2,072 research outputs found

    Determination of wind tunnel constraint effects by a unified pressure signature method. Part 1: Applications to winged configurations

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    A new, fast, non-iterative version of the "Wall Pressure Signature Method" is described and used to determine blockage and angle-of-attack wind tunnel corrections for highly-powered jet-flap models. The correction method is complemented by the application of tangential blowing at the tunnel floor to suppress flow breakdown there, using feedback from measured floor pressures. This tangential blowing technique was substantiated by subsequent flow investigations using an LV. The basic tests on an unswept, knee-blown, jet flapped wing were supplemented to include the effects of slat-removal, sweep and the addition of unflapped tips. C sub mu values were varied from 0 to 10 free-air C sub l's in excess of 18 were measured in some cases. Application of the new methods yielded corrected data which agreed with corresponding large tunnel "free air" resuls to within the limits of experimental accuracy in almost all cases. A program listing is provided, with sample cases

    Determinants of World Demand for U.S. Corn Seeds: The Role of Trade Costs

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    The United States is a large net exporter of corn seeds. Seed trade, including that of corn, has been expanding, but its determinants are not well understood. This paper econometrically investigates the determinants of world demand for U.S. corn seeds with a detailed analysis of trade costs impeding export flows to various markets, including costs associated with distance, tariffs, and sanitary and phytosanitary (SPS) regulations. The analysis relies on a gravity-like model based on an explicit specification of derived demand for seed by foreign corn producers, estimated based on data from 48 countries and for the years 1989 to 2004. An SPS count variable is incorporated as a shifter in the unit cost of seeds faced by foreign users. A sample selection framework is used to account for the determination of which trade flows are positive. All trade costs matter and have had a negative impact on U.S. corn seed exports. Tariffs matter most, followed by distance and SPS measures. ďż˝

    Determination of wind tunnel constraint effects by a unified pressure signature method. Part 2: Application to jet-in-crossflow

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    The development of an improved jet-in-crossflow model for estimating wind tunnel blockage and angle-of-attack interference is described. Experiments showed that the simpler existing models fall seriously short of representing far-field flows properly. A new, vortex-source-doublet (VSD) model was therefore developed which employs curved trajectories and experimentally-based singularity strengths. The new model is consistent with existing and new experimental data and it predicts tunnel wall (i.e. far-field) pressures properly. It is implemented as a preprocessor to the wall-pressure-signature-based tunnel interference predictor. The supporting experiments and theoretical studies revealed some new results. Comparative flow field measurements with 1-inch "free-air" and 3-inch impinging jets showed that vortex penetration into the flow, in diameters, was almost unaltered until 'hard' impingement occurred. In modeling impinging cases, a 'plume redirection' term was introduced which is apparently absent in previous models. The effects of this term were found to be very significant

    Privacy and Truthful Equilibrium Selection for Aggregative Games

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    We study a very general class of games --- multi-dimensional aggregative games --- which in particular generalize both anonymous games and weighted congestion games. For any such game that is also large, we solve the equilibrium selection problem in a strong sense. In particular, we give an efficient weak mediator: a mechanism which has only the power to listen to reported types and provide non-binding suggested actions, such that (a) it is an asymptotic Nash equilibrium for every player to truthfully report their type to the mediator, and then follow its suggested action; and (b) that when players do so, they end up coordinating on a particular asymptotic pure strategy Nash equilibrium of the induced complete information game. In fact, truthful reporting is an ex-post Nash equilibrium of the mediated game, so our solution applies even in settings of incomplete information, and even when player types are arbitrary or worst-case (i.e. not drawn from a common prior). We achieve this by giving an efficient differentially private algorithm for computing a Nash equilibrium in such games. The rates of convergence to equilibrium in all of our results are inverse polynomial in the number of players nn. We also apply our main results to a multi-dimensional market game. Our results can be viewed as giving, for a rich class of games, a more robust version of the Revelation Principle, in that we work with weaker informational assumptions (no common prior), yet provide a stronger solution concept (ex-post Nash versus Bayes Nash equilibrium). In comparison to previous work, our main conceptual contribution is showing that weak mediators are a game theoretic object that exist in a wide variety of games -- previously, they were only known to exist in traffic routing games

    Synthesis of size-controlled Bi particles by electrochemical deposition

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    Small sized bismuth particles are prepared by an electrochemical method using a triple voltage pulse technique. The bath composition and electrochemical parameters are optimized to yield monodisperse particles. The particles have been characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, UV-visible spectroscopy and X-ray diffraction technique. The particles, as deposited, are highly crystalline in nature and the particle size and shape get tuned depending on the conditions of deposition

    Prevalence of abnormal glucose tolerance in Indian women with polycystic ovarian syndrome

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    Background: Polycystic ovarian syndrome is a common endocrine condition affecting reproductive age women, associated with impaired glucose intolerance (IGT) and type 2 diabetes mellitus (DM). The aim of this study was to analyze the prevalence of IGT and type 2 DM in Indian polycystic ovarian syndrome patients as compared to control population.Methods: This prospective cross sectional study included 130 PCOS women and 76 control women attending OBG department Vydehi medical college and research centre. From all included subject’s clinical history, family history and anthropometric measurements were obtained. All women had a standard oral glucose tolerance test (OGTT) with measurement of fasting glucose and 2-hour glucose levels. Normal glucose tolerance (NGT), IGT, and type 2 diabetes were defined using glucose levels during the OGTT, according to the criteria proposed by the World Health Organization (WHO).Results: Among 130 PCOS women, glucose tolerance was normal in 101 (77.69%) women, 25 (19.2%) had IGT and 4 (3.07%) had type 2 DM; compared to 76 healthy controls, 70 (92.1%) had normal glucose tolerance and 6 (7.9%) had IGT. None of the controls had type 2 DM. This finding was statistically significant with P value 0.02.Conclusions: The prevalence of IGT and type 2 DM in women with PCOS is significantly more in comparison with healthy controls. Therefore, women with PCOS should periodically have an OGTT for diabetes screening

    Evaluation of tubal patency by sonosalpingography is as good as hysterosalpingography in infertile women

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    Background: Tubal pathology is one of the causes of infertility in sub fertile couples. Therefore, evaluation of fallopian tubes forms an essential part of evaluation in a sub fertile woman. The aim of the study was to compare the efficacy of sonosalpingography which is a less invasive method when compared to hysterosalpingogram for evaluation of utero-tubal factor in females.Methods: A total of 95 patients 69 with primary infertility and 26 with secondary infertility attending our Obstetrics and Gynecology department were recruited for the study from June 2016 to July 2017. All the study subjects underwent Sonosalpingography on day 5th to 7th and Hysterosalpingography on 7th to 9th day of the menstrual cycle. Data was collected and compared to assess the sensitivity and specificity of sonosalpingography over hysterosalpingography. Statistical analysis was done by using SPSS software version 16.0.Results: Sonosalpingography (SSG) has 97% sensitivity and 94% specificity in comparison to hysterosalpingography (HSG). Analysis of the raw data gave positive predictive value of 98.3% and negative predictive value of 75%. From the results of this study it clear that there is no statistically significant difference (p = 0.237) between the results of the two methods (SSG and HSG).Conclusions: As sonosalpingogrpahy has high sensitivity and specificity and is less invasive. It should be used initially to assess tubal patency in cases of infertility. SSG is found to be a reliable, relatively less expensive diagnostic and therapeutic procedure in the management of infertility in females. Easy availability and accessibility of ultrasound in all primary health care centers definitely can prove superior to conventional method of diagnosis of tubal patency in such patient
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