1,458 research outputs found
Computation of turbulent high speed mixing layers using a two-equation turbulence model
A two-equation turbulence model was extended to be applicable for compressible flows. A compressibility correction based on modelling the dilational terms in the Reynolds stress equations were included in the model. The model is used in conjunction with the SPARK code for the computation of high speed mixing layers. The observed trend of decreasing growth rate with increasing convective Mach number in compressible mixing layers is well predicted by the model. The predictions agree well with the experimental data and the results from a compressible Reynolds stress model. The present model appears to be well suited for the study of compressible free shear flows. Preliminary results obtained for the reacting mixing layers are included
The direct simulation of high-speed mixing-layers without and with chemical heat release
A direct numerical simulation of high speed reacting and non-reacting flows for H2-air systems is presented. The calculations are made for a convective Mach number of 0.38 with hyperbolic tangent initial profile and finite rate chemical reactions. A higher-order numerical method is used in time accurate mode to time advance the solution to a statistical steady state. About 600 time slices of all the variables are then stored for statistical analysis. It is shown that most of the problems of high-speed combustion with air are characterized by relatively weak heat release. The present study shows that: (1) the convective speed is reduced by heat release by about 10 percent at this convective Mach number M(sub c) = 0.38; (2) the variation of the mean and rms fluctuation of temperature can be explained on the basis of temperature fluctuation between the flame temperature and the ambient; (3) the growth rate with heat release is reduced by 7 percent; and (4) the entrainment is reduced by 25 percent with heat release. These differences are small in comparison with incompressible flow dynamics, and are argued to be due to the reduced importance of heat release in comparison with the large enthalpy gradients resulting from the large-scale vortex dynamics. It is finally suggested that the problems of reduced mixing in high-speed flows are not severely complicated by heat release
CONSERVATIVE MANAGEMENT OF HYDROCELE- CASE REPORT
In this case report, we present an event of a 65-year-old gentleman with a diagnosed solitary oval swelling of the size 6×4 cm present in the right side of the scrotum by ultrasonographic images. Hydrocele under tension may be at high risk of acute rupture of testis of reducing the spermatogenesis, and surgical correction may be the best therapeutic opinion in this case. We expectantly managed the patient's massive hydrocele and encountered by hydro celotomy and no complications throughout the course of his recovery.Keywords: Hydrocele, Ultrasonographic Image, Hydrocelectom
Settlement Analysis of Circular Footings on Layered Soil Systems
Many studies are available on the settlement analysis of footings on a homogeneous soil deposit underlain by a rigid base. However, the soil profile is seldom homogenous and typically a layered soil system is encountered in practice. The present study deals with the settlement profiles of soil underneath a circular footing of radius equal to a, and resting on a finite two-layered soil system with thicknesses equal to H1 and H2. The deformation moduli and Poisson’s ratios of the two layers are E1, υ1, and E2, υ2. The settlement profiles are proposed for varying H1/a and H2/a ratios (H1/a= 0.2, 0.5, 1, 2, 4 and 6, and H2/a= 1, 2, 4 and 6). The moduli ratio E1/E2is varied as 0.01, 0.05, 0.1, 0.5, 1, 2, 5 and 20. The extent of settlement due to load is also proposed from the surface settlement profile which can help in determining the influence of a footing on the neighboring footing or structure. The analysis is carried out using PLAXIS 2D vAE. In addition, the settlement influence factors are proposed for the above mentioned ratios to estimate the maximum settlement of the
footing on a layered system. The results are also compared with the settlement measured in a building on a layered system in Adelaide, Southern Australia, and the results are
found to be comparable
Magnetic heat conductivity in : linear temperature dependence
We present experimental results for the thermal conductivity of the
pseudo 2-leg ladder material . The strong buckling of the ladder
rungs renders this material a good approximation to a Heisenberg-chain.
Despite a strong suppression of the thermal conductivity of this material in
all crystal directions due to inherent disorder, we find a dominant magnetic
contribution along the chain direction.
is \textit{linear} in temperature, resembling the
low-temperature limit of the thermal Drude weight of the
Heisenberg chain. The comparison of and
yields a magnetic mean free path of \AA, in good agreement with magnetic measurements.Comment: appears in PR
Aggregation and biofilm formation of bacteria isolated from domestic drinking water
The objective of this study was to investigate the autoaggregation, coaggregation and biofilm
formation of four bacteria namely Sphingobium, Xenophilus, Methylobacterium and Rhodococcus
isolated from drinking water. Auto and coaggregation studies were performed by both qualitative
(DAPI staining) and semi-quantitative (visual coaggregation) methods and biofilms produced by either
pure or dual-cultures were quantified by crystal violet method. Results from the semi-quantitative
visual aggregation method did not show any immediate auto or coaggregation, which was confirmed
by the 40
,6 diamidino-2-phenylindole (DAPI) staining method. However, after 2 hours,
Methylobacterium showed the highest autoaggregation of all four isolates. The Methylobacterium
combinations showed highest coaggregation between dual species at extended period of times (72
hours). Biofilm formation by pure cultures was negligible in comparison to the quantity of biofilm
produced by dual-species biofilms. The overall results show that coaggregation of bacteria isolated
from drinking water was mediated by species-specific and time-dependent interactions with a
synergistic type of biofilm formation. The results of this study are therefore a useful step in assisting
the development of potential control strategies by identifying specific bacteria that promote
aggregation or biofilm formation in drinking water distribution systems
Flow sorting of marine bacterioplankton after fluorescence in situ hybridization
We describe an approach to sort cells from coastal North Sea bacterioplankton by flow cytometry after in situ hybridization with rRNA-targeted horseradish peroxidase-labeled oligonucleotide probes and catalyzed fluorescent reporter deposition (CARD-FISH). In a sample from spring 2003 >90% of the cells were detected by CARD-FISH with a bacterial probe (EUB338). Approximately 30% of the microbial assemblage was affiliated with the Cytophaga-Flavobacterium lineage of the Bacteroidetes (CFB group) (probe CF319a), and almost 10% was targeted by a probe for the beta-proteobacteria (probe BET42a). A protocol was optimized to detach cells hybridized with EUB338, BET42a, and CF319a from membrane filters (recovery rate, 70%) and to sort the cells by flow cytometry. The purity of sorted cells was >95%. 16S rRNA gene clone libraries were constructed from hybridized and sorted cells (S-EUB, S-BET, and S-CF libraries) and from unhybridized and unsorted cells (UNHYB library). Sequences related to the CFB group were significantly more frequent in the S-CF library (66%) than in the UNHYB library (13%). No enrichment of beta-proteobacterial sequence types was found in the S-BET library, but novel sequences related to Nitrosospira were found exclusively in this library. These bacteria, together with members of marine clade OM43, represented >90% of the beta-proteobacteria in the water sample, as determined by CARD-FISH with specific probes. This illustrates that a combination of CARD-FISH and flow sorting might be a powerful approach to study the diversity and potentially the activity and the genomes of different bacterial populations in aquatic habitats
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