CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
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INHOMOGENEITY OF ULTRASOUND FIELD DURING SONICATION EXPERIMENTS IN VITRO AND ITS INFLUENCE ON THE OVERALL AMOUNT OF ULTRASOUND ENERGY ENTERING A SONICATION VESSEL
Get PDFCurrent sonication experiments in vitro show immense variability in experimental set-ups and equipment used. Many factors such as presence of standing waves or position of sonicated sample in ultrasound field during the experiment affect ultrasound field parameters the sonicated samples actually experience. The main goal of this work was to quantify influence of position of sonicated sample on maximum acoustic intensity and overall amount of ultrasound energy entering sonication vessel when placed at different distances from ultrasound transducer. The measurements were performed in a water sonication tank with use of a circular unfocussed ultrasound transducer (d = 19 mm) and needle hydrophone (d = 0.5 mm). The measurements showed that the differences in amount of ultrasound energy (maximum and minimum energy were compared) entering particular well per time unit at different distances from ultrasound transducer range from 45.5% (48-well culture plate) to 109.9% (96-well culture plate). Moreover, the maximum acoustic intensity of ultrasound field entering particular well can differ by up to 233.2%. Therefore, position of sonicated sample in ultrasound field should not be neglected during sonication experiments in vitro
Enhancing Plasma Torch Efficiency: Wet Steam Cooling
Get PDFThe efficient use of wet steam for plasma torch cooling and water plasma generation is important for reliable plasma generator design. Wet steam, due to phase transformation capability, improves heat removal at lower gas flow rates if compared to liquid water. To evaluate the wet steam cooling potential, a numerical model is proposed, incorporating governing equations (mass, momentum, energy, current, and Ampere\u27s law) are expressed in the cylindrical coordinate system. The model is applied to investigate the wet steam cooling feasibility for the anode of a direct current plasma torch with non-transferred arc. Electric arc modeling examines anode spot location and anode surface temperature distribution for a 120 A arc current and gas flow rates of 42, 90, and 140 l/min under steady flow conditions. Analysis of spatial vapor content distribution in the refrigeration channel highlights unfavorable conditions when wet steam becomes dry
Study of electric field distribution on plasma and plasma catalysis reactor for different electrode configurations and pellet sizes
Get PDFIn various non thermal plasma based applications, the dynamics of electric fields and charged particle interactions are crucial. In order to find an efficient plasma reactor, the effects of different electrode configurations for the plasma approach and pellet packaging & optimal sizing for the plasma catalysis approach were studied for 6 different types of volume discharge and surface discharge reactor using COMSOL Multiphysics 6.0. The different electrode configurations viz. concentric cylindrical, square and helical as volume discharged reactors and floating & 2 types of non-floating electrodes as surface discharge reactors are considered. The effect of different size (diameter 1/3/5 mm) of pellets were studied for helical and cylindrical plasma reactors for plasma catalysis. The simulated results were then experimentally verified and validated for production of ozone and the conversion or reduction of NOx from diesel exhaust
CORSET PRESSURE PADS EVALUATION USING A CAD/CAM METHOD
Get PDFPressure pads are small hand-made corset components used for scoliotic curve correction by applying pressure to the body segment. The design and accuracy of these pads can be increased by using modern approaches like CAD modeling and additive manufacturing. The aim of this research was to apply these methods in the pressure pad development process and evaluate the suitability of the designed prototypes. A CAD software SOLIDWORKS was used for the pad design and 2 manufacturing technologies have been selected, specifically FDM and MJF, for the pad production. As for the material of which the pads could be manufactured, PLA, PETG and PA12 have been selected. Abaqus software, using the finite element method, has been chose for the 9 pad prototypes strength calculation, from which 6 have passed the test. It would be appropriate to expand the given research with CAD pressure pads of various optimized designs with different types and densities of infills
ROBUST CONTROL OF OXYGEN SATURATION DURING MECHANICAL VENTILATION
Get PDFAcute respiratory distress syndrome (ARDS) is a disease that has a high reported mortality rate. The treatment for ARDS typically involves mechanical ventilation that is tailored to each patient\u27s needs. A crucial aspect of this treatment is maintaining adequate oxygen saturation of haemoglobin by setting the fraction of inspired oxygen. This paper proposes a design method of robust proportional-integral-derivative (PID) controllers using a gas exchange model during ARDS. Several PID controllers were synthesized for different sub-operational ranges defined by measurable quantities of the mechanical ventilator and the patient using a mixed sensitivity H∞ approach. In simulations, the controller demonstrated high robustness to external changes and changes in the patient\u27s condition, with saturation always above 88%. Although further validation of the controller is required, the results indicate that the presented robust control method has the potential to be clinically relevant
Concrete and reliability of existing prestressed bridge structures
Get PDFA large number of post-tensioned concrete bridges were built in the second half of the last century. They have often been insufficiently maintained during their lifetime (usually around 50 years). Nowadays, these structures exhibit significant deterioration, mainly due to leakages and also due to various other deficiencies such as a small concrete cover. Their load-bearing capacity needs to be verified. This paper focuses on estimating the load-bearing capacity calculation of existing post-tensioned concrete bridges. In the engineering practice, this is carried out using the partial factor method according to the currently valid standards (Czech standards ČSN and the Eurocodes), which often impose more stringent requirements than the original standards. The partial factor method then often leads to low load-bearing capacities. This study deals with the bridge for which a very low load-bearing capacity has been determined. For this reason, a comparative probabilistic analysis was performed, allowing for a better description of the uncertainties in the resistance and load effect variables. The probabilistic approach appears to be less conservative and yields a higher load-bearing capacity
DESIGN OF INSTRUMENTED INSOLE FOR GAIT DYNAMICS MONITORING
Get PDFThis article focuses on the design and implementation of a device aimed at monitoring gait dynamics. In clinical settings, gait dynamics are conventionally observed within specialized motion laboratories that rely on camera systems or pressure-sensitive floor mats. Unfortunately, these methods provide clinicians with only a temporally restricted perspective on a patient\u27s health within the hospital environment. The objective of this study is to propose and develop a functional prototype of a measurement device that utilizes force-sensing resistors integrated into a sensorics insole placed within a shoe. By fusion of the 3D printing technology and force-sensing sensors, we developed a wearable prototype consisting of an instrumented insole and wireless data acquisition unit. This approach enables the capture of both static and dynamic parameters of gait, not only in clinical environments but also in non-hospital settings
FRACTURE ENERGY OF UNSTABILIZED RAMMED EARTH: INFLUENCE OF CLAY TYPE AND CONTENT IN THE MIXTURE
Get PDFThis study explores the fracture energy of unstabilized rammed earth, focusing on the influence of different types and amounts of clay within the mixtures. Utilizing a three-point bending test, this research evaluates the fracture energy of rammed earth to better understand how variations in clay type and content affect its structural integrity. The findings reveal significant differences in fracture energy values correlated with the clay\u27s molecular structure and the interlayer chemical bonds. Clays such as illitic-kaolinitic, montmorillonite, and illite were tested, each demonstrating unique responses to mechanical stress based on their respective chemical bonds. Mixtures containing illitic-kaolinitic clay exhibited the highest fracture energy values, attributed to the presence of kaolinite due to its robust interlayer bonds. The results contribute insights into the selection and optimization of rammed earth materials for sustainable construction, aligning with the growing emphasis on ecological and durable building resources
A geometry projection method for designing and optimizing additively manufactured variable-stiffness composite laminates
Get PDFA method for designing laminates is presented using geometry projection to optimize the layout of additively manufactured variable-stiffness composite laminates. By considering fiberreinforced bars as geometric primitives, the geometry projection methodology is extended to include optimizing regions with intersecting load paths. This is achieved by utilizing a dual representation of bars, which considers the geometric parameters and the element-wise density field representation. The dual representation enables the combining and overlapping of bars, resulting in a localized orthotropic material response at overlapping regions that mitigates the transverse compliant response of fiberreinforced components. The proposed method’s effectiveness is demonstrated through minimizing the compliance of the Messerschmitt-Bölkow-Blohm beam problem, a well-known benchmark problem in topology optimization
DETECTION METHOD OF TUNNEL SURROUNDING ROCK LEAKAGE CHANNEL BASED ON IMPROVED CHAOTIC PARTICLE SWARM OPTIMIZATION ALGORITHM
Get PDFLeakage channels in the tunnel lining and surrounding rock can cause water seepage on the tunnel walls, significantly impacting the safety and stability of tunnel operations. Therefore, precise detection of leakage channels within the tunnel lining and surrounding rock is essential for maintaining tunnel safety. In this paper, based on the theory of natural potential field exploration, the distribution of electric potential on the tunnel walls is investigated. An improved particle swarm optimization algorithm is applied to invert the spatial charge distribution within the tunnel lining and surrounding rock. The distribution of spatial charges is used to infer the location and direction of leakage channels within the tunnel lining and surrounding rock, providing guidance for accurate remediation measures. The research results show that the variance of charge distribution in the forward modeling inversion is 1.58%, and in the inversion of measured data, the variance is 7.6%. The inverted results display charge anomaly regions consistent with the actual locations of leakage channels