Hybrid Mix Research Articles

Flexural properties of fiber-reinforced concrete using hybrid recycled steel fibers and manufactured steel fibers

This study investigates the flexural properties of fiber-reinforced concrete (FRC) using a hybrid mix of recycled steel fibers (RSF) from waste tires and manufactured steel fibers (MSF). The aim of this study is to demonstrate hybrid steel fiber reinforcement as a more environmentally sustainable alternative to traditional single-fiber systems, by assessing whether hybrid reinforcement can achieve or surpass the performance of conventional single-manufactured steel fiber reinforcement. Using a novel four-stage methodology, this paper presents a comprehensive and detailed evaluation of mechanical and ductility performance through three-point bending tests, digital image correlation (DIC), CT-scans, and scanning electron microscopy (SEM). The results from flexural stress-deflection curves were used to evaluate the flexural strength and toughness. This was followed by an in-depth eight-stage DIC analysis and Surface Damage Index (SDI) curves throughout the test. CT-scan images were used to quantify the proportion of fibers classified as pulled-out, ruptured, or bridging the crack, while SEM analyzed the efficiency of fiber reinforcement through microstructural evaluations, further validating the findings of this study. Results show that hybrid reinforcement significantly enhances both toughness and ductility while reducing surface damage. MSFs in the hybrid system improve post-peak ductility and energy absorption by bridging large cracks, while RSFs prevent micro-cracks, increasing pre-peak rigidity. CT-scan analysis reveals that the inclusion of RSFs reduces pulled-out MSFs by 26%, further boosting flexural performance. SEM confirms the superior bond of MSFs with the concrete matrix in hybrid samples. Additionally, higher fiber content in FRC enhances toughness and ductility while reducing surface damage. This research advances our understanding of hybrid fiber-reinforced concrete and promotes more sustainable construction practices through the use of recycled steel fibers. By leveraging the combination of new methodologies, the study effectively targets gaps in the current research landscape, offering a comprehensive approach to improving performance and sustainability in construction materials.

Effect of fiber types on fire-induced spalling and thermal performance of UHPC circular columns

Ultra-high-performance concrete (UHPC) emerged as a promising material for modern construction, offering unparalleled strength, durability, and versatility. However, there is limited research regarding UHPC's response to fire, prompting urgent investigation and analysis. This paper presents an experimental study focused on evaluating the effect of different types of fibers on the fire performance of UHPC circular columns. The fiber types considered in this study included steel fibers (SF), a hybrid mix of steel and polypropylene fibers (SPPF), and polyvinyl alcohol fibers (PVAF). Additionally, a control column was cast without the inclusion of any fibers. All UHPC specimens were subjected to standard fire exposure, following the ASTM E119 fire test. The results indicated a substantial resistance to spalling with the incorporation of fibers. Moreover, the column featuring PVAF exhibited the lowest internal temperature readings among the columns. Columns reinforced with SF and SPPF exhibited uniform spalling on all sides.

An experimental investigation into crashworthiness of filament wound intra-yarn hybrid glass/jute epoxy composites tubes under quasi-static axial and lateral compression

The increasing demand for sustainable materials in the automotive industry has driven the research towards exploration of natural fiber composites for crash structures. This study investigates the quasi-static axial and lateral crushing behavior of hybrid glass/jute fiber epoxy tubes. Intra-yarn hybrid mixing ratios of jute and glass fibers were tested to evaluate the feasibility of using natural fibers as eco-friendly alternatives to traditional synthetic composites. A total of five different configurations were fabricated using filament winding process. The experimental results were analyzed for collapsing behavior, failure modes, and energy absorption characteristics. The hybrid epoxy tubes revealed fiber-matrix fracturing, local buckling, and delamination as three primary failure modes under crushing tests. The hybrid configuration with 25 % jute fiber and 75 % glass fiber demonstrated optimal crashworthiness performance, achieving the highest specific energy absorption (SEA) values of 15.85 J/g under axial loading and 2.96 J/g under lateral loading. The configurations with higher jute content of 50 % and 75 %, showed decreasing SEA and crush force efficiency (CFE) values, with brittle fracturing and delamination as dominant failure modes, indicating a trade-off between weight and energy absorption efficiency. The neat glass fiber configuration maintained nearly consistent CFE values of 0.55 and 0.56, between axial and lateral loadings respectively, demonstrating isotropic behavior in energy absorption. Conversely, the neat jute fiber configuration improved SEA to 12.14 J/g under axial loading but exhibited significant limitations under lateral loading, with SEA decreasing to 0.69 J/g. Visual examination of crushed samples highlighted local buckling in GF configurations and brittle fracturing in hybrid and neat jute fiber configurations. The scanning electron microscope (SEM) analysis provided detailed insights into the microstructural characteristics and failure mechanisms, highlighting the inter-laminar debonding between the jute and glass fibers in hybrid configuration. By evaluating the combined effects of hybridization and loading conditions, the present study contributes to developing eco-friendly and efficient materials for automotive safety, aligning with industry sustainability goals.

Effects of Hybrid Filler and Mixing Equipment on the Mechanical and Thermal Properties of NR/EPDM Rubber Blends

Effects of Hybrid Filler and Mixing Equipment on the Mechanical and Thermal Properties of NR/EPDM Rubber Blends

Halide tuning in derivative organic–inorganic perovskites, MAPb(Br1-xClx)3 (x = 0–1): exploring structural, optical and vibrational characteristics

Organic–inorganic metal halide perovskites (OIMHP’s), particularly CH3NH3PbX3 (X = I, Br, Cl) and their derivatives shows favorable properties for energy harvesting such as high absorption coefficients, adjustable band gaps, and low charge recombination rate. The structure and hence nature of bonding between different atoms of these perovskites is known to affect their properties significantly. Tuning of band gap can be achieved in these systems with the help of compositional variation. These systems are studied extensively in the single halide compositions (MAPbI3, MAPbBr3 and MAPbCl3); while, their derivatives seem to have gained less attention though being important for various applications. So, in this work, halide tuning is achieved in derivative perovskite, MAPb(Br1-xClx)3 (x = 0 to 1) and further studied for structural and optical properties along with vibrational properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy, and Raman spectroscopy techniques, respectively. A decrease in the lattice parameter is observed as the Chlorine content increases in the MAPb(Br1-xClx)3 (x = 0 to 1) perovskite. The substitution of Chlorine with Bromine also results in significant increase in the band gap value. In contrast to previous reports, it was clearly observed that the Urbach energy strongly depends on the composition. For the first time, appearance of two features for torsional mode of methylammonium (MA) is discussed even at room temperature, indicative of disorder. It is observed that although the band gap tuning is achieved with the help of halide mixing (Br and Cl), it is also found to introduce disorder in the intermediate compositions; while, the stability increases toward Chlorine compositions. Interestingly, the information of disorder is found to be contained in both the global as well as local measurements which opens up new pathways for studying these materials. This study will lay down a pathway for better understanding of key properties of these hybrid mix halide perovskites which are promising material for futuristic energy applications.

Yield line-based design of fibre reinforced concrete: assessment of suitability of material models

The present research is intended to address the adequacy of flexural toughness-based material models such as equivalent and residual flexural strength, and the deflection limits at which these parameters are estimated for design of fibre reinforced concrete (FRC), for various applications such as slabs-on-grade/pavements. The work is an experimental study using FRC concrete mixes with individual and hybrid combinations of hooked-end steel (SF) and macro polypropylene fibres (PF). The experimental investigation consisted of toughness testing unnotched and notched prisms and square slabs, prepared with a typical grade of concrete used for FRC pavement applications. To validate the material models, a comparison was made between the theoretical moment/load calculated based on material flexural toughness parameters and the actual moment obtained from slabs using actual yield line formed during testing. From the study it is observed that overall, both equivalent (from unnotched prism test) and residual (from notched prism test) flexural strength, are suitable for designing FRC slabs, however the equivalent strength parameter shows better correlation to the slab response. The results also indicate that the hybrid mixes of PF and SF, with a higher volume fraction of 0.6% Vf, shows a marginal increase in flexural performance, in comparison to the mixes with lower volume fraction but no or minimal synergy due to hybridisation.

Effect of Corn Stover Ash Reinforced with Cabuya Fiber on the Mechanical Properties of Concrete

Currently, organic wastes are an environmental problem generating pollution, bad odors and accumulation of residues in northern Peru, among these products are corn stover and cabuya, predominant materials in the area. Therefore, this research focuses on determining the effect of optimum temperature and optimum percentage of corn stover ash (CSA) reinforced with different proportions of cabuya fiber (CF) on the mechanical properties of concrete. Two conventional designs of standard concrete called A and B (21 and 28 MPa) were made, to these designs were added percentages of CSA in 7%, 10%, 12% and 15% by substitution of the weight of cement to determine the optimum percentage, which was reinforced with percentages of cabuya fiber in 0.5%, 1%, 1.5% and 2% in volume of the concrete. The results showed that the optimum mix was A/B+7CSA, evidencing an improvement in compressive strength of 2.7% as opposed to the optimum CSA +CF hybrid mix, where it was observed that its mechanical properties of compressive strength, tensile strength, flexural strength and static modulus of elasticity decreased to 15.8%, 11.30%, 5.14% and 10.5%, respectively. It is concluded that corn stover ash reinforced with cabuya fiber does not positively influence the mechanical properties of concrete; however, it is an environmentally sustainable alternative to be used in non-structural concrete.

Experimental study on the flexural fatigue performance of slag/fly ash geopolymer concrete reinforced with modified basalt and PVA hybrid fibers

Geopolymer, owing to its inherent low-carbon emission advantages, emerges as a potential substitute to diminish reliance on high-carbon-emitting Portland cement. Nonetheless, similar to ordinary Portland cement concrete, geopolymer concrete tends to exhibit brittle fracture under cyclic bending loads. To improve its flexural fatigue performance, this paper incorporated the modified basalt (MB) fiber and PVA fiber in hybrid form into the geopolymer concrete. The flexural fatigue behavior of hybrid fibers reinforced geopolymer concrete was investigated, with a focus on the influence of varying hybrid fibers volume fractions. Digital Image Correlation technology was utilized to accurately track the evolution of crack length and the local strain field during the fatigue failure process. The results revealed that the incorporation of both MB and PVA fibers effectively delayed the initiation and propagation of cracks, leading to a more complex path of fatigue cracks. The PVA fiber demonstrated significant efficacy in inhibiting microcracks, while the MB fiber played a crucial role in controlling the expansion of macroscopic cracks. When the proportion of MB fiber was predominant in the hybrid mix, the crack development pattern mirrored that of samples containing MB fiber alone, exhibiting a greater extent of crack length. At a volume fraction of 0.9% for MB fiber and 0.2% for PVA fiber, a significant improvement in the fatigue life of the concrete was observed, resulting in a remarkable 136.23% increase compared to the control. This study has developed geopolymer concrete featuring enhanced crack resistance and superior flexural fatigue endurance under cyclic loading, promoting the application of environmentally friendly building materials in practical engineering.

Multi-objective optimization for vector quantization via genetic algorithm

The issue of image compression continues to be a subject of ongoing research within the domain of image processing, particularly in the context of medical applications. The quality of the decompressed image can vary depending on the accuracy of the compression technique, resulting in either fine or distorted details. Therefore, the diagnostic procedure performed by medical professionals is contingent upon the precision of the compression and decompression process. In addition, the compression of medical images serves to decrease the amount of storage required, thereby enabling faster transmission over computer networks through the reduction of their bit size. This paper proposes a hybrid mix of the discrete wavelet transform (DWT) technique and vector quantization (VQ) to improve the compression technique of medical images. The aim of the proposed compression technique is to preserve diagnostic image information while achieving a high compression ratio. First, noise in medical images is caused by salt pepper noise. At the same time, the edges of the images are maintained in sharpness and context. Then, a lossless compression method is applied to the wavelet coefficients of the subband with the lowest frequency, while the thresholding method was used to efficiently construct coefficients for high-frequency sub-bands. This process will produce a traditional VQ, which is estimated via the Genetic Algorithm (GA) with fuzzy clustering. While Arithmetic encoded theory was being utilized to quantize coefficients, the proposed compression technique was evaluated by dividing the image into two levels and three levels of sub-bands, respectively, in two different scenarios. Comparing the decompressed image to the filtered image by means of different evaluation metrics, the proposed method can enhance compression performance and strike a balance between compression ratio and image visual quality.

Virtual Physical Therapy Practices in Canadian Exercise-Based Pulmonary Rehabilitation Programs

Purpose: To understand the current physical therapy virtual care practices in Canadian pulmonary rehabilitation programs. Methods: Exercise-based pulmonary rehabilitation programs were identified through Canadian pulmonary associations available on public websites. Physiotherapists at eligible sites were emailed a web-based survey (REDCap) between March and June 2023. Results: 31/61 survey recipients from 56 programs completed the survey (response rate = 51%). A majority of participants ( n = 20, 65%) reported using a hybrid (mix of virtual and in-person) delivery model in the preceding 6 months. Assessments of exercise capacity, respiratory status, exertional oxygen requirements, and physical function were primarily conducted in-person, whereas exercise prescription and progression, respiratory treatment, psychosocial support, vital sign monitoring, and education were conducted both in-person and virtually. Commonly reported enablers to virtual care were patient preference, medical stability, and availability of technological equipment. Clinical practice guidelines alongside continuing education and training opportunities were identified as important resources needed to optimize virtual or hybrid rehabilitation delivery. Conclusions: Following the COVID-19 pandemic there has been a shift towards a hybrid model of exercise-based pulmonary rehabilitation delivered by physiotherapists. Expanding the evidence base particularly around the clinical utility of virtual assessment may further inform virtual care practices.

Numerical Analysis of Hybrid Fibre-Reinforced Concrete Beam-Column Joint

Beam-column joint is the most vulnerable location of a moment-resisting reinforced concrete frame structure. The joint region experiences the maximum shear stress both in vertically and horizontally which is generated due to the shear transfer mechanism from the adjoining beams and columns. The shear capacity and bond stress capacity are the two major factors affecting the strength of a joint core in RC structure. An important discovery recently is the ductile behaviour of the whole structure under repeated loading. The behaviour of the concrete beyond elastic limit which is in the concrete hardening zone can drastically influence the ductility of the concrete. The non-linear stress-strain behaviour after the onset of the initial crack and up to ultimate compressive strength plays an important role in improving ductility. Beyond the ultimate compressive strength, concrete will undergo softening which is neglected in this study as once concrete reaches ultimate stress it is unsafe for service. This material ductility can be fulfilled with the application of high-strength fibres with ductile behaviour. However, the hybridization of two or more fibres can incorporate two different characteristics of the fibre used. The use of ordinary-grade of concrete moreover reduces the shear-resisting capacity of the joint. A hybrid mix of hooked-end steel fibre with basalt fibre and crimpled steel fibre with polypropylene fibre are used with a volume fraction of 1% to 1.4% of the concrete. In this study, ordinary M25 grade concrete and fibre mixed M25 grade concrete is employed under static and cyclic loading. The laboratory tests are also conducted to evaluate the compressive strength, split-tensile strength, and flexural strength of the hybrid mix fibre-reinforced concrete at the age of 28th days. Five full-scale models of the beam-column joint are designed as per the Bureau of Indian Standards. Numerical models of concrete and steel reinforcement are developed. Numerical analysis is carried out using finite element software ANSYS-v21. The behaviours of the beam-column joint are observed under static as well as cyclic loading. Crack patterns, first crack load, initial displacement, ultimate load, and ultimate displacement are observed under static conditions. And under cyclic loading, hysteresis load vs displacement, energy dissipation, and stiffness degradation are observed. The hybridization of hooked steel with basalt fibre gives better results in mechanical strengths and the hybrid effect of crimpled steel with polypropylene fibre gives better results in mechanical strengths. And also under numerical study, the above specimens show an improvement in energy dissipation capacity. Keywords beam-column joint, hybrid fibre reinforced concrete, numerical concrete model, ANSYS, static, reverse cyclic, energy dissipation, stiffness, crack

Enhancing mechanical properties of selective-laser-melting TiN/AISI 420 composites through Taguchi GRA and PCA multi-response optimization

The enhancement of mechanical properties in martensitic AISI 420 stainless steel is realized through the incorporation of TiN ceramic particles using the selective laser melting (SLM) method. This study introduces an innovative hybrid mixing method designed to uniformly disperse TiN within the AISI 420 matrix, ensuring the absence of agglomerations and contaminations in the feedstock for the SLM process. Employing a combined approach involving the Taguchi method, Grey Relational Analysis, and Principle Component Analysis, optimal processing parameters and TiN content are identified, encompassing a laser power of 350 W, laser speed of 370 mm/s, hatch distance of 0.07 mm, layer thickness of 0.05 mm, and one percent by weight of TiN particles. The optimized SLM sample showcases exceptional characteristics with a hardness of 743 ± 20 HV, tensile strength of 1822 ± 21 MPa, and a modulus of toughness of 99.7 ± 3.0 J/m3, surpassing existing results. Introducing TiN particles into the AISI 420 matrix with suitable SLM processing parameters induces significant microstructural alterations, reinforcing the matrix and elevating the mechanical properties. These results mark a substantial advancement in metal matrix composite materials by applying cutting-edge manufacturing techniques.

Optimal design and sizing of a hybrid energy system for water pumping applications

AbstractOne of the ways to increase the participation and penetration of renewable energy resources is to bring down the cost of these abundant resources for easy implementation and affordability. In this paper, a generalized reduced gradient (GRG) non‐linear optimization algorithm is implemented to solve a tri‐objective optimal design and sizing of a low‐cost hybrid mix consisting of a photovoltaic (PV) power plant, biomass power plant (BPP), and battery energy system for water pumping load applications in the University of Johannesburg, South Africa considering four different hybrids of biomass‐battery, PV‐battery, PV‐biomass, and PV‐biomass‐battery. The optimization model considers available energy and battery state of charge while minimizing least cost of energy (LCOE), carbon dioxide emission (tCO2eq), and loss of power supply probability (LPSP) including carbon tax incentive and penalty. The results when compared against particle swarm optimization (PSO) show the superiority of GRG over PSO with an optimal combination of PV‐biomass‐battery mix with optimal size of the PV power plant as 360.50 kW, the BPP 181.08 kW, and the battery size of 6,553.60 kWh giving a minimal optimal LCOE, CO2 emission and LPSP of 0.018 $/kWhr (with carbon tax), and 0.016 $/kWhr (without carbon tax), 28,067.73tCO2eq tCO2eq, and 1.7%, respectively. These values give a competitive advantage compared to the unit cost and values of CO2 emission and LPSP currently in the literature.

Mechanical, electrical and self-healing properties of carbon fibre-reinforced ultra-lightweight ECC

The hybrid mixes of carbon fibres (CF), fly ash cenosphere and polyethylene fibre could be used to develop smart ultra-lightweight engineered cementitious composites (ULW-ECCs). In this study, the effects of CF length (1, 3, 6, 9, 12, 15, 20 mm) with different volume fractions (0.0, 0.5 and 1.0 vol%) on the fundamental mechanical (compression, tension and flexure) and electrical properties of CF-reinforced ULW-ECCs were evaluated. Pseudo-strain-hardening indices, multiple micro-cracking behaviours and self-healing properties were also tested. The experimental results reveal that, except for the 1 mm particle CF, incorporating CF could improve the strength (compression, tension and flexure) of ULW-ECCs but decrease the strain ductility properties under tension; and CF lengths of 9- and 12-mm show better results. The electrical conductivity of ULW-ECCs was improved by CF, and the higher dosage further increased the conductivity. The conductivity increased first and then decreased with the increase in CF length and the 9 mm CF (1.0 vol%) shows higher conductivity. The conductive network was affected by the volume fraction, length, count under the same content, and possible fracture of CF. Long CFs work well at low content in forming conductive networks, while short CFs are more effective at high content. The conductivity decreased with the increase of curing age and reached a constant value after 90 d. Incorporating CF and increasing its length/content negatively impacted crack number and width. CF-reinforced ULW-ECCs exhibit excellent self-healing, with reduced ability as wet-dry cycles and curing age increase.

Hybrid mix-up contrastive knowledge distillation

Knowledge distillation (KD) aims to build a lightweight deep neural network model under the guidance of a large-scale teacher model for model simplicity. Despite improved model efficiency through the KD technique, the performance gap between a teacher model and the trained student model remains significant. This is because the knowledge of the teacher model is not effectively transferred to the student model since the mapping landscape of the large-scale teacher model is not fully explored. To tackle this research gap, we propose a novel Hybrid Mix-up Contrastive Knowledge Distillation (HMCKD) approach, which facilitates a thorough and reliable mapping solution space exploration in order to significantly improve the performance of the student model. Specifically, we design a hybrid mixing strategy, including image-level mixing and feature-level mixing, to form a smoother mapping landscape as a means to provide a stronger guidance in order to embed its richer dark knowledge from a teacher model to its student model. Additionally, we apply two other strategies, including contrastive learning and top-k guided selection, in order to ensure more effective knowledge transferability from the teacher model. Extensive experiments have proved that our proposed HMCKD approach outperforms state-of-the-art knowledge distillation methods when tested on 6 publicly available datasets, such as CIFAR-100, CIFAR-100-C, STL-10, SVHN, TinyImageNet, and ImageNet. Particularly on CIFAR-100 dataset, the average accuracy of students using HMCKD increased by 1.47%. Further, both the visualization results and similarity quantifications have confirmed the narrowed knowledge gap between the teacher and student models. Our source code is available at https://github.com/lambett/HMCKD.

Influence of hybrid basalt fibre with varied length on the mechanical properties of normal and high strength concrete

Hybrid fibre-reinforced concrete combines different types of fibres or fibres of varying lengths to maximize their individual advantages, which can potentially lead to a synergistic enhancement in overall performance. The main aim of this study is to explore the feasibility of integrating a hybrid fibre system to enhance the efficiency and properties of basalt fibre-reinforced concrete. Specifically, the research focuses on evaluating the mechanical characteristics of basalt hybrid fibre-reinforced concrete across two concrete grades: normal strength M30 and high strength M60. Basalt fibres of 12 mm and 30 mm lengths are used to hybridize the concrete, with a total fibre volume fraction of 1.5%. By incorporating both short and long basalt fibres into the concrete matrix, this study aims to assess how these variations impact essential properties such as workability, compressive strength, flexural strength, and Modulus of Elasticity (MOE). The hybrid mix, comprising 25% of 12 mm fibres and 75% of 30 mm fibres at a volume content of 1.5%, demonstrates enhanced mechanical properties across all concrete grades. The addition of basalt fibres, particularly those with higher proportions of longer fibres, results in a decrease in workability. Notably, hybridizing fibres have no discernible effect on compressive strength or MOE in both concrete grades. From the results it was observed that the flexural strength of the optimal hybrid mixes is significantly higher, surpassing conventional concrete by 39% and 54.35% for M30 and M60 grades of concrete, respectively.

Mechanical properties of concrete utilizing high volume palm oil fuel ash, fly ash and silica fume as blended binders

Palm oil fuel ash (POFA) has limited pozzolanic capability, only 10% can be used as cement replacement without decreasing concrete strength. Fly ash (FA) is known for low pozzolanic reactivity at early age. This study combines different ratios of hybrid POFA and FA to find an optimum combination that will produce optimum strength at early age. The fresh and mechanical properties were studied at ratios of POFA and FA at 60% replacing type II composite cement plus 2% silica fume (SF) addition. The experimental findings indicate that the highest and lowest slumps are POFA0FA60 and POFA30FA30, respectively. The compressive strength (7 days) of POFA30FA30 mix is the highest at 22 MPa and single replacement binders (POFA60FA0, POFA0FA60) are lowest at 12 MPa. However, at 28 days, mixes with higher ratios of FA shows higher increment of strength at 27 MPa, indicating that FA has started its pozzolanic activities and contributing to strength. The ratio of tensile and flexural strength POFA30FA30 to its corresponding compression strength is 25% and 61% lower than the control. For high early-age strength, POFA30FA30SF2 hybrid mix performs optimally, 7 days strength 80% of the 28 days and using a single material (60% POFA or FA), yields low early-age strength (50% at 7 days).

Optimal Sizing of Renewable Hybrid Energy System: A Review of Methodologies

The ever-growing energy demand, the intermittent nature of renewable energy resources such as wind, photovoltaic etc coupled with issues of reliability makes the hybrid renewable energy systems more preferred. Hybrid energy sources offers better reliability and cost effectiveness than a single energy source. One of the most important issues related to hybrid renewable energy systems is obtaining the optimal size of their parts so as to utilize them efficiently and economically. Determining the optimal size of hybrid energy systems helps to avoid over-sizing or under-sizing of the system which will subsequently affect the cost and reliability of the system. Optimal sizing becomes complex when considering multiple hybrid mix while at the same time considering various objectives such as cost, CO2 gas emission and reliability. This paper aims at critically reviewing the various optimization techniques used in optimal sizing of various combination of hybrid energy sources for effective selection of the appropriate sizing method for hybrid renewable energy systems. It has been found that meta-heuristic techniques are well suited for optimal sizing of the hybrid energy systems with Genetic Algorithm and Particle Swarm Optimization techniques being the most commonly used Algorithms.

Effect of macro-synthetic and hybrid fibres on the behaviour of square concrete columns reinforced with GFRP rebars under eccentric compression

GFRP rebars have emerged as a suitable alternative for steel rebars to tackle corrosion-related issues. However, the abrupt failure of GFRP-reinforced concrete (RC) elements due to the brittle behaviour of GFRP rebars is a significant concern. Fibre reinforced concrete (FRC) reduces brittleness by providing pseudo-ductility to GFRP RC members failing in compression. Moreover, fibre addition helps reduce crack widths by bridging them when subjected to tensile stresses. The current study aims to understand the influence of adding macro-synthetic Polyolefin (PO) and a hybrid mix of steel and PO fibres (HB) on the behaviour of GFRP-RC columns. Twenty-six square columns reinforced with GFRP rebars and discrete fibres are tested. A low-eccentricity to-width ratio (e/d of 0.2) and a high-eccentricity to-width ratio (e/d of 0.4) are chosen as loading parameters. The test matrix includes the following specimens: i) control with no fibres, ii) only PO fibres, and iii) a hybrid mix of steel and PO fibres. Test results show that specimens reinforced with hybrid fibres outperformed macro-synthetic fibres in energy absorption and strength improvement. They also had better post-peak behaviour under eccentric compression. Fibre addition increased the load resistance contribution of GFRP rebars and prevented the complete spalling of concrete cover. It also improved the deformabilty factors when compared to control columns with no fibres under eccentric compression.

A hybrid type I + III inverse seesaw mechanism in U(1)R−L-symmetric MSSM

We show that, in a U(1)R−L-symmetric supersymmetric model, the pseudo-Dirac bino and wino can give rise to three light neutrino masses through effective operators, generated at the messenger scale between a SUSY breaking hidden sector and the visible sector. The neutrino-bino/wino mixing follows a hybrid type I+III inverse seesaw pattern. The light neutrino masses are governed by the ratio of the U(1)R−L-breaking gravitino mass, m3/2, and the messenger scale ΛM. The charged component of the SU(2)L-triplet, here the lightest charginos, mix with the charged leptons and generate flavor-changing neutral currents at tree level. We find that resulting lepton flavor violating observables yield a lower bound on the messenger scale, ΛM ≳ (500 − 1000) TeV for a simplified hybrid mixing scenario. We identify interesting mixing structures for certain U(1)R−L-breaking singlino/tripletino Majorana masses. For example, in some parameter regimes, bino or wino has no mixing with the electron neutrino. We also describe the rich collider phenomenology expected in this neutrino-mass generation mechanism.