Wear Resistance of Carbide and Boride Coatings on U8A Steel

Wear resistance measurements have been made with U8A steel bearing protective coatings based on the carbides of titanium, vanadium, and chromium or iron borides, for various forms of wear. The carbide and boride coatings raise the wear resistance considerably (by factors of 6-30 in accordance with the type of wear). Measurements have been made on the microhardness, microbrittleness, and adhesion of the coating to the substrate, which are effective characteristics that quite fully reflect the effects of the microhardness and state of stress, structure, and defectiveness on the wear resistance.     

Effect of the Geometric Parameters of a Layered Powder Composite on Its Magnetic Properties

The effect of thickness of magnetic conductor and number of electrically insulating layers on the magnetic properties in an alternating field of a layered powder-metallurgy soft-magnetic material based on iron was investigated. It was determined that increasing the thickness of the magnetic conductor and frequency of the alternating current deteriorated the magnetic properties of the material. Creation of a layered structure in which ferromagnetic layers alternate with electrically insulating layers decreased specific magnetic losses.     

Coaxial Alginate Hydrogels: From Self-Assembled 3D Cellular Constructs to Long-Term Storage

Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell–cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability.     

Impact of the Zr-substitution on phase composition,structure, magnetic,and microwave properties of the BaM hexaferrite

Rapid developments in information technologies and a large rise in electrical and electronic equipment have generated different forms of electronic environmental contamination. Microwave absorption materials are important to avoid the damage that can be caused by electromagnetic radiation. A necessary condition for the absorption of the most incoming radiation is balanced wave impedance at the air/shield interface, which depends on the studied materials' magnetic and electrical properties. The paper introduces the preparation of BaFe_12-xZr_xO₁₉ (x = 0.1, 0.3, 0.6, 0.9, and 1.2) using a solid-state reaction technique. The studied samples were examined by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, and a vector network analyzer. The studied samples showed that controlling the grain size and the prepared samples' magnetic properties play an important role in enhancing the microwave radiation absorption. The examined samples can be a promising absorption material in electromagnetic shielding applications.     

Determination of contact points between workpiece and fixture elements as a tool for augmented reality in fixture design

Wireless Networks - Fixtures play a significant role in ensuring the quality of products in manufacturing engineering. The paper considers fork-type parts that have a complex spatial configuration...     

Experimental investigation of the dynamic behavior of railway track with sleeper voids

Railway Engineering Science - The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids. The increased dynamic loading in the voided zone and the...     

Structure Formation,Electrophysical and Mechanical Properties of an Electrically Conducting Ceramic Composite Based on Silicon and Boron Carbides

How the structure of electrically conducting ceramic composites in the SiC B₄C system is formed has been studied. The mechanical and electrophysical properties have been investigated as a function of the ratio of the components and the sintering conditions.     

Structure and Properties of La0.6Sr0.4 – xBaxMnO3 (0 ≤ x ≤ 0.4) Magnetoresistive Ceramics

The effect of Ba content on the phase composition, lattice parameter, ⁵⁵Mn NMR spectrum, resistance, and magnetoresistance of La_0.6Sr_{0.4 – x} Ba _x MnO₃ perovskites was studied. The lattice parameter of the single-phase ceramic samples was found to increase with increasing x. The tolerance factor increases and the ionic field strength decreases asx increases from 0 to 0.4. The ⁵⁵Mn NMR results obtained at 77 K indicate a high-frequency electron exchange between Mn³⁺ and Mn⁴⁺ in the ferromagnetic phase. The peak-magnetoresistance temperature tends to decrease with increasing x. The magnetoresistance of the ceramics is correlated with the bond covalence. It is inferred that the ceramics contain inhomogeneities differing in nature and length scale (macroscopic, mesoscopic, and microscopic), which influence their magnetoresistance.     

Peculiarities of Neurostimulation by Intense Nanosecond Pulsed Electric Fields: How to Avoid Firing in Peripheral Nerve Fibers

Intense pulsed electric fields (PEF) are a novel modality for the efficient and targeted ablation of tumors by electroporation. The major adverse side effects of PEF therapies are strong involuntary muscle contractions and pain. Nanosecond-range PEF (nsPEF) are less efficient at neurostimulation and can be employed to minimize such side effects. We quantified the impact of the electrode configuration, PEF strength (up to 20 kV/cm), repetition rate (up to 3 MHz), bi- and triphasic pulse shapes, and pulse duration (down to 10 ns) on eliciting compound action potentials (CAPs) in nerve fibers. The excitation thresholds for single unipolar but not bipolar stimuli followed the classic strength–duration dependence. The addition of the opposite polarity phase for nsPEF increased the excitation threshold, with symmetrical bipolar nsPEF being the least efficient. Stimulation by nsPEF bursts decreased the excitation threshold as a power function above a critical duty cycle of 0.1%. The threshold reduction was much weaker for symmetrical bipolar nsPEF. Supramaximal stimulation by high-rate nsPEF bursts elicited only a single CAP as long as the burst duration did not exceed the nerve refractory period. Such brief bursts of bipolar nsPEF could be the best choice to minimize neuromuscular stimulation in ablation therapies.     

Improvement of the Operating Processes in Boiler Furnaces of TÉTs-21 with the Help of Numerical Simulation of Thermal Gas Dynamic Processes

The use of numerical simulation and advanced means of computational hydrodynamics (domestic FlowVision software) for simulating the processes of flow and combustion in the systems for air and gas feeding, mixers, burners, and boiler furnaces has made it possible to advance the recirculation system and burners of the TÉTs-21 cogeneration plant and considerably reduce the NO_x emissions.