Optimization of physical distribution problem in logistics management

Physical distribution plays an imporant role in contemporary logistics management. Both satisfaction level of of customer and competitiveness of company can be enhanced if the distribution problem is solved optimally. The multi-depot vehicle routing problem (MDVRP) belongs to a practical logistics distribution problem, which consists of three critical issues: customer assignment, customer routing, and vehicle sequencing. According to the literatures, the solution approaches for the MDVRP are not satisfactory because some unrealistic assumptions were made on the first sub-problem of the MDVRP, ot the customer assignment problem. To refine the approaches, the focus of this paper is confined to this problem only. This paper formulates the customer assignment problem as a minimax-type integer linear programming model with the objective of minimizing the cycle time of the depots where setup times are explicitly considered. Since the model is proven to be MP-complete, a genetic algorithm is developed for solving the problem. The efficiency and effectiveness of the genetic algorithm are illustrated by a numerical example.

A class of perfect fluids in general relativity

This thesis is concerned with exact solutions of Einstein's field equations of general relativity, in particular, when the source of the gravitational field is a perfect fluid with a purely electric Weyl tensor. General relativity, cosmology and computer algebra are discussed briefly. A mathematical introduction to Riemannian geometry and the tetrad formalism is then given. This is followed by a review of some previous results and known solutions concerning purely electric perfect fluids. In addition, some orthonormal and null tetrad equations of the Ricci and Bianchi identities are displayed in a form suitable for investigating these space-times. Conformally flat perfect fluids are characterised by the vanishing of the Weyl tensor and form a sub-class of the purely electric fields in which all solutions are known (Stephani 1967). The number of Killing vectors in these space-times is investigated and results presented for the non-expanding space-times. The existence of stationary fields that may also admit 0, 1 or 3 spacelike Killing vectors is demonstrated. Shear-free fluids in the class under consideration are shown to be either non-expanding or irrotational (Collins 1984) using both orthonormal and null tetrads. A discrepancy between Collins (1984) and Wolf (1986) is resolved by explicitly solving the field equations to prove that the only purely electric, shear-free, geodesic but rotating perfect fluid is the Godel (1949) solution. The irrotational fluids with shear are then studied and solutions due to Szafron (1977) and Allnutt (1982) are characterised. The metric is simplified in several cases where new solutions may be found. The geodesic space-times in this class and all Bianchi type 1 perfect fluid metrics are shown to have a metric expressible in a diagonal form. The position of spherically symmetric and Bianchi type 1 space-times in relation to the general case is also illustrated.

Quantitative risk assessment of groundwater quality utilizing GIS technology and coupled groundwater models

The thesis presents a two-dimensional Risk Assessment Method (RAM) where the assessment of risk to the groundwater resources incorporates both the quantification of the probability of the occurrence of contaminant source terms, as well as the assessment of the resultant impacts. The approach emphasizes the need for a greater dependency on the potential pollution sources, rather than the traditional approach where assessment is based mainly on the intrinsic geo-hydrologic parameters. The risk is calculated using Monte Carlo simulation methods whereby random pollution events were generated to the same distribution as historically occurring events or a priori potential probability distribution. Integrated mathematical models then simulate contaminant concentrations at the predefined monitoring points within the aquifer. The spatial and temporal distributions of the concentrations were calculated from repeated realisations, and the number of times when a user defined concentration magnitude was exceeded is quantified as a risk. The method was setup by integrating MODFLOW-2000, MT3DMS and a FORTRAN coded risk model, and automated, using a DOS batch processing file. GIS software was employed in producing the input files and for the presentation of the results. The functionalities of the method, as well as its sensitivities to the model grid sizes, contaminant loading rates, length of stress periods, and the historical frequencies of occurrence of pollution events were evaluated using hypothetical scenarios and a case study. Chloride-related pollution sources were compiled and used as indicative potential contaminant sources for the case study. At any active model cell, if a random generated number is less than the probability of pollution occurrence, then the risk model will generate synthetic contaminant source term as an input into the transport model. The results of the applications of the method are presented in the form of tables, graphs and spatial maps. Varying the model grid sizes indicates no significant effects on the simulated groundwater head. The simulated frequency of daily occurrence of pollution incidents is also independent of the model dimensions. However, the simulated total contaminant mass generated within the aquifer, and the associated volumetric numerical error appear to increase with the increasing grid sizes. Also, the migration of contaminant plume advances faster with the coarse grid sizes as compared to the finer grid sizes. The number of daily contaminant source terms generated and consequently the total mass of contaminant within the aquifer increases in a non linear proportion to the increasing frequency of occurrence of pollution events. The risk of pollution from a number of sources all occurring by chance together was evaluated, and quantitatively presented as risk maps. This capability to combine the risk to a groundwater feature from numerous potential sources of pollution proved to be a great asset to the method, and a large benefit over the contemporary risk and vulnerability methods.

The use of driven equilibrium conditions in the measurement of NMR relaxation times

The further development of the use of NMR relaxation times in chemical, biological and medical research has perhaps been curtailed by the length of time these measurements often take. The DESPOT (Driven Equilibrium Single Pulse Observation of T1) method has been developed, which reduces the time required to make a T1 measurement by a factor of up to 100. The technique has been studied extensively herein and the thesis contains recommendations for its successful experimental application. Modified DESPOT type equations for use when T2 relaxation is incomplete or where off-resonance effects are thought to be significant are also presented. A recently reported application of the DESPOT technique to MR imaging gave good initial results but suffered from the fact that the images were derived from spin systems that were not driven to equilibrium. An approach which allows equilibrium to be obtained with only one non-acquisition sequence is presented herein and should prove invaluable in variable contrast imaging. A DESPOT type approach has also been successfully applied to the measurement of T1. T_1's can be measured, using this approach significantly faster than by the use of the classical method. The new method also provides a value for T1 simultaneously and therefore the technique should prove valuable in intermediate energy barrier chemical exchange studies. The method also gives rise to the possibility of obtaining simultaneous T1 and T1 MR images. The DESPOT technique depends on rapid multipulsing at nutation angles, normally less than 90^o. Work in this area has highlighted the possible time saving for spectral acquisition over the classical technique (90^o-5T_1)_n. A new method based on these principles has been developed which permits the rapid multipulsing of samples to give T_1 and M_0 ratio information. The time needed, however, is only slightly longer than would be required to determine the M_0 ratio alone using the classical technique. In ^1H decoupled ^13C spectroscopy the method also gives nOe ratio information for the individual absorptions in the spectrum.

Observing repetitive finger movements modulates response times of auditorily cued finger movements

Our motor and perceptual representations of actions seem to be intimately linked and the human mirror neuron system (MNS) has been proposed as the mediator. In two experiments, we presented biological or non-biological movement stimuli that were either congruent or incongruent to a required response prompted by a tone. When the tone occurred with the onset of the last movement in a series, i.e., it was perceived during the movement presentation, congruent biological stimuli resulted in faster reaction times than congruent non-biological stimuli. The opposite was observed for incongruent stimuli. When the tone was presented after visual movement stimulation, however, no such interaction was present. This implies that biological movement stimuli only affect motor behaviour during visual processing but not thereafter. These data suggest that the MNS is an “online” system; longstanding repetitive visual stimulation (Experiment 1) has no benefit in comparison to only one or two repetitions (Experiment 2).

Self-monitoring of blood glucose in Black Caribbean and South Asian Canadians with non-insulin treated Type 2 diabetes mellitus:a qualitative study of patients' perspectives

Background: To examine the views and current practice of SMBG among Black Caribbean and South Asian individuals with non-insulin treated Type 2 diabetes mellitus. Methods: Twelve participants completed semi-structured interviews that were guided by the Health Belief Model and analyzed using thematic network analysis. Results: The frequency of monitoring among participants varied from several times a day to once per week. Most participants expressed similar experiences regarding their views and practices of SMBG. Minor differences across gender and culture were observed. All participants understood the benefits, but not all viewed SMBG as beneficial to their personal diabetes management. SMBG can facilitate a better understanding and maintenance of self-care behaviours. However, it can trigger both positive and negative emotional responses, such as a sense of disappointment when high readings are not anticipated, resulting in emotional distress. Health care professionals play a key role in the way SMBG is perceived and used by patients. Conclusion: While the majority of participants value SMBG as a self-management tool, barriers exist that impede its practice, particularly its cost. How individuals cope with these barriers is integral to understanding why some patients adopt SMBG more than others. © 2013 Gucciardi et al.; licensee BioMed Central Ltd.

The non-violence of love:a Hildebrand-Girard encounter

If love is a social as well as a personal reality, it could be fruitful to compare Von Hildebrand’s understanding of love and desire with that of cultural anthropologist René Girard. Girard depicts love and desire as a triangular process which arises from imitation, rather than the result of auto-generative affection. In this sense, Girardian theory would seem to convict Von Hildebrand of what is called the romantic lie wherein desire is thought to arise through the mutual appreciation of two subjects. However, in The Nature of Love Von Hildebrand shows his awareness of the possibility that love can be awakened by imitation. Moreover, the lack of a sufficient reason in Girardian theory for avoiding violence can be answered by turning to Von Hildebrand’s appreciation of the ontological basis for desire.

Learner support and discovery in a virtual non-judgmental environment

This thesis is a qualitative case study that draws upon a grounded genre analysis approach situated within the social constructivist paradigm. The study describes the various obligatory, desired, and optional moves used by post-graduate students as they interacted within an online, non-judgmental environment in order to seek solutions to issues they were experiencing with their research projects or teaching. The postgraduate students or case participants met individually online with me at pre-arranged times to take part in Instant Messenger Cooperative Development (IMCD) (Boon, 2005) 30-minute to one hour sessions via the text-chat function of Skype. Participants took on the role of ‘Explorer’ in order to articulate their thoughts and ideas about their research. I took on the role of ‘Understander’ to provide support to each Explorer by reflecting my understanding of the ongoing articulations as the Explorers investigated their specific issues, determined possible ways to overcome them, made new discoveries, and formulated plans of action regarding the best way for them to move forward. The description of generic moves covers 32 IMCD sessions collected over a threeyear period (2009-2012) from 10 different participants (A-J). Data collected is drawn from live IMCD sessions, field notes, and post-session email feedback from participants. In particular, the thesis focuses on describing the specific generic moves of Explorers within IMCD sessions as they seek satisfactory resolutions to particular research or pedagogic puzzles. It also provides a detailed description of a longitudinal case (Participant A – four sessions), a one-session case (Participant B – one session), and an outlier case in which the Explorer underwent a negative IMCD experience. The thesis concludes by arguing that IMCD is a highly effective tool that helps facilitate the research process for both distance-learning and on-campus students and has the potential to be utilized across all disciplines at the tertiary level.

Fast and efficient user pairing and power allocation algorithm for non-orthogonal multiple access in cellular networks

Non-orthogonal multiple access (NOMA) is emerging as a promising multiple access technology for the fifth generation cellular networks to address the fast growing mobile data traffic. It applies superposition coding in transmitters, allowing simultaneous allocation of the same frequency resource to multiple intra-cell users. Successive interference cancellation is used at the receivers to cancel intra-cell interference. User pairing and power allocation (UPPA) is a key design aspect of NOMA. Existing UPPA algorithms are mainly based on exhaustive search method with extensive computation complexity, which can severely affect the NOMA performance. A fast proportional fairness (PF) scheduling based UPPA algorithm is proposed to address the problem. The novel idea is to form user pairs around the users with the highest PF metrics with pre-configured fixed power allocation. Systemlevel simulation results show that the proposed algorithm is significantly faster (seven times faster for the scenario with 20 users) with a negligible throughput loss than the existing exhaustive search algorithm.