Optimisation techniques for planning automatic under frequency load shedding in New Zealand’s power system

Electricity generation is vital in developed countries to power the many mechanical and electrical devices that people require. Unfortunately electricity generation is costly. Though electricity can be generated it cannot be stored efficiently. Electricity generation is also difficult to manage because exact demand is unknown from one instant to the next. A number of services are required to manage fluctuations in electricity demand, and to protect the system when frequency falls too low. A current approach is called automatic under frequency load shedding (AUFLS). This article proposes new methods for optimising AUFLS in New Zealand’s power system. The core ideas were developed during the 2015 Maths and Industry Study Group (MISG) in Brisbane, Australia. The problem has been motivated by Transpower Limited, a company that manages New Zealand’s power system and transports bulk electricity from where it is generated to where it is needed. The approaches developed in this article can be used in electrical power systems anywhere in the world.

Non-Gaussian Cosmological Perturbations from Hybrid Inflation and Preheating

This thesis consists of four research papers and an introduction providing some background. The structure in the universe is generally considered to originate from quantum fluctuations in the very early universe. The standard lore of cosmology states that the primordial perturbations are almost scale-invariant, adiabatic, and Gaussian. A snapshot of the structure from the time when the universe became transparent can be seen in the cosmic microwave background (CMB). For a long time mainly the power spectrum of the CMB temperature fluctuations has been used to obtain observational constraints, especially on deviations from scale-invariance and pure adiabacity. Non-Gaussian perturbations provide a novel and very promising way to test theoretical predictions. They probe beyond the power spectrum, or two point correlator, since non-Gaussianity involves higher order statistics. The thesis concentrates on the non-Gaussian perturbations arising in several situations involving two scalar fields, namely, hybrid inflation and various forms of preheating. First we go through some basic concepts -- such as the cosmological inflation, reheating and preheating, and the role of scalar fields during inflation -- which are necessary for the understanding of the research papers. We also review the standard linear cosmological perturbation theory. The second order perturbation theory formalism for two scalar fields is developed. We explain what is meant by non-Gaussian perturbations, and discuss some difficulties in parametrisation and observation. In particular, we concentrate on the nonlinearity parameter. The prospects of observing non-Gaussianity are briefly discussed. We apply the formalism and calculate the evolution of the second order curvature perturbation during hybrid inflation. We estimate the amount of non-Gaussianity in the model and find that there is a possibility for an observational effect. The non-Gaussianity arising in preheating is also studied. We find that the level produced by the simplest model of instant preheating is insignificant, whereas standard preheating with parametric resonance as well as tachyonic preheating are prone to easily saturate and even exceed the observational limits. We also mention other approaches to the study of primordial non-Gaussianities, which differ from the perturbation theory method chosen in the thesis work.

Optimized Policies for the Retransmission Probabilities in Slotted Aloha

In this paper, we study the behaviour of the slotted Aloha multiple access scheme with a finite number of users under different traffic loads and optimize the retransmission probability q(r) for various settings, cost objectives and policies. First, we formulate the problem as a parameter optimization problem and use certain efficient smoothed functional algorithms for finding the optimal retransmission probability parameter. Next, we propose two classes of multi-level closed-loop feedback policies (for finding in each case the retransmission probability qr that now depends on the current system state) and apply the above algorithms for finding an optimal policy within each class of policies. While one of the policy classes depends on the number of backlogged nodes in the system, the other depends on the number of time slots since the last successful transmission. The latter policies are more realistic as it is difficult to keep track of the number of backlogged nodes at each instant. We investigate the effect of increasing the number of levels in the feedback policies. Wen also investigate the effects of using different cost functions (withn and without penalization) in our algorithms and the corresponding change in the throughput and delay using these. Both of our algorithms use two-timescale stochastic approximation. One of the algorithms uses one simulation while the other uses two simulations of the system. The two-simulation algorithm is seen to perform better than the other algorithm. Optimal multi-level closed-loop policies are seen to perform better than optimal open-loop policies. The performance further improves when more levels are used in the feedback policies.

Towards a typology of hashtag publics: A large-scale comparative study of user engagement across trending topics

Twitter’s hashtag functionality is now used for a very wide variety of purposes, from covering crises and other breaking news events through gathering an instant community around shared media texts (such as sporting events and TV broadcasts) to signalling emotive states from amusement to despair. These divergent uses of the hashtag are increasingly recognised in the literature, with attention paid especially to the ability for hashtags to facilitate the creation of ad hoc or hashtag publics. A more comprehensive understanding of these different uses of hashtags has yet to be developed, however. Previous research has explored the potential for a systematic analysis of the quantitative metrics that could be generated from processing a series of hashtag datasets. Such research found, for example, that crisis-related hashtags exhibited a significantly larger incidence of retweets and tweets containing URLs than hashtags relating to televised events, and on this basis hypothesised that the information-seeking and -sharing behaviours of Twitter users in such different contexts were substantially divergent. This article updates such study and their methodology by examining the communicative metrics of a considerably larger and more diverse number of hashtag datasets, compiled over the past five years. This provides an opportunity both to confirm earlier findings, as well as to explore whether hashtag use practices may have shifted subsequently as Twitter’s userbase has developed further; it also enables the identification of further hashtag types beyond the “crisis” and “mainstream media event” types outlined to date. The article also explores the presence of such patterns beyond recognised hashtags, by incorporating an analysis of a number of keyword-based datasets. This large-scale, comparative approach contributes towards the establishment of a more comprehensive typology of hashtags and their publics, and the metrics it describes will also be able to be used to classify new hashtags emerging in the future. In turn, this may enable researchers to develop systems for automatically distinguishing newly trending topics into a number of event types, which may be useful for example for the automatic detection of acute crises and other breaking news events.

Unsteady mixed convection on the stagnation-point flow adjacent to a vertical plate with a magnetic field

An analysis is performed to study the unsteady combined forced and free convection flow (mixed convection flow) of a viscous incompressible electrically conducting fluid in the vicinity of an axisymmetric stagnation point adjacent to a heated vertical surface. The unsteadiness in the flow and temperature fields is due to the free stream velocity, which varies arbitrarily with time. Both constant wall temperature and constant heat flux conditions are considered in this analysis. By using suitable transformations, the Navier-Stokes and energy equations with four independent variables (x, y, z, t) are reduced to a system of partial differential equations with two independent variables (eta, tau). These transformations also uncouple the momentum and energy equations resulting in a primary axisymmetric flow, in an energy equation dependent on the primary flow and in a buoyancy-induced secondary flow dependent on both primary flow and energy. The resulting system of partial differential equations has been solved numerically by using both implicit finite-difference scheme and differential-difference method. An interesting result is that for a decelerating free stream velocity, flow reversal occurs in the primary flow after certain instant of time and the magnetic field delays or prevents the flow reversal. The surface heat transfer and the surface shear stress in the primary flow increase with the magnetic field, but the surface shear stress in the buoyancy-induced secondary flow decreases. Further the heat transfer increases with the Prandtl number, but the surface shear stress in the secondary flow decreases.

Steady flow of a maxwell fluid in a porous cylindrical annulus with circular cross-section

When a fluid with memory is injected into any flow region some assumptions regarding the initial state of stress have to be made in order to determine the state of stress at any subsequent instant. For a Maxwell fluid, it is assumed that the fluid near the surface of injection is suddenly stressed and responds by starting flow in accordance with the mechanical model chosen. The flow of a Maxwell fluid with a single relaxation time has been determined under the above assumption in the following two cases: (i) annulus between two porous concentric circular cylinders, and (ii) space between two porous and infinitely extending parallel plates. The nature of flow in the present case is similar to that of the Reiner-Rivlin fluids obtained by Narasimhan2).

Participes présents et gérondifs en traduction finnoise : perte ou changement de valeur ?

Les participes présents apparaissent, entre autres, dans des constructions à prédication seconde détachées : (1) Intervenant hier soir à Ankara, […], Vladimir Poutine s’est risqué à […]. (Le Figaro 7.12.2004 : 4) Même si les gérondifs, formes adverbiales du verbe (« converbes », cf. Haspelmath & König 1995), n’ont pas d’incidence nominale, contrairement aux participes présents, formes adjectivales du verbe, et ne sont donc pas toujours comptés parmi les constructions à prédication seconde (p.ex. Neveu 1998), les deux ont des emplois assez proches : dans des énoncés du type (2a-b), le participe adjoint peut être paraphrasé par un gérondif, même si son statut fonctionnel n’est pas le même (Halmøy, 2003 : 156-157) : (2a) Arrivant à Paris, Emile a proposé à Léa de [...]. (2b) En arrivant à Paris, Emile a proposé à Léa de[...]. (Halmøy, 2003 : 157) Le finnois ne connaît ni ce genre de constructions détachés ni de forme appelée ‘gérondif’, et les deux participes présents finnois (actif et passif) ne correspondent jamais à un participe présent détaché français : en plus de subordonnées, on trouve à leur place le deuxième infinitif, soit à l’inessif, soit à l’instructif, formes nominales qu’on trouve également dans la traduction des gérondifs : (3a) […] ? me demanda-t-elle sèchement en me montrant l’une des lignes incriminées. (Nothomb, p. 62) […] : hän kysyi minulta kuivakkaasti näyttäen erästä Unajin moittimaa riviä. (Suni, p. 4) (3b) L’espace d’un instant, il sourit, croyant que […] je m’étais trompée de commodités. (Nothomb, p. 138-139) Hetken hän hymyili luullen, että minä […] olin erehtynyt mukavuuslaitoksesta. (Suni, p. 94) : Dans cette communication, nous examinerons quatre traductions littéraires en nous demandant dans quels cas et de quelle manière la différence entre le participe et le gérondif a éventuellement été prise en considération.

An Estimator Algorithm For Learning Automata With Changing Number Of Actions

In many problems of decision making under uncertainty the system has to acquire knowledge of its environment and learn the optimal decision through its experience. Such problems may also involve the system having to arrive at the globally optimal decision, when at each instant only a subset of the entire set of possible alternatives is available. These problems can be successfully modelled and analysed by learning automata. In this paper an estimator learning algorithm, which maintains estimates of the reward characteristics of the random environment, is presented for an automaton with changing number of actions. A learning automaton using the new scheme is shown to be e-optimal. The simulation results demonstrate the fast convergence properties of the new algorithm. The results of this study can be extended to the design of other types of estimator algorithms with good convergence properties.

Eläimen tuttuus ja vieraus : Fenomenologisen empatiateorian uudelleentulkinta ja sen sovellus vieraslajisia eläimiä koskevaan kokemukseen

Within the field of philosophy, animals have traditionally been studied from two perspectives: that of self-knowledge and that of ethics. The analysis of the differences between humans and animals has served our desire to understand our own specificity, whereas ethical discussions have ultimately aimed at finding the right way to treat animals. This dissertation proposes a different way of looking at non-human animals: it investigates the question of how non-human animals appear to us humans in our perceptual experience. The analysis focuses on the empathetic, embodied understanding of animals diverse movements and other expressions. The theoretical point of departure for the research is phenomenological philosophy, in particular Maurice Merleau-Ponty s phenomenology of the body. Edmund Husserl s and Edith Stein s analyses of empathy and embodiment are also crucial to the work. In this tradition, empathy means understanding the other s experience through her bodily expressions and seeing the other body as living, as well as motivated and directed towards the surrounding world. The dissertation both explicates and criticizes the earlier phenomenological notions of empathy and human specificity. In order to elucidate the fundamental structures of our experience of non-human animals, it also applies the phenomenological method, which consists of a phenomenological reduction and a free variation of the different aspects of experience. It is shown that our experiences of non-human animals involve a recognition of both similarities and differences. This recognition, however, is not primarily based on intellectual comparisons but is lived as an embodied relationship to another body, and its manifestations vary from one instant to the next. The analysis also reveals that the object of empathy is not the other s experience as such, not even as it is manifested by the other s movements, but rather the other s embodied situation, enriched by elements that remain outside the scope of the other s experience. The dissertation shows that human existence is intertwined with the existence of non-human animals on four levels: those of empathetic sensations, reciprocal communication, experience of the surrounding world and self-definitions. The animals different modes of perception prove to expand our understanding of what is perceivable and how things can be perceived. The presence of non-human animals in our perceptual world is revealed as something that both shows us the limits of our own embodiment and enables us to overcome these limits in empathetic acts. Finally, it is demonstrated that the life of non-human animals is intertwined with ours in a far more complex way than has been presupposed in traditional descriptions of human-animal differences.

Unsteady mixed convection over two-dimensional and axisymmetric bodies

The unsteady laminar incompressible mixed convection flow over a two-dimensional body (cylinder) and an axisymmetric body (sphere) has been studied when the buboyancy forces arise from both thermal and mass diffusion and the unsteadiness in the flow field is introduced by the time dependent free stream velocity. The nonlinear partial differential equations with three independent variables governing the flow have been solved numerically using an implicit finite-difference scheme in combination with the quasilinearization technique. The results indicate that for the thermally assisting flow the local skin friction, heat transfer and mass diffusion are enhanced when the buoyancy force from mass diffusion assists the thermal buoyancy force. But this trend is opposite for the thermally opposing flow. The point of zero skin friction moves upstream due to unsteadiness. No singularity is observed at the point of zero skin friction for unsteady flow unlike steady flow. The flow reversal is observed after a certain instant of time. The velocity overshoot occurs for assisting flows.

Elämänmuutoksen, jännityksen ja asiantuntijuuden representointi Veikkaus Oy:n mainonnassa vuosina 1970— 2006

Aim of this master's thesis paper for consumer economics, is to research gambling advertisements in Finland over a period of 35 years, from 1970 to 2006. Veikkaus Oy (later Veikkaus), was founded in 1940, as one of the three licensed gambling organizations in Finland. Material for the current research comprised 1494 advertisements published by Veikkaus in newspapers and magazines at that time. Veikkaus has the exclusive licence to organize lotto games, sport games, instant games and other draw games in Finland. The other two operators, The Finnish Slot Machine Association RAY and Fintoto (on-track horse betting), were not included in the current analysis. This study has been completed according to research contract and grand by the Finnish Foundation for Gaming Research (Pelitoiminnan tutkimussäätiö). In general, advertisements reflect surrounding culture and time, and their message is built on stratified meanings, symbols and codes. Advertising draws the viewer's attention, introduces the advertised subject, and finally, affects the individual's consumption habits. However, advertisements not only work on individual level, but also influence public perception of the advertised product. Firstly, in order to assess gambling as a phenomenon, this paper discusses gambling as consumer behaviour, and also reviews history of gambling in Finland. Winning is a major feature of gambling, and dreaming about positive change of life is a centre of most gambling ads. However, perceived excitement through risk of losing can also be featured in gambling ads. Secondly, this study utilizes Veikkaus’ large advertising archives, were advertising data is analyzed by content analysis and the semiotic analysis. Two methods have been employed to support analyzing outcome in a synergistic way. Content analysis helps to achieve accuracy and comprehensiveness. Semiotic analysis allows deeper and more sensitive analysis to emerged findings and occurrences. It is important to understand the advertised product, as advertising is bound to the culture and time. Hence, to analyze advertising, it is important to understand the environment where the ads appear. Content analysis of Veikkaus data discovered the main gambling and principal advertisement style for each.period. Interestingly, nearly half of Veikkaus’ advertisements promoted topic other than “just winning the bet”. Games of change, like Lotto, typically advertised indirectly represented dreams about winning. In the category of skill gambling, features were represented as investment, and the excitement of sporting expertise was emphasized. In addition, there were a number of gambling ads that emphasize social responsibility of Veikkaus as a government guided organization. Semiotic methods were employed to further elaborate on findings of content analysis. Dreaming in the advertisements was represented by the product of symbols, (e.g. cars and homes) that were found to have significance connection with each other. Thus, advertising represents change of life obtained by the winning. Interestingly, gambling ads promoting jackpots were often representing religious symbolisms. Ads promoting social responsibility were found to be the most common during economical depression of the 90’s. Deeper analysis showed that at that time, advertisements frequently represented depression-related meanings, such as unemployment and bank loans. Skill gaming ads were often represented by sports expertise – late 90’s, their number started sky rocketing, and continued increasing until 2006 (when this study ended). One may conclude that sport betting draws its meanings from the relevant consumer culture, and from the rules and features of the betted sport.

Systems analysis for planning of air fleets and maintenance facilities

The high cost and extraordinary demands made on sophisticated air defence systems, pose hard challenges to the managers and engineers who plan the operation and maintenance of such systems. This paper presents a study aimed at developing simulation and systems analysis techniques for the effective planning and efficient operation of small fleets of aircraft, typical of the air force of a developing country. We consider an important aspect of fleet management: the problem of resource allocation for achieving prescribed operational effectiveness of the fleet. At this stage, we consider a single flying-base, where the operationally ready aircraft are stationed, and a repair-depot, where the planes are overhauled. An important measure of operational effectiveness is ‘ availability ’, which may be defined as the expected fraction of the fleet fit for use at a given instant. The tour of aircraft in a flying-base, repair-depot system through a cycle of ‘ operationally ready ’ and ‘ scheduled overhaul ’ phases is represented first by a deterministic flow process and then by a cyclic queuing process. Initially the steady-state availability at the flying-base is computed under the assumptions of Poisson arrivals, exponential service times and an equivalent singleserver repair-depot. This analysis also brings out the effect of fleet size on availability. It defines a ‘ small ’ fleet essentially in terms of the important ‘ traffic ’ parameter of service rate/maximum arrival rate.A simulation model of the system has been developed using GPSS to study sensitivity to distributional assumptions, to validate the principal assumptions of the analytical model such as the single-server assumption and to obtain confidence intervals for the statistical parameters of interest.

A new approach to the kinetics of size reduction in ball milling

The rate of breakage of feed in ball milling is usually represented in the form of a first-order rate equation. The equation was developed by treating a simple batch test mill as a well mixed reactor. Several case of deviation from the rule have been reported in the literature. This is attributed to the fact that accumulated fines interfere with the feed material and breaking events are masked by these fines. In the present paper, a new rate equation is proposed which takes into account the retarding effect of fines during milling. For this purpose the analogy of diffusion of ions through permeable membranes is adopted, with suitable modifications. The validity of the model is cross checked with the data obtained in batch grinding of ?850/+600 ?m size quartz. The proposed equation enables calculation of the rate of breakage of the feed at any instant of time.

Effect of microstructure and hardness on the grinding abrasive wear resistance of a ball bearing steel

Grinding media wear appears to be non-linear with the time of grinding in a laboratory-scale ball mill. The kinetics of wear can be expressed as a power law of the type w=atb, where the numerical constant a represents wear of a particular microstructure at time t = 1 min and b is the wear exponent which is independent of the particle size prevailing inside a ball mill at any instant of time of grinding. The wear exponent appears to be an indicator of the cutting wear mechanism in dry grinding: a plot of the inverse of the normalised wear exponent (Image ) versusHs (where Hs is the worn surface hardness of the media) yields a curve similar to that of a wear resistance plot obtained in the case of two-body sliding abrasive wear. This method of evaluating the cutting wear resistance of media is demonstrated by employing 15 different microstructures of AISI-SAE 52100 steel balls in dry grinding of quartz in a laboratory-scale ball mill.

E. C. G. Sudarshan and Symmetry in Classical Dynamics, Optics and Quantum Mechanics

We review work initiated and inspired by Sudarshan in relativistic dynamics, beam optics, partial coherence theory, Wigner distribution methods, multimode quantum optical squeezing, and geometric phases. The 1963 No Interaction Theorem using Dirac's instant form and particle World Line Conditions is recalled. Later attempts to overcome this result exploiting constrained Hamiltonian theory, reformulation of the World Line Conditions and extending Dirac's formalism, are reviewed. Dirac's front form leads to a formulation of Fourier Optics for the Maxwell field, determining the actions of First Order Systems (corresponding to matrices of Sp(2,R) and Sp(4,R)) on polarization in a consistent manner. These groups also help characterize properties and propagation of partially coherent Gaussian Schell Model beams, leading to invariant quality parameters and the new Twist phase. The higher dimensional groups Sp(2n,R) appear in the theory of Wigner distributions and in quantum optics. Elegant criteria for a Gaussian phase space function to be a Wigner distribution, expressions for multimode uncertainty principles and squeezing are described. In geometric phase theory we highlight the use of invariance properties that lead to a kinematical formulation and the important role of Bargmann invariants. Special features of these phases arising from unitary Lie group representations, and a new formulation based on the idea of Null Phase Curves, are presented.