Impact of off-diagonal cross-shell interaction on 14C
Yuan, Cen-Xi
2017-10-01
A shell-model investigation is performed to show the impact on the structure of 14C from the off-diagonal cross-shell interaction, 〈pp|V|sdsd〉, which represents the mixing between the 0 and 2ħω configurations in the psd model space. The observed levels of the positive states in 14C can be nicely described in 0-4ħω or a larger model space through the well defined Hamiltonians, YSOX and WBP, with a reduction of the strength of the 〈pp|V|sdsd〉 interaction in the latter. The observed B(GT) values for 14C can be generally described by YSOX, while WBP and their modifications of the 〈pp|V|sdsd〉 interaction fail for some values. Further investigation shows the effect of such interactions on the configuration mixing and occupancy. The present work shows examples of how the off-diagonal cross-shell interaction strongly drives the nuclear structure. Supported by National Natural Science Foundation of China (11305272), Special Program for Applied Research on Super Computation of the NSFC Guangdong Joint Fund (the second phase), the Guangdong Natural Science Foundation (2014A030313217), the Pearl River S&T Nova Program of Guangzhou (201506010060), the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong special support program (2016TQ03N575), and the Fundamental Research Funds for the Central Universities (17lgzd34)
Exact diagonalization library for quantum electron models
Iskakov, Sergei; Danilov, Michael
2018-04-01
We present an exact diagonalization C++ template library (EDLib) for solving quantum electron models, including the single-band finite Hubbard cluster and the multi-orbital impurity Anderson model. The observables that can be computed using EDLib are single particle Green's functions and spin-spin correlation functions. This code provides three different types of Hamiltonian matrix storage that can be chosen based on the model.
Quantum Monte Carlo diagonalization method as a variational calculation
Mizusaki, Takahiro; Otsuka, Takaharu; Honma, Michio.
1997-01-01
A stochastic method for performing large-scale shell model calculations is presented, which utilizes the auxiliary field Monte Carlo technique and diagonalization method. This method overcomes the limitation of the conventional shell model diagonalization and can extremely widen the feasibility of shell model calculations with realistic interactions for spectroscopic study of nuclear structure. (author)
Off-diagonal Bethe ansatz for exactly solvable models
Wang, Yupeng; Cao, Junpeng; Shi, Kangjie
2015-01-01
This book serves as an introduction of the off-diagonal Bethe Ansatz method, an analytic theory for the eigenvalue problem of quantum integrable models. It also presents some fundamental knowledge about quantum integrability and the algebraic Bethe Ansatz method. Based on the intrinsic properties of R-matrix and K-matrices, the book introduces a systematic method to construct operator identities of transfer matrix. These identities allow one to establish the inhomogeneous T-Q relation formalism to obtain Bethe Ansatz equations and to retrieve corresponding eigenstates. Several longstanding models can thus be solved via this method since the lack of obvious reference states is made up. Both the exact results and the off-diagonal Bethe Ansatz method itself may have important applications in the fields of quantum field theory, low-dimensional condensed matter physics, statistical physics and cold atom systems.
Benchmarking GW against exact diagonalization for semiempirical models
Kaasbjerg, Kristen; Thygesen, Kristian Sommer
2010-01-01
We calculate ground-state total energies and single-particle excitation energies of seven pi-conjugated molecules described with the semiempirical Pariser-Parr-Pople model using self-consistent many-body perturbation theory at the GW level and exact diagonalization. For the total energies GW capt...... (Hubbard models) where correlation effects dominate over screening/relaxation effects. Finally we illustrate the important role of the derivative discontinuity of the true exchange-correlation functional by computing the exact Kohn-Sham levels of benzene....
Exact diagonalization: the Bose-Hubbard model as an example
Zhang, J M; Dong, R X
2010-01-01
We take the Bose-Hubbard model to illustrate exact diagonalization techniques in a pedagogical way. We follow the route of first generating all the basis vectors, then setting up the Hamiltonian matrix with respect to this basis and finally using the Lanczos algorithm to solve low lying eigenstates and eigenvalues. Emphasis is placed on how to enumerate all the basis vectors and how to use the hashing trick to set up the Hamiltonian matrix or matrices corresponding to other quantities. Although our route is not necessarily the most efficient one in practice, the techniques and ideas introduced are quite general and may find use in many other problems.
Significance of matrix diagonalization in modelling inelastic electron scattering
Lee, Z. [University of Ulm, Ulm 89081 (Germany); Hambach, R. [University of Ulm, Ulm 89081 (Germany); University of Jena, Jena 07743 (Germany); Kaiser, U.; Rose, H. [University of Ulm, Ulm 89081 (Germany)
2017-04-15
Electron scattering is always applied as one of the routines to investigate nanostructures. Nowadays the development of hardware offers more and more prospect for this technique. For example imaging nanostructures with inelastic scattered electrons may allow to produce component-sensitive images with atomic resolution. Modelling inelastic electron scattering is therefore essential for interpreting these images. The main obstacle to study inelastic scattering problem is its complexity. During inelastic scattering, incident electrons entangle with objects, and the description of this process involves a multidimensional array. Since the simulation usually involves fourdimensional Fourier transforms, the computation is highly inefficient. In this work we have offered one solution to handle the multidimensional problem. By transforming a high dimensional array into twodimensional array, we are able to perform matrix diagonalization and approximate the original multidimensional array with its twodimensional eigenvectors. Our procedure reduces the complicated multidimensional problem to a twodimensional problem. In addition, it minimizes the number of twodimensional problems. This method is very useful for studying multiple inelastic scattering. - Highlights: • 4D problems are involved in modelling inelastic electron scattering. • By means of matrix diagonalization, the 4D problems can be simplified as 2D problems. • The number of 2D problems is minimized by using this approach.
Perturbation theory instead of large scale shell model calculations
Feldmeier, H.; Mankos, P.
1977-01-01
Results of large scale shell model calculations for (sd)-shell nuclei are compared with a perturbation theory provides an excellent approximation when the SU(3)-basis is used as a starting point. The results indicate that perturbation theory treatment in an SU(3)-basis including 2hω excitations should be preferable to a full diagonalization within the (sd)-shell. (orig.) [de
Nuclear spectroscopy in large shell model spaces: recent advances
Kota, V.K.B.
1995-01-01
Three different approaches are now available for carrying out nuclear spectroscopy studies in large shell model spaces and they are: (i) the conventional shell model diagonalization approach but taking into account new advances in computer technology; (ii) the recently introduced Monte Carlo method for the shell model; (iii) the spectral averaging theory, based on central limit theorems, in indefinitely large shell model spaces. The various principles, recent applications and possibilities of these three methods are described and the similarity between the Monte Carlo method and the spectral averaging theory is emphasized. (author). 28 refs., 1 fig., 5 tabs
Solving the nuclear shell model with an algebraic method
Feng, D.H.; Pan, X.W.; Guidry, M.
1997-01-01
We illustrate algebraic methods in the nuclear shell model through a concrete example, the fermion dynamical symmetry model (FDSM). We use this model to introduce important concepts such as dynamical symmetry, symmetry breaking, effective symmetry, and diagonalization within a higher-symmetry basis. (orig.)
Chaos in non-diagonal spatially homogeneous cosmological models in spacetime dimensions <=10
Demaret, Jacques; de Rop, Yves; Henneaux, Marc
1988-08-01
It is shown that the chaotic oscillatory behaviour, absent in diagonal homogeneous cosmological models in spacetime dimensions between 5 and 10, can be reestablished when off-diagonal terms are included. Also at Centro de Estudios Cientificos de Santiago, Casilla 16443, Santiago 9, Chile
Shell model in large spaces and statistical spectroscopy
Kota, V.K.B.
1996-01-01
For many nuclear structure problems of current interest it is essential to deal with shell model in large spaces. For this, three different approaches are now in use and two of them are: (i) the conventional shell model diagonalization approach but taking into account new advances in computer technology; (ii) the shell model Monte Carlo method. A brief overview of these two methods is given. Large space shell model studies raise fundamental questions regarding the information content of the shell model spectrum of complex nuclei. This led to the third approach- the statistical spectroscopy methods. The principles of statistical spectroscopy have their basis in nuclear quantum chaos and they are described (which are substantiated by large scale shell model calculations) in some detail. (author)
Novel extrapolation method in the Monte Carlo shell model
Shimizu, Noritaka; Abe, Takashi; Utsuno, Yutaka; Mizusaki, Takahiro; Otsuka, Takaharu; Honma, Michio
2010-01-01
We propose an extrapolation method utilizing energy variance in the Monte Carlo shell model to estimate the energy eigenvalue and observables accurately. We derive a formula for the energy variance with deformed Slater determinants, which enables us to calculate the energy variance efficiently. The feasibility of the method is demonstrated for the full pf-shell calculation of 56 Ni, and the applicability of the method to a system beyond the current limit of exact diagonalization is shown for the pf+g 9/2 -shell calculation of 64 Ge.
Mahomed, Ozayr Haroon; Asmall, Shaidah; Freeman, Melvyn
2014-11-01
The integrated chronic disease management model provides a systematic framework for creating a fundamental change in the orientation of the health system. This model adopts a diagonal approach to health system strengthening by establishing a service-linked base to training, supervision, and the opportunity to try out, assess, and implement integrated interventions.
Temporal structures in shell models
Okkels, F.
2001-01-01
The intermittent dynamics of the turbulent Gledzer, Ohkitani, and Yamada shell-model is completely characterized by a single type of burstlike structure, which moves through the shells like a front. This temporal structure is described by the dynamics of the instantaneous configuration of the shell...
Exact diagonalization of quantum lattice models on coprocessors
Siro, T.; Harju, A.
2016-10-01
We implement the Lanczos algorithm on an Intel Xeon Phi coprocessor and compare its performance to a multi-core Intel Xeon CPU and an NVIDIA graphics processor. The Xeon and the Xeon Phi are parallelized with OpenMP and the graphics processor is programmed with CUDA. The performance is evaluated by measuring the execution time of a single step in the Lanczos algorithm. We study two quantum lattice models with different particle numbers, and conclude that for small systems, the multi-core CPU is the fastest platform, while for large systems, the graphics processor is the clear winner, reaching speedups of up to 7.6 compared to the CPU. The Xeon Phi outperforms the CPU with sufficiently large particle number, reaching a speedup of 2.5.
Modeling animal-vehicle collisions using diagonal inflated bivariate Poisson regression.
Lao, Yunteng; Wu, Yao-Jan; Corey, Jonathan; Wang, Yinhai
2011-01-01
Two types of animal-vehicle collision (AVC) data are commonly adopted for AVC-related risk analysis research: reported AVC data and carcass removal data. One issue with these two data sets is that they were found to have significant discrepancies by previous studies. In order to model these two types of data together and provide a better understanding of highway AVCs, this study adopts a diagonal inflated bivariate Poisson regression method, an inflated version of bivariate Poisson regression model, to fit the reported AVC and carcass removal data sets collected in Washington State during 2002-2006. The diagonal inflated bivariate Poisson model not only can model paired data with correlation, but also handle under- or over-dispersed data sets as well. Compared with three other types of models, double Poisson, bivariate Poisson, and zero-inflated double Poisson, the diagonal inflated bivariate Poisson model demonstrates its capability of fitting two data sets with remarkable overlapping portions resulting from the same stochastic process. Therefore, the diagonal inflated bivariate Poisson model provides researchers a new approach to investigating AVCs from a different perspective involving the three distribution parameters (λ(1), λ(2) and λ(3)). The modeling results show the impacts of traffic elements, geometric design and geographic characteristics on the occurrences of both reported AVC and carcass removal data. It is found that the increase of some associated factors, such as speed limit, annual average daily traffic, and shoulder width, will increase the numbers of reported AVCs and carcass removals. Conversely, the presence of some geometric factors, such as rolling and mountainous terrain, will decrease the number of reported AVCs. Published by Elsevier Ltd.
Shell model and spectroscopic factors
Poves, P.
2007-01-01
In these lectures, I introduce the notion of spectroscopic factor in the shell model context. A brief review is given of the present status of the large scale applications of the Interacting Shell Model. The spectroscopic factors and the spectroscopic strength are discussed for nuclei in the vicinity of magic closures and for deformed nuclei. (author)
Conventional shell model: some issues
Vallieres, M.; Pan, X.W.; Feng, D.H.; Novoselsky, A.
1997-01-01
We discuss some important issues in shell-model calculations related to the effective interactions used in different regions of the periodic table; in particular the quality of different interactions is discussed, as well as the mass dependence of the interactions. Mention is made of the recently developed Drexel University shell-model (DUSM). (orig.)
Jiao, C. F.; Engel, J.; Holt, J. D.
2017-11-01
We use the generator-coordinate method (GCM) with realistic shell-model interactions to closely approximate full shell-model calculations of the matrix elements for the neutrinoless double-β decay of 48Ca, 76Ge, and 82Se. We work in one major shell for the first isotope, in the f5 /2p g9 /2 space for the second and third, and finally in two major shells for all three. Our coordinates include not only the usual axial deformation parameter β , but also the triaxiality angle γ and neutron-proton pairing amplitudes. In the smaller model spaces our matrix elements agree well with those of full shell-model diagonalization, suggesting that our Hamiltonian-based GCM captures most of the important valence-space correlations. In two major shells, where exact diagonalization is not currently possible, our matrix elements are only slightly different from those in a single shell.
Unified description of pf-shell nuclei by the Monte Carlo shell model calculations
Mizusaki, Takahiro; Otsuka, Takaharu [Tokyo Univ. (Japan). Dept. of Physics; Honma, Michio
1998-03-01
The attempts to solve shell model by new methods are briefed. The shell model calculation by quantum Monte Carlo diagonalization which was proposed by the authors is a more practical method, and it became to be known that it can solve the problem with sufficiently good accuracy. As to the treatment of angular momentum, in the method of the authors, deformed Slater determinant is used as the basis, therefore, for making angular momentum into the peculiar state, projected operator is used. The space determined dynamically is treated mainly stochastically, and the energy of the multibody by the basis formed as the result is evaluated and selectively adopted. The symmetry is discussed, and the method of decomposing shell model space into dynamically determined space and the product of spin and isospin spaces was devised. The calculation processes are shown with the example of {sup 50}Mn nuclei. The calculation of the level structure of {sup 48}Cr with known exact energy can be done with the accuracy of peculiar absolute energy value within 200 keV. {sup 56}Ni nuclei are the self-conjugate nuclei of Z=N=28. The results of the shell model calculation of {sup 56}Ni nucleus structure by using the interactions of nuclear models are reported. (K.I.)
Peregrin, Jaroslav
-, č. 2 (2017), s. 33-43 ISSN 0567-8293 R&D Projects: GA ČR(CZ) GA17-15645S Institutional support: RVO:67985955 Keywords : diagonalization * cardinality * Russell’s paradox * incompleteness of arithmetic Subject RIV: AA - Philosophy ; Religion OBOR OECD: Philosophy, History and Philosophy of science and technology
Connections between the dynamical symmetries in the microscopic shell model
Georgieva, A. I., E-mail: anageorg@issp.bas.bg [Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria); Drumev, K. P. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria)
2016-03-25
The dynamical symmetries of the microscopic shell model appear as the limiting cases of a symmetry adapted Pairing-Plus-Quadrupole Model /PQM/, with a Hamiltonian containing isoscalar and isovector pairing and quadrupole interactions. We establish a correspondence between each of the three types of pairing bases and Elliott’s SU(3) basis, that describes collective rotation of nuclear systems with quadrupole deformation. It is derived from their complementarity to the same LS coupling chain of the shell model number conserving algebra. The probability distribution of the S U(3) basis states within the pairing eigenstates is also obtained through a numerical diagonalization of the PQM Hamiltonian in each limit. We introduce control parameters, which define the phase diagram of the model and determine the role of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.
van der Waal, Jeroen; Daenekindt, Stijn; de Koster, Willem
2017-12-01
Various studies on the health consequences of socio-economic position address social mobility. They aim to uncover whether health outcomes are affected by: (1) social mobility, besides, (2) social origin, and (3) social destination. Conventional methods do not, however, estimate these three effects separately, which may produce invalid conclusions. We highlight that diagonal reference models (DRMs) overcome this problem, which we illustrate by focusing on overweight/obesity (OWOB). Using conventional methods (logistic-regression analyses with dummy variables) and DRMs, we examine the effects of intergenerational educational mobility on OWOB (BMI ≥ 25 kg/m 2 ) using survey data representative of the Dutch population aged 18-45 (1569 males, 1771 females). Conventional methods suggest that mobility effects on OWOB are present. Analyses with DRMs, however, indicate that no such effects exist. Conventional analyses of the health consequences of social mobility may produce invalid results. We, therefore, recommend the use of DRMs. DRMs also validly estimate the health consequences of other types of social mobility (e.g. intra- and intergenerational occupational and income mobility) and status inconsistency (e.g. in educational or occupational attainment between partners).
Intrinsic Density Matrices of the Nuclear Shell Model
Deveikis, A.; Kamuntavichius, G.
1996-01-01
A new method for calculation of shell model intrinsic density matrices, defined as two-particle density matrices integrated over the centre-of-mass position vector of two last particles and complemented with isospin variables, has been developed. The intrinsic density matrices obtained are completely antisymmetric, translation-invariant, and do not employ a group-theoretical classification of antisymmetric states. They are used for exact realistic density matrix expansion within the framework of the reduced Hamiltonian method. The procedures based on precise arithmetic for calculation of the intrinsic density matrices that involve no numerical diagonalization or orthogonalization have been developed and implemented in the computer code. (author). 11 refs., 2 tabs
Moments Method for Shell-Model Level Density
Zelevinsky, V; Horoi, M; Sen'kov, R A
2016-01-01
The modern form of the Moments Method applied to the calculation of the nuclear shell-model level density is explained and examples of the method at work are given. The calculated level density practically exactly coincides with the result of full diagonalization when the latter is feasible. The method provides the pure level density for given spin and parity with spurious center-of-mass excitations subtracted. The presence and interplay of all correlations leads to the results different from those obtained by the mean-field combinatorics. (paper)
Shell model Monte Carlo methods
Koonin, S.E.; Dean, D.J.; Langanke, K.
1997-01-01
We review quantum Monte Carlo methods for dealing with large shell model problems. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in fluctuating one-body fields; the resultant path integral is evaluated stochastically. We first discuss the motivation, formalism, and implementation of such Shell Model Monte Carlo (SMMC) methods. There then follows a sampler of results and insights obtained from a number of applications. These include the ground state and thermal properties of pf-shell nuclei, the thermal and rotational behavior of rare-earth and γ-soft nuclei, and the calculation of double beta-decay matrix elements. Finally, prospects for further progress in such calculations are discussed. (orig.)
Shell model Monte Carlo methods
Koonin, S.E.
1996-01-01
We review quantum Monte Carlo methods for dealing with large shell model problems. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in fluctuating one-body fields; resultant path integral is evaluated stochastically. We first discuss the motivation, formalism, and implementation of such Shell Model Monte Carlo methods. There then follows a sampler of results and insights obtained from a number of applications. These include the ground state and thermal properties of pf-shell nuclei, thermal behavior of γ-soft nuclei, and calculation of double beta-decay matrix elements. Finally, prospects for further progress in such calculations are discussed. 87 refs
New-generation Monte Carlo shell model for the K computer era
Shimizu, Noritaka; Abe, Takashi; Yoshida, Tooru; Otsuka, Takaharu; Tsunoda, Yusuke; Utsuno, Yutaka; Mizusaki, Takahiro; Honma, Michio
2012-01-01
We present a newly enhanced version of the Monte Carlo shell-model (MCSM) method by incorporating the conjugate gradient method and energy-variance extrapolation. This new method enables us to perform large-scale shell-model calculations that the direct diagonalization method cannot reach. This new-generation framework of the MCSM provides us with a powerful tool to perform very advanced large-scale shell-model calculations on current massively parallel computers such as the K computer. We discuss the validity of this method in ab initio calculations of light nuclei, and propose a new method to describe the intrinsic wave function in terms of the shell-model picture. We also apply this new MCSM to the study of neutron-rich Cr and Ni isotopes using conventional shell-model calculations with an inert 40 Ca core and discuss how the magicity of N = 28, 40, 50 remains or is broken. (author)
An efficient numerical progressive diagonalization scheme for the quantum Rabi model revisited
Pan, Feng; Bao, Lina; Dai, Lianrong; Draayer, Jerry P
2017-01-01
An efficient numerical progressive diagonalization scheme for the quantum Rabi model is revisited. The advantage of the scheme lies in the fact that the quantum Rabi model can be solved almost exactly by using the scheme that only involves a finite set of one variable polynomial equations. The scheme is especially efficient for a specified eigenstate of the model, for example, the ground state. Some low-lying level energies of the model for several sets of parameters are calculated, of which one set of the results is compared to that obtained from the Braak’s exact solution proposed recently. It is shown that the derivative of the entanglement measure defined in terms of the reduced von Neumann entropy with respect to the coupling parameter does reach the maximum near the critical point deduced from the classical limit of the Dicke model, which may provide a probe of the critical point of the crossover in finite quantum many-body systems, such as that in the quantum Rabi model. (paper)
Hagymási, I.; Itai, K.; Sólyom, J.
2012-06-01
We investigate an extended version of the periodic Anderson model (the so-called periodic Anderson-Hubbard model) with the aim to understand the role of interaction between conduction electrons in the formation of the heavy-fermion and mixed-valence states. Two methods are used: (i) variational calculation with the Gutzwiller wave function optimizing numerically the ground-state energy and (ii) exact diagonalization of the Hamiltonian for short chains. The f-level occupancy and the renormalization factor of the quasiparticles are calculated as a function of the energy of the f orbital for a wide range of the interaction parameters. The results obtained by the two methods are in reasonably good agreement for the periodic Anderson model. The agreement is maintained even when the interaction between band electrons, Ud, is taken into account, except for the half-filled case. This discrepancy can be explained by the difference between the physics of the one- and higher-dimensional models. We find that this interaction shifts and widens the energy range of the bare f level, where heavy-fermion behavior can be observed. For large-enough Ud this range may lie even above the bare conduction band. The Gutzwiller method indicates a robust transition from Kondo insulator to Mott insulator in the half-filled model, while Ud enhances the quasiparticle mass when the filling is close to half filling.
Shell Models of Superfluid Turbulence
Wacks, Daniel H; Barenghi, Carlo F
2011-01-01
Superfluid helium consists of two inter-penetrating fluids, a viscous normal fluid and an inviscid superfluid, coupled by a mutual friction. We develop a two-fluid shell model to study superfluid turbulence and investigate the energy spectra and the balance of fluxes between the two fluids in a steady state. At sufficiently low temperatures a 'bottle-neck' develops at high wavenumbers suggesting the need for a further dissipative effect, such as the Kelvin wave cascade.
Triple Diagonal modeling: A mechanism to focus productivity improvement for business success
Levine, L.O. [Pacific Northwest Lab., Richland, WA (United States); Villareal, L.D. [Army Depot, Corpus Christi, TX (United States)
1993-09-01
Triple Diagonal (M) modeling is a technique to help quickly diagnose an organization`s existing production system and to identify significant improvement opportunities in executing, controlling, and planning operations. TD modeling is derived from ICAM Definition Language (IDEF 0)-also known as Structured Analysis and Design Technique. It has been used successfully at several Department of Defense remanufacturing facilities trying to accomplish significant production system modernization. TD has several advantages over other modeling techniques. First, it quickly does ``As-ls`` analysis and then moves on to identify improvements. Second, creating one large diagram makes it easier to share the TD model throughout an organization, rather than the many linked 8 1/2 {times} 11`` drawings used in traditional decomposition approaches. Third, it acts as a communication mechanism to share understanding about improvement opportunities that may cross existing functional/organizational boundaries. Finally, TD acts as a vehicle to build a consensus on a prioritized list of improvement efforts that ``hangs togethers as an agenda for systemic changes in the production system and the improved integration of support functions.
Two-band model with off-diagonal occupation dependent hopping rate
Zawadowski, A.
1989-01-01
In this paper two-band hopping model is treated on a two-dimensional square lattice. The atoms are located at the corners and the middles of the edges of the squares. In addition to the strongly overlapping orbitals of the atoms, there are extra orbitals at the corners, which are weakly hybridized. The assumption is made that the Fermi level is inside the broad band and is every near to the narrow band formed by the extra orbitals. The hamiltonian is Hubbard type, but the off-diagonal part of the two-site interaction t is kept also where one creation or annihilation operator acts on the extra orbital and the others on one of its neighbors. The weak coupling t is enhanced by the on-site Coulomb repulsion at the corners, which enhancement is a power function of the ratio of the broad band width and the narrow bank position measured from the Fermi level. That enhancement is obtained by summation of logarithmic Kondo-type corrections of orbital origin, which reflects the formation of a ground state of new type with strong orbital and spin correlations. Interaction between the particles of the broad band is generated by processes with one heavy and one light particle in the intermediate state
Isogeometric shell formulation based on a classical shell model
Niemi, Antti
2012-09-04
This paper constitutes the first steps in our work concerning isogeometric shell analysis. An isogeometric shell model of the Reissner-Mindlin type is introduced and a study of its accuracy in the classical pinched cylinder benchmark problem presented. In contrast to earlier works [1,2,3,4], the formulation is based on a shell model where the displacement, strain and stress fields are defined in terms of a curvilinear coordinate system arising from the NURBS description of the shell middle surface. The isogeometric shell formulation is implemented using the PetIGA and igakit software packages developed by the authors. The igakit package is a Python package used to generate NURBS representations of geometries that can be utilised by the PetIGA finite element framework. The latter utilises data structures and routines of the portable, extensible toolkit for scientific computation (PETSc), [5,6]. The current shell implementation is valid for static, linear problems only, but the software package is well suited for future extensions to geometrically and materially nonlinear regime as well as to dynamic problems. The accuracy of the approach in the pinched cylinder benchmark problem and present comparisons against the h-version of the finite element method with bilinear elements. Quadratic, cubic and quartic NURBS discretizations are compared against the isoparametric bilinear discretization introduced in [7]. The results show that the quadratic and cubic NURBS approximations exhibit notably slower convergence under uniform mesh refinement as the thickness decreases but the quartic approximation converges relatively quickly within the standard variational framework. The authors future work is concerned with building an isogeometric finite element method for modelling nonlinear structural response of thin-walled shells undergoing large rigid-body motions. The aim is to use the model in a aeroelastic framework for the simulation of flapping wings.
Statistics and the shell model
Weidenmueller, H.A.
1985-01-01
Starting with N. Bohr's paper on compound-nucleus reactions, we confront regular dynamical features and chaotic motion in nuclei. The shell-model and, more generally, mean-field theories describe average nuclear properties which are thus identified as regular features. The fluctuations about the average show chaotic behaviour of the same type as found in classical chaotic systems upon quantisation. These features are therefore generic and quite independent of the specific dynamics of the nucleus. A novel method to calculate fluctuations is discussed, and the results of this method are described. (orig.)
History and future perspectives of the Monte Carlo shell model -from Alphleet to K computer-
Shimizu, Noritaka; Otsuka, Takaharu; Utsuno, Yutaka; Mizusaki, Takahiro; Honma, Michio; Abe, Takashi
2013-01-01
We report a history of the developments of the Monte Carlo shell model (MCSM). The MCSM was proposed in order to perform large-scale shell-model calculations which direct diagonalization method cannot reach. Since 1999 PC clusters were introduced for parallel computation of the MCSM. Since 2011 we participated the High Performance Computing Infrastructure Strategic Program and developed a new MCSM code for current massively parallel computers such as K computer. We discuss future perspectives concerning a new framework and parallel computation of the MCSM by incorporating conjugate gradient method and energy-variance extrapolation
Isogeometric shell formulation based on a classical shell model
Niemi, Antti; Collier, Nathan; Dalcí n, Lisandro D.; Ghommem, Mehdi; Calo, Victor M.
2012-01-01
The authors future work is concerned with building an isogeometric finite element method for modelling nonlinear structural response of thin-walled shells undergoing large rigid-body motions. The aim is to use the model in a aeroelastic framework for the simulation of flapping wings.
Domain wall partition function of the eight-vertex model with a non-diagonal reflecting end
Yang Wenli; Chen Xi; Feng Jun; Hao Kun; Shi Kangjie; Sun Chengyi; Yang Zhanying; Zhang Yaozhong
2011-01-01
With the help of the Drinfeld twist or factorizing F-matrix for the eight-vertex SOS model, we derive the recursion relations of the partition function for the eight-vertex model with a generic non-diagonal reflecting end and domain wall boundary condition. Solving the recursion relations, we obtain the explicit determinant expression of the partition function. Our result shows that, contrary to the eight-vertex model without a reflecting end, the partition function can be expressed as a single determinant.
Angular momentum dependence of the distribution of shell model eigenenergies
Yen, M.K.
1974-01-01
In the conventional shell model calculation the many-particle energy matrices are constructed and diagonalized for definite angular momentum and parity. However the resulting set of eigenvalues possess a near normal behavior and hence a simple statistical description is possible. Usually one needs only about four parameters to capture the average level densities if the size of the set is not too small. The parameters are essentially moments of the distribution. But the difficulty lies in the yet unsolved problem of calculating moments in the fixed angular momentum subspace. We have derived a formula to approximate the angular momentum projection dependence of any operator averaged in a shell model basis. This approximate formula which is a truncated series in Hermite polynomials has been proved very good numerically and justified analytically for large systems. Applying this formula to seven physical cases we have found that the fixed angular momentum projection energy centroid, width and higher central moments can be obtained accurately provided for even-even nuclei the even and odd angular momentum projections are treated separately. Using this information one can construct the energy distribution for fixed angular momentum projection assuming normal behavior. Then the fixed angular momentum level densities are deduced and spectra are extracted. Results are in reasonably good agreement with the exact values although not as good as those obtained using exact fixed angular momentum moments. (Diss. Abstr. Int., B)
Monte Carlo evaluation of path integral for the nuclear shell model
Lang, G.H.
1993-01-01
The authors present a path-integral formulation of the nuclear shell model using auxillary fields; the path-integral is evaluated by Monte Carlo methods. The method scales favorably with valence-nucleon number and shell-model basis: full-basis calculations are demonstrated up to the rare-earth region, which cannot be treated by other methods. Observables are calculated for the ground state and in a thermal ensemble. Dynamical correlations are obtained, from which strength functions are extracted through the Maximum Entropy method. Examples in the s-d shell, where exact diagonalization can be carried out, compared well with exact results. The open-quotes sign problemclose quotes generic to quantum Monte Carlo calculations is found to be absent in the attractive pairing-plus-multipole interactions. The formulation is general for interacting fermion systems and is well suited for parallel computation. The authors have implemented it on the Intel Touchstone Delta System, achieving better than 99% parallelization
Quark shell model using projection operators
Ullah, N.
1988-01-01
Using the projection operators in the quark shell model, the wave functions for proton are calculated and expressions for calculating the wave function of neutron and also magnetic moment of proton and neutron are derived. (M.G.B.)
Extensions to a nonlinear finite-element axisymmetric shell model based on Reissner's shell theory
Cook, W.A.
1981-01-01
Extensions to shell analysis not usually associated with shell theory are described in this paper. These extensions involve thick shells, nonlinear materials, a linear normal stress approximation, and a changing shell thickness. A finite element shell-of-revolution model has been developed to analyze nuclear material shipping containers under severe impact conditions. To establish the limits for this shell model, the basic assumptions used in its development were studied; these are listed in this paper. Several extensions were evident from the study of these limits: a thick shell, a plastic hinge, and a linear normal stress
Open source integrated modeling environment Delta Shell
Donchyts, G.; Baart, F.; Jagers, B.; van Putten, H.
2012-04-01
In the last decade, integrated modelling has become a very popular topic in environmental modelling since it helps solving problems, which is difficult to model using a single model. However, managing complexity of integrated models and minimizing time required for their setup remains a challenging task. The integrated modelling environment Delta Shell simplifies this task. The software components of Delta Shell are easy to reuse separately from each other as well as a part of integrated environment that can run in a command-line or a graphical user interface mode. The most components of the Delta Shell are developed using C# programming language and include libraries used to define, save and visualize various scientific data structures as well as coupled model configurations. Here we present two examples showing how Delta Shell simplifies process of setting up integrated models from the end user and developer perspectives. The first example shows coupling of a rainfall-runoff, a river flow and a run-time control models. The second example shows how coastal morphological database integrates with the coastal morphological model (XBeach) and a custom nourishment designer. Delta Shell is also available as open-source software released under LGPL license and accessible via http://oss.deltares.nl.
Correlation between eigenvalues and sorted diagonal matrix elements of a large dimensional matrix
Arima, A.
2008-01-01
Functional dependences of eigenvalues as functions of sorted diagonal elements are given for realistic nuclear shell model (NSM) hamiltonian, the uniform distribution hamiltonian and the GOE hamiltonian. In the NSM case, the dependence is found to be linear. We discuss extrapolation methods for more accurate predictions for low-lying states. (author)
Shell model calculations for exotic nuclei
Brown, B.A.; Wildenthal, B.H.
1991-01-01
A review of the shell-model approach to understanding the properties of light exotic nuclei is given. Binding energies including p and p-sd model spaces and sd and sd-pf model spaces; cross-shell excitations around 32 Mg, including weak-coupling aspects and mechanisms for lowering the ntw excitations; beta decay properties of neutron-rich sd model, of p-sd and sd-pf model spaces, of proton-rich sd model space; coulomb break-up cross sections are discussed. (G.P.) 76 refs.; 12 figs
No-Core Shell Model for A = 47 and A = 49
Vary, J P; Negoita, A G; Stoica, S
2006-11-13
We apply the no-core shell model to the nuclear structure of odd-mass nuclei straddling {sup 48}Ca. Starting with the NN interaction, that fits two-body scattering and bound state data, we evaluate the nuclear properties of A = 47 and A = 49 nuclei while preserving all the underlying symmetries. Due to model space limitations and the absence of three-body interactions, we incorporate phenomenological interaction terms determined by fits to A = 48 nuclei in a previous effort. Our modified Hamiltonian produces reasonable spectra for these odd-mass nuclei. In addition to the differences in single-particle basis states, the absence of a single-particle Hamiltonian in our no-core approach complicates comparisons with valence effective NN interactions. We focus on purely off-diagonal two-body matrix elements since they are not affected by ambiguities in the different roles for one-body potentials and we compare selected sets of fp-shell matrix elements of our initial and modified Hamiltonians in the harmonic oscillator basis with those of a recent model fp-shell interaction, the GXPF1 interaction of Honma et al. While some significant differences emerge from these comparisons, there is an overall reasonably good correlation between our off-diagonal matrix elements and those of GXPF1.
Collectivity in heavy nuclei in the shell model Monte Carlo approach
Özen, C.; Alhassid, Y.; Nakada, H.
2014-01-01
The microscopic description of collectivity in heavy nuclei in the framework of the configuration-interaction shell model has been a major challenge. The size of the model space required for the description of heavy nuclei prohibits the use of conventional diagonalization methods. We have overcome this difficulty by using the shell model Monte Carlo (SMMC) method, which can treat model spaces that are many orders of magnitude larger than those that can be treated by conventional methods. We identify a thermal observable that can distinguish between vibrational and rotational collectivity and use it to describe the crossover from vibrational to rotational collectivity in families of even-even rare-earth isotopes. We calculate the state densities in these nuclei and find them to be in close agreement with experimental data. We also calculate the collective enhancement factors of the corresponding level densities and find that their decay with excitation energy is correlated with the pairing and shape phase transitions. (author)
Modeling of microencapsulated polymer shell solidification
Boone, T.; Cheung, L.; Nelson, D.; Soane, D.; Wilemski, G.; Cook, R.
1995-01-01
A finite element transport model has been developed and implemented to complement experimental efforts to improve the quality of ICF target shells produced via controlled-mass microencapsulation. The model provides an efficient means to explore the effect of processing variables on the dynamics of shell dimensions, concentricity, and phase behavior. Comparisons with experiments showed that the model successfully predicts the evolution of wall thinning and core/wall density differences. The model was used to efficiently explore and identify initial wall compositions and processing temperatures which resulted in concentricity improvements from 65 to 99%. The evolution of trace amounts of water entering into the shell wall was also tracked in the simulations. Comparisons with phase envelope estimations from modified UNIFAP calculations suggest that the water content trajectory approaches the two-phase region where vacuole formation via microphase separation may occur
Shell model description of Ge isotopes
Hirsch, J G; Srivastava, P C
2012-01-01
A shell model study of the low energy region of the spectra in Ge isotopes for 38 ≤ N ≤ 50 is presented, analyzing the excitation energies, quadrupole moments, B(E2) values and occupation numbers. The theoretical results have been compared with the available experimental data. The shell model calculations have been performed employing three different effective interactions and valence spaces. We have used two effective shell model interactions, JUN45 and jj44b, for the valence space f 5/2 pg 9/2 without truncation. To include the proton subshell f 7/2 in valence space we have employed the fpg effective interaction due to Sorlin et al., with 48 Ca as a core and a truncation in the number of excited particles.
Pair shell model description of collective motions
Chen Hsitseng; Feng Dahsuan
1996-01-01
The shell model in the pair basis has been reviewed with a case study of four particles in a spherical single-j shell. By analyzing the wave functions according to their pair components, the novel concept of the optimum pairs was developed which led to the proposal of a generalized pair mean-field method to solve the many-body problem. The salient feature of the method is its ability to handle within the framework of the spherical shell model a rotational system where the usual strong configuration mixing complexity is so simplified that it is now possible to obtain analytically the band head energies and the moments of inertia. We have also examined the effects of pair truncation on rotation and found the slow convergence of adding higher spin pairs. Finally, we found that when the SDI and Q .Q interactions are of equal strengths, the optimum pair approximation is still valid. (orig.)
Diagonalization of Hamiltonian; Diagonalization of Hamiltonian
Garrido, L M; Pascual, P
1960-07-01
We present a general method to diagonalized the Hamiltonian of particles of arbitrary spin. In particular we study the cases of spin 0,1/2, 1 and see that for spin 1/2 our transformation agrees with Foldy's and obtain the expression for different observables for particles of spin C and 1 in the new representation. (Author) 7 refs.
Syaina, L. P.; Majidi, M. A.
2018-04-01
Single impurity Anderson model describes a system consisting of non-interacting conduction electrons coupled with a localized orbital having strongly interacting electrons at a particular site. This model has been proven successful to explain the phenomenon of metal-insulator transition through Anderson localization. Despite the well-understood behaviors of the model, little has been explored theoretically on how the model properties gradually evolve as functions of hybridization parameter, interaction energy, impurity concentration, and temperature. Here, we propose to do a theoretical study on those aspects of a single impurity Anderson model using the distributional exact diagonalization method. We solve the model Hamiltonian by randomly generating sampling distribution of some conducting electron energy levels with various number of occupying electrons. The resulting eigenvalues and eigenstates are then used to define the local single-particle Green function for each sampled electron energy distribution using Lehmann representation. Later, we extract the corresponding self-energy of each distribution, then average over all the distributions and construct the local Green function of the system to calculate the density of states. We repeat this procedure for various values of those controllable parameters, and discuss our results in connection with the criteria of the occurrence of metal-insulator transition in this system.
Wellposedness of a cylindrical shell model
McMillan, C.
1994-01-01
We consider a well-known model of a thin cylindrical shell with dissipative feedback controls on the boundary in the form of forces, shears, and moments. We show that the resulting closed loop feedback problem generates a s.c. semigroup of contractions in the energy space
Electromagnetic and weak observables in the context of the shell model
Wildenthal, B.H.
1984-01-01
Wave functions for A = 17-39 nuclei have been obtained from diagonalizations of a single Hamiltonian formulation in the complete sd-shell configuration space for each NTJ system. These wave functions are used to generate the one-body density matrices corresponding to weak and electromagnetic transitions and moments. These densities are combined with different assumptions for the single-particle matrix elements of the weak and electromagnetic operators to produce theoretical matrix elements. The predictions are compared with experiment to determine, in some ''linearly dependent'' fashion, the correctness of the wave functions themselves, the optimum values of the single-particle matrix elements, and the viability of the overall shell-model formulation. (author)
Importance-truncated shell model for multi-shell valence spaces
Stumpf, Christina; Vobig, Klaus; Roth, Robert [Institut fuer Kernphysik, TU Darmstadt (Germany)
2016-07-01
The valence-space shell model is one of the work horses in nuclear structure theory. In traditional applications, shell-model calculations are carried out using effective interactions constructed in a phenomenological framework for rather small valence spaces, typically spanned by one major shell. We improve on this traditional approach addressing two main aspects. First, we use new effective interactions derived in an ab initio approach and, thus, establish a connection to the underlying nuclear interaction providing access to single- and multi-shell valence spaces. Second, we extend the shell model to larger valence spaces by applying an importance-truncation scheme based on a perturbative importance measure. In this way, we reduce the model space to the relevant basis states for the description of a few target eigenstates and solve the eigenvalue problem in this physics-driven truncated model space. In particular multi-shell valence spaces are not tractable otherwise. We combine the importance-truncated shell model with refined extrapolation schemes to approximately recover the exact result. We present first results obtained in the importance-truncated shell model with the newly derived ab initio effective interactions for multi-shell valence spaces, e.g., the sdpf shell.
On the shell model connection of the cluster model
Cseh, J.; Levai, G.; Kato, K.
2000-01-01
Complete text of publication follows. The interrelation of basic nuclear structure models is a longstanding problem. The connection between the spherical shell model and the quadrupole collective model has been studied extensively, and symmetry considerations proved to be especially useful in this respect. A collective band was interpreted in the shell model language long ago as a set of states (of the valence nucleons) with a specific SU(3) symmetry. Furthermore, the energies of these rotational states are obtained to a good approximation as eigenvalues of an SU(3) dynamically symmetric shell model Hamiltonian. On the other hand the relation of the shell model and cluster model is less well explored. The connection of the harmonic oscillator (i.e. SU(3)) bases of the two approaches is known, but it was established only for the unrealistic harmonic oscillator interactions. Here we investigate the question: Can an SU(3) dynamically symmetric interaction provide a similar connection between the spherical shell model and the cluster model, like the one between the shell and collective models? In other words: whether or not the energy of the states of the cluster bands, defined by a specific SU(3) symmetries, can be obtained from a shell model Hamiltonian (with SU(3) dynamical symmetry). We carried out calculations within the framework of the semimicroscopic algebraic cluster model, in which not only the cluster model space is obtained from the full shell model space by an SU(3) symmetry-dictated truncation, but SU(3) dynamically symmetric interactions are also applied. Actually, Hamiltonians of this kind proved to be successful in describing the gross features of cluster states in a wide energy range. The novel feature of the present work is that we apply exclusively shell model interactions. The energies obtained from such a Hamiltonian for several bands of the ( 12 C, 14 C, 16 O, 20 Ne, 40 Ca) + α systems turn out to be in good agreement with the experimental
Independent oscillator model of a heat bath: exact diagonalization of the Hamiltonian
Ford, G.W.; Lewis, J.T.; O'Connell, R.F.
1988-01-01
The problem of a quantum oscillator coupled to an independent-oscillator model of a heat bath is discussed. The transformation to normal coordinates is explicitly constructed using the method of Ullersma. With this transformation an alternative derivation of an exact formula for the oscillator free energy is constructed. The various contributions to the oscillator energy are calculated, with the aim of further understanding this formula. Finally, the limitations of linear coupling models, such as that used by Ullersma, are discussed in the form of some critical remarks
Ogino, Masao
2016-01-01
Actual problems in science and industrial applications are modeled by multi-materials and large-scale unstructured mesh, and the finite element analysis has been widely used to solve such problems on the parallel computer. However, for large-scale problems, the iterative methods for linear finite element equations suffer from slow or no convergence. Therefore, numerical methods having both robust convergence and scalable parallel efficiency are in great demand. The domain decomposition method is well known as an iterative substructuring method, and is an efficient approach for parallel finite element methods. Moreover, the balancing preconditioner achieves robust convergence. However, in case of problems consisting of very different materials, the convergence becomes bad. There are some research to solve this issue, however not suitable for cases of complex shape and composite materials. In this study, to improve convergence of the balancing preconditioner for multi-materials, a balancing preconditioner combined with the diagonal scaling preconditioner, called Scaled-BDD method, is proposed. Some numerical results are included which indicate that the proposed method has robust convergence for the number of subdomains and shows high performances compared with the original balancing preconditioner. (author)
Extensions to a nonlinear finite element axisymmetric shell model based on Reissner's shell theory
Cook, W.A.
1981-01-01
A finite element shell-of-revolution model has been developed to analyze shipping containers under severe impact conditions. To establish the limits for this shell model, I studied the basic assumptions used in its development; these are listed in this paper. Several extensions were evident from the study of these limits: a thick shell, a plastic hinge, and a linear normal stress. (orig./HP)
Foroughi Pour, Ali; Dalton, Lori A
2018-03-21
Many bioinformatics studies aim to identify markers, or features, that can be used to discriminate between distinct groups. In problems where strong individual markers are not available, or where interactions between gene products are of primary interest, it may be necessary to consider combinations of features as a marker family. To this end, recent work proposes a hierarchical Bayesian framework for feature selection that places a prior on the set of features we wish to select and on the label-conditioned feature distribution. While an analytical posterior under Gaussian models with block covariance structures is available, the optimal feature selection algorithm for this model remains intractable since it requires evaluating the posterior over the space of all possible covariance block structures and feature-block assignments. To address this computational barrier, in prior work we proposed a simple suboptimal algorithm, 2MNC-Robust, with robust performance across the space of block structures. Here, we present three new heuristic feature selection algorithms. The proposed algorithms outperform 2MNC-Robust and many other popular feature selection algorithms on synthetic data. In addition, enrichment analysis on real breast cancer, colon cancer, and Leukemia data indicates they also output many of the genes and pathways linked to the cancers under study. Bayesian feature selection is a promising framework for small-sample high-dimensional data, in particular biomarker discovery applications. When applied to cancer data these algorithms outputted many genes already shown to be involved in cancer as well as potentially new biomarkers. Furthermore, one of the proposed algorithms, SPM, outputs blocks of heavily correlated genes, particularly useful for studying gene interactions and gene networks.
Neutrino nucleosynthesis in supernovae: Shell model predictions
Haxton, W.C.
1989-01-01
Almost all of the 3 · 10 53 ergs liberated in a core collapse supernova is radiated as neutrinos by the cooling neutron star. I will argue that these neutrinos interact with nuclei in the ejected shells of the supernovae to produce new elements. It appears that this nucleosynthesis mechanism is responsible for the galactic abundances of 7 Li, 11 B, 19 F, 138 La, and 180 Ta, and contributes significantly to the abundances of about 15 other light nuclei. I discuss shell model predictions for the charged and neutral current allowed and first-forbidden responses of the parent nuclei, as well as the spallation processes that produce the new elements. 18 refs., 1 fig., 1 tab
Shell model for warm rotating nuclei
Matsuo, M.; Yoshida, K. [Kyoto Univ. (Japan); Dossing, T. [Univ. of Copenhagen (Denmark)] [and others
1996-12-31
Utilizing a shell model which combines the cranked Nilsson mean-field and the residual surface and volume delta two-body forces, the authors discuss the onset of rotational damping in normal- and super-deformed nuclei. Calculation for a typical normal deformed nucleus {sup 168}Yb indicates that the rotational damping sets in at around 0.8 MeV above the yrast line, and about 30 rotational bands of various length exists at a given rotational frequency, in overall agreement with experimental findings. It is predicted that the onset of rotational damping changes significantly in different superdeformed nuclei due to the variety of the shell gaps and single-particle orbits associated with the superdeformed mean-field.
No-Core Shell Model and Reactions
Navratil, P; Ormand, W E; Caurier, E; Bertulani, C
2005-01-01
There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ab initio methods to describe nuclear reactions. In this contribution, we present a brief overview of the NCSM with examples of recent applications as well as the first steps taken toward nuclear reaction applications. In particular, we discuss cross section calculations of p+ 6 Li and 6 He+p scattering as well as a calculation of the astrophysically important 7 Be(p, γ) 8 B S-factor
Dynamical symmetries of the shell model
Van Isacker, P.
2000-01-01
The applications of spectrum generating algebras and of dynamical symmetries in the nuclear shell model are many and varied. They stretch back to Wigner's early work on the supermultiplet model and encompass important landmarks in our understanding of the structure of the atomic nucleus such as Racah's SU(2) pairing model and Elliot's SU(3) rotational model. One of the aims of this contribution has been to show the historical importance of the idea of dynamical symmetry in nuclear physics. Another has been to indicate that, in spite of being old, this idea continues to inspire developments that are at the forefront of today's research in nuclear physics. It has been argued in this contribution that the main driving features of nuclear structure can be represented algebraically but at the same time the limitations of the symmetry approach must be recognised. It should be clear that such approach can only account for gross properties and that any detailed description requires more involved numerical calculations of which we have seen many fine examples during this symposium. In this way symmetry techniques can be used as an appropriate starting point for detailed calculations. A noteworthy example of this approach is the pseudo-SU(3) model which starting from its initial symmetry Ansatz has grown into an adequate and powerful description of the nucleus in terms of a truncated shell model. (author)
On the shell-model-connection of the cluster model
Cseh, J.
2000-01-01
Complete text of publication follows. The interrelation of basic nuclear structure models is a longstanding problem. The connection between the spherical shell model and the quadrupole collective model has been studied extensively, and symmetry considerations proved to be especially useful in this respect. A collective band was interpreted in the shell model language long ago [1] as a set of states (of the valence nucleons) with a specific SU(3) symmetry. Furthermore, the energies of these rotational states are obtained to a good approximation as eigenvalues of an SU(3) dynamically symmetric shell model Hamiltonian. On the other hand the relation of the shell model and cluster model is less well explored. The connection of the harmonic oscillator (i.e. SU(3)) bases of the two approaches is known [2] but it was established only for the unrealistic harmonic oscillator interactions. Here we investigate the question: Can an SU(3) dynamically symmetric interaction provide a similar connection between the spherical shell model and the cluster model, like the one between the shell and collective models? In other words: whether or not the energy of the states of the cluster bands, defined by a specific SU(3) symmetries, can be obtained from a shell model Hamiltonian (with SU(3) dynamical symmetry). We carried out calculations within the framework of the semimicroscopic algebraic cluster model [3,4] in order to find an answer to this question, which seems to be affirmative. In particular, the energies obtained from such a Hamiltonian for several bands of the ( 12 C, 14 C, 16 O, 20 Ne, 40 Ca) + α systems turn out to be in good agreement with the experimental values. The present results show that the simple and transparent SU(3) connection between the spherical shell model and the cluster model is valid not only for the harmonic oscillator interactions, but for much more general (SU(3) dynamically symmetric) Hamiltonians as well, which result in realistic energy spectra. Via
Note on off-shell relations in nonlinear sigma model
Chen, Gang; Du, Yi-Jian; Li, Shuyi; Liu, Hanqing
2015-01-01
In this note, we investigate relations between tree-level off-shell currents in nonlinear sigma model. Under Cayley parametrization, all odd-point currents vanish. We propose and prove a generalized U(1) identity for even-point currents. The off-shell U(1) identity given in http://dx.doi.org/10.1007/JHEP01(2014)061 is a special case of the generalized identity studied in this note. The on-shell limit of this identity is equivalent with the on-shell KK relation. Thus this relation provides the full off-shell correspondence of tree-level KK relation in nonlinear sigma model.
Finite element model for nonlinear shells of revolution
Cook, W.A.
1979-01-01
Nuclear material shipping containers have shells of revolution as basic structural components. Analytically modeling the response of these containers to severe accident impact conditions requires a nonlinear shell-of-revolution model that accounts for both geometric and material nonlinearities. Existing models are limited to large displacements, small rotations, and nonlinear materials. The paper presents a finite element model for a nonlinear shell of revolution that will account for large displacements, large strains, large rotations, and nonlinear materials
A study of the Gaussian overlap approach in the two-center shell model
Reinhard, P.-G.
1976-01-01
The Gaussian overlap approach (GOA) to the generator coordinate method (GCM) is carried through up to fourth order in the derivatives. By diagonalizing the norm overlap, a collective Schroedinger equation is obtained. The potential therein contains the usual potential energy surface (PES) plus correction terms, which subtract the zero-point energies (ZPE) is the PES. The formalism is applied to BCS states obtained from a two-center shell model (TCSM). To understand the crucial role of the pairing contributions in the GOA a schematic picture, the multi-level model, is constructed. An explicit numerical study of the convergence of the GOA is given for the TCSM, with the result that the GOA seems to be justified for medium and heavy nuclei but critical for light nuclei. (Auth.)
Structural Acoustic Physics Based Modeling of Curved Composite Shells
2017-09-19
NUWC-NPT Technical Report 12,236 19 September 2017 Structural Acoustic Physics -Based Modeling of Curved Composite Shells Rachel E. Hesse...SUBTITLE Structural Acoustic Physics -Based Modeling of Curved Composite Shells 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...study was to use physics -based modeling (PBM) to investigate wave propagations through curved shells that are subjected to acoustic excitation. An
Type I Shell Galaxies as a Test of Gravity Models
Vakili, Hajar; Rahvar, Sohrab [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Kroupa, Pavel, E-mail: vakili@physics.sharif.edu [Helmholtz-Institut für Strahlen-und Kernphysik, Universität Bonn, Nussallee 14-16, D-53115 Bonn (Germany)
2017-10-10
Shell galaxies are understood to form through the collision of a dwarf galaxy with an elliptical galaxy. Shell structures and kinematics have been noted to be independent tools to measure the gravitational potential of the shell galaxies. We compare theoretically the formation of shells in Type I shell galaxies in different gravity theories in this work because this is so far missing in the literature. We include Newtonian plus dark halo gravity, and two non-Newtonian gravity models, MOG and MOND, in identical initial systems. We investigate the effect of dynamical friction, which by slowing down the dwarf galaxy in the dark halo models limits the range of shell radii to low values. Under the same initial conditions, shells appear on a shorter timescale and over a smaller range of distances in the presence of dark matter than in the corresponding non-Newtonian gravity models. If galaxies are embedded in a dark matter halo, then the merging time may be too rapid to allow multi-generation shell formation as required by observed systems because of the large dynamical friction effect. Starting from the same initial state, the observation of small bright shells in the dark halo model should be accompanied by large faint ones, while for the case of MOG, the next shell generation patterns iterate with a specific time delay. The first shell generation pattern shows a degeneracy with the age of the shells and in different theories, but the relative distance of the shells and the shell expansion velocity can break this degeneracy.
Transition sum rules in the shell model
Lu, Yi; Johnson, Calvin W.
2018-03-01
An important characterization of electromagnetic and weak transitions in atomic nuclei are sum rules. We focus on the non-energy-weighted sum rule (NEWSR), or total strength, and the energy-weighted sum rule (EWSR); the ratio of the EWSR to the NEWSR is the centroid or average energy of transition strengths from an nuclear initial state to all allowed final states. These sum rules can be expressed as expectation values of operators, which in the case of the EWSR is a double commutator. While most prior applications of the double commutator have been to special cases, we derive general formulas for matrix elements of both operators in a shell model framework (occupation space), given the input matrix elements for the nuclear Hamiltonian and for the transition operator. With these new formulas, we easily evaluate centroids of transition strength functions, with no need to calculate daughter states. We apply this simple tool to a number of nuclides and demonstrate the sum rules follow smooth secular behavior as a function of initial energy, as well as compare the electric dipole (E 1 ) sum rule against the famous Thomas-Reiche-Kuhn version. We also find surprising systematic behaviors for ground-state electric quadrupole (E 2 ) centroids in the s d shell.
Continuum shell-model with complicated configurations
Barz, H.W.; Hoehn, J.
1977-05-01
The traditional shell model has been combined with the coupled channels method in order to describe resonance reactions. For that purpose the configuration space is divided into two subspaces (Feshbach projection method). Complicated shell-model configurations can be included into the subspace of discrete states which contains the single particle resonance states too. In the subspace of scattering states the equation of motion is solved by using the coupled channels method. Thereby the orthogonality between scattering states and discrete states is ensured. Resonance states are defined with outgoing waves in all channels. By means of simple model calculations the special role of the continuum is investigated. In this connection the energy dependence of the resonance parameters, the isospin mixture via the continuum, threshold effect, as well as the influence of the number of channels taken into account on the widths, positions and dipole strengths of the resonance are discussed. The model is mainly applied to the description of giant resonances excited by the scattering of nucleons and photo-nucleus processes (source term method) found in reactions on light nuclei. The giant resonance observed in the 15 N(p,n) reaction is explained by the inclusion of 2p-2h states. The same is true for the giant resonance in 13 C(J = 1/2, 3/2) as well as for the giant resonance built on the first 3 - state in 16 O. By means of a correlation analysis for the reduced widths amplitudes an access to the doorway conception is found. (author)
Chaotic diagonal recurrent neural network
Wang Xing-Yuan; Zhang Yi
2012-01-01
We propose a novel neural network based on a diagonal recurrent neural network and chaos, and its structure and learning algorithm are designed. The multilayer feedforward neural network, diagonal recurrent neural network, and chaotic diagonal recurrent neural network are used to approach the cubic symmetry map. The simulation results show that the approximation capability of the chaotic diagonal recurrent neural network is better than the other two neural networks. (interdisciplinary physics and related areas of science and technology)
Oscillating shells: A model for a variable cosmic object
Nunez, Dario
1997-01-01
A model for a possible variable cosmic object is presented. The model consists of a massive shell surrounding a compact object. The gravitational and self-gravitational forces tend to collapse the shell, but the internal tangential stresses oppose the collapse. The combined action of the two types of forces is studied and several cases are presented. In particular, we investigate the spherically symmetric case in which the shell oscillates radially around a central compact object.
Shell model the Monte Carlo way
Ormand, W.E.
1995-01-01
The formalism for the auxiliary-field Monte Carlo approach to the nuclear shell model is presented. The method is based on a linearization of the two-body part of the Hamiltonian in an imaginary-time propagator using the Hubbard-Stratonovich transformation. The foundation of the method, as applied to the nuclear many-body problem, is discussed. Topics presented in detail include: (1) the density-density formulation of the method, (2) computation of the overlaps, (3) the sign of the Monte Carlo weight function, (4) techniques for performing Monte Carlo sampling, and (5) the reconstruction of response functions from an imaginary-time auto-correlation function using MaxEnt techniques. Results obtained using schematic interactions, which have no sign problem, are presented to demonstrate the feasibility of the method, while an extrapolation method for realistic Hamiltonians is presented. In addition, applications at finite temperature are outlined
Shell model the Monte Carlo way
Ormand, W.E.
1995-03-01
The formalism for the auxiliary-field Monte Carlo approach to the nuclear shell model is presented. The method is based on a linearization of the two-body part of the Hamiltonian in an imaginary-time propagator using the Hubbard-Stratonovich transformation. The foundation of the method, as applied to the nuclear many-body problem, is discussed. Topics presented in detail include: (1) the density-density formulation of the method, (2) computation of the overlaps, (3) the sign of the Monte Carlo weight function, (4) techniques for performing Monte Carlo sampling, and (5) the reconstruction of response functions from an imaginary-time auto-correlation function using MaxEnt techniques. Results obtained using schematic interactions, which have no sign problem, are presented to demonstrate the feasibility of the method, while an extrapolation method for realistic Hamiltonians is presented. In addition, applications at finite temperature are outlined.
Ground state energy fluctuations in the nuclear shell model
Velazquez, Victor; Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Zuker, Andres P.
2005-01-01
Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well-defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states
Shell model studies in the N = 54 isotones 99Rh, 100Pd
Ghugre, S.S.; Sarkar, S.; Chintalapudi, S.N.
1996-01-01
The shell model in reproducing the observed level is used to investigate the observed level sequences in 99 Rh and 100 Pd within the spherical shell model framework. Shell model calculations have been performed using the code OXBASH
Isospin invariant boson models for fp-shell nuclei
Van Isacker, P.
1994-01-01
Isospin invariant boson models, IBM-3 and IBM-4, applicable in nuclei with neutrons and protons in the same valence shell, are reviewed. Some basic results related to these models are discussed: the mapping onto the shell model, the relation to Wigner's supermultiplet scheme, the boson-number and isospin dependence of parameters, etc. These results are examined for simple single-j shell situations (e.g. f 7/2 ) and their extension to the f p shell is investigated. Other extensions discussed here concern the treatment of odd-mass nuclei and the classification of particle-hole excitations in light nuclei. The possibility of a pseudo-SU(4) supermultiplet scheme in f p -shell nuclei is discussed. (author) 4 figs., 3 tabs., 23 refs
Statistical properties of the nuclear shell-model Hamiltonian
Dias, H.; Hussein, M.S.; Oliveira, N.A. de
1986-01-01
The statistical properties of realistic nuclear shell-model Hamiltonian are investigated in sd-shell nuclei. The probability distribution of the basic-vector amplitude is calculated and compared with the Porter-Thomas distribution. Relevance of the results to the calculation of the giant resonance mixing parameter is pointed out. (Author) [pt
Shell model description of band structure in 48Cr
Vargas, Carlos E.; Velazquez, Victor M.
2007-01-01
The band structure for normal and abnormal parity bands in 48Cr are described using the m-scheme shell model. In addition to full fp-shell, two particles in the 1d3/2 orbital are allowed in order to describe intruder states. The interaction includes fp-, sd- and mixed matrix elements
Comparing several boson mappings with the shell model
Menezes, D.P.; Yoshinaga, Naotaka; Bonatsos, D.
1990-01-01
Boson mappings are an essential step in establishing a connection between the successful phenomenological interacting boson model and the shell model. The boson mapping developed by Bonatsos, Klein and Li is applied to a single j-shell and the resulting energy levels and E2 transitions are shown for a pairing plus quadrupole-quadrupole Hamiltonian. The results are compared to the exact shell model calculation, as well as to these obtained through use of the Otsuka-Arima-Iachello mapping and the Zirnbauer-Brink mapping. In all cases good results are obtained for the spherical and near-vibrational cases
Deriving the nuclear shell model from first principles
Barrett, Bruce R.; Dikmen, Erdal; Vary, James P.; Maris, Pieter; Shirokov, Andrey M.; Lisetskiy, Alexander F.
2014-09-01
The results of an 18-nucleon No Core Shell Model calculation, performed in a large basis space using a bare, soft NN interaction, can be projected into the 0 ℏω space, i.e., the sd -shell. Because the 16 nucleons in the 16O core are frozen in the 0 ℏω space, all the correlations of the 18-nucleon system are captured by the two valence, sd -shell nucleons. By the projection, we obtain microscopically the sd -shell 2-body effective interactions, the core energy and the sd -shell s.p. energies. Thus, the input for standard shell-model calculations can be determined microscopically by this approach. If the same procedure is then applied to 19-nucleon systems, the sd -shell 3-body effective interactions can also be obtained, indicating the importance of these 3-body effective interactions relative to the 2-body effective interactions. Applications to A = 19 and heavier nuclei with different intrinsic NN interactions will be presented and discussed. The results of an 18-nucleon No Core Shell Model calculation, performed in a large basis space using a bare, soft NN interaction, can be projected into the 0 ℏω space, i.e., the sd -shell. Because the 16 nucleons in the 16O core are frozen in the 0 ℏω space, all the correlations of the 18-nucleon system are captured by the two valence, sd -shell nucleons. By the projection, we obtain microscopically the sd -shell 2-body effective interactions, the core energy and the sd -shell s.p. energies. Thus, the input for standard shell-model calculations can be determined microscopically by this approach. If the same procedure is then applied to 19-nucleon systems, the sd -shell 3-body effective interactions can also be obtained, indicating the importance of these 3-body effective interactions relative to the 2-body effective interactions. Applications to A = 19 and heavier nuclei with different intrinsic NN interactions will be presented and discussed. Supported by the US NSF under Grant No. 0854912, the US DOE under
Clustering of 1p-shell nuclei in the framework of the shell model
Kwasniewicz, E.
1991-01-01
The two- and three-fragment clustering of the 1p-shell nuclei has been studied in the framework of the shell model. The absolute probabilities of the required types of clustering in a given nucleus have been obtained by projecting its realistic shell-model wavefunction onto the suitable subspace of the orthonormal, completely antisymmetric two- or three-cluster states. With the aid of these data the selectivity in population of final states produced in multinucleon transfer reactions has been discussed. This problem has also been considered in the approach where the exchange of nucleons between clusters has been neglected. This has enabled to demonstrate the role of the complete antisymmetrization in predicting the intensities of states populated in multinucleon transfer reactions. The compact theory of the multinucleon one- and two-cluster spectroscopic amplitudes has been formulated. The examples of studying the nuclear structure and reactions with the aid of these spectroscopic amplitudes have been presented. (author)
A finite element model for nonlinear shells of revolution
Cook, W.A.
1979-01-01
A shell-of-revolution model was developed to analyze impact problems associated with the safety analysis of nuclear material shipping containers. The nonlinear shell theory presented by Eric Reissner in 1972 was used to develop our model. Reissner's approach includes transverse shear deformation and moments turning about the middle surface normal. With these features, this approach is valid for both thin and thick shells. His theory is formulated in terms of strain and stress resultants that refer to the undeformed geometry. This nonlinear shell model is developed using the virtual work principle associated with Reissner's equilibrium equations. First, the virtual work principle is modified for incremental loading; then it is linearized by assuming that the nonlinear portions of the strains are known. By iteration, equilibrium is then approximated for each increment. A benefit of this approach is that this iteration process makes it possible to use nonlinear material properties. (orig.)
Modeling the carbon isotope composition of bivalve shells (Invited)
Romanek, C.
2010-12-01
The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., 90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope fractionation
Recent shell-model results for exotic nuclei
Utsuno Yusuke
2014-03-01
Full Text Available We report on our recent advancement in the shell model and its applications to exotic nuclei, focusing on the shell evolution and large-scale calculations with the Monte Carlo shell model (MCSM. First, we test the validity of the monopole-based universal interaction (VMU as a shell-model interaction by performing large-scale shell-model calculations in two different mass regions using effective interactions which partly comprise VMU. Those calculations are successful and provide a deeper insight into the shell evolution beyond the single-particle model, in particular showing that the evolution of the spin-orbit splitting due to the tensor force plays a decisive role in the structure of the neutron-rich N ∼ 28 region and antimony isotopes. Next, we give a brief overview of recent developments in MCSM, and show that it is applicable to exotic nuclei that involve many valence orbits. As an example of its applications to exotic nuclei, shape coexistence in 32Mg is examined.
Shell-model predictions for Lambda Lambda hypernuclei
Gal, A.; Millener, D.
2011-01-01
It is shown how the recent shell-model determination of ΛN spin-dependent interaction terms in Λ hypernuclei allows for a reliable deduction of ΛΛ separation energies in ΛΛ hypernuclei across the nuclear p shell. Comparison is made with the available data, highlighting # Lambda# # Lambda# 11 Be and # Lambda# # Lambda# 12 Be which have been suggested as possible candidates for the KEK-E373 HIDA event.
Ab Initio Symmetry-Adapted No-Core Shell Model
Draayer, J P; Dytrych, T; Launey, K D
2011-01-01
A multi-shell extension of the Elliott SU(3) model, the SU(3) symmetry-adapted version of the no-core shell model (SA-NCSM), is described. The significance of this SA-NCSM emerges from the physical relevance of its SU(3)-coupled basis, which – while it naturally manages center-of-mass spuriosity – provides a microscopic description of nuclei in terms of mixed shape configurations. Since typically configurations of maximum spatial deformation dominate, only a small part of the model space suffices to reproduce the low-energy nuclear dynamics and hence, offers an effective symmetry-guided framework for winnowing of model space. This is based on our recent findings of low-spin and high-deformation dominance in realistic NCSM results and, in turn, holds promise to significantly enhance the reach of ab initio shell models.
Experimental Damage Identification of a Model Reticulated Shell
Jing Xu
2017-04-01
Full Text Available The damage identification of a reticulated shell is a challenging task, facing various difficulties, such as the large number of degrees of freedom (DOFs, the phenomenon of modal localization and transition, and low modeling accuracy. Based on structural vibration responses, the damage identification of a reticulated shell was studied. At first, the auto-regressive (AR time series model was established based on the acceleration responses of the reticulated shell. According to the changes in the coefficients of the AR model between the damaged conditions and the undamaged condition, the damage of the reticulated shell can be detected. In addition, the damage sensitive factors were determined based on the coefficients of the AR model. With the damage sensitive factors as the inputs and the damage positions as the outputs, back-propagation neural networks (BPNNs were then established and were trained using the Levenberg–Marquardt algorithm (L–M algorithm. The locations of the damages can be predicted by the back-propagation neural networks. At last, according to the experimental scheme of single-point excitation and multi-point responses, the impact experiments on a K6 shell model with a scale of 1/10 were conducted. The experimental results verified the efficiency of the proposed damage identification method based on the AR time series model and back-propagation neural networks. The proposed damage identification method can ensure the safety of the practical engineering to some extent.
Many-body forces in nuclear shell-model
Rath, P.K.
1985-01-01
In the microscopic derivation of the effective Hamiltonian for the nuclear shell model many-body forces between the valence nucleons occur. These many-body forces can be discriminated in ''real'' many-body forces, which can be related to mesonic and internal degrees of freedom of the nucleons, and ''effective'' many-body forces, which arise by the confinement of the nucleonic Hilbert space to the finite-dimension shell-model space. In the present thesis the influences of such three-body forces on the spectra of sd-shell nuclei are studied. For this the two common techniques for shell-model calculations (Oak Ridge-Rochester and Glasgow representation) are extended in such way that a general three-body term in the Hamiltonian can be regarded. The studies show that the repulsive contributions of the considered three-nucleon forces become more important with increasing number of valence nucleons. By this the particle-number dependence of empirical two-nucleon forces can be qualitatively explained. A special kind of effective many-body force occurs in the folded diagram expansion of the energy-dependent effective Hamiltonian for the shell model. Thereby it is shown that the contributions of the folded diagrams with three nucleons are just as important as those with two nucleons. Thus it is to be suspected that the folded diagram expansion contains many-particle terms with arbitrary particle number. The present studies however show that four nucleon effects are neglegible so that the folded diagram expansion can be confined to two- and three-particle terms. In shell-model calculations which extend over several main shells the influences of the spurious center-of-mass motion must be regarded. A procedure is discussed by which these spurious degrees of freedom can be exactly separated. (orig.) [de
Computational Lower Bounds Using Diagonalization
Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 7. Computational Lower Bounds Using Diagonalization - Languages, Turing Machines and Complexity Classes. M V Panduranga Rao. General Article Volume 14 Issue 7 July 2009 pp 682-690 ...
Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian
Scalettar, R.T.; Batrouni, G.G.; Kampf, A.P.; Zimanyi, G.T.
1995-01-01
The Bose-Hubbard model exhibits a rich phase diagram consisting both of insulating regimes where diagonal long-range (solid) order dominates as well as conducting regimes where off-diagonal long-range order (superfluidity) is present. In this paper we describe the results of quantum Monte Carlo calculations of the phase diagram, both for the hard- and soft-core cases, with a particular focus on the possibility of simultaneous superfluid and solid order. We also discuss the appearance of phase separation in the model. The simulations are compared with analytic calculations of the phase diagram and spin-wave dispersion
Shell model truncation schemes for rotational nuclei
Halse, P.; Jaqua, L.; Barrett, B.R.
1990-01-01
The suitability of the pair condensate approach for rotational states is studied in a single j = 17/2 shell of identical nucleons interacting through a quadrupole-quadrupole hamiltonian. The ground band and a K = 2 excited band are both studied in detail. A direct comparison of the exact states with those constituting the SD and SDG subspaces is used to identify the important degrees of freedom for these levels. The range of pairs necessary for a good description is found to be highly state dependent; S and D pairs are the major constituents of the low-spin ground band levels, while G pairs are needed for those in the γ-band. Energy spectra are obtained for each truncated subspace. SDG pairs allow accurate reproduction of the binding energy and K = 2 excitation energy, but still give a moment of inertia which is about 30% too small even for the lowest levels
Mayer–Jensen Shell Model and Magic Numbers
Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 12. Mayer-Jensen Shell Model and Magic Numbers - An Independent Nucleon Model with Spin-Orbit Coupling. R Velusamy. General Article Volume 12 Issue 12 December 2007 pp 12-24 ...
Decaying and kicked turbulence in a shell model
Hooghoudt, Jan Otto; Lohse, Detlef; Toschi, Federico
2001-01-01
Decaying and periodically kicked turbulence are analyzed within the Gledzer–Ohkitani–Yamada shell model, to allow for sufficiently large scaling regimes. Energy is transferred towards the small scales in intermittent bursts. Nevertheless, mean field arguments are sufficient to account for the ens......Decaying and periodically kicked turbulence are analyzed within the Gledzer–Ohkitani–Yamada shell model, to allow for sufficiently large scaling regimes. Energy is transferred towards the small scales in intermittent bursts. Nevertheless, mean field arguments are sufficient to account...
The experimental and shell model approach to 100Sn
Grawe, H.; Maier, K.H.; Fitzgerald, J.B.; Heese, J.; Spohr, K.; Schubart, R.; Gorska, M.; Rejmund, M.
1995-01-01
The present status of experimental approach to 100 Sn and its shell model structure is given. New developments in experimental techniques, such as low background isomer spectroscopy and charged particle detection in 4π are surveyed. Based on recent experimental data shell model calculations are used to predict the structure of the single- and two-nucleon neighbours of 100 Sn. The results are compared to the systematic of Coulomb energies and spin-orbit splitting and discussed with respect to future experiments. (author). 51 refs, 11 figs, 1 tab
Major shell centroids in the symplectic collective model
Draayer, J.P.; Rosensteel, G.; Tulane Univ., New Orleans, LA
1983-01-01
Analytic expressions are given for the major shell centroids of the collective potential V(#betta#, #betta#) and the shape observable #betta# 2 in the Sp(3,R) symplectic model. The tools of statistical spectroscopy are shown to be useful, firstly, in translating a requirement that the underlying shell structure be preserved into constraints on the parameters of the collective potential and, secondly, in giving a reasonable estimate for a truncation of the infinite dimensional symplectic model space from experimental B(E2) transition strengths. Results based on the centroid information are shown to compare favorably with results from exact calculations in the case of 20 Ne. (orig.)
Application of shell model with the modified surface delta interaction to 42Ca and 42Sc nuclei
Jasielska, A.; Wiktor, S.
1975-01-01
The shell model with MSDI residual interaction is used to investigate properties of levels in the 42 Ca and 42 Sc nuclei. The 40 Ca core with two active outer nucleons is assumed. The energy matrices are diagonalized and the calculated level schemes for both 42 Ca and 42 Sc nuclei are presented. In both nuclei the density of the calculated levels is significantly less than of the observed levels. This fact leads to the conclusion, that some core excitation modes play an important role in the formation of low-lying states in the 42 Ca and 42 Sc nuclei. The calculated eigenvalues and eigenvectors of the states below 5 MeV are given. (author)
The alpha-particle and shell models of the nucleus
Perring, J.K.; Skyrme, T.H.R.
1994-01-01
It is shown that it is possible to write down α-particle wave functions for the ground states of 8 Be, 12 C and 16 O, which become, when antisymmetrized, identical with shell-model wave functions. The α-particle functions are used to obtain potentials which can then be used to derive wave functions and energies of excited states. Most of the low-lying states of 16 O are obtained in this way, qualitative agreement with experiment being found. The shell structure of the 0 + level at 6·06 MeV is analyzed, and is found to consist largely of single-particle excitations. The lifetime for pair-production is calculated, and found to be comparable with the experimental value. The validity of the method is discussed, and comparison made with shell-model calculations. (author). 5 refs, 1 tab
Shell model Monte Carlo investigation of rare earth nuclei
White, J. A.; Koonin, S. E.; Dean, D. J.
2000-01-01
We utilize the shell model Monte Carlo method to study the structure of rare earth nuclei. This work demonstrates the first systematic full oscillator shell with intruder calculations in such heavy nuclei. Exact solutions of a pairing plus quadrupole Hamiltonian are compared with the static path approximation in several dysprosium isotopes from A=152 to 162, including the odd mass A=153. Some comparisons are also made with Hartree-Fock-Bogoliubov results from Baranger and Kumar. Basic properties of these nuclei at various temperatures and spin are explored. These include energy, deformation, moments of inertia, pairing channel strengths, band crossing, and evolution of shell model occupation numbers. Exact level densities are also calculated and, in the case of 162 Dy, compared with experimental data. (c) 2000 The American Physical Society
Rajpoot, Subhash [California State University, Long Beach, CA (United States); Vacaru, Sergiu I. [Quantum Gravity Research, Topanga, CA (United States); University ' ' Al.I. Cuza' ' , Project IDEI, Iasi (Romania)
2017-05-15
Applying the anholonomic frame deformation method, we construct various classes of cosmological solutions for effective Einstein-Yang-Mills-Higgs, and two measure theories. The types of models considered are Freedman-Lemaitre-Robertson-Walker, Bianchi, Kasner and models with attractor configurations. The various regimes pertaining to plateau-type inflation, quadratic inflation, Starobinsky type and Higgs type inflation are presented. (orig.)
Sahito, Zafarullah; Vaisanen, Pertti
2017-01-01
The purpose of this study is to explore the strongest areas of all prime theories of job satisfaction and motivation to create a new multidimensional model. This model relies on all explored areas from the logical comparison of content and process theories to understand the phenomenon of job satisfaction and motivation of employees. The model…
Yurisman
2010-11-01
Full Text Available This paper presents results of numerical and experimental study of shear link behavior, utilizing diagonal stiffener on web of steel profile to increase shear link performance in an eccentric braced frame (EBF of a steel structure system. The specimen is to examine the behavior of shear link by using diagonal stiffener on web part under static monotonic and cyclic load. The cyclic loading pattern conducted in the experiment is adjusted according to AISC loading standards 2005. Analysis was carried out using non-linear finite element method using MSC/NASTRAN software. Link was modeled as CQUAD shell element. Along the boundary of the loading area the nodal are constraint to produce only one direction loading. The length of the link in this analysis is 400mm of the steel profile of WF 200.100. Important parameters considered to effect significantly to the performance of shear link have been analyzed, namely flange and web thicknesses, , thickness and length of web stiffener, thickness of diagonal stiffener and geometric of diagonal stiffener. The behavior of shear link with diagonal web stiffener was compared with the behavior of standard link designed based on AISC 2005 criteria. Analysis results show that diagonal web stiffener is capable to increase shear link performance in terms of stiffness, strength and energy dissipation in supporting lateral load. However, differences in displacement ductility’s between shear links with diagonal stiffener and shear links based on AISC standards have not shown to be significant. Analysis results also show thickness of diagonal stiffener and geometric model of stiffener to have a significant influence on the performance of shear links. To perform validation of the numerical study, the research is followed by experimental work conducted in Structural Mechanic Laboratory Center for Industrial Engineering ITB. The Structures and Mechanics Lab rotary PAU-ITB. The experiments were carried out using three test
Testing refined shell-model interactions in the sd shell: Coulomb excitation of Na26
Siebeck, B; Blazhev, A; Reiter, P; Altenkirch, R; Bauer, C; Butler, P A; De Witte, H; Elseviers, J; Gaffney, L P; Hess, H; Huyse, M; Kröll, T; Lutter, R; Pakarinen, J; Pietralla, N; Radeck, F; Scheck, M; Schneiders, D; Sotty, C; Van Duppen, P; Vermeulen, M; Voulot, D; Warr, N; Wenander, F
2015-01-01
Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal sd interaction (USD) describing nuclei within the sd shell yielded two new interactions—USDA and USDB—causing changes in the theoretical description of these nuclei. Purpose: Transition matrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent test for the newly derived interactions. The nucleus Na26 with 7 valence neutrons and 3 valence protons outside the doubly-magic 16O core is used as a test case. Method: A radioactive beam experiment with Na26 (T1/2=1,07s) was performed at the REX-ISOLDE facility (CERN) using Coulomb excitation at safe energies below the Coulomb barrier. Scattered particles were detected with an annular Si detector in coincidence with γ rays observed by the segmented MINIBALL array. Coulomb excitation cross sections...
Shell Model Far From Stability: Island of Inversion Mergers
Nowacki, F.; Poves, A.
2018-02-01
In this study we propose a common mechanism for the disappearance of shell closures far from stabilty. With the use of Large Scale Shell Model calculations (SM-CI), we predict that the region of deformation which comprises the heaviest Chromium and Iron isotopes at and beyond N=40 will merge with a new one at N=50 in an astonishing parallel to the N=20 and N=28 case in the Neon and Magnesium isotopes. We propose a valence space including the full pf-shell for the protons and the full sdg shell for the neutrons, which represents a come-back of the the harmonic oscillator shells in the very neutron rich regime. Our calculations preserve the doubly magic nature of the ground state of 78Ni, which, however, exhibits a well deformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability. This new Island of Inversion (IoI) adds to the four well documented ones at N=8, 20, 28 and 40.
Shell model test of the Porter-Thomas distribution
Grimes, S.M.; Bloom, S.D.
1981-01-01
Eigenvectors have been calculated for the A=18, 19, 20, 21, and 26 nuclei in an sd shell basis. The decomposition of these states into their shell model components shows, in agreement with other recent work, that this distribution is not a single Gaussian. We find that the largest amplitudes are distributed approximately in a Gaussian fashion. Thus, many experimental measurements should be consistent with the Porter-Thomas predictions. We argue that the non-Gaussian form of the complete distribution can be simply related to the structure of the Hamiltonian
Final Report Fermionic Symmetries and Self consistent Shell Model
Zamick, Larry
2008-01-01
In this final report in the field of theoretical nuclear physics we note important accomplishments.We were confronted with 'anomoulous' magnetic moments by the experimetalists and were able to expain them. We found unexpected partial dynamical symmetries--completely unknown before, and were able to a large extent to expain them. The importance of a self consistent shell model was emphasized.
Deformed shell model studies of spectroscopic properties of Zn and ...
2014-04-05
Apr 5, 2014 ... April 2014 physics pp. 757–767. Deformed shell model studies of ... experiments without isotopical enrichment thereby reducing the cost considerably. By taking a large mass of the sample because of its low cost, one can ...
Bursts and shocks in a continuum shell model
Andersen, Ken Haste; Bohr, Tomas; Jensen, M.H.
1998-01-01
We study a burst event, i.e., the evolution of an initial condition having support only in a finite interval of k-space, in the continuum shell model due to Parisi. We show that the continuum equation without forcing or dissipation can be explicitly written in characteristic form and that the right...
Symmetry-guided large-scale shell-model theory
Launey, K. D.; Dytrych, Tomáš; Draayer, J. P.
2016-01-01
Roč. 89, JUL (2016), s. 101-136 ISSN 0146-6410 R&D Projects: GA ČR GA16-16772S Institutional support: RVO:61389005 Keywords : Ab intio shell -model theory * Symplectic symmetry * Collectivity * Clusters * Hoyle state * Orderly patterns in nuclei from first principles Subject RIV: BE - Theoretical Physics Impact factor: 11.229, year: 2016
Projected shell model study of neutron- deficient 122Ce
Projected shell model; band diagram; yrast energies; electromagnetic quan- ... signed to 122Ce by detecting γ-rays in coincidence with evaporated charged particles .... 0.75 from the free nucleon values to account for the core-polarization and ...
A different interpretation of the nuclear shell model
Fabre de la Ripelle, M.
1984-12-01
In the first order approximation the nucleons are moving into a collective well extracted from the two-body N-N interaction. The nuclear shell model is explained by the structure of the first order solution of the Schroedinger equation. In the next step the two-body correlations generated by the N-N potential are introduced in the wave function
A shell-model calculation in terms of correlated subsystems
Boisson, J.P.; Silvestre-Brac, B.
1979-01-01
A method for solving the shell-model equations in terms of a basis which includes correlated subsystems is presented. It is shown that the method allows drastic truncations of the basis to be made. The corresponding calculations are easy to perform and can be carried out rapidly
Chaotic behaviour of the nuclear shell-model hamiltonian
Dias, H.; Hussein, M.S.; Oliveira, N.A. de; Wildenthal, B.H.
1987-11-01
Large scale nuclear shell-model calculations for several nuclear systems are discussed. In particular, the statistical baheviour of the energy eigenvalues and eigenstates, are discussed. The chaotic behaviour of the NSMH is then shown to be quite useful in calculating the spreading width of the highly collective multipole giant resonances. (author) [pt
Quantum chaos in the two-center shell model
Milek, B; Noerenberg, W; Rozmej, P [Gesellschaft fuer Schwerionenforschung m.b.H., Darmstadt (Germany, F.R.)
1989-11-01
Within an axially symmetric two-center shell model single-particle levels with {Omega}=1/2 are analyzed with respect to their level-spacing distributions and avoided level crossings as functions of the shape parameters. Only for shapes sufficiently far from any additional symmetry, ideal Wigner distributions are found as signature for quantum chaos. (orig.).
Quantum chaos in the two-center shell model
Milek, B; Noerenberg, W; Rozmej, P
1989-03-01
Within an axially symmetric two-center shell model single-particle levels with ..cap omega.. = 1/2 are analyzed with respect to their level-spacing distributions and avoided level crossings as functions of the shape parameters. Only for shapes sufficiently far from any additional symmetry, ideal Wigner distributions are found as signature for quantum chaos.
Intruder level and deformation in SD-pair shell model
Luo Yan'an; Ning Pingzhi; Pan Feng
2004-01-01
The influence of intruder level on nuclear deformation is studied within the framework of the nucleon-pair shell model truncated to an SD-pair subspace. The results suggest that the intruder level has a tendency to reduce the deformation and plays an important role in determining the onset of rotational behavior. (authors)
Acoustic modeling of shell-encapsulated gas bubbles
P.J.A. Frinking (Peter); N. de Jong (Nico)
1998-01-01
textabstractExisting theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents Quantison(TM) and Myomap(TM). An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and
Non-diagonal processes of singlet and ordinary quark production
Bejlin, V.A.; Vereshkov, G.M.; Kuksa, V.I.
1995-01-01
Non-diagonal processes of singlet and ordinary quark production are analyzed in the model where the down singlet quark mixes with the ordinary ones. The possibility of experimental selection of h-quark effects is demonstrated
Super-hypernuclei in the quark-shell model, 2
Terazawa, Hidezumi.
1989-07-01
By following the previous paper, where the quark-shell model of nuclei in quantum chromodynamics is briefly reviewed, a short review of the MIT bag model of nuclei is presented for comparison and a simple estimate of the Hλ ('hexalambda') mass is also made for illustration. Furthermore, an even shorter review of the 'nucleon cluster model' of nuclei is presented for further comparison. (J.P.N.)
In-medium no-core shell model for ab initio nuclear structure calculations
Gebrerufael, Eskendr
2017-01-01
In this work, we merge two successful ab initio nuclear-structure methods, the no-core shell model (NCSM) and the multi-reference in-medium similarity renormalization group (IM-SRG), to define a novel many-body approach for the comprehensive description of ground and excited states of closed- and open-shell medium-mass nuclei. Building on the key advantages of the two methods - the decoupling of excitations at the many-body level in the IM-SRG, and the exact diagonalization in the NCSM applicable up to medium-light nuclei - their combination enables fully converged no-core calculations for an unprecedented range of nuclei and observables at moderate computational cost. The efficiency and rapid model-space convergence of the new approach make it ideally suited for ab initio studies of ground and low-lying excited states of nuclei up to the medium-mass regime. Interactions constructed within the framework of chiral effective field theory provide an excellent opportunity to describe properties of nuclei from first principles, i.e., rooted in quantum chromodynamics, they overcome the lack of predictive power of phenomenological potentials. The hard core of these interactions causes strong short-range correlations, which we soften by using the similarity-renormalization-group transformation that accelerates the model-space convergence of many-body calculations. Three-nucleon effects, which are mandatory for the correct description of bulk properties of nuclei, are included in our calculations by using the normal-ordered two-body approximation, which has been shown to be sufficient to capture the main effects of the three-nucleon interaction. Using these interactions, we analyze energies of ground and excited states in the carbon and oxygen isotopic chains, where conventional NCSM calculations are still feasible and provide an important benchmark. Furthermore, we study the Hoyle state in 12 C - a three-alpha cluster state that cannot be converged in standard NCSM
The Nuclear Shell Model and its Relation with Other Nuclear Models
Elliott, J. P. [University of Sussex, Brighton (United Kingdom)
1963-01-15
The starting point of all versions of the shell model is the physical idea that the interaction between a given nucleon and all the others resembles that between a nucleon and a fixed field. From this starting point one might attempt to construct a field which is self-consistent but this approach is not followed in most shell-model calculations because of the complications that arise. The more usual approach has been to use the idea of an average field to provide a complete set of sin gle-particle wave functions. Then, if the parameters of the field (e.g. its size) are correctly chosen, we would expect to reach a good approximation to the nuclear-wave function by taking that configuration of single-particle wave functions which has lowest energy in this field. The wave functions could clearly be improved by allowing the mixing of excited configurations but this is rarely done because of the resulting complexity of the problem. Even in the lowest configuration there are in general many independent wave functions for a many-particle system which would all be degenerate in the average field. To find the nuclear energy levels and wave functions we must therefore build up the energy matrix in this degenerate set, using the inter-nucleon two-body forces, and then diagonalize this matrix. If the detailed form of the nuclear forces was known we might regard such calculations as the first step towards an exact calculation in which higher configurations were included but every indication is that the convergence would be extremely slow. It is more usual to treat an energy calculation in the lowest configuration unashamedly as a model calculation and to attempt to deduce, by comparisons with experimental data in the many-particle nuclei, the nature of the effective nuclear forces required in that configuration. If the model is realistic then we should not expect these effective forces to change very much in going from one nucleus to its neighbour and since there are many more
Diagonalization of the mass matrices
Rhee, S.S.
1984-01-01
It is possible to make 20 types of 3x3 mass matrices which are hermitian. We have obtained unitary matrices which could diagonalize each mass matrix. Since the three elements of mass matrix can be expressed in terms of the three eigenvalues, msub(i), we can also express the unitary matrix in terms of msub(i). (Author)
On diagonalization in map(M,G)
Blau, M.; Thompson, G.
1995-01-01
Motivated by some questions in the path integral approach to (topological) gauge theories, we are led to address the following question: given a smooth map from a manifold M to a compact group G, is it possible to smoothly ''diagonalize'' it, i.e. conjugate it into a map to a maximal torus T of G? We analyze the local and global obstructions and give a complete solution to the problem for regular maps. We establish that these can always be smoothly diagonalized locally and that the obstructions to doing this globally are non-trivial Weyl group and torus bundles on M. We explain the relation of the obstructions to winding numbers of maps into G/T and restrictions of the structure group of a principal G bundle to T and examine the behaviour of gauge fields under this diagonalization. We also discuss the complications that arise in the presence of non-trivial G-bundles and for non-regular maps. We use these results to justify a Weyl integral formula for functional integrals which, as a novel feature not seen in the finite-dimensional case, contains a summation over all those topological T-sectors which arise as restrictions of a trivial principal G bundle and which was used previously to solve completely Yang-Mills theory and the G/ G model in two dimensions. (orig.)
MVDR Algorithm Based on Estimated Diagonal Loading for Beamforming
Yuteng Xiao
2017-01-01
Full Text Available Beamforming algorithm is widely used in many signal processing fields. At present, the typical beamforming algorithm is MVDR (Minimum Variance Distortionless Response. However, the performance of MVDR algorithm relies on the accurate covariance matrix. The MVDR algorithm declines dramatically with the inaccurate covariance matrix. To solve the problem, studying the beamforming array signal model and beamforming MVDR algorithm, we improve MVDR algorithm based on estimated diagonal loading for beamforming. MVDR optimization model based on diagonal loading compensation is established and the interval of the diagonal loading compensation value is deduced on the basis of the matrix theory. The optimal diagonal loading value in the interval is also determined through the experimental method. The experimental results show that the algorithm compared with existing algorithms is practical and effective.
Determination of Hamiltonian matrix for IBM4 and compare it is self value with shells model
Slyman, S.; Hadad, S.; Souman, H.
2004-01-01
The Hamiltonian is determined using the procedure OAI and the mapping of (IBM4) states into the shell model, which is based on the seniority classification scheme. A boson sub-matrix of the shell model Hamiltonian for the (sd) 4 configuration is constructed, and is proved to produce the same eigenvalues as the shell model Hamiltonian for the corresponding fermion states. (authors)
A REMARK ON FORMAL MODELS FOR NONLINEARLY ELASTIC MEMBRANE SHELLS
无
2001-01-01
This paper gives all the two-dimensional membrane models obtained from formal asymptotic analysis of the three-dimensional geometrically exact nonlinear model of a thin elastic shell made with a Saint Venant-Kirchhoff material. Therefore, the other models can be quoted as flexural nonlinear ones. The author also gives the formal equations solved by the associated stress tensor and points out that only one of those models leads, by linearization, to the “classical” linear limiting membrane model, whose juetification has already been established by a convergence theorem.
Theoretical spectroscopy and the fp shell
Poves, A.; Zuker, A.
1980-01-01
The recently developed quasiconfiguration method is applied to fp shell nuclei. Second order degenerate perturbation theory is shown to be sufficient to produce, for low lying states, the same results as large diagonalizations in the f(7/2)p(3/2)p(1/2)f(5/2)sup(n) full space. due to the operation of linked cluster mechanisms. Realistic interactions with minimal monopole changes are shown to be successful in reproducing spectra, binding energies, quadrupole moments and transition rates. Large shell model spaces are seen to exhibit typical many body behaviour. Quasiconfigurations allow insight into the underlying coupling schemes
Dynamic model of open shell structures buried in poroelastic soils
Bordón, J. D. R.; Aznárez, J. J.; Maeso, O.
2017-08-01
This paper is concerned with a three-dimensional time harmonic model of open shell structures buried in poroelastic soils. It combines the dual boundary element method (DBEM) for treating the soil and shell finite elements for modelling the structure, leading to a simple and efficient representation of buried open shell structures. A new fully regularised hypersingular boundary integral equation (HBIE) has been developed to this aim, which is then used to build the pair of dual BIEs necessary to formulate the DBEM for Biot poroelasticity. The new regularised HBIE is validated against a problem with analytical solution. The model is used in a wave diffraction problem in order to show its effectiveness. It offers excellent agreement for length to thickness ratios greater than 10, and relatively coarse meshes. The model is also applied to the calculation of impedances of bucket foundations. It is found that all impedances except the torsional one depend considerably on hydraulic conductivity within the typical frequency range of interest of offshore wind turbines.
Binding energies of sd-shell nuclei with a realistic effective Hamiltonian
Dalton, B.J.; Vary, J.P.; Baldridge, W.J.
1977-01-01
The nuclear shell model with a second-order effective Hamiltonian derived within Brueckner theory from the free nucleon-nucleon interaction is shown to yield accurate binding energies of nuclei with 16 < A < 40. This agreement is obtained by choosing the spectrum of low-lying unoccupied orbitals in a justified manner and, when necessary, by employing a statistical method to approximate the lowest eigenvalue of very large shell-model diagonalizations
Cluster shell model: I. Structure of 9Be, 9B
Della Rocca, V.; Iachello, F.
2018-05-01
We calculate energy spectra, electromagnetic transition rates, longitudinal and transverse electron scattering form factors and log ft values for beta decay in 9Be, 9B, within the framework of a cluster shell model. By comparing with experimental data, we find strong evidence for the structure of these nuclei to be two α-particles in a dumbbell configuration with Z2 symmetry, plus an additional nucleon.
Projected shell model description of N = 114 superdeformed isotone nuclei
Guo, R S; Chen, L M; Chou, C H
2006-01-01
A systematic description of the yrast superdeformed (SD) bands in N 114, Z = 80-84 isotone nuclei using the projected shell model is presented. The calculated γ-ray energies, moment of inertia and M1 transitions are compared with the data for which spin is assigned. Excellent agreement with the available data for all isotones is obtained. The calculated electromagnetic properties provide a microscopic understanding of those measured nuclei. Some predictions in superdeformed nuclei are also discussed
The modified Gauss diagonalization of polynomial matrices
Saeed, K.
1982-10-01
The Gauss algorithm for diagonalization of constant matrices is modified for application to polynomial matrices. Due to this modification the diagonal elements become pure polynomials rather than rational functions. (author)
An IBM-3 hamiltonian from a multi-j-shell model
Evans, J.A.; Elliott, J.P.; Lac, V.S.; Long, G.L.
1995-01-01
The number and isospin dependence of the hamiltonian in the isospin invariant form (IBM-3) of the boson model is deduced from a seniority mapping onto a shell-model system of several shells. The numerical results are compared with earlier work for a single j-shell. (orig.)
Shell model calculations for stoichiometric Na β-alumina
Wang, J.C.
1985-01-01
Walker and Catlow recently reported the results of their shell model calculations for the structure and transport of Na β-alumina (Naβ). The main computer programs used by Walker and Catlow for their calculations are PLUTO and HADES III. The latter, a recent version of HADES II written for cubic crystals, is believed to be applicable to defects in crystals of both cubic and hexagonal symmetry. PLUTO is usually used in calculating properties of perfect crystals before defects are introduced into the structure. Walker and Catlow claim that, in some respects, their models are superior to those of Wang et al. Yet, their results are quite different from those observed experimentally. In this work these differences are investigated by using a computer program designed to calculate lattice energies for s Naβ using the same shell model parameters adopted by Walker and Catlow. The core and shell positions of all ions, as well as the lattice parameters, were fully relaxed. The calculated energy difference between aBR and BR sites (0.33 eV) is about twice as large as that reported by Walker and Catlow. The present results also show that the relaxed oxygen ion positions next to the conduction plane in this case are displaced from their observed sites reported. When the core-shell spring constant of the oxygen ion was adjusted to minimize these displacements, the above-mentioned energy difference increased to about 0.56 eV. These results cast doubt on the fluid conduction plane structure suggested by Walker and Catlow and on the defect structure and activation energy obtained from their calculations
Recent evolution of theoretical models in inner shell photoionization
Combet Farnoux, F.
1978-01-01
This paper is a brief review of various atomic theoretical models recently developed to calculate photoionization cross sections in the low energy range (from the far ultraviolet to the soft X ray region). For both inner and outer shells concerned, we emphasize the necessity to go beyond the independent particle models by means of the introduction of correlation effects in both initial and final states. The basic physical ideas of as elaborated models as Random Phase Approximation with exchange, Many Body Perturbation Theory and R matrix Theory are outlined and summarized. As examples, the results of some calculations are shown and compared with experiment
Phases and phase transitions in the algebraic microscopic shell model
Georgieva A. I.
2016-01-01
Full Text Available We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott’s SU(3 basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3 basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.
The creep analysis of shell structures using generalised models
Boyle, J.T.; Spence, J.
1981-01-01
In this paper a new, more complete estimate of the accuracy of the stationary creep model is given for the general case through the evaluation of exact and approximate energy surfaces. In addition, the stationary model is extended to include more general non-stationary (combined elastic-creep) behaviour and to include the possibility of material deterioration through damage. The resulting models are then compared to existing exact solutions for several shell structures - e.g. a thin pressurised cylinder, a curved pipe in bending and an S-bellows under axial extension with large deflections. In each case very good agreement is obtained. Although requiring similar computing effort, so that the same solution techniques can be utilised, the calculation times are shown to be significantly reduced using the generalised approach. In conclusion, it has been demonstrated that a new simple mechanical model of a thin shell in creep, with or without material deterioration can be constructed; the model is assessed in detail and successfully compared to existing solutions. (orig./HP)
A Shell Model for Free Vibration Analysis of Carbon Nanoscroll
Amin Taraghi Osguei
2017-04-01
Full Text Available Carbon nanoscroll (CNS is a graphene sheet rolled into a spiral structure with great potential for different applications in nanotechnology. In this paper, an equivalent open shell model is presented to study the vibration behavior of a CNS with arbitrary boundary conditions. The equivalent parameters used for modeling the carbon nanotubes are implemented to simulate the CNS. The interactions between the layers of CNS due to van der Waals forces are included in the model. The uniformly distributed translational and torsional springs along the boundaries are considered to achieve a unified solution for different boundary conditions. To study the vibration characteristics of CNS, total energy including strain energy, kinetic energy, and van der Waals energy are minimized using the Rayleigh-Ritz technique. The first-order shear deformation theory has been utilized to model the shell. Chebyshev polynomials of first kind are used to obtain the eigenvalue matrices. The natural frequencies and corresponding mode shapes of CNS in different boundary conditions are evaluated. The effect of electric field in axial direction on the natural frequencies and mode shapes of CNS is investigated. The results indicate that, as the electric field increases, the natural frequencies decrease.
Holographic shell model: Stack data structure inside black holes?
Davidson, Aharon
2014-03-01
Rather than tiling the black hole horizon by Planck area patches, we suggest that bits of information inhabit, universally and holographically, the entire black core interior, a bit per a light sheet unit interval of order Planck area difference. The number of distinguishable (tagged by a binary code) configurations, counted within the context of a discrete holographic shell model, is given by the Catalan series. The area entropy formula is recovered, including Cardy's universal logarithmic correction, and the equipartition of mass per degree of freedom is proven. The black hole information storage resembles, in the count procedure, the so-called stack data structure.
Nuclear deformation in the configuration-interaction shell model
Alhassid, Y.; Bertsch, G. F.; Gilbreth, C. N.; Mustonen, M. T.
2018-02-01
We review a method that we recently introduced to calculate the finite-temperature distribution of the axial quadrupole operator in the laboratory frame using the auxiliary-field Monte Carlo technique in the framework of the configuration-interaction shell model. We also discuss recent work to determine the probability distribution of the quadrupole shape tensor as a function of intrinsic deformation β,γ by expanding its logarithm in quadrupole invariants. We demonstrate our method for an isotope chain of samarium nuclei whose ground states describe a crossover from spherical to deformed shapes.
Realistic shell-model calculations for Sn isotopes
Covello, A.; Andreozzi, F.; Coraggio, L.; Gargano, A.; Porrino, A.
1997-01-01
We report on a shell-model study of the Sn isotopes in which a realistic effective interaction derived from the Paris free nucleon-nucleon potential is employed. The calculations are performed within the framework of the seniority scheme by making use of the chain-calculation method. This provides practically exact solutions while cutting down the amount of computational work required by a standard seniority-truncated calculation. The behavior of the energy of several low-lying states in the isotopes with A ranging from 122 to 130 is presented and compared with the experimental one. (orig.)
Morphing the Shell Model into an Effective Theory
Haxton, W. C.; Song, C.-L.
2000-01-01
We describe a strategy for attacking the canonical nuclear structure problem--bound-state properties of a system of point nucleons interacting via a two-body potential--which involves an expansion in the number of particles scattering at high momenta, but is otherwise exact. The required self-consistent solutions of the Bloch-Horowitz equation for effective interactions and operators are obtained by an efficient Green's function method based on the Lanczos algorithm. We carry out this program for the simplest nuclei, d and 3 He , in order to explore the consequences of reformulating the shell model as a controlled effective theory. (c) 2000 The American Physical Society
Shell-model Monte Carlo studies of nuclei
Dean, D.J.
1997-01-01
The pair content and structure of nuclei near N = Z are described in the frwnework of shell-model Monte Carlo (SMMC) calculations. Results include the enhancement of J=0 T=1 proton-neutron pairing at N=Z nuclei, and the maxked difference of thermal properties between even-even and odd-odd N=Z nuclei. Additionally, a study of the rotational properties of the T=1 (ground state), and T=0 band mixing seen in 74 Rb is presented
Shell model in-water frequencies of the core barrel
Takeuchi, K.; De Santo, D.F.
1980-01-01
Natural frequencies of a 1/24th-scale core barrel/vessel model in air and in water are measured by determining frequency responses to applied forces. The measured data are analyzed by the use of the one-dimensional fluid-structure computer code, MULTIFLEX, developed to calculate the hydraulic force. The fluid-structure interaction in the downcomer annulus is computed with a one-dimensional network model formed to be equivalent to two-dimensional fluid-structure interaction. The structural model incorporated in MULTIFLEX is substantially simpler than that necessary for structural analyses. Proposed for computation of structural dynamics is the projector method than can deal with the beam mode by modal analysis and the other shell modes by a direct integration method. Computed in-air and in-water frequencies agree fairly well with the experimental data, verifying the above MULTIFLEX technique
Shell-model-based deformation analysis of light cadmium isotopes
Schmidt, T.; Heyde, K. L. G.; Blazhev, A.; Jolie, J.
2017-07-01
Large-scale shell-model calculations for the even-even cadmium isotopes 98Cd-108Cd have been performed with the antoine code in the π (2 p1 /2;1 g9 /2) ν (2 d5 /2;3 s1 /2;2 d3 /2;1 g7 /2;1 h11 /2) model space without further truncation. Known experimental energy levels and B (E 2 ) values could be well reproduced. Taking these calculations as a starting ground we analyze the deformation parameters predicted for the Cd isotopes as a function of neutron number N and spin J using the methods of model independent invariants introduced by Kumar [Phys. Rev. Lett. 28, 249 (1972), 10.1103/PhysRevLett.28.249] and Cline [Annu. Rev. Nucl. Part. Sci. 36, 683 (1986), 10.1146/annurev.ns.36.120186.003343].
Hopping transport and electrical conductivity in one-dimensional systems with off-diagonal disorder
Ma Songshan; Xu Hui; Li Yanfeng; Song Zhaoquan
2007-01-01
In this paper, we present a model to describe hopping transport and electrical conductivity of one-dimensional systems with off-diagonal disorder, in which electrons are transported via hopping between localized states. We find that off-diagonal disorder leads to delocalization and drastically enhances the electrical conductivity of systems. The model also quantitatively explains the temperature and electrical field dependence of the conductivity in one-dimensional systems with off-diagonal disorder. In addition, we also show the dependence of the conductivity on the strength of off-diagonal disorder
Modeling plate shell structures using pyFormex
Bagger, Anne; Verhegghe, Benedict; Hertz, Kristian Dahl
2009-01-01
A shell structure made of glass combines a light-weight structural concept with glass’ high permeability to light. If the geometry of the structure is plane-based facetted (plate shell structure), the glass elements will be plane panes, and these glass panes will comprise the primary load...... (plate shells and triangulated lattice shells) may not differ in complexity regarding the topology, but when it comes to the practical generation of the geometry, e.g. in CAD, the plate shell is far more troublesome to handle than the triangulated geometry. The free software tool “pyFormex”, developed...
Nondestructive identification of the Bell diagonal state
Jin Jiasen; Yu Changshui; Song Heshan
2011-01-01
We propose a scheme for identifying an unknown Bell diagonal state. In our scheme the measurements are performed on the probe qubits instead of the Bell diagonal state. The distinct advantage is that the quantum state of the evolved Bell diagonal state ensemble plus probe states will still collapse on the original Bell diagonal state ensemble after the measurement on probe states; i.e., our identification is quantum state nondestructive. How to realize our scheme in the framework of cavity electrodynamics is also shown.
Equivalence of the spherical and deformed shell-model approach to intruder states
Heyde, K.; Coster, C. de; Ryckebusch, J.; Waroquier, M.
1989-01-01
We point out that the description of intruder states, incorporating particle-hole (p-h) excitation across a closed shell in the spherical shell model or a description starting from the Nilsson model are equivalent. We furthermore indicate that the major part of the nucleon-nucleon interaction, responsible for the low excitation energy of intruder states comes as a two-body proton-neutron quadrupole interaction in the spherical shell model. In the deformed shell model, quadrupole binding energy is gained mainly through the one-body part of the potential. (orig.)
Xiulan BAO
2017-04-01
Full Text Available Nuts are the important economic forest tree species of China. De-shell is the key operation of nut deep processing. There are some problems in the current nut cracking devices such as the low decorticating rate, the high nuts losses rate and nutmeat integrity problems, etc.. The foundation of force analysis is to establish contact model for nut and mechanical. The nut surface is rough and irregular, so the contact area cannot be modeled as regular shape. How to set up contact constraint model is the key problem to accomplish non-loss shelling. In order to study the shell-breaking mechanism and structural design of the nut shelling manipulation, a multi-fingered metamorphic manipulator is presented. An overview of the nut shelling technology and the contact manipulator modeling are proposed. The origin and application of metamorphic mechanisms are introduced. Then the research contents and development prospects of nut shelling manipulator are described.
A progressive diagonalization scheme for the Rabi Hamiltonian
Pan, Feng; Guan, Xin; Wang, Yin; Draayer, J P
2010-01-01
A diagonalization scheme for the Rabi Hamiltonian, which describes a qubit interacting with a single-mode radiation field via a dipole interaction, is proposed. It is shown that the Rabi Hamiltonian can be solved almost exactly using a progressive scheme that involves a finite set of one variable polynomial equations. The scheme is especially efficient for the lower part of the spectrum. Some low-lying energy levels of the model with several sets of parameters are calculated and compared to those provided by the recently proposed generalized rotating-wave approximation and a full matrix diagonalization.
Li, Qian; Matula, Thomas J; Tu, Juan; Guo, Xiasheng; Zhang, Dong
2013-02-21
It has been accepted that the dynamic responses of ultrasound contrast agent (UCA) microbubbles will be significantly affected by the encapsulating shell properties (e.g., shell elasticity and viscosity). In this work, a new model is proposed to describe the complicated rheological behaviors in an encapsulating shell of UCA microbubbles by applying the nonlinear 'Cross law' to the shell viscous term in the Marmottant model. The proposed new model was verified by fitting the dynamic responses of UCAs measured with either a high-speed optical imaging system or a light scattering system. The comparison results between the measured radius-time curves and the numerical simulations demonstrate that the 'compression-only' behavior of UCAs can be successfully simulated with the new model. Then, the shell elastic and viscous coefficients of SonoVue microbubbles were evaluated based on the new model simulations, and compared to the results obtained from some existing UCA models. The results confirm the capability of the current model for reducing the dependence of bubble shell parameters on the initial bubble radius, which indicates that the current model might be more comprehensive to describe the complex rheological nature (e.g., 'shear-thinning' and 'strain-softening') in encapsulating shells of UCA microbubbles by taking into account the nonlinear changes of both shell elasticity and shell viscosity.
Li Qian; Tu Juan; Guo Xiasheng; Zhang Dong; Matula, Thomas J
2013-01-01
It has been accepted that the dynamic responses of ultrasound contrast agent (UCA) microbubbles will be significantly affected by the encapsulating shell properties (e.g., shell elasticity and viscosity). In this work, a new model is proposed to describe the complicated rheological behaviors in an encapsulating shell of UCA microbubbles by applying the nonlinear ‘Cross law’ to the shell viscous term in the Marmottant model. The proposed new model was verified by fitting the dynamic responses of UCAs measured with either a high-speed optical imaging system or a light scattering system. The comparison results between the measured radius–time curves and the numerical simulations demonstrate that the ‘compression-only’ behavior of UCAs can be successfully simulated with the new model. Then, the shell elastic and viscous coefficients of SonoVue microbubbles were evaluated based on the new model simulations, and compared to the results obtained from some existing UCA models. The results confirm the capability of the current model for reducing the dependence of bubble shell parameters on the initial bubble radius, which indicates that the current model might be more comprehensive to describe the complex rheological nature (e.g., ‘shear-thinning’ and ‘strain-softening’) in encapsulating shells of UCA microbubbles by taking into account the nonlinear changes of both shell elasticity and shell viscosity. (paper)
I.R. Zachek
2011-12-01
Full Text Available We elaborate a modification of the deformable two-sublattice Mitsui model of [Levitskii R.R. et al., Phys. Rev. B. 2003, Vol. 67, 174112] and [Levitskii R.R. et al., Condens. Matter Phys., 2005, Vol. 8, 881] that consistently takes into account diagonal components of the strain tensor, arising either due to external pressures or due to thermal expansion. We calculate the related to those strains thermal, piezoelectric, and elastic characteristics of the system. Using the developed fitting procedure, a set of the model parameters is found for the case of Rochelle salt crystals, providing a satisfactory agreement with the available experimental data for the hydrostatic and uniaxial pressure dependences of the Curie temperatures, temperature dependences of spontaneous diagonal strains, linear thermal expansion coefficients, elastic constants cijE and ci4E, piezoelectric coefficients d1i and g1i (i=1,2,3. The hydrostatic pressure variation of dielectric permittivity is described using a derived expression for the permittivity of a partially clamped crystal. The dipole moments and the asymmetry parameter of Rochelle salt are found to increase with hydrostatic pressure.
Fermion dynamical symmetry and the nuclear shell model
Ginocchio, J.N.
1985-01-01
The interacting boson model (IBM) has been very successful in giving a unified and simple description of the spectroscopic properties of a wide range of nuclei, from vibrational through rotational nuclei. The three basic assumptions of the model are that: (1) the valence nucleons move about a doubly closed core, (2) the collective low-lying states are composed primarily of coherent pairs of neutrons and pairs of protons coupled to angular momentum zero and two, and (3) these coherent pairs are approximated as bosons. In this review we shall show how it is possible to have fermion Hamiltonians which have a class of collective eigenstates composed entirely of monopole and quadrupole pairs of fermions. Hence these models satisfy the assumptions (1) and (2) above but no boson approximation need be made. Thus the Pauli principle is kept in tact. Furthermore the fermion shell model states excluded in the IBM can be classified by the number of fermion pairs which are not coherent monopole or quadrupole pairs. Hence the mixing of these states into the low-lying spectrum can be calculated in a systematic and tractable manner. Thus we can introduce features which are outside the IBM. 11 refs
Towards a shell-model description of intruder states and the onset of deformation
Heyde, K.; Van Isacker, P.; Casten, R.F.; Wood, J.L.
1985-01-01
Basing on the nuclear shell-model and concentrating on the monopole, pairing and quadrupole corrections originating from the nucleon-nucleon force, both the appearance of low-lying 0 + intruder states near major closed shells (Z = 50, 82) and sub-shell regions (Z = 40, 64) can be described. Moreover, a number of new facets related to the study of intruder states are presented. 19 refs., 3 figs
Extrapolation method in the Monte Carlo Shell Model and its applications
Shimizu, Noritaka; Abe, Takashi; Utsuno, Yutaka; Mizusaki, Takahiro; Otsuka, Takaharu; Honma, Michio
2011-01-01
We demonstrate how the energy-variance extrapolation method works using the sequence of the approximated wave functions obtained by the Monte Carlo Shell Model (MCSM), taking 56 Ni with pf-shell as an example. The extrapolation method is shown to work well even in the case that the MCSM shows slow convergence, such as 72 Ge with f5pg9-shell. The structure of 72 Se is also studied including the discussion of the shape-coexistence phenomenon.
Elementary isovector spin and orbital magnetic dipole modes revisited in the shell model
Richter, A.
1988-08-01
A review is given on the status of mainly spin magnetic dipole modes in some sd- and fp-shell nuclei studied with inelastic electron and proton scattering, and by β + -decay. Particular emphasis is also placed on a fairly new, mainly orbital magnetic dipole mode investigated by high-resolution (e,e') and (p,p') scattering experiments on a series of fp-shell nuclei. Both modes are discussed in terms of the shell model with various effective interactions. (orig.)
Van der Waals coefficients beyond the classical shell model
Tao, Jianmin, E-mail: jianmint@sas.upenn.edu [Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 (United States); Fang, Yuan; Hao, Pan [Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118 (United States); Scuseria, G. E. [Department of Chemistry and Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892, USA and Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Ruzsinszky, Adrienn; Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)
2015-01-14
Van der Waals (vdW) coefficients can be accurately generated and understood by modelling the dynamic multipole polarizability of each interacting object. Accurate static polarizabilities are the key to accurate dynamic polarizabilities and vdW coefficients. In this work, we present and study in detail a hollow-sphere model for the dynamic multipole polarizability proposed recently by two of the present authors (JT and JPP) to simulate the vdW coefficients for inhomogeneous systems that allow for a cavity. The inputs to this model are the accurate static multipole polarizabilities and the electron density. A simplification of the full hollow-sphere model, the single-frequency approximation (SFA), circumvents the need for a detailed electron density and for a double numerical integration over space. We find that the hollow-sphere model in SFA is not only accurate for nanoclusters and cage molecules (e.g., fullerenes) but also yields vdW coefficients among atoms, fullerenes, and small clusters in good agreement with expensive time-dependent density functional calculations. However, the classical shell model (CSM), which inputs the static dipole polarizabilities and estimates the static higher-order multipole polarizabilities therefrom, is accurate for the higher-order vdW coefficients only when the interacting objects are large. For the lowest-order vdW coefficient C{sub 6}, SFA and CSM are exactly the same. The higher-order (C{sub 8} and C{sub 10}) terms of the vdW expansion can be almost as important as the C{sub 6} term in molecular crystals. Application to a variety of clusters shows that there is strong non-additivity of the long-range vdW interactions between nanoclusters.
Comparative study on diagonal equivalent methods of masonry infill panel
Amalia, Aniendhita Rizki; Iranata, Data
2017-06-01
Infrastructure construction in earthquake prone area needs good design process, including modeling a structure in a correct way to reduce damages caused by an earthquake. Earthquakes cause many damages e.g. collapsed buildings that are dangerous. An incorrect modeling in design process certainly affects the structure's ability in responding to load, i.e. an earthquake load, and it needs to be paid attention to in order to reduce damages and fatalities. A correct modeling considers every aspect that affects the strength of a building, including stiffness of resisting lateral loads caused by an earthquake. Most of structural analyses still use open frame method that does not consider the effect of stiffness of masonry panel to the stiffness and strength of the whole structure. Effect of masonry panel is usually not included in design process, but the presence of this panel greatly affects behavior of the building in responding to an earthquake. In worst case scenario, it can even cause the building to collapse as what has been reported after great earthquakes worldwide. Modeling a structure with masonry panel as consideration can be performed by designing the panel as compression brace or shell element. In designing masonry panel as a compression brace, there are fourteen methods popular to be used by structure designers formulated by Saneinejad-Hobbs, Holmes, Stafford-Smith, Mainstones, Mainstones-Weeks, Bazan-Meli, Liauw Kwan, Paulay and Priestley, FEMA 356, Durani Luo, Hendry, Al-Chaar, Papia and Chen-Iranata. Every method has its own equation and parameters to use, therefore the model of every method was compared to results of experimental test to see which one gives closer values. Moreover, those methods also need to be compared to the open frame to see if they can result values within limits. Experimental test that was used in comparing all methods was taken from Mehrabi's research (Fig. 1), which was a prototype of a frame in a structure with 0.5 scale and the
Core-shell particles as model compound for studying fouling
Christensen, Morten Lykkegaard; Nielsen, Troels Bach; Andersen, Morten Boel Overgaard
2008-01-01
Synthetic colloidal particles with hard cores and soft, water-swollen shells were used to study cake formation during ultrafiltration. The total cake resistance was lowest for particles with thick shells, which indicates that interparticular forces between particles (steric hindrance...... and electrostatic repulsion) influenced cake formation. At low pressure the specific cake resistance could be predicted from the Kozeny-Carman equation. At higher pressures, the resistance increased due to cake compression. Both cake formation and compression were reversible. For particles with thick shells...
The shell model. Towards a unified description of nuclear structure
Poves, Alfredo [Departamento de Fisica Teorica, Universidad Autonoma Cantoblanco, 28049 - Madrid (Spain); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)
1998-12-31
In this series of lectures we present the foundations of the spherical shell model that we treat as an approximation to the exact solution of the full secular problem. We introduce the notions of valence space, effective interaction and effective operator. We analyse the structure of the realistic effective interactions, identifying their monopole part with the spherical mean field. The multipole Hamiltonian is shown to have a universal (simple) form that includes pairing (isovector and isoscalar), quadrupole, octupole, deca-pole, and ({sigma}{center_dot}{tau})({sigma}{center_dot}{tau}). We describe the methods of resolution of the secular problem, in particular the Lanczos method. The model is applied to the description of nuclear deformation and its relationship with the deformed mean field theories is studied. We propose a new symmetry, `quasi`-SU3, to understand deformation in the spherical basis. Finally, we discuss the domain of nuclei very far from the valley of {beta} stability, addressing the vanishing of some magic closures that can be explained in terms of intruder states. (author) 53 refs., 20 figs., 3 tabs.
Recent Developments in No-Core Shell-Model Calculations
Navratil, P.; Quaglioni, S.; Stetcu, I.; Barrett, B.R.
2009-01-01
We present an overview of recent results and developments of the no-core shell model (NCSM), an ab initio approach to the nuclear many-body problem for light nuclei. In this aproach, we start from realistic two-nucleon or two- plus three-nucleon interactions. Many-body calculations are performed using a finite harmonic-oscillator (HO) basis. To facilitate convergence for realistic inter-nucleon interactions that generate strong short-range correlations, we derive effective interactions by unitary transformations that are tailored to the HO basis truncation. For soft realistic interactions this might not be necessary. If that is the case, the NCSM calculations are variational. In either case, the ab initio NCSM preserves translational invariance of the nuclear many-body problem. In this review, we, in particular, highlight results obtained with the chiral two- plus three-nucleon interactions. We discuss efforts to extend the applicability of the NCSM to heavier nuclei and larger model spaces using importance-truncation schemes and/or use of effective interactions with a core. We outline an extension of the ab initio NCSM to the description of nuclear reactions by the resonating group method technique. A future direction of the approach, the ab initio NCSM with continuum, which will provide a complete description of nuclei as open systems with coupling of bound and continuum states is given in the concluding part of the review.
Recent Developments in No-Core Shell-Model Calculations
Navratil, P; Quaglioni, S; Stetcu, I; Barrett, B R
2009-03-20
We present an overview of recent results and developments of the no-core shell model (NCSM), an ab initio approach to the nuclear many-body problem for light nuclei. In this aproach, we start from realistic two-nucleon or two- plus three-nucleon interactions. Many-body calculations are performed using a finite harmonic-oscillator (HO) basis. To facilitate convergence for realistic inter-nucleon interactions that generate strong short-range correlations, we derive effective interactions by unitary transformations that are tailored to the HO basis truncation. For soft realistic interactions this might not be necessary. If that is the case, the NCSM calculations are variational. In either case, the ab initio NCSM preserves translational invariance of the nuclear many-body problem. In this review, we, in particular, highlight results obtained with the chiral two- plus three-nucleon interactions. We discuss efforts to extend the applicability of the NCSM to heavier nuclei and larger model spaces using importance-truncation schemes and/or use of effective interactions with a core. We outline an extension of the ab initio NCSM to the description of nuclear reactions by the resonating group method technique. A future direction of the approach, the ab initio NCSM with continuum, which will provide a complete description of nuclei as open systems with coupling of bound and continuum states is given in the concluding part of the review.
The shell model. Towards a unified description of nuclear structure
Poves, Alfredo
1998-01-01
In this series of lectures we present the foundations of the spherical shell model that we treat as an approximation to the exact solution of the full secular problem. We introduce the notions of valence space, effective interaction and effective operator. We analyse the structure of the realistic effective interactions, identifying their monopole part with the spherical mean field. The multipole Hamiltonian is shown to have a universal (simple) form that includes pairing (isovector and isoscalar), quadrupole, octupole, deca-pole, and (σ·τ)(σ·τ). We describe the methods of resolution of the secular problem, in particular the Lanczos method. The model is applied to the description of nuclear deformation and its relationship with the deformed mean field theories is studied. We propose a new symmetry, 'quasi'-SU3, to understand deformation in the spherical basis. Finally, we discuss the domain of nuclei very far from the valley of β stability, addressing the vanishing of some magic closures that can be explained in terms of intruder states. (author)
Hamoudi, A.K.; Abdul Majeed Al-Rahmani, A.
2012-01-01
The spectral fluctuations and the statistics of electromagnetic transition intensities and electromagnetic moments in 44 V nucleus are studied by the framework of the interacting shell model, using the FPD6 as a realistic effective interaction in the isospin formalism for 4 particles move in the fp-model space with a 40 Ca core. To look for a regular-chaos transition in 44 V nucleus, we perform shell model calculations using various interaction strengths β to the off-diagonal matrix elements of the FPD6. The nearest-neighbors level spacing distribution P(s) and the distribution of electromagnetic transition intensities [such as, B(M1) and B(E2) transitions] are found to have a regular dynamic at β=0, a chaotic dynamic at β⩾0.3 and an intermediate situation at 0 3 statistic we have found a regular dynamic at β=0, a chaotic dynamic at β⩾0.4 and an intermediate situation at 0<β<0.4. It is also found that the statistics of the squares of M1 and E2 moments, which are consistent with a Porter-Thomas distribution, have no dependence on the interaction strength β.
On two-dimensionalization of three-dimensional turbulence in shell models
Chakraborty, Sagar; Jensen, Mogens Høgh; Sarkar, A.
2010-01-01
Applying a modified version of the Gledzer-Ohkitani-Yamada (GOY) shell model, the signatures of so-called two-dimensionalization effect of three-dimensional incompressible, homogeneous, isotropic fully developed unforced turbulence have been studied and reproduced. Within the framework of shell m......-similar PDFs for longitudinal velocity differences are also presented for the rotating 3D turbulence case....
Preparation of hollow shell ICF targets using a depolymerizing model
Letts, S.A.; Fearon, E.M.; Buckley, S.R.
1994-11-01
A new technique for producing hollow shell laser fusion capsules was developed that starts with a depolymerizable mandrel. In this technique we use poly(alpha-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. We have developed methods for controlling the size of the PAMS mandrel by either grinding to make smaller sizes or melt sintering to form larger mandrels. Sphericity and surface finish are improved by heating the PAMS mandrels in hot water using a surfactant to prevent aggregation. Using this technique we have made shells from 200 μm to 5 mm diameter with 15 to 100 μm wall thickness having sphericity better than 2 μm and surface finish better than 10 nm RMS
Nucleon-pair approximation to the nuclear shell model
Zhao, Y.M., E-mail: ymzhao@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Arima, A. [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Musashi Gakuen, 1-26-1 Toyotamakami Nerima-ku, Tokyo 176-8533 (Japan)
2014-12-01
Atomic nuclei are complex systems of nucleons–protons and neutrons. Nucleons interact with each other via an attractive and short-range force. This feature of the interaction leads to a pattern of dominantly monopole and quadrupole correlations between like particles (i.e., proton–proton and neutron–neutron correlations) in low-lying states of atomic nuclei. As a consequence, among dozens or even hundreds of possible types of nucleon pairs, very few nucleon pairs such as proton and neutron pairs with spin zero, two (in some cases spin four), and occasionally isoscalar spin-aligned proton–neutron pairs, play important roles in low-energy nuclear structure. The nucleon-pair approximation therefore provides us with an efficient truncation scheme of the full shell model configurations which are otherwise too large to handle for medium and heavy nuclei in foreseeable future. Furthermore, the nucleon-pair approximation leads to simple pictures in physics, as the dimension of nucleon-pair subspace is always small. The present paper aims at a sound review of its history, formulation, validity, applications, as well as its link to previous approaches, with the focus on the new developments in the last two decades. The applicability of the nucleon-pair approximation and numerical calculations of low-lying states for realistic atomic nuclei are demonstrated with examples. Applications of pair approximations to other problems are also discussed.
Virial expansion for almost diagonal random matrices
Yevtushenko, Oleg; Kravtsov, Vladimir E.
2003-08-01
Energy level statistics of Hermitian random matrices hat H with Gaussian independent random entries Higeqj is studied for a generic ensemble of almost diagonal random matrices with langle|Hii|2rangle ~ 1 and langle|Hi\
Strictly diagonal holomorphic functions on Banach spaces
O. I. Fedak
2016-01-01
Full Text Available In this paper we investigate the boundedness of holomorphic functionals on a Banach space with a normalized basis $\\{e_n\\}$ which have a very special form $f(x=f(0+\\sum_{n=1}^\\infty c_nx_n^n$ and which we call strictly diagonal. We consider under which conditions strictly diagonal functions are entire and uniformly continuous on every ball of a fixed radius.
Lai, Changliang; Wang, Junbiao; Liu, Chuang
2014-10-01
Six typical composite grid cylindrical shells are constructed by superimposing three basic types of ribs. Then buckling behavior and structural efficiency of these shells are analyzed under axial compression, pure bending, torsion and transverse bending by finite element (FE) models. The FE models are created by a parametrical FE modeling approach that defines FE models with original natural twisted geometry and orients cross-sections of beam elements exactly. And the approach is parameterized and coded by Patran Command Language (PCL). The demonstrations of FE modeling indicate the program enables efficient generation of FE models and facilitates parametric studies and design of grid shells. Using the program, the effects of helical angles on the buckling behavior of six typical grid cylindrical shells are determined. The results of these studies indicate that the triangle grid and rotated triangle grid cylindrical shell are more efficient than others under axial compression and pure bending, whereas under torsion and transverse bending, the hexagon grid cylindrical shell is most efficient. Additionally, buckling mode shapes are compared and provide an understanding of composite grid cylindrical shells that is useful in preliminary design of such structures.
Symmetry-dictated trucation: Solutions of the spherical shell model for heavy nuclei
Guidry, M.W.
1992-01-01
Principles of dynamical symmetry are used to simplify the spherical shell model. The resulting symmetry-dictated truncation leads to dynamical symmetry solutions that are often in quantitative agreement with a variety of observables. Numerical calculations, including terms that break the dynamical symmetries, are shown that correspond to shell model calculations for heavy deformed nuclei. The effective residual interaction is simple, well-behaved, and can be determined from basic observables. With this approach, we intend to apply the shell model in systematic fashion to all nuclei. The implications for nuclear structure far from stability and for nuclear masses and other quantities of interest in astrophysics are discussed
Symplectic no-core shell-model approach to intermediate-mass nuclei
Tobin, G. K.; Ferriss, M. C.; Launey, K. D.; Dytrych, T.; Draayer, J. P.; Dreyfuss, A. C.; Bahri, C.
2014-03-01
We present a microscopic description of nuclei in the intermediate-mass region, including the proximity to the proton drip line, based on a no-core shell model with a schematic many-nucleon long-range interaction with no parameter adjustments. The outcome confirms the essential role played by the symplectic symmetry to inform the interaction and the winnowing of shell-model spaces. We show that it is imperative that model spaces be expanded well beyond the current limits up through 15 major shells to accommodate particle excitations, which appear critical to highly deformed spatial structures and the convergence of associated observables.
Steady state model for the thermal regimes of shells of airships and hot air balloons
Luchev, Oleg A.
1992-10-01
A steady state model of the temperature regime of airships and hot air balloons shells is developed. The model includes three governing equations: the equation of the temperature field of airships or balloons shell, the integral equation for the radiative fluxes on the internal surface of the shell, and the integral equation for the natural convective heat exchange between the shell and the internal gas. In the model the following radiative fluxes on the shell external surface are considered: the direct and the earth reflected solar radiation, the diffuse solar radiation, the infrared radiation of the earth surface and that of the atmosphere. For the calculations of the infrared external radiation the model of the plane layer of the atmosphere is used. The convective heat transfer on the external surface of the shell is considered for the cases of the forced and the natural convection. To solve the mentioned set of the equations the numerical iterative procedure is developed. The model and the numerical procedure are used for the simulation study of the temperature fields of an airship shell under the forced and the natural convective heat transfer.
Off-Diagonal Geometric Phase in a Neutron Interferometer Experiment
Hasegawa, Y.; Loidl, R.; Baron, M.; Badurek, G.; Rauch, H.
2001-01-01
Off-diagonal geometric phases acquired by an evolution of a 1/2 -spin system have been observed by means of a polarized neutron interferometer. We have successfully measured the off-diagonal phase for noncyclic evolutions even when the diagonal geometric phase is undefined. Our data confirm theoretical predictions and the results illustrate the significance of the off-diagonal phase
Seniority truncation in an equations-of-motion approach to the shell model
Covello, A.; Andreozzi, F.; Gargano, A.; Porrino, A.
1989-01-01
This paper presents an equations-of-motion method for treating shell-model problems within the framework of the seniority scheme. This method can be applied at many levels of approximation and represents therefore a valuable tool to further reduce seniority truncated shell-model spaces. To show its practical value the authors report some results of an extensive study of the N = 82 isotones which is currently under way
Sinusoidal velaroidal shell – numerical modelling of the nonlinear ...
The nonlinearity, applied to a sinusoidal velaroidal shell with the inner radius r0, the outer variables radii from 10m to 20m and the number of waves n=8, will give rise to the investigation of its nonlinear buckling resistance. The building material is a high-performant concrete. The investigation emphasizes more on the ...
Why the South Pacific Convergence Zone is diagonal
Van Der Wiel, Karin; Matthews, Adrian; Joshi, Manoj; Stevens, David
2016-01-01
During austral summer, the majority of precipitation over the Pacific Ocean is concentrated in the South Pacific Convergence Zone (SPCZ). The surface boundary conditions required to support the diagonally (northwest-southeast) oriented SPCZ are determined through a series of experiments with an atmospheric general circulation model. Continental configuration and orography do not have a significant influence on SPCZ orientation and strength. The key necessary boundary condition is the zonally ...
Diagonal chromatography to study plant protein modifications.
Walton, Alan; Tsiatsiani, Liana; Jacques, Silke; Stes, Elisabeth; Messens, Joris; Van Breusegem, Frank; Goormachtig, Sofie; Gevaert, Kris
2016-08-01
An interesting asset of diagonal chromatography, which we have introduced for contemporary proteome research, is its high versatility concerning proteomic applications. Indeed, the peptide modification or sorting step that is required between consecutive peptide separations can easily be altered and thereby allows for the enrichment of specific, though different types of peptides. Here, we focus on the application of diagonal chromatography for the study of modifications of plant proteins. In particular, we show how diagonal chromatography allows for studying proteins processed by proteases, protein ubiquitination, and the oxidation of protein-bound methionines. We discuss the actual sorting steps needed for each of these applications and the obtained results. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock. Copyright © 2016 Elsevier B.V. All rights reserved.
Localization for off-diagonal disorder and for continuous Schroedinger operators
Delyon, F.; Souillard, B.; Simon, B.
1987-01-01
We extend the proof of localization by Delyon, Levy, and Souillard to accommodate the Anderson model with off-diagonal disorder and the continuous Schroedinger equation with a random potential. (orig.)
Hallez, Yannick; Meireles, Martine
2016-10-11
Electrostatic interactions play a key role in hollow shell suspensions as they determine their structure, stability, thermodynamics, and rheology and also the loading capacity of small charged species for nanoreservoir applications. In this work, fast, reliable modeling strategies aimed at predicting the electrostatics of hollow shells for one, two, and many colloids are proposed and validated. The electrostatic potential inside and outside a hollow shell with a finite thickness and a specific permittivity is determined analytically in the Debye-Hückel (DH) limit. An expression for the interaction potential between two such hollow shells is then derived and validated numerically. It follows a classical Yukawa form with an effective charge depending on the shell geometry, permittivity, and inner and outer surface charge densities. The predictions of the Ornstein-Zernike (OZ) equation with this pair potential to determine equations of state are then evaluated by comparison to results obtained with a Brownian dynamics algorithm coupled to the resolution of the linearized Poisson-Boltzmann and Laplace equations (PB-BD simulations). The OZ equation based on the DLVO-like potential performs very well in the dilute regime as expected, but also quite well, and more surprisingly, in the concentrated regime in which full spheres exhibit significant many-body effects. These effects are shown to vanish for shells with small thickness and high permittivity. For highly charged hollow shells, we propose and validate a charge renormalization procedure. Finally, using PB-BD simulations, we show that the cell model predicts the ion distribution inside and outside hollow shells accurately in both electrostatically dilute and concentrated suspensions. We then determine the shell loading capacity as a function of salt concentration, volume fraction, and surface charge density for nanoreservoir applications such as drug delivery, sensing, or smart coatings.
Stability of core–shell nanowires in selected model solutions
Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.
2015-01-01
Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods
Stability of core–shell nanowires in selected model solutions
Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.
2015-03-30
Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.
Inner shell Coulomb ionization by heavy charged particles studied by the SCA model
Hansteen, J.M.
1976-12-01
The seven papers, introduced by the most recent, subtitled 'A condensed status review', form a survey of the work by the author and his colleagues on K-, L-, and M-shell ionisation by impinging protons, deuterons and α-particles in the period 1971-1976. The SCA model is discussed and compared with other approximations for inner shell Coulomb ionisation. The future aspects in this field are also discussed. (JIW)
All (4,1): Sigma models with (4,q) off-shell supersymmetry
Hull, Chris [The Blackett Laboratory, Imperial College London,Prince Consort Road London SW7 @AZ (United Kingdom); Lindström, Ulf [The Blackett Laboratory, Imperial College London,Prince Consort Road London SW7 @AZ (United Kingdom); Department of Physics and Astronomy, Division of Theoretical Physics,Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)
2017-03-08
Off-shell (4,q) supermultiplets in 2-dimensions are constructed for q=1,2,4. These are used to construct sigma models whose target spaces are hyperkähler with torsion. The off-shell supersymmetry implies the three complex structures are simultaneously integrable and allows us to construct actions using extended superspace and projective superspace, giving an explicit construction of the target space geometries.
Mean field theory of nuclei and shell model. Present status and future outlook
Nakada, Hitoshi
2003-01-01
Many of the recent topics of the nuclear structure are concerned on the problems of unstable nuclei. It has been revealed experimentally that the nuclear halos and the neutron skins as well as the cluster structures or the molecule-like structures can be present in the unstable nuclei, and the magic numbers well established in the stable nuclei disappear occasionally while new ones appear. The shell model based on the mean field approximation has been successfully applied to stable nuclei to explain the nuclear structure as the finite many body system quantitatively and it is considered as the standard model at present. If the unstable nuclei will be understood on the same model basis or not is a matter related to fundamental principle of nuclear structure theories. In this lecture, the fundamental concept and the framework of the theory of nuclear structure based on the mean field theory and the shell model are presented to make clear the problems and to suggest directions for future researches. At first fundamental properties of nuclei are described under the subtitles: saturation and magic numbers, nuclear force and effective interactions, nuclear matter, and LS splitting. Then the mean field theory is presented under subtitles: the potential model, the mean field theory, Hartree-Fock approximation for nuclear matter, density dependent force, semiclassical mean field theory, mean field theory and symmetry, Skyrme interaction and density functional, density matrix expansion, finite range interactions, effective masses, and motion of center of mass. The subsequent section is devoted to the shell model with the subtitles: beyond the mean field approximation, core polarization, effective interaction of shell model, one-particle wave function, nuclear deformation and shell model, and shell model of cross shell. Finally structure of unstable nuclei is discussed with the subtitles: general remark on the study of unstable nuclear structure, asymptotic behavior of wave
Enumeration of diagonally colored Young diagrams
Gyenge, Ádám
2015-01-01
In this note we give a new proof of a closed formula for the multivariable generating series of diagonally colored Young diagrams. This series also describes the Euler characteristics of certain Nakajima quiver varieties. Our proof is a direct combinatorial argument, based on Andrews' work on generalized Frobenius partitions. We also obtain representations of these series in some particular cases as infinite products.
Diagonal Pade approximations for initial value problems
Reusch, M.F.; Ratzan, L.; Pomphrey, N.; Park, W.
1987-06-01
Diagonal Pade approximations to the time evolution operator for initial value problems are applied in a novel way to the numerical solution of these problems by explicitly factoring the polynomials of the approximation. A remarkable gain over conventional methods in efficiency and accuracy of solution is obtained. 20 refs., 3 figs., 1 tab
Structure of exotic nuclei by large-scale shell model calculations
Utsuno, Yutaka; Otsuka, Takaharu; Mizusaki, Takahiro; Honma, Michio
2006-01-01
An extensive large-scale shell-model study is conducted for unstable nuclei around N = 20 and N = 28, aiming to investigate how the shell structure evolves from stable to unstable nuclei and affects the nuclear structure. The structure around N = 20 including the disappearance of the magic number is reproduced systematically, exemplified in the systematics of the electromagnetic moments in the Na isotope chain. As a key ingredient dominating the structure/shell evolution in the exotic nuclei from a general viewpoint, we pay attention to the tensor force. Including a proper strength of the tensor force in the effective interaction, we successfully reproduce the proton shell evolution ranging from N = 20 to 28 without any arbitrary modifications in the interaction and predict the ground state of 42Si to contain a large deformed component
Vaidya spacetime in the diagonal coordinates
Berezin, V. A., E-mail: berezin@inr.ac.ru; Dokuchaev, V. I., E-mail: dokuchaev@inr.ac.ru; Eroshenko, Yu. N., E-mail: eroshenko@inr.ac.ru [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation)
2017-03-15
We have analyzed the transformation from initial coordinates (v, r) of the Vaidya metric with light coordinate v to the most physical diagonal coordinates (t, r). An exact solution has been obtained for the corresponding metric tensor in the case of a linear dependence of the mass function of the Vaidya metric on light coordinate v. In the diagonal coordinates, a narrow region (with a width proportional to the mass growth rate of a black hole) has been detected near the visibility horizon of the Vaidya accreting black hole, in which the metric differs qualitatively from the Schwarzschild metric and cannot be represented as a small perturbation. It has been shown that, in this case, a single set of diagonal coordinates (t, r) is insufficient to cover the entire range of initial coordinates (v, r) outside the visibility horizon; at least three sets of diagonal coordinates are required, the domains of which are separated by singular surfaces on which the metric components have singularities (either g{sub 00} = 0 or g{sub 00} = ∞). The energy–momentum tensor diverges on these surfaces; however, the tidal forces turn out to be finite, which follows from an analysis of the deviation equations for geodesics. Therefore, these singular surfaces are exclusively coordinate singularities that can be referred to as false fire-walls because there are no physical singularities on them. We have also considered the transformation from the initial coordinates to other diagonal coordinates (η, y), in which the solution is obtained in explicit form, and there is no energy–momentum tensor divergence.
Projected shell model study of odd-odd f-p-g shell proton-rich nuclei
Palit, R.; Sheikh, J.A.; Sun, Y.; Jain, H.C.
2003-01-01
A systematic study of two-quasiparticle bands of the proton-rich odd-odd nuclei in the mass A∼70-80 region is performed using the projected shell model approach. The study includes Br, Rb, and Y isotopes with N=Z+2 and Z+4. We describe the energy spectra and electromagnetic transition strengths in terms of the configuration mixing of the angular-momentum projected multi-quasiparticle states. Signature splitting and signature inversion in the rotational bands are discussed and are shown to be well described. A preliminary study of the odd-odd N=Z nucleus 74 Rb, using the concept of spontaneous symmetry breaking is also presented
Non-orthogonal tensor diagonalization
Tichavský, Petr; Phan, A. H.; Cichocki, A.
2017-01-01
Roč. 138, č. 1 (2017), s. 313-320 ISSN 0165-1684 R&D Projects: GA ČR(CZ) GA14-13713S; GA ČR GA17-00902S Institutional support: RVO:67985556 Keywords : multilinear models * canonical polyadic decomposition * parallel factor analysis Subject RIV: BB - Applied Statistics, Operational Research OBOR OECD: Statistics and probability Impact factor: 3.110, year: 2016 http://library.utia.cas.cz/separaty/2017/SI/tichavsky-0474387.pdf
The contribution of Skyrme Hartree-Fock calculations to the understanding of the shell model
Zamick, L.
1984-01-01
The authors present a detailed comparison of Skyrme Hartree-Fock and the shell model. The H-F calculations are sensitive to the parameters that are chosen. The H-F results justify the use of effective charges in restricted model space calculations by showing that the core contribution can be large. Further, the H-F results roughly justify the use of a constant E2 effective charge, but seem to yield nucleus dependent E4 effective charges. The H-F can yield results for E6 and higher multipoles, which would be zero in s-d model space calculations. On the other side of the coin in H-F the authors can easily consider only the lowest rotational band, whereas in the shell model one can calculate the energies and properties of many more states. In the comparison some apparent problems remain, in particular E4 transitions in the upper half of the s-d shell
Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model
Roth, R; Navratil, P
2007-05-22
We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for {sup 4}He and {sup 16}O. Then, we present the first converged calculations for the ground state of {sup 40}Ca within no-core model spaces including up to 16{h_bar}{Omega}-excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.
Large-scale exact diagonalizations reveal low-momentum scales of nuclei
Forssén, C.; Carlsson, B. D.; Johansson, H. T.; Sääf, D.; Bansal, A.; Hagen, G.; Papenbrock, T.
2018-03-01
Ab initio methods aim to solve the nuclear many-body problem with controlled approximations. Virtually exact numerical solutions for realistic interactions can only be obtained for certain special cases such as few-nucleon systems. Here we extend the reach of exact diagonalization methods to handle model spaces with dimension exceeding 1010 on a single compute node. This allows us to perform no-core shell model (NCSM) calculations for 6Li in model spaces up to Nmax=22 and to reveal the 4He+d halo structure of this nucleus. Still, the use of a finite harmonic-oscillator basis implies truncations in both infrared (IR) and ultraviolet (UV) length scales. These truncations impose finite-size corrections on observables computed in this basis. We perform IR extrapolations of energies and radii computed in the NCSM and with the coupled-cluster method at several fixed UV cutoffs. It is shown that this strategy enables information gain also from data that is not fully UV converged. IR extrapolations improve the accuracy of relevant bound-state observables for a range of UV cutoffs, thus making them profitable tools. We relate the momentum scale that governs the exponential IR convergence to the threshold energy for the first open decay channel. Using large-scale NCSM calculations we numerically verify this small-momentum scale of finite nuclei.
Exact boson mappings for nuclear neutron (proton) shell-model algebras having SU(3) subalgebras
Bonatsos, D.; Klein, A.
1986-01-01
In this paper the commutation relations of the fermion pair operators of identical nucleons coupled to spin zero are given for the general nuclear major shell in LST coupling. The associated Lie algebras are the unitary symplectic algebras Sp(2M). The corresponding multipole subalgebras are the unitary algebras U(M), which possess SU(3) subalgebras. Number conserving exact boson mappings of both the Dyson and hermitian form are given for the nuclear neutron (proton) s--d, p--f, s--d--g, and p--f--h shells, and their group theoretical structure is emphasized. The results are directly applicable in the case of the s--d shell, while in higher shells the experimentally plausible pseudo-SU(3) symmetry makes them applicable. The final purpose of this work is to provide a link between the shell model and the Interacting Boson Model (IBM) in the deformed limit. As already implied in the work of Draayer and Hecht, it is difficult to associate the boson model developed here with the conventional IBM model. The differences between the two approaches (due mainly to the effects of the Pauli principle) as well as their physical implications are extensively discussed
Almegaard, Henrik
2004-01-01
A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can...... be concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....
OWL: A code for the two-center shell model with spherical Woods-Saxon potentials
Diaz-Torres, Alexis
2018-03-01
A Fortran-90 code for solving the two-center nuclear shell model problem is presented. The model is based on two spherical Woods-Saxon potentials and the potential separable expansion method. It describes the single-particle motion in low-energy nuclear collisions, and is useful for characterizing a broad range of phenomena from fusion to nuclear molecular structures.
Off-diagonal series expansion for quantum partition functions
Hen, Itay
2018-05-01
We derive an integral-free thermodynamic perturbation series expansion for quantum partition functions which enables an analytical term-by-term calculation of the series. The expansion is carried out around the partition function of the classical component of the Hamiltonian with the expansion parameter being the strength of the off-diagonal, or quantum, portion. To demonstrate the usefulness of the technique we analytically compute to third order the partition functions of the 1D Ising model with longitudinal and transverse fields, and the quantum 1D Heisenberg model.
Shell Tectonics: A Mechanical Model for Strike-slip Displacement on Europa
Rhoden, Alyssa Rose; Wurman, Gilead; Huff, Eric M.; Manga, Michael; Hurford, Terry A.
2012-01-01
We introduce a new mechanical model for producing tidally-driven strike-slip displacement along preexisting faults on Europa, which we call shell tectonics. This model differs from previous models of strike-slip on icy satellites by incorporating a Coulomb failure criterion, approximating a viscoelastic rheology, determining the slip direction based on the gradient of the tidal shear stress rather than its sign, and quantitatively determining the net offset over many orbits. This model allows us to predict the direction of net displacement along faults and determine relative accumulation rate of displacement. To test the shell tectonics model, we generate global predictions of slip direction and compare them with the observed global pattern of strike-slip displacement on Europa in which left-lateral faults dominate far north of the equator, right-lateral faults dominate in the far south, and near-equatorial regions display a mixture of both types of faults. The shell tectonics model reproduces this global pattern. Incorporating a small obliquity into calculations of tidal stresses, which are used as inputs to the shell tectonics model, can also explain regional differences in strike-slip fault populations. We also discuss implications for fault azimuths, fault depth, and Europa's tectonic history.
Multi-shell model of ion-induced nucleic acid condensation
Tolokh, Igor S. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061 (United States); Drozdetski, Aleksander V. [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States); Pollack, Lois [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853-3501 (United States); Baker, Nathan A. [Advanced Computing, Mathematics, and Data Division, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Division of Applied Mathematics, Brown University, Providence, Rhode Island 02912 (United States); Onufriev, Alexey V. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States)
2016-04-21
We present a semi-quantitative model of condensation of short nucleic acid (NA) duplexes induced by trivalent cobalt(III) hexammine (CoHex) ions. The model is based on partitioning of bound counterion distribution around single NA duplex into “external” and “internal” ion binding shells distinguished by the proximity to duplex helical axis. In the aggregated phase the shells overlap, which leads to significantly increased attraction of CoHex ions in these overlaps with the neighboring duplexes. The duplex aggregation free energy is decomposed into attractive and repulsive components in such a way that they can be represented by simple analytical expressions with parameters derived from molecular dynamic simulations and numerical solutions of Poisson equation. The attractive term depends on the fractions of bound ions in the overlapping shells and affinity of CoHex to the “external” shell of nearly neutralized duplex. The repulsive components of the free energy are duplex configurational entropy loss upon the aggregation and the electrostatic repulsion of the duplexes that remains after neutralization by bound CoHex ions. The estimates of the aggregation free energy are consistent with the experimental range of NA duplex condensation propensities, including the unusually poor condensation of RNA structures and subtle sequence effects upon DNA condensation. The model predicts that, in contrast to DNA, RNA duplexes may condense into tighter packed aggregates with a higher degree of duplex neutralization. An appreciable CoHex mediated RNA-RNA attraction requires closer inter-duplex separation to engage CoHex ions (bound mostly in the “internal” shell of RNA) into short-range attractive interactions. The model also predicts that longer NA fragments will condense more readily than shorter ones. The ability of this model to explain experimentally observed trends in NA condensation lends support to proposed NA condensation picture based on the multivalent
Fast Approximate Joint Diagonalization Incorporating Weight Matrices
Tichavský, Petr; Yeredor, A.
2009-01-01
Roč. 57, č. 3 (2009), s. 878-891 ISSN 1053-587X R&D Projects: GA MŠk 1M0572 Institutional research plan: CEZ:AV0Z10750506 Keywords : autoregressive processes * blind source separation * nonstationary random processes Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 2.212, year: 2009 http://library.utia.cas.cz/separaty/2009/SI/tichavsky-fast approximate joint diagonalization incorporating weight matrices.pdf
Diagonalizing sensing matrix of broadband RSE
Sato, Shuichi; Kokeyama, Keiko; Kawazoe, Fumiko; Somiya, Kentaro; Kawamura, Seiji
2006-01-01
For a broadband-operated RSE interferometer, a simple and smart length sensing and control scheme was newly proposed. The sensing matrix could be diagonal, owing to a simple allocation of two RF modulations and to a macroscopic displacement of cavity mirrors, which cause a detuning of the RF modulation sidebands. In this article, the idea of the sensing scheme and an optimization of the relevant parameters will be described
Use of shell model calculations in R-matrix studies of neutron-induced reactions
Knox, H.D.
1986-01-01
R-matrix analyses of neutron-induced reactions for many of the lightest p-shell nuclei are difficult due to a lack of distinct resonance structure in the reaction cross sections. Initial values for the required R-matrix parameters, E,sub(lambda) and γsub(lambdac) for states in the compound system, can be obtained from shell model calculations. In the present work, the results of recent shell model calculations for the lithium isotopes have been used in R-matrix analyses of 6 Li+n and 7 Li+n reactions for E sub(n) 7 Li and 8 Li on the 6 Li+n and 7 Li+n reaction mechanisms and cross sections are discussed. (author)
2014-01-01
Background Life satisfaction research in China is in development, requiring new perspectives for enrichment. In China, occupational mobility is accompanied by changes in economic liberalization and the emergence of occupational stratification. On the whole, however, occupational mobility has rarely been used as an independent variable. Health status is always used as the observed or dependent variable in studies of the phenomenon and its influencing factors. A research gap still exists for enriching this field. Methods The data used in this study were obtained from the China Health and Nutrition Survey (CHNS). The study included nine provinces in China. The survey was conducted from 1989 to 2009.Every survey involved approximately 4400 families or 19,000 individual samples and parts of community data. Results First, we built a 5 × 5 social mobility table and calculated life satisfaction of Chinese residents of different occupations in each table. Second, gender, age, marital status, education level, annual income and hukou, health status, occupational mobility were used as independent variables. Lastly, we used logistic diagonal mobility models to analyze the relationship between life satisfaction and the variables. Model 1 was the basic model, which consisted of the standard model and controlled variables and excluded drift variables. Model 2 was the total model, which consisted of all variables of interest in this study. Model 3 was the screening model, which excluded the insignificant drift effect index in Model 2. Conclusion From the perspective of the analysis of controlled variables, health conditions, direction, and distance of occupational mobility significantly affected life satisfaction of Chinese residents of different occupations. (1) From the perspective of health status, respondents who have not been sick or injured had better life satisfaction than those who had been sick or injured. (2) From the perspective of occupational mobility direction
Liang, Ying; Lu, Peiyi
2014-02-08
Life satisfaction research in China is in development, requiring new perspectives for enrichment. In China, occupational mobility is accompanied by changes in economic liberalization and the emergence of occupational stratification. On the whole, however, occupational mobility has rarely been used as an independent variable. Health status is always used as the observed or dependent variable in studies of the phenomenon and its influencing factors. A research gap still exists for enriching this field. The data used in this study were obtained from the China Health and Nutrition Survey (CHNS). The study included nine provinces in China. The survey was conducted from 1989 to 2009.Every survey involved approximately 4400 families or 19,000 individual samples and parts of community data. First, we built a 5 × 5 social mobility table and calculated life satisfaction of Chinese residents of different occupations in each table. Second, gender, age, marital status, education level, annual income and hukou, health status, occupational mobility were used as independent variables. Lastly, we used logistic diagonal mobility models to analyze the relationship between life satisfaction and the variables. Model 1 was the basic model, which consisted of the standard model and controlled variables and excluded drift variables. Model 2 was the total model, which consisted of all variables of interest in this study. Model 3 was the screening model, which excluded the insignificant drift effect index in Model 2. From the perspective of the analysis of controlled variables, health conditions, direction, and distance of occupational mobility significantly affected life satisfaction of Chinese residents of different occupations. (1) From the perspective of health status, respondents who have not been sick or injured had better life satisfaction than those who had been sick or injured. (2) From the perspective of occupational mobility direction, the coefficients of occupational
Analysis of two colliding fractionally damped spherical shells in modelling blunt human head impacts
Rossikhin, Yury A.; Shitikova, Marina V.
2013-06-01
The collision of two elastic or viscoelastic spherical shells is investigated as a model for the dynamic response of a human head impacted by another head or by some spherical object. Determination of the impact force that is actually being transmitted to bone will require the model for the shock interaction of the impactor and human head. This model is indended to be used in simulating crash scenarios in frontal impacts, and provide an effective tool to estimate the severity of effect on the human head and to estimate brain injury risks. The model developed here suggests that after the moment of impact quasi-longitudinal and quasi-transverse shock waves are generated, which then propagate along the spherical shells. The solution behind the wave fronts is constructed with the help of the theory of discontinuities. It is assumed that the viscoelastic features of the shells are exhibited only in the contact domain, while the remaining parts retain their elastic properties. In this case, the contact spot is assumed to be a plane disk with constant radius, and the viscoelastic features of the shells are described by the fractional derivative standard linear solid model. In the case under consideration, the governing differential equations are solved analytically by the Laplace transform technique. It is shown that the fractional parameter of the fractional derivative model plays very important role, since its variation allows one to take into account the age-related changes in the mechanical properties of bone.
V. S. Zarubin
2015-01-01
Full Text Available Liquid hydrogen and oxygen are used as the oxidizer and fuel for liquid rocket engines. Liquefied natural gas, which is based on methane, is seen as a promising motor fuel for internal combustion engines. One of the technical problems arising from the use of said cryogenic liquid is to provide containers for storage, transport and use in the propulsion system. In the design and operation of such vessels it is necessary to have reliable information about their temperature condition, on which depend the loss of cryogenic fluids due to evaporation and the stress-strain state of the structural elements of the containers.Uneven temperature distribution along the generatrix of the cylindrical thin-walled shell of rocket cryogenic tanks, in a localized zone of cryogenic liquid level leads to a curvature of the shell and reduce the permissible axle load in a hazard shell buckling in the preparation for the start of the missile in flight with an increasing acceleration. Moving the level of the cryogenic liquid during filling or emptying the tank at a certain combination of parameters results in an increase of the local temperature distribution nonuniformity.Along with experimental study of the shell temperature state of the cryogenic container, methods of mathematical modeling allow to have information needed for designing and testing the construction of cryogenic tanks. In this study a mathematical model is built taking into account features of heat transfer in a cryogenic container, including the boiling cryogenic liquid in the inner surface of the container. This mathematical model describes the temperature state of the thin-walled shell of cylindrical cryogenic tank during filling and emptying. The work also presents a quantitative analysis of this model in case of fixed liquid level, its movement at a constant speed, and harmonic oscillations relative to a middle position. The quantitative analysis of this model has allowed to find the limit options
Model uncertainties of local-thermodynamic-equilibrium K-shell spectroscopy
Nagayama, T.; Bailey, J. E.; Mancini, R. C.; Iglesias, C. A.; Hansen, S. B.; Blancard, C.; Chung, H. K.; Colgan, J.; Cosse, Ph.; Faussurier, G.; Florido, R.; Fontes, C. J.; Gilleron, F.; Golovkin, I. E.; Kilcrease, D. P.; Loisel, G.; MacFarlane, J. J.; Pain, J.-C.; Rochau, G. A.; Sherrill, M. E.; Lee, R. W.
2016-09-01
Local-thermodynamic-equilibrium (LTE) K-shell spectroscopy is a common tool to diagnose electron density, ne, and electron temperature, Te, of high-energy-density (HED) plasmas. Knowing the accuracy of such diagnostics is important to provide quantitative conclusions of many HED-plasma research efforts. For example, Fe opacities were recently measured at multiple conditions at the Sandia National Laboratories Z machine (Bailey et al., 2015), showing significant disagreement with modeled opacities. Since the plasma conditions were measured using K-shell spectroscopy of tracer Mg (Nagayama et al., 2014), one concern is the accuracy of the inferred Fe conditions. In this article, we investigate the K-shell spectroscopy model uncertainties by analyzing the Mg spectra computed with 11 different models at the same conditions. We find that the inferred conditions differ by ±20-30% in ne and ±2-4% in Te depending on the choice of spectral model. Also, we find that half of the Te uncertainty comes from ne uncertainty. To refine the accuracy of the K-shell spectroscopy, it is important to scrutinize and experimentally validate line-shape theory. We investigate the impact of the inferred ne and Te model uncertainty on the Fe opacity measurements. Its impact is small and does not explain the reported discrepancies.
Abrosimov, N. A.; Novosel'tseva, N. A.
2017-05-01
A technique for numerically analyzing the dynamic strength of two-layer metal-plastic cylindrical shells under an axisymmetric internal explosive loading is developed. The kinematic deformation model of the layered package is based on a nonclassical theory of shells. The geometric relations are constructed using relations of the simplest quadratic version of the nonlinear elasticity theory. The stress and strain tensors in the composite macrolayer are related by Hooke's law for an orthotropic body with account of degradation of the stiffness characteristics of the multilayer package due to local failure of some its elementary layers. The physical relations in the metal layer are formulated in terms of a differential theory of plasticity. An energy-correlated resolving system of dynamic equations for the metal-plastic cylindrical shells is derived by minimizing the functional of total energy of the shells as three-dimensional bodies. The numerical method for solving the initial boundary-value problem formulated is based on an explicit variational-difference scheme. The reliability of the technique considered is verified by comparing numerical results with experimental data. An analysis of the ultimate strains and strength of one-layer basalt-and glass-fiber-reinforced plastic and two-layer metalplastic cylindrical shells is carried out.
Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles
Iglesias, Oscar; Batlle, Xavier; Labarta, Amilcar
2007-01-01
We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromagnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loop shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Overlap functions computed from the spin configurations along the loops have been obtained to explain the origin and magnitude of these features microscopically
Nonlinear Spinor Field in Non-Diagonal Bianchi Type Space-Time
Saha Bijan
2018-01-01
Full Text Available Within the scope of the non-diagonal Bianchi cosmological models we have studied the role of the spinor field in the evolution of the Universe. In the non-diagonal Bianchi models the spinor field distribution along the main axis is anisotropic and does not vanish in the absence of the spinor field nonlinearity. Hence within these models perfect fluid, dark energy etc. cannot be simulated by the spinor field nonlinearity. The equation for volume scale V in the case of non-diagonal Bianchi models contains a term with first derivative of V explicitly and does not allow exact solution by quadratures. Like the diagonal models the non-diagonal Bianchi space-time becomes locally rotationally symmetric even in the presence of a spinor field. It was found that depending on the sign of the coupling constant the model allows either an open Universe that rapidly grows up or a close Universe that ends in a Big Crunch singularity.
Shell-model calculations with a basis that contains correlated pairs
Boisson, J.P.; Silvestre-Brac, B.A.; Liotta, R.J.
1979-01-01
A method to solve the shell-model equations within a basis that contains correlated pairs of particles is presented. The method is illustrated for the three-identical-particle system. Applications in nuclei around 208 Pb are given and comparisons with both experimental data and other calculations are carried out. (Auth.)
Cluster model of s-and p-shell ΛΛ hypernuclei
The binding energy ( ) of the s- and p-shell hypernuclei are calculated variationally in the cluster model and multidimensional integrations are performed using Monte Carlo. A variety of phenomenological -core potentials consistent with the -core energies and a wide range of simulated s-state potentials are ...
Study of band structure in 78,80Sr using Triaxial Projected Shell Model
Behera, N.; Naik, Z.; Bhat, G.H.; Sheikh, J.A.; Palit, R.; Sun, Y.
2017-01-01
The purpose of present work is to carry out a systematic study of the yrast-band and gamma-band structure for the even-even 78-80 Sr nuclei using Triaxial Projected Shell Model (TPSM) approach. These nuclei were chosen because 78 Sr has well developed side band(unassigned configuration) and 80 Sr has well developed band observed experimentally
Large scale shell model calculations: the physics in and the physics out
Zuker, A.P.
1997-01-01
After giving a few examples of recent results of the (SM) 2 collaboration, the monopole modified realistic interactions to be used in shell model calculations are described and analyzed. Rotational motion is discussed in some detail, and some introductory remarks on level densities are made. (orig.)
First-Principles Modeling of Core/Shell Quantum Dot Sensitized Solar Cells
Azpiroz, Jon Mikel; Infante, Ivan; De Angelis, Filippo
2015-01-01
We report on the density functional theory (DFT) modeling of core/shell quantum dot (QD) sensitized solar cells (QDSSCs), a device architecture that holds great potential in photovoltaics but has not been fully exploited so far. To understand the working mechanisms of this kind of solar cells, we
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 3
Gwaltney, R.C.; Bolt, S.E.; Corum, J.M.; Bryson, J.W.
1975-06-01
The third in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: the experimental data provide design information directly applicable to nozzles in cylindrical vessels; and the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 3 had a 10 in. OD and the nozzle had a 1.29 in. OD, giving a d 0 /D 0 ratio of 0.129. The OD/thickness ratios for the cylinder and the nozzle were 50 and 7.68 respectively. Thirteen separate loading cases were analyzed. In each, one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for all the loadings were obtained using 158 three-gage strain rosettes located on the inner and outer surfaces. The loading cases were also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 4
Gwaltney, R.C.; Bolt, S.E.; Bryson, J.W.
1975-06-01
The last in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models in the series are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: (1) the experimental data provide design information directly applicable to nozzles in cylindrical vessels, and (2) the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 4 had an outside diameter of 10 in., and the nozzle had an outside diameter of 1.29 in., giving a d 0 /D 0 ratio of 0.129. The OD/thickness ratios were 50 and 20.2 for the cylinder and nozzle respectively. Thirteen separate loading cases were analyzed. For each loading condition one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for each of the 13 loadings were obtained using 157 three-gage strain rosettes located on the inner and outer surfaces. Each of the 13 loading cases was also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Proceedings of a symposium on the occasion of the 40th anniversary of the nuclear shell model
Lee, T.S.H.; Wiringa, R.B.
1990-03-01
This report contains papers on the following topics: excitation of 1p-1h stretched states with the (p,n) reaction as a test of shell-model calculations; on Z=64 shell closure and some high spin states of 149 Gd and 159 Ho; saturating interactions in 4 He with density dependence; are short-range correlations visible in very large-basis shell-model calculations?; recent and future applications of the shell model in the continuum; shell model truncation schemes for rotational nuclei; the particle-hole interaction and high-spin states near A-16; magnetic moment of doubly closed shell +1 nucleon nucleus 41 Sc(I π =7/2 - ); the new magic nucleus 96 Zr; comparing several boson mappings with the shell model; high spin band structures in 165 Lu; optical potential with two-nucleon correlations; generalized valley approximation applied to a schematic model of the monopole excitation; pair approximation in the nuclear shell model; and many-particle, many-hole deformed states
Realistic Gamow shell model for resonance and continuum in atomic nuclei
Xu, F. R.; Sun, Z. H.; Wu, Q.; Hu, B. S.; Dai, S. J.
2018-02-01
The Gamow shell model can describe resonance and continuum for atomic nuclei. The model is established in the complex-moment (complex-k) plane of the Berggren coordinates in which bound, resonant and continuum states are treated on equal footing self-consistently. In the present work, the realistic nuclear force, CD Bonn, has been used. We have developed the full \\hat{Q}-box folded-diagram method to derive the realistic effective interaction in the model space which is nondegenerate and contains resonance and continuum channels. The CD-Bonn potential is renormalized using the V low-k method. With choosing 16O as the inert core, we have applied the Gamow shell model to oxygen isotopes.
Pion-nucleus double charge exchange and the nuclear shell model
Auerbach, N.; Gibbs, W.R.; Ginocchio, J.N.; Kaufmann, W.B.
1988-01-01
The pion-nucleus double charge exchange reaction is studied with special emphasis on nuclear structure. The reaction mechanism and nuclear structure aspects of the process are separated using both the plane-wave and distorted-wave impulse approximations. Predictions are made employing both the seniority model and a full shell model (with a single active orbit). Transitions to the double analog state and to the ground state of the residual nucleus are computed. The seniority model yields particularly simple relations among double charge exchange cross sections for nuclei within the same shell. Limitations of the seniority model and of the plane-wave impulse approximation are discussed as well as extensions to the generalized seniority scheme. Applications of the foregoing ideas to single charge exchange are also presented
Permuting sparse rectangular matrices into block-diagonal form
Aykanat, Cevdet; Pinar, Ali; Catalyurek, Umit V.
2002-12-09
This work investigates the problem of permuting a sparse rectangular matrix into block diagonal form. Block diagonal form of a matrix grants an inherent parallelism for the solution of the deriving problem, as recently investigated in the context of mathematical programming, LU factorization and QR factorization. We propose graph and hypergraph models to represent the nonzero structure of a matrix, which reduce the permutation problem to those of graph partitioning by vertex separator and hypergraph partitioning, respectively. Besides proposing the models to represent sparse matrices and investigating related combinatorial problems, we provide a detailed survey of relevant literature to bridge the gap between different societies, investigate existing techniques for partitioning and propose new ones, and finally present a thorough empirical study of these techniques. Our experiments on a wide range of matrices, using state-of-the-art graph and hypergraph partitioning tools MeTiS and PaT oH, revealed that the proposed methods yield very effective solutions both in terms of solution quality and run time.
Lee, Hyeon-Hui; Lee, Jae-Chul; Joo, Yong-Jin; Oh, Min; Lee, Chang-Ha
2014-01-01
Highlights: • Detailed dynamic model for the Shell entrained flow gasifier was developed. • The model included sub-models of reactor, membrane wall, gas quench and slag flow. • The dynamics of each zone including membrane wall in the gasifier were analyzed. • Cold gas efficiency (81.82%), gas fraction and temperature agreed with Shell data. • The model could be used as part of the overall IGCC simulation. - Abstract: The Shell coal gasification system is a single-stage, up-flow, oxygen-blown gasifier which utilizes dry pulverized coal with an entrained flow mechanism. Moreover, it has a membrane wall structure and operates in the slagging mode. This work provides a detailed dynamic model of the 300 MW Shell gasifier developed for use as part of an overall IGCC (integrated gasification combined cycle) process simulation. The model consists of several sub-models, such as a volatilization zone, reaction zone, quench zone, slag zone, and membrane wall zone, including heat transfers between the wall layers and steam generation. The dynamic results were illustrated and the validation of the gasifier model was confirmed by comparing the results in the steady state with the reference data. The product gases (H 2 and CO) began to come out from the exit of the reaction zone within 0.5 s, and nucleate boiling heat transfer was dominant in the water zone of the membrane wall due to high heat fluxes. The steady state of the process was reached at nearly t = 500 s, and our simulation data for the steady state, such as the temperature and composition of the syngas, the cold gas efficiency (81.82%), and carbon conversion (near 1.0) were in good agreement with the reference data
On the absence of an α-nucleus structure in a two-centre shell model
Gupta, R.K.; Sharma, M.K.; Antonenko, N.V.; Scheid, W.
1999-01-01
The two-centre shell model, used within the Strutinsky macro-microscopic method, is a valid prescription for calculating adiabatic or diabatic potential energy surfaces. It is shown, however, that this model does not contain the appropriate α-nucleus structure effects, very much required for collisions between light nuclei. A possible way to incorporate such effects is suggested. (author). Letter-to-the-editor
Four shells atomic model to computer the counting efficiency of electron-capture nuclides
Grau Malonda, A.; Fernandez Martinez, A.
1985-01-01
The present paper develops a four-shells atomic model in order to obtain the efficiency of detection in liquid scintillation courting, Mathematical expressions are given to calculate the probabilities of the 229 different atomic rearrangements so as the corresponding effective energies. This new model will permit the study of the influence of the different parameters upon the counting efficiency for nuclides of high atomic number. (Author) 7 refs
Structures of $p$-shell double-$\\Lambda$ hypernuclei studied with microscopic cluster models
Kanada-En'yo, Yoshiko
2018-01-01
$0s$-orbit $\\Lambda$ states in $p$-shell double-$\\Lambda$ hypernuclei ($^{\\ \\,A}_{\\Lambda\\Lambda}Z$), $^{\\ \\,8}_{\\Lambda\\Lambda}\\textrm{Li}$, $^{\\ \\,9}_{\\Lambda\\Lambda}\\textrm{Li}$, $^{10,11,12}_{\\ \\ \\ \\ \\ \\Lambda\\Lambda}\\textrm{Be}$, $^{12,13}_{\\ \\ \\Lambda\\Lambda}\\textrm{B}$, and $^{\\,14}_{\\Lambda\\Lambda}\\textrm{C}$ are investigated. Microscopic cluster models are applied to core nuclear part and a potential model is adopted for $\\Lambda$ particles. The $\\Lambda$-core potential is a folding ...
Almonacid, S; Simpson, R; Teixeira, A
2007-11-01
Egg and egg preparations are important vehicles for Salmonella enteritidis infections. The influence of time-temperature becomes important when the presence of this organism is found in commercial shell eggs. A computer-aided mathematical model was validated to estimate surface and interior temperature of shell eggs under variable ambient and refrigerated storage temperature. A risk assessment of S. enteritidis based on the use of this model, coupled with S. enteritidis kinetics, has already been reported in a companion paper published earlier in JFS. The model considered the actual geometry and composition of shell eggs and was solved by numerical techniques (finite differences and finite elements). Parameters of interest such as local (h) and global (U) heat transfer coefficient, thermal conductivity, and apparent volumetric specific heat were estimated by an inverse procedure from experimental temperature measurement. In order to assess the error in predicting microbial population growth, theoretical and experimental temperatures were applied to a S. enteritidis growth model taken from the literature. Errors between values of microbial population growth calculated from model predicted compared with experimentally measured temperatures were satisfactorily low: 1.1% and 0.8% for the finite difference and finite element model, respectively.
Measurement of off-diagonal transport coefficients in two-phase flow in porous media.
Ramakrishnan, T S; Goode, P A
2015-07-01
The prevalent description of low capillary number two-phase flow in porous media relies on the independence of phase transport. An extended Darcy's law with a saturation dependent effective permeability is used for each phase. The driving force for each phase is given by its pressure gradient and the body force. This diagonally dominant form neglects momentum transfer from one phase to the other. Numerical and analytical modeling in regular geometries have however shown that while this approximation is simple and acceptable in some cases, many practical problems require inclusion of momentum transfer across the interface. Its inclusion leads to a generalized form of extended Darcy's law in which both the diagonal relative permeabilities and the off-diagonal terms depend not only on saturation but also on the viscosity ratio. Analogous to application of thermodynamics to dynamical systems, any of the extended forms of Darcy's law assumes quasi-static interfaces of fluids for describing displacement problems. Despite the importance of the permeability coefficients in oil recovery, soil moisture transport, contaminant removal, etc., direct measurements to infer the magnitude of the off-diagonal coefficients have been lacking. The published data based on cocurrent and countercurrent displacement experiments are necessarily indirect. In this paper, we propose a null experiment to measure the off-diagonal term directly. For a given non-wetting phase pressure-gradient, the null method is based on measuring a counter pressure drop in the wetting phase required to maintain a zero flux. The ratio of the off-diagonal coefficient to the wetting phase diagonal coefficient (relative permeability) may then be determined. The apparatus is described in detail, along with the results obtained. We demonstrate the validity of the experimental results and conclude the paper by comparing experimental data to numerical simulation. Copyright © 2015 Elsevier Inc. All rights reserved.
Large-scale shell model calculations for the N=126 isotones Po-Pu
Caurier, E.; Rejmund, M.; Grawe, H.
2003-04-01
Large-scale shell model calculations were performed in the full Z=82-126 proton model space π(Oh 9/2 , 1f 7/2 , Oi 13/2 , 2p 3/2 , 1f 5/2 , 2p 1/2 ) employing the code NATHAN. The modified Kuo-Herling interaction was used, no truncation was applied up to protactinium (Z=91) and seniority truncation beyond. The results are compared to experimental data including binding energies, level schemes and electromagnetic transition rates. An overall excellent agreement is obtained for states that can be described in this model space. Limitations of the approach with respect to excitations across the Z=82 and N=126 shells and deficiencies of the interaction are discussed. (orig.)
Self-consistent cluster theories for alloys with diagonal and off-diagonal disorder
Gonis, A.; Garland, J.W.
1978-01-01
The molecular coherent-potential approximation (MCPA) and other, simpler cluster approximations for disordered alloys are studied both analytically and numerically for alloys with diagonal and off-diagonal disorder (ODD). First, the MCPA for alloys with only diagonal disorder is rederived within the interactor formalism of Blackman, Esterling, and Berk. This formalism, which simplifies the numerical implementation of the MCPA, is then used to generalize the MCPA so as to take account of ODD. It is shown that the analytic properties of the MCPA are preserved under this generalization. Also, two computationally simple cluster approximations, the self-consistent central-site approximation (SCCSA) and the self-consistent boundary-site approximation (SCBSA), are generalized to include the effects of ODD. It is shown that for one-dimensional systems with only nearest-neighbor hopping the SCBSA yields Green's functions which are identical to those given by the MCPA and thus are analytic, even in the presence of ODD. Finally, the results of numerical calculations are reported for one-dimensional systems with only nearest-neighbor hopping but with both diagonal and off-diagonal disorder. These calculations were performed using the single-site approximation of Blackman, Esterling, and Berk and three different cluster approximations: the multishell method previously proposed by the authors, the SCCSA, and the SCBSA. The results of these calculations are compared with exact results and with previous results obtained using the truncated t-matix approximation and the recent method of Kaplan and Gray. These comparisons suggest that the multishell method and the generalization of the SCBSA given in this paper are more efficient and accurate for the calculation of densities of states for systems with ODD. On the other hand, as expected, the SCCSA was found to yield severely nonanalytic results for the values of band parameters used
Design and modeling of an additive manufactured thin shell for x-ray astronomy
Feldman, Charlotte; Atkins, Carolyn; Brooks, David; Watson, Stephen; Cochrane, William; Roulet, Melanie; Willingale, Richard; Doel, Peter
2017-09-01
Future X-ray astronomy missions require light-weight thin shells to provide large collecting areas within the weight limits of launch vehicles, whilst still delivering angular resolutions close to that of Chandra (0.5 arc seconds). Additive manufacturing (AM), also known as 3D printing, is a well-established technology with the ability to construct or `print' intricate support structures, which can be both integral and light-weight, and is therefore a candidate technique for producing shells for space-based X-ray telescopes. The work described here is a feasibility study into this technology for precision X-ray optics for astronomy and has been sponsored by the UK Space Agency's National Space Technology Programme. The goal of the project is to use a series of test samples to trial different materials and processes with the aim of developing a viable path for the production of an X-ray reflecting prototype for astronomical applications. The initial design of an AM prototype X-ray shell is presented with ray-trace modelling and analysis of the X-ray performance. The polishing process may cause print-through from the light-weight support structure on to the reflecting surface. Investigations in to the effect of the print-through on the X-ray performance of the shell are also presented.
Half-life calculation of one-proton emitters with a shell model potential
Rodrigues, M. M.; Duarte, S. B. [Centro Brasileiro de Pesquisas Fisicas-CBPF/MCT Rua Dr. Xavier Sigaud, 150, 22290-180, Rio de Janeiro-RJ (Brazil); Teruya, N. [Departamento de Fisica, Universidade Federal da Paraiba - UFPB Campus de Joao Pessoa, 58051-970, Joao Pessoa - PB (Brazil)
2013-03-25
The accumulated amount of data for half-lives of proton emitters still remains a challenge to the ability of nuclear models to reproduce them consistently. These nuclei are far from beta stability line in a region where the validity of current nuclear models is not guaranteed. A nuclear shell model is introduced to the calculation of the nuclear barrier of less deformed proton emitters. The predictions using the proposed model are in good agreement with the data, with the advantage of have used only a single parameter in the model.
Use of a finite range nucleon-nucleon interaction in the continuum shell model
Faes, Jean-Baptiste
2007-01-01
The unification of nuclear structure and nuclear reactions was always a great challenge of nuclear physics. The extreme complexity of finite quantum systems lead in the past to a separate development of the nuclear structure and the nuclear reactions. A unified description of structure and reactions is possible within the continuum shell model. All previous applications of this model used the zero-range residual interaction and the finite depth local potential to generate the single-particle basis. In the thesis, we have presented an extension of the continuum shell model for finite-range nucleon-nucleon interaction and an arbitrary number of nucleons in the scattering continuum. The great advantage of the present formulation is the same two-body interaction used both to generate the single-particle basis and to describe couplings to the continuum states. This formulation opens a possibility for an ab initio continuum shell model studies with the same nucleon-nucleon interaction generating the nuclear mean field, the configuration mixing and the coupling to the scattering continuum. First realistic applications of the above model has been shown for spectra of "1"7F and "1"7O, and elastic phase-shifts in the reaction "1"6O(p, p)"1"6O. (author)
Quantum mechanical treatment of the shell-of-influence model
Matta, M L [Regional Engineering Coll., Kurukshetra (India). Dept. of Physics; Sukheeja, B D [Thapa Engineering Coll., Patiala (India). Dept. of Physics; Narchal, M L [Punjabi Univ., Patiala (India). Dept. of Physics
1975-10-01
A quantum mechanical treatment ignoring nuclear exchange interactions has been used to compute steady dynamic nuclear polarization in dilute paramagnetic crystals. The calculation assumes dipolar interaction of a paramagnetic ion with a large number of nuclear spins. The results are in rough agreement with the phenomenological model proposed by T.J. Schmugge and C.D. Jeffries (1965).
Maier, K H; Dracoulis, G D; Boutachkov, P; Aprahamian, A; Byrne, A P; Davidson, P M; Lane, G L; Marie-Jeanne, Mélanie; Nieminen, P; Watanabe, H
2007-01-01
Conversion electrons from 208Bi have been measured using singles and coincidence techniques with the 208Pb(p,n)208Bi reaction at 9 MeV. The new information on multipolarities and spins complements that available from recent gamma-gamma-coincidence studies with the same reaction [Boutachkov et al., Nucl. Phys. A768, 22 (2006)]. The results on electromagnetic decays taken together with information on spectroscopic factors from earlier single-particle transfer reaction measurements represent an extensive data set on the properties of the one-proton one-neutron-hole states below 3 MeV, a spectrum which is virtually complete. Comparison of the experimental observables, namely, energies, spectroscopic factors, and gamma-branching ratios, with those calculated within the shell model allows extraction of the matrix elements of the shell model residual interaction. More than 100 diagonal and nondiagonal elements can be determined in this way, through a least squares fit to the experimental data. This adjustment of the...
One-dimensional σ-models with N = 5, 6, 7, 8 off-shell supersymmetries
Gonzales, M.; Toppan, F.; Rojas, M.
2008-12-01
We computed the actions for the 1D N = 5 σ-models with respect to the two inequivalent (2, 8, 6) multiplets. 4 supersymmetry generators are manifest, while the constraint originated by imposing the 5-th supersymmetry automatically induces a full N = 8 off-shell invariance. The resulting action coincides in the two cases and corresponds to a conformally flat 2D target satisfying a special geometry of rigid type. To obtain these results we developed a computational method (for Maple 11) which does not require the notion of superfields and is instead based on the nowadays available list of the inequivalent representations of the 1D N-extended supersymmetry. Its application to systematically analyze the σ-models off-shell invariant actions for the remaining N = 5, 6, 7, 8 (k, 8, 8 - k) multiplets, as well as for the N > 8 representations, only requires more cumbersome computations. (author)
Study of nickel nuclei by (p,d) and (p,t) reactions. Shell model interpretation
Kong-A-Siou, D.-H.
1975-01-01
The experimental techniques employed at the Nuclear Science Institute (Grenoble) and at Michigan State University are described. The development of the transition amplitude calculation of the one-or two-nucleon transfer reactions is described first, after which the principle of shell model calculations is outlined. The choices of configuration space and two-body interactions are discussed. The DWBA method of analysis is studied in more detail. The effects of different approximations and the influence of the parameters are examined. Special attention is paid to the j-dependence of the form of the angular distributions, on effect not explained in the standard DWBA framework. The results are analysed and a large section is devoted to a comparative study of the experimental results obtained and those from other nuclear reactions. The spectroscopic data obtained are compared with the results of shell model calculations [fr
Spectroscopy of 215Ra: the shell model and enhanced E3 transitions
Stuchbery, A.E.; Dracoulis, G.D.; Kibedi, T.; Fabricius, B.; Lane, G.J.; Poletti, A.R.; Baxter, A.M.
1998-01-01
Excited states in the N=127 nucleus 215 Ra have been studied using γ-ray and electron spectroscopy following reactions of 13 C on 206 Pb targets. Levels were identified up to spins of ∝61/2 ℎ and excitation energies of ∝6 MeV. Enhanced octupole transitions are a feature of the level scheme. Lifetimes and magnetic moments were measured for several isomeric levels. The level scheme, transition rates and magnetic moments are compared with empirical shell model calculations and multiparticle octupole-coupled shell model calculations. In general, the experimental data are well described, but in comparison with its success in describing enhanced E3 transitions between related states in the radon isotopes, some limitations of the multiparticle octupole-coupling approach are revealed in 215 Ra. (orig.)
Structure of liposome encapsulating proteins characterized by X-ray scattering and shell-modeling
Hirai, Mitsuhiro; Kimura, Ryota; Takeuchi, Kazuki; Hagiwara, Yoshihiko; Kawai-Hirai, Rika; Ohta, Noboru; Igarashi, Noriyuki; Shimuzu, Nobutaka
2013-01-01
Wide-angle X-ray scattering data using a third-generation synchrotron radiation source are presented. Lipid liposomes are promising drug delivery systems because they have superior curative effects owing to their high adaptability to a living body. Lipid liposomes encapsulating proteins were constructed and the structures examined using synchrotron radiation small- and wide-angle X-ray scattering (SR-SWAXS). The liposomes were prepared by a sequential combination of natural swelling, ultrasonic dispersion, freeze-throw, extrusion and spin-filtration. The liposomes were composed of acidic glycosphingolipid (ganglioside), cholesterol and phospholipids. By using shell-modeling methods, the asymmetric bilayer structure of the liposome and the encapsulation efficiency of proteins were determined. As well as other analytical techniques, SR-SWAXS and shell-modeling methods are shown to be a powerful tool for characterizing in situ structures of lipid liposomes as an important candidate of drug delivery systems
De Wit, P.; Looijesteijn, B.; Regeer, B.; Stip, B.
1995-03-01
In the bi-monthly issues of 'Shell Venster' (window on Shell) attention is paid to the activities of the multinational petroleum company Shell Nederland and the Koninklijke/Shell Groep by means of non-specialist articles
A model study of aggregates composed of spherical soot monomers with an acentric carbon shell
Luo, Jie; Zhang, Yongming; Zhang, Qixing
2018-01-01
Influences of morphology on the optical properties of soot particles have gained increasing attentions. However, studies on the effect of the way primary particles are coated on the optical properties is few. Aimed to understand how the primary particles are coated affect the optical properties of soot particles, the coated soot particle was simulated using the acentric core-shell monomers model (ACM), which was generated by randomly moving the cores of concentric core-shell monomers (CCM) model. Single scattering properties of the CCM model with identical fractal parameters were calculated 50 times at first to evaluate the optical diversities of different realizations of fractal aggregates with identical parameters. The results show that optical diversities of different realizations for fractal aggregates with identical parameters cannot be eliminated by averaging over ten random realizations. To preserve the fractal characteristics, 10 realizations of each model were generated based on the identical 10 parent fractal aggregates, and then the results were averaged over each 10 realizations, respectively. The single scattering properties of all models were calculated using the numerically exact multiple-sphere T-matrix (MSTM) method. It is found that the single scattering properties of randomly coated soot particles calculated using the ACM model are extremely close to those using CCM model and homogeneous aggregate (HA) model using Maxwell-Garnett effective medium theory. Our results are different from previous studies. The reason may be that the differences in previous studies were caused by fractal characteristics but not models. Our findings indicate that how the individual primary particles are coated has little effect on the single scattering properties of soot particles with acentric core-shell monomers. This work provides a suggestion for scattering model simplification and model selection.
Pseudo SU(3) shell model: Normal parity bands in odd-mass nuclei
Vargas, C.E.; Hirsch, J.G.; Draayer, J.P.
2000-01-01
A pseudo shell SU(3) model description of normal parity bands in 159 Tb is presented. The Hamiltonian includes spherical Nilsson single-particle energies, the quadrupole-quadrupole and pairing interactions, as well as three rotor terms. A systematic parametrization is introduced, accompanied by a detailed discussion of the effect each term in the Hamiltonian has on the energy spectrum. Yrast and excited band wavefunctions are analyzed together with their B(E2) values
Shell model for time-correlated random advection of passive scalars
Andersen, Ken Haste; Muratore-Ginanneschi, P.
1999-01-01
We study a minimal shell model for the advection of a passive scalar by a Gaussian time-correlated velocity field. The anomalous scaling properties of the white noise limit are studied analytically. The effect of the time correlations are investigated using perturbation theory around the white...... noise limit and nonperturbatively by numerical integration. The time correlation of the velocity field is seen to enhance the intermittency of the passive scalar. [S1063-651X(99)07711-9]....
Reexamination of shell model tests of the Porter-Thomas distribution
Grimes, S.M.
1983-01-01
Recent shell model calculations have yielded width amplitude distributions which have apparently not agreed with the Porter-Thomas distribution. This result conflicts with the present experimental evidence. A reanalysis of these calculations suggests that, although correct, they do not imply that the Porter-Thomas distribution will fail to describe the width distributions observed experimentally. The conditions for validity of the Porter-Thomas distribution are discussed
Region of validity of the Thomas–Fermi model with quantum, exchange and shell corrections
Dyachkov, S A; Levashov, P R; Minakov, D V
2016-01-01
A novel approach to calculate thermodynamically consistent shell corrections in wide range of parameters is used to predict the region of validity of the Thomas-Fermi approach. Calculated thermodynamic functions of electrons at high density are consistent with the more precise density functional theory. It makes it possible to work out a semi-classical model applicable both at low and high density. (paper)
ACORNS, Covariance and Correlation Matrix Diagonalization
Szondi, E.J.
1990-01-01
1 - Description of program or function: The program allows the user to verify the different types of covariance/correlation matrices used in the activation neutron spectrometry. 2 - Method of solution: The program performs the diagonalization of the input covariance/relative covariance/correlation matrices. The Eigen values are then analyzed to determine the rank of the matrices. If the Eigen vectors of the pertinent correlation matrix have also been calculated, the program can perform a complete factor analysis (generation of the factor matrix and its rotation in Kaiser's 'varimax' sense to select the origin of the correlations). 3 - Restrictions on the complexity of the problem: Matrix size is limited to 60 on PDP and to 100 on IBM PC/AT
Breaking Megrelishvili protocol using matrix diagonalization
Arzaki, Muhammad; Triantoro Murdiansyah, Danang; Adi Prabowo, Satrio
2018-03-01
In this article we conduct a theoretical security analysis of Megrelishvili protocol—a linear algebra-based key agreement between two participants. We study the computational complexity of Megrelishvili vector-matrix problem (MVMP) as a mathematical problem that strongly relates to the security of Megrelishvili protocol. In particular, we investigate the asymptotic upper bounds for the running time and memory requirement of the MVMP that involves diagonalizable public matrix. Specifically, we devise a diagonalization method for solving the MVMP that is asymptotically faster than all of the previously existing algorithms. We also found an important counterintuitive result: the utilization of primitive matrix in Megrelishvili protocol makes the protocol more vulnerable to attacks.
3D MODELS COMPARISON OF COMPLEX SHELL IN UNDERWATER AND DRY ENVIRONMENTS
S. Troisi
2015-04-01
Full Text Available In marine biology the shape, morphology, texture and dimensions of the shells and organisms like sponges and gorgonians are very important parameters. For example, a particular type of gorgonian grows every year only few millimeters; this estimation was conducted without any measurement instrument but it has been provided after successive observational studies, because this organism is very fragile: the contact could compromise its structure and outliving. Non-contact measurement system has to be used to preserve such organisms: the photogrammetry is a method capable to assure high accuracy without contact. Nevertheless, the achievement of a 3D photogrammetric model of complex object (as gorgonians or particular shells is a challenge in normal environments, either with metric camera or with consumer camera. Indeed, the successful of automatic target-less image orientation and the image matching algorithms is strictly correlated to the object texture properties and of camera calibration quality as well. In the underwater scenario, the environment conditions strongly influence the results quality; in particular, water’s turbidity, the presence of suspension, flare and other optical aberrations decrease the image quality reducing the accuracy and increasing the noise on the 3D model. Furthermore, seawater density variability influences its refraction index and consequently the interior orientation camera parameters. For this reason, the camera calibration has to be performed in the same survey conditions. In this paper, a comparison between the 3D models of a Charonia Tritonis shell are carried out through surveys conducted both in dry and underwater environments.
Corrections to the neutrinoless double-β-decay operator in the shell model
Engel, Jonathan; Hagen, Gaute
2009-06-01
We use diagrammatic perturbation theory to construct an effective shell-model operator for the neutrinoless double-β decay of Se82. The starting point is the same Bonn-C nucleon-nucleon interaction that is used to generate the Hamiltonian for recent shell-model calculations of double-β decay. After first summing high-energy ladder diagrams that account for short-range correlations and then adding diagrams of low order in the G matrix to account for longer-range correlations, we fold the two-body matrix elements of the resulting effective operator with transition densities from the recent shell-model calculation to obtain the overall nuclear matrix element that governs the decay. Although the high-energy ladder diagrams suppress this matrix element at very short distances as expected, they enhance it at distances between one and two fermis, so that their overall effect is small. The corrections due to longer-range physics are large, but cancel one another so that the fully corrected matrix element is comparable to that produced by the bare operator. This cancellation between large and physically distinct low-order terms indicates the importance of a reliable nonperturbative calculation.
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 2
Gwaltney, R.C.; Bolt, S.E.; Bryson, J.W.
1975-10-01
Model 2 in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. Both the cylinder and the nozzle of model 2 had outside diameters of 10 in., giving a d 0 /D 0 ratio of 1.0, and both had outside diameter/thickness ratios of 100. Sixteen separate loading cases in which one end of the cylinder was rigidly held were analyzed. An internal pressure loading, three mutually perpendicular force components, and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. In addition to these 13 loadings, 3 additional loads were applied to the nozzle (in-plane bending moment, out-of-plane bending moment, and axial force) with the free end of the cylinder restrained. The experimental stress distributions for each of the 16 loadings were obtained using 152 three-gage strain rosettes located on the inner and outer surfaces. All the 16 loading cases were also analyzed theoretically using a finite-element shell analysis. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good general agreement, and it is felt that the analysis would be satisfactory for most engineering purposes. (auth)
Saha, S.; Palit, R.; Sethi, J.
2012-01-01
The excited states of nuclei near N=50 closed shell provide suitable laboratory for testing the interactions of shell model states, possible presence of high spin isomers and help in understanding the shape transition as the higher orbitals are occupied. In particular, the structure of N = 49 isotones (and Z =32 to 46) with one hole in N=50 shell gap have been investigated using different reactions. Interestingly, the high spin states in these isotones have contribution from particle excitations across the respective proton and neutron shell gaps and provide suitable testing ground for the prediction of shell model interactions describing theses excitations across the shell gap. In the literature, extensive study of the high spin states of heavier N = 49 isotones starting with 91 Mo up to 95 Pd are available. Limited information existed on the high spin states of lighter isotones. Therefore, the motivation of the present work is to extend the high spin structure of 89 Zr and to characterize the structure of these levels through comparison with the large scale shell model calculations based on two new residual interactions in f 5/2 pg 9/2 model space
Quantum Glass of Interacting Bosons with Off-Diagonal Disorder
Piekarska, A. M.; Kopeć, T. K.
2018-04-01
We study disordered interacting bosons described by the Bose-Hubbard model with Gaussian-distributed random tunneling amplitudes. It is shown that the off-diagonal disorder induces a spin-glass-like ground state, characterized by randomly frozen quantum-mechanical U(1) phases of bosons. To access criticality, we employ the "n -replica trick," as in the spin-glass theory, and the Trotter-Suzuki method for decomposition of the statistical density operator, along with numerical calculations. The interplay between disorder, quantum, and thermal fluctuations leads to phase diagrams exhibiting a glassy state of bosons, which are studied as a function of model parameters. The considered system may be relevant for quantum simulators of optical-lattice bosons, where the randomness can be introduced in a controlled way. The latter is supported by a proposition of experimental realization of the system in question.
Test of the fermion dynamical symmetry model microscopy in the sd shell
Halse, P.
1987-01-01
The recently formulated fermion dynamical symmetry model treats low-lying collective levels as states classified in a pseudo-orbit pseudo-spin (k-i) basis having either k = 1 and zero i seniority, or i = (3/2) and zero k seniority. The validity of this suggestion, which has not previously been subjected to a microscopic examination, is determined for even-even nuclei in the sd shell, for which the model is phenomenologically successful, by comparing these states with the eigenfunctions of a realistic Hamiltonian. Most low-lying levels are almost orthogonal to the fermion dynamical symmetry model zero seniority subspaces
Finite-Time Attractivity for Diagonally Dominant Systems with Off-Diagonal Delays
T. S. Doan
2012-01-01
Full Text Available We introduce a notion of attractivity for delay equations which are defined on bounded time intervals. Our main result shows that linear delay equations are finite-time attractive, provided that the delay is only in the coupling terms between different components, and the system is diagonally dominant. We apply this result to a nonlinear Lotka-Volterra system and show that the delay is harmless and does not destroy finite-time attractivity.
Fragmentation of single-particle strength and the validity of the shell model
Brand, M.G.E.; Rijsdijk, G.A.; Muller, F.A.; Allaart, K.; Dickhoff, W.H.
1991-01-01
The problem of missing spectroscopic strength in proton knock-out reactions is addressed by calculating this strength with a realistic interaction up to about a hundred MeV missing energy. An interaction suitably modified for short-range correlations (G-matrix) is employed in the calculation of the self-energy including all orbitals up to and including three major shells above the Fermi level for protons. The spectroscopic strength is obtained by solving the Dyson equation for the Green function with a self-energy up to second order in the interaction. Results for 48 Ca and 90 Zr are compared with recent (e,e'p) data. The calculated strength overestimates the data by about 10-15% of the independent particle shell-model (IPSM) sum rule. This is in accordance with what is expected from depletions calculated in infinite nuclear matter. Inclusion of higher order terms into the self-energy, especially the correlated motion of particles and holes, is found to be necessary to reproduce the observed fragmentation of strength in the low-energy region. The widths of the strength distributions compare well with empirical formulas which have been deduced from optical potentials. The validity of the conventional shell-model picture is connected with the relevance of Landau's quasiparticle picture for strongly interacting Fermi systems. (orig.)
Spectroscopic information on light halo - nuclei within the framework of multiparticle shell model
Khaydarov, R.R.
2004-09-01
Aim of the inquiry: to develop the potential approach within the framework of multiparticle shell model; to obtain analytical expressions for a wave function and equations for widths off sub-barrier resonance states; to apply the theoretical approach for obtaining properties of 5 He, 5 Li, 8 B and 11 N nuclei; to estimate values of root-mean-square radiuses, radial density of nucleons, magnetic dipole and electrical quadrupole moments and spectroscopic information for 8 B and 8 Li with use of a method of expansion on functions of Storm - Liouville; to estimate the contribution of 2p - shell of 13 C and process of exchange replacement to the astrophysical S-factor of 13 C (α, n) 16 O reaction. Method of the research: theoretical approaches within the framework of multiparticle shell model. Achieved results and their novelty: new theoretical approach allowing to describe correctly the experimental static characteristics of sub-barrier one-particle resonance states in of 5 He, 5 Li, 8 B and 11 N light nuclei has been developed. Structure of 8 B and 8 Li light mirror nuclei with use of the approach for the description of one-particle resonance states based on the method of expansion on functions of Storm - Liouville has been investigated; The spectroscopic information for proton halo in 8 B and values of the magnetic dipole and electric quadrupole moments of 8 B and 8 Li with use of technique of genealogical coefficients have been obtained. The contribution of 2p - shell of 13 C (α, n) 16 O reaction has been estimated. (author)
Caty, O.; Maire, E.; Youssef, S.; Bouchet, R.
2008-01-01
Closed-cell cellular materials exhibit several interesting properties. These properties are, however, very difficult to simulate and understand from the knowledge of the cellular microstructure. This problem is mostly due to the highly complex organization of the cells and to their very fine walls. X-ray tomography can produce three-dimensional (3-D) images of the structure, enabling one to visualize locally the damage of the cell walls that would result in the structure collapsing. These data could be used for meshing with continuum elements of the structure for finite element (FE) calculations. But when the density is very low, the walls are fine and the meshes based on continuum elements are not suitable to represent accurately the structure while preserving the representativeness of the model in terms of cell size. This paper presents a shell FE model obtained from tomographic 3-D images that allows bigger volumes of low-density closed-cell cellular materials to be calculated. The model is enriched by direct thickness measurement on the tomographic images. The values measured are ascribed to the shell elements. To validate and use the model, a structure composed of stainless steel hollow spheres is firstly compressed and scanned to observe local deformations. The tomographic data are also meshed with shells for a FE calculation. The convergence of the model is checked and its performance is compared with a continuum model. The global behavior is compared with the measures of the compression test. At the local scale, the model allows the local stress and strain field to be calculated. The calculated deformed shape is compared with the deformed tomographic images
Moraes, Manoel; Diaz, Marcos
2009-01-01
The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Hα, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10 -4 M sun is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.
Bott–Kitaev periodic table and the diagonal map
Kennedy, R; Zirnbauer, M R
2015-01-01
Building on the ten-way symmetry classification of disordered fermions, the authors have recently given a homotopy-theoretic proof of Kitaev's ‘periodic table’ for topological insulators and superconductors. The present paper offers an introduction to the physical setting and the mathematical model used. Basic to the proof is the so-called diagonal map, a natural transformation akin to the Bott map of algebraic topology, which increases by one unit both the momentum-space dimension and the symmetry index of translation-invariant ground states of gapped free-fermion systems. This mapping is illustrated here with a few examples of interest. (Based on a talk delivered by the senior author at the Nobel Symposium on ‘New Forms of Matter: Topological Insulators and Superconductors’; Stockholm, 13–15 June, 2014.) (topical article)
Vibration test of spherical shell structure and replacing method into mathematical model
Takayanagi, M.; Suzuki, S.; Okamura, T.; Haas, E.E.; Krutzik, N.J.
1989-01-01
To verify the beam-type and oval-type vibratory characteristics of a spherical shell structure, two test specimens were made and vibration tests were carried out. Results of these tests are compared with results of detailed analyses using 3-D FEM and 2-D axisymmetric FEM models. The analytical results of overall vibratory characteristics are in good agreement with the test results, has been found that the effect of the attached mass should be considered in evaluating local vibration. The replacing method into equivalent beam model is proposed
Exotic muon-to-positron conversion in nuclei: partial transition sum evaluation by using shell model
Divari, P.C.; Vergados, J.D.; Kosmas, T.S.; Skouras, L.D.
2001-01-01
A comprehensive study of the exotic (μ - ,e + ) conversion in 27 Al, 27 Al(μ - ,e + ) 27 Na is presented. The relevant operators are deduced assuming one-pion and two-pion modes in the framework of intermediate neutrino mixing models, paying special attention to the light neutrino case. The total rate is calculated by summing over partial transition strengths for all kinematically accessible final states derived with s-d shell model calculations employing the well-known Wildenthal realistic interaction
Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants
Beck, R.; Drury, L.O.; Voelk, H.J.; Bogdan, T.J.
1985-01-01
The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium
Modelling by the SPH method of the impact of a shell containing a fluid
Maurel, B.
2008-01-01
The aim of this work was to develop a numerical simulation tool using a mesh-less approach, able to simulate the deformation and the rupture of thin structures under the impact of a fluid. A model of thick mesh-less shell (Mindlin-Reissner) based on the SPH method has then been carried out. A contact algorithm has moreover been perfected for the interactions between the structure and the fluid, it is modelled too by the SPH method. These studies have been carried out and been included in the CEA Europlexus fast dynamics software. (O.M.)
Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants
Beck, R.; Drury, L. O.; Voelk, H. J.; Bogdan, T. J.
1985-01-01
The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.
Shell model estimate of electric dipole moments in medium and heavy nuclei
Teruya E.
2014-03-01
Full Text Available It is evidence for an extension of the Standard Model in particle physics, if static electric dipole moments (EDMs are measured for any elementary particle. The nuclear EDM arises mainly from two sources: one comes from asymmetric charge distribution in a nucleus and the other is due to the nucleon intrinsic EDM. We estimate the nuclear EDMs from two sources for the 1/21+ states in Xe isotopes by a shell model approach using full orbitals between magic numbers 50 and 82.
Pasechnik, M V
1978-01-01
Major results of investigations into the shell structure of deformed nuclei with the number of neutrons of approximately 100, as well as new isotopic effects in the inelastic scattering of fast neutrons with nuclei are reported. The experiments conducted at the WWR-M research reactor have shown a substantial dependence of the nuclear excited energy-level density on the mass number and the number of neutrons. The fact resulted in a conclusion that the deformed nuclei possess filled shells, that was an incentive to revise the whole nuclear shell concept. In particular it was established that the property of magicity rests not only on the sphericity of nuclei but it may be also observed in strongly deformed nuclei. The isotope-spin dependence of the nuclear potential was studied at the AG-5 pulse electrostatic generator. The parameters of the potential were determined by comparing the experimental data on inelastic scattering and polarization of fast neutrons by nuclei from /sup 48/Ti to /sup 209/Bi with the calculations in terms of the optical model. Simple correlations were established between the optical potential and the nucleus asymmetry parameter ..cap alpha..=N-Z/A in wide ranges of mass numbers and neutron energy.
Virial expansion for almost diagonal random matrices
Yevtushenko, Oleg; Kravtsov, Vladimir E
2003-01-01
Energy level statistics of Hermitian random matrices H-circumflex with Gaussian independent random entries H i≥j is studied for a generic ensemble of almost diagonal random matrices with (vertical bar H ii vertical bar 2 ) ∼ 1 and (vertical bar H i≠j vertical bar 2 ) bF(vertical bar i - j vertical bar) parallel 1. We perform a regular expansion of the spectral form-factor K(τ) = 1 + bK 1 (τ) + b 2 K 2 (τ) + c in powers of b parallel 1 with the coefficients K m (τ) that take into account interaction of (m + 1) energy levels. To calculate K m (τ), we develop a diagrammatic technique which is based on the Trotter formula and on the combinatorial problem of graph edges colouring with (m + 1) colours. Expressions for K 1 (τ) and K 2 (τ) in terms of infinite series are found for a generic function F(vertical bar i - j vertical bar ) in the Gaussian orthogonal ensemble (GOE), the Gaussian unitary ensemble (GUE) and in the crossover between them (the almost unitary Gaussian ensemble). The Rosenzweig-Porter and power-law banded matrix ensembles are considered as examples
Model-based failure detection for cylindrical shells from noisy vibration measurements.
Candy, J V; Fisher, K A; Guidry, B L; Chambers, D H
2014-12-01
Model-based processing is a theoretically sound methodology to address difficult objectives in complex physical problems involving multi-channel sensor measurement systems. It involves the incorporation of analytical models of both physical phenomenology (complex vibrating structures, noisy operating environment, etc.) and the measurement processes (sensor networks and including noise) into the processor to extract the desired information. In this paper, a model-based methodology is developed to accomplish the task of online failure monitoring of a vibrating cylindrical shell externally excited by controlled excitations. A model-based processor is formulated to monitor system performance and detect potential failure conditions. The objective of this paper is to develop a real-time, model-based monitoring scheme for online diagnostics in a representative structural vibrational system based on controlled experimental data.
Approximate symmetries in atomic nuclei from a large-scale shell-model perspective
Launey, K. D.; Draayer, J. P.; Dytrych, T.; Sun, G.-H.; Dong, S.-H.
2015-05-01
In this paper, we review recent developments that aim to achieve further understanding of the structure of atomic nuclei, by capitalizing on exact symmetries as well as approximate symmetries found to dominate low-lying nuclear states. The findings confirm the essential role played by the Sp(3, ℝ) symplectic symmetry to inform the interaction and the relevant model spaces in nuclear modeling. The significance of the Sp(3, ℝ) symmetry for a description of a quantum system of strongly interacting particles naturally emerges from the physical relevance of its generators, which directly relate to particle momentum and position coordinates, and represent important observables, such as, the many-particle kinetic energy, the monopole operator, the quadrupole moment and the angular momentum. We show that it is imperative that shell-model spaces be expanded well beyond the current limits to accommodate particle excitations that appear critical to enhanced collectivity in heavier systems and to highly-deformed spatial structures, exemplified by the second 0+ state in 12C (the challenging Hoyle state) and 8Be. While such states are presently inaccessible by large-scale no-core shell models, symmetry-based considerations are found to be essential.
Magnetization of the Ising model on the Sierpinski pastry-shell
Chame, Anna; Branco, N. S.
1992-02-01
Using a real-space renormalization group approach, we calculate the approximate magnetization in the Ising model on the Sierpinski Pastry-shell. We consider, as an approximation, only two regions of the fractal: the internal surfaces, or walls (sites on the border of eliminated areas), with coupling constants JS, and the bulk (all other sites), with coupling constants Jv. We obtain the mean magnetization of the two regions as a function of temperature, for different values of α= JS/ JV and different geometric parameters b and l. Curves present a step-like behavior for some values of b and l, as well as different universality classes for the bulk transition.
Application of the Kishimoto-Tamura boson expansion theory to a single-j shell model
Li, C.T.; Pedrocchi, V.G.; Tamura, T.
1985-01-01
The boson expansion theory of Kishimoto and Tamura is applied to a single-j shell model. It is shown that this theory is quite accurate, giving results that agree very closely with those of the exact fermion calculations. The fast convergence of the boson expansion is also demonstrated. A critical discussion is then made of an earlier paper by Arima, in which he stated that the Kishimoto-Tamura theory gives rise to very poor numerical results. The source of the trouble encountered by Arima is unmasked
Recent developments of the projected shell model based on many-body techniques
Sun Yang
2015-01-01
Full Text Available Recent developments of the projected shell model (PSM are summarized. Firstly, by using the Pfaffian algorithm, the multi-quasiparticle configuration space is expanded to include 6-quasiparticle states. The yrast band of 166Hf at very high spins is studied as an example, where the observed third back-bending in the moment of inertia is well reproduced and explained. Secondly, an angular-momentum projected generate coordinate method is developed based on PSM. The evolution of the low-lying states, including the second 0+ state, of the soft Gd, Dy, and Er isotopes to the well-deformed ones is calculated, and compared with experimental data.
Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei
Ibanez-Sandoval, A.; Ortiz, M. E.; Velazquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.
2011-01-01
A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133 Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2) , kinetic moment of inertia J (1) , the crossing of rotational bands, and backbending effects.
Zero-point energies in the two-center shell model. II
Reinhard, P.-G.
1978-01-01
The zero-point energy (ZPE) contained in the potential-energy surface of a two-center shell model (TCSM) is evaluated. In extension of previous work, the author uses here the full TCSM with l.s force, smoothing and asymmetry. The results show a critical dependence on the height of the potential barrier between the centers. The ZPE turns out to be non-negligible along the fission path for 236 U, and even more so for lighter systems. It is negligible for surface quadrupole motion and it is just on the fringe of being negligible for motion along the asymmetry coordinate. (Auth.)
Zero-point energies in the two-center shell model
Reinhard, P.G.
1975-01-01
The zero-point energies (ZPE) contained in the potential-energy surfaces (PES) of a two-center shell model are evaluated. For the c.m. motion of the system as a whole the kinetic ZPE was found to be negligible, whereas it varies appreciably for the rotational and oscillation modes (about 5-9MeV). For the latter two modes the ZPE also depends sensitively on the changing pairing structure, which can induce strong local fluctuations, particularly in light nuclei. The potential ZPE is very small for heavy nuclei, but might just become important in light nuclei. (Auth.)
Accounting of inter-electron correlations in the model of mobile electron shells
Panov, Yu.D.; Moskvin, A.S.
2000-01-01
One studied the basic peculiar features of the model for mobile electron shells for multielectron atom or cluster. One offered a variation technique to take account of the electron correlations where the coordinates of the centre of single-particle atomic orbital served as variation parameters. It enables to interpret dramatically variation of electron density distribution under anisotropic external effect in terms of the limited initial basis. One studied specific correlated states that might make correlation contribution into the orbital current. Paper presents generalization of the typical MO-LCAO pattern with the limited set of single particle functions enabling to take account of additional multipole-multipole interactions in the cluster [ru
Symmetry analysis of many-body wave functions, with applications to the nuclear shell model
Novoselsky, A.; Katriel, J.
1995-01-01
The weights of the different permutational symmetry components of a nonsymmetry-adapted many-particle wave function are evaluated in terms of the expectation values of the symmetric-group class sums. This facilitates the evaluation of the weights without the construction of a complete set of symmetry adapted functions. Subspace projection operators are introduced, to be used when prior knowledge about the symmetry-species composition of a wave function is available. The permutational weight analysis of a recursively angular-momentum coupled (shell model) wave function is presented as an illustration
Shell-model calculations of beta-decay rates for s- and r-process nucleosyntheses
Takahashi, K.; Mathews, G.J.; Bloom, S.D.
1985-01-01
Examples of large-basis shell-model calculations of Gamow-Teller β-decay properties of specific interest in the astrophysical s- and r- processes are presented. Numerical results are given for: (1) the GT-matrix elements for the excited state decays of the unstable s-process nucleus 99 Tc; and (2) the GT-strength function for the neutron-rich nucleus 130 Cd, which lies on the r-process path. The results are discussed in conjunction with the astrophysics problems. 23 refs., 3 figs
Fixed J spectral distributions in large shell model spaces. Pt. 3
Jacquemin, C.; Auger, G.; Quesne, C.
1982-01-01
A method is developed to exactly calculate the fixed J quasiparticle centroid energies and partial widths. Some results obtained in the even-mass lead isotopes with various interactions are analysed. Fixed J quasiparticle distributions are used to predict an upper limit for the deviations between the quasiparticle approximation and the shell model results for the low-energy levels. The influence of the states with a high quasiparticle number in the low-energy region is seen to strongly depend upon the interaction. The importance of the dimensionalities and the internal widths is explaining the admixtures is stressed. (orig.)
Shell model estimate of electric dipole moments in medium and heavy nuclei
Teruya Eri
2015-01-01
Full Text Available Existence of the electric dipole moment (EDM is deeply related with time-reversal invariance. The EDMof a diamagnetic atom is mainly induced by the nuclear Schiff moment. After carrying out the shell model calculations to obtain wavefunctions for Xe isotopes, we evaluate nuclear Schiff moments for Xe isotopes to estimate their atomic EDMs. We estimate the contribution from each single particle orbital for the Schiff moment. It is found that the contribution on the Schiff moment is very different from orbital to orbital.
Separability of three qubit Greenberger-Horne-Zeilinger diagonal states
Han, Kyung Hoon; Kye, Seung-Hyeok
2017-04-01
We characterize the separability of three qubit GHZ diagonal states in terms of entries. This enables us to check separability of GHZ diagonal states without decomposition into the sum of pure product states. In the course of discussion, we show that the necessary criterion of Gühne (2011 Entanglement criteria and full separability of multi-qubit quantum states Phys. Lett. A 375 406-10) for (full) separability of three qubit GHZ diagonal states is sufficient with a simpler formula. The main tool is to use entanglement witnesses which are tri-partite Choi matrices of positive bi-linear maps.
Nielsen, Bo Bjerregaard; Nielsen, Martin S.; Santos, Ilmar
2017-01-01
The work gives a theoretical and experimental contribution to the problem of smart materials connected to double curved flexible shells. In the theoretical part the finite element modeling of a double curved flexible shell with a piezoelectric fiber patch with interdigitated electrodes (IDEs......) is presented. The developed element is based on a purely mechanical eight-node isoparametric layered element for a double curved shell, utilizing first-order shear deformation theory. The electromechanical coupling of piezoelectric material is added to all elements, but can also be excluded by setting...... the piezoelectric material properties to zero. The electrical field applied via the IDEs is aligned with the piezoelectric fibers, and hence the direct d33 piezoelectric constant is utilized for the electromechanical coupling. The dynamic performance of a shell with a microfiber composite (MFC) patch...
Off-diagonal ekpyrotic scenarios and equivalence of modified, massive and/or Einstein gravity
Sergiu I. Vacaru
2016-01-01
Full Text Available Using our anholonomic frame deformation method, we show how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates and undergoing a phase of ultra-slow contraction can be constructed in massive gravity. In this paper, there are found and studied new classes of locally anisotropic and (inhomogeneous cosmological metrics with open and closed spatial geometries. The late time acceleration is present due to effective cosmological terms induced by nonlinear off-diagonal interactions and graviton mass. The off-diagonal cosmological metrics and related Stückelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann–Lamaître–Robertson–Walker (FLRW coordinates. We show that the solutions include matter, graviton mass and other effective sources modeling nonlinear gravitational and matter fields interactions in modified and/or massive gravity, with polarization of physical constants and deformations of metrics, which may explain certain dark energy and dark matter effects. There are stated and analyzed the conditions when such configurations mimic interesting solutions in general relativity and modifications and recast the general Painlevé–Gullstrand and FLRW metrics. Finally, we elaborate on a reconstruction procedure for a subclass of off-diagonal cosmological solutions which describe cyclic and ekpyrotic universes, with an emphasis on open issues and observable signatures.
Angle-correlated cross sections in the framework of the continuum shell model
Moerschel, K.P.
1984-01-01
In the present thesis in the framework of the continuum shell modell a concept for the treatment of angle-correlated cross sections was developed by which coincidence experiments on electron scattering on nuclei are described. For this the existing Darmstadt continuum-shell-model code had to be extended to the calculation of the correlation coefficients in which nuclear dynamics enter and which determine completely the angle-correlated cross sections. Under inclusion of the kinematics a method for the integration over the scattered electron was presented and used for the comparison with corresponding experiments. As application correlation coefficients for the proton channel in 12 C with 1 - and 2 + excitations were studied. By means of these coefficients finally cross sections for the reaction 12 C (e,p) 11 B could be calculated and compared with the experiment whereby the developed methods were proved as suitable to predict correctly both the slope and the quantity of the experimental cross sections. (orig.) [de
Mathematical Modeling and Kinematics Analysis of Double Spherical Shell Rotary Docking Skirt
Gong Haixia
2017-01-01
Full Text Available In order to solve the problem of large trim and heel angles of the wrecked submarine, the double spherical shell rotating docking skirt is studied. According to the working principle of the rotating docking skirt, and the fixed skirt, the directional skirt, the angle skirt are simplified as the connecting rod. Therefore, the posture equation and kinematics model of the docking skirt are deduced, and according to the kinematics model, the angle of rotation of the directional skirt and the angle skirt is obtained when the wrecked submarine is in different trim and heel angles. Through the directional skirt and angle skirt with the matching rotation can make docking skirt interface in the 0°~2γ range within the rotation, to complete the docking skirt and the wrecked submarine docking. The MATLAB software is used to visualize the rotation angle of fixed skirt and directional skirt, which lays a good foundation for the development of the control of the double spherical shell rotating docking skirt in future.
Tensor-optimized shell model for the Li isotopes with a bare nucleon-nucleon interaction
Myo, Takayuki; Umeya, Atsushi; Toki, Hiroshi; Ikeda, Kiyomi
2012-08-01
We study the Li isotopes systematically in terms of the tensor-optimized shell model (TOSM) by using a bare nucleon-nucleon interaction as the AV8' interaction. The short-range correlation is treated in the unitary correlation operator method (UCOM). Using the TOSM + UCOM approach, we investigate the role of the tensor force on each spectrum of the Li isotopes. It is found that the tensor force produces quite a characteristic effect on various states in each spectrum and those spectra are affected considerably by the tensor force. The energy difference between the spin-orbit partner, the p1/2 and p3/2 orbits of the last neutron, in 5Li is caused by opposite roles of the tensor correlation. In 6Li, the spin-triplet state in the LS coupling configuration is favored energetically by the tensor force in comparison with jj coupling shell-model states. In 7,8,9Li, the low-lying states containing extra neutrons in the p3/2 orbit are favored energetically due to the large tensor contribution to allow the excitation from the 0s, orbit to the p1/2 orbit by the tensor force. Those three nuclei show the jj coupling character in their ground states which is different from 6Li.
Projected Shell Model Description of Positive Parity Band of 130Pr Nucleus
Singh, Suram; Kumar, Amit; Singh, Dhanvir; Sharma, Chetan; Bharti, Arun; Bhat, G. H.; Sheikh, J. A.
2018-02-01
Theoretical investigation of positive parity yrast band of odd-odd 130Pr nucleus is performed by applying the projected shell model. The present study is undertaken to investigate and verify the very recently observed side band in 130Pr theoretically in terms of quasi-particle (qp) configuration. From the analysis of band diagram, the yrast as well as side band are found to arise from two-qp configuration πh 11/2 ⊗ νh 11/2. The present calculations are viewed to have qualitatively reproduced the known experimental data for yrast states, transition energies, and B( M1) / B( E2) ratios of this nucleus. The recently observed positive parity side band is also reproduced by the present calculations. The energy states of the side band are predicted up to spin 25+, which is far above the known experimental spin of 18+ and this could serve as a motivational factor for future experiments. In addition, the reduced transition probability B( E2) for interband transitions has also been calculated for the first time in projected shell model, which would serve as an encouragement for other research groups in the future.
Understanding valence-shell electron-pair repulsion (VSEPR) theory using origami molecular models
Saraswati, Teguh Endah; Saputro, Sulistyo; Ramli, Murni; Praseptiangga, Danar; Khasanah, Nurul; Marwati, Sri
2017-01-01
Valence-shell electron-pair repulsion (VSEPR) theory is conventionally used to predict molecular geometry. However, it is difficult to explore the full implications of this theory by simply drawing chemical structures. Here, we introduce origami modelling as a more accessible approach for exploration of the VSEPR theory. Our technique is simple, readily accessible and inexpensive compared with other sophisticated methods such as computer simulation or commercial three-dimensional modelling kits. This method can be implemented in chemistry education at both the high school and university levels. We discuss the example of a simple molecular structure prediction for ammonia (NH 3 ). Using the origami model, both molecular shape and the scientific justification can be visualized easily. This ‘hands-on’ approach to building molecules will help promote understanding of VSEPR theory. (paper)
Understanding valence-shell electron-pair repulsion (VSEPR) theory using origami molecular models
Endah Saraswati, Teguh; Saputro, Sulistyo; Ramli, Murni; Praseptiangga, Danar; Khasanah, Nurul; Marwati, Sri
2017-01-01
Valence-shell electron-pair repulsion (VSEPR) theory is conventionally used to predict molecular geometry. However, it is difficult to explore the full implications of this theory by simply drawing chemical structures. Here, we introduce origami modelling as a more accessible approach for exploration of the VSEPR theory. Our technique is simple, readily accessible and inexpensive compared with other sophisticated methods such as computer simulation or commercial three-dimensional modelling kits. This method can be implemented in chemistry education at both the high school and university levels. We discuss the example of a simple molecular structure prediction for ammonia (NH3). Using the origami model, both molecular shape and the scientific justification can be visualized easily. This ‘hands-on’ approach to building molecules will help promote understanding of VSEPR theory.
Classical limit of diagonal form factors and HHL correlators
Bajnok, Zoltan [MTA Lendület Holographic QFT Group, Wigner Research Centre,H-1525 Budapest 114, P.O.B. 49 (Hungary); Janik, Romuald A. [Institute of Physics, Jagiellonian University,ul. Łojasiewicza 11, 30-348 Kraków (Poland)
2017-01-16
We propose an expression for the classical limit of diagonal form factors in which we integrate the corresponding observable over the moduli space of classical solutions. In infinite volume the integral has to be regularized by proper subtractions and we present the one, which corresponds to the classical limit of the connected diagonal form factors. In finite volume the integral is finite and can be expressed in terms of the classical infinite volume diagonal form factors and subvolumes of the moduli space. We analyze carefully the periodicity properties of the finite volume moduli space and found a classical analogue of the Bethe-Yang equations. By applying the results to the heavy-heavy-light three point functions we can express their strong coupling limit in terms of the classical limit of the sine-Gordon diagonal form factors.
Gruber, B.; Thomas, M.S.
1980-01-01
In this article the symmetry chains for the atomic shell model are classified in such a way that they lead from the group SU(4l+2) to its subgroup SOsub(J)(3). The atomic configurations (nl)sup(N) transform like irreducible representations of the group SU(4l+2), while SOsub(J)(3) corresponds to total angular momentum in SU(4l+2). The defining matrices for the various embeddings are given for each symmetry chain that is obtained. These matrices also define the projection onto the weight subspaces for the corresponding subsymmetries and thus relate the various quantum numbers and determine the branching of representations. It is shown in this article that three (interrelated) symmetry chains are obtained which correspond to L-S coupling, j-j coupling, and a seniority dependent coupling. Moreover, for l<=6 these chains are complete, i.e., there are no other chains but these. In articles to follow, the symmetry chains that lead from the group SO(8l+5) to SOsub(J)(3) will be discussed, with the entire atomic shell transforming like an irreducible representation of SO(8l+5). The transformation properties of the states of the atomic shell will be determined according to the various symmetry chains obtained. The symmetry lattice discussed in this article forms a sublattice of the larger symmetry lattice with SO(8l+5) as supergroup. Thus the transformation properties of the states of the atomic configurations, according to the various symmetry chains discussed in this article, will be obtained too. (author)
Study of the tensor correlation in oxygen isotopes using mean-field-type and shell model methods
Sugimoto, Satoru
2007-01-01
The tensor force plays important roles in nuclear structure. Recently, we have developed a mean-field-type model which can treat the two-particle-two-hole correlation induced by the tensor force. We applied the model to sub-closed-shell oxygen isotopes and found that an sizable attractive energy comes from the tensor force. We also studied the tensor correlation in 16O using a shell model including two-particle-two-hole configurations. In this case, quite a large attractive energy is obtained for the correlation energy from the tensor force
Determining Diagonal Branches in Mine Ventilation Networks
Krach, Andrzej
2014-12-01
The present paper discusses determining diagonal branches in a mine ventilation network by means of a method based on the relationship A⊗ PT(k, l) = M, which states that the nodal-branch incidence matrix A, modulo-2 multiplied by the transposed path matrix PT(k, l ) from node no. k to node no. l, yields the matrix M where all the elements in rows k and l - corresponding to the start and the end node - are 1, and where the elements in the remaining rows are 0, exclusively. If a row of the matrix M is to contain only "0" elements, the following condition has to be fulfilled: after multiplying the elements of a row of the matrix A by the elements of a column of the matrix PT(k, l), i.e. by the elements of a proper row of the matrix P(k, l ), the result row must display only "0" elements or an even number of "1" entries, as only such a number of "1" entries yields 0 when modulo-2 added - and since the rows of the matrix A correspond to the graph nodes, and the path nodes level is 2 (apart from the nodes k and l, whose level is 1), then the number of "1" elements in a row has to be 0 or 2. If, in turn, the rows k and l of the matrix M are to contain only "1" elements, the following condition has to be fulfilled: after multiplying the elements of the row k or l of the matrix A by the elements of a column of the matrix PT(k, l), the result row must display an uneven number of "1" entries, as only such a number of "1" entries yields 1 when modulo-2 added - and since the rows of the matrix A correspond to the graph nodes, and the level of the i and j path nodes is 1, then the number of "1" elements in a row has to be 1. The process of determining diagonal branches by means of this method was demonstrated using the example of a simple ventilation network with two upcast shafts and one downcast shaft. W artykule przedstawiono metodę wyznaczania bocznic przekątnych w sieci wentylacyjnej kopalni metodą bazującą na zależności A⊗PT(k, l) = M, która podaje, że macierz
DeBenedictis, Andrew; Atherton, Timothy J.; Rodarte, Andrea L.; Hirst, Linda S.
2018-03-01
A micrometer-scale elastic shell immersed in a nematic liquid crystal may be deformed by the host if the cost of deformation is comparable to the cost of elastic deformation of the nematic. Moreover, such inclusions interact and form chains due to quadrupolar distortions induced in the host. A continuum theory model using finite elements is developed for this system, using mesh regularization and dynamic refinement to ensure quality of the numerical representation even for large deformations. From this model, we determine the influence of the shell elasticity, nematic elasticity, and anchoring condition on the shape of the shell and hence extract parameter values from an experimental realization. Extending the model to multibody interactions, we predict the alignment angle of the chain with respect to the host nematic as a function of aspect ratio, which is found to be in excellent agreement with experiments.
Calculations of the energy spectra of Zn, Ga and Ge isotopes by the shell model
Sakakura, M.; Shikata, Y.; Arima, A.; Sebe, T.
1979-01-01
The effective Hamiltonian which was determined empirically by Koops and Glaudemans is tested in shell model calculations for the 65-68 Zn, 67-69 Ga, and 68-70 Ge nuclei in the full (1p 3 / 2 , 0f 5 / 2 , 1p 1 / 2 )n space. The resulting energy spectra are compared with the experimental spectra and results of previous calculations. The overall agreement with experiment is as satisfactory for these nuclei as for the Ni and Cu isotopes, by which the Hamiltonian was determined. It is noticed that the spectra of 67 Zn and 67 , 69 Ga calculated in this work are similar to those provided by the Alaga model. (orig.) [de
Inner-shell corrections to the Bethe stopping-power formula evaluated from a realistic atomic model
Inokuti, M.; Manson, S.T.
1985-01-01
Generalized oscillator strengths for K- and L-shell ionization have been calculated using a central potential derived from the Hartree-Slater model. In cases in which an ejected electron carries low kinetic energies, sizable differences with hydrogenic-model calculations are evident
Baptista Filho, Benedito Dias
1979-01-01
A numerical model has been developed to calculate the flow, pressure and temperature distribution of steady-state |for the tube and shell-side fluids in a shell-and-U-tubes heat exchanger with segmental baffles. It was based on the Subchannel Analysis Method- The model, checked with experimental results from one heat exchanger, predicted with good accuracy outlet temperatures for both fluids. The method, implemented ' in a computer program of low cost and easy application, can be used in the design and performance evaluation of commercial units.(author)
Pardo, D.; Branner, K.
2005-01-01
line load. The results are compared with result from similar shell models, which typically are used for practical design. Usually, good agreement between the shell models and the detailed 2D-solid model is found for the deflections, strains and stresses in regions with loads from pure bending. However...
Power take-off analysis for diagonally connected MHD channels
Pan, Y.C.; Doss, E.D.
1980-01-01
The electrical loading of the power take-off region of diagonally connected MHD channels is investigated by a two-dimensional model. The study examines the loading schemes typical of those proposed for the U-25 and U-25 Bypass channels. The model is applicable for the following four cases: (1) connection with diodes only, (2) connection with diodes and equal resistors, (3) connection with diodes and variable resistances to obtain a given current distribution, and (4) connection with diodes and variable resistors under changing load. The analysis is applicable for the power take-off regions of single or multiple-output systems. The general behaviors of the current and the potential distributions in all four cases are discussed. The analytical results are in good agreement with the experimental data. It is found possible to design the electrical circuit of the channel in the take-off region so as to achieve a fairly even load current output under changing total load current
M. Venkata Ramanan
2008-09-01
Full Text Available Cashew nut shell, a waste product obtained during deshelling of cashew kernels, had in the past been deemed unfit as a fuel for gasification owing to its high occluded oil content. The oil, a source of natural phenol, oozes upon gasification, thereby clogging the gasifier throat, downstream equipment and associated utilities with oil, resulting in ineffective gasification and premature failure of utilities due to its corrosive characteristics. To overcome this drawback, the cashew shells were de-oiled by charring in closed chambers and were subsequently gasified in an autothermal downdraft gasifier. Equilibrium modeling was carried out to predict the producer gas composition under varying performance influencing parameters, viz., equivalence ratio (ER, reaction temperature (RT and moisture content (MC. The results were compared with the experimental output and are presented in this paper. The model is quite satisfactory with the experimental outcome at the ER applicable to gasification systems, i.e., 0.15 to 0.30. The results show that the mole fraction of (i H2, CO and CH4 decreases while (N2 + H2O and CO2 increases with ER, (ii H2 and CO increases while CH4, (N2 + H2O and CO2 decreases with reaction temperature, (iii H2, CH4, CO2 and (N2 + H2O increases while CO decreases with moisture content. However at an equivalence ratio less than 0.15, the model predicts an unrealistic composition and is observed to be non valid below this ER.
A non-local shell model of hydrodynamic and magnetohydrodynamic turbulence
Plunian, F [Laboratoire de Geophysique Interne et Tectonophysique, CNRS, Universite Joseph Fourier, Maison des Geosciences, BP 53, 38041 Grenoble Cedex 9 (France); Stepanov, R [Institute of Continuous Media Mechanics, Korolyov 1, 614013 Perm (Russian Federation)
2007-08-15
We derive a new shell model of magnetohydrodynamic (MHD) turbulence in which the energy transfers are not necessarily local. Like the original MHD equations, the model conserves the total energy, magnetic helicity, cross-helicity and volume in phase space (Liouville's theorem) apart from the effects of external forcing, viscous dissipation and magnetic diffusion. The model of hydrodynamic (HD) turbulence is derived from the MHD model setting the magnetic field to zero. In that case the conserved quantities are the kinetic energy and the kinetic helicity. In addition to a statistically stationary state with a Kolmogorov spectrum, the HD model exhibits multiscaling. The anomalous scaling exponents are found to depend on a free parameter {alpha} that measures the non-locality degree of the model. In freely decaying turbulence, the infra-red spectrum also depends on {alpha}. Comparison with theory suggests using {alpha} = -5/2. In MHD turbulence, we investigate the fully developed turbulent dynamo for a wide range of magnetic Prandtl numbers in both kinematic and dynamic cases. Both local and non-local energy transfers are clearly identified.
Constrained-path quantum Monte Carlo approach for non-yrast states within the shell model
Bonnard, J. [INFN, Sezione di Padova, Padova (Italy); LPC Caen, ENSICAEN, Universite de Caen, CNRS/IN2P3, Caen (France); Juillet, O. [LPC Caen, ENSICAEN, Universite de Caen, CNRS/IN2P3, Caen (France)
2016-04-15
The present paper intends to present an extension of the constrained-path quantum Monte Carlo approach allowing to reconstruct non-yrast states in order to reach the complete spectroscopy of nuclei within the interacting shell model. As in the yrast case studied in a previous work, the formalism involves a variational symmetry-restored wave function assuming two central roles. First, it guides the underlying Brownian motion to improve the efficiency of the sampling. Second, it constrains the stochastic paths according to the phaseless approximation to control sign or phase problems that usually plague fermionic QMC simulations. Proof-of-principle results in the sd valence space are reported. They prove the ability of the scheme to offer remarkably accurate binding energies for both even- and odd-mass nuclei irrespective of the considered interaction. (orig.)
Continuum shell-model study of 16O and 40Ca
Heil, V.; Stock, W.
1976-06-01
Continuum shell-model calculations of the E1 and E2 strengths in 16 O and 40 Ca are presented. A consistent microscopic description of both the giant resonances and isospin forbidden E1- transitions between bound states can be achieved through 1) a careful choice of the single-particle potential, 2) the use of a finite-range residual interaction (including the Coulomb particle-hole force), and 3) the removal of spurious states. The results obtained within the separation expansion approximation of Birkholz are in reasonable agreement with measured photonucleon angular distributions and formfactors for electroexcitation. The influence of the continuum on the isospin mixing in bound states is found to be very strong. (orig.) [de
The contribution of the expanding shell test to the modeling of elastoplaticity at high strain rates
Llorca, Fabrice; Buy, Francois
2002-01-01
The expanding shell test allows to load a material in the domain of high strain levels while strain rate is about 104s-1. This test submits an hemisphere to a radial expanding free flight, using a pyrotechnic device. The experiment (experimental apparatus, measurements...) is described with the difficulties encountered for the interpretation of the experimental data. Under some assumptions, the numerical transformation of radial velocities gives indications about the evolution of the strain, stress, strain rate and temperature rise, this last one being related to plastic work. We show how it is possible to associate both analytical and numerical approaches. Numerical simulation of the test is presented in a companion paper (see [Buy01]). Results obtained for copper, tantalum and TA6V4 are presented. The contribution of this test to the modeling of elastoplastic behavior is discussed and further works are proposed
Time-dependent shell-model theory of dissipative heavy-ion collisions
Ayik, S.; Noerenberg, W.
1982-01-01
A transport theory is formulated within a time-dependent shell-model approach. Time averaging of the equations for macroscopic quantities lead to irreversibility and justifies weak-coupling limit and Markov approximation for the (energy-conserving) one- and two-body collision terms. Two coupled equations for the occupation probabilities of dynamical single-particle states and for the collective variable are derived and explicit formulas for transition rates, dynamical forces, mass parameters and friction coefficients are given. The applicability of the formulation in terms of characteristic quantities of nuclear systems is considered in detail and some peculiarities due to memory effects in the initial equilibration process of heavy-ion collisions are discussed. (orig.)
Off-shell dynamics of the O(3) NLS model beyond Monte Carlo and perturbation theory
Balog, J.; Niedermaier, M.
1997-01-01
The off-shell dynamics of the O(3) non-linear sigma model is probed in terms of spectral densities and two-point functions by means of the form factor approach. The exact form factors of the spin field, Noether current, EM tensor and the topological charge density are computed up to six particles. The corresponding n≤6 particle spectral densities are used to compute the two-point functions, and are argued to deviate at most a few per mille from the exact answer in the entire energy range below 10 3 in units of the mass gap. To cover yet higher energies we propose an extrapolation scheme to arbitrary particle numbers based on a novel scaling hypothesis for the spectral densities. It yields candidate results for the exact two-point functions at all energy scales and allows us to exactly determine the values of two, previously unknown, non-perturbative constants. (orig.)
Seniority structure of the cranked shell model wave function and the pairing phase transition
Wu, C.S.; Zeng, J.Y.; Center of Theoretical Physics, China Center of Advanced Science and Technology
1989-01-01
The accurate solutions to the low-lying eigenstates of the cranked shell model Hamiltonian are obtained by the particle-number-conserving treatment, in which a many-particle configuration truncation is adopted instead of the conventional single-particle level truncation. The variation of the seniority structures of low-lying eigenstates with rotational frequency ω is analyzed. The gap parameter of the yrast band decreases with ω very slowly, though the seniority structure has undergone a great change. It is suggested to use the seniority structure to indicate the possible pairing phase transition from a superconducting state to a normal state. The important blocking effects on the low-lying eigenstates are discussed
Identification of shell-model states in $^{135}$Sb populated via $\\beta^{-}$ decay of $^{135}$Sn
Shergur, J; Brown, B A; Cederkäll, J; Dillmann, I; Fraile-Prieto, L M; Hoff, P; Joinet, A; Köster, U; Kratz, K L; Pfeiffer, B; Walters, W B; Wöhr, A
2005-01-01
The $\\beta$- decay of $^{135}$Sn was studied at CERN/ISOLDE using a resonance ionization laser ion source and mass separator to achieve elemental and mass selectivity, respectively. $\\gamma$-ray singles and $\\gamma\\gamma$ coincidence spectra were collected as a function of time with the laser on and with the laser off. These data were used to establish the positions of new levels in $^{135}$Sb, including new low-spin states at 440 and 798 keV, which are given tentative spin and parity assignments of 3/2$^{+}$ and 9/2$^{+}$, respectively. The observed levels of $^{135}$Sb are compared with shell-model calculations using different single-particle energies and different interactions.
Fossez, Kevin
2014-01-01
Small open quantum systems, whose properties are profoundly affected by the environment of continuum states, are intensely studied in various fields of Physics: nuclear physics, atomic and molecular physics, quantum optics, etc. These different many-body systems, in spite of their specific features, have generic properties which are common to all weakly bound or unbound systems close to the threshold. Coupling to the continuum is essential to describe the low-energy nuclear reactions of astrophysical interest, the formation of halo states in nuclei, atomic clusters and dipolar anions, or the near-threshold two neutron and alpha particle correlations (clustering). Recently, the open quantum system extension of the nuclear shell model, the Gamow shell model (GSM), based on the Berggren ensemble, has been applied successfully for the description of resonant states spectra in atomic nuclei. The coupled-channel formulation of the GSM (GSM-CC) allows to describe various low-energy nuclear reactions. In this work, the GSM-CC is formulated and applied for the description of proton/neutron radiative capture reactions of astrophysical interest, such as: 17 F(p, γ) 18 Ne, 7 Be(p, γ) 8 B and 7 Li(n, γ) 8 Li. Moreover, for the first time, the GSM has been applied in atomic physics for the description of spectra of dipolar anions. Systematic investigation of the hydrogen cyanide dipolar anion (HCN - ) allowed to identify the collective bands of states both in the strong coupling regime, for weakly bound halo states, and in the weak coupling regime above the dissociation threshold. In the strong coupling regime, K J = 0 anion a rotational band has been found. Above the threshold, K J quantum number is not conserved. Resonances in this regime form rotational bands according to the angular momentum of the rotating molecule, whereas the band head energies and the lifetimes depend predominantly on the external electron wave function. (author) [fr
Scission-point model of nuclear fission based on deformed-shell effects
Wilkins, B.D.; Steinberg, E.P.; Chasman, R.R.
1976-01-01
A static model of nuclear fission is proposed based on the assumption of statistical equilibrium among collective degrees of freedom at the scission point. The relative probabilities of formation of complementary fission fragment pairs are determined from the relative potential energies of a system of two nearly touching, coaxial spheroids with quadrupole deformations. The total potential energy of the system at the scission point is calculated as the sum of liquid-drop and shell- and pairing-correction terms for each spheroid, and Coulomb and nuclear potential terms describing the interaction between them. The fissioning system at the scission point is characterized by three parameters: the distance between the tips of the spheroids (d), the intrinsic excitation energy of the fragments (tau/sub int/), and a collective temperature (T/sub coll/). No attempt is made to adjust these parameters to give optimum fits to experimental data, but rather, a single choice of values for d, tau/sub int/, and T/sub coll/ is used in the calculations for all fissioning systems. The general trends of the distributions of mass, nuclear charge, and kinetic energy in the fission of a wide range of nuclides from Po to Fm are well reproduced in the calculations. The major influence of the deformed-shell corrections for neutrons is indicated and provides a convenient framework for the interpretation of observed trends in the data and for the prediction of new results. The scission-point configurations derived from the model provide an interpretation of the ''saw-tooth'' neutron emission curve as well as previously unexplained observations on the variation of TKE for isotopes of U, Pu, Cm, and Cf; structure in the width of total kinetic energy release as a function of fragment mass ratio; and a difference in threshold energies for symmetric and asymmetric mass splits in the fission of Ra and Ac isotopes
Direct current hopping conductance in one-dimensional diagonal disordered systems
Ma Song-Shan; Xu Hui; Liu Xiao-Liang; Xiao Jian-Rong
2006-01-01
Based on a tight-binding disordered model describing a single electron band, we establish a direct current (dc) electronic hopping transport conductance model of one-dimensional diagonal disordered systems, and also derive a dc conductance formula. By calculating the dc conductivity, the relationships between electric field and conductivity and between temperature and conductivity are analysed, and the role played by the degree of disorder in electronic transport is studied. The results indicate the conductivity of systems decreasing with the increase of the degree of disorder, characteristics of negative differential dependence of resistance on temperature at low temperatures in diagonal disordered systems, and the conductivity of systems decreasing with the increase of electric field, featuring the non-Ohm's law conductivity.
Lefrancois, A.
1976-01-01
The method of dimensional analysis is applied to the evaluation of deformation, stress, and ideal buckling strength (which is independent of the values of the elastic range), of shells subject to external pressure. The relations obtained are verified in two examples: a cylindrical ring and a tube with free ends and almost circular cross-section. Further, it is shown how and to what extent the results obtained from model tests can be used to predict the behaviour of geometrically similar shells which are made of the same material, or even of a different material. (Author) [fr
Zhao, Yumin
1997-07-01
By the techniques of the Wick theorem for coupled clusters, the no-energy-weighted electromagnetic sum-rule calculations are presented in the sdg neutron-proton interacting boson model, the nuclear pair shell model and the fermion-dynamical symmetry model. The project supported by Development Project Foundation of China, National Natural Science Foundation of China, Doctoral Education Fund of National Education Committee, Fundamental Research Fund of Southeast University
Lacour, Thomas; Guédra, Matthieu; Valier-Brasier, Tony; Coulouvrat, François
2018-01-01
Nanodroplets have great, promising medical applications such as contrast imaging, embolotherapy, or targeted drug delivery. Their functions can be mechanically activated by means of focused ultrasound inducing a phase change of the inner liquid known as the acoustic droplet vaporization (ADV) process. In this context, a four-phases (vapor + liquid + shell + surrounding environment) model of ADV is proposed. Attention is especially devoted to the mechanical properties of the encapsulating shell, incorporating the well-known strain-softening behavior of Mooney-Rivlin material adapted to very large deformations of soft, nearly incompressible materials. Various responses to ultrasound excitation are illustrated, depending on linear and nonlinear mechanical shell properties and acoustical excitation parameters. Different classes of ADV outcomes are exhibited, and a relevant threshold ensuring complete vaporization of the inner liquid layer is defined. The dependence of this threshold with acoustical, geometrical, and mechanical parameters is also provided.
Shell-model Monte Carlo simulations of the BCS-BEC crossover in few-fermion systems
Zinner, Nikolaj Thomas; Mølmer, Klaus; Özen, C.
2009-01-01
We study a trapped system of fermions with a zero-range two-body interaction using the shell-model Monte Carlo method, providing ab initio results for the low particle number limit where mean-field theory is not applicable. We present results for the N-body energies as function of interaction...
Radiative capture reaction {sup 7}Be(p,{gamma}){sup 8}B in the continuum shell model
Bennaceur, K; Ploszajczak, M [Grand Accelerateur National d` Ions Lourds (GANIL), Caen (France); Nowacki, F [Grand Accelerateur National d` Ions Lourds (GANIL), Caen (France); [Lab. de Physique Theorique Strasbourg, Strasbourg (France); Okolowicz, J [Grand Accelerateur National d` Ions Lourds (GANIL), Caen (France); [Inst. of Nuclear Physics, Krakow (Poland)
1998-06-01
We present here the first application of realistic shell model (SM) including coupling between many-particle (quasi-)bound states and the continuum of one-particle scattering states to the calculation of the total capture cross section and the astrophysical factor in the reaction {sup 7}Be(p,{gamma}){sup 8}B. (orig.)
Praus, P.; Svoboda, L.; Tokarský, J.; Hospodková, Alice; Klemm, V.
2014-01-01
Roč. 292, Feb (2014), s. 813-822 ISSN 0169-4332 Institutional support: RVO:68378271 Keywords : core/shell nanoparticles * CdS/ZnS * molecular modelling * electron tunnelling * photocatalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.711, year: 2014
Welser-Sherrill, L.; Mancini, R. C.; Haynes, D. A.; Haan, S. W.; Koch, J. A.; Izumi, N.; Tommasini, R.; Golovkin, I. E.; MacFarlane, J. J.; Radha, P. B.; Delettrez, J. A.; Regan, S. P.; Smalyuk, V. A.
2007-01-01
The presence of shell mix in inertial confinement fusion implosion cores is an important characteristic. Mixing in this experimental regime is primarily due to hydrodynamic instabilities, such as Rayleigh-Taylor and Richtmyer-Meshkov, which can affect implosion dynamics. Two independent theoretical mix models, Youngs' model and the Haan saturation model, were used to estimate the level of Rayleigh-Taylor mixing in a series of indirect drive experiments. The models were used to predict the radial width of the region containing mixed fuel and shell materials. The results for Rayleigh-Taylor mixing provided by Youngs' model are considered to be a lower bound for the mix width, while those generated by Haan's model incorporate more experimental characteristics and consequently have larger mix widths. These results are compared with an independent experimental analysis, which infers a larger mix width based on all instabilities and effects captured in the experimental data
Loading factor and inclination parameter of diagonal type MHD generators
Ishikawa, Motoo
1979-01-01
Regarding diagonal type MHD generators is studied the relation between the loading factor and inclination parameter which is required for attaining the maximum power density with a given electrical efficiency on the assumption of infinitely segmented electrodes. The average current density on electrodes is calculated against the Hall parameter, loading factor, and inclination parameter. The diagonal type generator is compared with Faraday type generator regarding the average current density. Decreasing the loading factor from inlet to outlet is appropriate to small size generators but increasing to large size generators. The inclination parameter had better decrease in both generators, being smaller for small generators than for large ones. The average current density on electrodes of diagonal type generators varies less with the loading factor than the Faraday type. In large size generators its value can become smaller compared with that of the Faraday type. (author)
Development of surrogate models using artificial neural network for building shell energy labelling
Melo, A.P.; Cóstola, D.; Lamberts, R.; Hensen, J.L.M.
2014-01-01
Surrogate models are an important part of building energy labelling programs, but these models still present low accuracy, particularly in cooling-dominated climates. The objective of this study was to evaluate the feasibility of using an artificial neural network (ANN) to improve the accuracy of surrogate models for labelling purposes. An ANN was applied to model the building stock of a city in Brazil, based on the results of extensive simulations using the high-resolution building energy simulation program EnergyPlus. Sensitivity and uncertainty analyses were carried out to evaluate the behaviour of the ANN model, and the variations in the best and worst performance for several typologies were analysed in relation to variations in the input parameters and building characteristics. The results obtained indicate that an ANN can represent the interaction between input and output data for a vast and diverse building stock. Sensitivity analysis showed that no single input parameter can be identified as the main factor responsible for the building energy performance. The uncertainty associated with several parameters plays a major role in assessing building energy performance, together with the facade area and the shell-to-floor ratio. The results of this study may have a profound impact as ANNs could be applied in the future to define regulations in many countries, with positive effects on optimizing the energy consumption. - Highlights: • We model several typologies which have variation in input parameters. • We evaluate the accuracy of surrogate models for labelling purposes. • ANN is applied to model the building stock. • Uncertainty in building plays a major role in the building energy performance. • Results show that ANN could help to develop building energy labelling systems
Hamoudi, A.; Shahaliev, E.; Nazmitdinov, R. G.; Alhassid, Y.
2002-01-01
We study the fluctuation properties of ΔT=0 electromagnetic transition intensities and electromagnetic moments in A∼60 nuclei within the framework of the interacting shell model, using a realistic effective interaction for pf-shell nuclei with a 56 Ni core. The distributions of the transition intensities and of the electromagnetic moments are well described by the Gaussian orthogonal ensemble of random matrices. In particular, the transition intensity distributions follow a Porter-Thomas distribution. When diagonal matrix elements (i.e., moments) are included in the analysis of transition intensities, the distributions remain Porter-Thomas except for the isoscalar M1. This deviation is explained in terms of the structure of the isoscalar M1 operator
Diagonal Limit for Conformal Blocks in d Dimensions
Hogervorst, Matthijs; Rychkov, Slava
2013-01-01
Conformal blocks in any number of dimensions depend on two variables z, zbar. Here we study their restrictions to the special "diagonal" kinematics z = zbar, previously found useful as a starting point for the conformal bootstrap analysis. We show that conformal blocks on the diagonal satisfy ordinary differential equations, third-order for spin zero and fourth-order for the general case. These ODEs determine the blocks uniquely and lead to an efficient numerical evaluation algorithm. For equal external operator dimensions, we find closed-form solutions in terms of finite sums of 3F2 functions.
Spectral Sharpening of Color Sensors: Diagonal Color Constancy and Beyond
Vazquez-Corral, Javier; Bertalmío, Marcelo
2014-01-01
It has now been 20 years since the seminal work by Finlayson et al. on the use/nof spectral sharpening of sensors to achieve diagonal color constancy. Spectral sharpening is/nstill used today by numerous researchers for different goals unrelated to the original goal/nof diagonal color constancy e.g., multispectral processing, shadow removal, location of/nunique hues. This paper reviews the idea of spectral sharpening through the lens of what/nis known today in color constancy, describes the d...
Rivera, Gabriel; Stayton, C Tristan
2011-10-01
Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low-drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade-offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments; however, this flatter shape may also make the shells less capable of resisting predator-induced loads. We tested the idea that "lotic" shell shapes are weaker than "lentic" shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. "Lotic" shell shapes produced significantly higher stresses than "lentic" shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many-to-one mapping of shell shape onto strength, P. concinna experiences a trade-off in shell shape between hydrodynamic and mechanical performance. This trade-off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade-off in some cases, as changes in
Shell-model results in fp and fpg9/2 spaces for 61,63,65Co isotopes
Srivastava, P. C.; Kota, V. K. B.
2011-01-01
Low-lying spectra and several high-spin states of odd-even 61,63,65 Co isotopes are calculated in two different shell-model spaces. First set of calculations have been carried out in fp-shell valence space (full fp space for 63,65 Co and a truncated one for 61 Co) using two recently derived fp-shell interactions, namely GXPF1A and KB3G, with 40 Ca as core. Similarly, the second set of calculations have been performed in fpg 9/2 valence space using an fpg effective interaction due to Sorlin et al., with 48 Ca as core and imposing a truncation. It is seen that the results of GXPF1A and KB3G are reasonable for 61,63 Co. For 65 Co, shell-model results show that the fpg interaction adopted in the study is inadequate and also points out that it is necessary to include orbitals higher than 1g 9/2 for neutron-rich Co isotopes.
Three-fluid MHD-model of a current shell in Z-pinch
Bazdenkov, S.V.; Vikhrev, V.V.
1975-01-01
Formation and motion of the current shell in a power pulsed discharge (Z-pinch) are discussed. One-dimmensional nonstationary problem about a discharge in deuterium is solved in the three-liquid magnetohydrodynamic approximation with regard for gas ionization and motion of neutral atoms. It is shown that after the shell removal there remains a large quantity of an ionized gas near an isolating chamber wall. The quantity is sufficient that a secondary breakdown may take place in the ionized gas. The moving current shell has a double structure, i.e. a current ''piston'' and a current layer in the shock wave front
Wang, Xujing; Becker, Frederick F.; Gascoyne, Peter R. C.
2010-01-01
The scale-invariant property of the cytoplasmic membrane of biological cells is examined by applying the Minkowski–Bouligand method to digitized scanning electron microscopy images of the cell surface. The membrane is found to exhibit fractal behavior, and the derived fractal dimension gives a good description of its morphological complexity. Furthermore, we found that this fractal dimension correlates well with the specific membrane dielectric capacitance derived from the electrorotation measurements. Based on these findings, we propose a new fractal single-shell model to describe the dielectrics of mammalian cells, and compare it with the conventional single-shell model (SSM). We found that while both models fit with experimental data well, the new model is able to eliminate the discrepancy between the measured dielectric property of cells and that predicted by the SSM. PMID:21198103
Collapse of the random-phase approximation: Examples and counter-examples from the shell model
Johnson, Calvin W.; Stetcu, Ionel
2009-01-01
The Hartree-Fock approximation to the many-fermion problem can break exact symmetries, and in some cases by changing a parameter in the interaction one can drive the Hartree-Fock minimum from a symmetry-breaking state to a symmetry-conserving state (also referred to as a 'phase transition' in the literature). The order of the transition is important when one applies the random-phase approximation (RPA) to the of the Hartree-Fock wave function: if first order, RPA is stable through the transition, but if second-order, then the RPA amplitudes become large and lead to unphysical results. The latter is known as 'collapse' of the RPA. While the difference between first- and second-order transitions in the RPA was first pointed out by Thouless, we present for the first time nontrivial examples of both first- and second-order transitions in a uniform model, the interacting shell-model, where we can compare to exact numerical results.
Light neutron-rich hypernuclei from the importance-truncated no-core shell model
Roland Wirth
2018-04-01
Full Text Available We explore the systematics of ground-state and excitation energies in singly-strange hypernuclei throughout the helium and lithium isotopic chains — from HeΛ5 to HeΛ11 and from LiΛ7 to LiΛ12 — in the ab initio no-core shell model with importance truncation. All calculations are based on two- and three-baryon interaction from chiral effective field theory and we employ a similarity renormalization group transformation consistently up to the three-baryon level to improve the model-space convergence. While the absolute energies of hypernuclear states show a systematic variation with the regulator cutoff of the hyperon–nucleon interaction, the resulting neutron separation energies are very stable and in good agreement with available data for both nucleonic parents and their daughter hypernuclei. We provide predictions for the neutron separation energies and the spectra of neutron-rich hypernuclei that have not yet been observed experimentally. Furthermore, we find that the neutron drip lines in the helium and lithium isotopic chains are not changed by the addition of a hyperon. Keywords: Hypernuclei, Ab-initio methods, Neutron-rich nuclei, Neutron separation energies, Neutron drip line
Shell model study of high spin states in the N=50 nucleus 93Tc
Ghugre, S.S.; Patel, S.B.; Bhowmik, R.K.
1994-01-01
High spin states in the N=50 nucleus 93 Tc were reinvestigated by using the reaction 64 Zn ( 35 Cl, 4p 2n) at a beam energy of 140 MeV. This was done particularly with a view to observe any γ rays upto 2.7 MeV which may have been missed in our earlier study where the experimental conditions were set to observe γ rays upto 2 MeV. We found four new γ rays of energy: 2484, 2164, 2130 and 69 keV. We have placed these γ rays in the level scheme and it now gets extended to 49/2 - . Though there is no substantial change in the level scheme, placing the γ rays in the level scheme has resulted into two important conclusions: (1) We have performed shell model calculations for 93 Tc nucleus within a model space which encompasses an enlarged proton configuration and allows for the excitation of the neutron across the N=50 core. The excitation of a single neutron across the N=50 core satisfactorily explains the new level scheme. (2) The energy of the 17/2 - isomeric state is now unambiguously placed at 2185 keV. (orig.)
Light neutron-rich hypernuclei from the importance-truncated no-core shell model
Wirth, Roland; Roth, Robert
2018-04-01
We explore the systematics of ground-state and excitation energies in singly-strange hypernuclei throughout the helium and lithium isotopic chains - from He5Λ to He11Λ and from Li7Λ to Li12Λ - in the ab initio no-core shell model with importance truncation. All calculations are based on two- and three-baryon interaction from chiral effective field theory and we employ a similarity renormalization group transformation consistently up to the three-baryon level to improve the model-space convergence. While the absolute energies of hypernuclear states show a systematic variation with the regulator cutoff of the hyperon-nucleon interaction, the resulting neutron separation energies are very stable and in good agreement with available data for both nucleonic parents and their daughter hypernuclei. We provide predictions for the neutron separation energies and the spectra of neutron-rich hypernuclei that have not yet been observed experimentally. Furthermore, we find that the neutron drip lines in the helium and lithium isotopic chains are not changed by the addition of a hyperon.
Diagonalization of bosonic quadratic Hamiltonians by Bogoliubov transformations
Nam, Phan Thanh; Napiorkowski, Marcin; Solovej, Jan Philip
2016-01-01
We provide general conditions for which bosonic quadratic Hamiltonians on Fock spaces can be diagonalized by Bogoliubov transformations. Our results cover the case when quantum systems have infinite degrees of freedom and the associated one-body kinetic and paring operators are unbounded. Our...
Biomechanical pole and leg characteristics during uphill diagonal roller skiing.
Lindinger, Stefan Josef; Göpfert, Caroline; Stöggl, Thomas; Müller, Erich; Holmberg, Hans-Christer
2009-11-01
Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9 degrees; 11 km/h). Performance was correlated to cycle length (r = 0.77; P Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r= -0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.
Diagonalization of Bounded Linear Operators on Separable Quaternionic Hilbert Space
Feng Youling; Cao, Yang; Wang Haijun
2012-01-01
By using the representation of its complex-conjugate pairs, we have investigated the diagonalization of a bounded linear operator on separable infinite-dimensional right quaternionic Hilbert space. The sufficient condition for diagonalizability of quaternionic operators is derived. The result is applied to anti-Hermitian operators, which is essential for solving Schroedinger equation in quaternionic quantum mechanics.
Thermodynamics of Rh nuclear spins calculated by exact diagonalization
Lefmann, K.; Ipsen, J.; Rasmussen, F.B.
2000-01-01
We have employed the method of exact diagonalization to obtain the full-energy spectrum of a cluster of 16 Rh nuclear spins, having dipolar and RK interactions between first and second nearest neighbours only. We have used this to calculate the nuclear spin entropy, and our results at both positi...
Diagonal Cracking and Shear Strength of Reinforced Concrete Beams
Zhang, Jin-Ping
1997-01-01
The shear failure of non-shear-reinforced concrete beams with normal shear span ratios is observed to be governed in general by the formation of a critical diagonal crack. Under the hypothesis that the cracking of concrete introduces potential yield lines which may be more dangerous than the ones...
Images of a Bose-Einstein condensates: diagonal dynamical Bogoliubov vacuum
Dziarmaga, J.; Sacha, K.; Karkuszewski, Z.
2005-01-01
Evolution of a Bose-Einstein condensate subject to a time-dependent external perturbation can be described by a time-dependent Bogoliubov theory: a condensate initially in its ground state evolves into a time-dependent excited state which can be formally written as a time-dependent Bogoliubov vacuum annihilated by time-dependent quasiparticle annihilation operators. We prove that any Bogoliubov vacuum can be brought to a diagonal form in a time-dependent orthonormal basis. This diagonal form is taylored for simulations of quantum measurements on excited condensates. As an example we work out a model of atomic interferometer where a trap potential is split in two parts by a potential barrier, and then atoms are released by opening the double-well trap potential. In the Gross-Pitaevskii approximation the released atoms give a high contrast interference pattern with repeatable position of interference fringes. In the two-mode tight-binding approximation the effect of phase diffusion makes the position of fringes fluctuate from experiment to experiment but every single realisation of experiment gives a high quality interference pattern. The time-dependent Bogoliubov theory is a more realistic description of the experiment which goes beyond both approximations. Using the diagonal time-dependent Bogoliubov vacuum we show that in addition to position fluctuations the interference pattern is also loosing its high quality contrast. (author)
Neotectonics of Asia: Thin-shell finite-element models with faults
Kong, Xianghong; Bird, Peter
1994-01-01
As India pushed into and beneath the south margin of Asia in Cenozoic time, it added a great volume of crust, which may have been (1) emplaced locally beneath Tibet, (2) distributed as regional crustal thickening of Asia, (3) converted to mantle eclogite by high-pressure metamorphism, or (4) extruded eastward to increase the area of Asia. The amount of eastward extrusion is especially controversial: plane-stress computer models of finite strain in a continuum lithosphere show minimal escape, while laboratory and theoretical plane-strain models of finite strain in a faulted lithosphere show escape as the dominant mode. We suggest computing the present (or neo)tectonics by use of the known fault network and available data on fault activity, geodesy, and stress to select the best model. We apply a new thin-shell method which can represent a faulted lithosphere of realistic rheology on a sphere, and provided predictions of present velocities, fault slip rates, and stresses for various trial rheologies and boundary conditions. To minimize artificial boundaries, the models include all of Asia east of 40 deg E and span 100 deg on the globe. The primary unknowns are the friction coefficient of faults within Asia and the amounts of shear traction applied to Asia in the Himalayan and oceanic subduction zones at its margins. Data on Quaternary fault activity prove to be most useful in rating the models. Best results are obtained with a very low fault friction of 0.085. This major heterogeneity shows that unfaulted continum models cannot be expected to give accurate simulations of the orogeny. But, even with such weak faults, only a fraction of the internal deformation is expressed as fault slip; this means that rigid microplate models cannot represent the kinematics either. A universal feature of the better models is that eastern China and southeast Asia flow rapidly eastward with respect to Siberia. The rate of escape is very sensitive to the level of shear traction in the
Caurier, E.; Nowacki, F.; Menendez, J.; Poves, A.
2007-02-01
Large scale shell model calculations, with dimensions reaching 10 9 , are carried out to describe the recently observed deformed (ND) and superdeformed (SD) bands based on the first and second excited 0 + states of 40 Ca at 3.35 MeV and 5.21 MeV respectively. A valence space comprising two major oscillator shells, sd and pf, can accommodate most of the relevant degrees of freedom of this problem. The ND band is dominated by configurations with four particles promoted to the pf-shell (4p-4h in short). The SD band by 8p-8h configurations. The ground state of 40 Ca is strongly correlated, but the closed shell still amounts to 65%. The energies of the bands are very well reproduced by the calculations. The out-band transitions connecting the SD band with other states are very small and depend on the details of the mixing among the different np-nh configurations, in spite of that, the calculation describes them reasonably. For the in-band transition probabilities along the SD band, we predict a fairly constant transition quadrupole moment Q 0 (t) ∼ 70 e fm 2 up to J=10, that decreases toward the higher spins. We submit also that the J=8 states of the deformed and superdeformed band are maximally mixed. (authors)
Caurier, E.; Nowacki, F.; Menendez, J.; Poves, A.
2007-01-01
Large-scale shell-model calculations, with dimensions reaching 10 9 , are carried out to describe the recently observed deformed (ND) and superdeformed (SD) bands based on the first and second excited 0 + states of 40 Ca at 3.35 and 5.21 MeV, respectively. A valence space comprising two major oscillator shells, sd and pf, can accommodate most of the relevant degrees of freedom of this problem. The ND band is dominated by configurations with four particles promoted to the pf shell (4p-4h in short). The SD band by 8p-8h configurations. The ground state of 40 Ca is strongly correlated, but the closed shell still amounts to 65%. The energies of the bands are very well reproduced by the calculations. The out-band transitions connecting the SD band with other states are very small and depend on the details of the mixing among the different np-nh configurations; in spite of that, the calculation describes them reasonably. For the in-band transition probabilities along the SD band, we predict a fairly constant transition quadrupole moment Q 0 (t)∼170 e fm 2 up to J=10 that decreases toward the higher spins. We submit also that the J=8 states of the deformed and superdeformed bands are maximally mixed
Shell model calculations for levels and transition rates in 204Pb and 206Pb
Wang, D.; McEllistrem, M.T.
1990-01-01
Level energies and decay rates of both negative and positive parity levels of 206,204 Pb have been calculated through mixed-configuration shell model calculations using the modified surface delta interaction (MSDI), the Schiffer-True central interaction, and another two-body interaction. These calculations were all carried out with a full six-orbit neutron hole space. The predicted low-lying levels with the MSDI are in excellent agreement with experiments, accounting for the energies, spins, and parities of essentially all levels below 3 MeV excitation energy except known particle-hole collective excitations in both nuclei. Almost all calculated E2 and M1 transition rates are consistent with measured branching ratios for γ-ray decay of excited levels. The comparison of the observed and calculated levels demonstrates the important role played by the neutron-hole i 13/2 configuration in the levels of 204 Pb and 206 Pb, and interprets an apparent discrepancy over the character and energy spacings of 0 + levels in 204 Pb
Cluster form factor calculation in the ab initio no-core shell model
Navratil, Petr
2004-01-01
We derive expressions for cluster overlap integrals or channel cluster form factors for ab initio no-core shell model (NCSM) wave functions. These are used to obtain the spectroscopic factors and can serve as a starting point for the description of low-energy nuclear reactions. We consider the composite system and the target nucleus to be described in the Slater determinant (SD) harmonic oscillator (HO) basis while the projectile eigenstate to be expanded in the Jacobi coordinate HO basis. This is the most practical case. The spurious center of mass components present in the SD bases are removed exactly. The calculated cluster overlap integrals are translationally invariant. As an illustration, we present results of cluster form factor calculations for 5 He vertical bar 4 He+n>, 5 He vertical bar 3 H+d>, 6 Li vertical bar 4 He+d>, 6 Be vertical bar 3 He+ 3 He>, 7 Li vertical bar 4 He+ 3 H>, 7 Li vertical bar 6 Li+n>, 8 Be vertical bar 6 Li+d>, 8 Be vertical bar 7 Li+p>, 9 Li vertical bar 8 Li+n>, and 13 C vertical bar 12 C+n>, with all the nuclei described by multi-(ℎ/2π)Ω NCSM wave functions
IBM parameters derived from realistic shell-model Hamiltonian via Hn-cooling method
Nakada, Hitoshi
1997-01-01
There is a certain influence of non-collective degrees-of-freedom even in lowest-lying states of medium-heavy nuclei. This influence seems to be significant for some of the IBM parameters. In order to take it into account, several renormalization approaches have been applied. It has been shown in the previous studies that the influence of the G-pairs is important, but does not fully account for the fitted values. The influence of the non-collective components may be more serious when we take a realistic effective nucleonic interaction. To incorporate this influence into the IBM parameters, we employ the recently developed H n -cooling method. This method is applied to renormalize the wave functions of the states consisting of the SD-pairs, for the Cr-Fe nuclei. On this ground, the IBM Hamiltonian and transition operators are derived from corresponding realistic shell-model operators, for the Cr-Fe nuclei. Together with some features of the realistic interaction, the effects of the non-SD degrees-of-freedom are presented. (author)
Mass loss from OH/IR stars - Models for the infrared emission of circumstellar dust shells
Justtanont, K.; Tielens, A. G. G. M.
1992-01-01
The IR emission of a sample of 24 OH/IR stars is modeled, and the properties of circumstellar dust and mass-loss rate of the central star are derived. It is shown that for some sources the observations of the far-IR emission is well fitted with a lambda exp -1 law, while some have a steeper index of 1.5. For a few sources, the presence of circumstellar ice grains is inferred from detailed studies of the observed 10-micron feature. Dust mass-loss rates are determined from detailed studies for all the stars in this sample. They range from 6.0 x 10 exp -10 solar mass/yr for an optically visible Mira to 2.2 x 10 exp -6 solar mass/yr for a heavily obscured OH/IR star. These dust mass-loss rates are compared to those calculated from IRAS photometry using 12-, 25-, and 60-micron fluxes. The dust mass-loss rates are also compared to gas mass-loss rates determined from OH and CO observations. For stars with tenuous shells, a dust-to-gas ratio of 0.001 is obtained.
Shell model with several particles in the continuum: application to the two-proton decay
Rotureau, J.
2005-02-01
The recent experimental results concerning nuclei at the limit of stability close to the drip-lines and in particular the two-proton emitters require a development of new methodologies to reliably calculate and understand properties of those exotic physical systems. In this work we have extended the Shell Model Embedded in the Continuum (SMEC) in order to describe the coupling with two particles in the scattering continuum. We have obtained a microscopic description of the two-proton emission that takes into account the antisymmetrization of the total wavefunction, the configuration mixing and the three-body asymptotics. We have studied the decay of the 1 2 - state in 18 Ne in two limiting cases: (i) a sequential emission of two protons through the correlated continuum of 17 F and (ii) emission of 2 He cluster that disintegrates because of the final state interaction (diproton emission). Independently of the choice of the effective interaction we have observed that the two-proton emission of the 1 2 - in 18 Ne is mainly a sequential process; the ratio between the widths of the diproton emission and the sequential decay does not exceed 8% in any case. (author)
Spectroscopy of 96-98Ru and neighboring nuclei: shell model calculations and lifetime measurements
Kharraja, B.; Garg, U.; Ghugre, S.S.
1997-01-01
High Spin states in 94,95 Mo, 94-96 Tc, 96-98 Ru and 97,98 Rh were populated via the 65 Cu( 36 S,xpyn) reactions at 142 MeV. Level schemes of these nuclei have been extended up to a spin of J ∼ 20ℎ and an excitation energy of E x ∼12 -14 MeV. Information on the high spin structure for 96 Tc and 98 Rh has been obtained for the first time. Spherical shell model calculations have been performed and compared with the experimental excitation energies. The level structures of the N=51, 52 isotones exhibit single-particle nature even at the highest spins and excitation energies. A fragmentation of intensity into several branches after breaking of the N = 50 core has been observed. There are indications for the onset of collectivity around neutron number N = 53 in this mass region. A sequence of E2 transitions, reminiscent of vibrational degree of freedom, were observed in 98 Ru at spins just above the observed N = 50 core breaking. RDM lifetime measurements have been performed to ascertain the intrinsic structures of these level sequences. (author)
Microscopic calculation of level densities: the shell model Monte Carlo approach
Alhassid, Yoram
2012-01-01
The shell model Monte Carlo (SMMC) approach provides a powerful technique for the microscopic calculation of level densities in model spaces that are many orders of magnitude larger than those that can be treated by conventional methods. We discuss a number of developments: (i) Spin distribution. We used a spin projection method to calculate the exact spin distribution of energy levels as a function of excitation energy. In even-even nuclei we find an odd-even staggering effect (in spin). Our results were confirmed in recent analysis of experimental data. (ii) Heavy nuclei. The SMMC approach was extended to heavy nuclei. We have studied the crossover between vibrational and rotational collectivity in families of samarium and neodymium isotopes in model spaces of dimension approx. 10 29 . We find good agreement with experimental results for both state densities and 2 > (where J is the total spin). (iii) Collective enhancement factors. We have calculated microscopically the vibrational and rotational enhancement factors of level densities versus excitation energy. We find that the decay of these enhancement factors in heavy nuclei is correlated with the pairing and shape phase transitions. (iv) Odd-even and odd-odd nuclei. The projection on an odd number of particles leads to a sign problem in SMMC. We discuss a novel method to calculate state densities in odd-even and odd-odd nuclei despite the sign problem. (v) State densities versus level densities. The SMMC approach has been used extensively to calculate state densities. However, experiments often measure level densities (where levels are counted without including their spin degeneracies.) A spin projection method enables us to also calculate level densities in SMMC. We have calculated the SMMC level density of 162 Dy and found it to agree well with experiments
Dupuis, M.; Karataglidis, S.; Bauge, E.; Delaroche, J.P.; Gogny, D.
2006-01-01
The random phase approximation (RPA) long-range correlations are known to play a significant role in understanding the depletion of single particle-hole states observed in (e,e ' ) and (e,e ' p) measurements. Here the RPA theory, implemented using the D1S force is considered for the specific purpose of building correlated ground states and related one-body density matrix elements. These may be implemented and tested in a fully microscopic optical model for NA scattering off doubly closed-shell nuclei. A method is presented to correct for the correlations overcounting inherent to the RPA formalism. One-body density matrix elements in the uncorrelated (i.e., Hartree-Fock) and correlated (i.e., RPA) ground states are then challenged in proton scattering studies based on the Melbourne microscopic optical model to highlight the role played by the RPA correlations. Agreement between the parameter free scattering predictions and measurements is good for incident proton energies ranging from 200 MeV down to approximately 60 MeV and becomes gradually worse in the lower energy range. Those features point unambiguously to the relevance of the g-matrix method to build microscopic optical model potentials at medium energies, and emphasize the need to include nucleon-phonon coupling, that is, a second-order component of the Feshbach type in the potential at lower energies. Illustrations are given for proton scattering observables measured up to 201 MeV for the 16 O, 40 Ca, 48 Ca, and 208 Pb target nuclei
Microscopic theory of light exotic nuclei. Shell Models Embedded in the Continuum
Bennaceur, K.
1999-01-01
The recent advances in experimental nuclear physics make it possible to study nuclear systems far from the beta stability line. The discovery of new phenomena, like halos or neutron skins, requires the development of new theoretical models which enable to study these systems. The first part of this work is devoted to the development and the applications of the Shell Model Embedded in the Continuum (SMEC). This new formalism allows to take into account the correlations between the bound and scattering states of loosely bound nuclei. SMEC is applied here to the study of the spectroscopy of the Mirror nuclei 8 B- 8 Li and 17 F- 17 O. It can also be used to calculate the cross sections of the elastic scattering, the Coulomb breakup processes and the radiative n,p capture processes. The results concerning the reactions of astrophysical interest: 18 O(p, γ) 17 F and 7 Be(p, γ) 8 B, are discussed in details. This last reaction is very important because the disintegration of 8 B is the main source of High energy neutrinos in the sun. The second part of this work is related to the analysis of pairing interaction for weakly bound nuclei. We have developed a new approach, based on the Hartree-Fock-Bogolyubov (HFB) theory, that allows to study the pairing correlations between bound and scattering states, both resonant and not resonant ones. The 'particle-hole' potential is replaced by a model potential for which the solutions are analytically known. This method allows to analyse the effect of pairing on bound and resonant states, independently of their energy position. We have clearly demonstrated that the non-resonant continuum plays a crucial role in the loosely bound nuclei and that solving the HFB equations in the coordinate space is the only method that permits to treat this problem correctly. (author)
de-Shalit, Amos; Massey, H S W
1963-01-01
Nuclear Shell Theory is a comprehensive textbook dealing with modern methods of the nuclear shell model. This book deals with the mathematical theory of a system of Fermions in a central field. It is divided into three parts. Part I discusses the single particle shell model. The second part focuses on the tensor algebra, two-particle systems. The last part covers three or more particle systems. Chapters on wave functions in a central field, tensor fields, and the m-Scheme are also presented. Physicists, graduate students, and teachers of nuclear physics will find the book invaluable.
Dreyfuss, A. C.; Launey, K. D.; Dytrych, Tomáš; Draayer, J. P.; Baker, R. B.; Deibel, C. M.; Bahri, C.
2017-01-01
Roč. 95, č. 4 (2017), č. článku 044312. ISSN 2469-9985 R&D Projects: GA ČR GA16-16772S Institutional support: RVO:61389005 Keywords : C-12 * no-core shell-model * resonance Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 3.820, year: 2016
A study of the evolution of the nuclear structure along the zinc isotopic chain close to the doubly magic nucleus $^{78}$Ni is proposed to probe recent shell-model calculations in this area of the nuclear chart. Excitation energies and connecting B(E2) values will be measured through multiple Coulomb excitation experiment with laser ionized purified beams of $^{74-80}$Zn from HIE ISOLDE. The current proposal request 30 shifts.
Shell model description of 16O(p,γ)17F and 16O(p,p)16O reactions
Bennaceur, K.; Michel, N.; Okolowicz, J.; Ploszajczak, M.; Bennaceur, K.; Nowacki, F.; Okolowicz, J.
2000-01-01
We present shell model calculations of both the structure of 17 F and the reactions 16 O(p,γ) 17 F, 16 O(p,p) 16 O. We use the ZBM interaction which provides a fair description of the properties of 16 O and neighbouring nuclei and, in particular it takes account for the complicated correlations in coexisting low-lying states of 16 O. (authors)
Two-loop O(ααs) corrections to the on-shell fermion propagator in the standard model
Eiras, Dolors; Steinhauser, Matthias
2006-01-01
In this paper we consider mixed two-loop electroweak corrections to the top quark propagator in the Standard Model. In particular, we compute the on-shell renormalization constant for the mass and wave function, which constitute building blocks for many physical processes. The results are expressed in terms of master integrals. For the latter practical approximations are derived. In the case of the mass renormalization constant we find agreement with the results in the literature
Importance-truncated no-core shell model for fermionic many-body systems
Spies, Helena
2017-03-15
The exact solution of quantum mechanical many-body problems is only possible for few particles. Therefore, numerical methods were developed in the fields of quantum physics and quantum chemistry for larger particle numbers. Configuration Interaction (CI) methods or the No-Core Shell Model (NCSM) allow ab initio calculations for light and intermediate-mass nuclei, without resorting to phenomenology. An extension of the NCSM is the Importance-Truncated No-Core Shell Model, which uses an a priori selection of the most important basis states. The importance truncation was first developed and applied in quantum chemistry in the 1970s and latter successfully applied to models of light and intermediate mass nuclei. Other numerical methods for calculations for ultra-cold fermionic many-body systems are the Fixed-Node Diffusion Monte Carlo method (FN-DMC) and the stochastic variational approach with Correlated Gaussian basis functions (CG). There are also such method as the Coupled-Cluster method, Green's Function Monte Carlo (GFMC) method, et cetera, used for calculation of many-body systems. In this thesis, we adopt the IT-NCSM for the calculation of ultra-cold Fermi gases at unitarity. Ultracold gases are dilute, strongly correlated systems, in which the average interparticle distance is much larger than the range of the interaction. Therefore, the detailed radial dependence of the potential is not resolved, and the potential can be replaced by an effective contact interaction. At low energy, s-wave scattering dominates and the interaction can be described by the s-wave scattering length. If the scattering length is small and negative, Cooper-pairs are formed in the Bardeen-Cooper-Schrieffer (BCS) regime. If the scattering length is small and positive, these Cooper-pairs become strongly bound molecules in a Bose-Einstein-Condensate (BEC). In between (for large scattering lengths) is the unitary limit with universal properties. Calculations of the energy spectra
A diagonal address generator for a Josephson memory circuit
Suzuki, H.; Hasuo, S.
1987-01-01
The authors propose that a diagonal D address generator, which is useful for a single flux quantum (SFQ) memory cell in the triple coincidence scheme, can be performed by a full adder circuit. For the purpose of evaluating the D address generator for a 16-kbit memory circuit, a 6-bit full adder circuit, using a current-steering flip-flop circuit, has been designed and fabricated with the lead-alloy process. Operating times for the address latch, carry generator, and sum generator were 150 ps, 250 ps/stage, and 1.4 ns, respectively. From these results, they estimate that the time necessary for the diagonal signal generation is 2.8 ns
Diagonalizing quadratic bosonic operators by non-autonomous flow equations
Bach, Volker
2016-01-01
The authors study a non-autonomous, non-linear evolution equation on the space of operators on a complex Hilbert space. They specify assumptions that ensure the global existence of its solutions and allow them to derive its asymptotics at temporal infinity. They demonstrate that these assumptions are optimal in a suitable sense and more general than those used before. The evolution equation derives from the Brocketâe"Wegner flow that was proposed to diagonalize matrices and operators by a strongly continuous unitary flow. In fact, the solution of the non-linear flow equation leads to a diagonalization of Hamiltonian operators in boson quantum field theory which are quadratic in the field.
A CLT on the SNR of Diagonally Loaded MVDR Filters
Rubio, Francisco; Mestre, Xavier; Hachem, Walid
2012-08-01
This paper studies the fluctuations of the signal-to-noise ratio (SNR) of minimum variance distorsionless response (MVDR) filters implementing diagonal loading in the estimation of the covariance matrix. Previous results in the signal processing literature are generalized and extended by considering both spatially as well as temporarily correlated samples. Specifically, a central limit theorem (CLT) is established for the fluctuations of the SNR of the diagonally loaded MVDR filter, under both supervised and unsupervised training settings in adaptive filtering applications. Our second-order analysis is based on the Nash-Poincar\\'e inequality and the integration by parts formula for Gaussian functionals, as well as classical tools from statistical asymptotic theory. Numerical evaluations validating the accuracy of the CLT confirm the asymptotic Gaussianity of the fluctuations of the SNR of the MVDR filter.
Isovector and flavor-diagonal charges of the nucleon
Gupta, Rajan; Bhattacharya, Tanmoy; Jang, Yong-Chull; Lin, Huey-Wen; Yoon, Boram
2018-03-01
We present an update on the status of the calculations of isovector and flavor-diagonal charges of the nucleon. The calculations of the isovector charges are being done using ten 2+1+1-flavor HISQ ensembles generated by the MILC collaboration covering the range of lattice spacings a ≈ 0.12, 0.09, 0.06 fm and pion masses Mπ ≈ 310, 220, 130 MeV. Excited-states contamination is controlled by using four-state fits to two-point correlators and three-states fits to the three-point correlators. The calculations of the disconnected diagrams needed to estimate flavor-diagonal charges are being done on a subset of six ensembles using the stocastic method. Final results are obtained using a simultaneous fit in M2π, the lattice spacing a and the finite volume parameter MπL keeping only the leading order corrections.
Spectral properties and scaling relations in off diagonally disordered chains
Ure, J.E.; Majlis, N.
1987-07-01
We obtain the localization length L as a function of the energy E and the disorder width W for an off-diagonally disordered chain. This is done performing numerical simulations involving the continued fraction representations of the transfer matrix. The scaling relation L=W s is obtained with values of the exponent s in agreement with calculations of other authors. We also obtain the relation L ∼ |E| v for E → 0, and use it in the Herbert-Spencer-Thouless formula for L to describe the singularity of the density of states near E=0. We show that the slightest diagonal disorder obliterates this singularity. A practical method is presented to calculate the Green function by exploiting its continued fraction expansion. (author). 20 refs, 4 figs
Lee, Jun Chang; Nam, Kyoung Won; Jang, Dong Pyo; Kim, In Young
2015-12-01
Previously suggested diagonal-steering algorithms for binaural hearing support devices have commonly assumed that the direction of the speech signal is known in advance, which is not always the case in many real circumstances. In this study, a new diagonal-steering-based binaural speech localization (BSL) algorithm is proposed, and the performances of the BSL algorithm and the binaural beamforming algorithm, which integrates the BSL and diagonal-steering algorithms, were evaluated using actual speech-in-noise signals in several simulated listening scenarios. Testing sounds were recorded in a KEMAR mannequin setup and two objective indices, improvements in signal-to-noise ratio (SNRi ) and segmental SNR (segSNRi ), were utilized for performance evaluation. Experimental results demonstrated that the accuracy of the BSL was in the 90-100% range when input SNR was -10 to +5 dB range. The average differences between the γ-adjusted and γ-fixed diagonal-steering algorithms (for -15 to +5 dB input SNR) in the talking in the restaurant scenario were 0.203-0.937 dB for SNRi and 0.052-0.437 dB for segSNRi , and in the listening while car driving scenario, the differences were 0.387-0.835 dB for SNRi and 0.259-1.175 dB for segSNRi . In addition, the average difference between the BSL-turned-on and the BSL-turned-off cases for the binaural beamforming algorithm in the listening while car driving scenario was 1.631-4.246 dB for SNRi and 0.574-2.784 dB for segSNRi . In all testing conditions, the γ-adjusted diagonal-steering and BSL algorithm improved the values of the indices more than the conventional algorithms. The binaural beamforming algorithm, which integrates the proposed BSL and diagonal-steering algorithm, is expected to improve the performance of the binaural hearing support devices in noisy situations. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Direct calculation of off-diagonal matrix elements
Killingbeck, J P; Jolicard, G
2011-01-01
Gauss elimination is used in a sequence of calculations which give the squares of the off-diagonal matrix elements of x between quartic oscillator eigenstates, in a modification of the original sum rule approach of Tipping et al to the problem. New and more flexible methods are then devised and tested and are shown to permit the isolation and calculation of individual squared matrix elements of x and x 2 .
Hindmarsh, Mark
2018-02-01
A model for the acoustic production of gravitational waves at a first-order phase transition is presented. The source of gravitational radiation is the sound waves generated by the explosive growth of bubbles of the stable phase. The model assumes that the sound waves are linear and that their power spectrum is determined by the characteristic form of the sound shell around the expanding bubble. The predicted power spectrum has two length scales, the average bubble separation and the sound shell width when the bubbles collide. The peak of the power spectrum is at wave numbers set by the sound shell width. For a higher wave number k , the power spectrum decreases to k-3. At wave numbers below the inverse bubble separation, the power spectrum goes to k5. For bubble wall speeds near the speed of sound where these two length scales are distinguished, there is an intermediate k1 power law. The detailed dependence of the power spectrum on the wall speed and the other parameters of the phase transition raises the possibility of their constraint or measurement at a future space-based gravitational wave observatory such as LISA.
Hindmarsh, Mark
2018-02-16
A model for the acoustic production of gravitational waves at a first-order phase transition is presented. The source of gravitational radiation is the sound waves generated by the explosive growth of bubbles of the stable phase. The model assumes that the sound waves are linear and that their power spectrum is determined by the characteristic form of the sound shell around the expanding bubble. The predicted power spectrum has two length scales, the average bubble separation and the sound shell width when the bubbles collide. The peak of the power spectrum is at wave numbers set by the sound shell width. For a higher wave number k, the power spectrum decreases to k^{-3}. At wave numbers below the inverse bubble separation, the power spectrum goes to k^{5}. For bubble wall speeds near the speed of sound where these two length scales are distinguished, there is an intermediate k^{1} power law. The detailed dependence of the power spectrum on the wall speed and the other parameters of the phase transition raises the possibility of their constraint or measurement at a future space-based gravitational wave observatory such as LISA.
Soniat, Thomas M.; Klinck, John M.; Powell, Eric N.; Cooper, Nathan; Abdelguerfi, Mahdi; Hofmann, Eileen E.; Dahal, Janak; Tu, Shengru; Finigan, John; Eberline, Benjamin S.; La Peyre, Jerome F.; LaPeyre, Megan K.; Qaddoura, Fareed
2012-01-01
A numerical model is presented that defines a sustainability criterion as no net loss of shell, and calculates a sustainable harvest of seed (<75 mm) and sack or market oysters (≥75 mm). Stock assessments of the Primary State Seed Grounds conducted east of the Mississippi from 2009 to 2011 show a general trend toward decreasing abundance of sack and seed oysters. Retrospective simulations provide estimates of annual sustainable harvests. Comparisons of simulated sustainable harvests with actual harvests show a trend toward unsustainable harvests toward the end of the time series. Stock assessments combined with shell-neutral models can be used to estimate sustainable harvest and manage cultch through shell planting when actual harvest exceeds sustainable harvest. For exclusive restoration efforts (no fishing allowed), the model provides a metric for restoration success-namely, shell accretion. Oyster fisheries that remove shell versus reef restorations that promote shell accretion, although divergent in their goals, are convergent in their management; both require vigilant attention to shell budgets.
Brown, B.A.; Wildenthal, B.H.
1983-01-01
The magnetic dipole moments of states in mirror pairs of the sd-shell nuclei and the strengths of the Gamow-Teller beta decays which connect them are compared with predictions based on mixed-configuration shell-model wave functions. From this analysis we extract the average effective values of the single-particle matrix elements of the l, s, and [Y/sup( 2 )xs]/sup( 1 ) components of the M1 and Gamow-Teller operators acting on nucleons in the 0d/sub 5/2/, 1s/sub 1/2/, and 0d/sub 3/2/ orbits. These results are compared with the recent calculations by Towner and Khanna of the corrections to the free-nucleon values of these matrix elements which arise from the effects of isobar currents, mesonic-exchange currents, and mixing with configurations outside the sd shell
Thompson, Timothy F.; Clancey, William J.
This report describes the application of a shell expert system from the medical diagnostic system, Neomycin, to Caster, a diagnostic system for malfunctions in industrial sandcasting. This system was developed to test the hypothesis that starting with a well-developed classification procedure and a relational language for stating the…
2015-02-01
The 11th International Seminar on Nuclear Physics was held in Ischia from May 12 to May 16, 2014. This Seminar was dedicated to Aldo Covello, who has been the promoter of this series of meetings, which started in Sorrento in 1986 and continued with meetings held every two or three years in the Naples area. Aldo's idea was to offer to a group of researchers, actively working in selected fields of Nuclear Physics, the opportunity to confront their points of view in a lively and informal way. The choice for the period of the year, Spring, as well as the sites chosen reflected this intent. The first meeting was of a purely theoretical nature, but it was immediately clear that the scope of these conferences needed to be enlarged calling into play the experimental community. Then, starting from the second meeting, all the following ones have been characterized by fruitful discussion between theoretical and experimental researchers on current achievements and future developments of nuclear structure. This may be read, in fact, as one of the motivating factors for Aldo's election as Fellow of the American Physical Society in 2008 "... for his outstanding contributions to the international nuclear physics community by providing, for over two decades, a venue for theorists and experimentalists to share their latest ideas." The present meeting, organized by Aldo's former students and with the benefit of his suggestions, has maintained this tradition. The title "Shell model and nuclear structure: achievements of the past two decades" recalls that of the 2nd International Spring Seminar "Shell Model and Nuclear Structure: where do we stand?". The main aim of this 11th Seminar was, in fact, to discuss the changes of the past two decades on our view of nuclei in terms of shell structure as well as the perspectives of the shell model, which has been one of the key points in Aldo's research. This point is well accounted by the Opening Speech of Igal Talmi, one of the fathers of the
Modeling of Impact Properties of Auxetic Materials Phase 2
2014-03-01
over the more conventional engineering materials, such as higher indentation resistance, higher fracture toughness and greater resistance to impact...entrant materials were fixed at L=H=1.0 mm from which the rib lengths and thickness for each test case could be calculated using Equations (5) and (6...specimen. In all finite element models, the horizontal (2h) and diagonal (l) ribs shown in Figure 2 were idealized by ten and five shell elements
Study of neutron shell structure of even-even 40-56Ca isotopes by the dispersive optical model
Bespalova, O.V.; Boboshin, I.N.; Varlamov, V.V.; Ermakova, T.A.; Ishkhanov, B.S.; Romanovskij, E.A.; Spasskaya, T.I.; Timokhina, T.P.
2005-01-01
The single-particle energies and occupation probabilities of the bound neutron states in 40,42,44,46,48 Ca isotopes were obtained by the joint evaluation of the stripping and pick-up reaction data. The results were analyzed by the dispersive optical model and a good agreement was achieved. The dispersive optical potential was extrapolated to unstable 50,52,54,56 Ca nuclei. The calculated single-particle energies of the bound neutron states in unstable Ca isotopes were compared with the nuclear shell-model calculations, which predicted new magic number N = 34 for nuclei with Z = 20 [ru
Jackson, V.L.
2011-01-01
The primary purpose of the tank mixing and sampling demonstration program is to mitigate the technical risks associated with the ability of the Hanford tank farm delivery and celtification systems to measure and deliver a uniformly mixed high-level waste (HLW) feed to the Waste Treatment and Immobilization Plant (WTP) Uniform feed to the WTP is a requirement of 24590-WTP-ICD-MG-01-019, ICD-19 - Interface Control Document for Waste Feed, although the exact definition of uniform is evolving in this context. Computational Fluid Dynamics (CFD) modeling has been used to assist in evaluating scaleup issues, study operational parameters, and predict mixing performance at full-scale.
LANL* V1.0: a radiation belt drift shell model suitable for real-time and reanalysis applications
Koller, Josep [Los Alamos National Laboratory; Reeves, Geoffrey D [Los Alamos National Laboratory; Friedel, Reiner H W [Los Alamos National Laboratory
2008-01-01
Space weather modeling, forecasts, and predictions, especially for the radiation belts in the inner magnetosphere, require detailed information about the Earth's magnetic field. Results depend on the magnetic field model and the L* (pron. L-star) values which are used to describe particle drift shells. Space wather models require integrating particle motions along trajectories that encircle the Earth. Numerical integration typically takes on the order of 10{sup 5} calls to a magnetic field model which makes the L* calculations very slow, in particular when using a dynamic and more accurate magnetic field model. Researchers currently tend to pick simplistic models over more accurate ones but also risking large inaccuracies and even wrong conclusions. For example, magnetic field models affect the calculation of electron phase space density by applying adiabatic invariants including the drift shell value L*. We present here a new method using a surrogate model based on a neural network technique to replace the time consuming L* calculations made with modern magnetic field models. The advantage of surrogate models (or meta-models) is that they can compute the same output in a fraction of the time while adding only a marginal error. Our drift shell model LANL* (Los Alamos National Lab L-star) is based on L* calculation using the TSK03 model. The surrogate model has currently been tested and validated only for geosynchronous regions but the method is generally applicable to any satellite orbit. Computations with the new model are several million times faster compared to the standard integration method while adding less than 1% error. Currently, real-time applications for forecasting and even nowcasting inner magnetospheric space weather is limited partly due to the long computing time of accurate L* values. Without them, real-time applications are limited in accuracy. Reanalysis application of past conditions in the inner magnetosphere are used to understand
LANL* V1.0: a radiation belt drift shell model suitable for real-time and reanalysis applications
Koller, Josep; Reeves, Geoffrey D.; Friedel, Reiner H.W.
2008-01-01
Space weather modeling, forecasts, and predictions, especially for the radiation belts in the inner magnetosphere, require detailed information about the Earth's magnetic field. Results depend on the magnetic field model and the L* (pron. L-star) values which are used to describe particle drift shells. Space wather models require integrating particle motions along trajectories that encircle the Earth. Numerical integration typically takes on the order of 10 5 calls to a magnetic field model which makes the L* calculations very slow, in particular when using a dynamic and more accurate magnetic field model. Researchers currently tend to pick simplistic models over more accurate ones but also risking large inaccuracies and even wrong conclusions. For example, magnetic field models affect the calculation of electron phase space density by applying adiabatic invariants including the drift shell value L*. We present here a new method using a surrogate model based on a neural network technique to replace the time consuming L* calculations made with modern magnetic field models. The advantage of surrogate models (or meta-models) is that they can compute the same output in a fraction of the time while adding only a marginal error. Our drift shell model LANL* (Los Alamos National Lab L-star) is based on L* calculation using the TSK03 model. The surrogate model has currently been tested and validated only for geosynchronous regions but the method is generally applicable to any satellite orbit. Computations with the new model are several million times faster compared to the standard integration method while adding less than 1% error. Currently, real-time applications for forecasting and even nowcasting inner magnetospheric space weather is limited partly due to the long computing time of accurate L* values. Without them, real-time applications are limited in accuracy. Reanalysis application of past conditions in the inner magnetosphere are used to understand physical
Experimental and numerical modelling of ductile crack propagation in large-scale shell structures
Simonsen, Bo Cerup; Törnquist, R.
2004-01-01
plastic and controlled conditions. The test specimen can be deformed either in combined in-plane bending and extension or in pure extension. Experimental results are described for 5 and 10 mm thick aluminium and steel plates. By performing an inverse finite-element analysis of the experimental results......This paper presents a combined experimental-numerical procedure for development and calibration of macroscopic crack propagation criteria in large-scale shell structures. A novel experimental set-up is described in which a mode-I crack can be driven 400 mm through a 20(+) mm thick plate under fully...... for steel and aluminium plates, mainly as curves showing the critical element deformation versus the shell element size. These derived crack propagation criteria are then validated against a separate set of experiments considering centre crack specimens (CCS) which have a different crack-tip constraint...
Compressible convection in a rotating spherical shell. II. A linear anelastic model
Glatzmaier, G.A.; Gilman, P.A.
1981-01-01
We study the onset of convection for a compressible fluid in a rotating spherical shell via linear anelastic fluid equations for a depth of 40% of the radius, constant kinematic viscosity and thermometric diffusivity, Taylor numbers up to 10 5 , and density stratifications up to seven e-folds across the zone. The perturbations are expanded in spherical harmonics, and the radially dependent equations are solved with a Newton-Raphson relaxation method
Geyer, H.B.
1986-01-01
The qualitative ideas put forward by Geyer and Lee are given quantitative content by constructing a similarity transformation which reexpresses the Dyson boson images of the single-j shell fermion operators in terms of seniority bosons. It is shown that the results of Otsuka, Arima, and Iachello, or generalizations thereof which include g bosons or even bosons with J>4, can be obtained in an economic and transparent way without resorting to any comparison of matrix elements
Kai Li
2017-01-01
Full Text Available The piezoelectric micro-jet, which can achieve the drop-on-demand requirement, is based on ink-jet technology and small droplets can be ejected out by precise control. The droplets are driven out of the nozzle by the acoustic pressure waves which are generated by the piezoelectric vibrator. The propagation processes of the acoustic pressure waves are affected by the acoustic properties of the fluid and the shell material of the micro-jet, as well as the excitations and the structure sizes. The influences of the fluid density and acoustic velocity in the fluid on the nozzle pressure and support reaction force of the vibrator are analyzed in this paper. The effects of the shell material on the ejection performance are studied as well. In order to improve the ejection performance of the micro-jet, for ejecting a given fluid, the recommended methods of selecting the shell material and adjusting excitations are provided based on the results, and the influences of the factors on working frequencies are obtained as well.
Tunneling splitting in double-proton transfer: direct diagonalization results for porphycene.
Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio
2014-11-07
Zero-point and excited level splittings due to double-proton tunneling are calculated for porphycene and the results are compared with experiment. The calculation makes use of a multidimensional imaginary-mode Hamiltonian, diagonalized directly by an effective reduction of its dimensionality. Porphycene has a complex potential energy surface with nine stationary configurations that allow a variety of tunneling paths, many of which include classically accessible regions. A symmetry-based approach is used to show that the zero-point level, although located above the cis minimum, corresponds to concerted tunneling along a direct trans - trans path; a corresponding cis - cis path is predicted at higher energy. This supports the conclusion of a previous paper [Z. Smedarchina, W. Siebrand, and A. Fernández-Ramos, J. Chem. Phys. 127, 174513 (2007)] based on the instanton approach to a model Hamiltonian of correlated double-proton transfer. A multidimensional tunneling Hamiltonian is then generated, based on a double-minimum potential along the coordinate of concerted proton motion, which is newly evaluated at the RI-CC2/cc-pVTZ level of theory. To make it suitable for diagonalization, its dimensionality is reduced by treating fast weakly coupled modes in the adiabatic approximation. This results in a coordinate-dependent mass of tunneling, which is included in a unique Hermitian form into the kinetic energy operator. The reduced Hamiltonian contains three symmetric and one antisymmetric mode coupled to the tunneling mode and is diagonalized by a modified Jacobi-Davidson algorithm implemented in the Jadamilu software for sparse matrices. The results are in satisfactory agreement with the observed splitting of the zero-point level and several vibrational fundamentals after a partial reassignment, imposed by recently derived selection rules. They also agree well with instanton calculations based on the same Hamiltonian.
Hill, J.G.; Simpson, B.C.
1994-08-01
The Sort on Radioactive Waste Type (SORWT) model presents a method to categorize Hanford Site single-shell tanks (SSTs) into groups of tanks expected to exhibit similar chemical and physical characteristics based on their major waste types and processing histories. This model has identified 29 different waste-type groups encompassing 135 of the 149 SSTs and 93% of the total waste volume in SSTs. The remaining 14 SSTs and associated wastes could not be grouped according to the established criteria and were placed in an ungrouped category. This letter report will detail the assumptions and methodologies used to develop the SORWT model and present the grouping results. Included with this report is a brief description and approximate compositions of the single-shell tank waste types. In the near future, the validity of the predicted groups will be statistically tested using analysis of variance of characterization data obtained from recent (post-1989) core sampling and analysis activities. In addition, the SORWT model will be used to project the nominal waste characteristics of entire waste type groups that have some recent characterization data available. These subsequent activities will be documented along with these initial results in a comprehensive, formal PNL report cleared for public release by September 1994
Kuhnert, A.; Alber, D.; Grawe, H.; Kluge, H.; Maier, K.H.; Reviol, W.; Sun, X.; Beck, E.M.; Byrne, A.P.; Huebel, H.; Bacelar, J.C.; Deleplanque, M.A.; Diamond, R.M.; Stephens, F.S.
1992-01-01
High-spin states in 152 Er have been populated through the 116 Sn( 40 Ar,4n) 152 Er reaction. Prompt and delayed γ-γ-γ-t and γ-e-t coincidences have been measured. Levels and transitions are assigned up to an excitation energy of 15 MeV and spin and parities up to 28 + at 9.7 MeV. A new isomer [t 1/2 =11(1) ns] has been observed at 13.4 MeV. The results are discussed in comparison with neighboring nuclei and with shell-model calculations
Jhang, Hogun
2008-01-01
A study is conducted on the feedback stabilization of resistive wall modes (RWMs) in a tokamak plasma using a toroidal shell model. An analytically tractable form of the RWM dispersion relation is derived in the presence of a set of discrete feedback coil currents. A parametric study is carried out to optimize the feedback system configuration. It is shown that the total toroidal angle of a resistive wall spanned by the feedback coils and the poloidal angular extent of a feedback coil are crucial parameters to determine the efficacy of the feedback system
Modified Dynamical Supergravity Breaking and Off-Diagonal Super-Higgs Effects
Gheorghiu, Tamara; Vacaru, Sergiu
2015-01-01
We argue that generic off-diagonal vacuum and nonvacuum solutions for Einstein manifolds mimic physical effects in modified gravity theories (MGTs) and encode certain models of $f(R,T,...)$, Ho\\vrava type with dynamical Lorentz symmetry breaking, induced effective mass for graviton etc. Our main goal is to investigate the dynamical breaking of local supersymmetry determined by off--diagonal solutions in MGTs encoded as effective Einstein spaces. This includes the Deser-Zumino super--Higgs effect, for instance, for an one--loop potential in a (simple but representative) model of $\\mathcal{N}=1, D=4$ supergravity. We develop and apply a new geometric techniques which allows us to decouple the gravitational field equations and integrate them in very general forms with metrics and vierbein fields depending on all spacetime coordinates via various generating and integration functions and parameters. We study how solutions in MGTs may be related to dynamical generation of a gravitino mass and supergravity breaking.
On the performance of diagonal lattice space-time codes
Abediseid, Walid
2013-11-01
There has been tremendous work done on designing space-time codes for the quasi-static multiple-input multiple output (MIMO) channel. All the coding design up-to-date focuses on either high-performance, high rates, low complexity encoding and decoding, or targeting a combination of these criteria [1]-[9]. In this paper, we analyze in details the performance limits of diagonal lattice space-time codes under lattice decoding. We present both lower and upper bounds on the average decoding error probability. We first derive a new closed-form expression for the lower bound using the so-called sphere lower bound. This bound presents the ultimate performance limit a diagonal lattice space-time code can achieve at any signal-to-noise ratio (SNR). The upper bound is then derived using the union-bound which demonstrates how the average error probability can be minimized by maximizing the minimum product distance of the code. Combining both the lower and the upper bounds on the average error probability yields a simple upper bound on the the minimum product distance that any (complex) lattice code can achieve. At high-SNR regime, we discuss the outage performance of such codes and provide the achievable diversity-multiplexing tradeoff under lattice decoding. © 2013 IEEE.
Design of cryogenic tanks for space vehicles shell structures analytical modeling
Copper, Charles; Mccarthy, K.; Pilkey, W. D.; Haviland, J. K.
1991-01-01
The initial objective was to study the use of superplastically formed corrugated hat section stringers and frames in place of integrally machined stringers over separate frames for the tanks of large launch vehicles subjected to high buckling loads. The ALS was used as an example. The objective of the follow-on project was to study methods of designing shell structures subjected to severe combinations of structural loads and thermal gradients, with emphasis on new combinations of structural arrangements and materials. Typical applications would be to fuselage sections of high speed civil transports and to cryogenic tanks on the National Aerospace Plane.
Jacobs, A. M.; Zingale, M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Nonaka, A.; Almgren, A. S.; Bell, J. B. [Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
2016-08-10
The dynamics of helium shell convection driven by nuclear burning establish the conditions for runaway in the sub-Chandrasekhar-mass, double-detonation model for SNe Ia, as well as for a variety of other explosive phenomena. We explore these convection dynamics for a range of white dwarf core and helium shell masses in three dimensions using the low Mach number hydrodynamics code MAESTRO. We present calculations of the bulk properties of this evolution, including time-series evolution of global diagnostics, lateral averages of the 3D state, and the global 3D state. We find a variety of outcomes, including quasi-equilibrium, localized runaway, and convective runaway. Our results suggest that the double-detonation progenitor model is promising and that 3D dynamic convection plays a key role.
Noor, A. K.; Andersen, C. M.; Tanner, J. A.
1984-01-01
An effective computational strategy is presented for the large-rotation, nonlinear axisymmetric analysis of shells of revolution. The three key elements of the computational strategy are: (1) use of mixed finite-element models with discontinuous stress resultants at the element interfaces; (2) substantial reduction in the total number of degrees of freedom through the use of a multiple-parameter reduction technique; and (3) reduction in the size of the analysis model through the decomposition of asymmetric loads into symmetric and antisymmetric components coupled with the use of the multiple-parameter reduction technique. The potential of the proposed computational strategy is discussed. Numerical results are presented to demonstrate the high accuracy of the mixed models developed and to show the potential of using the proposed computational strategy for the analysis of tires.
Symmetry energies for A =24 and 48 and the USD and KB3 shell model Hamiltonians
Kingan, A.; Neergârd, K.; Zamick, L.
2017-12-01
Calculations in the sd and pf shells reported some time ago by Satuła et al. [Phys. Lett. B 407, 103 (1997), 10.1016/S0370-2693(97)00711-9] are redone for an extended analysis of the results. As in the original work, we do calculations for one mass number in each shell and consider in each case the sequence of lowest energies for isospins 0, 2, and 4, briefly the symmetry spectrum. Following further the original work, we study how this spectrum changes when parts of the two-nucleon interaction are turned off. The variation of its width is explored in detail. A differential combination ɛW of the three energies was taken in the original work as a measure of the so-called Wigner term in semiempirical mass formulas, and it was found to decrease drastically when the two-nucleon interaction in the channel of zero isospin is turned off. Our analysis shows that the width of the symmetry spectrum experiences an equally drastic decrease, which can be explained qualitatively in terms of schematic approximations. We therefore suggest that the decrease of ɛW be seen mainly as a side effect of a narrowing of the symmetry spectrum rather than an independent manifestation of the two-nucleon interaction in the channel of zero isospin.
Roman, E.; Wiecko, C.
1985-08-01
We study and characterize the eigenstates near the centre of the band of a 1-d tight binding model with off-diagonal disorder Wsub(T). We find a new exponent for the localization length lambda on an energy-dependent range of disorder Wsub(T). We correlate this feature with a change of structure of the wave-function displayed by the behaviour of its fractal dimensionality. (author)
Kinematic approach to off-diagonal geometric phases of nondegenerate and degenerate mixed states
Tong, D.M.; Oh, C.H.; Sjoeqvist, Erik; Filipp, Stefan; Kwek, L.C.
2005-01-01
Off-diagonal geometric phases have been developed in order to provide information of the geometry of paths that connect noninterfering quantal states. We propose a kinematic approach to off-diagonal geometric phases for pure and mixed states. We further extend the mixed-state concept proposed in [Phys. Rev. Lett. 90, 050403 (2003)] to degenerate density operators. The first- and second-order off-diagonal geometric phases are analyzed for unitarily evolving pairs of pseudopure states
Das, Subhojit; Paul, Anumita; Chattopadhyay, Arun
2013-09-01
We report on the generation of core-shell nanoparticles (NPs) having an organic nanocrystal (NC) core coated with an inorganic metallic shell, being dispersed in aqueous medium. First, NCs of p-hydroxyacetanilide (pHA)--known also as paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH paracetamol--were generated in an aqueous medium. Transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) evidenced the formation of pHA NCs and of their crystalline nature. The NCs were then coated with Au to form pHA@Au core-shell NPs, where the thickness of the Au shell was on the order of nanometers. The formation of Au nanoshell--surrounding pHA NC--was confirmed from its surface plasmon resonance (SPR) band in the UV/Vis spectrum and by TEM measurements. Further, on treatment of the core-shell particles with a solution comprising NaCl and HCl (pH < 3), the Au shell could be dissolved, subsequently releasing pHA molecules. The dissolution of Au shell was marked by a gradual diminishing of its SPR band, while the release of pHA molecules in the solution was confirmed from TEM and FTIR studies. The findings suggest that the core-shell NP could be hypothesized to be a model for encapsulating drug molecules, in their crystalline forms, for slow as well as targeted release. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr03566b
Serra, Maria; Husar, Attila; Feroldi, Diego; Riera, Jordi [Institut de Robotica i Informatica Industrial, Universitat Politecnica de Catalunya, Consejo Superior de Investigaciones Cientificas, C. Llorens i Artigas 4, 08028 Barcelona (Spain)
2006-08-25
This work is focused on the selection of operating conditions in polymer electrolyte membrane fuel cells. It analyses efficiency and controllability aspects, which change from one operating point to another. Specifically, several operating points that deliver the same amount of net power are compared, and the comparison is done at different net power levels. The study is based on a complex non-linear model, which has been linearised at the selected operating points. Different linear analysis tools are applied to the linear models and results show important controllability differences between operating points. The performance of diagonal control structures with PI controllers at different operating points is also studied. A method for the tuning of the controllers is proposed and applied. The behaviour of the controlled system is simulated with the non-linear model. Conclusions indicate a possible trade-off between controllability and optimisation of hydrogen consumption. (author)
Trevizol, Fabiola; Benvegnú, Dalila M; Barcelos, Raquel C S; Pase, Camila S; Segat, Hecson J; Dias, Verônica Tironi; Dolci, Geisa S; Boufleur, Nardeli; Reckziegel, Patrícia; Bürger, Marilise E
2011-08-01
Acute reserpine and subchronic haloperidol are animal models of extrapyramidal disorders often used to study parkinsonism, akinesia and tardive dyskinesia. In humans, these usually irreversible and disabling extrapyramidal disorders are developed by typical antipsychotic treatment, whose pathophysiology has been related to oxidative damages development. So far, there is no treatment to prevent these problems of the psychiatric clinic, and therefore further studies are needed. Here we used the animal models of extrapyramidal disorders cited above, which were performed in two distinct experiments: orofacial dyskinesia (OD)/catalepsy induced by acute reserpine and subchronic haloperidol after (experiment 1) and before (experiment 2) oral treatment with pecan shell aqueous extract (AE), a natural and promissory antioxidant. When administered previously (exp.1), the AE prevented OD and catalepsy induced by both reserpine and haloperidol. When reserpine and haloperidol were administered before the extract (exp.2), the animals developed OD and catalepsy all the same. However, the orofacial parameter (but not catalepsy) in both animal models was reversed after 7 and 14 days of AE treatment. These results indicate that, acute reserpine and subchronic haloperidol administrations induced similar motor disorders, although through different mechanisms, and therefore are important animal models to study the physiopathology of extrapyramidal disorders. Comparatively, the pecan shell AE was able to both prevent and reverse OD but only to prevent catalepsy. These results reinforce the role of oxidative stress and validate the two animal models used here. Our findings also favor the idea of prevention of extrapyramidal disorders, rather than their reversal. Copyright © 2011 Elsevier B.V. All rights reserved.
Self-consistent cluster theory for systems with off-diagonal disorder
Kaplan, T.; Leath, P.L.; Gray, L.J.; Diehl, H.W.
1980-01-01
A self-consistent cluster theory for elementary excitations in systems with diagonal, off-diagonal, and environmental disorder is presented. The theory is developed in augmented space where the configurational average over the disorder is replaced by a ground-state matrix element in a translationally invariant system. The analyticity of the resulting approximate Green's function is proved. Numerical results for the self-consistent single-site and pair approximations are presented for the vibrational and electronic properties of disordered linear chains with diagonal, off-diagonal, and environmental disorder
Losano, L.; Dias, H.; Krmpotic, F.; Wildenthal, B.H.
1988-01-01
A detailed study of the results of correcting BCS approximation for the effects of particle-number projection and blocking has been carried out. A low-seniority shell-model approximation was used as the frame of reference for investigating the mixing of one- and three-quasiparticle states in odd-mass Ni isotopes and in odd-mass N = 82 isotones. We discuss the results obtained for the energy spectra and electromagnetic decay properties. Effects of seniority-five configurations on the low-lying states have also been studied through the comparison of the low-seniority shell-model results with those which arose from the corresponding full shell-model calculations
Ab initio translationally invariant nonlocal one-body densities from no-core shell-model theory
Burrows, M.; Elster, Ch.; Popa, G.; Launey, K. D.; Nogga, A.; Maris, P.
2018-02-01
Background: It is well known that effective nuclear interactions are in general nonlocal. Thus if nuclear densities obtained from ab initio no-core shell-model (NCSM) calculations are to be used in reaction calculations, translationally invariant nonlocal densities must be available. Purpose: Though it is standard to extract translationally invariant one-body local densities from NCSM calculations to calculate local nuclear observables like radii and transition amplitudes, the corresponding nonlocal one-body densities have not been considered so far. A major reason for this is that the procedure for removing the center-of-mass component from NCSM wave functions up to now has only been developed for local densities. Results: A formulation for removing center-of-mass contributions from nonlocal one-body densities obtained from NCSM and symmetry-adapted NCSM (SA-NCSM) calculations is derived, and applied to the ground state densities of 4He, 6Li, 12C, and 16O. The nonlocality is studied as a function of angular momentum components in momentum as well as coordinate space. Conclusions: We find that the nonlocality for the ground state densities of the nuclei under consideration increases as a function of the angular momentum. The relative magnitude of those contributions decreases with increasing angular momentum. In general, the nonlocal structure of the one-body density matrices we studied is given by the shell structure of the nucleus, and cannot be described with simple functional forms.
SPH modeling of fluid-solid interaction for dynamic failure analysis of fluid-filled thin shells
Caleyron, F.; Combescure, A.; Faucher, V.; Potapov, S.
2013-05-01
This work concerns the prediction of failure of a fluid-filled tank under impact loading, including the resulting fluid leakage. A water-filled steel cylinder associated with a piston is impacted by a mass falling at a prescribed velocity. The cylinder is closed at its base by an aluminum plate whose characteristics are allowed to vary. The impact on the piston creates a pressure wave in the fluid which is responsible for the deformation of the plate and, possibly, the propagation of cracks. The structural part of the problem is modeled using Mindlin-Reissner finite elements (FE) and Smoothed Particle Hydrodynamics (SPH) shells. The modeling of the fluid is also based on an SPH formulation. The problem involves significant fluid-structure interactions (FSI) which are handled through a master-slave-based method and the pinballs method. Numerical results are compared to experimental data.
Nonlinear nonlocal vibration of embedded DWCNT conveying fluid using shell model
Ghorbanpour Arani, A., E-mail: aghorban@kashanu.ac.ir [Faculty of Mechanical Engineering, University of Kashan, Kashan (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan (Iran, Islamic Republic of); Zarei, M.Sh.; Amir, S.; Khoddami Maraghi, Z. [Faculty of Mechanical Engineering, University of Kashan, Kashan (Iran, Islamic Republic of)
2013-02-01
In this work nonlinear vibration of double-walled carbon nanotube (DWCNT) embedded in an elastic medium and subjected to an axial fluid flow (incompressible and non-viscose) is investigated. The elastic medium is simulated using Pasternak foundation in which adjacent layer interactions are assumed to have been coupled by van der Waals (VdW) force. The higher-order equation of motion is derived using Hamilton's principle and nonlocal-nonlinear shell theory. Galerkin and averaging methods are adopted to solve the higher-order governing equations. Elastic medium, small scale parameter, velocity and fluid density are taken into account to calculate the effects of axial and circumferential wave numbers in this study. Results reveal that increasing circumferential wave number, leads to enhanced nonlinearity. Critical flow velocities of DWCNT are inversely related to the non-local parameter (e{sub 0}a), so that increase in the later lead to reduced critical flow velocities.
Development of an Energy Biorefinery Model for Chestnut (Castanea sativa Mill. Shells
Alessandra Morana
2017-09-01
Full Text Available Chestnut shells (CS are an agronomic waste generated from the peeling process of the chestnut fruit, which contain 2.7–5.2% (w/w phenolic compounds and approximately 36% (w/w polysaccharides. In contrast with current shell waste burning practices, this study proposes a CS biorefinery that integrates biomass pretreatment, recovery of bioactive molecules, and bioconversion of the lignocellulosic hydrolyzate, while optimizing materials reuse. The CS delignification and saccharification produced a crude hydrolyzate with 12.9 g/L of glucose and xylose, and 682 mg/L of gallic acid equivalents. The detoxification of the crude CS hydrolyzate with 5% (w/v activated charcoal (AC and repeated adsorption, desorption and AC reuse enabled 70.3% (w/w of phenolic compounds recovery, whilst simultaneously retaining the soluble sugars in the detoxified hydrolyzate. The phenols radical scavenging activity (RSA of the first AC eluate reached 51.8 ± 1.6%, which is significantly higher than that of the crude CS hydrolyzate (21.0 ± 1.1%. The fermentation of the detoxified hydrolyzate by C. butyricum produced 10.7 ± 0.2 mM butyrate and 63.9 mL H2/g of CS. Based on the obtained results, the CS biorefinery integrating two energy products (H2 and calorific power from spent CS, two bioproducts (phenolic compounds and butyrate and one material reuse (AC reuse constitutes a valuable upgrading approach for this yet unexploited waste biomass.
Hu Yong; Liu Yan; Du An
2011-01-01
Zero-field-cooled (ZFC) and field-cooled (FC) hysteresis loops of egg- and ellipsoid-shaped nanoparticles with inverted ferromagnetic (FM)-antiferromagnetic (AFM) core-shell morphologies are simulated using a modified Monte Carlo method, which takes into account both the thermal fluctuations and energy barriers during the rotation of spin. Pronounced exchange bias (EB) fields and reduced coercivities are obtained in the FC hysteresis loops. The analysis of the microscopic spin configurations allows us to conclude that the magnetization reversal occurs by means of the nucleation process during both the ZFC and FC hysteresis branches. The nucleation takes place in the form of 'sparks' resulting from the energy competition and the morphology of the nanoparticle. The appearance of EB in the FC hysteresis loops is only dependent on that the movements of 'sparks' driven by magnetic field at both branches of hysteresis loops are not along the same axis, which is independent of the strength of AFM anisotropy. The tilt of 'spark' movement with respect to the symmetric axis implies the existence of additional unidirectional anisotropy at the AFM/FM interfaces as a consequence of the surplus magnetization in the AFM core, which is the commonly accepted origin of EB. Our simulations allow us to clarify the microscopic mechanisms of the observed EB behavior, not accessible in experiments. - Highlights: → A modified Monte Carlo method considers thermal fluctuations and energy barriers. → Egg and ellipsoid nanoparticles with inverted core-shell morphology are studied. → Pronounced exchange bias fields and reduced coercivities may be detected. → 'Sparks' representing nucleation sites due to energy competition are observed. → 'Sparks' can reflect or check directly and vividly the origin of exchange bias.
Diagonal ordering operation technique applied to Morse oscillator
Popov, Dušan, E-mail: dusan_popov@yahoo.co.uk [Politehnica University Timisoara, Department of Physical Foundations of Engineering, Bd. V. Parvan No. 2, 300223 Timisoara (Romania); Dong, Shi-Hai [CIDETEC, Instituto Politecnico Nacional, Unidad Profesional Adolfo Lopez Mateos, Mexico D.F. 07700 (Mexico); Popov, Miodrag [Politehnica University Timisoara, Department of Steel Structures and Building Mechanics, Traian Lalescu Street, No. 2/A, 300223 Timisoara (Romania)
2015-11-15
We generalize the technique called as the integration within a normally ordered product (IWOP) of operators referring to the creation and annihilation operators of the harmonic oscillator coherent states to a new operatorial approach, i.e. the diagonal ordering operation technique (DOOT) about the calculations connected with the normally ordered product of generalized creation and annihilation operators that generate the generalized hypergeometric coherent states. We apply this technique to the coherent states of the Morse oscillator including the mixed (thermal) state case and get the well-known results achieved by other methods in the corresponding coherent state representation. Also, in the last section we construct the coherent states for the continuous dynamics of the Morse oscillator by using two new methods: the discrete–continuous limit, respectively by solving a finite difference equation. Finally, we construct the coherent states corresponding to the whole Morse spectrum (discrete plus continuous) and demonstrate their properties according the Klauder’s prescriptions.
Performance Study of Diagonally Segmented Piezoelectric Vibration Energy Harvester
Kim, Jae Eun [Catholic Univ. of Daegu, Daegu (Korea, Republic of)
2013-08-15
This study proposes a piezoelectric vibration energy harvester composed of two diagonally segmented energy harvesting units. An auxiliary structural unit is attached to the tip of a host structural unit cantilevered to a vibrating base, where the two components have beam axes in opposite directions from each other and matched short-circuit resonant frequencies. Contrary to the usual observations in two resonant frequency-matched structures, the proposed structure shows little eigenfrequency separation and yields a mode sequence change between the first two modes. These lead to maximum power generation around a specific frequency. By using commercial finite element software, it is shown that the magnitude of the output power from the proposed vibration energy harvester can be substantially improved in comparison with those from conventional cantilevered energy harvesters with the same footprint area and magnitude of a tip mass.
The Diagonal Compression Field Method using Circular Fans
Hansen, Thomas
2005-01-01
This paper presents a new design method, which is a modification of the diagonal compression field method, the modification consisting of the introduction of circular fan stress fields. The traditional method does not allow changes of the concrete compression direction throughout a given beam...... if equilibrium is strictly required. This is conservative, since it is not possible fully to utilize the concrete strength in regions with low shear stresses. The larger inclination (the smaller -value) of the uniaxial concrete stress the more transverse shear reinforcement is needed; hence it would be optimal...... if the -value for a given beam could be set to a low value in regions with high shear stresses and thereafter increased in regions with low shear stresses. Thus the shear reinforcement would be reduced and the concrete strength would be utilized in a better way. In the paper it is shown how circular fan stress...
Modified conjugate gradient method for diagonalizing large matrices.
Jie, Quanlin; Liu, Dunhuan
2003-11-01
We present an iterative method to diagonalize large matrices. The basic idea is the same as the conjugate gradient (CG) method, i.e, minimizing the Rayleigh quotient via its gradient and avoiding reintroducing errors to the directions of previous gradients. Each iteration step is to find lowest eigenvector of the matrix in a subspace spanned by the current trial vector and the corresponding gradient of the Rayleigh quotient, as well as some previous trial vectors. The gradient, together with the previous trial vectors, play a similar role as the conjugate gradient of the original CG algorithm. Our numeric tests indicate that this method converges significantly faster than the original CG method. And the computational cost of one iteration step is about the same as the original CG method. It is suitable for first principle calculations.
Analytic proof of partial conservation of seniority in j=9/2 shells
Chong Qi; Xu, Z.X.; Liotta, R.J.
2012-01-01
A partial conservation of the seniority quantum number in j=9/2 shells has been found recently in a numerical application. In this paper an analytic proof for this problem is derived as an extension of the work [L. Zamick, P. Van Isacker, Phys. Rev. C 78 (2008) 044327]. We analyze the properties of the non-diagonal interaction matrix elements with the help of the one-particle and two-particle coefficients of fractional parentage (cfp's). It is found that all non-diagonal (and the relevant diagonal) matrix elements can be re-expressed in simple ways and are proportional to certain one-particle cfp's. This remarkable occurrence of partial dynamic symmetry is the consequence of the peculiar property of the j=9/2 shell, where all v=3 and 5 states are uniquely defined.
Validation of a FBC model for co-firing of hazelnut shell with lignite against experimental data
Kulah, Gorkem [Middle East Technical University, Department of Chemical Engineering, 06531 Ankara (Turkey)
2010-07-15
Performance of a comprehensive system model extended for modelling of co-firing of lignite and biomass was assessed by applying it to METU 0.3 MW{sub t} Atmospheric Bubbling Fluidized Bed Combustor co-firing lignite with hazelnut shell and validating its predictions against on-line temperature and concentration measurements of O{sub 2}, CO{sub 2}, CO, SO{sub 2} and NO along the same test rig fired with lignite only, lignite with limestone addition and lignite with biomass and limestone addition. The system model accounts for hydrodynamics; volatiles release and combustion, char combustion, particle size distribution for lignite and biomass; entrainment; elutriation; sulfur retention and NO formation and reduction, and is based on conservation equations for energy and chemical species. Special attention was paid to different devolatilization characteristics of lignite and biomass. A volatiles release model based on a particle movement model and a devolatilization kinetic model were incorporated into the system model separately for both fuels. Kinetic parameters for devolatilization were determined via thermogravimetric analysis. Predicted and measured temperatures and concentrations of gaseous species along the combustor were found to be in good agreement. Introduction of biomass to lignite was found to decrease SO{sub 2} emissions but did not affect NO emissions significantly. The system model proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in a bubbling fluidized bed combustor burning lignite with biomass. (author)
Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.
2017-04-01
Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.
Thernisien, A.
2011-06-01
The graduated cylindrical shell (GCS) model developed by Thernisien et al. has been used with the goal of studying the three-dimensional morphology, position, and kinematics of coronal mass ejections observed by coronagraphs. These studies focused more on the results rather than the details of the model itself. As more researchers begin to use the model, it becomes necessary to provide a deeper discussion on how it is derived, which is the purpose of this paper. The model is built using the following features and constraints: (1) the legs are conical, (2) the front is pseudo-circular, (3) the cross section is circular, and (4) it expands in a self-similar way. We derive the equation of the model from these constraints. We also show that the ice-cream cone model is a limit of the GCS when the two legs overlap completely. Finally, we provide formulae for the calculation of various geometrical dimensions, such as angular width and aspect ratio, as well as the pseudo-code that is used for its computer implementation.
Thernisien, A.
2011-01-01
The graduated cylindrical shell (GCS) model developed by Thernisien et al. has been used with the goal of studying the three-dimensional morphology, position, and kinematics of coronal mass ejections observed by coronagraphs. These studies focused more on the results rather than the details of the model itself. As more researchers begin to use the model, it becomes necessary to provide a deeper discussion on how it is derived, which is the purpose of this paper. The model is built using the following features and constraints: (1) the legs are conical, (2) the front is pseudo-circular, (3) the cross section is circular, and (4) it expands in a self-similar way. We derive the equation of the model from these constraints. We also show that the ice-cream cone model is a limit of the GCS when the two legs overlap completely. Finally, we provide formulae for the calculation of various geometrical dimensions, such as angular width and aspect ratio, as well as the pseudo-code that is used for its computer implementation.
Investigation of the rotational nuclei 167168Hf and 170171W and the shell-model nucleus 26Mg
Arciszewski, H.F.R.
1984-01-01
Two gamma-gamma coincidence experiments on neighbouring nuclei that exhibit the backbending phenomenon are described. The first experiment performed with the cyclotron of the KVI at Groningen is an investigation of 167 Hf and 168 Hf, whereas in the second experiment, performed at the cyclotron facility of Louvain University, high spin states are studied and compared with predictions of the cranked shell model. A new method for the correction of the large background of Compton-scattered events is described. Apart from this, an investigation of the single particle (d,p) transfer reaction at 26 Mg has been performed with the van de Graaff tandem accelerator at 14 MeV. Specroscopic factors are presented for many levels up to an excitation energy of 8 MeV. Several new spin assignments could be made. (Auth.)
Forssen, C.; Caurier, E.; Navratil, P.
2009-01-01
Recently, charge radii and ground-state electromagnetic moments of Li and Be isotopes were measured precisely. We have performed large-scale ab initio no-core shell model calculations for these isotopes using high-precision nucleon-nucleon potentials. The isotopic trends of our computed charge radii and quadrupole and magnetic-dipole moments are in good agreement with experimental results with the exception of the 11 Li charge radius. The magnetic moments are in particular well described, whereas the absolute magnitudes of the quadrupole moments are about 10% too small. The small magnitude of the 6 Li quadrupole moment is reproduced, and with the CD-Bonn NN potential, also its correct sign
Chen, F. Q.; Sun, Y.
2013-01-01
Description of the interplay between different nuclear shapes is an interesting but challenging problem. The original projected shell model (PSM) is applicable to nuclei with fixed shapes. We extend the PSM by superimposing (angular-momentum- and particle-number-) projected product wave functions in the spirit of the generate coordinate method. With this development, the Gd isotopes across the N = 90 region are studied, and the results indicate spectroscopic features of shape phase transition with varying neutron number. In order to illustrate the shape distribution in microscopic wave functions, we introduce a deformation representation and show that the collectively excited K π = 0 + states in the Gd isotopes have characters of shape vibration. (authors)
Casali, R. A.; Lasave, J.; Caravaca, M. A.; Koval, S.; Ponce, C. A.; Migoni, R. L.
2013-04-01
The pressure dependences of the structural, thermoelastic and vibrational properties of SnO2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl2-type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO2. A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure Pc. A zone-center phonon of B1g symmetry in the rutile phase involves such rotation and softens on approaching Pc. It becomes an Ag mode which stabilizes with increasing pressure in the CaCl2 phase. This behavior, together with the softening of the shear modulus (C11-C12)/2 related to the orthorhombic distortion, allows a precise determination of a value for Pc. An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B1g mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model.
Casali, R A; Ponce, C A; Lasave, J; Koval, S; Migoni, R L; Caravaca, M A
2013-01-01
The pressure dependences of the structural, thermoelastic and vibrational properties of SnO 2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl 2 -type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO 2 . A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure P c . A zone-center phonon of B 1g symmetry in the rutile phase involves such rotation and softens on approaching P c . It becomes an A g mode which stabilizes with increasing pressure in the CaCl 2 phase. This behavior, together with the softening of the shear modulus (C 11 −C 12 )/2 related to the orthorhombic distortion, allows a precise determination of a value for P c . An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B 1g mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model. (paper)
Shell model calculation of the nuclear moments of 9Li in a 2hω space
Chang, Y.; Meder, M.R.
1984-01-01
A recent measurement of the magnitude of quadrupole moment of the ground state of 9 Li, Q( 9 Li), finds that Vertical BarQ( 9 Li)/Q( 7 Li)Vertical Bar = 0.88 +- 0.18. A variety of shell-model calculations, using p-shell wave functions, predict Q( 9 Li)approx. =1.3Q( 7 Li) and yield quadrupole moments whose magnitudes are approximately half the experimental values. Agreement between theory and experiment is improved when effective charges are used, although the results are still not completely satisfactory. A calculation of the wave functions of the low-lying states of 7 Li and 9 Li using a modified version of the Sussex matrix elements in a model space, including all 0hω and 2hω excitations, has been performed. The resulting value for Q( 9 Li) was -3.46 fm 2 as ray transitions in /sup 52,53/Cr and /sup 54,55/Mn have been observed using 7 Li( 51 V,xn yp zα γ) fusion-evaporation reactions and γ-particle coincidence techniques. The experiment involved the same reaction at the same center-of-mass energy as the earlier work of Poletti et al., but with target and projectile interchanged. In the present work, eight additional transitions have been identified as occurring in 52 Cr. This provides corroboration of results obtained more recently via 50 Ti(α,2nγ) 52 Cr reaction studies. A simple, efficient approach to the spectroscopy of weakly populated nuclear states which provides for unambiguous isotopic assignments is thus demonstrated
FRACTIONAL CRYSTALLIZATION OF HANFORD SINGLE-SHELL TANK WASTES. A MODELING APPROACH
HAMILTON, D.W.
2006-01-01
The Hanford site has 149 underground single-shell tanks (SST) storing mostly soluble, multi-salt, mixed wastes resulting from Cold War era weapons material production. These wastes must be retrieved and the salts immobilized before the tanks can be closed to comply with an overall site closure consent order entered into by the U.S. Department of Energy (DOE), the Environmental Protection Agency, and Washington State. Water will be used to retrieve the wastes and the resulting solution will be pumped to the proposed treatment process where a high curie (primarily 137 Cs) waste fraction will be separated from the other waste constituents. The separated waste streams will then be vitrified to allow for safe storage as an immobilized high level waste, or low level waste, borosilicate glass. Fractional crystallization, a common unit operation for production of industrial chemicals and pharmaceuticals, was proposed as the method to separate the salt wastes; it works by evaporating excess water until the solubilities of various species in the solution are exceeded (the solubility of a particular species depends on its concentration, temperature of the solution, and the presence of other ionic species in the solution). By establishing the proper conditions, selected pure salts can be crystallized and separated from the radioactive liquid phase
Diagonalization of quark mass matrices and the Cabibbo-Kobayashi-Maskawa matrix
Rasin, A.
1997-08-01
I discuss some general aspect of diagonalizing the quark mass matrices and list all possible parametrizations of the Cabibbo-Kobayashi-Maskawa matrix (CKM) in terms of three rotation angles and a phase. I systematically study the relation between the rotations needed to diagonalize the Yukawa matrices and various parametrizations of the CKM. (author). 17 refs, 1 tab
Off-diagonal Bethe ansatz solution of the XXX spin chain with arbitrary boundary conditions
Cao, Junpeng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Wen-Li, E-mail: wlyang@nwu.edu.cn [Institute of Modern Physics, Northwest University, Xian 710069 (China); Shi, Kangjie [Institute of Modern Physics, Northwest University, Xian 710069 (China); Wang, Yupeng, E-mail: yupeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2013-10-01
Employing the off-diagonal Bethe ansatz method proposed recently by the present authors, we exactly diagonalize the XXX spin chain with arbitrary boundary fields. By constructing a functional relation between the eigenvalues of the transfer matrix and the quantum determinant, the associated T–Q relation and the Bethe ansatz equations are derived.
Off-diagonal Bethe ansatz solution of the XXX spin chain with arbitrary boundary conditions
Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2013-01-01
Employing the off-diagonal Bethe ansatz method proposed recently by the present authors, we exactly diagonalize the XXX spin chain with arbitrary boundary fields. By constructing a functional relation between the eigenvalues of the transfer matrix and the quantum determinant, the associated T–Q relation and the Bethe ansatz equations are derived
Diagonalization and Jordan Normal Form--Motivation through "Maple"[R
Glaister, P.
2009-01-01
Following an introduction to the diagonalization of matrices, one of the more difficult topics for students to grasp in linear algebra is the concept of Jordan normal form. In this note, we show how the important notions of diagonalization and Jordan normal form can be introduced and developed through the use of the computer algebra package…
Thin-shell wormholes in dilaton gravity
Eiroa, Ernesto F.; Simeone, Claudio
2005-01-01
In this work we construct charged thin-shell Lorentzian wormholes in dilaton gravity. The exotic matter required for the construction is localized in the shell and the energy conditions are satisfied outside the shell. The total amount of exotic matter is calculated and its dependence with the parameters of the model is analyzed
Thermoelectric behavior of conducting polymers: On the possibility of off-diagonal thermoelectricity
Mateeva, N; Niculescu, H; Schlenoff, J; Testardi, L
1997-07-01
Non-cubic materials, when structurally aligned, possess sufficient anisotropy to exhibit thermoelectric effects where the electrical and thermal currents are orthogonal (off-diagonal thermoelectricity). The authors discuss the benefits of this form of thermoelectricity for devices and describe a search for suitable properties in the air-stable conducting polymers polyaniline and polypyrrole. They find the simple and general correlation that the logarithm of the electrical conductivity scales linearly with the Seebeck coefficient on doping but with proportionality in excess of the conventional prediction for thermoelectricity. The correlation is unexpected in its universality and unfavorable for thermoelectric applications. A simple model suggests that mobile charges of both signs exist in these polymers, and this leads to reduced thermoelectric efficiency. They also briefly discuss non air-stable polyacetylene, where ambipolar transport does not appear to occur, and where properties seem more favorable for thermoelectricity.
Studies of dust shells around stars
Bedijn, P.J.
1977-01-01
This thesis deals with some aspects of circumstellar dust shells. This dust shell, emitting infrared radiation, is described by way of its absorptive and emissive properties as well as by the transfer of radiation through the dust shell itself. Model calculations are compared to experimental results and agree reasonably well. The author also discusses the dynamics of the extended shells of gas and dust around newly formed stars
Das, Y.C.; Kedia, K.K.
1977-01-01
No realistic analytical work in the area of Shells on Elastic Foundations has been reported in the literature. Various foundation models have been proposed by several authors. These models involve one or more than one parameters to characterise the foundation medium. Some of these models cannot be used to derive the basic equations governing the behaviour of shells on elastic foundations. In the present work, starting from an elastic continuum hypothesis, a mathematical model for foundation has been derived in curvilinear orthogonal coordinates by the help of principle of virtual displacements, treating one of the virtual displacements as known to satisfy certain given conditions at its edge surfaces. In this model, several foundation parameters can be considered and it can also be used for layered medium of both finite and infinite thickness. (Auth.)
Iterative algorithm for joint zero diagonalization with application in blind source separation.
Zhang, Wei-Tao; Lou, Shun-Tian
2011-07-01
A new iterative algorithm for the nonunitary joint zero diagonalization of a set of matrices is proposed for blind source separation applications. On one hand, since the zero diagonalizer of the proposed algorithm is constructed iteratively by successive multiplications of an invertible matrix, the singular solutions that occur in the existing nonunitary iterative algorithms are naturally avoided. On the other hand, compared to the algebraic method for joint zero diagonalization, the proposed algorithm requires fewer matrices to be zero diagonalized to yield even better performance. The extension of the algorithm to the complex and nonsquare mixing cases is also addressed. Numerical simulations on both synthetic data and blind source separation using time-frequency distributions illustrate the performance of the algorithm and provide a comparison to the leading joint zero diagonalization schemes.
Spangenberger, H.; Beck, F.; Richter, A.
The usual continuum shell model is extended so as to include a statistical treatment of multi-doorway processes. The total configuration space of the nuclear reaction problem is subdivided into the primary doorway states which are coupled by the initial excitation to the nuclear ground state and the secondary doorway states which represent the complicated nature of multi-step reactions. The latter are evaluated within the exciton model which gives the coupling widths between the various finestructure subspaces. This coupling is determined by a statistical factor related to the exciton model and a dynamical factor given by the interaction matrix elements of the interacting excitons. The whole structure defines the multi-doorway continuum shell model. In this work it is applied to the highly fragmented magnetic dipole strength in 58Ni observed in high resolution electron scattering.Translated AbstractAnwendung des Multi-Doorway-Kontinuum-Schalenmodells auf die Verteilung der magnetischen Dipolstärke von 58NiDas Kontinuum-Schalenmodell wurde so erweitert, daß auch statistische Multi-Doorway-Prozesse berücksichtigt werden können. Hierzu wird der Konfigurationsraum unterteilt in den Raum der primären Doorway-Zustände, die direkt aus dem Grundzustand angeregt werden, und den der sekundären Doorway-Zustände, die die komplizierte Struktur der Multi-Step-Reaktionen repräsentieren. Während die primären Doorway-Zustände inclusive ihrer Anregungen mittels üblicher Schalenmodellmethoden beschrieben werden können, werden die sekundären Doorway-Zustände sowie ihre verschiedenen Kopplungen im Rahmen des Exciton-Modells behandelt. Diese Kopplungen sind durch einen aus dem Exciton-Modell resultierenden Faktor sowie durch einen dynamischen Faktor bestimmt, der sich aus dem Matrixelement der wechselwirkenden Excitonen berechnet. Die Struktur der Kopplungen definiert das Multi-Doorway-Kontinuum-Schalenmodell, das hier auf die Beschreibung der stark fragmentierten
LANL* V1.0: a radiation belt drift shell model suitable for real-time and reanalysis applications
J. Koller
2009-07-01
Full Text Available We describe here a new method for calculating the magnetic drift invariant, L*, that is used for modeling radiation belt dynamics and for other space weather applications. L* (pronounced L-star is directly proportional to the integral of the magnetic flux contained within the surface defined by a charged particle moving in the Earth's geomagnetic field. Under adiabatic changes to the geomagnetic field L* is a conserved quantity, while under quasi-adiabatic fluctuations diffusion (with respect to a particle's L* is the primary term in equations of particle dynamics. In particular the equations of motion for the very energetic particles that populate the Earth's radiation belts are most commonly expressed by diffusion in three dimensions: L*, energy (or momentum, and pitch angle (the dot product of velocity and the magnetic field vector. Expressing dynamics in these coordinates reduces the dimensionality of the problem by referencing the particle distribution functions to values at the magnetic equatorial point of a magnetic "drift shell" (or L-shell irrespective of local time (or longitude. While the use of L* aids in simplifying the equations of motion, practical applications such as space weather forecasting using realistic geomagnetic fields require sophisticated magnetic field models that, in turn, require computationally intensive numerical integration. Typically a single L* calculation can require on the order of 10^{5} calls to a magnetic field model and each point in the simulation domain and each calculated pitch angle has a different value of L*. We describe here the development and validation of a neural network surrogate model for calculating L* in sophisticated geomagnetic field models with a high degree of fidelity at computational speeds that are millions of times faster than direct numerical field line mapping and integration. This new surrogate model has
Salvatore Brischetto
2015-12-01
Full Text Available The present paper talks about the free vibration analysis of simply supported Single- and Double-Walled Carbon Nanotubes (SWCNTs and DWCNTs. Refined 2D Generalized Differential Quadrature (GDQ shell methods and an exact 3D shell model are compared. A continuum approach (based on an elastic three-dimensional shell model is used for natural frequency investigation of SWCNTs and DWCNTs. SWCNTs are defined as isotropic cylinders with an equivalent thickness and Young modulus. DWCNTs are defined as two concentric isotropic cylinders (with an equivalent thickness and Young modulus which can be linked by means of the interlaminar continuity conditions or by means of van der Waals interactions. Layer wise approaches are mandatory for the analysis of van der Waals forces in DWCNTs. The effect of van der Waals interaction between the two cylinders is shown for different DWCNT lengths, diameters and vibration modes. The accuracy of beam models and classical 2D shell models in the free vibration analysis of SWCNTs and DWCNTs is also investigated.
Hill, J.G.; Simpson, B.C.
1994-04-01
The Sort on Radioactive Waste Type (SORWT) model presents a method to categorize Hanford Site single-shell tanks (SSTs) into groups of tank expected to exhibit similar chemical and physical characteristics based on their major waste types and processing histories. This model has identified 29 different waste-type groups encompassing 135 of the 149 SSTs and 93% of the total waste volume in SSTs. The remaining 14 SSTs and associated wastes could not be grouped according to the established criteria and were placed in an ungrouped category. This letter report will detail the assumptions and methodologies used to develop the SORWT model and present the grouping results. In the near future, the validity of the predicted groups will be statistically tested using analysis of variance of characterization data obtained from recent (post-1989) core sampling and analysis activities. In addition, the SORWT model will be used to project the nominal waste characteristics of entire waste type groups that have some recent characterization data available. These subsequent activities will be documented along with these initial results in a comprehensive, formal PNL report cleared for public release by September 1994
Vargas, Carlos E.; Bagatella-Flores, Norma [Universidad Veracruzana, Facultad de Fisica, Veracruz (Mexico); Velazquez, Victor [Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Mexico D.F. (Mexico); Lerma-Hernandez, Sergio [Universidad Veracruzana, Facultad de Fisica, Veracruz (Mexico); Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico D.F. (Mexico)
2017-04-15
The large collectivity observed in the rare-earth region of the nuclear landscape is well known. The microscopic studies are difficult to perform in this region due to the enormous size of the valence spaces, a problem that can be avoided by means of the use of symmetry-based models. Here we present calculations for electromagnetic properties of {sup 160-170}Dy nuclei within the pseudo-SU(3) scheme. The model Hamiltonian includes the preserving symmetry Q.Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized for all members of the chain. The model is used to calculate B(E2) and B(M1) inter-band transition strengths between the ground state, γ and β-bands. In addition, we present results for quadrupole moments and g factors in these rotational bands. The results show that the pseudo-SU(3) shell model is a powerful microscopic theory for a description of electromagnetic properties of states in the normal parity sector in heavy deformed nuclei. (orig.)
Devi, Jutika; Datta, Pranayee; Saikia, Rashmi
2016-01-01
The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications. (paper)
Devi, Jutika; Saikia, Rashmi; Datta, Pranayee
2016-10-01
The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.
Polotsky, A.; Charlaganov, M.; Xu, Y.P.; Leermakers, F.A.M.; Daoud, M.; Muller, A.H.E.; Dotera, T.; Borisov, O.V.
2008-01-01
We present theoretical arguments and experimental evidence for a longitudinal instability in core-shell cylindrical polymer brushes with a solvophobic inner (core) block and a solvophilic outer (shell) block in selective solvents. The two-gradient self-consistent field Scheutjens-Fleer (SCF-SF)
DOUBLE-SHELL TANK (DST) HYDROXIDE DEPLETION MODEL FOR CARBON DIOXIDE ABSORPTION
OGDEN DM; KIRCH NW
2007-01-01
This document generates a supernatant hydroxide ion depletion model based on mechanistic principles. The carbon dioxide absorption mechanistic model is developed in this report. The report also benchmarks the model against historical tank supernatant hydroxide data and vapor space carbon dioxide data. A comparison of the newly generated mechanistic model with previously applied empirical hydroxide depletion equations is also performed
Brunner, M.; Maercker, M.; Mecina, M.; Khouri, T.; Kerschbaum, F.
2018-06-01
Context. On the asymptotic giant branch (AGB), Sun-like stars lose a large portion of their mass in an intensive wind and enrich the surrounding interstellar medium with nuclear processed stellar material in the form of molecular gas and dust. For a number of carbon-rich AGB stars, thin detached shells of gas and dust have been observed. These shells are formed during brief periods of increased mass loss and expansion velocity during a thermal pulse, and open up the possibility to study the mass-loss history of thermally pulsing AGB stars. Aims: We study the properties of dust grains in the detached shell around the carbon AGB star R Scl and aim to quantify the influence of the dust grain properties on the shape of the spectral energy distribution (SED) and the derived dust shell mass. Methods: We modelled the SED of the circumstellar dust emission and compared the models to observations, including new observations of Herschel/PACS and SPIRE (infrared) and APEX/LABOCA (sub-millimeter). We derived present-day mass-loss rates and detached shell masses for a variation of dust grain properties (opacities, chemical composition, grain size, and grain geometry) to quantify the influence of changing dust properties to the derived shell mass. Results: The best-fitting mass-loss parameters are a present-day dust mass-loss rate of 2 × 10-10 M⊙ yr-1 and a detached shell dust mass of (2.9 ± 0.3) × 10-5 M⊙. Compared to similar studies, the uncertainty on the dust mass is reduced by a factor of 4. We find that the size of the grains dominates the shape of the SED, while the estimated dust shell mass is most strongly affected by the geometry of the dust grains. Additionally, we find a significant sub-millimeter excess that cannot be reproduced by any of the models, but is most likely not of thermal origin. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
A diagonal approach for the catalytic transformation of carbon dioxide
Gomes, Christophe
2013-01-01
Emissions of carbon dioxide are growing with the massive utilization of hydrocarbons for the production of energy and chemicals, resulting in a threatening global warming. The development of a more sustainable economy is urging to reduce the fingerprint of our current way of life. In this perspective, the organic chemistry industry will face important challenges in the next decades to replace hydrocarbons as a feedstock and use carbon-free energy sources. To tackle this challenge, new catalytic processes have been designed to convert CO 2 to high energy and value-added chemicals (formamides, N-heterocycles and methanol), using a novel diagonal approach. The energy efficiency of the new transformations is ensured by the utilization of mild reductants such as hydro-silanes and hydro-boranes. Importantly the reactions are promoted by organic catalysts, which circumvent the problems of cost, abundance and toxicity usually encountered with metal complexes. Based on theoretical and experimental studies, the understanding of the mechanisms involved in these reactions allowed the rational optimization of the catalysts as well as the reaction conditions, in order to match the requirements of sustainable chemistry. (author) [fr
Nuclear fuel rod grip with modified diagonal spring structures
DeMario, E.E.
1990-01-01
This patent describes a spring structure in a nuclear fuel rod grid including a plurality of inner and outer straps being interleaved with one another to form a matrix of hollow cells. Each of the cells is for receiving one fuel rod and being defined by pairs of opposing wall sections of the straps which wall sections are shared with adjacent cells. Each of the cells has a central longitudinal axis, a fuel rod engaging spring structure of resiliently yieldable material being integrally formed on each wall section of the inner straps. The spring structure comprising: a pair of spaced apart opposite outer portions being integrally attached at their outer ends to the respective wall section. The portions extending in alignment with one another and in generally diagonal relation to the direction of the central longitudinal axis of the one cell; and a middle portion disposed between and integrally connected at its outer ends with respective inner ends of the outer portions. The middle portion extending in generally transverse relation to the direction of the central longitudinal axis of the one cell
Separability of diagonal symmetric states: a quadratic conic optimization problem
Jordi Tura
2018-01-01
Full Text Available We study the separability problem in mixtures of Dicke states i.e., the separability of the so-called Diagonal Symmetric (DS states. First, we show that separability in the case of DS in $C^d\\otimes C^d$ (symmetric qudits can be reformulated as a quadratic conic optimization problem. This connection allows us to exchange concepts and ideas between quantum information and this field of mathematics. For instance, copositive matrices can be understood as indecomposable entanglement witnesses for DS states. As a consequence, we show that positivity of the partial transposition (PPT is sufficient and necessary for separability of DS states for $d \\leq 4$. Furthermore, for $d \\geq 5$, we provide analytic examples of PPT-entangled states. Second, we develop new sufficient separability conditions beyond the PPT criterion for bipartite DS states. Finally, we focus on $N$-partite DS qubits, where PPT is known to be necessary and sufficient for separability. In this case, we present a family of almost DS states that are PPT with respect to each partition but nevertheless entangled.
Improvement of child survival in Mexico: the diagonal approach.
Sepúlveda, Jaime; Bustreo, Flavia; Tapia, Roberto; Rivera, Juan; Lozano, Rafael; Oláiz, Gustavo; Partida, Virgilio; García-García, Lourdes; Valdespino, José Luis
2006-12-02
Public health interventions aimed at children in Mexico have placed the country among the seven countries on track to achieve the goal of child mortality reduction by 2015. We analysed census data, mortality registries, the nominal registry of children, national nutrition surveys, and explored temporal association and biological plausibility to explain the reduction of child, infant, and neonatal mortality rates. During the past 25 years, child mortality rates declined from 64 to 23 per 1000 livebirths. A dramatic decline in diarrhoea mortality rates was recorded. Polio, diphtheria, and measles were eliminated. Nutritional status of children improved significantly for wasting, stunting, and underweight. A selection of highly cost-effective interventions bridging clinics and homes, what we called the diagonal approach, were central to this progress. Although a causal link to the reduction of child mortality was not possible to establish, we saw evidence of temporal association and biological plausibility to the high level of coverage of public health interventions, as well as significant association to the investments in women education, social protection, water, and sanitation. Leadership and continuity of public health policies, along with investments on institutions and human resources strengthening, were also among the reasons for these achievements.
[Improvement of child survival in Mexico: the diagonal approach].
Sepúlveda, Jaime; Bustreo, Flavia; Tapia, Roberto; Rivera, Juan; Lozano, Rafael; Olaiz, Gustavo; Partida, Virgilio; García-García, Ma de Lourdes; Valdespino, José Luis
2007-01-01
Public health interventions aimed at children in Mexico have placed the country among the seven countries on track to achieve the goal of child mortality reduction by 2015. We analysed census data, mortality registries, the nominal registry of children, national nutrition surveys, and explored temporal association and biological plausibility to explain the reduction of child, infant, and neonatal mortality rates. During the past 25 years, child mortality rates declined from 64 to 23 per 1000 livebirths. A dramatic decline in diarrhoea mortality rates was recorded. Polio, diphtheria, and measles were eliminated. Nutritional status of children improved significantly for wasting, stunting, and underweight. A selection of highly cost-effective interventions bridging clinics and homes, what we called the diagonal approach, were central to this progress. Although a causal link to the reduction of child mortality was not possible to establish, we saw evidence of temporal association and biological plausibility to the high level of coverage of public health interventions, as well as significant association to the investments in women education, social protection, water, and sanitation. Leadership and continuity of public health policies, along with investments on institutions and human resources strengthening, were also among the reasons for these achievements.
Wang Peng
2016-01-01
Full Text Available A family of prismatic and hexahedral solid‒shell (SHB elements with their linear and quadratic versions is presented in this paper to model thin 3D structures. Based on reduced integration and special treatments to eliminate locking effects and to control spurious zero-energy modes, the SHB solid‒shell elements are capable of modeling most thin 3D structural problems with only a single element layer, while describing accurately the various through-thickness phenomena. In this paper, the SHB elements are combined with fully 3D behavior models, including orthotropic elastic behavior for composite materials and anisotropic plastic behavior for metallic materials, which allows describing the strain/stress state in the thickness direction, in contrast to traditional shell elements. All SHB elements are implemented into ABAQUS using both standard/quasi-static and explicit/dynamic solvers. Several benchmark tests have been conducted, in order to first assess the performance of the SHB elements in quasi-static and dynamic analyses. Then, deep drawing of a hemispherical cup is performed to demonstrate the capabilities of the SHB elements in handling various types of nonlinearities (large displacements and rotations, anisotropic plasticity, and contact. Compared to classical ABAQUS solid and shell elements, the results given by the SHB elements show good agreement with the reference solutions.
Hill, J.G.; Anderson, G.S.; Simpson, B.C.
1995-02-01
The Sort on Radioactive Waste Type (SORWT) Model is a method to categorize Hanford Site single-shell tanks (SSTS) into groups of tanks expected to exhibit similar chemical and physical characteristics based on their major waste types and processing histories. The model has identified 24 different waste-type groups encompassing 133 of the 149 SSTs and 93% of the total waste volume in SSTS. The remaining 16 SSTs and associated wastes could not be grouped. according to the established criteria and were placed in an ungrouped category. A detailed statistical verification study has been conducted that employs analysis of variance (ANOVA) and the core sample analysis data collected since 1989. These data cover eight tanks and five SORWT groups. The verification study showed that these five SORWT groups are highly statistically significant; they represent approximately 10% of the total waste volume and 26% of the total sludge volume in SSTS. Future sampling recommendations based on the SORWT Model results include 32 core samples from 16 tanks and 18 auger samples from six tanks. Combining these data with the existing body of information will form the basis for characterizing 98 SSTs (66%). These 98 SSTs represent 78% of the total waste volume, 61% of the total sludge volume, and 88 % of the salt cake volume
Harvey, E.; Redman, M. P.; Boumis, P.; Akras, S.
2016-10-01
Aims: The shaping mechanisms of old nova remnants are probes for several important and unexplained processes, such as dust formation and the structure of evolved star nebulae. To gain a more complete understanding of the dynamics of the GK Per (1901) remnant, an examination of symmetry of the nova shell is explored, followed by a kinematical analysis of the previously detected jet-like feature in the context of the surrounding fossil planetary nebula. Methods: Faint-object high-resolution echelle spectroscopic observations and imaging were undertaken covering the knots which comprise the nova shell and the surrounding nebulosity. New imaging from the Aristarchos telescope in Greece and long-slit spectra from the Manchester Echelle Spectrometer instrument at the San Pedro Mártir observatory in Mexico were obtained, supplemented with archival observations from several other optical telescopes. Position-velocity arrays are produced of the shell, and also individual knots, and are then used for morpho-kinematic modelling with the shape code. The overall structure of the old knotty nova shell of GK Per and the planetary nebula in which it is embedded is then analysed. Results: Evidence is found for the interaction of knots with each other and with a wind component, most likely the periodic fast wind emanating from the central binary system. We find that a cylindrical shell with a lower velocity polar structure gives the best model fit to the spectroscopy and imaging. We show in this work that the previously seen jet-like feature is of low velocity. Conclusions: The individual knots have irregular tail shapes; we propose here that they emanate from episodic winds from ongoing dwarf nova outbursts by the central system. The nova shell is cylindrical, not spherical, and the symmetry axis relates to the inclination of the central binary system. Furthermore, the cylinder axis is aligned with the long axis of the bipolar planetary nebula in which it is embedded. Thus, the
Zoeller, Ludwig
2016-04-01
such landforms could persist and develop longer and were uplifted only during the Tertiary and Quaternary, more or less coeval with the development of the Central European Rift System. The Upper Cretaceous basin inversion strongly influenced the present-day macrorelief east of the geomorphologic diagonal whereas west of it the macrorelief was shaped by younger morphotectonic activities. This hypothesis will be discussed with respect to recent tectonic models on the collision history of Africa and Europe, the impingement of the thinned Central European crust, and the rotating relative drifting direction of Africa and the Adriatic plate with respect to the Eurasian plate (Kley & Voigt 2008). NW-SE structures may have been revived by Quaternary glacial isostatic processes and even by historical earthquakes. References: von Eynatten, H. et al., (2008), Int J Earth Sci (Geol Rundsch) 97:1315-1330 Kley, J. & Voigt, T., (2008), Geology 36:839-842
MARMOSET: The Path from LHC Data to the New Standard Model via On-Shell Effective Theories
Arkani-Hamed, Nima; Schuster, Philip; Toro, Natalia; Thaler, Jesse; Wang, Lian-Tao; Mrenna, Stephen
2007-01-01
We describe a coherent strategy and set of tools for reconstructing the fundamental theory of the TeV scale from LHC data. We show that On-Shell Effective Theories (OSETs) effectively characterize hadron collider data in terms of masses, production cross sections, and decay modes of candidate new particles. An OSET description of the data strongly constrains the underlying new physics, and sharply motivates the construction of its Lagrangian. Simulating OSETs allows efficient analysis of new-physics signals, especially when they arise from complicated production and decay topologies. To this end, we present MARMOSET, a Monte Carlo tool for simulating the OSET version of essentially any new-physics model. MARMOSET enables rapid testing of theoretical hypotheses suggested by both data and model-building intuition, which together chart a path to the underlying theory. We illustrate this process by working through a number of data challenges, where the most important features of TeV-scale physics are reconstructed with as little as 5 fb -1 of simulated LHC signals
Boonlamp, M.
2005-03-01
Full Text Available A spherical double shell model (SDM for a single cell has been developed, using Laplace’s equation in spherical coordinates and boundary conditions. Electric field intensities and dielectric constants of each region inside and outside of the cell have been estimated. The dielectrophoretic spectrum of the real part of a complex function (Re[f ( ω] were computed using Visual Foxpro Version 6, which gave calculated values pertaining to electrical properties of the cell model as compared with experimental values. The process was repeated until the error percentile was in an acceptable range. The calculated parameters were the dielectric constants and the conductivities of the inner cytoplasm ( εic, σic, the outer cytoplasm ( εoc, σoc, the inner membrane ( εim, σim, the outer membrane ( εom, σom, the suspending solution( εs, σs and the thickness of each layer (dom, doc, dim, respectively. This computer program provides estimated values of cell electrical properties with high accuracy and required minimal computational time.
MARMOSET: The Path from LHC Data to the New Standard Model via On-Shell Effective Theories
Arkani-Hamed, Nima; Schuster, Philip; Toro, Natalia; /Harvard U., Phys. Dept.; Thaler, Jesse; /UC, Berkeley /LBL, Berkeley; Wang, Lian-Tao; /Princeton U.; Knuteson, Bruce; /MIT, LNS; Mrenna, Stephen; /Fermilab
2007-03-01
We describe a coherent strategy and set of tools for reconstructing the fundamental theory of the TeV scale from LHC data. We show that On-Shell Effective Theories (OSETs) effectively characterize hadron collider data in terms of masses, production cross sections, and decay modes of candidate new particles. An OSET description of the data strongly constrains the underlying new physics, and sharply motivates the construction of its Lagrangian. Simulating OSETs allows efficient analysis of new-physics signals, especially when they arise from complicated production and decay topologies. To this end, we present MARMOSET, a Monte Carlo tool for simulating the OSET version of essentially any new-physics model. MARMOSET enables rapid testing of theoretical hypotheses suggested by both data and model-building intuition, which together chart a path to the underlying theory. We illustrate this process by working through a number of data challenges, where the most important features of TeV-scale physics are reconstructed with as little as 5 fb{sup -1} of simulated LHC signals.
Development of surrogate models using artificial neural network for building shell energy labelling
Melo, A.P.; Costola, D.; Lamberts, R.; Hensen, J.L.M.
2014-01-01
Surrogate models are an important part of building energy labelling programs, but these models still present low accuracy, particularly in cooling-dominated climates. The objective of this study was to evaluate the feasibility of using an artificial neural network (ANN) to improve the accuracy of
Diagonal earlobe crease: Prevalence and association with medical ailments
Yugantara Ramesh Kadam
2018-01-01
Full Text Available Context: It has been hypothesized that diagonal earlobe crease (DELC, “Frank's sign” is indicative of coronary artery disease (CAD and/or diabetes mellitus (DM. Several studies have confirmed an association between DELC and cardiac morbidity, mortality, and hypertension (HTN. However, some studies have not found any significant association. Aims: This study aims to find out the prevalence of DELC and its association with CAD, DM, and HTN. Settings and Design: Sangli-Miraj-Kupwad Corporation area. This was a cross-sectional analytical study. Subjects and Methods: Study participants: Adults from 18 to 60 years age. Inclusion criteria: willing to participate in the study Exclusion criteria: Wearing heavy ear rings and excessive normal generalized wrinkling of the skin. Sample size: Sample size 6310, determined after a pilot study revealing DELC in 1.5%. Sampling technique: Two-stage cluster sampling. Duration of study: 6 months. Study tools: Predesigned, pilot tested pro forma. Statistical Analysis: Statistical analysis was done by using SPSS 22 software. Prevalence and percentages were calculated, and Chi-square test was applied. Results: Out of 6638 participants, 179 had DELC. The prevalence of bilateral DELC was 2.7%. The prevalence was significantly high among males (4.13% and in the 51–60 years age group (5.29%. The prevalence of Grade 3 DELC was high and 91% of young adults had Grade 3 DELC. There were 408 (6.15% participants who gave a history of CAD, 827 (12.46% of DM, and 670 (10.09% HTN. Significantly high association observed between DELC and CAD, DM, and HTN. CAD, DM, and HTN were significantly associated with Grade 3. Conclusions: The prevalence of bilateral DELC was 2.7% and is significantly associated with CAD, DM, and HTN.
Model Based Controller Design for a Shell and Tube Heat Exchanger
S. Nithya
2007-10-01
Full Text Available In all the process industries the process variables like flow, pressure, level and temperature are the main parameters that need to be controlled in both set point and load changes. The transfer of heat is one of the main important operation in the heat exchanger .The transfer of heat may be fluid to fluid, gas to gas i.e. in the same phase or the phase change can occur on either side of the heat exchanger. The control of heat exchanger is complex due to its nonlinear dynamics. For this nonlinear process of a heat exchanger the model is identified to be First Order plus Dead Time (FOPDT.The Internal Model Control (IMC is one of the model predictive control methods based on the predictive output of the process model. The conventional controller tuning is compared with IMC techniques and it found to be suitable for heat exchanger than the conventional PI tuning.
Inner shell coulomb ionization by heavy charged particles studied by the SCA model
Hansteen, J.M.
1976-06-01
An outline is given of the development of and some achievements hitherto gained from the semi-classical approximation (SCA) model of atomic Coulomb excitation by heavy charged particles. A few very recent results (1975-1976) are incorporated in the discussion. The SCA model has by now reached a mature state. Hence it seems reasonable to regard the atomic Coulomb excitation phenomenon as part of the extremely complicated excitation mechanism operative in the general ion-atom collision. A clear understanding of the complicated X-ray producing mechanisms in heavy-ion-atom collisions is lacking at present. Despite these facts, the conceptually simple SCA model has furthered our understanding far beyond initial expectations. Moreover, this model has at the same time provided a well-founded starting point for continued researches in this rapidly expanding field of physics. (JIW)
Acoustic coupling of two parallel shells in compressible fluid
Gerges, S.N.Y.
1982-01-01
Modifications are done in the acoustic impedance for a vibrating shell, due to the pressure of another similar shell. The multi-analysis method of scattering is used. The results of the impedance in function of the shell radius, the wave length, the distance between the shell axis and its vibration models are presented. (E.G.) [pt
Cao Jiacong; Lin Xingchun
2008-01-01
An accurate forecast of solar irradiation is required for various solar energy applications and environmental impact analyses in recent years. Comparatively, various irradiation forecast models based on artificial neural networks (ANN) perform much better in accuracy than many conventional prediction models. However, the forecast precision of most existing ANN based forecast models has not been satisfactory to researchers and engineers so far, and the generalization capability of these networks needs further improving. Combining the prominent dynamic properties of a recurrent neural network (RNN) with the enhanced ability of a wavelet neural network (WNN) in mapping nonlinear functions, a diagonal recurrent wavelet neural network (DRWNN) is newly established in this paper to perform fine forecasting of hourly and daily global solar irradiance. Some additional steps, e.g. applying historical information of cloud cover to sample data sets and the cloud cover from the weather forecast to network input, are adopted to help enhance the forecast precision. Besides, a specially scheduled two phase training algorithm is adopted. As examples, both hourly and daily irradiance forecasts are completed using sample data sets in Shanghai and Macau, and comparisons between irradiation models show that the DRWNN models are definitely more accurate
Escolano, C.; Carciofi, A. C.; Okazaki, A. T.; Rivinius, T.; Baade, D.; Štefl, S.
2015-04-01
Context. A large number of Be stars exhibit intensity variations of their violet and red emission peaks in their H i lines observed in emission. This is the so-called V/R phenomenon, usually explained by the precession of a one-armed spiral density perturbation in the circumstellar disk. That global-disk oscillation scenario was confirmed, both observationally and theoretically, in the previous series of two papers analyzing the Be shell star ζ Tauri. The vertically averaged (2D) global-disk oscillation model used at the time was able to reproduce the V/R variations observed in Hα, as well as the spatially resolved interferometric data from AMBER/VLTI. Unfortunately, that model failed to reproduce the V/R phase of Br15 and the amplitude of the polarization variation, suggesting that the inner disk structure predicted by the model was incorrect. Aims: The first aim of the present paper is to quantify the temporal variations of the shell-line characteristics of ζ Tauri. The second aim is to better understand the physics underlying the V/R phenomenon by modeling the shell-line variations together with the V/R and polarimetric variations. The third aim is to test a new 2.5D disk oscillation model, which solves the set of equations that describe the 3D perturbed disk structure but keeps only the equatorial (i.e., 2D) component of the solution. This approximation was adopted to allow comparisons with the previous 2D model, and as a first step toward a future 3D model. Methods: We carried out an extensive analysis of ζ Tauri's spectroscopic variations by measuring various quantities characterizing its Balmer line profiles: red and violet emission peak intensities (for Hα, Hβ, and Br15), depth and asymmetry of the shell absorption (for Hβ, Hγ, and Hδ), and the respective position (i.e., radial velocity) of each component. We attempted to model the observed variations by implementing in the radiative transfer code HDUST the perturbed disk structure computed with a
Iben, I. Jr.; Tutukov, A.V. (Illinois Univ., Urbana (USA); Astronomicheskii Sovet, Moscow (USSR))
1989-07-01
The characteristics of model stars consisting of a degenerate dwarf core and an envelope which is burning a nuclear fuel or fuels in its interior are explored. The models are relevant to stars which are accreting matter from a companion, to single stars in late stages of evolution, to stripped noninteracting remnants of binary star evolution, and to merging and merged degenerate dwarfs. For any given mass and choice of nuclear fuels, a sequence of models is constructed which differ with respect to the mass of the degenerate core and the envelope characteristics. Each sequence has at least three distinct branches: a degenerate dwarf branch along which envelope mass increases with decreasing luminosity, a plateau branch characterized by a very small envelope mass and by a nearly constant luminosity which reaches the maximum achievable value for the sequence, and an asymptotic giant branch which is at the lowest temperatures achievable and along which envelope mass decreases with increasing luminosity. 78 refs.
Iben, I. Jr.; Tutukov, A.V.
1989-01-01
The characteristics of model stars consisting of a degenerate dwarf core and an envelope which is burning a nuclear fuel or fuels in its interior are explored. The models are relevant to stars which are accreting matter from a companion, to single stars in late stages of evolution, to stripped noninteracting remnants of binary star evolution, and to merging and merged degenerate dwarfs. For any given mass and choice of nuclear fuels, a sequence of models is constructed which differ with respect to the mass of the degenerate core and the envelope characteristics. Each sequence has at least three distinct branches: a degenerate dwarf branch along which envelope mass increases with decreasing luminosity, a plateau branch characterized by a very small envelope mass and by a nearly constant luminosity which reaches the maximum achievable value for the sequence, and an asymptotic giant branch which is at the lowest temperatures achievable and along which envelope mass decreases with increasing luminosity. 78 refs
Self-consistent nonlinearly polarizable shell-model dynamics for ferroelectric materials
Mkam Tchouobiap, S.E.; Kofane, T.C.; Ngabireng, C.M.
2002-11-01
We investigate the dynamical properties of the polarizable shellmodel with a symmetric double Morse-type electron-ion interaction in one ionic species. A variational calculation based on the Self-Consistent Einstein Model (SCEM) shows that a theoretical ferroelectric (FE) transition temperature can be derive which demonstrates the presence of a first-order phase transition for the potassium selenate (K 2 SeO 4 ) crystal around Tc 91.5 K. Comparison of the model calculation with the experimental critical temperature yields satisfactory agreement. (author)
Nigro, G; Carbone, V
2015-01-01
Conventional surveys on the existence of singularities in fluid systems for vanishing dissipation have hitherto tried to infer some insight by searching for spatial features developing in asymptotic regimes. This approach has not yet produced a conclusive answer. One of the difficulties preventing us from getting a definitive answer is the limitations of direct numerical simulations which do not yet have a high enough resolution so far as to properly describe spatial fine structures in asymptotic regimes. In this paper, instead of searching for spatial details, we suggest seeking a principle, that would be able to discriminate between singular or not-singular behavior, among the integral and purely dynamical properties of a fluid system. We investigate the singularities developed by a hydromagnetic shell model during the magnetohydrodynamic turbulent cascade. Our results show that when the viscosity is equal to the magnetic diffusivity (unit magnetic Prandtl number) singularities appear in a finite time. A complex behavior is observed at extreme magnetic Prandtl numbers. In particular, the singularities persist in the limit of vanishing viscosity, while a complete regularization is observed in the limit of vanishing diffusivity. This dynamics is related to differences between the magnetic and the kinetic energy cascades towards small scales. Finally a comparison between the three-dimensional and the two-dimensional cases leads to conjecture that the existence of singularities may be related to the conservation of different ideal invariants. (paper)
Calculated Electronic Behavior and Spectrum of Mg+@C60 Using a Simple Jellium-shell Model
H. A. Schuessler
2004-11-01
Full Text Available Abstract: We present a method for calculating the energy levels and wave functions of any atom or ion with a single valence electron encapsulated in a Fullerene cage using a jelluim-shell model. The valence electron-core interaction is represented by a one-body pseudo-potential obtained through density functional theory with strikingly accurate parameters for Mg+ and which reduces to a purely Coulombic interaction in the case of H. We find that most energy states are affected little by encapsulation. However, when either the electron in the non-encapsulated species has a high probability of being near the jellium cage, or when the cage induces a maximum electron probability density within it, the energy levels shift considerably. Mg+ shows behavior similar to that of H, but since its wave functions are broader, the changes in its energy levels from encapsulation are slightly more pronounced. Agreement with other computational work as well as experiment is excellent and the method presented here is generalizable to any encapsulated species where a one-body electronic pseudo-potential for the free atom (or ion is available. Results are also presented for off-center hydrogen, where a ground state energy minimum of -14.01 eV is found at a nuclear displacement of around 0.1 ÃƒÂ….
Kostensalo, Joel; Suhonen, Jouni; Zuber, K.
2018-03-01
Charged-current (anti)neutrino-40Ar cross sections for astrophysical neutrinos have been calculated. The initial and final nuclear states were calculated using the nuclear shell model. The folded solar-neutrino scattering cross section was found to be 1.78 (23 ) ×10-42cm2 , which is higher than what the previous papers have reported. The contributions from the 1- and 2- multipoles were found to be significant at supernova-neutrino energies, confirming the random-phase approximation (RPA) result of a previous study. The effects of neutrino flavor conversions in dense stellar matter (matter oscillations) were found to enhance the neutrino-scattering cross sections significantly for both the normal and inverted mass hierarchies. For the antineutrino scattering, only a small difference between the nonoscillating and inverted-hierarchy cross sections was found, while the normal-hierarchy cross section was 2-3 times larger than that of the nonoscillating cross section, depending on the adopted parametrization of the Fermi-Dirac distribution. This property of the supernova-antineutrino signal could probably be used to distinguish between the two hierarchies in megaton LAr detectors.
Modelling loading and break-up of RC structure due to internal explosion of fragmenting shells
Weerheijm, J.; Stolz, A.; Riedel, W.; Mediavilla Varas, J.
2012-01-01
The Klotz Group (KG), an international group of experts on explosion safety, investigates the debris throw hazard associated with the accidental detonation of ammunition in reinforced concrete (RC-) structures. Experiments are combined with engineering models but also with results of advanced
Modelling loading and break-up of RC structure due to internal explosion of fragmenting shells
Weerheijm, J.; Stolz, A.; Riedel, W.; Mediavilla, J.
2012-01-01
The Klotz Group (KG), an mtemational group of experts on explosion safety, investigates the debris throw hazard associated with the accidental detonation of ammunition in reinforced concrete (RC-) structures. Experiments are combined with engineering models but also with results of advanced
Cluster model of s- and p-shell ΛΛ hypernuclei
simplifications the use of cluster model to S = −2 systems has given ..... constructed from Nijmegen soft-core NSC97e potential and are denoted as V e1. ΛΛ ..... This convergence of results reinforces the confidence in the methodology of all the.
Groenwold, A.A.; Wood, D.W.; Etman, L.F.P.; Tosserams, S.
2009-01-01
We implement and test a globally convergent sequential approximate optimization algorithm based on (convexified) diagonal quadratic approximations. The algorithm resides in the class of globally convergent optimization methods based on conservative convex separable approximations developed by
Off-diagonal helicity density matrix elements for vector mesons produced in polarized e+e- processes
Anselmino, M.; Murgia, F.; Quintairos, P.
1999-04-01
Final state q q-bar interactions give origin to non zero values of the off-diagonal element ρ 1,-1 of the helicity density matrix of vector mesons produced in e + e - annihilations, as confirmed by recent OPAL data on φ, D * and K * 's. New predictions are given for ρ 1,-1 of several mesons produced at large x E and small p T - i.e. collinear with the parent jet - in the annihilation of polarized 3 + and 3 - , the results depend strongly on the elementary dynamics and allow further non trivial tests of the standard model. (author)
Ma, Zhongqing; Chen, Dengyu; Gu, Jie; Bao, Binfu; Zhang, Qisheng
2015-01-01
Highlights: • Model-free integral kinetics method and analytical TGA–FTIR were conducted on pyrolysis process of PKS. • The pyrolysis mechanism of PKS was elaborated. • Thermal stability was established: lignin > cellulose > xylan. • Detailed compositions in the volatiles of PKS pyrolysis were determinated. • The interaction of biomass three components led to the fluctuation of activation energy in PKS pyrolysis. - Abstract: Palm kernel shell (PKS) from palm oil production is a potential biomass source for bio-energy production. A fundamental understanding of PKS pyrolysis behavior and kinetics is essential to its efficient thermochemical conversion. The thermal degradation profile in derivative thermogravimetry (DTG) analysis shown two significant mass-loss peaks mainly related to the decomposition of hemicellulose and cellulose respectively. This characteristic differentiated with other biomass (e.g. wheat straw and corn stover) presented just one peak or accompanied with an extra “shoulder” peak (e.g. wheat straw). According to the Fourier transform infrared spectrometry (FTIR) analysis, the prominent volatile components generated by the pyrolysis of PKS were CO 2 (2400–2250 cm −1 and 586–726 cm −1 ), aldehydes, ketones, organic acids (1900–1650 cm −1 ), and alkanes, phenols (1475–1000 cm −1 ). The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) method at different heating rates. The fluctuation of activation energy can be interpreted as a result of interactive reactions related to cellulose, hemicellulose and lignin degradation, occurred in the pyrolysis process. Based on TGA–FTIR analysis and model free integral kinetics method, the pyrolysis mechanism of PKS was elaborated in this paper
FEM Modelling of Lateral-Torsional Buckling Using Shell and Solid Elements
Valeš, Jan; Stan, Tudor-Cristian
2017-01-01
The paper describes two methods of FEM modelling of I-section beams loaded by bending moments. Series of random realizations with initial imperfections following the first eigenmode of lateral-torsional buckling were created. Two independent FEM software products were used for analyses of resista...... of resistance. At the end the difference and correlation between the results as well as advantages and disadvantages of both methods are discussed....
Effects of rotation on crystal settling in a terrestrial magma ocean: Spherical shell model
Maas, C.; Hansen, U.
2015-12-01
Like Moon or Mars, Earth experienced one or several deep magma ocean periods of globalextent in a later stage of its accretion. The crystallization of these magma oceans is of keyimportance for the chemical structure of Earth, the mantle evolution and the onset of platetectonics. Due to the fast rotation of early Earth and the small magma viscosity, rotationprobably had a profound effect on differentiation processes. For example, Matyska et al.[1994] propose that the distribution of heterogeneities like the two large low shear velocityprovinces (LLSVP) at the core mantle boundary is influenced by rotational dynamicsof early Earth. Further Garnero and McNamara [2008] suggest that the LLSVPs arevery long-living anomalies, probably reaching back to the time of differentiation andsolidification of Earth. However, nearly all previous studies neglect the effects of rotation.In our previous work using a Cartesian model, a strong influence of rotation as well asof latitude on the differentiation processes in an early magma ocean was revealed. Weshowed that crystal settling in an early stage of magma ocean crystallization cruciallydepends on latitude as well as on rotational strength and crystal density.In order to overcome the restrictions as to the geometry of the Cartesian model, we arecurrently developing a spherical model to simulate crystal settling in a rotating sphericalshell. This model will allow us not only to investigate crystal settling at the poles andthe equator, but also at latitudes in-between these regions, as well as the migration ofcrystals between poles and equator. ReferencesE. J. Garnero and A. K. McNamara. Structure and dynamics of earth's lower mantle.Science, 320(5876):626-628, 2008.C. Matyska, J. Moser, and D. A. Yuen. The potential influence of radiative heat transferon the formation of megaplumes in the lower mantle. Earth and Planetary ScienceLetters, 125(1):255-266, 1994.
Prediction of ratcheting behaviour of 304 SS cylindrical shell using the Chaboche model
Lee, Hyeong-Yeon; Kim, Jong Bum; Lee, Jae-Han; Yoo, Bong
1997-01-01
Ratcheting, that is, a progressive cyclic inelastic deformation can occur in a component subjected to thermal secondary stress, mechanical stress or both in the presence of a primary stress. The circumferential plastic strain may be accumulated with the increase of the number of cycles when a cylinder is subjected to a temperature front moving cyclically in the axial direction. This phenomenon of liquid surface induced thermal ratcheting is important in the design of liquid metal reactor. The ratcheting behaviour of a thin-walled 304 stainless steel cylinder under axially moving temperature distribution was analyzed using the constitutive theory of Chaboche. The constitutive model was implemented as a user subroutine of ABAQUS and it was verified through the comparison with the exact solutions for the uniaxial cyclic loading and test results available in the literature for the cylinder. In addition, ratcheting in pressurized push-pull pipes under loading conditions of ± 1% axial strain with steady hoop stress was analyzed with Chaboche model. It is shown that the elastic-plastic analysis using Chaboche model can evaluate properly the progressive strain accumulation under secondary cyclic loads. (author). 10 refs, 11 figs., 1 tab
Penner, Joyce E.; Andronova, Natalia; Oehmke, Robert C.; Brown, Jonathan; Stout, Quentin F.; Jablonowski, Christiane; van Leer, Bram; Powell, Kenneth G.; Herzog, Michael
2007-07-01
One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL.
Penner, Joyce E; Andronova, Natalia; Oehmke, Robert C; Brown, Jonathan; Stout, Quentin F; Jablonowski, Christiane; Leer, Bram van; Powell, Kenneth G; Herzog, Michael
2007-01-01
One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL
Ding, Wenjin; Lee, Seung Cheol; Li, Hui; Pfeifer, Peter; Dittmeyer, Roland [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Micro Process Engineering (IMVT)
2013-09-01
Until now, the main route for the production of DME from synthesis gas in industry is methanol synthesis on a metallic catalyst and subsequent dehydration of methanol on an acid catalyst (two-step process). A single-step process using bifunctional catalysts to perform the two steps simultaneously would be preferred e.g. due to thermodynamic considerations; but this is impeded by the higher volumetric heat release which may cause deactivation of the methanol synthesis catalyst function. Thus we propose to conduct the reaction in a microchannel reactor. However, in order to increase the productivity of the microchannel reactor and to lower the investment costs, we aim at a high selectivity and activity of the catalyst. The continuously removal of methanol by dehydration on an acidic ZSM-5 catalyst as shell improves the thermodynamic conditions of methanol synthesis in the CuO/ZnO/Al{sub 2}O{sub 3} core; thus, the synthesis gas conversion can be higher than that determined by the thermodynamics of pure methanol synthesis. The molecular sieving in the zeolite layer can further lead to higher selectivity of DME at milder reaction conditions. However, mass transport limitation of the synthesis gas to the catalyst core should not hinder the reaction, and therefore a more detailed investigation is required. In order to computer-aided optimize the catalyst structure and the operating conditions for core-shell catalysts, a simulation model should be developed to study the coupled reaction and transport processes in core-shell catalysts. In this simulation model the complicated interaction of diffusion and reaction in the zeolite layer (shell) must be detailed by a network model to describe its structure and the mechanisms effectively. In addition, suitable diffusion and kinetic models are required to describe the mass transport and reactions in the layer. Suitable networks, diffusion and kinetic models are discussed for 3D simulations in this contribution. (orig.)
Natural draft cooling tower with shell disconnected from the substructure
Diver, Marius
1982-01-01
The aim of this paper is the analysis of results of a research done by Electricite de France, concerning a new type of cooling tower. The traditional structure (i.e. a hyperbolic shell supported by X shaped or diagonal columns) is replaced by two independent structures: the shell, becoming a self-contained structure, the lower rim being stiffened by an annular beam; the substructure, resting on the soil. This new type of cooling tower has an improved thermal performance due to the increase of the area of air entrance. Bearing pads are provided between the lower ring beam of the shell and the substructure. Any differential settlement can be coped with by jacking. The water distribution structure can be laid out so as to benefit from advantages offered by the presence of the stiff ring and columns of the substructure [fr
Recent developments in anisotropic heterogeneous shell theory
Grigorenko, Alexander Ya; Grigorenko, Yaroslav M; Vlaikov, Georgii G
2016-01-01
This volume focuses on the relevant general theory and presents some first applications, namely those based on classical shell theory. After a brief introduction, during which the history and state-of-the-art are discussed, the first chapter presents the mechanics of anisotropic heterogeneous shells, covering all relevant assumptions and the basic relations of 3D elasticity, classical and refined shell models. The second chapter examines the numerical techniques that are used, namely discrete orthogonalization, spline-collocation and Fourier series, while the third highlights applications based on classical theory, in particular, the stress-strain state of shallow shells, non-circular shells, shells of revolution, and free vibrations of conical shells. The book concludes with a summary and an outlook bridging the gap to the second volume.
Configuration splitting and gamma-decay transition rates in the two-group shell model
Isakov, V. I.
2015-01-01
Expressions for reduced gamma-decay transition rates were obtained on the basis of the twogroup configuration model for the case of transitions between particles belonging to identical groups of nucleons. In practical applications, the present treatment is the most appropriate for describing decays for odd–odd nuclei in the vicinity of magic nuclei or for nuclei where the corresponding subshells stand out in energy. Also, a simple approximation is applicable to describing configuration splitting in those cases. The present calculations were performed for nuclei whose mass numbers are close to A ∼ 90, including N = 51 odd—odd isotones
Longhurst, M. J.; Quirke, N.
2006-11-01
We have previously shown that the upshift in the radial breathing mode (RBM) of closed (or infinite) carbon nanotubes in solution is almost entirely due to coupling of the RBM with an adsorbed layer of fluid on the nanotube surface. The upshift can be modeled analytically by considering the adsorbed fluid as an infinitesimally thin shell, which interacts with the nanotube via a continuum Lennard-Jones potential. Here we extend the model to include internally as well as externally adsorbed waterlike molecules, and find that filling the nanotubes leads to an additional upshift of two to six wave numbers. We show that using molecular dynamics, the RBM can be accurately reproduced by replacing the fluid molecules with a mean field harmonic shell potential, greatly reducing simulation times.
Gupta, Ravi; Gupta, Neha; Sharma, Suresh C.
2018-04-01
An analytical model to study the role of a metal catalyst nanofilm in the nucleation, growth, and resulting structure of carbon nanofibers (CNFs) in low-temperature hydrogen diluted acetylene plasma has been developed. The model incorporates the nanostructuring of thin catalyst films, growth of CNF, restructuring of catalyst nanoparticles during growth, and its repercussion on the resulting structure (alignment of rolled graphene sheets around catalyst nanoparticles) by taking into account the plasma sheath formalization, kinetics of neutrals and positively charged species in the reactive plasma, flux of plasma species onto the catalyst front surface, and numerous surface reactions for carbon generation. In order to examine the influence of the catalyst film on the growth of CNFs, the numerical solutions of the model equations have been obtained for experimentally determined initial conditions and glow discharge plasma parameters. From the solutions obtained, we found that nanostructuring of thin films leads to the formation of small nanoparticles with high surface number density. The CNF nucleates over these small-sized nanoparticles grow faster and attain early saturation because of the quick poisoning of small-sized catalyst particles, and contain only a few graphitic shells. However, thick nanofilms result in shorter CNFs with large diameters composed of many graphitic shells. Moreover, we found that the inclination of graphitic shells also depends on the extent up to which the catalyst can reconstruct itself during the growth. The small nanoparticles show much greater elongation along the growth axis and also show a very small difference between their tip and base diameter during the growth due to which graphitic shells align at very small angles as compared to the larger nanoparticles. The present study is useful to synthesize the thin and more extended CNFs/CNTs having a smaller opening angle (inclination angle of graphene layers) as the opening angle has a
Noritaka Shimizu
2016-02-01
Full Text Available We introduce a novel method to obtain level densities in large-scale shell-model calculations. Our method is a stochastic estimation of eigenvalue count based on a shifted Krylov-subspace method, which enables us to obtain level densities of huge Hamiltonian matrices. This framework leads to a successful description of both low-lying spectroscopy and the experimentally observed equilibration of Jπ=2+ and 2− states in 58Ni in a unified manner.
Mahidin Mahidin
2012-12-01
Full Text Available NOx and N2O emissions from coal combustion are claimed as the major contributors for the acid rain, photochemical smog, green house and ozone depletion problems. Based on the facts, study on those emissions formation is interest topic in the combustion area. In this paper, theoretical study by modeling and simulation on NOx and N2O formation in co-combustion of low-rank coal and palm kernel shell has been done. Combustion model was developed by using the principle of chemical-reaction equilibrium. Simulation on the model in order to evaluate the composition of the flue gas was performed by minimization the Gibbs free energy. The results showed that by introduced of biomass in coal combustion can reduce the NOx concentration in considerably level. Maximum NO level in co-combustion of low-rank coal and palm kernel shell with fuel composition 1:1 is 2,350 ppm, low enough compared to single low-rank coal combustion up to 3,150 ppm. Moreover, N2O is less than 0.25 ppm in all cases. Keywords: low-rank coal, N2O emission, NOx emission, palm kernel shell
Ana Tomé
2018-02-01
Full Text Available A research and development project has been conducted aiming to design and produce ultra-thin concrete shells. In this paper, the first part of the project is described, consisting of an innovative method for shape generation and the consequent production of reduced-scale models of the selected geometries. First, the shape generation is explained, consisting of a geometrically nonlinear analysis based on the Finite Element Method (FEM to define the antifunicular of the shell’s deadweight. Next, the scale model production is described, consisting of 3D printing, specifically developed to evaluate the aesthetics and visual impact, as well as to study the aerodynamic behaviour of the concrete shells in a wind tunnel. The goals and constraints of the method are identified and a step-by-step guidelines presented, aiming to be used as a reference in future studies. The printed geometry is validated by high-resolution assessment achieved by photogrammetry. The results are compared with the geometry computed through geometric nonlinear finite-element-based analysis, and no significant differences are recorded. The method is revealed to be an important tool for automatic shape generation and building scale models of shells. The latter enables the performing of wind tunnel tests to obtain pressure coefficients, essential for structural analysis of this type of structures.
Development of the α-decay theory of spherical nuclei by means of the shell model
Holan, S.
1978-01-01
The new results achieved within the α-decay theory of spherical nuclei with a (2)-(5) integral formula, unaffected by arbitrary parameters, taking into account the finite shape of the α particle and using a basis of Woods-Saxon uniparticle functions to describe initial and final nuclei, may be summarized as follows: Through α-width calculations performed for many spherical nuclei it has been proved that experimental classifying of α-transition into favoured and unfavoured transitions as well as the hyperfine structure of the transitions can be theoretically explained if considered the nucleon-nucleon correlations in the description of initial and final nuclei; The absolute values of the theoretical α-widths obtained are about 10 2 times smaller compared to the experimental ones. This might be due to an oversimplified approximation of the α-particle-daughter nucleus interaction potential or either to an inaccuracy of the model functions used in describing nucleus decay in the surface area. (author)
Quantitative cellular uptake of double fluorescent core-shelled model submicronic particles
Leclerc, Lara, E-mail: leclerc@emse.fr [Ecole Nationale Superieure des Mines, CIS-EMSE, LINA (France); Boudard, Delphine [LINA (France); Pourchez, Jeremie; Forest, Valerie [Ecole Nationale Superieure des Mines, CIS-EMSE, LINA (France); Marmuse, Laurence; Louis, Cedric [NANO-H S.A.S (France); Bin, Valerie [LINA (France); Palle, Sabine [Universite Jean Monnet, Centre de Microscopie Confocale Multiphotonique (France); Grosseau, Philippe; Bernache-Assollant, Didier [Ecole Nationale Superieure des Mines, CIS-EMSE, LINA (France); Cottier, Michele [LINA (France)
2012-11-15
The relationship between particles' physicochemical parameters, their uptake by cells and their degree of biological toxicity represent a crucial issue, especially for the development of new technologies such as fabrication of micro- and nanoparticles in the promising field of drug delivery systems. This work was aimed at developing a proof-of-concept for a novel model of double fluorescence submicronic particles that could be spotted inside phagolysosomes. Fluorescein isothiocyanate (FITC) particles were synthesized and then conjugated with a fluorescent pHrodo Trade-Mark-Sign probe, red fluorescence of which increases in acidic conditions such as within lysosomes. After validation in acellular conditions by spectral analysis with confocal microscopy and dynamic light scattering, quantification of phagocytosis was conducted on a macrophage cell line in vitro. The biological impact of pHrodo functionalization (cytotoxicity, inflammatory response, and oxidative stress) was also investigated. Results validate the proof-of-concept of double fluorescent particles (FITC + pHrodo), allowing detection of entirely engulfed pHrodo particles (green and red labeling). Moreover incorporation of pHrodo had no major effects on cytotoxicity compared to particles without pHrodo, making them a powerful tool for micro- and nanotechnologies.
Quadrupole moment of the 7/21- isomer state in 43S. Shell model study of sulfur isotopes around N=28
Chevrier, Raphael
2013-01-01
The goal of this work consists in providing new insights in the shape coexistence expected in neutron-rich nuclei around the N=28 shell closure. In 43 S, recent experimental data as well as their interpretation in the shell model framework were used to predict the coexistence between a J π =3/2 1 - prolate deformed ground state and a 7/2 1 - rather spherical isomer state. We report on the quadrupole moment measurement Q s of the 7/2 1 - isomer state [E*=320.5(5) keV, T 1/2 =415(3) ns] in 43 S. The TDPAD method was applied on 43 S nuclei produced by the fragmentation of a 48 Ca primary beam at 345 A.MeV, and selected in-flight through the BigRIPS spectrometer at RIKEN (Japan). The measured value, |Q s |=23(3) efm 2 , is in remarkable agreement with that calculated in the shell model framework, although it is significantly larger than that expected for a single-particle state. In order to understand the nature of the correlations responsible for the departure of the isomer state from a pure spherical shape, we report on the results of a shell model study using the modern SDPF-U interaction of the neighbors sulfur isotopes 42,44,46 S. Those calculations allowed to identify a slight triaxial degree of freedom in the structure of these nuclei, although the latter happens to be highly hindered at N=28 in 44 S. Spectroscopic factor calculations show that this slight triaxial degree of freedom also impacts the low-lying structure in 43 S. It allows to better understand the deviation of the spectroscopic quadrupole moment value of the isomer state from the limit case of a pure spherical state. (author) [fr
Mahadev, Sthanu
Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically
Carniato, S.; Selles, P.; Andric, L.; Palaudoux, J.; Penent, F.; Lablanquie, P.; Žitnik, M.; Bučar, K.; Nakano, M.; Hikosaka, Y.; Ito, K.
2015-01-01
We present in detail a theoretical model that provides absolute cross sections for simultaneous core-ionization core-excitation (K −2 V ) and compare its predictions with experimental results obtained on the water molecule after photoionization by synchrotron radiation. Two resonances of different symmetries are assigned in the main K −2 V peak and comparable contributions from monopolar (direct shake-up) and dipolar (conjugate shake-up) core-valence excitations are identified. The main peak is observed with a much greater width than the total experimental resolution. This broadening is the signature of nuclear dynamics
Ayoub, N.Y.
1980-02-01
The ground and some excited O + (J=O, T=O positive parity) energy levels of closed-shell nuclei are examined, in an oscillator basis, using matrix techniques. The effect of states outside the mixed (O+2(h/2π)ω). model space in 4 He (namely configurations at 4(h/2π)ω excitation) are taken into account by renormalization using the generalized Rayleigh-Schroedinger perturbation expressions for a mixed multi-configurational model space, where the resultant non-symmetric energy matrices are diagonalized. It is shown that the second-order renormalized O + energy spectrum is close to the corresponding energy spectrum obtained by diagonalizing the O+2+4(h/2π)ω 4 He energy matrix. The effect, on the ground state and the first few low-lying excited O + energy levels, of renormalizing certain parts of the model space energy matrix up to second order in various approximations is also studied in 4 He and 16 O. It is found that the low-lying O + energy levels in these various approximations behave similarly in both 4 He and 16 O. (author)
Kozinszky, Zoltan; Surányi, Andrea; Péics, Hajnalka; Molnár, András; Pál, Attila
2015-08-01
The aim of this study was to determine the utility of a new mathematical model in volumetric assessment of the placenta using 2-D ultrasound. Placental volumetry was performed in a prospective cross-sectional survey by virtual organ computer-aided analysis (VOCAL) with the help of a shell-off method in 346 uncomplicated pregnancies according to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. Furthermore, placental thickness, length and height were measured with the 2-D technique to estimate placental volume based on the mathematical formula for the volume of "the shell of the spherical sector." Fetal size was also assessed by 2-D sonography. The placental volumes measured by 2-D and 3-D techniques had a correlation of 0.86. In the first trimester, the correlation was 0.82, and later during pregnancy, it was 0.86. Placental volumetry using "the circle-shaped shell of the spherical sector" mathematical model with 2-D ultrasound technique may be introduced into everyday practice to screen for placental volume deviations associated with adverse pregnancy outcome. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.
Sargsyan, M M
1992-12-31
The effects of deeply bound nucleons are considered in the reaction of deuteron quasielastic electro disintegration, where the spectator nucleon and scattered electrons are registered in coincidence. Both, the off-shell influence on the description of nucleon motion in nuclear surrounding and the modification of deeply bound nucleon form - factors are investigated as two aspects of the off-shell effect manifestation. The possibility to control the extent of interacting nucleon binding energy by varying the spectator nucleon kinematic parameters (p{sub s},{theta}{sub s},{phi}{sub s}) is an advantage of the reactions considered. The cross section ratios of these processes are considered under specific kinematical conditions, which allow to investigate unambiguously the manifestations of deeply bound effects. To estimate the extent of the phenomena expected, we present the results of calculation of R ratios in the framework of models that take the off-shell effects into account differently. The effects of bound nucleon form - factor modification are estimated according to the model of mini delocalization, which predicts the bound nucleon swelling in nuclear environment. 28 refs.
Chee Zhou Kam
2013-01-01
Full Text Available A laminated composite plate element with an interface description is developed using the finite element approach to investigate the bending performance of two-layer cross-ply laminated composite plates in presence of a diagonally perturbed localized interfacial degeneration between laminae. The stiffness of the laminate is expressed through the assembly of the stiffnesses of lamina sub-elements and interface element, the latter of which is formulated adopting the well-defined virtually zero-thickness concept. To account for the extent of both shear and axial weak bonding, a degeneration ratio is introduced in the interface formulation. The model has the advantage of simulating a localized weak bonding at arbitrary locations, with various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. Numerical results show that the bending behavior of laminate is significantly affected by the aforementioned parameters, the greatest effect of which is experienced by those with a localized total interface degeneration, representing the case of local delamination.
Spin-1/2 Heisenberg antiferromagnet on the pyrochlore lattice: An exact diagonalization study
Chandra, V. Ravi; Sahoo, Jyotisman
2018-04-01
We present exact diagonalization calculations for the spin-1/2 nearest-neighbor antiferromagnet on the pyrochlore lattice. We study a section of the lattice in the [111] direction and analyze the Hamiltonian of the breathing pyrochlore system with two coupling constants J1 and J2 for tetrahedra of different orientations and investigate the evolution of the system from the limit of disconnected tetrahedra (J2=0 ) to a correlated state at J1=J2 . We evaluate the low-energy spectrum, two and four spin correlations, and spin chirality correlations for a system size of up to 36 sites. The model shows a fast decay of spin correlations and we confirm the presence of several singlet excitations below the lowest magnetic excitation. We find chirality correlations near J1=J2 to be small at the length scales available at this system size. Evaluation of dimer-dimer correlations and analysis of the nature of the entanglement of the tetrahedral unit shows that the triplet sector of the tetrahedron contributes significantly to the ground-state entanglement at J1=J2 .
Havasi, Ágnes; Kazemi, Ehsan
2018-04-01
In the modeling of wave propagation phenomena it is necessary to use time integration methods which are not only sufficiently accurate, but also properly describe the amplitude and phase of the propagating waves. It is not clear if amending the developed schemes by extrapolation methods to obtain a high order of accuracy preserves the qualitative properties of these schemes in the perspective of dissipation, dispersion and stability analysis. It is illustrated that the combination of various optimized schemes with Richardson extrapolation is not optimal for minimal dissipation and dispersion errors. Optimized third-order and fourth-order methods are obtained, and it is shown that the proposed methods combined with Richardson extrapolation result in fourth and fifth orders of accuracy correspondingly, while preserving optimality and stability. The numerical applications include the linear wave equation, a stiff system of reaction-diffusion equations and the nonlinear Euler equations with oscillatory initial conditions. It is demonstrated that the extrapolated third-order scheme outperforms the recently developed fourth-order diagonally implicit Runge-Kutta scheme in terms of accuracy and stability.
Miranda, Elder Assis; Batalha-Filho, Henrique; Congrains, Carlos; Carvalho, Antônio Freire; Ferreira, Kátia Maria; Del Lama, Marco Antonio
2016-01-01
The South America encompasses the highest levels of biodiversity found anywhere in the world and its rich biota is distributed among many different biogeographical regions. However, many regions of South America are still poorly studied, including its xeric environments, such as the threatened Caatinga and Cerrado phytogeographical domains. In particular, the effects of Quaternary climatic events on the demography of endemic species from xeric habitats are poorly understood. The present study uses an integrative approach to reconstruct the evolutionary history of Partamona rustica, an endemic stingless bee from dry forest diagonal in Brazil, in a spatial-temporal framework. In this sense, we sequenced four mitochondrial genes and genotyped eight microsatellite loci. Our results identified two population groups: one to the west and the other to the east of the São Francisco River Valley (SFRV). These groups split in the late Pleistocene, and the Approximate Bayesian Computation approach and phylogenetic reconstruction indicated that P. rustica originated in the west of the SFRV, subsequently colonising eastern region. Our tests of migration detected reduced gene flow between these groups. Finally, our results also indicated that the inferences both from the genetic data analyses and from the spatial distribution modelling are compatible with historical demographic stability.
Elder Assis Miranda
Full Text Available The South America encompasses the highest levels of biodiversity found anywhere in the world and its rich biota is distributed among many different biogeographical regions. However, many regions of South America are still poorly studied, including its xeric environments, such as the threatened Caatinga and Cerrado phytogeographical domains. In particular, the effects of Quaternary climatic events on the demography of endemic species from xeric habitats are poorly understood. The present study uses an integrative approach to reconstruct the evolutionary history of Partamona rustica, an endemic stingless bee from dry forest diagonal in Brazil, in a spatial-temporal framework. In this sense, we sequenced four mitochondrial genes and genotyped eight microsatellite loci. Our results identified two population groups: one to the west and the other to the east of the São Francisco River Valley (SFRV. These groups split in the late Pleistocene, and the Approximate Bayesian Computation approach and phylogenetic reconstruction indicated that P. rustica originated in the west of the SFRV, subsequently colonising eastern region. Our tests of migration detected reduced gene flow between these groups. Finally, our results also indicated that the inferences both from the genetic data analyses and from the spatial distribution modelling are compatible with historical demographic stability.
Nadrah, Peter, E-mail: peter.nadrah@zag.si [Slovenian National Building and Civil Engineering Institute, Dimičeva ul. 12, SI-1000 Ljubljana (Slovenia); Gaberšček, Miran [National Institute of Chemistry, Hajdrihova ul. 19, SI-1000 Ljubljana (Slovenia); Sever Škapin, Andrijana [Slovenian National Building and Civil Engineering Institute, Dimičeva ul. 12, SI-1000 Ljubljana (Slovenia)
2017-05-31
Highlights: • TiO{sub 2} encapsulated in mesoporous silica exhibits selective photocatalytic degradation of low-molecular-weight molecules. • Core@shell photocatalyst degrades rhodamine B in presence of fivefold mass concentration of starch, while pure TiO{sub 2} does not. • Potential use for removing water pollutants, while retaining non-harmful and beneficial macromolecules. - Abstract: Photocatalytic TiO{sub 2} degrades organic matter unselectively. However, in certain applications, such as degradation of pollutants, selectivity towards pollutants is beneficial. We synthesized core@shell TiO{sub 2}@SiO{sub 2} nanoparticles with photocatalytic activity featuring a significantly faster preferential degradation of model pollutant (rhodamine B) in presence of abundant concentration of natural organic matter compared to pure TiO{sub 2} (P25). The material’s photocatalytic activity was tested in aqueous medium. The selectivity of prepared effect of core@shell materials is explained based on transmission electron microscopy, nitrogen adsorption, X-ray powder diffraction and zeta potential measurements.
Damage and Fracture Model for Shell of PELE%PELE 弹丸壳体的损伤断裂模型
梁民族; 李翔宇; 覃金贵; 卢芳云; 王马法
2014-01-01
结合横向效应增强型侵彻体(PELE)侵彻金属靶板的数值模拟结果和实验结果，将PELE 弹丸壳体膨胀断裂过程分为加速膨胀和匀速膨胀两个阶段。在封加波提出的损伤度模型的基础上，推导得到 PELE 弹丸壳体的损伤断裂方程；并通过 PELE 壳体断裂实例计算了PELE 弹丸壳体膨胀断裂过程的参数，分析了弹丸着靶速度与壳体断裂之间的关系，为 PELE弹丸设计提供了理论指导。%Combining the simulation with the experimental results of the penetration process of pene-trator with enhanced lateral effect (PELE)in metallic target,the process of the shell expansion can be divided into two stages,the accelerating expansion and the uniform expansion.Based on the model of the damage function by Feng Jiabo,we obtained the damage and fracture evolution equation responsi-ble for the shell of PELE.According to the damage evolution equation responsible for the shell of PELE,the fracture process parameters of PELE were calculated.Moreover,the relationship between shell fracture critical strain and velocity of the projectile was analysised,which is useful in engineering design of PELE.
Ringwelski, S; Gabbert, U
2010-01-01
A recently developed approach for the simulation and design of a fluid-loaded lightweight structure with surface-mounted piezoelectric actuators and sensors capable of actively reducing the sound radiation and the vibration is presented. The objective of this paper is to describe the theoretical background of the approach in which the FEM is applied to model the actively controlled shell structure. The FEM is also employed to model finite fluid domains around the shell structure as well as fluid domains that are partially or totally bounded by the structure. Boundary elements are used to characterize the unbounded acoustic pressure fields. The approach presented is based on the coupling of piezoelectric and acoustic finite elements with boundary elements. A coupled finite element–boundary element model is derived by introducing coupling conditions at the fluid–fluid and fluid–structure interfaces. Because of the possibility of using piezoelectric patches as actuators and sensors, feedback control algorithms can be implemented directly into the multi-coupled structural–acoustic approach to provide a closed-loop model for the design of active noise and vibration control. In order to demonstrate the applicability of the approach developed, a number of test simulations are carried out and the results are compared with experimental data. As a test case, a box-shaped shell structure with surface-mounted piezoelectric actuators and four sensors and an open rearward end is considered. A comparison between the measured values and those predicted by the coupled finite element–boundary element model shows a good agreement