Experimental determination of optimum parameters for nano-grinding of optical fibre end faces

This study presents detailed experimental results that help to determine the optimal grit size, speed and in-feed rate for grinding end faces of optical fibres on a nano-grinding machine. The determination of these parameters was based on surface roughness, material removal rate and the surface and sub-surface damage investigations. The observations consisted of qualitative as well as quantitative evaluations. Qualitative assessment of surface quality was carried out using an optical microscope. The quantitative measurement of surface roughness was carried out using atomic force microscopy (AFM). The material removal rates were determined using feed rates of the nano-grinding machine. Using a focussed ion beam (FIB), the ground surfaces were milled to expose their cross sections. The ground surfaces and the cross sections were examined using scanning electron microscopy (SEM) for surface or sub-surface damage.     

Recognizing Patterns in Seasonal Variation of Pavement Roughness Using Minimum Message Length Inference

Abstract: Pavement roughness is a common measure of pavement condition regularly measured by road authorities. An approach to recognize patterns of seasonal variation in rural sealed granular pavement roughness by minimum message length (MML) inference is demonstrated in this article. MML solves two fundamental questions: First, is the seasonal variation a systematic pattern or merely the result of random scatter? Second, given evidence of seasonal variation to what level of complexity should the seasonal trend be modeled? The MML technique developed does not require user input rather will identify in a quantitative and consistent manner any patterns evident in the data. The patterns identified with MML can be used to remove seasonal variation effects. The analysis utilized 104,188 roughness values obtained from a particular region in Australia over 15 years. MML inference recognized patterns of seasonal variation and demonstrated that these are not merely due to random scatter. The optimum model selected by MML inference has four separate segments of variation. These segments correspond to changes in climatic conditions that support the inference.     

Modeling of creep and shrinkage behavior of polymeric films used in magnetic tapes

For ever increasing high recording densities of magnetic tape drives, improved dimensional stability of the polymeric films used as magnetic tape substrates is required. During storage and use, creep and shrinkage occur simultaneously and it needs to be minimized. To obtain constitutive relationships for creep and shrinkage, these contributions need to be separated and modeled. A mathematical model based on Kelvin–Voigt models has been developed to characterize simultaneous creep and shrinkage behavior to obtain the constitutive relationships for creep and shrinkage. Experiments have been performed to separate out creep and shrinkage effects and this model has been used to compensate the effect of shrinkage on creep data and to get true creep data. The experimental creep and shrinkage data of various films have been modeled to obtain viscoelastic parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 78–88, 2004     

A COMPARISON OF GRADIENT APPROXIMATIONS FOR USE IN FINITE-VOLUME COMPUTATIONAL MODELS FOR TWO-DIMENSIONAL DIFFUSION EQUATIONS

Finite-volume methods (FVMs) are now a popular choice among practitioners in scientific computation and engineering. This article focuses on generalized FVMs that can be implemented on any mesh structure. The accuracy of FVMs is primarily influenced by the numerical approximation of the flux term at the control-volume face. Here, different flux approximations are compared to identify which approximation is the most accurate, independent of the mesh structure. The accuracy of the classical two-node approximation can be improved significantly by using a local gradient reconstruction to capture the crossdiffusion term of the flux at the control-volume face. A simple two-dimensional isotropic diffusion equation for which an analytical solution is available is chosen for benchmarking purposes.     

Transport Properties of Bulk Thermoelectrics: An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat, and Thermal Conductivity

For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.     

State of the Art and Emerging Trends in Operations and Maintenance of Offshore Oil and Gas Production Facilities： Some Experiences and Observations

Plant maintenance has been a discipline that has gradually evolved with the industrial revolution. For quite some time, it has been a ``necessary evil' in production, manufacturing, and process settings. The changing business needs and industrial conditions have had various impacts on the maintenance process, particularly over the last few years. While some industries have inherent difficulties seeing what maintenance is all about, others have begun to add more flavor to the organizational maintenance practices. This article brings an overview of developments within the offshore oil and gas production sector.     

An extended transaction to maintain consistency and recovery in multidatabase systems

A complete practical solution to transaction management preserving multidatabase consistency in the presence of multidatabase updates and failures is presented. The approach developed does not require support for the two-phase commit (2PC) protocol in the participating local database management systems (LDBMSs). Furthermore, it does not violate local autonomy; the source code of the LDBMSs is not modified in any way and the multidatabase system (MDBS) does not access or modify any control information of the LDBMS. The principles of the 2PC protocol in the process of global transaction commitment are adopted. The presented method does not rely on any specific concurrency control mechanism for LDBMSs. Consideration is given to global transaction failures due to subtransaction aborts by the LDBMSs and local site crashes. The recovery process is based on undo operations. While a global transaction is in progress, the tables accessed by subtransactions of this transaction at each local site are locked using specially initiated table locks. These locks are stored and maintained in the local database itself as control tables. The approach taken is easy to implement, and its limitations are discussed.     

Modeling user perception of 3D video based on ambient illumination context for enhanced user centric media access and consumption

For enjoying 3D video to its full extent, it is imperative that access and consumption of it is user centric, which in turn ensures improved 3D video perception. Several important factors including video characteristics, users’ preferences, contexts prevailing in various usage environments, etc have influences on 3D video perception. Thus, to assist efficient provision of user centric media, user perception of 3D video should be modeled considering the factors affecting perception. Considering ambient illumination context to model 3D video perception is an interesting research topic, which has not been particularly investigated in literature. This context is taken into account while modeling video quality and depth perception of 3D video in this paper. For the video quality perception model: motion and structural feature characteristics of color texture sequences; and for the depth perception model: luminance contrast of color texture and depth intensity of depth map sequences of 3D video are used as primary content related factors in the paper. Results derived using the video quality and depth perception models demonstrate that these models can efficiently predict user perception of 3D video considering the ambient illumination context in user centric media access and consumption environments.