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Density dependence of the nuclear energy-density functional
Papakonstantinou, Panagiota,Park, Tae-Sun,Lim, Yeunhwan,Hyun, Chang Ho American Physical Society 2018 Physical Review C Vol.97 No.1
<P>Conclusions: Having been already determined for homogeneous matter, a functional of the present form can be mapped onto extended Skyrme-type functionals in a straightforward manner, as we outline here, for applications to finite nuclei. At the same time, the statistical analysis can be extended to higher orders and for different microscopic (ab initio) calculations with sufficient pseudodata points and for polarized matter.</P>
Tasiopoulou, Panagiota,Taiebat, Mahdi,Tafazzoli, Nima,Jeremic, Boris Techno-Press 2015 Coupled systems mechanics Vol.4 No.1
Numerical prediction of dynamic behavior of fully coupled saturated porous media is of great importance in many engineering problems. Specifically, static and dynamic response of soils - porous media with pores filled with fluid, such as air, water, etc. - can only be modeled properly using fully coupled approaches. Modeling and simulation of static and dynamic behavior of soils require significant Verification and Validation (V&V) procedures in order to build credibility and increase confidence in numerical results. By definition, Verification is essentially a mathematics issue and it provides evidence that the model is solved correctly, while Validation, being a physics issue, provides evidence that the right model is solved. This paper focuses on Verification procedure for fully coupled modeling and simulation of porous media. Therefore, a complete Solution Verification suite has been developed consisting of analytical solutions for both static and dynamic problems of porous media, in time domain. Verification for fully coupled modeling and simulation of porous media has been performed through comparison of the numerical solutions with the analytical ones. Modeling and simulation is based on the so called, u-p-U formulation. Of particular interest are numerical dispersion effects which determine the level of numerical accuracy. These effects are investigated in detail, in an effort to suggest a compromise between numerical error and computational cost.
Myrto-Panagiota Zacharof,Robert W. Lovitt 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1
Lactococcus lactis species have been and still are extensively investigated due to their significant commercial importance. Current scientific research focuses on strains utilized in food industry, due to their multiple uses in food and beverages fabrication. Biomass of Lactococcus lactis is of great interest as well as the end products of its metabolism such as lactic acid and nisin. However their production is constantly challenged due to end product inhibition occurring during intensive propagation of the coccus in reactor systems. To successfully predict the behavior of the culture, the approach of combining mathematics with biology, ergo the development of an unstructured mathematical model, was taken. Although Luedeking and Piret is the model that has been extensively used to demonstrate growth in end-product inhibition cultures, its applicability is limited due to its dependance on the specific growth and product coefficients, particularly related to the culturing conditions used. To overcome these hurdles, a combination of the non competitive single product end inhibition Taylor and Hinselwood models was used, with the significance of this model laying in the fact that it offers a feasible alternative to the commonly used model of Luedeking and Piret for describing fermentation kinetics governed by end-product inhibitions. The fitting with the experimental values, in batch mode, was tested in terms of the coefficient of determination (R²), having values 0.97 ~ 0.99 and suggesting a very good fitting with the experimental data. The model was further developed to achieve theoretical predictions of volumetric cell productivity in continuous and fed-batch mode of substrate feed in different culturring systems.
On validation of fully coupled behavior of porous media using centrifuge test results
Tasiopoulou, Panagiota,Taiebat, Mahdi,Tafazzoli, Nima,Jeremic, Boris Techno-Press 2015 Coupled systems mechanics Vol.4 No.1
Modeling and simulation of mechanical response of infrastructure object, solids and structures, relies on the use of computational models to foretell the state of a physical system under conditions for which such computational model has not been validated. Verification and Validation (V&V) procedures are the primary means of assessing accuracy, building confidence and credibility in modeling and computational simulations of behavior of those infrastructure objects. Validation is the process of determining a degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model. It is mainly a physics issue and provides evidence that the correct model is solved (Oberkampf et al. 2002). Our primary interest is in modeling and simulating behavior of porous particulate media that is fully saturated with pore fluid, including cyclic mobility and liquefaction. Fully saturated soils undergoing dynamic shaking fall in this category. Verification modeling and simulation of fully saturated porous soils is addressed in more detail by (Tasiopoulou et al. 2014), and in this paper we address validation. A set of centrifuge experiments is used for this purpose. Discussion is provided assessing the effects of scaling laws on centrifuge experiments and their influence on the validation. Available validation test are reviewed in view of first and second order phenomena and their importance to validation. For example, dynamics behavior of the system, following the dynamic time, and dissipation of the pore fluid pressures, following diffusion time, are not happening in the same time scale and those discrepancies are discussed. Laboratory tests, performed on soil that is used in centrifuge experiments, were used to calibrate material models that are then used in a validation process. Number of physical and numerical examples are used for validation and to illustrate presented discussion. In particular, it is shown that for the most part, numerical prediction of behavior, using laboratory test data to calibrate soil material model, prior to centrifuge experiments, can be validated using scaled tests. There are, of course, discrepancies, sources of which are analyzed and discussed.
( Georgios Karamanolis ),( Konstantinos Triantafyllou ),( Panagiota Psatha ),( Ioannis Vlachogiannakos ),( Asimina Gaglia ),( Dimitrios Polymeros ),( Smaragdi Fessatou ),( Maria Triantafyllou ),( Ioan 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2012 Journal of Neurogastroenterology and Motility (JNM Vol.18 No.2
Background/Aims In patients with non-cardiac chest pain (NCCP), gastroesophageal reflux disease (GERD) is the commonest cause and ambulatory pH is of great value in identifying these patients. However, parameters in the context of predicting therapeutic response are still unknown. By extending the monitoring period, we could better evaluate the best evidence for GERD association. Our aims were (1) to compare the outcomes of 48-hour pH monitoring to 24-hour and (2) to determine whether objective param - eters could predict the treatment success in patients with NCCP using Bravo pH system. Methods Pathological esophageal acid reflux (PEAR) and positive symptom index (SI) were calculated after 24-hour and compared to the 48-hour study. Evidence suggestive of GERD diagnosis was considered if PEAR and/or SI (+) were present on each different day. After pH study, all patients received proton pump inhibitor twice a day for 4 weeks. Treatment success was determined at the end of therapy. Results Thirty-two patients with NCCP participated. GERD was identified in 20 (62.5%) patients; 17 (53.1%) had PEAR, 3 (9.4%) SI (+) and 7 (22%) both. Twelve (41%) patients exhibited PEAR values on day 1, while 17 after 2 days; a 12.1 % gain. SI (+) was found in 6 patients (18.8%) on day 1 and in 4 more on day 2, a gain of 12.5%. Significantly higher proportion of patients with GERD indicators showed improvement compared to those without (90% vs 16.7%, P < 0.005). Conclusions In patients with NCCP, 48-hour pH measurement identified GERD as the cause of NCCP with an increased yield by almost 12% compared to 12 hours. Objective GERD parameters could predict response to antireflux therapy.
Skyrme-Type Nuclear Force for the KIDS Energy Density Functional
길하나,오용석,현창호,Panagiota PAPAKONSTANTINOU 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.4
We construct an effective nucleon-nucleon potential for describing the interactions of nucleons in nuclei or in nuclear matter. Starting from the KIDS (Korea: IBS-Daegu-Sungkyunkwan) nuclear energy density functional systematically expanded in powers of the Fermi momentum, or cubic root of the density, we fit the parameters of the model to a well-known theoretical equation of state of nuclear matter and the empirical data for symmetric nuclear matter. We then determine an effective potential that reproduces the given energy density functional in the mean-field approximation. The potential thus obtained is applied to calculate the binding energies and the sizes of the closed-shell nuclei, namely, $^{16}$O, $^{28}$O, $^{40}$Ca, and $^{60}$Ca. This process introduces one additional parameter, and calculations were made by varying the value of this parameter. We found that the model reasonably reproduced the observed data for the closed-shell nuclei to very good accuracy. Predictions on unobserved physical quantities are presented as well.
The evolution of complete non-compact graphs by powers of Gauss curvature
Choi, Kyeongsu,Daskalopoulos, Panagiota,Kim, Lami,Lee, Ki-Ahm W. de Gruyter 2019 Journal fur die reine und angewandte Mathematik Vol.2019 No.757
<P><B>Abstract</B></P><P>We prove the all-time existence of non-compact, complete, strictly convex solutions to the α-Gauss curvature flow for any positive power α.</P>