An approximate method for solving rarefied and transitional flows using TDEFM with isotropic mesh adaptation

DSMC [1] can become increasingly expensive when extended to the near-continuum regime. Because of the statistical nature of the results, long run times are required to build up samples of simulator particles large enough to reduce the statistical scatter to acceptable levels. Here we adapt a kinetic theory based flux method to produce a quick approximate solver for transition and near-continuum flows. The results have no statistical scatter. The CPU times are similar to those of traditional continuum (Navier-Stokes or Euler) solvers. The True Direction Equilibrium Flux Method (TDEFM) [2, 3] is a generalisation of Pullin's kinetic theory based EFM [4]. TDEFM can transfer fluxes of mass, momentum and energy in physically realistic directions from any source cell to any destination cell, even if the cells do not share an interface. TDEFM, as an Euler solver, has been shown to provide good results on a Cartesian grid for flows where standard continuum methods produce unphysical asymmetries apparently because the continuum fluxes are constrained (in one time step) to flow in the grid coordinate directions rather than the correct physical direction. [2, 3] The new method for rarefied flow does not try to produce the correct velocity distribution function, but does ensure that mass, momentum and energy are transported within the flow over the physically correct distances between “pseudo-collisions.” To ensure this, (1) the time step is restricted so that mass, momentum and energy are exchanged between contiguous cells only in one time step, and (2) the cells sizes are adapted, as steady state is approached, to be approximately equal to the local mean free path. The results for Mach 5 flow over a flat plate for varying Knudsen numbers show an average difference (compared to DSMC) in the X-velocity profile near the surface of the plate of less than 6 percent. TDEFM, employing adaptive mesh refinement, required less than 9 percent of the computational time required by DSMC for the same flow. Thus the approximate method could be useful for quick “first-estimate” solutions of otherwise time consuming design problems. ©2009 American Institute of Physic

Влияние неоднородностей температуры поверхности на теплообмен воздуха с Землей

В работе проведено моделирование процесса натекания воздуха с холодной поверхности воды на теплую поверхность суши и сравнение расчетов с результатами измерений. Из расчетов следует, что потоки тепла в прибрежной зоне могут более чем на 20% превышать значения потоков тепла, вычисленных из предположения о горизонтальной однородности приземного слоя. Таким образом, горизонтальную неоднородность атмосферы следует учитывать при расчетах охлаждения водоемов, горизонтальный размер которых имеет масштаб ~100 м.В роботі проведено моделювання процесу натікання повітря з холодної поверхні води на теплу поверхню суші та порівняння розрахунків із вимірюваннями. З розрахунків видно, що потоки тепла в прибережній зоні можуть більш ніж на 20% перевищувати значення потоків тепла, обчислених з припущення про горизонтальну однорідність приземного шару. Таким чином, горизонтальну неоднорідність атмосфери слід враховувати при розрахунках охолодження водойм, горизонтальний розмір яких має масштаб ~100 м.In the paper, the air flow process from the cold water surface onto the warm land surface was simulated. The comparisons of calculations with measurements were performed as well. The calculations show that the heat flux in the narrow coastal zone may be more than 20% higher than the values of heat fluxes calculated from the assumption of horizontal homogeneity of the surface layer. Thus, the horizontal inhomogeneity of the atmosphere must be taken into account in the calculation of the cooling water, the horizontal size of which has a scale of ~100 m

Mycobacterium tuberculosis Transmission between Cluster Members with Similar Fingerprint Patterns

Molecular epidemiologic studies provide evidence of transmission of Mycobacterium tuberculosis within clusters of patients whose isolates share identical IS6110-DNA fingerprint patterns. However, M. tuberculosis transmission among patients whose isolates have similar but not identical DNA fingerprint patterns (i.e., differing by a single band) has not been well documented. We used DNA fingerprinting, combined with conventional epidemiology, to show unsuspected patterns of tuberculosis transmission associated with three public bars in the same city. Among clustered TB cases, DNA fingerprinting analysis of isolates with similar and identical fingerprints helped us discover epidemiologic links missed during routine tuberculosis contact investigations

Modelling Unsteady Processes with the Direct Simulation Monte Carlo Technique

Over the past 40 years, the Direct Simulation Monte Carlo (DSMC) technique has been developed into a flexible and effective solver for flow problems in the rarefied to near continuum regime. However, even with modern parallelised code, the efficient computation of unsteady near-continuum flows, which are important in processes such as Pulsed Pressure Chemical Vapour Deposition (PP-CVD), remains a challenge. We have developed an unsteady parallel DSMC code (PDSC) utilising advanced features such as transient adaptive sub-cells to ensure nearest neighbour collisions and a temporal-variable time step to reduce computation time. This technique is combined with a unique post-processor called the DMSC Rapid Ensemble Averaging Method (DREAM) which reduces the statistical scatter in the data sets produced by PDSC. The combined method results in a significant memory and computational reduction over ensemble averaging DSMC, while maintaining low statistical scatter in the results. The unsteady code has been validated by simulation of shock-tube flow and unsteady Couette flow, and a number of test cases have been demonstrated including shock impingement on wedges. The technique is currently being used to model the development of an underexpanded jet in a PP-CVD reactor

MALDI TOF MS and currently related proteomic technologies in reconciling bacterial systematics

The chapter is on development and application of matrix assisted laser desorption ionisation time of flight mass spectrometry (MALDI-TOF) to identification and and classification of bacteria

Application of Luminex Gastrointestinal Pathogen Panel to human stool samples from Côte d'Ivoire

Gastrointestinal infections caused by viruses, bacteria, and parasites are endemic in most developing countries due to inadequate provision of safe water supplies, sanitation, and hygiene. To investigate the enteric pathogens infecting people living in Côte d'Ivoire, the Luminex Gastrointestinal Pathogen Panel (xTAG GPP) assay was used to analyze 34 human fecal samples. This study represents the first application of this technology to samples from a sub-Saharan African country

Judging the impact of leadership-development activities on school practice

The nature and effectiveness of professional-development activities should be judged in a way that takes account of both the achievement of intended outcomes and the unintended consequences that may result. Our research project set out to create a robust approach that school staff members could use to assess the impact of professional-development programs on leadership and management practice without being constrained in this judgment by the stated aims of the program. In the process, we identified a number of factors and requirements relevant to a wider audience than that concerned with the development of leadership and management in England. Such an assessment has to rest upon a clear understanding of educational leadership,a clearly articulated model of practice, and a clear model of potential forms of impact. Such foundations, suitably adapted to the subject being addressed, are appropriate for assessing all teacher professional development