BIOFOULING CONTROL IN HEAT EXCHANGERS USING HIGH VOLTAGE CAPACITANCE BASED TECHNOLOGY

Biofouling in industrial heat exchangers and piping systems is common in water from all sources. Problems generated by biofouling such as corrosion, sludge deposition and scale formation have a costly impact on industrial equipment and productivity. This paper describes an electronic approach using High Voltage Capacitance Based technology (HVCB) to control biofouling in industrial heat exchangers, focusing upon biofilm removal and the prevention of biofilm formation. Four different application case studies are presented in this paper in which the HVCB technology was used to control biofouling. The applications include an evaporative cooling wall in a greenhouse in Oracle, Arizona; a cooling tower–condenser application in Phoenix, Arizona (study performed by Arizona State University under a U.S. Department of Energy grant); a cooling tower system using reclaimed industrial waste water at a wafer facility in Camas, WA; and a piping system for a major utility plant (Tennessee Valley Authority – TVA) using river water. All four locations showed a significant improvement in biofouling control when the HVCB system was applied. Depending on the conditions of the water at each location, biofouling was controlled, while achieving a complete elimination of biocides, or with a significant reduction in biocide feed. From the data presented, the application of HVCB treatment programs can be successful in interfering with the three recognized stages of biofilm formation in industrial heat exchangers and piping systems

Improving the exchange and correlation potential in density-functional approximations through constraints

We review and expand on our work to impose constraints on the effective Kohn–Sham (KS) potential of local and semi-local density-functional approximations. Constraining the minimisation of the approximate total energy density-functional invariably leads to an optimised effective potential (OEP) equation, the solution of which yields the KS potential. We review briefly our previous work on this and demonstrate with numerous examples that despite the well-known mathematical issues of the OEP with finite basis sets, our OEP equations are numerically robust. We demonstrate that appropriately constraining the ‘screening charge’ which corresponds to the Hartree, exchange and correlation potential not only corrects its asymptotic behaviour but also allows the exchange and correlation potential to exhibit a non-zero derivative discontinuity, a feature of the exact KS potential that is necessary for the accurate prediction of band-gaps in solids but very hard to capture with semi-local approximations

The caries experience of 5 year-old children in Scotland in 2013-2014, and in England and Wales in 2014-2015. Reports of cross-sectional dental surveys using BASCD criteria

Objective: We report the findings from and comment on the surveys of the oral health of 5-year-old children undertaken in Scotland (2013-14), Wales (2014-15) and England (2014-15). This was the fourteenth survey in Scotland since 1988. In England and Wales it is the third survey since 2007 when changes were required in consent arrangements. Method: Representative samples were drawn within Health Boards across Scotland and local authorities across England and Wales. Consent was sought via opt-out parental consent in Scotland and opt-in parental consent in England and Wales. Children examined were those aged five in England and those in Primary 1 (school year aged 5 to 6) in Scotland and Wales. Examinations were conducted in schools by trained and calibrated examiners. Caries was visually diagnosed at the dentinal threshold. Results: There is a continuing decline in d3mft in all three countries. d3mft was 1.27 (opt-out consent) for Scotland, 0.84 for England (opt-in consent) and 1.29 for Wales (opt-in consent). Tooth decay levels remain higher in more deprived areas across Great Britain, with clear inequalities gradients demonstrated across all geographies. Attempts to measure changes in dental health inequalities across the three countries show no conclusive trends. Conclusion: Inter-country comparisons provide further oral health intelligence despite differences in approach and timing. The third surveys in England and Wales using the new consent arrangements have enabled trend analysis. Dental health inequalities gradients were shown across all geographies and all of the indicators of inequalit

Universally Coupled Massive Gravity

We derive Einstein's equations from a linear theory in flat space-time using free-field gauge invariance and universal coupling. The gravitational potential can be either covariant or contravariant and of almost any density weight. We adapt these results to yield universally coupled massive variants of Einstein's equations, yielding two one-parameter families of distinct theories with spin 2 and spin 0. The Freund-Maheshwari-Schonberg theory is therefore not the unique universally coupled massive generalization of Einstein's theory, although it is privileged in some respects. The theories we derive are a subset of those found by Ogievetsky and Polubarinov by other means. The question of positive energy, which continues to be discussed, might be addressed numerically in spherical symmetry. We briefly comment on the issue of causality with two observable metrics and the need for gauge freedom and address some criticisms by Padmanabhan of field derivations of Einstein-like equations along the way.Comment: Introduction notes resemblance between Einstein's discovery process and later field/spin 2 project; matches journal versio

Mode-coupling theory for multiple-time correlation functions of tagged particle densities and dynamical filters designed for glassy systems

The theoretical framework for higher-order correlation functions involving multiple times and multiple points in a classical, many-body system developed by Van Zon and Schofield [Phys. Rev. E 65, 011106 (2002)] is extended here to include tagged particle densities. Such densities have found an intriguing application as proposed measures of dynamical heterogeneities in structural glasses. The theoretical formalism is based upon projection operator techniques which are used to isolate the slow time evolution of dynamical variables by expanding the slowly-evolving component of arbitrary variables in an infinite basis composed of the products of slow variables of the system. The resulting formally exact mode-coupling expressions for multiple-point and multiple-time correlation functions are made tractable by applying the so-called N-ordering method. This theory is used to derive for moderate densities the leading mode coupling expressions for indicators of relaxation type and domain relaxation, which use dynamical filters that lead to multiple-time correlations of a tagged particle density. The mode coupling expressions for higher order correlation functions are also succesfully tested against simulations of a hard sphere fluid at relatively low density.Comment: 15 pages, 2 figure

Resource-Bound Quantification for Graph Transformation

Graph transformation has been used to model concurrent systems in software engineering, as well as in biochemistry and life sciences. The application of a transformation rule can be characterised algebraically as construction of a double-pushout (DPO) diagram in the category of graphs. We show how intuitionistic linear logic can be extended with resource-bound quantification, allowing for an implicit handling of the DPO conditions, and how resource logic can be used to reason about graph transformation systems

The stellar populations of spiral disks.II Measuring and modeling the radial distribution of absorption spectral indices

The radial distributions of the Mg2 and Fe5270 Lick spectral indices have been measured to large radial distances on the disks of NGC 4303 and NGC 4535 using an imaging technique based on interference filters. These data, added to those of NGC 4321 previously published in Paper I of this series are used to constraint chemical (multiphase) evolutionary models for these galaxies. Because the integrated light of a stellar disk is a time average over the history of the galaxy weighted by the star formation rate, these constraints complement the information on chemical gradients provided by the study of HII regions which, by themselves, can only provide the alpha-elements abundance accumulate over the life of the galaxy. The agreement between the observations and the model predictions shown here lends confidence to the models which are then used to describe the time evolution of galaxy parameters such as star formation rates, chemical gradients, and gradients in the mean age of the stellar population.Comment: to be published in Astrophysical Journa

The Schwarzschild black hole as a point particle

The description of a point mass in general relativity (GR) is given in the framework of the field formulation of GR where all the dynamical fields, including the gravitational field, are considered in a fixed background spacetime. With the use of stationary (not static) coordinates non-singular at the horizon, the Schwarzschild solution is presented as a point-like field configuration in a whole background Minkowski space. The requirement of a stable $\eta$-causality stated recently in [J.B.Pitts and W.C.Schieve, Found. Phys., v. 34, 211 (2004)] is used essentially as a criterion for testing configurations.Comment: LATEX, 8 pages, no figure