Shell Model

In-beam ␥-ray spectroscopy using fragmentation reactions of both stable and radioactive beams has been performed in order to study the structure of excited states in neutron-rich oxygen isotopes with masses ranging from A = 20 to 24. For the produced fragments, ␥-ray energies, intensities, and ␥-␥ coincidences have been measured. Based on this information new level schemes are proposed for 21,22 O up to the neutron separation energy. The nonobservation of any ␥-decay branch from 23 O and 24 O suggests that their excited states lie above the neutron decay thresholds. From this, as well as from the level schemes proposed for 21 O and 22 O, the size of the N = 14 and 16 shell gaps in oxygen isotopes is discussed in the light of shell-model calculations.

The time-dependent transition between a diabatic interaction potential in the entrance channel and an adiabatic potential during the fusion process is investigated within the two-center shell model. A large hindrance is obtained for the motion to smaller elongations of near symmetric dinuclear systems. The comparison of the calculated energy thresholds for the complete fusion in different relevant collective variables shows that the dinuclear system prefers to evolve in the mass asymmetry coordinate by nucleon transfer to the compound nucleus. q

Using a 58 Ni ( 46 Ti, α2n) reaction, a total of 24 different residual nuclei were identified. Among them were 98 Cd and 97 Ag. The level scheme of 98 Cd was extended to J π = (15 + ). An isomeric state at 6634 keV excitation energy was confirmed. This state decays by a 4207 keV transition feeding the known 8 + state. The level scheme of 97 Ag was also extended to J π = (33/2 + ) and the half-lives of two isomeric states were measured. Experimental energies of the excited states were compared with the results of ab initio shell-model calculations based on a realistic two-nucleon interaction.

The applications of the Shell model to modelling autoignition in gasoline and diesel engines are reported. The complexities of modelling autoignition in diesel sprays have been highlighted. In contrast to autoignition in gasoline engines, autoignition of diesel fuel sprays takes place at a wide range of equivalence ratios and temperatures. This makes it necessary to impose flammability limits to restrict the range of equivalence ratios in which the autoignition model is active. The autoignition chemical delay for n-dodecane is shown to be much less than the physical delay due to the droplet transit time, atomization, heating, evaporation and mixing. This enables the use of the less accurate but more computer efficient Shell model for diesel fuel chemical autoignition. Since experimental data for the chemical autoignition delay for ndodecane are not available, this study of the applicability of the Shell model to diesel fuels is based on data for n-heptane. The ignition time delays for premixed n-heptane predicted by calculations using the kinetic rate parameters corresponding to the primary reference fuel, RON70, show good agreement with experimental results when A f4 (preexponential factor in the rate of production of the intermediate agent) was chosen in the range between 3 × 10 6 and 6 × 10 6 . It is pointed out that the difference between the end-of-compression temperature, as predicted by the adiabatic law, and the actual end-of-compression temperature, taking into account the exothermic reactions at the end of compression, needs to be accounted for. The relation between the two temperatures is approximated by a linear function. It is considered that this approach can be extended to n-dodecane. ᭧ Fuel 78 (1999) 389-401 0016-2361/99/$ -see front matter ᭧ E.M. Sazhina et al. / Fuel 78 (1999) 389-401 390 Fig. 1. A comparison between the ignition delays calculated for primary reference fuels, RON90 and RON70, 0.9 stoichiometric mixtures using a CFD code and the experimental results reported by Halstead et al. [7].

Steel storage racks are three-dimensional framed structures fabricated from cold formed steel sections, wherein hook-in end connectors are used to make beam–column connections which are basically boltless and semi-rigid in nature. Different types of beam end connectors with different geometry of the connected members are available, making it impossible to develop a generalized analytical model. Only very few theoretical models are available to evaluate the performance of the joints for some typical connectors. More often experimental evaluation and numerical studies are needed to predict the behaviour of every different type of connectors. In the present study eighteen experiments were conducted on a commercially available pallet rack connection by varying the most influencing parameters such as thickness of the column, depth of the connector and the depth of the beam. The main objective of this work is to quantify the beam to column joint, flexibility of commonly used pallet rack frame and to develop a general Frye–Morris type/three parameter power model type moment versus relative rotation relationship. A companion finite element shell model that simulates the experimental behaviour closely is developed using ABAQUS finite element software, which is also used for further parametric studies. Using the three major variables as size parameters, a Frye–Morris type of equation has been proposed. Some calibration studies have also been carried out. Using the ultimate moment capacity, initial connection stiffness and the shape parameter obtained, a three parameter power model has also been proposed to represent the moment–rotation behaviour of the boltless connections.

The paper deals with the modelling of riveted joints in aircraft structures with Finite Element Method. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints, which will lead to an increase of the aircraft service life, a smaller number of inspections and lower operation costs of an aircraft. The project assumed FEM modelling of the operating aircraft 's structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various models, at global and local level, were presented and usefulness of them was discussed, influence of the following simplification was analysed; • neglection of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglection of contact phenomenon • neglection of secondary bending • neglection of residual stresses after riveting process The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analysed as well. The method of modelling residual stresses with temperature and thermal coefficient was used. In the second part, the example of analysis of riveted joint was demonstrated for a wing of PZL M28 Skytruck aircraft. It 's is a twin-engine, high-wing, cantilever monoplane of all-metal structure with maximum take-off and landing weight 7500 kg. A submodeling technique was used there. At first, part of the wing model, based on a CAD model, was built. It includes 7 ribs and 6 bulkheads between them. Dimensions of the model eliminate stress perturbation, connected with boundary conditions, in the area near the middle rib. It was a shell model. The boundary conditions were taken on a basis of operation data. Presence of rivets wasn't taken into account. Instead of this, parts were connected continuously (nodes were merged). The Linear model of material was used. The purpose of the part of the wing model was to gain accurate boundary conditions for next model of riveted joint on the middle rib. The behaviour of whole model is correct but stress distribution around rivets is not correct. A shell model of riveted joint was build. A boundary conditions were set on a basis of result from previous analysis. Forces, instead of displacements, were used, as boundary conditions, on account of a large stiffness difference between part models (part of wing and riveted joint model). The nonlinear model of material was used. A contact effect and secondary bending were taken into account. Thanks to that, phenomena around rivets were represented considerably better. Results from this analysis could be used as boundary conditions in a detailed calculation of one or few rivets with solid elements. Such a model was considered as well. The presented method allows to analyse phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN, NASTRAN and MARC software.

The last decade has witnessed both quantitative and qualitative progresses in Shell Model studies, which have resulted in remarkable gains in our understanding of the structure of the nucleus. Indeed, it is now possible to diagonalize matrices in determinantal spaces of dimensionality up to 10^9 using the Lanczos tridiagonal construction, whose formal and numerical aspects we will analyze. Besides, many new approximation methods have been developed in order to overcome the dimensionality limitations. Furthermore, new effective nucleon-nucleon interactions have been constructed that contain both two and three-body contributions. The former are derived from realistic potentials (i.e., consistent with two nucleon data). The latter incorporate the pure monopole terms necessary to correct the bad saturation and shell-formation properties of the realistic two-body forces. This combination appears to solve a number of hitherto puzzling problems. In the present review we will concentrate on those results which illustrate the global features of the approach: the universality of the effective interaction and the capacity of the Shell Model to describe simultaneously all the manifestations of the nuclear dynamics either of single particle or collective nature. We will also treat in some detail the problems associated with rotational motion, the origin of quenching of the Gamow Teller transitions, the double beta-decays, the effect of isospin non conserving nuclear forces, and the specificities of the very neutron rich nuclei. Many other calculations--that appear to have ``merely'' spectroscopic interest--are touched upon briefly, although we are fully aware that much of the credibility of the Shell Model rests on them.

This paper will explore the human factors involved in automated aircraft to include the SHEL model, human centered approach, situational awareness and fatigue.  These examples will show how inter related they can be and how they can affect flying whether its general aviation or in military drones.  As defined by the Federal Aviation Administration (FAA), Human Factors is a “multidisciplinary effort to generate and compile information about human capabilities and limitations and apply that information to equipment, systems, facilities, procedures, jobs, environments, training, staffing, and personnel management for safe, comfortable, and effective human performance ("Role of Human Factors," 2014, p. 1).  Aircraft automation is designed to improve the operation of flight systems as it provides an enhanced safety environment and more precise vehicle control.  The research will explore the potential hazard conditions during automated flight and the various potential obstacles to relying on automated conditions. 
Keywords: automation, SHEL model, human centered approach, situational awareness and fatigue

AN ATLAS OF [N ii] AND [O iii] IMAGES AND SPECTRA OF PLANETARY NEBULAE Arsen R. Hajian, 1 Steven M. Movit, 1, 2 Denis Trofimov, 1, 3 Bruce Balick, 4 Yervant Terzian, 5 Kevin H. Knuth, 6, 7 Domhnull Granquist-Fraser, 8 Karen A. Huyser, 9 Andre Jalobeanu, 10 ...

We outline two complementary approaches based on the no core shell model (NCSM) and present recent results. In the ab initio approach, nuclear properties are evaluated with two-nucleon (NN) and three-nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of the TNI generates good descriptions of light nuclei. In a second effort, an ab exitu approach, results are obtained with a realistic NN interaction derived by inverse scattering theory with off-shell properties tuned to fit light nuclei. Both approaches produce good results for observables sensitive to spin-orbit properties.

Magnetic properties of antiferromagnetic ͑AFM͒ Cr 2 O 3 nanoparticles have been studied as a function of the nanoparticle size. The synthesized nanoparticles present an ellipsoidal shape with the major axis of approximately 170 nm and the minor axis that increases with the synthesis temperature from 30 to 70 nm. By magnetization and electron paramagnetic resonance experiments, we have obtained the parameters that characterize the AFM nanoparticles system. We have found that the Néel temperature, T N , and the spin-flop field, H SF , increase with the particle size from T N = 288 K and H SF ͑5 K͒ = 10 kOe for the smaller nanoparticles and approach the bulk values ͓T N = 308 K and H SF ͑5 K͒ =60 kOe͔ for the larger particles. From the experimental results and the molecular-field theory applied to AFM coupled sublattices, we estimated the magnetic anisotropy, K, and the molecular-field constant, , as a function of the Cr 2 O 3 nanoparticle size. When the size is reduced, only diminishes ϳ8% with respect to its bulk value ͑4.9ϫ 10 4 Oe 2 g / erg͒; instead, K decreases more than an order of magnitude from K = 3.8ϫ 10 4 to 8.7ϫ 10 2 erg/ g. We analyzed the results on the basis of a core shell model where the nanoparticle internal order consists of an antiferromagnetically ordered core and a disordered surface shell, which presents a frustrated magnetic state.

The development of deformation and shape coexistence in the vicinity of doubly-magic 48 Ca, related to the weakening of the N = 28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive 44 Ar beam from the SPIRAL facility at GANIL. The 2 + 1 and 2 + 2 states in 44 Ar were excited on 208 Pb and 109 Ag targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 2 + 1 state were extracted from the differential Coulomb excitation cross sections, indicating prolate shape of the 44 Ar nucleus, and giving evidence for an onset of deformation already two protons and two neutrons away from doubly-magic 48 Ca. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for 44 Ar and neighboring nuclei using two different approaches: the angular-momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to the shell model and to relativistic mean field calculations. The new results give insight into the weakening of the N = 28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

Backbending properties of well-deformed (beta 0.25) nuclei at high spin are often described in terms of the Cranked Shell Model (CSM) [1]. However, weakly deformed and transitional N = 57 isotones around A 100 nuclei provide an excellent testing ground for the limits of the CSM approach, since these nuclei can be adequatley described at low spins as anharmonic vibrators [2,3]. With increasing spins however, alignment processes associated with rotational motion are obserbed, specifically assoated with crossing a a broken (h11/2) neutron pair. Somewhat paradoxically, the Coriolis effects which are associated with alignment processes in deformed nuclei are largest in systems with small deformations (beta0.15), and as such, nuclei in this region make excellent laboratories for probing the interface between vibrational and rotation motion [2-4]. In the current study [5], the near-yrast states of 101Ru were investigated via the fusion-evaporation reaction 96Zr(9Be,4n)101Ru at a beam energ...

Mineral carbonation is based on the reaction of carbon dioxide with metal-oxide bearing minerals, usually containing magnesium or calcium silicate, to form hardly soluble carbonates and other solid byproducts. The concept is based on acceleration of the naturally occurring rock weathering process. In the present work the calcium silicate is present in the mineral, wollastonite. To accelerate the process and make it potentially useful for practical applications, mineral carbonation is conducted here using an indirect two-step route in which the reactive component (Ca 2+ ions in considered case) is first extracted from the mineral matrix and afterwards carbonated. Two solid byproducts are formed in this process: silica in the extraction step and calcium carbonate in the carbonation step. In the experimental part of this work, both stages of mineral carbonation are investigated using three extraction media: acetic acid and two dicarboxylic acids, succinic and adipic. To interpret the extraction stage of the mineral carbonation process the shrinking core -shrinking shell model is proposed. In the model, the change of the unreacted core size is due to surface reaction that is affected by the porous layer diffusion, with the porous layer subject to abrasion. The model of abrasion is based on the theory of turbulence. Results of investigations show that succinic acid is most effective, followed by adipic acid and acetic acid when both stages of the process are considered in detail.

This paper presents a unified formulation for the modelling of doubly curved composite shell structures. Via this approach, higher-order, zig-zag, layer-wise and mixed theories can be easily formulated. Classical theories, such as Love’s and Mindlin’s models, can be obtained as particular cases. The governing differential equations of the static linear problem are derived in a compact general form, tackling the difficulties due to the higher than classical terms. These equations are solved via a Navier-type, closed form solution. Shells are subjected to distributed and localised loadings. Displacement and stress fields are investigated. Thin and moderately thick as well as shallow and deep shells are accounted for. Several stacking sequences are considered. Conclusions are drawn with respect to the accuracy of the theories for the considered loadings, lay-outs and geometrical parameters. The importance of the refined shell models for describing accurately the three-dimensional stress state is outlined. The proposed results might be useful as benchmark for the validation of new shell theories and finite elements.

Thin solar sail membranes of very large span are being envisioned for near-term space missions. One major design issue that is inherent to these very flexible structures is the formation of wrinkling patterns. Structural wrinkles may deteriorate a solar sail's performance and, in certain cases, structural integrity. In this paper, a geometrically nonlinear, updated Lagrangian shell formulation is employed using the ABAQUS finite element code to simulate the formation of wrinkled deformations in thin-film membranes. The restrictive assumptions of true membranes, i.e. Tension Field theory (TF), are not invoked. Two effective modeling strategies are introduced to facilitate convergent solutions of wrinkled equilibrium states. Several numerical studies are carried out, and the results are compared with recent experimental data. Good agreement is observed between the numerical simulations and experimental data.

The phenomenon of shape coexistence is discussed within the self-consistent Hartree-Fock method and the nuclear shell model. The occurrence of the coexisting configurations with different intrinsic shapes is traced back to the properties of the effective Hamiltonian.

In this work, Si quantum dots in SiO 2 /Si 3 N 4 hybrid matrix on quartz substrates were synthesized by magnetron sputtering of alternating silicon rich oxide and Si 3 N 4 layers followed by different postdeposition anneals. XRD results indicate that the average dimension of the Si nanocrystals varies from 1.6 to 5.2 nm. The size and crystallization of the Si nanocrystals are dependent on a number of factors, including the annealing method, the SRO thickness and the Si 3 N 4 barrier thickness, as evidenced in XRD and Raman measurements. In particular, thicker Si 3 N 4 barrier layers seem to be able to suppress the growth of Si nanocrystals more effectively. PL measurements suggest the apparent bandgap of the samples investigated in this work is in the range 1.12-1.67 eV, which demonstrates the effect of quantum confinement. More interestingly, analysis of the PL data using the modified EMA equations clearly suggests that the PL peak energy not only depends on the size of the nanocrystals but also gets affected by other details in nanocrystal growth. A tentative core-shell model is constructed to illustrate our explanation. These findings offer a preliminary understanding of the nanocrystal growth and radiative recombination processes in this newly synthesized material for photovoltaic applications.

This work reviews foundations and applications of the complex-energy continuum shell model that provides a consistent many-body description of bound states, resonances, and scattering states. The model can be considered a quasi-stationary open quantum system extension of the standard configuration interaction approach for well-bound (closed) systems.

The purposes of this study were to determine if there were differences in the frictional torque generated between spherical acetabular shells and acetabular shells deformed as a result of implantation and to evaluate how changes in polyethylene insert thickness and head diameter affected these frictional torque data. An established bench top model was used for mechanical testing. A total of 70 samples were tested. Acetabular shells were impacted into polyurethane foam that was designed to create spherical or deformed shell models. We found that deformed acetabular shells produced higher frictional torque than spherical shells. Also, larger femoral head sizes produced greater frictional torque than smaller femoral head sizes. For the deformed models, the thicker polyethylene inserts produced greater frictional torque than the thinner polyethylene inserts.

The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn, was investigated at the GSI on-line mass separator by using an array of germanium and silicon detectors. On the basis of a βγ γ coincidence measurement, the previously reported decay scheme has been considerably improved and evidence is presented for a spin-gap isomer with a spin-parity assignment of (21 + ), i.e., the highest spin ever observed in β decay. The half-life of the low-spin isomer (7 + ) was remeasured to be 0.59(2) s, whereas the half-life of the high-spin isomer was determined as 0.47(8) s. For the states in 94 Ag and 94 Pd, large-scale shell-model calculations that include up to 4p-4h excitations across the N = Z = 50 shell gap and employ a realistic interaction were carried out. These core excitations play a crucial role in generating the E4 isomerism required for the interpretation of the long half-life of the (21 + ) state in 94 Ag.

The band structures of the doubly odd '"Pr nucleus has been investigated via the '19Sn( 19F,4n) 'j4Pr and "'Pd( "Si,p3n) lWPr reactions at beam energies of 87 and 130 MeV, respectively. The three previously known rotational bands based on the 7r[541]3/2-(a=?~l/2)@~[514]9/2-and ~[413]5/2+@~[514]9/2-configurations have been extended to higher spins. The difference of M 2ti in the experimental alignment of the bands based on the signature partners of the [ 541]3/2-h11j2 proton orbital is discussed in terms of shape coexistence and coupling with the y-phonon but no consistent interpretation can be found. A new band consisting of quadrupole transitions has also been identified and linked unambiguously to the low-lying levels of the yrast band. Total routhian surface and cranked shell model calculations suggest a ( rrhll/:! )3&W [ 530 ] l/2-configuration for this band. The experimental ratios of reduced transition probabilities B(M1) lB(E2) of the various rotational structures are compared to the theoretical values obtained from a semiclassical model and from the two-particle plus triaxial-rotor model. Nuclear reactions '19Sn( 19F,4n), E = 87 MeV, 110Pd(2sSi,p3n), E = 130 MeV, measured E,, I,, DC0 ratios, W-coincidence, y-multiplicity. 134Pr deduced levels, J, ?r, y-branching, B(A) ratios, experimental routbians, aligned angular momenta. Enriched targets, HPGe detectors, BGO suppression shields, 4?r-BGO ball. Total routhian surface calculations, comparison with cranked shell model, semiclassical model and two-particle plus triaxial-rotor calculations.

We discuss a theoretical formulation of shell model accounting for through-the-thickness stretching, which allows for large deformations and direct use of 3d constitutive equations. Three different possibilities for implementing this model within the framework of the finite element method are examined: one leading to 7 nodal parameters and the remaining two to 6 nodal parameters. The 7-parameter shell model with no simplification of kinematic terms is compared to the 7-parameter shell model which exploits usual simplifications of the Green–Lagrange strains. Two different ways of implementing the incompatible mode method for reducing the number of parameters to 6 are presented. One implementation uses an additive decomposition of the strains and the other an additive decomposition of the deformation gradient. Several numerical examples are given to illustrate performance of the shell elements developed herein.

Heavy neutron-rich nuclei were populated via the fragmentation of a E/A = 1 GeV 208 82 Pb beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed γ rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. The newly discovered isomers are in 74 W, and 189 73 Ta. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as well as BCS calculations were performed.

Nuclear binding energies and two-neutron separation energies are analysed starting from the liquid-drop model and the nuclear shell model in order to describe the global trends of the above observables. We subsequently concentrate on the Interacting Boson Model (IBM) and discuss a new method in order to provide a consistent description of both, ground-state and excitedstate properties. We address the artefacts that appear when crossing midshell using the IBM formulation and perform detailed numerical calculations for nuclei situated in the 50−82 shell. We also concentrate on local deviations from the above global trends in binding energy and two-neutron separation energies that appear in the neutron-deficient Pb region. We address possible effects on the binding energy, caused by mixing of low-lying 0 + intruder states into the ground state, using configuration mixing in the IBM framework. We also study ground-state properties using a macroscopic-microscopic * Postdoctoral fellow of the Fund for Scientific Research-Flanders (Belgium). † Visiting postdoctoral fellow of the Fund for Scientific Research-Flanders (Belgium). 1 model. Detailed comparisons with recent experimental data in the Pb region are amply discussed.

The nucleus 49 Cr has been studied analysing γ − γ coincidences in the reaction 46 Ti(α,n) 49 Cr at the bombarding energy of 12 MeV. The level scheme has been greatly extended at low excitation energy and several new lifetimes have been determined by means of the Doppler Shift Attenuation Method.

High-spin states in the nucleus 102 Ru have been investigated via the 96 Zr( 13 C,α3n) reaction at beam energies of 51 and 58 MeV, using the Euroball IV γ-ray spectrometer and the Diamant charged particle array. Several new high-spin bands have been established. The ground state band has been extended up to Ex ∼12 MeV with I π =(26 + ), while the previously published negative-parity bands have been extended up to Ex ∼11 and ∼9 MeV with I π =(23 − ) and (20 − ), respectively. The deduced high-spin structure has been compared with Woods-Saxon trs calculations and, on the basis of the measured Routhians, aligned angular momenta, and B(M 1)/B(E2) ratios, νh 11/2 (g 7/2 , d 5/2 ) configurations are suggested for the negative-parity structures.

30 Ž . 31 The reaction Si d,p Si is studied at the incident deuteron energy of 12.3 MeV. Proton groups are analysed using a multi-angle magnetic spectrograph with the resolving power ErDE f 1000. Angular distributions of proton groups corresponding to 14 bound states and to 8 unbound states of the 31 Si nucleus are analysed using DWBA calculations. Deduced transferred orbital angular momenta and spectroscopic factors differ for some states from those obtained previously. In particular, we attribute l s 1 transfer to the state at 5.281 MeV. Shell-model calculations are performed in a complete 0" v model space for positive-parity states and in a restricted 1" v model space including f 7r2, p3r2 and p1r2 neutron orbits for negative-parity states. The excitation energies as well as spectroscopic strengths of most of strongly excited positive-and negative-parity states are reasonably well interpreted within the shell model. q

Modeling transient-dynamics of electronic assemblies is a multiscale problem requiring methodologies which allow the capture of layer dimensions of solder interconnects, pads, and chip-level interconnects simultaneously with assembly architecture and rigid-body motion. Computational effort needed to attain fine mesh to model chip interconnects while capturing the system-level dynamic behavior is challenging. Product-level testing depends heavily on experimental methods and is influenced by various factors such as the drop height, orientation of drop, and variations in product design. Modeling and simulation of integrated circuit (IC) packages are very efficient tools for design analysis and optimization. Previously, various modeling approaches have been pursued to predict the transient dynamics of electronics assemblies assuming symmetry of the electronic assemblies. In this paper, modeling approaches to predict the solder joint reliability in electronic assemblies subjected to high mechanical shocks have been developed. Two modeling approaches are proposed in this paper to enable life prediction under both symmetric and anti-symmetric transient-deformation. In the first approach, drop simulations of printed circuit board assemblies in various orientations have been carried out using beam-shell modeling methodologies without any assumptions of symmetry. This approach enables the prediction of full-field stress-strain distribution in the system over the entire drop event. Transient dynamic behavior of the board assemblies in free and JEDEC drop has been measured using high-speed strain and displacement measurements. Relative displacement and strain histories predicted by modeling have been correlated with experimental data. Failure data obtained by solder joint array tensile tests on ball grid array packages is used as a failure proxy to predict the failure in solder interconnections modeled using Timoshenko beam elements in the global model. In the second approach, cohesive elements have been incorporated in the local model at the solder joint-copper pad interface at both the printed circuit board (PCB) and package side. The constitutive response of the cohesive elements was based on a traction-separation behavior derived from fracture Manuscript

The nucleon-nucleon interaction is constructed by means of the J-matrix version of inverse scattering theory. Ambiguities of the interaction are eliminated by postulating tridiagonal and quasi-tridiagonal forms of the potential matrix in the oscillator basis in uncoupled and coupled waves, respectively. The obtained interaction is very accurate in reproducing the N N scattering data and deuteron properties. The interaction is used in the no-core shell model calculations of 3 H and 4 He nuclei. The resulting binding energies of 3 H and 4 He are very close to experimental values.

Accurate prediction of springback is essential for the design of tools used in automotive sheet stamping operations. The plane strain stretch/draw operation presents a complex form of springbaek occurring in sheet metal forming since the sheet undergoes stretching, bending and unbending deformations. The two-dimensional draw bending is an example of such an operation in which the complex stress-strain states in the sheet cause the formation of side wall curls after the sheet is allowed to unload. Accurate prediction of the side wall curl requires using finite element shell models which can account for curvature and through-thickness stresses caused by bending and unbending of the sheet. Since such models are generally slow and expensive to use, an alternative and efficient method of predicting side wall curls will be desirable. This paper describes a novel and robust method for predicting springback in general and side wall curls in the two-dimensional draw bending operation as a special case, using moment-curvature relationships derived for sheets undergoing plane strain stretching, bending and unbending deformations. This model modifies a membrane finite element solution to calculate through-thickness strains and stresses and springback. Accuracy of this model's predictions are verified by comparisons with finite element (ABAQUS) and experimental results. x,y Z C R k n K t W 0, g (7 v r E T M Subscripts C n B UB 0 T mem

We present the room temperature far-infrared reflectivity and Raman scattering spectra of NaV 2 O 5 single crystals. The frequencies of infrared active modes are obtained by an oscillator fitting procedure of reflectivity data. The assignment of the vibrational modes is given according to a lattice dynamical calculation based on the valence shell model. Besides phonon modes we observed broad features centered at about 280, 550 and 3500 cm Ϫ1 in infrared spectra for E k a polarization and at about 640 cm Ϫ1 in Raman spectra for (aa) polarization. These structures are explained as crystal-field-splitting-induced d-d electronic transitions of V 4ϩ ions. ᭧

In this work we consider the geometrically exact shell model subjected to ÿnite rotations, making use of rotation vector parameters for handling the corresponding constrained rotation for smooth shells. A modiÿcation of such a parameterization which is based on the incremental rotation vector and thus capable of avoiding the singularity problem is also discussed. Copyright ? 2001 John Wiley & Sons, Ltd.

A -decaying high-spin isomer in 96 Cd, with a half-life T 1=2 ¼ 0:29 þ0:11 À0:10 s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of 124 Xe on a 9 Be target. From the half-life and the observed decays in the daughter nucleus, 96 Ag, we conclude that the -decaying state is the long predicted 16 þ ''spin-gap'' isomer. Shell-model calculations, using the Gross-Frenkel interaction and the ðp 1=2 ; g 9=2 Þ model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N ¼ Z ¼ 50 gaps and the Gamow-Teller strength, BðGTÞ distributions have been studied via large-scale shell-model calculations using the ðg; d; sÞ model space to compare with the experimental BðGTÞ value obtained from the half-life of the isomer.

Electron scattering form factors from 12 C have been studied in the framework of the particle-hole shell model. Higher configurations are taken into account by allowing particle-hole excitations from the 1s and 1p shells core orbits up to the 1f -2p shell. The inclusion of the higher configurations modifies the form factors markedly and describes the experimental data very well in all momentum transfer regions.

Future Satellite Based Navigation Systems based on GPS, like US Wide Area Augmentation Sysytem (WAAS), are of global interest to the scientific community. Precise estimation of ionospheric delay is most crucial for successful implementation of the systems. Due to the complex ionospheric structure and large variation of Total Electron Content (TEC) in low latitudes, it is necessary to compare and validate the efficiency of the existing algorithms in this region. In this study, performances of the various interpolation algorithms for TEC calculation at ionospheric grid point (IGP) and user position for gridbased Single Shell Model have been tested for 72 test days of 2005. Based on the results obtained from this analysis, it has been found that, for the Indian region, it would be more suitable to use Ordinary Kriging in place of Planar Fit to estimate delay at an IGP (as used by US WAAS). It has also been found that Ordinary Kriging performs better than the Bilinear Interpolation technique at the user end.

In the U.S. Wide Area Augmentation System, European Geostationary Navigation Overlay Service, and Indian Global Positioning System Aided Geo Augmented Navigation, a near real-time grid-based single-shell model is proposed to correct the ionospheric delay at the user aircrafts. The single-shell model is based on the assumption that the whole ionosphere is compressed at a fixed altitude at 350 km. This assumption may not be appropriate for the Indian region, which falls in the Equatorial Ionospheric Anomaly belt. In this paper, a two-shell model which incorporates two different shells, at 300-and 500-km altitudes, having different weights at different time domains has been implemented. A statistical comparison between single-and two-shell models has been done for all quiet days of year 2005. Based on the results, it is observed that there is at least 60% improvement in the performance of the two-shell model in comparison to the single-shell model for the Indian region.

Molecular dynamics simulations of pure silica, sodium silicate, and soda-lime silicate glasses have been carried out using a developed potential that includes polarization effects through the shell model ͑SM͒. The potential has been validated using available experimental and ab initio structural data, such as density, radial and angular distributions, coordination environments, and network connectivity. In addition, Car-Parrinello molecular dynamics simulations of the soda-lime silicate glass have been carried out to obtain reference data for this system. The performances of the SM and of a rigid-ion potential have been compared with experimental and ab initio data, showing that the inclusion of polarization effects improves the description of the intertetrahedral structure and of the local environment surrounding modifier Na and Ca cations; significant improvements are also obtained in the Q n distribution of the sodium silicate glass. This shows that the inclusion of polarization effects in the potential, even at the approximate level of the shell model, is essential for a reliable modeling of modified bulk glasses. Moreover, the accurate reproduction of the glass density and the direct representation of polarization effects are important requisites that should enable the application of the potential to molecular dynamics simulations of modified glass surfaces.

The single-particle structure and shell gap of 100 Sn as inferred from previous in-beam γ-ray spectroscopy has been confirmed in recent studies of seniority and spin-gap isomers by γγ, βγ, βpγ, pγ and 2pγ spectroscopy. The results for 94,95 Ag, 98 Cd and its N = 50 isotones 96 Pd and 94 Ru stress the importance of large-scale shell model calculations employing realistic interactions for the isomerism, np-nh excitations, seniority mixing and E2 polarisation of the 100 Sn core. The strong monopole interaction of the ∆l = 0, 1 spin/isospin-flip partners πg 9/2 -νg 7/2 along the N = 50 isotones and the πf 5/2 -νg 9/2 pair of nucleons along the Z = 28 Ni isotopes are decisive for the evolution of the shell structure towards 100 Sn and 78 Ni. It can be traced back to the tensor force in the effective nucleon-nucleon interaction and provides a straightforward explanation for new shells in neutron-rich light nuclei, implying qualitative predictions for new N = 32, 34 subshells in Ca isotopes, persistence of the 78 Ni proton and neutron shell gaps and non-equivalence of the g 9/2 valence mirror Ni isotopes and N = 50 isotones. This is corroborated by recent experimental data on 56,58 Cr and 70-76 Ni. The implication of monopole driven shell evolution for apparent spin-orbit splitting towards N Z and structure along the astrophysical r-path between N = 50 and N = 82 is discussed.