Risk factors for the occurrence of cardovascular system diseases in students

Background/Aim. Cardiovascular diseases are a leading cause of death in the majority of developed, as well as in many developing countries. The aim of this study was to determine cardiovascular risk factors in student population and to suggest possible measures for prevention. Methods. The study was carried out during 2007-2008 at the School of Medicine, University of Niš. It included 824 students in their final year (220 males, 604 females). Results. There was no significant difference in prevalence of hypertension among the male (1.81%) and female students (0%). The prevalence of obesity (Body Mass Index - BMI > 30 kg/m2) was significantly higher (p < 0.001) in the male (7.27%) than in the female population (1.32%). Abdominal obesity was also more frequently encountered (p < 0.01) in the male (9.09%) than in female population (1.32%). Every fourth student smoked cigarettes with no significant difference between the male and female students. Alcohol consumption was a significantly higher problem (p < 0.001) in the male population (18.18%) than in the female one (2.65%). Physical inactivity was more often found (p < 0.001) in the female students (65.56%), than in male ones (36.36%). By the bivariate correlation of cardiovascular risk factors, it was determined that in the male student population systolic blood pressure correlated significantly with diastolic blood pressure, BMI and waist size, whereas age correlated with sistolic blood pressure, waist size and smoking. In the female students sistolic blood pressure correlated with diastolic blood pressure, BMI and waist size; diastolic blood pressure correlated with BMI and physical inactivity; cigarette smoking correlated with alcohol consumption and age. Conclusion. Cardiovascular risk factors are present in the final-year students of the School of Medicine, University of Niš. It is necessary to insist on decreasing obesity prevalence, cigarette and alcohol consumption, and on increasing physical activity of students in order to prevent cardiovascular diseases

Strategy for implementing stabilizer-based codes on solid-state qubits

We present a method for implementing stabilizer-based codes with encoding schemes of the operator quantum error correction paradigm, e.g., the "standard" five-qubit and CSS codes, on solid-state qubits with Ising or XY-type interactions. Using pulse sequences, we show how to induce the effective dynamics of the stabilizer Hamiltonian, the sum of an appropriate set of stabilizer operators for a given code. Within this approach, the encoded states (ground states of the stabilizer Hamiltonian) can be prepared without measurements and preserved against both the time evolution governed by the original qubit Hamiltonian, and energy-nonconserving errors caused by the environment.Comment: 5 pages, 1 figur

Preserving universal resources for one-way quantum computing

The common spin Hamiltonians such as the Ising, XY, or Heisenberg model do not have ground states that are the graph states needed in measurement-based quantum computation. Various highly-entangled many-body states have been suggested as a universal resource for this type of computation, however, it is not easy to preserve these states in solid-state systems due to their short coherence times. Here we propose a scheme for generating a Hamiltonian that has a cluster state as ground state. Our approach employs a series of pulse sequences inspired by established NMR techniques and holds promise for applications in many areas of quantum information processing.Comment: 5 pages, 2 figure

Neutral edge modes in a superconductor -- topological-insulator hybrid structure in a perpendicular magnetic field

We study the low-energy edge states of a superconductor -- 3D topological-insulator hybrid structure (NS junction) in the presence of a perpendicular magnetic field. The hybridization of electron-like and hole-like Landau levels due to Andreev reflection gives rise to chiral edge states within each Landau level. We show that by changing the chemical potential of the superconductor, this junction can be placed in a regime where the sign of the effective charge of the edge state within the zeroth Landau level changes more than once resulting in neutral edge modes with a finite value of the guiding-center coordinate. We find that the appearance of these neutral edge modes is related to the level repulsion between the zeroth and the first Landau levels in the spectra. We also find that these neutral edge modes come in pairs, one in the zeroth Landau level and its corresponding pair in the first.Comment: 5 page

Electron-phonon coupling in crystalline organic semiconductors: Microscopic evidence for nonpolaronic charge carriers

We consider electron(hole)-phonon coupling in crystalline organic semiconductors, using naphthalene for our case study. Employing a first-principles approach, we compute the changes in the self-consistent Kohn-Sham potential corresponding to different phonon modes and go on to obtain the carrier-phonon coupling matrix elements (vertex functions). We then evaluate perturbatively the quasiparticle spectral residues for electrons at the bottom of the lowest-unoccupied- (LUMO) and holes at the top of the highest-occupied (HOMO) band, respectively obtaining $Z_e\approx 0.74$ and $Z_h\approx 0.78$. Along with the widely accepted notion that the carrier-phonon coupling strengths in polyacenes decrease with increasing molecular size, our results provide a strong microscopic evidence for the previously conjectured nonpolaronic nature of band-like carriers in these systems.Comment: final, published versio

Legal Aspects of Tourism Development in Serbia

The tourism industry has recorded significant results both in the world and at the level of individual countries. The tourism destination policy is realized through the adoption of appropriate regulations and supporting documents. Therefore, the aim of the paper is to evaluate the Serbian legislation in this field, with an emphasis on the Law on Tourism. An analysis of the current regulations (laws, strategies, master plans, and rule books) was carried out. The results pointed to the key tourist products and sites followed by statistical data. At the same time, the organization of the tourism and hospitality sector was presented, with the rights and obligations of all stakeholders. It was pointed out the significance of the Tourism Registry as a unique base in Serbian tourism. Finally, through the SWOT analysis, all good and bad aspects of this sector were presented as well as possible challenges in the future

JOINT ESTIMATION OF STATES AND PARAMETERS OF LINEAR SYSTEMS WITH PARAMETER FAULTS UNDER NON-GAUSSIAN NOISES

Joint estimation of states and time-varying parameters of linear state space models is of practical importance for the fault diagnosis and fault tolerant control. Previous works on this topic consider the joint estimation in the Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of the joint parameter-state robust estimation of linear state space models in the presence of non-Gaussian noises. The case of parameter-dependent matrices is considered. Because of its good features in robust filtering, the extended Masreliez-Martin filter represents a cornerstone for realization of the robust algorithms for joint state-parameter estimation of linear time-varying stochastic systems in the presence of non-Gaussian noises. The good features of the proposed robust algorithm for joint estimation of linear time-varying stochastic systems are illustrated by intensive simulations

Vibration and stability of systems of elastically connected Timoshenko beams

The presented work consists of seven parts which are separately formed by chapters. The first chapter relates to the introductory discussion and review of previous research in the theory of elastic and related damaged structures. It is one of the ways to perform partial differential equations of motion of mechanical systems and provides a basic overview of the methods used. Chapters 2-6 are devoted to the analysis of linear elastic oscillations. The seventh chapter is devoted to geometric nonlinear oscillations of damaged beams using the new finite element method. Free oscillations and static stability of two elastically connected beams are considered in Chapter 2. At various examples it is shown analytically obtained results and impacts of some mechanical parameters of the system to the natural frequency and amplitudes. Verification of the obtained analytical results is shown by comparison with results of the existed classical models. New scientific contribution in this chapter is formulation of the new double-beam model described with new derived equations of motion with rotational inertia effects and with inertia of rotation with transverse shear (Timoshenko’s model, Reddy - Bickford 's model). It is formulized the static stability conditions of the two elastically connected beams of different types with analytical expressions for the values of critical forces. Numerical experiments confirmed the validity of the analytical results obtained by comparing the results of the models existing in the literature. From chapter 2 it can be concluded that the effects of rotational inertia and transverse shear must be taken into account in the model of thick beams because errors that occur by ignoring them increase with the mode of vibration. Chapter 3 presents the solution for forced vibrations of two elastically connected beams of Rayleigh’s, Timoshenko’s and Reddy – Bickford’s type under the influence of axial force. Scientific contribution is presented analytical solutions for forms of three types of forced vibration - Harmonic arbitrarily continuous excitation, the continuous uniform harmonic excitation and harmonic concentrated excitation. Analytical solutions were obtained by using the modal analysis method. The chapter also presents the analytical solutions of forced vibration for the case of harmonic excitation effects are concentrated on one of the beams under effect of compressive axial forces. Based on the results derived in this chapter, it can be made conclusion that the differences in the approximations of the solutions depending of the used model gave a good solutions just in case of Timoshenko and Reddy-Bickford theory for thick beams in higher modes. Classical theories don’t give a quite good results. Chapter 4 considers the static stability of the elastically connected two and three beams and single beam on elastic foundation. It is derived a new set of partial differential equations for static analysis of deflections and critical buckling force of the complex mechanical systems. It is analytically determined critical buckling force for each system individually. It is concluded that the system is the most stable in the case of one beam on elastic foundation. Chapters 5 and 6 analyzed free vibration of more elastically connected beams of Timoshenko and Reddy-Bickford's type on elastic foundation under the influence of axial forces. Analytical solutions for the natural frequencies and the critical force are determined by trigonometric method and verified numerically. Chapter 7 presents geometrically nonlinear forced vibrations of damaged Timoshenko beams. In the study it is developed new p-version of finite element method for damaged beams. The advantage of the new method is compared with the traditional method and provides better approximations of solutions with a small number of degrees of freedom used in numerical analysis. Scientific contribution is in two topics-computational mechanics and non-linear vibrations of beams. It is concluded that traditional method can’t give good approximations of solutions in the case of very small width of the damage. This benefit is also shown in comparison with obtained results in the commercial software Ansys. A new p-version finite element is suggested to deal with geometrically non-linear vibrations of damaged Timoshenko beams. The novelty of the p-element comes from the use of new displacement shape functions, which are function of the damage location and, therefore, provide for more efficient models, where accuracy is improved at lower computational cost. In numerical tests in the linear regime, coupling between cross sectional rotation and longitudinal vibrations is discovered, with longitudinal displacements suddenly changing direction at the damage location and with a peculiar change in the cross section rotation at the same place. Geometrically nonlinear, forced vibrations are then investigated in the time domain using Newmark’s method and further couplings between displacement components are found

Planiranje eksperimenta za robusnu identifikaciju dinamičkih sistema

Primenom principa crne kutije i teorija verovatnoće, stohastičkih procesa i matematičke statistike, uz korišćenje ulazno/izlaznih merenja razmatra se mogućnost dobijanja matematičkih modela. Okviri za dobijanje modela su opšti jer se pretpostavlja da su stohastički poremećaji negausovi. Takav model je preduslov za projektovanje široke klase industrijskih regulatora. Teorija planiranja eksperimenta ima važnu ulogu u povećanju brzine konvergencije rekurzivnih algoritama kao i u skraćenju vremena identifikacije. Povećana brzina konvergencije algoritama čini ih veoma povoljnim za praktičnu primenu. Ulazni signali za identifikaciju kreiraju se preko rekurzivne relacije za autokovarijacionu funkciju. Sinteza autokovarijacione funkcije zasnovana je na idejama iz prediktivnog upravljanja, pri čemu upravljački signal ima konačan alfabet. Praktična istraživanja pokazuju da poremećaj, u opštem slučaju, ima negausovu raspodelu. Posebno je važan slučaj kada se pojave opservacije koje su nekonzistentne u odnosu na glavninu populacije, autlajeri (outliers). Raspodele verovatnoće za taj slučaj su približno normalne (e -kontaminirane) i predmet su intenzivnog proučavanja u matematičkoj statistici. Za takav slučaj se predlažu robusni algoritmi identifikacije, pri čemu robusnost ima statistički karakter. Razmatra se primena robusnog Kalmanovog filtra u identifikaciji modela zasnovanih na grešci izlaza. Robusni prošireni Kalmanov filtar se koristi za identifikaciju opšte forme nelinearnog modela u prostoru stanja. Identifikacija procesa opisanih opštim modelom (nepoznati parametri i stanja procesa) zahteva uvođenje proširenog Masreljez-Martinovog filtra. Uvođenjem predloženih heurističkih modifikacija povećava se fleksibilnost, u smislu praktične primene kao i brzine konvergencije robusnog filtra. Prikazana je nadmoćnost predloženih robusnih algoritama u identifikaciji sistema sa vremenski promenljivim parametrima, koji zasnovani na OE klasi modela. Praktični aspekt dobijenih rezultata potvrđen je kroz eksperiment na pneumatskom cilindru koji se nalazi u laboratoriji centra za Automatsko upravljanje i fluidnu tehniku Fakulteta za mašinstvo i građevinarstvo u Kraljevu.By applying the principles of black boxes and probability theory, stochastic processes and mathematical statistics, with the use of input / output measurements, the possibility of obtaining mathematical models is considered. Frames for obtaining the model are general because it is assumed that the stochastic disturbances are non-Gaussian. Such a model is a prerequisite for the design of wide range of industrial controlers. The theory of experiment design plays an important role in increasing the speed of convergence of recursive algorithms as well as shortening the time of identification. Increased speed of convergence of algorithms makes them very favorable for practical application. The input signals for identification are created through the recursive relation for autocovariance. Design of autocovariance is based on the idea of predictive control, where the control signal has a finite alphabet. Practical studies show that disturbances, in general, have non-Gaussian distribution. Particularly important is the case when there are observations that are inconsistent with respect to the majority of population (outliers). Probability distribution for this case is approximately normal (e -contaminated) and is the subject of intensive study in mathematical statistics. In such case, the robust algorithms for identification, where robustness has a statistical nature, are proposed. It is considered the application of robust Kalman filter in identification of output error model. Robust extended Kalman filter is used for identification of the general form of the nonlinear statespace model. Identification of the processes described by general model (the unknown parameters and states of the process) requires the introduction of extended Masreliez-Martin's filter. By introducing of the proposed heuristic modification increases the flexibility in terms of practical application and the speed of convergence of the robust filter. The superiority of the proposed robust algorithms for system identification with timevarying parameters, which are based on OE models, has been shown. The practical aspects of the results have been confirmed by experiment on a pneumatic cylinder, which is located in the laboratory of the centre for automatic control and fluid technique of The Faculty of Mechanical and Civil Engineering in Kraljevo

Superfluid drag of two-species Bose-Einstein condensates in optical lattices

We study two-species Bose-Einstein condensates in quasi two-dimensional optical lattices of varying geometry and potential depth. Based on the numerically exact Bloch and Wannier functions obtained using the plane-wave expansion method, we quantify the drag (entrainment coupling) between the condensate components. This drag originates from the (short range) inter-species interaction and increases with the kinetic energy. As a result of the interplay between interaction and kinetic energy effects, the superfluid-drag coefficient shows a non-monotonic dependence on the lattice depth. To make contact with future experiments, we quantitatively investigate the drag for mass ratios corresponding to relevant atomic species.Comment: 6 pages, 4 figures. Accepted in its original form but minor changes have been don