Arc Plasma Flow Variation by Obstruction Structures between Anode and Cathode

Arc plasma flow between electrodes has been investigated in several studies. However, in the industrial field, arc plasma flow between electrodes is hindered by interfering materials such as filler metal in arc welding, substrates in chemical vapor deposition, and powders in sintering. Therefore, in this study, high temperature arc plasma flow analysis via three obstruction structure shapes was performed to understand the inter-electrode interference phenomena. COMSOL Multiphysics was used for the analysis; COMSOL interface such as electric field, magnetic field, heat transfer, and fluid flow (laminar flow) was applied and Multiphysics such as plasma heat source and temperature coupling were considered. The temperature and velocity of the arc plasma were determined and the energy transfer between the electrodes was analyzed. We confirmed that the concave shape has a lower average heat flux than the other shapes, with the arc pressure evenly distributed in the anode. It is concluded that the concave shape can reduce the flow of the plasma from the anode and obtain even distribution of the arc plasma in the radial direction.

Origin and evolution of chemical composition of mineral waters of Szczawno-Zdrój inferred from long-term variation of ionic ratios, Sudetes Mts. (SW Poland)

The archival records of chemical composition of mineral waters in Szczawno-Zdrój spa were analyzed in terms of variation of ionic ratios to explain the possible source and origin of the major compounds dissolved in water and evolution of groundwater chemical composition in time. The analyzed data contained the longest available series of chemical records, dating back to 1962, and related to waters discharged by five main springs: Dąbrówka, Marta, Młynarz, Mieszko and Mieszko 14. The research showed that mineral waters in Szczawno-Zdrój belong to shallow meteoric CO2-rich, Rn-containing groundwaters which form their chemical composition mainly through the interaction with aquifer rocks. Detailed analysis of long-term variation of ionic ratios revealed that (1) the carbonates weathering, mostly acid hydrolysis of limestones and dolomites, and (2) the ion exchange reactions with clay minerals, mainly the so-called natural softening, play a fundamental role in formation of the chemical composition of studied waters. Both processes are responsible for the occurrence of dominant ions in solution such as Ca2+, Mg2+, Na+, and HCO3−. The aluminosilicates hydrolysis occurs with variable extent, but plays rather secondary role in formation of chemical composition. The time distributions of major element concentrations in studied waters showed a characteristic “concave” shape, indicating the decrease in concentrations beginning in the 60s and ending around 2005–2010. Such “concave” shape trends are not reflected in time distribution of ionic ratios which strongly suggests the occurrence of a simple dilution of chemical composition of mineral waters by the influx of fresh water. The observed considerable fluctuations of chemical composition of mineral waters in Szczawno-Zdrój are most probably associated with climatic factors, namely: the increased amounts of atmospheric precipitation in particular periods of time and its seasonal distribution. Such influx of fresh waters reduces considerably mineralization of shallow groundwaters and directly increases springs discharge.

Increasing Performance Efficiency by Investigating the Surface of the Solar Air Heater Collector

This article discusses the issues of increasing the working surface of the device by giving a geometrically concave shape to the air ducts of the proposed solar air heater, designed to save energy and increase the possibility of efficient use of renewable energy sources, which is becoming increasingly important topical issue today. The influence of the concave shape on the air movement relative to the outer surface of the concave air duct is investigated.

Loading Effect of Prosthetic Feet’s Anthropomorphicity on Transtibial Osseointegrated Implant

ABSTRACT Introduction Osseointegrated implants for direct skeletal attachment of transtibial prosthesis carry risks that are yet to be fully resolved, such as early loosening, mechanical failure of percutaneous and medullar parts of implant, periprosthetic issues, and infections. Underloading could lead to early loosening and infection. Overloading might compromise the bone–implant interface. Therefore, Goldilocks loading regimen applied by transtibial bone-anchored prostheses is critical for safe and efficient development of osseointegration around the implant during rehabilitation and beyond. We hypothesized that Goldilocks loading could be achieved when ambulating with a so-called anthropomorphic prosthetic ankle showing moment–angle relationship similar to a sound ankle. Materials and Methods Quantitative characteristics of the moment–angle curve of the sound ankle during dorsiflexion phase of a free-pace walking were extracted for 4 able-bodied participants (experiment 1). A slope of the moment–angle curve (stiffness) was calculated twice: for the first half and for the second half of the moment–angle curve. The difference of stiffnesses (those at the second half minus at the first half) was called the index of anthropomorphicity (IA). By definition, positive IA is associated with concave shape of the moment–angle curve, and the negative IA is associated with convex shape. In experiment 2, the same recordings and calculations were performed for 3 participants fitted with transtibial osseointegrated fixation during walking with their usual feet and the Free-Flow Foot (Ohio Willow Wood). The Free-Flow Foot was selected for its anthropomorphicity demonstrated in the previous studies with amputees using traditional socket attachment. Results The IA was 5.88 ± 0.93 for the able-bodied participants, indicating that the stiffness during the first part of the dorsiflexion phase was substantially fewer than during the second parts, as the calf muscles resisted to angulation in ankle substantially less than during the second part of dorsiflexion phase. For amputees fitted with Free-Flow Foot, IA was 2.68 ± 1.09 and −2.97 ± 2.37 for the same amputees fitted with their usual feet. Conclusions Indexes of anthropomorphicity, while of different magnitude, were positive in control able-bodied group and in the amputee group wearing Free-Flow Foot, which was qualitatively associated with concave shape of their moment–angle curves. The 3 usual feet worn by the participants were classified as nonanthropomorphic as their individual moment–angle curves were convex and the corresponding IAs were negative. Furthermore, this study showed that a foot with anthropomorphic characteristics tends to decrease maximal loads at the bone–implant interface as compared to the nonanthropomorphic feet and possibly may minimize the risks to compromise the integrity of this interface.

Housing Profile Design for Improved Apex Seal Lubrication Using a Finite Length Roller Elastohydrodynamic Lubrication Model

Finite-length roller contacts are found in apex seal-housing interfaces in rotary engines, as well as in many other mechanical systems, such as those at the interfaces of meshing gear teeth, cam followers, and roller bearings. Rollers are usually designed with crowns and modified ends to mitigate the negative effects of misalignment, thermal deformation, and edge-induced non-uniform displacement. A crowned-roller elastohydrodynamic lubrication model is enriched and employed to investigate seven housing surface profiles, including a sinusoidal recess, sinusoidal ends, the combination design of a sinusoidal recess and sinusoidal ends, multiple sinusoidal recesses, a concave shape, and a concave shape with sinusoidal ends or round corners, aiming to improve the tribological performance of the interface via increasing the minimum film thickness but reducing the average and maximum film thicknesses, and lowering friction coefficient. The modified discrete convolution and fast Fourier transform method with duplicated padding is utilized to deal with the potential free-end-surface effect. The simulation results suggest that the combinations of a concave shape and sinusoidal ends, or round corners, are the best designs because they can help distribute the lubricant most uniformly without causing a negative edge effect.

Concave Shape Microstrip Patch Antenna using SRR for 5G Applications

A single band microstrip-fed patch antenna is presented which contains the radiating structure having concave shape slots and split ring resonator loaded in the partial ground plane. This partial ground plane has been used to enhance the bandwidth of proposed antenna. Both the partial ground plane and radiating patch are perfect electric conductors. The patch is imprinted on a substrate named as Epoxy Glass FR-4 having thickness 1.6 mm, relative permittivity 4.4, and loss tangent 0.0024. The designed concave shape microstrip patch antenna (MPA) is resonate at single frequency band from 3.4-3.8 GHz with 400 MHz bandwidth and corresponding return loss of -25dB. A parametric study has been performed for the concave shape slots located in the patch. Proposed MPA is simulated using Computer Simulation Technology Microwave Studio Version 14.0 (CST MWS V14.0). Furthermore, the radiation performance of antenna in terms of gain and radiation efficiency has been analyzed . The proposed antenna is having a peak gain of 3.2 dB and radiation efficiency of 94%.