Noisy random Boolean formulae:a statistical physics perspective

Properties of computing Boolean circuits composed of noisy logical gates are studied using the statistical physics methodology. A formula-growth model that gives rise to random Boolean functions is mapped onto a spin system, which facilitates the study of their typical behavior in the presence of noise. Bounds on their performance, derived in the information theory literature for specific gates, are straightforwardly retrieved, generalized and identified as the corresponding macroscopic phase transitions. The framework is employed for deriving results on error-rates at various function-depths and function sensitivity, and their dependence on the gate-type and noise model used. These are difficult to obtain via the traditional methods used in this field.

On the robustness of random Boolean formulae

Random Boolean formulae, generated by a growth process of noisy logical gates are analyzed using the generating functional methodology of statistical physics. We study the type of functions generated for different input distributions, their robustness for a given level of gate error and its dependence on the formulae depth and complexity and the gates used. Bounds on their performance, derived in the information theory literature for specific gates, are straightforwardly retrieved, generalized and identified as the corresponding typical-case phase transitions. Results for error-rates, function-depth and sensitivity of the generated functions are obtained for various gate-type and noise models. © 2010 IOP Publishing Ltd.

Typical case behaviour of spin systems in random graph and composite ensembles

This thesis includes analysis of disordered spin ensembles corresponding to Exact Cover, a multi-access channel problem, and composite models combining sparse and dense interactions. The satisfiability problem in Exact Cover is addressed using a statistical analysis of a simple branch and bound algorithm. The algorithm can be formulated in the large system limit as a branching process, for which critical properties can be analysed. Far from the critical point a set of differential equations may be used to model the process, and these are solved by numerical integration and exact bounding methods. The multi-access channel problem is formulated as an equilibrium statistical physics problem for the case of bit transmission on a channel with power control and synchronisation. A sparse code division multiple access method is considered and the optimal detection properties are examined in typical case by use of the replica method, and compared to detection performance achieved by interactive decoding methods. These codes are found to have phenomena closely resembling the well-understood dense codes. The composite model is introduced as an abstraction of canonical sparse and dense disordered spin models. The model includes couplings due to both dense and sparse topologies simultaneously. The new type of codes are shown to outperform sparse and dense codes in some regimes both in optimal performance, and in performance achieved by iterative detection methods in finite systems.

Beyond theory:an examination of lean new product introduction practices in the UK

Interest is growing around the application of lean techniques to new product introduction (NPI). Although a relatively emergent topic compared with the application of ‘lean’ within the factory, since 2000 there has been an exponential rise in the literature on this subject. However, much of this work focuses on describing and extolling the virtues of the ‘Toyota approach’ to design. Therefore, by way of a stock take for the UK, the present authors' research has set out to understand how well lean product design practices have been adopted by leading manufacturers. This has been achieved by carrying out in-depth case studies with three carefully selected manufacturers of complex engineered products. This paper describes these studies, the detailed results and subsequent findings, and concludes that both the awareness and adoption of practices is generally embryonic and far removed from the theory advocated in the literature.

Leadership in American Evangelical churches:an explanatory theory

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT This study is about leadership in American Evangelical Churches, which as a sub-set of American Christianity, are growing, while American Christianity as a whole is in decline. As a result evangelicalism is quickly becoming the dominate iteration of American Christianity. It is anecdotal that well led churches grow while poorly led churches do not, yet no one has identified what leadership, in the evangelical church context, is. Researchers have investigated a number of aspects of church leadership (much of it without identifying whether or not the churches under investigation were evangelical or not) but no one has put forth a unified theory linking these aspects together. The purpose of this research is to address that gap and develop a theory that explains how evangelicals view leadership in their local churches. In this study of three churches, dissimilar in size and governance, a purely qualitative approach to data collection and analysis was employed. The study involved 60 interviews that sought points-of-view from top and mid-level leadership along with congregant followers. The study borrowed heavily from Glaser and Strauss (1967) Grounded Theory approach to data analysis. The results developed a theory which provides a unified explanation of how leadership actually works in the three evangelical churches. Several implications for practice are discussed as to the theory's usefulness as a method of leadership education and evaluation. An original discovery was found that an individual's incumbency within the organization was identified as a social power. Limitations to this research are the limitations generally imputed to purely qualitative research in that questions are raised about the theory's applicability to evangelical churches beyond the three studied. The suggestions for further research involve addressing those limitations

Why are optimistic entrepreneurs successful? An application of the regulatory focus theory

Does entrepreneurial optimism affect business performance? Using a unique data set based on repeated survey design, we investigate this relationship empirically. Our measures of ëoptimismí and ërealismí are derived from comparing the turnover growth expectations of ...133 owners-managers with the actual outcomes one year later. Our results indicate that entrepreneurial optimists perform significantly better in terms of profits than pessimists. Moreover, it is the optimist-realist combination that performs best. We interpret our results using regulatory focus theory.

Why are optimistic entrepreneurs successful? An application of the regulatory focus theory

Does entrepreneurial optimism affect business performance? Using a unique data set based on repeated survey design, we investigate this relationship empirically. Our measures of ‘optimism’ and ‘realism’ are derived from comparing the turnover growth expectations of 133 owners-managers with the actual outcomes one year later. Our results indicate that entrepreneurial optimists perform significantly better in terms of profits than pessimists. Moreover, it is the optimist-realist combination that performs best. We interpret our results using regulatory focus theory.

Philosophy, theory, and practice of green operations management

This paper proposes a more profound discussion of the philosophical underpins of sustainability than currently exists in the MOT literature and considers their influence on the construction of the theories on green operations and technology management. Ultimately, it also debates the link between theory and practice on this subject area. The paper is derived from insights gained in three research projects completed during the past twelve years, primarily involving the first author. From 2000 to 2002, an investigation using scenario analysis, aimed at reducing atmospheric pollution in urban centres by substituting natural gas for petrol and diesel, provided the first set of insights about public policy, environmental impacts, investment analysis, and technological feasibility. The second research project, from 2003 to 2005, using a survey questionnaire, was aimed at improving environmental performance in livestock farming and explored the issues of green supply chain scope, environmental strategy and priorities. Finally, the third project, from 2006 to 2011, investigated environmental decisions in manufacturing organisations through case study research and examined the underlying sustainability drivers and decision-making processes. By integrating the findings and conclusions from these projects, the link between philosophy, theory, and practice of green operations and technology management is debated. The findings from all these studies show that the philosophical debate seems to have little influence on theory building so far. For instance, although ‘sustainable development’ emphasises ‘meeting the needs of current and future generation’, no theory links essentiality and environmental impacts. Likewise, there is a weak link between theory and the practical issues of green operations and technology management. For example, the well-known ‘life-cycle analysis’ has little application in many cases because the life cycle of products these days is dispersed within global production and consumption systems and there are different stakeholders for each life cycle stage. The results from this paper are relevant to public policy making and corporate environmental strategy and decision making. Most of the past and current studies in the subject of green operations and sustainability management deal with only a single sustainability dimension at any one time. Here the value and originality of this paper lies in its integration between philosophy, theory, and practice of green technology and operations management.

Research strategies for organizational history:a dialogue between historical theory and organization theory

If history matters for organization theory, then we need greater reflexivity regarding the epistemological problem of representing the past; otherwise, history might be seen as merely a repository of ready-made data. To facilitate this reflexivity, we set out three epistemological dualisms derived from historical theory to explain the relationship between history and organization theory: (1) in the dualism of explanation, historians are preoccupied with narrative construction, whereas organization theorists subordinate narrative to analysis; (2) in the dualism of evidence, historians use verifiable documentary sources, whereas organization theorists prefer constructed data; and (3) in the dualism of temporality, historians construct their own periodization, whereas organization theorists treat time as constant for chronology. These three dualisms underpin our explication of four alternative research strategies for organizational history: corporate history, consisting of a holistic, objectivist narrative of a corporate entity; analytically structured history, narrating theoretically conceptualized structures and events; serial history, using replicable techniques to analyze repeatable facts; and ethnographic history, reading documentary sources "against the grain." Ultimately, we argue that our epistemological dualisms will enable organization theorists to justify their theoretical stance in relation to a range of strategies in organizational history, including narratives constructed from documentary sources found in organizational archives. Copyright of the Academy of Management, all rights reserved.

Dynamics of linear polymers in random media

We study phenomenological scaling theories of the polymer dynamics in random media, employing the existing scaling theories of polymer chains and the percolation statistics. We investigate both the Rouse and the Zimm model for Brownian dynamics and estimate the diffusion constant of the center-of-mass of the chain in such disordered media. For internal dynamics of the chain, we estimate the dynamic exponents. We propose similar scaling theory for the reptation dynamics of the chain in the framework of Flory theory for the disordered medium. The modifications in the case of correlated disorders are also discussed. .

How optical spectrum of random fiber laser is formed

We experimentally and theoretically describe formation of random fiber laser's optical spectrum. We propose a new concept of active cycled wave kinetics from which we derive first ever nonlinear kinetic theory describing laser spectrum. © OSA 2015.

On reliable computation by noisy random Boolean formulas

We study noisy computation in randomly generated k-ary Boolean formulas. We establish bounds on the noise level above which the results of computation by random formulas are not reliable. This bound is saturated by formulas constructed from a single majority-like gate. We show that these gates can be used to compute any Boolean function reliably below the noise bound.

Hyper-random Phenomena: Definition and Description

The paper is dedicated to the theory which describes physical phenomena in non-constant statistical conditions. The theory is a new direction in probability theory and mathematical statistics that gives new possibilities for presentation of physical world by hyper-random models. These models take into consideration the changing of object’s properties, as well as uncertainty of statistical conditions.

Wave kinetics of random fibre lasers

Traditional wave kinetics describes the slow evolution of systems with many degrees of freedom to equilibrium via numerous weak non-linear interactions and fails for very important class of dissipative (active) optical systems with cyclic gain and losses, such as lasers with non-linear intracavity dynamics. Here we introduce a conceptually new class of cyclic wave systems, characterized by non-uniform double-scale dynamics with strong periodic changes of the energy spectrum and slow evolution from cycle to cycle to a statistically steady state. Taking a practically important example—random fibre laser—we show that a model describing such a system is close to integrable non-linear Schrödinger equation and needs a new formalism of wave kinetics, developed here. We derive a non-linear kinetic theory of the laser spectrum, generalizing the seminal linear model of Schawlow and Townes. Experimental results agree with our theory. The work has implications for describing kinetics of cyclical systems beyond photonics.

NLSE-based model of a random distributed feedback fiber laser

In this work we propose a NLSE-based model of power and spectral properties of the random distributed feedback (DFB) fiber laser. The model is based on coupled set of non-linear Schrödinger equations for pump and Stokes waves with the distributed feedback due to Rayleigh scattering. The model considers random backscattering via its average strength, i.e. we assume that the feedback is incoherent. In addition, this allows us to speed up simulations sufficiently (up to several orders of magnitude). We found that the model of the incoherent feedback predicts the smooth and narrow (comparing with the gain spectral profile) generation spectrum in the random DFB fiber laser. The model allows one to optimize the random laser generation spectrum width varying the dispersion and nonlinearity values: we found, that the high dispersion and low nonlinearity results in narrower spectrum that could be interpreted as four-wave mixing between different spectral components in the quasi-mode-less spectrum of the random laser under study could play an important role in the spectrum formation. Note that the physical mechanism of the random DFB fiber laser formation and broadening is not identified yet. We investigate temporal and statistical properties of the random DFB fiber laser dynamics. Interestingly, we found that the intensity statistics is not Gaussian. The intensity auto-correlation function also reveals that correlations do exist. The possibility to optimize the system parameters to enhance the observed intrinsic spectral correlations to further potentially achieved pulsed (mode-locked) operation of the mode-less random distributed feedback fiber laser is discussed.