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Algebraic and Probabilistic Aspects of Some Binary Recurrence Sequences
No full textSince its discovery in the year 1999, the sequence of balancing numbers (also known as the balancing sequence) has been motivating researchers to work on many algebraic and analytic properties associated with it. The sequence of Lucas-balancing numbers, which is closely entangled with the balancing numbers, also comes to picture while dealing with these properties. The solutions of certain Diophantine equations involving Lucas balancing numbers are expressible in terms of balancing, Lucas-balancing, Pell or associated Pell numbers. The balancing sequence is a strong divisibility sequence, but the Lucas balancing sequence is not a divisibility sequence. However, under some restrictions on the indices, certain subsets of balancing and Lucas-balancing numbers are divisible by the powers of balancing and Lucas-balancing numbers. The Pell and associated Pell sequences are very closely linked with the balancing sequence by multiple means. Similar divisibility properties also hold good for the Pell and associated Pell sequences. With a minor modification of the recurrence relation, the Pell numbers can be generalized to Pell polynomials. Certain products of Pell polynomials can be expressed in terms of some special orthogonal polynomials. Markov chains are a special class of stochastic processes where a probabilistic statement about any future state depends on the present state and is not affected by any additional information about the past states. The probability of passing from state i to state j in one transition is denoted by pij and is called an one step transition probability. The arrangement of these transition probabilities in a matrix is known as the transition probability matrix of the Markov chain. The probability of passing from state i to state j in n transitions is denoted by p(n) ij and is called an n-step transition probability. The n-step transition probability matrix is nothing but the n-th power of the one step transition probability matrix. As n increases, the dependence of the n-step transition probabilities p(n) ij decreases on i and pj = limn!1 p(n)\ ijdepends only on j and is known as a steady state transition probability. If the elements of a transition probability matrix are suitably chosen, then the numerators and denominators of the steady state probabilities can be seen to be balancing, Lucas-balancing, cobalancing, Lucas-cobalancing and balancing-like numbers. A balancing-like sequence, which generalizes the balancing sequence and the nonnegative integers sequence, is defined as xn = Axn xn1 with x0 = 0; x1 = 1. To avoid the viii nonnegative integers sequence, A is usually chosen to be a natural number greater than 2. But, this sequence admits further generalization, the coefficient A in the right hand side can be allowed to be a random variable with some given probability distribution having moments of all order. However, in this case, the resulting sequence will be a sequence of random polynomials in A, which is, indeed, a stochastic process, which can be better renamed as a random balancing-like sequence. Although, a balancing-like sequence is a binary recurrence sequence, the sequence of expectations may sometimes become a recurrence sequence of higher order. Moreover, if A is any random variable which is finite with probability 1, then the limit of the ratio of expectations of (n+1)-st term and n-th term remains finite; otherwise, this limit becomes infinite. It is an interesting work to study some of other differences associated with the deterministic and the random recurrence sequences
Studies on the Proficient Photocatalytic Applications of Versatile Semiconductor-Semiconductor Heterojunction System
No full textSeveral crucial characteristics must be met proficiently in order to develop a visible light active photocatalyst that can use sustainable solar energy efficiently. To begin with, the semiconductor material has to have a narrower band-gap so that it can absorb solar radiation over a wide spectrum. The semiconductor should also have a suitable valence and conduction band edge that has sufficient potential to carryout plentiful generation of both h+ for ˙OH radicals and e− for ˙O2 ̄. The disadvantage of these semiconductors, however, is that they cannot be used as solar energy- harvesting photocatalysts because of their wide band-gap, and photogenerated carrier recombination process, which renders the photocatalytic activity. Certain modifications to the semiconductor system have been made to improve the efficiency of their visible light responses to address this critical deficiency. Fabrication of a heterojunction system drastically reduces those concerns regarding the activity. Out of various heterojunction systems, semiconductor- semiconductor (S-S) heterojunction is most appropriate because of its easy band optimization and wider redox potential window results in versatile photocatalytic applications. Additionally, in photo-electrochemical processes, the semiconductor materials should have strong photo stability. The choice of semiconductor materials, morphological architecture, crystallinity, and surface properties have been taken into account when building an efficient and stable visible light- responsive photocatalytic system. Based on this, the following chapters describe the fabrication of different S-S heterojunction photocatalyst and their applications in diverse fields. Chapter 1 signifies a general introduction to photocatalysts, their unique properties, and their application in various fields. The use of safe unconventional water sources to increase water supply and improve water purification efficiency are both possible using visible light-responsive photocatalytic technology. This chapter mainly consists of underlying ideas that underpin photocatalysis in general and then about the many classes of photocatalytic materials, addressing various facets of their characteristics, including efficiency, stability, scalability, and cost. Recent advances are also reviewed in the design and fabrication of visible light-responsive photocatalysts using a variety of synthetic approaches, including the doping, dye sensitization, or heterostructure formation of conventional photocatalysts, as well as the significant efforts made in the exploration of novel visible light-responsive photocatalysts. The principles of heterogeneous photocatalysis, the photocatalytic pathways, and the distinctive characteristics of visible light-responsive photocatalysts are described in detail. Regarding the water treatment, the photocatalytic qualities of the resultant visible light-responsive photocatalysts are also discussed, i.e., on the subject of the photocatalytic disinfection, degradation, and removal of organic and inorganic contaminants. This chapter contains a summary of the present difficulties and future lines of inquiry in this developing field of study. Chapter 2 describes how a heterostructure is fabricated between the modified titania and g-C3N4 to separate the carriers efficiently. The nanostructured composite is created using a simple and affordable sol-gel procedure and a co-calcination approach. Photocatalytic studies were conducted after XRD, Raman, XPS, TEM, and PL analysis to determine their ideal dopant concentration and degree of doping. Electrochemical impedance analysis and UV-DRS are used to examine the influence on the band locations. The heterojunction band alignment promotes carrier mobility from the bulk to the active sites. The photogenerated electron and hole reserve the characteristic redox ability to generate both the ˙OH and ˙O2 ̄ through the Z-scheme mechanism. The persistent herbicide Bromoxynil was fragmented by the photocatalytic activity and also demonstrated improved photocatalytic H2 evolution. The improved photocatalytic performance for TiO2-Zr-N/g- C3N4 was attributed to g-C3N4 and Zr working together to extend the material's spectrum- absorptive nature into the visible region and NOx acting as a carrier mobilizer. The produced photocatalyst heterojunction creation not only made it easier to separate the photogenerated charge carriers but also preserved the oxidation and reduction abilities. Chapter 3 deals with the use of prospective materials for the degradation of organic pollutants from aqueous sources using stacked MOFs, a structural variation of the metal organic framework (MOFs), were examined. The development of a heterostructure photocatalyst with superior catalytic active sites and optoelectrical properties was optimized for the efficient mineralization of hazardous organic pollutants and the water splitting process. Through a simple hydrothermal process, a series of three-dimensional micro-rods mediator-free Z-scheme heterojunction photocatalysts were effectively produced. The morphology and composition show that the composite heterojunction materials have micro-rods with sparsely dispersed MOF spikes. 25- MOF/BVO stands out among these samples for photocatalytic H2 evolution and bromoxynil degradation effectiveness. The primary cause of the increased photocatalytic activity is thought to be the built-in electric field that facilitated carrier movement. Time-resolved fluorescence spectra and photoelectrochemical measurements provide to further support this. Additionally, it has been proven that the heterostructures adhere to a conventional Z-scheme charge transfer mechanism rather than a conventional Type-II heterojunction charge transfer mechanism based on the results of tests for free radical scavenging activity and EPR measurements. The ideal photocatalyst (25- MOF/BVO) displayed improved photocatalytic efficiency for the degradation of bromoxynil. Chapter 4 describes improved charge separation and migration performance in photocatalytic applications and how it has been extensively explored to fabricate binary p-n heterojunctions and the band alignment at the interface of the individual semiconductor photocatalyst. In this case, a straightforward wet chemical followed by a hydrothermal manufacturing technique was used to create binary p-n heterostructures. The tunable band structure of individual semiconductors with the work function (ϕ) witnessed a band bending at the space charge region. The bending at the interface induces a carrier concentration gradient and manifests a rectifying current transport diode. Different morphological and physicochemical methods verified the fabricated p-n heterostructures and carrier migration between n-type and p-type. The band banding at the interface, leading to a narrow depletion region, favours the tunneling of electron-hole pairs through a Z-scheme carrier transport mechanism. The electron-hole pair movement has further been confirmed by considering the band edge position after contact, photocatalytic scavengers, and the radical trapping experiment. The p-n heterojunction photocatalyst manifested H2 generation and endosulfan degradation efficiency. The p-n heterojunction photocatalyst displayed a higher current density with electron-hole migration efficiency, synergistically enhancing the catalytic activity through the interfacial space charge junction. Chapter 5 deals with the summary and conclusion as well as the future perspective of the work. The current study tackles the water remediation and energy demands of a growing population and increased industry. In this study, a series of different semiconductor heterojunction photocatalytic systems were designed and investigated for versatile photocatalytic applications. All the heterojunction photocatalysts were categorically classified based on their types (p-type or n-type) and aligned electron transfer process. The first observation investigated a doped n-n semiconductor heterojunction photocatalytic system with a Z-scheme carrier transfer mechanism. The band edge of TiO2 has been successfully tailored by doping Zr, which substantially replaced Ti from its lattice point and reduced the overall band threshold. To counterbalance the recombination process of individual semiconductor material (a consequence of the defect level TiO2), a heterojunction was fabricated with g-C3N4. The Physio-chemical evaluation showed an intimate architecture, suitable band edge position, low interfacial charge resistance, and reduced recombination rate. The redox potentials of resultant carriers could able to generate both ˙OH and ˙O2 ̄ through a direct Z-scheme mechanism, participating in the degradation of bromoxynil and H2 evolution process. Similarly, a semiconductor-based n-n semiconductor heterojunction system was developed with a Z-scheme carrier movement mechanism. A novel Mg-MOF-74/BiVO4 heterojunction hybrid with a hierarchical 3D micro-rod-shaped structure has been developed as a heterojunction photocatalyst using a simple hydrothermal process. The stratified heterostructure materials' unique structural and optoelectronic characteristics include high crystallinity, surface-exposed active sites, strong visible absorption, rapid charge carrier mobility, and excellent resistance to recombination. The scavenges and radical trapping experiment deduced a Z-scheme carrier transport system with a 93% bromoxynil decomposition and H2 generation (1.97 mmolg-1h-1) efficiency. Lastly, a visible light active binary Ag3PO4/Cu2O p-n heterojunction photocatalyst was developed for the rapid degradation of endosulfan along with the H2 evolution process. This synthetic approach ensured a uniform distribution of p-type Cu2O nanospheres (20-30 nm) over an n-type Ag3PO4 matrix through a nano-sized interfacial junction, which is confirmed by the morphological analysis. The built in potential developed at the p-n junction interface provides better carrier migration throughout the semiconductors, boosting visible light absorption capacity and higher exciton lifetime. The binary p-n heterojunction displayed splendid photocatalytic endosulfan degradation efficiency of 91% and hydrogen generation (HER) of 1017.8 μmolg-1
Thermohydrodynamic Analysis of Gas Foil Bearings for High-Speed Turbomachinery
No full textHigh-speed turbomachinery such as turboexpander, turbocompressors, turbogenerators, and many more whose applications lie in aircraft, etc. needs to have better and high-quality performance with no compromises. If for example in the case of a turboexpander a high-speed is a must-have criterion in order to achieve desired performance output and thus imposes a constraint on a turbo-pair design. To avoid the issue of contamination and implement a cost-effective design the obvious choice is to switch from ‘liquid film lubrication’ to ‘gas film lubrication’. Thus, the use of gas bearings is popular in the past few decades due to its merits such as low frictional losses, low power consumption, ability to operate at high temperatures, and low noise operations, etc. However, the demerits associated with simple gas bearings are low stiffness and damping characteristics.
The current dissertation proposes the use of gas foil bearings as they possess the ability to tailor the stiffness and damping characteristics by modifying the compliant structure along with all the merits of simple gas bearings which further increases its scope of applications to a wider range. The mathematical model is formulated to study the thermohydrodynamic behaviour of both gas foil thrust and journal bearing accounting gas rarefaction effects. The non-linear Reynold’s and energy equation using first-order velocity slip terms are coupled together to evaluate the pressure and temperature distribution of the gas foil bearings. Additionally, the dynamic coefficients are predicted for gas foil journal bearing. Further, the use of temperature-dependent viscosity is used in non-isothermal Reynold’s equation for analysing the thermohydrodynamic behaviour of gas foil bearings under the influence of slip flow. The various performance parameters like load carrying capacity, power loss, frictional torque, and temperature is investigated and compared for both no-slip and slip flow phenomenon.
Additionally, the thermal analysis of rotor supported on gas foil journal and thrust bearing is also attempted in the current dissertation. The rotor is divided into different regions on the basis of a component surrounding it. The rotor of any turbomachine operating on gas bearings tends to have gas frictional losses. The thesis attempts to evaluate frictional losses for different regions of a rotor analytically along with the heat flow and convective heat transfer coefficient which acts as boundary conditions. The ‘Steady State Thermal’ module of the ANSYS WORKBENCH is used to predict the temperature distribution of the rotor. The effect of a rise in temperature on the structural behaviour i.e. thermal deformation and induced thermal strain of the rotor is also investigated. Also, the transient analysis of the rotor to predict the time-varying temperature is attempted.
Further, the fabrication methodology of various components is presented in the current dissertation to test the performance of gas foil bearings. The fabrication methodology of components like rotor dies to form bump foils, top foils, bearing assembly, and bearing housing is presented. Additionally, the test setup is also developed to test the thermal performance of gas foil bearings. The K-type thermocouples are attached to the gas foil bearings via NI temperature card. The various sensors and equipment’s like pressure transducer, NI vibration card, oscilloscope, accelerometers, high-pressure compressor air facility, and test bench to mount turboexpander’s bearing housing are used to fully develop the experimental test facility. The preliminary vibrational and thermal analysis is conducted on an experimental setup and found to be in close agreement with the numerical results.
Overall, the thesis highlights the importance of using a full thermohydrodynamic model instead of using just an isothermal Reynold’s and energy equation to predict the hydrodynamic and thermal characteristics of gas foil bearings. The results also conclude that the no-slip assumptions underpredicts the performance of gas foil bearings and thus slip flow assumption should be involved while modelling. The temperature rises of the rotor due to low clearance bearings are also highlighted along with the methodology to predict it. Finally, the experimental investigation is carried out to validate the numerical models formulated in the thesis
Development and Evaluation of Stone Matrix Asphalt Containing Treated Recycled Concrete Aggregate
No full textThe recycling or utilization of construction and demolition (C&D) waste in a developing country like India is important for sustainability in pavement construction. This study attempts to investigate the utilization of waste material such as recycled concrete aggregate (RCA) in stone matrix asphalt (SMA) mixes. Because of its higher water absorption, the use of RCA in bituminous paving mixes for the surface course of a bituminous pavement is limited. Also, it does not satisfy the criteria for abrasion and impact characteristics for preparation of bituminous mixes used in the uppermost layer of a bituminous pavement. Therefore, RCA was only limited to concrete production or application in the lower bituminous layer, sub-base or base courses.
It is obvious that RCA as a replacement of aggregates, may not be able to directly sustain heavy wheel loads and resist the moisture induced damage when used in the uppermost part of the bituminous pavement as an SMA layer. Therefore, in this study, various attempts have been made to pre-treat the RCA to modify its properties in order to enable RCA to be considered a suitable alternative to conventional coarse aggregates for preparation of SMA mix. After several trails, a proper procedure for pre-treatment of RCA was developed by mixing RCA with nanosilica modified emulsion-water solution, which not only resulted in satisfactory water absorption value but also improved the abrasion value and impact value. In this study, the resulting RCA is termed as pre-treated recycled concrete aggregate (TRCA). Like normal use of fibers in conventional SMA mixes, the present study involved the use of cellulose fibers as a stabilizer for the production of SMA mixes. SMA mixes were made in this study with TRCA, RCA, or conventional aggregate (CA) as coarse aggregates, and two types of widely used bitumen, VG 30 or VG 40 bitumen, with or without cellulose fiber. The SMA mixes thus developed were evaluated in terms of various engineering properties such as Marshall parameters, indirect tensile strength, moisture susceptibility, resilient modulus, fatigue life and rutting resistance using wheel tracking test. It was observed that the mixes involving CA, RCA or TRCA in general, meet the requirements of Marshall test parameters and rutting criteria. However, SMA mixes with RCA (RCA-30, RCA-40, RCA-30-F) fail to satisfy the required moisture susceptibility criteria in terms of tensile strength ratio (TSR) (≥ 85%). Further, the maximum resilient modulus value was observed for mixes prepared with
TRCA and VG 40 bitumen, and stabilized by cellulose fiber, at all three test temperatures (namely 150C, 250C and 350C). SMA mixes prepared with TRCA also showed reasonably higher fatigue life, followed by mixes prepared with CA and RCA. It is observed that all SMA mixes with VG 40 bitumen with or without fiber result in somewhat better engineering properties as compared with that made up of VG 30 bitumen, with or without fiber. After examining various engineering properties of the various mixes under consideration, it was observed that mixes comprising pre-treated recycled concrete aggregate and VG 40 bitumen, with and without cellulose fiber, yield results equivalent to those containing natural aggregates. Based on Indian Roads Congress (IRC) method of bituminous pavement design, it is observed that there has been a reduction in thicknesses of SMA layer made with TRCA alone, or TRCA and fiber. When TRCA alone with VG 30 and VG 40 bitumen is used in a SMA layer there is a cost saving of about 5.8% and 4.6% respectively, while there is a cost saving of about 3.4% and 4% respectively when TRCA with VG 30 or VG 40 bitumen is used in respect of a pavement designed on the basis of assumed design inputs for bituminous pavement with an analysis period of 20 years
Alleviation of Diabetes using Prebiotic Inulin Extracted from Pachyrhizus Erosus with Probiotics in Drosophila Melanogaster
No full textThe increasing mortality due to hypertension and hypercholesterolemia is directly linked with type-2 diabetes (T2D). Reports suggest that the prebiotics along with probiotics help in lowering the risk of T2D. Inulin, a prebiotic is well-known for its anti-diabetic effect. The property of inulin is further linked with isolated source and technique. The current study optimizes the isolation of inulin from Jicama roots (Pachyrhizus erosus). Inulin was extracted from hot air-dried Jicama roots. After steam blanching, the hot air drying (50.86-79.14°C hot air temperature and 0.79-2.21 ms-1 air velocity) of Jicama root slices was done followed by extraction of inulin (0.68-2.81 W/g microwave power density (MWPD) and 2.59-5.41 min extraction time) by microwave heating. The 1H NMR, FT-IR, UV-Vis spectroscopy and Raman confirmed the functional groups and purity of inulin. The shape and size of the extracted inulin was determined from scanning electron microscopy, and X-ray diffractogram. The isolated inulin has phenolic and flavonoid content of 8.18 ± 0.62 mg gallic acid equivalent/g and 14.38 ± 4.19 mg rutin equivalent/g of dried polysaccharide, respectively. The inhibition percentage of DPPH and FRAP of isolated inulin was found to be 75.74 ± 4.5% and 0.11 ± 0.007, respectively. The isolated inulin also promotes the growth of probiotics. Inulin along with probiotic (Lactiplantibacillus plantarum (MZ540317) and Enterococcus faecium (MZ540315)) is utilized for treating T2D in high-fat diet-induced Drosophila melanogaster model. The high-fat diet-induced Drosophila showed deposition of lipid and formation of micronuclei in the gut. The larva and adult treated with probiotics and synbiotic (probiotic + prebiotic (inulin)) comparatively reduced the deposition of lipid and micronuclei number in the gut. The increased triglyceride and glucose in the whole body of the fatty larva and adult indicated the onset of diabetes. The overexpression of insulin-like genes (Dilp 2) and (Dilp 5) confirmed the insulin resistance, whereas the expression was reduced in the larva and adult supplemented with probiotics and synbiotic. The reactive oxygen species level was reduced after the supplementation of probiotics. The weight, larva size, crawling speed, and climbing were also altered in high-fat diet-induced Drosophila. The study confirmed that the effects of probiotics and synbiotic can successfully lower diabetes in Drosophila. The study also proved the anti-diabetic potential of the isolated inulin. Further, it was also confirmed that probiotics work better in the presence of prebiotics
Road and Vegetation Extraction from Aerial Images through Semantic Segmentation
No full textImages captured by satellites and unmanned aerial vehicles (UAVs) have the unique ability to present the view from an aerial perspective and see the earth from above. These images have a great significance that can be noticed from their wide range of applications in various sectors. Vision-based solutions have gained popularity with the help of machine learning algorithms. Object segmentation from aerial images plays a vital role in urban design, georeferencing, automated vehicle navigation, geospatial data integration, intelligent transportation system, and disaster management. Therefore, objects such as road and vegetation extractions are worth studying and have recently been of growing interest among researchers. Moreover, on account of various research challenges, such as diversity of object appearance, light illumination variation (due to timing of the day and weather) causing vision issues, scaling effect (due to variation in the height of flight of UAV), and occlusion (due to several objects), automatic road and vegetation extraction from remote sensing (RS) images is still at its infancy. Similarly, performing these tasks on board under limited resources to achieve real-time data processing is quite challenging. The existing deep learning frameworks also need massive computational and storage power to complete the segmentation tasks. Hence, in this doctoral research, an attempt has been made to analyze the technical challenges in the road and vegetation segmentation task concerning space-borne and air-borne platforms while providing computer vision-based deep learning solutions to overcome the current issues for semantic-level optimization. This research primarily involves the proposition of lightweight deep semantic segmentation models to perform pixel-level classification over satellites and UAVs on-board. The dissertation proposes four newly developed deep learning methodologies for RS image segmentation tasks, especially to segment the road and vegetation regions, including one proposed UAV-based RS image dataset. The dissertation starts by providing the solution for the classical (satellite-inspired) remote-sensing problems for road extraction. The first contribution introduces a superpixel-aided CNN architecture that can be deployed over the proposed three-layer IoT framework for achieving real-time road segmentation using satellite RS images. The experimentally obtained results show that the ensembling architecture not only performs better but also shows its efficiency with optimized space complexity, which is essential for IoT-based network frameworks. However, the satellite images may not be suitable for various RS applications, such as vegetation disease detection, a class of plant detection, visual surveillance in forests, etc. This can be analyzed from the operational height of the satellites that produce poor-resolution remote sensing images, which will be unsuitable for some RS tasks demanding higher-resolution imageries. Moreover, the cloud may also become an obstacle, especially in tropical regions. UAV-based aerial images have become a savior for such situations. The scarcity of UAV-based semantic segmentation datasets becomes one of the motivations to prepare and benchmark a UAV segmentation dataset known as the “NITRDrone dataset,” which contributes to the second contribution. While benchmarking the dataset, it has been observed that the existing encoder-decoder CNN architectures suffer from three significant issues: degradation problem, vanishing gradient problem, and overfitting. Therefore, as an immediate improvement, the third contribution of the thesis proposes a skip connection-based encoder-decoder architecture, also known as AerialSegNet. The proposed AerialSegNet significantly reduces the number of trainable parameters while improving the accuracy in terms of IoU and F-Score compared to state-of-the-art methods. However, AerialSegNet fails to capture scale-invariant features leading to poor generalization for several small-scale objects on the ground. To overcome these related issues, the fourth contribution involves the development of a superpixel-aided multiscale CNN architecture that improves the classification accuracy to a great extent, however, with an increase in the number of trainable parameters. Therefore, in the final and fifth contribution, a lightweight deep CNN architecture known as LW-AerialSegNet is suggested. The proposed lightweight architecture can produce better prediction accuracy while having 70% fewer parameters than the proposed AerialSegNet (in the third contribution) and state-of-the-art methods, solving all three issues of deep semantic segmentation architectures simultaneously. The performance of all the proposed methodologies is validated experimentally with multiple publicly available datasets, and the results are compared both quantitatively and quantitatively with state-of-the-art methods. The research outcomes can be extended further to perform remote sensing applications, such as urban planning, precision agriculture, forest management, disaster management, etc
Studies on Strength, Durability, and Structural Properties of Copper Slag Aggregate Concrete
No full textConcrete is the most versatile construction material because it can be designed to withstand the harshest environments while taking on the most inspirational forms. Engineers are continually pushing the limits to improve its performance with the help of innovative alternative aggregate and supplementary cementitious materials. Aggregates are usually obtained from natural rocks, either crushed stones or natural gravels, and comprise as much as 60% to 80% of a typical concrete mix. So they must be properly selected to be durable, blended for optimum efficiency, and also should exhibit a good bond with reinforcement after hardening. Initially, these are generally thought of as inert fillers within a concrete mix, but a closer look reveals the major role and influences aggregate plays in the properties of both fresh and hardened concrete. The rapid growth of industrialization gave birth to numerous kinds of industrial slags that are environmentally hazardous and create problems with storage and disposal. The consumption of these slags as a replacement for aggregates in concrete not only helps in saving natural resources but also helps in making environmentally friendly construction material. Hence, the management and utilization of industrial slag have become important for some researchers in the past couple of decades. Presently in India, due to limited modes of practices of utilization, a huge amount of copper slag is dumped in yards of each production unit and engaging important agricultural land and grave pollution to the whole environment. Currently, worldwide about 57 million tonnes of copper slag is generated annually with India contributing 12-16.5 million tonnes. Barely dumped copper slag pollutes the nearby soil and the adjacent water bodies ultimately contaminating groundwater, lakes, streams, rivers, or coastal waters. On the other hand, this copper slag is often mixed into municipal waste and hinders making accurate assessments difficult. An efficient approach to overcome these problems is slag utilization, which minimizes land disposal. The disposal of copper slag is an environmental challenge globally, and the only viable solution for its mass disposal is its use in the construction industry, especially for concrete production. However, the performance of a concrete structure is dependent upon the properties of the components such as cement, coarse aggregate, fine aggregate, and superplasticizer along with several other factors. Physical and chemical characterization of the slag is a deciding factor in its utilization as fine aggregate as recycled construction materials, etc. Basic physco-chemical properties like specific gravity, fineness modulus, particle size distribution, chemical composition, and strength activity index of both copper slag and natural sand are studied. Hence, the evaluation of copper slag aggregate concrete (CSAC) properties is essential for the quality construction of the concrete structure. The present research is an effort to study the engineering properties of CSAC which include strength properties, durability properties, and structural properties, establish the correlation among these properties, and quantify variability associated with different strength properties over a longer curing period of 90 days. Basic fresh concrete properties like workability and rate of bleeding, hardened concrete strength properties like compressive strength, split tensile strength, flexural strength, water absorption, void content, microhardness, and microcrack analysis are studied on a large no of CSAC samples and the obtained result is checked for its appropriateness in eminence construction. Better particle packing and due to the presence of natural pozzolana (Class N) in copper slag which strongly influences all the strength properties. Durability properties like slake durability, abrasion resistance, accelerated corrosion test, rapid chloride penetration test, and carbonation test are also studied on a large number of CSAC samples. Some efforts have been made to test the suitability of copper slag use in designing durable concrete. However, the evaluation of all these strength and durability properties needs admittance to polished instruments, which is normally not obtainable in the majority of construction sites. This demands the development of a substitute technique that could deliver first-hand information on the strength, durability, and quality of CSAC without the need for any huge testing apparatus. For this resolve, the correlation between the strength, durability, and other easily measurable parameters is studied and mathematical models are developed to predict the CSAC properties using other parameters through experimental results and statistical correlation. These models can be used as a quality control tool for CSAC production at the actual construction site. A proper mechanical interlocking between cement and aggregate results in good bond strength of structural concrete. If the aggregate possesses its own pozzolanic property, the interlocking improves due to secondary hydration products on the aggregate surface. Both strength and durability of concrete are influenced by the bond strength to a large degree. The strength properties of CSAC can show a significant variation because of several influencing factors like source and proportion of constituent materials, workmanship, and curing condition among others. Quantification of this uncertainty is essential for the reliability-based limit state design of masonry structures. Safety and strength assessment of structures made of CSAC often requires modelling the uncertainty of its properties. The present study investigates the variability associated with compressive strength, shear-, split tensile-, and flexure tensile-bond strength of copper slag aggregate concrete were analysed and proposes the most appropriate model for its statistical distribution. Four probability distributions are considered to conduct the three goodness of fit tests, namely Kolmogorov-Smirnov, Kolmogorov-Smirnov-Lilliefors, Anderson-Darling, and Chi-Square (CS) tests. The analysis shows that conventionally assumed normal distribution is not suitable for describing the strength properties of copper slag aggregate concrete as the experimentally obtained strength data is not symmetrical about its mean value. The best-fitted distribution functions that perform well in describing the variability in different strength properties of copper slag aggregate concrete are recommended. A case study on the seismic risk of a typical reinforced concrete framed building with CSAC is performed considering different probability distribution functions. The results of the case study indicate that the choice of the probability distribution of the random variables influences the seismic risk assessment of structures significantly and consideration of the appropriate distribution function is vital for the precise estimation of seismic risk
Processing And Characterization Of Walnut Shell Powder Filled Polyester Composites
No full textDue to generation of large volume of industrial, agricultural and biological wastages, disposal of these wastages now becomes a major challenge for whole world due to their harmful effect on the environment. So, waste management is the critical issue for the countries regarding collection transporting and disposal of these wastages. In this research, an agro-waste filler walnut shell powder (WSP) is used as filler material in polyester for composite making. This thesis has broadly four parts. The first part is about exploring the possibility of composite fabrication with walnut shell powder in polyester resin. This part also includes fabrication details of such composites along with its hybridization with short areca fibers as secondary reinforcement. The physical, micro-structural and mechanical characteristics of these composites are briefly discussed in the later part. The following part describes the theoretical models developed to predict effective thermal conductivity (Keff) of the polymer composites of the particulate filled and the hybrid composites. The evaluation of effective thermal conductivity, glass transition temperature coefficient of thermal expansion, dielectric and acoustic of these composites are discussed. The final part has reported about the experimental and analytical details on the sliding and erosion wear response of these composites. This report shows that successful fabrication of polyester composites filled with walnut shell powder and/or short areca fibers using solution casting technique is possible. The density and void fraction of the composites are greatly affected due to addition of WSP content. The tensile, flexural, compressive and impact strength of the composites also significantly influenced with the incorporation of the WSP filler. It is also observed that the thermal insulation capability of the composites is enhanced due to reinforcement of walnut shell powder and further improved by use of secondary short areca fibers. An improvement in glass transition temperature (Tg) and drop in coefficient of thermal expansion (CTE) of the composites is also reported with inclusion of walnut shell powder. At the same time, the walnut shell powder helps to improve acoustic insulation property of the composite. The dielectric constant of the composites shows an increasing trend with the reinforcement of both walnut shell powder. Correlations are developed and proposed for erosion and sliding wear rates with the independent process parameters by response surface method (RSM).From analysis of variance (ANOVA), the most significant factors affecting sliding and erosion wear rate of the composites are identified. The wear resistance capability of the composites is found to be improved by the incorporation hard walnut shell powder consisting of stone cells. The composites filled with walnut shell powder is found to be lower compared to that of composites consisting both walnut shell powder and short areca fibers.The developed composites have several advantages such low density, high mechanical strength, good corrosion resistance, low thermal conductivity, high resistance to wear and better sound absorption quality due to which these composites can be used in different domestic and industrial applications
Preparation and Characterization of 52S4.6 Bioactive Glass Reinforced Antheraea Mylitta (A. Mylitta) Silk Fibroin and Chitosan Scaffolds for Bone Tissue Engineering
No full textBone is a rare tissue that can mend itself after being damaged. However, certain fractures and abnormalities require therapeutic and surgical intervention for appropriate alignment and faster healing. In this study, 52S4.6 nano-bioactive (NBG), silk fibroin, and chitosan-based composite scaffolds with tailored architectures and properties with improved physicochemical, mechanical, and osteogenic properties were fabricated using the freeze drying method. 52S4.6 NBG was prepared by acid-mediated sol-gel process. Synthesized NBG exhibited a very narrow size distribution of about 1-2nm primarily because of a high zeta potential of about -40.8 mv with predominating amorphous phase as obtained from XRD data and SAED pattern. Scaffolds were prepared by degumming and dissolving Antheraea Mylitta (A. Mylitta) silk fibroin (SF) and chitosan (CH) at varying compositions of the SF to CH in from SF90/CH10 to SF50/CH50. Among all the compositions, SF80/CH20 scaffold showed superior properties compared to other fabricated composite scaffolds in terms of microstructure, porosity, and mechanical property. The composite scaffold was prepared by the addition of 5-15 wt% 52S4.6 NBG into SF80/CH20 scaffold at a fixed solid loading of 23.5 wt%. With the increase in NBG content, the compressive strength of the scaffold increased to 1.31 ±0.16 MPa for SF80/CH20/NBG15 composite scaffold from 0.146 ± 0.06 MPa for SF80/CH20 scaffold. Further better apatite deposition with controlled swelling and degradation was observed for SF80/CH20/NBG15 composite scaffold. In-vitro cell culture showed better flatter morphology of MG-63 cells for SF80/CH20/NBG10 and SF80/CH20/NBG15 composite scaffolds with a higher number of lamellipodia, filopodia extensions with apatite-like deposition onto the scaffold surface. In addition to in vitro cell culture, in-vivo bone remodeling showed the new bone formation of the implanted SF80/CH20, SF80/CH20/NBG5, SF80/CH20/NBG10, and SF80/CH20/NBG15 scaffold compared to control after 3 months at the host-implant interface. All the composite scaffolds demonstrated abundant osteoblast and osteoclast cells along with red blood cells and fibrinous deposits when compared to the control; however, better osteoblast and osteoclast cell along with red blood cells was observed for SF80/CH20/NBG15. Hence, in-vivo bone defect healing through histology and fluorochrome labeling showed better performance for SF80/CH20/NBG15 composite scaffold compared to control samples that could potentially be used for bone tissue regeneration
Stability Analysis of Boundary Layer Flows Admitting Multiple Solutions
No full textThe theme of this thesis is to investigate some boundary layer flow geometries driven by a stretching (shrinking) surface. The governing partial differential equations are reduced to fully coupled, non-linear system of ordinary differential equations by suitable similarity variables. The self-similar equations are solved numerically. This work is divided into two parts: steady and unsteady flow. All the problems investigated in this thesis are incorporated with a simple energy equation without viscous dissipation effect. It is interesting to observe that these governing equations admit dual solutions in a certain range of flow parameters. Both the solutions satisfy the terminal boundary conditions asymptotically. Different characteristics of these dual solutions on the velocity and temperature profiles, skin friction coefficient, heat transfer rate, and shear stresses raise questions on the physically acceptable and reliable solution. Thus emphasis has been laid to carry a linear temporal stability analysis which reveals the upper (first) branch solution is the stable solution and practically reliable and the lower (second) branch solution is unstable. The stability analysis is performed by the sign of the smallest eigenvalue, where the positive or negative sign of the smallest eigenvalue leads to a stable or unstable solution respectively. Effective numerical schemes have been used to determine the smallest eigenvalue. In addition, asymptotic solution behavior for large stretching and suction parameters are discussed for the steady flow problems. The effects of various material and flow parameters on the skin friction coefficient, Nusselt number, shear stresses, velocity and temperature profiles, and boundary and thermal layer thicknesses are shown through graphs and tabular forms. Emphasis has been given to the physical interpretation of the new findings of the considered problems for upper branch solution only as this is the only stable solution. It is observed that the momentum and thermal boundary thicknesses in upper branch solutions are thinner than the lower branch solutions in each flow problem