Papers by Keyword: CMC

Abstract: Multipath interference poses a significant challenge in satellite-based navigation systems, including NAVIC (Navigation with Indian Constellation), degrading the accuracy of position estimates. This study proposes a comprehensive approach to address multipath errors in NavIC receivers, combining multipath error calculation using the code minus carrier method with multipath reduction through mode decomposition techniques EMD- empirical mode decomposition, VMD-variational mode decomposition, and SVMD-successive variational mode decomposition. Data was collected from a NavIC receiver located at KLEF University in Guntur, India with latitude 16.44 N, and longitude 80.62 E during the period from April 12th to 14th, 2017. Initially, multipath errors are calculated by subtracting NavIC carrier phase measurements from code phase measurements, providing insights into the magnitude of multipath interference. Subsequently, the received signal is decomposed using EMD, VMD, and SVMD to extract intrinsic modes or oscillatory components representing different signal characteristics. The direct signal is reconstructed by selectively filtering or removing multipath-related modes, reducing multipath interference. To evaluate the effectiveness of each decomposition method, the SDE (standard deviation error) of the reconstructed multipath signal is computed. The decomposition method yielding the lowest SDE is identified as the optimal approach for multipath reduction in NavIC receivers. By integrating the code minus carrier method with mode decomposition techniques, significant enhancements in navigation performance can be achieved, facilitating reliable and precise positioning for various applications.

Abstract: In order to develop sustainable materials for a variety of industries, hybrid polymer composites reinforced with natural fibers are emerging as a critical option. The various forms of hybrid composites and the employment of various polymers—such as thermoplastics, thermosets, and elastomers—when paired with natural fibers are the main topics of this narrative theoretical review. The article examines the applications of various composites in industries such consumer products, construction, automotive, and aerospace, providing insights into how polymer choice affects a composite's applicability for a given application. Through an examination of recent advancements in hybrid composite design and polymer utilization, this analysis offers a thorough grasp of the present trends and potential applications of these materials in promoting sustainable engineering practices.

Abstract: This work presents the preparation of mechanically exfoliated graphene-CMC biocomposite ink which was utilized in the printing process of SC individual electrodes via InkJet printing (IJP) technique. Three individual electrodes were fabricated using such technique with high abilities to control the geometry and tuning both resulting sheet resistance and thickness. The printer showed a good command of printing computer-aided designs with high resolution and fabricated well-homogenised patterns. The electrochemical behaviour of the fabricated electrodes was investigated in 0.1M NaOH. Results illustrate that electrodes have shown good capacitive behaviour and EDLC was the main energy storage mechanism. There was a direct relationship between the number of the printed layers and the resulting electrical parameters. A maximum areal capacitance of 16.58 mF/cm² was achieved with printing 80 layers. Such results indicate that the formulated ink would be potential for electrochemical energy storage applications.

Abstract: Asymmetrical Four Point Bend test method is proposed for measurement of interlaminar shear strength in continuous fiber reinforced ceramic composites. The current standard ASTM test method (ASTM C1425) for interlaminar shear strength of composites uses a double edge notched compression (DNC) coupon. Large variation in measured strength is observed with the standard ASTM test method, possibly due to machining variability and damage at the notches. The proposed test AFPB method for ILSS is adapted from ASTM C1469 Standard Test Method for Shear Strength of Joints of Advanced Ceramics. This test method does not require any machining of notches and the sample size requirement is much smaller than the ASTM test method. The shear loading in this method is similar to the standard short beam shear test (ASTM D2344) with higher shear to tensile ratio compared to SBS with AFBP. Using finite element analysis, coupon geometry and the distance between the loading and support pins was optimized to maximize shear and minimize tensile and compressive stresses on the specimen. It was found that the variability in the measured ILSS strength was lower with this method compared to the ASTM standard method using the DNC specimen. In addition, the value of ILSS measured using AFPB method was found to be consistently higher than that measured using DNC coupons. It was also found that specimen preparation (cutting, polishing, etc.) did not have significant effect on the measured strength.

Abstract: In the electroless nickel-boron coating process, surfactant helps to minimize the surface tension between the substrate and the electrolyte in the bath. Despite, its high cost and the formation of micelles from monomeric surfactant molecules at its critical micelle concentration (CMC), it is essential to optimize the concentration while using in the bath. In this study, to solve this problem, mathematical models are developed using regression and artificial neural network (ANN) techniques to relate the concentration of amphoteric surfactant (0-0.162 g/L) as an independent variable and microhardness as a dependent variable. Then, the developed model was used to optimize microhardness at CMC using a genetic algorithm (GA). The goodness of fit of the models was evaluated using the coefficient of determination (R²). The ANN model was found to be the best fit with R² = 0.99. The maximum microhardness of 852 HV was achieved at the CMC of 0.064 g/L, from the GA using the validated model as a fitness function.

Abstract: The main objective of this study was to evaluate the effect of soda ash (SA) and carboxy methyl cellulose (CMC) on the rheological of white bentonite collected from Boyolali, Indonesia (BWB). The first work was the determination of BWB composition with XRF and the study on the effect of SA on the swelling index. The second step was to study adding SA and CMC on viscosity at 600 and 300 rpm. Another rheological parameter (yield point to plastic viscosity ratio, μ_P/μ_V) was determined based on the viscosity data. The results showed that the BWB sample tended to be categorized as Ca-bentonite with a calcium oxide content of 0.70 wt.% and contained montmorillonite, quartz, and pyrophyllite. SA and CMC in BWB increased the interlayer space of the montmorillonite. The addition of 14 wt.% SA to the BWB sample showed the maximum swelling index of 10 mL/2 g. The optimal formula meeting API 13A specifications is BWB sample of 81.23 wt.%, soda ash 14 % (w/w), and CMC 4.77 wt.%. This product results in the viscosity at a reading of 600 rpm of 30 cP and the μ_P/μ_V ratio of 1.0. Therefore, the product is potential as a candidate material for drilling mud.

Abstract: Fe₃O₄/Carboxymethyl Cellulose (CMC)/Polyvinyl Alcohol (PVA) hydrogel magnetic was successfully synthesized by using the freezing-thawing process. Meanwhile, the filler of Fe₃O₄ nanoparticles was successfully fabricated by co-precipitation method. Magnetic hydrogel and Fe₃O₄ was revealed by using X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Vibrating Sample Magnetometer (VSM), and Small Angle X-ray Scattering (SAXS) to investigate the content of elements in the Fe₃O₄ filler, the functional group network of samples, magnetic properties of magnetic hydrogel and Fe₃O₄, and nanostructure of magnetic hydrogel, respectively. The magnetic properties of magnetic hydrogel decreased as the decrease in the particle sizes of the Fe₃O₄ nanoparticles. On the other hand, the saturation magnetization of magnetic hydrogel decreased as the freezing-thawing route increased in number. This condition can be concluded that the distribution of the Fe₃O₄ filler in CMC/PVA magnetic hydrogel was more effective when the route number of freezing-thawing reached the maximum process (7x processes). Moreover, the nanostructure of magnetic hydrogel revealed the composition of the crystalline phase of CMC/PVA hydrogel of approximately 6 nm. By these characteristics, Fe₃O₄/CMC/PVA magnetic hydrogel is potential to be used as smart gel such as artificial muscle, switch-of, and the others.

Abstract: The increasing market share of highly volatile electricity generated from renewable sources like wind or solar energy, leads to enormous challenges in the energy sector. Since large-scale storage systems are neither currently nor in the near future available, the gap between electricity from renewable sources and current electricity demand has to be closed with flexibly operated conventional power plants. In order to be a viable, cost-effective option in tomorrow’s energy market future power plants must be highly efficient while having low CO₂ emissions. Furthermore, they have to be highly reactive to counter instabilities in the electrical grid due to fluctuations in renewable sources. Current materials used in power plants are only within limits suited to experience extreme changes in operational loads. However, extreme changes of operational loads will become increasingly severe with a growing share of renewables. Our project team has developed a new concept for CMC-jacketed pipes to alleviate these issues. Recently, this concept was further developed and tested in laboratory as well as a large-scale application test at Grosskraftwerk Mannheim (GKM). All tests are still ongoing. Additionally, to the use in modern highly efficient power plants such CMC-jacketed piping is also suitable for other high-temperature applications, like e.g. solar power plants or industrial chemical applications.

Abstract: Fiber coatings for BN/SiC-and BN/Si₃N₄-bilayer systems were developed for the use in SiC/SiC composites. All coatings were produced with high process velocities of 500 m/h by a continuous roll-to-roll dip-coating process. The fiber surface was fully covered with a homogeneous coating and without fiber bridging. Tensile tests of fiber bundles were used to examine potential degradation of the fiber properties due to the application of the coatings. The coated fiber bundles showed a reduction of the maximum tensile load to 90.0 % for the BN/Si₃N₄ and to 86.7 % for the BN/SiC coating in comparison to the fiber bundle in the as-received state. A thermal treatment of the coated fiber bundles up to 1650 °C led to no reduction of their maximum tensile load. SiC/SiC composites were fabricated by polymer infiltration and pyrolysis. The flexural strength and strain of composites with BN/SiC fiber coating were improved to 467 MPa and 0.42 % in comparison to the composites without fiber coating. The composites with BN/SiC coating showed toughened fracture behavior with fiber pull-out effects.

Abstract: Ceramic materials are suitable for use in the high temperature range. Oxide ceramics, in particular, have a high potential for long-term applications under thermal cycling and oxidising atmosphere. However, monolithic oxide ceramics are unsuitable for use in high-temperature technical applications because of their brittleness. Thin-walled, oxidation resistant, and high-temperature resistant materials can be developed by reinforcing oxide ceramics with ceramic fibres such as alumina fibres. The increase of the mechanical stability of the composites in comparison to the non-fibre reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fibre under mechanical stress or deformation. Components made of fibre-reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. Therefore, the manufacturing should be improved. The ceramic injection moulding (CIM) process is established in the production of monolithic oxide ceramics. This process is characterised by its excellent automation capability. In order to realise large scale production, the CIM-process should be transferred to the production of fibre-reinforced oxide ceramics. The CIM-process enables the production of complicated component shapes and contours without the need for complex mechanical post-treatment. This means that components with complex geometries can be manufactured in large quantities.To investigate the suitability of the injection moulding process for the production of OCMCs, two different feedstocks and alumina fibres (Nextel 610) were compounded in a laboratory-scale compounder. The fibre volume fractions were varied. In a laboratory-scale injection moulding device, microbending specimens were produced from the compounds obtained in this way. To characterise the test specimens, microstructure examinations and mechanical-static tests were done. It is shown that the injection moulding process is suitable for the production of fibre-reinforced oxide ceramics. The investigations show that the feedstocks used have potential for further research work and for future applications as material components for high-temperature applications in oxidising atmospheres.