A fractional Brownian motion model for the turbulent refractive index in lightwave propagation

It is discussed the limitations of the widely used markovian approximation applied to model the turbulent refractive index in lightwave propagation. It is well-known the index is a passive scalar field. Thus, the actual knowledge about these quantities is used to propose an alternative stochastic process to the markovian approximation: the fractional Brownian motion. This generalizes the former introducing memory; that is, there is correlation along the propagation path.Comment: 11 pages, no figures. Submitted and revised for Optics Communication

Impact of turbulence in long range quantum and classical communications

The study of the free-space distribution of quantum correlations is necessary for any future application of quantum as classical communication aiming to connect two remote locations. Here we study the propagation of a coherent laser beam over 143 Km (between Tenerife and La Palma Islands of the Canary archipelagos). By attenuating the beam we also studied the propagation at the single photon level. We investigated the statistic of arrival of the incoming photons and the scintillation of the beam. From the analysis of the data, we propose the exploitation of turbulence to improve the SNR of the signal.Comment: 5 Pages, 5 figures, 1 Table, revtex

Entrepreneurial dimensions of higher education institutions in selected European countries

Predmet istraživanja doktorske disertacije je identifikovanje ključnih pokazatelja, faktora ili indikatora preduzetničke orijentacije u funkciji kreiranja modela merenja preduzetničkog potencijala univerziteta u uslovima dinamičkih promena. Fokus istraživanja je na analizi anketiranog i analiziranog uzorka koji obuhvata odredjeni broj univerziteta. Sa teritorije Republike Srbije, Republike Crne Gore, Bosne i Hercegovine, Republike Makedonije, Republike Hrvatske i Republike Slovenije. U samoj disertaciji nastojaće da se prikažu potencijalne sličnosti i razlike izmedju ove dve grupe zemalja, kao i na koji način i u kojoj meri su univerziteti povezani sa privredom i državom (Triple helix model).The subject of research of doctoral dissertations is the identification of key indicators, factors or indicators of entrepreneurial orientations in the function of creating a model for measuring the entrepreneurial potential of the university in the conditions of dynamic changes. The focus of the research was analyzed by a surveyed and analyzed sample covering a number of universities. From the territory of the Republic of Serbia, the Republic of Montenegro, Bosnia and Herzegovina, the Republic of Macedonia, the Republic of Croatia and the Republic of Slovenia. The dissertation itself tries to show the potential similarities and differences between these two groups of countries, as well as in what way and to what extent universities are connected with the economy and the state (Triple helix model)

Subsonic Boundary-Layer Wavefront Spectra for a Range of Reynolds Numbers

Aero-optic measurements of turbulent boundary layers were performed in wind tunnels at the University of Notre Dame and California Institute of Technology for heated walls at a range of Reynolds numbers. Temporally resolved measurements of wavefronts were collected at a range of Mach numbers between 0.03 and 0.4 and the range of Re_θ between 1,700 and 20,000. Wavefront spectra for both heated and un-heated walls were extracted and compared to demonstrate that wall heating does not noticeably alter the shape of wavefront spectra in the boundary layer. The effect of Reynolds number on the normalized spectra was also presented, and an empirical spectral model was modified to account for Reynolds number dependence. Measurements of OPD_(rms) for heated walls were shown to be consistent with results from prior experiments, and a method of estimating OPD_(rms) and other boundary layer statistics from wavefront measurements of heated-wall boundary layers was demonstrated and discussed

Effiziente und schnelle Verarbeitung von Netzwerkpakten mittels DPDK

Aufgrund der stetig wachsenden Anforderungen an die Netzinfrastruktur, stellt der Einsatz von leistungsstarken Switches und Netzwerkkarten, die Datenraten von bis zu 100 Gbit/s bereitstellen, eine wesentliche Bedeutung für Rechenzentren dar. Weil jedoch die Systemsoftware von Servern nicht für solch hohe E/A-Geschwindigkeiten konzipiert wurde, ist es kaum möglich das Leistungspotential dieser Netzwerkgeräte vollumfänglich auszuschöpfen. Neben der Übergabe von Anwendungslogik an den Gerätetreiber (z.B. mittels eBPF) oder dem direkten Speichertransfer (z.B. via RDMA) sind Kernel-Bypass-Lösungen ein leistungsstarker Optimierungsansatz, um dem hohen Datenaufgebot von heutigen Netzwerkschnittstellen standzuhalten. Das von Intel entwickelte Framework DPDK hat sich dabei in verschiedenen Benchmarks als performanteste Kernel-Bypass-Lösungen herausgestellt. Diese Arbeit wird deshalb schwerpunktmäßig die Datenstrukturen und Mechanismen untersuchen, welche den Leistungsunterschied von DPDK gegenüber vergleichbaren Frameworks möglich machen

The Effect of Plantarflexor Strength Training on Gait Biomechanics in Healthy Old Adults

Locomotion is an important and inherent part of daily life and is integral in maintaining an independent lifestyle, especially in older adults whose functional capacity has declined. Physiological changes with aging, including loss of muscle mass, strength and power are manifested in walking, notably at the ankle joint. Old adults exhibit decreased power of the plantarflexors and increased power of the hip extensors. This distal to proximal shift in function could be due to plantarflexor weakness, so strengthening the plantarflexors may help reverse the negative physiological effects of aging and help preserve functional capacity in old adults. The purpose of this study was to determine the effect of plantarflexor strength training on gait biomechanics during level walking at a self-selected, a safe maximum and a standard speed of 1.5 m/s in healthy old adults. A total of 12 healthy adults between the ages of 65 and 85 participated in this study (6 strengthening, 6 stretching). After baseline tests, the strengthening group performed resistance exercises for gastrocnemius and soleus muscles and the stretching group stretched them three times per week for 12 weeks. All subjects underwent gait assessments and maximal strength testing at the beginning and end of the 12 week training period. A 2 by 2 analysis of variance was used to determine significant interactions and main effects with an alpha level of p<0.05. Plantarflexor strength increased in the strengthening group but not for the stretching group. Compared to the pretest, the subjects in the stretching group walked significantly faster, took longer strides, increased peak plantarflexor torque and ground reaction force during the self-selected walking condition, while there were no changes in the strengthening group. Based on these results, a twelve week strength training program does not affect the gait biomechanics of healthy old adults while stretching does produce some changes to the gait biomechanics of healthy old adults.M.S

Wavefront sensing with a brightest pixel selection algorithm

Astronomical adaptive optics systems with open-loop deformable mirror control have recently come on-line. In these systems, the deformable mirror surface is not included in the wavefront sensor paths, and so changes made to the deformable mirror are not fed back to the wavefront sensors. This gives rise to all sorts of linearity and control issues mainly centred on one question: Has the mirror taken the shape requested? Non-linearities in wavefront measurement and in the deformable mirror shape can lead to significant deviations in mirror shape from the requested shape. Here, wavefront sensor measurements made using a brightest pixel selection method are discussed along with the implications that this has for open-loop AO systems. Discussion includes elongated laser guide star spots and also computational efficiency.Comment: 10 pages, 12 figures, accepted by MNRA

Gravitational Waves in the Nonsymmetric Gravitational Theory

We prove that the flux of gravitational radiation from an isolated source in the Nonsymmetric Gravitational Theory is identical to that found in Einstein's General Theory of Relativity.Comment: 10 Page