Static Potential and Local Color Fields in Unquenched Three-Dimensional Lattice QCD

String breaking by dynamical quarks in (2+1)-d lattice QCD is demonstrated in this project, by measuring the static potential and the local color-electric field strength between a heavy quark and antiquark pair at large separations. Simulations are done for unquenched SU(2) color with two flavors of staggered quarks. An improved gluon action is used which allows simulations to be done on coarse lattices, providing an extremely efficient means to access the quark separations and propagation times at which string breaking occurs. The static quark potential is extracted using only Wilson loop operators and hence no valence quarks are present in the trial states. Results give unambiguous evidence for string breaking as the static quark potential completely saturates at twice the heavy-light meson mass at large separations. It is also shown that the local color-electric field strength between the quark pair tends toward vacuum values at large separations. Implications of these results for unquenched simulations of QCD in 4-d are drawn.Comment: 3 pages, contribution to Lattice 2002 proceedings (Confinement

Hong Kong's Mandatory Provident Fund system : a study of the evolution of governance and policy tools

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Topology and Staggered Fermion Action Improvement

It is conventional wisdom that staggered fermions do not feel gauge field topology. However, the response of staggered fermion eigenmodes to the topology of the gauge field can depend quite sensitively on the way in which the staggered fermion action is improved. We study this issue using a variety of improved staggered quark actions. We observe that the separation between the ``would be'' zero modes and the non-chiral modes increases with the level of improvement. This enables the ``zero modes'' to be identified unambiguously. The distribution of the remaining non-chiral modes is compared with the predictions of Random Matrix Theory. Satisfactory agreement is obtained.Comment: Lattice 2004 (topology

Perturbative Wilson loops from unquenched Monte Carlo simulations at weak couplings

Perturbative expansions of several small Wilson loops are computed through next-to-next-to-leading order in unquenched lattice QCD, from Monte Carlo simulations at weak couplings. This approach provides a much simpler alternative to conventional diagrammatic perturbation theory, and is applied here for the first time to full QCD. Two different sets of lattice actions are considered: one set uses the unimproved plaquette gluon action together with the unimproved staggered-quark action; the other set uses the one-loop-improved Symanzik gauge-field action together with the so-called ``asqtad'' improved-staggered quark action. Simulations are also done with different numbers of dynamical fermions. An extensive study of the systematic uncertainties is presented, which demonstrates that the small third-order perturbative component of the observables can be reliably extracted from simulation data. We also investigate the use of the rational hybrid Monte Carlo algorithm for unquenched simulations with unimproved-staggered fermions. Our results are in excellent agreement with diagrammatic perturbation theory, and provide an important cross-check of the perturbation theory input to a recent determination of the strong coupling $\alpha_{\bar{\rm MS}}(M_Z)$ by the HPQCD collaboration.Comment: 14 pages, 8 figure

Impact of Co-creation Footwear Workshops on Older Women in Elderly Centers in Hong Kong

Background: The use of appropriate footwear could reduce the risk of falls among the geriatric population. However, the elderly are generally reluctant to accept new footwear designs particularly with the incorporation of fabrication materials and functional design features that are perceived to be less comfortable. Co-creation activities that encourage user involvement during the product design process and development can therefore address this issue and provide unique benefits and better value for users, increase acceptance, and even lead to positive perception as well as positive psychological impacts, thereby increasing the practical use of newly designed footwear. Objective: This study aims to investigate the impact of hands-on footwear workshops on perceived functionality of geriatric footwear for older women. Method: Footwear co-design workshops for older women were carried out in two elderly centers in Hong Kong. Twenty-one healthy females between 64 and 80 years old (mean: 71; SD: 4.2), were recruited. Subjects were invited to decorate the prescribed geriatric footwear prototype and discuss their ideas on footwear design in a group of three. They were surveyed after completing the footwear decoration. Main outcome measures: The perceptions of the subjects on the geriatric footwear and related design features were analysed. Results: The questionnaire survey shows positive results in the psychological value of the workshops for older women. The participants express high levels of satisfaction with the co-design process and a strong sense of achievement with the newly designed geriatric footwear. The acceptance and awareness of the functions of the footwear are greatly enhanced. Conclusions: The co-design approach has positive psychological impacts on the elderly and their acceptance of the final product. This approach also better meets the aesthetic needs of the users

Modelling customer satisfaction for product development using genetic programming

Product development involves several processes in which product planning is the first one. Several tasksnormally are required to be conducted in the product-planning process and one of them is to determinesettings of design attributes for products. Facing with fierce competition in marketplaces, companies try to determine the settings such that the best customer satisfaction of products could be obtained.To achieve this, models that relate customer satisfaction to design attributes need to be developed first. Previous research has adopted various modelling techniques to develop the models, but those models are not able to address interaction terms or higher-order terms in relating customer satisfaction to design attributes, or they are the black-box type models. In this paper, a method based on genetic programming (GP) is presented to generate models for relating customer satisfaction to design attributes. The GP is first used to construct branches of a tree representing structures of a model where interaction terms and higher-order terms can be addressed. Then an orthogonal least-squares algorithm is used to determine the coefficients of the model. The models thus developed are explicit and consist of interaction terms and higher-order terms in relating customer satisfaction to design attributes. A case study of a digital camera design is used to illustrate the proposed method