Adaptive balancing of highly flexible rotors by using artificial neural networks

Saldarriaga, M. Villafane,Mahfoud, J.,Steffen, V. Jr.,Der Hagopian, J. Techno-Press 2009 Smart Structures and Systems, An International Jou Vol.5 No.5

The present work is an alternative methodology in order to balance a nonlinear highly flexible rotor by using neural networks. This procedure was developed aiming at improving the performance of classical balancing methods, which are developed in the context of linearity between acting forces and resulting displacements and are not well adapted to these situations. In this paper a fully experimental procedure using neural networks is implemented for dealing with the adaptive balancing of nonlinear rotors. The nonlinearity results from the large displacements measured due to the high flexibility of the foundation. A neural network based meta-model was developed to represent the system. The initialization of the learning procedure of the network is performed by using the influence coefficient method and the adaptive balancing strategy is prone to converge rapidly to a satisfactory solution. The methodology is tested successfully experimentally.

Adaptive balancing of highly flexible rotors by using artificial neural networks

M. Villafañe Saldarriaga,J. Mahfoud,V. Steffen Jr.,J. Der Hagopian 국제구조공학회 2009 Smart Structures and Systems, An International Jou Vol.5 No.5

The present work is an alternative methodology in order to balance a nonlinear highly flexible rotor by using neural networks. This procedure was developed aiming at improving the performance of classical balancing methods, which are developed in the context of linearity between acting forces and resulting displacements and are not well adapted to these situations. In this paper a fully experimental procedure using neural networks is implemented for dealing with the adaptive balancing of nonlinear rotors. The nonlinearity results from the large displacements measured due to the high flexibility of the foundation. A neural network based meta-model was developed to represent the system. The initialization of the learning procedure of the network is performed by using the influence coefficient method and the adaptive balancing strategy is prone to converge rapidly to a satisfactory solution. The methodology is tested successfully experimentally.

Toward Structural Health Monitoring of Civil Structures Based on Self-Sensing Concrete Nanocomposites: A Validation in a Reinforced-Concrete Beam

Diego L. Castaneda?Saldarriaga,Joham Alvarez?Montoya,Vladimir Martinez?Tejada,Julian Sierra?Perez 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.1

Self-sensing concrete materials, also known as smart concretes, are emerging as a promising technological development for the construction industry, where novel materials with the capability of providing information about thestructural integrity while operating as a structural material are required. Despite progress in the field, there are issues related to the integration of these composites in full-scale structural members that need to be addressed before broad practical implementations. This article reports the manufacturing and multipurpose experimental characterization of a cement-based matrix (CBM) composite with carbon nanotube (CNT) inclusions and its integration inside a representative structural member. Methodologies based on current–voltage (I–V) curves, direct current (DC), and biphasic direct current (BDC) were used to study and characterize the electric resistance of the CNT/CBM composite. Their self-sensing behavior was studied using a compression test, while electric resistance measures were taken. To evaluate the damage detection capability, a CNT/CBM parallelepiped was embedded into a reinforced-concrete beam (RC beam) and tested under three-point bending. Principal finding includes the validation of the material’s piezoresistivity behavior and its suitability to be used as strain sensor. Also, test results showed that manufactured composites exhibit an Ohmic response. The embedded CNT/CBM material exhibited a dominant linear proportionality between electrical resistance values, load magnitude, and strain changes into the RC beam. Finally, a change in the global stiffness (associated with a damage occurrence on the beam) was successfully self-sensed using the manufactured sensor by means of the variation in the electrical resistance. These results demonstrate the potential of CNT/CBM composites to be used in real-world structural health monitoring (SHM) applications for damage detection by identifying changes in stiffness of the monitored structural member.

Gigantomastia as a Cause of Pulmonary Hypertension

Juan Pablo Castillo,Ana María Robledo,Laura Torres-Canchala,Lady Roa-Saldarriaga 대한성형외과학회 2022 Archives of Plastic Surgery Vol.49 No.3

Reduction mammaplasty is the gold standard treatment for gigantomastia. We report one female patient with juvenile gigantomastia associated with severe pulmonary hypertension where her pulmonary pressure decreased significantly after the surgery, improving her quality of life. A 22-year-old female patient with gigantomastia since 10 years old, tricuspid regurgitation, and pulmonary thromboembolism antecedent was admitted to the emergency department. Her oxygen saturation was 89%. Acute heart failure management was initiated. An echocardiogram reported left ventricle ejection fraction (LVEF) of 70% with severe right heart dilation, contractile dysfunction, and arterial pulmonary pressure (PASP) of 110mm Hg. A multidisciplinary team considered gigantomastia could generate a restrictive pattern, so a Thorek reduction mammoplasty with Wise pattern was performed. Presurgical measurements were: sternal notch to nipple-areola complex, right 59 cm, left 56 cm. Three days after surgery, the patient could breathe without oxygen support. In the outpatient followup, patient referred reduction of her respiratory symptoms and marked improvement in her quality of life. Sixmonths after surgery, a control echocardiogram showed a LVEF of 62% and PASP of 85mm Hg. Pulmonary hypertension may be present in patients with gigantomastia. Reduction mammoplasty may be a feasible alternative to improve the cardiac signs and symptoms in patients with medical refractory management.

Synthesis and characterization of a silver nanoparticle-containing polymer composite with antimicrobial abilities for application in prosthetic and orthotic devices

Catalina Quintero-Quiroz,Luz E. Botero,Diana Zárate-Triviño,Natalia Acevedo-Yepes,Jorge Saldarriaga Escobar,Vera Z. Pérez,Luis Javier Cruz Riano 한국생체재료학회 2020 생체재료학회지 Vol.24 No.3

Background: The presence of skin problems in patients using external lower limb prosthesis is recurrent. This has generated the need to develop interfaces for prosthesis with the ability to control microbial growth. Silver nanoparticles (AgNPs) have been implemented in the development of biomaterials because of their high antimicrobial activity. This article discusses the development of an AgNP-containing polymer composite with antimicrobial activity for developing prosthetic liners. Methods: AgNPs were synthesized using a photochemical method and certain physicochemical properties were characterized. Furthermore, the antimicrobial activity of AgNPs against Staphylococcus aureus ATCC 25923 and methicillin-resistant Staphylococcus aureus (MRSA), was assessed on the basis of their minimum inhibitory concentrations (MICs). AgNPs were incorporated into a silicon elastomer to assess certain physicomechanical properties, antimicrobial activity and cytotoxic effect of the material. Results: Themaximum antimicrobial activity of the material against Staphylococcus aureus ATCC 25923 andMRSA was 41.58% ±2.97% at AgNP concentration of 32.98 μg/mL and 14.85% ±5.94% at AgNP concentration of 16.49 μg/mL, respectively. Additionally, the material exhibited tensile yield strength, rupture tensile strength, and tensile modulus of elasticity of 0.70 - 1.10 MPa, 0.71–1.06 MPa, and 0.20 - 0.30 MPa, respectively. The mechanical characteristics of the material were within the acceptable range for use in external lower limb prosthetic and orthotic interfaces. Conclusions: It was possible to incorporate the AgNPs in a silicone elastomer, finding that the composite developed presented antimicrobial activity against Staphylococcus aureus ATCC 25923 and MRSA when compared to non-AgNP material samples.

Optimization of silver nanoparticle synthesis by chemical reduction and evaluation of its antimicrobial and toxic activity

Catalina Quintero-Quiroz,Natalia Acevedo,Jenniffer Zapata-Giraldo,Luz E. Botero,Julián Quintero,Diana Zárate-Triviño,Jorge Saldarriaga,Vera Z. Pérez 한국생체재료학회 2020 생체재료학회지 Vol.24 No.1

Background: Chemical reduction has become an accessible and useful alternative to obtain silver nanoparticles (AgNPs). However, its toxicity capacity depends on multiple variables that generate differences in the ability to inhibit the growth of microorganisms. Thus, optimazing parameters for the synthesis of AgNPs can increase its antimicrobial capacity by improving its physical-chemical properties. Methods: In this study a Face Centered Central Composite Design (FCCCD) was carried out with four parameters: AgNO3 concentration, sodium citrate (TSC) concentration, NaBH4 concentration and the pH of the reaction with the objective of inhibit the growth of microorganisms. The response variables were the average size of AgNPs, the peak with the greatest intensity in the size distribution, the polydispersity of the nanoparticle size and the yield of the process. AgNPs obtained from the optimization were characterized physically and chemically. The antimicrobial activity of optimized AgNPs was evaluated against Staphylococcus aureus, Escherichia coli, Escherichia coli AmpC resistant, and Candida albicans and compared with AgNPs before optimization. In addition, the cytotoxicity of the optimized AgNPs was evaluated by the colorimetric assay MTT (3- (4,5- Dimethylthiazol- 2- yl)- 2, 5 - Diphenyltetrazolium Bromide). Results: It was found that the four factors studied were significant for the response variables, and a significant model (p <0.05) was obtained for each variable. The optimal conditions were 8 for pH and 0.01 M, 0.0 6M, 0.01 M for the concentration of TSC, AgNO3, and NaBH4, respectively. Optimized AgNPs spherical and hemispherical were obtained, and 67.66% of it had a diameter less than 10.30 nm. A minimum bactericidal concentration (MBC) and minimum fungicidal Concentration (MFC) of optimized AgNPs was found against Staphylococcus aureus, Escherichia coli, Escherichia coli AmpC resistant, and Candida albicans at 19.89, 9.94, 9.94, 2.08 μg/mL, respectively. Furthermore, the lethal concentration 50 (LC50) of optimized AgNPs was found on 19.11 μg/mL and 19.60 μg/mL to Vero and NiH3T3 cells, respectively. Conclusions: It was found that the factors studied were significant for the variable responses and the optimization process used was effective to improve the antimicrobial activity of the AgNPs.