INTERNATIONAL JOURNAL OF ENGINEERING RESEARCH & TECHNOLOGY (IJERT), 2022
Evolutionary algorithms are widely being used on any engineering field where optimizations are re... more Evolutionary algorithms are widely being used on any engineering field where optimizations are required over complex problems. Genetic Algorithm (GA) is one of the most popular algorithms over the evolutionary ones. GA are being taught on graduated and post-graduated university courses. Despite this wide spread of the GA usage and variety of applicable field, a correct setup of GA parameters is still not uniquely defined. In this material, the influence of GA parameters setup such as number of populations on each generation, elitism coefficient, mutation function used to generate and push genetic modifications over the population, parent selection functions and reproduction functions choice parameter influence are also analyzed. All parameters are being analyzed on a simple Yagi-Uda constrained antenna problem as a simple test case where linear constraints and genetic coding of variables are of immediate understanding to the reader. At the end, some discussions on the available functions used on GA and different parameter setup and their influence on the GA results are drown. The material concludes with conclusions and bibliographic references designed to help the reader expand his knowledge on optimization algorithms and in particular in the correct use of GA functions on constrained optimization problems.
This study is focused on the construction of a dipole meander textile antenna that exhibits a sta... more This study is focused on the construction of a dipole meander textile antenna that exhibits a stable communication system in military applications. The geometric shape of the antenna was calculated and determined based on the fact that dipole antennas geometry shows the highest performance at the Radio Frequency Identification (RFID) frequency band. The High Frequency Simulator Structure (HFSS) program was used for stimulation of the proposed antenna. The fabrication method chosen for the realization of this antenna is the automatic embroidery method, as this method offers high durability in use. The paper aimed to have a textile antenna to operate in the frequency band 868-970 MHz (frequency band defined by NATO), and this was achieved by the proposed textile antenna.
2018 26th International Conference on Software, Telecommunications and Computer Networks (SoftCOM), 2018
in this paper theoretical analysis and field test measurement are described and compared for the ... more in this paper theoretical analysis and field test measurement are described and compared for the possibility of reusing the existing analog TV transmitting antenna for DVB-T2 radio coverage in Albania. Antenna radiation characteristics are provided for the analog (existing) frequency plan and also for new frequency channels used on DVB-T2 according to Geneva’06 agreement for frequency assignment plans. Antenna coverage area simulations are performed using Longley Rice model for new frequency channels used on DVB-T2. The simulation results are compared with practical series of field measurements in the surrounding of Korça city in Albania. The obtained results show the main issues that need to be considered in reusing antennas at different frequencies rather of their design at the previous frequencies.
Advances in Internet, Data & Web Technologies, 2018
Settling down an efficient and reliable procedure for the evaluation of the EMF exposure, from th... more Settling down an efficient and reliable procedure for the evaluation of the EMF exposure, from the Base Station Antennas, is important for mobile communications. In this work a calculation method of the exposure under radiofrequency, due to the presence of some antennas of the cellular Base Stations is introduced. The model of wave diffusion in free space, under ideal conditions gives ground for a convenient calculation of the exposure, even in cases of a considerable distance from the antenna, whose covering area is considerably larger, thus resulting in overestimation of the exposure. The calculation of the electrical intensity of the radiation is possible when the technical specifications of the given antenna (provided by the manufacturer) are known and by defining the position of the given point in relation to the antenna.
In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the whe... more In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the wheels control is still a task due to road conditions and traffic. The Anti-lock Braking System (ABS) is a tool used in automobiles to prevent wheels from locking while brakes are pressed. The objective of this work is the maintenance of the wheel slip value to a desirable slip ratio as the vehicle model is simulated using a fuzzy logic controller. The analyses are made based on the slip ratio, angular velocity and stopping time.
ABSTRACT By properly exciting higher order modes at an aperture it is possible to achieve higher ... more ABSTRACT By properly exciting higher order modes at an aperture it is possible to achieve higher aperture efficiencies. High efficiency antennas are mandatory in many applications, as discrete lenses, since the single element efficiency deeply affects the efficiency of the whole lens. In this contribution a genetic algorithm is applied to the mode matching analysis of square horns to achieve high radiation efficiency over a relatively wide band.
International Journal of Advanced Computer Science and Applications, 2021
In this work, is presented the design of a linear multi-beam antenna. The designed procedure is f... more In this work, is presented the design of a linear multi-beam antenna. The designed procedure is focused on the possibility of switching off a part of antenna array elements, in active antenna systems, in order to preserve resources (power and heat dissipation). The behavior of the original multi beam antenna design is investigated on the radiation pattern alteration due to the switched off elements. The choice of switching on/off antenna elements requires less computational effort from the algorithms incorporated in the active antenna system. Antenna array beam design using progressive phase shifts permits beam orthogonality which is valuable over use multiple beam antenna. In this work, turning off part of antenna elements will inevitably change the beam orthogonality conditions. Despite this, the case presented in this paper, shows beam space discrimination better than 10dB. To rank the behavior of modified antenna, with the turned off elements, are used both Euclidean and Hausdorff distances to measure the changes resulted from the modified array performance. The obtained solutions show the applicability of binary operation on existing antenna array. The metric showed in here can be effectively used as ranking criteria.
International Journal of Advanced Computer Science and Applications, 2020
In this paper, field test measurement are described and statistically correlated to obtain useful... more In this paper, field test measurement are described and statistically correlated to obtain useful information about radiofrequency (RF) behavior of Digital Video Broadcasting-Terrestrial, second generation (DVB-T2) channels. Monitored radiofrequency data parameters are analyzed from statistical perspective and for finding, if any, linear correlation between them. Practical series of field measurements in the surrounding of Korça city in Albania are performed for consecutive 48 hours with sample data each second. The obtained results show the main issues that need to be considered in monitoring service reception quality which is not strongly related to the received channel power level but to the Modulation Error Rate (MER) parameter.
2016 Symposium on Communications and Vehicular Technologies (SCVT), 2016
Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Comm... more Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region, since LEO satellites move too fast relative to a fixed point (ground station) on the Earth. The major loss in communication between the LEO satellite and the ground station is the free space loss. Free space loss varies since the distance from the ground station to the satellite varies over time. Free space loss is usually compensated through variable satellite transmit power on the downlink. This paper tries another approach on free space loss compensation, through receiver bandwidth adjustability at the ground station, in order to obtain the constant margin at the receiver. For analytical and simulation purposes, the altitudes from 600km to 1200km are considered.
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
Method of moments in time domain (MoM-TD) is a comparatively recent yet very interesting numerica... more Method of moments in time domain (MoM-TD) is a comparatively recent yet very interesting numerical technique especially in the case of ultra wide band signals or transients. In this context, the method of moments in time domain (MoM-TD) is very interesting. Implementing the MoM-TD requires three different approaches using Wire Grid Model, Surface Patch Model and the Attachment Model. All MoM-TD implementations present severe late time instability issues. MoM-TD stability has different behavior in thin wire approximation, where MoM matrices can be computed analytically, in surface patch approximation, where MoM matrices need to be computed numerically, and the Attachment approximation where MoM matrixes partially can be evaluated analytically and partially numerically. In this paper a comparison between different interpolating time basis functions is performed for stability issues. Besides the effect of the different time bases it will be shown how a marching-in-time filtering scheme can improve late time stability.
Intelligent transportations system is a complex information and communication technologies platfo... more Intelligent transportations system is a complex information and communication technologies platform aimed for a better and cost effectiveness public transport organization. Our intent is to extend the basic of intelligent transportations system for the improvement of local transportation in marginal areas for suitable links with the existing network system. These tools are characterized by low cost if compared with the potential impact in improving direct and indirect transportation efficiency. The information and communication technologies mobile platform will have a double nature: on the one hand, it will be capable of gathering environmental data in realtime and at regular intervals serving as moving environmental city sensors. Information such as temperature, noise, humidity, gas levels, road conditions, and dust particle concentration can all be reported and analyzed. On the other hand, the platform will provide services to passengers such as internet/intranet access, through these connection resources, exploiting wisely a multi standard (3G cellular networks, WiFi networks) gateway. In exploring solutions to those challenges a balanced dual 3G mobile providers connectivity combined with a private WiFi network will be used for balanced data traffic and uninterruptable internet service for passengers. The same information and communication technologies platform is the aim of a basic intelligent transportations system platform and telematics fleet management.
International Journal of Advanced Computer Science and Applications, 2015
By nodal regression and apsidal precession, the Earth flattering at satellite low Earth orbits (L... more By nodal regression and apsidal precession, the Earth flattering at satellite low Earth orbits (LEO) is manifested. Nodal regression refers to the shift of the orbit's line of nodes over time as Earth revolves around the Sun. Nodal regression is orbit feature utilized for circular orbits to be Sun synchronized. A sun-synchronized orbit lies in a plane that maintains a fixed angle with respect to the Earth-Sun direction. In the low Earth Sun synchronized circular orbits are suited the satellites that accomplish their photo imagery missions. Nodal regression depends on orbital altitude and orbital inclination angle. For the respective orbital altitudes the inclination window for the Sun synchronization to be attained is determined. The apsidal precession represents major axis shift, respectively the argument of perigee deviation. The apsidal precession simulation, for inclination window of sun synchronized orbital altitudes, is provided through this paper.
2015 International Wireless Communications and Mobile Computing Conference (IWCMC), 2015
The proliferation of corporate and end user mobile internet services offered for smartphones and ... more The proliferation of corporate and end user mobile internet services offered for smartphones and tablets, makes it necessary to monitor the quality of service and experience provided by mobile internet service providers. In this context, we introduce a low cost tool for monitoring network parameters as received signal power and network responding time. The application is used for signal and latency monitoring for fast and slow moving users in a surveyed area especially for in car communication. The developed application can be useful for mobile operators in order to improve their network quality as well as for end users who can get an insight into the quality of service offered by their service provider. In the proposed application, two software tools are used; first, the capabilities of the android programming interface and second the PHP scripting for measured data post-processing and reporting on web servers. The application is currently tested in Tirana, Albania for evaluating the network parameters of mobile providers showing that only monitoring the received signal power level is not sufficient for assuming a good quality of service.
A ground-backed slim slot-sinuous antenna is analyzed. Proposed configuration allows for a single... more A ground-backed slim slot-sinuous antenna is analyzed. Proposed configuration allows for a single lobe, polarization-versatile, high efficiency and ultra-wide band antenna not needing a the cumbersome lossy back cavity typical of conventional single lobe sinuous antennas. Simulations shows attained performances as well as tuning possibilities.
The transition between a Coplanar Waveguide to Coplanar Waveguide for Flip-Chip bump-based mounti... more The transition between a Coplanar Waveguide to Coplanar Waveguide for Flip-Chip bump-based mounting is here analyzed via a full wave Finite Element based analysis. Such analysis is carried on so as to minimize the reflection coefficient. A preliminary tolerance analysis for chip mounting is also presented.
The transfer of satellites in too high orbits as geosynchronous one (geostationary), usually is a... more The transfer of satellites in too high orbits as geosynchronous one (geostationary), usually is achieved firstly by launching the satellite in Low Earth Orbit (LEO), then in elliptical transfer orbit and finally to the geosynchronous orbit. The three steps process is known as Hohmann transfer. The Hohmann transfer which involves two circular orbits with different orbital inclinations is known as non-coplanar Hohmann transfer. If both orbital planes are aligned the Hohmann transfer is known as coplanar what is further considered in this paper. In terms of propellant consumptions the Hohmann transfer is the best known transfer to be applied when transferring between circular coplanar orbits. For transfer between circular coplanar orbits, the given information usually consists of the radii of the initial and final orbits. The velocity to be applied into two orbit points in order to attain the dedicated final orbit is analyzed. The aim of this paper is to conclude about the velocitiy changes under the different initial low Earth altitudes. For different initial orbit altitudes, the velocities to be applied in process of Hohmann transfer are simulated. From respective simulations, the velocity variations on dependence of initial altitudes are derived. The eccentricity is considered, too.
Wiley Encyclopedia of Electrical and Electronics Engineering, 2014
Designing an electronic system is an engineering task bound to the satisfaction of a given set of... more Designing an electronic system is an engineering task bound to the satisfaction of a given set of requirements. If it is possible to express the compliance of the system to the requirements in a mathematical form giving a measure of how much a given system is far from compliance, then it would be possible to obtain the desired performances by seeking for the minimum of such a function. Seeking the minimum of a function is a daunting task to which a whole branch of mathematics, optimization, is devoted. In the case in which the design must comply to several requirements, it is usually more practical and interesting to define a set of functions to be minimized altogether. In this case the search for an optimal point, or a set of points, can be performed by applying a multi-objective optimization technique. This chapter will investigate popular multi-objective optimization techniques, giving both their basics and describing recent advancements. For the selected techniques, performances over a set of benchmarks will be presented, as well as results over relevant electronic engineering problems. Keywords: multi-objective optimization; evolutionary algorithms; genetic algorithms
INTERNATIONAL JOURNAL OF ENGINEERING RESEARCH & TECHNOLOGY (IJERT), 2022
Evolutionary algorithms are widely being used on any engineering field where optimizations are re... more Evolutionary algorithms are widely being used on any engineering field where optimizations are required over complex problems. Genetic Algorithm (GA) is one of the most popular algorithms over the evolutionary ones. GA are being taught on graduated and post-graduated university courses. Despite this wide spread of the GA usage and variety of applicable field, a correct setup of GA parameters is still not uniquely defined. In this material, the influence of GA parameters setup such as number of populations on each generation, elitism coefficient, mutation function used to generate and push genetic modifications over the population, parent selection functions and reproduction functions choice parameter influence are also analyzed. All parameters are being analyzed on a simple Yagi-Uda constrained antenna problem as a simple test case where linear constraints and genetic coding of variables are of immediate understanding to the reader. At the end, some discussions on the available functions used on GA and different parameter setup and their influence on the GA results are drown. The material concludes with conclusions and bibliographic references designed to help the reader expand his knowledge on optimization algorithms and in particular in the correct use of GA functions on constrained optimization problems.
This study is focused on the construction of a dipole meander textile antenna that exhibits a sta... more This study is focused on the construction of a dipole meander textile antenna that exhibits a stable communication system in military applications. The geometric shape of the antenna was calculated and determined based on the fact that dipole antennas geometry shows the highest performance at the Radio Frequency Identification (RFID) frequency band. The High Frequency Simulator Structure (HFSS) program was used for stimulation of the proposed antenna. The fabrication method chosen for the realization of this antenna is the automatic embroidery method, as this method offers high durability in use. The paper aimed to have a textile antenna to operate in the frequency band 868-970 MHz (frequency band defined by NATO), and this was achieved by the proposed textile antenna.
2018 26th International Conference on Software, Telecommunications and Computer Networks (SoftCOM), 2018
in this paper theoretical analysis and field test measurement are described and compared for the ... more in this paper theoretical analysis and field test measurement are described and compared for the possibility of reusing the existing analog TV transmitting antenna for DVB-T2 radio coverage in Albania. Antenna radiation characteristics are provided for the analog (existing) frequency plan and also for new frequency channels used on DVB-T2 according to Geneva’06 agreement for frequency assignment plans. Antenna coverage area simulations are performed using Longley Rice model for new frequency channels used on DVB-T2. The simulation results are compared with practical series of field measurements in the surrounding of Korça city in Albania. The obtained results show the main issues that need to be considered in reusing antennas at different frequencies rather of their design at the previous frequencies.
Advances in Internet, Data & Web Technologies, 2018
Settling down an efficient and reliable procedure for the evaluation of the EMF exposure, from th... more Settling down an efficient and reliable procedure for the evaluation of the EMF exposure, from the Base Station Antennas, is important for mobile communications. In this work a calculation method of the exposure under radiofrequency, due to the presence of some antennas of the cellular Base Stations is introduced. The model of wave diffusion in free space, under ideal conditions gives ground for a convenient calculation of the exposure, even in cases of a considerable distance from the antenna, whose covering area is considerably larger, thus resulting in overestimation of the exposure. The calculation of the electrical intensity of the radiation is possible when the technical specifications of the given antenna (provided by the manufacturer) are known and by defining the position of the given point in relation to the antenna.
In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the whe... more In today’s automobile industry, the need to adjust the speed of the vehicle and stabilize the wheels control is still a task due to road conditions and traffic. The Anti-lock Braking System (ABS) is a tool used in automobiles to prevent wheels from locking while brakes are pressed. The objective of this work is the maintenance of the wheel slip value to a desirable slip ratio as the vehicle model is simulated using a fuzzy logic controller. The analyses are made based on the slip ratio, angular velocity and stopping time.
ABSTRACT By properly exciting higher order modes at an aperture it is possible to achieve higher ... more ABSTRACT By properly exciting higher order modes at an aperture it is possible to achieve higher aperture efficiencies. High efficiency antennas are mandatory in many applications, as discrete lenses, since the single element efficiency deeply affects the efficiency of the whole lens. In this contribution a genetic algorithm is applied to the mode matching analysis of square horns to achieve high radiation efficiency over a relatively wide band.
International Journal of Advanced Computer Science and Applications, 2021
In this work, is presented the design of a linear multi-beam antenna. The designed procedure is f... more In this work, is presented the design of a linear multi-beam antenna. The designed procedure is focused on the possibility of switching off a part of antenna array elements, in active antenna systems, in order to preserve resources (power and heat dissipation). The behavior of the original multi beam antenna design is investigated on the radiation pattern alteration due to the switched off elements. The choice of switching on/off antenna elements requires less computational effort from the algorithms incorporated in the active antenna system. Antenna array beam design using progressive phase shifts permits beam orthogonality which is valuable over use multiple beam antenna. In this work, turning off part of antenna elements will inevitably change the beam orthogonality conditions. Despite this, the case presented in this paper, shows beam space discrimination better than 10dB. To rank the behavior of modified antenna, with the turned off elements, are used both Euclidean and Hausdorff distances to measure the changes resulted from the modified array performance. The obtained solutions show the applicability of binary operation on existing antenna array. The metric showed in here can be effectively used as ranking criteria.
International Journal of Advanced Computer Science and Applications, 2020
In this paper, field test measurement are described and statistically correlated to obtain useful... more In this paper, field test measurement are described and statistically correlated to obtain useful information about radiofrequency (RF) behavior of Digital Video Broadcasting-Terrestrial, second generation (DVB-T2) channels. Monitored radiofrequency data parameters are analyzed from statistical perspective and for finding, if any, linear correlation between them. Practical series of field measurements in the surrounding of Korça city in Albania are performed for consecutive 48 hours with sample data each second. The obtained results show the main issues that need to be considered in monitoring service reception quality which is not strongly related to the received channel power level but to the Modulation Error Rate (MER) parameter.
2016 Symposium on Communications and Vehicular Technologies (SCVT), 2016
Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Comm... more Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region, since LEO satellites move too fast relative to a fixed point (ground station) on the Earth. The major loss in communication between the LEO satellite and the ground station is the free space loss. Free space loss varies since the distance from the ground station to the satellite varies over time. Free space loss is usually compensated through variable satellite transmit power on the downlink. This paper tries another approach on free space loss compensation, through receiver bandwidth adjustability at the ground station, in order to obtain the constant margin at the receiver. For analytical and simulation purposes, the altitudes from 600km to 1200km are considered.
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
Method of moments in time domain (MoM-TD) is a comparatively recent yet very interesting numerica... more Method of moments in time domain (MoM-TD) is a comparatively recent yet very interesting numerical technique especially in the case of ultra wide band signals or transients. In this context, the method of moments in time domain (MoM-TD) is very interesting. Implementing the MoM-TD requires three different approaches using Wire Grid Model, Surface Patch Model and the Attachment Model. All MoM-TD implementations present severe late time instability issues. MoM-TD stability has different behavior in thin wire approximation, where MoM matrices can be computed analytically, in surface patch approximation, where MoM matrices need to be computed numerically, and the Attachment approximation where MoM matrixes partially can be evaluated analytically and partially numerically. In this paper a comparison between different interpolating time basis functions is performed for stability issues. Besides the effect of the different time bases it will be shown how a marching-in-time filtering scheme can improve late time stability.
Intelligent transportations system is a complex information and communication technologies platfo... more Intelligent transportations system is a complex information and communication technologies platform aimed for a better and cost effectiveness public transport organization. Our intent is to extend the basic of intelligent transportations system for the improvement of local transportation in marginal areas for suitable links with the existing network system. These tools are characterized by low cost if compared with the potential impact in improving direct and indirect transportation efficiency. The information and communication technologies mobile platform will have a double nature: on the one hand, it will be capable of gathering environmental data in realtime and at regular intervals serving as moving environmental city sensors. Information such as temperature, noise, humidity, gas levels, road conditions, and dust particle concentration can all be reported and analyzed. On the other hand, the platform will provide services to passengers such as internet/intranet access, through these connection resources, exploiting wisely a multi standard (3G cellular networks, WiFi networks) gateway. In exploring solutions to those challenges a balanced dual 3G mobile providers connectivity combined with a private WiFi network will be used for balanced data traffic and uninterruptable internet service for passengers. The same information and communication technologies platform is the aim of a basic intelligent transportations system platform and telematics fleet management.
International Journal of Advanced Computer Science and Applications, 2015
By nodal regression and apsidal precession, the Earth flattering at satellite low Earth orbits (L... more By nodal regression and apsidal precession, the Earth flattering at satellite low Earth orbits (LEO) is manifested. Nodal regression refers to the shift of the orbit's line of nodes over time as Earth revolves around the Sun. Nodal regression is orbit feature utilized for circular orbits to be Sun synchronized. A sun-synchronized orbit lies in a plane that maintains a fixed angle with respect to the Earth-Sun direction. In the low Earth Sun synchronized circular orbits are suited the satellites that accomplish their photo imagery missions. Nodal regression depends on orbital altitude and orbital inclination angle. For the respective orbital altitudes the inclination window for the Sun synchronization to be attained is determined. The apsidal precession represents major axis shift, respectively the argument of perigee deviation. The apsidal precession simulation, for inclination window of sun synchronized orbital altitudes, is provided through this paper.
2015 International Wireless Communications and Mobile Computing Conference (IWCMC), 2015
The proliferation of corporate and end user mobile internet services offered for smartphones and ... more The proliferation of corporate and end user mobile internet services offered for smartphones and tablets, makes it necessary to monitor the quality of service and experience provided by mobile internet service providers. In this context, we introduce a low cost tool for monitoring network parameters as received signal power and network responding time. The application is used for signal and latency monitoring for fast and slow moving users in a surveyed area especially for in car communication. The developed application can be useful for mobile operators in order to improve their network quality as well as for end users who can get an insight into the quality of service offered by their service provider. In the proposed application, two software tools are used; first, the capabilities of the android programming interface and second the PHP scripting for measured data post-processing and reporting on web servers. The application is currently tested in Tirana, Albania for evaluating the network parameters of mobile providers showing that only monitoring the received signal power level is not sufficient for assuming a good quality of service.
A ground-backed slim slot-sinuous antenna is analyzed. Proposed configuration allows for a single... more A ground-backed slim slot-sinuous antenna is analyzed. Proposed configuration allows for a single lobe, polarization-versatile, high efficiency and ultra-wide band antenna not needing a the cumbersome lossy back cavity typical of conventional single lobe sinuous antennas. Simulations shows attained performances as well as tuning possibilities.
The transition between a Coplanar Waveguide to Coplanar Waveguide for Flip-Chip bump-based mounti... more The transition between a Coplanar Waveguide to Coplanar Waveguide for Flip-Chip bump-based mounting is here analyzed via a full wave Finite Element based analysis. Such analysis is carried on so as to minimize the reflection coefficient. A preliminary tolerance analysis for chip mounting is also presented.
The transfer of satellites in too high orbits as geosynchronous one (geostationary), usually is a... more The transfer of satellites in too high orbits as geosynchronous one (geostationary), usually is achieved firstly by launching the satellite in Low Earth Orbit (LEO), then in elliptical transfer orbit and finally to the geosynchronous orbit. The three steps process is known as Hohmann transfer. The Hohmann transfer which involves two circular orbits with different orbital inclinations is known as non-coplanar Hohmann transfer. If both orbital planes are aligned the Hohmann transfer is known as coplanar what is further considered in this paper. In terms of propellant consumptions the Hohmann transfer is the best known transfer to be applied when transferring between circular coplanar orbits. For transfer between circular coplanar orbits, the given information usually consists of the radii of the initial and final orbits. The velocity to be applied into two orbit points in order to attain the dedicated final orbit is analyzed. The aim of this paper is to conclude about the velocitiy changes under the different initial low Earth altitudes. For different initial orbit altitudes, the velocities to be applied in process of Hohmann transfer are simulated. From respective simulations, the velocity variations on dependence of initial altitudes are derived. The eccentricity is considered, too.
Wiley Encyclopedia of Electrical and Electronics Engineering, 2014
Designing an electronic system is an engineering task bound to the satisfaction of a given set of... more Designing an electronic system is an engineering task bound to the satisfaction of a given set of requirements. If it is possible to express the compliance of the system to the requirements in a mathematical form giving a measure of how much a given system is far from compliance, then it would be possible to obtain the desired performances by seeking for the minimum of such a function. Seeking the minimum of a function is a daunting task to which a whole branch of mathematics, optimization, is devoted. In the case in which the design must comply to several requirements, it is usually more practical and interesting to define a set of functions to be minimized altogether. In this case the search for an optimal point, or a set of points, can be performed by applying a multi-objective optimization technique. This chapter will investigate popular multi-objective optimization techniques, giving both their basics and describing recent advancements. For the selected techniques, performances over a set of benchmarks will be presented, as well as results over relevant electronic engineering problems. Keywords: multi-objective optimization; evolutionary algorithms; genetic algorithms
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Papers by Elson Agastra