452 research outputs found
Op soek na\u27n Mediabestel vir Suid·Afrika: \u27n Voorlopige antwoord aan Keyan Tomaselli
No full textCOMMUNICARE encourages the scientific debate. Our last contribu tion is published in response to the article of Tomaselli & Louw In 9(1), who questioned some of the predie tions regarding post-apartheid media In an earlier article by the author pub lished In 8(1). These are his repiles... Prof Keyan Tomaselli, Director of the Cultural Studies Unit at the University of Natal (Durban), is without doubt one of most prolific writers in the field of South African media and communication studies. This is not a matter of c tention; what is at stake in this review article Is the way in which Tomaselll deals with statements and facts in his pub lications. It is argued that Tomaselli Is prone to state a debatable point as a "scientific fact" and then proceeds to build a whole theoretical argument on this and similar "facts". It is fur ther argued that his article: \u27Vrye Weekblad\u27 and post-apartheld mania; what to do with the press? is a case In point
CNN vs. SIFT for Image Retrieval: Alternative or Complementary?
No full textIn the past decade, SIFT is widely used in most vision tasks such as image retrieval. While in recent several years, deep convolutional neural networks (CNN) features achieve the state-of-the-art performance in several tasks such as image classification and object detection. Thus a natural question arises: for the image retrieval task, can CNN features substitute for SIFT? In this paper, we experimentally demonstrate that the two kinds of features are highly complementary. Following this fact, we propose an image representation model, complementary CNN and SIFT (CCS), to fuse CNN and SIFT in a multi-level and complementary way. In particular, it can be used to simultaneously describe scene level, object-level and point-level contents in images. Extensive experiments are conducted on four image retrieval benchmarks, and the experimental results show that our CCS achieves state-of-the-art retrieval results.CPCI-S(ISTP)[email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Abrupt shift to hotter and drier climate over inner East Asia beyond the tipping point
No full textUnprecedented heatwave-drought concurrences in the past two decades have been reported over inner East Asia. Tree-ring–based reconstructions of heatwaves and soil moisture for the past 260 years reveal an abrupt shift to hotter and drier climate over this region. Enhanced land-atmosphere coupling, associated with persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heatwaves that exacerbate soil drying. Our analysis demonstrates that the magnitude of the warm and dry anomalies compounding in the recent two decades is unprecedented over the quarter of a millennium, and this trend clearly exceeds the natural variability range. The “hockey stick”–like change warns that the warming and drying concurrence is potentially irreversible beyond a tipping point in the East Asian climate system
Ethical Procedures? A Critical Intervention: The sacred, the profane, and the planet
No full textIssues relating to ethical clearance, how these procedures relate to very different ontologies, ways of making sense,conditions of existence, and the ideological implications thereof are critically discussed. Written as an invited intervention, the author takes readers through a variety of paradigms: indigenous approaches involving the sacred and the profane, instrumentalization of research; multispeciesism and research as a lived practice. Comments are offered on the nature of science and some questions are posed on the contradictions of ethical practices that readers encounter. The method is eclectic, read through a Peirceian pragmatism, and the outcome proposes relationality rather than the inevitability of discrete findings. Some conclusions are offered on the geographical distribution of populations sampled.</jats:p
CALIBRATION OF THE JOHNSON-COOK FAILURE PARAMETERS AS THE CHIP SEPARATION CRITERION IN THE MODELLING OF THE ORTHOGONAL METAL CUTTING PROCESS
No full textThe finite element analysis (FEA) is a numerical method widely used to predict the metal-cutting performance in both academic and industrial studies, avoiding the high expense and time consumption of experimental methods. The problem is how to calibrate reliable fracture-parameters as chip-separation criterion are implemented into FEA modelling. This thesis introduces a calibration method of the Johnson-Cook fracture parameters used in the orthogonal metal cutting modelling with a positive rake angle for AISI 1045 steel. These fracture parameters were obtained based on a set of quasi-static tensile tests, with smooth and pre-notched round bars at room temperature and elevated temperatures. The fracture parameters were validated by low- and high-strain rate simulations corresponding to tensile tests and orthogonal metal-cutting processes respectively in ABAQUS/Explicit. Compared to literature calibration methods, this method is simpler, less expensive but valid.ThesisMaster of Applied Science (MASc
Asymmetric induction in the photochemistry of α-oxoamides and bicycle aryl ketones
No full textEnantioselective photochemical synthesis of a β-lactam (methyl 4-[3-hydroxy-2,2-
dimethyl-l-(l-methylethyl)-4-oxo-3-azetidinyl]benzoate) was investigated via the ionic
chiral auxiliary method. Solid state photolysis of the chiral salts formed from optically
pure amines and the achiral α-oxoamide reactant containing a carboxylic acid functional
group gave variable results, but through the use of a number of auxiliaries it was possible
to achieve a high degree of enantioselectivity in the β-lactam (up to 99 % ee at 99 %
conversion of the starting α-oxoamide). Suspension of the prolinamide salt in hexane
allowed the photoreaction to be carried out on a 500 mg scale, thus demonstrating the
synthetic utility of the solid state ionic chiral auxiliary approach to asymmetric synthesis.
The covalent chiral auxiliary method was also investigated for asymmetric synthesis
of the β-lactam. Solid state photolysis of a chiral ester formed from an optically pure
alcohol and the achiral α -oxoamide gave up to 95% de at 100 % conversion. Suspension
of the chiral ester in water allowed the photoreaction to be carried out on a 200 mg scale.
X-ray crystallographic data from a number of α-oxoamides provided insight on the
origin of the observed enantioselectivity/diastereoselectivity. The prediction of the
absolute configuration of the β-lactam based on the topochemical control principle was
validated by crystal structure-reactivity correlations.
Asymmetric induction in the Norrish/Yang photochemistry of a series of three bicyclic
aryl ketones, bicyclo[2.2.2]octyl ketones, bicyclo[2.2.1]heptyl ketones and dimethylated
bicyclo[2.2.1]heptyl ketones, was also studied by using the ionic chiral auxiliary method.
Photolysis of the chiral salts in the crystalline state gave high ee's for bicyclo[2.2.2]octyl
ketones, high de's for bicyclo[2.2.1]heptyl ketones, and both high ee's and de's for
dimethylated bicyclo[2.2.1]heptyl ketones.
Through the use of X-ray crystallography, the solid state reactivities were rationalized
based on topochemical expectations with the aid of strain energy calculations on the
photoproducts. Non-topochemical reactions were also found in this study.
Molecular mechanics calculations were conducted to predict the solid state
conformations of the substrates prior to the laboratory work. The calculations were
successful in the prediction of enantioselectivity for the three bicyclic aryl ketones
investigated. In this way, molecular mechanics serves as a basis for crystal engineering in
asymmetric synthesis.Science, Faculty ofChemistry, Department ofGraduat
A self-reflexive analysis of Communicare: Inter-paradigmatic repositioning
No full textThis partly autoethnographical account of my experiences as an author, editor and researcheroffers an experiential framework with which to make sense of publishing in the contemporaryera, governed as it is by neoliberal managerialist principles that tend to reduce activities tomeasureable units so as to render academic disciplines comparable. This is the context withinwhich Communicare is repositioning itself in communication and media studies, situated as it isbetween positivist communication science and interpretivist critical theory. Historical elements ofthe journal are examined via the author’s long-term association with it. The article ends with anexamination of the problems that scholarly work faces when universities measure finite productsat the expense of processes
The neural mechanism underlying illusory complex motions
No full text
PURPOSE: The Pinna illusion is a striking example of the perception of complex motion (rotation and radiation) in the absence of physical motion. For example, upon physically approaching or receding from the Pinna-Brelstaff figure, the observer experiences vivid illusory counter rotation of the figure. This visual phenomenon of illusory rotary motion is a well-known example of integration of local cues to form a global percept. Using psychophysical tests and functional magnetic resonance imaging (fMRI) of visual cortices, we recently found that the Pinna-Brelstaff figure (illusory rotation) and a real physical rotation control stimulus both predominantly activated subarea MST in hMT+, each with a similar response intensity. However, the detailed neural mechanisms underlying the Pinna illusory rotation as well as radiation remain unknown.
METHODS: By manipulation of the physical characteristics of the Pinna-Brelstaff figure, we could generate different types of illusory complex motion: rotation, expansion and contraction (radiation). We first test the illusory effect in human and nonhuman primate psychophysically, and then performed single-unit recordings of MST and MT in awake macaques.
RESULTS: We found that up to two-thirds of MST neurons encode Pinna illusory complex motions, with similar tuning preferences to their corresponding real physical motions. A subset of MT neurons was found to encode the local motion signals with earlier response latency than MST neurons.
CONCLUSIONS: These results demonstrate that neurons in area MST but not MT respond equivalently and respectively to Pinna illusory and real rotations, expansions and contractions. These findings suggest that the representation of illusory and real complex motion fields in primate MST relies on a similar cascade of neural integrative mechanisms from earlier visual areas to generate a global motion perception.</p
Analysis of Two-Grid Characteristic Finite Element Methods for Convection-Diffusion Equations
No full textIn this paper, two efficient two-grid algorithms for the convection-diffusion problem with a modified characteristic finite element method are studied. We present an optimal error estimate in Lp-norm for the characteristic finite element method unconditionally, while all previous works require certain time-step restrictions. To linearize the characteristic method equations, two-grid algorithms based on the Newton iteration approach and the correction method are applied. The error estimate and the convergence result of the two-grid method are derived in detail. It is shown that the coarse space can be extremely coarse and achieve asymptotically optimal approximations as long as the mesh sizes H=Oh1/3 in the first algorithm and H=Oh1/4 in the second algorithm, respectively. Finally, two numerical examples are presented to demonstrate the theoretical analysis
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