构与土木工程前沿（英文）》 2007年 第1卷 第1期   页码 63-70 doi: 10.1007/s11709-007-0006-2

摘要： Fracture toughening exhibited in quasi-brittle materials such as concrete is often mainly related to the action of aggregate bridging, which leads to the presence of a fracture process zone ahead of stress-free cracks in such materials. In this investigation, the fracture resistance induced by aggregate bridging, denoted by GI-bridging, is the primary focus. In order to quantitatively determine it, a general analytical formula is firstly developed, based on the definition of fracture energy by Hillerborg. After this, we further present the calculated procedures of determining this fracture resistance from the recorded load vs. crack opening displacement curve. Then, both numerical simulations and fracture experiments are performed on concrete three-point bending beams. Utilizing the obtained load against crack opening displacement curve, the value of G at any crack extension as well as the change of G with the crack extension is examined. It is found that G will firstly increase with the development of crack and then stay constant once the initial crack tip opening displacement reaches the characteristic crack opening displacement w0. The effects of material strength and specimen depth on this fracture resistance are also investigated. The results reveal that the values of G of different specimens at any crack propagation are strongly associated with the values of fracture energy of specimens. If the values of fracture energy between different specimens are comparable, the differences between G are ignored. Instead, if values of fracture energy are different, the G will be different. This shows that for specimens with different strengths, G will change greatly whereas for specimens that are different in depth, whether GI-bridging exhibits size effect depends on whether the fracture energy of specimens considered in the calculation of G is assumed to be a size-dependent material parameter.
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Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

《机械工程前沿（英文）》 2011年 第6卷 第2期   页码 203-213 doi: 10.1007/s11465-011-0131-4

摘要：

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.

关键词： rotor dynamics     slant crack     stability     torsional excitation     open and close    

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标题 作者 时间 类型 操作

Crack propagation with different radius local random damage based on peridynamic theory

期刊论文

Peridynamics versus XFEM: a comparative study for quasi-static crack problems

Jinhai ZHAO, Hesheng TANG, Songtao XUE

期刊论文

Mechanical responses of pristine and defective hexagonal boron-nitride nanosheets: A molecular dynamics investigation

Mohammad SALAVATI, Arvin MOJAHEDIN, Ali Hossein Nezhad SHIRAZI

期刊论文

Chidamide inhibits the NOTCH1-MYC signaling axis in T-cell acute lymphoblastic leukemia

期刊论文

Parametric equations for notch stress concentration factors of rib–deck welds under bending loading

期刊论文

Demand response based congestion management in a mix of pool and bilateral electricity market model

Ashwani KUMAR, Charan SEKHAR

期刊论文

Role of Wnt and Notch signaling in regulating hair cell regeneration in the cochlea

null

期刊论文

Unidirectional and stage-dependent roles of Notch1 in Wnt-responsive Lgr5

Hui Jiang, Shan Zeng, Wenli Ni, Yan Chen, Wenyan Li

期刊论文

Numerical investigation on the dryout point of annular flow in the upward narrow annuli with bilateral

SU Guanghui, QIU Suizheng, DUAN Feng, XIAO Zejun, HUANG Yanping

期刊论文

Dynamic crack propagation in plates weakened by inclined cracks: an investigation based on peridynamics

A. SHAFIEI

期刊论文

Prevention of laryngeal webs through endoscopic keel placement for bilateral vocal cord lesions

null

期刊论文

Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

期刊论文

Regeneration of hair cells in the mammalian vestibular system

null

期刊论文

Fracture resistance on aggregate bridging crack in concrete

ZHANG Xiufang, XU Shilang

期刊论文

Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

期刊论文