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Three-dimensional Printing of Shape Memory Alloys
Carreno-Morelli E.,Martinerie S.,Bidaux J.E. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
3D printing of NiTi alloys has been successfully achieved. A novel printing process has been developed and used, which consists in selective deposition of a solvent on a granule bed. The granules are composed of metal powders and thermoplastic binder, which are mixed and sieved by conventional methods. A sound green strength is obtained after solvent evaporation. Sintered parts exhibit good density, proper phase composition and shape memory behaviour.
Adaptive time-step control for modal methods to integrate the neutron diffusion equation
Carreno, A.,Vidal-Ferrandiz, A.,Ginestar, D.,Verdu, G. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2
The solution of the time-dependent neutron diffusion equation can be approximated using quasi-static methods that factorise the neutronic flux as the product of a time dependent function times a shape function that depends both on space and time. A generalization of this technique is the updated modal method. This strategy assumes that the neutron flux can be decomposed into a sum of amplitudes multiplied by some shape functions. These functions, known as modes, come from the solution of the eigenvalue problems associated with the static neutron diffusion equation that are being updated along the transient. In previous works, the time step used to update the modes is set to a fixed value and this implies the need of using small time-steps to obtain accurate results and, consequently, a high computational cost. In this work, we propose the use of an adaptive control time-step that reduces automatically the time-step when the algorithm detects large errors and increases this value when it is not necessary to use small steps. Several strategies to compute the modes updating time step are proposed and their performance is tested for different transients in benchmark reactors with rectangular and hexagonal geometry.
Time-dependent simplifi ed spherical harmonics formulations for a nuclear reactor system
A. Carreno,A. Vidal-Ferrandiz,D. Ginestar,G. Verdú 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12
The steady-state simplified spherical harmonics equations (SPN equations) are a higher order approximation to the neutron transport equations than the neutron diffusion equation that also have reasonablecomputational demands. This work extends these results for the analysis of transients by comparing oftwo formulations of time-dependent SPN equations considering different treatments for the time derivatives of the field moments. The first is the full system of equations and the second is a diffusiveapproximation of these equations that neglects the time derivatives of the odd moments. The spatialdiscretization of these methodologies is made by using a high order finite element method. For the timediscretization, a semi-implicit Euler method is used. Numerical results show that the diffusive formulation for the time-dependent simplified spherical harmonics equations does not present a relevant lossof accuracy while being more computationally efficient than the full system.
Aparna Shah,Flavia Regina Carreno,Alan Frazer 대한정신약물학회 2014 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.12 No.2
Treatment resistant depression (TRD) is a global health concern affecting a large proportion of depressed patients who thenrequire novel therapeutic options. One such treatment option that has received some attention in the past several years is vagalnerve stimulation (VNS). The present review briefly describes the relevance of this treatment in the light of other existing pharmacologicaland non-pharmacological options. It then summarizes clinical findings with respect to the efficacy of VNS. The anatomicalrationale for its efficacy and other potential mechanisms of its antidepressant effects as compared to those employed byclassical antidepressant drugs are discussed. VNS has been approved in some countries and has been used for patients withTRD for quite some time. A newer, fast-acting, non-invasive pharmacological option called ketamine is currently in the limelightwith reference to TRD. This drug is currently in the investigational phase but shows promise. The clinical and preclinical findingsrelated to ketamine have also been summarized and compared with those for VNS. The role of neurotrophin factors, specificallybrain derived neurotrophic factor and its receptor, in the beneficial effects of both VNS and ketamine have been highlighted. It can be concluded that both these therapeutic modalities, while effective, need further research that can reveal specific targetsfor intervention by novel drugs and address concerns related to side-effects, especially those seen with ketamine.
Daimon Shiraishi,Yusuke Nishimura,Isaac Aguirre-Carreno,Masahito Hara,Satoshi Yoshikawa,Kaoru Eguchi,Yoshitaka Nagashima,Hiroshi Ito,Shoichi Haimoto,Yu Yamamoto,Howard J. Ginsberg,Masakazu Takayasu,Ry 대한척추신경외과학회 2021 Neurospine Vol.18 No.4
Objective: The purpose of this study is to find the clinical and radiographic characteristics of traumatic craniocervical junction (CCJ) injuries requiring occipitocervical fusion (OC fusion) for early diagnosis and surgical intervention. Methods: We retrospectively reviewed 12 patients with CCJ injuries presenting to St. Michaels Hospital in Toronto who underwent OC fusion and looked into the following variables; (1) initial trauma data on emergency room arrival, (2) associated injuries, (3) imaging characteristics of computed tomography (CT) scan and magnetic resonance imaging (MRI), (4) surgical procedures, surgical complications, and neurological outcome. Results: All patients were treated as acute spinal injuries and underwent OC fusion on an emergency basis. Patients consisted of 10 males and 2 females with an average age of 47 years (range, 18–82 years). All patients sustained high-energy injuries. Three patients out of 6 patients with normal BAI (basion-axial interval) and BDI (basion-dens interval) values showed visible CCJ injuries on CT scans. However, the remaining 3 patients had no clear evidence of occipitoatlantal instability on CT scans. MRI clearly described several findings indicating occipitoatlantal instability. The 8 patients with normal values of ADI (atlanto-dens interval interval) demonstrated atlantoaxial instability on CT scan, however, all MRI more clearly and reliably demonstrated C1/2 facet injury and/or cruciate ligament injury. Conclusion: We advocate measures to help recognize CCJ injury at an early stage in the present study. Occipitoatlantal instability needs to be carefully investigated on MRI in addition to CT scan with special attention to facet joint and ligament integrity.
( J. A. Calderon ),( F. A. Vasquez ),( L. Arbelaez ),( J. A. Carreno ) 한국부식방식학회 2017 Corrosion Science and Technology Vol.16 No.2
Chelating solutions can be damaged by strong acids during oil production. To design effective corrosion inhibitors and other alternatives for corrosion control, it is important to understand not only the behavior of the system under operating condition but also the kinetics of electrochemical reactions during the corrosion process. In this study, the electrochemical behaviors of P-110 steel in aqueous fluids based on ethylenediaminetetraacetic acid (EDTA) compounds under various temperatures and hydrodynamic regime conditions were assessed. Electrochemical measurements were conducted using rotating disc electrodes manufactured. Electrolytes were prepared using aqueous compounds of EDTA like diammonium salt, disodium salt, and tetrasodium salt. Potentiodynamic polarization, electrochemical impedance, and mass loss tests were performed in order to assess the corrosion kinetic in electrolytes. Hydrodynamic effects were observed only in the cathodic polarization curve. This proves that hydrodynamic regime plays an important role in the corrosion of steel mainly in disodium and diammonium EDTA solutions. Two cathodic reactions controlled the corrosion process. However, oxygen level and pH of the electrolyte played the most important role in metal corrosion. Corrosion rates in those fluids were decreased drastically when oxygen concentration was reduced.
( Sandra Villanueva ),( Fernando Gonzalez ),( Eduardo Lorca ),( Andres Tapia ),( Valentina Lopez G ),( Rocio Strodthoff ),( Francisca Fajre ),( Juan E. Carreno ),( Ricardo Valjalo ),( Cesar Vergara ) 대한신장학회 2019 Kidney Research and Clinical Practice Vol.38 No.2
Background: Chronic kidney disease (CKD) is a growing public health concern, and available treatments are insufficient in limiting disease progression. New strategies, including regenerative cell-based therapies, have emerged as therapeutic alternatives. Results from several groups, including our own, have reported evidence of a supportive role for mesenchymal stromal cells (MSCs) in functional recovery and prevention of tissue damage in murine models of CKD. Prompted by these data, an open pilot study was conducted to assess the safety and efficacy of a single injection of autologous adipose tissue-derived MSCs (AT-MSCs) for treatment of CKD. Methods: AT-MSCs were infused intravenously into six CKD patients at a dose of 1 million cells/kg. Patients were stabilized and followed for one year prior to MSC infusion and one year following infusion. Results: No patients presented with adverse effects. Statistically significant improvement in urinary protein excretion was observed in AT-MSCs transplanted patients, from a median of 0.75 g/day (range, 0.15-9.57) at baseline to 0.54 g/day (range, 0.01-2.66) at month 12 (P = 0.046). The glomerular filtration rate was not significantly decreased post-infusion of AT-MSCs. Conclusion: Findings from this pilot study demonstrate that intravenous infusion of autologous expanded AT-MSCs into CKD patients was not associated with adverse effects and could benefit patients already undergoing standard medical treatment.