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The present thesis examines questionnaire responses regarding optimal environmental attributes of public outdoor spaces for Chinese grandparents who are taking care of their grandchildren within selected urban residential communities in Shanghai, China. This thesis also assesses the needs of these grandparents providing childcare against the environmental attributes of urban public spaces. It uses the results to formulate design recommendations that will facilitate increased social interaction between grandparents with grandchildren and other persons in open public spaces of residential communities. Public spaces are often excellent locations for social interaction between grandparents with other persons within communities. Recently, there has been an increase in the number of Chinese grandparents providing childcare for their grandchildren, and many choose to spend time with grandchildren in these public open spaces. However, the needs and preferences of this demographic do not necessarily align with those of the general population. The current literature has identified five primary environmental attributes (access, comfort, opportunities of meeting, potential sensory elements, visibility) related to social interaction, each composed of a variety of landscape elements and characteristics. A framework was constructed based on these five environmental attributes and a variety of landscape elements and characteristics, and used to formulate a questionnaire for 46 grandparents, who take care of their grandchildren and live in high-rise buildings were surveyed. The selected participants were witnessed watching over their grandchildren in open spaces or the accompanying facilities and were asked to express a level of preference for a series of landscape elements presented in a questionnaire. The survey also included questions regarding demographic information. Descriptive and inferential analysis were then carried out through the survey data. The intended result of the study involved establishing a set of landscape architectural design recommendations that could be used in order to meet the preferences of this portion of society. Ideally, the findings will assist those involved in designing and managing outdoor environments in identifying the most salient environmental attributes for this growing sector of the Chinese community. The study could also help to prioritize interventions aimed at improving the use of open spaces and promoting social interaction among grandparents or grandparents with other neighbors. The approach also identified which landscape elements were most likely to attract grandparents to visit and stay in neighborhoods' open spaces longer with their grandchildren. Ideally, an outdoor public space designed following this set of design recommendations would contain the preferred environmental attributes and landscape elements of grandparents and their grandchildren and would provide more opportunities for social interaction. / Master of Landscape Architecture

Our work focuses on performance modelling of TCP-controlled file transfers in infrastructure mode IEEE 802.11 wireless networks, and application of the models in developing association schemes. A comprehensive set of analytical models is used to study the behaviour of TCP-controlled long and short file transfers in IEEE 802.11 WLANs. The results can provide insight into the performance of TCP-controlled traffic in 802.11 WLANs in a variety of different network environments. First, we consider several WLAN stations associated at rates r1, r2, ...,rk with an Access Point. Each station (STA) is downloading a long file from a local server, located on the LAN to which the AP is attached, using TCP. We assume that a TCP ACK will be produced after the reception of d packets at an STA. We model these simultaneous TCP-controlled transfers using a semi-Markov process. Our analytical approach leads to a procedure to compute aggregate download as well as per-STA throughputs numerically, and the results match simulations very well. Performance analysis of TCP-controlled long file transfers in a WLAN in infrastructure mode is available in the literature with one of the main assumptions being equal window size for all TCP connections. We extend the analysis to TCP-controlled long file uploads and downloads with different TCP windows. Our approach is based on the semi- Markov process considered in above work, but with arbitrary window sizes. We present simulation results to show the accuracy of the analytical model. Then, we obtain an association policy for STAs in an IEEE 802.11 WLAN by taking into account explicitly an aspect of practical importance: TCP controlled short file downloads interspersed with read times (motivated by web browsing). Our approach is based on two steps. First, we consider the analytical model mentioned above to obtain the aggregate download throughput. Second, we present a 2-node closed queueing network model to approximate the expected average-sized file download time for a user who shares the AP with other users associated at a multiplicity of rates. These analytical results motivate the proposed association policy, called the Estimated Delay based Association (EDA) policy: Associate with the AP at which the expected file download time is the least. Simulations indicate that for a web-browsing type traffic scenario, EDA outperforms other policies that have been proposed earlier; the extent of improvement ranges from 12.8% to 46.4% for a 9-AP network. We extend the performance model by considering _le sizes drawn from heavy-tailed distributions. We represent heavy-tailed distributions using a 1 mixture of exponential distributions (following Cox's method). We provide a closed queueing network model to approximate the expected average-sized file download time for a user who shares the AP with other users associated at a multiplicity of rates. Further, we analyze TCP-controlled bulk file transfers in a single station WLAN with nonzero propagation delay between the file server and the WLAN. Our approach is to model the flow of packets as a closed queueing network (BCMP network) with 3 service centres, one each for the Access Point and the STA, and the third for the propagation delay. The service rates of the first two are obtained by analyzing the WLAN MAC. We extend this work to obtain throughputs in multirate scenarios. Simulations show that our approach is able to predict observed throughputs with a high degree of accuracy.

An understanding of Input/Output data access patterns of applications is useful in several situations. First, gaining an insight into what applications are doing with their data at a semantic level helps in designing efficient storage systems. Second, it helps to create benchmarks that mimic realistic application behavior closely. Third, it enables autonomic systems as the information obtained can be used to adapt the system in a closed loop. All these use cases require the ability to extract the application-level semantics of I/O operations. Methods such as modifying application code to associate I/O operations with semantic tags are intrusive. It is well known that network file system traces are an important source of information that can be obtained non-intrusively and analyzed either online or offline. These traces are a sequence of primitive file system operations and their parameters. Simple counting, statistical analysis or deterministic search techniques are inadequate for discovering application-level semantics in the general case, because of the inherent variation and noise in realistic traces. In this paper, we describe a trace analysis methodology based on Profile Hidden Markov Models. We show that the methodology has powerful discriminatory capabilities that enables it to recognize applications based on the patterns in the traces, and to mark out regions in a long trace that encapsulate sets of primitive operations that represent higher-level application actions. It is robust enough that it can work around discrepancies between training and target traces such as in length and interleaving with other operations. We demonstrate the feasibility of recognizing patterns based on a small sampling of the trace, enabling faster trace analysis. Preliminary experiments show that the method is capable of learning accurate profile models on live traces in an online setting. We present a detailed evaluation of this methodology in a UNIX environment using NFS traces of selected commonly used applications such as compilations as well as on industrial strength benchmarks such as TPC-C and Postmark, and discuss its capabilities and limitations in the context of the use cases mentioned above.

Systems can become misconfigured for a variety of reasons such as operator errors or buggy patches. When a misconfiguration is discovered, usually the first order of business is to restore availability, often by undoing the misconfiguration. To simplify this task, we propose Ocasta to automatically determine which files contain configuration state. Ocasta uses a novel {\em similarity} metric to measures how similar a file's versions are to each other, and a set of filters to eliminate non-persistent files from consideration. These two mechanisms enable Ocasta to identify all 72 configuration files out of 2363 versioned files from 6 common applications in two user traces, while mistaking only 33 non-configuration files as configuration files. Ocasta allows a versioning file system to eliminate roughly 66\% of non-configuration file versions from its logs, thus reducing the number of file versions that a user must manually examine to recover from a misconfiguration.

Systems can become misconfigured for a variety of reasons such as operator errors or buggy patches. When a misconfiguration is discovered, usually the first order of business is to restore availability, often by undoing the misconfiguration. To simplify this task, we propose Ocasta to automatically determine which files contain configuration state. Ocasta uses a novel {\em similarity} metric to measures how similar a file's versions are to each other, and a set of filters to eliminate non-persistent files from consideration. These two mechanisms enable Ocasta to identify all 72 configuration files out of 2363 versioned files from 6 common applications in two user traces, while mistaking only 33 non-configuration files as configuration files. Ocasta allows a versioning file system to eliminate roughly 66\% of non-configuration file versions from its logs, thus reducing the number of file versions that a user must manually examine to recover from a misconfiguration.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / There is a gulf that separates measurement and telemetry applications from the full benefits of Internet style communication. Whereas the Web provides ubiquitous infrastructure for the distribution of file-based “static” data, there is no general Web solution for real-time streaming data. At best, there are proprietary products that target consumer multimedia and resort to custom point-to-point data connections. This paper considers an extension of the static file paradigm to a dynamic file and introduces a streaming data solution integrated with the existing file-based infrastructure of the Web. The solution approach appears to maximize platform and application independence leading to improved application interoperability potential for large or complex measurement and telemetry networks.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Consultative Committee for Space Data Systems (CCSDS) is defining a CCSDS File Delivery Protocol (CFDP) capable of use between systems of multiple endpoints. A number of prototype CFDP implementations have been developed and some interoperability tests performed over UDP links. This paper reports on a study of CFDP running over more realistic packet telecommand and packet telemetry links. An integrated test system was constructed by adapting existing commercial and prototype software. This was used to study a number of scenarios which are likely to be important in early operational use of CFDP in space. This approach has been found to be useful both for testing a protocol during its development and specification and for verifying the impact of new approaches to Space Missions.