Simulacija širenja prsline u titanijumskim mini dentalnim implantima (MDI)

Developments in mini dental implants (MDI) manufacturing are aimed at making them more biocompatible and, at the same time, lighter, more durable and simultaneously safer than the existing implants. But, occasionally, during installation the failure of MDI may occur or cracks may appear, which could lead to the later failure of MDI. In order to understand and assess crack growth in titanium MDI, Finite Element (FE) software packages ANSYS v13 and FRANC3D v5 have been used. Using FRANC3D software different crack sizes and shapes have been modeled and simulations of crack propagations in three-dimensional model of MDI have been performed. Based on simulation results, the approximate fatigue life of damaged MDI was calculated.Unapređenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka povećanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeće implantate. Međutim, tokom ugradnje MDI-a može doći do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo širenje prsline u titanijumskom MDI-u, korišćeni su softveri za primenu metode konačnih elemenata (MKE) ANSYS v13 i FRANC3D v5. Korišćenjem FRANC3D programa izmodelirane su prsline različitih veličina i oblika na 3D geometriji MDI-a i izvršeno je simuliranje njihovog širenja. Na osnovu rezultata simulacije izračunat je približan zamorni vek oštećenog MDI-a

Advanced hardware control for seven DOFs robotic arm-neuro arm

In this paper we will implement new hardware control for 7 DOFs (Degrees of freedom) advanced robotic arm research platform (NeuroArm) equipped with various sensors. New hardware platform consists of Nano Pi platform which is used as a PC platform for standard PLC (programmable logic controller's) unit and will replace old system that consists of 7 16-bit ATmega processors. The goal of new PLC which is based on Linux operating system (Debian distribution) that is patched by Xenomai real time system for reducing control response time and better entire system control. Robotic arm is powered by 7 DC motors which are controlled by two PWM4 (Pulse Width Modulation) modules. Position data is acquired from 1kΩ resistive sensors using RI8 (Resistive module) module and from optical quadrature encoders using one DI16 (Digital Input) module. Also other modules PWM4, RI8 and DI16 communicate with PikoAtlas CPU module by I2C bus

Advanced hardware control for seven DOFs robotic arm-neuro arm

In this paper we will implement new hardware control for 7 DOFs (Degrees of freedom) advanced robotic arm research platform (NeuroArm) equipped with various sensors. New hardware platform consists of Nano Pi platform which is used as a PC platform for standard PLC (programmable logic controller's) unit and will replace old system that consists of 7 16-bit ATmega processors. The goal of new PLC which is based on Linux operating system (Debian distribution) that is patched by Xenomai real time system for reducing control response time and better entire system control. Robotic arm is powered by 7 DC motors which are controlled by two PWM4 (Pulse Width Modulation) modules. Position data is acquired from 1kΩ resistive sensors using RI8 (Resistive module) module and from optical quadrature encoders using one DI16 (Digital Input) module. Also other modules PWM4, RI8 and DI16 communicate with PikoAtlas CPU module by I2C bus

Application of multiparametric cardiac measurement system in ejection fraction calculation

Ejection fraction (EF) is the most used parameter for characterisation of Heart Failure (HF) condition. EF is commonly calculated using echocardiography, which is an expensive non–invasive method and not used in primary healthcare. Systolic time intervals (STI) represent a non-invasive and inexpensive method for determination of EF[1, 2]. Heart failure (HF) is the single most expensive diagnosis in medicine. 2–3% of adult population in developed countries have HF diagnosis. It is not detectable by ECG test and it is commonly detected in a late stage, when the process is irreversible [2-5]. In this paper, a multiparametric cardiac measurement system for determination of STI is presented. Measurement system consists of sensors for simultaneous acquisition of electrocardiographic (ECG), phonocardiographic (PCG), photopletysmographic (PPG) and cardiovascular (CV) pulsation signals. CV pulsation signals are measured by long period grating (LPG) fiber-optic sensors[6]. Two non-invasive methods for measuring systolic time intervals (STI) were applied on a set of 6 healthy volunteers, based on ECG, PCG and CV pulsation signals. CV pulsation signals were measured on carotide arthery with PPG and LPG sensors. In the first method, EF was calculated from the obtained STI signals, using CV carotide pulsations measured with the PPG sensor, giving EF values in the range from 0.60 to 0.68, with maximal standard deviation of 0.05. In the second method, EF was obtained using CV carotide pulsations measured with LPG sensor, giving EF values in the range from 0.60 to 0.66, with maximal standard deviation 0.06. Calculated values of EF with both methods were in the 0.55 to 0.75 range which corresponds to normal EF range in healthy individuals

Application of multiparametric cardiac measurement system in ejection fraction calculation

Ejection fraction (EF) is the most used parameter for characterisation of Heart Failure (HF) condition. EF is commonly calculated using echocardiography, which is an expensive non–invasive method and not used in primary healthcare. Systolic time intervals (STI) represent a non-invasive and inexpensive method for determination of EF[1, 2]. Heart failure (HF) is the single most expensive diagnosis in medicine. 2–3% of adult population in developed countries have HF diagnosis. It is not detectable by ECG test and it is commonly detected in a late stage, when the process is irreversible [2-5]. In this paper, a multiparametric cardiac measurement system for determination of STI is presented. Measurement system consists of sensors for simultaneous acquisition of electrocardiographic (ECG), phonocardiographic (PCG), photopletysmographic (PPG) and cardiovascular (CV) pulsation signals. CV pulsation signals are measured by long period grating (LPG) fiber-optic sensors[6]. Two non-invasive methods for measuring systolic time intervals (STI) were applied on a set of 6 healthy volunteers, based on ECG, PCG and CV pulsation signals. CV pulsation signals were measured on carotide arthery with PPG and LPG sensors. In the first method, EF was calculated from the obtained STI signals, using CV carotide pulsations measured with the PPG sensor, giving EF values in the range from 0.60 to 0.68, with maximal standard deviation of 0.05. In the second method, EF was obtained using CV carotide pulsations measured with LPG sensor, giving EF values in the range from 0.60 to 0.66, with maximal standard deviation 0.06. Calculated values of EF with both methods were in the 0.55 to 0.75 range which corresponds to normal EF range in healthy individuals

Coronary Artery Occlusion Detection Using 3-Lead ECG System Suitable for Credit Card-Size Personal Device Integration

Background Early coronary occlusion detection by portable personal device with limited number of electrocardiographic (ECG) leads might shorten symptom-to-balloon time in acute coronary syndromes. Objectives The purpose of this study was to compare the accuracy of coronary occlusion detection using vectorcardgiographic analysis of a near-orthogonal 3-lead ECG configuration suitable for credit card-size personal device integration with automated and human 12 lead ECG interpretation. Methods The 12-lead ECGs with 3 additional leads (“abc”) using 2 arm and 2 left parasternal electrodes were recorded in 66 patients undergoing percutaneous coronary intervention prior to (“baseline”, n = 66), immediately before (“preinflation”, n = 66), and after 90-second balloon coronary occlusion (“inflation”, n = 120). Performance of computer-measured ST-segment shift on vectorcardgiographic loops constructed from “abc” and 12 leads, standard 12-lead ECG, and consensus human interpretation in coronary occlusion detection were compared in “comparative” and “spot” modes (with/without reference to “baseline”) using areas under ROC curves (AUC), reliability, and sensitivity/specificity analysis. Results Comparative “abc”-derived ST-segment shift was similar to two 12-lead methods (vector/traditional) in detecting balloon coronary occlusion (AUC = 0.95, 0.96, and 0.97, respectively, P = NS). Spot “abc” and 12-lead measurements (AUC = 0.72, 0.77, 0.68, respectively, P = NS) demonstrated poorer performance (P < 0.01 vs comparative measurements). Reliability analysis demonstrated comparative automated measurements in “good” agreement with reference (preinflation/inflation), while comparative human interpretation was in “moderate” range. Spot automated and human reading showed “poor” agreement. Conclusions Vectorcardiographic ST-segment analysis using baseline comparison of 3-lead ECG system suitable for credit card-size personal device integration is similar to established 12-lead ECG methods in detecting balloon coronary occlusion

Air traffic modernization and control: ADS-B system implementation update 2022: A review

Automatic Dependent Surveillance-Broadcast (ADS-B) is a multiparameter surveillance system designed to improve key segments of air traffic: enabling real-time surveillance, raising safety and efficiency levels, and improving flight information and weather services. ADS-B consists of two subsystems, ADS-B Out and ADS-B In. Although only a complete system, ADS-B In/Out provides numerous benefits (additional situational awareness, more efficient oceanic routing, etc.) FAA and EASA only require ADS-B Out (by January and June 2020, respectively), whereby ADS-B In remains optional. Because of its many advantages, ADS-B In/Out will be popular, but there are some weaknesses, which are primarily related to its cyber vulnerabilities due to insufficient authentication and encryption in the applied protocol. In this paper, an overview of the ADS-B system is presented as an aid to understanding the security problems and the different ways of potential attack. In addition, this review deals with the current state of ADS-B deployment and its future perspective and challenges

Uticaj deficitarnog navodnjavanja na prinos zrna i karakteristike klipa kukuruza

In the Vojvodina region, drought is an important factor limiting grain yield in maize. The aims of this research were to compare irrigation scheduling in maize (cv. ZP SC 684), and to evaluate grain yield and ear characteristics. A 3-year field experiment was carried out in the Vojvodina region, a northern part of the Republic of Serbia (384 mm of rainfall in the maize-growing period). Maize was subjected to four irrigation levels (rainfed - I0 and supply at 80-85% - I1, 70-75% - I2 and 60-65% - I3 of field capacity). The results indicated a large yearly variability, mainly due to a rainfall event at the flowering, fertilization and grain filling stages. A significant irrigation effect was observed for all the variables under study, with significant differences between the three irrigation treatments. The grain yield ranged between 8.73 and 16.33 t ha-1. The highest grain yield of maize (average of 15.08 t ha-1) was in the I1 treatment, while the non-irrigated (I0) treatment had the lowest yield (average of 10.20 t ha-1), a 35% grain yield reduction. With the decrease of irrigation water, the grain yield of maize decreased. The most distinctive impact the irrigation had on maize yield was during the warm and very dry growth period of the year of 2008. Maize in the Vojvodina region can be cultivated with acceptable yields while saving irrigation water and maximizing resource-use efficiency.U Vojvodini, suša je važan faktor koji ograničava prinos kukuruza. Ciljevi ovog istraživanja bili su upoređivanje prirodnog i različitih irigacionih vodnih režima u kukuruzu (cv. ZP SC 684 - FAO 600), ocena prinosa i osobina klipa. Trogodišnja eksperimentalna istraživanja obavljena su u Zemun Polju (Vojvodini), odnosno u severnom delu Republike Srbije (dvadesetogodišnji prosek padavina u vegetacionom periodu kukuruza je 384 mm). Ispitivan je efekat četiri varijante vodnog režima kukuruza: I0 - bez navodnjavanja, I1 - sadržaj vode u zemljištu održavan je na nivou 80-85% poljskog vodnog kapaciteta (PVK) dopunskim navodnjavanjem kišenjem, I2 - 70-75% PVK i I3 - 60-65% PVK. Rezultati su pokazali veliku varijabilnost između godina, uglavnom zbog pojave padavina u fenofazi cvetanja, oplodnje i nalivanja zrna. Navodnjavanje je značajno uticalo na prinos zrna, karakteristike klipa i visinu biljaka kukuruza. Takođe, utvrđene su značajne razlike i između navodnjavanih varijanti. Prinos zrna varirao je između 8,73 i 16,33 t ha-1. Najveći prinos kukuruza (prosečno 15,08 t ha-1) ostvaren je u varijanti I1, a najmanji (10,20 t ha-1) u nenavodnjavanoj (I0) varijanti. Prinos se smanjivao i do 35% sa smanjenjem količine vode za navodnjavanje. Najizraženiji efekat dopunskog navodnjavanja na prinos zrna kukuruza ostvaren je u toplom i veoma sušnom vegetacionom periodu 2008. godine. Kukuruz u Vojvodini može da se gaji sa prihvatljivim prinosima uz uštedu vode za navodnjavanje, što će rezultirati efikasnijim korišćenjem vodnih resursa

Detuned primary RF coupling system for variable frequency cyclotrons

A new concept of impedance matching for an RF amplifier coupled to a cyclotron cavity, named detuned primary coupling, is proposed. It does not require the motion of the coupling loop in vacuum and the matching for different working frequencies is performed by detuning the eigenfrequency of the amplifier cabinet alone by means of a variable capacitor. A simple mathematical approach used in the design procedure is presented. Measurements on the 1 : 1 scale model of the VINCY cyclotron RF system have been carried out in the operating frequencies range. The results confirm the viability of the concept and the use of this approach in cyclotron RF amplifier coupling. (C) 1998 Elsevier Science B.V. All rights reserved

Aerodynamic airfoil at critical angles of attack / Аэродинамические характеристики крыла при критическом угле атаки / Aerodinamičke karakteristike aeroprofila pri kritičnim napadnim uglovima

Aircraft construction experts must not neglect the behavior of aircraft in extreme or closely extreme flight conditions, such as flights at critical angles of attack, where a normal flight can be easily converted into a stall. This paper highlights the essential factors that influence the behavior of aircraft in flight at critical angles of attack. Based on the available experimental results and estimations, the performances of airfoils were analysed depending on air flow conditions (categorized according to Mach and Reynolds numbers), airfoil shapes, dynamics of the transition of angles of attack, description of the flow around airfoils with increasing the angle of attack upon reaching a critical value, and the effect of roughness of airfoil surfaces at critical angles of attack. The paper gives a physical interpretation of a lift decrease and a stall. It minutely describes the origin of flow separation and categorizes airfoil sections by type of separation and their behavior during the flow at the critical angle of attack. Based on modern aerodynamics, this paper aims to show and explain the issues and the most important characteristics of the flow past the body at critical angles of attack and give practical recommendations for airfoil design. As such, it may be of interest to pilots and engineers as well as to educational and research institutions. / При разработке летательных аппаратов неследует пренебрегать фактором возникновения чрезвычайных ситуаций, а также условиями близкими критическим, так как при критическом угле атаки, обычный полет может перейти в аварийный режим. В данной работе приведены важные факторы, влияющие на состояние крыла в течение полета при критическом угле атаки. На основании доступных испытательных результатов и расчетов, произведен анализ поведения крыла в зависимости от условий обтекания (в соответствии с классификацией чисел Маха и Рейнольдса), формы крыла, динамики угла атаки. В работе также описано обтекание крыла при критическом увеличении угла атаки, и влияние неровностей на поверхности крыла в подобных условиях. В данной работе также представлены физические параметры критического режима полета, в т.ч. снижения подъемной силы и сваливания. Подробно описан процесс обтекания крыла с отрывом потока и выполнена классификация типов профелей с учетом срыва струи и поведения крыла в критическом режиме полета. Цель работы заключается в выявлении наиболее значимых характеристик обтекания крыла при критическом угле атаки и анализе, проведенного на основах современной аэродинамики, в результате которых предлагается практическая рекомендация для выбора аэродинамического профиля. Результаты данной работы могут представлять интерес как для летчиков и инженеров, так и для образовательных и исследовательских учреждений. / Prilikom konstrukcije vazduhoplova ne sme se zanemariti ponašanje letelice u ekstremnim, odnosno blisko ekstremnim uslovima leta, kakav je let pri kritičnim napadnim uglovima, gde se normalan let može lako preobratiti u prevučen let. U ovom radu naglašeni su bitni činioci koji utiču na ponašanje aeroprofila u letu pri kritičnim napadnim uglovima. Na osnovu dostupnih eksperimentalnih rezultata i proračuna izvršena je analiza ponašanja aeroprofila u zavisnosti od uslova strujanja (kategorisanih prema Mahovom i Rejnoldsovom broju), oblika aeroprofila, dinamike priraštaja napadnog ugla, opstrujavanja aeroprofila sa povećanjem napadnog ugla nakon dostizanja kritične vrednosti, kao i uticaja površinskih neravnina aeroprofila pri kritičnim napadnim uglovima. Prikazano je i fizičko tumačenje pada uzgona i pojave prevučenog leta. Detaljno je opisan nastanak otcepljenja strujanja oko aeroprofila i izvršena kategorizacija aeroprofila prema tipu otcepljenja i njegovom ponašanju pri kritičnim napadnim uglovima opstrujavanja. Cilj ovog rada jeste da na savremenim osnovama aerodinamike prikaže i obrazloži problematiku i najznačajnije osobenosti opstrujavanja aeroprofila pri kritičnim napadnim uglovima, da dâ praktične preporuke prilikom izbora aeroprofila, a može biti koristan i pilotima, inženjerima i istraživačima