A regenerative approach towards mucosal fenestration closure.
Gandi, Padma; Anumala, Naveen; Reddy, Amarender; Chandra, Rampalli Viswa
2013-06-06
Mucosal fenestration is an opening or an interstice through the oral mucosa. A lesion which occurs with greater frequency than generally realised, its occurrence is attributed to a myriad of causes. Mucogingival procedures including connective tissue grafts, free gingival grafts and lateral pedicle grafts are generally considered to be the treatment of choice in the closure of a mucosal fenestration. More often, these procedures are performed in conjunction with other procedures such as periradicular surgery and with bone grafts. However, the concomitant use of gingival grafts and bone grafts in mucosal fenestrations secondary to infections in sites exhibiting severe bone loss is highly debatable. In this article, we report two cases of mucosal fenestrations secondary to trauma and their management by regenerative periodontal surgery with the placement of guided tissue regeneration membrane and bone graft. The final outcome was a complete closure of the fenestration in both the cases.
Ochrymiuk, Tomasz
2016-06-01
Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensional discrete-hole film cooling arrangement. The effects of basic geometrical characteristics of the holes, i.e. diameter D, length L and pitch S/D were studied. Different turbulent heat transfer models based on constant and variable turbulent Prandtl number approaches were considered. The variability of the turbulent Prandtl number Pr t in the energy equation was assumed using an algebraic relation proposed by Kays and Crawford, or employing the Abe, Kondoh and Nagano eddy heat diffusivity closure with two differential transport equations for the temperature variance k θ and its destruction rate ɛ θ . The obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology. All implemented models for turbulent heat transfer performed sufficiently well for the considered case. It was confirmed, however, that the two- equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models.
Numerical Modeling of ROM Panel Closures at WIPP
Herrick, C. G.
2016-12-01
The Waste Isolation Pilot Plant (WIPP) in New Mexico is a U.S. DOE geologic repository for permanent disposal of defense-related transuranic (TRU) waste. Waste is emplaced in panels excavated in a bedded salt formation (Salado Fm.) at 655 m bgs. In 2014 the U.S. EPA approved the new Run-of-Mine Panel Closure System (ROMPCS) for WIPP. The closure system consists of 100 feet of run-of-mine (ROM) salt sandwiched between two barriers. Nuclear Waste Partnership LLC (the M&O contractor for WIPP) initiated construction of the ROMPCS. The design calls for three horizontal ROM salt layers at different compaction levels ranging from 70-85% intact salt density. Due to panel drift size constraints and equipment availability the design was modified. Three prototype panel closures were constructed: two having two layers of compacted ROM salt (one closure had 1% water added) and a third consisting of simply ROM salt with no layering or added water. Sampling of the prototype ROMPCS layers was conducted to determine the following ROM salt parameters: thickness, moisture content, emplaced density, and grain-size distribution. Previous modeling efforts were performed without knowledge of these ROM salt parameters. This modeling effort incorporates them. The program-accepted multimechanism deformation model is used to model intact salt room creep closure. An advanced crushed salt model is used to model the ROM salt. Comparison of the two models' results with the prototypes' behavior is given. Our goal is to develop a realistic, reliable model that can be used for ROM salt applications at WIPP. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This research is funded by WIPP programs administered by the Office of Environmental Management (EM) of the U.S Department of Energy SAND
Hybrid closure of atrial septal defect: A modified approach
Directory of Open Access Journals (Sweden)
Kshitij Sheth
2015-01-01
Full Text Available A 3.5-year-old girl underwent transcatheter closure of patent ductus arteriosus in early infancy during which time her secundum atrial septal defect (ASD was left alone. When she came for elective closure of ASD, she was found to have bilaterally blocked femoral veins. The defect was successfully closed with an Amplatzer septal occluder (ASO; St. Jude Medical, Plymouth, MN, USA using a hybrid approach via a sub-mammary mini-thoracotomy incision without using cardiopulmonary bypass. At the end of 1-year follow-up, the child is asymptomatic with device in a stable position without any residual shunt.
Stigter, C.J.
1988-01-01
At least an easier task than I have carried out the previous hour when we discussed the preliminary conclusions and recommendations has, as a compensation I guess, been given to me as well. To say a few words as a closure of this symposium. The beginning of such a series of closing statements is mos
Modern approaches in primary exstrophy closure.
Purves, J Todd
2011-05-01
Until the 1970s, bladder exstrophy was a frequently fatal birth defect that, at the very least, conferred a shortened life span with devastating consequences for afflicted patients. Beginning with the modern era of surgical management, survival has become routine, and now the focus is on optimizing a near-normal return to function and cosmesis while limiting the frequency and morbidity of reconstructive procedures. Here we discuss the most frequently used strategies, their principles, and most recent outcomes for the management of exstrophy worldwide. Advantages and disadvantages of each approach are discussed in broad terms with the understanding that one universally accepted technique for managing bladder exstrophy has yet to be developed.
[Percutaneous closure of patent foramen ovale: a wise approach].
Gaspardone, Achille; Iani, Cesare; Papa, Marco
2008-09-01
Patent foramen ovale (PFO) is a remnant of the normal fetal circulation consisting in a communication between septum primum and septum secundum. Postnatally, the two septa fuse completing separation of the atria. In 25% of normal individuals incomplete fusion leads to the persistence of the flap valve leaving a PFO. In the recent years a variety of clinical conditions has been associated with or attributed to PFO. In particular, PFO has been implicated in the pathogenesis of cryptogenic stroke/transient ischemic attack due to paradoxical embolism and to the pathogenesis of migraine headache. PFO has also been associated with decompression illness in divers and to minor diseases such as platypnea-orthodeoxia syndrome and high-altitude pulmonary edema. Meta-analyses and observational studies indicate that the prevalence of PFO is approximately 3-fold higher in patients with cryptogenic stroke and migraineurs compared controls. Conversely, observational evidences indicate a 2-3-fold increased prevalence of migraine and cerebrovascular events in PFO carriers. Observational studies and meta-analyses suggest that, compared to optimal medical treatment, transcatheter closure of PFO might significantly reduce the recurrence of ischemic cerebrovascular events in patients with previous stroke/transient ischemic attack; however, albeit mechanical closure of PFO is an attractive alternative to medical therapy, randomized trials supporting the efficacy of this approach have not been completed. Furthermore, about 80% of patients undergoing PFO closure for nonmigraine indications reported improvement in their migraine symptoms. However, these studies were predominantly retrospective, nonrandomized and conducted in highly selected populations. The recently published MIST trial, the only randomized study available, failed to demonstrate a significant favorable effect of PFO closure for migraine resolution and/or migraine improvement. At present, as insufficient evidence exists to
Natural processes and system evolution during mine closure: numerical simulation and visualization
Energy Technology Data Exchange (ETDEWEB)
Heller, M.; Poppei, J.; Schlickenrieder, L. [Colenco Power Engineering LTD, Baden (Switzerland); Forster, B. [Gsf-Forschungszentrum Fur Umwelt Und Gesundheit - Schachtanlage Asse, Remlingen (Germany)
2005-07-01
We have developed a numerical tool which is particularly suitable for the simulation of water and gas flow, mechanical and chemical phenomena as well as processes related to the transport of contaminants and radionuclides in underground structures over long periods of time. KAFKA was applied for investigations concerning the flooding and closure of the Asse research mine, a former salt mine. Given the complexity of the mine structure and the multitude of interconnected processes considered, the specifically designed visualization tool Assemblage is indispensable for the interpretation of intermittent and final simulation results. (authors)
Closure of the Mongol-Okhotsk Ocean: Insights from seismic tomography and numerical modelling
Fritzell, E. H.; Bull, A. L.; Shephard, G. E.
2016-07-01
The existence of the Palaeozoic and Mesozoic Mongol-Okhotsk Ocean is evident from the Mongol-Okhotsk suture, which stretches from central Mongolia to the Sea of Okhotsk. A lack of sufficient palaeomagnetic data and an otherwise diffuse suture with an abrupt termination to the west has led to difficulties in reconstructing the history, geometry and closure of this ocean. Both the timing and style of the ocean's closure are unclear and have led to several alternative reconstructions. Closure timing ranges between the Late Jurassic (∼155 Ma) and beginning of the Early Cretaceous (∼120 Ma), and the proposed kinematics include contemporaneous subduction along two opposite margins, subduction along only one margin or with a component of left-lateral shear. In the present study, numerical models of mantle convection are coupled with global plate reconstructions to investigate ambiguities regarding the closure of the Mongol-Okhotsk Ocean. In order to decipher the tectonic history of this enigmatic region, two end-member scenarios of subduction location - either along the present-day northern or the southern margins of the Mongol-Okhotsk Ocean - are imposed as kinematic surface boundary conditions for the past 230 Myrs. Through a comparison to seismic tomography, the results indicate a preferred subduction history along the Siberian margin (relative northern margin) of the Mongol-Okhotsk Ocean. At present-day, the slab remnant is predicted to be located farther west than previously proposed. Furthermore, we find that the subducting slabs in this region generate a hot, dense pile at the same location and with a similar shape as the Perm Anomaly.
Impact of the closure of Indonesian seaway on climate: A numerical modeling study
Institute of Scientific and Technical Information of China (English)
YU Yongqiang; ZHOU Zuyi; ZHANG Xuehong
2003-01-01
Using a global OGCM and its relevant coupled ocean-atmosphere GCM with the contemporary, 6 MaBP and 14 MaBP oceanic topography, respectively, a series of numerical experiments are implemented in order to investigate the effect of the north shift of Australian continent on the tropical oceanic circulation, especially the formation of the western Pacific warm pool. The numerical experiments of the individual OGCM forced by the modern atmospheric circulation indicate that the closure of Indonesian passage results in warming in the tropical Pacific Ocean and cooling in the tropical Indian Ocean; furthermore, it also results in change in source of the Indonesian Through Flow (ITF) water, e.g. ITF mainly originates from the south Pacific at 14 MaBP, but it mainly originates from the north Pacific now. The coupled model shows similar results as the individual OGCM qualitatively.
2005 Closure Assessments for WMA-C Tank Farms: Numerical Simulations
Energy Technology Data Exchange (ETDEWEB)
Freedman, Vicky L; Zhang, Z F; Waichler, Scott R; Wurstner, Signe K
2005-09-20
In support of CH2M HILL Hanford Group, Inc.'s (CHG) closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, numerical simulations of flow and solute transport were executed to investigate different potential contaminant source scenarios that may pose long-term risks to groundwater from the closure of the C Tank Farm. These simulations were based on the initial assessment effort (Zhang et al., 2003), but implemented a revised approach that examined a range of key parameters and multiple base cases. Four different potential source types were identified to represent the four base cases, and included past leaks, diffusion releases from residual wastes, leaks during retrieval, and ancillary equipment sources. Using a two-dimensional cross section through the C Tank Farm (Tanks C-103–C-112) and a unit release from Tank C-112, two solutes (uranium-238 (U-238) and technetium-99 (Tc 99)) were transported through the problem domain. To evaluate the effect of sorption on contaminant transport, seven different sorption coefficients were simulated for U 238. Apart from differences in source releases, all four base cases utilized the same median parameter values to describe flow and contaminant transport at the WMA C. Forty-six additional cases were also run that examined individual transport responses to the upper and lower limits of the median parameter values implemented in the base case systems. For the conservative solute, Tc-99, results amongst the base cases showed that the simulations investigating past leaks demonstrated the highest peak concentrations and the earliest arrival times (48 years) due to the proximity of the plume to the water table and the high recharge rate before surface barriers were installed. Simulations investigating leaks during retrieval predicted peak concentrations ~60 times smaller than the past leak cases, and corresponding arrival times that occurred ~70 years later. The diffusion release base case
Surgical closure of postlaryngectomy pharyngocutaneous fistula: a defect based approach.
Magdy, Emad A
2008-01-01
Surgical repair of postlaryngectomy pharyngocutaneous fistula (PCF) can be challenging. Although several studies describe separate reconstruction methods, only few address the variability in defect characteristics and hence flap selection. The current clinical study presents a retrospective review of 19 patients who underwent surgical repair of persistent PCFs, over a 4-year period in a tertiary referral institute by a single primary surgeon. All but one patient were men with a mean age of 61 +/- 10 years. Nine patients had previous unsuccessful attempts for surgical closure. Previous neck irradiation was the most common comorbid condition encountered (52.6%), followed by low hemoglobin level (47.4%), hepatic disease (36.8%) and diabetes mellitus (31.6%). According to defect characteristics, six patients received a local cervical skin procedure, ten patients had reconstructions using the pectoralis major musculocutaneous flap and three patients required a radial forearm free flap repair. All PCFs were eventually successfully closed with no major complications. Patients were followed-up for an average of 19.7 months (range, 5-38 months). Acceptable oral swallowing results were achieved in all but one patient. In conclusion, successful results are achievable in difficult persistent PCF cases with a defect based reconstruction approach kept in mind.
Transhepatic approach to closure of patent foramen ovale: report of 2 cases in adults.
Hussain, Jamal; Strumpf, Robert; Ghandforoush, Aslan; Jamal, Ayman; Diethrich, Edward
2010-01-01
Patent foramen ovale is increasingly diagnosed in patients who are undergoing clinical study for cryptogenic stroke or migraine. In addition, patent foramen ovale is often suspected as a cause of paradoxical embolism in patients who present with arterial thromboembolism. The femoral venous approach to closure has been the mainstay. When the femoral approach is not feasible, septal occluder devices have been deployed via a transjugular approach.Herein, we describe 2 cases of patent foramen ovale in which the transhepatic approach was used for closure. To our knowledge, this is the 1st report of a transhepatic approach to patent foramen ovale closure in an adult patient. Moreover, no previous case of patent foramen ovale closure has been reported in a patient with interrupted inferior vena cava.
Transcatheter closure of patent foramen ovale using the internal jugular venous approach.
Węglarz, Przemysław; Konarska-Kuszewska, Ewa; Zębik, Tadeusz; Kuszewski, Piotr; Drzewiecka-Gerber, Agnieszka; Motyka, Marek; Ludyga, Tomasz; Bajor, Grzegorz
2014-01-01
Transcatheter closure of patent foramen ovale is routinely performed using the transfemoral approach, which is safe and technically easy. Our case represents the rare situation where the procedure needs to be performed using the right internal jugular venous approach. According to our best knowledge this is the first report of a patent foramen ovale closure procedure with access through the internal jugular with necessity to advance the guide wire and transseptal sheath into the left ventricle. Developing alternative techniques of transcatheter patent foramen ovale closure seems to be especially important in rare cases where transfemoral access is unavailable.
Zhang, D.; Deen, N.G.; Kuipers, J.A.M.
2006-01-01
Numerical simulations of the bubbly flow in two square cross-sectioned bubble columns were conducted with the commercial CFD package CFX-4.4. The effect of the model constant used in the sub-grid scale (SGS) model, CS, as well as the interfacial closures for the drag, lift and virtual mass forces
Numerical Modeling of the Surface Fatigue Crack Propagation Including the Closure Effect
Guchinsky, Ruslan; Petinov, Sergei
2016-01-01
Presently modeling of surface fatigue crack growth for residual life assessment of structural elements is almost entirely based on application of the Linear Elastic Fracture Mechanics (LEFM). Generally, it is assumed that the crack front does not essentially change its shape, although it is not always confirmed by experiment. Furthermore, LEFM approach cannot be applied when the stress singularity vanishes due to material plasticity, one of the leading factors associated with the material degradation and fracture. Also, evaluation of stress intensity factors meets difficulties associated with changes in the stress state along the crack front circumference. An approach proposed for simulation the evolution of surface cracks based on application of the Strain-life criterion for fatigue failure and of the finite element modeling of damage accumulation. It takes into account the crack closure effect, the nonlinear behavior of damage accumulation and material compliance increasing due to the damage advance. The damage accumulation technique was applied to model the semi-elliptical crack growth from the initial defect in the steel compact specimen. The results of simulation are in good agreement with the published experimental data.
Energy Technology Data Exchange (ETDEWEB)
Andrea Prosperetti
2006-03-24
The report briefly describes the activities carried out in the course of the project. A first line of research was the development of systematic closure relations for averaged equations for disperse multiphase flow. A second line was the development of efficient numerical methods for the simulation of Navier-Stokes flows with many suspended particles. The report also lists the 21 journal articles in which this work is more fully decsribed.
Outcomes After Paravalvular Leak Closure: Transcatheter Versus Surgical Approaches.
Wells, John A; Condado, Jose F; Kamioka, Norihiko; Dong, Andy; Ritter, Andrew; Lerakis, Stamatios; Clements, Stephen; Stewart, James; Leshnower, Bradley; Guyton, Robert; Forcillo, Jessica; Patel, Ateet; Thourani, Vinod H; Block, Peter C; Babaliaros, Vasilis
2017-03-13
The aim of this study was to compare outcomes of transcatheter intervention (TI) versus surgical intervention (SI) for paravalvular leak (PVL). Data comparing the treatment of PVL with TI and SI are limited. A retrospective cohort study was conducted comparing baseline characteristics, procedural details, and 1-year survival in consecutive patients who underwent TI or SI for moderate or greater PVL from 2007 to 2016. The primary outcome was a composite of death, reintervention for PVL, or readmission for congestive heart failure-related symptoms at 1 year. Of 114 patients, 56 underwent TI and 58 underwent SI. PVL locations were mitral, aortic, and pulmonary in 69 (60.5%), 39 (34.2%), and 6 (5.3%) patients, respectively. At baseline, TI patients were older (age 71 vs. 62 years; p = 0.010) and had fewer cases of active endocarditis (0.0% vs. 25.9%, p < 0.001) than SI patients. The TI group had a shorter post-operative stay (4 vs. 8 days; p < 0.001), a shorter intensive care unit stay (0 vs. 3 days; p < 0.001), and fewer readmissions at 30 days (8.9% vs. 25.9%; p = 0.017). There were no differences in the primary endpoint (TI 33.9% vs. SI 39.7%; p = 0.526) or 1-year survival (TI 83.9% vs. SI 75.9%; p = 0.283) between groups. In this study, TI for PVL closure had comparable 1-year clinical outcomes with SI, even after adjusting for differences in baseline characteristics, with less in-hospital morbidity and 30-day rehospitalization. Although further study is needed, these findings support the increased implementation of TI for PVL closure at experienced institutions. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.
Multilevel Monte Carlo Approaches for Numerical Homogenization
Efendiev, Yalchin R.
2015-10-01
In this article, we study the application of multilevel Monte Carlo (MLMC) approaches to numerical random homogenization. Our objective is to compute the expectation of some functionals of the homogenized coefficients, or of the homogenized solutions. This is accomplished within MLMC by considering different sizes of representative volumes (RVEs). Many inexpensive computations with the smallest RVE size are combined with fewer expensive computations performed on larger RVEs. Likewise, when it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison to a standard Monte Carlo method. Numerical results are presented for both one-dimensional and two-dimensional test-cases that illustrate the efficiency of the approach.
Hato, Tai; Suzuki, Shigeki; Harada, Masahiko; Horio, Hirotoshi
2014-03-01
Although life-threatening situations can be avoided using an open window thoracostomy (OWT), the closure is often difficult. We investigated the predictors of a successful closure of an OWT at the time of OWT creation. Thirty-five consecutive patients who underwent an OWT at our institute between January 1991 and December 2010 were reviewed. We directly compared the patients with and without a successful OWT closure. A logistic regression analysis was employed to determine the predictive factors of a successful closure. OWT closure was only achieved in 12 patients. The closure of the OWT and absence of diabetes mellitus significantly influenced the survival of the OWT patients. The OWT in patients with preceding lung resection was difficult to close, especially if the underlying disease was lung cancer. The existence of a bronchopleural fistula (BPF) was not related to successful closure. Among the post-lung resection patients, the nutritional status tended to affect the success of the closure. Successful closure is difficult to predict at the time of the creation of an OWT. A comprehensive approach, including nutritional support and the precise timing of intervention is critical to promote a successful closure.
Numerical approach of the quantum circuit theory
Silva, J. J. B.; Duarte-Filho, G. C.; Almeida, F. A. G.
2017-03-01
In this paper we develop a numerical method based on the quantum circuit theory to approach the coherent electronic transport in a network of quantum dots connected with arbitrary topology. The algorithm was employed in a circuit formed by quantum dots connected each other in a shape of a linear chain (associations in series), and of a ring (associations in series, and in parallel). For both systems we compute two current observables: conductance and shot noise power. We find an excellent agreement between our numerical results and the ones found in the literature. Moreover, we analyze the algorithm efficiency for a chain of quantum dots, where the mean processing time exhibits a linear dependence with the number of quantum dots in the array.
Numerical approach of the quantum circuit theory
Energy Technology Data Exchange (ETDEWEB)
Silva, J.J.B., E-mail: jaedsonfisica@hotmail.com; Duarte-Filho, G.C.; Almeida, F.A.G.
2017-03-15
In this paper we develop a numerical method based on the quantum circuit theory to approach the coherent electronic transport in a network of quantum dots connected with arbitrary topology. The algorithm was employed in a circuit formed by quantum dots connected each other in a shape of a linear chain (associations in series), and of a ring (associations in series, and in parallel). For both systems we compute two current observables: conductance and shot noise power. We find an excellent agreement between our numerical results and the ones found in the literature. Moreover, we analyze the algorithm efficiency for a chain of quantum dots, where the mean processing time exhibits a linear dependence with the number of quantum dots in the array.
Laser-assisted multidisciplinary approach for closure and prevention of relapse of midline diastema
Directory of Open Access Journals (Sweden)
Amol Kamble
2017-01-01
Full Text Available Midline diastema, which occurs as spacing between the upper central incisors, is a common occurrence seen in the pediatric population. In the ugly duckling stage of development; no treatment is generally advocated as the diastema is a transient one. When diastemas occur due to other pathologies, they pose several problems in relation to esthetics and speech in a growing child. With the advent of time, patient's demand for esthetics has greatly increased. Along with this, a less time-consuming treatment option is a favorite. Proper diagnosis of the diastema, unfolding its etiology, helps in devising an adequate treatment plan. This eventually will lead to stability of the final result. The present case report presents a different and unique approach for the esthetic closure of midline diastema following frenectomy procedure. The approach proves to be a quick and simple option for closure of midline diastemas in cases with concomitant incisal edge irregularities.
Numerical approach for unstructured quantum key distribution
Coles, Patrick J.; Metodiev, Eric M.; Lütkenhaus, Norbert
2016-05-01
Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study `unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown.
A direct-numerical-simulation-based second-moment closure for turbulent magnetohydrodynamic flows
Kenjereš, S.; Hanjalić, K.; Bal, D.
2004-01-01
A magnetic field, imposed on turbulent flow of an electrically conductive fluid, is known to cause preferential damping of the velocity and its fluctuations in the direction of Lorentz force, thus leading to an increase in stress anisotropy. Based on direct numerical simulations (DNS), we have devel
Numerical modelling approach for mine backfill
Indian Academy of Sciences (India)
MUHAMMAD ZAKA EMAD
2017-09-01
Numerical modelling is broadly used for assessing complex scenarios in underground mines, including mining sequence and blast-induced vibrations from production blasting. Sublevel stoping mining methods with delayed backfill are extensively used to exploit steeply dipping ore bodies by Canadian hard-rockmetal mines. Mine backfill is an important constituent of mining process. Numerical modelling of mine backfill material needs special attention as the numerical model must behave realistically and in accordance with the site conditions. This paper discusses a numerical modelling strategy for modelling mine backfill material. Themodelling strategy is studied using a case study mine from Canadian mining industry. In the end, results of numerical model parametric study are shown and discussed.
Mazzi, Giacomo; Samaey, Giovanni
2012-01-01
In this paper, we present a study on how to develop an efficient multiscale simulation strategy for the dynamics of chemically active systems on low-dimensional supports. Such reactions are encountered in a wide variety of situations, ranging from heterogeneous catalysis to electrochemical or (membrane) biological processes, to cite a few. We analyzed in this context different techniques within the framework of an important multiscale approach known as the equation free method (EFM), which "bridges the multiscale gap" by building microscopic configurations using macroscopic-level information only. We hereby considered two simple reactive processes on a one-dimensional lattice, the simplicity of which allowed for an in-depth understanding of the parameters controlling the efficiency of this approach. We demonstrate in particular that it is not enough to base the EFM on the time evolution of the average concentrations of particles on the lattice, but that the time evolution of clusters of particles has to be in...
Numerical approach to multi-loop integrals
Kato, K; Hamaguchi, N; Ishikawa, T; Koike, T; Kurihara, Y; Shimizu, Y; Yuasa, F
2012-01-01
For the calculation of multi-loop Feynman integrals, a novel numerical method, the Direct Computation Method (DCM) is developed. It is a combination of a numerical integration and a series extrapolation. In principle, DCM can handle diagrams of arbitrary internal masses and external momenta, and can calculate integrals with general numerator function. As an example of the performance of DCM, a numerical computation of two-loop box diagrams is presented. Further discussion is given on the choice of control parameters in DCM. This method will be an indispensable tool for the higher order radiative correction when it is tested for a wider class of physical parameters and the separation of divergence is done automatically.
Brown, Helen; Mahler, Hanns-Christian; Mellman, James; Nieto, Alejandra; Wagner, Daniel; Schaar, Matthias; Mathaes, Roman; Kossinna, Juergen; Schmitting, Franz; Dreher, Sascha; Roehl, Holger; Hemminger, Markus; Wuchner, Klaus
2016-10-27
The assurance of sterility of a parenteral drug product, prior to any human use, is a regulatory requirement. Hence, all strategies related to container closure integrity (CCI) must demonstrate absence of microbial contamination through leaks as part of the container closure system (CCS) qualification, during manufacturing, for Quality Control purposes and to ensure microbiological integrity (sterility) during storage and shipment up to the end of product shelf life. Current regulatory guidances, which differ between countries and regions, provide limited detail on how to assess CCI. The new revision of USP aims to provide extensive and detailed guidance for CCI assessments for sterile products. However, practical questions and considerations are yet to be addressed by the pharmaceutical industry. These may include: (i) choice of method, e.g., whether a deterministic CCI method (e.g., helium leak) is preferable over probabilistic CCI method (e.g., microbial ingress), (ii) the type of primary packaging (e.g., vial, syringe, device) and (iii) dosage form (e.g., liquid vs lyophilisate), (iv) suitable acceptance criteria and (v) appropriate sample size, (vi) the most appropriate way to introduce artificial leaks into the CCS, (vii) ensure suitable assurance of CCI during Drug Product manufacturing, (viii) evaluate CCI under intended shipment and storage conditions (e.g., in the frozen state). A group of European industry peers have met to discuss these and other related questions in order to provide their viewpoint and best-practice on practical approaches to CCI. Their perspective is provided in this white paper. Through these discussions, it became clear that there is currently no gold standard for CCI test methods or for the generation of artificial leaks; therefore flexibility towards CCI approaches is required. Although there should be flexibility, any CCI approach must consider the intended use (e.g., CCS qualification, routine manufacturing, or Quality Control
Susy Theories and QCD: Numerical Approaches
Ita, Harald
2011-01-01
We review on-shell and unitarity methods and discuss their application to precision predictions for LHC physics. Being universal and numerically robust, these methods are straight-forward to automate for next-to-leading-order computations within Standard Model and beyond. Several state-of-the-art results including studies of W/Z+3-jet and W+4-jet production have explicitly demonstrated the effectiveness of the unitarity method for describing multi-parton scattering. Here we review central ideas needed to obtain efficient numerical implementations. This includes on-shell loop-level recursions, the unitarity method, color management and further refined tricks.
Jia, Yanting; Hongxin, Li; Wenbin, Guo; Zhang, Haizhou; Zou, Chengwei
2016-02-16
Current treatments for congenital coronary artery fistulas (CAFs) include surgical obliteration and transcatheter occlusion. However, surgical techniques involve significant trauma. Transcatheter occlusion is performed under fluoroscopy and angiography, in which radiation injury is inevitable. We present a patient, with a CAF from the left coronary artery to the right atrium, who underwent peratrial device closure of the CAF with a right parasternal approach under transesophageal echocardiography guidance. Complete occlusion was achieved by a symmetric ventricular septal occluder. We suggest that peratrial device closure of a congenital coronary artery fistula through a right parasternal approach may be a safe and effective option.
Laser-based Online Sliding-window Approach for UAV Loop-closure Detection in Urban Environments
Directory of Open Access Journals (Sweden)
Anqing Wang
2016-04-01
Full Text Available Online loop-closure detection serves as an essential task for Unmanned Aerial Vehicles (UAVs equipped with laser scanners. Due to the inherent errors in UAVs’ pose estimation, a 3-D reconstruction algorithm is adopted to perform 3-D map building, which establishes probabilistic models of the system according to the assumption of errors. To meet the demand of online loop-closure detection using sequential 2-D laser data, a robust ISW-NDT (incremental sliding-window-based NDT approach is proposed, which compares the appearance similarity between two scans by sliding a window with fixed size. Compared with the conventional 3-D NDT approach, the proposed loop-closure detection algorithm is capable of providing superior performance in large-scale outdoor environments, achieving higher recall rate at 100% precision and ensuring successful online implementation. Experimental results show the validity and robustness of the proposed method.
Susy theories and QCD: numerical approaches
Ita, Harald
2011-11-01
We review on-shell and unitarity methods and discuss their application to precision predictions for Large Hadron Collider (LHC) physics. Being universal and numerically robust, these methods are straightforward to automate for next-to-leading-order computations within standard model and beyond. Several state-of-the-art results including studies of (W/Z+3)-jet and (W+4)-jet production have explicitly demonstrated the effectiveness of the unitarity method for describing multi-parton scattering. Here we review central ideas needed to obtain efficient numerical implementations. This includes on-shell loop-level recursions, the unitarity method, color management and further refined tricks. This article is an invited review for a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Scattering amplitudes in gauge theories’.
Bolin, Michael
2010-01-01
If you're ready to use Closure to build rich web applications with JavaScript, this hands-on guide has precisely what you need to learn this suite of tools in depth. Closure makes it easy for experienced JavaScript developers to write and maintain large and complex codebases -- as Google has demonstrated by using Closure with Gmail, Google Docs, and Google Maps. Author and Closure contributor Michael Bolin has included numerous code examples and best practices, as well as valuable information not available publicly until now. You'll learn all about Closure's Library, Compiler, Templates, tes
Numerical Approach to Calculation of Feynman Loop Integrals
Yuasa, F; Kurihara, Y; Fujimoto, J; Shimizu, Y; Hamaguchi, N; de Doncker, E; Kato, K
2011-01-01
In this paper, we describe a numerical approach to evaluate Feynman loop integrals. In this approach the key technique is a combination of a numerical integration method and a numerical extrapolation method. Since the computation is carried out in a fully numerical way, our approach is applicable to one-, two- and multi-loop diagrams. Without any analytic treatment it can compute diagrams with not only real masses but also complex masses for the internal particles. As concrete examples we present numerical results of a scalar one-loop box integral with complex masses and two-loop planar and non-planar box integrals with masses. We discuss the quality of our numerical computation by comparisons with other methods and also propose a self consistency check.
Numerical homogenization on approach for stokesian suspensions.
Energy Technology Data Exchange (ETDEWEB)
Haines, B. M.; Berlyand, L. V.; Karpeev, D. A. (Mathematics and Computer Science); (Department of Mathematics, Pennsylvania State Univ.)
2012-01-20
In this technical report we investigate efficient methods for numerical simulation of active suspensions. The prototypical system is a suspension of swimming bacteria in a Newtonian fluid. Rheological and other macroscopic properties of such suspensions can differ dramatically from the same properties of the suspending fluid alone or of suspensions of similar but inactive particles. Elongated bacteria, such as E. coli or B. subtilis, swim along their principal axis, propelling themselves with the help of flagella, attached at the anterior of the organism and pushing it forward in the manner of a propeller. They interact hydrodynamically with the surrounding fluid and, because of their asymmetrical shape, have the propensity to align with the local flow. This, along with the dipolar nature of bacteria (the two forces a bacterium exerts on a fluid - one due to self-propulsion and the other opposing drag - have equal magnitude and point in opposite directions), causes nearby bacteria to tend to align, resulting in a intermittent local ordering on the mesoscopic scale, which is between the microscopic scale of an individual bacterium and the macroscopic scale of the suspension (e.g., its container). The local ordering is sometimes called a collective mode or collective swimming. Thanks to self-propulsion, collective modes inject momentum into the fluid in a coherent way. This enhances the local strain rate without changing the macroscopic stress applied at the boundary of the container. The macroscopic effective viscosity of the suspension is defined roughly as the ratio of the applied stress to the bulk strain rate. If local alignment and therefore local strain-rate enhancement, are significant, the effective viscosity can be appreciably lower than that of the corresponding passive suspension or even of the surrounding fluid alone. Indeed, a sevenfold decrease in the effective viscosity was observed in experiments with B. subtilis. More generally, local collective
Numerical homogenization on approach for stokesian suspensions.
Energy Technology Data Exchange (ETDEWEB)
Haines, B. M.; Berlyand, L. V.; Karpeev, D. A. (Mathematics and Computer Science); (Department of Mathematics, Pennsylvania State Univ.)
2012-01-20
In this technical report we investigate efficient methods for numerical simulation of active suspensions. The prototypical system is a suspension of swimming bacteria in a Newtonian fluid. Rheological and other macroscopic properties of such suspensions can differ dramatically from the same properties of the suspending fluid alone or of suspensions of similar but inactive particles. Elongated bacteria, such as E. coli or B. subtilis, swim along their principal axis, propelling themselves with the help of flagella, attached at the anterior of the organism and pushing it forward in the manner of a propeller. They interact hydrodynamically with the surrounding fluid and, because of their asymmetrical shape, have the propensity to align with the local flow. This, along with the dipolar nature of bacteria (the two forces a bacterium exerts on a fluid - one due to self-propulsion and the other opposing drag - have equal magnitude and point in opposite directions), causes nearby bacteria to tend to align, resulting in a intermittent local ordering on the mesoscopic scale, which is between the microscopic scale of an individual bacterium and the macroscopic scale of the suspension (e.g., its container). The local ordering is sometimes called a collective mode or collective swimming. Thanks to self-propulsion, collective modes inject momentum into the fluid in a coherent way. This enhances the local strain rate without changing the macroscopic stress applied at the boundary of the container. The macroscopic effective viscosity of the suspension is defined roughly as the ratio of the applied stress to the bulk strain rate. If local alignment and therefore local strain-rate enhancement, are significant, the effective viscosity can be appreciably lower than that of the corresponding passive suspension or even of the surrounding fluid alone. Indeed, a sevenfold decrease in the effective viscosity was observed in experiments with B. subtilis. More generally, local collective
Vannametee, Ekkamol; Karssenberg, Derek; Hendriks, Martin; Bierkens, Marc
2014-05-01
Physically-based hydrological modelling could be considered as an ideal approach for predictions in ungauged basins because observable catchment characteristics can be used to parameterize the model, avoiding model calibration using discharge data, which are not available. Lumped physically-based modelling at the watershed scale is possible with the Representative Elementary Watershed (REW) approach. A key to successful application of this approach is to find a reliable way of developing closure relations to calculate fluxes from different hydrological compartments in the REWs. Here, we present a bottom-up approach as a generic framework to identify the closure relations for particular hydrological processes that are scale-independent and can be directly parameterized using the local-scale observable REW characteristics. The approach is illustrated using the Hortonian runoff as an example. This approach starts from developing a physically-based high-resolution model describing the Hortonian runoff mechanism based on physically-based infiltration theory and runoff generation processes at a local scale. This physically-based model is used to generate a synthetic discharge data set of hypothetical rainfall events and HRUs (6×105 scenarios) as a surrogate for real-world observations. The Hortonian runoff closure relation is developed as a lumped process-based model, consisting of the Green-Ampt equation, a time-lagged linear reservoir model, and three scale-transfer parameters representing the processes within REWs. These scale-transfer parameters are identified by calibrating the closure relations against the synthetic discharge data set for each scenario run, which are, in turn, empirically related to their corresponding observable REW properties and rainstorm characteristics. This results in a parameter library, which allows direct estimation of scaling parameter for arbitrary REWs based on their local-scale observable properties and rainfall characteristics
Numerical method for dam break problem using Godunov approach
Directory of Open Access Journals (Sweden)
A. Kartono
2013-03-01
Full Text Available In this study a numerical scheme was developed in order to overcome the problem of shock wave for the test case of dam break. The numerical scheme was based on Godunov approach of finite volume method to solve the shallow water equation. In order to expedite and improve the solution an approximate Roe’s Riemann solver associated with Monotone Upstream-centred Scheme for Conservation Laws (MUSCL was applied. The results were presented in one and two dimensional and verifications were made with analytical solution. The results are comparable and a good agreement is achieved between numerical and analytical.
Novel Approaches To Numerical Solutions Of Quantum Field Theories
Petrov, D
2005-01-01
Two new approaches to numerically solving Quantum Field Theories are presented. The Source Galerkin technique is a direct approach to determining the generating functional of a theory by solving the Schwinger-Dyson equations. The properties of the Source Galerkin technique are tested by using it to determine the phase structure of the Ultralocal &phis;4 theory. A framework for applying this approach to solving O( N) Nonlinear Sigma model is constructed. The Sinc Function approximation is a highly efficient method of numerically evaluating Feynman diagrams. In the present dissertation the Sinc Function approximation is applied to fermionic fields. The Sinc expanded versions of fermion and photon propagators are derived. The accuracy of this approximation is tested by a direct comparison of the Sinc expanded propagators with exact propagators and by performing several sample calculations of one loop QED diagrams. An analysis of computational properties of the Sinc Function approach is presented.
Achieving Direct Closure of the Anterolateral Thigh Flap Donor Site—An Algorithmic Approach
Directory of Open Access Journals (Sweden)
Jaime Eduardo Pachón Suárez, MD
2014-10-01
Conclusions: Direct primary closure of the ALT donor site can be facilitated by the use of our simple algorithm. Certain strategies need to be adopted at the design stage; however, the techniques used are simple and reliable, produce superior cosmetic results at the donor site, save time, and spare the patient the morbidity associated with the harvest of a skin graft.
Multi-Physics Coupling Approaches for Aerospace Numerical Simulations.
Errera, M.; Dugeai, A.; Girodroux-Lavigne, P.; Garaud, J.D.; Poinot, M.; Cerqueira, S.; Chaineray, G.
2011-01-01
International audience; The purpose of this paper is to present coupling strategies for aerospace numerical calculations. In the first part, the basic approach used relies on the partitioned coupling of a finite-volume Navier-Stokes solver and a finite-element solid code. These two separate and independent simulation tools carry out exchanges via a coupling library. Two different applications illustrate the capabilities of this coupling method. The main advantage of this approach is to benefi...
A modular approach to numerical human body modeling
Forbes, P.A.; Griotto, G.; Rooij, L. van
2007-01-01
The choice of a human body model for a simulated automotive impact scenario must take into account both accurate model response and computational efficiency as key factors. This study presents a "modular numerical human body modeling" approach which allows the creation of a customized human body mod
A modular approach to numerical human body modeling
Forbes, P.A.; Griotto, G.; Rooij, L. van
2007-01-01
The choice of a human body model for a simulated automotive impact scenario must take into account both accurate model response and computational efficiency as key factors. This study presents a "modular numerical human body modeling" approach which allows the creation of a customized human body
A numerical modelling approach for biomass field drying
Bartzanas, T.; Bochtis, D.D.; Sørensen, C.G.; Sapounas, A.; Green, O.
2010-01-01
In grass conservation systems, the field drying process of cut grass is an important function since it determines subsequent losses and possible hazardous effects of during silage. The drying process of harvested grass was evaluated using two different numerical approaches. Firstly, an existing expe
A numerical modelling approach for biomass field drying
Bartzanas, T.; Bochtis, D.D.; Sørensen, C.G.; Sapounas, A.; Green, O.
2010-01-01
In grass conservation systems, the field drying process of cut grass is an important function since it determines subsequent losses and possible hazardous effects of during silage. The drying process of harvested grass was evaluated using two different numerical approaches. Firstly, an existing
Post-closure biosphere assessment modelling: comparison of complex and more stylised approaches
Energy Technology Data Exchange (ETDEWEB)
Walke, Russell C. [Quintessa Limited, The Hub, 14 Station Road, Henley-on-Thames (United Kingdom); Kirchner, Gerald [University of Hamburg, ZNF, Beim Schlump 83, 20144 Hamburg (Germany); Xu, Shulan; Dverstorp, Bjoern [Swedish Radiation Safety Authority, SE-171 16 Stockholm (Sweden)
2014-07-01
Geological facilities are the preferred option for disposal of high-level radioactive waste, due to their potential to provide isolation from the surface environment (biosphere) on very long time scales. Safety cases developed in support of geological disposal include assessment of potential impacts on humans and wildlife in order to demonstrate compliance with regulatory criteria. As disposal programmes move from site-independent/generic assessments through site selection to applications for construction/operation and closure, the degree of understanding of the present-day site increases, together with increased site-specific information. Assessments need to strike a balance between simple models and more complex approaches that draw more extensively on this site-specific information. This paper explores the relative merits of complex versus more stylised biosphere models in the context of a site-specific assessment. The complex biosphere model was developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) for the Formark candidate site for a spent nuclear fuel repository in Sweden. SKB's model is built on a landscape evolution model, whereby radionuclide releases to distinct hydrological basins/sub-catchments (termed 'objects') are represented as they evolve through land rise and climate change. The site is located on the Baltic coast with a terrestrial landscape including lakes, mires, forest and agriculture. The land at the site is projected to continue to rise due to post-glacial uplift leading to ecosystem transitions in excess of ten thousand years. The simple biosphere models developed for this study include the most plausible transport processes and represent various types of ecosystem. The complex biosphere models adopt a relatively coarse representation of the near-surface strata, which is shown to be conservative, but also to under-estimate the time scale required for potential doses to reach equilibrium with radionuclide fluxes
A multidisciplinary esthetic approach to single-tooth replacement and diastema closure.
Lyssova, Valentina; Estafan, Denise; Cunnigham, Ralph P
2008-05-01
Anterior tooth replacement has always posed an esthetic challenge for dentists. A multidisciplinary approach makes it possible to provide patients with esthetics and function. Treatment planning should involve other specialists when clinicians are faced with the additional esthetic concerns of the patient (such as anterior spatial anomalies and esthetically unpleasant existing restorations). Metal-ceramic fixed partial dentures have been used to allow the replacement of missing teeth for many years, providing both strength and esthetics. Several other options also are available, including implant placement. Dental implants in the esthetic zone are well-documented in the literature; numerous controlled clinical trials have shown overall implant survival and success rates. This article illustrates a step-by-step analysis and treatment option for a single-tooth replacement and maxillary anterior spatial dilemma using Captek crowns.
A covariant Hamiltonian tetrad approach to numerical relativity
Hamilton, Andrew J S
2016-01-01
A Hamiltonian approach to the equations of general relativity is proposed in which the gravitational coordinates are the 12 spatial components of the line interval (the vierbein) including their antisymmetric parts, and their 12 conjugate momenta. A feature of the proposed formalism is that it allows Lorentz gauge freedoms to be imposed on the Lorentz connections rather than on the vierbein, which may facilitate numerical integration in some challenging problems. The 40 Hamilton's equations comprise 12 + 12 = 24 equations of motion and 6 identities, along with 10 constraint equations. By comparison, the ADM formalism has 12 equations of motion and 18 identities, while the BSSN formalism has 15 equations of motion and 15 identities. I conjecture that, by maximizing the number of "good" causal equations of motion and minimizing the number of "bad" acausal identities, the proposed approach may have improved properties of numerical stability.
Directory of Open Access Journals (Sweden)
Ahmad El Sayed
2015-01-01
Full Text Available A lifted hydrogen/nitrogen turbulent jet flame issuing into a vitiated coflow is investigated using the conditional moment closure (CMC supplemented by the presumed mapping function (PMF approach for the modelling of conditional mixing and velocity statistics. Using a prescribed reference field, the PMF approach yields a presumed probability density function (PDF for the mixture fraction, which is then used in closing the conditional scalar dissipation rate (CSDR and conditional velocity in a fully consistent manner. These closures are applied to a lifted flame and the findings are compared to previous results obtained using β-PDF-based closures over a range of coflow temperatures (Tc. The PMF results are in line with those of the β-PDF and compare well to measurements. The transport budgets in mixture fraction and physical spaces and the radical history ahead of the stabilisation height indicate that the stabilisation mechanism is susceptible to Tc. As in the previous β-PDF calculations, autoignition around the “most reactive” mixture fraction remains the controlling mechanism for sufficiently high Tc. Departure from the β-PDF predictions is observed when Tc is decreased as PMF predicts stabilisation by means of premixed flame propagation. This conclusion is based on the observation that lean mixtures are heated by downstream burning mixtures in a preheat zone developing ahead of the stabilization height. The spurious sources, which stem from inconsistent CSDR modelling, are further investigated. The findings reveal that their effect is small but nonnegligible, most notably within the flame zone.
Mizuno, Y; Ohi, K; Sogabe, T; Yamamoto, Y; Kaneda, Y
2010-09-01
A numerical analysis is made on the four-point correlation function in a similarity range of a model of two-dimensional passive scalar field ψ advected by a turbulent velocity field with infinitely small correlation time. The model yields an exact closure equation for the four-point correlation Ψ{4} of ψ, which may be casted into the form of an eigenvalue problem in the similarity range. The analysis of the eigenvalue problem gives not only the scale dependence of Ψ{4} , but also the dependence on the configuration of the four points. The numerical analysis gives S4(R)∝R{ζ{4}} in the similarity range in which S2(R)∝R{ζ{2}} , where S_{N} is the structure function defined by S{N}(R)≡⟨[ψ(x+R)-ψ(x)]{N} and ζ{4}≠2ζ{2} . The estimate of ζ_{4} by the numerical analysis of the eigenvalue problem is in good agreement with numerical simulations so far reported. The agreement supports the idea of universality of the exponent ζ{4} in the sense that ζ_{4} is insensitive to conditions of ψ outside the similarity range. The numerical analysis also shows that the correlation C(R,r)≡[ψ(x+R)-ψ(x)]{2}[ψ(x+r)-ψ(x)]{2}> is stronger than that given by the joint-normal approximation, and scales like C(R,r)∝(r/R){χ} for r/R<1 with R and r in the similarity range, where χ is a constant depending on the angle between R and r .
An Efficient Numerical Approach for Nonlinear Fokker-Planck equations
Otten, Dustin; Vedula, Prakash
2009-03-01
Fokker-Planck equations which are nonlinear with respect to their probability densities that occur in many nonequilibrium systems relevant to mean field interaction models, plasmas, classical fermions and bosons can be challenging to solve numerically. To address some underlying challenges in obtaining numerical solutions, we propose a quadrature based moment method for efficient and accurate determination of transient (and stationary) solutions of nonlinear Fokker-Planck equations. In this approach the distribution function is represented as a collection of Dirac delta functions with corresponding quadrature weights and locations, that are in turn determined from constraints based on evolution of generalized moments. Properties of the distribution function can be obtained by solution of transport equations for quadrature weights and locations. We will apply this computational approach to study a wide range of problems, including the Desai-Zwanzig Model (for nonlinear muscular contraction) and multivariate nonlinear Fokker-Planck equations describing classical fermions and bosons, and will also demonstrate good agreement with results obtained from Monte Carlo and other standard numerical methods.
A numerical approach for the analysis of deformable journal bearings
Directory of Open Access Journals (Sweden)
D. Benasciutti
2012-07-01
Full Text Available This paper presents a numerical approach for the analysis of hydrodynamic radial journal bearings. The effect of shaft and housing elastic deformation on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a plane finite elements structural model is solved. Temperature and pressure effects on viscosity are also included with the Vogel-Barus model. The deformed lubrication gap and the overall stress state were calculated. Numerical results are presented with reference to a typical journal bearing configuration at two different inlet oil temperatures. Obtained results show the great influence of elastic deformation of bearing components on oil pressure distribution, compared with results for ideally rigid components obtained by Raimondi and Boyd solution.
Oscillation threshold of a clarinet model: a numerical continuation approach
Karkar, Sami; Cochelin, Bruno; 10.1121/1.3651231
2012-01-01
This paper focuses on the oscillation threshold of single reed instruments. Several characteristics such as blowing pressure at threshold, regime selection, and playing frequency are known to change radically when taking into account the reed dynamics and the flow induced by the reed motion. Previous works have shown interesting tendencies, using analytical expressions with simplified models. In the present study, a more elaborated physical model is considered. The influence of several parameters, depending on the reed properties, the design of the instrument or the control operated by the player, are studied. Previous results on the influence of the reed resonance frequency are confirmed. New results concerning the simultaneous influence of two model parameters on oscillation threshold, regime selection and playing frequency are presented and discussed. The authors use a numerical continuation approach. Numerical continuation consists in following a given solution of a set of equations when a parameter varie...
Modelling the effects of water-point closure and fencing removal: a GIS approach.
Graz, F Patrick; Westbrooke, Martin E; Florentine, Singarayer K
2012-08-15
Artificial water-points in the form of troughs or ground tanks are used to augment natural water supplies within rangelands in many parts of the world. Access to such water-points leads to the development of a distinct ecological sub-system, the piosphere, where trampling and grazing impact modify the vegetation. This study aims to consolidate existing information in a GIS based model to investigate grazing patterns within the landscape. The model focuses on the closure of water-points and removal of fences on Nanya Station, New South Wales, Australia. We found that the manipulation of water-points and fences in one management intervention may change grazing activity in a way different to that which would be experienced if each had been modified separately. Such effects are further modified by the spatial distribution of the water-points and the underlying vegetation.
Laser modeling a numerical approach with algebra and calculus
Csele, Mark Steven
2014-01-01
Offering a fresh take on laser engineering, Laser Modeling: A Numerical Approach with Algebra and Calculus presents algebraic models and traditional calculus-based methods in tandem to make concepts easier to digest and apply in the real world. Each technique is introduced alongside a practical, solved example based on a commercial laser. Assuming some knowledge of the nature of light, emission of radiation, and basic atomic physics, the text:Explains how to formulate an accurate gain threshold equation as well as determine small-signal gainDiscusses gain saturation and introduces a novel pass
NUMERICAL APPROACH TO DETERMINING INSTANTANEOUS CONTACT REGION FOR CONJUGATE SURFACES
Institute of Scientific and Technical Information of China (English)
WANG Taiyong; LI Jingcai; HE Gaiyun; FAN Shengbo; HAO Yongjiang
2008-01-01
According to the defect of traditional method of determining instantaneous contact regions for conjugate surfaces, a numerical approach to the determination is proposed. A local coordinate system is built by using the surface unit tangent and unit normal at the contact point. Considering that the gap forming the boundary of instantaneous contact region in the direction of the common normal vectors is given, a system of nonlinear equations is built to find the instantaneous contact boundary in local coordinate system, a modified Powell's hybrid algorithm of finite-difference approximation to the Jacobian used to solve the system. The new method simplifies the task of determining instantaneous contact regions without calculating curvature and relative curvature. The validity of the proposed approach is verified by an example of hypoid gears.
BOOK REVIEW Analytical and Numerical Approaches to Mathematical Relativity
Stewart, John M.
2007-08-01
The 319th Wilhelm-and-Else-Heraeus Seminar 'Mathematical Relativity: New Ideas and Developments' took place in March 2004. Twelve of the invited speakers have expanded their one hour talks into the papers appearing in this volume, preceded by a foreword by Roger Penrose. The first group consists of four papers on 'differential geometry and differential topology'. Paul Ehrlich opens with a very witty review of global Lorentzian geometry, which caused this reviewer to think more carefully about how he uses the adjective 'generic'. Robert Low addresses the issue of causality with a description of the 'space of null geodesics' and a tentative proposal for a new definition of causal boundary. The underlying review of global Lorentzian geometry is continued by Antonio Masiello, looking at variational approaches (actually valid for more general semi-Riemannian manifolds). This group concludes with a very clear review of pp-wave spacetimes from José Flores and Miguel Sánchez. (This reviewer was delighted to see a reproduction of Roger Penrose's seminal (1965) picture of null geodesics in plane wave spacetimes which attracted him into the subject.) Robert Beig opens the second group 'analytic methods and differential equations' with a brief but careful discussion of symmetric (regular) hyperbolicity for first (second) order systems, respectively, of partial differential equations. His description is peppered with examples, many specific to relativstic continuum mechanics. There follows a succinct review of linear elliptic boundary value problems with applications to general relativity from Sergio Dain. The numerous examples he provides are thought-provoking. The 'standard cosmological model' has been well understood for three quarters of a century. However recent observations suggest that the expansion in our Universe may be accelerating. Alan Rendall provides a careful discussion of the changes, both mathematical and physical, to the standard model which might be needed
Advanced numerical methods and software approaches for semiconductor device simulation
Energy Technology Data Exchange (ETDEWEB)
CAREY,GRAHAM F.; PARDHANANI,A.L.; BOVA,STEVEN W.
2000-03-23
In this article the authors concisely present several modern strategies that are applicable to drift-dominated carrier transport in higher-order deterministic models such as the drift-diffusion, hydrodynamic, and quantum hydrodynamic systems. The approaches include extensions of upwind and artificial dissipation schemes, generalization of the traditional Scharfetter-Gummel approach, Petrov-Galerkin and streamline-upwind Petrov Galerkin (SUPG), entropy variables, transformations, least-squares mixed methods and other stabilized Galerkin schemes such as Galerkin least squares and discontinuous Galerkin schemes. The treatment is representative rather than an exhaustive review and several schemes are mentioned only briefly with appropriate reference to the literature. Some of the methods have been applied to the semiconductor device problem while others are still in the early stages of development for this class of applications. They have included numerical examples from the recent research tests with some of the methods. A second aspect of the work deals with algorithms that employ unstructured grids in conjunction with adaptive refinement strategies. The full benefits of such approaches have not yet been developed in this application area and they emphasize the need for further work on analysis, data structures and software to support adaptivity. Finally, they briefly consider some aspects of software frameworks. These include dial-an-operator approaches such as that used in the industrial simulator PROPHET, and object-oriented software support such as those in the SANDIA National Laboratory framework SIERRA.
A finite difference, multipoint flux numerical approach to flow in porous media: Numerical examples
Osman, Hossam Omar
2012-06-17
It is clear that none of the current available numerical schemes which may be adopted to solve transport phenomena in porous media fulfill all the required robustness conditions. That is while the finite difference methods are the simplest of all, they face several difficulties in complex geometries and anisotropic media. On the other hand, while finite element methods are well suited to complex geometries and can deal with anisotropic media, they are more involved in coding and usually require more execution time. Therefore, in this work we try to combine some features of the finite element technique, namely its ability to work with anisotropic media with the finite difference approach. We reduce the multipoint flux, mixed finite element technique through some quadrature rules to an equivalent cell-centered finite difference approximation. We show examples on using this technique to single-phase flow in anisotropic porous media.
Organizational closure competencies and scaling: A realist approach to theorizing social enterprise
Seelos, Christian; Mair, Johanna
2016-01-01
Purpose Social entrepreneurs create novel approaches to social problems such as poverty. But scaling these approaches to the dimension of the problem can be a difficult task. In the social enterprise sector, the subject of scaling has become a key dimension of organizational performance. This chapter advances the scholarly literature on the scaling of social enterprises, a literature which is currently in an embryonic stage and characterized by conceptual ambiguity and fragmented perspecti...
Numerical Aspects of Solving Differential Equations: Laboratory Approach for Students.
Witt, Ana
1997-01-01
Describes three labs designed to help students in a first course on ordinary differential equations with three of the most common numerical difficulties they might encounter when solving initial value problems with a numerical software package. The goal of these labs is to help students advance to independent work on common numerical anomalies.…
Post-closure biosphere assessment modelling: comparison of complex and more stylised approaches.
Walke, Russell C; Kirchner, Gerald; Xu, Shulan; Dverstorp, Björn
2015-10-01
Geological disposal facilities are the preferred option for high-level radioactive waste, due to their potential to provide isolation from the surface environment (biosphere) on very long timescales. Assessments need to strike a balance between stylised models and more complex approaches that draw more extensively on site-specific information. This paper explores the relative merits of complex versus more stylised biosphere models in the context of a site-specific assessment. The more complex biosphere modelling approach was developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) for the Formark candidate site for a spent nuclear fuel repository in Sweden. SKB's approach is built on a landscape development model, whereby radionuclide releases to distinct hydrological basins/sub-catchments (termed 'objects') are represented as they evolve through land rise and climate change. Each of seventeen of these objects is represented with more than 80 site specific parameters, with about 22 that are time-dependent and result in over 5000 input values per object. The more stylised biosphere models developed for this study represent releases to individual ecosystems without environmental change and include the most plausible transport processes. In the context of regulatory review of the landscape modelling approach adopted in the SR-Site assessment in Sweden, the more stylised representation has helped to build understanding in the more complex modelling approaches by providing bounding results, checking the reasonableness of the more complex modelling, highlighting uncertainties introduced through conceptual assumptions and helping to quantify the conservatisms involved. The more stylised biosphere models are also shown capable of reproducing the results of more complex approaches. A major recommendation is that biosphere assessments need to justify the degree of complexity in modelling approaches as well as simplifying and conservative assumptions. In light of
Numerical approaches to complex quantum, semiclassical and classical systems
Energy Technology Data Exchange (ETDEWEB)
Schubert, Gerald
2008-11-03
In this work we analyse the capabilities of several numerical techniques for the description of different physical systems. Thereby, the considered systems range from quantum over semiclassical to classical and from few- to many-particle systems. In chapter 1 we investigate the behaviour of a single quantum particle in the presence of an external disordered background (static potentials). Starting from the quantum percolation problem, we address the fundamental question of a disorder induced (Anderson-) transition from extended to localised single-particle eigenstates. Distinguishing isolating from conducting states by applying a local distribution approach for the local density of states (LDOS), we detect the quantum percolation threshold in two- and three-dimensions. Extending the quantum percolation model to a quantum random resistor model, we comment on the possible relevance of our results to the influence of disorder on the conductivity in graphene sheets. For the calculation of the LDOS as well as for the Chebyshev expansion of the time evolution operator, the kernel polynomial method (KPM) is the key numerical technique. In chapter 2 we examine how a single quantum particle is influenced by retarded bosonic fields that are inherent to the system. Within the Holstein model, these bosonic degrees of freedom (phonons) give rise to an infinite dimensional Hilbert space, posing a true many-particle problem. Constituting a minimal model for polaron formation, the Holstein model allows us to study the optical absorption and activated transport in polaronic systems. Using a two-dimensional variant of the KPM, we calculate for the first time quasi-exactly the optical absorption and dc-conductivity as a function of temperature. In chapter 3 we come back to the time evolution of a quantum particle in an external, static potential and investigate the capability of semiclassical approximations to it. We address basic quantum effects as tunneling, interference and
Probing Modified Gravity with Atom-Interferometry: a Numerical Approach
Schlogel, Sandrine; Fuzfa, Andre
2015-01-01
Refined constraints on chameleon theories are calculated for atom-interferometry experiments, using a numerical approach consisting in solving for a four-region model the static and spherically symmetric Klein-Gordon equation for the chameleon field. By modeling not only the test mass and the vacuum chamber but also its walls and the exterior environment, the method allows to probe new effects on the scalar field profile and the induced acceleration of atoms. In the case of a weakly perturbing test mass, the effect of the wall is to enhance the field profile and to lower the acceleration inside the chamber by up to one order of magnitude. In the thin-shell regime, significant deviations from the analytical estimations are found, even when measurements are realized in the immediate vicinity of the test mass. Close to the vacuum chamber wall, the acceleration becomes negative and potentially measurable. This prediction could be used to discriminate between fifth-force effects and systematic experimental uncerta...
Unsteady flow phenomena in human undulatory swimming: a numerical approach.
Pacholak, Steffen; Hochstein, Stefan; Rudert, Alexander; Brücker, Christoph
2014-06-01
The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition.
Probing modified gravity with atom-interferometry: A numerical approach
Schlögel, Sandrine; Clesse, Sébastien; Füzfa, André
2016-05-01
Refined constraints on chameleon theories are calculated for atom-interferometry experiments, using a numerical approach consisting in solving for a four-region model the static and spherically symmetric Klein-Gordon equation for the chameleon field. By modeling not only the test mass and the vacuum chamber but also its walls and the exterior environment, the method allows one to probe new effects on the scalar field profile and the induced acceleration of atoms. In the case of a weakly perturbing test mass, the effect of the wall is to enhance the field profile and to lower the acceleration inside the chamber by up to 1 order of magnitude. In the thin-shell regime, results are found to be in good agreement with the analytical estimations, when measurements are realized in the immediate vicinity of the test mass. Close to the vacuum chamber wall, the acceleration becomes negative and potentially measurable. This prediction could be used to discriminate between fifth-force effects and systematic experimental uncertainties, by doing the experiment at several key positions inside the vacuum chamber. For the chameleon potential V (ϕ )=Λ4 +α/ϕα and a coupling function A (ϕ )=exp (ϕ /M ), one finds M ≳7 ×1016 GeV , independently of the power-law index. For V (ϕ )=Λ4(1 +Λ /ϕ ), one finds M ≳1014 GeV . A sensitivity of a ˜10-11 m /s2 would probe the model up to the Planck scale. Finally, a proposal for a second experimental setup, in a vacuum room, is presented. In this case, Planckian values of M could be probed provided that a ˜10-10 m /s2 , a limit reachable by future experiments. Our method can easily be extended to constrain other models with a screening mechanism, such as symmetron, dilaton and f(R) theories.
Chimera: A hybrid approach to numerical loop quantum cosmology
Diener, Peter; Singh, Parampreet
2013-01-01
The existence of a quantum bounce in isotropic spacetimes is a key result in loop quantum cosmology (LQC), which has been demonstrated to arise in all the models studied so far. In most of the models, the bounce has been studied using numerical simulations involving states which are sharply peaked and which bounce at volumes much larger than the Planck volume. An important issue is to confirm the existence of the bounce for states which have a wide spread, or which bounce closer to the Planck volume. Numerical simulations with such states demand large computational domains, making them very expensive and practically infeasible with the techniques which have been implemented so far. To overcome these difficulties, we present an efficient hybrid numerical scheme using the property that at the small spacetime curvature, the quantum Hamiltonian constraint in LQC, which is a difference equation with uniform discretization in volume, can be approximated by a Wheeler-DeWitt differential equation. By carefully choosi...
Numerical Methods for Stochastic Computations A Spectral Method Approach
Xiu, Dongbin
2010-01-01
The first graduate-level textbook to focus on fundamental aspects of numerical methods for stochastic computations, this book describes the class of numerical methods based on generalized polynomial chaos (gPC). These fast, efficient, and accurate methods are an extension of the classical spectral methods of high-dimensional random spaces. Designed to simulate complex systems subject to random inputs, these methods are widely used in many areas of computer science and engineering. The book introduces polynomial approximation theory and probability theory; describes the basic theory of gPC meth
A cubic B-spline Galerkin approach for the numerical simulation of the GEW equation
Directory of Open Access Journals (Sweden)
S. Battal Gazi Karakoç
2016-02-01
Full Text Available The generalized equal width (GEW wave equation is solved numerically by using lumped Galerkin approach with cubic B-spline functions. The proposed numerical scheme is tested by applying two test problems including single solitary wave and interaction of two solitary waves. In order to determine the performance of the algorithm, the error norms L2 and L∞ and the invariants I1, I2 and I3 are calculated. For the linear stability analysis of the numerical algorithm, von Neumann approach is used. As a result, the obtained findings show that the presented numerical scheme is preferable to some recent numerical methods.
Ye, Zuyang; Liu, Hui-Hai; Jiang, Qinghui; Liu, Yanzhang; Cheng, Aiping
2017-02-01
A systematic method has been proposed to estimate the two-phase flow properties of horizontal fractures under normal deformation condition. Based on Gaussian aperture distributions and the assumption of local parallel plate model, a simple model was obtained in closed form to predict the capillary pressure-saturation relationships for both wetting and non-wetting phases. Three conceptual models were also developed to characterize the relative permeability behaviors. In order to investigate the effect of normal deformation on two-phase flow properties, the normal deformation could be represented with the maximum void space closure on the basis of penetration model. A rigorous successive random addition (SRA) method was used to generate the aperture-based fractures and a numerical approach based on invasion percolation (IP) model was employed to model capillary-dominated displacements between wetting and non-wetting phases. The proposed models were partially verified by a laboratory dataset and numerical calculations without consideration of deformation. Under large normal deformations, it was found that the macroscopic model is in better agreement with simulated observations. The simulation results demonstrated that the two-phase flow properties including the relationships between capillary pressure, relative permeability and saturation, phase interference, phase structures, residual-saturation-rated parameters and tortuosity factor, were highly sensitive to the spatial correlation of aperture distribution and normal deformation.
Numerical approach of some three-body problems
Ixaru, L. Gr.
2016-12-01
On taking the two-proton decay in nuclear physics as a sample case we formulate a numerical method for three-body problems which are mathematically described by systems of coupled 2d Schrödinger equations in polar coordinates r , ϕ. With some minimal adaptations the method becomes applicable on other cases. The specific feature of the procedure consists in a shuttle propagation along r: two quantities are propagated, the log-derivative matrix and the solution itself, with a backwards propagation of the former, followed by a forwards propagation of the latter. The results show remarkable stability. Numerical illustrations from a simple test model are reported and we also explain how the data obtained in this way can be exploited to obtain useful physical information.
Numerical insight of a variational smeared approach to cohesive fracture
Freddi, F.; Iurlano, F.
2017-01-01
In the present paper we numerically investigate and validate a variational smeared model for cohesive crack, recently proposed and theoretically justified by Γ-convergence. To achieve this main goal, we first analyze the response of a bar subjected to traction. Possible solutions are discussed, reconstructing the classical cohesive fracture energy and its related stress-crack opening law through a backtracking procedure. Preliminary 2D investigations are also conducted by using a regularized version of the adopted formulation. This permits to explore the transition phase of the damage evolution and to determine the peculiarities of the model, such as mesh-objectivity and Γ-convergence as damage concentration is forced. Therefore, the numerical simulations confirm the analytical results and put the basis for further engineering applications and possible improvements of the model.
Density Functional Approach Based on Numerically Obtained Bridge Functional
Institute of Scientific and Technical Information of China (English)
ZHOU Shi-Qi
2002-01-01
The Ornstein Zernike equation is solved with the Rogers Young approximation for bulk hard sphere fluidand Lennard-Jones fluid for several state points. Then the resulted bulk fluid radial distribution function combinedwith the test particle method is employed to determine numerically the function relationship of bridge functional as afunction of indirect correlation function. It is found that all of the calculated points from different phase space statepoints for a same type of fluid collapse onto a same smooth curve. Then the numerically obtained curve is used tosubstitute the analytic expression of the bridge functional as a function of indirect correlation function required in themethodology [J. Chem. Phys. 112 (2000) 8079] to deterrnine the density distribution of non-uniform hard spherefluid and Lennard Jones fluid. The good agreement of theoretical predictions with the computer simulation data isobtained. The present numerical procedure incorporates the knowledge of bulk fluid radial distribution function intothe constructing of the density functional approximation and makes the original methodology more accurate and moreflexible for various interaction potential fluid.
Density Functional Approach Based on Numerically Obtained Bridge Functional
Institute of Scientific and Technical Information of China (English)
ZHOUShi－Qi
2002-01-01
The ornstein-zenike equation is solved with the Rogers-Young approximation for bulk hard sphere fluid and Lennard-Jones fluid for several state points.Then the resulted bulk fluid radial distribution function combined with the test particle method is employed to determine numerically the function relationship of bridge functional as a function of indirect correlation function.It is found that all of the calculated points from different phase space state points for a same type of fluid collapse onto a same smooth curve.Then the numerically obtained curve is used to substitute the analytic expression of the bridge functional as a function of indirect correlation function required in the methodology [J.Chem.Phys,112(2000)8079] to determine the density distribution of non-uniform hard sphere fluid and Lennard-Jones fluid.The good agreement of theoretical predictions with the computer simulation data is obtained.The present numerical procedure incroporates the knowledge of bulk fluid radial distribution function into the constructing of the density functional approximation and makes the original methodology more accurate and more filexible for various interaction potential fluid.
van de Kamp, Cornelis; Bongers, Raoul M.; Zaal, Frank T. J. M.
2010-01-01
Both in the catching and grasping component of prehension, the hand opens and closes before hand-object contact is made. The initiation of hand closure has to be coordinated with the time course of the decrease of the distance between the hand and the target object, i.e., with the reaching component
Energy Technology Data Exchange (ETDEWEB)
Munson, D.E.; Fossum, A.F.; Senseny, P.E. (Sandia National Labs., Albuquerque, NM (USA); Southwest Research Inst., San Antonio, TX (USA); RE/SPEC, Inc., Rapid City, SD (USA))
1989-08-01
The discrepancies between predicted and measured WIPP in situ Room D closures are markedly reduced through the use of a Tresca flow potential, an improved small strain constitutive model, an improved set of material parameters, and a modified stratigraphy. 12 refs., 5 figs., 1 tab.
Energy Technology Data Exchange (ETDEWEB)
Munson, D.E.; Fossum, A.F.; Senseny, P.E.
1989-01-01
The discrepancies between predicted and measured WIPP in situ Room D closures are markedly reduced through the use of a Tresca flow potential, an improved small strain constitutive model, an improved set of material parameters, and a modified stratigraphy. 17 refs., 8 figs., 1 tab.
Energy Technology Data Exchange (ETDEWEB)
Munson, D.E.; Fossum, A.F.; Senseny, P.E. (Sandia National Labs., Albuquerque, NM (USA))
1990-01-01
The discrepancies between predicted and measured Waste Isolation Pilot Plant (WIPP) in-situ Room D closures are markedly reduced through the use of a Tresca flow potential, an improved small strain constitutive model, an improved set of material parameters, and a modified stratigraphy. (author).
Novae Restauration
2012-01-01
Christmas Restaurant closures Please note that the Restaurant 1 and Restaurant 3 will be closed from Friday, 21 December at 5 p.m. to Sunday, 6 January, inclusive. They will reopen on Monday, 7 January 2013. Restaurant 2 closure for renovation To meet greater demand and to modernize its infrastructure, Restaurant 2 will be closed from Monday, 17 December. On Monday, 14 January 2013, Sophie Vuetaz’s team will welcome you to a renovated self-service area on the 1st floor. The selections on the ground floor will also be expanded to include pasta and pizza, as well as snacks to eat in or take away. To ensure a continuity of service, we suggest you take your break at Restaurant 1 or Restaurant 3 (Prévessin).
Li's criterion for the Riemann hypothesis - numerical approach
Directory of Open Access Journals (Sweden)
Krzysztof Maślanka
2004-01-01
Full Text Available There has been some interest in a criterion for the Riemann hypothesis proved recently by Xian-Jin Li [Li X.-J.: The Positivity of a Sequence of Numbers and the Riemann Hypothesis. J. Number Theory 65 (1997, 325-333]. The present paper reports on a numerical computation of the first 3300 of Li's coefficients which appear in this criterion. The main empirical observation is that these coefficients can be separated in two parts. One of these grows smoothly while the other is very small and oscillatory. This apparent smallness is quite unexpected. If it persisted till infinity then the Riemann hypothesis would be true.
A Numerical Simulation Approach for Reliability Evaluation of CFRP Composite
Liu, D. S.-C.; Jenab, K.
2013-02-01
Due to the superior mechanical properties of carbon fiber reinforced plastic (CFRP) materials, they are vastly used in industries such as aircraft manufacturers. The aircraft manufacturers are switching metal to composite structures while studying reliability (R-value) of CFRP. In this study, a numerical simulation method to determine the reliability of Multiaxial Warp Knitted (MWK) textiles used to make CFRP composites is proposed. This method analyzes the distribution of carbon fiber angle misalignments, from a chosen 0° direction, caused by the sewing process of the textile, and finds the R-value, a value between 0 and 1. The application of this method is demonstrated by an illustrative example.
Institute of Scientific and Technical Information of China (English)
李国岫; Roekaerts Dirk
2004-01-01
A numerical simulation of a bluff-body stabilized nonpremixed flame has been performed with second-moment turbulence closure(SMTC) models.To clarify the applicability of the existing-SMTC models in this complex flame, several typical SMTC models ,including LRR-IP model, JM model,SSC model as well as two modified LRR-IP mode, have been applied and evaluated in the numerical simulation of a bluff-body flame. Some of the above-mentioned SMTC models cannot provide overall satisfactory predictions for this challenging test. The difference in performance between the various SMTC models is quite significant. In the present study, the equilibrium chemistry model is employed and an assumed-shape beta function PDF approach is used to represent the interaction between turbulence and chemistry. It can be concluded that the modified LRR-IP models as well as SSG model are superior to other SMTC models in the turbulent nonpremixed bluff-body stabilized flame.%应用二阶矩封闭湍流模型进行了湍流非预混钝体稳定火焰数值模拟的研究.应用LRR-IP模型,JM模型,SSG模型以及两个修正后的LRR-IP模型等二阶矩封闭湍流模型,进行了钝体稳定火焰数值模拟的研究.对于复杂的钝体稳定火焰,一些模型无法给出令人满意的结果,而且不同模型的结果差异很大.在研究中,湍流燃烧模型采用了化学平衡模型和假设PDF模型.研究结果表明,对于钝体稳定火焰,SSG模型以及两个修正后的LRR-IP模型要优于其他几个二阶矩封闭湍流模型.
Elastohydrodynamic lubrication for line and point contacts asymptotic and numerical approaches
Kudish, Ilya I
2013-01-01
Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches describes a coherent asymptotic approach to the analysis of lubrication problems for heavily loaded line and point contacts. This approach leads to unified asymptotic equations for line and point contacts as well as stable numerical algorithms for the solution of these elastohydrodynamic lubrication (EHL) problems. A Unique Approach to Analyzing Lubrication Problems for Heavily Loaded Line and Point Contacts The book presents a robust combination of asymptotic and numerical techniques to solve EHL p
Planning for integrated mine closure
Energy Technology Data Exchange (ETDEWEB)
Linda Starke (ed.)
2008-07-01
This document presents an Integrated Mine Closure Planning Toolkit for the mining and metals sector. The toolkit is intended to be used to promote a more disciplined approach to integrated closure planning and to increase the uniformity of good practices across the sector. The concepts apply equally well to both large and small companies. The document is not intended to be prescriptive; it provides a suite of tools that can be brought to bear in formulating well-considered decisions when planning for closure. It uses a risk and opportunity based process to guide the practitioner through the iterative process of preparing for planned closure. The first section, with head office and mine management personnel as the primary audience, describes the participants of effective closure planning. Sections 2 and 3 provide the frameworks for a conceptual closure plan and a detailed plan. The key audiences for these two sections are mine management and head office personnel, financial modellers and estimators, governments, academics and non-governmental organizations. The forth section addresses decommissioning and post closure planning, and Section 5 draws together the conclusions and outlines several unresolved issues. The five narrative sections are followed by Section 6 which outlines 13 tools, some of which are already available in earlier ICMM publications, member practices and other sector-affiliated publications. Others have been developed to cover identified gaps. These tools provide the practitioner with practical work processes, examples and contexts within which to apply closure planning discipline.
Two-component jet simulations: Combining analytical and numerical approaches
Matsakos, T; Trussoni, E; Tsinganos, K; Vlahakis, N; Sauty, C; Mignone, A
2009-01-01
Recent observations as well as theoretical studies of YSO jets suggest the presence of two steady components: a disk wind type outflow needed to explain the observed high mass loss rates and a stellar wind type outflow probably accounting for the observed stellar spin down. In this framework, we construct numerical two-component jet models by properly mixing an analytical disk wind solution with a complementary analytically derived stellar outflow. Their combination is controlled by both spatial and temporal parameters, in order to address different physical conditions and time variable features. We study the temporal evolution and the interaction of the two jet components on both small and large scales. The simulations reach steady state configurations close to the initial solutions. Although time variability is not found to considerably affect the dynamics, flow fluctuations generate condensations, whose large scale structures have a strong resemblance to observed YSO jet knots.
An MLP based Approach for Recognition of Handwritten `Bangla' Numerals
Basu, Subhadip; Sarkar, Ram; Kundu, Mahantapas; Nasipuri, Mita; Basu, Dipak Kumar
2012-01-01
The work presented here involves the design of a Multi Layer Perceptron (MLP) based pattern classifier for recognition of handwritten Bangla digits using a 76 element feature vector. Bangla is the second most popular script and language in the Indian subcontinent and the fifth most popular language in the world. The feature set developed for representing handwritten Bangla numerals here includes 24 shadow features, 16 centroid features and 36 longest-run features. On experimentation with a database of 6000 samples, the technique yields an average recognition rate of 96.67% evaluated after three-fold cross validation of results. It is useful for applications related to OCR of handwritten Bangla Digit and can also be extended to include OCR of handwritten characters of Bangla alphabet.
A numerical approach to finding general stationary vacuum black holes
Adam, Alexander; Wiseman, Toby
2011-01-01
The Harmonic Einstein equation is the vacuum Einstein equation supplemented by a gauge fixing term which we take to be that of DeTurck. For static black holes analytically continued to Riemannian manifolds without boundary at the horizon this equation has previously been shown to be elliptic, and Ricci flow and Newton's method provide good numerical algorithms to solve it. Here we extend these techniques to the arbitrary cohomogeneity stationary case which must be treated in Lorentzian signature. For stationary spacetimes with globally timelike Killing vector the Harmonic Einstein equation is elliptic. In the presence of horizons and ergo-regions it is less obviously so. Motivated by the Rigidity theorem we study a class of stationary black hole spacetimes, considered previously by Harmark, general enough to include the asymptotically flat case in higher dimensions. We argue the Harmonic Einstein equation consistently truncates to this class of spacetimes giving an elliptic problem. The Killing horizons and a...
Numerical and Experimental Approaches Toward Understanding Lava Flow Heat Transfer
Rumpf, M.; Fagents, S. A.; Hamilton, C.; Crawford, I. A.
2013-12-01
We have performed numerical modeling and experimental studies to quantify the heat transfer from a lava flow into an underlying particulate substrate. This project was initially motivated by a desire to understand the transfer of heat from a lava flow into the lunar regolith. Ancient regolith deposits that have been protected by a lava flow may contain ancient solar wind, solar flare, and galactic cosmic ray products that can give insight into the history of our solar system, provided the records were not heated and destroyed by the overlying lava flow. In addition, lava-substrate interaction is an important aspect of lava fluid dynamics that requires consideration in lava emplacement models Our numerical model determines the depth to which the heat pulse will penetrate beneath a lava flow into the underlying substrate. Rigorous treatment of the temperature dependence of lava and substrate thermal conductivity and specific heat capacity, density, and latent heat release are imperative to an accurate model. Experiments were conducted to verify the numerical model. Experimental containers with interior dimensions of 20 x 20 x 25 cm were constructed from 1 inch thick calcium silicate sheeting. For initial experiments, boxes were packed with lunar regolith simulant (GSC-1) to a depth of 15 cm with thermocouples embedded at regular intervals. Basalt collected at Kilauea Volcano, HI, was melted in a gas forge and poured directly onto the simulant. Initial lava temperatures ranged from ~1200 to 1300 °C. The system was allowed to cool while internal temperatures were monitored by a thermocouple array and external temperatures were monitored by a Forward Looking Infrared (FLIR) video camera. Numerical simulations of the experiments elucidate the details of lava latent heat release and constrain the temperature-dependence of the thermal conductivity of the particulate substrate. The temperature-dependence of thermal conductivity of particulate material is not well known
Ogive Nose Hard Missile Penetrating Concrete Slab Numerical Simulation Approach
Directory of Open Access Journals (Sweden)
Qadir Bux
2011-01-01
Full Text Available Great demand exists for more efficient design to protect delicate and serious structures such as nuclear plants, Power plants, Weapon Industries, weapons storage places, water retaining structures, & etc, against impact of kinetic missiles generated both accidentally and deliberately such as dynamic loading, incident occurs in nuclear plants, terrorist attack, Natural disasters like tsunami and etc., in various impact and blast scenarios for both civilian and military activities. In many cases, projectiles can be treated as rigid bodies when their damage and erosion are not severe. Due to the intricacy of the local impact damages, investigations are generally based on experimental data. Conclusions of the experimental observations are then used to guide engineering models. Local damages studies normally fall into three categories, i.e. empirical formulae based on data fitting, idealised analytical models based on physic laws and numerical simulations based on computational mechanics and material models. In the present study, 2D asymmetrical numerical simulation have done on concrete slab against the impact of ogive nose hard missile of 26.90mm and 76.20mm diameter with CRH ratio 2.0 and 6.0 respectively, for penetration by using Concrete Damaged Plasticity Model, and ABAQUS/Explicit dynamic analysis in ABAQUS. It is found that the strains/stresses are induced in the concrete slab and a very nicely propagation of the stresses inside the concrete slab in the form of waves, which is a clear indication for vibrations of the concrete. The lack of failure criterion in concrete damaged plasticity model does not allow the removal of elements during the analyses. This means that spalling, scabbing, and perforation cannot be modelled with the Concrete Damage Plasticity Model. The penetration depth results shows that the deeper penetration requires higher critical impact kinetic energies, and comparison shows the simulation results are more accurate
PROBABILISTIC NUMERICAL APPROACH FOR PDE AND ITS APPLICATION IN THE VALUATION OF EUROPEAN OPTIONS
Institute of Scientific and Technical Information of China (English)
Dong-sheng Wu
2001-01-01
This paper suggests a probabilistic numerical approach for a class of PDE. First of all,by simulating Brownian motion and using Monte-Carlo method, we obtain a probabilistic numerical solution for the PDE. Then, we prove that the probabilistic numerical solution converges in probability to its solution. At the end of this paper, as an application, we give a probabilistic numerical approach for the valuation of European Options, where we see volatility σ, interest rate r and divident rate Do as functions of stock S, respectively.
A numerical approach for solving an extended Fisher-Kolomogrov-Petrovskii-Piskunov equation
Khuri, S. A.; Sayfy, A.
2010-02-01
In the present paper a numerical method, based on finite differences and spline collocation, is presented for the numerical solution of a generalized Fisher integro-differential equation. A composite weighted trapezoidal rule is manipulated to handle the numerical integrations which results in a closed-form difference scheme. A number of test examples are solved to assess the accuracy of the method. The numerical solutions obtained, indicate that the approach is reliable and yields results compatible with the exact solutions and consistent with other existing numerical methods. Convergence and stability of the scheme have also been discussed.
An efficient numerical approach to electrostatic microelectromechanical system simulation
Institute of Scientific and Technical Information of China (English)
Li Pu
2009-01-01
Computational analysis of electrostatic microelectromechanical systems (MEMS) requires an electrostatic analysis to compute the electrostatic forces acting on micromechanical structures and a mechanical analysis to compute the deformation of micromechanical structures. Typically, the mechanical analysis is performed on an undeformed geometry. However, the electrostatic analysis is performed on the deformed position of microstructures. In this paper, a new efficient approach to self-consistent analysis of electrostatic MEMS in the small deformation case is presented. In this approach, when the microstructures undergo small deformations, the surface charge densities on the deformed geometry can be computed without updating the geometry of the microstructures. This algorithm is based on the linear mode shapes of a microstructure as basis functions. A boundary integral equation for the electrostatic problem is expanded into a Taylor series around the undeformed configuration, and a new coupled-field equation is presented. This approach is validated by comparing its results with the results available in the literature and ANSYS solutions, and shows attractive features comparable to ANSYS.
Directory of Open Access Journals (Sweden)
M. Boumaza
2015-07-01
Full Text Available Transient convection heat transfer is of fundamental interest in many industrial and environmental situations, as well as in electronic devices and security of energy systems. Transient fluid flow problems are among the more difficult to analyze and yet are very often encountered in modern day technology. The main objective of this research project is to carry out a theoretical and numerical analysis of transient convective heat transfer in vertical flows, when the thermal field is due to different kinds of variation, in time and space of some boundary conditions, such as wall temperature or wall heat flux. This is achieved by the development of a mathematical model and its resolution by suitable numerical methods, as well as performing various sensitivity analyses. These objectives are achieved through a theoretical investigation of the effects of wall and fluid axial conduction, physical properties and heat capacity of the pipe wall on the transient downward mixed convection in a circular duct experiencing a sudden change in the applied heat flux on the outside surface of a central zone.
On closure parameter estimation in chaotic systems
Directory of Open Access Journals (Sweden)
J. Hakkarainen
2012-02-01
Full Text Available Many dynamical models, such as numerical weather prediction and climate models, contain so called closure parameters. These parameters usually appear in physical parameterizations of sub-grid scale processes, and they act as "tuning handles" of the models. Currently, the values of these parameters are specified mostly manually, but the increasing complexity of the models calls for more algorithmic ways to perform the tuning. Traditionally, parameters of dynamical systems are estimated by directly comparing the model simulations to observed data using, for instance, a least squares approach. However, if the models are chaotic, the classical approach can be ineffective, since small errors in the initial conditions can lead to large, unpredictable deviations from the observations. In this paper, we study numerical methods available for estimating closure parameters in chaotic models. We discuss three techniques: off-line likelihood calculations using filtering methods, the state augmentation method, and the approach that utilizes summary statistics from long model simulations. The properties of the methods are studied using a modified version of the Lorenz 95 system, where the effect of fast variables are described using a simple parameterization.
Numerical simulation in steam injection process by a mechanistic approach
Energy Technology Data Exchange (ETDEWEB)
De Souza, J.C.Jr.; Campos, W.; Lopes, D.; Moura, L.S.S. [Petrobras, Rio de Janeiro (Brazil)
2008-10-15
Steam injection is a common thermal recovery method used in very viscous oil reservoirs. The method involves the injection of heat to reduce viscosity and mobilize oil. A steam generation and injection system consists primarily of a steam source, distribution lines, injection wells and a discarding tank. In order to optimize injection and improve the oil recovery factor, one must determine the parameters of steam flow such as pressure, temperature and steam quality. This study focused on developing a unified mathematical model by means of a mechanistic approach for two-phase steam flow in pipelines and wells. The hydrodynamic and heat transfer mechanistic model was implemented in a computer simulator to model the parameters of steam injection while trying to avoid the use of empirical correlations. A marching algorithm was used to determine the distribution of pressure and temperature along the pipelines and wellbores. The mathematical model for steam flow in injection systems, developed by a mechanistic approach (VapMec) performed well when the simulated values of pressures and temperatures were compared with the values measured during field tests. The newly developed VapMec model was incorporated in the LinVap-3 simulator that constitutes an engineering supporting tool for steam injection wells operated by Petrobras. 23 refs., 7 tabs., 6 figs.
Energy Technology Data Exchange (ETDEWEB)
Olofsson, Isabelle; Fredriksson, Anders [Golder Associates AB, Stockholm (Sweden)
2005-05-15
The Swedish Nuclear and Fuel Management Company (SKB) is conducting Preliminary Site Investigations at two different locations in Sweden in order to study the possibility of a Deep Repository for spent fuel. In the frame of these Site Investigations, Site Descriptive Models are achieved. These products are the result of an interaction of several disciplines such as geology, hydrogeology, and meteorology. The Rock Mechanics Site Descriptive Model constitutes one of these models. Before the start of the Site Investigations a numerical method using Discrete Fracture Network (DFN) models and the 2D numerical software UDEC was developed. Numerical simulations were the tool chosen for applying the theoretical approach for characterising the mechanical rock mass properties. Some shortcomings were identified when developing the methodology. Their impacts on the modelling (in term of time and quality assurance of results) were estimated to be so important that the improvement of the methodology with another numerical tool was investigated. The theoretical approach is still based on DFN models but the numerical software used is 3DEC. The main assets of the programme compared to UDEC are an optimised algorithm for the generation of fractures in the model and for the assignment of mechanical fracture properties. Due to some numerical constraints the test conditions were set-up in order to simulate 2D plane strain tests. Numerical simulations were conducted on the same data set as used previously for the UDEC modelling in order to estimate and validate the results from the new methodology. A real 3D simulation was also conducted in order to assess the effect of the '2D' conditions in the 3DEC model. Based on the quality of the results it was decided to update the theoretical model and introduce the new methodology based on DFN models and 3DEC simulations for the establishment of the Rock Mechanics Site Descriptive Model. By separating the spatial variability into two
Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network.
Yin, Haodong; Han, Baoming; Li, Dewei; Wu, Jianjun; Sun, Huijun
2016-01-01
A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1) A basic passenger behavior optimization model is mathematically constructed based on 0-1 integer programming to describe passengers' responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2) An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1), the impact of the closure can be somewhat mitigated.
Energy Technology Data Exchange (ETDEWEB)
Zou, Ling [Idaho National Lab. (INL), Idaho Falls, ID (United States); Berry, R. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Martineau, R. C. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Andrs, D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, H. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hansel, J. E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sharpe, J. P. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johns, Russell C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-04-01
The RELAP-7 code is the next generation nuclear reactor system safety analysis code being developed at the Idaho National Laboratory (INL). The code is based on the INL’s modern scientific software development framework, MOOSE (Multi-Physics Object Oriented Simulation Environment). The overall design goal of RELAP-7 is to take advantage of the previous thirty years of advancements in computer architecture, software design, numerical integration methods, and physical models. The end result will be a reactor systems analysis capability that retains and improves upon RELAP5’s and TRACE’s capabilities and extends their analysis capabilities for all reactor system simulation scenarios. The RELAP-7 code utilizes the well-posed 7-equation two-phase flow model for compressible two-phase flow. Closure models used in the TRACE code has been reviewed and selected to reflect the progress made during the past decades and provide a basis for the colure correlations implemented in the RELAP-7 code. This document provides a summary on the closure correlations that are currently implemented in the RELAP-7 code. The closure correlations include sub-grid models that describe interactions between the fluids and the flow channel, and interactions between the two phases.
Verhagen, H.J.
2007-01-01
This chapter discusses the design aspects of estuary and river closures and those of reservoir dams and certain other hydraulic structures. The focus of this chapter is on closures, not on the situation after the closure has been completed.
Energy Technology Data Exchange (ETDEWEB)
Bailly, P.
1996-05-01
The modelling of turbulence - combustion interaction is considered in the case of flamelet turbulent premixed flames. In the flamelet regime, the combustion process is mainly controlled by the turbulence. Non-gradient and counter-gradient turbulent diffusion effects, leading to a strong generation of turbulence by the flame may appear in such situations. Two calculation configurations are considered: a turbulent flame stabilized by an obstacle and a turbulent flame stabilized by a backward-facing-step. The combustion - turbulence interaction modelling is realized with a BML flamelet model associated with the balance equations for all the turbulent fluxes. In the case of the flame stabilized by an obstacle, the non-gradient diffusion is found to be negligible. On the other hand, the properties of the isothermal and reactive flows are recovered with the Reynolds stress order modelling only. Concerning the flame stabilized by a backward-facing-step, the counter-gradient diffusion is largely dominant. So, we show that this phenomenon is well represented with the mass turbulent flux second order model only. (author) 100 refs.
Impact of Metal Droplets: A Numerical Approach to Solidification
Koldeweij, Robin; Mandamparambil, Rajesh; Lohse, Detlef
2016-11-01
Layer-wise deposition of material to produce complex products is a subject of increasing technological relevance. Subsequent deposition of droplets is one of the possible 3d printing technologies to accomplish this. The shape of the solidified droplet is crucial for product quality. We employ the volume-of-fluid method (in the form of the open-source code Gerris) to study liquid metal (in particular tin) droplet impact. Heat transfer has been implemented based on the enthalpy approach for the liquid-solid phase. Solidification is modeled by adding a sink term to the momentum equations, reducing Navier-Stokes to Darcy's law for high solid fraction. Good agreement is found when validating the results against experimental data. We then map out a phase diagram in which we distinguish between solidification behavior based on Weber and Stefan number. In an intermediate impact regime impact, solidification due to a retracting phase occurs. In this regime the maximum spreading diameter almost exclusively depends on Weber number. Droplet shape oscillations lead to a broad variation of the morphology of the solidified droplet and determine the final droplet height. TNO.
Evaluation of explicit and implicit LES closures for Burgers turbulence
Maulik, Romit
2016-01-01
In this work, we perform an aposteriori error analysis on implicit and explicit large eddy simulation closure models for solving the Burgers turbulence problem. Our closure modeling efforts include both functional and structural models equipped with various low-pass filters. We introduce discrete binomial smoothing filters and an enhanced version of the Van Cittert algorithm to accelerate the convergence of approximate deconvolution processes including regularization and relaxation filtering approaches. Our implicit modeling efforts consist of various high-order schemes including compact and non-compact fifth-order upwind schemes as well as weighted essential non-oscillatory (WENO) and compact reconstructed WENO (CRWENO) schemes, and the resulting schemes are shown to effectively converge to the direct numerical simulation (DNS) for increasing resolutions. Comparing with DNS and underresolved DNS computations, our numerical assessments illustrate the ability of these methods to capture the energy content near...
Towards a Numerical Unitarity Approach for Two-loop Amplitudes in QCD
Ita, Harald
2016-01-01
The numerical unitarity approach has been important for obtaining reliable QCD predictions for the LHC. Here I discuss the extension of the approach beyond the leading quantum corrections for computing multi-loop amplitudes. The numerical unitarity approach requires a suitable parametrisation of the loop integrands as a sum of terms that integrate to zero (surface terms) and master integrands. The construction and classification of suitable surface terms which match the propagators structures of Feynman amplitudes is the main technical advance discussed. A number of spin-offs for integral reduction and further formal questions are briefly reviewed.
Brezzi, Franco; Cangiani, Andrea; Georgoulis, Emmanuil
2016-01-01
This volume contains contributed survey papers from the main speakers at the LMS/EPSRC Symposium “Building bridges: connections and challenges in modern approaches to numerical partial differential equations”. This meeting took place in July 8-16, 2014, and its main purpose was to gather specialists in emerging areas of numerical PDEs, and explore the connections between the different approaches. The type of contributions ranges from the theoretical foundations of these new techniques, to the applications of them, to new general frameworks and unified approaches that can cover one, or more than one, of these emerging techniques.
Roets, Arne; Van Hiel, Alain
2011-03-01
The present research investigates how people's general epistemic motives may inspire essentialist beliefs about racial groups and racism. In three studies, we focus particularly on essentialist entitativity (EE, referring to beliefs about the uniformity, informativeness, and inherent core of racial groups), probing into its relationships with epistemic need for closure (NFC) and prejudice. In Study 1, we develop an EE scale, empirically distinguish it from the naturalness component of essentialism and non-EE beliefs, and establish its predictive utility for explaining racial prejudice. Study 2 provides experimental evidence for the causal effect of NFC on EE beliefs. Study 3 demonstrates in three different samples that EE beliefs mediate the relationship between dispositional NFC and racial prejudice. It is argued that EE beliefs about racial groups are an expression of motivated social cognition, serving people's seizing needs for quick and easy social judgment.
Indian Academy of Sciences (India)
Michel Boussuge
2001-04-01
Numerical simulation is now very often used to predict the behaviour of components in service conditions. This paper is interested in specific approaches concerning ceramic materials and refractories. Creep can be satisfactorily described by a kinematic hardening, and exhibits different creep rates in tension and compression. Concerning the thermal shock of materials, the numerical approach depends whether or not the material is able to develop a sprayed out damage, leading to micro- or macro-cracking. Finally, delayed failure at high temperature can be considered as a consequence of creep, but the random aspect of failure seriously complicates the numerical models. The lack of experimental data presently limits the calibration and the validation of the numerical models.
Directory of Open Access Journals (Sweden)
M. Boochi Babu
2013-07-01
Full Text Available Paravalvular leak (PVL is a rare but potentially serious complication of surgically implanted prosthetic heart valves. Patients who have PVL can be asymptomatic or present with haemolysis, heart failure, or endocarditis. The goldstandard treatment for prosthetic-valve PVL is surgery to repair or replace the valve but carries higher operative risk compared to the initial procedure. In view of this, percutaneous transcatheter closure of PVL is becoming an increasingly attractive alternative strategy. In this report, we describe a case of mitral PVL in a patient with double-valve replacement, which was successfully closed using Cocoon duct occluder device (Vascular Innovations Co., Ltd, Thailand via ante-grade approach, guided by transesophageal echocardiography (TEE and fluoroscopy and without complete arterio-venous loop.
Energy Technology Data Exchange (ETDEWEB)
Gutzeit, Andreas, E-mail: andreas.gutzeit@ksw.ch; Schie, Bram van, E-mail: Bram.vanschie@hotmail.com; Schoch, Eric, E-mail: eric.schoch@ksw.ch [Cantonal Hospital Winterthur, Department of Radiology (Switzerland); Hergan, Klaus, E-mail: k.hergan@salk.at [Paracelsus Medical University Salzburg, Department of Radiology (Austria); Graf, Nicole, E-mail: graf@biostatistics.ch; Binkert, Christoph A., E-mail: christoph.binkert@ksw.ch [Cantonal Hospital Winterthur, Department of Radiology (Switzerland)
2012-10-15
Introduction: The purpose of the present study was to analyze complications following antegrade puncture of the common femoral artery (CFA) and the superficial femoral artery (SFA) using vascular closure systems (VCS). Methods: A single-center, retrospective study was performed after obtaining approval from the institutional review board and informed consent from all patients. At our center, the CFA or SFA are used for arterial access. All patients were evaluated clinically on the same day. If there was any suspicion of an access site problem, Duplex ultrasound was performed. Results: Access location was the CFA in 50 patients and the SFA in 130 patients. The sheath size ranged from 4F to 10F. Two patients had to be excluded because of lack of follow-up. Successful hemostasis was achieved in 162 of 178 cases (91 %). The following complications were observed in 16 patients (8.9 %): 4 pseudoaneurysms (2.2 %), 11 hematomas (6.2 %), and 1 vascular occlusion (0.5 %). The two pseudoaneurysms healed spontaneously, in one case an ultrasound-guided thrombin injection was performed, and one aneurysm was compressed manually. No further medical therapy was needed for the hematomas. The one vascular occlusion was treated immediately with angioplasty using a contralateral approach. No significant difference was noted between the CFA and the SFA group with respect to complications (p = 1.000). Conclusions: The use of closure devices for an antegrade approach up to 10F is feasible and safe. No differences in low complication rates were observed between CFA and SFA.
Directory of Open Access Journals (Sweden)
Ahmad El Sayed
2014-01-01
Full Text Available A lifted H2/N2 turbulent jet flame issuing into a vitiated coflow is investigated using the conditional moment closure. The conditional velocity (CV and the conditional scalar dissipation rate (CSDR submodels are chosen such that they are fully consistent with the moments of the presumed β probability density function (PDF. The CV is modelled using the PDF-gradient diffusion model. Two CSDR submodels based on the double integration of the homogeneous and inhomogeneous mixture fraction PDF transport equations are implemented. The effect of CSDR modelling is investigated over a range of coflow temperatures (Tc and the stabilisation mechanism is determined from the analysis of the transport budgets and the history of radical build-up ahead of the stabilisation height. For all Tc, the balance between chemistry, axial convection, and micromixing, and the absence of axial diffusion upstream of the stabilisation height indicate that the flame is stabilized by autoignition. This conclusion is confirmed from the rapid build-up of HO2 ahead of H, O, and OH. The inhomogeneous CSDR modelling yields higher dissipation levels at the most reactive mixture fraction, which results in longer ignition delays and larger liftoff heights. The effect of the spurious sources arising from homogeneous modelling is found to be small but nonnegligible, mostly notably within the flame zone.
Off-pump transapical closure of a mitral periprosthetic leak: a new approach to a difficult problem.
Gaia, Diego Felipe; Breda, João Roberto; Fischer, Claudio Henrique; Palma, José Honório
2013-12-01
A 60-year old male patient with multiple risk factors and two previous interventions over the mitral valve was admitted to the emergency unit with symptoms of cardiac failure. Initial examination revealed a competent mitral bioprosthesis with severe perivalvular mitral insufficiency. Based on previous experiences with transapical procedures, a transapical transcatheter closure of the perivalvular leak was performed. The apex was punctured with a 7 French introducer sheath, and a hydrophilic guidewire was advanced with the aid of a right Judkins catheter and positioned across the defect in the left atrium. Fluoroscopic and tridimensional transoesophageal echocardiography was used to guide the manoeuvre. Next, a long introducer sheath was advanced through the guidewire and positioned inside the left atrium. Two Amplatzer Vascular Plug II (St Jude Medical) were deployed, resulting in a significant reduction in the perivalvular leak. The procedure was considered to be successful. The patient regained consciousness, and the orotracheal tube was removed in the operating theatre. No neurological deficits were detected, and the patient was transferred to the intensive care unit. The patient recovered well and was transferred to the ward after 1 day. Discharge was accomplished after 4 days.
Analytical and Numerical Approaches to Modelling of Reinforcement Corrosion in Concrete
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Vořechovská Dita
2014-06-01
Full Text Available Corrosion of reinforcement in concrete is one of the most influencing factors causing the degradation of RC structures. This paper attempts at the application of an analytical and numerical approaches to simulation of concrete cracking due to reinforcement corrosion. At first, a combination with detailed analysis of two analytical models proposed by Liu and Weyers (1998 and Li et al. (2006 is suggested and presented. Four distinct phases of the corrosion process are identified and a detailed guide through the mathematical development is described. Next, numerical computations obtained with nonlinear finite element code are presented. The model features the state-of-the-art in nonlinear fracture mechanics modelling and the heterogeneous structure of concrete is modelled via spatially varying parameters of the constitutive law. Finally, the results of the analytical studies are compared to numerical computations and the paper concludes with the sketch of a real-life numerical example.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A new numerical approach has been developed for vapor solid equilibrium calculations and for predicting vapor solid equilibrium constant and composition of vapor and solid phases in gas hydrate formation. Equation of state methods generally do a good job of determining vapor phase properties,but for solid phase it is much more difficult and inaccurate. This proposed new model calculates vapor solid equilibrium constant and vapor and solid phase composition as a function of temperature and partial pressure. The results of this proposed numerical approach, for vapor solid equilibrium, have a good agreement with the available reported data. This new numerical model also has an advantage to tune coefficients, to cover different sets of experimental data accurately.
Transcatheter vs. surgical closure of patent ductus arteriosus: outcomes and cost analysis
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Mulyadi M Djer
2013-07-01
Full Text Available Background Patent ductus arterious (PDA is a non-cyanotic congenital heart disease (CHD caused by the patency of the arterial duct after birth. For the last three decades, management of PDA with transcatheter closure has been gaining popularity, including in developing countries. However its effectiveness in terms of clinical outcomes and cost may vary among center and has not been thoroughly evaluated yet in Indonesia. Objectives To compare the cost and clinical effectiveness of PDA closure using transcatheter approach compared to surgical ligation. Methods We performed a retrospective review on patients underwent either transcatheter or surgical closure of PDA between January 2000 and December 2006 in Cipto Mangunkusumo Hospital, Jakarta, Indonesia. Clinical outcomes as well as cost were compared using the student T-test and Chi-square for numerical and categorical variables, respectively Results During the study period, 89 patients underwent transcatheter closure using an Amplatzer® device occluder (ADO device and 67 had surgical ligation. Successful PDA closure on first attempt was achieved in 87 (96% and 63 (94% children who underwent transcatheter and surgical closure, respectively (P=1.000. Two children with unsuccessful transcatheter closure eventually had their PDA closed by surgery, whereas one child with residual PDA after surgical closure had his PDA closed by coil. No residual PDA was found in the transcatheter closure group at one-week follow up. Duration of hospitalization was significantly less for patients having transcatheter closure compared to surgery [2.7 (SD 1.5 vs. 6.6 (SD 1.5 days, P<0.0001]. The cost for PDA closure with an Amplatzer® device was more expensive than surgical ligation [Rp. 29,930,000 (SD 57,200 vs. Rp. 12,205,000 (SD 89,300, P< 0.0001]. Conclusion Transcatheter closure is equally effective as surgical ligation in closing the PDA. Less hospitalization is required with transcatheter closure although the
Comparing approaches for numerical modelling of tsunami generation by deformable submarine slides
Smith, Rebecca C.; Hill, Jon; Collins, Gareth S.; Piggott, Matthew D.; Kramer, Stephan C.; Parkinson, Samuel D.; Wilson, Cian
2016-04-01
Tsunami generated by submarine slides are arguably an under-considered risk in comparison to earthquake-generated tsunami. Numerical simulations of submarine slide-generated waves can be used to identify the important factors in determining wave characteristics. Here we use Fluidity, an open source finite element code, to simulate waves generated by deformable submarine slides. Fluidity uses flexible unstructured meshes combined with adaptivity which alters the mesh topology and resolution based on the simulation state, focussing or reducing resolution, when and where it is required. Fluidity also allows a number of different numerical approaches to be taken to simulate submarine slide deformation, free-surface representation, and wave generation within the same numerical framework. In this work we use a multi-material approach, considering either two materials (slide and water with a free surface) or three materials (slide, water and air), as well as a sediment model (sediment, water and free surface) approach. In all cases the slide is treated as a viscous fluid. Our results are shown to be consistent with laboratory experiments using a deformable submarine slide, and demonstrate good agreement when compared with other numerical models. The three different approaches for simulating submarine slide dynamics and tsunami wave generation produce similar waveforms and slide deformation geometries. However, each has its own merits depending on the application. Mesh adaptivity is shown to be able to reduce the computational cost without compromising the accuracy of results.
A Numerical Approach to Solving the Hall MHD Equations Including Diamagnetic Drift (Preprint)
2008-02-19
Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER FA9300-06-D-0002 0003 A Numerical Approach to Solving the Hall MHD...Loverich and U. Shumlak. Nonlinear full two-fluid study of m=0 sausage instabilities in an axisymmetric z pinch. Physics of Plasmas, (13), 2006. [19
MAPPING CLOSURE APPROXIMATION FOR REACTIVE SCALARS IN RANDOM FLOWS
Institute of Scientific and Technical Information of China (English)
ZHANG Zifan; HE Guowei
2004-01-01
The Mapping Closure Approximation (MCA) approach is developed to describe the statistics of both conserved and reactive scalars in random flows. The statistics include Probability Density Function (PDF), Conditional Dissipation Rate (CDR) and Conditional Laplacian (CL). The statistical quantities are calculated using the MCA and compared with the results of the Direct Numerical Simulation (DNS). The results obtained from the MCA are in agreement with those from the DNS. It is shown that the MCA approach can predict the statistics of reactive scalars in random flows.
Numerical Simulation of Transit-Time Ultrasonic Flowmeters by a Direct Approach.
Luca, Adrian; Marchiano, Regis; Chassaing, Jean-Camille
2016-06-01
This paper deals with the development of a computational code for the numerical simulation of wave propagation through domains with a complex geometry consisting in both solids and moving fluids. The emphasis is on the numerical simulation of ultrasonic flowmeters (UFMs) by modeling the wave propagation in solids with the equations of linear elasticity (ELE) and in fluids with the linearized Euler equations (LEEs). This approach requires high performance computing because of the high number of degrees of freedom and the long propagation distances. Therefore, the numerical method should be chosen with care. In order to minimize the numerical dissipation which may occur in this kind of configuration, the numerical method employed here is the nodal discontinuous Galerkin (DG) method. Also, this method is well suited for parallel computing. To speed up the code, almost all the computational stages have been implemented to run on graphical processing unit (GPU) by using the compute unified device architecture (CUDA) programming model from NVIDIA. This approach has been validated and then used for the two-dimensional simulation of gas UFMs. The large contrast of acoustic impedance characteristic to gas UFMs makes their simulation a real challenge.
Directory of Open Access Journals (Sweden)
Ye. S. Sherina
2014-01-01
Full Text Available This research has been aimed to carry out a study of peculiarities that arise in a numerical simulation of the electrical impedance tomography (EIT problem. Static EIT image reconstruction is sensitive to a measurement noise and approximation error. A special consideration has been given to reducing of the approximation error, which originates from numerical implementation drawbacks. This paper presents in detail two numerical approaches for solving EIT forward problem. The finite volume method (FVM on unstructured triangular mesh is introduced. In order to compare this approach, the finite element (FEM based forward solver was implemented, which has gained the most popularity among researchers. The calculated potential distribution with the assumed initial conductivity distribution has been compared to the analytical solution of a test Neumann boundary problem and to the results of problem simulation by means of ANSYS FLUENT commercial software. Two approaches to linearized EIT image reconstruction are discussed. Reconstruction of the conductivity distribution is an ill-posed problem, typically requiring a large amount of computation and resolved by minimization techniques. The objective function to be minimized is constructed of measured voltage and calculated boundary voltage on the electrodes. A classical modified Newton type iterative method and the stochastic differential evolution method are employed. A software package has been developed for the problem under investigation. Numerical tests were conducted on simulated data. The obtained results could be helpful to researches tackling the hardware and software issues for medical applications of EIT.
Transient Process of Transport Through a Quantum Dot in a Stepped Bias: a Numerical Approach
Institute of Scientific and Technical Information of China (English)
熊永建; 熊诗杰
2001-01-01
The time evolution of the current though a quantum dot responding to a stepped bias voltage is studied by a numerical approach in the mixed-valence regime and the Kondo regime. Our numerical results show the quasiperiodic oscillations of the current with a short damping time. When the deviation of the Fermi energy from the resonant dot level is increased by changing the gate voltage, the frequency of the oscillations is increased, but the average current decreases. The results also show a relatively slow oscillation in the Kondo regime.
Craig, Steven E.; Bischof, Gary H.
Closure of the counseling relationship constitutes both an ending and a beginning. Although closure signifies the ending of the present counseling relationship, many family counselors conceptualize closure as the start of a working relationship between counselor and family that may be summoned in future times of crisis or during a difficult life…
Chang, Lin-Chau; Kang, Jaw-Jou; Gau, Churn-Shiouh
2016-06-01
The main concern for container closure systems of drugs is to ensure suitability for the intended use which is associated with issues regarding protection, compatibility, safety, and performance. Among various concerns, leachables may pose a safety hazard to patients, while risks might vary depending on the dosage form and the administration route. Stringent regulatory authorities such as the European Medicines Agency and the United States Food and Drug Administration have established risk-based regulatory requirements and published corresponding guidelines to facilitate implementation. Taiwan, a member of the Pharmaceutical Inspection Convention and Pharmaceutical Inspection Co-operation Scheme, makes every effort to harmonize with international regulations and to strengthen protection of public health through regulatory controls. The aim of the present study was to investigate the regulatory framework and policies set by stringent regulatory authorities. The strategy proposed for the development of an eventual guideline was sent to the Taiwan Food and Drug Administration for decision. A risk-based, phased-in approach which was extensively discussed in the expert committee was proposed. The approach proposed herein could also serve as a starting point which is worth considered by other countries in which international harmonization is in process.
Numerical Simulation of Die Casting Technology on End Closure of Aluminium Alloy%铝合金端盖件压铸工艺的数值模拟
Institute of Scientific and Technical Information of China (English)
江政
2012-01-01
运用铸造模拟软件Procast对一模四腔的A356铝合金压铸零件进行数值模拟，分析铸件的充型凝固过程，预测缺陷。结果显示：在压射速度为2．5m／s，浇注温度为650℃，模具温度为240℃的条件下四腔同时充填，充型平稳，排气良好，得到充型完整、无缩松缩孔、气孔倾向小的铸件。%The numerical simulation of filling and solidifying process alloy A356 casting with the mould of four cavities was performed with the casting simulation software Procast, and defect was forecasted according to the result＇s analysis. The technical parameters were as follows： injection speed of 2.5 m/s, pouring temperature of 650 ℃ ,mold initial temperature of 250 ℃, under which the four cavities were simultaneous and stably filled, and the castings of better quality were obtained.
A frequency-based numerical approach for unsteady radiative transfer in participating media
Energy Technology Data Exchange (ETDEWEB)
Rousse, Daniel R. [Department of Applied Sciences, Universite du Quebec a Chicoutimi, Chicoutimi (Canada)
2008-11-15
The one-dimensional transient radiative transfer problem in the Cartesian coordinate system - an absorbing and scattering medium illuminated by a short laser pulse - is solved by the use of a discrete ordinates-finite volume method. Previous works have shown that the original numerical approach, based in the space-time domain, induces transmitted flux emerging earlier than the minimal time required by the radiation to leave the medium. Therefore, a frequency-based numerical method is formulated, implemented, and validated in this paper. Results for transmittances are accurate, without physically unrealistic behaviors at early time periods. However, the frequency-dependent approach is computationally expensive; it requires approximately five times more computational time than its temporal counterpart. Ongoing research is devoted to the optimization of these CPU requirements. (author)
A Matrix Approach to Numerical Solution of the DGLAP Evolution Equations
Ratcliffe, P G
2001-01-01
A matrix-based approach to numerical integration of the DGLAP evolution equations is presented. The method arises naturally on discretisation of the Bjorken x variable, a necessary procedure for numerical integration. Owing to peculiar properties of the matrices involved, the resulting equations take on a particularly simple form and may be solved in closed analytical form in the variable t=ln(alpha_0/alpha). Such an approach affords parametrisation via data x bins, rather than fixed functional forms. Thus, with the aid of the full correlation matrix, appraisal of the behaviour in different x regions is rendered more transparent and free of pollution from unphysical cross-correlations inherent to functional parametrisations. Computationally, the entire programme results in greater speed and stability; the matrix representation developed is extremely compact. Moreover, since the parameter dependence is linear, fitting is very stable and may be performed analytically in a single pass over the data values.
Bloch, Isabelle
2010-01-01
The area of information fusion has grown considerably during the last few years, leading to a rapid and impressive evolution. In such fast-moving times, it is important to take stock of the changes that have occurred. As such, this books offers an overview of the general principles and specificities of information fusion in signal and image processing, as well as covering the main numerical methods (probabilistic approaches, fuzzy sets and possibility theory and belief functions).
Anantharaman, Arnaud
2010-01-01
This work is a follow-up to our previous work "A numerical approach related to defect-type theories for some weakly random problems in homogenization" (preprint available on this archive). It extends and complements, both theoretically and experimentally, the results presented there. Under consideration is the homogenization of a model of a weakly random heterogeneous material. The material consists of a reference periodic material randomly perturbed by another periodic material, so that its homogenized behavior is close to that of the reference material. We consider laws for the random perturbations more general than in our previous work cited above. We prove the validity of an asymptotic expansion in a certain class of settings. We also extend the formal approach introduced in our former work. Our perturbative approach shares common features with a defect-type theory of solid state physics. The computational efficiency of the approach is demonstrated.
Hales, Joel M.; Khachatrian, Ani; Roche, Nicolas J.; Buchner, Stephen; Warner, Jeffrey; McMorrow, Dale
2016-05-01
Two numerical approaches for determining the charge generated in semiconductors via two-photon absorption (2PA) under conditions relevant for laser-based single-event effects (SEE) experiments are presented. The first approach uses a simple analytical expression incorporating a small number of experimental/material parameters while the second approach employs a comprehensive beam propagation method that accounts for all the complex nonlinear optical (NLO) interactions present. The impact of the excitation conditions, device geometry, and specific NLO interactions on the resulting collected charge in silicon devices is also discussed. These approaches can provide value to the radiation-effects community by predicting the impacts that varying experimental parameters will have on 2PA SEE measurements.
Mallet, Vivien; Sportisse, Bruno
2006-01-01
International audience; This paper estimates the uncertainty in the outputs of a chemistry-transport model due to physical parameterizations and numerical approximations. An ensemble of 20 simulations is generated from a reference simulation in which one key parameterization (chemical mechanism, dry deposition parameterization, turbulent closure, etc.) or one numerical approximation (grid size, splitting method, etc.) is changed at a time. Intercomparisons of the simulations and comparisons w...
Ortleb, Sigrun; Seidel, Christian
2017-07-01
In this second symposium at the limits of experimental and numerical methods, recent research is presented on practically relevant problems. Presentations discuss experimental investigation as well as numerical methods with a strong focus on application. In addition, problems are identified which require a hybrid experimental-numerical approach. Topics include fast explicit diffusion applied to a geothermal energy storage tank, noise in experimental measurements of electrical quantities, thermal fluid structure interaction, tensegrity structures, experimental and numerical methods for Chladni figures, optimized construction of hydroelectric power stations, experimental and numerical limits in the investigation of rain-wind induced vibrations as well as the application of exponential integrators in a domain-based IMEX setting.
Review of numerical models of cavitating flows with the use of the homogeneous approach
Directory of Open Access Journals (Sweden)
Niedźwiedzka Agnieszka
2016-06-01
Full Text Available The focus of research works on cavitation has changed since the 1960s; the behaviour of a single bubble is no more the area of interest for most scientists. Its place was taken by the cavitating flow considered as a whole. Many numerical models of cavitating flows came into being within the space of the last fifty years. They can be divided into two groups: multi-fluid and homogeneous (i.e., single-fluid models. The group of homogenous models contains two subgroups: models based on transport equation and pressure based models. Several works tried to order particular approaches and presented short reviews of selected studies. However, these classifications are too rough to be treated as sufficiently accurate. The aim of this paper is to present the development paths of numerical investigations of cavitating flows with the use of homogeneous approach in order of publication year and with relatively detailed description. Each of the presented model is accompanied by examples of the application area. This review focuses not only on the list of the most significant existing models to predict sheet and cloud cavitation, but also on presenting their advantages and disadvantages. Moreover, it shows the reasons which inspired present authors to look for new ways of more accurate numerical predictions and dimensions of cavitation. The article includes also the division of source terms of presented models based on the transport equation with the use of standardized symbols.
Herbin, H.; Pujol, O.; Hubert, P.; Petitprez, D.
2017-10-01
The knowledge of aerosol complex refractive indices on wide spectral range with high spectral resolution is important for many research fields and applications. Various combinations of experimental/theoretical/numerical approaches have been employed to determine the optical indices of aerosol particles. However, each approach has its own advantages and limitations that restrict its generalization. This article is first part of a work aimed at proposing a new technique for determining the optical constants of aerosols. Experimentally, the method is based on recording transmittance spectra of an aerosol flow from thermal infrared to UV-visible combined with the size distribution measurements. Herein, we present the theoretical and numerical bases of the algorithm developed to retrieve the imaginary and real parts of refractive indices. This model associates the Mie theory, the single subtractive Kramers-Kronig relations, and the optimal estimation method with an iterative process. In order to quantify the capabilities of the algorithm to retrieve complex refractive indices, inverse calculations are performed from simulated extinction spectra of Quartz particles whose some of optical properties are available in the literature. We have detailed each step of the procedure and performed some comparisons with the most currently employed methods. The impact of experimental accuracy and numerical simulation are investigated in terms of errors, and uncertainties on the retrieved real and imaginary parts of the complex optical index.
Review of numerical models of cavitating flows with the use of the homogeneous approach
Niedźwiedzka, Agnieszka; Schnerr, Günter H.; Sobieski, Wojciech
2016-06-01
The focus of research works on cavitation has changed since the 1960s; the behaviour of a single bubble is no more the area of interest for most scientists. Its place was taken by the cavitating flow considered as a whole. Many numerical models of cavitating flows came into being within the space of the last fifty years. They can be divided into two groups: multi-fluid and homogeneous (i.e., single-fluid) models. The group of homogenous models contains two subgroups: models based on transport equation and pressure based models. Several works tried to order particular approaches and presented short reviews of selected studies. However, these classifications are too rough to be treated as sufficiently accurate. The aim of this paper is to present the development paths of numerical investigations of cavitating flows with the use of homogeneous approach in order of publication year and with relatively detailed description. Each of the presented model is accompanied by examples of the application area. This review focuses not only on the list of the most significant existing models to predict sheet and cloud cavitation, but also on presenting their advantages and disadvantages. Moreover, it shows the reasons which inspired present authors to look for new ways of more accurate numerical predictions and dimensions of cavitation. The article includes also the division of source terms of presented models based on the transport equation with the use of standardized symbols.
Two Approaches in the Lunar Libration Theory: Analytical vs. Numerical Methods
Petrova, Natalia; Zagidullin, Arthur; Nefediev, Yurii; Kosulin, Valerii
2016-10-01
Observation of the physical libration of the Moon and the celestial bodies is one of the astronomical methods to remotely evaluate the internal structure of a celestial body without using expensive space experiments. Review of the results obtained due to the physical libration study, is presented in the report.The main emphasis is placed on the description of successful lunar laser ranging for libration determination and on the methods of simulating the physical libration. As a result, estimation of the viscoelastic and dissipative properties of the lunar body, of the lunar core parameters were done. The core's existence was confirmed by the recent reprocessing of seismic data Apollo missions. Attention is paid to the physical interpretation of the phenomenon of free libration and methods of its determination.A significant part of the report is devoted to describing the practical application of the most accurate to date the analytical tables of lunar libration built by comprehensive analytical processing of residual differences obtained when comparing the long-term series of laser observations with numerical ephemeris DE421 [1].In general, the basic outline of the report reflects the effectiveness of two approaches in the libration theory - numerical and analytical solution. It is shown that the two approaches complement each other for the study of the Moon in different aspects: numerical approach provides high accuracy of the theory necessary for adequate treatment of modern high-accurate observations and the analytic approach allows you to see the essence of the various kind manifestations in the lunar rotation, predict and interpret the new effects in observations of physical libration [2].[1] Rambaux, N., J. G. Williams, 2011, The Moon's physical librations and determination of their free modes, Celest. Mech. Dyn. Astron., 109, 85-100.[2] Petrova N., A. Zagidullin, Yu. Nefediev. Analysis of long-periodic variations of lunar libration parameters on the basis of
Closure Operators and Closure Systems on Quantaloid-Enriched Categories
Institute of Scientific and Technical Information of China (English)
Min LIU; Bin ZHAO
2013-01-01
In this paper,we introduce the fundamental notions of closure operator and closure system in the framework of quantaloid-enriched category.We mainly discuss the relationship between closure operators and adjunctions and establish the one-to-one correspondence between closure operators and closure systems on quantaloid-enriched categories.
Testing turbulent closure models with convection simulations
Snellman, J E; Mantere, M J; Rheinhardt, M; Dintrans, B
2012-01-01
Aims: To compare simple analytical closure models of turbulent Boussinesq convection for stellar applications with direct three-dimensional simulations both in homogeneous and inhomogeneous (bounded) setups. Methods: We use simple analytical closure models to compute the fluxes of angular momentum and heat as a function of rotation rate measured by the Taylor number. We also investigate cases with varying angles between the angular velocity and gravity vectors, corresponding to locating the computational domain at different latitudes ranging from the pole to the equator of the star. We perform three-dimensional numerical simulations in the same parameter regimes for comparison. The free parameters appearing in the closure models are calibrated by two fit methods using simulation data. Unique determination of the closure parameters is possible only in the non-rotating case and when the system is placed at the pole. In the other cases the fit procedures yield somewhat differing results. The quality of the closu...
Physical and numerical modelling of biomimetic approaches of natural hydrophobic surfaces
Institute of Scientific and Technical Information of China (English)
YAN YuYing
2009-01-01
Physical and numerical models of the hydrophobic and self-cleaning characteristics of an object sur-face are developed, and a micro/meso scope numerical approach and simulation based on the lattice Boltzmann method (LBM) is achieved. The modelling focuses on surface tension dominated behaviour of water droplets in air spreading on hydrophilic surface with hydrophobic strips of different sizes and contact angles under different physical and interracial conditions. Applying the LBM model, the drop-lets behaviours on heterogeneous partial wetting surfaces are studied and simulated. In the simula-tions, the interactions between the fluid-fluid interface and the partial wetting wall are typically con-sidered; the phenomena of droplets spreading and breaking up, as well as the effect of hydrophobic strips on the surface wettability or self-cleaning characteristics are simulated and studied.
Numerical approach to data processing for gamma scans: A case study of naphtha splitter column
Razali, A. M.; Yusoff, N. H.; Yahya, R.; Zain, R. M.; Ithnin, H.; Rahman, M. F. A.
2017-01-01
This paper presents a numerical approach to data processing for gamma scanning in distillation columns. A numerical algorithm is developed and implemented in a programming code to detect the presence of column malfunctions. Raw data are segmented and evaluated separately according to the number of trays inside the column. For each tray, data are divided into 4 sections: section above tray (AT), section tray (T), section below tray (BT) and section in between tray (IBT), with each section, is tested with different conditions. Results from the tests will determine the state of the trays. If the conditions of all tests are satisfied, then the algorithm will output the tray's status as `Normal', whereas if there is any condition that is not satisfied, the algorithm will detect it as `Abnormal'. This direct method is proposed for the sake of algorithm simplification. Despite its simplicity, the algorithm is proved to generate a satisfactory result in detecting the presence of tray malfunctions.
Directory of Open Access Journals (Sweden)
Jagdev Singh
2017-07-01
Full Text Available In this paper, we propose a new numerical algorithm, namely q-homotopy analysis Sumudu transform method (q-HASTM, to obtain the approximate solution for the nonlinear fractional dynamical model of interpersonal and romantic relationships. The suggested algorithm examines the dynamics of love affairs between couples. The q-HASTM is a creative combination of Sumudu transform technique, q-homotopy analysis method and homotopy polynomials that makes the calculation very easy. To compare the results obtained by using q-HASTM, we solve the same nonlinear problem by Adomian’s decomposition method (ADM. The convergence of the q-HASTM series solution for the model is adapted and controlled by auxiliary parameter ℏ and asymptotic parameter n. The numerical results are demonstrated graphically and in tabular form. The result obtained by employing the proposed scheme reveals that the approach is very accurate, effective, flexible, simple to apply and computationally very nice.
Directory of Open Access Journals (Sweden)
A. H. Bhrawy
2014-01-01
Full Text Available One of the most important advantages of collocation method is the possibility of dealing with nonlinear partial differential equations (PDEs as well as PDEs with variable coefficients. A numerical solution based on a Jacobi collocation method is extended to solve nonlinear coupled hyperbolic PDEs with variable coefficients subject to initial-boundary nonlocal conservation conditions. This approach, based on Jacobi polynomials and Gauss-Lobatto quadrature integration, reduces solving the nonlinear coupled hyperbolic PDEs with variable coefficients to a system of nonlinear ordinary differential equation which is far easier to solve. In fact, we deal with initial-boundary coupled hyperbolic PDEs with variable coefficients as well as initial-nonlocal conditions. Using triangular, soliton, and exponential-triangular solutions as exact solutions, the obtained results show that the proposed numerical algorithm is efficient and very accurate.
A semi-nonlocal numerical approach for modeling of temperature-dependent crack-wave interaction
Martowicz, Adam; Kijanka, Piotr; Staszewski, Wieslaw J.
2016-04-01
Numerical tools, which are used to simulate complex phenomena for models of complicated shapes suffer from either long computational time or accuracy. Hence, new modeling and simulation tools, which could offer reliable results within reasonable time periods, are highly demanded. Among other approaches, the nonlocal methods have appeared to fulfill these requirements quite efficiently and opened new perspectives for accurate simulations based on crude meshes of the model's degrees of freedom. In the paper, the preliminary results are shown for simulations of the phenomenon of temperature-dependent crack-wave interaction for elastic wave propagation in a model of an aluminum plate. Semi-nonlocal finite differences are considered to solve the problem of thermoelasticity - based on the discretization schemes, which were already proposed by the authors and taken from the previously published work. Numerical modeling is used to examine wave propagation primarily in the vicinity of a notch. Both displacement and temperature fields are sought in the investigated case study.
Numerical prediction of kinetic model for enzymatic hydrolysis of cellulose using DAE-QMOM approach
Jamil, N. M.; Wang, Q.
2016-06-01
Bioethanol production from lignocellulosic biomass consists of three fundamental processes; pre-treatment, enzymatic hydrolysis, and fermentation. In enzymatic hydrolysis phase, the enzymes break the cellulose chains into sugar in the form of cellobiose or glucose. A currently proposed kinetic model for enzymatic hydrolysis of cellulose that uses population balance equation (PBE) mechanism was studied. The complexity of the model due to integrodifferential equations makes it difficult to find the analytical solution. Therefore, we solved the full model of PBE numerically by using DAE-QMOM approach. The computation was carried out using MATLAB software. The numerical results were compared to the asymptotic solution developed in the author's previous paper and the results of Griggs et al. Besides confirming the findings were consistent with those references, some significant characteristics were also captured. The PBE model for enzymatic hydrolysis process can be solved using DAE-QMOM method. Also, an improved understanding of the physical insights of the model was achieved.
Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution
Faranda, Davide; Turchetti, Giorgio; Vaienti, Sandro
2011-01-01
In this paper we perform an analytical and numerical study of Extreme Value distributions in discrete dynamical systems. In this setting, recent works have shown how to get a statistics of extremes in agreement with the classical Extreme Value Theory. We pursue these investigations by giving analytical expressions of Extreme Value distribution parameters for maps that have an absolutely continuous invariant measure. We compare these analytical results with numerical experiments in which we study the convergence to limiting distributions using the so called block-maxima approach, pointing out in which cases we obtain robust estimation of parameters. In regular maps for which mixing properties do not hold, we show that the fitting procedure to the classical Extreme Value Distribution fails, as expected. However, we obtain an empirical distribution that can be explained starting from a different observable function for which Nicolis et al. [2006] have found analytical results.
The basic approach to age-structured population dynamics models, methods and numerics
Iannelli, Mimmo
2017-01-01
This book provides an introduction to age-structured population modeling which emphasises the connection between mathematical theory and underlying biological assumptions. Through the rigorous development of the linear theory and the nonlinear theory alongside numerics, the authors explore classical equations that describe the dynamics of certain ecological systems. Modeling aspects are discussed to show how relevant problems in the fields of demography, ecology, and epidemiology can be formulated and treated within the theory. In particular, the book presents extensions of age-structured modelling to the spread of diseases and epidemics while also addressing the issue of regularity of solutions, the asymptotic behaviour of solutions, and numerical approximation. With sections on transmission models, non-autonomous models and global dynamics, this book fills a gap in the literature on theoretical population dynamics. The Basic Approach to Age-Structured Population Dynamics will appeal to graduate students an...
Indian Academy of Sciences (India)
Mrinal Kumar Das; Mahadev Patgiri; N Nimai Singh
2005-12-01
We briefly outline the two popular approaches on radiative corrections to neutrino masses and mixing angles, and then carry out a detailed numerical analysis for a consistency check between them in MSSM. We find that the two approaches are nearly consistent with a discrepancy factor of 4.2% with running vacuum expectation value (VEV) (13% for scale-independent VEV) in mass eigenvalues at low-energy scale but the predictions on mixing angles are almost consistent. We check the stability of the three types of neutrino models, i.e., hierarchical, inverted hierarchical and degenerate models, under radiative corrections, using both approaches, and find consistent conclusions. The neutrino mass models which are found to be stable under radiative corrections in MSSM are the normal hierarchical model and the inverted hierarchical model with opposite CP parity. We also carry out numerical analysis on some important conjectures related to radiative corrections in the MSSM, viz., radiative magnification of solar and atmospheric mixings in the case of nearly degenerate model having same CP parity (MPR conjecture) and radiative generation of solar mass scale in exactly two-fold degenerate model with opposite CP parity and non-zero 3 (JM conjecture). We observe certain exceptions to these conjectures. We find a new result that both solar mass scale and 3 can be generated through radiative corrections at low energy scale. Finally the effect of scale-dependent vacuum expectation value in neutrino mass renormalisation is discussed.
Shi, Guangyuan; Li, Song; Huang, Ke; Li, Zile; Zheng, Guoxing
2016-10-01
We have developed a new numerical ray-tracing approach for LIDAR signal power function computation, in which the light round-trip propagation is analyzed by geometrical optics and a simple experiment is employed to acquire the laser intensity distribution. It is relatively more accurate and flexible than previous methods. We emphatically discuss the relationship between the inclined angle and the dynamic range of detector output signal in biaxial LIDAR system. Results indicate that an appropriate negative angle can compress the signal dynamic range. This technique has been successfully proved by comparison with real measurements.
Minimal duality breaking in the Kallen Lehman approach to 3D Ising model: A numerical test
Astorino, Marco; Canfora, Fabrizio; Martínez, Cristián; Parisi, Luca
2008-06-01
A Kallen-Lehman approach to 3D Ising model is analyzed numerically both at low and high temperatures. It is shown that, even assuming a minimal duality breaking, one can fix three parameters of the model to get a very good agreement with the Monte Carlo results at high temperatures. With the same parameters the agreement is satisfactory both at low and near critical temperatures. How to improve the agreement with Monte Carlo results by introducing a more general duality breaking is shortly discussed.
A combined analytic-numeric approach for some boundary-value problems
Directory of Open Access Journals (Sweden)
Mustafa Turkyilmazoglu
2016-02-01
Full Text Available A combined analytic-numeric approach is undertaken in the present work for the solution of boundary-value problems in the finite or semi-infinite domains. Equations to be treated arise specifically from the boundary layer analysis of some two and three-dimensional flows in fluid mechanics. The purpose is to find quick but accurate enough solutions. Taylor expansions at either boundary conditions are computed which are next matched to the other asymptotic or exact boundary conditions. The technique is applied to the well-known Blasius as well as Karman flows. Solutions obtained in terms of series compare favorably with the existing ones in the literature.
Comparison of two inlet boundary approaches in numerical simulation of car ventilation outlet flow
Directory of Open Access Journals (Sweden)
Talanda Tomáš
2016-01-01
Full Text Available The paper is concerned with the comparison of two inlet boundary approaches of numerical simulations. The first approach is based on the simulation of a sufficiently long duct upstream the area of interest with known volumetric flow rate. The second approach rests on the experimental measurement of the section closer to the area of interest. The experimental measurement provides velocity profile and in addition turbulent intensity compared to the first approach where only a velocity profile can be computed according to known volumetric flow rate. A simplified model of car ventilation outlet was chosen as a test case. The model consists of circular and rectangular duct, area of interest (closing flap, vertical slats and horizontal slats and outlet box. We have compared the two mentioned inlet boundary approaches for two distinct values of volumetric flow rate for which the experimental data of the section upstream of the area of interest are available. The velocity and the turbulent kinetic energy profiles downstream of the area of interest were chosen as comparative characteristics.
Directory of Open Access Journals (Sweden)
Sonam Singh
2014-01-01
Full Text Available This paper presents a numerical study of natural convection within a wavy enclosure heated via corner heating. The considered enclosure is a square enclosure with left wavy side wall. The vertical wavy wall of the enclosure and both of the corner heaters are maintained at constant temperature, Tc and Th, respectively, with Th>Tc while the remaining horizontal, bottom, top and side walls are insulated. A penalty element-free Galerkin approach with reduced gauss integration scheme for penalty terms is used to solve momentum and energy equations over the complex domain with wide range of parameters, namely, Rayleigh number (Ra, Prandtl number (Pr, and range of heaters in the x- and y-direction. Numerical results are represented in terms of isotherms, streamlines, and Nusselt number. It is observed that the rate of heat transfer depends to a great extent on the Rayleigh number, Prandtl number, length of the corner heaters and the shape of the heat transfer surface. The consistent performance of the adopted numerical procedure is verified by comparison of the results obtained through the present meshless technique with those existing in the literature.
Directory of Open Access Journals (Sweden)
Qingxue Huang
2017-01-01
Full Text Available In this paper, a robust, effective, and accurate numerical approach is proposed to obtain the numerical solution of fractional differential equations. The principal characteristic of the approach is the new orthogonal functions based on shifted Legendre polynomials to the fractional calculus. Also the fractional differential operational matrix is driven. Then the matrix with the Tau method is utilized to transform this problem into a system of linear algebraic equations. By solving the linear algebraic equations, the numerical solution is obtained. The approach is tested via some examples. It is shown that the FLF yields better results. Finally, error analysis shows that the algorithm is convergent.
Kumar, J L G; Zhao, Y Q
2011-03-01
Constructed wetlands (CWs) for wastewater treatment have evolved substantially over the last decades and have been recognized as an effective means of "green technology" for wastewater treatment. This paper reviews the numerous modeling approaches ranging from simple first-order models to more complex dynamic models of treatment behaviour in CWs. The main objective of the modeling work is to better understand the process in CWs and optimize design criteria. A brief study in this review discusses the efforts taken to describe the process-based model for the efficient removal of pollutants in CWs. Obtaining better insights is essential to understand the hydraulic and biochemical processes in CWs. Currently, employed modeling approaches can be seen in two categories, i.e. "black-box models" and "process-based models". It is evident that future development in wetland technology will depend on improved scientific knowledge of internal treatment mechanisms.
A practical approach to extract symplectic transfer maps numerically for arbitrary magnetic elements
Li, Yongjun
2015-01-01
We introduce a practical approach to extract the symplectic transfer maps for arbitrary magnetic beam-line elements. Beam motion in particle accelerators depends on linear and nonlinear magnetic fields of the beam-line elements. These elements are usually modeled as magnetic multipoles with constant field strengths in the longitudinal direction (i.e., hard-edge model) in accelerator design and modeling codes. For magnets with complicated structures such as insertion devices or fields with significant longitudinal variation effects, the simplified models may not be sufficient to char- acterize beam dynamics behaviors accurately. A numerical approach has been developed to extract symplectic transfer maps from particle trajectory tracking simulation that uses magnetic field data provided by three-dimensional magnetic field modeling codes or experimental measurements. The extracted transfer maps can be used in linear optics design and nonlinear dynamics optimization to achieve more realistic results.
Investigation of numerical solution approaches to multicomponent batch distillation in packed beds
Energy Technology Data Exchange (ETDEWEB)
Wajge, R.M.; Wilson, J.M.; Pekny, J.F.; Reklaitis, G.V. [Purdue Univ., Lafayette, IN (United States). School of Chemical Engineering
1997-05-01
Finite difference and orthogonal collocation techniques are used to obtain numerical solution of the differential contactor model that represents a packed column. In the orthogonal collocation approach, polynomial approximation to the model equations results in a sparse system of equations that is much smaller in dimension than with the other methods. Exploiting this sparsity and choosing the proper order for approximating polynomial are the critical issues. Higher CPU time associated with higher order of the polynomial necessitates use of finite elements in the collocation techniques. The authors study the accuracy and efficiency issues underlying all these approaches with the help of hydrocarbon mixture and ethanol esterification examples. The later case study is considered with both with and without the presence of reaction.
Numerical and experimental approaches to study soil transport and clogging in granular filters
Kanarska, Y.; Smith, J. J.; Ezzedine, S. M.; Lomov, I.; Glascoe, L. G.
2012-12-01
Failure of a dam by erosion ranks among the most serious accidents in civil engineering. The best way to prevent internal erosion is using adequate granular filters in the transition areas where important hydraulic gradients can appear. In case of cracking and erosion, if the filter is capable of retaining the eroded particles, the crack will seal and the dam safety will be ensured. Numerical modeling has proved to be a cost-effective tool for improving our understanding of physical processes. Traditionally, the consideration of flow and particle transport in porous media has focused on treating the media as continuum. Practical models typically address flow and transport based on the Darcy's law as a function of a pressure gradient and a medium-dependent permeability parameter. Additional macroscopic constitutes describe porosity, and permeability changes during the migration of a suspension through porous media. However, most of them rely on empirical correlations, which often need to be recalibrated for each application. Grain-scale modeling can be used to gain insight into scale dependence of continuum macroscale parameters. A finite element numerical solution of the Navier-Stokes equations for fluid flow together with Lagrange multiplier technique for solid particles was applied to the simulation of soil filtration in the filter layers of gravity dam. The numerical approach was validated through comparison of numerical simulations with the experimental results of base soil particle clogging in the filter layers performed at ERDC. The numerical simulation correctly predicted flow and pressure decay due to particle clogging. The base soil particle distribution was almost identical to those measured in the laboratory experiment. It is believed that the agreement between simulations and experimental data demonstrates the applicability of the proposed approach for prediction of the soil transport and clogging in embankment dams. To get more precise understanding of
Macroscopic analysis of gas-jet wiping: Numerical simulation and experimental approach
Lacanette, Delphine; Gosset, Anne; Vincent, Stéphane; Buchlin, Jean-Marie; Arquis, Éric
2006-04-01
Coating techniques are frequently used in industrial processes such as paper manufacturing, wire sleeving, and in the iron and steel industry. Depending on the application considered, the thickness of the resulting substrate is controlled by mechanical (scraper), electromagnetic (if the entrained fluid is appropriated), or hydrodynamic (gas-jet wiping) operations. This paper deals with the latter process, referred to as gas-jet wiping, in which a turbulent slot jet is used to wipe the coating film dragged by a moving substrate. This mechanism relies on the gas-jet-liquid film interaction taking place on the moving surface. The aim of this study is to compare the results obtained by a lubrication one-dimensional model, numerical volume of fluid-large eddy simulation (VOF-LES) modeling and an experimental approach. The investigation emphasizes the effect of the controlling wiping parameters, i.e., the pressure gradient and shear stress distributions induced by the jet, on the shape of the liquid film. Those profiles obtained experimentally and numerically for a jet impinging on a dry fixed surface are compared. The effect of the substrate motion and the presence of the dragged liquid film on these actuators are analyzed through numerical simulations. Good agreement is found between the film thickness profile in the wiping zone obtained from the VOF-LES simulations and with the analytical model, provided that a good model for the wiping actuators is used. The effect of the gas-jet nozzle to substrate standoff distance on the final coating thickness is analyzed; the experimental and predicted values are compared for a wide set of conditions. Finally, the occurrence of the splashing phenomenon, which is characterized by the ejection of droplets from the runback film flow at jet impingement, thus limiting the wiping process, is investigated through experiments and numerical simulations.
A neural approach for the numerical modeling of two-dimensional magnetic hysteresis
Cardelli, E.; Faba, A.; Laudani, A.; Riganti Fulginei, F.; Salvini, A.
2015-05-01
This paper deals with a neural network approach to model magnetic hysteresis at macro-magnetic scale. Such approach to the problem seems promising in order to couple the numerical treatment of magnetic hysteresis to FEM numerical solvers of the Maxwell's equations in time domain, as in case of the non-linear dynamic analysis of electrical machines, and other similar devices, making possible a full computer simulation in a reasonable time. The neural system proposed consists of four inputs representing the magnetic field and the magnetic inductions components at each time step and it is trained by 2-d measurements performed on the magnetic material to be modeled. The magnetic induction B is assumed as entry point and the output of the neural system returns the predicted value of the field H at the same time step. A suitable partitioning of the neural system, described in the paper, makes the computing process rather fast. Validations with experimental tests and simulations for non-symmetric and minor loops are presented.
Lenarcic, M.; Bauer, Ch.; Giese, M.; Jung, A.
2016-11-01
The prediction of characteristics and flow phenomena in reversible pump-turbines becomes increasingly important, since operations under off-design conditions are required to respond to frequency fluctuations within the electrical grid as fast as possible. Fulfilling the requirements of a stable and reliable operation under continuously expanding operating ranges challenges the hydraulic design and requires ambitious developments. Beyond that, precise estimations of occurring flow phenomena combined with a detailed understanding of their causes and mechanisms are essential. This study aims at predicting the S-shaped characteristics of two reversible pump-turbines by using different numerical approaches. Therefore, measurements at a constant wicket-gate opening of Δγ = 10° were done. Based on these experimental data, unsteady flow simulations are performed under steady and transient operating conditions respectively: Starting from the best efficiency point in generating mode, through the runaway, along the S-curve, down to operation in reverse pump mode. The hydraulic machines are spatially discretized in model size with a near-wall refinement of y + mean ≤ 5 and y + mean ≥ 30. The application of two different solvers discloses deviations in underlying methods. The turbulence modeling is basically executed by the k-ω-SST and the standard k-ɛ model. Focusing on higher order numerics, the Explicit Algebraic Reynolds Stress Model (EARSM) is selected in the commercial code and extended with an approach for curvature correction (EARSM- CC). In the open-source software, the four-equation v2-f model assumes the role of higher order numerics. The temporal discretization errors are observed using three different time-step sizes. As a supplement, experimental data obtained from the HydroDyna pump-turbine are used as additional validation, providing integral quantities and local pressure distributions at an operating point set on the S-curve. To sum this work up, a
King, Ryan S; Richardson, Curtis J
2003-06-01
Ioassessment is used worldwide to monitor aquatic health but is infrequently used with risk-assessment objectives, such as supporting the development of defensible, numerical water-quality criteria. To this end, we present a generalized approach for detecting potential ecological thresholds using assemblage-level attributes and a multimetric index (Index of Biological Integrity-IBI) as endpoints in response to numerical changes in water quality. To illustrate the approach, we used existing macroinvertebrate and surface-water total phosphorus (TP) datasets from an observed P gradient and a P-dosing experiment in wetlands of the south Florida coastal plain nutrient ecoregion. Ten assemblage attributes were identified as potential metrics using the observational data, and five were validated in the experiment. These five core metrics were subjected individually and as an aggregated Nutrient-IBI to nonparametric changepoint analysis (nCPA) to estimate cumulative probabilities of a threshold response to TP. Threshold responses were evident for all metrics and the IBI, and were repeatable through time. Results from the observed gradient indicated that a threshold was > or = 50% probable between 12.6 and 19.4 microg/L TP for individual metrics and 14.8 microg/L TP for the IBI. Results from the P-dosing experiment revealed > or = 50% probability of a response between 11.2 and 13.0 microg/L TP for the metrics and 12.3 microg/L TP for the IBI. Uncertainty analysis indicated a low (typically > or = 5%) probability that an IBI threshold occurred at or = 95% certainty that the threshold was 12-15 microg/L is likely to cause degradation of macroinvertebrate assemblage structure and function, a reflection of biological integrity, in the study area. This finding may assist in the development of a numerical water-quality criterion for TP in this ecoregion, and illustrates the utility of bioassessment to environmental decision-making.
Comparison of Numerical Approaches to a Steady-State Landscape Equation
Bachman, S.; Peckham, S.
2008-12-01
A mathematical model of an idealized fluvial landscape has been developed, in which a land surface will evolve to preserve dendritic channel networks as the surface is lowered. The physical basis for this model stems from the equations for conservation of mass for water and sediment. These equations relate the divergence of the 2D vector fields showing the unit-width discharge of water and sediment to the excess rainrate and tectonic uplift on the land surface. The 2D flow direction is taken to be opposite to the water- surface gradient vector. These notions are combined with a generalized Manning-type flow resistance formula and a generalized sediment transport law to give a closed mathematical system that can, in principle, be solved for all variables of interest: discharge of water and sediment, land surface height, vertically- averaged flow velocity, water depth, and shear stress. The hydraulic geometry equations (Leopold et. al, 1964, 1995) are used to incorporate width, depth, velocity, and slope of river channels as powers of the mean-annual river discharge. Combined, they give the unit- width discharge of the stream as a power, γ, of the water surface slope. The simplified steady-state model takes into account three components among those listed above: conservation of mass for water, flow opposite the gradient, and a slope-discharge exponent γ = -1 to reflect mature drainage networks. The mathematical representation of this model appears as a second-order hyperbolic partial differential equation (PDE) where the diffusivity is inversely proportional to the square of the local surface slope. The highly nonlinear nature of this PDE has made it very difficult to solve both analytically and numerically. We present simplistic analytic solutions to this equation which are used to test the validity of the numerical algorithms. We also present three such numerical approaches which have been used in solving the differential equation. The first is based on a
National Research Council Canada - National Science Library
Hang Zhou; Yuehong Su; Michele Bottarelli; Marco Bortoloni; Shenyi Wu
2015-01-01
This study presents a numerical validation of a new approach to model single junction PV cell under non-uniform illumination for low-concentration solar collectors such as compound parabolic concentrators (CPC...
Reinforced concrete structures loaded by snow avalanches : numerical and experimental approaches.
Ousset, I.; Bertrand, D.; Brun, M.; Limam, A.; Naaim, M.
2012-04-01
Today, due to the extension of occupied areas in mountainous regions, new strategies for risk mitigation have to be developed. In the framework of risk analysis, these latter have to take into account not only the natural hazard description but also the physical vulnerability of the exposed structures. From a civil engineering point of view, the dynamic behavior of column or portico was widely investigated especially in the case of reinforced concrete and steel. However, it is not the case of reinforced concrete walls for which only the in-plan dynamic behavior (shear behavior) has been studied in detail in the field of earthquake engineering. Therefore, the aim of this project is to study the behavior of reinforced concrete civil engineering structures submitted to out-of-plan dynamic loadings coming from snow avalanche interaction. Numerical simulations in 2D or 3D by the finite element method (FEM) are presented. The approach allows solving mechanical problems in dynamic condition involving none linearities (especially none linear materials). Thus, the structure mechanical response can be explored in controlled conditions. First, a reinforced concrete wall with a L-like shape is considered. The structure is supposed to represent a French defense structure dedicated to protect people against snow avalanches. Experimental pushover tests have been performed on a physical model. The experimental tests consisted to apply a uniform distribution of pressure until the total collapse of the wall. A 2D numerical model has been developed to simulate the mechanical response of the structure under quasi-static loading. Numerical simulations have been compared to experimental datas and results gave a better understanding of the failure mode of the wall. Moreover, the influence of several parameters (geometry and the mechanical properties) is also presented. Secondly, punching shear experimental tests have also been carried out. Reinforced concrete slabs simply supported have
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-04-01
This report addresses the site characterization of three historical underground storage tank (UST) petroleum hydrocarbon release sites identified as 25-3101-1, 25-3102-3, and 25-3152-1. The sites are located within the Nevada Test Site in Area 25 at Buildings 3101, 3102, and 3152. The characterization was completed to support administrative closure of the sites. Characterization was completed using drilling equipment to delineate the extent of hydrocarbon impact. Clean closure had been previously attempted at each of these sites using backhoe equipment without success due to adjacent structures, buried utilities, or depth restrictions associated with each site. Although the depth and extent of hydrocarbon impact was determined to be too extensive for clean closure, it was verified through drilling that the sites should be closed through an administrative closure. The Nevada Administrative Code ``A Through K`` evaluation completed for each site supports that there is no significant risk to human health or the environment from the impacted soils remaining at each site.
Xu, Y.; Xia, J.; Miller, R.D.
2007-01-01
The need for incorporating the traction-free condition at the air-earth boundary for finite-difference modeling of seismic wave propagation has been discussed widely. A new implementation has been developed for simulating elastic wave propagation in which the free-surface condition is replaced by an explicit acoustic-elastic boundary. Detailed comparisons of seismograms with different implementations for the air-earth boundary were undertaken using the (2,2) (the finite-difference operators are second order in time and space) and the (2,6) (second order in time and sixth order in space) standard staggered-grid (SSG) schemes. Methods used in these comparisons to define the air-earth boundary included the stress image method (SIM), the heterogeneous approach, the scheme of modifying material properties based on transversely isotropic medium approach, the acoustic-elastic boundary approach, and an analytical approach. The method proposed achieves the same or higher accuracy of modeled body waves relative to the SIM. Rayleigh waves calculated using the explicit acoustic-elastic boundary approach differ slightly from those calculated using the SIM. Numerical results indicate that when using the (2,2) SSG scheme for SIM and our new method, a spatial step of 16 points per minimum wavelength is sufficient to achieve 90% accuracy; 32 points per minimum wavelength achieves 95% accuracy in modeled Rayleigh waves. When using the (2,6) SSG scheme for the two methods, a spatial step of eight points per minimum wavelength achieves 95% accuracy in modeled Rayleigh waves. Our proposed method is physically reasonable and, based on dispersive analysis of simulated seismographs from a layered half-space model, is highly accurate. As a bonus, our proposed method is easy to program and slightly faster than the SIM. ?? 2007 Society of Exploration Geophysicists.
A participatory modelling approach to developing a numerical sediment dynamics model
Jones, Nicholas; McEwen, Lindsey; Parker, Chris; Staddon, Chad
2016-04-01
Fluvial geomorphology is recognised as an important consideration in policy and legislation in the management of river catchments. Despite this recognition, limited knowledge exchange occurs between scientific researchers and river management practitioners. An example of this can be found within the limited uptake of numerical models of sediment dynamics by river management practitioners in the United Kingdom. The uptake of these models amongst the applied community is important as they have the potential to articulate how, at the catchment-scale, the impacts of management strategies of land-use change affect sediment dynamics and resulting channel quality. This paper describes and evaluates a new approach which involves river management stakeholders in an iterative and reflexive participatory modelling process. The aim of this approach was to create an environment for knowledge exchange between the stakeholders and the research team in the process of co-constructing a model. This process adopted a multiple case study approach, involving four groups of river catchment stakeholders in the United Kingdom. These stakeholder groups were involved in several stages of the participatory modelling process including: requirements analysis, model design, model development, and model evaluation. Stakeholders have provided input into a number of aspects of the modelling process, such as: data requirements, user interface, modelled processes, model assumptions, model applications, and model outputs. This paper will reflect on this process, in particular: the innovative methods used, data generated, and lessons learnt.
Numerical approach to model independently reconstruct f (R ) functions through cosmographic data
Pizza, Liberato
2015-06-01
The challenging issue of determining the correct f (R ) among several possibilities is revised here by means of numerical reconstructions of the modified Friedmann equations around the redshift interval z ∈[0 ,1 ] . Frequently, a severe degeneracy between f (R ) approaches occurs, since different paradigms correctly explain present time dynamics. To set the initial conditions on the f (R ) functions, we involve the use of the so-called cosmography of the Universe, i.e., the technique of fixing constraints on the observable Universe by comparing expanded observables with current data. This powerful approach is essentially model independent, and correspondingly we got a model-independent reconstruction of f (R (z )) classes within the interval z ∈[0 ,1 ]. To allow the Hubble rate to evolve around z ≤1 , we considered three relevant frameworks of effective cosmological dynamics, i.e., the Λ CDM model, the Chevallier-Polarski-Linder parametrization, and a polynomial approach to dark energy. Finally, cumbersome algebra permits passing from f (z ) to f (R ), and the general outcome of our work is the determination of a viable f (R ) function, which effectively describes the observed Universe dynamics.
A numerical approach to model independently reconstruct $f(R)$ functions through cosmographic data
Pizza, Liberato
2014-01-01
The challenging issue of determining the correct $f(R)$ among several possibilities is here revised by means of numerical reconstructions of the modified Friedmann equations around the redshift interval $z\\in[0,1]$. Frequently, a severe degeneracy between $f(R)$ approaches occurs, since different paradigms correctly explain present time dynamics. To set the initial conditions on the $f(R)$ functions, we involve the use of the so called cosmography of the Universe, i.e. the technique of fixing constraints on the observable Universe by comparing expanded observables with current data. This powerful approach is essentially model independent and correspondingly we got a model independent reconstruction of $f(z)$ classes within the interval $z\\in[0,1]$. To allow the Hubble rate to evolve around $z\\leq1$, we considered three relevant frameworks of effective cosmological dynamics, i.e. the $\\Lambda$CDM model, the CPL parametrization and a polynomial approach to dark energy. Finally cumbersome algebra permits to pass...
Directory of Open Access Journals (Sweden)
A D Macleod
2009-01-01
Full Text Available Aim: To observe the incidence of full or partial eyelid closure at death. Materials and Methods: The presence of ptosis was recorded in 100 consecutive hospice patient deaths. Results: Majority (63% of the patients died with their eyes fully closed, however, 37% had bilateral ptosis at death, with incomplete eye closure. In this study, central nervous system tumor involvement and/or acute hepatic encephalopathy appeared to be pre-mortem risk factors of bilateral ptosis at death. Conclusion: Organicity and not psychogenicity is, therefore, the likely etiology of failure of full eyelid closure at death.
Calibration of the 4pi gamma-ray spectrometer using a new numerical simulation approach.
Nafee, Sherif S; Badawi, Mohamed S; Abdel-Moneim, Ali M; Mahmoud, Seham A
2010-09-01
The 4pi gamma-counting system is well suited for analysis of small environmental samples of low activity because it combines advantages of the low background and the high detection efficiency due to the 4pi solid angle. A new numerical simulation approach is proposed for the HPGe well-type detector geometry to calculate the full-energy peak and the total efficiencies, as well as to correct for the coincidence summing effect. This method depends on a calculation of the solid angle subtended by the source to the detector at the point of entrance, (Abbas, 2006a). The calculations are carried out for non-axial point and cylindrical sources inside the detector cavity. Attenuation of photons within the source itself (self-attenuation), the source container, the detector's end-cap and the detector's dead layer materials is also taken into account. In the Belgium Nuclear Research Center, low-activity aqueous solutions of (60)Co and (88)Y in small vials are routinely used to calibrate a gamma-ray p-type well HPGe detector in the 60-1836keV energy range. Efficiency values measured under such conditions are in good agreement with those obtained by the numerical simulation.
Directory of Open Access Journals (Sweden)
Cheng Ma
2016-01-01
Full Text Available This paper is a study of the numerical implementation of the spatial elastoplastic damage model of concrete by isogeometric analysis (IGA method from three perspectives: the geometric modeling and the numerical formulation via IGA method, the constitutive model of concrete, and the solution algorithms for the local and global problems. The plasticity of concrete is considered on the basis of a nonassociated flow rule, where a three-parameter Barcelona yield surface and a modified Drucker-Prager plastic potential are used. The damage evolution of concrete driven by the internal variables is expressed by a piecewise function. In the study, the return-mapping algorithm and the substepping strategy are used for stress updating, and a new dissipation-based arc-length method with constraint path that considers the combined contribution of plasticity and damage to the energy dissipation is employed to trace the equilibrium path. After comparisons between simulation results and experimental data, the use of the elastoplastic damage model in the framework of IGA approach is proven to be practical in reflecting material properties of concrete.
3-D-numerical approach to simulate an avalanche impact into a reservoir
Directory of Open Access Journals (Sweden)
R. Gabl
2015-06-01
Full Text Available The impact of an avalanche into a reservoir induces an impulse wave, which poses a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting outflow volume over structures and dams, formulas, which base on different simplifying assumptions, can be used. Further project-specific investigations by means of a scale model test or numerical simulations are advisable for complex reservoirs as well as the inclusion of hydraulic structures such as spillways. The paper presents a new approach for a 3-D-numerical simulation of an avalanche impact into a reservoir. In this model concept the energy and mass of the avalanche are represented by accelerated water on the real hill slope. Instead of snow, only water and air are used to simulate the moving avalanche with the software FLOW-3D. A significant advantage of this assumption is the self-adaptation of the model avalanche onto the terrain. In order to reach good comparability of the results with existing research at the ETH Zürich, a simplified reservoir geometry is investigated. Thus, a reference case has been analysed including a variation of three geometry parameters (still water depth in the reservoir, freeboard of the dam and reservoir width.
A parallel approach for image segmentation by numerical minimization of a second-order functional
Zanella, Riccardo; Zanetti, Massimo; Ruggiero, Valeria
2016-10-01
Because of its attractive features, image segmentation has shown to be a promising tool in remote sensing. A known drawback about its implementation is computational complexity. Recently in [1] an effcient numerical method has been proposed for the minimization of a second-order variational approximation of the Blake-Zissermann functional. The method is an especially tailored version of the block-coordinate descent algorithm (BCDA). In order to enable the segmentation of large-size gridded data, such as Digital Surface Models, we combine a domain decomposition technique with BCDA and a parallel interconnection rule among blocks of variables. We aim to show that a simple tiling strategy enables us to treat large images even in a commodity multicore CPU, with no need of specific post-processing on tiles junctions. From the point of view of the performance, little computational effort is required to separate data in subdomains and the running time is mainly spent in concurrently solving the independent subproblems. Numerical results are provided to evaluate the effectiveness of the proposed parallel approach.
Numerical study of chiral plasma instability within the classical statistical field theory approach
Buividovich, P V
2015-01-01
We report on a numerical study of the real-time dynamics of chirally imbalanced lattice Dirac fermions coupled to dynamical electromagnetic field. To this end we use the classical statistical field theory approach, in which the quantum evolution of fermions is simulated exactly, and electromagnetic fields are treated as classical. Motivated by recent experiments on chirally imbalanced Dirac semimetals, we use the Wilson-Dirac lattice Hamiltonian for fermions in order to model the emergent nature of chiral symmetry at low energies. In general, we observe that the backreaction of fermions on the electromagnetic field prevents the system from acquiring large chirality imbalance. In the case of chirality pumping in parallel electric and magnetic fields, electric field is screened by the produced on-shell fermions and the accumulation of chirality is hence stopped. In the case of evolution with initially present chirality imbalance, axial charge tends to decay at the expense of nonzero helicity of electromagnetic ...
Numerical approach to the low-doping regime of the t-J model
Bonča, J.; Maekawa, S.; Tohyama, T.
2007-07-01
We develop an efficient numerical method for the description of a single-hole motion in the antiferromagnetic background. The method is free of finite-size effects and allows the calculation of physical properties at an arbitrary wave vector. A methodical increase of the functional space leads to results that are valid in the thermodynamic limit. We found good agreement with cumulant expansion, exact-diagonalization approaches on finite lattices as well as self-consistent Born approximations. The method allows a straightforward addition of other inelastic degrees of freedom, such as lattice effects. Our results confirm the existence of a finite quasiparticle weight near the band minimum for a single hole and the existence of stringlike peaks in the single-hole spectral function.
Droplet in micro-channels: A numerical approach using an adaptive two phase flow solver
Fullana, Jose-Maria; Popinet, Stéphane; Josserand, Christophe
2015-01-01
We propose a numerical approach to study the mechanics of a flowing bubble in a constraint micro channel. Using an open source two phase flow solver (Gerris, gfs.sourceforge.net) we compute solutions of the bubble dynamics (i.e. shape and terminal velocity) induced by the interaction between the bubble movement, the Laplace pressure variation, and the lubrication film near the channel wall. Quantitative and qualitative results are presented and compared against both theory and experimental data for small Capillary numbers. We discuss the technical issues of explicit integration methods on small Capillary numbers computations, and the possibility of adding Van der Walls forces to give a more precise picture of the Droplet-based microfluidic problem.
A Fractional PDE Approach to Turbulent Mixing; Part II: Numerical Simulation
Samiee, Mehdi; Zayernouri, Mohsen
2016-11-01
We propose a generalizing fractional order transport model of advection-diffusion kind with fractional time- and space-derivatives, governing the evolution of passive scalar turbulence. This approach allows one to incorporate the nonlocal and memory effects in the underlying anomalous diffusion i.e., sub-to-standard diffusion to model the trapping of particles inside the eddied, and super-diffusion associated with the sudden jumps of particles from one coherent region to another. For this nonlocal model, we develop a high order numerical (spectral) method in addition to a fast solver, examined in the context of some canonical problems. PhD student, Department of Mechanical Engineering, & Department Computational Mathematics, Science, and Engineering.
Spanu, A; Barsotti, S
2015-01-01
Since the seventies, several reconstruction techniques have been proposed, and are currently used, to extrapolate and quantify eruptive parameters from sampled deposit datasets. Discrete numbers of tephra ground loadings or stratigraphic records are usually processed to estimate source eruptive values. Reconstruction techniques like Pyle, Power law and Weibull are adopted as standard to quantify the erupted mass (or volume) whereas Voronoi for reconstructing the granulometry. Reconstructed values can be affected by large uncertainty due to complexities occurring within the atmospheric dispersion and deposition of volcanic particles. Here we want to quantify the sensitivity of reconstruction techniques, and to quantify how much estimated values of mass and grain size differ from emitted and deposited ones. We adopted a numerical approach simulating with a dispersal code a mild explosive event occurring at Mt. Etna, with eruptive parameters similar to those estimated for eruptions occurred in the last decade. T...
Institute of Scientific and Technical Information of China (English)
WANG Weizhong; ZHAO Jie; GAO Yongsheng; CAI Hegao
2006-01-01
A novel approach for collision-free path planning of a multiple degree-of-freedom (DOF)articulated robot in a complex environment is proposed. Firstly, based on visual neighbor point (VNP), a numerical artificial potential field is constructed in Cartesian space, which provides the heuristic information, effective distance to the goal and the motion direction for the motion of the robot joints. Secondly, a genetic algorithm, combined with the heuristic rules, is used in joint space to determine a series of contiguous configurations piecewise fiom initial configuration until the goal configuration is attained. A simulation shows that the method can not only handle issues on path planning of the articulated robots in environment with complex obstacles, but also improve the efficiency and quality of path planning.
Numerical probabilistic analysis for slope stability in fractured rock masses using DFN-DEM approach
Directory of Open Access Journals (Sweden)
Alireza Baghbanan
2017-06-01
Full Text Available Due to existence of uncertainties in input geometrical properties of fractures, there is not any unique solution for assessing the stability of slopes in jointed rock masses. Therefore, the necessity of applying probabilistic analysis in these cases is inevitable. In this study a probabilistic analysis procedure together with relevant algorithms are developed using Discrete Fracture Network-Distinct Element Method (DFN-DEM approach. In the right abutment of Karun 4 dam and downstream of the dam body, five joint sets and one major joint have been identified. According to the geometrical properties of fractures in Karun river valley, instability situations are probable in this abutment. In order to evaluate the stability of the rock slope, different combinations of joint set geometrical parameters are selected, and a series of numerical DEM simulations are performed on generated and validated DFN models in DFN-DEM approach to measure minimum required support patterns in dry and saturated conditions. Results indicate that the distribution of required bolt length is well fitted with a lognormal distribution in both circumstances. In dry conditions, the calculated mean value is 1125.3 m, and more than 80 percent of models need only 1614.99 m of bolts which is a bolt pattern with 2 m spacing and 12 m length. However, as for the slopes with saturated condition, the calculated mean value is 1821.8 m, and more than 80 percent of models need only 2653.49 m of bolts which is equivalent to a bolt pattern with 15 m length and 1.5 m spacing. Comparison between obtained results with numerical and empirical method show that investigation of a slope stability with different DFN realizations which conducted in different block patterns is more efficient than the empirical methods.
Directory of Open Access Journals (Sweden)
Yu Chen
2014-01-01
Full Text Available Up to the present, the optimal time to close an open abdomen remains controversial. This study was designed to evaluate whether early fascial abdominal closure had advantages over delayed approach for open abdomen populations. Medline, Embase, and Cochrane Library were searched until April 2013. Search terms included “open abdomen,” “abdominal compartment syndrome,” “laparostomy,” “celiotomy,” “abdominal closure,” “primary,” “delayed,” “permanent,” “fascial closure,” and “definitive closure.” Open abdomen was defined as “fail to close abdominal fascia after a laparotomy.” Mortality, complications, and length of stay were compared between early and delayed fascial closure. In total, 3125 patients were included for final analysis, and 1942 (62% patients successfully achieved early fascial closure. Vacuum assisted fascial closure had no impact on pooled fascial closure rate. Compared with delayed abdominal closure, early fascial closure significantly reduced mortality (12.3% versus 24.8%, RR, 0.53, P<0.0001 and complication incidence (RR, 0.68, P<0.0001. The mean interval from open abdomen to definitive closure ranged from 2.2 to 14.6 days in early fascial closure groups, but from 32.5 to 300 days in delayed closure groups. This study confirmed clinical advantages of early fascial closure over delayed approach in treatment of patients with open abdomen.
A Confidence Index Approach Based on ERA-40 Data for Numerical Short Range Forecasts
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Thomas Prenosil
2014-09-01
Full Text Available Critical weather related missions increasingly rely on highly automated numerical products, even if only limited computer capacities are available to generate them. This holds true especially for military tactical decision aids but also for civil requirements from firebrigades, the Red Cross or technical relief organizations. With respect to inherent atmospheric indeterminateness, a systematic quality control of numerical input turns out to become more and more essential for the users. As an economical alternative to the complex and expensive ensemble prediction method, the German Bundeswehr Geoinformation Centre has decided in favour of an analogue approach called similar synoptic situations (3s, which is based on ECMWF's ERA-40 re-analysis archive. Similarity is defined by a special distance measure for synoptic fields. The typical range of interest is 2500km×2500km$2500\\,\\text{km}\\times2500\\,\\text{km}$ in space with approximately one degree of horizontal resolution and up to 36 hours of forecast time. Historical 12, 24 and 36 hours ERA-40 forecast qualities are merged by 3s into a confidence index, indicating current anomalies of numerical quality versus monthly means in special areas of interest. As the results from the ERA-40 archive are used without any statistical adaption, this assessment is exclusively valid for trouble-free synoptic model runs in the short range. For a better understanding of the estimated anomalies in numerical forecast quality, the involved synoptic conditions are classified by a well established weather type classification. The overall method has been verified from 45 years of ERA-40 data and 10 years of GME forecasts from the Deutscher Wetterdienst. The 3s technique is highly flexible all over the globe with the exception of the tropics, because the present version includes the geostrophic approximation. At present, 3s runs operationally within four geographic areas: (1 Central Europe, (2 Kosovo with
Echocardiographic assessment and percutaneous closure of multiple atrial septal defects
Directory of Open Access Journals (Sweden)
Timperley Jonathan
2004-07-01
Full Text Available Abstract Atrial septal defect closure is now routinely performed using a percutaneous approach under echocardiographic guidance. Centrally located, secundum defects are ideal for device closure but there is considerable morphological variation in size and location of the defects. A small proportion of atrial septal defects may have multiple fenestrations and these are often considered unsuitable for device closure. We report three cases of multiple atrial septal defects successfully closed with two Amplatzer septal occluders.
Energy Technology Data Exchange (ETDEWEB)
Guedes, Solange da Silva
1998-07-01
Advances in petroleum reservoir descriptions have provided an amount of data that can not be handled directly during numerical simulations. This detailed geological information must be incorporated into a coarser model during multiphase fluid flow simulations by means of some upscaling technique. the most used approach is the pseudo relative permeabilities and the more widely used is the Kyte and Berry method (1975). In this work, it is proposed a multi-scale computational model for multiphase flow that implicitly treats the upscaling without using pseudo functions. By solving a sequence of local problems on subdomains of the refined scale it is possible to achieve results with a coarser grid without expensive computations of a fine grid model. The main advantage of this new procedure is to treat the upscaling step implicitly in the solution process, overcoming some practical difficulties related the use of traditional pseudo functions. results of bidimensional two phase flow simulations considering homogeneous porous media are presented. Some examples compare the results of this approach and the commercial upscaling program PSEUDO, a module of the reservoir simulation software ECLIPSE. (author)
Directory of Open Access Journals (Sweden)
Jairo A Navarrete
2017-08-01
Full Text Available Category Theory, a branch of mathematics, has shown promise as a modeling framework for higher-level cognition. We introduce an algebraic model for analogy that uses the language of category theory to explore analogy-related cognitive phenomena. To illustrate the potential of this approach, we use this model to explore three objects of study in cognitive literature. First, (a we use commutative diagrams to analyze an effect of playing particular educational board games on the learning of numbers. Second, (b we employ a notion called coequalizer as a formal model of re-representation that explains a property of computational models of analogy called "flexibility" whereby non-similar representational elements are considered matches and placed in structural correspondence. Finally, (c we build a formal learning model which shows that re-representation, language processing and analogy making can explain the acquisition of knowledge of rational numbers. These objects of study provide a picture of acquisition of numerical knowledge that is compatible with empirical evidence and offers insights on possible connections between notions such as relational knowledge, analogy, learning, conceptual knowledge, re-representation and procedural knowledge. This suggests that the approach presented here facilitates mathematical modeling of cognition and provides novel ways to think about analogy-related cognitive phenomena.
Numerical modelling of the laser cladding process using a dynamic mesh approach
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E.H. Amara
2006-02-01
Full Text Available Purpose: In this paper, a tridimensional modelling of laser cladding by powder injection is developed.Design/methodology/approach: In our approach, the task consists in the numerical resolution of the governing equations including heat transfer and flow dynamic assuming an unsteady state. The related differential equations are discretized using the finite volume method, allowing to obtain an algebraic set of equations. the clad formation is simulated by considering the finite volume mesh deformation.Findings: The shape of the deposited layer is determined as a function of the operating parameters related to the laser beam, the powder, the sample, and the environing atmosphere.Research limitations/implications: By including as much as possible of terms describing physical mechanisms in the general form of the equations, one can model more accurately the cladding process. Afterwards, a validation with experimental results must be done.Practical implications: The comprehension of the occurring physical processes would allow the enhancing of the products quality, the process can then be optimized since predictions on the results to be obtained can be made for given operating parameters.Originality/value: In our contribution, the introduction of the dynamic mesh method involving the use of user defined functions (UDF in the calculation procedure, have allowed to follow the variation of the cells volume and then to obtain the clad profiles as a function of the operating parameters.
Directory of Open Access Journals (Sweden)
Marco Altosole
2012-01-01
Full Text Available One of the key issues at early design stage of a high-speed craft is the selection and the performance prediction of the propulsion system because at this stage only few information about the vessel are available. The objective of this work is precisely to provide the designer, in the case of waterjet propelled craft, with a simple and reliable calculation tool, able to predict the waterjet working points in design and off-design conditions, allowing to investigate several propulsive options during the ship design process. In the paper two original dimensionless numerical procedures, one referred to jet units for naval applications and the other more suitable for planing boats, are presented. The first procedure is based on a generalized performance map for mixed flow pumps, derived from the analysis of several waterjet pumps by applying similitude principles of the hydraulic machines. The second approach, validated by some comparisons with current waterjet installations, is based on a complete physical approach, from which a set of non-dimensional waterjet characteristics has been drawn by the authors. The presented application examples show the validity and the degree of accuracy of the proposed methodologies for the performance evaluation of waterjet propulsion systems.
Energy Technology Data Exchange (ETDEWEB)
NONE
1999-06-01
This Closure Report provides documentation for the closure of Corrective Action Unit (CAU) 120 of the Federal Facilities Agreement and Consent Order (FFACO). CAU 120 consists of two Corrective Action Sites (CASs) located in Areas 5 and 6 of the Nevada Test Site (NTS), which are approximately 130 kilometers (80 miles) northwest of Las Vegas, Nevada. CAS 05-01-01 is located in Area 5 and consists of three 45,800-liter (12,100-gallon) aboveground storage tanks (ASTs), piping, and debris associated with Well RNM-1. CAS 06-01-01 consists of two ASTs and two tanker trailers (all portable) that were originally located at the Area 6 Cp-50 Hot Park and which had been moved to the Area 6 Waste Handling Facility. All of the items in CAU 120 have been used to contain or convey radiologically contaminated fluid that was generated during post-nuclear event activities at the NTS.
Energy Technology Data Exchange (ETDEWEB)
Allison Urban
1999-06-01
This Closure Report provides documentation for the closure of Corrective Action Unit 120. CAU 120 consists of two Corrective Action Sites located in Areas 5 and 6 of the Nevada Test Site. CAS 05-01-01 is located in Area 5 and consists of three 45,800-liter aboveground storage tanks, piping, and debris associated with Well RNM-1. CAS 06-01-01 in Area 6 consists of two aboveground storage tanks and two tanker trailers All the CAU 120 items have been used to convey or contain radiologically contaminated fluid from post-nuclear event activities at the NTS> Closure of this CAU was completed by collecting samples to identify the appropriate method of disposal for tanks, piping, debris, and tankers in each CAS. Placing low-level radioactive waste into the appropriate containers and disposing of waste in the Area 5 Radioactive Waste Management Site, the Area 9 10C Landfill, and the Area 3 Radioactive Waste Management Site.
Optimising GPR modelling: A practical, multi-threaded approach to 3D FDTD numerical modelling
Millington, T. M.; Cassidy, N. J.
2010-09-01
The demand for advanced interpretational tools has lead to the development of highly sophisticated, computationally demanding, 3D GPR processing and modelling techniques. Many of these methods solve very large problems with stepwise methods that utilise numerically similar functions within iterative computational loops. Problems of this nature are readily parallelised by splitting the computational domain into smaller, independent chunks for direct use on cluster-style, multi-processor supercomputers. Unfortunately, the implications of running such facilities, as well as time investment needed to develop the parallel codes, means that for most researchers, the use of these advanced methods is too impractical. In this paper, we propose an alternative method of parallelisation which exploits the capabilities of the modern multi-core processors (upon which today's desktop PCs are built) by multi-threading the calculation of a problem's individual sub-solutions. To illustrate the approach, we have applied it to an advanced, 3D, finite-difference time-domain (FDTD) GPR modelling tool in which the calculation of the individual vector field components is multi-threaded. To be of practical use, the FDTD scheme must be able to deliver accurate results with short execution times and we, therefore, show that the performance benefits of our approach can deliver runtimes less than half those of the more conventional, serial programming techniques. We evaluate implementations of the technique using different programming languages (e.g., Matlab, Java, C++), which will facilitate the construction of a flexible modelling tool for use in future GPR research. The implementations are compared on a variety of typical hardware platforms, having between one and eight processing cores available, and also a modern Graphical Processing Unit (GPU)-based computer. Our results show that a multi-threaded xyz modelling approach is easy to implement and delivers excellent results when implemented
Solomenko, Z; Fourati, Manel; Larachi, Faical; Boyer, Christophe; Augier, Frédéric
2015-01-01
Liquid spreading in gas-liquid concurrent trickle-bed reactors is simulated using an Eulerian twofluid CFD approach. In order to propose a model that describes exhaustively all interaction forces acting on each fluid phase with an emphasis on dispersion mechanisms, a discussion of closure laws available in the literature is proposed. Liquid dispersion is recognized to result from two main mechanisms: capillary and mechanical (Attou and Ferschneider, 2000; Lappalainen et al., 2009- The proposed model is then implemented in two trickle-bed configurations matching with two experimental set ups: In the first configuration, simulations on a 2D axisymmetric geometry are considered and the model is validated upon a new set of experimental data. Overall pressure drop and liquid distribution obtained from $\\gamma$-ray tomography are provided for different geometrical and operating conditions. In the second configuration, a 3D simulation is considered and the model is compared to experimental liquid flux patterns at th...
A novel approach to construct numerical methods for stochastic differential equations
Halidias, Nikolaos
2013-01-01
In this paper we propose a new numerical method for solving stochastic differential equations (SDEs). As an application of this method we propose an explicit numerical scheme for a super linear SDE for which the usual Euler scheme diverges.
Cheng, Jin; Hon, Yiu-Chung; Seo, Jin Keun; Yamamoto, Masahiro
2005-01-01
The Second International Conference on Inverse Problems: Recent Theoretical Developments and Numerical Approaches was held at Fudan University, Shanghai from 16-21 June 2004. The first conference in this series was held at the City University of Hong Kong in January 2002 and it was agreed to hold the conference once every two years in a Pan-Pacific Asian country. The next conference is scheduled to be held at Hokkaido University, Sapporo, Japan in July 2006. The purpose of this series of biennial conferences is to establish and develop constant international collaboration, especially among the Pan-Pacific Asian countries. In recent decades, interest in inverse problems has been flourishing all over the globe because of both the theoretical interest and practical requirements. In particular, in Asian countries, one is witnessing remarkable new trends of research in inverse problems as well as the participation of many young talents. Considering these trends, the second conference was organized with the chairperson Professor Li Tat-tsien (Fudan University), in order to provide forums for developing research cooperation and to promote activities in the field of inverse problems. Because solutions to inverse problems are needed in various applied fields, we entertained a total of 92 participants at the second conference and arranged various talks which ranged from mathematical analyses to solutions of concrete inverse problems in the real world. This volume contains 18 selected papers, all of which have undergone peer review. The 18 papers are classified as follows: Surveys: four papers give reviews of specific inverse problems. Theoretical aspects: six papers investigate the uniqueness, stability, and reconstruction schemes. Numerical methods: four papers devise new numerical methods and their applications to inverse problems. Solutions to applied inverse problems: four papers discuss concrete inverse problems such as scattering problems and inverse problems in
Sdowski, Aleksander; Tchekhovskoy, Alexander; Zhu, Yucong
2012-01-01
A numerical scheme is described for including radiation in multi-dimensional general-relativistic conservative fluid dynamics codes. In this method, a covariant form of the M1 closure scheme is used to close the radiation moments, and the radiative source terms are treated semi-implicitly in order to handle both optically thin and optically thick regimes. The scheme has been implemented in a conservative general relativistic radiation hydrodynamics code KORAL. The robustness of the code is demonstrated on a number of test problems, including radiative relativistic shock tubes, static radiation pressure supported atmosphere, shadows, beams of light in curved spacetime, and radiative Bondi accretion. The advantages of M1 closure relative to other approaches such as Eddington closure and flux-limited diffusion are discussed, and its limitations are also highlighted.
Kulikov, Igor
2016-01-01
An approach for constructing a low-dissipation numerical method is described. The method is based on a combination of the operator-splitting method, Godunov method, and piecewise-parabolic method on the local stencil. Numerical method was tested on a standard suite of hydrodynamic test problems. In addition, the performance of the method is demonstrated on a global test problem showing the development of a spiral structure in a gravitationally unstable gaseous galactic disk.
Connor, C.; Connor, L.; White, J.
2015-12-01
Explosive volcanic eruptions are often classified by deposit mass and eruption column height. How well are these eruption parameters determined in older deposits, and how well can we reduce uncertainty using robust numerical and statistical methods? We describe an efficient and effective inversion and uncertainty quantification approach for estimating eruption parameters given a dataset of tephra deposit thickness and granulometry. The inversion and uncertainty quantification is implemented using the open-source PEST++ code. Inversion with PEST++ can be used with a variety of forward models and here is applied using Tephra2, a code that simulates advective and dispersive tephra transport and deposition. The Levenburg-Marquardt algorithm is combined with formal Tikhonov and subspace regularization to invert eruption parameters; a linear equation for conditional uncertainty propagation is used to estimate posterior parameter uncertainty. Both the inversion and uncertainty analysis support simultaneous analysis of the full eruption and wind-field parameterization. The combined inversion/uncertainty-quantification approach is applied to the 1992 eruption of Cerro Negro (Nicaragua), the 2011 Kirishima-Shinmoedake (Japan), and the 1913 Colima (Mexico) eruptions. These examples show that although eruption mass uncertainty is reduced by inversion against tephra isomass data, considerable uncertainty remains for many eruption and wind-field parameters, such as eruption column height. Supplementing the inversion dataset with tephra granulometry data is shown to further reduce the uncertainty of most eruption and wind-field parameters. We think the use of such robust models provides a better understanding of uncertainty in eruption parameters, and hence eruption classification, than is possible with more qualitative methods that are widely used.
Stoisser, C. M.; Audebert, S.
2008-05-01
In order to describe the state-of-the-art on cracked rotor related problems, the current work presents the comprehensive theoretical, numerical and experimental approach adopted by EDF for crack detection in power plant rotating machinery. The work mainly focuses on the theoretical cracked beam model developed in the past years by S. Andrieux and C. Varé and associates both numerical and experimental aspects related to the crack detection problem in either turboset or turbo pump units. The theoretical part consists of the derivation of a lumped cracked beam model from the three-dimensional formulation of the general problem of elasticity with unilateral contact conditions on the crack lips, valid for any shape and number of cracks in the beam section and extended to cracks not located in a cross-section. This leads to the assessment of the cracked beam rigidity as a function of the rotation angle, in case of pure bending load or bending plus shear load. In this way the function can be implemented in a 1D rotordynamics code. An extension of the cracked beam model taking into account the torsion behaviour is also proposed. It is based on the assumption of full adherence between crack lips, when the crack closes, and on an incremental formulation of deformation energy. An experimental validation has been carried out using different cracked samples, both in static and dynamic configurations, considering one or three elliptic cracks in the same cross-section and helix-shaped cracks. Concerning the static configuration, a good agreement between numerical and experimental results is found. It is shown to be equal to 1% maximal gap of the beam deflection. Concerning the dynamical analysis, the main well-known indicator 2× rev. bending vibration component at half critical speed is approximated at maximum by 18% near the crack position. Our experiments also allowed for the observation of the bending and torsion resonance frequency shifts determined by the extra
Numerical simulations of two-phase Taylor-Couette turbulence using an Euler-Lagrange approach
Spandan, Vamsi; Verzicco, Roberto; Lohse, Detlef
2015-01-01
Two-phase turbulent Taylor-Couette (TC) flow is simulated using an Euler-Lagrange approach to study the effects of a secondary phase dispersed into a turbulent carrier phase (here bubbles dispersed into water). The dynamics of the carrier phase is computed using Direct Numerical Simulations (DNS) in an Eulerian framework, while the bubbles are tracked in a Lagrangian manner by modelling the effective drag, lift, added mass and buoyancy force acting on them. Two-way coupling is implemented between the dispersed phase and the carrier phase which allows for momentum exchange among both phases and to study the effect of the dispersed phase on the carrier phase dynamics. The radius ratio of the TC setup is fixed to $\\eta=0.833$, and a maximum inner cylinder Reynolds number of $Re_i=8000$ is reached. We vary the Froude number ($Fr$), which is the ratio of the centripetal to the gravitational acceleration of the dispersed phase and study its effect on the net torque required to drive the TC system. In a two-phase TC...
Fazanaro, Filipe I.; Soriano, Diogo C.; Suyama, Ricardo; Madrid, Marconi K.; Oliveira, José Raimundo de; Muñoz, Ignacio Bravo; Attux, Romis
2016-08-01
The characterization of nonlinear dynamical systems and their attractors in terms of invariant measures, basins of attractions and the structure of their vector fields usually outlines a task strongly related to the underlying computational cost. In this work, the practical aspects related to the use of parallel computing - specially the use of Graphics Processing Units (GPUS) and of the Compute Unified Device Architecture (CUDA) - are reviewed and discussed in the context of nonlinear dynamical systems characterization. In this work such characterization is performed by obtaining both local and global Lyapunov exponents for the classical forced Duffing oscillator. The local divergence measure was employed by the computation of the Lagrangian Coherent Structures (LCSS), revealing the general organization of the flow according to the obtained separatrices, while the global Lyapunov exponents were used to characterize the attractors obtained under one or more bifurcation parameters. These simulation sets also illustrate the required computation time and speedup gains provided by different parallel computing strategies, justifying the employment and the relevance of GPUS and CUDA in such extensive numerical approach. Finally, more than simply providing an overview supported by a representative set of simulations, this work also aims to be a unified introduction to the use of the mentioned parallel computing tools in the context of nonlinear dynamical systems, providing codes and examples to be executed in MATLAB and using the CUDA environment, something that is usually fragmented in different scientific communities and restricted to specialists on parallel computing strategies.
Stochastic approach to the numerical solution of the non-stationary Parker's transport equation
Wawrzynczak, A; Gil, A
2015-01-01
We present the newly developed stochastic model of the galactic cosmic ray (GCR) particles transport in the heliosphere. Mathematically Parker transport equation (PTE) describing non-stationary transport of charged particles in the turbulent medium is the Fokker-Planck type. It is the second order parabolic time-dependent 4-dimensional (3 spatial coordinates and particles energy/rigidity) partial differential equation. It is worth to mention that, if we assume the stationary case it remains as the 3-D parabolic type problem with respect to the particles rigidity R. If we fix the energy it still remains as the 3-D parabolic type problem with respect to time. The proposed method of numerical solution is based on the solution of the system of stochastic differential equations (SDEs) being equivalent to the Parker's transport equation. We present the method of deriving from PTE the equivalent SDEs in the heliocentric spherical coordinate system for the backward approach. The obtained stochastic model of the Forbu...
Numerical evaluation of the bispectrum in multiple field inflation—the transport approach with code
Dias, Mafalda; Frazer, Jonathan; Mulryne, David J.; Seery, David
2016-12-01
We present a complete framework for numerical calculation of the power spectrum and bispectrum in canonical inflation with an arbitrary number of light or heavy fields. Our method includes all relevant effects at tree-level in the loop expansion, including (i) interference between growing and decaying modes near horizon exit; (ii) correlation and coupling between species near horizon exit and on superhorizon scales; (iii) contributions from mass terms; and (iv) all contributions from coupling to gravity. We track the evolution of each correlation function from the vacuum state through horizon exit and the superhorizon regime, with no need to match quantum and classical parts of the calculation; when integrated, our approach corresponds exactly with the tree-level Schwinger or `in-in' formulation of quantum field theory. In this paper we give the equations necessary to evolve all two- and three-point correlation functions together with suitable initial conditions. The final formalism is suitable to compute the amplitude, shape, and scale dependence of the bispectrum in models with |fNL| of order unity or less, which are a target for future galaxy surveys such as Euclid, DESI and LSST. As an illustration we apply our framework to a number of examples, obtaining quantitatively accurate predictions for their bispectra for the first time. Two accompanying reports describe publicly-available software packages that implement the method.
Numerical Approaches to Identification of Characteristic Soil Layers in an Urban Environment
Institute of Scientific and Technical Information of China (English)
YUAN Da-Gang; ZHANG Gan-Lin; GONG Zi-Tong
2008-01-01
Pedogenetic soil horizons are one of the fundamental building blocks of modern soil classification; however,in soils of urban areas which are often strongly disturbed by human activities,horizons are difficult to distinguish but substitutive morphological layers may be identified.To identify the characteristic soil layers in an urban environment,224 soil layers of 36 in-situ pedons were examined and described in urban and suburban Nanjing,and 27 variables were extracted for multivariate analysis.Three groups and six subdivisions were identified by TwoStep cluster analysis combined with hierarchical cluster analysis based on factor scores.Soil forming factors and soil forming processes could be interpreted from the principal component analysis (PCA) of variables,cluster analysis of soil layers,and discriminant analysis of soil layer groups and their subdivisions.Parent materials,moisture regimes,organic matter accumulation,and especially nutrient accumulation were the main causes of characteristic soil layer formations.The numerical approaches used in this study were useful tools for characteristic soil layer identification of urban soils.
Stochastic approach to the numerical solution of the non-stationary Parker's transport equation
Wawrzynczak, A.; Modzelewska, R.; Gil, A.
2015-01-01
We present the newly developed stochastic model of the galactic cosmic ray (GCR) particles transport in the heliosphere. Mathematically Parker transport equation (PTE) describing non-stationary transport of charged particles in the turbulent medium is the Fokker-Planck type. It is the second order parabolic time-dependent 4-dimensional (3 spatial coordinates and particles energy/rigidity) partial differential equation. It is worth to mention that, if we assume the stationary case it remains as the 3-D parabolic type problem with respect to the particles rigidity R. If we fix the energy/rigidity it still remains as the 3-D parabolic type problem with respect to time. The proposed method of numerical solution is based on the solution of the system of stochastic differential equations (SDEs) being equivalent to the Parker's transport equation. We present the method of deriving from PTE the equivalent SDEs in the heliocentric spherical coordinate system for the backward approach. The advantages and disadvantages of the forward and the backward solution of the PTE are discussed. The obtained stochastic model of the Forbush decrease of the GCR intensity is in an agreement with the experimental data.
Comparison of different approaches to the numerical calculation of the LMJ focal
Directory of Open Access Journals (Sweden)
Bourgeade A.
2013-11-01
Full Text Available The beam smoothing in the focal plane of high power lasers is of particular importance to laser-plasma interaction studies in order to minimize plasma parametric and hydrodynamic instabilities on the target. Here we investigate the focal spot structure in different geometrical configurations where standard paraxial hypotheses are no longer verified. We present numerical studies in the cases of single flat top square beam, LMJ quadruplet and complete ring of quads with large azimuth angle. Different calculations are made with Fresnel diffraction propagation model in the paraxial approximation and full vector Maxwell's equations. The first model is based on Fourier transform from near to far field method. The second model uses first spherical wave decomposition in plane waves with Fourier transform and propagates them to the focal spot. These two different approaches are compared with Miró [1] modeling results using paraxial or Feit and Fleck options. The methods presented here are generic for focal spot calculations. They can be used for other complex geometric configurations and various smoothing techniques. The results will be used as boundary conditions in plasma interaction computations.
Ram pressure stripping in a galaxy formation model. I. A novel numerical approach
Tecce, Tomás E; Tissera, Patricia B; Abadi, Mario G; Lagos, Claudia del P
2010-01-01
We develop a new numerical approach to describe the action of ram pressure stripping (RPS) within a semi-analytic model of galaxy formation and evolution which works in combination with non-radiative hydrodynamical simulations of galaxy clusters. The new feature in our method is the use of the gas particles to obtain the kinematical and thermodynamical properties of the intragroup and intracluster medium (ICM). This allows a self-consistent estimation of the RPS experienced by satellite galaxies. We find that the ram pressure (RP) in the central regions of clusters increases approximately one order of magnitude between z = 1 and 0, consistent with the increase in the density of the ICM. The mean RP experienced by galaxies within the virial radius increases with decreasing redshift. In clusters with virial masses M_vir ~10^15 h^-1 M_Sun, over 50% of satellite galaxies have experienced RP ~10^(-11) h^-2 dyn cm^-2 or higher for z = 0.5.
A numerical multivariate approach to optimization of photovoltaic solar low energy building designs
Energy Technology Data Exchange (ETDEWEB)
Peippo, K.
1997-12-31
The large number of options available to the energy conscious building designer calls for careful assessment of the competitiveness of the various technologies, in order to find the best technology mix for each design. Here, a simplified rigorous numerical multivariate optimization scheme is introduced to address the energy efficient solar low energy building design problem at the early design stages. The approach is based on elementary building modeling and non-linear optimization techniques where the basic physical, technical and economical interactions between the building design options and energy flows are accounted for. The design features considered include building geometry, thermal insulation, windows, daylighting, solar thermal systems and photovoltaics. The applicability of the approach is assessed through a set of case studies for a single-family residential house and a large office building in three different climates in Europe: Helsinki, Finland (60 deg C N), Paris, France (49 deg C N) and Trapani, Italy (38 deg C N). The analysis is based on annual hourly simulations with Test Reference Years. First, the design minimizing the sum of annual capital and energy cost of the building is determined. Then, the optimal path is computed that gives the most economical design to reach a given level of annual primary energy requirements, should this desired level be lower than the one in the least cost option. The optimal values of the key design variables for the case studies are presented. As a typical low energy building design feature, photovoltaics is to be introduced at a relatively early stage in the designs, in order to further decrease the auxiliary energy requirements. This due to the rather high share of electricity in the energy balance of low energy buildings. However, it is crucial for the integrity of low energy building design, that also the other design features are optimized before one resorts to PV. In addition, it is notable that the somewhat
Boss, Pauline; Carnes, Donna
2012-12-01
Therapies for grief and loss have traditionally focused on the work of grieving. The goal was to reach an endpoint, now popularly called closure. There are, however, many people who, through no fault of their own, find a loss so unclear that there can be no end to grief. They have not failed in the work of grieving, but rather have suffered ambiguous loss, a type of loss that is inherently open ended. Instead of closure, the therapeutic goal is to help people find meaning despite the lack of definitive information and finality. Hope lies in increasing a family's tolerance for ambiguity, but first, professionals must increase their own comfort with unanswered questions. In this article, the authors, one a poet, the other a family therapist and theorist, offer a unique blending of theory, reflection, and poetry to experientially deepen the process of self-reflection about a kind of loss that defies closure. © FPI, Inc.
Energy Technology Data Exchange (ETDEWEB)
Bradburne, John; Patton, Tisha C.
2001-02-25
When Fluor Fernald took over the management of the Fernald Environmental Management Project in 1992, the estimated closure date of the site was more than 25 years into the future. Fluor Fernald, in conjunction with DOE-Fernald, introduced the Accelerated Cleanup Plan, which was designed to substantially shorten that schedule and save taxpayers more than $3 billion. The management of Fluor Fernald believes there are three fundamental concerns that must be addressed by any contractor hoping to achieve closure of a site within the DOE complex. They are relationship management, resource management and contract management. Relationship management refers to the interaction between the site and local residents, regulators, union leadership, the workforce at large, the media, and any other interested stakeholder groups. Resource management is of course related to the effective administration of the site knowledge base and the skills of the workforce, the attraction and retention of qualified a nd competent technical personnel, and the best recognition and use of appropriate new technologies. Perhaps most importantly, resource management must also include a plan for survival in a flat-funding environment. Lastly, creative and disciplined contract management will be essential to effecting the closure of any DOE site. Fluor Fernald, together with DOE-Fernald, is breaking new ground in the closure arena, and ''business as usual'' has become a thing of the past. How Fluor Fernald has managed its work at the site over the last eight years, and how it will manage the new site closure contract in the future, will be an integral part of achieving successful closure at Fernald.
Tao Min; Xing Chen; Yao Sun; Qiang Huang
2014-01-01
This paper is intended to provide a numerical algorithm involving the combined use of the Levenberg-Marquardt algorithm and the Galerkin finite element method for estimating the diffusion coefficient in an inverse heat conduction problem (IHCP). In the present study, the functional form of the diffusion coefficient is unknown a priori. The unknown diffusion coefficient is approximated by the polynomial form and the present numerical algorithm is employed to find the solution. Numerical experi...
Energy Technology Data Exchange (ETDEWEB)
Caldwell, T.B.
1997-04-18
A reducing grout has been developed for closing high level waste tanks at the Savannah River Site in Aiken, South Carolina. The grout has a low redox potential, which minimizes the mobility of Sr{sup 90}, the radionuclide with the highest dose potential after closure. The grout also has a high pH which reduces the solubility of the plutonium isotopes. The grout has a high compressive strength and low permeability, which enhances its ability to limit the migration of contaminants after closure. The grout was designed and tested by Construction Technology Laboratories, Inc. Placement methods were developed by the Savannah River Site personnel.
Choe, Yun Seon; Kim, Min-Woo; Jo, Seong Jin
2015-12-01
In full-thickness defects of the nasal alar rim, to achieve projection and maintain airway patency, cartilage graft is frequently needed. However, cartilage graft presents a challenge in considerations such as appropriate donor site, skeletal shape and size, and healing of the donor area. To avoid these demerits, we tried primary closure of alar rim defects by also making the contralateral normal ala smaller. We treated two patients who had a full-thickness nasal alar defect after tumor excision. Cartilage graft was considered for the reconstruction. However, their alar rims were overly curved and their nostril openings were large. To utilize their nasal shape, we did primary closure of the defect rather than cartilage graft, and then downsized the contralateral nasal ala by means of wedge resection to make the alae symmetric. Both patients were satisfied with their aesthetic results, which showed a smaller nostril and nearly straight alar rims. Moreover, functionally, there was no discomfort during breathing in both patients. We propose our idea as one of the reconstruction options for nasal alar defects. It is a simple and easy-to-perform procedure, in addition to enhancing the nasal contour. This method would be useful for patients with a large nostril and an overly curved alar rim.
Schaeffer, Blake A; Hagy, James D; Conmy, Robyn N; Lehrter, John C; Stumpf, Richard P
2012-01-17
Human activities on land increase nutrient loads to coastal waters, which can increase phytoplankton production and biomass and associated ecological impacts. Numeric nutrient water quality standards are needed to protect coastal waters from eutrophication impacts. The Environmental Protection Agency determined that numeric nutrient criteria were necessary to protect designated uses of Florida's waters. The objective of this study was to evaluate a reference condition approach for developing numeric water quality criteria for coastal waters, using data from Florida. Florida's coastal waters have not been monitored comprehensively via field sampling to support numeric criteria development. However, satellite remote sensing had the potential to provide adequate data. Spatial and temporal measures of SeaWiFS OC4 chlorophyll-a (Chl(RS)-a, mg m(-3)) were resolved across Florida's coastal waters between 1997 and 2010 and compared with in situ measurements. Statistical distributions of Chl(RS)-a were evaluated to determine a quantitative reference baseline. A binomial approach was implemented to consider how new data could be assessed against the criteria. The proposed satellite remote sensing approach to derive numeric criteria may be generally applicable to other coastal waters.
Systematic approach in optimizing numerical memory-bound kernels on GPU
Abdelfattah, Ahmad M.
2013-01-01
The use of GPUs has been very beneficial in accelerating dense linear algebra computational kernels (DLA). Many high performance numerical libraries like CUBLAS, MAGMA, and CULA provide BLAS and LAPACK implementations on GPUs as well as hybrid computations involving both, CPUs and GPUs. GPUs usually score better performance than CPUs for compute-bound operations, especially those characterized by a regular data access pattern. This paper highlights a systematic approach for efficiently implementing memory-bound DLA kernels on GPUs, by taking advantage of the underlying device\\'s architecture (e.g., high throughput). This methodology proved to outperform existing state-of-the-art GPU implementations for the symmetric matrix-vector multiplication (SYMV), characterized by an irregular data access pattern, in a recent work (Abdelfattah et. al, VECPAR 2012). We propose to extend this methodology to the general matrix-vector multiplication (GEMV) kernel. The performance results show that our GEMV implementation achieves better performance for relatively small to medium matrix sizes, making it very influential in calculating the Hessenberg and bidiagonal reductions of general matrices (radar applications), which are the first step toward computing eigenvalues and singular values, respectively. Considering small and medium size matrices (≤4500), our GEMV kernel achieves an average 60% improvement in single precision (SP) and an average 25% in double precision (DP) over existing open-source and commercial software solutions. These results improve reduction algorithms for both small and large matrices. The improved GEMV performances engender an averge 30% (SP) and 15% (DP) in Hessenberg reduction and up to 25% (SP) and 14% (DP) improvement for the bidiagonal reduction over the implementation provided by CUBLAS 5.0. © 2013 Springer-Verlag.
The numerical approach to quantum field theory in a non-commutative space
Panero, Marco
2016-01-01
Numerical simulation is an important non-perturbative tool to study quantum field theories defined in non-commutative spaces. In this contribution, a selection of results from Monte Carlo calculations for non-commutative models is presented, and their implications are reviewed. In addition, we also discuss how related numerical techniques have been recently applied in computer simulations of dimensionally reduced supersymmetric theories.
Parallel hierarchical evaluation of transitive closure queries
Houtsma, M.A.W.; Cacace, F.; Ceri, S.
1991-01-01
Presents a new approach to parallel computation of transitive closure queries using a semantic data fragmentation. Tuples of a large base relation denote edges in a graph, which models a transportation network. A fragmentation algorithm is proposed which produces a partitioning of the base relation
Parallel hierarchical evaluation of transitive closure queries
Houtsma, M.A.W.; Houtsma, M.A.W.; Cacace, F.; Ceri, S.
1991-01-01
Presents a new approach to parallel computation of transitive closure queries using a semantic data fragmentation. Tuples of a large base relation denote edges in a graph, which models a transportation network. A fragmentation algorithm is proposed which produces a partitioning of the base relation
Combined analytical and numerical approaches in Dynamic Stability analyses of engineering systems
Náprstek, Jiří
2015-03-01
Dynamic Stability is a widely studied area that has attracted many researchers from various disciplines. Although Dynamic Stability is usually associated with mechanics, theoretical physics or other natural and technical disciplines, it is also relevant to social, economic, and philosophical areas of our lives. Therefore, it is useful to occasionally highlight the general aspects of this amazing area, to present some relevant examples and to evaluate its position among the various branches of Rational Mechanics. From this perspective, the aim of this study is to present a brief review concerning the Dynamic Stability problem, its basic definitions and principles, important phenomena, research motivations and applications in engineering. The relationships with relevant systems that are prone to stability loss (encountered in other areas such as physics, other natural sciences and engineering) are also noted. The theoretical background, which is applicable to many disciplines, is presented. In this paper, the most frequently used Dynamic Stability analysis methods are presented in relation to individual dynamic systems that are widely discussed in various engineering branches. In particular, the Lyapunov function and exponent procedures, Routh-Hurwitz, Liénard, and other theorems are outlined together with demonstrations. The possibilities for analytical and numerical procedures are mentioned together with possible feedback from experimental research and testing. The strengths and shortcomings of these approaches are evaluated together with examples of their effective complementing of each other. The systems that are widely encountered in engineering are presented in the form of mathematical models. The analyses of their Dynamic Stability and post-critical behaviour are also presented. The stability limits, bifurcation points, quasi-periodic response processes and chaotic regimes are discussed. The limit cycle existence and stability are examined together with their
Directory of Open Access Journals (Sweden)
Pastore Antonio Luigi
2013-01-01
Full Text Available Abstract Introduction Fournier’s gangrene is an infectious necrotizing fasciitis of the perineum and genital regions and has a high mortality rate. It is a synergistic infection caused by a mixture of aerobic and anaerobic organisms and predisposing factors, including diabetes mellitus, alcoholism, malnutrition, and low socioeconomic status. We report a case of Fournier’s gangrene in a patient with unknown type II diabetes submitted to 24-hour catheterization 15 days before gangrene onset. Case presentation The patient, a 60-year-old Caucasian man, presented with a swollen, edematous, emphysematous scrotum with a crepitant skin and a small circle of necrosis. A lack of resistance along the dartos fascia of the scrotum and Scarpa’s lower abdominal wall fascia combined with the presence of gas and pus during the first surgical debridement also supported the diagnosis of Fournier’s gangrene. On the basis of the microbiological culture, the patient was given multiple antibiotic therapy, combined hypoglycemic treatment, hyperbaric oxygen therapy, and several surgical debridements. After five days the infection was not completely controlled and a vacuum-assisted closure device therapy was started. Conclusions This report describes the successful multistep approach of an immediate surgical debridement combined with hyperbaric oxygen and negative pressure wound therapy. The vacuum-assisted closure is a well-known method used to treat complex wounds. In this case study, vacuum-assisted closure treatment was effective and the patient did not require reconstructive surgery. Our report shows that bladder catheterization, a minimally invasive maneuver, may also cause severe infective consequences in high-risk patients, such as patients with diabetes.
Drag reduction in numerical two-phase Taylor–Couette turbulence using an Euler–Lagrange approach
Arza, Vamsi Spandan; Ostilla-Monico, Rodolfo; Verzicco, Roberto; Lohse, Detlef
2016-01-01
Two-phase turbulent Taylor–Couette (TC) flow is simulated using an Euler–Lagrange approach to study the effects of a secondary phase dispersed into a turbulent carrier phase (here bubbles dispersed into water). The dynamics of the carrier phase is computed using direct numerical simulations (DNS) in
Institute of Scientific and Technical Information of China (English)
马杭
2002-01-01
With the aid of the properties of the hypersingular kernels,a geometric conversion approach was presented in this paper.The conversion leads to a general approach for the accurate and reliable numerical evaluation of the hypersingular surface boundary integrals encountered in a variety of applications with boundary element method.Based on the conversion,the hypersingularity in the boundary integrals could be lowered by one order,resulting in the simplification of the computer code.Moreover,an integral transformation was introduced to damp out the nearly singular behavior of the kernels by the distance function defined in the local polar coordinate system for the nearly hypersingular case.The approach is simple to use,which can be inserted readily to computer code,thus getting rid of the dull routine deduction of formulae before the numerical implementatins,as the expressions of these kernels are in general complicated.The numerical examples were gien in three-dimensional elasticity,verifying the effectiveness of the proposed approach,which makes it possible to observe numerically the behavior of the boundary integral values with hypersingular kernels across the boundary.
López-García, Jeanett; Jiménez Zamudio, Jorge Javier
2017-01-01
It is very common to find in contemporary literature of Differential Equations, the need to incorporate holistically in teaching and learning the three different approaches: analytical, qualitative, and numerical, for continuous dynamical systems. However, nowadays, in some Bachelor of Science that includes only one course in differential…
2013-01-01
On the occasion of the annual closure of CERN, there will be no mail distributed on Friday 20 December 2013 but mail will be collected in the morning. Nevertheless, you will still be able to bring your outgoing mail to Building 555-R-002 until 12 noon.
DEFF Research Database (Denmark)
de Faria, Pedro; Preto, Miguel Torres; Sofka, Wolfgang
2013-01-01
We investigate the consequences of MNC subsidiary closures for employees who lose their jobs. We ask to what degree the foreign knowledge that they were exposed to is valued in their new job. We argue theoretically that this foreign knowledge is both valuable and not readily available in the host...
DEFF Research Database (Denmark)
de Faria, Pedro; Sofka, Wolfgang; Torres Preto, Miguel
We investigate the consequences of MNC subsidiary closures for employees who lose their jobs. We ask to what degree the foreign knowledge that they were exposed to is valued in their new job. We argue theoretically that this foreign knowledge is both valuable and not readily available in the host...
Transcatheter closure of patent ductus arteriosus: past, present and future.
Baruteau, Alban-Elouen; Hascoët, Sébastien; Baruteau, Julien; Boudjemline, Younes; Lambert, Virginie; Angel, Claude-Yves; Belli, Emre; Petit, Jérôme; Pass, Robert
2014-02-01
This review aims to describe the past history, present techniques and future directions in transcatheter treatment of patent ductus arteriosus (PDA). Transcatheter PDA closure is the standard of care in most cases and PDA closure is indicated in any patient with signs of left ventricular volume overload due to a ductus. In cases of left-to-right PDA with severe pulmonary arterial hypertension, closure may be performed under specific conditions. The management of clinically silent or very tiny PDAs remains highly controversial. Techniques have evolved and the transcatheter approach to PDA closure is now feasible and safe with current devices. Coils and the Amplatzer Duct Occluder are used most frequently for PDA closure worldwide, with a high occlusion rate and few complications. Transcatheter PDA closure in preterm or low-bodyweight infants remains a highly challenging procedure and further device and catheter design development is indicated before transcatheter closure is the treatment of choice in this delicate patient population. The evolution of transcatheter PDA closure from just 40 years ago with 18F sheaths to device delivery via a 3F sheath is remarkable and it is anticipated that further improvements will result in better safety and efficacy of transcatheter PDA closure techniques.
PRECL: A new method for interferometry imaging from closure phase
Ikeda, Shiro; Akiyama, Kazunori; Hada, Kazuhiro; Honma, Mareki
2016-01-01
For short-wavelength VLBI observations, it is difficult to measure the phase of the visibility function accurately. The closure phases are reliable measurements under this situation, though it is not sufficient to retrieve all of the phase information. We propose a new method, Phase Retrieval from Closure Phase (PRECL). PRECL estimates all the visibility phases only from the closure phases. Combining PRECL with a sparse modeling method we have already proposed, imaging process of VLBI does not rely on dirty image nor self-calibration. The proposed method is tested numerically and the results are promising.
Directory of Open Access Journals (Sweden)
Tao Min
2014-01-01
Full Text Available This paper is intended to provide a numerical algorithm involving the combined use of the Levenberg-Marquardt algorithm and the Galerkin finite element method for estimating the diffusion coefficient in an inverse heat conduction problem (IHCP. In the present study, the functional form of the diffusion coefficient is unknown a priori. The unknown diffusion coefficient is approximated by the polynomial form and the present numerical algorithm is employed to find the solution. Numerical experiments are presented to show the efficiency of the proposed method.
Modeling of Coaxial Slot Waveguides Using Analytical and Numerical Approaches: Revisited
Directory of Open Access Journals (Sweden)
Kok Yeow You
2012-01-01
Full Text Available Our reviews of analytical methods and numerical methods for coaxial slot waveguides are presented. The theories, background, and physical principles related to frequency-domain electromagnetic equations for coaxial waveguides are reassessed. Comparisons of the accuracies of various types of admittance and impedance equations and numerical simulations are made, and the fringing field at the aperture sensor, which is represented by the lumped capacitance circuit, is evaluated. The accuracy and limitations of the analytical equations are explained in detail. The reasons for the replacement of analytical methods by numerical methods are outlined.
Ring closure in actin polymers
Sinha, Supurna; Chattopadhyay, Sebanti
2017-03-01
We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-04-01
This report addresses the site characterization of two historical underground storage tank petroleum hydrocarbon release sites identified by Corrective Action Site (CAS) Numbers 02-02-03 and 09-02-01. The sites are located at the Nevada Test Site in Areas 2 and 9 and are concrete bunker complexes (Bunker 2-300, and 9-300). Characterization was completed using drilling equipment to delineate the extent of petroleum hydrocarbons at release site 2-300-1 (CAS 02-02-03). Based on site observations, the low hydrocarbon concentrations detected, and the delineation of the vertical and lateral extent of subsurface hydrocarbons, an ``A through K`` evaluation was completed to support a request for an Administrative Closure of the site.
Unger, André J. A.
2010-02-01
This work is the first installment in a two-part series, and focuses on the development of a numerical PDE approach to price components of a Bermudan-style callable catastrophe (CAT) bond. The bond is based on two underlying stochastic variables; the PCS index which posts quarterly estimates of industry-wide hurricane losses as well as a single-factor CIR interest rate model for the three-month LIBOR. The aggregate PCS index is analogous to losses claimed under traditional reinsurance in that it is used to specify a reinsurance layer. The proposed CAT bond model contains a Bermudan-style call feature designed to allow the reinsurer to minimize their interest rate risk exposure on making substantial fixed coupon payments using capital from the reinsurance premium. Numerical PDE methods are the fundamental strategy for pricing early-exercise constraints, such as the Bermudan-style call feature, into contingent claim models. Therefore, the objective and unique contribution of this first installment in the two-part series is to develop a formulation and discretization strategy for the proposed CAT bond model utilizing a numerical PDE approach. Object-oriented code design is fundamental to the numerical methods used to aggregate the PCS index, and implement the call feature. Therefore, object-oriented design issues that relate specifically to the development of a numerical PDE approach for the component of the proposed CAT bond model that depends on the PCS index and LIBOR are described here. Formulation, numerical methods and code design issues that relate to aggregating the PCS index and introducing the call option are the subject of the companion paper.
Boyer F.
2013-01-01
This article deals with the problem of computing numerical approximations of null-controls for parabolic equations or systems by using the Hilbert Uniqueness Method (HUM). We mainly review recent results on this subject but we also provide new elements to emphasize the main ideas underlying the penalised HUM approach which is at the heart of the methods used in practice. We give many numerical illustrations. Cet article est consacré à l’étude du problème du calcul approché de contrôles...
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Emran Tohidi
2016-01-01
Full Text Available This article contributes a matrix approach by using Taylor approximation to obtain the numerical solution of one-dimensional time-dependent parabolic partial differential equations (PDEs subject to nonlocal boundary integral conditions. We first impose the initial and boundary conditions to the main problems and then reach to the associated integro-PDEs. By using operational matrices and also the completeness of the monomials basis, the obtained integro-PDEs will be reduced to the generalized Sylvester equations. For solving these algebraic systems, we apply a famous technique in Krylov subspace iterative methods. A numerical example is considered to show the efficiency of the proposed idea.
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Olin, Doris
2005-01-01
Full Text Available Este artigo examina a objeção ao fechamento [dedutivo] que surge no contexto de certos paradoxos epistêmicos, paradoxos cuja conclusão é que a crença justificada pode ser inconsistente. É universalmente aceito que, se essa conclusão é correta, o fechamento deve ser rejeitado, para que se evite a crença justificada em enunciados contraditórios (P, ~P. Mas, mesmo que os argumentos desses paradoxos - o paradoxo da falibilidade (do prefácio e o paradoxo da loteria - seja mal sucedidos, eles, ainda assim, sugerem a existência de evidência independente para uma objeção mais direta contra o fechamento. O exame do argumento da falibilidade revela uma exigência de modéstia epistêmica que viola o fechamento a partir de múltiplas premissas. A reflexão sobre o paradoxo da loteria nos confronta com um dilema em que cada alternativa fornece um contra-exemplo ao fechamento a partir de uma única premissa. Seja ou não possível a inconsistência racional, há uma objeção contra o fechamento. This paper examines the case against closure that arises in the context of certain epistemic paradoxes, paradoxes whose conclusion is that it is possible for justified belief to be inconsistent. It is generally agreed that if this conclusion is correct, closure must be rejected in order to avoid justified belief in contradictory statements (P, ~P. But even if the arguments of these paradoxes – the fallibility (preface paradox and the lottery paradox – are unsuccessful, they nonetheless suggest independent grounds for a more direct case against closure. Examination of the fallibility argument reveals a requirement of epistemic modesty that violates multiple premise closure. Reflection on the lottery paradox presents us with a dilemma in which each alternative provides a counterexample to single premise closure. Whether or not rational inconsistency is possible, there is a case against closure.
Validation of engineering dynamic inflow models by experimental and numerical approaches
Yu, W.; Hong, V. W.; Ferreira, C.; van Kuik, G. A. M.
2016-09-01
The state of the art engineering dynamic inflow models of Pitt-Peters, Øye and ECN have been used to correct Blade Element Momentum theory for unsteady load prediction of a wind turbine for two decades. However, their accuracy is unknown. This paper is to benchmark the performance of these engineering models by experimental and numerical methods. The experimental load and flow measurements of an unsteady actuator disc were performed in the Open Jet Facility at Delft University of Technology. The unsteady load was generated by a ramp-type variation of porosity of the disc. A Reynolds Averaged Navier-Stokes (RANS) model, a Free Wake Vortex Ring (FWVR) model and a Vortex Tube Model (VTM) simulate the same transient load changes. The velocity field obtained from the experimental and numerical methods are compared with the engineering dynamic inflow models. Velocity comparison aft the disc between the experimental and numerical methods shows the numerical models of RANS and FWVR model are capable to predict the velocity transient behaviour during transient disc loading. Velocity comparison at the disc between the engineering models and the numerical methods further shows that the engineering models predict much faster velocity decay, which implies the need for more advanced or better tuned dynamic inflow models.
A numerical spectral approach for the derivation of piezometric head covariance functions
van Lent, Thomas; Kitanidis, Peter K.
1989-11-01
Relating the variability of permeability to the variability of head is a central part of linear estimation techniques such as cokriging. Only a few analytic relationships between log permeability covariances and head covariances presently exist. This paper describes a general numerical procedure which computes head covariances (ordinary or generalized) and cross covariances for any proper log permeability covariance. The numerical spectral method, a discrete analog of Fourier-Stieltjes analysis, employs the pertinent linearized (small-perturbation approximation) equations describing the physics of flow. The domain is taken as finite, with boundary effects considered negligible. The numerical spectral method can reproduce all pertinent analytic results with excellent agreement. Furthermore, we demonstrate the method's generality by finding the covariance relations for a case where no analytical results presently exist.
A novel Lagrangian approach for the stable numerical simulation of fault and fracture mechanics
Franceschini, Andrea; Ferronato, Massimiliano; Janna, Carlo; Teatini, Pietro
2016-06-01
The simulation of the mechanics of geological faults and fractures is of paramount importance in several applications, such as ensuring the safety of the underground storage of wastes and hydrocarbons or predicting the possible seismicity triggered by the production and injection of subsurface fluids. However, the stable numerical modeling of ground ruptures is still an open issue. The present work introduces a novel formulation based on the use of the Lagrange multipliers to prescribe the constraints on the contact surfaces. The variational formulation is modified in order to take into account the frictional work along the activated fault portion according to the principle of maximum plastic dissipation. The numerical model, developed in the framework of the Finite Element method, provides stable solutions with a fast convergence of the non-linear problem. The stabilizing properties of the proposed model are emphasized with the aid of a realistic numerical example dealing with the generation of ground fractures due to groundwater withdrawal in arid regions.
Stability of linear delay differential equations a numerical approach with Matlab
Breda, Dimitri; Vermiglio, Rossana
2015-01-01
This book presents the authors' recent work on the numerical methods for the stability analysis of linear autonomous and periodic delay differential equations, which consist in applying pseudospectral techniques to discretize either the solution operator or the infinitesimal generator and in using the eigenvalues of the resulting matrices to approximate the exact spectra. The purpose of the book is to provide a complete and self-contained treatment, which includes the basic underlying mathematics and numerics, examples from population dynamics and engineering applications, and Matlab programs implementing the proposed numerical methods. A number of proofs is given to furnish a solid foundation, but the emphasis is on the (unifying) idea of the pseudospectral technique for the stability analysis of DDEs. It is aimed at advanced students and researchers in applied mathematics, in dynamical systems and in various fields of science and engineering, concerned with delay systems. A relevant feature of the book is t...
A Numerical Approach for Hybrid Simulation of Power System Dynamics Considering Extreme Icing Events
DEFF Research Database (Denmark)
Chen, Lizheng; Zhang, Hengxu; Wu, Qiuwei
2017-01-01
The global climate change leads to more extreme meteorological conditions such as icing weather, which have caused great losses to power systems. Comprehensive simulation tools are required to enhance the capability of power system risk assessment under extreme weather conditions. A hybrid...... numerical simulation scheme integrating icing weather events with power system dynamics is proposed to extend power system numerical simulation. A technique is developed to efficiently simulate the interaction of slow dynamics of weather events and fast dynamics of power systems. An extended package for PSS....../E enabling hybrid simulation of icing event and power system disturbance is developed, based on which a hybrid simulation platform is established. Numerical studies show that the functionality of power system simulation is greatly extended by taking into account the icing weather events....
Jarauta, Alex; Ryzhakov, Pavel; Secanell, Marc; Waghmare, Prashant R.; Pons-Prats, Jordi
2016-08-01
An embedded Eulerian-Lagrangian formulation for the simulation of droplet dynamics within a polymer electrolyte fuel cell (PEFC) channel is presented. Air is modeled using an Eulerian formulation, whereas water is described with a Lagrangian framework. Using this framework, the gas-liquid interface can be accurately identified. The surface tension force is computed using the curvature defined by the boundary of the Lagrangian mesh. The method naturally accounts for material property changes across the interface and accurately represents the pressure discontinuity. A sessile drop in a horizontal surface, a sessile drop in an inclined plane and droplets in a PEFC channel are solved for as numerical examples and compared to experimental data. Numerical results are in excellent agreement with experimental data. Numerical results are also compared to results obtained with the semi-analytical model previously developed by the authors in order to discuss the limitations of the semi-analytical approach.
Summer season | Cafeteria closures
2013-01-01
Please note the following cafeteria closures over the summer season: Bldg. 54 closed from 29/07/2013 to 06/09/2013. Bldg. 13: closed from 13/07/2013 to 06/09/2013. Restaurant No. 2, table service (brasserie and restaurant): closed from 01/08/2013 to 06/09/2013. Bldg. 864: closed from 29/07/2013 to 06/09/2013. Bldg. 865: closed from 29/07/2013 to 06/09/2013.
Summer season | Cafeteria closures
2013-01-01
Please note the following cafeteria closures over the summer season: Bldg. 54 closed from 29/07/2013 to 06/09/2013. Bldg. 13: closed from 13/07/2013 to 06/09/2013. Restaurant No. 2, table service (brasserie and restaurant): closed from 01/08/2013 to 06/09/2013. Bldg. 864: closed from 29/07/2013 to 06/09/2013. Bldg. 865: closed from 29/07/2013 to 06/09/2013.
A numerical approach to calculate the induced voltage in the case of conduced perturbations
Energy Technology Data Exchange (ETDEWEB)
Andretzko, J.P.; Hedjiedj, A.; Babouri, A.; Guendouz, L.; Nadi, M. [Nancy-1 Univ. Henri Poincare, Lab. d' Instrumentation Electronique de Nancy, Faculte des Sciences, 54 - Vandoeuvre les Nancy (France)
2006-07-01
This paper presents a method of numerical simulation that makes it possible to calculate the induced tension to the terminals of the cardiac pacemaker subjected to conduced disturbances. The physical model used for simulation is an experimental test bed which makes it possible to study the behaviour of pacemaker, in vitro, subjected to electromagnetic disturbances in low frequencies range (50 hz - 500 khz). The test bed in which the pacemaker is implanted is described in this article. The process of calculation uses the admittance method adapted to the case of conducted disturbances. Results obtained by numerical simulation are close to experimental values. (authors)
Synthesis of Pyridoacridines through Anionic Cascade Ring Closure
DEFF Research Database (Denmark)
Petersen, I.N.; Kristensen, Jesper Langgaard
2014-01-01
A new synthesis of 13-deazaascididemin (AK-37) based on a recently developed anionic cascade ring closure is presented. Although the isolated yields are modest, the approach provides ready access to new substituted derivatives of 13-deazaascididemin. © Georg Thieme Verlag.......A new synthesis of 13-deazaascididemin (AK-37) based on a recently developed anionic cascade ring closure is presented. Although the isolated yields are modest, the approach provides ready access to new substituted derivatives of 13-deazaascididemin. © Georg Thieme Verlag....
Rahneshin, Vahid; Chierichetti, Maria
2016-09-01
In this paper, a combined numerical and experimental method, called Extended Load Confluence Algorithm, is presented to accurately predict the dynamic response of non-periodic structures when little or no information about the applied loads is available. This approach, which falls into the category of Shape Sensing methods, inputs limited experimental information acquired from sensors to a mapping algorithm that predicts the response at unmeasured locations. The proposed algorithm consists of three major cores: an experimental core for data acquisition, a numerical core based on Finite Element Method for modeling the structure, and a mapping algorithm that improves the numerical model based on a modal approach in the frequency domain. The robustness and precision of the proposed algorithm are verified through numerical and experimental examples. The results of this paper demonstrate that without a precise knowledge of the loads acting on the structure, the dynamic behavior of the system can be predicted in an effective and precise manner after just a few iterations.
Shao, W.; Bogaard, T.A.; Bakker, M.; Greco, R.
2014-01-01
The effect of preferential flow on the stability of landslides is studied through numerical simulation of two types of rainfall events on a hypothetical hillslope. A model is developed that consists of two parts. The first part is a model for combined saturated/unsaturated subsurface flow and is use
Simulation of a Diode Pumped Alkali Laser; a Three Level Numerical Approach
2010-03-01
further iteration of the three level numerical model should include this effect as it is a persistent issue for DPAL systems and without its effects a...1 26.24 * 10-9 H*Lewis Hz*L; A32@85D = 0; A32@87D = 0; III. Parameters Printed by Mathematica for Students 65 III. Parameters A. Enviromental
2010-06-01
Murff, and others, “Collapse loads for a cylinder embedded in trench in cohesive soil,” International Journal of Geomechanics , vol. 5, 2005, p. 320...International Journal for Numerical and Analytical Methods in Geomechanics , vol. 6, 1982, pp. 47-76. [16] P. Mott, J. Dorgan, and C. Roland, “The
Katzin, D.; Katzin, Naama; Salti, Moti; Leibovich, Tali; Henik, Avishai
2016-01-01
Non-symbolic stimuli (i.e., dot arrays) are commonly used to study numerical cognition. However, in addition to numerosity, non-symbolic stimuli entail continuous magnitudes (e.g., total surface area, convex-hull, etc.) that correlate with numerosity. Several methods for controlling for continuous m
Directory of Open Access Journals (Sweden)
Dr.A.B.Deoghare
2012-05-01
Full Text Available The modern treatment to solve differential equations of problems relies heavily on approximation methods. To keep the discussion simple while maintaining a general formulation of practical interest in engineering, the model problem considered is of an axially loaded bar having quadratic function of area. The unknown variable is the axial displacement of one dimensional continuum, u(x is attempted in the present research by means of numerical analysis technique where the basic inputs to a problem are known with arbitrary basic data.Numerically evaluating differential and integral is a rather common and usually stable task. Attempting the numerical solution with different approximation methods leads the errors while solving differential equations of the system. A genuine necessity for obtaining precise solution for the different numerical approximationmethods is overcome by developing in-house computer program. The developed code is resourceful enough to conquer the calculation result from round-off of arithmetic processes or truncation. The program is interactive and user friendly in operation to change the desired inputs. Graphically results can be displayed to know theeffect of considered weights and the constants assumed.
Airbag modelling for Out-of-Position: numerical approach and advanced airbag testing
Rekveldt, M.G.C.; Swartjes, F.H.M.; Steenbrink, A.C.
2002-01-01
There is an increasing pressure to reduce injuries and fatalities by effectively using airbags for side impact and out-of-position impact loading conditions. Numerical simulation, as an essential design tool for airbags, requires accuate models applicable to the various OOP loading cases. In this pa
Structures airbag modelling for Out-of-Position: numerical approach and advanced airbag testing
Rekveldt, M.G.C.; Lemmen, P.P.M.; Swartjes, F.H.M.
2002-01-01
There is an increasing pressure to reduce injuries and fatalities by effectively using airbags for side impact and out-of-position impact loading conditions. Numerical simulation, as an essential design tool for airbags, requires accurate models applicable to the many OOP loading cases. In this pape
Fuller, Nathaniel J
2016-01-01
Obtaining a detailed understanding of the physical interactions between a cell and its environment often requires information about the flow of fluid surrounding the cell. Cells must be able to effectively absorb and discard material in order to survive. Strategies for nutrient acquisition and toxin disposal, which have been evolutionarily selected for their efficacy, should reflect knowledge of the physics underlying this mass transport problem. Motivated by these considerations, in this paper we consider a two-dimensional advection-diffusion problem at small Reynolds number and large P\\'eclet number. We discuss the problem of mass transport for a circular cell in a uniform far-field flow. We approach the problem numerically, and also analytically through a rescaling of the concentration boundary layer. A biophysically motivated first-passage problem for the absorption of material by the cell demonstrates quantitative agreement between the numerical and analytical approaches.
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Andriantrehina Soanarivo Rinah
2016-01-01
Full Text Available This paper presents an experimental and numerical investigation funded by the French National Project “Terredurable”, which is devoted to the study of soils in quasi-saturated state. The experimental study is focused on the behavior of compacted soils on drying-wetting paths and the macroscopic effect of the drying path on shrinkage and cracking. Furthermore, a protocol for image analysis of crack in drying tests was developed. Two approaches are used for the measurement of surface strains and identification of the ultimate stress before the formation of the first crack, using VIC-2D software, and for the monitoring of crack evolution, using ImageJ software. The aim of the numerical approach is to reproduce the drying experiments with a finite difference code (FLAC 3D, in order to understand the stress conditions that can explain crack initiation, without modeling the crack formation itself.
Klein, E. C.; Le Corvec, N.; Galgana, G.
2014-12-01
Basaltic shield volcanoes are subjected to important gravitational loads that lead to their spreading. Such deformation influences the stress state within the volcano, thus the formation of faults and the location of earthquakes and the propagation of magmas and the potential eruption location. Using distinct numerical approaches constrained by geophysical data from the Hawai`i Island Shield Volcano (HISV), we studied the extent to which horizontal deviatoric stresses (HDS) induced from gravitational loading drives the process of volcanic spreading. Two distinct numerical approaches based on similar models were used: 1- the thin-sheet method, and 2- finite element models using COMSOL Multiphysics. We quantified depth integrals of vertical stress (i.e., the gravitational potential energy per unit area or GPE) and then we derived the HDS that balance the horizontal gradients in GPE. We performed the integration over series of single layers that encompasses the surface of variable topography down to a uniform depth of 10 km b.s.l. consistent with the base of the HISV. To compare the results of our numerical approaches we built a fine-scale, Island-wide, set of kinematically constrained deformation indicators (KCDI) using the slip-rate and fault style information from a comprehensive fault database for the HISV. We measure the success of each numerical approach by how well model HDS match the horizontal styles of the strain rates associated with KCDI. Thus far we find that the HDS obtained using the thin-sheet method match well with the KCDI. This may indicate that to first order that patterns of observed surface deformation on the HISV are governed by gradients in GPE. This provides a balance to the gravitationally-induced stresses associated with the volcano load. These HDS do not account for other competing sources of stress (e.g., flexure, magmatic, or hoop) that taken all together may combine to better explain the volcano spreading process for basaltic shield type
A Modal Approach to the Numerical Calculation of Primordial non-Gaussianities
Funakoshi, Hiroyuki
2012-01-01
We propose a new method to numerically calculate higher-order correlation functions of primordial fluctuations generated from any early-universe scenario. Our key-starting point is the realization that the tree-level In-In formalism is intrinsically separable. This enables us to use modal techniques to efficiently calculate and represent non-Gaussian shapes in a separable form well suited to data analysis. We prove the feasibility and the accuracy of our method by applying it to simple single-field inflationary models in which analytical results are available, and we perform non-trivial consistency checks like the verification of the single field consistency relation. We also point out that the i epsilon prescription is automatically taken into account in our method, preventing the need for ad-hoc tricks to implement it numerically.
Modelling of blast-induced damage in tunnels using a hybrid finite-discrete numerical approach
Directory of Open Access Journals (Sweden)
Amichai Mitelman
2014-12-01
Full Text Available This paper presents the application of a hybrid finite-discrete element method to study blast-induced damage in circular tunnels. An extensive database of field tests of underground explosions above tunnels is used for calibrating and validating the proposed numerical method; the numerical results are shown to be in good agreement with published data for large-scale physical experiments. The method is then used to investigate the influence of rock strength properties on tunnel durability to withstand blast loads. The presented analysis considers blast damage in tunnels excavated through relatively weak (sandstone and strong (granite rock materials. It was found that higher rock strength will increase the tunnel resistance to the load on one hand, but decrease attenuation on the other hand. Thus, under certain conditions, results for weak and strong rock masses are similar.
Directory of Open Access Journals (Sweden)
B. Kafash
2014-04-01
Full Text Available In this paper, we present a computational method for solving optimal control problems and the controlled Duffing oscillator. This method is based on state parametrization. In fact, the state variable is approximated by Boubaker polynomials with unknown coefficients. The equation of motion, performance index and boundary conditions are converted into some algebraic equations. Thus, an optimal control problem converts to a optimization problem, which can then be solved easily. By this method, the numerical value of the performance index is obtained. Also, the control and state variables can be approximated as functions of time. Convergence of the algorithms is proved. Numerical results are given for several test examples to demonstrate the applicability and efficiency of the method.
Fast calculation of two-electron-repulsion integrals: a numerical approach
Lopes, Pedro E M
2016-01-01
An alternative methodology to evaluate two-electron-repulsion integrals based on numerical approximation is proposed. Computational chemistry has branched into two major fields with methodologies based on quantum mechanics and classical force fields. However, there are significant shadowy areas not covered by any of the available methods. Many relevant systems are often too big for traditional quantum chemical methods while being chemically too complex for classical force fields. Examples include systems in nanomedicine, studies of metalloproteins, etc. There is an urgent need to develop fast quantum chemical methods able to study large and complex systems. This work is a proof-of-concept on the numerical techniques required to develop accurate and computationally efficient algorithms for the fast calculation of electron-repulsion integrals, one of the most significant bottlenecks in the extension of quantum chemistry to large systems. All concepts and calculations were developed for the three-center integral...
Thermosyphon assisted melting of PCM inside a rectangular enclosure:A synergistic numerical approach
Srikanth, R.; Nair, Rohit S.; Balaji, C.
2016-09-01
Melting of a phase change material assisted by a thermosyphon inside a two dimensional rectangular domain is numerically investigated. The PCM used is n-eicosane and the thermosyphon is made of copper. The working fluid is water. The fill ratio of the working fluid (water) is taken to be 50%. A lumped model is used for the simulation of transient operation of the thermosyphon and enthalpy-porosity method is employed for numerical simulation of melting of PCM. The effects of inclusion of multiple heat pipes on the melting of the PCM inside the enclosure is studied. Simulation results indicate that the addition of heat pipes enhances the performance of latent heat thermal energy storage system only upto a certain extent.
Numerical approach to the top coal caving process under different coal seam thicknesses
Directory of Open Access Journals (Sweden)
Yu Bin
2015-01-01
Full Text Available Numerical study of mining-induced stress evolution of coal during the top coal caving process under different coal seam thicknesses is carried out, and the numerical prediction agrees well with the field test data. Main characters on stress distribution and dangerous area are elucidated. For the same coal quality, coal layers under 7 m thick fail earlier than thicker coal layers; correspondingly, the internal fracture networks of thin layers are more easily developed. During the mining of a coal layer less than 7 m thick, stress monitoring of the “dangerous area” in the middle of the top coal should be emphasized, whereas during the mining of coal layers less than 11 m thick, stress monitoring of the “dangerous area” at the bottom of the top coal should be highlighted. The research is to optimize caving technique and extraction process.
Reed, P.A.S; Starink, M.J.; Gunn, S.R.; Sinclair, I.
2009-01-01
Many adaptive numerical modelling (ANM) techniques such as artificial neural networks, (including multi-layer perceptrons) support vector machines and Gaussian processes have now been applied to a wide range of regression and classification problems in materials science. Materials science offers a wide range of industrial applications and hence problem complexity levels from well physically characterised systems (e.g. high value, low volume products) to high volume low cost applications with ...
Qi, Shengqi; Hou, Deyi; Luo, Jian
2017-09-01
This study presents a numerical model based on field data to simulate groundwater flow in both the aquifer and the well-bore for the low-flow sampling method and the well-volume sampling method. The numerical model was calibrated to match well with field drawdown, and calculated flow regime in the well was used to predict the variation of dissolved oxygen (DO) concentration during the purging period. The model was then used to analyze sampling representativeness and sampling time. Site characteristics, such as aquifer hydraulic conductivity, and sampling choices, such as purging rate and screen length, were found to be significant determinants of sampling representativeness and required sampling time. Results demonstrated that: (1) DO was the most useful water quality indicator in ensuring groundwater sampling representativeness in comparison with turbidity, pH, specific conductance, oxidation reduction potential (ORP) and temperature; (2) it is not necessary to maintain a drawdown of less than 0.1 m when conducting low flow purging. However, a high purging rate in a low permeability aquifer may result in a dramatic decrease in sampling representativeness after an initial peak; (3) the presence of a short screen length may result in greater drawdown and a longer sampling time for low-flow purging. Overall, the present study suggests that this new numerical model is suitable for describing groundwater flow during the sampling process, and can be used to optimize sampling strategies under various hydrogeological conditions.
Salti, Moti; Katzin, Naama; Katzin, David; Leibovich, Tali; Henik, Avishai
2016-07-20
Non-symbolic stimuli (i.e., dot arrays) are commonly used to study numerical cognition. However, in addition to numerosity, non-symbolic stimuli entail continuous magnitudes (e.g., total surface area, convex-hull, etc.) that correlate with numerosity. Several methods for controlling for continuous magnitudes have been suggested, all with the same underlying rationale: disassociating numerosity from continuous magnitudes. However, the different continuous magnitudes do not fully correlate; therefore, it is impossible to disassociate them completely from numerosity. Moreover, relying on a specific continuous magnitude in order to create this disassociation may end up in increasing or decreasing numerosity saliency, pushing subjects to rely on it more or less, respectively. Here, we put forward a taxonomy depicting the relations between the different continuous magnitudes. We use this taxonomy to introduce a new method with a complimentary Matlab toolbox that allows disassociating numerosity from continuous magnitudes and equating the ratio of the continuous magnitudes to the ratio of the numerosity in order to balance the saliency of numerosity and continuous magnitudes. A dot array comparison experiment in the subitizing range showed the utility of this method. Equating different continuous magnitudes yielded different results. Importantly, equating the convex hull ratio to the numerical ratio resulted in similar interference of numerical and continuous magnitudes.
NUMERICAL MODELING OF COMPOUND CHANNEL FLOWS
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A numerical model capable of predicting flow characteristics in a compound channel was established with the 3-D steady continuity and momentum equations along with the transport equations for turbulence kinetic energy and dissipation rate. Closure was achieved with the aid of algebraic relations for turbulent shear stresses. The above equations were discretized with implicit difference approach and solved with a step method along the flow direction. The computational results showing the lateral distribution of vertical average velocities and the latio of total flow in the compound channel agree well with the available experimental data.
Nonlinear closures for scale separation in supersonic magnetohydrodynamic turbulence
Grete, Philipp; Schmidt, Wolfram; Schleicher, Dominik R G; Federrath, Christoph
2015-01-01
Turbulence in compressible plasma plays a key role in many areas of astrophysics and engineering. The extreme plasma parameters in these environments, e.g. high Reynolds numbers, supersonic and super-Alfvenic flows, however, make direct numerical simulations computationally intractable even for the simplest treatment -- magnetohydrodynamics (MHD). To overcome this problem one can use subgrid-scale (SGS) closures -- models for the influence of unresolved, subgrid-scales on the resolved ones. In this work we propose and validate a set of constant coefficient closures for the resolved, compressible, ideal MHD equations. The subgrid-scale energies are modeled by Smagorinsky-like equilibrium closures. The turbulent stresses and the electromotive force (EMF) are described by expressions that are nonlinear in terms of large scale velocity and magnetic field gradients. To verify the closures we conduct a priori tests over 137 simulation snapshots from two different codes with varying ratios of thermal to magnetic pre...
Approximate maximum-entropy moment closures for gas dynamics
McDonald, James G.
2016-11-01
Accurate prediction of flows that exist between the traditional continuum regime and the free-molecular regime have proven difficult to obtain. Current methods are either inaccurate in this regime or prohibitively expensive for practical problems. Moment closures have long held the promise of providing new, affordable, accurate methods in this regime. The maximum-entropy hierarchy of closures seems to offer particularly attractive physical and mathematical properties. Unfortunately, several difficulties render the practical implementation of maximum-entropy closures very difficult. This work examines the use of simple approximations to these maximum-entropy closures and shows that physical accuracy that is vastly improved over continuum methods can be obtained without a significant increase in computational cost. Initially the technique is demonstrated for a simple one-dimensional gas. It is then extended to the full three-dimensional setting. The resulting moment equations are used for the numerical solution of shock-wave profiles with promising results.
Mazzanti, P.; Bozzano, F.
2009-11-01
Coastal and subaqueous landslides can be very dangerous phenomena since they are characterised by the additional risk of induced tsunamis, unlike their completely-subaerial counterparts. Numerical modelling of landslides propagation is a key step in forecasting the consequences of landslides. In this paper, a novel approach named Equivalent Fluid/Equivalent Medium (EFEM) has been developed. It adapts common numerical models and software that were originally designed for subaerial landslides in order to simulate the propagation of combined subaerial-subaqueous and completely-subaqueous landslides. Drag and buoyancy forces, the loss of energy at the landslide-water impact and peculiar mechanisms like hydroplaning can be suitably simulated by this approach; furthermore, the change in properties of the landslide's mass, which is encountered at the transition from the subaerial to the submerged environment, can be taken into account. The approach has been tested by modelling two documented coastal landslides (a debris flow and a rock slide at Lake Albano) using the DAN-W code. The results, which were achieved from the back-analyses, demonstrate the efficacy of the approach to simulate the propagation of different types of coastal landslides.
Pennell, Kelly G; Scammell, Madeleine K; McClean, Michael D; Suuberg, Eric M; Moradi, Ali; Roghani, Mohammadyousef; Ames, Jennifer; Friguglietti, Leigh; Indeglia, Paul A; Shen, Rui; Yao, Yijun; Heiger-Bernays, Wendy J
2016-06-15
USEPA recommends a multiple lines of evidence approach to make informed decisions at vapor intrusion sites because the vapor intrusion pathway is notoriously difficult to characterize. Our study uses this approach by incorporating groundwater, soil gas, indoor air field measurements and numerical models to evaluate vapor intrusion exposure risks in a Metro-Boston neighborhood known to exhibit lower than anticipated indoor air concentrations based on groundwater concentrations. We collected and evaluated five rounds of field sampling data over the period of one year. Field data results show a steep gradient in soil gas concentrations near the groundwater surface; however as the depth decreases, soil gas concentration gradients also decrease. Together, the field data and the numerical model results suggest that a subsurface feature is limiting vapor transport into indoor air spaces at the study site and that groundwater concentrations are not appropriate indicators of vapor intrusion exposure risks in this neighborhood. This research also reveals the importance of including relevant physical models when evaluating vapor intrusion exposure risks using the multiple lines of evidence approach. Overall, the findings provide insight about how the multiple lines of evidence approach can be used to inform decisions by using field data collected using regulatory-relevant sampling techniques, and a well-established 3-D vapor intrusion model.
Directory of Open Access Journals (Sweden)
P. Mazzanti
2009-11-01
Full Text Available Coastal and subaqueous landslides can be very dangerous phenomena since they are characterised by the additional risk of induced tsunamis, unlike their completely-subaerial counterparts. Numerical modelling of landslides propagation is a key step in forecasting the consequences of landslides. In this paper, a novel approach named Equivalent Fluid/Equivalent Medium (EFEM has been developed. It adapts common numerical models and software that were originally designed for subaerial landslides in order to simulate the propagation of combined subaerial-subaqueous and completely-subaqueous landslides. Drag and buoyancy forces, the loss of energy at the landslide-water impact and peculiar mechanisms like hydroplaning can be suitably simulated by this approach; furthermore, the change in properties of the landslide's mass, which is encountered at the transition from the subaerial to the submerged environment, can be taken into account. The approach has been tested by modelling two documented coastal landslides (a debris flow and a rock slide at Lake Albano using the DAN-W code. The results, which were achieved from the back-analyses, demonstrate the efficacy of the approach to simulate the propagation of different types of coastal landslides.
Yamamoto, Y.; Ando, S.
1987-01-01
The unsteady aerodynamics of a two-dimensional wing at sonic speed are studied by using so-called classical sonic theories (linear), approached from supersonic flow (M=1+0) or subsonic flow (M=1-0). In the former approach, the exact expressions of lift and lift distribution are obtained in terms of Fresnel integrals, while in the latter approach an integral equation must be solved, the kernel function of which is obtained from the subsonic Possio's equation and has a root singularity. The discrete analysis is adopted on the basis of the semicircle method (SCM) and the weighting function for subsonic-flow-Gauss-quadrature, as well as modified characteristics obtained from both approaches agree quite well with each other. The results obtained by the present computations are compared with those of DLM-C (subsonic 2D code) developed by ANDO et al, and are found to give a reasonable outer boundary for subsonic unsteady aerodynamics.
An approach to first principles electronic structure calculation by symbolic-numeric computation
Directory of Open Access Journals (Sweden)
Akihito Kikuchi
2013-04-01
Full Text Available There is a wide variety of electronic structure calculation cooperating with symbolic computation. The main purpose of the latter is to play an auxiliary role (but not without importance to the former. In the field of quantum physics [1-9], researchers sometimes have to handle complicated mathematical expressions, whose derivation seems almost beyond human power. Thus one resorts to the intensive use of computers, namely, symbolic computation [10-16]. Examples of this can be seen in various topics: atomic energy levels, molecular dynamics, molecular energy and spectra, collision and scattering, lattice spin models and so on [16]. How to obtain molecular integrals analytically or how to manipulate complex formulas in many body interactions, is one such problem. In the former, when one uses special atomic basis for a specific purpose, to express the integrals by the combination of already known analytic functions, may sometimes be very difficult. In the latter, one must rearrange a number of creation and annihilation operators in a suitable order and calculate the analytical expectation value. It is usual that a quantitative and massive computation follows a symbolic one; for the convenience of the numerical computation, it is necessary to reduce a complicated analytic expression into a tractable and computable form. This is the main motive for the introduction of the symbolic computation as a forerunner of the numerical one and their collaboration has won considerable successes. The present work should be classified as one such trial. Meanwhile, the use of symbolic computation in the present work is not limited to indirect and auxiliary part to the numerical computation. The present work can be applicable to a direct and quantitative estimation of the electronic structure, skipping conventional computational methods.
Institute of Scientific and Technical Information of China (English)
陆贺; 胡志根; 刘全; 吕国轩; 叶建群; 任金明
2016-01-01
The river closure is a key step in the water dam construction, and the end-dump closure is a general way to cut off the river flow. The hydraulic characteristics at the closure gap are the main factors which affect the extent of closure difficulty. A method is proposed to reduce the difficulty of diversion channel closure by pre-building a closure structure called the backwater-sill at the downstream toe of the closure gap to change the flow pattern at the closure gap. The results of the physical model test and the three- dimensional numerical simulation indicate that the backwater-sill has the effects of raising the water level at the downstream toe of the closure gap, decreasing the water surface gradient, and reducing the closure drop and the flow velocity at the closure gap. The schemes with different dike widths, different closure gap widths, and different backwater-sill widths and heights are simulated. The results show that the height of the backwater-sill is the key factor affecting the hydro-indicators at the closure gap, while the influe- nce of the dike width, the closure gap width or the backwater-sill width can be ignored. The higher the backwater-sill is, the lower the hydro-indicators will be. Based on the numerical simulations and the physical model tests on the hydraulic characteristics at the closure gap of the backwater-sill assisted closure, the hydro-indicators and its calculation method are proposed to provide a theoreti- cal support for the river closure.
Numerical approach to the lowest bound state of muonic three-body systems
Khan, Md Abdul
2015-01-01
In this paper, calculated energies of the lowest bound state of Coulomb three-body systems containing an electron ($e^-$), a negatively charged muon ($\\mu^-$) and a nucleus ($N^{Z+}$) of charge number Z are reported. The 3-body relative wave function in the resulting Schr\\"odinger equation is expanded in the complete set of hyperspherical harmonics (HH). Use of the orthonormality of HH leads to an infinite set of coupled differential equations (CDE) which are solved numerically to get the energy E.
Józef Mitka
2014-01-01
Aconitum sect. Napellus in the Eastern Carpathians was explored with the use of methods of numerical taxonomy*. The taxon consists of A. bucovinense Zapał. pro hybr., A.firmum Rchb. subsp. firmum, A. firmum subsp. fissurae Nyarady, A. fimum nsubsp.fussianum Starmuhl (A.firmum subsp. firmum x subsp. f'issurae), A. x nanum (Baumg.) Simonk. (A. bucovinense x A. firmum) and a hybrid A. firmum x A. x nanum. The taxi form phenetic continuum in a character hyperspace and their delimitation bases on ...
Maron, Bernhard; Garthaus, Christian; Lenz, Florian; Hornig, Andreas; Hübner, Michael; Gude, Maik
2016-10-01
Continuous-reinforced thermoplastic composites are of growing importance for series production of lightweight components in manifold industrial areas. Novel manufacturing technologies allow the production of hollow semi-finished products that are post formed to enhance functionality. To maximize efficiency in the development process of such components it is necessary to map the forming processes numerically using Finite Elements(FE)-methods. The aim is to perform feasibility studies at an early stage, reduce development time by virtual process optimization and to generate a detailed understanding of the post formed fiber architecture for further structural-mechanical analysis.
Numerical and Experimental Approach for Identifying Elastic Parameters in Sandwich Plates
Directory of Open Access Journals (Sweden)
Sergio Ferreira Bastos
2002-01-01
Full Text Available This article deals with the identification of elastic parameters (engineering constants in sandwich honeycomb orthotropic rectangular plates. A non-destructive method is introduced to identify the elastic parameters through the experimental measurements of natural frequencies of a plate undergoing free vibrations. Four elastic constant are identified. The estimation of the elastic parameter problem is solved by minimizing the differences between the measured and the calculated natural frequencies. The numerical method to calculate the natural frequencies involves the formulation of Rayleigh-Ritz using a series of characteristic orthogonal polynomials to properly model the free edge boundary conditions. The analysis of the results indicates the efficiency of the method.
Sousa-Martins, J.; Kakogiannis, D.; Coghe, F.; Reymen, B.; Teixeira-Dias, F.
2012-05-01
The experimental characterisation of the dynamic (blast) behaviour of micro-agglomerated cork is presented. A 4-cable ballistic pendulum system was used to measure the transmitted impulse to a target subjected to a shock-wave originated from the detonation of an explosive. The displacement of the pendulum and the transmitted impulse were measured and the coefficient of restitution of the whole system when the cork compound is used was determined. A numerical study of the problem using the finite element method gave very good correlation with the experimental analysis leading to the development of a material constitutive model suited to the dynamic behaviour of these cork compounds in such solicitations.
A new approach to numerical analysis of reliability indices in electronics
Directory of Open Access Journals (Sweden)
Geniy Kuznetsov
2015-01-01
Full Text Available Spatial modeling of unsteady temperature fields is conducted in a microelectronic printed circuit board (PCB with an account of convective and radiation heat transfer with the environment. The data for numerical modeling of temperature fields serve as a basis for determining the aging characteristics of the polymer material as a structural component of electronic engineering products. The obtained results allow concluding on the necessity to consider spatial nonuniform temperature fields when estimating the degree of polymeric materials degradation at the continuous service of products, as well as on the impact of polymer aging on reliability features of microelectronic devices.
The ray projection method: a numerical approach for determining ideal camera placement.
Manal, Kurt; Gardinier, Joseph
2007-02-01
Data piloting is important to ensure accurate marker coordinate data and to minimize camera dropout. Camera dropout results when a camera fails to image a marker, which often occurs when markers merge or become occluded. In this article, we present the conceptual framework for a numerical method of determining where video cameras, if placed, would have an occluded or a merged view of the tracking markers. Experimental data are presented to demonstrate the efficacy of the method as a tool to complement existing data piloting procedures.
Coblation-assisted closure of persistent tracheocutaneous fistulae.
Walner, David L; Mularczyk, Chris; Kakodkar, Kedar
2016-06-01
Persistent tracheocutaneous fistulae (PTCFs) are sequelae of long-term tracheostomy tube use, and while many procedures exist to correct this issue, several are invasive and incur risk to the patient. This case study discusses a minimally invasive approach to closure of small PFTFs with a coblator device that may reduce the risks associated with other closure procedures. We demonstrated successful tracheocutaneous fistulae closure after coblation in all 4 patients that the operation was performed. We believe this technique can be considered for patients under select circumstances and can be part of a surgeon's armamentarium for the treatment of small PTCFs.
Use of bipedicular advancement flaps for intrauterine closure of myeloschisis.
Mangels, K J; Tulipan, N; Bruner, J P; Nickolaus, D
2000-01-01
Several groups have begun to explore the feasibility and utility of intrauterine closure of myelomeningocele. A subset of these fetuses have defects which fall into the category of myeloschisis, and therefore have inadequate skin to enable primary closure. After considerable discussion, it was decided to utilize bipedicular flaps to close these lesions. The procedure is described, and representative examples are shown. To date, 13 of 56 fetuses have required this approach for closure in utero. While this technique generally provides adequate coverage of the dural sac, the cosmetic results have been less than optimal.
Mazzolani, Federico M.
2008-07-01
The seismic protection of historical and monumental buildings, namely dating back from the ancient age up to the 20th Century, is being looked at with greater and greater interest, above all in the Euro-Mediterranean area, its cultural heritage being strongly susceptible to undergo severe damage or even collapse due to earthquake. The cultural importance of historical and monumental constructions limits, in many cases, the possibility to upgrade them from the seismic point of view, due to the fear of using intervention techniques which could have detrimental effects on their cultural value. Consequently, a great interest is growing in the development of sustainable methodologies for the use of Reversible Mixed Technologies (RMTs) in the seismic protection of the existing constructions. RMTs, in fact, are conceived for exploiting the peculiarities of innovative materials and special devices, and they allow ease of removal when necessary. This paper deals with the experimental and numerical studies, framed within the EC PROHITECH research project, on the application of RMTs to the historical and monumental constructions mainly belonging to the cultural heritage of the Euro-Mediterranean area. The experimental tests and the numerical analyses are carried out at five different levels, namely full scale models, large scale models, sub-systems, devices, materials and elements.
Generalized monotone method and numerical approach for coupled reaction diffusion systems
Sowmya, M.; Vatsala, Aghalaya S.
2017-01-01
Study of coupled reaction diffusion systems are very useful in various branches of science and engineering. In this paper, we provide a methodology to construct the solution for the coupled reaction diffusion systems, with initial and boundary conditions, where the forcing function is the sum of an increasing and decreasing function. It is known that the generalized monotone method coupled with coupled lower and upper solutions yield monotone sequences which converges uniformly and monotonically to coupled minimal and maximal solutions. In addition, the interval of existence is guaranteed by the lower and upper solutions, which are relatively easy to compute. Using the lower and upper solutions as the initial approximation, we develop a method to compute the sequence of coupled lower and upper solutions on the interval or on the desired interval of existence. Further, if the uniqueness conditions are satisfied, the coupled minimal and maximal solutions converge to the unique solution of the reaction diffusion systems. We will provide some numerical results as an application of our numerical methodology.
A combined experimental-numerical approach for two-phase flow boiling in a minichannel
Directory of Open Access Journals (Sweden)
Hożejowska Sylwia
2016-01-01
Full Text Available The paper addresses experimental and numerical modeling of the two-phase flows in an asymmetrically heated horizontal minichannel. Experimental measurements concerned flows of evaporating ethanol in a minichannel with rectangular cross section 1.8mm × 2 mm. In order to observe the flows, measuring system was designed and built. The system measured and recorded basic heat and flow parameters of flowing fluid, and the temperature of external surface of the heater by using infrared camera and recorded images of flow with high-speed camera. The second aim of the paper was to formulate appropriate flow boiling heat transfer model, which would minimises the use of experimentally determined constants. The procedure of calculating the temperature of the ethanol is coupled with concurrent process of determining the temperature distributions in the isolating foil and the heating surface. The two-dimensional temperature distributions in three subsequent domains were calculated with Trefftz method. Due to the Robin condition, heat transfer coefficient at the heating surface-ethanol interface was calculated based on the known temperature distributions of the foil and liquid. Additionally, the paper describes the relation between two sets of functions used in the calculation. Numerical calculations made by Trefftz method were performed with using experimental data.
Directory of Open Access Journals (Sweden)
Pratibha Singh
2014-08-01
Full Text Available A reliability evaluation system for the recognition of Devanagri Numerals is proposed in this paper. Reliability of classification is very important in applications of optical character recognition. As we know that the outliers and ambiguity may affect the performance of recognition system, a rejection measure must be there for the reliable recognition of the pattern. For each character image pre-processing steps like normalization, binarization, noise removal and boundary extraction is performed. After calculating the bounding box features are extracted for each partition of the numeral image. Features are calculated on three different zoning methods. Directional feature is considered which is obtained using chain code and gradient direction quantization of the orientations. The Zoning firstly, is considered made up of uniform partitions and secondly of non-uniform compartments based on the density of the pixels. For classification 1-nearest neighbor based classifier, quadratic bayes classifier and linear bayes classifier are chosen as base classifier. The base classifiers are combined using four decision combination rules namely maximum, Median, Average and Majority Voting. The framework is used to test the reliability of recognition system against ambiguity.
Perturbation approach to resonator state solution using the Fourier-Bessel numerical solver
Gauthier, Robert C.
2017-02-01
The Fourier-Bessel (FFB) numerical solver is a useful tool for obtaining the steady states of resonator structures that conform to a cylindrical symmetry. Recently the FFB solver has been greatly simplified by reconfiguring the matrix generating expressions using Maxwell's curl expressions rather than the standard wave equations. This presentation provides a numerical framework suitable for the application on non-degenerate perturbation theory within the theoretical structure of the reconfigured FFB computation environment. It is shown that the resonator structure's perturbation contribution can be isolated as a separate matrix which dictates the shift in resonator state properties. Two distinct application examples are provide; the first has the perturbation possess the same rotational symmetry as the original structure and preserves azimuthal mode order families; the second perturbation has a symmetry different than the original structure and promotes a mixing between azimuthal mode order families. The perturbation extension promises to amplify the potential usefulness of the FFB technique when theoretically considering photonic sensors such as whispering-gallery mode, photonic crystal hole infiltration and a host of others in which the measurand undergoes small changes in its optical properties.
40 CFR 265.280 - Closure and post-closure.
2010-07-01
... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Closure and post-closure. 265.280 Section 265.280 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES... location, topography, and surrounding land use, with respect to the potential effects of pollutant...
FINAL CLOSURE PLAN SURFACE IMPOUNDMENTS CLOSURE, SITE 300
Energy Technology Data Exchange (ETDEWEB)
Lane, J E; Scott, J E; Mathews, S E
2004-09-29
Lawrence Livermore National Laboratory of the University of California (LLNL) operates two Class II surface impoundments that store wastewater that is discharged from a number of buildings located on the Site 300 Facility (Site 300). The wastewater is the by-product of explosives processing. Reduction in the volume of water discharged from these buildings over the past several years has significantly reduced the wastewater storage needs. In addition, the impoundments were constructed in 1984, and the high-density polyethylene (HDPE) geomembrane liners are nearing the end of their service life. The purpose of this project is to clean close the surface impoundments and provide new wastewater storage using portable, above ground storage tanks at six locations. The tanks will be installed prior to closure of the impoundments and will include heaters for allowing evaporation during relatively cool weather. Golder Associates (Golder) has prepared this Final Closure Plan (Closure Plan) on behalf of LLNL to address construction associated with the clean closure of the impoundments. This Closure Plan complies with State Water Resources Control Board (SWRCB) Section 21400 of the California Code of Regulations Title 27 (27 CCR {section}21400). As required by these regulations and guidance, this Plan provides the following information: (1) A site characterization, including the site location, history, current operations, and geology and hydrogeology; (2) The regulatory requirements relevant to clean closure of the impoundments; (3) The closure procedures; and, (4) The procedures for validation and documentation of clean closure.
Numerical modeling of axi-symmetrical cold forging process by ``Pseudo Inverse Approach''
Halouani, A.; Li, Y. M.; Abbes, B.; Guo, Y. Q.
2011-05-01
The incremental approach is widely used for the forging process modeling, it gives good strain and stress estimation, but it is time consuming. A fast Inverse Approach (IA) has been developed for the axi-symmetric cold forging modeling [1-2]. This approach exploits maximum the knowledge of the final part's shape and the assumptions of proportional loading and simplified tool actions make the IA simulation very fast. The IA is proved very useful for the tool design and optimization because of its rapidity and good strain estimation. However, the assumptions mentioned above cannot provide good stress estimation because of neglecting the loading history. A new approach called "Pseudo Inverse Approach" (PIA) was proposed by Batoz, Guo et al.. [3] for the sheet forming modeling, which keeps the IA's advantages but gives good stress estimation by taking into consideration the loading history. Our aim is to adapt the PIA for the cold forging modeling in this paper. The main developments in PIA are resumed as follows: A few intermediate configurations are generated for the given tools' positions to consider the deformation history; the strain increment is calculated by the inverse method between the previous and actual configurations. An incremental algorithm of the plastic integration is used in PIA instead of the total constitutive law used in the IA. An example is used to show the effectiveness and limitations of the PIA for the cold forging process modeling.
Cater, Christopher; Xiao, Xinran; Goldberg, Robert K.; Kohlman, Lee W.
2015-01-01
A combined experimental and analytical approach was performed for characterizing and modeling triaxially braided composites with a modified subcell modeling strategy. Tensile coupon tests were conducted on a [0deg/60deg/-60deg] braided composite at angles of 0deg, 30deg, 45deg, 60deg and 90deg relative to the axial tow of the braid. It was found that measured coupon strength varied significantly with the angle of the applied load and each coupon direction exhibited unique final failures. The subcell modeling approach implemented into the finite element software LS-DYNA was used to simulate the various tensile coupon test angles. The modeling approach was successful in predicting both the coupon strength and reported failure mode for the 0deg, 30deg and 60deg loading directions. The model over-predicted the strength in the 90deg direction; however, the experimental results show a strong influence of free edge effects on damage initiation and failure. In the absence of these local free edge effects, the subcell modeling approach showed promise as a viable and computationally efficient analysis tool for triaxially braided composite structures. Future work will focus on validation of the approach for predicting the impact response of the braided composite against flat panel impact tests.
Jazar, Reza
2015-01-01
This book focuses on the latest applications of nonlinear approaches in different disciplines of engineering. For each selected topic, detailed concept development, derivations, and relevant knowledge are provided for the convenience of the readers. The topics range from dynamic systems and control to optimal approaches in nonlinear dynamics. The volume includes invited chapters from world class experts in the field. The selected topics are of great interest in the fields of engineering and physics and this book is ideal for engineers and researchers working in a broad range of practical topics and approaches. This book also: · Explores the most up-to-date applications and underlying principles of nonlinear approaches to problems in engineering and physics, including sections on analytic nonlinearity and practical nonlinearity · Enlightens readers to the conceptual significance of nonlinear approaches with examples of applications in scientific and engineering problems from v...
Maximum-entropy closure of hydrodynamic moment hierarchies including correlations.
Hughes, Keith H; Burghardt, Irene
2012-06-07
Generalized hydrodynamic moment hierarchies are derived which explicitly include nonequilibrium two-particle and higher-order correlations. The approach is adapted to strongly correlated media and nonequilibrium processes on short time scales which necessitate an explicit treatment of time-evolving correlations. Closure conditions for the extended moment hierarchies are formulated by a maximum-entropy approach, generalizing related closure procedures for kinetic equations. A self-consistent set of nonperturbative dynamical equations are thus obtained for a chosen set of single-particle and two-particle (and possibly higher-order) moments. Analytical results are derived for generalized Gaussian closures including the dynamic pair distribution function and a two-particle correction to the current density. The maximum-entropy closure conditions are found to involve the Kirkwood superposition approximation.
An Integrated Approach for the Numerical Modelling of the Spray Forming Process
DEFF Research Database (Denmark)
Hattel, Jesper; Thorborg, Jesper; Pryds, Nini
2003-01-01
In this paper, an integrated approach for modelling the entire spray forming process is presented. The basis for the analysis is a recently developed model which extents previous studies and includes the interaction between an array of droplets and the enveloping gas. The formulation of the depos......In this paper, an integrated approach for modelling the entire spray forming process is presented. The basis for the analysis is a recently developed model which extents previous studies and includes the interaction between an array of droplets and the enveloping gas. The formulation...
Energy Technology Data Exchange (ETDEWEB)
Guillemaud, V
2007-03-15
This thesis is devoted to the modelling and numerical simulation of liquid-vapor flows. In order to describe these phase transition flows, a two-fluid two-pressure approach is considered. This description of the liquid-vapor mixing is associated to the seven-equation model introduced by Baer and Nunziato. This work investigates the properties of this model in order to simulate the phase transition flows occurring in nuclear engineering. First, a theoretical thermodynamic framework is constructed to describe the liquid-vapor mixing. Provided with this framework, various modelling choices are suggested for the interaction terms between the phases. These closure laws comply with an entropy inequality. The mathematical properties of this model are thereafter examined. The convective part is associated to a nonconservative hyperbolic system. First, we focus on the definition of its weak solutions. Several flow regimes for the two-phase mixing derive from this analysis. Such regimes for the two-phase flows are analogous to the torrential and fluvial regimes for the shallow-water equations. Furthermore, we establish the linear and nonlinear stabilities of the liquid-vapor equilibrium. Finally, the implementation of a turbulence model and the introduction of a reconstruction process for the interfacial area are investigated in order to refine the description of the interfacial transfers. Using a fractional step approach, a Finite Volume method is at last constructed to simulate this model. First, various nonconservative adaptations of standard Riemann solvers are developed to approach the convective part. Unlike the classic nonconservative framework, these schemes converge towards the same solution. Furthermore, a new relaxation scheme is proposed to approach the interfacial transfers. Provided with these schemes, the whole numerical method preserves the liquid-vapor equilibria. Using this numerical method, a careful comparison between the one- and two-pressure two
Directory of Open Access Journals (Sweden)
Medjahed Bendida
2014-04-01
Full Text Available The MUST wind tunnel data set served as a validation case for obstacle-resolving micro-scale models in the COST Action 732 “Quality Assurance and Improvement of Micro-Scale Meteorological Models”.The code used for the numerical simulation is code CHENSI, simulations carried out showed a certain degree of agreement between the experimental results and those of the numerical simulation, they highlight the need for proceeding to an experimental campaign but with more measurements and the need for having a good control of determining factors in the exploitation of its results. The aim is to explain the experimental data obtained by atmospheric wind on the physical model. The site company of Mock Urban Setting Test (MUST was selected to be simulated by the code CEN CHENSI developed by the team of Dynamique of l’atmosphere Habitee of LME/ECN. The code was based on (K- ε model of (Launder and Spalding. For the integration of the PDE (Potential Dimensional equations constitute the mathematical model, the finite volume method of (Ferziger and Peric was used within the decade disposition of unknowns MAC of (Harlow and Welck for the discretisation of PDE terms. The boundary conditions were imposed according to the wall laws (In ground and on buildings or within Dirichlet condition (Inlet boundary or of Newman (Outlet boundary or top limit. The numerical domain used was comparable to the one of the atmospheric wind experiences within a three-dimensional Cartesian mesh. Numerical results presented in this study for the mean flow field, turbulent kinetic energy in the direction of wind incidence 0°. For an objective comparison of the CHENSI model performances within other European codes used for MUST configuration simulation. The results obtained by the numerical modelling approach are presented in this paper.
Performance Assessment for Pump-and-Treat Closure or Transition
Energy Technology Data Exchange (ETDEWEB)
Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Becker, Dave J. [U.S. Army Corps of Engineers Environmental and Munitions Center of Expertise, Huntsville, AL (United States); Lee, Michelle H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nimmons, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2015-09-29
A structured performance assessment approach is useful to evaluate pump-and-treat (P&T) groundwater remediation, which has been applied at numerous sites. Consistent with the U.S. Environmental Protection Agency’s Groundwater Road Map, performance assessment during remedy implementation may be needed, and should consider remedy optimization, transition to alternative remedies, or remedy closure. In addition, a recent National Research Council study examined groundwater remediation at complex contaminated sites and concluded that it may be beneficial to evaluate remedy performance and the potential need for transition to alternative approaches at these sites. The intent of this document is to provide a structured approach for assessing P&T performance to support a decision to optimize, transition, or close a P&T remedy. The process presented in this document for gathering information and performing evaluations to support P&T remedy decisions includes use of decision elements to distinguish between potential outcomes of a remedy decision. Case studies are used to augment descriptions of decision elements and to illustrate each type of outcome identified in the performance assessment approach. The document provides references to resources for tools and other guidance relevant to conducting the P&T assessment.
Extremum-Seeking Control and Applications A Numerical Optimization-Based Approach
Zhang, Chunlei
2012-01-01
Extremum seeking control tracks a varying maximum or minimum in a performance function such as a cost. It attempts to determine the optimal performance of a control system as it operates, thereby reducing downtime and the need for system analysis. Extremum Seeking Control and Applications is divided into two parts. In the first, the authors review existing analog optimization based extremum seeking control including gradient, perturbation and sliding mode based control designs. They then propose a novel numerical optimization based extremum seeking control based on optimization algorithms and state regulation. This control design is developed for simple linear time-invariant systems and then extended for a class of feedback linearizable nonlinear systems. The two main optimization algorithms – line search and trust region methods – are analyzed for robustness. Finite-time and asymptotic state regulators are put forward for linear and nonlinear systems respectively. Further design flexibility is achieved u...
Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches
DEFF Research Database (Denmark)
Baran, Ismet; Hattel, Jesper Henri; Akkerman, Remko
2015-01-01
The process induced variations such as residual stresses and distortions are a critical issue in pultrusion, since they affect the structural behavior as well as the mechanical properties and geometrical precision of the final product. In order to capture and investigate these variations......, a mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo......-chemical-mechanical analysis is carried out using 3D quadratic elements which is a novel application for the numerical modelling of the pultrusion process. It is found that the 2D mechanical models give relatively reasonable and accurate stress and displacement evolutions in the transverse direction as compared to the 3D...
Numerical damage models using a structural approach: application in bones and ligaments
Arnoux, P. J.; Bonnoit, J.; Chabrand, P.; Jean, M.; Pithioux, M.
2002-01-01
The purpose of the present study was to apply knowledge of structural properties to perform numerical simulations with models of bones and knee ligaments exposed to dynamic tensile loading leading to tissue damage. Compact bones and knee ligaments exhibit the same geometrical pattern in their different levels of structural hierarchy from the tropocollagen molecule to the fibre. Nevertheless, their mechanical behaviours differ considerably at the fibril level. These differences are due to the contribution of the joints in the microfibril-fibril-fibre assembly and to the mechanical properties of the structural components. Two finite element models of the fibrous bone and ligament structure were used to describe damage in terms of elastoplastic laws or joint decohesion processes.
The Mechanical Behavior Of A Nylon Seat Belt Exposed To Cyclical Loads: A Numerical Approach
Directory of Open Access Journals (Sweden)
Lucas Nogueira Assis,
2015-09-01
Full Text Available This work aims to study the mechanical behavior of a nylon seat belt when it is exposed to cyclical loads through the Finite Element Methods. This work used as base the brazilian regulamentoy standard ABNT NBR 7337:2011 to create the virtual model of the seat belt, with the following dimensions: 1.20mm thick, 48mm width and 250mm length. The next step was to import this CAD model to ANSYS 14.5 software, to create the correct material model for this case and apply the correct boundary conditions in order to analyze its behavior under a load that varies from 0 to 2000 N at a 10 Hz frequency. The final step was to analyze this numerical results that referring to this component under these conditions.
Numerical simulation of strained Si/SiGe devices: the hierarchical approach
Meinerzhagen, B.; Jungemann, C.; Neinhüs, B.; Bartels, M.
2004-03-01
Performance predictions for 25 nm strained Si CMOS devices which are based on full-band Monte Carlo (FBMC) device simulations and which are in good agreement with the most recent experimental trends are presented. The FBMC simulator itself is part of a hierarchical device simulation system which allows to perform time-efficient hierarchical hydrodynamic (HD) device simulations of modern SiGe HBTs. As demonstrated below, the accuracy of a such a hydrodynamic-based dc, ac, transient, and noise analysis is comparable to FBMC device simulations. In addition, the new hierarchical numerical noise simulation method is experimentally verified based on a modern rf-CMOS technology of Philips Research. The MC-enhanced simulation accuracy of the hierarchical hydrodynamic and drift diffusion (DD) models can be also exploited for mixed-mode circuit simulations, which is shown by typical power sweep simulations of an industrial rf power amplifier.
Continuity of the maximum-entropy inference: Convex geometry and numerical ranges approach
Energy Technology Data Exchange (ETDEWEB)
Rodman, Leiba [Department of Mathematics, College of William and Mary, P.O. Box 8795, Williamsburg, Virginia 23187-8795 (United States); Spitkovsky, Ilya M., E-mail: ims2@nyu.edu, E-mail: ilya@math.wm.edu [Department of Mathematics, College of William and Mary, P.O. Box 8795, Williamsburg, Virginia 23187-8795 (United States); Division of Science and Mathematics, New York University Abu Dhabi, Saadiyat Island, P.O. Box 129188, Abu Dhabi (United Arab Emirates); Szkoła, Arleta, E-mail: szkola@mis.mpg.de; Weis, Stephan, E-mail: maths@stephan-weis.info [Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, D-04103 Leipzig (Germany)
2016-01-15
We study the continuity of an abstract generalization of the maximum-entropy inference—a maximizer. It is defined as a right-inverse of a linear map restricted to a convex body which uniquely maximizes on each fiber of the linear map a continuous function on the convex body. Using convex geometry we prove, amongst others, the existence of discontinuities of the maximizer at limits of extremal points not being extremal points themselves and apply the result to quantum correlations. Further, we use numerical range methods in the case of quantum inference which refers to two observables. One result is a complete characterization of points of discontinuity for 3 × 3 matrices.
Malkov, Ewgenij A.; Poleshkin, Sergey O.; Kudryavtsev, Alexey N.; Shershnev, Anton A.
2016-10-01
The paper presents the software implementation of the Boltzmann equation solver based on the deterministic finite-difference method. The solver allows one to carry out parallel computations of rarefied flows on a hybrid computational cluster with arbitrary number of central processor units (CPU) and graphical processor units (GPU). Employment of GPUs leads to a significant acceleration of the computations, which enables us to simulate two-dimensional flows with high resolution in a reasonable time. The developed numerical code was validated by comparing the obtained solutions with the Direct Simulation Monte Carlo (DSMC) data. For this purpose the supersonic flow past a flat plate at zero angle of attack is used as a test case.
Bellotti, Filipe F.; Dehkharghani, Amin S.; Zinner, Nikolaj T.
2017-02-01
We investigate one-dimensional harmonically trapped two-component systems for repulsive interaction strengths ranging from the non-interacting to the strongly interacting regime for Fermi-Fermi mixtures. A new and powerful mapping between the interaction strength parameters from a continuous Hamiltonian and a discrete lattice Hamiltonian is derived. As an example, we show that this mapping does not depend neither on the state of the system nor on the number of particles. Energies, density profiles and correlation functions are obtained both numerically (density matrix renormalization group (DMRG) and exact diagonalization) and analytically. Since DMRG results do not converge as the interaction strength is increased, analytical solutions are used as a benchmark to identify the point where these calculations become unstable. We use the proposed mapping to set a quantitative limit on the interaction parameter of a discrete lattice Hamiltonian above which DMRG gives unrealistic results.
Makowski, Piotr L; Domanski, Andrzej W
2013-09-01
An efficient simulation technique is proposed for computing propagation of uniformly polarized statistically stationary fields in linear nonimage-forming systems that includes dispersion of linear birefringence to all orders. The method is based on the discrete-time Fourier transformation of modified frequency profiles of the spectral Stokes parameters. It works under the condition that all (linearly) birefringent sections present in the system are described by the same phase birefringence dispersion curve, being a monotonic function of the optical frequency within the bandwidth of the light. We demonstrate the technique as a supplement for the Mueller-Stokes matrix formalism extended to any uniformly polarized polychromatic illumination. Accuracy of its numerical implementation has been verified by using parameters of a Lyot depolarizer made of a highly birefringent and dispersive monomode photonic crystal fiber.
Energy Technology Data Exchange (ETDEWEB)
Ko, Soon Heum [Linkoeping University, Linkoeping (Sweden); Kim, Na Yong; Nikitopoulos, Dimitris E.; Moldovan, Dorel [Louisiana State University, Baton Rouge (United States); Jha, Shantenu [Rutgers University, Piscataway (United States)
2014-01-15
Numerical approaches are presented to minimize the statistical errors inherently present due to finite sampling and the presence of thermal fluctuations in the molecular region of a hybrid computational fluid dynamics (CFD) - molecular dynamics (MD) flow solution. Near the fluid-solid interface the hybrid CFD-MD simulation approach provides a more accurate solution, especially in the presence of significant molecular-level phenomena, than the traditional continuum-based simulation techniques. It also involves less computational cost than the pure particle-based MD. Despite these advantages the hybrid CFD-MD methodology has been applied mostly in flow studies at high velocities, mainly because of the higher statistical errors associated with low velocities. As an alternative to the costly increase of the size of the MD region to decrease statistical errors, we investigate a few numerical approaches that reduce sampling noise of the solution at moderate-velocities. These methods are based on sampling of multiple simulation replicas and linear regression of multiple spatial/temporal samples. We discuss the advantages and disadvantages of each technique in the perspective of solution accuracy and computational cost.
Numerical Approach to Wood Pyrolysis in Considerating Heat Transfer in Reactor Chamber
Idris, M.; Novalia, U.
2017-03-01
Pyrolysis is the decomposition process of solid biomass into gas, tar and charcoal through thermochemical methods. The composition of biomass consists of cellulose hemi cellulose and lignin, which each will decompose at different temperatures. Currently pyrolysis has again become an important topic to be discussed. Many researchers make and install the pyrolysis reactor to convert biomass waste into clean energy hardware that can be used to help supply energy that has a crisis. Additionally the clean energy derived from biomass waste is a renewable energy, in addition to abundant source also reduce exhaust emissions of fossil energy that causes global warming. Pyrolysis is a method that has long been known by humans, but until now little is known about the phenomenon of the pyrolysis process that occurs in the reactor. One of the Pyrolysis’s phenomena is the heat transfer process from the temperature of the heat source in the reactor and heat the solid waste of biomass. The solid waste of biomass question in this research is rubber wood obtained from one of the company’s home furnishings. Therefore, this study aimed to describe the process of heat transfer in the reactor during the process. ANSYS software was prepared to make the simulation of heat transfer phenomena at the pyrolysis reactor. That’s the numerical calculation carried out for 1200 seconds. Comparison of temperature performed at T1, T2 and T3 to ensure that thermal conductivity is calculated by numerical accordance with experimental data. The distribution of temperature in the reactor chamber specifies the picture that excellent heat conduction effect of the wood near or attached to wooden components, cellulose, hemicellulose and lignin down into gas.
Torgoev, Almaz; Havenith, Hans-Balder
2015-04-01
2D elasto-dynamic modelling of the seismic response was performed with the UDEC software (ver. 4.01, ITASCA). The numerical studies have been performed for six models constructed from real topographic settings of the landslide-prone slopes situated in the Mailuu-Suu River Valley, Southern Kyrgyzstan. The main focus of our studies was the development of proxies for a regional mapping of topographic site effects. The main parameter we studied was the Arias Intensity (Ia). This parameter is applied to the GIS-based Newmark method, which regionally maps the seismically-induced landslide susceptibility. This method performs a mapping of the Ia values via empirical attenuation laws, which mainly account for the regional geometric spreading. An input of site effects is generally not included in these laws. While total site effects normally integrate both geologic and topographic inputs, our paper focuses only on the pure topographic effects. The numerical studies showed that the amplification of the Arias Intensity depends on two main factors: the frequency content of the input signal and the site settings. The first parameter can be predicted for wide areas through attenuation laws. With respect to the impact of site settings on Ia amplification, our studies show that convex surface morphologies with a longer baseline induce amplification in the low frequency domain, while those with a shorter baseline amplify the seismic shaking in the higher frequency domain. The link between topographic site amplification and the size of a surface morphology is identified. Those developed proxies are adapted for application in conventional GIS software platforms.
A numerical approach to investigate the stability of equilibria for structured population models
Breda, D.; Diekmann, O.; Maset, S.; Vermiglio, R.
2013-01-01
We are interested in the asymptotic stability of equilibria of structured populations modelled in terms of systems ofVolterra functional equations coupled with delay differential equations. The standard approach based on studying the characteristic equation of the linearized system is often involved
A Three-Fold Approach to the Heat Equation: Data, Modeling, Numerics
Spayd, Kimberly; Puckett, James
2016-01-01
This article describes our modeling approach to teaching the one-dimensional heat (diffusion) equation in a one-semester undergraduate partial differential equations course. We constructed the apparatus for a demonstration of heat diffusion through a long, thin metal rod with prescribed temperatures at each end. The students observed the physical…
A Numerical Approach for the Solution of Schrödinger Equation With Pseudo-Gaussian Potentials
Directory of Open Access Journals (Sweden)
Iacob Theodor-Felix
2015-12-01
Full Text Available The Schrödinger equation with pseudo-Gaussian potential is investigated. The pseudo-Gaussian potential can be written as an infinite power series. Technically, by an ansatz to the wave-functions, exact solutions can be found by analytic approach [12]. However, to calculate the solutions for each state, a condition that will stop the series has to be introduced. In this way the calculated energy values may suffer modifications by imposing the convergence of series. Our presentation, based on numerical methods, is to compare the results with those obtained in the analytic case and to determine if the results are stable under different stopping conditions.
Stochastic particle acceleration and statistical closures
Energy Technology Data Exchange (ETDEWEB)
Dimits, A.M.; Krommes, J.A.
1985-10-01
In a recent paper, Maasjost and Elsasser (ME) concluded, from the results of numerical experiments and heuristic arguments, that the Bourret and the direct-interaction approximation (DIA) are ''of no use in connection with the stochastic acceleration problem'' because (1) their predictions were equivalent to that of the simpler Fokker-Planck (FP) theory, and (2) either all or none of the closures were in good agreement with the data. Here some analytically tractable cases are studied and used to test the accuracy of these closures. The cause of the discrepancy (2) is found to be the highly non-Gaussian nature of the force used by ME, a point not stressed by them. For the case where the force is a position-independent Ornstein-Uhlenbeck (i.e., Gaussian) process, an effective Kubo number K can be defined. For K << 1 an FP description is adequate, and conclusion (1) of ME follows; however, for K greater than or equal to 1 the DIA behaves much better qualitatively than the other two closures. For the non-Gaussian stochastic force used by ME, all common approximations fail, in agreement with (2).
Nonlinear mechanics of thin-walled structures asymptotics, direct approach and numerical analysis
Vetyukov, Yury
2014-01-01
This book presents a hybrid approach to the mechanics of thin bodies. Classical theories of rods, plates and shells with constrained shear are based on asymptotic splitting of the equations and boundary conditions of three-dimensional elasticity. The asymptotic solutions become accurate as the thickness decreases, and the three-dimensional fields of stresses and displacements can be determined. The analysis includes practically important effects of electromechanical coupling and material inhomogeneity. The extension to the geometrically nonlinear range uses the direct approach based on the principle of virtual work. Vibrations and buckling of pre-stressed structures are studied with the help of linearized incremental formulations, and direct tensor calculus rounds out the list of analytical techniques used throughout the book. A novel theory of thin-walled rods of open profile is subsequently developed from the models of rods and shells, and traditionally applied equations are proven to be asymptotically exa...
An Alternative Approach for Determining Photoionization Rate in H2+: Numerical Results
Institute of Scientific and Technical Information of China (English)
ZHOU Yu; ZHANG Gui-Zhong; XIANG Wang-Hua; W.T. Hill Ⅲ
2005-01-01
@@ We present an alternative approach for determining the photoionization rate of hydrogen molecules under the interaction of intense light, by calculating the spatial overlap integral between the potential function and the time-dependent wavefunction. The suggested method was applied to varying excitation pulse shapes: square envelope and chirped hyperbolic secant envelope. The computed results confirmed that our method was robust and could be extended to general molecular dynamics calculations.
Sustainable management of harbours : a numerical approach for the assessment of waters quality
Bonamano, Simone; Madonia, Alice; Piazzolla, Daniele; Paladini de Mendoza, Francesco; Piermattei, Viviana; Scanu, Sergio; Melchiorri, Cristiano; Marcelli, Marco
2017-04-01
Within the Water Framework Directive (WFD), harbours must reach or maintain the good ecological potential, being classified as heavily modified water bodies. To fulfill this task and to comply the Marine Spatial Planning (MSP) principles, port managers have to monitor the water quality that can be compromised by the numerous activities including the realization of new infrastructures. The port of Civitavecchia, located on the central west coast of Italy, is undergoing to major structural changes to become one of the first ports of the Mediterranean in terms of passenger traffic and goods, thus requiring the development of management tools for the predictive assessment of harbour water quality. This study focused on the evaluation of water degradation within Civitavecchia port trough the calculation of Flushing time (FT) and the development of the new Flushing Efficiency Index (FEI). FT was calculated through the use of a numerical model under different scenarios selected combining different weather conditions with the new port configurations. FT values was then used to estimate the FEI for the evaluation of the improvement (positive values) or the deterioration (negative values) of water quality in the different zones of the port. The increase in the harbour basin size due to the embankment extension results in high values of FT, particularly in the inner part of the port, in accordance with the highest values of the Enrichment Factor (EF) of the trace metals found in the sediment. The correlation between FT and EF confirms that renewal time can be used as a proxy to evaluate the water quality conditions in the harbour basin, as also stated by the WFD guidelines. Also the results of FEI calculation indicate the potential occurrence of water degradation due to the embankment extension. Otherwise, the realization of a second entrance in the southern part of Civitavecchia port produces FEI positive values, highlighting a drastic improvement in harbour water renewal
Simplified approaches for the numerical simulation of welding processes with filler material
Energy Technology Data Exchange (ETDEWEB)
Carmignani, B.; Toselli, G. [ENEA, Divisione Fisica Applicata, Centro Ricerche Ezio Clementel, Bologna (Italy)
2001-07-01
Due to the very high computation times, required by the methodologies pointed out during the studies carried out at ENEA-Bologna concerning the numerical simulations of welds with filler material of steel pieces of high thickness (studies presented also at the 12. and 13. International ABAQUS Users' Conferences), new simplified methodologies have been proposed and applied to an experimental model of significant dimensions. (These studies are of interest in the nuclear field for the construction of the toroidal field coil case, TFCC, for the international thermonuclear experimental reactor, ITER machine). In this paper these new methodologies are presented together the obtained results, which have been compared, successfully, with the ones obtained by the use of the previous numerical methodologies considered and also with the corresponding experimental measures. These new calculation techniques are in course of application for the simulation of welds of pieces constituting a real component of ITER TF coil case. [Italian] A causa dei tempi di calcolo molto elevati richiesti dalle metodologie individuate e messe a punto durante gli studi eseguiti in ENEA-Bologna riguardanti le simulazioni numeriche di saldature, con apporto di materiale, di pezzi di acciaio di grande spessore (studi presentati anche alle precedenti Conferenze Utenti ABAQUS, 12{sup 0} e 13{sup 0} ABAQUS Users' Conferences), sono state cercate e proposte nuove metodologie semplificate, che sono state poi applicate ad un modello sperimentale di dimensioni significative. (Si ricorda che questi studi sono di interesse nel campo nucleare per la costruzione delle casse per contenere le bobine che daranno luogo al campo magnetico della macchina ITER, reattore internazione sperimentale termonucleare). Nel lavoro qui presentato sono descritte queste nuove metodologie e sono riportati i risultati ottenuti dalla loro applicazione unitamente ai confronti (abbastanza soddisfacenti) con i risultati
Directory of Open Access Journals (Sweden)
Hang Zhou
2015-05-01
Full Text Available This study presents a numerical validation of a new approach to model single junction PV cell under non-uniform illumination for low-concentration solar collectors such as compound parabolic concentrators (CPC. The simulation is achieved by finite element modelling (FEM. To characterize the results, the model is simulated with five different non-uniform illumination profiles. The results indicate that increasing the non-uniformity of concentrated light will introduce more resistive losses and lead to a significant attenuation in the PV cell short-circuit current. The FEM modelling results are then used to validate the array modelling approach, in which a single junction PV cell is considered equivalent to a parallel-connected array of several cell splits. A comparison between the FEM and array modelling approaches shows good agreement. Therefore, the array modelling approach is a fast way to investigate the PV cell performance under non-uniform illumination, while the FEM approach is useful in optimizing design of fingers and bus-bars on a PV.
Direct numerical simulation of a compressible multiphase flow through the fast Eulerian approach
Cerminara, Matteo; Ongaro, Tomaso Esposti; Salvetti, Maria Vittoria
2014-01-01
Our work is motivated by the analysis of ash plume dynamics, arising in the study of volcanic eruptions. Such phenomena are characterized by large Reynolds number (exceeding $10^7$) and a large number of polydispersed particles~[1]. Thus, the choice of the methodology to be used is straightforward: we need LES of a multiphase gas-particles flow. Since the simulation of the behavior of a large number of dispersed particles is very difficult with Lagrangian methods, we model the particles as a continuum, Eulerian fluid (dust), by using reduced models involving two fluids, as proposed in Ref.~[2,3,4]. Moreover, we need a robust numerical scheme to simultaneously treat compressibility, buoyancy effects and turbulent dispersal dynamics. We analyze the turbulence properties of such models in a homogeneous and isotropic setting, with the aim of formulating a LES model. In particular, we examine the development of freely decaying homogeneous and isotropic turbulence in subsonic regime (the r.m.s. Mach number either 0...
Directory of Open Access Journals (Sweden)
Józef Mitka
2014-01-01
Full Text Available Aconitum sect. Napellus in the Eastern Carpathians was explored with the use of methods of numerical taxonomy*. The taxon consists of A. bucovinense Zapał. pro hybr., A.firmum Rchb. subsp. firmum, A. firmum subsp. fissurae Nyarady, A. fimum nsubsp.fussianum Starmuhl (A.firmum subsp. firmum x subsp. f'issurae, A. x nanum (Baumg. Simonk. (A. bucovinense x A. firmum and a hybrid A. firmum x A. x nanum. The taxi form phenetic continuum in a character hyperspace and their delimitation bases on a few traits, hitherto neglected, e.g. type of hairiness and flower morphology. A key is provided to identify taxa at all ranks within the supplemented of sect. Napellus. There is a regional pattern of particular OTUs distribution, which show local morphological uniqueness within a taxon. The phenomenon was inquired using the concept of "centers of phenetic coherence" (CPC based on overall morphological similarity. The CPC may be interpreteted as regions of neoendemism and/or may reflect a post-glacial migratory route. High-mountain flora of the Western Bieszczady Mts. (sect. Napelus as its example has features of neoendemism (schizoendemism, being most probably a result of geographical vicarism.
Dome and Keel dynamics in the hot Archean lithosphere: a numerical approach
Duclaux, G.; Thebaud, N.; Gessner, K.; Doublier, M.
2012-12-01
The long-term interactions between greenstone belts and adjacent granitoids domes is key for understanding hot lithosphere rheology, crustal evolution and major ore deposits formation in Archean terrains. Some few tectonic processes have been proposed to explain both local and regional granite/greenstone finite deformation patterns observed in Archean terrains such as the West Australian Pilbara or Yilgarn cratons, including crustal extension following gravitational collapse, metamorphic core complex formation, folding interferences, and gravity driven deformation associated with exhumation of granitoids relative to a supracrustal cover. We propose to assess gravity driven deformation processes from simplified 2-D and 3-D thermo-mechanical numerical experiments using Underworld. A series of visco-plastic experiments under controlled boundary conditions have allowed us to identify three distinct stages in the hot lithosphere tectonic evolution: (1) an internal heating phase, (2) an inversion phase where dense mafic materials fall toward the lower crust while mid-crustal granitoids raise toward the surface, and (3) a freezing phase where the system stops. The relative duration of these phases is dependent on models initial geometries and inherited structures, materials thermal properties and rheologies, and the rheological contrast between granitoids and greenstones. We compare our experimental results with field observations and geophysical data from the Yilgarn craton in order to validate the gravity driven tectonic model, and eventually constrain the range of thermal and mechanical parameters that best capture Archean crustal dynamics.
Manfredi, Simone; Cristobal, Jorge
2016-09-01
Trying to respond to the latest policy needs, the work presented in this article aims at developing a life-cycle based framework methodology to quantitatively evaluate the environmental and economic sustainability of European food waste management options. The methodology is structured into six steps aimed at defining boundaries and scope of the evaluation, evaluating environmental and economic impacts and identifying best performing options. The methodology is able to accommodate additional assessment criteria, for example the social dimension of sustainability, thus moving towards a comprehensive sustainability assessment framework. A numerical case study is also developed to provide an example of application of the proposed methodology to an average European context. Different options for food waste treatment are compared, including landfilling, composting, anaerobic digestion and incineration. The environmental dimension is evaluated with the software EASETECH, while the economic assessment is conducted based on different indicators expressing the costs associated with food waste management. Results show that the proposed methodology allows for a straightforward identification of the most sustainable options for food waste, thus can provide factual support to decision/policy making. However, it was also observed that results markedly depend on a number of user-defined assumptions, for example on the choice of the indicators to express the environmental and economic performance.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Solids phase chromatography for particle classification is based on different retention times of particles with different properties when they are elutriated through a confined geometry.This work aims at a fundamental understanding of such a technology by using the combined continuous and discrete method.A packed bed is employed as the model confined geometry.The numerical method is compared first with experimental observations,followed by a parametric analysis of the effects on the flow hydrodynamics and solids behaviour of various parameters including the number of injected particles,the superficial gas velocity,the contact stiffness and the diameter ratio of the packed column to the packed particles.The results show that the modelling captures some important features of the flow of an injected pulse of fine particles in a packed bed. An increase in the number of injected particles or the superficial gas velocity reduces the retention time,whereas the contact stiffness does not show much effect over the range of 5×102 to5×104 N/m.It is also found that the effect on the retention time of the diameter ratio of the packed column to the packed particles seems complex showing a non-monotonous dependence.
Perez-Benito, Joaquin F; Mulero-Raichs, Mar
2016-10-06
Many kinetic studies concerning homologous reaction series report the existence of an activation enthalpy-entropy linear correlation (compensation plot), its slope being the temperature at which all the members of the series have the same rate constant (isokinetic temperature). Unfortunately, it has been demonstrated by statistical methods that the experimental errors associated with the activation enthalpy and entropy are mutually interdependent. Therefore, the possibility that some of those correlations might be caused by accidental errors has been explored by numerical simulations. As a result of this study, a computer program has been developed to evaluate the probability that experimental errors might lead to a linear compensation plot parting from an initial randomly scattered set of activation parameters (p-test). Application of this program to kinetic data for 100 homologous reaction series extracted from bibliographic sources has allowed concluding that most of the reported compensation plots can hardly be explained by the accumulation of experimental errors, thus requiring the existence of a previously existing, physically meaningful correlation.
Numerical approach of collision avoidance and optimal control on robotic manipulators
Wang, Jyhshing Jack
1990-01-01
Collision-free optimal motion and trajectory planning for robotic manipulators are solved by a method of sequential gradient restoration algorithm. Numerical examples of a two degree-of-freedom (DOF) robotic manipulator are demonstrated to show the excellence of the optimization technique and obstacle avoidance scheme. The obstacle is put on the midway, or even further inward on purpose, of the previous no-obstacle optimal trajectory. For the minimum-time purpose, the trajectory grazes by the obstacle and the minimum-time motion successfully avoids the obstacle. The minimum-time is longer for the obstacle avoidance cases than the one without obstacle. The obstacle avoidance scheme can deal with multiple obstacles in any ellipsoid forms by using artificial potential fields as penalty functions via distance functions. The method is promising in solving collision-free optimal control problems for robotics and can be applied to any DOF robotic manipulators with any performance indices and mobile robots as well. Since this method generates optimum solution based on Pontryagin Extremum Principle, rather than based on assumptions, the results provide a benchmark against which any optimization techniques can be measured.
Catalina, Adrian V.; Sen, S.; Rose, M. Franklin (Technical Monitor)
2001-01-01
The evolution of cellular solid/liquid interfaces from an initially unstable planar front was studied by means of a two-dimensional computer simulation. The developed numerical model makes use of an interface tracking procedure and has the capability to describe the dynamics of the interface morphology based on local changes of the thermodynamic conditions. The fundamental physics of this formulation was validated against experimental microgravity results and the predictions of the analytical linear stability theory. The performed simulations revealed that in certain conditions, based on a competitive growth mechanism, an interface could become unstable to random perturbations of infinitesimal amplitude even at wavelengths smaller than the neutral wavelength, lambda(sub c), predicted by the linear stability theory. Furthermore, two main stages of spacing selection have been identified. In the first stage, at low perturbations amplitude, the selection mechanism is driven by the maximum growth rate of instabilities while in the second stage the selection is influenced by nonlinear phenomena caused by the interactions between the neighboring cells. Comparison of these predictions with other existing theories of pattern formation and experimental results will be discussed.
Early Earth plume-lid tectonics: A high-resolution 3D numerical modelling approach
Fischer, R.; Gerya, T.
2016-10-01
Geological-geochemical evidence point towards higher mantle potential temperature and a different type of tectonics (global plume-lid tectonics) in the early Earth (>3.2 Ga) compared to the present day (global plate tectonics). In order to investigate tectono-magmatic processes associated with plume-lid tectonics and crustal growth under hotter mantle temperature conditions, we conduct a series of 3D high-resolution magmatic-thermomechanical models with the finite-difference code I3ELVIS. No external plate tectonic forces are applied to isolate 3D effects of various plume-lithosphere and crust-mantle interactions. Results of the numerical experiments show two distinct phases in coupled crust-mantle evolution: (1) a longer (80-100 Myr) and relatively quiet 'growth phase' which is marked by growth of crust and lithosphere, followed by (2) a short (∼20 Myr) and catastrophic 'removal phase', where unstable parts of the crust and mantle lithosphere are removed by eclogitic dripping and later delamination. This modelling suggests that the early Earth plume-lid tectonic regime followed a pattern of episodic growth and removal also called episodic overturn with a periodicity of ∼100 Myr.
Directory of Open Access Journals (Sweden)
Szubel Mateusz
2016-01-01
Full Text Available It is possible to list numerous groups of heating units that are used in households, such as boilers, stoves and units used as supporting heat sources, namely fireplaces. In each case, however, the same operational problems may be evoked [1]. To understand the causes of energy losses in a boiler system, a proper definition of significant elements of the unit’s heat balance is necessary. In the group of energy losses, the flue gas loss and the incomplete combustion loss are the most significant factors. The problem with the loss resulting from incomplete combustion, which is related to the presence of combustible substances in the exhaust, is especially significant in case of biomass boilers [2, 3]. The paper presents results of the research and the optimisation of the biomass combustion process in the 180 kW batch boiler. The studies described have been focused on the reduction of the pollutants emission, which was primarily realised by the modifications of the air feeding system. Results of the experiments and the CFD simulations have been compared and discussed. Both in case of the model as well as the experiment, positive influence of the modifications on the emission have been observed.
Mackrory, Jonathan B.; Bhattacharya, Tanmoy; Steck, Daniel A.
2016-10-01
We present a worldline method for the calculation of Casimir energies for scalar fields coupled to magnetodielectric media. The scalar model we consider may be applied in arbitrary geometries, and it corresponds exactly to one polarization of the electromagnetic field in planar layered media. Starting from the field theory for electromagnetism, we work with the two decoupled polarizations in planar media and develop worldline path integrals, which represent the two polarizations separately, for computing both Casimir and Casimir-Polder potentials. We then show analytically that the path integrals for the transverse-electric polarization coupled to a dielectric medium converge to the proper solutions in certain special cases, including the Casimir-Polder potential of an atom near a planar interface, and the Casimir energy due to two planar interfaces. We also evaluate the path integrals numerically via Monte Carlo path-averaging for these cases, studying the convergence and performance of the resulting computational techniques. While these scalar methods are only exact in particular geometries, they may serve as an approximation for Casimir energies for the vector electromagnetic field in other geometries.
Directory of Open Access Journals (Sweden)
Shi-Wei Lo
2011-01-01
Full Text Available The moving bullet out of a rifle barrel is propelled by a fired explosive charge. Subsequently, a disturbed muzzle blast wave is initiated which lasts several milliseconds. In this study, axially symmetric, unsteady, Large Eddy Simulation (LES, and Ffowcs Williams and Hawkins (FWH equations were solved by the implicit-time formulation. For the spatial discretization, second order upwind scheme was employed. In addition, dynamic mesh model was used to where the ballistic domain changed with time due to the motion of bullet. Results obtained for muzzle flow field and for noise recorded were compared with those obtained from experimental data; these two batches of results were in agreement. Five cases of gunshot including one model of an unsuppressed rifle and four models of suppressors were simulated. Besides, serial images of species distributions and velocity vectors-pressure contours in suppressors and near muzzle field were displayed. The sound pressure levels (dB in far field that were post-processed by the fast Fourier transform (FFT were compared. The proposed physical model and the numerical simulations used in the present work are expected to be extended to solve other shooting weapon problems with three-dimensional and complex geometries.
DEFF Research Database (Denmark)
Christensen, Max la Cour; Villa, Umberto; Engsig-Karup, Allan Peter
2016-01-01
We study the application of a finite element numerical upscaling technique to the incompressible two-phase porous media total velocity formulation. Specifically, an element agglomeration based Algebraic Multigrid (AMGe) technique with improved approximation proper ties [37] is used, for the first...... discontinuous polynomial spaces, resulting in strong mass conservation for the upscaled systems. Due to the guaranteed approximation properties and the generic nature of the AMGe method, recursive multilevel upscaling is automatically obtained. Furthermore, this technique works for both structured...... that the proposed AMGe approach offers. Thus, the proposed approach can be seen as a rigorous bridge that merges the best properties of these two existing methods. The accuracy and stability of the studied multilevel AMGe upscaling technique is demonstrated on two challenging test cases....
DEFF Research Database (Denmark)
Christensen, Max la Cour; Villa, Umberto; Engsig-Karup, Allan Peter
2017-01-01
We study the application of a finite element numerical upscaling technique to the incompressible two-phase porous media total velocity formulation. Specifically, an element agglomeration based Algebraic Multigrid (AMGe) technique with improved approximation proper ties [37] is used, for the first...... discontinuous polynomial spaces, resulting in strong mass conservation for the upscaled systems. Due to the guaranteed approximation properties and the generic nature of the AMGe method, recursive multilevel upscaling is automatically obtained. Furthermore, this technique works for both structured...... that the proposed AMGe approach offers. Thus, the proposed approach can be seen as a rigorous bridge that merges the best properties of these two existing methods. The accuracy and stability of the studied multilevel AMGe upscaling technique is demonstrated on two challenging test cases....
Bilal, S.; Rehman, Khalil Ur; Malik, M. Y.; Hussain, Arif; Awais, M.
The current communication is carried to contemplate the unique and novel characteristics of nanofluids by constructing formulation of Prandtl fluid model. The fascinating aspects of thermo diffusion effects are also accounted in this communication. Mathematical modelling is performed by employing boundary layer approach. Afterwards, similarity variables are selected to convert dimensional non-linear system into dimensionless expressions. The solution of governing dimensionless problem is executed by shooting method (SM). Graphical evaluation is displayed to depict the intrinsic behavior of embedded parameters on dimensionless velocity, temperature, solutal concentration and nanoparticle concentration profiles. Furthermore, the numerical variation for skin friction coefficient, local Nusselt number, Sherwood number and nano Sherwood number is scrutinized through tables. The assurance of current analysis is affirmed by developing comparison with previous findings available in literature, which sets a benchmark for implementation of computational approach. It is inferred from the computation that concentration profile increases whereas Sherwood number decreases for progressive values of Dufour solutal number.
Principles and approaches for numerical modelling of sediment transport in sewers
DEFF Research Database (Denmark)
Mark, Ole; Larsen, Torben; Appelgren, Cecilia
1994-01-01
A study has been carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden with the objectives to describe the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A results of the study is a mathematical...... model MOUSE ST which describes the sediment transport in sewers. This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in MOUSE ST. The study was founded by the Swedish Water and Waste Works Association and the Nordic Industrial...
Principles and Approaches for Numerical Modelling of Sediment Transport in Sewers
DEFF Research Database (Denmark)
Mark, Ole; Appelgren, Cecilia; Larsen, Torben
1995-01-01
A study has been carried out with the objectives of describing the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A result of the study is a mathematical model MOUSE ST which describes sediment transport in sewers....... This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in in MOUSE ST. Further, the paper presents a simple application of MOUSE ST to the Rya catchment in Gothenburg, Sweden....
Yang, J.; Astitha, M.; Anagnostou, E. N.; Hartman, B.; Kallos, G. B.
2015-12-01
Weather prediction accuracy has become very important for the Northeast U.S. given the devastating effects of extreme weather events in the recent years. Weather forecasting systems are used towards building strategies to prevent catastrophic losses for human lives and the environment. Concurrently, weather forecast tools and techniques have evolved with improved forecast skill as numerical prediction techniques are strengthened by increased super-computing resources. In this study, we examine the combination of two state-of-the-science atmospheric models (WRF and RAMS/ICLAMS) by utilizing a Bayesian regression approach to improve the prediction of extreme weather events for NE U.S. The basic concept behind the Bayesian regression approach is to take advantage of the strengths of two atmospheric modeling systems and, similar to the multi-model ensemble approach, limit their weaknesses which are related to systematic and random errors in the numerical prediction of physical processes. The first part of this study is focused on retrospective simulations of seventeen storms that affected the region in the period 2004-2013. Optimal variances are estimated by minimizing the root mean square error and are applied to out-of-sample weather events. The applicability and usefulness of this approach are demonstrated by conducting an error analysis based on in-situ observations from meteorological stations of the National Weather Service (NWS) for wind speed and wind direction, and NCEP Stage IV radar data, mosaicked from the regional multi-sensor for precipitation. The preliminary results indicate a significant improvement in the statistical metrics of the modeled-observed pairs for meteorological variables using various combinations of the sixteen events as predictors of the seventeenth. This presentation will illustrate the implemented methodology and the obtained results for wind speed, wind direction and precipitation, as well as set the research steps that will be
Duan, Wenbo; Kirby, Ray; Mudge, Peter; Gan, Tat-Hean
2016-12-01
Ultrasonic guided waves are often used in the detection of defects in oil and gas pipelines. It is common for these pipelines to be buried underground and this may restrict the length of the pipe that can be successfully tested. This is because acoustic energy travelling along the pipe walls may radiate out into the surrounding medium. Accordingly, it is important to develop a better understanding of the way in which elastic waves propagate along the walls of buried pipes, and so in this article a numerical model is developed that is suitable for computing the eigenmodes for uncoated and coated buried pipes. This is achieved by combining a one dimensional eigensolution based on the semi-analytic finite element (SAFE) method, with a perfectly matched layer (PML) for the infinite medium surrounding the pipe. This article also explores an alternative exponential complex coordinate stretching function for the PML in order to improve solution convergence. It is shown for buried pipelines that accurate solutions may be obtained over the entire frequency range typically used in long range ultrasonic testing (LRUT) using a PML layer with a thickness equal to the pipe wall thickness. This delivers a fast and computationally efficient method and it is shown for pipes buried in sand or soil that relevant eigenmodes can be computed and sorted in less than one second using relatively modest computer hardware. The method is also used to find eigenmodes for a buried pipe coated with the viscoelastic material bitumen. It was recently observed in the literature that a viscoelastic coating may effectively isolate particular eigenmodes so that energy does not radiate from these modes into the surrounding [elastic] medium. A similar effect is also observed in this article and it is shown that this occurs even for a relatively thin layer of bitumen, and when the shear impedance of the coating material is larger than that of the surrounding medium.
Directory of Open Access Journals (Sweden)
W. Shao
2014-11-01
Full Text Available The effect of preferential flow on the stability of landslides is studied through numerical simulation of two types of rainfall events on a hypothetical hillslope. A model is developed that consists of two parts. The first part is a model for combined saturated/unsaturated subsurface flow and is used to compute the spatial and temporal water pressure response to rainfall. Preferential flow is simulated with a dual-permeability continuum model consisting of a matrix domain coupled to a preferential flow domain. The second part is a~soil mechanics model and is used to compute the spatial and temporal distribution of the local factor of safety based on the water pressure distribution computed with the subsurface flow model. Two types of rainfall events were considered: long duration, low-intensity rainfall, and short duration, high-intensity rainfall. The effect of preferential flow on slope stability is assessed through comparison of the failure area when subsurface flow is simulated with the dual-permeability model as compared to a single-permeability model (no preferential flow. For the low-intensity rainfall case, preferential flow has a positive effect on the slope stability as it drains the water from the matrix domain resulting in a smaller failure area. For the high-intensity rainfall case, preferential flow has a negative effect on the slope stability as the majority of rainfall infiltrates into the preferential flow domain when rainfall intensity exceeds the infiltration capacity of the matrix domain, resulting in larger water pressure and a larger failure area.
Impact of hydrothermal alteration on lava dome stability: a numerical modelling approach
Detienne, Marie; Delmelle, Pierre
2016-04-01
Lava domes are a common feature of many volcanoes worldwide. They represent a serious volcanic hazard as they are prone to repeated collapses, generating devastating debris avalanches and pyroclastic flows. While it has long been known that hydrothermal alteration degrades rock properties and weakens rock mass cohesion and strength, there is still little quantitative information allowing the description of this effect and its consequences for assessing the stability of a volcanic rock mass such as a lava dome. In this study, we use the finite difference numerical model FLAC 3D to investigate the impact of hydrothermal alteration on the stability of a volcanic dome lying on a flat surface. Different hydrothermal alteration distributions were tested to encompass the variability observed in natural lava domes. Rock shear strength parameters (minimum, maximum and mean cohesion "c" and friction angle "φ" values) representative of various degrees of hydrothermal rock alteration were used in the simulations. The model predicts that reduction of the basement rock's shear strength decreases the factor of safety significantly. A similar result is found by increasing the vertical and horizontal extension of hydrothermal alteration in the basement rocks. In addition, pervasive hydrothermal alteration within the lava dome is predicted to exert a strong negative influence on the factor of safety. Through reduction of rock porosity and permeability, hydrothermal alteration may also affect pore fluid pressure within a lava dome. The results of new FLAC 3D runs which simulate the effect of hydrothermal alteration-induced pore pressure changes on lava dome stability will be presented.
Tröster, A.; Oettel, M.; Block, B.; Virnau, P.; Binder, K.
2012-02-01
A recently proposed method to obtain the surface free energy σ(R) of spherical droplets and bubbles of fluids, using a thermodynamic analysis of two-phase coexistence in finite boxes at fixed total density, is reconsidered and extended. Building on a comprehensive review of the basic thermodynamic theory, it is shown that from this analysis one can extract both the equimolar radius Re as well as the radius Rs of the surface of tension. Hence the free energy barrier that needs to be overcome in nucleation events where critical droplets and bubbles are formed can be reliably estimated for the range of radii that is of physical interest. It is found that the conventional theory of nucleation, where the interface tension of planar liquid-vapor interfaces is used to predict nucleation barriers, leads to a significant overestimation, and this failure is particularly large for bubbles. Furthermore, different routes to estimate the effective radius-dependent Tolman length δ(Rs) from simulations in the canonical ensemble are discussed. Thus we obtain an instructive exemplification of the basic quantities and relations of the thermodynamic theory of metastable droplets/bubbles using simulations. However, the simulation results for δ(Rs) employing a truncated Lennard-Jones system suffer to some extent from unexplained finite size effects, while no such finite size effects are found in corresponding density functional calculations. The numerical results are compatible with the expectation that δ(Rs → ∞) is slightly negative and of the order of one tenth of a Lennard-Jones diameter, but much larger systems need to be simulated to allow more precise estimates of δ(Rs → ∞).
Jaruga, Anna; Arabas, Sylwester; Pawlowska, Hanna
2013-04-01
Aerosol interacts with clouds by serving as cloud condensation nuclei (CCN). Its physical and chemical properties are one of the factors defining cloud droplet size distribution. On the other hand, clouds process atmospheric aerosol taking part in its wet deposition and CCN regeneration through evaporation of cloud droplets and drizzle. Physical and chemical properties of the regenerated CCN may be altered if the evaporated droplets go through collisional growth or irreversible chemical reactions. The main challenge of representing these aerosol-cloud interactions in a numerical cloud model stems from the need to track the properties of the drop nuclei throughout the cloud lifecycle. A class of methods allowing such studies is the Lagrangian particle-based simulation technique. In a simulation of cloud, each modeled particle represents a multiplicity of particles of the same nucleus type, position and size. During the simulation particle sizes change in a continuous way from CCN-sized to rain drop particles. Tracking microphysical properties of modeled particles is an inherent feature of the particle-based frameworks, making them suitable for studying aerosol-cloud-aerosol interactions. Super-droplet method is a Lagrangian technique introduced by Shima et al. (2009) featuring an efficient Monte-Carlo type solver for particle coalescence. In this study a new implementation of the super-droplet method, using the kappa-Koehler parametrisation of aerosol composition and an aqueous chemistry module for representing irreversible oxidation, will be presented. Components of the developed model will be discussed using a single-eddy prescribed-flow framework, focusing solely on the microphysical aspects of simulations. Example case will mimic a Stratocumulus cloud and depict cloud-aerosol interactions resolved by the model.
Numerical Solution of Incompressible Navier-Stokes Equations Using a Fractional-Step Approach
Kiris, Cetin; Kwak, Dochan
1999-01-01
A fractional step method for the solution of steady and unsteady incompressible Navier-Stokes equations is outlined. The method is based on a finite volume formulation and uses the pressure in the cell center and the mass fluxes across the faces of each cell as dependent variables. Implicit treatment of convective and viscous terms in the momentum equations enables the numerical stability restrictions to be relaxed. The linearization error in the implicit solution of momentum equations is reduced by using three subiterations in order to achieve second order temporal accuracy for time-accurate calculations. In spatial discretizations of the momentum equations, a high-order (3rd and 5th) flux-difference splitting for the convective terms and a second-order central difference for the viscous terms are used. The resulting algebraic equations are solved with a line-relaxation scheme which allows the use of large time step. A four color ZEBRA scheme is employed after the line-relaxation procedure in the solution of the Poisson equation for pressure. This procedure is applied to a Couette flow problem using a distorted computational grid to show that the method minimizes grid effects. Additional benchmark cases include the unsteady laminar flow over a circular cylinder for Reynolds Numbers of 200, and a 3-D, steady, turbulent wingtip vortex wake propagation study. The solution algorithm does a very good job in resolving the vortex core when 5th-order upwind differencing and a modified production term in the Baldwin-Barth one-equation turbulence model are used with adequate grid resolution.
Early Earth tectonics: A high-resolution 3D numerical modelling approach
Fischer, R.; Gerya, T.
2014-12-01
Early Earth had a higher amount of remaining radiogenic elements as well as a higher amount of leftover primordial heat. Both contributed to the increased temperature in the Earth's interior and it is mainly this increased mantle potential temperature ΔTp that controls the dynamics of the crust and upper mantle and the style of Early Earth tectonics. For a minor increase in temperature ΔTp buckling, delamination and Rayleigh-Taylor style dripping of the plate is observed in addition. For higher temperatures ΔTp > 250 K no subduction can be observed anymore and tectonics is dominated by delamination and Rayleigh-Taylor instabilities. We conduct 3D petrological-thermomechanical numerical modelling experiments of the crust and upper mantle under Early Earth conditions and a plume tectonics model setup. For varying crustal structures and an increased mantle potential temperature ΔTp, a thermal anomaly in the bottom temperature boundary introduces a plume. The model is able to self-sufficiently form depleted mantle lithosphere after repeated melt removal. New crust can be produced in the form of volcanics or plutonics. To simulate differentiation the newly formed crust can have a range in composition from basaltic over dacitic to granitic depending on its source rock. Models show large amounts of subcrustal decompression melting and consequently large amounts of new formed crust which in turn influences the dynamics. Mantle and crust are convecting separately. Dome-shaped plutons of mafic or felsic composition can be observed in the crust. Between these domes elongated belts of upper crust, volcanics and sediments are formed. These structures look similar to, for example, the Kaapvaal craton in South Africa where the elongated shape of the Barberton Greenstone Belt is surrounded by multiple plutons.
Energy Technology Data Exchange (ETDEWEB)
Matsuda, K.; Uejima, H.; Tokushige, M.; Iwasaki, T. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)
1997-11-01
As bridges increase their size, verifying their aeroelastic stability becomes necessary for design purposes. This paper describes mainly a technology to estimate analytically the aeroelastic stability of bridges. Taking up four kinds of responses as the objects of assessing the aeroelastic stability, the paper introduces analytical approaches to each response. Comparison was made on the analytical values with wind tunnel experiment values, in which reasonability of the analytical approach was verified. Aeroelastic responses consist of (1) static transformation due to wind load, (2) gust response, (3) flutter, and (4) vortex-excited vibration. The item (1) is a static phenomenon of transformation due to steady-state air force generated by a mean component in wind velocity acting on a bridge. The item (2) is a dynamic phenomenon in which irregular vibration is caused as a result of variable component in the wind velocity acting on the bridge. The item (3) increases sharply the amplitude of vibration as a result of small increase in the wind velocity, which is caused once a vibration is generated. The item (4) is a dynamic phenomenon in which a bridge vibrates resonantly due to Karman`s vortex street. The analytic values derived by using respective analytic programs agreed well with the results derived from wind tunnel experiments. 12 refs., 12 figs., 1 tab.
Parkin, G.; Birkinshaw, S. J.; Younger, P. L.; Rao, Z.; Kirk, S.
2007-06-01
SummaryEvaluation of the impacts of groundwater abstractions on surface water systems is a necessary task in integrated water resources management. A range of hydrological, hydrogeological, and geomorphological factors influence the complex processes of interaction between groundwater and rivers. This paper presents an approach which uses numerical modeling of generic river-aquifer systems to represent the interaction processes, and neural networks to capture the impacts of the different controlling factors. The generic models describe hydrogeological settings representing most river-aquifer systems in England and Wales: high diffusivity (e.g. Chalk) and low diffusivity (e.g. Triassic Sandstone) aquifers with flow to rivers mediated by alluvial gravels; the same aquifers where they are in direct connection with the river; and shallow alluvial aquifers which are disconnected from regional aquifers. Numerical model simulations using the SHETRAN integrated catchment modeling system provided outputs including time-series and spatial variations in river flow depletion, and spatially distributed groundwater levels. Artificial neural network models were trained using input parameters describing the controlling factors and the outputs from the numerical model simulations, providing an efficient tool for representing the impacts of groundwater abstractions across a wide range of conditions. There are very few field data sets of accurately quantified river flow depletion as a result of groundwater abstraction under controlled conditions. One such data set from an experimental study carried out in 1967 on the Winterbourne stream in the Lambourne catchment over a Chalk aquifer was used successfully to test the modeling tool. This modeling approach provides a general methodology for rapid simulations of complex hydrogeological systems which preserves the physical consistency between multiple and diverse model outputs.
An Integrated Approach for the Numerical Modelling of the Spray Forming Process
DEFF Research Database (Denmark)
Hattel, Jesper; Thorborg, Jesper; Pryds, Nini;
2003-01-01
In this paper, an integrated approach for modelling the entire spray forming process is presented. The basis for the analysis is a recently developed model which extents previous studies and includes the interaction between an array of droplets and the enveloping gas. The formulation...... of the deposition is accomplished using a 3-D cylindrical heat flow model. This model is now coupled with an atomization model via a log-normal droplet size distribution. The coupling between the atomization and the deposition model is accomplished by ensuring that the total droplet size distribution of the spray...... is in fact the summation of "local" droplet size distributions along the r-axis. Furthermore, the deposition model proposed in the paper involves both the sticking efficiency of the droplets to the substrate as well as a geometrical model involving the effects of shadowing for the production of billet...
Numerical Approach to Spatial Deterministic-Stochastic Models Arising in Cell Biology.
Directory of Open Access Journals (Sweden)
James C Schaff
2016-12-01
Full Text Available Hybrid deterministic-stochastic methods provide an efficient alternative to a fully stochastic treatment of models which include components with disparate levels of stochasticity. However, general-purpose hybrid solvers for spatially resolved simulations of reaction-diffusion systems are not widely available. Here we describe fundamentals of a general-purpose spatial hybrid method. The method generates realizations of a spatially inhomogeneous hybrid system by appropriately integrating capabilities of a deterministic partial differential equation solver with a popular particle-based stochastic simulator, Smoldyn. Rigorous validation of the algorithm is detailed, using a simple model of calcium 'sparks' as a testbed. The solver is then applied to a deterministic-stochastic model of spontaneous emergence of cell polarity. The approach is general enough to be implemented within biologist-friendly software frameworks such as Virtual Cell.
Mullineux, G; Hicks, B J; Berry, C
2012-04-28
Understanding what happens in terms of delamination during buckling of laminate materials is of importance across a range of engineering sectors. Normally concern is that the strength of the material is not significantly impaired. Carton-board is a material with a laminate structure and, in the initial creation of carton nets, the board is creased in order to weaken the structure. This means that when the carton is eventually folded into its three-dimensional form, correct folding occurs along the weakened crease lines. Understanding what happens during creasing and folding is made difficult by the nonlinear nature of the material properties. This paper considers a simplified approach which extends the idea of minimizing internal energy so that the effects of delamination can be handled. This allows a simulation which reproduces the form of buckling-delamination observed in practice and the form of the torque-rotation relation.
Crosta, G. B.; De Blasio, F. V.; Locatelli, M.; Imposimato, S.; Roddeman, D.
2015-09-01
Landslides often collapse in areas covered by alluvial deposits forming an erodible layer. This erodible substrate may deform plastically under the intense shear stress of the landslide mass. In other cases, the collapse occurs onto a water basin or tidal flat, creating impulse water waves whilst the landslide may be lubricated by a water layer underneath. In either cases the presence of a medium underneath the landslide will change its dynamics introducing complex processes. While frictional, dry masses and taluses generally hamper the landslide motion. In this work, we present some experiments mimicking the collapse of a landslide onto shallow erodible or water layers. The landslide is simulated with a granular material (sand or gravel) flowing on an incline (35-66°) followed by a horizontal sector covered with a granular bed 1 to 2 cm thick or with a 0.5-1 cm of water. Monitoring evolution in time allows us to describe in detail the process of fluidization of the material at impact, the generation of impact waves, and the erosion process. Concerning impact on a sand layer, the apparent friction coefficient (H/L) is found to increase with the chute slope angle and with the thickness of the erodible layer, and to decrease with the volume. At low slope angles, the material accumulates backwards in a shock wave mode, while at larger slope angles (>45°) it accumulates by prograding forward. A granular avalanche falling from the slope is partially reflected at the sharp slope break where erosion occurs and then propagates initially as a wave partially eroding the superficial material. Folding and thrusting occur within the dense shear flow and the erodible layer. Experiments with a water layer show that the dynamics depends much on the permeability of the granular avalanche. FEM numerical simulations replicate and allow to describe and understand both the spreading and the erosion, and internal deformation recorded in the erodible layer. Experimental findings are
Energy Technology Data Exchange (ETDEWEB)
Rego, Valeria S.; Braga, Vinicius R.; Mansur Barros, Claudio R.; Martinez, Marcio B.; Piaulino, Pedro O.; Teixeira, Marcelo J.B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Gusmao, Luiz A.B. [Aquamodelo Consultoria e Engenharia Ltda., Rio de Janeiro, RJ (Brazil)
2005-07-01
Shore-approach engineering design of pipelines, including pipeline trenching specifications, presents great complexity due to comparatively (in relation to deeper waters) harsher environmental conditions and highly dynamic interaction between waves, currents and sediment transport. In general, pipelines should be buried in beach areas, but depending on the sea conditions and the trench depth, the pipeline may become unburied during its operational life. Unburied pipelines at shore-approach areas may suffer the action of unpredicted loads. The uncertainty related to these loads may decrease the structural reliability of the pipeline. the problem to be solved is how deep a pipeline requires to be trenched at the shore approach area, considering that it should be kept in this condition throughout its design life. This should be achieved with a cost-effective solution, assuring the structural reliability of the pipeline during operation, in addition to considering the feasibility of the project. Directional wave, water level, beach profile and sediment grain distribution data in the shore approach area permit determination of typical profiles, median sediment grain size, extreme and frequent wave and water level conditions, which are parameters to be used to simulate beach profile evolution through numerical model SBEACH and estimate the minimum burial depth profile. (author)
A numerical approach for pressure transient analysis of a vertical well with complex fractures
Institute of Scientific and Technical Information of China (English)
Yizhao Wan; Yuewu Liu; Wenchao Liu; Guofeng Han; Congcong Niu
2016-01-01
A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional (1-D) entities. The model overcomes the weakness of complex meshing, a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method. Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single ver-tical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures, fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripe-fracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh gen-eration, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10%less than stripe-fracture model, and computational efficiency increases by about 50%. The more fractures there are, the more the com-putational efficiency increases.
Directory of Open Access Journals (Sweden)
Sergiu Ciprian Catinas
2015-07-01
Full Text Available A detailed theoretical and practical investigation of the reinforced concrete elements is due to recent techniques and method that are implemented in the construction market. More over a theoretical study is a demand for a better and faster approach nowadays due to rapid development of the calculus technique. The paper above will present a study for implementing in a static calculus the direct stiffness matrix method in order capable to address phenomena related to different stages of loading, rapid change of cross section area and physical properties. The method is a demand due to the fact that in our days the FEM (Finite Element Method is the only alternative to such a calculus and FEM are considered as expensive methods from the time and calculus resources point of view. The main goal in such a method is to create the moment-curvature diagram in the cross section that is analyzed. The paper above will express some of the most important techniques and new ideas as well in order to create the moment curvature graphic in the cross sections considered.
Fluid structure interaction between rods and a cross flow - Numerical approach
Energy Technology Data Exchange (ETDEWEB)
Simoneau, Jan-patrice, E-mail: jan-patrice.simoneau@areva.com [Areva, 10, Rue J. Recamier, F 69456 Cedex 06, Lyon (France); Sageaux, Thomas, E-mail: thomas.sageaux@areva.com [Areva, 10, Rue J. Recamier, F 69456 Cedex 06, Lyon (France); Moussallam, Nadim, E-mail: nadim.moussallam@areva.com [Areva, 10, Rue J. Recamier, F 69456 Cedex 06, Lyon (France); Bernard, Olivier, E-mail: olivier.bernard1@areva.com [Areva, 1, Place J. Millet, F 92084 Paris la Defense (France)
2011-11-15
This paper presents a full coupled approach between fluid dynamics and structure analysis. It is conducted in order to further improve the assessment of fluid structure interaction problems, occurring in the nuclear field such as the behavior of PWR fuel rods, steam generators and other heat exchangers tubes, fast breeder fuel assemblies. The coupling is obtained by implementing a beam mechanical model in user routines of the CFD code Star-CD, and thanks to a moving grid procedure. The configurations considered are rods in a cross flow. The model is first validated on a single rod case. The lock-in effect is pointed out and both amplitude and frequency responses of the single rod are positively compared to experimental data. Secondly, the mutual influence of two rods, either in-line or parallely set, is investigated. Different behaviors, bounded by critical distances between the rods are highlighted. Finally, the stability of a 3 Multiplication-Sign 3 bundle is calculated for different impinging velocities. Stable and unstable areas are found when varying the impinging velocity. Above a limit, the vibrations amplify up to a contact between rods, this bound is found slightly greater than literature values for close configurations. It is therefore expected that further calculations, with model refinements, will bring valuable informations about bundle stability.
A closure relation to molecular theory of solvation for macromolecules
Kobryn, Alexander E.; Gusarov, Sergey; Kovalenko, Andriy
2016-10-01
We propose a closure to the integral equations of molecular theory of solvation, particularly suitable for polar and charged macromolecules in electrolyte solution. This includes such systems as oligomeric polyelectrolytes at a finite concentration in aqueous and various non-aqueous solutions, as well as drug-like compounds in solution. The new closure by Kobryn, Gusarov, and Kovalenko (KGK closure) imposes the mean spherical approximation (MSA) almost everywhere in the solvation shell but levels out the density distribution function to zero (with the continuity at joint boundaries) inside the repulsive core and in the spatial regions of strong density depletion emerging due to molecular associative interactions. Similarly to MSA, the KGK closure reduces the problem to a linear equation for the direct correlation function which is predefined analytically on most of the solvation shells and has to be determined numerically on a relatively small (three-dimensional) domain of strong depletion, typically within the repulsive core. The KGK closure leads to the solvation free energy in the form of the Gaussian fluctuation (GF) functional. We first test the performance of the KGK closure coupled to the reference interaction site model (RISM) integral equations on the examples of Lennard-Jones liquids, polar and nonpolar molecular solvents, including water, and aqueous solutions of simple ions. The solvation structure, solvation chemical potential, and compressibility obtained from RISM with the KGK closure favorably compare to the results of the hypernetted chain (HNC) and Kovalenko-Hirata (KH) closures, including their combination with the GF solvation free energy. We then use the KGK closure coupled to RISM to obtain the solvation structure and thermodynamics of oligomeric polyelectrolytes and drug-like compounds at a finite concentration in electrolyte solution, for which no convergence is obtained with other closures. For comparison, we calculate their solvation
Energy Technology Data Exchange (ETDEWEB)
1994-01-01
This report has been prepared to satisfy Section 3156(b) of Public Law 101-189 (Reports in Connection with Permanent Closures of Department of Energy Defense Nuclear Facilities), which requires submittal of a Closure Report to Congress by the Secretary of Energy upon the permanent cessation of production operations at a US Department of Energy (DOE) defense nuclear facility (Watkins 1991). This closure report provides: (1) A complete survey of the environmental problems at the facility; (2) Budget quality data indicating the cost of environmental restoration and other remediation and cleanup efforts at the facility; (3) A proposed cleanup schedule.
Yao, L.; Liang, Y.
2013-12-01
Closure temperature is an important concept to many diffusion related problems involving cooling. The basic idea and formulation were outlined in the seminal work of Dodson for cooling mono-mineralic systems [1, 2]. The Dodson's equation has been widely used to calculate closure temperatures for igneous and metamorphic rocks that usually contain more than one mineral. The purpose of this study is to systematically examine closure temperatures in cooling bi-mineralic systems. This study is also motivated by our quest for the physical meaning of temperatures derived from the REE-in-two-pyroxene thermometer that is based on temperature-dependent REE partitioning between coexisting orthopyroxene (opx) and clinopyroxene (cpx) in mafic and ultramafic rocks [3]. To better understand closure temperatures and their relations to the REE-in-two-pyroxene thermometer, we conduct numerical simulations of diffusive re-equilibration of trace elements between two coexisting minerals under prescribed cooling using temperature-dependent diffusion coefficient and partition coefficient. Following Dodson's approach for mono-mineralic systems, we define the closure temperature of a trace element in cooling bi-mineralic systems using two methods: (1) by following the evolution of average concentration of the trace element in each mineral; (2) by tracing the variation of an effective partition coefficient (ratio of the average concentrations between the two minerals). Closure temperatures calculated using the two definitions are identical for a wide range of grain sizes and cooling rates. Additional simulations for a range of temperature-dependent partition coefficients and diffusion coefficients reveal that in addition to parameters introduced in Dodson's equation (pre-exponential factor D0, activation energy E, mineral grain size, and cooling rate), temperature-dependent partition coefficients are also important in determining the closure temperature for the bi-mineralic systems. Our
Directory of Open Access Journals (Sweden)
Yanghui Li
2012-02-01
Full Text Available Several studies have demonstrated that methane production from hydrate-bearing porous media by means of depressurization-induced dissociation can be a promising technique. In this study, a 2D axisymmetric model for simulating the gas production from hydrates by depressurization is developed to investigate the gas production behavior with different depressurizing approaches. The simulation results showed that the depressurization process with depressurizing range has significant influence on the final gas production. On the contrary, the depressurizing rate only affects the production lifetime. More amount of cumulative gas can be produced with a larger depressurization range or lowering the depressurizing rate for a certain depressurizing range. Through the comparison of the combined depressurization modes, the Class 2 (all the hydrate dissociation simulations are performed by reducing the initial system pressure with the same depressurizing range initially, then to continue the depressurization process conducted by different depressurizing rates and complete when the system pressure decreases to the atmospheric pressure is much superior to the Class 1 (different depressurizing ranges are adopted in the initial period of the gas production process, when the pressure is reduced to the corresponding value of depressurization process at the different depressurizing range, the simulations are conducted at a certain depressurizing rate until the pressure reaches the atmospheric pressure for a long and stable gas production process. The parameter analysis indicated that the gas production performance decreases and the period of stable production increases with the initial pressure for the case of depressurizing range. Additionally, for the case of depressurizing range, the better gas production performance is associated with higher ambient temperature for production process, and the effect of thermal conductivity on gas production performance can be
NWP model forecast skill optimization via closure parameter variations
Järvinen, H.; Ollinaho, P.; Laine, M.; Solonen, A.; Haario, H.
2012-04-01
We present results of a novel approach to tune predictive skill of numerical weather prediction (NWP) models. These models contain tunable parameters which appear in parameterizations schemes of sub-grid scale physical processes. The current practice is to specify manually the numerical parameter values, based on expert knowledge. We developed recently a concept and method (QJRMS 2011) for on-line estimation of the NWP model parameters via closure parameter variations. The method called EPPES ("Ensemble prediction and parameter estimation system") utilizes ensemble prediction infra-structure for parameter estimation in a very cost-effective way: practically no new computations are introduced. The approach provides an algorithmic decision making tool for model parameter optimization in operational NWP. In EPPES, statistical inference about the NWP model tunable parameters is made by (i) generating an ensemble of predictions so that each member uses different model parameter values, drawn from a proposal distribution, and (ii) feeding-back the relative merits of the parameter values to the proposal distribution, based on evaluation of a suitable likelihood function against verifying observations. In this presentation, the method is first illustrated in low-order numerical tests using a stochastic version of the Lorenz-95 model which effectively emulates the principal features of ensemble prediction systems. The EPPES method correctly detects the unknown and wrongly specified parameters values, and leads to an improved forecast skill. Second, results with an ensemble prediction system emulator, based on the ECHAM5 atmospheric GCM show that the model tuning capability of EPPES scales up to realistic models and ensemble prediction systems. Finally, preliminary results of EPPES in the context of ECMWF forecasting system are presented.
Numerical results for near surface time domain electromagnetic exploration: a full waveform approach
Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.
2015-12-01
Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two
Pandkar, Anup Surendra
Bearings are an integral part of machine components that transmit rotary power such as cars, motors, engines etc. Safe bearing operation is essential to avoid serious failures and accidents, which necessitates their timely replacement. This calls for an accurate bearing life prediction methods. Based on the Lundberg-Palmgen (LP) model, current life models consistently under predict bearings lives. Improvement in life prediction requires understanding of the bearing failure mechanism i.e. Rolling Contact Fatigue (RCF). The goal of this research is to develop a mechanistic framework required for an improved bearing life prediction model. Such model should account for metal plasticity, influence of microstructural features and cyclically evolving stressstrain fields induced during RCF. To achieve this, elastic-plastic finite element (FE) study is undertaken to investigate the response of M50-NiL bearing steel during RCF. Specifically, a microstructure sensitive study of the influence of non-metallic inclusions on RCF response of bearings is presented. M50-NiL microstructure consists of carbides which are orders of magnitude smaller than bearing dimensions. To account for this size difference, a multi-scale FE modeling approach is employed. The FE results reveal that hard carbide particles act as local stress risers, alter surrounding stressstrain fields and cause micro-scale yielding of steel matrix. Moreover, they introduce a shear stress cycle with non-zero mean stress, which promotes micro-plastic strain accumulation via ratcheting mechanism. Localized ratcheting is primarily responsible for cyclic hardening within the RCF affected region. Such evolution of subsurface hardness can be used to quantify RCF induced damage. To investigate this further, cyclic hardening response of the RCF affected region is simulated. The results show good agreement with the experimental observations. The cyclic stress-strain fields obtained from these simulations and the knowledge of
Rooney, Matthew B; Mehl, Margo; Monnet, Eric
2004-01-01
To determine if transcostal thoracotomy closure resulted in less pain than circumcostal closure. Experimental cadaver and prospective clinical study. Two canine cadavers and 13 adult, 22-29 kg dogs. Phase 1: In 2 cadavers, 4 suture passage techniques were evaluated to determine the incidence of nerve entrapment in circumcostal intercostal thoracotomy closure. Phase 2: Pain after circumcostal closure (7 dogs) or transcostal closure (6 dogs) of a 4th intercostal space thoracotomy was evaluated by use of pain threshold scores, fentanyl administration rates, heart and respiratory rates, and numerical ratings for behavior. Arterial blood gas analyses were obtained 4 hours postoperatively. Transcostal closure was accomplished by drilling 5-6 small holes in the 5th rib and passing sutures through the holes and around the 4th rib to achieve closure. Pain threshold scores (PTS) were measured by an observer unaware of closure assignment, at 2, 4, 12, and 24 hours after closure by applying slowly increasing pressure to the incision line using a load cell. Rates of fentanyl administration were adjusted based on subjective impressions of dog comfort by a second observer unaware of closure assignment. A 70-100% incidence of nerve entrapment was found for all circumcostal techniques. PTS was higher (P=.045) and fentanyl infusion rates were lower (P=.001) for the transcostal group at 2, 4, 12, and 24 hour postoperatively compared with the circumcostal group. There is a high incidence of nerve entrapment using circumcostal closure techniques. A transcostal technique appears to be associated with less pain during the first 24 hours postoperatively. Based on lower pain scores, transcostal thoracotomy closure may be preferable to circumcostal closure techniques.
Transition probabilities for two-photon H(1-2) and He(11-21) transitions: A partial-closure approach
Indian Academy of Sciences (India)
Monika Bassi; K L Baluja
2000-03-01
Transition amplitudes and transition probabilities for the two-photon 1-2 transition in the hydrogen atom and 11-21 transition in helium atom have been calculated using a partialclosure approach. The dominant term is calculated exactly and the remaining sum over intermediate states is calculated using a mean excitation energy. Our value of the transition amplitudes agree within 2% with the exact results for the hydrogen case. Our value of the transition probability for hydrogen is 8.50 -1 which is in good accord with its known value 8.226 s-1. For helium, the photon energy distribution of the metastable 21 state is in good agreement with the accurate values. The corresponding transition probability is 53.7 s-1 which is in good agreement with the accurate value 51.3 s-1.
Scott, L Ridgway
2011-01-01
Computational science is fundamentally changing how technological questions are addressed. The design of aircraft, automobiles, and even racing sailboats is now done by computational simulation. The mathematical foundation of this new approach is numerical analysis, which studies algorithms for computing expressions defined with real numbers. Emphasizing the theory behind the computation, this book provides a rigorous and self-contained introduction to numerical analysis and presents the advanced mathematics that underpin industrial software, including complete details that are missing from m
VR closure rates for two vocational models.
Fraser, Virginia V; Jones, Amanda M; Frounfelker, Rochelle; Harding, Brian; Hardin, Teresa; Bond, Gary R
2008-01-01
The Individual Placement and Support (IPS) model of supported employment is an evidence-based practice for individuals with psychiatric disabilities. To be financially viable, IPS programs require funding from the state-federal vocational rehabilitation (VR) system. However, some observers have questioned the compatibility of IPS and the VR system. Using a randomized controlled trial comparing IPS to a well-established vocational program called the Diversified Placement Approach (DPA), we examined rates of VR sponsorship and successful VR closures. We also describe the establishment of an active collaboration between a psychiatric rehabilitation agency and the state VR system to facilitate rapid VR sponsorship for IPS clients. Both IPS and DPA achieved a 44% rate of VR Status 26 closure when considering all clients entering the study. IPS and DPA averaged similar amount of time to achieve VR sponsorship. Time from vocational program entry to Status 26 was 51 days longer on average for IPS. Even though several IPS principles seem to run counter to VR practices, such as zero exclusion and rapid job search, we found IPS closure rates comparable to those for DPA, a vocational model that screens for readiness, provides prevocational preparation, and extensively uses agency-run businesses.
Directory of Open Access Journals (Sweden)
Boyer F.
2013-12-01
Full Text Available This article deals with the problem of computing numerical approximations of null-controls for parabolic equations or systems by using the Hilbert Uniqueness Method (HUM. We mainly review recent results on this subject but we also provide new elements to emphasize the main ideas underlying the penalised HUM approach which is at the heart of the methods used in practice. We give many numerical illustrations. Cet article est consacré à l’étude du problème du calcul approché de contrôles à zéro pour des équations ou des systèmes paraboliques par le biais de la méthode HUM (Hilbert Uniqueness Method. On donne un aperçu des résultats récents sur le sujet tout en mettant en lumière certains aspects fondamentaux de la méthode HUM pénalisée, qui se trouve au coeur des algorithmes proposés. De nombreuses illustrations numériques sont également données.
Directory of Open Access Journals (Sweden)
Xiaojia Xiang
2014-07-01
Full Text Available In the past decade, biomimetic undulating fin propulsion has been one of the main topics considered by scientists and researchers in the field of robotic fish. This technology is inspired by the biological wave-like propulsion of ribbon-finned fish. The swimming modes have aquatic application potentials with greater manoeuvrability, less detectable noise or wake and better efficiency at low speeds. The present work concentrates on the evaluation of fin-ray trajectory tracking of biorobotic undulating fins at the levels of kinematics and hydrodynamics by using an experimental-numerical approach. Firstly, fin-ray tracking inconsistence between the desired and actual undulating trajectories is embodied with experimental data of the fin prototype. Next, the dynamics' nonlinearity is numerically and analytically unveiled by using the computational fluid dynamics (CFD method, from the viewpoint of vortex shedding and the hydro-effect. The evaluation of fin-ray tracking performance creates a good basis for control design to improve the fin-ray undulation of prototypes.
Salama, Amgad
2015-06-01
In this work, the experimenting fields approach is applied to the numerical solution of the Navier-Stokes equation for incompressible viscous flow. In this work, the solution is sought for both the pressure and velocity fields in the same time. Apparently, the correct velocity and pressure fields satisfy the governing equations and the boundary conditions. In this technique a set of predefined fields are introduced to the governing equations and the residues are calculated. The flow according to these fields will not satisfy the governing equations and the boundary conditions. However, the residues are used to construct the matrix of coefficients. Although, in this setup it seems trivial constructing the global matrix of coefficients, in other setups it can be quite involved. This technique separates the solver routine from the physics routines and therefore makes easy the coding and debugging procedures. We compare with few examples that demonstrate the capability of this technique.
Challis, K. J.
2016-12-01
We present a numerical study of the tight-binding approach to overdamped Brownian motion on a tilted periodic potential. In the tight-binding method the probability density is expanded on a basis of Wannier states to transform the Smoluchowski equation to a discrete master equation that can be interpreted in terms of thermal hopping between potential minima. We calculate the Wannier states and hopping rates for a variety of potentials, including tilted cosine and ratchet potentials. For deep potential minima the Wannier states are well localized and the hopping rates between nearest-neighbor states are qualitatively well described by Kramers' escape rate. The next-nearest-neighbor hopping rates are negative and must be negligible compared to the nearest-neighbor rates for the discrete master equation treatment to be valid. We find that the validity of the master equation extends beyond the quantitative applicability of Kramers' escape rate.
Nagai, Yuki; Shinohara, Yasushi; Futamura, Yasunori; Sakurai, Tetsuya
2017-01-01
We propose the reduced-shifted conjugate-gradient (RSCG) method, which is numerically efficient to calculate a matrix element of a Green's function defined as a resolvent of a Hamiltonian operator, by solving linear equations with a desired accuracy. This method does not calculate solution vectors of linear equations but does directly calculate a matrix element of the resolvent. The matrix elements with different frequencies are simultaneously obtained. Thus, it is easy to calculate the exception value expressed as a Matsubara summation of these elements. To illustrate a power of our method, we choose a nano-structured superconducting system with a mean-field Bogoliubov-de Gennes (BdG) approach. This method allows us to treat with the system with the fabrication potential, where one cannot effectively use the kernel-polynomial-based method. We consider the d-wave nano-island superconductor by simultaneously solving the linear equations with a large number (˜50000) of Matsubara frequencies.
DEFF Research Database (Denmark)
Johannesson, Björn; Nyman, U.
2010-01-01
A numerical approach for moisture transport in porous materials like concrete is presented. The model considers mass balance equations for the vapour phase and the water phase in the material together with constitutive equations for the mass flows and for the exchange of mass between the two phases....... History-dependent sorption behaviour is introduced by considering scanning curves between the bounding desorption and absorption curves. The method, therefore, makes it possible to calculate equilibrium water contents for arbitrary relative humidity variations at every material point considered......-Raphson equilibrium iteration scheme within the time steps. Examples are presented illustrating the performance and potential of the model. Two different types of measurements on moisture content profiles in concrete are used to verify the relevance of the novel proposed model for moisture transport and sorption...
Closure and Sealing Design Calculation
Energy Technology Data Exchange (ETDEWEB)
T. Lahnalampi; J. Case
2005-08-26
The purpose of the ''Closure and Sealing Design Calculation'' is to illustrate closure and sealing methods for sealing shafts, ramps, and identify boreholes that require sealing in order to limit the potential of water infiltration. In addition, this calculation will provide a description of the magma that can reduce the consequences of an igneous event intersecting the repository. This calculation will also include a listing of the project requirements related to closure and sealing. The scope of this calculation is to: summarize applicable project requirements and codes relating to backfilling nonemplacement openings, removal of uncommitted materials from the subsurface, installation of drip shields, and erecting monuments; compile an inventory of boreholes that are found in the area of the subsurface repository; describe the magma bulkhead feature and location; and include figures for the proposed shaft and ramp seals. The objective of this calculation is to: categorize the boreholes for sealing by depth and proximity to the subsurface repository; develop drawing figures which show the location and geometry for the magma bulkhead; include the shaft seal figures and a proposed construction sequence; and include the ramp seal figure and a proposed construction sequence. The intent of this closure and sealing calculation is to support the License Application by providing a description of the closure and sealing methods for the Safety Analysis Report. The closure and sealing calculation will also provide input for Post Closure Activities by describing the location of the magma bulkhead. This calculation is limited to describing the final configuration of the sealing and backfill systems for the underground area. The methods and procedures used to place the backfill and remove uncommitted materials (such as concrete) from the repository and detailed design of the magma bulkhead will be the subject of separate analyses or calculations. Post-closure
Doummar, Joanna; Kassem, Assaad
2017-04-01
In the framework of a three-year PEER (USAID/NSF) funded project, flow in a Karst system in Lebanon (Assal) dominated by snow and semi arid conditions was simulated and successfully calibrated using an integrated numerical model (MIKE-She 2016) based on high resolution input data and detailed catchment characterization. Point source infiltration and fast flow pathways were simulated by a bypass function and a high conductive lens respectively. The approach consisted of identifying all the factors used in qualitative vulnerability methods (COP, EPIK, PI, DRASTIC, GOD) applied in karst systems and to assess their influence on recharge signals in the different hydrological karst compartments (Atmosphere, Unsaturated zone and Saturated zone) based on the integrated numerical model. These parameters are usually attributed different weights according to their estimated impact on Groundwater vulnerability. The aim of this work is to quantify the importance of each of these parameters and outline parameters that are not accounted for in standard methods, but that might play a role in the vulnerability of a system. The spatial distribution of the detailed evapotranspiration, infiltration, and recharge signals from atmosphere to unsaturated zone to saturated zone was compared and contrasted among different surface settings and under varying flow conditions (e.g., in varying slopes, land cover, precipitation intensity, and soil properties as well point source infiltration). Furthermore a sensitivity analysis of individual or coupled major parameters allows quantifying their impact on recharge and indirectly on vulnerability. The preliminary analysis yields a new methodology that accounts for most of the factors influencing vulnerability while refining the weights attributed to each one of them, based on a quantitative approach.
Havaej, Mohsen; Coggan, John; Stead, Doug; Elmo, Davide
2016-04-01
Rock slope geometry and discontinuity properties are among the most important factors in realistic rock slope analysis yet they are often oversimplified in numerical simulations. This is primarily due to the difficulties in obtaining accurate structural and geometrical data as well as the stochastic representation of discontinuities. Recent improvements in both digital data acquisition and incorporation of discrete fracture network data into numerical modelling software have provided better tools to capture rock mass characteristics, slope geometries and digital terrain models allowing more effective modelling of rock slopes. Advantages of using improved data acquisition technology include safer and faster data collection, greater areal coverage, and accurate data geo-referencing far exceed limitations due to orientation bias and occlusion. A key benefit of a detailed point cloud dataset is the ability to measure and evaluate discontinuity characteristics such as orientation, spacing/intensity and persistence. This data can be used to develop a discrete fracture network which can be imported into the numerical simulations to study the influence of the stochastic nature of the discontinuities on the failure mechanism. We demonstrate the application of digital terrestrial photogrammetry in discontinuity characterization and distinct element simulations within a slate quarry. An accurately geo-referenced photogrammetry model is used to derive the slope geometry and to characterize geological structures. We first show how a discontinuity dataset, obtained from a photogrammetry model can be used to characterize discontinuities and to develop discrete fracture networks. A deterministic three-dimensional distinct element model is then used to investigate the effect of some key input parameters (friction angle, spacing and persistence) on the stability of the quarry slope model. Finally, adopting a stochastic approach, discrete fracture networks are used as input for 3D
Validity conditions for moment closure approximations in stochastic chemical kinetics
Energy Technology Data Exchange (ETDEWEB)
Schnoerr, David [School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR (United Kingdom); School of Informatics, University of Edinburgh, Edinburgh EH8 9LE (United Kingdom); Sanguinetti, Guido [School of Informatics, University of Edinburgh, Edinburgh EH8 9LE (United Kingdom); Grima, Ramon [School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR (United Kingdom)
2014-08-28
Approximations based on moment-closure (MA) are commonly used to obtain estimates of the mean molecule numbers and of the variance of fluctuations in the number of molecules of chemical systems. The advantage of this approach is that it can be far less computationally expensive than exact stochastic simulations of the chemical master equation. Here, we numerically study the conditions under which the MA equations yield results reflecting the true stochastic dynamics of the system. We show that for bistable and oscillatory chemical systems with deterministic initial conditions, the solution of the MA equations can be interpreted as a valid approximation to the true moments of the chemical master equation, only when the steady-state mean molecule numbers obtained from the chemical master equation fall within a certain finite range. The same validity criterion for monostable systems implies that the steady-state mean molecule numbers obtained from the chemical master equation must be above a certain threshold. For mean molecule numbers outside of this range of validity, the MA equations lead to either qualitatively wrong oscillatory dynamics or to unphysical predictions such as negative variances in the molecule numbers or multiple steady-state moments of the stationary distribution as the initial conditions are varied. Our results clarify the range of validity of the MA approach and show that pitfalls in the interpretation of the results can only be overcome through the systematic comparison of the solutions of the MA equations of a certain order with those of higher orders.
Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter
2016-04-01
A new method to retrieve cloud water content from in-situ measured 2D particle images from optical array probes (OAP) is presented. With the overall objective to build a statistical model of crystals' mass as a function of their size, environmental temperature and crystal microphysical history, this study presents the methodology to retrieve the mass of crystals sorted by size from 2D images using a numerical optimization approach. The methodology is validated using two datasets of in-situ measurements gathered during two airborne field campaigns held in Darwin, Australia (2014), and Cayenne, France (2015), in the frame of the High Altitude Ice Crystals (HAIC) / High Ice Water Content (HIWC) projects. During these campaigns, a Falcon F-20 research aircraft equipped with state-of-the art microphysical instrumentation sampled numerous mesoscale convective systems (MCS) in order to study dynamical and microphysical properties and processes of high ice water content areas. Experimentally, an isokinetic evaporator probe, referred to as IKP-2, provides a reference measurement of the total water content (TWC) which equals ice water content, (IWC) when (supercooled) liquid water is absent. Two optical array probes, namely 2D-S and PIP, produce 2D images of individual crystals ranging from 50 μm to 12840 μm from which particle size distributions (PSD) are derived. Mathematically, the problem is formulated as an inverse problem in which the crystals' mass is assumed constant over a size class and is computed for each size class from IWC and PSD data: PSD.m = IW C This problem is solved using numerical optimization technique in which an objective function is minimized. The objective function is defined as follows: 2 J(m)=∥P SD.m - IW C ∥ + λ.R (m) where the regularization parameter λ and the regularization function R(m) are tuned based on data characteristics. The method is implemented in two steps. First, the method is developed on synthetic crystal populations in
RCRA closure of mixed waste impoundments
Energy Technology Data Exchange (ETDEWEB)
Blaha, F.J. [Doty and Associates (United States); Greengard, T.C.; Arndt, M.B. [Rockwell International (United States)
1989-11-01
A case study of a RCRA closure action at the Rocky Flats Plant is presented. Closure of the solar evaporation ponds involves removal and immobilization of a mixed hazardous/radioactive sludge, treatment of impounded water, groundwater monitoring, plume delineation, and collection and treatment of contaminated groundwater. The site closure is described within the context of regulatory negotiations, project schedules, risk assessment, clean versus dirty closure, cleanup levels, and approval of closure plans and reports. Lessons learned at Rocky Flats are summarized.
Closure End States for Facilities, Waste Sites, and Subsurface Contamination
Energy Technology Data Exchange (ETDEWEB)
Gerdes, Kurt D.; Chamberlain, Grover S.; Wellman, Dawn M.; Deeb, Rula A.; Hawley, Elizabeth L.; Whitehurst, Latrincy; Marble, Justin
2012-11-21
of focusing on long-term cleanup requirements. An acknowledgement of the long timeframe for complete restoration and the need for long-term management can also help a site transition from the process of pilot testing different remedial strategies to selecting a final remedy and establishing a long-term management and monitoring approach. This approach has led to cost savings and the more efficient use of resources across the Department of Defense complex and at numerous industrial sites across the U.S. Defensible end states provide numerous benefits for the DOE environmental remediation programs including cost-effective, sustainable long-term monitoring strategies, remediation and site transition decision support, and long-term management of closure sites.
Epithelial gap closure governed by forces and geometry
Ladoux, Benoit
The closure of gaps within epithelia is crucial to maintain the integrity and the homeostasis of the tissue during wound healing or cell extrusion processes. Cells mediate gap closure through either the assembly of multicellular actin-based contractile cables (purse-string contraction) or the protrusive activity of border cells into the gap (cell crawling). I will present experimental data and numerical modeling that show how these mechanisms can mutually interact to promote efficient epithelial gap closure and how mechanical constraints can regulate these mechanisms. I will first present how geometrical constraints dictate mechanisms of epithelial gap closure. We determine the importance of tissue shape during closure and the role of curvature of cell boundaries in this process. An essential difference between the two closure mechanisms is that cell crawling always pulls the edge of the tissue forward (i.e. towards the gap) while purse string pulls the edge forward or backwards depending on the local geometry. Our study demonstrates how the interplay between these two mechanisms is crucial for closing gaps and wounds, which naturally come in arbitrary shapes. Then I will focus on epithelial closure mechanism during cell extrusion. Within confluent cell layers, cellular motions coupled between neighbors are tightly regulated by the packing density of the epithelium inducing drastic changes in the dynamics of these tissues. I will show how cell density and tissue mechanics regulate the extrusion of cells within a confluent epithelial cell sheet, simultaneously measuring collective movements and traction forces. Epithelial packing and collective cell dynamics dictate the modes of cellular extrusions from lamellipodia crawling of the neighboring cells at low densities to coordinated actin-based contractile purse-string mechanism at higher density.
Evolution of a turbulent pycnocline within the framework of a modified model of turbulent closure
Soustova, Irina; Troitskaya, Yuliya; Ezhova, Ekaterina; Rybushkina, Galina; Zilitinkevich, Sergej
2015-04-01
The formation and evolution of a turbulent pycnocline generated by internal wave breaking were investigated within the framework of a modified model of turbulent closure. Numerical computation based on closed Reynolds equations using closure hypotheses obtained in the framework of the kinetic approach showed a strong dependence of vertical distributions corresponding to hydrodynamic parameters on the anisotropy of turbulence and speed of pycnocline motion. Strongly anisotropic motion is characterized by the presence of stepwise variations in the vertical profiles of buoyancy frequency, turbulence scale, and kinetic and potential energy as compared to the known analytical solution obtained earlier without allowance for a non-steady-state term in the kinetic energy balance equation. In the case of a weaker anisotropy, no sharp changes are observed in spatial and energy characteristics of turbulence and the qualitative shape of their profiles in the pycnolcline region coincides with the known analytical dependences. The obtained result is important for development of numerical climatic models of the interaction between the atmosphere and the ocean. This work was supported by the Russian Foundation of Basic Research (13-05-00865, 14-05-91767, 15-45-02580).
Structural ensemble dynamics based closure model for wall-bounded turbulent flow
Institute of Scientific and Technical Information of China (English)
Zhen-Su She; Ning Hu; You Wu
2009-01-01
Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework called structural ensemble dynamics (SED), which aims at using systematically all relevant statistical properties of turbulent structures for a quantitative description of ensemble means. A new set of closure equations based on the SED approach for a turbulent channel flow is presented. SED order functions are defined, and numerically determined from data of direct numerical simulations (DNS). Computational results show that the new closure model reproduces accurately the solution of the original Navier-Stokes simulation, including the mean velocity profile, the kinetic energy of the stream-wise velocity component, and every term in the energy budget equation. It is suggested that the SED-based studies of turbulent structure builds a bridge between the studies of physical mechanisms of turbulence and the development of accurate model equations for engineering predictions.
NPAR- products, applications and closure
Energy Technology Data Exchange (ETDEWEB)
Vora, J.P.
1995-04-01
Almost a decade ago the Office of Nuclear Regulatory Research (RES) developed and implemented a comprehensive research program (NUREG-1144) widely known as NPAR or Nuclear Plant Aging Research. The NPAR program is a structured research program specifically oriented to understanding significant age-related degradation mechanisms and their long term effects on properties and performance of important components and systems and ways to mitigate detrimental effects of aging. It provided a road map and a phased approach to research that is applicable to any structure, system, or component of interest. This hardware-oriented engineering research program led the industry worldwide and communicated a need to understand and manage age-related degradation effects in selected but important structures and components. At the conclusion (1995) of the NPAR program, 22 electrical and mechanical components, 13 safety-related systems, and 10 special topics will have been studied and results summarized in 160 technical reports. This reference library of information listed and summarized in NUREG-1377, Rev. No. 4 provides a foundation upon which individual programs can be built for the specific needs of a utility, a regulator, or equipment manufacturers. During the life of the NPAR program, it has provided technical bases and support for license renewal, codes and standards, resolution of generic safety issues, information notices, regulatory guides and the standard Review Plan, as well as the Office of Nuclear Reactor Regulation and The NRC Regions. All ongoing NPAR activities will either be completed or terminated by the end of 1995. No new initiative will be undertaken. This paper summarizes NPAR products and accomplishments, application of the research results, and its status and closure.
Sozio, Gerry
2009-01-01
Senior secondary students cover numerical integration techniques in their mathematics courses. In particular, students would be familiar with the "midpoint rule," the elementary "trapezoidal rule" and "Simpson's rule." This article derives these techniques by methods which secondary students may not be familiar with and an approach that…
Shih, Tsan-Hsing; Liu, Nan-Suey
2008-01-01
This paper describes an approach which aims at bridging the gap between the traditional Reynolds-averaged Navier-Stokes (RANS) approach and the traditional large eddy simulation (LES) approach. It has the characteristics of the very large eddy simulation (VLES) and we call this approach the partially-resolved numerical simulation (PRNS). Systematic simulations using the National Combustion Code (NCC) have been carried out for fully developed turbulent pipe flows at different Reynolds numbers to evaluate the PRNS approach. Also presented are the sample results of two demonstration cases: nonreacting flow in a single injector flame tube and reacting flow in a Lean Direct Injection (LDI) hydrogen combustor.
Live 3D image overlay for arterial duct closure with Amplatzer Duct Occluder II additional size.
Goreczny, Sebstian; Morgan, Gareth J; Dryzek, Pawel
2016-03-01
Despite several reports describing echocardiography for the guidance of ductal closure, two-dimensional angiography remains the mainstay imaging tool; three-dimensional rotational angiography has the potential to overcome some of the drawbacks of standard angiography, and reconstructed image overlay provides reliable guidance for device placement. We describe arterial duct closure solely from venous approach guided by live three-dimensional image overlay.
From puncture to closure of the common femoral artery in endovascular aortic repair
DEFF Research Database (Denmark)
Lönn, Lars; Larzon, Thomas; Van Den Berg, Jos C
2010-01-01
or epidural anesthesia. The evolving stent-technology with smaller sheath sizes has broadened the scenario for alternative approaches for access and closure of the common femoral arteries. The following review presents an introduction on technical aspects of puncture of the femoral artery and closure...
Institute of Scientific and Technical Information of China (English)
2008-01-01
An efficient 2.5D finite element numerical modeling approach was developed to simulate wave motions generated in ground by high-speed train passages. Fourier transform with respect to the coordinate in the track direction was applied to re-ducing the three-dimensional dynamic problem to a plane strain problem which has been solved in a section perpendicular to the track direction. In this study, the track structure and supporting ballast layer were simplified as a composite Euler beam resting on the ground surface, while the ground with complicated geometry and physical properties was modeled by 2.5D quadrilateral elements. Wave dissipation into the far field was dealt with the transmitting boundary constructed with fre-quency-dependent dashpots. Three-dimensional responses of track structure and ground were obtained from the wavenumber expansion in the track direction. The simulated wave motions in ground were interpreted for train moving loads traveling at speeds below or above the critical velocity of a specific track-ground system. It is found that, in the soft ground area, the high-speed train operations can enter the transonic range, which can lead to resonances of the track structure and the sup-porting ground. The strong vibration will endanger the safe operations of high-speed train and accelerate the deterioration of railway structure.
Institute of Scientific and Technical Information of China (English)
BIAN XueCheng; OHEN YunMin; HU Ting
2008-01-01
An efficient 2.5D finite element numerical modeling approach was developed to simulate wave motions generated in ground by high-speed train passages.Fourier transform with respect to the coordinate in the track direction was applied to re-ducing the three-dimensional dynamic problem to a plane strain problem which has been solved in a section perpendicular to the track direction.In this study,the track structure and supporting ballast layer were simplified as a composite Euler beam resting on the ground surface,while the ground with complicated geometry and physical properties was modeled by 2.5D quadrilateral elements.Wave dissipation into the far field was dealt with the transmitting boundary constructed with fre-quency-dependent dashpots.Three-dimensional responses of track structure and ground were obtained from the wavenumber expansion in the track direction.The simulated wave motions in ground were interpreted for train moving loads traveling at speeds below or above the critical velocity of a specific track-ground system.It is found that,in the soft ground area,the high-speed train operations can enter the transonic range,which can lead to resonances of the track structure and the sup-porting ground.The strong vibration will endanger the safe operations of high-speed train and accelerate the deterioration of railway structure.
Institute of Scientific and Technical Information of China (English)
Un Ji; Eun-Kyung Jang; Gwonhan Kim
2016-01-01
The effects of sedimentation reduction at the Nakdong River Estuary Barrage (NREB) in Korea were quantitatively analyzed with respect to different sediment control methods using the calibrated and validated two-dimensional model. The countermeasures of sediment dredging, sediment flushing, channel geometry change, and a combination of flushing and channel geometry change were examined for the approach channel of the NREB. The flood event and channel geometries of the 3.8 km section upstream of the NREB surveyed before and after dredging in 2007 were used for modeling conditions. As a result, the half of sediments dredged in 2007 could be eliminated naturally by floods without dredging. The numerical simulation of sediment flushing indicated that the deposition height decreased in the entire simulation section with the minimum and maximum reductions from 0.3 m to 1.3 m in deposition height. The channel contraction method produced quantitatively the largest amount of sedimentation reduction and sediment flushing and dredging followed. Sedimentation reduction by a combination of flushing and channel contraction was up 10%compared to the individual method of channel contraction.
Yin, W.; Peyton, A. J.; Stefani, F.; Gerbeth, G.
2009-10-01
A completely contactless flow measurement technique based on the principle of EM induction measurements—contactless inductive flow tomography (CIFT)—has been previously reported by a team based at Forschungszentrum Dresden-Rossendorf (FZD). This technique is suited to the measurement of velocity fields in high conductivity liquids, and the possible applications range from monitoring metal casting and silicon crystal growth in industry to gaining insights into the working of the geodynamo. The forward problem, i.e. calculating the induced magnetic field from a known velocity profile, can be described as a linear relationship when the magnetic Reynolds number is small. Previously, an integral equation method was used to formulate the forward problem; however, although the sensitivity matrices were calculated, they were not explicitly expressed and computation involved the solution of an ill-conditioned system of equations using a so-called deflation method. In this paper, we present the derivation of the sensitivity matrix directly from electromagnetic field theory and the results are expressed very concisely as the cross product of two field vectors. A numerical method based on a finite difference method has also been developed to verify the formulation. It is believed that this approach provides a simple yet fast route to the forward solution of CIFT. Furthermore, a method for sensor design selection based on eigenvalue analysis is presented.
Directory of Open Access Journals (Sweden)
Yu Wang
2016-04-01
Full Text Available Multiple-factor analysis and optimization play a critical role in the the ability to maximizethe stimulated reservoir volume (SRV and the success of economic shale gas production. In this paper, taking the typical continental naturally fractured silty laminae shale in China as anexample, response surface methodology (RSM was employed to optimize multiple hydraulic fracturing parameters to maximize the stimulated area in combination with numerical modeling based on the coupled flow-stress-damage (FSD approach. This paper demonstrates hydraulic fracturing effectiveness by defining two indicesnamelythe stimulated reservoir area (SRA and stimulated silty laminae area (SLA. Seven uncertain parameters, such as laminae thickness, spacing, dip angle, cohesion, internal friction angle (IFA, in situ stress difference (SD, and an operational parameter-injection rate (IR with a reasonable range based on silty Laminae Shale, Southeastern Ordos Basin, are used to fit a response of SRA and SLA as the objective function, and finally identity the optimum design under the parameters based on simultaneously maximizingSRA and SLA. In addition, asensitivity analysis of the influential factors is conducted for SRA and SLA. The aim of the study is to improve the artificial ability to control the fracturing network by means of multi-parameteroptimization. This work promises to provide insights into the effective exploitation of unconventional shale gas reservoirs via optimization of the fracturing design for continental shale, Southeastern Ordos Basin, China.
Hafez, M.; Soliman, M.; White, S.
1992-01-01
A new formulation (including the choice of variables, their non-dimensionalization, and the form of the artificial viscosity) is proposed for the numerical solution of the full Navier-Stokes equations for compressible and incompressible flows with heat transfer. With the present approach, the same code can be used for constant as well as variable density flows. The changes of the density due to pressure and temperature variations are identified and it is shown that the low Mach number approximation is a special case. At zero Mach number, the density changes due to the temperature variation are accounted for, mainly through a body force term in the momentum equation. It is also shown that the Boussinesq approximation of the buoyancy effects in an incompressible flow is a special case. To demonstrate the new capability, three examples are tested. Flows in driven cavities with adiabatic and isothermal walls are simulated with the same code as well as incompressible and supersonic flows over a wall with and without a groove. Finally, viscous flow simulations of an oblique shock reflection from a flat plate are shown to be in good agreement with the solutions available in literature.
Di Lorenzo, R.; Filice, L.; Umbrello, D.; Micari, F.
2004-06-01
In the last years, the growing role of process flexibility in modern mechanical industries has driven a rising interest in optimisation of process/product design through innovative techniques. Moreover, the development of niche productions, which are characterised by low production volumes and small batches leads to the need of more flexible and rapid forming technologies. In this way, a great research effort is performed towards the study of new stamping processes: among them hydro forming finds a large interest in automotive industry since it allows to significantly reduce tooling costs and also to avoid some secondary operations. Different studies are available in the technical literature concerning the fundamentals of tube hydro forming processes as well as the industrial application of such operations. As process design issues are concerned, in the paper, the authors propose the integration of different tools, namely artificial intelligence techniques, numerical simulations and experimental knowledge to carry out tube hydro forming design. A fuzzy system was integrated with a FEM code for process simulation obtaining a sort of closed loop control system to be utilised in the process design phase. An experimental validation of the design procedure was developed as well proving the effectiveness of the proposed approach in order to obtain defect free components both as geometrical features and ductile fractures are concerned.
Directory of Open Access Journals (Sweden)
Davide Piovesan
Full Text Available This study presents and validates a Time-Frequency technique for measuring 2-dimensional multijoint arm stiffness throughout a single planar movement as well as during static posture. It is proposed as an alternative to current regressive methods which require numerous repetitions to obtain average stiffness on a small segment of the hand trajectory. The method is based on the analysis of the reassigned spectrogram of the arm's response to impulsive perturbations and can estimate arm stiffness on a trial-by-trial basis. Analytic and empirical methods are first derived and tested through modal analysis on synthetic data. The technique's accuracy and robustness are assessed by modeling the estimation of stiffness time profiles changing at different rates and affected by different noise levels. Our method obtains results comparable with two well-known regressive techniques. We also test how the technique can identify the viscoelastic component of non-linear and higher than second order systems with a non-parametrical approach. The technique proposed here is very impervious to noise and can be used easily for both postural and movement tasks. Estimations of stiffness profiles are possible with only one perturbation, making our method a useful tool for estimating limb stiffness during motor learning and adaptation tasks, and for understanding the modulation of stiffness in individuals with neurodegenerative diseases.
Institute of Scientific and Technical Information of China (English)
Chunan Tang; Tianhui Ma; Xiaoli Ding
2009-01-01
Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR), used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. However, it is rec-ognized that unless we can give reasonable explanations of these curious precursory phenomena that continue to be seren-dipitously observed fi'om time to time, such high technology of GPS or InSAR is difficult to be efficiently used. Therefore, a proper model revealing the relation between earthquake evolution and stress variation, such as the phenomena of stress buildup, stress shadow and stress transfer (SSS), is crucial to the GPS or lnSAR based earthquake prediction. Here we ad-dress this question through a numerical approach of earthquake development using an intuitive physical model with a map-like configuration of discontinuous fault system. The simulation provides a physical basis for the principle of stress-forecasting of earthquakes based on SSS and for the application of GPS or InSAR in earthquake prediction. The ob-served SSS associated phenomena with images of stress distribution during the failure process can be continuously simulated. It is shown that the SSS are better indicators of earthquake precursors than that of seismic foreshocks, suggesting a predict-ability of earthquakes based on stress-forecasting strategy.
[Laparotomy closure in advanced peritonitis].
Bensman, V M; Savchenko, Yu P; Shcherba, S N; Golikov, I V; Triandafilov, K V; Chaykin, V V; Pyatakov, S N; Saakyan, A S; Saakyan, E A
to improve the results of advanced peritonitis management. 743 patients with advanced peritonitis were studied. Patients were divided into 2 groups depending on treatment strategy. Programmed relaparotomy combined with removable draining musculoaponeurotic seams during laparotomy closure decreased mortality from 47.8±2.7% to 24.1±2.3% (pperitonitis management. Laparotomy closure with only cutaneous seams is indicated in case of persistent abdominal hypertension. Large eventration always requires abdominal wall repair. APACHE-III scale scores have significant prognostic value in patients with advanced peritonitis.
Closure phase and lucky imaging.
Rhodes, William T
2009-01-01
Since its introduction by Jennison in 1958, the closure-phase method for removing the effects of electrical path-length errors in radio astronomy and of atmospheric turbulence in optical astronomy has been based on the non-redundant-spacing triple interferometer. It is shown that through application of lucky imaging concepts it is possible to relax this condition, making closure-phase methods possible with redundantly spaced interferometer configurations and thereby widening their range of application. In particular, a quadruple-interferometer can, under lucky imaging conditions, be treated as though it were a triple interferometer. The slit-annulus aperture is investigated as a special case.
Homogeneous orbit closures and applications
Lindenstrauss, Elon
2011-01-01
We give new classes of examples of orbits of the diagonal group in the space of unit volume lattices in R^d for d > 2 with nice (homogeneous) orbit closures, as well as examples of orbits with explicitly computable but irregular orbit closures. We give Diophantine applications to the former, for instance we show that if x is the cubic root of 2 then for any y,z in R liminf |n|=0 (as |n| goes to infinity), where denotes the distance of a real number c to the integers.
Long-term cavity closure in non-linear rocks
Cornet, Jan; Dabrowski, Marcin; Schmid, Daniel Walter
2017-08-01
-field deformation rate. The solution remains valid in the limit of ideal power-law fluid when \\overline M_s = 1/n. The solution is based on an approximation which transforms the non-linear isotropic constitutive law into a linear anisotropic one in the far field. The proposed approximate solution for closure velocity for general far-field load is based on the two end-member analytical solutions. They are additively combined after replacing the material threshold viscosity μ0 by the apparent background viscosity due to the far-field shear. Benchmarking the solution shows that there is a 50 per cent misfit at most between the analytical and the numerical solution for closure rate. Comparing the closure velocities obtained with a Carreau viscosity model with the ones from a power-law material shows an increase of several orders of magnitude for pressure loads smaller than 2{μ _0}D_{II}^*. Far field shear can also increase hole closure rate by several orders of magnitude. Compared with other available solutions, the approximate solution presented here ensures that both speed ups are taken into account making it well suited for actual underground conditions where both diffusion creep and shear stresses occur. The additional closure mechanisms considered here can potentially explain the fast closure rates observed underground without referring to transient mechanisms.
Telephone switchboard closure | 19 December
2014-01-01
Exceptionally, the telephone switchboard will close at 4 p.m. on Friday, 19 December, instead of the usual time of 6 p.m., to allow time for closing all systems properly before the annual closure. Therefore, switchboard operator assistance to transfer calls from/to external lines will stop. All other phone services will run as usual.
Abdominal wound closure: current perspectives
Directory of Open Access Journals (Sweden)
Williams ZF
2015-12-01
Full Text Available Zachary F Williams, William W Hope Department of Surgery, South East Area Health Education Center, New Hanover Regional Medical Center, Wilmington, NC, USA Abstract: This review examines both early and late wound complications following laparotomy closure, with particular emphasis on technical aspects that reduce hernia formation. Abdominal fascial closure is an area of considerable variation within the field of general surgery. The formation of hernias following abdominal wall incisions continues to be a challenging problem. Ventral hernia repairs are among the most common surgeries performed by general surgeons, and despite many technical advances in the field, incisional hernia rates remain high. Much attention and research has been directed to the surgical management of hernias. Less focus has been placed on prevention of hernia formation despite its obvious importance. This review examines the effects of factors such as the type of incision, suture type and size, closure method, patient risk factors, and the use of prophylactic mesh. Keywords: incisional, abdominal, hernia, prevention, wound closure techniques
Vacuum assisted closure in coloproctology
Bemelman, W.A.
2009-01-01
Vacuum-assisted closure has earned its indications in coloproctology. It has been described with variable results in the treatment of large perineal defects after abdominoperineal excision, in the treatment of stoma dehiscence and perirectal abscesses. The most promising indication for
Infering and Calibrating Triadic Closure in a Dynamic Network
Mantzaris, Alexander V.; Higham, Desmond J.
In the social sciences, the hypothesis of triadic closure contends that new links in a social contact network arise preferentially between those who currently share neighbours. Here, in a proof-of-principle study, we show how to calibrate a recently proposed evolving network model to time-dependent connectivity data. The probabilistic edge birth rate in the model contains a triadic closure term, so we are also able to assess statistically the evidence for this effect. The approach is shown to work on data generated synthetically from the model. We then apply this methodology to some real, large-scale data that records the build up of connections in a business-related social networking site, and find evidence for triadic closure.
Energy Technology Data Exchange (ETDEWEB)
Lee, Sang-Bong
1993-09-01
Quantum manifestation of classical chaos has been one of the extensively studied subjects for more than a decade. Yet clear understanding of its nature still remains to be an open question partly due to the lack of a canonical definition of quantum chaos. The classical definition seems to be unsuitable in quantum mechanics partly because of the Heisenberg quantum uncertainty. In this regard, quantum chaos is somewhat misleading and needs to be clarified at the very fundamental level of physics. Since it is well known that quantum mechanics is more fundamental than classical mechanics, the quantum description of classically chaotic nature should be attainable in the limit of large quantum numbers. The focus of my research, therefore, lies on the correspondence principle for classically chaotic systems. The chaotic damped driven pendulum is mainly studied numerically using the split operator method that solves the time-dependent Schroedinger equation. For classically dissipative chaotic systems in which (multi)fractal strange attractors often emerge, several quantum dissipative mechanisms are also considered. For instance, Hoover`s and Kubo-Fox-Keizer`s approaches are studied with some computational analyses. But the notion of complex energy with non-Hermiticity is extensively applied. Moreover, the Wigner and Husimi distribution functions are examined with an equivalent classical distribution in phase-space, and dynamical properties of the wave packet in configuration and momentum spaces are also explored. The results indicate that quantum dynamics embraces classical dynamics although the classicalquantum correspondence fails to be observed in the classically chaotic regime. Even in the semi-classical limits, classically chaotic phenomena would eventually be suppressed by the quantum uncertainty.
Pechlivanidou, Sofia; Cowie, Patience; Finch, Emma; Gawthorpe, Robert; Attal, Mikael
2016-04-01
This study uses a numerical modelling approach to explore structural controls on erosional/depositional systems within rifts that are characterized by complex multiphase extensional histories. Multiphase-rift related topography is generated by a 3D discrete element model (Finch et al., Basin Res., 2004) of normal fault growth and is used to drive the landscape evolution model CHILD (Tucker et al., Comput. Geosci., 2001). Fault populations develop spontaneously in the discrete element model and grow by both tip propagation and segment linkage. We conduct a series of experiments to simulate the evolution of the landscape (55x40 km) produced by two extensional phases that differ in the direction and in the amount of extension. In order to isolate the effects of fault propagation on the drainage network development, we conduct experiments where uplift/subsidence rates vary both in space and time as the fault array evolves and compare these results with experiments using a fixed fault array geometry with uplift rate/subsidence rates that vary only spatially. In many cases, areas of sediment deposition become uplifted and vise-versa due to complex elevation changes with respect to sea level as the fault array develops. These changes from subaerial (erosional) to submarine (depositional) processes have implications for sediment volumes and sediment caliber as well as for the sediment routing systems across the rift. We also explore the consequences of changing the angle between the two phases of extension on the depositional systems and we make a comparison with single-phase rift systems. Finally, we discuss the controls of different erodibilities on sediment supply and detachment-limited versus transport-limited end-member models for river erosion. Our results provide insights into the nature and distribution of sediment source areas and the sediment routing in rift systems where pre-existing rift topography and normal fault growth exert a fundamental control on
Khatami, F.; Weide, van der E.T.A.; Hoeijmakers, H.W.M.
2015-01-01
In this paper a numerical simulation of unsteady sheet cavitation is presented as it occurs on an NACA-0015 hydrofoil. The computational approach is based on the Euler equations for unsteady compressible flow, using an equilibrium cavitation model of Schnerr, Schmidt, and Saurel. It was found that f
Deen, Niels G.; Sint Annaland, van Martin; Kuipers, J.A.M.
2007-01-01
In this paper a hybrid model is presented for the numerical simulation of gas-liquid-solid flows using a combined Volume Of Fluid (VOF) and Discrete Particle (DP) approach applied for respectively dispersed gas bubbles and solid particles present in the continuous liquid phase. The hard sphere DP mo
Deen, Niels G.; Sint Annaland, van Martin; Kuipers, J.A.M.
2006-01-01
In this paper a hybrid model is presented for the numerical simulation of gas-liquid-solid flows using a combined Volume Of Fluid (VOF) and Discrete Particle (DP) approach applied for respectively dispersed gas bubbles and solid particles present in the continuous liquid phase. The hard sphere DP mo
Gazzillo, Domenico; Giacometti, Achille
2004-03-08
We discuss structural and thermodynamical properties of Baxter's adhesive hard sphere model within a class of closures which includes the Percus-Yevick (PY) one. The common feature of all these closures is to have a direct correlation function vanishing beyond a certain range, each closure being identified by a different approximation within the original square-well region. This allows a common analytical solution of the Ornstein-Zernike integral equation, with the cavity function playing a privileged role. A careful analytical treatment of the equation of state is reported. Numerical comparison with Monte Carlo simulations shows that the PY approximation lies between simpler closures, which may yield less accurate predictions but are easily extensible to multicomponent fluids, and more sophisticate closures which give more precise predictions but can hardly be extended to mixtures. In regimes typical for colloidal and protein solutions, however, it is found that the perturbative closures, even when limited to first order, produce satisfactory results.
Hascoet, Sebastien; Fraisse, Alain; Elbaz, Meyer
2013-10-01
Percutaneous transcatheter closure of a patent foramen ovale (PFO) remains challenging when femoral venous approach is not available. We describe the successful closure of a PFO using the right internal jugular venous approach and a deflectable catheter delivery system in a patient with a PFO, recurrent stroke, and an inferior vena cava filter.
40 CFR 265.112 - Closure plan; amendment of plan.
2010-07-01
... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Closure plan; amendment of plan. 265... DISPOSAL FACILITIES Closure and Post-Closure § 265.112 Closure plan; amendment of plan. (a) Written plan... have a written closure plan. Until final closure is completed and certified in accordance with §...
COMPARATIVE STUDY OF LAPAROSCOPIC CLOSURE OPEN PEPTIC PERFORATION CLOSURE
Directory of Open Access Journals (Sweden)
Vivek
2015-10-01
Full Text Available Laparoscopic closure of perforated duodenal ulcer was first performed in the year 1990 . Due to its advantage of better view of the peritoneal cavity an opportunity for thorough lavage and avoidance of upper abdominal incision, with its related complication, especially in high – ri sk patients, this procedure has gained popularity all over the world. Approximately 10 - 20% of patients suffering from peptic ulcer develop perforation of stomach or duodenum in which, chemical peritonitis develop initially from gastric secretion and duoden al secretion the condition is life threatening. Early diagnosis and treatment is extremely important. Mortality will increase up if perforation exists more than 24 to 48 hours. Usually surgical intervention of simple closure with omental patch of the perforation is required. this study aims at evaluating efficacy , safety and outcome of laparoscopic surgery for perforated duodenal ulcer patients admitted during period Jan 2009 to Dec 2012 at tertiary hospital in north Karnataka A total of 61cases diagnosed as peritonitis secondary to duodenal ulcer perforation were involved in the study 30underwent open perforation closure and 31 cases underwent lap closure. Peptic ulcers are focal defects in the gastric or duodenal mucosa which extend into the sub mucosa or deeper. they may be acute or chronic and ultimately are caused by on imbalance between the action of peptic acid and mucosal defenses peptic ulcer remains a common outpatient diagnosis, but the number of elective operations for peptic ul cer disease have decreased dramatically over the past 30 decades due to the advent of H2 blockers However the incidence of emergency surgeries, and death rate associated with peptic ulcer are same
Institute of Scientific and Technical Information of China (English)
SUN Pei-de; GUO Mao-xin
2005-01-01
From the viewpoint of interaction mechanics for solid and gas, a coupled mathematical model was presented for solid coal/rock deformation and gas leak flow in parallel deformable coal seams. Numerical solutions using the SIP (Strong Implicit Procedure) method to the coupled mathematical model for double parallel coal seams were also developed in detail. Numerical simulations for the prediction of the safety range using protection layer mining were performed with experimental data from a mine with potential danger of coal/gas outbursts. Analyses show that the numerical simulation results are consistent with the measured data in situ.
Directory of Open Access Journals (Sweden)
JORGE CASTAÑO-GARCÍA
2008-12-01
Full Text Available With support in the works of Duval (2004 regarding the operation of conversion between semiotic registries, the studies of numerical “transcodification” are analyzed. It is stated that in the studies on the understanding process of the decimal system of numeration by children, it is convenient to relate the activity of conversion between the verbal and Hindu-Arabic registers to the operating activity of children, when they try to respond to the logical demands presented to them by the understanding of the syntax implied in the decimal system of numeration, as a form of revealing the mechanisms that govern the constructions built by the children in this field.
Mechanics of epithelial closure over non-adherent environments
Vedula, Sri Ram Krishna; Peyret, Grégoire; Cheddadi, Ibrahim; Chen, Tianchi; Brugués, Agustí; Hirata, Hiroaki; Lopez-Menendez, Horacio; Toyama, Yusuke; Neves de Almeida, Luís; Trepat, Xavier; Lim, Chwee Teck; Ladoux, Benoit
2015-01-01
The closure of gaps within epithelia is crucial to maintain its integrity during biological processes such as wound healing and gastrulation. Depending on the distribution of extracellular matrix, gap closure occurs through assembly of multicellular actin-based contractile cables or protrusive activity of border cells into the gap. Here we show that the supracellular actomyosin contractility of cells near the gap edge exerts sufficient tension on the surrounding tissue to promote closure of non-adherent gaps. Using traction force microscopy, we observe that cell-generated forces on the substrate at the gap edge first point away from the centre of the gap and then increase in the radial direction pointing into the gap as closure proceeds. Combining with numerical simulations, we show that the increase in force relies less on localized purse-string contractility and more on large-scale remodelling of the suspended tissue around the gap. Our results provide a framework for understanding the assembly and the mechanics of cellular contractility at the tissue level.
Adaptive change of basis in entropy-based moment closures for linear kinetic equations
Alldredge, Graham W; O'Leary, Dianne P; Tits, André L
2013-01-01
Entropy-based (M_N) moment closures for kinetic equations are defined by a constrained optimization problem that must be solved at every point in a space-time mesh, making it important to solve these optimization problems accurately and efficiently. We present a complete and practical numerical algorithm for solving the dual problem in one-dimensional, slab geometries. The closure is only well-defined on the set of moments that are realizable from a positive underlying distribution, and as the boundary of the realizable set is approached, the dual problem becomes increasingly difficult to solve due to ill-conditioning of the Hessian matrix. To improve the condition number of the Hessian, we advocate the use of a change of polynomial basis, defined using a Cholesky factorization of the Hessian, that permits solution of problems nearer to the boundary of the realizable set. We also advocate a fixed quadrature scheme, rather than adaptive quadrature, since the latter introduces unnecessary expense and changes th...
Weigand, T. M.; Miller, C. T.; Dye, A. L.; Gray, W. G.; McClure, J. E.; Rybak, I.
2015-12-01
The thermodynamically constrained averaging theory (TCAT) has been usedto formulate general classes of porous medium models, including newmodels for two-fluid-phase flow. The TCAT approach provides advantagesthat include a firm connection between the microscale, or pore scale,and the macroscale; a thermodynamically consistent basis; explicitinclusion of factors such as interfacial areas, contact angles,interfacial tension, and curvatures; and dynamics of interface movementand relaxation to an equilibrium state. In order to render the TCATmodel solvable, certain closure relations are needed to relate fluidpressure, interfacial areas, curvatures, and relaxation rates. In thiswork, we formulate and solve a TCAT-based two-fluid-phase flow model. We detail the formulation of the model, which is a specific instancefrom a hierarchy of two-fluid-phase flow models that emerge from thetheory. We show the closure problem that must be solved. Using recentresults from high-resolution microscale simulations, we advance a set ofclosure relations that produce a closed model. Lastly, we solve the model using a locally conservative numerical scheme and compare the TCAT model to the traditional model.
An Approach to Developing Numeric Water Quality Criteria for Using the SeaWiFS Satellite Data Record
Human activities on land increase nutrient loads to coastal waters, which can increase phytoplankton production and biomass and associated ecological impacts. Numeric nutrient water quality standards were needed to protect coastal waters from eutrophication impacts. The Environm...
Generalized Convective Quasi-Equilibrium Closure
Yano, Jun-Ichi; Plant, Robert
2016-04-01
Arakawa and Schubert proposed convective quasi-equilibrium as a basic principle for closing their spectrum mass-flux convection parameterization. In deriving this principle, they show that the cloud work function is a key variable that controls the growth of convection. Thus, this closure hypothesis imposes a steadiness of the cloud work function tendency. This presentation shows how this principle can be generalized so that it can also encompasses both the CAPE and the moisture-convergence closures. Note that the majority of the current mass-flux convection parameterization invokes a CAPE closure, whereas the moisture-convergence closure was extremely popular historically. This generalization, in turn, includes both closures as special cases of convective quasi-equilibrium. This generalization further suggests wide range of alternative possibilities for convective closure. In general, a vertical integral of any function depending on both large-scale and convective-scale variables can be adopted as an alternative closure variables, leading to an analogous formulation as Arakawa and Schubert's convective quasi-equilibrium formulation. Among those, probably the most fascinating possibility is to take a vertical integral of the convective-scale moisture for the closure. Use of a convective-scale variable for closure has a particular appeal by not suffering from a loss of predictability of any large-scale variables. That is a main problem with any of the current convective closures, not only for the moisture-convergence based closure as often asserted.
Energy Technology Data Exchange (ETDEWEB)
Viana, A., E-mail: Antoine.Viana@g2elab.grenoble-inp.f [Grenoble Electrical Engineering Lab (CNRS UMR5269), Universite de Grenoble, ENSE3, BP 46, 38402 Saint Martin d' Heres (France); Coulomb, J.-L.; Rouve, L.-L.; Cauffet, G. [Grenoble Electrical Engineering Lab (CNRS UMR5269), Universite de Grenoble, ENSE3, BP 46, 38402 Saint Martin d' Heres (France)
2010-01-15
The Langevin equation is classically used to model the anhysteretic magnetization curve. A modified version of this equation has been introduced by Jiles to take into account the effects of magnetostriction on the anhysteretic magnetization behavior when a ferromagnetic material undergoes mechanical stresses. The numerical resolution of the modified Langevin equation is usually performed with a root-finding algorithm. In this paper, a differential form of the modified Langevin equation is proposed, allowing a faster numerical resolution.
Closure Plan for Active Low Level Burial Grounds
Energy Technology Data Exchange (ETDEWEB)
SKELLY, W.A.
2000-11-16
This plan has been prepared in response to direction from the U.S. Department of Energy. The purpose of the plan is to define approaches that will be implemented to ensure protection of the public and the environment when active Low-Level Burial Grounds (LLBGs) at the Hanford Site are closed. Performance assessments for active burial grounds in the 200 East and West 200 Areas provide current estimates of potential environmental contamination and doses to the ''maximum exposed individual'' from burial ground operation and closure and compare dose estimates to performance objective dose limits for the facilities. This is an Operational Closure Plan. The intent of the guidance in DOE Order 435.1 is that this plan will be a living document, like the facility performance assessments, and will be revised periodically through the operational life of the LLBGs to reflect updated information on waste inventory. management practices, facility transition planning, schedule dates, assessments of post-closure performance, and environmental consequences. Out year dates identified in this plan are tentative. A Final Closure Plan will be prepared in the future when the timing and extent of closure-related activities for LLBGs can be established with greater certainty. After current operations at the LLBGs are concluded, this plan proposes transitioning of these facilities to the Environmental Restoration Program. This action will enable the Environmental Restoration Program to design and implement consistent and coordinated final remedial actions for active and inactive LLBGs. Active and inactive burial grounds in the 200 West and 200 East Areas are commingled. This plan describes approaches that will be implemented during Interim Closure, Final Closure, and Institutional Control Periods to prepare LLBGs for surface barriers, and the construction of barriers, as well as the scope of inspection, monitoring and maintenance practices that will be performed during
Directory of Open Access Journals (Sweden)
Zhang, M. Z.
2010-12-01
Full Text Available Concrete diffusivity is a function of its microstructure on many scales, ranging from nanometres to millimetres. Multi-scale techniques are therefore needed to model this parameter. Representative elementary volume (REV, in conjunction with the homogenization principle, is one of the most common multi-scale approaches. This study aimed to establish a procedure for establishing the REV required to determine cement paste diffusivity based on a three-step, numerical-statistical approach. First, several series of 3D cement paste microstructures were generated with HYMOSTRUC3D, a cement hydration and microstructure model, for different volumes of cement paste and w/c ratios ranging from 0.30 to 0.60. Second, the finite element method was used to simulate the diffusion of tritiated water through these microstructures. Effective cement paste diffusivity values for different REVs were obtained by applying Fick’s law. Finally, statistical analysis was used to find the fluctuation in effective diffusivity with cement paste volume, from which the REV was then determined. The conclusion drawn was that the REV for measuring diffusivity in cement paste is 100x100x100 μm^{3}.
La difusividad del hormigón depende de su microestructura a numerosas escalas, desde nanómetros hasta milímetros, por lo que se precisa de técnicas multiescala para representar este parámetro. Junto con el principio de homogeneización, uno de los métodos multiescala más habituales es el volumen elemental representativo (VER. El objeto de este estudio era establecer un procedimiento que permitiera determinar el VER necesario para calcular la difusividad de la pasta de cemento, basándose en un método numéricoestadístico que consta de tres etapas. Primero, se crearon varias series de microestructuras de pasta de cemento en 3D con HYMOSTRUC3D, un programa que permite crear un modelo de la hidratación y microestructura del cemento. Luego se empleó el método de
Energy Technology Data Exchange (ETDEWEB)
Hommel, S.; Fountain, D.
2012-03-28
The intent of this document is to provide clarification of critical assumptions regarding the internal configurations of liquid waste tanks at operational closure, with respect to F-Tank Farm (FTF) closure documentation. For the purposes of this document, FTF closure documentation includes: (1) Performance Assessment for the F-Tank Farm at the Savannah River Site (hereafter referred to as the FTF PA) (SRS-REG-2007-00002), (2) Basis for Section 3116 Determination for Closure of F-Tank Farm at the Savannah River Site (DOE/SRS-WD-2012-001), (3) Tier 1 Closure Plan for the F-Area Waste Tank Systems at the Savannah River Site (SRR-CWDA-2010-00147), (4) F-Tank Farm Tanks 18 and 19 DOE Manual 435.1-1 Tier 2 Closure Plan Savannah River Site (SRR-CWDA-2011-00015), (5) Industrial Wastewater Closure Module for the Liquid Waste Tanks 18 and 19 (SRRCWDA-2010-00003), and (6) Tank 18/Tank 19 Special Analysis for the Performance Assessment for the F-Tank Farm at the Savannah River Site (hereafter referred to as the Tank 18/Tank 19 Special Analysis) (SRR-CWDA-2010-00124). Note that the first three FTF closure documents listed apply to the entire FTF, whereas the last three FTF closure documents listed are specific to Tanks 18 and 19. These two waste tanks are expected to be the first two tanks to be grouted and operationally closed under the current suite of FTF closure documents and many of the assumptions and approaches that apply to these two tanks are also applicable to the other FTF waste tanks and operational closure processes.
Closure constraints for hyperbolic tetrahedra
Charles, Christoph
2015-01-01
We investigate the generalization of loop gravity's twisted geometries to a q-deformed gauge group. In the standard undeformed case, loop gravity is a formulation of general relativity as a diffeomorphism-invariant SU(2) gauge theory. Its classical states are graphs provided with algebraic data. In particular closure constraints at every node of the graph ensure their interpretation as twisted geometries. Dual to each node, one has a polyhedron embedded in flat space R^3. One then glues them allowing for both curvature and torsion. It was recently conjectured that q-deforming the gauge group SU(2) would allow to account for a non-vanishing cosmological constant Lambda, and in particular that deforming the loop gravity phase space with real parameter q>0 would lead to a generalization of twisted geometries to a hyperbolic curvature. Following this insight, we look for generalization of the closure constraints to the hyperbolic case. In particular, we introduce two new closure constraints for hyperbolic tetrahe...
Multivariate moment closure techniques for stochastic kinetic models
Lakatos, Eszter; Ale, Angelique; Kirk, Paul D. W.; Stumpf, Michael P. H.
2015-09-01
Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs.
Multivariate moment closure techniques for stochastic kinetic models
Energy Technology Data Exchange (ETDEWEB)
Lakatos, Eszter, E-mail: e.lakatos13@imperial.ac.uk; Ale, Angelique; Kirk, Paul D. W.; Stumpf, Michael P. H., E-mail: m.stumpf@imperial.ac.uk [Department of Life Sciences, Centre for Integrative Systems Biology and Bioinformatics, Imperial College London, London SW7 2AZ (United Kingdom)
2015-09-07
Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs.
Multivariate moment closure techniques for stochastic kinetic models.
Lakatos, Eszter; Ale, Angelique; Kirk, Paul D W; Stumpf, Michael P H
2015-09-07
Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs.
Su, Shih-Wei; Gou, Shih-Chuan; Horng, Tzyy-Leng; Yu, Ite A
2011-01-01
We present a numerical scheme to study the dynamics of slow light and light storage in an electromagneticallyinduced- transparency (EIT) medium at finite temperatures. Allowing for the motional coupling, we derive a set of coupled Schr\\"{o}dinger equations describing a boosted closed three-level EIT system according to the principle of Galilean relativity. The dynamics of a uniformly moving EIT medium can thus be determined by numerically integrating the coupled Schr\\"odinger equations for atoms plus one ancillary Maxwell-Schr\\"odinger equation for the probe pulse. The central idea of this work rests on the assumption that the loss of ground-state coherence at finite temperatures can be ascribed to the incoherent superposition of density matrices representing the EIT systems with various velocities. Close agreements are demonstrated in comparing the numerical results with the experimental data for both slow light and light storage. In particular, the distinct characters featuring the decay of ground-state coh...
Zhang, Junbo; Kitazawa, Daisuke
2016-09-15
With increasing concern over the aquatic environment in marine culture, the integrated multi-trophic aquaculture (IMTA) has received extensive attention in recent years. A three-dimensional numerical ocean model is developed to explore the negative impacts of aquaculture wastes and assess the bio-mitigation effect of IMTA systems on marine environments. Numerical results showed that the concentration of surface phytoplankton could be controlled by planting seaweed (a maximum reduction of 30%), and the percentage change in the improvement of bottom dissolved oxygen concentration increased to 35% at maximum due to the ingestion of organic wastes by sea cucumbers. Numerical simulations indicate that seaweeds need to be harvested in a timely manner for maximal absorption of nutrients, and the initial stocking density of sea cucumbers >3.9 individuals m(-2) is preferred to further eliminate the organic wastes sinking down to the sea bottom.
Occupational closure in nursing work reconsidered
DEFF Research Database (Denmark)
Traynor, Michael; Nissen, Nina; Lincoln, Carol
2015-01-01
In healthcare, occupational groups have adopted tactics to maintain autonomy and control over their areas of work. Witz described a credentialist approach to occupational closure adopted by nursing in the United Kingdom during the 19th and early 20th centuries. However, the recent advancement...... = 59). The aim was to examine how these workers positioned themselves as professionals and accounted for professional boundaries. A thematic analysis revealed a complex situation in which participants were divided between articulating an acceptance of a subordinate role within traditional occupational......, while nurses abandon it for largely administrative roles. We conclude that the participants are the not unwilling agents of a managerially led project to reshape the workforce that cuts across existing occupational boundaries....
Dynamics of electrochemical flows 3 Closure models
Xu, Chengjun
2013-01-01
The electrolyte (comprising of solute ions and solvents) flow-through the porous media is frequently encountered in nature or in many engineering applications, such as the electrochemical systems, manufacturing of composites, oil production, geothermal engineering, nuclear thermal disposal, soil pollution. Our previous work derived the interfacial interaction terms between the solid and the fluid, which can be used to investigate the details of transports of mass, heat, electric flied, potential, or momentum in the process of the electrochemical flows-through porous electrode. In this work, we establish the closure models for these interfacial interaction terms to close the governing equations from mathematical algebra. The interfacial interaction terms regard to the electric field, potential and electric force are firstly revealed. Our new theory provides a new approach to describe the electrochemical flows-through porous media.
Klimas, A. J.
1983-01-01
A numerical method is presented for studying one-dimensional electron plasma evolution under typical interplanetary conditions. The method applies the Fourier-Fourier transform approach to a plasma model that is a generalization of the electrostatic Vlasov-Poisson system of equations. Conservation laws that are modified to include the plasma model generalization and also the boundary effects of nonperiodic solutions are given. A new conservation law for entropy in the transformed space is then introduced. These conservation laws are used to verify the numerical solutions. A discretization error analysis is presented. Two numerical instabilities and the methods used for their suppression are treated. It is shown that in interplanetary plasma conditions, the bump-on-tail instability produces significant excitation of plasma oscillations at the Bohm-Gross frequency and its second harmonic. An explanation of the second harmonic excitation is given in terms of wave-wave coupling during the growth phase of the instability.
Effectiveness and Safety of Transcatheter Patent Foramen Ovale Closure for Migraine (EASTFORM) Trial
Xing, Ying-qi; Guo, Yu-Zhu; Gao, Yong-Sheng; Guo, Zhen-Ni; Niu, Peng-Peng; Yang, Yi
2016-01-01
We evaluated the safety and effectiveness of transcatheter patent foramen ovale (PFO) closure for the treatment of migraine in a Chinese population. This non-randomized clinical trial enrolled 258 consecutive substantial or severe migraineurs with a right-to-left shunt (RLS) (grade II–IV) and grouped subjects according to their election or refusal of PFO closure. Migraine was diagnosed according to the International Classification of Headache Disorders III-beta and evaluated using the Headache Impact Test-6 (HIT-6). In total, 241 participants (125 in the transcatheter closure group and 116 in the control group) were included in the study. In general, the PFO closure procedure was found to be safe. At 1 month after closure, 76.1% of patients returned for c-TCD evaluation; of these, 85.7% were downgraded to negative status or a grade-I shunt. Residual shunts and placebo effects were thought to resolve by 12 months post-procedure, when migraine impact was reported to decrease by 73.6%. Transcatheter PFO closure was demonstrated to be effective for the treatment of migraine by comparing HIT-6 scores between the transcatheter closure and control groups (p < 0.001). Our results suggest that transcatheter PFO closure is a safe and effective approach for the treatment of migraine in the Chinese population, especially in females with constant RLS. Clinical trial no. NCT02127294 (registered on April 29, 2014). PMID:27966652
Institute of Scientific and Technical Information of China (English)
DING Hao-jiang; WANG Hui-ming
2005-01-01
The elastodynamic problems of magneto-electro-elastic hollow cylinders in the state ofaxisymmetric plane strain case can be transformed into two Volterra integral equations of the second kind about two functions with respect to time. Interpolation functions were introduced to approximate two unknown functions in each time subinterval and two new recursive formulae are derived. By using the recursive formulae, numerical results were obtained step by step. Under the same time step, the accuracy of the numerical results by the present method is much higher than that by the traditional quadrature method.
Guillen, Ph.; Borrel, M.; Dormieux, M.
1990-10-01
A numerical scheme of the MUSCL type used for the numerical simulation of gas flow of different types around complex configurations is described. Approximate Riemann solvers of the Van Leer, Roc, and Osher types, developed for perfect gas flows are used. These solvers have been extended to non-reactive mixtures of two species and real gas flows by Abgrall, Montagne and Vinokur. The architecture of the code, dictated by constraints in geometrical considerations, computational aspects, the specific nature of the flow, and ergonomy, is described.
Newborn exstrophy closure without osteotomy: Is there a role?
Inouye, Brian M; Lue, Kathy; Abdelwahab, Mahmoud; Di Carlo, Heather N; Young, Ezekiel E; Tourchi, Ali; Grewal, Mehnaj; Hesh, Christopher; Sponseller, Paul D; Gearhart, John P
2016-02-01
Recent articles document successful classic bladder exstrophy (CBE) closure without osteotomy. Still, many patients require osteotomy if they have a large bladder template and pubic diastasis, or non-malleable pelvis. To understand the indications and outcomes of bladder closure with and without pelvic osteotomy in patients younger than 1 month of age. An institutional database of 1217 exstrophy-epispadias patients was reviewed for CBE patients closed at the authors' institution within the first month of life. Patient demographics, closure history, pubic diastasis distance, bladder capacity, and outcomes were recorded and compared using chi-square tests between osteotomy and non-osteotomy patients. Failure was defined as bladder dehiscence, prolapse, vesicocutaneous fistula, or bladder outlet obstruction requiring reoperation. Bladder capacity >100 mL was deemed sufficient for bladder neck reconstruction (BNR). One hundred CBE patients were included for analysis: 38 closed with osteotomy (26 male, 12 female), and 62 closed without osteotomy (42 male, 20 female). There were four failed closures in the osteotomy group (2 dehiscence, 2 prolapse) and four failed closures in the non-osteotomy group (2 dehiscence, 2 prolapse). This corresponded to statistically equivalent rates of failure between the osteotomy and non-osteotomy groups (10.5% vs. 6.5%, p = 0.466). There was no statistically significant difference between the groups' ability to achieve bladder capacity sufficient for BNR (82% vs. 71%, p = 0.234). A successful primary bladder closure, regardless of the use of osteotomy, has been shown to be the single most important predictor of eventual continence. Because of the complexity of exstrophy manifestations, a multidisciplinary team approach is of the utmost importance. Based on our institutional experience, closure without osteotomy is considered when patients are osteotomy in patients considered suitable for closure by both the pediatric urologist and
Inertial-particle accelerations in turbulence: a Lagrangian closure
Vajedi, S; Mehlig, B; Biferale, L
2016-01-01
The distribution of particle accelerations in turbulence is intermittent, with non-Gaussian tails that are quite different for light and heavy particles. In this article we analyse a closure scheme for the acceleration fluctuations of light and heavy inertial particles in turbulence, formulated in terms of Lagrangian correlation functions of fluid tracers. We compute the variance and the flatness of inertial particle accelerations and we discuss their dependency on the Stokes number. The closure incorporates effects induced by the Lagrangian correlations along the trajectories of fluid tracers, and its predictions agree well with results of direct numerical simulations of inertial particles in turbulence, provided that the effects induced by the inertial preferential sampling of heavy/light particles outside/inside vortices are negligible. In particular, the scheme predicts the correct functional behaviour of the acceleration variance, as a function of Stokes, as well as the presence of a minimum/maximum for ...
Ansari, Daniel
2010-01-01
The present paper provides a critical overview of how adult neuropsychological models have been applied to the study of the atypical development of numerical cognition. Specifically, the following three assumptions are challenged: 1. Profiles of strength and weaknesses do not change over developmental time. 2. Similar neuronal structures are…
Directory of Open Access Journals (Sweden)
Qian Guo
2014-01-01
Full Text Available Almost sure exponential stability of the split-step backward Euler (SSBE method applied to an Itô-type stochastic differential equation with time-varying delay is discussed by the techniques based on Doob-Mayer decomposition and semimartingale convergence theorem. Numerical experiments confirm the theoretical analysis.
A Space-Time Finite Element Approach to the Numerical Simulation of Vascular Fluid-Solid Interaction
Vlijm, E.J.; Van Brummelen, E.H.
2008-01-01
Numerical studies of cardiovascular diseases like arteriosclerosis have gained increasing attention the last decade. The modeling of blood, blood vessel and their coupling, shows to be a challenging problem. In this thesis a two-dimensional model has been constructed and its behaviour has been inves
Breugem, W.P.; Boersma, B.J.
2005-01-01
A direct numerical simulation (DNS) has been performed of turbulent channel flow over a three-dimensional Cartesian grid of 30×20×9 cubes in, respectively, the streamwise, spanwise, and wall-normal direction. The grid of cubes mimics a permeable wall with a porosity of 0.875. The flow field is resol
A new approach to river bank retreat and advance in 2D numerical models of fluvial morphodynamics
Spruyt, A.; Mosselman, E.; Jagers, B.
2011-01-01
River bank retreat and advance are modes of morphological evolution in addition to bed level changes and changes in bed sediment composition. They produce planform changes such as width adjustment and meander bend migration. However, their reproduction in a 2D numerical model still remains a challen
Directory of Open Access Journals (Sweden)
Mangovski Ljupčo
2015-01-01
Full Text Available Introduction. Transcatheter atrial septal defect (ASD closure is considered to be a gold standard for patients with the suitable anatomy as compared to cardiac surgery. Reocurrence of ASD after surgical closure is a very rare late complication which can be successfully managed with transcatheter procedure. Case report. We reported a female patient with Noonan syndrome who presented with hemodinamically significant ASD 37 years after the corrective cardiac surgery. Due to numerous comorbidities which included severe kyphoscoliosis, pectus excavatum and multiple surgeries we decided to perform transcatheter closure of ASD. The procedure itself was very challenging due to the patient’s short stature and heart’s orientation in the chest, but was performed successfully. The subsequent follow-up was uneventful and the patient reported improvement in the symptoms. Conclusion. Transcatheter closure of ASD in a patient with Noonan syndrome with the history of surgically corrected ASD can be performed successfully, despite challenging chest anatomy.
Closure technique for the hybrid girder cable stayed bridge of Edong Bridge
Institute of Scientific and Technical Information of China (English)
Liu Minghu; Tan Hao; Xu GuoPing; Zhao Canhui
2012-01-01
Based on Edong Yangtze River Bridge, which is the second longest hybrid girder cable stayed bridge with 926 m long main span, the influencing factors and crucial techniques of the main span closure method for long span hybrid girder cable stayed bridge are studied. After theoretical analysis, numerical evaluation and practical test, the loading assistant closure method is employed in Edong Yangtze River Bridge. The loading assistant closure method, with better thermal adaptability and less influence on bridge line and the forced status, can meet the requirements of the unstressed state control method. Based on the mentioned advantages, the loading assistant closure method is applicable to long span hybrid girder cable stayed bridges. The conclusion can provide a reference for the further design of the similar brid~es.
Optimal prediction for radiative transfer: A new perspective on moment closure
Frank, Martin
2008-01-01
A direct numerical solution of the radiative transfer equation is typically expensive, since the radiative intensity depends on time, space and direction. An expansion in the direction variables yields an equivalent system of infinitely many moments. A fundamental problem is how to truncate the system. Various closures have been presented in the literature. We formulate the method of optimal prediction, a strategy to approximate the mean solution of a large system by a smaller system, for radiation moment systems. To that end, the formalism is generalized to systems of partial differential equations. Using Gaussian measures, we re-derive linear closures, such as $P_N$, diffusion, and diffusion correction closures. In addition, we propose a modification to xisting closures. Although simple and with no extra cost, the newly derived crescendo-diffusion yields significantly better approximations in 1D and 2D tests.
Non-perturbative closure calculation for fluids and plasmas
Tang, Xianzhu; McDevitt, Chris; Guo, Zehua
2015-11-01
Closure calculation of the Chapman-Enskog type is based on a perturbative expansion in the small parameter of Knudsen number, which is defined as the ratio of the thermal particle mean-free-path and the system gradient length scale. The error in the analysis can be locally measured in phase space using the local Knudsen number, which for the energy squared dependence of the mean-free-path, is much larger for high energy particles. Such breakdown, if occurs at sufficiently high energy, has small impact on closure results, but in cases of strong spatial gradients, can have large effect and invalidate the perturbative calculation. Here we show a non-perturbative closure formulation and its application in calculating standard closure quantitities such as heat flux. This approach applies as long as the thermal bulk is close to a Maxwellian, where a perturbative analysis can be matched onto a non-perturbative treatment of the tail population. Work supported by DOE via LANL-LDRD.
Closure constraints for hyperbolic tetrahedra
Charles, Christoph; Livine, Etera R.
2015-07-01
We investigate the generalization of loop gravity's twisted geometries to a q-deformed gauge group. In the standard undeformed case, loop gravity is a formulation of general relativity as a diffeomorphism-invariant SU(2) gauge theory. Its classical states are graphs provided with algebraic data. In particular, closure constraints at every node of the graph ensure their interpretation as twisted geometries. Dual to each node, one has a polyhedron embedded in flat space {{{R}}3}. One then glues them, allowing for both curvature and torsion. It was recently conjectured that q-deforming the gauge group SU(2) would allow us to account for a non-vanishing cosmological constant Λ \
Contri, Rachele; Clivio, Sara; Torre, Tiziano; Cassina, Tiziano
2017-09-12
Left atrial appendage (LAA) closure prevents thromboembolic risk and avoids lifelong anticoagulation due to atrial fibrillation (AF). Nowadays, AtriClip, a modern epicardial device approved in June 2010, allows external and safe closure of LAA in patients undergoing cardiac surgery during other open-chest cardiac surgical procedures. Such a surgical approach and its epicardial deployment differentiates LAA closure with AtriClip from percutaneous closure techniques such as Watchman (Boston Scientific, Marlborough, MA, USA), Lariat (SentreHEART Inc., Redwood City, CA, USA), and Amplatzer Amulet (St. Jude Medical, St. Paul, MN, USA) device procedures. AtriClip positioning must consider perioperative transesophageal echocardiography (TEE) to confirm LAA anatomical features, to explore the links with neighboring structures, and finally to assess its successful closure. We report a sequence of images to document the role of intraoperative TEE during an elective aortic valve replacement and LAA external closure with AtriClip. © 2017, Wiley Periodicals, Inc.
Cîndea, Nicolae; Münch, Arnaud
2016-11-01
We introduce a direct method that makes it possible to solve numerically inverse type problems for linear hyperbolic equations posed in {{Ω }}× (0,T) - Ω, a bounded subset of {{{R}}}N. We consider the simultaneous reconstruction of both the state and the source term from a partial boundary observation. We employ a least-squares technique and minimize the L 2-norm of the distance from the observation to any solution. Taking the hyperbolic equation as the main constraint of the problem, the optimality conditions are reduced to a mixed formulation involving both the state to reconstruct and a Lagrange multiplier. Under usual geometric conditions, we show the well-posedness of this mixed formulation (in particular the inf-sup condition) and then introduce a numerical approximation based on space-time finite element discretization. We prove the strong convergence of the approximation and then discuss several examples in the one- and two-dimensional cases.
100-D Ponds closure plan. Revision 1
Energy Technology Data Exchange (ETDEWEB)
Petersen, S.W.
1997-09-01
The 100-D Ponds is a Treatment, Storage, and Disposal (TSD) unit on the Hanford Facility that received both dangerous and nonregulated waste. This Closure Plan (Rev. 1) for the 100-D Ponds TSD unit consists of a RCRA Part A Dangerous Waste Permit Application (Rev. 3), a RCRA Closure Plan, and supporting information contained in the appendices to the plan. The closure plan consists of eight chapters containing facility description, process information, waste characteristics, and groundwater monitoring data. There are also chapters containing the closure strategy and performance standards. The strategy for the closure of the 100-D Ponds TSD unit is clean closure. Appendices A and B of the closure plan demonstrate that soil and groundwater beneath 100-D Ponds are below cleanup limits. All dangerous wastes or dangerous waste constituents or residues associated with the operation of the ponds have been removed, therefore, human health and the environment are protected. Discharges to the 100-D Ponds, which are located in the 100-DR-1 operable unit, were discontinued in June 1994. Contaminated sediment was removed from the ponds in August 1996. Subsequent sampling and analysis demonstrated that there is no contamination remaining in the ponds, therefore, this closure plan is a demonstration of clean closure.
Chertock, A.
2012-02-02
Aquatic bacteria like Bacillus subtilis are heavier than water yet they are able to swim up an oxygen gradient and concentrate in a layer below the water surface, which will undergo Rayleigh-Taylor-type instabilities for sufficiently high concentrations. In the literature, a simplified chemotaxis-fluid system has been proposed as a model for bio-convection in modestly diluted cell suspensions. It couples a convective chemotaxis system for the oxygen-consuming and oxytactic bacteria with the incompressible Navier-Stokes equations subject to a gravitational force proportional to the relative surplus of the cell density compared to the water density. In this paper, we derive a high-resolution vorticity-based hybrid finite-volume finite-difference scheme, which allows us to investigate the nonlinear dynamics of a two-dimensional chemotaxis-fluid system with boundary conditions matching an experiment of Hillesdon et al. (Bull. Math. Biol., vol. 57, 1995, pp. 299-344). We present selected numerical examples, which illustrate (i) the formation of sinking plumes, (ii) the possible merging of neighbouring plumes and (iii) the convergence towards numerically stable stationary plumes. The examples with stable stationary plumes show how the surface-directed oxytaxis continuously feeds cells into a high-concentration layer near the surface, from where the fluid flow (recurring upwards in the space between the plumes) transports the cells into the plumes, where then gravity makes the cells sink and constitutes the driving force in maintaining the fluid convection and, thus, in shaping the plumes into (numerically) stable stationary states. Our numerical method is fully capable of solving the coupled chemotaxis-fluid system and enabling a full exploration of its dynamics, which cannot be done in a linearised framework. © 2012 Cambridge University Press.
Mahbub, A. M. Ishtiaque; Mawa, Zannatul
2017-06-01
Some polymers tend to possess affinity with water and eventually, absorb significant moisture content from the surrounding air, causing difficulties during their industrial processing. Drying of these hygroscopic polymers, therefore, plays a vital role in their usability in industrial applications. In this work, the drying kinetics of the polymeric granulates is numerically formulated and the influence of different parameters pertaining to the drying procedure has been investigated. Backward Euler or implicit algorithm has been considered for solving the second order partial differential heat and mass transfer equations for simulating the drying kinetics of Polyamide 6 (PA-6). At first, the conduction of heat from the granulate surface towards the core was formulated using one dimensional transient heat conduction law and corresponding diffusion coefficients were determined using Arrhenius diffusion model. Afterwards, the migration of moisture from the granulate core towards the surface has been calculated using Fick's second law of diffusion. The data obtained from the single polymer granulate was then used to calculate the amount of moisture removed and the drying rate. The numerical results showed similitude with the experimental data obtained from the literature, although deviated quantitatively. To investigate the influence of different parameters on the drying process, different cases with varying drying air temperature, granulate radius and initial moisture content were compared. The numerical analysis qualitatively predicted all the dependencies to be expected. With higher drying air temperature, drying rate was observed to be faster and with higher granulate radius, drying rate was slower. With better approximations of the applied parameters and algorithms, the accuracy of the developed numerical model could be improved and used as a prediction tool for the drying process of polymer samples with reasonable tolerance.
Misuth, Matus; Joniova, Jaroslava; Belej, Dominik; Hrivnak, Stanislav; Horvath, Denis; Huntosova, Veronika
2016-05-09
Golgi apparatus (GA) is a center for lipid metabolism and the final target of ceramide pathway, which may result in apoptosis. In this work localization of highly hydrophobic hypericin is followed by time-resolved imaging of NBDC6 (fluorescent ceramide) in U87 MG glioma cells. Decrease of NBDC6 fluorescence lifetimes in cells indicates that hypericin can also follow this pathway. It is known that both, ceramide and hypericin can significantly influence protein kinase C (PKC) activity. Western blotting analysis shows increase of PKCδ autophosphorylation at Ser645 (p(S645)PKCδ) in glioma cells incubated with 500 nM hypericin and confocal-fluorescence microscopy distinguishes p(S645)PKCδ localization between GA related compartments and nucleus. Experimental and numerical methods are combined to study p(S645)PKCδ in U87 MG cell line. Image processing based on conceptual qualitative description is combined with numerical treatment via simple exponential saturation model which describes redistribution of p(S645)PKCδ between nucleus and GA related compartments after hypericin administration. These results suggest, that numerical methods can significantly improve quantification of biomacromolecules (p(S645)PKCδ) directly from the fluorescence images and such obtained outputs are complementary if not equal to typical used methods in biology.
Numerical analysis of microholes film/effusion cooling effectiveness
Ochrymiuk, Tomasz
2017-10-01
Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three-dimensional discrete hole film cooling RSM-AKN turbulent heat transfer models based on variable turbulent Prandtl number approaches were considered. Obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology. All implemented models for turbulent heat transfer performed sufficiently well for the considered case. It was confirmed, however, that the two-equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models. The RSM-AKN turbulent model was used in micoholes case too. The main target of simulations was maintain the same level of cooling efficiency ratio in both cases and confirm that is possible significantly reduce mass flows of the coolant in microholes case.
Karimi, Mohsen; Hulsebus, Elise; Murdison, Kenneth; Wiles, Henry
2012-06-01
Complex muscular ventricular septal defect poses difficult surgical management and is associated with high morbidity and mortality despite advancements in surgical therapy. Device closure of muscular ventricular septal defect has been encouraging and has been used in hybrid approach at a few centres. However, device closure has some limitations in patients with complex muscular ventricular septal defect. We report a case of perventricular device closure of a complex muscular ventricular septal defect in a beating heart with entrapped right ventricular disc and its surgical management.
40 CFR 264.112 - Closure plan; amendment of plan.
2010-07-01
... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Closure plan; amendment of plan. 264... Closure and Post-Closure § 264.112 Closure plan; amendment of plan. (a) Written plan. (1) The owner or operator of a hazardous waste management facility must have a written closure plan. In addition,...
Roy, Subrata P.
2014-01-28
The method of moments with interpolative closure (MOMIC) for soot formation and growth provides a detailed modeling framework maintaining a good balance in generality, accuracy, robustness, and computational efficiency. This study presents several computational issues in the development and implementation of the MOMIC-based soot modeling for direct numerical simulations (DNS). The issues of concern include a wide dynamic range of numbers, choice of normalization, high effective Schmidt number of soot particles, and realizability of the soot particle size distribution function (PSDF). These problems are not unique to DNS, but they are often exacerbated by the high-order numerical schemes used in DNS. Four specific issues are discussed in this article: the treatment of soot diffusion, choice of interpolation scheme for MOMIC, an approach to deal with strongly oxidizing environments, and realizability of the PSDF. General, robust, and stable approaches are sought to address these issues, minimizing the use of ad hoc treatments such as clipping. The solutions proposed and demonstrated here are being applied to generate new physical insight into complex turbulence-chemistry-soot-radiation interactions in turbulent reacting flows using DNS. © 2014 Copyright Taylor and Francis Group, LLC.
Energy Technology Data Exchange (ETDEWEB)
U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office; Bechtel Nevada
2004-01-01
This closure report documents that the closure activities performed at Corrective Action Unit 358: Areas 18, 19, 20 Cellars/Mud Pits, were in accordance with the Nevada Division of Environmental Protection approved Streamlined Approach for Environmental Restoration Plan for Corrective Action Unit 358.
Structural determinants of hospital closure.
Longo, D R; Chase, G A
1984-05-01
In a retrospective case-control study, structural characteristics of hospitals that closed during the years 1976-1980 were contrasted with three comparison groups: hospitals that were acquired in a merger; hospitals that joined a multihospital system; and hospitals that remained autonomously opened, to investigate these characteristics as predictors of closure. Characteristics investigated included environmental, structural, and process variables. The independent variables were measured 5 years prior to outcome. Findings indicate that closed hospitals resemble hospitals acquired in a merger ("failure"), and likewise autonomous hospitals resemble hospitals that join a multihospital system ("success"). The most important predictors of hospital failure were the physician-to-population ratio, the East North Central and West North Central census regions, the level of diversification, low occupancy rate, location in a standard metropolitan statistical area, the chief executive officer's lack of affiliation in the American College of Hospital Administrators, profit status, bed size of less than 50, and presence in a state with a rate-setting agency. Surprisingly, this study shows the bed-to-population ratio to be unrelated to closure. In addition, the findings strongly support the open-system perspective, which, unlike the closed-system perspective, is concerned with the vulnerability of the organization to the uncontrollable and often unpredictable influences of the environment.
Schmitt, Sebastian; Anders, Frithjof B.
2010-04-01
The quantum transport through nanoscale junctions is governed by the charging energy U of the device. We employ the recently developed scattering-states numerical renormalization-group approach to open quantum systems to study nonequilibrium Green’s functions and current-voltage characteristics of such junctions for small and intermediate values of U . We establish the accuracy of the approach by a comparison with diagrammatic Kadanoff-Baym-Keldysh results which become exact in the weak-coupling limit U→0 . We demonstrate the limits of the diagrammatic expansions at intermediate values of the charging energy. While the numerical renormalization-group approach correctly predicts only one single, universal low-energy scale at zero bias voltage, some diagrammatic expansions yield two different low-energy scales for the magnetic and the charge fluctuations. At large voltages, however, the self-consistent second Born as well as the GW approximation reproduce the scattering-states renormalization-group spectral functions for symmetric junctions while for asymmetric junctions the voltage-dependent redistribution of spectral weight differs significantly in the different approaches. The second-order perturbation theory does not capture the correct single-particle dynamics at large bias and violates current conservation for asymmetric junctions.
Jiménez-Forteza, Xisco; Keitel, David; Husa, Sascha; Hannam, Mark; Khan, Sebastian; Pürrer, Michael
2017-03-01
Numerical relativity is an essential tool in studying the coalescence of binary black holes (BBHs). It is still computationally prohibitive to cover the BBH parameter space exhaustively, making phenomenological fitting formulas for BBH waveforms and final-state properties important for practical applications. We describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasicircular nonprecessing merging BBHs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. Particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. As an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. Fitting to 427 numerical relativity simulations, we obtain results broadly consistent with previously published fits, but improving in overall accuracy and particularly in the approach to extremal limits and for unequal-spin configurations. We also discuss the importance of data quality studies when combining simulations from diverse sources, how detailed error budgets will be necessary for further improvements of these already highly accurate fits, and how this first detailed study of unequal-spin effects helps in choosing the most informative parameters for future numerical relativity runs.
An Innovative Hybrid 3D Analytic-Numerical Approach for System Level Modelling of PEM Fuel Cells
Gregor Tavčar; Tomaž Katrašnik
2013-01-01
The PEM fuel cell model presented in this paper is based on modelling species transport and coupling electrochemical reactions to species transport in an innovative way. Species transport is modelled by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the gas-flow and coupling consecutive 2D solutions by means of a 1D numerical gas-flow model. The 2D solution is devised on a jigsaw puzzle of multiple coupled domains which enables the modell...
Nawa, S.; Tamagaki, R.; Tatsumi, T.; Yoro, S.
1990-12-01
Static interaction between two spherical chiral bags is studied in a numerical way. In order to get the solutions of the confined quark states and the outside chiral-field which should satisfy the boundary conditions at both bag surfaces in the chiral bag model, the finite element method is utilized as numerical procedure. We extract the static interaction by calculating the energy change as the two bags approach from large separation to contact distance. Results obtained for three typical configurations indicate that such an approach is workable: We can see that the asymptotic behavior gives the OPEP-tail, and some nonperturbative effects are noticeable in the intermediate region. Although the deviation of the interaction energy from the OPEP value is not so remarkable beyond the pion Compton wavelength due to the cancellation between the energy change of the quark system and that of the chiral field, there arises a significant deviation of the quark wave function and the chiral field from those of the hedgehog solution in the single-baryon case. The procedure in numerical calculations adopted in this paper is explained in detail.
An Innovative Hybrid 3D Analytic-Numerical Approach for System Level Modelling of PEM Fuel Cells
Directory of Open Access Journals (Sweden)
Gregor Tavčar
2013-10-01
Full Text Available The PEM fuel cell model presented in this paper is based on modelling species transport and coupling electrochemical reactions to species transport in an innovative way. Species transport is modelled by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the gas-flow and coupling consecutive 2D solutions by means of a 1D numerical gas-flow model. The 2D solution is devised on a jigsaw puzzle of multiple coupled domains which enables the modelling of parallel straight channel fuel cells with realistic geometries. Electrochemical and other nonlinear phenomena are coupled to the species transport by a routine that uses derivative approximation with prediction-iteration. A hybrid 3D analytic-numerical fuel cell model of a laboratory test fuel cell is presented and evaluated against a professional 3D computational fluid dynamic (CFD simulation tool. This comparative evaluation shows very good agreement between results of the presented model and those of the CFD simulation. Furthermore, high accuracy results are achieved at computational times short enough to be suitable for system level simulations. This computational efficiency is owed to the semi-analytic nature of its species transport modelling and to the efficient computational coupling of electrochemical kinetics and species transport.
Dannemann, Martin; Täger, Olaf; Modler, Niels
2017-09-01
In many applications, lightweight structures need to combine outstanding component properties and low weight. Here, fibre-reinforced polymers offer particular advantages, as their material-inherent anisotropic material damping behaviour facilitates the design of lightweight structures with both low sound radiation levels and low mass. At the same time, composite structures often have to fulfil a high level of stiffness and strength. These manifold requirements result in a complex design process with optimisation scenarios often involving contrary objectives in terms of weight, stiffness and sound radiation. Those objectives are in turn accompanied by many different design variables. The aim of the work presented in this paper was therefore to develop a material-specific design strategy for scenarios of this type. The authors developed semi-analytical models for the calculation of structural dynamics and sound radiation in composite structures before combining them with optimisation algorithms in order to perform effective sensitivity analyses. Parametric studies were used to define material-specific input parameters for physical characteristics, which in turn provided a basis for the detailed numerical simulation of the vibro-acoustic behaviour of complex geometries. This paper uses a trough-shaped structure as an application-oriented example of the optimisation of vibro-acoustic behaviour with the aid of the numerical model developed by the authors.
Hotta, Chisa; Nishimoto, Satoshi; Shibata, Naokazu
2013-03-01
The grand canonical numerical analysis recently developed for quantum many-body systems on a finite cluster [C. Hotta and N. Shibata, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.86.041108 86, 041108(R) (2012)] is the technique to efficiently obtain the physical quantities in an applied field. There, the observables are the continuous and real functions of fields, mimicking their thermodynamic limit, even when a small cluster is adopted. We develop a theory to explain the mechanism of this analysis based on the deformation of the Hamiltonian. The deformation spatially scales down the energy unit from the system center toward zero at the open edge sites, which introduces the renormalization of the energy levels in a way reminiscent of Wilson's numerical renormalization group. However, compared to Wilson's case, our deformation generates a number of far well-localized edge states near the chemical potential level, which are connected via a very small quantum fluctuation in k space with the “bulk” states which spread at the center of the system. As a response to the applied field, the particles on the cluster are self-organized to tune the particle number of the bulk states to their thermodynamic limit by using the “edges” as a buffer. We demonstrate the present analysis in two-dimensional quantum spin systems on square and triangular lattices, and determine the smooth magnetization curve with a clear (1)/(3) plateau structure in the latter.
Salehi Taleghani, Sara; Zamani Meymian, Mohammad Reza; Ameri, Mohsen
2016-10-01
In the present research, we report fabrication, experimental characterization and theoretical analysis of semi and full flexible dye sensitized solar cells (DSSCs) manufactured on the basis of bare and roughened stainless steel type 304 (SS304) substrates. The morphological, optical and electrical characterizations confirm the advantage of roughened SS304 over bare and even common transparent conducting oxides (TCOs). A significant enhancement of about 51% in power conversion efficiency is obtained for flexible device (5.51%) based on roughened SS304 substrate compared to the bare SS304. The effect of roughening the SS304 substrates on electrical transport characteristics is also investigated by means of numerical modeling with regard to metal-semiconductor and interfacial resistance arising from the metallic substrate and nanocrystalline semiconductor contact. The numerical modeling results provide a reliable theoretical backbone to be combined with experimental implications. It highlights the stronger effect of series resistance compared to schottky barrier in lowering the fill factor of the SS304-based DSSCs. The findings of the present study nominate roughened SS304 as a promising replacement for conventional DSSCs substrates as well as introducing a highly accurate modeling framework to design and diagnose treated metallic or non-metallic based DSSCs.
2010-07-01
... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Use and Management of Containers § 264.178 Closure. At closure, all hazardous waste and hazardous waste residues must be removed...
2010-07-01
... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Incinerators § 264.351 Closure. At closure the owner or operator must remove all hazardous waste and hazardous waste...
2010-10-01
... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Closures. 665.666 Section 665.666 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION... § 665.666 Closures. (a) If the Regional Administrator determines that the harvest quota for any...
Key financial ratios can foretell hospital closures.
Lynn, M L; Wertheim, P
1993-11-01
An analysis of various financial ratios sampled from open and closed hospitals shows that certain leverage, liquidity, capital efficiency, and resource availability ratios can predict hospital closure up to two years in advance of the closure with an accuracy of nearly 75 percent.
Spontaneous closure of traumatic tympanic membrane perforations
DEFF Research Database (Denmark)
Jellinge, Marlene Ersgaard; Kristensen, S.; Larsen, K
2015-01-01
BACKGROUND: The treatment of traumatic tympanic membrane perforations varies in different investigations, ranging from observation to early surgical repair. The present study aimed to focus on the closure rate and the closure time in a group of patients treated with a watchful waiting policy. MET...
Acute angle closure glaucoma following ileostomy surgery
Directory of Open Access Journals (Sweden)
Mariana Meirelles Lopes
2015-02-01
Full Text Available Angle-closure glaucoma can be induced by drugs that may cause pupillary dilatation. We report a case of a patient that developed bilateral angle closure glaucoma after an ileostomy surgery because of systemic atropine injection. This case report highlights the importance of a fast ophthalmologic evaluation in diseases with ocular involvement in order to make accurate diagnoses and appropriate treatments.
Jiménez-Forteza, Xisco; Husa, Sascha; Hannam, Mark; Khan, Sebastian; Pürrer, Michael
2016-01-01
Numerical relativity is an essential tool in studying the coalescence of binary black holes (BBHs). It is still computationally prohibitive to cover the BBH parameter space exhaustively, making phenomenological fitting formulas for BBH waveforms and final-state properties important for practical applications. We describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasi-circular non-precessing merging BBHs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. Particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. As an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. We obtain results broadly consistent with previously published fits, but with improvements in the approach to extremal limi...
Research on the closure and creep mechanism of circular tunnels
Institute of Scientific and Technical Information of China (English)
LI Lian-chong; TANG Chun-an; MA Tian-hui; ZHAO Xing-dong
2008-01-01
A numerical code called Rock Failure Process Analysis (RFPA2D) was employed to investigate the closure, damage and failure behavior of the horizontal tunnels. In his code the time-dependent deformation was described in terms of evolution of mesoscopic structure, leading to progressive degradation of elastic modulus and failure strength of material. In terms of material degradation, a series of numerical simulations were performed to study the convergence and subsequent failure in circular tunnels. The numerical esults provide a complete illumination for the closure, damage and failure behavior with different loading conditions. It is shown that the depth and the ratio of far field stresses play an important role in the creep behavior of tunnels. Creep failure is expected to occur in the direction of the smallest far field stress component, which means that rheological failure of tunnels is influenced not only by the rock characteristic around the tunnels but also by the orientation and distribution of far field stress on a global scale.
Comparison of Subcuticular Suture Materials in Cesarean Skin Closure
Directory of Open Access Journals (Sweden)
Pınar Solmaz Hasdemir
2015-01-01
Full Text Available Aim. Comparison of the rate of wound complications, pain, and patient satisfaction based on used subcuticular suture material. Methods. A total of 250 consecutive women undergoing primary and repeat cesarean section with low transverse incision were prospectively included. The primary outcome was wound complication rate including infection, dehiscence, hematoma, and hypertrophic scar formation within a 6-week period after operation. Secondary outcomes were skin closure time, the need for use of additional analgesic agent, pain score on numeric rating scale, cosmetic score, and patient scar satisfaction scale. Results. Absorbable polyglactin was used in 108 patients and nonabsorbable polypropylene was used in 142 patients. Wound complication rates were similar in primary and repeat cesarean groups based on the type of suture material. Skin closure time is longer in nonabsorbable suture material group in both primary and repeat cesarean groups. There was no difference between groups in terms of postoperative pain, need for additional analgesic use, late phase pain, and itching at the scar. Although the cosmetic results tended to be better in the nonabsorbable group in primary surgery patients, there was no significant difference in the visual satisfaction of the patients. Conclusions. Absorbable and nonabsorbable suture materials are comparable in cesarean section operation skin closure.
Physical simulations of cavity closure in a creeping material
Energy Technology Data Exchange (ETDEWEB)
Sutherland, H.J.; Preece, D.S.
1985-09-01
The finite element method has been used extensively to predict the creep closure of underground petroleum storage cavities in rock salt. Even though the numerical modeling requires many simplifying assumptions, the predictions have generally correlated with field data from instrumented wellheads, however, the field data are rather limited. To gain an insight into the behavior of three-dimensional arrays of cavities and to obtain a larger data base for the verification of analytical simulations of creep closure, a series of six centrifuge simulation experiments were performed using a cylindrical block of modeling clay, a creeping material. Three of the simulations were conducted with single, centerline cavities, and three were conducted with a symmetric array of three cavities surrounding a central cavity. The models were subjected to body force loading using a centrifuge. For the single cavity experiments, the models were tested at accelerations of 100, 125 and 150 g's for 2 hours. For the multi-cavity experiments, the simulations were conducted at 100 g's for 3.25 hours. The results are analyzed using dimensional analyses. The analyses illustrate that the centrifuge simulations yield self-consistent simulations of the creep closure of fluid-filled cavities and that the interaction of three-dimensional cavity layouts can be investigated using this technique.
Jurjiu, Aurel; Galiceanu, Mircea; Farcasanu, Alexandru; Chiriac, Liviu; Turcu, Flaviu
2016-12-01
In this paper, we focus on the relaxation dynamics of Sierpinski hexagon fractal polymer. The relaxation dynamics of this fractal polymer is investigated in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. In the Rouse-type approach, by performing real-space renormalization transformations, we determine analytically the complete eigenvalue spectrum of the connectivity matrix. Based on the eigenvalues obtained through iterative algebraic relations we calculate the averaged monomer displacement and the mechanical relaxation moduli (storage modulus and loss modulus). The evaluation of the dynamical properties in the Rouse-type approach reveals that they obey scaling in the intermediate time/frequency domain. In the Zimm-type approach, which includes the hydrodynamic interactions, the relaxation quantities do not show scaling. The theoretical findings with respect to scaling in the intermediate domain of the relaxation quantities are well supported by experimental results.
Gastrotomy closure using bioabsorbable plugs in a canine model.
Cios, Theodore J; Reavis, Kevin M; Renton, David R; Hazey, Jeffrey W; Mikami, Dean J; Narula, Vimal K; Allemang, Matthew T; Davis, S Scott; Melvin, W Scott
2008-04-01
The repair of gastric perforation commonly involves simple suture closure using an open or laparoscopic approach. An endolumenal approach using prosthetic materials may be beneficial. The role of bioprosthetics in this instance has not been thoroughly investigated, thus the authors evaluated the feasibility of gastric perforation repair using a bioabsorbable device and quantified gross and histological changes at the injury site. Twelve canines were anesthetized and underwent open gastrotomy. A 1-cm-diameter perforation was created in the anterior wall of the stomach and plugged with a bioabsorbable device. Intralumenal pH was recorded. Canines were sacrificed at one, four, six, eight, and 12 weeks. The stomach was explanted followed by gross and histological examination. The injury site was examined. The relative ability of the device to seal the perforation was recorded, as were postoperative changes. Tissue samples were analyzed for gross and microscopic tissue growth and compared to normal gastric tissue in the same animal as an internal control. A scoring system of -2 to +2 was used to measure injury site healing (-2= leak, -1= no leak and minimal ingrowth, 0= physiologic healing, +1= mild hypertrophic tissue, +2= severe hypertrophic tissue). In all canines, the bioprosthesis successfully sealed the perforation without leak under ex vivo insufflation. At one week, the device maintained its integrity but there was no tissue ingrowth. Histological healing score was -1. At 4-12 weeks, gross examination revealed a healed injury site in all animals. The lumenal portion of the plug was completely absorbed. The gross and histological healing score ranged from -1 to +1. The application of a bioabsorbable device results in durable closure of gastric perforation with physiologic healing of the injury site. This method of gastrotomy closure may aid in the evolution of advanced endoscopic approaches to perforation closure of hollow viscera.
Directory of Open Access Journals (Sweden)
Edris Yousefi Rad
2017-08-01
Full Text Available In the present research, considering the importance of desirable steam turbine design, improvement of numerical modeling of steam two-phase flows in convergent and divergent channels and the blades of transonic steam turbines has been targeted. The first novelty of this research is the innovative use of combined Convective Upstream Pressure Splitting (CUSP and scalar methods to update the flow properties at each calculation point. In other words, each property (density, temperature, pressure and velocity at each calculation point can be computed from either the CUSP or scalar method, depending on the least deviation criterion. For this reason this innovative method is named “hybrid method”. The next novelty of this research is the use of an inverse method alongside the proposed hybrid method to find the amount of the important parameter z in the CUSP method, which is herein referred to as “CUSP’s convergence parameter”. Using a relatively simple computational grid, firstly, five cases with similar conditions to those of the main cases under study in this research with available experimental data were used to obtain the value of z by the Levenberg-Marquardt inverse method. With this innovation, first, an optimum value of z = 2.667 was obtained using the inverse method and then directly used for the main cases considered in the research. Given that the aim is to investigate the two-dimensional, steady state, inviscid and adiabatic modeling of steam nucleating flows in three different nozzle and turbine blade geometries, flow simulation was performed using a relatively simple mesh and the innovative proposed hybrid method (scalar + CUSP, with the desired value of z = 2.667 . A comparison between the results of the hybrid modeling of the three main cases with experimental data showed a very good agreement, even within shock zones, including the condensation shock region, revealing the efficiency of this numerical modeling method innovation
Directory of Open Access Journals (Sweden)
Rajjoub LZ
2014-07-01
Full Text Available Lamise Z Rajjoub, Nisha Chadha, David A Belyea Department of Ophthalmology, The George Washington University, Washington, DC, USA Abstract: This is a case report describing recurrent intermittent acute angle closure episodes in the setting of topiramate use in a female suffering from migraines. Despite laser peripheral iridotomy placement for the pupillary block component, and the discontinuation of topiramate, the acute angle closure did not resolve in the left eye with chronic angle closure and the patient required urgent trabeculectomy. The right eye responded to laser peripheral iridotomy immediately and further improved after the cessation of topiramate. While secondary angle closure glaucoma due to topiramate use has been widely reported, its effects in patients with underlying primary angle closure glaucoma have not been discussed. Our report highlights the importance of recognizing the often multifactorial etiology of angle closure glaucoma to help guide clinical management. Keywords: angle closure glaucoma, plateau iris, topiramate, secondary glaucoma, drug-induced glaucoma
Energy Technology Data Exchange (ETDEWEB)
Maugis, P
2006-06-15
The feasibility and safety of nuclear waste storage containers is studied. The thermodynamics of water/air flow is described and applied, via a simplified numerical model, to a simple experimental apparatus yielding heat pipe effect. The 2D influence of deterministic boundary conditions is important on kinematics and transport. Dispersivity depends on the nonuniform flow type and integrates the often marginal Gaussian part of plume spreading. A new algorithm, based on jump locality and recalibration, avoids the small bias induced by inter-cell diffusive jumps. Several algorithms modeling transport of decaying, soluble, sorbing, or precipitating species are compared. Stability and precision criteria are analyzed. Up-stream over-precipitation and negative down-stream concentrations are observed for high solubility contrasts. (author)
da Silva, Roberto; Prado, Sandra D.; Fernandes, Henrique A.
2017-10-01
In this paper we explore the stability of an inverted pendulum with generalized parametric excitation described by a superposition of N sines with different frequencies and phases. We show that when the amplitude is scaled with the frequency we obtain the stabilization of the real inverted pendulum, i.e., with values of g according to planet Earth (g ≈ 9.8 m/s2) for high frequencies. By randomly sorting the frequencies, we obtain a critical amplitude in light of perturbative theory in classical mechanics which is numerically tested by exploring its validity regime in many alternatives. We also analyse the effects when different values of N as well as the pendulum size l are taken into account.
Sun, Shuyu
2012-06-02
A new technique for the numerical solution of the partial differential equations governing transport phenomena in porous media is introduced. In this technique, the governing equations as depicted from the physics of the problem are used without extra manipulations. In other words, there is no need to reduce the number of governing equations by some sort of mathematical manipulations. This technique enables the separation of the physics part of the problem and the solver part, which makes coding more robust and could be used in several other applications with little or no modifications (e.g., multi-phase flow in porous media). In this method, one abandons the need to construct the coefficient matrix for the pressure equation. Alternatively, the coefficients are automatically generated within the solver routine. We show examples of using this technique to solving several flow problems in porous media.
Institute of Scientific and Technical Information of China (English)
ZHU Chang-sheng; XIAO Rong-zhen; WANG Zhi-ping; FENG Li
2009-01-01
A accelerated arithmetic algorithm of the dynamic computing regions was designed, and 3-dimensional numerical simulation of isothermal solidification for a binary alloy was implemented. The dendritic growth and the recalescence of Ni-Cu binary alloy during the solidification at different cooling rates were investigated. The effects of cooling rate on dendritic patterns and microsegregation patterns were studied. The computed results indicate that, with the increment of the cooling rate, the dendritic growth velocity increases, both the main branch and side-branches become slender, the secondary dendrite arm spacing becomes smaller, the inadequate solute diffusion in solid aggravates, and the severity of microsegregation ahead of interface aggravates. At a higher cooling rate, the binary alloy presents recalescence; while the cooling rate is small, no recalescence occurs.
Directory of Open Access Journals (Sweden)
Changwei Zhou
2017-02-01
Full Text Available In this article, the analytical homogenization method of periodic discrete media (HPDM and the numerical condensed wave finite element method (CWFEM are employed to study the longitudinal and transverse vibrations of framed structures. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by the HPDM compared to that by the CWFEM is illustrated in functions of frequency and scale ratio. A parametric study on the thickness of the structure is carried out where the dispersion relation and the relative error are given for three different thicknesses. The dynamics of a finite structure such as natural frequency and forced response are also investigated using the HPDM and the CWFEM.
Energy Technology Data Exchange (ETDEWEB)
Gilmanov, Anvar, E-mail: agilmano@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Le, Trung Bao, E-mail: lebao002@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Sotiropoulos, Fotis, E-mail: fotis@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414 (United States)
2015-11-01
We present a new numerical methodology for simulating fluid–structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet–Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid–fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.
Ballan, Michele; Manzolaro, Mattia; Meneghetti, Giovanni; Andrighetto, Alberto; Monetti, Alberto; Bisoffi, Giovanni; Prete, Gianfranco
2016-06-01
The SPES project at INFN-LNL aims at the production of neutron-rich Radioactive Ion Beams (RIBs) using the ISOL (Isotope Separation On Line) technique. A 40 MeV 200 μA proton beam will directly impinge a uranium carbide target, generating approximately 1013 fissions per second. The target system is installed under vacuum inside a water-cooled chamber, and have to maintain high working temperatures, close to 2000 °C. During operation the proton beam provides the heating power required to keep the target at the desired temperature level. As a consequence, its characteristics have to be strictly controlled in order to avoid undesired overheating. According to the original design of the control system, the proton beam can be suddenly interrupted in case of out of range vacuum or cooling water flow levels. With the aim to improve the reliability of the control system a set of temperature sensors has been installed close to the target. Their types and installation positions were defined taking into consideration the detailed information coming from a dedicated thermal-electric model that allowed to investigate the most critical and inaccessible target hot-spots. This work is focused on the definition and experimental validation of the aforementioned numerical model. Its results were used to appropriately install two type C thermocouples, a PT100 thermo-resistance and a residual primary beam current detector. In addition the numerical model will be used for the definition of appropriate thresholds for each installed temperature sensor, since it allows to define a relationship between the locally measured values with the overall calculated temperature field. In case of over temperatures the monitoring system will send warning signals or in case interrupt the proton beam.
Gilmanov, Anvar; Le, Trung Bao; Sotiropoulos, Fotis
2015-11-01
We present a new numerical methodology for simulating fluid-structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet-Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid-fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.
Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing
2017-07-01
The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy
Closure of Microcosm for refurbishment
2014-01-01
Since 1994, the Microcosm exhibition has given the opportunity to visitors of all ages and backgrounds to have a first glimpse into the secrets of physics. To ensure that Microcosm can continue fulfilling its educational aims at the same level of quality for many years to come, it is closing for renovation work on 8 December 2014 and is expected to reopen during Summer 2015. During the closure, the “Fun with Physics” workshop will not take place, but the Universe of Particles exhibition in the Globe and the Passport to the Big Bang circuit will remain accessible to the public, free of charge and with no need to book in advance. Guided tours of CERN are also available (advance booking required via this page).
Closure for milliliter scale bioreactor
Klein, David L.; Laidlaw, Robert D.; Andronaco, Gregory; Boyer, Stephen G.
2010-12-14
A closure for a microreactor includes a cap that is configured to be inserted into a well of the microreactor. The cap, or at least a portion of the cap, is compliant so as to form a seal with the well when the cap is inserted. The cap includes an aperture that provides an airway between the inside of the well to the external environment when the cap is inserted into the well. A porous plug is inserted in the aperture, e.g., either directly or in tube that extends through the aperture. The porous plug permits gas within the well to pass through the aperture while preventing liquids from passing through to reduce evaporation and preventing microbes from passing through to provide a sterile environment. A one-way valve may also be used to help control the environment in the well.
Modification of closure depths by synchronisation of severe seas and high water levels
Soomere, Tarmo; Männikus, Rain; Pindsoo, Katri; Kudryavtseva, Nadezhda; Eelsalu, Maris
2017-02-01
The closure depth indicates the depth down to which storm waves maintain a universal shape of the coastal profile. It is thus a key parameter of the coastal zones for a variety of engineering and ecosystem applications. Its values are commonly estimated with respect to the long-term mean water level. The present study re-evaluates closure depths for microtidal water bodies where the wave loads are highly correlated with the course of the water level. The test area is the eastern Baltic Sea. The closure depth is calculated for the eastern Baltic Sea coast with a resolution of 5.5 km and the vicinity of Tallinn Bay with a resolution of 0.5 km. While the classic values of closure depth are extracted from statistics of the roughest seas, the present analysis is based on single values of a proxy of the instantaneous closure depth. These values are evaluated from numerically simulated time series of wave properties and water levels. The water level-adjusted closure depths are almost equal to the classic values at the coasts of Lithuania but are up to 10% smaller at the Baltic Proper coasts of Latvia and Estonia. The difference is up to 20% in bayheads of the Gulf of Finland.
Kindrachuk, Vitaliy M.; Galanov, Boris A.
2014-02-01
A computationally efficient solution scheme is presented for the mechanical problems whose formulations include the Kuhn-Tucker or Signorini-Fichera conditions. It is proposed to reformulate these problems replacing inequalities in these conditions by equations with respect to new unknowns. The solutions of the modified problems have simple physical meanings and determine uniquely the unknowns of the original problems. The approach avoids application of multi-valued operators (inclusions or inequalities) in formulation of the problems. Hence, the modified formulations are suitable for numerical analysis using established powerful mathematical methods and corresponding solvers developed for solving systems of non-linear equations.
Towards a collisionless fluid closure in plasma turbulence
Energy Technology Data Exchange (ETDEWEB)
Dif Pradalier, G
2005-07-01
In this work 2 generic possible descriptions of a plasma have been compared namely the kinetic and the fluid approaches. The latter focuses on the successive moments (n, u, p, q,...) of the distribution function, whereas the former describes the time-evolution in phase space of this distribution function, both being based on the Vlasov equation. The fluid description is attractive for the Vlasov equation is tractable with great difficulties. Nevertheless it rests on a major difficulty: as the set of fluid equations constitute an infinite hierarchy, a closure equation must be chosen. The first chapter details physical characteristics of a fundamental kinetic interaction mechanism between waves and particles. In chapter 2 we propose a fluid closure that allows analytic comparison with a linear fully kinetic result, near an homogeneous, electrostatic, Maxwellian equilibrium. This approach consists in adjusting chosen parameters in order to minimize the discrepancies between fluid and kinetic linear response functions. In chapter 3 we present a general frame for a fluid closure in a magnetized plasma. This is attempted in a linear, simplified model with low dimensionality.
Subpixel measurement of mangrove canopy closure via spectral mixture analysis
Institute of Scientific and Technical Information of China (English)
Minhe JI; Jing FENG
2011-01-01
Canopy closure can vary spatially within a remotely sensed image pixel,but Boolean logic inherent in traditional classification methods only works at the wholepixel level.This study attempted to decompose mangrove closure information from spectrally-mixed pixels through spectral mixture analysis (SMA) for coastal wetland management.Endmembers of different surface categories were established through signature selection and training,and memberships of a pixel with respect to the surface categories were determined via a spectral mixture model.A case study involving DigitalGlobe's Quickbird highresolution multispectral imagery of Beilun Estuary,China was used to demonstrate this approach.Mangrove canopy closure was first quantified as percent coverage through the model and then further grouped into eight ordinal categories.The model results were verified using Quickbird panchromatic data from the same acquisition.An overall accuracy of 84.4% (Kappa = 0.825) was achieved,indicating good application potential of the approach in coastal resource inventory and ecosystem management.
A numerical wave-optical approach for the simulation of analyzer-based x-ray imaging.
Bravin, A; Mocella, V; Coan, P; Astolfo, A; Ferrero, C
2007-04-30
An advanced wave-optical approach for simulating a monochromator-analyzer set-up in Bragg geometry with high accuracy is presented. The polychromaticity of the incident wave on the monochromator is accounted for by using a distribution of incoherent point sources along the surface of the crystal. The resulting diffracted amplitude is modified by the sample and can be well represented by a scalar representation of the optical field where the limitations of the usual 'weak object' approximation are removed. The subsequent diffraction mechanism on the analyzer is described by the convolution of the incoming wave with the Green-Riemann function of the analyzer. The free space propagation up to the detector position is well reproduced by a classical Fresnel-Kirchhoff integral. The preliminary results of this innovative approach show an excellent agreement with experimental data.
Bartzke, Gerhard; Rogers, Benedict D.; Fourtakas, Georgios; Mokos, Athanasios; Huhn, Katrin
2016-04-01
The processes that cause the creation of a variety of sediment morphological features, e.g. laminated beds, ripples, or dunes, are based on the initial motion of individual sediment grains. However, with experimental techniques it is difficult to measure the flow characteristics, i.e., the velocity of the pore water flow in sediments, at a sufficient resolution and in a non-intrusive way. As a result, the role of fluid infiltration at the surface and in the interior affecting the initiation of motion of a sediment bed is not yet fully understood. Consequently, there is a strong need for numerical models, since these are capable of quantifying fluid driven sediment transport processes of complex sediment beds composed of irregular shapes. The numerical method Smoothed Particle Hydrodynamics (SPH) satisfies this need. As a meshless and Lagrangian technique, SPH is ideally suited to simulating flows in sediment beds composed of various grain shapes, but also flow around single grains at a high temporal and spatial resolution. The solver chosen is DualSPHysics (www.dual.sphysics.org) since this is validated for a range of flow conditions. For the present investigation a 3-D numerical flume model was generated using SPH with a length of 4.0 cm, a width of 0.05 cm and a height of 0.2 cm where mobile sediment particles were deposited in a recess. An experimental setup was designed to test sediment configurations composed of irregular grain shapes (grain diameter, D50=1000 μm). Each bed consisted of 3500 mobile objects. After the bed generation process, the entire domain was flooded with 18 million fluid particles. To drive the flow, an oscillating motion perpendicular to the bed was applied to the fluid, reaching a peak value of 0.3 cm/s, simulating 4 seconds of real time. The model results showed that flow speeds decreased logarithmically from the top of the domain towards the surface of the beds, indicating a fully developed boundary layer. Analysis of the fluid
Schneider, Florian
2016-01-01
This paper provides a generalization of the realizability-preserving discontinuous-Galerkin scheme for quadrature-based minimum-entropy models to full-moment models of arbitrary order. It is applied to the class of Kershaw closures, which are able to provide a cheap closure of the moment problem. This results in an efficient algorithm for the underlying linear transport equation. The efficiency of high-order methods is demonstrated using numerical convergence tests and non-smooth benchmark problems.
Schneider, Florian
2016-10-01
This paper provides a generalization of the realizability-preserving discontinuous-Galerkin scheme given in [3] to general full-moment models that can be closed analytically. It is applied to the class of Kershaw closures, which are able to provide a cheap closure of the moment problem. This results in an efficient algorithm for the underlying linear transport equation. The efficiency of high-order methods is demonstrated using numerical convergence tests and non-smooth benchmark problems.
Directory of Open Access Journals (Sweden)
B. Reggiani
2016-01-01
Full Text Available The present study was aimed at predicting the time-dependent deformation of tools used in hot forming applications subjected to the creep-fatigue regime. An excessive accumulated plastic deformation is configured as one of the three main causes of premature failure of tools in these critical applications and it is accumulated cycle by cycle without evident marks leading to noncompliant products. With the aim of predicting this accumulated deformation, a novel procedure was developed, presented, and applied to the extrusion process as an example. A time-hardening primary creep law was used and novel regression equations for the law’s coefficients were developed to account not only for the induced stress-temperature state but also for the dwell-time value, which is determined by the selected set of process parameters and die design. The procedure was validated against experimental data both on a small-scale extrusion die at different stress, temperature, load states, and for different geometries and on an industrial extrusion die which was discarded due to the excessive plastic deformation after 64 cycles. A numerical-experimental good agreement was achieved.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In the present study, the indentation testing with a flat cylindrical indenter on typical multi-layer material systems was simulated successfully by finite element method. The emphasis was put on the methods of extracting the yield stresses and strain-hardening modulus of upper and middle-layers of three-layer material systems from the indentation testing. The slope of the indentation depth to the applied indentation stress curve was found to have a turning point, which can be used to determine the yield stress of the upper-layer. Then, a different method was also presented to determine the yield stress of the middle-layer. This method was based on a set of assumed applied indentation stresses which were to be intersected by the experimental results in order to meet the requirement of having the experimental indentation depth. At last, a reverse numerical algorithm was explored to determine the yield stresses of upper and middle-layers simultaneously by using the indentation testing with two different size indenters. This method assumed two ranges of yield stresses to simulate the indentation behavior. The experimental depth behavior was used to intersect the simulated indentation behavior. And the intersection corresponded to the values of yield stresses of upper and middle-layers. This method was also used further to determine the strain-hardening modulus of upper and middle-layers simultaneously.