Squeeze Film Dampers (SFD) provide viscous damping in rotor bearing systems to reduce lateral vibration amplitudes and to isolate mechanical components. Aircraft engine shafts, often supported on roller bearings, operate at high rotational speeds and are susceptible to large amplitude shaft whirl due to rotor imbalance. SFDs aid to reduce such large whirl amplitudes while also eliminating rotor instabilities. he current work quantifies experimentally the forced performance of two parallel squeeze SFDs separated by a central groove. Force coefficients are identified in a specialized SFD test rig constructed to undergo similar operating and loading conditions as in jet engines. Of interest is to quantify the effect of a central feed groove on the forced performance of SFDs and to validate predictions from a computational tool. The test rig comprises of an elastically supported bearing structure and one of two journals. Tests are conducted on two open ends SFDs, both with diameter D and nominal radial clearance c; each damper with two parallel film land lengths L= 1/5 D and 2L, separated by a feed groove of width L and depth 3/4 L. ISO VG 2 grade lubricant oil flows into the central groove via 3 orifices, 120 degrees apart, and then through the film lands to finally exit to ambient. In operation, a static loader pulls the bearing to various static off center positions with respect to the stationary journal, and electromagnetic shakers (2,200 N) excite the test system with single frequency loads over a frequency range to generate rectilinear, circular and elliptical orbits with specified motion amplitudes. A frequency domain method identifies the SFD mechanical parameters, viz., stiffness, damping, and added mass coefficients. The long damper generates 7 times more direct damping and 2 times more added mass compared to the short length damper. The damping coefficients are sensitive to the static eccentricity (up to 50 percent c) while showing lesser dependency on the amplitude of whirl motion (up to 20 percent c). On the other hand, added mass coefficients are nearly constant with static eccentricity and decrease with higher amplitudes of motion. The magnitudes of identified cross-coupled coefficients are insignificant for all imposed operating conditions for either damper. Large dynamic pressures recorded in the central groove demonstrate the groove does not isolate the film lands by merely acting as a source of lubricant, but contributes to the generation of large added mass coefficients. The recorded dynamic pressures in the film lands and central groove do not evidence lubricant vapor or gas cavitation for the tested static eccentricities and amplitudes of motion. The direct damping coefficients for both dampers are independent of excitation frequency over the frequency range of the tests. Predictions derived from a novel SFD computational tool that includes flow interactions in the central groove and oil supply orifices agree well with the experimental force coefficients for both dampers. The current work advances the state of the art in SFDs for jet engines.

La découverte des cellules souches embryonnaires et de leur immense potentiel thérapeutique a fait naître de grands espoirs. De nouvelles thérapies révolutionnaires pour traiter certaines des maladies les plus graves dont souffre l'humanité sont désormais envisageables. Le traitement de la vie à son stade le plus précoce est mis en cause. Le statut juridique reconnu au foetus et à l'embryon humain a des répercussions directes sur le domaine de la recherche et sur leur utilisation à des fins thérapeutiques. Nous avons examiné l'état du droit canadien quant au statut juridique du foetus et de l'embryon. De cette étude, nous avons constaté l'incertitude qui prévaut au Canada quant à leur statut. Par la suite, nous avons étudié les différentes normes canadiennes établies pour encadrer l'utilisation des cellules souches embryonnaires à des fins thérapeutiques et nous les avons analysées et comparées pour faire ressortir leurs similitudes et leurs différences. II est ressorti de notre analyse que les textes canadiens se rejoignent généralement sur l'essentiel et qu'il y a eu peu de changements de 1993 à aujourd'hui, en regard des activités de recherche interdites au Canada. Puis, nous avons examiné les systèmes normatifs applicables à ces recherches à l'étranger, soit aux États-Unis et en GrandeBretagne. Nous avons effectué une analyse comparative des trois systèmes normatifs étudiés, en évaluant différents paramètres communs à ces systèmes. Il est ressorti de cette analyse, que la Grande-Bretagne est le pays le plus libéral relativement à ces domaines de recherche, que les États-Unis sont les plus conservateurs sur ces questions et que le Canada se situe entre les deux. / The embryonic stem cells discovery and the immense therapeutic potential glven to them has created big hopes in the world of today. The appearance of new revolutionary therapies to treat sorne of the most serious known diseases are now conceivable. However, the treatment of life to its earliest stage is questionned. The legal status recognized to the foetus and the embryo has, in fact, a direct effect to the research area and industry as weil as to its therapeutic use. Therefore, we have examined and studied the CUITent canadian law with respect to the legal status of the foetus and embryo. Following this study, we have noticed the uncertainty that prevails in Canada concerning the said legal status. Afierwards, we have examined ail the different canadian norms and regulations already established regarding the use of embryonic stem cells for therapeutic ends. We also did the comparaison between those norms and regulations so as to see their differences and similarities. It appears from our analysis that ail the canadian litterature generally treat the subject in the same way and that there have been few changes from 1993 up until now with respect to the forbidden researchs activities in Canada. We also have analysed the foreign law standards and regulations in United States and Great Britain concerning those forbidden researchs activities. We did the exercise of comparing the state of the law in these three countries with different parameters. It emerges from that that Great Britain is the most liberal country, United States being the most conservative and Canada being in between them. / "Mémoire présenté à la Faculté des études supérieures en vue de l'obtention du grade de Maîtrise en droit (L.L.M.) Option recherche"

The overall aim of this thesis is to present a model for rational goal-setting and to illustrate how it can be applied in evaluations of public policies, in particular policies concerning sustainable development and environmental quality. The contents of the thesis are divided into two sections: a theoretical section (Papers I-IV) and an empirical section (Papers V-VII). Paper I identifies a set of rationality criteria for single goals and discusses them in relation to the typical function of goals. It is argued that goals are typically set to enhance goal achievement. A goal that successfully furthers its achievement is “achievement-inducing”. It holds for each of the identified criteria that, ceteris paribus, improved satisfaction of a criterion makes a goal better in the achievement-inducing sense.Paper II contains an analysis of the notion of goal system coherence. It is argued that the coherence of a goal system is determined by the relations that hold among the goals in the system, in particular the relations of operationalization, means and ends, support, and conflict. Paper III investigates the rationality of utopian goals. The paper analyzes four arguments that support the normative criterion of attainability: that utopian goals are (1) too imprecise and (2) too far-reaching to guide action effectively, (3) counterproductive, and (4) morally objectionable. A tentative defence of utopian goal-setting is built on counter-arguments that can be put forward to weaken each of the four objections. Paper IV investigates the nature of self-defeating goals. The paper identifies three types of situations in which self-defeating mechanisms obstruct goal achievement: (1) situations in which the goal itself carries the seeds of its own non-fulfilment (self-defeating goals), (2) situations in which the activity of goal-setting contributes to goal failure (self-defeating goal-setting), and (3) situations in which disclosure of the goal interferes with progress (self-defeating goal disclosure). Paper V provides a brief description of the Swedish system of environmental objectives and a preliminary inventory of the management difficulties that attach to this goal system.Paper VI contains an investigation into the rationality of five Swedish environmental objectives through an application of the rationality criteria identified in Papers I-II. The paper identifies and discusses some difficulties that are associated with management by objectives and the use of goals in environmental policy. Paper VII analyses the rationality of the Swedish environmental quality objective A good built environment. Among the conclusions drawn in the paper are that some of the sub-goals to the objective are formulated in terms that are unnecessarily vague from an action-guiding standpoint and that others are problematic from the viewpoint of evaluability. / QC 20100715

Notre laboratoire a récemment découvert un mode d’expression des gènes mitochondriaux inédit chez le protozoaire biflagellé Diplonema papillatum. Outre son ADNmt formé de centaines de chromosomes circulaires, ses gènes sont fragmentés. Le gène cox1 qui code pour la sous unité I de la cytochrome oxydase est formé de neuf modules portés par autant de chromosomes. L’ARNm de cox1 est obtenu par épissage en trans et il est également édité par insertion de six uridines entre deux modules. Notre projet de recherche a porté sur une étude globale des processus post-transcriptionnels du génome mitochondrial de diplonémides. Nous avons caractérisé la fragmentation de cox1 chez trois autres espèces appartenant aux deux genres du groupe de diplonémides à savoir : Diplonema ambulator, Diplonema sp. 2 et Rhynchopus euleeides. Le gène cox1 est fragmenté en neuf modules chez tous ces diplonémides mais les modules sont portés par des chromosomes de taille et de séquences différentes d’une espèce à l’autre. L’étude des différentes espèces a aussi montrée que l’édition par insertion de six uridines entre deux modules de l’ARNm de cox1 est commune aux diplonémides. Ainsi, la fragmentation des gènes et l’édition des ARN sont des caractères communs aux diplonémides. Une analyse des transcrits mitochondriaux de D. papillatum a permis de découvrir quatre autres gènes mitochondriaux édités, dont un code pour un ARN ribosomique. Donc, l'édition ne se limite pas aux ARNm. De plus, nous avons montré qu’il n’y a pas de motifs d’introns de groupe I, de groupe II, de type ARNt ou d’introns impliqués dans le splicéosome et pouvant être à l’origine de l’épissage des modules de cox1. Aucune complémentarité significative de séquence n’existe entre les régions flanquantes de deux modules voisins, ni de résidus conservés au sein d’une espèce ou à travers les espèces. Nous avons donc conclu que l’épissage en trans de cox1 chez les diplonémides fait intervenir un nouveau mécanisme impliquant des facteurs trans plutôt que cis. L’épissage et l’édition de cox1 sont dirigés probablement par des ARN guides, mais il est également possible que les facteurs trans soient des molécules protéiques ou d’ADN. Nous avons élucidé les processus de maturation des transcrits mitochondriaux de D. papillatum. Tous les transcrits subissent trois étapes coordonnées et précises, notamment la maturation des deux extrémités, l’épissage, la polyadénylation du module 3’ et dans certains cas l’édition. La maturation des extrémités 5’ et 3’ se fait parallèlement à l’épissage et donne lieu à trois types d’intermédiaires. Ainsi, un transcrit primaire avec une extrémité libre peut se lier à son voisin. Cet épissage se fait apparemment sans prioriser un certain ordre temporel alors que dans le cas des transcrits édités, l’édition précède l`épissage. Ces études donnant une vue globale de la maturation des transcrits mitochondriaux ouvrent la voie à des analyses fonctionnelles sur l’épissage et l’édition chez D. papillatum. Elles sont le fondement pour finalement élucider les mécanismes moléculaires de ces deux processus post-transcriptionnels de régulation dans ce système intriguant. / Our laboratory has recently discovered an unprecedented mode of expression of mitochondrial genes in D. papillatum, a biflagellate protozoan. In addition to its mtDNA formed of hundreds of circular chromosomes, genes are fragmented. For example, the cox1 gene which encodes the subunit one of the cytochrome oxidase complex, comprises nine modules carried by nine chromosomes. The cox1 mRNA is obtained by trans-splicing and is also edited by the insertion of six uridines between two modules. My thesis project focused on the study of post-transcriptional processes in diplonemid mitochondria. We characterized the fragmentation of cox1 in three other species belonging to two diplonemids genera: Diplonema ambulator, Diplonema sp. 2 and Rhynchopus euleeides. The cox1 gene is fragmented into nine modules in all species but the modules are carried by chromosomes of different size and sequences from one species to another. We have shown that there are no motifs for classical introns, including spliceosomal and archaeal introns, as well as introns of group I and II, that might be implicated in the trans-splicing of cox1 modules. No significant complementarity exists between the flanking regions of two neighboring modules, nor are any conserved residues within a species or across species. We therefore concluded that the trans-splicing of cox1 in diplonemids involves a novel mechanism implicating trans rather than cis-factors. Trans-splicing and editing of cox1 probably involve guide RNAs, but it is also possible that the trans-factors are proteins or DNA molecules. The study of different species has also shown that the insertion of six uridines between two cox1 modules in mRNA is a shared trait in these diplonemids. We discovered that four other mitochondrial genes are also edited in D. papillatum and that RNA editing is not limited to mRNA. So, fragmented genes and RNA editing are common characteristics of diplonemids. We elucidated D. papillatum’s mitochondrial transcript maturation steps. All transcripts undergo three coordinated and precise processes including end processing, trans-splicing and / or editing and polyadenylation. The processing of the 5 'and 3' ends gives rise to three kinds of maturation intermediates. A primary transcript with one free end can bind to its neighbor and trans-splicing occurs without directionality. In the case of edited transcripts, editing precedes trans-splicing. These studies have prepared the ground for functional studies of trans-splicing and RNA editing with the long term goal to elucidate the molecular mechanisms involved in post-transcriptional regulation in this intriguing system.

This dissertation explores the need to involve churches in mission according to the Lord Jesus Christ, whose mission was indeed holistic and comprehensive. To achieve this goal, the study calls upon churches to move from a “maintenance Christianity” status, which has been almost a way of life for churches, to a holistic and comprehensive approach to mission. Practically speaking, this is to be illustrated through a case study of churches in the North Kivu Province of the Democratic Republic of the Congo. The churches in this part of the world present many challenges that sustain such an exploration, namely, misunderstanding regarding mission, lack of well-skilled and visionary church leaders, maintenance Christianity mentality, spirit of tribalism among Christians, and poverty. The study concludes with practical recommendations on how the issues raised through the dissertation can be applied to a broader field than the churches in the North Kivu Province. / Christian Spirituality, Church History and Missiology) / M. Th. (Missiology)

One of the greatest challenges facing the clothing industry worldwide, including South Africa is to provide well fitting garments to a broadly defined target population (Ashdown, Loker & Rucker 2007:1; Schofield, Ashdown, Hethorn, LaBat & Salusso 2006:147). Yu (2004:32) further states that from the consumers’ perspective, physical and psychological comfort as well as appearance play an important role in determining a well fitting garment and these are most likely to be shaped by the individual’s personal values. According to Kaiser (1998:290), personal values refer to standards or principles that guide an individual’s actions and thoughts that help to define what is important by guiding one’s choices or preferences of how the garment should fit. Hence garment fit and the subsequent appearance serves as a personal expression, communicating some personal values to others (Kaiser 1998:290) that can be achieved through the fitting of the garment. When female consumers encounter garment fit problems either through body shapes, garment sizing or garment size label communication, an emotional experience may result due to the failure to attain the personal values they are aiming to uphold or achieve. Cognitive appraisal theory of emotions is one of the theories among others that attempts to understand why people experience emotions. Lazarus (2001:55) defines cognitive appraisal theory of emotions as a quick evaluation of a situation with respect to one’s wellbeing. The answers to these evaluations directly cause the emotions experienced by a person. Since clothing can be used to express personal values to others (Kaiser 1998:146), the social standards appraisal dimension which can be one of the evaluative questions in the theory of cognitive appraisal concerning a situation, was the relevant evaluative component which this study focused on. This appraisal dimension evaluates whether the situation, in this case the negative experience of an ill-fitting garment affects what the consumer aspires to achieve socially through garment fit. Numerous studies such as Horwaton and Lee (2010); Pisut and Connell (2007) and Alexander, Connell & Presley (2005) on the garment fit problems from a consumer’s perspective have mostly been conducted in developed countries with limited research focusing on the consumers and their emotional experiences with garment fit. Understanding the factors that contribution to the garment fit problem currently being faced by female consumers in South Africa is an essential step in creating awareness of how this problem affects female consumers emotionally and the influence it has on their purchasing decisions. The purpose of this study is, therefore, to determine the female consumers’ personal values attributed to garment fit and to identify the emotions resulting from the perceptions of garment fit. This study predominantly employed an exploratory qualitative research approach. Data were collected from a purposive and convenient sample of 62 females from the UNISA – Florida Campus and King David High School in Victory Park in Johannesburg, South Africa through a self-administered questionnaire. Data on the demographic profile that included the ethnicity and age of the participants as well as data on the psychographic profile of the participants concerning frequently patronized clothing retailers, garment fit preferences and self-reported body shapes were collected through closed-ended questions. These data were analysed using the quantitative method of descriptive analysis. In addition to the psychographic profile of the most frequently patronized clothing retailer and garment fit preferences, participants were further requested to provide reasons as to why they mostly patronized the clothing retailer they ranked number 1, and to provide a reason for their preferred garment fit option. Content analysis, a qualitative method, was used to analyse the reasons provided by the participants for both these questions. Content analysis was also performed on additional information on body shape and garment sizing as well as data on garment size label communication. Furthermore, the means-end chain approach through the hard laddering exercises was used to explore and determine the female consumers’ personal values and emotions depicted through the perceptions of garment fit. Data from the hard laddering interviews on body shapes and garment sizing were carefully coded and categorized into attributes, consequences and personal values. Data were presented through the hierarchical value maps (HVMs) which were constructed through the software program Mecanalyst V 9.1. The analysis established that attributes such as quality of garments, various garment styles, availability of sizes, and fashionable styles directed female consumers’ most frequented clothing retailers. These attributes seemed to be aligned with their personal values they seek when shopping for garments. The findings also showed that most female consumers in this study preferred semi-fitting pants, a blouse and garments in general, a reasonable number of the participants preferred tight-fitting pants (31%), and some participants preferred loose-fitting pants, a blouse and garments in general. The specific personal values such as the comfortability of the garment, modesty, cover-up perceived body shape “flaws” and slimming effect which female consumers in this study desire to achieved through clothing also influenced their garment fit preference. With regard to the perceived self-reported body shapes of the participants, the study reflected that the majority of the participants were triangular body shaped. The study further found that female consumers in this study have expectations of how a garment ought to fit their body. Their expectations seem to be shaped by certain personal values such as “confidence”, “freedom” or “look good” which they aspire to achieve through clothing and garment fit. However, due to variations in body shapes, problems of garment sizing they encounter when purchasing ready-to wear garments and the incorrect information communicated on the size labels or the lack thereof, the majority of the female consumers failed to achieve their personal values. As a result mainly negative emotions such as “frustrated”, “sad”, “confused” and “depressed” were expressed by the participants. With regards to the effect of the perceived garment fit on the purchasing decision, the study found that fit of the garment is an important determinant of making a purchase. However, where female consumers in this study showed an interest of purchasing, while aware of some fit problems, the study found that exceptional conditions such as the possibility of altering the garments and design features such as colours that would conceal their perceived “figure flaws, made it easier for them to decide to purchase. The study further highlighted that some participants only purchased their ready-to-wear garment at certain shops where their needs were catered for and only when they had enough time to try-on the garment they intend to purchase instead of relying on the garment sizing and garment size label communication. Where participants indicated they would not purchase a garment with fitting problems, the study found that some female consumers in this study copied the designs of the garments in the clothing retailers and had someone reproduce it for them, whilst a few female consumers refused to purchase a garment whose size label was incorrectly communicated. Lastly the study also revealed that most female consumers thought that body shape, garment sizing and garment size label communication contribute to garment fit problems female consumers are currently facing in South Africa. It is, therefore, recommended that clothing manufacturers consider the various body shapes in their garment charts, know the needs of their target market and also use uniform sizing and size labelling systems that are easily understood by consumers that purchase ready-to-wear garments from retailers in South Africa. / Life and Consumer Sciences / M. Sc. (Consumer Science)

Cette thèse est consacrée à l'étude de la topologie à l'infini d'espaces généralisant les graphes de Schreier. Plus précisément, on considère le quotient X/H d'un espace métrique géodésique propre hyperbolique X par un groupe quasi-convexe-cocompact H d'isométries de X. On montre que ce quotient est un espace hyperbolique. Le résultat principal de cette thèse indique que le nombre de bouts de l'espace quotient X/H est déterminé par les classes d'équivalence sur une sphère de rayon explicitement calculable. Dans le cadre de la théorie des groupes, on montre que l'on peut construire explicitement des groupes et des sous-groupes pour lesquels il n'existe pas d'algorithme permettant de déterminer le nombre de bouts relatifs. Si le sous-groupe est quasi-convexe, on donne un algorithme permettant de calculer le nombre de bouts relatifs. / This thesis is devoted to the study of the topology at infinity of spaces generalizing Schreier graphs. More precisely, we consider the quotient X/H of a geodesic proper hyperbolic metric space X by a quasiconvex-cocompact group H of isometries of X. We show that this quotient is a hyperbolic space. The main result of the thesis indicates that the number of ends of the quotient space X/H is determined by equivalence classes on a sphere of computable radius. In the context of group theory, we show that one can construct explicitly groups and subgroups for which there are no algorithm to determine the number of relative ends. If the subgroup is quasiconvex, we give an algorithm to compute the number of relative ends.

The doctoral thesis deals with spectrum sensing in cognitive radio networks (CRN). A number of international organizations are currently actively engaged in standardization of CRN and it points out to the fact that this technology will be widely used in the near future. One of the key features of this technology is a dynamic access to the spectrum, which can be affected by many different harmful factors occurring in the communication chain. The thesis investigates the influence of selected factors on the spectrum sensing process. Another contribution of the work is the optimization of the Kolmogorov - Smirnov statistical test that can be applied for the primary user signal detection. The work also incorporates the analysis of the influence of the harmful effects caused by the commonly used transmitters and receivers on various spectrum sensing methods. The investigations are verified by the results of the simulations and also by the measurements with experimental platforms based on the software-defined radio (SDR).

Le risk management d’entreprise (ERM) est un ensemble de politiques, de structures et de pratiques infuses d’idéaux sociaux de bonne gouvernance et de contrôlabilité. Nous nous demandons ici dans quelles mesures le travail des acteurs permet l’adoption durable de l’ERM dans l’organisation. Dans le cas du Groupe La Poste, l’appropriation des pressions externes par les auditeurs internes a été cruciale. Une fois introduit dans l’organisation postale, l’ERM a d’abord été confronté à l’indifférence du management. Les contenus réglementaires et normatifs ont été adoptés sans être mis en œuvre. Des structures partielles d’ERM ont été peuplées de risk managers détenant les compétences nécessaires pour répondre aux attentes externes. Ces risk managers ont ensuite travaillé à légitimer et structurer le dispositif conformément aux « meilleures pratiques » en réalisant un travail de recouplage – action intentionnelle des individus visant à aligner le risk management organisationnel avec les traits externes et abstraits de l’ERM. L’étude du cas La Poste suggère ainsi une explication organisationnelle au fait que l’ERM ne puisse être révoqué une fois en place. / Enterprise-wide risk management (ERM) is a set of policies, structures and practices infused with social ideals of good governance and controllability. In this research, we seek to know how actors’ work allows ERM lasting adoption in the organization. In La Poste, the enactment of external pressures by internal auditors turned out to be critical. When introduced in the postal organization, ERM first encountered management disregard. As a consequence, ERM regulatory and normative meanings and categories were adopted but not implemented in the business. Partial ERM structures were created and inhabited by risk managers who hold necessary skills to help organizational compliance with external expectations. Newly appointed risk managers worked internally to legitimize and structure the device consistently with external “best practices” performing what we named recoupling work - the purposive action of individuals and organizations aimed at aligning organizational risk management with external ERM abstract features. Thus, our case suggests an organizational explanation to the fact that risk management could not be rescinded after its initial settlement.

Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m^2/K, respectively), obtained using a narrowband (425 kHz bandwidth) prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include spectral line detection of hydroxyl (OH) sources W49N and W3OH, and some of the first radio camera images made using a PAF, including an image of the Cygnus X region. A novel array Y-factor technique for measuring the isotropic noise response of the array is shown along with experimental measurements for this PAF. Statistically optimal beamformers (Maximum SNR and MVDR) are used throughout the work. Radio-frequency interference (RFI) mitigation is demonstrated experimentally using spatial cancelation with the PAF. Improved RFI mitigation is achieved in the challenging cases of low interference-to-noise ratio (INR) and moving interference by combining subspace projection (SP) beamforming with a polynomial model to track a rank 1 subspace. Limiting factors in SP are investigated including sample estimation error, subspace smearing, noise bias, and spectral scooping; each of these factors is overcome with the polynomial model and prewhitening. Numerical optimization leads to the polynomial subspace projection (PSP) method, and least-squares fitting to the series of dominant eigenvectors over a series of short term integrations (STIs) leads to the eigenvector polynomial subspace projection (EPSP) method. Expressions for the gradient, Hessian, and Jacobian are given for use in numerical optimization. Results are given for simulated and experimental data, demonstrating deeper beampattern nulls by 6 to 30dB. To increase the system bandwidth toward the hundreds of MHz bandwidth required by astronomers for a fully science-ready instrument, an FPGA digital backend is introduced using a 64-input analog-to-digital converter running at 50 Msamp/sec and the ROACH processing board developed at the University of California, Berkeley. International efforts to develop digital back ends for large antenna arrays are considered, and a road map is proposed for development of a hardware correlator/beamformer at BYU using three ROACH boards communicating over 10 gigabit Ethernet.