Adelina Miteva - Academia.edu (original) (raw)
Papers by Adelina Miteva
Trakia Journal of Sciences
Purpose: The paper will give readers a reasonable idea of how the abstracts of the dissertations ... more Purpose: The paper will give readers a reasonable idea of how the abstracts of the dissertations are unnecessary today in the presence of scientific juries. The personal opinion of the author is expressed here on the subject of the abstracts of doctoral degree dissertations – for a doctor (Dr., PhD) and for a doctor of science (DSc.). Methods: Several scientific methods were used in the creation of this article: obtaining information on the topic through different search methods; experience and knowledge. Results: The history, essence, idea and goals of the dissertation abstract are briefly presented. The main elements of the structure of the abstract, as well as the practice of its printing today, are constructively critically examined. Conclusions: If there is a scientific jury, there is no need for an abstract. By giving up writing abstracts, it will save us a lot of energy and time, and therefore increase our standard of living.
Aerospace Research in Bulgaria, 2021
Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest... more Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest from industry and science, and are widely used due to their advantages. These advantages are due to their unique properties and, therefore, their many real and potential applications in various fields of industry, science and everyday life. In this literature review paper, we will briefly focus on some of the properties of FGMs and on some of the existing and expanding future applications of FGM in aerospace and related industries. A critical discussion is presented. Possible future expansion of work in this area is being considered.
Metallurgist, 2020
Resumo. O artigo analisa os elementos fundamentais à estruturação de um importante fenômeno polít... more Resumo. O artigo analisa os elementos fundamentais à estruturação de um importante fenômeno político brasileiro da Primeira República: o "Coronelismo". Associado aos resquícios de poder privado e à posse de terras; este fenômeno influenciou todo o funcionamento da política brasileira até 1930. Todavia, pouco se estudou, até então, acerca dos condicionantes necessários ao seu advento. Tal problemática enseja análises sobre o contexto político e econômico capaz de interferir em sua manifestação. As análises possuem como foco o Norte de Minas Gerais, mais especificamente a cidade de Montes Claros, à época, um pequeno núcleo urbano cindido pelas disputas de dois grupos parentelares.
Tribology in Industry, 2017
The tribological characteristics of spheroidal graphite cast irons with and without nanosized add... more The tribological characteristics of spheroidal graphite cast irons with and without nanosized additives are investigated. The tests are performed as in cast iron condition as well after austempering. The spheroidal graphite irons are undergone to austempering in the bainite field, including heating at 900 °С for an hour, after that isothermal retention at 280 °С, 2 h and at 380 °C, 2 h. The lower bainitic and upper bainitic structures are formed during the process. Nanosized additives of titanium carbonitride and titanium nitride TiCN+TiN influence on the graphite phase characteristics and on the microstructure of the cast and austempered spheroidal graphite irons. The changes in the micro structure the irons with nanoadditives lead to an abrasive wear resistance increase. The formation of the strain induced martensite from the retained austenite in the friction contact area during wear is determined in the austempered irons. This is the reason for the wear resistance increase of the irons. The experimental testing of the wear is carried out by cinematic scheme tapper-discunder friction on the fixed abrasive. The microstructure of the patterns is observed by optical and quantitative metallography, X-Ray analysis, SEM and EDX analysis. The hardness testing is performed by Brinnel and Vickers methods.
Advanced Engineering Letters
Aluminium alloys are used as lightweight materials especially in the aerospace and automotive ind... more Aluminium alloys are used as lightweight materials especially in the aerospace and automotive industries. They have a number of properties such as high corrosion resistance due to the surface oxide coating, low relative weight and better castability. At normal temperatures, metal oxides are more resistant than the metal itself. The oxide layer is much thinner than the metal but protects it from interacting with the air. The kinetics of oxidation processes is the subject of the current work. As the temperature rises, the oxidation process usually proceeds in the presence of water vapour, and its rate depends on various factors, including the initial oxide layer and oxidation kinetics. The values of the oxidation exponent n аrе calculated for aluminium ribbons with different contents of Fe, Mg and Sb. Their influence on the intensity and two-stage tendency of the oxidation process is established.
Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences)... more Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
Aerospace Research in Bulgaria, 2022
Nowadays, aluminium alloys are of growing interest to scientists and are widely used in aerospace... more Nowadays, aluminium alloys are of growing interest to scientists and are widely used in aerospace and allied industries due to their inherent lightness, high strength to weight ratio, excellent thermal and electrical conductance, good reflectivity and low working cost. Among the conventional structural materials used in aerospace applications aluminium alloys are frontrunners. This is due to the ability of modern aluminium alloys to achieve unique combination of properties, through alloying and heat treatment, tailored to particular applications. Aluminum alloy 7075 (B95) is a high-strength alloy that works in extreme conditions and is used in modern construction of aircraft, spacecraft and satellites. In this mini-review, we will briefly focus on some of the existing and growing applications of some 7xxx aluminum alloys, in particular 7075 (B95), in the aerospace industry. Possible options for continuing work in this area are considered, and some Bulgarian developments are presented.
The present work is motivated by the tremendous interest in the semiconductor nanostructures. The... more The present work is motivated by the tremendous interest in the semiconductor nanostructures. The study of the quantum confined Stark effect (QCSE) in semiconductor superlattices and semiconductor quantum wells has attracted a lot of attention, as it is important both for fundamental physics and in devices for optoelectronic applications. The present paper is a brief review of the main electronic properties, which are the basis for the QCSE device applications of semiconductor superlattices and semiconductor quantum wells.
The present work is motivated by the tremendous interest in the functionally graded materials (FG... more The present work is motivated by the tremendous interest in the functionally graded materials (FGMs). The properties of FGMs change gradually with the position. The property gradient in FGMs is caused by a position-dependent chemical composition, microstructure or atomic order. The overall properties of FMGs are unique and different from any of the individual material that forms it. One unique characteristic of FGMs is the ability to tailor a material for specific application. There is a wide range of applications of FGMs and it is expected to increase. In this paper we will make a brief survey of the most distinguished properties and some of the applications of FGMs.
Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest... more Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest from industry and science, and are widely used due to their advantages. These advantages are due to their unique properties and, therefore, their many real and potential applications in various fields of industry, science and everyday life. In this literature review paper, we will briefly focus on some of the properties of FGMs and on some of the existing and expanding future applications of FGM in aerospace and related industries. A critical discussion is presented. Possible future expansion of work in this area is being considered.
In this work we will introduce quantum dots, wires and wells as nanostructure objects with differ... more In this work we will introduce quantum dots, wires and wells as nanostructure objects with different dimensionality. We will demonstrate the effect of applied external static electric field on the example of semiconductor quantum wells and the appearance of Stark effect. We will briefly allude to some of the optoelectronic devices using Stark effect. The influence of quantum well concentration profile and width on Stark shifts will be examined in case of the system GaAs-AlGaAs. The applicability of the model investigations for preliminary evaluation e.g. of the optimal Al concentration profile in order to improve the Stark effect characteristics in quantum wells is considered.
This work is motivated by the tremendous interest in the semiconductor nanomaterials and heterost... more This work is motivated by the tremendous interest in the semiconductor nanomaterials and heterostructures and their applications in constructing of various electro-optical devices. Changes in the electrooptical properties of such materials have been induced under the influence of an external constant electric field, the so called quantum confined Stark effect (QCSE). The QCSE has found practical application in ultrafast optoelectronics, electroabsorption modulators and in telecommunications, as well as in such devices as solar cells, advanced tuneable semiconductor lasers, etc. In this paper we will make a survey of several such devices based on QCSE in semiconductor quantum-well materials. КВАНТОВО-РАЗМЕРЕН ЩАРК ЕФЕКТ В ПОЛУПРОВОДНИКОВИ НАНОСТРУКТУРИ – ПРИБОРНИ ПРИЛОЖЕНИЯ Аделина Митева, Валерия Стоянова Институт за космически изследвания и технологии – Българска академия на науките 2 Институт по физикохимия – Българска академия на науките e-mail: ad.miteva@gmail.com; valeria@ipc.b...
This paper is motivated by the present tremendous interest in the functionally graded materials (... more This paper is motivated by the present tremendous interest in the functionally graded materials (FGMs). The overall properties of FMGs are unique and different from any of the individual materials that form it. One unique characteristic of FGMs is the ability to tailor the materials for specific applications. There is a wide range of applications of FGMs. Here we present a brief overview on the most distinguished properties and applications of the FGMs. Planed future works in the area of FGMs include deeper study of the matter and consequently looking for new aluminium-based FGMs for potential space and other applications.
Strategies for Policy in Science and Education-Strategii na Obrazovatelnata i Nauchnata Politika
Nanotechnologies are practically applicable in all important areas of industry and everyday life.... more Nanotechnologies are practically applicable in all important areas of industry and everyday life. Nanotechnology is an interdisciplinary field covering natural and engineering sciences (e.g. mathematics, chemistry, physics, biology, military sciences, etc.), as well as health sciences due to its versatility. This article provides a brief overview of some of the current and potential applications of nanotechnology in sport and sports security. Some examples of what is and what can be created with the help of nanotechnology in these areas are given, for example: unique characteristic sports equipment, sportswear and architecture; ultra-small computers, durable and multifunctional materials for use in clothing, shoes, etc. A critical discussion is presented. Possible future extensions of work in this area are considered.
Applied Engineering Letters : Journal of Engineering and Applied Sciences
Aerospace Research in Bulgaria
This brief overview presents an attempt to systematize some of the available historical and recen... more This brief overview presents an attempt to systematize some of the available historical and recent data on the impact of zeolite science and engineering on the progress of various areas of Earth and Space development. The basic structural and chemical properties of natural and synthetic zeolites are presented. Valuable applications of the zeolites, such as catalysts, gas adsorbers and ion exchangers are also included. The most commonly used methods for the synthesis of zeolites from different materials are presented, as well as some Bulgarian developments for the reuse of waste materials to zeolites. The important role of zeolites as an indispensable material for improving the quality of soil, fuels, water, air, etc., required for the needs of orbiting space stations and spacecrafts has been confirmed by typical examples.
We study the influence of the different choice of unit cells on the Bloch solutions of Schr\c{c}d... more We study the influence of the different choice of unit cells on the Bloch solutions of Schr\c{c}dinger equation for one-dimensional periodic Kronig- Penney models with rectangular potential barriers or potential wells and partially constant effectiv mass. We obtain generalized Kronig-Penney relations for bulk states and exact expressions for the corresponding periodic parts of the Bloch wave functions for the two possible choices of the matching conditions in an unit cell. We show also that our analitic expressions reduce to the well known expressions for the Kronig-Penney relations and Bloch waves under constant effective mass and appropriate matching conditions.
Molekuliarnaia biologiia
A semi-empirical approach has been used to estimate the intramolecular electrostatic interactions... more A semi-empirical approach has been used to estimate the intramolecular electrostatic interactions in pepsin and penicillopepsin. The pH-dependence of the free energy electrostatic term was calculated, and the pH-dependence of the domain interactions has been estimated. As it was shown, the contribution of electrostatic interactions is rather small for the stabilization of the native structure. At the same time the electrostatic repulsion between domains increases with the increase of pH. The later can be the cause of the alkaline denaturation of pepsin and domain mobility.
Surface Science, 1999
ABSTRACT We study the Stark effect in rectangular quantum wells and in quantum wells with linear ... more ABSTRACT We study the Stark effect in rectangular quantum wells and in quantum wells with linear variation of the composition. The energies of the bound electronic states, the transition energies and their Stark shifts are calculated when a longitudinal electric field is applied. The spatial overlap of the electron and hole states and the intensity of the main optical transitions are considered, and their dependence on the electric field strength is discussed. We compare the Stark effect characteristics of the rectangular and graded composition quantum wells. Numerical calculations are performed within the framework of a semi-empirical sp3s∗ tight-binding model, the virtual crystal approximation and the surface Green function matching method. A comparison between the theoretical results and the experimental data available for these systems is made, and a critical discussion is presented.
Trakia Journal of Sciences
Purpose: The paper will give readers a reasonable idea of how the abstracts of the dissertations ... more Purpose: The paper will give readers a reasonable idea of how the abstracts of the dissertations are unnecessary today in the presence of scientific juries. The personal opinion of the author is expressed here on the subject of the abstracts of doctoral degree dissertations – for a doctor (Dr., PhD) and for a doctor of science (DSc.). Methods: Several scientific methods were used in the creation of this article: obtaining information on the topic through different search methods; experience and knowledge. Results: The history, essence, idea and goals of the dissertation abstract are briefly presented. The main elements of the structure of the abstract, as well as the practice of its printing today, are constructively critically examined. Conclusions: If there is a scientific jury, there is no need for an abstract. By giving up writing abstracts, it will save us a lot of energy and time, and therefore increase our standard of living.
Aerospace Research in Bulgaria, 2021
Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest... more Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest from industry and science, and are widely used due to their advantages. These advantages are due to their unique properties and, therefore, their many real and potential applications in various fields of industry, science and everyday life. In this literature review paper, we will briefly focus on some of the properties of FGMs and on some of the existing and expanding future applications of FGM in aerospace and related industries. A critical discussion is presented. Possible future expansion of work in this area is being considered.
Metallurgist, 2020
Resumo. O artigo analisa os elementos fundamentais à estruturação de um importante fenômeno polít... more Resumo. O artigo analisa os elementos fundamentais à estruturação de um importante fenômeno político brasileiro da Primeira República: o "Coronelismo". Associado aos resquícios de poder privado e à posse de terras; este fenômeno influenciou todo o funcionamento da política brasileira até 1930. Todavia, pouco se estudou, até então, acerca dos condicionantes necessários ao seu advento. Tal problemática enseja análises sobre o contexto político e econômico capaz de interferir em sua manifestação. As análises possuem como foco o Norte de Minas Gerais, mais especificamente a cidade de Montes Claros, à época, um pequeno núcleo urbano cindido pelas disputas de dois grupos parentelares.
Tribology in Industry, 2017
The tribological characteristics of spheroidal graphite cast irons with and without nanosized add... more The tribological characteristics of spheroidal graphite cast irons with and without nanosized additives are investigated. The tests are performed as in cast iron condition as well after austempering. The spheroidal graphite irons are undergone to austempering in the bainite field, including heating at 900 °С for an hour, after that isothermal retention at 280 °С, 2 h and at 380 °C, 2 h. The lower bainitic and upper bainitic structures are formed during the process. Nanosized additives of titanium carbonitride and titanium nitride TiCN+TiN influence on the graphite phase characteristics and on the microstructure of the cast and austempered spheroidal graphite irons. The changes in the micro structure the irons with nanoadditives lead to an abrasive wear resistance increase. The formation of the strain induced martensite from the retained austenite in the friction contact area during wear is determined in the austempered irons. This is the reason for the wear resistance increase of the irons. The experimental testing of the wear is carried out by cinematic scheme tapper-discunder friction on the fixed abrasive. The microstructure of the patterns is observed by optical and quantitative metallography, X-Ray analysis, SEM and EDX analysis. The hardness testing is performed by Brinnel and Vickers methods.
Advanced Engineering Letters
Aluminium alloys are used as lightweight materials especially in the aerospace and automotive ind... more Aluminium alloys are used as lightweight materials especially in the aerospace and automotive industries. They have a number of properties such as high corrosion resistance due to the surface oxide coating, low relative weight and better castability. At normal temperatures, metal oxides are more resistant than the metal itself. The oxide layer is much thinner than the metal but protects it from interacting with the air. The kinetics of oxidation processes is the subject of the current work. As the temperature rises, the oxidation process usually proceeds in the presence of water vapour, and its rate depends on various factors, including the initial oxide layer and oxidation kinetics. The values of the oxidation exponent n аrе calculated for aluminium ribbons with different contents of Fe, Mg and Sb. Their influence on the intensity and two-stage tendency of the oxidation process is established.
Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences)... more Not Available Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
Aerospace Research in Bulgaria, 2022
Nowadays, aluminium alloys are of growing interest to scientists and are widely used in aerospace... more Nowadays, aluminium alloys are of growing interest to scientists and are widely used in aerospace and allied industries due to their inherent lightness, high strength to weight ratio, excellent thermal and electrical conductance, good reflectivity and low working cost. Among the conventional structural materials used in aerospace applications aluminium alloys are frontrunners. This is due to the ability of modern aluminium alloys to achieve unique combination of properties, through alloying and heat treatment, tailored to particular applications. Aluminum alloy 7075 (B95) is a high-strength alloy that works in extreme conditions and is used in modern construction of aircraft, spacecraft and satellites. In this mini-review, we will briefly focus on some of the existing and growing applications of some 7xxx aluminum alloys, in particular 7075 (B95), in the aerospace industry. Possible options for continuing work in this area are considered, and some Bulgarian developments are presented.
The present work is motivated by the tremendous interest in the semiconductor nanostructures. The... more The present work is motivated by the tremendous interest in the semiconductor nanostructures. The study of the quantum confined Stark effect (QCSE) in semiconductor superlattices and semiconductor quantum wells has attracted a lot of attention, as it is important both for fundamental physics and in devices for optoelectronic applications. The present paper is a brief review of the main electronic properties, which are the basis for the QCSE device applications of semiconductor superlattices and semiconductor quantum wells.
The present work is motivated by the tremendous interest in the functionally graded materials (FG... more The present work is motivated by the tremendous interest in the functionally graded materials (FGMs). The properties of FGMs change gradually with the position. The property gradient in FGMs is caused by a position-dependent chemical composition, microstructure or atomic order. The overall properties of FMGs are unique and different from any of the individual material that forms it. One unique characteristic of FGMs is the ability to tailor a material for specific application. There is a wide range of applications of FGMs and it is expected to increase. In this paper we will make a brief survey of the most distinguished properties and some of the applications of FGMs.
Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest... more Functionally graded materials (FGMs) are currently the subject of great and ever-growing interest from industry and science, and are widely used due to their advantages. These advantages are due to their unique properties and, therefore, their many real and potential applications in various fields of industry, science and everyday life. In this literature review paper, we will briefly focus on some of the properties of FGMs and on some of the existing and expanding future applications of FGM in aerospace and related industries. A critical discussion is presented. Possible future expansion of work in this area is being considered.
In this work we will introduce quantum dots, wires and wells as nanostructure objects with differ... more In this work we will introduce quantum dots, wires and wells as nanostructure objects with different dimensionality. We will demonstrate the effect of applied external static electric field on the example of semiconductor quantum wells and the appearance of Stark effect. We will briefly allude to some of the optoelectronic devices using Stark effect. The influence of quantum well concentration profile and width on Stark shifts will be examined in case of the system GaAs-AlGaAs. The applicability of the model investigations for preliminary evaluation e.g. of the optimal Al concentration profile in order to improve the Stark effect characteristics in quantum wells is considered.
This work is motivated by the tremendous interest in the semiconductor nanomaterials and heterost... more This work is motivated by the tremendous interest in the semiconductor nanomaterials and heterostructures and their applications in constructing of various electro-optical devices. Changes in the electrooptical properties of such materials have been induced under the influence of an external constant electric field, the so called quantum confined Stark effect (QCSE). The QCSE has found practical application in ultrafast optoelectronics, electroabsorption modulators and in telecommunications, as well as in such devices as solar cells, advanced tuneable semiconductor lasers, etc. In this paper we will make a survey of several such devices based on QCSE in semiconductor quantum-well materials. КВАНТОВО-РАЗМЕРЕН ЩАРК ЕФЕКТ В ПОЛУПРОВОДНИКОВИ НАНОСТРУКТУРИ – ПРИБОРНИ ПРИЛОЖЕНИЯ Аделина Митева, Валерия Стоянова Институт за космически изследвания и технологии – Българска академия на науките 2 Институт по физикохимия – Българска академия на науките e-mail: ad.miteva@gmail.com; valeria@ipc.b...
This paper is motivated by the present tremendous interest in the functionally graded materials (... more This paper is motivated by the present tremendous interest in the functionally graded materials (FGMs). The overall properties of FMGs are unique and different from any of the individual materials that form it. One unique characteristic of FGMs is the ability to tailor the materials for specific applications. There is a wide range of applications of FGMs. Here we present a brief overview on the most distinguished properties and applications of the FGMs. Planed future works in the area of FGMs include deeper study of the matter and consequently looking for new aluminium-based FGMs for potential space and other applications.
Strategies for Policy in Science and Education-Strategii na Obrazovatelnata i Nauchnata Politika
Nanotechnologies are practically applicable in all important areas of industry and everyday life.... more Nanotechnologies are practically applicable in all important areas of industry and everyday life. Nanotechnology is an interdisciplinary field covering natural and engineering sciences (e.g. mathematics, chemistry, physics, biology, military sciences, etc.), as well as health sciences due to its versatility. This article provides a brief overview of some of the current and potential applications of nanotechnology in sport and sports security. Some examples of what is and what can be created with the help of nanotechnology in these areas are given, for example: unique characteristic sports equipment, sportswear and architecture; ultra-small computers, durable and multifunctional materials for use in clothing, shoes, etc. A critical discussion is presented. Possible future extensions of work in this area are considered.
Applied Engineering Letters : Journal of Engineering and Applied Sciences
Aerospace Research in Bulgaria
This brief overview presents an attempt to systematize some of the available historical and recen... more This brief overview presents an attempt to systematize some of the available historical and recent data on the impact of zeolite science and engineering on the progress of various areas of Earth and Space development. The basic structural and chemical properties of natural and synthetic zeolites are presented. Valuable applications of the zeolites, such as catalysts, gas adsorbers and ion exchangers are also included. The most commonly used methods for the synthesis of zeolites from different materials are presented, as well as some Bulgarian developments for the reuse of waste materials to zeolites. The important role of zeolites as an indispensable material for improving the quality of soil, fuels, water, air, etc., required for the needs of orbiting space stations and spacecrafts has been confirmed by typical examples.
We study the influence of the different choice of unit cells on the Bloch solutions of Schr\c{c}d... more We study the influence of the different choice of unit cells on the Bloch solutions of Schr\c{c}dinger equation for one-dimensional periodic Kronig- Penney models with rectangular potential barriers or potential wells and partially constant effectiv mass. We obtain generalized Kronig-Penney relations for bulk states and exact expressions for the corresponding periodic parts of the Bloch wave functions for the two possible choices of the matching conditions in an unit cell. We show also that our analitic expressions reduce to the well known expressions for the Kronig-Penney relations and Bloch waves under constant effective mass and appropriate matching conditions.
Molekuliarnaia biologiia
A semi-empirical approach has been used to estimate the intramolecular electrostatic interactions... more A semi-empirical approach has been used to estimate the intramolecular electrostatic interactions in pepsin and penicillopepsin. The pH-dependence of the free energy electrostatic term was calculated, and the pH-dependence of the domain interactions has been estimated. As it was shown, the contribution of electrostatic interactions is rather small for the stabilization of the native structure. At the same time the electrostatic repulsion between domains increases with the increase of pH. The later can be the cause of the alkaline denaturation of pepsin and domain mobility.
Surface Science, 1999
ABSTRACT We study the Stark effect in rectangular quantum wells and in quantum wells with linear ... more ABSTRACT We study the Stark effect in rectangular quantum wells and in quantum wells with linear variation of the composition. The energies of the bound electronic states, the transition energies and their Stark shifts are calculated when a longitudinal electric field is applied. The spatial overlap of the electron and hole states and the intensity of the main optical transitions are considered, and their dependence on the electric field strength is discussed. We compare the Stark effect characteristics of the rectangular and graded composition quantum wells. Numerical calculations are performed within the framework of a semi-empirical sp3s∗ tight-binding model, the virtual crystal approximation and the surface Green function matching method. A comparison between the theoretical results and the experimental data available for these systems is made, and a critical discussion is presented.