55,431 research outputs found
Modification of nektonic fish distribution by piers and pile fields in an urban estuary
No full textLarge urban piers degrade habitat value for several estuarine benthic fish species by shading, but their effects on mobile nektonic species is less well understood due to sampling challenges. Dual Frequency Identification Sonar (DIDSON) allowed equal access to sampling in the water column of structured shaded and unshaded vs. open environments in both dark and light conditions by methods similar to video but without light. Sampling (n = 228, 5-minute transects) occurred under and around four large municipal piers of varying dimensions in the Hudson River estuary during day and night from summer and fall in 2007 - 2009. The distribution of small (5 - 25 cm in length) and large (25 – 850 cm) fishes were analyzed separately in recognition of functional guild differences. Small fishes occupied open water, shaded under-pier, and un-decked relict piling habitats, but were significantly more abundant during the day in open unshaded water than under adjacent piers or in piling habitats.. Small fish occurred under 3 of 4 piers of varying size and configuration at 10 - 20% of the median abundances of adjacent open water. However, while schools were rare under piers they could be very large, so that abundance greatly exceeded mean open water abundance variance so as to preclude confidence in differences among piers. The differences among habitats was not significant at night, and the difference among piers was also not significant at night. School membership for small fish appeared to mitigate adverse effects of shading and may influence scaling of their response to shading and could therefore influence pier design. Large (>25 cm) predatory fish were uncommon but responded similarly to habitat effects as did small fish. Habitats did not segregate fish by guild as small forage fish co-occurred in 65.8% of samples with large piscivores. Studies that provide species-specific and mechanistic interpretation of dynamic habitat use as well as further quantification of scaling effects could improve our understanding of how fishes respond to piers and other structures on urban shorelines.Peer reviewed
Study of the mechanical behavior of LM20 alloy at various temperatures processed by die-casting
No full textAbstract: Nowadays in the current domain, manufacturing industries are competing to reduce the cost and fuel consumption rates. Especially, in automobile and aerospace applications because of the improvement of lightweight metal advantages. Magnesium, aluminum and other few materials are considered as lightweight materials to use in required applications due to their inherent properties. Therefore, in this paper tried to characterize the advances of LM20 aluminum alloy rods by using the die-casting processes at various processing temperatures followed by room temperature, 373 K, and 473 K. The main aim is to study the effect of various processing temperature on microstructures and mechanical properties of LM20 alloy. Also, this paper reveals the stability of the microstructures of LM20 aluminum alloy though the processing temperature has been increased. The tensile strength, hardness of the LM20 aluminum alloy was decreased with increase in processing temperature. Similarly, the wear, and surface roughness tests were performed on the LM20 alloy rods to understand the effect at various processing temperature
Study of the Mechanical Behavior of LM20 Alloy at Various Temperatures Processed By Die Casting
No full textMeasure beyond Pleasure: Evaluating the Impact on Learning of Out-of-School Programmes for Able and Gifted Pupils in England
No full textFirst published in International Journal of Learning, Volume 10, 2003School-education in England is replete with new projects and initiatives of various kinds. Many require formal evaluation of their impact and effectiveness, often carried out by researchers from higher education. One of these initiatives has been the development in recent years of ‘Advanced Learning Centres’ – out-of-school programmes for school-pupils. The author of this paper is now undertaking a three-year national evaluation of the impact on learning of pupils’ attendance at these Centres. This paper presents and analyses some of the issues and obstacles of doing this evaluation. These include facing the ‘Hawthorne effect’ of initial enthusiasm, the need to identify the historical context of out-of-school learning for able pupils, the difficulties of measuring against goals and intended outcomes, and tensions between the need for measurement and the ethos of the Centres themselves. The paper identifies ways forward for the evaluation process and relates this to evaluation of other similar projects elsewhere
Microstructure evolution in AZ61 alloy processed by Equal Channel Angular Pressing
No full textAbstract: Magnesium and its alloys have play an strategic role in many applications like aerospace, automobile, nuclear, electrical and structural engineering due to its strength to weight ratio is very low when compared to aluminum, Titanium and steel. In the present work, AZ61 wrought magnesium alloy was processed by using Equal Channel Angular Pressing (ECAP) at three different temperatures of 483 K, 523 K and 573 K using up to four ECAP passes. A microstructural study was conducted by measuring the average grain size after each pass, for the three different processing temperatures. The mechanical properties of the processed samples were noted to improve due to the reduction in the grain size after each ECAP pass. After four ECAP passes, the average grain size of the AZ61 samples was found to be reduced to 85%, 81%, and 70% for the pressing temperatures of 483 K, 523 K and 573 K respectively. The tensile strength of the AZ61 alloy increased with increase in number of ECAP passes for each of the temperatures when compared to as-received alloy. For instances, for the processing temperature of 483 K, 523 K and 573 K, the tensile strength increased to 24%, 10%, and 12% respectively at four ECAP pass. Also, the percentage elongation of the alloy was increased with increase in processing temperatures. Moreover, fracture topographies of the tensile surfaces are illustrated through scanning electron microcopy and reveal ductile fracture than as received alloy for four passes at each ECAP processing temperature
Equipment maintenance challenges and solutions for capacity building and sustainability in the training of engineers : the case for the University of Zimbabwe
No full textAbstract: Engineering equipment in some Higher Education Institutions (HEIs) in Sub-Saharan Africa is underutilized, obsolete or in poor working condition owing to lack of expertise, aging or maintenance-related challenges respectively. A research initiated by the Network of Users of Scientific Equipment in Eastern and Southern Africa (NUSESA) and funded by the Swedish International Development Cooperation Agency (Sida) was carried out by 4 faculties of engineering in Southern Africa to establish common challenges, their causes and to propose solutions. The study revealed that the faculties shared similar problems such as no proper maintenance documentation, no local suppliers for spares and inadequate expertise. The importation of spares usually leads to prolonged lead times and delays in timely repairs to malfunctioning equipment and thus obsolescence. This paper proposes smart procurement partnerships between industry and HEIs, based on the findings from the University of Zimbabwe (UZ). Following the survey and analysis of data obtained, recommendations were made and implemented and have assisted in building capacity in acquisition, maintenance and management of laboratory equipment and sustaining these in the training of engineers
Ibn Jinni's Role And Contributions To Arabic Semantics [PJ6184. R165 2007 f rb].
No full textKajian ini menganalisis peranan dan sumbangan Ibn Jinni terhadap semantik Arab melalui tinjauan idea-idea dan pandangan-pandangannya yang terdapat dalam buku-bukunya seperti, “al-Muhtasab” – Perbendaharaan -, “al-Hasais” –
Yang Tertentu -, dan “al-Munsif” – Manusia yang Adil. Kajian ini juga membincangkan pandangan dan idea Ibn Jinni terhadap isu-isu tertentu tentang semantik, seperti semantik sosial, semantik morfologi, semantik fonetik, dan
semantik tatabahasa.
This study analyzes Ibn Jinni’s role and contribution to Arabic semantics by surveying his ideas and opinions presented in his books, such as “al Muhtasab”- The Treasurer-, “al-Hasa’is”-The Particularity-, and “al- Munsif”-The Just Man. It discusses Ibn Jinni’s opinions on certain issues of semantics, such as, social semantics, morphological semantics, phonetic semantics, and grammatical semantics
The influence of subgrid-scale modelling on the performance of a new non-equilibrium wall-model for large-eddy simulation
No full textThe computational cost of wall-resolved large-eddy simulations (LES) rapidly becomes prohibitive with increasing Reynolds number. Wall-modelled LES attempts to significantly reduce the computational cost of simulating wall-bounded turbulent flows by modelling the effect of the near-wall small-scale motions, rather than fully or partially resolving them. The present study concentrates on a new wall-model that is able to predict fluctuating wall-shear stress given a large-scale velocity input. The velocity input for the model is affected by the choice of subgrid-scale (SGS) model. Therefore, this study also focusses on the impact of the SGS-model on the distribution of quantities at the wall. Results show that the new wall-model is able to resolve more of the wall shear-stress variance than a standard wall-model; and that the SGS-model affects the distribution of fluctuations of both wall-shear stress and wall-pressure
Gated relational stacked denoising autoencoder with localized author embedding for global citation recommendation
No full textCitation recommendation is an effective and efficient way to facilitate authors finding desired references. This paper presents a novel neural network based model, called gated relational probabilistic stacked denoising autoencoder with localized author (GRSLA) embedding, for global citation recommendation task. Our model is comprised of two modules with different neural network architecture. For each citing and cited papers, we use a gated paper embedding module, which is extended from probabilistic stacked denoising autoencoder (PSDAE) by adding gated units, to obtain their paper vectors. The added gated units are able to utilize text information of cited paper to refine the vector representation of citing paper in multiple semantic levels. For an author in papers, we first apply topic model to obtain his/her semantic neighbors, and then use a localized author embedding (LAE) module to excavate author vector representation from semantic and explicit neighbors. Unlike most graph convolutional network (GCN) based methods, the LAE module is able to avoid computing global Laplacian in whole graph by taking limited neighbors. Moreover, the LAE module can also be stacked to absorb more neighbors, which makes our model have high extendibility. Based on the generation process of GRSLA, we also derive a learning algorithm of our model by maximum a posteriori (MAP) estimation. We conduct experiments on the AAN, DBLP and CORD-19 datasets, and the results show that GRSLA model works well than previous global citation recommendation methods
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