Hydrodynamics and Heat Transfer Associated with Condensation on a Moving Drop: Solutions for Intermediate Reynolds Numbers

The hydrodynamics and heat/mass transport associated with condensation on a moving drop have been investigated for the intermediate Reynolds-number range of drop motion (Re = O(100)). The drop environment is a mixture of saturated vapour and a non-condensable. The formulation entails a simultaneous solution of the quasi-steady elliptic partial differential equations that describe the flow field and transport in the gaseous phase, and the motion inside the liquid drop. The heat transport inside the drop is treated as a transient process. Results are reported for the interfacial velocities, drag, external and internal flow structure, heat flux, drop growth rate and temperature-time history inside the drop. The results obtained here have been compared with experimental data where available, and these show excellent agreement. The results reveal several novel features. The surface-shear stress increases with condensation. The pressure level in the rear of the drop is higher. As a consequence, the friction drag is higher and the pressure drag is lower. The total drag coefficient increases with condensation rate for small values of drop size or temperature differential, and it decreases for large values of these parameters. The volume of the separated-flow region in the rear of the drop decreases with condensation. At very high rates of condensation, the recirculatory wake is completely suppressed. Condensation also delays the appearance of the weak secondary internal vortex motion in the drop. The heat and mass fluxes are significantly affected by the presence of the non-condensable in the gaseous phase and by the circulation inside the drop

Biomarkers in the diagnosis and study of psychogenic nonepileptic seizures: A systematic review

AbstractObjectiveVideo electroencephalography (vEEG) is the gold-standard method for diagnosing psychogenic nonepileptic seizures (PNES), but such assessment is expensive, unavailable in many centers, requires prolonged hospitalization, and many times is unable to capture an actual seizure episode. This paper systematically reviews other non-vEEG candidate biomarkers that may facilitate both diagnosis and study of PNES as differentiated from epileptic seizures (ES).MethodsPubMed database was searched to identify articles between 1980 and 2015 (inclusion: adult PNES population with or without controls, English language; exclusion: review articles, meta-analyses, single case reports).ResultsA total of 49 studies were examined, including neuroimaging, autonomic nervous system, prolactin, other (non-prolactin) hormonal, enzyme, and miscellaneous marker studies. Functional MRI studies have shown PNES is hyperlinked with dissociation and emotional dysregulation centers in the brain, although conflicting findings are seen across studies and none used psychiatric comparators. Heart rate variability suggests increased vagal tone in PNES when compared to ES. Prolactin is elevated in ES but not PNES, although shows low diagnostic sensitivity. Postictal cortisol and creatine kinase are nonspecific. Other miscellaneous biomarkers (neuron specific enolase, brain derived neurotropic factor, ghrelin, leptin, leukocytosis) showed no conclusive evidence of utility. Many studies are limited by lack of psychiatric comparators, size, and other methodological issues.ConclusionNo single biomarker successfully differentiates PNES from ES; in fact, PNES is only diagnosed via the negation of ES. Clinical assessment and rigorous investigation of psychosocial variables specific to PNES remain critical, and subtyping of PNES is warranted. Future investigational and clinical imperatives are discussed

Computation of Flow through an Annular Diffuser and Volute Exhaust

Turbulent flow in a diffuser with swirl occurs in many commonly used fluid mechanicaldevices,eg, diffusers located downstream of a gas turbine, and in certain types of combustionchambers. Diffusers are widely used for converting kinetic energy to pressure, and a reliableprediction method of such flows with the required flow conditions would lead to the design offluid machinery with improved efficiency. As a first step, turbulent swirling flow through a 12oincluded angle conical diffuser for a swirl parameter, m = 0.18 was numerically investigated usingvarious turbulence models like standard k- , RNG-based k- , shear-stress transport (SST) kandReynolds stress model (RSM). Though the comparison between the experimental and thepredicted mean velocity profile by RSM is superior to that by RNG kandSST models, the lattertwo models give closer comparison with the experimental pressure distribution. Subsequently,computation of flow inside a complex duct involving axisymmetric annular diffuser, transitionfrom rectangular to circular cross section, and exit pipe have been carried out using RNG kandSST k models.The comparison of computed and experimental results indicates that theSST k modelgives predictions with reasonable accuracy

Anomalous size dependent rheological behavior of alumina based nanofluids

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Rheological behaviour of Alumina (Al2O3) based nanofluids (NFs) has been studied and found to be exhibit unexpected behaviour. Two base-fluids viz, water and ethylene glycols (EG). Three particle sizes (11, 45 and 150 nm), varying over an order of magnitude, were used to analyze the effect of particle size. The experimental data has shown typical Newtonian behavior for both W based and EG based alumina NFs The viscosity of EG based NFs is found to be anomalously reduced compared to the base fluid. This reduction in viscosity may be due to hygroscopic nature of EG or due to the presence of water in as-received high concentration sample also, as told by some researchers. However, this phenomenon was absent for water based NFs. The inter-related effects of particle size, concentration and mode of dispersion (mono or poly-dispersed) were investigated. To eliminate the effect of size variation, mono dispersed NFs are obtained by centrifuging and re-suspension of parent NFs. Particle migration under shear is attributed to the reduction of viscosity. The increase in bulk viscosity with particle size reduction is attributed to the surface forces acting between the particles and the medium in a suspension

Energy efficient cache architectures for single, multi and many core processors

With each technology generation we get more transistors per chip. Whilst processor frequencies have increased over the past few decades, memory speeds have not kept pace. Therefore, more and more transistors are devoted to on-chip caches to reduce latency to data and help achieve high performance. On-chip caches consume a significant fraction of the processor energy budget but need to deliver high performance. Therefore cache resources should be optimized to meet the requirements of the running applications. Fixed configuration caches are designed to deliver low average memory access times across a wide range of potential applications. However, this can lead to excessive energy consumption for applications that do not require the full capacity or associativity of the cache at all times. Furthermore, in systems where the clock period is constrained by the access times of level-1 caches, the clock frequency for all applications is effectively limited by the cache requirements of the most demanding phase within the most demanding application. This motivates the need for dynamic adaptation of cache configurations in order to optimize performance while minimizing energy consumption, on a per-application basis. First, this thesis proposes an energy-efficient cache architecture for a single core system, along with a run-time support framework for dynamic adaptation of cache size and associativity through the use of machine learning. The machine learning model, which is trained offline, profiles the application’s cache usage and then reconfigures the cache according to the program’s requirement. The proposed cache architecture has, on average, 18% better energy-delay product than the prior state-of-the-art cache architectures proposed in the literature. Next, this thesis proposes cooperative partitioning, an energy-efficient cache partitioning scheme for multi-core systems that share the Last Level Cache (LLC), with a core to LLC cache way ratio of 1:4. The proposed cache partitioning scheme uses small auxiliary tags to capture each core’s cache requirements, and partitions the LLC according to the individual cores cache requirement. The proposed partitioning uses a way-aligned scheme that helps in the reduction of both dynamic and static energy. This scheme, on an average offers 70% and 30% reduction in dynamic and static energy respectively, while maintaining high performance on par with state-of-the-art cache partitioning schemes. Finally, when Last Level Cache (LLC) ways are equal to or less than the number of cores present in many-core systems, cooperative partitioning cannot be used for partitioning the LLC. This thesis proposes a region aware cache partitioning scheme as an energy-efficient approach for many core systems that share the LLC, with a core to LLC way ratio of 1:2 and 1:1. The proposed partitioning, on an average offers 68% and 33% reduction in dynamic and static energy respectively, while again maintaining high performance on par with state-of-the-art LLC cache management techniques

Bronchial carcinoid in children

Bronchial carcinoids (BCs) are uncommon, slow growing, low-grade malignant neoplasm comprising 0.5-2.5% of all primary lung cancers. Although BC’s in childhood often have an endobronchial location causing airway obstruction, they are frequently misdiagnosed as benign conditions, resulting in a delay in definitive diagnosis and treatment. Lung sparing surgery should be done whenever possible, more so in children, for better quality of life and minimizing skeletal abnormality which follows pneumonectomy. We present two cases of bronchial carcinoid in young children