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Search Results: 1 - 10 of 225107 matches for " Popovi? Milo? R. "
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Experimental study on low velocity friction compensation and tracking control
PopoviMiloR.,Liu Guangjun,Goldenberg Andrew A.
Journal of Automatic Control , 2003, DOI: 10.2298/jac0302017p
Abstract: Stick-slip phenomenon is often associated with the control of low velocity motion because of the positional dependency of friction and negative damping friction that decreases as the motion speed increases. In this paper, smooth low velocity tracking control of a commercial robot joint is demonstrated experimentally using a combination of high gain PID control, fast sampling rate and high position sensor resolution. The experimental results also reveal that the main source of instability is not negative damping friction but position dependant friction that has been widely neglected. The short sampling period and a high resolution encoder have allowed us to compensate for the position dependant friction with a PID controller with sufficiently high gains.
Functional electrical stimulation therapy improves grasping in chronic cervical spinal cord injury: Two case studies
Miller Rosalynn C.,PopoviMiloR.,Thrasher Adam T.,Verrier Molly
Journal of Automatic Control , 2008, DOI: 10.2298/jac0802053m
Abstract: OBJECTIVE AND IMPORTANCE: To present case studies of two individuals with chronic cervical spinal cord injury (SCI) who participated in functional electrical stimulation (FES) therapy with the objective to restore voluntary grasp function. CLINICAL PRESENTATION: Both individuals (right hand dominant males, age 24 and 31) had a sustained a cervical SCI (C6 and C4-5, respectively) at least 8 years prior to participation in this study. INTERVENTION: Both individuals participated in an individualized FES therapy program for 6 weeks. FES therapy was administered through a regimen of three, one-hour sessions, per week for three months. A single arm of each participant (n = 2) was treated. FES therapy is an integrative intervention strategy combining muscle strengthening, functional movement training and stretching. The participant's hand movement abilities were assessed pre and post FES therapy using the Manual Muscle Test (MMT), a modified Sollerman Hand Function Test (mSHFT), and the Reach, Grasp, Transport and Release Task (RGTR). DISCUSSION: As the injuries of participants in the current study were chronic and thus neurologically stable, no spontaneous improvements/recovery in hand function was expected. However, FES as part of an integrated therapeutic approach affected restoration and improvement of hand function in both participants. CONCLUSION: The concurrent improvement in strength, integrated motor function and object contact following FES therapy, demonstrated that there is potential for affecting change in hand function of individuals with chronic SCI.
Triply-resonant micro-optical parametric oscillators based on Kerr nonlinearity: nonlinear loss, unequal resonance-port couplings, and coupled-cavity implementations
Xiaoge Zeng,Milo? A. Popovi
Physics , 2013,
Abstract: We develop a theoretical model of triply-resonant optical parametric oscillators (OPOs) based on degenerate four-wave mixing (FWM) that includes physics and degrees of freedom relevant to microphotonic (on-chip) device implementations, including nonlinear loss, a general resonant mode field structure, and mode-selective coupling to external ports. The coupled mode theory model addresses the effect of two-photon absorption and free-carrier absorption on parametric gain and oscillation thresholds, and ultimately on the optimum design for an OPO. The model goes beyond a typical free-space cavity configuration by incorporating a full modal analysis that admits distributed modes with non-uniform field distribution, relevant to photonic microcavity systems on chip. This leads to a generalization of the concept of nonlinear figure of merit (NFOM) to a vector of coefficients. In addition, by considering unconstrained signal, pump and idler resonance coupling strengths to excitation ports, not usually available in simple cavity geometry, we show that the efficiency-maximizing design will have unequal external Q for the three resonances. We arrive at generalized formulas for OPO oscillation threshold that include nonlinear absorption and free carrier lifetime, and provide a normalized solution to the design problem in the presence of nonlinear loss in terms of optimum choice of coupling. Based on the results, we suggest a family of coupled-cavity systems to implement optimum FWM, where control of resonant wavelengths can be separated from optimizing nonlinear conversion efficiency, and where furthermore pump, signal, and idler coupling to bus waveguides can be controlled independently, using interferometric cavity supermode coupling as an example. Using the generalized NFOM, we address the efficiency of single and multi-cavity geometry, as well as standing and traveling wave excitation.
High-Q Contacted Ring Microcavities with Scatterer-Avoiding "Wiggler" Bloch Wave Supermode Fields
Yangyang Liu,Milo? A. Popovi
Physics , 2014, DOI: 10.1063/1.4878337
Abstract: High-Q ring resonators with contacts to the waveguide core provide a versatile platform for various applications in chip-scale optomechanics, thermo- and electro-optics. We propose and demonstrate a novel approach to implement azimuthally periodic contacted ring resonators based on multi-mode Bloch matching that support contacts on both the inner and outer radius edges with small degradation to the optical Q. Radiative coupling between degenerate modes of adjacent transverse spatial order leads to imaginary frequency (Q) splitting and a scatterer avoiding high-Q "wiggler" supermode field. We experimentally measure Q's up to 258,000 in devices fabricated in a silicon device layer on buried oxide undercladding, and up to 139,000 in devices fully suspended in air using an undercut step. Wiggler supermodes are true modes of the microphotonic system that offer new degrees of freedom in electrical, thermal and mechanical design.
Comment on "Linear and passive silicon optical isolator" in Scientific Reports 2, 674
Alexander Petrov,Dirk Jalas,Manfred Eich,Wolfgang Freude,Shanhui Fan,Zongfu Yu,Roel Baets,MiloPopovi,Andrea Melloni,John D. Joannopoulos,Mathias Vanwolleghem,Christopher R. Doerr,Hagen Renner
Physics , 2013,
Abstract: Wang et al. [1] demonstrated different power transmission coefficients for forward and backward propagation in simulation and experiment. From such a demonstration, the central claim of their paper is that "the spatial inversion symmetry breaking diode can construct an optical isolator in no conflict with any reciprocal principle". Their claim contradicts the Lorentz reciprocity theorem, from which it is well known that one cannot construct an isolator this way.
Irradiation Effects on Phenolic Content, Lipid and Protein Oxidation and Scavenger Ability of Soybean Seeds
Dubravka ?tajner,Mirjana Milo?evi?,Boris M. Popovi
International Journal of Molecular Sciences , 2007, DOI: 10.3390/i8070618
Abstract: The effect of medium doses of γ-irradiation (1-10 kGy) on total phenolic andtannin contents, lipid peroxidation, protein oxidation intensity and soluble protein contentof soybean seeds, (genotype Ana), was investigated. Screening for antioxidant ability wasperformed using FRAP and DPPH methods. Total phenolic and tannin contents and DPPHscavenger activity were increased, while protein oxidation intensity was decreased byapplied doses of γ-irradiation. Gamma irradiation provoked insignificant changes in lipidperoxidation and soluble protein content, while protein oxidation intensity wassignificantly decreased when dose of 10 kGy was applied. Presented results implicated thatincreased antioxidant capacity and protein stability of soybean seeds were increased afterapplication of γ-irradiation.
Variability and correlations between yield components of soybean [Glycine max (L.) Merr.]
Popovi? Vera,Vidi? Milo,Jockovi? ?or?e,Ikanovi? Jela
Genetika , 2012, DOI: 10.2298/gensr1201033p
Abstract: NS soybean cultivars were assessed for variability of and correlations between yield components and the effect of genotype - environment interaction on yield, yield component and morphological characteristics. Experiments were carried out at Rimski an evi experiment field in 2009 and 2010. The following characteristics were evaluated: plant height (cm), height of first pod (cm), 1000-grain weight (g), grain yield (kg/ha) and the combined content of oil and protein in grain (%). Combined contents of oil and protein in grain soybean were determined by a non destructive method of near infrared spectroscopy on PERTEN DA 7000 (NIR/VIS Spectrophotometer). The studied characteristics varied significantly depending on genotype and year. The highest yield of 5273 kg/ha was obtained in 2009 with the genotype Victoria. Highest 1000-grain weights, 2009-2010, were achieved with the genotypes Valjevka and Victoria (149.27 g and 147.23 g). Maximum heights of first pod (19.40 cm) were recorded for the genotype Victoria, 2009-2010. Highest protein contents were obtained with the genotypes Valjevka and Victoria, 2009-2010, were and highest oil contents (21.73%) with the genotype Tea. Protein content was positively significantly correlated with 1000-grain weight and negatively significantly correlated with oil content, and negatively correlated with yield and the height of first pod. Oil content was positively correlated with the height of first pod. Thousand-grain weight was negatively highly significantly correlated with oil content in grain and negatively significantly correlated the height of first pod. The results of this study should facilitate further soybean breeding for improved seed yield and protein and oil contents.
Use of vacuum-assisted closure device in a disastrous form of abdominal sepsis and stoma site infection: Systematic review and report of a case
PopoviMilo,Bari?i? Goran,Markovi? Velimir,Petrovi? Jelena
Acta Chirurgica Iugoslavica , 2012, DOI: 10.2298/aci1202111p
Abstract: Use of Vacuum-Assisted Closure (VAC) for treatment of open abdomen has been established predominantly in cases of severe abdominal trauma, resulting with high percentage of primary fascial closure. The role of VAC technique in cases of severe diffuse peritonitis is not definitely incorrigible. However, in cases of severe complicated abdominal sepsis VAC come up as a last resort.
Impact of climatic factors to the percentage of young in the population of brown hare (Lepus europaeus P) in the Ba ka district
Beukovi? Milo,Beukovi? D.,Popovi? Z.,?or?evi? N.
Acta Veterinaria , 2013, DOI: 10.2298/avb1301111b
Abstract: Climatic factors, especially temperature and precipitations, greatly affect the dynamics of the hare number and population. Climatic factors directly affect the physiological and reproductive processes of both individuals and entire populations, or indirectly, through the availability of food, competition with other species, predators and other. The age structure of the hare population at the end of the period of reproduction is an important indicator of the population growth that is used for planning the level of explotation of the hare population (hunting). The rational use of the hare's population is one of the most important protection procedures and it should be well monitored and controlled by the hunting professionals. We used the average monthly temperature and the sum of monthly precipitations in the hare reproductive period (March-September) during ten years (2000 - 2009), together with the percent of young in the hare population, on the territory of Ba ka, for multiple regression (stepwise) analysis. Results of the regression analysis show an association between the percentage of young hares and the influence of climatic factors. The average temperature and sum of precipitation in June, are the strongest predictor of the percent of young in the hare’s population in Ba ka. According to the coefficient of determination (R2=0.50) climatic parameters account for 50% of variance in the percentage of young hares in Ba ka. The regression correlation coefficient of all factors was R=0.70, which is on the border line between medium and high correlation.
Surgical treatment of big splenic artery aneurysm: Case report
Ka?anski Milo,Markovi? Vladimir,Pasternak Janko,Popovi? Vladan
Medicinski Pregled , 2009, DOI: 10.2298/mpns0908363k
Abstract: An aneurysm has been defined as a permanent local dilatation of the diameter of an artery by at least 50% of its normal value. A splenic artery aneurysm is most frequently a visceral artery aneurysm and clinically it is usually asymptomatic but potentially life-threatening at the same time, with the incidence of its rupturing being 2-10% and then the mortality rate ranges from 20 to 36%. A 51-year-old female patient was admitted to the Department of Vascular and Transplantation Surgery in Novi Sad having been found to have a big splenic artery aneurysm during the ultrasound examination of her abdomen after cholecystectomy. The additional diagnostic procedure - computerized tomography of the abdomen with i.v contrast subtraction angiography-confirmed the splenic artery aneurysm to have the diameter of 5 cm and therefore the elective surgical treatment was indicated after the preoperative preparation and risk assessment. The aneurysm was exposed through Chevron incision, and the detailed surgical exploration was done after the omental bursa had been opened. The aneurysmectomy and the reconstruction of the splenic artery by the termino-terminal anastomosis were performed after the weakening of the wall had been verified. The biopsies of the liver and the aneurysmal sac were done during the surgery. The pathohistological finding confirmed the atherosclerotic etiology of the aneurysm. Since the postoperative course was normal, the patient was discharged on the eighth postoperative day.
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