On numerical integration and computer implementation of viscoplastic models

Due to the stringent design requirement for aerospace or nuclear structural components, considerable research interests have been generated on the development of constitutive models for representing the inelastic behavior of metals at elevated temperatures. In particular, a class of unified theories (or viscoplastic constitutive models) have been proposed to simulate material responses such as cyclic plasticity, rate sensitivity, creep deformations, strain hardening or softening, etc. This approach differs from the conventional creep and plasticity theory in that both the creep and plastic deformations are treated as unified time-dependent quantities. Although most of viscoplastic models give better material behavior representation, the associated constitutive differential equations have stiff regimes which present numerical difficulties in time-dependent analysis. In this connection, appropriate solution algorithm must be developed for viscoplastic analysis via finite element method

A computer program for predicting nonlinear uniaxial material responses using viscoplastic models

A computer program was developed for predicting nonlinear uniaxial material responses using viscoplastic constitutive models. Four specific models, i.e., those due to Miller, Walker, Krieg-Swearengen-Rhode, and Robinson, are included. Any other unified model is easily implemented into the program in the form of subroutines. Analysis features include stress-strain cycling, creep response, stress relaxation, thermomechanical fatigue loop, or any combination of these responses. An outline is given on the theoretical background of uniaxial constitutive models, analysis procedure, and numerical integration methods for solving the nonlinear constitutive equations. In addition, a discussion on the computer program implementation is also given. Finally, seven numerical examples are included to demonstrate the versatility of the computer program developed

On the threshold-width of graphs

The GG-width of a class of graphs GG is defined as follows. A graph G has GG-width k if there are k independent sets N1,...,Nk in G such that G can be embedded into a graph H in GG such that for every edge e in H which is not an edge in G, there exists an i such that both endpoints of e are in Ni. For the class TH of threshold graphs we show that TH-width is NP-complete and we present fixed-parameter algorithms. We also show that for each k, graphs of TH-width at most k are characterized by a finite collection of forbidden induced subgraphs

Estimating Price Effects in an Almost Ideal Demand Model of Outbound Thai Tourism to East Asia

This paper analyzes the responsiveness of Thai outbound tourism to East Asian destinations, namely China, Hong Kong, Japan, Taiwan and Korea, to changes in effective relative price of tourism, total real total tourism expenditure, and one-off events. The nonlinear and linear Almost Ideal Demand (AID) models are estimated with monthly data to identify the price competitiveness and interdependencies of tourism demand for competing destinations in both long run (static) and short run error correction (dynamic) specifications. The homogeneity and symmetry restricted long run and short run AID models are estimated to calculate elasticities. The income elasticities, and the compensated and uncompensated own-price and cross-price elasticities, provide useful information for public and private tourism agents at the various destinations to maintain and improve price competitiveness. The empirical results show that price competitiveness is important for tourism demand for Japan, Korea and Hong Kong in the long run, and for Hong Kong and Taiwan in the short run. With regard to long run cross-price elasticities, the substitution effect can be found in the following pairs of destinations: China-Korea, Japan-Hong Kong, Taiwan-Hong Kong, Japan-Korea, and Taiwan-Korea. In addition to the substitution effect, the complementary effect can be found in the following pairs of destinations: China-Hong Kong, China-Japan, China-Taiwan, Japan-Taiwan, and Korea-Hong Kong. Contrary to the findings obtained from the long run AID specification, Japan-Korea and Taiwan-Korea are complements in the short run. Furthermore, the real total tourism expenditure elasticities indicate that China’s share of real total tourism expenditure is inelastic in response to a change in real total tourism expenditure, while Korea’s share of real total tourism expenditure is most sensitive to changes in expenditure in the long run. The greatest impact on the share of real total tourism expenditure in the short run is tourism demand for Taiwan.tourism demand;almost ideal Demand (AID) model;compensated prices;budget shares;complements;error correction;monthly frequency;price competitiveness;substitutes;uncompensated prices

IV Estimation of a Panel Threshold Model of Tourism Specialization and Economic Development

The significant impact of international tourism in stimulating economic growth is especially important from a policy perspective. For this reason, the relationship between international tourism and economic growth would seem to be an interesting and topical empirical issue. The purpose of this paper is to investigate whether tourism specialization is important for economic development in 159 countries over the period 1989-2008. The results from panel threshold regressions show a positive relationship between economic growth and tourism. Instrumental variable estimation of a threshold regression is used to quantify the contributions of tourism specialization to economic growth, while correcting for endogeneity between the regressors and error term. The significant impact of tourism specialization on economic growth in most regressions is robust to different specifications of tourism specialization, as well as to differences in real GDP measurement. However, the coefficients of the tourism specialization variables in the two regimes are significantly different, with a higher impact of tourism on economic growth found in the low regime. These findings do not change with changes in the threshold variables. The empirical results suggest that tourism growth does not always lead to substantial economic growth.panel data;instrumental variables;economic development;international tourism;tourism specialization;cross-sectional data;threshold regression

On a class of reductions of Manakov-Santini hierarchy connected with the interpolating system

Using Lax-Sato formulation of Manakov-Santini hierarchy, we introduce a class of reductions, such that zero order reduction of this class corresponds to dKP hierarchy, and the first order reduction gives the hierarchy associated with the interpolating system introduced by Dunajski. We present Lax-Sato form of reduced hierarchy for the interpolating system and also for the reduction of arbitrary order. Similar to dKP hierarchy, Lax-Sato equations for $L$ (Lax fuction) due to the reduction split from Lax-Sato equations for $M$ (Orlov function), and the reduced hierarchy for arbitrary order of reduction is defined by Lax-Sato equations for $L$ only. Characterization of the class of reductions in terms of the dressing data is given. We also consider a waterbag reduction of the interpolating system hierarchy, which defines (1+1)-dimensional systems of hydrodynamic type.Comment: 15 pages, revised and extended, characterization of the class of reductions in terms of the dressing data is give

Energy Spectra and Energy Correlations in the Decay H→ZZ→μ+μ−μ+μ−H\to ZZ\to \mu^+\mu^-\mu^+\mu^-

It is shown that in the sequential decay $H\to ZZ\to (f_1\bar{f_1})+ (f_2\bar{f_2})$, the energy distribution of the final state particles provides a simple and powerful test of the $HZZ$ vertex. For a standard Higgs boson, the energy spectrum of any final fermion, in the rest frame of $H$, is predicted to be $d\Gamma /dx\sim 1+\beta^4-2(x-1)^2$, with $\beta = \sqrt{1-4m^2_Z/m^2_H}$ and $1-\beta \le x=4E/m_H\le 1+\beta$. By contrast, the spectrum for a pseudoscalar Higgs is $d\Gamma /dx \sim \beta^2+(x-1)^2$. There are characteristic energy correlations between $f_1$ and $f_2$ and between $f_1$ and $\bar{f_2}$. These considerations are applied to the ``gold--plated'' reaction $H\to ZZ\to \mu^+\mu^-\mu^+\mu^-$, including possible effects of CP--violation in the $HZZ$ coupling. Our formalism also yields the energy spectra and correlations of leptons in the decay $H\to W^+W^-\to l^+\nu_ll^- \bar{\nu_l}$.Comment: 14 pages + 4 figure

Impurity scattering and Friedel oscillations in mono-layer black phosphorus

We study the effect of impurity scattering effect in black phosphorurene (BP) in this work. For single impurity, we calculate impurity induced local density of states (LDOS) in momentum space numerically based on tight-binding Hamiltonian. In real space, we calculate LDOS and Friedel oscillation analytically. LDOS shows strong anisotropy in BP. Many impurities in BP are investigated using $T$-matrix approximation when the density is low. Midgap states appear in band gap with peaks in DOS. The peaks of midgap states are dependent on impurity potential. For finite positive potential, the impurity tends to bind negative charge carriers and vise versa. The infinite impurity potential problem is related to chiral symmetry in BP