Grid generation methodology and CFD simulations in sliding vane compressors and expanders

The limiting factor for the employment of advanced 3D CFD tools in the analysis and design of rotary vane machines is the unavailability of methods for generation of computational grids suitable for fast and reliable numerical analysis. The paper addresses this challenge presenting the development of an analytical grid generation for vane machines that is based on the user defined nodal displacement. In particular, mesh boundaries are defined as parametric curves generated using trigonometrical modelling of the axial cross section of the machine while the distribution of computational nodes is performed using algebraic algorithms with transfinite interpolation, post orthogonalisation and smoothing. Algebraic control functions are introduced for distribution of nodes on the rotor and casing boundaries in order to achieve good grid quality in terms of cell size and expansion. In this way, the moving and deforming fluid domain of the sliding vane machine is discretized and the conservation of intrinsic quantities in ensured by maintaining the cell connectivity and structure. For validation of generated grids, a mid-size air compressor and a small-scale expander for Organic Rankine Cycle applications have been investigated in this paper. Remarks on implementation of the mesh motion algorithm, stability and robustness experienced with the ANSYS CFX solver as well as the obtained flow results are presente

Age is not just a number: Naive T cells increase their ability to persist in the circulation over time

The processes regulating peripheral naive T-cell numbers and clonal diversity remain poorly understood. Conceptually, homeostatic mechanisms must fall into the broad categories of neutral (simple random birth-death models), competition (regulation of cell numbers through quorum-sensing, perhaps via limiting shared resources), adaptation (involving cell-intrinsic changes in homeostatic fitness, defined as net growth rate over time), or selection (involving the loss or outgrowth of cell populations deriving from intercellular variation in fitness). There may also be stably maintained heterogeneity within the naive T-cell pool. To distinguish between these mechanisms, we confront very general models of these processes with an array of experimental data, both new and published. While reduced competition for homeostatic stimuli may impact cell survival or proliferation in neonates or under moderate to severe lymphopenia, we show that the only mechanism capable of explaining multiple, independent experimental studies of naive CD4+ and CD8+ T-cell homeostasis in mice from young adulthood into old age is one of adaptation, in which cells act independently and accrue a survival or proliferative advantage continuously with their post-thymic age. However, aged naive T cells may also be functionally impaired, and so the accumulation of older cells via 'conditioning through experience' may contribute to reduced immune responsiveness in the elderly

Kozmološki model sa strunama i stranom kvarkovskom tvari u Kantowski-Sachsovom prostoru-vremenu

We study the string cloud cosmological model in the context of Kantowski-Sachs space-time. For this purpose, the Einstein\u27s field equations are solved for Kantowski-Sachs space-time with strange quark matter coupled to the string cloud by using the relation between metric potentials. The physical and kinematical parameters of the models are studied.Proučavamo kozmološki model s oblakom struna u Kantowski-Sachsovom prostoruvremenu. S tim su ciljem riješene Einsteinove jednadžbe polja za Kantowski-Sachsov prostor-vrijeme, sa stranom kvarkovskom tvari vezanom s oblakom struna, primjenom relacija među metričkim potencijalima. Razmatraju se fizički i kinematički parametri modela

Electrical & Catalytic Properties of Lithium Doped Molybdenum Trioxide

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The Structure of Diosbulbine

A novel norditerpene lactone, diosbulbine, has been isolated from the tubers of Dioscorea bulbifera Linn. The structure (III) for the diterpene lactone has been assigned on the basis of spectroscopic and degradative evidence

Role of cetrorelix in the prevention and treatment of ovarian hyperstimulation syndrome: a prospective case control study

Background: Ovarian hyperstimulation syndrome (OHSS) has intrigued clinicians for many years because of its devastating consequences. As an iatrogenic condition resulting from elective ovarian stimulation in the quest for pregnancy, the need to completely prevent the syndrome is evident. Gonadotropin releasing hormone (GnRH) antagonist Cetrorelix has found to be effective in treatment of OHSS and some studies have found it to be helpful in prevention of this condition. Hence, we designed a hospital-based study to investigate the effect of Cetrorelix in preventing and treating OHSS in in-vitro fertilization – embryo transfer (IVF–ET) patients at risk of OHSS undergoing long and short protocol. Methods: The study includes total 102 patients undergoing controlled ovarian stimulation COS for IVF/ICSI. All cases were stimulated using long and short protocol. Depending on whether a GnRH antagonist was given after ovum pick-up (OPU) the patients were divided in two groups: Cetrorelix (antagonist) group (n=51) and control group (n=51). The study group was treated with Cetrorelix 0.25 mg for 5 days commencing on the day of ovum pick up. Results: Incidence of mild OHSS was significantly higher (p=0.01) whereas moderate to severe OHSS was significantly lower in the antagonist group (p<0.05). None of the patients had critical OHSS. Conclusions: GnRH antagonist Cetrorelix administration in early luteal phase in patients undergoing long or short protocol is effective in prevention and treatment of OHSS

Ease of use and accuracy of a perinatal measuring device (Episiometer) to ensure correct angle and length of a mediolateral episiotomy: a mixed methods study

Introduction: To guide clinicians in performing mediolateral episiotomies (MLEs) at 60‐degrees, a new clinical innovation called the 'Episiometer' was developed. The aim of this study was to assess the usability and accuracy of the Episiometer in guiding clinicians to perform a safe episiotomy in both low‐ and high‐resource settings. Design: A prospective, multi‐site Phase‐I clinical trial was conducted between January 2017 and July 2018, involving three international study sites: Australia; Papua New Guinea; and India. The study design was mixed‐methods, incorporating an explanatory sequential design using surveys, clinician interviews and patient chart review to determine the usability and accuracy of the Episiometer. The patient chart review and results of this are discussed in an accompanying article. Methods: The Episiometer is the clinical innovation designed to attain an episiotomy cutting angle of 60‐degrees. The instrument is designed to assist clinicians to make an accurate and consistent episiotomy cutting angle within a 'safe' green zone between 45–60 degrees and length of at least 4 cm. The instrument also improves the visibility of the 60‐degree line to clinicians, and provides an exact measurement for length (located on the 60‐degree angle line). Clinicians from all three sites were recruited to provide feedback and measurements of incisions performed using the Episiometer (n = 135) following attendance at a minimum of at least one training session with site coordinators. Twenty of these clinicians were then recruited randomly from the sample who responded in the surveys and interviewed face‐to‐face. Patients were followed up 6‐weeks postpartum to monitor potential complications (n = 120). Results: Overall, the Episiometer was well received by clinicians – particularly by more junior staff members who were significantly more likely to report the Episiometer as being beneficial in guiding a safe MLE compared to their more senior counterparts (P = 0.003 and P = 0.011, respectively). In addition, 89% of incisions (107/120) were within the 'safe zone' between 45‐60 degrees, and 40% (48/120) were made at exactly 60‐degrees. No patient had any degree of perineal tear at follow up. Conclusion: The Episiometer is a well‐received clinical innovation in both high‐resource and lower resource settings. When used as directed, the Episiometer produces an accurate and safe incision, and reduces variation in clinicians' performance of episiotomy

COMPARISON OF DESIGN AND ANALYSIS OF TUBE SHEET THICKNESS BY USING UHX CODE OF ASME AND TEMA STANDARD

ABSTRACT In order to investigate the optimized tube sheet thickness different methodologies are used. For the mechanical design of existing fixed tube sheet heat exchanger of a waste heat Boiler various code solutions are compared with each other. Solutions of Finite Element Analysis are used to optimize the design parameters. The purpose of this paper is to compare and analyse tube sheet design code UHX of ASME section VIII Div. 1 with TEMA standards. From the design methodology it is found that both standards are based on different theory of design. It is also found that FE analysis results are closed to exact solution and these results can be accepted with a reasonable degree of accuracy. Thus FEA can be used as an optimization tool for tube sheet thickness