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Alejandro Tapia-Hernandez,Mario Ponce-Silva,Victor Hugo Olivares-Peregrino,Jesus Elias Valdez-Resendiz,Leobardo Hernandez-Gonzalez 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.
Hernandez Alejandro,Nuñez Jorge H.,Sallent Andrea,Gargallo-Margarit Albert,Gallardo-Calero Irene,Barro Victor 대한정형외과학회 2020 Clinics in Orthopedic Surgery Vol.12 No.2
Background: Untreated osteonecrosis of the femoral head ultimately leads to secondary coxarthrosis. The aim of this study was to determinate if the core decompression of the femoral head combined with implantation of autologous bone marrow concentrate with tricalcium phosphate could be used to prevent radiographic progression of early stage osteonecrosis of the hip. We also sought to determine whether this treatment improved clinical outcomes and reduced the need for total hip arthroplasty. Methods: Eighteen hips were included in the present study. All of them underwent core decompression of the femoral head combined with implantation of autologous bone marrow concentrate with tricalcium phosphate between 2007 and 2012. The cell concentrate was obtained from the posterior iliac crest and processed and implanted during the same surgical procedure. Patient demographic data, clinical data including modified Harris hip score, and radiological data were collected preoperatively, postoperatively, and during the follow-up period. Also, survival endpoints were analyzed: time of femoral head collapse and need for total hip arthroplasty. Results: The mean age of patients was 37.8 years (standard deviation [SD], 9.31 years). The mean follow-up was 68.9 months (SD, 15.0 months). In most cases (70.6%), the etiology of the osteonecrosis of the femoral head was corticosteroid use; in the remaining cases, secondary to alcohol use. Core decompression of the femoral head combined with implantation of autologous bone marrow concentrate with tricalcium phosphate did not prevent progression to collapse (< 80% at 5 years) although modified Harris hip scores improved. Overall median survival with the total hip arthroplasty as endpoint was 23 months (95% confidence interval [CI], 14.9 to 31.1 months). Overall median survival time with any degree of collapse as endpoint was 7 months (95% CI, 2.0 to 12.0 months). Conclusions: The results obtained in this study suggest that core decompression combined with implantation of autologous bone marrow concentrate and tricalcium phosphate will not prevent radiographic progression of early stage osteonecrosis of the hip. These finding also suggest that the absence of indications for hip replacement alone is not an indicator of good response to the treatment, and it is important to note the radiological results.
Ischiofemoral Impingement Syndrome: Outcomes of Endoscopic Resection of the Lesser Trochanter
Alejandro Hernandez,Sleiman Haddad,Jorge H. Nuñez,Albert Gargallo-Margarit,Andrea Sallent,Victor Barro 대한정형외과학회 2017 Clinics in Orthopedic Surgery Vol.9 No.4
Ischiofemoral impingement syndrome is a rare clinical entity characterized by chronic groin, buttock or hip pain associated with radiographic evidence of narrowing of the space between the lesser femoral trochanter and the ischial tuberosity. Introduction of magnetic resonance imaging to the clinical practice as well as the establishment of the radiological definition of the abnormal ischiofemoral distance has led to an increasing interest in this condition. Ischiofemoral impingement syndrome is a poorly understood disorder of chronic pain, especially regarding its treatment. The authors present two cases of primary ischiofemoral impingement syndrome successfully treated with a minimally invasive surgical technique. With this endoscopic technique, it was possible to resect the lesser trochanter and restore the ischiofemoral space. Immediate clinical and functional improvement was reported by both patients.
Tapia-Hernandez, Alejandro,Ponce-Silva, Mario,Olivares-Peregrino, Victor Hugo,Valdez-Resendiz, Jesus Elias,Hernandez-Gonzalez, Leobardo The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.
Physical Modeling of SiC Power Diodes with Empirical Approximation
Hernandez, Leobardo,Claudio, Abraham,Rodriguez, Marco A.,Ponce, Mario,Tapia, Alejandro The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3
This article presents the development of a model for SiC power diodes based on the physics of the semiconductor. The model is able to simulate the behavior of the dynamics of the charges in the N- region based on the stored charge inside the SiC power diode, depending on the working regime of the device (turn-on, on-state, and turn-off). The optimal individual calculation of the ambipolar diffusion length for every phase of commutation allows for solving the ambipolar diffusion equation (ADE) using a very simple approach. By means of this methodology development a set of differential equations that models the main physical phenomena associated with the semiconductor power device are obtained. The model is developed in Pspice with acceptable simulation times and without convergence problems during its implementation.
Structural Performance of RC Beams containing Tension-Only Nodes
Manuel Alejandro Fernandez-Rui,Luisa Marı´a Gil-Martin,Enrique Hernandez-Montes 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.1
Strut and Tie (S&T) models are used for the design of what are known as ‘‘discontinuity regions’’ in reinforced concrete (RC) structures. Building codes such as ACI-318 and Eurocode 2 do not give information on the nodes that only connect ties in S&T models (called TTT or tension-only nodes). However, their use is not explicitly prohibited in the design of RC structures. In this work, a comparison between solutions which have been designed both considering and not considering TTT nodes is evaluated. Four RC beams (designed with and without TTT nodes) were subjected to three-point bending. Experimental results show that TTT nodes are a good design solution for special cases of discontinuity regions in RC structures. However, the experimental campaign has proven that this type of node is more vulnerable to errors during construction than solutions designed without TTT nodes.
REMOTE NUMERICAL SIMULATIONS OF THE INTERACTION OF HIGH VELOCITY CLOUDS WITH RANDOM MAGNETIC FIELDS
Santikkan, Alfredo,Hernandez-Cervantes, Liliana,Gonzalez-Ponce, Alejandro,Kim, Jong-Soo The Korean Astronomical Society 2007 Journal of The Korean Astronomical Society Vol.40 No.4
The numerical simulations associated with the interaction of High Velocity Clouds (HVC) with the Magnetized Galactic Interstellar Medium (ISM) are a powerful tool to describe the evolution of the interaction of these objects in our Galaxy. In this work we present a new project referred to as Theoretical Virtual i Observatories. It is oriented toward to perform numerical simulations in real time through a Web page. This is a powerful astrophysical computational tool that consists of an intuitive graphical user interface (GUI) and a database produced by numerical calculations. In this Website the user can make use of the existing numerical simulations from the database or run a new simulation introducing initial conditions such as temperatures, densities, velocities, and magnetic field intensities for both the ISM and HVC. The prototype is programmed using Linux, Apache, MySQL, and PHP (LAMP), based on the open source philosophy. All simulations were performed with the MHD code ZEUS-3D, which solves the ideal MHD equations by finite differences on a fixed Eulerian mesh. Finally, we present typical results that can be obtained with this tool.