Search

The Pb(Mg1/3Nb2/3)O3-based ceramic system was obtained by using a modified variant of the conventional ceramic method in order to get pyrochlore-free compositions. Solid solutions obtained from Pb(Mg1/3Nb2/3)O3 and Ln(Mg1/2Ti1/2)O3 with Ln = Y3+, La3+, Pr3+, Nd3+ and Sm3+, were synthesized using a 3-step columbite precursor method and appropriate milling and sintering conditions. The structural phases of all sintered compositions were investigated in detail. The X-ray diffraction results demonstrate that all the samples possess a perovskite structure. The influence of dopant on the incorporation degree in the solid solutions was studied. The dielectric constants at three frequencies were measured and the influence of the dopant on these values was discussed.

The ferroelectric solid solutions described by a general formula 0.98Pb(Zr1-xTix)O3 – 0.02La(Fe3+0.5, Nb5+0.5)O3 have been obtained by solid state reaction technique, where x assumes the following values: 0.42, 0.48 and 0.58. The structure of these ferroelectric compositions has been investigated in detail using X-ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM). The results obtained by XRD have evidenced that all obtained samples have a perovskite structure. The influence of the sintering temperature on the degree of incorporation of the elements in the solid solution have been studied too. The dielectric and piezoelectric constants have been determined and the influence of temperature on obtained values are presented and discussed. The performed experimental results have pointed out that the materials are characterized by a high anisotropy. Furthermore, the obtained values of the electromechanical coupling factor (kp) is situated between 0.40÷0.65 depending on the composition and the sintering temperature too.

The influence of the sintering temperature on the structure and on the hysteresis loops of Fe3+ doped Pb(ZrxTi1-x)O3 system has been investigated. Three compositions have been selected in the following mode: one in rhombohedral region, one in MPB region and one in tetragonal region have been obtained by solid state reaction technique. Sintering has been carried out at 12000C and 12500C respectively. The nature of the phases has been investigated in detail using X-ray diffraction analysis (XRD). All the sintered samples reveal a perovskite type structure. The surfaces have been lapped and metalized in order to obtaine the hysteresis loops at room temperature. The results showed a similar behaviour with “hard” PZT ceramics.

The addition of inorganic phase consisting of Ce-doped PbZrO3, a promising solution to increase the thermal and radiation strengths of electroinsulating alkyd resin EZ 528 used in rotating machines is studied. The delay of oxidation of filler is based on the electronic interaction between the former degradation intermediates and lattice defects.

In the present paper (1-x)Pb (Zr1-yTiy)O3 – xPb (Mn1/3Sb2/3)O3 – z at%E system, with E = Pr3+, Nd5+ and Gd3+ where x = 0.12; y = 0.48; z = 0 and 0.02 ceramic synthesized by solid state reaction technique is analysed. The investigation aims studying of the effect of dopants on the dielectric and piezoelectric properties of such piezoelectric ceramic. The prepared powders have been uniaxially pressed into discs with diameter of 10 – 12 mm and thickness of 1.2 mm. Sintering has been carried out in air atmosphere at temperatures of 1150°C and 1200°C, respectively, for 2 hours each, followed by a controlled cooling at a rate of 200°C /h. The piezoelectric properties have been investigated after a suitable preparation, including polishing, metallization. The structure of the samples has been determined by X-ray diffractometry (XRD), while the morphology and grains size have been investigated by the scanning electron microscopy (SEM). The piezoelectric properties have been studied by the resonance - antiresonance method. XRD analysis reveals a perovskite tetragonal structure and, as expected for ceramic materials, SEM analysis indicates that the average grain size increases as sintering temperature increases. The dielectric and piezoelectric properties have been determined measuring the ceramic discs, and properties, as dielectric permittivity (εr), dielectric loss (tg δ), and the electromechanical coupling factor (kp) have been obtained. The acquired results indicate a significant effect of the dopants on the dielectric and piezoelectric properties of such materials.

In this paper, some compositions described by the general formula Pb(ZrxTi1-x)0.99Fe0.01O3 have been considered and investigated. The compositions considered have been obtained by solid state reaction technique, where x corresponds to 0.42, 0.52 and 0.58. Sintering has been performed for 2 hours at temperatures between 1100oC and 1250oC. The influence of the sintering temperature on the microstructure and on the hysteresis loops of Fe3+ doped Pb(ZrxTi1-x)O3 system has been investigated. The crystallographic phase and microstucture of the sintered compositions have been studied in detail using X-ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM). The experimental results obtained by XRD have revealed that all the sintered samples have a perovskite structure. In order to correlate the behavior of the sintered materials to their microscopic structure, the domain structures have been defined by SEM. The dielectric properties, as relative dielectric permittivity (εr) and dielectric loss (tan δ) have been measured. The hysteresis loops at room temperature of all un-poled sintered compositions reveal a similar behaviour with “hard” PZT ceramics. The piezoelectric properties like electromechanical coupling factor (kp) have been investigated after polarization.

0.88Pb(Zr0.52Ti0.48)O3 – 0.12Pb(Mn1/3Sb2/3)O3 – 0,02 at%E piezoelectric ceramics, with E = Pr3+ were synthesized by using a conventional method, namely a solid state reaction technique. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were employed for the structural and microstructural investigations. Piezoelectric methods were used for the dielectric and piezoelectric properties determination. The results of XRD show a perovskite structure and XRD patterns, indexing on a tetragonal cell structure, was carried out for the most common phases. The SEM micrographs of the sintered compositions reveal a homogenous structure with a sharp or rounded grain boundary. The modified PZT ceramic presents still superior piezoelectric properties. Based on the results obtained, one can conclude that the analysed piezoelectric ceramics are useful for device applications.

Endocrine disruptors (ED) are exogenous agents that interfere with the normal function of the endocrine system and they are considered environmental chemicals with estrogen-like and/or anti-androgenic activity with important impact on the reproductive axis. They act via nuclear receptors, non-nuclear steroid receptors, nonsteroidal receptors, orphan receptors, and different enzyme pathways involved in the biosynthesis and/or metabolism of steroids. The molecules identified as ED and sources of exposure are diverse and vary worldwide, including from natural chemicals found in human and animal food (the main source) up to synthetic chemicals, such as as solvents, plasticizers, pesticides, fungicides, pharmaceuticals etc. ED are incriminated in the occurrence of malignant tumors, birth defects, attention deficit disorders, cognitive impairment, brain development, deformations of the body (including limbs), disturbance of sexual development, menstrual irregularity, precocious puberty, feminizing or masculinizing effects, abortion, not least obesity and decreased fertility. The principles of action are still studied and controversial, therefore, it is difficult to determine the minimum level at which adverse effect occurs and further studies are required.

This paper presents a methodology for choosing the best location of a distributed generation (DG) unit in a distribution grid considering the short-circuit current values. The optimum position into the grid is searched according to the minimum short circuit current. A three bus network was used in order to test the methodology and a real distribution network in Romania was proposed.

The simulation and the optimisation of some industrial processes represents a modern and efficient direction for multifunctional testing platforms. These platforms are designed for complex developments of technologic scenarios in order to improve and implement the control schemes with the help of modern technologies. The cost and the amount of time needed for deploying the system are reduced with the simulation of the process. The process control simulator presented in this paper is used for design and test control diagrams of the complex power plant processes. The entire process of a power plant is divided into hierarchical subsystems which are simulated separately. With the help of the process control simulator the different types of processes are simulated and can be optimisated. For each process a functional masks is associated, corresponding to different types of applications and with different complexity factors. The goal is to develop algorithms for practical work in different areas and implement them into the programmable logical controller (PLC) unit. A simulation block is used for all the applications having different replaceable masks according to the desired application as well as a PLC program simulator.

This paper presents a case study on a practical implementation of a fuzzy-PLC system for a servomechanism. The method presented achieves smooth fuzzy control, that can be easily implemented in a PLC system. The speed of the servomechanism is controlled.

Mitochondrial diseases often exhibit tissue-specific pathologies, but this phenomenon is poorly understood. Here we present regulation of mitochondrial translation by the Mitochondrial Translation Optimization Factor 1, MTO1, as a novel player in this scenario. We demonstrate that MTO1 mediates tRNA modification and controls mitochondrial translation rate in a highly tissue-specific manner associated with tissue-specific OXPHOS defects. Activation of mitochondrial proteases, aberrant translation products, as well as defects in OXPHOS complex assembly observed in MTO1 deficient mice further imply that MTO1 impacts translation fidelity. In our mouse model, MTO1-related OXPHOS deficiency can be bypassed by feeding a ketogenic diet. This therapeutic intervention is independent of the MTO1-mediated tRNA modification and involves balancing of mitochondrial and cellular secondary stress responses. Our results thereby establish mammalian MTO1 as a novel factor in the tissue-specific regulation of OXPHOS and fine tuning of mitochondrial translation accuracy.

Recently, mutations in the mitochondrial translation optimization factor 1 gene (MTO1) were identified as causative in children with hypertrophic cardiomyopathy, lactic acidosis and respiratory chain defect. Here, we describe an MTO1-deficient mouse model generated by gene trap mutagenesis that mirrors the human phenotype remarkably well. As in patients, the most prominent signs and symptoms were cardiovascular and included bradycardia and cardiomyopathy. In addition, the mutant mice showed a marked worsening of arrhythmias during induction and reversal of anaesthesia. The detailed morphological and biochemical workup of murine hearts indicated that the myocardial damage was due to complex I deficiency and mitochondrial dysfunction. In contrast, neurological examination was largely normal in Mto1-deficient mice. A translational consequence of this mouse model may be to caution against anaesthesia-related cardiac arrhythmias which may be fatal in patients.

Data centers energy efficiency has become an issue given the rising of energy prices and the increase of Web applications, which are hosted, mainly in data centers. In order to understand the opportunities for improving data center energy efficiency, it is necessary to determinate the real energy requirements for one computer application. This article will examine the power chain starting from the facility level and ending at the processor level. In this paper a data center energy model is proffered along with two important indicators that address energy efficiency: the first one is addressing Facility Efficiency and the second one is addressing IT Efficiency. The energy model is taking into account a global overview of the data center (power distribution units, cooling system and the IT system). The aim of the research is to find effective solutions to make data center reduce power consumption while keeping the desired quality of service or service level agreement.

In our days, data centers provide the global community with an indispensable service: nearly unlimited access to almost any kind of information by supporting Internet services such as Web hosting or E-commerce services. With the increasing demand of information, data centers consume a great amount of energy. The resulting high utility costs is reason enough to address power consumption. In this paper a data center energy model is proffered along with an optimization energy management algorithm designed to increase the overall IT energy efficiency. The energy model and the optimization algorithm are taking into account a global overview of the data center (power distribution units, cooling system and the IT system). A power management algorithm is proposed and it is shown that it yiels good energy gain in comparison with the known scheduling algorithms.

Data centers provide the global community withan indispensable service: nearly unlimited access to almost any kind of information we can imagine. With the increasing demand of information, the high energy costs has raised the issue of power consumption. The main goal in achieving data center energy efficiency can be translated into the ensuring that IT equipment uses, as maximum power as possible from the power entering the data center to compute useful work but at the same time the service level agreement between costumers and managers has to be satisfied. In this paper, different concepts of efficiency that are linked with multiple methods of increasing energy efficiency into a data center, will be presented, as well as different principles of energy management. A comprehensive overview of the currently available energy metrics will be provided, followed by an in-depth analysis of their commonalities and differences. An analyze about the degree of freedom encountered into the process of energy management, will be afforded. This paper presents a global overview of the energy efficiency management process into a data center.

This paper focuses on load frequency regulation, as a major function of automatic generation control (AGC) in the context of a versatile power system structure, environmental constrains and emerging new uncertainties. Generation units models are determined in order to build a control diagram used for load dispatch. The optimal parameters for the secondary controller were determined using a gradient descent algorithm.

The simulation of physical processes represents a modern and efficient direction for multifunctional testing platforms. This paper will present a Process Control Simulator and its applications in system simulation. The Process Control Simulator can be used for students training as well as for the conception, simulation and improvement of control schemes in modern technologies. The simulation of industrial processes reduces the cost and the amount of time needed for deploying the system. The various types of applications, with different complexity factors, are associated with several functional masks. The Process Control Simulator uses a simulation block and a microcontroller for all the applications with different replaceable masks according to the desired application.

In the paper the elaboration of Pb(Mg1/3Nb2/3)O3 � PbTiO3 with a perovskite structure by using a variant of the columbite method is presented. Very often, in the elaboration process of this compound a secondary pyrochlore (Pb3Nb4O13) phase is obtained, due both to its high stability in comparison with the perovskite and to the evaporation of the lead oxide (PbO) during the processing. A new preparation variant has been used in order to avoid the formation of the secondary compound, namely a three step columbite method. The best sintering conditions were established by studying the densification of the material by scanning electronic microscopy. The crystalline perovskite phase was put into evidence by using X-Ray diffraction. The results showed the formation of the pyrochlore free Pb(Mg1/3Nb2/3)O3 � PbTiO3 (PMN-PT) ceramics in all the samples sintered at 1100 0C.