109,185 research outputs found
Marginal likelihood calculation for gelfand-dey and Chib Method
No full textOne advantage of Bayesian estimation is its solid theoretical ground on model comparison, which relies heavily upon the accurate calculation of marginal likelihood. The Gelfand-Dey (1994) and Chib (1995) methods are two popular means of calculating marginal likelihood. A trade-off exists between these two methods. The Gelfand-Dey method is simpler and faster to conduct, while Chib method is more accurate, yet intricate. In this paper, we compare the two methods by their ability to identify structural breaks in a reduced form volatility model. Using the Markov Chain Monte Carlo method, we demonstrate that the performance of the two methods is fairly close. Since the Chib method is normally more di±cult to implement in many econometric problems, it is safe to choose Gelfand-Dey method when calculating marginal likelihood.Model Comparison; Structural Break; Heterogeneous Autoregressive Model; Bayesain Estimation
Urban T. Holmes Jr, Alfred G. Engstrom and Sturgis E. Leavitt, ed de Romance Studies presented to William Morton Dey.
No full textAubrun Charles Vincent. Urban T. Holmes Jr, Alfred G. Engstrom and Sturgis E. Leavitt, ed de Romance Studies presented to William Morton Dey. . In: Bulletin Hispanique, tome 54, n°1, 1952. p. 97
Recommendation domains for pond aquaculture: country case study: development and status of freshwater aquaculture in Bangladesh
No full textThis report is an output of the project ôDetermination of high-potential aquaculture development areas and impact in Africa and Asiaö. This monograph is the case study for Bangladesh. Written in three parts, it describes the historical background, practices, stakeholder profiles, production levels, economic and institutional environment, policy issues, and prospects for aquaculture in the country. First, it documents the history and current status of the aquaculture in the country. Second, it assesses the technologies and approaches that either succeeded or failed to foster aquaculture development and discusses why. Third, it identifies the key reasons for aquaculture adoption.Freshwater aquaculture, Economic analysis, Trade, Ecosystems, Pond culture, Fish consumption, Food security, Policies, Regulations, Legislation, Socioeconomic aspects, Yield, Bangladesh,
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Stochastic Investigation of Natural Frequency for Functionally Graded Plates
No full textThis paper presents the stochastic natural frequency analysis of functionally graded plates by applying artificial neural network (ANN) approach. Latin hypercube sampling is utilised to train the ANN model. The proposed algorithm for stochastic natural frequency analysis of FGM plates is validated and verified with original finite element method and Monte Carlo simulation (MCS). The combined stochastic variation of input parameters such as, elastic modulus, shear modulus, Poisson ratio, and mass density are considered. Power law is applied to distribute the material properties across the thickness. The present ANN model reduces the sample size and computationally found efficient as compared to conventional Monte Carlo simulation.</p
A Stochastic Investigation of Effect of Temperature on Natural Frequencies of Functionally Graded Plates
No full textThe present paper deals with thermal uncertainty quantification in the free vibration of functionally graded materials (FGMs) cantilever plate by using the finite element method coupled with multivariate adaptive regression splines surrogate (MARS) model. The combined effects of uncertainty in material properties on the natural frequency are examined. The power law is employed for gradation of material properties across the depth of FGM plate, while the Touloukian model is used to evaluate temperature effects on the material properties. In finite element analysis (FEA), eight noded iso-parametric elements are considered with each element having five degrees of freedoms. In MARS, Sobol sampling is employed to train the model, which results in better convergence and accuracy. The results of MARS model are validated with Monte Carlo simulation results. The results reveal that MARS model can achieve a significant level of accuracy without compromising the accuracy of results.</p
Spatial vulnerability analysis for the first ply failure strength of composite laminates including effect of delamination
No full textThe present investigation deals with the first ply failure strength of laminated composite plates for spatial variation of loading position, which can render a clear idea about the locational sensitivity of the loading positions in a two dimensional space. In this context, the effect of delamination is investigated on the failure strengths considering angle ply and cross ply laminates. A finite element model is developed based on different failure criteria of composites, such as maximum stain, maximum stress, Tsai-Hill, Tsai-Wu-Hahn and Tsai-Hill-Hoffman. An eight noded isoparametric quadratic element is considered in the present finite element formulation incorporating transverse shear and rotary inertia. Results are presented in deterministic as well as stochastic regime. For obtaining the probabilistic descriptions of failure strengths following different failure criteria, Monte Carlo simulation is carried out in conjunction with the finite element model following a non-intrusive approach. The variation of failure strength is portrayed considering the effect of stacking sequence, ply orientation, number of layers, degree of orthotropy and ply thickness. In this article, consideration of stochastic material and structural attributes along with critical service-life characteristics such as delamination for spatially varying loading positions provides a comprehensive understanding about the failure strength of composite laminates for practical applications.</p
8. Fuzzy-based frequency response function analysis of functionally graded plates
No full textIn the present chapter, fuzzy approach is utilized in the assessment of frequency response function (FRF) analysis of functionally graded plates (FGPs). FGP has significant applications in aerospace, marine, medical, and civil structures due to its unique properties such as high-temperature resistance, non-corrosiveness, and high strength and stiffness. The uncertainty quantification of FRF is portrayed. The fuzziness is considered due to its variability in material properties corresponding to the various α-cuts. The power law is implied for characterizing the material modelling. A parametric study is carried out to observe the effect of location of drive point and cross points on uncertain bounds of FRF with respect to crisp values.</p
Stochastic dynamic analysis of twisted functionally graded plates
No full textThis paper presents a stochastic dynamic analysis of functionally graded plates by following an efficient neural network based approach coupled with the finite element method. An isoparametric quadratic element having eight nodes is considered for the finite element analysis of pre-twisted functionally graded cantilever plates subjected to variation in geometric parameters, material properties and temperature. Both individual and compound effects of stochasticity in the uncertain input parameters are accounted to quantify their influence on the first three natural frequencies, mode shapes, and frequency response functions of functionally graded plates. A sensitivity analysis is conducted to ascertain the relative effects of various prospective sources of uncertainty. Latin hypercube sampling is utilised to train the efficient surrogate models, which are employed as a medium of uncertainty propagation. The comparative performance of artificial neural network and polynomial neural network is assessed in the stochastic dynamic analysis of the pre-twisted functionally graded plates from the viewpoint of accuracy and computational efficiency. The results are validated with respect to direct Monte Carlo simulation based on the finite element model of the functionally graded plates. It is observed that the artificial neural network based algorithm can achieve a significant level of computational efficiency without compromising the accuracy of results. The results presented in this article reveal that the source uncertainties of functionally graded plates have a significant effect on the dynamic responses of the structure.</p
Rhopalum gulmargense Saini & Dey. A 2022, sp. nov.
No full textRhopalum (s. str.) gulmargense Saini & Dey, sp. nov. (Figs 1−9) Diagnosis. The new species is close to R. cornilabiatum Li & He, 1999 and R. adamsi Leclercq, 2011. It shares with R. cornilabiatum the anterior margin of the clypeus dentate with conspicuous lateral indentation and pronotal collar rounded laterally, and with R. adamsi the inconspicuous supra-antennal projection, distinct admedian line, pronotal collar rounded laterally and antennomere III longer than wide. The new species differs from R. cornilabiatum and R. adamsi by body length (7.4−7.6 mm), presence of orbital fovea, broader face, antennal sockets contiguous, supraorbital projection, carina on inner margin of compound eyes, median lobe of clypeus, trochanters and femora of all legs ventro-laterally with sparse long silver pubescence, hindtibia largely inflated and pygidial area broad basally & rounded apically. Description. FEMALE. Holotype ♀. BL= 7.4−7.6 mm; FWL= 5.03 mm Color. Body dark brown except metasoma (Fig. 2). Yellow are: antennal scape (except dorsal region), pronotal lobe, mouth parts, pedicel basally, apical part of coxae of all legs, forefemur apically, foretibia except ventral part, fore and midbasitarsi completely, foretarsomeres except apically; dorsal part of all legs and mandible except apically, dark brown; petiole, basal part of terga II to V, tergum VI entirely and sterna reddish brown; wing veins and flagellum, light to dark brown. Head. Shiny, subcubical, densely micro-punctured dorsally, length 0.6× shorter than width; orbital fovea indistinct, elliptical, close to compound eye; ocelli equilateral in position; inner margin of compound eyes slightly convergent below, with carina; supra-antennal projection inconspicuous, covered with silvery setae; inner orbit of compound eyes near scapal basin with dense silvery pubescence; distinct longitudinal line extends from anterior ocellus to frontoclypeal groove; face broad (Fig. 4); clypeus broad, slightly swollen medially, anterior margin with one median and two lateral projections (Fig. 4), basal part of clypeus touching compound eyes, anterior tentorial pit joining antennal socket through frontoclypeal suture on each side (Fig. 4); vertex with fine longitudinal line starting at post-ocellar area, almost reaching occiput; hypostomal carina wide U-shaped, separated from occipital carina; mandible bifid at apex; antennal sockets contiguous, POD equal to 0.46 × of OOD; relative length of antennomere I: II: III: IV: V: VI: VII: VIII: IX: X: XI and XII = 4.8: 1.2: 1.3: 1.3: 1.3: 1.2: 1.4: 1.2: 1.1: 1: 0.8 and 1.4. Mesosoma. Dull compared to head; pronotal collar rounded laterally with slight longitudinal groove medially (Fig. 3); scutum densely micro-punctured with well-defined admedian and parapsidal lines; scutellum and metanotum dorsally with micro-punctures; mesopleuron appearing micro-punctured dorsally; epicnemial sulcus with distinct large foveolae, reaching tegula; precoxal area with small foveolae compared to those on epicnemial sulcus (Fig. 5), mesopleural suture without fovea; metapleuron smooth and shiny; propodeum smooth, shiny, its anterior margin with well-defined foveolae, longitudinal furrow inconspicuous anteriorly, with weak longitudinal striae; posterior surface dorsally covered with fine pubescence, not striate; side smooth and shiny (Fig. 6); foretibia without dorsal spines, midtibia simple and covered with 2-4 spines dorsally, hindtibia largely inflated apically with 9-10 short spines dorsally, ventrally with dense silvery pubescence. Metasoma. Petiolate, petiole longer than combined length of hindtrochanter and hindfemur, distinctly nodose at apex; tergum II longer than wide, following terga subequal (Fig. 7); pygidial plate dull, microsculptured, broader at base, without longitudinal carina, depressed and rounded apically, carinate laterally before middle, PPL= 0.37 mm (Fig. 8). MALE. Unknown. Etymology. Species name is based on the type locality (Fig. 9). Distribution. India (Jammu & Kashmir: Gulmarg). Material Examined. Holotype ♀, India: Jammu and Kashmir: Gulmarg, (34°03’13.4”N 74°22’52.8”E, 8500ft), 23.vii.1923, coll. T. B. Fletcher (NPC−IARI) (Fig. 1). Paratypes: 2♀♀, India: Jammu and Kashmir: Gulmarg, (34°03’13.4”N 74°22’52.8”E, 8500ft), 12.vii.1903, 17−24.vii.1923, coll. T. B. Fletcher (NPC−IARI).Published as part of Saini, Varun & Dey, Debjani, 2022, Description of Rhopalum (s. str.) gulmargense n. sp. with a key to the Indian species of the subgenus Rhopalum Stephens, 1829 s. str. (Hymenoptera: Crabronidae: Crabronini), pp. 139-144 in Zootaxa 5105 (1) on pages 140-142, DOI: 10.11646/zootaxa.5105.1.6, http://zenodo.org/record/633249
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