Alternative Methods of Describing Structure Formation in the Lemaitre-Tolman Model

We describe several new ways of specifying the behaviour of Lemaitre-Tolman (LT) models, in each case presenting the method for obtaining the LT arbitrary functions from the given data, and the conditions for existence of such solutions. In addition to our previously considered `boundary conditions', the new ones include: a simultaneous big bang, a homogeneous density or velocity distribution in the asymptotic future, a simultaneous big crunch, a simultaneous time of maximal expansion, a chosen density or velocity distribution in the asymptotic future, only growing or only decaying fluctuations. Since these conditions are combined in pairs to specify a particular model, this considerably increases the possible ways of designing LT models with desired properties.Comment: Accepted by Phys Rev D. RevTeX 4, 13 pages, no figures. Part of a series: gr-qc/0106096, gr-qc/0303016, gr-qc/0309119. Replacement contains very minor correction

Optimization of chemical pretreatment for removing cobalt on tungsten carbide substrate using response surface methodology

Diamond coating are commonly used in industries especially for application such as cutting tools, biomedical components, optical lenses, microelectronics, engineering, and thermal management systems. The diamond coating quality is strongly depending on substrate preparation prior to diamond coating. Thus, the several process parameters must be studied to obtain optimal parameters which lead high quality diamond coating. In this present work, an attempt was made to optimize pretreatment parameters namely temperature and time on cobalt removal of tungsten carbide. Full factorial experimental designs followed by Response Surface Methodology (RSM) were employed in this study to plan and analyze the experiment. The cobalt removal was the independent response variables. Empirical model was successfully developed to predict amount of cobalt removal on the substrate after single step etching process. Experimental results have shown that the temperature, time and time2 are found to be the most significant factors for cobalt removal. Whereas for interaction of time and temperature were insignificant factors to influence cobalt removal. According to this study, the minimum cobalt content can be obtained at working temperature from 48º to 50ºC for 3 minute

Shrinking II -- The Distortion of the Area Distance-Redshift Relation in Inhomogeneous Isotropic Universes

This paper and the others in the series challenge the standard model of the effects of gravitational lensing on observations at large distances. We show that due to the cumulative effect of lensing, areas corresponding to an observed solid angle can be quite different than would be estimated from the corresponding Friedmann-Lema\^{\i}tre model, even when averaged over large angular scales. This paper concentrates on the specific example of spherically symmetric but spatially inhomogeneous dust universes, the Lema\^{\i}tre-Tolman-Bondi models, and shows that radial lensing significantly distorts the area distance-redshift and density-redshift relations in these exact solutions compared with the standard ones for Friedmann-Lema\^{\i}tre models. Thus inhomogeneity may introduce significant errors into distance estimates based on the standard FL relations, even after all-sky averaging. In addition a useful new gauge choice is presented for these models, solving the problem of locating the past null cone exactly.Comment: Minor technical refinement, 16 pages, RevTex, 8 eps figure

Numerical solution of third order three-point boundary value problems of ordinary differential equations with variable coefficients using variational-composite hybrid fixed point iterative method

This paper explores variational–composite hybrid fixed point iterative scheme for the solution of third order three-point boundary value problems. The method shows a strong convergence which makes it an efficient and reliable technique for finding approximate analytical solutions for third order three-point boundary value problems of ordinary differential equations with variable coefficients. From the numerical experiments carried out, the accuracy of the method was confirmed through the order of convergence obtained

Phantom Black Holes and Sigma Models

We construct static multicenter solutions of phantom Einstein-Maxwell-dilaton theory from null geodesics of the target space, leading to regular black holes without spatial symmetry for certain discrete values of the dilaton coupling constant. We also discuss the three-dimensional gravitating sigma models obtained by reduction of phantom Einstein-Maxwell, phantom Kaluza-Klein and phantom Einstein-Maxwell-dilaton-axion theories. In each case, we generate by group transformations phantom charged black hole solutions from a neutral seed.Comment: 19 page

Assessment of regulation compliance and quality of sachet water factories In Ibadan North Local Government, Oyo State, Nigeria

Provision of clean drinking water is one of the basic human necessities for healthy livelihood. In Nigeria, many people relied on sachet waters as an alternative source of clean drinking water. However, complaints abound regarding lack of proper water quality standard being used which is a major health concern. This study assessed the regulatory compliance of some sachet water production companies and water quality standard in Ibadan North Local Government Area, Oyo State, Nigeria. Questionnaires were administered on factory’s organisational structure and staffing; facilities and equipment; water treatment processes and sanitation practices, Also, Sachet water samples were analysed for the contaminants of Turbidity, Colour, Odour, pH, Nitrate, Chloride, Iron, Electrical conductivity and E-coli count. From the questionnaire analysis, the adherence level with the regulations was poor as majority (60%) of the sachet water factories have poor organisational structure and only 33% have adequate facilities and equipment. However, water quality analysis showed that most of the sachet water parameters tested were within the standard range except for pH values and E Coli count which majority (70%) falls below standard for both. The study concludes that most sachet water brands produced are unsafe for human consumption. There is need for proper monitoring by relevant agencies towards ensuring sachet water factories continuously complied with standard operations for better public health in the study area

On the kinematics of the cross body abduction and hand behind the back tests to assess osteoarthritis of the acromioclavicular joint

Background: Osteoarthritis of the acromioclavicular joint is one of the most common sources of shoulder pain. One of the current standard clinical physical examination tests is the cross body adduction test which has been shown to signal the presence of osteoarthritis. Another test referred to as the hand behind the back test has been described to provide a more accurate diagnosis than the CBA test for some patients. Through this work, both the CBA and the HBB tests were modeled in order to determine if there is merit for the HBB test to be used as a diagnostic tool for clinicians. Methods: Both tests were modeled using the zygote solid 3D 50th percentile male human anatomy model and MSC-ADAMS Software to compile and run the simulations. Within MSC-ADAMS the bones were outfitted with joints. During simulation, the bones were moved from the anatomical position to the final position for each test and the corresponding minimum distances between the bones at the acromioclavicular joint were then determined. Results: It was found that the distance between the acromioclavicular joint articulating surfaces decreased by 0.3 mm from the anatomical position during the CBA test and by 1.65 mm from the anatomical position during the HBB. This shows that the minimum space decreased from the anatomical position by more than 5 folds during the HBB test than during the CBA test. Conclusions: These results indicate that the HBB test may be a better diagnostic test due to the greater stress and irritation it places upon the acromioclavicular joint

Dynamical dark energy: Current constraints and forecasts

We consider how well the dark energy equation of state $w$ as a function of red shift $z$ will be measured using current and anticipated experiments. We use a procedure which takes fair account of the uncertainties in the functional dependence of $w$ on $z$, as well as the parameter degeneracies, and avoids the use of strong prior constraints. We apply the procedure to current data from WMAP, SDSS, and the supernova searches, and obtain results that are consistent with other analyses using different combinations of data sets. The effects of systematic experimental errors and variations in the analysis technique are discussed. Next, we use the same procedure to forecast the dark energy constraints achieveable by the end of the decade, assuming 8 years of WMAP data and realistic projections for ground-based measurements of supernovae and weak lensing. We find the $2 \sigma$ constraints on the current value of $w$ to be $\Delta w_0 (2 \sigma) = 0.20$, and on $dw/dz$ (between $z=0$ and $z=1$) to be $\Delta w_1 (2 \sigma)=0.37$. Finally, we compare these limits to other projections in the literature. Most show only a modest improvement; others show a more substantial improvement, but there are serious concerns about systematics. The remaining uncertainty still allows a significant span of competing dark energy models. Most likely, new kinds of measurements, or experiments more sophisticated than those currently planned, are needed to reveal the true nature of dark energy.Comment: 24 pages, 20 figures. Added SN systematic uncertainties, extended discussio

The bonded macro fiber composite (MFC) and woven kenaf effect analyses on the micro energy harvester performance of kenaf plate using modal testing and Taguchi method

The demand on wind energy application will continue to increase as fossil fuel prices keep increasing and the reservoir keeps decreasing. In wind energy, wind turbine application should be properly selected. The material selection for turbine blade fabrication is highlighted as well in recent research. For green material application, the usage of natural fiber reinforced composite, especially kenaf fiber, in the fabrication of wind turbines needs to be given due attention. Woven and unwoven kenaf fiber is employed to fabricate composite plates which replicate the simple turbine blade model. At the same time, Macro Fiber Composite (MFC) is attached to the kenaf plates for micro energy harvester purposes. There are two methods to attach the MFC used in this study which are surface bonded and embedding into the plate. In order to investigate the effects of bonding MFC technique, modal Testing analysis and Taguchi method is employed. It is found out that the damping percentage of both woven and unwoven kenaf plates increase at 100 % and 50 % respectively when bonded with MFC on their surfaces. Bonded technique is suggested as the most influenced factor in micro energy harvesting at the vibration range of 20 to 60 Hz. It summarized that, the kenaf woven type, the distance from structure neutral axis, the stiffness of structure, the excitation vibration and the neutral frequency of a structure are highlighted as the factors influencing the performance of micro energy harvester as well

The isotropic blackbody CMB as evidence for a homogeneous universe

The question of whether the Universe is spatially homogeneous and isotropic on the largest scales is of fundamental importance to cosmology, but has not yet been answered decisively. Surprisingly, neither an isotropic primary CMB nor combined observations of luminosity distances and galaxy number counts are sufficient to establish such a result. The inclusion of the Sunyaev-Zel'dovich effect in CMB observations, however, dramatically improves this situation. We show that even a solitary observer who sees an isotropic blackbody CMB can conclude that the universe is homogeneous and isotropic in their causal past when the Sunyaev-Zel'dovich effect is present. Critically, however, the CMB must either be viewed for an extended period of time, or CMB photons that have scattered more than once must be detected. This result provides a theoretical underpinning for testing the Cosmological Principle with observations of the CMB alone.Comment: 5 pages, 1 figur