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...     

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.     

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.     

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.     

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.     

Comparison analysis of graphene oxide reduction methods

Abstract

Graphene oxide was reduced by aspartic acid, β-mercaptoethanol in the acidic mixture, hydrothermal method and by atomic hydrogen (deuterium and tritium). Raman spectroscopy and FTIR indicate high reduction efficiency of hydrothermal method. FTIR indicates that atomic hydrogen results in the formation C_sp3H-bonds on the graphene surface. Graphene oxide can be effectively reduced by β-mercaptoethanol in the acidic mixture even at room temperature.     

Generating flat patterns for folded structures: Search space reduction

A significant number of packaging products can be represented as folded structures. This contribution demonstrates an approach for generating a set of feasible flat patterns based upon a graph representation of the folded structures. It presents algorithms to detect several typical design features. In order to present alternative flat patterns with different properties to the designer, it is preferred to first generate all feasible spanning trees. Two options to decrease the number of generated spanning trees are then proposed: user constraints and overlapping features. Each of these reduction possibilities is examined, and several practical examples with outcomes are shown. The presented framework shows a decrease of up to 98.5% in the number of possible flat patterns for the investigated parts.     

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.