NONLINEARITY COMPENSATION AND ACCURACY IMPROVEMENT METHOD FOR AN OPTICAL ROTARY ENCODER

This paper presents a method for the nonlinearity compensation of an optical rotary encoder. The proposed method is based on the application of 1) a special 4-bit mixed analog-digital circuit used for the generation of a quasi-linear signal, and 2) a two-stage nonlinear ADC which performs linearization and digital conversion of the quasi-linear signal at the same time. The quasi-linear signal is obtained by combining fragments of phase-shifted sinusoidal signals, where each fragment is presented with a 4-bit digital code. In the continuation, the quasi-linear signal is linearized with the two-stage nonlinear ADC of a compact design based on the application of a single flash ADC in both conversion stages. Additionally, the design of the flash ADC is modified so that the number of employed comparators is equal to the resolution of the flash ADC. For instance, by linearizing an optical rotary encoder using the 4-bit mixed analog-digital circuit and the 20-bit two-stage nonlinear ADC containing 10 comparators, the maximal value of the absolute measurement error can be reduced to 3.23·10-5°

ERW in the Republic of Serbia

As a result of operations conducted during the Balkan Wars, World Wars and Yugoslav Wars, Serbia remains affected by numerous pieces of unexploded ordnance. The author explores the extent of UXO contamination and reveals the extensive process by which it is removed from and destroyed within southern Serbia, areas that have been plagued by explosive remnants of war for the past century

STRESSING ISSUE OF A PIEZOCERAMIC CANTILEVER WITH LONGITUDINAL POLARISATION AND ELECTRODE COATINGS

The main subject of this study is the investigation of the free vibration of a rectangular prismatic piezoceramic cantilever with longitudinal polarization and electrode coatings. Based on the general solution of coupled equations for piezoceramic material, applying the equations of electro-elasticity and satisfying electrical and mechanical conditions for the stress of a cantilever made from PZT4 piezoceramic material, componential displacements, electric potential, specific strain, electric field, and piezoelectric displacement, are determined and numerically obtained with Matlab software package. Based on the obtained equations and simulation results, it is possible to optimize the dimensions of the cantilever and determine the type of piezoceramic

Motorne funkcije i kognicija kod starih osoba

The prolonging of a lifespan and the increasing proportion of elderly people in general population are setting new healthcare tasks. One of them is researching and clarifying the relations and links between motoric and cognitive functions in elderly. 'Impoverishment' of cognitive capacities occurs during the aging process. Many studies show a strong link between cognition and the function of walking. There is growing evidence that the decline in cognitive functions is resulting in deterioration of walking. Usually described as characteristic of the later stages of dementia, the distortion of ambulation may also be present in the earlier stages, even before the prodromal stage of mild cognitive impairment. Speed and temporal and spatial variability of steps are the main gait characteristics which are connected to the degree of decline in cognitive processes. Those characteristics are motor phenotype that reflects the deterioration of cognitive performance and which can be used for prediction of dementia. It is assumed that physical activity provides beneficial effects at cognitive and psychological levels, including prevention and improvement of depressive states and anxiety disorders, enhancing stress reduction, improved self-confidence and above all it delays cognitive decline in the elderly. Disruption of axons and myelin in the cerebral white matter is considered one of the primary mechanisms underlying age-related cognitive decline. Therefore, maintaining white matter structural connectivity in the old age may be one of the key factors in preserving brain function and high cognitive performance necessary for independent living. Physical activity also influences cerebrovascular mechanisms, such as preserving higher blood vessel elasticity and wall integrity. Moreover, there is an association between light physical activity and white matter integrity especially in the temporal lobe. The conclusion of some studies shows a relationship between the ε4 allele and brain derived neurotrophic factor (BDNF) response to physiologic adaptation which likely impacts the extent of neuroprotective benefit gained from engagement in physical exercise. Some authors propose a program of exercises which consist of a combined aerobic and resistance training. Motoric function and cognition are closely related and using regular physical activity is important for maintaining physical and mental health in the elderly.Produžetak životnog veka i povećanje udela starijih ljudi u opštoj populaciji postavlja nove zadatke za zdravstvene službe. Jedan od njih je istraživanje i razjašnjavanje odnosa i povezanosti između motoričkih i kognitivnih funkcija kod osoba starijeg životnog doba. Tokom procesa starenja odigrava se 'osiromašenje' kognitivnih kapaciteta. Mnoge studije ukazuju na postojanje izrazite povezanosti između kognitivnih funkcija i funkcije hoda. Postoji sve više dokaza da opadanje kognitivnih funkcija rezultuje deterioracijom funkcije hoda. Poremećaj funkcije hoda se obično povezuje sa kasnijim stadijumima demencije, međutim, ona može biti narušena i u ranijim stadijumima pa čak i pre nastanka prodromalnog stadijuma tj. blagog kognitivnog poremećaja. Brzina koraka i vremenska i prostorna varijabilnost koraka su glavne karakteristike koje se povezuju sa stepenom pada kognitivnih procesa. Ove karakteristike su motorni fenotip koji reflektuje stepen deterioracije kognitivnog funkcionisanja i koji može biti upotrebljen kao prediktivni pokazatelj nastanka demencija. Pretpostavlja se da fizička aktivnost obezbeđuje pozitivne efekte na kognitivnom i psihološkom planu, uključujući prevenciju i poboljšanje depresivnih i anksioznih stanja, da redukuje stres, unapređuje samopouzdanje i konačno, odlaže nastanak procesa opadanja kognitivnih funkcija kod osoba starijeg doba. Prekidi aksonskih puteva i mijelina u beloj masi se smatraju jednim od primarnih mehanizama za nastanak opadanja kognitivnih funkcija tokom procesa starenja. Zbog toga se pretpostavlja da je održavanje strukturalne celovitosti bele mase jedan od ključnih faktora koji doprinose očuvanju viših kognitivnih funkcija koje su neophodne za nezavisno funkcionisanje u starijem životnom dobu. Fizička aktivnost takođe deluje preko cerebrovaskulnih mehanizama kao što su očuvanost elastičnosti i integriteta zidova krvnih sudova. Osim pomenutog, postoji povezanost između lagane fizičke aktivnosti i integriteta bele mase posebno u temporalnom lobusu. Zaključci pojedinih istraživanja ukazuju na postojanje odnosa između ε4 genskog alela i brain derived neurotrophic factor (BDNF) odgovora na fiziološku adaptaciju nastalu fizičkim vežbanjem, za koju se pretpostavlja da pozitivno utiče na neuroprotekciju. Neki autori predlažu program fizičkog vežbanja kao kombinaciju aerobnog i treninga sa primenjenim otporom. Motorička funkcija i kognicija su blisko poezani, a redovna fizička aktivnost i vežbanje je važno za održavanje fizičkog i mentalnog zdravlja

Theoretical analysis of the cumulative costs of different diesel bus alternatives for a public transport in the city of Belgrade

This paper includes comparative analysis of the environmental, energetic, and financial costs of different bus propulsion, possibly applied on the public transport in the city of Belgrade. It considers the modern diesel bus, the trolleybus, the natural gas bus with the spark ignition engine, the electric bus using LiFePO4 battery, and the electric bus with ultra-capacitor. The results are presented according to the real data and the real electro-energetic situation in Serbia, with the dominantly used lignite coal as primary fuel. This model gives the exact exhaust emission of electric vehicles at the thermal power plant, enables its comparison to the internal combustion engine vehicles. The result in analysis shows that the natural gas bus is the most cost efficient in economical way with overall exploitation price of $87 per 100 km. The trolleybus is more economical then the natural gas powered bus only at high departures rate, higher than 230 per workday

POTENTIAL STRAIN ENERGY SURFACES AT THE CRACK TIP VICINITY

Results of reconstruction of potential strain energy surfaces at the region of crack and basic procedures of the reconstruction method are presented. Pertinent limitations and specifications of the method are pointed out in evaluating the best fitting curves and the best fitting three-dimensional surfaces of stress components and potential strain energy. Examples of cracks named in the paper as PR-Z-16 and PR-P-22, with exactly the same geometry of crack and plate are analyzed. The same finite element lattice for calculation in both cases is selected. The first example of a plate is loaded with  in y - direction on the outer border of the plate, perpendicularly on the plane of crack, while in the example PR-P-22 the plate is loaded with  continually and perpendicularly on the crack contour surface. The reconstruction procedure of potential strain energy surfaces for two sections of plates y=0 and z=0, and graphical presentation of these surfaces, are carried out. Based on reconstructed potential strain energy surfaces, isoenergy lines at the region in front of the crack tip for both analyzed examples, are obtained. It is observed that the distribution of stresses as well as the distribution of potential strain energy are very similar in both cases, which indicates a significant influence of geometric shape of contour surfaces of the crack. For comparison, stress state and potential strain energy state, which are obtained by using relations from literature, are shown

Symmetry of k·p Hamiltonian in pyramidal InAs/GaAs quantum dots: Application to the calculation of electronic structure

A method for the calculation of the electronic structure of pyramidal self-assembled InAs/GaAs quantum dots is presented. The method is based on exploiting the C-4 symmetry of the 8-band k·p Hamiltonian with the strain taken into account via the continuum mechanical model. The operators representing symmetry group elements were represented in the plane wave basis and the group projectors were used to find the symmetry adapted basis in which the corresponding Hamiltonian matrix is block diagonal with four blocks of approximately equal size. The quantum number of total quasiangular momentum is introduced and the states are classified according to its value. Selection rules for interaction with electromagnetic field in the dipole approximation are derived. The method was applied to calculate electron and hole quasibound states in a periodic array of vertically stacked pyramidal self-assembled InAs/GaAs quantum dots for different values of the distance between the dots and external axial magnetic field. As the distance between the dots in an array is varied, an interesting effect of simultaneous change of ground hole state symmetry, type, and the sign of miniband effective mass is predicted. This effect is explained in terms of the change of biaxial strain. It is also found that the magnetic field splitting of Kramer's double degenerate states is most prominent for the first and second excited state in the conduction band and that the magnetic field can both separate otherwise overlapping minibands and concatenate otherwise nonoverlapping minibands

Preparation and Characterization of Poly-l-lactide Microspheres

Poster presented at the International Workshop and Summer School Cell and Tissue Engineering, Faculty of Technology and Metallurgy, University of Belgrade, July 1-8, 2006

Endoscopically removed giant submucosal lipoma

Background. Although uncommon, giant submucosal colon lipomas merit attention as they are often presented with dramatic clinical features such as bleeding, acute bowel obstruction, perforation and sometimes may be mistaken for malignancy. There is a great debate in the literature as to how to treat them. Case report. A patient, 67-year old, was admitted to the Clinic due to a constipation over the last several months, increasing abdominal pain mainly localized in the left lower quadrant accompanied by nausea, vomiting and abdominal distension. Physical examination was unremarkable and the results of the detailed laboratory tests and carcinoembryonic antigen remained within normal limits. Colonoscopy revealed a large 10 cm long, and 4 to 5 cm in diameter, mobile lesion in his sigmoid colon. Conventional endoscopic ultrasound revealed 5 cm hyperechoic lesion of the colonic wall. Twenty MHz mini-probe examination showed that lesion was limited to the submucosa. Since polyp appeared too large for a single transaction, it was removed piecemeal. Once the largest portion of the polyp has been resected, it was relatively easy to place the opened snare loop around portions of the residual polyp. Endoscopic resection was carried out safely without complications. Histological examination revealed the common typical histological features of lipoma elsewhere. The patient remained stable and eventually discharged home. Four weeks later he suffered no recurrent symptoms. Conclusion. Colonic lipomas can be endoscopically removed safely eliminating unnecessary surgery

Clinical, histopathological and immunohistological study of lymphoid disorders in the parotid gland of patients with Sjögren's syndrome

Bacground/Aim. Sjögren's syndrome is a chronic autoimmune systemic disease characterized by polyglandular tissue destruction, leading to keratoconjunctivitis sicca and xerostomia. These patients have 44-fold increased risk of developing salivary gland lymphoma, of which 80% are marginal zone (MALT) type. Having in mind that criteria for distinguishing benign lymphoepithelial lesions from MALT lymphoma are obscure, the aim of this study was to provide practical information that could be integrated into diagnostic practice. Methods. Among 32 parotidectomies, 27 cases were identified as having benign lymphoepithelial disorders and 5 cases low grade MALT lymphoma. Histological sections were stained routinely with hematoxylin and eosin (H&E and special stains. Immunohistochemical study was performed by LSAB2 method, by using primary antibodies for CD20, CD3, Kappa and Lambda light chains and Cytokeratin (Dako Denmark). Results. The 27 patients with Sjögren's sialoadenitis (22 women and 5 men), and 5 patients with MALT lymphoma (only women) were included in this analysis. According to the Ann Harbor Classification, all patients with MALT lymphoma had stage IE. Both groups of patients had an indolent clinical course, except permanent, rapid parotid enlargement in the patients with MALT lymphoma. Histologically, the periductal lymphoid infiltrate, gradually extended to the acini, completely replacing them by a sea of polyclonal lymphocytes, immunoblasts, germinal centers and plasma cells (confirmed immunohistochemically), but sparing the ducts and preserving lobular appearance. The histological feature of salivary gland MALT lymphoma included heterogeneous B-cell infiltrate that totally or subtotally had effaced the normal glandular structure. Malign lymphoepithelial lesions, representing infiltration of the ductal and epithelial structures by monoclonal neoplastic Bcells, positive for CD20, were highlighted by antibody to cytokeratin. Conclusion. The optimal diagnosis of salivary gland MALT lymphoma requires careful integration of clinical, morphological and immunohistochemical results