A washoff model for stormwater pollutants

A washoff rate equation for stormwater pollutants is presented based on linear buildup of pollutant mass in the watershed. The expression was applied to residential and open land areas that have not previously been considered even though these areas are major sources of metals, nutrients, and bacteria in stormwater runoff. The transport coefficient c was determined from the nearly constant portion of the hydrograph at the peak of each runoff event. Values of c (cm(-1)) for seven metals, i.e., Zn, Cu, Cd, Ni, Pb, Hg, and Ag (3.03+/-1.34-6.10+/-2.55 cm(-1)), TSS, BOD(5), total phosphorus (TP), E. coli, and fecal coliform (2.12+/-0.907-7.16+/-2.72 cm(-1)) were estimated using this equation. The washoff rate was developed to reflect mixed land uses based on mass deposition and effective area. The order of transport coefficients for metals is Pb>Ag>Zn>Cu>Ni>Hg>Cd reflecting decreasing particle association. For all parameters this order is TSS>fecal coliform>E. coli>Pb>BOD(5) BOD(5)>Ag>Zn>Cu>Ni>Hg>Cd>TP. The washoff rate and a related pollutant concentration model are expected to be useful for the development of best management practices for stormwater.     

Avoided crossing of rattler modes in thermoelectric materials

Engineering of materials with specific physical properties has recently focused on the effect of nano-sized 'guest domains' in a 'host matrix' that enable tuning of electrical, mechanical, photo-optical or thermal properties. A low thermal conductivity is a prerequisite for obtaining effective thermoelectric materials, and the challenge is to limit the conduction of heat by phonons, without simultaneously reducing the charge transport. This is named the 'phonon glass-electron crystal' concept and may be realized in host-guest systems. The guest entities are believed to have independent oscillations, so-called rattler modes, which scatter the acoustic phonons and reduce the thermal conductivity. We have investigated the phonon dispersion relation in the phonon glass-electron crystal material Ba(8)Ga(16)Ge(30) using neutron triple-axis spectroscopy. The results disclose unambiguously the theoretically predicted avoided crossing of the rattler modes and the acoustic-phonon branches. The observed phonon lifetimes are longer than expected, and a new explanation for the low kappa(L) is provided.     

Insights in distributed secondary gas injection in a bubbling fluidized bed via discrete particle simulations

Experiments have shown that distributed secondary gas injection via a fractal injector in fluidized beds can significantly reduce the bubble size, and may also decrease the bubble fraction. In order to gain insight into the distribution of the gas between the phases and the mechanisms behind these effects simulations of small bubbling fluidized beds with one or two secondary gas injection points were carried out using a discrete particle model. Although the systems are very small, so that wall effects cannot be excluded, the model predicts that the bubble size and bubble fraction both decrease with secondary gas injection, while the gas flow through the dense phase increases. The secondary gas tends to stay in the dense phase, which limits the amount of gas available to form bubbles and is the main contributor to the decrease in the bubble size and fraction. The gas-solid contact improves as a result.     

IN-SITU FT-IR SPECTROSCOPIC STUDIES OF FUEL CELL ELECTRO-CATALYSIS: FROM SINGLE-CRYSTAL TO NANOPARTICLE SURFACES

The work presented in this article shows the power of the variable temperature, in-situ FT-IR spectroscopy system developed in Newcastle with respect to the investigation of fuel cell electro-catalysis. On the Ru(0001) electrode surface, CO co-adsorbs with the oxygen-containing adlayers to form mixed [CO + (2 × 2)-O(H)] domains. The electro-oxidation of the Ru(0001) surface leads to the formation of active (1 × 1)-O(H) domains, and the oxidation of adsorbed CO then takes place at the perimeter of these domains. At 20°C, the adsorbed CO is present as rather compact islands. In contrast, at 60°C, the CO_ads is present as a relatively looser and weaker adlayer. Higher temperature was also found to facilitate the surface diffusion and oxidation of CO_ads. No dissociation or electro-oxidation of methanol was observed at potentials below approximately 950 mV; however, the Ru(0001) surface at high anodic potentials was observed to be very active. On both Pt and PtRu nanoparticle surfaces, only one linear bond CO adsorbate was formed from methanol adsorption, and the PtRu surface significantly promoted both methanol dissociative adsorption to CO and its further oxidation to CO₂. Increasing temperature from 20° to 60°C significantly facilitates the methanol turnover to CO₂.     

Wind forces on and excitation of a 130-m concrete chimney

A field experiment concerned with wind forces on a large concrete chimney and the vibrations caused by these forces is presented.Some preliminary results concerning the consistency of the measurements are discussed, and some conclusions regarding chimney vibrations are given.A method for on-line dynamic calibration of wind pressure transducers is presented. The method has worked satisfactorily, but improvements concerning zero-pressure biases are needed.A universal mean-pressure distribution for the Stigsnaes chimney is presented. An estimated drag coefficient of 0.64 (independent of height above the ground) seems reasonable for transcritical Reynolds numbers.The roughness parameter of the sea for on-shore wind directions is found to be of the order of centimetres. A slight indication of increasing roughness with increasing wind speed is observed.     

Harmonic analysis of environmental time series with missing data or irregular sample spacing

The Lomb periodogram and discrete Fourier transform are described and applied to harmonic analysis of two typical data sets, one air quality time series and one water quality time series. The air quality data is a 13 year series of 24 hour average particulate elemental carbon data from the IMPROVE station in Washington, D.C. The water quality data are from the stormwater monitoring network in Milwaukee, WI and cover almost 2 years of precipitation events. These data have irregular sampling periods and missing data that preclude the straightforward application of the fast Fourier transform (FFT). In both cases, an anthropogenic periodicity is identified; a 7-day weekday/ weekend effect in the Washington elemental carbon series and a 1 month cycle in several constituents of stormwater. Practical aspects of application of the Lomb periodogram are discussed, particularly quantifying the effects of random noise. The proper application of the FFT to data that are irregularly spaced with missing values is demonstrated on the air quality data. Recommendations are given when to use the Lomb periodogram and when to use the FFT.     

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

In this work, we study the structure–topology–property relations of a series of melt-quenched lithium germanate glasses. These glasses exhibit the so-called germanate anomaly, that is, the germanium atoms feature a distribution of four-coordinated and higher coordinated germanium species, manifesting itself as anomalies in several material properties. Here, we couple variations in the number of atomic bond constraints with measured variations in thermal and mechanical properties, including thermal conductivity, Vickers hardness, and fracture toughness. For thermal conductivity, a strong correlation is found with sound velocity as well as with the volumetric constraint density. For hardness, a good correlation with volumetric constraint density is found, whereas, for fracture toughness, variations in network topology alone are insufficient to explain the composition–property relation. To account for this, we apply a recent model which incorporates knowledge of local structure, mechanical properties, and fracture patterns to predict the fracture toughness, showing a good qualitative agreement with the experimental data.     

Aircraft and balloon in situ measurements of methane and hydrochloric acid using interband cascade lasers

Aircraft and balloon in situ measurements of CH4 and HCl using cw distributed feedback (DFB) interband cascade (IC) lasers are reported. In the stratosphere and upper troposphere, sensitivity toward CH4 and HCl is better than 10 ppbv (1 s) and 90 pptv (50 s), respectively. These are the first flight measurements of trace gas-phase species using cw DFB IC lasers.     

A Digital Measurement of Earth Fault Loop-Impedance Using a Parameter Estimation Algorithm

ABSTRACT

In electrical low voltage power system, a neutral earthing is used for protection against electrical shock hazards. Testing of the effectiveness of the earthing system could be achieved by measuring the system fault loop impedance Z. This paper presents a new application of least error squares (LES) parameter estimation algorithm for measurement of earth fault impedance, the proposed method uses the digitized samples of the instantaneous voltage across the fault loop impedance, effects of data window size, sampling rate and the voltage frequency drift on the accuracy of the impedance measurements are studied. Simulated test results are reported in this paper, which from the basis of our conclusion.