Non-adiabatic processes in the radiation damage of materials from first principles

115 p.El paso rápido de iones a través de un sistema de materia condensadaconstituye un problema cuánntico de muchos cuerpos dependientedel tiempo. La complejidad del problema hace que sea extremadamentedifícil encontrar una descripción exacta del mismo. Para resolver elproblema se han aplicado varios modelos que siendo cuantitativamenteprecisos proporcionan un grado de éxito variable. En primer lugar,describimos el problema general de la interacción radiación-materia,sus antecedentes, la bibliografía en el campo de la interacción radiación materia,y campos asociados tales como el estudio del consiguientedaño por radiación. Cuando un ión de movimiento rápido penetraa través de un sólido, pierde energía a través de diferentes mecanismostales como excitaciones electrónicas en el objetivo, ionización delproyectil, movimiento y desplazamiento de los iones objetivo, emisiónde radiación y reacciones químicas o nucleares. Estos mecanismos sonextremadamente complicados y la importancia de cada proceso varía dependiendodel material objetivo, del tipo de proyectil, y especialmentedel rango de energía. Sin embargo, la pérdida de energía asociadaa excitaciones electrónicas, caracterizada como el poder de parada(stopping power) electrónico, es con diferencia el mecanismo más dominantee importante. Los primeros modelos de poder de parada debidosa Bohr, Bethe y Bloch presentaban una validez limitada para ionesligeros en régimen de alta velocidad

Non-adiabatic processes in the radiation damage of materials from first principles

115 p.El paso rápido de iones a través de un sistema de materia condensadaconstituye un problema cuánntico de muchos cuerpos dependientedel tiempo. La complejidad del problema hace que sea extremadamentedifícil encontrar una descripción exacta del mismo. Para resolver elproblema se han aplicado varios modelos que siendo cuantitativamenteprecisos proporcionan un grado de éxito variable. En primer lugar,describimos el problema general de la interacción radiación-materia,sus antecedentes, la bibliografía en el campo de la interacción radiación materia,y campos asociados tales como el estudio del consiguientedaño por radiación. Cuando un ión de movimiento rápido penetraa través de un sólido, pierde energía a través de diferentes mecanismostales como excitaciones electrónicas en el objetivo, ionización delproyectil, movimiento y desplazamiento de los iones objetivo, emisiónde radiación y reacciones químicas o nucleares. Estos mecanismos sonextremadamente complicados y la importancia de cada proceso varía dependiendodel material objetivo, del tipo de proyectil, y especialmentedel rango de energía. Sin embargo, la pérdida de energía asociadaa excitaciones electrónicas, caracterizada como el poder de parada(stopping power) electrónico, es con diferencia el mecanismo más dominantee importante. Los primeros modelos de poder de parada debidosa Bohr, Bethe y Bloch presentaban una validez limitada para ionesligeros en régimen de alta velocidad

Vacuum gas carburizing fate of hydrocarbons

This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with propane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor. arburizing is the case-hardening process in which carbon is added to the surface of low-carbon steels at temperatures generally between 850 and 1050 °C. In the conventional gas carburizing at atmospheric pressure, the carbon potential is controlled by adjusting the flow rate of the carburizing gas. Carbon potential of the furnace atmosphere can be related to partial pressure of CO2 or O2 or vapour pressure of water by equilibrium relationships and a sensor can be used to measure it. This method of carbon-potential control cannot be used for vacuum gas carburizing due to the absence of thermodynamic equilibrium which is one of the main difficulties of the vacuum carburizing process. The formation of soot during carburization isalso undesirable and the process parameters should be selected such that the formation of soot is minimized. The amount of carbon available for carburizing the steel depends on the partial pressure of the carburizing gas, carbon content in the carburizing gas and the pyrolysis reactions of the carburizing gas. The pyrolysis reactions of the carburizing gas are also affected by the contacting pattern or how the gas flows through and contacts with the steel parts being carburized. This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with ropane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor. Two different approaches have been used to model the pyrolysis of propane and acetylene under vacuum carburizing conditions of steel. One approach is based on formal or global kinetic mechanisms together with the computational fluid dynamics (CFD) tool. The other approach is based on detailed chemistry with simplified or ideal flow models. Two global mechanisms developed at the Engler-Bunte-Institut for pyrolysis of propane and acetylene respectively were used in this work. One detailed mechanism developed at the Institute of Chemical Technology by the research group of Professor Deutschmann was used for modeling the pyrolysis of both the propane and acetylene. Experimental data from investigations on vacuum carburizing conducted at the Engler-Bunte-Institut were used to validate the modeling results

Single-trial extraction of event-related potentials (ERPs) and classification of visual stimuli by ensemble use of discrete wavelet transform with Huffman coding and machine learning techniques

BackgroundPresentation of visual stimuli can induce changes in EEG signals that are typically detectable by averaging together data from multiple trials for individual participant analysis as well as for groups or conditions analysis of multiple participants. This study proposes a new method based on the discrete wavelet transform with Huffman coding and machine learning for single-trial analysis of evenal (ERPs) and classification of different visual events in the visual object detection task.MethodsEEG single trials are decomposed with discrete wavelet transform (DWT) up to the level of decomposition using a biorthogonal B-spline wavelet. The coefficients of DWT in each trial are thresholded to discard sparse wavelet coefficients, while the quality of the signal is well maintained. The remaining optimum coefficients in each trial are encoded into bitstreams using Huffman coding, and the codewords are represented as a feature of the ERP signal. The performance of this method is tested with real visual ERPs of sixty-eight subjects.ResultsThe proposed method significantly discards the spontaneous EEG activity, extracts the single-trial visual ERPs, represents the ERP waveform into a compact bitstream as a feature, and achieves promising results in classifying the visual objects with classification performance metrics: accuracies 93.60, sensitivities 93.55, specificities 94.85, precisions 92.50, and area under the curve (AUC) 0.93 using SVM and k-NN machine learning classifiers.ConclusionThe proposed method suggests that the joint use of discrete wavelet transform (DWT) with Huffman coding has the potential to efficiently extract ERPs from background EEG for studying evoked responses in single-trial ERPs and classifying visual stimuli. The proposed approach has O(N) time complexity and could be implemented in real-time systems, such as the brain-computer interface (BCI), where fast detection of mental events is desired to smoothly operate a machine with minds

Climatic Changes and Their Effect on Wildlife of District Dir Lower, Khyber Pakhtunkhwa, Pakistan

Climatic changes and their impact are increasingly evident in Pakistan, especially in the mountainous regions. Mountain ecosystems are considered to be sensitive indicators of global warming; even slight variations in temperature can lead to significant shifts in local climate, which can, in turn, drastically affect the natural environment, subsequently altering people’s lifestyle and wildlife habitats. The targeted area for the present research was Lower Dir District, Pakistan. The study gathered the required information from primary and secondary sources. Secondary data on temperature and precipitation were obtained from various sources, i.e., local CBO, including WWF Pakistan. Based on information gathered on climate change and wildlife, a detailed questionnaire was designed. Results showed that no regular pattern of the increase was found in temperature from 2010 to 2018; the same was noticed in the rainfall decrease pattern. Results also showed that the leading causes behind climatic changes are an increase in greenhouse gases due to pollution by industries, vehicles, crushing plants, deforestation, and some natural phenomena such as floods. The study showed that more than 80% of the respondents agreed that climatic effects have a significant impact on wildlife, i.e., the existence of wildlife falls in danger due to climatic changes as it may lead to habitat change, making it difficult for the survival and adaptation of the wildlife. Hence, in consequence, it leads to migration, low growth rate, an increase in morbidity and mortality rate, and finally leading to the extinction of the species or population. It is concluded from the study that people are severely noticing the climatic change and its leading causes are greenhouse gases and deforestation. To control climatic changes and wildlife extinction, we need an appropriate policy for forest conservation, wildlife conservation, prevent hunting, industrial pollution control, vehicle pollution control, increase in plantation, awareness of policy for the control of climatic changes, etc

Vacuum gas carburizing - fate of hydrocarbons

This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with propane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor. arburizing is the case-hardening process in which carbon is added to the surface of low-carbon steels at temperatures generally between 850 and 1050 °C. In the conventional gas carburizing at atmospheric pressure, the carbon potential is controlled by adjusting the flow rate of the carburizing gas. Carbon potential of the furnace atmosphere can be related to partial pressure of CO2 or O2 or vapour pressure of water by equilibrium relationships and a sensor can be used to measure it. This method of carbon-potential control cannot be used for vacuum gas carburizing due to the absence of thermodynamic equilibrium which is one of the main difficulties of the vacuum carburizing process. The formation of soot during carburization isalso undesirable and the process parameters should be selected such that the formation of soot is minimized. The amount of carbon available for carburizing the steel depends on the partial pressure of the carburizing gas, carbon content in the carburizing gas and the pyrolysis reactions of the carburizing gas. The pyrolysis reactions of the carburizing gas are also affected by the contacting pattern or how the gas flows through and contacts with the steel parts being carburized. This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with ropane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor. Two different approaches have been used to model the pyrolysis of propane and acetylene under vacuum carburizing conditions of steel. One approach is based on formal or global kinetic mechanisms together with the computational fluid dynamics (CFD) tool. The other approach is based on detailed chemistry with simplified or ideal flow models. Two global mechanisms developed at the Engler-Bunte-Institut for pyrolysis of propane and acetylene respectively were used in this work. One detailed mechanism developed at the Institute of Chemical Technology by the research group of Professor Deutschmann was used for modeling the pyrolysis of both the propane and acetylene. Experimental data from investigations on vacuum carburizing conducted at the Engler-Bunte-Institut were used to validate the modeling results