Abstract A 16-year-old male underwent bilateral sagittal split osteotomy of the mandible to correct a mandibular deficiency. Twenty-one years later, a routine panoramic radiograph revealed a ...radiolucent lesion on the left side of the mandible. The lesion was biopsied. As the patient did not have symptoms and the lesion was connected to the inferior alveolar nerve, the lesion was not totally excised in order to preserve nerve function. The histological features were consistent with traumatic neuroma, and no further surgical procedure was planned.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Digital twins seek to replicate a physical structure in a digital domain. For a digital twin to have close correspondence to its physical twin, data are required. However, it is not always possible, ...or cost-effective, to collect a complete set of data for a structure in all configurations of interest. It is nonetheless useful to repurpose data to help validate predictions for different configurations and scenarios. This statement is true in drilling applications, where, for example, the length of the drill string is altered throughout operation. This paper demonstrates how transfer learning, in the form of three domain-adaptation methods, — transfer component analysis (TCA), maximum independence domain adaptation (MIDA) and geodesic flow kernel (GFK) — can be used to construct a digital twin for localising torsional friction in deviated wells under structural changes (e.g., when the drill column gets longer). The method uses a physics-based torsional model to train a machine-learning classifier that can localise torsional friction for a given drill string length and diameter, where friction localisation labels are known (source). As the length or diameter of the drill string are altered in the field, transfer learning is utilised to map the classifier from the labelled (source) scenario onto these unlabelled (target) scenarios. As a result, transfer learning improves the performance of the classifier when applied to the target data, and increases the domain of validity for the classifier. The performance of the classifier, and therefore its suitability to new drill-string configurations, is estimated by utilising two different distance metrics between the source and a proposed target dataset.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Novel hysteretic (non-reversible) bit/rock interaction model.•Finite element method and a reduced-order model.•Model fitted with field data from a 5 km drill string.•Torsional stability map.•The ...hysteretic model affects the stability region.
The present paper proposes a novel hysteretic (non-reversible) bit/rock interaction model for the torsional dynamics of a drill string. Non-reversible means that the torque-on-bit depends not only on the bit speed, but also on the bit acceleration, producing a type of hysteretic cycle. The continuous drill string system is discretized by means of the finite element method and a reduced-order model is constructed using the normal modes of the associated conservative system. The parameters of the proposed hysteretic bit/rock interaction model is fitted with field data. The non-linear torsional vibration and the stability map of the drill string system are analyzed employing the proposed bit/rock interaction model and also a commonly used reversible model (without hysteresis). It turns out that the hysteretic model affects the stability region of the system.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This paper aims at constructing a stochastic model for the hysteretic behavior of the nonlinear bit–rock interaction of a drill string under torsional vibrations. The proposed model takes into ...account the fluctuations of the stick–slip oscillations observed during the drilling process. These fluctuations are modeled by introducing a stochastic process associated with the variations of the torque on bit, which is a function of the bit speed. The parameters of the stochastic model are calibrated with field data. The response of the proposed stochastic model, considering the random bit–rock interaction, is analyzed, and statistics related to the stability of the drill string are estimated.
Full text
Available for:
NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
The random matrix theory emerged in the mid-1950 in the context of nuclear physics. Since the early 2000s, it has been used in computational mechanics for taking into account uncertainties in the ...operators of mechanical models. The theory has been used successfully associated with symmetric and positive-definite matrices. On the other hand, applications of random matrices to anti-symmetric operators have been largely ignored in the literature. Our work makes a review of the most important random matrix ensembles for computational mechanics, proposes a novel anti-symmetric ensemble and explores applications in rotary systems. We present four different methods for uncertainty quantification in anti-symmetric operators, apply them to a simple rotor-dynamic system, compare the stochastic results, and comment on the advantages and disadvantages of each method.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ethnopharmacological Relevance: The traditional herbal medicinal product Funchicórea® has been widely used in clinical practice for the treatment of intestinal colic and constipation in newborns. ...However, no scientific data on the herbal product to prove its efficacy is available.
Aim of the Study: This study aimed to evaluate the laxative and spasmolytic actions of Funchicórea®.
Materials and Methods: Wistar rats (Rattus norvegicus) and Swiss mice (Mus musculus) of both sex, were used. In vivo pharmacological assays were performed to evaluate the stimulating effect on the gastrointestinal tract, and in vitro studies to verify its spasmodic activity.
Results: Funchicórea® increased the motility of the small intestine in male mice at doses of 100 mg/kg (161.66±14.86 %, n=6) and 200 mg/kg (151.04±17.17 %, n=6) compared to control (100.00±10.49 %, n=6). However, this drug did not induce any change in intestinal transit in female mice. The intestinal transit of male mice treated with loperamide (3 mg/kg/day, during three days) was reduced 66.25±7.49 % (n=8) compared to the control group (100.00±5.16%, n=8) and we observed the normalization of the intestinal transit in constipated animals treated with Funchicórea® 100 mg/Kg (98.42±6.33 %, and 200 mg/kg (99.32±8.47%, n=7). Similar results were observed in the quantification for 24 hours of male and female rats faeces constipated by loperamide (3 mg/kg/day three days), however, in both animals groups treated with Funchicórea® 100 mg/kg (1.24±2.90 g, male; 3.60±0.80 g, female, n=6) and 200 mg/Kg (8.70±2.01 g, male, 10.03±1.30 g, female, n=6) the levels of faeces returned to basal values compared to constipated group (4.01±1.43 g, male; 1.70±0.10 g, female, n=6). In addition, Funchicórea® (0.01-1000 μg/mL) elicited relaxation in rat ileum pre-contracted by KCl 40 mM (Emax=97.5±7.0 %, n=7) and carbachol (1 μM, Emax=100.0±7.0 %, n=7).
Conclusion: The results obtained demonstrated that the herbal medicine Funchicórea® acts by stimulating the intestine of rats and mice and has spasmolytic activity in isolated rat ileum.
The aim of this paper is to propose a new way to measure the efficiency of the proper orthogonal decomposition (POD) to construct a reduced-order model in Structural Dynamics. It investigates the ...efficiency of three reduced-order models for a vibroimpact problem: (1) PODdir-basis, which is the basis constructed using the direct method of the proper orthogonal decomposition; (2) PODsnap-basis, which is the basis constructed using the snapshot method of the POD; and (3) LIN-basis, which is the basis composed by the normal modes of the associated linear (LIN) conservative system. The efficiency is measured in terms of (1) number of elements to represent the dynamics with a given precision and (2) computational cost to simulate the time response within a given precision.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper deals with the problem of a pipe conveying fluid of interest in several engineering applications, such as micro-systems or drill-string dynamics. The deterministic stability analysis ...developed by Paidoussis and Issid (1974) is extended to the case for which there are model uncertainties induced by modeling errors in the computational model. The aim of this work is twofold: (1) to propose a probabilistic model for the fluid–structure interaction considering modeling errors and (2) to analyze the stability and reliability of the stochastic system. The Euler–Bernoulli beam model is used to model the pipe and the plug flow model is used to take into account the internal flow in the pipe. The resulting differential equation is discretized by means of the finite element method and a reduced-order model is constructed from some eigenmodes of the beam. A probabilistic approach is used to model uncertainties in the fluid–structure interaction. The proposed strategy takes into account global uncertainties related to the noninertial coupled fluid forces (related to damping and stiffness). The resulting random eigenvalue problem is used to analyze flutter and divergence unstable modes of the system for different values of the dimensionless flow speed. The numerical results show the random response of the system for different levels of uncertainty, and the reliability of the system for different dimensionless speeds and levels of uncertainty.
•An uncertainty analysis is proposed for the problem of a pipe conveying fluid.•A probabilistic model that takes into account modeling errors is developed.•Confidence regions are analyzed for the eigenvalues and the dynamical response.•A reliability analysis related to the probability of being unstable is done.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper is interested in the dynamics of a horizontal pipe conveying a two-phase fluid (gas and liquid), which is a problem of great regard for the oil and gas industry. The purpose of this paper ...is twofold. First, it introduces dimensionless coefficients that carry the information of the two-phase flow, allowing the dynamic equation to be written analogously to the equation of a single-phase fluid. Second, a probabilistic model is developed considering uncertainties in three flow parameters, (1) the flow profile factor, (2) the slip ratio and (3) the vapour quality, in order to analyse the influence of these parameters on the dynamic stability and on the frequency response of the system. The pipe is described using the linear elastic Euler–Bernoulli beam theory, and the fluid is modelled taking into account a constant tangential velocity of the flow. The coupled system is discretized by means of the finite element method, and the stochastic problem is approximated using the Monte Carlo method. The flow parameters affect greatly the system response, and different values of the critical flow velocity are obtained, depending on the level of uncertainty of the parameters.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The aim of this paper is to investigate the influence of uncertainties on the torsional vibration of drill-strings, in order to find out which uncertainty affects most significantly the torsional ...stability. The unstable torsional behavior is commonly associated to polycrystalline diamond compact bits, and manifests itself in the form of stick-slip oscillations. The stick-slip is a severe type of self-excited vibration characterized by large fluctuations in the rotation of the bit. It not only increases the bit wear, but also can cause drill-string failures. The analysis were done using a mathematical model of the drill-string based on classical torsion theory discretized by means of the finite element method. The bit-rock torque was included in the model as a nonlinear boundary condition at the bottom end of the drill-string. The values of the model parameters are typical values of a real drilling situation, which are subject to a high degree of uncertainty, what justifies a stochastic analysis. We have built probability distributions for the uncertain parameters and used Monte Carlo method to obtain the stochastic stability maps.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
