81 research outputs found
OUTSTANDING RUSSIAN SCIENTISTS: DIMITRY AND ELENA WENTZEL
No full textThe paper presents the scientific biographies of two outstanding Soviet mathematicians and teachers Elena Sergeevna and Dimitry Alexandrovich Wentzel. The main attention is paid to the restoration of genuine events related to the scientific, pedagogical and social activities of these people. The paper extensively uses published materials, as well as oral memoirs of the participants of these events – friends and acquaintances of our heroes. Special attention is paid to the history and activities of the country’s largest military university – the Air Force Engineering Academy named after Zhukovsky (VVIA). Almost the whole life of the Wentzels was closely connected with the Academy. The life and customs of the Petersburg (Petrograd) University in the 1920s are described in detail, where E.S. Wentzel learned. The paper provides the information about many famous professors and teachers of both universities, reconstructs and analyzes the pedagogical activities of E.S. Wentzel in VVIA and MIIT (Moscow), her scientific and publishing activities in the field of probability theory and operations research. The author reconstructs and dwells on her literary activity under a pen name I. Grekova. As a writer, E.S. Wentzel contacted with the famous literary men (A.T. Tvardovsky, K.I. Chukovsky, A. Galich, etc.). The paper also describes the scientific activity of D.A. Wentzel in the field of ballistics, his contribution to publishing textbooks for military universities, his experience in training highly qualified personnel (candidates, doctors, academicians), his scientific and organizational activities (the creation of the Faculty of Armaments in the VVIA, the foundation of the Academy of Artillery Sciences of the USSR and others). The special aim of the paper was to recreate the human images of Elena and Dimitry Wentzel
Updatable Probabilistic Evaluation of Failure Rates of Mechanical Components in Power Take-Off Systems of Tidal Stream Turbines
Full text linkThis paper presents a method for the probabilistic evaluation of the failure rates of mechanical components in a typical power take-off (PTO) system of a horizontal-axis tidal stream turbine (HATT). The method is based on a modification of the method of the influence factors, when base failure rates, relevant influence factors and, subsequently, resulting failure rates are treated as random variables. The prior (i.e., initial) probabilistic distribution of the failure rates of a HATT component is generated using data for similar components from other industries, while taking into account actual characteristics of the component and site-specific operating and environmental conditions of the HATT. A posterior distribution of the failure rate is estimated numerically based on a Bayesian approach as new information about the component performance in an operating HATT becomes available. The posterior distribution is then employed to obtain the updated mean and lower and upper confidence limits of the failure rate. The proposed method is illustrated by applying it to the evaluation of the failure rates of two key components of the PTO system of a typical HATT—main seal and main bearing. In particular, it is shown that uncertainty associated with the method itself has a major influence on the failure rate evaluation. The proposed method is useful for the reliability assessment of both PTO designs of new HATTs and PTO systems of operating HATTs
Resilience of Critical Infrastructure Systems to Floods:A Coupled Probabilistic Network Flow and LISFLOOD-FP Model
No full textIn this paper, a network-flow model was constructed to simulate the performance of interdependent critical infrastructure systems during flood hazards, when there is shortage of commodities such as electrical power and water. The model enabled us to control the distribution of commodities among different consumers whose demand cannot be fully met. Incorporating time-variance in the model allowed for evaluating the time evolution of the functional level of the infrastructure systems and quantifying their resilience. As a demonstration of the model’s capability, the network model was coupled with a raster-based hydraulic flooding model in the way of Monte Carlo simulations. It was then used to investigate the cascading effects of flood-related failures of individual infrastructure assets on the performance of the critical infrastructure systems of a coastal community under different flooding scenarios and future climate impacts. The coupled modelling framework is essential for correctly assessing the interdependences and cascading effects in the infrastructure systems in the case of flood hazards. While in the considered example, the extent of inundation becomes less severe with a changing climate, the risk to infrastructure does not recede because of the cascading effects. This behaviour could not be captured by the flood model alone
Reliability of Marine Energy Converters
No full textThe oceans cover 71% of Earth’s surface and are an enormous source of renewable energy which comes from tides, waves, ocean currents, and salinity and temperature differences [...
Serviceability Reliability of Reinforced Concrete Beams with Corroded Reinforcement
No full textTo date, attention of researchers concentrated mainly on the serviceability failure of corroded reinforced concrete (RC) beams caused by excessive cracking. However, cracking of the concrete cover and a reduction in the bond strength (which may result in slip between the corroding reinforcement and the concrete) also decrease the stiffness of RC beams. As a result of it, displacements of the RC beams increase and may exceed a limit value specified in a code, i.e., it has been noted that corrosion may also cause the serviceability failure due to excessive displacements. In this paper the effect of corrosion on deflections of RC beams and, subsequently, on the probability of serviceability failure due to excessive deflection is considered. A nonlinear finite element model is used to describe the structural behavior of RC beams with corroding reinforcement. Uncertainties associated with the model and available data are taken into account. Results show that an increase in deflections due to corrosion has a lesser effect on serviceability of RC beams than corrosion-induced cracking.</p
Models for reliability assessment of reinforced concrete structures in corrosive environments in conditions of a changing climate
Full text linkReinforced concrete (RC) structures deteriorate with time and corrosion of reinforcing steel is one of the main causes for that. In the paper a framework for reliability-based assessment of durability of RC concrete structures in corrosive environments will be briefly described. Existing models for corrosion initiation, corrosion-induced cracking, and effects of corrosion on stiffness and strength of RC members will be considered. Special attention will be paid to the effects of a changing climate on corrosion risks to RC structures.</p
Polymorphisms in the <it>Mn-SOD</it> and <it>EC-SOD</it> Genes and Their Relationship to Diabetic Neuropathy in Type 1 Diabetes Mellitus
No full textAbstract Background Oxidative stress, resulting in a marked increase in the level of oxygen free radicals (OFR), has been implicated in the etiology of diabetic neuropathy (DN). Antioxidant enzymes may protect against the rapid onset and progression of DN, by reducing the excess of OFR and peroxide. Mutations and polymorphisms in the genes encoding such enzymes may therefore result in predisposition to DN. We investigated the role of genes encoding two antioxidant enzymes, mitochondrial (Mn-SOD) and extracellular (EC-SOD) superoxide dismutase, in DN pathogenesis in a Russian population. We studied Ala(-9)Val and Ile58Thr polymorphisms of the Mn-SOD gene and Arg213Gly dimorphism of the EC-SOD gene in type 1 diabetic patients with (n = 82) and without DN (n = 84). Results We developed and used a new polymerase chain reaction (PCR) assays for rapid detection of polymorphisms. These assays involved the use of mismatch PCR primers to create restriction sites in the amplified product only in presence of the polymorphic base. The PCR product was than digested with BshTI, Eco32I or Eco52I to detect Ala(-9)Val, Ile58Thr or Arg213Gly polymorphic site respectively. The frequencies of the Ala allele (50.6% vs. 68.5%, p Mn-SOD gene were significantly lower in DN patients than in diabetic subjects without DN. In contrast, the Val allele (49.4% vs. 31.5%, p Conclusions Ala(-9)Val substitution in the Mn-SOD gene was associated with DN in a Russian population</p
Erratum to: Neuromodulation of lumbosacral spinal networks enables independent stepping after complete paraplegia (Nature Medicine, (2018), 24, 11, (1677-1682), 10.1038/s41591-018-0175-7)
No full text© 2018, Springer Nature America, Inc. In the version of this article originally published, Dimitry G. Sayenko’s affiliations were not correct. The following affiliation for this author was missing: Department of Neurosurgery, Center for Neuroregeneration, Houston Methodist Research Institute, Houston, TX, USA. This affiliation has been added for the author, and the rest of the affiliations have been renumbered accordingly. The error has been corrected in the HTML and PDF versions of this article
Life-cycle cost analysis as a tool for decision making
No full textMeasures that improve durability of a structure usually increase its initial cost. Thus, in order to make a decision about a cost-effective solution life-cycle cost of a structure including cost of structural failure needs to be considered. Due to uncertainties associated with structural properties, loads and environmental conditions the cost of structural failure is a random variable. The paper derives probability distributions of the cost of failure of a single structure and a group of identical structures when single or multiple failures are possible during the service life of a structure. The probability distributions are based on cumulative probabilities of failure of a single structure over its service life. The probability distributions can be employed to evaluate the expected life-cycle cost or the expected utility, which is then used in decision making. An example, which considers the selection of durability specifications for a reinforced concrete structure built on the coast, illustrates the use of the derived probability distributions.</p
Evaluation of expected utility for decision analysis of structures
No full textIn order to make a rational decision about a cost-effective solution the life-cycle cost of a structure including cost of structural failure needs to be considered. Due to uncertainties associated with structural properties, loads and environmental conditions the cost of structural failure is a random variable. The paper derives probability distributions of the cost of failure of a single structure and a group of identical structures when single or multiple failures are possible during the service life of a structure. The probability distributions are based on cumulative probabilities of failure of a single structure over its service life. The probability distributions can be employed to evaluate the expected utility, which is then used in decision making. An example, which considers the selection of durability specifications for a reinforced concrete structure built in marine environments, illustrates the use of the derived probability distributions.</p
- …
