2015 - Repozytorium publikacji - Politechnika Gdańska

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Publikacje z roku 2015

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Face Recognition: Shape versus Texture
- Maciej Smiatacz
2015
This paper describes experiments related to the application of well-known techniques of the texture feature extraction (Local Binary Patterns and Gabor filtering) to the problem of automatic face verification. Results of the tests show that simple image normalization strategy based on the eye center detection and a regular grid of fiducial points outperforms the more complicated approach, employing active models that are able to accurately locate several landmarks. On the other hand, the proposed shape descriptor provides promising results, while the texture features appear to be very sensitive to realistic illumination changes.
Facial emotion recognition using depth data
- Mariusz Szwoch
- Pawel Pieniazek
2015
In this paper an original approach is presented for facial expression and emotion recognition based only on depth channel from Microsoft Kinect sensor. The emotional user model contains nine emotions including the neutral one. The proposed recognition algorithm uses local movements detection within the face area in order to recognize actual facial expression. This approach has been validated on Facial Expressions and Emotions Database using 169 recordings of 25 persons. Though an average recognition accuracy is slightly above 50% this approach is highly independent of illumination conditions and also accepts low distance between sensor and the user. Thus, the proposed approach can be used to support other algorithms based on optical channel, as well as using skeleton or face tracking information.
Facile preparation of extremely photoactive boron-doped TiO2 nanotubes arrays
- Mariusz Szkoda
- Katarzyna Siuzdak
- Anna Lisowska-Oleksiak
- Jakub Karczewski
- Jacek Ryl
2015 ELECTROCHEMISTRY COMMUNICATIONS
Doping of TiO2 nanotube arrays with boron was realized via electrochemical treatment of as-anodized titania immersed in electrolyte containing boric acid. The photoactivity of doped and pure titania was examined by means of photoelectrochemical and photocatalytic response under UV-vis irradiation. The results showed that photocurrent density of B-TNTs is remarkably higher (7.5 times) than density of pure TiO2 nanotube arrays. Furthermore, the usage of doped samples as a catalytic material leads to a significant improvement in decomposition efficiency of methylene blue and in the efficient formation of hydroxyl radicals than is the case in the presence of titania.
Factors influencing decisions to retire – case study of Poland
- Anita Richert-Kaźmierska
2015 Kwartalnik Prawo-Społeczeństwo-Ekonomia
The main objective of the article is to present the factors influencing the decisions of the Poles from the older age groups to withdraw from the labour market by retirement, or on the contrary – to remain economically active, also upon reaching the formal retirement age.
Fading Modelling in Dynamic Off-Body Channels
- Sławomir Ambroziak
- Kenan Turbić
- Carla Oliveira
- Luis M. Correia
- Ryszard Katulski
2015
This paper presents an off-body fading channel model for Body Area Networks (BANs) in indoor environments. The proposed model, which is based on both simulations and measurements in a realistic environment, consists of three components: mean path loss, body shadowing, and multipath fading. Seven scenarios in an indoor environment (a medium-size room with furniture, mostly consisting of wooden tables and chairs) have been measured: five were static (three standing and two sitting) and two dynamic (walk in a fixed place and real walk). The mean path loss component is modelled as a log function of distance, the path loss exponent being in the range between 0.4 and 1.6, while a statistical perspective is taken for the other two components, i.e., body shadowing is found to be well modelled by a Lognormal Distribution, and multipath fading by Rice or Nakagami-m Distributions, depending on body motion characteristics. The correlation between the selected distributions and empirical data is not lower than 0.95, typically being greater than 0.98. This model takes the statistical influence of various parameters and features present in BANs into account, such as body influence, placement of the wearable antennas, user orientation in the environment, dynamism of the BAN scenario, and propagation conditions.
Fast bubble dynamics and sizing
- Krzysztof Czarnecki
- Damien Fouan
- Younes Achaoui
- Serge Mensah
2015 JOURNAL OF SOUND AND VIBRATION
Single bubble sizing is usually performed by measuring the resonant bubble response using the Dual Frequency Ultrasound Method. However, in practice, the use of millisecond-duration chirp-like waves yields nonlinear distortions of the bubble oscillations. In comparison with the resonant curve obtained under harmonic excitation, it was observed that the bubble dynamic response shifted by up to 20 percent of the resonant frequency with bubble radii of less than 100 μm. In the case of low pressure waves (View the MathML source), an approximate formula for the apparent frequency shift is derived. Simulated and experimental bubble responses are analyzed in the time–frequency domain using an enhanced concentrated (reassigned) spectrogram. The difference in the resonant frequency resulted from the persistence of the resonant mode in the bubble response. Numerical simulations in which these findings are extended to pairs of coupled bubbles and to bubble clouds are also presented.
Fast collaborative graph exploration
- Dariusz Dereniowski
- Yann Disser
- Adrian Kosowski
- Dominik Pająk
- Przemysław Uznański
2015 Pełny tekst INFORMATION AND COMPUTATION
We study the following scenario of online graph exploration. A team of k agents is initially located at a distinguished vertex r of an undirected graph. At every time step, each agent can traverse an edge of the graph. All vertices have unique identifiers, and upon entering a vertex, an agent obtains the list of identifiers of all its neighbors. We ask how many time steps are required to complete exploration, i.e., to make sure that every vertex has been visited by some agent. We consider two communication models: one in which all agents have global knowledge of the state of the exploration, and one in which agents may only exchange information when simultaneously located at the same vertex. As our main result, we provide the first strategy which performs exploration of a graph with n vertices at a distance of at most D from r in time O(D), using a team of agents of polynomial size k=Dn^(1+ϵ)<n^(2+ϵ), for any ϵ>0. Our strategy works in the local communication model, without knowledge of global parameters such as n or D. We also obtain almost-tight bounds on the asymptotic relation between exploration time and team size, for large k. For any constant c>1, we show that in the global communication model, a team of k=Dn^c agents can always complete exploration in D(1+1/(c−1)+o(1)) time steps, whereas at least D(1+1/c−o(1)) steps are sometimes required. In the local communication model, D(1+2/(c−1)+o(1)) steps always suffice to complete exploration, and at least D(1+2/c−o(1)) steps are sometimes required. This shows a clear separation between the global and local communication models.
Fast EM-driven size reduction of antenna structures by means of adjoint sensitivities and trust regions
- Sławomir Kozieł
- Adrian Bekasiewicz
2015 IEEE Antennas and Wireless Propagation Letters
In this letter, a simple yet robust and computationally efficient optimization technique for explicit size reduction of antenna structures is presented. Our approach directly handles the antenna size as the main design objective, while ensuring satisfactory electrical performance by means of suitably defined penalty functions. For the sake of accuracy, the antenna structure is evaluated using high-fidelity EM simulation. In order to maintain computational efficiency of the design optimization process, it is carried out using cheap adjoint sensitivities and trust region framework utilized as convergence safeguard. Our technique is illustrated through a design of a compact quasi-isotropic dielectric resonator antenna and a UWB monopole. Numerical results are supported by physical measurements of a fabricated prototype.
Fast Multi-Objective Antenna Optimization Using Sequential Patching and Variable-Fidelity EM Models
- Sławomir Kozieł
- Adrian Bekasiewicz
2015
In this work, a technique for fast multi-objective design optimization of antenna structures is presented. In our approach, the initial approximation of the Pareto set representing the best possible trade-offs between conflicting design objectives is obtained by means of sequential patching of the design space. The latter is a stencil-based search that aims at creating a path that connects the extreme Pareto-optimal designs (obtained by means of single-objective optimization runs). For the sake of computational efficiency, the patching process is realized at the level of coarse-discretization EM simulation model. The final Pareto front is obtained through surrogate-based optimization, and it is reusing the EM simulation data acquired at the initial design stage. The proposed approach is demonstrated using the example of an ultra-wideband monopole antenna.
Fast Multi-Objective Optimization of Narrow-Band Antennas Using RSA Models and Design Space Reduction
- Sławomir Kozieł
- Adrian Bekasiewicz
2015 IEEE Antennas and Wireless Propagation Letters
Computationally efficient technique for multi-objective design optimization of narrow-band antennas is presented. In our approach, the corrected low-fidelity antenna model (obtained through coarse-discretization EM simulations) is enhanced using frequency scaling and response correction, sampled, and utilized to obtain a fast response surface approximation (RSA) antenna surrogate. The RSA model is constructed in the reduced design space. The initial set of Pareto-optimal designs is then utilized to confine the design space further by identifying designs that satisfy minimum requirements with respect to antenna reflection response. The updated RSA model set up in the confined space is subsequently optimized to yield the final Pareto set at the low computational cost. The proposed methodology is illustrated using the example of compact quasi-isotropic dielectric resonator antenna.
Fast Simulation-Driven Design of a Planar UWB Dipole Antenna with an Integrated Balun
- Sławomir Kozieł
- Stanislav Ogurtsov
- Włodzimierz Zieniutycz
- Adrian Bekasiewicz
2015
The paper presents a design of an ultra-wideband (UWB) antenna with an integrated balun. A fully planar balun interfacing the microstrip input of the structure to the coplanar stripline (CPS) input of the dipole antenna is introduced. The electromagnetic (EM) model of the structure includes the dipole, the balun, and the microstrip input to account for interactions over the UWB band. The EM model is adjusted for low reflection over the UWB band by means of fast simulation-driven surrogate-based optimization. This allows us to obtain the final design at low computational costs. Measurements of the manufactured optimal design validate the use of the balun as well as the design approach.
Fault diagnosing system of wheeled tractors
- Ryszard Arendt
- Ryszard Michalski
2015
A defect of complex wheeled tractor assembles most frequently negative influence on exploitation efficiency, safety and exhaust gases emission. Structure complexity of wheeled tractors requires more and more advanced diagnostic methods for identification of their serviceable possibilities as well in manufacturing step as in exploitation. In classical diagnosing methods of wheeled tractor defects states mapping by measured diagnostic parameters of different symptoms: operation’s efficiency, thermal state, vibrations, leak proof etc is applied. Diagnoses quality depends on knowledge level of defect mapping by diagnostic parameters. During realization of research projects occurring great disparity between data achieved from analytic models and from exploitation tests is indicated. In the elaboration mixed approach is applied connecting rule knowledge with phenomena knowledge about wheeled tractor defects, achieved from analytic (model), simulations and exploitations tests. Correctness are recognized, i.e. relationships and connections between occurring phenomena in destruction process of wheeled tractors, which we can assign features of stability, significance and necessity, what constitutes about fault diagnostics. Aspiration of the authors was dissemination relatively new and original information techniques and methods of diagnostic relation creations and on this base to elaborate mechatronic diagnostic system of wheeled tractor. The proposed set of diagnostic methods based on application on-line diagnosing of wheeled tractor and simultaneously (parallel) measurement of some chosen diagnostic signals, to reduce diagnoses’ risk and to create trustworthy database about critical faults and essential for operation, safety and emission of wheeled tractor. In the elaboration modern technical solutions of wheeled tractors, applied monitoring, diagnostic devices, used methods and diagnostic models are presented. Application of board networks especially CANS networks with DeviceNet and CANopen protocols are shown. Developed hardware structure of mechatronic diagnostic system and developed software is described. Operation of the diagnostic system by registered plots of chosen diagnostic signals is illustrated.
FDTD-Compatible Green's function based on scalar discrete Green's function and multidimensional Z-transform
- Tomasz Stefański
2015
In this contribution, a new formulation of the discrete Green's function (DGF) is presented for the finitedifference time-domain (FDTD) grid. Recently, dyadic DGF has been derived from the impulse response of the discretized scalar wave equation (i.e., scalar DGF) with the use of the multidimensional Z-transform. Its software implementation is straightforward because only elementary functions are involved and a single function requires computations in the multipleprecision arithmetic. Since the proposed formulation is based on scalar DGF, it allows to estimate steady-state values of dyadic DGF with the use of the windowing technique applied to scalar DGF. Applications of the proposed DGF formulation are demonstrated in basic simulation scenarios facilitated by the time-domain diakoptics approach.
FE investigations of the effect of fluctuating local tensile strength on coupled energetic-statistical size effect in concrete beams
- Ewelina Korol
- Andrzej Tejchman-Konarzewski
- Z. Mróz
2015 ENGINEERING STRUCTURES
The effect of fluctuating local tensile strength on a coupled energetic-statistical size effect in plain concrete beams under bending was numerically investigated. First, the influence of varying autocorrelation length of the random field describing a spatial variation of local tensile strength was studied. Next, the influence of the coefficient of variation of local tensile strength was analyzed. The numerical FE investigations were performed for unnotched concrete beams of similar geometry under quasi-static three point bending within elasto-plastic model assumptions, accounting for non-local softening. The FE analyses were carried out for four different beam sizes. In the calculations, the tensile strength took the form of spatially correlated random field described by a Gaussian distribution. FE investigations of the effect of fluctuating local tensile strength on coupled energetic–statistical size effect in concrete beams. Available from: http://www.researchgate.net/publication/282353190_FE_investigations_of_the_effect_of_fluctuating_local_tensile_strength_on_coupled_energeticstatistical_size_effect_in_concrete_beams [accessed Dec 2, 2015].
Feasibility Study for Food Intake Tasks Recognition Based on Smart Glasses
- Martin Biallas
- Aliaksei Andrushevich
- Rolf Kistler
- Alexander Klapproth
- Krzysztof Czuszyński
- Adam Bujnowski
2015 Journal of Medical Imaging and Health Informatics
In this exploratory study 13 adult test subjects have performed different food intake tasks while wearing a three axis accelerometer mounted at a temple of glasses. Two different algorithms for task recognition have been applied and compared. The retrospective data processing leads to better task recognition results when the frequency range of 50 Hz to 100 Hz is analysed within accelerometer signal recordings. A straightforward variance threshold algorithm is able to detect the intake of crunchy food with a sensitivity of 0.923 and a specificity of 0.991. Furthermore it identifies calm behaviour of test subjects with a sensitivity of 0.923 and a specificity of 0.914. Drinking from a cup can be detected with a sensitivity of 0.846 and a specificity of 0.986 by application of a k-nearest neighbour classification approach. By demonstrating the feasibility to recognise different food intake tasks based on analysing the acceleration of glasses, the door for employing accelerometer related data from smart glasses also in specific domains, such as dietary profiling, has been opened.
FEM modelling of stress and strain distribution in weld joints of steel sandwich panels
- Janusz Kozak
- Karol Niklas
2015 Welding International
The development of laser welding technology has enabled the mass production of thin-walled structures, including steel sandwich panels. The technology of joining plating panels with stiffeners by welding allows us to create joints with a specific geometry and material properties. In comparison with other types of joints, laser welds are characterized by their specific behaviour under cyclic load and, as a consequence, a different model of fatigue damage. The basis of fatigue analysis of laser-welded joints was the determination of stress concentrations in the notches. For this purpose, a numerical finite element method model of a laser-welded joint was created. The article presents the main aspects of the numerical model and the results concerning the influence of the modelling method on the strain and stress distribution in the notches. For the weld root notch, the theoretical results have been compared with experimental data of strain distributions obtained by the laser extensometry grid technique.
Fenomenologi Husserla a tradycja filozofii transcendentalnej
- Andrzej Lisak
2015 Pełny tekst Archiwum Historii Filozofii i Myśli Społecznej
Celem tekstu jest opisanie miejsca transcendentalnej fenomenologii Husserla w obrębie pokantowskiej filozofii transcendentalnej.
Ferro- and antiferro-magnetism in (Np, Pu)BC
- Tomasz Klimczuk
- A. Shick
- Agnieszka Kozub
- J.-C. Griveau
- E. Colineau
- M. Falmbigl
- F. Wastin
- P. Rogl
2015 Pełny tekst APL Materials
Two new transuranium metal boron carbides, NpBC and PuBC, have been synthesized. Rietveld refinements of powder XRD patterns of {Np,Pu} BC confirmed in both cases isotypism with the structure type of UBC. Temperature dependent magnetic susceptibility data reveal antiferromagnetic ordering for PuBC below T-N = 44 K, whereas ferromagnetic ordering was found for NpBC below T-C = 61 K. Heat capacity measurements prove the bulk character of the observed magnetic transition for both compounds. The total energy electronic band structure calculations support formation of the ferromagnetic ground state for NpBC and the antiferromagnetic ground state for PuBC.
Fertility rebound and economic growth. New evidence for 18 countries over the period 1970-2011.
- Piotr Dominiak
- Ewa Lechman
- Anna Okonowicz
2015 Pełny tekst EQUILIBRIUM Quarterly Journal of Economics and Economic Policy
Long-run impact of economic growth on fertility trends is ambiguous and sensitive for in-time variations. Noticeably, over last decades, economic growth has led in many countries to significant falls in total fertility rates. However, recently, in high-income economies a kind of ‘fertility rebound’ emerged (Goldstein, 2009; Luci and Thevenon, 2011; Day, 2012), which supports the hypothesis that reversal trends in total fertility rates are mainly attributed to economic growth. The paper unveils the relationship between total fertility rate changes and economic growth in 18 selected countries with fertility rebound observed, over the period 1970-2011, and detects the GDP-threshold at which the fertility rebound emerged. To report on the relationship we deploy longitudinal data analysis assuming non-linearity between examined variables. Data applied are exclusive derived from World Development Indicators 2013. Our main findings support the hypothesis on U-shaped relationship between total fertility rate and economic growth in analyzed countries in 1970-2011. Along with the previous we project the minimum level of GDP per capita (GDP-threshold) when the fertility rebound takes place.
Field investigations of stack ventilation in a residential building with multiple chimneys and tilted window in cold climate
- Marek Krzaczek
- Jarosław Florczuk
- Andrzej Tejchman-Konarzewski
2015 ENERGY AND BUILDINGS
Artykuł przedstawia wyniki pomiarów wykonanych w budynku mieszkalnym w północnej Polsce w zimnym klimacie podczas zimy i lata. Budynek zawierał kominy i uchylne okna. Pomierzono lokalne i wewnętrzne warunki klimatu oraz prędkości powietrza. Zaproponowano zmodyfikowany model uchylnych okien oparty na modelu wentylacji jednokierunkowej.