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Yayli, Mustafa Özgür. "Variational Iteration Technique and Weighted Residual Methods for Gradient Elastic Microbeams." Journal of Computational and Theoretical Nanoscience 11, no. 9 (September 1, 2014): 2023–33. http://dx.doi.org/10.1166/jctn.2014.3602.
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Clark, M. P. A., B. D. Westerberg, and D. M. Fenton. "The ongoing dilemma of residual cholesteatoma detection: are current magnetic resonance imaging techniques good enough?" Journal of Laryngology & Otology 124, no. 12 (March 5, 2010): 1300–1304. http://dx.doi.org/10.1017/s0022215110000332.
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AbstractIntroduction:There is a clear clinical need to reliably detect residual cholesteatoma after canal wall up mastoid surgery. Ideally, this would be achieved through non-invasive radiological means rather than second-look surgery, thus preventing morbidity in those patients in whom no residual disease is found.Case report:We describe a case in which non-echo-planar, diffusion-weighted magnetic resonance imaging sequences were used pre-operatively, and compared with subsequent surgical findings. This case highlights both the potential of this increasingly popular magnetic resonance technique and also its current limitations.Discussion:Various magnetic resonance sequencing types have been employed to try to reliably detect residual cholesteatoma, each with varying success. Non-echo-planar, fast-spin echo, diffusion-weighted sequences currently appear to be the most reliable at detecting even the smallest pearl of cholesteatoma, down to 2 mm in diameter. In our unit, a propeller, diffusion-weighted image sequence is employed on a GE Signa scanner. However, both this case study and other reports show that the accuracy of the technique is not 100 per cent. This begs the question of how much one can rely on the findings of such techniques when deciding whether second-look surgery is indicated. Scan-negative patients will require continued follow up as, at the time of imaging, residual disease may not have reached a detectable size.
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Journal, Baghdad Science. "Approximated Methods for Linear Delay Differential Equations Using Weighted Residual Methods." Baghdad Science Journal 4, no. 4 (December 2, 2007): 658–65. http://dx.doi.org/10.21123/bsj.4.4.658-665.
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The main work of this paper is devoted to a new technique of constructing approximated solutions for linear delay differential equations using the basis functions power series functions with the aid of Weighted residual methods (collocations method, Galerkin’s method and least square method).
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Ravindran, Varadarajan, Badri N. Badriyha, Massoud Pirbazari, and Sung-Hyun Kim. "Modeling of bioactive carbon adsorbers: A hybrid weighted residual-finite difference numerical technique." Applied Mathematics and Computation 76, no. 2-3 (May 1996): 99–131. http://dx.doi.org/10.1016/0096-3003(95)00151-4.
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Vercruysse, J.-P., B. De Foer, T. Somers, J. Casselman, and E. Offeciers. "Long-term follow up after bony mastoid and epitympanic obliteration: radiological findings." Journal of Laryngology & Otology 124, no. 1 (September 24, 2009): 37–43. http://dx.doi.org/10.1017/s002221510999106x.
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AbstractObjective:The canal wall up bony obliteration technique lowers the incidence of recurrent cholesteatoma, but carries the potential risk of obliterating residual cholesteatoma. The objective of this study was to report long-term follow-up radiological findings after performing a canal wall up bony obliteration technique procedure, in order to detect residual and/or recurrent cholesteatoma.Patients:Fifty-one patients presenting with a cholesteatoma or a troublesome cavity were operated upon using the canal wall up bony obliteration technique, and were evaluated by follow-up imaging a mean of 76.4 months post-operatively (range, 53.8–113.6 months).Intervention:All patients were evaluated with high resolution computed tomography and magnetic resonance imaging (including delayed contrast, T1-weighted imaging and non-echo-planar, diffusion-weighted imaging).Results:Imaging revealed the presence of one residual, one recurrent and one congenital petrosal apex cholesteatoma. On high resolution computed tomography, completely obliterated mastoid filled with bone was observed in 74.5 per cent (38/51) of patients, and an aerated middle-ear cavity in 64.7 per cent (33/51). High resolution computed tomography clearly detected any associated soft tissue present in the middle-ear cavity (18/51) and in the obliterated mastoids (13/51), but could not characterise this tissue. Non-echo-planar, diffusion-weighted magnetic resonance imaging clearly identified all three cholesteatomas, and differentiated them from other associated soft tissues. No cholesteatoma was found within the obliterated mastoids.Conclusion:Long-term follow up indicated that the canal wall up bony obliteration technique is a safe method with which to treat primary and recurrent cholesteatoma and to reconstruct unstable cavities. Soft tissue was found quite often in the middle ear and obliterated mastoids. High resolution computed tomography identified its presence but could not further characterise it. However, non-echo-planar, diffusion-weighted magnetic resonance imaging succeeded in differentiating soft tissues, enabling detection of residual or recurrent cholesteatoma after a canal wall up bony obliteration technique procedure.
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Kim, Wooram, Sang-Shin Park, and J. N. Reddy. "A Cross Weighted-Residual Time Integration Scheme for Structural Dynamics." International Journal of Structural Stability and Dynamics 14, no. 06 (June 24, 2014): 1450023. http://dx.doi.org/10.1142/s0219455414500230.
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In this article, we develop a novel stable time integration scheme for the transient analysis of structural dynamics problems. A second-order (in time) differential operator equation (e.g. obtained after finite element discretization in space) is written as a pair of first-order equations in terms of displacements and velocities. Then the solution is sought by minimizing the inner product of the residuals in the two equations (an unconventional approach) over typical time interval to obtain a symmetric set of algebraic equations involving displacements and velocities at two subsequent intervals. The new time integration scheme is termed the cross weighted-residual (CWR) time integration scheme because each of the two residuals takes the other one as a weight function in the minimization. The CWR time integration scheme is developed by using a uniform linear time approximation of the displacement and velocity fields to yield only a single step time integration scheme, which is comparable to the Newmark family of time integration scheme. A reduced integration technique is used to prevent velocity locking, which is caused by linear approximation of both the displacement and velocity fields. For the verification of the consistency and the stability, the CWR time integration scheme is tested with single-degree as well as multi-degree of freedom problems. The scheme performs extremely well compared with those of the well-known Newmark family of time integration schemes.
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K.Ravi Kumar, K. Ravi Kumar. "A New Speech Enhancement Technique to Reduce Residual Noise Using Perceptual Constrained Spectral Weighted Factors." IOSR Journal of Electronics and Communication Engineering 6, no. 3 (2013): 28–33. http://dx.doi.org/10.9790/2834-0632833.
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Slater, Joseph C., Chris L. Pettit, and Philip S. Beran. "In-Situ Residual Tracking in Reduced Order Modelling." Shock and Vibration 9, no. 3 (2002): 105–21. http://dx.doi.org/10.1155/2002/540189.
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Proper orthogonal decomposition (POD) based reduced-order modelling is demonstrated to be a weighted residual technique similar to Galerkin's method. Estimates of weighted residuals of neglected modes are used to determine relative importance of neglected modes to the model. The cumulative effects of neglected modes can be used to estimate error in the reduced order model. Thus, once the snapshots have been obtained under prescribed training conditions, the need to perform full-order simulations for comparison is eliminates. This has the potential to allow the analyst to initiate further training when the reduced modes are no longer sufficient to accurately represent the predominant phenomenon of interest. The response of a fluid moving at Mach 1.2 above a panel to a forced localized oscillation of the panel at and away from the training operating conditions is used to demonstrate the evaluation method.
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Ketelslagers, Katrien, Thomas Somers, Bert De Foer, Andrzej Zarowski, and Erwin Offeciers. "Results, Hearing Rehabilitation, and Follow-up with Magnetic Resonance Imaging after Tympanomastoid Exenteration, Obliteration, and External Canal Overclosure for Severe Chronic Otitis Media." Annals of Otology, Rhinology & Laryngology 116, no. 9 (September 2007): 705–11. http://dx.doi.org/10.1177/000348940711600914.
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Objectives: We sought to evaluate the results, auditory rehabilitation, and follow-up with magnetic resonance imaging (MRI) after tympanomastoid exenteration with obliteration of the mastoid cavity and overclosure of the external ear canal in patients with severe chronic otitis media that was resistant to medical therapy and conventional surgery and was associated with a profound sensorineural or severe conductive hearing loss. Methods: Twenty-nine patients were analyzed and underwent this surgical technique. Twelve patients had, during the same or later stage, either cochlear implantation, fixture implantation for a bone-anchored hearing aid, or middle ear implantation. For follow-up control of the obliterated cavity, delayed gadolinium-enhanced, T1-weighted MRI in combination with non-echo planar imaging diffusion weighted sequences were used. Results: No patient had recurrent otorrhea after an average follow-up period of 4.75 years. One patient had a residual cholesteatoma as shown by new MRI techniques, and this was successfully resected. One patient developed complications 6 months after 1-stage tympanomastoid exenteration and cochlear implantation. Conclusions: This technique is very useful in selected patients with severe chronic otitis media that is resistant to medical therapy and surgery and is associated with a profound sensorineural or severe conductive hearing loss. New sequences in MRI are used for postoperative follow-up of these obliterated cavities and seem reliable for the detection of residual or recurrent cholesteatoma. Middle ear implantation and cochlear implantation can be relatively safely performed in these patients in a second stage.
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Sarndal, Carl-Erik, Bengt Swensson, and Jan H. Wretman. "The Weighted Residual Technique for Estimating the Variance of the General Regression Estimator of the Finite Population Total." Biometrika 76, no. 3 (September 1989): 527. http://dx.doi.org/10.2307/2336118.
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SÄRNDAL, CARL-ERIK, BENGT SWENSSON, and JAN H. WRETMAN. "The weighted residual technique for estimating the variance of the general regression estimator of the finite population total." Biometrika 76, no. 3 (1989): 527–37. http://dx.doi.org/10.1093/biomet/76.3.527.
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Syal, R., H. Singh, and K. K. Duggal. "Otogenic brain abscess: management by otologist." Journal of Laryngology & Otology 120, no. 10 (July 6, 2006): 837–41. http://dx.doi.org/10.1017/s0022215106001903.
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Introduction: Fifty per cent of brain abscesses in adults and 25 per cent of those in children are otogenic in origin. The current neurosurgical options are to drain the abscess repeatedly through burr holes or to excise it completely with the capsule. We successfully managed 10 cases of brain abscess by draining through the transmastoid route. The technique and its advantages are discussed.Material and methods: The patients underwent surgery at two different institutions. Computed tomography scanning and magnetic resonance imaging were performed, along with diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy. The abscesses were drained via a transmastoid route.Results: In eight cases, ear disease and brain abscess were treated in a single-stage procedure. In the remaining two cases, residual brain abscess was excised subsequently by our neurosurgical colleagues.Conclusions: Transmastoid drainage of pus can successfully treat mastoid disease and brain abscess in a single surgical intervention. Residual abscess can be subsequently excised, with relatively reduced morbidity. Repeated needling is also avoided with this approach. Diffusion-weighted imaging and proton magnetic resonance spectroscopy are helpful.
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He, Liang Yu, Yin Biao Guo, Hao Huang, Zhe Wang, and Jian Wang. "The Technique of Online Measurement and Data Processing for Aspheric Machining." Advanced Materials Research 97-101 (March 2010): 4313–18. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.4313.
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In the traditional precision machining, it is easy to introduce positioning error because of the separation of the machining and the measurement. In order to solve this problem, an online measurement technique for aspheric grinding has been put forward. It measured the workpiece with sensor which was fixed to the high-precision machine tool. It processed data with the algorithm of Two-dimensional weighted average filtering and curve fitting based on Gauss-Newton and Levenberg-Marquardt least-square method. The experimental results indicated that the fitting residual error was less than 3×10-6 mm. In the grinding process, the measurement error was of the order of the magnitude of 10-3 mm. It can be concluded that the technique measures the surface exactly, and improves the machining accuracy effectively by providing accurate data for compensation.
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Adewumi, Adebayo O., Saheed O. Akindeinde, Adebayo A. Aderogba, and Babatunde S. Ogundare. "Laplace Transform Collocation Method for Solving Hyperbolic Telegraph Equation." International Journal of Engineering Mathematics 2017 (April 10, 2017): 1–9. http://dx.doi.org/10.1155/2017/3504962.
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This article presents a new numerical scheme to approximate the solution of one-dimensional telegraph equations. With the use of Laplace transform technique, a new form of trial function from the original equation is obtained. The unknown coefficients in the trial functions are determined using collocation method. The efficiency of the new scheme is demonstrated with examples and the approximations are in excellent agreement with the analytical solutions. This method produced better approximations than the ones produced with the standard weighted residual methods.
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Schoenberger, Michael. "Optimum weighted stack for multiple suppression." GEOPHYSICS 61, no. 3 (May 1996): 891–901. http://dx.doi.org/10.1190/1.1444014.
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In water deeper than about 300 m, common midpoint stack is moderately effective at suppressing multiple reflections. The stacking process acts as a low‐pass multiple filter, rejecting, to some extent, frequencies greater than the reciprocal of the multiple’s residual moveout on the farthest offset trace. A weighted stack can often be even more effective at attenuating multiples, if the weights are chosen such that the multiple filter response has low amplitudes at those frequencies where the multiple is strong. A least‐squares technique is developed to determine optimum weights, based on the multiple’s frequency content, the water depth, the primary velocity, and on a stabilization factor equivalent to white noise in deconvolution filter design. To be truly optimum, the weights must vary both spatially, to account for water‐depth changes, and temporally, to account for sediment velocity changes and mute patterns; but the filter responses are not very sensitive to the input parameters and need to be redesigned only infrequently. The superiority of weighted stacks to uniform stacks is demonstrated by application to three deep‐water examples. In all cases, weighted stacks attenuate multiples more effectively than do conventional uniform stacks.
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Evlice, A., Ö. Tarkan, M. Kiroğlu, K. Biçakci, S. Özdemir, Ü. Tuncer, and E. Çekiç. "Detection of recurrent and primary acquired cholesteatoma with echo-planar diffusion-weighted magnetic resonance imaging." Journal of Laryngology & Otology 126, no. 7 (May 15, 2012): 670–76. http://dx.doi.org/10.1017/s0022215112000679.
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AbstractObjective:To evaluate the diagnostic value of echo-planar diffusion-weighted magnetic resonance imaging in pre-operative detection of suspected primary acquired, residual and/or recurrent cholesteatoma.Materials and methods:Fifty-eight chronic otitis media patients with suspected cholesteatoma were thus evaluated two weeks pre-operatively, and divided into group one (41 patients, no previous surgery, suspected primary acquired cholesteatoma) and group two (17 patients, previous surgery, scheduled ‘second-look’ or revision surgery for suspected residual or recurrent cholesteatoma). Patients' operative, histopathology and radiological findings were compared.Results:Cholesteatoma was found in 63 per cent of group one patients and 58 per cent of group two patients at surgery. Histopathological examination of surgical specimens indicated that imaging accurately predicted the presence or absence of cholesteatoma in 90 per cent of group one (37/41; 23 true positives, 14 true negatives) and 76 per cent of group two (13/17; seven true positives, six true negatives). Three patients in both groups were false negative diagnoses and one patient in both groups was a false positive. The sensitivity, specificity, and positive and negative predictive values of echo-planar diffusion-weighted magnetic resonance imaging of cholesteatoma were respectively 88, 93, 95 and 82 per cent in group one and 70, 85, 87 and 66 per cent in group two.Conclusion:Echo-planar diffusion-weighted magnetic resonance imaging is a valuable technique with high sensitivity and specificity for cholesteatoma imaging.
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Velthuis, S., K. J. van Everdingen, J. J. Quak, and D. R. Colnot. "The value of non echo planar, diffusion-weighted magnetic resonance imaging for the detection of residual or recurrent middle-ear cholesteatoma." Journal of Laryngology & Otology 128, no. 7 (July 2014): 599–603. http://dx.doi.org/10.1017/s0022215114001418.
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AbstractObjective:To determine the value of non echo planar, diffusion-weighted magnetic resonance imaging for detection of residual and recurrent middle-ear cholesteatoma after combined-approach tympanoplasty.Method:The magnetic resonance imaging findings after primary surgery for cholesteatoma were compared with intra-operative findings at ‘second-look’ surgery or with clinical follow-up findings.Results:Forty-eight magnetic resonance imaging studies were performed in 38 patients. Second-look surgery was performed 21 times in 18 patients. The remaining patients were followed up at the out-patient clinic. There were no false-positive findings with non echo planar, diffusion-weighted magnetic resonance imaging; however, there were four false-negative findings. The mean maximum diameter of recurrent cholesteatoma, as assessed using magnetic resonance imaging, was 11.7 mm (range, 4.4–25.3 mm). The sensitivity of non echo planar, diffusion-weighted magnetic resonance imaging for detecting cholesteatoma prior to second-look surgery was 0.76, with a specificity of 1.00. When clinical follow up of the non-operated ears was included in the analysis, sensitivity was 0.81 and specificity was 1.00.Conclusion:Recurrent cholesteatoma can be accurately detected using non echo planar, diffusion-weighted magnetic resonance imaging. Our study, however, also showed some false-negative results. Therefore, strict out-patient follow up is mandatory for those considering using this technique instead of standard second-look surgery.
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Mazars, Emmanuel, Imad M. Jaimoukha, and Zhenhai Li. "Computation of a Reference Model for Robust Fault Detection and Isolation Residual Generation." Journal of Control Science and Engineering 2008 (2008): 1–12. http://dx.doi.org/10.1155/2008/790893.
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This paper considers matrix inequality procedures to address the robust fault detection and isolation (FDI) problem for linear time-invariant systems subject to disturbances, faults, and polytopic or norm-bounded uncertainties. We propose a design procedure for an FDI filter that aims to minimize a weighted combination of the sensitivity of the residual signal to disturbances and modeling errors, and the deviation of the faults to residual dynamics from a fault to residual reference model, using theℋ∞-norm as a measure. A key step in our procedure is the design of an optimal fault reference model. We show that the optimal design requires the solution of a quadratic matrix inequality (QMI) optimization problem. Since the solution of the optimal problem is intractable, we propose a linearization technique to derive a numerically tractable suboptimal design procedure that requires the solution of a linear matrix inequality (LMI) optimization. A jet engine example is employed to demonstrate the effectiveness of the proposed approach.
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Lois, Athanasios, Efthimios Sokos, Nikolaos Martakis, Paraskevas Paraskevopoulos, and G.-Akis Tselentis. "A new automatic S-onset detection technique: Application in local earthquake data." GEOPHYSICS 78, no. 1 (January 1, 2013): KS1—KS11. http://dx.doi.org/10.1190/geo2012-0050.1.
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Algorithms that deal with the automatic [Formula: see text]-onset time identification problem are a topic of ongoing research. Modern dense seismic networks used for earthquake location, seismic tomography investigations, source studies, early warning, etc., demand accurate automatic S-wave picking. Most of the techniques that have been proposed up to now are mainly based on the polarization features of the seismic waves. We propose a new time domain method for the automatic determination of the [Formula: see text]-phase arrival onsets, and present its implementation on local earthquake data. Eigenvalue analysis takes place over small time intervals, and the maximum eigenvalue which is obtained on each step is retained for further processing. In this way, a time series of maximum eigenvalues is formed, which serves as a characteristic function. We obtain a first [Formula: see text]-phase arrival time estimation by applying the kurtosis criterion on the derived characteristic function. Furthermore, a multiwindow approach combined with an energy-based weighting scheme is also applied, to reduce the algorithm’s dependence on the moving window’s length and provide a weighted [Formula: see text]-phase onset. Automatic picks were compared against manual reference picks, resulting in mean residual time of 0.051 s. Moreover, the proposed technique was subjected to a noise robustness test and sustained a good performance. The mean residual time remained lower than 0.1 s, for noise levels between [Formula: see text] up to 8 dB. The proposed method is easy to implement, because it is almost parameter free and demands low computational resources.
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Wen, Weibin, Shanyao Deng, Shengyu Duan, and Daining Fang. "A high‐order accurate explicit time integration method based on cubic b‐spline interpolation and weighted residual technique for structural dynamics." International Journal for Numerical Methods in Engineering 122, no. 2 (October 7, 2020): 431–54. http://dx.doi.org/10.1002/nme.6543.
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T.M, Sreenivasa Murthy, Anita Nagadi, and Sneha Krishna Mohan. "Utility of Non-EPI DWI MRI in the Management of Pediatric Cholesteatoma." Annals of Otology and Neurotology 02, no. 01 (January 29, 2019): 43–45. http://dx.doi.org/10.1055/s-0039-1678467.
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Abstract Introduction Cholesteatoma in children can be acquired or congenital and is generally extensive. The most commonly used technique for the removal of cholesteatoma is intact canal wall mastoidectomy. This invariably leads to second-look surgery to assess for recurrence or residual cholesteatoma. Magnetic resonance imaging (MRI) with non–echo-planar imaging (non-EPI) diffusion-weighted imaging (DWI) is an accurate noninvasive imaging option that can be used in diagnosing primary cholesteatoma. This can also be used to diagnose residual or recurrent cholesteatoma in patients who have undergone intact canal wall mastoidectomy. Case Report A 7-year-old male patient presented with a 1-week history of foul-smelling discharge from the right ear. On examination, a polypoidal mass with keratinized debris was seen. A diagnosis of cholesteatoma of right ear was made. Imaging with high-resolution computed tomography (HRCT) of the temporal bone and non-EPI DWI MRI confirmed the same. The child underwent an intact canal wall mastoidectomy and was followed up at 2 years with non-EPI DWI MRI to monitor any residual or recurrent cholesteatoma. Conclusion Non-EPI DWI MRI provides a convenient, accurate, and noninvasive method of evaluating and monitoring for residual or recurrent cholesteatoma and thus helps avoid unnecessary second-look surgery.
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SAHU, O. P., M. K. SONI, and I. M. TALWAR. "DESIGNING QUADRATURE MIRROR FILTER BANKS USING STEEPEST DESCENT METHOD." Journal of Circuits, Systems and Computers 15, no. 01 (February 2006): 29–41. http://dx.doi.org/10.1142/s0218126606002903.
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This paper proposes a new technique for the design of quadrature mirror filter (QMF) banks by exploiting steepest descent method. The design problem is formulated to minimize an objective function, which is a weighted sum of the pass band error and stop band residual energy of the low pass analysis filter of the QMF bank. The minimization has been carried out gradually by respective optimum step lengths in the corresponding steepest descent directions of a linear combination of the objective function and square of the reconstruction error of the QMF bank at the quadrature frequency by optimizing the filter tap weights. The design results show that the proposed method gives a comparable performance to the already existing methods.
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Alhichri, Haikel, Yakoub Bazi, and Naif Alajlan. "Assisting the Visually Impaired in Multi-object Scene Description Using OWA-Based Fusion of CNN Models." Arabian Journal for Science and Engineering 45, no. 12 (July 29, 2020): 10511–27. http://dx.doi.org/10.1007/s13369-020-04799-7.
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AbstractAdvances in technology can provide a lot of support for visually impaired (VI) persons. In particular, computer vision and machine learning can provide solutions for object detection and recognition. In this work, we propose a multi-label image classification solution for assisting a VI person in recognizing the presence of multiple objects in a scene. The solution is based on the fusion of two deep CNN models using the induced ordered weighted averaging (OWA) approach. Namely, in this work, we fuse the outputs of two pre-trained CNN models, VGG16 and SqueezeNet. To use the induced OWA approach, we need to estimate a confidence measure in the outputs of the two CNN base models. To this end, we propose the residual error between the predicted output and the true output as a measure of confidence. We estimate this residual error using another dedicated CNN model that is trained on the residual errors computed from the main CNN models. Then, the OAW technique uses these estimated residual errors as confidence measures and fuses the decisions of the two main CNN models. When tested on four image datasets of indoor environments from two separate locations, the proposed novel method improves the detection accuracy compared to both base CNN models. The results are also significantly better than state-of-the-art methods reported in the literature.
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Fukushima, Hisaki, Suetaka Nishiike, Tsutomu Tamada, Shigetoshi Yoda, and Tamotsu Harada. "S204 – Postoperative Residual Cholesteatoma: Value of MR Imaging." Otolaryngology–Head and Neck Surgery 139, no. 2_suppl (August 2008): P144. http://dx.doi.org/10.1016/j.otohns.2008.05.379.
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Objectives This study was carried out to evaluate the utility of diffusion-weighted imaging (DWI) and contrast-enhanced MR imaging (CE-MRI) for the detection of postoperative residual cholesteatoma in cases where computed tomographic (CT) findings were not conclusive. Methods 14 ears from 13 patients, who had undergone canal wall-up tympanoplasty for cholesteatoma and nonspecific opacity images on postoperative follow-up CT, underwent MR imaging before revision surgery. T1WI, T2WI DWI (using b-factors of 0 and 800 sec/mm2) and CE-MRI were performed using a 1.5-T MR unit. MR imaging examination was generally completed within 30 min. In all cases, imaging findings were compared with second- or third-look operative findings. Results MR imaging depicted 9 out of 10 residual cholesteatomas (sensitivity, 90.0%). In a remaining (false-negative) case, a 3-mm cholesteatoma pearl that was encircled by granulation tissue was not depicted. There were no false-positive cases (specificity, 100%). The positive predictive value and negative predicitive value were 100% and 75%, respectively. DWI showed cholesteatoma high signal intensity in peculiarity. However, the spatial resolution was low and artifacts appeared at the base of skull in DWI. In the case with a small cholesteatoma in the dura mater, CE-MRI was effective. The minimum size of the cholesteatomas detected by the MR imaging including DWI was 4 mm. Conclusions When postoperative CT is not conclusive, DWI combined with CE-MRI is a valuable technique for the detection of residual cholesteatoma.
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Du, Jian Jun, Ying Xue Yao, D. Liu, and D. W. Feng. "Analysis of the Static Performance of Externally Pressurized Gas Journal-Thrust Bearing with Slot Restrictors." Key Engineering Materials 315-316 (July 2006): 838–42. http://dx.doi.org/10.4028/www.scientific.net/kem.315-316.838.
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The externally pressurized gas journal-thrust bearing with slot restrictors is investigated by the finite element technique. A consistent transform principle is proposed in this paper to simplify the analysis of Reynolds equation for journal and thrust bearing. The second-order partial differential equation, Reynolds equation, is reduced by one-order with weighted residual method in the discretization procedure, which releases the requirement of continuity degree of the interpolation function while finite element method is adopted. The static characteristics of externally journal-thrust gas bearing are analyzed. Factors that influence the radial and axial bearing capacity are discussed. The interactional rules that exist between the journal bearing part and thrust bearing part are discovered. Predicted characteristics are in good agreement with experimental results.
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Majer, David, and Matjaž Finšgar. "Single-Drop Analysis of Epinephrine and Uric Acid on a Screen-Printed Carbon Electrode." Biosensors 11, no. 8 (August 19, 2021): 285. http://dx.doi.org/10.3390/bios11080285.
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This work demonstrates the analysis of epinephrine (EP) and uric acid (UA) in a single drop (the volume of the test solution was only 50 µL) using a screen-printed carbon electrode (SPCE) sensor and square-wave voltammetry (SWV). The limit of detection, limit of quantification, linearity, accuracy, precision, and robustness were validated. The normality of the experimental data was tested and confirmed for both methods. Heteroscedasticity was checked by residual analysis followed by a statistical F-test. The latter was confirmed for both analytes. The low relative standard deviations (RSD) at all calibration points and repetitive slopes justified the use of a calibration curve; therefore, the standard addition methodology was avoided (the latter is common in electroanalysis, but time-consuming). Since the conditions for using an ordinary least squares (OLS) regression were not met, weighted linear regression (WLR) was used to improve the accuracy of the analytical results at low concentrations of the analytes. In this manner, the best weighted model was determined and used for the quantification. A comparison was made between the OLS and WLR methods to show the necessity of using the WLR method for EP and UA analysis. The newly developed and validated methods were also shown to be effective in the analysis of real samples. The content of EP in an EP auto-injector and UA in human urine was tested by employing the best weighted model. For EP and UA, the accuracy in terms of the average recovery value was 101.01% and 94.35%, and precision in terms of RSD was 5.65% and 2.75%, respectively. A new analytical methodology is presented that uses a low volume (a single drop), and it offers the advantage of electroanalysis for on-site analysis, where conventional chromatographic techniques cannot be easily employed. Furthermore, the developed technique has additional advantages in terms of speed, cost, and miniaturization.
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Rungamornrat, Jaroon, Son Ngoc Nguyen, Supawat Wongthongsiri, Keerati Panupattanapong, Teerapong Senjuntichai, and Thai Binh Nguyen. "FE SOLUTIONS OF NEAR-TIP FIELD FOR MODE-I CRACKS WITH RESIDUAL SURFACE TENSION." ASEAN Engineering Journal 9, no. 2 (December 1, 2019): 28–43. http://dx.doi.org/10.11113/aej.v9.15511.
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This paper presents finite element solutions of a near-tip elastic field of a straight, nano-scale crack in a two-dimensional, linear elastic, whole plane subjected to mode-I crack-face loads. The mathematical model is formulated using a continuum-based theory of classical linear elasticity together with Gurtin-Murdoch surface model to capture the role of the residual surface tension present on the crack-face material layer. The formulation finally yields a second-order, integrodifferential equation governing the crack opening displacement. A weighted residual technique along with the regularization procedure is applied to establish a weakly singular weak-form equation with the involved kernel of O(ln )r . Galerkin strategy and the finite element procedure are then employed to discretize the weak-form equation. Various types of element shape functions, generated by standard C0 -elements, standard C1 -elements, and special elements with built-in crack-tip functions, are considered. A proper quadrature rule is selected to efficiently and accurately evaluate both nearly and weakly singular double line integrals over pairs of elements resulting from the discretization and the solution of a dense system of linear algebraic equations is obtained using an efficient indirect solver. The rate of convergence of finite element solutions is fully investigated and such information is then used to conclude the influence of the residual surface tension on the behavior of the near-tip field.
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Guo, Li, Tang Chen, Jun Hong, Ling Qiao, and Xiao Ming Guo. "Study on Chloride Diffusion in Concrete with Non-Homogenous Coefficient Using Meshless Boundary Element Method." Materials Science Forum 650 (May 2010): 38–46. http://dx.doi.org/10.4028/www.scientific.net/msf.650.38.
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A new robust numerical technique was proposed for analyzing chloride transient diffusion in concrete with non-homogenous coefficient. The method was based on a meshless boundary element method which results in an integral equation for explicitly evaluating field chloride quantities. Weighted residual method and Green’s function were adopted to derive domain and boundary integral equations. A radial integration method coupling with radial basis function approximation technology was used to convert domain integral into equivalent boundary integral. With central finite difference method, an explicit time iteration scheme was established for solving transient diffusion equation. Two numerical examples for 2D diffusion problem were given to demonstrate the robustness of the proposed method. Numerical results show that the non-homogenous diffusion coefficient causes the chloride distribution non-uniform, and the diffusion process is nonlinear with respect to time.
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Ashrafi, H., and M. Shariyat. "A mathematical boundary integral equation for analysis of the heterogeneous media, using the functionally graded elements." International Journal of Computational Materials Science and Engineering 04, no. 03 (September 2015): 1550017. http://dx.doi.org/10.1142/s2047684115500177.
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In the present research, a functionally graded (FG) boundary integral equation method capable of modeling quasistatic behavior of heterogeneous media fabricated from functionally graded materials (FGMs) whose distributions of the material properties obey either power or exponential laws is developed. Two heterogeneous material gradation models were employed to present the numerical formulations and solution algorithm. Somigliana's identity in 2D displacement fields of the isotropic heterogeneous domains is numerically implemented, employing FG elements. Based on the constitutive and governing equations and the weighted residual technique, the proposed boundary integral equation formulations are implemented for behavior analysis of the elastic heterogeneous isotropic solid structures. Results are verified and the proposed boundary element (BE) formulation is employed for behavior analysis of the plates and cylinders to demonstrate the proposed procedure more adequately.
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Luo, Xiaomin, Yidong Lou, Xiaopeng Gong, Shengfeng Gu, and Biyan Chen. "Benefit of Sparse Reference Network in BDS Single Point Positioning with Single-Frequency Measurements." Journal of Navigation 71, no. 2 (November 23, 2017): 403–18. http://dx.doi.org/10.1017/s0373463317000765.
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The current positioning accuracy of the BeiDou Navigation Satellite System (BDS) Single Point Positioning (SPP) with code measurement is in the order of several metres due to systematic errors. To further reduce the systematic errors in SPP, this contribution develops a new strategy to BDS SPP with a sparse reference network, named Augmented SPP (A-SPP). In this method, the Combined Residual Errors (CRE) products of BDS B1I measurement are integrated with three optional base stations that are close to the rover station. Based on the Satellite Elevation Angle Weighted (SEAW) average technique, the code residual errors of each BDS satellite observed by the rover station can be acquired epoch-by-epoch. Finally, the corrected code observations for the rover station can be utilised to achieve an A-SPP solution. The validation of this method is confirmed by both static and kinematic tests. Results clearly show that the accuracies of the A-SPP solution for horizontal and vertical directions are better than 0·5 m and 1·0 m. This study suggests that the proposed A-SPP solution is a good option for single-frequency GNSS users to improve their positioning performance.
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YAZDANI, A., and V. NASSEHI. "FINITE ELEMENT SOLUTION OF MULTI-SCALE TRANSPORT PROBLEMS USING THE LEAST SQUARES-BASED BUBBLE FUNCTION ENRICHMENT." International Journal of Modeling, Simulation, and Scientific Computing 03, no. 04 (November 18, 2012): 1250019. http://dx.doi.org/10.1142/s1793962312500195.
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This paper presents a technique for deriving least-squares-based polynomial bubble functions to enrich the standard linear finite elements, employed in the formulation of Galerkin weighted-residual statements. The element-level linear shape functions are enhanced using supplementary polynomial bubble functions with undetermined coefficients. The enhanced shape functions are inserted into the model equation and the residual functional is constructed and minimized by using the method of the least squares, resulting in an algebraic system of equations which can be solved to determine the unknown polynomial coefficients in terms of element-level nodal values. The stiffness matrices are subsequently formed with the standard finite elements assembly procedures followed by using these enriched elements which require no additional nodes to be introduced and no extra degree of freedom incurred. Furthermore, the proposed technique is tested on a number of benchmark linear transport equations where the quadratic and cubic bubble functions are derived and the numerical results are compared against the exact and standard linear element solutions. It is demonstrated that low order bubble enriched elements provide more accurate approximations for the exact analytical solutions than the standard linear elements at no extra computational cost in spite of using relatively crude meshes. On the other hand, it is observed that a satisfactory solution of the strongly convection-dominated transport problems may require element enrichment by using significantly higher order polynomial bubble functions in addition to the use of extremely fine computational meshes.
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Hatiboglu, Mustafa Aziz, Jeffrey S. Weinberg, Dima Suki, Ganesh Rao, Sujit S. Prabhu, Komal Shah, Ed Jackson, and Raymond Sawaya. "IMPACT OF INTRAOPERATIVE HIGH-FIELD MAGNETIC RESONANCE IMAGING GUIDANCE ON GLIOMA SURGERY." Neurosurgery 64, no. 6 (June 1, 2009): 1073–81. http://dx.doi.org/10.1227/01.neu.0000345647.58219.07.
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Abstract OBJECTIVE To determine the impact of intraoperative magnetic resonance imaging (iMRI) on the decision to proceed with additional glioma resection during surgery and to maximize extent of resection (EOR). METHODS Patients who underwent craniotomy for glioma resection with high-field iMRI guidance were prospectively evaluated between September 2006 and August 2007. Volumetric analysis and EOR were assessed with iMRI, using postcontrast T1-weighted images for tumors showing contrast enhancement and T2-weighted images for nonenhancing tumors. RESULTS Forty-six patients underwent resection using iMRI guidance, with iMRI being used to evaluate the EOR in 44 patients and for reregistration in 2 patients. Surgery was terminated after iMRI in 23 patients (52%) because gross total resection was achieved or because of residual tumor infiltration in an eloquent brain region. Twenty-one patients (47%) underwent additional resection of residual tumor after iMRI. For enhancing gliomas, the median EOR increased significantly from 84% (range, 59%–97%) to 99% (range, 85%–100%) with additional tumor removal after iMRI (P < 0.001). For nonenhancing gliomas, the median EOR increased (from 63% to 80%) with additional tumor removal after iMRI, but not significantly, owing to the small sample size (7 patients). Overall, the EOR increased from 76% (range, 35%–97%) to 96% (range, 48%–100%) (P < 0.001). Gross total resection was achieved after additional tumor removal after iMRI in 15 of 21 patients (71%). Overall, 29 patients (65%) experienced gross total resection, and in 15 (52%), this was achieved with the contribution of iMRI. CONCLUSION High-field iMRI is a safe and reliable technique, and its use optimizes the extent of glioma resection.
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D'ALESSIO, S. J. D., J. P. PASCAL, H. A. JASMINE, and K. A. OGDEN. "Film flow over heated wavy inclined surfaces." Journal of Fluid Mechanics 665 (October 27, 2010): 418–56. http://dx.doi.org/10.1017/s0022112010004003.
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The two-dimensional problem of gravity-driven laminar flow of a thin layer of fluid down a heated wavy inclined surface is discussed. The coupled effect of bottom topography, variable surface tension and heating has been investigated both analytically and numerically. A stability analysis is conducted while nonlinear simulations are used to validate the stability predictions and also to study thermocapillary effects. The governing equations are based on the Navier–Stokes equations for a thin fluid layer with the cross-stream dependence eliminated by means of a weighted residual technique. Comparisons with experimental data and direct numerical simulations have been carried out and the agreement is good. New interesting results regarding the combined role of surface tension and sinusoidal topography on the stability of the flow are presented. The influence of heating and the Marangoni effect are also deduced.
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Iwan, W. D., and H. Jensen. "On the Dynamic Response of Continuous Systems Including Model Uncertainty." Journal of Applied Mechanics 60, no. 2 (June 1, 1993): 484–90. http://dx.doi.org/10.1115/1.2900819.
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This paper presents a technique for obtaining the response of linear continuous systems with parameter uncertainties subjected to deterministic excitation. The parameter uncertainties are modeled as random fields and are assumed to be time independent. The general formulation of the method is developed for a particular class of partial differential equations with random coefficients. Random shape functions are introduced to approximate the solution in the spatial domain and in the random space. A system of linear ordinary differential equations for the unknowns of the problem is derived using the weighted residual method. The system of equations is integrated in time and the response variability is computed. Application of the new method is made to a continuum described by the one-dimensional wave equation in which the stiffness properties exhibit a spatial random variation. Validation calculations show that the results from the method agree well with those obtained by direct numerical integration.
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Hashimoto, H. "Effects of Foil Bending Rigidity on Spacing Height Characteristics of Hydrostatic Porous Foil Bearings for Web Handling Processes." Journal of Tribology 119, no. 3 (July 1, 1997): 422–27. http://dx.doi.org/10.1115/1.2833510.
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In this paper, the effects of foil bending rigidity on the spacing height characteristics of hydrostatic foil bearings with a hollow porous shaft for web handling processes are analyzed by the finite width bearing theory. In the analysis, in order to save computation time and to improve the convergence of solutions, the two-dimensional modified Reynolds equation considering the added flow through porous shaft is reduced to an ordinary differential equation based on the weighted residual method. The reduced Reynolds equation and elastic equation for the foil are discretized by the finite difference method and solved numerically by the iterative technique. The numerical solutions for the pressure and film thickness distributions between foil and shaft are obtained for a wide range of bearing width-to-diameter ratio under various combinations of foil bending rigidity and foil wrap angle, and the spacing height characteristics of the foil bearings are examined theoretically.
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Lee, Vincent W., and Heather P. Brandow. "Weighted Residual Method for Diffraction of Plane P-Waves in a 2D Elastic Half-Space Revisited: On an Almost Circular Arbitrary-Shaped Canyon." Journal of Earthquakes 2015 (September 30, 2015): 1–21. http://dx.doi.org/10.1155/2015/543128.
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Scattering and diffraction of elastic in-plane P- and SV-waves by a surface topography such as an elastic canyon at the surface of a half-space is a classical problem which has been studied by earthquake engineers and strong-motion seismologists for over forty years. The case of out-of-plane SH-waves on the same elastic canyon that is semicircular in shape on the half-space surface is the first such problem that was solved by analytic closed-form solutions over forty years ago by Trifunac. The corresponding case of in-plane P- and SV-waves on the same circular canyon is a much more complicated problem because the in-plane P- and SV-scattered-waves have different wave speeds and together they must have zero normal and shear stresses at the half-space surface. It is not until recently in 2014 that analytic solution for such problem is found by the author in the work of Lee and Liu. This paper uses the technique of Lee and Liu of defining these stress-free scattered waves to solve the problem of the scattering and diffraction of these in-plane waves on an on an almost-circular surface canyon that is arbitrary in shape.
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Wu, Qisong, Teng Gao, Zhichao Lai, and Dianze Li. "Hybrid SVM-CNN Classification Technique for Human–Vehicle Targets in an Automotive LFMCW Radar." Sensors 20, no. 12 (June 21, 2020): 3504. http://dx.doi.org/10.3390/s20123504.
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Human–vehicle classification is an essential component to avoiding accidents in autonomous driving. The classification technique based on the automotive radar sensor has been paid more attention by related researchers, owing to its robustness to low-light conditions and severe weather. In the paper, we propose a hybrid support vector machine–convolutional neural network (SVM-CNN) approach to address the class-imbalance classification of vehicles and pedestrians with limited experimental radar data available. A two-stage scheme with the combination of feature-based SVM technique and deep learning-based CNN is employed. In the first stage, the modified SVM technique based on these distinct physical features is firstly used to recognize vehicles to effectively alleviate the imbalance ratio of vehicles to pedestrians in the data level. Then, the residual unclassified images will be used as inputs to the deep network for the subsequent classification, and we introduce a weighted false error function into deep network architectures to enhance the class-imbalance classification performance at the algorithm level. The proposed SVM-CNN approach takes full advantage of both the locations of underlying class in the entire Range-Doppler image and automatical local feature learning in the CNN with sliding filter bank to improve the classification performance. Experimental results demonstrate the superior performances of the proposed method with the F 1 score of 0.90 and area under the curve (AUC) of the receiver operating characteristic (ROC) of 0.99 over several state-of-the-art methods with limited experimental radar data available in a 77 GHz automotive radar.
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Ashrafi, H., M. R. Bahadori, H. Keshmiri, and M. Shariyat. "Boundary Integral Equation Analysis of an Inhomogeneous Medium Made of Functionally Graded Materials." Advanced Materials Research 685 (April 2013): 285–89. http://dx.doi.org/10.4028/www.scientific.net/amr.685.285.
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The present work develops direct graded boundary integral equation formulation for behavior investigation of the inhomogeneous media made of functionally graded materials. The isoparametric boundary elements, the elastostatic governing equations and a weighted residual technique are implemented with the material characteristics that vary continuously along a given dimension. The resulting algorithm is capable of solving the quasistatic problems for elastic functionally graded media with a variety of the boundary conditions and loadings. The inhomogeneous media is made of a ceramic–metal mixture, in which the material properties vary continuously according to a power law graded distribution in a given direction. Avoiding the use of internal elements in the graded boundary element formulation is one of the main objectives of this paper, which results only in numerical discretization of the boundaries of the considered media. Some examples with continuously inhomogeneous isotropic materials were provided under different boundary conditions to evaluate the proposed numerical formulation for the FGMs.
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Ashrafi, H., and M. Shariyat. "A Three-Dimensional Comparative Study of the Isoparametric Graded Boundary and Finite Element Methods for Nonhomogeneous FGM Plates with Eccentric Cutouts." International Journal of Computational Methods 14, no. 01 (January 11, 2017): 1750006. http://dx.doi.org/10.1142/s0219876217500062.
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In the present paper, a comparative study is presented between three-dimensional (3D) graded finite element and boundary integral equation methods capable of modeling quasi-static behaviors of heterogeneous plates with circular holes made of functionally graded materials (FGMs). The formulations are derived based on the 3D theory of elasticity. The volume fractions of the constituent materials of the FGM plates are assumed to vary through the thickness direction according to an exponential law. The graded finite element formulations are developed based on the Rayleigh–Ritz energy method. Somigliana stress identity is implemented numerically for 3D elasticity analysis of the heterogeneous isotropic plates, employing graded elements. Based on the resulting governing equations and the weighted residual technique, an effective boundary element formulation is implemented for the elastic FGM plates. To verify numerical results of the present work, several examples are provided. The comparison made for a homogenous plate shows an excellent concordance between the results.
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Şimon-Marinică, Adrian Bogdan, Nicolae-Ioan Vlasin, Florin Manea, and Gheorghe-Daniel Florea. "Finite element method to solve engineering problems using ansys." MATEC Web of Conferences 342 (2021): 01015. http://dx.doi.org/10.1051/matecconf/202134201015.
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The Finite Element Analysis method, is a powerful computational technique for approximate solutions to a variety of real – world engineering problems having complex domains subjected to general boundary conditions. The method itself has become an essential step in the design or modelling of a physical phenomenon in various engineering disciplines. A physical phenomenon usually occurs in a continuum of matter (solid, liquid or gas) involving several field variables. The field variables vary from point to point, thus possessing an infinite number of solutions in the domain. The basis of finite volume method relies on the decomposition of the domain into a finite number of subdomains (elements) for which the systematic approximate solution is constructed by applying the variational or weighted residual methods. In effect, finite volume method reduces the problem to that of a finite number of unknowns by dividing the domain into elements and by expressing the unknown field variable in term of the assumed approximating functions within each element.
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Schultz, Ward E., Gordon L. Moake, and Charles E. Jackson. "Field Examples of Ultrasonically-Enhanced Density, Neutron-Porosity, and Caliper Logs Obtained While Drilling." SPE Reservoir Evaluation & Engineering 1, no. 03 (June 1, 1998): 252–60. http://dx.doi.org/10.2118/36545-pa.
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Abstract Density, Pe, and neutron-porosity measurements made while drilling are extremely sensitive to the distance between the sensors and the borehole wall (standoff). To minimize these effects, an ultrasonic transducer is positioned collinearly with the nuclear sensors. Rapid pulsing of the transducer provides frequent measurements of the standoff. These measurements are used to average the nuclear data in a manner that emphasizes the smallest standoff data. This greatly improves the quality of the density, Pe, and neutron-porosity logs. Additionally, the standoff measurements are used to correct the neutron log for residual standoff effects. Measurements from the standoff transducer are also combined with those from two other ultrasonic transducers to obtain a high-resolution caliper log. Besides providing useful borehole information, the caliper readings are used to correct the nuclear measurements for hole-size effects. This new technology is illustrated with log examples from a variety of wells. One of the examples illustrates the effectiveness of an enhanced-vertical-resolution processing technique in identifying thin beds. Introduction Density and neutron porosity logging-while-drilling (LWD) measurements have been available for several years. However, accuracy often has been inferior to that obtained by wireline tools. The lower accuracy is primarily caused by rapid variations in sensor standoff from the borehole wall due to tool rotation. Although full-gauge density sleeves reduce standoff, they hinder drilling; and standoff still occurs when the borehole is enlarged. Refs. 1-3 describe statistical and orientational techniques for emphasizing nuclear data with small standoff. This paper illustrates another technique that directly measures standoff with an ultrasonic transducer. Weighted averages are used to emphasize nuclear data having the smallest standoff. This technique also utilizes a caliper measurement that is obtained from three ultrasonic transducers located at 1200 intervals around the tool. Field examples include a comparison of unweighted and weighted data processing, as well as a comparison of standoff-weighted results to wireline. Another example shows LWD logs obtained in a 9.875-in. borehole with a tool designed for 8.5-in. bits. Directionality of the nuclear readings also is illustrated. An example with heavy mud illustrates the value of two new density-correction curves. The final example shows logs with enhanced vertical resolution. Measurement Technique Fig. 1 shows two sizes of the Density-Neutron-Standoff-Caliper (DNSC) tool, The smaller size was designed for drilling with an 8.5-in. bit and the larger with a 12.25-in. bit. Both sizes measure density, photoelectric factor (Pe), neutron porosity, tool standoff, and borehole diameter (caliper). Data is processed and stored in nonvolatile tool memory. When a mud-pulser section is included, selected results are transmitted to the surface for real-time display. The DNSC tool also can be combined with resistivity and acoustic LWD-devices. Standoff Weighting. Nuclear data is acquired in 0.02-second intervals. During each interval, standoff of the nuclear sensors from the borehole wall is measured by an ultrasonic transducer using the pulse-echo method. Weighted averages are calculated from hundreds of nuclear data samples (Fig. 2), which typically correspond to 10 seconds. As shown in Fig. 3, the weight factors decrease exponentially with standoff, and range from 65,535 down to 1. This method yields nuclear counting rates characteristic of the smallest standoffs encountered during the averaging period.
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Kashani, Mir Tahmaseb, and Seyed M. Hashemi. "A Finite Element Formulation for Bending-Torsion Coupled Vibration Analysis of Delaminated Beams under Combined Axial Load and End Moment." Shock and Vibration 2018 (September 25, 2018): 1–12. http://dx.doi.org/10.1155/2018/1348970.
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Free vibration analysis of beams with single delamination undergoing bending-torsion coupling is made, using traditional finite element technique. The Galerkin weighted residual method is applied to convert the coupled differential equations of motion into to a discrete problem, where, in addition to the conventional mass and stiffness matrices, a delamination stiffness matrix, representing the extra stiffening effects at the delamination tips, is introduced. The linear eigenvalue problem resulting from the discretization along the length of the beam is solved to determine the frequencies and modes of free vibration. Both “free mode” and “constrained mode” delamination models are considered in formulation, and it is shown that the continuity (both kinematic and force) conditions at the beam span-wise locations corresponding to the extremities of the delaminated region, in particular, play a great role in “free mode” model formulation. Current trends in the literature are examined, and insight into different types of modeling techniques and constraint types are introduced. In addition, the data previously available in the literature and those obtained from a finite element-based commercial software are utilized to validate the presented modeling scheme and to verify the correctness of natural frequencies of the systems analyzed here. The paper ends with general discussions and conclusions on the presented theories and modeling approaches.
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Akiniwa, Yoshiaki, and Taku Sakaue. "X-Ray Measurement of Residual Stress Distribution in Sputtered Cu Thin Films." Materials Science Forum 706-709 (January 2012): 1649–54. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1649.
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Three kinds of copper thin films were fabricated by RF-magnetron sputtering. The target power was selected to be 10 and 150 W to change the properties of the films. Thin glass sheet was used as a substrate. For the target power of 150 W, the deposition time was selected to be 7 and 40 min. The thickness was 0.6 μm and 2.9 μm, and the grain size measured was 243 nm and 450 nm, respectively. The grain size of thicker film was larger than that of thinner one. On the other hand, for the target power of 10 W, the thickness and grain size were 2.4 μm and 54 nm, respectively. The grain size depends on the target power. The residual stress distribution in the films was measured by X-ray method. Several methods such as the grazing incidence X-ray diffraction method, the constant penetration depth method and the conventional sin2ψ method were adopted. The measured weighted average stress increased with increasing depth. After taking the maximum value at about 0.3 μm from the surface, the value decreased with increasing depth. The stress distribution near the surface in the films deposited at 150 W was almost identical irrespective of thickness. On the other hand, for the target power of 10 W, the stress distribution shifted to compression side. The reason could be explained by the effect of the thermal residual stress. The real stress distribution was estimated by using the optimization technique. The stress took the maximum value at 0.5 μm from the surface, and was compressive near the substrate. .
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Jamet, Bastien, Elena Zamagni, Cristina Nanni, Clément Bailly, Thomas Carlier, Cyrille Touzeau, Anne-Victoire Michaud, Philippe Moreau, Caroline Bodet-Milin, and Françoise Kraeber-Bodere. "Functional Imaging for Therapeutic Assessment and Minimal Residual Disease Detection in Multiple Myeloma." International Journal of Molecular Sciences 21, no. 15 (July 29, 2020): 5406. http://dx.doi.org/10.3390/ijms21155406.
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Serum markers and bone marrow examination are commonly used for monitoring therapy response in multiple myeloma (MM), but this fails to identify minimal residual disease (MRD), which frequently persists after therapy even in complete response patients, and extra-medullary disease escape. Positron emission tomography with computed tomography using 18F-deoxyglucose (FDG-PET/CT) is the reference imaging technique for therapeutic assessment and MRD detection in MM. To date, all large prospective cohort studies of transplant-eligible newly diagnosed MM patients have shown a strong and independent pejorative prognostic impact of not obtaining complete metabolic response by FDG-PET/CT after therapy, especially before maintenance. The FDG-PET/CT and MRD (evaluated by flow cytometry or next-generation sequencing at 10−5 and 10−6 levels, respectively) results are complementary for MRD detection outside and inside the bone marrow. For patients with at least a complete response, to reach double negativity (FDG-PET/CT and MRD) is a predictive surrogate for patient outcome. Homogenization of FDG-PET/CT interpretation after therapy, especially clarification of complete metabolic response definition, is currently underway. FDG-PET/CT does not allow MRD to be evaluated when it is negative at initial workup of symptomatic MM. New PET tracers such as CXCR4 ligands have shown high diagnostic value and could replace FDG in this setting. New sensitive functional magnetic resonance imaging (MRI) techniques such as diffusion-weighted MRI appear to be complementary to FDG-PET/CT for imaging MRD detection. The goal of this review is to examine the feasibility of functional imaging, especially FDG-PET/CT, for therapeutic assessment and MRD detection in MM.
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Hillengass, Jens, Sofia Ayyaz, Kerstin Kilk, Marc-André Weber, Thomas Hielscher, Gerlinde Egerer, Hans-Ulrich Kauczor, et al. "Correlation of Serological and MRI-Based Treatment Response to Systemic Chemotherapy In 100 Patients with Multiple Myeloma." Blood 116, no. 21 (November 19, 2010): 2977. http://dx.doi.org/10.1182/blood.v116.21.2977.2977.
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Abstract Abstract 2977 Findings of magnetic resonance imaging (MRI) are increasingly being applied to assess disease activity and tumor mass in patients with multiple myeloma (MM), since it has been shown that this technique is the most sensitive to detect bone marrow infiltration in monoclonal plasma cell disease. However, the correlation of serological response to systemic treatment with alterations in MRI has not been investigated. We therefore analyzed changes in diffuse infiltration and in number and size of focal lesions (FL) in whole body-MRI (wb-MRI) in 100 patients after systemic therapy in order to learn whether the degree of remission would differ for morphological, MRI-based and serological criteria. Median age of patients was 59 years (range 28–74 years). Autologous stem cell transplantation was performed in 93, and conventional chemotherapy including novel agents in 7 patients. MRI protocol included T1 and T2 weighted sequences in coronal orientation of the whole body (excluding T2 of the lower legs to maintain acceptable examination time) as well as T1 and T2 weighted sequences of the whole spine in sagittal orientation. MRI-remission was assessed by two experienced radiologists in consensus for focal and diffuse infiltration separately and in combination. Definitions of MRI-response were determined with focal complete remission (fCR) indicating total disappearance of focal lesions, focal partial remission (fPR) being defined as reduction of the number of FL of 50% or more, focal stable disease (fSD) as unchanged number of FL and focal progressive disease (fPD) as any increase in number of focal lesions after therapy. For diffuse infiltration dCR was defined as total disappearance of diffuse infiltration. If diffuse infiltration was reduced after therapy but was still detectable in MRI it was defined as dPR. Constancy of diffuse infiltration was defined as dSD and increase in diffuse infiltration as dPD. Serological remission was determined summarizing near CR and CR as seroCR and VGPR and PR as seroPR to simplify statistical analysis. A weak but significant correlation of MRI-derived with serological remission was found for focal response with a correlation coefficient (CC) of 0.26 and a p-value of 0.003 and for diffuse response with a CC of 0.27 and a p-value of 0.003 respectively. In diffuse infiltration the remission stage would be more favorable if determined with MRI than with serological criteria, whereas in focal or multifocal disease patterns serological criteria would indicate a better response than would MRI changes. However, these differences were not significant. In contrary to a recent publication of the Arkansas group no better progression free survival (PFS) was seen for patients with more favorable MRI-response. Comparison of the 8 out of 40 patients in serological CR or near CR who also achieved a MRI-CR showed no significantly better PFS compared to patients in whom serological CR was achieved but residual infiltration was detected in MRI. We conclude that serological response to chemotherapy goes along with a similar trend of changes in MRI after systemic chemotherapy. The fact that the correlation in our study was rather weak and no survival benefit was found for MRI-CR, may be at least in part due to the inability of conventional MRI to differentiate between vital lesions and residual changes after treatment as well as between plasma cell infiltration and increased cellularity because of bone marrow regeneration after chemotherapy. Furthermore, residual lesions may consist of hyposecretory myeloma cells which can eventually lead to relapse of disease. Functional imaging methods such as positron emission tomography and new MRI techniques e.g. dynamic contrast-enhanced MRI and diffusion weighted imaging may contribute to solve these questions. If treatment of residual changes in MRI for example by local irradiation leads to a better outcome by deepening remission is another issue arising from our results. Disclosures: No relevant conflicts of interest to declare.
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Ahuja, Jyoti, and Urvashi Gupta. "Rayleigh-Bénard Convection for Nanofluids for More Realistic Boundary Conditions (Rigid-Free and Rigid-Rigid) Using Darcy Model." International Journal of Mathematical, Engineering and Management Sciences 4, no. 1 (February 1, 2019): 139–56. http://dx.doi.org/10.33889/ijmems.2019.4.1-013.
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In this article, Rayleigh-Bénard convection for nanofluids for more realistic boundary conditions (rigid-free and rigid-rigid) under the influence of the magnetic field is investigated. Presence of nanoparticles in base fluid has introduced one additional conservation equation of nanoparticles that incorporates the effect of thermophoretic forces and Brownian motion and the inclusion of magnetic field has introduced Lorentz’s force term in the momentum equation along with Maxwell’s equations. The solution of the Eigen value problem is found in terms of Rayleigh number by implementing the technique of normal modes and weighted residual Galerkin approximation. It is found that the stationary as well as oscillatory motions come into existence and heat transfer takes place through oscillatory motions. The critical Rayleigh number for alumina water nanofluid has an appreciable increase in its value with the rise in Chandrasekhar number and it increases moderately as we move from rigid-free to both rigid boundaries. The effect of different nanofluid parameters on the onset of thermal convection for two types of boundaries is investigated.
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Samanta, A., B. Goyeau, and C. Ruyer-Quil. "A falling film on a porous medium." Journal of Fluid Mechanics 716 (January 25, 2013): 414–44. http://dx.doi.org/10.1017/jfm.2012.550.
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AbstractA gravity-driven falling film on a saturated porous inclined plane is studied via a continuum approach, where the liquid and porous layers are considered as a single composite layer. Using a weighted residual technique, a two-equation model is derived in terms of the local flow rate $q(x, t)$ and the entire layer thickness $H(x, t)$. Its linear stability analysis has been satisfactorily compared to the results of the Orr–Sommerfeld problem. The principal effect of the porous substrate on the film flow is to displace the liquid–porous interface to an effective liquid–solid interface located at the lower boundary of the upper momentum boundary layer in the porous medium. The stability and dynamics of the film is thus only weakly affected by the presence of a permeable substrate. In both the linear and the nonlinear regimes, the spatial response of a falling film on a porous medium is not very different from that observed on an impermeable inclined wall. However, the wavy motion of the film triggers a significant exchange of mass at the liquid–porous interface.
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Spilker, Robert L., Jun-Kyo Suh, and Van C. Mow. "Effects of Friction on the Unconfined Compressive Response of Articular Cartilage: A Finite Element Analysis." Journal of Biomechanical Engineering 112, no. 2 (May 1, 1990): 138–46. http://dx.doi.org/10.1115/1.2891164.
Full textAbstract:
A finite element analysis is used to study a previously unresolved issue of the effects of platen-specimen friction on the response of the unconfined compression test; effects of platen permeability are also determined. The finite element formulation is based on the linear KLM biphasic model for articular cartilage and other hydrated soft tissues. A Galerkin weighted residual method is applied to both the solid phase and the fluid phase, and the continuity equation for the intrinsically incompressible binary mixture is introduced via a penalty method. The solid phase displacements and fluid phase velocities are interpolated for each element in terms of unknown nodal values, producing a system of first order differential equations which are solved using a standard numerical finite difference technique. An axisymmetric element of quadrilateral cross-section is developed and applied to the mechanical test problem of a cylindrical specimen of soft tissue in unconfined compression. These studies show that interfacial friction plays a major role in the unconfined compression response of articular cartilage specimens with small thickness to diameter ratios.
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Sunjka, Dragana, and Sanja Lazic. "Water sampling techniques for continous monitoring of pesticides in water." Pesticidi i fitomedicina 32, no. 2 (2017): 85–93. http://dx.doi.org/10.2298/pif1702085s.
Full textAbstract:
Good ecological and chemical status of water represents the most important aim of the Water Framework Directive 2000/60/EC, which implies respect of water quality standards at the level of entire river basin (2008/105/EC and 2013/39/EC). This especially refers to the control of pesticide residues in surface waters. In order to achieve the set goals, a continuous monitoring program that should provide a comprehensive and interrelated overview of water status should be implemented. However, it demands the use of appropriate analysis techniques. Until now, the procedure for sampling and quantification of residual pesticide quantities in aquatic environment was based on the use of traditional sampling techniques that imply periodical collecting of individual samples. However, this type of sampling provides only a snapshot of the situation in regard to the presence of pollutants in water. As an alternative, the technique of passive sampling of pollutants in water, including pesticides has been introduced. Different samplers are available for pesticide sampling in surface water, depending on compounds. The technique itself is based on keeping a device in water over a longer period of time which varies from several days to several weeks, depending on the kind of compound. In this manner, the average concentrations of pollutants dissolved in water during a time period (time-weighted average concentrations, TWA) are obtained, which enables monitoring of trends in areal and seasonal variations. The use of these techniques also leads to an increase in sensitivity of analytical methods, considering that pre-concentration of analytes takes place within the sorption medium. However, the use of these techniques for determination of pesticide concentrations in real water environments requires calibration studies for the estimation of sampling rates (Rs). Rs is a volume of water per time, calculated as the product of overall mass transfer coefficient and area of the receiving phase exposed to the external environment, and it is substance specific.
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ElShayeb, Mohamed, Abdul Rashid Ab Malik, Fazril Ideris, Zolman Hari, Norhaida Ab Razak, Jacqueline Eng Ling Siang, and Zulfika Anuar. "Utilization of Numerical Techniques to Predict the Thermal Behavior of Wood Column Subjected to Fire. Part A: Using Finite Element Methods to Develop Mathematical Model for Wood Column." Key Engineering Materials 306-308 (March 2006): 577–82. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.577.
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The mathematical model to predict the temperature history for wood column is needed in order to determine its fire resistance when exposed to fire. In this paper, an intelligent methodology called Finite Element Method (FEM) of performing analysis for the square and circular wood columns by virtually or artificially developing a temperature history mathematical model. Numerical simulation model has been developed for the wood column by using two-dimensional mathematical model. The two-dimensional mathematical model was developed by using Galerkin’s Weighted Residual technique. This model focuses on the regional material of the wood column for describing its thermal behavior. When the temperature history in a column and relevant materials properties are known, the strength of the column can be calculated at any time during fire. Therefore, the development of the temperature history mathematical model is a must before any further study to be carried out for the wood columns. The flow of convection will result in minimal increase in the rate of heat energy reaching the column core. The analysis shows that the temperature of the column increases with respect to the duration of exposure to fire.