Autotuning digital controller for current sensorless power factor corrector stage in continuous conduction mode

Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, 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 component of this work in other works. V. M. López, F. J. Azcondo, F. J. Díaz, and Á. de Castro, "Autotuning digital controller for current sensorless power factor corrector stage in continuous conduction mode", 2010 IEEE 12th Workshop on Control and Modeling for Power Electronics (COMPEL), Boulder (CO), 2010, pp. 1-8A circuit that compensates the volt-seconds error across the inductor in current sensorless digital control for continuous conduction mode power factor correction (PFC) stage is presented. Low cost ad-hoc sigma-delta analog to digital converters (ΣΔ ADCs) are used to sample the PFC input and output voltage. Instead of being measured, the input current is estimated in a digital circuit to be used in the current loop. A nonlinear carrier control is implemented in the digital controller in order to obtain the power factor correction. Drive signal delays cause differences between the digital current and the real current, producing that volt-seconds error. The control algorithm is compensated taking into account the delays. The influence of a wrong compensation is presented. Experimental results show power factor values and harmonic content within the IEC 61000-3-2 Class C standard in different operation conditions. Furthermore, the use of this PFC stage for electronic ballasts to compensate the effect of the utility voltage fluctuation in HID lamps is also verified taking advantage of the digital device capabilities.This work is sponsored by the Spanish Ministry of Education and Science through the project CICYT-TEC 2008-0175

Simulation and Optimization Models of Steady-state Gas Transmission Networks

Managing a gas transport network is a complex problem because of the number of possibilities of routing the gas through the pipes. The most important aim in this kind of systems is to fulfill the demand within the pressure bounds, independently of its associated costs. However, in the present work some cost drivers are also taken into account by means of different objective functions in order to manage the network in an efficient way. This work deals with mathematical modeling and optimization of gas transport networks, where a two-stage procedure is proposed. In the first stage, optimization algorithms based on mathematical programming are applied to make some decisions (whether to activate compressor stations, control valves and other control elements) and gives an initial solution to the second stage. This last stage, which is based on control theory techniques, refines the solution to obtain more accurate results. Due to the reduced complexity in each stage, both can be solved within reasonable runtimes for relatively large gas networks. Based on the mathematical methods involved, a software called GANESOTM has been developedThe authors would like to acknowledge the support of Reganosa LNG Company and also Ministerio de Economía y Competitividad (Spain) under research project MTM2008-02483 and Xunta de Galicia (Spanish region) under research project EM2012/111S

Ovine mesenchymal stromal cells for osteochondral tissue engineering

Resume

A Family of High Frequency AC-LED Drivers Based on ZCS-QRCs

A family of dimmable AC-LED drivers fed from dc voltages, is presented in this paper based on Zero Current Switching Quasi-Resonant Converters (ZCS-QRCs). The proposed family of drivers is based on replacing the diode in conventional converter topologies (i.e. buck, boost or buck-boost) by a string of High-Brightness Light-Emitting Diodes (HB-LED). Hence, the HB-LED string will be working as the rectifier diode and the load, switching at the same frequency of the main switch. In this case, the output current, which is experimentally validated, shows a negative current peak due to the reverse-recovery effect of the HB-LEDs. In order to reduce the reverse-recovery effect on the HB-LEDs, the main switch of the proposed topologies is replaced with a full-wave resonant switch, which makes possible to reduce the di/dt during the turn-off of the HB-LED string, therefore the reverse recovery effect is eliminated. Moreover, the dimming of the HB-LEDs is done by means of changing the switching frequency of the converter, by varying the turn-off while keeping a constant turn-on time. In order to validate the analysis, the proposed topologies have been experimentally tested on a constructed prototype with an output power of 7.5

Human cartilage engineering in an in vitro repair model using collagen scaffolds and mesenchymal stromal cells

[Abstract] The purpose of this study was to investigate cartilage repair of in vitro lesion models using human bone marrow mesenchymal stromal cells (hBMSCs) with different collagen (Col) scaffolds. Lesions were made in human cartilage biopsies. Injured samples were pre-treated with interleukin 1β (IL1β) for 24 h; also, samples were not pre-treated. hBMSCs were seeded on different types of collagen scaffolds. The resulting constructs were placed into the lesions, and the biopsies were cultured for 2 months in chondrogenic medium. Using the modified ICRSII scale, neotissues from the different scaffolds showed ICRS II overall assessment scores ranging from 50% (fibrocartilage) to 100% (hyaline cartilage), except for the Col I +Col II +HS constructs (fibrocartilage/hyaline cartilage, 73%). Data showed that hBMSCs cultured only on Col I +Col II +HS scaffolds displayed a chondrocyte-like morphology and cartilage-like matrix close to native cartilage. Furthermore, IL1β pre-treated biopsies decreased capacity for repair by hBMSCs and decreased levels of chondrogenic phenotype of human cartilage lesions.Instituto de Salud Carlos III; CB06/01/0040Xunta de Galicia ; R2016/036Xunta de Galicia; R2014/050Xunta de Galicia; GPC2014/048Ministerio de Esconomía, Industria y Competitividad; RTC-2016-5386-1Madrid (Comunidad Autónoma); S2009/MAT-147

Ovine mesenchymal stromal cells: morphologic, phenotypic and functional characterization for osteochondral tissue engineering

[Abstract] Introduction. Knowledge of ovine mesenchymal stromal cells (oMSCs) is currently expanding. Tissue engineering combining scaffolding with oMSCs provides promising therapies for the treatment of osteochondral diseases. Purpose. The aim was to isolate and characterize oMSCs from bone marrow aspirates (oBMSCs) and to assess their usefulness for osteochondral repair using β-tricalcium phosphate (bTCP) and type I collagen (Col I) scaffolds. Methods. Cells isolated from ovine bone marrow were characterized morphologically, phenotypically, and functionally. oBMSCs were cultured with osteogenic medium on bTCP and Col I scaffolds. The resulting constructs were evaluated by histology, immunohistochemistry and electron microscopy studies. Furthermore, oBMSCs were cultured on Col I scaffolds to develop an in vitro cartilage repair model that was assessed using a modified International Cartilage Research Society (ICRS) II scale. Results. oBMSCs presented morphology, surface marker pattern and multipotent capacities similar to those of human BMSCs. oBMSCs seeded on Col I gave rise to osteogenic neotissue. Assessment by the modified ICRS II scale revealed that fibrocartilage/hyaline cartilage was obtained in the in vitro repair model. Conclusions. The isolated ovine cells were demonstrated to be oBMSCs. oBMSCs cultured on Col I sponges successfully synthesized osteochondral tissue. The data suggest that oBMSCs have potential for use in preclinical models prior to human clinical studies

Generation of osteoarthritis and healthy mesenchymal cell lines for research on regenerative medicine for osteoarthritis

[Purpose] Bone-marrow mesenchymal stem cells (BM-MSCs) are multipotent self-renewal adult cells with potential to regenerate the damaged tissues in degenerative diseases such as osteoarthritis (OA). Nevertheless, research require in vitro expansion of BM-MSCs, a process which eventually causes cell senescence. To overcome this problem cell lines can be used but, currently, BM-MSC lines available are scarce and present limitations regarding their differentiation capacities. For this reason, the aim of this study was to generate and characterize human BM-MSCs lines, derived from an OA patient and a healthy donor, with high chondrogenic and osteogenic capacities for their use in research on Regenerative Medicine for OA

Establishment of human induced pluripotent stem cell-lines (IPSC) for in vitro modelling hand ostheoarthritis.

ResumenInstituto de Salud Carlos III; PI17/0219

Generation of osteoarthritic mesenchymal stromal cell lines.

ResumenXunta de Galicia; R2016/036Xunta de Galicia; R2014/050Xunta de Galicia; CN2012/142Xunta de Gaicia; GPC2014/048Instituto de salud Carlos III; PI17/0219

Generation and Characterization of Human Induced Pluripotent Stem Cells (iPSCs) From Hand Osteoarthritis Patient-Derived Fibroblasts

[Abstract] Knowledge and research results about hand osteoarthritis (hOA) are limited due to the lack of samples and animal models of the disease. Here, we report the generation of two induced pluripotent stem cell (iPSC)-lines from patients with radiographic hOA. Furthermore, we wondered whether these iPSC-lines carried single nucleotide polymorphisms (SNPs) within genes that have been associated with hOA. Finally, we performed chondrogenic differentiation of the iPSCs in order to prove their usefulness as cellular models of the disease. We performed a non-integrative reprogramming of dermal fibroblasts obtained from two patients with radiographic rhizarthrosis and non-erosive hOA by introducing the transcriptional factors Oct4, Sox2, Klf4 and c-Myc using Sendai virus. After reprogramming, embryonic stem cell-like colonies emerged in culture, which fulfilled all the criteria to be considered iPSCs. Both iPSC-lines carried variants associated with hOA in the four studied genes and showed differences in their chondrogenic capacity when compared with a healthy control iPSC-line. To our knowledge this is the first time that the generation of iPSC-lines from patients with rhizarthrosis and non-erosive hOA is reported. The obtained iPSC-lines might enable us to model the disease in vitro, and to deeper study both the molecular and cellular mechanisms underlying hOA.This study was carried out thanks to the funding from Fundación Española de Reumatología (Proyectos 2014), Proyectos de Investigación 2016 (PI16/02124) and 2017 (PI17/02197) from Instituto de Salud Carlos III-General Subdirection of Assesment and Promotion of the Research – European Regional Development Fund (FEDER) “A way of making Europe”, Rede Galega de Terapia Celular and Grupos con Potencial de Crecemento, Xunta de Galicia (R2016/036, R2014/050, CN2012/142 and GPC2014/048); Deputación da Coruña (BINV-CS/2015); University of A Coruña; Centro de Investigación Biomédica en Red-Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN). Rocío Castro-Viñuelas, María Piñeiro-Ramil and Silvia Rodríguez-Fernández are granted by a predoctoral fellowship from Xunta de Galicia and European Union (European Social Fund) and Clara Sanjurjo-Rodríguez is beneficiary of a postdoctoral fellowship from Xunta de GaliciaXunta de Galicia; R2016/036Deputación da Coruña; BINV-CS/2015Xunta de Galicia; R2014/050Xunta de Galicia; CN2012/142Xunta de Galicia; GPC2014/04