Critical State

NorSand Cambridge type models employ a single yield surface plasticity with an associated flow rule, whereas SaniSand type models are formulated using bounding surface plasticity with a non-associated flow rule. Despite their distinct formulations, their approaches to simulating the monotonic behavior of sand rely on similar concepts. Both models measure the distance from the current stress condition to a specific moving target toward critical state in the stress space to calculate their hardening behavior. This paper presents how these entirely different frameworks share this similar concept in simulating the monotonic behavior of sand and shows a comparison of their modeling abilities.

Determining the rock properties that permit or impede the growth of compaction bands in sedimentary sequences is a critical problem of importance to studies of strain localization and characterization of subsurface geologic reservoirs. We determine the porosity and average grain size of a sequence of stratigraphic layers of Navajo Sandstone that are then used in a critical state model to infer plastic yield envelopes for the layers. Pure compaction bands are formed in layers having the largest average grain sizes (0.42–0.45 mm) and porosities (28%), and correspondingly the smallest values of critical pressure (∼22 MPa) in the sequence. The results suggest that compaction bands formed in these layers after burial to ∼1.5 km depth in association with thrust faulting beneath the nearby East Kaibab monocline, and that hardening of the yield caps accompanied compactional deformation of the layers.

The elevated tanks are considered as very sensitive structures in seismic movement condition. Moreover, the conical steel tank manufacturing without local geometric imperfection seems to be too difficult. In generally, the latter is the most responsible factor to define the shell structures buckling capacity. For this reason, several theoretical and experimental researchers studied the performance of this type of structure under seismic loading. The present study aims to demonstrate the local geometric imperfection effect on dynamic buckling of elevated water tank. Using the three dimensions finite element technique to study the seismic response of perfect and imperfect elevated water tank was established taking into account the following factors; the interaction fluid structure (FSI), the wall flexibility, the local geometric imperfection, the nonlinear time history analysis, the material and geometric nonlinearity, and this by the application of three different instability criteria for the critical PGA estimate. The critical PGA of the imperfect elevated water tank numerical models decreased by 45, 45% compared to the elevated water tank numerical model without local geometric imperfection. The obtained results confirm the local geometric imperfection effect on dynamic buckling of elevated water tanks.

We introduce a class of critical states which are embedded in the continuum (CSC) of onedimensional optical waveguide array with one non-Hermitian defect. These states are at the verge of being fractal and have real propagation constant. They emerge at a phase transition which is driven by the imaginary refractive index of the defect waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super -radiance. Below this point the states are extended while above they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states to bound states in the continuum.

Statecharts are one of the most popular modeling formalisms that is used in a diversity of real world applications, such as cyber-physical systems, mobile computing, and bioinformatics. Following common step-wise refinement strategies, modelers often develop and evolve Statecharts models incrementally to satisfy requirements and changes. Although there are already several existing Statecharts refinement approaches, they provide insufficient guarantees to support reasoning about the preservation of both its internal structure, to enhance development and maintenance, and its behavior, which external components using the Statecharts model may depend on. In this paper, we formulate formal requirements to minimally limit the allowable Statecharts refinement operations such that certain assumptions on the structure and reachability of the Statecharts model will hold. To satisfy these requirements, we propose a set of practical bounding refinement rules that allows the modeler to achieve such refinements for which notions of behavior and structure preservation can be statically verified under some assumptions. Our implementation shows how these rules can be applied in realistic scenarios.

Artificial Neural Network (ANN) has proven to be very successful in forecasting a variety of irregular magnetospheric/ionospheric processes like geomagnetic storms and substorms. SYMH and ASYH indices represent longitudinal symmetric and the asymmetric component of the ring current. Here, an attempt is made to develop a prediction model for these indices using ANN. The ring current state depends on its past conditions therefore, it is necessary to consider its history for prediction. To account for this effect Nonlinear Autoregressive Network with exogenous inputs (NARX) is implemented. This network considers input history of 30 min and output feedback of 120 min. Solar wind parameters mainly velocity, density, and interplanetary magnetic field are used as inputs. SYMH and ASYH indices during geomagnetic storms of 1998–2013, having minimum SYMH < −85 nT are used as the target for training two independent networks. We present the prediction of SYMH and ASYH indices during nine geo...

In this paper we study the evolution of the kinetic features of the martensitic transition in a Cu-Al-Mn single crystal under thermal cycling. The use of several experimental techniques including optical microscopy, calorimetry, and acoustic emission, has enabled us to perform an analysis at multiple scales. In particular, we have focused on the analysis of avalanche events ͑associated with the nucleation and growth of martensitic do-mains͒, which occur during the transition. There are significant differences between the kinetics at large and small length scales. On the one hand, at small length scales, small avalanche events tend to sum to give new larger events in subsequent loops. On the other hand, at large length scales the large domains tend to split into smaller ones on thermal cycling. We suggest that such different behavior is the necessary ingredient that leads the system to the final critical state corresponding to a power-law distribution of avalanches.

ABSTRACTWe present a time-resolved magneto-optical (MO) imaging study of high-temperature superconductor (HTS) in high-frequency alternating current (AC) regime. The evolution of the magnetic flux density distribution in YBa2Cu3O7-d (YBCO) thin film samples is studied in small steps of the phase of the applied AC current. The flux distribution at 10 K exhibits instabilities including flux jumps and flux creep. A quantitative analysis of the data allows us to obtain the current density evolution. The current profile changes considerably with the phase differently from the prediction of the critical state model. These observations can be explained by the higher self-field at the sample edge and the effects of flux creep.

A parametric study of an embankment on soft soils reinforced with stone columns is performed using a computer program based on the finite element method. The cylindrical unit cell formulation is used by modeling one column and its surrounding soft soil with confined axisymmetric behaviour. The computer program incorporates the Biot consolidation theory (coupled formulation of the flow and equilibrium equations) with constitutive relations simulated by the p-q-h critical state model. The following parameters are analysed: the replacement area ratio, the deformability of the column material, the thickness of the soft soil, the deformability of the fill and the friction angle of the column material. Based on the results of this study, a new design method is proposed, relating the settlement improvement factor to the two factors that revealed major influence: the replacement area ratio and the ratio between the deformability of the soft soil and the deformability of the column material.

Geotechnical behaviour of a reinforced embankment on soft ground is studied by a numerical model based on the ®nite element method. Special emphasis is given to the stress states (stress levels and pore pressures), displacements, tensile forces in the geosynthetic and overall stability, during and after construction. The in¯uence of some parameters, namely geosynthetic stiness and viscosity, embankment width and construction sequence, is also analysed. Several conclusions are obtained.

A non-associated plasticity theory is developed for granular materials based on the concept of a characteristic stress state of vanishing incremental dilation. The theory makes use of a common format for yield surface and ¯ow potential, representing the surfaces in terms of stress invariants and a single shape function for each. The ¯ow potential surface is determined by an approximate friction hypothesis. Plastic work hardening is introduced in a linear invariant form, that permits dilation before the ultimate state, by including the work associated with shape change in addition to the traditional contribution from volume change. The model is fully three-dimensional and is de®ned by only six parameters: two for elastic stiness, one for plastic stiness, two for the shape of yield and plastic potential surfaces, and one for the dilation at failure. Typical material response is illustrated, while model calibration and its ability to represent experimental data are discussed in Part II.

The aim of the study was to determine the shear strength of mineral and anthropogenic soil of similar grain size as a function of the applied shear rate and water saturation. Stability calculations using the finite element method of the road embankment model were also carried out to demonstrate the variation in factor of safety values depending on the adopted values of the angle of internal friction and cohesion. The tests were carried out in a direct shear apparatus in a 100 × 100 mm box with a sample height of 20.5 mm. The samples were formed directly in the apparatus box at optimum moisture content until a compaction index of I S = 1.00 was obtained. Tests were carried out under conditions without and with water saturation at shear rates of 0.01, 0.05, 0.1, 0.5 and 1.0 mm•min -1 until 18% horizontal displacement was achieved. The results showed that the effect of shear rate on the strength parameters was not unequivocal and was much smaller than the changes caused by saturation of samples. An increase in shear rate resulted in small changes in the angle of internal friction with a tendency towards a decrease. In contrast, cohesion varied over a much larger range with increasing shear rate, with an apparent initial decrease and subsequent increase. The saturation of the samples resulted in a decrease in the angle of internal friction of the cohesive soil and an increase for the ash-slag mixture. The cohesion of both soils decreased. The results obtained from the road embankment model stability calculations confirmed that soil saturation had a greater influence on the factor of safety values obtained than the shear rate.

This study investigated chemical, physical-mechanical and environmental characteristics of weathered blast furnace slag (WBFS) and freshly produced slag (FBFS) for their potential utilisation as granular road base and subbase aggregates. The X-ray fluorescence analysis revealed that each material exhibited a strong CaO-SiO 2 -MgO-Al 2 O 3 chemical system. The X-ray diffraction analysis detected the major mineral phases in WFBS as akermanite, gehlenite and monticellite that accounted for 91.4% of the total mineralogical phase composition. Akermanite and gehlenite accounted for 91% of the total mineralogical phase composition in FBFS. Both slags have weak cementitious properties. The aggregate crushing value, 10% fines aggregate crushing value, flakiness index, plasticity and compaction characteristics of both slag aggregates complied with the South African specifications for crushed stone base and subbase aggregate materials. Soaked California bearing ratio (CBR) values of 153% and 128% for WBFS and FBFS respectively meet the bearing strength requirement for their use in base and subbases. The two materials may also be considered as solid waste with low-risk environmental pollution. Low long term expansion values of 0.32% and 0.39% were observed for WBFS and FBFS respectively. The investigated characteristics indicate that these slags are suitable alternative materials for granular road base construction.

The ac susceptibilities of YBa2(Cu& "Fe")307 z polycrystals for 0 ~x (0.05 have been measured as a function of temperature and magnetic-field strength. Two different types of behavior of the irreversibili- ty line, T (H), obeying the law 1 -T /T, -Hq have been found. One corresponds to pure Y-Ba-Cu-0 (x =0) and shows the commonly observed change of the power exponent q from 3 to 1 with increasing field. For the iron-doped samples an additional unusual crossover from q = 1 to q = -, is observed practi-

Magnetic shielding efficiency was measured on high-T c superconducting hollow cylinders subjected to either an axial or a transverse magnetic field in a large range of field sweep rates, dB app /dt. The behaviour of the superconductor was modelled in order to reproduce the main features of the field penetration curves by using a minimum number of free parameters suitable for both magnetic field orientations. The field penetration measurements were carried out on Pb-doped Bi-2223 tubes at 77 K by applying linearly increasing magnetic fields with a constant sweep rate ranging between 10 µT/s and 10 mT/s for both directions of the applied magnetic field. The experimental curves of the internal field vs. the applied field, B in (B app ), show that, at a given sweep rate, the magnetic field for which the penetration occurs, B lim , is lower for the transverse configuration than for the axial configuration. A power law dependence with large exponent, n', is found between B lim and dB app /dt. The values of n' are nearly the same for both configurations. We show that the main features of the curves B in (B app ) can be reproduced using a simple 2-D model based on the method of Brandt involving a E(J) power law with an n-exponent and a field-dependent critical current density, J c (B), (following the Kim model: J c = J c0 (1+B/B 1 ) -1 ). In particular, a linear relationship between the measured n'-exponents and the nexponent of the E(J) power law is suggested by taking into account the field dependence of the critical current density. Differences between the axial and the transverse shielding properties can be simply attributed to demagnetizing fields.

We have studied numerically and experimentally the magnetic flux penetration in high-superconducting tube subjected to a uniform magnetic field parallel to its long axis. This study is carried in view of designing low-frequency magnetic shields by exploiting the diamagnetic properties of high-superconducting ceramics. We have measured the field attenuation for applied magnetic fields in the frequency range 5 mHz-0.1 Hz by Hall probe measurements and at audio frequencies using a sensing coil. A simple 1D analysis using the Kim critical state model was found to be able to reproduce the experimental data satisfactorily. We have also determined the phase shift between the internal and the applied field both experimentally and numerically. Finally, we have studied the sweep rate dependence of the magnetic shielding properties, using data recorded either at several constant sweep rates d d or at several AC fields of various amplitudes and frequencies. Both methods agree with each other and lead to a -value of the n law equal to 40 at 77 K.

We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material. We use an axisymmetric finite-element model in which the electrical properties of the superconducting tube are modeled by a nonlinear E-J power law with a magnetic-field-dependent critical current density whereas the magnetic properties of the ferromagnetic material take saturation into account. We study and compare the penetration of a uniform axial magnetic field in two cases: 1) a ferromagnetic tube placed inside a larger superconducting tube (Ferro-In configuration) and 2) a ferromagnetic tube placed outside the superconducting one (Ferro-Out configuration). In both cases, we assess how the ferromagnetic tube improves the shielding properties of the sole superconducting tube. The influence of the geometrical parameters of the ferromagnetic tube is also studied: It is shown that, upon an optimal choice of the geometrical parameters, the range of magnetic fields that are efficiently shielded by the hightemperature superconductor tube alone can be increased by a factor of up to 7 (2) in a Ferro-Out (Ferro-In) configuration. The optimal configuration uses a 1020 carbon steel with a thickness of 2 mm and a height that is half that of the superconducting cylinder (80 mm). Index Terms-Ferromagnetic/high-temperature superconductors (HTSs) hybrid structure, finite element, magnetic shield. S UPERCONDUCTIVITY and ferromagnetism are two seemingly different material properties, which, when allowed to interact, lead to numerous interesting physical effects at both the microscopic and macroscopic scales. At the microscopic scale, ferromagnetism and superconductivity are different electronic long-range orders that thermodynamically compete . While singlet superconductivity and ferromagnetism are not likely to coexist in bulk compounds, coexisting correlations may be found in layered ferromagnetic/ superconductor (F/S) heterostructures [2] due to the proximity Manuscript

DOE "tank-farm" sites consist of a large number of underground high-level waste storage tanks (HLWST). Seismic analysis and design of HLWSTs requires proper evaluation of fluid-structure interaction and hydrodynamic pressure. Although simplified guidelines for such tanks are available, a rigorous analysis invariably necessitates detailed finite element modeling. A systematic step-by-step approach for dynamic analysis of a HLWST using ADINA fluid elements is presented here. Initially, an open liquidfilled cylindrical ground-supported tank model is set up and frequency analysis studies for different tank configurations conducted with displacement-based (D-fluid) and potential-based (P-fluid) elements. The results are compared with the available data. The procedure is then extended to analyze the response of the tank to El Centro 1940 earthquake ground history and results verified for displacements and hydrodynamic pressure. Although ADINA's P-fluid elements give more accurate frequencies and pressure distributions than D-fluid elements, they cannot be at present used for seismic loading. The D-fluid elements are shown to perform adequately for practical problems under consideration.

DOE "tank-farm" sites consist of a large number of underground high-level waste storage tanks (HLWST). Seismic analysis and design of HLWSTs requires proper evaluation of fluid-structure interaction and hydrodynamic pressure. Although simplified guidelines for such tanks are available, a rigorous analysis invariably necessitates detailed finite element modeling. A systematic step-by-step approach for dynamic analysis of a HLWST using ADINA fluid elements is presented here. Initially, an open liquidfilled cylindrical ground-supported tank model is set up and frequency analysis studies for different tank configurations conducted with displacement-based (D-fluid) and potential-based (P-fluid) elements. The results are compared with the available data. The procedure is then extended to analyze the response of the tank to El Centro 1940 earthquake ground history and results verified for displacements and hydrodynamic pressure. Although ADINA's P-fluid elements give more accurate frequencies and pressure distributions than D-fluid elements, they cannot be at present used for seismic loading. The D-fluid elements are shown to perform adequately for practical problems under consideration.

that matched the pentane blank within 10%. The background for CH3CC13 was 3.3 pmol kg-' (±5%). All samples were corrected for these backgrounds. The CH3CCl3 and CC14 concentra- tions in samples storcd overnight in the extraction bottles were the same as the concentrations analyzed immediately after collection. Bottom water CH3CCl3 levels were below the detection limit even though CH3CCl3 is the most soluble of the com- pounds measured; these data indicate that contami- nation during sampling was negligible. 21. H. Gever et al., Chennosphere 13, 269 (1984). We assume that estimated or measured bioaccumulation factors for the freshwater alga Chlorella fiisca are roughlv appropriate for partitioning of halocarbons between seawater and marine organic matter. The bioaccumulation factor is defined as [concentration in Chilorella (gram per gram dry weight)] = [concentration in water (gram per gram)]

Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of commercially available Nb foil samples affects their superconducting behavior. DC magnetization and AC susceptibility measurements at cryogenic temperatures and with magnetic fields of different amplitude and orientation are thus analyzed and reported. This study pays special attention to the surface superconducting layer that persists above the upper critical magnetic field strength H c2 , and disappears at a higher nucleation field strength H c3 . Characteristic changes were distinguished between the surface properties of the laser-irradiated samples, as compared to the corresponding reference samples (non-irradiated). Clear correlations have been observed between the surface nanostructures and the nucleation field H c3 , which depends on the relative orientation of the magnetic field and the surface patterns developed by the laser irradiation.

Seismicity induced by the waste water injection has become an important issue in the recent years, including several regions in United States, such as Oklahoma and Texas. However, many techniques that are used to evaluate whether a particular earthquake is induced or natural are not based on the law of physics, and as a consequence these techniques do not provide much insight into nature of that type of seismicity. In this study we combine the analytic solution of coupled hydromechanical problem with numerical dynamic rupture simulation to study the influence of different properties of the rocks and fluids, as well as the geometry of the operations on the potential for earthquake triggering. We find three main driving factors are the distance between the injection well and the fault, permeability of the medium and shear modulus of the rocks. We also observe that keeping injecting the fluid at the same rate after first occurrence of seismic event, escalates the size of earthquakes with time.

During the last years we collected data of abdominal septic shock patients from clinics all over Germany. The mortality of septic shock is about 50%. Septic shock is related to immune system reactions and unusual measurements. Septic shock patients are intensely medicated during their stay at the intensive care unit. To help physicians recognizing the critical states of their patients as early as possible, we built a rule based alarm system based on a neuro-fuzzy inference machine. Analysing the patient data in a time window, we show the time dependency of the classification results. We give detailed classification results and explanation by rules. The results are compared to results obtained by using the most common scores in intensive care medicine. We discuss the advantages of the paradigms "neural networks" and "scores", and we answer the important question: Is a neural network more performant than scores for abdominal septic shock patient data?

Self-organization in an experimental braided river is studied. It is shown that the experimental braided river self-organizes into a critical state where it shows dynamic scaling; that is, small and large parts of the river evolve statistically identically after proper renormalization of space and time. The dynamic scaling emerges during the process of approaching the critical state which involves self-adjustment of both profile (vertical selforganization) and braiding pattern (horizontal self-organization). The obtained result corroborates the hypothesis suggested by the authors earlier ] that braided rivers are self-organized critical systems. The results are also important for understanding and statistically predicting the behavior of natural braided rivers because, owing to external conditions (e.g., sudden streamflow changes), some of them may be driven out of the critical state and therefore may show deviation from dynamic scaling.

Except for fair copying, no part of this publication may be reproduced, stored in a retrieval system, or transmttted, in any form or by any means electronic, mechanical, photocopying, recording or otherwiSe, without the prior written permtsston of the Geotechmcal Engmeering Group Papers or other contributions in AAU Geotechnical Engineering Papers and the statements made or opinions expressed therem are published on the understanding that the author of the contribution ts solely reponsible for the opmions expressed in it and that tts publication does not necessarily imply that such statements or opmions are or reflect the VIews of the AA U Geotechmcal Engmeering Group. The AAU Geotechmcal Engineering Papers -AGEP-are issued for early dissemination and book keeping of research results from the Geotechnical Engmeering Group at Aalborg Umversi(y (Department of Civil Engineering). Moreover, the papers accommodate proliferation and dpcumentation of field and laboratory test series not directly sutted for publication m journals or proceedings. The papers are numbered lSSN 1398-6465 R<two digit year code><two digit consecuttve number> For Internal purposes the papers are, funher, submitted with coloured covers m the followmg senes• Series Colour Laboratory testmg papers sand Field tesung papers grey Manuals & gutdes red Soli "'lechantcs papers blue Foundauon Engmeermg papers green Engmeering Geology papers yellow Envrronmental Engmeermg pape" brown In general the AGEP papers are 'uhmlltcd ''' 111urnal,, confcrc'tlcc' or ~ctenttfic meetings and hence, whenever poSSIble, refercntc should be gtven tll the linal puhllcatrun ( J<JUmul, procccdmg cl c) and nut 10 the AGEP paper

From solar radio burst data we computed wavelet transforms and frequency distribution for investigation of self-similar temporal variability and power-laws, as the fundamental conditions for characterization of dynamical criticality (self or forced) in the solar active regions. The main result indicates that, as for the global activity, the local coronal magnetic field, in millisecond time scales, can be in a critical state where the dynamics of solar active regions works as avalanches of many small intermittent particle acceleration events.

Deformation bands form in porous granular rocks by localized inelastic yielding that is well described by a modified Cam cap model. All five kinematic varieties of bands observed in the field, including dilation bands, dilation bands with shear, shear bands, compaction bands with shear, and compaction bands, can be explained by this unifying mechanical framework once their localization criteria are also specified. The growth of dilation bands with shear has been observed in the field and in the laboratory for low-pressure conditions. More commonly, however, strain hardening of compaction bands with shear will lead to faulting within, and eventually through, the resulting damage zone if the associated yield cap grows outward sufficiently to intersect the frictional strength surface. This sequence is best explained by replacing the critical state line with a frictional failure criterion in the general Cam cap approach. Given recent advances in localization theory and continuing refinement of field observations, the term bfractureQ must now be expanded to include both weak and strong discontinuities, or deformation bands and displacement discontinuities (i.e., cracks, joints, veins, solution surfaces, anticracks, dikes, sills, faults), respectively. Shear zones and fault zones that accommodate both continuous and discontinuous changes in shear offset within them should also be considered as fractures according to this expanded definition.

MgB2 is one of the most unstable superconducting materials, where flux jumps are commonly observed at low temperatures jeopardizing its potential for applications. We present a detailed MO imaging study of the jumps in MgB2 films, where we observe large dendritic flux patterns as well as much smaller jumps down to 50 flux quanta. The large jumps destroy the critical

The ac susceptibility, X = X'+ ix", of a superconducting thin disk in a perpendicular magnetic field is calculated in the critical-state model assuming a field-dependent critical current, J¢(B). We find both analytically and numerically that the asymptotic behavior at large he-field amplitudes B,,~ changes from X' oc B~/2 and X" oc B~ --3 X~v --2 for the Bean model, to X' oc Ba,, and cx Barn for J¢ decreasing with IBI as IBI -~ or faster. In the parametric X"(X') plot the peak of X" increases in magnitude and shifts toward X' = 0. This allows an easy experimental discrimination between a Bean model behavior, one with J~(B), and one where flux creep is an ingredient. Account of the B-dependence of J~ improves substantially agreement with available experimental X"(X') data.

A model for the calculation of the magnetic levitation force for finite type-II superconductors in the critical state is presented in a series of two papers. In the first paper, we describe the main features of the model and understand the effect of demagnetizing fields in the magnetic properties of finite superconductors by considering the case of a superconducting cylinder in the presence of a homogeneous applied field. Field and current profiles are calculated from a minimization of the magnetic energy in the superconductor after a change in the applied field. Results are presented for both constant and field-dependent critical currents. The procedure is general enough to be applied to the case of nonuniform applied fields, as long as the cylindrical geometry is preserved.

The crisis and its reading necessarily entail a sense of negativity, as a method and possibility to understand its terms and its extension. The negativity, that is a movement from the sociability placed by the value form, breaks the premise that the space proposed as simultaneity and replacement of the value terms, presents itself as a rearrangement strategy for the critical state. Thus the crisis, resulting in the level of possible in the disaster, would find into the governance while its maintaining while critical state, introducing the idea of crisis management, and negatively, deepening this toward the catastrophic.

Transcritical working cycles for refrigerants have led to increased interest in heat transfer near the Critical State. In general, experimental results for this region differ significantly from those far from it because some fluid properties vary much more there than at a greater distance. In this paper, measurements for two-phase and single-phase free convective heat transfer from an electrically heated copper tube with 25 mm O.D. to refrigerant R125 are discussed for fluid states very close to the Critical Point and far from it. It is shown that heat transfer for film boiling slightly below and for free convection slightly above the critical pressure is very similar. The new e and also previous e experimental data for nucleate boiling, film boiling, and single-phase free convection are compared with calculated results between atmospheric and critical pressure. It can be concluded that the Principle of Corresponding States in its simplest form is very well suited to transfer the results to other refrigerants. In Part II, particular attention will be given to a minimum superheat for nucleate boiling and a maximum superheat for film boiling and single-phase free convection within the circumferential variation of the isobaric wall superheat on the lower parts of the tube.

The paper describes the Stože landslide that occurred in western Slovenia in November, 2000. It presents the landslide particularities and laboratory tests results. A numerical analysis of the slope failure was performed. It indicated the important role of the ground water level, and the dependence of slope stability upon it. Special laboratory equipment, a large-scale shear cell, was constructed in order to test the landslide material and to indicate the roles of the water content and loading velocities on the residual shear strength of material. A testing method is presented. It was assumed that the behaviour of material with a grain size of 4 mm or less could indicate the general behaviour of the landslide. Taking into account the possibility of an earthquake occurring in this region, attention was paid to the behaviour of this material at very small strains, and to the effect of different water contents and densities of the material. The deformation characteristics of reconstituted samples were investigated in a resonant column test at IST, Lisbon. Showing the influence of the water content and confining stress, empirical equations defining the small strain shear modulus have been proposed for different water contents.

Rocks around petroleum wells are subjected to cyclic loading due to repeated changes in the effective stresses in the rock. It may experience many loading cycles via injection start-up and shut-in cycles and injection/production rate fluctuations. Every cycle of unloading-reloading gives rise to energy dissipation and thus plastic deformation which leads to the degradation of cementation bonds. A constitutive model is required to address stress-strain behavior and mechanical degradation of soft sandstone in the course of cyclic loading. First, different types of cyclic loading (namely slow and fast cyclic loadings, which both can occur during wellbore operation) and their differences are discussed. Then famous elastoplastic theories, which are usually used for simulation of cyclic loading, and their effectiveness in describing cyclic loading are reviewed. Ultimately, a methodology is proposed to come up with a suitable constitutive model that can be employed for replicating the cyclic behavior of weakly cemented sands.

Several theoretical expressions of the at rest earth pressure coefficient for normally consolidated soils ( 0( NC ) k ) are available in the literature. Some of them have been derived using Critical State Soil Mechanics constitutive models. However, these models usually over-predict the 0( NC ) k values. The possibility to improve, in principle, the 0( NC ) k prediction simply changing the plastic potential surface shape of the Modified Cam-Clay model, i.e. adopting a non-associated flow rule, is described in the paper.

Direct correlation functions for binary fluid mixtures of Lennard-Jones spheres were calculated with the Percus-Yevick integral equation. Calculations were restricted to infinitely dilute solutions. The dependence of Vz-and ( a p / a ~) F , ~ on the relative values of the molecular parameters was established, including the near-critical region. It is clear that V2-diverges strongly as the critical point is approached and that its amplitude, ( a p / a ~) F , ~, is well behaved and changes smoothly in the critical region. The presence of azeotropes may be established on the basis of the signs of the initial slopes (dp/ax)F,T: Differences between the results of this study and others which employ a van der Waals equation of state are shown to arise essentially in the different combining rules used to express the cross energy parameter e12. The way (ap/ax);,? varies with the ratio of molecular parameters is calculated showing that very strong cross interactions imply a tendency to colmearity of (ap/aT)&, with the extension of the solvent's vapor pressure curve.

LIQUEFACTION AND RING SHEAR DEVICE By: Julian A. Sandoval University of New Hampshire, May, 2012 Liquefaction flow slides triggered by earthquakes or heavy rainfall in saturated granular soils have produced great damage in landslide-prone areas worldwide. A major aspect that needs more study is how the &#39;residual strength&#39; remaining in the liquefied material evolves at the high strain levels imposed as the slide progresses. Strength of liquefied granular soils is usually studied in the lab by means of the triaxial test, since the strains required to trigger liquefaction are low, compared with those observed after it has been produced. More sophisticated devices are necessary in order to apply the high strains and shear strain rates that could replicate those of typical flowslides; In particular, these are required to investigate the behavior of the resistance of the flow, which is termed residual undrained strength (Sur). Preliminary tests by de Alba and Ballestero (2004) wit...

Steady-state pyroxene dissolution rates in aqueous solutions have been measured at temperatures from 25 to 374 C at a pressure of 23 MPa and at neutral pH. The pyroxene is hedenbergitic clinopyroxene, of composition Na 0.04 Ca 0.95 Mg 0.3 Fe 2þ 0.64 Fe 3þ 0.06 Al 0.04 Si 1.97 O 6 . All experiments were performed at conditions far from equilibrium in Ti-alloy mixed-flow reactors. In most runs, the reactive solutions were undersaturated with respect to pyroxene and secondary minerals were rarely found at the reacted surface. The dissolution is non-stoichiometric in most cases, while the different chemical elements of the pyroxene are released at different rates. Stoichiometric steady-state dissolution was obtained in neutral solution at 100 C. The release rates of the different elements vary with temperature and solution chemistry. The dissolution rates (r Si ) in neutral pH conditions increase with temperature from 25 to 300 C, reach a maximum at 300 C, and then decrease with continued temperature increase. At a given temperature, the rates decrease significantly with increasing pH of the reactive fluid and are also affected by the activities of Ca, Mg, Fe in the solution. At neutral pH, the dependence of the pyroxene dissolution rates on activities of Ca, Mg, Fe and H þ in the fluid can be expressed by the relation: where r þ is the far-from-equilibrium dissolution rate, R the gas constant, T the absolute temperature, Z i valence of metal M i and a i represents the activity of the subscript aqueous species. E a equals 22.667 kJ/mole/K and A ¼ 2.011 Â 10 À7 mole/cm 2 /s; a is the empirical reaction rate order, which can be derived from the experimental results. At temperatures below 300 C, the exchange reactions 2H þ $M i 2þ , where M i 2þ refers to divalent cations Mg 2þ , Fe 2þ or Ca 2þ , dominate in the dissolution. The following evolution of the dissolution with temperature is proposed: at 300 C, the tetrahedral Si-O bonds break after the M i 2þ -O bonds in adjacent octahedral positions have been removed by proton exchange reaction, whereas, above 300 C, the breaking of the octahedral M i 2þ -O bonds occurs after adjacent tetrahedral Si-O bonds have been broken.

This paper analyzes a model for the competition dynamics of web sites in the Internet, based on the Lotka-Volterra competition equations. This model shows the well known appearance of a winner-take-all characteristic and is based in the nonvalidity of traditional o er and demand equilibrium theory of these kinds of markets. From the stability analysis of the model, we establish a series of rules which are useful for deÿning strategies in the Internet market. One of the most important results that emerge from this simple model is the appearance of some unexpected phenomena related to the collaboration and competition between sites.

Highlights • Use of multi-stage triaxial tests to investigate the post-cyclic behaviour of liquefied sand • Derivation of instability curves for assessment of post-cyclic deformation of liquefied sloping grounds • Demonstration of use of instability curves through real case study of post-liquefaction failure of Lower San Fernando Dam

The field-cooled (FC) magnetization M is measured as a function of the applied external field, H a , for various bulk, Nd-based 123 superconductors which exhibit different magnetization-field characteristics (i.e. with and without secondary peak effect). We find that the FC magnetization data reproduce directly the M(H a ) behaviour measured after zero-field cooling. Based on the critical state model, we derive expressions for the field-cooled magnetization, and show that a large M(0) is essential to achieve large trapped fields in superconducting permanent magnets.

Large-scale fluctuations of the H component magnetic field at Earth&#x27;s equator during the period from 1981 to 2002 were examined using multifractal tools. We computed, analyzed, and modeled a measure representation of the Dst data. This representation can be viewed as a probability measure that characterizes the Dst series. The measure representation in fact gives the probabilities of specific strings of events in the complete Dst time series. The raw time series clearly shows intermittency and non-Gaussianity, which are reflective of ...

A phase diagram was constructed from experimental data to study the phase behavior of the liquid-liquid ternary system of acetone, ethyl acetate, and water in a solution. To achieve this, the following objectives are assigned: (1) to determine the solubility data of the three-component system at equilibrium by titrating miscible mixtures until cloudy, (2) to determine the tie-lines of the two-phase mixtures, and (3) to apply the tie-lines and equilibrium concentrations to illustrate the ternary phase diagram of the three-component mixture of acetone, ethyl acetate, and water.