Application of a leakage model to assess exfiltration from sewers.

The exfiltration of wastewater from sewer systems in urban areas causes a deterioration of soil and possibly groundwater quality. Beside the simulation of transport and degradation processes in the unsaturated zone and in the aquifer the analysis of the potential impact requires the estimation of quantity and temporal variation of wastewater exfiltration. Exfiltration can be assessed by the application of a leakage model. The hydrological approach was originally developed to simulate the interactions between the groundwater and surface water, it was adapted to allow for modelling of interactions between groundwater and sewer system. In order to approximate the exfiltration specific model parameters infiltration specific parameters were used as a basis. Scenario analysis of the exfiltration in the City of Dresden from 1997 to 1999 and during the flood event in August 2002 shows the variation and the extent of exfiltration rates.     

THE COMMUNITy AND SCHOOL DESEGREGATION: THE SEARCH FOR HOUSING MARKET EFFECTS

This paper attempts to measure the effect of a court-ordered desegregation plan on three aspects of the housing market in Dallas County, Texas. The indicators include sale price, number of sales, and proportion of home sales financed by conventional mortgages. Monthly data from 1969 to 1979 are analyzed using Box-Jenkins time series models. After best fit models are determined, various intervention terms are introduced into the models to assess the impact of both a 1975 Circuit Court Order and a 1976 District Court Order. The analysis suggests neither order had a measurable effect on the housing market in Dallas.     

Analysis and synthesis of on-chip spiral inductors

This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs.     

Failure loads for notched graphite/epoxy laminates with a softening strip

The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory.     

FMR and EXAFS modeling of heat-treated Fe-rich and Co-rich TM-M thin films

Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedures, magnetic properties were calculated with no adjustable parameters. Correlation between perpendicular FMR measurements and EXAFS first-shell modeling suggests a low-temperature formation of cobalt-borides in the Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ alloy. Annealed Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ samples did not display evidence of structural and/or magnetic instabilities until the onset of long-range crystallization near T/sub ann/=400 degrees C.<>     

Study of the nutrient distribution in root tips of the tropical forage Brachiaria

A Brachiaria breeding project is being conducted at CIAT, Colombia to combine acid soil adaptation of B. decumbens with other favourable traits of Brachiaria species that are less adapted to acid soils. Micro-PIXE was applied to investigate nutrient uptake and distribution in root tips of different species grown in hydroponic culture under control and simulated acid soil stress conditions. Different sample measurement approaches were evaluated, including: (1) linear scans with single point measurements along the root axis; (2) mapping of whole root tips; and (3) mapping of root cross sections. Different tissue types could be distinguished on the base of differences in nutrient concentrations and/or Al stress. Al, if supplied under nutrient stress conditions, increased P accumulation in the central vascular tissue of the meristematic and elongation zone of B. decumbens and B. brizantha. Furthermore, a negative correlation was found between Al and Cl accumulation in the root cap of B. decumbens.     

Hypercoagulability and chronic atrial fibrillation: the role of markers of thrombin generation

BACKGROUND: We have studied 64 patients with congestive heart failure, half of them also with chronic nonvalvular atrial fibrillation (AF). Patients were also stratified according to a history of prior stroke. METHODS: The generation of thrombin was investigated by means of the molecular markers prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT), because AF patients may have a hypercoagulable state. There was only a trend toward higher values of TAT and F1 + 2 for AF patients, while subjects with previous stroke (irrespective of AF) had increased levels of the markers of thrombin generation (TAT stroke+ 18.95 +/- 5.15 vs TAT stroke- 8.34 +/- 2.41; F1 + 2 stroke+ 2.22 +/- 0.29 vs F1 + 2 stroke- 1.32 +/- 0.12). The presence of spontaneous echo contrast (SEC) within left atrium was also investigated in 32 AF patients by transesophageal echocardiography. RESULTS: TAT were significantly higher in subjects (n = 11) with SEC (TAT sec+ 37.5 +/- 13.41 vs TAT sec- 8.7 +/- 2.51, p = 0.008). CONCLUSIONS: Finally, when we grouped into 1) those with both AF and stroke, 2) AF alone, 3) stroke alone and 4) sinus rhythm without stroke, levels of F1 + 2 were higher (and marginally higher TAT) in patients with AF and stroke than in those without stroke, revealing that there is a true clotting activation state in these subjects.     

Comparison of the effects of nonlinear gain and weak opticalfeedback on the dynamics of semiconductor lasers

The influence of nonlinear gain and optical feedback on the dynamics of single-mode semiconductor lasers are numerically investigated based on the Lang and Kobayashi model. It is well known that the nonlinear gain tends to stabilize the dynamics, while the optical feedback tends to increase the instabilities. In this paper, we study the behavior of the attractors when the feedback level k and the gain saturation coefficient ε vary and show that the effects of these parameters are surprisingly opposite. For example, we find that the route to chaos that the external cavity modes follow for increasing k is reversed for increasing ε in an almost identical manner. When the feedback increases the modes follow the usual quasi-periodic route and turn into torus. If k continues to increase, the torus become chaotic attractors as the result of several period-doubling bifurcations or a third Hopf bifurcation. Further increase of k causes the chaotic attractors to lose stability, Contrarily, if the value of the parameter ε is increased, the attractors recover their stability and reverse the route becoming simple torus again. If ε is increased further, the torus reverse the quasi-periodic route and turn into stable modes again. We also find that on the contrary to k, the parameter ε enhances the stability region of an attractor. We show that the feedback level above which a limit cycle emerges from a stable mode, the feedback level above which a torus emerges from a limit cycle, and the feedback level above which a chaotic attractor loses stability are all increasing functions of ε     

Effect of rotor profiles on the torque of a switched-reluctancemotor

The authors examine effects on the torque that simple variations of the standard rotor pole face profile could have, basically from an elementary viewpoint of how the modified profiles affect the distribution and magnitude of the radial and tangential components of the flux density. It is observed that the average torque is mostly affected by changes that alter the dominant radial component, such as changes in the effective air gap length. The other observation that an increase in the average torque can also be obtained by a favorable shift in the torque versus angle characteristics by relatively simple changes of the rotor pole profile is not so well known. Such a shift that reduces the slope of the torque angle characteristic, skewing the curve towards the unaligned position, has two advantages: one is that the phase inductance is at its maximum positive slop and, hence, the maximum torque, when the phase is energized; second, the flatter inductance profile near the aligned position when the phase current is to be commutated would allow a faster drop off of the commutated current and, thus, a smaller negative torque