1,720,982 research outputs found
Feasibility analysis of a MHD inductive generator coupled with a thermoacoustic resonator
No full textThis paper pertains to the feasibility analysis of a Magneto-Hydrodynamic (MHD) inductive generator, coupled with a Thermo Acoustic (TA) resonator. The MHD and TA processes have the great advantage to convert energy without mechanical moving components. In this work, first the design criteria are given, then the order of magnitude of the obtained parameters is used to model the system by using the finite element method (FEM) to confirm the theoretical results. The conceptual idea and the FEM model are described
Feasibility analysis of a mhd inductive generator coupled with a thermo acoustic energy conversion system
No full textThis paper fits in the feasibility analysis of a Magneto-Hydrodynamic (MHD) inductive generator, coupled with a Thermo Acoustic (TA) energy conversion system. The MHD and TA processes have the great advantage to convert energy without mechanical moving components. In conventional MHD generator a plasma passes through an intense magnetic field, so, by closing the circuit on a load, the induced electromotive force determines in the fluid an electric current. Instead in the proposed generator the charge carriers are first created by means of an electrical discharge and then separated by an HVDC electrostatic field. Once the equilibrium is reached, if the gas inside the duct gets to vibrate, the charge carriers give rise to an alternating electric current; this induces an electromotive force in a toroidal coil wrapped around the duct and connected to the electrical load. In this work, first the design criteria are given; then the order of magnitude of the obtained parameters is used to model the system by using the FEM analysis. A thermo-acoustic analysis has been done in order to study the velocity profiles within the duct. As assumption we have an homogeneous fluid with no steady flow, and sinusoidal perturbations of small amplitude (no circulation and no turbulence). Furthermore the tube is long enough, so that end effects are negligible. Different velocity profiles were obtained by varying the radius of the duct and the frequency of the vibration. The numerical results confirm the theoretical ones retrieved from the literature. The axial velocity shows a parabolic profile for a low shear wave number (s = R*sqrt[ρ*ω/μ]); for higher values of said parameter the velocity becomes smaller in the center and the profile becomes more and more uniform. For very high values of shear wave number the profile is almost completely flat, with small peaks close to the tube wall. An electromagnetic analysis has been performed in a glass tube containing a ionized gas with two sleeve copper electrodes connected to an HVDC power supply. Near the sleeves a space charge density has been thickened. Applying the right voltage to the electrodes, we obtained an electrical potential profile that is null and flat in the zone between the electrodes where the electric field is thus equal to zero.
Starting from a homogeneous distribution, the third FEM model has been used to study the dynamics of separation and accumulation of charges. The fluid is considered macroscopically stationary, so we can neglect the convective phenomena. The electrons move under the action of a transverse external electric field and of diffusion phenomena linked to the electronic concentration gradient, tending to thicken near to the electrodes.
The results obtained make apparent that with appropriately frequency and radius, one can get a velocity profile with the best shape for ensure a sufficiently strong vibration of the particles thickened near the electrodes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
COMPARISON OF TRABECULAR BONE MICROARCHITECTURE AND REMODELING IN GLUCOCORTICOID-INDUCED AND POST-MENOPAUSAL OSTEOPOROSIS
Full text linkLong-term treatment with glucocorticoids (GCs) leads to a rapid bone loss and to a greater risk of fractures. To evaluate the specific effects of this treatment on cancellous bone remodeling, structure, and microarchitecture, we compared 22 transiliac biopsy specimens taken in postmenopausal women (65 +/- 6 years) receiving GCs (> or = 7.5 mg/day, for at least 6 months) and 22 biopsy specimens taken in age-matched women with postmenopausal osteoporosis (PMOP), all untreated and having either at least one vertebral fracture or a T score < -2.5 SD. On these biopsy specimens, we measured static and dynamic parameters reflecting trabecular bone formation and resorption. Also, we performed the strut analysis and evaluated the trabecular bone pattern factor (TBPf), Euler number/tissue volume (E/TV), interconnectivity index (ICI), and marrow star volume (MaSV). Glucocorticoid-induced osteoporosis (GIOP), when compared with PMOP, was characterized by lower bone volume (BV/TV), trabecular thickness (Tb.Th), wall thickness (W.Th), osteoid thickness (O.Th), bone formation rate/bone surface (BFR/BS), adjusted mineral apposition rate/bone surface (Aj.AR/BS), and higher ICI and resorption parameters. After adjustment for BV/TV, the W.Th remained significantly lower in GIOP (p < 0.0001). The active formation period [FP(a+)] was not different. Patients with GIOP were divided into two groups: high cumulative dose GCs (HGCs; 23.7 +/- 9.7 g) and low cumulative dose GCs (LGCs; 2.7 +/- 1.2 g). HGC when compared with LGC was characterized by lower W.Th (p < 0.05), BV/TV (p < 0.001), Tb.Th (p < 0.05), trabecular number (Tb.N; p < 0.05), FP(a+)(p < 0.05), and nodes (p < 0.05), and higher E/TV (p < 0.05), ICI (p < 0.005), and TBPf (p < 0.05). When HGC was compared with PMOP, the results were similar except for the MaSV, which was significantly higher (p < 0.005). In summary, GIOP was characterized by lower formation and higher resorption than in PMOP, already present after LGC. With HGCs, these changes were associated with a more dramatic bone loss caused by a major loss of trabecular connectivity
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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