Temporal laser pulse shape effects in nonlinear Thomson scattering

The influence of the laser pulse temporal shape on the Nonlinear Thomson Scattering on-axis photon spectrum is analyzed in detail. Using the classical description, analytical expressions for the temporal and spectral structure of the scattered radiation are obtained for the case of symmetric laser pulse shapes. The possibility of reconstructing the incident laser pulse from the scattered spectrum averaged over interference fringes in the case of high peak intensity and symmetric laser pulse shape is discussed.Comment: 18 pages, 8 figure

Production optimization using discrete simulation

Mestrado APNOR e Universidade de S. PetersburgoProduction and manufacturing setups involving lean solutions and customer driven “pull” logic (e.g. kanban systems) are more and more common. Usually, these systems allow companies to increase efficiency, quality levels, work force motivation and general productivity. Although these systems are not too difficult to plan and operate, in complex situations, even small adjustments can produce some unforeseen effects. In this scenario, discrete simulation can provide the tools to model the underlying systems and test the desired changes before implementation. In this work we modelled typical pull production systems with more or less complexity using a commercial discrete simulation software (SIMIO). Once the modelling phase was completed, different adjustments in the number of Kanban cards in the system were tested and evaluated, in order to optimize the system. Also, the final simulation model was built generic enough to be used in classroom environment to familiarize students with pull production concepts.As configurações de produção e fabricação envolvendo soluções lean e a lógica pull orientada ao cliente (por exemplo, sistemas kanban) são cada vez mais comuns. Normalmente, estes sistemas permitem que as empresas aumentem a eficiência, os níveis de qualidade, a motivação da força de trabalho e a produtividade geral. Embora esses sistemas não sejam muito difíceis de planear e operar, em situações complexas, mesmo pequenos ajustes podem produzir alguns efeitos imprevistos. Nesse cenário, a simulação discreta pode fornecer as ferramentas para modelar os sistemas subjacentes e testar as alterações desejadas antes da implementação. Neste trabalho modelamos sistemas típicos de produção puxada com maior ou menor complexidade usando um software comercial para simulação discreta (SIMIO). Uma vez concluída a fase de modelação, foram testados e avaliados diferentes ajustes no número de cartões kanban no sistema, a fim de otimizar o sistema. Além disso, o modelo de simulação final foi construído de forma suficientemente genérica para ser usado em ambiente de sala de aula para familiarizar os alunos com conceitos de produção puxada (pull).Организация производства и технологическая наладка с применением концепций «бережливого» и «вытягивающего» производства, ориентированных на нужды потребителя (например, система канбан) получают все более широкое распространение. Обычно, данные системы позволяют компаниям повышать эффективность, уровень качества, мотивацию сотрудников и производительность в целом. И хотя реализация данных подходов не является слишком трудоемкой, в сложных ситуациях даже малейшие корректировки могут привести к непредвиденным последствиям. В таком случае, дискретное моделирование может предоставить инструменты для создания базовых моделей и их тестирования, до внесения изменений в реальную систему. В данной работе было смоделировано типичное, более-менее сложное вытягивающее производство с применением коммерческого программного средства дискретного имитационного моделирования (SIMIO). После создания симуляции было протестировано и оценено использование разного количества канбан карт в системе с целью ее оптимизации. Также, финальная симуляция была создана достаточно общей, чтобы ее можно было использовать во время аудиторных занятий для ознакомления студентов с концепцией вытягивающего производства

Vertical price transmission along the diary supply chain in Russia

Many studies have analysed vertical price transmission using time-series econometric methods but vertical price transmission in the milk market in Russia has not been investigated. This paper studies vertical price transmission along the whole milk supply chain in the Russian market using the autoregressive distributed lags model. Monthly farm-gate and retail prices in Voronezh Oblast, a historically large agrarian region located to the south of Moscow, covering the period from 2002 to 2014 were used in the analysis. When estimating the vertical price transmission in the dairy market, seasonality should be taken into account. Using a cointegration technique, no empirical evidence is found for cointegration between farm-gate and retail prices. There is unidirectional Granger causality from retail to farm prices and not vice versa. The results support the assumption that price changes are not transmitted efficiently from one level to another and support the view that Russian retailers have more market power than farmers

The relationship between sea surface temperature anomalies and atmospheric circulation in GCM experiments

Several 19-year integrations of the Hamburg version of the ECMWF/T21 general circulation model driven by the monthly mean sea surface temperature (SST) observed in 1970-1988 were examined to study extratropical response of the atmospheric circulation to SST anomalies in the Northern Hemisphere in winter. In the first 19-years run SST anomalies were prescribed globally (GAGO run), and in two others SST monthly variability was limited to extratropical regions (MOGA run) and to tropics (TOGA run), respectively. A canonical correlation analysis (CCA), which select from two time-dependent fields optimally correlated pairs of patterns, was applied to monthly anomalies of SST in the North Alantic and Pacific Oceans and monthly anomalies of sea level pressure and 500 hPa geopotential height in the Northern Hemisphere. In the GAGO run the best correlated atmospheric pattern is global and is characterized by north-south dipole structures of the same polarity in the North Atlantic and the North Pacific sectors. In the MOGA and TOGA experiments the atmospheric response is more local than in the GAGO run with main centers in the North Atlantic and North Pacific, respectively. The extratropical response in the GAGO run is not equal to the sum of the responses in the MOGA and TOGA runs. The artificial meridional SST gradients at 25 degrees 30 degrees N probably influence the results of the MOGA and TOGA runs. The atmopsheric modes found by the CCA were compared with the normal modes of the barotropic vorticity equation linearized about the 500 hPa. winter climate. The normal modes with smallest eigenvalues are similar to the model leading variability modes and canonical patterns of 500 hPa geopotential height. The corresponding eigenvectors of the adjoint operator, which represent an external forcing optimal for exciting normal modes, have a longitudinal structure with maxima in regions characterized by enhanced high frequency baroclinic activity over both oceans

Model Selection for Signal Processing: a Minimum Error Approach and a General Performance Analysis

Estimation of the number of signals in the presence of noise is an important problem in several areas of statistical signal processing. There are a number of modern works on the design of an optimal solution to this problem in terms of some criteria. Each criterion generates a model order selection (MOS) algorithm. However, the minimum error probability criterion has not received significant attention, although errors in the estimation of the number of signals might directly affect the performance of the signal processing system as a whole. In this paper, we propose a new approach to the design of MOS algorithms partially based on the minimum error probability criterion. Also, we pay a lot of attention to the performance and consistency analysis of the MOS algorithms. In this study, an abridged error probability is used as a universal performance measure of the MOS algorithms. We propose a theoretical framework that makes it possible to obtain closed-form expressions for the abridged error probabilities of a wide range of MOS algorithms. Moreover, a parametric consistency analysis of the presented MOS algorithms is provided. Using the obtained results, we provide a parametric optimization of the presented MOS algorithms. Finally, we examinate a quasilikelihood (QL) approach to the design and analysis of the MOS algorithms. The proposed theoretical framework is used to obtain the abridged error probabilities as functions of the unknown signal parameter. These functions, in turn, allow us to find the scope of the QL approach.Comment: improved presentatio

Towards photoacoustic mammography

This research deals with developing the photoacoustic imaging technique\ud for breast cancer detection. Photoacoustics brings together the strong aspects of ultrasound and optical imaging. Medical imaging with photoacoustics is relatively new, and promising for a lot of applications, one of which is breast cancer detection

The methodological features of managing the value of companies introducing "green" innovations

Although it is a common assumption that innovations are one of the most important factors of economic development, there is a need to review some provisions of innovation methodology so that new fundamental values are taken into account more fully. Most recent business models are based on the depletion of natural environment, whose potential has been almost exhausted. It is necessary to introduce new ideas that are of use for society and create values for companies. One way of achieving this goal is “green” (environmental) innovations. The next decade is expected to see a rapid growth in environmental innovations. Their organization and management will require modern — and adequate to the objectives set — technologies. One of those is the quest for value methodology. To date, the quest for value methodology has given rise to several conceptual approaches, which can be used to evaluate the effectiveness of environmental innovations. This article discusses the advantages and disadvantages of major approaches. The author comes to a conclusion that that the modern theory and practice of corporate finance still lacks a generally accepted approach to assessing the value of companies that explicitly takes into account the impact of environmental factors on the cost. The article outlines the basic theoretical frameworks for the formation of such approach

Minimax Robustness of Bayesian Forecasting under Functional Distortions of Probability Densities

The problems of robustness in Bayesian forecasting are considered under distortions of the hypothetical probability densities. The expressions for the guaranteed upper risk functional are obtained and the robust prediction statistics under certain types of distortions are constructed

Role of plasticity-induced crack closure in fatigue crack growth

The premature contact of crack surfaces attributable to the near-tip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure (PICC), has long been focused as supposedly controlling factor of fatigue crack growth (FCG). Nevertheless, when the plane-strain near-tip constraint is approached, PICC lacks of straightforward evidence, so that its significance in FCG, and even the very existence, remain debatable. To add insights into this matter, large-deformation elastoplastic simulations of plane-strain crack under constant amplitude load cycling at different load ranges and ratios, as well as with an overload, have been performed. Modeling visualizes the Laird-Smith conceptual mechanism of FCG by plastic blunting and re-sharpening. Simulation reproduces the experimental trends of FCG concerning the roles of stress intensity factor range and overload, but PICC has never been detected. Near-tip deformation patterns discard the filling-in a crack with material stretched out of the crack plane in the wake behind the tip as supposed PICC origin. Despite the absence of closure, load-deformation curves appear bent, which raises doubts about the trustworthiness of closure assessment from the compliance variation. This demonstrates ambiguities of PICC as a supposedly intrinsic factor of FCG and, by implication, favors the stresses and strains in front of the crack tip as genuine fatigue drivers