178,051 research outputs found
Threat-Independent Column Removal and Fire-Induced Progressive Collapse: Numerical Study and Comparison
No full textProgressive collapse is defined as the spread of an initial failure from element to element, eventually resulting in the collapse of an entire structure or a disproportionately large part of it. The current progressive collapse analyses and design methods in guidelines and codes focus on the alternate load path method. This method is suitable especially in the case of blast-induced progressive collapse. In this paper, fire-induced and threat-independent progressive collapse potential is numerically investigated in steel moment resisting frames. Affecting parameters such as location of initial failure and number of floors are considered in this study. Two different mechanisms were observed in threat-independent and fire-induced progressive collapse: while in threat-independent column removal alternative load paths play major role, in fire-induced progressive collapse the weight of the structure above the failure region is the most important parameter
Progressive collapse of framed structures: Suggestions for robustness assessment
No full textThe term \progressive collapse" has been used to describe the spread of local
failure in a manner analogous to a chain reaction that leads to partial or total collapse of a
structure. Robustness is de ned as a fundamental property of structural systems to prevent
damage propagation and to mitigate the potential of progressive collapse. In this paper, the
progressive collapse capacity of steel moment-resisting frames was rst investigated using
the alternative load path method, then suggestions are made for assessment of structural
robustness, and the robustness of frames is quanti ed. According to the results, the
robustness and progressive collapse potential of the frames varied signi cantly, depending
on the location of the initial local failure and number of building stories
Numerical study of progressive collapse in framed structures: A new approach for dynamic column removal
No full textProgressive collapse is a situation where local failure of a primary structural component leads to the
collapse of adjoining members which, in turn, leads to additional collapse. Hence, the total damage is
disproportionate to the original cause. The most common local failure in framed structure is assumed to
be column failure. In this paper, a new approach for dynamic column removal in framed structures was
proposed. Using this approach, the structural response of a 5-story steel frame building under the
sudden loss of columns for different scenarios of column removal was numerically assessed. Both
material and geometric nonlinearities were taken into account in the analysis. The modeling techniques
were described in details. Special emphasis was focused on the evolution of vertical displacements of
column removal point. According to the results progressive collapse potential are strongly dependent
on location of column loss. It could be concluded that the proposed approach offers the advantages of
computational simplicity and practicality for dynamic column removal of framed structures
Numerical dynamic analysis of stiffened plates under blast loading
No full textUsing the general purpose finite element package Abaqus, an
investigation has been carried out to examine the dynamic response of steel stiffened plates subjected to uniform blast loading.
The main objective of this study is to determine the dynamic
response of the stiffened plates considering the effect of stiffener
configurations. Several parameters, such as boundary conditions,
mesh dependency and strain rate, have been considered in this
study. Special emphasis is focused on the evaluation of midpoint
displacements and energy of models. The modeling techniques
were described in details. The numerical results provide better
insight into the effect of stiffener configurations on the nonlinear
dynamic response of the stiffened plates subjected to uniform blast
loading
Investigation of entropy generation, PEC, and efficiency of parabolic solar collector containing water/Al2O3?MWCNT hybrid nanofluid in the presence of finned and perforated twisted tape turbulators using a two-phase flow scheme
No full textRenewable energy is a type of convenient energy obtained from renewable sources, which can be replaced naturally again on the human time scale. One of the most broadly employed types of renewable energy is solar energy. In the present study, the entropy generation, performance evaluation criterion (PEC), and efficiency of parabolic solar collector containing water/Al2O3_MWCNT hybrid nanofluid are numerically examined in the presence of finned and perforated twisted tape turbulators by employing two-phase flow approach. The volume fraction of nanoparticles (phi) changes from 0 to 3% and the Reynolds number (Re) range is 5000-35,000. The two-phase Eulerian-Eulerian model (EEM), k-omega turbulence model, finite volume method (FVM) method, and SIMPLEC algorithm are used for numerical simulations. The results demonstrate that the maximum change in the total entropy generation is 40.07% by changing the type of turbulator from a perforated tape to the finned vane turbulator which occurs at Re = 30,000 and phi= 3%. The maximum change in the collector efficiency is 1.62% by changing the type of turbulator from finned turbulator to perforated tape one which occurs at Re = 20,000 and phi = 0%. The maximum change in ANU is 13.65%, which occurs at Re = 15,000 and phi = 1%.It is more desirable to use the perforated twisted tape from the point of view of heat transfer, total entropy generation, PEC, and collector efficiency
Influence of sudden column loss on dynamic response of steel moment frames under blast loading
No full textModeling buildings response to blast and subsequent progressive collapse interested more and more
researchers during the past two decades. Due to the threat from extreme loading, efforts have been
made to develop methods of structural analysis and design. In this paper, progressive collapse capacity
of steel moment frames was first investigated using alternate load path method, then a nonlinear
dynamic analysis was carried out to examine the response of the steel moment frames in blast and
sudden column loss scenario. The structural response of the building under sudden loss of column for
different scenarios of column removal, with or without external blast loading was assessed in detail.
According to the results, progressive collapse potential are strongly dependent on location of column
loss. Loss of column can affect overall response of structure under external blast loads. The obtained
results provide better insight into the influence of sudden column loss on dynamic response of steel
moment frames under blast loading
Performance evaluation criteria and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles
No full textImproving the thermo-hydraulic performance of shell-and-tube heat exchangers is of interest to researchers due to their broad applications in the industry. Thermo-hydraulic behavior and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles are numerically examined using the two-phase Eulerian-Eulerian Model (EEM). The volume fraction of nanoparticles (phi) changes from 0 to 2% and the Reynolds number (ReNumber) varies from 25000 to 45000. EEM, Realizable k-epsilon turbulence model, finite volume method (FVM), and SIMPLE algorithm are used for modeling. According to the numerical results obtained in terms of pressure drop, total entropy generation, and performance evaluation criteria (PEC), baffle 1 is more appropriate. In terms of heat transfer rate and average Nusselt number values, baffle 2 is more suitable. The PEC maximum change was 5.13% at Re = 45000 and phi = 0% by changing the type of baffle from the second type to the first type. The maximum rise in the total entropy generation was 73.68% for phi = 0% for the first type of baffles
Isocolus karimpouri Melika & Tavakoli 2008, new species
No full text<i>Isocolus karimpouri</i> Melika & Tavakoli, new species <p>(Figs 6a–j, 7a–c)</p> <p> <b>Etymology.</b> The species is named in honour of Younes Karimpour, researcher of the Department of Plant Protection, College of Agriculture, Urmia University, Urmia, Iran.</p> <p> <b>Type material</b>. HOLOTYPE female: Iran, West Azarbaijan, Urmia, ex flower head of <i>Serratula cerinthifolia</i>, IV.2006. coll. Y. Karimpour. PARATYPES: 6 females and 4 males with the same labels as the holotype. The holotype female and one male paratype are deposited in HNHM; one female and one male paratypes in RIFR; 5 female and 2 male paratypes in SPL.</p> <p> <b>Diagnosis.</b> Belongs to the group of <i>Isocolus</i> species with antero-lateral patch of setae on the metasomal tergite 2 (<i>Isocolus serratulae</i> (Mayr), <i>I. lichtensteini</i> (Mayr) and <i>I. leuzeae</i> Nieves-Aldrey & Parra (Melika 2006). Most similar to a common European species, <i>Isocolus serratulae</i> (Mayr), which is known to induce galls in flower heads of <i>Serratula</i> species. However, in <i>I</i>. <i>karimpouri</i> <b>n. sp.</b> the mesoscutum with strong transverse rugae, the mesoscutellum dull rugose, while in <i>I. serratulae</i> the mesoscutum and mesoscutellum are delicately coriaceous to regularly reticulate, without transverse rugae.</p> <p> <b>Description.</b> FEMALE (holotype). Body black; scape and last flagellomere dark brown to black, rest of antenna yellowish brown; coxae, trochanters and basal 2/3 of femora dark brown, tibiae and tarsi yellowish brown; mandibles and palpi yellowish brown, with dark tips; wing veins distinct, dark brown.</p> <p>Head (Figs 6a–b) alutaceous to very delicately coriaceous, only slightly broader than high in front view; 1.9 times as broad as long in dorsal view; slightly broader than mesosoma. POL 1.4 times as long as OOL and 2.1 times as long as LOL, LOL 1.5 times as long as length of lateral ocellus. Gena not broadened behind eye in front view; vertex, interocellar area, occiput alutaceous to very finely coriaceous; postocciput and postgena delicately coriaceous, with more dense white setae as on front. Transfacial distance 1.2 times as long as height of eye, 1.4 times as long as height of lower face (measuring from antennal sockets to ventral edge of clypeus); transfacial distance 4.1 times as long as distance between antennal socket and inner margin of eye; diameter of antennal socket 2.6 times as large as distance between antennal sockets. Lower face alutaceous, with delicate striae, radiating from clypeus and extending into area between antennal socket and eye. Malar space 0.7 times as long as height of eye, with delicate striae, radiating from clypeus and nearly reaching eye margin. Clypeus rectangular, alutaceous to smooth, shiny, rounded ventrally, medially not incised, not emarginated; anterior tentorial pits small, indistinct; epistomal sulcus distinct, broad, impressed, smooth, shiny; clypeo-pleurostomal line indistinct. Antenna with 11 flagellomeres, F1 1.25 times as long as pedicel and slightly shorter than F2; F2–F4 equal in length, subsequent flagellomeres slightly shorter; F11 2.0 times as long as F10; placodeal sensilla on F2–F11 (Fig. 6c). Mesosoma black, slightly longer than high in lateral view. Pronotum dorsomedially alutaceous, 1.5 times as short as greatest length measuring on outer margin; uniformly alutaceous to delicately coriaceous laterally; with some parallel wrinkles along antero-ventral margin; with dense white setae along anterior margin, less setae laterally and few setae dorso-medially. Submedian pronotal pit distinct, transversely ovate and deep, separated by broad carina which slightly at least 2.5 times narrower than width of submedian pit; pronotal carina well-delimited in very anterior part, just behind pit, alutaceous (Fig. 6e). Mesoscutum black, with strong transverse rugae, with very few sparse short scattered setae; slightly broader than long. Notauli distinctly impressed, complete, smooth, shiny, slightly broadened and converging posteriorly; anterior parallel lines delicate, very short; parapsidal lines indistinct, very narrow, smooth, shiny, extending to 2/3 of mesoscutum length; median mesoscutal line in form of short triangle (Fig. 6f). Mesoscutellum rounded, nearly as broad as long; disk uniformly dull rugose, with slightly more delicate sculpture between scutellar foveae, which transverse, broader than high, with dull rugose bottom, indistinctly separated from disk posteriorly and separated from one another by broad median carina (Fig. 6f). Dorso-axillar area coriaceous. Mesopleuron, including speculum with uniform transverse delicate striae. Metapleural sulcus reaching mesopleuron in upper 1/3 of its height; axillula delicately coriaceous, with relatively dense white setae; subaxillular bar smooth, shiny, in most posterior part at least 2.0 times as high as height of metanotal trough (Fig. 6g). Propodeum black, laterally coriaceous, with relatively dense white setae; lateral propodeal carinae distinct, thin, subparallel, only very slightly curved outwards in posterior half; narrow central propodeal area smooth, mat,without setae, with delicate irregular wrinkles. Metascutellum mat, uniformly coriaceous, very narrow; ventral impressed area of metascutellum indistinct, very short or absent; metanotal trough smooth, without setae; propodeal spiracle transverse, with strong raised carina along anterior border (Fig. 6h). Forewing with cilia on margin; R1 and Rs running on a short distance along wing margin, without reaching it; radial cell opened, 3.2 times as long as broad; areolet large, triangular, distinct; Rs+M nearly reaching basalis in its lower half (Fig. 6i). Tarsal claws simple, without basal lobe.</p> <p>Metasoma slightly shorter than head+mesosoma, metasomal tergite 2 antero-laterally with a patch of dense white setae, without punctures; all subsequent tergites and hypopygium with uniform dense punctures; prominent part of ventral spine of hypopygium very short, as long as broad, with very few sparse short white setae (Fig. 6j). Body length 2.0– 2.5 mm, holotype female – 2.4 mm.</p> <p>MALE. Similar to female, antenna with 12 flagellomeres, F1 longest flagellomere, slightly curved and excavated, placodeal sensilla from F2, absent on F1 (Fig. 6d). Body length 1.8–2.2 mm.</p> <p> <b>Gall</b> (Figs 7a–c) in stems. Galled stems are without external deformation. Inside the stem slightly elongated (up to 3.5–4.0 mm) where galls are forming, with a thin wall which is not detachable from the inner tissues of the stem; larval chambers are located along the axis of the stem, never across; one larva per cavity (Fig. 7a). There are no other <i>Isocolus</i> species, known to induce such a galls. Some Aylacini species such as <i>Panteliella fedtschenkoi</i> (Rübsaamen), <i>Aulacidea phlomica</i> Belizin, and <i>Phanacis phlomidis</i> Belizin induce such kind of galls in stems of <i>Phlomis tuberosa</i> L. (Lamiaceae), however, the larval cells (chambers) in the dry stems are free-rolling; its outer wall is separated from the tissues of the stem, especially after the gall is mature.</p> <p> <b>Biology.</b> Adults emerge in late April, most likely overwintering in the larval cell in the plant. The only known host plant is <i>Serratula cerinthifolia</i> (Sm.) Boiss. (Asteraceae).</p> <p> <b>Distribution.</b> Iran, Western Azarbaijan, Urmia (Ghasemloo, Shohada Valley).</p>Published as part of <i>Karimpour, Y., Tavakoli, M. & Melika, G., 2008, New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini), pp. 16-32 in Zootaxa 1854 (1)</i> on pages 28-31, DOI: 10.11646/zootaxa.1854.1.2, <a href="http://zenodo.org/record/5133089">http://zenodo.org/record/5133089</a>
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
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