The effect of strain path change on subgrain volume fraction determined from in situ X-ray measurements

DEFF Research Database (Denmark)

Wejdemann, Christian; Poulsen, Henning Friis; Lienert, U.

2009-01-01

to additional 5% strain is performed in situ while mapping a selected X-ray reflection from one particular bulk grain with high angular resolution. The reciprocal space maps are analyzed with a recently developed fitting method, and a correlation is found between the evolution of the subgrain volume fraction...

Drift time variations in CdZnTe detectors measured with alpha-particles: Their correlation with the detector’s responses

Energy Technology Data Exchange (ETDEWEB)

Bolotnikov A. E.; Butcher, J.; Hamade, M.; Petryk, M.; Bolotnikov, A.; Camarda, G.; Cui, Y.; Hossain, A.; Kim, K.; Yang, G.; and James, R.

2012-05-14

Homogeneity of properties related to material crystallinity is a critical parameter for achieving high-performance CdZnTe (CZT) radiation detectors. Unfortunately, this requirement is not always satisfied in today's commercial CZT material due to high concentrations of extended defects, in particular subgrain boundaries, which are believed to be part of the causes hampering the energy resolution and efficiency of CZT detectors. In the past, the effects of subgrain boundaries have been studied in Si, Ge and other semiconductors. It was demonstrated that subgrain boundaries tend to accumulate secondary phases and impurities causing inhomogeneous distributions of trapping centers. It was also demonstrated that subgrain boundaries result in local perturbations of the electric field, which affect the carrier transport and other properties of semiconductor devices. The subgrain boundaries in CZT material likely behave in a similar way, which makes them responsible for variations in the electron drift time and carrier trapping in CZT detectors. In this work, we employed the transient current technique to measure variations in the electron drift time and related the variations to the device performances and subgrain boundaries, whose presence in the crystals were confirmed with white beam X-ray diffraction topography and infrared transmission microscopy.

Twin boundary cavitation in aged type 304 stainless steel

International Nuclear Information System (INIS)

Sikka, V.K.; Swindeman, R.W.; Brinkman, C.R.

1975-10-01

A transition from grain to twin boundary cavitation was observed in aged-and-creep-tested type 304 stainless steel. Evidence of twin boundary cavitation has also been observed for unaged material under certain test conditions. This same behavior was also found in aged type 316 stainless steel. Several possible reasons have been suggested for the absence of frequently observed grain boundary cavitation

The Interaction between Particles and Low Angle Boundaries during Recovering of Aluminium-Alumina Alloys

DEFF Research Database (Denmark)

Jones, A.R.; Hansen, Niels

1981-01-01

Certain quantitative and qualitative aspects both of subgrain growth and of the interaction between particles and low angle grain boundaries during recovery have been investigated in two aluminium alloys containing low volume fractions of small alumina particles. Quantitative data have been...... pinning. The discrepancies between the experimental and theoretical results can be rationalised in terms of the limited nature of the physical effects modelled in the Zener analysis....

EBSD in Antarctic and Greenland Ice

Science.gov (United States)

Weikusat, Ilka; Kuiper, Ernst-Jan; Pennock, Gill; Sepp, Kipfstuhl; Drury, Martyn

2017-04-01

Ice, particularly the extensive amounts found in the polar ice sheets, impacts directly on the global climate by changing the albedo and indirectly by supplying an enormous water reservoir that affects sea level change. The discharge of material into the oceans is partly controlled by the melt excess over snow accumulation, partly by the dynamic flow of ice. In addition to sliding over bedrock, an ice body deforms gravitationally under its own weight. In order to improve our description of this flow, ice microstructure studies are needed that elucidate the dominant deformation and recrystallization mechanisms involved. Deformation of hexagonal ice is highly anisotropic: ice is easily sheared in the basal plane and is about two orders of magnitude harder parallel to the c-axis. As dislocation creep is the dominant deformation mechanism in polar ice this strong anisotropy needs to be understood in terms of dislocation activity. The high anisotropy of the ice crystal is usually ascribed to a particular behaviour of dislocations in ice, namely the extension of dislocations into partials on the basal plane. Analysis of EBSD data can help our understanding of dislocation activity by characterizing subgrain boundary types thus providing a tool for comprehensive dislocation characterization in polar ice. Cryo-EBSD microstructure in combination with light microscopy measurements from ice core material from Antarctica (EPICA-DML deep ice core) and Greenland (NEEM deep ice core) are presented and interpreted regarding substructure identification and characterization. We examined one depth for each ice core (EDML: 656 m, NEEM: 719 m) to obtain the first comparison of slip system activity from the two ice sheets. The subgrain boundary to grain boundary threshold misorientation was taken to be 3-5° (Weikusat et al. 2011). EBSD analyses suggest that a large portion of edge dislocations with slip systems basal gliding on the basal plane were indeed involved in forming subgrain

The evolution of disorientations for several types of boundaries

DEFF Research Database (Denmark)

Pantleon, W.

2001-01-01

During plastic deformation dislocation boundaries appear separating regions of different orientation. A model for the occurrence of disorientations across these boundaries is proposed and discussed with emphasis on several types of boundaries. For incidental dislocation boundaries a statistical...... origin of disorientations is considered, additional deterministic contributions arising from geometrical reasons are taken into account for geometrically necessary boundaries. The resulting diversity in the modelled boundary behaviour explains the experimentally observed differences in the dependence...

Discrete transparent boundary conditions for Schroedinger-type equations

International Nuclear Information System (INIS)

Schmidt, F.; Yevick, D.

1997-01-01

We present a general technique for constructing nonlocal transparent boundary conditions for one-dimensional Schroedinger-type equations. Our method supplies boundary conditions for the θ-family of implicit one-step discretizations of Schroedinger's equation in time. The use of Mikusinski's operator approach in time avoids direct and inverse transforms between time and frequency domains and thus implements the boundary conditions in a direct manner. 14 refs., 9 figs

The corrosion behavior of the T1 (Al2CuLi) intermetallic compound in aqueous environments

Science.gov (United States)

Buchheit, R. G.; Stoner, G. E.

1989-01-01

The intermetallic compound T1 (Al2CuLi) is suspected to play an important role in the localized corrosion at subgrain boundaries in Al-Li-Cu alloys. The intermetallic was synthesized for characterization of its corrosion behavior. Experiments performed included open circuit potential measurements, potentiodynamic polarization, and corrosion rate vs. pH in solutions whose pH was varied over the range of 3 to 11. Subgrain boundary pitting and continuous subgrain boundary corrosion are discussed in terms of the data obtained. Evidence suggesting the dealloying of copper from this compound is also presented.

Microstructural analysis of the type-II boundary region in Alloy 152 weld

Energy Technology Data Exchange (ETDEWEB)

Yoo, Seung Chang; Choi, Kyoung Joon; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2014-10-15

The weld metals are more susceptible to SCC growth and that most cracks are blunted by the fusion boundary. However, they also found that some cracking occurs along the fusion boundary, often in an area with high hardness. Nelson et al. investigated a DMW of Monel 409 stainless steel and American Iron and Steel Institute (AISI) 1080 alloy and found a type-II boundary, which exists parallel to the fusion boundary in the dilution zone. They conclude that the type-II boundary is a potential path for crack growth. While there are several theories for the mechanisms of the type-II boundary formation, they conclude that the type-II boundary forms from the allotropic δ-γ transformation at the base metal in the elevated austenitic temperature range. As the operation time of nuclear power plants using DMWs of Alloy 152 and A533 Gr. B increases, these DMWs must be evaluated for their resistance to SCC for long-term operations. However, only few studies have investigated the thermal aging effects induced by long-term operations at high temperature. Type-II boundary is known as a potential crack path from the results of crack growth test at DMW without any heat treatment. So the analysis about type-II boundary with applying heat treatment could be helpful to evaluate the susceptibility to SCC of structural materials. The objective of this study is to analyze the detailed microstructure of the type-II boundary region in the DMW of Alloy 152 and A533 Gr. B, after applying heat treatment simulating thermal aging effect of a nuclear power plant operation condition to evaluate the susceptibility of this region to SCC. The microstructure of the type-II boundary region in the DMW of Alloy 152 and A533 Gr. B were analyzed with an energy dispersive x-ray spectroscope attached to a scanning electron microscope (SEM-EDS), electron backscatter diffraction (EBSD), and a nanoindentation test. Microstructural, grain boundary orientation, nanohardness analysis were conducted in the type

Microstructural analysis of the type-II boundary region in Alloy 152 weld

International Nuclear Information System (INIS)

Yoo, Seung Chang; Choi, Kyoung Joon; Kim, Ji Hyun

2014-01-01

The weld metals are more susceptible to SCC growth and that most cracks are blunted by the fusion boundary. However, they also found that some cracking occurs along the fusion boundary, often in an area with high hardness. Nelson et al. investigated a DMW of Monel 409 stainless steel and American Iron and Steel Institute (AISI) 1080 alloy and found a type-II boundary, which exists parallel to the fusion boundary in the dilution zone. They conclude that the type-II boundary is a potential path for crack growth. While there are several theories for the mechanisms of the type-II boundary formation, they conclude that the type-II boundary forms from the allotropic δ-γ transformation at the base metal in the elevated austenitic temperature range. As the operation time of nuclear power plants using DMWs of Alloy 152 and A533 Gr. B increases, these DMWs must be evaluated for their resistance to SCC for long-term operations. However, only few studies have investigated the thermal aging effects induced by long-term operations at high temperature. Type-II boundary is known as a potential crack path from the results of crack growth test at DMW without any heat treatment. So the analysis about type-II boundary with applying heat treatment could be helpful to evaluate the susceptibility to SCC of structural materials. The objective of this study is to analyze the detailed microstructure of the type-II boundary region in the DMW of Alloy 152 and A533 Gr. B, after applying heat treatment simulating thermal aging effect of a nuclear power plant operation condition to evaluate the susceptibility of this region to SCC. The microstructure of the type-II boundary region in the DMW of Alloy 152 and A533 Gr. B were analyzed with an energy dispersive x-ray spectroscope attached to a scanning electron microscope (SEM-EDS), electron backscatter diffraction (EBSD), and a nanoindentation test. Microstructural, grain boundary orientation, nanohardness analysis were conducted in the type

Contribution on creep polygonization study in crystals. Creep of single crystalline silver chloride and sodium chloride

International Nuclear Information System (INIS)

Pontikis, Vassilis

1977-01-01

Subgrain formation and their influence on plastic behavior of materials has been studied in the case of single crystals of silver chloride and sodium chloride crept at high temperature (T > 0.5 T melting ). It is shown that the creep rate ε is a function of the mean subgrain diameter d. For secondary creep ε ∝ d k with k = 2 for NaCl and AgCl. During secondary creep, the substructure changes continuously: sub-boundaries migrate and sub-grains rotate. We find that sub-boundaries migration accounts for 35 pc of the total strain and that subgrain misorientation θ increases linearly with strain ε: θ ∝ 0.14 ε. The stability of permanent creep seems related to the power that the substructure is able to dissipate. The possible subgrain formation mechanisms are examined. It is shown that subgrain formation is closely related to the geometrical conditions of deformation and to the heterogeneities of this later. (author) [fr

Hydrogenation of GaAs covered by GaAlAs and subgrain boundary passivation

Science.gov (United States)

Djemel, A.; Castaing, J.; Chevallier, J.; Henoc, P.

1992-12-01

Cathodoluminescence (CL) has been performed to study the influence of hydrogen on electronic properties of GaAs with and without a GaAlAs layer. Recombination at sub-boundaries has been examined. These extended defects have been introduced by high temperature plastic deformation. The results show that they are passivated by hydrogen. The penetration of hydrogen is slowed down by the GaAlAs layer. La cathodoluminescence (CL) a été utilisée pour étudier l'influence de l'hydrogène sur les propriétés électroniques de GaAs nu et recouvert d'une couche de GaAlAs. Le caractère recombinant des sous-joints de grains a été examiné. Ces défauts étendus ont été introduits par déformation plastique à chaud. Les résultats montrent que l'hydrogène passive ces défauts. La pénétration de l'hydrogène à l'intérieur de GaAs est retardée par la présence de la couche de GaAlAs.

Microstructure and crystallographic preferred orientation of polycrystalline microgarnet aggregates developed during progressive creep, recovery, and grain boundary sliding

Science.gov (United States)

Massey, M.A.; Prior, D.J.; Moecher, D.P.

2011-01-01

Optical microscopy, electron probe microanalysis, and electron backscatter diffraction methods have been used to examine a broad range of garnet microstructures within a high strain zone that marks the western margin of a major transpression zone in the southern New England Appalachians. Garnet accommodated variable states of finite strain, expressed as low strain porphyroclasts (Type 1), high strain polycrystalline aggregates (Type 2), and transitional morphologies (Type 3) that range between these end members. Type 1 behaved as rigid porphyroclasts and is characterized by four concentric Ca growth zones. Type 2 help define foliation and lineation, are characterized by three Ca zones, and possess a consistent bulk crystallographic preferred orientation of (100) symmetrical to the tectonic fabric. Type 3 show variable degrees of porphyroclast associated with aggregate, where porphyroclasts display complex compositional zoning that corresponds to lattice distortion, low-angle boundaries, and subgrains, and aggregate CPO mimics porphyroclast orientation. All aggregates accommodated a significant proportion of greenschist facies deformation through grain boundary sliding, grain rotation and impingement, and pressure solution, which lead to a cohesive behavior and overall strain hardening of the aggregates. The characteristic CPO could not have been developed in this manner, and was the result of an older phase of partitioned amphibolite facies dislocation creep, recovery including chemical segregation, and recrystallization of porphyroclasts. This study demonstrates the significance of strain accommodation within garnet and its affect on composition under a range of PT conditions, and emphasizes the importance of utilizing EBSD methods with studies that rely upon a sound understanding of garnet. ?? 2010 Elsevier Ltd.

Vragov’s boundary value problem for an implicit equation of mixed type

Science.gov (United States)

Egorov, I. E.

2017-10-01

We study a Vragov boundary value problem for a third-order implicit equation of mixed type with an arbitrary manifold of type switch. These Sobolev-type equations arise in many important applied problems. Given certain constraints on the coefficients and the right-hand side of the equation, we demonstrate, using nonstationary Galerkin method and regularization method, the unique regular solvability of the boundary value problem. We also obtain an error estimate for approximate solutions of the boundary value problem in terms of the regularization parameter and the eigenvalues of the Dirichlet spectral problem for the Laplace operator.

Boundary Observability and Stabilization for Westervelt Type Wave Equations without Interior Damping

International Nuclear Information System (INIS)

Kaltenbacher, Barbara

2010-01-01

In this paper we show boundary observability and boundary stabilizability by linear feedbacks for a class of nonlinear wave equations including the undamped Westervelt model used in nonlinear acoustics. We prove local existence for undamped generalized Westervelt equations with homogeneous Dirichlet boundary conditions as well as global existence and exponential decay with absorbing type boundary conditions.

Genetic relationship between deformation and low-Ca content in olivine from magmatic systems: evidence from the Poyi ultramafic intrusion, NW China

Science.gov (United States)

Yao, Zhuo-sen; Qin, Ke-zhang; Xue, Sheng-chao

2017-12-01

The deformation features (e.g., undulose extinction and subgrain boundaries) and low Ca content (causing the widespread deformation observed in Ca-depleted olivine from Poyi and other intrusions. What is more important, this work fills the gaps in the interpretation of this type of olivine in volcanic rocks.

Grain-size distributions and grain boundaries of chalcopyrite-type thin films

International Nuclear Information System (INIS)

Abou-Ras, D.; Schorr, S.; Schock, H.W.

2007-01-01

CuInSe 2 , CuGaSe 2 , Cu(In,Ga)Se 2 and CuInS 2 thin-film solar absorbers in completed solar cells were studied in cross section by means of electronbackscatter diffraction. From the data acquired, grain-size distributions were extracted, and also the most frequent grain boundaries were determined. The grain-size distributions of all chalcopyrite-type thin films studied can be described well by lognormal distribution functions. The most frequent grainboundary types in these thin films are 60 - left angle 221 right angle tet and 71 - left angle 110 right angle tet (near) Σ3 twin boundaries. These results can be related directly to the importance of {112} tet planes during the topotactical growth of chalcopyrite-type thin films. Based on energetic considerations, it is assumed that the most frequent twin boundaries exhibit a 180 - left angle 221 right angle tet constellation. (orig.)

Metallographic screening of grain boundary engineered type 304 austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Hanning, F., E-mail: Fabian.Hanning@googlemail.com; Engelberg, D.L., E-mail: Dirk.engelberg@manchester.ac.uk

2014-08-15

An electrochemical etching method for the identification of grain boundary engineered type 304 austenitic stainless steel microstructures is described. The method can be applied for rapid microstructure screening to complement electron backscatter diffraction analysis. A threshold parameter to identify grain boundary engineered microstructure is proposed, and the application of metallographic etching for characterising the degree of grain boundary engineering discussed. - Highlights: • As-received (annealed) and grain boundary engineered microstructures were compared. • Electro-chemical polarisation in nitric acid solutions was carried out. • A metallographic screening method has been developed. • The screening method complements EBSD analysis for microstructure identification.

The role of anodic dissolution in the stress corrosion cracking of Al-Li-Cu alloy 2090

International Nuclear Information System (INIS)

Buchheit, R.G. Jr.; Wall, F.D.; Stoner, G.E.; Moran, J.P.

1991-01-01

The short-transverse (S-T) stress corrosion cracking (SCC) behavior of Al-Li-CU alloy 2090 was studied using a static load SCC test technique. Time to failure was measured as a function of applied potential in several different environments. Rapid SCC failures ( br, T1 applied br, matrix where potentials refer to the breakaway potentials of the subgrain boundary T 1 (Al 2 CuLi) phase and the α-Al matrix phase. E br values were measured using potentiodynamic polarization of bulk materials intended to simulate the individual phases found in the subgrain boundary region. Results strongly suggest an anodic dissolution based SCC mechanism for this alloy where selective dissolution of T 1 on the subgrain boundary is a critical step. The unusual pre-exposure embrittlement phenomenon demonstrated by Al- Li alloys is also shown to be consistent with these simple SCC criteria. 21 refs., 9 figs., 6 tabs

Application of the perturbation iteration method to boundary layer type problems.

Science.gov (United States)

Pakdemirli, Mehmet

2016-01-01

The recently developed perturbation iteration method is applied to boundary layer type singular problems for the first time. As a preliminary work on the topic, the simplest algorithm of PIA(1,1) is employed in the calculations. Linear and nonlinear problems are solved to outline the basic ideas of the new solution technique. The inner and outer solutions are determined with the iteration algorithm and matched to construct a composite expansion valid within all parts of the domain. The solutions are contrasted with the available exact or numerical solutions. It is shown that the perturbation-iteration algorithm can be effectively used for solving boundary layer type problems.

Matrix-type multiple reciprocity boundary element method for solving three-dimensional two-group neutron diffusion equations

International Nuclear Information System (INIS)

Itagaki, Masafumi; Sahashi, Naoki.

1997-01-01

The multiple reciprocity boundary element method has been applied to three-dimensional two-group neutron diffusion problems. A matrix-type boundary integral equation has been derived to solve the first and the second group neutron diffusion equations simultaneously. The matrix-type fundamental solutions used here satisfy the equation which has a point source term and is adjoint to the neutron diffusion equations. A multiple reciprocity method has been employed to transform the matrix-type domain integral related to the fission source into an equivalent boundary one. The higher order fundamental solutions required for this formulation are composed of a series of two types of analytic functions. The eigenvalue itself is also calculated using only boundary integrals. Three-dimensional test calculations indicate that the present method provides stable and accurate solutions for criticality problems. (author)

Study of Microstructure of the Al-Fe Alloys After Hot Rolling Deformation

Science.gov (United States)

Jabłońska, Magdalena Barbara; Rodak, Kinga; Bednarczyk, Iwona

The aim of the paper is a microstructure analysis of alloys from the Al-Fe system after hot rolling tests, conducted by using a scanning transmission electron microscopy STEM and scanning electron microscope equipped with EBSD detector. Hot rolling was carried out at Technical University of Ostrava, Faculty of Metallurgy and Material Engineering, Institute of Modelling and Control of Forming Processes. The samples were heated to a temperature of 1200°C. The EBSD and STEM techniques have been applied in order to determine the influence of chemical composition and deformation parameters on structural changes. The microstructure analysis has included parameters such us: grain/sub-grain size, area fraction of grains/subgrains, misorientation angles, grains/subgrains shape aspect ratio and dislocations structure. The research structure techniques in scanning-transmission electron microscopy revealed numerous FeAl28 alloy phase separations of secondary nucleating sites favoured energetically, which are the boundary of grains/subgrains and dislocations. These changes in the structure of the test results have been confirmed by EBSD, which revealed the presence of grains/subgrains misorientation angle boundaries above 15°.

Heat conduction in a plate-type fuel element with time-dependent boundary conditions

International Nuclear Information System (INIS)

Faya, A.J.G.; Maiorino, J.R.

1981-01-01

A method for the solution of boundary-value problems with variable boundary conditions is applied to solve a heat conduction problem in a plate-type fuel element with time dependent film coefficient. The numerical results show the feasibility of the method in the solution of this class of problems. (Author) [pt

The effect of hot isostatic pressing on the microstructure and tensile properties of an unmodified A356-T6 cast aluminum alloy

International Nuclear Information System (INIS)

Ran Guang; Zhou Jingen; Wang, Q.G.

2006-01-01

In this paper, the effect of HIPping process on the microstructure and tensile properties of an unmodified sand cast A356-T6 aluminum alloy was studied. The microstructure and tensile fracture surfaces of the alloy were examined by transmission electron microscope (TEM), scanning electron microscope (SEM) and optical microscope. The results show that sub-grain boundaries are formed by HIPping process, and some silicon precipitates are formed at the sub-grain boundaries during aging hardening. The needle-shape precipitates are Mg 2 Si particles according to SED pattern analysis. The lattice misfit between Mg 2 Si and aluminum matrix is about 0.256% for [111] Al //[410] Mg 2 Si HIPping process significantly reduces porosity volume fraction and pore sizes and thus improves ductility. However, the tensile strength is improved very marginally due to the brittle nature of the unmodified coarse microstructure. The sub-grain boundary formed in the HIPping process has not shown significant influence on the tensile properties. For the studied alloy with large secondary dendrite arm spacing (SDAS) (above 80μm), the tensile fracture exhibits a transgranular mode (along the cell boundaries) with quasi-cleavage feature

Nonlinear $q$-fractional differential equations with nonlocal and sub-strip type boundary conditions

Directory of Open Access Journals (Sweden)

Bashir Ahmad

2014-06-01

Full Text Available This paper is concerned with new boundary value problems of nonlinear $q$-fractional differential equations with nonlocal and sub-strip type boundary conditions. Our results are new in the present setting and rely on the contraction mapping principle and a fixed point theorem due to O'Regan. Some illustrative examples are also presented.

Analytic approximations to nonlinear boundary value problems modeling beam-type nano-electromechanical systems

Energy Technology Data Exchange (ETDEWEB)

Zou, Li [Dalian Univ. of Technology, Dalian City (China). State Key Lab. of Structural Analysis for Industrial Equipment; Liang, Songxin; Li, Yawei [Dalian Univ. of Technology, Dalian City (China). School of Mathematical Sciences; Jeffrey, David J. [Univ. of Western Ontario, London (Canada). Dept. of Applied Mathematics

2017-06-01

Nonlinear boundary value problems arise frequently in physical and mechanical sciences. An effective analytic approach with two parameters is first proposed for solving nonlinear boundary value problems. It is demonstrated that solutions given by the two-parameter method are more accurate than solutions given by the Adomian decomposition method (ADM). It is further demonstrated that solutions given by the ADM can also be recovered from the solutions given by the two-parameter method. The effectiveness of this method is demonstrated by solving some nonlinear boundary value problems modeling beam-type nano-electromechanical systems.

Defect sink characteristics of specific grain boundary types in 304 stainless steels under high dose neutron environments

International Nuclear Information System (INIS)

Field, Kevin G.; Yang, Ying; Allen, Todd R.; Busby, Jeremy T.

2015-01-01

Radiation induced segregation (RIS) is a well-studied phenomena which occurs in many structurally relevant nuclear materials including austenitic stainless steels. RIS occurs due to solute atoms preferentially coupling with mobile point defect fluxes that migrate and interact with defect sinks. Here, a 304 stainless steel was neutron irradiated up to 47.1 dpa at 320 °C. Investigations into the RIS response at specific grain boundary types were used to determine the sink characteristics of different boundary types as a function of irradiation dose. A rate theory model built on the foundation of the modified inverse Kirkendall (MIK) model is proposed and benchmarked to the experimental results. This model, termed the GiMIK model, includes alterations in the boundary conditions based on grain boundary structure and expressions for interstitial binding. This investigation, through experiment and modeling, found specific grain boundary structures exhibiting unique defect sink characteristics depending on their local structure. Such interactions were found to be consistent across all doses investigated and to have larger global implications, including precipitation of Ni–Si clusters near different grain boundary types

On the rutile alpha-PbO"2-type phase boundary of TiO"2

DEFF Research Database (Denmark)

Olsen, J.S.; Gerward, Leif; Jiang, Jianzhong

1999-01-01

The high-pressure, high-temperature phase quilibria of TiO"2 have been studied with special emphasis on the rutile and alpha-PbO"2-type phases. It is found that the phase boundary, when plotted in a pressure-temperature diagram, changes from having a negative to having a positive slope...... with increasing temperature at about 6GPa and 850^oC. For nanophase material, the phase boundary is shifted towards lower pressure. The room-temperature bulk moduli are 210(120)GPa, 258(8)GPa and 290(20)GPa for rutile, the alpha-PbO"2-type phase and the baddeleyite-type phase, respectively....

Influence of Boundary Conditions on the Simulation of a Diamond-Type Lattice Structure: A Preliminary Study

Directory of Open Access Journals (Sweden)

Patrick Terriault

2017-01-01

Full Text Available Emergent additive manufacturing processes allow the use of metallic porous structures in various industrial applications. Because these structures comprise a large number of ordered unit cells, their design using conventional modeling approaches, such as finite elements, becomes a real challenge. A homogenization technique, in which the lattice structure is simulated as a fully dense volume having equivalent material properties, can then be employed. To determine these equivalent material properties, numerical simulations can be performed on a single unit cell of the lattice structure. However, a critical aspect to consider is the boundary conditions applied to the external faces of the unit cell. In the literature, different types of boundary conditions are used, but a comparative study is definitely lacking. In this publication, a diamond-type unit cell is studied in compression by applying different boundary conditions. If the porous structure’s boundaries are free to deform, then the periodic boundary condition is found to be the most representative, but constraint equations must be introduced in the model. If, instead, the porous structure is inserted in a rigid enclosure, it is then better to use frictionless boundary conditions. These preliminary results remain to be validated for other types of unit cells loaded beyond the yield limit of the material.

Comparison of the effects of long-term thermal aging and HFIR irradiation on the microstructural evolution of 9Cr-1MoVNb steel

International Nuclear Information System (INIS)

Maziasz, P.J.; Klueh, R.L.

1990-01-01

Both thermal aging at 482--704 degree C for up to 25,000h and HFIR irradiation at 300--600 degree C for up to 39 dpa produce substantial changes in the as-tempered microstructure of 9Cr-1MoVNb martensitic/ferritic steel. However, the changes in the dislocation/subgrain boundary and the precipitate structures caused by thermal aging or neutron irradiation are quite different in nature. During thermal aging, the as-tempered lath/subgrain boundary and carbide precipitate structures remain stable below 650 degree C, but coarsen and recover somewhat at 650--704 degree C. The formation of abundant intergranular Laves phase, intra-lath dislocation networks, and fine dispersions of VC needles are thermal aging effects that are superimposed upon the as-tempered microstructure at 482--593 degree C. HFIR irradiation produces dense dispersions of very small ''black'' dislocations loops at 300 degree C and produces helium bubbles and voids at 400 degree C At 300--500 degree C, there is considerable recovery of the as-tempered lath/subgrain boundary structure and microstructural/microcompositional instability of the as-tempered carbide precipitates during irradiation. By contrast, the as-tempered microstructure remains essentially unchanged during irradiation at 600 degree C. Comparison of thermally aged with irradiation material suggests that the instabilities of the as-tempered lath/subgrain boundary and precipitate structures at lower irradiation temperatures are radiation-induced effects, whereas the absence of both Laves phase and fine VC needles during irradiation is a radiation-retarded thermal effect

Three Types of Earth's Inner Core Boundary

Science.gov (United States)

Tian, D.; Wen, L.

2017-12-01

The Earth's inner core boundary (ICB) is the site where the liquid outer core solidifies and the solid inner core grows. Thus, the fine-scale structure of the ICB is important for our understanding of the thermo-compositional state of the Earth's core. In this study, we collect a large set of seismic records with high-quality pre-critical PKiKP and PcP phase pairs, recorded by two dense seismic arrays, Hi-net in Japan and USArray in US. This dataset samples the ICB regions beneath East Asia, Mexico and the Bering Sea. We use differential travel times, amplitude ratios and waveform differences between PKiKP and PcP phases to constrain fine-scale structure of the ICB. The sampled ICB can be grouped into three types based on their seismic characteristics: (1) a simple ICB with a flat and sharp boundary, (2) a bumpy ICB with topographic height changes of 10 km, and (3) a localized mushy ICB with laterally varying thicknesses of 4-8 km. The laterally varying fine-scale structure of the ICB indicates existence of complex small-scale forces at the surface and a laterally varying solidification process of the inner core due to lateral variation of thermo-compositional condition near the ICB.

Effects of thermal aging on the microstructure of Type-II boundaries in dissimilar metal weld joints

Science.gov (United States)

Yoo, Seung Chang; Choi, Kyoung Joon; Bahn, Chi Bum; Kim, Si Hoon; Kim, Ju Young; Kim, Ji Hyun

2015-04-01

In order to investigate the effects of long-term thermal aging on the microstructural evolution of Type-II boundary regions in the weld metal of Alloy 152, a representative dissimilar metal weld was fabricated from Alloy 690, Alloy 152, and A533 Gr.B. This mock-up was thermally aged at 450 °C to accelerate the effects of thermal aging in a nuclear power plant operation condition (320 °C). The microstructure of the Type-II boundary region of the weld root, which is parallel to and within 100 μm of the fusion boundary and known to be more susceptible to material degradation, was then characterized after different aging times using a scanning electron microscope equipped with an energy dispersive X-ray spectroscope for micro-compositional analysis, electron backscattered diffraction detector for grain and grain boundary orientation analysis, and a nanoindenter for measurement of mechanical properties. Through this, it was found that a steep compositional gradient and high grain average misorientation is created in the narrow zone between the Type-II and fusion boundaries, while the concentration of chromium and number of low-angle grain boundaries increases with aging time. A high average hardness was also observed in the same region of the dissimilar metal welds, with hardness peaking with thermal aging simulating an operational time of 15 years.

Mechanisms of fine extinction band development in vein quartz: new insights from correlative light and electron microscopy

Science.gov (United States)

Derez, Tine; Van Der Donck, Tom; Plümper, Oliver; Muchez, Philippe; Pennock, Gill; Drury, Martyn R.; Sintubin, Manuel

2017-07-01

Fine extinction bands (FEBs) (also known as deformation lamellae) visible with polarized light microscopy in quartz consist of a range of nanostructures, inferring different formation processes. Previous transmission electron microscopy studies have shown that most FEB nanostructures in naturally deformed quartz are elongated subgrains formed by recovery of dislocation slip bands. Here we show that three types of FEB nanostructure occur in naturally deformed vein quartz from the low-grade metamorphic High-Ardenne slate belt (Belgium). Prismatic oriented FEBs are defined by bands of dislocation walls. Dauphiné twin boundaries present along the FEB boundaries probably formed after FEB formation. In an example of two sub-rhombohedral oriented FEBs, developed as two sets in one grain, the finer FEB set consists of elongated subgrains, similar to FEBs described in previous transmission electron microscopy studies. The second wider FEB set consists of bands with different dislocation density and fluid-inclusion content. The wider FEB set is interpreted as bands with different plastic strain associated with the primary growth banding of the vein quartz grain. The nanometre-scale fluid inclusions are interpreted to have formed from structurally bounded hydroxyl groups that moreover facilitated formation of the elongate subgrains. Larger fluid inclusions aligned along FEBs are explained by fluid-inclusion redistribution along dislocation cores. The prismatic FEB nanostructure and the relation between FEBs and growth bands have not been recognized before, although related structures have been reported in experimentally deformed quartz.

Influence of grain structure on quench sensitivity relative to localized corrosion of high strength aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Liu, ShengDan, E-mail: csuliusd@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha 410083 (China); Li, ChengBo [Light Alloy Research Institute, Central South University, Changsha 410083 (China); Deng, YunLai; Zhang, XinMing [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha 410083 (China)

2015-11-01

The influence of grain structure on quench sensitivity relative to localized corrosion of high strength aluminum alloy 7055 was investigated by electrochemical test, accelerated exfoliation corrosion test, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The decrease of quench rate led to lower corrosion resistance of both the homogenized and solution heat treated (HS) alloy with equiaxed grains and the hot-rolled and solution heat treated (HRS) alloy with elongated grains, but there was a higher increment in corrosion depth and corrosion current density and a higher decrement in corrosion potential for the latter alloy, which therefore exhibited higher quench sensitivity. It is because in this alloy the larger amount of (sub) grain boundaries led to a higher increment in the amount of quench-induced η phase and precipitates free zone at (sub) grain boundaries with the decrease of quench rate, and there was a larger increment in the content of Zn, Mg and Cu in the η phase at grain boundaries due to slow quenching. The presence of subgrain boundaries in the HRS alloy tended to increase corrosion resistance at high quench rates higher than about 630 °C/min but decrease it at lower quench rates. - Highlights: • (Sub)Grain boundaries increase quench sensitivity relative to localized corrosion. • Subgrain boundaries decrease corrosion resistance below quench rate of 630 °C/min. • More (sub) grain boundaries leads to more GBPs and PFZ with decreasing quench rate.

Nonlinear parabolic problems with Neumann-type boundary conditions and L^1-data

Directory of Open Access Journals (Sweden)

Abderrahmane El Hachimi

2007-11-01

$$ \\frac{\\partial u}{\\partial t}-\\triangle_{p}u+\\alpha(u=f \\quad \\text{in } ]0,\\ T[\\times\\Omega, $$ with Neumann-type boundary conditions and initial data in $L^1$. Our approach is based essentially on the time discretization technique by Euler forward scheme.

Microstructure changes in the low stacking fault energy steel

International Nuclear Information System (INIS)

Rodak, K.; Kuc, D.; Niewielski, G.; Hetmanczyk, M.

1999-01-01

A Cr-Ni austenitic steel (type 304) was investigated using TEM. It is shown that some structural parameters (dislocations density within the subgrains and the subgrains size) change with temperature and strain rate after hot temperature deformation. The subgrain microstructure was characterized quantitatively for different characteristics. (author)

Strengthening mechanisms, creep, and fatigue processes in dispersion-hardened niobium alloy. Final scientific report, 1 Feb 89-31 Jan 92

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, A.K.; Gibeling, J.C.

1992-04-20

The creep and fatigue properties of pure Nb and Nb-l%Zr alloy were investigated. A model was developed based on the migration of subgrain boundary that can explain the anomalous primary creep transients found in Nb-l%Zr alloy, due to coarsening of subgrain structure. TEM investigations confirmed that such subgrain coarsening occurs during primary creep of Nb-l%Zr. Baseline low cycle fatigue studies of Nb and Nb-l%Zr were completed. Cyclic hardening is observed and there is a microplastic plateau in Nb. The Nb-1%Zr is stronger in cyclic deformation than Nb, with little influence of strain rate. The deformation in the alloy at both high and low strain rates is controlled by the interaction between gliding edge dislocation and solute atoms.

Invariant TAD Boundaries Constrain Cell-Type-Specific Looping Interactions between Promoters and Distal Elements around the CFTR Locus.

Science.gov (United States)

Smith, Emily M; Lajoie, Bryan R; Jain, Gaurav; Dekker, Job

2016-01-07

Three-dimensional genome structure plays an important role in gene regulation. Globally, chromosomes are organized into active and inactive compartments while, at the gene level, looping interactions connect promoters to regulatory elements. Topologically associating domains (TADs), typically several hundred kilobases in size, form an intermediate level of organization. Major questions include how TADs are formed and how they are related to looping interactions between genes and regulatory elements. Here we performed a focused 5C analysis of a 2.8 Mb chromosome 7 region surrounding CFTR in a panel of cell types. We find that the same TAD boundaries are present in all cell types, indicating that TADs represent a universal chromosome architecture. Furthermore, we find that these TAD boundaries are present irrespective of the expression and looping of genes located between them. In contrast, looping interactions between promoters and regulatory elements are cell-type specific and occur mostly within TADs. This is exemplified by the CFTR promoter that in different cell types interacts with distinct sets of distal cell-type-specific regulatory elements that are all located within the same TAD. Finally, we find that long-range associations between loci located in different TADs are also detected, but these display much lower interaction frequencies than looping interactions within TADs. Interestingly, interactions between TADs are also highly cell-type-specific and often involve loci clustered around TAD boundaries. These data point to key roles of invariant TAD boundaries in constraining as well as mediating cell-type-specific long-range interactions and gene regulation. Copyright © 2016 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

Effect of stacking fault energy on high-temperature creep parameters of nickel-cobalt alloys

International Nuclear Information System (INIS)

Nerodenko, L.M.; Dabizha, E.V.

1982-01-01

Results of creep investigation are discussed for two alloys of the Ni-Co system. In terms of the structural creep model an analysis is made for the effect of stacking fault energy on averaged parameters of the dislocation structure: inovable dislocation density subgrain size, activation volume. The rate of steady-state creep is determined by the process of dislocation passing through the subgrain boundaries with activation energy of 171.0 and 211.5 kJ/mol for the Ni-25% Co and Ni-65% Co alloys, respectively

Characterization of laser welds in Al-10 wt.%Si coated ferritic stainless steel

International Nuclear Information System (INIS)

Kong, Jong Pan; Park, Tae Jun; Kim, Jeong Kil; Uhm, Sang Ho; Woo, In Su; Lee, Jong Sub; Park, Bong Gyu; Kang, Chung Yun

2011-01-01

409L stainless steel hot-dipped with Al-10 wt.%Si was welded using CO 2 laser and the microstructure and hardness of the weld were investigated. When the specimen was welded with laser power of 5 kW and welding speed of 5 m/min, full-penetrated sound weld was obtained. With that specimen, the relationship between the microstructure and hardness of the weld was examined. The hardness of the weld was the highest in the fusion zone (FZ) and decreased to the base metal (BM) via heat affected zone (HAZ). The hardness of the HAZ near bond line was also higher than that near the base metal. The maximum hardness in the fusion zone could be explained by the existence of the precipitates, that is, TiN, Ti(C,N), Al 2 O 3 and Al 2 O 3 + TiN mixed compounds with the size of 500 nm, and solution strengthening due to the elements Al and Si dissolved from the coating layer to the fusion zone. There were subgrains within the HAZ and more in the area near the bond line. In addition, fine TiC particles with the size under 50 nm was precipitated in the sub-grain boundaries. The formation of sub-grain boundaries and the particles precipitated in the boundaries might contributed to the high hardness in the HAZ.

Mode solutions for a Klein-Gordon field in anti-de Sitter spacetime with dynamical boundary conditions of Wentzell type

Science.gov (United States)

Dappiaggi, Claudio; Ferreira, Hugo R. C.; Juárez-Aubry, Benito A.

2018-04-01

We study a real, massive Klein-Gordon field in the Poincaré fundamental domain of the (d +1 )-dimensional anti-de Sitter (AdS) spacetime, subject to a particular choice of dynamical boundary conditions of generalized Wentzell type, whereby the boundary data solves a nonhomogeneous, boundary Klein-Gordon equation, with the source term fixed by the normal derivative of the scalar field at the boundary. This naturally defines a field in the conformal boundary of the Poincaré fundamental domain of AdS. We completely solve the equations for the bulk and boundary fields and investigate the existence of bound state solutions, motivated by the analogous problem with Robin boundary conditions, which are recovered as a limiting case. Finally, we argue that both Robin and generalized Wentzell boundary conditions are distinguished in the sense that they are invariant under the action of the isometry group of the AdS conformal boundary, a condition which ensures in addition that the total flux of energy across the boundary vanishes.

Boron content effect on the high-temperature plasticity of corrosion resistant low-carbon austenite type steels

International Nuclear Information System (INIS)

Gol'dshtejn, Ya.E.; Shmatko, M.N.; Chuvatina, S.N.

1976-01-01

With the concept that the state of grain and subgrain boundaries influences the hot plasticity of corrosion resistant steel as a starting point, the study was undertaken of the effect of boron microalloying up on the intergranular strength and of the action boron exerts upon the distribution (redistribution) of other phases present in austenitic 03Kh16N14M3 steels. An electron microscope study of the composition of redundant phases and that of the fine structure of steel have shown the effect of small additions of boron upon the hot plasticity of steel to be linked directly to its influence upon austenite disintegration and the precipitation along the boundaries of crystals of redundant phases in the course of hot plastic deformation. The action of boron upon the process plasticity of steel depends on the temperature and the rate of deformation which govern the kinetics of the precipitation of the redundant phases

Evaluation of Haney-Type Surface Thermal Boundary Conditions Using a Coupled Atmosphere and Ocean Model

National Research Council Canada - National Science Library

Chu, Peter C; Chen, Yuchun; Lu, Shihua

2001-01-01

... (Russell et al,, 1995) was used to verify the validity of Haney-type surface thermal boundary condition, which linearly connects net downward surface heat flux Q to air / sea temperature difference DeltaT by a relaxation coefficient K...

Stratification of TAD boundaries reveals preferential insulation of super-enhancers by strong boundaries.

Science.gov (United States)

Gong, Yixiao; Lazaris, Charalampos; Sakellaropoulos, Theodore; Lozano, Aurelie; Kambadur, Prabhanjan; Ntziachristos, Panagiotis; Aifantis, Iannis; Tsirigos, Aristotelis

2018-02-07

The metazoan genome is compartmentalized in areas of highly interacting chromatin known as topologically associating domains (TADs). TADs are demarcated by boundaries mostly conserved across cell types and even across species. However, a genome-wide characterization of TAD boundary strength in mammals is still lacking. In this study, we first use fused two-dimensional lasso as a machine learning method to improve Hi-C contact matrix reproducibility, and, subsequently, we categorize TAD boundaries based on their insulation score. We demonstrate that higher TAD boundary insulation scores are associated with elevated CTCF levels and that they may differ across cell types. Intriguingly, we observe that super-enhancers are preferentially insulated by strong boundaries. Furthermore, we demonstrate that strong TAD boundaries and super-enhancer elements are frequently co-duplicated in cancer patients. Taken together, our findings suggest that super-enhancers insulated by strong TAD boundaries may be exploited, as a functional unit, by cancer cells to promote oncogenesis.

Boundary layer effects on the vortex shedding in a Donaldson- type hydrofoil

International Nuclear Information System (INIS)

Fontanals, A; Guardo, A; Egusquiza, E; Zobeiri, A; Farhat, M; Avellan, F

2014-01-01

Fluid - Structure Interaction (FSI) phenomena is becoming a relevant study field for the design or revamping of hydropower plants. The generalized trend of increasing flow rates and reducing rotor blades/stay vanes thickness in order to improve the efficiency of the machine together with a major push from plant owners/operators for production flexibility (partial load operation is more common nowadays) make the FSI between the vortex shedding phenomenon and the vanes/blades of the machine an area of interest. From a design point of view, the machine structure has to resist all the hydrodynamic forces generated and maintain tension stresses under the fatigue limit to ensure a machine lifetime of several decades. To accomplish that goal, designers have to assure there is no presence of strong coupling phenomena (lock-in) between the vortex shedding frequency and the eigenfrequencies of the structure. As the vortex street is directly related to the state of the boundary layer along the hydrofoil, in this paper the effect of the boundary layer on the vortex shedding in a Donaldson-type hydrofoil is studied using Computational Fluid Dynamics (CFD). The development of the boundary layer along the Donaldson trailing edge hydrofoil chord is presented under lock-off conditions. The results are validated against previously obtained experimental results. Since the Donaldson trailing edge is non-symmetric, the boundary layer velocity profiles are reported for the suction and pressure side of the hydrofoil. In addition, the effect of the Donaldson trailing edge on laminar-to-turbulent transition on both sides of the hydrofoil is studied

Geometrically necessary dislocation densities in olivine obtained using high-angular resolution electron backscatter diffraction

Energy Technology Data Exchange (ETDEWEB)

Wallis, David, E-mail: davidwa@earth.ox.ac.uk [Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3AN (United Kingdom); Hansen, Lars N. [Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3AN (United Kingdom); Ben Britton, T. [Department of Materials, Imperial College London, Royal School of Mines, Exhibition Road, London SW7 2AZ (United Kingdom); Wilkinson, Angus J. [Department of Materials, University of Oxford, Parks Road, Oxford, Oxfordshire, OX1 3PH (United Kingdom)

2016-09-15

Dislocations in geological minerals are fundamental to the creep processes that control large-scale geodynamic phenomena. However, techniques to quantify their densities, distributions, and types over critical subgrain to polycrystal length scales are limited. The recent advent of high-angular resolution electron backscatter diffraction (HR-EBSD), based on diffraction pattern cross-correlation, offers a powerful new approach that has been utilised to analyse dislocation densities in the materials sciences. In particular, HR-EBSD yields significantly better angular resolution (<0.01°) than conventional EBSD (~0.5°), allowing very low dislocation densities to be analysed. We develop the application of HR-EBSD to olivine, the dominant mineral in Earth's upper mantle by testing (1) different inversion methods for estimating geometrically necessary dislocation (GND) densities, (2) the sensitivity of the method under a range of data acquisition settings, and (3) the ability of the technique to resolve a variety of olivine dislocation structures. The relatively low crystal symmetry (orthorhombic) and few slip systems in olivine result in well constrained GND density estimates. The GND density noise floor is inversely proportional to map step size, such that datasets can be optimised for analysing either short wavelength, high density structures (e.g. subgrain boundaries) or long wavelength, low amplitude orientation gradients. Comparison to conventional images of decorated dislocations demonstrates that HR-EBSD can characterise the dislocation distribution and reveal additional structure not captured by the decoration technique. HR-EBSD therefore provides a highly effective method for analysing dislocations in olivine and determining their role in accommodating macroscopic deformation. - Highlights: • Lattice orientation gradients in olivine were measured using HR-EBSD. • The limited number of olivine slip systems enable simple least squares inversion for GND

Microstructural evolution of AZ31 magnesium alloy subjected to sliding friction treatment

Science.gov (United States)

Zhang, Wei; Lu, Jinwen; Huo, Wangtu; Zhang, Yusheng; Wei, Q.

2018-06-01

Microstructural evolution and grain refinement mechanism in AZ31 magnesium alloy subjected to sliding friction treatment were investigated by means of transmission electron microscopy. The process of grain refinement was found to involve the following stages: (I) coarse grains were divided into fine twin plates through mechanical twinning; then the twin plates were transformed to lamellae with the accumulation of residual dislocations at the twin boundaries; (II) the lamellae were separated into subgrains with increasing grain boundary misorientation and evolution of high angle boundaries into random boundaries by continuous dynamic recrystallisation (cDRX); (III) the formation of nanograins. The mechanisms for the final stage, the formation of nanograins, can be classified into three types: (i) cDRX; (ii) discontinuous dynamic recrystallisation (dDRX); (iii) a combined mechanism of prior shear-band and subsequent dDRX. Stored strain energy plays an important role in determining deformation mechanisms during plastic deformation.

Mixed basin boundary structures of chaotic systems

International Nuclear Information System (INIS)

Rosa, E. Jr.; Ott, E.

1999-01-01

Motivated by recent numerical observations on a four-dimensional continuous-time dynamical system, we consider different types of basin boundary structures for chaotic systems. These general structures are essentially mixtures of the previously known types of basin boundaries where the character of the boundary assumes features of the previously known boundary types at different points arbitrarily finely interspersed in the boundary. For example, we discuss situations where an everywhere continuous boundary that is otherwise smooth and differentiable at almost every point has an embedded uncountable, zero Lebesgue measure set of points at which the boundary curve is nondifferentiable. Although the nondifferentiable set is only of zero Lebesgue measure, the curve close-quote s fractal dimension may (depending on parameters) still be greater than one. In addition, we discuss bifurcations from such a mixed boundary to a 'pure' boundary that is a fractal nowhere differentiable curve or surface and to a pure nonfractal boundary that is everywhere smooth. copyright 1999 The American Physical Society

Symmetry analysis and exact solutions of one class of (1+3)-dimensional boundary-value problems of the Stefan type

OpenAIRE

Kovalenko, S. S.

2014-01-01

We present the group classification of one class of (1+3)-dimensional nonlinear boundary-value problems of the Stefan type that simulate the processes of melting and evaporation of metals. The results obtained are used for the construction of the exact solution of one boundary-value problem from the class under study.

On the quench sensitivity of 7010 aluminum alloy forgings in the overaged condition

Energy Technology Data Exchange (ETDEWEB)

Tiryakioğlu, Murat, E-mail: m.tiryakioglu@unf.edu [School of Engineering, University of North Florida, Jacksonville, FL 32224 (United States); Robinson, Jeremy S. [Department of Mechanical, Aeronautical and Biomedical Engineering, University of Limerick, Limerick (Ireland); Eason, Paul D. [School of Engineering, University of North Florida, Jacksonville, FL 32224 (United States)

2014-11-17

The quench sensitivity of an overaged 7010 alloy forging was characterized by tensile and Vickers hardness tests, as well as scanning electron microscopy. Longitudinal tensile specimens, excised from a rectilinear open die forging were cooled from the solution treatment temperature following thirty-two different cooling paths including interrupted and delayed quenches. SEM analysis of the microstructure showed that quench precipitates were (i) Al{sub 2}CuMg (S) which nucleated heterogeneously on grain boundaries and (ii) Mg(Zn,Cu,Al){sub 2} (η) on grain boundaries, dispersoid bands, subgrain boundaries as well as in the aluminum matrix. The quench sensitivity of the alloy's yield strength and Vickers hardness was modeled simultaneously by quadruple-C curves, using an improved methodology for Quench Factor Analysis. The four C-curves used in the model represented loss of solute by (i) precipitation of S on grain boundaries, and precipitation of η (ii) on grain boundaries and dispersoid bands, (iii) on subgrain boundaries and (iv) in the matrix. The model yielded coefficient of determination (R{sup 2}) values of 0.967 and 0.974 for yield strength and Vickers hardness, respectively. The model and the implications of the results are discussed in this paper.

Microstructural evolution in copper subjected to severe plastic deformation: Experiments and analysis

International Nuclear Information System (INIS)

Mishra, A.; Kad, B.K.; Gregori, F.; Meyers, M.A.

2007-01-01

The evolution of microstructure and the mechanical response of copper subjected to severe plastic deformation using equal channel angular pressing (ECAP) was investigated. Samples were subjected to ECAP under three different processing routes: B C , A and C. The microstructural refinement was dependent on processing with route B C being the most effective. The mechanical response is modeled by an equation containing two dislocation evolution terms: one for the cells/subgrain interiors and one for the cells/subgrain walls. The deformation structure evolves from elongated dislocation cells to subgrains to equiaxed grains with diameters of ∼200-500 nm. The misorientation between adjacent regions, measured by electron backscatter diffraction, gradually increases. The mechanical response is well represented by a Voce equation with a saturation stress of 450 MPa. Interestingly, the microstructures produced through adiabatic shear localization during high strain rate deformation and ECAP are very similar, leading to the same grain size. It is shown that both processes have very close Zener-Hollomon parameters (ln Z ∼ 25). Calculations show that grain boundaries with size of 200 nm can rotate by ∼30 deg. during ECAP, thereby generating and retaining a steady-state equiaxed structure. This is confirmed by a grain-boundary mobility calculation which shows that their velocity is 40 nm/s for a 200 nm grain size at 350 K, which is typical of an ECAP process. This can lead to the grain-boundary movement necessary to retain an equiaxed structure

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

Directory of Open Access Journals (Sweden)

Florian Steinbach

2017-09-01

Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

Science.gov (United States)

Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-09-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

Existence and Analytic Approximation of Solutions of Duffing Type Nonlinear Integro-Differential Equation with Integral Boundary Conditions

Directory of Open Access Journals (Sweden)

Alsaedi Ahmed

2009-01-01

Full Text Available A generalized quasilinearization technique is developed to obtain a sequence of approximate solutions converging monotonically and quadratically to a unique solution of a boundary value problem involving Duffing type nonlinear integro-differential equation with integral boundary conditions. The convergence of order for the sequence of iterates is also established. It is found that the work presented in this paper not only produces new results but also yields several old results in certain limits.

Fragmentation of α2 plates in a fully lamellar TiAl during creep

International Nuclear Information System (INIS)

Wang, J.G.; Hsiung, L.M.; Nieh, T.G.

1999-01-01

The fragmentation and spheroidization of α 2 laths in a fully-lamellar TiAl alloy during creep were examined. Three possible mechanisms, Rayleigh's perturbation model, subgrain boundary groove mechanism and intersection of deformation twins with α 2 lamellae were presented and discussed. During creep deformation, the pile-up of interfacial dislocations leads to a change of planar interface, which, in turn, causes a difference in local chemical potential, and further results in the spheroidization of α 2 lamellae. On the other hand, the deformation of the α 2 phase is expected to be induced by the high local stress concentration introduced by the pile up of interfacial dislocations. The dynamic recovery process may lead to the formation of subgrain boundaries in the α 2 lamellae, which results in the spheroidization and termination of α 2 lamellae with the aid of diffusion during creep

Microstructural evolution in copper processed by severe plastic deformation

International Nuclear Information System (INIS)

Mishra, A.; Richard, V.; Gregori, F.; Asaro, R.J.; Meyers, M.A.

2005-01-01

The mechanisms of microstructural evolution in copper subjected to equal channel angular pressing (ECAP) have been investigated after successive passes. The first few passes are the most efficient in grain refinement while the microstructure becomes gradually more equiaxed as the number of passes increases. The texture evolution is discussed based on electron back scattered diffraction (EBSD) results. These experimental results are interpreted in terms of a preliminary model with four successive stages: homogeneous dislocation distribution; elongated sub-cell formation; elongated subgrain formation; break-up of subgrains into equiaxed units; sharpening of grain boundaries and final equiaxed ultrafine structure

Discrete Boltzmann Method with Maxwell-Type Boundary Condition for Slip Flow

Science.gov (United States)

Zhang, Yu-Dong; Xu, Ai-Guo; Zhang, Guang-Cai; Chen, Zhi-Hua

2018-01-01

The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model (DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation. It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model. Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model. To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified. Support of National Natural Science Foundation of China under Grant Nos. 11475028, 11772064, and 11502117 Science Challenge Project under Grant Nos. JCKY2016212A501 and TZ2016002

Non-axisymmetric vibrations of a transversely isotropic piezoelectric cylinder with different types of electric boundary conditions

CSIR Research Space (South Africa)

Shatalov, MY

2007-04-01

Full Text Available with different types of electric boundary conditions Michael Y. Shatalov*, Arthur G. Every**, Alfred S. Yenwong –Fai*** *Sensor Science and Technology (SST) of CSIR Material Science and Manufacturing, P.O. Box 395, Pretoria 0001, CSIR, South Africa...

Static recrystallisation and precipitation after hot deformation of austenitic stainless steels containing molybdenum and niobium

International Nuclear Information System (INIS)

Lombry, R.; Rossard, C.; Thomas, B.J.

1981-01-01

In general the hot workability of austenite depends on the work hardening during deformation and the kinetics of the dynamic and static restoration processes. Static recrystallisation is a very important factor in the case of hot rolling. The present work was undertaken to determine the effect of additions of molybdenum or niobium on the kinetics of static recrystallisation. The results show that the rate of static recrystallisation of type 304, 316 and 347 stainless steels decreases in this order for a given amount of prior deformation (epsilon=0,44). The differences in the rates of recrystallisation increases as the temperature is lowered towards 900 deg C. The effect of molybdenum appears to be attribuable to a solute drag effect on the mobility of dislocations, subgrain boundaries or grain boundaries whereas niobium additions lead to the formation of NbC precipitates on the dislocation cell walls and sub boundaries. It is also shown that in the case of type 316 and type 347 steels the dynamic recrystallisation process (observed in type 304 steels at all temperatures above 900 deg C) is replaced by dynamic recovery at temperatures egal to or below about 1000 deg C [fr

Mixed problem with integral boundary condition for a high order mixed type partial differential equation

OpenAIRE

M. Denche; A. L. Marhoune

2003-01-01

In this paper, we study a mixed problem with integral boundary conditions for a high order partial differential equation of mixed type. We prove the existence and uniqueness of the solution. The proof is based on energy inequality, and on the density of the range of the operator generated by the considered problem.

BOUNDARY VALUE PROBLEM FOR A LOADED EQUATION ELLIPTIC-HYPERBOLIC TYPE IN A DOUBLY CONNECTED DOMAIN

Directory of Open Access Journals (Sweden)

O.Kh. Abdullaev

2014-06-01

Full Text Available We study the existence and uniqueness of the solution of one boundary value problem for the loaded elliptic-hyperbolic equation of the second order with two lines of change of type in double-connected domain. Similar results have been received by D.M.Kuryhazov, when investigated domain is one-connected.

Deformation effects on the development of grain boundary chronium depletion (sensitization) in type 316 austenitic stainless steels

International Nuclear Information System (INIS)

Atteridge, D.G.; Wood, W.E.; Advani, A.H.; Bruemmer, S.M.

1990-01-01

Deformation induces an acceleration in the kinetics and reduction in the thermodynamic barrier to carbide precipitation and grain boundary chromium depletion (GBCD) development of a high carbon Type 316 stainless steel (SS). This was observed in a study on strain effects on GBCD (or sensitization) development in the range of 575 degree C to 775 degree C. Grain boundary chromium depletion behavior of SS was examined using the indirect electrochemical potentiokinetic reactivation (EPR) test and supported by studies on carbide precipitation using transmission electron microscopy (TEM). 99 refs., 84 figs., 9 tabs

A new boundary control scheme for simultaneous achievement of H-mode and radiative cooling (SHC boundary)

International Nuclear Information System (INIS)

Ohyabu, N.

1995-05-01

We have proposed a new boundary control scheme (SHC boundary), which could allow simultaneous achievement of the H-mode type confinement improvement and radiative cooling with wide heat flux distribution. In our proposed configuration, a low m island layer sharply separates a plasma confining region from an open 'ergodic' boundary. The degree of openness in the ergodic boundary must be high enough to make the plasma pressure constant along the field line, which in turn separates low density plasma just outside the plasma confining region (the key external condition for achieving a good H-mode discharge) from very high density, cold radiative plasma near the wall (required for effective edge radiative cooling). Examples of such proposed SHC boundaries for Heliotron typed devices and tokamaks are presented. (author)

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Science.gov (United States)

Sheikhzada, Ahmad K.

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

Nonlinear Dynamics of Vortices in Different Types of Grain Boundaries

Energy Technology Data Exchange (ETDEWEB)

Sheikhzada, Ahmad [Old Dominion Univ., Norfolk, VA (United States)

2017-05-01

As a major component of linear particle accelerators, superconducting radio-frequency (SRF) resonator cavities are required to operate with lowest energy dissipation and highest accelerating gradient. SRF cavities are made of polycrystalline materials in which grain boundaries can limit maximum RF currents and produce additional power dissipation sources due to local penetration of Josephson vortices. The essential physics of vortex penetration and mechanisms of dissipation of vortices driven by strong RF currents along networks of grain boundaries and their contribution to the residual surface resistance have not been well understood. To evaluate how GBs can limit the performance of SRF materials, particularly Nb and Nb3Sn, we performed extensive numerical simulations of nonlinear dynamics of Josephson vortices in grain boundaries under strong dc and RF fields. The RF power due to penetration of vortices both in weakly-coupled and strongly-coupled grain boundaries was calculated as functions of the RF field and frequency. The result of this calculation manifested a quadratic dependence of power to field amplitude at strong RF currents, an illustration of resistive behavior of grain boundaries. Our calculations also showed that the surface resistance is a complicated function of field controlled by penetration and annihilation of vortices and antivortices in strong RF fields which ultimately saturates to normal resistivity of grain boundary. We found that Cherenkov radiation of rapidly moving vortices in grain boundaries can produce a new instability causing generation of expanding vortex-antivortex pair which ultimately drives the entire GB in a resistive state. This effect is more pronounced in polycrystalline thin film and multilayer coating structures in which it can cause significant increase in power dissipation and results in hysteresis effects in I-V characteristics, particularly at low temperatures.

Reaction kinetic analysis of reactor surveillance data

Energy Technology Data Exchange (ETDEWEB)

Yoshiie, T., E-mail: yoshiie@rri.kyoto-u.ac.jp [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka-fu 590-0494 (Japan); Kinomura, A. [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka-fu 590-0494 (Japan); Nagai, Y. [The Oarai Center, Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

2017-02-15

In the reactor pressure vessel surveillance data of a European-type pressurized water reactor (low-Cu steel), it was found that the concentration of matrix defects was very high, and a large number of precipitates existed. In this study, defect structure evolution obtained from surveillance data was simulated by reaction kinetic analysis using 15 rate equations. The saturation of precipitation and the growth of loops were simulated, but it was not possible to explain the increase in DBTT on the basis of the defect structures. The sub-grain boundary segregation of solutes was discussed for the origin of the DBTT increase.

New developments in geometric dynamic recrystallization

International Nuclear Information System (INIS)

Kassner, M.E.; Barrabes, S.R.

2005-01-01

The concept of geometric dynamic recrystallization (GDX) originated in 1980s with work on elevated-temperature deformation aluminum to large strains. In this case, substantial grain refinement occurs through a process of grain elongation and thinning leading to a dramatic increase in grain boundary area. The grain boundaries become serrated as a result of subgrain (low angle) boundary formation. Pinching off and annihilation of high-angle grain boundaries occurs as the original grains thin to about twice the subgrain diameter to and a 'steady-state' structure. This concept has since been carefully verified in pure Al, as well as Al-Mg alloys deforming in the three-power regime. Large strain deformation of Al single crystals is also consistent with the concept. Also, data in the literature on large strain deformation of a bcc iron alloy are consistent with GDX. Recent experiments on α-zirconium show that GDX applies to this hcp metal. Thus, it appears that GDX is a general phenomenon that can lead to grain refinement in the absence of any discontinuous dynamic recrystallization (DRX) or continuous dynamic recrystallization (CDX). A discussion of continuous dynamic recrystallization and geometric necessary boundaries in relation to GDX will also be discussed. This may be particularly relevant to severe plastic deformation such as rolling and equal-channel angular pressing where dramatic increases in the number of high-angle boundaries are observed

Substructures developed during creep and cyclic tests of type 304 stainless steel (heat 9T2796)

International Nuclear Information System (INIS)

Swindeman, R.W.; Bhargava, R.K.; Sikka, V.K.; Moteff, J.

1977-09-01

Substructures developed in tested specimens of a reference heat of type 304 stainless steel (heat 9T2796) are examined. Data include dislocation densities, cell and subgrain sizes, and carbide precipitate sizes. Testing conditions range for temperatures from 482 to 649 0 C, for stresses from 28 to 241 MPa, and for times from 4 to 15,000 hr. As expected, it is observed that temperature, stress, and time have strong influences on substructure. The change in the dislocation density is too small to measure for conditions which produce less than 1 percent monotonic strain. No cells form, and the major alteration of substructure is the precipitation of M 23 C 6 carbides on grain boundaries, on twin boundaries, and on some dislocations. At stresses ranging from 69 to 172 MPa and at temperatures ranging from 482 to 593 0 C, the dislocation density increases with increasing stress and is generally higher than expected from studies made at higher temperatures. Dislocations are arranged in fine networks stabilized by carbides. At stresses above 172 MPa and temperatures to 649 0 C, the dislocation density is too great to measure. Cells develop which are finer in size than cells developed at similar stresses but at higher temperatures. Dislocation densities and cell sizes for cyclic specimens are comparable to data for creep-tested specimens. On the basis of the observed substructures, recommendations are made regarding further studies which would assist in the development of constitutive equations for high-temperature inelastic analysis of reactor components

Symmetry Aspects of Dislocation-Effected Crystal Properties: Material Strength Levels and X-ray Topographic Imaging

Directory of Open Access Journals (Sweden)

Ronald W. Armstrong

2014-03-01

Full Text Available Several materials science type research topics are described in which advantageous use of crystal symmetry considerations has been helpful in ferreting the essential elements of dislocation behavior in determining material properties or for characterizing crystal/polycrystalline structural relationships; for example: (1 the mechanical strengthening produced by a symmetrical bicrystal grain boundary; (2 cleavage crack formation at the intersection within a crystal of symmetrical dislocation pile-ups; (3 symmetry aspects of anisotropic crystal indentation hardness measurements; (4 X-ray diffraction topography imaging of dislocation strains and subgrain boundary misorientations; and (5 point and space group aspects of twinning. Several applications are described in relation to the strengthening of grain boundaries in nanopolycrystals and of multiply-oriented crystal grains in polysilicon photovoltaic solar cell materials. A number of crystallographic aspects of the different topics are illustrated with a stereographic method of presentation.

Development of mapped stress-field boundary conditions based on a Hill-type muscle model.

Science.gov (United States)

Cardiff, P; Karač, A; FitzPatrick, D; Flavin, R; Ivanković, A

2014-09-01

Forces generated in the muscles and tendons actuate the movement of the skeleton. Accurate estimation and application of these musculotendon forces in a continuum model is not a trivial matter. Frequently, musculotendon attachments are approximated as point forces; however, accurate estimation of local mechanics requires a more realistic application of musculotendon forces. This paper describes the development of mapped Hill-type muscle models as boundary conditions for a finite volume model of the hip joint, where the calculated muscle fibres map continuously between attachment sites. The applied muscle forces are calculated using active Hill-type models, where input electromyography signals are determined from gait analysis. Realistic muscle attachment sites are determined directly from tomography images. The mapped muscle boundary conditions, implemented in a finite volume structural OpenFOAM (ESI-OpenCFD, Bracknell, UK) solver, are employed to simulate the mid-stance phase of gait using a patient-specific natural hip joint, and a comparison is performed with the standard point load muscle approach. It is concluded that physiological joint loading is not accurately represented by simplistic muscle point loading conditions; however, when contact pressures are of sole interest, simplifying assumptions with regard to muscular forces may be valid. Copyright © 2014 John Wiley & Sons, Ltd.

Mixed problem with nonlocal boundary conditions for a third-order partial differential equation of mixed type

OpenAIRE

Denche, M.; Marhoune, A. L.

2001-01-01

We study a mixed problem with integral boundary conditions for a third-order partial differential equation of mixed type. We prove the existence and uniqueness of the solution. The proof is based on two-sided a priori estimates and on the density of the range of the operator generated by the considered problem.

Diffraction-based study of fatigue crack initiation and propagation in aerospace aluminum alloys

Science.gov (United States)

Gupta, Vipul K.

The crack initiation sites and microstructure-sensitive growth of small fatigue cracks are experimentally characterized in two precipitation-hardened aluminum alloys, 7075-T651 and 7050-T7451, stressed in ambient temperature moist-air (warm-humid) and -50°C dry N2 (cold-dry) environmental conditions. Backscattered electron imaging (BSE) and energy dispersive spectroscopy (EDS) of the fracture surfaces showed that Fe-Cu rich constituent particle clusters are the most common initiation sites within both alloys stressed in either environment. The crack growth within each alloy, on average, was observed to be slowed in the cold-dry environment than in the warm-humid environment, but only at longer crack lengths. Although no overwhelming effects of grain boundaries and grain orientations on small-crack growth were observed, crack growth data showed local fluctuations within individual grains. These observations are understood as crack propagation through the underlying substructure at the crack surface and frequent interaction with low/high-angle grain and subgrain boundaries, during cyclic loading, and, are further attributed to periodic changes in crack propagation path and multiple occurrences of crack-branching observed in the current study. SEM-based stereology in combination with electron backscattered diffraction (EBSD) established fatigue crack surface crystallography within the region from ˜1 to 50 mum of crack initiating particle clusters. Fatigue crack facets were parallel to a wide variety of crystallographic planes, with pole orientations distributed broadly across the irreducible stereographic triangle between the {001} and {101}-poles within both warm-humid and cold-dry environments. The results indicate environmentally affected fatigue cracking in both cases, given the similarity between the observed morphology and crystallography with that of a variety of aerospace aluminum alloys cracked in the presence of moist-air. There was no evidence of

GENERAL DECAY FOR A DIFFERENTIAL INCLUSION OF KIRCHHOFF TYPE WITH A MEMORY CONDITION AT THE BOUNDARY

Institute of Scientific and Technical Information of China (English)

Jum-Ran KANG

2014-01-01

In this article, we consider a differential inclusion of Kirchhoff type with a memory condition at the boundary. We prove the asymptotic behavior of the corresponding solutions. For a wider class of relaxation functions, we establish a more general decay result, from which the usual exponential and polynomial decay rates are only special cases.

Existence theory for sequential fractional differential equations with anti-periodic type boundary conditions

Directory of Open Access Journals (Sweden)

Aqlan Mohammed H.

2016-01-01

Full Text Available We develop the existence theory for sequential fractional differential equations involving Liouville-Caputo fractional derivative equipped with anti-periodic type (non-separated and nonlocal integral boundary conditions. Several existence criteria depending on the nonlinearity involved in the problems are presented by means of a variety of tools of the fixed point theory. The applicability of the results is shown with the aid of examples. Our results are not only new in the given configuration but also yield some new special cases for specific choices of parameters involved in the problems.

Breather type solutions of the vector nonlinear Schroedinger equation with quasi-constant boundary conditions

International Nuclear Information System (INIS)

Makhan'kov, V.G.; Slavov, S.I.

1989-01-01

Vector nonlinear Schroedinger equations (VS3) is investigated under quasi-constant boundary conditions. New two-soliton solutions are obtained with such non-trivial dynamics that they may be called the breather solutions. A version of the basic Novikov-Dubrovin-Krichever algebro-geometrical approach is applied to obtain breather like solutions existing for all types of internal symmetry is specified are formulated in terms of the soliton velocity expressed via the parameters of the problem. 4 refs

Influence of aging at 200 C on the corrosion resistance of Al-Li and AI-Li-Cu alloys

International Nuclear Information System (INIS)

Kumai, C.; Kusinski, J.; Devine, T.M.

1989-01-01

This paper presents an investigation of the influence of heat treatment on the microstructure and corrosion resistance of an aluminum lithium alloy and two aluminum-lithium-copper alloys. Aging the Al-Li alloy resulted in the precipitation of δ with precipitate-free zone (PFZ) formation along the grain boundaries. The intragranular precipitation of δ did not influence either the morphology of pitting or the magnitude of the pitting potential. Pits appeared to consist of aggregates of submicron-sized cuboidal volumes. Their faceted shape suggests the strong influence of crystallographic factors. Anodic polarization of the Al-Li-Cu alloy is the T8 condition in aqueous solutions containing chloride ions resulted in blistering of the passive film and the formation of pits that were hemispherical in shape. Aging the Al-Li-Cu resulted in the precipitation of Cu-rich phases with PFZ formation along the grain and subgrain boundaries. Energy dispersive x-ray (EDX) microchemical analyses indicated the PFZ was depleted of copper. Anodic polarization of aged samples in chloride ion media resulted in localized attack along the subgrain and grain boundaries. Such attack did not occur in solutions free of chloride ions. The electrochemical tests and microchemical analyses suggest that the boundary corrosion was caused by the pitting corrosion of copper-depleted zones

Prodosic cues to discourse boundaries in experimental dialogues

NARCIS (Netherlands)

Geluykens, R.; Swerts, M.G.J.

1994-01-01

In a dialogue, there are at least two sorts of boundaries between discourse units. One type of boundary signals the end of a topical unit; another type of boundary the end of a turn at talk. These two do not necessarily coincide, as a speaker may wish to a new topical unit without wanting to be

Role of grain boundaries in the conduction of Eu–Ni substituted Y-type hexaferrites

Energy Technology Data Exchange (ETDEWEB)

Ali, Irshad, E-mail: irshadalibzu@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Islam, M.U. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Naeem Ashiq, Muhammad, E-mail: naeemashiqqau@yahoo.com [Institute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800 (Pakistan); Asif Iqbal, M. [National University of Sciences and Technology, EME College, Islamabad (Pakistan); Khan, Hasan M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Murtaza, G. [Centre for Advanced Studies in Physics, Government College University, Lahore 54000 (Pakistan)

2014-08-01

Single phase nanostructured (Eu–Ni) substituted Y-type hexaferrites with nominal composition of Sr{sub 2}Co{sub 2−x}Ni{sub x}Eu{sub y}Fe{sub 12−y}O{sub 22} (x=0.0–1, y=0.0–0.1) were synthesized by the microemulsion method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The presence of Debye peaks in imaginary electric modulus curves confirmed the existence of relaxation phenomena in given frequency range. The AC conductivity follows power law, with exponent (n) value, ranges from 0.81–0.97, indicating that the mechanism is due to polaron hopping. In the present ferrite system, Cole–Cole plots were used to separate the grain and grain boundary effects. Eu–Ni substitution leads to a remarkable rise of grain boundary resistance as compared to the grain resistance. As both AC conductivity and Cole–Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. It was also observed that the AC activation energy is lower than the DC activation energy. Appreciable improved values of quality factor suggested the possible use of these synthesized materials for power applications and high frequency multilayer chip inductors. - Highlights: • Single phase nanostructures were synthesized by the micro-emulsion method. • Substitution leads to a remarkable rise of grain boundary resistance. • The AC activation energy is lower than the DC activation energy. • Improved values of quality factor make these materials useful for high frequency multilayer chip inductors.

Effect of thermal aging on grain structural characteristic and Ductile-to-Brittle transition temperature of CLAM steel at 550 °C

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230031 (China); Chen, Jianwei [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Xu, Gang, E-mail: gang.xu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

2017-02-15

Highlights: • The grain boundary length per unit area decreased with the increasing aging time. • The fraction of LABs increased obviously after thermal aging. • Prior austenitic grain refinement is more important to improve low temperature toughness. - Abstract: In this work, electron backscatter diffraction (EBSD) was used to investigate the grain structure evolution of China low activation martensitic (CLAM) steel samples which were aged at 550 °C for 0 h, 2000 h, 4000 h and 10,000 h. The results showed that the prior austenitic grain size increased with the aging time, which led to the decrease of grain boundary length. The fraction of misorientation angle in a range from about 4 to 10° increased obviously after thermal aging for 10,000 h, and it indicated that the fine subgrains formed in the CLAM steel during the long-term thermal exposure. Furthermore, Charpy impact experiments were carried out to analyze the toughness of the CLAM steel before and after aging, particularly the Ductile-to-Brittle Transition Temperature (DBTT). Though amounts of fine subgrians formed in matrix, a substantial increase in DBTT (∼40.1 °C) had been noticed after aging for 10,000 h. The results showed that the high angle boundaries such as prior austenitic grain boundaries are more effective in retarding the propagation of cleavage crack than subgrain boundaries.

Classical solutions for discrete potential boundary value problems with generalized Leray-Lions type operator and variable exponent

Directory of Open Access Journals (Sweden)

Bila Adolphe Kyelem

2017-04-01

Full Text Available In this article, we prove the existence of solutions for some discrete nonlinear difference equations subjected to a potential boundary type condition. We use a variational technique that relies on Szulkin's critical point theory, which ensures the existence of solutions by ground state and mountain pass methods.

The Boundary Function Method. Fundamentals

Science.gov (United States)

Kot, V. A.

2017-03-01

The boundary function method is proposed for solving applied problems of mathematical physics in the region defined by a partial differential equation of the general form involving constant or variable coefficients with a Dirichlet, Neumann, or Robin boundary condition. In this method, the desired function is defined by a power polynomial, and a boundary function represented in the form of the desired function or its derivative at one of the boundary points is introduced. Different sequences of boundary equations have been set up with the use of differential operators. Systems of linear algebraic equations constructed on the basis of these sequences allow one to determine the coefficients of a power polynomial. Constitutive equations have been derived for initial boundary-value problems of all the main types. With these equations, an initial boundary-value problem is transformed into the Cauchy problem for the boundary function. The determination of the boundary function by its derivative with respect to the time coordinate completes the solution of the problem.

Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.

Science.gov (United States)

Qian, B; Saeidi, K; Kvetková, L; Lofaj, F; Xiao, C; Shen, Z

2015-12-01

CrCoMo alloy specimens were successfully fabricated using selective laser melting (SLM). The aim of this study was to carefully investigate microstructure of the SLM specimens in order to understand the influence of their structural features inter-grown on different length scales ranging from nano- to macro-levels on their mechanical properties. Two different sets of processing parameters developed for building the inner part (core) and the surface (skin) of dental prostheses were tested. Microstructures were characterized by SEM, EBSD and XRD analysis. The elemental distribution was assessed by EDS line profile analysis under TEM. The mechanical properties of the specimens were measured. The microstructures of both specimens were characterized showing formation of grains comprised of columnar sub-grains with Mo-enrichment at the sub-grain boundaries. Clusters of columnar sub-grains grew coherently along one common crystallographic direction forming much larger single crystal grains which are intercrossing in different directions forming an overall dendrite-like microstructure. Three types of microstructural defects were occasionally observed; small voids (10 μm). Despite the presence of these defects, the yield and the ultimate tensile strength (UTS) were 870 and 430MPa and 1300MPa and 1160MPa, respectively, for the skin and core specimens which are higher than casted dental alloy. Although the formation of microstructural defects is hard to be avoided during the SLM process, the SLM CoCrMo alloys can achieve improved mechanical properties than their casted counterparts, implying they are "defect-tolerant". Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Nucleation and thickening of shear bands in nano-scale twin/matrix lamellae of a Cu-Al alloy processed by dynamic plastic deformation

DEFF Research Database (Denmark)

Hong, C.S.; Tao, N.R.; Huang, Xiaoxu

2010-01-01

dislocation structure (DDS) into a nano-sized (sub)grain structure (NGS). On the two sides of a core region, two transition layers (TRLs) exist where the T/M lamellae experienced much less shear strain. The interface boundaries separating the core region and the TRLs are characterized by very large shear...

Conformal boundaries of warped products

DEFF Research Database (Denmark)

Kokkendorff, Simon Lyngby

2006-01-01

In this note we prove a result on how to determine the conformal boundary of a type of warped product of two length spaces in terms of the individual conformal boundaries. In the situation, that we treat, the warping and conformal distortion functions are functions of distance to a base point....... The result is applied to produce examples of CAT(0)-spaces, where the conformal and ideal boundaries differ in interesting ways....

Solution of a Problem Linear Plane Elasticity with Mixed Boundary Conditions by the Method of Boundary Integrals

Directory of Open Access Journals (Sweden)

Nahed S. Hussein

2014-01-01

Full Text Available A numerical boundary integral scheme is proposed for the solution to the system of …eld equations of plane. The stresses are prescribed on one-half of the circle, while the displacements are given. The considered problem with mixed boundary conditions in the circle is replaced by two problems with homogeneous boundary conditions, one of each type, having a common solution. The equations are reduced to a system of boundary integral equations, which is then discretized in the usual way, and the problem at this stage is reduced to the solution to a rectangular linear system of algebraic equations. The unknowns in this system of equations are the boundary values of four harmonic functions which define the full elastic solution and the unknown boundary values of stresses or displacements on proper parts of the boundary. On the basis of the obtained results, it is inferred that a stress component has a singularity at each of the two separation points, thought to be of logarithmic type. The results are discussed and boundary plots are given. We have also calculated the unknown functions in the bulk directly from the given boundary conditions using the boundary collocation method. The obtained results in the bulk are discussed and three-dimensional plots are given. A tentative form for the singular solution is proposed and the corresponding singular stresses and displacements are plotted in the bulk. The form of the singular tangential stress is seen to be compatible with the boundary values obtained earlier. The efficiency of the used numerical schemes is discussed.

Pressure effect on grain boundary diffusion

International Nuclear Information System (INIS)

Smirnova, E.S.; Chuvil'deev, V.N.

1997-01-01

The influence of hydrostatic pressure on grain boundary diffusion and grain boundary migration in metallic materials is theoretically investigated. The model is suggested that permits describing changes in activation energy of grain boundary self-diffusion and diffusion permeability of grain boundaries under hydrostatic pressure. The model is based on the ideas about island-type structure of grain boundaries as well as linear relationship of variations in grain boundary free volume to hydrostatic pressure value. Comparison of theoretical data with experimental ones for a number of metals and alloys (α-Zr, Sn-Ge, Cu-In with Co, In, Al as diffusing elements) shows a qualitative agreement

Oblique derivative problems for generalized Rassias equations of mixed type with several characteristic boundaries

Directory of Open Access Journals (Sweden)

Guo Chun Wen

2009-05-01

Full Text Available This article concerns the oblique derivative problems for second-order quasilinear degenerate equations of mixed type with several characteristic boundaries, which include the Tricomi problem as a special case. First we formulate the problem and obtain estimates of its solutions, then we show the existence of solutions by the successive iterations and the Leray-Schauder theorem. We use a complex analytic method: elliptic complex functions are used in the elliptic domain, and hyperbolic complex functions in the hyperbolic domain, such that second-order equations of mixed type with degenerate curve are reduced to the first order mixed complex equations with singular coefficients. An application of the complex analytic method, solves (1.1 below with $m=n=1$, $a=b=0$, which was posed as an open problem by Rassias.

Subgroup report on grain boundary and interphase boundary structure and properties

International Nuclear Information System (INIS)

Balluffi, R.W.; Cannon, R.M.; Clarke, D.R.; Heuer, A.H.; Ho, P.S.; Kear, B.H.; Vitek, V.; Weertman, J.R.; White, C.L.

1979-01-01

In many high temperature structural applications, the performance characteristics of a materials system are largely controlled by the properties of its grain and interphase boundaries. Failure in creep and fatigue frequently occurs by cavitation, or cracking along grain boundaries. In a few special cases, this failure problem has been overcome by directional alignment of grain and interphase boundaries by various types of metallurgical processing such as directional solidification and directional recrystallization. A good example is to be found in the application of directionally aligned structures in high performance gas-turbine airfoils. However, where fine, equiaxed grain structures are desirable, other methods of controlling grain boundary properties have been developed. Important among these has been the introduction of improvements in primary melting practices, designed to control important impurities. This is of decisive importance because even traces of certain impurity elements present in grain boundaries in high temperature materials can seriously affect properties. Impurities are deleterious and need to be removed. However, in certain cases, (e.g., creep fracture) controlled impurity additions can be beneficial and result in improved properties

On the microstructural basis of creep strength and creep-fatigue interaction in 9-12 % Cr steels for application in power plants

Energy Technology Data Exchange (ETDEWEB)

Chilukuru, H

2007-03-06

As part of the efforts of preserving the environment it is necessary to reduce of the CO2 emissions from power plants. This can be done by increasing the plant efficiency. Research groups around the world are engaged in developing new steels capable of sustaining higher stresses and temperatures envisaged for high-efficiency power plants. Research carried out in Europe is organized within the COST Programme (Co-Operation in Science and Technology) aiming at replacing the conventional steels of type X20CrMoV121 by the new class of 9-12% Cr-steels with modified composition. The resistance of materials against deformation at elevated temperatures depends on their microstructure. Frequently in 9-12% Cr-steels improved short-term creep properties do not persist in the long-term service [1, 2, 3, 4, 5, 6]. This is related with insufficient microstructural stability. Hardening contributions in 9-12% Cr-steels come from solute atoms of the ferritic matrix, from dislocations, and from precipitates of foreign phases within the matrix. The term ''carbide stabilized substructure hardening'' of 9-12% Cr steels [7, 8] indicates that the hardening contributions are interdependent. The dislocations are the carriers of plastic deformation. They interact with each other, with solute atoms and with precipitates. The dislocation-dislocation interaction leads to formation of planar dislocation networks constituting low-angle boundaries. They form a subgrain structure within the grains. At present, a full and detailed understanding of the effects exerted by the different components of microstructure on creep strength is still lacking. The present work makes a contribution to the efforts of understanding the microstructural basis of creep strength and of creep-fatigue interaction by transmission electron microscopic structure investigations coupled with creep tests. Investigations by transmission electron microscopy (TEM) were carried out with regard to hardening by subgrain boundaries

On the microstructural basis of creep strength and creep-fatigue interaction in 9-12 % Cr steels for application in power plants

Energy Technology Data Exchange (ETDEWEB)

Chilukuru, H.

2007-03-06

As part of the efforts of preserving the environment it is necessary to reduce of the CO2 emissions from power plants. This can be done by increasing the plant efficiency. Research groups around the world are engaged in developing new steels capable of sustaining higher stresses and temperatures envisaged for high-efficiency power plants. Research carried out in Europe is organized within the COST Programme (Co-Operation in Science and Technology) aiming at replacing the conventional steels of type X20CrMoV121 by the new class of 9-12% Cr-steels with modified composition. The resistance of materials against deformation at elevated temperatures depends on their microstructure. Frequently in 9-12% Cr-steels improved short-term creep properties do not persist in the long-term service [1, 2, 3, 4, 5, 6]. This is related with insufficient microstructural stability. Hardening contributions in 9-12% Cr-steels come from solute atoms of the ferritic matrix, from dislocations, and from precipitates of foreign phases within the matrix. The term ''carbide stabilized substructure hardening'' of 9-12% Cr steels [7, 8] indicates that the hardening contributions are interdependent. The dislocations are the carriers of plastic deformation. They interact with each other, with solute atoms and with precipitates. The dislocation-dislocation interaction leads to formation of planar dislocation networks constituting low-angle boundaries. They form a subgrain structure within the grains. At present, a full and detailed understanding of the effects exerted by the different components of microstructure on creep strength is still lacking. The present work makes a contribution to the efforts of understanding the microstructural basis of creep strength and of creep-fatigue interaction by transmission electron microscopic structure investigations coupled with creep tests. Investigations by transmission electron microscopy (TEM) were carried out with regard to hardening by

Boundary conditions in random sequential adsorption

Science.gov (United States)

Cieśla, Michał; Ziff, Robert M.

2018-04-01

The influence of different boundary conditions on the density of random packings of disks is studied. Packings are generated using the random sequential adsorption algorithm with three different types of boundary conditions: periodic, open, and wall. It is found that the finite size effects are smallest for periodic boundary conditions, as expected. On the other hand, in the case of open and wall boundaries it is possible to introduce an effective packing size and a constant correction term to significantly improve the packing densities.

A Semilinear Wave Equation with a Boundary Condition of Many-Point Type: Global Existence and Stability of Weak Solutions

Directory of Open Access Journals (Sweden)

Giai Giang Vo

2015-01-01

Full Text Available This paper is devoted to the study of a wave equation with a boundary condition of many-point type. The existence of weak solutions is proved by using the Galerkin method. Also, the uniqueness and the stability of solutions are established.

Mechanical Behavior of UO2 at Sub-grain Length Scales: Quantification of Elastic, Plastic and Creep Properties via Microscale Testing

Energy Technology Data Exchange (ETDEWEB)

Peralta, Pedro

2018-04-16

Techniques were developed to measure properties at sub-grain scales using depleted Uranium Oxide (d-UO2) samples heat-treated to obtain different grain sizes and oxygen stoichiometries, through three main tasks: 1) sample processing and characterization, 2) microscale and conventional testing and 3) modeling. Grain size and crystallography were characterized using Scanning Electron Microscopy (SEM), in conjunction with Electron Backscattering Diffraction (EBSD) and Electron Channeling Contrast Imaging (ECCI). Grains were then carefully selected based on their crystallographic orientations to perform ex-situ micromechanical tests with samples machined via Focused Ion Beam (FIB), with emphasis on micro-cantilever bending. These experiments were performed under controlled atmospheres, to insure stoichiometry control, at temperatures up to 700 °C and allowed measurements involving elastic (effective Young’s modulus), plastic (critical resolved shear stresses) and creep (creep strain rates) behavior. Conventional compression experiments were performed simultaneously to compare with the ex-situ measurements and study potential size effects. Modeling was implemented using anisotropic elasticity and inelastic constitutive relations for plasticity and creep based on kinematics and kinetics of dislocation glide that account for the effects of crystal orientation, and stress. The models will be calibrated and validated using the experimental data. This project provided insight on correlations among stoichiometry, crystallography and mechanical behavior in advanced oxide fuels, provided valuable experimental data to validate and calibrate mesoscale fuel performance codes and also a framework to measure sub-grain scale mechanical properties that should be suitable for use with irradiated samples due to small volumes required. The goals and metrics of the ongoing study of thermo-mechanical behavior in depleted uranium dioxide (d-UO2) outlined in this project have been

Computer generated structures of grain boundaries in Li2-type ordered alloys

International Nuclear Information System (INIS)

DeHosson, J.Th.M.; Pestman, B.J.; Schapink, F.W.; Tichelaar, F.D.

1988-01-01

In recent years, the influence of the establishment of long-range order in cubic alloys on the structure of grain boundaries in Li 2 alloys has been considered. Thus, for example, for the Σ = 5 (310) tilt boundary the various possible structures have been investigated that are generated upon ordering, starting from plausible structures in the disordered state. However, apart from some rough energy estimates based upon nearest neighbor interactions, no reliable energy calculations have been performed of these different possible structures. In this paper, computer calculations based upon interatomic pair potentials constructed in such a way that the Li 2 structure is stable with respect to disordering, are reported for the Σ = 5 (310) boundary. The relative stability of various possible structures, with associated different boundary compositions, has been investigated

The effect of trace additions of Zn on the precipitation behavior of alloy 8090 during artificial aging

Science.gov (United States)

Kilmer, R. J.; Stoner, G. E.

1991-01-01

The effect(s) of trace additions of Zn to the artificial aging behavior of alloy 8090 (Al-Li-Cu-Mg-Zr) was investigated in the approximate composition range 0-1 wt-pct Zn. Trace Zn additions were found to delay aging and under equivalent aging treatments (100 hrs at 160 C) the alloy without Zn and the 1.07 wt-pct Zn alloy developed delta-prime-free zones along subgrain boundaries, while the alloys of 0.21 and 0.58 wt-pct Zn did not. DSC analysis indicated that Zn was being incorporated into the delta-prime, shifting it's exotherm to higher temperatures, while having little if any effect on its associated endotherm making it unlikely that it is an artifact of a solvus shift. In the 8090 + 1.07 wt-pct Zn alloy, coarse precipitates were found to reside on subgrain boundaries and EDS indicated that they were rich in Cu and Zn. It was also noted that in the Zn containing 8090 varients, the S prime precipitates were more coarse in size than the baseline 8090.

Fundamental modelling of particle strengthened 9-12% Cr steels

Energy Technology Data Exchange (ETDEWEB)

Magnusson, Hans; Sandstroem, Rolf [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering; Royal Inst. of Tech., Stockholm (Sweden). Brinell Centre

2010-07-01

Creep strength of particle strengthened 9-12% Cr steels can be predicted by fundamental modelling. The creep strength is evaluated from the state of the microstructure during creep. Particle hardening at high temperatures can be predicted by taking dislocation climb across particles into account. Work hardening is calculated from immobile dislocations in subgrain interiors and at boundaries using the composite theory. Subgrain coarsening will lower the influence of the mechanically hard boundaries. Recovery in dislocation density is predicted through static recovery by climb and dynamic recovery by locking and dipole formation. Solid solution hardening is needed in order to explain the difference in creep strength between different 9-12% Cr steels. The accumulation of large atoms such as Mo and W will slow down the dislocation climb velocity, and thereby the microstructure recovery rate. 100000h rupture strength is predicted for X20, P91, P92 steels without any use of fitting parameters. The creep strength of P91 steel with different microstructure due to Al additions. Z-phase transformation and heat affected material is presented. (orig.)

Role of grain boundary nature and residual strain in controlling sensitisation of type 304 stainless steel

International Nuclear Information System (INIS)

Ahmedabadi, Parag M.; Kain, Vivekanand; Dangi, Bhupinder Kumar; Samajdar, I.

2013-01-01

Highlights: ► Low-level of residual strain improved resistance to sensitisation. ► High fraction of special boundaries did not always reduce sensitisation. ► Area attacked during the EPR test correlated well with degree of sensitisation. ► Volume loss during the EPR test also correlated well with degree of sensitisation. - Abstract: The effects of residual strain and grain boundary character distribution on sensitisation of type 304 stainless steel at 525 °C were evaluated using electrochemical potentiokinetic reactivation (EPR) technique. The results indicated that a very low level of residual strain and a high fraction of annealing twins significantly improved the resistance to sensitisation. Image analysis indicated that the fraction of area attacked during the EPR test correlated well with the EPR data. The volume loss, calculated using atomic force microscopic examinations, during the EPR tests also correlated well with the EPR results.

Observations of ’Economical’ Fixed Prosthodontic Alloys,

Science.gov (United States)

1982-01-01

Office) 15. SECURITY CLASS. (of this ,.portj Ia. OS7RI~fl3 ~TATM~T1of5sA. DECLASSIFICATION/OO44GRAUTIV S Unlimited 17. 0137 PI3UT10ON STATEMENT (of the...however, the silver-palladium and silver-indium materials require ~DA~3 47 EOfl4O tO’/SfOBOLTE UNCLASSIFIED 8 2’ 02 R -/ SECURITY CLASSIFICATION OF...ous grain boundary netowrk , whereas those of Salivan revealed large grains, discontinuous grain boundaries and prominent subgrains. Microstructures

A simplified treatment of the boundary conditions of the k- ε model in coarse-mesh CFD-type codes

International Nuclear Information System (INIS)

Analytis, G.Th.; Andreani, M.

1999-01-01

In coarse-mesh, CFD-type codes such as the containment analysis code GOTHIC, one of the options that can be used for modelling of turbulence is the k - ε model. However, in contrast to most other CFD codes which are designed to perform detailed CFD calculations with a large number of spatial meshes, codes such as GOTHIC are primarily aimed at simplified calculation of transients in large spaces (e.g., reactor containments), and generally use coarse meshes. The solution of the two parabolic equations for the k - ε model requires the definition of boundary conditions at physical boundaries and this, in turn, requires very small spatial meshes near these boundaries. Hence, while in codes like CFX this is done in a rigorous and consistent manner, codes like GOTHIC adopt an indirect and heuristic approach, due to the fact that the spatial meshes are usually large. This can have adverse consequences during the calculation of a transient and in this work, we shall give some examples of this and outline a method by which this problem can be avoided. (author)

Grain boundary composition and irradiation-assisted stress corrosion cracking resistance in Type 348 stainless steel

International Nuclear Information System (INIS)

Jacobs, A.J.; Wozadlo, G.P.; Nakata, K.

1994-01-01

Scanning transmission electron microscopy (STEM) analyses, in-reactor swelling mandrel tests, and laboratory constant extension rate tensile (CERT) tests were conducted on nine custom type 348 (UNS S34800) stainless steel (SS) alloys in an attempt to correlate grain boundary composition with irradiation-assisted stress corrosion cracking (IASCC) resistance. Phosphorus (P) enrichment showed the best correlation with in-reactor test results, and chromium (Cr) depletion showed the best correlation with laboratory results. Silicon (Si) and P enrichment were found to depend quantitatively on the bulk concentrations of these elements. The amount of Cr depletion seemed dependent at least partially on the amounts of Si and/or P enrichment. Si and P enrichment and Cr depletion were suppressed by higher carbon (C) contents, such as that present in commercial-purity type 348 SS

Heat Kernel Asymptotics of Zaremba Boundary Value Problem

Energy Technology Data Exchange (ETDEWEB)

Avramidi, Ivan G. [Department of Mathematics, New Mexico Institute of Mining and Technology (United States)], E-mail: iavramid@nmt.edu

2004-03-15

The Zaremba boundary-value problem is a boundary value problem for Laplace-type second-order partial differential operators acting on smooth sections of a vector bundle over a smooth compact Riemannian manifold with smooth boundary but with discontinuous boundary conditions, which include Dirichlet boundary conditions on one part of the boundary and Neumann boundary conditions on another part of the boundary. We study the heat kernel asymptotics of Zaremba boundary value problem. The construction of the asymptotic solution of the heat equation is described in detail and the heat kernel is computed explicitly in the leading approximation. Some of the first nontrivial coefficients of the heat kernel asymptotic expansion are computed explicitly.

Conformal boundary loop models

International Nuclear Information System (INIS)

Jacobsen, Jesper Lykke; Saleur, Hubert

2008-01-01

We study a model of densely packed self-avoiding loops on the annulus, related to the Temperley-Lieb algebra with an extra idempotent boundary generator. Four different weights are given to the loops, depending on their homotopy class and whether they touch the outer rim of the annulus. When the weight of a contractible bulk loop x≡q+q -1 element of (-2,2], this model is conformally invariant for any real weight of the remaining three parameters. We classify the conformal boundary conditions and give exact expressions for the corresponding boundary scaling dimensions. The amplitudes with which the sectors with any prescribed number and types of non-contractible loops appear in the full partition function Z are computed rigorously. Based on this, we write a number of identities involving Z which hold true for any finite size. When the weight of a contractible boundary loop y takes certain discrete values, y r ≡([r+1] q )/([r] q ) with r integer, other identities involving the standard characters K r,s of the Virasoro algebra are established. The connection with Dirichlet and Neumann boundary conditions in the O(n) model is discussed in detail, and new scaling dimensions are derived. When q is a root of unity and y=y r , exact connections with the A m type RSOS model are made. These involve precise relations between the spectra of the loop and RSOS model transfer matrices, valid in finite size. Finally, the results where y=y r are related to the theory of Temperley-Lieb cabling

Boundary and sub-boundary hardening in high-Cr ferritic steels during long-term creep at 650 C

Energy Technology Data Exchange (ETDEWEB)

Abe, F. [National Institute for Materials Science (NIMS) (Japan)

2008-07-01

The sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the sub-boundary hardening. This improves long-term creep strength. The enhancement of boundary and subboundary hardening by fine distribution of precipitates along boundaries is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steels P92 and P122. In NIMS 9% Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. (orig.)

Microstructure and hardness studies of Inconel 718 manufactured by selective laser melting before and after solution heat treatment

International Nuclear Information System (INIS)

Tucho, Wakshum M.; Cuvillier, Priscille; Sjolyst-Kverneland, Atle; Hansen, Vidar

2017-01-01

The microstructure of Additive Manufactured (AM) Inconel 718 in general and Selective Laser Melting (SLM), in particular is different from the material produced by conventional methods due to the rapid solidification process associated with the former. As a result, the widely adapted standard solution heat treatment temperature (<1100 °C) for conventional material is found to be not high enough for materials fabricated with SLM method in order to dissolve Laves and other microsegregated phases for releasing the ageing constituents (Nb, Ti, Al) sufficiently into the alloy matrix. In this study, sample of Inconel 718 fabricated with SLM method were solution heat-treated to 1100 °C or 1250 °C at different hold times to investigate the dissolution of macro- and micro-segregated precipitates. Investigations of microstructure and segregation in as-printed and solution heat-treated states have been studied using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM). Measurement of material hardness was performed with Vickers hardness tests. The microstructure of the as-printed parts exhibit non-columnar grains, but contain well-shaped columnar/cellular sub-grains. The intergranular boundaries are decorated with high density of dislocations and segregated particles. Tremendous stress relief and grain coarsening were observed with solution heat treatment. In particular, at 1250 °C annealing, the sub-grains, including precipitates and dislocation networks along the sub-grain boundaries, were entirely dissolved. However, the 1100/1250 °C solution heat treatment scheme could not dissolve microsegregated precipitates and carbides completely. Details of the analysis on microstructure, dissolution of precipitates and hardness are presented.

Microstructure and hardness studies of Inconel 718 manufactured by selective laser melting before and after solution heat treatment

Energy Technology Data Exchange (ETDEWEB)

Tucho, Wakshum M., E-mail: wakshum.m.tucho@uis.no [Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger (Norway); Cuvillier, Priscille [Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger (Norway); Sjolyst-Kverneland, Atle [Roxar/Emerson Process Management, POB 112, 4065 Stavanger (Norway); Hansen, Vidar [Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger (Norway)

2017-03-24

The microstructure of Additive Manufactured (AM) Inconel 718 in general and Selective Laser Melting (SLM), in particular is different from the material produced by conventional methods due to the rapid solidification process associated with the former. As a result, the widely adapted standard solution heat treatment temperature (<1100 °C) for conventional material is found to be not high enough for materials fabricated with SLM method in order to dissolve Laves and other microsegregated phases for releasing the ageing constituents (Nb, Ti, Al) sufficiently into the alloy matrix. In this study, sample of Inconel 718 fabricated with SLM method were solution heat-treated to 1100 °C or 1250 °C at different hold times to investigate the dissolution of macro- and micro-segregated precipitates. Investigations of microstructure and segregation in as-printed and solution heat-treated states have been studied using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM). Measurement of material hardness was performed with Vickers hardness tests. The microstructure of the as-printed parts exhibit non-columnar grains, but contain well-shaped columnar/cellular sub-grains. The intergranular boundaries are decorated with high density of dislocations and segregated particles. Tremendous stress relief and grain coarsening were observed with solution heat treatment. In particular, at 1250 °C annealing, the sub-grains, including precipitates and dislocation networks along the sub-grain boundaries, were entirely dissolved. However, the 1100/1250 °C solution heat treatment scheme could not dissolve microsegregated precipitates and carbides completely. Details of the analysis on microstructure, dissolution of precipitates and hardness are presented.

Non-equilibrium grain boundary segregation of boron in austenitic stainless steel - IV. Precipitation behaviour and distribution of elements at grain boundaries

International Nuclear Information System (INIS)

Karlsson, L.; Norden, H.

1988-01-01

The distribution of elements and the precipitation behaviour at grain boundaries have been studied in boron containing AISI 316L and ''Mo-free AISI 316L'' type austenitic stainless steels. A combination of microanalytical techniques was used to study the boundary regions after cooling at 0.29-530 0 C/s from 800, 1075 or 1250 0 C. Tetragonal M/sub 2/B, M/sub 5/B/sub 3/ and M/sub 3/B/sub 2/, all rich in Fe, Cr and Mo, precipitated in the ''high B'' (40 ppm) AISI 316L steel whereas orthorhombic M/sub 2/B, rich in Cr and Fe was found in the ''Mo-free steel'' with 23 ppm B. In the ''high B steel'' a thin (<2nm), continuous layer, containing B, Cr, Mo and Fe and having a stoichiometry of typically M/sub 9/B, formed at boundaries after cooling at intermediate cooling rates. For both types of steels a boundary zone was found, after all heat treatments, with a composition differing significantly from the bulk composition. The differences were most marked after cooling at intermediate cooling rates. In both types of steel boundary depletion of Cr and enrichment of B and C occurred. It was found that non-equilibrium grain boundary segregation of boron can affect the precipitation behaviour by making the boundary composition enter a new phase field ''Non-equilibrium phases'' might also form. The synergistic effect of B and Mo on the boundary composition and precipitation behaviour, and the observed indications of C non-equilibrium segregation are discussed

Nonlinear Elliptic Boundary Value Problems at Resonance with Nonlinear Wentzell Boundary Conditions

Directory of Open Access Journals (Sweden)

Ciprian G. Gal

2017-01-01

Full Text Available Given a bounded domain Ω⊂RN with a Lipschitz boundary ∂Ω and p,q∈(1,+∞, we consider the quasilinear elliptic equation -Δpu+α1u=f in Ω complemented with the generalized Wentzell-Robin type boundary conditions of the form bx∇up-2∂nu-ρbxΔq,Γu+α2u=g on ∂Ω. In the first part of the article, we give necessary and sufficient conditions in terms of the given functions f, g and the nonlinearities α1, α2, for the solvability of the above nonlinear elliptic boundary value problems with the nonlinear boundary conditions. In other words, we establish a sort of “nonlinear Fredholm alternative” for our problem which extends the corresponding Landesman and Lazer result for elliptic problems with linear homogeneous boundary conditions. In the second part, we give some additional results on existence and uniqueness and we study the regularity of the weak solutions for these classes of nonlinear problems. More precisely, we show some global a priori estimates for these weak solutions in an L∞-setting.

Boundary stabilization of memory-type thermoelasticity with second sound

Science.gov (United States)

Mustafa, Muhammad I.

2012-08-01

In this paper, we consider an n-dimensional thermoelastic system of second sound with a viscoelastic damping localized on a part of the boundary. We establish an explicit and general decay rate result that allows a wider class of relaxation functions and generalizes previous results existing in the literature.

Dual nature of localization in guiding systems with randomly corrugated boundaries: Anderson-type versus entropic

International Nuclear Information System (INIS)

Tarasov, Yu.V.; Shostenko, L.D.

2015-01-01

A unified theory for the conductance of an infinitely long multimode quantum wire whose finite segment has randomly rough lateral boundaries is developed. It enables one to rigorously take account of all feasible mechanisms of wave scattering, both related to boundary roughness and to contacts between the wire rough section and the perfect leads within the same technical frameworks. The rough part of the conducting wire is shown to act as a mode-specific randomly modulated effective potential barrier whose height is governed essentially by the asperity slope. The mean height of the barrier, which is proportional to the average slope squared, specifies the number of conducting channels. Under relatively small asperity amplitude this number can take on arbitrary small, up to zero, values if the asperities are sufficiently sharp. The consecutive channel cut-off that arises when the asperity sharpness increases can be regarded as a kind of localization, which is not related to the disorder per se but rather is of entropic or (equivalently) geometric origin. The fluctuating part of the effective barrier results in two fundamentally different types of guided wave scattering, viz., inter- and intramode scattering. The intermode scattering is shown to be for the most part very strong except in the cases of (a) extremely smooth asperities, (b) excessively small length of the corrugated segment, and (c) the asperities sharp enough for only one conducting channel to remain in the wire. Under strong intermode scattering, a new set of conducting channels develops in the corrugated waveguide, which have the form of asymptotically decoupled extended modes subject to individual solely intramode random potentials. In view of this fact, two transport regimes only are realizable in randomly corrugated multimode waveguides, specifically, the ballistic and the localized regime, the latter characteristic of one-dimensional random systems. Two kinds of localization are thus shown to

Effect of the Size of Al3(Sc,Zr) Precipitates on the Structure of Multi-Directionally Isothermally Forged Al-Mg-Sc-Zr Alloy

Science.gov (United States)

Sitdikov, O. Sh.; Avtokratova, E. V.; Mukhametdinova, O. E.; Garipova, R. N.; Markushev, M. V.

2017-12-01

The effect of Al3(Sc,Zr) dispersoids on the evolution of the cast Al-Mg-Sc-Zr alloy structure under multi-directional isothermal forging (MIF) has been investigated. The alloy, which has an equiaxed grain structure with a grain size of 25 μm and contains dispersoids 5-10 and 20-50 nm in size after onestage (at 360°C for 6 h) and two-stage (360°C for 6 h + 520°C for 1 h) annealing, respectively, was deformed at 325°C ( 0.65 T m) up to cumulative strains of e = 8.4. In the initial stages of MIF, new fine (sub)grains surrounded by low-angle and high-angle boundaries (HABs) were formed near the initial grain boundaries. With increasing strain, the volume fraction and misorientation of these crystallites increased, which led to the replacement of a coarse-grained structure with a fine-grained one with a grain size of 1.5-2.0 μm. Dynamic recrystallization occurred in accordance to a continuous mechanism and was controlled by the interaction of lattice dislocations and/or (sub)grain boundaries with dispersoids that effectively inhibited the migration of boundaries, as well as the rearrangement of lattice dislocations and their annihilation. The particle size and the density of their distribution significantly affected the parameters of the evolved structure; in an alloy with smaller particles, a structure with a smaller grain size and a larger HAB fraction developed.

Generalized Robin Boundary Conditions, Robin-to-Dirichlet Maps, and Krein-Type Resolvent Formulas for Schr\\"odinger Operators on Bounded Lipschitz Domains

OpenAIRE

Gesztesy, Fritz; Mitrea, Marius

2008-01-01

We study generalized Robin boundary conditions, Robin-to-Dirichlet maps, and Krein-type resolvent formulas for Schr\\"odinger operators on bounded Lipschitz domains in $\\bbR^n$, $n\\ge 2$. We also discuss the case of bounded $C^{1,r}$-domains, $(1/2)

Existence and Uniqueness of Solutions for a Discrete Fractional Mixed Type Sum-Difference Equation Boundary Value Problem

Directory of Open Access Journals (Sweden)

Weidong Lv

2015-01-01

Full Text Available By means of Schauder’s fixed point theorem and contraction mapping principle, we establish the existence and uniqueness of solutions to a boundary value problem for a discrete fractional mixed type sum-difference equation with the nonlinear term dependent on a fractional difference of lower order. Moreover, a suitable choice of a Banach space allows the solutions to be unbounded and two representative examples are presented to illustrate the effectiveness of the main results.

Contributions to Internal Stress from Free Dislocations and from Substructure Boundaries in Dislocation Structure Formed in High Temperature Creep

Czech Academy of Sciences Publication Activity Database

Orlová, Alena; Dobeš, Ferdinand

2008-01-01

Roč. 567-568, - (2008), s. 173-176 ISSN 0255-5476. [MSMF /5./. Brno, 27.06.2007-29.06.2007] R&D Projects: GA AV ČR 1QS200410502 Institutional research plan: CEZ:AV0Z20410507 Keywords : creep * internal stress * subgrain * dislocation density Subject RIV: BM - Solid Matter Physics ; Magnetism

Aerosol climatology and planetary boundary influence at the Jungfraujoch analyzed by synoptic weather types

Directory of Open Access Journals (Sweden)

M. Collaud Coen

2011-06-01

Full Text Available Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coefficients, aerosol number concentration and trace gases (CO, NO_x, SO₂ measured at the Jungfraujoch (JFJ, 3580 m a.s.l. have been analyzed as a function of different synoptic weather types. The Schüepp synoptic weather type of the Alps (SYNALP classification from the Alpine Weather Statistics (AWS was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO₂ and NO_x concentrations were used as precursor tracers for new particle formation and growth, respectively. The aerosol optical parameters and number concentration show elevated loadings during advective weather types during the December–March period and for the convective anticyclonic and convective indifferent weather types during the April–September period. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in winter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The fraction of PBL air transported to the JFJ was estimated by the relative increase of the specific humidity and CO.

Boundary and sub-boundary hardening in tempered martensitic 9Cr steel during long-term creep at 650 C

Energy Technology Data Exchange (ETDEWEB)

Abe, Fujio [National Institute for Materials Science, Sengen, Tsukuba (Japan)

2010-07-01

The boundary and sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening. This improves long-term creep strength of base metal. The enhancement of boundary and sub-boundary hardening is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steel P92. In NIMS 9Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. Newly alloy-designed 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits much higher creep rupture strength of base metal than P92 and also no Tpe-IV fracture in welded joints at 650 C. (orig.)

Observation of potential barriers on barium strontium titanate PTCR ceramics by electrostatic force microscopy

International Nuclear Information System (INIS)

Manfredini, J.P.; Paulin Filho, P.I.; Gheno, S.M.

2011-01-01

A composition of PTCR ceramic based in barium titanate with isovalent replacement of part of barium by strontium using lanthanum and manganese as additives was investigated. The transition temperature, typical of these materials, was shifted below the room temperature by the presence of strontium, whose behavior was detected by tests of DC resistivity and impedance spectroscopy. The observation of potential barriers at grain boundaries was possible through the technique of electrostatic force microscopy (EFM). The results also showed the presence of space charges in regions inside grains, possibly at subgrain boundaries. (author)

Composition-Driven Phase Boundary and Piezoelectricity in Potassium-Sodium Niobate-Based Ceramics.

Science.gov (United States)

Zheng, Ting; Wu, Jiagang; Xiao, Dingquan; Zhu, Jianguo; Wang, Xiangjian; Lou, Xiaojie

2015-09-16

The piezoelectricity of (K,Na)NbO3 ceramics strongly depends on the phase boundary types as well as the doped compositions. Here, we systematically studied the relationships between the compositions and phase boundary types in (K,Na) (Nb,Sb)O3-Bi0.5Na0.5AO3 (KNNS-BNA, A=Hf, Zr, Ti, Sn) ceramics; then their piezoelectricity can be readily modified. Their phase boundary types are determined by the doped elements. A rhombohedral-tetragonal (R-T) phase boundary can be driven in the compositions range of 0.035≤BNH≤0.040 and 0.035≤BNZ≤0.045; an orthorhombic-tetragonal (O-T) phase boundary is formed in the composition range of 0.005≤BNT≤0.02; and a pure O phase can be only observed regardless of BNS content (≤0.01). In addition, the phase boundary types strongly affect their corresponding piezoelectricities. A larger d33 (∼440-450 pC/N) and a higher d33* (∼742-834 pm/V) can be attained in KNNS-BNA (A=Zr and Hf) ceramics due to the involvement of R-T phase boundary, and unfortunately KNNS-BNA (A=Sn and Ti) ceramics possess a relatively poor piezoelectricity (d33≤200 and d33*piezoelectricity and phase boundary types were also discussed. We believe that comprehensive research can design more excellent ceramic systems concerning potassium-sodium niobate.

Migration mechanisms of a faceted grain boundary

Science.gov (United States)

Hadian, R.; Grabowski, B.; Finnis, M. W.; Neugebauer, J.

2018-04-01

We report molecular dynamics simulations and their analysis for a mixed tilt and twist grain boundary vicinal to the Σ 7 symmetric tilt boundary of the type {1 2 3 } in aluminum. When minimized in energy at 0 K , a grain boundary of this type exhibits nanofacets that contain kinks. We observe that at higher temperatures of migration simulations, given extended annealing times, it is energetically favorable for these nanofacets to coalesce into a large terrace-facet structure. Therefore, we initiate the simulations from such a structure and study as a function of applied driving force and temperature how the boundary migrates. We find the migration of a faceted boundary can be described in terms of the flow of steps. The migration is dominated at lower driving force by the collective motion of the steps incorporated in the facet, and at higher driving forces by the step detachment from the terrace-facet junction and propagation of steps across the terraces. The velocity of steps on terraces is faster than their velocity when incorporated in the facet, and very much faster than the velocity of the facet profile itself, which is almost stationary. A simple kinetic Monte Carlo model matches the broad kinematic features revealed by the molecular dynamics. Since the mechanisms seem likely to be very general on kinked grain-boundary planes, the step-flow description is a promising approach to more quantitative modeling of general grain boundaries.

Inference of boundaries in causal sets

Science.gov (United States)

Cunningham, William J.

2018-05-01

We investigate the extrinsic geometry of causal sets in (1+1) -dimensional Minkowski spacetime. The properties of boundaries in an embedding space can be used not only to measure observables, but also to supplement the discrete action in the partition function via discretized Gibbons–Hawking–York boundary terms. We define several ways to represent a causal set using overlapping subsets, which then allows us to distinguish between null and non-null bounding hypersurfaces in an embedding space. We discuss algorithms to differentiate between different types of regions, consider when these distinctions are possible, and then apply the algorithms to several spacetime regions. Numerical results indicate the volumes of timelike boundaries can be measured to within 0.5% accuracy for flat boundaries and within 10% accuracy for highly curved boundaries for medium-sized causal sets with N  =  214 spacetime elements.

Grain boundary precipitation strengthening mechanism in W containing advanced creep resistant ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Shibata, T.; Hasegawa, Y. [Tohoku Univ., Sendai (Japan)

2010-07-01

Grain boundary precipitation strengthening is expected to be a decisive factor in developing ferritic creep resistant steels. This study examined the grain boundary precipitation strengthening mechanism extracting the effect of the tempered martensitic microstructure and precipitates on the high angle grain boundary in M{sub 23}C4{sub 6} type carbide and the Fe{sub 2}W type Laves phase effect of the creep deformation fixing the grain boundary according to transmission electron microscope (TEM) observation. A creep test was carried out at high temperature in order to evaluate the high angle boundary strengthening effect simulating the long-term creep deformation microstructure by the lath structure disappearance. The correlation of the creep rupture time and the grain boundary shielding ratio were found to be independent of precipitate type. The creep deformation model represents block boundary shielding by precipitates as the decisive factor for W containing ferritic creep resistant steels. (orig.)

Two-point boundary correlation functions of dense loop models

Directory of Open Access Journals (Sweden)

Alexi Morin-Duchesne, Jesper Lykke Jacobsen

2018-06-01

Full Text Available We investigate six types of two-point boundary correlation functions in the dense loop model. These are defined as ratios $Z/Z^0$ of partition functions on the $m\\times n$ square lattice, with the boundary condition for $Z$ depending on two points $x$ and $y$. We consider: the insertion of an isolated defect (a and a pair of defects (b in a Dirichlet boundary condition, the transition (c between Dirichlet and Neumann boundary conditions, and the connectivity of clusters (d, loops (e and boundary segments (f in a Neumann boundary condition. For the model of critical dense polymers, corresponding to a vanishing loop weight ($\\beta = 0$, we find determinant and pfaffian expressions for these correlators. We extract the conformal weights of the underlying conformal fields and find $\\Delta = -\\frac18$, $0$, $-\\frac3{32}$, $\\frac38$, $1$, $\\tfrac \\theta \\pi (1+\\tfrac{2\\theta}\\pi$, where $\\theta$ encodes the weight of one class of loops for the correlator of type f. These results are obtained by analysing the asymptotics of the exact expressions, and by using the Cardy-Peschel formula in the case where $x$ and $y$ are set to the corners. For type b, we find a $\\log|x-y|$ dependence from the asymptotics, and a $\\ln (\\ln n$ term in the corner free energy. This is consistent with the interpretation of the boundary condition of type b as the insertion of a logarithmic field belonging to a rank two Jordan cell. For the other values of $\\beta = 2 \\cos \\lambda$, we use the hypothesis of conformal invariance to predict the conformal weights and find $\\Delta = \\Delta_{1,2}$, $\\Delta_{1,3}$, $\\Delta_{0,\\frac12}$, $\\Delta_{1,0}$, $\\Delta_{1,-1}$ and $\\Delta_{\\frac{2\\theta}\\lambda+1,\\frac{2\\theta}\\lambda+1}$, extending the results of critical dense polymers. With the results for type f, we reproduce a Coulomb gas prediction for the valence bond entanglement entropy of Jacobsen and Saleur.

Localised corrosion in AA 2099-T83 aluminium-lithium alloy: The role of grain orientation

International Nuclear Information System (INIS)

Ma, Y.; Zhou, X.; Liao, Y.; Yi, Y.; Wu, H.; Wang, Z.; Huang, W.

2016-01-01

Highlights: • Schmid factor of the grain/subgrain can indicate its corrosion susceptibility. • The localised corrosion prefers the grain with relatively large Schmid factor. • The localised corrosion is related to selective dissolution of T_1 phase. - Abstract: The mechanism for localised corrosion in AA 2099-T83 alloy during immersion in 3.5% NaCl solution is investigated. It is found that localised corrosion tends to occur in the grain with relatively large Schmid factor. The localised corrosion is related to selective dissolution of T_1 (Al_2CuLi) phase that preferentially precipitates at grain/subgrain boundaries and dislocations within grain interiors. A model is proposed to explain the development of the localised corrosion in the alloy by taking into account heterogeneous plastic deformation during cold working and preferential precipitation of T_1 phase at crystallographic defects within deformed grains.

Boundary element method for internal axisymmetric flow

Directory of Open Access Journals (Sweden)

Gokhman Alexander

1999-01-01

Full Text Available We present an accurate fast method for the computation of potential internal axisymmetric flow based on the boundary element technique. We prove that the computed velocity field asymptotically satisfies reasonable boundary conditions at infinity for various types of inlet/exit. Computation of internal axisymmetric potential flow is an essential ingredient in the three-dimensional problem of computation of velocity fields in turbomachines. We include the results of a practical application of the method to the computation of flow in turbomachines of Kaplan and Francis types.

Some observations on the relationship between microstructures, fatigue and creep behaviours in a type 316 stainless steel

International Nuclear Information System (INIS)

Horton, C.A.P.; Lai, J.K.L.; Skelton, R.P.

Comparisons have been made between microstructures in Type 316 steel after high strain fatigue or creep at 625 deg. C and which had been subjected to various pre-test ageing treatments. The microstructures observed in the specimens generally consisted of a three dimensional dislocation network together with 'cells' delineated by dislocation sub-boundaries. In fatigue, under strain control conditions, pre-ageing reduced the dislocation density and coarsened the cell structure produced during test. This was related to less solute hardening and strain induced precipitation after pre-ageing and was accompanied by a lower rate of cyclic strain hardening. During fatigue with dwell, the dislocations introduced led to five times more precipitation than that observed during stress free ageing solution treated material. The 'cell' structure produced by fatigue was retained even after solution treatment at 1050 deg. C. In creep, under constant loads, a coarser and more clearly defined dislocation sub-grain structure developed and its size was not influenced by pre-ageing. However, creep testing after various pre-treatments, including fatigue, demonstrated that the creep resistance was dependent on a combination of solution strengthening, cell size and dislocation density. Consequently prior fatigue considerably increased the creep resistance. The work has demonstrated the microstructural aspects of creep-fatigue interaction and that the use of creep data obtained from solution treated material is likely to lead to errors in creep-fatigue life fraction summations

Boundary scattering in the ϕ{sup 4} model

Energy Technology Data Exchange (ETDEWEB)

Dorey, Patrick [Department of Mathematical Sciences, Durham University,Durham DH1 3LE (United Kingdom); Halavanau, Aliaksei [Department of Theoretical Physics and Astrophysics,BSU, Minsk Independence Avenue 4 (Belarus); Fermi National Laboratory,Pine St. and Kirk Rd., ZIP 60511, Mail Station 221, Batavia, Illinois (United States); Mercer, James [Department of Mathematical Sciences, Durham University,Durham DH1 3LE (United Kingdom); Deloitte MCS Limited,Hill House, 1 Little New Street, London, EC4A 3TR (United Kingdom); Romanczukiewicz, Tomasz [Institute of Physics, Jagiellonian University,Lojasiewicza 11, 30-348 Krakow (Poland); Shnir, Yasha [Department of Theoretical Physics and Astrophysics,BSU, Minsk Independence Avenue 4 (Belarus); BLTP, JINR,141980 Dubna (Russian Federation); Institute of Physics, Oldenburg University,Postfach 2503 D-26111 Oldenburg (Germany)

2017-05-19

We study boundary scattering in the ϕ{sup 4} model on a half-line with a one-parameter family of Neumann-type boundary conditions. A rich variety of phenomena is observed, which extends previously-studied behaviour on the full line to include regimes of near-elastic scattering, the restoration of a missing scattering window, and the creation of a kink or oscillon through the collision-induced decay of a metastable boundary state. We also study the decay of the vibrational boundary mode, and explore different scenarios for its relaxation and for the creation of kinks.

Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling.

Science.gov (United States)

Klimova, Margarita; Stepanov, Nikita; Shaysultanov, Dmitry; Chernichenko, Ruslan; Yurchenko, Nikita; Sanin, Vladimir; Zherebtsov, Sergey

2017-12-29

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20-23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (<40%), while grain (twin) boundary strengthening prevailed at higher strains.

Electron paramagnetic resonance studies of defects in dilute magnetic alloys

International Nuclear Information System (INIS)

Suss, J.T.; Raizman, A.

1980-01-01

The EPR spectrum of erbium was used to study the effects of cold-working (rolling and mechanical polishing) in dilute gold-erbium alloys. Variation in the EPR linewidth, intensity and asymmetry parameter (A/B ratio) were investigated. Most of the results could be interpreted in terms of segregation of erbium ions to subgrain boundaries (dislocations) in a surface layer of a few thousand Angstroms. (author)

The microstructure of Incoloy 800 H after long-time creep

International Nuclear Information System (INIS)

Sheng Zhongqi; Katerbau, K.

1993-01-01

The microstructural change of Incoloy 800 H after creep tests with low loads and long rupture time has been investigated. Cavities nucleate at one side of M 23 C 6 carbide particles on grain boundaries. Microcrack propagate by passing through a string of these cavities, M 23 C 6 carbide particles on grain boundaries have a coherent relationship with one of both neighbouring grains, so grain boundaries are strengthened, and the strengthening effect can be estimated for enhanced activation energy. G phase precipitation can be observed on grain boundaries, but no γ' phase particles can be found. Dislocation substructure is different from the typical recovery creep. Dislocation piles appear near M 23 C 6 carbide particles on grain boundaries. Subgrain structure poorly develop and network distribution of dislocation can remain after relative long creep

Anelasticity of olivine single crystals investigated by stress-reduction tests and high-angular resolution electron backscatter diffraction

Science.gov (United States)

Wallis, D.; Hansen, L. N.; Kempton, I.; Wilkinson, A. J.

2017-12-01

Geodynamic phenomena, including glacial isostatic adjustment and postseismic deformation, can involve transient deformation in response to changes in differential stress acting on mantle rocks. As such, rheological models of transient deformation are incorporated in predictions of associated processes, including sea-level rise and stress redistribution after earthquakes. However, experimental constraints on rheological models for transient deformation of mantle materials are sparse. In particular, experiments involving stress reductions have been lacking. Moreover, a material's response to a reduction in stress can provide clues to the microphysical processes controlling deformation. To constrain models of transient deformation of mantle rocks we performed stress-reduction tests on single crystals of olivine at 1250-1300°C. Mechanical and piezoelectric actuators controlled constant initial stress during creep. At various strain intervals stress was reduced near-instantaneously using the piezoelectric actuator, inducing both elastic and anelastic (time-dependent) lengthening of the samples. A range of magnitudes of stress reduction were applied, typically unloading 10-90% of the initial stress. High-angular resolution electron backscatter diffraction (HR-EBSD), based on cross-correlation of diffraction patterns, was used to map dislocation density and elastic strain distributions in the recovered samples. Magnitudes of anelastic back-strain increase with increasing magnitudes of stress reduction and show a marked increase when stress reductions exceed 50% of the initial stress, consistent with previous observations in metals and alloys. This observation is inconsistent with the Burgers rheological model commonly used to describe transient behaviour and suggests that the style of rheological behaviour depends on the magnitude of stress change. HR-EBSD maps reveal that the crystal lattices are smoothly curved and generally lack subgrain boundaries and elastic strain

Quantum walk with one variable absorbing boundary

International Nuclear Information System (INIS)

Wang, Feiran; Zhang, Pei; Wang, Yunlong; Liu, Ruifeng; Gao, Hong; Li, Fuli

2017-01-01

Quantum walks constitute a promising ingredient in the research on quantum algorithms; consequently, exploring different types of quantum walks is of great significance for quantum information and quantum computation. In this study, we investigate the progress of quantum walks with a variable absorbing boundary and provide an analytical solution for the escape probability (the probability of a walker that is not absorbed by the boundary). We simulate the behavior of escape probability under different conditions, including the reflection coefficient, boundary location, and initial state. Moreover, it is also meaningful to extend our research to the situation of continuous-time and high-dimensional quantum walks. - Highlights: • A novel scheme about quantum walk with variable boundary is proposed. • The analytical results of the survival probability from the absorbing boundary. • The behavior of survival probability under different boundary conditions. • The influence of different initial coin states on the survival probability.

Antiphase boundaries, inversion, and ferroelastic domains in the striped-type superstructure of γ-brass Cu-Al alloys

Science.gov (United States)

Koyama, Y.; Hatano, M.; Tanimura, M.

1996-05-01

Features of the striped-type superstructure in γ-brass Cu-Al alloys have been investigated mainly by transmission electron microscopy in order to understand the role of a rhombohedral distortion in its stability. From dark field images taken from alloys exhibiting the superstructure, it was found that there exist two types of ferroelastic rhombohedral domains, which are in a twin relation. In other words, the superstructure is characterized by a periodic array of the ferroelastic domains as well as inversion antiphase boundaries. Because charge density waves should be responsible for the formation of the superstructure, as suggested in our previous paper [Phys. Rev. B 40, 5378 (1989)], the rhombohedral distortion must play a crucial role in their appearance. Presumably the distortion enlarges parallel portions of the Fermi surface. On the basis of the present experimental data, the interplay between the striped-type superstructure and the rhombohedral γ-brass structure is also discussed.

On the Boussinesq-Burgers equations driven by dynamic boundary conditions

Science.gov (United States)

Zhu, Neng; Liu, Zhengrong; Zhao, Kun

2018-02-01

We study the qualitative behavior of the Boussinesq-Burgers equations on a finite interval subject to the Dirichlet type dynamic boundary conditions. Assuming H1 ×H2 initial data which are compatible with boundary conditions and utilizing energy methods, we show that under appropriate conditions on the dynamic boundary data, there exist unique global-in-time solutions to the initial-boundary value problem, and the solutions converge to the boundary data as time goes to infinity, regardless of the magnitude of the initial data.

Stabilization of the hypersonic boundary layer by finite-amplitude streaks

Science.gov (United States)

Ren, Jie; Fu, Song; Hanifi, Ardeshir

2016-02-01

Stabilization of two-dimensional disturbances in hypersonic boundary layer flows by finite-amplitude streaks is investigated using nonlinear parabolized stability equations. The boundary-layer flows at Mach numbers 4.5 and 6.0 are studied in which both first and second modes are supported. The streaks considered here are driven either by the so-called optimal perturbations (Klebanoff-type) or the centrifugal instability (Görtler-type). When the streak amplitude is in an appropriate range, i.e., large enough to modulate the laminar boundary layer but low enough to not trigger secondary instability, both first and second modes can effectively be suppressed.

Microstructural characteristics of new type γ-γ` Co-9Al-9W cobalt-based superalloys in as-cast state

Directory of Open Access Journals (Sweden)

A. Tomaszewska

2018-01-01

Full Text Available The paper presented deals primary with the structure characteristics of a new type of cobalt-based superalloys Co-9Al-9W type, casted via induction melting process with partially dosing of Common problems described in literature are focused on difficulties in obtaining uniform distribution of tungsten, particularly in interdendritic areas. That was the reason for the modified casting process to be applied. The method of tungsten dosing into liquid melts of Co and Al allows to obtain microstructure characterized by considerably decreased microsegregation. The material obtained was analyzed by standard methods such as light and scanning microscopy with analysis of chemical composition in micro-areas. Additionally, the detailed analysis of the sub-grain level was made by S/TEM on thin foils collected from equiaxed grains zone of the ingot.

Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium-copper alloys

Science.gov (United States)

Wall, Douglas; Stoner, Glenn E.

1991-01-01

Summary information is included for electrochemical aspects of stress corrosion cracking in alloy 2090 and an introduction to the work to be initiated on the new X2095 (Weldalite) alloy system. Stress corrosion cracking (SCC) was studied in both S-T and L-T orientations in alloy 2090. A constant load TTF test was performed in several environments with a potentiostatically applied potential. In the same environments the electrochemical behavior of phases found along subgrain boundaries was assessed. It was found that rapid failure due to SCC occurred when the following criteria was met: E(sub BR,T1) is less than E(sub applied) is less than E(sub Br, matrix phase). Although the L-T orientation is usually considered more resistant to SCC, failures in this orientation occurred when the stated criteria was met. This may be due to the relatively isotropic geometry of the subgrains which measure approximately 12 to 25 microns in diameters. Initial studies of alloy X2095 includes electrochemical characterization of three compositional variations each at three temperatures. The role of T(sub 1) dissolution in SCC behavior is addressed using techniques similar to those used in the research of 2090 described. SCC susceptibility is also studied using alternate immersion facilities at Reynolds Metals Corporation. Pitting is investigated in terms of stability, role of precipitate phases and constituent particles, and as initiation sites for SCC. In all research endeavors, attempts are made to link electrochemistry to microstructure. Previous work on 2090 provides a convenient basis for comparison since both alloys contain T(sub 1) precipitates but with different distributions. In 2090 T(sub 1) forms preferentially on subgrain boundaries whereas in X2095 the microstructure appears to be more homogeneous with finer T(sub 1) particles. Another point for comparison is the delta prime strengthening phase found in 2090 but absent in X2095.

Spectral asymmetry for bag boundary conditions

International Nuclear Information System (INIS)

Beneventano, C G; Santangelo, E M; Wipf, A

2002-01-01

We give an expression, in terms of boundary spectral functions, for the spectral asymmetry of the Euclidean Dirac operator in two dimensions, when its domain is determined by local boundary conditions and the manifold is of product type. As an application, we explicitly evaluate the asymmetry in the case of a finite-length cylinder and check that the outcome is consistent with our general result. Finally, we study the asymmetry in a disc, which is a non-product case, and propose an interpretation

Different slip systems controlling crystallographic preferred orientation and intracrystalline deformation of amphibole in mylonites from the Neyriz mantle diapir, Iran

Science.gov (United States)

Elyaszadeh, Ramin; Prior, David J.; Sarkarinejad, Khalil; Mansouri, Hadiseh

2018-02-01

A deformed layered gabbro and a mylonitic gabbro sample from the marginal shear zone of the Neyriz mantle diapir in Iran were analyzed using electron backscatter diffraction (EBSD). Both samples have the common amphibole crystallographic preferred orientation (CPO) in which (100) lies perpendicular to foliation and parallel to lineation. Amphibole grains in the layered gabbro sample have little internal deformation, whereas in the mylonitic gabbro sample the amphibole grains are strongly distorted and contain low angle grain boundaries. There is a subtle change in CPO as a function of grain size in the mylonitic gabbro. Coarse grains (porphyroclasts) have a (100) CPO oriented with the main foliation reference frame whilst fine grains have a (100) CPO oriented with the C‧ shear bands. Detailed analysis of porphyroclast distortions and subgrain boundary trace analysis suggests that hard slip systems, most particularly (110) control intracrystalline deformation. Schmid factor analysis suggest that these slip systems are not involved in foliation formation but are linked kinematically to C‧ shear bands. It is unlikely that the slip systems that control intracrystalline deformation are important in CPO formation. We interpret that subgrain rotation recrystallization lead to grain size reduction and the elongate recrystallized grains were rotated towards the C‧ shear bands by grain boundary sliding. This rigid body rotation, possibly in combination with easy slip on (100) are considered the main cause of CPO formation. Amphibole zonation patterns in the layered gabbro sample suggest that oriented growth of amphibole may have contributed to CPO.

Critical effects of downstream boundary conditions on vortex breakdown

Science.gov (United States)

Kandil, Osama; Kandil, Hamdy A.; Liu, C. H.

1992-01-01

The unsteady, compressible, full Navier-Stokes (NS) equations are used to study the critical effects of the downstream boundary conditions on the supersonic vortex breakdown. The present study is applied to two supersonic vortex breakdown cases. In the first case, quasi-axisymmetric supersonic swirling flow is considered in a configured circular duct, and in the second case, quasi-axisymmetric supersonic swirling jet, that is issued from a nozzle into a supersonic jet of lower Mach number, is considered. For the configured duct flow, four different types of downstream boundary conditions are used, and for the swirling jet flow from the nozzle, two types of downstream boundary conditions are used. The solutions are time accurate which are obtained using an implicit, upwind, flux-difference splitting, finite-volume scheme.

Analytic solutions to a family of boundary-value problems for Ginsburg-Landau type equations

Science.gov (United States)

Vassilev, V. M.; Dantchev, D. M.; Djondjorov, P. A.

2017-10-01

We consider a two-parameter family of nonlinear ordinary differential equations describing the behavior of a critical thermodynamic system, e.g., a binary liquid mixture, of film geometry within the framework of the Ginzburg-Landau theory by means of the order-parameter. We focus on the case in which the confining surfaces are strongly adsorbing but prefer different components of the mixture, i.e., the order-parameter tends to infinity at one of the boundaries and to minus infinity at the other one. We assume that the boundaries of the system are positioned at a finite distance from each other and give analytic solutions to the corresponding boundary-value problems in terms of Weierstrass and Jacobi elliptic functions.

Grain boundary precipitation in an austenitic stainless steel

International Nuclear Information System (INIS)

Jones, A.R.; Howell, P.R.; Ralph, B.

The precipitation of second phase particles of niobium carbide in an austenitic stainless steel is shown to be considerably influenced by the degree of deformation introduced prior to the ageing treatment. Sites for the nucleation of second phase particles are identified and the importance of one type of nucleation site, extrinsic dislocations, to the evolution of the final boundary precipitate distributions is emphasized. Further, it is shown that the presence of a grain boundary can effect precipitation processes for some considerable distance into the matrix on either side of the boundary. (author)

An(1) affine Toda field theories with integrable boundary conditions revisited

International Nuclear Information System (INIS)

Doikou, Anastasia

2008-01-01

Generic classically integrable boundary conditions for the A n (1) affine Toda field theories (ATFT) are investigated. The present analysis rests primarily on the underlying algebra, defined by the classical version of the reflection equation. We use as a prototype example the first non-trivial model of the hierarchy i.e. the A 2 (1) ATFT, however our results may be generalized for any A n (1) (n > 1). We assume here two distinct types of boundary conditions called some times soliton preserving (SP), and soliton non-preserving (SNP) associated to two distinct algebras, i.e. the reflection algebra and the (q) twisted Yangian respectively. The boundary local integrals of motion are then systematically extracted from the asymptotic expansion of the associated transfer matrix. In the case of SNP boundary conditions we recover previously known results. The other type of boundary conditions (SP), associated to the reflection algebra, are novel in this context and lead to a different set of conserved quantities that depend on free boundary parameters. It also turns out that the number of local integrals of motion for SP boundary conditions is 'double' compared to those of the SNP case.

Polarity of translation boundaries in antiferroelectric PbZrO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Wei, Xian-Kui, E-mail: xiankui.wei@epfl.ch [Ceramics Laboratory, EPFL–Swiss Federal Institute of Technology, Lausanne 1015 (Switzerland); Peter Grünberg Institute and Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Research Center Jülich, 52425 Jülich (Germany); Jia, Chun-Lin [Peter Grünberg Institute and Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Research Center Jülich, 52425 Jülich (Germany); International Centre of Dielectric Research, The School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Roleder, Krystian [Institute of Physics, University of Silesia, Katowice 40007 (Poland); Setter, Nava [Ceramics Laboratory, EPFL–Swiss Federal Institute of Technology, Lausanne 1015 (Switzerland)

2015-02-15

Graphical abstract: Strain-free rigid model and aberration-corrected transmission electron microscopes are used to investigate the polarity of translation boundaries in antiferroelectric PbZrO{sub 3}. - Highlights: • Domain boundaries in antiferroelectric PbZrO{sub 3} show polar and antipolar property. • The antiphase boundary can split into “sub-domains”. • Polarization reversal possibly exists inside the translation boundaries. • Thermal treatment can alter morphology and density of the translation boundaries. - Abstract: The polarity of translation boundaries (TBs) in antiferroelectric PbZrO{sub 3} is investigated. We show that previous experimentally reported polar property of R{sub III-1} type TB can be well approximated by a strain-free rigid model. Based on this, the modeling investigation suggests that there are two additional polar TBs, three antipolar-like TBs and one antipolar antiphase boundary. High-resolution scanning-transmission-electron-microscopy study reveals that the straight R{sub III-1} type TB can split into “sub-domains” with possible polarization reversal, suggesting the occurrence of ferroic orders at the TBs. In addition, dependence of morphology and density of the TBs on thermal treatments is discussed according to our results.

Pushing Boundaries while Maintaining Stability

DEFF Research Database (Denmark)

Lippke, Lena; Wegener, Charlotte

at the same time. The exploration of transforming practices shows how disturbances in relation to the ‘normal’ practices are created and thus makes invisible conventions which are taken for granted visible. Thus, this paper addresses two types of invisibility: the unnoticed boundary-pushing practices...

The theory of discrete barriers and its applications to linear boundary-value problems of the 'Dirichlet type'; Theorie des barrieres discretes et applications a des problemes lineaires elliptiques du ''type de dirichlet''

Energy Technology Data Exchange (ETDEWEB)

Jamet, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

This report gives a general presentation of barrier theory for finite difference operators, with its applications to some boundary value problems. (author) [French] Ce rapport est un expose synthetique de la theorie des barrieres pour les operateurs aux differences finies et ses applications a certaines classes de problemes lineaires elliptiques du 'type de Dirichlet'. (auteur)

The interior regularity of pressure associated with a weak solution to the Navier-Stokes equations with the Navier-type boundary conditions

Czech Academy of Sciences Publication Activity Database

Neustupa, Jiří; Al Baba, Hind

2018-01-01

Roč. 463, č. 1 (2018), s. 222-234 ISSN 0022-247X R&D Projects: GA ČR(CZ) GA17-01747S Institutional support: RVO:67985840 Keywords : Navier-Stokes equation * Navier-type boundary conditions * interior regularity Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.064, year: 2016 https://www.sciencedirect.com/science/article/pii/S0022247X18302233?via%3Dihub

Forecasting of mechanical - and structural behavior of 316 austenitic stainless steels by deformation charts

International Nuclear Information System (INIS)

Monteiro, S.N.

1980-01-01

The utilization of deformation charts applied to AISI 316 austenitic stainless steel with the purpose of foreseeing its behavior associated with structural and mechanical phenomena, is evaluated. The ocurrence of phenomena such as dynamic aging, martensite transformation, static aging, failure at creep curve, cells, subgrains and boundary slips is discussed in the different regions of the chart. A practical example of the charts' utilization for components of fast reactors is finally presented. (Author) [pt

Changes in grain boundary composition induced by neutron irradiation of austenitic stainless steels

International Nuclear Information System (INIS)

Asano, K.; Nakata, K.; Fukuya, K.; Kodama, M.

1992-01-01

The radiation induced segregation of solutes to the grain boundary in austenitic stainless steels were studied. Type 304 and type 316 steel samples neutron irradiated at 561K up to 9.2x10 25 n/m 2 were obtained and minute compositional profiles across grain boundaries were examined using an analytical scanning transmission electron microscope equipped with a field emission electron gun. Chromium was slightly enriched at grain boundaries at the lowest irradiation dose but decreased with increasing fluence. Higher fluence irradiation resulted in depletion in chromium and molybdenum, and enrichment in nickel, silicon and phosphorus. These changes in grain boundary chemistry were limited within about 5nm of the boundary. Significant depletion of chromium and enrichment of impurities on the grain boundary occurred at fluences roughly coincidental with that of SCC susceptibility change obtained from another project

Embrittlement of Intercritically Reheated Coarse Grain Heat-Affected Zone of ASTM4130 Steel

Science.gov (United States)

Li, Liying; Han, Tao; Han, Bin

2018-04-01

In this investigation, a thermal welding simulation technique was used to investigate the microstructures and mechanical properties of the intercritically reheated coarse grain heat-affected zone (IR CGHAZ) of ASTM4130 steel. The effect of post weld heat treatment (PWHT) on the toughness of IR CGHAZ was also analyzed. The toughness of IR CGHAZ was measured by means of Charpy impact, and it is found that IR CGHAZ has the lowest toughness which is much lower than that of the base metal regardless of whether PWHT is applied or not. The as-welded IR CGHAZ is mainly composed of ferrite, martensite, and many blocky M-A constituents distributing along grain boundaries and subgrain boundaries in a near-connected network. Also, the prior austenite grains are still as coarse as those in the coarse grain heat-affected zone (CGHAZ). The presence of the blocky M-A constituents and the coarsened austenite grains result in the toughness deterioration of the as-welded IR CGHAZ. Most of the blocky M-A constituents are decomposed to granular bainite due to the effect of the PWHT. However, PWHT cannot refine the prior austenite grains. Thus, the low toughness of IR CGHAZ after PWHT can be attributed to two factors, i.e., the coarsened austenite grains, and the presence of the remaining M-A constituents and granular bainite, which are located at grain boundaries and subgrain boundaries in a near-connected network. The absorbed energy of the IR CGHAZ was increased by about 3.75 times, which means that the PWHT can effectively improve the toughness but it cannot be recovered to the level of base metal.

Urban CO2 emissions in China: Spatial boundary and performance comparison

International Nuclear Information System (INIS)

Cai, Bofeng; Zhang, Lixiao

2014-01-01

Different names/concepts and therefore different spatial boundaries for cities in China are responsible for the conflicting and confusing results associated with urban CO 2 emissions accounting. In this study, four types of urban boundaries, i.e., city administrative boundary (UB 1 ), city district boundary (UB 2 ), city built-up area (UB 3 ) and urban proper (UB 4 ), were identified and defined. Tianjin was subsequently selected as the case city to illustrate the different performances of CO 2 emissions with respect to these four boundaries using a 1-km grid dataset built bottom-up by point-emission sources. Different urban boundaries can induce a difference in CO 2 emissions as large as 654%. UB 1 and UB 2 are not the appropriate proxies for urban boundaries in the analysis of urban CO 2 emissions, although UB 1 is a widely adopted boundary. UB 3 is a good representative of city clusters and urban sprawl in a certain region, whereas UB 4 is the appropriate system boundary for such issues as urban CO 2 emissions in light of landscape characteristics and pertinent human activities, as well as the comparability to counterparts in developed countries. These results provide sound policy implications for the improvement of urban energy management and carbon emission abatement in China. - highlights: • Four types of urban boundaries in China were clarified and defined. • Different urban boundaries will induce deviation in CO 2 emissions as large as 654%. • The UB 4 stands for appropriate urban boundary for urban CO 2 emissions analysis. • Gridded data proves to be supplementary tools for urban CO 2 emissions accounting

Cadmium Telluride and Grain Boundaries: A Preliminary Study

Science.gov (United States)

Liao, Michael Evan

roughness for direct wafer bonding. High resolution x-ray diffraction is used to study the strain of the CdTe epilayer at the epilayer-substrate interface by generating reciprocal space maps of the (004), (115), and (335) crystallographic planes. It is found that CdTe grown on an (001) InSb substrate at a low growth temperature exhibits nearly 0% relaxation. As a result, the in-plane lattice parameter of the CdTe layer is maximally strained to match the smaller lattice parameter of the InSb substrate. Consequently, the CdTe lattice is tetragonally strained normal to the substrate surface, which causes the out-of-plane lattice parameter of CdTe to be larger than its intrinsic value. Lastly, a CdCl2-treated CdTe-CdS (p-type CdTe on n-type CdS) solar cell structure is simulated using a semiconductor-heterojunction simulation program. In literature, it has been reported that chlorine atoms from the treatment segregate along grain boundaries in polycrystalline CdTe and cause the formation of local p-n junctions by inverting the grain boundaries to n-type. The simulated structure includes one grain and 2 grain boundaries. The grain/bulk CdTe material is p-type while the grain boundaries are made to be n-type with varying doping concentrations. Both the conduction band and valence band energy exhibit downward sloping from the CdTe surface to the CdTe-CdS interface. This structure assumes that the grain boundaries are parallel to the CdTe-CdS interface. While these simulations do not prove the existence of the local type-inversion hypothesis, they do entertain a novel possibility for future devices fabrication methods.

Cyclic compressive creep-elastoplastic behaviors of in situ TiB_2/Al-reinforced composite

International Nuclear Information System (INIS)

Zhang, Qing; Zhang, Weizheng; Liu, Youyi; Guo, BingBin

2016-01-01

This paper presents a study on the cyclic compressive creep-elastoplastic behaviors of a TiB_2-reinforced aluminum matrix composite (ZL109) at 350 °C and 200 °C. According to the experimental results, under cyclic elastoplasticity and cyclic coupled compressive creep-elastoplasticity, the coupled creep will cause changes in isotropic stress and kinematic stress. Isotropic stress decreases with coupled creep, leading to cyclic softening. Positive kinematic stress, however, increases with coupled creep, leading to cyclic hardening. Transmission electron microscopy (TEM) observations of samples under cyclic compressive creep-elastoplasticity with different temperatures and strain amplitudes indicate that more coupled creep contributes to more subgrain boundaries but fewer intracrystalline dislocations. Based on the macro tests and micro observations, the micro mechanism of compressive creep's influence on cyclic elastoplasticity is elucidated. Dislocations recovering with coupled creep leads to isotropic softening, whereas subgrain structures created by coupled creep lead to kinematic hardening during cyclic deformation.

Helmholtz bright and boundary solitons

International Nuclear Information System (INIS)

Christian, J M; McDonald, G S; Chamorro-Posada, P

2007-01-01

We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts

Study of some properties of point defects in grain boundaries

International Nuclear Information System (INIS)

Martin, Georges

1973-01-01

With the aim of deducing simple informations on the grain boundary core structure, we investigated self diffusion under hydrostatic pressure, impurity diffusion (In and Au), electromigration (Sb) along certain types of grain boundaries in Ag bicrystals, and the Moessbauer effect of 57 Co located in the grain boundaries of polycrystalline Be. Our results lead to the following conclusions: the formation of a vacancy like defects is necessary to grain boundary diffusion; solute atoms may release most of their elastic energy of dissolution as they segregate at the boundary; in an electrical field, the drift of Sb ions parallel to the boundary takes place toward the anode as in the bulk. The force on the grain boundary ions is larger than in the bulk; Moessbauer spectroscopy revealed the formation of Co-rich aggregates, which may proves important in the study of early stages of grain boundary precipitation. (author) [fr

A finite difference method for free boundary problems

KAUST Repository

Fornberg, Bengt

2010-04-01

Fornberg and Meyer-Spasche proposed some time ago a simple strategy to correct finite difference schemes in the presence of a free boundary that cuts across a Cartesian grid. We show here how this procedure can be combined with a minimax-based optimization procedure to rapidly solve a wide range of elliptic-type free boundary value problems. © 2009 Elsevier B.V. All rights reserved.

Anti-phase boundaries and magnetic domain structures in Ni{sub 2}MnGa-type Heusler alloys

Energy Technology Data Exchange (ETDEWEB)

Venkateswaran, S.P. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Nuhfer, N.T. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); De Graef, M. [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)]. E-mail: degraef@cmu.edu

2007-05-15

The microstructure and magnetic domain structure of austenitic Heusler Ni{sub 2}MnGa are investigated as a function of heat treatment to study the interplay of anti-phase boundaries and magnetic domain walls. Conventional electron microscopy observations on arc-melted polycrystalline samples show that anti-phase boundaries in this system are invisible for standard two-beam imaging conditions, due to the large extinction distance of the Heusler superlattice reflections. Lorentz Fresnel and Foucault observations on quenched samples reveal a wavy magnetic domain morphology, reminiscent of curved anti-phase boundaries. A close inspection of the domain images indicates that the anti-phase boundaries have a magnetization state different from that of the matrix. Fresnel image simulations for a simple magnetization model are in good agreement with the observations. Magnetic coercivity measurements show a decrease in coercivity with annealing, which correlates with the microscopy observations of reduced anti-phase boundary density for annealed samples.

A physical approach to the numerical treatment of boundaries in gas dynamics

Science.gov (United States)

Moretti, G.

1981-01-01

Two types of boundaries are considered: rigid walls, and artificial (open) boundaries which were arbitrarily drawn somewhere across a wider flow field. A set of partial differential equations (typically, the Euler equations) has an infinite number of solutions, each one defined by a set of initial and boundary conditions. The initial conditions remaining the same, any change in the boundary conditions will produce a new solution. To pose the problem well, a necessary and sufficient number of boundary conditions are prescribed.

Spin-1/2 Triangular-Lattice Heisenberg Antiferromagnet with √{3} × √{3} -Type Distortion — Behavior around the Boundaries of the Intermediate Phase

Science.gov (United States)

Shimada, Alisa; Nakano, Hiroki; Sakai, Tôru; Yoshimura, Kazuyoshi

2018-03-01

The S = 1/2 triangular-lattice Heisenberg antiferromagnet with distortion is investigated by the numerical-diagonalization method. The examined distortion type is √{3} × √{3} . We study the case when the distortion connects the undistorted triangular lattice and the dice lattice. For the intermediate phase reported previously in this system, we obtain results of the boundaries of the intermediate phase for a larger system than those in the previous report and examine the system size dependence of the boundaries in detail. We also report the specific heat of this system, which shows a marked peak structure related to the appearance of the intermediate state.

The interior regularity of pressure associated with a weak solution to the Navier-Stokes equations with the Navier-type boundary conditions

Czech Academy of Sciences Publication Activity Database

Neustupa, Jiří; Al Baba, Hind

2018-01-01

Roč. 463, č. 1 (2018), s. 222-234 ISSN 0022-247X R&D Projects: GA ČR(CZ) GA17-01747S Institutional support: RVO:67985840 Keywords : Navier-Stokes equation * Navier-type boundary conditions * interior regularity Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.064, year: 2016 https://www. science direct.com/ science /article/pii/S0022247X18302233?via%3Dihub

A nonlinear free boundary problem with a self-driven Bernoulli condition

OpenAIRE

Dipierro, Serena; Karakhanyan, Aram; Valdinoci, Enrico

2017-01-01

We study a Bernoulli type free boundary problem with two phases J[u]=∫Ω|∇u(x)|2dx+Φ(M−(u),M+(u)),u−u¯∈W1,20(Ω), where u¯∈W1,2(Ω) is a given boundary datum. Here, M1 and M2 are weighted volumes of {u≤0}∩Ω and {u>0}∩Ω, respectively, and Φ is a nonnegative function of two real variables. We show that, for this problem, the Bernoulli constant, which determines the gradient jump condition across the free boundary, is of global type and it is indeed determined by the weighted volumes of the phas...

In Situ Observation of the Dislocation Structure Evolution During a Strain Path Change in Copper

DEFF Research Database (Denmark)

Wejdemann, Christian; Poulsen, Henning Friis; Lienert, Ulrich

2013-01-01

The evolution of deformation structures in individual grains embedded in polycrystalline copper specimens during strain path changes is observed in situ by high-resolution reciprocal space mapping with high-energy synchrotron radiation. A large number of individual subgrains is resolved; their be......The evolution of deformation structures in individual grains embedded in polycrystalline copper specimens during strain path changes is observed in situ by high-resolution reciprocal space mapping with high-energy synchrotron radiation. A large number of individual subgrains is resolved...... and orientation of the resolved subgrains change only slightly, while their elastic stresses are significantly altered. This indicates the existence of a microplastic regime during which only the subgrains deform plastically and no yielding of the dislocation walls occurs. After reloading above 0.3% strain......, the elastic stresses of individual subgrains are about the same as in unidirectionally deformed reference specimens. They increase only slightly during further straining—accompanied by occasional emergence of new subgrains, abundant orientation changes, and disappearance of existing subgrains....

Interactions between Dislocations and Grain Boundaries

NARCIS (Netherlands)

Soer, Wouter Anthon

2006-01-01

Dislocations (line defects) and grain boundaries (planar defects) are two types of lattice defects that are crucial to the deformation behavior of metals. Permanent deformation of a crystalline material is microscopically associated with the nucleation and propagation of dislocations, and extensive

Dynamical simulation of structural multiplicity in grain boundaries

International Nuclear Information System (INIS)

Majid, I.; Bristowe, P.D.

1987-06-01

Work on a computer simulation study of a low-energy high-angle boundary structure which is not periodic have been recently reported. This result is of interest since grain boundary structures are usually assumed to have a periodicity corresponding to the appropriate coincidence site lattice (CSL) and many experimental observations of the structure of grain boundaries performed using conventional and high-resolution electron microscopy, electron diffraction and x-ray diffraction appear to support this work. However, this work, using empirical interatomic pair potentials and the relaxation method of molecular statics, have simulated a Σ = 5 36.87 0 (001) twist boundary and found a low energy structure having a larger repeat cell than the CSL and is composed of two different types of structural unit that are randomly distributed in the boundary plane. This result, which has been termed the multiplicity of grain boundary structures, has also been found in the simulation of tilt boundaries. The multiplicity phenomenon is of special interest in twist boundaries since it is used as a structural model to explain the x-ray scattering from a Σ = 5 boundary in gold. These scattering patterns had previously remained unexplained using stable structures that had simple CSL periodicity. Also, the effect of having a multiple number of low energy structural units coexisting in the grain boundary is of more general interest since it implies that the boundary structures may be quasi-periodic and, in some circumstances, may even result in a roughening of the boundary plane. This paper extends this work by showing, using molecular dynamics, that a multiplicity of structural units can actually nucleate spontaneously in a high-angle grain boundary at finite temperatures

Slovenian-Croatian boundary: backgrounds of boundary-making and boundary-breaking in Istria regarding the contemporary boundary dispute

Directory of Open Access Journals (Sweden)

Damir Josipovič

2012-06-01

Full Text Available Boundary-making in Istria is an old undertaking. It has actually never ceasesed, not even today. Istrian peninsula has thus undergone substantial boundary shifts during the last couple of centuries (especially after the Venetian demise in 1797. But Istria carries its worldwide fame also due to one of probably the harshest disputes on the post-war European grounds – the Trieste territory dispute. In author's perspective, this dispute is one of the four main corner-stones of the current Slovenian-Croatian boundary dispute. The remaining three include the Kozler's boundary around Dragonja (Rokava River, the ungraspable notions of Austrian censuses in Istria, and the narratives of partisan settlements on military jurisdiction. However, there are other very important aspects which significantly shaped the development of the dispute, but we will focus at assessing the importance of the aforementioned ones. In this sense, the analysis of the effects of the outcome of the Trieste dispute and its implications to the contemporary interstate dispute is set forth. By unveiling its material and consequently its psychological effects upon the contemporary bilateral relations, its analyses simultaneously reveals backgrounds of never answered question, why Kozler's proposed linguistic boundary around Dragonja (Rokava River turned out to become a boundary of national character. Though nowadays disputed, there is absolutely no chance for both involved parties to substantially draw away from once decisively drawn line of a layman. Despite the fierce battle of words in Slovenian public media on whether should the interstate boundary be placed on Mirna (Quieto or Dragonja Rivers, it will be argued here that the actual choice of the Valley of Dragonja as a boundary is by all means Slovenian. The arguments are based on extensive analyses of cartographic materials, relevant literature, documents, and statistical data.

Slovenian-Croatian boundary: backgrounds of boundary-making and boundary-breaking in Istria regarding the contemporary boundary dispute

Directory of Open Access Journals (Sweden)

Damir Josipovič

2012-01-01

Full Text Available Boundary-making in Istria is an old undertaking. It has actually never ceasesed, not even today. Istrian peninsula has thus undergone substantial boundary shifts during the last couple of centuries (especially after the Venetian demise in 1797. But Istria carries its worldwide fame also due to one of probably the harshest disputes on the post-war European grounds – the Trieste territory dispute. In author's perspective, this dispute is one of the four main corner-stones of the current Slovenian-Croatian boundary dispute. The remaining three include the Kozler's boundary around Dragonja (Rokava River, the ungraspable notions of Austrian censuses in Istria, and the narratives of partisan settlements on military jurisdiction. However, there are other very important aspects which significantly shaped the development of the dispute, but we will focus at assessing the importance of the aforementioned ones. In this sense, the analysis of the effects of the outcome of the Trieste dispute and its implications to the contemporary interstate dispute is set forth. By unveiling its material and consequently its psychological effects upon the contemporary bilateral relations, its analyses simultaneously reveals backgrounds of never answered question, why Kozler's proposed linguistic boundary around Dragonja (Rokava River turned out to become a boundary of national character. Though nowadays disputed, there is absolutely no chance for both involved parties to substantially draw away from once decisively drawn line of a layman. Despite the fierce battle of words in Slovenian public media on whether should the interstate boundary be placed on Mirna (Quieto or Dragonja Rivers, it will be argued here that the actual choice of the Valley of Dragonja as a boundary is by all means Slovenian. The arguments are based on extensive analyses of cartographic materials, relevant literature, documents, and statistical data.

Helmholtz bright and boundary solitons

Energy Technology Data Exchange (ETDEWEB)

Christian, J M [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); McDonald, G S [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); Chamorro-Posada, P [Departmento de TeorIa de la Senal y Comunicaciones e IngenierIa Telematica, Universidad de Valladolid, ETSI Telecomunicacion, Campus Miguel Delibes s/n, 47011 Valladolid (Spain)

2007-02-16

We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts.

Constraint-preserving boundary treatment for a harmonic formulation of the Einstein equations

Energy Technology Data Exchange (ETDEWEB)

Seiler, Jennifer; Szilagyi, Bela; Pollney, Denis; Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany)

2008-09-07

We present a set of well-posed constraint-preserving boundary conditions for a first-order in time, second-order in space, harmonic formulation of the Einstein equations. The boundary conditions are tested using robust stability, linear and nonlinear waves, and are found to be both less reflective and constraint preserving than standard Sommerfeld-type boundary conditions.

Constraint-preserving boundary treatment for a harmonic formulation of the Einstein equations

International Nuclear Information System (INIS)

Seiler, Jennifer; Szilagyi, Bela; Pollney, Denis; Rezzolla, Luciano

2008-01-01

We present a set of well-posed constraint-preserving boundary conditions for a first-order in time, second-order in space, harmonic formulation of the Einstein equations. The boundary conditions are tested using robust stability, linear and nonlinear waves, and are found to be both less reflective and constraint preserving than standard Sommerfeld-type boundary conditions

A Novel Mesh Quality Improvement Method for Boundary Elements

Directory of Open Access Journals (Sweden)

Hou-lin Liu

2012-01-01

Full Text Available In order to improve the boundary mesh quality while maintaining the essential characteristics of discrete surfaces, a new approach combining optimization-based smoothing and topology optimization is developed. The smoothing objective function is modified, in which two functions denoting boundary and interior quality, respectively, and a weight coefficient controlling boundary quality are taken into account. In addition, the existing smoothing algorithm can improve the mesh quality only by repositioning vertices of the interior mesh. Without destroying boundary conformity, bad elements with all their vertices on the boundary cannot be eliminated. Then, topology optimization is employed, and those elements are converted into other types of elements whose quality can be improved by smoothing. The practical application shows that the worst elements can be eliminated and, with the increase of weight coefficient, the average quality of boundary mesh can also be improved. Results obtained with the combined approach are compared with some common approach. It is clearly shown that it performs better than the existing approach.

A boundary-fitted staggered difference method for incompressible flow using Riemann geometry

International Nuclear Information System (INIS)

Koshizuka, Seiichi; Kondo, Shunsuke; Oka, Yoshiaki.

1990-01-01

A boundary-fitted staggered difference method (BFSDM) is investigated for incompressible flow in nuclear plants. BFSDM employs control cells for scalars, staggered location of velocity components, and integrated formulation of div=0. Governing equations are written as coordinate-free forms using Riemann geometry. Flow velocity is represented with contravariant physical components in the present method. Connection terms emerge as source terms in the coordinate-free governing equations. These terms are studied from the viewpoints of physical meaning, numerical stability, and conservative property. Some flows on a round or slant boundary are solved using boundary-fitted curvilinear (BFC) grids and rectangular grids to compare the present method and the rectangular-type (R-type) staggered difference method (SDM). Supercomputing of the present method, including vector processing, is also discussed compared with the R-type method. (author)

Grain-boundary microchemistry and intergranular cracking of irradiated austenitic stainless steels

International Nuclear Information System (INIS)

Chung, H.M.; Ruther, W.E.; Sanecki, J.E.; Kassner, T.F.

1993-01-01

Constant-extension-rate tensile tests and grain-boundary analysis by Auger electron spectroscopy were conducted on high and commercial-purity (HP and CP) Type 304 stainless steel (SS) specimens from irradiated boiling-water reactor (BWR) components to identify the mechanisms of irradiation-assisted stress corrosion cracking (IASCC). Contrary to previous beliefs, susceptibility to intergranular fracture could not be correlated with radiation-induced segregation of impurities such as Si, P, C, or S, but a correlation was obtained with grain-boundary Cr concentration, indicating a role for Cr depletion. Detailed analysis of grain-boundary chemistry was conducted on BWR neutron absorber tubes that were fabricated from two similar heats of HP Type 304 SS of virtually identical bulk chemical composition but exhibiting a significant difference in susceptibility to IASCC after irradiation to ∼2 x 10 21 n/cm 2 (E > 1 MeV). Grain-boundary concentrations of Cr Ni, Si, P, S, and C of the cracking-resistant and -susceptible HP heats were virtually identical. However, grain boundaries of the cracking-resistant material contained less N and more B and Li than those of the cracking-susceptible material. This observation indicates that, besides the deleterious effect of grain-boundary Cr depletion, a synergism between grain-boundary segregation of N and B and transmutation to H and Li plays an important role in IASCC

Technology for Boundaries

DEFF Research Database (Denmark)

Bødker, Susanne; Kristensen, Jannie Friis; Nielsen, Christina

2003-01-01

.After analysing the history and the current boundary work, the paper will propose new technological support for boundary work. In particular the paper will suggest means of supporting boundaries when these are productive and for changing boundaries when this seems more appropriate. In total, flexible technologies......This paper presents a study of an organisation, which is undergoing a process transforming organisational and technological boundaries. In particular, we shall look at three kinds of boundaries: the work to maintain and change the boundary between the organisation and its customers; boundaries...... seem a core issue when dealing with technology for boundaries....

The investigation of recrystallization developed in the largely undercooled Ni–3 at.% Sn alloy

International Nuclear Information System (INIS)

Chen, Q.; Chen, Z.; Liu, F.; Cui, R.X.; Liang, T.

2015-01-01

Highlights: • The grain refinement occurred at ΔT ⩾ 230 K. • Plastic deformation and recrystallization led to grain refinement. • Grain refinement was evidenced directly by TEM. • Misorientation and different plane spacing were detected by high-resolution TEM. - Abstract: Using the molten glass purification combined with the cycle superheating methods, a refined grain was achieved in undercooled Ni–3 at.% Sn alloy. The characteristics of microstructures and substructures of the refined grain were investigated by the classical nucleation theory, the dimensionless superheating model and the stress accumulation model. The grain refinement occurring inevitably at high undercooling (ΔT) was ascribed to the plastic deformation of dendrites and subsequent recrystallization, which were evidenced by the transmission electron microscopy (TEM) (e.g. different types of dislocations, defects and sub-grain boundaries) and high-resolution TEM (e.g. misorientation and different plane spacings)

Model-based estimation with boundary side information or boundary regularization

International Nuclear Information System (INIS)

Chiao, P.C.; Rogers, W.L.; Fessler, J.A.; Clinthorne, N.H.; Hero, A.O.

1994-01-01

The authors have previously developed a model-based strategy for joint estimation of myocardial perfusion and boundaries using ECT (Emission Computed Tomography). The authors have also reported difficulties with boundary estimation in low contrast and low count rate situations. In this paper, the authors propose using boundary side information (obtainable from high resolution MRI and CT images) or boundary regularization to improve both perfusion and boundary estimation in these situations. To fuse boundary side information into the emission measurements, the authors formulate a joint log-likelihood function to include auxiliary boundary measurements as well as ECT projection measurements. In addition, the authors introduce registration parameters to align auxiliary boundary measurements with ECT measurements and jointly estimate these parameters with other parameters of interest from the composite measurements. In simulated PET O-15 water myocardial perfusion studies using a simplified model, the authors show that the joint estimation improves perfusion estimation performance and gives boundary alignment accuracy of <0.5 mm even at 0.2 million counts. The authors implement boundary regularization through formulating a penalized log-likelihood function. The authors also demonstrate in simulations that simultaneous regularization of the epicardial boundary and myocardial thickness gives comparable perfusion estimation accuracy with the use of boundary side information

From boundaries to boundary work: middle managers creating inter-organizational change.

Science.gov (United States)

Oldenhof, Lieke; Stoopendaal, Annemiek; Putters, Kim

2016-11-21

Purpose In healthcare, organizational boundaries are often viewed as barriers to change. The purpose of this paper is to show how middle managers create inter-organizational change by doing boundary work: the dual act of redrawing boundaries and coordinating work in new ways. Design/methodology/approach Theoretically, the paper draws on the concept of boundary work from Science and Technology Studies. Empirically, the paper is based on an ethnographic investigation of middle managers that participate in a Dutch reform program across health, social care, and housing. Findings The findings show how middle managers create a sense of urgency for inter-organizational change by emphasizing "fragmented" service provision due to professional, sectoral, financial, and geographical boundaries. Rather than eradicating these boundaries, middle managers change the status quo gradually by redrawing composite boundaries. They use boundary objects and a boundary-transcending vocabulary emphasizing the need for societal gains that go beyond production targets of individual organizations. As a result, work is coordinated in new ways in neighborhood teams and professional expertise is being reconfigured. Research limitations/implications Since boundary workers create incremental change, it is necessary to follow their work for a longer period to assess whether boundary work contributes to paradigm change. Practical implications Organizations should pay attention to conditions for boundary work, such as legitimacy of boundary workers and the availability of boundary spaces that function as communities of practice. Originality/value By shifting the focus from boundaries to boundary work, this paper gives valuable insights into "how" boundaries are redrawn and embodied in objects and language.

Adiabatic shear localization in a near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Sun, Jieying; Wang, Xiaoyan; Fu, Ao [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China)

2015-07-15

Adiabatic shear localization plays an important role in the deformation and failure of near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy used in aircraft's gear at high rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of an adiabatic shear band under controlled shock-loading experiments. When the nominal shear strain is about 0.68, unstable shear deformation of the alloy emerges after the true flow stress reaches 1100 MPa, the first vibration peak during the split Hopkinson pressure bar testing, and the whole process lasts about 62 μs. The microstructures within the shear band in the Ti–5Al–5Mo–5V–1Cr–1Fe alloy are investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. Phase transformation occurs in the shear band when the nominal shear strain increases to 0.68. A number of equiaxed grains with sizes 50–200 nm and alpha″-phase are in the center of the shear band. Kinetic calculations indicate that during the deformation process, the recrystallized nanosized grains can be formed in the shear band by way of the subgrain boundaries rotation, and the alpha″ phase transformation start after the subgrain boundaries rotated to 30°.

Dual boundary spanning

DEFF Research Database (Denmark)

Li-Ying, Jason

2016-01-01

The extant literature runs short in understanding openness of innovation regarding and the different pathways along which internal and external knowledge resources can be combined. This study proposes a unique typology for outside-in innovations based on two distinct ways of boundary spanning......: whether an innovation idea is created internally or externally and whether an innovation process relies on external knowledge resources. This yields four possible types of innovation, which represent the nuanced variation of outside-in innovations. Using historical data from Canada for 1945...

Diamagnetic boundary layers: a kinetic theory

International Nuclear Information System (INIS)

Lemaire, J.; Burlaga, L.F.

1976-01-01

A kinetic theory for boundary layers associated with MHD tangential 'discontinuities' in a collisionless magnetized plasma such as those observed in the solar wind is presented. The theory consists of finding self-consistent solutions of Vlasov's equation and Maxwell's equation for stationary, one-dimensional boundary layers separating two Maxwellian plasma states. Layers in which the current is carried by electrons are found to have a thickness of the order of a few electron gyroradii, but the drift speed of the current-carrying electrons is found to exceed the Alfven speed, and accordingly such layers are not stable. Several types of layers, in which the current is carried by protons are discussed; in particular, cases in which the magnetic field intensity and/or direction changed across the layer were considered. In every case, the thickness was of the order of a few proton gyroradii and the field changed smoothly , although the characteristics depended somewhat on the boundary conditions. The drift speed was always less than the Alfven speed, consistent with stability of such structures. The results are consistent with the observations of boundary layers in the solar wind near 1 AU. (Auth.)

Fundamental solutions and dual boundary element methods for fracture in plane Cosserat elasticity.

Science.gov (United States)

Atroshchenko, Elena; Bordas, Stéphane P A

2015-07-08

In this paper, both singular and hypersingular fundamental solutions of plane Cosserat elasticity are derived and given in a ready-to-use form. The hypersingular fundamental solutions allow to formulate the analogue of Somigliana stress identity, which can be used to obtain the stress and couple-stress fields inside the domain from the boundary values of the displacements, microrotation and stress and couple-stress tractions. Using these newly derived fundamental solutions, the boundary integral equations of both types are formulated and solved by the boundary element method. Simultaneous use of both types of equations (approach known as the dual boundary element method (BEM)) allows problems where parts of the boundary are overlapping, such as crack problems, to be treated and to do this for general geometry and loading conditions. The high accuracy of the boundary element method for both types of equations is demonstrated for a number of benchmark problems, including a Griffith crack problem and a plate with an edge crack. The detailed comparison of the BEM results and the analytical solution for a Griffith crack and an edge crack is given, particularly in terms of stress and couple-stress intensity factors, as well as the crack opening displacements and microrotations on the crack faces and the angular distributions of stresses and couple-stresses around the crack tip.

Open membranes in a constant C-field background and noncommutative boundary strings

International Nuclear Information System (INIS)

Kawamoto, Shoichi; Sasakura, Naoki

2000-01-01

We investigate the dynamics of open membrane boundaries in a constant C-field background. We follow the analysis for open strings in a B-field background, and take some approximations. We find that open membrane boundaries do show noncommutativity in this case by explicit calculations. Membrane boundaries are one dimensional strings, so we face a new type of noncommutativity, that is, noncommutative strings. (author)

Structure of grain boundaries in hexagonal materials

International Nuclear Information System (INIS)

Sarrazit, F.

1998-05-01

The work presented in this thesis describes experimental and theoretical aspects associated with the structure of grain boundaries in hexagonal materials. It has been found useful to classify grain boundaries as low-angle, special or general on the basis of their structure. High-angle grain boundaries were investigated in tungsten carbide (WC) using conventional electron microscopy techniques, and three examples characteristic of the interfaces observed in this material were studied extensively. Three-dimensionally periodic patterns are proposed as plausible reference configurations, and the Burgers vectors of observed interfacial dislocations were predicted using a theory developed recently. The comparison of experimental observations with theoretical predictions proved to be difficult as contrast simulation techniques require further development for analysis to be completed confidently. Another part of this work involves the characterisation of high-angle grain boundaries in zinc oxide (ZnO) using circuit mapping. Two boundaries displayed structural features characteristic of the 'special' category, however, one boundary presented features which did not conform to this model. It is proposed that the latter observation shows a structural transition from the special to a more general type. Material fluxes involved in defect interactions were considered using the topological framework described in this work. A genera) expression was derived for the total flux arising which allows the behaviour of line-defects to be studied in complex interfacial processes. (author)

On a strong solution of the non-stationary Navier-Stokes equations under slip or leak boundary conditions of friction type

Science.gov (United States)

Kashiwabara, Takahito

Strong solutions of the non-stationary Navier-Stokes equations under non-linearized slip or leak boundary conditions are investigated. We show that the problems are formulated by a variational inequality of parabolic type, to which uniqueness is established. Using Galerkin's method and deriving a priori estimates, we prove global and local existence for 2D and 3D slip problems respectively. For leak problems, under no-leak assumption at t=0 we prove local existence in 2D and 3D cases. Compatibility conditions for initial states play a significant role in the estimates.

Refraction of polarized neutrons on the boundary in thick magnetic film FeAlSi

Energy Technology Data Exchange (ETDEWEB)

Aksenov, V L; Kozhevnikov, S V; Nikitenko, Yu V [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Frank Lab. of Neutron Physics

1999-07-01

Complete text of publication follows. Refraction of polarized neutrons in multilayer structure FeAlSi(20 mkm)/Cr(0.05 mkm)/CaTiO{sub 3}(1000 mkm) has been investigated. An external magnetic field was applied under an angle to the sample surface. Refraction on themagnetic boundaries of two types has been investigated. First type is the boundary vacuum-magnetic film. Second type is magnetic film - non-magnetic substrate CaTiO{sub 3} (thin non-magnetic Cr layer doesn't refract the beam). On the boundary there are spin-flip and beam-splitting. Four spatial splitted beams were observed for different spin transitions on each type of the boundary: '+-', '++', '-+' and '--'. From the experimental values of the glancing angles of refracted beam the following parameters has been derives: the nuclear potentials of the magnetic film and the non-magnetic substrate, the magnitude and the direction of a magnetic induction in the magnetic film. It has been shown that the method of refractometry of polarized neutrons can be used for investigation of thick (about mkm) magnetic films. (author)

General boundary stabilization result of memory-type thermoelasticity with second sound

Directory of Open Access Journals (Sweden)

Fairouz Boulanouar

2014-09-01

Full Text Available In this article we consider an n-dimensional system of visco-thermoelasticity with second sound, where a viscoelastic dissipation is acting on a part of the boundary. We prove an explicit general decay rate result without imposing $u_0=0$ as in [17]. This allows a larger class of relaxation functions and initial data, hence, generalizes some previous results existing in the literature.

Discussion of boundary-layer characteristics near the casing of an axial-flow compressor

Science.gov (United States)

Mager, Artur; Mahoney, John J; Budinger, Ray E

1951-01-01

Boundary-layer velocity profiles on the casing of an axial-flow compressor behind the guide vanes and rotor were measured and resolved into two components: along the streamline of the flow and perpendicular to it. Boundary-layer thickness and the deflection of the boundary layer at the wall were the generalizing parameters. By use of these results and the momentum-integral equations, the characteristics of boundary on the walls of axial-flow compressor are qualitatively discussed. Important parameters concerning secondary flow in the boundary layer appear to be turning of the flow and the product of boundary-layer thickness and streamline curvature outside the boundary layer. Two types of separation are shown to be possible in three dimensional boundary layer.

Boundaries of dreams, boundaries of dreamers: thin and thick boundaries as a new personality measure.

Science.gov (United States)

Hartmann, E

1989-11-01

Previous work by the author and his collaborators on frequent nightmare sufferers demonstrated that these people had striking personality characteristics which could be called "thin boundaries" in a number of different senses. In order to measure thin and thick boundaries, a 145-item questionnaire, the Boundary Questionnaire, has been developed which has now been taken by over 1,000 persons. Preliminary results are presented indicating that, as predicted a priori, several new groups of nightmare sufferers and groups of art students scored usually "thin," whereas a group of naval officers had usually "thick" boundaries. Overall, thinness on the Boundary Questionnaire correlated highly positively (r = .40) with frequency of dream recall and also significantly (r = .16) with length of sleep.

The application of in-situ 3D X-ray diffraction in annealing experiments: First interpretation of substructure development in deformed NaCl

DEFF Research Database (Denmark)

Borthwick, Verity; Schmidt, Søren; Piazolo, Sandra

2012-01-01

In-situ 3D X-ray diffraction (3DXRD) annealing experiments were conducted at the ID-11 beamline at the European Synchrotron Radiation Facility in Grenoble. This allowed us to nondestructively document and subsequently analyse the development of substructures during heating, without the influence...... subgrain boundary formation. These results demonstrate that 3DXRD coupled with in-situ heating is a successful non-destructive technique for examining real-time postdeformational annealing in strongly deformed crystalline materials with complicated microstructures. © (2012) Trans Tech Publications...

HREM studies on the microstructure of severely cold-rolled TiNi alloy after reverse martensitic transformation

International Nuclear Information System (INIS)

Zheng, Y.F.; Zhao, L.C.

2000-01-01

The microstructure of Ti-49.8at.%Ni alloy, which was cold rolled to about 30% reduction in thickness in its martensitic condition and subsequently heated up to 200 C for half an hour, has been studied by high resolution electron microscopy. The interface between parent phase and martensite is not smooth and well coherent. The boundary between two subgrains of the parent phase is not straight but perfectly coherent, with partial dislocation observed at the interface. Inside some parent phase grains, thin plate-like {114} and spear-like {112} twin-related parent phase variant pairs are observed. The {114} twinning boundary is relatively straight, but with two or three atomic-height blurred layers existing near the interface. (orig.)

Diffusion processes in the magnetopause boundary layer

International Nuclear Information System (INIS)

Tsurutani, B.T.; Thorne, R.M.

1982-01-01

Anomalous cross-field diffusion of magnetosheath ions and electrons is a direct consequence of cyclotron-resonant scattering by electrostatic and electromagnetic emissions which are continuously present within the magnetopause boundary layer. Expressions for the rate of cross-field diffusion involving either type of wave are developed and expressed in terms of the absolute upper limit referred to as Bohm diffusion. For the typical average intensity of waves observed in the boundary layer, resonant electron cross-field diffusion is always insignificant. However, magnetosheath ions, resonant with low frequency electrostatic waves, may be transported inward at a rate approaching one tenth the Bohm rate (D/sub perpendiculartsperpendicular/roughly-equal10 3 km 2 /s). While this is not the only mechanism capable of explaining the presence of the low latitude boundary layer it is adequate to account for the typical boundary layer thickness and it should occur at all local times and under all interplanetary conditions. It consequently provides a continuous mechanism for significant mass and momentum transfer across the magnetopause under conditions when field merging is inoperative

Strain-Annealing Based Grain Boundary Engineering to Evaluate its Sole Implication on Intergranular Corrosion in Extra-Low Carbon Type 304L Austenitic Stainless Steel

Science.gov (United States)

Pradhan, S. K.; Bhuyan, P.; Kaithwas, C.; Mandal, Sumantra

2018-07-01

Strain-annealing based thermo-mechanical processing has been performed to promote grain boundary engineering (GBE) in an extra-low carbon type austenitic stainless steel without altering the grain size and residual strain to evaluate its sole influence on intergranular corrosion. Single-step processing comprising low pre-strain ( 5 and 10 pct) followed by annealing at 1273 K for 1 hour have resulted in a large fraction of Σ3 n boundaries and significant disruption in random high-angle grain boundaries (RHAGBs) connectivity. This is due to the occurrence of prolific multiple twinning in these specimens as confirmed by their large twin-related domain and twin-related grain size ratio. Among the iterative processing, the schedule comprising two cycles of 10 and 5 pct deformation followed by annealing at 1173 K for 1 hour has yielded the optimum GBE microstructure with the grain size and residual strain akin to the as-received condition. The specimens subjected to the higher number of iterations failed to realize GBE microstructures due to the occurrence of partial recrystallization. Owing to the optimum grain boundary character distribution, the GBE specimen has exhibited remarkable resistance against sensitization and intergranular corrosion as compared to the as-received condition. Furthermore, the lower depth of percolation in the GBE specimen is due to the significant disruption of RHAGBs connectivity as confirmed from its large twin-related domain and lower fractal dimension.

Boundary condition effect on response modification factor of X-braced steel frames

Directory of Open Access Journals (Sweden)

Walid A. Attia

2018-04-01

Full Text Available Design of the structures to resist seismic force depends on the theory of dissipation in elastic energy that already exists in response modification factor “R-factor”. The main problem in codes gives a constant value for R-factor, since change in boundary conditions of building change in behavior of braced steel frame structures and that effects on R-factor. This study is an attempt to assess overstrength, ductility and response modification factor of X-braced steel frame under change in boundary conditions, as change in the direction of strong axis of column and connection support type of column besides variation in storey and bays numbers to be 21 frames and each frame has 8 different boundary conditions as sum of 168 cases for analysis. These frames were analyzed by using nonlinear static “pushover” analysis. As results of this study change in support type and direction of strong axis of column give large change in value of R-factor; the minimum value was 4.37 and maximum value 10.97. Minimum value is close to code value that’s mean the code is more conservative in suggesting of R-factor and gives a large factor of safety. Change in the location of bracing gives change in value of R-factor for all boundary conditions. Change in direction of strong axis of columns and support type didn’t give change in value of fundamental period, all boundary conditions. Keywords: Response modification factor, Ductility reduction factor, Overstrength factor, Boundary conditions, Brace frame, Nonlinear static analysis “Pushover”

Microstructure and stress corrosion cracking of the fusion boundary region in an alloy 182-A533B low alloy steel dissimilar weld joint

International Nuclear Information System (INIS)

Hou, Juan; Peng, Qunjia; Takeda, Yoichi; Kuniya, Jiro; Shoji, Tetsuo

2010-01-01

Research highlights: → High-angle misorientation at FB, type-II and type-I boundaries. → Highest residual strain and hardness in the zone between FB and type-II boundary. → Type-II and type-I boundaries had lower resistance to SCC growth than the FB. → Crack growth blunted by pitting at the FB. → Reactivation of crack growth from the pitting by oxidation along the grain boundary. - Abstract: Stress corrosion cracking (SCC) in the fusion boundary (FB) region of an Alloy 182-A533B low alloy steel (LAS) dissimilar weld joint in high temperature water doped with sulfate was studied following a microstructure characterization of the FB region. The microstructure characterization suggested the type-II and type-I boundaries in the dilution zone (DZ) adjacent to the FB had lower resistance to SCC growth than the FB. Crack propagating perpendicular to the FB in the DZ was observed to be blunted by pitting at the FB, followed by the reactivation from the pitting by localized oxidation along the grain boundary in LAS.

Can inequality be tamed through boundary work? A qualitative study of health promotion aimed at reducing health inequalities.

Science.gov (United States)

Pedersen, Pia Vivian; Hjelmar, Ulf; Høybye, Mette Terp; Rod, Morten Hulvej

2017-07-01

This paper examines the organisational dynamics that arise in health promotion aimed at reducing health inequalities. The paper draws on ethnographic fieldwork among public health officers in Danish municipalities and qualitative interviews from an evaluation of health promotion programmes targeting homeless and other marginalised citizens. Analytically, we focus on 'boundary work', i.e. the ways in which social and symbolic boundaries are established, maintained, transgressed and negotiated, both at the administrative level and among frontline professionals. The paper discusses three types of boundary work: (i) demarcating professional domains; (ii) setting the boundaries of the task itself; and (iii) managing administrative boundaries. The main argument is that the production, maintenance and transgression of these three types of boundaries constitute central and time-consuming aspects of the practices of public health professionals, and that boundary work constitutes an important element in professional practices seeking to 'tame a wicked problem', such as social inequalities in health. A cross-cutting feature of the three types of boundary work is the management of the divide between health and social issues, which the professionals seemingly seek to uphold and transgress at the same time. The paper thus contributes to ongoing discussions of intersectoral action to address health inequalities. Furthermore, it extends the scope and application of the concept of boundary work in the sociology of public health by suggesting that the focus in previous research on professional demarcation be broadened in order to capture other types of boundaries that shape, and are shaped by, professional practices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long-lived force patterns and deformation waves at repulsive epithelial boundaries

Science.gov (United States)

Rodríguez-Franco, Pilar; Brugués, Agustí; Marín-Llauradó, Ariadna; Conte, Vito; Solanas, Guiomar; Batlle, Eduard; Fredberg, Jeffrey J.; Roca-Cusachs, Pere; Sunyer, Raimon; Trepat, Xavier

2017-10-01

For an organism to develop and maintain homeostasis, cell types with distinct functions must often be separated by physical boundaries. The formation and maintenance of such boundaries are commonly attributed to mechanisms restricted to the cells lining the boundary. Here we show that, besides these local subcellular mechanisms, the formation and maintenance of tissue boundaries involves long-lived, long-ranged mechanical events. Following contact between two epithelial monolayers expressing, respectively, EphB2 and its ligand ephrinB1, both monolayers exhibit oscillatory patterns of traction forces and intercellular stresses that tend to pull cell-matrix adhesions away from the boundary. With time, monolayers jam, accompanied by the emergence of deformation waves that propagate away from the boundary. This phenomenon is not specific to EphB2/ephrinB1 repulsion but is also present during the formation of boundaries with an inert interface and during fusion of homotypic epithelial layers. Our findings thus unveil a global physical mechanism that sustains tissue separation independently of the biochemical and mechanical features of the local tissue boundary.

Evolution of deformation structures under varying loading conditions followed in situ by high angular resolution 3DXRD

DEFF Research Database (Denmark)

Pantleon, Wolfgang; Wejdemann, Christian; Jakobsen, B.

2009-01-01

copper to different loading conditions are presented: during uninterrupted tensile deformation, formation of subgrains can be observed concurrently with broadening of the Bragg reflection shortly after onset of plastic deformation. With continued tensile deformation, the subgrain structure develops...... intermittently. When the traction is terminated, stress relaxation occurs and number, size and orientation of subgrains are found to be constant. The subgrain structure freezes and only a minor clean-up of the dislocation structure is observed. When changing the tensile direction after pre-deformation in tension...

Quantum effective action in spacetimes with branes and boundaries

International Nuclear Information System (INIS)

Barvinsky, A.O.; Nesterov, D.V.

2006-01-01

We construct quantum effective action in spacetime with branes/boundaries. This construction is based on the reduction of the underlying Neumann type boundary value problem for the propagator of the theory to that of the much more manageable Dirichlet problem. In its turn, this reduction follows from the recently suggested Neumann-Dirichlet duality which we extend beyond the tree-level approximation. In the one-loop approximation this duality suggests that the functional determinant of the differential operator subject to Neumann boundary conditions factorizes into the product of its Dirichlet counterpart and the functional determinant of a special operator on the brane--the inverse of the brane-to-brane propagator. As a byproduct of this relation we suggest a new method for surface terms of the heat kernel expansion. This method allows one to circumvent well-known difficulties in the heat kernel theory on manifolds with boundaries for a wide class of generalized Neumann boundary conditions. In particular, we easily recover several lowest-order surface terms in the case of Robin and oblique boundary onditions. We briefly discuss multiloop applications of the suggested Dirichlet reduction and the prospects of constructing the universal background-field method for systems with branes/boundaries, analogous to the Schwinger-DeWitt technique

The complex variable boundary element method: Applications in determining approximative boundaries

Science.gov (United States)

Hromadka, T.V.

1984-01-01

The complex variable boundary element method (CVBEM) is used to determine approximation functions for boundary value problems of the Laplace equation such as occurs in potential theory. By determining an approximative boundary upon which the CVBEM approximator matches the desired constant (level curves) boundary conditions, the CVBEM is found to provide the exact solution throughout the interior of the transformed problem domain. Thus, the acceptability of the CVBEM approximation is determined by the closeness-of-fit of the approximative boundary to the study problem boundary. ?? 1984.

The effect of neutron irradiation on the recuperation and recristallization of the polycrystalline niobium

International Nuclear Information System (INIS)

Monteiro, W.A.

1978-01-01

Through the measurements in Transmission Electron Microscopy and Microhardness is studied the effect of fast neutron irradiation (E > or = 0,1 MeV) on the Recovery and Recrystallization in very pure grade Niobium. The range of temperature is 25 0 C - 1200 0 C for one hour. The sigmoidal curve of the Recovery in Niobium shows a initial increase in the microhardness in the range of temperature of 25 0 C - 300 0 C, who is related to the intersticial migration (impurity atoms) O, C and N to the dislocations and to the defects clusters produced by cold work and radiation. The Recrystallization in cold worked Niobium comes by subgrain growth (subgrains coalescence) and by strain induced grain boundary migration. The radiation with fast neutrons (O=1,3 x 10 18 nvt) acelerates the overall nucleation process of Recrystallization by about 150 0 C with respect to the only deformed Niobium. The activation energy for the Recrystallization process is obtained in both cases, in the rolling Niobium and in Nb deformed and irradiated by fast neutrons (1,2 x 10 17 nvt) [pt

Recent development in crystal growth of large-diameter Y-QMG (reg sign) bulk superconductors; Y kei ogata QMG (reg sign) baruku koonchodendotai no kaihatsu jokyo

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, T.; Morita, M. [Nippon Steel Corporation, Tokyo (Japan); Masahashi, N. [Tohoku University, Miyagi (Japan). Institute for Materials Research

1999-11-25

The current status of large-diameter Y-Ba-Cu-O OMG(reg sign) bulk superconductors is described. 75 mm-diameter QMG(reg sign) samples with fairly concentric trapped-magnetic-flux-density distributions have been successfully grown. In addition, a record-high value of the magnetic levitation force, 171 kgf, measured at 77 K using a 90 mm-diameter Nd-Fe-B magnet has been obtained for a 100 mm-diameter sample. The crystal orientation of subgrains in the sample was determined using Electron Back-Scattering Diffraction as well as using a conventional optical apparatus including a He-Ne-laser. For the sample grown under normal process conditions, the maximum value of the [001]-axis misorientation angles at the subgrain-boundaries we obtained in the c-substructure region is 2.9 degree. However, in the a/b-substructure regions, the misorientation angles are larger, and the maximum value obtained is 6.6 degree, exceeding the critical angle at which a significant reduction of the critical current density occurs in Y123 thin films due to the weak-link problem. (author)

Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

International Nuclear Information System (INIS)

Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

High purity W and W-0.9La 2 O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 o C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

Using X-ray microbeam diffraction to study the long-range internal stresses in aluminum processed by ECAP

International Nuclear Information System (INIS)

Lee, I-Fang; Phan, Thien Q.; Levine, Lyle E.; Tischler, Jonathan Z.; Geantil, Peter T.; Huang, Yi; Langdon, Terence G.; Kassner, Michael E.

2013-01-01

Aluminum alloy 1050 was processed by equal-channel angular pressing (ECAP) using a single pass (equivalent uniaxial strain of about 0.88). Long-range internal stresses (LRISs) were assessed in the grain/subgrain interiors using X-ray microbeam diffraction to measure the spacing of {5 3 1} planes, with normals oriented approximately +27.3°, +4.9° and −17.5° off the pressing (axial) direction. The results are consistent with mechanical analysis that suggests the maximum tensile plastic-strain after one pass is expected for +22.5°, roughly zero along the pressing axis, and maximum compressive strain for the −67.5° direction. The magnitude of the measured maximum compressive long-range internal stress is about 0.13σ a (applied stress) in low-dislocation regions within the grain/subgrain interiors. This work is placed in the context of earlier work where convergent beam electron diffraction was used to analyze LRISs in close proximity to the deformation-induced boundaries. The results are complementary and the measured stresses are consistent with a composite model for long-range internal stresses

Thermodynamic investigation of the phase equilibrium boundary between TiO2 rutile and its α-PbO2-type high-pressure polymorph

Science.gov (United States)

Kojitani, Hiroshi; Yamazaki, Monami; Kojima, Meiko; Inaguma, Yoshiyuki; Mori, Daisuke; Akaogi, Masaki

2018-06-01

Heat capacity (C P) of rutile and α-PbO2 type TiO2 (TiO2-II) were measured by the differential scanning calorimetry and thermal relaxation method. Using the results, standard entropies at 1 atm and 298.15 K of rutile and TiO2-II were determined to be 50.04(4) and 46.54(2) J/mol K, respectively. Furthermore, thermal expansivity (α) determined by high-temperature X-ray diffraction measurement and mode Grüneisen parameters obtained by high-pressure Raman spectroscopy suggested the thermal Grüneisen parameter (γ th) for TiO2-II of 1.7(1). By applying the obtained low-temperature C P and γ th, the measured C P and α data of TiO2-II were extrapolated to higher temperature region using a lattice vibrational model calculation, as well as rutile. Internally consistent thermodynamic data sets of both rutile and TiO2-II assessed in this study were used to thermodynamically calculate the rutile‒TiO2-II phase equilibrium boundary. The most plausible boundary was obtained to be P (GPa) = 0.0074T (K) - 1.7. Our boundary suggests that the crystal growth of TiO2-II observed below 5.5 GPa and 900 K in previous studies advanced in its stability field. The phase boundary calculation also suggested small, exothermic phase transition enthalpy from rutile to TiO2-II at 1 atm and 298.15 K of - 0.5 to - 1.1 kJ/mol. This implies that the thermodynamic stability of rutile at 1 atm above room temperature is due to larger contribution of entropy term.

Negotiating boundaries

DEFF Research Database (Denmark)

Aarhus, Rikke; Ballegaard, Stinne Aaløkke

2010-01-01

to maintain the order of the home when managing disease and adopting new healthcare technology. In our analysis we relate this boundary work to two continuums of visibility-invisibility and integration-segmentation in disease management. We explore five factors that affect the boundary work: objects......, activities, places, character of disease, and collaboration. Furthermore, the processes are explored of how boundary objects move between social worlds pushing and shaping boundaries. From this we discuss design implications for future healthcare technologies for the home.......To move treatment successfully from the hospital to that of technology assisted self-care at home, it is vital in the design of such technologies to understand the setting in which the health IT should be used. Based on qualitative studies we find that people engage in elaborate boundary work...

Dirac-like operators on the Hilbert space of differential forms on manifolds with boundaries

Science.gov (United States)

Pérez-Pardo, Juan Manuel

The problem of self-adjoint extensions of Dirac-type operators in manifolds with boundaries is analyzed. The boundaries might be regular or non-regular. The latter situation includes point-like interactions, also called delta-like potentials, in manifolds of dimension higher than one. Self-adjoint boundary conditions for the case of dimension 2 are obtained explicitly.

Administrative Area Boundaries 2 (State Boundaries), Region 9, 2010, NAVTEQ

Data.gov (United States)

U.S. Environmental Protection Agency — NAVTEQ Administrative Area Boundaries 2 (State Boundaries) for Region 9. There are five Administrative Area Boundaries layers (1, 2, 3, 4, 5). These layers contain...

Administrative Area Boundaries 4 (City Boundaries), Region 9, 2010, NAVTEQ

Data.gov (United States)

U.S. Environmental Protection Agency — NAVTEQ Administrative Area Boundaries 4 (City Boundaries) for Region 9. There are five Administrative Area Boundaries layers (1, 2, 3, 4, 5). These layers contain...

Microstructural degradation mechanisms during creep in strength enhanced high Cr ferritic steels and their evaluation by hardness measurement

International Nuclear Information System (INIS)

Ghassemi Armaki, Hassan; Chen, Ruiping; Kano, Satoshi; Maruyama, Kouichi; Hasegawa, Yasushi; Igarashi, Masaaki

2011-01-01

Graphical abstract: Effect of static recovery on the acceleration of subgrain coarsening during creep plastic deformation. Display Omitted Highlights: → Short-term 'H' and long-term 'L' creep regions have different creep characteristics. → Strain-induced recovery of subgrains proceeds in the both creep regions 'H' and 'L'. → In region ''L', two additional degradation mechanisms accelerate creep failure. → Thermal coarsening of precipitates and subgrains appear during long-term creep ''L'. → In region 'L', strain-induced coarsening of precipitates accelerates creep failure. - Abstract: There are two creep regions with different creep characteristics: short-term creep region 'H', where precipitates and subgrains are thermally stable, and long-term creep region 'L', where thermal coarsening of precipitates and subgrains appear. In region 'H', the normalized subgrain size (λ-λ 0 )/(λ * -λ 0 ) has a linear relation with creep strain and its slope is 10ε -1 . But, region L is the time range in which the static recovery and the strain-induced recovery progress simultaneously. In this region, the static recovery accelerates the strain-induced recovery, and subgrain size is larger than that line which neglects the contribution of the static recovery. In region 'L', the Δλ/Δλ * -strain present a linear relation with a slope 35ε -1 . There is a linear relation between hardness and subgrain size. Hardness drop, H 0 - H, as a function of Larson-Miller parameter can be a good measure method for assessment of hardness drop and consequently degradation of microstructure. Hardness drop shows an identical slope in creep region 'H', whereas hardness drop due to thermal aging and creep in region 'L' show together a similar slope. In region 'H', degradation of microstructure is mainly due to recovery of subgrains controlled by creep plastic deformation, and precipitates do not have a major role. However, in creep region 'L', there are three degradation mechanisms

Micro tectonic milonitas analysis in the extreme south of the Sarandi del Yi shear zone: Kinematics and deformation conditions

International Nuclear Information System (INIS)

Oyhantçabal, P; Suarez, I; Seluchi, N; Martinez, X.

2010-01-01

The Shear Zone divides Sarandi del Yi Craton River Plate in Piedra Alta and Nico Perez land . The southern end of this zone extends to north - south from the vicinity of the town of Minas to Punta Solis. The predominant lithology of the study area consists of a granitic mylonite with abundant muscovite and biotite. Structural data of foliation , stretching lineation and kinematic indicators were surveyed .Petrographic analysis shows that quartz is presented as ribbons polycrystalline product subgrain rotation recrystallization and grain boundary migration . Feldspar porphyroclasts are partially recrystallized in developing type structures c ore and mantle . Kinematic indicators such as sigma porphyroclasts , mica fish and oblique foliation defined consistently sinistral sense . The presence of stable and mirmequitas in the plane of biotite foliation along the microstructures described in quartz and feldspar , can be inferred temperature conditions between 450 ° C and 550° C during deformation

The influence of boundary features on grassland-edge communities of Alta Murgia

OpenAIRE

Cassano, Stefania; Alignier, Audrey; Forte, Luigi; Labadessa, Rocco; Mairota, Paola

2016-01-01

Many studies suggest the importance of boundary features on plant community dynamics. Our aim was to investigate the influence of boundary features on edge plant assemblages in semi-natural dry grasslands. For this purpose we selected 16 grassland edges in the central portion of the Natura 2000 site Murgia Alta, in southeastern Italy. These sites were selected according to a combination of boundary features, i.e. the adjoining land use type (road or cereal crop), slope (grassland tilted towar...

Stress dependence of microstructures in experimentally deformed calcite

Science.gov (United States)

Platt, John P.; De Bresser, J. H. P.

2017-12-01

Optical measurements of microstructural features in experimentally deformed Carrara marble help define their dependence on stress. These features include dynamically recrystallized grain size (Dr), subgrain size (Sg), minimum bulge size (Lρ), and the maximum scale length for surface-energy driven grain-boundary migration (Lγ). Taken together with previously published data Dr defines a paleopiezometer over the range 15-291 MPa and temperature over the range 500-1000 °C, with a stress exponent of -1.09 (CI -1.27 to -0.95), showing no detectable dependence on temperature. Sg and Dr measured in the same samples are closely similar in size, suggesting that the new grains did not grow significantly after nucleation. Lρ and Lγ measured on each sample define a relationship to stress with an exponent of approximately -1.6, which helps define the boundary between a region of dominant strain-energy-driven grain-boundary migration at high stress, from a region of dominant surface-energy-driven grain-boundary migration at low stress.

Boundary element analysis of earthquake induced hydrodynamic pressures in a water reservoir

International Nuclear Information System (INIS)

Jablonski, A.M.

1988-11-01

The seismic analysis of concrete gravity and arch dams is affected by the hydrodynamic pressures in the water reservoir. Boundary element method (BEM) formulations are derived for the hydrodynamic pressures arising in a gravity dam-reservoir-foundation system, treating both 2- and 3-dimensional cases. The formulations are based on the respective mathematical models which are governed by two- and three-dimensional Helmholtz equations with appropriate boundary conditions. For infinite reservoirs, loss of energy due to pressure waves moving away toward infinity strongly influence response. Since it is not possible to discretize an infinite extent, the radiation damping due to outgoing waves is accounted for by incorporating special boundary conditions at the far end, and in a similar manner the loss of energy due to absorption of waves by a flexible bottom of reservoir and banks can be accounted for by a special condition along the boundaries. Numerical results are obtained and compared with available classical solutions and convergence of numerical results with the size and number of boundary elements is studied. It is concluded that the direct boundary element method is an effective tool for the evaluation of the hydrodynamic pressures in finite and infinite dam-reservoir-foundation systems subjected to harmonic-type motion, and can easily be extended to any type of random motion with fast Fourier transform techniques. 82 refs., 65 figs., 25 tabs

Boundary layer energies for nonconvex discrete systems

NARCIS (Netherlands)

Scardia, L.; Schlömerkemper, A.; Zanini, C.

2011-01-01

In this work we consider a one-dimensional chain of atoms which interact through nearest and next-to-nearest neighbour interactions of Lennard-Jones type. We impose Dirichlet boundary conditions and in addition prescribe the deformation of the second and last but one atoms of the chain. This

Scientific advice and public policy: expert advisers' and policymakers' discourses on boundary work

NARCIS (Netherlands)

Hoppe, Robertus

2008-01-01

This article reports on considerable variety and diversity among discourses on their own jobs of boundary workers of several major Dutch institutes for science-based policy advice. Except for enlightenment, all types of boundary arrangements/work in the Wittrock-typology (Social knowledge and public

Effects of Boundary Layer Height on the Model of Ground-Level PM2.5 Concentrations from AOD: Comparison of Stable and Convective Boundary Layer Heights from Different Methods

Directory of Open Access Journals (Sweden)

Zengliang Zang

2017-06-01

Full Text Available The aerosol optical depth (AOD from satellites or ground-based sun photometer spectral observations has been widely used to estimate ground-level PM2.5 concentrations by regression methods. The boundary layer height (BLH is a popular factor in the regression model of AOD and PM2.5, but its effect is often uncertain. This may result from the structures between the stable and convective BLHs and from the calculation methods of the BLH. In this study, the boundary layer is divided into two types of stable and convective boundary layer, and the BLH is calculated using different methods from radiosonde data and National Centers for Environmental Prediction (NCEP reanalysis data for the station in Beijing, China during 2014–2015. The BLH values from these methods show significant differences for both the stable and convective boundary layer. Then, these BLHs were introduced into the regression model of AOD-PM2.5 to seek the respective optimal BLH for the two types of boundary layer. It was found that the optimal BLH for the stable boundary layer is determined using the method of surface-based inversion, and the optimal BLH for the convective layer is determined using the method of elevated inversion. Finally, the optimal BLH and other meteorological parameters were combined to predict the PM2.5 concentrations using the stepwise regression method. The results indicate that for the stable boundary layer, the optimal stepwise regression model includes the factors of surface relative humidity, BLH, and surface temperature. These three factors can significantly enhance the prediction accuracy of ground-level PM2.5 concentrations, with an increase of determination coefficient from 0.50 to 0.68. For the convective boundary layer, however, the optimal stepwise regression model includes the factors of BLH and surface wind speed. These two factors improve the determination coefficient, with a relatively low increase from 0.65 to 0.70. It is found that the

Algebraic structures in generalized Clifford analysis and applications to boundary value problems

Directory of Open Access Journals (Sweden)

José Játem

2015-12-01

Full Text Available The present article has a threefold purpose: First it is a survey of the algebraic structures of generalized Clifford-type algebras and shows the main results of the corresponding Clifford-type analysis and its application to boundary value problems known so far. Second it is aimed to implement algorithms to provide the fast and accurate computation of boundary value problems for inhomogeneous equations in the framework of the generalized Clifford analysis. Finally it is also aimed to encourage the development of a generalized discrete Clifford analysis.

Time Temperature-Precipitation Behavior in An Al-Cu-Li Alloy 2195

Science.gov (United States)

Chen, P. S.; Bhat, B. N.

1999-01-01

Al-Cu-Li alloy 2195, with its combination of good cryogenic properties, low density, and high modulus, has been selected by NASA to be the main structural alloy of the Super Light Weight Tank (SLWT) for the Space Shuttle. Alloy 2195 is strengthened by an aging treatment that precipitates a particular precipitate, labeled as T1(Al2CuLi). Other phases, such as GP zone, (theta)', (theta)", theta, (delta)', S' are also present in this alloy when artificially aged. Cryogenic strength and fracture toughness are critical to the -SLWT application, since the SLWT will house liquid oxygen and hydrogen. Motivation for the Time-Temperature-Precipitation (TTP) study at lower temperature (lower than 350 F) comes in part from a recent study by Chen, The study found that the cryogenic fracture toughness of alloy 2195 is greatly influenced by the phases present in the matrix and subgrain boundaries. Therefore, the understanding of TTP behavior can help develop a guideline to select appropriate heat treatment conditions for the desirable applications. The study of TTP behavior at higher temperature (400 to 1000 F) was prompted by the fact that the SLWT requires a welded construction. Heat conduction from the weld pool affects the microstructure in the heat-affected zone (HAZ), which leads to changes in the mechanical properties. Furthermore, the SLWT may need repair welding for more than one time and any additional thermal cycles will increase precipitate instability and promote phase transformation. As a result considerable changes in HAZ microstructure and mechanical properties are expected during the construction of the SLWT. Therefore, the TTP diagrams can serve to understand the thermal history of the alloy by analyzing the welded microstructure. In the case welding, the effects of thermal cycles on the microstructure and mechanical properties can be predicted with the aid of the TTP diagrams. The 2195 alloy (nominally Al + 4 pct Cu + 1 pct Li + 0.3 pct Ag + 0.3 pct Mg + 0

Role of Grain Boundaries under Long-Time Radiation

Science.gov (United States)

Zhu, Yichao; Luo, Jing; Guo, Xu; Xiang, Yang; Chapman, Stephen Jonathan

2018-06-01

Materials containing a high proportion of grain boundaries offer significant potential for the development of radiation-resistant structural materials. However, a proper understanding of the connection between the radiation-induced microstructural behavior of a grain boundary and its impact at long natural time scales is still missing. In this Letter, point defect absorption at interfaces is summarized by a jump Robin-type condition at a coarse-grained level, wherein the role of interface microstructure is effectively taken into account. Then a concise formula linking the sink strength of a polycrystalline aggregate with its grain size is introduced and is well compared with experimental observation. Based on the derived model, a coarse-grained formulation incorporating the coupled evolution of grain boundaries and point defects is proposed, so as to underpin the study of long-time morphological evolution of grains induced by irradiation. Our simulation results suggest that the presence of point defect sources within a grain further accelerates its shrinking process, and radiation tends to trigger the extension of twin boundary sections.

Fiat or bona fide boundary--a matter of granular perspective.

Directory of Open Access Journals (Sweden)

Lars Vogt

Full Text Available Distinguishing bona fide (i.e. natural and fiat (i.e. artificial physical boundaries plays a key role for distinguishing natural from artificial material entities and is thus relevant to any scientific formal foundational top-level ontology, as for instance the Basic Formal Ontology (BFO. In BFO, the distinction is essential for demarcating two foundational categories of material entity: object and fiat object part. The commonly used basis for demarcating bona fide from fiat boundary refers to two criteria: (i intrinsic qualities of the boundary bearers (i.e. spatial/physical discontinuity, qualitative heterogeneity and (ii mind-independent existence of the boundary. The resulting distinction of bona fide and fiat boundaries is considered to be categorial and exhaustive.By Referring to various examples from biology, we demonstrate that the hitherto used distinction of boundaries is not categorial: (i spatial/physical discontinuity is a matter of scale and the differentiation of bona fide and fiat boundaries is thus granularity-dependent, and (ii this differentiation is not absolute, but comes in degrees. By reducing the demarcation criteria to mind-independence and by also considering dispositions and historical relations of the bearers of boundaries, instead of only considering their spatio-structural properties, we demonstrate with various examples that spatio-structurally fiat boundaries can nevertheless be mind-independent and in this sense bona fide.We argue that the ontological status of a given boundary is perspective-dependent and that the strictly spatio-structural demarcation criteria follow a static perspective that is ignorant of causality and the dynamics of reality. Based on a distinction of several ontologically independent perspectives, we suggest different types of boundaries and corresponding material entities, including boundaries based on function (locomotion, physiology, ecology, development, reproduction and common history

Diffusion of hydrogen from plasma source by grain boundaries in EFG silicon

International Nuclear Information System (INIS)

Fedotov, A.; Saad, Anis M.H.; Drozdov, N.; Mazanik, A.; Ulyashin, A.; Fahrner, W.R.; Stognii, A.

2001-01-01

Diffusion of atomized hydrogen along grain boundaries (GBs) studied by transformation of their electrical activity in p-type silicon bi crystalline samples cut from EFG silicon crystals was investigated. The changes in electrical activity of GBs was estimated relative to both minority (MiC) and majority (MaC) carriers and demonstrated the correlation between the type, structure and thermal pre-history of GBs. It was shown on the base of this study that diffusion along GBs depends essentially on three factors: type of GBs, state of ribbons (as-grown or annealed) and concurrence of grain boundary dangling bonds and boron passivation effects. The model of the longitudinal hydrogen diffusion that explains these results is proposed

The effect of deformation temperature on the microstructure evolution of Inconel 625 superalloy

Science.gov (United States)

Guo, Qingmiao; Li, Defu; Guo, Shengli; Peng, Haijian; Hu, Jie

2011-07-01

Hot compression tests of Inconel 625 superalloy were conducted using a Gleeble-1500 simulator between 900 °C and 1200 °C with different true strains and a strain rate of 0.1 s -1. Scanning electron microscope (SEM) and electron backscatter diffraction technique (EBSD) were employed to investigate the effect of deformation temperature on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). It is found that the relationship between the DRX grain size and the peak stress can be expressed by a power law function. Significant influence of deformation temperatures on the nucleation mechanisms of DRX are observed at different deformation stages. At lower deformation temperatures, continuous dynamic recrystallization (CDRX) characterized by progressive subgrain rotation is considered as the main mechanism of DRX at the early deformation stage. However, discontinuous dynamic recrystallization (DDRX) with bulging of the original grain boundaries becomes the operating mechanism of DRX at the later deformation stage. At higher deformation temperatures, DDRX is the primary mechanism of DRX, while CDRX can only be considered as an assistant mechanism at the early deformation stage. Nucleation of DRX can also be activated by the twinning formation. With increasing the deformation temperature, the effect of DDRX accompanied with twinning formation grows stronger, while the effect of CDRX grows weaker. Meanwhile, the position of subgrain formation shifts gradually from the interior of original grains to the vicinity of the original boundaries.

The fatigue response of the aluminium-lithium alloy, 8090

Science.gov (United States)

Birt, M. J.; Beevers, C. J.

1989-01-01

The fatigue response of an Al-Li-Cu-Mg-Zr (8090) alloy has been studied at room temperature. The initiation and growth of small and long cracks has been examined at R = 0.1 and at a frequency of 100 Hz. Initiation was observed to occur dominantly at sub-grain boundaries. The growth of the small cracks was crystallographic in character and exhibited little evidence of retardation or arrest at the grain boundaries. The long crack data showed the alloy to have a high resistance to fatigue crack growth with underaging providing the optimum heat treatment for fatigue crack growth resistance. In general, this can be attributed to high levels of crack closure which resulted from the presence of extensive microstructurally related asperities.

SILICON CARBIDE GRAIN BOUNDARY DISTRIBUTIONS, IRRADIATION CONDITIONS, AND SILVER RETENTION IN IRRADIATED AGR-1 TRISO FUEL PARTICLES

Energy Technology Data Exchange (ETDEWEB)

Lillo, T. M.; Rooyen, I. J.; Aguiar, J. A.

2016-11-01

Precession electron diffraction in the transmission electron microscope was used to map grain orientation and ultimately determine grain boundary misorientation angle distributions, relative fractions of grain boundary types (random high angle, low angle or coincident site lattice (CSL)-related boundaries) and the distributions of CSL-related grain boundaries in the SiC layer of irradiated TRISO-coated fuel particles. Two particles from the AGR-1 experiment exhibiting high Ag-110m retention (>80%) were compared to a particle exhibiting low Ag-110m retention (<19%). Irradiated particles with high Ag-110m retention exhibited a lower fraction of random, high angle grain boundaries compared to the low Ag-110m retention particle. An inverse relationship between the random, high angle grain boundary fraction and Ag-110m retention is found and is consistent with grain boundary percolation theory. Also, comparison of the grain boundary distributions with previously reported unirradiated grain boundary distributions, based on SEM-based EBSD for similarly fabricated particles, showed only small differences, i.e. a greater low angle grain boundary fraction in unirradiated SiC. It was, thus, concluded that SiC layers with grain boundary distributions susceptible to Ag-110m release were present prior to irradiation. Finally, irradiation parameters were found to have little effect on the association of fission product precipitates with specific grain boundary types.

Boundary-value problems with free boundaries for elliptic systems of equations

CERN Document Server

Monakhov, V N

1983-01-01

This book is concerned with certain classes of nonlinear problems for elliptic systems of partial differential equations: boundary-value problems with free boundaries. The first part has to do with the general theory of boundary-value problems for analytic functions and its applications to hydrodynamics. The second presents the theory of quasiconformal mappings, along with the theory of boundary-value problems for elliptic systems of equations and applications of it to problems in the mechanics of continuous media with free boundaries: problems in subsonic gas dynamics, filtration theory, and problems in elastico-plasticity.

Feynman Integrals with Absorbing Boundaries

OpenAIRE

Marchewka, A.; Schuss, Z.

1997-01-01

We propose a formulation of an absorbing boundary for a quantum particle. The formulation is based on a Feynman-type integral over trajectories that are confined to the non-absorbing region. Trajectories that reach the absorbing wall are discounted from the population of the surviving trajectories with a certain weighting factor. Under the assumption that absorbed trajectories do not interfere with the surviving trajectories, we obtain a time dependent absorption law. Two examples are worked ...

Mechanism for boundary crises in quasiperiodically forced period-doubling systems

International Nuclear Information System (INIS)

Kim, Sang-Yoon; Lim, Woochang

2005-01-01

We investigate the mechanism for boundary crises in the quasiperiodically forced logistic map which is a representative model for quasiperiodically forced period-doubling systems. For small quasiperiodic forcing ε, a chaotic attractor disappears suddenly via a 'standard' boundary crisis when it collides with the smooth unstable torus. However, when passing a threshold value of ε, a basin boundary metamorphosis occurs, and then the smooth unstable torus is no longer accessible from the interior of the basin of the attractor. For this case, using the rational approximations to the quasiperiodic forcing, it is shown that a nonchaotic attractor (smooth torus or strange nonchaotic attractor) as well as a chaotic attractor is destroyed abruptly through a new type of boundary crisis when it collides with an invariant 'ring-shaped' unstable set which has no counterpart in the unforced case

Mechanism for boundary crises in quasiperiodically forced period-doubling systems

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang-Yoon [Department of Physics, Kangwon National University, Chunchon, Kangwon-Do 200-701 (Korea, Republic of)]. E-mail: sykim@kangwon.ac.kr; Lim, Woochang [Department of Physics, Kangwon National University, Chunchon, Kangwon-Do 200-701 (Korea, Republic of)]. E-mail: wclim@kwnu.kangwon.ac.kr

2005-01-10

We investigate the mechanism for boundary crises in the quasiperiodically forced logistic map which is a representative model for quasiperiodically forced period-doubling systems. For small quasiperiodic forcing {epsilon}, a chaotic attractor disappears suddenly via a 'standard' boundary crisis when it collides with the smooth unstable torus. However, when passing a threshold value of {epsilon}, a basin boundary metamorphosis occurs, and then the smooth unstable torus is no longer accessible from the interior of the basin of the attractor. For this case, using the rational approximations to the quasiperiodic forcing, it is shown that a nonchaotic attractor (smooth torus or strange nonchaotic attractor) as well as a chaotic attractor is destroyed abruptly through a new type of boundary crisis when it collides with an invariant 'ring-shaped' unstable set which has no counterpart in the unforced case.

Model-based estimation with boundary side information or boundary regularization [cardiac emission CT].

Science.gov (United States)

Chiao, P C; Rogers, W L; Fessler, J A; Clinthorne, N H; Hero, A O

1994-01-01

The authors have previously developed a model-based strategy for joint estimation of myocardial perfusion and boundaries using ECT (emission computed tomography). They have also reported difficulties with boundary estimation in low contrast and low count rate situations. Here they propose using boundary side information (obtainable from high resolution MRI and CT images) or boundary regularization to improve both perfusion and boundary estimation in these situations. To fuse boundary side information into the emission measurements, the authors formulate a joint log-likelihood function to include auxiliary boundary measurements as well as ECT projection measurements. In addition, they introduce registration parameters to align auxiliary boundary measurements with ECT measurements and jointly estimate these parameters with other parameters of interest from the composite measurements. In simulated PET O-15 water myocardial perfusion studies using a simplified model, the authors show that the joint estimation improves perfusion estimation performance and gives boundary alignment accuracy of <0.5 mm even at 0.2 million counts. They implement boundary regularization through formulating a penalized log-likelihood function. They also demonstrate in simulations that simultaneous regularization of the epicardial boundary and myocardial thickness gives comparable perfusion estimation accuracy with the use of boundary side information.

Local Seebeck coefficient near the boundary in touching Cu/Bi-Te/Cu composites

International Nuclear Information System (INIS)

Yamashita, O.; Odahara, H.

2007-01-01

The thermo-emf ΔV and temperature difference ΔT across the boundary were measured as a function of r for the touching p- and n-type Cu/Bi-Te/Cu composites composed of a combination of t Bi-Te =2.0 mm and t Cu =0.3 mm, where ΔT is produced by imposing a constant voltage of 1.7 V on two Peltier modules connected in series and r is the distance from the boundary that corresponds to the interval s between two thermocouples. The resultant Seebeck coefficient α across the boundary was obtained from the relation α=ΔV/ΔT. As a result, the resultant α of the touching p- and n-type composites have surprisingly great local maximum values of 1330 and -1140 μV/K at r∼0.03 mm, respectively, and decreased rapidly with an increase of r to approach the Seebeck coefficients of the intrinsic Bi-Te compounds. The resultant maximum α of the touching p- and n-type Cu/Bi-Te/Cu composites are approximately 5.4 and 5.5 times higher in absolute value than those of the intrinsic Bi-Te compounds, respectively. It was thus clarified for the first time that the local Seebeck coefficient is enhanced most strongly in the Bi-Te region where there is an approximately 30-μm distance from the boundary, not at the boundary between Bi-Te compounds and copper. (orig.)

Boundary organizations to boundary chains: Prospects for advancing climate science application

Directory of Open Access Journals (Sweden)

Christine J. Kirchhoff

2015-01-01

Full Text Available Adapting to climate change requires the production and use of climate information to inform adaptation decisions. By facilitating sustained interaction between science producers, boundary organizations narrow the gap between science and decision-making and foster the co-production of actionable knowledge. While traditional boundary organization approaches focused on intense one-on-one interactions between producers and users increases usability, this approach requires significant time and resources. Forming “boundary chains”, linking complimentary boundary organizations together, may reduce those costs. In this paper, we use longitudinal observations of a boundary chain, interviews and surveys to explore: (1 how producer-user interactions increase understanding and information usability and (2 if and how efficiencies in climate information production, dissemination and use arise as a result of the boundary chain. We find that forming and sustaining an effective boundary chain requires not only interest, commitment and investment from every link in the chain but also a level of non-overlapping mutual dependency and complementary skill sets. In this case, GLISA’s strength in producing scientific information and their credibility as climate scientists and HRWC’s strengths in facilitation, connection with potential information users, and their recognition and reputation in the watershed add value to the boundary chain enabling the boundary chain to accomplish more with greater efficiency than if each organization in the chain tried to work independently. Finally, data show how the boundary chain increased efficiencies in educating potential users about the strengths and limitations of climate science and improving the production, dissemination, and use of climate information.

Influence of thermo-mechanical processing on the microstructure of Cu-based shape memory alloys produced by powder metallurgy

International Nuclear Information System (INIS)

Rodriguez, P.P.; Ibarra, A.; Iza-Mendia, A.; Recarte, V.; Perez-Landazabal, J.I.; San Juan, J.; No, M.L.

2003-01-01

Cu-Al-Ni shape memory alloys processed by powder metallurgy show very good thermo-mechanical properties, much better than those found in alloys produced by conventional casting. In this paper, we present the microstructural characterisation of these powder metallurgy alloys in order to find the microscopic mechanisms, linked to the powder metallurgy processing method, which are indeed responsible of such good thermo-mechanical behaviour. Electron microscopy studies [scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM)] show that powder metallurgy processing creates a sub-grain structure characterised by the presence of low angle sub-boundaries. These sub-boundaries are found to be lying on {1 1 0} and {1 1 2} lattice planes and are composed by an arrangement of superdislocations. These sub-boundaries may improve ductility in two ways: acting as a sink of dislocations which promotes plastic deformation and decreasing stress concentration at grain boundaries. Moreover, since sub-boundaries act as weak obstacles for the movement of martensite plates, the improvement on ductility is accomplished by an adequate thermo-mechanical behaviour

Classification with an edge: Improving semantic image segmentation with boundary detection

Science.gov (United States)

Marmanis, D.; Schindler, K.; Wegner, J. D.; Galliani, S.; Datcu, M.; Stilla, U.

2018-01-01

We present an end-to-end trainable deep convolutional neural network (DCNN) for semantic segmentation with built-in awareness of semantically meaningful boundaries. Semantic segmentation is a fundamental remote sensing task, and most state-of-the-art methods rely on DCNNs as their workhorse. A major reason for their success is that deep networks learn to accumulate contextual information over very large receptive fields. However, this success comes at a cost, since the associated loss of effective spatial resolution washes out high-frequency details and leads to blurry object boundaries. Here, we propose to counter this effect by combining semantic segmentation with semantically informed edge detection, thus making class boundaries explicit in the model. First, we construct a comparatively simple, memory-efficient model by adding boundary detection to the SEGNET encoder-decoder architecture. Second, we also include boundary detection in FCN-type models and set up a high-end classifier ensemble. We show that boundary detection significantly improves semantic segmentation with CNNs in an end-to-end training scheme. Our best model achieves >90% overall accuracy on the ISPRS Vaihingen benchmark.

New Boundary Constraints for Elliptic Systems used in Grid Generation Problems

Science.gov (United States)

Kaul, Upender K.; Clancy, Daniel (Technical Monitor)

2002-01-01

This paper discusses new boundary constraints for elliptic partial differential equations as used in grid generation problems in generalized curvilinear coordinate systems. These constraints, based on the principle of local conservation of thermal energy in the vicinity of the boundaries, are derived using the Green's Theorem. They uniquely determine the so called decay parameters in the source terms of these elliptic systems. These constraints' are designed for boundary clustered grids where large gradients in physical quantities need to be resolved adequately. It is observed that the present formulation also works satisfactorily for mild clustering. Therefore, a closure for the decay parameter specification for elliptic grid generation problems has been provided resulting in a fully automated elliptic grid generation technique. Thus, there is no need for a parametric study of these decay parameters since the new constraints fix them uniquely. It is also shown that for Neumann type boundary conditions, these boundary constraints uniquely determine the solution to the internal elliptic problem thus eliminating the non-uniqueness of the solution of an internal Neumann boundary value grid generation problem.

Horses for courses: analytical tools to explore planetary boundaries

Science.gov (United States)

van Vuuren, Detlef P.; Lucas, Paul L.; Häyhä, Tiina; Cornell, Sarah E.; Stafford-Smith, Mark

2016-03-01

There is a need for more integrated research on sustainable development and global environmental change. In this paper, we focus on the planetary boundaries framework to provide a systematic categorization of key research questions in relation to avoiding severe global environmental degradation. The four categories of key questions are those that relate to (1) the underlying processes and selection of key indicators for planetary boundaries, (2) understanding the impacts of environmental pressure and connections between different types of impacts, (3) better understanding of different response strategies to avoid further degradation, and (4) the available instruments to implement such strategies. Clearly, different categories of scientific disciplines and associated model types exist that can accommodate answering these questions. We identify the strength and weaknesses of different research areas in relation to the question categories, focusing specifically on different types of models. We discuss that more interdisciplinary research is need to increase our understanding by better linking human drivers and social and biophysical impacts. This requires better collaboration between relevant disciplines (associated with the model types), either by exchanging information or by fully linking or integrating them. As fully integrated models can become too complex, the appropriate type of model (the racehorse) should be applied for answering the target research question (the race course).

Boundary element simulation of petroleum reservoirs with hydraulically fractured wells

Science.gov (United States)

Pecher, Radek

The boundary element method is applied to solve the linear pressure-diffusion equation of fluid-flow in porous media. The governing parabolic partial differential equation is transformed into the Laplace space to obtain the elliptic modified-Helmholtz equation including the homogeneous initial condition. The free- space Green's functions, satisfying this equation for anisotropic media in two and three dimensions, are combined with the generalized form of the Green's second identity. The resulting boundary integral equation is solved by following the collocation technique and applying the given time-dependent boundary conditions of the Dirichlet or Neumann type. The boundary integrals are approximated by the Gaussian quadrature along each element of the discretized domain boundary. Heterogeneous regions are represented by the sectionally-homogeneous zones of different rock and fluid properties. The final values of the interior pressure and velocity fields and of their time-derivatives are found by numerically inverting the solutions from the Laplace space by using the Stehfest's algorithm. The main extension of the mostly standard BEM-procedure is achieved in the modelling of the production and injection wells represented by internal sources and sinks. They are treated as part of the boundary by means of special single-node and both-sided elements, corresponding to the line and plane sources respectively. The wellbore skin and storage effects are considered for the line and cylindrical sources. Hydraulically fractured wells of infinite conductivity are handled directly according to the specified constraint type, out of the four alternatives. Fractures of finite conductivity are simulated by coupling the finite element model of their 1D-interior with the boundary element model of their 2D- exterior. Variable fracture width, fractures crossing zone boundaries, ``networking'' of fractures, fracture-tip singularity handling, or the 3D-description are additional advanced

High speed observation of HIFU-induced cavitation cloud near curved rigid boundaries

International Nuclear Information System (INIS)

Zuo, Z G; Wang, F B; Liu, S H; Wu, S J

2015-01-01

This paper focuses on the experimental study of the influence of surface curvature to the behaviour of HIFU-induced cavitation cloud. A Q-switched ruby pulse laser is used to induce cavitation nuclei in deionized water. A piezoelectric ultrasonic transducer (1.7 MHz) provides a focused ultrasound field to inspire the nucleus to cavitation cloud. A PZT probe type hydrophone is applied for measuring the HIFU sound field. It was observed that the motion of cavitation cloud located near the boundary is significantly influenced by the distance between cloud and boundary, as well as the curvature of the boundary. The curvature was defined by parameters λ and ξ. Convex boundary, concave boundary, and flat boundary correspond to ξ <1, ξ >1 and ξ = 1, respectively. Different behaviours of the cloud, including the migration of the cloud, the characteristics of oscillation, etc., were observed under different boundary curvatures by high-speed photography. Sonoluminescence of the acoustic cavitation bubble clouds were also studied to illustrate the characteristics of acoustic streaming

Brain response to prosodic boundary cues depends on boundary position

Directory of Open Access Journals (Sweden)

Julia eHolzgrefe

2013-07-01

Full Text Available Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer’s syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name as compared to later in the utterance (i.e., after the second name. A closure positive shift (CPS — marking the processing of a prosodic phrase boundary — was elicited only for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context.

The disconnection mechanism of coupled migration and shear at grain boundaries

International Nuclear Information System (INIS)

Khater, H.A.; Serra, A.; Pond, R.C.; Hirth, J.P.

2012-01-01

The mechanism of coupled migration and shear is studied in a range of [0 0 0 1] tilt boundaries in hexagonal close-packed metal using atomic-scale computer simulation. Symmetrical tilt boundaries spanning the low- and high-angle regimes and comprising regular arrays of grain boundary dislocations are simulated. For each misorientation, θ, the perfect boundary (pristine) is investigated as well as one containing a disconnection. Both types of structures are subjected to incremental applied strains to determine the stress that produces coupled migration and shear. The stress for motion in the pristine case, entailing nucleation, is higher than the Peierls stress for motion when disconnections are present. We conclude that the applied stresses in our simulations exert a Peach–Koehler force on pre-existing disconnections, thereby providing a feasible mechanism with a well-defined driving force that produces coupled migration and shear. This mechanism is feasible for the lower-angle boundaries studied, and facile for the high-angle cases.

A Method for Extracting Road Boundary Information from Crowdsourcing Vehicle GPS Trajectories.

Science.gov (United States)

Yang, Wei; Ai, Tinghua; Lu, Wei

2018-04-19

Crowdsourcing trajectory data is an important approach for accessing and updating road information. In this paper, we present a novel approach for extracting road boundary information from crowdsourcing vehicle traces based on Delaunay triangulation (DT). First, an optimization and interpolation method is proposed to filter abnormal trace segments from raw global positioning system (GPS) traces and interpolate the optimization segments adaptively to ensure there are enough tracking points. Second, constructing the DT and the Voronoi diagram within interpolated tracking lines to calculate road boundary descriptors using the area of Voronoi cell and the length of triangle edge. Then, the road boundary detection model is established integrating the boundary descriptors and trajectory movement features (e.g., direction) by DT. Third, using the boundary detection model to detect road boundary from the DT constructed by trajectory lines, and a regional growing method based on seed polygons is proposed to extract the road boundary. Experiments were conducted using the GPS traces of taxis in Beijing, China, and the results show that the proposed method is suitable for extracting the road boundary from low-frequency GPS traces, multi-type road structures, and different time intervals. Compared with two existing methods, the automatically extracted boundary information was proved to be of higher quality.

A Method for Extracting Road Boundary Information from Crowdsourcing Vehicle GPS Trajectories

Directory of Open Access Journals (Sweden)

Wei Yang

2018-04-01

Full Text Available Crowdsourcing trajectory data is an important approach for accessing and updating road information. In this paper, we present a novel approach for extracting road boundary information from crowdsourcing vehicle traces based on Delaunay triangulation (DT. First, an optimization and interpolation method is proposed to filter abnormal trace segments from raw global positioning system (GPS traces and interpolate the optimization segments adaptively to ensure there are enough tracking points. Second, constructing the DT and the Voronoi diagram within interpolated tracking lines to calculate road boundary descriptors using the area of Voronoi cell and the length of triangle edge. Then, the road boundary detection model is established integrating the boundary descriptors and trajectory movement features (e.g., direction by DT. Third, using the boundary detection model to detect road boundary from the DT constructed by trajectory lines, and a regional growing method based on seed polygons is proposed to extract the road boundary. Experiments were conducted using the GPS traces of taxis in Beijing, China, and the results show that the proposed method is suitable for extracting the road boundary from low-frequency GPS traces, multi-type road structures, and different time intervals. Compared with two existing methods, the automatically extracted boundary information was proved to be of higher quality.

Rigid supersymmetry with boundaries

Energy Technology Data Exchange (ETDEWEB)

Belyaev, D.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Van Nieuwenhuizen, P. [State Univ. of New York, Stony Brook, NY (United States). C.N. Yang Inst. for Theoretical Physics

2008-01-15

We construct rigidly supersymmetric bulk-plus-boundary actions, both in x-space and in superspace. For each standard supersymmetric bulk action a minimal supersymmetric bulk-plus-boundary action follows from an extended F- or D-term formula. Additional separately supersymmetric boundary actions can be systematically constructed using co-dimension one multiplets (boundary superfields). We also discuss the orbit of boundary conditions which follow from the Euler-Lagrange variational principle. (orig.)

Application of He's variational iteration method to the fifth-order boundary value problems

International Nuclear Information System (INIS)

Shen, S

2008-01-01

Variational iteration method is introduced to solve the fifth-order boundary value problems. This method provides an efficient approach to solve this type of problems without discretization and the computation of the Adomian polynomials. Numerical results demonstrate that this method is a promising and powerful tool for solving the fifth-order boundary value problems

On solving wave equations on fixed bounded intervals involving Robin boundary conditions with time-dependent coefficients

Science.gov (United States)

van Horssen, Wim T.; Wang, Yandong; Cao, Guohua

2018-06-01

In this paper, it is shown how characteristic coordinates, or equivalently how the well-known formula of d'Alembert, can be used to solve initial-boundary value problems for wave equations on fixed, bounded intervals involving Robin type of boundary conditions with time-dependent coefficients. A Robin boundary condition is a condition that specifies a linear combination of the dependent variable and its first order space-derivative on a boundary of the interval. Analytical methods, such as the method of separation of variables (SOV) or the Laplace transform method, are not applicable to those types of problems. The obtained analytical results by applying the proposed method, are in complete agreement with those obtained by using the numerical, finite difference method. For problems with time-independent coefficients in the Robin boundary condition(s), the results of the proposed method also completely agree with those as for instance obtained by the method of separation of variables, or by the finite difference method.

High-Reynolds Number Viscous Flow Simulations on Embedded-Boundary Cartesian Grids

Science.gov (United States)

2016-05-05

AFRL-AFOSR-VA-TR-2016-0192 High- Reynolds Number Viscous Flow Simulations on Embedded-Boundary Cartesian Grids Marsha Berger NEW YORK UNIVERSITY Final...TO THE ABOVE ORGANIZATION. 1. REPORT DATE (DD-MM-YYYY) 30/04/2016 2. REPORT TYPE Final 3. DATES COVERED (From - To) High- Reynolds 4. TITLE AND...SUBTITLE High- Reynolds Number Viscous Flow Simulations on Embedded-Boundary Cartesian Grids 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-13-1

The Influence on Modal Parameters of Thin Cylindrical Shell under Bolt Looseness Boundary

Directory of Open Access Journals (Sweden)

Hui Li

2016-01-01

Full Text Available The influence on modal parameters of thin cylindrical shell (TCS under bolt looseness boundary is investigated. Firstly, bolt looseness boundary of the shell is divided into two types, that is, different bolt looseness numbers and different bolt looseness levels, and natural frequencies and mode shapes are calculated by finite element method to roughly master vibration characteristics of TCS under these conditions. Then, the following measurements and identification techniques are used to get precise frequency, damping, and shape results; for example, noncontact laser Doppler vibrometer and vibration shaker with excitation level being precisely controlled are used in the test system; “preexperiment” is adopted to determine the required tightening torque and verify fixed constraint boundary; the small-segment FFT processing technique is employed to accurately measure nature frequency and laser rotating scanning technique is used to get shape results with high efficiency. Finally, based on the measured results obtained by the above techniques, the influence on modal parameters of TCS under two types of bolt looseness boundaries is analyzed and discussed. It can be found that bolt looseness boundary can significantly affect frequency and damping results which might be caused by changes of nonlinear stiffness and damping and in bolt looseness positions.

Modeling the summertime Arctic cloudy boundary layer

Energy Technology Data Exchange (ETDEWEB)

Curry, J.A.; Pinto, J.O. [Univ. of Colorado, Boulder, CO (United States); McInnes, K.L. [CSIRO Division of Atmospheric Research, Mordialloc (Australia)

1996-04-01

Global climate models have particular difficulty in simulating the low-level clouds during the Arctic summer. Model problems are exacerbated in the polar regions by the complicated vertical structure of the Arctic boundary layer. The presence of multiple cloud layers, a humidity inversion above cloud top, and vertical fluxes in the cloud that are decoupled from the surface fluxes, identified in Curry et al. (1988), suggest that models containing sophisticated physical parameterizations would be required to accurately model this region. Accurate modeling of the vertical structure of multiple cloud layers in climate models is important for determination of the surface radiative fluxes. This study focuses on the problem of modeling the layered structure of the Arctic summertime boundary-layer clouds and in particular, the representation of the more complex boundary layer type consisting of a stable foggy surface layer surmounted by a cloud-topped mixed layer. A hierarchical modeling/diagnosis approach is used. A case study from the summertime Arctic Stratus Experiment is examined. A high-resolution, one-dimensional model of turbulence and radiation is tested against the observations and is then used in sensitivity studies to infer the optimal conditions for maintaining two separate layers in the Arctic summertime boundary layer. A three-dimensional mesoscale atmospheric model is then used to simulate the interaction of this cloud deck with the large-scale atmospheric dynamics. An assessment of the improvements needed to the parameterizations of the boundary layer, cloud microphysics, and radiation in the 3-D model is made.

On boundary superalgebras

International Nuclear Information System (INIS)

Doikou, Anastasia

2010-01-01

We examine the symmetry breaking of superalgebras due to the presence of appropriate integrable boundary conditions. We investigate the boundary breaking symmetry associated with both reflection algebras and twisted super-Yangians. We extract the generators of the resulting boundary symmetry as well as we provide explicit expressions of the associated Casimir operators.

Grain boundary structure and properties

International Nuclear Information System (INIS)

Balluffi, R.W.

1979-01-01

An attempt is made to distinguish those fundamental aspects of grain boundaries which should be relevant to the problem of the time dependent fracture of high temperature structural materials. These include the basic phenomena which are thought to be associated with cavitation and cracking at grain boundaries during service and with the more general microstructural changes which occur during both processing and service. A very brief discussion of the current state of our knowledge of these fundamentals is given. Included are the following: (1) structure of ideal perfect boundaries; (2) defect structure of grain boundaries; (3) diffusion at grain boundaries; (4) grain boundaries as sources/sinks for point defects; (5) grain boundary migration; (6) dislocation phenomena at grain boundaries; (7) atomic bonding and cohesion at grain boundaries; (8) non-equilibrium properties of grain boundaries; and (9) techniques for studying grain boundaries

Boundary-Layer Characteristics of Persistent Regional Haze Events and Heavy Haze Days in Eastern China

Directory of Open Access Journals (Sweden)

Peng Huaqing

2016-01-01

Full Text Available This paper analyzed the surface conditions and boundary-layer climate of regional haze events and heavy haze in southern Jiangsu Province in China. There are 5 types with the surface conditions which are equalized pressure (EQP, the advancing edge of a cold front (ACF, the base of high pressure (BOH, the backside of high pressure (BAH, the inverted trough of low pressure (INT, and saddle pressure (SAP with the haze days. At that time, 4 types are divided with the regional haze events and each of which has a different boundary-layer structure. During heavy haze, the surface mainly experiences EQP, ACF, BOH, BAH, and INT which also have different boundary-layer structures.

Defects and boundary layers in non-Euclidean plates

International Nuclear Information System (INIS)

Gemmer, J A; Venkataramani, S C

2012-01-01

We investigate the behaviour of non-Euclidean plates with constant negative Gaussian curvature using the Föppl–von Kármán reduced theory of elasticity. Motivated by recent experimental results, we focus on annuli with a periodic profile. We prove rigorous upper and lower bounds for the elastic energy that scales like the thickness squared. In particular we show that are only two types of global minimizers—deformations that remain flat and saddle shaped deformations with isolated regions of stretching near the edge of the annulus. We also show that there exist local minimizers with a periodic profile that have additional boundary layers near their lines of inflection. These additional boundary layers are a new phenomenon in thin elastic sheets and are necessary to regularize jump discontinuities in the azimuthal curvature across lines of inflection. We rigorously derive scaling laws for the width of these boundary layers as a function of the thickness of the sheet. (paper)

Emerging boundaries

DEFF Research Database (Denmark)

Løvschal, Mette

2014-01-01

of temporal and material variables have been applied as a means of exploring the processes leading to their socioconceptual anchorage. The outcome of this analysis is a series of interrelated, generative boundary principles, including boundaries as markers, articulations, process-related devices, and fixation...

Changing Boundaries

DEFF Research Database (Denmark)

Brodkin, Evelyn; Larsen, Flemming

2013-01-01

project that is altering the boundary between the democratic welfare state and the market economy. We see workfare policies as boundary-changing with potentially profound implications both for individuals disadvantaged by market arrangements and for societies seeking to grapple with the increasing...

Impurity effects on the grain boundary cohesion in copper

Science.gov (United States)

Li, Yunguo; Korzhavyi, Pavel A.; Sandström, Rolf; Lilja, Christina

2017-12-01

Segregated impurities at grain boundaries can dramatically change the mechanical behavior of metals, while the mechanism is still obscure in some cases. Here, we suggest a unified approach to investigate segregation and its effects on the mechanical properties of polycrystalline alloys using the example of 3 s p impurities (Mg, Al, Si, P, or S) at a special type Σ 5 (310 )[001 ] tilt grain boundary in Cu. We show that for these impurities segregating to the grain boundary, the strain contribution to the work of grain boundary decohesion is small and that the chemical contribution correlates with the electronegativity difference between Cu and the impurity. The strain contribution to the work of dislocation emission is calculated to be negative, while the chemical contribution is calculated to be always positive. Both the strain and chemical contributions to the work of dislocation emission generally become weaker with the increasing electronegativity from Mg to S. By combining these contributions together, we find, in agreement with experimental observations, that a strong segregation of S can reduce the work of grain boundary separation below the work of dislocation emission, thus embrittling Cu, while such an embrittlement cannot be produced by a P segregation because it lowers the energy barrier for dislocation emission relatively more than for work separation.

Second-order domain derivative of normal-dependent boundary integrals

KAUST Repository

Balzer, Jonathan

2010-03-17

Numerous reconstruction tasks in (optical) surface metrology allow for a variational formulation. The occurring boundary integrals may be interpreted as shape functions. The paper is concerned with the second-order analysis of such functions. Shape Hessians of boundary integrals are considered difficult to find analytically because they correspond to third-order derivatives of an, in a sense equivalent, domain integral. We complement previous results by considering cost functions depending explicitly on the surface normal. The correctness and practicability of our calculations are verified in the context of a Newton-type shape reconstruction method. © 2010 Birkhäuser / Springer Basel AG.

NOT LOCAL PROBLEM OF TYPE OF THE PROBLEM BITSADZE – SAMARSKY FOR THE EQUATION THE MIXED TYPE IN UNLIMITED AREA

Directory of Open Access Journals (Sweden)

Zunnunov R.T.

2010-04-01

Full Text Available In this paper the existence and uniqueness of the solution of the nonlocal boundary value problem for the mixed type equation in unbounded domain are proved.In this paper the existence and uniqueness of the solution of the non-local boundary value problem for the mixed type equation in unbounded domain are proved.

Microstructural change and its influence on fission gas release in high burnup UO 2 fuel

Science.gov (United States)

Une, K.; Nogita, K.; Kashibe, S.; Imamura, M.

1992-06-01

The microstructural change of UO 2 fuel pellets (burnup: 6-83 GWd/t), base irradiated under LWR conditions, has been studied by detailed postirradiation examinations. The lattice parameter near the fuel rim in the irradiated UO 2 increased with burnup and appeared to become constant beyond about 50 GWd/t. This lattice dilation was mainly due to the accumulation of radiation induced point defects. Moreover, the dislocation density in the UO 2 matrix developed progressively with burnup, and eventually the tangled dislocations organized many sub-grain boundaries in the highest burnup fuel of 83 GWd/t. This sub-grain structure induced by accumulated radiation damage was compatible in appearance with SEM fractography results which revealed sub-divided grains of sub-micron size in as-fabricated grains. The influence of burnup on 85Kr release from the UO 2 fuels has been examined by means of a postirradiation annealing technique. The higher fractional release of high burnup fuels was mainly due to the burnup dependence of the fractional burst release evolved on temperature ramp. The fractional burst release was represented in terms of the square root of burnup from 6 to 83 GWd/t.

Grain boundary segregation and intergranular stress corrosion cracking susceptibility of austenitic stainless steels in high temperature water

International Nuclear Information System (INIS)

Shoji, T.; Yamaki, K.; Ballinger, R.G.; Hwang, I.S.

1992-01-01

The effects of grain boundary segregation on intergranular stress corrosion cracking of austenitic stainless steels in high temperature water have been examined as a function of heat treatment. The materials investigated were: (1) two commercial purity Type 304; (2) low sulfur Type 304; (3) nuclear grade Type 304; (4) ultra high purity Type 304L; and (5) Type 316L and Type 347L. Specimens were solution treated at 1050 degrees C for 0.5 hour and given a sensitization heat treatment at 650 degrees C for 50 hours. Some of the specimens were then subjected to an aging heat treatment at 850 degrees C for from one to ten hours to cause Cr recovery at the grain boundaries. The effects of heat treatments on degree of sensitization and grain boundary segregation were evaluated by Electrochemical Potentiokinetic Reactivation (EPR) and Coriou tests, respectively. The susceptibility to stress corrosion (SCC) was evaluated using slow strain rate tests technique (SSRT) in high temperature water. SSRT tests were performed in an aerated pure water (8 ppm dissolved oxygen) at 288 degrees C at a strain rate of 1.33 x 10 -6 /sec. Susceptibility to intergranular stress corrosion cracking was compared with degree of sensitization and grain boundary segregation. The results of the investigation indicate that EPR is not always an accurate indicator of SCC susceptibility. The Coriou test provides a more reliable measure of SCC susceptibility especially for 304L, 304NG, 316L, and 347L stainless steels. The results also indicate that grain boundary segregation as well as degree of sensitization must be considered in the determination of SCC susceptibility

Collaboration in Healthcare Through Boundary Work and Boundary Objects

DEFF Research Database (Denmark)

Meier, Ninna

2015-01-01

This article contributes to our understanding of how boundary work is practiced in healthcare settings. Previous studies have shown how boundaries are constantly changing, multiple, and co-existing, and can also be relatively stable cognitive and social distinctions between individuals and groups...

Study of rapid grain boundary migration in a nanocrystalline Ni thin film

International Nuclear Information System (INIS)

Kacher, Josh; Robertson, I.M.; Nowell, Matt; Knapp, J.; Hattar, Khalid

2011-01-01

Research highlights: → Abnormal growth is distributed randomly in the foil and initiates at different times. → Growth occurs from seemingly uncorrelated regions of the grain boundary. → Growth twins are created during all stages of abnormal grain growth. → Grain growth patterns are qualitatively similar to a vacancy diffusion model. → Grain boundaries and orientations evolve during growth to minimize system energy. - Abstract: Grain boundary migration associated with abnormal grain growth in pulsed-laser deposited Ni was studied in real time by annealing electron transparent films in situ in the transmission electron microscope. The resulting texture evolution and grain boundary types produced were evaluated by ex situ electron backscatter diffraction of interrupted anneals. The combination of these two techniques allowed for the investigation of grain growth rates, grain morphologies, and the evolution of the orientation and grain boundary distributions. Grain boundaries were found to progress in a sporadic, start/stop fashion with no evidence of a characteristic grain growth rate. The orientations of the abnormally growing grains were found to be predominately //ND throughout the annealing process. A high fraction of twin boundaries developed during the annealing process. The intermittent growth from different locations of the grain boundary is discussed in terms of a vacancy diffusion model for grain growth.

Initializing a Mesoscale Boundary-Layer Model with Radiosonde Observations

Science.gov (United States)

Berri, Guillermo J.; Bertossa, Germán

2018-01-01

A mesoscale boundary-layer model is used to simulate low-level regional wind fields over the La Plata River of South America, a region characterized by a strong daily cycle of land-river surface-temperature contrast and low-level circulations of sea-land breeze type. The initial and boundary conditions are defined from a limited number of local observations and the upper boundary condition is taken from the only radiosonde observations available in the region. The study considers 14 different upper boundary conditions defined from the radiosonde data at standard levels, significant levels, level of the inversion base and interpolated levels at fixed heights, all of them within the first 1500 m. The period of analysis is 1994-2008 during which eight daily observations from 13 weather stations of the region are used to validate the 24-h surface-wind forecast. The model errors are defined as the root-mean-square of relative error in wind-direction frequency distribution and mean wind speed per wind sector. Wind-direction errors are greater than wind-speed errors and show significant dispersion among the different upper boundary conditions, not present in wind speed, revealing a sensitivity to the initialization method. The wind-direction errors show a well-defined daily cycle, not evident in wind speed, with the minimum at noon and the maximum at dusk, but no systematic deterioration with time. The errors grow with the height of the upper boundary condition level, in particular wind direction, and double the errors obtained when the upper boundary condition is defined from the lower levels. The conclusion is that defining the model upper boundary condition from radiosonde data closer to the ground minimizes the low-level wind-field errors throughout the region.

Optimal boundary control and boundary stabilization of hyperbolic systems

CERN Document Server

Gugat, Martin

2015-01-01

This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary.  The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization.  Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples.  To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled.  Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.

On Existence of Solutions to the Caputo Type Fractional Order Three-Point Boundary Value Problems

Directory of Open Access Journals (Sweden)

B.M.B. Krushna

2016-10-01

Full Text Available In this paper, we establish the existence of solutions to the fractional order three-point boundary value problems by utilizing Banach contraction principle and Schaefer's fixed point theorem.

Combined macroscopic and microscopic approach to the fracture of metals. Technical progress report, July 1977--June 1978

International Nuclear Information System (INIS)

Gurland, J.; Rice, J.R.; Asaro, R.J.; Needleman, A.

1978-06-01

The work reported includes studies on: (1) The role of particles and interfaces in the initiation of fracture, including fundamentals of brittle versus ductile response of interfaces and observations on cavity growth by the cracking of grain or sub-grain boundaries adjacent to carbides in spheroidized steels; (2) Environment sensitive fracture mechanisms, particularly the effect of hydrogen in reducing tensile ductility by acceleration of the crack-like mode of cavity growth along grain boundaries in steels; (3) Models for elevated temperature diffusive processes of cavity growth on grain interfaces, including non-equilibrium effects and crack-like growth modes; (4) Localization of plastic deformation and the inception of ductile rupture; and (5) Elastic-plastic stress analysis, by finite elements, of growing cracks and examination of criteria for stable crack growth

The effect of hot working on structure and strength of a precipitation strengthened austenitic stainless steel

International Nuclear Information System (INIS)

Mataya, M.C.; Carr, M.J.; Krauss, G.

1984-01-01

The development of microstructure and strength during forging a γ' strengthened austenitic stainless steel, JBK-75, was investigated. The specimens were deformed in a strain range of 0.16 to 1.0, from 800 0 C to 1080 0 C at approximate strain rates of 2 (press forging) and 2 X 10 3 S -1 (high energy rate forging). Mechanical properties were determined by tensile testing as-forged and forged and aged specimens. The alloy exhibited a wide variety of structures and properties within the range of forging parameters studied. Deformation at the higher strain rate via high energy rate forging resulted in unrecovered substructures and high strengths at low forging temperatures, and static recrystallization and low strengths at high temperatures. In contrast, however, deformation at the lower strain rate via press forging resulted in retention of the well developed subgrain structure and associated high strength produced at high forging temperatures and strains. At lower temperatures and strains during press forging a subgrain structure formed preferentially at high angle grain boundaries, apparently by a creep-type deformation mechanism. Dynamic recrystallization was not an important restoration mechanism for any of the forging conditions. The results are interpreted on the basis of stacking fault energy and the accumulation of strain energy during hot working. The significance of microstructural differences for equivalent deformation conditions (iso-Z, where Z is the Zener-Holloman parameter) is discussed in relation to the utilization of Z for predicting hot work structures and strengths. Aging showed that γ' precipitation is not affected by substructure and that the strengthening contributions were independent and additive. Applications for these findings are discussed in terms of process design criteria

Dislocation content of geometrically necessary boundaries aligned with slip planes in rolled aluminium

DEFF Research Database (Denmark)

Hong, Chuanshi; Huang, Xiaoxu; Winther, Grethe

2013-01-01

Previous studies have revealed that dislocation structures in metals with medium-to-high stacking fault energy, depend on the grain orientation and therefore on the slip systems. In the present work, the dislocations in eight slip-plane-aligned geometrically necessary boundaries (GNBs) in three...... expected active dominate. The dislocations predicted inactive are primarily attributed to dislocation reactions in the boundary. Two main types of dislocation networks in the boundaries were identified: (1) a hexagonal network of the three dislocations in the slip plane with which the boundary was aligned......; two of these come from the active slip systems, the third is attributed to dislocation reactions (2) a network of three dislocations from both of the active slip planes; two of these react to form Lomer locks. The results indicate a systematic boundary formation process for the GNBs. Redundant...

Scale-invariant solutions to partial differential equations of fractional order with a moving boundary condition

International Nuclear Information System (INIS)

Li Xicheng; Xu Mingyu; Wang Shaowei

2008-01-01

In this paper, we give similarity solutions of partial differential equations of fractional order with a moving boundary condition. The solutions are given in terms of a generalized Wright function. The time-fractional Caputo derivative and two types of space-fractional derivatives are considered. The scale-invariant variable and the form of the solution of the moving boundary are obtained by the Lie group analysis. A comparison between the solutions corresponding to two types of fractional derivative is also given

A boundary integral equation for boundary element applications in multigroup neutron diffusion theory

International Nuclear Information System (INIS)

Ozgener, B.

1998-01-01

A boundary integral equation (BIE) is developed for the application of the boundary element method to the multigroup neutron diffusion equations. The developed BIE contains no explicit scattering term; the scattering effects are taken into account by redefining the unknowns. Boundary elements of the linear and constant variety are utilised for validation of the developed boundary integral formulation

Vortex Formation During Unsteady Boundary-Layer Separation

Science.gov (United States)

Das, Debopam; Arakeri, Jaywant H.

1998-11-01

Unsteady laminar boundary-layer separation is invariably accompanied by the formation of vortices. The aim of the present work is to study the vortex formation mechanism(s). An adverse pressure gradient causing a separation can be decomposed into a spatial component ( spatial variation of the velocity external to the boundary layer ) and a temporal component ( temporal variation of the external velocity ). Experiments were conducted in a piston driven 2-D water channel, where the spatial component could be be contolled by geometry and the temporal component by the piston motion. We present results for three divergent channel geometries. The piston motion consists of three phases: constant acceleration from start, contant velocity, and constant deceleration to stop. Depending on the geometry and piston motion we observe different types of unsteady separation and vortex formation.

Perceptions of boundary ambiguity in the process of leaving an abusive partner.

Science.gov (United States)

Khaw, Lyndal; Hardesty, Jennifer L

2015-06-01

The process of leaving an abusive partner has been theorized using the Stages of Change Model. Although useful, this model does not account for changes in relational boundaries unique to the process of leaving. Using family stress and feminist perspectives, this study sought to integrate boundary ambiguity into the Stages of Change Model. Boundary ambiguity is defined as a perception of uncertainty as to who is in or out of a family system (Boss & Greenberg, 1984). Twenty-five mothers who had temporarily or permanently left their abusers were interviewed. Data were analyzed using constructivist grounded theory methods. Results identify types, indicators of, and mothers' responses to boundary ambiguity throughout the five stages of change. Most mothers and abusers fluctuated between physical and psychological presence and absence over multiple separations. The integration of boundary ambiguity into the Stages of Change Model highlights the process of leaving an abusive partner as systemic, fluid, and nonlinear. © 2014 Family Process Institute.

Grain boundary cavity growth under applied stress and internal pressure

International Nuclear Information System (INIS)

Mancuso, J.F.

1977-08-01

The growth of grain boundary cavities under applied stress and internal gas pressure was investigated. Methane gas filled cavities were produced by the C + 4H reversible CH4 reaction in the grain boundaries of type 270 nickel by hydrogen charging in an autoclave at 500 0 C with a hydrogen pressure of either 3.4 or 14.5 MPa. Intergranular fracture of nickel was achieved at a charging temperature of 300 0 C and 10.3 MPa hydrogen pressure. Cavities on the grain boundaries were observed in the scanning electron microscope after fracture. Photomicrographs of the cavities were produced in stereo pairs which were analyzed so as to correct for perspective distortion and also to determine the orientational dependence of cavity growth under an applied tensile stress

Microstructure evolution and grain refinement of Ti-6Al-4V alloy by laser shock processing

Energy Technology Data Exchange (ETDEWEB)

Ren, X.D., E-mail: renxd@mail.ujs.edu.cn [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Research Center of Fluid Machinery Engineering and Technical, Jiangsu University, Zhenjiang, 212013 (China); Zhou, W.F.; Liu, F.F.; Ren, Y.P. [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China); Yuan, S.Q. [Research Center of Fluid Machinery Engineering and Technical, Jiangsu University, Zhenjiang, 212013 (China); Ren, N.F.; Xu, S.D.; Yang, T. [Department of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013 (China)

2016-02-15

Graphical abstract: The grain refinement process of Ti-6Al-4V alloy under LSP: (a) LDD in original grains; (b) Dislocations in β phase; (c) DTIs in α phase; (d) DTs transform into DCs; (e) DWs develop into sub-GBs; (f) GR accomplishes. - Highlights: • LSP could repair the surface defects and reduce the surface roughness. • Microstructure evolution of α phase in Ti-6Al-4V alloy processed by LSP is distinct from β phase. • Multidirectional twin intersections and subgrain boundaries are the main mechanism of grain refinement of Ti-6Al-4V alloy. • Grain refinement process of the Ti-6Al-4V alloy was illustrated. - Abstract: Microstructure evolution and grain refinement of Ti-6Al-4V alloy after laser shock processing (LSP) are systematically investigated in this paper. Laser shock waves were induced by a Q-switched Nd:YAG laser system operated with a wave-length of 1064 nm and 10 ns pulse width. The microstructures of LSP samples were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Present results indicate that the surface hardness of samples subjected to LSP impacts has significantly improved. Multidirectional twin intersections and dislocation movements lead to grain subdivision in α phase with ultra-high plastic deformation. High-density dislocations are found in β phase. Multidirectional twin intersections and division of sub-grain boundaries play an important role in the grain refinement of Ti-6Al-4V alloy under LSP loading conditions.

DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS

NARCIS (Netherlands)

JUFFER, AH; BERENDSEN, HJC

1993-01-01

A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the

Extension Theory and Krein-type Resolvent Formulas for Nonsmooth Boundary Value Problems

DEFF Research Database (Denmark)

Abels, Helmut; Grubb, Gerd; Wood, Ian Geoffrey

2014-01-01

The theory of selfadjoint extensions of symmetric operators, and more generally the theory of extensions of dual pairs, was implemented some years ago for boundary value problems for elliptic operators on smooth bounded domains. Recently, the questions have been taken up again for nonsmooth domains....... In the present work we show that pseudodifferential methods can be used to obtain a full characterization, including Kreĭn resolvent formulas, of the realizations of nonselfadjoint second-order operators on

Tangential boundary values of Laplace transforms. Applications to Muntz-Szasz type approximation

Science.gov (United States)

Sedletskii, A. M.

2003-02-01

We consider the Laplace transforms (LT) of functions in L^q(\\mathbb R_+), 1, with a slowly varying weight. We prove that if the weight satisfies certain conditions, then each LT of this class has tangential boundary values almost everywhere on the imaginary axis, and the structure of the corresponding neighbourhoods depends on the weight only. This result is applied to distinguish a wide class of weighted L^p spaces on the half-line such that the Szasz condition is not necessary for the completeness of the system \\exp(-\\lambda_n t) in these spaces.

A two-dimensional embedded-boundary method for convection problems with moving boundaries

NARCIS (Netherlands)

Y.J. Hassen (Yunus); B. Koren (Barry)

2010-01-01

htmlabstractIn this work, a two-dimensional embedded-boundary algorithm for convection problems is presented. A moving body of arbitrary boundary shape is immersed in a Cartesian finite-volume grid, which is fixed in space. The boundary surface is reconstructed in such a way that only certain fluxes

Stability, interaction and influence of domain boundaries in Ge/Si(111)-5 × 5

International Nuclear Information System (INIS)

Ondráček, Martin; Mutombo, Pingo; Chvoj, Zdeněk; Chromcová, Zdeňka; Jelínek, Pavel; Mark, Andrew G; McLean, Alastair B

2012-01-01

We present a theoretical investigation of the influence of domain boundaries on the Ge/Si(111)-5 × 5 phase using both large-scale DFT simulations and an analytical model. It is shown that different boundary types modify the atomic and electronic structure of the adjoining 5 × 5 domains in very different ways. A simple theoretical model, that describes the energy interaction J between the boundaries and the 5 × 5 phase, is presented and the interaction energy decay J(x) ≈ x -n for different domain boundaries is estimated. Additionally, the influence of the boundaries on the atomic and electronic structure of adatoms in the parental 5 × 5 phase is analyzed and it is argued that the presence of domain boundaries may strongly affect not only the physical but also the chemical properties of the Ge/Si(111)-5 × 5 phase.

Three-dimensional turbulent boundary layers; Proceedings of the Symposium, Berlin, West Germany, March 29-April 1, 1982

Science.gov (United States)

Fernholz, H. H.; Krause, E.

Papers are presented on recent research concerning three-dimensional turbulent boundary layers. Topics examined include experimental techniques in three-dimensional turbulent boundary layers, turbulence measurements in ship-model flow, measurements of Reynolds-stress profiles in the stern region of a ship model, the effects of crossflow on the vortex-layer-type three-dimensional flow separation, and wind tunnel investigations of some three-dimensional separated turbulent boundary layers. Also examined are three-dimensional boundary layers in turbomachines, the boundary layers on bodies of revolution spinning in axial flows, the effect on a developed turbulent boundary layer of a sudden local wall motion, three-dimensional turbulent boundary layer along a concave wall, the numerical computation of three-dimensional boundary layers, a numerical study of corner flows, three-dimensional boundary calculations in design aerodynamics, and turbulent boundary-layer calculations in design aerodynamics. For individual items see A83-47012 to A83-47036

African boundary politics: a case of Ethiopian-Eritrean boundary ...

African Journals Online (AJOL)

This paper examined the boundary discord between Ethiopia and Eritrea over the region around Badme which started as a result of artificial boundaries created by the Italian imperialists. The study depicts the evolution of Italian colonialism in Ethiopia between 1936 and 1941. It exposes the differentials existing between the ...

Structural characteristics of the shock-induced boundary layer separation extended to the leading edge

Science.gov (United States)

Tao, Y.; Liu, W. D.; Fan, X. Q.; Zhao, Y. L.

2017-07-01

For a better understanding of the local unstart of supersonic/hypersonic inlet, a series of experiments has been conducted to investigate the shock-induced boundary layer separation extended to the leading edge. Using the nanoparticle-based planar laser scattering, we recorded the fine structures of these interactions under different conditions and paid more attention to their structural characteristics. According to their features, these interactions could be divided into four types. Specifically, Type A wave pattern is similar to the classic shock wave/turbulent boundary layer interaction, and Type B wave configuration consists of an overall Mach reflection above the large scale separation bubble. Due to the gradual decrease in the size of the separation bubble, the separation bubble was replaced by several vortices (Type C wave pattern). Besides, for Type D wave configuration which exists in the local unstart inlet, there appears to be some flow spillage around the leading edge.

Making Boundaries Great Again: Essentialism and Support for Boundary-Enhancing Initiatives.

Science.gov (United States)

Roberts, Steven O; Ho, Arnold K; Rhodes, Marjorie; Gelman, Susan A

2017-12-01

Psychological essentialism entails a focus on category boundaries (e.g., categorizing people as men or women) and an increase in the conceptual distance between those boundaries (e.g., accentuating the differences between men and women). Across eight studies, we demonstrate that essentialism additionally entails an increase in support for boundary-enhancing legislation, policies, and social services, and that it does so under conditions that disadvantage social groups, as well as conditions that benefit them. First, individual differences in essentialism were associated with support for legislation mandating that transgender people use restrooms corresponding with their biological sex, and with support for the boundary-enhancing policies of the 2016 then-presumptive Republican presidential nominee (i.e., Donald Trump). Second, essentialism was associated with support for same-gender classrooms designed to promote student learning, as well as support for services designed to benefit LGBTQ (lesbian, gay, bisexual, transgender, queer) individuals. These findings demonstrate the boundary-enhancing implications of essentialism and their social significance.

Delineation of peatland lagg boundaries from airborne LiDAR

Science.gov (United States)

Langlois, Melanie N.; Richardson, Murray C.; Price, Jonathan S.

2017-09-01

In Canada, peatlands are the most common type of wetland, but boundary delineation in peatland complexes has received little attention in the scientific literature. Typically, peatland boundaries are mapped as crisp, absolute features, and the transitional lagg zone—the ecotone found between a raised bog and the surrounding mineral land—is often overlooked. In this study, we aim (1) to advance existing approaches for detecting and locating laggs and lagg boundaries using airborne LiDAR surveys and (2) to describe the spatial distribution of laggs around raised bog peatlands. Two contrasting spatial analytical approaches for lagg detection were tested using five LiDAR-derived topographic and vegetation indices: topography, vegetation height, topographic wetness index, the standard deviation of the vegetation's height (as a proxy for the complexity of the vegetation's structure), and local indices of elevation variance. Using a dissimilarity approach (edge-detection, split-moving window analysis), no one variable accurately depicted both the lagg-mineral land and bog-lagg boundaries. Some indicators were better at predicting the bog-lagg boundary (i.e., vegetation height) and others at finding the lagg-mineral land boundary (i.e., topography). Dissimilarity analysis reinforces the usefulness of derived variables (e.g., wetness indices) in locating laggs, especially for those with weak topographic and vegetation gradients. When the lagg was confined between the bog and the adjacent upland, it took a linear form, parallel to the peatland's edge and was easier to predict. When the adjacent mineral land was flat or sloping away from the peatland, the lagg was discontinuous and intermittent and more difficult to predict.

Intrinsic Compressive Stress in Polycrystalline Films is Localized at Edges of the Grain Boundaries

Science.gov (United States)

Vasco, Enrique; Polop, Celia

2017-12-01

The intrinsic compression that arises in polycrystalline thin films under high atomic mobility conditions has been attributed to the insertion or trapping of adatoms inside grain boundaries. This compression is a consequence of the stress field resulting from imperfections in the solid and causes the thermomechanical fatigue that is estimated to be responsible for 90% of mechanical failures in current devices. We directly measure the local distribution of residual intrinsic stress in polycrystalline thin films on nanometer scales, using a pioneering method based on atomic force microscopy. Our results demonstrate that, at odds with expectations, compression is not generated inside grain boundaries but at the edges of gaps where the boundaries intercept the surface. We describe a model wherein this compressive stress is caused by Mullins-type surface diffusion towards the boundaries, generating a kinetic surface profile different from the mechanical equilibrium profile by the Laplace-Young equation. Where the curvatures of both profiles differ, an intrinsic stress is generated in the form of Laplace pressure. The Srolovitz-type surface diffusion that results from the stress counters the Mullins-type diffusion and stabilizes the kinetic surface profile, giving rise to a steady compression regime. The proposed mechanism of competition between surface diffusions would explain the flux and time dependency of compressive stress in polycrystalline thin films.

Defect structures in MgB2 wires introduced by hot isostatic pressing

International Nuclear Information System (INIS)

Liao, X Z; Serquis, A; Zhu, Y T; Civale, L; Hammon, D L; Peterson, D E; Mueller, F M; Nesterenko, V F; Gu, Y

2003-01-01

The microstructures of MgB 2 wires prepared by the powder-in-tube technique and subsequent hot isostatic pressing were investigated using transmission electron microscopy. A large amount of crystalline defects including small-angle twisting, tilting and bending boundaries, in which high densities of dislocations reside, was found forming sub-grains within MgB 2 grains. It is believed that these defects resulted from particle deformation during the hot isostatic pressing process and are effective flux pinning centres that contribute to the high critical current densities of the wires at high temperatures and at high fields

Grain boundary migration

International Nuclear Information System (INIS)

Dimitrov, O.

1975-01-01

Well-established aspects of grain-boundary migration are first briefly reviewed (influences of driving force, temperature, orientation and foreign atoms). Recent developments of the experimental methods and results are then examined, by considering the various driving of resistive forces acting on grain boundaries. Finally, the evolution in the theoretical models of grain-boundary motion is described, on the one hand for ideally pure metals and, on the other hand, in the presence of solute impurity atoms [fr

Analytic Approximations to the Free Boundary and Multi-dimensional Problems in Financial Derivatives Pricing

Science.gov (United States)

Lau, Chun Sing

This thesis studies two types of problems in financial derivatives pricing. The first type is the free boundary problem, which can be formulated as a partial differential equation (PDE) subject to a set of free boundary condition. Although the functional form of the free boundary condition is given explicitly, the location of the free boundary is unknown and can only be determined implicitly by imposing continuity conditions on the solution. Two specific problems are studied in details, namely the valuation of fixed-rate mortgages and CEV American options. The second type is the multi-dimensional problem, which involves multiple correlated stochastic variables and their governing PDE. One typical problem we focus on is the valuation of basket-spread options, whose underlying asset prices are driven by correlated geometric Brownian motions (GBMs). Analytic approximate solutions are derived for each of these three problems. For each of the two free boundary problems, we propose a parametric moving boundary to approximate the unknown free boundary, so that the original problem transforms into a moving boundary problem which can be solved analytically. The governing parameter of the moving boundary is determined by imposing the first derivative continuity condition on the solution. The analytic form of the solution allows the price and the hedging parameters to be computed very efficiently. When compared against the benchmark finite-difference method, the computational time is significantly reduced without compromising the accuracy. The multi-stage scheme further allows the approximate results to systematically converge to the benchmark results as one recasts the moving boundary into a piecewise smooth continuous function. For the multi-dimensional problem, we generalize the Kirk (1995) approximate two-asset spread option formula to the case of multi-asset basket-spread option. Since the final formula is in closed form, all the hedging parameters can also be derived in

3D additive manufactured 316L components microstructural features and changes induced by working life cycles

Science.gov (United States)

Pace, M. L.; Guarnaccio, A.; Dolce, P.; Mollica, D.; Parisi, G. P.; Lettino, A.; Medici, L.; Summa, V.; Ciancio, R.; Santagata, A.

2017-10-01

The ability of processing through laser beams different kinds of metallic powders for direct production of 3D components with complex geometries has been gaining an impressive and growing attention for specific industrial applications. The process which can be distinguished as Selective Laser Sintering or Selective Laser Melting is even considered, more generally, as Additive Manufacturing where layer by layer material is built by the interaction between a laser beam and a powder bed. The rapid heating of the powder due to the laser beam energy transfer process followed by a rapid cooling rate induces within the manufactured material a cellular structure with fine sub-grains, which are in the range of few hundreds of micrometers. These metastable structures, which are smaller than the grain size in conventionally manufactured 316L stainless steel components, can undertake towards a recrystallization process due to either heat or mechanical treatments. For instance, when sub-grain boundaries of the cells are enriched with Mo and higher concentration of dislocation, dynamical processes occur generating local residual stresses. In these circumstances the segregation of Mo in cell boundaries is out of thermodynamic equilibrium conditions so that microstructures and phases are metastable. In the range of 1100-1400 °C heat treatments a complete dissolution of Mo in the Fe matrix with a gradual disappearance of sub-microns cell is observed feeding the growth of larger austenitic sub-grains formation. It follows a higher degree of Mo dissolution in the material matrix and a decrease of dislocation's concentration (Saeidi et al., 2015) [1]. In the work here presented we point out which are the microstructural features of stainless steel 316L components realized by Additive Manufacturing. Furthermore, the occurrence of a microstructural evolution is presented after experiencing to fatigue of 80000 cycles some door joints obtained by this technique. A decrease of dislocation

Grain boundaries of nanocrystalline materials - their widths, compositions, and internal structures

International Nuclear Information System (INIS)

Fultz, B.; Frase, H.N.

2000-01-01

Nanocrystalline materials contain many atoms at and near grain boundaries. Sufficient numbers of Moessbauer probe atoms can be situated in grain boundary environments to make a clear contribution to the measured Moessbauer spectrum. Three types of measurements on nanocrystalline materials are reported here, all using Moessbauer spectrometry in conjunction with X-ray diffractometry, transmission electron microscopy, or small angle neutron scattering. By measuring the fraction of atoms contributing to the grain boundary component in a Moessbauer spectrum, and by knowing the grain size of the material, it is possible to deduce the average width of grain boundaries in metallic alloys. It is found that these widths are approximately 0.5 nm for fcc alloys and slightly larger than 1.0 nm for bcc alloys.Chemical segregation to grain boundaries can be measured by Moessbauer spectrometry, especially in conjunction with small angle neutron scattering. Such measurements on Fe-Cu and Fe 3 Si-Nb were used to study how nanocrystalline materials could be stabilized against grain growth by the segregation of Cu and Nb to grain boundaries. The segregation of Cu to grain boundaries did not stabilize the Fe-Cu alloys against grain growth, since the grain boundaries were found to widen and accept more Cu atoms during annealing. The Nb additions to Fe 3 Si did suppress grain growth, perhaps because of the low mobility of Nb atoms, but also perhaps because Nb atoms altered the chemical ordering in the alloy.The internal structure of grain boundaries in nanocrystalline materials prepared by high-energy ball milling is found to be unstable against internal relaxations at low temperatures. The Moessbauer spectra of the nanocrystalline samples showed changes in the hyperfine fields attributable to movements of grain boundary atoms. In conjunction with SANS measurements, the changes in grain boundary structure induced by cryogenic exposure and annealing at low temperature were found to be

Boundary terms and junction conditions for the DGP π-Lagrangian and galileon

International Nuclear Information System (INIS)

Dyer, Ethan; Hinterbichler, Kurt

2009-01-01

In the decoupling limit of DGP, π describes the brane-bending degree of freedom. It obeys second order equations of motion, yet it is governed by a higher derivative Lagrangian. We show that, analogously to the Einstein-Hilbert action for GR, the π-Lagrangian requires Gibbons-Hawking-York type boundary terms to render the variational principle well-posed. These terms are important if there are other boundaries present besides the DGP brane, such as in higher dimensional cascading DGP models. We derive the necessary boundary terms in two ways. First, we derive them directly from the brane-localized π-Lagrangian by demanding well-posedness of the action. Second, we calculate them directly from the bulk, taking into account the Gibbons-Hawking-York terms in the bulk Einstein-Hilbert action. As an application, we use the new boundary terms to derive Israel junction conditions for π across a sheet-like source. In addition, we calculate boundary terms and junction conditions for the galileons which generalize the DGP π-Lagrangian, showing that the boundary term for the n-th order galileon is the (n-1)-th order galileon.

Grain Boundary Segregation in Metals

CERN Document Server

Lejcek, Pavel

2010-01-01

Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.

Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei [University of Tennessee (UT); Gao, Yanfei [ORNL; Nieh, T. G. [University of Tennessee, Knoxville (UTK)

2018-01-01

In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the applied stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.

Stability and boundary stabilization of 1-D hyperbolic systems

CERN Document Server

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...

Tangential boundary values of Laplace transforms. Applications to Muntz-Szasz type approximation

Energy Technology Data Exchange (ETDEWEB)

Sedletskii, A M [M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2003-02-28

We consider the Laplace transforms (LT) of functions in L{sup q}(R{sub +}), 1boundary values almost everywhere on the imaginary axis, and the structure of the corresponding neighbourhoods depends on the weight only. This result is applied to distinguish a wide class of weighted L{sup p} spaces on the half-line such that the Szasz condition is not necessary for the completeness of the system exp(-{lambda}{sub n}t) in these spaces.

Atomic structure of surface defects in alumina studied by dynamic force microscopy: strain-relief-, translation- and reflection-related boundaries, including their junctions

International Nuclear Information System (INIS)

Simon, G H; König, T; Heinke, L; Lichtenstein, L; Heyde, M; Freund, H-J

2011-01-01

We present an extensive atomic resolution frequency modulation dynamic force microscopy study of ultrathin aluminium oxide on a single crystalline NiAl(110) surface. One-dimensional surface defects produced by domain boundaries have been resolved. Images are presented for reflection domain boundaries (RDBs), four different types of antiphase domain boundaries, a nucleation-related translation domain boundary and also domain boundary junctions. New structures and aspects of the boundaries and their network are revealed and merged into a comprehensive picture of the defect arrangements. The alumina film also covers the substrate completely at the boundaries and their junctions and follows the structural building principles found in its unit cell. This encompasses square and rectangular groups of surface oxygen sites. The observed structural elements can be related to the electronic signature of the boundaries and therefore to the electronic defects associated with the boundaries. A coincidence site lattice predicted for the RDBs is in good agreement with experimental data. With Σ = 19 it can be considered to be of low-sigma type, which frequently coincides with special boundary properties. Images of asymmetric RDBs show points of good contact alternating with regions of nearly amorphous disorder in the oxygen sublattice. (paper)

A question of fit: reflections on boundaries, organizations and social-ecological systems.

Science.gov (United States)

Sternlieb, Faith; Bixler, R Patrick; Huber-Stearns, Heidi; Huayhuaca, Ch'aska

2013-11-30

Although there is acknowledgment that the complexity of social-ecological systems governance demands representation from diverse perspectives, there is little agreement in the literature on how to cross both fiat (human-demarcated) and bona fide (physical) boundaries to address such complexities. As a cohort of interdisciplinary scholars, we navigate the boundary between science and practice to address the question of fit regarding the role of organizations in transcending boundaries. We found there is a need to rectify discrepancies between theories about boundaries and theories about organizations. To this end, we propose a conceptual framework to analyze transboundary organizations, an umbrella term to group the literature on boundary organizations, intermediaries and bridging organizations; we introduce this term to illustrate they are not mutually exclusive and to facilitate interdisciplinary research. We first examine social-ecological systems (SES), a framework intended to improve understandings of boundaries and governance. We then continue to unpack the complexity of boundaries and organizations, specifically through important transboundary concepts such as scale and organizational learning. This helps frame our examination of the literature on: 1) boundary organizations; 2) bridging organizations (third-party entities); and 3) intermediaries (distinguished by their position between other actors). Our review identifies a number of discrepancies that pertain to the types of boundaries discussed and the roles assigned to organizations governing SES. Important characteristics have emerged from our review of transboundary organizations including legitimacy, saliency, urgency, and credibility. In developing a conceptual framework, we argue that transboundary organizations: 1) expand upon the boundary spectrum, 2) incorporate transboundary concepts, and 3) hybridize characteristics of boundary, bridging, and intermediary organizations. We conclude with a number

Auto and hetero-diffusion along grain and interphase boundaries in α-Zr and Zr-2.5wt%Nb

International Nuclear Information System (INIS)

Dyment, F.; Iribarren, M.J.; Vieregge, K.; Herzig, C.

1993-01-01

Grain-boundary diffusion measurements made in α-Zr and interphase-boundary diffusion measurements made in the (α+β) region of Zr-2.5wt%Nb were considered together with the aim of gaining a better understanding of the behaviour of these boundaries in Zr-based materials which are relevant for the nuclear industry. When comparing the total set of data it turns out that, from the diffusion point of view, both types of boundaries provide similar short-circuit diffusion paths. (orig.)

Interpretation of horizontal well performance in complicated systems by the boundary element method

Energy Technology Data Exchange (ETDEWEB)

Jongkittinarukorn, K.; Tiab, D. [Oklahoma Univ., School of Petroleum and Geological Engineering (United States); Escobar, F. H. [Surcolombiana Univ., Dept. of Petroleum Engineering (Colombia)

1998-12-31

A solution obtained by using the boundary element method to simulate pressure behaviour of horizontal wells in complicated reservoir-wellbore configurations is presented. Three different types of well bore and reservoir models were studied, i.e. a snake-shaped horizontal wellbore intersecting a two-layer reservoir with cross flow, a horizontal well in a three-layer reservoir with cross flow, and a vertical well intersecting a two-layer reservoir without cross flow. In each case, special attention was paid to the influence of wellbore inclination angle, the distance from the wellbore to the different boundaries and the permeability ratio. Performance of each of these types of wells are discussed. 9 refs., 18 figs.

Development of boundary layers

International Nuclear Information System (INIS)

Herbst, R.

1980-01-01

Boundary layers develop along the blade surfaces on both the pressure and the suction side in a non-stationary flow field. This is due to the fact that there is a strongly fluctuating flow on the downstream blade row, especially as a result of the wakes of the upstream blade row. The author investigates the formation of boundary layers under non-stationary flow conditions and tries to establish a model describing the non-stationary boundary layer. For this purpose, plate boundary layers are measured, at constant flow rates but different interferent frequency and variable pressure gradients. By introducing the sample technique, measurements of the non-stationary boundary layer become possible, and the flow rate fluctuation can be divided in its components, i.e. stochastic turbulence and periodical fluctuation. (GL) [de

Effect of prior deformation on microstructural development and Laves phase precipitation in high-chromium stainless steel.

Science.gov (United States)

Hsiao, Z-W; Chen, D; Kuo, J-C; Lin, D-Y

2017-04-01

This study investigated the influence of deformation on precipitation behaviour and microstructure change during annealing. Here, the prior deformation of high-chromium stainless steel was tensile deformation of 3%, 6% and 10%, and the specimens were then annealed at 700˚C for 10 h. The specimens were subsequently analyzed using backscattered electron image and electron backscattering diffraction measurements with SEM. Compared with the deformation microstructure, the grains revealed no preferred orientation. The precipitates of TiN and NbC were formed homogenously in the grain interior and at grain boundaries after annealing. Fine Laves phase precipitates were observed in grains and along subgrain boundaries as the deformation increased. Furthermore, the volume fraction of Laves phase increased, but the average particle diameter of precipitate was reduced as the deformation increased. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Microstructure evolution and dislocation behaviour in high chromium, fully ferritic steels strengthened by intermetallic Laves phases.

Science.gov (United States)

Lopez Barrilao, Jennifer; Kuhn, Bernd; Wessel, Egbert

2018-05-01

In the present study a stainless, high strength, ferritic (non-martensitic) steel was analysed regarding microstructure and particle evolution. The preceding hot-rolling process of the steel results in the formation of sub-grain structures, which disappear over time at high temperature. Besides that the formation of particle-free zones was observed. The pronounced formation of these zones preferentially appears close to high angle grain boundaries and is considered to be responsible for long-term material failure under creep conditions. The reasons for this are lacking particle hardening and thus a concentration and accumulation of deformation in the particle free areas close to the grain boundaries. Accordingly in-depth investigations were performed by electron microscopy to analyse dislocation behaviour and its possible effect on the mechanical response of these weak areas. Copyright © 2018 Elsevier Ltd. All rights reserved.

Prosodic boundaries in writing: Evidence from a keystroke analysis

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Susanne Fuchs

2016-11-01

Full Text Available The aim of the paper is to investigate duration between successive keystrokes during typing in order to examine whether prosodic boundaries are expressed in the process of writing. In particular, we are interested in interkey durations that occur next to punctuation marks (comma and full stops while taking keystrokes between words as a reference, since these punctuation marks are often realized with minor or major prosodic boundaries during reading. A two-part experiment was conducted: first, participants’ keystrokes on a computer keyboard were recorded while writing an email to a close friend (in two conditions: with and without time pressure. Second, participants read the email they just wrote. Interkey durations were compared to pause durations at the same locations during read speech. Results provide evidence of significant differences between interkey durations between words, at commas and at full stops (from shortest to longest. These durations were positively correlated with silent pause durations during reading. A more detailed analysis of interkey durations revealed patterns that can be interpreted with respect to prosodic boundaries in speech production, namely as phrase-final and phrase-initial lengthening occurring at punctuation marks. This work provides initial evidence that prosodic boundaries are reflected in the writing process.

Prosodic Boundaries in Writing: Evidence from a Keystroke Analysis.

Science.gov (United States)

Fuchs, Susanne; Krivokapić, Jelena

2016-01-01

The aim of the paper is to investigate duration between successive keystrokes during typing in order to examine whether prosodic boundaries are expressed in the process of writing. In particular, we are interested in interkey durations that occur next to punctuation marks (comma and full stops while taking keystrokes between words as a reference), since these punctuation marks are often realized with minor or major prosodic boundaries during overt reading. A two-part experiment was conducted: first, participants' keystrokes on a computer keyboard were recorded while writing an email to a close friend (in two conditions: with and without time pressure). Second, participants read the email they just wrote. Interkey durations were compared to pause durations at the same locations during read speech. Results provide evidence of significant differences between interkey durations between words, at commas and at full stops (from shortest to longest). These durations were positively correlated with silent pause durations during overt reading. A more detailed analysis of interkey durations revealed patterns that can be interpreted with respect to prosodic boundaries in speech production, namely as phrase-final and phrase-initial lengthening occurring at punctuation marks. This work provides initial evidence that prosodic boundaries are reflected in the writing process.

Analytic Solution to Shell Boundary – Value Problems

Directory of Open Access Journals (Sweden)

Yu. I. Vinogradov

2015-01-01

Full Text Available Object of research is to find analytical solution to the shell boundary – value problems, i.e. to consider the solution for a class of problems concerning the mechanics of hoop closed shells strain.The objective of work is to create an analytical method to define a stress – strain state of shells under non-axisymmetric loading. Thus, a main goal is to derive the formulas – solutions of the linear ordinary differential equations with variable continuous coefficients.The partial derivative differential equations of mechanics of shells strain by Fourier's method of variables division are reduced to the system of the differential equations with ordinary derivatives. The paper presents the obtained formulas to define solutions of the uniform differential equations and received on their basis formulas to define a particular solution depending on a type of the right parts of the differential equations.The analytical algorithm of the solution of a boundary task uses an approach to transfer the boundary conditions to the randomly chosen point of an interval of changing independent variable through the solution of the canonical matrix ordinary differential equation with the subsequent solution of system of algebraic equations for compatibility of boundary conditions at this point. Efficiency of algorithm is based on the fact that the solution of the ordinary differential equations is defined as the values of Cauchy – Krylova functions, which meet initial arbitrary conditions.The results of researches presented in work are useful to experts in the field of calculus mathematics, dealing with solution of systems of linear ordinary differential equations and creation of effective analytical computing methods to solve shell boundary – value problems.

Compressible stability of growing boundary layers using parabolized stability equations

Science.gov (United States)

Chang, Chau-Lyan; Malik, Mujeeb R.; Erlebacher, Gordon; Hussaini, M. Y.

1991-01-01

The parabolized stability equation (PSE) approach is employed to study linear and nonlinear compressible stability with an eye to providing a capability for boundary-layer transition prediction in both 'quiet' and 'disturbed' environments. The governing compressible stability equations are solved by a rational parabolizing approximation in the streamwise direction. Nonparallel flow effects are studied for both the first- and second-mode disturbances. For oblique waves of the first-mode type, the departure from the parallel results is more pronounced as compared to that for the two-dimensional waves. Results for the Mach 4.5 case show that flow nonparallelism has more influence on the first mode than on the second. The disturbance growth rate is shown to be a strong function of the wall-normal distance due to either flow nonparallelism or nonlinear interactions. The subharmonic and fundamental types of breakdown are found to be similar to the ones in incompressible boundary layers.

TESTING GARCH-X TYPE MODELS

DEFF Research Database (Denmark)

Pedersen, Rasmus Søndergaard; Rahbek, Anders

2017-01-01

We present novel theory for testing for reduction of GARCH-X type models with an exogenous (X) covariate to standard GARCH type models. To deal with the problems of potential nuisance parameters on the boundary of the parameter space as well as lack of identification under the null, we exploit...... a noticeable property of specific zero-entries in the inverse information of the GARCH-X type models. Specifically, we consider sequential testing based on two likelihood ratio tests and as demonstrated the structure of the inverse information implies that the proposed test neither depends on whether...... the nuisance parameters lie on the boundary of the parameter space, nor on lack of identification. Our general results on GARCH-X type models are applied to Gaussian based GARCH-X models, GARCH-X models with Student's t-distributed innovations as well as the integer-valued GARCH-X (PAR-X) models....

Inside Out: Organizations as Service Systems Equipped with Relational Boundaries

Directory of Open Access Journals (Sweden)

María Jimena Crespo Garrido

2017-04-01

Full Text Available Currently, literature on organizational boundaries is at the center of a heated debate, characterized by a shift from a transactional approach to a broader immaterial perspective centered on the concept of boundless organizations. However, the overestimation of the effects of contemporary dematerialization on business processes can lead to the progressive neglect of the existence of corporate borders. In light of this consideration, the present work aims at proposing a new type of criterion for defining organizational boundaries, halfway between the conception of the firm’s total openness and total closure. To this end, the authors envisage the use of a new interpretive logic defined as “relational”, resulting from the specification of the systemic view (and as the sum of the logic underlying the viable systems approach (VSA. This approach views the definition of boundaries. Therefore, in the large and intricate scenery of the studies dedicated to organizational boundaries, this work contributes to a better understanding of border selection as an interactive and changeable process capable of pushing organizations towards a greater awareness of their strategic dimension. This paper also offers some insights for future research, suggesting that both scholars and professionals investigate, firstly, new frontiers for the identification of organizational boundaries and, secondly, the possible positive repercussions that new organizational redesign modes could determine for a greater competitive success.

Experimental measurements and modelling of the WEGA boundary layer plasma

International Nuclear Information System (INIS)

El Shaer, M.; Ichtchenko, G.

1983-02-01

The boundary layer of the WEGA Tokamak has been investigated by using specific diagnostics: movable 4 mm microwave interferometer, several types of movable and fixed probes, Katsumata probe, and multigrid electrostatic analyzer. During the RF heating at the lower hybrid frequency, some modifications in the parameters of the boundary layer are observed which are interpreted by the ponderomotive force effects. A comparison between the measured reflection coefficients of the grill waveguides and their predicted values by a coupling theory (not taking into account the real conditions facing the Grill) is presented. A diffusion model was also made to describe this particular region and to fit the experimental results

Coupling the Gaussian Free Fields with Free and with Zero Boundary Conditions via Common Level Lines

Science.gov (United States)

Qian, Wei; Werner, Wendelin

2018-06-01

We point out a new simple way to couple the Gaussian Free Field (GFF) with free boundary conditions in a two-dimensional domain with the GFF with zero boundary conditions in the same domain: Starting from the latter, one just has to sample at random all the signs of the height gaps on its boundary-touching zero-level lines (these signs are alternating for the zero-boundary GFF) in order to obtain a free boundary GFF. Constructions and couplings of the free boundary GFF and its level lines via soups of reflected Brownian loops and their clusters are also discussed. Such considerations show for instance that in a domain with an axis of symmetry, if one looks at the overlay of a single usual Conformal Loop Ensemble CLE3 with its own symmetric image, one obtains the CLE4-type collection of level lines of a GFF with mixed zero/free boundary conditions in the half-domain.

A New Spectral Local Linearization Method for Nonlinear Boundary Layer Flow Problems

Directory of Open Access Journals (Sweden)

S. S. Motsa

2013-01-01

Full Text Available We propose a simple and efficient method for solving highly nonlinear systems of boundary layer flow problems with exponentially decaying profiles. The algorithm of the proposed method is based on an innovative idea of linearizing and decoupling the governing systems of equations and reducing them into a sequence of subsystems of differential equations which are solved using spectral collocation methods. The applicability of the proposed method, hereinafter referred to as the spectral local linearization method (SLLM, is tested on some well-known boundary layer flow equations. The numerical results presented in this investigation indicate that the proposed method, despite being easy to develop and numerically implement, is very robust in that it converges rapidly to yield accurate results and is more efficient in solving very large systems of nonlinear boundary value problems of the similarity variable boundary layer type. The accuracy and numerical stability of the SLLM can further be improved by using successive overrelaxation techniques.

Chern-Simons supergravity plus matter near the boundary of AdS3

International Nuclear Information System (INIS)

Deger, N.S.; Kaya, A.; Sezgin, E.; Sundell, P.; Tanii, Y.

2001-01-01

We examine the boundary behaviour of the gauged N=(2,0) supergravity in D=3 coupled to an arbitrary number of scalar supermultiplets which parametrize a Kaehler manifold. In addition to the gravitational coupling constant, the model depends on two parameters, namely the cosmological constant and the size of the Kaehler manifold. It is shown that regular and irregular boundary conditions can be imposed on the matter fields depending on the size of the sigma model manifold. It is also shown that the super AdS transformations in the bulk produce the transformations of the N=(2,0) conformal supergravity and scalar multiplets on the boundary, containing fields with nonvanishing Weyl weights determined by the ratio of the sigma model and the gravitational coupling constants. Various types of (2,0) superconformal multiplets are found on the boundary and in one case the superconformal symmetry is shown to be realized in an unconventional way

Structure and motion of junctions between coherent and incoherent twin boundaries in copper

Energy Technology Data Exchange (ETDEWEB)

Brown, J.A. [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Ghoniem, N.M., E-mail: ghoniem@ucla.edu [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States)

2009-09-15

The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent {Sigma}=3[110](112) twin boundary (ITB), pinned between two {Sigma}=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

Structure and motion of junctions between coherent and incoherent twin boundaries in copper

International Nuclear Information System (INIS)

Brown, J.A.; Ghoniem, N.M.

2009-01-01

The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent Σ=3[110](112) twin boundary (ITB), pinned between two Σ=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

Evaluation of the effects of the radial constant-head boundary in slug tests

Science.gov (United States)

Dai, Yunfeng; Zhou, Zhifang; Zhao, Yanrong; Cui, Ziteng

2015-03-01

A semianalytical model of slug tests, conducted in a completely penetrating well within a radial constant-head boundary, was derived. The model, based on the Cooper et al. (1967) model, estimates the hydraulic conductivity and storage coefficient through the matching of type curves. Type curves of the semianalytical solution were plotted, and the effect of the distance of the radial constant-head boundary is discussed. For different storage coefficients, the critical distances of the effect of the constant-head boundary were determined. The effect of the storage coefficient on the response of the water head in slug tests with a radial constant-head boundary of a certain distance is also shown. To verify the model, laboratory slug-test experiments were carried out using a cylindrical test platform, in which an artificial confined coarse-sand aquifer was built. Pumping tests were also executed using the test platform. The Cooper et al. (1967) model and new semianalytical model were used to analyze measurements; the hydraulic conductivity and storage coefficient determined using the two methods were compared to demonstrate the importance of the radial constant-head boundary. A model considering the inertial effect was also used to analyze the slug-test measurements, and although the water head response did not oscillate greatly, the inertial effect affected the slug-test calculation result. The laboratory experiments indicate that the proposed semianalytical model is reasonable and reliable. Cooper HH, Bredehoeft JD, Papadopulos IS (1967) Response of a finite-diameter well to an instantaneous charge of water, Water Resour Res 3(1):263-269.

Attractor of Beam Equation with Structural Damping under Nonlinear Boundary Conditions

Directory of Open Access Journals (Sweden)

Danxia Wang

2015-01-01

Full Text Available Simultaneously, considering the viscous effect of material, damping of medium, and rotational inertia, we study a kind of more general Kirchhoff-type extensible beam equation utt-uxxtt+uxxxx-σ(∫0l‍(ux2dxuxx-ϕ(∫0l‍(ux2dxuxxt=q(x, in  [0,L]×R+ with the structural damping and the rotational inertia term. Little attention is paid to the longtime behavior of the beam equation under nonlinear boundary conditions. In this paper, under nonlinear boundary conditions, we prove not only the existence and uniqueness of global solutions by prior estimates combined with some inequality skills, but also the existence of a global attractor by the existence of an absorbing set and asymptotic compactness of corresponding solution semigroup. In addition, the same results also can be proved under the other nonlinear boundary conditions.

Boundary Spanning

DEFF Research Database (Denmark)

Zølner, Mette

The paper explores how locals span boundaries between corporate and local levels. The aim is to better comprehend potentialities and challenges when MNCs draws on locals’ culture specific knowledge. The study is based on an in-depth, interpretive case study of boundary spanning by local actors in...... approach with pattern matching is a way to shed light on the tacit local knowledge that organizational actors cannot articulate and that an exclusively inductive research is not likely to unveil....

Towards Adaptive Grids for Atmospheric Boundary-Layer Simulations

Science.gov (United States)

van Hooft, J. Antoon; Popinet, Stéphane; van Heerwaarden, Chiel C.; van der Linden, Steven J. A.; de Roode, Stephan R.; van de Wiel, Bas J. H.

2018-02-01

We present a proof-of-concept for the adaptive mesh refinement method applied to atmospheric boundary-layer simulations. Such a method may form an attractive alternative to static grids for studies on atmospheric flows that have a high degree of scale separation in space and/or time. Examples include the diurnal cycle and a convective boundary layer capped by a strong inversion. For such cases, large-eddy simulations using regular grids often have to rely on a subgrid-scale closure for the most challenging regions in the spatial and/or temporal domain. Here we analyze a flow configuration that describes the growth and subsequent decay of a convective boundary layer using direct numerical simulation (DNS). We validate the obtained results and benchmark the performance of the adaptive solver against two runs using fixed regular grids. It appears that the adaptive-mesh algorithm is able to coarsen and refine the grid dynamically whilst maintaining an accurate solution. In particular, during the initial growth of the convective boundary layer a high resolution is required compared to the subsequent stage of decaying turbulence. More specifically, the number of grid cells varies by two orders of magnitude over the course of the simulation. For this specific DNS case, the adaptive solver was not yet more efficient than the more traditional solver that is dedicated to these types of flows. However, the overall analysis shows that the method has a clear potential for numerical investigations of the most challenging atmospheric cases.

Off-wall boundary conditions for turbulent flows obtained from buffer-layer minimal flow units

Science.gov (United States)

Garcia-Mayoral, Ricardo; Pierce, Brian; Wallace, James

2012-11-01

There is strong evidence that the transport processes in the buffer region of wall-bounded turbulence are common across various flow configurations, even in the embryonic turbulence in transition (Park et al., Phys. Fl. 24). We use this premise to develop off-wall boundary conditions for turbulent simulations. Boundary conditions are constructed from DNS databases using periodic minimal flow units and reduced order modeling. The DNS data was taken from a channel at Reτ = 400 and a zero-pressure gradient transitional boundary layer (Sayadi et al., submitted to J . FluidMech .) . Both types of boundary conditions were first tested on a DNS of the core of the channel flow with the aim of extending their application to LES and to spatially evolving flows. 2012 CTR Summer Program.

Moho vs crust-mantle boundary: Evolution of an idea

Science.gov (United States)

O'Reilly, Suzanne Y.; Griffin, W. L.

2013-12-01

The concept that the Mohorovicic Discontinuity (Moho) does not necessarily coincide with the base of the continental crust as defined by rock-type compositions was introduced in the early 1980s. This had an important impact on understanding the nature of the crust-mantle boundary using information from seismology and from deep-seated samples brought to the surface as xenoliths in magmas, or as tectonic terranes. The use of empirically-constrained P-T estimates to plot the locus of temperature vs depth for xenoliths defined a variety of geotherms depending on tectonic environment. The xenolith geotherms provided a framework for constructing lithological sections through the deep lithosphere, and revealed that the crust-mantle boundary in off-craton regions commonly is transitional over a depth range of about 5-20 km. Early seismic-reflection data showed common layering near the Moho, correlating with the petrological observation of multiple episodes of basaltic intrusion around the crust-mantle boundary. Developments in seismology, petrophysics and experimental petrology have refined interpretation of lithospheric domains. The expansion of in situ geochronology (especially zircon U-Pb ages and Hf-isotopes; Os isotopes of mantle sulfides) has defined tectonic events that affected whole crust-mantle sections, and revealed that the crust-mantle boundary can change in depth through time. However, the nature of the crust-mantle boundary in cratonic regions remains enigmatic, mainly due to lack of key xenoliths or exposed sections. The observation that the Moho may lie significantly deeper than the crust-mantle boundary has important implications for modeling the volume of the crust. Mapping the crust using seismic techniques alone, without consideration of the petrological problems, may lead to an overestimation of crustal thickness by 15-30%. This will propagate to large uncertainties in the calculation of elemental mass balances relevant to crust-formation processes

Boundary singularities produced by the motion of soap films.

Science.gov (United States)

Goldstein, Raymond E; McTavish, James; Moffatt, H Keith; Pesci, Adriana I

2014-06-10

Recent work has shown that a Möbius strip soap film rendered unstable by deforming its frame changes topology to that of a disk through a "neck-pinching" boundary singularity. This behavior is unlike that of the catenoid, which transitions to two disks through a bulk singularity. It is not yet understood whether the type of singularity is generally a consequence of the surface topology, nor how this dependence could arise from an equation of motion for the surface. To address these questions we investigate experimentally, computationally, and theoretically the route to singularities of soap films with different topologies, including a family of punctured Klein bottles. We show that the location of singularities (bulk or boundary) may depend on the path of the boundary deformation. In the unstable regime the driving force for soap-film motion is the mean curvature. Thus, the narrowest part of the neck, associated with the shortest nontrivial closed geodesic of the surface, has the highest curvature and is the fastest moving. Just before onset of the instability there exists on the stable surface the shortest closed geodesic, which is the initial condition for evolution of the neck's geodesics, all of which have the same topological relationship to the frame. We make the plausible conjectures that if the initial geodesic is linked to the boundary, then the singularity will occur at the boundary, whereas if the two are unlinked initially, then the singularity will occur in the bulk. Numerical study of mean curvature flows and experiments support these conjectures.

Persistent Identifiers as Boundary Objects

Science.gov (United States)

Parsons, M. A.; Fox, P. A.

2017-12-01

In 1989, Leigh Star and Jim Griesemer defined the seminal concept of `boundary objects'. These `objects' are what Latour calls `immutable mobiles' that enable communication and collaboration across difference by helping meaning to be understood in different contexts. As Star notes, they are a sort of arrangement that allow different groups to work together without (a priori) consensus. Part of the idea is to recognize and allow for the `interpretive flexibility' that is central to much of the `constructivist' approach in the sociology of science. Persistent Identifiers (PIDs) can clearly act as boundary objects, but people do not usually assume that they enable interpretive flexibility. After all, they are meant to be unambiguous, machine-interpretable identifiers of defined artifacts. In this paper, we argue that PIDs can fill at least two roles: 1) That of the standardized form, where there is strong agreement on what is being represented and how and 2) that of the idealized type, a more conceptual concept that allows many different representations. We further argue that these seemingly abstract conceptions actually help us implement PIDs more effectively to link data, publications, various other artifacts, and especially people. Considering PIDs as boundary objects can help us address issues such as what level of granularity is necessary for PIDs, what metadata should be directly associated with PIDs, and what purpose is the PID serving (reference, provenance, credit, etc.). In short, sociological theory can improve data sharing standards and their implementation in a way that enables broad interdisciplinary data sharing and reuse. We will illustrate this with several specific examples of Earth science data.

Effect of Fe- and Si-Enriched Secondary Precipitates and Surface Roughness on Pore Formation on Aluminum Plate Surfaces During Anodizing

Science.gov (United States)

Zhu, Yuanzhi; Wang, Shizhi; Yang, Qingda; Zhou, Feng

2014-09-01

Two twin roll casts (TRCs) and one hot rolled (HR) AA 1235 aluminum alloy plates with different microstructures are prepared. The plates were electrolyzed in a 1.2 wt% HCl solution with a voltage of 21 V and a current of 1.9 mA. The shape, size, and number of pores formed on the surfaces of these plates were analyzed and correlated with the microstructures of the plates. It is found that pores are easier to form on the alloy plates containing subgrains with a lower dislocation density inside the subgrains, rather than along the grain boundaries. Furthermore, Fe- and Si-enriched particles in the AA1235 aluminum alloys lead to the formation of pores on the surface during electrolyzing; the average precipitate sizes of 4, 3.5, and 2 μm in Alloy 1#, Alloy 2# and Alloy 3# result in the average pore sizes of 3.78, 2.76, and 1.9 μm on the surfaces of the three alloys, respectively; The G.P zone in the alloy also facilitates the surface pore formation. High-surface roughness enhances the possibility of entrapping more lubricants into the plate surface, which eventually blocks the formation of the pores on the surface of the aluminum plates in the following electrolyzing process.

Effects of homogenization treatment on recrystallization behavior of 7150 aluminum sheet during post-rolling annealing

International Nuclear Information System (INIS)

Guo, Zhanying; Zhao, Gang; Chen, X.-Grant

2016-01-01

The effects of two homogenization treatments applied to the direct chill (DC) cast billet on the recrystallization behavior in 7150 aluminum alloy during post-rolling annealing have been investigated using the electron backscatter diffraction (EBSD) technique. Following hot and cold rolling to the sheet, measured orientation maps, the recrystallization fraction and grain size, the misorientation angle and the subgrain size were used to characterize the recovery and recrystallization processes at different annealing temperatures. The results were compared between the conventional one-step homogenization and the new two-step homogenization, with the first step being pretreated at 250 °C. Al_3Zr dispersoids with higher densities and smaller sizes were obtained after the two-step homogenization, which strongly retarded subgrain/grain boundary mobility and inhibited recrystallization. Compared with the conventional one-step homogenized samples, a significantly lower recrystallized fraction and a smaller recrystallized grain size were obtained under all annealing conditions after cold rolling in the two-step homogenized samples. - Highlights: • Effects of two homogenization treatments on recrystallization in 7150 Al sheets • Quantitative study on the recrystallization evolution during post-rolling annealing • Al_3Zr dispersoids with higher densities and smaller sizes after two-step treatment • Higher recrystallization resistance of 7150 sheets with two-step homogenization

The Effect of Hot Working on Structure and Strength of a Precipitation Strengthened Austenitic Stainless Steel

Science.gov (United States)

Mataya, M. C.; Carr, M. J.; Krauss, G.

1984-02-01

The development of microstructure and strength during forging in a γ' strengthened austenitic stainless steel, JBK-75, was investigated by means of forward extrusion of cylindrical specimens. The specimens were deformed in a strain range of 0.16 to 1.0, from 800°C to 1080°C, and at approximate strain rates of 2 (press forging) and 2 × 103 s-1 (high energy rate forging), and structures examined by light and transmission microscopy. Mechanical properties were determined by tensile testing as-forged and forged and aged specimens. The alloy exhibited an extremely wide variety of structures and properties within the range of forging pzrameters studied. Deformation at the higher strain rate via high energy rate forging resulted in unrecovered substructures and high strengths at low forging temperatures, and static recrystallization and low strengths at high temperatures. In contrast, however, deformation at the lower strain rate via press forging resulted in retention of the well developed subgrain structure and associated high strength produced at high forging temperatures and strains. At lower temperatures and strains during press forging a subgrain structure formed preferentially at high angle grain boundaries, apparently by a creep-type deformation mechanism. Dynamic recrystallization was not an important restoration mechanism for any of the forging conditions. The results are interpreted on the basis of stacking fault energy and the accumulation of strain energy during hot working. The significance of observed microstructural differences for equivalent deformation conditions (iso-Z, where Z is the Zener-Holloman parameter) is discussed in relation to the utilization of Z for predicting hot work structures and strengths. Aging showed that the γ' precipitation process is not affected by substructure and that the strengthening contributions, from substructure and precipitation, were independent and additive. Applications for these findings are discussed in terms

An experimental study of deformation mechanism and microstructure evolution during hot deformation of Ti–6Al–2Zr–1Mo–1V alloy

International Nuclear Information System (INIS)

He, D.; Zhu, J.C.; Lai, Z.H.; Liu, Y.; Yang, X.W.

2013-01-01

Highlights: ► Isothermal tensile deformations were carried on Ti–6Al–2Zr–1Mo–1V titanium alloy. ► Deformation activations were calculated based on kinetics rate equations. ► Deformation mechanisms are dislocation creep and self-diffusion at 800 and 850 °C. ► Microstructure globularization mechanisms varied with deformation temperature. ► Recrystallization mechanism changed from CDRX to DDRX as temperature increasing. - Abstract: Isothermal tensile tests have been performed to study the deformation mechanisms and microstructure evolution of Ti–6Al–2Zr–1Mo–1V titanium alloy in the temperature range 750–850 °C and strain rate range 0.001–0.1 s −1 . The deformation activations have been calculated based on kinetics rate equation to investigate the hot deformation mechanism. Microstructures of deformed samples have been analyzed by electron backscatter diffraction (EBSD) to evaluate the influences of hot deformation parameters on the microstructure evolution and recrystallization mechanism. The results indicate that deformation mechanisms vary with deformation conditions: at medium (800 °C) and high (850 °C) temperature, the deformation is mainly controlled by the mechanisms of dislocation creep and self-diffusion, respectively. The microstructure globularization mechanisms also depend on deformation temperature: in the temperature range from 750 to 800 °C, the high angle grain boundaries are mainly formed via dislocation accumulation or subgrain boundaries sliding and subgrains rotation; while at high temperature of 850 °C, recrystallization is the dominant mechanism. Especially, the evolution of the recrystallization mechanism with the deformation temperature is first observed and investigated in TA15 titanium alloy

Consistent boundary conditions for open strings

International Nuclear Information System (INIS)

Lindstroem, Ulf; Rocek, Martin; Nieuwenhuizen, Peter van

2003-01-01

We study boundary conditions for the bosonic, spinning (NSR) and Green-Schwarz open string, as well as for (1+1)-dimensional supergravity. We consider boundary conditions that arise from (1) extremizing the action, (2) BRST, rigid or local supersymmetry, or κ(Siegel)-symmetry of the action, (3) closure of the set of boundary conditions under the symmetry transformations, and (4) the boundary limits of bulk Euler-Lagrange equations that are 'conjugate' to other boundary conditions. We find corrections to Neumann boundary conditions in the presence of a bulk tachyon field. We discuss a boundary superspace formalism. We also find that path integral quantization of the open string requires an infinite tower of boundary conditions that can be interpreted as a smoothness condition on the doubled interval; we interpret this to mean that for a path-integral formulation of open strings with only Neuman boundary conditions, the description in terms of orientifolds is not just natural, but is actually fundamental

Spark formation as a moving boundary process

Science.gov (United States)

Ebert, Ute

2006-03-01

The growth process of spark channels recently becomes accessible through complementary methods. First, I will review experiments with nanosecond photographic resolution and with fast and well defined power supplies that appropriately resolve the dynamics of electric breakdown [1]. Second, I will discuss the elementary physical processes as well as present computations of spark growth and branching with adaptive grid refinement [2]. These computations resolve three well separated scales of the process that emerge dynamically. Third, this scale separation motivates a hierarchy of models on different length scales. In particular, I will discuss a moving boundary approximation for the ionization fronts that generate the conducting channel. The resulting moving boundary problem shows strong similarities with classical viscous fingering. For viscous fingering, it is known that the simplest model forms unphysical cusps within finite time that are suppressed by a regularizing condition on the moving boundary. For ionization fronts, we derive a new condition on the moving boundary of mixed Dirichlet-Neumann type (φ=ɛnφ) that indeed regularizes all structures investigated so far. In particular, we present compact analytical solutions with regularization, both for uniformly translating shapes and for their linear perturbations [3]. These solutions are so simple that they may acquire a paradigmatic role in the future. Within linear perturbation theory, they explicitly show the convective stabilization of a curved front while planar fronts are linearly unstable against perturbations of arbitrary wave length. [1] T.M.P. Briels, E.M. van Veldhuizen, U. Ebert, TU Eindhoven. [2] C. Montijn, J. Wackers, W. Hundsdorfer, U. Ebert, CWI Amsterdam. [3] B. Meulenbroek, U. Ebert, L. Schäfer, Phys. Rev. Lett. 95, 195004 (2005).

Critical boundary sine-Gordon revisited

International Nuclear Information System (INIS)

Hasselfield, M.; Lee, Taejin; Semenoff, G.W.; Stamp, P.C.E.

2006-01-01

We revisit the exact solution of the two space-time dimensional quantum field theory of a free massless boson with a periodic boundary interaction and self-dual period. We analyze the model by using a mapping to free fermions with a boundary mass term originally suggested in Ref. [J. Polchinski, L. Thorlacius, Phys. Rev. D 50 (1994) 622]. We find that the entire SL (2, C) family of boundary states of a single boson are boundary sine-Gordon states and we derive a simple explicit expression for the boundary state in fermion variables and as a function of sine-Gordon coupling constants. We use this expression to compute the partition function. We observe that the solution of the model has a strong-weak coupling generalization of T-duality. We then examine a class of recently discovered conformal boundary states for compact bosons with radii which are rational numbers times the self-dual radius. These have simple expression in fermion variables. We postulate sine-Gordon-like field theories with discrete gauge symmetries for which they are the appropriate boundary states

Solution of moving boundary problems with implicit boundary condition

International Nuclear Information System (INIS)

Moyano, E.A.

1990-01-01

An algorithm that solves numerically a model for studying one dimensional moving boundary problems, with implicit boundary condition, is described. Landau's transformation is used, in order to work with a fixed number of nodes at each instant. Then, it is necessary to deal with a parabolic partial differential equation, whose diffusive and convective terms have variable coefficients. The partial differential equation is implicitly discretized, using Laasonen's scheme, always stable, instead of employing Crank-Nicholson sheme, as it has been done by Ferris and Hill. Fixed time and space steps (Δt, Δξ) are used, and the iteration is made with variable positions of the interface, i.e. varying δs until a boundary condition is satisfied. The model has the same features of the oxygen diffusion in absorbing tissue. It would be capable of estimating time variant radiation treatments of cancerous tumors. (Author) [es

Influences of triple junctions on stress-assisted grain boundary motion in nanocrystalline materials

International Nuclear Information System (INIS)

Aramfard, Mohammad; Deng, Chuang

2014-01-01

Stress-assisted grain boundary motion is among the most studied modes of microstructural evolution in crystalline materials. In this study, molecular dynamics simulations were used to systematically investigate the influences of triple junctions on the stress-assisted motion of symmetric tilt grain boundaries in Cu by considering a honeycomb nanocrystalline model. It was found that the grain boundary motion in nanocrystalline models was highly sensitive to the loading mode, and a strong coupling effect which was prevalent in bicrystal models was only observed when simple shear was applied. In addition, the coupling factor extracted from the honeycomb model was found to be larger and more sensitive to temperature change than that from bicrystal models for the same type of grain boundary under the same loading conditions. Furthermore, the triple junctions seemed to exhibit unusual asymmetric pinning effects to the migrating grain boundary and the constraints by the triple junctions and neighboring grains led to remarkable non-linear grain boundary motion in directions both parallel and normal to the applied shear, which was in stark contrast to that observed in bicrystal models. In addition, dislocation nucleation and propagation, which were absent in the bicrystal model, were found to play an important role on shear-induced grain boundary motion when triple junctions were present. In the end, a generalized model for shear-assisted grain boundary motion was proposed based on the findings from this research. (paper)

Information dynamics of boundary perception

DEFF Research Database (Denmark)

Kragness, Haley; Hansen, Niels Christian; Vuust, Peter

It has long been noted that expert musicians lengthen notes at phrase boundaries in expressive performance. Recently, we have extended research on this phenomenon by showing that undergraduates with no formal musical training and children as young as 3 years lengthen phrase boundaries during self...... uncertain than low-entropy contexts. Because phrase boundaries tend to afford high-entropy continuations, thus generating uncertain expectations in the listener, one possibility is that boundary perception is directly related to entropy. In other words, it may be hypothesized that entropy underlies...... on predictive uncertainty to the timing domain, as well as potentially answer key questions relating to boundary perception in musical listening....

Direct imaging of grain boundaries

International Nuclear Information System (INIS)

Gronsky, R.

1979-09-01

There are currently two types of microscopes which, in principle, are capable of imaging atom positions at grain boundaries. One, the field ion microscope (FIM), yields a projection of the specimen surface (approximately stereographic) by field ionization of an imaging gas at protruding atom sites, and provides topographic information in high-index pole regions which may be interpreted atom-by-atom. The other, a transmission electron microscope (TEM), yields a projection (approximately linear) of the entire specimen thickness by electron optical imaging, and provides atomic resolution detail throughout the illuminated area. In this paper, both methods are described and compared, using examples from practical materials systems

The Community Boundary De-paradoxifyed

DEFF Research Database (Denmark)

Dragsdahl Lauritzen, Ghita; Salomo, Søren

2012-01-01

. In order to improve connections and collaborations across interfaces, it is therefore necessary to improve our understanding of the community boundary construct. Existing studies of community boundaries within the user innovation literature predominantly describe boundaries as incentives for user...

Stable Boundary Layer Issues

OpenAIRE

Steeneveld, G.J.

2012-01-01

Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The development of robust stable boundary layer parameterizations for use in NWP and climate models is hampered by the multiplicity of processes and their unknown interactions. As a result, these models suffer ...

Parametrices and exact paralinearization of semi-linear boundary problems

DEFF Research Database (Denmark)

Johnsen, Jon

2008-01-01

The subject is parametrices for semi-linear problems, based on parametrices for linear boundary problems and on non-linearities that decompose into solution-dependent linear operators acting on the solutions. Non-linearities of product type are shown to admit this via exact paralinearization...... of homogeneous distributions, tensor products and halfspace extensions have been revised. Examples include the von Karman equation....

Political State Boundary (National)

Data.gov (United States)

Department of Transportation — State boundaries with political limit - boundaries extending into the ocean (NTAD). The TIGER/Line Files are shapefiles and related database files (.dbf) that are an...

Characterization of hot isostatically pressed Bi-Sr-Ca-Cu-O as a function of consolidation variables

International Nuclear Information System (INIS)

Goretta, K.C.; Miller, D.J.; Poeppel, R.B.; Nash, A.S.

1992-01-01

This paper reports that fully dense, bulk Bi 2 Sr 1.7 CaCu 2 O x superconductor pellets were made by hot isostatic pressing in an inert atmosphere. Electron microscopy revealed that rotation and bending of the platelike 2212 grains were responsible for much of the densification. Under processing conditions of 825 degrees C and 105 MPa, dense pellets were obtained in 15 min. Many dislocations, planar faults, and, perhaps, intergrowths of the Bi 2 Cr 2 CuO x phase were produced during pressing. The dislocations were largely present in subgrain boundaries when the pressing times were increased to 45-120 min

Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox

International Nuclear Information System (INIS)

Miller, D.J.; Sengupta, S.; Hettinger, J.D.; Shi, D.; Gray, K.E.; Nash, A.S.; Goretta, K.C.

1992-01-01

Magnetic hysteresis data were taken from 4.2 to 35 K on Bi 2 Sr 2 CaCu 2 O x samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 degree C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning

State Agency Administrative Boundaries

Data.gov (United States)

Kansas Data Access and Support Center — This database comprises 28 State agency boundaries and point of contact. The Kansas Geological Survey collected legal descriptions of the boundaries for various...

Tungsten particle reinforced Al 5083 composite with high strength and ductility

Energy Technology Data Exchange (ETDEWEB)

Bauri, Ranjit, E-mail: rbauri@iitm.acin; Yadav, Devinder; Shyam Kumar, C.N.; Balaji, B.

2015-01-03

Tungsten particles were incorporated into an Al 5083 matrix by friction stir processing (FSP). FSP resulted in uniform dispersion of the tungsten particles with excellent interfacial bonding and more importantly without the formation of any harmful intermetallics. For the first time, the particles penetrated to a depth equal to the full pin length of the tool. A novel aspect of the 5083 Al–W composite is that it showed an improvement of more than 100 MPa in the UTS and at the same time exhibited a high ductility (30%). The ductility was also evident from the well defined dimples in the fracture surface which also revealed the superior bonding between the particles and the matrix. FSP also resulted in substantial grain refinement of the Al matrix. Electron backscatter diffraction (EBSD) and transmission electron microscopy analysis revealed that the fine grains formed by dynamic recrystallization. A gradual transformation from sub-grain to high-angle grain boundaries was observed from EBSD analysis pointing towards the occurrence of a continuous type of dynamic recrystallization process.

Formation of incoherent deformation twin boundaries in a coarse-grained Al-7Mg alloy

Science.gov (United States)

Jin, S. B.; Zhang, K.; Bjørge, R.; Tao, N. R.; Marthinsen, K.; Lu, K.; Li, Y. J.

2015-08-01

Deformation twinning has rarely been observed in coarse grained Al and its alloys except under some extreme conditions such as ultrahigh deformation strain or strain rates. Here, we report that a significant amount of Σ3 deformation twins could be generated in a coarse-grained Al-7 Mg alloy by dynamic plastic deformation (DPD). A systematic investigation of the Σ3 boundaries shows that they are Σ3{112} type incoherent twin boundaries (ITBs). These ITBs have formed by gradual evolution from copious low-angle deformation bands through -twist Σ boundaries by lattice rotation. These findings provide an approach to generate deformation twin boundaries in high stacking fault energy metallic alloys. It is suggested that high solution content of Mg in the alloy and the special deformation mode of DPD played an important role in formation of the Σ and ITBs.

Work and personal life boundary management: boundary strength, work/personal life balance, and the segmentation-integration continuum.

Science.gov (United States)

Bulger, Carrie A; Matthews, Russell A; Hoffman, Mark E

2007-10-01

While researchers are increasingly interested in understanding the boundaries surrounding the work and personal life domains, few have tested the propositions set forth by theory. Boundary theory proposes that individuals manage the boundaries between work and personal life through processes of segmenting and/or integrating the domains. The authors investigated boundary management profiles of 332 workers in an investigation of the segmentation-integration continuum. Cluster analysis indicated consistent clusters of boundary management practices related to varying segmentation and integration of the work and personal life domains. But, the authors suggest that the segmentation-integration continuum may be more complicated. Results also indicated relationships between boundary management practices and work-personal life interference and work-personal life enhancement. Less flexible and more permeable boundaries were related to more interference, while more flexible and more permeable boundaries were related to more enhancement.

Physics of grain boundaries in polycrystalline photovoltaic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Yan, Yanfa, E-mail: yanfa.yan@utoledo.edu; Yin, Wan-Jian; Wu, Yelong; Shi, Tingting; Paudel, Naba R. [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); Li, Chen [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Poplawsky, Jonathan [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, Zhiwei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Moseley, John; Guthrey, Harvey; Moutinho, Helio; Al-Jassim, Mowafak M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Pennycook, Stephen J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2015-03-21

Thin-film solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this paper, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. However, in each solar cell device, the GBs can be chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. Therefore, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.

Stabilization of time domain acoustic boundary element method for the interior problem with impedance boundary conditions.

Science.gov (United States)

Jang, Hae-Won; Ih, Jeong-Guon

2012-04-01

The time domain boundary element method (BEM) is associated with numerical instability that typically stems from the time marching scheme. In this work, a formulation of time domain BEM is derived to deal with all types of boundary conditions adopting a multi-input, multi-output, infinite impulse response structure. The fitted frequency domain impedance data are converted into a time domain expression as a form of an infinite impulse response filter, which can also invoke a modeling error. In the calculation, the response at each time step is projected onto the wave vector space of natural radiation modes, which can be obtained from the eigensolutions of the single iterative matrix. To stabilize the computation, unstable oscillatory modes are nullified, and the same decay rate is used for two nonoscillatory modes. As a test example, a transient sound field within a partially lined, parallelepiped box is used, within which a point source is excited by an octave band impulse. In comparison with the results of the inverse Fourier transform of a frequency domain BEM, the average of relative difference norm in the stabilized time response is found to be 4.4%.

Analysis of turbulent boundary layers

CERN Document Server

Cebeci, Tuncer

1974-01-01

Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculati

Correlated XANES, TEM, and NanoSIMS of presolar graphite grains

Science.gov (United States)

Groopman, Evan E.; Nittler, Larry R.

2018-01-01

We report correlated XANES, TEM, and NanoSIMS measurements of twelve presolar graphite grains extracted from primitive meteorites and for which isotopic data indicate predominantly Type-II supernovae origins. We find continued evidence for isotopic heterogeneities in presolar graphite grains, including the first observation of a radial gradient in the inferred initial 26Al/27Al within a presolar graphite grain. The XANES spectra of these samples show a variety of minor absorbances near the C K-edge, attributable to vinyl-keto, aliphatic, carboxyl, and carbonate molecules, as well as possible damage during sample preparation. Each sample exhibits homogeneous C K-edge XANES spectra within the graphite, however, showing no correlation with isotopic heterogeneities. Gradients in the isotope ratios of C, N, O, and Al could be due to both processes during condensation, e.g., mixing in stellar ejecta and granular transport, and post-condensation effects, such as isotope dilution and exchange with isotopically normal material in the early Solar System or laboratory, the latter of which is a significant issue for high-density presolar graphite grains. It remains unknown whether the mechanisms behind isotope exchange would also affect the local chemistry and therefore the XANES spectra. Ti L-edge XANES from most Ti-rich subgrains match standard spectra for TiC and potentially TiCN. A rare rutile (TiO2) subgrain has been identified, though it lacks the lowest energy L3 peak typically seen in standard spectra. Ca has also been identified by EDXS in TiC subgrains, likely due to the decay of live 44Ti at the time of formation. Future NanoSIMS measurements will determine the variability of initial 44Ti in TiC subgrains, an important constraint on mixing in the ejecta of the grains' parent supernovae.

A numerical solution of a singular boundary value problem arising in boundary layer theory.

Science.gov (United States)

Hu, Jiancheng

2016-01-01

In this paper, a second-order nonlinear singular boundary value problem is presented, which is equivalent to the well-known Falkner-Skan equation. And the one-dimensional third-order boundary value problem on interval [Formula: see text] is equivalently transformed into a second-order boundary value problem on finite interval [Formula: see text]. The finite difference method is utilized to solve the singular boundary value problem, in which the amount of computational effort is significantly less than the other numerical methods. The numerical solutions obtained by the finite difference method are in agreement with those obtained by previous authors.

HUD GIS Boundary Files

Data.gov (United States)

Department of Housing and Urban Development — The HUD GIS Boundary Files are intended to supplement boundary files available from the U.S. Census Bureau. The files are for community planners interested in...

Magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake

Energy Technology Data Exchange (ETDEWEB)

Chen, Yan; Ming-Wu, Fan [Institute of Atomic Energy, Peking (China)

1984-01-01

A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake.

Bifurcation of solutions to Hamiltonian boundary value problems

Science.gov (United States)

McLachlan, R. I.; Offen, C.

2018-06-01

A bifurcation is a qualitative change in a family of solutions to an equation produced by varying parameters. In contrast to the local bifurcations of dynamical systems that are often related to a change in the number or stability of equilibria, bifurcations of boundary value problems are global in nature and may not be related to any obvious change in dynamical behaviour. Catastrophe theory is a well-developed framework which studies the bifurcations of critical points of functions. In this paper we study the bifurcations of solutions of boundary-value problems for symplectic maps, using the language of (finite-dimensional) singularity theory. We associate certain such problems with a geometric picture involving the intersection of Lagrangian submanifolds, and hence with the critical points of a suitable generating function. Within this framework, we then study the effect of three special cases: (i) some common boundary conditions, such as Dirichlet boundary conditions for second-order systems, restrict the possible types of bifurcations (for example, in generic planar systems only the A-series beginning with folds and cusps can occur); (ii) integrable systems, such as planar Hamiltonian systems, can exhibit a novel periodic pitchfork bifurcation; and (iii) systems with Hamiltonian symmetries or reversing symmetries can exhibit restricted bifurcations associated with the symmetry. This approach offers an alternative to the analysis of critical points in function spaces, typically used in the study of bifurcation of variational problems, and opens the way to the detection of more exotic bifurcations than the simple folds and cusps that are often found in examples.

Two-point functions and logarithmic boundary operators in boundary logarithmic conformal field theories

International Nuclear Information System (INIS)

Ishimoto, Yukitaka

2004-01-01

Amongst conformal field theories, there exist logarithmic conformal field theories such as c p,1 models. We have investigated c p,q models with a boundary in search of logarithmic theories and have found logarithmic solutions of two-point functions in the context of the Coulomb gas picture. We have also found the relations between coefficients in the two-point functions and correlation functions of logarithmic boundary operators, and have confirmed the solutions in [hep-th/0003184]. Other two-point functions and boundary operators have also been studied in the free boson construction of boundary CFT with SU(2) k symmetry in regard to logarithmic theories. This paper is based on a part of D. Phil. Thesis [hep-th/0312160]. (author)

Near shore seismic movements induced by seaquakes using the boundary element method

Institute of Scientific and Technical Information of China (English)

Manuel Carbajal-Romero; Norberto Flores-Guzmán; J.Efraín Rodríguez-Sánchez; Andriy Kryvko

2017-01-01

This study quantifies seismic amplifications in near-shore arising from seaquakes.Within the Boundary Element Method,boundary elements are used to irradiate waves and force densities obtained for each element.Huygens Principle is implemented since the diffracted waves are constructed at the boundary from which they are radiated,which is equivalent to Somigliana's theorem.Application of boundary conditions leads to a system of integral equations of the Fredholm type of second kind and zero order.Several numerical configurations are analyzed:The first is used to verify the present formulation with ideal sea floor configurations to estimate seismic amplifications.With the formulation verified,simple slope configurations are studied to estimate spectra of seismic motions.It is found that P-waves can produce seismic amplifications from 1.2 to 3.9 times the amplitude of the incident wave.SV-waves can generate seismic amplifications up to 4.5 times the incident wave.Another relevant finding is that the highest amplifications are at the shore compared to the ones at the sea floor.

Holographic quantum error-correcting codes: toy models for the bulk/boundary correspondence

Energy Technology Data Exchange (ETDEWEB)

Pastawski, Fernando; Yoshida, Beni [Institute for Quantum Information & Matter and Walter Burke Institute for Theoretical Physics,California Institute of Technology,1200 E. California Blvd., Pasadena CA 91125 (United States); Harlow, Daniel [Princeton Center for Theoretical Science, Princeton University,400 Jadwin Hall, Princeton NJ 08540 (United States); Preskill, John [Institute for Quantum Information & Matter and Walter Burke Institute for Theoretical Physics,California Institute of Technology,1200 E. California Blvd., Pasadena CA 91125 (United States)

2015-06-23

We propose a family of exactly solvable toy models for the AdS/CFT correspondence based on a novel construction of quantum error-correcting codes with a tensor network structure. Our building block is a special type of tensor with maximal entanglement along any bipartition, which gives rise to an isometry from the bulk Hilbert space to the boundary Hilbert space. The entire tensor network is an encoder for a quantum error-correcting code, where the bulk and boundary degrees of freedom may be identified as logical and physical degrees of freedom respectively. These models capture key features of entanglement in the AdS/CFT correspondence; in particular, the Ryu-Takayanagi formula and the negativity of tripartite information are obeyed exactly in many cases. That bulk logical operators can be represented on multiple boundary regions mimics the Rindler-wedge reconstruction of boundary operators from bulk operators, realizing explicitly the quantum error-correcting features of AdS/CFT recently proposed in http://dx.doi.org/10.1007/JHEP04(2015)163.

Influence of minor combined addition of Cr and Pr on microstructure, mechanical properties and corrosion behaviors of an ultrahigh strength Al-Zn-Mg-Cu-Zr alloy.

Science.gov (United States)

Wang, Ming; Huang, Lanping; Chen, Kanghua; Liu, Wensheng

2018-01-01

This work focuses on controlling grain boundary structure in an ultra-high strength Al-8.6Zn-2.5Mg-2.2Cu-0.16Zr (wt.%) alloy by the combined addition of trace Cr (0.1wt.%) and Pr (0.14wt.%), and evaluating mechanical properties and localized corrosion behaviors of the alloy in the peak aged condition. The introduction of trace Cr and Pr leads to the formation of nanoscale Cr, Pr-containing Al 3 Zr and Zr-containing PrCr 2 Al 20 dispersoids which can obviously inhibit the recrystallization and sub-grain growth of the super-high strength Al-Zn-Mg-Cu alloys, and retain the deformation-recovery microstructure dominated by low-angle grain boundaries. The nearly ellipsoidal dispersoids with a size of 10-35nm are discretely distributed and precipitate free zones are hardly formed in low-angle grain boundaries. This new alloy composition exhibits better combined properties, higher resistance to stress corrosion, exfoliation corrosion and inter-granular corrosion with the undamaged strength, ductility and fracture toughness. Copyright © 2017 Elsevier Ltd. All rights reserved.

Protected-area boundaries as filters of plant invasions.

Science.gov (United States)

Foxcroft, Llewellyn C; Jarošík, Vojtěch; Pyšek, Petr; Richardson, David M; Rouget, Mathieu

2011-04-01

Human land uses surrounding protected areas provide propagules for colonization of these areas by non-native species, and corridors between protected-area networks and drainage systems of rivers provide pathways for long-distance dispersal of non-native species. Nevertheless, the influence of protected-area boundaries on colonization of protected areas by invasive non-native species is unknown. We drew on a spatially explicit data set of more than 27,000 non-native plant presence records for South Africa's Kruger National Park to examine the role of boundaries in preventing colonization of protected areas by non-native species. The number of records of non-native invasive plants declined rapidly beyond 1500 m inside the park; thus, we believe that the park boundary limited the spread of non-native plants. The number of non-native invasive plants inside the park was a function of the amount of water runoff, density of major roads, and the presence of natural vegetation outside the park. Of the types of human-induced disturbance, only the density of major roads outside the protected area significantly increased the number of non-native plant records. Our findings suggest that the probability of incursion of invasive plants into protected areas can be quantified reliably. ©2010 Society for Conservation Biology.

Contaminant Boundary at the Faultless Underground Nuclear Test

International Nuclear Information System (INIS)

Greg Pohll; Karl Pohlmann; Jeff Daniels; Ahmed Hassan; Jenny Chapman

2003-01-01

The U.S. Department of Energy (DOE) and the Nevada Division of Environmental Protection (NDEP) have reached agreement on a corrective action strategy applicable to address the extent and potential impact of radionuclide contamination of groundwater at underground nuclear test locations. This strategy is described in detail in the Federal Facility Agreement and Consent Order (FFACO, 2000). As part of the corrective action strategy, the nuclear detonations that occurred underground were identified as geographically distinct corrective action units (CAUs). The strategic objective for each CAU is to estimate over a 1,000-yr time period, with uncertainty quantified, the three-dimensional extent of groundwater contamination that would be considered unsafe for domestic and municipal use. Two types of boundaries (contaminant and compliance) are discussed in the FFACO that will map the three-dimensional extent of radionuclide contamination. The contaminant boundary will identify the region wi th 95 percent certainty that contaminants do not exist above a threshold value. It will be prepared by the DOE and presented to NDEP. The compliance boundary will be produced as a result of negotiation between the DOE and NDEP, and can be coincident with, or differ from, the contaminant boundary. Two different thresholds are considered for the contaminant boundary. One is based on the enforceable National Primary Drinking Water Regulations for radionuclides, which were developed as a requirement of the Safe Drinking Water Act. The other is a risk-based threshold considering applicable lifetime excess cancer-risk-based criteria The contaminant boundary for the Faultless underground nuclear test at the Central Nevada Test Area (CNTA) is calculated using a newly developed groundwater flow and radionuclide transport model that incorporates aspects of both the original three-dimensional model (Pohlmann et al., 1999) and the two-dimensional model developed for the Faultless data decision

Effect of Quenching Rate on Microstructure and Hardness of Al-Zn-Mg-Cu-Cr Alloy Extruded Bar

Directory of Open Access Journals (Sweden)

HAN Su-qi

2017-04-01

Full Text Available The effect of quenching rate on microstructure and hardness of Al-Zn-Mg-Cu-Cr alloy extruded bar was studied by hardness test, scanning electron microscopy and transmission electron microscopy. The results show that at quenching rate below 100℃/s, during the cooling process, the hardness begins to fall significantly; and it decreases by 43% at the quenching rate of 2℃/s. At quenching rate below 100℃/s, the number and size of equilibrium η phase heterogeneously nucleated at(subgrain boundaries and on dispersoids inside grains increase obviously with the decrease of quenching rate, leading to greatly reduced age-hardening response. At the same quenching rate, the equilibrium η phase inside grains is larger than that at grain boundaries. In the range of the studied quenching rates, a quantitative relationship between hardness and equilibrium η phase area fraction has been established.

Radiation-induced segregation in desensitized type 304 austenitic stainless steel

International Nuclear Information System (INIS)

Ahmedabadi, Parag; Kain, V.; Arora, K.; Samajdar, I.; Sharma, S.C.; Bhagwat, P.

2011-01-01

Graphical abstract: Schematic representation of overall experimental and results, indicating attack, after the DL-EPR test, on grain boundaries, twin boundaries and pit-like features within grains at the depth of maximum attack. The sensitized specimen also showed severe attack on grain boundaries, however, attack on twin-boundaries and pit-like features were not noticed. Display Omitted Highlights: → Characterization of radiation-induced segregation done by EPR and AFM examination. → Cr depletion adjacent to carbides due to RIS in irradiated desensitized 304 SS. → Effectiveness as defect sink: twins > pit-like features > grain boundary. - Abstract: Radiation-induced segregation (RIS) in desensitized type 304 stainless steel (SS) was investigated using a combination of electrochemical potentiokinetic reactivation (EPR) test and atomic force microscopy (AFM). Desensitized type 304 SS was irradiated to 0.43 dpa (displacement per atom) using 4.8 MeV protons at 300 deg. C. The maximum attack in the EPR test for the irradiated desensitized SS was measured at a depth of 70 μm from the surface. Grain boundaries and twin boundaries got attacked and pit-like features within the grains were observed after the EPR test at the depth of 70 μm. The depth of attack, as measured by AFM, was higher at grain boundaries and pit-like features as compared to twin boundaries. It has been shown that the chromium depletion due to RIS takes place at the carbide-matrix as well as at the carbide-carbide interfaces at grain boundaries. The width of attack at grain boundaries after the EPR test of the irradiated desensitized specimen appeared larger due to the dislodgement of carbides at grain boundaries.

Radiation-induced segregation in desensitized type 304 austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ahmedabadi, Parag, E-mail: adit@barc.gov.in [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kain, V. [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Arora, K. [PEC University of Technology, Chandigarh (India); Samajdar, I. [Department of Metallurgical Engineering and Materials Science, Indian Institute Technology Bombay, Powai, Mumbai 400 076 (India); Sharma, S.C.; Bhagwat, P. [Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

2011-09-30

Graphical abstract: Schematic representation of overall experimental and results, indicating attack, after the DL-EPR test, on grain boundaries, twin boundaries and pit-like features within grains at the depth of maximum attack. The sensitized specimen also showed severe attack on grain boundaries, however, attack on twin-boundaries and pit-like features were not noticed. Display Omitted Highlights: > Characterization of radiation-induced segregation done by EPR and AFM examination. > Cr depletion adjacent to carbides due to RIS in irradiated desensitized 304 SS. > Effectiveness as defect sink: twins > pit-like features > grain boundary. - Abstract: Radiation-induced segregation (RIS) in desensitized type 304 stainless steel (SS) was investigated using a combination of electrochemical potentiokinetic reactivation (EPR) test and atomic force microscopy (AFM). Desensitized type 304 SS was irradiated to 0.43 dpa (displacement per atom) using 4.8 MeV protons at 300 deg. C. The maximum attack in the EPR test for the irradiated desensitized SS was measured at a depth of 70 {mu}m from the surface. Grain boundaries and twin boundaries got attacked and pit-like features within the grains were observed after the EPR test at the depth of 70 {mu}m. The depth of attack, as measured by AFM, was higher at grain boundaries and pit-like features as compared to twin boundaries. It has been shown that the chromium depletion due to RIS takes place at the carbide-matrix as well as at the carbide-carbide interfaces at grain boundaries. The width of attack at grain boundaries after the EPR test of the irradiated desensitized specimen appeared larger due to the dislodgement of carbides at grain boundaries.

Louisiana Territorial Boundary, Geographic NAD83, LDOTD (1999) [state_boundary_la_LDOTD_1999

Data.gov (United States)

Louisiana Geographic Information Center — The dataset defines the state 'territorial' boundary of Louisiana. The state boundary extends 3 miles out into the Gulf of Mexico from the coastline. This data set...

Allegheny County Municipal Boundaries

Data.gov (United States)

Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset demarcates the municipal boundaries in Allegheny County. Data was created to portray the boundaries of the 130 Municipalities in Allegheny County the...

Boundary Fixed Points, Enhanced Gauge Symmetry and Singular Bundles on K3

CERN Document Server

Fuchs, J; Lerche, Wolfgang; Lütken, C A; Schweigert, C; Walcher, J

2001-01-01

We investigate certain fixed points in the boundary conformal field theory representation of type IIA D-branes on Gepner points of K3. They correspond geometrically to degenerate brane configurations, and physically lead to enhanced gauge symmetries on the world-volume. Non-abelian gauge groups arise if the stabilizer group of the fixed points is realized projectively, which is similar to D-branes on orbifolds with discrete torsion. Moreover, the fixed point boundary states can be resolved into several irreducible components. These correspond to bound states at threshold and can be viewed as (non-locally free) sub-sheaves of semi-stable sheaves. Thus, the BCFT fixed points appear to carry two-fold geometrical information: on the one hand they probe the boundary of the instanton moduli space on K3, on the other hand they probe discrete torsion in D-geometry.

Numerical simulation of two-dimensional flows over a circular cylinder using the immersed boundary method

International Nuclear Information System (INIS)

Lima E Silva, A.L.F.; Silveira-Neto, A.; Damasceno, J.J.R.

2003-01-01

In this work, a virtual boundary method is applied to the numerical simulation of a uniform flow over a cylinder. The force source term, added to the two-dimensional Navier-Stokes equations, guarantees the imposition of the no-slip boundary condition over the body-fluid interface. These equations are discretized, using the finite differences method. The immersed boundary is represented with a finite number of Lagrangian points, distributed over the solid-fluid interface. A Cartesian grid is used to solve the fluid flow equations. The key idea is to propose a method to calculate the interfacial force without ad hoc constants that should usually be adjusted for the type of flow and the type of the numerical method, when this kind of model is used. In the present work, this force is calculated using the Navier-Stokes equations applied to the Lagrangian points and then distributed over the Eulerian grid. The main advantage of this approach is that it enables calculation of this force field, even if the interface is moving or deforming. It is unnecessary to locate the Eulerian grid points near this immersed boundary. The lift and drag coefficients and the Strouhal number, calculated for an immersed cylinder, are compared with previous experimental and numerical results, for different Reynolds numbers

Boundary Drawing in Clinical Work

DEFF Research Database (Denmark)

Meier, Ninna

The aim of this paper is to show how health care professionals temporarily dissolve and redraw boundaries in their everyday work, in order to coordinate clinical work and facilitate collaboration in patient pathways. Boundaries are social constructions that help us make sense of our complex, social...... world. In health care, formal boundaries are important distinctions that separate health care practitioners into medical specialties, professions and organizational departments. But clinical work also relies on the ability of health care practitioners to collaborate around patients in formal...... arrangements or emergent, temporary teams. Focusing on the cognitive and social boundaries we draw to establish identity and connection (to a profession, team or person) the paper shows how health care professionals can use inter-personal relationships to temporarily dismiss formal boundaries. By redrawing...

Prediction of dislocation boundary characteristics

DEFF Research Database (Denmark)

Winther, Grethe

Plastic deformation of both fcc and bcc metals of medium to high stacking fault energy is known to result in dislocation patterning in the form of cells and extended planar dislocation boundaries. The latter align with specific crystallographic planes, which depend on the crystallographic......) and it is found that to a large extent the dislocations screen each other’s elastic stress fields [3]. The present contribution aims at advancing the previous theoretical analysis of a boundary on a known crystallographic plane to actual prediction of this plane as well as other boundary characteristics....... Crystal plasticity calculations combined with the hypothesis that these boundaries separate domains with local differences in the slip system activity are introduced to address precise prediction of the experimentally observed boundaries. The presentation will focus on two cases from fcc metals...

Professional boundary violations: a literature review.

Science.gov (United States)

Manfrin-Ledet, Linda; Porche, Demetrius J; Eymard, Amanda S

2015-06-01

The purpose of this article is to review the nursing literature related to professional boundary violations in nursing. A search was conducted using CINAHL, MEDLINE, Ebscohost, and NCSBN. The key words searched were professional boundaries, boundary violation, boundary crossings, nurse, home health nurses, and home nursing. The search returned over 40 publications related specifically to boundary violations and nursing although only four of them are published research studies and one as a dissertation. Seven common characteristics emerged from the nonresearch nursing articles on professional boundaries: (1) Dual relations/role reversal, (2) Gifts and money, (3) Excessive self-disclosure, (4) Secretive behavior, (5) Excessive attention/overinvolvement, (6) Sexual behavior, and (7) Social media. Additional nursing research is greatly needed in the area of professional boundaries. The nurse-patient relationship should always be maintained for the benefit of the patient and not the personal gain of the nurse. Ongoing education in nursing practice regarding professional boundaries is needed. Nurses need to be mindful of state practice acts, codes of conduct, and employer policies.

Quantum Gravitational Effects on the Boundary

Science.gov (United States)

James, F.; Park, I. Y.

2018-04-01

Quantum gravitational effects might hold the key to some of the outstanding problems in theoretical physics. We analyze the perturbative quantum effects on the boundary of a gravitational system and the Dirichlet boundary condition imposed at the classical level. Our analysis reveals that for a black hole solution, there is a contradiction between the quantum effects and the Dirichlet boundary condition: the black hole solution of the one-particle-irreducible action no longer satisfies the Dirichlet boundary condition as would be expected without going into details. The analysis also suggests that the tension between the Dirichlet boundary condition and loop effects is connected with a certain mechanism of information storage on the boundary.

Mapping travelling convection vortex events with respect to energetic particle boundaries

Directory of Open Access Journals (Sweden)

T. Moretto

1998-08-01

Full Text Available Thirteen events of high-latitude ionospheric travelling convection vortices during very quiet conditions were identified in the Greenland magnetometer data during 1990 and 1991. The latitudes of the vortex centres for these events are compared to the energetic electron trapping boundaries as identified by the particle measurements of the NOAA 10 satellite. In addition, for all events at least one close DMSP overpass was available. All but one of the 13 cases agree to an exceptional degree that: the TCV centres are located within the region of trapped, high energy electrons close to the trapping boundary for the population of electrons with energy greater than >100 keV. Correspondingly, from the DMSP data they are located within the region of plasmasheet-type precipitation close to the CPS/BPS precipitation boundary. That is, the TCV centres map to deep inside the magnetosphere and not to the magnetopause.Key Words. Ionosphere (Electric fields and currents; Particle precipitation · Magnetospheric physics (Magnetosphere-ionosphere interaction

DDF construction and D-brane boundary states in pure spinor formalism

International Nuclear Information System (INIS)

Mukhopadhyay, Partha

2006-01-01

Open string boundary conditions for non-BPS D-branes in type II string theories discussed in hep-th/0505157 give rise to two sectors with integer (R sector) and half-integer (NS sector) modes for the combined fermionic matter and bosonic ghost variables in pure spinor formalism. Exploiting the manifest supersymmetry of the formalism we explicitly construct the DDF (Del Giudice, Di Vecchia, Fubini) states in both the sectors which are in one-to-one correspondence with the states in light-cone Green-Schwarz formalism. We also give a proof of validity of this construction. A similar construction in the closed string sector enables us to define a physical Hilbert space in pure spinor formalism which is used to project the covariant boundary states of both the BPS and non-BPS instantonic D-branes. These projected boundary states take exactly the same form as those found in light-cone Green-Schwarz formalism and are suitable for computing the cylinder diagram with manifest open-closed duality

Self-adjoint elliptic operators with boundary conditions on not closed hypersurfaces

Science.gov (United States)

Mantile, Andrea; Posilicano, Andrea; Sini, Mourad

2016-07-01

The theory of self-adjoint extensions of symmetric operators is used to construct self-adjoint realizations of a second-order elliptic differential operator on Rn with linear boundary conditions on (a relatively open part of) a compact hypersurface. Our approach allows to obtain Kreĭn-like resolvent formulae where the reference operator coincides with the ;free; operator with domain H2 (Rn); this provides an useful tool for the scattering problem from a hypersurface. Concrete examples of this construction are developed in connection with the standard boundary conditions, Dirichlet, Neumann, Robin, δ and δ‧-type, assigned either on a (n - 1) dimensional compact boundary Γ = ∂ Ω or on a relatively open part Σ ⊂ Γ. Schatten-von Neumann estimates for the difference of the powers of resolvents of the free and the perturbed operators are also proven; these give existence and completeness of the wave operators of the associated scattering systems.

The boundary-scan handbook

CERN Document Server

Parker, Kenneth P

2016-01-01

Aimed at electronics industry professionals, this 4th edition of the Boundary Scan Handbook describes recent changes to the IEEE1149.1 Standard Test Access Port and Boundary-Scan Architecture. This updated edition features new chapters on the possible effects of the changes on the work of the practicing test engineers and the new 1149.8.1 standard. Anyone needing to understand the basics of boundary scan and its practical industrial implementation will need this book. Provides an overview of the recent changes to the 1149.1 standard and the effect of the changes on the work of test engineers;   Explains the new IEEE 1149.8.1 subsidiary standard and applications;   Describes the latest updates on the supplementary IEEE testing standards. In particular, addresses: IEEE Std 1149.1                      Digital Boundary-Scan IEEE Std 1149.4                      Analog Boundary-Scan IEEE Std 1149.6                      Advanced I/O Testing IEEE Std 1149.8.1           �...

Blurring Boundaries

DEFF Research Database (Denmark)

Neergaard, Ulla; Nielsen, Ruth

2010-01-01

of welfare functions into EU law both from an internal market law and a constitutional law perspective. The main problem areas covered by the Blurring Boundaries project were studied in sub-projects on: 1) Internal market law and welfare services; 2) Fundamental rights and non-discrimination law aspects......; and 3) Services of general interest. In the Blurring Boundaries project, three aspects of the European Social Model have been particularly highlighted: the constitutionalisation of the European Social Model, its multi-level legal character, and the clash between market access justice at EU level...... and distributive justice at national level....

On the elastic stiffness of grain boundaries

International Nuclear Information System (INIS)

Zhang Tongyi; Hack, J.E.

1992-01-01

The elastic softening of grain boundaries is evaluated from the starting point of grain boundary energy. Several examples are given to illustrate the relationship between boundary energy and the extent of softening. In general, a high grain boundary energy is associated with a large excess atomic volume in the boundary region. The consequent reduction in grain boundary stiffness can represent a significant fraction of that observed in bulk crystals. (orig.)

Method of making quasi-grain boundary-free polycrystalline solar cell structure and solar cell structure obtained thereby

Science.gov (United States)

Gonzalez, Franklin N.; Neugroschel, Arnost

1984-02-14

A new solar cell structure is provided which will increase the efficiency of polycrystalline solar cells by suppressing or completely eliminating the recombination losses due to the presence of grain boundaries. This is achieved by avoiding the formation of the p-n junction (or other types of junctions) in the grain boundaries and by eliminating the grain boundaries from the active area of the cell. This basic concept can be applied to any polycrystalline material; however, it will be most beneficial for cost-effective materials having small grains, including thin film materials.

Interplanetary sector boundaries 1971--1973

International Nuclear Information System (INIS)

Klein, L.; Burlaga, L.F.

1980-01-01

Eighteen interplanetary sector boundary crossings observed at 1 AU during the period January 1971 to January 1974 by the magnetometer on the Imp 6 spacecraft was discussed. The events were examined on many different time scales ranging from days on either side of the boundary to high-resolution measurements of 12.5 vectors per second. Two categories of boundaries were found, one group being relatively thin (averaging approx. =10 4 km) and the other being thick (averaging approx. =10 6 km). In many cases the field vector rotated in a plane from polarity to the other. Only two of the transitions were null sheets. Using the minimum variance analysis to determine the normals to the plane of rotationa and assuming that this is the same as the normal to the sector boundary surface, it was found that the normals were close to ( 0 ) the ecliptic plane. The high inclination of the sector boundary surfaces during 1971--1973 verifies a published prediction and may be related to the presence of large equatorial coronal holes at this time. An analysis of tangential discontinuities contained in 4-day periods about our events showed that their orientations were generally not related to the orientations of the sector boundary surface, but rather their characteristics were about the same as those for discontinuities outside the sector boundaries. Magnetic holes were found in thick sector boundaries, at a rate about 3 times that elsewhere. The holes were especially prevalent near stream interfaces, suggesting that they might be related to the convergence and/or slip of adjacent solar wind streams

Creating technological boundaries to protect bedtime: examining work-home boundary management, psychological detachment and sleep.

Science.gov (United States)

Barber, Larissa K; Jenkins, Jade S

2014-08-01

This study examined the mechanism by which information and communication technology (ICT) use at home for work purposes may affect sleep. In this investigation, data from 315 employees were used to examine the indirect effect of ICT use at home on sleep outcomes through psychological detachment, and how boundary creation may moderate this effect. Results revealed the indirect effect of increased work-home boundary crossing on sleep (quantity, quality and consistency) through psychological detachment occurred only among individuals with low boundaries around ICT use and not among those with high boundaries. These results suggest that creating boundaries around work-relevant ICT use while at home is beneficial to sleep as a recovery process through being able to psychologically disengage from work. Copyright © 2013 John Wiley & Sons, Ltd.

Stable Boundary Layer Issues

NARCIS (Netherlands)

Steeneveld, G.J.

2012-01-01

Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

Ferroelectric domain continuity over grain boundaries

DEFF Research Database (Denmark)

Mantri, Sukriti; Oddershede, Jette; Damjanovic, Dragan

2017-01-01

Formation and mobility of domain walls in ferroelectric materials is responsible for many of their electrical and mechanical properties. Domain wall continuity across grain boundaries has been observed since the 1950's and is speculated to affect the grain boundary-domain interactions, thereby...... impacting macroscopic ferroelectric properties in polycrystalline systems. However detailed studies of such correlated domain structures across grain boundaries are limited. In this work, we have developed the mathematical requirements for domain wall plane matching at grain boundaries of any given...... orientation. We have also incorporated the effect of grain boundary ferroelectric polarization charge created when any two domains meet at the grain boundary plane. The probability of domain wall continuity for three specific grain misorientations is studied. Use of this knowledge to optimize processing...

A Semianalytical Model for Pumping Tests in Finite Heterogeneous Confined Aquifers With Arbitrarily Shaped Boundary

Science.gov (United States)

Wang, Lei; Dai, Cheng; Xue, Liang

2018-04-01

This study presents a Laplace-transform-based boundary element method to model the groundwater flow in a heterogeneous confined finite aquifer with arbitrarily shaped boundaries. The boundary condition can be Dirichlet, Neumann or Robin-type. The derived solution is analytical since it is obtained through the Green's function method within the domain. However, the numerical approximation is required on the boundaries, which essentially renders it a semi-analytical solution. The proposed method can provide a general framework to derive solutions for zoned heterogeneous confined aquifers with arbitrarily shaped boundary. The requirement of the boundary element method presented here is that the Green function must exist for a specific PDE equation. In this study, the linear equations for the two-zone and three-zone confined aquifers with arbitrarily shaped boundary is established in Laplace space, and the solution can be obtained by using any linear solver. Stehfest inversion algorithm can be used to transform it back into time domain to obtain the transient solution. The presented solution is validated in the two-zone cases by reducing the arbitrarily shaped boundaries to circular ones and comparing it with the solution in Lin et al. (2016, https://doi.org/10.1016/j.jhydrol.2016.07.028). The effect of boundary shape and well location on dimensionless drawdown in two-zone aquifers is investigated. Finally the drawdown distribution in three-zone aquifers with arbitrarily shaped boundary for constant-rate tests (CRT) and flow rate distribution for constant-head tests (CHT) are analyzed.

Experimental study on effects of inlet boundary layer thickness and boundary layer fence in a turbine cascade

International Nuclear Information System (INIS)

Jun, Y. M.; Chung, J. T.

2000-01-01

The working fluid from the combustor to the turbine stage of a gas turbine makes various boundary layer thickness. Since the inlet boundary layer thickness is one of the important factors that affect the turbine efficiency, It is necessary to investigate secondary flow and loss with various boundary layer thickness conditions. In the present study, the effect of various inlet boundary layer thickness on secondary flow and loss and the proper height of the boundary layer fences for various boundary layer thickness were investigated. Measurements of secondary flow velocity and total pressure loss within and downstream of the passage were taken under 5 boundary layer thickness conditions, 16, 36, 52, 69, 110mm. It was found that total pressure loss and secondary flow areas were increased with increase of thickness but they were maintained almost at the same position. At the following research about the boundary layer fences, 1/6, 1/3, 1/2 of each inlet boundary layer thickness and 12mm were used as the fence heights. As a result, it was observed that the proper height of the fences was generally constant since the passage vortex remained almost at the same position. Therefore once the geometry of a cascade is decided, the location of the passage vortex and the proper fence height are appeared to be determined at the same time. When the inlet boundary layer thickness is relatively small, the loss caused by the proper fence becomes bigger than end wall loss so that it dominates secondary loss. In these cases the proper fence height is decided not by the cascade geometry but by the inlet boundary layer thickness as previous investigations

Boundary Management Preferences, Boundary Control, and Work-Life Balance among Full-Time Employed Professionals in Knowledge-Intensive, Flexible Work

Directory of Open Access Journals (Sweden)

Christin Mellner

2015-01-01

Full Text Available Profound changes are taking place within working life, where established boundaries between work and personal life are challenged by increased global competition, ever-faster changing markets, and rapid development of boundary transcending information and communication technologies (ICT. The aim of this study was to investigate boundary management preferences in terms of keeping work and personal life domains separated or integrated, that is, segmenting or blending of domains, the perception of being in control of one´s preferred boundaries, and work-life balance among employees at a Swedish telecom company (N = 1,238, response rate 65%, men 73%, mean age 42 years. Psychosocial work factors, individual characteristics, sociodemographic factors, and work-life balance were investigated in relation to boundary management preferences and perceived boundary control. For high boundary control among segmenters, nearly all the studied psychosocial work factors were significant. Among integrators, this was the case only for clear expectations in work. For both groups, the individual capacity for self-regulation was associated with high boundary control. Regarding sociodemographic factors, cohabiting women with children who preferred segmentation had low boundary control. Finally, there was a main effect of boundary control on work-life balance. In particular, male segmenters perceiving high boundary control had better work-life balance than all others. Conclusions of the study are that segmenters need external boundaries in work for succesful boundary management. Moreover, self-regulation seems a crucial boundary competence in knowledge- intensive, flexible work. Results are of value for health promotion in modern work organizations in supporting employees achieving successful boundary control and subsequent work-life balance.

Matrix factorisations for rational boundary conditions by defect fusion

International Nuclear Information System (INIS)

Behr, Nicolas; Fredenhagen, Stefan

2015-01-01

A large class of two-dimensional N=(2,2) superconformal field theories can be understood as IR fixed-points of Landau-Ginzburg models. In particular, there are rational conformal field theories that also have a Landau-Ginzburg description. To understand better the relation between the structures in the rational conformal field theory and in the Landau-Ginzburg theory, we investigate how rational B-type boundary conditions are realised as matrix factorisations in the SU(3)/U(2) Grassmannian Kazama-Suzuki model. As a tool to generate the matrix factorisations we make use of a particular interface between the Kazama-Suzuki model and products of minimal models, whose fusion can be realised as a simple functor on ring modules. This allows us to formulate a proposal for all matrix factorisations corresponding to rational boundary conditions in the SU(3)/U(2) model.

Matrix factorisations for rational boundary conditions by defect fusion

Energy Technology Data Exchange (ETDEWEB)

Behr, Nicolas [Department of Mathematics, Heriot-Watt University,Riccarton, Edinburgh, EH14 4AS (United Kingdom); Maxwell Institute for Mathematical Sciences,Edinburgh (United Kingdom); Fredenhagen, Stefan [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut,D-14424 Golm (Germany)

2015-05-11

A large class of two-dimensional N=(2,2) superconformal field theories can be understood as IR fixed-points of Landau-Ginzburg models. In particular, there are rational conformal field theories that also have a Landau-Ginzburg description. To understand better the relation between the structures in the rational conformal field theory and in the Landau-Ginzburg theory, we investigate how rational B-type boundary conditions are realised as matrix factorisations in the SU(3)/U(2) Grassmannian Kazama-Suzuki model. As a tool to generate the matrix factorisations we make use of a particular interface between the Kazama-Suzuki model and products of minimal models, whose fusion can be realised as a simple functor on ring modules. This allows us to formulate a proposal for all matrix factorisations corresponding to rational boundary conditions in the SU(3)/U(2) model.

Boundary Control of Linear Evolution PDEs - Continuous and Discrete

DEFF Research Database (Denmark)

Rasmussen, Jan Marthedal

2004-01-01

Consider a partial di erential equation (PDE) of evolution type, such as the wave equation or the heat equation. Assume now that you can influence the behavior of the solution by setting the boundary conditions as you please. This is boundary control in a broad sense. A substantial amount...... of literature exists in the area of theoretical results concerning control of partial differential equations. The results have included existence and uniqueness of controls, minimum time requirements, regularity of domains, and many others. Another huge research field is that of control theory for ordinary di...... erential equations. This field has mostly concerned engineers and others with practical applications in mind. This thesis makes an attempt to bridge the two research areas. More specifically, we make finite dimensional approximations to certain evolution PDEs, and analyze how properties of the discrete...

Large eddy simulation of atmospheric boundary layer over wind farms using a prescribed boundary layer approach

DEFF Research Database (Denmark)

Chivaee, Hamid Sarlak; Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming

2012-01-01

Large eddy simulation (LES) of flow in a wind farm is studied in neutral as well as thermally stratified atmospheric boundary layer (ABL). An approach has been practiced to simulate the flow in a fully developed wind farm boundary layer. The approach is based on the Immersed Boundary Method (IBM......) and involves implementation of an arbitrary prescribed initial boundary layer (See [1]). A prescribed initial boundary layer profile is enforced through the computational domain using body forces to maintain a desired flow field. The body forces are then stored and applied on the domain through the simulation...... and the boundary layer shape will be modified due to the interaction of the turbine wakes and buoyancy contributions. The implemented method is capable of capturing the most important features of wakes of wind farms [1] while having the advantage of resolving the wall layer with a coarser grid than typically...

Investigation and optimization of YBa2Cu3O7-δ grain boundaries and coated conductors

International Nuclear Information System (INIS)

Held, Rainer Robert Martin

2010-01-01

With increasing misorientation angle grain boundaries strongly reduce the critical current density of high temperature superconductors. For this reason costly techniques are used in production of modern Coated Conductors to induce sharp textures in the polycrystalline superconductor layers. In this dissertation measurements of the critical current density of different grain boundary types are presented showing that out-of-plane grain boundaries exhibit, also in applied magnetic fields, much higher critical current densities than expected. In further analysis of the grain boundaries indications for a microstructural reason of the high critical current densities were found. The high critical current densities of the out-of-plane grain boundaries should in fabrication of Coated Conductors allow for a relaxation of the out-of-plane grain alignment requirements and a concomitant cost reduction. In this work also results of a industrial cooperation with Nexans are presented demonstrating that the critical current density of metal-organic deposited grain boundaries and Coated Conductor layers can be increased by selective Calcium-doping. In the experiments selective Calcium-doping most effectively increased the critical current density of weak spots. (orig.)

Boundary element methods applied to two-dimensional neutron diffusion problems

International Nuclear Information System (INIS)

Itagaki, Masafumi

1985-01-01

The Boundary element method (BEM) has been applied to two-dimensional neutron diffusion problems. The boundary integral equation and its discretized form have been derived. Some numerical techniques have been developed, which can be applied to critical and fixed-source problems including multi-region ones. Two types of test programs have been developed according to whether the 'zero-determinant search' or the 'source iteration' technique is adopted for criticality search. Both programs require only the fluxes and currents on boundaries as the unknown variables. The former allows a reduction in computing time and memory in comparison with the finite element method (FEM). The latter is not always efficient in terms of computing time due to the domain integral related to the inhomogeneous source term; however, this domain integral can be replaced by the equivalent boundary integral for a region with a non-multiplying medium or with a uniform source, resulting in a significant reduction in computing time. The BEM, as well as the FEM, is well suited for solving irregular geometrical problems for which the finite difference method (FDM) is unsuited. The BEM also solves problems with infinite domains, which cannot be solved by the ordinary FEM and FDM. Some simple test calculations are made to compare the BEM with the FEM and FDM, and discussions are made concerning the relative merits of the BEM and problems requiring future solution. (author)

On some boundary value problems in quantum statistical mechanics

International Nuclear Information System (INIS)

Angelescu, N.

1978-01-01

The following two topics of equilibrium quantum statistical mechanics are discussed in this thesis: (i) the independence of the thermodynamic limit of grand-canonical pressure on the boundary conditions; (ii) the magnetic properties of free quantum gases. Problem (i) is handled with a functional integration technique. Wiener-type conditional measures are constructed for a given domain and a general class of mixed conditions on its boundary, these measures are used to write down Feynman-Kac formulae for the kernels of exp(-βH), where H is the Hamiltonian of N interacting particles in the given domain. These measures share the property that they assign the same mass as the usual Wiener measure to any set of trajectories not intersecting the boundary. Local estimates on the kernels of exp(-βH) are derived, which imply independence of the pressure on the boundary conditions in the thermodynamic limit. Problem (ii) has a historical development: since Landau's work (1930), much discussion has been devoted to the influence of the finite size on the susceptibility. In finite volume, Dirichlet boundary conditions are imposed, on the ground that they ensure gauge invariance. The thermodynamic limit of the pressure is proved, using again functional integration. The functional measure is now complex but absolutely continuous with respect to Wiener measure, so the usual local estimates hold true. The controversy in the literature was concentrated on the commutativity of the operations of H-derivation and thermodynamic limit, so the existence of this limit for the zero-field susceptibility and its surface term are proved separately, demonstrating this commutativity. The proof relies on the following result of independent interest: the perturbation theory of self-adjoint trace-class semigroups is trace-class convergent and analytic. (author)

Tricritical Ising model with a boundary

International Nuclear Information System (INIS)

De Martino, A.; Moriconi, M.

1998-03-01

We study the integrable and supersymmetric massive φ (1,3) deformation of the tricritical Ising model in the presence of a boundary. We use constraints from supersymmetry in order to compute the exact boundary S-matrices, which turn out to depend explicitly on the topological charge of the supersymmetry algebra. We also solve the general boundary Yang-Baxter equation and show that in appropriate limits the general reflection matrices go over the supersymmetry preserving solutions. Finally, we briefly discuss the possible connection between our reflection matrices and boundary perturbations within the framework of perturbed boundary conformal field theory. (author)

Improvement of corrosion resistance in austenitic stainless steel by grain boundary character distribution control

International Nuclear Information System (INIS)

Wang, Yun; Kaneda, Junya; Kasahara, Shigeki; Shigenaka, Naoto

2012-01-01

Strauss test, Coriou test and Huey test were conducted on a Type 316L austenitic stainless steel. Improvement in grain boundary corrosion resistance was verified after raising low Σ coincidence site lattice (CSL) grain boundary (GB) frequency by controlling grain boundary character distribution (GBCD). During crevice corrosion test under gamma-ray irradiation, initiation frequency of GB corrosion after GBCD controlled specimens decreased to 1/10 of GBCD uncontrolled counterpart along with lower depth of corrosion. Stress corrosion cracking (SCC) propagation rate of GBCD controlled specimen decreased to less than 1/2 of GBCD uncontrolled specimen in high temperature and high pressure water. Based on these results, we expect that GBCD control will improve corrosion resistance of austenitic material in a wide range of application and environment. (author)

Grain boundary segregation and intergranular failure

International Nuclear Information System (INIS)

White, C.L.

1980-01-01

Trace elements and impurities often segregate strongly to grain boundaries in metals and alloys. Concentrations of these elements at grain boundaries are often 10 3 to 10 5 times as great as their overall concentration in the alloy. Because of such segregation, certain trace elements can exert a disproportionate influence on material properties. One frequently observed consequence of trace element segregation to grain boundaries is the occurrence of grain boundary failure and low ductility. Less well known are incidences of improved ductility and inhibition of grain boundary fracture resulting from trace element segregation to grain boundaries in certain systems. An overview of trace element segregation and intergranular failure in a variety of alloy systems as well as preliminary results from studies on Al 3% Li will be presented

Diffusion mechanisms in grain boundaries in solids

International Nuclear Information System (INIS)

Peterson, N.L.

1982-01-01

A critical review is given of our current knowledge of grain-boundary diffusion in solids. A pipe mechanism of diffusion based on the well-established dislocation model seems most appropriate for small-angle boundaries. Open channels, which have atomic configurations somewhat like dislocation cores, probably play a major role in large-angle grain-boundary diffusion. Dissociated dislocations and stacking faults are not efficient paths for grain-boundary diffusion. The diffusion and computer modeling experiments are consistent with a vacancy mechanism of diffusion by a rather well-localized vacancy. The effective width of a boundary for grain-boundary diffusion is about two atomic planes. These general features of grain-boundary diffusion, deduced primarily from experiments on metals, are thought to be equally applicable for pure ceramic solids. The ionic character of many ceramic oxides may cause some differences in grain-boundary structure from that observed in metals, resulting in changes in grain-boundary diffusion behavior. 72 references, 5 figures

Order-disorder transformations in the Σ3 (111)/[110] symmetrical tilt boundary in tungsten

International Nuclear Information System (INIS)

Wang, G.J.; Vitek, V.

1996-01-01

The structure of the Σ3 (111)/[110] symmetrical tilt boundary in tungsten was modeled by molecular statics using Finnis-Sinclair type many body potentials. Several multiple structures have been found which are composed of two types of structural units and the interaction energy between these units is negative. Hence, order-disorder structural transitions may occur in the boundary with structures being ordered and/or disordered mixtures of the two units. the transition temperature is found to be 1,158 K if only the internal energy and configurational entropy are included when evaluating the free energy. However, the transition temperature is 782 K if the vibrational entropy is also incorporated. This demonstrates that the vibrational contribution to the entropy may be as important as the configurational contribution when considering the interfacial transformations

Empirical reconstruction and long-duration tracking of the magnetospheric boundary in single- and multi-spacecraft contexts

Directory of Open Access Journals (Sweden)

J. De Keyser

2005-06-01

Full Text Available The magnetospheric boundary is always moving, making it difficult to establish its structure. This paper presents a novel method for tracking the motion of the boundary, based on in-situ observations of the plasma velocity and of one or more additional observables. This method allows the moving boundary to be followed for extended periods of time (up to several hours and aptly deals with limitations on the time resolution of the data, with measurement errors, and with occasional data gaps; it can exploit data from any number of spacecraft and any type of instrument. At the same time the method is an empirical reconstruction technique that determines the one-dimensional spatial structure of the boundary. The method is illustrated with single- and multi-spacecraft applications using data from Ampte/Irm and Cluster.

A magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake

International Nuclear Information System (INIS)

Yan Chen; Fan Ming-Wu

1984-01-01

A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake

High order methods for incompressible fluid flow: Application to moving boundary problems

Energy Technology Data Exchange (ETDEWEB)

Bjoentegaard, Tormod

2008-04-15

Fluid flows with moving boundaries are encountered in a large number of real life situations, with two such types being fluid-structure interaction and free-surface flows. Fluid-structure phenomena are for instance apparent in many hydrodynamic applications; wave effects on offshore structures, sloshing and fluid induced vibrations, and aeroelasticity; flutter and dynamic response. Free-surface flows can be considered as a special case of a fluid-fluid interaction where one of the fluids are practically inviscid, such as air. This type of flows arise in many disciplines such as marine hydrodynamics, chemical engineering, material processing, and geophysics. The driving forces for free-surface flows may be of large scale such as gravity or inertial forces, or forces due to surface tension which operate on a much smaller scale. Free-surface flows with surface tension as a driving mechanism include the flow of bubbles and droplets, and the evolution of capillary waves. In this work we consider incompressible fluid flow, which are governed by the incompressible Navier-Stokes equations. There are several challenges when simulating moving boundary problems numerically, and these include - Spatial discretization - Temporal discretization - Imposition of boundary conditions - Solution strategy for the linear equations. These are some of the issues which will be addressed in this introduction. We will first formulate the problem in the arbitrary Lagrangian-Eulerian framework, and introduce the weak formulation of the problem. Next, we discuss the spatial and temporal discretization before we move to the imposition of surface tension boundary conditions. In the final section we discuss the solution of the resulting linear system of equations. (Author). refs., figs., tabs

Fuselage Boundary Layer Ingestion Propulsion Applied to a Thin Haul Commuter Aircraft for Optimal Efficiency

Science.gov (United States)

Mikic, Gregor Veble; Stoll, Alex; Bevirt, JoeBen; Grah, Rok; Moore, Mark D.

2016-01-01

Theoretical and numerical aspects of aerodynamic efficiency of propulsion systems are studied. Focus is on types of propulsion that closely couples to the aerodynamics of the complete vehicle. We discuss the effects of local flow fields, which are affected both by conservative flow acceleration as well as total pressure losses, on the efficiency of boundary layer immersed propulsion devices. We introduce the concept of a boundary layer retardation turbine that helps reduce skin friction over the fuselage. We numerically investigate efficiency gains offered by boundary layer and wake interacting devices. We discuss the results in terms of a total energy consumption framework and show that efficiency gains offered depend on all the elements of the propulsion system.

The atmospheric boundary layer over land and sea: Focus on the off-shore Southern Baltic and Southern North Sea region

DEFF Research Database (Denmark)

Larsen, Søren Ejling

Lecture notes for a short course on the ideal atmospheric boundary layer and its characteristics for different types of real boundary layers, aiming at a discussion of the coastal conditions at the Southern Baltic and North Sea region. The notes are aimed at young scientists (e.g. PhD students......) that study the physics of the atmospheric boundary layer with the purpose of applying this knowledge for remote sensing techniques within offshore wind energy....

Numerical study of the atomic and electronic structure of some silicon grain boundaries

International Nuclear Information System (INIS)

Torrent, M.

1996-01-01

This work contributes to the theoretical study of extended defects in covalent materials. The study is especially devoted to the tilt grain boundaries in silicon as a model material. The theoretical model is based on the self-consistent tight-binding approximation and is applied within two numerical techniques: the fast 'order N' density-matrix method and the diagonalization technique which allows the sampling of the reciprocal space. Total energy parameters of the model have been fitted in order to reproduce the silicon band structure (with a correct gap value) and the transferability of crystalline and mechanical properties of this material. A new type of boundary conditions is proposed and tested. These conditions, named 'ante-periodic' or 'Moebius', allow only one grain boundary per box instead of two and decrease the CPU time by a factor of two. The model is then applied to the study of the Σ=25 [001] (710) grain boundary. The results show the possible presence in this boundary of low energy non-reconstructed atomic structures which are electrically active. This confirms what had been suggested by some experimental observations. The same study is also performed for the Σ=13 [001] (510) grain boundary. In order to compare the intrinsic electrical activity in the previous grain boundaries with the one induced by impurities, a total energy parametrization for the silicon-nickel bond is achieved and used in preliminary calculations. Finally the two variants of the Σ=11 [011] (2-33) interface are studied, especially their respective interfacial energies. The result disagrees with previous calculations using phenomenological potentials. (author)

Practical boundary surveying legal and technical principles

CERN Document Server

Gay, Paul

2015-01-01

This guide to boundary surveying provides landowners, land surveyors, students and others with the necessary foundation to understand boundary surveying techniques and the common legal issues that govern boundary establishment.  Boundary surveying is sometimes mistakenly considered a strictly technical discipline with simple and straightforward technical solutions.  In reality, boundary establishment is often a difficult and complex matter, requiring years of experience and a thorough understanding of boundary law.  This book helps readers to understand the challenges often encountered by boundary surveyors and some of the available solutions. Using only simple and logically explained mathematics, the principles and practice of boundary surveying are demystified for those without prior experience, and the focused coverage of pivotal issues such as easements and setting lot corners will aid even licensed practitioners in untangling thorny cases. Practical advice on using both basic and advanced instruments ...

On two-point boundary correlations in the six-vertex model with domain wall boundary conditions

Science.gov (United States)

Colomo, F.; Pronko, A. G.

2005-05-01

The six-vertex model with domain wall boundary conditions on an N × N square lattice is considered. The two-point correlation function describing the probability of having two vertices in a given state at opposite (top and bottom) boundaries of the lattice is calculated. It is shown that this two-point boundary correlator is expressible in a very simple way in terms of the one-point boundary correlators of the model on N × N and (N - 1) × (N - 1) lattices. In alternating sign matrix (ASM) language this result implies that the doubly refined x-enumerations of ASMs are just appropriate combinations of the singly refined ones.

Elliptic boundary value problems with fractional regularity data the first order approach

CERN Document Server

Amenta, Alex

2018-01-01

In this monograph the authors study the well-posedness of boundary value problems of Dirichlet and Neumann type for elliptic systems on the upper half-space with coefficients independent of the transversal variable and with boundary data in fractional Hardy-Sobolev and Besov spaces. The authors use the so-called "first order approach" which uses minimal assumptions on the coefficients and thus allows for complex coefficients and for systems of equations. This self-contained exposition of the first order approach offers new results with detailed proofs in a clear and accessible way and will become a valuable reference for graduate students and researchers working in partial differential equations and harmonic analysis.

Boundary fluxes for nonlocal diffusion

Science.gov (United States)

Cortazar, Carmen; Elgueta, Manuel; Rossi, Julio D.; Wolanski, Noemi

We study a nonlocal diffusion operator in a bounded smooth domain prescribing the flux through the boundary. This problem may be seen as a generalization of the usual Neumann problem for the heat equation. First, we prove existence, uniqueness and a comparison principle. Next, we study the behavior of solutions for some prescribed boundary data including blowing up ones. Finally, we look at a nonlinear flux boundary condition.

About oxide dispersion particles chemical compatibility with areas coherent dissipation/sub-grains of bcc-alloys in Fe - (Cr, V, Mo, W systems

Directory of Open Access Journals (Sweden)

Udovsky A.

2016-01-01

Full Text Available A concept of partial magnetic moments (PMM of the iron atoms located in the first ч four coordination spheres (1÷4 CS for bcc lattice have been introduced based on analysis of results obtained by quantum-mechanical calculations (QMC for volume dependence of the average magnetic moment ferromagnetic (FM Fe. The values of these moments have been calculated for pure bcc Fe and bcc - Fe-Cr alloys. This concept has been used to formulate a three sub-lattice model for binary FM alloys of the Fe-M systems (M is an alloying paramagnetic element. Physical reason for sign change dependence of the short-range order and mixing enthalpy obtained by QMCs for Fe-(Cr, V bcc phases has been found. Using this model it has been predicted that static displacements of Fe - atoms in alloy matrix increase with increasing the of CS number and result in reducing of the area of coherent dissipation (ACD size with growth of the dimension factor (DF in the Fe-(Cr, V, Mo, W systems in agreement with the X-ray experiments. It has been shown theoretically that anisotropy of spin- density in bcc lattice Fe and DF in binary Fe - (Cr, V, Mo, W systems is main factor for origins of segregations on small angle boundaries of ACD and sub-grains boundaries To prevent the coagulation of both ACD and sub-grains, and to increase the strength of alloys, it is advisable to add oxide dispersion particles into ferrite steel taking into account their chemical compatibility and coherent interfacing with the crystalline lattice of a ferrite matrix. Application of phase diagrams for binary and ternary the Fe-(Y, Zr-O systems to verify chemical compatibility of oxide dispersion particles with ferrite matrix have been discussed

The effect of deformation temperature on the microstructure evolution of Inconel 625 superalloy

Energy Technology Data Exchange (ETDEWEB)

Guo Qingmiao [General Research Institute for Non-Ferrous Metals, Beijing 100088 (China); Li Defu, E-mail: lide_fu@163.com [General Research Institute for Non-Ferrous Metals, Beijing 100088 (China); Guo Shengli; Peng Haijian; Hu Jie [General Research Institute for Non-Ferrous Metals, Beijing 100088 (China)

2011-07-31

Highlights: > The relationship between the stable DRX grain size and peak stress can be expressed by a power law function. > Deformation temperature has a significant influence on the nucleation mechanisms of DRX at different deformation stages. > With increasing the deformation temperature, the effect of DDRX accompanied with twinning formation grows stronger, while the effect of CDRX grows weaker. -- Abstract: Hot compression tests of Inconel 625 superalloy were conducted using a Gleeble-1500 simulator between 900 deg. C and 1200 deg. C with different true strains and a strain rate of 0.1 s{sup -1}. Scanning electron microscope (SEM) and electron backscatter diffraction technique (EBSD) were employed to investigate the effect of deformation temperature on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). It is found that the relationship between the DRX grain size and the peak stress can be expressed by a power law function. Significant influence of deformation temperatures on the nucleation mechanisms of DRX are observed at different deformation stages. At lower deformation temperatures, continuous dynamic recrystallization (CDRX) characterized by progressive subgrain rotation is considered as the main mechanism of DRX at the early deformation stage. However, discontinuous dynamic recrystallization (DDRX) with bulging of the original grain boundaries becomes the operating mechanism of DRX at the later deformation stage. At higher deformation temperatures, DDRX is the primary mechanism of DRX, while CDRX can only be considered as an assistant mechanism at the early deformation stage. Nucleation of DRX can also be activated by the twinning formation. With increasing the deformation temperature, the effect of DDRX accompanied with twinning formation grows stronger, while the effect of CDRX grows weaker. Meanwhile, the position of subgrain formation shifts gradually from the interior of original grains to the vicinity of the

Recognition of boundary feedback systems

DEFF Research Database (Denmark)

Pedersen, Michael

1989-01-01

A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback stabili...... stabilizability. It is shown that it is possible to use the calculus to consider more general feedback systems in a variational setup.......A system that has been the object of intense research is outlined. In view of that and recent progress of the theory of pseudodifferential boundary operator calculus, the author describes some features that could prove to be interesting in connection with the problems of boundary feedback...

Atomic-scale investigations of grain boundary segregation in astrology with a three dimensional atom-probe

Energy Technology Data Exchange (ETDEWEB)

Blavette, D. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut Universitaire de France (France); Letellier, L. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Duval, P. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Guttmann, M. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut de Recherches de la Siderurgie Francaise (IRSID), 57 - Maizieres-les-Metz (France)

1996-08-01

Both conventional and 3D atom-probes were applied to the investigation of grain-boundary (GB) segregation phenomena in two-phase nickel base superalloys Astroloy. 3D images as provided by the tomographic atom-probe reveal the presence of a strong segregation of both boron and molybdenum at grain-boundaries. Slight carbon enrichment is also detected. Considerable chromium segregation is exhibited at {gamma}`-{gamma}` grain-boundaries. All these segregants are distributed in a continuous manner along the boundary over a width close to 0.5 nm. Experiments show that segregation occurs during cooling and more probably between 1000 C and 800 C. Boron and molybdenum GB enrichments are interpreted as due to an equilibrium type-segregation while chromium segregation is thought to be induced by {gamma}` precipitation at GB`s and stabilised by the presence of boron. No segregation of zirconium is detected. (orig.)

The effect of grain boundary chemistry on the slip transmission process through grain boundaries in Ni3Al

International Nuclear Information System (INIS)

Robertson, I.M.; Lee, T.C.; Subramanian, R.; Birnbaum, H.K.

1992-01-01

This paper reports on the conditions established in disordered FCC systems for predicting the slip system that will be activated by a grain boundary to relieve a local stress concentration that have been applied to the ordered FCC alloy Ni 3 Al. The slip transfer behavior in hypo-stoichiometric Ni 3 Al with (0.2 at. %B) and without boron was directly observed by performing the deformation experiments in situ in the transmission electron microscope. In the boron-free and boron-doped alloys, lattice dislocations were incorporated in the grain boundary, but did not show evidence of dissociation to grain boundary dislocations or of movement in the grain boundary plane. The stress concentration associated with the dislocation pileup at the grain boundary are relieved by the emission of dislocations from the grain boundary in the boron-doped alloy. The slip system initiated in the adjoining grain obeyed the conditions established for disordered FCC systems. In the boron-free alloy, the primary stress relief mechanism was grain-boundary cracking, although dislocation emission from the grain boundary also occurred and accompanied intergranular crack advance

Causal boundary for stably causal space-times

International Nuclear Information System (INIS)

Racz, I.

1987-12-01

The usual boundary constructions for space-times often yield an unsatisfactory boundary set. This problem is reviewed and a new solution is proposed. An explicit identification rule is given on the set of the ideal points of the space-time. This construction leads to a satisfactory boundary point set structure for stably causal space-times. The topological properties of the resulting causal boundary construction are examined. For the stably causal space-times each causal curve has a unique endpoint on the boundary set according to the extended Alexandrov topology. The extension of the space-time through the boundary is discussed. To describe the singularities the defined boundary sets have to be separated into two disjoint sets. (D.Gy.) 8 refs

Pressure Fluctuations Induced by a Hypersonic Turbulent Boundary Layer

Science.gov (United States)

Duan, Lian; Choudhari, Meelan M.; Zhang, Chao

2016-01-01

Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a spatially-developed Mach 5.86 turbulent boundary layer. The unsteady pressure field is analyzed at multiple wall-normal locations, including those at the wall, within the boundary layer (including inner layer, the log layer, and the outer layer), and in the free stream. The statistical and structural variations of pressure fluctuations as a function of wall-normal distance are highlighted. Computational predictions for mean velocity pro les and surface pressure spectrum are in good agreement with experimental measurements, providing a first ever comparison of this type at hypersonic Mach numbers. The simulation shows that the dominant frequency of boundary-layer-induced pressure fluctuations shifts to lower frequencies as the location of interest moves away from the wall. The pressure wave propagates with a speed nearly equal to the local mean velocity within the boundary layer (except in the immediate vicinity of the wall) while the propagation speed deviates from the Taylor's hypothesis in the free stream. Compared with the surface pressure fluctuations, which are primarily vortical, the acoustic pressure fluctuations in the free stream exhibit a significantly lower dominant frequency, a greater spatial extent, and a smaller bulk propagation speed. The freestream pressure structures are found to have similar Lagrangian time and spatial scales as the acoustic sources near the wall. As the Mach number increases, the freestream acoustic fluctuations exhibit increased radiation intensity, enhanced energy content at high frequencies, shallower orientation of wave fronts with respect to the flow direction, and larger propagation velocity.

Diversified boundaries of the firm

OpenAIRE

Kimura, Koichiro

2012-01-01

We analyze diversification of boundaries of local firms in developing countries under the economic globalization. The globalization has an aspect of homogenization of the world economy, but also has another aspect of diversification through international economic activities. Focusing on boundary-level of the firm, this article shows that the diversification from a comparison with boundaries of foreign firms in developed countries is brought by a disadvantage of technology deficit and a home a...

Formation of intra-island grain boundaries in pentacene monolayers.

Science.gov (United States)

Zhang, Jian; Wu, Yu; Duhm, Steffen; Rabe, Jürgen P; Rudolf, Petra; Koch, Norbert

2011-12-21

To assess the formation of intra-island grain boundaries during the early stages of pentacene film growth, we studied sub-monolayers of pentacene on pristine silicon oxide and silicon oxide with high pinning centre density (induced by UV/O(3) treatment). We investigated the influence of the kinetic energy of the impinging molecules on the sub-monolayer growth by comparing organic molecular beam deposition (OMBD) and supersonic molecular beam deposition (SuMBD). For pentacene films fabricated by OMBD, higher pentacene island-density and higher polycrystalline island density were observed on UV/O(3)-treated silicon oxide as compared to pristine silicon oxide. Pentacene films deposited by SuMBD exhibited about one order of magnitude lower island- and polycrystalline island densities compared to OMBD, on both types of substrates. Our results suggest that polycrystalline growth of single islands on amorphous silicon oxide is facilitated by structural/chemical surface pinning centres, which act as nucleation centres for multiple grain formation in a single island. Furthermore, the overall lower intra-island grain boundary density in pentacene films fabricated by SuMBD reduces the number of charge carrier trapping sites specific to grain boundaries and should thus help achieving higher charge carrier mobilities, which are advantageous for their use in organic thin-film transistors.

Working with boundaries in systems psychodynamic consulting

Directory of Open Access Journals (Sweden)

Henk Struwig

2012-03-01

Research purpose: The purpose of the research was to produce a set of theoretical assumptions about organisational boundaries and boundary management in organisations and, from these, to develop a set of hypotheses as a thinking framework for practising consulting psychologists when they work with boundaries from a systems psychodynamic stance. Motivation for the study: The researcher used the belief that organisational boundaries reflect the essence of organisations. Consulting to boundary managers could facilitate a deep understanding of organisational dynamics. Research design, approach and method: The researcher followed a case study design. He used systems psychodynamic discourse analysis. It led to six working hypotheses. Main findings: The primary task of boundary management is to hold the polarities of integration and differentiation and not allow the system to become fragmented or overly integrated. Boundary management is a primary task and an ongoing activity of entire organisations. Practical/managerial implications: Organisations should work actively at effective boundary management and at balancing integration and differentiation. Leaders should become aware of how effective boundary management leads to good holding environments that, in turn, lead to containing difficult emotions in organisations. Contribution/value-add: The researcher provided a boundary-consulting framework in order to assist consultants to balance the conceptual with the practical when they consult.

Variational multiscale enrichment method with mixed boundary conditions for elasto-viscoplastic problems

Science.gov (United States)

Zhang, Shuhai; Oskay, Caglar

2015-04-01

This manuscript presents the formulation and implementation of the variational multiscale enrichment (VME) method for the analysis of elasto-viscoplastic problems. VME is a global-local approach that allows accurate fine scale representation at small subdomains, where important physical phenomena are likely to occur. The response within far-fields is idealized using a coarse scale representation. The fine scale representation not only approximates the coarse grid residual, but also accounts for the material heterogeneity. A one-parameter family of mixed boundary conditions that range from Dirichlet to Neumann is employed to study the effect of the choice of the boundary conditions at the fine scale on accuracy. The inelastic material behavior is modeled using Perzyna type viscoplasticity coupled with flow stress evolution idealized by the Johnson-Cook model. Numerical verifications are performed to assess the performance of the proposed approach against the direct finite element simulations. The results of verification studies demonstrate that VME with proper boundary conditions accurately model the inelastic response accounting for material heterogeneity.

Boundary Transgressions: An Issue In Psychotherapeutic Encounter ...

African Journals Online (AJOL)

Boundary transgressions tend to be conceptualized on a continuum ranging from boundary crossings to boundary violations. Boundary crossings (e.g. accepting an inexpensive holiday gift from a client, unintentionally encountering a client in public, or attending a client's special event) are described in the literature as ...

Grain boundaries in Ni3Al. 2

International Nuclear Information System (INIS)

Kung, H.; Sass, S.L.

1992-01-01

This paper discusses the dislocation structure of small angle tilt and twist boundaries in ordered Ni 3 Al, with and without boron, investigated using transmission electron microscopy. Dislocation with Burgers vectors that correspond to anti-phase boundary (APB)-coupled superpartials were found in small angle twist boundaries in both boron-free and boron-doped Ni 3 Al, and a small angle tilt boundary in boron-doped Ni 3 Al. The boundary structures are in agreement with theoretical models proposed by Marcinkowski and co-workers. The APB energy determined from the dissociation of the grain boundary dislocations was lower than values reported for isolated APBs in Ni 3 Al. For small angle twist boundaries the presence of boron reduced the APB energy at the interface until it approached zero. This is consistent with the structure of these boundaries containing small regions of increased compositional disorder in the first atomic plane next to the interface

Cost-effective computations with boundary interface operators in elliptic problems

International Nuclear Information System (INIS)

Khoromskij, B.N.; Mazurkevich, G.E.; Nikonov, E.G.

1993-01-01

The numerical algorithm for fast computations with interface operators associated with the elliptic boundary value problems (BVP) defined on step-type domains is presented. The algorithm is based on the asymptotically almost optimal technique developed for treatment of the discrete Poincare-Steklov (PS) operators associated with the finite-difference Laplacian on rectangles when using the uniform grid with a 'displacement by h/2'. The approach can be regarded as an extension of the method proposed for the partial solution of the finite-difference Laplace equation to the case of displaced grids and mixed boundary conditions. It is shown that the action of the PS operator for the Dirichlet problem and mixed BVP can be computed with expenses of the order of O(Nlog 2 N) both for arithmetical operations and computer memory needs, where N is the number of unknowns on the rectangle boundary. The single domain algorithm is applied to solving the multidomain elliptic interface problems with piecewise constant coefficients. The numerical experiments presented confirm almost linear growth of the computational costs and memory needs with respect to the dimension of the discrete interface problem. 14 refs., 3 figs., 4 tabs

Microstructure evolution of titanium after tensile test

International Nuclear Information System (INIS)

Wronski, S.; Wierzbanowski, K.; Jędrychowski, M.; Tarasiuk, J; Wronski, M.; Baczmanski, A.; Bacroix, B.

2016-01-01

The qualitative and quantitative behavior of titanium T40 during tensile loading with a special emphasis on the presence of deformation twins in the observed microstructures is described. The samples for tensile tests were cut out from the rolled titanium sheet along the rolling and transverse directions. Several microstructure maps were determined using Electron Backscatter Diffraction technique (EBSD). These data were used to obtain crystallographic textures, misorientation distributions, grain size, twin boundary length, grain orientation spread, low and high angle boundary fractions and Schmid and Taylor factors. The deformation mechanisms and microstructure characteristics are different in the samples stretched along rolling and transverse directions. A strong appearance of tensile twins was observed in the samples deformed along transverse direction. On the other hand, more frequent subgrain formation and higher orientation spread was observed in the sample deformed along rolling direction, which caused’‘orientation blurring’ leading to an increase of grain size with deformation, as determined from OIM analysis.

Comparison between diffraction contrast tomography and high-energy diffraction microscopy on a slightly deformed aluminium alloy

Directory of Open Access Journals (Sweden)

Loïc Renversade

2016-01-01

Full Text Available The grain structure of an Al–0.3 wt%Mn alloy deformed to 1% strain was reconstructed using diffraction contrast tomography (DCT and high-energy diffraction microscopy (HEDM. 14 equally spaced HEDM layers were acquired and their exact location within the DCT volume was determined using a generic algorithm minimizing a function of the local disorientations between the two data sets. The microstructures were then compared in terms of the mean crystal orientations and shapes of the grains. The comparison shows that DCT can detect subgrain boundaries with disorientations as low as 1° and that HEDM and DCT grain boundaries are on average 4 µm apart from each other. The results are important for studies targeting the determination of grain volume. For the case of a polycrystal with an average grain size of about 100 µm, a relative deviation of about ≤10% was found between the two techniques.

Influence of Solution and Aging Treatment Conditions on the Formation of Ultrafine-Grained Structure of CuFe2 Alloy Processed by Rolling with Cyclic Movement of Rolls

Directory of Open Access Journals (Sweden)

Urbańczyk-Gucwa A.

2016-06-01

Full Text Available The effect of second phase particles on grain refinement in CuFe2 alloy has been investigated by using rolling with the cyclic movement of rolls (RCMR method. Two different population of second phase particles of Fe: coherent, about 10 nm in diameter and about 100 nm in size were obtained by applying aging treatment followed at 500°C for 2 h and at 700°C for 24 h respectively. In addition, solution treated samples were deformed by RCMR method at the same parameters. The microstructures of the CuFe2 alloy were analyzed using light microscope (LM, electron backscattered diffraction (EBSD microscope technique and scanning transmission electron microscope (STEM. The presence of high-density of coherent Fe particles in the matrix inhibits recovery process and in the result obtained grain/subgrain boundaries have diffused character and are weakly visible. The largest particles which are not coherent with the matrix act as an effective barrier against the boundary motion.

Analysis of steady-state creep of Fe-Mo alloys from the viewpoint of recovery

International Nuclear Information System (INIS)

Maruyama, K.; Karashima, S.; Oikawa, H.

1979-01-01

A theoretical equation to d evaluate the steady-state creep-rates, d epsilon/dtsub(s), based on a recovery creep model is derived: epsilonsub(s)/dt proportional to r/sigma 2 sub(a) x lambda 2 , where r is the recovery rate, which can be determined from results of stress-reduction tests, deltasub(a) the applied stress, and lambda the dislocation link-length. Two cases of recovery are considered, i.e., recovery of dislocation networks at sub-boundaries and that of three-dimensional networks within subgrains. The high-temperature steady-state creep of Fe-Mo solid solutions, creep characteristics of which have been reported to be well rationalized as viscous glide creep, is analyzed using this equation. It is shown that stress dependence of d epsilon/dtsub(s) is well explained from the viewpoint of recovery, in which the activation and the annihilation of dislocations at sub-boundaries are considered to take place. (orig.) [de

Modifications of the κ-ε model in GOTHIC near physical boundaries

International Nuclear Information System (INIS)

Analytis, G.Th.; Andreani, M.

2000-01-01

In CFD-type codes like the containment analysis code GOTHIC, one of the options that can be used for modelling of turbulence is the k - ε model. Though, in contrast to other CFD codes which are tailored for performing detailed CFD calculations with a large number of spatial meshes, in codes like GOTHIC which are primarily aiming at calculating transients in reactor containments, one generally uses coarse meshes. The solution of the two parabolic k - ε model equations requires the definition of boundary conditions at physical boundaries and this, in rum, requires very small spatial meshes near these boundaries. Hence, while in codes like CFX this is properly done, in codes like GOTHIC, this is done in an indirect and non-rigorous fashion, exactly due to the fact that the spatial meshes are usually large; this can have catastrophic consequences during the calculation of a transient and in this work, we shall give some examples of this and outline a method by which this problem can be by-passed. (author)

Experimental verification of electrostatic boundary conditions in gate-patterned quantum devices

Science.gov (United States)

Hou, H.; Chung, Y.; Rughoobur, G.; Hsiao, T. K.; Nasir, A.; Flewitt, A. J.; Griffiths, J. P.; Farrer, I.; Ritchie, D. A.; Ford, C. J. B.

2018-06-01

In a model of a gate-patterned quantum device, it is important to choose the correct electrostatic boundary conditions (BCs) in order to match experiment. In this study, we model gated-patterned devices in doped and undoped GaAs heterostructures for a variety of BCs. The best match is obtained for an unconstrained surface between the gates, with a dielectric region above it and a frozen layer of surface charge, together with a very deep back boundary. Experimentally, we find a  ∼0.2 V offset in pinch-off characteristics of 1D channels in a doped heterostructure before and after etching off a ZnO overlayer, as predicted by the model. Also, we observe a clear quantised current driven by a surface acoustic wave through a lateral induced n-i-n junction in an undoped heterostructure. In the model, the ability to pump electrons in this type of device is highly sensitive to the back BC. Using the improved boundary conditions, it is straightforward to model quantum devices quite accurately using standard software.

The energetic ion substorm injection boundary

International Nuclear Information System (INIS)

Lopez, R.E.; Sibeck, D.G.; McEntire, R.W.; Krimigis, S.M.

1990-01-01

The substorm injection boundary model has enjoyed considerable success in explaining plasma signatures in the near-geosynchronous region. However, the injection boundary has remained primarily a phenomenological model. In this paper the authors examine 167 dispersionless energetic ion injections which were observed by AMPTE CCE. The radial and local time distribution of the events as a function of Kp is qualitatively similar to that envisioned in the injection boundary model of Mauk and McIlwain (1974). They argue that particles observed during dispersionless injections are locally energized during the disruption of the cross-tail current sheet. Therefore they identify the injection boundary, as derived from the spatial distribution of dispersionless injections, with the earthward edge of the region of the magnetotail which undergoes current sheet disruption during the substorm expansion phase. The authors show that this qualitative model for the generation of the injection boundary can provide an explanation for the dispersionless nature, the double spiral shape, and the Kp dependence of the boundary

Boundary conditions and subelliptic estimates for geometric Kramers-Fokker-Planck operators on manifolds with boundaries

CERN Document Server

Nier, Francis

2018-01-01

This article is concerned with the maximal accretive realizations of geometric Kramers-Fokker-Planck operators on manifolds with boundaries. A general class of boundary conditions is introduced which ensures the maximal accretivity and some global subelliptic estimates. Those estimates imply nice spectral properties as well as exponential decay properties for the associated semigroup. Admissible boundary conditions cover a wide range of applications for the usual scalar Kramer-Fokker-Planck equation or Bismut's hypoelliptic laplacian.

High Enthalpy Effects on Two Boundary Layer Disturbances in Supersonic and Hypersonic Flow

Science.gov (United States)

Wagnild, Ross Martin

The fluid flow phenomenon of boundary layer transition is a complicated and difficult process to model and predict. The importance of the state of the boundary layer with regard to vehicle design cannot be understated. The high enthalpy environment in which high speed vehicles operate in further complicates the transition process by adding several more degrees of freedom. In this environment, the internal properties of the gas can stabilize or destabilize the boundary layer as well as modify the disturbances that cause transition. In the current work, the interaction of two types of disturbances with the high enthalpy flow environment are analyzed. The first is known as a second mode disturbance, which is acoustic in nature. The second type is known as a transient growth disturbance and is associated with flows behind roughness elements. Theoretical analyses, linear stability analyses, and computation fluid dynamics (CFD) are used to determine the ways in which these disturbances interact with the high enthalpy environment as well as the consequences of these interactions. First, acoustic wave are directly studied in order to gain a basic understanding of the response of second mode disturbances in the high enthalpy boundary layer. Next, this understanding is used in interpreting the results of several computations attempting to simulate the flow through a high enthalpy flow facility as well as experiments attempting to take advantage of the acoustic interaction with the high enthalpy environment. Because of the difficulty in modeling these experiments, direct simulations of acoustic waves in a hypersonic flow of a gas with molecular vibration are performed. Lastly, compressible transient growth disturbances are simulated using a linear optimal disturbance solver as well as a CFD solver. The effect of an internal molecular process on this type of disturbance is tested through the use of a vibrational mode. It is the goal of the current work to reinforce the

Substitutional Boron in Nanodiamond, Bucky-Diamond, and Nanocrystalline Diamond Grain Boundaries

Energy Technology Data Exchange (ETDEWEB)

Barnard, Amanda S.; Sternberg, Michael G.

2006-10-05

Although boron has been known for many years to be a successful dopant in bulk diamond, efficient doping of nanocrystalline diamond with boron is still being developed. In general, the location, configuration, and bonding structure of boron in nanodiamond is still unknown, including the fundamental question of whether it is located within grains or grain boundaries of thin films and whether it is within the core or at the surface of nanoparticles. Presented here are density functional tight-binding simulations examining the configuration, potential energy surface, and electronic charge of substitutional boron in various types of nanocrystalline diamond. The results predict that boron is likely to be positioned at the surface of isolated particles and at the grain boundary of thin-film samples.

County and Parish Boundaries - COUNTY_GOVERNMENT_BOUNDARIES_IDHS_IN: Governmental Boundaries Maintained by County Agencies in Indiana (Indiana Department of Homeland Security, Polygon feature class)

Data.gov (United States)

NSGIC State | GIS Inventory — COUNTY_GOVERNMENT_BOUNDARIES_IDHS_IN is a polygon feature class that contains governmental boundaries maintained by county agencies in Indiana, provided by personnel...

Fabrication of Well-Ordered Three-Phase Boundary with Nanostructure Pore Array for Mixed Potential-Type Zirconia-Based NO2 Sensor.

Science.gov (United States)

Wang, Bin; Liu, Fangmeng; Yang, Xue; Guan, Yehui; Ma, Ce; Hao, Xidong; Liang, Xishuang; Liu, Fengmin; Sun, Peng; Zhang, Tong; Lu, Geyu

2016-07-06

A well-ordered porous three-phase boundary (TPB) was prepared with a polystyrene sphere as template and examined to improve the sensitivity of yttria-stabilized zirconia (YSZ)-based mixed-potential-type NO2 sensor due to the increase of the electrochemical reaction active sites. The shape of pore array on the YSZ substrate surface can be controlled through changing the concentration of the precursor solution (Zr(4+)/Y(3+) = 23 mol/L/4 mol/L) and treatment conditions. An ordered hemispherical array was obtained when CZr(4+) = 0.2 mol/L. The processed YSZ substrates were used to fabricate the sensors, and different sensitivities caused by different morphologies were tested. The sensor with well-ordered porous TPB exhibited the highest sensitivity to NO2 with a response value of 105 mV to 100 ppm of NO2, which is approximately twice as much as the smooth one. In addition, the sensor also showed good stability and speedy response kinetics. All these enhanced sensing properties might be due to the structure and morphology of the enlarged TPB.

Boundary correlators in supergroup WZNW models

Energy Technology Data Exchange (ETDEWEB)

Creutzig, T.; Schomerus, V.

2008-04-15

We investigate correlation functions for maximally symmetric boundary conditions in the WZNW model on GL(11). Special attention is payed to volume filling branes. Generalizing earlier ideas for the bulk sector, we set up a Kac-Wakimotolike formalism for the boundary model. This first order formalism is then used to calculate bulk-boundary 2-point functions and the boundary 3-point functions of the model. The note ends with a few comments on correlation functions of atypical fields, point-like branes and generalizations to other supergroups. (orig.)

Mechanisms of submicron inclusion re-equilibration during host mineral deformation

Science.gov (United States)

Griffiths, Thomas; Habler, Gerlinde; Abart, Rainer; Rhede, Dieter; Wirth, Richard

2014-05-01

data, and no subgrain boundaries. Secondly, garnet lattice rotation of up to 10° around rational garnet crystal axes is observed in connection with some already coarsened inclusions. Strain concentrations are widespread in some trails, but rare in others. A TEM foil transecting a garnet domain with concentrated lattice rotation in association with inclusions reveals well developed polygonal subgrain walls with few free dislocations. Where dislocation density is greatest, almost no <100nm inclusions are observed, whereas these are more abundant in unstrained garnet domains despite the foil being located entirely within the optically visible bleaching zone. Chlorite inclusions and formation of etch pits at dislocations at the garnet-chlorite interface demonstrate the presence of fluid along subgrain boundaries during this second bleaching process. In summary, brittle deformation in these garnets led to enhanced transport and inclusion re-equilibration by coarsening, forming inclusion trails. The precise mechanism allowing enhanced transport is still to be determined and may have involved fluid supply with or without pipe diffusion along introduced dislocations. Later ductile deformation via dislocations, concentrated at already coarsened inclusions and enhanced by fluid availability, further affected the nanoinclusion population. The inclusion trail microstructure records complex small-scale interaction between deformation and reaction, shedding light on the mechanisms by which re-equilibration and strain localisation can influence each other in deforming host-inclusion systems. Bestmann et al. (2008) Journal of Structural Geology 30: 777-790

Large modulation of carrier transport by grain-boundary molecular packing and microstructure in organic thin films

KAUST Repository

Rivnay, Jonathan

2009-11-08

Solution-processable organic semiconductors are central to developing viable printed electronics, and performance comparable to that of amorphous silicon has been reported for films grown from soluble semiconductors. However, the seemingly desirable formation of large crystalline domains introduces grain boundaries, resulting in substantial device-to-device performance variations. Indeed, for films where the grain-boundary structure is random, a few unfavourable grain boundaries may dominate device performance. Here we isolate the effects of molecular-level structure at grain boundaries by engineering the microstructure of the high-performance n-type perylenediimide semiconductor PDI8-CN 2 and analyse their consequences for charge transport. A combination of advanced X-ray scattering, first-principles computation and transistor characterization applied to PDI8-CN 2 films reveals that grain-boundary orientation modulates carrier mobility by approximately two orders of magnitude. For PDI8-CN 2 we show that the molecular packing motif (that is, herringbone versus slip-stacked) plays a decisive part in grain-boundary-induced transport anisotropy. The results of this study provide important guidelines for designing device-optimized molecular semiconductors. © 2009 Macmillan Publishers Limited. All rights reserved.

Cross-boundary substance uses among Hong Kong Chinese young adults.

Science.gov (United States)

Lau, Joseph T F; Tsui, Hi Yi; Lam, Lawrence T; Lau, Mason

2007-09-01

The study documents the characteristics of Hong Kong residents who used substances in mainland China. Characteristics of such users were compared with those using substances elsewhere. A cross-sectional survey was used. Data analyses were stratified by gender, and multivariate analyses were performed. Respondents, Hong Kong adults aged 18-30 (n = 6,528), were interviewed using a mixed interviewer and computerized mobile phone method, at the Hong Kong-mainland China boundary. Cross-border substance users and other types of substance users had characteristics that were quite different (e.g., education level, perceived harmfulness of substance use in general, having friends who frequently used substances in mainland China). Cross-boundary substance users also found it easier to obtain substances in mainland China than in Hong Kong (males: 60.5%, females: 39.6%) and perceived no chance of being arrested in mainland China because of substance use (men: 28.8%, women: 24.5%). They tended to use substances in discos/rave parties together with friends (men: 77%, women: 81%), and substances were often obtained for free (men: 63.2%, women: 78%). Ecstasy and ketamine were often used (men: 86.5% & 79.4%, women: 81% & 70.2%), and multiple uses of different substances were common (men: 81.3%, women: 68.6%). Lower price, peer influence, and better availability were reasons behind cross-boundary substance use behaviors. Cross-boundary substance users have specific characteristics. Prevention policies should take these characteristics into account. Regional collaborations are highly warranted.

Boundary control of fluid flow through porous media

DEFF Research Database (Denmark)

Hasan, Agus; Foss, Bjarne; Sagatun, Svein Ivar

2010-01-01

The flow of fluids through porous media can be described by the Boussinesq’s equation with mixed boundary conditions; a Neumann’s boundary condition and a nonlinear boundary condition. The nonlinear boundary condition provides a means to control the fluid flow through porous media. In this paper,......, some stabilizing controllers are constructed for various cases using Lyapunov design.......The flow of fluids through porous media can be described by the Boussinesq’s equation with mixed boundary conditions; a Neumann’s boundary condition and a nonlinear boundary condition. The nonlinear boundary condition provides a means to control the fluid flow through porous media. In this paper...

Microstructure evolution during cyclic tests on EUROFER 97 at room temperature. TEM observation and modelling

Energy Technology Data Exchange (ETDEWEB)

Giordana, M.F., E-mail: giordana@ifir-conicet.gov.ar [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Giroux, P.-F. [Commissariat a l' Energie Atomique, DEN/DANS/DMN/SRMA, 91191 Gif-sur-Yvette Cedex (France); Alvarez-Armas, I. [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Sauzay, M. [Commissariat a l' Energie Atomique, DEN/DANS/DMN/SRMA, 91191 Gif-sur-Yvette Cedex (France); Armas, A. [Instituto de Fisica Rosario, CONICET-UNR, Bv. 27 de Febrero 210 Bis, 2000 Rosario (Argentina); Kruml, T. [CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, Brno, 616 62 (Czech Republic)

2012-07-30

Highlights: Black-Right-Pointing-Pointer Low cycle fatigue test are carried out on EUROFER 97 at room temperature. Black-Right-Pointing-Pointer EUROFER 97 shows a pronounced cyclic softening accompanied by microstructural changes. Black-Right-Pointing-Pointer Cycling induces a decrement in dislocation density and subgrain growth. Black-Right-Pointing-Pointer A simple mean-field model based on crystalline plasticity is proposed. Black-Right-Pointing-Pointer The mean subgrain size evolution is predicted by modelling. - Abstract: The 9% Cr quenched and tempered reduced-activation ferritic/martensitic steel EUROFER 97 is one of the candidates for structural components of fusion reactors. Isothermal, plastic strain-controlled, low-cycle fatigue tests are performed. Tested at room temperature, this steel suffers a cyclic softening effect linked to microstructural changes observed by transmission electron microscopy, such as the decrease of dislocation density inside subgrains or the growth of subgrain size. From the assumed mechanisms of softening a simple mean-field model based on crystalline plasticity is proposed to predict these microstructure evolutions during cycling and monotonic deformation.

Variational principle for gravity with null and non-null boundaries: a unified boundary counter-term

Energy Technology Data Exchange (ETDEWEB)

Parattu, Krishnamohan; Chakraborty, Sumanta; Padmanabhan, T. [IUCAA, Post Bag 4, Pune (India)

2016-03-15

It is common knowledge that the Einstein-Hilbert action does not furnish a well-posed variational principle. The usual solution to this problem is to add an extra boundary term to the action, called a counter-term, so that the variational principle becomes well-posed. When the boundary is spacelike or timelike, the Gibbons-Hawking-York counter-term is the most widely used. For null boundaries, we had proposed a counter-term in a previous paper. In this paper, we extend the previous analysis and propose a counter-term that can be used to eliminate variations of the ''off-the-surface'' derivatives of the metric on any boundary, regardless of its spacelike, timelike or null nature. (orig.)

Rearranging social space: Boundary-making and boundary-work in a joint forest management project, Andhra Pradesh, India

Directory of Open Access Journals (Sweden)

Saito-Jensen Moeko

2010-01-01

Full Text Available Since the 1990s, there has been an increasing trend in developing countries to shift from state driven approaches to Community-based Natural Resource Management (CBNRM. In order to ensure sustainability of resources, the need for creating and maintaining clear resource use boundaries has been emphasised, both theoretically and in practice. However, there has been less attention to the varied social consequences for involved villages (whose inhabitants can access resources within the new boundaries and for excluded villages (whose inhabitants are prevented from accessing resources due to these boundaries. Drawing on a case study of three villages affected by the Joint Forest Management project in Andhra Pradesh, India, this article shows how resource use boundaries interact with social categories such as caste, gender and livelihood occupation in ways that facilitate asymmetric distribution of costs and benefits among local people. The article calls for more consultative processes in constituting new resources use boundaries and for flexible interventions to reconcile conflicts arising from boundary-making.

Computation of airfoil buffet boundaries

Science.gov (United States)

Levy, L. L., Jr.; Bailey, H. E.

1981-01-01

The ILLIAC IV computer has been programmed with an implicit, finite-difference code for solving the thin layer compressible Navier-Stokes equation. Results presented for the case of the buffet boundaries of a conventional and a supercritical airfoil section at high Reynolds numbers are found to be in agreement with experimentally determined buffet boundaries, especially at the higher freestream Mach numbers and lower lift coefficients where the onset of unsteady flows is associated with shock wave-induced boundary layer separation.

Reconstucted topographs of polycrystalline (110) Fe-3 wt% Si samples and the observation of their magnetic domain images using synchrotron radiation

International Nuclear Information System (INIS)

Stephenson, J.D.; Kelhae, V.; Tilli, M.; Tuomi, T.

1978-01-01

'White' synchrotron radiation topography has been employed to reconstruct almost complete, though slightly shape distorted topographs of polycrystalline samples. Those used in the experiments were commercial (110) Fe-3wt%Si crystals containing several misorientated subgrains and were of thickness between 0.15 and 0.20 mm. The topographs were reassembled 'jig-saw puzzle' fashion from photographically enlarged subgrain mini-topographs located near the centres of each film. Magnetic domains were observed in several subgrain topographs recorded in the Laue-reflection and Laue-transmission modes. The technique emphasizes one of the advantages in using 'white' synchrotron radiation to produce rapid high resolution topographs of polycrystalline samples in relatively hazard free radiation conditions. (Auth.)

Typing is writing: Linguistic properties modulate typing execution.

Science.gov (United States)

Pinet, Svetlana; Ziegler, Johannes C; Alario, F-Xavier

2016-12-01

Typing is becoming our preferred way of writing. Perhaps because of the relative recency of this change, very few studies have investigated typing from a psycholinguistic perspective. In addition, and despite obvious similarities between typing and handwriting, typing research has remained rather disconnected from handwriting research. The current study aimed at bridging this gap by evaluating how typing is affected by a number of psycholinguistic variables defined at the word, syllable, and letter levels. In a writing-to-dictation task, we assessed typing performance by measuring response accuracy, onset latencies - an index of response preparation and initiation - and interkeystroke intervals (IKIs) - an index of response execution processes. The lexical and sublexical factors revealed a composite pattern of effects. Lexical frequency improved response latencies and accuracy, while bigram frequency speeded up IKIs. Sound-spelling consistency improved latencies, but had an inhibitory effect on IKI. IKIs were also longer at syllable boundaries. Together, our findings can be fit within a framework for typed production that combines the previously developed theories of spelling and typing execution. At their interface, we highlight the need for an intermediate hierarchical stage, perhaps in the form of a graphemic buffer for typing.

Analytical and experimental investigation on transmission loss of clamped double panels: implication of boundary effects.

Science.gov (United States)

Xin, F X; Lu, T J

2009-03-01

The air-borne sound insulation performance of a rectangular double-panel partition clamp mounted on an infinite acoustic rigid baffle is investigated both analytically and experimentally and compared with that of a simply supported one. With the clamped (or simply supported) boundary accounted for by using the method of modal function, a double series solution for the sound transmission loss (STL) of the structure is obtained by employing the weighted residual (Galerkin) method. Experimental measurements with Al double-panel partitions having air cavity are subsequently carried out to validate the theoretical model for both types of the boundary condition, and good overall agreement is achieved. A consistency check of the two different models (based separately on clamped modal function and simply supported modal function) is performed by extending the panel dimensions to infinite where no boundaries exist. The significant discrepancies between the two different boundary conditions are demonstrated in terms of the STL versus frequency plots as well as the panel deflection mode shapes.

Experimental investigation of wave boundary layer

DEFF Research Database (Denmark)

Sumer, B. Mutlu

2003-01-01

A review is presented of experimental investigation of wave boundary layer. The review is organized in six main sections. The first section describes the wave boundary layer in a real-life environment and its simulation in the laboratory in an oscillating water tunnel and in a water tank...... with an oscillating seabed. A brief account is given of measured quantities, measurement techniques (LDA, PIV, flow visualization) and limitations/constraints in the experimental investigation of the wave boundary layer in the laboratory. The second section concentrates on uniform oscillating boundary layers...

Quantum “violation” of Dirichlet boundary condition