Textual case-based reasoning for spam filtering: a comparison of feature-based and feature-free approaches

Spam filtering is a text classification task to which Case-Based Reasoning (CBR) has been successfully applied. We describe the ECUE system, which classifies emails using a feature-based form of textual CBR. Then, we describe an alternative way to compute the distances between cases in a feature-free fashion, using a distance measure based on text compression. This distance measure has the advantages of having no set-up costs and being resilient to concept drift. We report an empirical comparison, which shows the feature-free approach to be more accurate than the feature-based system. These results are fairly robust over different compression algorithms in that we find that the accuracy when using a Lempel-Ziv compressor (GZip) is approximately the same as when using a statistical compressor (PPM). We note, however, that the feature-free systems take much longer to classify emails than the feature-based system. Improvements in the classification time of both kinds of systems can be obtained by applying case base editing algorithms, which aim to remove noisy and redundant cases from a case base while maintaining, or even improving, generalisation accuracy. We report empirical results using the Competence-Based Editing (CBE) technique. We show that CBE removes more cases when we use the distance measure based on text compression (without significant changes in generalisation accuracy) than it does when we use the feature-based approach.     

Prolonged rewarding stimulation of the rat medial forebrain bundle: Neurochemical and behavioral consequences.

Extracellular dopamine levels were measured in the rat nucleus accumbens by means of in vivo microdialysis. Delivery of rewarding medial forebrain bundle stimulation at a low rate (5 trains/min) produced a sustained elevation of dopamine levels, regardless of whether train onset was predictable. When the rate of train delivery was increased to 40 trains/min, dopamine levels rose rapidly during the first 40 min but then declined toward the baseline range. The rewarding impact of the stimulation was reduced following prior delivery of stimulation at the high, but not the low, rate. These results support the idea that dopamine tone plays an enabling role in brain stimulation reward and is elevated similarly by predictable and unpredictable stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effective Communication in Requirements Elicitation: A Comparison of Methodologies

The elicitation or communication of user requirements comprises an early and critical but highly error-prone stage in system development. Socially oriented methodologies provide more support for user involvement in design than the rigidity of more traditional methods, facilitating the degree of user–designer communication and the ‘capture’ of requirements. A more emergent and collaborative view of requirements elicitation and communication is required to encompass the user, contextual and organisational factors. From this accompanying literature in communication issues in requirements elicitation, a four-dimensional framework is outlined and used to appraise comparatively four different methodologies seeking to promote a closer working relationship between users and designers. The facilitation of communication between users and designers is subject to discussion of the ways in which communicative activities can be ‘optimised’ for successful requirements gathering, by making recommendations based on the four dimensions to provide fruitful considerations for system designers.     

The feasibility and outcome of clinic plus Internet delivery of cognitive-behavior therapy for childhood anxiety.

Seventy-two clinically anxious children, aged 7 to 14 years, were randomly allocated to clinic-based, cognitive-behavior therapy, the same treatment partially delivered via the Internet, or a wait-list control (WL). Children in the clinic and clinic-plus-Internet conditions showed significantly greater reductions in anxiety from pre- to posttreatment and were more likely to be free of their anxiety diagnoses, compared with the WL group. Improvements were maintained at 12-month follow-up for both therapy conditions, with minimal difference in outcomes between interventions. The Internet treatment content was highly acceptable to families, with minimal dropout and a high level of therapy compliance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microstructure and domain configurations in ferroelectric PbTiO3 and Pb(Zr,Ti)O3 thin fims

Ferroelectric domain configurations in PbTiO₃ and Pb(Zr_xT_1−x)O₃ (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO₃ and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near the morphotropic phase boundary. The effects of grain sizes are briefly discussed.     

Digit pipelined arithmetic on fine-grain array processors

In this paper, we present a novel scheme for performing fixed-point arithmetic efficiently on fine-grain, massively parallel, programmable architectures including both custom and FPGA-based systems. We achieve anO(n) speedup, wheren is the operand precision, over the bit-serial methods of existing fine-grain systems such as the DAP, the MPP and the CM2, within the constraints of regular, near neighbor communication and only a small amount of on-chip memory. This is possible by means of digit pipelined algorithms which avoid broadcast and which operate in a fully systolic manner by pipelining at the digit level. A base 4, signed-digit, fully redundant number system and on-line techniques are used to limit carry propagation and minimize communication costs. p ]Although our algorithms are digit-serial, we are able to match the performance of the bit-parallel methods, while retaining low communication complexity. Reconfigurable hardware systems built using field programmable gate arrays (FPGA's) can share in the speed benefits of these algorithms. By using the organization of logic blocks suggested in this paper, problems of placement and routing that exist in such systems can be avoided. Since the algorithms are amenable to pipelining, very high throughput can be obtained.     

Addiction to altruism? Opponent-process theory and habitual blood donation.

Explores the possibility that one of undoubtedly several interacting motives behind commitment to regular blood donation is the development of an affective "addiction" to the behavior, based on initial anxiety, through the mechanisms postulated by opponent-process theory. Pre- and post-donation responses to 1,846 blood donation experiences were subjected to correlational and regression analyses. Support was found for the relevance of opponent-process theory to the development of positive affective responses to donation. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dependence of electrical properties of polycrystalline cvd si films on grain size and impurity doping concentrationa,b

The electrical properties of sets of simultaneously grown p-type polycrystalline Si films, deposited by SiH₄ pyrolysis on polycrystalline high-purity alumina substrates and B-doped during growth, were determined by Hall-effect measurements in the temperature range 77-420K as functions both of impurity doping concentration N (~10^l5 to ~10²⁰cm⁻³) and average grain size (≈1 to ≈125μm) in the film. Room temperature data showed rapidly increasing resistivities and rapidly decreasing free-carrier concentrations for doping below a critical concentration N_m and distinct mobility minima at that concentration, with the value of N_m being larger the smaller the average grain size. Measurements as a function of sample temperature showed the intergrain barrier height E_b, decreasing from a maximum value of ~0.4eV at the critical concentration to very small values (~0.01eV) for concentrations above 10¹⁹cm⁻³, with a functional dependence close to E_b ∝l/N^1/2 and E_b for any given concentration being larger the smaller the average grain size. Results are interpreted in terms of the grain-boundary trapping model. Trapped carrier densities in the grain boundaries were calculated to range from ~5×l0¹¹cm⁻² at N≈N_m to ~5×l0¹²cm⁻² for N>10¹⁹cm⁻³, the density being higher the smaller the grain size, and evidence was found for an energy distribution of traps in the Si bandgap, rather than a fixed density at a single discrete energy level. The observed relationship between N_m and average grain size nearly coincides with that of the model for films with ~lμm grain size but sharply departs from it for larger grain sizes, indicating probable applicability of the model for grain sizes up to that range. ^aThis work was supported by the U.S. Department of Energythrough its San Francisco Operations Office under Contract DE-AC03-79ET23045 and monitored by the Solar Energy Research Institute, Golden, CO. bThese results were first described at the 22nd Electronic Materials Conference, Ithaca, NY, June 21–27, 1980, Paper No. M4.     

Sex differences in children's response to training on a visual-spatial test.

In a study with 133 children in Grades 1, 3, and 5, a brief training procedure designed to improve performance on the Children's Embedded Figures Test, a test of visual ability, resulted in significant improvement for girls but not for boys. No sex difference was observed among children receiving this training. The implications for theories of sex differences in visual–spatial ability are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)