7,460 research outputs found
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
Richardson, Barbauld, and the construction of an early modern fan club
No full textMPhilMuch has been written about the life and long works of the eighteenth century epistolary novelist, Samuel Richardson, but the prospect of his position as the first celebrity novelist – responsible for courting his own fame as well as initiating his own fan club – has largely been ignored. The body of manuscripts housed at the National Art Library in the Victoria and Albert Museum in London provides the modern scholar with evidence of the skeletal beginnings of an early fan club. This thesis aims to show how these manuscripts were turned into a saleable commodity by the publisher and entrepreneur Richard Phillips, while under the guiding hand of another, slightly later, literary celebrity, Anna Laetitia Barbauld. In order to restore Richardson’s reputation amongst a new nineteenth century audience, Barbauld was required to construct her own idea of him as an eighteenth century celebrity author, and in doing so the insecurities of a self-professed, apparently diffident man, are revealed. Barbauld’s capacious, but heavily edited selection of letters is analyzed in this thesis, providing ample evidence that Richardson’s correspondents were more than just eager letter writers. By using Barbauld’s biography of Richardson this thesis aims to show how she manipulates the genre of life writing in her construction of him.
This thesis offers an alternative reading of how the Richardson manuscripts are viewed, redefining them as not simply a collection of letters, but as a collective entity, deliberately selected and archived as evidence of an early modern fan club, and its celebrity managing director
Development of a rotor model for the numerical simulation of helicopter exterior flow-fields
No full textIncludes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena
Fan Fiction and Copyright: Outsider Works and Intellectual Property Protection
No full textAs long as there have been fans, there has been fan fiction. There seems to be a fundamental human need to tell additional stories about the characters after the book, series, play or movie is over. But developments in information technology and copyright law have put these fan stories at risk of collision with the content owners’ intellectual property rights. Fan fiction has long been a nearly invisible form of outsider art, but over the past decade it has grown exponentially in volume and in legal importance. Because of its nature, authorship, and underground status, fan fiction stands at an intersection of key issues regarding property, sexuality, and gender. In Fan Fiction and Copyright, author Aaron Schwabach examines various types of fan-created content and asks whether and to what extent they are protected from liability for copyright infringement. Professor Schwabach discusses examples of original and fan works from a wide range of media, genres, and cultures. From Sherlock Holmes to Harry Potter, fictional characters, their authors, and their fans are sympathetically yet realistically assessed. Fan Fiction and Copyright looks closely at examples of three categories of disputes between authors and their fans: Disputes over the fans’ use of copyrighted characters, disputes over online publication of fiction resembling copyright work, and in the case of J.K. Rowling and a fansite webmaster, a dispute over the compiling of a reference work detailing an author's fictional universe. Offering more thorough coverage of many such controversies than has ever been available elsewhere, and discussing fan works from the United States, Brazil, China, India, Russia, and elsewhere, Fan Fiction and Copyright advances the understanding of fan fiction as transformative use and points the way toward a safe harbor\u9d for fan fiction
Learning of algorithms: a theoretical model with focus on cognitive development
No full textTaking a broad perspective on algorithm in mathematics, the author presents a theoretical model about the learning and teaching of algorithm with focus on students’ cognitive development. The model consists of three cognitive levels: 1. Knowledge and Skills, 2. Understanding and Comprehension, and 3. Evaluation and Construction. The model suggests that teaching and learning of algorithm does not simply mean routine learning, memorization, or lead to a low level of cognition. The paper also discusses different teaching strategies and activities that can be used to support students’ cognitive development at different cognitive levels
The effect of one valence electron: Contrasting (PNP)Ni(CO) with (PNP)Ni(NO) to understand the half-bent NINO unit
No full textReaction of a (PNP)Ni radical with NO finishes in the time of mixing to form a 1:1 adduct with a NO stretching frequency of 1654 cm(-1). NMR data of this diamagnetic product indicate C-2v symmetry, which is contradicted by the X-ray structure, which shows it to be nonplanar at Ni, with a geometry intermediate between planar and tetrahedral; the planar geometry is thus the transition state for fluxionality giving time-averaged C, symmetry. The X-ray structure, together with DFT calculations, reveals that the "half-bent" NiNO unit and the intermediate coordination geometry result from a Ni NO charge transfer, which has a nonintegral value, resulting in a continuum between NO+ (hence Ni-0) and NO- (hence Ni-II). This is related to the nonaxially symmetric character of the Ni -> NO back-donation caused by the (PNP) environment on Ni. Steric effects of Bu-t and even chelate constraints are ruled out as the cause of the unusual electronic and structural features
Lewis Acid Stabilized Methylidene and Oxoscandium Complexes
No full textThe methylidene scandium complex (PNP)Sc(mu(3)-CH(2))(mu(2)-CH(3))(2)[Al(CH(3))(2)](2) (PNP=N[2-P(CHMe(2))2-4-methylpheyl](2)(-)) can be prepared from the reaction of (PNP)Sc(CH(3))(2) and 2 equiv of Al(CH(3))(3). The Lewis acid stabilized methylidenes candium complex has been crystallographically characterized, and its bonding scheme analyzed by DFT. In addition, we report preliminary reactivity studies of the Sc-CH(2) ligand with substrates such as H(2)NAr and OCPh(2). While the former results in an Bronsted acid-base reaction, the latter reagent produces the olefin H(2)C-CPh(2) along with the novel oxoscandium complex (PNP)Sc(mu(3)-O)(mu(2)-CH(3))(2)[Al(CH(3))(2)](2), quantitatively
Intermolecular C-H bond activation reactions promoted by transient titanium alkylidynes. Synthesis, reactivity, kinetic, and theoretical studies of the Ti C linkage
No full textThe neopentylidene-neopentyl complex (PNP)(TiCHBu)-Bu-t((CH2Bu)-Bu-t) (2;PNP- = N[2-P(CHMe2)(2)-4-methylphenyl](2)), prepared from the precursor (PNP)(TiCHBu)-Bu-t(OTf) (1) and (LiCH2Bu)-Bu-t, extrudes neopentane in neat benzene under mild conditions (25 degrees C) to generate the transient titanium alkylidyne, (PNP)(TiCBu)-Bu-t (A), which subsequently undergoes 1,2-CH bond addition of benzene across the TiC linkage to generate (PNP)(TiCHBu)-Bu-t(C6H5) (3). Kinetic, mechanistic, and theoretical studies suggest the C-H activation process to obey pseudo-first-order in titanium, the alpha-hydrogen abstraction to be the rate-determining step (KIE for 2/2-d(3) conversion to 3/3-d(3) = 3.9(5) at 40 degrees C) with activation parameters Delta H = 24(7) kcal/mol and Delta S = -2(3) cal/mol center dot K, and the post-rate-determining step to be C-H bond activation of benzene (primary KIE = 1.03(7) at 25 degrees C for the intermolecular C-H activation reaction in C6H6 vs C6D6). A KIE of 1.33(3) at 25 degrees C arose when the intramolecular C-H activation reaction was monitored with 1,3,5-C6H3D3. For the activation of aromatic C-H bonds, however, the formation of the sigma-complex becomes rate-determining via a hypothetical intermediate (PNP)(TiCBu)-Bu-t(C6H5), and C-H bond rupture is promoted in a heterolytic fashion by applying standard Lewis acid/base chemistry. Thermolysis of (3) in C6D6 at 95 degrees C over 48 h generates 3-d(6), thereby implying that 3 can slowly equilibrate with A under elevated temperatures with k = 1.2(2) x 10(-5) s(-1), and with activation parameters Delta H = 31(16) kcal/mol and Delta S = 3(9) cal/mol.K. At 95 degrees C for one week, the EIE for the 2-3 reaction in 1,3,5-C6H3D3 was found to be 1.36(7). When 1 is alkylated with LiCH2SiMe3 and KCH2Ph, the complexes (PNP)(TiCHBu)-Bu-t(CH2SiMe3) (4) and (PNP)(TiCHBu)-Bu-t(CH2Ph) (6) are formed, respectively, along with their corresponding tautomers (PNP)TiCHSiMe3((CH2Bu)-Bu-t) (5) and (PNP)TiCHPh((CH2Bu)-Bu-t) (7). By means of similar alkylations of (PNP)TiCHSiMe3(OTf) (8), the degenerate complex (PNP)TiCHSiMe3(CH2SiMe3) (9) or the non-degenerate alkylidene-alkyl complex (PNP)TiCHPh(CH2SiMe3) (11) can also be obtained, the latter of which results from a tautomerization process. Compounds 4/5 and 9, or 6/7 and (11), also activate benzene to afford (PNP)TiCHR(C6H5) (R = SiMe3 (10), Ph (12). Substrates such as FC6H5, 1,2-F2C6H4, and 1,4-F2C6H4 react at the aryl C-H bond with intermediate A, in some cases regioselectively, to form the neopentylidene-aryl derivatives (PNP)(TiCHBu)-Bu-t(aryl). Intermediate A can also perform stepwise alkylidene-alkyl metatheses with 1,3,5-Me<INF>3</INF>C<INF>6</INF>H<INF>3</INF>, SiMe<INF>4</INF>, 1,2-bis(trimethylsilyl)alkyne, and bis(trimethylsilyl)ether to afford the titanium alkylidene-alkyls (PNP)TiCHR(R') (R = 3,5-Me<INF>2</INF>C<INF>6</INF>H<INF>2</INF>, R' = CH<INF>2</INF>-3,5-Me<INF>2</INF>C<INF>6</INF>H<INF>2</INF>; R = SiMe<INF></INF>, R' = CH<INF>2</INF>SiMe<INF>3</INF>; R = SiMe<INF>2</INF>CCSiMe<INF>3</INF>, R' = CH<INF>2</INF>SiMe<INF>2</INF>CCSiMe<INF>3</INF>; R = SiMe<INF>2</INF>OSiMe<INF>3</INF>, R' = CH<INF>2</INF>SiMe<INF>2</INF>OSiMe<INF>3</INF>)
The author in the postinternet age: Fan works, authorial function, and the archive
No full textFifty years since Roland Barthes proclaimed the death of the author, there still exists difficulty in framing the nature of interaction between commercial (professional) creators and fan (transformative) authors. In the postinternet age, the visibility of unsanctioned (or tacitly sanctioned) derivative fictional works has only increased, as have the number of commercial creators with experience in creating derivative works for a fan audience. It has therefore become necessary to interrogate whether the author has truly died in the Barthian sense, and if not, what role the construct of the author plays in today's popular mediascape. In an analysis of the Foucauldian author function (that is, the role discursively constructed authors play relative to their work) assessing both Euro-American and Japanese histories of fan practice, a move to a more open-source style of fan practice is evident. The author in an open-source fandom functions as a heuristic device through which fans may access and search the database, as well as a means of decentralizing commercial authority over media content
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