Papers by Popescu Dumitru
Present simulations based on a full 3-D particle electromagnetic code are performed in order to a... more Present simulations based on a full 3-D particle electromagnetic code are performed in order to analyze the impact of a dawnward IMF field on the internal dynamics of the global 3-D magnetosphere. In the case that the northward IMF is switched gradually to dawnward, analysis of magnetic fields in the magnetopause confirms a signature of magnetic reconnection at both the
In this paper we describe only the first part of the duty cycle of a pulsatory liposome. A unilam... more In this paper we describe only the first part of the duty cycle of a pulsatory liposome. A unilamellar lipid liposome filled with an aqueous solution of an impermeant solute is introduced into a hypotonic aqueous environment. Because of the mechanical tension induced by an osmotic flow, the vesicle swells up to a critical size, when suddenly a transbilayer pore appears. A part of the intracellular material leaks out through this pore, and the liposome membrane relaxes and finally recovers. The swelling begins again and the liposome experiences a periodical process. For this reason we have named it a pulsatory liposome. In this paper we have obtained the differential equation of the swelling stage. Its analytical solution is the dependence of time on vesicle radius, which is the inverse of the direct function that would be of interest. We have also computed several parameters related to the swelling process: the critical swelling time and the duration of the last cycle of vesicle act...
Present simulations based on a full 3-D particle electromagnetic code are performed in order to a... more Present simulations based on a full 3-D particle electromagnetic code are performed in order to analyze the impact of a dawnward IMF field on the internal dynamics of the global 3-D magnetosphere. In the case that the northward IMF is switched gradually to dawnward, analysis of magnetic fields in the magnetopause confirms a signature of magnetic reconnection at both the dawnside and duskside. Arrival of dawnward IMF to the magnetopause creates a reconnection groove (where magnetic field is min- imum) which causes particle entry into the deep region of the magnetosphere via field lines that go near the magnetopause. This deep connection is more fully recognized tailward of Earth. The flank weak-field region (so called "sash") joins onto the plasma sheet and the plasma sheet to form a geometrical feature called the cross-tail S that structurally integrates the magnetopause and the tail interior. This structure might con- tribute to direct entry between the magnetosheath to p...
Within the present work we determined the conditions for transbilayer pore formation due to therm... more Within the present work we determined the conditions for transbilayer pore formation due to thermal group motion of phospholipid bilayer molecules. The radius of the area containing molecules that move almost simultaneously perpendicular to the bilayer surface is within the range [R min , R max ]. Bilayer deformation is characterized by its wavelength, which is also confined to a limited and continuous range. The limits of both R and the wavelength depend on the thickness of the bilayer's hydrophobic core, on temperature, polar group size, surface tension, and on the bilayer's elastic properties (elastic compression and splay). The conditions for transbilayer pore formation depend quantitatively on the radius of the perturbation area and on the bilayer deformation wavelength.
Membrane Science and Technology, 2003
Knee Surgery, Sports Traumatology, Arthroscopy, 2011
Purpose This paper reports a prospective review of patients who, between 2004 and 2007, underwent... more Purpose This paper reports a prospective review of patients who, between 2004 and 2007, underwent secondary patellar resurfacing (SPR) due to anterior knee pain after a primary total knee arthroplasty (TKA). The aim was to evaluate the clinical outcomes obtained with the SPR and to compare them with radiological findings. Methods A total of twenty-seven consecutive patients met the inclusion criteria. There were twenty-three (85%) women and four (15%) men with a median age of 70 years. The patients were evaluated before and after the surgery with the same functional scores and radiological parameters. Bone scintigraphy was also used in the assessment, and a CT-scan was performed in order to evaluate the femoral component rotation. The median time between TKA and SPR was 18 months. Results With a median follow-up of 23 months, seventeen patients (63%) reported a clear subjective improvement after SPR, and patellofemoral scores (primary outcome measure), KSS and WOMAC (secondary outcome measures) showed a statistically significant improvement following the procedure. There were no significant changes after SPR in the Insall-Salvati ratio, the lateral patellar displacement or the lateral patellar tilt. The mean time between TKA and SPR had no statistically significant effect on outcome. The bone scintigraphy revealed increased patellar uptake in seven cases, but this was not related to subsequent improvement after SPR. Rotational computed tomography showed a median internal rotation of the femoral component of 18. The complications observed were a patellar component loosening and an acute post-infection. Conclusion No clinical or radiological parameter was found to be related to the final outcome after SPR. There was a discrepancy between functional scale scores and the patient's subjective satisfaction. Level of evidence Prospective case series with no comparison group, Level IV.
In this paper it is investigated how fractal properties can be used to characterize a mammographi... more In this paper it is investigated how fractal properties can be used to characterize a mammographic lesion. The idea is suggested by the similarity between the breast tissue and a synthetically generated fractal image. Fractals are pertinent tools to describe the complexity of a shape; meanwhile, radiologists use the complexity of the lesion's contour to classify the abnormality. Tests on 30 cases mammographic lesions shows that fractal dimension of the lesion's contour is higher in cancer cases and lower in benign cases. This could be an important observation in order to classify BI-RADS 4 lesions, with no need of further examination (biopsy).
Bulletin of Mathematical Biology, 2006
Thermally-induced fluctuations of individual phospholipids in a bilayer lipid membrane (BLM) are ... more Thermally-induced fluctuations of individual phospholipids in a bilayer lipid membrane (BLM) are converted into collective motions due to the intermolecular interactions. Here, we demonstrate that transbilayer stochastic pores can be generated via collective thermal movements (CTM). Using the elastic theory of continuous media applied to smectic-A liquid crystals, we estimate the pore radius and the energetic requirements for pore appearance. Three types of thermally-induced transbilayer pores could be formed through BLMs: open and stable, open and unstable, and closed. In most of the situations, two open and stable pores with different radii could be generated. Notably, the two pores have the same generation probability. Unstable pores are possible to appear across thin bilayers that contain phospholipids with a large polar headgroup. Closed pores are present throughout the cases that we have inspected. The effects of hydrophobic thickness, polar headgroup size of phospholipids, temperature, surface tension, and elastic compression on the pore formation and pore stability have been examined as well.
Biology of Blood and Marrow Transplantation, 2003
Biology of Blood and Marrow Transplantation, 2004
... Advanced Control and Optimization for Thermo-energetic Installations TB Airimitoaie, D. Popes... more ... Advanced Control and Optimization for Thermo-energetic Installations TB Airimitoaie, D. Popescu, C. Dimon Page 2. Tudor-Bogdan Airimitoaie, Dumitru Popescu, Cătălin Dimon Advanced Control and Optimization for Thermo-Energetic Installations 84 ...
2Nd International Conference on Systems and Computer Science, Aug 1, 2013
Automatics was born in Romania in the ’60s, as a branch of Energetic Engineering. Quickly, it bec... more Automatics was born in Romania in the ’60s, as a branch of Energetic Engineering. Quickly, it became a self-sustained research field with an interdisciplinary opening towards a great variety of industrial applications. The foundation of Automatics has been built around 3 disciplines: one with a rather theoretical approach – Systems Theory – and two others with a practical perspective – System Identification and Automatic Control. This book describes some modern techniques of automatic process control with examples of a major importance in industry. L’Automatique est apparue en Roumanie dans les années ’60, comme une branche de l’Énergétique. Rapidement, elle s’est constituée comme un domaine de recherche indépendant, en épatant surtout par son ouverture à l’interdisciplinarité et l’orientation vers une vaste panoplie d’application industrielles. Le fondement de l’Automatique est en effet constitué par 3 piliers: un ayant une nature plutôt théorique – la Théorie des Systèmes – et deu...
Cuprins Capitolul 1. Introducere 1 1.1 Instrumentele Automaticii 1 1.2 Modelarea si identificarea... more Cuprins Capitolul 1. Introducere 1 1.1 Instrumentele Automaticii 1 1.2 Modelarea si identificarea proceselor 3 1.2.1 Modele de cunoastere 3 1.2.2 Modele de comportament 4 1.2.3 Modele de comanda 6 1.3 Sisteme de control automat 8 1.4 Conexiunea identificare - comanda 11 1.5 Supervizare in conducerea proceselor industriale 16 1.5.1 Optimizare si decizii optime de conducere 17 1.5.2 Diagnosticarea sistemelor 18 Bibliografie 20 Capitolul 2. Sisteme conventionale de reglare automata 21 2.1 Reglarea automata a debitului 21 2.1.1 Modelarea proceselor de curgere 21 2.1.1.1 Calculul modelului dinamic al unei conducte scurte 22 2.1.1.2 Calculul modelului dinamic al unei conducte lungi 23 2.1.2 Proiectarea sistemelor pentru reglarea automata a debitului 24 2.1.3 Implementarea sistemelor pentru reglarea debitului 28 2.2 Reglarea automata a nivelului 29 2.2.1 Modelarea proceselor de umplere - golire 29 2.2.1.1 Calculul modelului dinamic pentru evacuare la debit constant 30 2.2.1.2 Calculul mode...
Control Engineering and Applied Informatics
A system with multiple models and adaptive control will be presented. The advantages of this cont... more A system with multiple models and adaptive control will be presented. The advantages of this control with respect to the classical control will be illustrated on a level control system with nonlinear model plant. A recent recursive method in open and closed-loop identification and an R-S-T controller design has been proposed to guarantee the performances in the adaptive control scheme. The real time control system implementation confirms the opportunity of using the multi-models adaptive control architecture in the case when the nonlinear plant model introduces a typical large parameter variation. The article presents also an method to switch the algorithms. The obtained results for tested instalation show that the control strategy based on a single model and on a single controller generates a time response that is more affected by noise than the response given by an adaptive strategy. The multiple models adaptive control procedure proposed has the following advantages: a more preci...
As the world is currently facing an energy and climate crisis, the development and utilization of... more As the world is currently facing an energy and climate crisis, the development and utilization of alternative sources of energy has become an important challenge. From all types of renewable energy sources, wind turbines proved to be one of the cleanest and most reliable solutions for energy production. Wind energy conversion systems have in the last decades been subject of a strong interest as they could offer a viable source of electrical energy. This is why, it is important to focus on complex algorithms that meet with multiple objectives such as speed regulation, blade load and mode stabilization with simultaneously maximizing energy capture. This paper starts with a state of the art of wind turbines and their problematic and continues with the presentation of a polynomial control method designed for the third functioning zone of a wind turbine.
The systems with multiple models or multicontroller structure represent one of success solutions ... more The systems with multiple models or multicontroller structure represent one of success solutions for real time control of nonlinear or multi regime process. Utilization of these structures imposes solving of some specific problems like best algorithm selection or switching of control algorithm. The paper proposes a method for switching of the algorithms of multimodel structure based on principles of manual to automate bumpless transfer. The method is presented for a real time structure with RST control algorithm
Uploads
Papers by Popescu Dumitru