An Unmatched Radio Frequency Chain for Low-Field Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) is a safe and versatile diagnostic tool for intracranial imaging, however it is also one of the most expensive and specialized making it scarce in low- to middle-income countries (LMIC). The affordability and portability of low-field MRI offers the potential for increased access to brain imaging for diseases like Hydrocephalus in LMIC. In this tutorial style work, we show the design of a low powered and low cost radio frequency chain of electronics to be paired with a previously reported prepolarized low-field MRI for childhood hydrocephalus imaging in sub-Saharan Africa where the incidence of this condition is high. Since the Larmor frequency for this system is as low as 180 kHz, we are able to minimize the impedance of the transmit coil to 5 ohms rather than match to 50 ohms as is traditionally the case. This reduces transmit power consumption by a factor of 10. We also show the use of inexpensive and commonly available animal enclosure fencing (“chicken wire”) as a shield material at this frequency and compare to more traditional shield designs. These preliminary results show that highly portable and affordable low-field MRI systems could provide image resolution and signal-to-noise sufficient for planning hydrocephalus treatment in areas of the world with substantial resource limitations. Employment of these technologies in sub-Saharan Africa offers a cost-effective, sustainable approach to neurological diagnosis and treatment planning in this disease burdened region.Fil: Harper, Joshua R.. Pennsylvania State University; Estados UnidosFil: Zárate Evers, Cristhian Manuel. Universidad Nacional de Asunción; Paraguay. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Krauch, Federico. Universidad Nacional de Asunción; ParaguayFil: Muhumuza, Ivan. Mbarara University Of Science And Technology; UgandaFil: Molina, Jorge. Universidad Nacional de Asunción; ParaguayFil: Obungoloch, Johnes. Mbarara University Of Science And Technology; UgandaFil: Schiff, Steven J.. Pennsylvania State University; Estados Unido

Modeling of vegetable oils cloud point, pour point, cetane number and iodine number from their composition using genetic programming

Vegetable oils (VOs) are composed of 90–98% of triglycerides, i.e. esters composed of three fatty acids and glycerol, and small amounts of mono- and di-glycerides. Due to their physico-chemical properties, VOs have been considered for uses especially in large ships, in stationary engines and low and medium speed diesel engines, in pure form or in blends with fuel oil, diesel, biodiesel and alcohols. There are about 350 VOs with potential as fuel sources, and for most of them, physico-chemical properties values have not yet been measured. In this context, regression models using only VOs fatty acid composition are very useful. In the present paper, regression analysis of VOs cloud point (CP), pour point (PP), cetane number (CN) and iodine number (IN) as a function of saturated and unsaturated fatty acids is conducted. The study is done by using 4 experimental databases including 88 different data of VOs. Concerning the regression technique, genetic programming (GP) has been chosen. The cost function of GP is defined to minimize the Mean Absolute Error (MAE) between experimental and predicted values of each property. The resulting GP models consisting of terms including saturated and unsaturated fatty acids reproduce correctly the dependencies of all four properties on those acids. And they are validated by showing that their results are in good agreement to the experimental databases. In fact, MAE values of the proposed models with respect to the databases for CP, PP, CN and IN are lower than 4.51 °C, 4.54 °C, 3.64 and 8.01, respectively.Fil: Alviso, Dario. Universidad Nacional de Asunción; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zárate Evers, Cristhian Manuel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duriez, Thomas Pierre Cornil. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Regressions of the dielectric constant and speed of sound of vegetable oils from their composition and temperature using genetic programming

The dielectric constant (DC) and speed of sound (SoS) have been measured in many studies on vegetable oils (VOs). These measurements can be applied for quality control, for the detection of contaminants, and in works related to heated and frying VOs. There are several hundreds of VOs with potential use in the food industry, and for most of them, the DC and SoS values are not yet available. This paper proposes regression models of the DC and SoS of VOs as a function of their composition (saturated and unsaturated fatty acids) and the temperature. A regression study was conducted using available experimental databases including a total of 57 and 56 data in the range of 20−50 °C for the DC and SoS, respectively. The equations are obtained using genetic programming (GP). The goal is to minimize the mean absolute error (MAE) between the values of the measured and predicted DC and SoS for several VOs. The resulting GP regression equations reproduce correctly the dependencies of the DC and SoS of VOs on the saturated and unsaturated fatty acids. The validation of these equations is carried out by comparing their results to those of the experimental databases. The MAE values of the regression equations concerning the databases for DC and SoS of VOs are 0.02 and 1.0 m/s, respectively.Fil: Alviso, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Universidad María Auxiliadora; ParaguayFil: Zárate Evers, Cristhian Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Artana, Guillermo Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Duriez, Thomas Pierre Cornil. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Universidad de la Marina Mercante; Argentin

Light refraction effects in counterflow non-premixed flames

This paper presents the influence of light refraction on the broadening of CH∗ and C2 ∗ species experimental profiles in laminar counterflow non-premixed flames. In fact, by comparing CH∗ and C2 ∗ experimental and numerical profiles in a counterflow configuration, a broadening of these species experimental profiles is observed, and these species are frequently employed experimentally to determine important macroscopic combustion properties. Therefore in this work, in order to give an explanation of these phenomena, light refraction due to a high temperature gradient was considered. The Gladstone–Dale relation was used to estimate the medium refractive index along the burner axis, taking into account the gas density and composition. Then, a simple procedure for light refraction estimation of rays reaching the solid angle of the camera in counterflow non-premixed flames was proposed. Finally, the influence of refraction of light on CH∗ and C2 ∗ species thicknesses appears to be significant depending on the operating conditions of counterflow non-premixed flames. However, taking into account the difference between the experimental and numerical profiles thicknesses, this effect is not fully responsible for the experimental broadening. Nonetheless, the same procedure described here can be used in order to study the light refraction for other experimental configurations, such as those of transcritical flames, where the gas density variation is much higher, and consequently the light refraction would be greater.Fil: Alviso, Dario. Universidad Nacional de Asunción; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zárate Evers, Cristhian Manuel. Universidad Nacional de Asunción; Paraguay. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Krauch, Federico. Universidad Nacional de Asunción; ParaguayFil: Artana, Guillermo Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Rolón, Juan Carlos. Universidad Nacional de Asunción; Paragua