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- ItemOptimized Automatic Fault Electrode Management of Structural Health Monitoring of Aircraft Composites(IEEE, 2024-09-18) Pham, Ngoc Nam; Leuchter, Jan; Blasch, ErikDetecting the structural integrity of composite material used in an airframe includes passive nondestructive testing (NDT) and active electrical impendence tomography (EIT). EIT benefits enhance real-time response and accuracy but require pragmatic approaches to analyze the electrode errors from faulty or nonresponsive readings. The nonfunctional connections of measuring electrodes often occur during onboard aircraft operations for various reasons, such as deterioration. The deterioration of the electrode impedance impacts the quality of the EIT reconstructed image. This article compares different EIT methods and proposes surface fault detection EIT (SURFEIT). The proposed SURFEIT techniques that detect and compensate for faults are verified and evaluated using models with different locations of inside damages. Results prove the effectiveness of SURFEIT techniques, when the number of faulty electrodes is up to one-fourth of the total electrodes. The biggest benefit of the SURFEIT techniques is that they do not require any additional simulation work, lead to significant reduction of computation time, and afford very fast indications of damage locations. © 2024 IEEE.
- ItemLow-Voltage Low-Power Differential Difference Current Conveyor Transconductance Amplifier and Its Application to a Versatile Analog Filter(IEEE, 2024-07-12) Kumngern, Montree; Khateb, Fabian; Kulej, TomaszThis paper presents a new low-voltage low-power differential difference current conveyor transconductance amplifier (DDCCTA). The proposed DDCCTA utilizes a multiple-input gate-driven MOS transistor (MIGD-MOST) operating in the subthreshold region to achieve low supply voltage, minimum number of MOS differential pairs and minimum power consumption. To show the advantages of the proposed DDCCTA, it was used to realize a versatile analog filter. The filter uses three DDCCTAs, two grounded capacitors, and two grounded resistors to realize 65 transfer functions of low-pass, high-pass, band-pass, band-stop, and all-pass filters by appropriately selecting the input and output terminals without changing the filter topology. The filter also has the advantages of high-input impedance, which is ideal for voltage-mode circuits, independent control of the natural frequency and quality factor, and the ability to electronically tune the natural frequency. The proposed DDCCTA and versatile analog filter were designed and simulated using SPICE with TSMC 0.18 mu m CMOS technology to verify the new circuits. The proposed filter uses +/- 0.5 V of supply voltage and 103 mu W of power.
- ItemThermodynamics of Crystals Formation and Growth in a Sessile Droplet(Cell Press, 2024-05-09) Zhu, Hanliang; Zhang, Yue; Lu, Haiyang; Feng, Jianguo; Yan, Qi-Long; Brodský, Jan; Gablech, Imrich; Neužil, PavelAccurately detecting subtle thermodynamics during crystallization and associated water evaporation processes, especially around seed formation, has been challenging. Here, we report a method to investigate the complex energy changes during these simultaneous endothermic and exothermic events. We employ an open-space microcalorimeter, coupled with optical observation using a microscope equipped with a camera for real-time monitoring. This method reveals crystal formation by observing energy changes and simultaneously visualizing the sample. The concentration influence for potassium chloride crystallization is analyzed, including energy released and the evaporation thermodynamics using isothermal microcalorimetry. We also monitor the energy dissipation during crystallization, showing an 4.2 s period for potassium chloride crystal seed formation with a released energy of 11.9 J. This method can potentially reshape strategies for controlled crystallization across diverse industrial and laboratory settings. Extending beyond potassium chloride, our findings shed light on broader crystallization dynamics, paving the way for innovations in materials and energy sciences.
- ItemCompact 3D-Printed Unit for Separation of Simple Gas Mixtures Combined with Chemiresistive Sensors(MDPI, 2024-07-06) Zvonková, Magdaléna; Adámek, Martin; Skowronková, Nela; Dlabaja, Stepan; Matyáš, Jiří; Jaššo, Miroslav; Adámková, Anna; Mlček, Jiří; Salek, Richardos Nikolaos; Búran, MartinInexpensive chemiresistive sensors are often insufficiently selective as they are sensitive to multiple components of the gas mixture at the same time. One solution would be to insert a device in front of the sensor that separates the measured gas mixture and possibly isolates the unwanted components. This study focused on the fabrication and characterization of a compact unit, which was fabricated by 3D printing, for the separation and detection of simple gas mixtures. The capillary, the basic part of the compact unit, was 4.689 m long and had a diameter of 0.7 mm. The compact unit also contained a mixing chamber on the inlet side and a measuring chamber with a MiCS-6814 sensor on the outlet side. Mixtures of ethanol and water at different concentrations were chosen for characterization. The measured calibration curve was found to have a reliability of R2 = 0.9941. The study further addressed the elements of environmental friendliness of the materials used and their sustainability.
- ItemPlasma nanocoatings developed to control the shear strength of polymer composites(MDPI, 2019-07-15) Zvonek, Milan; Širjovová, Veronika; Bránecký, Martin; Plichta, Tomáš; Skácel, Josef; Čech, VladimírAll reinforcements for polymer-matrix composites must be coated with a suitable material in the form of thin film to improve compatibility and interfacial adhesion between the reinforcement and the polymer matrix. In this study, plasma nanotechnology was used to synthetize such functional nanocoatings using pure tetravinylsilane (TVS) and its mixtures with oxygen gas (O2) as precursors. The plasma-coated glass fibers (GFs) were unidirectionally embedded in a polyester resin to produce short composite beams that were analyzed by a short-beam-shear test to determine the shear strength characterizing the functionality of the nanocoatings in a GF/polyester composite. The developed plasma nanocoatings allowed controlling the shear strength between 26.2 – 44.1 MPa depending on deposition conditions, i.e., the RF power and the oxygen fraction in the TVS/O2 mixture. This range of shear strength appears to be sufficiently broad to be used in the design of composites.