Water-lubricated Ni-based Composite (Ni-Al2O3, Ni-SiC and Ni-ZrO2) Thin Film Coatings for Industrial Applications

In this work, pure nickel and Ni-based nanocomposite coatings (Ni-Al2O3, Ni-SiC and Ni-ZrO2) were produced on steel substrate by pulse electrodeposition technique. The industrial performance tests were conducted to evaluate the wear-resistance, corrosion-resistance, adhesion strength and wettability behavior of newly developed coatings. Rolling contact ball-on-disc tribometer was used to assess anti-wear behaviour of these coatings under water-lubricated contacts. The results showed that the wear and corrosion resistance properties of nickel alumina and Ni-SiC composite coatings significantly improved than that of pure Ni and Ni-ZrO2 coatings. The adhesion and wettability results of Ni-Al2O3 composite showed better performance when compared to the rest of the coatings. The effects of incorporating nanoparticles on the surface microstructure, interface adhesion and distribution of the particles were also investigated. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and 3D white light interferometry. The wear failure behaviour of these coatings was further examined by post-test surface observation under optical microscope

Virtual Urbanity: A parametric tool for the generation of virtual cities

Which are the underlying rules that govern urban growth and the structure of the street network? Which are the distinctive characteristics that define highways and the differentiation of the various street patterns? How can we combine the above information and incorporate them in a computer aided urban simulation in order to successfully model a virtual city in which people will be able to successfully orientate and navigate? This research aims to address and investigate the above issues and proposes the development of a parametrically adjustable computer program in order to conduct navigational and way-finding experiments. Virtual Urbanity is a simulation engine which is capable of procedurally generating a vast and diverse variety of virtual 3D urban configurations. It uses an operational grammar which consists of a local generative process which is based on a Lindenmayer system, and a prescriptive set of global parametric rules. This combination defines the topology, the geometry, the width, the length, the density and the spatial significance of the streets, ultimately setting an effective street hierarchy. The program engages in the methodological exploration of existing and theoretical urban configurations and the analysis of the human perception about the structure of the built environment, and builds towards a working algorithm (rule-set) for the on the fly generation of city structures in the next generation video games. In accordance, a trial experiment regarding the mental correlations of the roads’ width and their hierarchical significance and function within the street network was conducted and its findings were discussed

Effect of bath ionic strength on adhesion and tribological properties of pure nickel and nickel composite coatings

The effect of electrolytic chemical concentration on wear-resistant, corrosion-resistant, adhesion and wettability properties of pure nickel and nickel-alumina composite coatings has been investigated in this paper. Coatings were electroplated over steel substrates under constant pulse conditions using pulse electrodeposition technique. Corrosion-resistant results show that the anti-corrosion properties are increasing with medium concentration both for pure nickel and nickel-alumina composite coating. For anti-wear properties the medium concentration showed increasing trend in case of pure nickel coatings but decreased in nickel-alumina composite coatings. In composite coating the higher and low concentrations of electrolyte showed the higher wear resistance properties. Furthermore, the influence of electrolyte concentration on changing surface morphologies, mechanical, wettability and adhesion properties have been investigated and reported here. Surface morphologies of the coatings were examined using scanning electron microscopy and energy-dispersive spectroscopy. Surface mapping and wear analyses were conducted through 3D white light interferometry

Corrosion of aluminium metal in OPC- and CAC-based cement matrices

Corrosion of aluminium metal in ordinary Portland cement (OPC) based pastes produces hydrogen gas and expansive reaction products causing problems for the encapsulation of aluminium containing nuclear wastes. Although corrosion of aluminium in cements has been long known, the extent of aluminium corrosion in the cement matrices and effects of such reaction on the cement phases are not well established. The present study investigates the corrosion reaction of aluminium in OPC, OPC-blast furnace slag (BFS) and calcium aluminate cement (CAC) based systems. The total amount of aluminium able to corrode in an OPC and 4:1 BFS:OPC system was determined, and the correlation between the amount of calcium hydroxide in the system and the reaction of aluminium obtained. It was also shown that a CAC-based system could offer a potential matrix to incorporate aluminium metal with a further reduction of pH by introduction of phosphate, producing a calcium phosphate cement

Koopman Operator Based Modeling and Control of Rigid Body Motion Represented by Dual Quaternions

In this paper, we systematically derive a finite set of Koopman based observables to construct a lifted linear state space model that describes the rigid body dynamics based on the dual quaternion representation. In general, the Koopman operator is a linear infinite dimensional operator, which means that the derived linear state space model of the rigid body dynamics will be infinite-dimensional, which is not suitable for modeling and control design purposes. Recently, finite approximations of the operator computed by means of methods like the Extended Dynamic Mode Decomposition (EDMD) have shown promising results for different classes of problems. However, without using an appropriate set of observables in the EDMD approach, there can be no guarantees that the computed approximation of the nonlinear dynamics is sufficiently accurate. The major challenge in using the Koopman operator for constructing a linear state space model is the choice of observables. State-of-the-art methods in the field compute the approximations of the observables by using neural networks, standard radial basis functions (RBFs), polynomials or heuristic approximations of these functions. However, these observables might not providea sufficiently accurate approximation or representation of the dynamics. In contrast, we first show the pointwise convergence of the derived observable functions to zero, thereby allowing us to choose a finite set of these observables. Next, we use the derived observables in EDMD to compute the lifted linear state and input matrices for the rigid body dynamics. Finally, we show that an LQR type (linear) controller, which is designed based on the truncated linear state space model, can steer the rigid body to a desired state while its performance is commensurate with that of a nonlinear controller. The efficacy of our approach is demonstrated through numerical simulations