Parallax is a distributed storage system that uses virtualization to provide storage facilities specifically for virtual environments. The system employs a novel archi-tecture in which storage features that have traditionally been implemented directly on high-end storage arrays and switches are relocated into a federation of storage VMs, sharing the same physical hosts as the VMs that they serve. This architecture retains the single administrative domain and OS agnosticism achieved by array- and switch-based approaches, while lowering the bar on hardware requirements and facilitating the development of new features. Parallax offers a comprehensive set of storage features including frequent, low-overhead snapshot of virtual disks, the “gold-mastering” of template images, and the ability to use local disks as a persistent cache to dampen burst demand on networked storage.

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Two experimental configurations of linear slot nozzle virtual impactors were constructed and experimentally investigated for use as bioaerosol concentrators. In one configuration, the Linear Slot Virtual Impactor (LSVI), the nozzle was a straight slot having a length of 89 mm (3.5"). In the second configuration, the Circumferential Slot Virtual Impactor (CSVI), the nozzle was curvilinear following a circular path having a diameter of 152.4 mm (6.0") and the resulting total slot length was 479 mm (18.8"). Multiple prototypes of the two configurations were constructed having nozzle widths that varied from 0.508 mm (0.015") to 0.203 mm (0.008"). Optical and physical measurements were made of the nozzle dimensions in the critical region of the virtual impactor units. For the LSVI units the misalignment between the acceleration nozzle and the receiver nozzle was measured between 6 µm (0.00025") and 29 µm (0.00114"). This represented a range of 2% to 10% misalignment relative to the acceleration nozzle width. The CSVI Unit 1 and 2 misalignments were measured to be 15 µm (0.00061") and 9 µm (0.00036"), or 10% and 1.8% relative misalignment, respectively. The virtual impactors were tested with liquid and solid monodisperse aerosol particles. For operation at flow rate conditions predicted from the literature to produce a cutpoint of 0.8 µm AD, an acoustic resonance was observed, corresponding to significant nozzle wall losses of particles and an absence of normal particle separation in the virtual impactor. The onset of the resonance phenomenon was observed to begin at a nozzle Reynolds number of approximately 500 for the LSVI configuration, and 300 for the CSVI configuration. For flow rates just below the onset of resonance, normal virtual impactor behavior was observed. The value of Stk50 was 0.58 for both devices, corresponding to a particle cutpoint size of 1.1 µm AD for the LSVI configuration and 2.2 µm AD for the CSVI. The collection efficiency was greater than 72% for all particle sizes larger than twice the cutpoint up to the largest particle size tested (≈ 10 µm AD). The peak collection efficiency for both concentrators was greater than 95%.

In this research project composed of multiple case studies, I focused on how bona fide virtual groups appropriated multiple media to facilitate group boundary construction and boundary management, which are preconditions of group identity formation. Specific topics explored in the study included how virtual groups socially constructed their group boundaries through recurring patterns of media use as well as other communication practices, how the group boundaries were preserved and blurred in both internal and external communication, and how bona fide groups managed dialectal tensions in interacting with external groups. To explore those research questions, I conducted four in-depth case studies of real life groups operating in natural contexts. Multiple qualitative methods of data collection were employed in the study and a modified grounded theory method was used in analyzing the collected data. As a result, the study found that the groups studied constructed group boundaries through communication practices such as making sense of common goals, negotiation of task jurisdiction with other interlocking groups, distinguishing patterns of ingroup interaction from those of outgroup interactions, and through developing group specific patterns and norms of media combination and media use. Group boundaries were preserved when the influence of outgroup members were constrained through media use, such as excluding them from team conference calls, filtering messages from external groups or members, and using boundary spanners to interact with external members. Group boundaries were blurred when intergroup communication impacted internal dynamics and when norms and practices were transferred from other contexts into a given group context. The study suggested that technology adaptation and boundary management occurred simultaneously. In addition, the groups experienced dialectical tensions in face of the permeability of group boundaries and developed communication tactics to deal with those tensions. Theoretical implications of the study were also discussed.

Over the past decade, researches on operating systems have been shifted from monolithic kernels towards microkernels for several reasons. Of them are: (1) It is easier to understand and debug because the kernel is much smaller. (2) It is much more secure and flexible because the kernel is small, and most of the kernel functions can be implemented as servers running in the user space instead of in the kernel space. (3) The message passing technique that is in the core of the microkernel has been improved, and thus the overhead required for the message passing has been highly reduced. Minix 3 is one of the microkernels developed over the past decade and is aimed for educational purpose and small PCs. It is implemented on the IA-32 architecture and is based on the segmented memory model of IA-32. The purpose of this thesis is to use Minix 3 as a case study and to convert the segmented memory model adopted by the current implementation to coexisted with the demand paged memory model, which is also supported by the IA-32 architecture. That said, the thesis can be divided into two parts: The first part is to implement a new server called pager, which would take over the memory management subsystem of the Minix 3 microkernel and be used to offload the overhead of the kernel. The second part is to implement a virtual memory management subsystem that uses the segmentation with paging memory model of the IA-32 architecture.

Due to the fast speed of broadband and the advanced level of bandwidth, Internet users love to spend a lot of time surfing the Internet and the e-life concept has become a very popular living style. Recently, the trend towards food shopping in groups has overwhelmed traditional shopping habits. In the past, people bought food after a free taste and now the food lovers share their experiences on their blogs. The unknown shops therefore will become famous after being introduced by food lovers forwarding their relevant e-mails. The establishment of virtual communities for shopping in groups helps consumers to acquire a better price after negotiating with shop owners. The estimated variables, including comments of group leaders, life styles and intensity of relations, were used to analyze the buying willingness in the virtual communities. The results of questionnaires were collected from the ihergo website, run by a Delicacies Discovery Team in Kaohsiung. All data were analyzed and verified via: descriptive statistics, reliability factors, correlation and regression etc. The results are described as follows: 1.The positive comments of group leaders impacted buying willingness in the virtual communities. 2.The positive intensity of relations affected the buying willingness in the virtual communities. 3.The ¡§creativity and trends¡¨ in lifestyle revealed a positive correlation with the buying willingness in virtual communities

<p>This project is associated with the field of Information Systems and more specifically with Virtual Learning Environments (VLEs). These environments are becoming very popular the last years, especially in higher education. However we decided to focus in lower level education since there is lack of these learning platforms and their spreading is limited.</p><p>More specifically our project will focus on the description of a Virtual Learning Environment for preliminary schools. The target age will be 5-8 years old. The design of our system is based on the guidelines of a preliminary schoolteacher in Spain, who is actually our stakeholder. Designing a system for so young students means that various aspects have to be taken into consideration such as their level of computer knowledge, their maturity, their not still developed studying abilities and the fact that it is their first approach to school as a learning environment. However we believe that if they can be integrated in the information society in such an early age, it will be beneficial for their future and the future of information technologies as well. We hope that through this project we will be able to contribute to computer based education and equip the young students with new ways and potentials of learning.</p><p>On a theoretical basis, we could say that our project contains two different parts: a theoretical part and a more practical one. In the theoretical part, all the related work of similar VLEs is presented in an effort to see what products already exist in the market and try to create a new, innovative system taking into consideration various educational aspects. In addition, a review of our literature research concerning computer based education and VLEs is included in order to provide the necessary theoretical background before starting to design our system. Finally, a summary of our research made including questionnaires and interviews as well as the analysis and the conclusions of this research are presented since before designing our system we tried to include the opinion of the different people involved in this system like the students and their parents, the teachers and the pedagogues. On the other hand, the second more practical part focuses on the description of the learning platform. The architecture of the system as well as the use cases is included here. A prototype of the system is also provided but we were not able to complete the whole implementation due to time limitations.</p>

Vortrag UNIX-Stammtisch 10/97

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 133-147).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 229-242). Available also in a digital version from Dissertation Abstracts.