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51.
Prospects for lensed supernovae behind galaxy clusters with the James Webb Space Telescope
Tanja Petrushevska, 2018, published scientific conference contribution abstract

Abstract: Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. I will also report our discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia. I will also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST).
Keywords: Strong lensing, Hubble constant, measuring expansion history with time delays, lensed supernovae
Published in RUNG: 09.07.2018; Views: 3481; Downloads: 139
.pdf Full text (4,14 MB)

52.
Negative field‐dependent charge mobility in crystalline organic semiconductors with delocalized transport
Fei Tong, Andrey Kadashchuk, Egon Pavlica, Gvido Bratina, 2018, original scientific article

Abstract: Charge-carrier mobility has been investigated by time-of-flight (TOF) transient photocurrent in a lateral transport con- figuration in highly crystalline thin films of 2,7-dioctyl[1]benzothieno [3,2-b][1] benzothiophene (C8-BTBT) grown by a zone-casting alignment technique. High TOF mobility has been revealed that it is consistent with the delocalized nature of the charge transport in this material, yet it featured a positive temperature dependence at T ≥ 295 K. Moreover, the mobility was surprisingly found to decrease with electric field in the high-temperature region. These observations are not compat- ible with the conventional band-transport mechanism. We have elaborated an analytic model based on effective-medium approximation to rationalize the puzzling findings. The model considers the delocalized charge transport within the energy landscape formed by long-range transport band-edge variations in imperfect organic crystalline materials and accounts for the field-dependent effective dimensionality of charge transport percolative paths. The results of the model calculations are found to be in good agreement with experimental data.
Keywords: time of flight, organic semiconductors, single crystals
Published in RUNG: 07.05.2018; Views: 5224; Downloads: 0
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53.
Role of transport band edge variation on delocalized charge transport in high-mobility crystalline organic semiconductors
Gvido Bratina, Andrey Kadashchuk, Egon Pavlica, Fei Tong, 2017, original scientific article

Abstract: We demonstrate that the degree of charge delocalization has a strong impact on polarization energy and thereby on the position of the transport band edge in organic semiconductors. This gives rise to long-range potential fluctuations, which govern the electronic transport through delocalized states in organic crystalline layers. This concept is employed to formulate an analytic model that explains a negative field dependence coupled with a positive temperature dependence of the charge mobility observed by a lateral time-of-flight technique in a high-mobility crystalline organic layer. This has important implications for the further understanding of the charge transport via delocalized states in organic semiconductors.
Keywords: organic semiconducotrs, time of flight, transport
Published in RUNG: 13.09.2017; Views: 4215; Downloads: 0
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54.
Introduction to Electronic Properties and Dynamics of Organic Complexes as Self‐Assembled Monolayers
Maddalena Pedio, 2017, independent scientific component part or a chapter in a monograph

Abstract: Self‐assembled monolayers (SAMs) of organic‐conjugated transition metal complexes on surfaces is a focus of both device engineering and basic science, since it is a key factor in nearly all important aspects of device performances, including operation voltages, degradation, and efficiency. The huge amount of literature results related to the first monolayer, and reorganization and self‐assembling processes are due to the general accepted result that structural and chemical properties of the first monolayer are the key parameters for controlled thin film growth. Optical and magneto‐electronic properties are intimately connected, and the accurate determination of electronic levels, excitation, and relaxation dynamics is mandatory for the optimization of electronic, photovoltaic, and opto‐electronic devices. Quite a number of electronic states is generated by the interaction of light with complex organic molecules. Time‐resolved spectroscopies are a new investigation tool that gives the possibility of correctly addressing their origin and life time. Examples of prototypical systems are presented and discussed. We review on complementary techniques, trying to single out how different approaches are fundamental to fully characterize these complex systems.
Keywords: self‐assembled monolayer (SAM), surface structures molecular layers, nanotechnology, electronic properties, spectroscopies, time resolved
Published in RUNG: 12.06.2017; Views: 4505; Downloads: 208
.pdf Full text (5,78 MB)

55.
Stability by linear approximation for time scale dynamical systems
Sergey Kryzhevich, Alexander Nazarov, 2017, original scientific article

Abstract: We study systems on time scales that are generalizations of classical differential or difference equations and appear in numerical methods. In this paper we consider linear systems and their small nonlinear perturbations. In terms of time scales and of eigenvalues of matrices we formulate conditions, sufficient for stability by linear approximation. For non-periodic time scales we use techniques of central upper Lyapunov exponents (a common tool of the theory of linear ODEs) to study stability of solutions. Also, time scale versions of the famous Chetaev’s theorem on conditional instability are proved. In a nutshell, we have developed a completely new technique in order to demonstrate that methods of non-autonomous linear ODE theory may work for time-scale dynamics.
Keywords: Time scale system, Linearization, Lyapunov functions, Millionschikov rotations, Stability
Published in RUNG: 15.03.2017; Views: 3955; Downloads: 160
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The role of local potential minima on charge transport in thin organic semiconductor layers
Egon Pavlica, Raveendra Babu Penumala, Gvido Bratina, 2016, original scientific article

Abstract: We have performed a systematic study of dependence of time-resolved photocurrent on the point of charge excitation within the organic semiconductor channel formed by two coplanar metal electrodes. The results confirm that spatial variation of electric field between the electrodes crucially determines transport of photogenerated charge carriers through the organic layer. Time-of-flight measurements of photocurrent demonstrate that the transit time of photogenerated charge carrier packets drifting between the two electrodes decreases with increasing travelling distance. Such counterintuitive result cannot be reconciled with the spatial distribution of electric field between coplanar electrodes, alone. It is also in contrast to expected role of space-charge screening of external electric field. Supported by Monte Carlo simulations of hopping transport in disordered organic semiconductor layer, we submit that the space-charge screens the external electric field and captures slower charge carriers from the photogenerated charge carrier packet. The remaining faster carriers, exhibit velocity distribution with significantly higher mean value and shorter transit time.
Keywords: Charge transport, Organic semiconductors, Time of flight, Mobility, Traps
Published in RUNG: 23.12.2016; Views: 5289; Downloads: 0
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59.
Time restrictions in forest operations planning
Boštjan Kepic, 2016, master's thesis

Abstract: This master’s thesis deals with annual harvest operations (AHO) planning with consideration of time restrictions. We developed five models of binary integer linear programming (BILP) that schedule working groups to harvest unit areas (HUAs) according to the lowest cost possible. Total AHO costs include felling and skidding costs, transportation costs, and machine relocation costs. The first model is based on the presumption that harvesting can be planned and executed freely throughout the year. In other four, scheduling was subject to time restrictions in HUAs and differed according to the extent of time restrictions. The second model takes into account time restrictions due to unfavourable natural conditions, the third model due to disturbance-free areas of animal species, the fourth and fifth model concurrently include the impact of time restrictions due to natural conditions and disturbance-free areas. The annual workplace time in Model 2 is reduced by 14.2 %, in Model 3 by 16.9 %, in Model 4 by 29.3 % and in Model 5 by 42.3 %. The model tool used to test all the models was designed in Microsoft Excel. All five models were tested with OpenSolver 2.7.1 software. Increasing the extent of time restrictions in forest operations reduces the utilization of the annual workplace time. In testing the second model, we demonstrated that with proper organisation of an AHO plan the planner can influence the working days fallout. In the other three models, we were able to ensure the implementation of AHO plan by introducing extra working groups. Further, we confirmed that time restrictions affect the scheduling of the working groups and the sequencing of tasks. The increases in total AHO costs were explained as an increase in working groups’ costs due to lower utilization rate, an increase in depreciation costs of machines and costs due to unrealized allowable annual cut and timber sales planned for the current year. We tested each model on two examples.
Keywords: time restrictions, binary integer programming, forestry, annual harvest operations planning, harvesting, scheduling working teams
Published in RUNG: 20.09.2016; Views: 6419; Downloads: 250
.pdf Full text (4,11 MB)

60.
About Time
Una Rebić, 2016, master's thesis

Abstract: The practical work of my master project about time was carried out as processbased experiments in practice. As a result, the thesis is a combination of theoretical research taken from several fields—examining the notion of time from perspective of psychology, sociology, science and spirituality. Alongside mentioned research the thesis pairs artistic practices associated with each field discussed— considering most significant artist and his/her practice or project(s) in which they explore time. The third layer of the thesis pairs each section with my own personal practice through experiments carried out in the process—each exploring time from a different perspective. Since the thesis is the final project of the study developed within a certain time frame, the last chapter discusses how I approached this project in regard to my artistic practice.
Keywords: time, perception, On Kawara, sociology, speed, Hamish Fulton, quantum entanglement, arrow of time, Hiroshi Sugimoto, spirituality, consciousness, Marina Abramović, Ulay
Published in RUNG: 14.09.2016; Views: 4595; Downloads: 1
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