Stabilization of Three-Dimensional Collective Motion
Scardovi, Luca; Sepulchre, Rodolphe
2008-01-01
This paper proposes a methodology to stabilize relative equilibria in a model of identical, steered particles moving in three-dimensional Euclidean space. Exploiting the Lie group structure of the resulting dynamical system, the stabilization problem is reduced to a consensus problem on the Lie algebra. The resulting equilibria correspond to parallel, circular and helical formations. We first derive the stabilizing control laws in the presence of all-to-all communication. Providing each agent with a consensus estimator, we then extend the results to a general setting that allows for unidirectional and time-varying communication topologies.
On 3-Dimensional Stability of Reshaping Breakwaters
Burcharth, Hans F.; Frigaard, Peter
1989-01-01
The paper deals with the 3-dimensional stability of the type of rubble mound breakwaters where reshaping of the mound due to wave action is foreseen in the design. Such breakwaters are commonly named sacrificial types and berm types. The latter is due to the relatively large volume of armour stones...
Ligand-Stabilized Reduced-Dimensionality Perovskites
Quan, Li Na
2016-02-03
Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.
Ligand-Stabilized Reduced-Dimensionality Perovskites.
Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H
2016-03-02
Metal halide perovskites have rapidly advanced thin-film photovoltaic performance; as a result, the materials' observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions. These drive an increased formation energy and should therefore improve material stability. Here we report reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieve the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.
Dimensional stability of heat treated wood floorings
Vjekoslav Živković
2008-07-01
Full Text Available Heat treated wood (HTW is successfully applied for floorings due to its better moisture resistance, increased dimensional stability, and uniform colour change to darker, brownish colours. The aim of this work was to define the hygroscopic range and equilibrium moisture content at ambient conditions of heat treated wood of two wood species – ash and beech. Material was treated at two temperature levels, 190 and 210 °C, and the properties were compared with native wood. The reduction in dimensional changes is expressed by volumetric shrinking and Anti Shrink Efficiency (ASE. Additionally, parquet elements were made out of such HTW, oil-impregnated and waxed, and subsequently tested for water vapour and liquid water permeability. Shrinking gradients of HTW were not reduced in comparison with native beech wood, but the absolute reduction in water uptake resulted in cca 50 % lower EMC values and up to cca 60 % improved ASE values. Surface treatment further improved the hygroscopic properties of HTW.
Stability of three-dimensional boundary layers
Nayfeh, A. H.
1979-01-01
A theory is presented for the three-dimensional stability of boundary layers. Equations are derived for the evolution of a disturbance having a given frequency and originating at a given curve. These equations are used to determine the rays along which the disturbance energy propagates. It is shown that the results can be obtained by using the saddle-point method, or kinematic wave theory, or the method of multiple scales. Extension of the theory to the case of a wave packet is also presented.
Nonparallel stability of three-dimensional flows
Padhye, A. R.; Nayfeh, A. H.
1981-01-01
The linear stability of three-dimensional incompressible, isothermal, nonparallel boundary-layer flows has been investigated. The method of multiple scales is used to derive the partial-differential equations that describe the spatial modulations of the amplitude, phase and wavenumber of a disturbance. Group velocities are used to determine the disturbance growth direction. The envelope method is used to calculate the logarithmic amplitude growth rate N. The theory is applied to the flows over a swept-back tapered wing with boundary-layer suction. Results of such analysis for the X-21 wing are discussed. It is found that the nonparallel effects for this wing is substantial.
Moduli stabilization in higher dimensional brane models
Flachi, Antonino; Pujolas, Oriol [IFAE, Campus UAB, 08193 Bellaterra, Barcelona (Spain)]. E-mail: pujolas@ifae.es; Garriga, Jaume [IFAE, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Departament de Fisica Fonamental and C.E.R. en Astrofisica, Fisica de Particules i Cosmologia Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Tanaka, Takahiro [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford MA 02155 (United States); Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
2003-08-01
We consider a class of warped higher dimensional brane models with topology M x {sigma} x S{sup 1}/Z{sub 2}, where {sigma} is a D2 dimensional manifold. Two branes of co-dimension one are embedded in such a bulk space-time and sit at the orbifold fixed points. We concentrate on the case where an exponential warp factor (depending on the distance along the orbifold) accompanies the Minkowski M and the internal space {sigma} line elements. We evaluate the moduli effective potential induced by bulk scalar fields in these models, and we show that generically this can stabilize the size of the extra dimensions. As an application, we consider a scenario where supersymmetry is broken not far below the cutoff scale, and the hierarchy between the electroweak and the effective Planck scales is generated by a combination of redshift and large volume effects. The latter is efficient due to the shrinking of {sigma} at the negative tension brane, where matter is placed. In this case, we find that the effective potential can stabilize the size of the extra dimensions (and the hierarchy) without fine tuning, provided that the internal space {sigma} is flat. (author)
Optical metrology techniques for dimensional stability measurements
Ellis, Jonathan David
2010-01-01
This thesis work is optical metrology techniques to determine material stability. In addition to displacement interferometry, topics such as periodic nonlinearity, Fabry-Perot interferometry, refractometry, and laser stabilization are covered.
Optical metrology techniques for dimensional stability measurements
Ellis, Jonathan David
2010-01-01
This thesis work is optical metrology techniques to determine material stability. In addition to displacement interferometry, topics such as periodic nonlinearity, Fabry-Perot interferometry, refractometry, and laser stabilization are covered.
Stability of compressible three-dimensional boundary-layer flows
Reed, H. L.; Nayfeh, A. H.
1982-01-01
For compressible three-dimensional flow, the method of multiple scales to formulate the three-dimensional stability problem and determine the partial-differential equations governing variations of the amplitude and complex wavenumbers is used. A method for following one specific wave along its trajectory to ascertain the characteristics of the most unstable disturbance is proposed. Numerical results using the flow over the X-21 wing as calculated from the Kaups-Cebeci code will be presented.
Linear Dimensional Stability of Irreversible Hydrocolloid Materials Over Time.
Garrofé, Analía B; Ferrari, Beatriz A; Picca, Mariana; Kaplan, Andrea E
2015-12-01
The aim of this study was to evaluate the linear dimensional stability of different irreversible hydrocolloid materials over time. A metal mold was designed with custom trays made of thermoplastic sheets (Sabilex, sheets 0.125 mm thick). Perforations were made in order to improve retention of the material. Five impressions were taken with each of the following: Kromopan 100 (LASCOD) [AlKr], which has dimensional stability of 100 hours, and Phase Plus (ZHERMACK) [AlPh], which has dimensional stability of 48 hours. Standardized digital photographs were taken at different time intervals (0, 15, 30, 45, 60, 120 minutes; 12, 24 and 96 hours), using an "ad-hoc" device. The images were analyzed with software (UTHSCSA Image Tool) by measuring the distance between intersection of the lines previously made at the top of the mold. The results were analyzed by ANOVA for repeated measures. Initial and final values were (mean and standard deviation): AlKr: 16.44 (0.22) and 16.34 (0.11), AlPh: 16.40 (0.06) and 16.18 (0.06). Statistical evaluation showed significant effect of material and time factors. Under the conditions in this study, time significantly affects the linear dimensional stability of irreversible hydrocolloid materials.
Dimensional accuracy and stability of acrylic resin denture bases.
Huggett, R; Zissis, A; Harrison, A; Dennis, A
1992-10-01
Proponents of injection molding systems have claimed a number of benefits over conventional press-pack dough molding systems. The aim of this study was to evaluate a recently developed injection (dry heat) procedure of processing compared with press-pack dough molding utilizing three curing cycles. The dimensional accuracy and stability of acrylic resin bases produced by the two molding procedures were compared. Dimensional changes were assessed over a period of 4 months using an optical comparator. The results demonstrate that baseplates produced by the injection molding procedure exhibit less shrinkage than those produced by the conventional press-pack procedures.
Hydrogen peroxide stabilization in one-dimensional flow columns
Schmidt, Jeremy T.; Ahmad, Mushtaque; Teel, Amy L.; Watts, Richard J.
2011-09-01
Rapid hydrogen peroxide decomposition is the primary limitation of catalyzed H 2O 2 propagations in situ chemical oxidation (CHP ISCO) remediation of the subsurface. Two stabilizers of hydrogen peroxide, citrate and phytate, were investigated for their effectiveness in one-dimensional columns of iron oxide-coated and manganese oxide-coated sand. Hydrogen peroxide (5%) with and without 25 mM citrate or phytate was applied to the columns and samples were collected at 8 ports spaced 13 cm apart. Citrate was not an effective stabilizer for hydrogen peroxide in iron-coated sand; however, phytate was highly effective, increasing hydrogen peroxide residuals two orders of magnitude over unstabilized hydrogen peroxide. Both citrate and phytate were effective stabilizers for manganese-coated sand, increasing hydrogen peroxide residuals by four-fold over unstabilized hydrogen peroxide. Phytate and citrate did not degrade and were not retarded in the sand columns; furthermore, the addition of the stabilizers increased column flow rates relative to unstabilized columns. These results demonstrate that citrate and phytate are effective stabilizers of hydrogen peroxide under the dynamic conditions of one-dimensional columns, and suggest that citrate and phytate can be added to hydrogen peroxide before injection to the subsurface as an effective means for increasing the radius of influence of CHP ISCO.
DIMENSIONAL STABILITY OF METHYL METHACRYLATE HARDENED HYBRID POPLAR WOOD
Wei-Dan Ding,
2011-11-01
Full Text Available This study examines the dimensional stability of fast-growing poplar clones wood after treatment by impregnation with methyl methacrylate (MMA. Six hybrid poplar clones from one plantation in Quebec were sampled. The effects of hardening with MMA on density as well as longitudinal, radial, tangential, and volumetric swelling properties (S, water uptake capacity (D, anti-swelling efficiency (ASE, and water repellent efficiency (WRE after soaking were investigated. Hardening treatment increased the density of all poplar woods by 1.2 to 1.6 and decreased the inner water migration rate during soaking. S and D values of hardened woods were significantly lower than those of controls, depending on the clone type. ASE and WRE values suggested that incorporating MMA effectively improved the dimensional stability of poplar wood at the early soaking stage, but was less effective in the long term.
Design guidelines for high dimensional stability of CFRP optical bench
Desnoyers, Nichola; Boucher, Marc-André; Goyette, Philippe
2013-09-01
In carbon fiber reinforced plastic (CFRP) optomechanical structures, particularly when embodying reflective optics, angular stability is critical. Angular stability or warping stability is greatly affected by moisture absorption and thermal gradients. Unfortunately, it is impossible to achieve the perfect laminate and there will always be manufacturing errors in trying to reach a quasi-iso laminate. Some errors, such as those related to the angular position of each ply and the facesheet parallelism (for a bench) can be easily monitored in order to control the stability more adequately. This paper presents warping experiments and finite-element analyses (FEA) obtained from typical optomechanical sandwich structures. Experiments were done using a thermal vacuum chamber to cycle the structures from -40°C to 50°C. Moisture desorption tests were also performed for a number of specific configurations. The selected composite material for the study is the unidirectional prepreg from Tencate M55J/TC410. M55J is a high modulus fiber and TC410 is a new-generation cyanate ester designed for dimensionally stable optical benches. In the studied cases, the main contributors were found to be: the ply angular errors, laminate in-plane parallelism (between 0° ply direction of both facesheets), fiber volume fraction tolerance and joints. Final results show that some tested configurations demonstrated good warping stability. FEA and measurements are in good agreement despite the fact that some defects or fabrication errors remain unpredictable. Design guidelines to maximize the warping stability by taking into account the main dimensional stability contributors, the bench geometry and the optical mount interface are then proposed.
Dimensional stability and weight changes of tissue conditioners.
Murata, H; Kawamura, M; Hamada, T; Saleh, S; Kresnoadi, U; Toki, K
2001-10-01
The dimensional stability of tissue conditioners characterizes the ability of the materials to yield accurate functional impressions of oral mucosa. This study evaluated the linear dimensional changes with time of six tissue conditioners (COE Comfort, FITT, GC Soft-Liner, Hydro-Cast, SR-Ivoseal and Visco-Gel) using a travelling microscope, and relationship between these changes and weight changes. The absorption and solubility of these materials were also determined. The percentage changes in dimension and weight in water storage were measured at 2 (baseline), 8 and 24 h, and 2, 4, 7, 14 and 21 days after specimen preparation. All materials except SR-Ivoseal exhibited shrinkage and weight loss during water storage, whilst SR-Ivoseal exhibited expansion and an increase in weight. The percentage solubility for all materials except SR-Ivoseal was higher than the percentage absorption. A positive linear relationship was found between the percentage changes in linear dimension and those in weight (r=0.797 - 0.986, P forming functional impressions would be 24 h after insertion in the mouth. In addition, it is important to select tissue conditioners suitable for functional impressions because of the wide ranges of dimensional stability among the materials.
Evaluation of dimensional stability of autoclavable elastomeric impression material.
Surendra, G P; Anjum, Ayesha; Satish Babu, C L; Shetty, Shilpa
2011-03-01
Impressions are important sources of cross contamination between patients and dental laboratories. As a part of infection control impressions contaminated with variety of micro-organisms via blood and oral secretions should be cleaned and disinfected or sterilized before being handled in dental laboratory. The purpose of this study was to determine the effect of autoclaving on dimensional stability of elastomeric impression material (polyvinyl siloxane-Affinis). In this in vitro study standardized stainless steel die as per ADA specification number 19 was fabricated. Polyvinyl siloxane (Affinis) light body and putty viscosity elastomeric impression materials were used. A total of 40 impressions of the stainless steel die were made and numeric coding system was used to identify the samples. Measurements were made using a measuring microscope. Distance between the cross lines CD and C'D' reproduced in the impression were measured before autoclaving, immediately after autoclaving and 24 hours after autoclaving and dimensional change was calculated. The data obtained was subjected to statistical analysis. The mean difference in dimensional change between the three groups was not statistically significant (P > 0.05). However the results revealed that there was higher mean dimensional change immediately after autoclaving when compared to the other 2 time intervals. It is desirable to delay the casting of an autoclavable elastomeric impression material by about 24 hours. Though disinfection of impression is routinely followed autoclaving of impression is an effective method of sterilization.
Goldilocks Models of Higher-Dimensional Inflation (including modulus stabilization)
Burgess, C P; Hayman, Peter; Patil, Subodh P
2016-01-01
We explore the mechanics of inflation in simplified extra-dimensional models involving an inflaton interacting with the Einstein-Maxwell system in two extra dimensions. The models are Goldilocks-like in that they are just complicated enough to include a mechanism to stabilize the extra-dimensional size, yet simple enough to solve the full 6D field equations using basic tools. The solutions are not limited to the effective 4D regime with H m_KK, but when they do standard 4D fluctuation calculations need not apply. When in a 4D regime the solutions predict eta ~ 0 hence n_s ~ 0.96 and r ~ 0.096 and so are ruled out if tensor modes remain unseen. Analysis of general parameters is difficult without a full 6D fluctuation calculation.
Standard Test Method for Dimensional Stability of Sandwich Core Materials
American Society for Testing and Materials. Philadelphia
2002-01-01
1.1 This test method covers the determination of the sandwich core dimensional stability in the two plan dimensions. 1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given may be approximate. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Goldilocks models of higher-dimensional inflation (including modulus stabilization)
Burgess, C. P.; Enns, Jared J. H.; Hayman, Peter; Patil, Subodh P.
2016-08-01
We explore the mechanics of inflation within simplified extra-dimensional models involving an inflaton interacting with the Einstein-Maxwell system in two extra dimensions. The models are Goldilocks-like inasmuch as they are just complicated enough to include a mechanism to stabilize the extra-dimensional size (or modulus), yet simple enough to solve explicitly the full extra-dimensional field equations using only simple tools. The solutions are not restricted to the effective 4D regime with H ll mKK (the latter referring to the characteristic mass splitting of the Kaluza-Klein excitations) because the full extra-dimensional Einstein equations are solved. This allows an exploration of inflationary physics in a controlled calculational regime away from the usual four-dimensional lamp-post. The inclusion of modulus stabilization is important because experience with string models teaches that this is usually what makes models fail: stabilization energies easily dominate the shallow potentials required by slow roll and so open up directions to evolve that are steeper than those of the putative inflationary direction. We explore (numerically and analytically) three representative kinds of inflationary scenarios within this simple setup. In one the radion is trapped in an inflaton-dependent local minimum whose non-zero energy drives inflation. Inflation ends as this energy relaxes to zero when the inflaton finds its own minimum. The other two involve power-law scaling solutions during inflation. One of these is a dynamical attractor whose features are relatively insensitive to initial conditions but whose slow-roll parameters cannot be arbitrarily small; the other is not an attractor but can roll much more slowly, until eventually transitioning to the attractor. The scaling solutions can satisfy H > mKK, but when they do standard 4D fluctuation calculations need not apply. When in a 4D regime the solutions predict η simeq 0 and so r simeq 0.11 when ns simeq 0.96 and so
N-dimensional hypervolumes to study stability of complex ecosystems.
Barros, Ceres; Thuiller, Wilfried; Georges, Damien; Boulangeat, Isabelle; Münkemüller, Tamara
2016-07-01
Although our knowledge on the stabilising role of biodiversity and on how it is affected by perturbations has greatly improved, we still lack a comprehensive view on ecosystem stability that is transversal to different habitats and perturbations. Hence, we propose a framework that takes advantage of the multiplicity of components of an ecosystem and their contribution to stability. Ecosystem components can range from species or functional groups, to different functional traits, or even the cover of different habitats in a landscape mosaic. We make use of n-dimensional hypervolumes to define ecosystem states and assess how much they shift after environmental changes have occurred. We demonstrate the value of this framework with a study case on the effects of environmental change on Alpine ecosystems. Our results highlight the importance of a multidimensional approach when studying ecosystem stability and show that our framework is flexible enough to be applied to different types of ecosystem components, which can have important implications for the study of ecosystem stability and transient dynamics. © 2016 John Wiley & Sons Ltd/CNRS.
Gravitational stability of three-dimensional stratovolcano edifices
Reid, M.E.; Christian, S.B.; Brien, D.L.
2000-01-01
Catastrophic flank collapses have occurred at many stratovolcanoes worldwide. We present a three-dimensional (3-D) slope stability analysis for assessing and quantifying both the locations of minimum edifice stability and the expected volumes of potential failure. Our approach can search the materials underlying a topographic surface, represented as a digital elevation model (DEM), and determine the relative stability of all parts of the edifice. Our 3-D extension of Bishop's [1955] simplified limit-equilibrium analysis incorporates spherical failure surfaces, variable material properties, pore fluid pressures, and earthquake shaking. Although a variety of processes can trigger collapse, we focus here on gravitationally induced instability. Even homogeneous rock properties strongly influence the depth and volume of the least stable potential failure. For large failures in complex topography, patterns of potential instability do not mimic local ground surface slope alone. The May 18, 1980, catastrophic failure of the north flank of Mount St. Helens provides the best documented case history to test our method. Using the undeformed edifice topography of Mount St. Helens in an analysis of dry, static slope stability with homogeneous materials, as might be conducted in a precollapse hazard analysis, our method identified the northwest flank as the least stable region, although the north flank stability was within 5% of the minimum. Using estimates of the conditions that existed 2 days prior to collapse, including deformed topography with a north flank bulge and combined pore pressure and earthquake shaking effects, we obtained good estimates of the actual failure location and volume. Our method can provide estimates of initial failure volume and location to aid in assessing downslope or downstream hazards.
Asymptotic Stability of High-dimensional Zakharov-Kuznetsov Solitons
Côte, Raphaël; Muñoz, Claudio; Pilod, Didier; Simpson, Gideon
2016-05-01
We prove that solitons (or solitary waves) of the Zakharov-Kuznetsov (ZK) equation, a physically relevant high dimensional generalization of the Korteweg-de Vries (KdV) equation appearing in Plasma Physics, and having mixed KdV and nonlinear Schrödinger (NLS) dynamics, are strongly asymptotically stable in the energy space. We also prove that the sum of well-arranged solitons is stable in the same space. Orbital stability of ZK solitons is well-known since the work of de Bouard [Proc R Soc Edinburgh 126:89-112, 1996]. Our proofs follow the ideas of Martel [SIAM J Math Anal 157:759-781, 2006] and Martel and Merle [Math Ann 341:391-427, 2008], applied for generalized KdV equations in one dimension. In particular, we extend to the high dimensional case several monotonicity properties for suitable half-portions of mass and energy; we also prove a new Liouville type property that characterizes ZK solitons, and a key Virial identity for the linear and nonlinear part of the ZK dynamics, obtained independently of the mixed KdV-NLS dynamics. This last Virial identity relies on a simple sign condition which is numerically tested for the two and three dimensional cases with no additional spectral assumptions required. Possible extensions to higher dimensions and different nonlinearities could be obtained after a suitable local well-posedness theory in the energy space, and the verification of a corresponding sign condition.
Stability and electronic properties of two-dimensional indium iodide
Wang, Jizhang; Dong, Baojuan; Guo, Huaihong; Yang, Teng; Zhu, Zhen; Hu, Gan; Saito, Riichiro; Zhang, Zhidong
2017-01-01
Based on ab initio density functional calculations, we studied the stability and electronic properties of two-dimensional indium iodide (InI). The calculated results show that monolayer and few-layer InI can be as stable as its bulk counterpart. The stability of the monolayer structure is further supported by examining the electronic and dynamic stability. The interlayer interaction is found to be fairly weak (˜160 meV/atom) and mechanical exfoliation to obtain monolayer and few-layer structures will be applicable. A direct band gap of 1.88 eV of the bulk structure is obtained from the hybrid functional method, and is comparable to the experimental one (˜2.00 eV). The electronic structure can be tuned by layer stacking and external strain. The size of the gap is a linear function of an inverse number of layers, suggesting that we can design few-layer structures for optoelectronic applications in the visible optical range. In-plane tensile or hydrostatic compressive stress is found to be useful not only in varying the gap size to cover the whole visible optical range, but also in inducing a semiconductor-metal transition with an experimentally accessible stress. The present result strongly supports the strategy of broadening the scope of group-V semiconductors by looking for isoelectronic III-VII atomic-layered materials.
XU Quan; TIAN Qiang
2007-01-01
Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.
Three-dimensional stability of growing boundary layers
Nayfeh, A. H.
1980-01-01
A theory is developed for the linear stability of three-dimensional growing boundary layers. The method of multiple scales is used to derive partial-differential equations describing the temporal and spatial evolution of the complex amplitudes and wavenumbers of the disturbances. In general, these equations are elliptic unless certain conditions are satisfied. For a monochromatic disturbance, these conditions demand that the ratio of the components of the complex group velocity be real and thereby relate the direction of growth of the disturbance to the disturbance wave angle. For a nongrowing boundary layer, this condition reduces to d-alpha/d-beta being real, in agreement with the result obtained by using the saddle-point method. For a wavepacket, these conditions demand that the components of the group velocity be real.
Stability analysis of lower dimensional gravastars in noncommutative geometry
Banerjee, Ayan [Jadavpur University, Department of Mathematics, Kolkata (India); Hansraj, Sudan [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa)
2016-11-15
The Banados et al. (Phys. Rev. Lett 69:1849, 1992), black hole solution is revamped from the Einstein field equations in (2 + 1)-dimensional anti-de Sitter spacetime, in a context of noncommutative geometry (Phys. Rev. D 87:084014, 2013). In this article, we explore the exact gravastar solutions in three-dimensional anti-de Sitter space given in the same geometry. As a first step we derive BTZ solution assuming the source of energy density as point-like structures in favor of smeared objects, where the particle mass M, is diffused throughout a region of linear size √(α) and is described by a Gaussian function of finite width rather than a Dirac delta function. We matched our interior solution to an exterior BTZ spacetime at a junction interface situated outside the event horizon. Furthermore, a stability analysis is carried out for the specific case when χ < 0.214 under radial perturbations about the static equilibrium solutions. To give theoretical support we are also trying to explore their physical properties and characteristics. (orig.)
Three-dimensional thermal aging and dimensional stability of cellular plastic insulation
Fan, Youchen; Kokko, E. [VTT Building Technology, Espoo (Finland). Building Physics, Puilding Services and Fire Technology
1996-12-31
The requirement of producing environmental-friendly plastic foam results in the replacement of the traditional blowing agents, CFCs (chlorofluorocarbons), with zero ozone depletion potential (ODP) alternatives. The tool which is able to evaluate the quality of the new generation of plastic foams becomes practically important. A 3-dimensional (3-D) heat and mass (gases) transfer model with respect to rigid closed-cell cellular plastics has been carefully deduced and furnished based on our previous understanding of such problems. To solve the 3-D parabolic partial differential equations subject to the third type of boundary conditions, a modified alternative direction implicit (AD I) finite difference method was developed by using the natural laws. To predict the long-term dimensional stability of a plastic foam insulation in air, a simplified mechanical model has been presented. In addition, to closure the prediction of foam dimensional stability, we have deduced a general relationship between the elastic modulus (Young`s modulus) of a rigid closed-cell cellular plastic, E{sub f} and its density, {phi}{sub p}. In comparison to the published measurements and other two well-known E{sub f} - {phi}{sub p} models, it is found that our E{sub f} - up relationship gives better prediction and is valid over the entire rigid plastic foam density range. Thermal aging and average volume change of zero ODP foams with different facing will be addressed. In addition, the application of the model shows the effects of foam dimension and facing on its thermal aging and deformation. (orig.) (13 refs.)
Dimensional Stability of Color-Changing Irreversible Hydrocolloids after Disinfection
Khaledi AAR
2015-03-01
Full Text Available Statement of Problem: Disinfection of dental impressions is a weak point in the dental hygiene chain. In addition, dental office personnel and dental technicians are endangered by cross-contamination. Objectives: This study aimed to investigate the dimensional stability of two color-changing irreversible hydrocolloid materials (IH after disinfection with glutaraldehyde. Materials and Methods: In this in vitro study, impressions were made of a master maxillary arch containing three reference inserts on the occlucal surface of the left and right maxillary second molars and in the incisal surface of the maxillary central incisors. Two types of color-changing irreversible hydrocolloid (tetrachrom, cavex were used. Glutaraldehyde 2% was used in two methods of spraying and immersion to disinfect the impressions. The control group was not disinfected. Casts were made of type IV gypsum. The linear dimensional change of the stone casts was measured with a profile projector. For statistical analysis, Kruskall-Wallis and Mann-Witney tests were used (α=0.05. Results: By immersion method, the casts fabricated from tetrachrom were 0.36% larger in the anteroposterior (AP and 0.05% smaller in cross arch (CA dimensions; however, the casts prepared after spraying of tetrachrom were 0.44% larger in the AP and 0.10% smaller in CA dimensions. The casts made from Cavex were 0.05% smaller in the AP and 0.02% smaller in CA dimensions after spraying and 0.01% smaller in the AP and 0.003% smaller in CA dimensions after immersion. Generally there were not significant differences in AP and CA dimensions of the experimental groups compared to the control (p > 0.05. Conclusions: Disinfection of the tested color-changing irreversible hydrocolloids by glutaraldahyde 2% did not compromise the accuracy of the obtained casts.
Stability analysis of Lower Dimensional Gravastars in noncommutative geometry
Banerjee, Ayan
2016-01-01
The Ba\\~{n}ados, Teitelboim and Zanelli \\cite{BTZ1992}, black hole solution is revamped from the Einstein field equations in (2 + 1)-dimensional anti-de Sitter spacetime, in a context of noncommutative geometry \\cite{Rahaman(2013)}. In this article, we explore the exact gravastar solutions in three-dimension anti-de Sitter space given in the same geometry. As a first step we derive BTZ solution assuming the source of energy density as point-like structures in favor of smeared objects, where the particle mass M, is diffused throughout a region of linear size $\\sqrt{\\alpha}$ and is described by a Gaussian function of finite width rather than a Dirac delta function. We matched our interior solution to an exterior BTZ spacetime at a junction interface situated outside the event horizon. Furthermore, stability analysis is carried out for the dynamic case for the specific case when $\\chi < 0. 214$ under radial perturbations about static equilibrium solutions. To give theoretical support we also trying to explore...
Stability of permeative flows in 1 dimensionally ordered systems
Prost, J.; Pomeau, Y.; Guyon, E.
1991-03-01
Layered structures are met in dissipative systems, such as Rayleigh Bénard rolls, as well as in liquid crystalline phases (smectics and cholesterics). We present here a general description, in the framework of phase dynamics, of the stability of these structures when submitted to an external force field (flow, electric field) acting perpendicular to the roll axis for various boundary conditions. The one-dimensional equilibrium solution with fixed boundary conditions leads to an effect, discovered experimentally by Pocheau and Croquette on Rayleigh-Bérnard rolls in the presence of a transverse flow, and involving the coexistence of compressed and dilated rolls; this effect has a known counterpart in cholesterics. Using the same boundary conditions, we generalize the well known undulation instability obtained under a dilative stress to the case of the action of a transverse force both from the point of view of linear stability and in the highly nonlinear limit. The possibility of observing fractal structures is indicated. For mixed boundary conditions, it is possible to have a sustained time dependent behavior involving the nucleation of new layers as also observed in the above mentioned experiments. On rencontre des structures en couches dans des systèmes dissipatifs tels que les rouleaux convectifs de Rayleigh-Bénard et dans les cristaux liquides (smectiques et cholestériques). Nous présentons ici une description générale de la stabilité de ces structures dans le cadre du formalisme de la diffusion de phase, lorsqu'elles sont soumises à un champ de force extérieur (écoulement, champ électrique) agissant à angle droit de la direction des rouleaux, en fonction des conditions aux limites. La solution unidimensionnelle d'équilibre avec des conditions aux limites rigides pour la phase conduit à un effet découvert par Pocheau et Croquette (P.C.) dans la convection de R.B. et mettant en jeu la coexistence de zones dilatée et comprimée. Cet effet a un
Dimensional stability ofautoclave sterilised addition cured impressions and trays.
Deb, S; Etemad-Shahidi, S; Millar, B J
2014-03-01
The aim of this study was to investigate the dimensional accuracy of impressions following sterilisation by autoclaving. Dental impressions (75) were of a dentoform containing 6 reference points. The impressions were split into 5 groups of 15, each group used a different impression technique. Groups were divided into 3 subgroups with 5 impressions as control, 5 for disinfection by Perform-ID and 5 being autoclaved. Measurements were made using a travelling light microscope. A minimal significant dimensional difference (0.01impression method. No significant dimensional differences were observed for all other groups (P>0.05). The trays and materials tested were suitable for the autoclave sterilisation.
Infinite-Dimensional Feedback Systems : The Circle Criterion and Input-to-State Stability
Jayawardhana, Bayu; Logemann, Hartmut; Ryan, Eugene P.
2008-01-01
An input-to-state stability theory, which subsumes results of circle criterion type, is developed in the context of a class of infinite-dimensional systems. The generic system is of Lur’e type: a feedback interconnection of a well-posed infinite-dimensional linear system and a nonlinearity. The
Md. Saiful Islam; Sinin Hamdan; Mohamad Rusop; Md. Rezaur Rahman; Abu Saleh Ahmed; M. A. M. Mohd Idrus
2012-01-01
Chemical modification is an often-followed route to improve physical and mechanical properties of solid wood materials. In this study five kinds of tropical light hardwoods species, namely jelutong (Dyera costulata), terbulan (Endospermum diadenum), batai (Paraserianthes moluccana), rubberwood (Hevea brasiliensis), and pulai (Alstonia pneumatophora), were chemically modified with benzene diazonium salt to improve their dimensional stability and water repellent efficiency. The dimensional stab...
Stabilization of three-dimensional chaotic systems via single state feedback controller
Yu Wenguang, E-mail: smilewgyu@163.co [School of Statistics and Mathematics, Shandong Economic University, Jinan 250014 (China)
2010-03-29
This Letter investigates the stabilization of three-dimensional chaotic systems, and proposes a novel simple adaptive-feedback controller for chaos control. In comparison with previous methods, the present controller which only contains single state feedback, to our knowledge, is the simplest control scheme for controlling the three-dimensional chaotic system. The results are validated using numerical simulations.
Evaluation of the dimensional stability in the PWR assemblies in Ringhals
Nordlander, Joakim
2015-01-01
Dimensional stability is an important aspect of fuel mechanical design and licensing of new fuel designs for nuclear power plants. Dimensional changes within the reactor can affect the safety margins against overheating of the cladding and the pellets, therefore it is crucial that the dimensional changes are kept to a minimum. The profits per produced kiloWatt hour continue to decrease for the Swedish nuclear power plants. Some reactors are even operated with a calculated loss. To reduce fuel...
A Comparative Study of Stability Testing Approaches of Two-Dimensional Recursive Digital Filters
K. R. Santhi; M.Ponnavaikko; N. Gangatharan
2008-01-01
There are many problems in science and engineering whose solution is applied in the design of Multi-Dimensional (MD) digital filters. Digital filtering finds an important position in the field of digital signal and image processing. Recently there had been a great deal of interest in the design and stability analysis of Two-Dimensional (2-D) recursive digital filters. The design techniques for stable One Dimensional (1-D) digital filters are relatively well developed; but their extension to 2...
Stability analysis of cracks propagating in three dimensional solids
Larralde, H.; Al-Falou, A.A.; Ball, R.C. [Cavendish Lab., Cambridge (United Kingdom)
1996-12-01
The authors present a theory for the morphology of the fracture surface left behind by slowly propagating cracks in linear, isotropic and homogeneous three dimensional solids. The results are based on first order perturbation theory of the equations of elasticity for cracks whose shape is slightly perturbed from planar. For cracks propagating under pure type 1 loading they find that all perturbation modes are linearly stable, from which they can predict the roughness of the fracture surface induced by fluctuations in the material. The authors compare their results with the classical results for cracks propagating in two dimensional systems, and discuss the effects in the three dimensional analysis which result from taking into account contributions from non-singular terms of the stress field, as well as the effects arising from finite speeds of crack propagation.
STABILITY OF N-DIMENSIONAL LINEAR SYSTEMS WITH MULTIPLE DELAYS AND APPLICATION TO SYNCHRONIZATION
Weihua DENG; Jinhu L(U); Changpin LI
2006-01-01
This paper further investigates the stability of the n-dimensional linear systems with multiple delays. Using Laplace transform, we introduce a definition of characteristic equation for the n-dimensional linear systems with multiple delays. Moreover, one sufficient condition is attained for the Lyapunov globally asymptotical stability of the general multi-delay linear systems. In particular, our result shows that some uncommensurate linear delays systems have the similar stability criterion as that of the commensurate linear delays systems. This result also generalizes that of Chen and Moore (2002). Finally, this theorem is applied to chaos synchronization of the multi-delay coupled Chua's systems.
XU Quan; TIAN Qiang
2009-01-01
We restrict our attention to the discrete two-dimensional monatomic β-FPU lattice. We look for twodimensional breather lattice solutions and two-dimensional compact-like discrete breathers by using trying method and analyze their stability by using Aubry's linearly stable theory. We obtain the conditions of existence and stability of two-dimensional breather lattice solutions and two-dimensional compact-like discrete breathers in the discrete twodimensional monatomic β-FPU lattice.
Drift solitons and their two-dimensional stability
Gell, Y.
1977-07-01
The nonlinear equation governing low-frequency drift waves is considered. Utilizing the linear dispersion relation for such waves, it is shown that there exists a parameter range for which the drift waves are governed by a modified Korteweg--de Vries equation having a solitary solution in one and two dimensions. The one-dimensional solitons are unstable with respect to perturbations in the direction perpendicular to their motion.
Moreno Amália
2010-12-01
Full Text Available Abstract Background We evaluated the influence of chemical disinfection and accelerated aging on the dimensional stability and detail reproduction of a silicone elastomer containing one of two opacifiers. Methods A total of 90 samples were fabricated from Silastic MDX 4-4210 silicone and divided into groups (n = 10 according to opacifier content (barium sulfate or titanium dioxide and disinfectant solution (neutral soap, Efferdent, or 4% chlorhexidine. The specimens were disinfected 3 times per week during 60 days and then subjected to accelerated aging for 1008 hours. Dimensional stability and detail reproduction tests were performed after specimens' fabrication (baseline, chemical disinfection and periodically during accelerated aging (252, 504, and 1008 hours. The results were analyzed using 3-way repeated-measures ANOVA and the Tukey HSD test (α = 0.05. Results All groups exhibited dimensional changes over time. The opacifier (p = .314, period (p Conclusions Incorporation of opacifiers alters the dimensional stability of silicones used in facial prosthetics, but seems to have no influence on detail reproduction. Accelerated aging is responsible for most of the dimensional changes in Silastic MDX4 4210, but all dimensional changes measured in this study remained within the limits of stability necessary for this application.
Dimensional Stability of Complex Shapes Manufactured by the VARTM Process
Hubert, Pascal; Grimsley, Brian W.; Cano, Roberto J.; Pipes, R. Byron
2002-01-01
The vacuum assisted resin transfer molding (VARTM) process is a cost effective, innovative method that is being considered for manufacture of large aircraft-quality components where high mechanical properties and dimensional tolerance are essential. In the present work, carbon fiber SAERTEX fabric/SI-ZG-5A epoxy resin C-shaped laminates were manufactured by VARTM using different cure cycles followed by the same post-cure cycle. The final part thickness was uniform except at the corner were thinning was observed. The cure cycle selected is shown to significantly affect the part spring-in and a long cycle at 66 C followed by a 178 C post-cure produced a part with negligible spring-in.
Infinite-Dimensional Feedback Systems: The Circle Criterion and Input-to-State Stability
2008-01-01
An input-to-state stability theory, which subsumes results of circle criterion type, is developed in the context of a class of infinite-dimensional systems. The generic system is of Lur’e type: a feedback interconnection of a well-posed infinite-dimensional linear system and a nonlinearity. The class of nonlinearities is subject to a (generalized) sector condition and contains, as particular subclasses, both static nonlinearities and hysteresis operators of Preisach type.
Gaidachuk, V. E.; Kondratiev, A. V.; Chesnokov, A. V.
2017-01-01
Based on the theory of reinforcement of polymer composites, approximate relations for the physicomechanical and strength properties of a carbon-carbon composite material are synthesized, which are used to perform a finite-element analysis of the degree and character of changes in the thermal and dimensional stability of its structure after carbonization. Using approximate criteria of structural optimization of carbon-carbon composites ensuring their maximum dimensional stability, a [0/±45/90] package of thermally nonquilibrium layers is investigated and compared with an analogous carbon-fiber-reinforced plastic.
Stability of a compressible two-dimensional vortex under a three-dimensional perturbation
Broadbent, E. G.
1984-04-01
It was shown by Kelvin that a two-dimensional vortex under a two-dimensional disturbance in incompressible flow responds at a discrete set of eigenvalues. These were found by Broadbent and Moore (1979) to become unstable in a compressible fluid. Three-dimensional perturbations are shown here also to be unstable, provided that the wavelength is greater than some critical value that depends on the Mach number of the vortex. A definition is given of a critical boundary dividing stable from unstable modes. Whereas the results for the most part relate to a Rankine vortex, some are also given for a vortex with a different velocity profile within the core; qualitatively, the same type of behavior is observed.
Dimensional Stability of Two Polyvinyl Siloxane Impression Materials in Different Time Intervals
Aalaei Sh
2015-12-01
Full Text Available Statement of the Problem: Dental prosthesis is usually made indirectly; there- fore dimensional stability of the impression material is very important. Every few years, new impression materials with different manufacturers’ claims regarding their better properties are introduced to the dental markets which require more research to evaluate their true dimensional changes. Objectives: The aim of this study was to evaluate dimensional stability of additional silicone impression material (Panasil® and Affinis® in different time intervals. Materials and Methods: In this experimental study, using two additional silicones (Panasil® and Affinis®, we made sixty impressions of standard die in similar conditions of 23 °C and 59% relative humidity by a special tray. The die included three horizontal and two vertical lines that were parallel. The vertical line crossed the horizontal ones at a point that served as reference for measurement. All impressions were poured with high strength dental stone. The dimensions were measured by stereo-microscope by two examiners in three interval storage times (1, 24 and 168 hours.The data were statistically analyzed using t-test and ANOVA. Results: All of the stone casts were larger than the standard die. Dimensional changes of Panasil and Affinis were 0.07%, 0.24%, 0.27% and 0.02%, 0.07%, 0.16% after 1, 24 and 168 hours, respectively. Dimensional change for two impression materials wasn’t significant in the interval time, expect for Panasil after one week (p = 0.004. Conclusions: According to the limitations of this study, Affinis impressions were dimensionally more stable than Panasil ones, but it was not significant. Dimensional change of Panasil impression showed a statistically significant difference after one week. Dimensional changes of both impression materials were based on ADA standard limitation in all time intervals (< 0.5%; therefore, dimensional stability of this impression was accepted at least
Heidari
2013-06-01
Full Text Available Background Numerous factors have an effect on the accuracy of an impression and resultant cast, and these include: impression material, impression technique, tray selection, impression disinfection, storage time of impression before pouring, stone type used for fabrication of cast. Up to now, there has been little research conducted on the effect of contact time of a cast with an impression, on the dimensional stability of a cast. Objectives The purpose of this study was to evaluate the effect of the contact time of silicone impression materials with stone casts, on the dimensional stability of resultant casts. Materials and Methods A total of 44 impressions were made from a stainless steel master model, with each one of two silicone impression materials (Elite HD+ and Speedex, and poured with Elite Master Type IV. The thickness of the light-body material (1 mm was provided by using four copings. The resulting casts from each material were placed in four groups(n = 11 after each contact time with the impression (1 hour, 24 hours, 48 hours, 1 week. Distance between anterior and posterior abutments was measured for the casts and master model. Data were analyzed by two-way analysis of variance and a Tukey test. Results The relationship between the dimensional stability of the casts and the simultaneous effect of the impression material and contact time of the cast with the impression was not statistically significant (P = 0.099. Type of impression material on the dimensional stability of the cast had no significant effect (P = 0.163. Increased contact time of the cast with the impression resulted in increased dimensional change (P < 0.001. Conclusions Dimensional stability of the casts after different contact time with the impression was acceptable. The best time to separate the cast from the impression was one hour after pouring the impression.
Equilibrium Initialization and Stability of Three-Dimensional Gas Disks
Wang, Hsiang-Hsu; /Heidelberg, Max Planck Inst. Astron. /ZAH, Heidelberg; Klessen, Ralf S.; /ZAH, Heidelberg /KIPAC, Menlo Park; Dullemond, Cornelis P.; /Heidelberg, Max Planck Inst. Astron.; Bosch, Frank C.van den; /Utah U.; Fuchs, Burkhard; /KIPAC, Menlo Park
2010-08-25
We present a new systematic way of setting up galactic gas disks based on the assumption of detailed hydrodynamic equilibrium. To do this, we need to specify the density distribution and the velocity field which supports the disk. We first show that the required circular velocity has no dependence on the height above or below the midplane so long as the gas pressure is a function of density only. The assumption of disks being very thin enables us to decouple the vertical structure from the radial direction. Based on that, the equation of hydrostatic equilibrium together with the reduced Poisson equation leads to two sets of second-order non-linear differential equation, which are easily integrated to set-up a stable disk. We call one approach 'density method' and the other one 'potential method'. Gas disks in detailed balance are especially suitable for investigating the onset of the gravitational instability. We revisit the question of global, axisymmetric instability using fully three-dimensional disk simulations. The impact of disk thickness on the disk instability and the formation of spontaneously induced spirals is studied systematically with or without the presence of the stellar potential. In our models, the numerical results show that the threshold value for disk instability is shifted from unity to 0.69 for self-gravitating thick disks and to 0.75 for combined stellar and gas thick disks. The simulations also show that self-induced spirals occur in the correct regions and with the right numbers as predicted by the analytic theory.
Roger M. Rowell; Rebecca E. Ibach; James McSweeny; Thomas Nilsson
2009-01-01
Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat-treated wood depend on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to small organic molecules, water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in...
Stability of a Two-Dimensional Poiseuille-Type Flow for a Viscoelastic Fluid
Endo, Masakazu; Giga, Yoshikazu; Götz, Dario; Liu, Chun
2017-03-01
A viscoelastic flow in a two-dimensional layer domain is considered. An L 2-stability of the Poiseuille-type flow is established provided that both Poiseuille flow and perturbation is sufficiently small. Our analysis is based on a stream function formulation introduced by Lin et al. (Commun Pure Appl Math 58(11):1437-1471, 2005).
Stability of two-dimensional spatial solitons in nonlocal nonlinear media
Skupin, S.; Bang, Ole; Edmundson, D.;
2006-01-01
We discuss the existence and stability of two-dimensional solitons in media with spatially nonlocal nonlinear response. We show that such systems, which include thermal nonlinearity and dipolar Bose-Einstein condensates, may support a variety of stationary localized structures, including rotating...
Oostveen, JC; Curtain, RF
1997-01-01
We solve the problem of robust stabilization with respect to normalized coprime factor perturbations for a new class of infinite-dimensional systems with finite-rank, colocated actuators and sensors and possibly infinitely many unstable eigenvalues on the imaginary axis. Such systems are often used
Gravity in a stabilized brane world model in five-dimensional Brans-Dicke theory
Mikhailov, A S; Smolyakov, M N; Volobuev, I P
2008-01-01
Linearized equations of motion for gravitational and scalar fields are found and solved in a stabilized brane world model in five-dimensional Brans-Dicke theory. The physical degrees of freedom are isolated, the mass spectrum of Kaluza-Klein excitations is found and the coupling constants of these excitations to matter on the negative tension brane are calculated.
Stabilizing chaotic vortex trajectories an example of high-dimensional control
Pentek, A; Toroczkai, Z
1997-01-01
A chaos control algorithm is developed to actively stabilize unstable periodic orbits of higher-dimensional systems. The method assumes knowledge of the model equations and a small number of experimentally accessible parameters. General conditions for controllability are discussed. The algorithm is applied to the Hamiltonian problem of point vortices inside a circular cylinder with applications to an experimental plasma system.
Stability of massive graviton around BTZ black hole in three dimensional massive gravities
Moon, Taeyoon
2013-01-01
We investigate the massive graviton stability of the BTZ black hole obtained from three dimensional massive gravities which are classified into the parity-even and parity-odd gravity theories. In the parity-even gravity theory, we perform the $s$-mode stability analysis by using the BTZ black string perturbations, which gives two Schr\\"odinger equations with frequency-dependent potentials. The $s$-mode stability is consistent with the generalized Breitenlohner-Freedman bound for spin-2 field. It seems that for the parity-odd massive gravity theory, the BTZ black hole is stable when the imaginary part of quasinormal frequencies of massive graviton is positive. However, this condition is not consistent with the $s$-mode stability based on the second-order equation obtained after squaring the first-order equation. Finally we explore the black hole stability connection between the parity-odd and parity-even massive gravity theories.
Akbarov, Surkay
2013-01-01
This book investigates stability loss and buckling delamination problems of the viscoelastic composite materials and structural members made from these materials within the framework of the Three-Dimensional Linearized Theory of Stability (TDLTS). The investigation of stability loss problems is based on the study of an evolution of the initial infinitesimal imperfection in the structure of the material or of the structural members with time (for viscoelastic composites) or with external compressing forces (for elastic composites). This study is made within the scope of the Three-Dimensional Geometrically Non-Linear Theory of the Deformable Solid Body Mechanics. The solution to the corresponding boundary-value problems is presented in the series form in a small parameter which characterizes the degree of the initial imperfection. The boundary form perturbation technique is employed and nonlinear problems for the domains bounded by noncanonical surfaces are reduced to the same nonlinear problem for the correspo...
M. Farzin
2010-12-01
Full Text Available Objective: The aim of this study was to evaluate the dimensional stability of casts made from an alginate impression material poured immediately and stored after specific periods.Materials and Methods: The common alginate used in Iran (Super; Iralgin, Golchai Co.,Tehran, Iran was tested. A master model was mounted on a special device and used to obtain the impressions. These impressions were stored at 23°C (SD=1 and 4°C (SD=1 in100% relative humidity, then poured with gypsum immediately and again after 12, 25, 45 and 60 minutes. The casts were measured with a traveling microscope with the precision of 0.5 micrometer.Results: The dimensional stability of the alginate and impressions were both significantly time and temperature dependent. The impressions were dimensionally stable significantly until 12 minutes of storage at room temperature and until 45 minutes of storage at 4°C(SD=1.Conclusion: The dimensional stability of the alginate impressions was influenced by the storage time and environment temperature, but a humid environment and 4°C (SD=1temperature may delay the pouring.
Crofts, Jonathan J; Davidchack, Ruslan L
2009-09-01
We explore the possibility of extending the stabilizing transformations approach [J. J. Crofts and R. L. Davidchack, SIAM J. Sci. Comput. (USA) 28, 1275 (2006)]. to the problem of locating large numbers of unstable periodic orbits in high-dimensional flows, in particular those that result from spatial discretization of partial differential equations. The approach has been shown to be highly efficient when detecting large sets of periodic orbits in low-dimensional maps. Extension to low-dimensional flows has been achieved by the use of an appropriate Poincare surface of section [D. Pingel, P. Schmelcher, and F. K. Diakonos, Phys. Rep. 400, 67 (2004)]. For the case of high-dimensional flows, we show that it is more efficient to apply stabilizing transformations directly to the flows without the use of the Poincare surface of section. We use the proposed approach to find many unstable periodic orbits in the model example of a chaotic spatially extended system-the Kuramoto-Sivashinsky equation. The performance of the proposed method is compared against other methods such as Newton-Armijo and Levenberg-Marquardt algorithms. In the latter case, we also argue that the Levenberg-Marquardt algorithm, or any other optimization-based approach, is more efficient and simpler in implementation when applied directly to the detection of periodic orbits in high-dimensional flows without the use of the Poincare surface of section or other additional constraints.
Dimensional stability of materials based on Portland cement at the early stages
Mesa Yandy, Angélica; Zerbino, Raúl L.; Giaccio, Graciela M.; Russo, Nélida A.; Duchowicz, Ricardo
2014-09-01
In this work two fiber optic sensing techniques are used to study the dimensional stability in fresh state of different cementitious materials. A conventional Portland cement mortar and two commercial grouts were selected. The measurements were performed by using a Bragg grating embedded in the material and a non-contact Fizeau interferometer. The first technique was applied in a horizontal sample scheme, and the second one, by using a vertical configuration. In addition, a mechanical length comparator was used in the first case in order to compare the results. The evolution with time of the dimensional changes of the samples and the analysis of the observed behavior are included.
The contribution of particle swarm optimization to three-dimensional slope stability analysis.
Kalatehjari, Roohollah; Rashid, Ahmad Safuan A; Ali, Nazri; Hajihassani, Mohsen
2014-01-01
Over the last few years, particle swarm optimization (PSO) has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D) slope stability analysis. This paper applied PSO in three-dimensional (3D) slope stability problem to determine the critical slip surface (CSS) of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes.
The Contribution of Particle Swarm Optimization to Three-Dimensional Slope Stability Analysis
Roohollah Kalatehjari
2014-01-01
Full Text Available Over the last few years, particle swarm optimization (PSO has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D slope stability analysis. This paper applied PSO in three-dimensional (3D slope stability problem to determine the critical slip surface (CSS of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes.
Stability conditions for one-dimensional optical solitons in cubic-quintic-septimal media
Reyna, Albert S; de Araujo, Cid B
2015-01-01
Conditions for stable propagation of one-dimensional bright spatial solitons in media exhibiting optical nonlinearities up to the seventh-order are investigated. The results show well-defined stability regions even when all the nonlinear terms are focusing. Conditions for onset of the supercritical collapse of the optical beam are identified too. A variational approximation is used to predict dependence of the soliton propagation constant on the norm, and respective stability regions are identified using the Vakhitov-Kolokolov criterion. Analytical results obtained by means of the variational approximation are corroborated by numerical simulations of the cubic-quintic-septimal nonlinear Schroedinger equation.
Influence of Nanosized Silicon Carbide on Dimensional Stability of Al/SiC Nanocomposite
S. M. Zebarjad
2008-01-01
Full Text Available This study concentrated on the role of particle size of silicon carbide (SiC on dimensional stability of aluminum. Three kinds of Al/SiC composite reinforced with different SiC particle sizes (25 μm, 5 μm, and 70 nm were produced using a high-energy ball mill. The standard samples were fabricated using powder metallurgy method. The samples were heated from room temperature up to 500∘C in a dilatometer at different heating rates, that is, 10, 30, 40, and 60∘C/min. The results showed that for all materials, there was an increase in length change as temperature increased and the temperature sensitivity of aluminum decreased in the presence of both micro- and nanosized silicon carbide. At the same condition, dimensional stability of Al/SiC nanocomposite was better than conventional Al/SiC composites.
Effect of Heat Treatment upon Dimensional Stability and Static Bending Strength of Sessile Oak Wood
Alin OLARESCU
2011-06-01
Full Text Available The paper presents the results of an experimentalstudy performed with sessile oak wood (Quercuspetrea L.. After drying and conditioning at 12%MC,the test pieces were heat-treated at three differenthigh temperatures (120, 130 and 140°C for 1h, 2hand 3h. After the treatment and cooling, standardsamples for physical and mechanical tests were cut,in order to determine comparatively the density, thedimensional stability, the static bending strength andMOE of the differently treated samples.Based on the obtained results, the optimumtreatment schedule was established, namely the onewhich enables improved dimensional stability withoutaffecting significantly the wood strength. Theseresults can be applied at the manufacturing of solidwood panels with improved dimensional stabilityusing heat-treated wood lamellas.
Note: Silicon Carbide Telescope Dimensional Stability for Space-based Gravitational Wave Detectors
Sanjuah, J.; Korytov, D.; Mueller, G.; Spannagel, R.; Braxmaier, C.; Preston, A.; Livas, J.
2012-01-01
Space-based gravitational wave detectors are conceived to detect gravitational waves in the low frequency range by measuring the distance between proof masses in spacecraft separated by millions of kilometers. One of the key elements is the telescope which has to have a dimensional stability better than 1 pm Hz(exp -1/2) at 3 mHz. In addition, the telescope structure must be light, strong, and stiff. For this reason a potential telescope structure consisting of a silicon carbide quadpod has been designed, constructed, and tested. We present dimensional stability results meeting the requirements at room temperature. Results at -60 C are also shown although the requirements are not met due to temperature fluctuations in the setup.
3-dimensional slope stability analyses using non-associative stress-strain relationships
CHEN ZuYu; SUN Ping; WANG YuJie; ZHANG HongTao
2009-01-01
The research work presented in this paper refers to a new slope stability analysis method used for landslide risk evaluations. It is an extension of the 3-dimensional upper-bound slope stability analysis method proposed by Chen et sl. in 2001, which employs the Mohr-Coulomb's associative flow rule. It has been found that in a 3-dimensional area, a prism may not be able to move at friction angles to all its surrounding interfaces, as required by this associative rule, and convergence problems may occa-sionally arise. The new method establishes two velocity fields: (i) The plastic one that represents a non-associative and the best representative dilation behavior, and (ii) the virtual one that permits the solution for factor of safety in the work and energy balance equation. The new method can then allow any input value of dilation angle and thus solve the convergence problem. A practical application to a concrete dam foundation is illustrated.
DIMENSIONAL STABILITY PERFORMANCE OF FIRE RETARDANT TREATED VENEER-ORIENTED STRANDBOARD COMPOSITES
Zeki Candan
2011-02-01
Full Text Available This study investigated dimensional stability properties of oriented strandboard (OSB panels faced with fire retardant treated (FRT veneers. The beech (Fagus orientalis Lipsky veneers were treated with monoammonium phosphate (MAP, diammonium phosphate (DAP, lime water (LW, and a borax/boric acid (BX/BA (1:1 mixture. Dimensional stability tests were performed according to ASTM D-1037. The results revealed that facing veneers impregnated with fire-retardant chemicals had significant effects on the linear expansion (LE properties. The lowest LE value was obtained from the panels faced with MAP treated veneers, while the highest LE value was found in the panels faced with BX/BA treated veneers. The FRT treated veneer facing technique also affected the thickness swelling (TS properties of the OSB panels. The panels faced with LW treated veneers had the highest TS, whereas the panels faced with MAP treated veneers had the lowest TS values.
Md Saiful Islam,
2012-01-01
Full Text Available Chemical modification is an often-followed route to improve physical and mechanical properties of solid wood materials. In this study five kinds of tropical light hardwoods species, namely jelutong (Dyera costulata, terbulan (Endospermum diadenum, batai (Paraserianthes moluccana, rubberwood (Hevea brasiliensis, and pulai (Alstonia pneumatophora, were chemically modified with benzene diazonium salt to improve their dimensional stability and water repellent efficiency. The dimensional stability of treated samples in terms of volumetric swelling coefficient (S and anti-swelling-efficiency (ASE were found to improve with treatment. The water repellent efficiency (WRE values also seemed to improve considerably with treatment of wood samples. Furthermore, treated wood samples had lower water and moisture absorption compared to that of untreated ones.
Esteves,Bruno; Nunes, Lina; Domingos, Idalina; Pereira, Helena
2014-01-01
Paraffin has been used as surface protection of wood throughout the ages but its use for impregnation to improve wood resistance to biodegradation is recent. This study determined the main improvements on wood properties with paraffin impregnation. Healthy Pinus pinaster Ait. wood was impregnated with paraffin at different levels using a hot–cold process. Weight gain, equilibrium moisture content and dimensional stability (ASE) at 35 and 65 % relative humidity, termite durability against Reti...
Silva, Sávio Marcelo Leite Moreira da; Salvador, Milton Carlos Gonçalves
2004-01-01
The purpose of this study was to evaluate the dimensional stability of heavy and light bodied condensation silicones after immersion in disinfectant solution for 10 or 20 minutes. The impression materials were Optosil Comfort and Xantopren VL Plus and the disinfectant solutions were 1% sodium hypochlorite and 2% glutaraldehyde. Impressions were made on a perforated stainless steel tray, according to the American Dental Association specification No. 19, adding up to a total of 50 samples. The ...
Counter-rotational effects on stability of 2 + 1-dimensional thin-shell wormholes
Mazharimousavi, S.H.; Halilsoy, M. [Eastern Mediterranean University, Department of Physics, Gazimagusa (Turkey)
2014-09-15
The role of angular momentum in a 2 + 1-dimensional rotating thin-shell wormhole (TSW) is considered. Particular emphasis is given to stability when the shells (rings) are counter-rotating. We find that counter-rotating halves make the TSW supported by the equation of state of a linear gas more stable. Under a small velocity dependent perturbation, however, it becomes unstable. (orig.)
Thermal expansion of a fused quartz tube in a dimensional stability test facility.
Wolff, E G; Eselun, S A
1979-04-01
A facility to monitor the dimensional stability of structures of arbitrary size or shape under varying temperature and pressure conditions is described. Real-time linear displacements are measured with a modified Michelson laser interferometer to a resolution of less than one part in 10(7) and an accuracy of approximately 2 parts in 10(7) for approximately 1 m gauge lengths. Verification of the system accuracy with a quartz tube required considerations of its fabrication and compositional characteristics.
Stability and Bifurcation of Two Kinds of Three-Dimensional Fractional Lotka-Volterra Systems
Jinglei Tian
2014-01-01
Full Text Available Two kinds of three-dimensional fractional Lotka-Volterra systems are discussed. For one system, the asymptotic stability of the equilibria is analyzed by providing some sufficient conditions. And bifurcation property is investigated by choosing the fractional order as the bifurcation parameter for the other system. In particular, the critical value of the fractional order is identified at which the Hopf bifurcation may occur. Furthermore, the numerical results are presented to verify the theoretical analysis.
Sinobad Tamara; Obradović-Đuričić Kosovka; Nikolić Zoran; Dodić Slobodan; Lazić Vojkan; Sinobad Vladimir; Jesenko-Rokvić Aleksandra
2014-01-01
Background/Aim. Dimensional stability and accuracy of an impression after chemical disinfection by immersion in disinfectants are crucial for the accuracy of final prosthetic restorations. The aim of this study was to assess the deformation of addition and condensation silicone impressions after disinfection in antimicrobial solutions. Methods. A total of 120 impressions were made on the model of the upper arch representing three full metal-ceramic crown pr...
STUDIES ON NONLINEAR STABILITY OF THREE-DIMENSIONAL H-TYPE DISTURBANCE
王伟志; 唐登斌
2003-01-01
The three-dimensional H-type nonlinear evolution process for the problem of boundary layer stability is studied by using a newly developed method called parabolic stability equations (PSE).The key initial conditions for sub-harmonic disturbances are obtained by means of the secondary instability theory. The initial solutions of two-dimensional harmonic waves are expressed in Landau expansions. The numerical techniques developed in this paper, including the higher order spectrum method and the more effective algebraic mapping for dealing with the problem of an infinite region,increase the numerical accuracy and the rate of convergence greatly. With the predictor-corrector approach in the marching procedure, the normalization, which is very important for PSE method, is satisfied and the stability of the numerical calculation can be assured. The effects of different pressure gradients, including the favorable and adverse pressure gradients of the basic flow, on the "H-type"evolution are studied in detail. The results of the three-dimensional nonlinear "H-type" evolution are given accurately and show good agreement with the data of the experiment and the results of the DNS from the curves of the amplitude variation, disturbance velocity profile and the evolution of velocity.
DENSIFICATION OF WOOD VENEERS COMBINED WITH OIL-HEAT TREATMENT. PART I: DIMENSIONAL STABILITY
Chang-Hua Fang
2011-02-01
Full Text Available Although wood densification by compression improves wood mechanical strength, dimensional stability is often a problem due to compression recovery. Alternatively, oil-heat treatment (OHT improves wood dimensional stability and enhances resistance to biological attack. This study examined combined wood densification and OHT. Large wood veneer 700 × 700 mm specimens prepared with aspen (Populus tremuloides were densified using heat, steam, and pressure at 160ºC, 180ºC, and 200°C, respectively. OHT at 180ºC, 200ºC, and 220ºC for 1, 2, and 3h was then applied to the densified veneers. Results show that OHT efficiently improved dimensional stability and reduced compression set recovery. OHT temperature and duration markedly influenced the reduction of compression set recovery: the higher the OHT temperature and duration, the lower the recovery. Less than 5% recovery was obtained under various OHT conditions, and almost 0% recovery under some OHT conditions. Radial and tangential swellings of densified veneers were reduced dramatically. Compared to OHT duration, OHT temperature had a pronounced higher impact on radial and tangential swelling. Irreversible swelling (IS in the compression direction of densified veneers decreased after OHT, particularly with high temperature and long duration, and anti-swelling efficiency (ASE in the compression direction improved significantly.
The relation between temporal and spatial stability in three-dimensional flows
Nayfeh, A. H.; Padhye, A.
1978-01-01
An analysis is presented of the nonparallel spatial or temporal stability of three-dimensional incompressible, isothermal boundary-layer flows taking into account the transverse velocity component as well as the axial and crossflow variations of the mean flow. The method of multiple scales is used to derive partial differential equations that describe the axial and crossflow variations of the disturbance amplitude, phase and wavenumbers. This equation is used to derive the expressions that relate the temporal and spatial instabilities. These relations are functions of the complex group velocities. Moreover, this equation is used to derive the expression that relates the spatial amplification in any direction to a calculated amplification in any other direction. These relations are verified by numerical results obtained for two- and three-dimensional disturbances in two- and three-dimensional flows.
Gomez-Polo, Miguel; Celemin, Alicia; del Rio, Jaime; Sanchez, Andres
2012-01-01
This study aimed to determine how impression technique and pouring time affect casts obtained using polyvinyl siloxane (PVS) and polyether (PE) impressions. A total of 480 impressions were taken using three techniques: single-step (SS), two-step (TS), and two-step with a spacer (TSS). Impressions were poured after 1 and 24 hours and 7 and 14 days. Significant differences (P < .01) were found between the TS technique and the SS and TSS methods as well as between PE and PVS (P < .01) in terms of the effects of pouring time. SS and TSS yielded similar dimensional results, while greater dimensional change was induced with TS. PE impressions had to be poured no later than 7 days after preparation to ensure dimensional stability.
Three-dimensional stability analysis of the dam foundation at Baise
XU Qianjun; LI Xu; CHEN Zuyu
2007-01-01
It is usually difficult to determine the actual safety factors of rock masses in an ordinary two-dimensional stability analysis if the safety factors of the different cross sections in the rock mass vary significantly. In addition to the actual slope, arch dam abutment, and the actual foundation of a high building, another example is that the different cross sections of the foundation in the monolith of a gravity dam vary significantly, just like the condition at the overflow dam in the Baise project. A three-dimensional stability analysis method based on the upper-bound theorem was employed to solve this problem. The parameters used in the analysis were obtained from geomechanics tests, as well as continuity simu- lations of the randomly distributed joints. Two failure patterns against sliding are analyzed. One pattern is the foundation slide along deep-seated planes which were determined by cal- culations. The other pattern is the foundation slide along the planes across the bottom of the high steps in the foundation pit. The results indicate that a special overflow dam monolith can be considered to be safe in case of considering the three dimensional effect. However, a key wall with a depth of 5m must be constructed at the upper side of this monolith in order to ensure the safety of the foundation.
Influence of elastic recovery time on the Dimensional Stability of Polydimethylsiloxane (PDS
Leonardo de Cesero
2013-01-01
Full Text Available The aim of this study was to determine the influence from the recovering time on the dimensional stability of polydimethylsiloxane (Speedex, Coltène/Whaledent Company, Altstätten, Switzerland prior to type IV dental stone pouring. The double impression technique was utilized with uniform spacing of 1 mm for the wash paste, at 30 minutes, 24 hours and 72 hours after making the impression using an individual perforated metal tray. After the preparation of the impressions, six stone models were made by the standard procedure for all the impressions. The dimensional alterations (mm of the models obtained were submitted to analysis of variance (ANOVA and Tukey's test (α = 0.05. No statistically significant difference between the three groups (30 minutes, 24 hours and 72 hours were recorded for either the height or diameter of the samples. However, upon comparing the results of the three groups with the metal standard model, there was a significant difference between group 1 (30 min in relation to the diameter of the standard metal die (p = 0,047. The condensation silicone Speedex shows satisfactory dimensional stability, where dental stone models can be poured with assurance up to 72 hours after preparation of the impression.
Logemann, H; Curtain, RF
2000-01-01
We derive absolute stability results for well-posed infinite-dimensional systems which, in a sense, extend the well-known circle criterion to the case that the underlying linear system is the series interconnection of an exponentially stable well-posed infinite-dimensional system and an integrator a
Arafa, Khalid A O
2016-01-01
Background. Type of materials used in fabrication of denture base has an effect on dimension during denture base material processing and other factors related to clinical use. Objective. The study aims were to assess the dimensional stability including thermal changes of three different denture base materials. Methods. Ninety patients were selected to construct complete dentures with different denture base materials. They were randomly divided into three groups: group 1, patients with cobalt chrome metallic base; group 2, patients with heat curing acrylic resin fabricated by injection moulding technique; and group 3, patients with denture bases fabricated by conventional heat curing acrylic resin. The dimensional changes were assessed using digital caliper. Results. After the twelfth month, injection moulding acrylic resin had significantly the highest dimensional change followed by the conventional heat curing acrylic resin. There were no significant differences in the dimensions between the three types of denture base materials at normal mouth temperature, while, after hot tea drinking at 45°C, the dimensional change was significantly the highest in cobalt chrome metallic denture base group. Conclusion. Cobalt chrome metallic denture base has stable dimension compared to denture bases fabricated of acrylic resin but it was more affected by altered mouth temperature. The study was registered in the International Standard Randomized Controlled Trials Number (ISRCTN) registry with study ID (ISRCTN94238244).
Khalid A. O. Arafa
2016-01-01
Full Text Available Background. Type of materials used in fabrication of denture base has an effect on dimension during denture base material processing and other factors related to clinical use. Objective. The study aims were to assess the dimensional stability including thermal changes of three different denture base materials. Methods. Ninety patients were selected to construct complete dentures with different denture base materials. They were randomly divided into three groups: group 1, patients with cobalt chrome metallic base; group 2, patients with heat curing acrylic resin fabricated by injection moulding technique; and group 3, patients with denture bases fabricated by conventional heat curing acrylic resin. The dimensional changes were assessed using digital caliper. Results. After the twelfth month, injection moulding acrylic resin had significantly the highest dimensional change followed by the conventional heat curing acrylic resin. There were no significant differences in the dimensions between the three types of denture base materials at normal mouth temperature, while, after hot tea drinking at 45°C, the dimensional change was significantly the highest in cobalt chrome metallic denture base group. Conclusion. Cobalt chrome metallic denture base has stable dimension compared to denture bases fabricated of acrylic resin but it was more affected by altered mouth temperature. The study was registered in the International Standard Randomized Controlled Trials Number (ISRCTN registry with study ID (ISRCTN94238244.
Evaluation of linear dimensional stability of various combinations of dental stone and plaster.
Adegbulugbe, I C; Oderinu, O H; Shaba, O P; Oremosu, O A
2011-01-01
It has been observed that due to the cheaper cost of dental plaster compared to dental stone, casts on which most of the dental prostheses and appliances were being fabricated in various laboratories were often mixtures of dental stone and dental plaster in order to reduce production cost. To evaluate the dimensional stability of various combinations of Dental Stone and Dental Plaster mixtures used to make dental casts. Alginate impressions of a master model of truncated metal cones were made and casts were produced by pouring with various combinations of dental stone and dental plaster mixtures. The linear dimensional differences between the inter-abutment distances on the casts were measured with an electronic caliper. One sample t-test and percentage differences were calculated. Dimensional variations for the distances measured using either 50% dental stone or 25% dental stone with plaster were statistically significant (p d" 0.05). Mixture of 75% dental stone and 25% dental plaster produced casts with no statistically significant dimensional variation from the master model (p e" 0.05). A mixture of 75% dental stone and 25% dental plaster could be used for procedures not requiring very accurate replica like mounting of teeth for dental training and for study models.
Arpin, Kevin A.; Losego, Mark D.; Cloud, Andrew N.; Ning, Hailong; Mallek, Justin; Sergeant, Nicholas P.; Zhu, Linxiao; Yu, Zongfu; Kalanyan, Berç; Parsons, Gregory N.; Girolami, Gregory S.; Abelson, John R.; Fan, Shanhui; Braun, Paul V.
2013-10-01
Selective thermal emission in a useful range of energies from a material operating at high temperatures is required for effective solar thermophotovoltaic energy conversion. Three-dimensional metallic photonic crystals can exhibit spectral emissivity that is modified compared with the emissivity of unstructured metals, resulting in an emission spectrum useful for solar thermophotovoltaics. However, retention of the three-dimensional mesostructure at high temperatures remains a significant challenge. Here we utilize self-assembled templates to fabricate high-quality tungsten photonic crystals that demonstrate unprecedented thermal stability up to at least 1,400 °C and modified thermal emission at solar thermophotovoltaic operating temperatures. We also obtain comparable thermal and optical results using a photonic crystal comprising a previously unstudied material, hafnium diboride, suggesting that refractory metallic ceramic materials are viable candidates for photonic crystal-based solar thermophotovoltaic devices and should be more extensively studied.
Pastur, L R; Lusseyran, F; Basley, J
2012-01-01
Three-dimensional direct numerical simulations of an incompressible open square cavity flow are conducted. Features of the permanent (non-linear) regime together with the linear stability analysis of a two-dimensional steady base flow are discussed. Spanwise boundary conditions are periodic and control parameters set such that the shear layer is stable against Kelvin-Helmholtz modes. Three branches of destabilising modes are found. The most destabilising branch is associated with steady modes, over a finite range of spanwise wavenumbers. The two other branches provide unsteady modes. Features of each branches are recovered in the permanent regime: wavelength of the most powerful spanwise Fourier mode, swaying phenomenon, angular frequencies, indicating that modes of each branches are selected and interact in the permanent flow.
XU Quan; TIAN Qiang
2007-01-01
@@ Compact-like discrete breathers in discrete one-dimensional monatomic chains are investigated by discussing a generalized discrete one-dimensional monatomic model. It is proven that compact-like discrete breathers exist not only in soft φ4 potential but also in hard φ4 potential and K4 chains. The measurements of compact-like discrete breathers' core in soft and hard φ4 potential are determined by coupling parameter K4, while the measurements of compact-like discrete breathers' core in K4 chains are not related to coupling parameter K4. The stabilities of compact-like discrete breathers correlate closely to coupling parameter K4 and the boundary condition of lattice.
Study of Thermal Stress Influence on Dimensional Stability of Silicone Molds
Bajčičák Martin
2014-06-01
Full Text Available The paper is focused on the study of temperature influence on dimensional stability of silicone molds used for spin casting of the low melting points alloys. The silicone material denoted as TEKSIL Silicone-GP-S was used to produce samples during experiments. The samples were heated to temperatures in the range from 100 up to 250oC for 30 up to 120 min. Dimensional changes of the samples in the radial and axial directions aa well as their change of weight were evaluated. The results of experiments proved that thermal stress of silicone molds can influence the size and shape of mold cavities. These results can also explain the possible mechanism of degradation process of silicone molds under thermal stress.
Influence of Thermal Treatment on the Hygroscopicity and Dimensional Stability of Oak Wood
Inga JUODEIKIENĖ
2013-03-01
Full Text Available The influence of thermal treatment on moisture exchange between wood and natural environment with variable air parameters as well as on dimensional stability of wood samples was investigated. The experiments were carried out with oak wood samples indoors and outside. The thickness of samples was 30 mm, width was 30 mm and length was 20 mm; conventional density varied from 500 kg/m3 to 580 kg/m3. Initially, the wood was air-dried down to 7 % – 9 % of moisture content. In order to decrease possibility of the both moisture absorption and evaporation during wood application thermal treatment must be applied. Due to that the samples were heated at temperature of 60, 80, 100 and 120 ºC for 24, 48, 72 and 96 hours. The moisture content of wood and its variations after thermal treatment depends on the both heating temperature and duration. The higher temperature and the longer heating duration, the lower wood hygroscopicity can be achieved. The effect of thermal treatment on the moisture content and its changes were observed for wood samples stored indoor and outside. In dependence of thermal treatment conditions moisture content in wood samples independently on storing conditions (indoor or outside can decrease down to 30 % compare to the untreated ones. The change of moisture content during various seasons after 24 hours of storing indoor decreases down to 60 %, while outside that is only 39 %. Dimensional stability of wood samples also depends on the both thermal treatment temperature and duration. The higher treatment temperature and the longer duration, the higher dimensional stability can be obtained. The heat treatment of oak wood samples at selected regimes allows to decrease values of shrinkage and swelling coefficients down to 40 %.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3825
Verification of dimensional stability on ITER blanket shield block after stress relieving
Kim, Sa-Woong, E-mail: swkim12@nfri.re.kr; Jung, Hun-Chea; Ha, Min-Su; Shim, Hee-Jin
2016-11-01
Highlights: • The SB#08 FSP were manufactured by using conventional manufacturing processes such as cutting, milling, drilling and welding. • Especially, a strong back system was adopted in order to prevent welding deformation during cover plate welding process. • Post-Welding Heat Treatment (PWHT) for stress relieving and Hot He Leak Test (HHLT) were waived from the lake of huge test facility in the pre-qualification program. • The PWHT combined with the HHLT, however, were implemented to remove the residual stress and to confirm the soundness of welded parts as an internal R&D activities after the pre-qualification program. • Three dimensional inspection also carried out after the PWHT to check the dimensional stabilization. - Abstract: The tight tolerance requirement is one of key issue to manufacture the ITER blanket shield blocks (SBs) which have many interfaces with the First Wall (FW) and Vacuum Vessel (VV). Manufactured SB shall be satisfied with general tolerances (Class “C” of ISO 2768-1 and “L” of ISO 2768-2) and specific tolerance in 2D general assembly drawings. In order to fulfill the tight tolerance requirements in the final stage of SB, stress relieving after welding operations in the manufacturing process shall be performed. Hot helium leak test, Post Welding Heat Treatment (PWHT) and three-dimensional inspection before and after heat treatment were implemented by using the Full Scale Prototype (FSP) of SB in the framework of domestic R&D activities. The hot He leak test was performed at 250 °C for 30 min, and the result was satisfied the requirements. PWHT was carried out at 400 °C for 24 h by brazing furnace with test chamber. The deformation value before and after was measured by contact type coordinate measuring machine. The objective of this study is to verify dimensional stability of SB after stress relieving. The results will support to determine the machining allowance prior to welding process.
P A Subha; C P Jisha; V C Kuriakose
2007-08-01
The nonlinear Schrödinger equation which governs the dynamics of two-dimensional spatial solitons in Kerr media with periodically varying diffraction and nonlinearity has been analyzed in this paper using variational approach and numerical studies. Analytical expressions for soliton parameters have been derived using variational analysis. Variational equations and partial differential equation have been simulated numerically. Analytical and numerical studies have shown that nonlinearity management and diffraction management stabilize the pulse against decay or collapse providing undisturbed propagation even for larger energies of the incident beam.
Dimensional-stability studies of candidate space-telescope mirror-substrate materials
Jerke, J. M.; Platt, R. J., Jr.
1972-01-01
The effects of aging, vacuum exposure, and thermal cycling on the dimensional stability of mirror-substrate materials, fused silica, Cer-Vit, Kanigen-coated beryllium, polycrystalline silicon, and U.L.E. fused silica were investigated. A multiple-beam interferometer was used to determine nonrecoverable surface-shape changes of the 12.7-cm-diameter mirrors with substrates of these materials. Thermal cycling and aging in vacuum produced the largest changes, but only a few were as large as 1/30 wavelength, where the wavelength was 632.8 nm.
Effect of Temperature on Polaron Stability in a One-Dimensional Organic Lattice
LIU Wen; LI Yuan; QU Zhen; GAO gun; YIN Sun; LIU De-Sheng
2009-01-01
Effect of temperature on the polaron stability in a one-dimensional organic lattice is investigated within the Su-Schrieffer-Heeger model.The temperature effect is simulated by introducing random forces to the equation of the lattice motion.It is found that the localized polaron state becomes delocalized even at low temperatures.The time of polaron keeping localized depends on the magnitude of temperatures.By taking into account the thermal effect,we find that the dissociation field is weaker as compared with earlier works.
The PLSI Method of Stabilizing Two-Dimensional Nonsymmetric Half-Plane Recursive Digital Filters
Gangatharan N; Reddy PS
2003-01-01
Two-dimensional (2D) recursive digital filters find applications in image processing as in medical X-ray processing. Nonsymmetric half-plane (NSHP) filters have definitely positive magnitude characteristics as opposed to quarter-plane (QP) filters. In this paper, we provide methods for stabilizing the given 2D NSHP polynomial by the planar least squares inverse (PLSI) method. We have proved in this paper that if the given 2D unstable NSHP polynomial and its PLSI are of the same degree, the P...
LUO Xiao-Bing; HAI Wen-Hua
2005-01-01
@@ We have studied the dynamics of two-dimensional (2D) trapped and untrapped Bose-Einstein condensates (BECs) with a rapid periodic modulation of the scattering length via a Feshbach resonance technique, a → ao + a1 sin(Ωt) with an attractive (negative) mean value and the large constants ao, a1 and Ω.Applying a variation approximation (VA), the critical threshold for the collapse of the 2D trapped vortex BEC is predicted and the collapse is prevented by causing the scattering length oscillating rapidly.On the other hand, with analytical calculation, we prove that the stabilization of a bright soliton in a 2D untrapped BEC is impossible for enough large interaction intensity and the upper limit of the intensity for the soliton stabilization is derived.
Kinkhabwala, Ali
2013-01-01
The connection between network topology and stability remains unclear. General approaches that clarify this relationship and allow for more efficient stability analysis would be desirable. In this manuscript, I examine the mathematical notion of influence topology, which is fundamentally based on the network reaction stoichiometries and the first derivatives of the reactions with respect to each species at the steady state solution(s). The influence topology is naturally represented as a signed directed bipartite graph with arrows or blunt arrows connecting a species node to a reaction node (positive/negative derivative) or a reaction node to a species node (positive/negative stoichiometry). The set of all such graphs is denumerable. A significant reduction in dimensionality is possible through stoichiometric scaling, cycle compaction, and temporal scaling. All cycles in a network can be read directly from the graph of its influence topology, enabling efficient and intuitive computation of the principal minor...
Alessi, Roberto; Pham, Kim
2016-02-01
This paper presents a variational framework for the three-dimensional macroscopic modelling of superelastic shape memory alloys in an isothermal setting. Phase transformation is accounted through a unique second order tensorial internal variable, acting as the transformation strain. Postulating the total strain energy density as the sum of a free energy and a dissipated energy, the model depends on two material scalar functions of the norm of the transformation strain and a material scalar constant. Appropriate calibration of these material functions allows to render a wide range of constitutive behaviours including stress-softening and stress-hardening. The quasi-static evolution problem of a domain is formulated in terms of two physical principles based on the total energy of the system: a stability criterion, which selects the local minima of the total energy, and an energy balance condition, which ensures the consistency of the evolution of the total energy with respect to the external loadings. The local phase transformation laws in terms of Kuhn-Tucker relations are deduced from the first-order stability condition and the energy balance condition. The response of the model is illustrated with a numerical traction-torsion test performed on a thin-walled cylinder. Evolutions of homogeneous states are given for proportional and non-proportional loadings. Influence of the stress-hardening/softening properties on the evolution of the transformation domain is emphasized. Finally, in view of an identification process, the issue of stability of homogeneous states in a multi-dimensional setting is answered based on the study of second-order derivative of the total energy. Explicit necessary and sufficient conditions of stability are provided.
State, Mihai; Brands, Peter J; van de Vosse, Frans N
2010-04-01
Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast(1265)), a commonly used backing material, was considered reference material and polyurethane composites (PU(2305), PU(2350)) were proposed as better alternatives. When compared to the reference, the PU(2350) filled with a mixture of Al(2)O(3) and tungsten exhibited an approximately 15 times lower glassy transition temperature and a 2.5 time lower longitudinal thermal expansion at 20 degrees C. This ensures that within the entire operational temperature range the backing material is flexible, minimizing the thermal stresses induced onto transducer elements soldered joints and piezoceramic core. For the same material, the attenuation at 5MHz was similar to the reference material while at 7 and 8.5MHz it was 33% and 54% higher respectively. From these analyses it is concluded that the newly developed polyurethane composites outperform the reference backing with respect to the thermal dimensional stability as well as to the damping properties. An integrated rigorous mechano-acoustical approach is being proposed as an appropriate passive material design path. It can be easily extended to any other passive materials used for ultrasound transducer conception.
On the sensitivity of dimensional stability of high density polyethylene on heating rate
2007-02-01
Full Text Available Although high density polyethylene (HDPE is one of the most widely used industrial polymers, its application compared to its potential has been limited because of its low dimensional stability particularly at high temperature. Dilatometry test is considered as a method for examining thermal dimensional stability (TDS of the material. In spite of the importance of simulation of TDS of HDPE during dilatometry test it has not been paid attention by other investigators. Thus the main goal of this research is concentrated on simulation of TDS of HDPE. Also it has been tried to validate the simulation results and practical experiments. For this purpose the standard dilatometry test was done on the HDPE specimens. Secant coefficient of linear thermal expansion was computed from the test. Then by considering boundary conditions and material properties, dilatometry test has been simulated at different heating rates and the thermal strain versus temperature was calculated. The results showed that the simulation results and practical experiments were very close together.
The stability of aluminium oxide monolayer and its interface with two-dimensional materials.
Song, Ting Ting; Yang, Ming; Chai, Jian Wei; Callsen, Martin; Zhou, Jun; Yang, Tong; Zhang, Zheng; Pan, Ji Sheng; Chi, Dong Zhi; Feng, Yuan Ping; Wang, Shi Jie
2016-07-06
The miniaturization of future electronic devices requires the knowledge of interfacial properties between two-dimensional channel materials and high-κ dielectrics in the limit of one atomic layer thickness. In this report, by combining particle-swarm optimization method with first-principles calculations, we present a detailed study of structural, electronic, mechanical, and dielectric properties of Al2O3 monolayer. We predict that planar Al2O3 monolayer is globally stable with a direct band gap of 5.99 eV and thermal stability up to 1100 K. The stability of this high-κ oxide monolayer can be enhanced by substrates such as graphene, for which the interfacial interaction is found to be weak. The band offsets between the Al2O3 monolayer and graphene are large enough for electronic applications. Our results not only predict a stable high-κ oxide monolayer, but also improve the understanding of interfacial properties between a high-κ dielectric monolayer and two-dimensional material.
3-dimensional slope stability analyses using non-associative stress-strain relationships
无
2009-01-01
The research work presented in this paper refers to a new slope stability analysis method used for landslide risk evaluations. It is an extension of the 3-dimensional upper-bound slope stability analysis method proposed by Chen et al. in 2001,which employs the Mohr-Coulomb’s associative flow rule. It has been found that in a 3-dimensional area,a prism may not be able to move at friction angles to all its surrounding interfaces,as required by this associative rule,and convergence problems may occasionally arise. The new method establishes two velocity fields:(i) The plastic one that represents a non-associative and the best representative dilation behavior,and (ii) the virtual one that permits the solution for factor of safety in the work and energy balance equation. The new method can then allow any input value of dilation angle and thus solve the convergence problem. A practical application to a concrete dam foundation is illustrated.
Xu, Tong-kai; Sun, Zhi-hui; Jiang, Yong
2012-03-01
To evaluate the dimensional stability and detail reproduction of five additional silicone impression materials after autoclave sterilization. Impressions were made on the ISO 4823 standard mold containing several marking lines, in five kinds of additional silicone. All the impressions were sterilized by high temperature and pressure (135 °C, 212.8 kPa) for 25 min. Linear measurements of pre-sterilization and post-sterilization were made with a measuring microscope. Statistical analysis utilized single-factor analysis with pair-wise comparison of mean values when appropriate. Hypothesis testing was conducted at alpha = 0.05. No significant difference was found between the pre-sterilization and post-sterilization conditions for all locations, and all the absolute valuse of linear rate of change less than 8%. All the sterilization by the autoclave did not affect the surfuce detail reproduction of the 5 impression materials. The dimensional stability and detail reproduction of the five additional silicone impression materials in the study was unaffected by autoclave sterilization.
Yatsuda, Regis A; Lima, Adriano F; Yatsuda, Regiane; Cavalcanti, Andrea N; Capp, Cláudia I; Novelli, Moacyr D; de Cara, Antonio A
2010-01-01
This study evaluated the effect of retentive areas on onlay preparations on the dimensional alterations in condensation and addition silicone materials. A standard model with an onlay preparation was made. Each impression material was used through the double or simultaneous impression technique (n=25), resulting in a hundred impressions of the same model. Impressions were poured with type IV dental stone. Digital images were taken with a light microscope and the distances between the reference points created on the plaster dies were compared with the ones on the standard model. In the occlusal, mesial-medium and mesial-cervical segments, the double impression (DI) with condensation silicone presented similar values compared to the standard model. The values of the addition silicone with DI were similar to the standard model only in the mesial-occlusal segment. In the other segments (distal-cervical, distal-medium and distal-occlusal), all groups were statistically different from the control. It could be concluded that addition and condensation silicone impressions provided plaster dies with significant dimensional alterations in most of the evaluated areas when compared to the standard model. The retentive areas related to the onlay preparation influenced the dimensional stability of the addition and condensation silicone impressions.
Reddy, Subash M; Vijitha, D; Karthikeyan, S; Balasubramanian, R; Satish, A
2013-12-01
Dimensionally stable autoclavable impressions will be effective in controlling the cross-infection and contamination caused by patient's saliva and other oral secretions. The accuracy of newly introduced autoclavable polyvinyl siloxane impression material was assessed for its dimensional stability and accuracy. A standard metal model (Dentoform, U-501, Columbia) was customised for impression making. The impressions were made using the newly introduced polyvinyl siloxane impression materials (AFFINIS, Coltene/Whaledent AG, 9450 Alstalten, Switzerland). Fifty impressions were made and were divided into two groups A and B of 25 each. Group A was the control sample (non-autoclaved impressions) and group B was the test sample (autoclaved impressions), which was subjected to the steam autoclave procedure at 134 °C for 18 min, casts were poured in type IV gypsum products. The customised metal model, casts obtained from control and test group were subjected to laboratory evaluation with help of a travelling microscope (×10 magnification), and digital vernier calliper (0.01 mm/10 μm accuracy). Data analysis was done using one-way ANOVA and One-Sample t test to evaluate the overall accuracy (P polyvinyl siloxane impression material is accurate and dimensional stable for clinical use when steam autoclaved at 134 °C for 18 min.
Woods, Sean R.
Cellulose-based material absorbs or releases moisture in relation to atmospheric conditions. This research looks to minimize dimensional change with the use of low molecular weight (LMW) monomers polymerized by electron beam (EB) ionizing radiation. Sisal, jute, coir, and hemp natural fibers with average natural swelling of 26.55%, 29.46%, 9.06%, and 32.69%, respectively, and glass fiber as control were used for analysis. Three LMW bulk monomers, hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), and polyethylene glycol diacrylate (EGDA), as well as an encapsulating agent, isodecyl acrylate, and cross-linker, ethoxylated trimethylolpropane triacrylate, were evaluated for resin formulation. In total, 1015 specimens were measured for swelling. Moisture uptake characteristics of the specimens were analyzed. A new method of measuring specimen dimensional changes by a light microscope and image analysis software was used. Results indicate dimensional stability improvement of 39.34% - 91.46% for hemp with HEA and cross-linker, and sisal with HEMA and cross-linker respectively.
Effect of Storage Period on Dimensional Stability of Alginplus and Hydrogum 5
Shima Aalaei
2017-02-01
Full Text Available Objectives: This study aimed to evaluate the effect of storage period on dimensional stability of Alginplus and Hydrogum 5.Materials and Methods: In this in vitro experimental study, 60 impressions were taken of an upper jaw typodont, including 10 impressions for each storage period to be tested (12 minutes, 24 and 120 hours for each type of alginate. Then, the impressions were stored in an incubator with stable temperature and humidity, and poured using a type III dental stone. Subsequently, the mesiodistal dimension, occlusogingival height, and interarch distance were measured using a digital caliper with an accuracy of 0.01mm. The data were analyzed using ANOVA and t-test (P<0.05.Results: Alginplus and Hydrogum 5 impressions were not significantly different from the master model after 12 minutes and 24 hours in terms of dimensions (P>0.05. After 120 hours, all dimensions measured on casts were significantly different from those measured on the master model, except for the mesiodistal dimension of the Hydrogum 5 impressions.Conclusions: At a consistent temperature and humidity, the Alginplus and Hydrogum 5 impressions were dimensionally stable for at least 24 hours.Keywords: Dimensional Measurement Accuracy; Dental Impression Materials; Alginic Acid
Allouche, M H; Millet, S; Botton, V; Henry, D; Ben Hadid, H; Rousset, F
2015-12-01
Squire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional.
Obese elderly women exhibit low postural stability: a novel three-dimensional evaluation system
José Ailton O. Carneiro
2012-01-01
Full Text Available OBJECTIVE: The aim of this study was to evaluate the multisegmental static postural balance of active eutrophic and obese elderly women using a three-dimensional system under different sensory conditions. METHODS: A cross-sectional study was conducted on 31 elderly women (16 eutrophic and 15 obese aged 65 to 75 years. The following anthropometric measurements were obtained: weight, height, waist and hip circumference, and handgrip strength. The physical activity level was evaluated using the International Physical Activity Questionnaire. Body composition was measured using the deuterium oxide dilution technique. The Polhemus® Patriot (three-dimensional equipment was used to measure the parameters of postural balance along the anteroposterior and laterolateral axes. The data acquisition involved one trial of 60 s to test the limit of stability and four trials of 90 s each under the following conditions: (1 eyes open, stable surface; (2 eyes closed, stable surface; (3 eyes open, unstable surface; and (4 eyes closed, unstable surface. RESULTS: For the limit of stability, significant differences were observed in the maximum anteroposterior and laterolateral displacement (p<0.01 and in the parameter maximum anteroposterior displacement in the eyes closed stable surface condition (p<0.01 and maximum anteroposterior and laterolateral displacement in the eyes open unstable surface (p<0.01 and p = 0.03 and eyes closed unstable surface (p<0.01 and p<0.01 conditions. CONCLUSIONS: Obese elderly women exhibited a lower stability limit (lower sway area compared with eutrophic women, leaving them more vulnerable to falls.
Sinobad Tamara
2014-01-01
Full Text Available Background/Aim. Dimensional stability and accuracy of an impression after chemical disinfection by immersion in disinfectants are crucial for the accuracy of final prosthetic restorations. The aim of this study was to assess the deformation of addition and condensation silicone impressions after disinfection in antimicrobial solutions. Methods. A total of 120 impressions were made on the model of the upper arch representing three full metal-ceramic crown preparations. Four impression materials were used: two condensation silicones (Oranwash L - Zhermack and Xantopren L Blue - Heraeus Kulzer and two addition silicones (Elite H-D + regular body - Zhermack and Flexitime correct flow - Heraeus Kulzer. After removal from the model the impressions were immediately immersed in appropriate disinfectant (gluta-raldehyde, benzalkonium chloride - Sterigum and 5.25% NaOCl for a period of 10 min. The control group consisted of samples that were not treated with disinfectant solution. Consecutive measurements of identical impressions were realized with a Canon G9 (12 megapixels, 2 fps, 6x/24x, and automated with a computer Asus Lamborghini VX-2R Intel C2D 2.4 GHz, by using Remote Capture software package, so that time-depending series of images of the same impression were obtained. Results. The dimensional changes of all the samples were significant both as a function of time and the applied disinfectant. The results show significant differences of the obtained dimensional changes between the group of condensation silicones and the group of addition silicones for the same time, and the same applied disinfectant (p = 0.026, F = 3.95. Conclusion. The greatest dimensional changes of addition and condensation silicone impressions appear in the first hour after their separation from the model.
Corrections to the Eckhaus' stability criterion for one-dimensional stationary structures
Malomed, B. A.; Staroselsky, I. E.; Konstantinov, A. B.
1989-01-01
Two amendments to the well-known Eckhaus' stability criterion for small-amplitude non-linear structures generated by weak instability of a spatially uniform state of a non-equilibrium one-dimensional system against small perturbations with finite wavelengths are obtained. Firstly, we evaluate small corrections to the main Eckhaus' term which, on the contrary so that term, do not have a universal form. Comparison of those non-universal corrections with experimental or numerical results gives a possibility to select a more relevant form of an effective nonlinear evolution equation. In particular, the comparison with such results for convective rolls and Taylor vortices gives arguments in favor of the Swift-Hohenberg equation. Secondly, we derive an analog of the Eckhaus criterion for systems degenerate in the sense that in an expansion of their non-linear parts in powers of dynamical variables, the second and third degree terms are absent.
Jalalzadeh, S; Sepangi, H R
2003-01-01
We study the classical and quantum cosmology of a $(4+d)$-dimensional spacetime minimally coupled to a scalar field and present exact solutions for the resulting field equations for the case where the universe is spatially flat. These solutions exhibit signature transition from a Euclidean to a Lorentzian domain and lead to stabilization of the internal space, in contrast to the solutions which do not undergo signature transition. The corresponding quantum cosmology is described by the Wheeler-DeWitt equation which has exact solutions in the mini-superspace, resulting in wavefunctions peaking around the classical paths. Such solutions admit parametrizations corresponding to metric solutions of the field equations that admit signature transition.
One dimensional simulation on stability of detached plasma in a tokamak divertor
Nakazawa, Shinji; Nakajima, Noriyoshi; Okamoto, Masao; Ohyabu, Nobuyoshi [National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-06-01
The stability of radiation front in the Scrape-Off-Layer (SOL) of a tokamak is studied with a one dimensional fluid code; the time-dependent transport equations are solved in the direction parallel to a magnetic field line. The simulation results show that stable detached solutions exist, where the plasma temperature near the divertor target is {approx}2 eV. It is found that whenever such stable detached states are attained, the strong radiation front is contact with or at a small distance from the divertor target. When the energy externally injected into the SOL is decreased below a critical value, the radiation front starts to move towards the X-point, cooling the SOL plasma. In such cases, no stationary solutions such that the radiation front rests in the divertor channel are observed in our parameter space. This qualitatively corresponds to the results of tokamak divertor experiments which show the movement of radiation front. (author)
Two-Dimensional Transition Metal Dichalcogenide Alloys: Stability and Electronic Properties.
Komsa, Hannu-Pekka; Krasheninnikov, Arkady V
2012-12-06
Using density-functional theory calculations, we study the stability and electronic properties of single layers of mixed transition metal dichalcogenides (TMDs), such as MoS2xSe2(1-x), which can be referred to as two-dimensional (2D) random alloys. We demonstrate that mixed MoS2/MoSe2/MoTe2 compounds are thermodynamically stable at room temperature, so that such materials can be manufactured using chemical-vapor deposition technique or exfoliated from the bulk mixed materials. By applying the effective band structure approach, we further study the electronic structure of the mixed 2D compounds and show that general features of the band structures are similar to those of their binary constituents. The direct gap in these materials can continuously be tuned, pointing toward possible applications of 2D TMD alloys in photonics.
Stability of two-dimensional PN monolayer sheets and their electronic properties.
Ma, ShuangYing; He, Chaoyu; Sun, L Z; Lin, Haiping; Li, Youyong; Zhang, K W
2015-12-21
Three two-dimensional phosphorus nitride (PN) monolayer sheets (named as α-, β-, and γ-PN, respectively) with fantastic structures and properties are predicted based on first-principles calculations. The α-PN and γ-PN have a buckled structure, whereas β-PN shows puckered characteristics. Their unique structures endow these atomic PN sheets with high dynamic stabilities and anisotropic mechanical properties. They are all indirect semiconductors and their band gap sensitively depends on the in-plane strain. Moreover, the nanoribbons patterned from these three PN monolayers demonstrate a remarkable quantum size effect. In particular, the zigzag α-PN nanoribbon shows size-dependent ferromagnetism. Their significant properties show potential in nano-electronics. The synthesis of the three phases of the PN monolayer sheet is proposed theoretically, which is deserving of further study in experiments.
The PLSI Method of Stabilizing Two-Dimensional Nonsymmetric Half-Plane Recursive Digital Filters
Gangatharan N
2003-01-01
Full Text Available Two-dimensional (2D recursive digital filters find applications in image processing as in medical X-ray processing. Nonsymmetric half-plane (NSHP filters have definitely positive magnitude characteristics as opposed to quarter-plane (QP filters. In this paper, we provide methods for stabilizing the given 2D NSHP polynomial by the planar least squares inverse (PLSI method. We have proved in this paper that if the given 2D unstable NSHP polynomial and its PLSI are of the same degree, the PLSI polynomial is always stable, irrespective of whether the coefficients of the given polynomial have relationship among its coefficients or not. Examples are given for 2D first-order and second-order cases to prove our results. The generalization is done for the th order polynomial.
Effect of Heat Treatment on Sorption Properties and Dimensional Stability of Wood
Povilas NAVICKAS
2013-09-01
Full Text Available This research was performed in order to determine how the heating process affects sorption properties and dimensional and shape stability of oak, lime and birch wood. By subjecting specimens to 3 hours heating at 130, 160, 190 and 220 ºC temperatures, a decrease in volume, density and mass was observed in proportion to the applied temperature. It was established that when oak wood specimens underwent heating at 220 ºC temperature, the decline of mass was 1.2 times higher than in the case of birch specimens. Both heated and unheated specimens underwent moistening in air at 25 ºC ±1 ºC temperature for 3 weeks with relative humidity being 85 % ±1 % and were soaked in water at room temperature for 4 hours. It was found that after applying high temperature heating, specimens absorbed smaller amounts of moisture. It was demonstrated that during the soaking process, the volume of unheated specimens was 3 times higher than in the case of specimens heated at 220 ºC temperature. The change in the volume of unheated oak was 1.27 times smaller than in the case of lime specimens and 1.16 times larger than in the case of birch specimens, which underwent heating at 220 ºC temperature. In addition, specimens that were exposed to heat had more stable measurements and shapes. It was noticed that the heating process caused significant changes in moisture and dimensional stability of specimens, when higher temperatures ranging from 190 ºC to 220 ºC were used. DOI: http://dx.doi.org/10.5755/j01.ms.19.3.5239
The dimensional stability of impression materials and its effect on in vitro tooth wear studies.
Rodriguez, Jose M; Bartlett, David W
2011-03-01
To assess the dimensional stability of 8 impression materials over 12 weeks relevant to in vitro tribology studies. Ten impressions from eight impression materials were taken of a metal block (ADA block) conforming to the American Dental Association specification for impression materials and of another metal block (custom block) which allowed measurements over a larger surface area. The impressions and blocks were scanned on a non-contacting laser profilometer (Taicaan® - Southampton, UK) and using surface metrology software Boddies® (Taicaan® - Southampton, UK) measurements were made at 24h, 2, 4, 8 and 12 weeks. The impression materials tested were [1] Aquasil®, [2] Aquasil® DECA, [3] Affinis®, [4] Express®, [5] Extrude®, [6] Impregum®, [7] President® and [8] Take 1®. Seven addition silicones and one polyether [6] were tested. [2] and [6] were monophasic, the rest were putty-wash. The results from impressions of the ADA block showed that all materials contracted compared to measurements obtained directly from the block [1] expanded over time (+31.5 μm) (p1.5% and were stable for 12 weeks. Nevertheless, the range of changes would affect tribology studies were cut-offs lesser than the reported changes are selected. All impressions should be processed after similar time delays to reduce the errors introduced by dimensional changes. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Melilli, Dario; Rallo, Antonio; Cassaro, Angelo; Pizzo, Giuseppe
2008-12-01
The aim of this study was to determine the effect of immersion disinfection procedures on the dimensional stability of two elastomeric impression materials. Impressions of a stainless steel die were made with polyether (PE) and with addition-polymerized silicone rubber (PVS). The test specimens underwent disinfection treatment by immersion in two commercially available solutions containing quaternary ammonium compounds (Sterigum Powder, SP) and glutaraldehyde plus an amino derivative (MD520, MD), respectively. The impressions were measured at 4 different time points: before any disinfection treatment (T0); after the first disinfection (T1); 6 hours after the first disinfection (T2); after the second disinfection, carried out 6 hours after the first one (T3). Impressions which were not disinfected served as controls. When both impression materials were disinfected with SP, significant differences were detected among all measurements (P 0.05). On the other hand, when MD was used, significant differences were found when T0 measurement was compared to T1, T2 and T3 measurements (P = 0.0043 for PE, and P = 0.0014 for PVS). The dimensional change of all material/disinfectant combinations was always disinfection on the dimension of elastomers in SP or MD are not clinically relevant.
Sareh Habibzadeh
2016-10-01
Full Text Available Objectives: This study aimed to assess the effect of storage time and temperature on dimensional stability of impressions made with Cavex Outline zinc oxide impression paste.Materials and Methods: A round stainless steel mold with five grooves (three horizontal and two vertical was used in this in-vitro experimental study. Cavex Outline impression paste was prepared according to the manufacturer’s instructions and applied to the mold. The mold was placed on a block and stored at 35°C and 100% humidity for setting. The impressions were poured with stone immediately and also after 30, 120, 240 and 420 minutes and 24 hours. The distance between the vertical lines on the casts was measured and compared with that in the immediately poured cast.Results: Storage in a refrigerator and at room temperature for zero to seven hours had no significant effect on dimensional stability of the impressions; however, 24 hours of storage in a refrigerator or at room temperature decreased the dimensional stability of Cavex Outline (P=0.001. Also, a significant association was found between dimensional changes following 24 hours of storage in a refrigerator (4°C and at room temperature (23°C; P<0.01.Conclusions: The optimal pouring time of Cavex Outline impressions with stone is between zero to seven hours, and 24 hours of storage significantly decreases the dimensional stability.Keywords: Dental Impression Materials; Zinc Oxide; Cavex
Stabilization and strengthening effects of functional groups in two-dimensional titanium carbide
Fu, Z. H.; Zhang, Q. F.; Legut, D.; Si, C.; Germann, T. C.; Lookman, T.; Du, S. Y.; Francisco, J. S.; Zhang, R. F.
2016-09-01
Two-dimensional (2D) materials have attracted considerable interest due to their remarkable properties and potential applications for nanoelectronics, electrodes, energy storage devices, among others. However, many well-studied 2D materials lack appreciable conductivity and tunable mechanical strength, limiting their applications in flexible devices. Newly developed MXenes open up the opportunity to design novel flexible conductive electronic materials. Here, using density functional theory (DFT), we investigate systematically the effects of several functional groups on the stabilization, mechanical properties, and electronic structures of a representative MXene. It is found that oxygen possesses the largest adsorption energy as compared to other functional groups, indicating its good thermodynamic stabilization. In comparison with bare and other functionalized titanium carbides, the oxygen functionalized one exhibits the most superior ideal strength; however, the premature softening of the long-wave phonon modes might limit the intrinsic strength for T i3C2O2 . Furthermore, the introduction of functional groups can induce a strong anisotropy under tensile loading. By analyzing the deformation paths and the electronic instability under various loadings, we demonstrate that the unique strengthening by oxygen functional groups is attributed to a significant charge transfer from inner bonds to outer surface ones after functionalization. Our results shed a novel view into exploring a variety of MXenes for their potential applications in flexible electronic and energy storage devices.
Two-dimensional simulations of steady perforated-plate stabilized premixed flames
Altay, H. Murat
2010-03-17
The objective of this work is to examine the impact of the operating conditions and the perforated-plate design on the steady, lean premixed flame characteristics. We perform two-dimensional simulations of laminar flames using a reduced chemical kinetics mechanism for methane-air combustion, consisting of 20 species and 79 reactions. We solve the heat conduction problem within the plate, allowing heat exchange between the gas mixture and the solid plate. The physical model is based on a zero-Mach-number formulation of the axisymmetric compressible conservation equations. The results suggest that the flame consumption speed, the flame structure, and the flame surface area depend significantly on the equivalence ratio, mean inlet velocity, the distance between the perforated-plate holes and the plate thermal conductivity. In the case of an adiabatic plate, a conical flame is formed, anchored near the corner of the hole. When the heat exchange between themixture and the plate is finite, the flame acquires a Gaussian shape stabilizing at a stand-off distance, that grows with the plate conductivity. The flame tip is negatively curved; i.e. concave with respect to the reactants. Downstream of the plate, the flame base is positively curved; i.e. convex with respect to the reactants, stabilizing above a stagnation region established between neighboring holes. As the plate\\'s thermal conductivity increases, the heat flux to the plate decreases, lowering its top surface temperature. As the equivalence ratio increases, the flame moves closer to the plate, raising its temperature, and lowering the flame stand-off distance. As the mean inlet velocity increases, the flame stabilizes further downstream, the flame tip becomes sharper, hence raising the burning rate at that location. The curvature of the flame base depends on the distance between the neighboring holes; and the flame there is characterized by high concentration of intermediates, like carbon monoxide. © 2010 Taylor
无
2011-01-01
Even Unzen volcano has been declared to be in a state of relative dormancy,the latest formed lava lobe No.11 now represents a potential slope failure mass based on the latest research.This paper concentrates on the stability of the lava lobe No.11 and its possible critical sliding mass.It proposes geographic information systems (GIS) based three-dimensional (3D) slope stability analysis models.It uses a 3D locating approach to identify the 3D critical slip surface and to analyze the 3D stability of the lava...
Wang Jia; Hui Guo-Tao; Xie Xiang-Peng
2013-01-01
We study the stability analysis and control synthesis of uncertain discrete-time two-dimensional (2D) systems.The mathematical model of the discrete-time 2D system is established upon the well-known Roesser model,and the uncertainty phenomenon,which appears typically in practical environments,is modeled by a convex bounded (polytope type) uncertain domain.The stability analysis and control synthesis of uncertain discrete-time 2D systems are then developed by applying the Lyapunov stability theory.In the processes of stability analysis and control synthesis,the obtained stability/stabilzaition conditions become less conservative by applying some novel relaxed techniques.Moreover,the obtained results are formulated in the form of linear matrix inequalities,which can be easily solved via standard numerical software.Finally,numerical examples are given to demonstrate the effectiveness of the obtained results.
Kallel, Hichem
Three classes of postural adjustments are investigated with the view of a better understanding of the control mechanisms involved in human movement. The control mechanisms and responses of human or computer models to deliberately induced disturbances in postural adjustments are the focus of this dissertation. The classes of postural adjustments are automatic adjustments, (i.e. adjustments not involving voluntary deliberate movement), adjustments involving imposition of constraints for the purpose of maintaining support forces, and adjustments involving violation and imposition of constraints for the purpose of maintaining balance, (i.e. taking one or more steps). For each class, based on the physiological attributes of the control mechanisms in human movements, control strategies are developed to synthesize the desired postural response. The control strategies involve position and velocity feedback control, on line relegation control, and pre-stored trajectory control. Stability analysis for constrained and unconstrained maneuvers is carried out based on Lyapunov stability theorems. The analysis is based on multi-segment biped robots. Depending on the class of postural adjustments, different biped models are developed. An eight-segment three dimensional biped model is formulated for the study of automatic adjustments and adjustments for balance. For the study of adjustments for support, a four segment lateral biped model is considered. Muscle synergies in automatic adjustments are analyzed based on a three link six muscle system. The muscle synergies considered involve minimal muscle number and muscle co-activation. The role of active and passive feedback in these automatic adjustments is investigated based on the specified stiffness and damping of the segments. The effectiveness of the control strategies and the role of muscle synergies in automatic adjustments are demonstrated by a number of digital computer simulations.
Stabilizing the electroweak vacuum by higher dimensional operators in a Higgs-Yukawa model
Hegde, Prasad [National Taiwan Univ., Taipei (China); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Lin, C.J. David [National Chaio Tung Univ., Hsinchu (China); Nagy, Attila [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany)
2013-11-15
The Higgs boson discovery at the LHC with a mass of approximately 126 GeV suggests, that the electroweak vacuum of the standard model may be metastable at very high energies. However, any new physics beyond the standard model can change this picture. We want to address this important question within a lattice Higgs-Yukawa model as the limit of the standard model (SM). In this framework we will probe the effect of a higher dimensional operator for which we take a ({phi}{sup {dagger}}{phi}){sup 3}-term. Such a term could easily originate as a remnant of physics beyond the SM at very large scales. As a first step we investigate the phase diagram of the model including such a ({phi}{sup {dagger}}{phi}){sup 3} operator. Exploratory results suggest the existence of regions in parameter space where first order transitions turn to second order ones, indicating the existence of a tri-critical line. We will explore the phase structure and the consequences for the stability of the SM, both analytically by investigating the constraint effective potential in lattice perturbation theory, and by studying the system non-perturbatively using lattice simulations.
Dimensional stability of polyvinyl siloxane impression material reproducing the sulcular area.
Levartovsky, Shifra; Levy, Guy; Brosh, Tamar; Harel, Noga; Ganor, Yehuda; Pilo, Raphael
2013-01-01
The dimensional stability of a thin intra sulcular impression material reproducing the preparation finish line was evaluated. Impressions were taken of a stainless-steel master model of a simulated abutment with a 'gingival sulcus' using Express regular, Express fast and Aquasil. The putty-wash two-step technique was applied with spacer thicknesses of 0.5, 1 and 1.5 mm. Mid mesiodistal and bucco-lingual measurements were taken directly from the sulcular impression material after 0.5, 2, 24, 48 and 72 h via a Toolmaker's microscope. The discrepancies between the measurements of the impression material and the master model were calculated. The discrepancies changed significantly over time (p<0.001). The use of a 0.5 mm spacer resulted in a negative deviation from the model (2-46 µm), minimally after 2 h. The use of 1 and 1.5 mm spacers showed a positive deviation from the model (21-52 µm) and both are equally recommended. Investment can be postponed until 72 h.
Ioannis Barboutis
2014-09-01
Full Text Available Thermal modification of wood permanently alters several of its chemical and physical properties. Beech wood is one of the most important hardwoods in Central and Eastern Europe and is extensively used in furniture production. In this study the effects of thermal modification of beech wood (Fagus sylvatica L. on hygroscopic properties were examined and the color changes of the treated wood were determined. Beech wood has been subjected to a heat treatment at the temperature of 180 °C for five different durations ranging from 2 to 10 h. A more intense, gradual color change of the treated samples was observed after 4-h treatment, whereas in some other cases the recorded alterations were less intense. The most pronounced color differentiations compared to untreated samples occurred in 8-h and 10-h treatments. Dimensional stability and absorption were measured after 1-h, 3-h, 6-h, 1 day and 3 days immersion in water. The 8-h treatment duration exhibits the greatest reduction of swelling and absorption percentage.
Three-Dimensional Simulations of Jets from Keplerian Disks Self--Regulatory Stability
Ouyed, R; Pudritz, R E
2002-01-01
We present the extension of previous two-dimensional simulations of the time-dependent evolution of non-relativistic outflows from the surface of Keplerian accretion disks, to three dimensions. The accretion disk itself is taken to provide a set of fixed boundary conditions for the problem. The 3-D results are consistent with the theory of steady, axisymmetric, centrifugally driven disk winds up to the Alfv\\'en surface of the outflow. Beyond the Alfv\\'en surface however, the jet in 3-D becomes unstable to non-axisymmetric, Kelvin-Helmholtz instabilities. We show that jets maintain their long-term stability through a self-limiting process wherein the average Alfv\\'enic Mach number within the jet is maintained to order unity. This is accomplished in at least two ways. First, poloidal magnetic field is concentrated along the central axis of the jet forming a ``backbone'' in which the Alfv\\'en speed is sufficiently high to reduce the average jet Alfv\\'enic Mach number to unity. Second, the onset of higher order K...
Improved convergence and stability properties in a three-dimensional higher-order ice sheet model
J. J. Fürst
2011-12-01
Full Text Available We present a finite difference implementation of a three-dimensional higher-order ice sheet model. In comparison to a conventional centred difference discretisation it enhances both numerical stability and convergence. In order to achieve these benefits the discretisation of the governing force balance equation makes extensive use of information on staggered grid points. Using the same iterative solver, a centred difference discretisation that operates exclusively on the regular grid serves as a reference. The reprise of the ISMIP-HOM experiments indicates that both discretisations are capable of reproducing the higher-order model inter-comparison results. This setup allows a direct comparison of the two numerical implementations also with respect to their convergence behaviour. First and foremost, the new finite difference scheme facilitates convergence by a factor of up to 7 and 2.6 in average. In addition to this decrease in computational costs, the accuracy for the resultant velocity field can be chosen higher in the novel finite difference implementation. Changing the discretisation also prevents build-up of local field irregularites that occasionally cause divergence of the solution for the reference discretisation.
The improved behaviour makes the new discretisation more reliable for extensive application to real ice geometries. Higher accuracy and robust numerics are crucial in time dependent applications since numerical oscillations in the velocity field of subsequent time steps are attenuated and divergence of the solution is prevented.
Dimensional stability control of ultrathin core%薄芯板尺寸稳定性控制
罗晓帆
2014-01-01
任意层互连板件制作过程中，板件变形导致盲孔底部连接盘偏是最常见的失效模式，特别第一次薄芯板压合，尺寸稳定性控制极有难度。本文通过研究板料、芯板配本及压合参数，分析其对拼板整体变形的影响，从而得出薄芯板尺寸稳定性控制的最佳方案。%During ALIVH PCB manufacturing process, the misregistration of target pad due to the PCB dimensional change is the most common failure modes. Especially, when the first pressing cycle, dimensional stability control of the ultrathin core is very difficult. By means of analyzing laminate material, core stack-up and press parameter, which affect the PCB dimensional stability, this article sheds light on the best method of dimensional stability control.
Yu, L; Batlle, F
2011-12-01
Limited space for accommodating the ever increasing mounds of municipal solid waste (MSW) demands the capacity of MSW landfill be maximized by building landfills to greater heights with steeper slopes. This situation has raised concerns regarding the stability of high MSW landfills. A hybrid method for quasi-three-dimensional slope stability analysis based on the finite element stress analysis was applied in a case study at a MSW landfill in north-east Spain. Potential slides can be assumed to be located within the waste mass due to the lack of weak foundation soils and geosynthetic membranes at the landfill base. The only triggering factor of deep-seated slope failure is the higher leachate level and the relatively high and steep slope in the front. The valley-shaped geometry and layered construction procedure at the site make three-dimensional slope stability analyses necessary for this landfill. In the finite element stress analysis, variations of leachate level during construction and continuous settlement of the landfill were taken into account. The "equivalent" three-dimensional factor of safety (FoS) was computed from the individual result of the two-dimensional analysis for a series of evenly spaced cross sections within the potential sliding body. Results indicate that the hybrid method for quasi-three-dimensional slope stability analysis adopted in this paper is capable of locating roughly the spatial position of the potential sliding mass. This easy to manipulate method can serve as an engineering tool in the preliminary estimate of the FoS as well as the approximate position and extent of the potential sliding mass. The result that FoS obtained from three-dimensional analysis increases as much as 50% compared to that from two-dimensional analysis implies the significance of the three-dimensional effect for this study-case. Influences of shear parameters, time elapse after landfill closure, leachate level as well as unit weight of waste on FoS were also
Improved convergence and stability properties in a three-dimensional higher-order ice sheet model
J. J. Fürst
2011-07-01
Full Text Available We present a novel finite difference implementation of a three-dimensional higher-order ice sheet model that performs well both in terms of convergence rate and numerical stability. In order to achieve these benefits the discretisation of the governing force balance equation makes extensive use of information on staggered grid points. Using the same iterative solver, an existing discretisation that operates exclusively on the regular grid serves as a reference. Participation in the ISMIP-HOM benchmark indicates that both discretisations are capable of reproducing the higher-order model inter-comparison results. This allows a direct comparison not only of the resultant velocity fields but also of the solver's convergence behaviour which holds main differences. First and foremost, the new finite difference scheme facilitates convergence by a factor of up to 7 and 2.6 in average. In addition to this decrease in computational costs, the precision for the resultant velocity field can be chosen higher in the novel finite difference implementation. For high precisions, the old discretisation experiences difficulties to converge due to large variation in the velocity fields of consecutive Picard iterations. Finally, changing discretisation prevents build-up of local field irregularites that occasionally cause divergence of the solution for the reference discretisation.
The improved behaviour makes the new discretisation more reliable for extensive application to real ice geometries. Higher precision and robust numerics are crucial in time dependent applications since numerical oscillations in the velocity field of subsequent time steps are attenuated and divergence of the solution is prevented. Transient applications also benefit from the increased computational efficiency.
Buha, Joka; Castillo, Antonio Esau Del Rio; Bonaccorso, Francesco; Manna, Liberato
2016-01-01
The structural and compositional stabilities of two dimensional 2D Bi2Te3 and Bi2Se3 nanocrystals, produced by both colloidal synthesis and by liquid phase exfoliation, were studied by in situ transmission electron microscopy TEM during annealing at temperatures between 350 and 500 C. The sublimation process induced by annealing is structurally and chemically anisotropic and takes place through the preferential dismantling of the prismatic 011-0 type planes, and through the preferential sublimation of Te or Se.
Jagger, D C; Vowles, R W; McNally, L; Davis, F; O'Sullivan, D J
2007-03-01
Disinfection of dental impressions should be considered as a routine procedure in dental surgeries and dental laboratories. Disinfectants can have deleterious effects on some properties of impression materials. The aim of this study was to evaluate the dimensional accuracy and dimensional stability of a model dental stone, reproduced from five commonly used impression materials (Aquasil soft putty/Aquasil Ultra LV; Aquasil Monophase; Aquasil Ultra Heavy; Impregum F and Provil putty/Provil Light CD wash) retained by their adhesives in acrylic resin trays and exposed to three disinfectant solutions (Perform ID; Haz-Tabs and MD 520). Two hundred models were used to investigate the effect of the three disinfectants on the dimensional accuracy of the five impression materials. Five impressions were taken for each impression material for each disinfection treatment group. Measurements were carried out using a High Precision Reflex Microscope. All materials demonstrated a percentage change in dimensions when subjected to no disinfection when compared to the brass master die and all materials demonstrated a percentage change in dimension when subjected to the different disinfection procedures. The results of this study have demonstrated that for all of the materials investigated, the changes in dimensional stability were small in the order of microns. These changes may however be of clinical significance for procedures requiring a high degree of accuracy, for example fixed prosthodontics. The materials respond differently depending on the disinfectant used and it may therefore be appropriate that manufacturers recommend the use of particular disinfectants for their products in order to ensure optimum dimensional accuracy and stability.
Izadi
2014-10-01
Full Text Available Background To prevent diseases transmission, infection control in dental offices without reducing the accuracy and dimensional stability of impression materials is very important. Objectives The aim of this study was to evaluate the effects of Sanosil disinfectants on the dimensional stability of some usual impression materials. Materials and Methods Three types of impression material, namely, alginate, condensational silicone, and polyether, were used in this study. Impressions were obtained from the master steel model. Fifteen impressions of each material (control group were immersed in water for ten minutes and impressions of study groups were disinfected by immersion in 2% Sanosil for ten minutes. Then impressions were poured by type III gypsum according to the manufacture's instruction. Dimensions of casts in the two anterior dimensions, i.e. interval between the anterior abutments and interval between anterior-posterior abutments, were recorded by a digital caliper with the accuracy of 0.01 mm. Data were analyzed with SPSS through two-way ANOVA test. Results The results showed that there was no significant difference in the mean dimension of casts prepared by different impression materials in anterior and anterior-posterior dimensions in comparison to the original model after disinfection with Sanosil. Conclusions The study revealed that disinfection with 2% Sanosil has no significant effect on casts dimensions of alginate, silicone, and polyether impression and dimensional stability is maintained.
Zhang, Yanxiang; Ni, Meng; Yan, Mufu; Chen, Fanglin
2015-12-01
Nanostructured electrodes are widely used for low temperature solid oxide fuel cells, due to their remarkably high activity. However, the industrial applications of the infiltrated electrodes are hindered by the durability issues, such as the microstructure stability against thermal aging. Few strategies are available to overcome this challenge due to the limited knowledge about the coarsening kinetics of the infiltrated electrodes and how the potentially important factors affect the stability. In this work, the generic thermal aging kinetics of the three-dimensional microstructures of the infiltrate electrodes is investigated by a kinetic Monte Carlo simulation model considering surface diffusion mechanism. Effects of temperature, infiltration loading, wettability, and electrode configuration are studied and the key geometric parameters are calculated such as the infiltrate particle size, the total and percolated quantities of three-phase boundary length and infiltrate surface area, and the tortuosity factor of infiltrate network. Through parametric study, several strategies to improve the thermal aging stability are proposed.
Zhou, Hua-Cheng; Guo, Bao-Zhu
2017-08-01
In this paper, we consider boundary output feedback stabilization for a multi-dimensional wave equation with boundary control matched unknown nonlinear internal uncertainty and external disturbance. A new unknown input type extended state observer is proposed to recover both state and total disturbance which consists of internal uncertainty and external disturbance. A key feature of the proposed observer in this paper is that we do not use the high-gain to estimate the disturbance. By the active disturbance rejection control (ADRC) strategy, the total disturbance is compensated (canceled) in the feedback loop, which together with a collocated stabilizing controller without uncertainty, leads to an output feedback stabilizing feedback control. It is shown that the resulting closed-loop system is well-posed and asymptotically stable under weak assumption on internal uncertainty and external disturbance. The numerical experiments are carried out to show the effectiveness of the proposed scheme.
Milledge, D.; Bellugi, D.; McKean, J. A.; Dietrich, W.
2012-12-01
The infinite slope model is the basis for almost all watershed scale slope stability models. However, it assumes that a potential landslide is infinitely long and wide. As a result, it cannot represent resistance at the margins of a potential landslide (e.g. from lateral roots), and is unable to predict the size of a potential landslide. Existing three-dimensional models generally require computationally expensive numerical solutions and have previously been applied only at the hillslope scale. Here we derive an alternative analytical treatment that accounts for lateral resistance by representing the forces acting on each margin of an unstable block. We apply 'at rest' earth pressure on the lateral sides, and 'active' and 'passive' pressure using a log-spiral method on the upslope and downslope margins. We represent root reinforcement on each margin assuming that root cohesion is an exponential function of soil depth. We benchmark this treatment against other more complete approaches (Finite Element (FE) and closed form solutions) and find that our model: 1) converges on the infinite slope predictions as length / depth and width / depth ratios become large; 2) agrees with the predictions from state-of-the-art FE models to within +/- 30% error, for the specific cases in which these can be applied. We then test our model's ability to predict failure of an actual (mapped) landslide where the relevant parameters are relatively well constrained. We find that our model predicts failure at the observed location with a nearly identical shape and predicts that larger or smaller shapes conformal to the observed shape are indeed more stable. Finally, we perform a sensitivity analysis using our model to show that lateral reinforcement sets a minimum landslide size, while the additional strength at the downslope boundary means that the optimum shape for a given size is longer in a downslope direction. However, reinforcement effects cannot fully explain the size or shape
Karakus, M.; Kirkland, T.P.; Liu, K.C.; Moore, R.E.; Pint, B.A.; Wereszczak, A.A.
1999-03-01
Advanced Industrial Materials program is sponsoring work to conduct creep testing and analysis on refractories of interest to the glass industry. An earlier stage of the project involved identifying which refractories to test and this is described elsewhere. Conventional silica was one such identified refractory category, and the present report describes the creep behavior of this class of refractories. To portray a more complete understanding of how these refractories perform at service temperatures, their fundamental corrosion resistances, dimensional stabilities, and microstructure were characterized as well.
Weakly nonlinear stability of vicsous vortices in three-dimensional boundary layers
Bassom, Andrew P.; Otto, S. R.
1993-01-01
Attention is given to the weakly nonlinear stability of essentially viscous vortices in 3D boundary layers. These modes are unstable in the absence of crossflow, but the imposition of small crossflow has a stabilizing effect. Bassom and Hall (1991) demonstrated the existence of neutrally stable vortices for certain crossflow/wave number combinations, and the weakly nonlinear stability properties of these disturbances are described. It is shown that the effect of crossflow is to stabilize the nonlinear modes, and the present calculations allow stable finite-amplitude vortices to be found. Predictions are made concerning the likelihood of observing some of these viscous modes within a practical setting.
Haaparanta, Anne-Marie; Uppstu, Peter; Hannula, Markus; Ellä, Ville; Rosling, Ari; Kellomäki, Minna
2015-11-01
Bone tissue engineering requires highly porous three-dimensional (3D) scaffolds with preferable osteoconductive properties, controlled degradation, and good dimensional stability. In this study, highly porous 3D poly(d,l-lactide-co-glycolide) (PLGA) - bioactive glass (BG) composites (PLGA/BG) were manufactured by combining highly porous 3D fibrous BG mesh skeleton with porous PLGA in a freeze-drying process. The 3D structure of the scaffolds was investigated as well as in vitro hydrolytic degradation for 10weeks. The effect of BG on the dimensional stability, scaffold composition, pore structure, and degradation behaviour of the scaffolds was evaluated. The composites showed superior pore structure as the BG fibres inhibited shrinkage of the scaffolds. The BG was also shown to buffer the acidic degradation products of PLGA. These results demonstrate the potential of these PLGA/BG composites for bone tissue engineering, but the ability of this kind of PLGA/BG composites to promote bone regeneration will be studied in forthcoming in vivo studies.
Vadapalli, Sriharsha Babu; Atluri, Kaleswararao; Putcha, Madhu Sudhan; Kondreddi, Sirisha; Kumar, N. Suman; Tadi, Durga Prasad
2016-01-01
Objectives: This in vitro study was designed to compare polyvinyl-siloxane (PVS) monophase and polyether (PE) monophase materials under dry and moist conditions for properties such as surface detail reproduction, dimensional stability, and gypsum compatibility. Materials and Methods: Surface detail reproduction was evaluated using two criteria. Dimensional stability was evaluated according to American Dental Association (ADA) specification no. 19. Gypsum compatibility was assessed by two crit...
ASYMPTOTIC SIMILARITY OF INFINITE-DIMENSIONAL LINEAR SYSTEMS AND APPLICATIONS TO STABILITY
WU Jingbo
2000-01-01
In this note a generalization of the concept of similarity called asymptotic similarity for infinite-dimensional linear systems is introduced. We show that this asymptotic similarity preserves the spectrum and the exponential growth bound.
Amiralireza Khaledi
2011-01-01
Conclusion: The results showed that the disinfectant solutions used in this study did not have a significant effect on the surface quality and dimensional accuracy of Visco-gel as a functional impression material.
Alexandre Florian da Costa
2010-08-01
Full Text Available In search for alternative uses of a petroliferous oily residue known as “LCO” (Liquid Cycle Oil, its capacity to improve the dimensional stability of the wood was evaluated using Pinus sp. (pinus and Mimosa scabrella Bentham (bracatinga. The LCO was tested in its original composition and also diluted in different proportions into a commercial kerosene. The dimensional stability in the three anatomic axis, volumetric changes, shrinkage and anisotropy coefficients, basic density and 12% relative humidity density changes were evaluated, in different stages during the investigation process. The results show no significant differences in maximum swelling and shrinkage between treated and untreated wood blocks at 5% probability level for both species. However, a reduction in the shrinkage coefficient was observed with the increase of LCO concentration, for both species. In general, pinus showed lowest values in all parameter evaluated. The shrinkage and anisotropy coefficient were higher for bracatinga than pinus, nevertheless, no significant differences were observed between treated and untreated wood blocks. These results indicated that changes between tangential and radial faces were minimal, possible due to a poor penetration of LCO into the cell walls. This result, as a consequence, could be associated with a weak performance of the tested chemical, which could not improve the dimensional stability of wood for both species. The increasing LCO concentrations increased the density of both species at 12% relative humidity. This result could be associated to the presence of part of the chemical remaining in the walls of the cellular lumen and the resiniferous channels. Besides, the external aspect of the treated wood was also other restrictive factor to the use of LCO.
Continuation and stability deduction of resonant periodic orbits in three dimensional systems
Antoniadou, Kyriaki I; Varvoglis, Harry
2014-01-01
In dynamical systems of few degrees of freedom, periodic solutions consist the backbone of the phase space and the determination and computation of their stability is crucial for understanding the global dynamics. In this paper we study the classical three body problem in three dimensions and use its dynamics to assess the long-term evolution of extrasolar systems. We compute periodic orbits, which correspond to exact resonant motion, and determine their linear stability. By computing maps of dynamical stability we show that stable periodic orbits are surrounded in phase space with regular motion even in systems with more than two degrees of freedom, while chaos is apparent close to unstable ones. Therefore, families of stable periodic orbits, indeed, consist backbones of the stability domains in phase space.
周学华; 李津如; 刘春艳; 江龙
2002-01-01
Gold nanoparticles modified with C10NH2, C12NH2, C16NH2 and C18NH2 respectively have been prepared by the reverse micelle method. Nanoparticles stability and their two-dimensional (2D) ordered arrangement were studied by UV-Vis absorption spectra and LB technique. The factors, such as the chain length and the size distribution of particles, which affect the 2D ordered arrangement formation, are discussed. Experimental results show that the longer the chain length of surfactants capping the gold nanoparticles, the more stable the nanoparticles, and the more ordered 2D arrangement of gold nanoparticles.
Li, Bing; Li, Yongkun; Zhang, Xuemei
2016-01-01
In this paper, by using the existence of the exponential dichotomy of linear dynamic equations on time scales and the theory of calculus on time scales, we study the existence and global exponential stability of periodic solutions for a class of n-dimensional neutral dynamic equations on time scales. We also present an example to illustrate the feasibility of our results. The results of this paper are completely new and complementary to the previously known results even in both the case of differential equations (time scale [Formula: see text]) and the case of difference equations (time scale [Formula: see text]).
Watanabe, Tomohiko; Sugitani, Yoshiki; Konishi, Keiji; Hara, Naoyuki
2017-01-01
The present paper studies amplitude death in high-dimensional maps coupled by time-delay connections. A linear stability analysis provides several sufficient conditions for an amplitude death state to be unstable, i.e., an odd number property and its extended properties. Furthermore, necessary conditions for stability are provided. These conditions, which reduce trial-and-error tasks for design, and the convex direction, which is a popular concept in the field of robust control, allow us to propose a design procedure for system parameters, such as coupling strength, connection delay, and input-output matrices, for a given network topology. These analytical results are confirmed numerically using delayed logistic maps, generalized Henon maps, and piecewise linear maps.
Zhang, Kelan; Wrzesinski, Krzysztof; Fey, Stephen J;
2008-01-01
Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) followed by mass spectrometric identification of the proteins in the protein spots has become a central tool in proteomics. CMT167(H), CMT64(M) and CMT170(L) cell lines, selected from a spontaneous mouse lung adenocarcinoma, with high......-, middle- or low-metastatic potential have been characterized in vivo. In this study, the comprehensive protein expression profiles of the CMT cell lines were analyzed at passages 5, 15 and 35 in order to assess the cell line stability. During the passages 5 to 15, the expression profiles of CMT cells...... to be a useful tool for assessing differences in cell line stability. This approach provided a tool to select the best cell line and optimal subculture period for studies of cancer related phenomena and for testing the effect of potential anticancer drugs....
Yuejiao Yang
2016-06-01
Full Text Available D-(+-glucose (Glc was added to the original Fricke polyvinyl alcohol–glutaraldehyde–xylenol orange (FPGX hydrogel dosimeter system to make a more stable FPGX hydrogel three-dimensional dosimeter in this paper. Polyvinyl alcohol was used as a substrate, which was combined with Fricke solution. Various concentrations of Glc were tested with linear relevant fitting for optimal hydrogel production conditions. The effects of various formulations on the stability and sensitivity of dosimeters were evaluated. The results indicated that D-(+-Glc, as a free radical scavenger, had a great effect on stabilizing the dose response related to absorbency and reducing the auto-oxidization of ferrous ions. A careful doping with Glc could slow down the color change of the dosimeter before and after radiation without any effect on the sensitivity of the dosimeter.
Yang, Yue Jiao; Chen, Jie; Yang, Liming; Chen, Bin; Sheng, Zhenmei; Luo, Wen Yun [School of Environmental and Chemical Engineering, Shanghai University, Shanghai (China); Chen, Jian Xin; Lu, Xun; Sui, Guo Ping [Chemical and Ionizing Radiation Metrology Institute, Shanghai Institute of Measurement and Testing Technology, Shanghai (China)
2016-06-15
D-(+)-glucose (Glc) was added to the original Fricke polyvinyl alcohol-glutaraldehyde-xylenol orange (FPGX) hydrogel dosimeter system to make a more stable FPGX hydrogel three-dimensional dosimeter in this paper. Polyvinyl alcohol was used as a substrate, which was combined with Fricke solution. Various concentrations of Glc were tested with linear relevant fitting for optimal hydrogel production conditions. The effects of various formulations on the stability and sensitivity of dosimeters were evaluated. The results indicated that D-(+)-Glc, as a free radical scavenger, had a great effect on stabilizing the dose response related to absorbency and reducing the auto-oxidization of ferrous ions. A careful doping with Glc could slow down the color change of the dosimeter before and after radiation without any effect on the sensitivity of the dosimeter.
Stability Estimates for a Twisted Rod Under Terminal Loads: A Three-dimensional Study
Majumdar, Apala
2012-03-01
The stability of an inextensible unshearable elastic rod with quadratic strain energy density subject to end loads is considered. We study the second variation of the corresponding rod-energy, making a distinction between in-plane and out-of-plane perturbations and isotropic and anisotropic cross-sections, respectively. In all cases, we demonstrate that the naturally straight state is a local energy minimizer in parameter regimes specified by material constants. These stability results are also accompanied by instability results in parameter regimes defined in terms of material constants. © 2012 Springer Science+Business Media B.V.
Huang, Yang; Li, Xin-Zhou
2016-01-01
Gaining insight into the behavior of a perturbed black hole surrounded by a reflecting mirror in asymptotically anti-de Sitter space-time is of great interest for current fundamental and practical research. In this work, a detailed analysis for superradiant stability of the system composed by a $D$-dimensional Reissner-Nordstr\\"{o}m-anti-de Sitter (RN-AdS) black hole and a reflecting mirror under charged scalar perturbations are presented in the linear regime. It is found that the stability of the system is heavily affected by the mirror radius as well as the mass of the scalar perturbation, AdS radius and the dimension of space-time. In a higher dimensional space-time, the degree of instability of the superradiant modes will be severely weakened. Nevertheless, the degree of instability can be magnified significantly by choosing a suitable value of the mirror radius. Remarkably, when the mirror radius is smaller than a threshold value the system becomes stable. We also find that massive charged scalar fields ...
Iswanto, A. H.; Sucipto, T.; Nadeak, S. S. D.; Fatriasari, W.
2017-03-01
In general, the weakness of particleboard using urea formaldehyde (UF) resin has a low dimensional stability. This reasearch intends to improve its properties by post-treatment technique using several water repellent materials. The post-treatment effect on dimensional stability and durability properties of particleboard against to subterranean and dry termites has been evaluated. Sample was dipped into water reppelent solution namely parafin, palm oil, silicon and water proof for 3 minutes. Furthermore, they were oven dried at 50°C for 24 hours. The results showed that the density varied of 0.60 to 0.74 g/cm3. The post-treatment of particleboard increases the density value. Water absorption and thickness swelling of board were varied of 29.35% to 114.99% and 13.23 to 37.31%, respectively. This treatment also improved up the thickness swelling to 65%. The best durability of board to subterranean and dry termite attack has found on silicon and waterproof treatment, respectively.
Mergili, M.; Marchesini, I.; Fellin, W.; Rossi, M.; Raia, S.; Guzzetti, F.
2012-04-01
Landslide risk depends on landslide hazard, i.e. the probability of occurrence of a slope failure of a given magnitude within a specified period and in a given area. The occurrence probability of slope failures in an area characterized by a set of geo-environmental parameters gives the landslide susceptibility. Statistical and deterministic methods are used to assess landslide susceptibility. Deterministic models based on limit equilibrium techniques are applied for the analysis of particular types of landslides (e.g., shallow soil slips, debris flows, rock falls), or to investigate the effects of specific triggers, i.e., an intense rainfall event or an earthquake. In particular, infinite slope stability models are used to calculate the spatial probability of shallow slope failures. In these models, the factor of safety is computed on a pixel basis, assuming a slope-parallel, infinite slip surface. Since shallow slope failures coexist locally with deep-seated landslides, infinite slope stability models fail to describe the complexity of the landslide phenomena. Limit equilibrium models with curved sliding surfaces are geometrically more complex, and their implementation with raster-based GIS is a challenging task. Only few attempts were made to develop GIS-based three-dimensional applications of such methods. We present a preliminary implementation of a GIS-based, three-dimensional slope stability model capable of dealing with deep-seated and shallow rotational slope failures. The model is implemented as a raster module (r.rotstab) in the Open Source GIS package GRASS GIS, and makes use of the three-dimensional sliding surface model proposed by Hovland (1977). Given a DEM and a set of thematic layers of geotechnical and hydraulic parameters, the model tests a large number of randomly determined potential ellipsoidal slip surfaces. In addition to ellipsoidal slip surfaces, truncated ellipsoids are tested, which can occur in the presence of weak layers or hard
On stability of vortices in three-dimensional self-attractive Bose-Einstein condensates
Malomed, Boris A. [Department of Interdisciplinary Studies, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)]. E-mail: malomed@eng.tau.ac.il; Lederer, Falk [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-077743 Jena (Germany); Mazilu, Dumitru [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-077743 Jena (Germany); Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 407 Atomistilor, Magurele-Bucharest 077125 (Romania); Mihalache, Dumitru [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-077743 Jena (Germany); Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 407 Atomistilor, Magurele-Bucharest 077125 (Romania)
2007-02-05
Results of accurate analysis of stability are reported for localized vortices in the Bose-Einstein condensate (BEC) with the negative scattering length, trapped in an anisotropic potential with the aspect ratio {omega}. The cases of {omega}-bar 1 and {omega}-bar 1 correspond to the 'pancake' (nearly-2D) and 'cigar-shaped' (nearly-1D) configurations, respectively (in the latter limit, the vortices become 'tubular' solitons). The analysis is based on the 3D Gross-Pitaevskii equation. The family of solutions with vorticity S=1 is accurately predicted by the variational approximation. The relative size of the stability area for the vortices with S=1 (which was studied, in a part, before) increases with the decrease of {omega} in terms of the number of atoms, but decreases in terms of the chemical potential. All states with S>=2 are unstable, while the stability of the ordinary solitons (S=0) obeys the Vakhitov-Kolokolov criterion. The stability predictions are verified by direct simulations of the full 3D equation.
Ham, C J; Kirk, A; Saarelma, S
2013-01-01
It is known that magnetic perturbations can mitigate edge localized modes (ELMs) in experiments, for example MAST (Kirk et al 2013 Nucl. Fusion 53 043007). One hypothesis is that the magnetic perturbations cause a three dimensional corrugation of the plasma and this corrugated plasma has different stability properties to peeling-ballooning modes compared to an axisymmetric plasma. It has been shown in an up-down symmetric plasma that magnetic perturbations in tokamaks will break the usual axisymmetry of the plasma causing three dimensional displacements (Chapman et al 2012 Plasma Phys. Control. Fusion 54 105013). We produce a free boundary three-dimensional equilibrium of a lower single null MAST relevant plasma using VMEC (S P Hirshman and J C Whitson 1983 Phys. Fluids 26 3553). The current and pressure profiles used for the modelling are similar to those deduced from axisymmetric analysis of experimental data with ELMs. We focus on the effect of applying $n=3$ and $n=6$ magnetic perturbations using the RMP ...
Wong Kelvin KL
2012-02-01
Full Text Available Abstract Background This study characterizes the distribution and components of plaque structure by presenting a three-dimensional blood-vessel modelling with the aim of determining mechanical properties due to the effect of lipid core and calcification within a plaque. Numerical simulation has been used to answer how cap thickness and calcium distribution in lipids influence the biomechanical stress on the plaque. Method Modelling atherosclerotic plaque based on structural analysis confirms the rationale for plaque mechanical examination and the feasibility of our simulation model. Meaningful validation of predictions from modelled atherosclerotic plaque model typically requires examination of bona fide atherosclerotic lesions. To analyze a more accurate plaque rupture, fluid-structure interaction is applied to three-dimensional blood-vessel carotid bifurcation modelling. A patient-specific pressure variation is applied onto the plaque to influence its vulnerability. Results Modelling of the human atherosclerotic artery with varying degrees of lipid core elasticity, fibrous cap thickness and calcification gap, which is defined as the distance between the fibrous cap and calcification agglomerate, form the basis of our rupture analysis. Finite element analysis shows that the calcification gap should be conservatively smaller than its threshold to maintain plaque stability. The results add new mechanistic insights and methodologically sound data to investigate plaque rupture mechanics. Conclusion Structural analysis using a three-dimensional calcified model represents a more realistic simulation of late-stage atherosclerotic plaque. We also demonstrate that increases of calcium content that is coupled with a decrease in lipid core volume can stabilize plaque structurally.
Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping
Ming, Fangfei; Mulugeta, Daniel; Tu, Weisong; Smith, Tyler S.; Vilmercati, Paolo; Lee, Geunseop; Huang, Ying-Tzu; Diehl, Renee D.; Snijders, Paul C.; Weitering, Hanno H.
2017-03-01
Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Its formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.
STABILITY OF SYSTEM OF TWO-DIMENSIONAL NON-HYDROSTATIC REVOLVING FLUIDS
无
2006-01-01
Applying the theory of stratification, it is proved that the system of the two-dimensional non-hydrostatic revolving fluids is unstable in the two-order continuous function class. The construction of solution space is given and the solution approach is offered. The sufficient and necessary conditions of the existence of formal solutions are expressed for some typical initial and boundary value problems and the calculating formulae to formal solutions are presented in detail.
Dynamics and Stability of Blind Grasping of a 3-Dimensional Object under Non-holonomic Constraints
Suguru Arimoto; Morio Yoshida; Ji-Hun Bae
2006-01-01
A mathematical model expressing the motion of a pair of multi-DOF robot fingers with hemi-spherical ends,grasping a 3-D rigid object with parallel flat surfaces, is derived, together with non-holonomic constraints. By referring to the fact that humans grasp an object in the form of precision prehension, dynamically and stably by opposable forces, between the thumb and another finger (index or middle finger), a simple control signal constructed from finger-thumb opposition is proposed, and shown to realize stable grasping in a dynamic sense without using object information or external sensing (this is called "blind grasp" in this paper). The stability of grasping with force/torque balance under non-holonomic constraints is analyzed on the basis of a new concept named "stability on a manifold". Preliminary simulation results are shown to verify the validity of the theoretical results.
Stabilization of Extra Dimensions and The Dimensionality of the Observed Space
Rador, T
2005-01-01
We present a simple model for the late time stabilization of extra dimensions. The basic idea is that brane solutions wrapped around extra dimensions, which is allowed by string theory, will resist expansion due to their winding mode, the momentum modes in principle work in the opposite way, it is this interplay that leads to dynamical stabilization. We use the idea of democratic wrapping \\cite{art5}-\\cite{art6}, where in a given decimation of extra dimensions, all possible winding cases are considered. To simplify the study further we assumed a symmetric decimation in which the total number of extra dimensions is taken to be $Np$ where N can be called the order of the decimation. We also assumed that the extra dimensions all have the topology of tori. We show that with these rather general assumptions, there exists solutions to the field equations in which the extra dimensions are stabilized and that the conditions do not depend on $p$. This fact means that there exists at least one solution to the asymmetri...
Experimental studies on the stability and transition of 3-dimensional boundary layers
Nitschke-Kowsky, P.
1987-01-01
Three-dimensional unstable boundary layers were investigated as to their characteristic instabilities, leading to turbulence. Standing cross-flow instabilities and traveling waves preceding the transition were visualized with the hydrogen bubble technique in the boundary layer above the wall of a swept cylinder. With the sublimation method and hot film technique, a model consisting of a swept flat plate with a pressure-inducing displacement body in the 1 m wind tunnel was studied. Standing waves and traveling waves in a broad frequency are observed. The boundary layer of this model is close to the assumptions of the theory.
Castellani, Marco; Giuli, Massimiliano, E-mail: massimiliano.giuli@univaq.it [University of L’Aquila, Department of Information Engineering, Computer Science and Mathematics (Italy)
2016-02-15
We study pseudomonotone and quasimonotone quasivariational inequalities in a finite dimensional space. In particular we focus our attention on the closedness of some solution maps associated to a parametric quasivariational inequality. From this study we derive two results on the existence of solutions of the quasivariational inequality. On the one hand, assuming the pseudomonotonicity of the operator, we get the nonemptiness of the set of the classical solutions. On the other hand, we show that the quasimonoticity of the operator implies the nonemptiness of the set of nonzero solutions. An application to traffic network is also considered.
Stability of trapped Bose-Einstein condensates in one-dimensional tilted optical lattice potential
Fang Jian-Shu; Liao Xiang-Ping
2011-01-01
Using the direct perturbation technique, this paper obtains a general perturbed solution of the Bose-Einstein condensates trapped in one-dimensional tilted optical lattice potential. We also gave out two necessary and sufficient conditions for boundedness of the perturbed solution. Theoretical analytical results and the corresponding numerical results show that the perturbed solution of the Bose-Einstein condensate system is unbounded in general and indicate that the Bose-Einstein condensates are Lyapunov-unstable. However, when the conditions for boundedness of the perturbed solution are satisfied, then the Bose-Einstein condensates are Lyapunov-stable.
Chen, Li-Hao; Liu, Zong-Pei; Pan, Yung-Ning
2016-08-01
In this paper, the effect of homogenization heat treatment on α value [coefficient of thermal expansion (10-6 K-1)] of low thermal expansion cast irons was studied. In addition, constrained thermal cyclic tests were conducted to evaluate the dimensional stability of the low thermal expansion cast irons with various heat treatment conditions. The results indicate that when the alloys were homogenized at a relatively low temperature, e.g., 1023 K (750 °C), the elimination of Ni segregation was not very effective, but the C concentration in the matrix was moderately reduced. On the other hand, if the alloys were homogenized at a relatively high temperature, e.g., 1473 K (1200 °C), opposite results were obtained. Consequently, not much improvement (reduction) in α value was achieved in both cases. Therefore, a compound homogenization heat treatment procedure was designed, namely 1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ, in which a relatively high homogenization temperature of 1473 K (1200 °C) can effectively eliminate the Ni segregation, and a subsequent holding stage at 1023.15 K (750 °C) can reduce the C content in the matrix. As a result, very low α values of around (1 to 2) × 10-6 K-1 were obtained. Regarding the constrained thermal cyclic testing in 303 K to 473 K (30 °C to 200 °C), the results indicate that regardless of heat treatment condition, low thermal expansion cast irons exhibit exceedingly higher dimensional stability than either the regular ductile cast iron or the 304 stainless steel. Furthermore, positive correlation exists between the α 303.15 K to 473.15 K value and the amount of shape change after the thermal cyclic testing. Among the alloys investigated, Heat I-T3B (1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ) exhibits the lowest α 303 K to 473 K value (1.72 × 10-6 K-1), and hence has the least shape change (7.41 μm) or the best dimensional stability.
Ham, C. J., E-mail: christopher.ham@ccfe.ac.uk; Chapman, I. T.; Kirk, A.; Saarelma, S. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
2014-10-15
It is known that magnetic perturbations can mitigate edge localized modes (ELMs) in experiments, for example, MAST [Kirk et al., Nucl. Fusion 53, 043007 (2013)]. One hypothesis is that the magnetic perturbations cause a three dimensional corrugation of the plasma and this corrugated plasma has different stability properties to peeling-ballooning modes compared to an axisymmetric plasma. It has been shown in an up-down symmetric plasma that magnetic perturbations in tokamaks will break the usual axisymmetry of the plasma causing three dimensional displacements [Chapman et al., Plasma Phys. Controlled Fusion 54, 105013 (2012)]. We produce a free boundary three-dimensional equilibrium of a lower single null MAST relevant plasma using VMEC [S. P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)]. The safety factor and pressure profiles used for the modelling are similar to those deduced from axisymmetric analysis of experimental data with ELMs. We focus on the effect of applying n = 3 and n = 6 magnetic perturbations using the resonant magnetic perturbation (RMP) coils. A midplane displacement of over ±1 cm is seen when the full current is applied. The current in the coils is scanned and a linear relationship between coil current and midplane displacement is found. The pressure gradient in real space in different toroidal locations is shown to change when RMPs are applied. This effect should be taken into account when diagnosing plasmas with RMPs applied. The helical Pfirsch-Schlüter currents which arise as a result of the assumption of nested flux surfaces are estimated for this equilibrium. The effect of this non-axisymmetric equilibrium on infinite n ballooning stability is investigated using COBRA [Sanchez et al., J. Comput. Phys. 161, 576–588 (2000)]. The infinite n ballooning stability is analysed for two reasons; it may give an indication of the effect of non-axisymmetry on finite n peeling-ballooning modes, responsible for ELMs; and
Nonparallel stability of two-dimensional nonuniformly heated boundary-layer flows
Nayfeh, A. H.; El-Hady, N. M.
1979-01-01
An analysis is presented for the linear stability of water boundary-layer flows over nonuniformly flat plates. Included in the analysis are disturbances due to velocity, pressure, temperatures, density, and transport properties as well as variations of the liquid properties with temperature. The method of multiple scales is used to account for the nonparallelism of the mean flow. In contrast with previous analyses, the nonsimilarity of the mean flow is taken into account. No analysis agrees, even qualitatively, with the experimental data when similar profiles are used. However, both the parallel and nonparallel results qualitatively agree with the experimental results of Strazisar and Reshotko when nonsimilar profiles are used.
Youngblood, G.E.; Henager, C.H. Jr.; Senor, J. [Pacific Northwest Lab., Richland, WA (United States)] [and others
1995-04-01
The objective of this work is to assess the development and the performance of continuous fiber SiC{sub f}/SiC composites as a structural material for advanced fusion reactor application. The dimensional stability and some mechanical properties of two similar 2D 0-90{degree} weave SiC{sub f}/SiC composites made with Nacalon{trademark} ceramic-grade fiber were characterized and compared after neutron irradiation to those properties for {beta}-SiC. The major difference between these two composites was that one had a thin (150 nm) and the other a thick (1000 nm) graphite interface layer. The irradiation conditions consisted of relatively high doses (4.3 to 26 dpa-SiC) at high temperature (430-1200{degree}C).
Smitadhi Ganguly; A Nandi; S Neogy
2014-06-01
Unlike structural dynamics, the three-dimensional finite-element model of non-axisymmetric rotors on orthotropic bearings generates a large gyroscopic system with parametric stiffness. The present work explores the use of mass-lumping in stability analysis of such systems. Using a variant of Hill’s method, the problem reduces to a generalized Eigen value problem of order $nm \\times nm$, with as the order of the system in state vector representation and as the number of terms in the assumed solution. The matrices in both the sides of the Eigen value problem are expressed in terms of Kronecker products where the mass-matrix appears twice as a sub-matrix in both the sides of the equation. A particular one or both of them can be made diagonal. Both options produce sufficiently accurate results with considerable savings, even with a coarse mesh.
Range-Gated Metrology: An Ultra-Compact Sensor for Dimensional Stabilization
Lay, Oliver P.; Dubovitsky, Serge; Shaddock, Daniel A.; Ware, Brent; Woodruff, Christopher S.
2008-01-01
Point-to-point laser metrology systems can be used to stabilize large structures at the nanometer levels required for precision optical systems. Existing sensors are large and intrusive, however, with optical heads that consist of several optical elements and require multiple optical fiber connections. The use of point-to-point laser metrology has therefore been limited to applications where only a few gauges are needed and there is sufficient space to accommodate them. Range-Gated Metrology is a signal processing technique that preserves nanometer-level or better performance while enabling: (1) a greatly simplified optical head - a single fiber optic collimator - that can be made very compact, and (2) a single optical fiber connection that is readily multiplexed. This combination of features means that it will be straightforward and cost-effective to embed tens or hundreds of compact metrology gauges to stabilize a large structure. In this paper we describe the concept behind Range-Gated Metrology, demonstrate the performance in a laboratory environment, and give examples of how such a sensor system might be deployed.
Ng, C S; Yasin, E
2011-01-01
Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region, and in association with shocks, turbulence, and magnetic reconnection. Due to potentially large amplitude of electric fields within these structures, their effects on particle heating, scattering, or acceleration can be important. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. BGK modes have been studied extensively for many decades, predominately in one dimension (1D), although there have been observations showing that some of these structures have clear 3D features. While there have been approximate solutions of higher dimensional BGK modes, an exact 3D BGK mode solution in a finite magnetic field has not been found yet. Recently we have constructed exact solutions of 2D B...
Holtan, J R; Olin, P S; Rudney, J D
1991-04-01
Polyvinlsiloxane impressions were made from a stainless steel master die machined to stimulate five full veneer crown preparations symmetrically placed in an arch form. Three groups of 10 impressions each were made. Treatment groups were sterilized using an ethylene oxide gas and a conventional steam autoclave. Casts were poured and intrapreparation, height, and diameter measurements were made using a stereomicroscope, a digital electronic caliper, and a 1-inch travel dial indicator. Analysis of dimensional changes for the two groups showed that casts made from impressions sterilized by ethylene oxide are acceptable for use in the construction of fixed or removable prostheses. Casts made from impressions sterilized in a steam autoclave can be used for the fabrication of diagnostic casts and some transitional prostheses, but not for routine construction of crowns or fixed partial dentures.
A novel two-dimensional MgB6 crystal: metal-layer stabilized boron kagome lattice.
Xie, Sheng-Yi; Li, Xian-Bin; Tian, Wei Quan; Chen, Nian-Ke; Wang, Yeliang; Zhang, Shengbai; Sun, Hong-Bo
2015-01-14
Based on first-principles calculations, we designed for the first time a boron-kagome-based two-dimensional MgB6 crystal, in which two boron kagome layers sandwich a triangular magnesium layer. The two-dimensional lattice is metallic with several bands across the Fermi level, and among them a Dirac point appears at the K point of the first Brillouin zone. This metal-stabilized boron kagome system displays electron-phonon coupling, with a superconductivity critical transition temperature of 4.7 K, and thus it is another possible superconducting Mg-B compound besides MgB2. Furthermore, the proposed 2D MgB6 can also be used for hydrogen storage after decoration with Ca. Up to five H2 molecules can be attracted by one Ca with an average binding energy of 0.225 eV. The unique properties of 2D MgB6 will spur broad interest in nanoscience and technology.
P Dutt; Akhlaq Husain; A S Vasudeva Murthy; C S Upadhyay
2015-08-01
This is the second of a series of papers devoted to the study of ℎ- spectral element methods for three dimensional elliptic problems on non-smooth domains. The present paper addresses the proof of the main stability theorem.We assume that the differential operator is a strongly elliptic operator which satisfies Lax–Milgram conditions. The spectral element functions are non-conforming. The stability estimate theorem of this paper will be used to design a numerical scheme which give exponentially accurate solutions to three dimensional elliptic problems on non-smooth domains and can be easily implemented on parallel computers.
Muhammad H. Al-Malack
2016-07-01
Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.
Bifurcations and stability of nondegenerated homoclinic loops for higher dimensional systems.
Jin, Yinlai; Li, Feng; Xu, Han; Li, Jing; Zhang, Liqun; Ding, Benyan
2013-01-01
By using the foundational solutions of the linear variational equation of the unperturbed system along the homoclinic orbit as the local current coordinates system of the system in the small neighborhood of the homoclinic orbit, we discuss the bifurcation problems of nondegenerated homoclinic loops. Under the nonresonant condition, existence, uniqueness, and incoexistence of 1-homoclinic loop and 1-periodic orbit, the inexistence of k-homoclinic loop and k-periodic orbit is obtained. Under the resonant condition, we study the existence of 1-homoclinic loop, 1-periodic orbit, 2-fold 1-periodic orbit, and two 1-periodic orbits; the coexistence of 1-homoclinic loop and 1-periodic orbit. Moreover, we give the corresponding existence fields and bifurcation surfaces. At last, we study the stability of the homoclinic loop for the two cases of non-resonant and resonant, and we obtain the corresponding criterions.
Persistence, Permanence and Global Stability for an $n$ n -Dimensional Nicholson System
Faria, Teresa; Röst, Gergely
2014-09-01
For a Nicholson's blowflies system with patch structure and multiple discrete delays, we analyze several features of the global asymptotic behavior of its solutions. It is shown that if the spectral bound of the community matrix is non-positive, then the population becomes extinct on each patch, whereas the total population uniformly persists if the spectral bound is positive. Explicit uniform lower and upper bounds for the asymptotic behavior of solutions are also given. When the population uniformly persists, the existence of a unique positive equilibrium is established, as well as a sharp criterion for its absolute global asymptotic stability, improving results in the recent literature. While our system is not cooperative, several sharp threshold-type results about its dynamics are proven, even when the community matrix is reducible, a case usually not treated in the literature.
Wang, Yu; Liu, Bao-lin; Zhu, Hai-yan; Yan, Chuan-liang; Li, Zhi-jun; Wang, Zhi-qiao
2014-01-01
When exploiting the deep resources, the surrounding rock readily undergoes the hole shrinkage, borehole collapse, and loss of circulation under high temperature and high pressure. A series of experiments were conducted to discuss the compressional wave velocity, triaxial strength, and permeability of granite cored from 3500 meters borehole under high temperature and three-dimensional stress. In light of the coupling of temperature, fluid, and stress, we get the thermo-fluid-solid model and governing equation. ANSYS-APDL was also used to stimulate the temperature influence on elastic modulus, Poisson ratio, uniaxial compressive strength, and permeability. In light of the results, we establish a temperature-fluid-stress model to illustrate the granite's stability. The compressional wave velocity and elastic modulus, decrease as the temperature rises, while poisson ratio and permeability of granite increase. The threshold pressure and temperature are 15 MPa and 200 °C, respectively. The temperature affects the fracture pressure more than the collapse pressure, but both parameters rise with the increase of temperature. The coupling of thermo-fluid-solid, greatly impacting the borehole stability, proves to be a good method to analyze similar problems of other formations.
Static stability of a three-dimensional space truss. M.S. Thesis - Case Western Reserve Univ., 1994
Shaker, John F.
1995-01-01
In order to deploy large flexible space structures it is necessary to develop support systems that are strong and lightweight. The most recent example of this aerospace design need is vividly evident in the space station solar array assembly. In order to accommodate both weight limitations and strength performance criteria, ABLE Engineering has developed the Folding Articulating Square Truss (FASTMast) support structure. The FASTMast is a space truss/mechanism hybrid that can provide system support while adhering to stringent packaging demands. However, due to its slender nature and anticipated loading, stability characterization is a critical part of the design process. Furthermore, the dire consequences surely to result from a catastrophic instability quickly provide the motivation for careful examination of this problem. The fundamental components of the space station solar array system are the (1) solar array blanket system, (2) FASTMast support structure, and (3) mast canister assembly. The FASTMast once fully deployed from the canister will provide support to the solar array blankets. A unique feature of this structure is that the system responds linearly within a certain range of operating loads and nonlinearly when that range is exceeded. The source of nonlinear behavior in this case is due to a changing stiffness state resulting from an inability of diagonal members to resist applied loads. The principal objective of this study was to establish the failure modes involving instability of the FASTMast structure. Also of great interest during this effort was to establish a reliable analytical approach capable of effectively predicting critical values at which the mast becomes unstable. Due to the dual nature of structural response inherent to this problem, both linear and nonlinear analyses are required to characterize the mast in terms of stability. The approach employed herein is one that can be considered systematic in nature. The analysis begins with one
Huck, Thierry; Vallis, Geoffrey K.
2001-08-01
What can we learn from performing a linear stability analysis of the large-scale ocean circulation? Can we predict from the basic state the occurrence of interdecadal oscillations, such as might be found in a forward integration of the full equations of motion? If so, do the structure and period of the linearly unstable modes resemble those found in a forward integration? We pursue here a preliminary study of these questions for a case in idealized geometry, in which the full nonlinear behavior can also be explored through forward integrations. Specifically, we perform a three-dimensional linear stability analysis of the thermally-driven circulation of the planetary geostrophic equations. We examine the resulting eigenvalues and eigenfunctions, comparing them with the structure of the interdecadal oscillations found in the fully nonlinear model in various parameter regimes. We obtain a steady state by running the time-dependent, nonlinear model to equilibrium using restoring boundary conditions on surface temperature. If the surface heat fluxes are then diagnosed, and these values applied as constant flux boundary conditions, the nonlinear model switches into a state of perpetual, finite amplitude, interdecadal oscillations. We construct a linearized version of the model by empirically evaluating the tangent linear matrix at the steady state, under both restoring and constant-flux boundary conditions. An eigen-analysis shows there are no unstable eigenmodes of the linearized model with restoring conditions. In contrast, under constant flux conditions, we find a single unstable eigenmode that shows a striking resemblance to the fully-developed oscillations in terms of three-dimensional structure, period and growth rate. The mode may be damped through either surface restoring boundary conditions or sufficiently large horizontal tracer diffusion. The success of this simple numerical method in idealized geometry suggests applications in the study of the stability of
Neng Wan
2014-01-01
Full Text Available In terms of the poor geometric adaptability of spline element method, a geometric precision spline method, which uses the rational Bezier patches to indicate the solution domain, is proposed for two-dimensional viscous uncompressed Navier-Stokes equation. Besides fewer pending unknowns, higher accuracy, and computation efficiency, it possesses such advantages as accurate representation of isogeometric analysis for object boundary and the unity of geometry and analysis modeling. Meanwhile, the selection of B-spline basis functions and the grid definition is studied and a stable discretization format satisfying inf-sup conditions is proposed. The degree of spline functions approaching the velocity field is one order higher than that approaching pressure field, and these functions are defined on one-time refined grid. The Dirichlet boundary conditions are imposed through the Nitsche variational principle in weak form due to the lack of interpolation properties of the B-splines functions. Finally, the validity of the proposed method is verified with some examples.
Muñoz Mateo, A.; Brand, J.
2015-12-01
We analyse the dynamical properties of three-dimensional solitary waves in cylindrically trapped Bose-Einstein condensates. Families of solitary waves bifurcate from the planar dark soliton and include the solitonic vortex, the vortex ring and more complex structures of intersecting vortex lines known collectively as Chladni solitons. The particle-like dynamics of these guided solitary waves provides potentially profitable features for their implementation in atomtronic circuits, and play a key role in the generation of metastable loop currents. Based on the time-dependent Gross-Pitaevskii equation we calculate the dispersion relations of moving solitary waves and their modes of dynamical instability. The dispersion relations reveal a complex crossing and bifurcation scenario. For stationary structures we find that for μ /{\\hslash }{ω }\\perp \\gt 2.65 the solitonic vortex is the only stable solitary wave. More complex Chladni solitons still have weaker instabilities than planar dark solitons and may be seen as transient structures in experiments. Fully time-dependent simulations illustrate typical decay scenarios, which may result in the generation of multiple separated solitonic vortices.
Stability and electronic structure of two-dimensional allotropes of group-IV materials
Matusalem, Filipe; Marques, Marcelo; Teles, Lara K.; Bechstedt, Friedhelm
2015-07-01
We study six different two-dimensional (2D) allotropes of carbon, silicon, germanium, and tin by means of the ab initio density functional theory for the ground state and approximate methods to calculate their electronic structures, including quasiparticle effects. Four of the investigated allotropes are based on dumbbell geometries, one on a kagome lattice, and one on the graphenelike hexagonal structure for comparison. Concerning carbon, our calculations of the cohesive energies clearly show that the hexagonal structure (graphene) is most stable. However, in the case of Si and Ge, the dumbbell structures, particularly the large honeycomb dumbbell (LHD) geometries, are energetically favored compared to the s p2/s p3 -bonded hexagonal lattice (i.e., silicene and germanene). The main reason for this is the opening of a band gap in the honeycomb dumbbell arrangements. The LHD sheet crystals represent indirect semiconductors with a K →Γ gap of about 0.5 eV. In the Sn case we predict the MoS2-like symmetry to be more stable, in contrast to the stanene and LHD geometries predicted in literature. Our results for freestanding group-IV layers shine new light on recent experimental studies of group-IV overlayers on various substrates.
Salem, Mohamed Shaker; Ibrahim, Shaimaa Moustafa; Amin, Mohamed
2017-07-01
A novel silicon-based optical microcavity composed of a defect layer sandwiched between two parallel rugate mirrors is created by the electrochemical anodization of silicon in a hydrofluoric acid-based electrolyte using a precisely controlled current density profile. The profile consists of two sinusoidally modulated current waveforms separated by a fixed current that is applied to produce a defect layer between the mirrors. The spectral response of the rugate-based microcavity is simulated using the transfer matrix method and compared to the conventional Bragg-based microcavity. It is found that the resonance position of both microcavities is unchanged. However, the rugate-based microcavity exhibits a distinct reduction of the sidebands' intensity. Further attenuation of the sidebands' intensity is obtained by creating refractive index matching layers with optimized thickness at the bottom and top of the rugate-based microcavity. In order to stabilize the produced microcavity against natural oxidation, atomic layer deposition of an ultra-thin titanium dioxide layer on the pore wall is carried out followed by thermal annealing. The microcavity resonance position shows an observable sensitivity to the deposition and annealing processes.
Imagawa, Haruo; Itahara, Hiroshi
2017-03-14
A Ca-bridged siloxene (Ca-siloxene) composed of two-dimensional siloxene planes with Ca bridging was synthesized via a solid state metathesis reaction using TaCl5 to extract Ca from CaSi2. Three different Ca-siloxenes synthesized at Cl2/Ca molar ratios of 0.25, 1.25 and 2.5 (CS0.25, CS1.25 and CS2.5, respectively) were fabricated and investigated as anode active materials for lithium-ion batteries. Both secondary and primary Ca-siloxene particles, which serve to increase the contact interfaces with conductive materials and to generate accessible sites for lithium ions, respectively, were found to become smaller and to have increased pore volumes as the Cl2/Ca molar ratio was increased. These Ca-siloxenes exhibited stable charge/discharge performance as anode materials, with 69-99% capacity retention after 50 charge/discharge cycles (compared with 36% retention for a conventional Kautsky-type siloxene). The charge capacity also increased with increases in the Cl2/Ca molar ratio, such that the CS2.5 showed the highest capacity after 50 charge/discharge cycles. This may reflect the formation of Si6Li6 rather than SiLi4.4 and suggests the maintenance of layered Si planes for large capacity retention after charge/discharge cycling. The increase of contact interfaces between acetylene black (as a conductive material) and Ca-siloxenes was found to effectively increase the lithium-ion capacity of Ca-siloxene during high rate charge/discharge cycling.
Stability and bistability in a one-dimensional model of coastal foredune height
Goldstein, Evan B.; Moore, Laura J.
2016-05-01
On sandy coastlines, foredunes provide protection from coastal storms, potentially sheltering low areas—including human habitat—from elevated water level and wave erosion. In this contribution we develop and explore a one-dimensional model for coastal dune height based on an impulsive differential equation. In the model, coastal foredunes continuously grow in a logistic manner as the result of a biophysical feedback and they are destroyed by recurrent storm events that are discrete in time. Modeled dunes can be in one of two states: a high "resistant-dune" state or a low "overwash-flat" state. The number of stable states (equilibrium dune heights) depends on the value of two parameters, the nondimensional storm frequency (the ratio of storm frequency to the intrinsic growth rate of dunes) and nondimensional storm magnitude (the ratio of total water level during storms to the maximum theoretical dune height). Three regions of phase space exist (1) when nondimensional storm frequency is small, a single high resistant-dune attracting state exists; (2) when both the nondimensional storm frequency and magnitude are large, there is a single overwash-flat attracting state; (3) within a defined region of phase space model dunes exhibit bistable behavior—both the resistant-dune and the low overwash-flat states are stable. Comparisons to observational studies suggest that there is evidence for each state to exist independently, the coexistence of both states (i.e., segments of barrier islands consisting of overwash-flats and segments of islands having large dunes that resist erosion by storms), as well as transitions between states.
Maassen, G.H; Steenbeek, H.W.; Van Geert, P. L. C.
2004-01-01
This study aimed at comparing the stability of three methods for two-dimensional sociometric status determination, including (1) the recently developed SSrat technique (Maassen, Akkermans, & Van der Linden, 1996), as well as (2) the procedure of Howes (1988), which is based on the algorithm and clas
Thota, Kiran Kumar; Jasthi, Sujana; Ravuri, Rajyalakshmi; Tella, Suchita
2014-10-01
The purpose of the study was to determine the effect of autoclaving on the dimensional stability of three different elastomeric impression materials at three different time intervals. Standardized stainless steel master die as per ADA specification number 19 was fabricated. The impression materials used for the study were condensation silicone (GP1), addition silicone (GP2) and polyether (GP3). A total of 45 samples of the stainless steel die were made (n = 45), that is 15 samples for each group. Impression materials were mixed according to the manufacturer's instructions and were loaded into the mold to make an impression of the die. Impressions were identified with the help of numerical coding system and measurements were made using stereomicroscope (MAGNUS MSZ-Bi) of 0.65x magnification with the help of image analysis software (IMACE PRO-INSIGHT VERSION.The results were subjected to statistical analysis using one way analysis of variance and student t-test for comparison between the groups. Within the limitations of the study statistically significant dimensional changes were observed for all the three impression materials at three different time intervals but this change was not clinically significant. It is well-known fact that all impressions should be disinfected to avoid possible transmission of infectious diseases either by direct contact or cross contamination. Immersion and spray disinfection as well as various disinfection solutions have been tested and proven to be effective for this purpose. But for elastomeric impression materials these methods have proven to be ineffective as they do not prevent cross contamination among the dental team. So autoclaving was one of the most effective sterilization procedure for condensation silicone and addition silicone. Since polyether is hydrophilic it is better to disinfect the impressions as recommended by the manufacturer or by immersion or spray atomization.
Wang, Hong-mei; Liu, Yue-jie; Wang, Hong-xia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xuan-zhang
2013-12-01
Motivated by the great advance in graphene hydroxide--a versatile material with various applications--we performed density functional theory (DFT) calculations to study the functionalization of the two-dimensional hexagonal boron nitride (h-BN) sheet with hydroxyl (OH) radicals, which has been achieved experimentally recently. Particular attention was paid to searching for the most favorable site(s) for the adsorbed OH radicals on a h-BN sheet and addressing the roles of OH radical coverage on the stability and properties of functionalized h-BN sheet. The results indicate that, for an individual OH radica, the most stable configuration is that it is adsorbed on the B site of the h-BN surface with an adsorption energy of -0.88 eV and a magnetic moment of 1.00 μ(B). Upon adsorption of more than one OH radical on a h-BN sheet, however, these adsorbates prefer to adsorb in pairs on the B and its nearest N atoms from both sides of h-BN sheet without magnetic moment. An energy diagram of the average adsorption energy of OH radicals on h-BN sheet as a function of its coverage indicates that when the OH radical coverage reaches to 60 %, the functionalized h-BN sheet is the most stable among all studied configurations. More importantly, this configuration exhibits good thermal and dynamical stability at room temperature. Owing to the introduction of certain impurity levels, the band gap of h-BN sheet gradually decreases with increasing OH coverage, thereby enhancing its electrical conductivity.
Nada S. Abdelwahab
2017-05-01
Full Text Available The present work concerns with the development of stability indicating the RP-HPLC method for simultaneous determination of guaifenesin (GUF and pseudoephedrine hydrochloride (PSH in the presence of guaifenesin related substance (Guaiacol. GUC, and in the presence of syrup excepients with minimum sample pre-treatment. In the developed RP-HPLC method efficient chromatographic separation was achieved for GUF, PSH, GUC and syrup excepients using ODS column as a stationary phase and methanol: water (50:50, v/v, pH = 4 with orthophosphoric acid as a mobile phase with a flow rate of 1 mL min−1 and UV detection at 210 nm. The chromatographic run time was approximately 10 min. Calibration curves were drawn relating the integrated area under peak to the corresponding concentrations of PSH, GUF and GUC in the range of 1–8, 1–20, 0.4–8 μg mL−1, respectively. The developed method has been validated and met the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated method was successfully applied for determination of the studied drugs in triaminic chest congestion® syrup; moreover its results were statistically compared with those obtained by the official method and no significant difference was found between them.
Rosario Dell’Aquila
Full Text Available The soil aggregate stability is determined generally by sifting the soil samples in water using a sieve-shaker (wet sieving. The Author has developed an original model of automatic sieve-shaker using a vertical oscillation system to the aim of an its possible use to determine the soil aggregate stability and dimensional distribution. The purpose of this note is to describe the construction and performance of the prototype currently used in the Laboratory for the Soil Structure Study of the ISAFOM – CNR. The proposed sieve-shaker, with the introduction of some innovations (protected by Italy Patent 0001332102, realizes the submersion and levelling of the soil samples using a lifter to support the containers with the water. With 6 workplaces it allows to process simultaneously up to 6 soil samples according to different test cycles. By means of the control panel it is possible to set up various determinations with the stroke of 3 cm and the oscillation frequency from 4 up to 80 oscillations per minute. The performance of the proposed sieve-shaker was verified with a technical test to verify the performance of the 6 workplaces to oscillation speed increasing up to 60 oscillations per minute and an agronomic test. The results have been submitted to analysis of variance considering the plots of the field from which have been taken the samples for repetitions and the six workplaces of the proposed sieve-shaker for experimental theses. The differences between the various workplaces have not been significant. This demonstrates that the behavior of the various workplaces is uniform. The dispersion in water at constant shaking time and increasing oscillation speed has evidenced a very significant inverse relation between the index of aggregate stability in water (IASW and number of oscillations per minute. This result demonstrates a constant performance of the proposed sieve-shaker to varying of the oscillation speed. The agnonomic test has demonstrated
Xu, H.; Kevrekidis, P. G.; Kapitula, T.
2017-06-01
In the present work, we consider a variety of two-component, one-dimensional states in nonlinear Schrödinger equations in the presence of a parabolic trap, inspired by the atomic physics context of Bose-Einstein condensates. The use of Lyapunov-Schmidt reduction methods allows us to identify persistence criteria for the different families of solutions which we classify as (m, n), in accordance with the number of zeros in each component. Upon developing the existence theory, we turn to a stability analysis of the different configurations, using the Krein signature and the Hamiltonian-Krein index as topological tools identifying the number of potentially unstable eigendirections for each branch. A perturbation expansion for the eigenvalue problems associated with nonlinear states found near the linear limit permits us to obtain explicit asymptotic expressions for the eigenvalues. Finally, when the states are found to be unstable, typically by virtue of Hamiltonian Hopf bifurcations, their dynamics is studied in order to identify the nature of the respective instability. The dynamics is generally found to lead to a vibrational evolution over long time scales.
Ruith, Michael Rudolf
Vortex breakdown of nominally axisymmetric, swirling incompressible jets and wakes issuing into a semi-infinite domain is studied by means of direct numerical simulations, as well as local and global linear stability analyses. From the point of view of specifying conditions at the open boundaries, this class of flows is particularly challenging due to its ability to support traveling waves. Several boundary conditions, ranging from free-slip and various homogeneous Neumann conditions to radiation conditions, are implemented in a staggered grid, finite difference algorithm that solves the unsteady Navier-Stokes equations in cylindrical coordinates by means of a fractional step method. Their advantages and shortcomings are evaluated in detail, and the question of the proper implementation of intermediate step boundary conditions is addressed. The data obtained from a large variety of test simulations points to the radiation condition as the most suitable lateral and outflow boundary condition for both high and low entrainment jets and wakes. A two-parameterc low entrainment velocity profile for which the steady, axisymmetric breakdown is well studied is selected for further investigation. Hence, issues regarding the role of three-dimensionality and unsteadiness with respect to the existence, mode selection, and internal structure of vortex breakdown can be addressed in terms of the two governing parameters and the Reynolds number. Low Reynolds numbers are found to yield flow fields lacking breakdown bubbles or helical breakdown modes even for high swirl. In contrast, highly swirling flows at large Reynolds numbers exhibit bubble, helical or double helical breakdown modes, where the axisymmetric mode is promoted by a jet-like axial velocity profile, while a wake-like profile renders the flow helically unstable and ultimately yields non-axisymmetric breakdown modes. It is shown that a transition from super- to subcritical flow, accurately predicts the parameter
N. N. Nefedov
2016-01-01
Full Text Available Parabolic singularly perturbed problems have been actively studied in recent years in connection with a large number of practical applications: chemical kinetics, synergetics, astrophysics, biology, and so on. In this work a singularly perturbed periodic problem for a parabolic reaction-diﬀusion equation is studied in the two-dimensional case. The case when there is an internal transition layer under unbalanced nonlinearity is considered. The internal layer is localised near the so called transitional curve. An asymptotic expansion of the solution is constructed and an asymptotics for the transitional curve is determined. The asymptotical expansion consists of a regular part, an interior layer part and a boundary part. In this work we focus on the interior layer part. In order to describe it in the neighborhood of the transition curve the local coordinate system is introduced and the stretched variables are used. To substantiate the asymptotics thus constructed, the asymptotic method of diﬀerential inequalities is used. The upper and lower solutions are constructed by suﬃciently complicated modiﬁcation of the asymptotic expansion of the solution. The Lyapunov asymptotical stability of the solution was proved by using the method of contracting barriers. This method is based on the asymptotic comparison principle and uses the upper and lower solutions which are exponentially tending to the solution to the problem. As a result, the solution is locally unique.The article is published in the authors’ wording.
Buha, Joka; Gaspari, Roberto; Del Rio Castillo, Antonio Esau; Bonaccorso, Francesco; Manna, Liberato
2016-07-13
The structural and compositional stabilities of two-dimensional (2D) Bi2Te3 and Bi2Se3 nanocrystals, produced by both colloidal synthesis and by liquid phase exfoliation, were studied by in situ transmission electron microscopy (TEM) during annealing at temperatures between 350 and 500 °C. The sublimation process induced by annealing is structurally and chemically anisotropic and takes place through the preferential dismantling of the prismatic {011̅0} type planes, and through the preferential sublimation of Te (or Se). The observed anisotropic sublimation is independent of the method of nanocrystal's synthesis, their morphology, or the presence of surfactant molecules on the nanocrystals surface. A thickness-dependent depression in the sublimation point has been observed with nanocrystals thinner than about 15 nm. The Bi2Se3 nanocrystals were found to sublimate below 280 °C, while the Bi2Te3 ones sublimated at temperatures between 350 and 450 °C, depending on their thickness, under the vacuum conditions in the TEM column. Density functional theory calculations confirm that the sublimation of the prismatic {011̅0} facets is more energetically favorable. Within the level of modeling employed, the sublimation occurs at a rate about 700 times faster than the sublimation of the {0001} planes at the annealing temperatures used in this work. This supports the distinctly anisotropic mechanisms of both sublimation and growth of Bi2Te3 and Bi2Se3 nanocrystals, known to preferentially adopt a 2D morphology. The anisotropic sublimation behavior is in agreement with the intrinsic anisotropy in the surface free energy brought about by the crystal structure of Bi2Te3 or Bi2Se3.
覆铜板尺寸稳定性测试方法研究%Research of the test method of CCL dimensional stability
潘华林; 潘俊健; 陈虎
2016-01-01
目前IPC-TM-650标准测试方法已无法有效帮助PCB厂评估CCL的尺寸稳定性。本文对IPC-TM-650测试方法和PCB生产流程进行分析，提出一种新的尺寸稳定性评估方法，并通过测试样品和PCB模型验证该新方法的有效性。%The current standard test method of IPC-TM-650 is unable to help PCB manufacturer to evaluate the CCL’s dimensional stability effectively. In this paper, a new evaluation method of dimensional stability is put forward by analyzing test method of IPC-TM-650 and PCB production processes. Meanwhile, the effectiveness of the new method is veriifed by the test sample and the PCB model.
Julie Bossu
Full Text Available Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes.
Bossu, Julie; Beauchêne, Jacques; Estevez, Yannick
2016-01-01
Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes. PMID:27007687
中密度纤维板的尺寸稳定性改良技术%Dimensional Stability Modification Techniques of the MDF
欧阳靓; 曹金珍; 朱愿
2013-01-01
The medium density fiberboard (MDF) is one of the most widely used wood-based panels,whose dimensional stability significantly influences the performance,the service life,the application area's extension,and the added value's promotion of the products.The authors of this paper mainly present the influencing factors and current research progress of the dimensional stability on the MDF.Based on these,a feasible direction for research of MDF dimensional stability has been pointed out.%中密度纤维板(MDF)是目前家具、室内装修等最常用的木质复合材料之一,其尺寸稳定性直接影响到产品的使用性能、使用寿命以及产品应用领域的拓展和附加值的提高.笔者概述了中密度纤维板尺寸稳定性的影响因素以及中密度纤维板尺寸稳定性方面的相关研究进展,并在此基础上提出今后研究的方向.
Vo, Tony; Pothérat, Alban; Sheard, Gregory J.
2017-03-01
This study considers the linear stability of Poiseuille-Rayleigh-Bénard flows subjected to a transverse magnetic field, to understand the instabilities that arise from the complex interaction between the effects of shear, thermal stratification, and magnetic damping. This fundamental study is motivated in part by the desire to enhance heat transfer in the blanket ducts of nuclear fusion reactors. In pure magnetohydrodynamic flows, the imposed transverse magnetic field causes the flow to become quasi-two-dimensional and exhibit disturbances that are localized to the horizontal walls. However, the vertical temperature stratification in Rayleigh-Bénard flows feature convection cells that occupy the interior region, and therefore the addition of this aspect provides an interesting point for investigation. The linearized governing equations are described by the quasi-two-dimensional model proposed by Sommeria and Moreau [J. Fluid Mech. 118, 507 (1982), 10.1017/S0022112082001177], which incorporates a Hartmann friction term, and the base flows are considered fully developed and one-dimensional. The neutral stability curves for critical Reynolds and Rayleigh numbers, Rec and Rac, respectively, as functions of Hartmann friction parameter H have been obtained over 10-2≤H ≤104 . Asymptotic trends are observed as H →∞ following Rec∝H1 /2 and Rac∝H . The linear stability analysis reveals multiple instabilities which alter the flow both within the Shercliff boundary layers and the interior flow, with structures consistent with features from plane Poiseuille and Rayleigh-Bénard flows.
Tejo, Sampath Kumar; Kumar, Anil G; Kattimani, Vivekanand S; Desai, Priti D; Nalla, Sandeep; Chaitanya K, Krishna
2012-10-05
The introduction of different interocclusal recording materials has put clinicians in dilemma that which material should be used in routine clinical practice for precise recording and transferring of accurate existing occlusal records for articulation of patient's diagnostic or working casts in the fabrication of good satisfactory prosthesis. In the era of developing world of dentistry the different materials are introduced for interocclusal record with different brand names because of this; the utility of the material is confusing for successful delivery of prosthesis with lack of in vitro or in vivo studies which will predict the property of the material with utility recommendations. The aim of this multicenter research is to evaluate the time dependent linear dimensional stability of three types of interocclusal recording materials; which gives very clear idea to clinicians in regard to its usage in routine practice and recommendations for usage of the different materials. Also to find out ideal time for articulation of three types of interocclusal recording materials with accuracy. Commercially available and ADA approved Polyether bite registration paste (Ramitec), Poly vinyl siloxane bite registration paste (Jetbite) and Zinc oxide eugenol (ZOE) bite registration paste (Super bite) were used in the study.A stainless steel die was made according to modified American dental Associations (ADA) specification no. 19. Each one of the tested materials were manipulated according to manufacturers' instructions. The materials separated from die, 3-mins after their respective setting time, resulted in disks of standard diameter. Two parallel lines and three perpendicular lines reproduced on the surface. The distance between two parallel lines was measured at different time intervals i.e. 1 hour, 24, 48 and 72 hours by using travelling microscope (magnus) and compared with standard die measurements made according to ADA specification no.19 to find out the dimensional
Moon, Sung-Jun; Kim, Tae-Ho
2017-01-01
Three-dimensional spine stabilization exercise can strengthen the trunk muscles with minimal spine movement. To investigate the effects of the newly developed Spine Balance three-dimensional (3D) system on trunk strength and gait abilities of chronic stroke patients. Twenty-four chronic stroke patients were randomly assigned to an experimental (n = 12) or control group (n = 12). The experimental and control groups performed spine stabilization exercise by using the newly developed Spine Balance 3D system and the well-known Bridge exercise thrice a week for 30 min per day for 7 weeks. Timed up and go (TUG) test, 10-m walking test (10-m WT), trunk muscle strength, and gait ability were evaluated before and after 7 weeks of intervention. The 10-m WT, TUG, walking speed, non-affected side step length, and distance in the experimental group, wherein trunk muscle strength was checked by using the Spine Balance 3D system evaluation program, showed more significant improvement than those in the control group (p Spine Balance 3D system can be a more useful therapeutic tool for rehabilitation of trunk muscle strength and gait abilities than bridge exercise-based spine stabilization exercise in chronic stroke patients.
Tejo Sampath
2012-10-01
Full Text Available Abstract Background The introduction of different interocclusal recording materials has put clinicians in dilemma that which material should be used in routine clinical practice for precise recording and transferring of accurate existing occlusal records for articulation of patient’s diagnostic or working casts in the fabrication of good satisfactory prosthesis. In the era of developing world of dentistry the different materials are introduced for interocclusal record with different brand names because of this; the utility of the material is confusing for successful delivery of prosthesis with lack of in vitro or in vivo studies which will predict the property of the material with utility recommendations. Purpose of the study The aim of this multicenter research is to evaluate the time dependent linear dimensional stability of three types of interocclusal recording materials; which gives very clear idea to clinicians in regard to its usage in routine practice and recommendations for usage of the different materials. Also to find out ideal time for articulation of three types of interocclusal recording materials with accuracy. Materials and method Commercially available and ADA approved Polyether bite registration paste (Ramitec, Poly vinyl siloxane bite registration paste (Jetbite and Zinc oxide eugenol (ZOE bite registration paste (Super bite were used in the study. A stainless steel die was made according to modified American dental Associations (ADA specification no. 19. Each one of the tested materials were manipulated according to manufacturers’ instructions. The materials separated from die, 3-mins after their respective setting time, resulted in disks of standard diameter. Two parallel lines and three perpendicular lines reproduced on the surface. The distance between two parallel lines was measured at different time intervals i.e. 1 hour, 24, 48 and 72 hours by using travelling microscope (magnus and compared with standard die
Al-Maaitah, Ayman A.; Nayfeh, Ali H.; Ragab, Saad A.
1989-01-01
The effect of suction on the stability of compressible flows over backward-facing steps is investigated. Mach numbers up to 0.8 are considered. The results show that continuous suction stabilizes the flow outside the separation bubble, but it destabilizes the flow inside it. Nevertheless, the overall N factor decreases as the suction level increases due to the considerable reduction of the separation bubble. For the same suction flow rate, properly distributed suction strips stabilize the flow more than continuous suction. The size of the separation bubble, and hence its effect on the instability can be considerably reduced by placing strips with high suction velocities in the separation region.
Godbole, Surekha R; Dahane, Trupti M; Nimonkar, Sharayu V
2014-01-01
Introduction: Infection control is an important concept in the present day practice of dentistry. The prosthodontists are at an added risk of transmission because of the infection spreading through the contaminated lab equipments while working in the lab. The purpose of this study is to evaluate the effect of UV light disinfection on dimensional stability of polyvinyl siloxane impressions. Materials and Methods : Impressions were made in perforated custom tray. After polymerization of impression, half the samples were disinfected in UV light and remaining samples were not subjected to disinfection and poured in die stone which served as control group. Linear dimensions were measured on the cast with travelling microscope of 0.001accuracy. Result : The result showed that UV light disinfectant showed no significant dimensional changes on impressions. Conclusion: Hence, it can be safely used to disinfect impressions in clinical prosthodontic procedures. PMID:25386528
Vadapalli, Sriharsha Babu; Atluri, Kaleswararao; Putcha, Madhu Sudhan; Kondreddi, Sirisha; Kumar, N Suman; Tadi, Durga Prasad
2016-01-01
This in vitro study was designed to compare polyvinyl-siloxane (PVS) monophase and polyether (PE) monophase materials under dry and moist conditions for properties such as surface detail reproduction, dimensional stability, and gypsum compatibility. Surface detail reproduction was evaluated using two criteria. Dimensional stability was evaluated according to American Dental Association (ADA) specification no. 19. Gypsum compatibility was assessed by two criteria. All the samples were evaluated, and the data obtained were analyzed by a two-way analysis of variance (ANOVA) and Pearson's Chi-square tests. When surface detail reproduction was evaluated with modification of ADA specification no. 19, both the groups under the two conditions showed no significant difference statistically. When evaluated macroscopically both the groups showed statistically significant difference. Results for dimensional stability showed that the deviation from standard was significant among the two groups, where Aquasil group showed significantly more deviation compared to Impregum group (P impregum and aquasil performed better in dry condition than in moist; impregum performed better than aquasil in both the conditions. When tested for surface detail reproduction according to ADA specification, under dry and moist conditions both of them performed almost equally. When tested according to macroscopic evaluation, impregum and aquasil performed significantly better in dry condition compared to moist condition. In dry condition, both the materials performed almost equally. In moist condition, aquasil performed significantly better than impregum. Regarding gypsum compatibility according to ADA specification, in dry condition both the materials performed almost equally, and in moist condition aquasil performed better than impregum. When tested by macroscopic evaluation, impregum performed better than aquasil in both the conditions.
无
2010-01-01
Natural convection of air is numerically simulated in a 3-dimensional rectangular cavity heated from below using SIMPLE algorithm with a QUICK scheme.The results suggest that when all lateral walls are adiabatic,the fluid rolls occur along the long axis.When the Rayleigh number is smaller,the flow is of 2-dimensional character,and the rolls shapes are similar.The average Nusselt numbers in the central part of the cavity are similar.The average Nusselt numbers in the part near by the cavity are different.According to the comparison of 3-dimensional results with 2-dimensional results,the flow patterns and heat transfer in the central part of the cavity can be assumed as a 2-dimensional flow,While those in the part near by the cavity can not.With increasing Rayleigh number,the flow is 3-dimensional characteristic.The 3-dimensional result accords with the experimental result.When all lateral walls are adiabatic,the ten rolls occur along the long axis.But when lateral walls are heated or cooled,the rolls disappear along the long axis and two rolls occur along the short axis.The rotation direction of the rolls is reversed.When Rayleigh number is over some critical value,flow and heat transfer will be asymmetry,indicating unsteady oscillation occurs.By nonlinear analyses,it is shown that with increasing Rayleigh number,flow and heat transfer will change from steady state to unsteady state through HOPF bifurcation,and transition to chaos will occur through multi-periodical oscillation.
Ahmet Kursad Culhaoglu
2014-01-01
Full Text Available Purpose: Irreversible hydrocolloid impression materials are some of the most common impression materials in dentistry. Preparation of alginate is critical for dental appliance fabricated upon the cast made directly from the impression. This study compared the effect of two mixing methods i.e. hand mixing or device mixing on the physical properties of two different brands of irreversible hydrocolloid. Materials and Methods: Two alginate impression materials: Cavex Tulip (Tulip, Cavex Holland BV, Haarlem, Holland and Hydrogum Soft (Zhermack, Rovigo, Italy, were mixed according to manufacturers instroductions with two mixing methods. Mixing was performed at room temperature using tap water. The material was allowed to set in a water bath at 35°C (±1°C, simulating intra-oral setting conditions. For each tested material, nine standardized samples were used. The first method was hand mixing; the other method was with a device. Detail reproduction and dimensional changes of impressions were compared. One-way analysis of variance was performed to compare the dimensional differences between the four groups. Results: The device mixed speciemens showed better surface detail than hand-mixed samples. Cavex alginate demonstrated better surface detail than Hydrogum. Cavex Tulip alginate showed better dimensional stability than Hydrogum Soft in both hand-mixed and device-mixed samples. Furthermore, all device mixed samples were better than hand-mixed in terms of dimensional stability. A two-way analysis of variance and Fisher′s protected least significant difference test at the 0.05 level of significance were used to analyze the data. Conclusion: Of the two mixing methods, the vacuum mixer had the best performance overall in reducing the number, percent and volume of porosities in the mixed alginate.
Tak, Young Joo; Jang, Woosun; Richter, Norina A; Soon, Aloysius
2015-04-21
Platinum is known as a catalyst with exceptional reactivity for many important reactions, e.g. the oxygen reduction reaction. To reduce the high cost of pure platinum catalysts, platinum on a carbon support is widely used in industrial fuel cell applications. However, these Pt/C systems suffer from poor stability. As a cost-efficient and more durable alternative, Pt single-atom catalysts on a TiN support have recently been suggested, and it has been shown that the single-atom catalysts are stable when anchored at a nitrogen vacancy site on the TiN surface in a nitrogen-lean environment. To further explore the perspective of Pt/TiN catalytic systems, we provide insights into the stability and morphology of Pt nanostructures at the TiN(100) surface, using a density-functional theory approach in combination with ab initio atomistic thermodynamics. Our results show that the formation of two-dimensional Pt nano-layers is preferred over the formation of three-dimensional Pt nano-clusters on the TiN substrate. Similar to the single-atom catalysts, nano-layers of Pt can be stabilized on the TiN(100) surface by surface nitrogen vacancies under nitrogen-lean conditions. By analyzing the electronic metal-support interaction (EMSI) between the Pt nano-layer and the TiN surface with surface defects, we demonstrate that a strong EMSI between the surrounding Ti and Pt atoms is important for stabilizing the catalyst nano-layer at the TiN surface, and that N vacancies lead to stronger Pt-Ti interaction. This work provides a rational computational platform for the design of new generation high-performance Pt-based fuel cells.
Rosenfeld, G.; Morgenstern, Karina; Beckmann, Ingo; Wulfhekel, Wulf; Wulfhekel, W.C.U.; Laegsgaard, Erik; Besenbacher, Flemming; Comsa, George
1998-01-01
An overview is given of recent work on the decay of two-dimensional clusters on a Ag(111) surface. Experimental studies using scanning tunnelling microscopy are presented, and various approaches to extract quantitative information on the relevant atomic processes from cluster decay experiments are
Talebi, A.
2008-01-01
Key words: Hillslope geometry, Hillslope hydrology, Hillslope stability, Complex hillslopes, Modeling shallow landslides, HSB model, HSB-SM model. The hydrologic response of a hillslope to rainfall involves a complex, transient saturated-unsaturated interaction that usually leads to a water table
Talebi, A.
2008-01-01
Key words: Hillslope geometry, Hillslope hydrology, Hillslope stability, Complex hillslopes, Modeling shallow landslides, HSB model, HSB-SM model. The hydrologic response of a hillslope to rainfall involves a complex, transient saturated-unsaturated interaction that usually leads to a water table
Higashino, Toshiki; Ueda, Akira; Yoshida, Junya; Mori, Hatsumi
2017-02-27
A dihydroxy-substituted benzothienobenzothiophene, BTBT(OH)2, was synthesized, and its charge-transfer (CT) salt, β-[BTBT(OH)2]2ClO4, was successfully obtained. Thanks to the introduced hydroxy groups, a hydrogen-bonded chain structure connecting the BTBT molecules and counter anions was formed in the CT salt, which effectively increases the dimensionality of the electronic structure and consequently leads to a stable metallic state.
Gounder, Revathy; Vikas, B V J
2016-01-01
To evaluate and compare the effect of 0.5% chlorhexidine gluconate, 1% sodium hypochlorite, and 2% glutaraldehyde by immersion and spray atomization technique on the linear dimensional stability of Jet bite, Aluwax and Ramitec interocclusal recording materials. Three representative materials: Jet bite (addition silicone), Aluwax and Ramitec (polyether) were mixed according to manufacturer's instructions and then specimens were prepared according to the specifications of ISO 4823. All the specimens except the control (distilled water) were treated with disinfectant solutions (0.5% chlorhexidine gluconate, 1% sodium hypochlorite, and 2% glutaraldehyde) for 30 and 60 min (n = 10) by spray and immersion technique. Once removed from the solutions, the test samples were washed in water for 15 s, dried and measured after 24 h 3 times using a measuring microscope with an accuracy of 0.0001 mm. Two-way ANOVA and Tukey's test with significance level of 5% were used to assess the statistical data (α = 0.05). All groups showed no significant difference statistically, in linear dimension when disinfected for 30 min by spray or immersion technique. Polyether had significantly higher dimensional variation when immersed in sodium hypochlorite for 60 min. Addition silicone showed the least dimensional change which ranged from 0.024% to 0.05%, followed by polyether from 0.004% to 0.171% and Aluwax from 0.146% to 0.228%. To preserve the dimensions and surface of the recording materials and effective microbial elimination, restrictions should be applied in the method of disinfection and time duration. However, using the disinfectants either by spray or immersion technique, the dimensional change was <0.5% which was not clinically significant according to the American Dental Association specification no. 19 criteria within the first 24 h.
Majumdar, Apala
2013-06-01
We analyze the dynamical stability of a naturally straight, inextensible and unshearable elastic rod, under tension and controlled end rotation, within the Kirchhoff model in three dimensions. The cases of clamped boundary conditions and isoperimetric constraints are treated separately. We obtain explicit criteria for the static stability of arbitrary extrema of a general quadratic strain energy. We exploit the equivalence between the total energy and a suitably defined norm to prove that local minimizers of the strain energy, under explicit hypotheses, are stable in the dynamic sense due to Liapounov. We also extend our analysis to damped systems to show that static equilibria are dynamically stable in the Liapounov sense, in the presence of a suitably defined local drag force. © 2013 Elsevier B.V. All rights reserved.
Hansen, Jesper
2003-01-01
The three-dimensional bin packing problem is concerned with packing a given set of rectangular items into rectangular bins. We are interested in solving real-life problems where rotations of items are allowed and the packings must be packable and stable. Load bearing of items is taken into account...... as well. An on-line heuristic and an exact method have been developed and compared on real-life instances and as well on some benchmark instances. The on-line algorithm consistently reaches good solutions within a few seconds. The exact method is able to improve the solutions, but a significant amount...
Hugo F. Lopez
2016-05-01
Full Text Available In this work an automotive Al-A319 was given a solid solution heat treatment (T4 at 753 K (480 °C for 4.5 hours and an ageing treatment (T7 at 513 K (240 °C for various times up to 3.0 h. The alloy in the T4 condition was dilatometrically tested at various temperatures in order to measure its relative dimensional changes. It was found that the dimensional changes are due to both, alloy thermal expansion and nucleation and growth of second phases. In addition, in the T7 condition the alloy strength and ductility were determined as a function of ageing times. Ageing promoted alloy strength but at the expenses of a rather poor alloy ductility (down to 1%. Apparently, Cu rich intermetallic phases and regions provided a brittle path for fracturing. In particular, microstructural characterization using high resolution transmission electron microscopy indicated that not all the Cu in the matrix was dissolved during the T4 treatment. Hence, after ageing (T7 these Cu-rich regions seemed to coarsen into spherical particles.
D' Adamo, Juan; Gronskis, Alejandro; Artana, Guillermo [Laboratorio de Fluidodinamica, Facultad de Ingenieria, Universidad de Buenos Aires (Argentina); Gonzalez, Leo M, E-mail: leo.gonzalez@upm.es [Canal de Ensayos Hidrodinamicos, School of Naval Arquitecture, Universidad Politecnica de Madrid (Spain)
2012-10-01
We propose to study the stability properties of an air flow wake forced by a dielectric barrier discharge (DBD) actuator, which is a type of electrohydrodynamic (EHD) actuator. These actuators add momentum to the flow around a cylinder in regions close to the wall and, in our case, are symmetrically disposed near the boundary layer separation point. Since the forcing frequencies, typical of DBD, are much higher than the natural shedding frequency of the flow, we will be considering the forcing actuation as stationary. In the first part, the flow around a circular cylinder modified by EHD actuators will be experimentally studied by means of particle image velocimetry (PIV). In the second part, the EHD actuators have been numerically implemented as a boundary condition on the cylinder surface. Using this boundary condition, the computationally obtained base flow is then compared with the experimental one in order to relate the control parameters from both methodologies. After validating the obtained agreement, we study the Hopf bifurcation that appears once the flow starts the vortex shedding through experimental and computational approaches. For the base flow derived from experimentally obtained snapshots, we monitor the evolution of the velocity amplitude oscillations. As to the computationally obtained base flow, its stability is analyzed by solving a global eigenvalue problem obtained from the linearized Navier-Stokes equations. Finally, the critical parameters obtained from both approaches are compared. (paper)
Ali Ben Moussa
2012-10-01
Full Text Available In this work, the problem of hydrodynamic, heat and mass transfer and stability in a salt gradient solar pond has been numerically studied by means of computational fluid dynamics in transient regime. The body of the simulated pond is an enclosure of height H and length L wherein an artificial salinity gradient is created in order to suppress convective motions induced by solar radiation absorption and to stabilize the solar pond during the period of operation. Here we show the distribution of velocity, temperature and salt concentration fields during energy collection and storage in a solar pond filled with water and constituted by three different salinity zones. The bottom of the pond is blackened and the free-surface is subjected to heat losses by convection, evaporation and radiation while the vertical walls are adiabatic and impermeable. The governing equations of continuity, momentum, thermal energy and mass transfer are discretized by finite–volume method in transient regime. Velocity vector fields show the presence of thin convective cells in the upper convective zone (UCZ and large convective cells in the lower convective zone (LCZ. This study shows the importance of buoyancy ratio in the decrease of temperature in the UCZ and in the preservation of high temperature in the LCZ. It shows also the importance of the thickness of Non-Convective Zone (NCZ in the reduction of the upwards heat losses.
A. C. A. Prado
2008-12-01
Full Text Available As propriedades do revestimento cerâmico queimado estão intrinsecamente ligadas às características da massa, dentre estas se encontram o tamanho, a distribuição, o formato e o arranjo das partículas. O efeito da distribuição granulométrica de partículas sobre a estabilidade dimensional de placas cerâmicas para revestimentos de base vermelha foi estudado em três massas, todas continham no mínimo 57% de material advindo da Formação Corumbataí. Foram estudadas duas distribuições granulométricas - uma parecida com aquelas usadas no Pólo Cerâmico de Santa Gertrudes e, outra, com uma massa de grés. De uma maneira geral, granulações mais grossas, semelhantes à massa de Santa Gertrudes, variaram menos dimensionalmente quando as placas apresentaram médias e altas porosidades (absorção de água entre 3,0 e 10,0%. Já, granulações mais finas, similares a massas de grés, foram necessárias para a produção de placas de baixa absorção (menor que 3,0%.The properties of final ceramic tiles are related with the mass characteristics, among them the size, shape, distribution and arrange of particles. The effect of particle size distribution on dimensional stability of red ceramic tiles was studied in three masses; all of them composed with, at minimum, 57% of Corumbataí Formation's materials. Two particle size distributions were investigated: the first was similar to the masses that are used in the Santa Gertrudes Ceramic Pole's factories and the other was similar to the stoneware mass. In general, masses with larger particle sizes, similar to that of Santa Gertrudes, had greater dimensional stability in the products with 3 to 10% of water absorption. On the other hand, in the manufacture of low porosity tiles (water absorption capacity < 3% it is recommended the use of smaller grain size.
Hirose, S; Tanuma, S; Shibata, K; Takahashi, M; Tanigawa, T; Sasaqui, T; Noro, A; Uehara, K; Takahashi, K; Taniguchi, T
2003-01-01
The Kelvin-Helmholtz (KH) and tearing instabilities are likely to be important for the process of fast magnetic reconnection that is believed to explain the observed explosive energy release in solar flares. Theoretical studies of the instabilities, however, typically invoke simplified initial magnetic and velocity fields that are not solutions of the governing magnetohydrodynamic (MHD) equations. In the present study, the stability of a reconnecting current sheet is examined using a class of exact global MHD solutions for steady state incompressible magnetic reconnection (Craig & Henton 1995). Numerical simulation indicates that the outflow solutions where the current sheet is formed by strong shearing flows are subject to the KH instability. The inflow solutions where a fast and weakly sheared inflow leads to a strong magnetic field pile-up at the entrance to the sheet are shown to be tearing unstable. Although the observed instability of the solutions can be interpreted qualitatively by applying standa...
Yanagisawa, Takatoshi; Kameyama, Masanori; Ogawa, Masaki
2016-09-01
We explore thermal convection of a fluid with a temperature-dependent viscosity in a basally heated 3-D spherical shell using linear stability analyses and numerical experiments, while considering the application of our results to terrestrial planets. The inner to outer radius ratio of the shell f assumed in the linear stability analyses is in the range of 0.11-0.88. The critical Rayleigh number Rc for the onset of thermal convection decreases by two orders of magnitude as f increases from 0.11 to 0.88, when the viscosity depends sensitively on the temperature, as is the case for real mantle materials. Numerical simulations carried out in the range of f = 0.11-0.55 show that a thermal boundary layer (TBL) develops both along the surface and bottom boundaries to induce cold and hot plumes, respectively, when f is 0.33 or larger. However, for smaller f values, a TBL develops only on the bottom boundary. Convection occurs in the stagnant-lid regime where the root mean square velocity on the surface boundary is less than 1 per cent of its maximum at depth, when the ratio of the viscosity at the surface boundary to that at the bottom boundary exceeds a threshold that depends on f. The threshold decreases from 106.5 at f = 0.11 to 104 at f = 0.55. If the viscosity at the base of the convecting mantle is 1020-1021 Pa s, the Rayleigh number exceeds Rc for Mars, Venus and the Earth, but does not for the Moon and Mercury; convection is unlikely to occur in the latter planets unless the mantle viscosity is much lower than 1020 Pa s and/or the mantle contains a strong internal heat source.
Renn, J.; Steinmann, A.
1986-07-01
The upper bound for the ultraviolet stability of the two-dimensional cosine interaction ..integral../sub ..lambda../:cos ..cap alpha..phi/sub xi/:dxi, ..lambda..is contained inR/sup 2/, in finite volume ..lambda.. is proven for ..cap alpha../sup 2/ element of (4..pi..,8..pi..(, where the theory has been shown to be superrenormalizable (see, e.g., G. Gallavotti, Rev. Mod. Phys. 57, 471 (1985)). Ultraviolet stability in this interval was proven previously (F. Nicolo, J. Renn, and A.Steinmann, ''On the massive sine--Gordon equation in all regions of collapse,'' preprint II Universita di Roma, 1985). Here we give a second proof using renormalization group methods based on a multiscale decomposition of the field by showing that the large fluctuations may be controlled by their small probability. The method essentially follows the one given by Nicolo (F. Nicolo, Commun. Math. Phys. 88, 681 (1983)) for ..cap alpha../sup 2/ element of (4..pi.., (32)/(5) ..pi..(.
Hneda, M. L.; da Cunha, J. B. M.; Gusmão, M. A.; Neto, S. R. Oliveira; Rodríguez-Carvajal, J.; Isnard, O.
2017-01-01
This paper presents the physical properties of a nonstandard orthorhombic form of MnV2O6 , including a comparison with the isostructural orthorhombic niobate MnNb2O6 , and with the usual MnV2O6 monoclinic polymorph. Orthorhombic (P b c n ) MnV2O6 is obtained under extreme conditions of high pressure (6.7 GPa) and high temperature (800 ∘C ). A negative Curie-Weiss temperature θCW is observed, implying dominant antiferromagnetic interactions at high temperatures, in contrast to the positive θCW of the monoclinic form. Specific-heat measurements are reported down to 1.8 K for all three compounds, and corroborate the magnetic-transition temperatures obtained from susceptibility data. Orthorhombic MnV2O6 presents a transition to an ordered antiferromagnetic state at TN=4.7 K. Its magnetic structure, determined by neutron diffraction, is unique among the columbite compounds, being characterized by a commensurate propagation vector k =(0 ,0 ,1/2 ) . It presents antiferromagnetic chains running along the c axis, but with a different spin pattern in comparison to the chains observed in MnNb2O6 . By a comparative discussion of our observations in this three compounds, we are able to highlight the interplay between competing interactions and dimensionality that yield their magnetic properties.
Djokic, Marko R; Dijkmans, Thomas; Yildiz, Guray; Prins, Wolter; Van Geem, Kevin M
2012-09-28
Bio-oils produced by fast pyrolysis of lignocellulosic biomass have proven to be a promising, clean, and renewable energy source. To better assess the potential of using bio-oils for the production of chemicals and fuels a new comprehensive characterization method is developed. The combination of the analyical power of GC×GC-FID and GC×GC-TOF-MS allows to obtain an unseen level of detail for both crude and hydrotreated bio-oils originated from pine wood biomass. The use of GC×GC proves to be essential to capture the compositional differences between crude and stabilized bio-oils. Our method uses a flame ionization detector to quantify the composition, while GC×GC-TOF-MS is used for the qualitative analysis. This method allows quantification of around 150 tentatively identified compounds, describing approximately 80% of total peak volume. The number of quantified compounds in bio-oils is increased with a factor five compared to the present state-of-the-arte. The necessity of using multiple internal standards (dibutyl ether and fluoranthene) and a cold-on column injector is also verified. Copyright © 2012 Elsevier B.V. All rights reserved.
2016-01-01
Objective To investigate the effects of the newly developed Spine Balance 3D system on the balance and gait abilities of hemiplegic stroke patients. Methods Twenty-eight hemiplegic patients with chronic stroke were randomly assigned to an experimental (n=14) or control group (n=14). The experimental and control groups performed balance training by using the newly developed Spine Balance 3D system and the well-known Biodex Balance System 30 minutes per day, three times a week for 7 weeks. The Berg Balance Scale (BBS), 10-m walking test (10mWT), Timed Up and Go Test (TUG), Functional Reach Test (FRT), the Korean version of the Fall Efficacy Scale-International (KFES-I), trunk muscle strength and stability were evaluated before and after 7 weeks of intervention. Results The 10mWT improved significantly (p=0.001) in the experimental group (using the Spine Balance 3D system) but not in the control group, and core muscle strength, which we checked using Spine Balance 3D system evaluation program, improved more in the experimental group as well. The results of the BBS, FRT, TUG, KFES-I, and Biodex Balance System evaluation program improved in both groups after 7 weeks of balance training. Conclusion We suggest that the newly-developed Spine Balance 3D system can be a more useful therapeutic tool for gait and dynamic balance rehabilitation in hemiplegic patients than a conventional 2D-based balance training system. A large-scale randomized controlled study is needed to prove the effect of this system. PMID:28119826
Chun, Jin-Young; Seo, Jeong-Hwan; Park, Sung-Hee; Won, Yu Hui; Kim, Gi-Wook; Moon, Sung-Jun; Ko, Myoung-Hwan
2016-12-01
To investigate the effects of the newly developed Spine Balance 3D system on the balance and gait abilities of hemiplegic stroke patients. Twenty-eight hemiplegic patients with chronic stroke were randomly assigned to an experimental (n=14) or control group (n=14). The experimental and control groups performed balance training by using the newly developed Spine Balance 3D system and the well-known Biodex Balance System 30 minutes per day, three times a week for 7 weeks. The Berg Balance Scale (BBS), 10-m walking test (10mWT), Timed Up and Go Test (TUG), Functional Reach Test (FRT), the Korean version of the Fall Efficacy Scale-International (KFES-I), trunk muscle strength and stability were evaluated before and after 7 weeks of intervention. The 10mWT improved significantly (p=0.001) in the experimental group (using the Spine Balance 3D system) but not in the control group, and core muscle strength, which we checked using Spine Balance 3D system evaluation program, improved more in the experimental group as well. The results of the BBS, FRT, TUG, KFES-I, and Biodex Balance System evaluation program improved in both groups after 7 weeks of balance training. We suggest that the newly-developed Spine Balance 3D system can be a more useful therapeutic tool for gait and dynamic balance rehabilitation in hemiplegic patients than a conventional 2D-based balance training system. A large-scale randomized controlled study is needed to prove the effect of this system.
Synthesis and thermal stability of two-dimensional carbide MXene Ti{sub 3}C{sub 2}
Li, Zhengyang; Wang, Libo; Sun, Dandan; Zhang, Yude; Liu, Baozhong; Hu, Qianku; Zhou, Aiguo, E-mail: zhouag@hpu.edu.cn
2015-01-15
Graphical abstract: - Highlights: • Ti{sub 3}C{sub 2} from PLS-Ti{sub 3}AlC{sub 2} was highly oriented compared to that from HP-Ti{sub 3}AlC{sub 2}. • Small balls of possible AlF{sub 3} attached on the edge of MXene sheets were observed. • MXene is thermally stable in Ar atmosphere up to 800 °C. • A structure of nano-anatase on 2D Ti{sub 3}C{sub 2} was formed by 200 °C oxidization. - Abstract: We investigated the synthesis of quasi-two-dimensional carbide (Ti{sub 3}C{sub 2}), with the name of MXene, by immersing Ti{sub 3}AlC{sub 2} in 40% or 49% hydrofluoric acid (HF) at 0 °C, 15 °C or 60 °C. The influences of time, temperature, and source of Ti{sub 3}AlC{sub 2} on the synthesis were researched. It was found that Ti{sub 3}C{sub 2} synthesized from pressureless synthesized Ti{sub 3}AlC{sub 2} was highly oriented compared to that from hot-pressed Ti{sub 3}AlC{sub 2}. As-synthesized Ti{sub 3}C{sub 2} could be further exfoliated by intercalation with urea, dimethylsulfoxide or ammonia. From the results of thermogravimetry and differential scanning calorimetry, Ti{sub 3}C{sub 2} MXene with F/OH termination was found to be stable in argon atmosphere at temperature up to 800 °C. In oxygen atmosphere, at 200 °C, parts of MXene layers were oxidized to obtain an interesting structure: anatase nano-crystals were evenly distributed on 2D Ti{sub 3}C{sub 2} layers. At 1000 °C, MXene layers were completely oxidized and anatase phase fully transformed to rutile in oxygen atmosphere.
The Comparative Analysis of Dimensional Stability on Four Kinds of Wood%四种木材吸湿尺寸稳定性的比较分析
陈凤义; 魏路; 孙照斌; 马淑玲; 酆志博; 姚建龙
2015-01-01
在温度(20±2)℃，相对湿度(65±5)%、(86±5)%、(33±5)%的条件下，对樟子松、云杉、杨木和榉木四种木材进行了尺寸稳定性测定。结果表明：①四种木材大小试件吸湿率的大小排序为：云杉>榉木>杨木>樟子松；解吸率的大小排序为：樟子松>杨木>云杉>榉木。②湿胀率和收缩率径向取平均值后大小排序为：榉木（0.988%）>云杉（0.715%）>杨木（0.585%）>樟子松（0.487%）；弦向湿胀收缩率取平均值后大小排序为：榉木（1.247%）>云杉（1.021%）>杨木（0.908%）>樟子松（0.858%）。可以认为：樟子松的尺寸稳定性较好，杨木次之，再次是云杉，榉木的稳定性较差。%Dimensional stability for four wood of pinus sylvestris,picea asperata,beech and populus tomentosa was tested. This research was completed under the conditions of(20±2)℃from(65±5)% to(86±5)% and(33±5)% of relative humidity as materials to study their dimensional stability. Results indicate that in the aspect of the moisture absorption rate:spruce is the maximum,beech followed,populus tomentosa next,pinus sylvestris is the minimum .In the aspect of the mois-ture desorption rate:pinus sylvestris is the maximum,populus tomentosa followed,spruce next,beech is the minimum .In the aspect of swelling and shrinkage,the length is very small,the biggest is 0.06%. Four woods in string,Beech is the maximum 1.247%,picea asperata is the next 1.021%,then is populus tomentosa 0.908%,pinus sylvestris is the minimum 0.858%. In the aspect of diameter of four woods Beech is the maximum 0.988%,picea asperata is the next 0.715%,then is populus to-mentosa 0.585%,pinus sylvestris is the minimum 0.487% .To sum up,the dimensional stability of pinus sylvestris is the best,populus tomentosa followed,then is picea asperata,and beech is the worst .
热处理木材吸湿性及尺寸稳定性研究%Heat Treatment of Wood Hygroscopicity and Dimensional Stability
冯德君; 赵泾峰
2011-01-01
以毛白杨(Populus tomentosa)、云衫(Picea asperata)和樟子松(Pinus sylvestris)为试验材料,通过蒸汽法进行热处理后,与未处理材相比,毛白杨的吸湿率降低28.8 %～41.9%;弦向吸湿膨胀率降低20.9 %～51.7%.云衫吸湿率降低19.5%～31.4%;弦向吸湿膨胀率降低22.2%～50.8%.樟子松吸湿率降低27.7%～34.4%;弦向吸湿膨胀率降低22.8 %～50.0%.结果表明,热处理能够极大地降低木材的吸湿性,同时提高木材的尺寸稳定性,解决了室外用木材的吸水性强及尺寸不稳定性.%Three kinds of woods of Populus tomentosa, Picea asperata and Pinus sylvestris were used as materials to studey their hygroscopicity and dimensional stability by steam treatment method. The moisture absorption rate of the wood of P. tomentosa decreased by 28.8 ％ to 41.9 ％, tangential expansion rate by moisture absorption decreased by 20.9 ％ to 51.7 ％. The moisture absorption rate of the wood of Picea asperata decreased by 19.5 ％ to 31.4 ％, tangential expansion rate by moisture absorption decreased by 22.2 ％ to 50.8 ％. The moisture absorption rate of P. sylvestris decreased of by 27.7 ％ to 34.4 ％, and the tangential expansion rate by moisture absorption decreased by 22.8 ％ to 50.0 ％. It was concluded that heat treatment could significantly reduce the wood moisture, while improving the dimensional stability.
Okubo, C.H.; Tornabene, L.L.; Lanza, N.L.
2011-01-01
The value of slope stability analyses for gaining insight into the geologic conditions that would facilitate the growth of gully alcoves on Mars is demonstrated in Gasa crater. Two-dimensional limit equilibrium methods are used in conjunction with high-resolution topography derived from stereo High Resolution Imaging Science Experiment (HiRISE) imagery. These analyses reveal three conditions that may produce observed alcove morphologies through slope failure: (1) a ca >10m thick surface layer that is either saturated with H2O ground ice or contains no groundwater/ice at all, above a zone of melting H2O ice or groundwater and under dynamic loading (i.e., seismicity), (2) a 1-10m thick surface layer that is saturated with either melting H2O ice or groundwater and under dynamic loading, or (3) a >100m thick surface layer that is saturated with either melting H2O ice or groundwater and under static loading. This finding of three plausible scenarios for slope failure demonstrates how the triggering mechanisms and characteristics of future alcove growth would be affected by prevailing environmental conditions. HiRISE images also reveal normal faults and other fractures tangential to the crowns of some gully alcoves that are interpreted to be the result of slope instability, which may facilitate future slope movement. Stability analyses show that the most failure-prone slopes in this area are found in alcoves that are adjacent to crown fractures. Accordingly, crown fractures appear to be a useful indicator of those alcoves that should be monitored for future landslide activity. ?? 2010.
Sahu, R.
2017-03-08
We report on the various types of Peierls like two dimensional structural modulations and relative phase stability of 2H and 1T poly-types in the RexMo1-xS2 and RexW1-xS2 alloy system. Theoretical calculation predicts a polytype phase transition cross over at ∼50 at. % of Mo and W in ReS2 in both monolayer and bulk form, respectively. Experimentally, two different types of structural modulations at 50% and a modulation corresponding to trimerization at 75% alloy composition are observed for RexMo1-xS2 and only one type of modulation is observed at the 50% RexW1-xS2 alloy system. The 50% alloy system is found to be a suitable monolithic candidate for metal semiconductor transition with minute external perturbation. ReS2 is known to be in the 2D Peierls distorted 1Td structure and forms a chain like superstructure. Incorporation of Mo and W atoms into the ReS2 lattice modifies the metal-metal hybridization between the cations and influences the structural modulation and electronic properties of the system. The results offer yet another effective way to tune the electronic structure and poly-type phases of this class of materials other than intercalation, strain, and vertical stacking arrangement.
P Dutt; Akhlaq Husain; A S Vasudeva Murthy; C S Upadhyay
2015-05-01
This is the first of a series of papers devoted to the study of ℎ- spectral element methods for solving three dimensional elliptic boundary value problems on non-smooth domains using parallel computers. In three dimensions there are three different types of singularities namely; the vertex, the edge and the vertex-edge singularities. In addition, the solution is anisotropic in the neighbourhoods of the edges and vertex-edges. To overcome the singularities which arise in the neighbourhoods of vertices, vertex-edges and edges, we use local systems of coordinates. These local coordinates are modified versions of spherical and cylindrical coordinate systems in their respective neighbourhoods. Away from these neighbourhoods standard Cartesian coordinates are used. In each of these neighbourhoods we use a geometrical mesh which becomes finer near the corners and edges. The geometrical mesh becomes a quasi-uniform mesh in the new system of coordinates. We then derive differentiability estimates in these new set of variables and state our main stability estimate theorem using a non-conforming ℎ- spectral element method whose proof is given in a separate paper.
ZHANG; Lei; WEI; Zuoan; LIU; Xiaoyu; LI; Shihai
2005-01-01
Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stage process of landslide under fissure water pressure in the opencast mine, according to the actual state of landslide in Panluo iron mine where landslide happened in 1990 and was fathered in 1999. The calculation results show that fissure water pressure on the sliding surface is the main reason causing landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in good agreement; while if the assumption is not adopted in the discrete element method, the critical φ numerically calculated is less than the one calculated by use of the limit equilibrium method for the sameC. Thus, from an engineering point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.
Feng, D.; Neuweiler, I.; Nackenhorst, U.
2017-02-01
We consider a model for biofilm growth in the continuum mechanics framework, where the growth of different components of biomass is governed by a time dependent advection-reaction equation. The recently developed time-discontinuous Galerkin (TDG) method combined with two different stabilization techniques, namely the Streamline Upwind Petrov Galerkin (SUPG) method and the finite increment calculus (FIC) method, are discussed as solution strategies for a multi-dimensional multi-species biofilm growth model. The biofilm interface in the model is described by a convective movement following a potential flow coupled to the reaction inside of the biofilm. Growth limiting substrates diffuse through a boundary layer on top of the biofilm interface. A rolling ball method is applied to obtain a boundary layer of constant height. We compare different measures of the numerical dissipation and dispersion of the simulation results in particular for those with non-trivial patterns. By using these measures, a comparative study of the TDG-SUPG and TDG-FIC schemes as well as sensitivity studies on the time step size, the spatial element size and temporal accuracy are presented.
Mihaela CAMPEAN
2012-12-01
Full Text Available The paper presents the results of anexperimental study performed with black pine (Pinusnigra L. and spruce (Picea abies L. wood, originatingfrom mature trees and thinnings cut from the sameparcel from the Stroesti-Arges region in Romania.After air drying and conditioning, the defect-freeboards were cut into standard samples 30x20x20mm.These were first dried to oven-dry state, then heattreatedat high temperatures (180 and 200ºC for 1, 2,3 and 4 hours. Weightings before and after heattreatmentallowed establishing the mass loss. Thetotal linear and volumic swelling coefficients were alsodetermined both for the heat-treated and untreatedsamples, in order to establish the effect of the heattreatmentupon the dimensional stability. The resultswere comparatively analyzed for the two species (pineand spruce, for the two grades (mature and thinwood, in order to establish for each the optimumtreating conditions, namely the ones which allow forthe maximum improvement of the dimensionalstability, without affecting significantly the wood mass(and implicitely the mechanical strengths. The resultsof the present research are to be valorized at themanufacturing of solid wood panels made from heattreatedlamellas
Dong, Yucheng; Xia, Yang; Chui, Ying-San; Cao, Chenwei; Zapien, Juan Antonio
2015-02-01
We report a facile, one-pot hydrothermal strategy to prepare self-assembled three-dimensional mesoporous ZnFe2O4 submicron-sized spheres wrapped in graphene sheets as high-performance anode material for lithium ion batteries. The mesoporous submicron-sized spheres are composed of numerous nanoparticles where the void spaces between the neighboring nanoparticles provide a cushion to alleviate volume variation issues during the conversion/alloying process and also provide large contact areas with the electrolyte to facilitate lithium ion diffusion and electron transport during cycling. The synergistic effects between ZnFe2O4 submicron-sized spheres and graphene sheets are another positive effect to enhance the electrochemical performance. The electrochemical characterization of ZnFe2O4-graphene composites exhibits a high specific capacity of 1182 mAh g-1 cycling at a specific current of 100 mA g-1, and significantly enhanced rate capability and cycling stability after long-term testing resulting from their unique structure features.
Feng, D.; Neuweiler, I.; Nackenhorst, U.
2017-06-01
We consider a model for biofilm growth in the continuum mechanics framework, where the growth of different components of biomass is governed by a time dependent advection-reaction equation. The recently developed time-discontinuous Galerkin (TDG) method combined with two different stabilization techniques, namely the Streamline Upwind Petrov Galerkin (SUPG) method and the finite increment calculus (FIC) method, are discussed as solution strategies for a multi-dimensional multi-species biofilm growth model. The biofilm interface in the model is described by a convective movement following a potential flow coupled to the reaction inside of the biofilm. Growth limiting substrates diffuse through a boundary layer on top of the biofilm interface. A rolling ball method is applied to obtain a boundary layer of constant height. We compare different measures of the numerical dissipation and dispersion of the simulation results in particular for those with non-trivial patterns. By using these measures, a comparative study of the TDG-SUPG and TDG-FIC schemes as well as sensitivity studies on the time step size, the spatial element size and temporal accuracy are presented.
Conejero Ortega, G.; Candela Vazquez, N.; Pichel Martinez, M.; Barea del Cerro, R.; Carsi Cebrian, M.
2014-07-01
Austenite-martensite transformation influence on the dimensional stability of a new experimental tool steel alloyed with niobium (0.08% wt.) and vanadium (0.12% wt.) has been studied. The dimensional stability of this new steel was compared with the dimensional stability of commercial steel, after and before two thermal treatments, T1 (860 degree centigrade) and T2 (900 degree centigrade). The thermal treatments consisted on heating and cooling, at 1 atmosphere of pressure, in N{sub 2} atmosphere furnace, following by heating in a conventional furnace at 180 degree centigrade during 1 hour. Initially, the experimental steel composition and Ac{sub 1} and Ac{sub 3} transformation temperatures were determined by glow-discharge luminescence (GDL) and dilatometric tests, respectively, in order to select the austenization temperatures of T1 and T2 treatments. After hardness measurement, the microstructure of both steels was characterized by X-Ray Diffraction (XRD) and optical metallography, before and after of T1 and T2 thermal treatments. Finally, longitudinal and angular dimensional stability analyses were realized for both commercial and experimental steels. After a contrastive hypothesis analysis, the results showed that the longitudinal relative variation of the experimental steel calculated was around 0.2% and the angular relative variation was not significant. (Author)
Sávio Marcelo Leite Moreira da Silva
2004-09-01
Full Text Available The purpose of this study was to evaluate the dimensional stability of heavy and light bodied condensation silicones after immersion in disinfectant solution for 10 or 20 minutes. The impression materials were Optosil Comfort and Xantopren VL Plus and the disinfectant solutions were 1% sodium hypochlorite and 2% glutaraldehyde. Impressions were made on a perforated stainless steel tray, according to the American Dental Association specification No. 19, adding up to a total of 50 samples. The double mixing method (one time, two viscosities was used. Impressions were removed from the roulette block after 7 minutes to ensure complete curing and then immersed in the solutions. Impressions not submitted to treatment composed the control group. After these steps, the impressions were removed from the solution, rinsed in running water and air-dried. Three-dimensional measurements were calculated using an optic microscope graduated at 0.001 mm. The two-way ANOVA indicated no differences (p>0.05 for any combination between variables. The results showed that the solution studied can be safely used to disinfect condensation silicone in clinical prosthodontic procedures.O objetivo deste trabalho foi avaliar a estabilidade dimensional das siliconas de condensação pesada e leve para moldagem odontológica, quando imersas em solução desinfetante por 10 e 20 minutos, relacionando a importância da biossegurança no manuseio destes materiais. Os materiais de moldagem testados foram: Optosil Confort e Xantopren VL Plus; e as soluções desinfetantes foram o hipoclorito de sódio a 1% (Solução de Milton e o glutaraldeído a 2% (Glutaron II. Impressões foram obtidas através de moldeiras perfuradas de aço inoxidável, de acordo com a especificação n.º 19 da ADA, perfazendo um total de 50 moldagens, que foram executadas pela técnica em passo único. Para assegurar a completa polimerização o material foi removido após 7 minutos e submetido à imers
Vojdani M
2006-01-01
Full Text Available Background and Aim: Infection control is an integral part of dentistry and dental impressions are considered an important issue in cross contamination. The aim of this study was to investigate the dimensional stability of two irreversible hydrocolloid materials, Alginoplast and Iralgin after disinfection with 5.2% sodium hypochlorite, used with immersion and spraying methods. Material and Methods: In this experimental study, impressions were made of a master mandibular arch (Typodont containing three stainless steel inserts on the occlucal surface of both mandibular first molars and in the lingual surface of the mandibular central incisors, which served as reference marks for making measurements. Two types of irreversible hydrocolloid (Iralgin and Alginoplast were tested. 5.2% sodium hypochlorite was used in two methods of spraying and immersion to disinfect the samples. The control group was not disinfected. Casts were made of type III gypsum. Stone casts were measured with a Nikon profile projector.Kruskall-Wallis and Mann-Witney test were used for statistical analysis using p<0.05 as the limit of significance. Results: Casts prepared from Alginoplast disinfected by spraying method, were 0.38 % larger in anteroposterior and 0.06% smaller in cross arch dimensions, whereas those prepared from Alginoplast immersed in hypochlorite were 0.47% larger in anteroposterior and 0.11% smaller in cross arch dimensions. Casts made from Iralgin were smaller after both methods of disinfecting, (0.01% smaller in anteroposterior and 0.001% smaller in cross-arch dimensions after spraying and 0.04% smaller in anteroposterior and 0.03% smaller in cross-arch dimensions after immersing in sodium hypochlorite. Conclusion: Alginoplast and Iralgin impressions can be immersed or sprayed for disinfection without compromising the accuracy needed for diagnostic and opposing casts, as well as removable partial denture construction.
Bawden, Gerald W.; Howle, James; Bond, Sandra; Shriro, Michelle; Buck, Peter
2014-01-01
A full scale field seepage test was conducted on a north-south trending levee segment of a now bypassed old meander belt on Twitchell Island, California, to understand the effects of live and decaying root systems on levee seepage and slope stability. The field test in May 2012 was centered on a north-south trench with two segments: a shorter control segment and a longer seepage test segment. The complete length of the trench area measured 40.4 meters (m) near the levee centerline with mature trees located on the waterside and landside of the levee flanks. The levee was instrumented with piezometers and tensiometers to measure positive and negative porewater pressures across the levee after the trench was flooded with water and held at a constant hydraulic head during the seepage test—the results from this component of the experiment are not discussed in this report. We collected more than one billion three-dimensional light detection and ranging (lidar) data points before, during, and after the centerline seepage test to assess centimeter-scale stability of the two trees and the levee crown. During the seepage test, the waterside tree toppled (rotated 20.7 degrees) into the water. The landside tree rotated away from the levee by 5 centimeters (cm) at a height of 2 m on the tree. The paved surface of the levee crown had three regions that showed subsidence on the waterside of the trench—discussed as the northern, central, and southern features. The northern feature is an elongate region that subsided 2.1 cm over an area with an average width of 1.35 m that extends 15.8 m parallel to the trench from the northern end of the trench to just north of the trench midpoint, and is associated with a crack 1 cm in height that formed during the seepage test on the trench wall. The central subsidence feature is a semicircular region on the waterside of the trench that subsided by as much as 6.2 cm over an area 3.4 m wide and 11.2 m long. The southern feature is an elongate
Metallic alloy stability studies
Firth, G. C.
1983-01-01
The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.
Betchov, R
2012-01-01
Stability of Parallel Flows provides information pertinent to hydrodynamical stability. This book explores the stability problems that occur in various fields, including electronics, mechanics, oceanography, administration, economics, as well as naval and aeronautical engineering. Organized into two parts encompassing 10 chapters, this book starts with an overview of the general equations of a two-dimensional incompressible flow. This text then explores the stability of a laminar boundary layer and presents the equation of the inviscid approximation. Other chapters present the general equation
Lund, Teija; Nydegger, Thomas; Rathonyi, Gabor; Nolte, Lutz-Peter; Schlenzka, Dietrich; Oxland, Thomas R
2003-10-01
We performed an in vitro study to investigate the stabilization (i.e. motion reduction) provided by the external spinal fixator (ESF), and to compare the three configurations of the ESF with two internal fixation techniques. Six human cadaveric lumbar spine specimens (L3-S1) were subjected to multidirectional flexibility testing in six configurations: (1) intact, (2) ESF in neutral, (3) ESF in distraction, (4) ESF in compression, (5) translaminar facet screw fixation, and (6) internal transpedicular fixation. Both the ESF and the internal fixation systems stabilized the specimens from L4 to S1. In each testing configuration, pure bending moments of flexion-extension, bilateral axial rotation, and bilateral lateral bending were applied to the uppermost vertebra stepwise to a maximum of 10 Nm. The rigid body motion between the vertebrae was measured using an optoelectronic camera system, and custom software was used to calculate the intervertebral rotations. For each applied motion in all testing configurations, the total range of motion (ROM) of L4-S1 is reported. All three ESF configurations stabilized the spine significantly when compared to the intact specimen. The ESF in compression provided significantly more stabilization in flexion-extension than the two other ESF configurations, but no other significant differences were found between the three ESF modes. In flexion-extension the ESF stabilized the spine significantly when compared with the two internal fixation devices. Only in bilateral lateral bending was the ESF inferior to internal transpedicular fixation in providing stabilization. The results of the present study suggest that the ESF provides a high degree of stabilization for preoperative assessment of selected low back pain patients. Whether other non-mechanical factors affect the pain relief experienced by the patients remains unknown.
The role of stabilization centers in protein thermal stability
Magyar, Csaba [Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok krt 2, H-1117 Budapest (Hungary); Gromiha, M. Michael [Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036 (India); Sávoly, Zoltán [Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok krt 2, H-1117 Budapest (Hungary); Simon, István, E-mail: simon.istvan@ttk.mta.hu [Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok krt 2, H-1117 Budapest (Hungary)
2016-02-26
The definition of stabilization centers was introduced almost two decades ago. They are centers of noncovalent long range interaction clusters, believed to have a role in maintaining the three-dimensional structure of proteins by preventing their decay due to their cooperative long range interactions. Here, this hypothesis is investigated from the viewpoint of thermal stability for the first time, using a large protein thermodynamics database. The positions of amino acids belonging to stabilization centers are correlated with available experimental thermodynamic data on protein thermal stability. Our analysis suggests that stabilization centers, especially solvent exposed ones, do contribute to the thermal stabilization of proteins. - Highlights: • Stabilization centers contribute to thermal stabilization of protein structures. • Stabilization center content correlates with melting temperature of proteins. • Exposed stabilization center content correlates with stability even in hyperthermophiles. • Stability changing mutations are frequently found at stabilization centers.
Voss, Clifford I.; Simmons, Craig T.; Robinson, Neville I.
2010-01-01
This benchmark for three-dimensional (3D) numerical simulators of variable-density groundwater flow and solute or energy transport consists of matching simulation results with the semi-analytical solution for the transition from one steady-state convective mode to another in a porous box. Previous experimental and analytical studies of natural convective flow in an inclined porous layer have shown that there are a variety of convective modes possible depending on system parameters, geometry and inclination. In particular, there is a well-defined transition from the helicoidal mode consisting of downslope longitudinal rolls superimposed upon an upslope unicellular roll to a mode consisting of purely an upslope unicellular roll. Three-dimensional benchmarks for variable-density simulators are currently (2009) lacking and comparison of simulation results with this transition locus provides an unambiguous means to test the ability of such simulators to represent steady-state unstable 3D variable-density physics.
El-Hady, N. M.
1981-01-01
A computer program HADY-I for calculating the linear incompressible or compressible stability characteristics of the laminar boundary layer on swept and tapered wings is described. The eigenvalue problem and its adjoint arising from the linearized disturbance equations with the appropriate boundary conditions are solved numerically using a combination of Newton-Raphson interative scheme and a variable step size integrator based on the Runge-Kutta-Fehlburh fifth-order formulas. The integrator is used in conjunction with a modified Gram-Schmidt orthonormalization procedure. The computer program HADY-I calculates the growth rates of crossflow or streamwise Tollmien-Schlichting instabilities. It also calculates the group velocities of these disturbances. It is restricted to parallel stability calculations, where the boundary layer (meanflow) is assumed to be parallel. The meanflow solution is an input to the program.
K stability and stability of chiral ring
Collins, Tristan C; Yau, Shing-Tung
2016-01-01
We define a notion of stability for chiral ring of four dimensional N=1 theory by introducing test chiral rings and generalized a maximization. We conjecture that a chiral ring is the chiral ring of a superconformal field theory if and only if it is stable. We then study N=1 field theory derived from D3 branes probing a three-fold singularity X, and show that the K stability which implies the existence of Ricci-flat conic metric on X is equivalent to the stability of chiral ring of the corresponding field theory.
Udphuay, Suwimon; Günther, Thomas; Everett, Mark E.; Warden, Robert R.; Briaud, Jean-Louis
2011-04-01
Pointe du Hoc overlooking the English Channel in Normandy, France was host to one of the most important military engagements of World War II but is vulnerable to cliff collapses that threaten important German fortifications including the forward observation post (OP) and Rudder's command post. The objective of this study is to apply advanced 3-D resistivity tomography towards a detailed site stability assessment with special attention to the two at-risk buildings. 3-D resistivity tomography data sets at Pointe du Hoc in the presence of extreme topography and dense cultural clutter have been successfully acquired, inverted and interpreted. A cliff stability hazard assessment scheme has been designed in which regions of high resistivity are interpreted as zones of open, dry fractures with a moderate mass movement potential. Regions of low resistivity are zones of wet, clay-filled fractures with a high mass movement potential. The OP tomography results indicate that the highest mass movement hazard appears to be associated with the marine caverns at the base of the cliff that are positioned at the point of strongest wave attack. These caverns likely occupy the future site of development of a sea arch that will threaten the OP building. The mass movement potential at the Rudder's command post area is low to moderate. The greatest risk there is associated with soil wedge failures at the top of the cliffs.
Vargas, M.; Schumaker, W.; He, Z.-H.; Zhao, Z.; Behm, K.; Chvykov, V.; Hou, B.; Krushelnick, K.; Maksimchuk, A.; Yanovsky, V.; Thomas, A. G. R., E-mail: agrt@umich.edu [Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States)
2014-04-28
High intensity, short pulse lasers can be used to accelerate electrons to ultra-relativistic energies via laser wakefield acceleration (LWFA) [T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979)]. Recently, it was shown that separating the injection and acceleration processes into two distinct stages could prove beneficial in obtaining stable, high energy electron beams [Gonsalves et al., Nat. Phys. 7, 862 (2011); Liu et al., Phys. Rev. Lett. 107, 035001 (2011); Pollock et al., Phys. Rev. Lett. 107, 045001 (2011)]. Here, we use a stereolithography based 3D printer to produce two-stage gas targets for LWFA experiments on the HERCULES laser system at the University of Michigan. We demonstrate substantial improvements to the divergence, pointing stability, and energy spread of a laser wakefield accelerated electron beam compared with a single-stage gas cell or gas jet target.
Hudaya, Chairul; Halim, Martin; Pröll, Johannes; Besser, Heino; Choi, Wonchang; Pfleging, Wilhelm; Seifert, Hans Jürgen; Lee, Joong Kee
2015-12-01
The interfacial instabilities, including side reactions due to electrolyte decompositions and Cobalt (Co) dissolutions, are the main detrimental processes at LiCoO2 cathode when a high-voltage window (>4.2 V) is applied. Nevertheless, cycling the cathode with a voltage above 4.2 V would deliver an increased gravimetric capacity, which is desired for high power battery operation. To address these drawbacks, we demonstrate a synergistic approach by manufacturing the three-dimensional high-temperature LiCoO2 electrodes (3D HT-LCO) using laser-microstructuring, laser-annealing and subsequent coating with polymerized C60 thin films (C60@3D HT-LCO) by plasma-assisted thermal evaporation. The C60@3D HT-LCO cathode delivers higher initial discharge capacity compared to its theoretical value, i.e. 175 mA h g-1 at 0.1 C with cut-off voltage of 3.0-4.5 V. This cathode combines the advantages of the 3D electrode architecture and an advanced C60 coating/passivation concept leading to an improved electrochemical performance, due to an increased active surface area, a decreased charge transfer resistance, a prevented Co dissolution into the electrolyte and a suppressed side reaction and electrolyte decomposition. This work provides a novel solution for other cathode materials having similar concerns in high potential regimes for application in lithium-ion microbatteries.
Goto, T.; Wakita, T. (Kyoto Institute of Technology, Kyoto (Japan). Faculty of Engineering and Design); Hosotani, T. (Unitika Research Laboratories Inc., Osaka (Japan))
1991-07-10
This report describes the effect of low temperature plasma treatment, which has been developed for fabric processing, on wool fabrics. In the experiment, wool fabrics were treated by low temperature plasma using O{sub 2}, Ar, CH{sub 4}, CHF{sub 3}, and CF{sub 4}. Low temperature plasma treatment did not influence moisture regain of wool fabrics, but influenced hygral expansion. There was no difference in the area of low humidity, however, dimensional change was restricted by half in the area of high humidity. Low temperature plasma treatment also improved felt shrinkage caused by home laundering. Moreover, it was found that friction coefficient of wool fabrics increased remarkably after low temperature plasma treatment. Therefore, the subsequent reactive silicone elastmer softening agent was used for finishing process after low temperature plasma treatment. As a result, wool fabrics hardened by low temperature plasma treatment regained their soft condition and washing resistant shrinkage percentage was also improved. Thus this treatment was proved to be used practically. 15 refs., 6 figs., 5 tabs.
Bulat, A.F.; Chekhov, V.N. [S.P. Timoshenko Inst. of Mechanics, Kiev (Ukraine)
1995-02-01
As the depth of mining operations increases, control over the stress-stain state (SSS) of the rock mass to ensure safe and effective exploitation of coal deposits is becoming a basic underground procedural process. An arbitrary change in the SSS of the mass under conditions where it is acted upon by large compressive loads may lead, in turn, however, to local buckling and fracture of the free surface of the rock in the near-face zone of a cleaned working during the mining of mineral resources. Individual classes of rock-stability problems that arise in the three-diumensional statement are formulated in this paper on the basis of analysis of actual conditions and technology for the mining of mineral resources at great depths. The rock mass is treated as a inhomogeneous semi-restrained medium of laminar structure; these studies were therefore conducted within the framework of the model of a piecewise-homogeneous medium on the basis of approaches developed previously. 8 refs., 2 figs., 2 tabs.
Increasing entropy for colloidal stabilization
Mo, Songping; Shao, Xuefeng; Chen, Ying; Cheng, Zhengdong
2016-11-01
Stability is of paramount importance in colloidal applications. Attraction between colloidal particles is believed to lead to particle aggregation and phase separation; hence, stability improvement can be achieved through either increasing repulsion or reducing attraction by modifying the fluid medium or by using additives. Two traditional mechanisms for colloidal stability are electrostatic stabilization and steric stabilization. However, stability improvement by mixing attractive and unstable particles has rarely been considered. Here, we emphasize the function of mixing entropy in colloidal stabilization. Dispersion stability improvement is demonstrated by mixing suspensions of attractive nanosized titania spheres and platelets. A three-dimensional phase diagram is proposed to illustrate the collaborative effects of particle mixing and particle attraction on colloidal stability. This discovery provides a novel method for enhancing colloidal stability and opens a novel opportunity for engineering applications.
Mazilu, Traian; Dumitriu, Mădălina; Tudorache, Cristina
2011-07-01
The paper herein deals with the study of the dynamic behaviour generated by the instability of the vibration of a loaded mass, uniformly moving along an Euler-Bernoulli beam on a viscoelastic foundation, induced by the anomalous Doppler waves excited in the beam. This issue is relevant for the case of modern trains travelling along a track with soft soil when the trains speed exceeds the phase velocity of the waves induced in the track. The model corresponds to a railway vehicle reduced to a loaded wheel running along a (half) track. The beam takes account of the bending stiffness of the rail and the mass of the track, including the mass of the rail, semi-sleepers and half of the ballast layer, where the viscoelastic foundation represents the subgrade. The model includes the wheel/rail Hertzian contact and it allows the simulation of the possibility of contact loss. The nonlinear equations of motion are integrated using a numerical approach based on the Green's function method. When the vibration becomes unstable, the system evolution is a limit cycle characterised by a succession of shocks, due to the action of two opposite factors: the anomalous Doppler waves that pump energy at the interface between the moving mass and the beam, thus forcing the mass to take off, and the static load that push the mass downwards. The frequency of the shocks increases at higher velocity and the magnitude of the impact force decreases; the most dangerous velocity is the critical one, which represents the stability limit of the linear approximation of the motion equations. The transient behaviour that precedes the limit cycle appearance is being analysed. The Hertzian contact influences the time history of the limit cycle and the magnitude of the impact force and, therefore, it is essential to be included in the model. To the authors' knowledge, this problem has never been dealt with.
钟卫; 杨涛; 孔纪名
2011-01-01
通过工程地质学中的赤平投影原理对各个结构面产状进行统计分析,找出优势结构面组合,再对非确定位置的结构面按一定间距进行搜索,利用运动学分析方法对各个块体进行分析,确定出可能从坡体上滑出的块体.结合三维刚体极限平衡法,计算出各个可能块体组合在不同工况下的稳定系数,找出最危险滑块,进而对边坡进行稳定性评价,通过具体的工程实例进行了验证.结果表明,将工程地质学方法、运动学分析方法与刚体极限平衡法结合起来分析复杂岩质边坡可以提高边坡稳定性评价的准确性,对工程具有很好的指导意义.%Preferred structural plane combinations are determined by using stereographic projection principle in the engineering geology to statistically analyze the strike-dip of structural surfaces.And to the uncertain position surfaces, they are searched by a certain distance.Then.the kinematic analysis of every combination block is done by kinematic analysis method; and the blocks that can slide out from slope body are finally gained Combined with three-dimensional rigid limit equilibrium method the stability factor of each block in different cases is cakulated; and the most dangerous slip body is found.Furthermore, the stability evaluation is done.This method is verified by case study.The results show that this method of analyzing complex rock slope combined engineering geology with kinematic analysis and rigid limit equilibrium method can improve the accuracy of slope stability assessment.The results provide a good guidance for slope design and stability analysis.
Kalantari, Mohammad Hasan; Malekzadeh, Afsaneh; Emami, Ameneh
2014-01-01
Statement of the Problem: Impression materials are concerned as a significant source of cross-contamination because of exposure to blood and saliva. Purpose: Considering the importance of infection control in the dental environments, this study is performed to investigate the dimensional changes of two condensation silicone impression materials, Speedex and Irasil, after immersion in 0.5% sodium hypochlorite. Materials and Method: In this in-vitro study, two condensation silicone impression materials, Speedex and Irasil, were used on a prefabricated metal model having two dies, one with and the other without undercut. Each impression material was used to prepare 30 impressions; half of each group was immersed in 0.5% sodium hypochlorite for 20 min. The casts were prepared and a profile projector was used to measure the casts in terms of height and diameter of the die without undercut, distance between the two dies, die diameter below the undercut, and the height of the die above the undercut. The results were statistically analyzed using Student t-test. Results: In Speedex group, an increase was detected in the height of die without undercut and the height of the die above the undercut, but other dimensions have decreased. No significant change was observed in dimensions of Speedex group except for the distance between the two dies and die height above the undercut. In Irasil group, the height of the die without undercut, the distance between the two dies and the height of the die above the undercut have increased; while decrease was observed in other dimensions. Compared with the original sample, no significant difference was observed in dimensions except for the height of the die above the undercut. Conclusion: These changes for Speedex group include changes in distance between the two dies and the height above the undercut which can impede proper placement of prosthesis, particularly fixed partial dentures in which the accuracy of the distance between the two
Kennouche, David O.
This thesis focuses on Solid Oxide Fuel Cells (SOFCs). The 21st century will see major changes in the way energy is produced, stored, and used around the world. SOFCs, which provide an efficient, scalable, and low-pollution alternative method for electricity generation, are expected to play an important role. SOFCs can also be operated in electrolysis mode for energy storage, important since health and economic reasons are causing a shift towards intermittent renewable energy resources. However, multiple limitations mainly linked to cost and durability have prevented the expansion of this technology to mass markets. This work focuses on the Nickel - Yttria Stabilized Zirconia (Ni-YSZ) anode that is widely used in SOFCs. Coarsening of Ni in the Ni-YSZ anode has been widely cited as a primary cause of long-term SOFC degradation. While there have been numerous studies of Ni coarsening reported, these have typically only tracked the evolution of Ni particle size, not the entire microstructure, and have typically not been correlated directly with electrochemical performance. In this thesis, the advanced tomography techniques Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) tomography and Trans- mission X-ray Microscopy (TXM) have been utilized to enable insight into the evolution of Ni-YSZ structure and how it relates to performance degradation. Extensive anode aging studies were done for relatively short times using temperatures higher than in normal SOFC operation in order to accelerate microstructural evolution. In addition the microstructure changes were correlated with changes in anode polarization resistance. While most of the measurements were done by comparing different anodes aged under different conditions, the first example of a "pseudo in situ" measurement where the same anode was 3D imaged repeatedly with intervening aging steps, was also demonstrated. A microstructural evolution model that focuses on the active three-phase boundary density was
Effect of Post-Heat Treatment on Dimensional Stability of Compressed Wood%后期热处理对压缩木尺寸稳定性的影响
陈太安; 蒋明; 王昌命; 高力勇
2011-01-01
The timber of Pinus armandii and Alnus cremastogyne was experimented to evaluate the dimensional stability by taking thickness swelling ( TS) as the major evaluation index after the compressed wood was individually treated under 170℃ and 210℃ for 2 h with the heated air or conductive oil heat transfer media. The results showed that both of the moisture-uptake and water-uptake of the compressed wood could be reduced by post heat-treating, so the dimensional stability of the compressed wood was improved. The conductive oil treatment had better effect than that of the hot air, while the treatment effect under 210℃ was better than that of under 170℃. The best technological condition was conductive oil treatment under 210℃, which could reduce moisture uptake TS index by 50% while reduce TS value after 24 h water uptake by 85%. The results also showed that the effect of heat treatment varied with tree species, The heat treatment effect on Pinus armandii wood was better than that of on Alnus cremastogyne wood.%以华山松和西南桤木为研究试材,以热空气和导热油为加热介质,在温度为170℃和210℃时分别对2种压缩木进行2 h的热处理,以厚度膨胀率为主要指标评价其尺寸稳定性.结果表明:后期热处理可以降低压缩木吸湿率和吸水率,改善压缩木的尺寸稳定性,油浴处理的效果优于热空气处理,210℃处理效果优于170℃；在所有工艺条件中,以210℃油浴处理效果最佳,可使吸湿厚度膨胀率下降50％左右,使24h吸水厚度膨胀率减小85％左右；热处理对树种具有一定的选择性,对西南桤木的效果略优于华山松.
Andrew Agbontalor Erakhrumen
2009-11-01
Full Text Available Bamboo culm is a hygroscopic lignocellulosic material. Hygroscopic properties may be disadvantageous in bamboo material if applied in certain applications and modes where and when extreme moisture variations are likely to occur. This study was aimed at evaluating the moisture absorption and resistance including dimensional stability properties of neem seed oil-treated split bamboo samples using two methods of treatment. Split bamboo samples from the same source were oven-dried at 103±2oC, conditioned to 11.76% mean moisture content, and treated by completely soaking them in oil at room temperature for 24 hours and by soaking in hot oil at 60oC for 4 hours, with untreated samples as control. Results showed that samples soaked in hot oil at 60oC for 4 hours had both the least percentage water absorption and higher anti-swell efficiency, followed by samples soaked in oil at room temperature for 24 hours. Shrinkage in the longitudinal, radial, and tangential directions also followed the same trend. Conclusions and recommendations were made in line with the outcome of the study.
蔡家斌; 丁涛; 杨留; 杨旭
2012-01-01
为改善杨木质软、强度低的特点,同时提高其尺寸稳定性,首先对杨木试样进行压缩处理,再进行热处理,并检测压缩杨木和热处理压缩杨木的吸湿、吸水膨胀率.结果表明:压缩率愈大,压缩杨木试样厚度方向和体积膨胀率愈大；经热处理后,试样的尺寸稳定性明显提高.%Poplar samples were hot pressed for 15 ～ 35 min with different compression temperatures from 130～170 ℃ and then heat treated from 180 ～ 200 ℃ for 1. 5 ～ 3. 5 hours. The results showed that adsorption and water absorption expansion rates of the densified samples increased when the compression temperatures increased. The heat treatment could improve the dimensional stability of densified poplar wood.
Rapport med bidrag fra symposiet Nye Dimensioner 24.-26. nov. 2011 samt nye selvstændige bidrag......Rapport med bidrag fra symposiet Nye Dimensioner 24.-26. nov. 2011 samt nye selvstændige bidrag...
Three-Dimensional Icosahedral Phase Field Quasicrystal
Subramanian, P.; Archer, A. J.; Knobloch, E.; Rucklidge, A. M.
2016-08-01
We investigate the formation and stability of icosahedral quasicrystalline structures using a dynamic phase field crystal model. Nonlinear interactions between density waves at two length scales stabilize three-dimensional quasicrystals. We determine the phase diagram and parameter values required for the quasicrystal to be the global minimum free energy state. We demonstrate that traits that promote the formation of two-dimensional quasicrystals are extant in three dimensions, and highlight the characteristics required for three-dimensional soft matter quasicrystal formation.
Stability of Rocket Flight during Burning
T. N. Srivastava
1967-10-01
Full Text Available Stability of the rocket motion during burning is discussed taking into consideration gravity, aerodynamic forces and torques. Conditions for stabilizing the rocket motion are investigated. Analysis for initial and final phases of burning is given separately. Stability regions of the projected motions on two dimensional co-ordinate planes are obtained and thereby stability region of the actual motion is derived. Stability diagrams illustrate statically and dynamically stable and unstable regions.
Dimensional Stabilization of Wood in Use.
1981-01-01
wall hydroxyl groups (which are brief description of each type will be in a volatile solvent forms an internal available in all three major cell wall...little recent attention is Parly research was done with com- wood. replacing cell wall water with waxes. mon beeswax and it would be in- Chemicals
彭成山; 于丽红; 范冰
2015-01-01
Because the gravity arch dam is gravity based which puts great stress on the beams ,so stability issue becomes the main problem of these dams .In order to verify the safety and feasibility of the gravity arch dam design of a reservoir , the finite element software ADINA was adopted to carry out a three dimensional stability analysis for the dam .The defor-mation of the dam under different stress at the normal storage level ,the design flood level and check flood level were cal-culated through the simulation .The results indicate that the distribution of stress and strain of the dam body are in line with the actual situation and the values are within the allowed range .This study will not only provide an important techni-cal support for practical engineering design and construction ,but also an effective reference for the similar engineering constructions .%由于重力拱坝主要依靠梁的作用即以重力作用为主，所以稳定问题显得更重要。为了验证某水库重力拱坝坝体设计的安全性与可行性，采用有限元计算软件 ADINA 对该重力拱坝进行了三维稳定分析，模拟计算出了正常蓄水位、设计洪水位、校核洪水位下的坝体应力变形情况。从计算结果可以看出，该坝坝体的应力应变分布规律均符合实际情况且应力值都在允许的范围内。不仅为实际工程的设计和修建提供了重要的技术依据，同时也为同类工程建设提供了有效的参考。
徐康; 吕建雄; 李贤军; 吴义强
2015-01-01
The poplar wood and phenol formaldehyde ( PF) impregnated wood were subjected to heat treatment at 160, 180, 200 and 220 ℃ for 1 to 4 hrs. Hydroscopicity, hygroscopicity, linear ( radial and tangential) and volume swelling, and surface wettability of the control and PF impregnated wood after heat treatment were measured. The results showed that the dimensional stability can be improved considerably after heat treatment. The water absorption of PF impregnated wood was reduced by 17. 37%compared with that of control group after soaking in water for eight days, and the maximum decline could reach up to 63. 8% and 74. 7% for heat-treated wood and PF impregnated heat-treated wood, respectively. The swelling ratio of PF impregnated wood was reduced by 14. 71%, 36. 93%, and 30. 19% for radial, tangential, and volume, respectively, as compared to that of untreated wood, whereas the maximum reduction could reach up to 64. 99%, 74. 94%, and 72. 33% for heat-treated wood and 94. 4%, 90. 61%, and 91. 37% for PF impregnated heat-treated wood. The adsorption moisture content decreased by 11. 14% for PF impregnated wood compared with that of control group, while 55. 57% and 60. 62% reduction was observed for heat-treated wood and PF impregnated heat-treated wood, respectively. The contact angle of PF impregnated was close to that of control group, while the maximum increase could reach up to 143. 7% and 139. 4% for heat-treated wood and PF impregnated heat-treated wood, respectively, indicating that the surface wettability of heat-treated wood and PF impregnated heat-treated wood were decreased significantly. After heat treatment, significant changes can be found in infrared spectrogram. The improved dimensional stability of PF impregnated heat-treated wood was attributed to the reduction of hydroxyl, carboxyl and carbonyl which was mainly caused by the degradation of hemicellulose and the formation of chemical bonds between PF resin components and the cell wall polymers. PF
Stability of boundary measures
Chazal, Frédéric; Mérigot, Quentin
2007-01-01
We introduce the boundary measure at scale r of a compact subset of the n-dimensional Euclidean space. We show how it can be computed for point clouds and suggest these measures can be used for feature detection. The main contribution of this work is the proof a quantitative stability theorem for boundary measures using tools of convex analysis and geometric measure theory. As a corollary we obtain a stability result for Federer's curvature measures of a compact, allowing to compute them from point-cloud approximations of the compact.
Dimensional reduction of nonlinear time delay systems
M. S. Fofana
2005-01-01
infinite-dimensional problem without the assumption of small time delay. This dimensional reduction is illustrated in this paper with the delay versions of the Duffing and van der Pol equations. For both nonlinear delay equations, transcendental characteristic equations of linearized stability are examined through Hopf bifurcation. The infinite-dimensional nonlinear solutions of the delay equations are decomposed into stable and centre subspaces, whose respective dimensions are determined by the linearized stability of the transcendental equations. Linear semigroups, infinitesimal generators, and their adjoint forms with bilinear pairings are the additional candidates for the infinite-dimensional reduction.
Nesterenko, Mikhail
2009-01-01
We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.
丁涛; 顾炼百; 蔡家斌
2015-01-01
Heat treatment of Pinus sylvestris and Quercus mongolica boards were carried out in atmospheric stream or 0�45 MPa pressurized steam. Hygroscopicity and dimensional stability of the treated wood were compared with the con⁃trol. The results showed that heat treatments not only lowered the equilibrium moisture contents ( EMC) of the wood, but also altered the pattern of its moisture adsorption in high humidity environment. When the environmental relative humidity increased from 69% to 94%, the EMC change rates of the heat treated samples were just one third of those of the control samples. This might be attributed to the reconstruction of wood cell wall during the heat treatments. Dimen⁃sional stability of heat treated samples was significantly improved as a result. The radial and tangential swelling of pres⁃surized⁃steam treated Pinus sylvestris samples decreased by 34% and 47% compared to those of the control ones. For Quercus mongolica samples, the corresponding values were 46% and 51%. Most tangential anti⁃swelling efficiency ( ASE) values of the heat treated samples were higher than their radial ASE values. That means swelling difference be⁃tween radial direction and tangential direction was also reduced after heat treatments. It was also showed that pressurized steam induces more pronounced property modification than atmospheric steam.%分别在常压蒸汽与0．45 MPa加压蒸汽条件下，对樟子松和柞木进行热处理，比较了热处理材和未处理材的水分吸湿性及尺寸稳定性差异。结果表明：两种试材经过热处理后不仅吸湿量明显降低，在高湿条件下的吸湿特性也发生了显著变化，当环境相对湿度从69％增至94％时，热处理材的平衡含水率变化率仅为对照材的1／3，细胞壁微观构造在高温条件下的变化可能是造成这一现象的主要原因；吸湿性的降低使热处理材的尺寸稳定性获得了大幅度提高，樟子松试材加压蒸汽
Giedt, J
2002-01-01
The matter sector of four-dimensional effective supergravity models obtained from the weakly coupled heterotic string contains many moduli. In particular, flat directions of the D-term part of the scalar potential in the presence of an anomalous U(1) give rise to massless chiral multiplets which have been referred to elsewhere as D-moduli. The stabilization of these moduli is necessary for the determination of the large vacuum expectation values of complex scalar fields induced by the corresponding Fayet-Illiopoulos term. This stabilization is of phenomenological importance since these background values determine the effective theory below the scale of the anomalous U(1) symmetry breaking. In some simple models we illustrate the stabilization of these moduli due to the nonperturbative dynamics associated with gaugino condensation in a hidden sector. We find that background field configurations which are stable above the condensation scale no longer represent global minima once dynamical supersymmetry breaking...
Smith, J D H; Zhang, C
2015-08-01
The recently developed macroscopic approach to demography describes the age distribution of mothers and the net maternity function for a given human population entirely in terms of five parameters. Tracking of these parameters provides a number of new tools for analyzing populations and predicting their future states. Within the macroscopic approach, the new concept of generalized Lotka stability is presented in this paper, as an extension of a strong version of classic Lotka stability. The two leading parameters of the macroscopic approach, the Malthusian parameter r and the perturbation s, are computed from population data and plotted in two-dimensional parameter space. Generalized Lotka stability is then defined in terms of the movement of the (r,s)-vector over time. It may be observed in a number of human populations at specific periods of their history.
罗子源; 许晶晶; 唐亮
2014-01-01
,and also no sta-tistical difference(P >0.05)in volumetric change rates between ExpressXT Penta H silicone and Imp-regum Penta polyether samples either.Statistical differences of volumetric change rates were found be-tween alginate materials and elastomers.Conclusion:Dimensional stability of elastomeric materials was better than that of alginate materials.The space-labeling method is a feasible and direct measurement for dimensional staability of impression materials.
Stability of laminated composites
Guz`, A.N.; Chekhov, V.N. [Inst. of Mechanics of the Academy of Sciences of the Ukrainian, Kiev (Ukraine)
1992-02-01
The characteristic special feature of deformation behavior of modern laminated composite materials and structural elements fabricated from these materials, at current levels of loading and operating conditions is the occurrence of the purely three-dimensional stress-deformed state. In this process some specific mechanical phenomena and effects may occur, which is impossible to describe within the framework of applied or approximate approaches existing currently in deformable solid body mechanics. The structure of massive laminated materials may be included in this class of phenomena when the critical parameters of the problem depend only on the ratio between mechanical and geometrical characteristics of single layers and are independent of the dimensions and the form of the total laminated body as a whole. Since this phenomenon may be the beginning of the process of fracture of these materials, and the loss of the load-carrying capacity of structure elements fabricated from them, we consider below, in three-dimensional formulation, the problem of the surface and internal instability in laminated composite materials under compressive surface loads. The classification of the existing types of stability problems is presented for laminated materials and approaches for their solution presented in the literature. On the basis of three-dimensional linearized stability theory, within the framework of the piecewise-homogeneous media model, the general formulation of the most characteristic classes of stability problems of laminated materials is given in Langrangian coordinates at small and finite, homogeneous and inhomogeneous precritical deformation. Analytic and variational methods of investigation of formulated problems are given with application to various models of laminated bodies models, in accordance with accepted stability criteria. The accuracy of these models is evaluated, based on th example of the solution of certain model problems.
Burns, Daniel; Wang, Zuoqin
2008-01-01
In this article we discuss the role of stability functions in geometric invariant theory and apply stability function techniques to problems in toric geometry. In particular we show how one can use these techniques to recover results of Burns-Guillemin-Uribe and Shiffman-Tate-Zelditch on asymptotic properties of sections of holomorphic line bundles over toric varieties.
Vibrational stability of graphene
Yangfan Hu
2013-05-01
Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.
Homological stability of diffeomorphism groups
Berglund, Alexander; Madsen, Ib Henning
2013-01-01
In this paper we prove a stability theorem for block diffeomorphisms of 2d -dimensional manifolds that are connected sums of S d ×S d . Combining this with a recent theorem of S. Galatius and O. Randal-Williams and Morlet’s lemma of disjunction, we determine the homology of the classifying space ...
NONLINEAR STABILITY FOR EADY'S MODEL
LIU Yong-ming; QIU Ling-cun
2005-01-01
Poincaré type integral inequality plays an important role in the study of nonlinear stability ( in the sense of Arnold's second theorem) for three-dimensional quasigeostophic flow. The nonlinear stability of Eady's model is one of the most important cases in the application of the method. But the best nonlinear stability criterion obtained so far and the linear stability criterion are not coincident. The two criteria coincide only when the period of the channel is infinite.additional conservation law of momentum and by rigorous estimate of integral inequality. So the new nonlinear stability criterion was obtained, which shows that for Eady 's model in the periodic channel, the linear stable implies the nonlinear stable.
无
2011-01-01
"Stable"will be a key word for China’s economy in 2012.That’s the beat set at the annual Central Economic Work Conference held in Beijing on December 12-14,which reviewed this year’s development and mapped out plans for the next year.Policymakers at the conference decided to keep macroeconomic policies stable,seek a stable and relatively fast economic growth,stabilize consumer prices and maintain social stability in 2012.On the basis of stability,the government will transform the development model,deepen reform and improve people’s livelihood.
Radion cosmology and stabilization
Chakraborty, Sumanta [IUCAA, Ganeshkhind, Pune University Campus, Post Bag 4, Pune (India); SenGupta, Soumitra [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)
2014-09-15
We solve the Einstein equation in five-dimensional space-time for Randall-Sundrum Brane world model with time dependent radion field to study the variation of brane scale factor with time. We have shown that as the radion field decreases with time compactifying the extra dimension, the scale factor increases exponentially with time leading to an inflationary scenario. We have also proposed a time dependent generalization of the Goldberger-Wise moduli stabilization mechanism to explain the time evolution of the radion field to reach a stable value, after which the scale factor on the brane exits from inflationary expansion. (orig.)
Panchapakesan, N.; Lohiya, D.
1985-04-01
The stability of the de Sitter metric and the relevance of the initial state of a domain which approaches a de Sitter universe asymptotically are investigated analytically, adapting the one-dimensional wave equation with effective potential derived by Khanal and Panchapakesan (1981), for the perturbations of the de Sitter-Schwarzschild metric, to the de Sitter case. It is demonstrated that initial nonspherical perturbations do not increase exponentially with time but rather decay, the frozen modes exponentially and the backscattered perturbations of finite angular momentum l as t to the -(2l - l). It is concluded that the cosmic horizon is stable and has no hair. 14 references.
MHD equilibrium and stability in heliotron plasmas
Ichiguchi, Katsuji [National Inst. for Fusion Science, Toki, Gifu (Japan)
1999-09-01
Recent topics in the theoretical magnetohydrodynamic (MHD) analysis in the heliotron configuration are overviewed. Particularly, properties of three-dimensional equilibria, stability boundary of the interchange mode, effects of the net toroidal current including the bootstrap current and the ballooning mode stability are focused. (author)
Carlsen, Bent Erik; Jensen, Bjarne Chr.; Olesen, Frits Bolonius;
Indholdet af nærværende rapport, er identisk med den indstilling, som pr. 1. september 1977 er afgivet til Dansk Ingeniør-forening, Normstyrelsen, af det i forsommeren 1976 nedsatte udvalg vedrørende brandteknisk dimensionering. Indstillingen, hvis primære formål har været at give Normstyrelsen et...... grundlag for at vurdere, om - og i givet fald hvordan - brandteknisk dimensionering af bærende konstruktioner vil kunne indføres i DIF's konstruktionsnormer, indeholder et skitseforslag til, efter hvilke principper dette vil kunne gøres. Men derudover har udvalget i fire dataoplæg (rapportens bilag 1...
Hahonou, Eric Komlavi
international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...
Classifying spaces with virtually cyclic stabilizers for linear groups
Degrijse, Dieter Dries; Köhl, Ralf; Petrosyan, Nansen
2015-01-01
We show that every discrete subgroup of GL(n, ℝ) admits a finite-dimensional classifying space with virtually cyclic stabilizers. Applying our methods to SL(3, ℤ), we obtain a four-dimensional classifying space with virtually cyclic stabilizers and a decomposition of the algebraic K-theory of its...
Classifying spaces with virtually cyclic stabilizers for linear groups
Degrijse, Dieter Dries; Köhl, Ralf; Petrosyan, Nansen
2015-01-01
We show that every discrete subgroup of GL(n, ℝ) admits a finite-dimensional classifying space with virtually cyclic stabilizers. Applying our methods to SL(3, ℤ), we obtain a four-dimensional classifying space with virtually cyclic stabilizers and a decomposition of the algebraic K-theory of its...
陈泽君; 王勇; 马芳; 范友华; 邓腊云
2012-01-01
The research that temperature and time of heat treatment affected the performance of dimensional stability and mechanical properties on heat-treated plantation poplar wood was conducted by taking steam as medium, and with high temperature treatments. The results show that the dimensional stability and mechanical properties of heat-treated wood were easily susceptible to temperature and time. After considering comprehensively, the optimal parameters of hot-treated wood are as followings: temperature 180 "C , hot-processing time 3.5 hours.%以蒸汽为介质,采用高温热处理法对杨木木材进行热处理,研究了处理温度和处理时间对杨木木材的物理力学性能和尺寸稳定性的影响.结果表明:处理温度和处理时间对木材物理力学性能和尺寸稳定性均有较大影响.综合考虑处理温度和处理时间对木材物理力学性能和尺寸稳定性的影响及成本等因素,较佳的热处理工艺参数为:温度180℃,时间3.5 h.
J.L.LIONS
1999-01-01
A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.
Stabilizing Moduli with String Cosmology
Watson, S
2005-01-01
In this talk I will discuss the role of finite temperature quantum corrections in string cosmology and show that they can lead to a stabilization mechanism for the volume moduli. I will show that from the higher dimensional perspective this results from the effect of states of enhanced symmetry on the one-loop free energy. These states lead not only to stabilization, but also suggest an alternative model for cold dark matter. At late times, when the low energy effective field theory gives the appropriate description of the dynamics, the moduli will begin to slow-roll and stabilization will generically fail. However, stabilization can be recovered by considering cosmological particle production near the points of enhanced symmetry leading to the process known as moduli trapping.
THREE-DIMENSIONAL SLOPE STABILITY ANALYSIS BASED ON NONLINEAR FAILURE ENVELOPE%基于非线性破坏包络线的三维边坡稳定性分析
蒋景彩; 山上拓男; Baker R
2003-01-01
The effects of nonlinearity of strength envelopes on 3D slope stability analysis are investigated. A power relation for the nonlinear envelope is employed to derive the 3D factor of safety equations of an extended Spencer method which satisfies both force equilibrium and moment equilibrium. Then,a search procedure is presented based on dynamic programming to determine the 3D critical slip surface for a general slope. Linear and nonlinear strength envelopes used for slope stability computations are obtained by fitting curves to the 103 strength data of consolidated-undrained (CU) triaxial compression tests for compacted Israeli clay. Results of a typical 3D problem show that a linear approximation of the nonlinear strength envelope may lead to a significant overestimation of calculated safety factors.
Jespersen, Jesper
2004-01-01
It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...
Green, Daniel; /SLAC /Stanford U., Phys. Dept.; Lawrence, Albion; /Brandeis U.; McGreevy, John; /MIT, LNS; Morrison, David R.; /Duke U., CGTP /UC, Santa Barbara; Silverstein,; /SLAC /Stanford U., Phys. Dept.
2007-05-18
We show that string theory on a compact negatively curved manifold, preserving a U(1)b1 winding symmetry, grows at least b1 new effective dimensions as the space shrinks. The winding currents yield a ''D-dual'' description of a Riemann surface of genus h in terms of its 2h dimensional Jacobian torus, perturbed by a closed string tachyon arising as a potential energy term in the worldsheet sigma model. D-branes on such negatively curved manifolds also reveal this structure, with a classical moduli space consisting of a b{sub 1}-torus. In particular, we present an AdS/CFT system which offers a non-perturbative formulation of such supercritical backgrounds. Finally, we discuss generalizations of this new string duality.
王毅; 宋卫东; 郭庆伟; 李超旺; 张晓强
2015-01-01
在研究固定鸭舵式二维弹道修正弹受力的基础上，建立描述弹丸运动状态的7自由度刚体弹道模型。采用小扰动法将所建立的刚体弹道模型线性化，建立弹丸的扰动运动方程组，并给出李雅普诺夫意义下的稳定性判据。固定鸭舵式二维弹道修正迫弹的飞行试验表明，所建立的7自由度刚体弹道模型可精确描述弹丸的运动状态。在针对迫弹的研究中发现，弹丸扰动运动方程组的动力学系数具有对应相等的关系，进而将扰动运动方程组简化，得到低速滚转迫弹的稳定性判据，并验证判据正确性。%The force of the trajectory correction projectile with fixed canards changes great because of the dual-spin structure,so the motion state changes.The purpose of this paper is to establish an accurate model for this type of projectiles,and to find out a method to analyze the stability.On the basis of studying the force on the projectile,7 degree of freedom rigid body trajectory model is established.Then the trajectory model is linearized,and the perturbation equations of projectile motion are obtainedand a stability criterion is given.The flight experiment shows that the model can describe the motion state accurately,and can judge the stability of this projectile.In the later study for the mortar shell,the equations are simplified,because the coefficients of the corresponding terms are equal to each other.The stability criterion of the mortar shell which spins at a low speed is obtained,and the data of the experiment prove the correctness of the criterion.
孟新珍; 刘晓明; 丁魁
2015-01-01
Objective:To explore the application of the Diener's life satisfaction scale in stability mili-tia groups.Methods:Randomly to choose 832 stability militia groups in Xinjiang by cluster sampling,and carry on exploratory factor analysis and confirmatory factor analysis of the data.Results:The formal scale contained five entries,a factor,61.309% of the total variance explained.Cronbach's a coefficient of the scale was 0.832,Split-half reliability was 0.737.Confirmatory factor display fitting effect of the first-order three factors model was ideal ( GFI =0.998, AGFI =0.976, NFI =0.998, CFI =0.999, IFI =0.999,RMSEA=0.053).Life satisfaction of the stability militia was different due to diversity of cultural, geographical origin,management methods.Conclusion:Diener's life satisfaction scale has good reliability and validity,can be used for life satisfaction measurement in stability militia groups;Life satisfaction in stability militia shows the characteristics of culture,geographical origin,management mode.%目的：探讨迪纳生活满意度量表在维稳民兵群体中的应用情况。方法：采用分层抽样方法，随机整群选取新疆维稳民兵832名，进行数据的探索性因素分析和验证性因素分析。结果：正式量表包含5个条目，一个因子，解释了总变异的61．309％。量表Cronbach，sa系数为0．832，折半信度为0．737。验证性因素显示一阶三因素模型（GFI＝0．998、AGFI＝0．976、NFI＝0．998、CFI＝0．999、IFI＝0．999、RMSEA＝0．053）拟合效果比较理想。维稳民兵生活满意度因文化、地域来源、管理方式而异。结论：迪纳生活满意度量表具有较好的信效度，可用于维稳民兵群体生活满意度的测量；维稳民兵生活满意度呈现出文化、地域来源、管理方式的特征。
Matlab Stability and Control Toolbox: Trim and Static Stability Module
Crespo, Luis G.; Kenny, Sean P.
2006-01-01
This paper presents the technical background of the Trim and Static module of the Matlab Stability and Control Toolbox. This module performs a low-fidelity stability and control assessment of an aircraft model for a set of flight critical conditions. This is attained by determining if the control authority available for trim is sufficient and if the static stability characteristics are adequate. These conditions can be selected from a prescribed set or can be specified to meet particular requirements. The prescribed set of conditions includes horizontal flight, take-off rotation, landing flare, steady roll, steady turn and pull-up/ push-over flight, for which several operating conditions can be specified. A mathematical model was developed allowing for six-dimensional trim, adjustable inertial properties, asymmetric vehicle layouts, arbitrary number of engines, multi-axial thrust vectoring, engine(s)-out conditions, crosswind and gyroscopic effects.
Hahonou, Eric Komlavi
international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...... rule constitute the only realistic path to defend their own interests. The report suggests that international support of Nigerien security forces could be counter-productive for the re-establishment of state authority and legitimacy in the long-term. Brutal repression and violation of human rights...
Wang, Xiujuan; Liu, Xiaojie; Wang, Gang; Zhou, Yixuan; Wang, Hui
2017-02-01
Metal sulfides have a highly promising potential as anode materials for next-generation lithium-ion batteries (LIBs) due to their environmental friendliness, abundant resources, and low-cost. Unfortunately, the implementation of such novel anodes is severely hindered by their low electronic conductivity and large volume expansion during the repetitive lithiation/delithiation process. Herein, we report a specifically designed anode structure to overcome these obstacles, that is, to incorporate MxSy (M = Ni, Zn, and Fe) with graphene nanosheets (GNS) and carbon nanotubes (CNTs) to form three-dimensional interconnected MxSy-graphene nanosheets-carbon nanotubes aerogels. Morphology and structure results confirm that MxSy particles were uniformly and closely attached on the 3D complex network structure of GNS-CNT. As a result, when used as anode materials for half and full LIBs, the MxSy-GNS-CNT aerogels exhibit remarkable high reversible capacities, ultra-long cycle life, and super high rate performance (For example, the NiS-GNS-CNT, ZnS-GNS-CNT, and FeS2-GNS-CNT aerogels could deliver high capacities of 735, 800, and 850 mAh g-1 after 100 cycles, respectively). Our results indicate that 3D interconnected MxSy-GNS-CNT aerogels are promising anode materials for the next generation LIBs with high-performance.
UPWIND DISCONTINUOUS GALERKIN METHODS FOR TWO DIMENSIONAL NEUTRON TRANSPORT EQUATIONS
袁光伟; 沈智军; 闫伟
2003-01-01
In this paper the upwind discontinuous Galerkin methods with triangle meshes for two dimensional neutron transport equations will be studied.The stability for both of the semi-discrete and full-discrete method will be proved.
田巍巍; 吴彬; 杜明亮; 王传宝
2013-01-01
The soil-rock composite slope stability of the joint intake of Kenswat hydro-junction engineering is simulated and analyzed here by using the strength reduction finite-difference method .The simulation results show that faint plastic displacement would occur in the superficial zone of the soil-rock composite slope’s feet and face owing to the shear stress and local tension stress.Under the slope,the rock slope of lower cretaceous Hutubi river group (k1h1)would be basical-ly in elastic deformation,and the upper gravel soil slope would form the most dangerous sliding face .From the prediction of evolution process,the unconsolidated layers of the Middle to Upper Pleistocene of Quaternary (Qal3 )and the glued layer of the Upper Pleistocene of Quaternary (Qal2-3)would cause the creep slip and be in the danger of collapse .The simula-tion results are of an important reference for the stability control of soil-rock composite slope .%运用有限差分强度折减法对肯斯瓦特水利枢纽工程联合进水口土-岩复合边坡的稳定性进行了模拟分析.模拟结果表明:联合进水口土-岩复合边坡在坡脚和坡面浅表层由于剪应力和局部的拉应力作用发生过微弱的塑性位移,下部白垩系下统呼图壁河组(k.h1)岩质边坡基本上处于弹性变形,上部卵砾石土质边坡形成最危险的滑移面；从演变过程预测,坡顶处第四系中～上更新统(Q2al-3)松散层和第四系上更新统(Q3al)胶结层会出现蠕动滑移和崩塌的危险.模拟结果将对土-岩复合边坡的稳定性控制具有重要的参考作用.
Effect of constant heat flux at outer cylinder on stability of viscous ...
DR OKE
dimensional linear stability analysis of the Couette flow between two axial cylinders for ... variable or constant heat flux at the inner cylinder while the outer cylinder is ... differential equations have been obtained to govern the stability of the ...
Stovel, Katherine; Golub, Benjamin; Milgrom, Eva M Meyersson
2011-12-27
A variety of social and economic arrangements exist to facilitate the exchange of goods, services, and information over gaps in social structure. Each of these arrangements bears some relationship to the idea of brokerage, but this brokerage is rarely like the pure and formal economic intermediation seen in some modern markets. Indeed, for reasons illuminated by existing sociological and economic models, brokerage is a fragile relationship. In this paper, we review the causes of instability in brokerage and identify three social mechanisms that can stabilize fragile brokerage relationships: social isolation, broker capture, and organizational grafting. Each of these mechanisms rests on the emergence or existence of supporting institutions. We suggest that organizational grafting may be the most stable and effective resolution to the tensions inherent in brokerage, but it is also the most institutionally demanding.
Sunarsih Sunarsih
2013-01-01
Full Text Available This paper presents a model for natural syst ems used in Wastewater Treatment Plant (WWTP Sewon Bantul. The model is m odeling development, derived from the physical and biochemical phenomena involved in the biological treatment process. The numerical solution of the resulting on 13 simultaneous systems of nonlinear equations by the Quasi_Newton. Data validation is measured by facultative pond at the inlet and outlet of the pond to the concentration of b acteria, algae, zooplankton, organic matter, detritus, organic nitrogen, NH3, organi c phosphor, dissolved phosphorus, Dissolved Oxygen (DO, total coliform, faecal coliform and Biochemical Oxygen Demand (BOD. A simulation model is presented to predict performance regime steady state of domestic wastewater treatment facultative stabilization pond. The high degree of significant of at least 10% indicates that the effluent parameters can be reasonably accurately predicted.
Alves, Maria Cechinel
2005-01-01
Full Text Available O propósito deste estudo foi verificar o comportamento de moldes de polissulfeto (Permlastic e poliéter (Impregum Soft obtidos por meio da técnica do casquete de resina acrílica. Avaliou-se a estabilidade dimensional dos moldes confeccionados de uma matriz metálica contendo dois preparos protéticos, com diâmetros e alturas diferentes. Os moldes de cada material foram vazados com gessos pedra IV (Vel-mix e gesso pedra V (Exadur, perfazendo um total de quatro combinações experimentais: (polissulfeto/gesso-pedra IV, polissulfeto/gesso-pedra V, poliéter/gesso-pedra IV e poliéter/gesso-pedra V. Os troquéis de gesso foram mensurados com um paquímetro digital, 24 horas após sua obtenção. Os resultados obtidos foram submetidos a ANOVA a 5%. Pode-se concluir que os moldes de poliéter vazados com gesso pedra tipo V apresentaram melhor estabilidade dimensional em relação às outras condições experimentais
Non-commutative multi-dimensional cosmology
Khosravi, N; Sepangi, H R
2006-01-01
A non-commutative multi-dimensional cosmological model is introduced and used to address the issues of compactification and stabilization of extra dimensions and the cosmological constant problem. We show that in such a scenario these problems find natural solutions in a universe described by an increasing time parameter.
Two-dimensional subwavelength plasmonic lattice solitons
Ye, F; Hu, B; Panoiu, N C
2010-01-01
We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai
6-dimensional brane world model
Kanti, Panagiota; Madden, Richard; Olive, Keith A.
2001-08-15
We consider a 6-dimensional spacetime which is periodic in one of the extra dimensions and compact in the other. The periodic direction is defined by two 4-brane boundaries. Both static and nonstatic exact solutions, in which the internal spacetime has a constant radius of curvature, are derived. In the case of static solutions, the brane tensions must be tuned as in the 5-dimensional Randall-Sundrum model; however, no additional fine-tuning is necessary between the brane tensions and the bulk cosmological constant. By further relaxing the sole fine-tuning of the model, we derive nonstatic solutions, describing de Sitter or anti--de Sitter 4-dimensional spacetimes, that allow for the fixing of the interbrane distance and the accommodation of pairs of positive--negative and positive--positive tension branes. Finally, we consider the stability of the radion field in these configurations by employing small, time-dependent perturbations around the background solutions. In analogy with results drawn in five dimensions, the solutions describing a de Sitter 4-dimensional spacetime turn out to be unstable while those describing an anti--de Sitter geometry are shown to be stable.
How good are one-dimensional Josephson junction models?
Lomdahl, P. S.; Olsen, O.H.; Eilbeck, J. C.
1985-01-01
A two-dimensional model of Josephson junctions of overlap type is presented and shown to reduce to the usual one-dimensional (1D) model in the limit of a very narrow junction. Comparisons between the stability limits for fluxon reflection obtained from the two models suggest that the many results...
Two-dimensional effects in nonlinear Kronig-Penney models
Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim
1997-01-01
An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...
Basin stability in delayed dynamics
Leng, Siyang; Lin, Wei; Kurths, Jürgen
2016-02-01
Basin stability (BS) is a universal concept for complex systems studies, which focuses on the volume of the basin of attraction instead of the traditional linearization-based approach. It has a lot of applications in real-world systems especially in dynamical systems with a phenomenon of multi-stability, which is even more ubiquitous in delayed dynamics such as the firing neurons, the climatological processes, and the power grids. Due to the infinite dimensional property of the space for the initial values, how to properly define the basin’s volume for delayed dynamics remains a fundamental problem. We propose here a technique which projects the infinite dimensional initial state space to a finite-dimensional Euclidean space by expanding the initial function along with different orthogonal or nonorthogonal basis. A generalized concept of basin’s volume in delayed dynamics and a highly practicable calculating algorithm with a cross-validation procedure are provided to numerically estimate the basin of attraction in delayed dynamics. We show potential applicabilities of this approach by applying it to study several representative systems of biological or/and physical significance, including the delayed Hopfield neuronal model with multistability and delayed complex networks with synchronization dynamics.
Spectral stability of unitary network models
Asch, Joachim; Bourget, Olivier; Joye, Alain
2015-08-01
We review various unitary network models used in quantum computing, spectral analysis or condensed matter physics and establish relationships between them. We show that symmetric one-dimensional quantum walks are universal, as are CMV matrices. We prove spectral stability and propagation properties for general asymptotically uniform models by means of unitary Mourre theory.
High dimensional neurocomputing growth, appraisal and applications
Tripathi, Bipin Kumar
2015-01-01
The book presents a coherent understanding of computational intelligence from the perspective of what is known as "intelligent computing" with high-dimensional parameters. It critically discusses the central issue of high-dimensional neurocomputing, such as quantitative representation of signals, extending the dimensionality of neuron, supervised and unsupervised learning and design of higher order neurons. The strong point of the book is its clarity and ability of the underlying theory to unify our understanding of high-dimensional computing where conventional methods fail. The plenty of application oriented problems are presented for evaluating, monitoring and maintaining the stability of adaptive learning machine. Author has taken care to cover the breadth and depth of the subject, both in the qualitative as well as quantitative way. The book is intended to enlighten the scientific community, ranging from advanced undergraduates to engineers, scientists and seasoned researchers in computational intelligenc...
Neutral stability calculations for boundary-layer flows
Nayfeh, A. H.; Padhye, A.
1980-01-01
An analysis is presented of the parallel neutral stability of three-dimensional incompressible, isothermal boundary-layer flows. A Taylor-series expansion of the dispersion relation is used to derive the general eigenvalues. These equations are functions of the complex group velocity. These relations are verified by numerical results obtained for two- and three-dimensional disturbances in two- and three-dimensional flows.
张磊; 李辉武; 胡梁宾
2012-01-01
本文利用半经典的自旋密度矩阵方法对二维自旋轨道耦合电子气中持续自旋螺旋态的稳定性进行了一些研究，重点研究了自旋螺旋态的寿命与其波矢、载流子迁移率、温度、自旋轨道耦合强度、外电场强度等因素之间的关系，并将部分理论计算结果与最近的一些相关实验结果进行了比较，发现两者之间大致是符合的．%We study theoretically the stability of persistent spin helix in two-dimensional electron gases with spin-orbit coupling by a semi-classical spin density matrix method. The possible influences of disordering scattering, temperature, spin-orbit coupling strength and external electric field on the lifetime of persistent spin helix state are investigated. The theoretical results are found to be in agreement with some recent relevant experimental results.
Tannenbaum, Eric P; Burns, Geoffrey T; Oak, Nikhil R; Lawton, Jeffrey N
2017-03-01
Metacarpal fractures are commonly treated by a variety of means including casting or open reduction internal fixation when unacceptable alignment is present following attempted closed reduction. Dorsal plating with either single-row 2-dimensional or double-row 3-dimensional plates has been proposed. This study's purpose was to determine if there are any differences in fixation construct stability under cyclic loading and subsequent load to failure between the lower profile 3-dimensional and the larger 2-dimensional plates in a metacarpal fracture gap sawbone model. Thirty metacarpal cortico-cancellous synthetic bones were cut with a 1.75-mm gap between the 2 fragments simulating mid-diaphyseal fracture comminution. Half of the metacarpals were plated with 2.0-mm locking 2-dimensional plates and half with 1.5-mm locking 3-dimensional plates. The plated metacarpals were mounted into a materials testing apparatus and cyclically loaded under cantilever bending for 2,000 cycles at 70 N, then 2,000 cycles at 120 N, and finally monotonically loaded to failure. Throughout testing, fracture gap sizes were measured, failure modes were recorded, and construct strength and stiffness values were calculated. All 3-dimensional constructs survived both cyclic loading conditions. Ten (67%) 2-dimensional constructs survived both loading conditions, whereas 5 (33%) failed the 120-N loading at 1377 ± 363 cycles. When loaded to failure, the 3-dimensional constructs failed at 265 N ± 21 N, whereas the 2-dimensional constructs surviving cyclic loading failed at 190 N ± 17 N. The shorter, thinner 3-dimensional metacarpal plates demonstrated increased resistance to failure in a cyclic loading model and increased load to failure compared with the relatively longer, thicker 2-dimensional metacarpal plates. The lower-profile 3-dimensional metacarpal plate fixation demonstrated greater stability for early postoperative resistance than the thicker 2-dimensional fixation, whereas the smaller
Vacuum stability of asymptotically safe gauge-Yukawa theories
Litim, Daniel F.; Mojaza, Matin; Sannino, Francesco
2016-01-01
We study the phase diagram and the stability of the ground state for certain four-dimensional gauge-Yukawa theories whose high-energy behaviour is controlled by an interacting fixed point. We also provide analytical and numerical results for running couplings, their crossover scales, the separatrix......, and the Coleman-Weinberg effective potential. Classical and quantum stability of the vacuum is established....
Internal Stabilization of a Mutualistic Reaction Diffusion System
Wang Yuan DONG
2007-01-01
We study the internal stabilization of steady-state solutions to a 2-species mutualistic reaction diffusion system via finite-dimensional feedback controllers. Our main idea is to use differ- ent internal controllers to stabilize different steady-state solutions. The controllers are provided by considering LQ problems associated with the lineaxized systems at steady-state solutions.
Vacuum stability of asymptotically safe gauge-Yukawa theories
Litim, Daniel F; Sannino, Francesco
2016-01-01
We study the phase diagram and the stability of the ground state for certain four-dimensional gauge-Yukawa theories whose high-energy behaviour is controlled by an interacting fixed point. We also provide analytical and numerical results for running couplings, their crossover scales, the separatrix, and the Coleman-Weinberg effective potential. Classical and quantum stability of the vacuum is established.
Aerodynamic stability of cable-stayed-suspension hybrid bridges
ZHANG Xin-jun; SUN Bing-nan
2005-01-01
Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.
陈为坚; 段扬; 林周胜; 李贵涛; 孙鸿涛; 刘燕芳
2015-01-01
目的：基于三维有限元建模方法，建立腰椎弓根动态稳定钉棒系统的模型，初步分析处于不同载荷下腰椎的应力分布及各节段的活动度。方法对一名健康成年男性志愿者行CT扫描，用Mimics 10.01、Abaqus 6.10软件建立正常人L3～S2节段模型。结合Bioflex动态稳定系统建立模型。对模型施加150 N预载荷，在3个主平面施加10 Nm扭矩，获得前屈、后伸、侧屈及旋转6种运动状态下的Bioflex钉棒应力分布和各节段的椎间活动度，初步测定后伸及旋转运动的活动度。结果建立的腰椎L3～S2节段和动态稳定系统有限元模型符合生物力学模型，初步分析显示腰椎动态稳定系统的应力主要集中于螺旋固定棒；在各种加载下，腰椎动态固定的节段活动度明显降低。结论基于三维有限元方法建立的Bioflex腰椎弓动态固定模型能很好地模拟腰椎的动态固定力学活动，可以对固定后的腰椎的应力和各种活动进行很好的模拟，具有很好的研究价值。%Objective To construct the dynamic lumbar pedicle scree system based on the three -dimensional fi-nite element model , thus to preliminarily analyze the stress distribution under different loads and the range of motion (ROM).Methods CT scan of the L3 ~S2 section of a healthy adult male volunteer was performed , while Mimics 10.01 and Abaqus 6.10 software were introduced to establish normal segmental model .Bioflex pedicle screw and elastic rod were used to establish dynamic stability system model .Under 150 N preload, and 10 Nm torque to three principal planes , the stress distribution in flexion , extension , lateral bending and torsion were simulated , while the ROMs of extension and tor-sion were also analyzed .Results The establishment of a lumbar L 3 ~S2 segmental finite element model and the dynamic stability system conformed to biomechanical model .Stress mainly concentrated on the elastic rods , when
Robust Stabilization of a Class of passive Nonlinear Systems
Joshi, Suresh M.; Kelkar, Atul G.
1996-01-01
The problem of feedback stabilization is considered for a class of nonlinear, finite dimensional, time invariant passive systems that are affine in control. Using extensions of the Kalman-Yakubovch lemma, it is shown that such systems can be stabilized by a class of finite demensional, linear, time-invariant controllers which are strictly positive real in the weak or marginal sense. The stability holds regardless of model uncertainties, and is therefore, robust.
Two dimensional fermions in three dimensional YM
Narayanan, R
2010-01-01
Dirac fermions in the fundamental representation of $SU(N)$ live on the surface of a cylinder embedded in $R^3$ and interact with a three dimensional $SU(N)$ Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the circumference of the cylinder is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit at a typical bulk scale. Replacing three dimensional YM by four dimensional YM introduces non-trivial renormalization effects.
Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice
XU Quan; QIANG Tian
2009-01-01
We study the existence and stability of two-dimensional discrete breathers in a two-dimensional discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling.Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive)and the center of the two-dimensional gap breather (on a light or a heavy atom).
Stability properties of autonomous homogeneous polynomial differential systems
Samardzija, Nikola
A geometrical approach is used to derive a generalized characteristic value problem for dynamic systems described by homogeneous polynomials. It is shown that a nonlinear homogeneous polynomial system possesses eigenvectors and eigenvalues, quantities normally associated with a linear system. These quantities are then employed in studying stability properties. The necessary and sufficient conditions for all forms of stabilities characteristic of a two-dimensional system are provided. This result, together with the classical theorem of Frommer, completes a stability analysis for a two-dimensional homogeneous polynomial system.
Bryngelson, Spencer H.; Freund, Jonathan B.
2016-07-01
Elastic capsules flowing in small enough tubes, such as red blood cells in capillaries, are well known to line up into regular single-file trains. The stability of such trains in somewhat wider channels, where this organization is not observed, is studied in a two-dimensional model system that includes full coupling between the viscous flow and suspended capsules. A diverse set of linearly amplifying disturbances, both long-time asymptotic (modal) and transient (nonmodal) perturbations, is identified and analyzed. These have a range of amplification rates and their corresponding forms are wavelike, typically dominated by one of five principal perturbation classes: longitudinal and transverse translations, tilts, and symmetric and asymmetric shape distortions. Finite-amplitude transiently amplifying perturbations are shown to provide a mechanism that can bypass slower asymptotic modal linear growth and precipitate the onset of nonlinear effects. Direct numerical simulations are used to verify the linear analysis and track the subsequent transition of the regular capsule trains into an apparently chaotic flow.
Dimensional Enhancement via Supersymmetry
M. G. Faux
2011-01-01
of supersymmetry in one time-like dimension. This is enabled by algebraic criteria, derived, exhibited, and utilized in this paper, which indicate which subset of one-dimensional supersymmetric models describes “shadows” of higher-dimensional models. This formalism delineates that minority of one-dimensional supersymmetric models which can “enhance” to accommodate extra dimensions. As a consistency test, we use our formalism to reproduce well-known conclusions about supersymmetric field theories using one-dimensional reasoning exclusively. And we introduce the notion of “phantoms” which usefully accommodate higher-dimensional gauge invariance in the context of shadow multiplets in supersymmetric quantum mechanics.
Two dimensional fermions in four dimensional YM
Narayanan, R
2009-01-01
Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.
Navigating the complexity of ecological stability.
Donohue, Ian; Hillebrand, Helmut; Montoya, José M; Petchey, Owen L; Pimm, Stuart L; Fowler, Mike S; Healy, Kevin; Jackson, Andrew L; Lurgi, Miguel; McClean, Deirdre; O'Connor, Nessa E; O'Gorman, Eoin J; Yang, Qiang
2016-09-01
Human actions challenge nature in many ways. Ecological responses are ineluctably complex, demanding measures that describe them succinctly. Collectively, these measures encapsulate the overall 'stability' of the system. Many international bodies, including the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, broadly aspire to maintain or enhance ecological stability. Such bodies frequently use terms pertaining to stability that lack clear definition. Consequently, we cannot measure them and so they disconnect from a large body of theoretical and empirical understanding. We assess the scientific and policy literature and show that this disconnect is one consequence of an inconsistent and one-dimensional approach that ecologists have taken to both disturbances and stability. This has led to confused communication of the nature of stability and the level of our insight into it. Disturbances and stability are multidimensional. Our understanding of them is not. We have a remarkably poor understanding of the impacts on stability of the characteristics that define many, perhaps all, of the most important elements of global change. We provide recommendations for theoreticians, empiricists and policymakers on how to better integrate the multidimensional nature of ecological stability into their research, policies and actions.
Plutonium inventories for stabilization and stabilized materials
Williams, A.K.
1996-05-01
The objective of the breakout session was to identify characteristics of materials containing plutonium, the need to stabilize these materials for storage, and plans to accomplish the stabilization activities. All current stabilization activities are driven by the Defense Nuclear Facilities Safety Board Recommendation 94-1 (May 26, 1994) and by the recently completed Plutonium ES&H Vulnerability Assessment (DOE-EH-0415). The Implementation Plan for accomplishing stabilization of plutonium-bearing residues in response to the Recommendation and the Assessment was published by DOE on February 28, 1995. This Implementation Plan (IP) commits to stabilizing problem materials within 3 years, and stabilizing all other materials within 8 years. The IP identifies approximately 20 metric tons of plutonium requiring stabilization and/or repackaging. A further breakdown shows this material to consist of 8.5 metric tons of plutonium metal and alloys, 5.5 metric tons of plutonium as oxide, and 6 metric tons of plutonium as residues. Stabilization of the metal and oxide categories containing greater than 50 weight percent plutonium is covered by DOE Standard {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides{close_quotes} December, 1994 (DOE-STD-3013-94). This standard establishes criteria for safe storage of stabilized plutonium metals and oxides for up to 50 years. Each of the DOE sites and contractors with large plutonium inventories has either started or is preparing to start stabilization activities to meet these criteria.
Dimensional stability of an addition silicone after disinfection/sterilization
Viana, J; Martins, F.; Reis, J.; Maurício, P.; Félix, S.
2015-01-01
Poster presented at the “From Basic Sciences to Clinical Research” – First International Congress of CiiEM. Egas Moniz, Caparica, Portugal, 27-28 November 2015 "Dental impressions play a key role in clinical practice, and it is crucial to know the impact of disinfection or sterilization on it. The success of oral rehabilitation depends on the accuracy and reproducibility of the oral impressions [1,2,3]. The addition silicones and polyethers tend to be used most frequently for its physical ...
Linear stability analysis of heated parallel channels
Nourbakhsh, H. P.; Isbin, H. S.
An analyis is presented of thermal hydraulic stability of flow in parallel channels covering the range from inlet subcooling to exit superheat. The model is based on a one-dimensional drift velocity formulation of the two phase flow conservation equations. The system of equations is linearized by assuming small disturbances about the steady state. The dynamic response of the system to an inlet flow perturbation is derived yielding the characteristic equation which predicts the onset of instabilities. A specific application is carried out for homogeneous and regional uniformly heated systems. The particular case of equal characteristic frequencies of two-phase and single phase vapor region is studied in detail. The D-partition method and the Mikhailov stability criterion are used for determining the marginal stability boundary. Stability predictions from the present analysis are compared with the experimental data from the solar test facility.
The dimensional accuracy of the sintered billets
Чингиз Ариф оглы Алиев
2016-01-01
Full Text Available The article presents the results of assessing the impact of the behaviour stability of the components included in the compositions and process parameters of their production, on the dimensional accuracy of workpieces. It was found that by increasing the amount of oxide in the composition is greater compaction of the sintered billet in the process of heat treatment. This also increases the density of all components of the composition
DIMENSIONALLY STABLE, CORROSION RESISTANT NUCLEAR FUEL
Kittel, J.H.
1963-10-31
A method of making a uranium alloy of improved corrosion resistance and dimensional stability is described. The alloy contains from 0-9 weight per cent of an additive of zirconium and niobium in the proportions by weight of 5 to 1 1/ 2. The alloy is cold rolled, heated to two different temperatures, air-cooled, heated to a third temperature, and quenched in water. (AEC)
Life and space dimensionality: A brief review of old and new entangled arguments
Caruso, Francisco
2016-01-01
A general sketch on how the problem of space dimensionality depends on anthropic arguments is presented. Several examples of how life has been used to constraint space dimensionality (and vice-versa) are reviewed. In particular, the influences of three-dimensionality in the solar system stability and the origin of life on Earth are discussed. New constraints on space dimensionality and on its invariance in very large spatial and temporal scales are also stressed.
罗巨利; 詹新立; 肖增明; 贺聚良; 刘会江; 赵卫东
2011-01-01
BACKGROUND: There are few reports about in vitro biomechanical studies of anterior cervical locking plate for upper thoracic reconstruction .OBJECTIVE: To evaluate the biomechanical characters of self-designed upper thoratic anterior titanium plate fixed system.METHODS: Intact C7-T6 specimens from 15 fresh corpses were randomly divided into three groups: group B with upper thoracic anterior titanium plate fixation (UTAPF), group C with prespred anterior cervical plate fixation (ACPF), group D with imprespred ACPF. Range of motion (ROM) was tested for the natural intact specimens. Measurement of three-dimensional stability was performed in flexion, extension and lateral bending and rotation state in groups B, C, D after fixation.RESULTS AND CONCLUSION: ROM of the natural intact specimens in the three groups had no significant difference (P ＞ 0.05).The stability of flexion arranged as follows: B＞D＞C>intact specimens (A). Significant difference between B and A was found (P=0.012). The stability of extension arranged as follows: B＞C＞A＞D, but there was no significant difference among different groups. The stability of rotation arranged B＞C＞A＞D. Between groups no significant difference was found in the rotation condition.The order of stabilities under the lateral bending was A＞B＞C＞D. There were significant differences between A and C as well as between A and D (P=0.005, P=0.002). The findings indicate that the upper thoracic anterior titanium plate has a better biomechanical stability than cervical plate. If cervical anterior plate was applied to upper thoratic spine, plate should be prespred according to kyphosis of the upper thoratic spine.%背景:国内外少见颈前路带锁钢板重建上胸椎的体外生物力学报道.目的:从生物力学角度评价自行研制的上胸椎前路钛板内固定装置.方法:15具成人尸体上胸椎标本分成3组,即上胸椎前路钛板内固定组(B),颈前路钛板预弯内固定组(C),颈前路
Thermomechanical stability of graphite/epoxy composites.
Goggin, W R
1974-02-01
Results are reported on an investigation to evaluate the usefulness of selected graphite/epoxy composite structures for applications requiring precision tolerancing and dimensional stability. Thornel 75S/ELRB 4617 and Modmor 1/ELRB 4617 laminate composites in a six-ply design were tested, as well as a honeycomb design having two Thornel/ELRB faceplates bonded to an aluminum honeycomb core. Measurements were made of thermal expansion coefficient and its directional variations, microyielding and microcreep behavior, thermal and temporal stabilities. Data, discussion of results, and recommendations for applicable areas are given for the specific material and design types tested.
Clustering high dimensional data
Assent, Ira
2012-01-01
High-dimensional data, i.e., data described by a large number of attributes, pose specific challenges to clustering. The so-called ‘curse of dimensionality’, coined originally to describe the general increase in complexity of various computational problems as dimensionality increases, is known...... to render traditional clustering algorithms ineffective. The curse of dimensionality, among other effects, means that with increasing number of dimensions, a loss of meaningful differentiation between similar and dissimilar objects is observed. As high-dimensional objects appear almost alike, new approaches...
Liang, Liying; Xu, Yimeng; Lei, Yong; Liu, Haimei
2014-04-07
Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability.
Lattice Three-Dimensional Skyrmions Revisited
Charalampidis, E G; Kevrekidis, P G
2014-01-01
In the continuum a skyrmion is a topological nontrivial map between Riemannian manifolds, and a stationary point of a particular energy functional. This paper describes lattice analogues of the aforementioned skyrmions, namely a natural way of using the topological properties of the three-dimensional continuum Skyrme model to achieve topological stability on the lattice. In particular, using fixed point iterations, numerically exact lattice skyrmions are constructed; and their stability under small perturbations is verified by means of linear stability analysis. While stable branches of such solutions are identified, it is also shown that they possess a particularly delicate bifurcation structure, especially so in the vicinity of the continuum limit. The corresponding bifurcation diagram is elucidated and a prescription for selecting the branch asymptoting to the well-known continuum limit is given. Finally, the robustness of the solutions by virtue of direct numerical simulations is corroborated.
Stability of Bianchi attractors in Gauged Supergravity
Inbasekar, Karthik
2013-01-01
In this paper, we analyse the stability of extremal black brane horizons with homogeneous symmetry in the spatial directions in five dimensional gauged supergravity, under the fluctuations of the scalar fields about their attractor values. We examine the scalar fluctuation equations at the linearised level and demand that the fluctuations vanish as one approaches the horizon. Imposing certain restrictions on the Killing vectors used for gauging we find that the necessary conditions for stability are satisfied only by a subclass of the Bianchi metrics whose symmetry group factorises into a two dimensional Lifshitz symmetry and any homogeneous symmetry group given by the Bianchi classification. We apply these results to a simple example of a gauged supergravity model with one vector multiplet to find the stable attractors.
Stability and Restoration phenomena in Competitive Systems
Uechi, Lisa
2012-01-01
A conservation law and stability, recovering phenomena and characteristic patterns of a nonlinear dynamical system have been studied and applied to biological and ecological systems. In our previous study, we proposed a system of symmetric 2n-dimensional conserved nonlinear differential equations with external perturbations. In this paper, competitive systems described by 2-dimensional nonlinear dynamical (ND) model with external perturbations are applied to population cycles and recovering phenomena of systems from microbes to mammals. The famous 10-year cycle of population density of Canadian lynx and snowshoe hare is numerically analyzed. We find that a nonlinear dynamical system with a conservation law is stable and generates a characteristic rhythm (cycle) of population density, which we call the {\\it standard rhythm} of a nonlinear dynamical system. The stability and restoration phenomena are strongly related to a conservation law and balance of a system. The {\\it standard rhythm} of population density ...
Semigroup approximation and robust stabilization of distributed parameter systems
Kurdila, A. J.; Fabiano, R.; Strganac, T.; Hsu, S.
1994-01-01
Theoretical results that enable rigorous statements of convergence and exponential stability of Galerkin approximations of LQR controls for infinite dimensional, or distributed parameter, systems have proliferated over the past ten years. In addition, extensive progress has been made over the same time period in the derivation of robust control design strategies for finite dimensional systems. However, the study of the convergence of robust finite dimensional controllers to robust controllers for infinite dimensional systems remains an active area of research. We consider a class of soft-constrained differential games evolving in a Hilbert space. Under certain conditions, a saddle point control can be given in feedback form in terms of a solution to a Riccati equation. By considering a related LQR problem, we can show a convergence result for finite dimensional approximations of this differential game. This yields a computational algorithm for the feedback gain that can be derived from similar strategies employed in infinite dimensional LQR control design problems. The approach described in this paper also inherits the additional properties of stability robustness common to game theoretic methods in finite dimensional analysis. These theoretical convergence and stability results are verified in several numerical experiments.
On the Stability of Bilinear Stochastic Systems
1988-08-01
d’Equations Differentielles Stochastiques Lineaires", Journees Stabilite Asymptotique des Systemes Differentiels a Perturbation Aleatoire. CNRS, 1986. [3...for the Lyapunov numbers associated with this equation are given. Bilinear noise models are, after linear ones, the second simplest case of stochastic...give a condition for the stability with probability one of the d-dimensional Ito equation which describes the behavior of such a system dYs = AYs ds
Dimensional behavior of Ni-YSZ composites during redox cycling
Pihlatie, Mikko; Kaiser, Andreas; Larsen, Peter Halvor;
2009-01-01
The dimensional behavior of Ni-yttria-stabilized zirconia (YSZ) cermets during redox cycling was tested in dilatometry within the temperature range 600-1000 degrees C. The effect Of humidity oil redox stability was investigated at intermediate and low temperatures. We show that both the sintering...... of nickel depending on temperature of the initial reduction and the operating conditions, and the temperature of reoxidation are very important for the size of the dimensional change. Cumulative redox strain (CRS) is shown to be correlated with temperature. Measured maximum CRS after three redox cycles...
Brorsen, Michael; Burcharth, Hans F.; Larsen, Torben
The stability of dolos armour blocks against wave attack has been investigated in wave model studies.......The stability of dolos armour blocks against wave attack has been investigated in wave model studies....
Three dimensional strained semiconductors
Voss, Lars; Conway, Adam; Nikolic, Rebecca J.; Leao, Cedric Rocha; Shao, Qinghui
2016-11-08
In one embodiment, an apparatus includes a three dimensional structure comprising a semiconductor material, and at least one thin film in contact with at least one exterior surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the three dimensional structure. In another embodiment, a method includes forming a three dimensional structure comprising a semiconductor material, and depositing at least one thin film on at least one surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the structure.
Dimensional Enhancement via Supersymmetry
Faux, M G; Landweber, G D
2009-01-01
We explain how the representation theory associated with supersymmetry in diverse dimensions is encoded within the representation theory of supersymmetry in one time-like dimension. This is enabled by algebraic criteria, derived, exhibited, and utilized in this paper, which indicate which subset of one-dimensional supersymmetric models describe "shadows" of higher-dimensional models. This formalism delineates that minority of one-dimensional supersymmetric models which can "enhance" to accommodate extra dimensions. As a consistency test, we use our formalism to reproduce well-known conclusions about supersymmetric field theories using one-dimensional reasoning exclusively. And we introduce the notion of "phantoms" which usefully accommodate higher-dimensional gauge invariance in the context of shadow multiplets in supersymmetric quantum mechanics.
Stability and boundary stabilization of 1-D hyperbolic systems
Bastin, Georges
2016-01-01
This monograph explores the modeling of conservation and balance laws of one-dimensional hyperbolic systems using partial differential equations. It presents typical examples of hyperbolic systems for a wide range of physical engineering applications, allowing readers to understand the concepts in whichever setting is most familiar to them. With these examples, it also illustrates how control boundary conditions may be defined for the most commonly used control devices. The authors begin with the simple case of systems of two linear conservation laws and then consider the stability of systems under more general boundary conditions that may be differential, nonlinear, or switching. They then extend their discussion to the case of nonlinear conservation laws and demonstrate the use of Lyapunov functions in this type of analysis. Systems of balance laws are considered next, starting with the linear variety before they move on to more general cases of nonlinear ones. They go on to show how the problem of boundary...
Global analysis on slope stability and its engineering application
无
2009-01-01
In hydraulic engineering, sometimes it is necessary to consider the stability of sliding bodies with lateral frictional boundaries. Neither the existing three dimensional limit equilibrium methods nor the commercial software products are able to treat such situations. The three dimensional factor of safety is accordingly underestimated; while the shearing strength based on the three dimensional back analysis is overestimated. In this study, the lateral boundaries are regarded as the part of the slip surface. Based on the expression of the normal pressure on the slip surface and the patch interpolation, a rigorous solution for the three dimensional limit equilibrium analysis is realized. Meanwhile, the proposed procedure is applied to the stability analysis of the slope with a cable platform on the right bank in Da Gang Shan hydraulic project under construction.
Khare, A.; Rasmussen, K. O.; Samuelsen, Mogens Rugholm
2010-01-01
We show that the two-dimensional, nonlinear Schrodinger lattice with a saturable nonlinearity admits periodic and pulse-like exact solutions. We establish the general formalism for the stability considerations of these solutions and give examples of stability diagrams. Finally, we show that the e......We show that the two-dimensional, nonlinear Schrodinger lattice with a saturable nonlinearity admits periodic and pulse-like exact solutions. We establish the general formalism for the stability considerations of these solutions and give examples of stability diagrams. Finally, we show...
Dimensional comparison theory.
Möller, Jens; Marsh, Herb W
2013-07-01
Although social comparison (Festinger, 1954) and temporal comparison (Albert, 1977) theories are well established, dimensional comparison is a largely neglected yet influential process in self-evaluation. Dimensional comparison entails a single individual comparing his or her ability in a (target) domain with his or her ability in a standard domain (e.g., "How good am I in math compared with English?"). This article reviews empirical findings from introspective, path-analytic, and experimental studies on dimensional comparisons, categorized into 3 groups according to whether they address the "why," "with what," or "with what effect" question. As the corresponding research shows, dimensional comparisons are made in everyday life situations. They impact on domain-specific self-evaluations of abilities in both domains: Dimensional comparisons reduce self-concept in the worse off domain and increase self-concept in the better off domain. The motivational basis for dimensional comparisons, their integration with recent social cognitive approaches, and the interdependence of dimensional, temporal, and social comparisons are discussed.
Stability of a tachyon braneworld
German, Gabriel; Kuerten, Andre M; Malagon-Morejon, Dagoberto; da Rocha, Roldao
2016-01-01
Within the braneworld paradigm the tachyonic scalar field has been used to generate models that attempt to solve some of the open problems that physics faces nowadays, both in cosmology and high energy physics as well. When these field configurations are produced by the interplay of higher dimensional gravity with some matter content, braneworld models must prove to be stable under small fluctuations of the background matter fields, among other consistency tests. Here we present a complete proof of the stability under scalar perturbations of tachyonic thick braneworlds with an embedded maximally symmetric 4D space-time, revealing its physical consistency. This family contains a recently reported tachyonic de Sitter thick braneworld which possesses a series of appealing properties. These features encompasses complete regularity, asymptotic flatness (instead of being asymptotically dS/AdS even when it contains a negative bulk cosmological constant and the relevant 3-brane has dS symmetry), and a graviton spectr...
A stability tool for use within TELEGRIP
Son, W.H.; Trinkle, J.C. [Texas A and M Univ., College Station, TX (United States)
1998-12-01
During the assembly of a product, it is vital that the partially-completed assembly be stable. To guarantee this, one must ensure that contacts among the parts and the fixtures are sufficient to stabilize the assembly. Thus, it would be desirable to have an efficient method for testing an assembly stability, and, if this is not possible, generating a set of additional fixture contact points, known as fixels, that will stabilize it. One can apply this method to the situation of safe handling of special nuclear material (SNM). To have these functionalities should help improve the safety and enhance the performance of special nuclear material (SNM) handling and storage operations, since some methods are needed for gripping objects in a stable manner. Also, one may need a way to find a pit-holding fixture inserted into containers. In this paper, the authors present a stability tool, which they call Stab Tool, which was developed to test the stability of objects grasped by robotic hands, objects placed in fixtures, or sets of objects piled randomly on top of one another. Stab Tool runs on top of a commercial software package, TELEGRIP, which is used for geometry modeling and motion creation. The successful development of the stability depends strongly on TELEGRIP`s ability to compute the distances between pairs of three-dimensional bodies in the simulated environment. The interbody distance computation tool takes advantage of the polyhedral representations of bodies used by TELEGRIP and of linear programming techniques to yield an efficient algorithm.
Analysis of the gyroscopic stabilization of a system of rigid bodies
Kliem, Wolfhard; Seyranian, Alexander P.
1997-01-01
We study the gyroscopic stability of a three-body system. A new method of finding stability regions, based on mechanism and criteria for gyroscopic stabilization, is presented. Of particular interest in this connection is the theory of interaction of eigenvalues. This leads to a complete 3......-dimensional analysis, which shows the regions of stability, divergence, and flutter of a simple model of a rotating spaceship....
On stability of randomly switched nonlinear systems
Chatterjee, Debasish
2007-01-01
This article is concerned with stability analysis and stabilization of randomly switched nonlinear systems. These systems may be regarded as piecewise deterministic stochastic systems: the discrete switches are triggered by a stochastic process which is independent of the state of the system, and between two consecutive switching instants the dynamics are deterministic. Our results provide sufficient conditions for almost sure global asymptotic stability using Lyapunov-based methods when individual subsystems are stable and a certain ``slow switching'' condition holds. This slow switching condition takes the form of an asymptotic upper bound on the probability mass function of the number of switches that occur between the initial and current time instants. This condition is shown to hold for switching signals coming from the states of finite-dimensional continuous-time Markov chains; our results therefore hold for Markov jump systems in particular. For systems with control inputs we provide explicit control s...
Stability of a tachyon braneworld
Germán, Gabriel [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico); Herrera-Aguilar, Alfredo [Instituto de Física, Benemérita Universidad Autónoma de Puebla,Apartado Postal J-48, 72570, Puebla, Puebla (Mexico); Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo,Ciudad Universitaria, CP 58040, Morelia, Michoacán (Mexico); Kuerten, André Martorano [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC (UFABC),Avenida dos Estados, 5001, Santo André, SP (Brazil); Malagón-Morejón, Dagoberto [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apartado Postal 48-3, 62251, Cuernavaca, Morelos (Mexico); Rocha, Roldão da [Centro de Matemática, Computação e Cognição, Universidade Federal do ABC (UFABC),Avenida dos Estados, 5001, Santo André, SP (Brazil)
2016-01-26
Within the braneworld paradigm the tachyonic scalar field has been used to generate models that attempt to solve some of the open problems that physics faces nowadays, both in cosmology and high energy physics as well. When these field configurations are produced by the interplay of higher dimensional warped gravity with some matter content, braneworld models must prove to be stable under the whole set of small fluctuations of the gravitational and matter fields background, among other consistency tests. Here we present a complete proof of the stability under scalar perturbations of tachyonic thick braneworlds with an embedded maximally symmetric 4D space-time, revealing its physical consistency. This family of models contains a recently reported tachyonic de Sitter thick braneworld which possesses a series of appealing properties. These features encompass complete regularity, asymptotic flatness (instead of being asymptotically dS or AdS) even when it contains a negative bulk cosmological constant, a relevant 3-brane with dS metric which naturally arises from the full set of field equations of the 5D background (it is not imposed), qualitatively describing the inflationary epochs of our Universe, and a graviton spectrum with a single zero mode bound state that accounts for the 4D graviton localised on the brane and is separated from the continuum of Kaluza-Klein massive graviton excitations by a mass gap. The presence of this mass gap in the graviton spectrum makes the extra-dimensional corrections to Newton’s law decay exponentially. Gauge vector fields with a single massless bound state in its mass spectrum are also localised on this braneworld model a fact that allows us to recover the Coulomb’s law of our 4D world. All these properties of the above referred tachyonic braneworld together with the positive stability analysis provided in this work, constitute a firm step towards the construction of realistic cosmological models within the braneworld paradigm.
Stability of a tachyon braneworld
Germán, Gabriel; Herrera-Aguilar, Alfredo; Martorano Kuerten, André; Malagón-Morejón, Dagoberto; da Rocha, Roldão
2016-01-01
Within the braneworld paradigm the tachyonic scalar field has been used to generate models that attempt to solve some of the open problems that physics faces nowadays, both in cosmology and high energy physics as well. When these field configurations are produced by the interplay of higher dimensional warped gravity with some matter content, braneworld models must prove to be stable under the whole set of small fluctuations of the gravitational and matter fields background, among other consistency tests. Here we present a complete proof of the stability under scalar perturbations of tachyonic thick braneworlds with an embedded maximally symmetric 4D space-time, revealing its physical consistency. This family of models contains a recently reported tachyonic de Sitter thick braneworld which possesses a series of appealing properties. These features encompass complete regularity, asymptotic flatness (instead of being asymptotically dS or AdS) even when it contains a negative bulk cosmological constant, a relevant 3-brane with dS metric which naturally arises from the full set of field equations of the 5D background (it is not imposed), qualitatively describing the inflationary epochs of our Universe, and a graviton spectrum with a single zero mode bound state that accounts for the 4D graviton localised on the brane and is separated from the continuum of Kaluza-Klein massive graviton excitations by a mass gap. The presence of this mass gap in the graviton spectrum makes the extra-dimensional corrections to Newton's law decay exponentially. Gauge vector fields with a single massless bound state in its mass spectrum are also localised on this braneworld model a fact that allows us to recover the Coulomb's law of our 4D world. All these properties of the above referred tachyonic braneworld together with the positive stability analysis provided in this work, constitute a firm step towards the construction of realistic cosmological models within the braneworld paradigm.
Stability Analysis of the LHC Cables for Transient Heat Depositions
Granieri, P P; Xydi, P; Baudouy, B; Bocian, D; Bottura, L; Breschi, M; Siemko, A
2008-01-01
The commissioning and the exploitation of the LHC require a good knowledge of the stability margins of the superconducting magnets with respect to beam induced heat depositions. Previous studies showed that simple numerical models are suitable to carry out stability calculations of multi-strands cables, and highlighted the relevance of the heat transfer model with the surrounding helium. In this paper we present a systematic scan of the stability margin of all types of LHC cables working at 1.9 Kagainst transient heat depositions. We specifically discuss the dependence of the stability margin on the parameters of the model, which provide an estimate of the uncertainty of the values quoted. The stability margin calculations have been performed using a zero-dimensional (0-D) numerical model, and a cooling model taking into account the relevant helium phases which may appear during a stability experiment: it includes Kapitza thermal resistance in superfluid He, boundary layer formation and heat transfer in He I,...
Control of Collagen Triple Helix Stability by Phosphorylation.
Acevedo-Jake, Amanda M; Ngo, Daniel H; Hartgerink, Jeffrey D
2017-03-10
The phosphorylation of the collagen triple helix plays an important role in collagen synthesis, assembly, signaling, and immune response, although no reports detailing the effect this modification has on the structure and stability of the triple helix exist. Here we investigate the changes in stability and structure resulting from the phosphorylation of collagen. Additionally, the formation of pairwise interactions between phosphorylated residues and lysine is examined. In all tested cases, phosphorylation increases helix stability. When charged-pair interactions are possible, stabilization via phosphorylation can play a very large role, resulting inasmuch as a 13.0 °C increase in triple helix stability. Two-dimensional NMR and molecular modeling are used to study the local structure of the triple helix. Our results suggest a mechanism of action for phosphorylation in the regulation of collagen and also expand upon our understanding of pairwise amino acid stabilization of the collagen triple helix.
Dimensional regularization is generic
Fujikawa, Kazuo
2016-01-01
The absence of the quadratic divergence in the Higgs sector of the Standard Model in the dimensional regularization is usually regarded to be an exceptional property of a specific regularization. To understand what is going on in the dimensional regularization, we illustrate how to reproduce the results of the dimensional regularization for the $\\lambda\\phi^{4}$ theory in the more conventional regularization such as the higher derivative regularization; the basic postulate involved is that the quadratically divergent induced mass, which is independent of the scale change of the physical mass, is kinematical and unphysical. This is consistent with the derivation of the Callan-Symanzik equation, which is a comparison of two theories with slightly different masses, for the $\\lambda\\phi^{4}$ theory without encountering the quadratic divergence. We thus suggest that the dimensional regularization is generic in a bottom-up approach starting with a successful low-energy theory. We also define a modified version of t...
Experimental higher dimensional entanglement
Richart, Daniel L.; Wieczorek, Witlef; Weinfurter, Harald [MPI fuer Quantenoptik, Hans Kopfermannstr. 1, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet, Schellingstr. 4, D-80797 Muenchen (Germany)
2009-07-01
Higher dimensional states (qudits) allow to implement quantum communication schemes of increasing complexity, as e.g. superdense coding. Similarly, qudits allow further research into the fundaments of quantum theory. Here we report on first steps towards the implementation of states with correlated photon pairs in a 2 x 8 dimensional Hilbert space. To this end the photon pairs are prepared in the energy-time basis, as initially proposed in: Using unbalanced interferometers, information can be encoded in the different arrival times of the photon pairs, early and late, as was experimentally realized in. Here, we extend this scheme by proposing and characterizing a scalable multiple time delay interferometer. This interferometer system allows an exponential increase in the dimensionality of the entangled state with only a linear increase in the optical components used. Using the proposed interferometer system, first experimental tests on a two-dimensional state yielded a violation of a Bell inequality by four standard deviations.
Scalar field perturbation on six-dimensional ultra-spinning black holes
Morisawa, Y; Morisawa, Yoshiyuki; Ida, Daisuke
2004-01-01
We studied the stability of scalar field perturbation on six-dimensional ultra-spinning black holes. We numerically calculated the quasinormal modes. Our results suggest that such perturbations are stable.
Dirac quasinormal modes of two-dimensional charged dilatonic black holes
Becar, Ramon [Universidad Catolica de Temuco, Departamento de Ciencias Matematicas y Fisicas, Temuco (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica, Facultad de Ciencias, La Serena (Chile)
2014-06-15
We study charged fermionic perturbations in the background of two-dimensional charged dilatonic black holes, and we present the exact Dirac quasinormal modes. Also, we study the stability of these black holes under charged fermionic perturbations. (orig.)
Asymptotical stability analysis of linear fractional differential systems
LI Chang-pin; ZHAO Zhen-gang
2009-01-01
It has been recently found that many models were established with the aid of fractional derivatives, such as viscoelastic systems, colored noise, electrode-electrolyte polarization, dielectric polarization, boundary layer effects in ducts,electromagnetic waves, quantitative finance, quantum evolution of complex systems, and fractional kinetics. In this paper, the asymptotical stability of higher-dimensional linear fractional differential systems with the Riemann-Liouville fractional order and Caputo fractional order were studied. The asymptotical stability theorems were also derived.
On a stabilization mechanism for low-velocity detonations
Sow, Aliou
2017-03-08
We use numerical simulations of the reactive Lula equations to analyse the nonlinear stability of steady-state one-dimensional solutions for gaseous detonations in the presence of both momentum and heat losses. Our results point to a possible stabilization mechanism for the low-velocity detonations in such systems. The mechanism stems from the existence of a one-parameter family of solutions found in Semenko el al.
Stability of Hyperthermophilic Proteins
Stiefler-Jensen, Daniel
cheaper products. One aspect that can have a large impact on the efficiency of an enzyme is its stability. By increasing the enzyme stability production cost and time can be reduced, and consumers will have a better product with longer activity. In the past it was only possible to increasing enzymes...... stability by randomly generate mutants and lengthy screening processes to identify the best new mutants. However, with the increase in available genomic sequences of thermophilic or hyperthermophilic organisms a world of enzymes with intrinsic high stability are now available. As these organisms are adapted...... to life at high temperatures so are their enzymes, as a result the high stability is accompanied by low activity at moderate temperatures. Thus, much effort had been put into decoding the mechanisms behind the high stability of the thermophilic enzymes. The hope is to enable scientist to design enzymes...
Radiative decay of the one-dimensional large acoustic polaron
Ivic, Zoran; Zekovic, Slobodan; Przulj, Zeljko
2002-12-30
Finite temperature dynamics and stability of the adiabatic large acoustic polaron in one-dimensional systems have been examined by means of the perturbation method based upon the inverse scattering transform. Polaron life-time was estimated in dependence of temperature and electron (exciton)-phonon coupling constant.
Internet Addiction: Stability and Change
Huang, Chiungjung
2010-01-01
This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability…
Internet Addiction: Stability and Change
Huang, Chiungjung
2010-01-01
This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability…
On the four-dimensional formulation of dimensionally regulated amplitudes
Fazio, A.R. [Universidad Nacional de Colombia, Departamento de Fisica, Bogota (Colombia); Mastrolia, P. [Universita di Padova, Dipartimento di Fisica e Astronomia, Padua (Italy); Max-Planck-Institut fuer Physik, Munich (Germany); INFN, Padova (Italy); Mirabella, E. [Max-Planck-Institut fuer Physik, Munich (Germany); Torres Bobadilla, W.J. [Universidad Nacional de Colombia, Departamento de Fisica, Bogota (Colombia); Universita di Padova, Dipartimento di Fisica e Astronomia, Padua (Italy); INFN, Padova (Italy)
2014-12-01
Elaborating on the four-dimensional helicity scheme, we propose a pure four-dimensional formulation (FDF) of the d-dimensional regularization of one-loop scattering amplitudes. In our formulation particles propagating inside the loop are represented by massive internal states regulating the divergences. The latter obey Feynman rules containing multiplicative selection rules which automatically account for the effects of the extra-dimensional regulating terms of the amplitude. We present explicit representations of the polarization and helicity states of the four-dimensional particles propagating in the loop. They allow for a complete, four-dimensional, unitarity-based construction of d-dimensional amplitudes. Generalized unitarity within the FDF does not require any higher-dimensional extension of the Clifford and the spinor algebra. Finally we show how the FDF allows for the recursive construction of d-dimensional one-loop integrands, generalizing the four-dimensional open-loop approach. (orig.)
Triphenylphosphine Stabilized Silver Carboxylates
Jian Lin HAN; Ying Zhong SHEN; Yi PAN
2005-01-01
A series of novel triphenylphosphine stabilized silver carboxylates, potential precursors for CVD growth of ultrafast interconnection link in microelectronic devices, have been prepared and characterized.
G. Kondrat'ev
1999-10-01
Full Text Available In this article some ideas of Hamilton mechanics and differential-algebraic Geometry are used to exact definition of the potential function (Bellman-Lyapunov function in the optimal stabilization problem of smooth finite-dimensional systems.
On the Stability of Rarefaction Wave Solutions for Viscous p-system with Boundary Effect
Xiao-ding Shi
2003-01-01
The inflow problem in the supersonic case for a one-dimensional compressible viscous gas on the half line (0, +∞) is investigated. A stability theorem concerning the long time behaviour of rarefaction wave is established.
G. Kondrat'ev
1999-12-01
Full Text Available In this article some ideas of Hamilton mechanics and differential-algebraic Geometry are used to exact definition of the potential function (Bellman-Lyapunov function in the optimal stabilization problem of smooth finite-dimensional systems.
Lagrangian Navier-Stokes diffusions on manifolds: variational principle and stability
Arnaudon, Marc
2010-01-01
We prove a variational principle for stochastic Lagrangian Navier-Stokes trajectories on manifolds. We study the behaviour of such trajectories concerning stability as well as rotation between particles; the two-dimensional torus case is described in detail.
KAM Type-Theorem for Lower Dimensional Tori in Random Hamiltonian Systems*
LI YONG; XU LU
2011-01-01
In this paper, we study the persistence of lower dimensional tori for random Hamiltonian systems, which shows that majority of the unperturbed tori persist as Cantor fragments of lower dimensional ones under small perturbation. Using this result, we can describe the stability of the non-autonomous dynamic systems.
Three-Dimensional Complex Variables
Martin, E. Dale
1988-01-01
Report presents new theory of analytic functions of three-dimensional complex variables. While three-dimensional system subject to more limitations and more difficult to use than the two-dimensional system, useful in analysis of three-dimensional fluid flows, electrostatic potentials, and other phenomena involving harmonic functions.
Three dimensional dilatonic gravity's rainbow: exact solutions
Hendi, Seyed Hossein; Panahiyan, Shahram
2016-01-01
Deep relations of dark energy scenario and string theory results with dilaton gravity, on one hand, and the connection between quantum gravity with gravity's rainbow, on the other hand, motivate us to consider three dimensional dilatonic black hole solutions in gravity's rainbow. We obtain two classes of the solutions which are polynomial and logarithmic forms. We also calculate conserved and thermodynamic quantities, and examine the first law of thermodynamics for both classes. In addition, we study thermal stability and show that one of the classes is thermally stable while the other one is unstable.
Dynamics of film. [two dimensional continua theory
Zak, M.
1979-01-01
The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.
Scalar perturbations of higher dimensional rotating and ultra-spinning black holes
Cardoso, V; Yoshida, S; Cardoso, Vitor; Siopsis, George; Yoshida, Shijun
2005-01-01
We investigate the stability of higher dimensional rotating black holes against scalar perturbations. In particular, we make a thorough numerical and analytical analysis of six-dimensional black holes, not only in the low rotation regime but in the high rotation regime as well. Our results suggest that higher dimensional Kerr black holes are stable against scalar perturbations, even in the ultra-spinning regime.
Three-Dimensional Waves in Tilt Thermal Boundary Layers
TAO Jian-Jun; YUAN Xiang-Jiang
2009-01-01
We numerically and theoretically study the stabilities of tilt thermal boundary layers immersed in stratified air. An interesting phenomenon is revealed: the stationary longitudinal-roll mode becomes unstable to some oscillating state even when the Grashof number is smaller than its corresponding critical value. By stability analysis, this phenomenon is explained in terms of a new three-dimensional wave mode. The effect of the tilt angle on the stability of the boundary flows is investigated. Since the new three-dimensional wave is found to be the most unstable mode when the title angle is between 30° and 64°, it is expected to play an important role in the transition to turbulence.
王旭; 常素芹; 冯钠; 戚晓霞
2013-01-01
the dimensional stability of BR/SBR/NR foams,and shrinkage ratio drop to 3. 88%,and the utilization ratio of blowing agent could enhance to 31. 67% at most.
Stability of flow over plates with porous suction strips
Reed, H. L.; Nayfeh, A. H.
1981-01-01
This paper addresses the stability of two-dimensional, incompressible boundary-layer flow over plates with suction through porous strips. The mean flow is calculated using linearized triple-deck, closed-form solutions. The stability results of the triple-deck theory are shown to be in good agreement with those of the interacting boundary layers. Then different configurations of number, spacing, and mass flow rate through such porous strips are analyzed and compared with nonsimilar uniform-suction stability results from the point of view of applicability to laminar flow control.
On a new approach to asymptotic stabilization problems
Ivanchikov, A. A.; Kornev, A. A.; Ozeritskii, A. V.
2009-12-01
A numerical algorithm for solving the asymptotic stabilization problem by the initial data to a fixed hyperbolic point with a given rate is proposed and justified. The stabilization problem is reduced to projecting the resolving operator of the given evolution process on a strongly stable manifold. This approach makes it possible to apply the results to a wide class of semidynamical systems including those corresponding to partial differential equations. By way of example, a numerical solution of the problem of the asymptotic stabilization of unstable trajectories of the two-dimensional Chafee-Infante equation in a circular domain by the boundary conditions is given.
Stability index jump for cmc hypersurfaces of spheres
Perdomo, Oscar M
2012-01-01
It is known that the totally umbilical hypersurfaces in the (n+1)-dimensional spheres are characterized as the only hypersurfaces with weak stability index 0. That is, a compact hypersurface with constant mean curvature, cmc, in S^{n+1}, different from an Euclidean sphere, must have stability index greater than or equal to 1. In this paper we prove that the weak stability index of any non-totally umbilical compact hypersurface M\\subset S^{n+1} with cmc cannot take the values 1,2,3... n.
Studies of stability of blade cascade suction surface boundary layer
DONG Xue-zhi; YAN Pei-gang; HAN Wan-jin
2007-01-01
Compressible boundary layers stability on blade cascade suction surface was discussed by wind tunnel experiment and numerical solution. Three dimensional disturbance wave Parabolized Stability Equations(PSE) of orthogonal Curvilinear Coordinates in compressible flow was deducted. The surface pressure of blade in wind tunnel experiment was measured. The Falkner-Skan equation was solved under the boundary conditions of experiment result, and velocity, pressure and temperature of average flow were obtained. Substituted this result for discretization of the PSE Eigenvalue Problem, the stability problem can be solved.
Basic principles of stability.
Egan, William; Schofield, Timothy
2009-11-01
An understanding of the principles of degradation, as well as the statistical tools for measuring product stability, is essential to management of product quality. Key to this is management of vaccine potency. Vaccine shelf life is best managed through determination of a minimum potency release requirement, which helps assure adequate potency throughout expiry. Use of statistical tools such a least squares regression analysis should be employed to model potency decay. The use of such tools provides incentive to properly design vaccine stability studies, while holding stability measurements to specification presents a disincentive for collecting valuable data. The laws of kinetics such as Arrhenius behavior help practitioners design effective accelerated stability programs, which can be utilized to manage stability after a process change. Design of stability studies should be carefully considered, with an eye to minimizing the variability of the stability parameter. In the case of measuring the degradation rate, testing at the beginning and the end of the study improves the precision of this estimate. Additional design considerations such as bracketing and matrixing improve the efficiency of stability evaluation of vaccines.
Visual attention and stability
Mathot, Sebastiaan; Theeuwes, Jan
2011-01-01
In the present review, we address the relationship between attention and visual stability. Even though with each eye, head and body movement the retinal image changes dramatically, we perceive the world as stable and are able to perform visually guided actions. However, visual stability is not as co
Ornithopter flight stabilization
Dietl, John M.; Garcia, Ephrahim
2007-04-01
The quasi-steady aerodynamics model and the vehicle dynamics model of ornithopter flight are explained, and numerical methods are described to capture limit cycle behavior in ornithopter flight. The Floquet method is used to determine stability in forward flight, and a linear discrete-time state-space model is developed. This is used to calculate stabilizing and disturbance-rejecting controllers.
Conformational stability of calreticulin
Jørgensen, C.S.; Trandum, C.; Larsen, N.
2005-01-01
The conformational stability of calreticulin was investigated. Apparent unfolding temperatures (T-m) increased from 31 degrees C at pH 5 to 51 degrees C at pH 9, but electrophoretic analysis revealed that calreticulin oligomerized instead of unfolding. Structural analyses showed that the single C......-terminal a-helix was of major importance to the conformational stability of calreticulin....
Uncontrolled Stability in Freely Flying Insects
Melfi, James, Jr.; Wang, Z. Jane
2015-11-01
One of the key flight modes of a flying insect is longitudinal flight, traveling along a localized two-dimensional plane from one location to another. Past work on this topic has shown that flying insects, unless stabilized by some external stimulus, are typically unstable to a well studied pitching instability. In our work, we examine this instability in a computational study to understand whether it is possible for either evolution or an aero-vehicle designer to stabilize longitudinal flight through changes to insect morphology, kinematics, or aerodynamic quantities. A quasi-steady wingbeat averaged flapping flight model is used to describe the insect. From this model, a number of non-dimensional parameters are identified. The effect of these parameters was then quantified using linear stability analysis, applied to various translational states of the insect. Based on our understanding of these parameters, we demonstrate how to find an intrinsically stable flapping flight sequence for a dragonfly-like flapping flier in an instantaneous flapping flight model.
Circular block matching based video stabilization
Xu, Lidong; Fu, Fangwen; Lin, Xinggang
2005-07-01
Video sequences captured by handheld digital camera need to be stabilized to eliminate the tiresome effects caused by camera"s undesirable shake or jiggle. The key issue of video stabilization is to estimate the global motion parameters between two successive frames. In this paper, a novel circular block matching algorithm is proposed to estimate the global motion parameters. This algorithm can deal with not only translational motion but even large rotational motion. For an appointed circular block in current frame, a four-dimensional rotation invariant feature vector is firstly extracted from it and used to judge if it is an effective block. Then the rotation invariant features based circular block matching process is performed to find the best matching blocks in reference frame for those effective blocks. With the matching results of any two effective blocks, a two-dimensional motion model is constructed to produce one group of frame motion parameters. A statistical method is proposed to calculate the estimated global motion parameters with all groups of global motion parameters. Finally, using the estimated motion parameters as the initial values, an iteration algorithm is introduced to obtain the refined global motion parameters. The experimental results show that the proposed algorithm is excellent in stabilizing frames with even burst global translational and rotational motions.
Bruce, Duncan W; O'Hare, Dermot
2010-01-01
With physical properties that often may not be described by the transposition of physical laws from 3D space across to 2D or even 1D space, low-dimensional solids exhibit a high degree of anisotropy in the spatial distribution of their chemical bonds. This means that they can demonstrate new phenomena such as charge-density waves and can display nanoparticulate (0D), fibrous (1D) and lamellar (2D) morphologies. Low-Dimensional Solids presents some of the most recent research into the synthesis and properties of these solids and covers: Metal Oxide Nanoparticles; Inorganic Nanotubes and Nanowir
Dimensional Metrology for Microtechnology
Bariani, Paolo
2005-01-01
of the (large) CMM positioning errors. A geometrical (three dimensional) model, for the Large range AFM was produced and calibration issues discussed following the three dimensional approach. Furthermore, a novel measuring procedure, based on two images, for eliminating the effects of vertical drift...... of one percent, with this instrument. Uncertainty is dominated by residual non linearity after off line correction. SEM based stereo-photogrammetry was also studied. A commercially available software package was purchased. The working hypothesis for the package in use was eucentric tilting. This is only...
Three-dimensional photovoltaics
Myers, Bryan; Bernardi, Marco; Grossman, Jeffrey C.
2010-03-01
The concept of three-dimensional (3D) photovoltaics is explored computationally using a genetic algorithm to optimize the energy production in a day for arbitrarily shaped 3D solar cells confined to a given area footprint and total volume. Our simulations demonstrate that the performance of 3D photovoltaic structures scales linearly with height, leading to volumetric energy conversion, and provides power fairly evenly throughout the day. Furthermore, we show that optimal 3D shapes are not simple box-like shapes, and that design attributes such as reflectivity can be optimized in new ways using three-dimensionality.
Stabilizing Randomly Switched Systems
Chatterjee, Debasish
2008-01-01
This article is concerned with stability analysis and stabilization of randomly switched systems under a class of switching signals. The switching signal is modeled as a jump stochastic (not necessarily Markovian) process independent of the system state; it selects, at each instant of time, the active subsystem from a family of systems. Sufficient conditions for stochastic stability (almost sure, in the mean, and in probability) of the switched system are established when the subsystems do not possess control inputs, and not every subsystem is required to be stable. These conditions are employed to design stabilizing feedback controllers when the subsystems are affine in control. The analysis is carried out with the aid of multiple Lyapunov-like functions, and the analysis results together with universal formulae for feedback stabilization of nonlinear systems constitute our primary tools for control design
The statistical stability phenomenon
Gorban, Igor I
2017-01-01
This monograph investigates violations of statistical stability of physical events, variables, and processes and develops a new physical-mathematical theory taking into consideration such violations – the theory of hyper-random phenomena. There are five parts. The first describes the phenomenon of statistical stability and its features, and develops methods for detecting violations of statistical stability, in particular when data is limited. The second part presents several examples of real processes of different physical nature and demonstrates the violation of statistical stability over broad observation intervals. The third part outlines the mathematical foundations of the theory of hyper-random phenomena, while the fourth develops the foundations of the mathematical analysis of divergent and many-valued functions. The fifth part contains theoretical and experimental studies of statistical laws where there is violation of statistical stability. The monograph should be of particular interest to engineers...
Khare, Avinash; Samuelsen, Mogens R; Saxena, Avadh; 10.1088/1751-8113/43/37/375209
2010-01-01
We show that the two-dimensional, nonlinear Schr\\"odinger lattice with a saturable nonlinearity admits periodic and pulse-like exact solutions. We establish the general formalism for the stability considerations of these solutions and give examples of stability diagrams. Finally, we show that the effective Peierls-Nabarro barrier for the pulse-like soliton solution is zero.
Interferometric system for PM-level stability characterization
Verlaan, A.L.; Ellis, J.D.; Voigt, D.; Spronck, J.W.; Munnig Schmidt, R.H.
2010-01-01
We present a double sided, single pass Michelson heterodyne interferometer for dimensional stability measurements. In preliminary measurements, the double deadpath configuration (no sample) showed better than ±1.5 nm (2/) over 13 hours. A 30 mm stainless gauge block was then measured with a stabilit
Breakwater stability with damaged single layer armour units
De Rover, R.; Verhagen, H.J.; Van den Berge, A.; Reedijk, B.
2008-01-01
The effect of single layer interlocking armour unit breakage on the hydraulic armour layer stability and potential damage progression is addressed in this paper. A 2-dimensional scale model of a rubble mound breakwater with an armour layer consisting of Xbloc armour units was tested. The residual
QUANTITATIVE METHODOLOGY FOR STABILITY ANALYSIS OF NONLINEAR ROTOR SYSTEMS
ZHENG Hui-ping; XUE Yu-sheng; CHEN Yu-shu
2005-01-01
Rotor-bearings systems applied widely in industry are nonlinear dynamic systems of multi-degree-of-freedom. Modem concepts on design and maintenance call for quantitative stability analysis. Using trajectory based stability-preserving and dimensional-reduction, a quanttative stability analysis method for rotor systems is presented. At first, an n-dimensional nonlinear non-autonomous rotor system is decoupled into n subsystems after numerical integration. Each of them has only onedegree-of-freedom and contains time-varying parameters to represent all other state variables. In this way, n-dimensional trajectory is mapped into a set of one-dimensional trajectories. Dynamic central point (DCP) of a subsystem is then defined on the extended phase plane, namely, force-position plane. Characteristics of curves on the extended phase plane and the DCP's kinetic energy difference sequence for general motion in rotor systems are studied. The corresponding stability margins of trajectory are evaluated quantitatively. By means of the margin and its sensitivity analysis, the critical parameters of the period doubling bifurcation and the Hopf bifurcation in a flexible rotor supported by two short journal beatings with nonlinear suspensionare are determined.
Vacuum stability of asymptotically safe gauge-Yukawa theories
Litim, Daniel F.; Mojaza, Matin; Sannino, Francesco
2016-01-01
We study the phase diagram and the stability of the ground state for certain four-dimensional gauge-Yukawa theories whose high-energy behaviour is controlled by an interacting fixed point. We also provide analytical and numerical results for running couplings, their crossover scales, the separatrix...
Dimensionality Reduction Mappings
Bunte, Kerstin; Biehl, Michael; Hammer, Barbara
2011-01-01
A wealth of powerful dimensionality reduction methods has been established which can be used for data visualization and preprocessing. These are accompanied by formal evaluation schemes, which allow a quantitative evaluation along general principles and which even lead to further visualization schem
Larsen, Mihail
De fire dimensioner er en humanistisk håndbog beregnet især på studerende og vejledere inden for humaniora, men kan også læses af andre med interesse for, hvad humanistisk forskning er og kan. Den er blevet til over et langt livs engageret forskning, uddannelse og formidling på Roskilde Universitet...... og udgør på den måde også et bidrag til universitetets historie, som jeg var med til at grundlægge. De fire dimensioner sætter mennesket i centrum. Men det er et centrum, der peger ud over sig selv; et centrum, hvorfra verden anskues, erfares og forstås. Alle mennesker har en forhistorie og en...... fremtid, og udstrakt mellem disse punkter i tiden tænker og handler de i rummet. Den menneskelige tilværelse omfatter alle fire dimensioner. De fire dimensioner udgør derfor også et forsvar for en almen dannelse, der gennemtrænger og kommer kulturelt til udtryk i vores historie, viden, praksis og kunst....
Larsen, Mihail
De fire dimensioner er en humanistisk håndbog beregnet især på studerende og vejledere inden for humaniora, men kan også læses af andre med interesse for, hvad humanistisk forskning er og kan. Den er blevet til over et langt livs engageret forskning, uddannelse og formidling på Roskilde Universitet...... og udgør på den måde også et bidrag til universitetets historie, som jeg var med til at grundlægge. De fire dimensioner sætter mennesket i centrum. Men det er et centrum, der peger ud over sig selv; et centrum, hvorfra verden anskues, erfares og forstås. Alle mennesker har en forhistorie og en...... fremtid, og udstrakt mellem disse punkter i tiden tænker og handler de i rummet. Den menneskelige tilværelse omfatter alle fire dimensioner. De fire dimensioner udgør derfor også et forsvar for en almen dannelse, der gennemtrænger og kommer kulturelt til udtryk i vores historie, viden, praksis og kunst....
A Numerical Solution of the Two-Dimensional Fusion Problem with Convective Boundary Conditions
Gülkaç, Vildan
2010-01-01
In this paper, we present an LOD method for solving the two-dimensional fusion problem with convective boundary conditions. In this study, we extend our earlier work [1] on the solution of the two-dimensional fusion problem by considering a class of time-split finite-difference methods, namely locally one-dimensional (LOD) schemes. In addition, following the idea of Douglas [2, 3], a Douglas-like splitting scheme is presented. A stability analysis by Fourier series method (von Neumann stability) of the scheme is also investigated. Computational results obtained by the present method are in excellent agreement with the results reported previously by other research.
Three-Dimensional Dynamical Instabilities in Galactic Ionization Fronts
Whalen, D J; Whalen, Daniel J.; Norman, Michael L.
2007-01-01
Ionization front instabilities have long been of interest for their suspected role in a variety of phenomena in the galaxy, from the formation of bright rims and 'elephant trunks' in nebulae to triggered star formation in molecular clouds. Numerical treatments of these instabilities have historically been limited in both dimensionality and input physics, leaving important questions about their true evolution unanswered. We present the first three-dimensional radiation hydrodynamical calculations of both R-type and D-type ionization front instabilities in galactic environments (i.e., solar metallicity gas). Consistent with linear stability analyses of planar D-type fronts, our models exhibit many short-wavelength perturbations growing at early times that later evolve into fewer large-wavelength structures. The simulations demonstrate that both self-consistent radiative transfer and three-dimensional flow introduce significant morphological differences to unstable modes when compared to earlier two-dimensional ...
Spatiotemporal dissipative solitons in two-dimensional photonic lattices.
Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S
2008-11-01
We analyze spatiotemporal dissipative solitons in two-dimensional photonic lattices in the presence of gain and loss. In the framework of the continuous-discrete cubic-quintic Ginzburg-Landau model, we demonstrate the existence of novel classes of two-dimensional spatiotemporal dissipative lattice solitons, which also include surface solitons located in the corners or at the edges of the truncated two-dimensional photonic lattice. We find the domains of existence and stability of such spatiotemporal dissipative solitons in the relevant parameter space, for both on-site and intersite lattice solitons. We show that the on-site solitons are stable in the whole domain of their existence, whereas most of the intersite solitons are unstable. We describe the scenarios of the instability-induced dynamics of dissipative solitons in two-dimensional lattices.
Boundary control design for extensible marine risers in three dimensional space
Do, K. D.
2017-02-01
A design of boundary controllers is proposed for (practical) exponential stabilization of extensible marine risers in three-dimensional (3D) space under sea loads. The design removes flaws in existing works. Two Lyapunov-type theorems are developed for study of existence and uniqueness, and stability of nonlinear evolution systems in Hilbert space. These theorems have their potential use in control design and stability analysis for flexible systems including marine risers.
Stability analysis of ferrofluids
Katharina Duda
2015-09-01
Full Text Available Superparamagnetic iron oxides (SPIOs are used as tracer for the new imaging technique Magnetic Particle Imaging. The stability of ferrofluids for medical application has a great importance, in addition to the particle size. The shell material, which protects the iron core prior from agglomeration and sedimentation, can be degraded by various processes. Another important aspect of stability is the constant performance of magnetisation. Therefore, the measurement of the magnetisation of the particles must be controlled in order to ensure the stability of the samples.
Radnofsky, M. I.; Barnett, J. H., Jr.; Harrison, F. L.; Marak, R. J. (Inventor)
1973-01-01
An improved life raft stabilizer for reducing rocking and substantially precluding capsizing is discussed. The stabilizer may be removably attached to the raft and is defined by flexible side walls which extend a considerable depth downwardly to one another in the water. The side walls, in conjunction with the floor of the raft, form a ballast enclosure. A weight is placed in the bottom of the enclosure and water port means are provided in the walls. Placement of the stabilizer in the water allows the weighted bottom to sink, producing submerged deployment thereof and permitting water to enter the enclosure through the port means, thus forming a ballast for the raft.
Viscous, resistive magnetohydrodynamic stability computed by spectral techniques.
Dahlburg, R B; Zang, T A; Montgomery, D; Hussaini, M Y
1983-09-01
Expansions in Chebyshev polynomials are used to study the linear stability of one-dimensional magnetohydrodynamic quasiequilibria, in the presence of finite resistivity and viscosity. The method is modeled on the one used by Orszag in accurate computation of solutions of the Orr-Sommerfeld equation. Two Reynolds-like numbers involving Alfvén speeds, length scales, kinematic viscosity, and magnetic diffusivity govern the stability boundaries, which are determined by the geometric mean of the two Reynolds-like numbers. Marginal stability curves, growth rates versus Reynolds-like numbers, and growth rates versus parallel wave numbers are exhibited. A numerical result that appears general is that instability has been found to be associated with inflection points in the current profile, though no general analytical proof has emerged. It is possible that nonlinear subcritical three-dimensional instabilities may exist, similar to those in Poiseuille and Couette flow.
Viscous, resistive MHD stability computed by spectral techniques
Dahlburg, R. B.; Zang, T. A.; Montgomery, D.; Hussaini, M. Y.
1983-01-01
Expansions in Chebyshev polynomials are used to study the linear stability of one dimensional magnetohydrodynamic (MHD) quasi-equilibria, in the presence of finite resistivity and viscosity. The method is modeled on the one used by Orszag in accurate computation of solutions of the Orr-Sommerfeld equation. Two Reynolds like numbers involving Alfven speeds, length scales, kinematic viscosity, and magnetic diffusivity govern the stability boundaries, which are determined by the geometric mean of the two Reynolds like numbers. Marginal stability curves, growth rates versus Reynolds like numbers, and growth rates versus parallel wave numbers are exhibited. A numerical result which appears general is that instability was found to be associated with inflection points in the current profile, though no general analytical proof has emerged. It is possible that nonlinear subcritical three dimensional instabilities may exist, similar to those in Poiseuille and Couette flow.
Viscous, resistive magnetohydrodynamic stability computed by spectral techniques
Dahlburg, R. B.; Zang, T. A.; Montgomery, D.; Hussaini, M. Y.
1983-01-01
Expansions in Chebyshev polynomials are used to study the linear stability of one-dimensional magnetohydrodynamic quasi-equilibria, in the presence of finite resistivity and viscosity. The method is modeled on the one used by Orszag in accurate computation of solutions of the Orr-Sommerfeld equation. Two Reynolds-like numbers involving Alfven speeds, length scales, kinematic viscosity, and magnetic diffusivity govern the stability boundaries, which are determined by the geometric mean of the two Reynolds-like numbers. Marginal stability curves, growth rates versus Reynolds-like numbers, and growth rates versus parallel wave numbers are exhibited. A numerical result that appears general is that instability has been found to be associated with inflection points in the current profile, though no general analytical proof has emerged. It is possible that nonlinear subcritical three-dimensional instabilities may exist, similar to those in Poiseuille and Couette flow.
Liang, Xiao; Wang, Linshan; Wang, Yangfan; Wang, Ruili
2016-09-01
In this paper, we focus on the long time behavior of the mild solution to delayed reaction-diffusion Hopfield neural networks (DRDHNNs) driven by infinite dimensional Wiener processes. We analyze the existence, uniqueness, and stability of this system under the local Lipschitz function by constructing an appropriate Lyapunov-Krasovskii function and utilizing the semigroup theory. Some easy-to-test criteria affecting the well-posedness and stability of the networks, such as infinite dimensional noise and diffusion effect, are obtained. The criteria can be used as theoretic guidance to stabilize DRDHNNs in practical applications when infinite dimensional noise is taken into consideration. Meanwhile, considering the fact that the standard Brownian motion is a special case of infinite dimensional Wiener process, we undertake an analysis of the local Lipschitz condition, which has a wider range than the global Lipschitz condition. Two samples are given to examine the availability of the results in this paper. Simulations are also given using the MATLAB.
Stability of compressible reacting mixing layer
Shin, D. S.; Ferziger, J. H.
1991-01-01
Linear instability of compressible reacting mixing layers is analyzed with emphasis on the effects of heat release and compressibility. Laminar solutions of the compressible boundary-layer equations are used as the base flows. The parameters of this study are the adiabatic flame temperature, the Mach number of the upper stream, frequency, wavenumber, and the direction of propagation of the disturbance wave. Stability characteristics of the flow are presented. Three groups of unstable modes are found when the Mach number and/or heat release are large. Finally, it is shown that the unstable modes are two-dimensional for large heat release even in highly compressible flow.
Seismic Stability of Reinforced Soil Slopes
Tzavara, I.; Zania, Varvara; Tsompanakis, Y.
2012-01-01
Over recent decades increased research interest has been observed on the dynamic response and stability issues of earth walls and reinforced soil structures. The current study aims to provide an insight into the dynamic response of reinforced soil structures and the potential of the geosynthetics...... to prevent the development of slope instability taking advantage of their reinforcing effect. For this purpose, a onedimensional (SDOF) model, based on Newmark’s sliding block model as well as a two-dimensional (plane-strain) dynamic finite-element analyses are conducted in order to investigate the impact...
On the topological stability of magnetostatic equilibria
Tsinganos, K. C.; Rosner, R.; Distler, J.
1984-01-01
The topological stability of MHD equilibria is investigated by exploring the formal analogy, in the ideal MHD limit, between the topology of magnetic lines of force in coordinate space and the topology of integral surfaces of one- and two-dimensional Hamiltonian systems in phase space. It is demonstrated that in an astrophysical setting, symmetric magnetostatic equilibria satisfying the ideal MHD equations are exceptional. The principal result of the study is that previous infinitesimal perturbation theory calculations can be generalized to include finite-amplitude and symmetry-breaking effects. The effect of the ergodicity of perturbed symmetric equilibria on heat dispersal in magnetically dominated plasmas is discussed.
Distributional Methods for a Class of Functional Equations and Their Stabilities
Jae Young CHUNG
2007-01-01
We consider a class of n-dimensional Pompeiu equations and that of Pexider equations and their Hyers-Ulam stability problems in the spaces of Schwartz distributions. First, reducing the given distribution version of functional equations to differential equations we find their solutions. Secondly,using approximate identities we prove the Hyers-Ulam stability of the equations.
Stability analysis of a class of fractional order nonlinear systems with order lying in (0, 2).
Zhang, Ruoxun; Tian, Gang; Yang, Shiping; Cao, Hefei
2015-05-01
This paper investigates the stability of n-dimensional fractional order nonlinear systems with commensurate order 0 nonlinear systems with order lying in (0, 2). According to this theory, stabilizing a class of fractional order nonlinear systems only need a linear state feedback controller. Simulation results demonstrate the effectiveness of the proposed theory.
Stability of Difference Schemes for Fractional Parabolic PDE with the Dirichlet-Neumann Conditions
Zafer Cakir
2012-01-01
boundary conditions are presented. Stability estimates and almost coercive stability estimates with ln (1/(+|ℎ| for the solution of these difference schemes are obtained. A procedure of modified Gauss elimination method is used for solving these difference schemes of one-dimensional fractional parabolic partial differential equations.
STABILITY AND BIFURCATION OF A HUMAN RESPIRATORY SYSTEM MODEL WITH TIME DELAY
沈启宏; 魏俊杰
2004-01-01
The stability and bifurcation of the trivial solution in the two-dimensional differential equation of a model describing human respiratory system with time delay were investigated. Formulas about the stability of bifurcating periodic solution and the direction of Hopf bifurcation were exhibited by applying the normal form theory and the center manifold theorem. Furthermore, numerical simulation was carried out.
Brane Gases and Stabilization of Shape Moduli with Momentum and Winding Stress
Kaya, A
2005-01-01
In a toy model with gases of membranes and strings wrapping over a two-dimensional internal torus, we study the stabilization problem for the shape modulus. It is observed that winding modes of partially wrapped strings and momentum modes give rise to stress in the energy momentum tensor. We show that this stress dynamically stabilizes the shape modulus of the two torus.
Stabilization and shape control of a 1D piezoelectric Timoshenko beam
Voss, T.; Scherpen, J. M. A.
2011-01-01
In this paper we show how to perform stabilization and shape control for a finite dimensional model that recasts the dynamics of an inflatable space reflector in port-Hamiltonian (pH) form. We show how to derive a decentralized passivity-based controller which can be used to stabilize a 1D piezoelec
Asymptotic Linear Stability of Solitary Water Waves
Pego, Robert L.; Sun, Shu-Ming
2016-12-01
We prove an asymptotic stability result for the water wave equations linearized around small solitary waves. The equations we consider govern irrotational flow of a fluid with constant density bounded below by a rigid horizontal bottom and above by a free surface under the influence of gravity neglecting surface tension. For sufficiently small amplitude waves, with waveform well-approximated by the well-known sech-squared shape of the KdV soliton, solutions of the linearized equations decay at an exponential rate in an energy norm with exponential weight translated with the wave profile. This holds for all solutions with no component in (that is, symplectically orthogonal to) the two-dimensional neutral-mode space arising from infinitesimal translational and wave-speed variation of solitary waves. We also obtain spectral stability in an unweighted energy norm.
Stability in dynamical systems I
Courant, E.D.; Ruth, R.D.; Weng, W.T.
1984-08-01
We have reviewed some of the basic techniques which can be used to analyze stability in nonlinear dynamical systems, particularly in circular particle accelerators. We have concentrated on one-dimensional systems in the examples in order to simply illustrate the general techniques. We began with a review of Hamiltonian dynamics and canonical transformations. We then reviewed linear equations with periodic coefficients using the basic techniques from accelerator theory. To handle nonlinear terms we developed a canonical perturbation theory. From this we calculated invariants and the amplitude dependence of the frequency. This led us to resonances. We studied the cubic resonance in detail by using a rotating coordinate system in phase space. We then considered a general isolated nonlinear resonance. In this case we calculated the width of the resonance and estimated the spacing of resonances in order to use the Chirikov criterion to restrict the validity of the analysis. Finally the resonance equation was reduced to the pendulum equation, and we examined the motion on a separatrix. This brought us to the beginnings of stochastic behavior in the neighborhood of the separatrix. It is this complex behavior in the neighborhood of the separatrix which causes the perturbation theory used here to diverge in many cases. In spite of this the methods developed here have been and are used quite successfully to study nonlinear effects in nearly integrable systems. When used with caution and in conjunction with numerical work they give tremendous insight into the nature of the phase space structure and the stability of nonlinear differential equations. 14 references.
Dimensional characteristics of low-dimensional structures
Blood, Peter
2000-07-01
The purpose of this paper is to examine the dimensional aspects of the optical properties of quantum well and dot systems, without assuming that the carriers are localized to the geometrical extent of the confining potential. We show that optical absorption normal to the plane of a well cannot be expressed as an absorption coefficient but should be specified as a fraction of light transmitted or absorbed per well. The modal gain for light propagating along the plane of a well does not scale with well width and the variation of the material gain inversely proportional to the well width is a consequence of the definition of the confinement factor and has no independent physical significance. Optical absorption by quantum dots should be expressed as a cross section per dot. The radiative recombination rate is correctly expressed in terms of a 2D recombination coefficient and use of an equivalent 3D coefficient introduces an artificial dependence on well width which can lead to errors in the comparison of quantum well systems.
Thermodynamic Stability of Wormholes
Sajadi, S N
2016-01-01
In the context of GR, we study the thermodynamic stability of evolving Lorentzian wormholes at the apparent horizon. The average pressure of the anisotrropic components is considered as the pressure of the wormhole. According to the requirements of stable equilibrium in conventional thermodynamics, we calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of the wormhole.
Tetraphenylborate Solids Stability Tests
Walker, D.D. [Westinghouse Savannah River Company, AIKEN, SC (United States)
1997-06-25
Tetraphenylborate solids are a potentially large source of benzene in the slurries produced in the In-Tank Precipitation (ITP) process. The stability of the solids is an important consideration in the safety analysis of the process and we desire an understanding of the factors that influence the rate of conversion of the solids to benzene. This report discusses current testing of the stability of tetraphenylborate solids.
Food Fortification Stability Study
Sirmons, T. A.; Cooper, M. R.; Douglas, G. L.
2017-01-01
This study aimed to assess the stability of vitamin content, sensory acceptability and color variation in fortified spaceflight foods over a period of two years. Findings will help to identify optimal formulation, processing, and storage conditions to maintain stability and acceptability of commercially available fortification nutrients. Changes in food quality were monitored to indicate whether fortification affects quality over time (compared to the unfortified control), thus indicating their potential for use on long-duration missions.
Shearing stability of lubricants
Shiba, Y.; Gijyutsu, G.
1984-01-01
Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.
Shearing stability of lubricants
Shiba, Y.; Gijyutsu, G.
1984-03-01
Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.
Aftanas, B.L.
1996-04-30
This Functional Design Criteria (FDC) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage.
Narcis Eduard Mitu
2013-11-01
Full Text Available Policies or institutions (built into an economic system that automatically tend to dampen economic cycle fluctuations in income, employment, etc., without direct government intervention. For example, in boom times, progressive income tax automatically reduces money supply as incomes and spendings rise. Similarly, in recessionary times, payment of unemployment benefits injects more money in the system and stimulates demand. Also called automatic stabilizers or built-in stabilizers.
METHOD FOR STABILIZING KLYSTRONS
Magnuson, D.W.; Smith, D.F.
1959-04-14
High-frequency oscillators for the generation of microwaves, particularly a system for stabilizing frequency-modulated klystron oscillators of the reflex type, are described. The system takos advantage of the fact that a change in oscillator frequency will alter the normal phase displacement between the cavity and its modulator, creating an error voltage which is utilized to regulate the frequency of the oscillator and stabilize it.
Food Fortification Stability Study
Sirmons, T. A.; Cooper, M. R.; Douglas, G. L.
2016-01-01
This study aims to assess the stability of vitamin content, sensory acceptability and color variation in fortified spaceflight foods over a period of 2 years. Findings will identify optimal formulation, processing, and storage conditions to maintain stability and acceptability of commercially available fortification nutrients. Changes in food quality are being monitored to indicate whether fortification affects quality over time (compared to the unfortified control), thus indicating their potential for use on long-duration missions.
Two-dimensional optical spectroscopy
Cho, Minhaeng
2009-01-01
Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.
Dimensionally regulated pentagon integrals
Bern, Z; Kosower, D A
1994-01-01
We present methods for evaluating the Feynman parameter integrals associated with the pentagon diagram in 4-2 epsilon dimensions, along with explicit results for the integrals with all masses vanishing or with one non-vanishing external mass. The scalar pentagon integral can be expressed as a linear combination of box integrals, up to O(epsilon) corrections, a result which is the dimensionally-regulated version of a D=4 result of Melrose, and of van Neerven and Vermaseren. We obtain and solve differential equations for various dimensionally-regulated box integrals with massless internal lines, which appear in one-loop n-point calculations in QCD. We give a procedure for constructing the tensor pentagon integrals needed in gauge theory, again through O(epsilon^0).
Dimensional Metrology for Microtechnology
Bariani, Paolo
2005-01-01
This ph. D. project was aimed at developing and validating techniques for dimensional metrology of: miniaturized items, microsystem components, and surfaces. In particular the study was focused on techniques based on: AFM-CMM integration and Scanning Electron Microscopy (SEM). Development...... was proposed and the principle demonstrated on software gauges. Simulations of Surface Mapping were done, based on the model developed. Direct performance verification of the Large Range AFM was eventually carried out, and lateral metrology was possible, in the millimeter range, with accuracy in the order...... at high magnifications was, proposed and this has resulted into a patent application. The final part of the thesis is devoted to applications of dimensional metrology to case studies. Three applications are presented, two of them are investigations of surface metrology, while the third is about extraction...
Kerstein, A.R. [Sandia National Lab., Livermore, CA (United States)
1996-12-31
One-Dimensional Turbulence is a new turbulence modeling strategy involving an unsteady simulation implemented in one spatial dimension. In one dimension, fine scale viscous and molecular-diffusive processes can be resolved affordably in simulations at high turbulence intensity. The mechanistic distinction between advective and molecular processes is thereby preserved, in contrast to turbulence models presently employed. A stochastic process consisting of mapping {open_quote}events{close_quote} applied to a one-dimensional velocity profile represents turbulent advection. The local event rate for given eddy size is proportional to the velocity difference across the eddy. These properties cause an imposed shear to induce an eddy cascade analogous in many respects to the eddy cascade in turbulent flow. Many scaling and fluctuation properties of self-preserving flows, and of passive scalars introduced into these flows, are reproduced.
Dimensional analysis for engineers
Simon, Volker; Gomaa, Hassan
2017-01-01
This monograph provides the fundamentals of dimensional analysis and illustrates the method by numerous examples for a wide spectrum of applications in engineering. The book covers thoroughly the fundamental definitions and the Buckingham theorem, as well as the choice of the system of basic units. The authors also include a presentation of model theory and similarity solutions. The target audience primarily comprises researchers and practitioners but the book may also be suitable as a textbook at university level.
Stability of Linear Stochastic Differential Equations with Respect to Fractional Brownian Motion
SHU Hui-sheng; CHEN Chun-li; WEI Guo-liang
2009-01-01
This paper is concerned with the stochastically stability for the m -dimensional linear stochastic differential equations with respect to fractional Brownian motion (FBM) with Hurst parameter H∈ (1/2, 1). On the basis of the pioneering work of Duncan and Hu, a Ito's formula is given.An improved derivative operator to Lyapunov functions is constructed, and the sufficient conditions for the stochastically stability of linear stochastic differential equations driven by FBM are established. These extend the stochastic Lyapunov stability theories.
3 - Dimensional Body Measurement Technology
ZHOU Xu-dong; LI Yan-mei
2002-01-01
3 - dimensional body measurement technology, the basis of developing high technology in industry, accelerates digital development of aplparel industry. This paper briefly introduces the history of 3 - dimensional body measurement technology, and recounts the principle and primary structure of some types of 3 - dimensional automatic body measurement system. With this understanding, it discusses prospect of 3- dimensional CAD and virtual technology used in apparel industry.
Friederike Helm
2016-05-01
Full Text Available Dimensional comparison theory (DCT defines dimensional comparisons as intraindividual comparisons that a person draws between his or her own achievements in two domains or subjects. DCT assumes that dimensional comparisons influence students’ academic self-concepts, causing stronger self-concept differences between subjects perceived as dissimilar, such as math and English, than between subjects perceived as more similar, like math and physics. However, there have been no experimental studies testing the causal effect of perceived subject similarity on domain-specific self-concepts. In the present research, three experimental studies analyzed the effects of experimentally induced higher or lower perceived subject similarity on academic self-concept differences: Study 1 (N = 351, with math and German; Study 2a (N = 148, with math and physics; and Study 2b (N = 161, with English and German, show that, in line with expectations, induced lower perceived subject similarity led to stronger self-concept differences than did higher perceived similarity. Some implications of the results for DCT are discussed.
齐洁; 汪定伟
2005-01-01
A class of map in which chaotic synchronization can occur is defined. The transverse Lyapunov exponents are used to determine the stability of synchronized trajectories. Some complex phenomena closely related to chaotic synchronization, namely riddled basin, riddling bifurcation and blowout bifurcation are theoretically analyzed. Riddling bifurcation and blowout bifurcation may change the synchronization stability of the system. And two types of riddled basins, i.e., global riddled basin and local riddled basin, may come into being after riddling bifurcation. An advertising competing model based on Vidale-Wolfe model is proposed and analyzed by the above theories at the end of the paper.
Strongly Zero-Dimensional Locales
KOU Hui; LUO Mao Kang
2002-01-01
New kinds of strongly zero-dimensional locales are introduced and characterized, whichare different from Johnstone's, and almost all the topological properties for strongly zero-dimensionalspaces have the pointless localic forms. Particularly, the Stone-Cech compactification of a stronglyzero-dimensional locale is stongly zero-dimensional.
One-Dimensionality and Whiteness
Calderon, Dolores
2006-01-01
This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…
One-Dimensionality and Whiteness
Calderon, Dolores
2006-01-01
This article is a theoretical discussion that links Marcuse's concept of one-dimensional society and the Great Refusal with critical race theory in order to achieve a more robust interrogation of whiteness. The author argues that in the context of the United States, the one-dimensionality that Marcuse condemns in "One-Dimensional Man" is best…
The stability of protoplanet systems
Yoshinaga, K; Makino, J
1999-01-01
The authors investigated the stability of 10 protoplanet systems using three-dimensional N-body simulations. They found that the time scale of instability T depends strongly on the initial random velocities nu (eccentricities e and inclinations i) and orbital separations Delta a. For zero initial random velocities, they confirmed the result of Chambers et al. (1996, Icarus 119, 261-268) that T is proportional to exp( Delta a). For finite random velocities, they found that T depends strongly on the initial random velocities. The relation between T and Delta a is still expressed as log T=b+c Delta a. However, both b and c depend on initial random velocities and the slope, b, becomes smaller for larger nu . Even for relatively small initial eccentricities such as e~2r/sub H//a, where r/sub H/ is the Hill radius, the time scale can be reduced by a factor of 10 compared with the case of the zero random velocity. Therefore, the time scale of the formation of inner planets might be much shorter than what implied by ...
A class of auxetic three-dimensional lattices
Cabras, Luigi
2015-01-01
We propose a class of auxetic three-dimensional lattice structures. The elastic microstructure can be designed in order to have omni-directional Poisson's ratio arbitrarily close to the stability limit -1. The cubic behavior of the periodic system has been fully characterized; the minumum and maximum Poisson's ratio and the associated principal directions are given as a function of the microstructural parameters. The initial microstructure is then modified into a body centered-cubic system that can achieve a Poisson's ratio lower than -1 and that can also behave as an isotropic three-dimensional auxetic structure.
Drift modes of a quasi-two-dimensional current sheet
Artemyev, A. V.; Malova, Kh. V.; Popov, V. Yu.; Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2012-03-15
Stability of a plasma configuration consisting of a thin one-dimensional current sheet embedded into a two-dimensional background current sheet is studied. Drift modes developing in plasma as unstable waves along the current direction are considered. Dispersion relations for kink and sausage perturbation modes are obtained depending on the ratio of parameters of thin and background current sheets. It is shown that the existence of the background sheet results in a decrease in the instability growth rates and a significant increase in the perturbation wavelengths. The role of drift modes in the excitation of oscillations observed in the current sheet of the Earth's magnetotail is discussed.
Measurements of dimensional accuracy using linear and scanning profile techniques.
Harrison, A; Huggett, R; Zissis, A
1992-01-01
Various measurement methods have been described for the determination of dimensional accuracy and stability of denture base materials. This investigation introduces a computerised coordinate measuring machine (CCMM) and compares it with two methods routinely used for assessment of the accuracy of fit of denture base materials. The results demonstrate that the three methods (digital calipers, optical comparator, and CCMM) are acceptable for linear measurement. The CCMM was also used in its scanning mode to define and to quantify the contour changes of the resin bases. The advantages of the CCMM become apparent when two-dimensional changes require assessment.
On the Physical Problem of Spatial Dimensions: An Alternative Procedure to Stability Arguments
Caruso, Francisco
2012-01-01
Why is space 3-dimensional? The first answer to this question, entirely based on Physics, was given by Ehrenfest, in 1917, who showed that the stability requirement for $n$-dimensional two-body planetary system very strongly constrains space dimensionality, favoring 3-d. This kind of approach will be generically called "stability postulate" throughout this paper and was shown by Tangherlini, in 1963, to be still valid in the framework of general relativity as well as for quantum mechanical hydrogen atom, giving the same constraint for space-dimensionality. In the present work, before criticizing this methodology, a brief discussion has been introduced, aimed at stressing and clarifying some general physical aspects of the problem of how to determine the number of space dimensions. Then, the epistemological consequences of Ehrenfest's methodology are critically reviewed. An alternative procedure to get at the proper number of dimensions, in which the stability postulate (and the implicit singularities in three...
Three-Dimensional Model Test Study of a CUBIPOD Armoured Roundhead
Burcharth, Hans F.; Andersen, Thomas Lykke; Aldama, J. M. Urrutia
The present report presents results from a three‐dimensional model test study carried out at Aalborg University in the period September 2008 - December 2008. The model tests were carried out to study the stability of a CUBIPOD armoured roundhead under short‐crested wave attack. Few long‐crested w......The present report presents results from a three‐dimensional model test study carried out at Aalborg University in the period September 2008 - December 2008. The model tests were carried out to study the stability of a CUBIPOD armoured roundhead under short‐crested wave attack. Few long......‐crested wave tests were performed as well. One objective of the tests was to compare the stability of CUBIPOD armoured roundheads to the stability of cube armoured roundheads. This could be done by choosing a model test setup identical to that previous used in a study of the stability of a cube armoured...
Three-dimensional ultrasound scanning.
Fenster, Aaron; Parraga, Grace; Bax, Jeff
2011-08-06
The past two decades have witnessed developments of new imaging techniques that provide three-dimensional images about the interior of the human body in a manner never before available. Ultrasound (US) imaging is an important cost-effective technique used routinely in the management of a number of diseases. However, two-dimensional viewing of three-dimensional anatomy, using conventional two-dimensional US, limits our ability to quantify and visualize the anatomy and guide therapy, because multiple two-dimensional images must be integrated mentally. This practice is inefficient, and may lead to variability and incorrect diagnoses. Investigators and companies have addressed these limitations by developing three-dimensional US techniques. Thus, in this paper, we review the various techniques that are in current use in three-dimensional US imaging systems, with a particular emphasis placed on the geometric accuracy of the generation of three-dimensional images. The principles involved in three-dimensional US imaging are then illustrated with a diagnostic and an interventional application: (i) three-dimensional carotid US imaging for quantification and monitoring of carotid atherosclerosis and (ii) three-dimensional US-guided prostate biopsy.
Hydrodynamic and hydromagnetic stability
Chandrasekhar, S
1981-01-01
Dr. Chandrasekhar's book received high praise when it first appeared in 1961 as part of Oxford University Press' International Series of Monographs on Physics. Since then it has been reprinted numerous times in its expensive hardcover format. This first lower-priced, sturdy paperback edition will be welcomed by graduate physics students and scientists familiar with Dr. Chandrasekhar's work, particularly in light of the resurgence of interest in the Rayleigh-Bénard problem. This book presents a most lucid introduction to the Rayleigh-Bénard problem: it has also been applauded for its thorough, clear coverage of the theory of instabilities causing convection. Dr. Chandrasekhar considers most of the typical problems in hydromagnetic stability, with the exception of viscous shear flow; a specialized domain deserving a book unto itself. Contents include: Rotation; Stability of More General Flows; Bénard Problem; Gravitational Equilibrium and Instability; Stability of a Magnetic Field; Thermal Instability of a L...
Marital stability and repartnering
Martins, Mariana V; Costa, Patrício; Peterson, Brennan D
2014-01-01
starting a new cycle of fertility treatment and observed for a 5-year period of unsuccessful treatments. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Marital stability and infertility-related stress. RESULT(S): The majority of patients (86%) remained with their initial partner, but 14% of participants...... separated and repartnered while pursuing fertility treatments. Marital stability significantly predicted the initial status of infertility stress and infertility stress growth levels. Specifically, patients who repartnered had higher infertility stress levels at all time points compared with those who...... a second union have higher initial levels of stress in their original relationship and higher changes in stress levels over the course of treatments. These findings suggest that high infertility-related stress levels before entering fertility treatment can negatively affect the stability of marital...
Higher (odd dimensional quantum Hall effect and extended dimensional hierarchy
Kazuki Hasebe
2017-07-01
Full Text Available We demonstrate dimensional ladder of higher dimensional quantum Hall effects by exploiting quantum Hall effects on arbitrary odd dimensional spheres. Non-relativistic and relativistic Landau models are analyzed on S2k−1 in the SO(2k−1 monopole background. The total sub-band degeneracy of the odd dimensional lowest Landau level is shown to be equal to the winding number from the base-manifold S2k−1 to the one-dimension higher SO(2k gauge group. Based on the chiral Hopf maps, we clarify the underlying quantum Nambu geometry for odd dimensional quantum Hall effect and the resulting quantum geometry is naturally embedded also in one-dimension higher quantum geometry. An origin of such dimensional ladder connecting even and odd dimensional quantum Hall effects is illuminated from a viewpoint of the spectral flow of Atiyah–Patodi–Singer index theorem in differential topology. We also present a BF topological field theory as an effective field theory in which membranes with different dimensions undergo non-trivial linking in odd dimensional space. Finally, an extended version of the dimensional hierarchy for higher dimensional quantum Hall liquids is proposed, and its relationship to quantum anomaly and D-brane physics is discussed.
Higher (odd) dimensional quantum Hall effect and extended dimensional hierarchy
Hasebe, Kazuki
2017-07-01
We demonstrate dimensional ladder of higher dimensional quantum Hall effects by exploiting quantum Hall effects on arbitrary odd dimensional spheres. Non-relativistic and relativistic Landau models are analyzed on S 2 k - 1 in the SO (2 k - 1) monopole background. The total sub-band degeneracy of the odd dimensional lowest Landau level is shown to be equal to the winding number from the base-manifold S 2 k - 1 to the one-dimension higher SO (2 k) gauge group. Based on the chiral Hopf maps, we clarify the underlying quantum Nambu geometry for odd dimensional quantum Hall effect and the resulting quantum geometry is naturally embedded also in one-dimension higher quantum geometry. An origin of such dimensional ladder connecting even and odd dimensional quantum Hall effects is illuminated from a viewpoint of the spectral flow of Atiyah-Patodi-Singer index theorem in differential topology. We also present a BF topological field theory as an effective field theory in which membranes with different dimensions undergo non-trivial linking in odd dimensional space. Finally, an extended version of the dimensional hierarchy for higher dimensional quantum Hall liquids is proposed, and its relationship to quantum anomaly and D-brane physics is discussed.
A stabilized pairing functional
Erler, J; Reinhard, P --G
2008-01-01
We propose a modified pairing functional for nuclear structure calculations which avoids the abrupt phase transition between pairing and non-pairing states. The intended application is the description of nuclear collective motion where the smoothing of the transition is compulsory to remove singularities. The stabilized pairing functional allows a thoroughly variational formulation, unlike the Lipkin-Nogami (LN) scheme which is often used for the purpose of smoothing. First applications to nuclear ground states and collective excitations prove the reliability and efficiency of the proposed stabilized pairing.
Magnetohydrodynamic stability of tokamaks
Zohm, Hartmut
2014-01-01
This book bridges the gap between general plasma physics lectures and the real world problems in MHD stability. In order to support the understanding of concepts and their implication, it refers to real world problems such as toroidal mode coupling or nonlinear evolution in a conceptual and phenomenological approach. Detailed mathematical treatment will involve classical linear stability analysis and an outline of more recent concepts such as the ballooning formalism. The book is based on lectures that the author has given to Master and PhD students in Fusion Plasma Physics. Due its strong lin
Stability of dynamical systems
Liao, Xiaoxin; Yu, P 0
2007-01-01
The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents
Thermodynamic Stability of Nanobubbles
Attard, Phil
2015-01-01
The observed stability of nanobubbles contradicts the well-known result in classical nucleation theory, that the critical radius is both microscopic and thermodynamically unstable. Here nanoscopic stability is shown to be the combined result of two non-classical mechanisms. It is shown that the surface tension decreases with increasing supersaturation, and that this gives a nanoscopic critical radius. Whilst neither a free spherical bubble nor a hemispherical bubble mobile on an hydrophobic surface are stable, it is shown that an immobilized hemispherical bubble with a pinned contact rim is stable and that the total entropy is a maximum at the critical radius.
Progress on plutonium stabilization
Hurt, D. [Defense Nuclear Facilities Safety Board, Washington, DC (United States)
1996-05-01
The Defense Nuclear Facilities Safety Board has safety oversight responsibility for most of the facilities where unstable forms of plutonium are being processed and packaged for interim storage. The Board has issued recommendations on plutonium stabilization and has has a considerable influence on DOE`s stabilization schedules and priorities. The Board has not made any recommendations on long-term plutonium disposition, although it may get more involved in the future if DOE develops plans to use defense nuclear facilities for disposition activities.
A Dynamic Stability Criterion for Ice Shelves and Tidewater Glaciers
Bassis, J. N.; Fricker, H. A.; Minster, J.
2006-12-01
The collapse of the Antarctic ice shelves could have dramatic consequences for the mass balance of the Antarctic ice sheet and, as a result, sea level rise. It is therefore imperative to improve our knowledge of the mechanisms that lead to ice shelf retreat. The mechanism that has the potential to remove the largest amounts of mass rapidly is iceberg calving. However, the processes and mechanisms that lead to iceberg calving are still poorly understood. Motivated by the complexity of the short-time scale behavior of ice fracture we seek a dynamic stability criterion that predicts the onset of ice shelf retreat based on dimensional analysis. In our approach, rather than attempt to model the initiation and propagation of individual fractures, we look for a non-dimensional number that describes the overall ice shelf stability. We also make the assumption that the same criterion, valid for ice shelves, also applies to tidewater glaciers. This enables us to test our criterion against a larger set of ice shelves and calving glaciers. Our analysis predicts that retreat will occur when a non-dimensional number that we call the "terminus stability number", decreases below a critical value. We show that this criterion is valid for calving glaciers in Alaska, for several glaciers around Greenland as well as for three Antarctic ice shelves. This stability analysis has much in common with classic hydrodynamic stability theory, where the onset of instability is related to non-dimensional numbers that are largely independent of geometry or other situation specific variables.
Dimensional Equations of Entropy
Sparavigna, Amelia Carolina
2015-01-01
Entropy is a quantity which is of great importance in physics and chemistry. The concept comes out of thermodynamics, proposed by Rudolf Clausius in his analysis of Carnot cycle and linked by Ludwig Boltzmann to the number of specific ways in which a physical system may be arranged. Any physics classroom, in its task of learning physics, has therefore to face this crucial concept. As we will show in this paper, the lectures can be enriched by discussing dimensional equations linked to the entropy of some physical systems.
Three-dimensional metamaterials
Burckel, David Bruce [Albuquerque, NM
2012-06-12
A fabrication method is capable of creating canonical metamaterial structures arrayed in a three-dimensional geometry. The method uses a membrane suspended over a cavity with predefined pattern as a directional evaporation mask. Metallic and/or dielectric material can be evaporated at high vacuum through the patterned membrane to deposit resonator structures on the interior walls of the cavity, thereby providing a unit cell of micron-scale dimension. The method can produce volumetric metamaterial structures comprising layers of such unit cells of resonator structures.
Osserman, Robert
2011-01-01
The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o
Juday, Richard D. (Inventor)
1992-01-01
A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.
Javidi, Bahram; Andres, Pedro
2014-01-01
Provides a broad overview of advanced multidimensional imaging systems with contributions from leading researchers in the field Multi-dimensional Imaging takes the reader from the introductory concepts through to the latest applications of these techniques. Split into 3 parts covering 3D image capture, processing, visualization and display, using 1) a Multi-View Approach and 2.) a Holographic Approach, followed by a 3rd part addressing other 3D systems approaches, applications and signal processing for advanced 3D imaging. This book describes recent developments, as well as the prospects and
Dimensional analysis made simple
Lira, Ignacio
2013-11-01
An inductive strategy is proposed for teaching dimensional analysis to second- or third-year students of physics, chemistry, or engineering. In this strategy, Buckingham's theorem is seen as a consequence and not as the starting point. In order to concentrate on the basics, the mathematics is kept as elementary as possible. Simple examples are suggested for classroom demonstrations of the power of the technique and others are put forward for homework or experimentation, but instructors are encouraged to produce examples of their own.
Three dimensional system integration
Papanikolaou, Antonis; Radojcic, Riko
2010-01-01
Three-dimensional (3D) integrated circuit (IC) stacking is the next big step in electronic system integration. It enables packing more functionality, as well as integration of heterogeneous materials, devices, and signals, in the same space (volume). This results in consumer electronics (e.g., mobile, handheld devices) which can run more powerful applications, such as full-length movies and 3D games, with longer battery life. This technology is so promising that it is expected to be a mainstream technology a few years from now, less than 10-15 years from its original conception. To achieve thi
Stability of constant gain systems with vector feedback
Vonpragenau, G. L.
1978-01-01
The state space, the controllability, and the observability concepts are discussed in connection with the proposed stability analysis which permits drastic dimensional reductions for a vector feedback problem. Any constant gain system's stability can thus be analyzed in the frequency domain with a single Nyquist plot. The analysis considers the total system with all loops closed, a disturbance vector as input, and the feedback vector as output. All constant gain systems are shown to be decomposable into stable subsystems where the degree of the decomposition determines the dimensions. The maximum decomposition results in the state-space approach which is the limit case. The method is demonstrated with the stability analysis of the pogo phenomenon, an oscillatory interaction between the propulsion and the structure of a space vehicle. This problem, with eigenvalues over a hundred, was drastically but rigorously reduced to a stability analysis of a 4x4 matrix.
Note on moduli stabilization, supersymmetry breaking and axiverse
Higaki, Tetsutaro [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics
2011-06-15
We study properties of moduli stabilization in the four dimensional N=1 supergravity theory with heavy moduli and would-be saxion-axion multiplets including light string-theoretic axions. We give general formulation for the scenario that heavy moduli and saxions are stabilized while axions remain light, assuming that moduli are stabilized near the supersymmetric solution. One can find stable vacuum, i.e. nontachyonic saxions, in the non-supersymmetric Minkowski vacua. We also discuss the cases, where the moduli are coupled to the supersymmetry breaking sector and/or moduli have contributions to supersymmetry breaking. Furthermore we study the models with axions originating from matter-like fields. Our analysis on moduli stabilization is applicable even if there are not light axion multiplets. (orig.)
ON NONLINEAR STABILITY IN NONPARALLEL BOUNDARY LAYER FLOW
TANG Deng-bin; WANG Wei-zhi
2004-01-01
The nonlinear stability problem in nonparallel boundary layer flow for two-dimensional disturbances was studied by using a newly presented method called Parabolic Stability Equations (PSE). A series of new modes generated by the nonlinear interaction of disturbance waves were tabulately analyzed, and the Mean Flow Distortion (MFD) was numerically given. The computational techniques developed, including the higher-order spectral method and the more effective algebraic mapping, increased greatly the numerical accuracy and the rate of convergence. With the predictor-corrector approach in the marching procedure, the normalization condition was satisfied, and the stability of numerical calculation could be ensured. With different initial amplitudes, the nonlinear stability of disturbance wave was studied. The results of examples show good agreement with the data given by the DNS using the full Navier-Stokes equations.
Computational Stability Analysis of Lotka-Volterra Systems
Polcz Péter
2016-12-01
Full Text Available This paper concerns the computational stability analysis of locally stable Lotka-Volterra (LV systems by searching for appropriate Lyapunov functions in a general quadratic form composed of higher order monomial terms. The Lyapunov conditions are ensured through the solution of linear matrix inequalities. The stability region is estimated by determining the level set of the Lyapunov function within a suitable convex domain. The paper includes interesting computational results and discussion on the stability regions of higher (3,4 dimensional LV models as well as on the monomial selection for constructing the Lyapunov functions. Finally, the stability region is estimated of an uncertain 2D LV system with an uncertain interior locally stable equilibrium point.
Global Transient Stability and Voltage Regulation for Multimachine Power Systems
Gordon, Mark; Hill, David J.
2008-01-01
This paper addresses simultaneously the major fundamental and difficult issues of nonlinearity, uncertainty, dimensionality and globality to derive performance enhancing power system stability control. The main focus is on simultaneous enhancement of transient stability and voltage regulation...... law is implemented to coordinate transient stabilizer and voltage regulator for each machine. Digital simulation studies show that global control scheme achieves unified transient stability and voltage regulation in the presence of parametric uncertainties and significant sudden changes in the network...... of power systems. This problem arises from the practical concern that both frequency and voltage control are important indices of power system control and operation but they are ascribed to different stages of system operation, i.e. the transient and post transient period respectively. The Direct Feedback...
QCD and dimensional deconstruction
Son, D T
2003-01-01
Motivated by phenomenological models of hidden local symmetries and the ideas of dimensional deconstruction and gauge/gravity duality, we consider the model of an "open moose". Such a model has a large number K of hidden gauge groups as well as a global chiral symmetry. In the continuum limit K->infinity the model becomes a 4+1 dimensional theory of a gauge field propagating in a dilaton background and an external space-time metric with two boundaries. We show that the model reproduces several well known phenomenological and theoretical aspects of low-energy hadron dynamics. We derive the general formulas for the mass spectrum, the decay constants of the pion and vector mesons, and the couplings between mesons. We then consider two simple realizations, one with a flat metric and another with a "cosh" metric interpolating between two AdS boundaries. For the pion form-factor, the single pole rho-meson dominance is exact in the latter case and approximate in the former case. We discover that an AdS/CFT-like pres...
On the Stability of Squashed Kaluza-Klein Black Holes
Kimura, Masashi; Murata, Keiju; Ishihara, Hideki; Soda, Jiro
2007-01-01
The stability of squashed Kaluza-Klein black holes is studied. The squashed Kaluza-Klein black hole looks like five dimensional black hole in the vicinity of horizon and four dimensional Minkowski spacetime with a circle at infinity. In this sense, squashed Kaluza-Klein black holes can be regarded as black holes in the Kaluza-Klein spacetimes. Using the symmetry of squashed Kaluza-Klein black holes, $SU(2)\\times U(1)\\simeq U(2)$, we obtain master equations for a part of the metric perturbatio...
Three-Dimensional Model Test Study of a CUBIPOD Armoured Roundhead
Burcharth, Hans F.; Andersen, Thomas Lykke; Aldama, J. M. Urrutia
The present report presents results from a three‐dimensional model test study carried out at Aalborg University in the period September 2008 - December 2008. The model tests were carried out to study the stability of a CUBIPOD armoured roundhead under short‐crested wave attack. Few long......‐crested wave tests were performed as well. One objective of the tests was to compare the stability of CUBIPOD armoured roundheads to the stability of cube armoured roundheads. This could be done by choosing a model test setup identical to that previous used in a study of the stability of a cube armoured...
Purnell, Thomas
2004-05-01
In accordance with proper perception of linguistic sound units, past research has demonstrated some degree of acoustic and physiological stability. In contrast, articulatory stability has been thought to be inconsistent because articulations may vary so long as the vocal tract area function results in appropriate formant structure [Atal et al., J. Acoust. Soc. Am. 63, 1535-1555 (1978)]. However, if the area function for the constriction and its anterior region can maintain acoustic stability, articulatory stability should be observed in the relational behavior of four tongue pellets used in xray microbeam data. Previous work examined normalized pellet data in order to arrive at an average posture for each vowel [Hashi et al., J. Acoust. Soc. Am. 104, 2426-2437 (1998)]. But by assuming static (average) gestures, the research fell short of a correct postural characterization. This study of tongue pellet speed and normalized pellet displacement of front vowels spoken by ten microbeam database subjects reports that the tongue tip pellet speed maxima identify vowel edges (end of vowel onset, beginning of offset) while displacement of the three anterior pellets identify changes in formant structure (e.g., two stable regions in the Northern Cities English front low vowel).
Conformational stability of calreticulin
Jørgensen, Charlotte S; Trandum, Christa; Larsen, Nanna Brink
2005-01-01
The conformational stability of calreticulin was investigated. Apparent unfolding temperatures (Tm) increased from 31 degrees C at pH 5 to 51 degrees C at pH 9, but electrophoretic analysis revealed that calreticulin oligomerized instead of unfolding. Structural analyses showed that the single C-...
Orbit Stabilization of Nanosat
JOHNSON,DAVID J.
1999-12-01
An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.
Sprinkler Bifurcations and Stability
Sorensen, Jody; Rykken, Elyn
2010-01-01
After discussing common bifurcations of a one-parameter family of single variable functions, we introduce sprinkler bifurcations, in which any number of new fixed points emanate from a single point. Based on observations of these and other bifurcations, we then prove a number of general results about the stabilities of fixed points near a…
2013-12-05
relationship between the steering wheel angle and lateral acceleration varies among vehicles because of differences in steering gear ratios, suspension...on-road, untripped truck rollovers by automatically decelerating the vehicle by applying the foundation brakes and reducing engine torque output...attributes: (1) Augments vehicle directional stability by applying and adjusting vehicle brake torques individually at each wheel position on at least
E.A. de Groot (Bert); Ph.H.B.F. Franses (Philip Hans)
2006-01-01
textabstractEconomic variables like GDP growth, employment, interest rates and consumption show signs of cyclical behavior. Many variables display multiple cycles, with lengths ranging in between 5 to even up to 100 years. We argue that multiple cycles can be associated with long-run stability of th
Groot, de E.A. (Bert); Franses, P.H.P.H.
2008-01-01
Economic variables like GDP growth, employment, interest rates and consumption show signs of cyclical behavior. Many variables display multiple cycles, with periods ranging in between 5 to even up to 100 years. We argue that multiple cycles can be associated with long-run stability of the economic s
Groot, de E.A. (Bert); Franses, P.H.P.H.
2006-01-01
Economic variables like GDP growth, employment, interest rates and consumption show signs of cyclical behavior. Many variables display multiple cycles, with lengths ranging in between 5 to even up to 100 years. We argue that multiple cycles can be associated with long-run stability of the economic s
Nonequilibrium statistical mechanics in one-dimensional bose gases
Baldovin, F.; Cappellaro, A.; Orlandini, E.; Salasnich, L.
2016-06-01
We study cold dilute gases made of bosonic atoms, showing that in the mean-field one-dimensional regime they support stable out-of-equilibrium states. Starting from the 3D Boltzmann-Vlasov equation with contact interaction, we derive an effective 1D Landau-Vlasov equation under the condition of a strong transverse harmonic confinement. We investigate the existence of out-of-equilibrium states, obtaining stability criteria similar to those of classical plasmas.
Finding four dimensional symplectic maps with reduced chaos: Preliminary results
Weishi Wan; Cary, J.R.; Shasharina, S.G.
1998-06-01
A method for finding integrable four-dimensional symplectic maps is outlined. The method relies on solving for parameter values at which the linear stability factors of the fixed points of the map have the values corresponding to integrability. This method is applied to accelerator lattices in order to increase dynamic aperture. Results show a increase of the dynamic aperture after correction, which implies the validity of the method.
Lyapunov Computational Method for Two-Dimensional Boussinesq Equation
Mabrouk, Anouar Ben
2010-01-01
A numerical method is developed leading to Lyapunov operators to approximate the solution of two-dimensional Boussinesq equation. It consists of an order reduction method and a finite difference discretization. It is proved to be uniquely solvable and analyzed for local truncation error for consistency. The stability is checked by using Lyapunov criterion and the convergence is studied. Some numerical implementations are provided at the end of the paper to validate the theoretical results.
Spirals and Skyrmions in two dimensional oxide heterostructures.
Li, Xiaopeng; Liu, W Vincent; Balents, Leon
2014-02-14
We construct the general free energy governing long-wavelength magnetism in two dimensional oxide heterostructures, which applies irrespective of the microscopic mechanism for magnetism. This leads, in the relevant regime of weak but non-negligible spin-orbit coupling, to a rich phase diagram containing in-plane ferromagnetic, spiral, cone, and Skyrmion lattice phases, as well as a nematic state stabilized by thermal fluctuations.
ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES
Nikola Stefanović
2007-06-01
Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.
Christiansen, Peter Leth; Gaididei, Yuri Borisovich; Rasmussen, Kim
1996-01-01
The dynamics of two-dimensional discrete structures is studied in the framework of the generalized two-dimensional discrete nonlinear Schrodinger equation. The nonlinear coupling in the form of the Ablowitz-Ladik nonlinearity and point impurities is taken into account. The stability properties...
Marginal Stability Boundaries for Infinite-n Ballooning Modes in a Quasi-axisymmetric Stellarator
S.R. Hudson; C.C. Hegna
2003-09-15
A method for computing the ideal-MHD stability boundaries in three-dimensional equilibria is employed. Following Hegna and Nakajima [Phys. Plasmas 5 (May 1998) 1336], a two-dimensional family of equilibria are constructed by perturbing the pressure and rotational-transform profiles in the vicinity of a flux surface for a given stellarator equilibrium. The perturbations are constrained to preserve the magnetohydrodynamic equilibrium condition. For each perturbed equilibrium, the infinite-n ballooning stability is calculated. Marginal stability diagrams are thus constructed that are analogous to (s; a) diagrams for axisymmetric configurations. A quasi-axisymmetric stellarator is considered. Calculations of stability boundaries generally show regions of instability can occur for either sign of the average magnetic shear. Additionally, regions of second-stability are present.