54 research outputs found
Investigation of the technical properties of the tyre re-treading compund formulated with RSS/SCRAP rubber blends
No full textDue to higher demand of petroleum and petroleum based synthetic rubbers, the price of Ribbed Smoked Sheets (RSS) has been gone up. Therefore, local rubber industries, particularly re-treading tyre industry has started replacing RSS grade partly with a cheaper scrap grade of Natural Rubber (NR) in their re-treading tyre compounds, in arbitrary ratios without considering the quality of tyre treads.
In the project work, the tyre re-treading compounds based on blends of (RSS) and scrap grade in different proportions are investigated to identify the most suitable blend for obtaining optimum technical properties. The first step of the study reveals that the blend having RSS and scrap rubber in the ratio 80 : 20 is the most suitable economical blend to obtain a balance of technical properties .
To get the optimum technical properties of the re-treading tyre compounds, the amount of carbon black should be added separately into the two types of rubber and prepared in the form of master batches, prior to mixing the two types of rubber together. Different weight. ratios are used for the two portions and correspondingly different compounds are prepared.
The second step of the project work reveals that the addition of carbon black-oil mix should be made separately into each grade of rubber (of the chosen formulation from the first step of the project work), preferably 80% by weight t~ RSS and 20% by weight to scrap rubber, for optimum quality tyre treads
Further increase of carbon black in scrap rubber is observed to give deleterious effects on both, cure and vulcanisate properties, due to non uniform dispersion of carbon black in scrap, possibly due to higher loading of carbon black in scrap rubbe
Surface engineering of Dental Tools with diamond for improved life and performance
No full textIn this chapter the application of chemical vapour deposition technologies to dental burs and tools is presented. The types of dental burs and Chemical Vapour Deposition (CVD) technologies employed to surface engineer them are reviewed briefly. Hot Filament CVD is used as a case study to demonstrate the power of CVD to deposit adherent diamond coatings onto complex 3-D shapes presented by burs in the CVD reactor is highlighted. Diamond is a material with unique combination of excellent properties such as high hardness, chemical inertness and thermal conductivity which lends itself well to this application. Diamond has been applied to dental burs using a hot filament CVD technique. New methods have been developed for testing the performance and life of dental burs. A comparison of coated and uncoated burs has been made in terms of surface morphology, coating and substrate characteristics and the bur performances and life
Alkali Activated Systems: Understanding the Influence of Curing Conditions and Activator Type/Chemistry on the Mechanical Strength and Chemical Structure of Fly Ash/Slag Systems
No full textabstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed.Dissertation/ThesisM.S. Engineering 201
P479 Laparoscopic cystectomy in a very obese (115 kg) female with a huge benign ovarian cyst
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Finite Element Based Microstructural Modeling of Cementitious Composites
No full textabstract: This study employs a finite element method based modeling of cementitious composite microstructure to study the effect of presence of inclusions on the stress distribution and the constitutive response of the composite. A randomized periodic microstructure combined with periodic boundary conditions forms the base of the finite element models. Inclusion properties of quartz and light weight aggregates of size 600μm obtained from literature were made use of to study the effect of their material (including inclusion stiffness, stiffness of interfacial transition zone and matrix stiffening) and geometric properties (volume fraction of inclusion, particle size distribution of inclusion and thickness of the interfacial transition zone) on the composite. Traction-separation relationship was used to incorporate the effect of debonding at the interface of the matrix and the inclusion to study the effect on stress distribution in the microstructure. The stress distributions observed upon conducting a finite element analysis are caused due to the stiffness mismatch in both the quartz and the light weight aggregates as expected. The constitutive response of the composite microstructure is found to be in good conformance with semi-analytical models as well as experimental values. The effect of debonding throws up certain important observations on the stress distributions in the microstructure based on the stress concentrations and relaxations caused by the stiffness of the individual components of the microstructure. The study presented discusses the different micromechanical models employed, their applicability and suitability to correctly predict the composite constitutive response.Dissertation/ThesisMasters Thesis Civil Engineering 201
Association of angiotensin converting enzyme gene insertion/deletion polymorphism with essential hypertension in south Indian population
No full textAbstractGenetic, environmental and demographic factors contribute to the development of essential hypertension. Genetic polymorphism of Rennin-angiotensin-aldosterone system (RAAS) has been extensively studied to determine the genetic susceptibility to hypertension. The insertion/deletion (I/D) angiotensin converting enzyme (ACE) polymorphism has been established as a cardiovascular risk factor in some population, but its association with essential hypertension is controversial. This study sought to determine the association of I/D polymorphism of the ACE gene in south Indian essential hypertensive subjects. A total of 208 clinically diagnosed essential hypertensive patients without any associated diseases and 220 healthy control subjects were included in this study. Distribution and allelic frequency of Insertion (I) and Deletion (D) polymorphism at the 287 base pair Alu repeat sequence in the intron 16 of ACE gene were analyzed. The distribution of II, ID, DD genotypes of ACE gene was 28.3%, 32.6% and 38.9% respectively in essential hypertensive patients and to 53.6%, 26.3% and 20% in controls. The allele frequency for D allele is 0.58 in essential hypertension as compared to 0.34 of control subjects. The genotype and allele frequency of ACE gene polymorphism is significantly differed in patients when compared to controls. In conclusion, the I/D polymorphism of ACE gene is associated with Indian essential hypertension
Salivary Interleukin-6 - A pioneering marker for correlating diabetes and chronic periodontitis: A comparative study
No full textThe morbidly adherent placenta: early accurate diagnosis is essential for the meaningful interpretation of outcomes
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