10,045 research outputs found
Comparison of Tooth Size Discrepancy of Three Main Ethnics in Malaysia with Bolton's Ratio
No full textThe objective of this study was to investigate the applicability of Bolton's ratios in orthodontic population of Malaysian main ethnics; Malay, Chinese and Indians. Ninety convenient samples consisting of 30 pre-orthodontic study casts from each ethnic that fits the inclusion criteria were selected. The greatest mesiodistal widths of each tooth from six to six for overall ratio and three to three for anterior ratio were measured using a digital callipers linked to Hamilton Arch Tooth System software to the nearest 0.01mm. Means of the ratios were calculated using Bolton analysis. One sample t-test statistic analysis was carried out to compare the means with Bolton values of anterior ratio and overall ratio and one-way ANOVA was used to analyze comparison between ethnic groups of the anterior ratio and the overall ratio with the level of statistical significance set at p < 0.05. However, there were no significant differences when comparing Bolton values with Chinese and Indian anterior and overall ratios. The Bolton standards could be applied to Malaysian Chinese, Indians and Malay's female. Subsequently, a specific standard should be used for the Malays orthodontic population.Article URL : http://www.ukm.my/jsm/pdf_files/SM-PDF-41-2-2012/17%20Aida%20Nur%20Ashikin.pd
The collapse of diaphragm walls retaining clay
No full textFive centrifugal model tests are reported which illustrate aspects of the collapse of stiff cantilever retaining walls embedded in overconsolidated clay. The drainage of a heavy fluid in flight was used to simulate the effects of excavation, following the establishment of a high initial groundwater level. Two modes of collapse were observed with unpropped walls. The temporary stability of walls with small penetration was interrupted by the hydraulic action of a water-filled crack opening on the retained side of the wall. The long-term rotational failure of walls of deeper penetration was also observed, involving distributed strains in ‘active’ and ‘passive’ zones which could lead ultimately to sliding on shear rupture surfaces. An analysis was developed based on admissible stress fields, with active and passive zones switching about a pivot point, so that the unpropped wall could satisfy the conditions of both moment and force equilibrium. A back analysis of the two sudden failures using an undrained strength based on the overconsolidation ratio was successful in matching the critical penetration ratio and pivot position observed in the tests. A drained analysis using φ′ derived from triaxial and plane strain tests was equally successful in comparison with the data of long-term failure. A similar stress analysis for a wall propped at the top was shown to be conservative. This was thought to be due to the kinematic restraint of the prop which produced a rupture surface on the active side which was much steeper than those observed before. A back analysis of the observed failure mechanism generated a credible value of mobilized soil friction close to the peak observed in soil tests. This value also gave a consistent match for the bending moments and propping force measured in the test. Care must be taken to account for the possible effects of progressive failure. Critical state soil angles, with fully mobilized wall friction, can be anticipated to relate to the gross long-term deformation of walls. Loss of retained height and heave in the excavation lead eventually to self-stabilization
Field studies, analysis and numerical modelling of in situ walls propped at formation level
No full textCepstral techniques in the measurement of acoustic reflection coefficients with applications to determination of acoustic properties of elastic porous materials
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Hypoponera dis Bolton & Fisher, 2011, sp. n.
No full textHypoponera dis Bolton & Fisher sp. n. (Figs 31 – 33) WORKER (holotype in parentheses). Measurements: HL 0.50 – 0.52 (0.51), HW 0.38 – 0.40 (0.39), HS 0.440 – 0.460 (0.450), SL 0.33 – 0.35 (0.34), PrW 0.29 – 0.30 (0.29), WL 0.64 – 0.68 (0.65), HFL 0.32 – 0.34 (0.33), PeNL 0.15 – 0.16 (0.15), PeH 0.30 – 0.32 (0.30), PeNW 0.23 – 0.24 (0.23), PeS 0.227 – 0.237 (0.227) (8 measured). Indices: CI 75 – 78 (76), SI 83 – 88 (87), PeNI 77 – 81 (79), LPeI 47 – 53 (50), DPeI 145 – 160 (153). Eyes absent. Apex of scape, when laid straight back from its insertion, distinctly fails to reach the midpoint of the posterior margin in full-face view; SL/HL 0.65 – 0.67. Cephalic dorsum finely but distinctly reticulate-punctate. Pronotal dorsum almost smooth, with spaced minute, superficial punctures; obviously much less strongly and densely sculptured than cephalic dorsum. Latroventral surfaces of head with spaced minute punctures. Metanotal groove absent on dorsum of mesosoma. Mesonotal-mesopleural suture absent on side of mesosoma. Propodeum angulate between declivity and side. Posterior surface of petiole node without short cuticular ridges that radiate upward from the peduncle. Node of petiole in profile with the anterior and posterior faces somewhat convergent dorsally so that the node is broader just above the tubercle than at its apex. Subpetiolar process with an obtuse ventral angle. Maximum width of first gastral tergite in dorsal view distinctly greater than the width of the second gastral tergite at its midlength. Base of cinctus of second gastral tergite glossy and polished, without trace of cross-ribs. Midline length of second gastral posttergite, from posterior margin of cinctus to apex, is greater than the width of the segment at its midlength. Disc of second gastral tergite with superficial small punctures. First and second gastral tergites dorsally pubescent and with a number of short standing setae that project above the level of the pubescence in profile. Full adult colour light to medium brown. Holotype worker, Ta n z a n i a: Pwani Region, Mlolo Forest, Mafia Island, 20 m., 9-13.iii.2008, CEPF-TZ-18.2-F08, 7.89576S, 39.82842E, AFRC-TZ-02, primary forest leaf litter, Winkler (P. Hawkes, Y. Mlacha, F. Ninga) (SAMC). Paratypes. 9 workers with same data as holotype; 1 worker with same data but CEPF-TZ-18.2-F71 (SAMC, CASC, AFRC, BBRC). H. dis resembles aprora in most respects, but differs strikingly because the latter lacks the prora on the first gastral sternite, a structure that is obviously present in dis (as well as in all other known Afrotropical species). In addition, aprora is darker brown and has the anterior and posterior faces of the petiole node less convergent dorsally when viewed in profile. Petiolar indices are also different, compare aprora PeNI 84 – 87, DPeI 163 – 173, with the indices for dis, above. An isolated worker from Tanzania (AFRC, details below) is darker in colour than the type-series of dis, and some of its dimensions and indices (HW 0.42, PrW 0.32, WL 0.72, CI 81, SI 81) are very slightly outside the range of dis, while others are within it. As only a single specimen is known, and its resemblance to dis is so striking, it is retained in that species for the present. Non-paratypic material examined. Ta n z a n i a: Tanga Region, Nilo Forest Reserve (Hawkes, Makwati & Mtana).Published as part of Bolton, B. & Fisher, B. L., 2011, Taxonomy of Afrotropical and West Palaearctic ants of the ponerine genus Hypoponera Santschi (Hymenoptera: Formicidae)., pp. 1-118 in Zootaxa 2843 on pages 42-4
Finite element analysis of a centrifuge model retaining wall embedded in overconsolidated clay
No full textThe current study is aimed at the behaviour right upto collapse of a retaining wall embedded in overconsolidated clay. It is found that the excess pore pressures generated due to the excavation are fairly well simulated. The rupture lines on the passive side in the centrifuge model test were closely matched by two lines along which the stress state was reaching the critical state in the analysis. The displacements on the active side were not well matched especially the vertical settlements near to the wall. The bending moments were significantly overpredicted. The prop force due to excavation was also overpredicted. This is to be expected because the prop was modelled as rigid in the analysis.<br/
The design of stiff in situ walls retaining overconsolidated clay part 1: short term behaviour
No full textThis paper contains the summary of a previously published paper and for the abstract see IRRD 827411. It also contains clearer diagrams, a worked example which illustrates the new method of calculation, and the references and the conclusions as there was insufficient space to include these in the previous edition of the paper. The conclusions given are as follows:- (1) mobilised soil strengths depend only on the assumed shape of the lateral pressure diagram; (2) the calculation of mobilised strength in the temporary works condition can depend significantly on the possibility that water can enter tension cracks; (3) the influence of differences in shear strain between different soil zones can be explained; and (4) the undrained deflection of in-situ walls, either unpropped or propped near the top, can be estimated by assuming them to be rigid. Both parts 1 and 2 of the paper have also been published as a Transport and Road Research Laboratory Contractor Report CR 199 (see IRRD 830155)
Effects on diaphragm walls of groundwater pressure rising in clays
No full textData are presented of the behaviour of model walls in overconsolidated clay, tested in a centrifuge at 125 g. The removal in flight of a heavy fluid in front of the model wall was used to simulate excavation in front of a prototype in-situ construction. Measurements of bending moment, prop force, wall deflection and ground movement were made as pore pressure transducers responded to imposed variations in groundwater conditions. In particular two walls, one unpropped and one propped, are investigated. The consequential deformations of the unpropped wall, and the bending moments in the propped wall, are described and discussed in relation to the anticipated behaviour of a full-scale construction. (A
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