ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / The requirements for a seismic telemetry-network are even more stringent than the well known problems of sensor networks. Existing medium access control (MAC) protocols suggest reducing energy consuming network activity by reducing costly transmissions and idle listening. Furthermore, it is required to set up communication patterns in different priority levels as well as ensuring fast handling of critical events. A protocol is proposed that operates with two parallel sets of time schedules in a time-division-multiple-access (TDMA) sense of periodic activity for listening and for transmitting. Synchronization packets sent from a central base station ensure optimal response times.

This thesis contributes towards understanding the dynamic phenomenon of entrepreneurship by exploring how entrepreneurs developed resilience within institutional constraints at the lived experience level. This is a qualitative research based on several assumptions of the phenomenological paradigm. The research describes the experiences of thirty-four participants - twenty-three practising entrepreneurs, and eleven Directors whose institutions support entrepreneurship, particularly the dimensions of the institutional profile, as well as how they developed resilience within institutional constraints. The study proposes that entrepreneurial resilience development is dynamic reflecting the context in which it arises. Institutions determine the rule of the game for entrepreneurs, in that entrepreneurs fit within the limitations provided by the institutional framework (North, 1990). The institutions shape opportunity fields for entrepreneurship, determine the ease and transaction cost of entrepreneurship, determine the stability and certainty of the environment, guide the strategic activities of entrepreneurs, confer legitimacy on entrepreneurs, (re)allocate entrepreneurship, and counter market failures for entrepreneurs. The experiences of the individuals indicate such constraint limits what the entrepreneurs are capable of doing. The research therefore focuses on how the entrepreneurs survived within such constraints, especially operating within underdeveloped institutions. In particular, the participants described how they were able to survive within such institutional constraints. The term 'resilience' can sometimes be trivialized to mean 'ego-resilience', which basically talks about certain characteristics that individuals' exhibit to show their resilience. Instead, apart from individuals exhibiting certain characteristics, there are several contextual activities that must be put in place to ensure survival or recovery within institutional constraints. These activities represent the resilience strategies that the entrepreneurs designed and implemented so as to survive institutional constraints - breakthrough, circumvent, destructive, and other strategies. The study concludes that entrepreneurial resilience strategy occupies a central role within three complex, interactive and interdependent processes - institutions, entrepreneurship, and resilience. Furthermore, entrepreneurship is engulfed in institutions, which act as the "determinant", "promoter", and "inhibitor" of entrepreneurial activities. Hence, entrepreneurs need to develop resilience through preventative, reactive or agility strategies, so as to be able to survive the institutional arrangements. The research therefore works towards a more integrated perspective of entrepreneurship development.

Higher education institutions are always directed through policy reforms to promote graduates employability by developing skills in students that contribute to human capital. This interest in employability through education system in the development of skills reflects is part of human capital theory. Considering this, underlying research investigates the expectation-performance gap in the development of generic skills for the purpose of employability offered by the accounting institutes of Pakistan. For the purpose of answering the research question, this research, adopted the theoretical framework of ‘expectation-performance gap’ by Bui and Porter and analysed it within the context of Pakistan. Adoption of this theoretical framework implies the evaluation of three constituent factors as research objectives; the ‘expectation gap’ (reflecting the differences in the expectations of accounting educators and employers), the ‘constraints gap’ (limiting factors to develop generic skills into the student learning process) and the ‘performance gap’ (reflecting the ineffectiveness of teaching activities). However, there is also a fourth objective, that is, to evaluate an outline of the ‘skills acquisition framework’ considering the context of Pakistan’s accounting job-market. Principally this research adopts the survey strategy of a questionnaire with closed-ended questions in order to collect the data. But for the purpose of refining the content of the questionnaire for relevance to the context of Pakistan there are also cognitive interviews. Thus, this research entails a mixed-method approach. The qualitative data from the interviews was analysed using content analysis, thematic analysis and textual analysis. Whereas the quantitative data from the questionnaires was analysed using numerous statistical techniques such as Mann-Whitney U-test, Independent sample t-test, Statistical mean and Principal Component Analysis. The findings related to the ‘expectation gap’ were that there are 19 skills where the accounting educators have dissimilar expectation from employers in terms of skill base education, such skills include decision making, economics, ability to analyse and reason logically, teamwork etc. The findings related to the ‘constraints gap’ were that there are 6 constraining elements which are prevailing within the context of professional accounting education, such constraints include ‘training organisations are not following standard procedures to develop skills in students’, ‘people (potential students) have misperception about accounting education’, 'enrolling students have weak academic background', ‘inadequate stipend offered by training organisations to trainees’, ‘accounting institutes are not appreciating teaching activities, and lack of training opportunities for academics’. The findings related to the ‘performance gap’ were that there are 24 skills where the accounting educators found to be ineffective in the development of skills in students as expected by employers for employment purpose, such skills include inter or multidisciplinary perspective, financial risk analysis, think and behave ethically, independent thinking etc. From the perspective of the ‘skills acquisition framework’, overall 6 skills components were identified from the perspective of Pakistan's accounting job-market, such skills components include appreciative skills, interpersonal skills, technical and functional skills, organisational and business management skills, personal skills and professional skills. Considering the novelty of the adopted theoretical framework (expectation-performance gap by Bui and Porter, 2010) there was a related paucity of literature employing it for empirical investigation using the questionnaire based approach. Therefore, this research provides such theoretical underpinning to this framework that now enables it to be used within the questionnaire based approach. Further this research has described all the generic skills used in this study from the accounting disciplinary perspective and highlights the constraining elements that are assumed to limit the ability of professional accounting institutes. This research also provides a skill acquisition framework which could be used as a reference point for new entrants to the accounting job-market.

Small and medium size enterprises (SMEs, hereafter) are important drivers of the global economic development. For the SMEs, to establish and growth, having access to the sources of finance is of great importance. Anecdotal evidence suggeststhat while the importance of having access for the SMEs is apparent, they have been disadvantageous in many different ways. The disadvantage position of the SMEs can even be worse when they are younger (e.g., The World bank, 2001, p. 6-7). Prior research documents many factors that affect the financial constraints of SMEs. In this study, we investigate the association between SMEs age and financial constraints. In addition, we test the moderating effect of collectivism on SMEs’ financial constraints, as collectivism is documented to have an effect on bank corruption. We first hypothesize that there is a negative association between SMEs’ age and financial constraints. We further propose that the negative association between SMEs’ age and financial constraints decreases as collectivism (at the country level) increases. Using a World Bank’s sample of 31422 firms across 38 countries, we find that younger firms, compared to the older firms, experience higher level of financial constraints.Further, we observe an insignificant results regarding the moderating effect of collectivism on the proposed association.We offer contribution to the existing empirical evidence onfactors that affect financial constraints. Providing such an evidence may be found relevant to the economic institutions such as the World Bank and regulatory bodies, as they are allocating resources and making macro level decisions regarding the economicdevelopment through SMEs around the world.

The cognitive radio network (CRN) concept has been proposed as a solution to the growing demand and underutilization of the radio spectrum. To improve the radio spectrum utilization, CRN technology allows the coexistence of licensed and unlicensed systems over the same spectrum. In an underlay spectrum sharing system, secondary users (SUs) transmit simultaneously with the primary users (PUs) in the same frequency band given that the interference caused by the SU to the PU remains below a tolerable interference limit. Besides the transmission power limitation, a secondary network is subject to distinct channel impairments such as fading and interference from the primary transmissions. Also, CRNs face new security threats and challenges due to their unique cognitive characteristics.This thesis analyzes the performance of underlay CRNs and underlay cognitive relay networks under spectrum sharing constraints and security constraints. Distinct SU transmit power policies are obtained considering various interference constraints such as PU outage constraint or PU peak interference power constraint. The thesis is divided into an introduction and two research parts based on peer-reviewed publications. The introduction provides an overview of radio spectrum management, basic concepts of CRNs, and physical layer security. In the first research part, we study the performance of underlay CRNs with emphasis on a multiuser environment.In Part I-A, we consider a secondary network with delay-tolerant applications and analyze the ergodic capacity. Part I-B analyzes the secondary outage capacity which characterises the maximum data rate that can be achieved over a channel for a given outage probability. In Part I-C, we consider a secondary network with delay constrained applications, and derive expressions of the outage probability and delay-limited throughput. Part I-D presents a queueing model that provides an analytical tool to evaluate the secondary packet-level performance with multiple classes of traffic considering general interarrival and service time distributions. Analytical expressions of the SU average packet transmission time, waiting time in the queue, andtime spent in the system are provided.In the second research part, we analyze the physical layer security for underlay CRNs and underlay cognitive relay networks. Analytical expressions of the probability of non-zero secrecy capacity and secrecy outage probability are derived.Part II-A considers a single hop underlay CRN in the presence of multiple eavesdroppers (EAVs) and multiple SU-Rxs. In Part II-B, an underlay cognitive relay network in the presence of multiple secondary relays and multiple EAVs is studied.Numerical examples illustrate that it is possible to exploit the physical layer characteristics to achieve both security and quality of service in CRNs while satisfying spectrum sharing constraints.

Thesis (MBA)--Stellenbosch University, 2001. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: In a world of increased global competition and the need of customer specific product customisation, the management of projects gets more and more important in order to achieve competitive advantages. By shortening the duration of projects and making project controlling tools more accurate (according to reality), the process of management-decision making is supported and companies can achieve higher profit margins as they are able to concentrate on value-adding parts and to plan future steps efficiently. Critical Chain is a new methodology, which applies Eli Goldratt's Theory of Constraints to project management in order to complete projects faster and with higher predictability while simultaneously making more efficient use of related resources. The Critical Chain methodology uses different concepts to reach these goals: • Average task durations • Aggregating buffer at the end of projects • Counteract against unplanned iterations and other delays • De-conflict resources, both within and across projects. The new project management methodology "Critical Chain" is subject of this research paper. The document is a high-level methodology study, which gives indications, whether, where - and if, how - the concept can be implemented in business environments. The argumentation is based on literature reviews and practical experiences of two pilot implementations in a German heavy industry company, which is internationally operating. In addition, the mini thesis explains basic principles of the Critical Chain approach. Furthermore, main strengths, weaknesses and ideas to improve the methodology are part of the study. Finally, experiences of companies using this methodology as well as an introduction to a Microsoft Project™ add-on, named ProChain©, benchmark the usability of Critical Chain. Critical Chain appears to minimize schedule risk while at the same time minimizing project durations, and has the potential to improve both communication and employee moral. Especially cultural .challenges will be explained, because the human-typical 'resistance to change' is a major hurdle in implementing Critical Chain in a company's project management system. Due to these cultural challenges, Critical Chain is not easy to implement in all parts of a heavy industry company. As the concept is based on mathematical formulas, it is highly recommended that in the beginning only smaller projects with highly qualified employees with a mathematical background (e.g. engineers or other studies in the field of natural sciences) use this concept. As the success of the methodology is dependent on the input of the project members, the whole project team has to understand the principles in front. As such, it is very important that a training course for all people involved is part of the implementation process. / AFRIKAANSE OPSOMMING: Geen

Thesis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: To maximise the throughput of a production system the capacity constrained resource needs to be protected from variation and uncertainty. In the Theory of Constraints philosophy such protection is provided by means of time buffers and protective capacity. Time buffers are protective time that is allowed in the production schedule to buffer against disruptions, whereas protective capacity is defined as a given amount of extra capacity at non-constraints above the system constraint's capacity. In this research an analytical procedure was developed to more accurately determine the required time buffer lengths. This procedure uses an open queuing network modelling approach where workstations are modelled as GIIG/m queues. A simulation experiment was performed to evaluate the time buffer estimation procedure on the operations of an actual fifteen station flow shop. The results from the study suggest that the analytical procedure is sufficiently accurate to provide an initial quick estimate of the needed time buffer lengths at the design stage of the line. This dissertation also investigated the effect of protective capacity levels at a secondary constraint resource as well as at the other non-constraint resources on the mean flow time, the bottleneck probability of the primary constraint resource, as well as the output of flow production systems using simulation models and ANOV A. Two different types of flow production systems were investigated: (1) a flow shop with a fixed number of stations and unlimited queue or buffer space between stations, and (2) an assembly line where a total work content is distributed among stations in a certain fashion and the number of stations are not fixed. The experimental studies show that flow shop performance in the form of flow time and line output is not that much influenced by low protective capacity levels at the secondary constraint resource. Low protective capacity levels at a single station however can significantly reduce the bottleneck probability for the primary constraint resource when it is located before and relatively close or near to the primary constraint in the process flow, or after but relatively far from the primary constraint. An after-far secondary constraint location also causes slightly longer job flow times, and should therefore be avoided if possible. The research further shows that quite high protective capacity levels at the nonconstraint resources are needed to ensure a more stable and therefore manageable primary constraint. However low average levels of protective capacity at non-constraint resources are sufficient to ensure that the maximum designed output level as determined by the utilisation of the primary constraint resource is obtained. The results for the assembly line experiment showed that an unbalanced line configuration where less work is assigned to the non-constraint stations than to the primary constraint station (but nonconstraint stations have an equal work content) can lead to significant reductions in the mean flow time while maintaining the same line output, without resulting in too many additional stations. Low protective capacity levels in the range of 2% to 5% are sufficient to cause substantial improvements in flow time without resulting in too many additional stations in the line. / AFRIKAANSE OPSOMMING: Om die finale uitset van 'n produksiestelsel te maksimeer is dit noodsaaklik dat die bottelnek beskerm word teen fluktuasies en onderbrekings. In die "Theory of Constraints" filosofie word van twee soorte beskermingsmeganismes gebruik gemaak: tydbuffers en beskermende kapasiteit. Tydbuffers is beskermende tyd wat in die produksieskedule gevoeg word om sodoende die bottelnek teen onderbrekings te beskerm, terwyl beskermende kapasiteit ekstra produksiekapasiteit relatief tot die bottelnek se kapasiteit is wat by nie-bottelnekke gevoeg word. In hierdie navorsing IS 'n analitiese prosedure ontwikkel om meer akkurate berekenings van tydbuffergroottes te verkry in produksiestelsels wat volgens 'n "Theory of Constraints" filosofie bestuur word. Die prosedure maak gebruik van oop toustaan netwerk modellering waar werkstasies gemodelleer word as GIIG/m toue. Die analitiese prosedure is ge-evalueer met 'n simulasie eksperiment op 'n werklike vyftien stasie vloeiwinkel. Die resultate dui aan dat die analitiese prosedure akkuraat genoeg is om vinnig aanvanklike beramings vir die benodigde tydbuffergroottes tydens die ontwerpsfase van die produksiestelsel te verskaf. Verder is ook ondersoek ingestel na die effek van beskermende kapasiteitsvlakke by die sekondêre bottelnek asook die ander nie-bottelnekke op die gemiddelde deurvloeityd, die totale uitset, asook die bottelnek waarskynlikheid vir die primêre bottelnek in vloei produksiestelsels deur gebruik te maak van simulasie modelle en ANOVA. Twee verskillende tipes vloei produksiestelsels is ondersoek: (1) 'n vloeiwinkel met 'n vaste aantal stasies en 'n onbeperkte buffer spasie tussen stasies, en (2) 'n monteerlyn waar 'n totale werksinhoud op 'n bepaalde wyse onder stasies verdeel moet word en die aantal stasies nie vas is nie. Die eksperimentele studies dui aan dat die deurvloeitye en totale uitset van 'n vloeiwinkel me noemenswaardig beïnvloed word deur lae beskermende kapasiteitsvlakke by die sekondêre bottelnek nie. Hierdie maatstawwe word meer beïnvloed word deur die gemiddelde beskermende kapasiteitsvlakke by al die nie-bottelnekke. Lae beskermende kapasiteit by 'n enkele werkstasie kan egter die bottelnek waarskynlikheid vir die primêre bottelnek aansienlik verlaag indien dit voor en relatief na aan die primêre bottelnek in die prosesvloei geleë is, of na, maar relatief ver, vanaf die primêre bottelnek. 'n Sekondêre bottelnek ligging na maar relatief ver vanaf die primêre bottelnek in die prosesvloei veroorsaak ook langer deurvloeitye, en moet dus vermy word. Verder dui die navorsing aan dat redelike hoë gemiddelde beskermende kapasiteit by nie-bottelnekke benodig word om 'n meer stabiele primêre bottelnek te verseker. In vloeiwinkels met lae vlakke van variasie en onderbrekings is egter lae gemiddelde vlakke van beskermende kapasiteit by nie-bottelnekke voldoende om te verseker dat die maksimum ontwerpte uitset soos bepaal deur die benutting van die primêre bottelnek behaal word. Die resultate vir die monteerlyn eksperiment dui aan dat 'n ongebalanseerde lynkonfigurasie waar minder werk aan die nie-bottelnek stasies as aan die primêre bottelnek stasie toegeken word (maar niebottelnek stasies het 'n gelyke werksinhoud), aansienlike verlagings in deurvloeityd teweeg kan bring terwyl dieselfde lyn uitset behou word. Dit is moontlik sonder te veel addisionele stasies in die lyn. Die eksperimentele resultate dui aan dat lae beskermende kapasiteitsvlakke van tussen 2% tot 5% voldoende is om beduidende verlagings in deurvloeityd teweeg te bring sonder te veel addisionele stasies.

It is frequently the case that deterministic optimization models could be made more practical by explicitly incorporating uncertainty. The resulting stochastic optimization problems are in general more difficult to solve than their deterministic counterparts, because the objective function cannot be evaluated exactly and/or because there is no explicit relation between the objective function and the corresponding decision variables. This thesis develops random search algorithms for solving optimization problems with continuous decision variables when the objective function values can be estimated with some noise via simulation. Our algorithms will maintain a set of sampled solutions, and use simulation results at these solutions to guide the search for better solutions. In the first part of the thesis, we propose an Adaptive Search with Resampling and Discarding (ASRD) approach for solving continuous stochastic optimization problems. Our ASRD approach is a framework for designing provably convergent algorithms that are adaptive both in seeking new solutions and in keeping or discarding already sampled solutions. The framework is an improvement over the Adaptive Search with Resampling (ASR) method of Andradottir and Prudius in that it spends less effort on inferior solutions (the ASR method does not discard already sampled solutions). We present conditions under which the ASRD method is convergent almost surely and carry out numerical studies aimed at comparing the algorithms. Moreover, we show that whether it is beneficial to resample or not depends on the problem, and analyze when resampling is desirable. Our numerical results show that the ASRD approach makes substantial improvements on ASR, especially for difficult problems with large numbers of local optima. In traditional simulation optimization problems, noise is only involved in the objective functions. However, many real world problems involve stochastic constraints. Such problems are more difficult to solve because of the added uncertainty about feasibility. The second part of the thesis presents an Adaptive Search with Discarding and Penalization (ASDP) method for solving continuous simulation optimization problems involving stochastic constraints. Rather than addressing feasibility separately, ASDP utilizes the penalty function method from deterministic optimization to convert the original problem into a series of simulation optimization problems without stochastic constraints. We present conditions under which the ASDP algorithm converges almost surely from inside the feasible region, and under which it converges to the optimal solution but without feasibility guarantee. We also conduct numerical studies aimed at assessing the efficiency and tradeoff under the two different convergence modes. Finally, in the third part of the thesis, we propose a random search method named Gaussian Search with Resampling and Discarding (GSRD) for solving simulation optimization problems with continuous decision spaces. The method combines the ASRD framework with a sampling distribution based on a Gaussian process that not only utilizes the current best estimate of the optimal solution but also learns from past sampled solutions and their objective function observations. We prove that our GSRD algorithm converges almost surely, and carry out numerical studies aimed at studying the effects of utilizing the Gaussian sampling strategy. Our numerical results show that the GSRD framework performs well when the underlying objective function is multi-modal. However, it takes much longer to sample solutions, especially in higher dimensions.

Variable symmetries in constraint satisfaction problems can be broken by adding lexicographic ordering constraints. Existing general methods of generating such sets of ordering constraints can produce a huge number of additional constraints. This adds an unacceptable overhead to the solving process. Methods exist by which this large set of constraints can be reduced to a much smaller set automatically, but their application is also prohibitively costly. In contrast, this thesis takes a bottom up approach to generating symmetry breaking constraints. This will involve examining some commonly-occurring families of mathematical groups and deriving a general formula to produce a minimal set of ordering constraints which are sufficient to break all of the symmetry that each group describes. In some cases it is known that there exists no manageable sized sets of constraints to break all symmetries. One example of this occurs with matrix row and column symmetries. In such cases, incomplete symmetry breaking has been used to great effect. Double lex is a commonly used incomplete symmetry breaking technique for row and column symmetries. This thesis also describes another similar method which compares favourably to double lex. The general formulae investigated are used as building blocks to generate small sets of ordering constraints for more complex groups, constructed by combining smaller groups. Through the utilisation of graph automorphism tools and the groups and permutations software GAP we provide a method of defining variable symmetries in a problem as a group. Where this group can be described as the product of smaller groups, with known general formulae, we can construct a minimal set of ordering constraints for that problem automatically. In summary, this thesis provides the theoretical background necessary to apply efficient static symmetry breaking to constraint satisfaction problems. It also goes further, describing how this process can be automated to remove the necessity of having an expert CP practitioner, thus opening the field to a larger number of potential users.

The research described in this thesis stems from ROBOCARE1, a three year research project aimed at developing software and robotic technology for providing intelligent support for elderly people. This thesis deals with two problems which have emerged in the course of the project’s development: Multi-agent coordination with scarce resources. Multi-agent planning is concerned with automatically devising plans or strategies for the coordinated enactment of concurrently executing agents. A common realistic constraint in applications which require the coordination of multiple agents is the scarcity of resources for execution. In these cases, concurrency is affected by limited capacity resources, the presence of which modifies the structure of the planning/coordination problem. Specifically, the first part of this thesis tackles this problem in two contexts, namely when planning is carried out centrally (planning from first principles), and in the context of distributed multi-agent coordination. Domain modeling for scheduling applications. It is often the case that the products of research in AI problem solving are employed to develop applications for supporting human decision processes. Our experience in ROBOCARE as well as other domains has often called for the customization of prototypical software for real applications. Yet the gap between what is often a research prototype and a complete decision support system is seldom easy to bridge.The second part of the thesis focuses on this issue from the point of view of scheduling software deployment.Overall, this thesis presents three contributions within the two problems mentioned above. First, we address the issue of planning in concurrent domains in which the complexity of coordination is dominated by resource constraints. To this end, an integrated planning and scheduling architecture is presented and employed to explore the structural trademarks of multi-agent coordination problems in function of their resource-related characteristics. Theoretical and experimental analyses are carried out revealing which planning strategies are most fit for achieving plans which prescribe efficient coordination subject to scarce resources.We then turn our attention to distributed multi-agent coordination techniques (specifically, a distributed constraint optimization (DCOP) reduction of the coordination problem). Again, we consider the issue of achieving coordinated action in the presence of limited resources. Specifically, resource constraints impose n-ary relations among tasks. In addition, as the number of n-ary relations due to resource contention are exponential in the size of the problem, they cannot be extensionally represented in the DCOP representation of the coordination problem. Thus, we propose an algorithm for DCOP which retains the capability to dynamically post n-ary constraints during problem resolution in order to guarantee resource-feasible solutions. Although the approach is motivated by the multi-agent coordination problem, the algorithm is employed to realize a general architecture for n-ary constraint reasoning and posting.Third, we focus on a somewhat separate issue stemming from ROBOCARE, namely a software engineering methodology for facilitating the process of customizing scheduling components in real-world applications. This work is motivated by the strong applicative requirements of ROBOCARE. We propose a software engineering methodology specific to scheduling technology development. Our experience in ROBOCARE as well as other application scenarios has fostered the development of a modeling framework which subsumes the process of component customization for scheduling applications. The framework aims to minimize the effort involved in deploying automated reasoning technology in practise, and is grounded on the use of a modeling language for defining how domain-level concepts are grounded into elements of a technology-specific scheduling ontology.