Enhanced Energy Product Research Articles

Energetic-Environmental Enhancement of Waste and Agricultural Biomass by Anaerobic Digestion Process

AbstractThe sustainable production of energy is one of the major challenges facing humanity. In recent years, enhancement of energy production from waste biomass has become a pressing issue. This article presents an energetic-environmental analysis of a biogas plant equipped with an internal combustion engine able to work as an energetic system of distributed micro-cogeneration, in order to be able to pursue both the goals of energetic and environmental sustainability. Biogas generation, mainly that of methane and carbon dioxide with traces of other gases, occurs through the process of anaerobic digestion of organic matter. This study of a typical 1-MW power plant assumes it is localized near a livestock farm, where it can be supplied with the main waste biomass produced by the same farm: manure and agricultural biomass. Using Buswell’s chemical model, data of biogas producibility of different organic matrices are compared with data obtained from the plant considered, and an analysis of quality on the com...

Anisotropic Sm2Co17 nano-flakes produced by surfactant and magnetic field assisted high energy ball milling

Anisotropic Sm2Co17 flakes with high aspect ratio were prepared by magnetic field assisted high energy ball milling in the presence of heptane and oleic acid (OA). The thickness of flakes was only tens of nanometers. Coercivity of 3 kOe was achieved in the nano-flakes. Most interestingly, the magnetic crystalline anisotropy of Sm2Co17 flakes was improved compared to that of particles made by traditional ball milling. These anisotropic Sm2Co17 nano-flakes could be the building blocks for the future high-performance nano-composite permanent magnets with an enhanced energy product.

Prospects for nanoparticle-based permanent magnets

Magnetic nanoparticles smaller than ∼15nm in diameter and with high magnetocrystalline anisotropies K1⩾1MJm−3 can be used as building blocks for next-generation permanent magnets. Advances in processing steps are discussed, such as self-assembly, alignment of the easy axes and appropriate nanostructuring that will enable the fabrication of densely packed nanoparticle assemblies with improved permanent-magnet properties. This study also proposes an idealized nanocomposite structure for nanoparticle-based future permanent magnets with enhanced energy products.

Random magnetic anisotropy in isotropic nanocrystalline composite permanent magnets

In this study, the random magnetic anisotropy in isotropic nanocrystalline composite permanent magnets was investigated by means of numerical simulations. The magnetization reversal of randomly oriented hard-soft exchange-coupled grains was simulated using the Landau–Lifshitz–Gilbert equation in which the magnetization in a particular grain is assumed to align in the same direction (single-spin model). The calculations show that the energy product (BH)max of nanocomposite magnets has a peak value 50 MGOe at 6 nm. It is about 80% of that of single-crystal Nd2Fe14B. The coercivity HC exhibits a steep decrease toward smaller grain size, which is the result of the suppression of the random magnetic anisotropy by exchange interaction. Therefore, in isotropic nanocomposite magnets, the enhancement of energy product is limited by the suppression of the random magnetic anisotropy by exchange interaction.

Enhancement in energy product in Sm-Co/Fe exchange coupled magnetic layers with molybdenum interlayers

Trilayers of Sm-Co/Mo/Fe were deposited by DC and RF magnetron sputtering on Si (100) substrate at 650 °C. Effect of very thin Mo interlayers on energy product of magnetic layers was studied. All the samples showed strong exchange coupling and single phase behavior. With increasing Mo interlayer thickness, we observed oscillating behavior of saturation magnetization and energy product. The rise in energy product was observed as 22% for 0.3 nm Mo interlayer as compared to sample without Mo interlayer.

Bimagnetic nanoparticles with enhanced exchange coupling and energy products

Bimagnetic FePt/Fe3O4 nanoparticles with core/shell or heterodimer structure have been prepared using a sequential synthetic method. The dimension of both FePt and Fe3O4 was tuned by varying the synthesis parameters. The as-synthesized bimagnetic nanoparticles were superparamagnetic at room temperature. After being annealed in a reducing atmosphere, the FePt/Fe3O4 bimagnetic nanoparticles were converted to a hard magnetic nanocomposite with enhanced energy products due to the exchange coupling between the hard and soft magnetic phases. It was found that the exchange coupling in nanocomposites made from the core/shell nanoparticles is stronger than that from the heterodimer nanoparticles. By tuning the dimensions of the FePt and Fe3O4 phases, the energy product up to 17.8 MGOe was achieved in the annealed nanocomposites, which is 36% higher than the isotropic single-phase FePt counterpart.

Neuroprotective effects of near-infrared light in an in vivo model of mitochondrial optic neuropathy.

Near-infrared light (NIL) promotes a wide range of biological effects including enhancement of energy production, gene expression and prevention of cell death. This is the first report of the in vivo neuroprotective effects of NIL against optic neuropathy induced by mitochondrial complex I inhibition. Subjects were pigmented rats that received single bilateral intravitreal doses of rotenone, a mitochondrial complex I inhibitor, or rotenone plus one of three different doses of NIL. Treatment effects were evaluated at behavioral, structural and neurochemical levels. Rotenone induced a decrease in visual function, as determined by changes in the dark-adapted illuminance sensitivity threshold, escape latency and rate of successful trials in a two-choice visual task, compared with vehicle-treated controls. Behavioral impairment correlated with a decrease in retinal and visual pathway metabolic activity, retinal nerve fiber layer thickness and ganglion cell layer cell density. These changes were prevented by NIL treatments in a dose-dependent manner. Whole-brain cytochrome oxidase and superoxide dismutase activities were also increased in NIL-treated subjects in a dose-dependent manner, suggesting an in vivo transcranial effect of NIL. In whole-brain membrane isolates, NIL prevented the rotenone-induced decrease in cell respiration. The results show that NIL treatment can effectively prevent the neurotoxic effects of rotenone and that it might be used in the treatment of neurodegenerative disorders associated with mitochondrial dysfunction.

Microstructure analysis of a SmCo/Fe exchange spring bilayer

The microstructure of a magnetron sputtered Cr(20 nm)/Sm–Co(20 nm)/Fe(20 nm)/Cr(5 nm) exchange spring magnet was studied using an advanced analytical transmission electron microscopy to better understand the relationship between its chemistry and structure to enhance the energy product. It is shown that the Fe atoms diffuse into the well textured Sm–Co layer, causing a transition from the stoichiometric Sm2Co7 near the Sm–Co/Cr interface to a defected Sm(Co,Fe)5 in the Sm–Co–Fe intermixed area. The graded intermixed layer between Sm–Co and pure Fe gives rise to a compositionally enhanced energy product.

Magnetic property improvement of Pt-lean FePt∕Fe–B-type nanocomposites by Co substitution

Effects of Co content on the magnetic properties and microstructure of melt-spun [(Fe1−xCox)0.675Pt0.325]84B16 (x=0–0.5) and [(Fe1−yCoy)0.725Pt0.275]85B15 (y=0 and 0.3) nanocomposite ribbons have been investigated. The substitution of Co for Fe in [(Fe1−xCox)0.675Pt0.325]84B16 ribbons enhances the coercivity (Hci) from 7.5kOe for x=0to10kOe for x=0.3, due to the formation of ordered L10-(Fe,Co)Pt phase with higher anisotropy field. The effect of Co substitution for Fe in [(Fe1−yCoy)0.725Pt0.275]85B15 series ribbons is similar to that in [(Fe1−xCox)0.675Pt0.325]84B16 system. Interestingly, larger magnetization could be obtained by decreasing the boron and Pt content simultaneously. Moreover, L10-(Fe,Co)Pt phase provides [(Fe0.7Co0.3)0.725Pt0.275]85B15 ribbons sufficient high coercivity Hci=5.4kOe, resulting in a remarkable enhancement of energy product from 10.0MGOe for Co-free ribbons to 15.7MGOe for ribbons with y=0.3.

Improvement of energy product in exchange coupled Fe49−xCoxPt51 (x=0.0,0.7,1.3,2.2) thin films

Magnetic properties and crystal structure of the Fe49−xCoxPt51 (x=0.0,0.7,1.3,2.2) thin films deposited on a quartz substrate heated at 500°C were investigated. A significantly enhanced energy product of 18.4MGOe (87% larger than that of the binary film) was obtained in the x=1.3 sample. This improvement can be attributed to the well exchange coupling between the Ll0 and the residual disordered FePt regions. Unlike the common exchange spring (coupled) magnets or films showing a well defined two-phase structure, the chemical ordering of Fe–Co–Pt films changes continuously from the ordered regions to the disordered regions. We consider that this continuous change of chemical ordering enhances exchange coupling. Furthermore, the addition of cobalt also accompanied the decrease of crystal domain (subgrain) size in FePt grains. The fine-grain dispersion also can be a reason for the high energy product.

Energy product enhancement of CoPt films by the alloy addition of Ti

Ternary (Co 48Pt 52) 100− x Ti x ( x = 0 , 0.8, 3.7, 5.3) films were deposited on quartz substrates by RF sputtering at the annealing temperatures T a=500–800 °C. The addition of Ti was found to suppress the formation of the CoPt-ordered phase. The coercivity squareness parameters ( S*) were also increased with the addition of titanium. TEM observations indicated that the Ti addition significantly reduces the grain size of the CoPt film, thus enhances the exchange interaction between the magnetic grains. The advantages result in the increase of ( BH) max values from 2.91 MGOe for x=0.0 to 6.09 MGOe for x=5.3 after the samples is annealed at an optimum temperature of 700 °C.

Thermodynamic assessment of power requirements and impact of different gas-turbine inlet air cooling techniques at two different locations in Oman

Gas-turbine inlet air cooling has been considered for boosting the power output during hot seasons. In this paper, the power requirements of several inlet air cooling techniques for gas-turbine power plants in two locations; namely, Marmul and Fahud, in Oman have been evaluated using typical meteorological year (TMY) data. The considered techniques are evaporative cooling, fogging cooling, absorption cooling using both LiBr–H 2O and aqua-ammonia, and vapour-compression cooling systems. For evaporative cooling, an 88% approach to the wet-bulb temperature has been considered, compared with a 98% approach for fogging cooling. A design compressor inlet air temperature of 14 °C has been assigned to LiBr–water chilling systems. For both aqua-ammonia absorption and vapour-compression refrigerating systems, a design compressor inlet air temperature of 8 °C has been selected to avoid the formation of ice fragments as the air is drawn into the mouth of the compressor. These technologies have been compared with respect to their effectiveness in power boosting of small-size gas-turbine power plants used in two oil fields at Marmul and Fahud in the Sultanate of Oman. Fogging cooling is accompanied with 11.4% more electrical energy in comparison with evaporative cooling in both locations. The LiBr–H 2O cooling offers 40% and 55% more energy than fogging cooling at Fahud and Marmul, respectively. Applying aqua-ammonia–water and vapour-compression cooling, a further annual energy production enhancement of 39% and 46% is expected in comparison with LiBr–H 2O cooling at Fahud and Marmul, respectively.

Bimagnetic Core/Shell FePt/Fe3O4 Nanoparticles

Bimagnetic core/shell Fe58Pt42/Fe3O4 nanoparticles are synthesized from high-temperature solution phase coating of 4 nm Fe58Pt42 core with Fe3O4 shell. The shell is tunable from 0.5 to 3 nm. Magnetic properties of the as-synthesized core/shell particles are dependent on shell thickness due to the exchange coupling between core and shell. Upon reductive annealing, an assembly of the core/shell nanoparticles is transformed into a hard magnetic nanocomposite with enhanced energy product.

Nanocomposite PrCo 5/Pr 2Co 17 magnets with enhanced maximum energy product

Nanocomposite PrCo 5/Pr 2Co 17 powders, with different volume fraction of the Pr 2Co 17 phase, were synthesized by mechanical milling mixtures of PrCo 5 and Pr 2Co 17 alloy powders with the aim of enhancing the maximum energy product of PrCo 5-based powders. It is found that the saturation magnetization increases monotonously with the volume fraction of the Pr 2Co 17 phase while the coercivity decreases. As a result, the maximum energy product first increases with the Pr 2Co 17 phase, going through a broad peak, and then decreases with further increase of the Pr 2Co 17 phase. The highest maximum energy product of 11.8 MG Oe is obtained in a mixture consisting of 70% PrCo 5 and 30% Pr 2Co 17 phase. Microstructural studies reveal that a uniform nanoscale PrCo 5/Pr 2Co 17 microstructure with an average grain size of about 20 nm is developed in these PrCo 5/Pr 2Co 17 powders. Evidence of intergranular exchange coupling is found in the PrCo 5/Pr 2Co 17 powders, suggesting that the enhanced energy product is due to exchange coupling between the magnetically hard PrCo 5 and soft Pr 2Co 17 nanograins.

Myocardial protection for transplantation

PROGRESS in the development of new techniques in surgery of heart transplantation had considerable influence on the creation of new methods for heart preservation. Currently, various cardioplegic solutions, developed for cardiac surgery, provide safe preservation of myocardial function for 5 to 6 hours, but remain unsatisfactory. The process of clinical heart preservation usually begins with identification of the brain death of the donor. Effective preservation allows time for confirmatory tests of brain death, organization of cooperating teams for organ removal, HLA-typing and crossmatching of donor tissues against a pool of waiting recipients, excluding associated transplantable disease such as infection or neoplasm of the donor, selecting and locating recipients, and arranging recipient operating teams and time to transport organs over long distances. In the course of cardiac transplantation, donor hearts undergo a four-step sequence of events (cardiac arrest, cold storage, global ischemia during implantation, and reperfusion) during which time myocardial damage can occur. Simple cooling markedly enhances ischemic tolerance, diminishes metabolic activity, curtails oxygen demand, and slows degradation of energy stores. Transmembrane passive diffusion of ions is not appreciably affected by hypothermia, while active transport mechanisms, such as those governed by Na1/K1 ATP-ase and Mg21/Ca21 ATP-ase are inhibited below 10° C. Therefore, a major requirement for a cold flushing solution is an impermeant-providing osmotic force to oppose cellular oedema. High molecular weight anions (lactobionate) or nonelectrolytes (saccharoids, raffinose, sucrose) or chelates of citrate and magnesium can achieve this. An effective buffer (phosphate, citrate, histidine) counters cellular acidosis. The presence of glutathione in cardioplegic solution prevents oxygen-derived free radical injury, whereas the presence of glutamate prevents concracture by enhancement of energy production. The present study is a randomized clinical trial assessing preservation of the donor heart using three common cardioplegic solutions (Table 1). The Belzer solution developed at the University of Wisconsin (UW) contains a high concentration of K1 2125 mmol/L, which causes depolarization of the myocytes, enzyme dysfunction, decreases membrane stability, and Ca11 sequestration. The original Bretschneider solution (HTK) causes nondepolarizing cardiac arrest due to the presence of histidine. The Celsior cardioplegic solution offers the possibility of being used not only as a storage medium, but also as a perfusion fluid during initial donor heart arrest, poststorage graft reimplantation, and early reperfusion.

Containerless solidification of undercooled NdFeZrB alloy droplets in a drop tube

Containerless solidification of undercooled Nd13Fe79.9Zr0.1B7 alloy droplets was investigated using a 3-m drop tube. It was found that the solidification mechanism of droplets depends strongly on their sizes. Due to small undercoolings and high cooling rates, large droplets (≥300 μm) are solidified via an incomplete peritectic reaction, thus leading to a large amount of preserved primary iron dendrites. However, most of small droplets (<300 μm) are solidified by the primary crystallization of Nd2Fe14B phase owing to enhanced undercooling levels. As a result, a microstructure consisting of coarse dendritic Nd2Fe14B grains is formed. It was therefore suggested that large undercooling prior to solidification is able to avoid the formation of primary free iron in near-stoichiometric NdFeB alloys, thus providing a promising way to prepare master alloys for the fabrication of magnets with enhanced energy products.

Maximizing loop squareness by minimizing gradients in the microstructure

Enhanced energy product and higher operating fields can be achieved by improving the squareness of the demagnetization loop. In isotropic materials, increasing loop squareness can be achieved by minimizing microstructural gradients and maximizing homogeneity. Achieving homogeneity by melt spinning can be difficult due to localized changes in cooling conditions from extrinsic factors such as gas entrapment between the melt and the chill surface and intrinsic effects resulting from the stochastic nature of nucleation on a surface. These localized variations are reduced by altering the solidification kinetics of the alloy, thus reducing its sensitivity to localized changes in cooling conditions. This was achieved through development of a nine-element modified Nd–Fe–B alloy which solidified with a uniform glass structure at much lower cooling rates. After crystallization, enhanced microstructural homogeneity was verified by electron microscopy and described by parameters based on the loop shape. The nine-element alloy had squarer loops and uniformly high hard magnetic properties (&amp;gt;12 MG Oe) for cooling rates over 10 m/s.

Magnetic Properties of .ALPHA.-Fe-Nd2Fe14B Exchange Spring Magnets Synthesized by Mechanical Alloying.

The possibility of producing isotropic permanent magnets with enhanced energy product has drawn lot of attention recently. The synthesis of two phase (hard and soft) nanocrystalline exchange coupled magnets by many research groups using different techniques and the various combination of two phases is an indication to the level of research interest in this area. The nitrogenated or carburized rare earth compounds with 2:17 or 1:12 structure as the hard phase was the focal point of many groups. However, the choice of Nd2Fe14B as the hard phase with the attractive advantages of single stage heat treatment, no drawbacks of incomplete nitrogenation or carburization and the possibility of higher sintering temperature has tilted the scale in its favor. The present article reports on the results of the synthesis of exchange spring magnets of Nd2Fe14B and α-Fe and their magnetic properties by mechanically alloying the powder mixture of Nd2Fe14B and iron. The magnets exhibit a spring back greater than 80% and a maximum energy product of 45 kJ/m3. The observed large spring back is an indication of the good coupling between the hard and the soft phases. The low energy product is attributed to the low coercivity of the starting Nd2Fe14B powder and requires further improvement.

Magnetic Properties of .ALPHA.-Fe-Nd(Fe,TM)12Nx Exchange Spring Magnets Synthesized by Mechanical Alloying.

The possibility of producing isotropic permanent magnets with enhanced energy product has drawn lot of attention recently. The synthesis of two phase (hard and soft) nanocrystalline exchange coupled magnets by many research groups using different techniques and the various combination of two phases is an indication to the level of research interest in this area. The nitrogenated or carburized rare earth compounds with 2:17 or 1:12 structure as the hard phase was the focal point of many groups. However, the choice of Nd2Fe14B as the hard phase with the attractive advantages of single stage heat treatment, no drawbacks of incomplete nitrogenation or carburization and the possibility of higher sintering temperature has tilted the scale in its favor. The present article reports on the results of the synthesis of exchange spring magnets of Nd2Fe14B and α-Fe and their magnetic properties by mechanically alloying the powder mixture of Nd2Fe14B and iron. The magnets exhibit a spring back greater than 80% and a maximum energy product of 45 kJ/m3. The observed large spring back is an indication of the good coupling between the hard and the soft phases. The low energy product is attributed to the low coercivity of the starting Nd2Fe14B powder and requires further improvement.

Experimental evaluation Celsior, a new heart preservation solution

An original heart preservation solution (Celsior) has been developed, the formulation of which has been designed to fulfil two major objectives: (1) to combine the general principles of hypothermic organ preservation with those specific for the myocardium, and (2) to offer the possibility of being used not only as a storage medium but also as a perfusion fluid during initial donor heart arrest, poststorage graft reimplantation and early reperfusion. The major principles addressed by the Celsior formulation include (1) prevention of cell swelling (by mannitol and lactobionate), (2) prevention of by the Celsior formulation include (1) prevention of cell swelling (by mannitol and lactobionate), (2) prevention of oxygen-derived free radical injury (by reduced glutathione, histidine and mannitol), and (3) prevention of contracture by enhancement of energy production (glutamate) and limitation of calcium overload (high magnesium content, slight degree of acidosis). Two experimental preparations were used: The isolated isovolumic buffer-perfused rat heart model and the heterotopic rabbit heart transplantation model. In isolated heart experiments, hearts were arrested with and stored in Celsior for 5 h at 4 degrees C and subsequently reperfused for 1 h. A similar protocol was used in the transplantation experiments except that the total ischemic time was approximately 1 1/2 h longer (corresponding to 6 h of storage followed by the 25 additional minutes of cold ischemia required for graft implantation.(ABSTRACT TRUNCATED AT 250 WORDS)