We were able to accurately predict the shadow path and successfully observe an occultation of a bright star by Chiron on December 15, 2022. The Kottamia Astronomical Observatory in Egypt did not ...detect the occultation by the solid body, but we found three extinction features in the light curve that had symmetrical counterparts with respect to the central time of the occultation. One of the features is broad and shallow, whereas the other two features are sharper, with a maximum extinction of ∼25% at the achieved spatial resolution of 19 km per data point. From the Wise Observatory in Israel, we detected the occultation caused by the main body and several extinction features surrounding the body. When all the secondary features are plotted in the sky plane, we find that they can be caused by a broad ∼580 km disk with concentrations at radii of 325 ± 16 km and 423 ± 11 km surrounding Chiron. At least one of these structures appears to be outside the Roche limit. The ecliptic coordinates of the pole of the disk are
λ
= 151° ±8° and
β
= 18° ±11°, in agreement with previous results. We also reveal our long-term photometry results, indicating that Chiron had suffered a brightness outburst of at least 0.6 mag between March and September 2021 and that Chiron was still somewhat brighter at the occultation date than at its nominal pre-outburst phase. The outermost extinction features might be consistent with a bound or temporarily bound structure associated with the brightness increase. However, the nature of the brightness outburst is unclear, and it is also unclear whether the dust or ice released in the outburst could be feeding a putative ring structure or whether it is emanating from it.
A combined numerical and experimental study of lap-shear testing of solder joints was carried out. The primary objective was to provide a quantitative evaluation of shear deformation experienced by ...the solder. The numerical analysis was based on finite element modeling of deformation in the substrate–solder assembly. The calculated shear response, utilizing both the commonly adopted far-field measurements and the actual shear strain in solder, was found to differ significantly. The geometric and material parameters during lap shear were explored to provide physical insight into the problem. The nature of deformation of the substrate was seen to greatly influence the shear behavior of the solder. The “transmission” of shear strain into the solder is very ineffective when the solder is in the elastic state, resulting in smaller shear strains in the solder than the nominal values. This effect is also true even when the solder is deforming plastically. Experimental measurements of solder shear using direct optical measurements confirmed the numerical findings. Subtraction of the average deformation of the Cu substrate provides a reasonable, albeit not complete, approximation of the solder strain.
This study examines the effects of uncertain travel time on public bus operators' monthly returns or profit margin in metropolitan Lagos, Nigeria. Importantly, the study relied on four objectives to ...achieve its purpose, and these are to; evaluate the demographic profile of public bus drivers; determine the daily cost of operating the buses and the percentage of bus returns spent on bus maintenance; analyze the bus running time and the associated cost attached to prolonged bus operations, and determine the number of trips made and lose daily due to prolonged journey time in metropolitan Lagos. The study relied on a survey research design and the use of primary data, which is derived from a questionnaire instrument administered at the three study locations. Further, the combination of clustered, stratified, and simple random sampling techniques was used while respondents (bus operators/drivers) were selected at different bus stop segments for questionnaire administration. The statistical correlation technique from the SPSS software was used for data relationship analysis, while descriptive tools were utilized for the presentation of the results. Furthermore, the severity of the problems encountered by bus operators shows that loss of daily revenue (52.9%) is the highest, followed by loss of bus trips (35.4%), and constant vehicle breakdown (11.7%). This poses a significant challenge to their business success as it grossly reduces their bus return and monthly profit margin. The study concluded that prolonged bus journey time has a negative socio-economic impact on the Intra-City public bus operators in metropolitan Lagos. Therefore, recommends among others: road highway expansion; provision of extended bus stop lay-bys, BRT corridor extension to other major highways, traffic agents' commitment and patriotism, and intensive enforcement of laws prohibiting bus stop obstructions by public bus drivers.
► We examine coal gasification in fast fluidized beds. ► A 2D computational particle fluid dynamics is implemented. ► The model predicts flows in the near feeding region, helping prevent suspension ...chocking. ► The model provides close gas compositions with respect to a PFR.
Coal gasification in fluidized beds is a process that can be strongly influenced by gas–solid suspension flow patterns. Fast fluidized beds can be designed to maximize coal gasification yields providing an optimum syngas composition with minimum operational upsets. In order to accomplish this, a comprehensive model for steam coal gasification is valuable. With this end, a 2D CPFD (computational particle fluid dynamics) dynamic model is considered in the present study. The proposed model uses a Lagrangian–Eulerian approach and describes the flow patterns in the gasifier feeding section, as well as the local particle velocities, particle solid fractions and gas composition. As a reference and for comparison, an ideal PFR (plug flow reactor) model is also considered. It is found that compositions from the 2D CPFD model provide close gas compositions with respect to the PFR. It is observed that the 2D CPFD model is valuable for predicting particle flows in the feeding near region keeping it unaffected by fast fluidized bed upsets such as suspension chocking. It is also found that the 2D CPFD model is particularly useful for describing fast fluidized beds operation involving significant amounts of rich ash recycled feeds.
This study is devoted to thermomechanical response and modeling of copper thin films and interconnects. The constitutive behavior of encapsulated copper film is first studied by fitting the ...experimentally measured stress-temperature curves during thermal cycling. Significant strain hardening is found to exist. Within the continuum plasticity framework, the measured stress-temperature response can only be described with a kinematic hardening model. The constitutive model is subsequently used for numerical thermomechanical modeling of Cu interconnect structures using the finite element method. The numerical analysis uses the generalized plane strain model for simulating long metal lines embedded within the dielectric above a silicon substrate. Various combinations of oxide and polymer-based low-k dielectric schemes, with and without thin barrier layers surrounding the Cu line, are considered. Attention is devoted to the thermal stress and strain fields and their dependency on material properties, geometry, and modeling details. Salient features are compared with those in traditional aluminum interconnects. Practical implications in the reliability issues for modern copper/low-k dielectric interconnect systems are discussed.
Objective. Oxygen-derived free radicals have been suggested as important in degeneration after spinal cord ischemia. The aim of this study was to investigate whether erdosteine has a protective ...effect against spinal cord ischemia during aortic cross clamping.
Materials and methods. New Zealand White rabbits (n=21) were divided into three groups. In the ischemia/reperfusion group (I/R) (n=8), the infrarenal aorta of rabbits was cross clamped for 21 min and then reperfused. In erdosteine group, the administration of erdosteine solution (50 mg/kg) was started two days before aortic cross-clamping and rabbits (n=8) were subjected to ischemia and reperfusion. Animals in control group (n=5) underwent a surgical procedure similar to the other groups but the aorta was not clamped. The animals were sacrificed at 72 h and histopathological, and biochemical analyses were carried out on the lumbar spinal cords.
Results. Erdosteine treatment was associated with improved neurological function in the postoperative period. Histopathological examination of spinal cord tissues in erdosteine group revealed changes consistent with mild ischemic injury, but rabbits in I/R group with paraplegia had total destruction of the motor neurons. Biochemical analyses of spinal cord tissues, in the I/R group, revealed a significant increase in the superoxide dismutase, xanthine oxidase, adenosine deaminase and myeloperoxidase activities, and a significant depletion in glutathione peroxidase activity when compared to that of control rabbits. Erdosteine treatment prevented the increase of all these enzymes except adenosine deaminase. Ischemia/reperfusion produced a significant increase in the tissue malondialdehyde levels. Ischemia/reperfusion-induced increments in malondialdehyde content of the spinal cord were significantly prevented by erdosteine treatment.
Conclusions. The present study demonstrated that erdosteine treatment before aortic cross clamping ameliorates neurological outcome, neuronal injury and oxidative stress in the rabbit spinal cord.
The effect of pre-operative atorvastatin on systemic inflammatory response syndrome (SIRS), often seen after coronary artery bypass grafting (CABG) was evaluated in 40 patients undergoing elective ...CABG. Patients were divided into two groups: group I (pre-operative LDL cholesterol ≤ 100 mg/dl; n = 20) received 20 mg/day atorvastatin for at least 15 days pre-operatively; group II (pre-operative LDL cholesterol < 100 mg/dl; n = 20) did not receive antihyperlipidaemic agents. All patients underwent CABG with cardiopulmonary bypass. Blood samples were taken pre-operatively and 24 h post-operatively. There were no significant differences between the two groups in terms of demographic, pre-operative or operative parameters. At 24 h post-operatively, median high-sensitivity C-reactive protein and mean interleukin-6 levels were significantly lower in group I compared with group II. There were no other significant differences in postoperative parameters between the two groups, except for duration of stay in the intensive care unit, which was shorter in group I patients. In conclusion, pre-operative atorvastatin treatment in patients undergoing elective CABG decreased inflammation parameters and could be effective in preventing SIRS.
The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have conducted a parametric experimental and modeling study, on the effect of ...testing and geometrical parameters on solder/copper joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain (measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response. The solder response moves progressively closer to "true" shear response with increasing joint thickness. Numerical modeling using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens. The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior of the solder. PUBLICATION ABSTRACT Key words: Lap-shear, Pb-free solder, finite element modeling (FEM)
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