Finite Element Analysis of Piston for Structural Assessments

This paper presents the assessment of different piston head geometry made of aluminum and magnesium alloy. ANSYS finite element analysis is used to analyze the piston under static and transient conditions. Round and flat piston head is constructed using SOLIDWORK software and the exported to ANSYS WORKBENCH. According to static analysis, it is found that flat head piston produced higher stress compared with round head piston. Similar trend is observed when transient analysis is conducted where round piston head capable to produce almost stress consistency with respect to time.

Analytical results in transient brush tyre models: theory for large camber angles and classic solutions with limited friction

This paper establishes new analytical results in the mathematical theory of brush tyre models. In the first part, the exact problem which considers large camber angles is analysed from the perspective of linear dynamical systems. Under the assumption of vanishing sliding, the most salient properties of the model are discussed with some insights on concepts as existence and uniqueness of the solution. A comparison against the classic steady-state theory suggests that the latter represents a very good approximation even in case of large camber angles. Furthermore, in respect to the classic theory, the more general situation of limited friction is explored. It is demonstrated that, in transient conditions, exact sliding solutions can be determined for all the one-dimensional problems. For the case of pure lateral slip, the investigation is conducted under the assumption of a strictly concave pressure distribution in the rolling direction.

Numerical calculations of the autorotating rotor under transient conditions

It is necessary to evaluate the performance of the main rotor in design stages of a rotorcraft to obtain the assumed lift force and low aerodynamic drag. This paper presents the CFD numerical analysis of the autorotating rotor under transient conditions. Auto-rotation is particularly important in the case of gyrocopters, while in the case of helicopters it is related to flight safety. The calculations allowed us to obtain aerodynamic forces and torque as a function of rotor azimuth for individual rotor blades. The analysis was performed for a rotor tilted by 15 degrees toward the airflow direction. A geometric model was created for the calculations and then a computational model was created in Ansys Fluent software. The k-ω SST model was adopted as the turbulence model which considers the turbulence kinetic energy and its unit dissipation. The obtained results are presented in a rotor and flow coordinate system.

Water Vapour Sorption and Moisture Transport in and Across Fibre Direction of Wood

Water vapour sorption experiments are frequently used to characterise the absorption and desorption of water in wood during transient conditions in relative humidity. When interpreting such experiments, it is still unclear to what extend the resulting time-dependent change of sample mass (i.e. sorption kinetics) is influenced by moisture transport, sorption and sorption related processes. To evaluate the impact of water vapour diffusion under such transient conditions, this study investigates the sorption kinetics of small wood samples with different lengths of transport pathways in and across fibre direction. For this purpose, water vapour sorption experiments on Norway spruce ( Picea abies ) samples were performed under identical climatic conditions at ambient air pressure and ambient standard temperature. The results showed that sample thickness has an impact on the sorption kinetics along the whole tested range of relative humidity. Differences between the sorption kinetics for samples in and across fibre direction were considerable at low relative humidity, indicating the relevance of water vapour diffusion through the lumen-pit-ray system. In contrast at high relative humidity, differences between the sorption kinetics for samples in and across fibre direction started to disappear while the impact of sample thickness was still considerable. Therefore, it seems as if an additional or modified process that depends on the number of sorption sites becomes relevant at an increased moisture content of wood. This process, as well as the increasing uptake and release of water across fibre direction, should be further investigated to gain a better understanding of the absorption and desorption of water in wood.

Dynamic Pressure Test and Analysis of Marine Ballasted Centrifugal Pump under Rapid Changing Conditions

Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and inner flow for the ballast pump are tested and analyzed. The results show that the dynamic pressure of each study scheme has cyclical increasing trends, however, the larger the amplitude of the flow rate reduction is, the greater the pressure increasing rate of the two measuring points. While the flow rate decreases to 0.4× Qd and 0.2× Qd, the rate of pressure increase is first fast and then slow. The dynamic pressure pulsation intensity is higher than the corresponding steady-state conditions after the transient conditions. With the increase in flow rate reduction, the characteristic frequencies of the dynamic pressure are 1APF (axial passing frequency) and 1BPF (blade passing frequency) and their harmonic frequency. The rapid decrease in flow rate causes the separation vortex in the impeller channel to be generated in advance, and the scale increases, which reduces the pulsation intensity of the pump outlet to prevent an increase in the level of broadband pulsation between 2APF and 1BPF.

ADAPTATION OF EARLY NEONATAL CHILDREN BORN FROM MOTHERS WHO REHIVED COVID-19 DURING PREGNANCY (DESCRIPTION OF TWO CASES)

The frequency of detection of infected children with SARS-CoV-2, which is 10% of the total number of infected, including newborns, suggests the need for careful diagnosis of pathological conditions that may occur in children, particularly in the neonatal period. If at the beginning of the detection of COVID-19 it was claimed that the coronavirus SARS-CoV-2 does not affect children, then analyzing the new data we see that 2% of patients with diagnosed clinical cases of COVID-19 are children, including newborns. The article describes observations of several clinical cases of early neonatal adaptation of children born to women who had mild to severe COVID-19 during the first and third trimesters of pregnancy, respectively, because these children at birth had vesicular rash, symptom, which is considered rare for this category of newborns. In 2020, 2,300 newborns were born in the neonatal department of the 3rd City Clinical Hospital of Lviv, with every 5th woman in labor (20%) relapsed to COVID-19 during pregnancy.Analyzing the course of early neonatal adaptation, we found that the adaptation period of such children may not differ from the adaptation of newborns in the number and manifestations of transient conditions characteristic of the first days of life, whose mothers did not suffer from COVID-19 during pregnancy. However, coronavirus infection in women in both the first and third trimesters of pregnancy may be associated with signs of congenital vesiculosis in children, accompanied by inflammatory changes in the blood and blood clotting in the period of early neonatal adaptation in the newborn. Children had no other signs of pathological symptoms (fever, lethargy, drowsiness, hypotension, rhinorrhea, pharyngitis, cough, respiratory disorders (tachypnea, wheezing), vomiting, diarrhea and feeding disorders)), characteristic of infectious diseases specific to newborns, which can be masked by transient states. Manifestations of transient conditions in the observed children were: milia, simple erythema, desquamative peeling of the epidermis, toxic erythema, physiological jaundice.Treatment of the affected areas of the skin with rash elements with 0.05% aqueous solution of chlorhexidine, a three-day course of ampicillin, administered to the child from the first hours of life at a dose of 100 mg / kg / day intravenously contributed to the disappearance of vesiculosis. The maintenance therapy was a multiprobiotic in the form of drops. In the presented cases, no obstacles to breastfeeding and cohabitation of mother and child were observed. In the departments of newborn maternity hospitals, it is necessary to find opportunities, for diagnostic purposes, to conduct microbiological studies of pustules and biomaterial from the mucous membranes of the genital tract to further compare the results and establish etiological factors of vesiculosis, determine biochemical blood tests - CRP, ALT, AST, LD serum, coagulation parameters.