bluuebunny/crossref_metadata_2025_split huggingface dataset:
A fixed grid algorithm for simulating the propagation of a shallow hydraulic fracture with a fluid lag
Authors: Gordeliy E. , Detournay E. 
Published: April 2010

AbstractThis paper describes a fixed grid algorithm to simulate the propagation of shallow hydraulic fractures, under plane strain or axisymmetric conditions. Because of the low stress environment that exists near a free surface, these fractures are generally characterized by a fluid front that lags behind the fracture edge. The simulation of shallow hydraulic fractures requires therefore the tracking of two distinct fronts. The proposed algorithm, which traces its roots to the one described by Zhang et al. (Int. J. Numer. Anal. Methods Geomech. 2005; 29:1317–1340), advances the fracture by a constant step and computes the corresponding time required to reach this new fracture configuration as well as the matching location of the fluid front within the fixed grid. For any trial value of the time and of the front position, a non‐linear system of algebraic equations is solved using either Newton's method or a fixed point iteration scheme, with preconditioning. The non‐linear system is formulated by combining an implicit finite volume method for solving the lubrication equation and the displacement discontinuity method for solving the elasticity equation. The critical difference with the algorithm of Zhang et al. lays in the approach chosen to update the fluid front position. Rather than using a filling fraction method, the new algorithm adopts a velocity treatment of the fluid‐front location that is akin to a one‐dimensional implementation of a level set algorithm for front tracking. This conversion from a fluid volume to a fluid velocity‐based approach to update the front position increases the degree of implicitness of the algorithm, which is responsible for a significant reduction of the CPU time by about two orders of magnitude. Copyright © 2010 John Wiley & Sons, Ltd.
Cauchy problem of three‐dimensional critical slip surfaces of slopes
Authors: Zheng Hong , Sun Guan Hua , Li Chun Guang 
Published: April 2010

AbstractUsing the continuum‐based finite element approach in conjunction with the strength reduction technique, one can easily find out the factor of safety of a slope with rather high precision, but will encounter some obstacles in the accurate location of the corresponding three‐dimensional critical slip surface (CSS). On the basis of the Mohr–Coulomb failure criterion and the stress field in the limit equilibrium state of the slope, it is deduced that the three‐dimensional CSS is the solution of the Cauchy problem of a quasi‐linear partial differential equation (PDE) of first order. By means of the method of characteristics for the problem, the three‐dimensional CSS that may take any shape can be determined without the specification of its geometry. Copyright © 2010 John Wiley & Sons, Ltd.
Coupling of BEM with a large displacement and rotation algorithm
Authors: Asadollahi Pooyan , Tonon Fulvio 
Published: April 2010

AbstractIn stability analysis of rock blocks, the deformability of the blocks can conveniently be simulated using the boundary element method (BEM). However, all boundary conditions are given as stresses. Thus, the displacement solution is not unique. In this paper, an algorithm is proposed to remove rigid body motions in the solution of the boundary form of Somigliana identity discretized by the direct BEM formulation. The algorithm is applied to the calculation of the normal stiffness of rock blocks and coupled with BS3D, large displacement and rotation algorithm for the general stability of rock blocks. Copyright © 2010 John Wiley & Sons, Ltd.
A simulation study of microstructure evolution inside the shear band in biaxial compression test
Authors: Mahmood Zafar , Iwashita Kazuyoshi 
Published: April 2010

AbstractWe study the development of microstructure inside the shear band in granular media consisting of elliptical‐shaped particles. Plane strain biaxial compression test was simulated using two‐dimensional distinct element method. The generation of large voids and concentration of excessive particle rotation inside a shear band are found in a quite similar manner to those observed in natural soils. Evolution of the microstructure inside and outside the shear band is studied. The magnitude and direction of particle rotation inside the shear band is influenced by orientation of long axes of elliptical particles. Because of such particle rotations inside the shear band, the preferred alignment of particles becomes horizontal in the residual state, which results in a more anisotropic contact normal distribution oriented along the major principal stress axis. Copyright © 2010 John Wiley & Sons, Ltd.
A non‐coaxial and unbalanced plastic flow rule for geomaterials and its application to the shear band orientation prediction
Authors: Wang G. S. , Kong L. W. 
Published: April 2010

AbstractIn this paper, the non‐coaxial relation between the principal plastic strain increments and the principal stresses, which results from the internal friction in geomaterials, is analyzed, and the phenomenon of the unbalanced development of plastic flow in two conjugate directions is discussed. A non‐coaxial, unbalanced plastic flow model for Coulomb frictional materials is developed and used to determine the orientation of shear band in geomaterials. It is shown that the unbalanced indexrof plastic flow has important effect on the orientation of the shear band, and the orientation determined by the conventional plastic flow theory is only a special case of the proposed model whenr=0. This result soundly explains the reason that the geomaterials with the same internal friction angle and dilatancy angle can have very different shear band orientations. In addition, the difference between the intrinsic and apparent dilatancy angles is analyzed, and it is emphasized that the dilatancy angle commonly used in practice is indeed the apparent dilatancy angle. Copyright © 2010 John Wiley & Sons, Ltd.
Application of extended Kalman filter to back analysis of the natural stress state accounting for measuring uncertainties
Authors: Yang Cheng Xiang , Wu Yong Hong , Hon Tung , Feng Xia‐Ting 
Published: April 2010

AbstractIn this work, we present a numerical procedure for determining the nature stress state in the rock mass around a tunnel. A finite element method is applied for analyzing the direct problems of tunneling during the back analysis of parameter estimation, in which a no‐tension elastic–plastic model is used to simulate the elastic–tensile and elastic–plastic‐tensile failure states which often occur in the cases of underground excavation in heavily jointed rock masses. By considering the natural stress state as random parameters of the tunneling system, the Kalman filter method is employed for feedback analysis to modify the parameter values in a statistical context, which uses the prior information in the process of estimation and employs a set of displacements obtained from field measurements. To verify the effectiveness of the proposed method of inverse analysis, the developed numerical procedure is applied to a synthetic example of deep tunnels in yielding rock masses. The relative importance of the a priori and updating information is investigated, as is the importance of their uncertainty. The results show great potential of the proposed approach. Copyright © 2010 John Wiley & Sons, Ltd.
Elastoplastic modelling of diffuse instability response of geomaterials
Authors: Wan R. G. , Pinheiro M. , Guo P. J. 
Published: April 2010

AbstractIn this paper, we study material instabilities in geomaterials through an elastoplastic constitutive model endowed with appropriate attributes, such as stress, density and fabric dependencies. The analyses reveal the possibility of having diffuse instability, bifurcation and loss of uniqueness within the plastic limit surface. The resulting domain of bifurcation encompasses the intrinsic effects of stress–strain history, direction of loading, type of loading and fabric. The computations start at a material point level and are later on extended to an initial boundary value setting where diffuse failure of a three‐dimensional sand specimen with a random distribution of void ratio is examined. We restrict our simulations to the study of a q‐constant laboratory experimental test under different sets of control parameters. Diffuse failure is also revealed in a slope analysis under water infiltration following similar loading paths as in the q‐constant test. The analysis shows common material instability features observed in the above test. Copyright © 2010 John Wiley & Sons, Ltd.
A new method to calculate the equivalent Mohr–Coulomb friction angle for cohesive and frictional materials
Authors: Jiang Hua , Wang Xiaowo 
Published: April 2010

AbstractIn this note, a new method to calculate the equivalent Mohr–Coulomb friction angle ϕ′mc for cohesive and frictional materials is presented. This method makes a transformation from the failure surface for cohesive materials to the failure surface for cohesionless materials and obtains ϕ′mc as well as the principal stress ratio σ′1/σ′3 for cohesionless materials in the transformed space first, then obtains ϕ′mc for cohesive materials by linking σ′1/σ′3 in the transformed space and in the original space. In the application example, an analytical solution of the invariant stress ratio L is derived from the failure function in the transformed space. The influence of the intermediate effective principal stress σ′2 is also demonstrated using the already calculated ϕ′mc. Copyright © 2010 John Wiley & Sons, Ltd.
Seismic wave propagation analysis in vertical arrays at Kashiwazaki–Kariwa nuclear power plant site by using modified normalized input–output minimization (mod‐NIOM) method
Authors: Shrestha Santa Man , Kawakami Hideji 
Published: April 2010

AbstractA new approach on numerical modeling of wave propagation is introduced and is used to analyze the effect of earthquake magnitudes (ground motion amplitudes) on wave propagation. In this method, the sum of the maximum amplitudes of the first output model at time 0 s and rest of the output models at different times are normalized to unity. Considering this as a constraint, the sum of the weighted‐squared Fourier amplitudes is minimized by using the Lagrange multiplier method. The proposed method can reveal the relationship of actual time histories by showing simple clear peaks. This method is used to analyze the time histories of various earthquake events at different vertical array sites of the Kashiwazaki–Kariwa nuclear power plant of Tokyo electric power company (TEPCO). The wave arrival times obtained from this method and down‐hole measurements are compared. The results show increase in the arrival times at surface layer when the magnitude of earthquake is large. The results reveal that the amplitudes of small magnitude earthquakes at depths are small and are largely amplified at surface, whereas in case of large magnitude earthquakes, the amplitudes are large at depths and are deamplified at surface reflecting the effects of the strain‐dependent soil properties that result in non‐linear site response to strong shaking. The results also show that the reflected peak amplitudes are higher for small magnitude earthquakes than for large magnitude earthquakes. Copyright © 2010 John Wiley & Sons, Ltd.
Investigation of model uncertainty for block stability analysis
Authors: Bagheri Mehdi , Stille Håkan 
Published: April 2010

AbstractThe application of probabilistic design, such as FORM, is expanding rapidly in the design of geotechnical structures. The analytical solution proposed by Crawford and Bray for analyzing block stability can be used as a performance function to carry out probabilistic design. The solution benefits from considering both clamping forces and joint stiffness. However, imperfect assumptions and simplifications in the solution generate model uncertainties. The amount of model uncertainty must be considered in order to assess a reliable design. The purpose of this paper is to identify when the analytical solution is applicable and quantify the model uncertainty of the solution. The amount of model uncertainty for the analytical solution has been assessed for different conditions. The results show that at a shallow depth with a low value of in situ stress ratio (horizontal stress/vertical stress), the analytical solution predicts that the block is stable whereas DEM shows that the block is unstable. The results of the analyses indicate that in cases with low stress ratio, cases with high anisotropy of joint stiffness or the case of a semiapical angle close to the friction angle, the accuracy of the analytical solution is low. Neglecting key parameters, such as the absolute value of joint shear and normal stiffness, vertical in situ stress and its influence on joint relaxation generate model uncertainty in the analytical solution. The analyses show that by having more information about the key parameters, the model uncertainty factor could be identified more precisely. Copyright © 2010 John Wiley & Sons, Ltd.
A fully integrated noise robust strategy for the identification of constitutive laws from digital images
Authors: Réthoré Julien 
Published: April 2010

AbstractConstitutive parameter identification has been greatly improved by the achievement of full‐field measurements. In this context, noise sensitivity has been shown to be of great importance. It is crucial to incorporate noise sensitivity minimization in the design of robust identification procedures. In this paper, we investigate noise sensitivity reduction techniques for constitutive parameter identification based on Finite Element Model Updating. After examining the existing strategies, we propose a single step algorithm based on a mixed optical/mechanical cost function. The key point of this novel procedure is that no boundary conditions are needed. A first example on a real case illustrates the advantages of the proposed methodology in terms of noise sensitivity. A second example shows its capabilities to identify a non‐linear consitutive law. Copyright © 2010 John Wiley & Sons, Ltd.
A partition of unity finite element method for obtaining elastic properties of continua with embedded thin fibres
Authors: Radtke F. K. F. , Simone A. , Sluys L. J. 
Published: April 2010

AbstractThe numerical analysis of large numbers of arbitrarily distributed discrete thin fibres embedded in a continuum is a computationally demanding process. In this contribution, we propose an approach based on the partition of unity property of finite element shape functions that can handle discrete thin fibres in a continuum matrix without meshing them. This is made possible by a special enrichment function that represents the action of each individual fibre on the matrix. Our approach allows to model fibre‐reinforced materials considering matrix, fibres and interfaces between matrix and fibres individually, each with its own elastic constitutive law. Copyright © 2010 John Wiley & Sons, Ltd.
The skeleton of a medieval male with multiple traumatic fractures from Piazza della Signoria, Florence, Italy
Authors: Boccone S. , Chilleri F. , Pacciani E. , Cecchi J. Moggi , Salvini M. 
Published: April 2010

AbstractWe report on the palaeopathology of a medieval skeleton of a young adult male with multiple traumatic fractures found in 1989 in Piazza della Signoria, Florence, Italy. The skeleton presents ante mortem fractures of the right ulna and femur, and left tibia and fibula. We reconstruct the dynamics of the accident based on the location and type of fractures. Then we discuss the impact of this severe trauma on the subject's living conditions based on articular and enthesic modifications of the skeleton. Copyright © 2010 John Wiley & Sons, Ltd.
Application of capillary electrophoresis in anion binding studies: complexation and separation of nitrate and nitrite by an azacryptand
Authors: Wu Hao , Saeed Musabbir A. , Hwang Huey‐Min , Zhao Shulin , Liu Yi‐Ming , Hossain Md. Alamgir 
Published: April 2010

AbstractCapillary electrophoresis (CE) was employed to study the complexation of an azacryptand with nitrate and nitrite in aqueous solution. CE separation of a mixture of nitrate and nitrite with 10 mM acetate buffer (pH 3.3) showed two peaks at the retention times of 2.8 and 3.1 min for nitrate and nitrite, respectively. However, when the ligand (2 mM) was added to the running buffer, the peaks emerged in the reverse order and at shorter retention times of 2.7 and 2.5 min for nitrate and nitrite, respectively. The longer retention time for nitrate compared with nitrite indicates a stronger complex formation between the ligand and nitrate, which reduces the migration speed of nitrate as compared with the less strongly bound nitrite. The 1H NMR titrations of L with these two anions at the pH 3.3 gave the binding constants (log K), 3.75 and 4.23, for nitrite and nitrate, respectively which were consistent with the results obtained from the CE method. Copyright © 2010 John Wiley & Sons, Ltd.
Kinetics of the gas‐phase homogeneous unimolecular elimination of selected ethyl esters of 2‐oxo‐carboxylic acids
Authors: Reyes Andreina , Domínguez Rosa M. , Tosta Maria , Herize Armando , Chuchani Gabriel 
Published: April 2010

AbstractThe gas‐phase elimination kinetics of selected ethyl esters of 2‐oxo‐carboxylic acid have been studied over the temperature range of 270–415 °C and pressures of 37–114 Torr. The reactions are homogeneous, unimolecular, and follow a first‐order rate law in a seasoned static reaction vessel, with an added free radical suppressor toluene. The observed overall and partial rate coefficients are expressed by the following Arrhenius equations:

Ethyl oxalyl chloride
log koverall (s−1) = (13.22 ± 0.45) − (179.4 ± 4.9) kJ mol−1 (2.303 RT)−1
Ethyl piperidineglyoxylate
log k(CO2) (s−1) = (12.00 ± 0.30) −  (191.2 ± 3.9) kJ mol−1 (2.303 RT)−1
log k(CO) (s−1) = (12.60 ± 0.09) − (210.7 ± 1.2) kJ mol−1 (2.303 RT)−1
log kt(overall) (s−1) = (12.22 ± 0.26) − (193.4 ± 3.4) kJ mol−1 (2.303 RT)−1
Ethyl benzoyl formate
log k(CO2) (s−1) = (12.89 ± 0.72) − (203.8 ± 9.0) kJ mol−1 (2.303 RT)−1
log k(CO) (s−1) = (13.39 ± 0.31) − (213.3 ± 3.9) kJ mol−1 (2.303 RT)−1
log kt(overall) (s−1) = (13.24 ± 0.60) − (205.8 ± 7.6) kJ mol−1 (2.303 RT)−1
The kinetic and thermodynamic parameters of these reactions, together with those reported in the literature, lead to consider three different mechanistic pathways of elimination. Copyright © 2010 John Wiley & Sons, Ltd.
The crystal structure of ribonuclease A in complex with thymidine‐3′‐monophosphate provides further insight into ligand binding
Authors: Doucet Nicolas , Jayasundera Thusitha B. , Simonović Miljan , Loria J. Patrick 
Published: April 2010

AbstractThymidine‐3′‐monophosphate (3′‐TMP) is a competitive inhibitor analogue of the 3′‐CMP and 3′‐UMP natural product inhibitors of bovine pancreatic ribonuclease A (RNase A). Isothermal titration calorimetry experiments show that 3′‐TMP binds the enzyme with a dissociation constant (Kd) of 15 μM making it one of the strongest binding members of the five natural bases found in nucleic acids (A, C, G, T, and U). To further investigate the molecular properties of this potent natural affinity, we have determined the crystal structure of bovine pancreatic RNase A in complex with 3′‐TMP at 1.55 Å resolution and we have performed NMR binding experiments with 3′‐CMP and 3′‐TMP. Our results show that binding of 3′‐TMP is very similar to other natural and non‐natural pyrimidine ligands, demonstrating that single nucleotide affinity is independent of the presence or absence of a 2′‐hydroxyl on the ribose moiety of pyrimidines and suggesting that the pyrimidine binding subsite of RNase A is not a significant contributor of inhibitor discrimination. Accumulating evidence suggests that very subtle structural, chemical, and potentially motional variations contribute to ligand discrimination in this enzyme. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Predicting order of conformational changes during protein conformational transitions using an interpolated elastic network model
Authors: Tekpinar Mustafa , Zheng Wenjun 
Published: April 2010

AbstractThe decryption of sequence of structural events during protein conformational transitions is essential to a detailed understanding of molecular functions ofvarious biological nanomachines. Coarse‐grained models have proven useful by allowing highly efficient simulations of protein conformational dynamics. By combining two coarse‐grained elastic network models constructed based on the beginning and end conformations of a transition, we have developed an interpolated elastic network model to generate a transition pathway between the two protein conformations. For validation, we have predicted the order of local and global conformational changes during key ATP‐driven transitions in three important biological nanomachines (myosin, F1 ATPase and chaperonin GroEL). We have found that the local conformational change associated with the closing of active site precedes the global conformational change leading to mechanical motions. Our finding is in good agreement with the distribution of intermediate experimental structures, and it supports the importance of local motions at active site to drive or gate various conformational transitions underlying the workings of a diverse range of biological nanomachines. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Preparation of ZnO thin films by MO‐CVD method using bis(acetylacetonato) zinc(II) anhydrate fiber
Authors: Seki Shigeyuki , Onodera Hisashi , Sekizawa Takumi , Sakuma Mio , Haga Koichi , Seki Yoshiyuki , Sawada Yutaka , Shishido Toetsu 
Published: April 2010

AbstractThe MO‐CVD method as a deposition process corresponding to the mass production of the high‐quality ZnO film that can be used as an active layer in the thin film transistor is paid to attention. Bis(acetylacetonato) zinc(II) (Zn(acac)2) which has chemical stability and low toxicity is promising as the inexpensive raw material for CVD. The problem includes (1) pollution with water in process by character to easily take water of crystallization, and (2) the supply of the gas‐phase raw material by sublimation should be not able to be controlled easily because it is a fine particle. In this study, Zn(acac)2 anhydrate fiber was prepared from Zn(acac)2 monohydrate powder by the sublimation process. Melting point of this fiber was almost same (∼134 °C) as the monohydrate powder in N2 atmosphere. ZnO film was deposited on r‐face sapphire substrate by MO‐CVD process using Zn(acac)2 anhydrate fiber, successfully. RMS of the film flatness was 0.48 nm. This film had resistivity of 4.6 × 10–1 Ω·cm, carrier electron density of 9.1 × 1017 cm–3 and Hall mobility of 15 cm2·V–1·s–1. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of Al2O3 incorporation on device performance of HfO2 gate dielectric AlGaN/GaN MIS‐HFETs
Authors: Tian Feng , Chor Eng Fong 
Published: April 2010

AbstractWe report the effects of Al2O3 interfacial layer incorporation on the dc performance of AlGaN/GaN metal‐insulator‐semiconductor field effect transistors (MIS‐HFETs) using HfO2 as the gate dielectric and surface passivation layer. The HfO2/Al2O3 bi‐layer MIS‐HFETs exhibit a larger maximum drain current by ∼8.5%, larger gate voltage swing by ∼6.3%, and smaller gate leakage by 4∼5 times, compared to the HfO2 single layer MIS‐HFETs at room temperature. Furthermore, the HfO2/Al2O3 transistors are observed to have better thermal stability than the HfO2 transistors, and the estimated lifetime (in hour) of the former is longer than that of the latter by over an order of magnitude from 25 to 150 °C (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)