Hydraulic linkage of a storm water tank to a karst spring (Gallusquelle)

Grundwasser - A significant proportion of the global water supply is ensured by karst aquifers. However, these are often highly vulnerable to contamination. A storm water tank...     

Globally optimal transmitter placement for indoor wireless communication systems

A global optimization technique is applied to solve the optimal transmitter placement problem for indoor wireless systems. An efficient pattern search algorithm - DIviding RECTangles (DIRECT) of Jones et al.- has been connected to a parallel three-dimensional radio propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations. Surrogate functions for a parallel wideband code-division multiple-access (WCDMA) simulator were used to estimate the system performance for the global optimization algorithm. Power coverage and bit-error rate are considered as two different criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. This paper briefly describes the underlying radio propagation and WCDMA simulations and focuses on the design issues of the optimization loop.     

Observations of the preferential loss of major ions from melting snow and laboratory ice

Two types of laboratory experiments were undertaken to understand changes in the ionic composition of solutions from melting snows: (1) a set of field-laboratory experiments which involved partially melting recently collected snows and (2) experiments on the controlled melting of artificial ices of known composition. Sulphate and nitrate ions are preferentially lost with respect to chloride during the melting process so apparent elution sequence may be written SO₄²⁻ > NO₃⁻ > Cl⁻. Of the cations, sodium appears to be removed least readily giving an elution sequence Mg²⁺ = K⁺ > Na⁺. In the laboratory the differences in the efficiency of removal of ions from ice are small in the first stages of melting, but pronounced by the end of the melt. Sodium and chloride are expected to be proportionally enriched in residual leached snow packs. This is generally born out by field observations. The preferential loss of some ions is more evident in aged laboratory ice than in the freshly made ice. The changes in the ice and meltwater composition throughout the process of melting may be understood to arise from the mixing of two types of solutions: (i) an intergranular surficial brine with high solute concentration that occupies the ice grain boundaries and (ii) the meltwater from the ice grains.     

Efficient simulation of multicarrier digital communication systemsin nonlinear channel environments

When simulating multicarrier digital communication systems operating over nonlinear channels, the required high sampling rate contributes significantly to long execution times. A new method that reduces the sampling rate of simulations of such systems is developed. The partial rate of products (ParSOP) method reduces the sampling rate by generating only the intermodulation products that lie in a frequency band of interest. The ParSOP method requires that the bandpass nonlinearity be represented by memoryless operations on the complex envelope of the signal and that the subcarriers constituting the frequency-division multiplexed signal are sufficiently separated to prevent significant adjacent channel interference. Simulation results for such systems show that an order of magnitude reduction in the sampling rate is possible while producing only minimal error in the bit error rate estimate     

Acupuncture in Australian general practice: practitioner characteristics

The purpose of this study was to examine the role of diabetes mellitus (DM) in infrainguinal bypass graft outcome. One hundred forty-four patients who underwent 170 infrainguinal bypass grafts from 1990 to 1995 were reviewed retrospectively. Seventy-eight patients (94 bypasses) had DM and were followed for an average of 15.4 months; 13 patients were lost to follow up. The mean age was 68 years; 44 (56.4%) were men. The major indication for intervention was limb salvage for the DM (87/94, 92.6%) and non-DM (56/76, 73.7%) groups. No significant difference was found for perioperative wound complications, hematoma, myocardial infarction, or deep venous thrombosis between the DM and non-DM groups. Early mortalities were three for DM and one for non-DM patients. No significant difference was found between primary patency (p = 0.71), secondary patency (p = 0.32), limb salvage (p = 0.99), and survival (p = 0.72) between DM and non-DM groups. DM patients were more likely to have significant tissue loss (p = 0.009) and a longer hospital stay (p = 0.01). In conclusion, infrainguinal vein bypass grafting can be performed successfully in diabetic patients with comparable patency and limb-salvage rates to those without DM.     

The Bacterial Quality of an Upland Stream

Faecal coliform concentrations were determined at stream and water inflow sampling sites within an upland catchment in North Derbyshire containing rough, semiimproved and improved pastures. The results indicated that, during its passage through the catchment, the faecal indicators of the stream increased, and this may constitute a health risk to cavers using a popular recreational cave into which the stream drains. The decline in streamwater quality suggests that a semipermanent store of bacteria existed in catchment soils, and hydrological processes operated to transfer bacteria from the land to the stream channel. Contrary to expectations, intra-catchment differences in the bacterial quality of water at inflow and stream sampling sites could not be related to the intensity of agricultural land use in adjacent areas. This is explained with reference to changes in the nature of hydrological transport pathways associated with the improvement of pastures.     

Relationships between interest in motor racing and driver attitudes and behaviour amongst mature drivers: an Australian case study

Interest in motor racing is investigated as a possible source of influence on driver attitudes toward speeding and driver behaviour. Previous studies have identified links between motor racing and road accidents on public roads. One study found that the level of interest in motor racing was positively correlated with risky driving behaviours of young male drivers. This paper outlines a conceptual framework for investigating the association between interest in motor racing and speeding violations on public roads. A sample survey of households in Queanbeyan, NSW, was used to examine the relationship between the level of interest in motor racing and attitudes to speeding and driving violations in a group of mature drivers. Results indicate that the level of interest in motor racing is significantly related to attitudes towards speeding, controlling for age, education level and sensation seeking propensity. Higher levels of interest in motor racing are associated with higher pro-speeding attitudes. Unlike the previous research on young male drivers, there was no significant relationship between interest in motor racing and speeding violations for this study of mature drivers. The implications of the study for road safety interventions are discussed.     

Shock tube/time-of-flight mass spectrometer for high temperature kinetic studies

A shock tube (ST) with online, time-of-flight mass spectrometric (TOF-MS) detection has been constructed for the study of elementary reactions at high temperature. The ST and TOF-MS are coupled by a differentially pumped molecular beam sampling interface, which ensures that the samples entering the TOF-MS are not contaminated by gases drawn from the cold end wall thermal boundary layer in the ST. Additionally, the interface allows a large range of postshock pressures to be used in the shock tube while maintaining high vacuum in the TOF-MS. The apparatus and the details of the sampling system are described along with an analysis in which cooling of the sampled gases and minimization of thermal boundary layer effects are discussed. The accuracy of kinetic measurements made with the apparatus has been tested by investigating the thermal unimolecular dissociation of cyclohexene to ethylene and 1,3-butadiene, a well characterized reaction for which considerable literature data that are in good agreement exist. The experiments were performed at nominal reflected shock wave pressures of 600 and 1300 Torr, and temperatures ranging from 1260 to 1430 K. The rate coefficients obtained are compared with the earlier shock tube studies and are found to be in very good agreement. As expected no significant difference is observed in the rate constant between pressures of 600 and 1300 Torr.