Dynamics of pattern writing and erasure in photorefractive lithium niobate for data storage applications

The present rate of technological advance continues to place significant demands on data storage devices. The sheer amount of digital data being generated each year along with consumer expectations, fuels these demands. At present, most digital data is stored magnetically, in the form of hard disk drives or on magnetic tape. The increase in areal density (AD) of magnetic hard disk drives over the past 50 years has been of the order of 100 million times, and current devices are storing data at ADs of the order of hundreds of gigabits per square inch. However, it has been known for some time that the progress in this form of data storage is approaching fundamental limits. The main limitation relates to the lower size limit that an individual bit can have for stable storage. Various techniques for overcoming these fundamental limits are currently the focus of considerable research effort. Most attempt to improve current data storage methods, or modify these slightly for higher density storage. Alternatively, three dimensional optical data storage is a promising field for the information storage needs of the future, offering very high density, high speed memory. There are two ways in which data may be recorded in a three dimensional optical medium; either bit-by-bit (similar in principle to an optical disc medium such as CD or DVD) or by using pages of bit data. Bit-by-bit techniques for three dimensional storage offer high density but are inherently slow due to the serial nature of data access. Page-based techniques, where a two-dimensional page of data bits is written in one write operation, can offer significantly higher data rates, due to their parallel nature. Holographic Data Storage (HDS) is one such page-oriented optical memory technique. This field of research has been active for several decades, but with few commercial products presently available. Another page-oriented optical memory technique involves recording pages of data as phase masks in a photorefractive medium. A photorefractive material is one by which the refractive index can be modified by light of the appropriate wavelength and intensity, and this property can be used to store information in these materials. In phase mask storage, two dimensional pages of data are recorded into a photorefractive crystal, as refractive index changes in the medium. A low-intensity readout beam propagating through the medium will have its intensity profile modified by these refractive index changes and a CCD camera can be used to monitor the readout beam, and thus read the stored data. The main aim of this research was to investigate data storage using phase masks in the photorefractive crystal, lithium niobate (LiNbO3). Firstly the experimental methods for storing the two dimensional pages of data (a set of vertical stripes of varying lengths) in the medium are presented. The laser beam used for writing, whose intensity profile is modified by an amplitudemask which contains a pattern of the information to be stored, illuminates the lithium niobate crystal and the photorefractive effect causes the patterns to be stored as refractive index changes in the medium. These patterns are read out non-destructively using a low intensity probe beam and a CCD camera. A common complication of information storage in photorefractive crystals is the issue of destructive readout. This is a problem particularly for holographic data storage, where the readout beam should be at the same wavelength as the beam used for writing. Since the charge carriers in the medium are still sensitive to the read light field, the readout beam erases the stored information. A method to avoid this is by using thermal fixing. Here the photorefractive medium is heated to temperatures above 150�C; this process forms an ionic grating in the medium. This ionic grating is insensitive to the readout beam and therefore the information is not erased during readout. A non-contact method for determining temperature change in a lithium niobate crystal is presented in this thesis. The temperature-dependent birefringent properties of the medium cause intensity oscillations to be observed for a beam propagating through the medium during a change in temperature. It is shown that each oscillation corresponds to a particular temperature change, and by counting the number of oscillations observed, the temperature change of the medium can be deduced. The presented technique for measuring temperature change could easily be applied to a situation where thermal fixing of data in a photorefractive medium is required. Furthermore, by using an expanded beam and monitoring the intensity oscillations over a wide region, it is shown that the temperature in various locations of the crystal can be monitored simultaneously. This technique could be used to deduce temperature gradients in the medium. It is shown that the three dimensional nature of the recording medium causes interesting degradation effects to occur when the patterns are written for a longer-than-optimal time. This degradation results in the splitting of the vertical stripes in the data pattern, and for long writing exposure times this process can result in the complete deterioration of the information in the medium. It is shown in that simply by using incoherent illumination, the original pattern can be recovered from the degraded state. The reason for the recovery is that the refractive index changes causing the degradation are of a smaller magnitude since they are induced by the write field components scattered from the written structures. During incoherent erasure, the lower magnitude refractive index changes are neutralised first, allowing the original pattern to be recovered. The degradation process is shown to be reversed during the recovery process, and a simple relationship is found relating the time at which particular features appear during degradation and recovery. A further outcome of this work is that the minimum stripe width of 30 ìm is required for accurate storage and recovery of the information in the medium, any size smaller than this results in incomplete recovery. The degradation and recovery process could be applied to an application in image scrambling or cryptography for optical information storage. A two dimensional numerical model based on the finite-difference beam propagation method (FD-BPM) is presented and used to gain insight into the pattern storage process. The model shows that the degradation of the patterns is due to the complicated path taken by the write beam as it propagates through the crystal, and in particular the scattering of this beam from the induced refractive index structures in the medium. The model indicates that the highest quality pattern storage would be achieved with a thin 0.5 mm medium; however this type of medium would also remove the degradation property of the patterns and the subsequent recovery process. To overcome the simplistic treatment of the refractive index change in the FD-BPM model, a fully three dimensional photorefractive model developed by Devaux is presented. This model shows significant insight into the pattern storage, particularly for the degradation and recovery process, and confirms the theory that the recovery of the degraded patterns is possible since the refractive index changes responsible for the degradation are of a smaller magnitude. Finally, detailed analysis of the pattern formation and degradation dynamics for periodic patterns of various periodicities is presented. It is shown that stripe widths in the write beam of greater than 150 ìm result in the formation of different types of refractive index changes, compared with the stripes of smaller widths. As a result, it is shown that the pattern storage method discussed in this thesis has an upper feature size limit of 150 ìm, for accurate and reliable pattern storage.

Seeking a life in the literary position : the writing of Charmian Clift

An examination of the published and unpublished writing of Charmian Clift.

International students in Australian universities : gap between student expectations and realities

Australian Universities are very successful in attracting large number of international students. A large proportion of University revenue comes from the full fee paying international students. However, there have been many reports that international students face numerous problems when they arrive in Australia. The common management practice is to provide support staff services to deal with the orientation and welfare of international students. Such service units act as intermediaries between the students and the teaching and learning community of the university. However, the actual experience of international students may be difficult for support staff, counsellors, advisers and academic staff to anticipate. There is little information on the actual experience of students relative to their expectations. This study aimed at securing a deeper understanding of the contextually relevant issues facing by international students in Australian universities in order to develop management strategies aimed at improved teaching and learning outcomes for international students. Using a highly reliable survey questionnaire, a questionnaire survey was conducted among the international students at Queensland University of Technology (QUT), Brisbane, Australia. About 180 engineering students responded in the survey resulting in a response rate of 81%. Results indicate that international students face many difficulties including understanding colloquial language, Australian accent, cost of tuition, feelin isolation, safety, security, health services, accommodation and part time jobs. They also face difficulty in coping with learning methods in Australia, particularly in research report writing. However, they are happy with their lecturers and find them very helpful. Many of the students lacked the information regarding various community groups, recreational and sports facilities in Australia before arriving. Findings of the study show that there is a significant gap between the expectation of the students before coming to Australia and actual experience they experience here. Importantly, there is a lack of coordination between international students, international student services (ISS) and university management and as a consequence there have been little improvement in conditions. There is no direct link between student experience and University management. Many important suggestions arisen from this study and most important suggestion is that the student information system should be integrated with the University enterprise resource planning (ERP) to reduce the huge gap between international student expectation and actual experiences.

Implementing low intensity CBT in case management of clients with severe mental illness

In a previous chapter (Dean and Kavanagh, Chapter 37), the authors made a case for applying low intensity (LI) cognitive behaviour therapy (CBT) to people with serious mental illness (SMI). As in other populations, LI CBT interventions typically deal with circumscribed problems or behaviours. LI CBT retains an emphasis on self-management, has restricted content and segment length, and does not necessarily require extensive CBT training. In applying these interventions to SMI, adjustments may be needed to address cognitive and symptomatic difficulties often faced by these groups. What may take a single session in a less affected population may require several sessions or a thematic application of the strategy within case management. In some cases, the LI CBT may begin to appear more like a high-intensity (HI) intervention, albeit simple and with many LI CBT characteristics still retained. So, if goal setting were introduced in one or two sessions, it could clearly be seen as an LI intervention. When applied to several different situations and across many sessions, it may be indistinguishable from a simple HI treatment, even if it retains the same format and is effectively applied by a practitioner with limited CBT training. ----- ----- In some ways, LI CBT should be well suited to case management of patients with SMI. treating staff typically have heavy workloads, and find it difficult to apply time-consuming treatments (Singh et al. 2003). LI CBT may allow provision of support to greater numbers of service users, and allow staff to spend more time on those who need intensive and sustained support. However, the introduction of any change in practice has to address significant challenges, and LI CBT is no exception. ----- ----- Many of the issues that we face in applying LI CBT to routine case management in a mnetal health service and their potential solutions are essentially the same as in a range of other problem domains (Turner and Sanders 2006)- and, indeed, are similar to those in any adoption of innovation (Rogers 2003). Over the last 20 years, several commentators have described barriers to implementing evidence-based innovations in mental health services (Corrigan et al. 1992; Deane et al. 2006; Kavanagh et al. 1993). The aim of the current chapter is to present a cognitive behavioural conceptualisation of problems and potential solutions for dissemination of LI CBT.

Changing academic practice to prepare nursing undergraduates for an evidence-based approach

Evidence based practice (EBP) has been accepted as a process to assist health professionals in clinical decision making to improve patient outcomes. It requires applying skills in a prescribed sequence to critique existing practices. Many countries, including Australia, require nurses to demonstrate competencies in EBP skills to be registered. In the last ten years, this has lead to universities incorporating EBP in undergraduate nursing degree courses. The literature reports many challenges including students’ difficulties in critically appraising research evidence, and their need for both simplification of the process and extensive support. The purpose of our study was to investigate the effectiveness of a standalone introductory EBP subject for a diverse group of third-year undergraduates, based on a novel but challenging approach to assessment. Despite many changes made in the second iteration of the subject, most students’ perceptions of the subject’s difficulty remained unchanged. This research aligns with the issues identified in the literature and has wider applicability to the teaching of rapidly changing disciplines, where evidence-driven consumers have easy access to information and expect up-to-date practices.

Expression and connection : the integration of the reflective learning process and the writing process into social network sites

A number of instructors have recently adopted social network sites (SNSs) for learning. However, the learning design of SNSs often remains at a preliminary level similar to a personal log book because it does not properly include reflective learning elements such as individual reflection and collaboration. This article looks at the reflective learning process and the public writing process as a way of improving the quality of reflective learning on SNSs. It proposes a reflective learning model on SNSs based on two key pedagogical concepts for social networking: individual expression and collaborative connection. It is expected that the model would be helpful for instructors in designing a reflective learning process on SNSs in an effective and flexible way.

Critical literacy finds a "Place": Writing and social action in a low-income Australian grade 2/3 classroom

In a study of socioeconomically disadvantaged children's acquisition of school literacies, a university research team investigated how a group of teachers negotiated critical literacies and explored notions of social power with elementary children in a suburban school located in an area of high poverty. Here we focus on a grade 2/3 classroom where the teacher and children became involved in a local urban renewal project and on how in the process the children wrote about place and power. Using the students' concerns about their neighborhood, the teacher engaged her class in a critical literacy project that not only involved a complex set of literate practices but also taught the children about power and the possibilities for local civic action. In particular, we discuss examples of children's drawing and writing about their neighborhoods and their lives. We explore how children's writing and drawing might be key elements in developing "critical literacies" in elementary school settings. We consider how such classroom writing can be a mediator of emotions, intellectual and academic learning, social practice, and political activism.

Portrayal of librarians in Australian creative writing

An exploration is made of the ways in which librarians have been depicted in Australian creative writing. Reference is made to characters in novels, short stories, drama and poetry. With respect to novels, there is some consideration of characterisation and its relationship to plot.

The concealed difficulties of aligning CRE decisions to corporate goals

Realisation of the importance of real estate asset strategic decision making has inspired a burgeoning corporate real estate management (CREM) literature. Much of this criticises the poor alignment between strategic business direction and the ‘enabling’ physical environment. This is based on the understanding that corporate real estate assets represent the physical resource base that supports business, and can either complement or impede that business. In the hope of resolving this problem, CRE authors advocate a deeper integration of strategic and corporate real estate decisions. However this recommendation appears to be based on a relatively simplistic theoretical approach to organization where decision-making tends to be viewed as a rationally managed event rather than a complex process. Defining decision making as an isolated event has led to an uncritical acceptance of two basic assumptions: ubiquitous, conflict-free rationality and profit maximisation. These assumptions have encouraged prescriptive solutions that clearly lack the sophistication necessary to come to grips with the complexity of the built and organizational environment. Alternatively, approaching CREM decision making from a more sophisticated perspective, such as that of the “Carnegie School”, leads to conceptualise it as a ‘process’, creating room for bounded rationality, multiple goals, intra-organizational conflict, environmental matching, uncertainty avoidance and problem searching. It is reasonable to expect that such an approach will result in a better understanding of the organizational context, which will facilitate the creation of organizational objectives, assist with the formation of strategies, and ultimately will aid decision.

Pedagogy of feedback on student academic writing : research supervisor practices for the end of the research degree candidature

All academic writing is advanced with the benefit of feedback about the writing. In the case of the academic writing genres of the research proposal and the dissertation, feedback is usually provided by the research supervisor. Given that academic writing development is a process, and in the case of the research proposal and dissertation, writing which develops over time, it seems likely that the nature of feedback on drafts written early in the candidature may be different from feedback provided by the research supervisor later in a student’s candidature. ----- ----- When a research supervisor has been reading a student’s writing over a period of time, their own familiarity with the writing generates a risk to their ability to provide critical and objective feedback. Particularly by the end of a student’s candidature, the research supervisor’s familiarity with the work may cause them to miss elements of writing improvement. ----- ----- The author, as a research supervisor, has developed a feedback grid to facilitate feedback on the final drafts of a dissertation. This feedback grid is generated by the embedded promises in the early sections of the dissertation, which are then used to audit the content of the final sections of the dissertation to ascertain whether promises made have been fulfilled. This provides a strategy for the research supervisor to step back from the work and read the dissertation with the agenda of a dissertation examiner. ----- ----- The grid is one strategy within a broader pedagogy of providing feedback on writing samples.

An obsession with storytelling : conducting oral history interviews for creative writing

Anna Hirsch and Clare Dixon (2008, 190) state that creative writers’ ‘obsession with storytelling…might serve as an interdisciplinary tool for evaluating oral histories.’ This paper enters a dialogue with Hirsch and Dixon’s statement by documenting an interview methodology for a practice-led PhD project, The Artful Life Story: Oral History and Fiction, which investigates the fictionalising of oral history. ----- ----- Alistair Thomson (2007, 62) notes the interdisciplinary nature of oral history scholarship from the 1980s onwards. As a result, oral histories are being used and understood in a variety of arts-based settings. In such contexts, oral histories are not valued so much for their factual content but as sources that are at once dynamic, emotionally authentic and open to a multiplicity of interpretations. How can creative writers design and conduct interviews that reflect this emphasis? ----- ----- The paper briefly maps the growing trend of using oral histories in fiction and ethnographic novels, in order to establish the need to design interviews for arts-based contexts. I describe how I initially designed the interviews to suit the aims of my practice. Once in the field, however, I found that my original methods did not account for my experiences. I conclude with the resulting reflection and understanding that emerged from these problematic encounters, focusing on the technique of steered monologue (Scagliola 2010), sometimes referred to as the Biographic Narrative Interpretative Method (Wengraf 2001, Jones 2006).

Investigating and theorizing discourse during analogy writing in chemistry

Explanations of the role of analogies in learning science at a cognitive level are made in terms of creating bridges between new information and students’ prior knowledge. In this empirical study of learning with analogies in an 11th grade chemistry class, we explore an alternative explanation at the "social" level where analogy shapes classroom discourse. Students in the study developed analogies within small groups and with their teacher. These classroom interactions were monitored to identify changes in discourse that took place through these activities. Beginning from socio-cultural perspectives and hybridity, we investigated classroom discourse during analogical activities. From our analyses, we theorized a merged discourse that explains how the analog discourse becomes intertwined with the target discourse generating a transitional state where meanings, signs, symbols, and practices are in flux. Three categories were developed that capture how students intertwined the analog and target discourses—merged words, merged utterances/sentences, and merged practices.