Nonlinear and detuning effects of the nutation angle in precessionally-forced rotating cylinder flow

The flow in a rapidly rotating cylinder forced to precess through a nutation angle a is investigated numerically, keeping all parameters constant except a, and tuned to a triadic resonance at a = 1º. When increasing a, the flow undergoes a sequence of well- characterized bifurcations associated with triadic resonance, involving heteroclinic and homoclinic cycles, for a up to about 4º. For larger a, we identify two chaotic regimes. In the first regime, with a between about 4º and 27º, the bulk flow retains remnants of the helical structures associated with the triadic resonance, but there are strong nonlinear interactions between the various azimuthal Fourier components of the flow. For the larger a regime, large detuning effects lead to the triadic resonance dynamics being completely swamped by boundary layer eruptions. The azimuthal mean flow at large angles results in a large mean deviation from solid-body rotation and the flow is characterized by strong shear at the boundary layers with temporally chaotic eruptions.Postprint (author's final draft

A New Framework for the Performance Analysis of Wireless Communications under Hoyt (Nakagami-q) Fading

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI:10.1109/TIT.2017.2655342We present a novel relationship between the distribution of circular and non-circular complex Gaussian random variables. Specifically, we show that the distribution of the squared norm of a non-circular complex Gaussian random variable, usually referred to as the squared Hoyt distribution, can be constructed from a conditional exponential distribution. From this fundamental connection we introduce a new approach, the Hoyt transform method, that allows to analyze the performance of a wireless link under Hoyt (Nakagami-q) fading in a very simple way. We illustrate that many performance metrics for Hoyt fading can be calculated by leveraging well-known results for Rayleigh fading and only performing a finite-range integral. We use this technique to obtain novel results for some information and communication-theoretic metrics in Hoyt fading channels.Universidad de Málaga. Campus de Execelencia Internacional. Andalucía Tech

An improved layer-by-layer self-assembly technique to generate biointerfaces for platelet adhesion studies: Dynamic LbL

Layer-by-layer self-assembly (LbL) is a technique that generates engineered nano-scale films, coatings, and particles. These nanoscale films have recently been used in multiple biomedical applications. Concurrently, microfabrication methods and advances in microfluidics are being developed and combined to create Lab-on-a-Chip technologies. The potential to perform complex biological assays in vitro as a first-line screening technique before moving on to animal models has made the concept of lab on a chip a valuable research tool. Prior studies in the Biofluids Laboratory at Louisiana Tech have used layer-by-layer and in vitro biological assays to study thrombogenesis in a controlled, repeatable, engineered environment. The reliability of these previously established techniques was unsatisfactory for more complex cases such as chemical and shear stress interactions. The work presented in this dissertation was performed to test the principal assumptions behind the established laboratory methodologies, suggest improvements where needed, and test the impact of these improvements on accuracy and repeatability. The assumptions to be tested were: (1) The fluorescence microscopy (FM) images of acridine orange-tagged platelets accurately provide a measure of percent area of surface covered by platelets; (2) fibrinogen coatings can be accurately controlled, interact with platelets, and do not interfere with the ability to quantify platelet adhesion; and (3) the dependence of platelet adhesion on chemical agents, as measured with the modified methods, generally agrees with results obtained from our previous methods and with known responses of platelets that have been documented in the literature. The distribution of fibrinogen on the final LbL surface generated with the standard, static process (s-LbL) was imaged by tagging the fibrinogen with an anti-fibrinogen antibody bound to fluorescein isothiocyanate (FITC). FITC FM images and acridine orange FM images were taken sequentially at selected surface locations to generate a composite overlap of presumed platelet adhesion as a function of fibrinogen distribution. The method was unable to distinguish the surface from the adhered cells. The surface inhomogeneity and porosity retained a large amount of acridine orange stain, even in the absence of platelets, and components in the platelet-rich plasma (PRP) were found to fix acridine orange in a mode that fluoresced in the FITC imaging FM. Both of these problems obfuscated the platelet adhesion FM results when using s-LbL surfaces and acridine orange staining of platelets. A dynamic process (d-LbL) was developed in which a solution of the molecule to be layered was constantly washed over the surface, and was constantly mixed to maintain a more homogeneous distribution of solute relative to the surface during the layering process. The d-LbL surfaces were tested as described above, and found to reduce the size and number of regions of anomalous acridine orange pooling trapped by the surface, providing a greater consistency and reliability in identifying platelets. The improved surface was then used in a series of platelet adhesion experiments under static and dynamic flow conditions, and with and without the chemical additive L-arginine. The complex microcharmel system used in prior studies was replaced with a simpler system involving fewer nuisance variables for these tests. The tests were performed on both collagen and fibrinogen surfaces. Collagen has been used as a thrombogenic surface in multiple studies in the literature, but produces additional variables in thrombogenesis control that are avoided when fibrinogen is used. In these tests, fibrinogen was found to be as thrombogenic as collagen, and platelet coverage of both biointerfaces was reduced by L-arginine in a manner similar to previously reported work. The simpler system differed from the previous microchannel system in important factors: (1) It exposed the platelets to much lower shear stresses; (2) It introduced an oscillatory flow, which introduced a higher degree of variability in the adhesion than previously reported; (3) the previous work had not removed the acridine orange surface problems. Therefore, a direct comparison between results was not possible. The new d-LbL surface process was successful in testing the basic assumptions. Testing showed that the new process eliminated the anomalous acridine orange retention problem during fluorescence imaging. This improvement in fluorescence response meant that the FM results matched the platelet adhesion on plain glass slides and adhesion reported by others in microfluidic flows. The chemical additive responses behaved as expected, with an increase in L-arginine contributing to a decrease in thrombogenesis under dynamic conditions, but not under static conditions

Asymptotically Exact Approximations for the Symmetric Difference of Generalized Marcum-Q Functions

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2014.2337263In this paper, we derive two simple and asymptotically exact approximations for the function defined as ΔQm(a, b) =Δ Qm(a, b) - Qm(b, a). The generalized Marcum Q-function Qm(a, b) appears in many scenarios in communications in this particular form and is referred to as the symmetric difference of generalized Marcum Q-functions or the difference of generalized Marcum Q-functions with reversed arguments. We show that the symmetric difference of Marcum Q-functions can be expressed in terms of a single Gaussian Q-function for large and even moderate values of the arguments a and b. A second approximation for ΔQm(a, b) is also given in terms of the exponential function. We illustrate the applicability of these new approximations in different scenarios: 1) statistical characterization of Hoyt fading; 2) performance analysis of communication systems; 3) level crossing statistics of a sampled Rayleigh envelope; and 4) asymptotic approximation of the Rice Ie-function.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech

Analysis of energy detection of unknown signals under Beckmann fading channels

(c) 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The Beckmann fading is a general multipath fading model which includes Rice, Hoyt and Rayleigh fading as particular cases. However, the generality of the Beckmann fading also implies a significant increased mathematical complexity. Thus, relatively few analytical results have been reported for this otherwise useful fading model. The performance of energy detection for multi-branch receivers operating under Beckmann fading is here studied, and the inherent analytical complexity is here circumvented by the derivation of a closed-form expression for the generalized moment generating function (MGF) of the received signal-to-noise ratio (SNR), which is a new and useful result, as it is key for evaluating the receiver operating characteristics. The impact of fading severity on the probability of missed detection is shown to be less critical as the SNR decreases. Monte Carlo simulations have been carried out in order to validate the obtained theoretical expressions.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto MINECO-FEDER TEC2013-42711-R y TEC2013-44442-P. Junta de Andalucía P11-TIC-7109

Resource-Based View and SMEs Performance Exporting through Foreign Intermediaries: The Mediating Effect of Management Controls

Following the resource-based view, this research empirically explores the role of formal and informal management control in mobilizing export resources to develop export capabilities, influencing the export performance of small and medium-sized enterprises (SMEs) in an interorganizational relationship context. Empirical data were collected using a survey administrated online to finance managers in Spanish SMEs which use foreign intermediaries to access export markets. In this setting, evidence mainly suggests, first, that management control systems (MCSs) play a relevant mediating role between the effect of, on the one hand, resources on capabilities, and, on the other hand, resources and capabilities on performance. Second, that MCSs and capabilities play a interrelated double mediating effect between the impact of resources on performance; more specifically, a significant double indirect effect is found (1) between financial resources, behavior control, customer relationship building capability and performance, and (2) between physical resources, behavior control, customer relationship building capability and performanc

Age and growth of the highly exploited narrownose smooth-hound (Mustelus schmitti) (Pisces: Elasmobranchii)

The narrownose smoothhound (Mustelus schmitti) is the most exploited elasmobranch of Argentina, Brazil, and Uruguay and is considered endangered (IUCN Red List of Threatened Species). Providing information on age and growth can improve efforts for conservation of this species. Therefore, our objective was to provide accurate estimates of the age structure and growth parameters for narrownose smooth-hound from Anegada Bay, an important shark nursery area in Argentina. In vertebrae of narrownose smooth-hound, we observed a pattern of alternating opaque and translucent bands and a yearly periodicity in the deposition of this pattern. Ages determined from vertebral band counts ranged from 0 to 11 years. Calculated longevity and total natural mortality rates were 20.87 years and 0.19/year for females and 12.24 years and 0.26/year for males, respectively. This species reached a size of approximately 400 mm in total length in the initial year of growth, and the age at first maturity was 7.61 years for females and 6.79 years for males. The slow growth and late age at maturity of the narrownose smoothhound indicate a need for additional conservation measures to rebuild the population and achieve a sustainable fishery in the 3 countries in which it is distributed.Fil: Molina, Juan Manuel. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Blasina, Gabriela Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Lopez Cazorla, Andrea Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin

On the Calculation of the Incomplete MGF with Applications to Wireless Communications

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TCOMM.2016.2626440The incomplete moment generating function (IMGF) has paramount relevance in communication theory, since it appears in a plethora of scenarios when analyzing the performance of communication systems. We here present a general method for calculating the IMGF of any arbitrary fading distribution. Then, we provide exact closed-form expressions for the IMGF of the very general κ-μ shadowed fading model, which includes the popular κ-μ, η-μ, Rician shadowed, and other classical models as particular cases. We illustrate the practical applicability of this result by analyzing several scenarios of interest in wireless communications: 1) physical layer security in the presence of an eavesdropper; 2) outage probability analysis with interference and background noise; 3) channel capacity with side information at the transmitter and the receiver; and 4) average bit-error rate with adaptive modulation, when the fading on the desired link can be modeled by any of the aforementioned distributions.Universidad de Málaga. Campus de Execelencia Internacional. Andalucía Tech

The κ-µ Shadowed Fading Model with Integer Fading Parameters

(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2017.2678430We show that the popular and general κ-μ shadowed fading model with integer fading parameters μ and m can be represented as a mixture of squared Nakagami- m̂ (or Gamma) distributions. Thus, its PDF and CDF can be expressed in closed-form in terms of a finite number of elementary functions (powers and exponentials). The main implications arising from such connection are then discussed, which can be summarized as: (1) the performance evaluation of communication systems operating in κ-μ shadowed fading becomes as simple as if a Nakagami- m̂ fading channel was assumed; (2) the κ-μ shadowed distribution can be used to approximate the κ-μ distribution using a closed-form representation in terms of elementary functions, by choosing a sufficiently large value of m; and (3) restricting the parameters μ and m to take integer values has limited impact in practice when fitting the κ-μ shadowed fading model to field measurements. As an application example, the average channel capacity of communication systems operating under κ-μ shadowed fading is obtained in closed-form.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech