Finite element analysis of stress distribution and the effects of geometry in a laser-generated single-stage ceramic tile grout seal using ANSYS

Optimisation of the geometry (curvature of the vitrified enamel layer) of a laser-generated single-stage ceramic tile grout seal has carried out with a finite element (FE) model. The overall load bearing capacities and load-displacement plots of three selected geometries were determined experimentally by the indentation technique. Simultaneously, a FE model was developed utilising the commercial ANSYS package to simulate the indentation. Although the load-displacement plots generated by the FE model consistently displayed stiffer identities than the experimentally obtained results, there was reasonably close agreement between the two sets of results. Stress distribution profiles of the three FE models at failure loads were analysed and correlated so as to draw an implication on the prediction of a catastrophic failure through an analysis of FE-generated stress distribution profiles. It was observed that although increased curvatures of the vitrified enamel layer do enhance the overall load-bearing capacity of the single-stage ceramic tile grout seal and bring about a lower nominal stress, there is a higher build up in stress concentration at the apex that would inevitably reduce the load-bearing capacity of the enamel glaze. Consequently, the optimum geometry of the vitrified enamel layer was determined to be flat

Satellite Structure In Laser-assisted Charge-transfer Cross Sections

A six-state coupled-channel calculation has been performed on the laser-assisted charge-transfer collision H++Na+Latin small letter h with stroke. A greatly enhanced charge-transfer cross section is observed for low-energy collisions if the photon energy is matched to the classical satellite frequency. This frequency is determined by the location of an extremum in the difference of potential energies between the laser-pumped initial and final molecular states. The stationary-phase method has been used to reproduce the general features and the magnitude of the cross-section structure. © 1985 The American Physical Society

Optimal logistics planning for modular construction using two-stage stochastic programming

The construction sector is currently undergoing a shift from stick-built construction to modular building systems that take advantage of modern prefabrication techniques. Long established in-situ construction practices are thus being replaced by processes imported from the manufacturing sector, where component fabrication takes place within a factory environment. As a result of this transformation, current construction supply chains, which have focused on the delivery of raw materials to sites, are no longer apt and need to make way to new, strengthened, and time-critical logistics systems. The aim of this study is to establish a mathematical model for the optimisation of logistics processes in modular construction covering three tiers of operation: manufacturing, storage and assembly. Previous studies have indicated that construction site delays constitute the largest cause of schedule deviations. Using the model outlined in this paper we seek to determine how factory manufacturing and inventory management should react to variations in the demand on construction sites. A two-stage stochastic programming model is developed to capture all possible demand variations on site. The model is evaluated using a case study from the residential construction sector. The application shows that the model is effective and can serve as decision support to optimise modular construction logistics

Rational Approximate Symmetries of KdV Equation

We construct one-parameter deformation of the Dorfman Hamiltonian operator for the Riemann hierarchy using the quasi-Miura transformation from topological field theory. In this way, one can get the approximately rational symmetries of KdV equation and then investigate its bi-Hamiltonian structure.Comment: 14 pages, no figure

The Development and Impact of the Quality Assurance System on Higher Education in Taiwan

The purpose of this thesis is to analyse the development of the national quality assurance (QA) system, introduced in Taiwan in 2005, and identify the impact it had on four higher education institutions (HEIs), each with a very different mission and features. The study addresses two broad research questions: firstly, how has the current QA system developed in Taiwan, and what are its features and characteristics? Secondly, how do university staff prepare for and perceive the impact of the QA system undertaken by the Higher Education Evaluation and Accreditation Council of Taiwan (HEEACT)? The key features of the QA system are identified by using documentary analysis and interviews. The documentary analysis focuses on HEEACT publications. Having analysed the documents, policymakers who were involved in the development of the QA system were interviewed. A case study approach is utilised to analyse the perceived impact of the QA system on four universities. The four universities were chosen to cover the range of higher education institutions in Taiwan. Two are prestigious institutions which have received generous funding (one public and one private), while the other two (also one public and one private) are less prestigious institutions which have received less funding than the first two. Since 2005, the Taiwan government has distributed expenditure, and restructured higher education according to the results of the QA system conducted by HEEACT. All HEIs are therefore under pressure to meet the demands of the QA system as the results of evaluations will affect their resources and reputation, as well as whether they will be able to win competitive research and teaching funds. The HEIs perceive that in order to satisfy the requirements of HEEACT, they have to introduce new processes and structures, and the characteristics of individual HEIs have changed as a consequence. The Taiwanese approach to QA is a hybrid of different approaches to QA, including the accreditation system borrowed from the U.S.A. Its key distinctive features are that: (a) it evaluates both teaching and research within one single assessment exercise; (b) its results are used to determine resource allocation of the higher education system; (c) it has also been used to merge and close HEIs by the government; and (d) some of the terminology used is ambiguous. A number of organisational changes occurred in the four universities as they prepared for the QA exercise. The internal measures introduced were categorised into three types: rewards, staff evaluations and structures. However, the changes initiated in the four universities varied and are driven by their different features including their institutional purpose, mission and whether they are public or private institutions. Together, these changes have resulted in a new form of management in the HEIs and this can be seen as an unanticipated consequence of the QA system. The contrast between research-oriented and teaching-led universities has been sharpened by the QA system as it has forced Taiwan’s HEIs to choose one path or the other in order to be successfully evaluated by HEEACT. The public university with a good reputation built on its strong points and its original advantages and reinforced its position as a research-led university, whilst universities with less prestigious reputations were forced to focus on teaching regardless of whether they were public or private institutions. Academic staff also felt that they had to choose either to improve their teaching expertise or to focus on research in response to the QA system. The changes triggered by the QA system have influenced the nature of the academic profession and this, in turn, appears to have reshaped academic identities and professionalisation. This thesis offers three main contributions. First, the thesis has identified the distinctive features of the Taiwanese approach to QA. Although Taiwan’s QA system was influenced by Western approaches to QA, it is in effect a hybrid of different approaches, and represents its own distinctive QA model. Second, the thesis contributes to understanding the impact of QA systems on universities. By combining the approach from Morley (2004) with the model of Brennan and Shah (2000), the resulting analytical framework explains the impact of the QA exercise on HEIs in the context of Taiwan, and possibly in the East Asia region. Finally, the thesis contributes to the QA literature by analysing the differential impact of a QA system has had on four universities with very different missions

A review of Monte Carlo simulations of polymers with PERM

In this review, we describe applications of the pruned-enriched Rosenbluth method (PERM), a sequential Monte Carlo algorithm with resampling, to various problems in polymer physics. PERM produces samples according to any given prescribed weight distribution, by growing configurations step by step with controlled bias, and correcting "bad" configurations by "population control". The latter is implemented, in contrast to other population based algorithms like e.g. genetic algorithms, by depth-first recursion which avoids storing all members of the population at the same time in computer memory. The problems we discuss all concern single polymers (with one exception), but under various conditions: Homopolymers in good solvents and at the $\Theta$ point, semi-stiff polymers, polymers in confining geometries, stretched polymers undergoing a forced globule-linear transition, star polymers, bottle brushes, lattice animals as a model for randomly branched polymers, DNA melting, and finally -- as the only system at low temperatures, lattice heteropolymers as simple models for protein folding. PERM is for some of these problems the method of choice, but it can also fail. We discuss how to recognize when a result is reliable, and we discuss also some types of bias that can be crucial in guiding the growth into the right directions.Comment: 29 pages, 26 figures, to be published in J. Stat. Phys. (2011

Laser-assisted Charge-transfer Collisions: K++Na

A theory has been formulated to characterize charge-transfer collisions in the presence of an external laser field. The molecular-state-expansion method is used to describe the scattering process within the impact-parameter formalism. Electron translation factors are included in the molecular-state expansion so that the scattering wave function satisfies the correct boundary conditions. The theory is applied to the process K++NaK+Na+. In addition, we have made a detailed analysis of laser-assisted charge transfer for low-energy collisions. In this case, a Landau-Zener formula can be derived which shows that the cross section increases with decreasing incident energy. In general the laser coupling is dominant in the low-energy region, while the dynamical coupling becomes important as the collision energy increases. © 1985 The American Physical Society

Dragging a polymer chain into a nanotube and subsequent release

We present a scaling theory and Monte Carlo (MC) simulation results for a flexible polymer chain slowly dragged by one end into a nanotube. We also describe the situation when the completely confined chain is released and gradually leaves the tube. MC simulations were performed for a self-avoiding lattice model with a biased chain growth algorithm, the pruned-enriched Rosenbluth method. The nanotube is a long channel opened at one end and its diameter $D$ is much smaller than the size of the polymer coil in solution. We analyze the following characteristics as functions of the chain end position $x$ inside the tube: the free energy of confinement, the average end-to-end distance, the average number of imprisoned monomers, and the average stretching of the confined part of the chain for various values of $D$ and for the number of monomers in the chain, $N$. We show that when the chain end is dragged by a certain critical distance $x^*$ into the tube, the polymer undergoes a first-order phase transition whereby the remaining free tail is abruptly sucked into the tube. This is accompanied by jumps in the average size, the number of imprisoned segments, and in the average stretching parameter. The critical distance scales as $x^*\sim ND^{1-1/\nu}$. The transition takes place when approximately 3/4 of the chain units are dragged into the tube. The theory presented is based on constructing the Landau free energy as a function of an order parameter that provides a complete description of equilibrium and metastable states. We argue that if the trapped chain is released with all monomers allowed to fluctuate, the reverse process in which the chain leaves the confinement occurs smoothly without any jumps. Finally, we apply the theory to estimate the lifetime of confined DNA in metastable states in nanotubes.Comment: 13pages, 14figure

Quantitative Simulation of the Superconducting Proximity Effect

A numerical method is developed to calculate the transition temperature of double or multi-layers consisting of films of super- and normal conductors. The approach is based on a dynamic interpretation of Gorkov's linear gap equation and is very flexible. The mean free path of the different metals, transmission through the interface, ratio of specular reflection to diffusive scattering at the surfaces, and fraction of diffusive scattering at the interface can be included. Furthermore it is possible to vary the mean free path and the BCS interaction NV in the vicinity of the interface. The numerical results show that the normalized initial slope of an SN double layer is independent of almost all film parameters except the ratio of the density of states. There are only very few experimental investigations of this initial slope and they consist of Pb/Nn double layers (Nn stands for a normal metal). Surprisingly the coefficient of the initial slope in these experiments is of the order or less than 2 while the (weak coupling) theory predicts a value of about 4.5. This discrepancy has not been recognized in the past. The autor suggests that it is due to strong coupling behavior of Pb in the double layers. The strong coupling gap equation is evaluated in the thin film limit and yields the value of 1.6 for the coefficient. This agrees much better with the few experimental results that are available. PACS: 74.45.+r, 74.62.-c, 74.20.F