Discontinuous Conditions Research Articles

A thermodynamically consistent plastic-damage framework for localized failure in quasi-brittle solids: Material model and strain localization analysis

Aiming for the modeling of localized failure in quasi-brittle solids, this paper addresses a thermodynamically consistent plastic-damage framework and the corresponding strain localization analysis. A unified elastoplastic damage model is first presented based on two alternative kinematic decompositions assuming infinitesimal deformations, with the evolution laws of involved internal variables characterized by a dissipative flow tensor. For the strong (or regularized) discontinuity to form in such inelastic quasi-brittle solids and to evolve eventually into a fully softened one, a novel strain localization analysis is then suggested. A kinematic constraint more demanding than the classical discontinuous bifurcation condition is derived by accounting for the traction continuity and the loading/unloading states consistent with the kinematics of a strong (or regularized) discontinuity. More specifically, the strain jumps characterized by Maxwell’s kinematic condition have to be completely inelastic (energy dissipative). Reproduction of this kinematics implies vanishing of the aforesaid dissipative flow tensorial components in the directions orthogonal to the discontinuity orientation. This property allows naturally developing a localized plastic-damage model for the discontinuity (band), with its orientation and the traction-based failure criterion consistently determined a posteriori from the given stress-based counterpart. The general results are then particularized to the 2D conditions of plane stress and plane strain. It is found that in the case of plane stress, strain localization into a strong (or regularized) discontinuity can occur at the onset of strain softening. Contrariwise, owing to an extra kinematic constraint, in the condition of plane strain some continuous inelastic deformations and substantial re-orientation of principal strain directions in general have to take place in the softening regime prior to strain localization. The classical Rankine, Mohr–Coulomb, von Mises (J2) and Drucker–Prager criteria are analyzed as illustrative examples. In particular, both the closed-form solutions for the discontinuity angles validated by numerical simulations and the corresponding traction-based failure criteria are obtained.

SOLUTION OF HEAT CONDUCTION PROBLEM WITH DISCONTINUOUS BOUNDARY CONDITIONS IN NONHOMOGENOUS MOVING CYLINDER USING MAPLE

T his paper presents a heat conduction problem with discontinuous boundary conditions in nonhomogeneous moving entire cylinder, which moves on the axis oz with any movement law z = S(t). The temperature field is determined in the cylindrical coordinates system linked with motionless cylinder as a system in a single movement. Using the method inversion of the unit function �(t − S 1 (z)), method a sequence of integral transformations like Fourier transform with respect to z, Hankel transform with respect to r, Bessel functions theory,general integral transforms theory, a solution in the form of the series is obtained. And in order to illustrate theoretical results in this paper,we wrote special programming in Maple program and for a special cases, where numerical solutions were presented with explained graphics and discussed.

Comparing Nuclear Power Trajectories in Germany and the UK: From 'Regimes' to 'Democracies' in Sociotechnical Transitions and Discontinuities

This paper focuses on arguably the single most striking contrast in contemporary major energy politics in Europe (and even the developed world as a whole): the starkly differing civil nuclear policies of Germany and the UK. Germany is seeking entirely to phase out nuclear power by 2022. Yet the UK advocates a ‘nuclear renaissance’, promoting the most ambitious new nuclear construction programme in Western Europe.Here,this paper poses a simple yet quite fundamental question: what are the particular divergent conditions most strongly implicated in the contrasting developments in these two countries. With nuclear playing such an iconic role in historical discussions over technological continuity and transformation, answering this may assist in wider understandings of sociotechnical incumbency and discontinuity in the burgeoning field of‘sustainability transitions’. To this end, an ‘abductive’ approach is taken: deploying nine potentially relevant criteria for understanding the different directions pursued in Germany and the UK. Together constituted by 30 parameters spanning literatures related to socio-technical regimes in general as well as nuclear technology in particular, the criteria are divided into those that are ‘internal’ and ‘external’ to the ‘focal regime configuration’ of nuclear power and associated ‘challenger technologies’ like renewables. It is ‘internal’ criteria that are emphasised in conventional sociotechnical regime theory, with ‘external’ criteria relatively less well explored. Asking under each criterion whether attempted discontinuation of nuclear power would be more likely in Germany or the UK, a clear picture emerges. ‘Internal’ criteria suggest attempted nuclear discontinuation should be more likely in the UK than in Germany– the reverse of what is occurring. ‘External’ criteria are more aligned with observed dynamics –especially those relating to military nuclear commitments and broader ‘qualities of democracy’. Despite many differences of framing concerning exactly what constitutes ‘democracy’, a rich political science literature on this point is unanimous in characterising Germany more positively than the UK. Although based only on a single case,a potentially important question is nonetheless raised as to whether sociotechnical regime theory might usefully give greater attention to the general importance of various aspects of democracy in constituting conditions for significant technological discontinuities and transformations. If so, the policy implications are significant. A number of important areas are identified for future research, including the roles of diverse understandings and specific aspects of democracy and the particular relevance of military nuclear commitments– whose under-discussion in civil nuclear policy literatures raises its own questions of democratic accountability.

Analysis of the resonant LCL circuit operation: the case of discontinuous current

The article is focused on the analysis of the LCL resonant circuit, which operates under discontinuous input current condition. This condition leads to the LCL topology variability phenomenon what drastically changes Inverter-LCL system properties. The LCL topology variability phenomenon is precisely described. The analytical analysis presents formulae that express VSI-LCL converter features. The theoretical results are compared with laboratory tests. The concept of Controlled Variable Frequency Resonant Converter is presented and illustrated by simulation tests. The principle of CVFRC operation is based on the LCL topology variability phenomenon.

Scattering in quantum mechanics under quaternionic Dirac delta potential

In this paper, the Schrödinger equation for quaternionic quantum mechanics with a Dirac delta potential has been investigated. The derivative discontinuity condition for the quaternionic wave function has been derived and the boundary conditions for the quaternionic wave function have been applied. Probability current densities for different regions of the problem have been determined along with reflection and transmission coefficients.

Joint Analysis to Evaluate Geological Over-break in Excavation of Surge Chamber Cavern

The geological over-break is a failure beyond any designed line of excavation due to geological condition as discontinuity condition (wedge) and or stress field in the rock mass surrounding the excavation. In this study, the geological over-break occurred during excavation were analysed based on joint properties. The evaluation of geological over-break on the SCC done by studying the joint properties include joint position to the cavern orientation, in situ stresses, and type of joint sets and analysis using Dips v6 and Unwedge v.3 software (Rocscience,2014). The result shown that the inter-section zone of crossed by 2-3 joint sets has the biggest potential to fail as geological over-break. The risk geological over-break happened were due to late supporting and ineffective placement of systematic rock bolt.

About a Problem for Loaded Parabolic-Hyperbolic Type Equation with Fractional Derivatives

An existence and uniqueness of solution of local boundary value problem with discontinuous matching condition for the loaded parabolic-hyperbolic equation involving the Caputo fractional derivative and Riemann-Liouville integrals have been investigated. The uniqueness of solution is proved by the method of integral energy and the existence is proved by the method of integral equations. Let us note that, from this problem, the same problem follows with continuous gluing conditions (atλ=1); thus an existence theorem and uniqueness theorem will be correct and on this case.

Smart Carbon Fiber Bicycle Seat Post with Light and Sensor Integration

The development of high-performance sports equipment is nowadays focused on lightweight structure designs with integrated functions. Even in cycling an increasing number of manufacturers prefer to use fiber reinforced plastics (FRP) in their frames and further bicycle parts. During the manufacturing of these FRP-components it is possible to integrate flat and flexible electronics and sensors such as stitched strain gauges into semi-finished reinforcement textiles.Seat posts made of aluminum with integrated Light Emitting Didoes (LED) for taillight already exist, but the LEDs must be applied subsequent to the manufacturing process, thus damaging the structure to some degree. The new innovative seat post presented here is made of carbon fiber reinforced plastic (CFRP) and contains LED lights as well as sensors for ambient light illuminance and acceleration, which are integrated into the laminate structure during the manufacturing process. In that way a highly functional smart lightweight seat post with fully integrated taillight can be realized. The seat post can be designed with several layers of braided carbon textiles, which can drape around the single LED lights with a minimum influence on the mechanical properties and resulting in a high-quality carbon surface.Due to the integrated sensors, the seat post will detect the motion of the bike and the illuminance of the ambient light to activate the taillight when necessary. The thresholds for acceleration and illuminance can be programmed also using a timer function, so that the lighting stays constant even in discontinuous lighting conditions (for example due to traffic lights at night) but will turn on when necessary and stay off in a daytime ride. A prototype with all integrated sensors and electronics could successfully put into operation.The main innovation and advantage of the new smart and lightweight seat post is the automated activation of the taillight without intervention of the cyclist. This guarantees maximum safety and comfort especially while biking through tunnels or underpasses. A second advantage is the nearly unaffected performance because of minimum additional weight as well as no aerodynamic disadvantages resulting from external lighting, which allows the use of the new seat post in high-performance bicycle disciplines in training and competition.

Rock bolt supporting factor: rock bolting capability of rock mass

Rock mass classification has played a crucial role in underground construction and mining projects in the past fifty years, especially the Rock Mass Rating (RMR) and Rock Tunneling Quality Index (Q) systems, which have been applied in many cases. The parameters of discontinuity conditions in the RMR system, along with the related ratings, were used to develop a new equation in order to introduce an intrinsic quality of a given rock mass, namely, rock bolt supporting factor (RSF). The RSF was used to develop a mathematical theory of the rock bolt supporting mechanism as a new principle in explaining rock bolting effects. Finally, using the parameters of the discontinuities in the Q-system, the QRSF is defined to present the capability of a given rock mass to be reinforced by rock bolting. The RSF leads to more reliable judgment of rock bolting capability of a given rock mass than the QRSF since it uses five parameters of discontinuity conditions while the QRSF uses only two parameters.

Comparison between two models of absorption of matter waves by a thin time-dependent barrier

We report a quantitative, analytical and numerical, comparison between two models of the interaction of a non-relativistic quantum particle with a thin time-dependent absorbing barrier. The first model represents the barrier by a set of time-dependent discontinuous matching conditions, which are closely related to Kottler boundary conditions used in stationary wave optics as a mathematical basis for Kirchhoff diffraction theory. The second model mimics the absorbing barrier with an off-diagonal $\delta$-potential with a time-dependent amplitude. We show that the two models of absorption agree in their predictions in a semiclassical regime -- the regime readily accessible in modern experiments with ultracold atoms.

Evolution of Joint Roughness Degradation from Cyclic Loading and Its Effect on the Elastic Wave Velocity

The application of stress to the rock joint has a significant impact on morphological and mechanical properties of the joint. In particular, the evolution of the joint condition is dramatic on the surface of the weathered rock whose material integrity is altered in a manner similar to the rock joint behavior from weathering effects (Resende et al. 2010). As indicated in Kabeya and Legge (1997), a significant change in the weathered rock joint surface can be induced by the modification of grain properties of the joint surface. The grain size distribution has been found to be strongly correlated with the shear behavior and the joint roughness coefficient (JRC). The open joint or gouge dominates in weathered joints of the rock mass structure, thereby providing access for weathering agents to increase the failure likelihood from a slickenside (Wooet al. 2010).This granular disintegration leads to surface flakes to transform the joint aperture into a wider opening. In the rock mass rating (RMR) system, the geomechanic classification method for rock masses is associated with the roughness of the rock joint surface as the discontinuity condition (Hoek 2007). Conventionally, the roughness of a rock joint surface is rated and quantified in term of the JRC, which ranges from 0 to 20 (Barton and Choubey 1977). However, the validity of techniques and the accuracy of measurement methods for identifying and classifying rock joint surfaces are generally questioned because of the subjectivity of JRC results. The undulation and unevenness of a rock joint surface are recognized by its peak-to-valley height (Hotar and Novotny 2005) to classify the rock joint surface profile. In particular, Mohd-Nordin et al. (2014) applied the JRC to naturally fractured rock surfaces using the scan line technique through the implementation of the peak-to-valley height. In this regard, the maximum peak-to-valley height (Pmax) can be used as a meaningful quantitative indicator of the degree of roughness of a rock joint surface. Previous studies have examined the propagation of elastic waves across multiple jointed rock masses by considering joint surface conditions (Mohd-Nordin et al. 2014; Huang et al. 2014a; Cha et al. 2009). One of the main findings is that the roughness and unevenness of a replicated natural rock joint surface have significant effects on the propagation of elastic waves. However, changes in & Ki-Il Song ksong@inha.ac.kr

Short-time heat diffusion in compact domains with discontinuous transmission boundary conditions

We consider a heat problem with discontinuous diffusion coefficients and discontinuous transmission boundary conditions with a resistance coefficient. For all bounded (ϵ, δ)-domains Ω ⊂ ℝn with a d-set boundary (for instance, a self-similar fractal), we find the first term of the small-time asymptotic expansion of the heat content in the complement of Ω, and also the second-order term in the case of a regular boundary. The asymptotic expansion is different for the cases of finite and infinite resistance of the boundary. The derived formulas relate the heat content to the volume of the interior Minkowski sausage and present a mathematical justification to the de Gennes' approach. The accuracy of the analytical results is illustrated by solving the heat problem on prefractal domains by a finite elements method.

Nonlinear localization, passive wave arrest and traveling breathers in two-dimensional granular networks with discontinuous lateral boundary conditions

We study nonlinear pulse propagation, breather formation and nonlinear localization leading to passive wave arrest in an impulsively forced two-dimensional granular network composed of two geometrically coupled ordered granular chains of spherical (heavy) beads with interstitial spherical (light) intruders, possessing discontinuous lateral boundary conditions. A striking feature of this network is that it completely lacks any linear acoustics, and, hence, it sustains zero speed of sound (as defined in classical acoustics). We show that this system possesses strongly nonlinear dynamics and acoustics that depend on the stiffness and mass ratios between the heavy beads and the light intruders. Moreover, polydispersity and nonlinearity within this granular network lead to complex phenomena, such as pulse propagation, motion localization, and formation of propagation and attenuation zones. In particular, depending on the design of this network the applied impulsive energy is either axially transmitted to its far field, or it is heavily scattered and localized close to the point of its generation by means of low-to-high energy transfers in its intrinsic dynamics. Such passive motion localization phenomena are due to nonlinear on-site potentials caused by the discontinuous lateral boundary conditions of the network, as well as to strongly nonlinear interactions between the heavy beads and the interstitial intruders, and, to the authors’ knowledge, are reported for the first time in the field of granular networks. These results demonstrate the high tunability of the nonlinear response of this system to energy and material properties.

Boundary conditions for gas flow problems from anisotropic scattering kernels

The paper presents an interface model for gas flowing through a channel constituted of anisotropic wall surfaces. Using anisotropic scattering kernels and Chapman Enskog phase density, the boundary conditions (BCs) for velocity, temperature, and discontinuities including velocity slip and temperature jump at the wall are obtained. Two scattering kernels, Dadzie and Méolans (DM) kernel, and generalized anisotropic Cercignani-Lampis (ACL) are examined in the present paper, yielding simple BCs at the wall fluid interface. With these two kernels, we rigorously recover the analytical expression for orientation dependent slip shown in our previous works [Pham et al., Phys. Rev. E 86, 051201 (2012) and To et al., J. Heat Transfer 137, 091002 (2015)] which is in good agreement with molecular dynamics simulation results. More important, our models include both thermal transpiration effect and new equations for the temperature jump. While the same expression depending on the two tangential accommodation coefficients is obtained for slip velocity, the DM and ACL temperature equations are significantly different. The derived BC equations associated with these two kernels are of interest for the gas simulations since they are able to capture the direction dependent slip behavior of anisotropic interfaces.

Enhancing the vitamin B12 production and growth of Propionibacterium freudenreichii in tofu wastewater via a light-induced vitamin B12 riboswitch.

The vitamin B12-dependent riboswitch is a crucial factor that regulates gene transcription to mediate the growth of and vitamin B12 synthesis by Propionibacterium freudenreichii. In this study, the effect of various wavelengths of light on the growth rate and vitamin B12 synthesis was studied. Red, green, and blue light-emitting diodes (LEDs) were selected, and a dark condition was used as the control. The microorganism growth rate was measured using a spectrophotometer and plate counting, while the vitamin B12 content was determined using an HPLC-based method. The optical density at 600nm (OD600) values indicated that P. freudenreichii grew better under the continuous and discontinuous blue light conditions. Moreover, under the blue light condition, P. freudenreichii tended to have a higher growth rate (0.332h(-1)) and vitamin B12 synthesis (ca. 10μg/mL) in tofu wastewater than in dark conditions. HPLC analysis also showed that more methylcobalamin was produced under the blue light conditions than in the other conditions. The cbiB gene transcription results showed that blue light induced the synthesis of this vitamin B12 synthesis enzyme. Moreover, the results of inhibiting the expression of green fluorescent protein indicated that blue light removed the inhibition by the vitamin B12-dependent riboswitch. This method can be used to reduce fermentation time and produce more vitamin B12 in tofu wastewater.

The Occurrence and Thermal Disequilibrium State of Permafrost in Forest Ecotopes of the Great Slave Region, Northwest Territories, Canada

ABSTRACTPermafrost underlies peatlands of the Great Slave region, Northwest Territories, Canada, but permafrost relations beneath other ecotopes of black spruce (Picea mariana), white birch (Betula papyrifera) and mixed forests remain unknown. Permafrost‐ecotope relations examined over a 3 year period (2010–13) establish the occurrence and thermal state of permafrost under these different types of forest. Air temperatures and snow depths are regionally consistent. Ground temperature variation primarily reflects latent heat effects during the freezing season, with the duration of season‐normalised active‐layer freezeback explaining 76% of 1 m ground temperature variation among all sites except xeric peatland. Low apparent thermal diffusivities from substantial latent heat effects strongly attenuate ground temperature variation with depth, and yield zero annual amplitude depths of 7 m or less where annual mean ground temperatures range among sites from ‐1.4 °C to 0.0 °C. Extensive discontinuous permafrost conditions, related to the extent of forested ecotopes, are commonly in thermal disequilibrium. Whereas permafrost in peatlands may be ecosystem‐protected, this represents only about 2% of the area of the region. Permafrost in other forested ecotopes, occurring in ice‐rich unconsolidated sediments, is climate‐driven and ecosystem‐protected because of latent heat effects. Though the rate of permafrost degradation may be reduced, an eventual transition to isolated permafrost retained primarily within ecosystem‐driven peatlands implies substantial reductions of permafrost extent in this region. Copyright © 2015 John Wiley & Sons, Ltd.

Distribution of maxillofacial fracture treatment using a titanium plate

Introduction: Maxillofacial fracture is a condition of the facial bones discontinuity in the mandible, maxilla, nasal, zygoma, palate, frontal and orbital. Treatment method of maxillofacial fractures is a close reduction or open reduction by internal fixation using titanium plates. This study was aimed to describe the fixation of maxillofacial fractures using titanium plates and also, to determine the further use of titanium plates as a fixation device at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry Universitas Padjadjaran and Hasan Sadikin Hospital. Methods: The research was a descriptive retrospective study with accidental sampling technique on the maxillofacial fracture fixation cases using titanium plates at the Department of Oral and Maxillofacial Surgery Hasan Sadikin Hospital. The samples were 135 medical records diagnosed with maxillofacial fractures. Results: The result shows that the use of titanium plates were 82.24% of the total maxillofacial fracture cases. Conclusion: There are 135 patients with a diagnosis of maxillofacial fractures treated at the Oral and Maxillofacial Surgery, Faculty of Dentistry Universitas Padjadjaran and Hasan Sadikin Hospital in 2006-2010. Most cases were treated with open reduction (108 cases) and fixed by using a titanium plate (88 cases) as well as the combination of a titanium plate with a wire (12 cases).

Development of High-Resolution Total Variation Diminishing Scheme for Linear Hyperbolic Problems

A high-resolution, total variation diminishing (TVD) stable scheme is derived for scalar hyperbolic problems using the method of flux limiters. The scheme was constructed by combining the 1st-order upwind scheme and the 3rd-order quadratic upstream interpolation scheme (QUICK) using new flux limiter function. The new flux limiter function was established by imposing several conditions to ensure the TVD properties of the scheme. For temporal discretization, the theta method was used, and values for the parameter θ were chosen such that the scheme is unconditionally stable. Numerical results are presented for one-dimensional pure advection problems with smooth and discontinuous initial conditions and are compared to those of other known numerical schemes. The results show that the proposed numerical method is stable and of higher order than other common schemes.

Effects of hypergravity on adipose-derived stem cell morphology, mechanical property and proliferation

Alteration in specific inertial conditions can lead to changes in morphology, proliferation, mechanical properties and cytoskeleton of cells. In this report, the effects of hypergravity on morphology of Adipose-Derived Stem Cells (ADSCs) are indicated. ADSCs were repeatedly exposed to discontinuous hypergravity conditions of 10 g, 20 g, 40 g and 60 g by utilizing centrifuge (three times of 20 min exposure, with an interval of 40 min at 1 g). Cell morphology in terms of length, width and cell elongation index and cytoskeleton of actin filaments and microtubules were analyzed by image processing. Consistent changes observed in cell elongation index as morphological change. Moreover, cell proliferation was assessed and mechanical properties of cells in case of elastic modulus of cells were evaluated by Atomic Force Microscopy. Increase in proliferation and decrease in elastic modulus of cells are further results of this study. Staining ADSC was done to show changes in cytoskeleton of the cells associated to hypergravity condition specifically in microfilament and microtubule components. After exposing to hypergravity, significant changes were observed in microfilaments and microtubule density as components of cytoskeleton. It was concluded that there could be a relationship between changes in morphology and MFs as the main component of the cells.

Transportation costs: A tool for evaluating the effect of rock mass mechanical parameters on blasting results in open pit mining

Blasting is one of the most important stages of open pit mines extraction which plays an essential role in changing the extraction costs. Mechanical parameters of rock mass as fixed parameters are results of effective blasting. In this paper, the costs of transportation have been introduced as a tool for determining the blasting quality and transportation operation in open pit mine of Angouran (the largest lead and zinc mine in the Middle East) has been discussed. Approximately, 55 percent of the piles from blasting conducted in Angouran mine are appropriate for loading by hydraulic shovel and the rest of the piles are not appropriate for loading by most machines. This has led to a significant change in transportation costs caused by blasting quality. First, the mechanical parameters of the rock mass (compression strength of intact rock, RQD, discontinuity conditions, the angle between the joints and direction of drilling and slope discontinuities) as well as all transportation costs (total cost of loading, hauling, and bulldozers work) in the 104 blocks of extractive mining of Angouran were surveyed. Regarding blasting pattern which is constant approximately in studied blocks, an equation was proposed to determine the relation of geotechnical parameters associated with the transportation costs. Ultimately by conducting a sensitivity analysis it was determined that uniaxial compressive strength of rock and difference of bench face dip and joint dip have the greatest impact on the quality of fragmentation and thus changes in the cost of transportation in Angouran mine