1,620 research outputs found
On using deterministic FEA software to solve problems in stochastic structural mechanics
No full textOver the last three decades there has been an outstanding growth in the development of deterministic finite element codes with extensive analysis capabilities. Extension of such deterministic codes to solve problems in stochastic mechanics is of much interest to the academic research community and industry. In this paper we discuss some of the issues involved in integrating fully grown third-party deterministic finite element codes with stochastic projection schemes. The objective of this study is to lay the foundation for development of an easy-to-use general-purpose stochastic finite element software for carrying out probabilistic analysis of large-scale engineering systems. We present a brief introduction to stochastic reduced basis projection schemes and the steps involved in coupling them with a typical deterministic finite element software. We demonstrate with the help of a number of case studies how a coupled framework can be used for solving problems in probabilistic mechanics
Meshless solution of the Burgers equation
No full textThis paper presents a two-step meshless scheme using radial basis functions for the two-dimensional unsteady Burgers equation. The proposed scheme naturally incorporates an extra dissipation term which reduces the errors in the numerical approximation at high convective rates
Radial basis function meshless method for the steady incompressible Navier-Stokes equations
No full textA meshless collocation method based on radial basis functions is proposed for solving the steady incompressible Navier-Stokes equations. This method has the capability of solving the governing equations using scattered nodes in the domain. We use the streamfunction formulation, and a trust-region method for solving the nonlinear problem. The no-slip boundary conditions are satisfied using a ghost node strategy. The efficiency of this method is demonstrated by solving three model problems: the driven cavity flows in square and rectangular domains and flow over a backward-facing step. The results obtained are in good agreement with benchmark solutions
Comparative study of projection schemes for stochastic finite element analysis
No full textWe present a comparison of subspace projection schemes for stochastic finite element analysis in terms of accuracy and computational efficiency. More specifically, we compare the polynomial chaos projection scheme with reduced basis projection schemes based on the preconditioned stochastic Krylov subspace. Numerical studies are presented for two problems: (1) static analysis of a plate with random Young’s modulus and (2) settlement of a foundation supported on a randomly heterogeneous soil. Monte Carlo simulation results based on exact structural analysis are used to generate benchmark results against which the projection schemes are compared. We show that stochastic reduced basis methods require significantly less computer memory and execution time compared to the polynomial chaos approach, particularly for large-scale problems with many random variables. For the class of problems considered, we find that stochastic reduced basis methods can be up to orders of magnitude faster, while providing results of comparable or better accuracy
Rehabilitation of a Patient with Completely Edentulous Maxillary Arch using “All on 4” Concept of Implantation
No full textABSTRACT
Treatment options for insufficient ridge morphology includes the use of short implants, vertical ridge augmentation procedures, or cantilever prostheses in completely edentulous patients. Due to the less predictable long-term prognosis associated with the above-mentioned procedures, the “All on 4” technique was proposed for the rehabilitation in edentulous jaws. The All on 4 treatment concept meets the patient requirements with an immediately loaded fixed prosthesis supported by four implants. This article depicts a clinical report in which an “All on 4” implant treatment is done with delayed loading protocol due to inadequate primary stability obtained.
How to cite this article
Harshakumar K, Abraham NB, Lylajam S, Prasanth V. Rehabilitation of a Patient with Completely Edentulous Maxillary Arch using “All on 4” Concept of Implantation. Int J Prosthodont Restor Dent 2017;7(2):66-70.
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Embelia villosa Wallich 1824
No full text7. Embelia villosa Wallich (1824: 289) Lectotype (designated here):— INDIA, Jharkhand, Rajmahal hills, 1823, Wallich Cat. No. 2313 (K, K001115624!); isolectotype: (G, G00138770!). Fig. 4 Wallich (1824) described this species based on Roxburgh’s collection. This species was introduced into the Botanic garden along with E. robusta by Roxburgh (Wallich 1824). Major collections of Wallich are now deposited at K herbarium (Stafleu & Cowan 1988). Our search in K resulted in finding an HBC specimen with Wallich catalogue no. 2313, which is cited in the protologue. The specimen (K001115624) from K has two species of Embelia mounted on a single sheet, on top with E. villosa (three flowering twigs) and at bottom a single reproductive twig of E. ribes. Additionally, we could trace one more specimen deposited in G herbarium which is annotated as isotype on the sheet with Wallich catalogue no. 2313 and both the specimens are matching with the protologue. Hence, here we designate the specimen with barcode K001115624 available at K herbarium as lectotype.Published as part of Prasanth, Arun & Sardesai, Milind M., 2021, Nomenclatural notes on type materials of eight names in Embelia (Primulaceae) from Peninsular India, pp. 230-238 in Phytotaxa 491 (3) on page 237, DOI: 10.11646/phytotaxa.491.3.3, http://zenodo.org/record/575443
Embelia adnata Beddome ex Clarke 1882
No full text1. Embelia adnata Beddome ex Clarke (1882: 514) Lectotype (designated here):— INDIA, Tamil Nadu, Coimbatore, Bolampatti Hills, 5000ft, Jan, Beddome s. n. (K barcode K000756499 [digital image!]). Fig.1 Clarke (1882) described E. adnata based on manuscript publication of Beddome (1872) from ‘Forester Manual of Botany’ in J.D. Hooker’s Flora. Clarke has cited the specimen of E. adnata which was collected by Beddome from 5000 ft. at Bolampatti hills in flowering condition. A major part of Beddome’s collection is available in BM, some types at K and further materials at CAL (Stafleu & Cowan 1976). All the three herbaria were consulted (virtually and by contacting the curators). Providentially, we traced two specimens mounted on same sheet with separate barcode (K000756499 & K000756500) both collected by Beddome from two different localities. The specimen mounted on top of the sheet (K000756499) with a flowering twig, was collected in January from 5000 ft of Bolampatti hills, Tamil Nadu whereas the specimen at bottom (K000756500) depicts vegetative twig collected from Palghat hills, Kerala. As the type locality and the specimen K000756499 (K) matches with the protologue, we designate the specimen as lectotype for the name E. adnata.Published as part of Prasanth, Arun & Sardesai, Milind M., 2021, Nomenclatural notes on type materials of eight names in Embelia (Primulaceae) from Peninsular India, pp. 230-238 in Phytotaxa 491 (3) on page 230, DOI: 10.11646/phytotaxa.491.3.3, http://zenodo.org/record/575443
Data-driven spatial modeling of historic and future land change at global scale
No full textAssessing the historic and future impacts of land-use and land-cover change (LULCC) on climate requires spatially and temporally explicit data sets on LULCC spanning several decades to centuries, because climate change is a long-term problem. Though remote sensing data provides a globally consistent picture of land cover, these data are only available from the past four decades. Therefore, existing LULCC reconstructions are modeled estimates that combine remote sensing data with relatively coarser-resolution inventory statistics that covers longer historical period. The uncertainties in modeling assumptions, and limited availability and inconsistencies across inventory datasets among other reasons introduce uncertainties in LULCC reconstructions. These uncertainties not only limit our ability to model future LULCC, but also translate as uncertainties in both historic and future environmental assessments.
The objectives of my PhD work are as follows: (1) systematically investigate the causes of uncertainties in existing historical LULCC datasets, (2) test the sensitivity of LULCC quantification uncertainty in estimating CO2 emissions from LULCC (historic and future) using a process-based land-surface model, the Integrated Science Assessment Model (ISAM), (3) compare the relative uncertainties from various drivers (e.g. LULCC datasets, model processes e.g. nitrogen cycle, environmental factors such as climate) in estimating historic and future LULCC emissions, and (4) explore statistical techniques to model future LULCC that takes into account the uncertainties in quantifying the spatial and temporal patterns of LULCC, and (5) as a case-study, identify a key regional hotspot of historic LULCC quantification uncertainty (here, India), and reduce uncertainty through improved understanding of the dynamics and drivers of land change in the case-study region. I address the above goals by integrating land-surface modeling (ISAM), remote sensing and GIS, data collected through ground transects, and geospatial data on socioeconomics.
ISAM simulations show that the estimated net global emissions from LULCC (mean and range) across three different historical LULCC reconstructions are 1.88 (1.7 to 2.21) GtC/yr for the 1980’s, 1.66 (1.48 to 1.83) GtC/yr for the 1990's, and 1.44 (1.22 to 1.65) for the 2000's. The estimates are higher than other published estimates that range from 0.80 to 1.5 GtC/yr for the 1990’s and 1.1 GtC/yr for the 2000’s. These results are higher than other published estimates because they include the effects of nitrogen limitation on regrowth of forests following wood harvest and agricultural abandonment. The estimated LULUC emissions for the tropics are 0.79±0.25 for the 1980’s, 0.78±0.29 for the 1990’s and 0.71±0.33 GtC/yr for the 2000’s, and for the non-tropics regions are 1.08±0.52, 0.90±0.19 and 0.69±0.12 GtC/yr for the three decades. The model results indicate that failing to account for the nitrogen cycle underestimates LULCC emissions by about 40% globally (0.66 GtC/yr), 10% in the tropics (0.07 GtC/yr) and 70% in the non-tropics (0.59 GtC/yr). If LULCC emissions are higher than assessed, it means fossil fuel emissions would have to be even lower to meet the same mitigation target.
Extending ISAM simulations to the 21st century resulted in two key insights. First, nitrogen limitation of CO2 uptake is substantial and sensitive to nitrogen inputs. In ISAM, excluding nitrogen limitation underestimated global total LULUC emissions by 34-52 PgC (~21-29%) during the 20th century and by 128-187 PgC (90-150%) during the 21st century. The difference increases with time because nitrogen limitation will progressively down-regulate the magnitude of CO2 fertilization effect on regrowing forests, due to decreasing supply of plant-usable mineral nitrogen. Second, historically, the indirect effects of anthropogenic activity through environmental changes in land experiencing LULCC (indirect emissions) are small compared to direct effects of anthropogenic LULCC activity (direct emissions). As a result, including or excluding indirect emissions had a minor influence on the estimated total LULUC emissions historically. In contrast, the indirect LULCC emissions for the 21st century are a much larger source to the atmosphere, in simulations with nitrogen limitation. This is because of the gradual weakening of the photosynthetic response to elevated (CO2) caused by nitrogen limitation. Therefore, what fluxes are including in LULCC emissions across different models is a crucial source of uncertainty in future LULCC emissions estimates.
A detailed investigation of the sensitivity of different global-scale LULCC modeling techniques show that land use allocation approaches based solely on previous land use history (but disregarding the impact of driving factor), or those based on mechanistically fitting models for the spatial processes of land use change do not reproduce well long-term historical land use patterns. With an example application to the terrestrial carbon cycle, I show that such inaccuracies in land use allocation can translate into significant implications for global environmental assessments. In contrast to previous approaches, I present a statistical land use downscaling model and show that the model can reproduce the broad spatial features of the past 100 years of evolution of cropland and pastureland patterns. Therefore, the modeling approach and its evaluation provide an example that can be useful to the land use, Integrated Assessment, and the Earth system modeling communities.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Prasanth Meiyappan, accepted the attached license on 2016-04-13 at 20:33.The student, Prasanth Meiyappan, submitted this Dissertation for approval on 2016-04-13 at 20:39.This Dissertation was approved for publication on 2016-04-18 at 14:23.DSpace SAF Submission Ingestion Package generated from Vireo submission #9216 on 2016-07-07 at 14:16:41Made available in DSpace on 2016-07-07T21:14:41Z (GMT). No. of bitstreams: 3
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