3,072 research outputs found
The ALE-method with triangular elements: direct convection of integration point values
The arbitrary Lagrangian-Eulerian (ALE) finite element method is applied to the simulation of forming processes where material is highly deformed. Here, the split formulation is used: a Lagrangian step is done with an implicit finite element formulation, followed by an explicit (purely convective) Eulerian step. The purpose of this study is to investigate the Eulerian step for quadratic triangular elements. To solve the convection equation for integration point values, a new method inspired by Van Leer is constructed. The new method is based on direct convection of integration point values without intervention of nodal point values.\ud
The Molenkamp test and a so-called block test were executed to check the performance and stability of the convection scheme. From these tests it is concluded that the new convection scheme shows accurate results. The scheme is extended to an ALE-algorithm. An extrusion process was simulated to test the applicability of the scheme to engineering problems. It is concluded that direct convection of integration point values with the presented algorithm leads to accurate results and that it can be applied to ALE-simulation
Few-cycle soliton propagation
Soliton propagation is usually described in the ``slowly varying envelope
approximation'' (SVEA) regime, which is not applicable for ultrashort pulses.
We present theoretical results and numerical simulations for both NLS and
parametric () ultrashort solitons in the ``generalised few-cycle
envelope approximation'' (GFEA) regime, demonstrating their altered
propagation.Comment: 4 pages, 4 figure
Model anionic block copolymer vesicles provide important design rules for efficient nanoparticle occlusion within calcite
Nanoparticle occlusion within growing crystals is of considerable interest because (i) it can enhance our understanding of biomineralization and (ii) it offers a straightforward route for the preparation of novel nanocomposites. However, robust design rules for efficient occlusion remain elusive. Herein, we report the rational synthesis of a series of silica-loaded poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(ethylene glycol dimethacrylate)-poly(methacrylic acid) tetrablock copolymer vesicles using polymerization-induced self-assembly. The overall vesicle dimensions remain essentially constant for this series; hence systematic variation of the mean degree of polymerization (DP) of the anionic poly(methacrylic acid) steric stabilizer chains provides an unprecedented opportunity to investigate the design rules for efficient nanoparticle occlusion within host inorganic crystals such as calcite. Indeed, the stabilizer DP plays a decisive role in dictating both the extent of occlusion and the calcite crystal morphology: sufficiently long stabilizer chains are required to achieve extents of vesicle occlusion of up to 41 vol %, but overly long stabilizer chains merely lead to significant changes in the crystal morphology, rather than promoting further occlusion. Furthermore, steric stabilizer chains comprising anionic carboxylate groups lead to superior occlusion performance compared to those composed of phosphate, sulfate, or sulfonate groups. Moreover, occluded vesicles are subjected to substantial deformation forces, as shown by the significant change in shape after their occlusion. It is also demonstrated that such vesicles can act as "Trojan horses", enabling the occlusion of non-functional silica nanoparticles within calcite. In summary, this study provides important new physical insights regarding the efficient incorporation of guest nanoparticles within host inorganic crystals
SUSY-QCD Effect on Top-Charm Associated Production at Linear Collider
We evaluate the contribution of SUSY-QCD to top-charm associated production
at next generation linear colliders. Our results show that the production cross
section of the process could be as large as 0.1
fb, which is larger than the prediction of the SM by a factor of .Comment: version to appear in PR
Risk Spillovers in Returns for Chinese and International Tourists to Taiwan
Fluctuations in the numbers of visitors directly affect the rates of return on tourism
business activities. Therefore, maintaining a firm grasp of the relationship between the
changes in the numbers of Chinese tourists and international travellers visiting Taiwan
is conducive to the formulation of an effective and practical tourism strategy. Although
the topic of international visitors to Taiwan is important, existing research has discussed
the issue of the travel demand between Chinese tourists and international travellers
visiting Taiwan. This paper is the first to examine the spillover effects between the rate
of change in the numbers of Chinese tourist arrivals and the rate of change in the
numbers of international traveller arrivals. Using daily data for Chinese tourists and
international travellers visiting Taiwan over the period from 1 January 2014 to 31
October 2016, together with the Diagonal BEKK model, the paper analyses the covolatility
spillover effects between the rate of change in the numbers of international
travellers and the rate of change in the numbers of Chinese tourists visiting Taiwan. The
empirical results show that there is no dependency relationship between the rate of
change in the numbers of Chinese tourists and the rate of change in the numbers of
international travellers visiting Taiwan. However, there is a significant negative covolatility
spillover effect between the rate of change in the numbers of Chinese tourists
and the rate of change in the numbers of international travellers. The empirical findings
suggest that Taiwan should abandon its development strategy of focusing only on a
single market, namely China, and to be pro-active in encouraging visits by international
travellers to Taiwan for sightseeing purposes, thereby increasing the willingness of
international travellers to visit Taiwan. Moreover, with the reduction in the numbers of
Chinese tour groups visiting Taiwan, and increases in the numbers of individual
travellers, the Taiwan Government should change its previous travel policies of mainly
attracting Chinese tour group travellers and actively promoting in-depth tourism among
international tourists, by developing tourism that focuses on the special characteristics
of different localities. In this way, the government can enhance the quality of Taiwanâs
tourism, and also attract travellers with high spending power
An Event Study of Chinese Tourists to Taiwan
The number of Chinese tourists visiting Taiwan has been closely related to the political relationship across the Taiwan Strait. The occurrence of political events and disasters or accidents have had, and will continue to have, a huge impact on the Taiwan tourism market. To date, there has been relatively little empirical research conducted on this issue.
In this paper, tourists are characterized as being involved in one of three types of tourism: group tourism (group-type), individual tourism (individual-type), and medical cosmetology (medical-type). We use McAleerâs (2015) fundamental equation in tourism finance to examine the correlation that exists between the rate of change in the number of tourists and the rate of return on tourism.
Second, we use the event study method to observe whether the numbers of tourists have changed abnormally before and after the occurrence of major events on both sides of the Strait. Three different types of conditional variance models, namely, GARCH (1,1), GJR (1,1) and EGARCH (1,1), are used to estimate the abnormal rate of change in the number of tourists. The empirical results concerning the major events affecting the changes in the numbers of tourists from China to Taiwan are economically significant, and confirm which types of tourists are most likely to be affected by such major events
What dictates the spatial distribution of nanoparticles within calcite?
Crystallization is widely used by synthetic chemists as a purification technique because it usually involves the expulsion of impurities. In this context, the efficient occlusion of guest nanoparticles within growing host crystals can be regarded as a formidable technical challenge. Indeed, although there are various reports of successful nanoparticle occlusion within inorganic crystals in the literature, robust design rules remain elusive. Herein, we report the synthesis of two pairs of sterically stabilized diblock copolymer nanoparticles with identical compositions but varying particle size, morphology, stabilizer chain length, and stabilizer chain surface density via polymerization-induced self-assembly (PISA). The mean degree of polymerization of the stabilizer chains dictates the spatial distribution of these model anionic nanoparticles within calcite (CaCO3): relatively short stabilizer chains merely result in near-surface occlusion, whereas sufficiently long stabilizer chains are essential to achieve uniform occlusion. This study reconciles the various conflicting literature reports of occluded nanoparticles being either confined to surface layers or uniformly occluded throughout the host matrix and hence provides important new insights regarding the criteria required for efficient nanoparticle occlusion within inorganic crystals
Some Applications of the Extended Bendixson-Dulac Theorem
During the last years the authors have studied the number of limit cycles of
several families of planar vector fields. The common tool has been the use of
an extended version of the celebrated Bendixson-Dulac Theorem. The aim of this
work is to present an unified approach of some of these results, together with
their corresponding proofs. We also provide several applications.Comment: 19 pages, 3 figure
The Local Velocity Anomaly
There is a velocity discontinuity at about 7 Mpc between the galaxies of the
Local Sheet that are moving together with low internal velocity dispersion and
the adjacent structures. The Local Sheet bounds the Local Void. The Local Sheet
is determined to have a peculiar velocity of 260 km/s away from the center of
the void. In order for this large velocity to be generated by an absence of
gravity, the Local Void must be at least 45 Mpc in diameter and be very empty.Comment: Invited review, "Galaxies in the Local Volume", Sydney, 8-13 July,
2007. eds. B. Koribalski & H. Jerjen, Astrophys. & Space Sci. Proceed. 10
pages with 7 figure
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