Multi-sensor acquisition system for noninvasive detection of heart failure

To research the possibility of noninvasive detection of heart failure we developed an acquisition system with multiple sensors. The system synchronously measures cardiovascular pulsations, heart sounds and ECG using different types of sensors positioned only on the patient’s body. The system has a modular structure with five modules: 1. Module for controlling the light source (MWLS) 2. Module for data acquisition from fiber optical sensors (FBGA) with the compact optical spectral analyzer 3. Module for the acquisition of hearth sounds (PCG) with four ports for microphones; 4. Module for the acquisition of standard ECG signals; 5. Module for data acquisition from three accelerometers and three photoplethysmography sensors (ACC/PPG)

Impact of Ball Bearing Geometry and Operational Load on the Volume of the Lubricant in the Bearing's Loaded Zone

This paper presents the mathematical model for determining the quantity of lubricant in contact between balls and raceways of a deep groove ball bearing. In the deep groove ball bearing, balls participate in transferring the load from one ring to another, as they pass through the contact zone [1]. In doing so, the balls are in mutual elastohydrodynamic lubrication (EHL) contact with the raceways [2]. In the EHL contact between the balls and the raceway, there is a certain amount of lubricant between contacting surfaces. The volume of lubricant in contact can be determined as the product of the contact zone's area multiplied by the thickness of the lubricant film between them. The relationship between the lubricant volume VLq (q = 1 for ball-outer ring contact, q = 2 for ball-inner ring contact) within the contact zone and the relative radial clearance e/δ0 (e – radial clearance; δ0 – contact deformation between ball and raceway) as well as the relative operational load FR/C (FR – operational load; C – bearing dynamic load rating) of the deep groove ball bearing 6206 is shown in Figure below. Based on the known quantity of lubricant volume VL within both contact zones, it becomes possible to estimate the concentration of contaminating particles that are entrapped in contact between ball raceways. This estimation can be related to the overall known concentration of abrasive particles within the bearing lubricant. Through this approach, it becomes feasible to assess and predict the level of abrasive wear occurring within bearing components during operation

Testing Surface Properties of 3D Printed Metals

The rapid development of additive manufacturing technologies has opened novel opportunities for producing metal components with a variety of uses. 3D printing of metals provides the capability to produce parts with complex geometry and offers design freedom that cannot be achieved through conventional methods. That is the reason why 3D printed metal parts are increasingly finding applications in areas such as automotive, aerospace, and tool manufacturing. Surface properties of 3D printed metal components are of great importance for the functionality of machine systems, because they often operate under conditions where contact stresses occur. There is just one standard that deals with the measurement and characterization of the surface texture of 3D printed metals – ASTM F3624-23 [1]. Generally, methods for testing surface properties are divided into two groups: non-destructive and destructive methods. The most commonly nondestructive methods for the determination of surface roughness are SEM, EDS, and XRD analysis. Also, all other ultrasonic thermographic, laser, atomic force microscopy (AFM), X-ray, magnetic, and eddy current methods (ETC) can be applied, but their limitations must be taken into account. Usually, post-processing methods are used to reduce the roughness of parts. It has been shown for stainless steel 316L that shot peening can reduce up to 50% of the average surface roughness [2]. Tribological properties are very important in cases where contacting parts is in the relative motion.For determining tribological properties well-known testing methods are adapted for 3D printed metals. The most commonly used are dry erosion, slurry erosion and high-stress abrasion tests on stainless steel 316. Testing procedures of ASTM B611 and ASTM G65 standards are used for determining wear properties of 3D printed cemented carbide, which is not metal, but that procedures can be applied on 3D printed metals [3]. For measuring the hardness of 3D printed metals the Vickers method is most frequently used. A large number of parameters such as AM technology, printing direction, postprocessing, and layer thickness influence surface properties. In general, surface characteristics of 3D printed metals are not extensively researched and can represent a significant area for investigation, especially when considering all influencing parameters

Impact of Ball Bearing Geometry and Operational Load on the Volume of the Lubricant in the Bearing's Loaded Zone

This paper presents the mathematical model for determining the quantity of lubricant in contact between balls and raceways of a deep groove ball bearing. In the deep groove ball bearing, balls participate in transferring the load from one ring to another, as they pass through the contact zone [1]. In doing so, the balls are in mutual elastohydrodynamic lubrication (EHL) contact with the raceways [2]. In the EHL contact between the balls and the raceway, there is a certain amount of lubricant between contacting surfaces. The volume of lubricant in contact can be determined as the product of the contact zone's area multiplied by the thickness of the lubricant film between them. The relationship between the lubricant volume VLq (q = 1 for ball-outer ring contact, q = 2 for ball-inner ring contact) within the contact zone and the relative radial clearance e/δ0 (e – radial clearance; δ0 – contact deformation between ball and raceway) as well as the relative operational load FR/C (FR – operational load; C – bearing dynamic load rating) of the deep groove ball bearing 6206 is shown in Figure below. Based on the known quantity of lubricant volume VL within both contact zones, it becomes possible to estimate the concentration of contaminating particles that are entrapped in contact between ball raceways. This estimation can be related to the overall known concentration of abrasive particles within the bearing lubricant. Through this approach, it becomes feasible to assess and predict the level of abrasive wear occurring within bearing components during operation

Electrical characteristics of female and male human skin

Bioimpedance spectroscopy (BIS) is a popular method for characterizing the electrical properties of biological tissues. In this study, BIS measurement data of female and male human skin were analyzed and compared. The electrical characteristics of tissue were followed according to four-parameters of the Cole-Cole model: low frequency resistance R0; high frequency resistance R∞; relaxation time t and parameter a. Individual electrical characteristics of human skin were determined for 30 women and 30 men. The distribution and one-way analysis of variance (one-way ANOVA) of the Cole-Cole parameters R0, R∞, t, a within the human population indicated their different dependence on gender. Parameter a, which is higher in the female subjects (a =0.83±0.03) than in the male subjects (a=0.7±0.05), is strongly dependent on gender (p=0). Parameter R∞ also significantly depends on gender (p=0.002), while t and R0 seem to be slightly related to gender (p>0.05)

Multistep generalized transformation method applied to solving equations of discrete and continuous time-fractional enzyme kinetics

In this paper, Caputo based Michaelis–Menten kinetic model based on Time Scale Calculus (TSC) is proposed. The main reason for its consideration is a study of tumor cells population growth dynamics. In the particular case discrete-continuous time kinetics, Michaelis–Menten model is numerically treated, using a new algorithm proposed by authors, called multistep generalized difference transformation method (MSGDETM). In addition numerical simulations are performed and is shown that it represents the upgrade of the multi-step variant of generalized differential transformation method (MSGDTM). A possible conditions for its further development are discussed and possible experimental verification is described.This is the peer-reviewed version of the article: Vosika, Z., Mitić, V.V., Vasić, A., Lazović, G., Matija, L., Kocić, L.M., 2017. Multistep generalized transformation method applied to solving equations of discrete and continuous time-fractional enzyme kinetics. Communications in Nonlinear Science and Numerical Simulation 44, 373–389. [https://doi.org/10.1016/j.cnsns.2016.08.024

The Nano-Scale Modified BaTiO3 Morphology Influence on Electronic Properties and Ceramics Fractal Nature Frontiers

Featured Application The nano BaTiO3 modification could lead towards innovation in nanocoating of ceramic grains in function of submicron intergranular capacitors. The electronic parameters integration in the frame of microelectronics in intergranular phenomena by fractals is opening novel route in miniaturization and integrations. Fractal analysis and calculations provide necessary fractal corrections for sample synthesis. Abstract The BaTiO3 ceramics applications based on electronic properties have very high gradient scientific and industrial-technological interests. Our scientific research has been based on nano BaTiO3 modified with Yttrium based organometallic salt (MOD-Y). The samples have been consolidated at a sintering temperature of 1350 degrees C. Within the study, the new frontiers for different electronic properties between the layers of BaTiO3 grains have been introduced. The research target was grain boundary investigations and the influence on dielectric properties. After scanning electron microscopy and dielectric measurements, it has been established that modified BaTiO3 samples with larger grains showed a better compact state that led to a higher dielectric constant value. DC bias stability was also investigated and showed a connection between the grain size and capacitance stability. Analyses of functions that could approximate experimental curves were successfully employed. Practical application of fractal corrections was performed, based on surface (alpha (s)) and pore size (alpha (p)) corrections, which resulted in obtainment of the relation between the capacitance and Curie temperature. Successful introduction of fractal corrections for capacitance-Curie temperature dependence for a set of experimental data is an important step towards further miniaturization of intergranular capacitors

The Nano-Scale Modified BaTiO3 Morphology Influence on Electronic Properties and Ceramics Fractal Nature Frontiers

The BaTiO3 ceramics applications based on electronic properties have very high gradient scientific and industrial-technological interests. Our scientific research has been based on nano BaTiO3 modified with Yttrium based organometallic salt (MOD-Y). The samples have been consolidated at a sintering temperature of 1350 °C. Within the study, the new frontiers for different electronic properties between the layers of BaTiO3 grains have been introduced. The research target was grain boundary investigations and the influence on dielectric properties. After scanning electron microscopy and dielectric measurements, it has been established that modified BaTiO3 samples with larger grains showed a better compact state that led to a higher dielectric constant value. DC bias stability was also investigated and showed a connection between the grain size and capacitance stability. Analyses of functions that could approximate experimental curves were successfully employed. Practical application of fractal corrections was performed, based on surface (αs) and pore size (αp) corrections, which resulted in obtainment of the relation between the capacitance and Curie temperature. Successful introduction of fractal corrections for capacitance-Curie temperature dependence for a set of experimental data is an important step towards further miniaturization of intergranular capacitors. © 2020 by the authors