Fermi coordinates and modified Franklin transformation : A comparative study on rotational phenomena

Employing a relativistic rotational transformation to study and analyze rotational phenomena, instead of the rotational transformations based on consecutive Lorentz transformations and Fermi coordinates, leads to different predictions. In this article, after a comparative study between Fermi metric of a uniformly rotating eccentric observer and the spacetime metric in the same observer's frame obtained through the modified Franklin transformation, we consider rotational phenomena including transverse Doppler effect and Sagnac effect in both formalisms and compare their predictions. We also discuss length measurements in the two formalisms.Comment: 21 pages, 2 figures, replaced with the published versio

Cylindrical solutions in braneworld gravity

In this article we investigate exact cylindrically symmetric solutions to the modified Einstein field equations in the brane world gravity scenarios. It is shown that for the special choice of the equation of state $2U+P=0$ for the dark energy and dark pressure, the solutions found could be considered formally as solutions of the Einstein-Maxwell equations in 4-D general relativity.Comment: 12 pages, RevTex format, typos corrected and references added. Accepted for publication in PR

Cyclic Response of Clay Deposits: Developing a Constitutive Model

This study aims at developing a generalized elasto-plastic constitutive model for clays able to describe stress-strain response, accumulation of permanent deformations, and excess pore pressure in monotonic and cyclic loading. This constitutive model takes advantage of the nonlinear elasticity and bounding surface plasticity concepts to mimic generation of excess pore pressure and plastic deformation within the yield surface upon cycles of unloading and reloading during cyclic excitation. The generalized formulation of the model also facilitates the prediction of multi-directional cyclic response of the fine-grained material. Capabilities of the model are evaluated using the available experimental database on Boston Blue Clay (BBC). The model is successful to mimic a wide range of monotonic drained and undrained stress paths as well as the complicated cyclic response of clays. Implementation of the model in numerical packages will facilitate the simulation of different boundary value problems under various loading conditions.United States National Science Foundation CAREER grant (NSF Award No. CMMI-0449021

Undrained sliding resistance of shallow foundations subject to torsion

While the behavior of shallow foundations under vertical load combinations has been the subject of numerous studies, the response of shallow foundations subjected to combined horizontal and torsional loading has received considerably less attention. New offshore applications of shallow foundations for LNG facilities and other subsea structures have underscored the importance of the behavior of shallow embedded foundations subjected to combined in-plane translation and torsion. This study investigates the undrained bearing capacity of rectangular and square shallow foundations under eccentric horizontal loads through comparisons of various limit equilibrium and plastic limit analysis solutions to 3-D finite element solutions. In general, the plastic limit approach considered in this paper agrees well with the finite element solutions, although it has some tendency to over-predict capacity at greater embedment depths. The studies revealed a general insensitivity in the shape of the yield envelope to variations in embedment depth, which permits a simplified analysis suitable for first order estimates of load capacity. The variables considered in this study include footing aspect ratio, embedment depth, and load direction in addition to eccentricity.This is the author's accepted manuscript. The final version can be found published by ASCE in the Journal of Geotechnical and Geoenvironmental Engineering here: http://ascelibrary.org/doi/abs/10.1061/(ASCE)GT.1943-5606.0001138

Agro-economic and socio-environmental assessments of food and virtual water trades of Iran

Ending hunger and ensuring food security are among targets of 2030 s SDGs. While food trade and the embedded (virtual) water (VW) may improve food availability and accessibility for more people all year round, the sustainability and efficiency of food and VW trade needs to be revisited. In this research, we assess the sustainability and efficiency of food and VW trades under two food security scenarios for Iran, a country suffering from an escalating water crisis. These scenarios are (1) Individual Crop Food Security (ICFS), which restricts calorie fulfillment from individual crops and (2) Crop Category Food Security (CCFS), which promotes eating local by suggesting food substitution within the crop category. To this end, we simulate the water footprint and VW trades of 27 major crops, within 8 crop categories, in 30 provinces of Iran (2005 2015). We investigate the impacts of these two scenarios on (a) provincial food security (FSp) and exports; (b) sustainable and efficient blue water consumption, and (c) blue VW export. We then test the correlation between agro-economic and socio-environmental indicators and provincial food security. Our results show that most provinces were threatened by unsustainable and inefficient blue water consumption for crop production, particularly in the summertime. This water mismanagement results in 14.41 and 8.45 billion m3 y-1 unsustainable and inefficient blue VW exports under ICFS. Eating local improves the FSp value by up to 210% which lessens the unsustainable and inefficient blue VW export from hotspots. As illustrated in the graphical abstract, the FSp value strongly correlates with different agro-economic and socio-environmental indicators, but in different ways. Our findings promote eating local besides improving agro-economic and socio-environmental conditions to take transformative steps toward eradicating food insecurity not only in Iran but also in other countries facing water limitations. © 2021, The Author(s).We would like to thank the reviewers of the manuscript for their constructive comments. Thanks to Ms. Manuela Rosso—Brugnach for proofreading the article. This Project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Earth@lternatives Project, Grant agreement No 834716). Brugnach is supported by the Spanish Government through María de Maeztu excellence accreditation 2018–2022 (Ref. MDM-2017-0714) of BC3

Gauged motion in general relativity and in Kaluza-Klein theories

In a recent paper [1] a new generalization of the Killing motion, the {\it gauged motion}, has been introduced for stationary spacetimes where it was shown that the physical symmetries of such spacetimes are well described through this new symmetry. In this article after a more detailed study in the stationary case we present the definition of gauged motion for general spacetimes. The definition is based on the gauged Lie derivative induced by a threading family of observers and the relevant reparametrization invariance. We also extend the gauged motion to the case of Kaluza-Klein theories.Comment: 42 pages, revised version, typos correction along with some minor changes, Revtex forma

A comparative study of maximum power point tracking techniques for a photovoltaic grid-connected system

Purpose. In recent years, the photovoltaic systems (PV) become popular due to several advantages among the renewable energy. Tracking maximum power point in PV systems is an important task and represents a challenging issue to increase their efficiency. Many different maximum power point tracking (MPPT) control methods have been proposed to adjust the peak power output and improve the generating efficiency of the PV system connected to the grid. Methods. This paper presents a Beta technique based MPPT controller to effectively track maximum power under all weather conditions. The effectiveness of this algorithm based MPPT is supplemented by a comparative study with incremental conductance (INC), particle swarm optimization (PSO), and fuzzy logic control (FLC). Results Faster MPPT, lower computational burden, and higher efficiency are the key contributions of the Beta based MPPT technique than the other three techniques.Мета. В останні роки фотоелектричні системи набули популярності завдяки низці переваг серед відновлюваних джерел енергії. Відстеження точки максимальної потужності у фотоелектричних системах є важливим завданням і складною проблемою для підвищення їх ефективності. Було запропоновано безліч різних методів керування відстеженням точки максимальної потужності (ВТМП) для регулювання пікової вихідної потужності та підвищення ефективності генерації фотоелектричної системи, підключеної до мережі. Методи. У цій статті представлений контролер ВТМП, заснований на бета-методі, для ефективного відстеження максимальної потужності за будь-яких погодних умов. Ефективність ВТМП на основі цього алгоритму доповнюється порівняльним дослідженням з інкрементною провідністю, оптимізацією рою частинок та нечітким логічним управлінням. Результати. Швидше ВТМП, менші витрати на обчислення та більша ефективність є ключовими перевагами методу ВТМП на основі бета-методу порівняно з трьома іншими методами

Recombinant erythropoietin and blood transfusion in very low birth weight infants

Background: Very low birth weight infants (<1500 g) frequently require blood transfusions because of repeated blood sampling accompanied by anemia of prematurity. Methods: In an attempt to identify the effect of human recombinant erythropoietin to decrease the requirement for blood transfusions, erythropoietin was administered to 24 preterm infants less than 1500 g prospectively from September 1999 till December 2000. Data about the characteristics of the population, the severity of diseases, and treatment with erythropoietin, clinical diagnosis, initial and subsequent hemoglobin, volume of blood loss, and the number of blood transfusions were recorded. These results were compared with data from the recorded information of 49 infants who did not receive erythropoietin during those past 2 years. There were no differences between the 2 groups with regard to the gestational age, birth weight, clinical diagnosis, severity of the illness, primary causes of admission, and initial hematologic parameters such as hemoglobin, hematocrit and reticulocytes. Erythropoietin was administered in a dose of 200 IU/kg three times weekly for 6-8 weeks accompanied with iron supplement 6 mg/kg/day. Transfusions were administered according to protocol. Results: There was no significant difference between the number of blood transfusion among these 2 groups (p=0.07). However, transfusions in the erythropoietin treated group were fewer in comparison to the other group (1.9 +/- 1.6 to 3.2 +/- 1.1). No difference was observed between final hemoglobin and hematocrit levels among the two groups (10.3 +/- 0.9 vs. 10.4 +/- 0.7 and 33.7 +/- 2.3 vs. 32.2 +/- 2.2). Conclusion: Very low birth weight infants receive frequent blood transfusions but a reduction in transfusion requirements was not apparent after administration of erythropoietin and iron in preterm infants in this study. However, the lack of impact on transfusion requirements fails to support routine use of erythropoietin

Attenuation of serum laminin concentrations upon treatment of chronic hepatitis

Objectives: The aim of this work was to determine the serum laminin level cutoff point for predicting liver fibrosis highlighting its diagnostic value and determining the effect of treatment on serum laminin concentrations. Methods: Serum laminin concentrations in chronic hepatitis patients (n=62) and controls (n=20) were compared by ELISA and stages of fibrosis were assessed according to the modified Knodell score system. Results: Mean serum laminin concentration in patients (91.9 ± 20.9 ng/ml) was greater than controls (46.2 ± 10.2 ng/ml; p <0.001). Serum concentrations of laminin in all stages of hepatic fibrosis were significantly higher than those of healthy controls (p <0.05). A cutoff point of 52ng laminin/ml of serum was obtained for the discrimination of various stages of liver fibrosis showing a good sensitivity (96.8%) and specificity (80%). After 6 months of treatment, a gradual decrease in serum laminin concentrations were observed, however the level was still higher than that of the healthy group (p<0.05). Conclusions: Our findings suggest that the serum laminin concentration is a useful noninvasive marker of liver fibrosis and shows a strong positive correlation with different stages of the disease