A vector quantization approach to universal noiseless coding and quantization

A two-stage code is a block code in which each block of data is coded in two stages: the first stage codes the identity of a block code among a collection of codes, and the second stage codes the data using the identified code. The collection of codes may be noiseless codes, fixed-rate quantizers, or variable-rate quantizers. We take a vector quantization approach to two-stage coding, in which the first stage code can be regarded as a vector quantizer that “quantizes” the input data of length n to one of a fixed collection of block codes. We apply the generalized Lloyd algorithm to the first-stage quantizer, using induced measures of rate and distortion, to design locally optimal two-stage codes. On a source of medical images, two-stage variable-rate vector quantizers designed in this way outperform standard (one-stage) fixed-rate vector quantizers by over 9 dB. The tail of the operational distortion-rate function of the first-stage quantizer determines the optimal rate of convergence of the redundancy of a universal sequence of two-stage codes. We show that there exist two-stage universal noiseless codes, fixed-rate quantizers, and variable-rate quantizers whose per-letter rate and distortion redundancies converge to zero as (k/2)n -1 log n, when the universe of sources has finite dimension k. This extends the achievability part of Rissanen's theorem from universal noiseless codes to universal quantizers. Further, we show that the redundancies converge as O(n-1) when the universe of sources is countable, and as O(n-1+ϵ) when the universe of sources is infinite-dimensional, under appropriate conditions

Weighted universal image compression

We describe a general coding strategy leading to a family of universal image compression systems designed to give good performance in applications where the statistics of the source to be compressed are not available at design time or vary over time or space. The basic approach considered uses a two-stage structure in which the single source code of traditional image compression systems is replaced with a family of codes designed to cover a large class of possible sources. To illustrate this approach, we consider the optimal design and use of two-stage codes containing collections of vector quantizers (weighted universal vector quantization), bit allocations for JPEG-style coding (weighted universal bit allocation), and transform codes (weighted universal transform coding). Further, we demonstrate the benefits to be gained from the inclusion of perceptual distortion measures and optimal parsing. The strategy yields two-stage codes that significantly outperform their single-stage predecessors. On a sequence of medical images, weighted universal vector quantization outperforms entropy coded vector quantization by over 9 dB. On the same data sequence, weighted universal bit allocation outperforms a JPEG-style code by over 2.5 dB. On a collection of mixed test and image data, weighted universal transform coding outperforms a single, data-optimized transform code (which gives performance almost identical to that of JPEG) by over 6 dB

Perceived interaction needs of distance learners participating in an agricultural distance education degree program

This study was conducted to gather data on the perceived interaction needs of distance learners. To accomplish this 113 students participating in the Off-Campus Professional Agriculture Program were mailed a Learning Experiences questionnaire designed to identify their interaction needs. The objectives were to describe student demographic characteristics, determine distance delivery method preferred, compare student performances to mode of taking a course and identify overall interaction needs of participants. Sixty-seven students participated in this study. More than seventy-five percent of the participants were seeking a degree. Students did not express a preference for mode to take distance education courses and were satisfied with the courses they had taken. In order to determine student perceived interaction needs the items on the questionnaire were divided into subscales according to the review of literature.Overall, there were no significant interaction needs among the Off-Campus Professional Agriculture students. A major interaction concern of the participants was the content given in course work. The findings from this study indicated that the profile of the participants in the Off-Campus Professional Agriculture Program does not affect how students choose to take courses. Students who take the course by videotape or ICN are not different, and the two modes can be treated the same when making preparations for these courses

Balance and Power in Older Adults With and Without a History of Falls

The purpose of this study was to observe the differences between power and balance in older adults over the age of 65 with and without falls. A total of 62 community dwelling older adults between the ages of 65 and 92 participated in the study. Two groups consisted of 25 fallers and 37 non-fallers. No statistical differences were found between groups on age, height, weight, or BMI. Testing included the Berg Balance Scale (BBS) to test balance, the Tendo Weightlifting Analyzer (TWA) during a sit-to-stand to test lower body power, and the Physical Activity Scale for the Elderly (PASE) to assess physical activity. Results demonstrate the fallers had significantly lower balance (50.4 ± 6.2; p = .02) and average power (325.5 ± 114.3 watts; p = .01) when compared to the non-fallers (53.5 ± 3.1; p = .02, 420.6 ± 154.9 watts; p = .01). Physical activity was significantly correlated to balance (r = .33; p = .01). Lastly, power and balance were found to be significantly correlated (r = .43; p = .001). Overall, this study shows fallers have significantly lower power and balance compared to age matched non-fallers. The study also demonstrates balance and power, when measuring power in a way that is associated with activities of daily living, are strongly correlated

A SOCIAL CONVERSATION ON ASEXUALITY: QUEER SPACES AND MEDIA REPRESENTATION

Asexuality is a sexual orientation in which someone may experience little, situational, or nosexual attraction. From its complicated existence in queer spaces to its complete invisibility insociety and media representation, why does it continue to lack an understanding even as queertopics continue to enter the mainstream conversation? How is this orientation, seeminglystraightforward, shrouded in confusion, mystification, and false stereotypes? As an asexual andaromantic woman, I believe that the cultural obsession with glamorizing sex and romance andportraying it as essential to a fulfilling life plays a part in confusing the general public on howone could live without the desire to participate fully or at all with these cultural norms andexpectations. To better represent these points and how they affect the lives of asexual people ofvarying intersecting identities, I intend to use an ethnographic approach in this study to betterunderstand these shared experiences and the diversity of the asexual subjectivity. My researchengages with an individual method, including descriptive survey, interview, interaction, andobservation, especially participant observation. My aim in this research is to establish a dialogueon asexuality for a better understanding of an orientation underdeveloped in theory. I identifythis as an opportunity to examine and better understand the spectrum of sexuality. In general, Iintend to interrogate the ways the mainstream norm of sexuality itself still seeps into media andqueer spaces and how to further encourage new forms of asexual inclusivity and acceptance invarious areas of society

An iterative joint codebook and classifier improvement algorithm for finite-state vector quantization

A finite-state vector quantizer (FSVQ) is a multicodebook system in, which the current state (or codebook) is chosen as a function of the previously quantized vectors. The authors introduce a novel iterative algorithm for joint codebook and next state function design of full search finite-state vector quantizers. They consider the fixed-rate case, for which no optimal design strategy is known. A locally optimal set of codebooks is designed for the training data and then predecessors to the training vectors associated with each codebook are appropriately labelled and used in designing the classifier. The algorithm iterates between next state function and state codebook design until it arrives at a suitable solution. The proposed design consistently yields better performance than the traditional FSVQ design method (under identical state space and codebook constraints)

A mean-removed variation of weighted universal vector quantization for image coding

Weighted universal vector quantization uses traditional codeword design techniques to design locally optimal multi-codebook systems. Application of this technique to a sequence of medical images produces a 10.3 dB improvement over standard full search vector quantization followed by entropy coding at the cost of increased complexity. In this proposed variation each codebook in the system is given a mean or 'prediction' value which is subtracted from all supervectors that map to the given codebook. The chosen codebook's codewords are then used to encode the resulting residuals. Application of the mean-removed system to the medical data set achieves up to 0.5 dB improvement at no rate expense

Case study: South African Review of Sociology

This case study describes the use of ICTs in the publication of a scholarly society journal, the South African Review of Sociology, in a context in which the Scientific Editor is a senior member of an academic department at the University of Cape Town. It provides insights into the challenges and opportunities that are faced in society publishing in a South African context.and explores the problems faced when editorship of a journal is held by a senior academic who receives little or no institutional support in the publishing endeavour. The case study reveals the difficulties faced by small society publishers struggling to ensure the survival of established journals that represent significant knowledge capital, but which are undermined by an environment characterised by a lack of national and institutional support for scholarly publishing; rapid technological development; shrinking library budgets and increasing international competition

Case study: Feminist Africa

This case study describes the use of ICTs in the publication of a journal, Feminist Africa, in the context of an academic department at the University of Cape Town. The journal is of particular interest, because, being situated in the African Gender Institute (AGI), it provides insights into challenges and opportunities that are faced when a university unit takes on the role of journal publisher. This case study is enriched by the fact that the journal aims to pull together the research dimensions of the AGI’s interests in the development of curriculum and teaching materials for African feminist studies in the context of its outreach work through the GWS African feminist network. The case study reveals the difficulties faced by volunteer editors in a university departmental context. While the journal received donor support, the main difficulty transpires as the lack of support from the university for publishing activities. This leads to a level of ‘invisibility’ except when it comes to bureaucratic control and to levels of overwork in dedicated staff trying to juggle multiple roles

A Progressive Universal Noiseless Coder

The authors combine pruned tree-structured vector quantization (pruned TSVQ) with Itoh's (1987) universal noiseless coder. By combining pruned TSVQ with universal noiseless coding, they benefit from the “successive approximation” capabilities of TSVQ, thereby allowing progressive transmission of images, while retaining the ability to noiselessly encode images of unknown statistics in a provably asymptotically optimal fashion. Noiseless compression results are comparable to Ziv-Lempel and arithmetic coding for both images and finely quantized Gaussian sources