On the prediction of turbulent secondary flows

The prediction of turbulent secondary flows, with Reynolds stress models, in circular pipes and non-circular ducts is reviewed. Turbulence-driven secondary flows in straight non-circular ducts are considered along with turbulent secondary flows in pipes and ducts that arise from curvature or a system rotation. The physical mechanisms that generate these different kinds of secondary flows are outlined and the level of turbulence closure required to properly compute each type is discussed in detail. Illustrative computations of a variety of different secondary flows obtained from two-equation turbulence models and second-order closures are provided to amplify these points

Scenarios of Building Information Modelling-Based Design Education in Architecture Schools

Due to the rapid development of computer technologies and trends in digital design, including building information modeling (BIM) and its diffusion into architectural design practice, it was necessary to introduce BIM into architectural curricula in order to prepare students for practice. This article therefore aims to identify scenarios for teaching BIM to architecture students worldwide. To achieve this objective, a thematic analysis of BIM teaching experiences in several selected academic institutions was conducted. The data studied included published articles and official university websites dealing with BIM teaching. A theoretical framework for BIM education was determined, comprising two aspects: pedagogical methods for BIM education and specifications for BIM courses in architecture programs. The document identified several scenarios for teaching BIM in multidisciplinary or architecture-specific courses. BIM teaching can be offered as part of a single course integrated with other courses, or as a separate course. It may be taught as part of related or unrelated courses. Related courses can be organized in parallel with an academic semester, or over several semesters. In addition, there are different types of input to project-based BIM teaching, such as a new design project, the results of a previous design course or an actual project. These scenarios can serve as a reference for universities wishing to integrate BIM into their programs

Effects of EGTA and cytochalasin-B during freezing and vitrification of immature and mature bovine and rhesus monkey (M. mulatta) oocytes.

Cryopreservation procedures have been shown to be extremely disruptive to the plasma membrane and intracellular organization of mammalian oocyte. Cytochalasin-B (Cyt-B) or EGT A may stabilize oocyte cytoskeletal elements prior to Cryopreservation and make the plasma membrane less rigid and more elastic to avoid injury during the osmotic stresses of freezing. Experiments were conducted to assess the morphological viability and developmental potential of bovine and rhesus monkey oocytes roter exposure to Cyt-B or EGTA prior to freezing and vitrification. ln the bovine experiments: The methods of oocyte isolation, in vitro maturation (IVM), in vitro fertilization (IVF) , and embryonic development (IVC) were as described elsewhere (Biol Reprod. 55:333-339, 1996). AIl data were analyzed by ANOV A and Chi-square using "StatMost" for Windows. ln an initial experiment, a group of ilnmature (GV) oocytes and oocytes roter IVM (ova) were randomly selected and pretreated for 5 min with EGTA (O.IM) or Cyt-B (Img/ml) without cryoprotectant (CPA), and another group were equilibrated for 15 min with the CPA (1.5 M ethylene glycol mixed with 0.5 M glycerol in PHS) roter pretreatment with EGTA or Cyt-B. AIl oocytes were diluted and/or washed and immediately used for IVM and/or IVF and IVC. No significant differences in cleavage (C) development and blastocyst (B) hatching among treatments in the GV oocytes group. Percentages of early C, morula (M), B, and expanded B (EB) development ranged 72-82%, 53-65%, 40-47% and 25-35% respectively. Ova treated with EGTA without CPA produced significantly (P<.05) higher C (31/41,75%), M (48.8%), B (40%) and EB (24.4%) than with Cyt-B. ln the slow freezing experiment, a total of 105 GV oocytes and 155 ova were exposed to (a) zero (b EGTA, or ~) Cyt-B before equilibration with CPA + 0.5 sucrose in PHS plus 15% Fetal bovine serum (PBS/FBS). Gametes were loaded into sterile cryovials, cooled at 2°Chnin to -7°C, seeded, cooled at 0.3°Chnin to -32°C, then plunged in LN2. They were thawed.in air (10 sec), then wann water (35°C), and diluted out of CPA in 3 steps (1, 0.5, 0.2 M sucrose). Three replicated showed that although many of the frozen-thawed oocytes/ova survived as judged by morphology (range 70-80%), their developmental potential was severely retarded. C ranged between 0% to 14.3%. ln the vitrification experiment, a total of 135 GV oocytes and 90 ova were grouped as above and vitrified in straws containing a mixture of 3.25M glycerol and 4.5M ethylene glycol plus 0.5 sucrose in PBS/FBS. Here, higher (P<.05) morphological survival rates (98%) foIlowed pretreatment with EGT A. However, the developmental potential was very low among aIl groups ranging between 0% to 17.7%. ln the monkey experiments: The methods of oocyte isolation, IVM and IVF was as described ( Theriogenology 43:362, 1995). A total of 72 GV oocytes and 42 ova were subjected to slow rate freezing and vitrification in groups as described for cow oocytes above. Pretreatment of both GV oocytes or ova with EGTA or Cyt-B prior to freezing or vitrification resulted in 77.6% morphological survival which was significantly (P<.OI) higher than for the control (50%). No differen?s in fertilization and development were detected mnong treatment. Per?ntages of C to 4-?Il stage ranged from 50-67%. Results suggest prefreeze treatment with EGTA and/or Cyt-B may be useful in enhancement of oocyte/ovum cryopreservation.Proceedings Annual Conference of the International Embryo Transfer Society, Nice Acropolis, Nice, France, Jan., 1997

On the prediction of free turbulent jets with swirl using a quadratic pressure-strain model

Data from free turbulent jets both with and without swirl are used to assess the performance of the pressure-strain model of Speziale, Sarkar and Gatski which is quadratic in the Reynolds stresses. Comparative predictions are also obtained with the two versions of the Launder, Reece and Rodi model which are linear in the same terms. All models are used as part of a complete second-order closure based on the solution of differential transport equations for each non-zero component of the Reynolds stress tensor together with an equation for the scalar energy dissipation rate. For non-swirling jets, the quadratic model underestimates the measured spreading rate of the plane jet but yields a better prediction for the axisymmetric case without resolving the plane jet/round jet anomaly. For the swirling axisymmetric jet, the same model accurately reproduces the effects of swirl on both the mean flow and the turbulence structure in sharp contrast with the linear models which yield results that are in serious error. The reasons for these differences are discussed

Stellar Image Interpretation System using Artificial Neural Networks: Unipolar Function Case

An artificial neural network based system for interpreting astronomical images has been developed. The system is based on feed-forward Artificial Neural Networks (ANNs) with error back-propagation learning. Knowledge about images of stars, cosmic ray events and noise found in images is used to prepare two sets of input patterns to train and test our approach. The system has been developed and implemented to scan astronomical digital images in order to segregate stellar images from other entities. It has been coded in C language for users of personal computers. An astronomical image of a star cluster from other objects is undertaken as a test case. The obtained results are found to be in very good agreement with those derived from the DAOPHOTII package, which is widely used in the astronomical community. It is proved that our system is simpler, much faster and more reliable. Moreover, no prior knowledge, or initial data from the frame to be analysed is required

Trapping cold atoms using surface-grown carbon nanotubes

We present a feasibility study for loading cold atomic clouds into magnetic traps created by single-wall carbon nanotubes grown directly onto dielectric surfaces. We show that atoms may be captured for experimentally sustainable nanotube currents, generating trapped clouds whose densities and lifetimes are sufficient to enable detection by simple imaging methods. This opens the way for a novel type of conductor to be used in atomchips, enabling atom trapping at sub-micron distances, with implications for both fundamental studies and for technological applications

Numerical Treatment of Allen’s Equation Using Semi Implicit Finite Difference Methods

This paper aims to propose the semi implicit finite difference method for discretizing Cahn-Allen equation. The stability and convergence analysis are proved. It is shown that the suggest scheme is stable for the usage of the Fourier-Von Neumann technique. The accuracy of the proposed method is first order in time and second order in space. A comparison between the numerical and the exact solutions is supported with two examples. Numerical results are shown that there is a good agreement between the approximate solution and exact solution

A mathematical model describing the localization and spread of influenza A virus infection within the human respiratory tract

Within the human respiratory tract (HRT), viruses diffuse through the periciliary fluid (PCF) bathing the epithelium, and travel upwards via advection towards the nose and mouth, as the mucus escalator entrains the PCF. While many mathematical models (MMs) to date have described the course of influenza A virus (IAV) infections in vivo, none have considered the impact of both diffusion and advection on the kinetics and localization of the infection. The MM herein represents the HRT as a one-dimensional track extending from the nose down to a depth of 30 cm, wherein stationary cells interact with the concentration of IAV which move along within the PCF. When IAV advection and diffusion are both considered, the former is found to dominate infection kinetics, and a 10-fold increase in the virus production rate is required to counter its effects. The MM predicts that advection prevents infection from disseminating below the depth at which virus first deposits. Because virus is entrained upwards, the upper HRT sees the most virus, whereas the lower HRT sees far less. As such, infection peaks and resolves faster in the upper than in the lower HRT, making it appear as though infection progresses from the upper towards the lower HRT. When the spatial MM is expanded to include cellular regeneration and an immune response, it can capture the time course of infection with a seasonal and an avian IAV strain by shifting parameters in a manner consistent with what is expected to differ between these two types of infection. The impact of antiviral therapy with neuraminidase inhibitors was also investigated. This new MM offers a convenient and unique platform from which to study the localization and spread of respiratory viral infections within the HRT.Comment: 27 pages, 11 figures, 2 supplementary video