Diesel fuel and olive-cake slurry: Atomization and combustion performance

Because of possible future energy crises, it is increasingly desirable to search for alternative and renewable energy resources. This paper presents a detailed experimental study of direct combustion of a diesel and olive-cake (OC) slurry in a vertical, cylindrical, water-cooled combustor. An air-atomized nozzle was used in this study and experiments were undertaken to characterize the atomizer's performance. Axial and radial flame temperature profiles, the heat transfer distribution for the water jacket, flame stability and combustion efficiency were obtained over wide ranges of air:fuel ratios, and at different percentages of OC in the diesel fuel.

The rate of heat transfer to the water jacket and the combustion efficiency were improved as the percentage of OC in the diesel fuel was increased to 7 wt%. Also, as the percentage of OC in the diesel fuel increased, the stability loop became narrower. Stable flames were observed for up to 20 wt% of OC. Based on these results and on the availability of the OC, it may be concluded that the potential of OC as a source of energy is significant.     

Enhancing sulphur self-retention by building-in CaO in straw–bitumen pellets

Combined straw–bitumen pellets have been proposed as an alternative fuel. An interesting finding is the potentiality of straw ash constituents to retain sulphur as bitumen that has relatively high sulphur content. The aim of the present work is to enhance sulphur self-retention to directly meet the environmental regulations by building-in CaO in the pellet instead of feeding sorbent separately. CaO powder has been mixed with the pellet constituents during production processes.     

Influence of Co content on the characterization and magnetic properties of magnetite

Preparation of nanosized Co_xFe_3−xO₄; 0.05 ≤ x ≤ 0.20 particles from metal nitrates solution through citrate–precursor method was performed. XRD pattern of all prepared systems showed single phase with cubic spinel structure. The crystallite size was determined from TEM and found to agree with that calculated from Sherrer's equation (60–76 nm) The magnetic constants such as molar magnetic susceptibility (χ_M), Curie temperature (T_C) and saturation magnetization (M_S) were measured and the results indicated that, at x = 0.2 the values of χ_M, M_S, remanent magnetization (M_r,) and coercive field (H_c) are 23 emu/g mol, 77.62 emu/g, 33.17 emu/g and 574.5 Oe, respectively_.     

Linear and nonlinear optical properties and luminescence of Dy+3-doped aluminoborate glasses: Judd–Ofelt investigation

The nominal glasses composition ((40-x) % H₃BO₃—30% CaO—30% Al₂O₃—x Dy₂O₃), where x?=?1, 2, 3, 4, 5 and 6) were prepared using the melt quenching technique. The absorption spectra reveal the common normal 13 transition peaks of the Dy₂O₃-doped glasses. The linear and nonlinear optical properties were calculated. The Photoluminescence spectra and the decay lifetime were examined. The Judd–Ofelt parameters trend was Ω₄?>?Ω₂?>?Ω₆. The oscillator strength of the experimental, and calculated electronic dipole absorption transition were estimated. The radiative life-time, the radiative branching ratio, the emission and absorption transition cross section were also calculated. The gain coefficient of the transitions was predicted. All the calculated parameters were compared with the previous work. The results reveal that the current glasses composition is a good candidate as a lasing host material and the glasses are highly efficient composition when using in the optical communication fibers.

     

Sequential laser and mechanical micro-drilling of Ni superalloy for aerospace application

Laser percussion drilling is inherently associated with poor geometry and thermal defects. While mechanical micro-drilling produces good quality holes, premature drill breakage often occurs and it is difficult to drill holes at acute angles. This paper presents the feasibility and basic characteristics of a new approach for micro-drilling In718 alloy sheets at an acute angle, using sequential laser and mechanical drilling. The results demonstrate that sequential laser-mechanical micro-drilling alleviates the defects associated with laser-drilled holes, reduces burr size and machining time and increases the tool life compared with mechanical drilling.     

Lifetime-oriented multi-objective optimization of structural maintenance considering system reliability, redundancy and life-cycle cost using GA

The need to design and construct structural systems with adequate levels of reliability and redundancy is widely acknowledged. It is as crucial that these desired levels are maintained above target levels throughout the life of the structure. Optimization has served well in providing safer and more economical maintenance strategies. Lifetime maintenance optimization based on system reliability has already been proposed. It is still needed, however, to incorporate redundancy in the lifetime maintenance optimization process. Treating both system reliability and redundancy as criteria in the lifetime optimization process can be highly rewarding. The complexity of the process, however, requires the automation of solving the optimization problem. Genetic algorithms (GAs) are used in this study to obtain solutions to the multi-objective optimization problems considering system reliability, redundancy and life-cycle cost (LCC). An approach to provide the optimization program the ability to optimally select what maintenance actions are applied, when they are applied, and to which structural components they are applied is presented. Two different strategies are proposed. The first strategy has the ability to optimally select mixed maintenance types to apply to different parts of the structure at the same time. This strategy can be used in cases where any combination of different maintenance options can be practically applied to any part of the structure. The application of this strategy on truss structures is shown in a numerical example. The second strategy can be used when a limited number of possibilities of practical maintenance options are available. The application of this strategy to bridge structures is shown in a numerical example. The greatest advantage of the proposed approach (both strategies) is its ability to avoid the application of maintenance interventions to structural components that are not critical.     

Advanced Modeling for Efficient Computation of Life-Cycle Performance Prediction and Service-Life Estimation of Bridges

The rapid progress in computational hardware and software has brought about advanced capabilities enabling more accurate modeling of structures and better understanding of their lifetime behavior. Unfortunately, research in life-cycle performance prediction and service-life estimation of bridges has not fully caught up with the impressive advances in today’s technology, and has not taken enough advantage of the power offered by these advances. In this paper, a computational methodology for the life-cycle prediction and service-life estimation of bridges using advanced modeling tools and techniques is presented. The methodology employs incremental nonlinear finite element analyses, quadratic response surface modeling using design of experiments concepts, and Latin hypercube sampling, among other techniques. The methodology is illustrated on an existing bridge in the state of Wisconsin.     

Synchrotron X-ray absorption fine structure study and dielectric performance of Li0.5Fe2.5O4/BaTiO3 multiferroic

Journal of Materials Science: Materials in Electronics - Multiferroic nanocomposites (1?y)Li0.5Fe2.5O4/(y)BaTiO3 (y?=?0.0, 0.2, 0.4, 0.6, 0.8, and1.0) were synthesized by modified...     

Preparation and characterization of nanometric Mn ferrite via different methods

The structure and magnetic properties of MnFe(2)O(4) ferrites have been investigated using five different preparation methods, including the ceramic technique, flash combustion, co-precipitation, sol-gel and citrate methods. The characteristics of one sample prepared by different methods have been studied to select the better method, i.e.?the one that is the simplest and does not require an elaborate instrumental set-up. The results indicated that the citrate method gives the lowest value for the lattice parameter and particle size (14.1?nm), while the highest values are obtained with the ceramic method. The smallest nanosizes were obtained in the citrate and flash methods (14.1 and 40.7?nm, respectively).     

Mechanical microdrilling of negative-tapered laser-predrilled holes: a new approach for burr minimization

Despite considerable research effort being concentrated on improving hole quality, minimisation of burrs still remains a key challenge in mechanical microdrilling of ductile materials. Recently, a sequential laser-mechanical microdrilling technique, which was developed by the authors, has proved effective in improving tool life and reducing burr size. The improvement in burr size was achieved by means of laser predrilling a pilot hole before utilising a twist drill to finish the hole. This paper presents further development of the sequential laser-mechanical microdrilling process based on negative-tapered laser-drilled pilot holes. In the sequential laser-mechanical microdrilling process, although a large predrilled hole reduces the burr size, it has a negative effect on roundness and cylindricity of the hole. The results of further studies highlight that a smaller entry hole size supports the drill and suppresses tool wander which, in turn, improves hole cylindricity. Furthermore, a larger exit hole size significantly reduces burr size. Compared to pure mechanical drilling without any pilot hole, the reduction in burr size for the mechanical microdrilling of near zero tapper and negatively tapered laser-predrilled holes was observed to be 2.5 and 6 times, respectively. Moreover, the mechanical finishing of these holes does not compromise tool life and/or surface integrity. Thus, the use of a negative taper laser-predrilled hole presents a significant improvement in burr control in microdrilling of nickel-based super alloys in addition to providing a step change increase in tool life.