Aušrius Juozapavičius | The General Jonas Žemaitis Military Academy of Lithuania (original) (raw)

Uploads

Papers by Aušrius Juozapavičius

The article analyzes problems of Vilnius city transportation system and reveals drawbacks of stre... more The article analyzes problems of Vilnius city transportation system and reveals drawbacks of street infrastructure and traffic organization, which are responsible for traffic congestion and its consequences in many cities including Vilnius. A new high capacity road interchange Pinavia is presented. Mathematical model of the new interchange is described enabling to optimize and adapt it in a given location. Unique features of the new Pinavia interchange are used to develop an improvement strategy of Vilnius city transportation system.

Journal of Cybersecurity, 2022

Active usage of threat intelligence information supports effective prevention, mitigation and def... more Active usage of threat intelligence information supports effective prevention, mitigation and defence against cyberattacks by threat actors ranging from individual amateurs to state organizations. However, threat intelligence highly depends on security specialists’ ability to share incident data on threat information-sharing platforms. Unfortunately, business managers and educational institutions undervalue the information-sharing aspect when planning the professional development of cybersecurity-related specialists. Consequently, cybersecurity specialists are insufficiently motivated to correctly communicate and propagate relevant information with team members, superiors, relevant institutions and the global community about the impact of the incident. Literature review reveals many technological, legal and psychological obstacles hindering successful information exchange. This research aims to improve threat information sharing by focusing on the educational aspect of the problem a...

Applied Sciences

Password hygiene plays an essential part in securing systems protected with single-factor authent... more Password hygiene plays an essential part in securing systems protected with single-factor authentication. A significant fraction of security incidents happen due to weak or reused passwords. The reasons behind differences in security vulnerable behaviour between various user groups remains an active research topic. The paper aims to identify the impact of age and gender on password strength using a large password dataset. We recovered previously hashed passwords of 102,120 users from a leaked customer database of a car-sharing company. Although the measured effect size was small, males significantly had stronger passwords than females for all age groups. Males aged 26–45 were also significantly different from all other groups, and password complexity decreased with age for both genders equally. Overall, very weak password hygiene was observed, 72% of users based their password on a word or used a simple sequence of digits, and passwords of over 39% of users were found in word lists ...

Acta Physica Polonica A, 2005

We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the... more We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/AlGaAs superlattice after pulsed optical excitation at low temperature. The electric field dynamics is investigated by tracing the spectral position of the Wannier–Stark transitions as a function of delay time. We determine the electron sweep-out time, extract detailed information about the picosecond-time-scale drift of the charge carriers by comparing the measured data with the results of semi-classical self-consistent model calculations, and evaluate the two experimental techniques with respect to their ability to provide information about the carrier and field dynamics.

Rising numbers and sophistication of security threats in the digital domain cause an increase in ... more Rising numbers and sophistication of security threats in the digital domain cause an increase in the demand for skilled cybersecurity professionals. In response, cybersecurity exercises, and in particular—cyber defence exercises (CDX) are becoming ever more popular. They provide a training platform to simulate real-life situations. CDX are significant events involving months of preparation, and previous studies show a lack of objective evidence of their relevance regarding the learning impact. Skills of exercise participants are usually different and vary from tech-savvy to beginners. Also, trainees are diverse when considering their background, current work profile (position and institution), and experience. Assessment of their competencies is essential to ensure quality in training. The complexity and multi-dimensionality of the usual CDX make it challenging. Additionally, the costly event usually focuses on just a subset of participants, and non-technical members of an organisati...

Growing world population and increasing urbanization continues to stress cities and negatively im... more Growing world population and increasing urbanization continues to stress cities and negatively impact people mobility. Morning and evening peaks of traffic congestion threaten to merge into a continuous never-ending congestion. Two main causes create this problem: an over-concentration of working places in city centers and a dis-proportionately large share of private cars in the traffic. Ownership and use of private vehicles are naturally encouraged by a typical layout of modern cities with living areas in suburbs which are dissolving passenger flows and making public transport ineffective there. A classical Park & Ride system is designed to attract and eliminate private cars coming from suburbs and transfer passengers to public transport for further travel towards the city center. However, most of these systems have limitations - if the parking space is large enough it requires a lot of real estate and it is difficult to access and exit, and if it is small enough to be convenient i...

Environmental Research Engineering and Management, Oct 19, 2010

ABSTRACT

We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al0.3Ga0.7As superlatti... more We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al0.3Ga0.7As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of the densities of electrons and holes and on the internal electric field is obtained by tracing Wannier-Stark photocurrent spectra as a function of delay time for various bias fields and pump excitation intensities. The experimental results are supplemented by simulations. We employ the combined information to define the conditions to be met for succesful pump-probe Bloch gain experiments. In particular, we find that field screening sets on upper limit for the carrier density of 1016 cm–3, and that the time window during which gain should be found is defined by the duration of the sweep-out of the optically injected electrons from the superlattice which occurs within about 10 ps after excitation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

City road transport contributes significantly to climate change, and the ongoing world urbanizati... more City road transport contributes significantly to climate change, and the ongoing world urbanization is only increasing the problem. The paper describes a city planning concept minimizing the number of vehicles on the roads while increasing overall mobility. This becomes possible by utilizing a recently invented two-level road junction with a unique property of serving both as an intersection of uninterrupted traffic and an easily accessible transport hub capable of accumulating private vehicles, and therefore becoming an especially effective park-and-ride solution, and a logistics or business center. Optimized layouts of city road infrastructure, living and work areas, and major roads are presented. The layouts are suitable both for the development of new cities as well as for the expansion of existing ones. Costs of the infrastructure and a positive impact on climate are evaluated in comparison to current city growth patterns. Keywords—Congestion, city infrastructure, park-and-ride...

Semiconductor Science and Technology, 2004

ABSTRACT We propose a microwave diode based on a modulation-doped GaAs/Al0.25Ga0.75As structure. ... more ABSTRACT We propose a microwave diode based on a modulation-doped GaAs/Al0.25Ga0.75As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in microwave electric fields arising due to the asymmetric shape of the device. The voltage sensitivity of the diode at room temperature is close to 0.3 V W−1 at 10 GHz, which is comparable to the value obtained using similarly shaped and sized diodes based on bulk n-GaAs. At liquid nitrogen temperature, the voltage sensitivity strongly increases reaching a value of 20 V W−1 due to the high mobility of the two-dimensional electron gas. The detected signal depends linearly on power over 20 dB, until hot-electron real-space-transfer effects begin to predominate. We discuss noise temperature measurements at 10 GHz, consider the frequency dependence of the voltage sensitivity in the microwave range and compare the performance data of the proposed device and the asymmetrically shaped bulk GaAs diode within the 10 GHz–2.5 THz frequency range.

Applied Physics Letters, 2005

We report on photocurrent spectroscopy on undoped GaAs∕AlGaAs semiconductor superlattices subject... more We report on photocurrent spectroscopy on undoped GaAs∕AlGaAs semiconductor superlattices subjected to femtosecond optical excitation. The evolution of the carrier-drift-induced inhomogeneity of the electric field is studied by tracing the shifting and broadening of Wannier–Stark transitions as a function of delay time and bias field. Based on experimental data and results of numerical simulations, we find that the superlattice rapidly splits into two moving field regions, one with strong field gradient and low electron density, the other with partially screened field at low gradient and high electron density. Concerning future Bloch-gain measurements, we find that gain is expected in spite of the inhomogeneous field if the electron-rich region is not heavily screened. The time window during which Bloch gain exists is determined by the sweep out of the electrons (10–30 ps).

We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al 0.3 Ga 0.7 As superl... more We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al 0.3 Ga 0.7 As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of the densities of electrons and holes and on the internal electric field is obtained by tracing Wannier-Stark photocurrent spectra as a function of delay time for various bias fields and pump excitation intensities. The experimental results are supplemented by simulations. We employ the combined information to define the conditions to be met for succesful pump-probe Bloch gain experiments. In particular, we find that field screening sets on upper limit for the carrier density of 10 16 cm-3 , and that the time window during which gain should be found is defined by the duration of the sweep-out of the optically injected electrons from the superlattice which occurs within about 10 ps after excitation.

The article analyzes problems of Vilnius city transportation system and reveals drawbacks of stre... more The article analyzes problems of Vilnius city transportation system and reveals drawbacks of street infrastructure and traffic organization, which are responsible for traffic congestion and its consequences in many cities including Vilnius. A new high capacity road interchange Pinavia is presented. Mathematical model of the new interchange is described enabling to optimize and adapt it in a given location. Unique features of the new Pinavia interchange are used to develop an improvement strategy of Vilnius city transportation system.

Journal of Cybersecurity, 2022

Active usage of threat intelligence information supports effective prevention, mitigation and def... more Active usage of threat intelligence information supports effective prevention, mitigation and defence against cyberattacks by threat actors ranging from individual amateurs to state organizations. However, threat intelligence highly depends on security specialists’ ability to share incident data on threat information-sharing platforms. Unfortunately, business managers and educational institutions undervalue the information-sharing aspect when planning the professional development of cybersecurity-related specialists. Consequently, cybersecurity specialists are insufficiently motivated to correctly communicate and propagate relevant information with team members, superiors, relevant institutions and the global community about the impact of the incident. Literature review reveals many technological, legal and psychological obstacles hindering successful information exchange. This research aims to improve threat information sharing by focusing on the educational aspect of the problem a...

Applied Sciences

Password hygiene plays an essential part in securing systems protected with single-factor authent... more Password hygiene plays an essential part in securing systems protected with single-factor authentication. A significant fraction of security incidents happen due to weak or reused passwords. The reasons behind differences in security vulnerable behaviour between various user groups remains an active research topic. The paper aims to identify the impact of age and gender on password strength using a large password dataset. We recovered previously hashed passwords of 102,120 users from a leaked customer database of a car-sharing company. Although the measured effect size was small, males significantly had stronger passwords than females for all age groups. Males aged 26–45 were also significantly different from all other groups, and password complexity decreased with age for both genders equally. Overall, very weak password hygiene was observed, 72% of users based their password on a word or used a simple sequence of digits, and passwords of over 39% of users were found in word lists ...

Acta Physica Polonica A, 2005

We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the... more We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/AlGaAs superlattice after pulsed optical excitation at low temperature. The electric field dynamics is investigated by tracing the spectral position of the Wannier–Stark transitions as a function of delay time. We determine the electron sweep-out time, extract detailed information about the picosecond-time-scale drift of the charge carriers by comparing the measured data with the results of semi-classical self-consistent model calculations, and evaluate the two experimental techniques with respect to their ability to provide information about the carrier and field dynamics.

Rising numbers and sophistication of security threats in the digital domain cause an increase in ... more Rising numbers and sophistication of security threats in the digital domain cause an increase in the demand for skilled cybersecurity professionals. In response, cybersecurity exercises, and in particular—cyber defence exercises (CDX) are becoming ever more popular. They provide a training platform to simulate real-life situations. CDX are significant events involving months of preparation, and previous studies show a lack of objective evidence of their relevance regarding the learning impact. Skills of exercise participants are usually different and vary from tech-savvy to beginners. Also, trainees are diverse when considering their background, current work profile (position and institution), and experience. Assessment of their competencies is essential to ensure quality in training. The complexity and multi-dimensionality of the usual CDX make it challenging. Additionally, the costly event usually focuses on just a subset of participants, and non-technical members of an organisati...

Growing world population and increasing urbanization continues to stress cities and negatively im... more Growing world population and increasing urbanization continues to stress cities and negatively impact people mobility. Morning and evening peaks of traffic congestion threaten to merge into a continuous never-ending congestion. Two main causes create this problem: an over-concentration of working places in city centers and a dis-proportionately large share of private cars in the traffic. Ownership and use of private vehicles are naturally encouraged by a typical layout of modern cities with living areas in suburbs which are dissolving passenger flows and making public transport ineffective there. A classical Park & Ride system is designed to attract and eliminate private cars coming from suburbs and transfer passengers to public transport for further travel towards the city center. However, most of these systems have limitations - if the parking space is large enough it requires a lot of real estate and it is difficult to access and exit, and if it is small enough to be convenient i...

Environmental Research Engineering and Management, Oct 19, 2010

ABSTRACT

We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al0.3Ga0.7As superlatti... more We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al0.3Ga0.7As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of the densities of electrons and holes and on the internal electric field is obtained by tracing Wannier-Stark photocurrent spectra as a function of delay time for various bias fields and pump excitation intensities. The experimental results are supplemented by simulations. We employ the combined information to define the conditions to be met for succesful pump-probe Bloch gain experiments. In particular, we find that field screening sets on upper limit for the carrier density of 1016 cm–3, and that the time window during which gain should be found is defined by the duration of the sweep-out of the optically injected electrons from the superlattice which occurs within about 10 ps after excitation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

City road transport contributes significantly to climate change, and the ongoing world urbanizati... more City road transport contributes significantly to climate change, and the ongoing world urbanization is only increasing the problem. The paper describes a city planning concept minimizing the number of vehicles on the roads while increasing overall mobility. This becomes possible by utilizing a recently invented two-level road junction with a unique property of serving both as an intersection of uninterrupted traffic and an easily accessible transport hub capable of accumulating private vehicles, and therefore becoming an especially effective park-and-ride solution, and a logistics or business center. Optimized layouts of city road infrastructure, living and work areas, and major roads are presented. The layouts are suitable both for the development of new cities as well as for the expansion of existing ones. Costs of the infrastructure and a positive impact on climate are evaluated in comparison to current city growth patterns. Keywords—Congestion, city infrastructure, park-and-ride...

Semiconductor Science and Technology, 2004

ABSTRACT We propose a microwave diode based on a modulation-doped GaAs/Al0.25Ga0.75As structure. ... more ABSTRACT We propose a microwave diode based on a modulation-doped GaAs/Al0.25Ga0.75As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in microwave electric fields arising due to the asymmetric shape of the device. The voltage sensitivity of the diode at room temperature is close to 0.3 V W−1 at 10 GHz, which is comparable to the value obtained using similarly shaped and sized diodes based on bulk n-GaAs. At liquid nitrogen temperature, the voltage sensitivity strongly increases reaching a value of 20 V W−1 due to the high mobility of the two-dimensional electron gas. The detected signal depends linearly on power over 20 dB, until hot-electron real-space-transfer effects begin to predominate. We discuss noise temperature measurements at 10 GHz, consider the frequency dependence of the voltage sensitivity in the microwave range and compare the performance data of the proposed device and the asymmetrically shaped bulk GaAs diode within the 10 GHz–2.5 THz frequency range.

Applied Physics Letters, 2005

We report on photocurrent spectroscopy on undoped GaAs∕AlGaAs semiconductor superlattices subject... more We report on photocurrent spectroscopy on undoped GaAs∕AlGaAs semiconductor superlattices subjected to femtosecond optical excitation. The evolution of the carrier-drift-induced inhomogeneity of the electric field is studied by tracing the shifting and broadening of Wannier–Stark transitions as a function of delay time and bias field. Based on experimental data and results of numerical simulations, we find that the superlattice rapidly splits into two moving field regions, one with strong field gradient and low electron density, the other with partially screened field at low gradient and high electron density. Concerning future Bloch-gain measurements, we find that gain is expected in spite of the inhomogeneous field if the electron-rich region is not heavily screened. The time window during which Bloch gain exists is determined by the sweep out of the electrons (10–30 ps).

We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al 0.3 Ga 0.7 As superl... more We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al 0.3 Ga 0.7 As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of the densities of electrons and holes and on the internal electric field is obtained by tracing Wannier-Stark photocurrent spectra as a function of delay time for various bias fields and pump excitation intensities. The experimental results are supplemented by simulations. We employ the combined information to define the conditions to be met for succesful pump-probe Bloch gain experiments. In particular, we find that field screening sets on upper limit for the carrier density of 10 16 cm-3 , and that the time window during which gain should be found is defined by the duration of the sweep-out of the optically injected electrons from the superlattice which occurs within about 10 ps after excitation.